A Strong Energy Portfolio for a Strong America 

Energy efficiency and clean, renewable energy will mean a stronger economy, a cleaner environment, 

and greater energy independence for America. Working with a wide array of state, community, industry, and 

university partners, the U.S. Department of Energy’s Office of Energy Efficiency and Renewable Energy 

invests in a diverse portfolio of energy technologies.

For more information contact:

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1-877-EERE-INF (1-877-337-3463)

www.eere.energy.gov
Acknowledgment

We would like to thank our program participants for their contributions to the programs, 

and all the authors who prepared the project abstracts that make up this report. In 

addition, we would like to express our sincere appreciation to Brenda Hickey for 

compiling this report and to Deborah Counce and Brenda Phillips for their contributions 

in preparing and publishing it. 
U.S. Department of Energy 

Office of FreedomCAR and Vehicle Technologies 

1000 Independence Avenue S.W. 

Washington, DC 20585-0121 

FY 2005 

Progress Report for Automotive Propulsion 

Materials Program 

Energy Efficiency and Renewable Energy 

Office of FreedomCAR and Vehicle Technologies 

Edward Wall 

Program Manager 

December 2005 

Automotive Propulsion Materials FY 2005 Annual Report 

CONTENTS 

1. INTRODUCTION .............................................................................................................. 1

2. POWER ELECTRONICS .................................................................................................. 7 

A. Low-Cost, High-Energy-Product Permanent Magnets................................................. 7 

B. Characterization of Rare Earth Permanent Magnets for Automotive Applications ..... 11 

C. Carbon Foam for Cooling Power Electronics............................................................... 16 

D. Mechanical Characterization of Electronic Materials and Electronic Devices ............ 23 

3. CIDI ENGINES .................................................................................................................. 27 

A. Round Pleated Ceramic Fiber Diesel Particulate Filter Cartridge 

Durability Improvement................................................................................................ 27 

B. Fabrication of Small Fuel Injector Orifices .................................................................. 32 

C. Electrochemical NOx Sensor for Monitoring Diesel Emissions................................... 38 

D. Hydrogen Compatibility of Materials for Automotive Applications............................ 42 

E. Advanced Materials Development through Computational Design for 

HCCI Engine Applications ........................................................................................... 50 

APPENDIX A: ACRONYMS AND ABBREVIATIONS ....................................................... 57 

iii 
Automotive Propulsion Materials FY 2005 Annual Report 

iv 
Automotive Propulsion Materials FY 2005 Annual Report 

1. INTRODUCTION 

Automotive Propulsion Materials R&D: 

Enabling Technologies to Meet FreedomCAR Program Goals 

The Department of Energy’s (DOE’s) Office of FreedomCAR and Vehicle Technologies (OFCVT) is 

pleased to introduce the FY 2005 Annual Progress Report for the Automotive Propulsion Materials Research 

and Development Program. Together with DOE national laboratories and in partnership with private industry 

and universities across the United States, the program continues to engage in research and development 

(R&D) that provides enabling materials technology for fuel-efficient and environmentally friendly light-duty 

vehicles. 

This introduction summarizes the objectives, progress, and highlights of the program in FY 2005. It also 

describes the technical barriers remaining and the future direction of the program. The FY 2005 annual 

progress reports on Combustion and Emission Control for Advanced CIDI Engines and Power Electronics 

provide additional information on OFCVT’s R&D activities that support the development of propulsion 

materials technology. 

In August of 2005, President Bush signed the Energy Policy Act of 2005. This comprehensive energy 

policy specifically addresses the development of energy-efficient vehicle technologies, including hybrid 

systems, advanced emission control technologies, fuel cells, and 

hydrogen-based systems. The Energy Policy Act is a strong indicator of 

the continuing federal support for advanced automotive technologies and 

the materials work that supports them. 

The Automotive Propulsion Materials (APM) R&D Program has 

supported the FreedomCAR Program since its inception. FreedomCAR is 

not an automobile or prototype but rather a new approach to developing 

the technologies for vehicles of the future. In research areas where 

industry views the risks as too high and uncertain, the FreedomCAR 

Program conducts long-term research, development, and demonstration 

activities that bring the technology to a stage of maturity such that 

industry can undertake the final commercialization stages. 

The APM Program is a partner with the OFCVT programs for Power 

Electronics and Electric Machines and for Combustion and Emissions 

Control for Advanced CIDI Engines. Projects within the APM Program 

address materials concerns that directly impact the critical technical 

barriers in each of these programs—barriers such as thermal 

management, emissions reduction, and reduced manufacturing costs. The 

program engages only the barriers that involve fundamental, high-risk materials issues. 

Enabling Technologies 

The APM Program focuses on enabling materials technologies that are critical in removing barriers to the 

power electronics and compression-ignition, direct-injection (CIDI) engine and emissions control research 

programs. The program supports these two core technology areas by providing materials expertise, testing 

capabilities, and technical solutions for materials problems. The component development, materials 

processing, and characterization that the program provides are enablers of the successful development of 

efficient electric drive systems and emissions-compliant CIDI engines. 

1
The Propulsion Materials Program 

focuses on two applications. 

FY 2005 Annual Report Automotive Propulsion Materials 

Thermal management is a crosscutting 

engineering issue that affects both the power 

electronics and CIDI programs. The components 

necessary for high-fuel-economy, low-emission 

hybrid electric and fuel cell vehicles require that 

power electronics be smaller and lighter and 

operate at higher temperatures than those for 

conventional vehicles. These requirements are 

being addressed by developing electronic 

materials (i.e., materials for low-cost dc bus 

capacitors) that operate at higher temperatures 

and by improving the capability to dissipate heat 

generated in electronic devices. The APM 

Program has been addressing electric drive system heat dissipation issues through the development of 

advanced carbon foam technology. 

Current CIDI engines must strike a delicate balance between high efficiency and low tailpipe emissions. 

CIDI engine and aftertreatment system development will greatly benefit from the Program’s efforts to 

develop improved engine components and subsystems. The APM Program featured a project to develop 

technology to produce very small (~50 micron) orifices for fuel injectors used in high-pressure common rail 

systems. The smaller orifices can enable better control of fuel atomization that will increase efficiency and 

reduce emissions. An exploratory study was initiated in FY 2004 at Pacific Northwest National Laboratory 

(PNNL) to determine the frictional behavior of metals—like those used in fuel injectors—in the hydrogen 

environment of a hydrogen internal combustion engine or fuel cell. The friction and wear characteristics of 

metallic materials depend largely on surface oxide films. However, a hydrogen environment is chemically 

reducing, so the loss of the surface oxide by wear will result in bare surface contact and an increase in friction 

and wear. The Program is also working to reduce emissions through the development of advanced particulate 

filters. 

A new project was initiated to identify materials requirements for the operating conditions in 

homogeneous charge compression-ignition (HCCI) engines and demonstrate the feasibility of the “materials 

by design” approach to developing advanced materials for the most critical engine components. 

Collaborations have already been established with two companies to work together on materials needs. 

Interaction with industrial partners throughout the project is expected to result in the rapid transfer of 

materials improvements to industry. 

Collaboration and Cooperation 

As with other programs under FreedomCAR, collaboration and cooperation across organizations is a 

critical part of the APM Program. Throughout the FreedomCAR Program, scientists at the national 

laboratories are collaborating with manufacturers to identify and refine the materials characteristics necessary 

for meeting system performance requirements. Researchers at Lawrence Livermore National Laboratory 

(LLNL) are working with Ford Motor Company and Oak Ridge National Laboratory (ORNL) to develop 

low-cost, rapid-response nitrogen oxides (NOx) sensors that can be used in feedback control loops to monitor 

and minimize NOx emissions from diesel engines. There is also cooperation among national laboratories to 

take advantage of the expertise of each facility. ORNL and Argonne National Laboratory, for example, are 

collaborating in the development of higher-strength NdFeB permanent magnets that will enable significant 

reductions in the size, weight, and cost of electric motors used in hybrid vehicles. In another project, ORNL is 

characterizing ~5-micron-thick polymer films that are being developed by Sandia National Laboratories 

(SNL). SNL is funded by the Power Electronics Program to develop smaller, higher-temperature dc bus 

capacitors. SNL is using the information provided by ORNL to optimize the properties of the films in order to 

minimize manufacturing defects during capacitor winding. These electric drive system projects in turn are 

2
Automotive Propulsion Materials 

regularly reviewed by the EE Technical Team 

of the U.S. Council for Automotive Research 

to get feedback on research direction and 

progress. 

In addition to participation by national 

laboratories and large industries, the FY 2005 

APM Program included important R&D 

conducted by a small business. Industrial 

Ceramic Solutions, LLC (ICS), located in Oak 

Ridge, Tennessee, is developing a ceramic 

filter to reduce particulate emissions from 

diesel engines. As in the collaborative efforts 

of national laboratories with industry, 

researchers at ICS are working closely with 

representatives from DaimlerChrysler, Ford, 

General Motors, and ORNL to develop a filter 

that will meet the emissions targets of the 

program. 

Accomplishments 

FY 2005 featured significant 

advancements in the two newest materials 

program areas. The following section 

highlights some of these noteworthy 

accomplishments. 

FY 2005 Annual Report 

Contractor-industry collaboration 

Technology Industrial partner 

Capacitors  TPL, Inc. 

 Brady Corporation 

 Steiner Film, Inc. 

 AVX, Inc. 

 Custom Electronics 

Magnets 



IAP, Inc. 

Magnaquench, UG, Inc. 

 Ability Engineering Technology 

 Electron Energy Corporation 

 Bronson and Bratton, Inc. 

Carbon foam heat  Ford Scientific Research Laboratory 

sinks  DaimlerChysler 

 General Motors Corporation 

 Delphi 

 Visteon 

Fuel injectors 



Siemens, USA 

Siemens, AG 

 Navistar/International Harvester 

 Imagineering Finishing Technologies 

NOx sensors  Ford 

 Cummins Engine Company 

 Detroit Diesel 

 Honeywell 

 DuPont 

Particulate traps 



Ford-Jaguar 

GE Locomotive 

 Ahlstrom Paper 

 Tennaco Automotive 

 Arvin Meritor 

Hydrogen Compatibility of Materials 

Materials used in fuel cells or in internal combustion engines powered by hydrogen operate in a different 

environment from materials employed in gasoline or diesel engines. Engine manufacturers need to know how 

constant exposure to hydrogen affects the properties and performance of materials used for engine 

components. The friction and wear characteristics of metallic materials depend largely on surface oxide films. 

However, since a hydrogen environment is chemically reducing, the loss of the surface oxide film by wear 

will result in bare surface contact and an increase in friction and wear. 

An exploratory study began at PNNL in 2004 to 

determine the frictional behavior of metals such as those 

used in fuel injectors in the environment of a hydrogen 

engine or fuel cell. The purpose is to understand and 

quantify the mechanisms that determine the friction 

coefficient and surface properties of materials in a 100% 

hydrogen service environment by comparing materials 

as received from the manufacturer with hydrogenexposed samples. During FY 2005, PNNL and ORNL 

tested metallic injector materials used by Westport An injector material sample as-received (left) and Innovations, a maker of fuel injectors. A high-pressure after 47-h hydrogen exposure (right). Peak height 

hydrogen test vessel was designed and built and used to maximum is 4–5 μm. expose injector components and materials samples to 

hydrogen at various pressures and temperatures for 

47 hours. Following the exposure period, the materials were analyzed using electron microscopy and 

nanoindentation and nanoscratch measurements. 

3
Microstructural

Characterization

Property

Measurements

Thermodynamic

Modeling

Understand Behavior of

Existing Materials

Microstructural

Characterization

Property

Measurements

Thermodynamic

Modeling

Develop New

Compositions

Microstructural

Characterization

Property

Measurements

Thermodynamic

Modeling

Understand Behavior of

Existing Materials

Microstructural

Characterization

Property

Measurements

Thermodynamic

Modeling

Develop New

Compositions

FY 2005 Annual Report Automotive Propulsion Materials 

VALIDATIONPREDICTION

Microstructural 

Characterization 

Property 

Measurements 

Thermodynamic 

Modeling 

Understand Behavior of 

Existing Materials 

VALIDATION PREDICTION

Microstructural 

Characterization 

Property 

Measurements 

Thermodynamic 

Modeling 

Develop New 

Compositions 

PREDICTION

Overall approach for materials by design. 

The analysis revealed material surface phenomena on the metal surfaces that appear to result from the 

formation of facets composed of a molybdenum/tungsten compound. The results showed that the friction 

coefficient of the materials increases with hydrogen exposure, largely as a result of the facet formation. 

Ongoing research will focus on evaluating new coatings, alloys, and piezo barrier materials under hydrogen 

explore and analyzing sliding and impact wear. 

HCCI Materials 

Interest in HCCI combustion has grown because of its potential to increase engine combustion efficiency 

and reduce emissions. However, HCCI will subject engine components to higher temperatures and pressures. 

Operating temperatures for diesel engines will exceed 1600°F, and pressures may exceed 2000 psi, 

approximately four times the pressure in a conventional combustion engine. Such severe operating conditions 

will require much improved materials performance to take advantage of the HCCI engine concept. The APM 

Program has initiated an effort to identify materials requirements for HCCI engines in automotive and truck 

applications and develop advanced, cost-effective materials through computational design. 

The work is based on “materials by design,” a concept and collection of materials R&D techniques 

involving modeling, correlation, and materials modification. Materials by design is ideally suited to cast and 

heavily thermally processed materials such as stainless steels, nickel alloys, cast irons, alloy steels, and 

brazed wrought aluminum alloys. 

The initial task is to identify critical materials 

requirements for HCCI engines based on 

operating conditions. This task will include 

interaction with several advanced 

engine/component design companies. The 

outcome of this task will be ranking the highestpriority items for study with materials by design. 

Task 2 is to demonstrate the feasibility of 

materials by design for the highest-priority item, 

and task 3 is to use modeling and experimental 

validation to improve the materials performance. 

Discussions with automotive and truck 

companies in 2005 identified four materials 

needs to support advanced engine concepts such as HCCI: aluminum for charge air coolers, cast iron for 

exhaust manifolds, nickel alloys for exhaust valves, and alloy steels for fuel injectors. Collaborations were 

established with two companies to work together on materials needs. 

As a first step in materials development through computational design, phase equilibrium calculations 

were conducted on three published nickel-based alloy compositions. The weight percent of γ′ showed a 

qualitative agreement with published fatigue data for two of three alloys used. Ongoing work will quantify 

the correlation between fatigue properties and phase type and will validate weight percent on experimentalsize heats of selected compositions. 

Future Direction 

The APM Program will continue to work closely with FreedomCAR partners and industry to understand 

requirements related to propulsion materials. Building upon the recent advances in materials technologies, 

many of this year’s projects will be moved out of the laboratory and over to industry for testing. For example, 

ICS will work with identified strategic manufacturing partners in the automotive industry to move the 

durability and soot-holding capacity performance of the diesel particulate filter cartridge into compliance with 

the system requirements of automotive original equipment manufacturers. LLNL, Ford, and ORNL have 

formed a partnership to develop and prototype a NOx sensor and control system to control the operation of 

NOx traps and engine emissions. Other projects will continue to refine manufacturing requirements and 

necessary characteristics to meet the challenges of the FreedomCAR program. 

4
Automotive Propulsion Materials FY 2005 Annual Report 

As advanced automotive technology developments uncover new challenges, the APM Program will 

continue to provide breakthrough technology solutions through collaboration with industry, FreedomCAR 

partners, national laboratories, and small businesses. 

Project Abstracts 

The remainder of this report communicates the progress achieved during FY 2005 under the APM 

Program. It consists of nine abstracts of national laboratory projects—four that address power electronics and 

five that address combustion and emission technologies. The abstracts provide an overview of the critical 

work being conducted to improve these systems, reduce overall cost, and maintain component performance. 

In addition, they provide insight into the challenges and opportunities associated with advanced materials for 

high-efficiency automobiles. 

Rogelio Sullivan 

Team Leader, Materials Technologies 

Office of FreedomCAR and Vehicle Technologies 

Energy Efficiency and Renewable Energy 

5
FY 2005 Annual Report Automotive Propulsion Materials 

6
Automotive Propulsion Materials FY 2005 Progress Report 

2. POWER ELECTRONICS 

A. Low-Cost, High-Energy-Product Permanent Magnets 

Y. S. Cha and John R. Hull 

Energy Technology Division, Bldg. 335 

Argonne National Laboratory, Argonne, IL 60439 

(630) 252-5899; fax: (630) 252-5568; e-mail: yscha@anl.gov 

DOE Materials Technologies Team Leader: Rogelio Sullivan 

(202) 586-8042; fax: (202) 586-1600; e-mail: rogelio.sullivan@ee.doe.gov 

ORNL Technical Advisor: David Stinton 

(865) 574-4556; fax: (865) 241-0411; e-mail: stintondp@ornl.gov 

Contractor: Argonne National Laboratory, Argonne, Illinois 

Prime Contract No.: W-31-109-Eng-38 

Objective 

• Develop a low-cost process to fabricate anisotropic NdFeB permanent magnets (PMs) with an increase of up to 

25% in energy product to enable significant size and weight reductions in traction motors for hybrid vehicles. 

Approach 

• Use high fields of superconducting solenoids to improve magnetic grain alignment while pressing compacts for 

sintering, thus producing higher-performance magnets. 

• Develop an automated press system, including the superconducting magnet, for the fabrication of NdFeB PMs. 

• Conduct an economic analysis of the automated superconducting PM fabrication system and compare it with 

the conventional system. 

Accomplishments 

• Designed and fabricated a new tapered die and punch set to avoid the cracking problem during compact ejection 

from the die. 

• Fabricated near-final-shape powdered compacts under various alignment fields using the modified and the new 

die and punch sets to demonstrate that compacts can be fabricated at much faster rates, which is essential for the 

low-cost production of the permanent magnets. 

Future Direction 

• Conclude the project and prepare a final report that will include all the data and information obtained from the 

entire duration of the project. 

Introduction magnetically aligned and pressed. Large blocks can 

The strength of sintered NdFeB magnets greatly 

depends on the method by which the compact is 

be made by cold-isostatic pressing that are within 

5% of their theoretical maximum; but these must be 

sliced, diced, and ground to final shape, making the 

7 
FY 2005 Progress Report 

magnets very expensive. Magnets that are axial-diepressed and sintered to near-final shape are the least 

expensive to make, but they have magnetic 

properties farthest from their theoretical maximums. 

The current industry goal is to fabricate higherenergy-product magnets by near-net-shape 

processing to avoid expensive machining operations. 

The major objectives of this project are to increase 

the energy product of the sintered PMs by 10 to 15% 

(to within ~10% of the theoretical maximum) and to 

develop low-cost methods of production for highenergy-product, near-final-shape PMs. The higherperformance magnets will replace ones made by 

traditional powder metallurgy processing and will 

enable significant size and weight reductions in 

traction motors for hybrid vehicles. 

Approach 

Our approach is to align the NdFeB powder in a 

superconducting magnet, which can generate 

magnetic fields much higher than those generated by 

the electromagnets presently used in industry. 

Alignment of the powder in these higher magnetic 

fields improves the properties of the PMs. To 

develop a low-cost mass-production method for 

high-energy-product PMs, we plan to design, 

fabricate, and demonstrate a semi-automated axialdie-press system for making near-final-shape NdFeB 

PMs. 

Previously, a 9-T superconducting solenoid was 

procured and made operational. Production-grade 

magnet powder was obtained from Magnequench 

UG. The 3- to 5-micron single-crystal grains of 

powder were aligned and compacted at Argonne 

National Laboratory (ANL). Then the anisotropic 

compacts, with their grains mechanically locked in 

place, were returned to Magnequench UG for 

sintering, annealing, machining, and measuring of 

engineering magnetic properties. 

Previously, we demonstrated that significant 

improvement of energy product (10–15%) can be 

achieved by using higher alignment fields (>2 T).1

 It 

was also demonstrated that near-net-shape PMs 

(with a diameter-to-length ratio as low as 0.25) can 

be fabricated using the present technology. Industry 

considers an improvement in energy product of as 

little as 3–5% over current PMs to be significant. 

The progress achieved so far is based on a batch 

process at ANL. Major issues remaining for 

acceptance of the technology by industry are (1) to 

Automotive Propulsion Materials 

demonstrate that PMs can be made at a much faster 

rate than in the batch process, and (2) to demonstrate 

that the superconducting magnet and its associated 

press systems are economically feasible by 

conducting an economic analysis. 

Results 

In previous investigations, we encountered the 

problem that air is not being released fast enough 

during compact pressing, which may have caused 

the compact to crack during ejection from the die. 

To avoid this problem, the rate of pressure increase 

during compact pressing was kept quite slow. In 

order to make the production cost lower, the present 

process must be improved and the rate of pressing 

must be increased significantly. In FY 2005, we 

modified the existing 5/8-in. die and punch set to 

alleviate the trapped air problem during compact 

pressing. We worked with engineers and designers 

at Bronson and Bratton, Inc. (a powder metallurgy 

tooling company located in a suburb of Chicago) on 

the design of the die and punch system. To allow air 

to escape more easily during compact pressing, it 

was decided to cut six flats (0.192 in. wide and 60°

apart) along the axial direction of the punch and a 

0.20-in.-wide circular groove near the face of the 

punch. A contract was issued to Bronson and 

Bratton to modify the existing 5/8-in. die and punch 

system. A photograph of the finished punches is 

shown in Figure 1. This design will reduce the 

resistance to air flow and still maintain relatively 

tight clearance between the die and punch during 

compact pressing. After the punches were delivered, 

we fabricated 10 compacts using the new punches, 

all at a magnetic field of 2 Tesla, to determine if 

there is any improvement in processing the 

compacts. We observed that the pressurization rate 

of the compact can be increased significantly over 

that of previous compacts made by using the original 

punches. We also noticed that pressure fluctuations 

were reduced during the early stage of the pressing. 

These observations clearly indicate qualitatively that 

air was able to escape faster and easier from the die 

because the resistance to air flow was reduced. 

Another indication that the modified die and punch 

set reduces hydraulic resistance came during powder 

filling of the die under gravity. After the die was 

filled with an appropriate amount of powder, it was 

observed that the top punch fell to its final position 

8 
Automotive Propulsion Materials FY 2005 Progress Report 

Figure 1. Photograph of the punches modified to 

alleviate the trapped air problem. 

in about 15 seconds, compared with 3 minutes when 

the old die and punch set was used. 

In the past, powdered compacts frequently 

cracked during ejection from the die. To improve the 

success rate of compact ejection, a new die and 

punch set was designed in collaboration with 

Bronson and Bratton. The die is tapered slightly as 

shown in Figure 2. The thickness of the compact is 

0.235 in. (5.969 mm), and the diameter changes 

from 0.6250 to 0.6293 in. (15.875 to 15.984 mm) 

over the thickness of the compact. These dimensions 

are based on previous experience that the average 

diameter of the compact increased from 0.625 to 

0.6290 in. (15.875 to 15.977 mm) during ejection 

from the die. The slightly tapered design is supposed 

to reduce the friction during compact ejection, which 

may alleviate the cracking problem encountered 

previously. Following the completion of the design, 

a purchase order was issued to fabricate the tapered 

die and punch set. We received the new die and 

punch set at the end of March of 2005. We restarted 

the superconducting magnet and fabricated about a 

dozen compacts under different magnetic fields. We 

had 100% success, and not a single compact cracked 

during and after ejection from the die. The results 

are very encouraging. In addition to alleviating the 

cracking problem using this tapered die and punch 

set, we were able to further increase the rate of 

pressurization during compact pressing without 

causing cracks in the ejected compact. 

Last year, we contracted with Data Decisions to 

conduct an economic study of the superconducting 

PM manufacturing system, which was recommended 

after the 2003 DOE review meeting. The main 

objective is to compare the cost of manufacturing 

Figure 2. Schematic diagram and dimensions of the 

tapered die. 

PMs using the superconducting technology and the 

cost with conventional technology using 

electromagnets. A preliminary report was received. 

Review comments were received from DOE, ANL, 

and Oak Ridge National Laboratory. These 

comments were transmitted to Data Decisions and a 

revised report was received. A major conclusion of 

the economic study is that the capital cost of the 

superconducting PM fabricating system is about the 

same as for a conventional system, while the energy 

product of magnets products by the superconducting 

system is approximately 15% higher than in magnets 

produced by a conventional system. The report is 

being finalized and will be issued in the near future. 

Conclusions 

Previously, we demonstrated that significant 

improvement of energy product (10–15%) can be 

achieved by using higher alignment fields (>2 T). 

Industry considers an improvement of 3–5% in the 

energy product of current PMs to be significant. It 

was also demonstrated that near-final-shape PMs 

(with a diameter-to-length ratio as low as to 0.25) 

can be fabricated with this new technology. Major 

issues remaining for acceptance of the technology 

by industry are (1) to demonstrate that PMs can be 

made at a much faster rate than in the batch process 

and (2) to demonstrate that the superconducting 

PM fabrication technology can be cost-effective by 

conducting an economic analysis. In FY 2005, we 

modified the existing 5/8-in. die and punch set to 

alleviate the trapped air problem during compact 

pressing. We also designed and fabricated (in 

9
FY 2005 Progress Report Automotive Propulsion Materials 

collaboration with Bronson and Bratton) a tapered 

die and punch set to avoid compact cracking during 

ejection from the die. We fabricated a total of 

24 compacts under different alignment fields using 

the modified and the new tapered die and punch sets. 

The results are very encouraging. By using the 

tapered die and punch set, we were able to eliminate 

the compact cracking problem during ejection from 

the die. Furthermore, we were able to increase 

significantly the rate of pressurization during 

compact pressing. Both of these results demonstrate 

that the PMs can be fabricated at much faster rate 

than with the batch process employed before. This is 

essential for the low-cost production of PMs using 

the superconducting technology. 

In FY 2005, we reviewed and revised the report 

on the economic analysis of the superconducting 

PM manufacturing technology. It was concluded 

that the capital cost of the superconducting 

PM fabricating system is about the same as for a 

conventional system, while the energy product 

obtained using the former is approximately 15% 

higher than that obtained with the latter. 

In FY 2006, we plan to have an orderly closeout of the project by preparing a final technical 

report, which will include all the results and 

accomplishments from the inception of the project. 

References 

1. 2003 Annual Progress Report, Automotive 

Propulsion Materials, U.S. Department of 

Energy, Office of Energy Efficiency and 

Renewable Energy, Office of FreedomCar and 

Vehicle Technologies, Washington, D.C. 

Publications/Presentations 

Y. S. Cha and J. R. Hull, “Low-Cost HighEnergy-Product Permanent Magnets,” presented at 

the Annual Review of Advanced Power Electronics 

and Electrical Machines, DOE FreedomCAR and 

Vehicle Technologies Program, May 3–5, 2005, Oak 

Ridge, TN. 

R. E. Wolf, An Economic Study of the 

Manufacture of High Energy Permanent Magnets for 

Traction Motors in Hybrid Electric Vehicles, 

submitted by Data Decisions to Argonne National 

Laboratory, revised April 2005. 

10 
Automotive Propulsion Materials FY 2005 Progress Report 

B. Characterization of Rare Earth Permanent Magnets for Automotive 

Applications 

Edgar Lara-Curzio, Andrew Payzant, and Chris Cofer 

Building 4515, MS-6069 

Oak Ridge National Laboratory 

(865) 574-1749; fax: (865) 574-6098; e-mail: laracurzioe@ornl.gov 

DOE Materials Technologies Team Leader: Rogelio Sullivan 

 (202) 586-3976; fax: (202) 586-9811; e-mail: rogelio.sullivan@ee.doe.gov 

ORNL Technical Advisor: David Stinton 

(865) 574-4556; fax: (865) 241-0411; e-mail: stintondp@ornl.gov 

Contractor: Oak Ridge National Laboratory 

Prime Contract No.: DE-AC05-00OR22725 

Objective 

• Determine the effect of thermal cycling on the magnetic and mechanical properties of sintered and bonded rare 

earth permanent magnets. 

Approach 

• Develop a test facility with an environmental chamber capable of cycling temperature between –40 and 300°C. 

• Develop instrumentation to determine in real time the magnetic strength of test specimens as a function of 

temperature and number of thermal cycles. 

• Evaluate the residual mechanical properties of sintered and bonded rare earth permanent magnets after thermal 

cycling. 

Accomplishments 

• Developed a test facility capable of cycling temperature between –40 and 300°C. The test facility is 

instrumented to determine, in real time, the magnetic strength of sintered and bonded rare earth permanent 

magnets. 

• Determined that the magnetic strengths of bonded and sintered permanent NdFeB magnets decrease linearly 

with temperature and, at a given temperature, decrease exponentially with the number of thermal cycles. 

Future Direction 

• The project was completed at the end of FY 2005. 

Introduction 

Achieving FreedomCAR and Fuel Partnership 

goals will require the development of new 

technologies for electric machinery. The new 

technologies must be compatible with high-volume 

manufacturing; must ensure high reliability, 

efficiency, and ruggedness; and must simultaneously 

reduce cost, weight, and volume. Key components 

for hybrid vehicles include motors, sensors, and 

control systems.1 

While permanent magnet motors have the 

highest power density, they don’t have a sufficient 

constant power speed range; and their cost is too 

high because of the costs of magnet materials, 

11 
FY 2005 Progress Report 

magnet manufacturing, and rotor fabrication. 

Sintered and polymer-bonded particulate magnets 

are being developed with the objectives of 

increasing their useful operating temperature to 

150°C and decreasing the cost to about 25% of the 

current price of approximately $90/kg. Furthermore, 

these magnets should be rugged and reliable enough 

to operate in harsh environments—including 

extreme temperatures, humidity, and thermal 

cycling—for 150,000 miles or 15 years. The 

objective of this project is to determine the 

resistance of sintered and bonded NeFeB permanent 

magnets to thermal cycling between –40 and 

150°C.1 

Approach 

In FY 2004, a test facility was designed and 

constructed to evaluate the resistance of sintered and 

bonded rare earth permanent magnets to thermal 

cycling. The test facility consists of a chamber 

capable of cycling temperature between –40 and 

300°C. Temperatures below ambient temperature are 

achieved by dispersing liquid nitrogen into the 

chamber using compressed air and a solenoid valve, 

while heating is achieved using compressed air and a 

set of cartridge heaters. The interior of the chamber, 

which has dimensions of 61 × 30 × 30 cm, is lined 

with one layer of insulating material. Temperature 

measurements are obtained with type K 

thermocouples. By placing thermocouples at various 

locations it was demonstrated that the temperature 

was uniform within 3°C anywhere within the 

chamber. 

A computer-based system was assembled for 

controlling the operation of the test facility and for 

data acquisition. The system consists of a personal 

computer, a high-speed A/D data acquisition card, a 

customized computer application using the 

commercially available package LabView, and a 

digital temperature controller. Figure 1 depicts the 

experimental setup developed for this project. 

Magnetic Properties 

Changes in magnetic properties were determined 

as a function of temperature and number of thermal 

cycles by measuring the voltage induced when the 

magnets under evaluation move through a coil at a 

given temperature and after a predetermined number 

of thermal cycles. 

Automotive Propulsion Materials 

Figure 1. Experimental setup for the project. 

The permanent magnets under evaluation, which 

were shaped in the form of prismatic beams, were 

bonded at various locations along 6.5-mm-diameter 

stainless steel rods. A set of 16 rods was attached to 

a frame that was coupled to a pneumatic actuator. 

Figure 2 depicts the array of 16 stainless steel rods 

and their position within the chamber. The 

reciprocating motion of the pneumatic actuator 

resulted in the motion of the permanent magnets 

through coils, which are placed around plastic tubes 

that are concentric to the rods (Figure 3). The 

motion of the magnets through the coils induces a 

voltage in the coils. According to Faraday’s law,2 

the voltage induced in the coil will be proportional 

to the change in the magnetic flux through the coil 

( Φ ), according to 

dΦ V =− , (1) dt 

where the magnetic flux through the coil is given by 

Φ(t) = B(t) N A . (2) 

B(t) is the magnetic field of the magnet, N is the 

number of turns in the coil, and A is the crosssectional area of the coil. 

The voltage induced across the terminals of the 

coil is recorded as a function of temperature and as a 

function of the number of thermal cycles. Figure 4 

shows a voltage trace resulting from the 

displacement of a bonded permanent NdFeB magnet 

through one of the coils. 

12 
Automotive Propulsion Materials FY 2005 Progress Report 

Figure 2. Array of 16 stainless steel rods within the 

chamber. 

Figure 3. Stainless steel rods, with magnets attached, 

move through coils placed around plastic tubes that 

surround the rods. 

Figure 4. Voltage trace resulting from the movement of a 

magnet through a coil 

Materials 

Bonded and sintered permanent NdFeB magnets 

were used in this investigation. Test specimens 

shaped in the form of prismatic beams 2.0 × 1.5 × 

26.0 mm were obtained from larger pieces by 

diamond grinding. In the case of bonded magnets, 

they were obtained from cylindrically shaped test 

specimens that had been processed by dynamic 

magnetic compaction. To reduce stress 

concentrations for subsequent mechanical testing, 

the test specimens were chamfered at the corners. 

Figure 5 is a picture of bonded NdFeB test 

specimens along one of the cylindrical magnets 

processed by dynamic magnetic compaction. 

Figure 5. Test specimens along a cylindrical magnet 

processed by dynamic magnetic compaction. 

Experimental 

Test specimens were subjected to the 

temperature schedule shown in Figure 6. The 

temperature of the test chamber was increased/ 

decreased at a constant rate of 10°C/min. After 

reaching a set point (– 40°, 0°, 50°, 100° and 

150°C), the chamber was allowed to reach thermal 

equilibrium in 15 minutes. Then the pneumatic 

actuator was operated and the voltages induced by 

the motion of the test specimens through their 

corresponding coil were recorded. After a prescribed 

number of thermal cycles, a set of test specimens 

was removed from the chamber and their flexural 

strength was determined at ambient conditions. 

Results 

Figure 7 shows the magnitude of the voltage 

recorded for a sintered NdFeB permanent magnet as 

a function of temperature and number of thermal 

cycles. It was found that the magnitude of the 

voltage decreased both with temperature and with 

number of thermal cycles. Figure 8 shows the 

temperature dependence of the voltage recorded 

after different numbers of cycles. It was found that 

the magnitude of the voltage decreased linearly with 

temperature, whereas for a given temperature, the 

13 
FY 2005 Progress Report Automotive Propulsion Materials 

Figure 6. Temperature schedule to which magnet 

specimens were subjected. 

Figure 7. Voltage recorded for sintered permanent 

magnet as a function of temperature and number of 

thermal cycles. 

voltage decreased with number of thermal cycles 

according to the following equation: 

V =Voe−kN , (3) 

where Vo and k are constants and N is the number of 

thermal cycles. Because the magnitude of the 

voltage is directly proportional to the strength of the 

magnetic field induced by the magnet, then it can be 

concluded that the strength of the magnetic field of 

Figure 8. Temperature dependence of voltage recorded 

after various numbers of cycles. 

NdFeB decreased with temperature and with the 

number of thermal cycles between –40° and 150°C. 

The flexural strength of bonded and sintered 

NdFeB permanent magnets was determined in 

4-point bending according to ASTM standard test 

method C1161. The flexural strength was calculated 

according to the following relationship: 

σ flexural = 4

3

b

P

d

L 

2 , (4) 

where P is the peal load, L is the support span 

(20.52 mm), and b and d are the width and 

thickness, respectively, of the test specimen. The 

flexural strength values were corrected for the 

chamfered corners. 

Figure 9 shows a plot with the results from the 

flexural evaluation of bonded and sintered NdFeB 

permanent magnets. It was found that sintered 

NdFeB permanent magnets were stronger than 

bonded NdFeB permanent magnets by almost one 

order of magnitude and that their flexural strength 

decreased with the number of thermal cycles 

according to the following equation: 

σ=σ oN −a , (5) 

where σo and a are constants. It was found that after 

250 cycles, a=0.02 for sintered NdFeB magnets 

while a=0.03 for bonded NdFeB magnets. 

14 
Automotive Propulsion Materials FY 2005 Progress Report 

Figure 9. Results of flexural evaluation of bonded and 

sintered permanent magnets. 

The fracture surfaces of a selected number of 

test specimens were examined by scanning electron 

microscopy to identify strength-limiting flaws and 

microstructural changes, if any, that might have 

been induced by thermal cycling. Figure 10 shows a 

scanning electron micrograph of the fracture surface 

of a sintered magnet after 100 thermal cycles. It was 

found that, in most cases, failure originated at 

locations of non-uniform microstructure. 

Figure 10. Scanning electron micrograph of the fracture 

surface of a sintered magnet after 100 thermal cycles. 

Summary 

A test facility was designed and fabricated to 

evaluate the effect of thermal cycling on the 

magnetic and mechanical properties of sintered and 

bonded PMs. The test facility is capable of operating 

between –40 and 300°C and of providing real-time 

measurement of the magnetic strength of test 

specimens. It was found that the magnetic strength 

of bonded and sintered permanent NdFeB decreases 

linearly with temperature and that at a given 

temperature, it decreases exponentially with the 

number of thermal cycles. It was also found that 

sintered NdFeB magnets were 10 times stronger 

than bonded NdFeB magnets and that the flexural 

strength of both decreased with the number of 

thermal cycles. 

References 

1. 2002 Annual Progress Report, Automotive 

Propulsion Materials, U.S. Department of 

Energy, Office of Energy Efficiency and 

Renewable Energy, Office of FreedomCar and 

Vehicle Technologies, Washington, D.C. 

2. J.D. Jackson, Classical Electrodynamics, 

John Wiley and Sons, New York, 1967. 

15 
FY 2005 Progress Report Automotive Propulsion Materials 

16 

C. Carbon Foam for Cooling Power Electronics 

Nidia C. Gallego 

Oak Ridge National Laboratory 

P.O. Box 2008, MS 6087, Bldg. 4508 

Oak Ridge, TN 37831-6087 

(865) 241-9459; fax: (865) 576-8424; e-mail: gallegonc@ornl.gov 

Albert Shih, Steve White 

S. M. Wu Manufacturing Research Center 

University of Michigan 

Anthony G. Straatman 

Department of Mechanical and Materials Engineering 

University of Western Ontario 

London, Canada 

Brian E. Thompson and Qijun Yu 

Foam Application Technologies Inc. 

Mayaguez, Puerto Rico 

DOE Materials Technologies Team Leader: Rogelio Sullivan 

(202) 586-8042; fax: (202) 586-1600; e-mail: rogelio.sullivan@ee.doe.gov 

ORNL Technical Advisor: David P. Stinton 

(865) 574-4556; fax: (865) 241-0411; e-mail: stintondp@ornl.gov 

Contractor: Oak Ridge National Laboratory, Oak Ridge, Tennessee 

Prime Contract No.: DE-AC05-00OR22725 

Objectives 

• Collaborate with an automotive partner to develop a carbon foam heat exchanger and heat sink designs that 

dissipate more than 30 W/cm2

 using standard cooling fluids. 

• Develop and demonstrate designs for reducing weight and enhancing heat transfer in power electronic thermal 

management systems using high-thermal-conductivity carbon foam. 

• Determine the foam structure or morphology that results in optimum heat transfer for various thermal 

management applications. 

Approach 

• Study fundamental mechanisms of heat transfer in carbon foam and develop an engineering model that allows 

comparison of conventional and carbon foam heat exchangers. 

• Redesign and build a test apparatus for measuring the heat transfer coefficients and pressure drops of heat sinks 

made of carbon foam. 

• Design and build a thermosyphon test rig to study the performance of carbon foams in this system. 
Automotive Propulsion Materials FY 2005 Progress Report 

17 

Accomplishments 

• Formed a team consisting of Oak Ridge National Laboratory (ORNL), the University of Western Ontario, and 

Ford Motor Company to develop a test setup for evaluating the performance of carbon foam heat sinks. 

• Produced foams with a variety of pore structures; measured the heat transfer and pressure drop obtained by 

passing water through the foam samples. 

• Demonstrated the capability of a graphite foam–based thermosyphon to cool 65 W/cm2

 at a temperature of 

56°C. 

• Developed an engineering model for use in the development of electronic heat sinks. 

Future Direction 

• Modify designs of foam-based heat exchangers based on new foam properties. 

• Determine whether the foam’s increased surface area or internal volume assists the most in boiling heat 

transfer. 

• Develop a design for a carbon foam-based heat sink for use in automotive power electronics. 

Introduction

Porous carbon foam developed at ORNL1,2 is 

being investigated as a material to improve both 

single-phase and multiphase heat transfer. Carbon 

foam has a high effective conductivity (40–

160 W/m K)2

 because of the high material 

conductivity of the graphitized carbon material 

(800–1900 W/m K). In comparison, similar porous 

aluminum foams have effective conductivities of 

2–26 W/m K, resulting from material conductivities 

of only 140–237 W/m K (for various aluminum 

alloys).3

 The high effective conductivity of the 

porous carbon foam combined with the open, 

interconnected pore structure is conducive to high 

internal heat transfer and the potential for high 

convective heat transfer enhancements. 

This year’s work focused on the characterization 

of the hydrodynamic and thermodynamic 

performance of the foam and how it impacts the 

development of modern heat exchangers and 

electronic heat sinks. A combination of experiments 

and modeling is being conducted to explore the use 

of porous carbon foam in the removal of heat from 

power electronics. 

Additionally, a thermosyphon test rig was 

designed and built for the evaluation of the 

performance of carbon foam in these types of 

cooling systems. 

Experimental Study

Experiments are being conducted on a smallscale test rig to measure the heat transfer and 

pressure drop across blocks of porous carbon foam. 

The test setup shown in Figure 1 consists of a 

channel with a fluid inlet and outlet, a heating 

element, and instrumentation to measure the flow 

rate, the heat input, and the fluid pressure drop 

across the foam block (from position 1 to 2). Porous 

carbon foam blocks of different porosities and pore 

diameters were subjected to a range of flow rates 

and power densities to quantify variations in 

pressure drop and thermal effectiveness in the foam 

structure (characterized by porosity, ε, and void 

diameter, Dp) and the flow Reynolds number 

(defined as Re= ρVpbDep/μ, where ρ is the density of 

the fluid, Vpb is the channel bulk velocity, Dep is the 

equivalent solid particle diameter of the foam and μ

is the dynamic viscosity of the fluid). 

For all specimens tested, the fluid pressure-drop 

was observed to vary linearly with Re for low 

Reynolds numbers, followed by a parabolic 

variation for higher Reynolds numbers. Figure 2 

2 1

out in 

Q 

Figure 1. Schematic of experimental setup showing the 

position of the carbon foam, the fluid inlet (in) and outlet 

(out), and the heat input (Q). 
FY 2005 Progress Report Automotive Propulsion Materials 

18 

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

5.0

0 10 20 30 40

Reynolds Number

Pressure Drop [psi]

Figure 2. Variation of pressure-drop with Reynolds 

number for a specimen of porous carbon foam of porosity 

0.88 and pore diameter 400 μm. 

shows the pressure drop as a function of Reynolds 

number for a foam specimen of porosity 0.88 and 

pore diameter 400 μm. The pressure data are used to 

obtain permeability and form drag coefficients based 

on the classical Darcy-Forchheimer law for porous 

media. The permeability of the foam is seen to be a 

strong function of both porosity and pore diameter, 

as might be expected, but it is also seen to be 

dependent on the structure of the cell windows 

connecting the cells. The permeability is 

considerably lower than the ideal permeability 

predicted by the unit-cube model of Yu et al.4

 and 

the permeability of aluminum foams. 

The thermal performance of the foam specimens 

was determined based on the temperature rise of the 

fluid across the specimen and by a thermal model 

that considers the block to be an extended surface 

heated from one side. Figure 3 shows variations of 

the inlet and outlet water temperatures over a range 

of power densities for a Reynolds number Re= 13. 

The thermal performance is observed to be 

considerably better than that of an equivalent 

aluminum (or other metal foam) block owing to the 

higher effective conductivity and the increased 

surface-area-to-volume ratio of the porous carbon 

foam. 

Modeling Study

For the modeling work, the cylindrical cavity-style 

heat sink shown in Figure 4 was considered. The 

heat sink is attached to a metal substrate, which is 

then pressed firmly against the electronic 

component. The resistant analog for the heat sink 

0

15

30

45

0 5 10 15 20

Power Density [W/cm2]

Temperature [oC]

Inlet T

Outlet T

Figure 3. Variation of temperature rise (outlet – inlet) 

with power density at a Reynolds number of Re= 13 

for a specimen of porous carbon foam of porosity 0.88 

and pore diameter 400 μm. 

Figure 4. CAD image of a cylindrical-shaped electronic 

heat sink. 

shown in Figure 4 is given in Figure 5. Expressions 

for the resistances in the thermal circuit were 

derived using the unit-cube model of Yu et al.4

 and 

established expressions for the Nusselt number 

modified to be suitable for porous carbon foam. 

Thermal Resistances 

R1: Bond contact thermal resistance between the 

integrated heat spreader (IHS) of the processor and 

the heat spreader (HS) of the heat sink 

R2: Conduction thermal resistance through the HS 

of the heat sink 

R3: Bond contact resistance between the HS and the 

carbon fin of the heat sink 
Automotive Propulsion Materials FY 2005 Progress Report 

19 

2 3 45

6

T T

T

R2 R3 R4 R5

R6

R2: Conduction resistance through the HS

R3: Contact between the HS and the CF fin

R4: Fouling in the CF pore channel

R6: Fouling on the bare surface of the HS

R5: Convection in the CF pore channel

R7: Convection of the bare surface of the HS

R1

1

R1: Contact resistance between IHS and HS

R7

7 IHS: Integrated heat spreader of the processor

HS: Heat spreader of the heatsink

CF: Carbon foam

T : Case temperature of the IHS

T : Air temperture at the inlet of the heatsink

A

C

A

C

C

Figure 5. Electrical analog of thermal circuit for 

cylindrical heat sink.

R4: Fouling resistance in the pore channel of the 

carbon foam 

R5: Convection thermal resistance in the pore 

channel of the carbon foam fin 

R6: Fouling on the bare surface of the HS at the 

carbon foam fin root 

R7: Convection thermal resistance on the bare 

surface of the HS at the carbon foam fin root 

Air Pressure Loss 

e

2

a pba

f

pba a a V L

K

c

V

K

P ⎟

⎟

⎠

⎞

⎜

⎜

⎝

⎛ = + ρ μ Δ , (1) 

where μa and ρa are the air viscosity and density 

evaluated at the air average temperature. cf is the 

Forchheimer coefficient of the carbon foam. Le is the 

equivalent length of the pore channel, and is 

determined by 

e TF 2

1 2 L ⎟

⎟

⎠

⎞

⎜

⎜

⎝

⎛ + = . (2) 

Sample Design of Carbon Foam Heat Sink with 

Aluminum Spreader 

Carbon foam: 

• ORNL 219 carbon foam with a permeability of 

8.3781E-10 m2 (equivalent of fpb=0.1) and a 

Forchheimer coefficient of 0.0982 

• Pore diameter D: 500 um 

• Porosity ε: 90% 

• Thermal conductivity of the solid phase ks: 

1500 W/m.K 

• Density of the solid phase ρs: 2.15 g/cm3 

Heat sink configuration: 

• Inside diameter of the carbon foam fin Di: 

50.8 mm (2 in.) 

• Outside diameter of the carbon foam fin 

(average) Do: 76.85 mm (3.0256 in.); 

Do=(a+b)/2 

• Long axis a: 83.2 mm (3.2756 in.) 

• Short axis b: 70.5 mm (2.7756 in.) 

• Thickness of the heat spreader tHS: 6.35 mm 

(0.25 in.) 

• Thermal conductivity of the heat spreader kHS: 

218 W/m.K 

• Density of the heat spreader ρHS: 2.15 g/cm3

• Thermal conductivity of the bonding material k1

and k3: 48 W/m.K 

• Thickness of the bonding layer t1 and t3: 

0.3969 mm (0.015625 in.) 

Table 1 compares the size and volume of the 

heat sink made from a carbon foam fin attached to 

the aluminum heat spreader (Figure 4) with an 

equivalent-performance aluminum fin heat sink. 

Thermosyphon System

A thermosyphon test rig was designed and built 

for the evaluation of carbon foams in this type of 

cooling system. A thermosyphon uses the latent heat 

of vaporization of a low-boiling-point fluid to 

dissipate heat. The heat is transferred from the 

source to the graphite foam, which is submerged in 

the fluid. The foam increases the surface area and 

nucleation sites for boiling to occur. The vapor 

formed rises into the condenser section of the system 

where it is condensed and drips back down to the 

evaporator section. This forms a closed-loop system 

that allows the heat to be transferred from a small 

source to a larger area where the condensing takes 

place. 

 In previous work, Coursey et al.5

 used a 

thermosyphon with carbon foam to study the effects 

of fluid level and type, and chamber pressure. Fluid 

level and type (FC-72 compared with FC-87) were 

both found to be insignificant as long as the fluid 

covered the entire piece of foam. Lower saturation 

pressures provided higher heat fluxes at lower wall 

temperatures. They cooled 50 W/cm2

 at a wall 

temperature of 85°C. Park, Kang, and Kim6

 also 

investigated fluid levels or charge ratios and 

determined them not to be significant. The 

limitations in heat transport were different for the 
FY 2005 Progress Report Automotive Propulsion Materials 

20 

Table 1. Comparisons between the size and weight of the sample carbon foam heat 

sink and an aluminum-finned heat sink with equivalent performance 

 Aluminum fin heat sink Carbon foam fin heat sink Reduction 

Size: cm3 108.63 128.94 38.20% 

Weight: g 150.00 92.05 38.63% 

different charge ratios. For low ratios, dry-out 

occurred, causing the temperature in the evaporator 

to increase from the bottom; while for higher charge 

ratios, flooding limitation caused the evaporator 

temperature to increase from the top. Klett and 

Trammell7

 constructed a thermosyphon to cool a 

silicon CMOS chip using carbon foam as the heat 

spreader and FC-72 as the working fluid. They 

report a maximum heat flux of 118 W/cm2 at a 

superheat of 24°C for a block of foam, while a 

slotted piece of foam reached 149 W/cm2

 at a 

superheat of only 11°C. 

A photo and a schematic of the thermosyphon 

system built for the current project are shown in 

Figures 6 and 7, respectively. A generic heat source 

was created by using a cartridge heater embedded in 

a copper rod that was insulated in a low-conductivity 

PTFE housing. The heat is transferred axially along 

the copper rod and monitored by measuring the 

temperature of the rod at three different locations. 

This allows for the heat flux to be calculated and the 

surface temperature of the rod to be extrapolated. 

The graphite foam is attached to the copper by first 

coating the bottom surface of the foam with copper 

and then soldering the two surfaces together. 

The fluid used was HFE-7000, which is a 3m 

Novec Engineered Fluid that has a boiling point of 

34°C. The fluid submerges the foam in a 5.08-cmdiameter and 5.08-cm-tall cylindrical Plexiglas 

housing. The vapor rises into a water-circulating 

copper coil condenser. The condenser flowed 21.5°C 

tap water at a rate of 7.57 L/h. 

The thermosyphon was first tested without any 

foam attached to the copper. To show the 

temperatures reaching steady state, the system was 

degassed and then allowed to run at a setting of 

55 V. The resulting temperature distribution over 

time is shown in Figure 8 for the three 

thermocouples located along the copper rod. Also 

the corresponding calculated heat flux is shown in 

Figure 9 as a function of time corresponding to the 

temperature difference between the middle and low 

thermocouples (q lm), the middle and high 

thermocouples (q mh), the low and high 

thermocouples (q lh), and the heat flux 

Figure 6. Picture of thermophyson test 

rig. 

corresponding to the input voltage (q v). Both of the 

temperatures and heat fluxes reach a steady state 

setting in roughly 20 minutes from the start of 

recording. Typically the system takes a half hour to 

an hour to reach steady state, depending on the 

power increase. Only about 50% of the heat input 

into the system travels along the copper rod; the rest 

goes into heating the PTFE insulator. 

The system was then run with and without using 

the degassing process, to show its importance. First 

there was a significant pressure buildup when no 

degassing occurred, which caused a loud hiss from 

the vapor escaping when the valve was opened. A 

properly degassed system exhibits lower wall 

temperatures at the same power input, as well as an 

increase in the critical heat flux, the transition from 

nucleate to film boiling. 

The thermosyphon was tested with the graphite 

foam soldered to copper. The sample was 13.4 mm 

in diameter and 6.5 mm tall. The system was 

degassed and a sweep of input voltages was 

performed. The resulted boiling curve is shown in 

Figure 10. The heat flux was calculated using the 

measured temperature gradient, and the wall 
Automotive Propulsion Materials FY 2005 Progress Report 

21 

Figure 7. Schematic of thermophyson test rig. 

0

10

20

30

40

50

60

70

80

0 20 40 60

Time (min)

Temperature (oC)

Low Mid High

Figure 8. Temperature at three locations along 

the copper rod versus time for a voltage input of 

55 V with bare copper rod exposed. 

temperature was extrapolated using the heat flux and 

the temperature of the top thermocouple on the 

copper rod. The wall temperature represents the 

temperature of the copper rod just before the solder 

and does not account for variations in temperature 

across the solder. The maximum heat flux reached 

0

5

10

15

20

25

0 20 40 60

Time (min)

Heat Flux (W/cm2

)

q-lm q-mh q-lh q-v

Figure 9. Heat input versus time for a voltage 

input of 55 V with bare copper exposed.

0

10

20

30

40

50

60

70

0 20 40 60 80

Wall Temperature (o

C)

Heat Flux (W/cm2

)

Figure 10. Boiling curve for foam sample of 13.4 mm 

diameter and 6.5 mm height..

for this sample was 61 W/cm2

 at a wall temperature 

of 56°C. 

Next, the influence of foam dimensions, i.e. 

diameter and height, as well as the foaming pressure 

of the foam, will be investigated to optimize the 

parameters of the graphite foam used in the system. 

Summary

Work in FY 2005 focused on characterizing the 

hydrodynamic and thermodynamic performance of 

carbon foam and its impact on the development of 

heat exchangers and electronic heat sinks. 

Experiments and simulations were conducted to 

explore the use of carbon foam to remove heat from 

power electronics, and a thermosyphon test rig was 

designed and built to evaluate its thermal 

performance. 

A small-scale test rig measured heat transfer and 

variations in pressure drop across blocks of carbon 

foam of different porosities and pore diameters. For 

all specimens tested, the fluid pressure-drop 
FY 2005 Progress Report Automotive Propulsion Materials 

22 

variation was linear with Reynolds number for low 

Reynolds numbers and parabolic for higher 

numbers. The thermal performance of carbon foam 

was observed to be considerably better than that of 

an equivalent aluminum (or other metal foam) block. 

The modeling study indicated that a carbon foam 

heat sink could be more than 38% smaller in size 

and weight than an aluminum finned heat sink of 

equivalent performance. The model also indicated 

that more porous carbon foams would be required to 

optimize the design of novel heat exchangers. 

References

1. W.J. Klett, R. Hardy, E. Romine, C. Walls, 

T. Burchell, “High-Thermal-Conductivity, 

Mesophase-Pitch-Derived Carbon Foam: Effect 

of Precursor on Structure and Properties,” 

Carbon 38, 953–973 (2000). 

2. N.C. Gallego and W.J. Klett, “Carbon Foams for 

Thermal Management,” Carbon 41, 1461–1466 

(2003). 

3. W.J. Paek, H.B. Kang, Y.S. Kim, and 

M.J. Hyum, “Effective Thermal Conductivity 

and Permeability of Aluminum Foam 

Materials,” Int. J. of Thermophysics, 21(2), 

453–464 (2000). 

4. Q. Yu, B.E. Thompson, and A.G. Straatman, 

“A Unit-Cube-Based Model for Heat Transfer 

and Pressure Drop in Porous Carbon Foam,” 

submitted for publication to ASME J. Heat 

Transfer, 2004. 

5. J.S. Coursey, H. Roh, K. Jungho, and 

P.J. Boudreaux, “Graphite Foam Thermosyphon 

Evaporator Performance Parametric 

Investigation of the Effects of Working Fluid, 

Liquid Level and Chamber Pressure,” pp. 1–6 in 

Proceedings of IMECE200, November 2002. 

6. Y.J. Park, H.K. Kang, and C.J. Kim, “Heat 

Transfer Characteristics of a Two-Phase Closed 

Thermosyphon to the Fill Charge Ratio,” 

International Journal of Heat and Mass 

Transfer 45, 4655–4661 (2002). 

7. J.W. Klett and M. Trammell, “Parametric 

Investigation of a Graphite Foam Evaporator in 

a Thermosyphon with Fluorinert and a Silicon 

CMOS Chip,” IEEE Transactions on Device 

and Materials Reliability 4(3), 626–637 

(September 2004). 

Publications/Presentations

A.G. Straatman, N.C. Gallego, B.E. Thompson, 

H. Hangan, “Thermal Characterization of Porous 

Carbon Foam: Convection in Parallel Flow,” 

International Journal of Heat and Mass Transfer, in 

press. 

S.B. White, N.C. Gallego, D.D. Johnson; 

K.P. Pipe, A.J. Shih, and E. Jih, “Graphite Foam for 

Cooling of Automotive Power Electronics,” 

pp. 61–65 in IEEE Workshop on Power Electronics 

in Transportation, 8th IEEE Workshop on Power 

Electronics in Transportation, October 2004. 
Automotive Propulsion Materials FY 2005 Progress Report 

D. Mechanical Characterization of Electronic Materials and Electronic Devices 

A.A. Wereszczak, T.P. Kirkland, and H.-T. Lin 

Ceramic Science and Technology Group 

Oak Ridge National Laboratory 

P.O. Box 2008, MS 6068, Bldg. 4515 

Oak Ridge, TN 37831-6068 

(865) 576-1169; fax: (865) 574-6098; e-mail: wereszczakaa@ornl.gov 

DOE Materials Technologies Team Leader: Rogelio Sullivan 

(202) 586-8042; fax: (202) 586-1600; e-mail: rogelio.sullivan@ee.doe.gov 

ORNL Technical Advisor: David Stinton 

(865) 574-4556; fax: (865) 241-0411; e-mail: stintondp@ornl.gov 

Contractor: Oak Ridge National Laboratory, Oak Ridge, Tennessee 

Prime Contract No.: DE-AC05-00OR22725 

Objectives 

• Mechanically characterize hydroxylated polystyrene (PVOH) dielectric films being developed by Sandia 

National Laboratories (SNL) for fabrication into higher-temperature, more compact dc bus capacitors. 

• Quantify the mechanical performance of FY 2004 down-selected PVOH films as a function of temperature and 

link performances to allowable manufacturing and service conditions. 

Approach 

• Conduct tensile testing on SNL-supplied PVOH films and measure their strain-to-failure as a function of 

temperature. 

• Using strain-to-failure, predict the minimum allowable radius of curvature that each film can withstand during 

processing into dc bus capacitors without failure. 

Accomplishments 

• Developed a bilaminate tensile test that enables both valid dielectric film mechanical characterization and ease 

of testing. 

• Determined the average strain-to-failure of three PVOH films between room temperature and 140°C. 

• Determined that one PVOH film (30 wt % 4010 Vectomer, no rubberizer, 40 wt % total solids, annealed at 

225°C) consistently exhibited the largest strain-to-failure throughout the investigated temperature range. 

Future Direction 

• Develop a test method to enable quick evaluation of brittle-to-ductile temperature transition. 

• Measure mechanical response of next-generation polymer dielectric films. 

Introduction to develop polymer capacitor technology that will 

A primary focus of the Power Electronics effort replace current electrolytic, dc bus capacitors for 

in the Automotive Propulsion Materials Program is power electronic modules in hybrid electric 

vehicles. The ultimate objective is to make the 

23 
FY 2005 Progress Report 

power modules more compact while maintaining 

tight voltage and temperature requirements and long 

service life without compromise caused by 

mechanical breakdown of the dielectric film. 

An anticipated capacitor geometry containing 

these dielectric films is a cylindrical one. The 

dielectric films would be subjected to rolling or 

mandrel wrapping during capacitor manufacture. If 

the films cannot mechanically withstand those 

bending actions, they will fail or fracture, rendering 

the capacitor inoperable. Therefore, it is desirable to 

identify an allowable radius of curvature to which 

the films can be subjected by measuring their 

mechanical properties (i.e., strain-to-failure) and 

linking the two. 

The effort to identify an SNL-provided PVOH 

film with superior mechanical performance has been 

a consequence of a 2-year (FYs 2004 and 2005) 

effort. The room temperature mechanical properties 

of a large suite of PVOH films were first determined 

in FY 2004. The better performing films from that 

matrix then were further mechanically evaluated in 

FY 2005 to explore the effects of temperature on 

them, and that has been the focus this year. 

Results 

Three films were evaluated, and the following 

designations were used: 

1. 58042: 30 wt % Vectomer, 5 wt % 58042, and 

40 wt % total solids, 225°C anneal 

2. No rubberizer: 30 wt % Vectomer and 

40 wt % total solids, 225°C anneal 

3. Brady: 30 wt % 4010 Vectomer and 33 wt % 

total solids, annealed at 163°C 

Film strips were cut from SNL-supplied disks or 

rolls into 12.7-mm widths and then tensile tested in 

displacement control using the test setup shown in 

Figure 1. Tensile load and elongation were 

continuously monitored. 

Tensile testing was performed between room 

temperature (25°C) and 140°C. At least ten 

specimens were tested at 25°C (77°F), 60°C 

(140°F), and 105°C (221°F) in an attempt to 

generate improved statistics. Specimens were also 

tested at other temperatures in an attempt to identify 

the transition temperature between where the films 

failed in a brittle or ductile fashion. 

Automotive Propulsion Materials 

Figure 1. Tensile test setup. 

Removal of the PVOH film from the Mylar 

carrier embrittled the film (see Figure 2), so an 

alternative approach was pursued to avoid 

embrittlement. Because the PVOH film was thin 

compared with the Mylar carrier, had a very weak 

bond with it, and had a lower strain to failure, testing 

commenced by testing both films in tension without 

removing the PVOH from the carrier. A typical 

measured response for this bilaminate testing is 

shown in Figure 3 with a characteristic load drop 

that is associated with the fracture of the PVOH 

film. This effect is also shown in Figure 4. Using 

classical fracture mechanics, the measured response 

Figure 2. The act of removing the dielectric film from the 

Mylar carrier deleteriously affected the dielectric film, so 

bilaminate film testing was pursued. 

24 
Automotive Propulsion Materials FY 2005 Progress Report 

Figure 3. Example of tensile load–tensile elongation 

curve showing a load drop associated with the 

fracture of the dielectric film. 

Figure 5. Deconvolution of tensile load and 

elongation for the dielectric and Mylar films. 

Figure 6. Stress–strain comparison of dielectric film 

and Mylar carrier during a test. 

Figure 4. Fractured dielectric film shown while 

Mylar carrier still withstands tensile strain. The 

withstood load is associated with the residual load 

shown in Figure 3 after the load drop. 

in Figure 3 can be readily deconvoluted into the 

Mylar and PVOH contributions that are illustrated in 

Figure 5, or compared as shown in Figure 6. Such an 

analysis was used to determine strain-to-failure as a 

function of temperature for the three films. 

The “no-rubberizer” PVOH film composition 

exhibited the largest average strain-to-failure for a 

given temperature to 140°C, as shown in Figure 7. 

The bars shown in Figure 7 are standard deviations, 

but their presence also qualitatively indicates 

(brittle) fracture. For example, the no-rubberizer 

PVOH film fractured when tested to ~ 90°C, 

whereas it continued to elongate and elongate when 

tested above that temperature (tests were terminated 

if ~15% strain was accumulated without fracture). 

That ~90°C temperature is near the brittle-to-ductile 

Figure 7. Tensile strain-to-failure as a function of 

temperature. The “no-rubberizer” composition was 

able to withstand larger strain-to-failure than the other 

two films for a given temperature up to 140°C. 

transition for the no-rubberizer composition. The 

Brady PVOH film had a similar transition 

temperature, but the 58042 PVOH transition 

temperature neared 130°C. 

25 
FY 2005 Progress Report Automotive Propulsion Materials 

The larger strain-to-failure exhibited by the norubberizer PVOH film means that it can be subjected 

to a smaller radius of curvature (R) during capacitor 

manufacture (see Figure 8) or service than the Brady 

or 58042 PVOH films when they are all subjected to 

the same temperature or 

t R = 2ε tens

where t is the film thickness and εtens is strain-tofailure. 

Figure 8. Dielectric films are subjected to curvature 

during capacitor manufacture, so it is desirable for 

them to be able to withstand a maximum strain-tofailure to enable more confident manufacture and 

smaller cylindrical capacitor diameters. 

Conclusions 

The PVOH film containing 30 wt % Vectomer 

and 40 wt % total solids, annealed at 225°C, and 

designated as no-rubberizer was able to withstand 

larger strains without failure than the 58042 and 

Brady PVOH dielectric films. That allows it to be 

successfully used in cylindrical capacitors with 

smaller diameters. 

26 
Automotive Propulsion Materials FY 2005 Progress Report 

3. CIDI ENGINES 

A. Round Pleated Ceramic Fiber Diesel Particulate Filter Cartridge Durability 

Improvement 

Richard Nixdorf 

Industrial Ceramic Solutions, LLC 

1010 Commerce Park Drive, Suite I 

Oak Ridge, TN 37830 

(865) 482-7552; fax: (865) 482-7505; e-mail: nixdorfr@indceramicsolns.com 

DOE Materials Technologies Team Leader: Rogelio Sullivan 

(202) 586-8042; fax: (202) 586-1600; e-mail: rogelio.sullivan@ee.doe.gov 

ORNL Technical Advisor: David Stinton 

(865) 574-4556; fax: (865) 241-0411; e-mail: stintondp@ornl.gov 

Contractor: Industrial Ceramic Solutions, Oak Ridge, Tennessee 

Prime Contract No.: 4000000723 

Subcontractors: Springboard Technology, Pittsfield, MA 

Objectives 

• Design a round pleated ceramic fiber diesel particulate filter (DPF) cartridge suitable for a heavy-duty pickup 

truck, using a 7.3-L Ford F250 truck as a model. 

• Develop a ceramic fiber filter medium with improved strength and soot-holding capacity. 

• Conduct road testing on the 7.3-L Ford truck to verify the durability and soot-loading capacity of the improved 

filter medium and cartridge. 

Approach 

• Investigate the effect on strength and soot-holding capacity of using various species of ceramic fibers and 

binders in the filter medium. 

• Manufacture and road-test the improved cartridge system on a 7.3-L diesel vehicle to verify durability. 

Accomplishments 

• Improved ceramic fiber filter media burst strength from 6 to 15 psi and improved soot-loading capacity from 

0.86 to 1.67 grams /ft

2

. 

• As a result of filter improvements, entered into a joint development program with a major diesel locomotive 

company to develop a commercial DPF system for locomotive engines. 

• Entered into a joint development program with a worldwide Tier 1 automotive supplier to develop a 

commercial DPF system for the automotive market. 

27
FY 2005 Progress Report Automotive Propulsion Materials 

Future Direction 

• Install a pilot production line to supply the developed DPF filter cartridges to automotive original equipment 

manufacturers for testing. 

• Market DPF improvements worldwide to provide second-generation DPF systems to the auto industry. 

• Enter a joint development agreement with a progressive exhaust system supplier to implement a more efficient 

DPF control system. 

• Conduct high-mileage durability testing (> 100,000 miles) on the improved Industrial Ceramic Solutions (ICS) 

DPF cartridge. 

Introduction 

Diesel emissions regulations in the United 

States, Europe and Japan have now become a reality 

for all diesel engine manufacturers. Every diesel 

engine and vehicle supplier in the world has selected 

a particulate control device to comply with the 

2007/2008 regulations. These wall-flow, catalystregenerated systems, which require high exhaust 

temperatures, seem to be working reasonably well in 

all of the application testing. The principal 

remaining problem is that the soot-loading capacity 

of the devices must be limited to avoid destruction 

of the filter cartridge during low-exhaust-flow 

regeneration. Smaller vehicles with low exhaust 

temperatures—such as medium-duty trucks, buses, 

delivery vans, pickup trucks, passenger cars, future 

diesel SUVs, and off-road vehicles—are also an 

issue. Emission control engineers are trying to avoid 

the need for an auxiliary-heated particulate filter that 

might be required to enable regeneration under all 

engine conditions. 

Most of the problems associated with currently 

available extruded wall-flow ceramic filters are due 

to their high thermal mass and inability to conduct 

regeneration heat. These problems open a market 

opportunity for the ICS pleated ceramic fiber DPF 

cartridge in small diesels, 90% of the diesel engine 

market. Its open structure for regeneration heat 

release and its reduced thermal mass provide 

significant advantages in low-temperature exhaust 

systems. A number of actively heated DPFs are 

under development, but none have a proven record 

of performance, maintenance history, and desirable 

price for commercial diesel vehicles. ICS’s 

completion of the FY 2005 DOE Propulsion 

Materials Program vehicle road test will place the 

ICS round pleated ceramic fiber filter cartridge high 

on the list of potential active and passive heated 

DPF systems for the next generation of products. 

During FY 2004, ICS developed a round pleated 

DPF cartridge to control diesel particulates across all 

market applications. The design produced a thermal 

mass that is 30% that of the preferred silicon carbide 

wall-flow extruded ceramic filter. Experiments 

conducted by ICS in FY 2004 demonstrated reduced 

exhaust backpressure on the diesel engine from the 

pleated ceramic fiber DPF. This will improve engine 

performance and reduce the fuel penalty imposed by 

the particulate matter control device. The pleated 

ceramic fiber DPF, weighing significantly less than 

the extruded wall-flow filter, has a lower thermal 

mass to achieve lower-energy soot combustion and 

adds less weight to the vehicle. The open structure 

prevents cartridge destruction by temperature 

excursions when the filter is overloaded with soot. 

The ICS pleated ceramic fiber filter cartridge will be 

able to handle approximately two times the soot 

loading of an equivalent extruded wall-flow filter. 

Approach 

In FY 2005, ICS developed a round pleated 

ceramic fiber filter cartridge. Many experiments 

were conducted to determine the optimum geometry 

of the filter and the best means to fabricate this 

geometry in the laboratory. A pleating process, 

using a ceramic binder, was optimized. Several 

designs of the round pleated fiber cartridge were 

investigated. These prototypes are shown in 

Figure 1. During FY 2005, ICS developed a round 

pleated filter cartridge based on diesel engine testing 

data from our rectangular pleated filter cartridge. 

Extensive road testing on the Ford F250 diesel truck 

showed that the 7 ft2 of media in the rectangular 

pleated filters is approximately 30% less than that 

required for optimum filter operation. ICS selected a 

round pleated filter approximately 6 in. in diameter 

and 12 in. long. This design will yield 10 ft2

 of 

effective filter media surface area to accommodate a 

28
Automotive Propulsion Materials FY 2005 Progress Report 

Figure 1. Round pleated filter prototypes. 

full spectrum of diesel exhaust flow rates on the 

truck. The filter length can be reduced to 6 in. by 

employing the design shown in Figure 2. This 

design will continue to provide the 10 ft

2

 of filter 

media required for the 7.3-L diesel engine. 

Figure 2. Round pleated filter commercial design 

concept, 

The durability improvements achieved with 

FY 2005 funding were a result of investigating the 

ceramic binder and the ceramic fiber mix of the filter 

medium. Experiments were conducted in the ICS 

laboratory with a number of commercial binders and 

commercially available ceramic fibers. The binder 

and fiber mix was optimized in the laboratory. These 

improvements were transferred to commercial 

papermaking equipment to produce continuous rolls 

of filter media to be pleated and converted to pleated 

filter cartridges for testing. These cartridges were 

then road-tested on the 7.3-L Ford truck under 

routine driving conditions (Figure 3). 

Figure 3. Road test apparatus for pleated filters, 

Results 

ICS was convinced that surface chemistry 

adjustment would improve binder adhesion to the 

ceramic fibers in our filter media. Beth Armstrong 

and Glen Kirby of Oak Ridge National Laboratory 

(ORNL) conducted experiments and materials 

analysis on the components of the ICS filter media 

to improve binder adhesion. The results showed ICS 

that surface chemistry adjustment was inadequate to 

achieve the 3× improvement in filter media strength 

that is required. This work by ORNL directed ICS to 

investigate other areas such as media fiber 

component alternatives and new papermaking 

techniques to obtain the needed 3× strength 

improvement, which eventually led to the desired 

results. The filter media burst strength was improved 

from 233 in. of water in 2004 to 415 inches of water 

in 2005. The burst strength improvement over the 

life of this program is shown in Figure 4. The soot29
FY 2005 Progress Report Automotive Propulsion Materials 

Figure 4. Filter media strength improvement. 

loading capacity was increased from 0.86 g/ft2

 in 

2004 to 1.86 g/ft2

 in 2005. 

The improved filter media, converted to 

continuous paper and filter cartridges, was roadtested on the Ford 7.3-L truck. Twenty road tests 

were completed to load the filter to over 80 in. of 

water backpressure during each test. The filter was 

regenerated at 700°C after each road test. There was 

no damage to the filter cartridge during the road 

testing or regeneration. Figure 5 shows the clean 

entry and dirty exit sides of the filter prior to 

regeneration after the twentieth cycle. 

Figure 5 . Twenty-cycle truck test filters. 

Conclusions 

The pleated ceramic fiber filter cartridge has 

demonstrated lower backpressure and thermal mass 

than conventional wall-flow DPFs. These two 

advantages make it a valuable addition to all types 

of diesel particulate matter control systems. ICS is 

working with a major international filter 

manufacturer to license the use of the technology to 

supply the large volume of filter cartridges 

necessary to supply the worldwide diesel industry. It 

is also working with several vehicle manufacturers 

to develop improved commercial exhaust control 

systems. The gasoline engine catalytic converter was 

introduced in 1975; in 2005, it is just reaching a 

stage of optimum efficiency. The selected diesel 

engine DPF control systems will be installed on 

diesel vehicles in 2006. These systems have an 

unproven operating record in volume use. There is 

significant opportunity for improved technologies to 

enter the commercial marketplace. The advantages 

offered by the ICS DPF technology will be a 

contributor to optimization of the diesel emission 

control systems. 

Publications/Presentations 

“Round Pleated Ceramic Fiber Filter,” presented 

at the DEER Conference, Chicago, August 2005. 

“Advances in Filter Media Development for 

Diesel Exhaust Systems, Ceramic Bonded Ceramic 

30
Automotive Propulsion Materials FY 2005 Progress Report 

Fiber Pleated DPF Cartridge” presented at the 

American Filtration and Separation Society Diesel 

and Gas Engine Emissions Solutions Conference, 

Ann Arbor, MI, September 2005. 

Awards/Patents Issued 

“Ceramic and Fiber-Based Filter Web and 

Method,” U.S. Patent 6,913,059 B2, July 2005. 

31
FY 2005 Progress Report Automotive Propulsion Materials 

B. Fabrication of Small Fuel Injector Orifices 

John B. Woodford, George R. Fenske 

Argonne National Laboratory 

9700 South Cass Avenue 

Argonne, IL 60439 

(630)252-0910; fax (630)252-4798; e-mail gfenske@anl.gov 

DOE Technology Development Manager: Rogelio Sullivan 

(202) 586-4082; fax: (202) 586-1600; e-mail: rogelio.sullivan@ee.doe.gov 

Contractor: Argonne National Laboratory, Argonne, Illinois 

Prime Contract No.: W-31-109-Eng-38 

Objectives 

• Develop a methodology for reducing the diameter of fuel injector orifices to 50 μm by applying material to the 

internal diameter (ID) of the orifice. Smaller orifices should improve fuel distribution, improve efficiency, and 

reduce emissions. 

• Characterize the spray and combustion properties of the fuel injector system coated with electroless nickel 

(EN). 

• Transfer the developed technology to DOE industrial partners. 

Approach 

• Transfer EN plating deposition technology for reducing the orifice diameter to a commercial plating company. 

• Evaluate the potential of EN plating for improving surface finish and reducing deposit formation on injector 

nozzles. 

Accomplishments 

• Devised a new approach for preparing test nozzles in concert with the U.S. Environmental Protection Agency– 

National Vehicle and Fuel Emissions Laboratory (EPA-NVFEL). Also initiated collaboration with a major fuel 

injector manufacturer for further engine testing of plated nozzles for deposit mitigation. 

• In concert with Imagineering, Inc., a commercial plating company, developed a method for improving the 

surface finish of commercial-scale-plated nozzles. 

• In the area of deposit formation testing, refined the test method to include examination of oxidative volatiles 

and characterized the effect of phosphorus levels in the EN plating on deposit formation. Provided alloy 

samples for testing to Pennsylvania State University and began to work with Northern Illinois University (NIU) 

on studying this issue. 

Future Direction 

• Characterize spray characteristics of coated injectors in collaboration with Argonne National Laboratory– 

Energy Systems (ANL–ES) and ANL–Advanced Photon Source (ANL–APS). 

• Provide coated injector tips to EPA-NVFEL personnel for spray characterization and combustion tests. 

• Apply advanced characterization methods for detailed examination of surface chemistry during deposit 

formation, particularly extended X-ray absorption fine structure (EXAFS). 

32
Automotive Propulsion Materials 

Introduction 

In 2007, EPA regulations mandate diesel engine 

emission reductions to 0.01 grams of particulate 

matter (PM) per engine horsepower per hour and 

0.2 grams of nitrogen oxides (NOx) per engine 

horsepower per hour. Further reductions are 

expected for 2010. In order to achieve these levels, 

engines are being redesigned to reduce in-cylinder 

soot production. One design change under 

consideration is the reduction of the fuel injector 

orifice diameter. 

Pickett and coworkers1,2

 have shown elimination 

of soot in a test cylinder by reducing the injector 

orifice diameter to 50 μm, even with high levels of 

exhaust gas recirculation, and concomitant reduction 

in NOx emissions. NVFEL researchers have 

observed reduced PM emissions from a light-duty 

diesel engine equipped with 75-μm-diameter 

injector orifices. These reductions arise from 

increases in fuel atomization efficiency, leading to 

more complete combustion.3

 Although it is currently 

possible to economically mass-produce injectors 

with 100-μm diameter-orifices using 

electrodischarge machining, further reductions in 

hole size are accompanied by unacceptable 

fabrication error rates at this point. 

Reducing orifice diameter carries with it a 

number of penalties, however. It is inevitable that a 

marked reduction in orifice area (e.g., from 150 to 

50 μm) will lead to a reduction in the amount of fuel 

that can be delivered to the combustion chamber 

without increasing the number of spray holes, the 

injection pressure, and/or the discharge coefficient. 

The potential impact of coking on smaller orifices is 

also much greater, as smaller holes will be more 

readily blocked by coking deposits on the injector 

tip and in the spray holes themselves. Coking 

deposits are a particular problem with taperedorifice nozzles, another technique for increasing fuel 

atomization and thus reducing PM emissions. 

Another issue is alternative fuels. One method to 

minimize dependence on foreign oil is the increased 

use of bioderived fuels such as vegetable oil esters. 

Because of the presence of carbon-carbon double 

bonds in the carboxylic acid chain precursors, these 

fuels readily form coking deposits in the combustion 

chamber—a major problem in concert with smaller 

spray holes. Other alternative fuels include alcohols 

such as methanol or ethanol. These are not typically 

used neat but are blended with conventional diesel 

FY 2005 Progress Report 

fuel. One emissions reduction strategy is to inject an 

ethanol/water mixture along with conventional fuel, 

reducing combustion temperature and NOx 

emissions. However, alcohol partial oxidation 

products can include corrosive carboxylic acids, 

which will damage the steel nozzles over time. 

In concert with more commonly-used 

fabrication techniques, EN plating has been used to 

prepare fuel injector nozzles with orifice diameters 

as small as 50 μm. EN plating also promises to 

mitigate or solve all of the difficulties described 

above: It is corrosion-resistant; plated surfaces are 

smoother than unplated surfaces; it increases the 

discharge coefficient of the plated orifices; and it 

can be used to deposit a wide variety of alloys, 

offering the possibility of tailoring surface chemistry 

to reduce or eliminate deposit formation. 

Approach 

As described in previous reports, the reduction 

of orifice diameter is accomplished by coating the 

orifice interior with EN plating. EN plating is a 

method of depositing nickel/phosphorus or 

nickel/boron alloys onto metallic surfaces from 

aqueous solution. This approach has been 

successfully used in previous years to reduce orifice 

diameter from 200 to 50 μm on a bench scale, and 

from 180 to 75–80 μm on a commercial scale. Other 

metal alloys have been deposited using the same 

principle. 

Having demonstrated that it is possible to use 

EN plating to reduce orifice diameter to the desired 

size, the next goal is to demonstrate the usefulness 

of EN-plated nozzles for solving the problems 

described in the Introduction: improving spray 

properties and discharge coefficient, reducing 

deposit formation, and resisting corrosion. 

Results 

The critical milestone for this project has been to 

characterize the spray properties and engine 

performance of plated nozzles. Efforts to that end 

are progressing. These include collegial agreements 

with EP-NVFEL to evaluate plated nozzles in a 

4-cylinder light-duty engine, as well as with a major 

light-duty injector manufacturer to evaluate deposit 

formation properties of EN-plated nozzles. Internal 

R&D funds have also been solicited to perform 

optical and X-ray imaging studies of plated nozzle 

fuel sprays. The latter studies will cover a range of 

33
FY 2005 Progress Report 

orifice diameters and fuel types, including 

conventional diesel, bioderived diesel, and ethanol 

blends. 

One of the issues raised in the FY 2004 report 

was the finish on surfaces plated by Imagineering 

(Figure 1a). That issue has been resolved 

(Figure 1b). The company’s method of removing EN 

from a plated surface without damaging the 

substrate did not work for keeping the needle guide 

free of plating, however (cf. Figure 2), and its use of 

conventional maskants on the guide area did not 

allow sufficient plating bath flow to coat the orifices 

uniformly. Imagineering suggested that the plating 

be removed mechanically, as EN plating can be 

ground off. This proved to be feasible. The same 

approach can be used to remove overcoating from 

the needle seat area (cf. Figure 3), which might 

otherwise adversely impact needle sealing. 

These issues all arise from the use of existing 

nozzles with matching needles. In production, it is 

anticipated that needles and nozzles will be ground 

and lapped after plating. Thus no net cost or increase 

in time will accrue from the machining, and the only 

increases in cost will be from the plating process 

itself. 

Deposit formation tests using the test method 

developed two years ago, dropping diesel fuel onto 

heated plated and unplated surfaces, are continuing. 

The test protocol has been expanded to include 

different materials, EN compositions, and 

temperatures of 200, 250, and 300°C. The test 

method has also been refined for use with lessvolatile fluids, in this case a high-oleic-content 

sunflower oil lubricant. This has been done as a 

worst case for deposit formation, in that the oil has a 

large number of carbon-carbon double bonds and 

contains no antideposit additives. By weighing the 

samples before and after heating, and again 

following rinsing with hexane, the mass loss due to 

the formation of volatiles by oxidative cleavage can 

be decoupled from the mass gain due to deposit 

formation. 

Figures 4 and 5 are plots of deposit mass gain 

and volatiles mass loss from tests of nickel and EN 

plating with three different phosphorus 

concentrations at 250°C. The mid-phosphorus 

plating is similar to the commercial plating bath that 

was used for previous tests. Although there is 

considerable scatter in the data, it is clear that all of 

these are superior to unplated steel, and that the midphosphorus coating is actually inferior in deposit 

Automotive Propulsion Materials 

(a) 

(b) 

Figure 1. Optical micrographs of injectors 

plated at Imagineering early last year (a) and late 

last year (b), showing differences in surface 

finish. 

Figure 2. Plan sketch of nozzle, indicating the 

pintle guide area. 

resistance to the low- and high-phosphorus coatings. 

Figure 6 is a plot of deposit mass for diesel tests 

with the different EN plating compositions at 

different temperatures. At lower temperatures, all of 

the plating compositions are superior to unplated 

steel, but at 300°C only low-phosphorus EN is still 

34
90 

10 

15 

Automotive Propulsion Materials FY 2005 Progress Report 

Normalized Diesel Deposit Mass on EN 

1.2 

Figure 3. Plan sketch of nozzle tip region, 

indicating the needle seat area. 

High-Oleic Sunflower Oil Deposit Tests at 250°C 

Deposit Mass% 80 

70 

60 

50 

40 

30 

20 

10 

0 

Ni Steel Ni Steel 

Substrate Type 

Pure Ni Test Deposit Mass% Low-P EN Test Deposit Mass% 

Mid-P EN Test Deposit Mass% High-P EN Test Deposit Mass% 

Figure 4. Deposit mass % on nickel, EN plating with 

Deposit Mass, normalized to unplated

steel 

1 

0.8 

0.6 

0.4 

0.2 

0 

250°C 300°C 

Test Temperature 

Low-P EN Deposit Mass Mid-P EN Deposit Mass High-P EN Deposit Mass 

Figure 6. Diesel deposit mass on the different EN 

compositions at different temperatures, normalized to 

deposit mass on unplated steel in the same tests. 

better than steel. Considering the scatter in the data, 

the other two compositions are no worse than steel, 

though. This contrasts sharply with another 

corrosion-resistant alloy, 304 stainless steel 

(Figure 7). Although stainless steel is superior to 

mild steel at 200°C, at higher temperatures it is 

markedly inferior to mild steel. The reason for this is 

not fully understood, but it may relate to the 

catalytic activity of chromium ions in fuel oxidation. 

Further investigation was undertaken, as will now be 

detailed. 

According to Cochrac and Rizvi,4

 partial 

oxidation is catalyzed by the presence of metal 

carboxylates, and they gave an example of the different levels of phosphorus, and unplated steel catalytic activity of iron octanoate. In the past year, 

deposit test sample dishes made from mild steel and 

stainless steel have been sent to Professor Charles 

following deposit tests with sunflower oil at 250°C. 

High-Oleic Sunflower Oil Volatiles Test 250°C 

Johnson of NIU and APS, for Mößbauer 35 

30 

Normalized Deposit Mass on Stainless Steel at Different 

Temperatures 25 

1.6 

20

Volatiles Mass% 

Stainless Steel 

EN Plating 

0.6 

0.4 

0.2 

1.4 

1.2 

Normalized Deposit Mass

1 

0.8 

Ni Steel Ni Steel 

Substrate Type 

Pure Ni Test Volatiles Mass% Low-P EN Test Volatiles Mass% 

Mid-P EN Test Volatiles Mass% High-P EN Test Volatiles Mass% 

Figure 5. Volatiles mass % on nickel, EN plating with 

different levels of phosphorus, and unplated steel 

following deposit tests with sunflower oil at 250°C. 

0

200°C 250°C 300°C

Test Temperature 

Figure 7. Diesel deposit mass on stainless steel at 

different temperatures, normalized to deposit mass 

on mild steel in the same tests. Normalized deposit 

mass for commercial mid-phosphorus EN at 250°C 

is shown for comparison 

35

0 

5 
FY 2005 Progress Report Automotive Propulsion Materials 

spectroscopy. This technique is used to measure the Fischer-Tropsch Diesel Deposit Test, Open Air at 250°C 

oxidation state of iron in the near-surface region of 0.0003 

the sample. Comparing mild steel and stainless steel 

will determine if any iron ions are present in the 0.00025 

stainless steel deposit. 0.0002 

In other tests, the effect of surface finish on 

Deposit Mass, g 

deposit formation has been examined (Figure 8). No 0.00015 

consistent influence was seen in the initial tests, but 0.0001 

they will be repeated in more detail in the next year. 

A test has been performed using Fischer-Tropsch 

synthetic diesel fuel (Figure 9), which is free of 

detergent additives, sulfur, and aromatic compounds. 

As expected, total deposit mass is lower, but the 

superiority of EN plating over steel is also more 

pronounced. 

The data from Professor Joseph Perez’s prior 

tests have been revisited and analyzed in greater 

detail, particularly the gel permeation chromatography results (Figure 10). These show the 

distribution of molecular weights in the apparentlyunreacted oil following the PSMO tests. 

Little change in average molecular weight of the 

oil over the course of the test indicates that little 

partial oxidation has taken place. High-molecularweight species are deposit precursors created by 

incomplete oxidation of the test fluid. Apparently, 

although a substantial amount of deposit precursors 

builds up in the oil over the EN-plated surfaces, it 

does not condense into insoluble deposits very 

readily. The reason for this is unclear. As a result of 

PSMO tests on other coating materials, NiMo, NiCu, 

and NiMoCu coatings have been produced and 

provided to Professor Perez. The results are 

forthcoming. 

Diesel Deposit Mass on Different Surface Finishes 

0.001 

0.0008 

0.0006 

0.0004 

0.0002 

0 

A As-made B Ground- C As-made D Ground- E Ground- F Assteel oxide surface steel steel surface steel surface steel ste 

-0.0002 control oxide control 

Substrate Type 

120 grit steel run 320 grit steel run 

Deposit Mass, g 

0.00005 

0 

Unplated Steel Commercial EN Unplated Steel, oxide only 

Substrate Type 

Figure 9. Fischer-Tropsch synthetic diesel deposit 

mass on EN plating and steel at 250°C. 

(a) 

(b) 

Figure 10. Plots of same-molecular-weight fraction 

(a) and high-molecular-weight fraction (b) as a 

function of time on unplated and EN-plated steel 

Figure 8. Diesel deposit mass on mild steel at surfaces. 

250°C after roughening with different grades of 

silicon carbide abrasive paper. 

36 
Automotive Propulsion Materials 

Conclusions 

A candidate method has been developed for 

fabricating nozzles for spray testing, and 

arrangements have been made with EPA-NVFEL 

and a major fuel injector manufacturer to perform 

engine tests in the next year. Imagineering has been 

able to provide plated nozzles with satisfactory 

surface finishes as well. In the area of deposit 

analysis, the Mößbauer spectroscopy work 

performed in concert with Northern Illinois 

University will provide baseline data to apply to a 

more detailed surface analysis of deposits using 

EXAFS to determine oxidation state and local 

bonding structure around different elements in the 

coatings. In-house deposit tests have begun to 

elucidate the relationship between phosphorus level 

in the plating and deposit formation propensity. 

References 

1. Lyle M. Pickett and Dennis L. Siebers, Paper 

No. 2001-ICE-399, ICE Vol. 37-1, 2001 Fall 

Technical Conference, American Society of 

Mechanical Engineers 2001, ed. V.W. Wong. 

FY 2005 Progress Report 

2. L.M. Pickett, D.L. Siebers, A.F. Morales, 

J. Hachman, and A.K. Sinensky, “An 

Investigation of Diesel Soot Formation 

Processes Using High Aspect Ratio MicroOrifices,” presented at HARMST 2003 HighAspect Ratio Micro-Structure Technology 

Workshop, Monterey CA, 2003. 

3. John B. Heywood, Internal Combustion Engine 

Fundamentals, McGraw-Hill, 1988. 

4. G. Cochrac and S.Q.A. Rizvi, “Oxidation of 

Lubricants and Fuels”, Chapter 30 in Fuels and 

Lubricants Handbook, ed. G.E. Totten, 

American Society for Testing and Materials, 

2003. 

Publications and Presentations 

J. Woodford, J.M. Perez, and G. Fenske, 

Deposit Formation on Electroless Nickel, in press 

Poster, DOE Advanced Combustion Engine 

R&D Merit Review, April 19–21, 2005, Argonne 

National Laboratory 

37
FY 2005 Progress Report Automotive Propulsion Materials 

C. Electrochemical NOx Sensor for Monitoring Diesel Emissions 

L. Peter Martin, Seung Wan Song, and Robert S. Glass 

Lawrence Livermore National Laboratory 

P.O. Box 808, MS L-353 

Livermore, CA 94551-0808 

(925) 423-7140; fax: (925) 423-7914; e-mail: glass3@llnl.gov 

DOE Materials Technologies Team Leader: Rogelio Sullivan 

(202) 586-8042; fax: (202) 586-1600; e-mail: rogelio.sullivan@ee.doe.gov 

Contractor: Lawrence Livermore National Laboratory, Livermore, California 

Prime Contract No.: W-7405-Eng-48 

Objectives 

• Develop a compact, rapid-response electrochemical nitrogen oxide (NO) or total nitrogen oxides (NOx) sensor 

for compression-ignition, direct-injection (CIDI) exhaust gas monitoring. 

• Collaborate with the Ford Research Center and Oak Ridge National Laboratory to optimize sensor materials, 

operating parameters, and performance. 

• Identify materials issues pertaining to aging and performance for candidate sensor materials. 

Approach 

• Use an ionic (O2−) conducting ceramic as a solid electrolyte and a catalytic metal oxide as a working electrode. 

• Apply a constant voltage- or current-bias (through the electrolyte) between a working and counter electrode. 

• Correlate the NOx concentration with the current-voltage behavior of the sensor. 

• Evaluate sensing mechanism and aging during operation using electrochemical and analytical techniques. 

Accomplishments 

• Identified aging processes in strontium (Sr) -doped LaCrO3−δ (LSC) perovskite electrodes. 

• Gave an invited presentation at the 207th meeting of the Electrochemical Society, Quebec, May 2005. 

Future Direction 

• Continue to explore materials issues related to sensitivity and stability by investigating sensing mechanisms 

using electrochemical and analytical techniques and by evaluating microstructural evolution during sensor 

aging. 

• Evaluate cross-sensitivity to important redox gases and perform dynomometer testing. 

• Demonstrate the commercialization potential of the current-biased sensor technique. 

• Transfer the technology to a commercial entity. 

38 
Automotive Propulsion Materials 

Introduction 

Increasingly stringent emissions regulations will 

require the development of comprehensive on-board 

diagnostic systems for exhaust-gas monitoring and 

feedback control of regulated pollutants, including 

hydrocarbons, carbon monoxide, and NOx. For 

example, an on-board NOx sensor will be needed to 

monitor the regeneration of the NOx reduction 

catalyst in the next generation of CIDI engines. To 

that end, NOx sensors based on ionically-conducting, 

solid-state electrochemical devices have been 

proposed.1,2

 Typical operating conditions for these 

sensors can include elevated O2 concentrations of 

5–15%, temperatures in the range of 600–700°C, 

and NOx concentrations in the range of 

10–1000 ppm.

3–5 Strontium-doped LaCrO3-δ (LSC) 

perovskite has been identified as a potential NOx 

sensor electrode when coupled with a yttriastabilized zirconia (YSZ) electrolyte.6,7

 Other 

perovskite-type metal oxides such as LaFeO3 and 

Sr-doped LaCoO3 have also been investigated as 

NOx sensor electrodes.8 

The NOx sensing performance of these electrode 

materials is strongly dependent on microstructure; 

however, quantifying this dependence is not 

straightforward. In addition, electrode performance 

often changes significantly with extended operation 

(aging). Aging can affect the particle morphology, 

stoichiometry, and electrode-electrolyte interface 

structure. A better understanding of these effects is 

required for optimization of sensor performance and 

long-term reliability. While there have been few, if 

any, reported investigations of the aging behavior of 

these materials as sensor electrodes, there is a 

substantial body of literature describing aging 

effects in related solid oxide fuel cell cathode 

materials.9,10 Those reports describe significant 

cathodic polarization and aging effects and suggest a 

strong need for systematic analyses of the aging 

processes in perovskite materials used as sensor 

electrodes. 

In this work, LSC/YSZ/platinum (Pt) 

electrochemical cells were prepared in a threeelectrode configuration by depositing LSC working 

electrodes (WE) and Pt counter (CE) and reference 

(RE) electrodes on sintered YSZ electrolyte 

substrates. LSC electrodes were prepared from 

La0.85Sr0.15Cr1.01O3 powder sintered at 1200°C, while 

Pt electrodes were prepared from a commercial Pt 

ink sintered at 1000°C. Selected cells were 

FY 2005 Progress Report 

electrochemically aged at 600–700°C in 10% O2 and 

0–500 ppm NOx by applying a positive bias of 250 

mV to the LSC WE (relative to the Pt reference 

electrode). Detailed characterization of the 

electrodes—using scanning electron microscopy 

(SEM), X-ray photoelectron spectroscopy (XPS), 

and X-ray diffraction (XRD)—was used to elucidate 

the effects of aging. The effects of the observed 

aging processes were evaluated with respect to the 

electrochemical performance and NOx sensing 

characteristics of the cell. Before proceeding further 

with the development of prototypes for more 

advanced testing, it is necessary to develop a 

thorough understanding of materials aging and 

electrochemical properties for LSC and other 

prospective sensor materials. 

Results 

SEM was used to examine both the un-aged and 

aged electrodes to characterize the morphology and 

porosity and to evaluate any changes due to aging. 

Figure 1(a) shows the surface of a typical un-aged 

LSC electrode. The LSC is porous and consists of 

Figure 1. (a) SEM image of the surface of an 

un-aged LSC electrode. (b) SEM image of the 

surface of an LSC electrode aged for one week 

in 10% O2 at 600oC. 

39 
FY 2005 Progress Report Automotive Propulsion Materials 

particles ranging from ~100–500 nm in size. After 

aging at 600°C, numerous cracks appear at the 

electrode surface (Figure 1b). Higher-magnification 

images show that the average particle size increases 

slightly. The origin of the surface cracks is not 

currently understood; however they do not develop 

in LSC electrodes aged in the absence of applied 

bias, suggesting that the current flow through the 

cell has a significant effect on their evolution. 

XRD patterns for LSC electrodes sintered onto 

the YSZ substrate before aging show an impurity 

phase that is believed to be SrCrO4. This is 

consistent with prior reports indicating that ACrO4 

(A=Ca, Sr) is often present in doped lanthanum 

chromites. After aging at 700°C, there are 

indications of the formation of SrZrO3. It is 

postulated that the SrZrO3 forms as a result of a 

reaction between SrCrO4 and Zr at the YSZ-LSC 

interface. The formation of an SrZrO3 reaction 

product is limited by the availability of the SrCrO4 

impurity at or near the interface. Also apparent in 

the pattern for the aged electrode is a splitting and 

sharpening of the peaks at high 2θ. This indicates 

grain coarsening consistent with the particle growth 

observed in the SEM images. 

Detailed surface composition analyses were 

performed on the LSC electrodes, before and after 

aging at 600-700°C, using XPS. The results are 

shown in Table 1. These data indicate that the 

surface of the un-aged LSC is initially O-rich and 

Sr-rich. They deviate significantly from the 

theoretical values obtained based on the chemical 

formula La0.85Sr0.15Cr1.01O3-δ. Table 1 also shows the 

surface composition after aging at 600°C under both 

anodic and cathodic polarization. The most notable 

effect is that the O-content at the surface decreases 

under cathodic polarization and increases under 

anodic polarization. In addition, there is some 

indication of changing La/Sr stoichiometry with the 

bias direction. 

Ar-ion sputtering was used to remove the 

electrode surface, exposing the subsurface for XPS 

analysis. In contrast to the surface, the bulk of the 

LSC is relatively stoichiometric. For the un-aged 

LSC, the material is approximately stoichiometric at 

a depth of ~28 nm below the surface. After anodic 

aging, however, the chromium and lanthanum 

contents approach the theoretical values more 

quickly with depth, ~12–16 nm. This occurs despite 

the fact that the surface is still highly 

nonstoichiometric, as discussed earlier. 

Table 1. Surface atomic ratios from the XPS for 

the LSC before and after aging at 600oC 

Polarization 

UnRatio Theory aged Anodic Cathodic 

O/La ~3.5 6.8 9.7 5.0 

O/Cr ~3 5.1 6.3 4.0 

Cr/La 1.2 1.3 1.6 1.2 

La/Sr 5.7 1.2 1.3 2.5 

Cr/Sr 6.7 1.6 2.1 3.0 

In an attempt to gain insight into the practical 

effects of long-term aging on NOx sensing 

performance, an LSC/YSZ/Pt cell was evaluated for 

its response to varying NOx concentrations during 

long-term aging in 10% O2. Figure 2 compares the 

NOx response of the cell before and after anodic 

polarization at 600°C for 15 days. Note that this cell 

was designed to allow evaluation of the electrode 

response for obtaining purely mechanistic 

information and was not configured for optimal 

performance as an actual sensor. Before aging (i), 

the baseline was unstable and the NOx response was 

poor, particularly to NO. After aging (ii), the 

baseline stabilized, and both the NO and NO2 

response became significantly enhanced. In addition, 

the NOx response time improved significantly over 

the duration of the experiment. These results 

underscore that aging of the NOx sensing electrodes 

is crucial for obtaining stable and reproducible 

behavior. Similar remarks may also pertain to 

sensors for other gases, although different aging 

characteristics may be evident. 

Figure 2. Cell performance before (i) and 

after (ii) aging for 15 days at 600oC in 10% 

O2. 

40 
Automotive Propulsion Materials FY 2005 Progress Report 

Conclusions 

The performance of metal oxide electrodes 

proposed for use in electrochemical NOx sensors is 

highly dependent upon microstructure and surface 

stoichiometry, which are influenced by aging in test 

gas atmospheres. This is particularly true in the case 

of doped perovskites, which are known to be 

potentially non-stoichiometric. Currently, LSC is 

being evaluated as a potential sensor electrode 

material. For this material in particular we have 

noted significant aging-related microstructural and 

chemical changes when it is tested under simulated 

operating conditions. This aging is not necessarily 

deleterious, and in fact seems to improve the NOx 

sensing performance. The findings are significant, 

however, in that they demonstrate the need for 

careful pre-aging (i.e., burn-in) of the sensors before 

use and demonstrate that performance characteristics 

reported prior to aging may not be representative of 

real-world sensor performance. 

References 

1. N. Miura, G. Lu, and N. Yamazoe, Solid State 

Ionics 136–137, 533 (2000). 

2. W. Gopel, R. Gotz, and M. Rosch, Solid State 

Ionics 136–137, 519 (2001). 

3. F. Menil, V. Coillard, and C. Lucat, Sensors and 

Actuators B 67, 1 (2000). 

4. J. Kaspar, P. Fornasiero, and N. Hickey, Catal. 

Today 77, 419 (2003). 

5. M. Zheng, G.T. Reader, and J.G. Hawley, 

Energy Convers. Management 45, 883 (2004). 

6. D.L. West, F.C. Montgomery, and T.R. 

Armstrong, Sensors & Actuators B 106, 758 

(2005). 

7. I.V. Bruser, U. Lawrenz, S. Jacobs, 

H.-H. Mobius, and U. Schonauer, Solid State 

Phenomena 39–40, 269 (1994). 

8. M.L. Grilli, E.D. Bartonlomeo, and E. Traversa, 

J. Electrochem. Soc. 148, H98 (2002). 

9. S.P. Jiang and J.G. Love, Solid State Ionics 158, 

45 (2003). 

10. H.Y. Lee, W.S. Cho, S.M. Oh, H.D. Wiemhöfer, 

and W. Göpel, J. Electrochem. Soc. 142, 2659 

(1995). 

Publications/Presentations 

“Aging Studies of Sr-doped LaCrO3/YSZ/Pt 

Cell for a NOx Sensor,” presented at the 207th 

meeting of the Electrochemical Society, Quebec 

City, Canada, May 18, 2005. 

“Aging Studies of Sr-doped LaCrO3/YSZ/Pt 

Cells for an Electrochemical NOx Sensor,” in 

preparation, to be submitted to The Journal of the 

Electrochemical Society. 

41 
FY 2005 Progress Report Automotive Propulsion Materials 

D. Hydrogen Compatibility of Materials for Automotive Applications 

James Holbery, Chuck Henager, Stan Pitman, Russ Jones, and Thomas Gallant 

Pacific Northwest National Laboratory 

P.O. Box 999 

Richland, Washington 99354 

(509) 375-3686; fax: (509) 375-2379; e-mail: james.holbery@pnl.gov 

Peter Blau, Laura Riester 

Oak Ridge National Laboratory 

Oak Ridge, TN 37831 

(865) 574-5377; fax: (865) 574-6918; e-mail: blaupj@ornl.gov 

DOE Materials Technologies Team Leader: Rogelio Sullivan 

(202) 586-8042; fax: (202) 586-1600; e-mail: rogelio.sullivan@ee.doe.gov 

Contractor: Pacific Northwest National Laboratory, Richland, Washington 

Prime Contract No.: DE AC06 76RLO 1830 

Objectives 

• Measure the friction and wear characteristics of injector materials in hydrogen environments. 

• Measure the performance of actuators and actuator materials in hydrogen environments. 

Approach 

• Use atomic force microscopy (AFM) and nanomechanical measuring techniques to evaluate the friction and 

wear characteristics of injector materials in hydrogen environments. 

• Perform in situ voltage/current pulses of fuel injector actuators in high-pressure hydrogen gas simulating engine 

conditions. 

Accomplishments 

• Completed the design, construction, safety check, and full operation of a high-pressure hydrogen test apparatus 

for actuator and injector materials, including a complete system for in-situ monitoring of piezo materials. 

• Conducted AFM and nanomechanical testing on “as-received” and hydrogen-exposed injector materials and 

showed that the friction coefficient increases with H2 exposure, largely as a result of surface facet formation, 

and is not limited to one material system. 

• Conducted multi-pass friction tests at constant load that indicate a significant increase in coefficient of friction, 

with indications of wear track and third-body contributions. 

Future Direction 

• Evaluate the durability of needle-nozzle engine materials as a result of service within a hydrogen environment, 

including hydrogen diffusion, barrier coatings, and material selection. 

• Evaluate new coatings, alloys, and piezo barrier materials under hydrogen service environments. 

• Evaluate sliding and impact wear, with special attention to surface galling, to determine needle-nozzle longterm durability. 

• Develop concepts for an engineering wear simulation test in high-pressure hydrogen. 

42
Automotive Propulsion Materials 

Introduction 

The friction and wear characteristics of metallic 

materials depend largely on surface oxide films. 

However, a hydrogen environment is chemically 

reducing, so the loss of the surface oxide by wear 

will result in bare surface contact and an increase in 

friction and wear. An exploratory study was undertaken to determine the frictional behavior of metals 

in a hydrogen environment using in situ AFM/ 

friction force microscopy and nanoindentation– 

nanoscratch measurement. Measurements were 

made in a hydrogen environment on metallic 

injector materials used by Westport Innovations, Inc. 

and materials analysis was conducted on the relevant 

material features. 

Piezoelectric actuators use the piezoelectric 

materials PZT, which is lead and zirconium titanate 

embedded in epoxy or other polymer materials. 

Potential degradation mechanisms include changes 

in the capacitance1–3 and cracking4 of the PZT 

material, separation of the PZT wafers within the 

stack, loss of electrical contact, or degradation of the 

epoxy or polymer holding the PZT materials. Any of 

these processes will result in loss of performance. 

Tests were conducted on actuators and PZT material 

in a high-pressure hydrogen environment at up to 

100°C, typical of conditions in engine applications. 

The actuators were monitored during in situ voltage 

cycling that matches the actuator conditions. 

Surface Properties of Injector Materials in 

Hydrogen 

Hydrogen internal combustion engines have four 

primary types of fueling systems, including 

carburetion, throttle body-injection, intake port fuel 

injection (PFI), and direct in-cylinder injection. 

While PFI offers very good cylinder-to-cylinder fuel 

distribution, minimum fuel charge in the intake 

manifold, and low cost, there is still much to learn 

pertaining to the details of using PFI equipment for 

direct injection in a hydrogen fuel environment.5 

This study aims to better understand and 

quantify the mechanisms that determine friction 

coefficient and surface properties of injector needles 

and nozzles within a 100% hydrogen service 

environment by comparing hydrogen-exposed and 

“as-received” actuator materials. These are needle 

and nozzle designs; the corresponding material 

information is listed in Table 1 for two materials, J2 

and S1. 

FY 2005 Progress Report 

Table 1. List of injectors and corresponding 

material specifics in the test matrix 

Injector 

name Component Material 

No. S1 Needle Carburizing steel 

No. S1 Nozzle Carburizing steel 

No. J2 Needle AISI M2 

No. J2 Nozzle AISI H13 

Using a combination of nano-mechanical measurement techniques combined with experimental 

analysis, we analyzed the effects of hydrogen on 

needle and nozzle materials with the purpose of 

determining sliding contact degradation and 

extended wear behavior. 

Nanomechanics 

Nanoindentation and scratch friction measurements were conducted with a conical diamond tip 

with a tip radius of approximately 400 nm. Working 

in conjunction with Peter Blau and Laura Reister of 

Oak Ridge National Laboratory, we used a state-ofthe-art Hysitron® Nanoscratch® apparatus to 

determine localized nano-mechanical properties 

(hardness, modulus of elasticity, and friction) of 

cross-sectioned injector parts. A series of tests were 

conducted that enabled us to quantify surface 

mechanical and friction properties of the two 

injector materials. Surface properties were 

determined with a 200-nm-radius diamond tip 

mounted to a precision transducer, both before and 

after hydrogen exposure. In addition, AFM and 

precision profilometry were deployed to characterize 

surface topography. 

A JEOL scanning electron microscope (SEM) 

with an X-ray energy dispersive spectrometer (EDS) 

and attached Cambridge backscattered electron 

detector was used to characterize surface topology 

and elemental constituents. 

Samples were exposed to hydrogen by including 

these samples in the autoclave pressure vessel at the 

same time piezo actuator tests were conducted. 

Images in Figures 1 and 2 show the pressure 

vessel apparatus. These samples were placed in steel 

cups and exposed for the following schedule: 

• 21 h at 2850 psi ambient temperature 

• 5 h at 4500 psi ambient temperature 

• 21 h at 4500 psi 100°C 

43
FY 2005 Progress Report Automotive Propulsion Materials 

Figure 1. High-pressure autoclave and 

control systems. 

Figure 2. High-pressure autoclave in 

open position. 

Samples were removed from the vessel after 

47 h and stored in liquid nitrogen until tests were 

performed. 

Results and Discussion 

Surface Analysis of Injector Materials 

Both designs were imaged via SEM with EDS 

analysis, and the surface roughness was characterized using both AFM and a Taylor-Hobson 

profilometer.6 

Generally, the J2 surface was non-uniform. 

Areas along the needle and nozzle exhibit a more 

uniform surface roughness (Table 2) than the 

transition area of the nozzle, which contains several 

severe pits that EDS indicates have large portions of 

Table 2. Output of surface roughness from 

Taylor–Hobson profilometer 

Part 

number Description 

Ra 

(μm) 

Slope 

(degrees) 

Nozzle—short 

end, near impact 

A. J2 zone 0.16 −2.75 

Nozzle— 

B. J2 transition 0.16 −1.40 

Nozzle—long 

end, near top of 

C. J2 injector 0.04 −0.42 

A. S1 Nozzle—middle 0.19 −0.12 

B. S1 Nozzle—end 0.07 −0.58 

C. S1 Needle—middle 0.19 −0.34 

D. S1 Needle—end 0.06 −2.04 

copper. The S1 surface is very uniform, with the 

roughness of the impact zone exhibiting fewer 

machine marks than the middle of the needle-nozzle 

sliding surface (Table 2). The roughness of each 

nozzle is highly dependent upon the location of the 

measurement. 

Figure 3 illustrates the surface of the S1 injector 

seat depicted in both the AFM and SEM images (top 

and bottom, respectively). Machine marks are 

clearly visible on the surface; the peak-to-peak 

distance is approximately 6 μm, with a surface RMS 

reported in the AFM image of 87 nm. The entire 

surface RMS is between 80 and 100 nm. EDS 

analysis (not shown) indicates constituents typical of 

carburizing steel. 

Figure 4 indicates the surface topography of the 

S1 nozzle before exposure to hydrogen, with clearly 

defined machine marks. Figure 5 indicates the S1 

needle after hydrogen exposure and the surface 

facets that formed in a localized region. 

The J2 surface appears to have been pitted by 

the effects of corrosion at the end of the needle/ 

nozzle impact zone (Figure 6). The SEM image of 

the nozzle seat illustrates the severity of the 

condition (scale bar at the lower left of the image is 

200 μm). Pits vary in size, with an apparent depth of 

up to several microns. 

The EDS analysis clearly indicates there is a 

high concentration of copper on the surface, as high 

as 30 wt % in some cases. The origin of this copper, 

we surmise, is the plating process, although we 

cannot be certain. It will have an adverse effect on 

both the performance and long-term stability of the 

injector. 

44
Automotive Propulsion Materials FY 2005 Progress Report 

Figure 3. S1 Seat AFM image (top) and SEM 

image (bottom). Surface exhibits an RMS 

roughness of 87.3 nm, Ra = 17.52 nm, striations 

of approximately 6 μm peak-to-peak. EDS results 

indicate the primary material constituent is iron. 

Figure 5. An S1 needle after exposure to 

hydrogen. The image indicates repeatable 

crystallites/facets on the surface, although 

they appear in a localized region. The 

image size is 13×13 μm. 

Figure 4. S1 nozzle image obtained with a 

scanning diamond tip via the Hysitron 

Nanoscratch® instrument. The image is not 

as clear as a true AFM, but it indicates 

nanoscale features. The image is 

13×13 μm. 

Weight % 

Element Weight% Std. dev Atomic % 

Si K 0.81 0.11 1.63 

V K 0.92 0.11 1.02 

Cr K 5.13 0.16 5.59 

Fe K 73.84 0.47 74.94 

Cu K 17.97 0.40 16.03 

Mo L 1.34 0.29 0.79 

Totals 100.00 

Figure 6. SEM/EDAX results from the J2 

nozzle. Note the surface pitting due to 

corrosion; image scale bar is 200 μm. 

Images of the hydrogen-exposed surfaces reveal 

unique features that developed. Figure 7 showing the 

J2 needle indicates that faceting features consistently 

formed across the surface. 

45
FY 2005 Progress Report Automotive Propulsion Materials 

Figure 8. This image of the J2 nozzle 

illustrates a layered faceted feature formation 

on the surface after exposure to hydrogen. 

Image size is 15×15 μm. 

Figure 9. EDS of J2 needle surface after 

hydrogen exposure. The EDS plot reflects the 

elemental constituents in accurate proportions. 

Distinct differences are a result of the effect of 

hydrogen exposure on each material surface. As an 

example, the S1 nozzle shows a distinct decrease in 

modulus as the result of hydrogen exposure; 

however, hardness shows a less dramatic effect. The 

correlation with friction will be addressed in the next 

section. 

Figure 7. Images depict the J2 needle, 

both as-received (top) and after 47-h 

hydrogen exposure (bottom). Images are 

25×25 μm. Peak height maximum is 

4–5 μm. 

These features need to be investigated further, 

using high-resolution SEM and TEM combined 

with field ion beam spectroscopy to verify the 

composition. Similar features, although far less 

dense, appear in Figure 8 on the J2 nozzle. 

Figure 9 illustrate EDS images of the J2 needle 

with particular emphasis on the facet structure, 

which appears to be a combination of molybdenum 

and tungsten. This implies formation of 

molybdenum (5% in AISI M2 steel) and tungsten 

(6.25% in AISI M2, WCC coating) occurs under 

these test conditions. 

Nanoindentation 

Nanoindentation measurements were performed 

in similar areas of the S1 and J2 needle and nozzle. 

Table 3 is a compilation of the measurements taken. 

46
Automotive Propulsion Materials 

Table 3. Surface mechanical properties of the S1 

and J2 needle-nozzle area. Each zone was 

measured with 9 indents, each indent in a 

3×3 grid, a minimum of 5 mm apart. 

Er Std. Std. 

Sample (GPa) dev. H(GPa) dev. 

S1-needle 197 11.6 11.2 1.0 

S1-H2 needle 214 34.4 15.8 4.3 

S1-nozzle 107 28.9 3.2 0.6 

S1-H2 nozzle 42 17.5 2.5 0.3 

J2-needle 178 16.1 7.9 0.8 

J2-H2 needle 190 16.0 8.2 1.7 

J2-nozzle - - - -

J2-H2 nozzle 216 30.1 13.0 2.1 

Friction Measurements 

Friction measurements were generated using a 

Hysitron Nanoscratch apparatus fixed with a 200-nm 

radius diamond tip. Scratch testing represents a test 

form where some degree of controlled abrasive wear 

or adhesion between one material medium and 

another can be quantified under controlled 

conditions. In conventional scratch testing, a 

diamond stylus is drawn across a sample under 

either a constant or progressively increasing normal 

load; in these experiments, a constant load was 

employed. While the test can be used to measure the 

adhesion of a coating to a substrate, in these tests, 

we used the technique to measure the friction 

coefficient between the stylus and surface and, more 

important, to measure the change of friction under 

repeated stylus-surface passes. 

Friction coefficient is determined from 

Amoton’s First Law, which indicates that friction 

coefficient is defined as lateral force divided by the 

normal force as follows: 

μ = FL/FN . 

Findings: Single-pass measurements 

Single-pass friction measurements were performed on all samples. The measurements indicate 

differences as a function of material and exposure to 

hydrogen. A single-pass test, depending upon the 

load, will leave a scribe mark on the surface, as 

depicted in Figure 10. The applied normal force will 

dictate the amount of material removed from the 

scratch track. 

A summary of the friction coefficient of each 

material tested is in Table 4. Figure 11 illustrates the 

friction coefficient of the S1 nozzle in “as-received” 

FY 2005 Progress Report 

condition. The data output of 10 tests on the S1 asreceived nozzle is illustrated in Figure 12. The 

estimated friction coefficient is 0.39. 

Findings: Multi-pass measurements 

A multi-pass measurement technique was developed 

in the course of this project. This entailed 

programming the Hysitron Nanoscratch instrument 

to perform repeated, lateral passes at a constant load 

to model the sliding friction between the needle and 

nozzle. Because of time constraints, we were able to 

perform only sets of 20 passes; complete results are 

listed in Table 5. Tests were performed with a 

diamond stylus, and the actual friction between 

needle-nozzle may behave differently. Multi-pass 

tests were conducted on all surfaces at a constant 

load; on some materials, the friction coefficient was 

Figure 10. Single scratch on S1 nozzle 

after exposure to hydrogen. Image is 

15×15 μm. Note the facet formation on the 

left of the scratch. 

Table 4. Summary of the friction coefficient 

values of both J2 and S1 samples. 

Friction 

Material coefficient 

J2-needle as-received 0.24 

J2-needle hydrogen exposed 0.26 

J2-nozzle as-received 0.18 

J2-nozzle hydrogen exposed 0.27 

S1-needle as-received 0.22 

S1-needle hydrogen exposed 0.30 

S1-nozzle as-received 0.34 

S1-nozzle hydrogen exposed 0.39 

47
FY 2005 Progress Report Automotive Propulsion Materials 

Comparison of Multi-Pass Friction Coefficient, Duap Needle 

Red H2 Values, Blue "As Received" 

1 

0.9 

0.8 

Friction Coefficient 

0.7 

0.6 

0.5 

0.4 

0.3 

0.2 

0.1 

0 

Figure 11. S1 needle scratch

pattern. Image is 15×15 μm.

Several scratches were made on

the sample at various loading

conditions. 

Duap Nozzle - H2 Exposure, Multiple Tests 

1 

0.9 

0.8 

0.7 

Figure 13. Multi-pass measurement of the S1 needle, 

both as-received (solid line) and after hydrogen exposure 

(dots). The friction coefficient is estimated to increase by 

0.13 as a result of the hydrogen exposure.

For example, Figure 13 indicates that the S1 

needle multi-pass experiment is relatively constant, 

regardless of the exposed condition. While the 

overall friction coefficient increased by 0.13, the 

value of each condition was constant. On the other 

hand, a multi-pass measurement on the J2 nozzle in 

Friction Coefficeint 0.6 the as-received condition reveals that there is an 0.5 increase in friction coefficient with each successive 0.4 pass. Perhaps this increase in friction coefficient is 0.3 

0.2 due to the removal of material resulting in greater 0.1 depth of penetration and subsequently more and 0 

more surface oxides and hydrogen-exposed 

Figure 12. Comparison of the S1 nozzle friction coeffi­ materials removed. cient in as-received condition. These are four plots taken

at 250 mN. Friction coefficient is estimated to be 0.39.

Table 5. Summary of the multi-pass friction 

coefficient values of both J2 and S1 samples 

Material Friction coefficient 

J2-needle as-received 0.53* 

J2-needle hydrogen exposed 0.51* 

J2-nozzle as-received 0.55 

J2-nozzle hydrogen exposed 0.73* 

S1-needle as-received 0.45 

S1-needle hydrogen exposed 0.58 

S1-nozzle as-received 0.53 

S1-nozzle hydrogen exposed 0.68 

* One sample data point; additional test necessary.

constant, while on others the friction coefficient in 

creased with each successive pass. This likely

indicates that the diffusion rate of hydrogen is quite 

different in the materials tested, as well as the 

change in surface hardness as a function of 

penetration. 

In the course of this project, Pacific Northwest 

National Laboratory (PNNL) researchers in 

conjunction with Oak Ridge National Laboratory

researchers established nano- and micro-scale 

techniques to measure the friction of sliding 

hydrogen injector interfaces. Using a hydrogenspecific pressure vessel developed at PNNL during 

the course of this project, injector materials supplied 

by Westport Innovations were exposed to 47 h in a 

pressurized hydrogen environment, and the surfaces 

were subsequently analyzed using SEM, EDS, 

AFM, nanoindentation, and nanoscratch techniques. 

A summary of the material properties tested is 

provided in Table 6. 

Material surface phenomena were discovered on 

the surfaces that appear to be the result of facet 

formation composed of a molybdenum-tungsten 

compound. They range from 100 nm to 5 μm in

diameter and up to 4 μm in height. At this time, the 

structure is not well defined, and the rate of 

48
Automotive Propulsion Materials FY 2005 Progress Report 

Table 6. Summary of friction coefficient and surface property data of J2 and S1 samples. 

(*) indicates one sample data point. 

Er H Friction Multi-pass 

Sample (GPa) (GPa) coefficient friction Comments 

S1 needle as-received 197 11.2 0.22 0.45 

S1 needle hydrogen exposed 214 15.8 0.30 0.58 

No facets prior to 

S1 nozzle as-received 107 3.2 0.34 0.53 hydrogen 

S1 nozzle hydrogen-exposed 42 2.5 0.39 0.68 Facets present 

J2 needle as-received 178 7.9 0.27 0.53* 

J2 needle hydrogen exposed 190 8.2 0.26 0.51* Facet formation 

J2 nozzle as-received – – 0.18 0.55 Copper present 

evolution is not understood. Further research is 

required to determine the nature of the crystal 

formations; the lamellar nature will require 

structural analysis to determine their exact impact on 

sliding surfaces. 

Industrial samples analyzed in the course of this 

study showed various degrees of contamination 

including copper and other species. The surface 

roughness Ra of the samples was between 0.03 and 

0.16 μm, with friction coefficients determined using 

a 200-nm radius diamond tip. Hydrogen exposure 

appears to increase slightly the friction coefficient of 

all materials. The S1 materials showed increases in 

single-pass tests of up 0.08 and 0.05 for the needle 

and nozzle, respectively. Given that the only 

decrease in friction coefficient was determined on 

the J2 needle, which maintained the greatest 

distribution of facet formation, we believe the 

formation of these facets may assist in stabilizing the 

friction coefficient of the surface. This trend was 

also present in the case of the multi-pass testing, 

although with only a single data point. Further 

testing is necessary to better understand this material 

characteristic. 

Multi-pass friction testing indicates that for the 

S1 materials—the only set fully tested with the 

technique developed herein—under a 100-mN load, 

the friction coefficient increases by 0.13 and 0.15 for 

the needle and nozzle, respectively. Further testing 

and characterization is needed to support our 

findings. This will require a dedicated effort and will 

include model sample substrates that will add to the 

body of data created thus far on industrial samples. 

References 

1. W.P. Chen, X.P. Jian, Y. Wang, Z. Peng, 

H.L.W. Chan, “Water-Induced Degradation of 

Barium Titanate Ceramics Studied by 

Electrochemical Hydrogen Charging,” J. of the 

American Ceramic Society 86 (4), 735–737 

(April 2003). 

2. T. Shimada, C. Wen, N. Taniguchi, J. Otomo, 

H. Takahashi, “The High-Temperature Proton 

Conductor BaZr0.4Ce0.4In0.2O3-alpha,” J. of 

Power Sources 131 (1–2), 289–292 (May 14, 

2004). 

3. D.J. Jung, F.D. Morrison, M. Dawber, 

H.H. Kim, K. Kim, J.F. Scott, “Effect of 

Microgeometry on Switch and Transport in 

Lead Zironcate Titanate Capacitors: 

Implications for Etching of Nano-Ferritics,” 

Journal of Applied Physics 95 (9), 4968–4975 

(May 1, 2004). 

4. Y. Wang, X. Peng, W.Y. Chu, Y.J. Su, 

L.J. Qiao, K.W. Gao, “Anisotropy of Hydrogen 

Fissure and Hydrogen-Induced Delayed Fracture 

of a PZT Ferroelectric Ceramic,” in Proceedings 

of the 2nd International Conference on 

Environment Induced Cracking of Metals, 

October 2004, Banff, Canada, in press. 

5. W.F. Stockhausen, R.J. Natkin, D.M. Kabat, 

L. Reams, X. Tang, S. Hashemi, 

S.J. Szwabowski, V.P. Zanardelli, “Ford P2000 

Hydrogen Engine Design and Vehicle 

Development Program,” SAE 2002-01-0240, 

SAE World Congress, Detroit, March 4–7, 

2002. 

6. J.D. Holbery et al., “High-Pressure Hydrogen 

Effect on Sliding Contact Surfaces,” MRS paper 

Y9.4, MRS Fall Meeting, Boston, 

November 28–December 2, 2005. 

49
FY 2005 Progress Report Automotive Propulsion Materials 

E. Advanced Materials Development through Computational Design for HCCI 

Engine Applications 

Vinod K. Sikka, G. (Murali) Muralidharan, and Paul C. Becker 

Metals and Ceramics Division 

(865)574-5112;, fax: (865) 574-4357; e-mail: sikkavk@ornl.gov 

Bruce G. Bunting 

Engineering Science and Technology Division 

(865) 946-1512; fax: (865) 946-354;, e-mail: buntingbg@ornl.gov 

DOE Materials Technologies Team Leader: Rogelio Sullivan 

(202) 586-8042; fax: (202) 586-1600; e-mail: rogelio.sullivan@ee.doe.gov 

ORNL Technical Advisor: David Stinton 

(865) 574-4556; fax: (865) 241-0411; e-mail: stintondp@ornl.gov 

Contractor: Oak Ridge National Laboratory, Oak Ridge, Tennessee 

Prime Contract No.: DE-AC05-00OR22725 

Objectives 

• Identify and catalog the materials operating conditions in homogeneous charge compression-ignition (HCCI) 

engines and use computational design concepts to develop advanced materials for such applications. 

• Interact with designers of HCCI engines and manufacturers of components in order to identify the components 

that will be affected by the harsh operating conditions resulting from the HCCI design. 

• Identify the highest-priority component(s) that are critical to the implementation of the HCCI concept. 

Approach 

• Identify engine components, currently used materials, and current operating conditions and compare them with 

the expected component operating conditions for HCCI engines. 

• Demonstrate the feasibility of the “materials by design” approach for the highest-priority item. Improve 

material performance for HCCI application through computational modeling and experimental validation. 

Accomplishments 

• Based on discussion with seven automotive and truck companies, identified four improved materials 

needs/opportunities in support of advanced engine concepts such as HCCI [i.e., aluminum for charge air 

coolers, cast irons for exhaust manifolds, nickel (Ni) alloys for exhaust valves, and alloy steels for fuel 

injectors]. 

• Identified opportunities for leveraging DOE funds. Collaborations have been established with two companies to 

work on two of the materials needs. 

• Completed initial calculations of materials development through computational design for Ni-based alloy 

compositions. The weight percent of γ′ shows a qualitative agreement with published fatigue data. 

50
Automotive Propulsion Materials FY 2005 Progress Report 

Future Direction 

• Communicate with automotive companies, Diesel Cross-Cut Team, FreedomCAR, and 21st Century Truck on 

the progress made through computational design. 

• Develop correlation of phases with properties. 

Introduction 

There has been an increasing interest in HCCI 

combustion in recent years because of its potential to 

increase engine combustion efficiency and reduce 

emissions. However, the use of HCCI combustion 

will subject the engine components to significantly 

higher temperatures and pressures. The temperatures 

for diesel engines will reach over 1600°F, and 

pressure may reach > 2000 psi, which is 

approximately four times that of the normal 

combustion engine. Such severe engine operating 

conditions will require a significant improvement in 

materials performance in order to take advantage of 

the HCCI engine concept. This project deals with 

identifying materials requirements for HCCI engines 

for automotive and truck applications and the 

development of advanced, yet cost-effective 

materials through computational design. 

“Materials by design” is an Oak Ridge National 

Laboratory (ORNL) concept and collection of 

materials-related techniques involving modeling, 

correlation, and materials modification. The premise 

behind materials by design is that mechanical 

properties are correlated to microstructure and phase 

chemistry. The phase composition and 

microstructure can be achieved through 

thermodynamic equilibrium or through nonequilibrium techniques such as quenching, rapid 

casting solidification, or mechanical working. These 

characteristics can then be correlated to desired 

mechanical properties through equilibrium 

thermodynamics or through a variety of correlation 

techniques. These correlations or modeling allow 

untested compositions or treatments to be modeled 

so that desired trends can be rapidly established. 

Small heats of targeted materials can then be 

processed to confirm the modeled properties and to 

broaden the correlation data base. 

Finally, there are several techniques such as 

magnetic processing or low-temperature carburizing 

that can be applied to allow further modification and 

optimization of desired properties. Materials by 

design is ideally suited to cast and heavily thermally 

processed materials such as stainless steels, Ni 

alloys, cast irons, alloy steels, and brazed wrought 

aluminum alloys and has been successfully applied 

in such diverse areas as high-temperature furnace 

components, exhaust valves, exhaust manifolds, and 

tube fittings. Figure 1 and Table 1 provide an outline 

of the materials by design approach and a summary 

of the techniques that can be applied. 

Microstructural 

Characterization 

Property 

Measurements 

Thermodynamic 

Modeling 

Understand Behavior of 

Existing Materials 

VALIDATION 

Microstructural 

Characterization 

Property 

Measurements 

Thermodynamic 

Modeling 

Develop New 

Compositions 

PREDICTION 

Microstructural

Characterization

Property

Measurements

Thermodynamic

Modeling

Understand Behavior of

Existing Materials

VALIDATION

Microstructural

Characterization

Property

Measurements

Thermodynamic

Modeling

Understand Behavior of

Existing Materials

VALIDATION

Microstructural

Characterization

Property

Measurements

Thermodynamic

Modeling

Develop New

Compositions

PREDICTION

Microstructural

Characterization

Property

Measurements

Thermodynamic

Modeling

Develop New

Compositions

PREDICTION

Figure 1. Overall approach for Materials by Design. 

In our approach, we examined critical heavyduty diesel engine materials and identified means to 

reduce their cost for acceptance in HCCI 

applications. This was accomplished through the 

following tasks: 

Task 1. Identify critical material 

requirements for HCCI engines based on their 

operating conditions. The outcome of this task will 

be accomplished through interactions with advanced 

engine and component designers. The interactions 

will include personal visits to six companies: 

Caterpillar, Cummins Engine, Deer, International 

Truck, Eaton Corp., and General Motors. Visits will 

be supplemented by literature search, review of 

advanced engine design studies, and further 

discussion following the visits. The key outcome 

from this task will include (1) identifying operating 

conditions for advanced engine concepts with a 

focus on the HCCI concept; (2) identifying 

components most affected by these operating 

conditions; (3) identifying currently used materials, 

new requirements, and performance targets; and 

(4) ranking the highest-priority items for study by 

the materials by design approach. 

51
FY 2005 Progress Report Automotive Propulsion Materials 

Table 1. ORNL Materials by Design toolbox 

ORNL Materials by Design Toolbox 

Modeling Experimentation Characterization 

Thermodynamic modeling of Ultra-high-gauss magnetic Advanced microscopy 

material properties vs alloy stabilization of alloy steels techniques 

composition 

Neural-network modeling of Low-temperature gas X- ray and neutron scattering 

diverse, nonlinear materials carburization of finished 

properties and process components Surface and bulk property 

variations measuring techniques 

Ability to produce small 

Detailed microstructure quantities of materials and 

based empirical modeling fabricate them into test bars for 

property measurements and 

Non-equilibrium modeling of production of prototype 

solidified structures components by a variety of 

methods, including sand and 

Extrapolation of properties die casting, extrusion, forging 

from simple alloy systems to and rolling 

complex systems using 

interaction parameters 

Task 2. Demonstrate the feasibility of output based on computational analysis for 

materials by design approach for the highest- validation. 

priority item. In this task, we will identify the 2. Scale up the validated composition into 20- to 

details of the currently used material for the highest- 100-lb heats and cast them into ingots for 

priority item. This will include material processing trials. In most cases, the material is 

compositions, processing methods, mechanical expected to be used in the wrought condition. 

properties, corrosion properties, and cost. However, if it is to be used in the cast condition, 

Based on the available mechanical properties we will save part of the ingots for analysis of asdata, microstructural analysis, and thermodynamic cast properties. 

phase stability calculations, we will identify the 3. Subject cast ingots to processing steps that are 

underlying mechanism that delivers the current currently used by industry. Develop optimum 

properties. processing and heat-treatment conditions to 

Task 3. Improve material performance for obtain the desired microstructure. 

HCCI application through computational 4. Carry out microstructural analysis and 

modeling and experimental validation. In this mechanical properties analysis on the material 

task, we will use computational modeling (key basis processed and heat-treated with optimum 

for the material by design concept) to identify conditions. 

compositions that will deliver the desired phases for 5. Prepare autotype components for HCCI engine 

two purposes: improving the property performance tests. 

and finding alternatives to reduce cost for current 

and improved performance. The outcome of the A strong interaction with industrial partners will 

analysis will be validated through experimentation. occur during all three tasks. This interaction is 

The validation will be carried out in the following expected to result in the rapid transfer of materials 

steps: improvement from this project to industry for use in 

HCCI and other advanced engine concepts. 

1. Prepare compositions identified based on 

computational design in 1-lb heats for 

microstructural analysis and very limited 

property determination; compare the results with 

52
Automotive Propulsion Materials 

Results 

The scope of this project was presented to the 

Diesel Cross-Cut Team that represents experts from 

the FreedomCAR and 21st Century Truck programs. 

Seven companies were interviewed. The companies 

interviewed, their business, and type of interview are 

summarized in Table 2. The following needs and 

opportunities were identified based on the interviews 

to date: 

1. High-strength, thermally stable, corrosionresistant aluminum for charge air coolers. 

2. Optimization of Ni alloys for exhaust valves to 

reduce cost, extend high-temperature 

performance, and improve high-temperature 

fatigue life. 

3. For cast irons, effect of alloying elements on 

cost, high-temperature capability, and greater 

crack resistance under temperature and stress 

cycling. 

4. Wear-resistant, higher-strength, highertemperature, capable alloy steels for fuel 

injection components. 

Table 2. List of companies interviewed. 

Company Business 

Type of 

interview 

Cummins Diesel engines Meeting at ORNL 

Caterpillar Diesel engines, 

off-road 

equipment 

Meeting at 

Caterpillar plus 

white paper 

International Engines and 

vehicles 

E-mail interviews 

MIT Sloan 

Automotive 

Lab 

Engine and 

Combustion 

reserach 

Off-site 

meeting 

General 

Motors 

Powertrain 

Vehicle 

manufacturing 

Meeting at GM 

Eaton Valves and value 

train components, 

EGR 

Meeting at Eaton 

Delphi Diesel 

Systems 

(formerly 

Lucas) 

Diesel fuel 

injection 

Off-site meeting 

FY 2005 Progress Report 

Most of the needs identified are not showstoppers; but opportunities for significant 

improvements are available through incremental 

advances in materials, and research capability at 

ORNL can help speed this process. We have also 

identified leveraging opportunities for funds-in 

projects or substantial cost share with interviewees 

in the areas of cast exhaust manifolds and Ni alloy 

use for exhaust valves. There is an opportunity for 

additional interaction with industry through new 

DOE-funded high-efficiency clean combustion 

partnerships. 

In addition to the materials needs listed earlier, 

comments from our interactions with interviewees 

indicated that light-duty truck needs are not the same 

as heavy-duty truck concerns. The specific 

differences are listed in Table 3. 

Table 3. Differences in needs for heavy- and light-duty 

trucks 

Heavy duty Light duty 

Heavy-duty engines are Light-duty engines are 

designed to run at full designed to run at full 

load a large portion of load only briefly and 

time with an average load operate with an average 

factor of up to 70%. load factor of about 20%. 

Emissions certification for Emissions certification for 

heavy duty requires light duty is done using a 

steady state full-load simulated driving cycle 

operation. with brief full-load 

operation. 

Heavy-duty engine Light-duty engine tuning 

designers are concerned is restrained by limits for 

mainly about structural engine harshness and 

integrity and fuel noise. 

efficiency; noise is 

secondary 

. 

Heavy-duty engines use Heavy-duty materials 

higher-performance, more could trickle down to light 

expensive materials duty if needed. 

today. 

Heavy-duty Light-duty manufacturers 

manufacturers know they are currently studying 

need higher-performance lighter-weight, lower-cost 

materials. materials, such as plastics, 

to see if HCCI will enable 

their use due to lower 

temperatures and less 

radiant heat transfer. 

53
FY 2005 Progress Report 

Initial Results from Materials Development 

through Computational Design 

As a first step to materials development through 

the computational design approach, phase 

equilibrium calculations were carried out on 

published candidate compositions of Ni-based 

alloys. The alloys used for calculations were 70Ni19Cr, IN751, and Nimonic 90A. An example of the 

phase equilibrium for IN751 [Ni-1.23-1.0Co15.5Cr-7.0Fe-0.5Mn-0.45Nb-0.5Si-0.5Ta-2.3Ti0.5W (at. %)] is shown in Figure 2. This plot shows 

the weight percent of various phases and their 

stability as a function of temperature. The γ′ phase in 

Ni-based alloys is considered to control their 

properties. The relative weight percent and the 

stability of γ′ for the three alloys investigated are 

shown in Figure 3. There is less γ′ in IN751, and it is 

stable only up to approximately 830°C. The other 

Figure 2. Phase equilibria in IN751. 

16

14

12

' 10 γ

Wt. % 8

6

4

2

0

600 700 800 900 1000 1100 

Temperature (o

C) 

IN751 

Nimonic 

70Ni-19Cr 

Figure 3. Comparison of weight percent γ′ in three Nibased alloys. 

Automotive Propulsion Materials 

two alloys have higher amounts of the γ′ phase, and 

they are stable to higher temperatures. 

Published data on fatigue properties of several 

alloys are shown in Figure 4. Comparison of the γ′

phase in Figure 3 with Figure 4 shows that there is a 

qualitative agreement between the weight percent of 

γ′ and the fatigue properties (i.e., IN751 with the 

lowest weight percent of γ′ has lower fatigue 

strength than alloy 70Ni-19Cr, which has the highest 

weight percent of γ′ (Figure 2). 

Work will continue to quantify the correlation 

between fatigue properties and phase type, and 

weight percent will be validated on experimentalsize heats of selected compositions. Results of this 

study will be shared with the industrial partner. 

Figure 4. Comparison of fatigue properties of IN751 and 

70Ni-19Cr with various alloys.

1 

Conclusions 

Seven automotive and truck companies were 

contacted. Based on discussions with these 

companies, four materials improvement needs and 

opportunities were identified in support of advanced 

engine concepts such as HCCI. 

Initial calculations of materials development 

through computational design were completed for 

three published Ni-based alloy compositions. The 

weight percent of γ′ phase shows a qualitative 

agreement with the published fatigue data for two of 

the three alloys used in the calculations. 

References 

1. K. Sato, Y. Takagi, and T. Saka, “The Progress 

of Valvetrain Design and Exhaust Valve 

Material Research for Automobiles,” in 

54
Automotive Propulsion Materials FY 2005 Progress Report 

Proceedings of the International Symposium on 

Valvetrain System Design and Materials. 

Publications/Presentations 

Vinod K. Sikka, Govindarajan Muralidharan, 

Paul C. Becker, and Bruce Bunting, “Materials for 

HCCI: A Materials by Design Approach,” 

presentation to Rogelio Sullivan of DOE, at ORNL, 

May 5, 2005. 

Vinod K. Sikka, Govindarajan Muralidharan, 

Paul C. Becker, and Bruce Bunting, “Materials for 

HCCI: A Materials by Design Approach (Revised 

on June 20, 2005),” presentation to Diesel Cross-Cut 

Team, at ORNL, July 21, 2005. 

55
FY 2005 Progress Report Automotive Propulsion Materials 

56
Automotive Propulsion Materials FY 2005 Progress Report 

APPENDIX A: ACRONYMS AND ABBREVIATIONS 

AFM atomic force microscopy 

ANL Argonne National Laboratory 

ANL–ES ANL–Energy Systems 

APS Advanced Photon Source 

APM Automotive Propulsion Materials 

ASTM American Society for Testing and Materials 

CIDI compression-ignition direct-injection 

DOE U.S. Department of Energy 

DPF diesel particulate filter 

DSC differential scanning calorimetry

EDM electrodischarge machining 

EDX energy-dispersive X-ray spectroscopy 

EE Electrical and Electronics 

EGR exhaust gas recirculation 

EN electroless nickel 

EPA Environmental Protection Agency 

EPA–NVFEL EPA National Vehicle and Fuel Emissions Laboratory 

EXAFS X-ray absorption fine structure 

FCVT FreedomCAR and Vehicle Technologies 

ffm friction force microscopy 

FTP Federal Test Protocol 

FY fiscal year 

H hardness 

H+

 hydrogen ion 

H2 hydrogen gas 

H2RV hydrogen hybrid research vehicle 

HCCI homogeneous charge compression-ignition 

I-V current-voltage 

ICS Industrial Ceramic Solutions 

ID internal diameter 

ITO tin-doped indium oxide 

LANL Los Alamos National Laboratory 

L/D length-to-diameter 

LLNL Lawrence Livermore National Laboratory 

LSC LaCoO3 

MEA membrane electrode assembly 

57
FY 2005 Progress Report Automotive Propulsion Materials 

NdFeB neodymium-iron-boron 

Nd neodymium 

Ni nickel 

NIST National Institute for Standards and Testing 

NIU Northern Illinois University 

nm nanometer, 10–9 meters 

NO nitrogen oxide, nitric oxide 

NOx oxides of nitrogen 

NVFEL National Vehicle and Fuel Emissions Laboratory 

OEM original equipment manufacturer 

OFCVT Office of FreedomCAR and Vehicle Technologies 

ORNL Oak Ridge National Laboratory 

Pd palladium 

PM permanent magnet or particulate matter 

PNNL Pacific Northwest National Laboratory 

PPS polyphenylene sulfonate 

Pt platinum 

PVOH hydroxylated polystyrene 

PZT lead zirconium titanate 

R&D research and development 

S sulfur 

Sr strontium 

SAE Society of Automotive Engineers 

SEM scanning electron microscope/scanning electron microscopy 

SNL Sandia National Laboratories 

T Tesla 

TGA thermogravimetric analysis 

WC tungsten carbide 

XPS X-ray photoelectron spectroscopy 

XRD X-ray diffraction 

YSZ yttria-stabilized zirconium 

58

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