A Strong Energy Portfolio for a Strong America

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

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

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

invests in a diverse portfolio of energy technologies.

For more information contact:

EERE Information Center

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

www.eere.energy.gov
U.S. Department of Energy 

Office of FreedomCAR and Vehicle 

Technologies 

 1000 Independence Avenue S.W. 

 Washington, DC 20585-0121 

FY 2004 

Progress Report for Automotive Propulsion 

Materials Program 

Energy Efficiency and Renewable Energy 

Office of FreedomCAR and Vehicle Technologies 

Edward Wall Program Manager 

February 2005 

Propulsion Materials FY 2004 Progress Report

iii

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 ........................ 13 

C. Carbon Foam for Cooling Power Electronics.................................................................................. 17 

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

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

A. Round Pleated Ceramic Fiber Diesel Particulate Filter Cartridge................................................... 27 

B. Fabrication of Small Fuel Injector Orifices..................................................................................... 31 

C. Electrochemical NOx Sensor for Monitoring Diesel Emissions...................................................... 37 

D. Hydrogen Compatibility of Materials for Automotive Applications............................................... 41 

4. OTHER ................................................................................................................................................. 45 

A. Proton Exchange Membrane Materials for Fuel Cell Applications 

 at Elevated Temperature.................................................................................................................. 45 

APPENDIX A: ACRONYMS AND ABBREVIATIONS....................................................................... 51 
FY 2004 Progress Report Propulsion Materials

iv
Propulsion Materials FY 2004 Progress Report 

1 

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 2004 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 2004. It also 

describes the technical barriers remaining and the future direction of the program. The FY 2004 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 May of 2001, the President’s National Energy Policy 

Development Group published the National Energy Policy 

(NEP). 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 NEP 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 longterm 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. 
FY 2004 Progress Report Propulsion Materials 

2

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 emissionscompliant CIDI engines. 

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 also initiated to develop a low-cost, higher-temperature polymer electrolyte membrane 

(PEM) capable of operating at 120°C without significant degradation due to CO poisoning. This is a 

collaborative project between Oak Ridge National Laboratory (ORNL), The University of Tennessee, and 

The University of Southern Mississippi. Funding for this project will be provided for one year only; if 

successful, the project will be transferred to the Office of Hydrogen, Fuel Cells, and Infrastructure or to 

private 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 ORNL to develop low-cost, rapid-response nitrogen oxides (NOx) 

The Propulsion Materials Program 

focuses on two applications. 
Propulsion Materials FY 2004 Progress Report 

3 

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 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 2004 

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 2004 featured significant advancements in both materials 

program areas. The following section highlights some of these 

noteworthy accomplishments. 

Power Electronics 

High-power electronic components such as power modules and 

computer chips being developed for hybrid electric and fuel cell 

vehicles have ever-growing power requirements (see the graph). 

Dissipation of the heat generated by these devices in hybrid electric 

vehicles often requires an additional cooling loop and water-cooled 

heat sink to prevent overheating and failure of the devices. The 

increasing power requirements of electronic devices require that 

more-sophisticated heat sinks be developed to keep the temperature 

of the electronics below about 120°C. High-thermal-conductivity, 

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 

sinks 

 Ford Scientific Research Laboratory 

 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 
FY 2004 Progress Report Propulsion Materials 

4

high-surface-area carbon foam is an innovative new material that offers 

great potential for advanced heat sinks and heat spreaders. 

 

Porous carbon foam developed at ORNL has an extremely high specific 

conductivity and an interconnected internal structure that potentially 

will allow reduction of the thermal resistance of heat transfer devices. 

Measured cooling rates from a prototype air-water radiator made of 

carbon foam fins confirm that it can reduce the air-side thermal 

resistance. During FY 2003/2004, a thermal engineering model to 

represent heat transfer from porous carbon foam was developed for use 

in design processes for heat exchangers with finned tubes. 

Characteristic parameters for carbon foam geometries—exposed surface 

absolute roughness, exposed surface area factor, effective thermal 

conductivity, surface-area-to-volume ratio and permeability—are calculated with a simple geometric model 

of a unit cube with a spherical void surrounded by carbon-foam ligaments. The air-side thermal resistance is 

calculated with an engineering model derived from conventional correlations that are extended to represent 

the effects of the rough, porous foam. 

During FY 2004, the use of a similar engineering model developed at the University of Western Ontario and 

tested at ORNL led to the consideration of an alternative design in which all of the cooling air is forced 

through a thin cylinder of foam (see heat sink designs). Calculations predict that this simple configuration 

should dissipate approximately 2× the heat dissipated by conventional heat sinks and aluminum foam devices 

of similar design. Prototype devices will be built and tested in FY 2005 to verify the designs. Subsequently, it 

appears that the continued use of models to investigate and develop new carbon foam configurations will be 

valuable in meeting the increased demand for higher, more efficient heat dissipation. 

Advanced Combustion 

Engine and Emissions 

R&D 

In addition to particulate 

emissions, NOx gaseous 

pollutants in tailpipe emissions 

are becoming increasingly 

regulated. Reduction of NOx

emissions is an important issue 

for both CIDI and lean-burn 

gasoline engines. Several 

technologies are being 

developed to reduce NOx

emissions, including the lean NOx trap and urea injection systems. Regardless of the method used, accurate 

and durable NOx sensors will be needed for on-board diagnostics to monitor NOx exhaust levels and for 

feedback engine control systems to minimize NOx emissions. Electrochemical solid state NOx sensors based 

on oxide ceramics are being developed at LLNL in collaboration with ORNL and Ford. Prototype sensors 

have shown initially promising sensing characteristics, and ongoing work is being performed to demonstrate 

the viability of the sensor concept. 

Graphite foam material developed 

at ORNL 
Propulsion Materials FY 2004 Progress Report 

5 

Work conducted at LLNL during FY 2004 concentrated on evaluating and characterizing the aging process 

for the sensors. The sensors use yttria-stabilized zirconia, an oxygen-ion-conducting ceramic, for the 

electrolyte and porous metal oxides for the electrodes. Scanning electron microscopy (SEM), X-ray 

diffraction (XRD), and X-ray photoelectron 

spectroscopy (XPS) have been used to evaluate the 

changes occurring within the electrode materials, and 

at the electrode/electrolyte interfaces, after extended 

operation. SEM and XRD indicate coarsening of the 

electrode microstructure driven by the electrochemical 

process. This is shown in the figure at left, where there 

is clearly a larger average particle size after aging. 

XPS shows changes in the surface stoichiometry of the 

electrode material. These changes in the electrodes can 

cause drifting of the sensor response during the first 

50–100 hours of operation, implying a minimum 

“burn-in” that must be achieved before the sensors can provide stable results. Ongoing work is directed 

toward developing a better understanding of this aging process, longer-term aging effects, and sensing 

mechanisms. 

High-Temperature Polymer Electrolyte Membrane 

Robust, highly conductive, and inexpensive, PEMs allow practical and reliable fuel cell operation at elevated 

temperatures. The performance of fuel cells is currently limited at temperatures higher than 90°C because of 

CO and peroxide formation. The use of polymeric membranes able to operate at 120°C would deter CO 

adsorption, but polymeric membranes are expensive, exhibit limited thermal stability, and are not well suited 

for high-humidity operation above 100°C. The current benchmark PEM material, Nafion®, is a perfluorinated 

copolymer with sulfonation to promote water retention and proton conduction, but its conductivity 

performance drops with increasing temperature and decreasing relative humidity. Furthermore, as a 

proprietary, fluorated material, it is relatively expensive. The production of hydrocarbon-based polymers for 

PEM materials is critical to the development of marketable high-performance membranes. 

ORNL and University of Tennessee collaborators have synthesized two new classes of materials for potential 

PEM applications. Poly(phenylene sulfonate) has been synthesized into a thin-film configuration that 

demonstrates outstanding thermal stability and resistance to inexpensive conventional processing techniques, 

such as hot-pressing. A fluorinated, sulfonated copolymer of methyl styrene and cyclohexadiene has also 

been developed that exhibits high thermal stability and improved workability. The application of these 

materials can prepare the way for energy-efficient fuel cell vehicles by providing thermal and chemical 

stability under system operating conditions, improved humidity performance through use of functional 

modifiers, and low-cost processing of non-fluoronated polymers 

into thin-film configurations. 

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 
FY 2004 Progress Report Propulsion Materials 

6

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. 

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 2004 under the APM Program. It 

consists of nine abstracts of national laboratory projects—four that address power electronics, four that 

address combustion and emission technologies, and one that addresses advanced PEMs. 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 
Propulsion Materials FY 2004 Progress Report 

7 

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. 

• Fabricate near-final-shape PMs for cost reduction. 

• Characterize, compare, and correlate engineering and microscopic magnetic properties of magnets processed 

under varying conditions. 

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

conventional system. 

Accomplishments 

• Modified the hydraulic system for more precise indication and control of initial pressure during compact pressing. 

• Procured and installed a new glove box for better oxygen control and operation during pre- and post-compact 

pressing and alignment. 

• Fabricated near-final-shape powdered compacts under various alignment fields (1 to 8 Tesla) for L/D ratios of 

less than 0.25. 

• Completed the conceptual design of a semi-automated superconducting PM fabrication system. 

• Completed the economic study (comparison of superconducting and conventional systems). 
FY 2004 Progress Report Propulsion Materials 

8 

Future Direction 

• Continue to work with industrial partners on sintering and annealing the compacts and on measuring the magnetic properties of the PMs. 

• Improve the success rate of making compacts with L/D ratios of less than 0.25. The approach includes considering (1) a vacuum powder-filling system and (2) compact ejection under pressure; both may help to alleviate 

the cracking problems. 

• Finalize the conceptual design of the superconducting fabrication system, including powder-filling and compact ejection systems. 

• Fabricate compacts with shapes other than a circular disk. 

Introduction

The strength of sintered NdFeB magnets greatly 

depends on the method by which the compact is 

magnetically aligned and pressed. Large blocks can 

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 

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 higher-energyproduct 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 high-energyproduct, 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-energyproduct PMs, we plan to design, fabricate, and demonstrate a semi-automated axial-die-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 engineering magnetic properties. Finally, selected PMs were 

sent to Oak Ridge National Laboratory (ORNL) for 

measurement of microscopic properties and texture 

(the alignment of the crystals’ easy magnetic axes). 

Previously, we demonstrated that significant improvement of energy product (10–15%) can be 

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

Industry considers an improvement in energy product of as little as 3–5% compared with 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 demonstrate that PMs can be made at a 

much faster rate than in the batch process, (2) to 

demonstrate that near-final-shape PMs can be processed, resulting in greater cost reduction, and (3) to 

demonstrate that the superconducting magnet and its 

associated press systems are economically feasible 

by conducting an economic analysis. 

Results

 In FY 2004, we modified the hydraulic loop for 

better indication and control of the pressure during 

the initial stage of the compact pressing operation. 

As shown in Figure 1, we installed a low-pressure 

gauge upstream of and a needle control valve downstream of the press tube. These modifications allowed better pressure control and resulted in smooth 

(less pressure fluctuation) operation during the early 
Propulsion Materials FY 2004 Progress Report 

9 

stage of the pressing. We believe that it is very important to remove the trapped air from the powder; 

otherwise, the compact is likely to crack when it is 

ejected from the die. Sufficient time and a passageway must be provided to allow air to escape from 

the die before the powder is completely pressed into 

the final compact. We also procured a new glove 

box, shown in Figure 2, for better control of oxygen 

during pre- and post-compact-press operation. The 

new glove box can provide an environment with less 

than 300 parts per million of oxygen, which is 

needed to avoid oxidation of the powder and degradation of the magnetic properties of the PM. This is 

particularly important for the laboratory environment at ANL because the compacts will be stored in 

the glove box for an undetermined period before 

shipping to Magnaquench for sintering. 

The most effective use of the high alignment 

fields that can be provided by superconducting solenoids is in making near-final-shape magnets. Their 

finite and usually short length in the direction of 

magnetization makes alignment of the powder grains 

especially difficult. When subjected to a uniform 

alignment field, the powder in the die cavity develops a highly non-uniform self-field. Because grains 

align along the total field lines, unidirectional 

alignment can be achieved only by increasing the 

strength of the applied alignment field until the effects of the self-field become negligible. Because the 

self-field distortion becomes greater for shorter 

magnets, conventional 2-T electromagnets cannot 

adequately provide alignment. We fabricated, with 

limited success, a number of near-final-shape compacts with L/D ratios smaller than 0.25 in various 

alignment fields from 1 to 8 T. Figure 3 shows such 

a compact with L/D = 0.21. These compacts are 

quite fragile because they are very thin (only 3.3 mm 

thick) and must be handled with extreme care. 

The success rate is low (~25%). We still do not 

know exactly what causes the compact to fail (crack) 

after ejection from the die, although we suspect the 

main culprit is trapped air. We need to improve the 

success rate in the future. Two dozen compacts were 

sent to Electron Energy Corporation for sintering 

and annealing. (Magnequench UG recently moved 

Figure 1. Schematic diagram of the modified hydraulic system. The low-pressure gauge and the 

needle control valve are installed for better pressure indication and control.

Figure 3. Near-final-shape compact with an L/D ratio 

of 0.21 (L = 15.9 mm). 

Figure 2. New glove box for better oxygen control 

during pre- and post-compact-press operation.
FY 2004 Progress Report Propulsion Materials 

10 

its factory to China and can no longer heat-treat the 

compacts). 

We completed a conceptual design of a semiautomated superconducting PM fabrication system. 

As shown in Figure 4, the system includes mainly a 

dual-ended, four-position, horizontal press system 

and an actively shielded, helium-cooled, superconducting magnet with a horizontal room-temperature 

bore. The horizontal press can be slid into and out of 

the bore of the superconducting magnet. The four 

arms of the press, 90° apart, rotate around a pivot 

point. The four positions represent the pressing, 

ejection, cleaning, and filling stations. It is estimated 

that the system can produce eight compacts per minute. 

The superconducting magnet is similar to the 

one currently in use at ANL. In designing the superconducting PM fabrication system, we collaborated 

with Ability Engineering Technology, Inc., a local 

design engineering firm. After the conceptual design 

was completed, vendors were contacted and quotations were received. The cost information was sent 

to Data Decisions and employed in the economic 

study. 

We contracted 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 PMs using the 

superconducting technology and the cost with conventional technology using electromagnets. The 

economic study is near completion, and we expect a 

final report will be issued by the end of FY 2004. 

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. 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 near-final-shape PMs 

can be processed, resulting in greater cost reduction. 

In FY 2004, we modified the hydraulic loop to provide better indication and control of the pressure 

during early stages of compact pressing. We procured a new glove box to provide better oxygen control during the pre– and post–compact- pressing operation. We fabricated a number of near-final-shape 

compacts with L/D ratios of less than 0.25 with an 

alignment field ranging from 1 to 8 T. However, the 

success rate is low (~25%). We completed the conceptual design of a superconducting PM manufacturing system and received quotations from vendors for 

major components (the superconducting magnet and 

the semi-automated hydraulic press system). An 

economic study was carried out to compare the cost 

of manufacturing PMs using the superconducting 

magnet and using the conventional electromagnet. 

In FY 2005, we plan to continue to collaborate 

with our industrial partners (Magnequench UG and 

Electron Energy Corp.) for compact sintering and 

annealing and for measuring magnetic properties of 

the sintered magnets. We want to improve the success rate of making near-final-shape compacts by 

considering (1) compact ejection under pressure and 

(2) powder-filling under vacuum; both may help to 

alleviate the cracking problem. We would like to 

finalize the conceptual design of the semi-automated 

superconducting PM manufacturing system, including the powder-filling and compact-ejection systems. Another task would be to fabricate PMs with 

shapes other than a circular cylinder or disk, such as 

the rectangular-shaped PM used in the motor of a 

hybrid car. Our long-term and final goal is to demonstrate the technical and economic feasibilities of 

this new technology by designing, fabricating, and 

operating an automated superconducting magnet and 

press system in continuous-mode operation. 

Figure 4. Schematic diagram of the conceptual 

design of a superconducting magnet and a fourposition press system.
Propulsion Materials FY 2004 Progress Report 

11 

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, June 7–9, 2004, 

Knoxville, TN. 

R. E. Wolf, “Low-Cost High-Energy-Product 

Permanent Magnets, An Economic Study,” presented at the Annual Review of Advanced Power 

Electronics and Electrical Machines, DOE FreedomCAR and Vehicle Technologies Program, June 

7–9, 2004, Knoxville, TN. 

R. E. Wolf, An Economic Study of the Manufacture of High Energy Permanent Magnets for Traction Motors in Hybrid Electric Vehicles, report submitted by Data Decisions to Argonne National 

Laboratory, July 2004.

Propulsion Materials FY 2004 Progress Report 

13 

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 (PMs). 

Approach 

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

• Instrument environmental chamber to determine in real time the magnetic strength of test specimens as a function of temperature and thermal cycling. 

• Evaluate the residual mechanical properties of sintered and bonded rare earth PMs 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 PMs. 

Future Direction 

• Utilize test facility to evaluate bonded and sintered NdFeB magnets. 

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

 PM motors have the highest power density; but 

they don’t have a sufficient constant power speed 

range; and their cost is too high because of the cost 

of magnet materials, magnet manufacturing, and 
FY 2004 Progress Report Propulsion Materials 

14 

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 rare earth PMs 

to thermal cycling between –40 and 150°C.

Approach and Results

 A test facility was designed and fabricated to 

evaluate the resistance of sintered and bonded rare 

earth PMs to thermal cycling. The test facility 

consists of a chamber, shown in Figures 1 and 2, 

capable of cycling temperature between –40 and 

300°C. Cooling is achieved using liquid nitrogen, 

compressed air, and a solenoid valve, while heating 

is achieved using compressed air and two 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 obtained with type K thermocouples placed at various 

locations inside the chamber demonstrated that it is 

possible to attain a very uniform temperature distribution inside the chamber. Figure 3 shows the temperature history recorded by seven thermocouples 

during heating/cooling. Results from these tests also 

provided information on the time required to achieve 

thermal equilibrium. 

 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 system, 

customized software using the commercially available package LabView, and a digital temperature 

controller. Inside the box, an array of sixteen 6.5-

mm-diam rods is attached to a frame, which in turn 

is connected to a pneumatic actuator. The PMs under 

evaluation, which are shaped in the form of prismatic beams, are placed at various locations along 

the rods. The reciprocating motion induced by the 

pneumatic actuator will slide the PMs through coils, 

which are placed around plastic tubes that are concentric to the rods (Figure 4). The motion of the 

magnets through the coils will induce a voltage in 

Figure 1. Environmental chamber for thermal 

cycling.

Figure 2. Detail of environmental chamber showing 

pneumatic actuator and frame with sixteen 6.5-mm 

diameter rods.

Figure 3. Temperature history recorded with seven 

thermocouples located at different locations within the 

environmental chamber. These results demonstrate 

that it is possible to achieve nearly isothermal conditions within the chamber. 
Propulsion Materials FY 2004 Progress Report 

15 

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 

dt

d V Φ =− , (1) 

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 number of thermal cycles. Figure 5 shows 

voltage traces resulting from the displacement of a 

bonded permanent NdFeB magnet sample through 

the coils; Figure 6 illustrates the effect of temperature on the magnitude of the voltage and therefore 

on the magnitude of the magnetic field of the test 

specimen. 

 After a prescribed number of thermal cycles, test 

specimens are removed from the chamber and 

evaluated in a 4-point bending to assess the effect of 

thermal cycling on their mechanical strength. During 

FY 2005, the effect of thermal cycling on the magnetic and mechanical properties of bonded NdFeB 

magnets, received from IAP (Columbus, OH) will be 

evaluated. 

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. The effect of thermal cycling on the mechanical strength of sintered and bonded PMs is determined by 4-point bending after subjecting test 

specimens to a prescribed number of thermal cycles. 

 

Figure 4. Schematic of test configuration illustrating the relative location of the coils with 

respect to the supporting rods and the permanent magnet test specimens.

Figure 6. Voltage traces associated with the motion 

of magnet through coil as a function of temperature. 

Changes in voltage are proportional to changes in 

magnetic strength.

Figure 5. Voltage trace associated with the motion of 

magnet through coil.
FY 2004 Progress Report Propulsion Materials 

16 

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 & Sons, New York, 1967. 
Propulsion Materials FY 2004 Progress Report 

17 

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 

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 automotive partner to develop 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. 

Accomplishments 

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

Motor Co. to develop a carbon foam–based heat sink for cooling the power electronics of Ford’s H2RV (hydrogen hybrid research vehicle). 

• Produced designs that showed potential for foam liquid-cooled heat exchangers in automotive applications, as 

well as the need for a more precise test rig. 

• Produced foams with a variety of pore structures. 

• Designed and built an improved heat sink test rig. 
FY 2004 Progress Report Propulsion Materials 

18 

Future Direction 

• Characterize the different bonding techniques and their influence on overall performance of foam-based heat 

exchangers. 

• Evaluate alternative cooling systems (such as passive evaporative coolers) for thermal management of power 

electronics. 

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

Introduction

 In recent decades, performance improvements in 

electronic components, such as higher-power computer chips and power converters, have led to significantly increased heat generation at small size 

scales and require more efficient strategies for microscale heat dissipation. A range of techniques such 

as micro-channels, heat pipes, and other novel designs to improve the efficiency of heat transfer from 

devices have been explored with limited success. 

These devices must incorporate very effective heat 

spreaders into the design of the heat sink to prevent 

localized hot spots and ensure that the temperature 

of the silicon (Si) -based electronic components does 

not exceed 125°C. 

 The high-conductivity carbon foam developed at 

ORNL is an open-cell structure with highly aligned 

graphitic ligaments (see Figure 1); studies have 

shown the typical interlayer spacing (d002) to be 

0.3356 nm, very near that of perfect graphite 

(0.3354 nm). As a result of its near-perfect structure, 

thermal conductivities along the ligament are calculated to be approximately 1700 W/m•K, with bulk 

conductivities > 180 W/m•K. Furthermore, the material exhibits low density (0.25-0.6 g/cm3

) such that 

the specific thermal conductivity is approximately 

four to five times greater than that of copper. This 

high conductivity, combined with the very large surface area, results in overall heat transfer coefficients 

for foam-based heat exchangers that are up to two 

orders of magnitude greater than those of conventional heat exchangers. As a result, foam-based heat 

exchangers or heat sinks can be dramatically smaller 

and lighter than conventional ones. 

 This year we have teamed with Ford to evaluate 

the application of carbon foam for cooling of the 

power inverter of Ford’s H2RV; both forced-air and 

circulating-water systems were evaluated. Simultaneously, effort was directed toward further understanding of the relationship between processing and 

foam structure in order to obtain foams with a more 

open structure that allows access to the internal surface area of the foam, therefore maximizing its performance in thermal management applications. Also, 

the test rig used to quantify pressure drop and heat 

transfer coefficients was redesigned. 

Results

Design of Cooling System for Ford’s 

H2RV 

 Hybrid and fuel cell vehicles using electric 

wheel motors require high-power electronics for motor control. These electronics create a considerable 

amount of heat and require a heat exchanger and 

separate radiator. Ford’s H2RV currently has three 

cooling systems: one for the combustion engine, one 

for the power electronics, and one for the transmission. This project explored the use of high-thermalconductivity carbon foam as a heat exchanger in the 

cooling systems of hybrid vehicle power electronics. Figure 1. Graphite foam material developed at 

ORNL.
Propulsion Materials FY 2004 Progress Report 

19 

The current aluminum pin-type heat exchanger used 

is being redesigned using carbon foam to increase 

the heat transferred from the electronics while maintaining or reducing the pressure drop of the coolant. 

A corrugated foam geometry was used in the design 

because the corrugations force the fluid to flow 

through instead of around the pores. Table 1 lists the 

engineering specifications for Ford’s H2RV cooling 

system. 

Table 1. List of engineering specifications for heat sink 

for power electronics of H2RV

Engineering specifications 

1 Dissipate 650 W of power 

2 Maintain a chip operating temperature at or 

below 125°C 

3 Operate in the temperature range −40 to 

125 °C 

4 Maximum coolant pressure drop of 0.5 psi 

5 Fluid inlet temperature 60–65 °C 

6 Insulate the 300 V necessary to power the circuits 

7 Hold circuit board (~110 × 60 × 1 mm) 

8 Fit in a similar-size case as Ford’s current design 

9 Work for the life of the vehicle (~10 years or 

200,000 cycles) 

 Two approaches were evaluated: (1) liquidcooled heat exchanger and (2) forced-air heat exchanger. 

Liquid-cooled heat exchanger 

 Testing the corrugated foam geometry with a 

liquid-cooled heat exchanger shows that it performs 

in the operating temperature range with heat transfer 

of approximately 15–20 W/cm2

. For Ford’s application, it would need to dissipate an amount of heat 

near 30 W/cm2

. This means that engineering specifications 1 and 2 from Table 1 were not met. Knowing 

the foam and fluid could operate over this temperature range validated specifications 3 and 5. Specifications 6, 7, and 8 were met using the foam as a replacement for the pin-fin aluminum heat exchanger; 

and no life-cycle estimate was done to validate 

specification 9. The test setup is shown in Figure 2. 

This design potentially allows the existing pin-fin 

heat exchanger to be replaced with a corrugated 

foam 

 

Figure 2. Experimental test setup. 

geometry, reducing the number of cooling systems 

in the hybrid car from 3 to 2. Calculations showed 

an average heat transfer coefficient of 1064 W/m2

K, 

suggesting that the design could be improved considerably through flow rate control and foam porosity, based on comparisons with carbon foam characterization studies at ORNL. 

 To characterize the pressure drop imposed by 

the liquid-cooled carbon foam heat exchanger, the 

pressure drop across the housing was recorded (1) 

when no foam was present, (2) when corrugated 

foam was present, and (3) when blind-hole foam 

was present (holes drilled parallel to the flow in a 

solid block). All three data sets were within 10% of 

each other, with no distinct separation, implying that 

the housing is the dominant source of pressure drop. 

This can be attributed to the change in crosssectional area from inlet to housing and from housing to outlet. While we cannot verify the expected 

pressure drop of the system to be less than 0.5 psi 

(engineering specification 4), we can conclude that 

the drop is relatively small. 

Forced-air heat exchanger 

 Table 1 lists the engineering specifications for 

the forced-air packaging system design. Two specifications, 1 and 2, were not met. To validate the operating temperature range (no. 3), the thermal properties of each material were used to ensure that they 

could withstand extreme temperatures. Since the 

design was air cooled, the pressure drop (no. 4) and 

inlet coolant temperature (no. 5) were not needed. 

Specification 6 was validated through an electrical 

resistivity analysis. Specifications 7 and 8 were validated by choosing dimensions that were similar. 

There was no life-cycle estimate to validate specification 9. The prototype maintains the chip tempera-
FY 2004 Progress Report Propulsion Materials 

20 

ture at below 125°C at a maximum power density of 

2.4 ± 0.4 W/cm2

. The carbon foam has a maximum 

heat transfer coefficient of 320 ±100 W/m2

•K. 

These results were obtained with a flow rate of 12.1 

± 0.5 cfm and are shown in Figure 3. 

Figure 3. Heater temperature vs. power density shows the 

prototype did not deliver the expected performance 

(points correspond to experimental data). 

 Both design teams found the convective coefficient of the foam to be lower than expected, possibly 

because of the lack of a bonding agent between the 

foam and the heat sink, lack of data on the heating 

element, and the inability to control water and air 

flow rates over a large range. More precise test setups and heater designs should be used in future testing. 

Processing Foams with Varied Pore 

Structures 

 Based upon B.E. Thompson’s modeling work1, 

which shows the importance of controlling pore 

density and maintaining an open structure to maximize the benefits of the foam’s porous surface in 

thermal management applications, we have directed 

our materials development efforts toward understanding the relationship between graphite foam 

structure and both roughness and area-recruitment 

phenomena. We have produced foam samples at different pressures (this being the processing variable 

that most affects pore size) to obtain foams of various pore structures. The density, thermal diffusivity, 

and compressive strength of the samples were measured. Figure 4 show the variations in thermal conductivity and density for samples produced at low, 

middle and high foaming pressures; Figure 5 shows 

Figure 4. Thermal conductivity versus density for carbon 

foams produced at varying foaming pressures. 

Figure 5. Pore structure of foams produced at varying 

foaming pressures. 

scanning electron microscope images of the varied 

pore structures produced. 

Redesigned Heat-Sink Test Rig 

 Accurate measurements of pressure drop and 

heat transfer coefficients are necessary in order to 

properly design carbon-foam–based heat exchangers. We identified several limitations of our previous 

test rig that may have caused inaccurate measurements. A new design was developed and a new test 

rig built. Samples produced at various foaming pressures will be tested in this rig to measure pressure 

drop and heat transfer coefficients. 

Conclusions

 Liquid-cooled heat exchangers show potential 

for use in automotive applications. The setup at 

the University of Michigan showed the need for 

more accurate pressure and temperature measurement. The further redesign of the test setup will provide a more accurate description of the foam’s capabilities in these applications. 

 The foam structure of carbon foam can be modified by varying the processing conditions. The improved access to the foam internal surface area will 
Propulsion Materials FY 2004 Progress Report 

21 

greatly influence the performance of foam-based 

heat exchangers. 

References

1. B. E. Thompson, A. G. Straatman, R. Culham, 

M. Yovanovich, A. G. Hunt, Q. Yu, and P. 

Oosthuisen, Modeling of Porous-Carbon-Foam 

Heat Exchangers, AGS Scientific, February 28, 

2003. 

Publications/Presentations

N.C. Gallego, A. Shih, D. P. Stinton, E. Jih, 

“Graphite Foam for Cooling of Automotive Power 

Electronics,”presented at the Carbon 2004 Conference, Providence, RI, July 11–16, 2004. 

DOE Office of FreedomCAR and Vehicle Technologies Program Power Electronics Review Meeting, National Transportation Research Center, 

Knoxville, TN, June 7–9, 2004.
22 
Propulsion Materials FY 2004 Progress Report 

23 

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. 

• Interpret and quantify the mechanical performance of PVOH films and their derivatives and rank them based 

on their potential for manufacturing scale-up. 

Approach 

• Conduct tensile testing on SNL-supplied PVOH films and measure their ultimate strengths and elastic moduli. 

• Using ultimate strength and elastic modulus, predict the minimum allowable radius of curvature that each film 

can withstand during processing into dc bus capacitors without breaking. 

Accomplishments 

• Determined the average ultimate strength and elastic modulus of nine PVOH film sets comprising three 

different elastomer additives, anneal temperatures, and elastomer content. 

• Identified one PVOH film (30% 4010 elastomer annealed at 225°C) as having the best combination of average 

tensile strength and minimum scatter in strength. It is predicted that this film can withstand being subjected to a 

radius of curvature of ~ 290 μm (0.011”) without breaking. 

Future Direction 

• Measure the tensile strength distribution of additional derivatives of PVOH films as a function of temperature. 

• Measure and interpret the tear resistance of PVOH films. 

Introduction

A primary focus of the Power Electronics effort in 

the Automotive Propulsion Materials Program is to 

develop polymer capacitor technology that will 

replace current electrolytic, dc bus capacitors for 

power electronic modules in hybrid electric vehicles. 

The ultimate objective is to make the power modules 

more compact while maintaining tight voltage and 

temperature requirements and long service life 
FY 2004 Progress Report Propulsion Materials 

24 

without compromise caused by mechanical 

breakdown of the dielectric film. Toward that end, 

we collaborated with SNL in this project to 

mechanically evaluate a suite of SNL-manufactured 

PVOH dielectric polymers that have the potential to 

satisfy the objectives. The present effort has two 

objectives: 

• Measure baseline mechanical properties of that 

suite of PVOH compositions and interpret their 

results so as to suggest which are most suitable 

for manufacturing scale-up 

• Quantify the mechanical performance of those 

manufactured films so manufacturers and endusers of these dielectric films may use them 

without mechanical breakdown. 

Results

SNL provided three sets of PVOH-elastomer 

film sets for testing of tensile strength (Sten) and 

elastic modulus (E). The tests examined two 

elastomers (designated as 4010 and 5015) having 

equal additive contents (16%). The effect of the 

additive content was also examined in the 

PVOH/4010 and a third set of films with 30% 

additive. The effect of annealing temperature (190, 

225, and 250°C) on each of the three sets also was 

examined. The nine film combinations are listed in 

Table 1. 

Table 1. Film test matrix

Dielectric 

film 

Elastomer 

content Anneal (oC) 

PVOH/4010 16% 190 

 16% 225 

 16% 250 

 

PVOH/4010 30% 190 

 30% 225 

 30% 250 

 

PVOH/5015 16% 190 

 16% 225 

 16% 250 

Sheets of film of the nominal size 125 mm × 125 

mm × 10 μm (see Figure 1) were received and cut 

into 12.5-mm or 19-mm widths. Different widths 

were examined to see if specimen size had an effect 

on strength (it was found that it did not). An 

example of the cut cross-section of one of the PVOH 

films is shown in Figure 2. Specimens were “endtabbed” with tape, producing a 25-mm gage length. 

The specimens were then mounted into 

pneumatically activated, face-loading flat grips 

housed in an electromechanical universal test 

machine (see Figure 3). Tests adhered to ASTM 

D8821

 and were conducted in displacement control 

at a crosshead speed of 0.5 mm/min until specimen 

fracture was produced. 

Tensile load and crosshead displacement were 

measured and used to calculate true tensile stress 

and strain, respectively. Examples of true stressstrain curves for the PVOH film with 30% 4010 

elastomer additive annealed at 225°C is shown in 

Figure 4; this film had the greatest average strength 

and least amount of scatter of the nine films, as 

shown in Figure 5 and listed in Table 2. Generally, 

the 5015/16% elastomer systems were weaker than 

their 4010/16% and 4010/30% counterparts; the 

250°C anneal produced more scatter in strength than 

Figure 2. Example of PVOH film cross-section. 

Figure 1. Example of as-received PVOH film. 
Propulsion Materials FY 2004 Progress Report 

25 

the 190 and 225°C anneals; and the 225°C anneal 

produced higher strengths than the 190°C anneal. 

 

 These films are subjected to winding during 

their processing or during the capacitor 

manufacturing (Figure 6), so the (minimum) radius, 

R, of curvature was determined for each film that 

would produce a stress equal to the measured 

strength according to ref. 2: 

R = Et

2Stens

where t is the film thickness. A smaller radius of 

curvature is promoted with a less stiff film, a thinner 

film or a film with greater tensile strength. Based on 

this expression, then PVOH film with 4010/30% 

elastomer annealed at 225°C would survive being 

wound around the smallest radius (i.e., smallest 

mandrel). See Figure 7 and Table 3. 

Table 2. Film test matrix

Dielectric film Ave Stens

(MPa) Ave E (GPa) 

4010_16_190 23.9 ± 6.0 1.37 ± 0.15 

4010_16_225 29.6 ± 6.3 2.02 ± 0.15 

4010_16_250 42.2 ± 9.4 2.31 ± 0.32 

 

4010_30_190 29.6 ± 6.0 1.74 ± 0.08 

4010_30_225 40.7 ± 2.7 1.97 ± 0.12 

4010_30_250 28.0 ± 13.5 1.85 ± 0.26 

 

5015_16_190 16.4 ± 3.6 1.38 ± 0.27 

5015_16_225 22.1 ± 3.0 1.80 ± 0.43 

5015_16_250 22.3 ± 13.0 1.38 ± 0.19 

Figure 4. True tensile stress as a function of true 

tensile strain for all the test specimens from the PVOH30% 4010 film annealed at 225°C. 

Figure 3. Film tensile test setup. 

Figure 6. Dielectric films are subjected to winding 

during their fabrication and capacitor manufacturing. 

Images supplied by SNL. 

Figure 5. Comparison of average tensile strength. 
FY 2004 Progress Report Propulsion Materials 

26 

Conclusions

The PVOH-4010/30% film annealed at 225°C 

had the best combination of high average strength 

and minimum strength scatter of all nine films 

tested. The 5015/16% elastomer systems were 

weaker than their 4010/16% and 4010/30% 

counterparts. The 250°C anneal produced more 

scatter in strength than the 190 and 225°C anneals 

and higher strengths than the 190°C anneal. There 

was no obvious effect of specimen size on ultimate 

tensile strength. 

References

1. “Standard Test Method for Tensile Properties of 

Thin Plastic Sheeting,” ASTM D882-02, 

Vol. 08.01, ASTM International, West 

Conshohocken, PA. 

2. E. P. Popov, Mechanics of Materials, 2nd

Edition, Prentice-Hall, Englewood Cliffs, NJ, 

1976. 

Publications

C. H. Hsueh and A. A. Wereszczak, “Multiple 

Cracking of Brittle Coatings on Strained 

Substrates,” Journal of Applied Physics, September 

2004. 

Table 3. Minimum average radius of curvature

Dielectric film Radius of curvature (mm) 

4010_16_190 0.43 

4010_16_225 0.34 

4010_16_250 0.30 

 

4010_30_190 0.38 

4010_30_225 0.29 

4010_30_250 0.49 

 

5015_16_190 0.59 

5015_16_225 0.41 

5015_16_250 0.37 

Figure 7. The PVOH-30% 4010 film annealed at 225°C 

can be subjected to the smallest radius of curvature 

without fracturing. 
Propulsion Materials FY 2004 Progress Report 

27 

3. CIDI ENGINES 

A. Round Pleated Ceramic Fiber Diesel Particulate Filter Cartridge 

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 the exhaust flow of a 

7.3-L Ford F250 truck. 

• Develop a ceramic injection molding or casting process capable of producing the structural frame for the 

pleated filter media. 

• Develop, fabricate, and road test the round pleated ceramic fiber filter cartridge, which reduces engine backpressure and filter thermal mass compared with conventional particulate filters. 

• Conduct an independent laboratory stationary diesel test cell evaluation on the round pleated cartridge to validate particulate removal efficiency. 

Approach 

• Contract with a skilled design engineer to calculate dimensions and produce drawings of the round pleated cartridge. 

• Subcontract structural frame development for the pleated cartridge to a ceramic injection molding company. 

• Fabricate and road test the round cartridge system on a 7.3-L diesel vehicle to optimize shape and size and verify durability. 

Accomplishments 

• Produced several sets of engineering drawings, along with a computer model to accurately calculate available 

filtration surface resulting from any dimensional design changes. 

• Developed an injection molding material and application technique for the ceramic structural frame on the filter 

media. 

• Road-tested several flat pleated filter cartridge systems to investigate various structural support designs for the 

pleated filter on a 7.3-L Ford F250 truck. 
FY 2004 Progress Report Propulsion Materials 

28 

• Designed a specifically sized round pleated filter cartridge for testing by a major vehicle manufacturer. 

Future Direction

• Enlist exhaust system, catalyst, engine, and vehicle manufacturers in a joint product development effort to 

move toward commercialization of the ceramic fiber pleated particulate filter in 2005.

• Work with multiple ceramic subcontractors to reduce the cost of the fabricated ceramic components. 

• Conduct joint development with a ceramic fiber media company to improve the soot and ash capacity of the 

round pleated filter. 

• Partner with a volume filter cartridge manufacturer to provide large quantities of the pleated filter cartridges 

necessary to the diesel industry over the next 10 years. 

Introduction

Diesel emissions regulations in the United 

States, Europe, and Japan have become a reality for 

all diesel engine manufacturers. Diesel engine and 

vehicle suppliers worldwide are working on particulate control devices. Catalyst-regenerated systems, 

which require high exhaust temperatures, seem to be 

working reasonably well on heavy duty diesel trucks 

(>10-L engine sizes). These engines account for 

about 10% of the diesel engine market in the world. 

Smaller vehicles with lower exhaust temperatures—

such as medium-duty trucks, buses, delivery vans, 

pickup trucks, passenger cars, future diesel sport 

utility vehicles, and off-road vehicles—will need an 

auxiliary-heated particulate filter to operate under all 

engine conditions. This creates an opportunity in 

90% of the diesel engine market for the pleated ceramic fiber Industrial Ceramic Solutions (ICS) DPF 

cartridge because of its lower backpressure and reduced thermal mass. A number of actively heated 

DPFs are under development, but none have the 

proven record of performance, maintenance, and 

price required for commercial diesel vehicles. ICS’s 

completion of the FY 2004 DOE Propulsion Materials Program vehicle road test will place the ICS 

round pleated ceramic fiber filter cartridge high on 

the list of potential actively heated DPF systems. 

 In FY 2003, a second product alternative to control diesel particulates across all market applications 

emerged—the ceramic fiber pleated filter cartridge 

itself. All approaches to particulate matter (PM) control must use some form of a ceramic filter. To date, 

that filter choice has been an extruded honeycomb 

“wall-flow” product. Experiments conducted by ICS 

and others under the FY 2003 program demonstrated 

that the pleated ceramic DPF results in much lower 

exhaust backpressure on the diesel engine, which 

will improve engine performance and reduce the fuel 

penalty imposed by the PM control device. The 

pleated ceramic fiber DPF, which weighs significantly less than the extruded wall-flow filter, is 

lower in thermal mass, so it achieves soot combustion temperatures more quickly and adds less 

weight. The transition from the flat pleated filter to 

the round pleated filter cartridge is necessary because of the demands of exhaust manufacturers for a 

round DPF shape to fit their current canning processes. ICS is in discussions with several diesel engine and exhaust system manufacturers to test the 

pleated ceramic fiber filter cartridge in their existing 

regeneration technologies. 

Approach

 ICS’s FY 2003 work developed the flat 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 developed. A number of structural designs to enclose and support the pleated fiber 

media in the exhaust were investigated. That product 

is shown in Figure 1. During FY 2004, ICS designed 

a round pleated filter cartridge based upon the diesel 

engine testing data from its rectangular pleated filter 

cartridge. Extensive road testing on the Ford F250 

diesel truck has shown that the 8 ft2

 of media in the 

rectangular pleated filters is approximately 20% less 

than that required for optimum filter operation. 

 ICS approached the project with an initial round 

pleated filter that is approximately 7 in. in diameter 

and 12 in. long. This will yield 10 ft2

 of effective 

filter media surface area to accommodate a full 
Propulsion Materials FY 2004 Progress Report 

29 

spectrum of diesel exhaust flow rates on the truck. 

ICS employed a mechanical engineer to design and 

model the optimum pleat geometry and cartridge 

size to accommodate the Ford truck’s exhaust flow. 

ICS worked with an experienced ceramic injection 

molding company to develop structural support for 

the pleated filter media. We have contracted with 

this company to provide the injection molding tooling for the round pleated filter structural frame. The 

efforts of the filter cartridge design engineer and the 

injection molding company are being coordinated to 

arrive at a robust round filter cartridge structure for 

the first attempt at a diesel exhaust prototype test 

cartridge. 

 The injection molding tooling will produce a 

cartridge for road testing on the ICS 7.3-L diesel 

Ford truck. Cartridges and exhaust can assemblies 

will be manufactured for the Ford truck testing. ICS 

will contract with an independent diesel engine testing laboratory, such as Oak Ridge National Laboratory, to evaluate the mechanical behavior, durability, 

and filtration efficiency. Then the round pleated filter assembly will be installed on the ICS Ford test 

vehicle. Road testing will be performed at a full 

range of engine operating conditions. 

 Issues with the filter design and performance 

will be identified and resolved. Several iterations of 

design adjustments may be necessary to arrive at the 

optimum prototype configuration. These will be 

confirmed using the Ford truck testing. When a robust and durable cartridge is available, these cartridges will be provided to selected U.S. diesel 

manufacturers for in-house testing and evaluation. 

Results

 The first engineering design of the round pleated 

filter, including the ceramic support structure, was a 

7-in.-diam by 12-in.-long filter cartridge, as shown 

in Figure 2. A laboratory replica of this prototype 

was fabricated to investigate feasibility. Figure 3 

shows the laboratory model. The filter media surface 

available in this design was approximately 8 ft2

. 

Discussions and bench testing with commercial vehicle manufacturers pointed to a need for more filter 

surface. Therefore, a second concept was designed 

by the ICS engineers to provide slightly more than 

10 ft2

 of surface area. This 6-in.-diam by 12-in.-long 

cartridge concept, shown in Figure 4, will be the 

design that ICS pursues for future prototype vehicle 

testing. 

 

Figure 2. Initial engineering design of the round 

pleated filter. 

Figure 3. Laboratory model of the initial prototype design. 

Figure 1. ICS flat pleated filter cartridge.
30 

Figure 4. Cartridge design with improved surface 

area. 

 The injection molding development for the ceramic support structure was accomplished on a flat 

pleated filter to minimize injection-molding tooling 

cost for the initial materials and injection molding 

parameter investigations. The ceramic frame material selected for this development was silicon carbide, as this seems to be the material preferred by 

diesel manufacturers. The final product from that 

preliminary injection molding work is shown in Figure 5. ICS is currently working with the injection 

molding company to design the tooling for the round 

pleated filter cartridge. 

Figure 5. Injection-molded structure on a pleated 

filter. 

 

 ICS has fabricated a can assembly to test the 

pleated filters on the Ford F250 truck. The exhaust is 

directed through the bed of the truck to facilitate 

easy installation and removal of filter cartridges for 

evaluation. That test apparatus is shown in Figure 6. 

ICS can test both round and flat pleated filters in this 

test device. It has been valuable in investigating the 

durability of support structures and soot loading capacity of the pleated filter cartridges. 

Figure 6. Ford truck filter cartridge test apparatus. 

Conclusions

 The pleated ceramic fiber filter cartridge has 

demonstrated lower backpressure and thermal mass 

properties that can make it a valuable addition to all 

types of PM control systems. ICS is negotiating with 

a major international filter manufacturer to license 

the use of the technology to supply the large volumes of filter cartridges that will be necessary to 

supply the worldwide diesel industry. Completion of 

the successful road testing of the Ford diesel truck 

will allow ICS to begin supplying test cartridge 

samples to diesel engine and vehicle manufacturers 

in 2005. Support by the diesel engine manufacturers 

and the vehicle original equipment manufacturers is 

expected to lead to fleet testing and eventual commercial use. The round pleated ceramic fiber filter 

cartridge DPF can solve many problems that exist 

for companies seeking diesel particulate control solutions for 2007 and beyond. 

Publications/Presentations

 “Microwave-Regenerated Particulate Filter,” 

presented at the American Filtration Society Diesel 

and Gasoline Engine Emission Solutions Conference, Ann Arbor, MI, October 2003. 

Patents Issued

 “Manufacturing Process for Whisker-Free Silicon Carbide Fibers,” June 2004. 
Propulsion Materials FY 2004 Progress Report 

31 

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 um 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 

• Worked with a commercial plating company to successfully reduce the orifice diameter of diesel engine fuel injectors from 180 to 80 um with EN plating. 

• Characterized the relative vulnerability of injectors plated with different alloys to deposit formation. 

• Collaborated with Pennsylvania State University (Penn State) on deposit formation testing using Penn State’s 

micro-oxidation test method, and with the U.S. Environmental Protection Agency (EPA) National Vehicle and 

Fuel Emissions Laboratory (NVFEL) on plating injectors for EPA’s Clean Diesel program. 

• Initiated contact with Siemens AG through International Harvester/Navistar regarding possible transfer of the 

plating technology. 

 Future Direction 

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

Energy Systems (ANL–ES). 

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

• Refine test method for measuring deposit formation on coated surfaces. 
FY 2004 Progress Report Propulsion Materials 

32 

Introduction

 In 2007, EPA regulations mandate a reduction in 

diesel engine emissions to 0.01 g of particulate matter (PM) per engine horsepower per hour, and 0.2 g 

nitrogen oxides (NOx) per engine horsepower per 

hour. Further reductions are expected for 2010. To 

achieve these levels, a great deal of research is being 

performed on engine design changes and aftertreatment devices. One design change under consideration is the reduction of the fuel injector orifice 

diameter. 

 Pickett and coworkers1,2 have demonstrated 

elimination of soot in a test cylinder by reducing the 

injector orifice diameter to 50 μm, even with high 

levels of exhaust gas recirculation (EGR) and concomitant reduction in NOx emissions. NVFEL researchers have observed reduced PM emissions from 

a light-duty diesel engine equipped with 

75-μm-diam 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-diam orifices using electrical 

discharge machining (EDM), further reductions in 

hole size are accompanied by unacceptable fabrication error rates. 

 While reducing orifice diameter has the potential 

to reduce PM emissions, the reduction leads to a 

number of potential difficulties. Smaller orifices are 

more susceptible to partial or complete blockage by 

coking deposits. In addition, in its as-made state, the 

interiors of EDM-fabricated orifices are extremely 

rough and must be smoothed with an abrasive slurry. 

The average RA of these internal surfaces is about 

0.5 μm, with sharp peaks and valleys. This roughness actually promotes coking deposit formation, 

starting in the deeper valleys. In addition, the rough 

orifice wall creates a highly turbulent layer adjacent 

to it during injection, reducing the volume of fuel 

delivered. The effect of this reduction increases 

markedly as the orifice diameter decreases. 

 We have demonstrated the potential of EN plating as a method for production of small-orifice injectors. It also offers a route to minimizing deposit 

formation by tailoring surface chemistry, and we 

have previously shown that EN-plated orifice interior surfaces are smoother than the underlying substrate. 

Approach

As described in previous reports, we are using EN 

plating to reduce orifice diameter. EN plating is a 

method of depositing nickel/phosphorus or 

nickel/boron alloys onto metallic surfaces from 

aqueous solution, and we have deposited other metals using the same principle.

 Having previously shown that EN plating can be 

used on a bench scale to reduce orifice diameter 

from 200 to 50 μm and to reduce the RA of plated 

surfaces, we plan to scale up the technique. We will 

also continue to evaluate the ability of EN plating to 

mitigate deposit formation. 

Results

 In last year’s peer review of this project, many 

of the reviewers strongly urged us to characterize the 

spray properties of plated nozzles. To that end, we 

have begun a collaboration with EPA–NVFEL, under which we will coat nozzles for EPA’s Clean 

Diesel program and EPA will provide us with the 

results of spray and single-cylinder engine tests on 

the nozzles. If these initial tests go well, EPA–

NVFEL plans to do light-duty engine tests on plated 

nozzles as well. We are also working with ANL-ES 

personnel on plating nozzles for optical spray characterization. In addition, SNL researchers have expressed an interest in testing some of our plated 

nozzles. 

 We are working with Imagineering, Inc., a 

commercial plating company, to scale up nozzle 

plating. It has provided us with a number of plated 

nozzles for evaluation in the key areas of coverage, 

uniformity, surface finish, and adhesion. 

• Coverage has been excellent (Figures 1 and 2); 

even the first set of injectors Imagineering sent 

had plating along the entire length of the orifices. 

• Uniformity is likewise as good as we saw in 

bench-scale tests, with one exception related to 

surface finish (see below).

• The company is still having minor problems 

with surface finish, which also negatively impacts uniformity. Areas of thinner coating are 

caused by the presence of hydrogen bubbles on 

the surface during the plating process. Greater 

agitation of the bath during the course of plating 

is expected to resolve this issue. The variability 

in orifice diameter seen in Figure 1 is likewise 
Propulsion Materials FY 2004 Progress Report 

33 

due to the presence of bubbles in the orifice during 

plating. 

While adhesion was poor in the first set of injectors plated, Imagineering rapidly resolved 

that issue, and all of the plated injectors we have 

received since then have had excellent adhesion. We 

evaluate adhesion by indenting the plated surfaces 

under load and examining the indentation. If adhesion is poor, there is substantial loss of coating 

around the indentation. If adhesion is good, the coating remains adherent around the indentation. Imagineering personnel estimate that plating the nozzles 

should add $0.25 or less to the cost. 

 Because of the superior adhesion it has 

achieved, Imagineering will coat the nozzles for 

evaluation by NVFEL and ANL-ES as soon as it has 

resolved the surface finish issue. For the nozzles to 

be suitable for testing, there must be no coating in 

the pintle guide area (cf. Figure 3). 

 

 We have shown the feasibility of using commercially available masking compounds to keep that 

area from being coated. Imagineering has the capability to keep the critical area free of EN and will do 

so when all other coating parameters are acceptable. 

 As reported last year, we tested deposit formation by dropping diesel fuel onto plated and unplated 

surfaces at approximately 240o C and measuring the 

mass gain. These initial tests showed EN plating to 

be less prone to coking than the base metal of the 

nozzle. We have expanded upon that work, using the 

same test method to determine the coking potential 

of several different alloys. Figure 4 is a plot of deposit mass on different alloys expressed as a fraction 

of the deposit mass on an unplated surface. It appears that the commercial plating 

bath we have been using is still as good as or better 

than any of the alloy coatings we have tested. A review of the literature on metal-based catalysts for 

reactions of organic molecules has suggested a numFigure 1. Orifice diameter as a function of position in a 

nozzle plated by Imagineering.

Figure 2. Optical micrograph of a cross-section of 

the plated nozzle in the orifice region.

Figure 3. Plan sketch of nozzle, indicating the 

pintle guide area.

Figure 4. Deposit mass on different alloys, normalized to deposit mass on unplated surfaces in the same 

test run.
FY 2004 Progress Report Propulsion Materials 

34 

ber of other candidate metals for examination. 

 Because our test method was not in general use, 

we provided plated sample dishes to Professor Joseph Perez at Penn State. He performed Penn State 

micro-oxidation tests on the plated dishes and confirmed our results. These tests entail heating dishes 

with fixed initial volumes of fuel or lubricant to 

200oC and flowing air over them for varying lengths 

of time. Figure 5 is a plot of deposit mass vs. time at 

temperature, showing the results for EN plating, for 

unplated dishes, and for a silicon-based coating that 

was tested at the same time. Figure 6 is a plot of 

mass loss vs. time at temperature for the same three 

samples. High mass loss is an indication of oxidative 

fragmentation of the test fluid; when long-chain organic molecules partially oxidize, they can break 

apart in the vicinity of more reactive hydrogens and 

carbons, such as those around carbon-carbon double 

bonds. The fragmented molecules are both volatile 

and reactive. Some evaporate quickly, as shown by 

the mass loss; the rest condense into deposit precursors, as shown by the increase in deposit mass. Professor Perez has also provided invaluable insights 

into the nature of the deposit formation reactions. 

 We are investigating methods of measuring or 

estimating the cavitation erosion resistance of ENplated surfaces. There is a wide range of opinion in 

the literature regarding the relationship between basic material properties such as hardness and cavitation erosion resistance; however, it appears that 

erosion resistance for widely dissimilar materials 

(e.g., brittle ceramic coatings vs. ductile metals) can 

be predicted from different properties. In the case of 

EN plating, it should be possible to estimate erosion 

resistance from hardness. Now that we have been 

able to obtain highly adherent coatings from Imagineering, we plan to consider the possible effect of 

thermal fatigue on coating durability. 

 To address the issue of engine tests in heavyduty diesel engines, we initiated contact with Siemens AG research personnel. They expressed an 

interest in the technology but cautioned that reducing orifice diameter will require extensive changes 

in heavy-duty engine design. They were also concerned about the long-term durability of the coatings, as well as their propensity for deposit 

formation. 

Conclusions

 This year’s work has shown that scaling up the 

technique is technically and economically feasible. 

We have seen that there is still strong interest on the 

part of fuel system original equipment manufacturers (OEMs), and we are already working to address 

their primary concerns about the technology. The 

next step is spray visualization; positive results from 

those tests will lead to engine tests, where success 

should increase OEM interest and drive application 

and use of the technology in light-duty engines. 

Figure 6. Plot of Pennsylvania State micro-oxidation 

mass loss as a function of time for unplated, EN-plated, 

and Si-coated samples.

Figure 5. Plot of Pennsylvania State micro-oxidation 

deposit mass as a function of time for unplated, ENplated, and Si-coated samples.
Propulsion Materials FY 2004 Progress Report 

35 

References

1. L. M. Pickett and D. L. Siebers, “Orifice Diameter Effects on Diesel Fuel Jet Flame Structure,” 

American Society of Mechanical Engineers, Internal Combustion Engine Division, 

ICE 37(1) 65–76, Proceedings of the 2001 Fall 

Technical Conference of the ASME Internal 

Combustion Engine Division, 2001, Ed.: V. W. 

Wong. 

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 Micro-Orifices,” presented at 

HARMST 2003 High-Aspect Ratio MicroStructure Technology Workshop, Monterey CA, 

2003. 

3. J. B. Heywood, Internal Combustion Engine 

Fundamentals, McGraw-Hill, 1988. 

Publications and Presentations

J. Woodford and G. Fenske, Use of Autocatalytically-Deposited Coatings to Fabricate SmallOrifice Fuel Injectors, Argonne National Laboratory, in press. 

J. Woodford and G. Fenske, Fuel Deposit Formation on Electroless Nickel Coatings, Argonne 

National Laboratory, in press 

Poster, DOE Advanced Combustion Engine 

R&D Merit Review, May 18–20, 2004, Argonne 

National Laboratory 

Patents

J. Woodford, J. Perez, A. Erdemir, and G. Fenski, “Use of Catalytic Metal Coatings to Mitigate 

Deposit Formation on Engine Components,” invention disclosure ANL-IN-04-063. 

Propulsion Materials FY 2004 Progress Report

37 

C. Electrochemical NOx Sensor for Monitoring Diesel Emissions 

L. Peter Martin and Robert S. Glass 

Lawrence Livermore National Laboratory 

P.O. Box 808, MS L-353 

Livermore, CA 94551-0808 

(925) 423-9831; fax: (925) 423-7040; e-mail: martin89@llnl.gov 

DOE Materials Technologies Team Leader: Rogelio Sullivan 

(202) 586-78042; 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 nitric oxide (NO) or total nitrogen oxides (NOx) sensor for 

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

• Demonstrate the commercialization potential of a new NOx sensor technology. 

• Collaborate with Ford Research Laboratory and Oak Ridge National Laboratory (ORNL) to optimize sensor 

materials, operating parameters, and performance. 

Approach 

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

• Apply a constant current-bias between the working electrode and a second, “counter” electrode. 

• Correlate the NOx concentration with the potential developed across the cell in response to the applied currentbias. 

• Optimize the sensor performance (sensitivity, response speed, cross sensitivity, and stability) by identifying and 

resolving materials-related and design issues. 

Accomplishments 

• Performed more extensive testing of a tin-doped indium oxide (ITO) sensor reported last year. 

• Identified new electrode material with better NO selectivity and higher operating temperature. 

• Expanded collaboration with Ford Research Lab and with ORNL. 

Future Direction 

• Continue to explore materials issues related to sensitivity and stability. 

• Investigate sensing mechanism using electrochemical and analytical techniques. 

• Evaluate microstructural evolution during sensor aging. 

• Evaluate cross-sensitivity to important redox species. 

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

• Transfer technology to a commercial entity. 
FY 2004 Progress Report Propulsion Materials 

38 

Introduction 

 New emissions regulations will increase the 

need for compact, inexpensive sensors for monitoring and control of automotive exhaust gas pollutants. 

Species of interest include hydrocarbons, carbon 

monoxide, and NOx. The most promising NO sensors for exhaust gas monitoring are based on ionically conducting solid state electrochemical devices.1, 2 These devices typically consist of a solid 

ceramic electrolyte onto which two or more metal or 

metal-oxide electrodes are deposited, and they can 

be operated in either potentiometric or amperometric 

modes. Significant progress has been made toward 

the development of deployable sensors using yttriastabilized zirconia (YSZ) as the electrolyte and catalytically active metal oxides as the sensing electrodes.3

 However, improvement is still needed in 

sensitivity, response time, reliability, and crosssensitivity. The current work is directed toward the 

development of fast, high-sensitivity electrochemical NOx sensors for automotive diesel engine applications. 

 NOx sensing technology providing fast response 

time and high sensitivity to NO at 600–750o

C has 

been developed. The sensor is based on a novel current-biased mode of operation in which a fixed current is applied between the sensing and counter electrodes and the resultant potential is measured. Target 

operating parameters have been determined for the 

proposed sensor based on discussion with industry 

collaborators at Ford Research Lab. 

Approach

 The proposed approach is to develop a sensor 

using catalytic metal oxide electrodes on a solid 

ionic conductor electrolyte. Similar technology has 

been widely investigated for various gas sensing 

applications and has been successfully developed for 

use in exhaust gas oxygen sensors. The current effort approaches the problem by the application of 

novel materials and fabrication processes designed 

to optimize electrode microstructures. In addition, a 

novel mode of operation has been identified that 

yields enhanced NO response sensitivity and speed. 

 Sensors are prepared by spray deposition or spin 

coating of metal oxide working electrodes onto 

dense YSZ electrolyte substrates, followed by sintering at 900–1100°C. Working electrodes are composed of nanocrystalline metal oxides. Initial success was encountered using n-type semi-conducting 

oxides, such as ITO or ZnO. More recently, it has 

been demonstrated that promising performance can 

be achieved using various perovskite-type oxides. 

Counter electrodes are generally made from platinum, although they can also be fabricated from 

metal oxides. NOx sensing experiments were performed in a quartz tube inside a furnace using a 

standard gas handling apparatus. All tests were performed in the temperature range of 600 to 750°C. 

 Sensors are typically first characterized through 

generation of current-voltage (I-V) curves in various 

atmospheres. The measured current is directly related to the amount of oxygen being “pumped” 

through the electrolyte by the reaction 

 1/2O2 + VO + 2e−

 = O2− , (1) 

where VO represents an oxygen vacancy and O2−

represents an oxide ion in the electrolyte lattice. At 

the anode, oxygen is liberated: 

 2O2− = O2 + 2VO + 2e− . (2) 

 Because all tests are performed in high O2

(~10%) and low NOx (≤ 500 ppm) concentrations, 

any changes in the I-V behavior upon changing the 

NOx concentration can be attributed to reactions involving oxidation or reduction of these species. 

Once the I-V behavior is determined, the operating 

bias condition can be selected based on the desired 

NO and NO2 sensitivities. Sensor testing under a 

constant current bias is then performed to determine 

the sensitivity, selectivity, response time, and stability characteristics of the sensor. 

Results

 Figure 1 shows the response of a biased sensor 

using an ITO electrode to 500 ppm of both NO and 

NO2. The sampling interval in the figure is 0.25 s, 

and the test temperature is 650°C. Figure 1 shows a 

similar response to both NO and NO2. These data 

were reported last year, and they show turn-on and 

turn-off times (τ90) ~1.25 and 2.5 seconds, respectively, for the NO response. This fast response is 

attributed to the enhancement of the electrode kinetics caused by the biasing current. In the past year, 

continued testing has been performed to investigate 

some of potential cross-sensitivities of the ITObased sensor. 
Propulsion Materials FY 2004 Progress Report

39 

Figure 1. Response time vs. time for an ITO-based sensor 

exposed to 500 ppm NO and NO2 at 650)C in 10% O2. 

Last year it was reported that the NO2 and NO 

responses of the ITO-based sensor are affected by 

the oxygen concentration very strongly and not at 

all, respectively. Figure 2 shows the effect of H2O 

and O2 concentration on the baseline of the sensor. 

The baseline is defined as the sensor voltage required to maintain the pumping current in Eq. (1) in 

the absence of NOx. The data in Figure 2 show that 

the baseline is slightly affected by the O2 concentration and strongly affected by the H2O concentration. 

This behavior could be problematic for a sensor of 

this composition, since the H2O concentration varies 

widely in CIDI exhaust. Therefore, alternative electrode materials have been investigated. 

 Figure 3 shows the NO and NO2 response of a 

similar sensor using a ZnO sensing electrode and 

tested at 750°C. Note the very high selectivity for 

NO versus NO2. Such high selectivity enables the 

sensor to function as an NO sensor or, by the use of 

an NO2 decomposition catalyst, as a total NOx sensor. The high operating temperature mediates some 

of the concerns regarding interfering gases, which 

are easily oxidized to less reactive species above 

700°C. 

 Figure 4 shows the response to 400 ppm NO and 

NO2, and the sensor baseline, as a function of the 

oxygen concentration. The data show some dependFigure 2. Baseline vs. O2 concentration for the ITO-based 

sensor in 3 (♦), 10 (▲), and 15% (■) H2O. 

Figure 3. Sensor response vs concentration of NO (♦) 

and NO2 (■) for a ZnO-based sensor at 750o

C in 10% O2.

ence on O2 concentration, which is to be expected 

for a sensor of this type. This effect can be corrected 

for by the incorporation of a second sensor for monitoring O2 concentration. The effect of H2O concentration on this sensor has not been carefully evaluated yet for the ZnO sensor. 

 Ongoing investigations are being performed to 

elucidate the sensing mechanism of this type of sensor. It has been observed during testing that there is 

a tendency for the sensor baseline to drift over time 

(~1-5 mV/hour). This may be attributable to coarsening of the electrode microstructure during testing 

or to changes in the stoichiometry at the electrode 

surface. Future efforts will involve identifying the 

mechanism for the baseline drift and evaluating 

means for stabilizing this effect. Possible techniques 
FY 2004 Progress Report Propulsion Materials 

40 

Figure 4. Sensor baseline (●), and response to 400 ppm 

NO (♦) and NO2 (■) vs oxygen concentration for a ZnObased sensor at 750°C. 

for doing so are modifying the electrode microstructure (for example, by incorporation of a more refractory phase), intentionally aging the electrodes, or 

selecting alternate electrode materials. 

Conclusions

 A novel current-biased mode of operation is being investigated for NOx sensing in automotive diesel exhaust. Electrode materials have been identified 

that provide excellent sensitivity and response time 

for sensing NO at 650–750°C in 10% O2. Sensor 

stability and cross-sensitivity will be further addressed in future efforts. Long-term dynamometer 

testing is to be performed by Ford, and planning has 

been intiated for ultimate technology transfer to a 

commercial entity. 

References

1. F. Menil, V. Coillard, and C. Lucat, “Critical 

Review of Nitrogen Monoxide Sensors for Exhaust Gases of Lean-Burn Engines,” Sensors 

and Actuators B, 67, pp. 1–23 (2000). 

2. N. Miura, G. Lu, and N. Yamazoe, “Progress in 

Mixed-Potential Type Devices Based on Solid 

Electrolyte for Sensing Redox Gases,” Solid 

State Ionics, 136–137, pp. 533–542 (2000). 

3. T. Ono, M. Hasei, A. Kunimoto, T. Yamamoto, 

and A. Noda, “Performance of the NOx Sensor 

Based on Mixed Potential for Automobiles in 

Exhaust Gases,” JSAE Rev., 22, pp. 49–55 

(2001). 

4. Rick Soltis and Dave Kubinski, Ford Research 

Center, Dearborn, MI. 

Publications/Presentations

 L. P. Martin, D. Kubinski, R. Soltis, J. Visser, 

M. Parsons and R. S. Glass, “A Current-Biased NOx

Sensor for Automotive Diesel Exhaust,” presented at 

the 204th Meeting of The Electrochemical Society, 

Orlando, FL, October 12–17, 2003. 

Patents Issued

 Patent application by L. P. Martin and A.- Q. 

Pham, “Current-Biased Potentiometric NOx Sensor 

for Vehicle Emissions,” LLNL Docket #: IL-11022, 

submitted April 2003. 
Propulsion Materials FY 2004 Progress Report 

41 

D. Hydrogen Compatibility of Materials for Automotive Applications 

Russell H. Jones, James Holbery, and Thomas Gallant 

Pacific Northwest National Laboratory 

P.O. Box 999 

Richland, Washington 99354 

(509) 376-4276; fax: (509) 376-0418; e-mail: rh.jones@pnl.gov 

DOE Technology Development Manager: 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) in friction force microscopy (FFM) mode 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

• Established a testing and research plan in collaboration with Westport Innovations, Inc., and Ford Motor Company. 

• Conducted initial AFM and FFM testing of injector materials. 

• Acquired actuators and actuator materials for high-pressure hydrogen testing. 

• Defined the required apparatus and initiated the design and construction of apparatus for the high-pressure hydrogen testing of fuel injector actuators. 

Future Direction

• Complete AFM/FFM tests on several fuel injector materials in ambient and hydrogen environments. 

• Complete in situ actuator tests on two types of actuators in high-pressure hydrogen gas. 

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

• Evaluate durability of other engine materials such as steels and aluminum alloys in hydrogen environments. 
FY 2004 Progress Report Propulsion Materials 

42 

Introduction

The friction and wear characteristics of metallic 

materials depend largely on surface oxide films. 

However, a hydrogen environment is chemically 

reducing so that the loss of the surface oxide by 

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

will be undertaken to determine the frictional behavior of metals in a hydrogen environment using in 

situ AFM/FFM. Measurements will be made in a 

hydrogen environment on metallic materials used by 

Westport Innovations in its actuators. These materials include AISI H13, M2 and 4140 steels, 400 and 

316L series stainless steels, and Aquamet 22. 

This study aims to better understand and quantify the mechanisms that determine friction coefficient and surface properties of actuator needles and 

nozzles within a 100% hydrogen service environment by comparing hydrogen-exposed and asreceived actuator materials. Using a combination of 

AFM in FFM mode and nanomechanical measurement techniques, we will analyze hydrogen effects 

on needle and nozzle materials to determine sliding 

contact degradation and extended wear behavior. In 

addition, we will perform repeated indentations at a 

single spot to simulate cyclical impact. This work 

will be coordinated with Westport Innovations, a 

manufacturer of hydrogen internal combustion injectors. The two sets of tests will be correlated and used 

to provide guidance on selection of hydrogen injector materials. 

Piezoelectric injectors made by KCI and 

EPCOS use the piezoelectric material PZT, a lead 

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 will be conducted on actuators and the PZT material in a high-pressure hydrogen environment of up to 100°C, typical of that 

in the engine application. The actuators and materials will be monitored during in situ voltage cycling 

that matches the actuator conditions. 

 

Approach

Nanomechanical surface properties and the 

relative friction coefficient of each candidate material will be determined using apparatus in place at 

Pacific Northwest National Laboratory (PNNL). 

Candidate materials to be evaluated are all currently 

used by Westport Innovations to produce injector 

needle and nozzles. They include the following: 

carburized steel, AISI M2 (heat treated, with WCC 

coating), AISI H13 (gas nitride case-hardened), and 

400 stainless steel. These samples will be tested both 

in the as-received condition and after exposure to 

100% hydrogen under the following conditions: 50–

100oC, a pressure of 31 MPa, and a test duration of 

100 h or greater. 

Nanomechanical surface properties will be determined in the ambient environment of each material listed using a Hysitron Picoindenter® mounted 

on a Digital Instrument Nanoscope® II AFM. We 

will perform two series of experiments: surface 

property characterization, including modulus and 

hardness, and repeated impact testing by repeating 

an indentation at the same location to determine material pile-up around the indent as a measure of deformation under a repeat load condition. Subsequently, the surface will be imaged with the AFM to 

quantify the impact zone. 

The relative friction coefficient between an 

Si3N4 AFM tip and each candidate material will be 

measured, in both the as-received and hydrogenexposed conditions, using the AFM in FFM mode. 

These tests will be run in both an ambient and a 

100% hydrogen atmosphere, the first time this is 

known to have been attempted. Using a multi-pass 

cantilever tip contact technique, whereby the AFM 

cantilever tip is in contact and passed across the surface under a constant load dependent upon the cantilever stiffness, the objective will be to determine the 

duration of surface wear necessary to measurably 

increase the material pair friction coefficient. We 

anticipate that each material will act differently, a 

reflection of their end-of-life wear properties; and 

we will make an attempt to relate these nano-scale 

measurements with larger bulk tests through a wellcharacterized material system, namely 316 stainless 

steel. 

The performance of EPCOS and KCI piezoelectric actuators will be evaluated in a highpressure hydrogen environment. A high-pressure 

autoclave with a pressure rating of 60 MPa will be 

used. The actuators will be electrically energized in 

situ in a high-pressure hydrogen environment under 

conditions consistent with injector operation. The 

voltage will be applied with a KCI power sup-
Propulsion Materials FY 2004 Progress Report 

43 

ply/driver unit. The actuators will be held in specially designed holders that allow the application of 

a compressive force during the test. The autoclave 

will have an oxygen monitor to ensure the environment remains at 100 ppm of oxygen or less. 

The test conditions that will be used are these: 

EPCOS actuator: peak voltage, 150 V; frequency, 

80 Hz; pulse width, 1.0 ms; rise time, 100–200 microseconds; fall time, 100–200 microseconds; temperature, 50–100°C; hydrogen pressure, 31 MPa 

(4500 psi); test duration, 100 h or greater. 

KCI actuator: peak voltage 450 V; frequency, 80 

Hz; pulse width, 1.0 ms; rise time, 300–500 microseconds; fall time, 300–500 microseconds; temperature, 50–100°C; hydrogen pressure, 31 MPa (4500 

psi); test duration, 100 h or greater. 

The output of these tests will include the voltage, current, and capacitance of the actuators as a 

function of time. Breakdown time and probable 

breakdown mechanisms will be determined as warranted by the results. 

Results

AFM and nanoindentation testing has begun in 

ambient conditions using a Digital Instrument multimode II fixed with a Hysitron Nanoindenter. The 

Park CP 5 AFM, located in PNNL Building 325, is 

currently being retrofitted to accept 100% hydrogen 

in the chamber; this process and safety procedure are 

scheduled to be complete by December 1, 2004. In 

preparation, Radiation II training by James Holbery 

has been completed. Testing using the Park CP5 is 

to begin in November, starting with ambient condition friction force microscopic surface measurements on candidate materials. 

Actuator testing is due to begin in early December. The actuators are in hand, the power supply 

is on order, and other autoclave systems such as the 

oxygen analyzer and valves are in hand and being 

checked out. The safety issues have been identified, 

and a safety procedure has been written. A preliminary safety review was completed. 

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 BaZr0.4Ce)0.4In0.2O3-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). 

Propulsion Materials FY 2004 Progress Report 

45 

4. OTHER 

A. Polymer Electrolyte Membrane Materials for Fuel Cell Applications at 

Elevated Temperature 

J. M. Simonson 

Oak Ridge National Laboratory 

P.O. Box 2008, MS 6064 

Oak Ridge, TN 37831-6110 

(865) 574-4962; fax: (865) 574-4961; e-mail: simonsonjm@ornl.gov 

J. W. Mays 

University of Tennessee, Knoxville, and Oak Ridge National Laboratory 

655 Dabney-Buehler Hall, 1416 Joe Johnson Drive 

Knoxville, TN 37996 

(865) 974-0747; e-mail: jimmymays@utk.edu 

K. A. Mauritz 

University of Southern Mississippi 

P.O. Box 10076 

118 College Drive 

Hattiesburg, MS 39406-0001 

(601) 266-559-5865; e-mail: kenneth.mauritz@usm.edu 

DOE Technology Development Manager: Susan Rogers 

(202) 586-3976; fax: (202) 586-9811; e-mail: susan.rogers@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, TN 

Prime Contract No.: DE-AC0500OR22721 

Objective 

• Develop a low-cost, high-performance polymer membrane material that operates at temperatures of up to 

120°C for transportation fuel cell applications. 

Approach 

• Synthesize new membrane materials, based on polyphenylene sulfonate, with potential for high ionic conductance, long-term stability, and low cost. 

• Test membrane material performance for electrical conductivity and test in single-cell test stand to assess potential applicability. 

• Improve performance characteristics of novel membrane materials through chemical and morphological modification and through the addition of functional inorganic modifiers. 
FY 2004 Progress Report Propulsion Materials 

46 

Accomplishments 

• Demonstrated synthesis of polyphenylene sulfonate, including polymerization, aromatization, crosslinking, and 

sulfonation steps. 

• Carried out initial water-swelling tests of novel membrane materials. 

• Identified inorganic functional modifiers with potential for membrane improvement. 

Future Direction 

• Complete the testing of membrane conductance and single-cell test stand performance with current membrane 

materials. 

• Initiate parametric determinations of membrane performance to assess optimal structural, functional, and modifier characteristics. 

• Establish additional capabilities for rapid assessment of novel membrane material performance. 

• Partner with the private sector to advance application of novel membrane materials for fuel cell applications to 

120°C. 

Introduction

Robust, highly conductive, and inexpensive 

polymer electrolyte membranes (PEMs) are needed 

for practical and reliable fuel cell operation at elevated temperatures. The current class of PEM fuel 

cells operating at 90°C is plagued by sensitivities to 

CO and peroxide formation that limit performance 

and require the use of high-purity fuels. A polymeric 

membrane able to operate at temperatures of up to 

120°C will minimize issues with CO, since adsorption is no longer kinetically favorable. The nature of 

the polymeric membrane plays a crucial role in determining the performance of the fuel cell. Unfortunately, current membranes based on polymers such 

as NafionTM suffer serious disadvantages, including 

high cost and limited thermal stability at temperatures above 100oC. Our approach combines novel 

material synthesis, characterization, and testing with 

the goal of demonstrating capabilities of new classes 

of PEMs for sustained operation at elevated temperatures. We have synthesized new polymeric 

membrane materials and are currently performing 

initial screening studies of their thermal, electrical, 

and transport properties. 

Approach

Our approach is to apply advanced synthetic 

techniques to prepare membrane materials with potential for high performance at low cost and to test 

these materials under fuel cell operating conditions. 

Polyphenylene sulfonate (PPS) has been selected as 

the initial candidate material for high-performance 

membrane applications at elevated temperatures 

(120°C). The material is synthesized using cyclohexadiene monomer starting material. After livingionic polymerization, the polymer is aromatized for 

thermal stability and resistance to attack from peroxides, crosslinked to control morphology and provide 

ion-conduction channel architecture, and sulfonated 

for ion conductance and water retention. 

Membrane materials are tested for thermal stability using thermal [differential scanning calorimetry (DSC)] and thermogravimetric analysis 

(TGA) techniques. Water-sorption measurements are 

used to assess the conditions for humidification of 

the PEM. Agreements are in place to test membrane 

materials using standard four-point-probe conductance measurements, and to prepare and test membrane-electrode assemblies (MEAs) based on these 

new materials, at Battelle Memorial Institute. This 

testing is designed to establish proof-of-principle for 

the novel membrane materials. 

Further improvement in membrane performance, 

both temperature capability and water retention, is 

anticipated through the addition of inorganic modifiers such as silica, either in a co-synthesis process or 

by incorporation as particulate materials. 

Results

In FY 2004, we focused on the preparation of 

new membrane materials, starting from polycyclo-
Propulsion Materials FY 2004 Progress Report 

47 

hexadiene (PCHD). The basis of the synthetic approach is to prepare the polymer in the desired molecular weight. Then the materials can be 

aromatized, crosslinked, and sulfonated as shown in 

the schematic in Figure 1. 

The form of material obtained from the steps in 

Figure 1 depends on the details of the synthesis 

route. The crosslinked polyphenylene is poorly 

soluble in most solvents tested and not amenable to 

straightforward solution casting of thin films appropriate for direct use as membranes. We have pursued 

two approaches to membrane preparation. In the 

first, PPS is synthesized by straightforward batch 

processing with subsequent purification of the material. This approach gives granular samples, as shown 

in Figure 2. 

While it has proved difficult to form reproducible membranes from this granular material, given its 

high thermal stability and high glass-transition temperature, further efforts to prepare these membranes 

are in progress. Alternatively, we are investigating 

the preparation of membranes from solvent deposition of PCHD thin films (step 1 of Figure 1), with 

subsequent crosslinking, aromatization and sulfonation. These efforts are currently in progress in parallel with membrane fabrication from granular 

materials. 

Thermal stability of the membrane is a key issue 

in sustained performance at the target temperature of 

120°C. PPS has been tested for thermal stability by 

DSC and TGA, and results from these tests are 

shown in Figure 3. 

The primary decomposition temperature for the 

material is near 500°C, as indicated by the strong 

peak in the derivative plot shown in Figure 3. Hotpressing the granular material results in thermal 

traces that show essentially no features in DSC to 

temperatures above 200°C. Thus it appears that the 

N

CHD PCHD

n

s-Buli

S2Cl2

PCHD

n

n

n

S2

Cl

Cl

Cross-linked PCHD

S2

n

Crosslink PCHD

P- Chloranil

m

Ac2O

SO3H

S2

n

m

H2SO4 S2

n

m

Crosslink PPP Crosslink PPS

SO3H

Figure 1. Synthetic preparation of crosslinked 

polyphenylene sulfonate membrane material from 

cyclohexadiene starting material. 

Figure 2. Polyphenylene sulfonate granular samples. 
FY 2004 Progress Report Propulsion Materials 

48 

pressing process, or alternatively, initial heat treatment of the membrane material, “burns out” 

residual solvent and/or volatile components of the 

membrane and the stability of the material is subsequently improved through the intended working 

temperature range. Further testing, including analysis of thermal decomposition products by gas chromatography or mass spectrometry, is needed to 

confirm the stability of the material after initial heat 

treatment. 

Capabilities for rapid screening (i.e., four-probe 

conductance measurements) and fuel cell test environments are being assembled at Oak Ridge National Laboratory for membrane and MEA tests. 

Until these facilities are available, to demonstrate 

proof-of-principle of the new membrane materials, 

agreements are in place with Battelle Memorial Institute in Columbus, Ohio, for testing in membrane 

and MEA configurations. 

It is anticipated that membranes based on PPS 

material can be further improved through a parametric investigation of the effects on performance of 

molecular weight (chain length) and the extent of 

aromatization, crosslinking, and sulfonation. In addition, it is anticipated that addition of inorganic functional modifiers (e.g., silica) to the membrane will 

help improve performance at relatively low humidity. A target has been established for operation at 

20% relative humidity at 120°C, and efforts under 

contract at the University of Southern Mississippi 

are aimed toward improving performance through 

addition of candidate modifiers. As shown in Figure 4, in addition to improvements expected from 

potential preferential adsorption of water on 

nanoparticle sites within the membrane, addition of 

these modifiers can also affect the polymer structure. 

We are working toward establishing a network structure that will promote the formation of ion- conducting channels at the nanoscale, while minimizing gas 

flow through the membrane. 

Conclusions

We have demonstrated that PPS, a candidate 

material for PEM transportation applications at 

120°C, can be readily synthesized from PCHD starting material; and we have demonstrated straightforward chemistry for aromatization, crosslinking, and 

sulfonation. Particularly if the precursor cyclohexadiene monomer becomes a readily-available 

commodity chemical, as is currently under market 

investigation, this new polymer electrolyte has the 

potential to provide a very cost-effective route to 

high-temperature membrane applications. Thermal 

stability testing has shown that the primary decomposition temperature of PPS is near 500°C. Thus in 

addition to its potential for low cost, the thermal stability of the polymer electrolyte is promising for applications even above the current target temperature 

of 120°C. 

Collaborative agreements are in place for nearterm testing of novel membrane materials, and for 

AFM: [sPS-b-EB-b-sPS]/Silicate

Self-Assembled Nanocomposite

Mauritz Research Group, USM

sPS = sulfonated PS

Lamellar rather than usual rodlike morphology

AFM: [sPS-b-EB-b-sPS]/Silicate

Self-Assembled Nanocomposite

Mauritz Research Group, USM

sPS = sulfonated PS

AFM: [sPS-b-EB-b-sPS]/Silicate

Self-Assembled Nanocomposite

Mauritz Research Group, USM

AFM: [sPS-b-EB-b-sPS]/Silicate

Self-Assembled Nanocomposite

Mauritz Research Group, USM

sPS = sulfonated PS

Lamellar rather than usual rodlike morphology

Figure 4. Lamellar structure in polymer matrix created through silica addition. 

135.76°C

87.68% 223.05°C

82.01%

592.85°C

74.41% Loss

(3.044 mg)

499.21°C

Temperature (°C)

Percent Sample Weight

0 200 400 600 800 1000

20

40

60

80

100

Loss Derivative (%/°C)

2.0

1.5

1.0

0.5

0.0

Thermogravimetric Analysis of PPS Sample

Figure 3. Thermogravimetric analysis of membrane 

material, indicating primary thermal decomposition 

near 500°C. 
Propulsion Materials FY 2004 Progress Report 

49 

the addition of functional inorganic modifiers to further improve membrane performance under conditions of elevated temperature and low relative 

humidity. In-house capabilities for expanded testing 

of PEM systems are being established and tested. 

Proof-of-principle of PPS as a membrane material for high-temperature applications is expected in 

FY 2004. Major issues remaining for deployment of 

fuel cells based on this material are optimization of 

membrane performance through variation of major 

synthetic variables (molecular weight; degree of 

aromatization, crosslinking and sulfonation), demonstration of acceptable ion conductance and membrane durability in test-stand environments, 

investigation of the potential for addition of inorganic functional modifiers for improved performance at low humidity levels, and estimation of 

material cost based on optimized membrane configuration. Initial contacts with potential industrial collaborators indicate significant interest in the 

possibilities of this new material for PEM applications, and these contacts will be pursued further as 

the technical status of the project matures. 

In FY 2005, we plan to continue synthesis and 

parametric testing of a range of PPS membrane materials and MEAs to assess the effects of changing 

material properties and treatment protocols on cell 

performance. Benchmarking test results and estimated costs against commercially available materials 

will provide the basis for selection of optimized synthesis, modification, and processing procedures. Our 

long-term goal is to define conditions needed for 

membrane performance in order to permit industrial 

scale-up of membrane production. 

Publications/Presentations

J. M. Simonson, J. W. Mays, and K. A. Mauritz, 

“Cost Effective Proton Exchange Membrane Materials for High-Temperature Fuel Cell Applications,” 

poster presentation at the Hydrogen and Fuel Cell 

Program Review, Philadelphia, PA.

51

APPENDIX A: ACRONYMS AND ABBREVIATIONS 

AFM atomic force microscopy 

ANL Argonne National Laboratory 

ANL–ES ANL–Energy Systems 

APM Automotive Propulsion Materials 

ASTM American Society for Testing and Materials 

CIDI compression-ignition direct-injection 

CO carbon monoxide 

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 

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 

I-V current-voltage 

ICS Industrial Ceramic Solutions 

ID internal diameter 

ITO tin-doped indium oxide 

kg kilogram 

LANL Los Alamos National Laboratory 

L/D length-to-diameter 

LLNL Lawrence Livermore National Laboratory 

MEA membrane electrode assembly 
52

NdFeB neodymium-iron-boron 

ND neodymium 

NEP National Energy Policy 

NIST National Institute for Standards and Testing 

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 

PCHD polycyclohexadiene 

PEM polymer electrolyte membrane 

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 

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

programs and to all the authors who prepared the project abstracts that comprise

this report. In addition, we would like to express our sincere appreciation to

XXXXXXXXX for compiling this report and to XXXXX for their artistic and technical

contributions in preparing and publishing this report.
A Strong Energy Portfolio for a Strong America

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

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

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

invests in a diverse portfolio of energy technologies.

For more information contact:

EERE Information Center

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

www.eere.energy.gov