Research Topics

Kaneaki TSUZAKI(Professor)

Faculty of Engineering

Faculty of Engineering

Fatigue and Fracture of Materials Laboratory

Hydrogen Utilization Processes Laboratory

Hisao MATSUNAGA

Yoshihiro FUKUSHIMA(Associate Professor)(Assistant Professor)

Kazunari SASAKI(Distinguished Professor)▶http://www.mech.kyushu-u.ac.jp/~force/Shunsuke TANIGUCHI

Yusuke SHIRATORI(Professor)(Associate Professor)▶http://www.mech.kyushu-u.ac.jp/~hup/index.html

How and why hydrogen can weaken steels?

Advanced Fuel Cell Materials and Systems

Steels are widely used for machine components and structures since they havesuperior strength as well as high toughness, which are however affected by impurity
elements. It is well-known that HYDROGEN can be one of the deleterious elements forthese properties of steels, and such a degradation is termed“Hydrogen Embrittlement(HE)”
As we move towards the commercial use of hydrogen stations and fuel cell vehicles(FCVs) in the near future, there are a number of technological and scientific issues
to be overcome. Among them, our task is to build and/or design methodology to use
commercial steels safely under high pressure hydrogen gas. For example, in thecurrent regulation in Japan, a limited number of high grade austenitic stainless steels(e.g. type 316L) that has been proved to possess a sufficient resistance against HE,
are permitted to be used for high pressure hydrogen gas applications. However, thesestainless steels are expensive due to the large amounts of alloying elements such as
Cr and Ni required during their production. To reduce the manufacturing cost of thesystem, the use of lower-cost materials (e.g. lower grade stainless steels, low alloysteels, cast iron etc.) is strongly required in industries. To ensure the safer use of such
low-cost materials, it is essential to understand the mechanism of HE as well as toobtain reliable data for various materials when they are exposed to hydrogen.
In general, steels are not homogenies but heterogeneous in microstructure;they have secondary particles, inclusions, and lattice imperfections such as grainboundaries. Accordingly, crack initiation and propagation occurs locally; the so-called
weakest link. Thus, it is important to clarify how hydrogen intrudes into steels aswell as how hydrogen facilitates the process of crack initiation and propagation. Wetackle the underlying problems with the aid of advanced experimental equipment in
the Research Center for Hydrogen Industrial Use and Storage (HYDROGENIUS), e.g.
fatigue and tensile testing machines with high pressure hydrogen gas up to 120 MPa,
precise hydrogen analyzer, microstructure characterizer such as SEM and TEM, etc.

Fuel cells are promising environmentally-compatible technologies for this century.
For technological development and their commercialization, however, various
scientific as well as engineering aspects should be clarified and established. Ourlaboratory, the Hydrogen Utilization Processes Laboratory, wishes to contributeto this promising technological field, based on more than 20 years of researchexperience in the field of fuel cell technology.
So far, we have built up the highest level research infrastructure in Japan,
and our own facilities enable us to conduct a wide range of fuel cell R&D, frommaterials to systems. Fuel cell fabrication equipment, facilities for electrical,
thermal, and electrochemical analysis including 55 fuel-cell evaluation systems
and characterization instruments, such as the highest-resolution FESEM-EDX andSTEM-FIB systems are available exclusively to our group members. At this moment,
we address the development of novel electrode materials, establishment of systemdesign criteria, elucidation of mechanisms and processes and breakthroughs intechnical issues concerned.

01 Research on electrode materials and reaction processes for Solid Oxide Fuel Cells (SOFCs)
One of the most appealing benefits of the solid oxide fuel cell (SOFC) overother types of fuel cells is the fuel flexibility: producing electricity from a varietyof fuels, including renewable biomass, natural gas, or even gasoline with lesspollution-forming emissions. Nevertheless, it is likely that various kinds of minor
fuel impurities could cause fatal degradation of cell performance or affect overall
SOFC system durability. Since 2008, we have been involved in a national project
supported by NEDO and are formulating the world’s first database concerning thelong-term impurity tolerance of SOFC.

02 Application of bio-fuels to SOFC
Biogas, generated by anaerobic fermentation of organic wastes, consists of60% CH4 and 40% CO2. In principle, biogas containing natural reforming agent,
CO 2, can be directly fed into high temperature SOFC without pre-reformer toobtain electricity. Therefore, hydrogen production and purification systems can besimplified leading to cost cutback and enhancement of overall system efficiency.
Our group has demonstrated the long-term stabilityof internal reforming SOFC running on biogas
using anode-supported single cell. At this moment,
thermomechanical reliability of internal reforming SOFC
is being evaluated using a SOFC visualization system
which enables us to perform in-situ measurement oftemperature distribution in SOFC.

●Visualization where hydrogen atoms locate

Visualization system of SOFC

03 Development of metal supported SOFC
Fig.1 SEM images showing hydrogen segregation in the microstructure of a cast iron;
Ag decoration method.

We are also conducting research and development of metal supported SOFC cellusing heat-resistant stainless steel for substrate, aiming to create a highly-robust
SOFC cell which withstands thermal shock, fuel shortage, etc.

●Observation how cracks propagate

04 Research on electrode materials and reaction processes for Polymer Electrolyte Fuel Cells (PEFCs)
We are focusing on the development of novel
electrocatalysts and formulation of electrode designfor polymer electrolyte fuel cells (PEFCs), a promisingenergy conversion system in hydrogen-relatedtechnologies. Recently, we have made considerable
progress in the development of a carbon-freeelectrocatalyst to fundamentally reduce the problem ofcarbon corrosion.

Carbon-free electrocatalyst for PEFC

05 Fundamentals of hydrogen related engineering
We wish to establish scientific principles of fuel cells and related hydrogentechnologies. Such activities include defect chemistry on ionic, electronic, andmolecular levels; solid state electrochemistry; thermodynamics and transportphenomena; electrode processes; acceleration testing; and experimental techniques
for electrochemical characterization, advanced microscopy, and simulation.

Fig. 2 ECC images showing crack propagation along twin boundaries in a high Mnaustenitic steel under hydrogen atmosphere.

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