Hitachi Metals, Ltd. has developed metal interconnect materials with higher oxidation resistance and strength for use in solid oxide fuel cells (SOFC).
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Interconnects, an important component in SOFCs, electrically connect individual cells. Among the characteristics demanded in such materials are oxidation resistance over sustained periods of time at certain operating temperature ranges (700–850 °C, for example); excellent electrical conductivity at the operating temperature; and a coefficient of thermal expansion close to that of zirconia ceramic electrolyte material (YSZ).
General stainless steel (430ss, etc.) does not have sufficient oxidation resistance. For nickel-based alloys (Alloy 600, etc.), which have excellent oxidation resistance, the coefficient of thermal expansion is large. Likewise, alloys containing aluminum have excellent oxidation resistance, but the electrical conductivity of their oxide scale is insufficient, Hitachi says.
Hitachi Metals has been working for some time to develop interconnect materials capable of satisfying these required properties. In 2005, Hitachi completed work on ZMGTM232L, which is a Fe-22%Cr ferritic alloy with a small addition of special elements for SOFC interconnector applications.
The new interconnect materials, ZMGTM232J3 and ZMGTM232G10, further improve electrical conductivity, oxidation resistance, and strength beyond the levels achieved in ZMGTM232L. ZMG232J3 has better oxidation resistance and better electrical conductivity than those of ZMG232L. ZMG232G10 has lower Cr evaporation than that of ZMG232L and ZMG232J3.
Hitachi Metals has begun supplying samples. The company is targeting sales of ¥ 500 million (US 6.2 million) per year by Fiscal 2015, and ¥5 billion (US$62 million) per year by Fiscal 2020.
This announcement contains results obtained through research into the development of systems and elemental technology on SOFCs commissioned from the New Energy and Industrial Technology Development Organization (NEDO).