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Products and solutions, 2011-12-23, 11:00 AM

ThyssenKrupp VDM offers improved high-performance material for fuel cells for vehicles and households

ThyssenKrupp VDM, together with the Jülich Research Center, has developed Crofer 22 H, an improved high-performance material for solid oxide fuel cells (SOFC). Crofer 22 H was readied for market in a multi-year project with the involvement of other industrial partners. The new material can be used to produce lightweight fuel cell stacks, e.g. for use in vehicles. “A particular emphasis of our work on Crofer 22 H was to develop a commercial-scale production process,” says Dr. Jutta Klöwer, head of research and development at ThyssenKrupp VDM. “As a result, we can now supply a lower-cost alloy with superior properties to steel for use in fuel cell interconnects.” The material is suitable for large-scale energy supply systems, small decentralized household units and automotive applications.

Solid oxide or high-temperature fuel cells deliver clean energy in the form of heat and electricity with a high degree of efficiency and are therefore an innovative energy source for the future. This kind of fuel cell technology generates the required hydrogen-rich gas from fuels such as diesel, gasoline and methanol at temperatures up to 900 degrees. Conditions inside the fuel cells call for special materials: Crofer 22 H was specifically developed for high-temperature fuel cells. It contains between 20 and 24 percent chromium and other alloying elements such as tungsten, niobium, titanium and lanthanum. The new material is characterized by high corrosion resistance at temperatures up to 900 degrees, good electrical conductivity of the oxide layer, and high mechanical strength at operating temperature. It is also readily formable. ThyssenKrupp VDM optimized the properties of Crofer 22 H under the “ZEUS III” research program in collaboration with the Jülich Research Center.

In fuel cells, the high-performance material is used in the so-called interconnects – plates that connect the individual cells into an efficient stack. For this it needs to display numerous characteristics such as electrical conductivity, corrosion resistance and mechanical strength; it must also be readily formable and have no adverse effects on the cell. Crofer 22 H meets all these very specific requirements. A further advantage is its thermal expansion, which matches that of the ceramic materials used in the cell. This prevents mechanical stresses between the two materials that could damage the ceramics. “By manufacturing the material on a commercial scale, we can keep fuel cell production costs down. Ultimately it’s about reducing system costs,” says Dr. Robert Steinberger-Wilckens from the Jülich Research Center. “Crofer 22 H doesn’t need to be melted in a vacuum induction furnace, which significantly reduces production costs,” adds Dr. Jutta Klöwer. In addition to Crofer 22 H, further materials from ThyssenKrupp VDM are used in fuel cells. For example, high-temperature nickel alloys feature in other SOFC parts such as heat exchangers and reformers.

In addition to mobile use as an auxiliary power unit in cars, trucks, aircraft or ships, fuel cells can be used in many stationary applications to supply power to buildings or in large and small combined heat and power plants. They open up a more efficient way of producing heat and electricity for private homes and vehicles. With fossil fuels very expensive, this innovative development is a sustainable, low-cost alternative suitable for use on a widespread basis. Mini power plants are on the rise: They display excellent energy efficiency and deliver heat and electricity with no hazardous emissions – all properties of a successful future technology.

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