Research outline of Intermetallic Catalyst Group

♦ We have studied to solve the grain boundary brittleness of intermetallic compound Ni₃Al which is known as excellent high-temperature structural materials. In this study we developed a technique of grain boundary character in Ni₃Al using unidirectional solidification, and succeeded in achieving more than several 10% of tensile elongation without boron addition. Eventually we for the first time succeeded in fabricating thin foils of Ni₃Al by cold rolling. The cold-rolled foils are brittle as a result of heavy reduction, but we established an effective heat-treatment technique to enhance the ductility enough for foil forming. With their excellent high-temperature properties, the Ni₃Al foils can be used as structural component for a small scale high-temperature chemical device such as micro-reactor.

♦ Very recently, we for the first time found that the Ni₃Al foils exhibit a high catalytic activity for methanol decomposition, resulting in production of hydrogen. The result means that the Ni₃Al foils can be used as catalyst, which is quite unusual in catalyst because the foils are in flat form. Combining the two unique properties of Ni₃Al foils, i.e., high-temperature structural and catalytic properties, we have started a novel project on developing Ni₃Al foils aimed at application to microreactor for hydrogen production.

Research topics

Subject-1 Test assembling of microreactor
Though Ni₃Al foils have a potential for microreactor as mentioned above, it is not clear yet if the foils exhibit a high performance in the system. We are planning to assemble a test microreactor to evaluate the performance of the foils and also to search the subjects to solve.

Subject-2 Study on catalytic properties
We have clarified that the reason of the observed catalytic activity is due to the spontaneous formation of fine Ni particles on the Ni₃Al foils during catalytic reaction. The formation of such nano-surface structure contributes to effectively enhance the catalytic activity of the Ni₃Al foils. We are now carrying out to enhance the catalytic activity by surface treatment such as alkali leaching and oxidation. Also, we are investigating the catalytic properties for methane steam reforming. In this study, precise analysis of the evolution of foil surface is crucial because it leads to the understanding of the development mechanism of catalytic activity. We are using a variety of sophisticated analyzing techniques for this purpose.

Subject-3 Composition and microstructure control of the Ni₃Al foils
So far, we found that the catalytic activity the Ni3Al foils is sensitive to the chemical composition. We can expect that refinement of the microstructure increases the surface area, which leads to enhance the catalytic activity. We are investigating an optimum chemical composition and heat treatment conditions for this purpose.

Subject-4 Mechanical properties and welding technique
We are evaluating the mechanical properties of the modified Ni₃Al foils mentioned above and also developing welding and jointing techniques for assembling microreactor.

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