Takanori Suda*, Ryouichi Kobayashi*, Seiichi Watanabe*, Somei Ohnuki*, Heishitirou Takahashi**, Hironobu Arashima*** and Toshiki Kabutomori***
* Department of Materials Science, Faculty of Engineering, Hokkaido University, Sapporo 060-8628 ** Center for Advanced Research of Energy Technology, Hokkaido University, Sapporo 060-8628 *** Muroran Research Laboratory, The Japan Steel Works, LTD., Muroran 051-8505Most of hydrogen storage alloys show decrepitation during hydriding-dehydriding cycles. The decrepitation assists initial activity and reaction rate. However, it causes lowering of thermal conductivity, difficulties of handling, degradation and others. In this work, the decrepitation process was examined with regard to mechanical properties and microstructure.
Four types of alloys; LaNi5, TiMn1.5, TiFe0.8C0.1 and ZrNi are used for this work. Compression test, Vickers hardness measurement and high-resolution electron microscopy observation were carried out before and after hydrogenation. Ductile alloys did not show remarkable decrepitation. Brittle alloys showed typical decrepitation, in which the nano crystal grains were observed by use of high-resolution microscopy. These results emphasize that the decrepitation process is different each other's, depending on the ductility or brittleness of the alloys.
hydrogen storage alloys, decrepitation, high-resolution electron microscopy, mechanical properties, nano crystal grain