REACTIVE MECHANICAL GRINDING OF ZRNI UNDER VARIOUS PARTIAL PRESSURES OF HYDROGEN

The intermetallic compound ZrNi was mechanically ground under various partial pressures of hydrogen. At the beginning of the grinding, hydri de phases (ZrNiH and/or ZrNiH3) are formed, which lowers the free ener gy of the compound, and the particle size are effectively reduced. Mor eover, with progression of the grinding, an amorphous phase starts to grow. Finally, depending on the partial pressure of hydrogen, a compos ite particle of the amorphous and crystalline phases is formed. Conseq uently, such a grinding technique under various partial pressures of h ydrogen promotes the synthesis of fine composite particles, each of wh ich consists of amorphous hydride and the crystalline hydride phases. In addition, the grinding enhances the decomposition to form ZrH2 even at room temperature. During the heating process under an argon atmosp here, the dehydrogenation of ZrH2 can progress even at low temperature s of around 750 K, which is caused by preferential crystallization of the amorphous phases in the fine composite particles.