DISINTEGRATION AND POWDER FORMATION OF NB75M25 (M = AL, SI, GA, GE, AND SN) DUE TO HYDROGENATION IN AN ARC-MELTING CHAMBER

Nb75M25 (M = Al, Si, Ga, Ge, and Sn) alloy ingots were prepared by the conventional are-melting method and then were directly reacted with h igh purity hydrogen of 0.1 MPa in an are-melting chamber without expos ing the ingots to air. As the clean surface of the are-melted ingots i s preserved, the ingots rapidly absorb a large amount of hydrogen with out any activation treatments and disintegrate violently into fine par ticles. The disintegration of ingots depends on the M element. The col lected particles are investigated by x-ray diffraction, electron micro scopy, chemical analysis, and thermal analysis. The particles are hydr ides of Nb75M25 after hydrogenation and have a sharp-edged polygonal a ppearance. After dehydriding, fine Nb3M powders with Al5 crystalline s tructure are obtained except for Nb75Si25. In comparison with the atom ized Nb3M powders, the Nb3M powders prepared by the present study have a smaller average particle size and lower impurity contents.