Preparation of fine Nb₃Al powder by hydriding and dehydriding in an arc-melting chamber

The disintegration due to hydrogenation of Nb-Al alloys with eight different compositions has been studied. The hydrogenation is performed directly in an arc-melting chamber without exposing Nb-Al ingots to air after arc-melting. Because the active surface resulting from arc-melting is preserved, Nb-Al alloys absorb a large amount of hydrogen and disintegrate rapidly into fine particles, even though the pressure of hydrogen is only at 0.1 MPa. This disintegration is closely related to the arc-melting atmosphere and the composition of the alloys. Structural changes of Nb-Al alloys before and after hydrogenation and dehydrogenation have been examined by X-ray diffraction, electron microscopy and chemical analysis. A fine powder of single Nb₃Al phase with an average particle size of less than 14 μm can easily be obtained by hydriding Nb-Al alloy buttons with aluminum compositions from 22 to 28 at.% in an arc-melting chamber, followed by dehydrogenation at 1073 K for 3.6 ks.