Pseudobinary intermetallic compounds in Hf_2M'- Hf_2M''(M',M''=Mn, Fe, Ni, Cu) systems and their interaction with hydrogen at high pressures

摘要

Ternary alloys in the Hf_2Ni-Hf_2Mn, Hf_2Ni-Hf_2Fe, Hf_2Ni-Hf_2Cu and Hf_2Fe-Hf_2Cu systems have beenprepared and characterised by X-ray diffraction and pressure-composition isotherm measurements. Single phase compoundshave been obtained for all Ni-containing alloys with a generalcomposition of Hf_2Ni_0.5M_0.5. These compounds retained thestructure type of parent Hf_2M intermetallics: cubic Ti_2Ni typefor Hf_2Ni_0.5Fe_0.5 and Hf_2Ni_0.5Mn_0.5 and tetragonalMoSi_2 type for Hf_2Ni_0.5Cu_0.5. The new hydrides obtainedfrom ternary intermetallics had the composition ofHf_2Ni_0.5M_0.5H_x where x=3.1 (M=Cu) and 4.9-5.0 (M=Mn,Fe). Formation of hydride phases from cubic Mn- or Fe containingcompounds occurred without any change in structure type but wasaccompanied by unit cell volume expansion of 23-24 percent. Inthe case of Cu, here was a tetragonal to orthorhombictransformation. An absence of phase transformations in highpressure range of 100 to 2000 atm for new compounds unlike theearlier studied Hf_2M-H_2 systems has to be noted. 1999 ElsevierScience S.A. All rights reserved.