Hydrogen absorption studies in Zr0.2Tb0.8Co3 and decrepitation and cyclic stabilities in Zr0.2Tb0.8Co3 and ZrMnFe

Pressure-composition isotherms have been determined for a Zr0.2Tb0.8Co3 alloy in the ranges 10 less than or equal to P (mbar)less than or equal to 900 and 75 less than or equal to T (degrees C)less than or equal to 200. The hydrogen absorption study shows that the substitution of Zr for Tb in TbCo3 results in the shift of the plateau region to higher equilibrium pressures with a reduction in the hydrogen capacity. An X-ray study on the hydrogenated Zr0.2Tb0.8Co3 alloy reveals that the alloy does not decompose upon hydrogenation. Particle size measurements in Zr0.2Tb0.8Co3 and ZrMnFe alloys before and after hydrogenation show that the decrepitation in Zr0.2Tb0.8Co3 is far less than that in the much harder material ZrMnFe. A plateau pressure of near 1 bar at a temperature suitable for practical applications can be conveniently obtained by appropriate replacement of Tb by Zr in TbCo3. (C) 1997 Elsevier Science S.A.