DEUTERIUM ABSORPTION AND MATERIAL PHASE CHARACTERISTICS OF ZR2FE

Deuterium absorption and material phase characteristics of Zr2Fe (SAES St 198) were studied. Scanning electron microscope images of polished surfaces, electron probe microanalysis and X-ray powder diffractometry indicated the presence of a continuous Zr2Fe phase with secondary phases of ZrFe2, Zr5FeSn, alpha-Zr and Zr6Fe3O. A statistically-designed experiment to determine the effects of temperature, time and vacuum quality on activation of St 198 revealed that when activated at low temperature (350-degrees-C) deuterium absorption rate at 350-degrees-C was slower when the vacuum quality was poor (2.5 Pa vs. 3 X 10(-4) Pa). However, at higher activation temperature (500-degrees-C), deuterium absorption rate at 350-degrees-C was fast and was independent of vacuum quality. Deuterium pressure-composition-temperature (P-C-T) data are reported for St 198 in the temperature range 200-500-degrees-C. The P-C-T data over the full range of deuterium loading and at temperatures of 350-degrees-C and below are described by the following expression given in terms of the equilibrium D2 absorption pressure, P(D2), and the getter loading, q: K0e- (DELTAH(a)/RT) = q2/P(D2)(q*-q)2 where DELTAH(a) and K0 have values of 101.8 kJ mol-1 and 3.24 X 10(-8) Pa-1, respectively, and q* is 15.998 kPa L-1 g-1. At higher temperatures, one or more secondary reactions in the solid phase occur that slowly consume D2 from the gas phase. X-ray diffraction and other data suggest these reactions to be: 2Zr2FeDx --> xZrD2 + x/3 ZrFe2 +(2 - 2/3x)Zr2Fe Zr2FeDx +(2- 1/2x)D2 --> 2ZrD2+Fe where 0<x<3. Reaction between gas phase deuterium and Zr2Fe formed in the first reaction accounts for the observed consumption of deuterium from the gas phase by this reaction.