ANALYSIS OF FETI HYDRIDE ALLOYS BY THERMAL-ANALYSIS, SMALL-ANGLE NEUTRON-SCATTERING AND POSITRON-ANNIHILATION

Samples of vapour deposited FeTi and electrochemically loaded with hyd rogen from LiOH solution have been examined by thermal analysis, posit ron annihilation and small angle neutron scattering techniques. Therma l analysis shows that the FeTi loads hydrogen without the need for act ivation although there was not a good correlation between the amount o f hydrogen loaded and duration of loading. Positron annihilation and S ANS on the untreated sample showed that the alloy was highly disordere d in nature and contained a large concentration of vacancy clusters. S ANS also showed an increase in the interfacial scattering surface area following hydrogen loading, consistent with an increase in voidage wi thin the structure. Positron annihilation on the other hand suggested a decrease in the concentration of vacancies following hydrogen loadin g. It was concluded that some of the voids within the structure were f illed by hydrogen gas which caused a decrease in the positron lifetime . However, not all of the voids were filled with gas.