Structural, electrical and thermodynamical aspects of hydrogenated La-Ni-Si alloy

Abstract

The structural, electrical and thermodynamic properties of a La-Ni-Si [La = 28.9%, Ni = 67.5%, Si = 3.6%] alloy have been investigated. Powder XRD results show that the lattice constants and unit cell volume of the alloy increase after hydrogen storage. It was also found that the resistance of the alloy increased with dissolved hydrogen concentration. Hydrogen absorption pressure composition Isotherms have also been investigated which show the presence of two single a and β regions and one mixed (α + β) phase. The thermodynamic parameters viz. the relative partial molar enthalpy (ΔH) and relative partial molar entropy (ΔS) of dissolved hydrogen, are found to be in the range 8-18 kJ (mol H)-1 and 25-63 JK-1 (mol H)-1. From the dependence of ΔH on the hydrogen concentration, X, the different phases [α, α + β, β] and phase boundaries of the alloy-H system are identified. Thermal conductivity and diffusivity of La-Ni-Si and its hydride have been measured at room temperature by using TPS technique. Thermal conductivity was found to decrease due to absorbed hydrogen in the alloy. © Indian Academy of Sciences.