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PCT isotherms; hydrogen storage materials; TPS; thermodynamics; thermal properties; electrical properties.

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 𝛼 and 𝛽 regions and one mixed (𝛼 + 𝛽) phase. The thermodynamic parameters viz. the relative partial molar enthalpy (𝛥 𝐻) and relative partial molar entropy (𝛥 𝑆) 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 𝛥 𝐻 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.

Ankur Jain¹ R K Jain¹ Shivani Agarwal¹ I P Jain¹

1. Material Science Laboratory, Centre for Non-Conventional Energy Resources, 14, Vigyan Bhawan, University of Rajasthan, Jaipur 302 004, India

Manuscript received

18 May 2005

Manuscript revised

29 December 2005