Silica-Metal Composite for Hydrogen Storage Applications
In spite of their favourable chemical characteristics, using AB5 alloys as fixed bed for hydrogen storage devices requires proper management of a number of technological aspects. Among these, the mechanical stability of metal particle grains under hydrogen cycling and the overall thermal conductivity of the material bed constitute crucial features. We developed by High Energy Ball Milling HEBM a mechanically stable silica-based AB5 composite with enhanced thermal conductivity. Here, focusing on the material’s physical-chemical properties, we report on the silica-AB5 composite development and characterization. Particularly, we studied the material consolidation process, the resulting composite morphology and the system behaviour under hydrogen loading/unloading cycling.
Metal Hydride-Based Composite Materials with Improved Thermal Conductivity and Dimensional Stability Properties
To address the issues of poor thermal conductivity and fragmentation of metal hydride particles undergoing hydriding/dehydriding reactions, a metal hydride-based composite material was developed. The active metal phase was embedded in a silica matrix and a graphite filler was incorporated by ball milling. A set of compact pellet samples at different composition were prepared and tested. Experimental data obtained from the thermal conductivity measurements shown that using powder graphite produced a quite linear increase in the thermal conductivity of the metal hydride – silica composite. Ongoing studies include composition optimization as well as long-term testing upon cycling of such metal hydride composites to evaluate their potentiality in technological hydrogen storage applications.
Metal hydride hydrogen storage for near-ambient temperature and atmospheric pressure applications, a PDSC study
Pressure differential scanning calorimetry (PDSC) has been used to study the applicability of six hydrogen absorbing pseudobinary AB5 and AB2 alloys for near ambient temperature (10–50 °C) and atmospheric pressure (1–10 … 20 bar) applications. Van't Hoff plots of the materials have been determined from thermal absorption and desorption peak positions at different pressures. The pressure and temperature ranges were 1–70 bar and 20–150 °C, respectively. 
 
A large hysteresis effect and sloping P-C-T plateaux are the most serious problems of MmNi4.5Mn0.45Zr0.05 and Zr0.7Ti0.3MnFe La1 −xNdxNi5(x = 0.05–0.1), LmNi(1) (JMC) and Hydralloy C15 (GfE) are all well-suited for the pressure and temperature ranges mentioned above. Zr(Fe0.75Cr0.25)2 suffers both from hysteresis and sloping P-C-T. plateaux, but it can be used as a hydrogen storage material between an electrolyzer and a fuel cell, especially if the temperature range can be slightly narrowed.