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.
Nanostructured metal hydride – Polymer composite as fixed bed for sorption technologies. Advantages of an innovative combined approach by high-energy ball milling and extrusion techniques
Different metal alloys can react highly exothermically and reversibly with hydrogen to form metal hydrides. Based on these reactions several application have been developed, e.g. in fuel cell, in storage for hydrogen gas and in sorption heat pumps. By exploiting the thermodynamical properties of some metal hydriding alloys, cooling energy can be generated by using renewable, sustainable and/or disposable energy sources. However, hydriding alloys show some limitations in their behaviour mainly regarding their intrinsic low thermal conductivity and mechanical stability during the hydriding process. A proper management of these issues is required in practical applications in particular when the metal hydrides have to be stably packed as fixed beds with good mechanical stability, high thermal conductivity, fast kinetics, reproducibility, durability.
Selective absorption of hydrogen by Ti-Mn-based alloys from gas mixtures containing CO or CH4
Abstract The kinetics of the pressure-induced repetitive hydriding and dehydriding of the alloy Ti 1.2 Mn 1.8 and the related compound Ti 0.98 Zr 0.02 V 0.45 -Fe 0.1 Cr 0.05 Mn 1.4 using hydrogen mixtures containing CO or CH 4 was investigated at room temperature. The absorption rates of both alloys were slightly retarded in hydrogen containing 5 vol.% CH 4 , whereas the reversible storage capacities remained unchanged. However, the decrease in the absorption rate of Ti 0.98 Zr 0.02 V 0.45 Fe 0.1 Cr 0.05 Mn 1.4 could not be explained by the lower partial pressure of hydrogen alone. Contamination of hydrogen by CO leads to passivation of both alloys after several hydriding-dehydriding cycles. If the samples are only partially passivated by CO, reactivation without any heat treatment is possible. A fully passivated sample of Ti 0.98 Zr 0.02 V 0.45 Fe 0.1 Cr 0.05 Mn 1.4 cannot be reactivated to the initial state by means of heat treatment.