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.
Electrochemical hydrogen storage properties of NiAl2O4/NiO nanostructures using TiO2, SiO2 and graphene by auto-combustion method using green tea extract
Abstract NiAl2O4/NiO nanostructures were synthesized via an auto-combustion method using green tea extract. TiO2, SiO2, and graphene were used in order to enhance the electrochemical hydrogen storage performance of NiAl2O4. The structural analysis of host texture confirmed the formation of NiO alongside with NiAl2O4. Furthermore, the formation of nanocomposites and distribution of the additives on the surface of NiAl2O4/NiO nanostructures were affirmed by XRD and EDS spectra. The morphological analyses were displayed the nanoscale formation of the particles. Interestingly, the electrochemical hydrogen storage of the nanocomposites indicated that upon addition of TiO2, SiO2 and graphene, the discharge capacity enhanced as compare to the host material. The maximum discharge capacities of NiAl2O4/NiO and its respective nanocomposites containing SiO2, graphene, and TiO2 were observed at 850, 2000, 2750 and 3000 mA h/g, respectively.
Energy Transfer in Mechanical Alloying (Overview)
It is essential to understand in which way and how much energy is transferred from the milling tools to the powder in the milling process. We have attempted to quantify the energy transferred per impact and per unit of mass in a planetary mill assuming that collision is the dominant energy transfer event. Further, attrition mechanism (rolling/sliding) has been considered by evaluating the effect of filling the milling vessel. The energy transfers evaluated by the above modelization have been proved to be able to correlate the input energy and the different solid state reaction undergone by the Pd-Si system submitted to the milling action in both planetary and shaker mills. Measurements of power consumption during the milling process have been also performed and compared with those based on theoretical modelization. The fairly good agreement obtained gives a strong support to the validity of the theoretical background.