Papers by Keyword: Mg-Ni Alloy

Abstract: New Mg-10wt%Ni hydrogen storage alloys were fabricated by casting which is a very simple and cost effective production process. Alloying elements such as Nb and Ti, which have relatively high melting temperatures and very low solubility in solid Mg, were successfully dissolved into the liquid Mg-Ni alloy. The Mg-Mg2Ni alloys contain a well-refined lamellar eutectic microstructure after solidification with a large interfacial area between the Mg and Mg2Ni phases which provides for good hydrogen sorption properties. This is considered to be due to the high diffusivity of hydrogen along the interphase boundaries. Addition of transition metals such as Nb and Ti results in the formation of intermetallic phases with a size about 10-20μm during solidification. Furthermore, Ti was found to be strongly segregated to the eutectic Mg-Mg2Ni interface. In the presence of Nb and Ti, the hydrogen sorption kinetics of the Mg-Mg2Ni alloy is further improved. This suggests that the transition metals act as active catalysts that eases and accelerates the hydrogen diffusion during hydrogenation and dehydrogenation. In this paper, we present the hydrogen storage properties and their relationship to the microstructure of the cast Mg-10wt%Ni alloys. Detailed microstructural analysis was carried out in order to further understand the hydrogen diffusion and storage mechanisms.

Abstract: Hydrogen is suggested as a promising fuel of the near future for the utilization in automotive and mobile applications. Therefore, safe and effective hydrogen storage systems need to be developed. One of the possibilities, suitable especially for mobile applications, is the storage of hydrogen in the form of light-metal hydrides. In this work we studied microstructure and hydrogen absorption and desorption kinetics in selected Mg-Ni alloys. Hydrogen saturation was carried out by the cathodic polarization in alkaline water-based solution. It was confirmed that hydrogen could be stored in the Mg2Ni intermetallic phase forming Mg2NiH0.3 phase using this technology. MgH2 hydride is also formed when the temperature of 90 °C is applied. The total content of hydrogen in the material after saturation is approx. 0.7 wt. % according to the thermogravimetry analysis. This low value is caused probably by the surface oxidation, blocking further hydrogen diffusion. Thermal hydrogen desorption tests showed that the Mg2NiH0.3 phase is able to release hydrogen even at temperatures lower than 100 °C.

Abstract: Amorphous Mg-Ni alloy was prepared by mechanical alloying (MA). The state of the amorphous phase was analyzed by X-ray diffraction (XRD). The hydrogen desorption capabilities and electrochemical properties were tested. The analysis of the relationship among the ball-milling parameters, microstructures and properties of the alloy showed that the milling velocities have a critical influence on the formation of Mg-Ni amorphous phase. The higher the milling velocity is, the less the forming time of the amorphous phase is. And with the increasing of the ball-milling time, the amount of Mg-Ni amorphous phase increases. Whereas the hydrogen desorption capabilities and electrochemical properties will decrease if the alloy is ball-milled for a long time after the complete amorphization occurs. Mg, Ni atom ratio also has some obvious influence on the formation of the amorphous phase and the properties of the alloy. Increasing the content of Ni appropriately will improve the efficiency of formation of the amorphous phase, the hydrogen desorption capabilities and electrochemical properties of the alloy.