Pressure-Composition-Temperature Properties of Hydriding Combustion-Synthesized Mg<SUB>2</SUB>NiH<SUB>4</SUB>

Abstract

Pure Mg 2 NiH 4 was first prepared by Hydriding Combustion Synthesis (HCS), under which pressure and temperature were sensitively controlled. The purpose of this paper was to study "Pressure-Composition-Temperature (PCT)" properties of the HCSed product, in which hydrogen storage capacity, hydriding reaction rate, and PCT curves were mainly examined, in comparison to the commercially available product, i.e., Ingot Metallurgy product. The results showed that the HCSed Mg 2 NiH 4 has 3.6 mass%, same as theoretical value, in hydrogen storage capacity in the first cycle just after synthesized without activation treatment, and very large reaction rate; only five minutes for full charge. Plateau pressure of the HCSed Mg 2 NiH 4 in PCT curves also became relatively lower than the conventional one. One of the most interesting results is the high activity of our product: it stored hydrogen even at room temperature. These results appealed a possibility of new productive process of hydrogen storage alloy from the viewpoint of product property.

Self-ignition combustion synthesis of LaNi5 utilizing hydrogenation heat of metallic calcium

“…This was the reason why the hydrogenation proceeded very quickly. The product obtained in Run 2 showed 1.54 mass% in hydrogen storage capacity, as the same as the value of commercial-available LaNi 5 . Meanwhile, the product obtained in Run 1 stored hydrogen as much as 1.33 mass%; this value is corresponds to 86% of the value commercial-available LaNi 5 .…”

“…Nickel rare-earth metal compounds, so-called AB 5 -type hydrogen storage alloys, have been extensively studied because of their good hydrogenation properties and potential applications such as hydrogen storage, chemical heat pumps, hydrogen purification and Ni-metal hydride batteries [1]. In general, hydrogen storage alloys are conventionally produced by using a melting method that requires several time-and energy-consuming processes such as heat treatment, pulverization, and activation treatment.…”

“…In 1997, one of the authors proposed the hydriding combustion synthesis (HCS) of the self-propagation mode as an innovative manufacturing process for a Mg-based hydrogen storage alloy [4,5]. The product, synthesized from a mixture of metallic powders in a hydrogen atmosphere, was pure hydride without any activation treatment.…”

Electrochemical properties of Mg-based hydrogen storage alloys prepared by hydriding combustion synthesis and subsequent mechanical milling (HCS+MM)

“…However, it usually takes a long time and the sample is easily contaminated during the milling process. Hydriding combustion synthesis (HCS) was developed in 1997 by Akiyama et al, which has been regarded recently as an innovative processing and fabrication to produce magnesium-based hydrogen storage alloys [6][7][8][9]. Some advantages of HCS are short time and lower energy requirement of the process and high purity and activity of the product [10].…”

Volumetric Thermal Analysis of Hydrogen Desorption from Mg-13.5wt%Ni Hydride

“…However, its hydriding and dehydriding rates are very slow. To improve the reaction rate, many works have been done by alloying with many transition metals 1,2) and by different alloying methods, such as conventional melting, mechanical alloy and Hydriding Combustion Synthesis (HCS) [3][4][5][6][7][8][9][10][11][12] .…”