Thermal analysis on the Li-Mg-B-H systems

Thermal analyses of the mixture of MgH₂ and LiBH₄ doped with TiCl₃, and each element MgH₂ or LiBH₄ doped with TiCl₃ were performed under an inert gas flow and 0.5 MPa H₂-gas conditions. It was indicated that the hydrogen desorption reaction of MgH₂ + 2LiBH₄ to MgB₂ + 2LiH + 4H₂ phases proceeded at temperature above 400 °C under 0.5 MPa hydrogen, whereas, under an inert gas atmosphere, the reaction of the same mixture was transformed into Mg + 2B + 2LiH + 4H₂ phases in a temperature range from 350 to 430 °C. Before these reactions, the dehydrogenation of MgH₂ and the melting of LiBH₄ took place under both hydrogen and the inert gas atmospheres with increasing temperature. In addition, the molten LiBH₄ did not decompose into LiH, B and H₂ below 450 °C under 1 MPa H₂, while the LiBH₄ decomposed even below 450 °C under an inert gas atmosphere. From these results, it is deduced that the reaction producing MgB₂ is a solid-liquid reaction between solid Mg and liquid LiBH₄ above 400 °C without decomposition of molten LiBH₄ under a hydrogen atmosphere, while MgH₂ dehydrogenate. A characteristic solid-liquid reaction is realized under a hydrogen atmosphere for proceeding of the MgB₂ producing reaction in this system.