Dispersion and phase transformations of intermetallic compounds and alloys of Ti, Zr, and Y with iron and nickel in the reaction with ammonia

Abstract

The review collates the results of studies on the chemical dispersion and phase transformations of Ti, Zr, and Y alloys with iron and nickel during the reaction with ammonia at a pressure of 0.6—0.8 MPa in the temperature range of 100—500 °C in the presence of NH₄Cl as the activator. Promising working materials for metal hydride hydrogen storage, including alloys (Ti₉₀Mg₁₀, Y₆₇Fe₃₃, and Ti₆₇Fe₃₃) and intermetallics (Ti₂Ni, Zr₂Ni, Zr₃Al₂, ZrV₂), are considered. At 150—250 °C, the mentioned intermetallics absorb considerable amounts of hydrogen with conservation of the initial metallic lattice and formation of the highly dispersed hydrides Ti₂NiH_3.3, Zr₂NiH_4.7, Zr₃Al₂H_1.1, and ZrV₂H_2.2. The phase transformations taking place on heating of the intermetallics from 250 to 500 °C, resulting in mixtures of intermetallic hydridonitrides and metal nitrides, are elucidated. The transformation products of the Ti₉₀Mg₁₀, Y₆₇Fe₃₃, and Ti₆₇Fe₃₃ alloys in ammonia atmosphere in the temperature range of 100—500 °C are established.