Decomposition reactions and phase transformations in the lithium-nitrogen-hydrogen system.

The lithium-nitrogen-hydrogen system has been studied by anelastic spectroscopy (AS), thermogravimetric analysis (TGA) and mass spectrometry (MS). In particular, we report studies of the elastic modulus in lithium amide (LiNH 2) during its high temperature decomposition into imide (Li 2NH). We found that the reaction rates are remarkably faster than those usually reported, and that the time required to complete the reaction depends on the sample mass. The anelastic spectrum was measured also in Li 3N, between 300 and 500 K. In this compound the elastic modulus presents a strong variation above 500 K, corresponding to the transformation from the ? to the ? phase. During the heat treatment, pressure and mass spectroscopy measurements made it possible also to follow secondary processes such as the decomposition of Li 3N.