Metallamide und Metallnitride, 25. Mitteilung. Zur Kenntnis des Lithiumimides

Abstract

Es wurde Lithiumimid durch thermische Zersetzung des Amides hergestellt. Seine Dichte ist 1,48. Li2N kristallisiert dem CaF2 antiisomorph, ist also dem Li2O isomorph; es hat die Gitterkonstante 5,047 Å. Der univalente Radius des NH2−‐IOs ist 2,00 Å. Durch tensimetrische Untersuchung wird festgestellt, daß Lithiumamid kein Ammoniakat bildet. Das Amid gibt zunächst einphasig Ammoniak ab, es schließt sich ein Zweiphasengebiet an, bestehend aus einem ammoniakarmen Amid‐Mischkristall und dem Lithiumimid.

Reactivity of hydrogen and ternary nitrides containing lithium and 13 group elements

“…Two broad peaks were observed at 2θ = 31 • and 52.5 • in addition to the peaks of GaN and LiH and very small peaks of Li 3 GaN 2 . These two peaks were probably related to the 1 1 1 and 0 2 2 of Li 2 NH (cubic, a = 5.047Å, Fm-3m) [15], but they were shifted at higher diffraction angles. The lattice parameter calculated from the peak positions was 4.96Å.…”

Decomposition kinetics of lithium amide for hydrogen storage materials

“…The effect appears to be nearly saturated at 11 mg, and it does not continue to still larger sample sizes; ∼350 mg LiNH 2 samples measured in the high-pressure TGA apparatus have decomposition rates that are comparable to these values. A likely explanation for this behavior lies in the very low equilibrium vapor pressure of NH 3 for the LiNH 2 decomposition reaction [8]. At 300 • C, for example, an NH 3 partial pressure of ∼1 kPa is sufficient to inhibit LiNH 2 decomposition.…”

“…In analogy with NaAlH 4 , Ichikawa et al [7] found that the kinetics of hydrogen release near 200 • C were improved by incorporating TiCl 3 into mixed LiNH 2 + LiH powders. Of critical importance for application of Li-N-H materials to hydrogen storage is the existence of a competing reaction in which lithium amide decomposes by releasing ammonia [8]:…”

Crystal structure and charge density analysis of Li2NH by synchrotron X-ray diffraction

“…The Li 2 O amorphous-like phase, which diffraction peak width is broader and lattice constant is larger than Li 2 O crystalline phase, mostly changed into the crystalline phase during the heat treatment. It has been reported that the crystal structure of Li 2 NH is anti-fluorite type structure (space group Fm3m) consisting of Li + and NH 2− [14]. However, hydrogen atom positions in Li 2 NH crystal have not yet been determined.…”