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The equilibrium constant for the reaction of trimethylgallium and ammonia has been determined at 40−100 °C via direct pressure measurements. The reaction enthalpy found from experimental data (−15.2 ± 1.5 kcal/mol) is in good agreement with the value obtained from ab initio calculations (−15.9 kcal/mol) using a series of Dunning's basis sets. Presented data should be useful for modeling of gallium nitride chemical vapor deposition reactors as well as for further theoretical analysis of thermodynamic and kinetic processes in gallium chemistry.

Combustion synthesis (CS) of NiAl-based materials reinforced by TiB 2 particles was investigated under both terrestrial and microgravity conditions. The synthesized metal matrix composites (MMC) are characterized by very fine (<1 m) reinforced particulates, which have strong bonding along their entire surface with matrix (NiAl) and are distributed uniformly in it. It was found that microgravity leads to a decrease in the average TiB 2 particle size, while higher volume fraction of NiAl component in the material leads to the formation of coarser reinforced particulates. The mechanism of structure formation of different MMCs during CS was identified by using the quenching technique. For example, it was shown that TiB 2 grains appear due to crystallization from the complex (Ni-Al-Ti-B) liquid solution formed in the combustion front. An overall decrease of microstructural transformation rates was observed under microgravity.

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