Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
9693919 | Thermochimica Acta | 2005 | 8 Pages |
Abstract
The purpose of this work was to re-measure the enthalpy ÎrHT° of free-surface vaporization of hexagonal (h) Mg3N2, AlN, GaN, InN and Si3N4 and cubic (c) BN by the third-law method and by comparing them with the enthalpies calculated from thermodynamics to deduce the composition of primary products (bN and cN2) for the generalized decomposition reaction: MaNb+2c â aM + bN + cN2. In addition to these nitrides, the literature data were used for the investigation of vaporization of h-Be3N2 and c-AlN and c-GaN. The relative standard deviation in determination of ÎrHT° values is â¤1% and in determination of b/(b + 2c) ratio is better than 2-4%. As a result of this study, some important features in the decomposition mechanism of different nitrides were revealed: the identity in composition of primary products for h-Be3N2 and h-Mg3N2 (b/(b + 2c) = 0.75) and h-AlN and h-GaN (b/(b + 2c) = 0.42) and the release of only molecular nitrogen in cases of c-BN, c-AlN and c-GaN (b/(b + 2c) = 0). The last feature that was observed earlier for cubic metal oxides [B.V. L'vov, V.L. Ugolkov, F.F. Grekov, Kinetics and mechanism of free-surface vaporization of zinc, cadmium and mercury oxides analyzed thermogravimetrically by the third-law method, Thermochim. Acta 411 (2004) 187-193.] supports the effect of crystal symmetry on the decomposition mechanism. The distance between the closest atoms (NN) in a crystalline lattice has a secondary or no effect on the composition of primary products. These features might be useful for the development/improving of appropriate technologies (including nano-technologies) for production of solid materials by the chemical vapour deposition.
Keywords
Related Topics
Physical Sciences and Engineering
Chemical Engineering
Fluid Flow and Transfer Processes
Authors
Boris V. L'vov, Valery L. Ugolkov,