Nitrides Oxynitrides Formation by Metal Powder Combustion in Air

The combustion of boron powder in air was studied by bomb calorimetry [22]. 

The CCP of Mg and Be particles in air are oxides [21], because for these metals nitrides are unstable phases at high temperatures. For Ti and Zr, on the contrary, the formation of nitrides on the surface of particles, and even on the bulky metal was recorded in the works of Glassman in the 1960s. 

Nitrides (Oxynitrides) Formation by Metal Powder Combustion in Air 

The appearance of experimentally observed nitrogen-containing phases in CCP is in contradiction with the equilibrium thermodynamic calculations (see Section 5.1) First, metals should react with Oj as a significantly more active gas than N2. Second, if the formation of nitrogen-containing intermediate products is possible, they must be immediately oxidized by O2, especially at high temperatures [60-62]. 

According to the equilibrium thermodynamics and experimental data [74-76], AlN should be oxidized in air with the heat release. pAlN powder ( j 63 pm) is oxidized in air, starting with 800 °C. AlN oxidation was observed in [76] even for the sintered AlN samples at room temperature. 

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J Nitrides (Oxynitrides) Formation by Metal Powder Combustion in Air 149 Table 5.4 Composition of CCP of metals in air. 

Nitrides and oxynitrides could be produced by SHS (CS) of nano- and micronsized metal powders (Al, B, Zr, and Ti) and their mixtures with additives in with the high yield (up to 80 mass%) in air (Chapter 5). The physics and chemistry of the nitride formation by the combustion process, new combustion mechanisms, the stabilization of nonequilibrium products in air, the characteristics of the combustion of metal nanopowders are comprehensively discussed along with technological aspects of the CS of nitride ceramics. 

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