The reaction behavior of a-Boron nitride (BN) powder in wet air was investigated at 1273 K using thermogravimetric (TG) analysis, X-ray diffraction (XRD), and mass spectrometry. Scanning electron microscopy and electron probe X-ray microanalysis (EPMA) were used to analyze the morphological and elemental development of the sample. The results show that the reaction process consists of two stages: the oxidation of BN powder to form B 2 O 3 and the further reaction of B 2 O 3 with H 2 O. In the first stage, the oxidation reaction occurs very quickly and can be described by Chou's model. In the second stage, the reaction rate followed the linear rate law.

Single crystalline β-SiAlON (z = 1.0) nanowhiskers with uniform morphology were prepared using a reaction sintering method at 1773 K for 6 h under flowing nitrogen atmosphere. The as-synthesized whiskers were well-crystallized with about 100-200 nm in diameter and a few hundred microns in length. According to the thermodynamic calculation, Al(g) and SiO(g) are important intermediate reactants to synthesize β-SiAlON whiskers. In the experiment, the two phases was controlled by changing the flow rate of nitrogen to make β-SiAlON whiskers grow in a stable way. The formation of β-SiAlON whiskers occurred through a vapor-solid (VS) mechanism. SiAlON was found to grow as a single crystal whisker from the (10 ̅10) plane of the granule. Furthermore, an enhanced oxidation resistance for β-SiAlON whiskers at high temperature was also observed using the thermogravimetry method (TG), demonstrating that β-SiAlON whiskers with uniform morphology is a promising candidate as a reinforcing agent in composite.

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The reaction of hexagonal BN powder in wet air at 1073–1373 K for 18 h was investigated using TG, XRD, and SEM analysis. Initially, the oxidation occurred rapidly with simultaneous volatile reaction. At long times, a steady state was achieved and the degradation rate was determined by the volatilization reaction. Temperature affected the reaction behavior. At 1073 K, it consisted of two linear processes. With temperature increasing, initially, the paralinear kinetics was observed and then followed the linear rate. The sample shape also affected the reaction behavior. The reaction kinetics was dealt with Chou's model and gotten good agreement.

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