Effect of Temperature on Reaction of Hexagonal BN Powder in Wet Air Between 1073 and 1373 K

Abstract

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.

Oxidation‐led decomposition of hexagonal boron nitride coatings on alloy substrates at 900 °C: Chromia‐formers

“…This is consistent with the findings of Podobeda et al who measured a decrease in specific surface area with oxidation . It is similarly consistent with models that propose that a layer of molten boron trioxide forms around the individual basal plane peripheries, which causes them to agglomerate as it thickens . This effect can be understood from the reaction stoichiometry and the molar volumes of h‐BN and boron trioxide at 900 °C, ca.…”

“…The early rapid phase of oxidation followed by a slower phase that has been previously reported can be clearly seen in the Figure (a) TGA plot . The first derivative of this data reveals that there are actually three stages to the kinetics of oxidation of h‐BN (Figure (b)).…”

“…The equivalency of these Δm values to those from the dry atmosphere TGA run indicates that it was not. By comparison, Hou et al measured a net mass loss for exposures longer than 16 h at 900 °C in an atmosphere containing 6.5 wt% water …”

“…Thereafter, oxidation becomes increasingly controlled by liquid‐state diffusion . Similarly, Hou et al propounded that as the boron oxide layer thickens, the powder particles connect together to form a compact bulk that impedes oxygen from reaching the reaction sites …”

Reaction of CVD BN ceramics in water vapor at 1023–1173 K using different kinetic model

“…To further validating the performance of RPP model, the reaction behavior of hexagonal BN powder exposed to wet air (containing 6.5 mass % H 2 O) at 11731373 K for 18 h was carried out in our recent work. 18) The reaction kinetics was adopted using RPP model and the paralinear kinetics respectively with the relative errors to be 6.86 and 15.7%, indicating RPP model is prefer.…”