Hydrolysis Mechanism of Borazine-derived Boron Nitride Pyrolysized below 1200 °C

Boron nitride (BN) powders were synthesized by pyrolysis at various temperatures to investigate the hydrolysis mechanism of borazine-derived BN pyrolysized below 1200 °C. The BN was hydrolysized near room temperature at 65% or 90% relative humidity (RH) over 45 days. The long-term hydrolysis mechanism and structure evolution were investigated by a measurement of mass growth and by X-ray diffraction (XRD), Fourier-transform infrared (FT-IR) spectroscopy, and scanning electron microscopy (SEM) analyses. The samples pyrolysized below 1200 °C were very sensitive to moisture, and their mass growth was closely related to the pyrolysis temperature. At 25 °C and 65% RH, the sample pyrolysized at 400 °C exhibited almost 100 wt% mass growth within 8 days, while the sample pyrolysized at 1200 °C exhibited about 20 wt% mass growth. The XRD analysis suggested a hydrolysis mechanism that corresponded to the interlayer spacing in the BN, which was consistent with the results reported. On the other hand, the instability of borazine-derived BN should be directly due to the residual N–H bonds in the compound, as suggested by FT-IR analysis.