Oxidation Resistance and Dielectrical Properties of Boron Nitride by Pyrolysis of Poly (isopropylamino) borazine

Poly[tri(isopropylamino)borazine] (PTP(i)AB), a soluble and fusible precursor to hexagonal-BN (h-BN), was synthesized under mild conditions using isopropylamme and trichloroborazine(TCB) as starting materials. h-BN was obtained by pyrolysis of PTP(i)AB in NH3 and Ar. The compositions, structures and properties of PTP(i)AB and pyrolytic product were investigated via elemental analysis, FTIR, XRD, TGA and Network Analyzer. The results indicate that N-H, C-H, C-N bonds and B3N3 units exist in the structure of PTP(i)AB. The melting point is 70 C. The weight loss mainly occurs below 800 degrees C and ceramic yields for the precursor in NH3 and Ar are 45.9% and 52.8% at 1000 degrees C respectively. Crystallization occurs at around 1000 degrees C and the (002) interlayer spacing and density are 0.334 nm and 2.03 g/cm(3) at 1800 degrees C, respectively. Furthermore, the BN illustrates superior oxidation resistance with weight increase lower than 0.3% below 900 degrees C in air. The BN also displays low dielectric constants with real part of 2.45 and loss tangent of 0.03 at 10 GHz at ambient temperature, respectively.