Papers by Keyword: Borazine

Abstract: Borazine-silicon-containing arylacetylene (PBZSA) resin was a novel organic inorganic hybrid polymer and prepared through condensation reaction among B,B’,B’’-trichloroborazine, dichlorosilane and arylacetylene Grignard reagent. The chemical structure of PBZSA resin was characterized by FT-IR and ¹H NMR. The thermal stability and dielectric properties of cured PBZSA were investigated by TGA and broadband dielectric spectrometer. The results indicated that cured PBZSA showed high thermal stability with char yield up to 87.1% at 1000°C and at decompose temperature (T_d5) 580°C, and low dielectric constant (2.8-2.9) and dielectric loss (<0.005).

Abstract: SiBCN powders have been prepared by chemical vapor deposition using borazine and liquid polycarbosilane as source precursors in the deposition temperature range from 800 °C to 1100 °C, with the pressure of 10 kPa. The effect of the temperatures on the surface morphologies of the as-received powders was investigated by SEM. FTIR analysis of the powders was used to obtain the composition of the powders, and the XRD analysis was used to determine the crystalline state of the deposits. The results showed the powders were amorphous and composed of normally spherical grains.

Abstract: Si₃N₄-BN composites were prepared by die-pressing and precursor infiltration and pyrolysis (PIP) route using borazine as the precursor. The composition, microstructure, mechanical, and dielectric properties of the composites with different porosities were investigated. With the adoption of starch as pore forming substance, drawn the Si₃N₄ preform from the liquid precursor borazine and decrease the pressure during curing, the porosity of the Si₃N₄-BN composites were effectively increased. Along with the increase of the porosity of the composites, the mechanical properties were decreased and the dielectric properties were improved. With 20 wt.% starch and drawn Si₃N₄ preform from borazine before curing, the density, porosity, flexural strength and elastic modulus of the composites were 1.70 g·cm^-3, 29.78%, 48.05MPa and 32.45GPa, respectively. The dielectric constants and loss tangents were 4.20~4.44 and 0.48~3.42×10^-3 at the frequency 7~ 18GHz. Composites with various dielectric and mechanical properties can be designed and prepared according to the application needs.

Abstract: The processible and high yield polyborosilazane (PBSZ) precursor for SiBN ceramics was prepared by coammonolysis reaction of dichlorosilane and trichloroborazine. The synthesized PBSZ precursor was characterized by Fourier Transform Infrared spectroscopy (FTIR), ¹H, ¹¹B, and ²⁹Si Nuclear Magnetic Resonance (NMR), and its ceramic conversion chemistry was investigated by differential scanning calorimetric (DSC), X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and thermal gravimetric analysis (TGA). The PBSZ precursor is a viscous liquid and changes to an insoluble solid via a cross-linking reaction between the N-H group and Si-H group as post-heated from 60 to 180°C. The insoluble solid is transformed to Si₃N₄ and BN amorphous structures with an approximately 95% ceramic yield after being pyrolyzed to 1000°C.

Abstract: Boron nitride coatings have been prepared by chemical vapor deposition using borazine as single precursor at 900 °C. The effect of the total pressure on the surface morphologies of the coatings was investigated. For low total pressures (≤ 3 kPa), the deposits presents a compact pebble-like surface structure. However, when high total pressures (> 3 kPa) were used, the surface of the coatings presents a loose grain-like feature. When the total pressure increases up to 12 kPa, the coatings shows a porous surface structure. The composition and structure of the deposited coatings were investigated by means of FTIR and XRD analysis. It shows that the coatings have a structure of turbostratic boron nitride.

Abstract: Boron nitride (B1.0N0.9) nanoparticles have been prepared by the spray-pyrolysis of borazine. Characterization of the B1.0N0.9 nanoparticles by SEM, and HRTEM demonstrated that samples form elementary blocks containing slightly agglomerated nanocrystalline particles with sizes ranging from 55 to 120 nm. Their thermal behavior has been investigated and thermogravimetric analyses of B1.0N0.9 nanoparticles showed that they are relatively stable in air atmospheres.

Abstract: Microelectromechanical systems (MEMS) including microchemical devices have been widely concerned, in particular, when made of an extremely stable ceramic material for their use at harsh conditions. SiCBN preceramic polymer was derived from borazine (B3N3H6) modified allylhydridopolycarbosilane (AHPCS) via hydroboration of allyl groups with B-H groups at 0oC for 24 h by following the standard Schenk technique. The extent of polymer-to-ceramic conversion with an ultimate ceramic yield of 92 wt% was investigated by simultaneous TGA, 1H, 13C-NMR, IR, and XRD measurements. The polymer-derived SiCBN ceramic remained as an amorphous solid up to 1400oC. The ceramic product obtained after pyrolysis at 1000-1400oC exhibited excellent oxidation resistance in air. In addition, ceramic microstructures were fabricated by employing soft lithographic technique.