Weijian Han

Pyrolysis of polyborosilazane and its conversion into SiBN ceramic

Abstract The polyborosilazane was prepared by coammonolysis of boron trichloride and methyldichlorosilane with hexamethyldisilazane. The decarburisation process of the polyborosilazane under ammonia was studied. The results suggested carbon was effectively removed under ammonia and the removal of carbon mainly occurred during the temperature range of 400–600°C. After pyrolysed at 900°C under ammonia, the carbon content was only 0·29 wt-%. Further heat treatment at 1500°C under argon yielded SiBN ceramic. The structure and morphological properties of SiBN ceramic were studied by solid 29Si nuclear magnetic resonance, X-ray diffraction and scanning electron microscopy. The results showed that the SiBN ceramic was amorphous and possessed a smooth surface. The contents of boron, silicon and nitrogen in the SiBN ceramic are 10·9, 42·6 and 38·48 wt-% respectively.

A Novel Silicon-containing Ethynylarene Resin as Heat-resistant Thermoset

A series of novel processable and heat-resistant silicon-containing resins (PSA-E resins) were successfully synthesized by the reaction of 1,3,5-tris-(4-ethynylphenyl)benzene (TEPHB) with silylene-acetylene polymer (PSA resin) with high yields. The molecular structure, thermal curing processes and thermal properties were characterized by FTIR, 1HNMR, GPC, DSC and TGA. The results indicated that these novel resins could be melted at room temperature and thermally cured at 200–250 °C with low exothermal heat. Owing to the complete crosslinking of ethynyl groups, the Td5 (temperature of 5% weight loss) for all the thermosets are above 500 °C, and the overall char yields were above 87% at 900 °C under nitrogen.