Yubao Bi

Low-temperature catalytic synthesis of SiC nanopowder from liquid phenolic resin and diatomite

ABSTRACT 3C–SiC nanopowder was catalytically synthesised at 1400°C for 3 h in argon using industrial diatomite powder and phenolic resin as raw materials, and cobalt nitrate as a catalyst precursor. Phase composition and microstructure of product samples were characterised using X-ray diffraction analysis, scanning electronic microscopy and transmission electronic microscopy. The effects of temperature, catalyst content and reaction time on the formation of SiC were examined. The results indicated that (1) phase pure 3C–SiC can be synthesised at 1400°C for 3 h using 1.0 wt-% Co catalyst; (2) if no catalyst was used, only little 3C–SiC was formed under the identical firing condition; (3) as-prepared 3C–SiC nanoparticles had irregular shapes with overall sizes of 30–300 nm. Density functional theory calculations further reveal that the Co catalyst assisted Si–O bond breaking and thus the SiC formation.

Synthesis of hierarchically porous mullite ceramics with improved thermal insulation via foam-gelcasting combined with pore former addition

ABSTRACT To further improve the thermal insulation performance of porous mullite ceramics used in important industrial sectors, a combined foam-gelcasting and pore-former addition approach was investigated in this work, by which hierarchical porous mullite ceramics with excellent properties, in particular, thermal insulation property, were prepared. Both mesopores (2–50 nm) and macropores (117.8–202.7 μm) were formed in porous mullite ceramics resultant from 2 h firing at 1300°C with various amounts of submicron-sized CaCO3 pore former. The former mainly arose from the decomposition of CaCO3, and the latter from the foam-gelcasting process. The porous samples prepared with CaCO3 addition had low linear shrinkage of 2.35–4.83%, high porosity of 72.98–79.07% and high compressive strength of 5.52–14.82 MPa. Most importantly, they also exhibited a very low thermal-conductivity, e.g. 0.114 W m−1 K−1 at 200°C, which was much lower than in the cases of their counterparts prepared via the conventional foam-gelcasting route.