Preparation of non-oxide SiC membrane for gas purification by spray coating

Ceramic membrane such as SiC membrane was widely used in gas filtration to remove dust. However, oxidation of SiC is unavoidable when sintered in air, which limited the SiC membrane application. How to controlling oxidation of SiC to prepare non-oxide SiC membrane is an important industrial requiring. In this study, a SiC whisker layer was used to modify the surface pore channels of SiC supports before coating. Then a layer of SiC membrane was prepared on the surface of the SiC supports using a spray-coating procedure. The coated samples were sintered using a specific sintering procedure by switching sintering atmospheres over different temperature ranges to produce a homogeneous, defect-free microstructure of a non-oxide SiC membrane. The average pore size of the SiC membrane was 2.31 mu m. In addition, the membrane displayed a 31% increase in nitrogen flux compared to the membrane without SiC whisker layer. The SiC membrane exhibited excellent chemical and thermal resistance owing to the properties of the membrane compositions (mullite, ZrSiO4, CaSiO3 and SiC) that have a matched thermal expansion coefficient. The SiC membrane effectively reduced the dust concentration from 250 mg m(-3) to 0.12 mg m(-3) in the filtration tests with dust of d(50) = 0.3 mu m, exhibiting filtration efficiency of 99.95% when the gas filtration permeability of 105.2 m(3) m(-2) h(-1) kPa(-1).