Fabrication Of SiC Foam Ceramics And The Properties Of Al-Si Co-doping TiO₂Nano-coating On The Surface

SiC foam ceramics are one of the most suitable candidates for the photocatalystcarrier due to their excellent properties such as high temperature resistance, corrosionresistance, low thermal conductivity, low thermal expansion coefficient and the uniqueinterconnected3-D network structure. We coated the Al-Si co-doping TiO2nano-coating on the surface of SiC foam ceramics, not only could solved the problemof photocatalyst particles immobilized for recycling, but also benefit from the specialstructure of SiC foam ceramics, improving photocatalysis efficiency of TiO2photocatalyst. In this paper, the research contents mainly including three parts asfollowing:In the first part, by using polymeric sponge impregnation process, high porosityand high compressive strength SiC foam ceramics were prepared. The relationshipbetween pretreatment of polyurethane skeleton, Al(H2PO4)3contents, slurry immerseprocess, sintering temperature and mechanical properties of SiC foam ceramics werediscussed. Accordingly, a reasonable sintering system was builded. At the same time,the transformation of sintering additives and the mechanism of properties improvingwere researched. The experiment results shows that SiC foam ceramics fabricated bythis route can obtain the sample which have75%porosity with1.08MPa compressivestrength.In the second part, the effect of water-bath temperature, pH value and contents ofglacial acetic acid (GAA) on the prepare routes of sol-gel process to fabricated Al-Sico-doping TiO2photocatalysis were researched. The effects of Si and Al co-doping onthermal stability, primary particle size, surface area, microstructure and photocatalytic activity of TiO2nanoparticles were investigated. Photocatalytic activities wereevaluated by the degradation of methylene blue under UV light irradiation. What’smore, we discussed the mechanism of the effect of Al-Si co-doping on TiO2photocatalysis. The experiment and analysis results shows as following:(1) By the Aland Si co-doping, crystallite phase transition temperature of TiO2nanoparticles wasincreased to1200oC, primary particle size of Al and Si co-doped samples wereobviously decreased and the BET results also indicated that there was an increase insurface area of the catalyst, which enhanced the photocatalytic degradation ofmethylene blue under UV light irradiation. The Al and Si co-doped TiO2nanoparticlesphotocatalyst showed a significant blue-shift and an enhanced photoresponse in UVabsorption spectrum, which made its photocatalytic oxidation capability obviouslyhigher than the undoped one.(2) The incorporated Al3+and Si4+could enter TiO2crystal lattice occur solid solutions reaction and formation defects on the surface ofanatase grain boundary, which are finally shows remarkable enhancement of thermalstability, decreasing of particle size and improvement of photocatalysis performance ofTiO2photocatalyst.In the third part, we coated Al-Si co-doping TiO2nano-coating on the surface ofSiC foam ceramic by the immerse-coating process. The optimal immerse-coating times,micromorphology of TiO2coating and the effect of coating on the photocatalysisefficiency of TiO2photocatalyst were investigated. The experiment result shows thatspecial structure of SiC foam ceramics improved the photocatalysis surface areas,which enhanced the photocatalysis efficiency of TiO2to photodegradation ofmethylene blue under UV light irradiation.