The Research On Preparation And Properties Of Composite Silicon Carbide Porous Ceramics Support As High Temperature Gas Filtration

High temperature filtration with composite porous silicon carbide is a new material used in high temperature gas solid filtration, separation, and purification. It enjoys performances of high temperature and pressure tolerance, strong acid and alkali corrosion-resisting character, good thermal shock resistance, high filtration efficiency and durability. It can be used to make core components of high temperature filter. Mullite and cordierite are stable compounds in silicate system. Their performances of high temperature stability enable them to react with silicon carbide substrates to form composite ceramic materials. Porous silicon carbide composite material is the preferred material of high temperature filter by virtue of its superior performance and low preparation cost.Using solid phase sintering reaction technology, high temperature gas-solid separation with silicon carbide phase of new ceramics is prepared in the experiments. The main raw materials are silicon carbide, alumina, talc, diatomite, bauxite etc. The paper explores the impact of sintering temperature, sintering additives, ratio of raw material on the performance of the duplex ceramic material. It also discusses the mechanical properties,microstructure morphology, phase composition, pore size distribution etc. of the porous ceramics prepared.(1) Molten lithium carbonate can reduce the silicon dioxide-rich liquid concentration,make free alumina fully enter the reaction system, strengthen the reaction between aluminum oxide and silicon dioxide, make it easier for macroscopic phase transition to occur, thus greatly promote the transformation and effectively reduce the transformation temperature of mullite. When adding 1.0 wt % of lithium carbonate, porous ceramics'filtering quality achieved optimal performance, with flexural strength of 49.61 MPa, open pore rate 34.62 %;(2) Experiments explore systematically the preparation of cordierite bonded silicon carbide porous ceramic with different aluminum compounds as aluminum source.Experiments show that when choosing AIN as aluminum source, diatomite as silicon source,cordierite bonded silicon carbide porous ceramics with both high flexural strength and open porosity is acquired at the sintering temperature of 1200 ?. Its flexural strength can reach 86.20 MPa and its open porosity 31.99 % when sintering for 3 h under such temperature; in addition, the percentages of graphite content has an interventional effect on the porosity and flexural strength of ceramics substrate. The flexural strength and porosity of cordierite bonded silicon carbide porous ceramics achieve optimal performances when sintering at 1200 ? with AlN as aluminum source and graphite content at 15 %;(3) The neck binding of cordierite phase during the sintering process is greatly accelerated with natural inorganic mineral bauxite as aluminum source and diatomite as silicon source. Also, the matrix between SiC particles is made more solid, and the performance of composite ceramics is effectively improved; through further exploratin,experiments show that sintering temperature takes great effects on the preparation and performance of cordierite bonded porous SiC ceramics, and that the performance of cordierite bonded porous SiC ceramics formation reached its optima at 1200 ?; moreover,its comprehensive performance is comparatively good with its flexural strength being 54.04 MPa and porosity 32.69 % when sintering for 3 h at 1200 ? with 2 % of CeO2 as sintering additives. CeO2 effectively improved the phase composition of composite ceramic.