Preparation Of Porous Silicon Carbide Honeycomb Ceramics

Honeycomb ceramics with many parallel through channel have widely been used as car exhaust catalyst carrier because of its impact resistance, light weight etc. At present, the carrier are cordierite honeycomb ceramics, based on the thin hole wall, the characteristics of small coefficient of thermal expansion, but cordierite has several disadvantages, firing range narrow, low thermal conductivity, load of the catalyst is easy to fall off lead to the failure of catalytic, limits the broader application. SiC honeycomb ceramics are high wear resistance, high corrosion resistance, high coefficient of thermal conductivity, thermal stability result in irreplaceable research value as a catalyst carrier.Based on the research of porous SiC ceramics and honeycomb ceramic, carried out the preparation of porous SiC honeycomb ceramics, with adding pore-forming agent, by pressureless sintering and extrusion molding technology, finally prepared high porosity porous SiC honeycomb ceramics, analysed the sintering properties, mechanical properties, m icrostructure, physical phase composition and pore structure characteristics, layed an important foundation for the application of porous SiC honeycomb ceramics. The main research contents and conclusions were as follows:(1) Preparation of porous SiC ceramics with pore-forming agentPrepared porous SiC ceramics with bamboo charcoal/silica sol, starch and iron oxide as pore-forming agent, by pressureless sintering technology, research shows that:with bamboo charcoal/silica sol as pore-forming agent, the relative density of porous SiC ceramic as pore-forming agent reduces with the increasing of the content, the line shrinkage and weightlessness rate are ascendant, the bending strength, by contrast, gradually increases; Starch as pore-forming agent, density rules is the former similar, line contraction changes unstably, weight loss rate and strength are down; Iron oxide as pore-forming agent, the density falls as pore-forming agent content rising, line contraction reduces, weight loss rate increases, the bending strength of change and pore-forming agent content, contains through hole structure. Adding pore-forming agent to SiC has no effect on the content of phase composition.(2) Preparation of SiC honeycomb ceramics by extrusion molding technologyUsing extrusion molding technology, change different moisture content, smooth surface SiC honeycomb ceramic body are prepared, with pressureless sintering technology, prepared SiC honeycomb ceramic. Research shows that the relative density of SiC honeycomb ceramics first increases and then decreases with the rising of water content, line shrinkage and weightlessness rate are adverse, bending strength increases at first and then decreases but are more than10MPa. Adding pore-forming agent additives to SiC have no effect on the content of honeycomb ceramics phase composition.(3) Preparation of porous SiC honeycomb ceramics with pore-forming agent combined with extrusion molding technologyWith starch, iron oxide as pore-forming agent, by extrusion molding technology and pressureless sintering technology, prepared porous SiC honeycomb ceramics. Research shows that, with increasing of pore-forming agent content, the relative density of porous SiC honeycomb ceramics gradually declines, line shrinkage rate reduces, weight loss rate rises, bending strength is reduced, strength values are more than8MPa; Holes are spherical structure, total pore volume increase. To iron oxide as pore-forming agent, sintering and mechanical properties are similar rule of starch, but the holes are through hole structure, pore sizes distribution between0.2～0.9μm.