ρ-Al2O3添加量对原位反应结合碳化硅膜支撑体性能的影响

以黑色碳化硅为骨料，添加不同含量的ρ-Al2O3，在1430℃、无压条件下，用碳化硅表面氧化产生的SiO2与Al2O3反应制备多孔碳化硅膜支撑体，研究了ρ-Al2O3添加量对碳化硅支撑体粘结相组成及性能的影响。结果表明，ρ-Al2O3添加量由3wt%增加到15wt%时，试样烧结后粘结相中莫来石相增多，石英相减少但不能完全消除，支撑体的显气孔率降低，孔径减小，透气度由1127.8 m3?cm/(m2?h?kPa)下降到210.4 m3?cm/(m2?h?kPa)；支撑体抗弯强度先增大后降低，ρ-Al2O3添加量为9wt%时，支撑体抗弯强度为25.1 MPa，透气度为372.7 m3?cm/(m2?h?kPa)，支撑体的综合性能满足高温含尘气体过滤的要求。

Effect of ρ-Al2O3 addition on the properties of in situ reaction-bonded porous SiC membrane support

The silicon carbide ceramic membrane support bonded by mullite (3Al2O3?2SiO2) which formed by in situ reaction has good thermal shock resistance, however, few studies have been made for in situ reaction by adding ρ-Al2O3. In this paper, the porous SiC membrane support using black silicon carbide as aggregate, and by adding different content of ρ-Al2O3, was prepared by the reaction of Al2O3 and SiO2 which produced by the oxidation of the SiC particles surface under pressureless sintering at 1430℃ for 3 h in a muffle furnace. The effects of ρ-Al2O3 addition on the phase composition and properties of silicon carbide support were studied. The results showed that the mullite content in the bonding phase increased with the addition amount of ρ-Al2O3 powder increased, and the cristobalite content decreased relatively but could not be completely eliminated. The interconnected pores of support were produced mainly by SiC coarse particles (150?180 μm) packing. The surface of SiC was oxidized to amorphous SiO2 that further crystallized to form cristobalite during sintering at higher temperatures in air. Meanwhile, pre-added ρ-Al2O3 eventually converted into highly activated α-Al2O3 after a series of crystal transformation with increasing temperature. The mullite was formed by in situ reaction between the obtained cristobalite and α-Al2O3 at higher temperature. SiC particles were strongly bonded by mullite and oxidation-derived SiO2 to obtain porous SiC membrane support. The open porosity of the samples decreased from 37.4% to 34.8% with the amount of ρ-Al2O3 powder increasing from 3wt% to 15wt%, and the air permeability of the samples dropped from 1127.8 m3?cm/(m2?h?kPa) to 210.4 m3?cm/(m2?h?kPa) with median pore diameter reduced, accordingly. However, the bending strength increased at the first stage and then decreased with the increase of ρ-Al2O3 powder addition. The support with the flexural strength of 25.1 MPa and air permeability of 372.7 m3?cm/(m2?h?kPa) were developed by adding 9wt% ρ-Al2O3. The porous SiC membrane support could meet the needs of high temperature gas filtration under normal pressure.