水基冷冻干燥工艺制备莫来石结合多孔SiC陶瓷

Fabrication of Mullite Bonded Porous SiC Ceramics by Freeze-drying of Aqueous Slurries

以微米级SiC和纳米级α-Al_2O_3为原料,经水基冷冻干燥及原位反应烧结工艺制备莫来石结合多孔SiC陶瓷。XRD分析表明多孔陶瓷主相是α-SiC,结合相是莫来石。多孔陶瓷的孔径分布呈现双峰分布特点,大孔孔径峰值介于3~20μm,小孔孔径峰值为0.5~1μm。体系中SiC固相含量及烧结温度对多孔陶瓷显微结构及性能有显著影响。当SiC固相含量由20vol%增至30vol%时,多孔陶瓷的孔结构由间距为20~30μm、且定向排列的层状结构演变为孔径约为4μm的定向通孔结构。当烧结温度由1200℃升至1500℃时,多孔SiC陶瓷开气孔率由66%下降至64%,抗压缩强度由4.5 MPa升至16 MPa。

Using sub-micrometer SiC and nano-α-Al2O3 as raw materials,mullite bonded porous SiC ceramics were fabricated by combined freeze drying of aqueous slurries with in-situ reactive sintering technique. The XRD results showed that the main phase was α-SiC,the bonded phase was mullite. The pore diameter of porous ceramics ranged from 3 μm to 20 μm,and the diameter of small pore was in the range of 0. 5-1 μm. The microstructure and properties depended on the content of SiC and sintering temperature. When the SiC content increased from 20vol% to 30vol%,the distance between holes was20-30 μm,and a directional-alignment-layerd structure changed into directional- via holes structure and the pore size was about 4 μm. Meanwhile,the porosity decreased from 66% to 64%,and compressive strength increased from 4. 5 MPa to 16 MPa when the sintering temperature increased from 1200 ℃ to1500 ℃.