材料期刊网

采用浸渍法制备SiO2凝胶／铝硅纤维复合材料。研究Si粉质量分数为0％，0．2％，0．4％，0．6％和0．8％时，SiO2凝胶／铝硅纤维复合材料的微观形貌、体积密度、回弹率和物相组成。结果表明：Si粉质量分数低于0．6％时，其氧化产生的体积膨胀填补了纤维与凝胶间的裂纹，体积密度由0．468g／cm3增大到0．723g／cm3，回弹率由43．1％升高为59.6％，并且Si粉高温下的结晶化抑制了纤维析晶和促进了辉石的生成，这是材料的力学性能提高及高温损坏程度降低的重要原因；Si粉质量分数为0．8％时，高温下的Si粉产生了过分的体积膨胀，导致复合材料内部出现较大裂纹，压缩回弹率降低为44．5％。

SiO2 gel/alumina‐silica fibers composites were prepared by impregnation method .Silicon powder with different mass fractions of 0% ,0 .2% ,0 .4% ,0 .6% and 0 .8% was added in the slurry , and the effects of silicon powder on the microstructure ,bulk density ,compression‐resilience ratio and phase compositions of the SiO2 gel/alumina‐silica fiber composites were investigated . The results show that when the mass fraction of the silicon powder is lower than 0 .6% ,the volume expansion of silicon resulting from the silicon oxidation fills the cracks between fibers and gel ,the volume density of the composites increases from 0 .468g/cm3 to 0 .723g/cm3 ,and the resilience ratios increase from 43 .1% to 59 .6% .Besides ,it is found that the mechanical property is improved and the degree of high‐temperature damage for the composites is decreased by the silicon crystallization ,w hich restrains the fibers crystallization and facilitates the generation of pyroxene .However ,when the mass fraction of silicon powder is 0 .8% ,the compression‐resilience ratio of the composites significantly declines to 44 .5% ,w hich is attributed to the big cracks generated from the excessive volume expansion of silicon powder at high temperature .