非晶硅酸铝纤维晶体化对纤维预制体真空过滤成型性的影响

EFFECT OF CRYSTALLIZATION OF AMORPHOUS ALUMINA-SILICA FIBERS ON THE VACUUM-FILTRATION FORMABILITY OF FIBER PREFORMS

本文研究了两种非晶硅酸铝纤维经热处理产生的莫来石晶相(3Al_2O_3·2SiO_2),纤维截面上Al^(+3)、Si^(+4)和O^(-2)分布变化规律,以及它对纤维预制体真空过滤成型性的影响,并阐明其机理。结果表明:晶体化热处理后,非晶纤维出现占重量约50％的莫来石相,其余为非晶相;晶体化过程中,纤维截面上距表面约400A的薄层内,伴随人Al^(+3),Si^(+4)和O^(-2)分布变化,表面薄层富集Si^(+4),即SiO_2。这些变化,为单根纤维抗拉强度下降三分之二左右的原因;经热处理、机械打断和湿过程处理后,纤维的平均长度明显降低,环状预制体自由形成表面的粗糙度Ra急剧下降,内表面光滑圆整,真空过滤成型性比原始纤维好得多。

The study of the mullite formation of two types amorphous alumina-silica fibers was performed with the help of heat treatment. The change in the distribution of Al + 3, Si + 4 and O-2 on the cross section of fibers was studied. The effect of the mullitephase on the vacuum-filtration formability of fiber preforms and its mechanism were investigated. The experimental results reveal that the mullitephase of aluminasilica fibers reaches approximately 50 mass-% with the help of heat treatment, rest, amorphous.In the process of crystallization, the change in the distribution of Al+3, Si+4 and O-2 on the measured layer of approx. 400 A from the surface of fibers was companied. In the thin layer Si+4, namely SiO2, was concentrated. It resulted in that the tensile strengths of the single fibers decrease about 2/3 of that of original fibers,After the heat treatment and mechanical chopping and wet process, the average fiber lengths decrease greately and the roughness R. of the free forming surface of ring preforms klowers distinctly,in other words, the inside surface of ring preforms gets smoother and circular. The vacuum-filtration formability of the heat tre-ated alumina-silica fibers is much better than that of original fibers and it results from the crystallization of the fibers.