Method for making porous mullite-tialite composites

Porous composites of acicular mullite and tialite are formed by firing an acicular mullite body in the presence of an oxide of titanium. In some variations of the process, the oxide of titanium is present when the acicular mullite body is formed. In other variations, the oxide of titanium is applied to a previously-formed acicular mullite body. Surprisingly, the composites have coefficients of linear thermal expansion that are intermediate to those of acicular mullite and tialite alone. Some of the tialite is believed to form at grain boundaries and/or points of intersection between acicular mullite needles, rather than merely coating the needles. The presence of the titanium oxide(s) during acicular mullite formation does not significantly affect the ability to produce a highly porous network of mullite needles. 在钛的氧化物存在下，通过烧灼针状莫来石体形成针状莫来石和铝假板钛矿的多孔复合材料。在所述方法的些变化形式中，在形成针状莫来石体时存在钛的氧化物。在其它变化形式中，向之前形成的针状莫来石体施加钛的氧化物。意外的是，所述复合材料的线性热膨胀系数在单独的针状莫来石和铝假板钛矿的线性热膨胀系数中间。认为在针状莫来石针之间的晶粒边界和/或相交点处形成些铝假板钛矿，而不是仅仅涂布所述针。针状莫来石形成期间存