Entrapment of organosilicon molecules in nonhydrolytic alumina gels and thermal behavior of the resulting composite

This work describes the entrapment of tetrakis(trimethylsilyl)silane (TK) a nd tetrakis(chlorodimethylsilyl)silane (TKCl) in nonhydrolytic alumina gels , and the materials' thermal behavior. During gelation and drying TK and TK Cl are physically entrapped in the gel up to a limit of Si/Al = 0.33. Above this limit, sublimation and decomposition of TK and TKCl occur during heat ing. A larger fraction of TKCl decomposition products is retained due to th eir higher reactivity. Below and above Si/Al = 0.33, the gel converts to mu llite + alpha -Al(2)O(3)or mullite + amorphous silica, respectively. Conver sion to hexagonal mullite indicates atomic scale homogeneity of Si and Al d uring firing.