CHEMICAL-REACTIONS ON THE SURFACE OF DISPERSED SILICA DURING GAS-PHASE MODIFICATION WITH MOCL5 VAPORS

Thee characteristic features of the gas-phase modification of silica b y molybdenum pentachloride vapors were investigated. The grafted molyb denum choloride groups = SiOMoCl4 formed as a result of the reaction o f MoCl5 with the silanol groups and siloxane bridges of the SiO2 surfa ce undergo a rearrangement as a result of their thermal instability, f orming chlorosilyl groups and molybdenum oxychloride, which is removed from the silica surface. In the presence of an excess of the modifier MoCl5, the reaction with siloxane bridges of the surface layer leads to the formation of silicon tetrachloride and is accompanied by etchin g of the surface of the dispersed silica globules.