Microfibrous solids derived from SiO and from other main group oxide vapours

Abstract

The composition of “Monox”, the microfibrous or particulate solid formed by condensing gaseous silicon monoxide in inert gas streams, has been shown to be close to SiO if the solid was collected and analysed in the total absence of oxygen, but the solid oxidised quickly in air to the previously reported composition, Si₄O₅. Heating mixtures of Si, SiO₂ with lithium or calcium silicates to 1800°C, allowed co-liberation of SiO with Li or Ca vapours which gave microfibres of high aspect ratio when condensed in argon, an effect believed to be due to promotion of fibre growth by SiO₂/Li₂SiO₃ or SiO₂/CaSiO₃ eutectics. Novel silicon-free microfibrous solids have been prepared by condensation of the vapours liberated at 1700–1800°C when calcium gallate is reduced by carbon under argon, or when aluminium and gallium oxides are reduced by boron in hydrogen; in each case fibre growth is thought possible because of the formation of both metal and oxide phases in the hot condensate.