Transparent fiber reinforced glass composites

Abstract

The paper deals with transparent composites on the basis of a glass matrix and nanocrystalline oxidie (Nextel) fibers. In order to hinder or prevent the reaction between the fibers and the matrix glass and - in consequence - to influence the mechanical behaviour of the composite, the fibers are definedly coated. BN, TiO₂ or a double layer of both were applied. BN-layers allow sliding between the fibers and surrounding matrix glass. It is of greatest importance to choose compatible fiber and matrix glasses; especially the thermal expansion coefficient and the refractive index must correspond. The composites were hot pressed. In case of processing in vacuum there is the possibility of BN-decomposition and of appearance of atomic lead in lead oxide containing matrix glass, which turns the colour of the composite grey. The protection of the BN by a TiO₂-Iayer and hot pressing in oxidie atmosphere prevet this effect. Moreover one can avoid small bubles by increasing pressure during hot pressing or vacuum at low temperatures and pressures at high temperatures.