GB1041996A - Method of improving high temperature characteristics of silica fibers - Google Patents

Abstract

Silica fibres are treated to improve their high temperature stability by contacting all the exposed surface of the fibres with an organic chromium salt, bonding the salt to the surface and thereafter heat decomposing the salt on the fibres by oxidative heat decomposition to chromium sesquioxide which adheres as a bonded layer enclosing the silica fibres. The fibres may contain at least 96% silica and may be treated in bulk, felt, mat or woven textile form. The organic chromium salt may be chromic acetate, chromic formate or chromium naphthenate. The salt may be dissolved or dispersed in a medium, e.g. water and the contacting may be carried out by spraying or painting the fibre with the salt or by immersing in a bath of the salt, the silica fibres being maintained in the salt until saturated. After the contacting step, the medium is removed by draining and drying the coated fibres at, near or above the boiling-point of the medium causing the coating to be bonded firmly to the surface of the fibre. The dried, coated fibres are then heat treated in a free oxygen-containing atmosphere at a temperature sufficient to decompose the organic chromium salt in the case of chromium acetate or formate to chromic carbide and to convert the chromic carbide in situ to chromium sesquioxide, e.g. 1600 DEG to 2000 DEG F. The concentration of chromium sesquioxide may be between 0.5 and 20% calculated as chromium. The process may be repeated several times, and may be carried out on a batch, semi-continuous or continuous basis. The treated fibres show increased resistance at 2400 DEG to 2600 DEG F. to degradation of flexibility, softness, breaking strength, and decreased thermal conductivity.ALSO:Silica fibres in bulk, felt, mat or woven textile form are treated to improve their high temperature stability by contacting all of the exposed surfaces of the silica fibres with an organic chromium salt, bonding the salt to the fibres and thereafter decomposing the salt by oxidative heat decomposition to chromium sesquioxide which adheres as a bonded layer enclosing the silica fibres. The chromium salt may be chromic acetate, formate and chromium naphthenate, dissolved or dispersed in say water, and the solution or dispersion applied by dipping, spraying or painting. The process may be repeated several times and may be carried out on a batch, semi-continuous or continuous basis.