Reliability of aluminum-coated fibers at high temperature

At temperatures higher than 400 degree(s)C the decrease of aluminum coated fiber strength due to interaction between glass and aluminum was observed. The rate of this decrease appears to depend on the interface between glass and metal. The influence of atmosphere above the metallizer at the application of a metal coating by the freezing method was investigated. Some decrease of the initial bending strength, yet longer lifetime at high temperatures, have been observed for fibers sealed in atmosphere containing oxygen, which can create an alumina layer between silica glass and aluminum. In order to exclude the chemical reaction between silica and aluminum, an intermediate layer of carbon was applied during the fiber drawing. Results of the carbon coating influence on strength and lifetime of aluminum coated fibers at high temperatures are presented.