Study on performance stability of the sapphire fiber and cladding under high temperature

This paper concentrates on the performance stability of sapphire fiber thermometer probe and the development of an alumina fiber cladding durable under high temperature and of high transparency. Analysis was made on the performance stability of sapphire fiber probe under high temperature when using different kinds of protective tube. It is found that direct contacting of the fiber with protective tube is the most important factor that result in performance deterioration and the dirtying of evaporating substance is another important factor. Then it is applicable to design a suitable protective tube to assure the performance stability. An alumina cladding is being developed by means of sol-gel method. It uses a chelated aluminum but-oxide as the sol. This sol is also combined with a small fraction of MgNO3 . 6H(2)O. It is found that the cladding layer by this means has higher transparency than the common used sol-gel method. Sintering under special air condition is also very important to assure the transparency. The cladding will still keep transparent even if worked under 1600 degrees C. By now, thickness up to I um has been made with good transparency and a refractive index of about 1.35.