SURFACE MODIFICATION OF ALUMINA FIBERS WITH SI-ALKOXIDE AND AL-ALKOXIDE AND THEIR THERMAL-BEHAVIOR

Chemical coating on polycrystalline alumina fibers with smooth surface was carried out using a sol obtained by the hydrolysis of Al-sec-trib utoxide (TBOA) or Si-tetraethoxide (TEOS) in ethanol. Partial depositi on of TBOA-derived granules or the entire deposition of TEOS-derived t hin him could be observed on the fiber. The former showed no change in appearance when heated at temperatures lower than 1400 degrees C, and exhibited integration with the original fiber above that temperature. It was also noted that the thin film in the latter was thermally stab le, keeping the smooth surface below 1400 degrees C, while geometrical patterns evolved on the naked surface of the original fiber at the sa me temperature. The film thickness was estimated to be 3 nm after bein g dried at 90 degrees C.