CERAMIC FIBERS FROM SI-B-C POLYMER PRECURSORS

Non-oxide ceramics such as silicon carbide (SiC), silicon nitride (Si3 N4), and silicon borides (SiB4, SiB6) have thermal stability, oxidatio n resistance, hardness, and varied electrical properties. All these ma terials can be prepared in a fiber form from a suitable polymer precur sor. Silicon carbide fiber (Nicalon), for example, has been successful ly produced by the polymer-pyrolysis route, and is presently available from Nippon Carbon. More recently, other fibers have been made availa ble, such as the silicon nitride fiber from Dow Corning Co. and Tyrann o fiber from Textron Specialty Materials. The above mentioned fibers, when tested over a temperature range from 25-degrees-C to 1400-degrees -C, experience degradation at elevated temperatures. Past work in cera mic materials has shown that the strength of ceramics containing both carbides and borides is sustained at elevated temperatures, with minim um oxidation. The work presented here describes the formation of ceram ic fibers containing both elements, boron and silicon, prepared via th e polymer precursor route previously reported by the authors, and disc usses the fiber mechanical properties that are retained over the tempe rature range studied.