Abstract: A process for forming a uniform, boron nitride coating on a boron-doped, refractory carbide body, and in particular on a sintered, boron-doped, silicon carbide fiber, where the body is exposed to a nitrogen-containing atmosphere at a temperature equal to or greater than the densification or sintering temperature. The coated fibers exhibit no loss in strength properties and show improved creep resistance.

Abstract: A high strength, high creep resistant, boron-doped, silicon carbon fiber having no boron nitride coating, originally formed by sintering, is produced by exposing the fiber to a nitrogen atmosphere at a temperature equal to or preferably elevated above the sintering temperature and also exposing the fiber to a carbon monoxide-containing atmosphere at a temperature sufficient to remove boron and boron nitride. The nitrogen atmosphere step may be performed before or after the carbon monoxide-containing atmosphere step. The resulting, uncoated SiC fibers have tensile strengths greater than approximately 2.0 GPa and Morscher-DiCarlo BSR test creep resistance M values greater than approximately 0.75 at 1400 degrees C for one hour in argon. The method is applicable to non-sintered fibers as well, in which case the nitrogen exposure is carried out at between approximately 1750 to 2250 degrees C and the carbon monoxide exposure is carried out at between approximately 1600 to 2200 degrees C.

Abstract: A high strength, high creep resistant, boron-doped, silicon carbon fiber having no boron nitride coating, originally formed by sintering, is produced by exposing the fiber to a nitrogen atmosphere at a temperature equal to or preferably elevated above the sintering temperature and also exposing the fiber to a carbon monoxide-containing atmosphere at a temperature sufficient to remove boron and boron nitride. The nitrogen atmosphere step may be performed before or after the carbon monoxide-containing atmosphere step. The resulting, uncoated SiC fibers have tensile strengths greater than approximately 2.0 GPa and Morscher-DiCarlo BSR test creep resistance M values greater than approximately 0.75 at 1400 degrees C. for one hour in argon. The method is applicable to non-sintered fibers as well, in which case the nitrogen exposure is carried out at between approximately 1750 to 2250 degrees C. and the carbon monoxide exposure is carried out at between approximately 1600 to 2200 degrees C.

Abstract: A process for forming a uniform, boron nitride coating on a boron-doped, refractory carbide body, and in particular on a sintered, boron-doped, silicon carbide fiber, where the body is exposed to a nitrogen-containing atmosphere at a temperature equal to or greater than the densification or sintering temperature. The coated fibers exhibit no loss in strength properties and show improved creep resistance.

Abstract: Silicon carbide (SiC) fibers, or SiC bodies such as coatings, thin films, substrates or bulk objects, which have been sintered with boron containing additives to promote densification and pore removal, are further treated to remove a substantial amount of the residual boron from the SiC fibers. The SiC fibers, subsequent to the sintering steps and either before or after cooling, are exposed to a carbon monoxide (CO) containing atmosphere at elevated temperatures from approximately 1600-2200.degree. C., but more preferably from approximately 1700-2000.degree. C., with treatment times ranging from seconds to hours to days depending on the chosen treatment temperature. The resulting SiC fibers show a significant reduction of residual boron content, a reduction of greater than 90% in some cases, while retaining high tensile strength. Fibers with less than 0.1 wt % residual boron have been obtained.

Abstract: A method of preparing polymer derived silicon fibers comprising the steps of providing a spin dope solution comprising a silicon carbide forming organosilicon polymer, preferably polycarbosilane, a solvent, a soluble boron precursor, preferably solid boron hydride, and a nitrogen containing precursor, preferably polyvinylsilazane; spinning the solution to form high strength green fibers; and heat treating the green fibers to produce high strength, homogeneously doped, boron containing fibers. The fibers produced are high strength, homogeneously boron doped silicon carbide fibers with average tensile strength in the range of from about 2.0 to 4.0 GPa at room temperature.

Abstract: A method of preparing polymer derived silicon fibers comprising the steps of providing a spin dope solution comprising a silicon carbide forming organosilicon polymer, preferably polycarbosilane, a solvent, a soluble boron precursor, preferably solid boron hydride, and a nitrogen containing precursor, preferably polyvinylsilazane; spinning the solution to form high strength green fibers; and heat treating the green fibers to produce high strength, homogeneously doped, boron containing fibers. The fibers produced are high strength, homogeneously boron doped silicon carbide fibers with average tensile strength in the range of from about 2.0 to 4.0 GPa at room temperature.

Abstract: A SiC whisker-reinforced ceramic article produced by subjecting the SiC whiskers to acid- and/or base-washing; subjecting ceramic particles and SiC whiskers to fluid classification; forming a suspension of the powdered ceramic and SiC whiskers; consolidating the suspension to form a green compact; optionally infiltrating the green compact with an aluminum compound which is a precursor to Al.sub.2 O.sub.3, and pressureless sintering the green compact to produce an SiC whisker-reinforced composite having high relative density at high SiC whisker loading.