Scheelite coatings on SiC fiber: Effect of coating temperature and atmosphere

Scheelite coating was deposited on SiC fiber tows from various liquid-phase precursors followed by heat treatments between 900 degrees C and 1100 degrees C in different atmospheres. The tensile strength was fully retained for the coated fibers treated at 900 degrees C in vacuum. Subsequent heat treatment at 1100 degrees C in Ar had little effect on the fiber strength, which is explained by the excepted good thermal stability between the scheelite coating and SiC fiber. However, larger strength degradation and poor spool ability of coated fibers prepared in Ar/air were found. Assisted oxidation of SiC fiber by calcium salts is suggested to be responsible for the much larger strength degradation of fibers prepared in Ar/air.

Automated summary

The experiment showed that SiC fibers with scheelite coating treated in vacuum exhibited good thermal stability, while fibers prepared in Ar/air had significantly degraded strength and poor spool ability. This difference is attributed to the assisted oxidation of SiC fiber by calcium salts in Ar/air atmosphere.