Effect of acid treatment on the formation of SiC whiskers from raw rice husks

Raw rice husks have been treated by boiling for I h in 5 N hydrochloric acid. The washed and dried acid-treated raw rice husks (TRRH) and untreated raw rice husks (RRH) were directly pyrolysed (without precoking) in argon atmosphere at different temperatures between 1050 and 1600 degrees C. Silica obtained from TRRH has a lower level of impurities than that obtained from RRH. Acid treatment has been found to decrease the degree of crystallization of silica and carbon in rice husks. The whisker formation has been decreased in TRRH. As the carbon loss due to the formation of CO was high, the SiC content in the pyrolysed TRRH was higher than that in pyrolysed RRH.