Carbon/silica composite fabricated from rice husk by means of binderless hot-pressing

A carbon/silica composite designed for use under compressive loads was fabricated from rice husk (RH), an agricultural waste material. RH was pulverized by using a planetary ball mill, then carbonized and molded into the precursor by means of hot-pressing without using any binders. A compression of 100 MPa was intermittently applied to the RH powder heated from room temperature to 150 degrees C, and then to 280 degrees C. The precursor, the bulk density of which was 1.37 g/cm(3), was sintered for further densification at up to 1400 degrees C without compression, in nitrogen gas. The smaller particle size of the pulverized RH was beneficial for densifying the carbon/silica composite and increasing its compressive strength. Sintering at 800 degrees C for 1h in nitrogen gas provided the maximum bulk density of 1.52 g/cm(3) and the maximum Vickers hardness at the surface of 343 HV. The maximum compressive strength was measured to be 55.7 MPa using a sintering temperature of 1200 degrees C.