Hollow beads composed of nanosize Ca alpha-SiAlON grains

Carbothermal reduction-nitridation (CRN) of SiO2, is an attractive method t o manufacture Si3N4 powders with controlled grain morphology, Moreover, bet a-SiAlON powders could also be synthesized from either pure powder mixture or some inexpensive raw minerals by CRN and the resulting powders favored t he sintering of SiAlON product. However, there have been few works on prepa ring alpha-SiAlON powders so far. In this work, Ca alpha-SiAlON powder was synthesized by CRN: of a SiO2-Al2O3-CaCO3 mixture. An unusual morphology of hollow beads 200 to 500 nm in diameter with a great deal of nanosize alpha -SiAlON particles around 10 to 30 nm in diameter was observed from the resu ltant Ca alpha-SiAlON powders, which has not been reported for SiAlON ceram ics before.