Formation of Gehlenite (Ca2Al2SiO7) by Carbothermal Reduction of Carbonized Rice Hulls

Vapor deposition products were formed in the cold zone (920-1120°C) during synthesis of SiC from carbonized rice hulls (CRHs) in the reaction zone (1500°C) of a vacuum tube furnace during carbothermal reduction. Crystals of gehlenite (Ca2Al2SiO7) and β-SiC whiskers were identified by X-ray diffraction (XRD) and scanning transmission electron microscopy (STEM) to be the major deposits. A minor product, suessite (Fe3Si), appeared to have catalyzed the growth of gehlenite. The results of this study suggest the feasibility of preparing gehlenite materials by a vapor deposition process.