Characterization of vapour deposited products in furnace tube during SiC synthesis from carbonized rice hulls

The vapour deposited products on graphite substrates in the cold zone (1270-600 degrees C) for the preparation of SiC from carbonized rice hulls (CRH) in a vacuum tube furnace, which is operated at a reacting sample chamber temperature of 1300 degrees C, have been characterized by various analytical techniques, such as SEM/EDS, XRD, FTIR, XPS and AES. Morphology/size, chemical composition, lattice/electronic structure, and molecular vibration modes of these products have been obtained. The primary deposited product in zone A (1270-1050 degrees C) was a thin film, consisting of SiOxCy and SiC; in zone B (105-820 degrees C) were whiskers aggregates, consisting of crystalline Si and amorphous SiO2; in addition, in zone C (820-600 degrees C) spheroids aggregates have been observed consisting of amorphous Si and SiO2. The morphology sequence of the deposits in the cold zone, e.g. the thin film (SiOxCy/SiC)-->whiskers (Si/SiO2)-->spheroids (Si/SiO2), seem to be related to the substrate temperature and degree of supersaturation of the reacting gas (SiO). (C) 1999 Elsevier Science Ltd and Techna S.r.l. All rights reserved.