Growth and characterization of nanostructured beta-SiC via carbothermal reduction of SiO2 xerogels containing carbon nanoparticles

Sol-gel route was used to prepare SiO2 xerogels containing carbon nanoparti cles. Three kinds of beta-SiC nanostructures were obtained by carbothermal reduction of the xerogels under different conditions. XRD and IR studies sh ow that the powders, obtained from carbothermal reduction at 1650 degrees f or 2.5 h in static argon atmosphere, are beta-SiC. TEM reveals that the pow ders are nanoparticles with diameters ranging from 30 to 100 nm. The specif ic surface area of the powders are 15.7 m(2)/g. TEM, SAED and EDX show that the products, synthesized by carbothermal reduction at 1650 degrees C for 1.5 h, and followed by heating to 1800 degrees C, holding for 30 min in flo wing argon atmosphere, are nanowires that consist of 10- to 25-nm-diameter crystalline beta-SiC cores surrounded by amorphous SiO2 sheathes with outer diameters of between 20 and 70 nm. While TEM and SAED demonstrate that the products, formed by carbothermal reduction at 1650 degrees for 2.5 h in fl owing argon atmosphere, are bare SiC nanowires with diameters in the range of 15-30 nm. (C) 2000 Elsevier Science B.V. All rights reserved.