Synthesis of silicon carbide nanowhiskers by microwave heating: effect of heating duration

SiC nanowhiskers (SiCNWs), due to their unique properties such as high thermal stability, high strength, high thermal conductivity and large band gap, lead to a wide range of applications. In this article, synthesis of SiCNWs was performed by using microwave heating. Silica and graphite in the ratio of 1: 3 were mixed in an ultrasonic bath, dried on a hotplate and cold pressed uniaxially into a pellet die. The pellets were heated by using a laboratory microwave furnace to 1400 degrees Cwith a heating rate of 20 degrees C min(-1) and heated for 20, 40 and 60 min. Characterizations of the as synthesized SiCNWs were done to study the effect of heating duration on the morphology and properties of SiCNWs. A time of 40 min was found to be the most ideal heating duration for the synthesis of SiCNWs. beta-SiC appeared as the only phase in the x-ray diffraction pattern for SiCNWs formed by using 40 and 60 min of heating duration with no traces of unreacted silica and graphite. Field emission scanning electron microscopy imaging confirmed that no trace of graphite or silica was present in SiCNWs synthesized by a heating duration of 40 and 60 min. Energy dispersive x-ray spectroscopy analysis revealed that only elemental Cand Si were present for SiCNWs synthesized at 40 and 60 min. Meanwhile, photoluminescence spectroscopy indicated the presence of single phase beta-SiC peak at 440 nmwas associated with band gap of 2.8 eV. Absorption bands of Si-Cbond were detected at 802.4 cm(-1) in the spectra of fourier transform infrared analysis. SiCNWs produced by heating at 40 and 60 min have high thermal stability with weight loss lower than 6%. A simple process that involved two steps of ultrasonic mixing and microwave heating of graphite and SiO2 is proposed as a new route for the synthesis of SiCNWs.