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

SiC nanowhiskers (SiCNWs), dueto 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 performedby 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 heatedbyusingalaboratory microwave furnaceto 1400 °C witha heating rate of 20 °C min-1and heated for 20,40and60 min. Characterizationsof the as synthesized SiCNWs were done tostudy the effect ofheating duration onthe morphology and properties of SiCNWs. A time of 40 min was foundto bethe most ideal heating duration for the synthesisof SiCNWs. β-SiC appeared as the only phaseinthe x-ray diffraction pattern for SiCNWs formed byusing40and 60 min of heating duration with no traces of unreacted silica and graphite. Field emission scanning electron microscopy imaging confirmed thatnotrace of graphiteor 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 C and Siwere present for SiCNWs synthesizedat 40and60 min. Meanwhile, photoluminescence spectroscopy indicated the presence of single phase β-SiC peakat 440 nmwas associated with band gap of 2.8 eV. Absorption bands of Si-C bond were detected at 802.4 cm-1 in the spectra of fourier transform infrared analysis. SiCNWs produced byheatingat40 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 synthesisof SiCNWs.