Microstructures and thermal conductivities of reaction sintered SiC ceramics

Abstract

Reaction sintered SiC ceramics were prepared by the silicon melt infiltration method over temperatures of 145021550uC. The effects of the carbon and silicon contents of the starting materials as well as the sintering temperature and time on the thermal conductivities and microstructures of the ceramic materials were studied. The thermal conductivities and microstructures of the samples were characterised using thermal conductivity measurements, X-ray diffraction analysis, scanning electron microscopy, energy-dispersive X-ray spectroscopy and mercury injection porosimetry. The results showed that sintering temperature and time as well as the carbon and silicon contents of the green specimens are the main factors affecting the microstructure and porosity of reaction bonded SiC ceramics. Increasing the reaction temperature and time decreased the porosity of the ceramics. This was due to the infiltration of the silicon melt into the ceramic specimens. The thermal conductivity and porosity of the sample sintered at 1550uC for 3 h in an argon atmosphere were 102?5 W m K 21 and 0?3% respectively.

Polycarbosilane facilitated growth of SiC nanowires from biowaste coconut shell

“…The reaction (2) and reaction (3) liberate the SiO and CO, which in turn follows the reaction ( 5) and reaction (6), and this cycle is repeated. Initially, a nucleation of tiny SiC nanoparticles takes place by the reduction of SiO with the solid carbon source by vapour-solid mechanism.…”

“…The large band gap, high electron mobility and chemical inertness of SiC nanowires make them a strong candidate for optoelectronic devices, power electronics, light emitting diodes, sensors and magnetic applications [1][2][3]. The SiC nanowires are single crystal in structure with properties like high thermal conductivity and low thermal expansion coefficient that make them a strong candidate for field emission devices and structural ceramics applications [4][5][6]. The quantum confinement, size and shape factor of SiC nanostructures are expected to result in their behaviour that is different than their bulk counterparts.…”

Thermophysical properties and processing of ceramics

“…The thermal expansion of sintered specimens showed linear and hysteresis loop changes: Hysteresis loop obtained with increased zirconia content resulted in the t-m phase transformation. Kwon et al 2 show the thermal conductivities of reaction-sintered SiC ceramics prepared by the silicon-melt infiltration method. In this work, the effect of the carbon and silicon content of the starting materials on the thermal conductivities and microstructures of the ceramics, as well as the effect of sintering temperature and time were studied.…”