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SiC ceramics with graphene additives have been fabricated by a pressureless-sintered method. The effects of graphene contents on the densification, thermal conductivity, electrical conductivity, phase compositions, and microstructure evolutions of the SiC ceramics were investigated in detail. As the graphene content increased from 0 to 5.0 wt%, the relative density of the SiC samples monotonically decreased, the electrical conductivity monotonically increased, whereas the thermal conductivity initially increased and then decreased. The highest thermal conductivity of 145.14 W/(m K) was obtained for SiC sample with 2.0 wt% graphene sintered at 2130 °C for 1 h in Ar. [ABSTRACT FROM AUTHOR]

Abstract ZrB 2 -SiC composite powders were synthesized through one-step reduction process of ZrO 2 , B 4 C, carbon black, silicon or silica under flowing argon. Effects of B 4 C contents, calcination temperatures and different silicon sources on the phase composition and morphology were investigated. Combining the X-ray diffraction (XRD) results and scanning electron microscope (SEM) images, the spherical ZrB 2 -SiC powders ranging from 100 nm to 300 nm would be prepared with silicon at 1500 °C for 60 min when n(B)/n(Zr) was at 2.4. As using silica as the raw material, the obtained ZrB 2 and SiC particles in the powders exhibited different shapes and sizes. The SiC grains were uniformly formed among the ZrB 2 grains. [ABSTRACT FROM AUTHOR]

ZrB 2 powders were successfully prepared via carbothermal reduction of ZrO 2 with H 3 BO 3 and carbon black under flowing argon. By introducing SiC species into reaction mixtures, the effects of SiC addition on phase composition and morphology of ZrB 2 powders thermally treated at different temperatures were investigated. The resultant samples were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), and energy dispersive spectrometer (EDS). The highly pure ZrB 2 with the mean size of 5 µm could be obtained at 1600 °C for 90 min and the grains presented columnar shapes. After addition of SiC, ZrB 2 revealed relatively better crystallinity and finer particle size. Regular columnar ZrB 2 grains ranging from 1 to 2 µm were seen existing after reaction at 1500 °C for 90 min. [ABSTRACT FROM AUTHOR]

The SiCN precursor was prepared by cross-linking process using polysilazane (PSZ) as raw materials. The cross-linking behavior and dielectric properties of SiCN precursor were analyzed. The results indicated that the main reactions during cross-linking process were double bond addition reaction, hydrosilylation reaction, dehydrogenation coupling reaction and transamination reaction. The SiCN precursor was made up of Si-C-N network structure and the main chemical bonds were Si-C, Si-N and C-C. The appropriate cross-linking temperature of SiCN precursor was 600 °C. Furthermore, the increasing content and crystallization degree of free carbon could improve the dielectric properties of SiCN precursor. [ABSTRACT FROM AUTHOR]

ZrB 2 -SiC powders with different amounts of SiC (10–30 wt%) were in-situ synthesized at 1600 °C for 90 min in Ar atmosphere. Effects of SiC addition on the formation of ZrB 2 via carbothermal reduction of ZrO 2 , H 3 BO 3 and carbon black were investigated. The samples were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), energy dispersive spectrometer (EDS) and transmission electron microscope (TEM). The grain size of ZrB 2 in final powders decreased with adding SiC. Columnar ZrB 2 and granular SiC were combined interactively when the SiC content was 25 wt%. Layer-like hexagonal SiC was obtained in the product containing 30 wt% SiC, whereas the ZrB 2 grain growth was strongly inhibited. Furthermore, the growth mechanisms of ZrB 2 and SiC were studied. [ABSTRACT FROM AUTHOR]