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4H silicon carbide (4H‐SiC) holds great promise for high‐power and high‐frequency electronics, in which high‐quality 4H‐SiC wafers with both global and local planarization are cornerstones. Chemical–mechanical polishing (CMP) is the key processing technology in the planarization of 4H‐SiC wafers. Enhancing the performance of CMP is critical to improving the surface quality and reducing the processing cost of 4H‐SiC wafers. In this review, the superior properties of 4H‐SiC and the processing of 4H‐SiC wafers are introduced. The development of CMP with chemical, mechanical, and chemical–mechanical synergistic approaches to improve the performance of CMP is systematically reviewed. The basic principle and processing system of each improvement approach are presented. By comparing the material removal rate of CMP and the surface roughness of CMP‐treated 4H‐SiC wafers, the prospect on the chemical, mechanical, and chemical–mechanical synergistic improvement approaches is finally provided. [ABSTRACT FROM AUTHOR]

Wettability control of laser textured SiC ceramic surfaces through the addition of pure elements was studied in this work. A correlation analysis between the elements C/O/Si/B/Al/Fe and the contact angle demonstrates that elements C/O/Si/B are all highly correlated with the wettability. The correlation of elements Fe/Al with the contact angle is relatively lower. Because elements C/Si are inherent elements in a SiC material, element O is derived from oxidation, and element B is added along with the additives during the sintering process. A more hydrophilic SiC surface was obtained by controlling the addition of element B. [ABSTRACT FROM AUTHOR]

Silicon carbide (SiC) precursor was obtained by sol–gel used tetraethoxysilane as silicon source and saccharose as carbon source, and then the precursor was used to prepare SiC by carbothermal reduction under dynamic vacuum condition. The samples were characterized by X-ray diffraction, scanning electron microscope, and low-temperature nitrogen adsorption–desorption measurement. The results showed that the carbothermal temperature for synthesizing SiC needed to be at 1,100 °C under dynamic vacuum. At this temperature, the obtained sample is composed of agglomerated regular grains with size ranging from 20 to 40 nm and has a high surface area of 167 m2/g and the main pore size center at 5.3 nm. [ABSTRACT FROM AUTHOR]

In view of technical difficulties in preparing ceramics with complex shapes, gel casting combined with 3D printing was here adopted to prepare silicon carbide ceramic green body, and gaseous silicon infiltration sintering was used to prepare 3D lattice-structured ceramics. The preparation of the slurry, gel curing, and ceramic molding was investigated. Results demonstrate that the ratio of components affects the fluidity and stability of slurry. However, when volume fraction of the solid phase of the slurry reaches 56%, the viscosity of slurry is only 300 mPa s, and drying shrinkage rate of green body is 6.6%; these characteristics make slurry suitable for 3D complex model injection molding. Furthermore, both the temperature and the initiator affect gel curing speed. As the temperature and initiator content increase, the induction and gel time are rapidly shortened. When demolding at 300 °C and when gaseous silicon infiltration sintering is carried out at 1550 °C, a 3D lattice-structured ceramic with relative density of 87% and average compressive strength of 433 MPa can be obtained. [ABSTRACT FROM AUTHOR]

A diffusion-modified HfC/HfC SiC bilayer system was innovatively designed and synthesized onto cemented carbide (WC-Co) substrate by reactive double glow plasma surface alloying (DGPSA) technique for adherent diamond deposition. The microstructure, phase composition and adhesion of the bilayer system were investigated, as well as its effect on the diamond coating system. The results showed that the bilayer system was made up of a 1.0-μm-thick nanostructured HfC-dominant inner layer and a 0.7-μm-thick HfC SiC mixed outer layer. As the gradient element distributions existed at the bilayer/substrate interface, the bilayer system displayed a superior adherence to the substrate. And the surface microhardness improved from 1802 HV 0.1 to 2857 HV 0.1 after the reactive DGPSA treatment. Subsequently, a uniform and dense nanocrystalline diamond coating with thickness of 4.0 μm was successfully deposited onto the HfC/HfC SiC interlayered substrate. Benefit from the effective suppression of Co diffusion by the interlayer and the reasonable design in its hardness and thermal expansion coefficient (TEC), the obtained diamond coating possessed an excellent adhesion. Therefore, the diffusion-modified HfC/HfC SiC bilayer systems synthesized via reactive DGPSA technique can be considered as a novel interlayer option for depositing adherent diamond coatings on WC–Co substrates. [ABSTRACT FROM AUTHOR]

Abstract: A series of C/SiC composites was successfully synthesized via the carbothermal reduction of carbonaceous silicon xerogel, which was prepared from the sol gel method by using tetraethoxysilane TEOS and saccharose as the raw materials The obtained samples were characterized by X ray powder diffraction XRD and N2 physical adsorption The specific surface areas of the as prepared C/SiC composites varied from 329 to 849m2/g The average pore diameters and the total pore volumes were in the range of 4.5–7.6nm and 0.53–1.12cm3/g, respectively The as prepared C/SiC composites were proved to be effective supports for Ru catalysts for ammonia synthesis At 435°C, 10.0MPa and a N2/H2 (1/3) flow rate of 10000h−1, the optimum activity of 15.9% ammonia in the effluent was reached when C/SiC-5 (C/TEOS molar ratio=5) was used as the catalyst support. [Copyright &y& Elsevier]