Porous silicon carbide ͑SiC͒ ceramics are produced using carbon matrices derived from natural wood. Such material is especially promising as it is environmentally friendly with attractive physical properties, including a high level of biocompatibility, chemical inertness, and mechanical strength. We have developed a forced impregnation process with further synthesis of SiC using natural wood as well as a variety of industrial carbon materials and compared the properties of these ceramics. The structure and composition of the materials obtained were investigated by Raman scattering spectroscopy. The hardness of the samples was estimated using the Vickers technique. It was shown that the phase composition and mechanical properties of synthesized SiC ceramics can be effectively controlled by the initial Si contents and temperature of the synthesis process. A large variety of options are demonstrated for materials development taking into account an optimal porosity selection for various practical applications.

Porous ceramic materials of SiC were synthesized from carbon matrices obtained via pyrolysis of natural cork as precursor. We propose a method for the fabrication of complex-shaped porous ceramic hardware consisting of separate parts prepared from natural cork. It is demonstrated that the thickness of the carbon-matrix walls can be increased through their impregnation with Bakelite phenolic glue solution followed by pyrolysis. This permits to modify the mechanical and thermophysical properties of the prepared SiC ceramics. Both the carbon matrices (resulted from the pyrolysis step) and the SiC ceramics are shown to be pseudomorphous to the structure of initial cork. Depending on the synthesis temperature, 3C-SiC, 6H-SiC, or a mixture of these polytypes, can be obtained. By varying the mass ratio of initial carbon and silicon components, stoichiometric SiC or SiC:С:Si, SiC:С, and SiC:Si ceramics could be produced. The structure, as well as chemical and phase composition of the prepared materials were studied by means of Raman spectroscopy and scanning electron microscopy.

We have studied the temperature behavior of the electron spin resonance (ESR) spectra of nitrogen (N) donors in n-type 6H SiC crystals grown by Lely and sublimation sandwich methods (SSM) with donor concentration of 10 17 cm -3 at T = 60-150 K. A broad signal in the ESR spectrum was observed at T > 80 K with Lorentzian lineshape and g || = 2.0043(3), g  = 2.0030(3), which was previously assigned in the literature to the N donors in the 1s(E) excited state. Based on the analysis of the ESR lineshape, _____________________________ a)

Biomorphic SiC ceramics produced by the forced infiltration with liquid silicon of carbon matrices derived from hardwood precursors were investigated. The phase composition of the ceramics obtained was found to be dependent on the mass ratio of the initial silicon and carbon components, the synthesis temperature, and the process duration. Raman spectroscopy (RS) investigations showed that the 3C polytype is formed at a synthesis temperature of about 1550 °C, and that both 3C and 6H‐SiC are formed at temperatures of about 1800 °C. Further temperature rises up to 2100 °C lead to an increase in the fraction of the 6H polytype. In the specimens obtained by impregnation under excess Si conditions, the residual silicon inside the SiC pores is recorded. Analysis of the parameters of phonon peaks allowed us to conclude that the residual silicon in these samples is under significant compressive strain. Surface morphology of axial profiles of SiC ceramics produced from pear‐tree wood for ψ = 2.33 component mass ratio.