Structure and electronic properties of biomorphic carbon matrices and SiC ceramics prepared on their basis

Biomorphic carbon matrices (BCMs) were produced by pyrolysis from wood species of different forest and garden trees, after which the as-prepared BCMs were converted to SiC ceramics through their impregnation with liquid silicon and further heat-treatment. Both types of obtained samples were studied by scanning electron microscopy (SEM), Raman scattering (RS), and electron spin resonance (ESR) methods. The SEM data reveal that all BCM samples contain large (10–50 μm) and small (1–5 μm) micro-pores with surface densities ∼109 m−2 and 1011 m−2, respectively. Analysis of RS allowed to estimate carbon cluster sizes of about 5–11 nm depending on the sample type. The study of the electronic structure using ESR spectroscopy is carried out for BCM and SiC ceramics samples. Using theoretical analysis of the ESR spectra, it was found that spin resonance in BCMs is due to the contribution of three spin systems: free electron spins, “pseudo-free” electron spins from the tail of density states below the conduction band...