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This paper reports on measurement of the heat capacity at constant pressure C p of silicon bio-carbide prepared within the 5–300 K temperature interval from beech tree wood (bio-SiC(BE)), and within 80–300 K, from tree wood of sapele (bio-SiC(SA)), as well as SiC/Si ecoceramics of beech, sapele, and white eucalyptus wood. It has been shown that in bio-SiC(BE) the measured heat capacity contains a significant contribution of surface heat capacity, whose magnitude decreases with increasing temperature. Of the ecoceramics, only SiC/Si(SA) characterized by a high enough porosity has revealed a small contribution to the heat capacity coming from its surface component. The experimental results obtained are discussed.

The thermopower coefficients of bio-SiC and SiC/Si ecoceramics prepared from sapele tree wood have been measured in the temperature interval 5–300 K. The measurements have been performed both along and perpendicular to empty (bio-SiC), as well as empty and partially silicon-filled (SiC/Si) channels in the samples. In bio-SiC, a contribution to thermopower associated with electron drag by phonons has been shown to exist within the temperature interval 5–200 (250) K. No such effect is realized in SiC/Si. This is assumed to derive from the presence in this material of heavily doped silicon embedded in SiC channels and the dominant part it plays in the behavior of the thermopower of this ceramics. The results obtained for the thermopower are compared with the available data for bio-SiC prepared from white eucalyptus tree wood and heavily doped bismuth.

Samples of β-SiC/Si ecoceramics with a silicon concentration of ∼21 vol % have been prepared using a series of consecutive procedures (carbonization of sapele wood biocarbon, synthesis of high-porosity biocarbon with channel-type pores, infiltration of molten silicon into empty channels of the biocarbon, formation of β-SiC, and retention of residual silicon in channels of β-SiC). The electrical resistivity ρ and thermal conductivity κ of the β-SiC/Si ecoceramic samples have been measured in the temperature range 5–300 K. The values of ρ Si chan (T) and κ Si chan (T) have been determined for silicon Sichan located in β-SiC channels of the synthesized β-SiC/Si ecoceramics. Based on the performed analysis of the obtained results, the concentration of charge carriers (holes) in Sichan has been estimated as p ∼ 1019 cm−3. The factors that can be responsible for such a high value of p have been discussed. The prospects for practical application of β-SiC/Si ecoceramics have been considered.

The electrical resistivity and thermal conductivity of high-porosity (∼52 vol %, channel-type pores) bio-SiC samples prepared from sapele wood biocarbon templates have been measured in the temperature range 5–300 K. An analysis has been made of the obtained results in comparison with the data for bio-SiC samples based on beech and eucalyptus, as well as for polycrystalline β-SiC. The conclusion has been drawn that the electrical resistivity and thermal conductivity of bio-SiC samples based on natural wood are typical of heavily doped polycrystalline β-SiC.

This paper reports on measurements of the heat capacity at constant pressure Cp in the 80–300-K temperature interval and the thermopower coefficient S at 5–300 K of the carbon preform of sapele wood, which was prepared at the carbonization temperature of 1000°C. Measurements of Cp(T), our previous data on the phonon thermal conductivity, and literature information on the sound velocity have been used to calculate the phonon mean free path l(T) for this material. It has been shown that within the temperature interval 200–300 K, l is constant and equal to 11 A, a figure matching the size of the nanocrystallites (“graphite fragments”) making up the carbon framework of the sapele carbon preform. The high-temperature parts of S(T) have been found to follow a linear course characteristic of diffusive thermopower for the degenerate state of charge carriers, with only one type of charge carriers present. The anisotropy of the thermopower coefficient has been estimated.

This paper reports on measurements (in the temperature range T = 5–300 K) of the thermal conductivity κ(T) and electrical conductivity σ(T) of the high-porosity (∼63 vol %) amorphous biocarbon preform with cellular pores, prepared by pyrolysis of sapele wood at the carbonization temperature 1000°C. The preform at 300 K was characterized using X-ray diffraction analysis. Nanocrystallites 11–30 A in ize were shown to participate in the formation of the carbon network of sapele wood preforms. The dependences κ(T) and σ(T) were measured for the samples cut across and along empty cellular pore channels, which are aligned with the tree growth direction. Thermal conductivity measurements performed on the biocarbon sapele wood preform revealed a temperature dependence of the phonon thermal conductivity that is not typical of amorphous (and X-ray amorphous) materials. The electrical conductivity σ was found to increase with the temperature increasing from 5 to 300 K. The results obtained were analyzed.

The effect of the vibrational strain amplitude on the Young’s modulus and ultrasound absorption (internal friction) of a SiC/Si biomorphic composite prepared by pyrolysis of sapele wood followed by infiltration of silicon were investigated. The studies were conducted in air and in vacuum by the acoustic resonance method with the use of a composite vibrator in longitudinal vibrations at frequencies of about 100 kHz. Measurements performed on sapele wood-based bio-SiC/Si samples revealed a substantial effect of adsorption-desorption of molecules contained in air on the effective elasticity modulus and elastic vibration decrement. Microplastic characteristics of the SiC/Si composites prepared from wood of different tree species were compared.

The acoustic investigations of the elastic (Young’s modulus) and microplastic properties of a composite material, the SiC/Al-13Si-9Mg biomorphic metal ceramic, were performed. The ceramic was prepared by infiltration of the Al-13Si-9Mg melt into porous silicon carbide derived from wood of two species of trees, beech and sapele. The measurements were performed with a composite piezoelectric vibrator under resonance conditions, with rod-shaped samples vibrated longitudinally at about 100 kHz over a wide range of vibrational strain amplitudes, which included both the linear (amplitude-independent) and nonlinear (microplastic) regions. It was shown that the Young’s modulus and the microplastic properties of the composite are anisotropic and depend substantially on the tree species, particularly when longitudinal vibrations are excited in samples cut along the tree fibers.

The electrical resistivity of Sapele-based biomorphic SiC/Si materials was measured in a wide temperature range from 10 K to room temperature. The samples were fabricated by the reactive infiltration of molten silicon into a carbonized Sapele (African Entandrophragma Cylindricum) wood preform. All the samples studied contained residual Si (10–35 wt %). It was found that the resistivity-temperature (ρ(T)) dependences have semimetallic behavior which becomes very close to linear metallic behavior at 100 < T < 300 K. The obtained values of resistivity were quite low (ρ ≈ 0.002–0.02 Ω cm) and showed strong anisotropy: the resistivity along the wood growth axis was several times lower than that in the perpendicular direction. The extent of this anisotropy was in correlation with the amount of residual Si (and, hence, with the amount of residual porosity) in a sample. The resistivity perpendicular to the wood growth axis drastically increased with the Si content, whereas the resistivity parallel to it was practically independent of the Si content. It is suggested that the presence of residual carbon in the samples and carrier scattering at SiC/Si interphases could determine the observed character of ρ(T) dependences.