António Ramirez de Arellano-López

The amplitude and temperature dependences of the Young’s modulus and the internal friction (ultrasonic absorption) of biomorphic carbon, silicon carbide, and SiC/Si composite produced from medium density fiberboard (MDF) by pyrolysis (carbonization), followed by infiltration of molten silicon into the prepared carbon preform have been studied in the temperature range 100–293 K in air and under vacuum. The measurements have been performed by the acoustic resonance method with the use of a composite vibrator for longitudinal vibrations at frequencies of approximately 100 kHz. The data obtained by acoustic measurements of the amplitude dependences of the elastic modulus have been used for evaluating the microplastic properties of samples under study. It has been shown that the Young’s modulus, the decrement of elastic vibrations, and the conventional microyield strength of the MDF samples differ from the corresponding data for previously studied similar materials produced from natural eucalyptus, beech, sapele, and pine woods. In particular, the desorption of environmental molecules at small amplitudes of vibrations, which is typical of biomorphic materials based on natural wood, is almost absent for the MDF samples. The results obtained have been explained by different structures and the influence of pores and other defects, which, to a large extent, determine the mechanical characteristics of the biomaterials under investigation.

This pa per re ports on measurements of the heat ca pacity at constant pressure C p in the 80–300-K tem perature interva l and the thermo power coefficient S at 5–300 K of the carbon preform of sa pe

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...

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.

Single‐crystal sapphire exhibits a highly anisotropic fracture behavior. The surfaces of specimens fractured along prismatic planes are wavy, with fractographic features appearing as small areas of contrast under an optical microscope. Optical microscopy, atomic force microscopy, X‐ray topography, and confocal microscopy are used to demonstrate a correlation between the areas of contrast and dislocations penetrating the sample surface. The surface features are argued to be a consequence of the stress field surrounding the dislocations, which deflect the crack approximately 10 nm normal to the surface as the crack cuts the dislocations. The lateral extent of measurable surface deflection is of the order of 5 μm. These images can be compared directly to show the equivalence of the position of the dislocations observed by X‐ray topography and the surface contrast observed optically.

BioSiC is a biomimetic SiC-based ceramic material fabricated by Si melt infiltration of carbon preforms obtained from wood. The microstructure of bioSiC mimics that of the wood precursor, which can be chosen for tailored properties. When the remaining, unreacted Si is removed, a SiC material with interconnected porosity is obtained. This porous bioSiC is under study for its use as a medical implant material. We have successfully fabricated bioSiC from Sipo wood and studied the kinetics of Si removal by wet etching. The results suggest that the reaction is diffusion-limited, and the etch rate follows at^−0.5law. The etching rate is found to be anisotropic, which can be explained attending to the anisotropy of the pore distribution. The compressive strength was studied as a function of etching time, and the results show a quadratic dependence with density. In the attainable range of densities, the strength is similar or better than that of human bone.