The dependence on the composition of Young's modulus, fracture toughness and flexural strength of a reaction-sintered (RS) silicon-silicon carbide (Si-SiC) composite was determined at room temperature over a wide range of SiC content (0–90 vol%). The results were compared with those of two commercial reaction-bonded (RB) Si-SiC materials. Young's modulus follows two-phase models over the whole compositional range when a value of 432 GPa is assumed for the Young's modulus of β-SiC. At low SiC contents (< 60 vol%), the RS composites show fracture behaviour consistent with a crack-deflection toughening model, while at SiC content higher than about 70 vol%, they exhibit much higher surface energies than the equivalent RB commercial Si-SiC. Between 60 and 70 vol% SiC an abrupt change of fracture behaviour is observed. Such differences in surface energies are attributed to quite different microstructures and crack propagation mechanisms.

The study described in this paper is specifically related to the thermal and elastic properties of Al2O3 matrix with SiC whisker reinforcements. Measurements of Young's modulus and thermal diffusivity/conductivity were performed on various Al2O3-SiCw compositions obtained by varying both the I aw materials and the whisker volume fractions, While the Young's modulus was quite independent of the choice of raw materials, a remarkable difference was found for the thermal conductivity of composites processed with different whisker sources.

Starting from three different commercial powders, AIN materials were densified by pressureless sintering under various temperature and time values in order to investigate the influence of microstructure on thermal conductivity. The influence of the sintering aids (3 wt% Y2O3 and 2 wt% CaC2) and of the forming processes (cold isostatic pressing and thermocompression of tape cast pieces) were also been evaluated. Thermal conductivity increased with the purity level of the starting powder and with an increasing the sintering temperature and soaking time. The highest thermal conductivity values (196 Wm−1 K−1) were obtained with the purest powder and high temperature (1800 °C) sintering over long periods (6 h). No influence on thermal conductivity was detected from the forming technique.

Measurements of thermal diffusivity/conductivity were performed by the laser-flash method on several Si/SiC composites developed on a laboratory scale by using reaction bonding and reaction sintering techniques. Furthermore, the influence of the average grain size on the thermal conductivity was discussed. The values obtained range among the highest so far reported in the literature for this class of ceramics.

Laser-pulse method is a well-known technique for measuring thermal diffusivity of solids and is based on several assumptions, i.e., adiabatic conditions, short laser-pulse length, temperature independence of thermal properties, and uniform heating of sample surface. However, very little has been published on the nonuniform heating effect that can limit the accuracy of measurements of several percent. In this paper the solution of heat equations under particular nonuniform conditions has been presented. Moreover, a heuristic model has been introduced in order to describe nonuniform heating effects arising under a general laser energy distribution. In both cases a good agreement with experimental results has been obtained.

Photovoltaic systems based on luminescent sheets, using spectral distributions different from the solar spectrum, are analyzed according to a simple unified approach. Introducing “spectral transfer functions”, effective spectral responses and photocurrents are calculated. In particular performances expected for planar luminescent concentrators and flat modules covered with fluorescent plates are evaluated and discussed.

An extensive study is presented on photovoltaic devices fabricated by the vacuum deposition of indium-doped CdS films onto p-type silicon substrates.

Scanning light‐spot techniques can be advantageously employed to gain microscopic information on the photoelectrochemical behavior of surface defects and on the spatial distribution of diffusion length. Such techniques have been used in systems based on and layer‐type, semiconductor anodes to measure both photocurrent profiles at fixed wavelengths and photocurrent spectral responses at fixed points on the photoelectrode surface.

New results on photovoltaic performance of n-CdS/p-Si heterojunctions are reported. Conversion efficiencies up to 11.1% for single crystal Si and 9.2% for semi-crystal Si have been obtained (without ARC and BSF) by a systematic study of CdS film doping, Silicon substrate preparation and interfacial oxide thickness.

Photovoltaic methods using spectral distributions different from the solar spectrum are analyzed according to a simple unified approach. Introducing a “spectral transfer function”, effective spectral responses and photocurrents are calculated for a few representative situations. In particular thermophotovoltaic converters, planar luminescent concentrators and flat modules covered with fluorescent covers are analyzed and discussed.

Heterojunctions between silicon and transparent semiconductors are promising alternative solar cells. n-CdS/p-Si junctions, in particu lar, show Voc up to 570 mV,J up to 29 mA/cm2 and overall efficien cies up to 10% (without ARC). Transport mechanism in these devices can be described as a multistep thermal assisted tunneling, unchanged by illumination. Photoresponses show the expected band-pass behaviour with internal quantum yields of about 1.