Silicon Oxycarbide and Silicon Oxycarbonitride Materials under Concentrated Solar Radiation

The potential application of silicon oxycarbonitride (SiOCN), silicon oxycarbide (SiOC) and silicon oxycarbide–SiC (SiOC–SiC) for photothermal devices such as volumetric solar absorbers has been studied evaluating the response to thermal shock from a Fresnel lens. The accelerated ageing test comprises fast heating (32 °C min(−1)) and cooling rates (27 °C min(−1)) from 100 to 1000 °C and dwelling times of 10 min. Porous materials (SiOCN(p) and SiOC(p)) failed the thermal shock tests; they were massively degraded by the formation of a large depression in the focus of solar radiation. Dense materials (SiOC(d) and SiOC–SiC(d)) withstood 100 cycles of thermal shock ageing tests due to the formation of a protective silica layer. The absorptance values for dense materials remained fairly constant before and after thermal shock tests: from 94.5 to 94.3% for SiOC(d) and from 93.3 to 93.3% for SiOC–SiC(d). These preliminary studies indicate their potential for high-temperature solar receiver applications.