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 (SiOCNp and SiOCp) failed the thermal shock tests; they were massively degraded by the formation of a large depression in the focus of solar radiation. Dense materials (SiOCd and SiOC-SiCd) 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 SiOCd and from 93.3 to 93.3% for SiOC-SiCd. These preliminary studies indicate their potential for high-temperature solar receiver applications.
Keywords: concentrated solar radiation; high temperature solar receivers; silicon oxycarbide; silicon oxycarbonitride; thermal shock test.