Evaluation of thermal shock resistance of silicon oxycarbide materials for high-temperature receiver applications

Abstract

Materials used as solar receivers in concentrated solar power technology must withstand severe operational conditions caused by concentrated solar radiation. For this solar technology several ceramic material candidates (silicon carbide, porous and dense silicon oxycarbide) have been subjected to thermal shock resistance test by using Fresnel lens, the equipment available, that concentrates the solar radiation more than 2600 times. Fast heating (37 ºCs -1 ) and cooling rates (28 ºCs -1 ) from 100 to 1200 ºC and dwelling time of 10 minutes are employed. The evolution of materials surface has been evaluated during test by spectroscopic methods and both confocal and electronic microscopies. It has been obtained the surface map of each analyzed sample in materials to thermal shock under concentrated solar radiation makes these materials suitable candidates of being used as high temperature solar receivers.

Silicon Oxycarbide and Silicon Oxycarbonitride Materials under Concentrated Solar Radiation

“…The roughness value ( R a : arithmetic average value of roughness) (ISO 4287/1 and DIN 4768) was determined by analysing three different zones placed at three different distances from the focus centre: the nearest focus area (at 2–3 mm from the focus centre), an intermediate zone (middle zone, at 5–6 mm from the focus centre) and, the furthest area (at 12–13 mm from the focus centre). As we stated in a previous work [ 18 ], there is a thermal gradient of at least 500–600 °C from focus to the most distant areas of the tested sample, so small variations (few millimeters) from focus zone lead to great differences in temperature.…”

“…The accelerated ageing test involved a thermal shock test under concentrated solar radiation using a Fresnel lens. A detailed description of the concentrated solar facility was previously reported [ 4 , 18 ]. To reach the desired temperature and maintain it throughout the test time, the experiments were carried out on sunny and unclouded days between 10:00 and 14:00 (apparent solar time), when levels of direct solar irradiance were close to 1000 W m −2 .…”

“…Morris et al [ 4 ] studied the behaviour of metallic and intermetallic alloys using a Fresnel Lens. Recently, Mazo et al [ 18 ] analysed the thermal shock behaviour of ceramic materials (i.e., SiC and silicon oxycarbide (SiOC)) using the same solar concentrator facility. Palacios et al [ 15 ] carried out an isothermal ageing treatment over the samples (SiC, sand and Fe 2 O 3 ) and studied the changes by the variation of colour, specific heat capacity, absorptance and XRD.…”

“…Based on previous results [ 17 , 18 ], this work proposes the use of SiOC and silicon oxycarbonitride (SiOCN) materials for their potential as high temperature solar receivers. SiOC materials have interesting intrinsic properties such as good resistance to oxidation in harsh environments, high and tunable mechanical properties, low creep, high absorbance, low CTE, in addition to tunable thermal and electrical properties [ 18 , 19 , 20 , 21 , 22 , 23 , 24 ]. It is important to note that many of these properties can be designed and adjusted simply by varying the composition, microstructure and processing conditions such as temperature and type of sintering.…”

“…In this work preliminary experiments on the behaviour of novel promising candidates for solar receivers have been carried out., but another experiments are required in other to ensure the suitability at industrial scale. In the earlier studies [ 18 ], porous SiOC (SiOC p ) underwent a massive degradation of its surface at 1200 °C during the first cycles of accelerated solar ageing, making it necessary to test its suitability at lower temperatures (i.e., 1000 °C). Due to their very high resistance at 1200 °C, further insight is required of the behaviour of dense SiOC materials (SiOC d ) at lower temperatures (i.e., 1000 °C) in order to complete the study of their thermal shock resistance.…”