Search

The absorptivity of solar thermal absorber materials affects the heliothermal conversion efficiency of concentrated solar power systems. The solar absorbing ceramics were prepared by the fixed mixture of bauxit, Fe2O3, and TiO2 with adding CuO in different percentages. The absorptivity and thermal shock resistance with the effect of adding CuO in different percentages were studied. Fe2O3 and TiO2 have excellent optical properties, and CuO decreases the material's band gap to boost the electronic transition and increase the material absorptivity. The results showed that the material is sintered at 1380°C with an excellent absorptivity of 94.00% in the spectrum range of 0.3–2.5 μm, and the bending strength is 132.94 MPa. The bending strength was increased by 21.07% after 30 thermal shock cycles (1000°C‐room temperature, air cooling). The liquid phase facilitates the synthesis of hercynite with excellent high temperature properties. The hercynite improves the thermal shock resistance of the material. [ABSTRACT FROM AUTHOR]

Zirconia‐corundum‐mullite composites were prepared from andalusite, ZrO2, and α‐Al2O3 and evaluated for application as solar thermal storage materials in this study. The effects of ZrO2 concentration (0–25 wt%) and sintering temperature(1500–1650°C) on the bending strength, phase composition, microstructure, dimensional stability, and thermal shock resistance of the samples were investigated. The results showed that sample C2 (containing 10 wt% ZrO2) sintered at 1600°C exhibited the best properties. A portion of Y2O3 existed in ZrO2, which excited a small amount of t‐ZrO2 in the sample after sintering, while the other portion of Y2O3 was separated from ZrO2 and participated in the formation of a high‐temperature liquid phase. The liquid phase reduced the dimensional stability of the sample. However, the liquid phase could also promote sintering, reducing the optimal sintering temperature, with lower sintering temperatures increasing the dimensional stability of the sample. Once again, the C2 sample exhibited the highest thermal shock resistance, with a strength loss of 2.76 MPa after 30 thermal shock tests. The thermal storage density(25–1100°C) of C2 was 1121 kJ/kg. In summary, sample C2 exhibits a high degree of dimensional stability and thermal shock resistance and can thus be used as a reliable solar thermal storage material. [ABSTRACT FROM AUTHOR]

Anorthite solar thermal energy storage ceramics were fabricated from magnesium slag solid waste by pressureless sintering. The effects of CaO/SiO 2 ratio and sintering temperature on the physical, chemical, and thermophysical properties of ceramics were explored. X-ray diffraction results demonstrated that thermal shock process contributed to the formation of anorthite, and increasing CaO/SiO 2 ratio promoted the transformation of anorthite (CAS 2) into melilite (C 2 AS). Some micro-cracks were found according to SEM analysis, forming by the mismatch of thermal expansion coefficients among phases. The combined effects of the low thermal expansion coefficient of anorthite and micro-crack toughing endowed the ceramic with good thermal shock resistance. Optimum comprehensive performances were observed in the sample with a CaO/SiO 2 ratio of 0.58 sintered at 1160°C, of which the specific thermal storage capacity was 0.63 J·g-1·°C-1(room temperature). The bending strength increased by 0.22% after 30 thermal shock times (room temperature-800°C, wind cooling). Therefore, the anorthite ceramics exhibited great potential for solar thermal energy storage. [ABSTRACT FROM AUTHOR]

Mullite ceramic materials have a number of excellent properties that make them an excellent choice for solar heat absorber materials in Concentrating Solar Power (CSP) systems. In this study, the effects of adding Co 2 O 3 and Fe 2 O 3 on the properties of mullite-based ceramics were studied, aiming to get excellent absorption rate and thermal shock resistance. The results show that the sample C2 (45.05 wt% 75 calcined bauxite, 45.05 wt% Suzhou clay, 9 wt% Fe 2 O 3 , 3 wt% Co 2 O 3) sintered at 1400 °C has the best comprehensive performance, with a bending strength of 143.28 MPa and a solar absorption rate of 92.2 % in the wavelength range of 0.3–2.5 μm. The bending strength increased by 31.36 % after thermal shock cycles for 30 times (1000 °C ∼ room temperature, air cooling). Generation of iron cobalt spinel and lattice distortion caused by Fe3+ and Co3+ into the mullite lattice combined to promote the absorption rate. In the meantime, the main crystalline phase columnar mullite showed a tight continuous interlaced network structure. The fracture mode was mainly transgranular fracture, which endowed C2 excellent thermal shock resistance. [ABSTRACT FROM AUTHOR]

Solar high-temperature thermal power generation systems require thermal storage materials with excellent thermal shock resistance due to the large temperature difference during operation (in the range of 20–800 °C). In this study, mullite-based absorption and storage integrated ceramics were prepared using low-cost bauxite and kaolin as raw materials and Fe 2 O 3 as additive. The effect of Fe 2 O 3 on the thermal shock resistance of mullite-based ceramics was investigated. The results showed that the absorption and bending strength of sample BK4 (bauxite: 50 wt%, kaolin: 50 wt%, Fe 2 O 3 : additional 11 wt%) increased by 2.98% (89.8%) and 8.00% (147.10 MPa), with a storage thermal density of 1185.75 kJ kg−1 after 30 thermal shock cycles. The mechanism for the excellent thermal shock resistance of the ceramics is revealed from the aspect of the changes in phase and microstructure of the samples induced by the changes in the mass transfer rate during the thermal shock process. It was calculated that a unit volume of BK4 (with a raw material cost of about 154.22 USD) could generate 974.95 kW h of electricity (saving 119.92 kg of coal) when used in a solar thermal storage system. [ABSTRACT FROM AUTHOR]

ZrO 2 –Al 2 O 3 -A 3 S 2 (3Al 2 O 3 ·2SiO 2) composites are ideal Casting filter materials with excellent mechanical properties and thermal shock resistance. In this paper, 3Y–ZrO 2 (3 mol% Y 2 O 3 -stabilized ZrO 2) was added to kaolin and α-Al 2 O 3 to prepare ZrO 2 –Al 2 O 3 -A 3 S 2 composites by pressureless sintering. The results showed that when the addition amount of 3Y–ZrO 2 is 15 wt%, the bending strength and fracture toughness of the composites sintered at 1600 °C are 152.51 MPa and 3.52 MPa m1/2, respectively. The bending strength increased to 161.83 MPa after 30 thermal shocks (1100 °C to room temperature), with an increase rate of 6.11 %. The ZrO 2 crystals are evenly distributed between corundum and mullite crystals, effectively preventing abnormal growth of corundum and mullite crystals, and a small number of pores exist in the samples, which could act as a "buffer zone" to prevent the expansion of cracks in the thermal shock, resulting in high mechanical strength and excellent thermal shock resistance for composites. [ABSTRACT FROM AUTHOR]