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Solar energy absorption and storage of integrated ceramic materials is both the absorption of sunlight and storage of sunlight into thermal energy functional materials. In this paper, the effect of Fe 2 O 3 on the solar absorptivity, thermal storage properties, sintering temperature, and physical properties of mullite-based thermal storage ceramics was investigated. The results show that the absorptivity and thermal storage density of the sample AF4 (Bauxite:50 wt%, Clay:50 wt%, Fe 2 O 3 :11 wt%) after sintering at 1420 °C are 87.2% and 1116.5 kJ kg−1, respectively; and the unit volume of the AF4 sample can provide the power grid with 918.01 kW h of electricity, save 112.91 kg of coal, and reduce 361.33 kg of CO 2 emission. This study systematically elucidated the mechanism of the enhancement of sample absorption caused by Fe3+ doping-induced changes in substrate color, reduction in material forbidden bandwidth, and lattice anharmonic vibration effect, in addition to comprehensively evaluating the feasibility of the optimal AF4 sample for use in solar energy absorbing and storing integrated ceramic materials. [ABSTRACT FROM AUTHOR]

Thermal storage materials are typically made of materials with high thermal storage density, high thermal conductivity and high temperature stability. In this study, corundum-mullite composite thermal storage ceramics were prepared by solid-phase sintering using widely available and low-cost α-Al 2 O 3 , kaolin, and quartz as raw materials. The effects of silicon source and Al 2 O 3 /SiO 2 ratio on the physical properties and structural properties of corundum-mullite composite ceramics were investigated. The results showed that the A3 sample (α-Al 2 O 3 : 85.77 wt%, kaolin: 14.23 wt%) after sintering at 1650 °C had the excellent performance, with thermal conductivity of 15.01 W (m K)−1 (25 °C), thermal storage density of 965.15 kJ kg−1, and bending strength of 145.9 MPa. The multiple ions introduced by kaolin can effectively promote the liquid-phase mass transfer at high temperatures, accelerate the diffusion rate of Si4+, increase the growth rate of mullite, and accelerate the densification process of the samples, which in turn improves the physical properties of the samples. When used in a solar thermal storage system, the A3 sample per unit volume can provide 911.53 kW h of electricity to the grid, saving 112.12 kg of coal and reducing 358.78 kg of CO 2 emissions. [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]

In this paper, steel slag foamed ceramics were fabricated by using steel slag, kaolin, feldspar, and quartz as main raw materials, and adding SiC as high‐temperature foaming agent. The effects of steel slag content and SiC particle size on porosity and mechanical properties of foamed ceramics were researched. Results indicate that when content of steel slag is 40 wt%, and particle size of SiC is 20 µm, foamed ceramics exhibited optimized properties: water absorption rate of 2.59%, total porosity of 55.91%, bulk density of 1.33 g·cm−3, and compressive strength of 1.21 MPa. The results show that with the increase of steel slag content, the phase composition of foamed ceramics changes, and foam process is hindered. The increase of steel slag content contributes to the formation of diopside. Fe3+, Fe2+ in liquid phase enter into diopside by solid solution, the amount of liquid phase decreases. Liquid phase mass transfer slows down, and content of SiC in liquid phase decreases, so that the porosity decreases. At the same steel slag content, different SiC particle size affects the difference between pressure inside the closed pore and surface pressure, thereby the porosity changes. [ABSTRACT FROM AUTHOR]

In order to study the performance and feasibility of magnesia‐alumina spinel (MgAl2O4) ceramics for thermal storage in solar thermal power generation, MgAl2O4 was prepared by theoretical composition using α‐Al2O3 as aluminium source, fused magnesia, magnesite, and light burned magnesia as different magnesium sources and kaolin as additive. The effects of magnesium source and the additive on sintering properties, thermal shock resistance and thermal properties of MgAl2O4 ceramics were researched. The results shown sample A1 (with fused magnesia) sintered at 1670°C possessed the optimum comprehensive properties, the bending strength increased by 7.71% after 30 thermal shock times (room temperature‐1000°C, air cooling), the specific heat capacity was 1.05 J/ (g·K). Therefore, the MgAl2O4 ceramics exhibited great potential in high‐temperature thermal storage material. [ABSTRACT FROM AUTHOR]

Zirconia-alumina composite ceramics are the preferred materials for high temperature and thermal shock applications because of their excellent mechanical properties. In this paper, La 2 O 3 doped zirconia-alumina composite ceramics were prepared by using fused zirconia corundum and ZrO 2 as starting materials. The effects of La 2 O 3 on the phase composition, microstructure and properties of the composite ceramics were investigated by XRD and SEM. The results show that La 2 O 3 can reduce the sintering temperature and improve the bending strength of the samples. The bending strength and fracture toughness of the composite ceramics with 1.5 wt% La 2 O 3 sintered at 1480 °C are 299.17 MPa and 5.61 MPa m1/2, respectively. The strength loss rate of the sample after 30 thermal shocks (room temperature ∼ 1000 °C) is 2.67%, SEM shows that the grain sizes of alumina and zirconia in the sintered sample were about 5 μm and 2 μm, respectively. After 30 thermal shocks, the phase composition and microstructure of the sample have no significant change, indicating good thermal shock resistance of the composite ceramics. The excellent thermal shock resistance ensures porous medium combustion materials has a long service life. [ABSTRACT FROM AUTHOR]

Selecting suitable ceramic powders for the preparation of UV‐curable ceramic suspensions, which are well suited for printing processes and production of high‐performance ceramic components, is a crucial factor in the practical industrial application of digital light processing (DLP) stereolithography. Therefore, this study aims to provide a comprehensive evaluation of alumina ceramic parts fabricated via DLP stereolithography using a variety of alumina powders with varying sizes and morphologies. Experiments were conducted to examine the rheological response, recoating performance, and curing behavior of UV‐curable alumina suspensions. Additionally, the thermal decomposition behavior of three‐dimensional (3D)‐printed green‐bodies, as well as the physical and mechanical properties of 3D‐printed sintered alumina components were thoroughly investigated. The best physical and mechanical performances were achieved by printing 55 vol% suspensions prepared using near‐spherical AA04 alumina powders (median diameter.4 μm). This study elucidates the effects of ceramic particle size and morphology on the entire technological process of DLP‐based ceramic stereolithography, thereby establishing the guidelines for the fabrication of high‐performance 3D‐printed ceramic objects in industrial and engineering production by selecting appropriate ceramic powders. [ABSTRACT FROM AUTHOR]

Solar absorption and thermal storage integrated ceramics (SATS ceramics) are new thermal storage materials that directly absorb sunlight, which improve the solar-to-thermal conversion efficiency. In this paper, SATS ceramics were developed by using calcium and iron-rich steel slag as the starting material. On the basis of composition characteristics of steel slag and performance requirements of SATS ceramics, the target phases of magnesioferrite spinel (MgFe 2 O 4) and monticellite (CaMgSiO 4) were designed and successfully synthesized in the SATS ceramics by the addition of magnesite and quartz. Phase composition, microstructure, physical properties, thermal shock resistance, solar absorptance and thermal storage performance were investigated. The results show that SATS ceramics with the addition of magnesite and quartz possess better properties than the ceramics prepared from 100 wt% steel slag. Particularly, the solar absorptance and thermal storage density of the SATS ceramics with the target phase of MgFe 2 O 4 are 84.7% and 1057.57 kJ kg−1 (25–800 °C), which increased by 3.04% and 21.87% compared to reference sample, respectively. In addition, it still presents higher strength of 64.83 MPa after 30 thermal shock cycles (25–800 °C) than the other samples, indicating good thermal shock resistance. Surprisingly, the utilization rate of steel slag reaches up to 97.89 wt%. This work not only develops a low-cost SATS ceramics, but also provides a new high-value utilization approach to steel slag. [ABSTRACT FROM AUTHOR]

Al 2 O 3 ceramics were prepared by introducing Fe 2 O 3 –TiO 2 -Sm 2 O 3 composite additive, in which the content and ratios of Fe 2 O 3 and TiO 2 remained constant, but Sm 2 O 3 was variable. The phase transformation, micromorphology, physical properties and thermal properties were investigated. The results showed that Fe 2 O 3 and TiO 2 made the grains high sintering activity through a solid solution mechanism, which promoted grain growth, but Sm 2 O 3 preferred to form SmFe 4 Al 8 O 19 at the grain boundaries, which slowed grain growth and refined the grains. With the increase in Sm 2 O 3 , the grain refinement of SmFe 4 Al 8 O 19 became outstanding, and the grain diameter gradually decreased, which is favorable for denser sintering. However, only a proper amount of Sm 2 O 3 in the Fe 2 O 3 –TiO 2 -Sm 2 O 3 composite additive resulted in better thermal shock resistance. The Al 2 O 3 ceramics with 9 wt% Fe 2 O 3 -1 wt% TiO 2 -5 wt% Sm 2 O 3 sintered at 1520 °C exhibited the optimum properties, yielding an increase in the bending strength by 6.60% after 30 thermal shocks, a thermal conductivity of 13.33–5.64 W/(m·K) (25–800 °C) and a specific heat capacity of 0.94–1.25 J/(g·K) (25–800 °C), all of which demonstrate the potential for thermal storage. [ABSTRACT FROM AUTHOR]

High-temperature thermal storage materials have received urgent attention for efficient thermal transfer in solar thermal power generation. Corundum ceramics doped with Fe 2 O 3 and TiO 2 were prepared via a pressureless sintering. A Fe 2 O 3 –TiO 2 system with different Fe 2 O 3 /TiO 2 ratios was applied to corundum ceramics. Phase composition, microstructural evolution, sintering properties, high temperature resistance and thermophysical properties were evaluated. The results indicated that Fe 2 O 3 and TiO 2 rendered the grains highly active and enhanced the bonding between grains due to existing stably in the lattice of corundum. In addition, decrease in the Fe 2 O 3 /TiO 2 ratio led to a new phase of FeAlTiO 5 , which refined the grains. These effects gave the samples good sintering properties and thermal shock resistance, but the thermal expansion coefficient mismatch between FeAlTiO 5 and corundum deteriorated the high-temperature (1300 °C) stability. Formula C1 (Fe 2 O 3 /TiO 2 ratio of 9:1) sintered at 1600 °C had the optimum comprehensive properties, possessing a bending strength loss rate of 1.54% after 30 cycles of thermal shock (1100 °C-room temperature, air cooling) and a constant strength retention rate of approximately 71.34% after 90 h high-temperature cycle. The corresponding thermal conductivity and specific heat capacity were 18.81 W/(m·K) and 1.02 J/(g·K) at 25 °C, which was suitable as a high-temperature thermal storage material. [ABSTRACT FROM AUTHOR]

Digital light processing (DLP)-based ceramic stereolithography has attracted significant attentions due to the high printing speed and high dimensional accuracy of DLP printers. However, undesired dropping of unfinished ceramic parts during printing, owing to inadequate adhesion between the first cured layer and the substrate of the building platform, still remains a challenge. In this study, the relationship between the adhesion properties of ultraviolet (UV)-curable alumina (α-Al 2 O 3) suspensions and the functionalities and structures of UV-curable acrylate monomers was investigated. With an increase in the proportions of monofunctional monomers, the adhesion abilities of UV-curable alumina suspensions enhanced because of reduced volume shrinkage, however, inferior curing performances were observed due to a decrease in the double bond densities. Furthermore, the large-volume branched chain structures in monofunctional monomers and ethyoxyl groups in polyfunctional monomers effectively decreased the volume contraction, improving the adhesion performances of UV-curable alumina suspensions and facilitating the conversion of double bonds to provide excellent curing properties, further guaranteeing strong adhesion of these suspensions to the substrate. [ABSTRACT FROM AUTHOR]

Corundum-based ceramics were prepared by two methods. The first used Fe 2 O 3 and TiO 2 as additives to react with α-Al 2 O 3. The second made full use of Al 2 O 3 , SiO 2 and TiO 2 in calcined bauxite, and Fe 2 O 3 was used as an additive. The SiO 2 -TiO 2 -Fe 2 O 3 system was designed to influence corundum. The effects of Fe 2 O 3 , TiO 2 and SiO 2 on physical properties, phase transformation, microstructure, thermophysical properties and thermal shock resistance were investigated. Results showed that Fe 2 O 3 and TiO 2 realized densification sintering through entering in the lattice of corundum, and the solubility of Fe 2 O 3 was higher than that of TiO 2. In addition, the excess TiO 2 tend to synthesize iron aluminum titanate in the grain boundaries, which could refine the grains and improve the mechanical properties. The SiO 2 -TiO 2 -Fe 2 O 3 system reduced significantly the sintering temperature, but the imperfect microstructure impaired the properties. Corundum-based ceramics prepared by Fe 2 O 3 , TiO 2 and α-Al 2 O 3 had the optimal properties. The thermal conductivity and thermal storage density were 14.81 W/(m·K) (25 °C), 837 kJ/kg (25–800 °C), respectively. No cracks were formed after 30 thermal shock cycles (1100 °C-room, air cooling), and the bending strength increased by 2.59%. This study supports the application of corundum-based ceramics as a promising thermal storage candidate. [ABSTRACT FROM AUTHOR]

Porous mullite ceramics with ultra-low shrinkage and high porosity were prepared by solid state reaction between MoO 3 and mullite precursor powders which were synthesized from tetraethylorthosilicate and aluminium nitrate nonahydrate via sol-gel methods. The synthetic process of mullite precursor powder and effects of MoO 3 amount on the phase composition, microstructure, physical properties such as firing shrinkage, open porosity, bending strength, water absorption and bulk density of porous mullite ceramics were investigated. The results indicated that the addition of MoO 3 not only lowered the mullite forming temperature from 985.4 to 853.3 °C, but also restrained densification behavior of samples due to the formation of mullite and Al 2 O 3 –MoO 3 solid solution, besides, MoO 3 also improves the formability, open porosity and bending strength of samples. The optimal amounts of MoO 3 is 8 wt%, and the resultant samples exhibit outstanding properties, including a low shrinkage rate of 1.86 ± 0.07%, an open porosity of 61.91 ± 0.16% and a bending strength of 9.35 ± 1.11 MPa. [ABSTRACT FROM AUTHOR]

The influence of binder content, firing temperature, SiC particle size, activated carbon content and activated carbon particle size on gas permeability parameters of porous SiC ceramics were investigated according to their pore structure performances and microstructure. The influencing degree of these preparing conditions on gas permeability parameters were also compared. The results showed that Darcian permeability parameter k 1 and non-Darcian permeability parameter k 2 increase with increasing of SiC particle size, activated carbon content and activated carbon particle size, but with decreasing of binder content and firing temperature. Binder content and activated carbon particle size have more significant effects on k 1 than other three preparing conditions which their influencing degree in descending order are activated carbon content, SiC particle size and firing temperature. The influencing degree of preparing conditions on k 2 and k 1 / k 2 are ambiguous, but it is clear that SiC particle size have largest influence on k 2 and k 1 / k 2. [ABSTRACT FROM AUTHOR]

In this paper, sialon/SiC composite ceramics were synthesized in situ from SiC, α-Si3N4, AlN, calcined bauxite, quartz, and Y2O3 via layered buried sintering at different temperatures (1540–1640 °C). The sialon/SiC composite ceramics designed in this study are expected to be used as thermal absorb materials in solar thermal power generation based on the good mechanical character and thermal shock resistance. The results showed that the β-sialon/SiC sample with 60 wt% silicon carbide sintered at 1600 °C exhibited the optimal performances with dense microstructure, high bending strength, and good thermal shock resistance. After 30 thermal shock cycles, the bending strength of β-sialon/SiC sample with 60 wt% silicon carbide was 66.68 MPa with a decrease of 4.79%. In thermal shock tests, SiC and Si3N4 in the sample were oxidized into amorphous SiO2, and small amount of sialon was decomposed into mullite, which resulted in good thermal shock resistance. It was believed that in situ sialon/SiC composite ceramics can be a promising candidate for solar absorber owing to good thermal shock resistance. [ABSTRACT FROM AUTHOR]

Coal series kaolin (CSK) is used as the raw material to prepare CSK cordierite electronic ceramics. Sintering process is analyzed by a heating microscope. The microstructure of green body, phase transformation, and microstructure evolution during sintering process is elucidated by scanning electron microscope (SEM) and X-ray diffraction (XRD). Comprehensive evaluations of our product are made for physical properties, electrical properties, and coefficient of thermal expansion (CTE), respectively. According to test results of the obtained CSK cordierite ceramic, the sintering temperature range is 1280~1420 °C, synthetic temperature is 1160~1280 °C, densification process is 1360~1420 °C, and large deformations of cordierite ceramic happen above 1420 °C. The optimum performance of the obtained CSK cordierite ceramics is summarized as follows: volume density is 1.81 g·cm3, apparent porosity is 28%, bending strength is 65 MPa, CTE is 1.41 × 10−6 °C−1 (600 °C), and dielectric constant is 4.6 (100 Hz). As a result, this cordierite electronic ceramics from CSK have great potential to do with applications in electric heater supports, such as electric stove, ceramic heater base, and electric heater cooling plate. [ABSTRACT FROM AUTHOR]

Andalusite composite ceramics used for solar heat transmission pipeline were fabricated via pressureless sintering from andalusite, PSZ, Suzhou kaolin and talc. The effects of dolomite and spodumene on densification, mechanical properties, phase transformation, microstructure and thermal shock resistance of the composite ceramics were investigated. Results demonstrated that dolomite and spodumene used as flux materials promoted densification greatly, and the lowest sintering temperature of the composite ceramics was decreased significantly by 90–150 °C, comparing with the previous works with the usage of potassium feldspar and albite as flux materials. Introducing an appropriate amount(7 wt%) of spodumene improved thermal shock resistance of the composite ceramics since no cracks formed after 30 thermal shock cycles (air cooling from 1100 °C to RT) with a bending strength increasing rate of 22.41%. XRD patterns indicated that the dominant phases of samples before and after 30 thermal shock cycles were consistently mullite, ZrSiO 4 and m-ZrO 2 , while the content of mullite increased after thermal shock, resulting in the enhancement of bending strength. It is believed that the andalusite composite ceramics can be a promising candidate material for heat transmission pipeline in the solar thermal power generation. [ABSTRACT FROM AUTHOR]

For lowering the sintering temperature of silicon carbide ceramics used for solar thermal energy storage technology, O'-Sialon and silicon nitride were employed as composite phases to construct Sialon-Si3N4-SiC composite ceramics. The composite ceramics were synthesized using SiC, Si3N4, quartz, and different alumina sources as starting materials with noncontact graphite-buried sintering method. Influences of alumina sources on the physical properties and thermal shock resistance of the composites were studied. The results revealed that the employment of O'-Sialon and silicon nitride could decrease the sintering temperature greatly to 1540°C. The optimum formula G2 prepared from mullite as alumina source achieved the best performances: 66.7 MPa of bending strength, 10.0 W/(m·K) of thermal conductivity. The composition parameter x = 0.4 of O'-Sialon decreased to 0.04 after 30 cycles thermal shock, and the bending strength increased with a rate of 11.0% due to the increase of O'-Sialon grain size, and the optimization of microstructure caused by the transformation of O'-Sialon grains and densification within the samples. The good thermal shock resistance makes the composites suitable for the use as thermal storage materials of concentrated solar power generation. [ABSTRACT FROM AUTHOR]

Si3 N4- Si C composite ceramics used for volumetric receivers were fabricated by pressureless sintering of micrometer Si C, Si3 N4, andalusite, and other minor additions powders. Mechanical, thermal expansion, thermal conductivity, and thermal shock resistance properties were tested at different sintering temperatures. The best sintering temperature of optimum formula A2 is 1360°C, and the bending strength reaches 79.60 Mpa. And moreover, its thermal expansion coefficient is 6.401 × 10−6/°C, thermal conductivity is 7.83 W/(m K), and no crack occurs even subjected to 30 cycles thermal shock with a bending strength increase rate of 4.72%. X-ray diffraction results show that the phase constituents of the sintered products mainly consist of Si C, Si3 N4, mullite, and quartz. Microstructure that is most appropriate and exhibits maximal thermal shock resistance was detected using SEM. The porosity of Si3 N4- Si C ceramic foam prepared from formula A2 is 95%, which provides a rapid and steady action for the receiver. The evaluation of the present foam shows that Si3 N4- Si C ceramic composite is a good candidate for volumetric receivers. [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]

Ho 2 O 3 was employed to improve the microstructural densification and performances of pressureless sintered corundum–mullite ceramic composites. This study investigated the influences of Ho 2 O 3 addition on the microstructure, physical properties and thermal shock resistances of the composites. The results indicated that sample AH5 (80 wt% Al 2 O 3 , 20 wt% coal series kaolin, and 5 wt% additional Ho 2 O 3), which was sintered at 1550 °C, showed the best comprehensive properties. In this Al 2 O 3 -rich and SiO 2 -poor system, a reaction between the Ho 2 O 3 and Al 2 O 3 –SiO 2 system produced an Ho 2 O 3 –Al 2 O 3 –SiO 2 liquid phase. This liquid phase increased the microstructural densification and resulted in a lower sintering temperature. The generation of mullite and holmium disilicate during thermal shocks improved the thermal shock resistance. The high bending strength and satisfactory thermal shock resistance of the as-prepared corundum–mullite ceramic composites showed their potential for use in heat transmission pipelines. [ABSTRACT FROM AUTHOR]

Gd 2 O 3 was added to increase the properties of corundum–mullite ceramic composites by enhancing the microstructural densification using coal-series kaolin and α-Al 2 O 3. The effect of Gd 2 O 3 addition on the microstructure and properties of ceramic composites was explored. The results showed that the formation of Gd 2 O 3 –Al 2 O 3 –SiO 2 liquid phase could improve the bending strength, hardness, and acid resistance, since such liquid phase promoted microstructural densification via a reaction between Gd 2 O 3 and Al 2 O 3 –SiO 2 binary system in this Al 2 O 3 -rich and SiO 2 -poor system. The precipitation of mullite and gadolinium disilicate during thermal shocks resulted in enhanced bending strength. In particular, sample AG5 (80 wt% Al 2 O 3 , 20 wt% coal-series kaolin, and 5 wt% additional Gd 2 O 3) sintered at 1550 °C was considered as candidate for heat transmission pipeline for the optimum comprehensive performance. [ABSTRACT FROM AUTHOR]

In order to obtain ceramic materials for high-temperature gas-solid separation, the cordierite-mullite-corundum porous ceramics were prepared by particle stacking and pore-forming agent method, with bauxite as aggregate and in-situ synthesized cordierite as binder. Designed four-factor four-level orthogonal experiments for the first time to improve the porosity of the samples. The phase composition and microstructure of the samples were studied by XRD, SEM and other testing methods. The results show that: X6 sample (firing temperature of 1340 °C, 50 wt% binder, aggregate coarse, medium and fine mass percentage 30:50:20, plus 20 wt% charcoal powder, 10 wt% graphite) has the best comprehensive performance, with porosity of 41.51 % and bending strength of 17.88 MPa. Pore size distribution range from 10 to 40 μm. Corundum and mullite, with excellent high-temperature properties formed by the aggregate, are tightly bonded together by cordierite, contributing to the strength of the porous ceramics. The addition of pore-forming agent improves the porosity and forms a stable and uniform pore structure in the porous ceramics. The high porosity and large connected pore size reduce the viscous resistance of the porous ceramics to the gas, improve the filtration performance of the material, and make it expected to be applied in the field of hot gas clean-up. [ABSTRACT FROM AUTHOR]

O'-Sialon/Si 3 N 4 composite ceramics for solar absorber were prepared in situ through pressureless sintering from Si 3 N 4 and low pure Al 2 O 3 with different rare-earth oxides (i.e., Yb 2 O 3 and Gd 2 O 3). This study investigates the effects of Yb 2 O 3 and Gd 2 O 3 on phase composition, microstructure, densification, oxidation resistance and solar absorptance. The results revealed that Yb 2 O 3 and Gd 2 O 3 , which were applied as flux materials, significantly reduced the sintering temperature and improved the densification, oxidation resistance of the composite ceramics. Moreover, the introduction of the two sintering aids promoted the formation of O'-Sialon through the liquid-phase sintering mechanism. The samples doped with Gd 2 O 3 exhibited more O'-Sialon content, lower porosity, and better oxidation resistance compared with those doped with Yb 2 O 3. Especially, sample A2 (6 wt% Gd 2 O 3 additional) sintered at 1600 °C exhibited the best comprehensive properties for 10.10% water absorption, 23.29% porosity, 105.57 MPa bending strength, 75.16% solar absorption. Dense oxide layers were generated on sample surfaces after oxidation at 1300 °C, which protected the ceramics samples from further oxidation. However, the two additives had characteristic reflection peaks in the ultraviolet–visible region (300–400 nm) and were also blamed for high reflectivity in the near–infrared region, which resulted in the decrease in absorption. [ABSTRACT FROM AUTHOR]

High-temperature stable thermal storage materials are urgently needed to meet the demand for solar thermal power generation. Herein, Cu–20Si alloy-corundum ceramic composite thermal storage materials are prepared. The thermal storage performance of the composite, and the erosion resistance of ceramic matrix to alloy are investigated during high-temperature (1000 °C) service for 1000 h. The results show that the latent heat of Cu–20Si alloy is increased by 130.76 % to 201.2 kJ/kg compared with the original. Meanwhile, the alloy forms a dense transition layer on the ceramic matrix surface by melting and spreading. Furthermore, the ceramic matrix shows superior erosion resistance to the alloy, owing to the dense structure of ceramic and no chemical reactions between the alloy and ceramic matrix. Finally, test results of long-time service confirm the stability of the composite, which can be used stably for high temperature thermal storage. [ABSTRACT FROM AUTHOR]

β-Sialon/Si 3 N 4 composites were fabricated via pressureless sintering method at 1580 °C using α-Si 3 N 4 , calcined bauxite, AlN as the main raw materials, Y 2 O 3 and La 2 O 3 as the sintering additives. Mechanical properties, phase composition, microstructure, thermal shock resistance, oxidation resistance, thermophysical properties and solar absorptance were investigated. The results show that the sample with 3 wt% Y 2 O 3 and 3 wt% La 2 O 3 as additives exhibits the best mechanical properties, which also has high thermal conductivity and solar absorptance: 7.96 W/(m K) and 91.10%, respectively. The sample has intact morphology after 30 thermal shock cycles (wind cooling from 1100 °C to 25 °C), and the bending strength remains as high as 138.36 MPa. Its weight gain rate after oxidation at 1100 °C for 100 h is just 0.9331 mg/cm 2 , which shows the excellent oxidation resistance. A dense oxide layer is found to be formed on the surface during the process which protects the sample from further oxidation. It is believed that this in-situ β-Sialon/Si 3 N 4 ceramic could be a promising candidate for solar heat absorbing material. [ABSTRACT FROM AUTHOR]

TiO 2 is employed to improve the performance of pressureless sintered MgAl 2 O 4 –Si 3 N 4 ceramics in this study, aiming to make the ceramics more suitable for solar thermal absorbing materials in concentrating solar power. Effects of TiO 2 content on the microstructure and properties of the composites were the focus, especially the thermal shock and oxidation resistance. The results show that composite with 2 wt% TiO 2 sintered at 1620 °C has the highest bending strength exceed 320 MPa, which contributes to resist the thermal stress. Instead of being damaged after 30 thermal shock cycles (ΔT ≈ 1100 °C), the bending strength of the sample increases 12.03%. The weight gain rate is only 0.8964 mg/cm2 when finishing the oxidized process at 1300 °C for 100 h, and the oxidation kinetic obeys the parabolic low. Solar absorptance and thermal conductivity of the composite reach 93.5% and 13.27 W/(m·K) respectively. MgAl 2 O 4 –Si 3 N 4 composite can be presureless sintered at lower temperature, and it has better high temperature stability than Si 3 N 4 and SiC ceramics prepared via the same procedure, which makes it an ideal choice for solar thermal absorbing material. [ABSTRACT FROM AUTHOR]