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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]

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]

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]

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]

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]

Solar thermal absorbing materials are the key components of concentrating solar power. In this study, Fe 2 O 3 and TiO 2 co-doped corundum ceramics were prepared by pressureless sintering. The effects of different Fe 2 O 3 /TiO 2 ratios on the phase composition, microstructure, thermal shock resistance and solar absorptance were investigated via XRD and EPMA testing. The results showed that, with the decrease of Fe 2 O 3 /TiO 2 ratio, the appropriate amount of FeAlTiO 5 would decompose into ferrite particles, which played a bridging role between the corundum grains making the samples have excellent thermal shock resistance. A6 (90% bauxite, 9.5% Fe 2 O 3 and 0.5% TiO 2) sintered at 1460 °C had the optimum comprehensive properties, with a bending strength of 154.80 MPa and an absorptance of 89.20% in the spectral range from 0.3 to 2.5 μm. After 30 thermal shock cycles (1000 °C–25 °C, air-cooled), the bending strength of A6 was 222.05 MPa, and the absorptance was 90.40%, which were 43.44% and 1.35% higher than those before thermal shock, respectively. Therefore, it was suitable as an excellent solar thermal absorbing materials. [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]

Summary: Compared with current research of simply improving the efficiency of thermal absorber or thermal storage, integrating two devices into one fundamentally avoids the heat transfer loss between the two devices. In‐situ self‐assembled SiCw(SiC whisker)/SiC composite ceramics for integrated thermal absorber and thermal storage were pressurelessly prepared from graded SiC, AlN, and Si powders by layered powder embedded sintering in a low temperature range from 1450°C to 1650°C. After sintered at 1550°C, sample A4 with 10.39 wt% Si not only exhibits optimal mechanical properties and excellent thermal shock resistance, but also has high thermal conductivity, thermal storage capacity, and solar absorptance as 6.74 W·(m K)−1, 984.75 kJ·kg−1, and 91.12%, respectively. Results indicate that the in‐situ self‐assembled SiC whiskers, formed by carburization reaction via VS mechanism in the stacking voids of SiC matrix, could greatly enhance the mechanical and thermal properties. We creatively proposed that the as‐prepared SiCw/SiC is promising to apply in integrated thermal absorber and storage system of solar thermal power generation. [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]

Al 2 O 3 –CaAl 12 O 19 composites are ideal high-temperature structural ceramics, however, their poor thermal shock resistance limits their application under thermal shock conditions. In this work, ferrotitanium slag was used as the main raw material for composites preparation. Enhanced thermal shock resistance were obtained by adding 12.5 wt.% unstabilized monoclinic zirconia. A systematic analysis of the phase compositions and microstructural evolution with particular attention to crack propagation was performed. The improvement in thermal shock resistance is attributed to the enhanced crack propagation resistance. Furthermore, the enhanced crack propagation resistance is caused by multiple mechanisms, including the t -ZrO 2 -related stress-induced t → m phase transformation mechanism and the m -ZrO 2 -related microcracking mechanism. Coarsened ZrO 2 particles doped with TiO 2 from the ferrotitanium slag are beneficial to the occurrences of stress-induced transformation and microcracking. [ABSTRACT FROM AUTHOR]

To obtain composite ceramics with excellent thermal shock resistance and satisfactory high−temperature service performance for solar thermal transmission pipelines, SiC additive was incorporated into Al 2 O 3 −mullite−ZrO 2 composite ceramics through a pressureless sintering process. The effect of the SiC additive on thermal shock resistance was studied. Also, the variations in the microstructure and physical properties during thermal cycles at 1300 °C were discussed. The results showed that both thermal shock resistance and thermal cycling performance could be improved by adding 20 wt% SiC. In particular, the sample with 50 wt% Al 2 O 3 , 35 wt% Coal Series Kaolin (CSK), 15 wt% partially yttria−stabilized zirconia (PSZ), and 20 wt% SiC additional (denoted as sample A2) exhibited the best overall performance after firing at 1600 °C. Furthermore, the bending strength of sample A2 increased to 124.58 MPa, with an increasing rate of 13.63% after 30 thermal shock cycles. The increase in thermal conductivity and the formation of mullite were the factors behind the enhancement of thermal shock resistance. During the thermal cycles, the oxidation of SiC particles was favorable as it increased the microstructure densification and also facilitated the generation of mullite, which endowed the composite ceramics with a self−reinforcing performance. [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]

For increasing working stability of cordierite-spodumene composite ceramics for solar heat transmission pipeline, andalusite was utilized as modified additive to improve mechanical strength and thermal shock resistance of the composite ceramics. The effects of andalusite on densification, mechanical strength, thermal stability, phase composition and microstructure were studied. The experiment results showed that andalusite significantly influenced bending strength and thermal shock resistance of the composite ceramics. Especially, specimen B1 with 5 wt% andalusite sintered at 1400 °C achieved the best performances. The linear shrinkage, water absorption, apparent porosity, bulk density and bending strength were 5.62%, 0.02%, 0.06%, 2.19 g cm −3 and 104.94 MPa, respectively. After 30 thermal shock cycles (wind cooling from 1100 °C to room temperature), the residual strength of the specimen increased to 110.65 MPa, accompanying with −5.44% strength loss rate. The XRD and SEM analysis illustrated that mullite grains with short rod-like shape could prevent crack growth of inter-granular fracture to enhance bending strength of the specimens. Furthermore, the generation of β-spodumene grains with low thermal expansion coefficient after thermal shock improved thermal shock resistance of the composite ceramics. It is considered that the cordierite-spodumene composite ceramics with high densification, good mechanical strength and excellent thermal stability can be a potential material for high temperature thermal transmission pipeline in solar thermal power generation. [ABSTRACT FROM AUTHOR]

To develop more reliable solar thermal absorbing materials, MgAl 2 O 4 -Si 3 N 4 ceramics were in-situ synthesized via pressureless sintering method. The effects of Sm 2 O 3 on the phase composition, microstructure, densification, thermal shock resistance, oxidation resistance and solar absorptance were investigated. Results show that Sm 2 O 3 cannot only facilitate the densification for the composites via liquid phase sintering mechanism but also improve all above properties. After sintered at 1620 °C, bending strength and solar absorptance of the composite with 1 wt% Sm 2 O 3 were 339.4 MPa and 92.0%. No damage was found after thermal shock, and the bending strength experienced an improvement of 2.6%, which could be attributed to the well-grown grains and formation of glass phase. A dense oxide layer was found on the surface after oxidation at 1300 °C, which protected the sample from being oxidized. The oxidation kinetics of the composites transformed from passivation into activation when the Sm 2 O 3 content exceeded 2 wt%. These MgAl 2 O 4 -Si 3 N 4 composites should be a promising candidate for solar thermal absorbing material. [ABSTRACT FROM AUTHOR]

Cordierite-spodumene composite ceramics used for solar heat transmission pipeline were prepared via pressureless sintering from kaolin, talc, γ-Al 2 O 3 and spodumene. Effects of andalusite and zircon on densification, mechanical properties, phase composition, microstructure and thermal shock resistance of the composite ceramics were investigated. The results showed that andalusite and zircon additives effectively affected mechanical strength and thermal stability of the composite ceramics. Expecially, sample B5 with 15 wt% zircon additive sintered at 1360 °C achieved the highest bending strength and thermal shock resistance. The bending strengths of the sample before and after 30 thermal shock cycles (wind cooling from 1100 °C to room temperature) were 100.17 MPa and 101.90 MPa, respectively. XRD analysis indicated that the main phases of the sample before 30 thermal shock cycles were α-cordierite, spinel, corundum, α-quartz and zirconium silicate, while β-spodumene grains generated after thermal shock. SEM micrographs illustrated that the existence of zirconium silicate and β-spodumene at the grain boundaries after 30 thermal shock cycles endowed the composite ceramics with a high residual strength. It is believed that the cordierite-spodumene composite ceramics can be a potential material to apply in the field of solar thermal transmission pipeline. [ABSTRACT FROM AUTHOR]

Cordierite-spodumene composite ceramics with 5, 10, 15 wt% spodumene used for solar heat transmission pipeline were in-situ prepared via pressureless sintering from kaolin, talc, γ-Al 2 O 3 and spodumene. Effects of spodumene on densification, mechanical properties, thermal shock resistance, phase composition and microstructure of the composite ceramics were investigated. The results showed that spodumene used as flux material decreased the sintering temperature greatly by 40–80 °C, and improved densification and mechanical properties of the composite ceramics. Especially, sample A3 with 10 wt% spodumene additive sintered at 1380 °C exhibited the best bending strength and thermal shock resistance. The bending strengths of A3 before and after 30 thermal shock cycles (wind cooling from 1100 °C to room temperature) were 102.88 MPa and 96.29 MPa, respectively. XRD analysis indicated that the main phases of the samples before 30 thermal shock cycles were α-cordierite, α-quartz and MgAl 2 O 4 , and plenty of β-spodumene appeared after thermal shock. SEM micrographs illustrated that the submicron β-spodumene grains generated at the grain boundaries after thermal shock improved the thermal shock resistance. It is believed that the cordierite-spodumene composite ceramics can be a promising candidate material for heat transmission pipeline in the solar thermal power generation. [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]

Abstract: An innovative thermal storage material, in-situ synthesised cordierite combined andalusite (Al2O3·SiO2), was prepared via semi-dry pressing followed by pressureless sintering. The samples were mainly composed of andalusite (the main raw material), with in-situ synthesised cordierite added to improve the thermal shock resistance. The results indicate that the formula L4 (70% andalusite, 13% talcum, 13% kaolin and 4% γ-Al2O3) sintered at 1400°C has the best thermal stock resistance, physical properties and chemical properties. The L4 sample can withstand 30 thermal shock test cycles without cracking (wind cooling from 1100°C to 25°C), and the bending strength after the thermal shock cycle test increased 26.20% rather than decreasing. Other properties are as follows: apparent porosity: 22.95%; water absorption: 10.71%; bulk density: 2.14g/cm3; bending strength: 92.74MPa; coefficient of thermal expansion: 4.11×10−6/°C; specific heat capacity: 0.95kJ·(kgK)−1; thermal conductivity coefficient: 0.58×10−2 cm2 s−1; and thermal conductivity: 1.17W·(mK)−1. The examination of the phase composition indicates that cordierite, mullite, sillimanite, cristobalite and α-quartz are the main phase elements. Analysis of the microstructure shows that the cordierite crystals were formed during the sintering process and were dispersed evenly in the mullite crystals, which gave the samples a favourable thermal shock resistance. It was concluded that the ceramic material, a combination of cordierite and andalusite, is an excellent candidate for solar thermal storage material due to its high thermal shock resistance, temperature resistance and strength. [Copyright &y& Elsevier]

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]

To guarantee the efficiency of solar thermal power generation, the solar thermal storage material is required to have excellent thermal shock resistance to withstand the process of long-term thermal cycles. In this study, solar thermal storage ceramics were prepared using high calcium and high iron steel slag as the main raw material, adding cordierite and using the pressureless sintering method. The effects of cordierite addition on the physical properties, phase composition, microstructure, thermal storage and thermal shock resistance of the samples were investigated by XRD, SEM and so on. The results show that the addition of cordierite promotes densification and improves thermal shock resistance. The optimal level of addition is 10 %. When the temperature is 1240 °C, the bulk density and bending strength of the B5 (10 wt% cordierite) are 3.03 g cm−3 and 92.52 MPa, respectively. The bending strength of B5 after 30 thermal shock cycles is 97.06 MPa, which is 4.91 % higher than that before 30 thermal shock cycles. The thermal storage density is 867.95 kJ kg−1. This work not only analyzes the feasibility of this material for high-temperature service but also provides a new way for high-value utilization of high calcium and high iron steel slag. [ABSTRACT FROM AUTHOR]

Corundum-mullite composite ceramics have high hardness, small plastic deformation and other excellent performances at high temperature. Corundum-mullite composite ceramics were fabricated from andalusite and α-Al 2 O 3 by in-situ synthesis technology. Effects of mullite/corundum ratio and sintering temperatures on the water absorption, apparent porosity, bulk density, bending strength, thermal shock resistance, phase composition and microstructure of the sample were investigated. Results indicated that the in-situ synthesized mullite from andalusite combined with corundum satisfactorily, which significantly improved the thermal shock resistance as no crack formed after 30 cycles of thermal shock (1100 °C-room temperature, air cooling). Formula A4 (andalusite: 37.31 wt %, α-Al 2 O 3 : 62.69 wt %, TiO 2 in addition: 1 wt %, mullite: corundum=6:4 in wt %) achieved the optimum properties when sintering at 1650 °C, which were listed as follows: water absorption of 0.15%, apparent porosity of 0.42%, and bulk density of 3.21 g⋅cm −3 , bending strength of 117.32 MPa. The phase composition of the sintered samples before and after thermal shock tests were mullite and corundum constantly. The fracture modes of the crystals were transgranular and intergranular fractures, which could endow the samples with high thermal shock resistance. [ABSTRACT FROM AUTHOR]

Cordierite-based glass–ceramic adhesives for bonding solar heat transmission ceramic pipelines were fabricated successfully using Suzhou kaolin, talc and commercial alumina as the main raw materials, TiO 2 as nucleation agent, waste glass powder and frit 242 as high-temperature fluxes. Bonding behavior, phase transformation, microstructure, thermal shock resistance and thermal cycling properties of the adhesives were investigated, and bonding mechanism was studied. The results indicated that adhesives B4 (composed of 60 wt% cordierite glass–ceramic and 40 wt% frit 242) after heat treatment (nucleated at 800 °C for 2 h and then crystallized at 950 °C for 2 h) exhibited the optimal performances with a shear strength of 10.26 MPa, which exceeded the industrial standard (JC/T 547-2005) of 1 MPa. The analysis of bonding mechanism showed that the glass of adhesive that filled up the pores in matrix surface and penetrated inside contributed to the high shear strength. Adhesives B4 had good thermal shock resistance and thermal cycling properties, as the shear strength of samples after 30 thermal shock cycles (1100 °C-room temperature, air cooling) was 8.51 MPa, which increased to 26.93 MPa with an increase rate of 162.48% after 100 thermal cycles (200–1100 °C). During thermal shocks or thermal cycles, cordierite particles crystallized at the interfaces to form a pinning-in effect, contributing to a higher shear strength. [ABSTRACT FROM AUTHOR]

Cordierite-mullite-corundum composite ceramics for solar heat transmission pipeline were fabricated via pressureless sintering at a low sintering temperature with added Sm 2 O 3 . The effects of Sm 2 O 3 on sintering behaviors, mechanical property, phase transformation, microstructure, thermal shock resistance and thermal conductivity of the composite ceramics were investigated. TEM analysis results demonstrated that Sm 3+ located in glass and grain boundaries to facilitate the densification via the liquid-phase sintering mechanism and improve bending strength by grain refinement, respectively. Proper addition (3 wt%) of Sm 2 O 3 could promote the crystallization of cordierite, and improve thermal shock resistance of the composite ceramics with an increasing rate of 16.70% for bending strength after 30 thermal shock cycles (air cooling from 1100 °C to RT). The composite ceramics possessed a superior thermal shock resistance, where a large amount of particles were formed to suppress crack initiation and propagation during thermal shock. Cordierite-mullite-corundum composite ceramics with proper Sm 2 O 3 addition (3 wt%) had a lower thermal conductivity than that of composite ceramics without Sm 2 O 3 addition by strengthening the scattering of phonon, which could reduce the heat loss during solar heat transmission process. [ABSTRACT FROM AUTHOR]

Cordierite/silicon carbide (SiC) composite ceramics with 10, 20 and 30 wt% cordierite were in-situ prepared via pressureless firing technique using silicon carbide, alumina, Kaolin and talc as starting materials. The results show that the synthesized composites all exhibited the good physical and mechanical properties. Among those, A2 composite with 20 wt% in-situ cordierite fired at 1280 °C exhibited the better bending strength and thermal shock resistance. The improvement of thermal shock resistance could be attributed to the proper cordierite wrapped around SiC, the homogeneous distribution of pores, the well-grown grains, as well as the formation of some glass phase. During the thermal shock test, a small amount of glass phases generated from the oxidation of SiC could react with Al 2 O 3 and MgO, and then more cordierite was formed due to the incorporation of nucleating agent TiO 2 . With in-situ cordierite content rising, both absorptance and emittance of composite reduced, but A2 composite had the better absorbing ability for the solar energy. It is believed that these in-situ cordierite/SiC composites should be a promising candidate to apply in the field of solar absorber coating owing to the better thermal shock resistance and absorptance of solar energy. [ABSTRACT FROM AUTHOR]