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Calcium carbonate (CaCO 3) is an innovative pore-former for fabricating the Yttria-Stabilized Zirconia (YSZ) abradable sealing coatings (ASCs). Both conventional YSZ + PHB and YSZ + CaCO 3 ASCs were fabricated by the atmospheric plasma spraying (APS). The spindle shaped CaCO 3 in granulated particles and XPS results of ASCs jointly confirm that CaCO 3 undergoes decomposition. Zr atoms in ZrO₂ have the potential to be substituted by Ca atoms, thereby giving rise to the formation of a YSZ@Ca solid solution. Density Functional Theory (DFT) and first principles molecular dynamics (AIMD) simulations have demonstrated that YSZ@Ca has a relatively high phase transition temperature and can exist stably. Compared with the conventional YSZ + PHB coating, due to the addition of Ca2⁺ which increases the phase transition temperature of YSZ, the residual stress of the YSZ + CaCO₃ coating has been significantly reduced, and thus the ASCs shows more excellent performance in the thermal shock resistance. This study not only deepens the understanding of the behavior of CaCO 3 during flame spraying, but also opens up a new path for the development of high-performance ASCs that can withstand extreme thermal cycles. [ABSTRACT FROM AUTHOR]

YSZ-Y 2 O 3 and YSZ-Y 2 Zr 2 O 7 double ceramic layered coatings were fabricated atmospheric plasma spraying on superalloy substrate with NiCrAlY as the bond coat. The thermal shock behavior and CMAS corrosion resistances of the two coatings were investigated at 1100 °C and 1250 °C, respectively. The results indicated that the thermal shock resistance of YSZ-Y 2 Zr 2 O 7 TBCs was better than that of YSZ-Y 2 O 3 TBCs. However, the YSZ-Y 2 O 3 coating had a longer spallation lifetime than YSZ-Y 2 Zr 2 O 7 coating under the CMAS corrosion conditions. The YSZ-Y 2 O 3 coating failed due to corrosion within its ceramic layer, while the YSZ-Y 2 Zr 2 O 7 coating failed at the interface between the ceramic layer and the TGO/bonding layer. The failure mechanisms of both YSZ-Y 2 O 3 and YSZ-Y 2 Zr 2 O 7 coatings were compared and investigated systematically. [ABSTRACT FROM AUTHOR]

Modified magnesia aggregates coated with Si powder were prepared and their effects on the phase composition, microstructure and thermal shock resistance of the MgO-C refractories were investigated. The Si powder coating can bond tightly with the prepared modified magnesia aggregates, fulfilling the requirements for mixing and molding of the MgO-C refractories. At high temperatures, the Si powder coating around the magnesia aggregates transformed into Mg 2 SiO 4 -SiC ceramic coating layer, causing microcracks formation between the ceramic coating and aggregates due to their thermal mismatch. Within the microcracks, SiC and Mg 2 SiO 4 whiskers were generated by chemical vapor deposition and vapor-liquid-solid mechanism, respectively. The Mg 2 SiO 4 -SiC ceramic coating and microcracks could accommodate thermal expansion and relieve the thermal stress on the aggregates, and the Mg 2 SiO 4 and SiC whiskers within microcracks can create a toughening effect, effectively improving the thermal shock resistance of MgO-C refractories. [ABSTRACT FROM AUTHOR]

In order to overcome the inherent brittleness of ZrB 2 -based ceramics, ZrB 2 -SiC composites toughened by BN fiber and C fiber were prepared by hot pressing. The mechanical properties, residual strength after oxidation and ablation performance of BN f /ZrB 2 -SiC (ZSB) and C f /ZrB 2 -SiC (ZSC) ceramics were investigated. The flexural strength and fracture toughness of ZSB at room temperature were 610 ± 21 MPa and 5.5 ± 0.3 MPa m1/2, respectively. After plasma flame ablation for 60 s, the mass and linear ablation rates of ZSB were −0.14 mg/s and −0.33 μm/s, respectively. ZSB ceramics exhibited non-ablative characteristics. And the sample remained intact after ablation, while ZSC was catastrophically destroyed. The superior ablation resistance of ZSB was attributed to the introduction of BN f , which gave ZSB higher toughness, lower thermal expansion coefficient and modulus. The thermal shock resistance of ZSB was improved. In addition, the oxidation of BN f was slowed down by the formation of liquid phase. C f directly generated gas. Gas volatilization provided a preferential path for oxidation to accelerate oxidation. [ABSTRACT FROM AUTHOR]

In order to investigate the effects of in-situ spinel on the mechanical properties and corrosion behaviors of corundum-spinel castables, tabular corundum, magnesia fine powders and pre-synthesized spinel fine powders were used as raw materials to prepare corundum-spinel castables. The results showed that corundum-spinel castables with 3 wt% of magnesia fine powders and pre-synthesized spinel exhibited the best physical properties, thermal shock stability and corrosion resistance. The cold modulus of rupture was 28.6 MPa and cold compressive strength was 141.7 MPa. The residual strength ratio after thermal shock was 55.87 %. For the corrosion behaviors, the corrosion index and penetration index were 8 % and 11.86 %, respectively. Due to the better ceramic bonding interface by the in-situ spinel and the weaker volume expansion effect by the pre-synthesized spinel, densification of the samples could be significantly improved, which could enhance the properties of the samples. Besides, according to the thermodynamic calculation, spinel and corundum underwent obvious phase transition during the corrosion process. The ability of the samples with 3 wt% magnesia fine powders and pre-synthesized spinel to maintain the primary crystalline phases was relatively stable when reacting with slag, which made the castables show preferable slag penetration resistance. [ABSTRACT FROM AUTHOR]

The high thermal expansion coefficient exhibited by magnesia particles typically results in significant volume changes under extreme cooling and heating conditions, thereby exacerbating thermal stress and accelerating the damage to MgO-C refractories. To mitigate the thermal stress in the vicinity of magnesia particles, flake graphite coated magnesia (MgO@FG) particles with a core shell structure were prepared. Subsequently, the MgO and MgO@FG particles were utilized as aggregates for preparing MgO-C refractories. The thermal shock resistances of these materials were compared using the oil quenching method, and their fracture behaviours before and after the thermal shock test were investigated using the Brazilian splitting test combined with the digital image correlation method and acoustic emission technique. The results indicated that the addition of MgO@FG particles reduced the thermal expansion coefficient of the MgO-C refractories and mitigated their microstructural deterioration during the thermal shock test. Furthermore, the crack branching or deflection induced by the reduced interfacial bonding properties between MgO@FG particles and matrix; the relatively decreased graphite content within the matrix; and more ceramic phases generation (MgAl 2 O 4 , AlN), collectively contributed to the strengthening and toughening of MgO-C refractories. Moreover, the addition of the MgO@FG particles resulted in an increase in the fractal dimension of the fracture surface and enhanced the resistance to deformation failure of the MgO-C refractories, thereby improving their energy dissipating capability. [ABSTRACT FROM AUTHOR]

Based on the requirements for solar thermal storage materials, thermal storage ceramics must possess not only excellent thermal storage and thermal conductivity but also high strength and thermal shock resistance. This study investigates the effects of zirconia-molybdenum oxide composite additives on the properties of corundum-mullite composite ceramics. It has been shown that at high temperatures, the solid solution formed by the reaction between MoO 3 and Al 2 O 3 decomposes to generate highly reactive nano-sized alumina grains, which not only promote the densification process of the matrix but also act as a second phase to form an "intragranular" structure within the corundum grains. The "intragranular" structure, along with the presence of added zirconia, significantly enhances the mechanical and thermal shock resistance of the samples. After sintering at 1650 °C, the water absorption, porosity, bulk density, bending strength, thermal conductivity, and thermal storage density of the C3 sample containing 4 wt% ZrO 2 and 3 wt% MoO 3 were measured as 0.26 %, 0.93 %, 3.55 g/cm³, 245.06 MPa, 10.13 W (m K)⁻1 (25 °C), and 1363.54 kJ kg⁻1 (1000 °C). After undergoing 30 thermal shocks, the bending strength of the C3 sample increased by 9.13 %, reaching 267.44 MPa. [ABSTRACT FROM AUTHOR]

An alumina-fiber-reinforced alumina ceramic matrix (Al 2 O 3 /Al 2 O 3) composite is fabricated by a slurry infiltration process in this study. The slurry contains Al 2 O 3 powders with broad particle size distribution (d 10 = 0.35 μm, d 50 = 0.57 μm, d 90 = 1.90 μm). The resultant Al 2 O 3 /Al 2 O 3 composite exhibits a density of 2.95 ± 0.02 g/cm3 and porosity of 25 ± 1 %. Mechanical properties are assessed via three-point flexural tests, revealing a high flexural strength of 400 ± 8 MPa at room temperature. The high-temperature mechanical properties and thermal shock resistance are further examined. The flexural strength remains stable from room temperature to 1100 °C, while temperatures up to 1200 °C induces superplastic behavior. After thermal shock tests (5, 10 and 20 cycles at 1100 °C), the composite maintains a stable microstructure and flexural strength. The Al 2 O 3 powders with broad particle size distribution are beneficial to the high-temperature mechanical properties and thermal shock resistance of the Al 2 O 3 /Al 2 O 3 composite. [ABSTRACT FROM AUTHOR]

In this work, Dy 2 O 3 -Al 2 O 3 -SiO 2 glass was used to infiltrate dense alumina ceramics for fabricating alumina/glass composites. At the infiltration temperature of 1450–1500 °C, the infiltration only occurred along the three or multi-grain junctions. When the infiltration temperature reached 1550 °C, the glass was uniformly distributed at the grain boundaries of alumina ceramics. The obtained composites exhibited an optimal flexural strength of 525±25 MPa and a fracture toughness of 5.87 MPa·m1/2. Moreover, the composites demonstrated excellent thermal shock resistance and self-healing characteristics. After undergoing two cycles of thermal shock treatment from 4 °C to 800 °C, the composites still maintained a flexural strength of 118±15 MPa. Heat treatment of the composites with cracks at 1450 °C for 2 h could restore their mechanical properties to levels comparable to those before thermal shock. Meanwhile, this method can also be applied to repair cracked alumina ceramics. The flexural strength of the repaired alumina ceramics was up to 623±30 MPa. [ABSTRACT FROM AUTHOR]

Thermal management of proton exchange membrane water electrolysis (PEMWE) stacks under renewable energy fluctuations remains a challenge for large-scale hydrogen production. This study investigated dynamical thermal behavior of membrane electrode assembly (MEA) and developed targeted control strategies for different renewable energy scenarios. Through in-situ temperature measurements with 0.05 mm thermocouples, we observed and quantified significant thermal shock phenomena, defined as rapid and substantial temperature variation of MEA during current step changes. The MEA temperature exhibited rise rates up to 69.6 °C min−1 under these conditions, due to the mismatch between rapid electrochemical reactions and slower heat transfer. Our investigation of mitigation strategies revealed that elevated inlet temperature effectively reduced thermal shock but led to high equilibrium temperatures, while enhanced flow rates provided better final temperatures control but showed limited effectiveness in thermal shock reduction. These findings led to scenario-specific management strategies: wind power integration benefits from combining moderate inlet temperature elevation with flow rate control, while solar photovoltaic applications rely on flow rate adjustment. This study provides fundamental insights and practical guidelines for thermal management in renewable energy-powered PEMWE stacks. • The dynamic thermal behavior of MEA was tested using an in-situ method. • The transient thermal shock on MEA could peak at 69.6 °C min-1. • Significant mismatch between electrochemical reactions and heat transfer was observed. • Photovoltaic scenario prefers flow rate control to relieve thermal shock. • Wind power scenario prefers flow rate control with elevating temperature. [ABSTRACT FROM AUTHOR]

MgAl 2 O 4 coated corundum aggregates were prepared by impregnating tabular corundum aggregates with sizes of 1–6 mm in magnesium citrate solution followed by heat-treatment at 1500 °C, which were further used in Al 2 O 3 -MgO castables. The effects of the Mg2+ concentration in the solution on the characteristics of the MgAl 2 O 4 coated corundum aggregates as well as the effects of the MgAl 2 O 4 coating on the properties and microstructure of the castables were investigated. It is found that the MgAl 2 O 4 coating exhibits optimal continuity and uniformity with a thickness of about 20 μm adjusting the mole concentration of 1.0 mol/L. The Al 2 O 3 -MgO castables exhibit the best thermal shock resistance at this concentration, where the residual strength value of 6.5 MPa and the residual strength ratio of 19.4 %. Furthermore, specific energy at micro scales of the aggregate/matrix interface was measured by nanoindentation method. The specific fracture energy of the aggregate/matrix interface region in S10 is 135.0 J m−2, which is 80 % higher than S0 (243.5 J m−2). The improvement in thermal shock resistance is mainly attributed to the MgAl 2 O 4 interface layer causing multiple deviations in the crack path, reducing the occurrence of cracks across the aggregate. [ABSTRACT FROM AUTHOR]

An ASSC-type cast-type blast furnace with a vertical stage of about 2500 m3 was dissected in present study. There is an iron penetration erosion area with a thickness of about 170 mm in the hot side castable on the hearth sidewall. Iron penetration erosion is concentrated on the hottest surface of the castable. Along the radial direction, from the hot to cold surface, the erosion is different, divided into a metamorphic layer, an erosion layer, and a transition layer. The phase composition and microstructure of the hot surface of the castable after service were studied by chemical analysis and SEM-EDS. The penetration model was applied to calculate the critical pore size of molten iron penetrating the castable, and the universality of molten iron penetrating the castable was proved. Combined with the thermodynamic calculation results, it is shown that in the hearth environment, the molten iron penetrating the castable will react with SiO 2 and C to form ferrosilicon and CO gas. CO reacts with SiC and Al 2 O 3 in the castable, and the products are mullite phase and C phase. The two reactions occur at the same time, resulting in the continuous erosion of the aggregate silicon-containing phase of the castable. The Al 2 O 3 in the castable will gradually disintegrate under the erosion of high-temperature molten iron and periodic thermal shock and finally form the erosion phenomenon in the hot surface area of the castable. [ABSTRACT FROM AUTHOR]

High-flux molten iron and intermittent circulation accelerated the damage process of Al 2 O 3 -SiC-C castables under alternating thermal stress. A continuous TiC coated graphite was prepared using sol-gel combined with carbothermal reduction to investigate its influence on the flow properties, microstructure, mechanical properties and thermal shock resistance of Al 2 O 3 -SiC-C castables. The results show that a lower Ti/C molar ratio and higher heat treatment temperature are more favorable for the synthesis of TiC and the formation of a continuous and complete TiC coated graphite layer on the graphite surface. The introduction of TiC coated graphite significantly enhance the mechanical properties and thermal shock stability of Al 2 O 3 -SiC-C castables, with a remarkable 227 % increase in residual strength after thermal shock. In addition, during the oxidation process of the samples with TiC coated graphite, TiO 2 generated from the oxidation of TiC fills the pores and facilitates the growth of Al 6 Si 2 O 13 , which enhances the tightness of the bonding of the castable matrix, thus contributing to the improvement of the overall performance. [ABSTRACT FROM AUTHOR]

To solve the serious environmental pollution of low-grade magnesite tailings, MgO-Mg 2 SiO 4 refractories were prepared by low-grade magnesite tailings, materials and silica fume and quicklime as raw materials. The effects of calcium-silicate ratio (mol ratio) on the phase composition, microstructure, sintering behavior and thermal shock resistance of MgO-Mg 2 SiO 4 refractories were investigated. When calcium-silicate ratio was 5/5, the samples showed the optimum bulk density and apparent porosity of 2.81 g/cm3 and 16.37 %, respectively. Controlled the calcium-silicate ratio of samples to 5/5 significantly improved the thermal shock resistance of samples, the residual compressive strength rate of 69.78 % and the residual flexural strength rate of 19.86 %, while the thermal parameter R was 34.45. The improvement in the thermal shock resistance can be attributed to the bonding phase transformation from monticellite phase to forsterite phase, thereby enhancing the bond strength between aggregate and matrix. [ABSTRACT FROM AUTHOR]

The thermal shock behaviors of the multiple crack system based on aluminum titanate (Al 2 TiO 5 , AT) flexible ceramics are investigated. Two (fine/coarse-grained) systems are employed in this study to observe the influence of the grain size and microcrack size on the thermal shock behaviors of AT flexible ceramics. The findings reveal that these two systems exhibit markedly different adversarial strategies against high-temperature thermal shock. The coarse-grained system disperses the thermal stress by introducing new cracks and making stress evenly dispersed, while the fine-grained one can only concentrate thermal stress on limited microcracks. This is because almost all the grain boundaries in the coarse-grained system could serve as crack source sites, while that was only approximately 1/3 in the fine-grained one. Consequently, as the thermal shock temperature increases, the strain of the coarse-grained system first increases and then decreases, while its strength shows double peaks and double valleys. As for the fine-grained one, the strain decreases with the temperature increase, while its strength first increases and then decreases. Therefore, it can be concluded that the mechanical properties of AT flexible ceramics are closely related to microcracks' size and stress state. And, the conclusion that there exists a favorable state of internal stress and a favorable influence of microcracks that is beneficial to the mechanical performance of AT flexible ceramics could be drawn. [ABSTRACT FROM AUTHOR]

This paper presents the results of the adhesion resistance before and after cyclic thermal treatments in NiCoCrAlY bond-coat (BC) coatings reinforced with dispersed SiC-ZrB 2 particles and conventional NiCoCrAlY. The ASTM-C-633 standard test method for the adhesion or cohesion strength of thermal spray coatings was used. The microstructure and morphology of the coatings were characterized using X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques. Microhardness and coefficient of thermal expansion were also measured. The addition of SiC-ZrB 2 particles improved the long-term adhesion resistance by 1825 % compared to the system without reinforcement after 275 cycles. This improvement is attributed firstly to a self-healing mechanism and secondly to the lower thermal expansion coefficient (32.60 % lower) of the BC layer reinforced with SiC-ZrB 2 , which delayed the formation of cracks at earlier stages associated with CTE mismatch. [ABSTRACT FROM AUTHOR]

Cr 3 C 2 /WC-based cermet coating is widely used on the surface of mechanical equipment to strengthen its wear and corrosion resistance. Improving the high-temperature performance of cermet coating is the key to its industrial application. In this study, a novel type of bimodal microstructure cermet coating with the design of functional sites was fabricated via high-velocity air fuel (HVAF) spray technology. The toughness NiCrAlY superalloy particles are introduced into the traditional Cr 3 C 2 /WC-NiCr cermet structure to construct the thermal stress release site, which significantly improved the thermal shock resistance and thermal oxidation properties of the coating. The addition of NiCrAlY superalloy particle reduces the porosity of Cr 3 C 2 /WC-NiCr coating to 0.29 % and creates high-quality interface bonding and surface passivation layer. The newly structured cermet coating exhibits outstanding high-temperature performance. In a 1000 °C oxidation environment, the new coating remained intact after 120 h of exposure, while the traditional Cr 3 C 2 /WC-NiCr cermet coating exfoliated completely after 48 h of exposure. Further, in the thermal shock condition at 1000 °C, the lifetime of the new coating is 50 times greater than that of the traditional cermet coating, displaying excellent ability to relieve thermal stress. Additionally, the new coating shows good wear resistance and stability during high-temperature thermal exposure. After thermal exposure for 24 h and 72 h, the wear rates of the coating are 5.28 and 5.83 × 10−5 mm3 N−1 m−1, respectively, which is slightly lower than that of the as-sprayed coating. This study provides guidance for the improvement of high temperature resistance of thermally sprayed Cr 3 C 2 /WC-based cermet coatings. [ABSTRACT FROM AUTHOR]

The high-entropy ceramic (HEC) (La 0.35 Gd 0.35 Y 0.35 Sm 0.35 Yb 0.6)Zr 2 O 7 has emerged as a strong candidate for thermal barrier coatings (TBCs) due to its exceptional thermal properties. We investigated the thermal shock resistance of HEC–lanthanum zirconate (LZ)/yttria partially stabilized zirconia (YSZ) (i.e., the HEC coating) and LZ/YSZ (i.e., the LZ coating) double-ceramic-layer TBCs fabricated via plasma spraying. During thermal shock testing at 1100 °C, the LZ coating failed after 60 ± 3 cycles, while the HEC coating had a considerably longer thermal cycling lifetime of 135 ± 5 cycles. The HEC coating's superior performance is attributable to its enhanced oxygen barrier properties and inherent lattice disorder; the former reduced the growth rate of the thermally grown oxide, and the latter increased lattice defects and distortion. These factors helped improve the thermal expansion coefficient and reduced interlayer thermal stress accumulation. Furthermore, the higher fracture toughness of the HEC layer impeded crack propagation, collectively enhancing the TBCs' thermomechanical shock resistance. These findings underscore the potential of (La 0.35 Gd 0.35 Y 0.35 Sm 0.35 Yb 0.6)Zr 2 O 7 as a robust material for extending the service life of TBCs in high-temperature environments. [ABSTRACT FROM AUTHOR]

The slag corrosion resistance and thermal shock and of MgO-C refractories are crucial in the steelmaking industry. The current study presents a novel approach to enhance these properties by incorporating reinforcing particles such as zircon and silicon carbide. MgO-C refractories containing various amounts of ZrSiO 4 and SiC were prepared and subjected to slag corrosion and thermal shock tests. X-ray diffraction analysis (XRD), scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDS) were used to characterize the microstructure and chemical composition of the samples. The findings demonstrated significant improvements in the overall performance of the refractories with the addition of zircon and silicon carbide. Thermal shock resistance increased from 11 cycles for MgO to 18 and 15 cycles due to the increased fracture toughness and altering crack propagation paths with the addition of ZrSiO 4 and SiC particles. The formation of a CaZrO 3 phase within pores significantly improved slag corrosion resistance. This led to a reduced slag penetration depth and a thinner decarburized layer compared to the unreinforced MgO-C refractory. SiC decomposition formed a protective silica layer, while zircon particles locked MgO grain boundaries, further enhancing corrosion resistance. The study proposes a corrosion mechanism based on the formation of microstructure containing dense and decarburized layers. These findings highlight the potential of reinforcing particles to improve the performance of MgO-C refractories in steelmaking applications. [ABSTRACT FROM AUTHOR]

In this work, the microporous MgO-MgAl 2 O 4 refractory aggregates were prepared by in-situ decomposition synthesis method. The effect of Al 2 O 3 nano/micro powder ratio on the microstructures and properties was studied under the premise that the fixed total content of Al 2 O 3 was 15 wt%. The results demonstrated that the aggregates were composed of microporous MgO microparticles with nano pores as well as MgAl 2 O 4 grains located among them. The ratio not only influenced the volume expansion through changing the lattice constant of in-situ MgAl 2 O 4 , but also affected the formation of two different positions of MgAl 2 O 4 bonds, thereby influencing the microstructures and properties. When the ratio was 4:6, the combined effect of the shrinkage of MgO microparticles and the expansion of in-situ MgAl 2 O 4 grains promoted the formation of the bonds between MgAl 2 O 4 grains and MgO microparticles, as well as among the MgAl 2 O 4 grains, which resulted in the best comprehensive properties of the microporous MgO-MgAl 2 O 4 refractory aggregates, characterized by micro-nano pores, an apparent porosity of 26 %, a flexural strength of 23.2 MPa, a flexure strength after thermal shock of 20.4 MPa and a low thermal conductivity of 2.99 W/(m·K) at 800 °C. [ABSTRACT FROM AUTHOR]

A bone china grouting slurry was prepared using two different milling methods: low-energy ball milling (Named LBC) for 24 h and high-energy ball milling (Named HBC) for 1 h. Bone china green bodies were formed by grouting, and the dried green bodies were calcined at different temperatures points in the temperature range from 1235 °C to 1255 °C. The slurry characteristics, as well as the structure and properties of the calcined samples, were analyzed and evaluated. The particle sizes of LBC and HBC slurry D50 are 5.819 μm and 3.571 μm, respectively, accounting for 80.4 % and 98.7 % of their respective proportions. The particle size distribution range of HBC samples was relatively concentrated, and the viscosity of the two slurries was 1040 mPa s and 2800 mPa s, respectively. The ball milling method significantly influenced the formation of product phases. The content of calcium feldspar and β-TCP phases in HBC samples calcined at 1245 °C was higher than that in their LBC counterparts, while the quartz content in LBC was higher than that in HBC samples. The water absorption and porosity of the HBC samples were lower than those of the LBC samples, with a flexural strength of 205 MPa, heat shock temperature difference of 190 °C, and light transmittance of 5.18 %/3.73 mm, which were 22.4 %, 26.7 %, and 4.2 % higher than those of the LBC samples, respectively. These results indicate that bone china prepared using the high-energy ball milling method exhibits excellent performance. [Display omitted] [ABSTRACT FROM AUTHOR]

This study investigates the effect of pre-dehydrated magnesium-silicate-hydrate (PMSH) on the properties of HMC-bonded castables (HMCC), aiming to enhance the medium-temperature mechanical performance of HMCC through the structural memory characteristics of PMSH. The results indicate that adding M-S-H-300 (PMSH treated at 300 °C) improves the mid-temperature mechanical properties of HMCC. Specifically, the cold modulus of rupture (CMOR) for the samples 300MSH increases by 605.9 % at 500 °C and 582.6 % at 800 °C compared to control samples due to the excellent thermal stability of M-S-H-300 and a 38.3 % improvement in castable sintering performance. Additionally, M-S-H-300 improves the thermal shock resistance and setting properties of HMCC, extending the castable's setting time by 19 %. The conductivity test results indicate that the addition of M-S-H-300 inhibits the ionization of HMC, thereby delaying its hydration process. Castables with M-S-H-300 demonstrate higher CMOR and residual strength ratio before and after thermal shock. Further testing reveals that adding M-S-H-300 increased the castable's elastic modulus by 482.6 % and fracture toughness by 35.6 % after sintering at 1500 °C, enhancing resistance to microcrack propagation during thermal shock. Furthermore, adding M-S-H-300 reduces the aspect ratio of HMC hydration products, optimizing microstructure and reducing porosity. However, this modification slightly decreases the mechanical properties of the green body. [ABSTRACT FROM AUTHOR]

The current study aimed at the preparation of high strength magnesia porcelain. In this study, a coating basic formula of natural ceramic materials of Longyan kaolin (41.94 wt%), burnt talc (52.68 wt%) and Al 2 O 3 (5.38 wt%) were used. In addition, right amount of potassium feldspar and ZnO were added to adjust the coating properties. High strength magnesia porcelain was obtained by the difference of thermal expansion coefficient between coating and substrate. The study focused on the changes in the cross-sectional area ratio and thermal expansion coefficient between the coating and matrix, as well as the effect of adding potassium feldspar and ZnO on the flexural strength of ceramics. Following the addition of 4 wt% ZnO and 13 wt% potassium feldspar, the results indicated a thermal expansion coefficient difference of 3.25 × 10−6/°C and a cross-sectional area ratio of approximately 54.40. The resulting composite ceramics sintered at 1220 °C for 60 min had their flexural strength reached 237.09 ± 26.70 MPa, which was 56.53 % higher than the matrix's flexural strength of 151.70 ± 5.32 MPa. Additionally, a study of the composite ceramics' resistance to thermal shock showed an increase in the critical temperature of decrease in flexural strength from 200 °C to 220 °C. [ABSTRACT FROM AUTHOR]

This paper examines the performance and failure mechanisms of atmospheric plasma sprayed (Gd, Yb)-doped YSZ (RYSZ) thermal barrier coatings (TBCs) under oxy-acetylene flame thermal shock conditions. The study involved cyclic thermal shock testing at temperatures of 1400 °C, 1500 °C, and 1600 °C for 10-min intervals until failure occurred, with failure counts recorded as 6, 2, and 2, respectively. During the thermal shock tests, tensile stress in the top coat (TC) caused vertical cracks. The growth of the thermally grown oxide (TGO) layer concentrated stress at the top coat/bond coat interface, leading to transverse interfacial cracks. As the shock temperature increased, the density of vertical cracks and the length of transverse interfacial cracks also increased. Additionally, transverse cracks developed in the TC due to sintering of the surface region at higher shock temperatures. The interaction between vertical and transverse cracks was critical to the spalling of the TC. Variations in crack densities and lengths resulted in different failure modes of the TBCs, depending on the thermal shock temperatures (1400 °C, 1500 °C, and 1600 °C). [ABSTRACT FROM AUTHOR]

TiNi alloys with excellent mechanical properties and unique functional characteristics show substantial potential for producing engineered structural components and biomedical materials. However, the high reactivity of molten TiNi poses significant challenges when ceramic crucibles are used in vacuum induction melting, inevitably resulting in severe ingot contamination. In this study, we report an innovative method for producing high-purity, low-contamination TiNi ingots by using a ZrN/AlN composite ceramic crucible. Fundamentally, this ZrN/AlN composite crucible fabricated with vacuum pressureless sintering technology, is characterized by its high relative density (>95 %) and absence of cracks. The ZrN/AlN composites exhibit impressive properties, including excellent flexural strength, high thermal conductivity, and exceptional thermal shock resistance. Notably, during induction melting, the crucible surface forms a dense TiN barrier layer, thereby protecting the crucible substrate. Compared with traditional oxide refractories, the as-prepared ingots have a low interstitial atom content (Wt. (O, N) < 1000 ppm), demonstrating the superior corrosion resistance of the ZrN/AlN composite crucible. This work provides a comprehensive understanding of crucible-melt interaction mechanisms and a promising method for producing high-purity TiNi alloys. [ABSTRACT FROM AUTHOR]

Al 2 O 3 with the desired electrical insulating properties and thermal shock resistivity has been extensively applied in the field of solid oxide fuel cells and oxygen sensors. However, degradation of the insulating Al 2 O 3 layer is an intractable issue in practical applications. In this study, different point defect structures of Al 2 O 3 were realized with the substitutional doping effect of ZrO 2 and MgO. The MgO dopant provides positively charged oxygen vacancies, whereas the ZrO 2 dopant tends to trigger negatively charged vacancy formation at Al3+ sites. The oxygen vacancy concentration of Al 2 O 3 exhibits the following trend: MgO-doped Al 2 O 3 > Al 2 O 3 > ZrO 2 -doped Al 2 O 3. Furthermore, the densification morphology, insulating properties, and oxygen vacancy migration of Al 2 O 3 have been confirmed to be largely affected by the extrinsic factors. This study indicates that oxygen vacancy migration depends on the applied electric field at high temperatures. As the voltage and temperature increase, oxygen vacancy migration shows obvious electric-field-dependent characteristics, and its aggregation macroscopically shows hole defects. The defect position of Al 2 O 3 is nonstoichiometric Al 2 O 3-x with poor crystallinity. Therefore, it is believed that the oxygen vacancy migration triggered by the second phase directly determines the insulation performance and causes the degradation of Al 2 O 3 materials. [ABSTRACT FROM AUTHOR]

The key challenge of producing titanium-aluminum alloy by vacuum induction melting technology is to develop crucible materials with excellent thermal stability and thermal shock resistance. In this work, Ba 0.8 Ca 0.2 ZrO 3 ceramic materials were synthesized by pressure-less sintering of BaZrO 3 and CaZrO 3. In order to improve the thermal shock resistance of Ba 0.8 Ca 0.2 ZrO 3 , a pore-forming agent of BaCO 3 was introduced into the material. The thermal shock resistance of the material improved significantly and reached its maximum when 9 wt% BaCO 3 was added (the retained flexural strength increased from 2.61 MPa to 3.52 MPa). At the same time, the addition of BaCO 3 significantly reduced the penetration of the crucible material by the melt and the pollution of the secondary-phase alloy in the material (the penetration depth decreased from ∼200 μm to ∼100 μm). Based on the combination effect of Ba 0.8 Ca 0.2 ZrO 3 solid solution and fine closed pores, a potential titanium-aluminum alloy smelting material with excellent chemical stability and thermal shock resistance was obtained. [ABSTRACT FROM AUTHOR]

Y 2 O 3 ceramics are increasingly recognized for their excellent vacuum stability and high-temperature chemical stability in the field of functional materials research. However, their poor thermal shock resistance renders them susceptible to spalling and damage during use, thus restricting further applications. To address this issue, the low thermal expansion coefficients of Y 2 SiO 5 materials were leveraged. Through an in situ reaction between SiO 2 and Y 2 O 3 , a Y 2 SiO 5 phase was generated that induced a thermal expansion mismatch with Y 2 O 3 , thereby enhancing the thermal shock resistance of the ceramic. Using Y 2 O 3 fine powder as the primary material, silica sol and nano-SiO 2 were selected as reactive silicon sources to prepare Y 2 O 3 –Y 2 SiO 5 composite ceramics at 1750 °C. The impact of the different silicon sources and Y 2 SiO 5 phase content on the microstructure, mechanical, and thermal properties of the composite ceramics was studied. The results demonstrated that the in situ formation of Y 2 SiO 5 significantly improved the thermal shock resistance of the composite ceramic. Specifically, increasing the SiO 2 content led to a gradual rise in the volume fraction of Y 2 SiO 5 formed between Y 2 O 3 grains, thereby increasing the residual flexural strength and enhancing the hardness and elastic modulus. The low thermal expansion coefficient of Y 2 SiO 5 reduced the overall thermal expansion coefficient of the composite material, thereby improving the thermal shock resistance. Moreover, the thermal expansion coefficient mismatch between the Y 2 O 3 and Y 2 SiO 5 phases induced numerous microcracks within the material, providing thermal stress relief within the microcracks and markedly improving the resistance of the ceramic to thermal shock. [ABSTRACT FROM AUTHOR]

To develop a high-temperature-resistant adhesive specifically for quartz glass, several groups of aluminum phosphate-based adhesives with different P/Al ratios and Si/B 4 C ratios were prepared, and the bonding performance and mechanism were systematically analyzed. Adding Si and B 4 C affected the decomposition process of phosphates, mainly in terms of the types of decomposition products and the crystal transformation of phosphates. Their addition avoided the generation of metaphosphate and improved the component stability of the adhesive matrix. The oxidation of Si and B 4 C brought about considerable quality compensation, which was crucial for maintaining the structural integrity of the adhesive layer. Besides, the oxidation products further reacted with the adhesive and quartz substrate to form ceramic or glass phases, significantly improving the bonding performance. When the P/Al ratio and Si/B 4 C ratio were 2:3 and 10:3, APSB adhesive presented the best performance. After curing at room temperature or pre-treatment at 1200 °C, the bonding strength reached 16.3 MPa and 14.6 MPa, respectively. After pre-treatment at 1200 °C, APSB could provide above 6 MPa in extreme environments with the range of RT∼1200 °C. The thermal shock resistance of APSB was superior to its thermal cycling resistance. After 10 thermal shocks at 600 °C, 800 °C, and 1000 °C, the bonding strength of APSB is 4.52 MPa, 4.33 MPa, and 7.33 MPa, respectively. Nevertheless, the CTE of APSB adhesive after sintering remained stable at 5.4 × 10−6 K−1, which was still significantly different from the CTE (0.5 × 10−6 K−1) of quartz glass. Therefore, there is great potential for developing low-expansion adhesives in the near future. [ABSTRACT FROM AUTHOR]

MgO-SiC-C refractories demonstrate distinguished thermal shock resistance and slag resistance, making them a promising alternative to magnesia-chrome refractories in matte smelting furnaces. Herein, we propose a novel approach to enhance both oxidation resistance and slag penetration resistance of such refractories by incorporating Si 3 N 4 -Fe powder. The results demonstrated that adding Si 3 N 4 -Fe powder effectively enhanced their overall performance. The oxidation resistance of the specimen with 6 wt% Si 3 N 4 -Fe was greatly improved because Si 3 N 4 in Si 3 N 4 -Fe could promote in-situ reactions to form more forsterite, and the FeO formed by iron oxidation could react with SiC to form Fe-Si alloys; the formed forsterite and Fe-Si alloys worked together to prevent oxygen intrusion. Meanwhile, Si 3 N 4 in Si 3 N 4 -Fe promoted the formation of forsterite layer in the corrosion area of refractories, and the reaction of Si 3 N 4 and Fe in Si 3 N 4 -Fe formed Fe-Si alloys to prevent slag penetration, which greatly improved the resistance to matte slag penetration of the refractories. [ABSTRACT FROM AUTHOR]

Aiming to further improve the properties of novel MgAl 2 O 4 -Si 3 N 4 ceramic used as solar thermal absorbing material in concentrating solar power, effects of Sm 2 O 3 and TiO 2 on performance of the composites were investigated especially the mechanisms of different additives on microstructure and high temperature stability. The results show that both additives can accelerate sintering, reduce sintering temperature, improve the density and high temperature stability via liquid phase sintering mechanism. Besides, TiO 2 can form displacement solid solution with Al 2 O 3 to promote the sintering process. Sm 2 O 3 is more conducive to improving the bending strength due to its function of increasing the length diameter ratio of β-Si 3 N 4. TiO 2 is more favorable for improving solar absorption owing to the distinctive absorption spectrum and large number of cation vacancy caused by substitution of Al3+ by Ti4+. MgAl 2 O 4 -Si 3 N 4 composites with Sm 2 O 3 and TiO 2 additives have better performance than MgAl 2 O 4 -Si 3 N 4 , Si 3 N 4 and SiC ceramics prepared via the same procedure, which makes it a certain choice for solar thermal absorbing material. [ABSTRACT FROM AUTHOR]

As the most prospective media material for porous media burners, silicon carbide reticulated porous ceramic (SiC RPC) is required to possess a high porosity to fulfill efficient combustion, as well as exceptional thermal shock resistance to withstand the thermal stress generated during the start-up and shutdown processes. To achieve the strengthening and toughening of highly porous SiC RPC, three-layered struts were constructed, and in-situ whiskers were formed in SiC RPC through vacuum infiltration and sintering under a nitrogen atmosphere in this work. The results indicated that the three-layered struts were formed after the preform was conducted with vacuum infiltration, encompassing a mullite coating, a silicon carbide layer and a mullite inner layer. When Si powder and flake graphite were incorporated into the SiC slurry, numerous SiC whiskers were formed in situ within the SiC skeleton. The formation of SiC whiskers was attributed to the enhancement of SiC RPC, resulting in an increase in CCS from 0.22 MPa to 0.55 MPa. Additionally, the residual strength retention rate after water quenching at 1100 °C was elevated from 41.6 % to 70.2 %. Moreover, the SiC RPC containing SiC whiskers exhibited an impressively high porosity of 83 %, leading to a surface temperature of 688 °C and a heating efficiency of 16.4 °C/min during the combustion process. [ABSTRACT FROM AUTHOR]

The hydrated magnesium carboxylate cement (HMC) with varying C 6 H 5 O 7 2−/Mg2+ ratios was prepared by adjusting the ratio of citric acid to magnesia in this study, and its effect on the performances of corundum-spinel refractory castables were investigated. The results revealed that the HMC bonded castable's workability was improved by increasing the C₆H₅O₇³⁻/Mg2⁺ ratio. Specifically, the sample C-EX (citric acid/magnesia = 4.5) compared to the standard sample NO (citric acid/magnesia = 3.5), the setting time was extended by 100 min, and the flow value increased by 77.6 %. Hydration kinetics experiments demonstrate that this phenomenon was due to the excess citric acid inhibiting HMC ionization. Furthermore, increasing the C₆H₅O₇³⁻/Mg2⁺ ratio also enhanced castables' medium-temperature mechanical properties and thermal shock resistance. The excess citric acid enhanced the castable slurry's performance, resulting in a 37.8 % increase in cold modulus of rupture for the C-EX sample after sintering at 500 °C compared to the sample NO. The fracture strength after thermal shock is 27.9 % higher in sample C-EX than in sample NO. This improvement is attributed to the 82.1 % increase in toughness of the sample C-EX, which facilitates the micro-cracks formation but inhibits their propagation. However, it should be noted that increasing the proportion of citric acid reduced the aspect ratio of HMC hydration products, leading to decreased mechanical properties of the castables. [ABSTRACT FROM AUTHOR]

Because of the fatigue resistance and light weight, carbon fiber reinforced resin composite (CFRP) has widely used in expanded solar panels, key components of space stations and antenna panels. However, the space environment of solar irradiation will cause the CFRP temperature rise due to its high solar absorption, which affects the long-term application. It is necessary to prepare thermal control coating (TCC) on the surface of CFRP. In this paper, a new preparation method of CFRP surface coating by gravity deposition is reported to obtain ZrO 2 and polytetrafluoroethylene particle stacking structure with low solar absorption. The high scattering intensity of particle stacking structure coating was verified by simulation. Through the analysis of the morphologies and XPS of the coating, the optimal ZrO 2 content was determined, and the particle stacking structure was proved. The coating exhibits good thermal shock property. The solar absorption of the coating is as low as 0.08, with a surface density of 196 g/m2, and the surface temperature can be reduced by 38.8 °C under irradiation, which provides a new prospect for the application of thermal control coating on the CFRP. [ABSTRACT FROM AUTHOR]

The sagger, primarily composed of aluminum-silicon, serves as an essential vessel in the sintering process of ternary lithium battery anode materials (LiNi x Co y Mn 1-x-y O 2 , LNCM). However, the acidic oxide SiO 2 in the sagger material readily reacts with Li 2 O in the cathode material, forming substances such as LiAlO 2 or LiAlSiO 4 , resulting in volume expansion, which makes the sagger spalled and damaged. In this study, β-Al 2 O 3 –MgAl 2 O 4 multiphase materials with excellent alkali resistance were prepared using the high-temperature solid-state method. The effects of anhydrous sodium carbonate content and heat treatment temperature on the properties of the composites were investigated, and the thermal shock resistance of the specimens was evaluated by the water-rapid-cooling method, as well as the LNCM corrosion resistance of the specimens was evaluated by the static crucible method. The results showed that the overall performance of the specimens was the best at a anhydrous sodium carbonate content of 6 wt%, with a compressive strength of 57.50 MPa and a flexural strength of 42.49 MPa after firing at 1600 °C for 4 h. The strength retention of the specimens was 33.21 % after one thermal shock at a thermal shock temperature of 900 °C. The specimens showed excellent resistance to erosion as there were no obvious erosion traces on the surface of the specimens after undergoing five cycles of erosion. [ABSTRACT FROM AUTHOR]

Alumina-spinel and alumina-magnesia castables are important for steel ladle applications primarily for the bottom and side wall areas respectively. Presence of spinel in alumina castables enhances the resistances against corrosion and thermal shock and improves the performance and service life of the steel ladles. Development of these type of castables is planned in the present study in presence of Cr 2 O 3 as an additive using high alumina cement as binder. Variation in spinel (10 and 20 wt%) and MgO (2.8 and 5.6 wt%) content was also explored, along with two different particle size distributions (q value 0.21 and 0.29) for different flow consistencies. The castable compositions were processed conventionally and evaluated for various refractory properties after heat treatments at 110, 1000 and 1550 °C. Both the castables showed well developed refractory properties with alumina-magnesia castable having better slag resistance due to greater extent of calcium hexa aluminate phase formation protecting the refractory. [ABSTRACT FROM AUTHOR]

A self-built automatic platform was built to evaluate the thermal shock performances of Cansas-III SiC fibers at 1200 °C in air up to 500 cycles, the corresponding oxidation and damage mechanisms were then revealed. The results showed that oxide scale was formed during thermal shock with a thickness of about 1 μm, the core was not oxidized via its protection. The fiber roughness increased before 100 cycles due to the decomposition of the amorphous SiC x O y phase, and then decreased as the formation of oxide scale. Within Cansas-III SiC fibers, structural defects of free carbon increased as the increasing I D /I G values, in addition, the TO peak shifted to the left, which both demonstrated that the relative movements occurred among SiC grains and residual stresses were then emerged. To clarify the axis and radial cracking of the oxide scale, a modified formulation considering nonzero shear strain components was then proposed to calculate the related residual stresses. The peeling and cracking of the oxide scale was ascribed to the residual stresses of GPa level among SiC grains and the thermal expansion mismatch between the oxide scale and the core. [ABSTRACT FROM AUTHOR]

In this study, corundum-magnesium aluminate spinel (C-MAS) composite heat storage ceramics were synthesized by co-adding MgO and TiO 2 to Al 2 O 3. The effects of TiO 2 and the Al 2 O 3 /MgO ratio on the heat storage performance were evaluated. The findings reveal that Ti4+ integrates into the corundum and MAS lattice, leading to lattice distortion and facilitating solid-phase reaction and MAS generation. Optimal performance is observed at an Al 2 O 3 /MgO ratio of 95:5, with dense structure, minimal pores, and uniform grain size, exhibiting exceptional thermal shock resistance. They withstand 30 thermal shocks (RT-1100 °C) with a 7.12 % increase in bending strength. Moreover, the addition of MgO and TiO 2 significantly enhances the specific heat capacity, characterized by an average specific heat capacity of 1.06 J·g−1·°C−1 and a heat storage density of 1443.83 kJ·kg−1 (RT-1100 °C). TiO₂ introduces additional point defects or alters existing ones in the Al₂O₃ matrix, increasing heat capacity through defect thermal motion. The formation of MAS leads to higher specific heat capacity, due to the greater degrees of freedom and complex lattice vibrations of the spinel structure. These properties position C-MAS composite ceramics as promising candidates for the heat storage materials of the new generation of solar thermal power generation. [ABSTRACT FROM AUTHOR]

Thermal shock behaviors of porous alumina samples with different porosities (4.6–16.0 %) and mean grain sizes (2.72–5.02 μm) were investigated under different quenching temperatures. The slit island method was used to analyze the structures of the pores. The effect of the pore structure on the thermal shock resistance of alumina ceramics was described quantitatively. The results revealed that the thermal shock resistance decreased when the fractal dimension of the pores increased. Alumina ceramic strips with a porosity and mean grain size of 4.6 % and 5.02 μm, respectively, were fabricated using raw powders with a mean particle size of ∼0.3 μm. These samples possessed the highest residual strength ratio (∼46.16 % at 600 °C) and critical temperature difference (∼262 °C). In addition, the fractal characterization of cracks on the surfaces of the alumina ceramics after thermal shock was carried out using the box-counting dimension method. In addition, we investigated the correlation between the mechanical properties and fractal dimensions of the surface cracks. The box-counting dimension increased with crack propagation and negatively correlated with the residual strength. Furthermore, the propagation rate of the surface cracks decreased as the temperature difference increased, resulting in a decrease in the growth rate of the fractal dimension. [ABSTRACT FROM AUTHOR]