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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]

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]

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]

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]

Industrial boilers operate in extreme environments and are prone to degradation caused by high temperature oxidation, corrosion, and erosion. Protective coatings provide boiler components with protection to prolong their operation lifetime. Thus, a glass-ceramic coating has been developed using a slurry spray technique on carbon steel AS/NZS 3678 substrates. Microstructure, mechanical characteristics, and high temperature performance of the coating were investigated. The coating composed of chemically inert oxide ceramics dispersed in a glassy silicate binder matrix. The adhesion strength of the coating was 10.79 ± 0.86 MPa. Coating mass loss after abrasion test was 0.013 % of the tested specimen. The coating withstood at least 75 air quenched thermal shock cycles from 800 °C to the room temperature without any visible spallation and cracks. The coating mostly remained undamaged after cyclic oxidation at 800 °C for 10 cycles. However, minor iron oxide formation was observed, specifically, in relatively thin sections of the coating. The oxidation resistance of the boiler steel has been improved with the developed coating. The linear oxidation rate constant of the boiler steel has been statistically reduced from 6.90 × 10−4 mg cm−2 s−1 to 1.95 × 10−4 mg cm−2 s−1 for coated steel (p = 0.007). The developed slurry spray glass-ceramic coating is a potential candidate for boiler environments. [ABSTRACT FROM AUTHOR]

Excellent properties are required for refractories used for secondary refining because of the harsh service conditions. The current study investigated the effect of calcium boride (CaB 6) on the properties of magnesium oxide (MgO)‒based refractories. The sample with 0.4 wt% CaB 6 exhibited excellent properties. It possessed the highest bulk density indicating that a suitable content of CaB 6 can increase the compactness of the refractories. The in-situ formation of aluminum oxycarbonitride (Al 3 CON) at high temperatures in the MgO-based refractories was from the reaction of Al, Al 4 C 3 , AlN, and Al 2 O 3 due to the addition of Al powders, which endowed them with high strength. The refractory containing 0.4 wt% CaB 6 also exhibited the highest hot modulus of rupture (HMOR) of 26.6 MPa, which was around 2.5 times the strength of commercial MgO‒CaO bricks and 1.5 times that of the samples without CaB 6 addition. In addition, it exhibited the best oxidation resistance revealed by the minimum thickness of the decarbonization zone, because the addition of CaB 6 promoted the formation of a dense magnesium aluminate spinel (MgAl 2 O 4 , MA) layer between the oxidized and non-decarburized zone in the refractories, thereby promoting the resistance of the samples to oxidation. It also exhibited excellent thermal shock resistance, and the residual strength ratio reached 76.6 %. The corrosion depth of the sample containing 0.4 wt% CaB 6 was 9.8 % that of the MgO‒CaO bricks. This work indicates a potential alternative for producing high‒performance resin‒bonded MgO-based refractories with CaB 6 in secondary refining furnaces. [ABSTRACT FROM AUTHOR]

Thermal shock resistance and mechanical reliability of aluminum nitride (AlN) ceramic substrates are essential in electronic device modules. In this study, the thermal shock behavior of AlN doped with aluminum - yttrium oxide (Al - Y 2 O 3) was explored. The results indicate that adding Al to AlN ceramics increases its flexural strength, thermal conductivity, and thermal expansion coefficient. The microcracks caused by thermal mismatch between the AlN matrix and the secondary phases relieved internal stress, thereby improving thermal shock resistance of AlN ceramics. Furthermore, the addition of Al isolates and homogenizes the secondary phases, resulting in a more uniform microstructure and strengthened grain boundaries, which enhance the flexural strength, Weibull modulus, and thermal shock resistance. After introducing 0.5 wt% Al, the Weibull modulus of AlN ceramics increased by 73.37 %, and their critical thermal shock temperature difference exceeded 800 °C, with a maximum residual strength of 488.01 ± 48.26 MPa at 600 °C. Overall, an appropriate amount of Al improves the reliability and thermal shock resistance of AlN ceramics. [ABSTRACT FROM AUTHOR]

Hierarchical design was applied to core-shell B 2 O 3 @SiO 2 microcapsule, followed by fabrication of the SiC–B 2 O 3 @SiO 2 coating by a combination of entrapping and hot dip processes. Among the C/C-SiC-BS2, C/C-SiC-BS4 and C/C-SiC-BS6 samples, the C/C-SiC-BS4 composite exhibits long-term antioxidant capabilities, with only a 2.30 % mass loss as oxidized at 973 K for 1500 h, and 2.35 % at 1073 K for 2600 h. Furthermore, after enduring 150 thermal shocks between 293 K and 1173 K, its mass loss is only 2.07 %. The XRD patterns detected the existence of B 2 O 3 and SiO 2 phases, and the SEM and EDS analysis proved the borosilicate glass, indicating the excellent performances came from the synergistic self-healing effects of the B 2 O 3 , SiO 2 phases, and borosilicate glass. Thus, within the temperature ranges from 873 K to 1273 K, the oxygen penetration shifts from osmotic state to defect diffusion in coating. This research emphasizes the significance of hierarchical designs for core-shell sacrificial phase in silicate coatings, thereby enhancing their long-term applicability. • Hierarchical design was applied to the B 2 O 3 @SiO 2 microcapsule by a simple sol-gel technique. • Core-shell microcapsule successively activated the SiO 2 , B 2 O 3 phases and borosilicate glass in self-healing. • The composite yielded excellent combinations of long-term antioxidant and thermal shock resistances. • This study highlights the hierarchical designs for core-shell sacrificial phase in silicate coatings. [ABSTRACT FROM AUTHOR]

The durability of thermal barrier coatings (TBCs) is significantly influenced both by the ceramic top coat and the bond coat. In this study, novel YbGdZrO ceramic coats were deposited on the surfaces of three types of Cr-modified (Ni, Pt)Al bond coats via electron beam physical vapor deposition (EB-PVD) technique. These Cr-modified (Ni, Pt)Al bond coats were fabricated by magnetic sputtering Cr onto the (Ni, Pt)Al bond coats with varying sputtering times of 30, 60, and 90 min. The results indicates that the thickness of the Cr-modified layer increases with the extension of sputtering time. A short deposition time of 30 min is adequate for achieving an appropriate Cr content in the (Ni, Pt)Al bond coats, which ensures selective oxidation of Al element within the bond coat and further enhances the metallurgical interfacial bonding strength with the ceramic coat by adapting to the concentration gradient diffusion. However, as the sputtering time is extended to 60 and 90 min, α-Cr begins to form in the Cr-modified (Ni, Pt)Al bond coats, which negatively affects the oxidation resistance of the bond coat. Consequently, the thermal shock life of the TBCs samples is significantly reduced with increasing sputtering time. The longest thermal shock lifetime is obtained on the bond coat with Cr plating time of 30 min owing to a differing thermally grown oxide formation and failure mechanism. [ABSTRACT FROM AUTHOR]

Ceramic industry consumes large amounts of raw materials, including costly and environmental impact iron based-pigments. Steel rolling (SR) and wire drawing (WD) waste, rich in iron (>67 wt %), present a viable alternative. This study aims to develop high value stoneware pastes for tableware products by substituting commercial pigments with SR and WD. The influence of incorporation content (3, 5 and 10 wt %) and pre-treatments (sieving at 250, 150 and 63 μm, and grinding followed by sieving at 63 μm) on the samples properties was assessed including weight loss, firing shrinkage, apparent density, flexural resistance, and water absorption. The laboratory scale results revealed that darker hues, ranging from grey to reddish, were obtained when SR and WD were incorporated in the stoneware paste (beige colour). The smaller the particle size, more homogeneous is the developed colour, which is intensified as higher is the incorporation level. The prototypes (plates) were characterized in terms of thermal shock, edge impact, cracking and microwaves resistance, water absorption, and leaching behaviour, demonstrating that they met the industrial requirements. Thermal shock resistance was enhanced and the levels of leached Fe, Pb, Cd, Ni, Cr, Mo, V, Zn, and Cu, were below permissible limits (EU Ceramic Directive 84/500/EEC, Decree-Law n°152/2017, Decree-Law n°236/98 and WHO Guidelines for Drinking-Water Quality) confirming their effective immobilization. Concluding, this work shows the viability of using mill scale waste as a valuable secondary raw material in stoneware pastes acting as a chromophore agent. Dark colours are obtained while preserving the product technical characteristics, promoting sustainable production and reducing landfilled waste. [ABSTRACT FROM AUTHOR]

This study aims to advance the application of magnesia-zirconia (MgO–ZrO 2) refractories in non-ferrous metal smelting furnaces by enhancing their thermal shock resistance. To fabricate MgO–ZrO 2 –MgAl 2 O 4 refractories, tabular corundum particles and activated α-Al 2 O 3 powder are integrated into MgO–ZrO 2 refractories. The analysis of thermal shock resistance, phase composition, and microstructure of the samples was conducted to gain insights into the toughening mechanisms. The results reveal a substantial enhancement in thermal shock resistance with the addition of 15 wt% tabular corundum (1–0.5 mm) and activated α-Al 2 O 3. Compared to samples without these additives, a notable increase of over 50.0 % in the ratio of residual cold modulus of rupture is shown. The enhancement in thermal shock resistance is primarily attributed to the in-situ generated MgAl 2 O 4 spinel. This process involves volume expansion and increased thermal expansion mismatch, which induce microcrack toughening. Additionally, larger tabular corundum particles form in-situ MgAl 2 O 4 spinel, causing crack deflection and branching, thus extending the crack propagation pathway. Furthermore, the presence of micropores in the spinel zone absorbs the energy required for crack propagation, thereby improving toughness and thermal shock resistance. Consequently, the MgO–ZrO 2 –MgAl 2 O 4 refractories containing in-situ MgAl 2 O 4 spinel with micropores are promising candidate for chrome-free refractories used in non-ferrous metal smelting furnaces. [ABSTRACT FROM AUTHOR]

The utilization of in-situ ceramic combination effectively addressed the issue of weak bonding at the interface in low carbon Al 2 O 3 –C refractories, enhancing the material service performances. In this study, nano-MgSiN 2 synthesized from molten salt was utilized for incorporation of Al 2 O 3 –C refractories, as well as in assessment of mechanical properties, thermal shock stability, oxidation resistance and corrosion resistance. The findings demonstrate that the molten salt medium can lower synthesis temperature and decrease particle size of nano-MgSiN 2. In addition, nano-MgSiN 2 undergone phase reconfiguration at 1500 °C to form Mg (g) and Si 3 N 4(s). The folding structure Mg-Sialon/MgAl 2 O 4 were formed through phase reconfiguration of Mg (g) and Si 3 N 4(s). This change enhanced interfacial bonding strength of Mg-Sialon/Al 2 O 3 and MgAl 2 O 4 /Al 2 O 3. The mechanical properties and thermal shock stability of refractories were enhanced by novel reconfiguration technology, resulting in CCS value of 176.9 MPa. Simultaneously, Mg-Sialon transformation facilitated the interconnection of the oxide layer, enhancing oxidation resistance and corrosion resistance. [ABSTRACT FROM AUTHOR]

Incorporation of MAX phase to fabricate low-carbon refractories has been recently proposed. Among them, Cr 2 AlC was the undoubtedly one which was regarded as the most potential candidates for applications, due to the excellent chemical stability of chromium oxide. In this work, the influence of Cr 2 AlC on the thermal shock resistance and corrosion resistance of Al 2 O 3 -Cr 2 AlC-C refractories were investigated. The results indicated that the residual strength ratio still maintained stability when flake graphite content reduced from 9 wt% to 4 wt%. While the corrosion resistance of the sample with 4 wt% graphite and 5 wt% Cr 2 AlC increased approximately 40% compared with regular Al 2 O 3 -C refractories with 9 wt% graphite. The degradation mechanisms and interactions of Al 2 O 3 -Cr 2 AlC-C refractories in contact with MnO-rich slag were studied, and the role of Cr 2 AlC was elucidated. [ABSTRACT FROM AUTHOR]

Lightweight composites with excellent thermal shock performance exhibit significant potential for thermal structural components. Herein, HfC nanowires modified carbon/carbon (HfC NWs -C/C) composites are fabricated, establishing a three-dimensional network within the matrix. The microstructure of the composites before and after thermal shock cycles were characterized by SEM, XRD and TEM. Additionally, the flexural strength with varied thermal shock were analyzed, which were initially increasing before subsequently decreasing with the number of thermal shock cycles under Ar atmosphere, exhibiting thermal shock strengthening phenomena. While within oxy-acetylene system, the strength of HfC NWs -C/C exhibit an increasement of 75 % compared with C/C after ablation for 6 cycles, which can be attributed to the sintering and the generation of molten film of partial HfO 2 phases that can mitigates oxidation of the matrix, but still lead to a declining trend in the strength following ablative thermal cycles. [ABSTRACT FROM AUTHOR]

Thermal insulation devices play an extremely important role in enhancing microwave heating efficiency. However, existing wave-transparent insulation materials often exhibit high heat storage, low microwave transmittance at high temperatures, and poor oxidation and thermal shock resistance, hindering high-temperature applications for microwave sintering. To address this issue, we developed an ultralight and wave-transparent BN@SiO 2 aerogel, which was fabricated through the in situ growth of SiO 2 on the surfaces of BN fibers. The resulting composite aerogel demonstrated excellent high-temperature oxidation resistance and an impressively low density of 0.07 g/cm3. Furthermore, the dielectric constant of the BN@SiO 2 aerogel ranged from 2.58 to 2.80, and its dielectric loss tangent was as low as 5.13 × 10−3–7.98 × 10−3 within the 2–10 GHz frequency range. The successful synthesis of BN@SiO 2 aerogel provides new progress and research ideas for the development of wave transparent and thermal insulation materials. [ABSTRACT FROM AUTHOR]

SiC/SiC composites in aerospace applications are exposed to a variety of thermal conditions, in particular, thermal stress due to rapid heating and cooling. Therefore, it is crucial to investigate and evaluate the resistance of SiC/SiC composites to repeated temperature cycling. This paper investigates the evolution of properties and damage mechanisms of 2D and 2.5D SiC/SiC composites after different thermal shock cycles at 1300 °C. It was found that SiC/SiC composites exhibit a temporary weight increase at the beginning of the thermal shock cycle. Subsequently, the weight decreases and stabilizes as the number of thermal shocks increases. After 10–30 thermal shocks at 1300 °C, the density of SiC/SiC composites decreases while the porosity increases. The fracture behavior of SiC/SiC composites remains the same as that of the initial composites, with 2D SiC/SiC composites exhibiting pseudo-tough fracture and 2.5D SiC/SiC composites exhibiting brittle fracture. The residual strength of the SiC/SiC composites decreased slightly while the residual modulus remained stable. This is related to the reaction of the SiC, and BN with water and oxygen at high-temperature. The thermal shock damage of SiC/SiC composites is anisotropic and is influenced by the structure of the fiber preforms. This is due to the difference in thermal expansion coefficients of the components within the composites and the structural properties of the fiber preforms. [ABSTRACT FROM AUTHOR]

Carbon fibers (C f) were incorporated into Al 2 O 3 –C refractories to enhance their toughness in this work. The results indicated the 0.3 wt% C f -adding improved the high-temperature bending strength to 1.93 MPa from 1.07 MPa, and led to a 55 % enhancement in thermal shock resistance. The above enhancement could attributed to the in-situ formed SiC coating which was observed on the carbon fiber's surface and strengthened the interface bonding between the carbon fiber and refractory matrix. A solid-liquid diffusion reaction was employed to describe the formation process of in-situ SiC layer on the carbon fibers. Furthermore, the wedge-splitting test with digital images was carried out to investigate the crack-growth trajectory during the splitting process. It was confirmed that C f -adding could enhance the strength and reduce brittleness with the crack-bridging, pullout, and interlock behaviors of carbon fibers in the refractory matrix. [ABSTRACT FROM AUTHOR]

MgO–ZrO 2 refractories were produced by combining MgO refractories (with a CaO/SiO 2 ratio of 2.1) with monoclinic ZrO 2 powder using wet-bag cold isostatic pressing. The phase composition and mechano-physical properties of the MgO–ZrO 2 materials were influenced by the interaction between ZrO 2 and MgO refractories. ZrO 2 enhanced the cold modulus of fracture of MgO refractories but decreased the hot modulus of fracture due to changes in bonding phases. The addition of 1 wt% ZrO 2 transformed Ca 2 SiO 4 into CaMgSiO 4 and CaZrO 3. CaMgSiO 4 with a low melting point deteriorated the hot modulus of fracture of MgO–ZrO 2 refractories from 13.3 to 2.97 MPa. With an increase in ZrO 2 to 3–5 wt.%, CaMgSiO 4 remained while CaZrO 3 gradually transformed into the solid-solution Ca 0.2 Zr 0.8 O 1.8. This transformation occurred because ZrO 2 seized CaO from CaZrO 3 to stabilize itself. Based on thermodynamic equilibrium ZrO 2 preferentially reacts with CaO-containing phases in the MgO matrix in the following order: Ca 3 SiO 5 > Ca 2 SiO 4 > CaZrO 3 > CaMgSiO 4. The thermal shock resistance of MgO–ZrO 2 refractories with less than 5 wt% ZrO 2 was not significantly improved by assessing their strength loss and coefficient of thermal expansion. In conclusion, it is recommended to incorporate ZrO 2 into MgO refractories with low SiO 2 or CaO to develop high-performance MgO–ZrO 2 refractories. [ABSTRACT FROM AUTHOR]

The Al 2 W 3 O 12 ceramic with near-zero thermal expansion is a promising candidate for thermal shock resistance applications. However, the often-reported microcracks in the microstructure hinder the practical use of Al 2 W 3 O 12. This work focuses on optimising the material processing—powder synthesis, calcination, milling, and sintering—to prepare dense polycrystalline Al 2 W 3 O 12 with fine microcrack-free microstructure. The amorphous powder produced by the co-precipitation method had the highest specific surface area reported for this material, resulting in improved sinterability. Two rapid sintering methods were employed—Rapid Pressure-less Sintering and Spark Plasma Sintering. Both methods led to shorter processing times and lower sintering temperatures. However, Al 2 W 3 O 12 samples produced by Spark Plasma Sintering were nearly fully dense with a density of ∼98% of theoretical density, the best value reported to date for this phase. The obtained fine crack-free microstructure of the samples led to a superior mechanical response compared to that achieved by Rapid Pressure-less Sintering. [ABSTRACT FROM AUTHOR]

Protective ceramic coatings are frequently the most common solutions for problems like corrosion and wear. Polymer derived ceramics technology is suitable for the preparation of ceramic coatings by pyrolysis in a furnace but requires high temperatures for the ceramization. To overcome this restriction a Nd:YVO 4 laser (λ = 1064 nm) as energy source was used to process a novel ceramic coating system composed of an organosilazane with zirconia and alumina particles specially to protect magnesium. The resulting dense ceramic coating with a thickness up to 20 µm exhibits very good adhesion (25.9 ± 2.7 MPa) to the magnesium substrate, exceptionally high hardness (19.79 ± 1.90 GPa), an outstanding thermal shock stability but also a low coefficient of friction (0.21 ± 0.02) and a very good wear protection towards a SiC counter body. Furthermore, the coating protects the magnesium substrate effectively against corrosion (5 wt% aqueous NaCl solution). [ABSTRACT FROM AUTHOR]

The green and efficient use of coal gangue (CG) is urgently required in the Chinese coal industry to avoid its adverse environmental impact. This study proposed an Al-assisted carbothermal reduction method to synthesise SiC–Al 2 O 3 ceramics using high-C CG. The optimised experimental conditions for sintering SiC and their effects on the phase composition and related properties of the composites were investigated. The addition of Al optimised the in-situ synthesis pathway of SiC and significantly improved the carbothermal reaction efficiency, making the reactive temperature decrease from 1500 to 1200 °C. Additionally, sintering temperatures could modulate the SiC morphology by affecting the generation of SiO (gas) and the liquid phase of melting Al. The H3 formulation sintered at 900 °C was appropriate for producing SiC w /Al 2 O 3 ceramics with a bending strength of 49.24 MPa, a thermal conductivity of 1.720 W (m K)−1 and good thermal shock resistance (no cracks forming after 20 cycles). This study aimed to fully combine the reactivity changes of CG with the melting reduction reaction of Al. Findings in this work offer novel insights into the synthesis of structural ceramics and the cleaner use of CG for solar thermal storage. [ABSTRACT FROM AUTHOR]

Achieving an optimal balance between mechanical properties, dielectric properties, and thermal shock resistance presents a significant challenge in the development of advanced ceramics. This study investigates Si 3 N 4 -BN composite materials, prepared by hot-press sintering with magnesium aluminum silicate (MAS) as the sintering additive, to assess the impact of varying hexagonal boron nitride (h -BN) content on their mechanical and dielectric properties, as well as their thermal shock resistance. At an h -BN content of 20 wt%, the BN layers act as a toughening phase through a pull-out mechanism, minimally impacting the composite's density. This composition results in superior fracture toughness (7.4 MPa m1/2), high strength (598 MPa), low dielectric constants (∼6.8), and dielectric loss (∼7.4 × 10−3). Notably, after a thermal shock at 1000 °C, the composite exhibits a peak residual strength of 621 MPa, surpassing its initial strength. This enhanced performance is attributed to the formation of a dense Mg–Al–Si–B–O oxide glass layer on the surface during thermal shock, which not only repairs surface defects but also induces compressive stress. The development of the Si 3 N 4 -BN-MAS composite, with its outstanding comprehensive performance, marks a significant advancement for materials used in high-temperature wave transmission applications. [ABSTRACT FROM AUTHOR]

Developing and designing carbon-free refractory materials is an effective alternative to MgO–C refractory materials to produce large-scale, high-quality, low-carbon special steels. Therefore, in this work, excessive MgO is introduced into MgAlON to prepare a series of MgO–MgAlON composite refractories. The enhancement mechanism of comprehensive performance is systematically evaluated, where MgO as a reinforcer features intergranular phase strengthening and grain boundary purification effects. Besides, the pore structure of MgO–MgAlON composite refractories is also optimized to regulate the molten slag wetting behavior. The results demonstrated that MgO–MgAlON composite refractories have apparent porosity of 13.86%–15.84 %, bulk density of 2.78–2.97 mg cm−3, and compressive strength of 204.17–253.97 MPa. When 42.8 % MgO is introduced, the sample strength retention ratio after thermal shock measurement and slag corrosion experiments are 64 % and 75 %, respectively. Consequently, a cost-effective and feasible reinforcement strategy for MgO–MgAlON composite refractories is proposed, paving the way for. [ABSTRACT FROM AUTHOR]

A Mg(OH) 2 –2Al(OH) 3 composite gel, synthesized via the sol-gel method, served as a modifier in the preparation of modified yttria partially stabilized zirconia (Y-PSZ) ceramics. The volume density, apparent porosity, compressive strength, thermal shock resistance, phase composition, and microstructure of the ceramics were systematically characterized. The findings reveal that, upon sintering, the Mg(OH) 2 –2Al(OH) 3 composite gel decomposes into MgO–Al 2 O 3 powder, which in turn in-situ generates a MgAl 2 O 4 spinel reinforcing phase, characterized by its uniform size and distribution. The presence of this MgAl 2 O 4 spinel applies compressive stress to the adjacent zirconia grains, effectively inhibiting their abnormal growth. By occupying the grain boundaries and establishing a mosaic structure, the compressive strength and thermal shock resistance of the Y-PSZ ceramics are significantly enhanced. Notably, an increase in the composite gel quantity correlates with a reduction in both volume density and apparent porosity of the Y-PSZ samples, whereas the compressive strength initially rises before diminishing, and the thermal shock resistance markedly improves. When the amount of Mg(OH) 2 –2Al(OH) 3 composite gel introduced reaches 9 %, the comprehensive performance of the modified Y-PSZ ceramics is optimized. At this point, its compressive strength is increased by 1.26 times compared to the unmodified Y-PSZ ceramics, reaching 732 MPa; moreover, after undergoing 60 thermal shocks, its residual strength retention rate still remains as high as 59.15 %. [ABSTRACT FROM AUTHOR]

Mullite fibers possess low thermal conductivity, excellent high-temperature stability, and thermal shock resistance, making them extensively utilized in high-temperature heat-insulating components. However, the majority of current mullite fibers have solid structures, limiting the potential for further enhancement of their heat-insulating properties. Metaplexis fiber, a plant fiber with a hollow structure, effectively obstructs heat transfer, and therefore exhibits excellent heat-insulating properties. In this study, we employed metaplexis fibers as templates to fabricate mullite fibers with hollow structures. First, a precursor solution was prepared using Al(NO 3) 3 ·9H 2 O and ethyl orthosilicate as the solute and anhydrous ethanol as the solvent. The metaplexis fibers were immersed in the solution, removed, and dried to obtain precursor fibers. Finally, the precursor fibers were heated to the target temperature to obtain hollow mullite fibers. The investigation focused on the impact of preparation parameters such as sintering temperature, precursor solution concentration, and aluminum–silicon molar ratio on the morphologies, phases, pore-size distributions, and thermal conductivities of the resulting hollow mullite fibers. The results demonstrated that the prepared mullite fibers inherited the hollow structure of metaplexis fibers, with the cavity diameter in the range of 3–6 μm and porosity of 91 %. Compared to traditional solid mullite fibers, the thermal insulation performance was improved by more than 59 %. These findings highlight the significant potential of hollow ceramic fibers for the development of heat-insulating materials. Using the unique characteristics of their hollow structure, these fibers offer improved heat-insulating properties compared to their solid counterparts. [ABSTRACT FROM AUTHOR]

Ceramic whiskers exhibit excellent performance due to their special structure, making them widely used in the field of refractories. In this work, a novel Al 4 SiC 4 whisker was designed to improve the mechanical properties and thermal shock resistance of Al 2 O 3 –SiC–C (ASC) refractories. By introducing nickel nitrate as a catalyst, the Al 4 SiC 4 whiskers with a special "stalactite" structure could be directly grown in situ at the operating temperature of ASC (1450 °C). Combining the experimental results and first-principles calculations, the AlNi 2 Si alloy formed during the heat treatment process acted as catalyst sites, AlO, SiO and CO were easily absorbed on the Ni 55 surface. Subsequently, the Al–O, Si–O and C–O bonds were broken and reacted with each other to grow Al 4 SiC 4 whiskers according to the vapor-liquid-solid mechanism. As expected, the incorporation of Al 4 SiC 4 whiskers resulted in a 57.4 % increase in cold compressive strength (CCS) and a 47.2 % increase in residual strength ratio (RSR) of the ASC refractories due to the strengthening mechanism of whisker bridging. This study presents a novel research strategy for enhancing the properties of refractories. [ABSTRACT FROM AUTHOR]

Addressing the issue of carbon contamination during the smelting of specialty metals or alloys, utilizing graphite crucibles, has attracted considerable research attention, prompting the exploration of novel ceramic crucible materials. AlN ceramic, renowned for their exceptional high-temperature stability and resistance to corrosion, have emerged as promising candidates to mitigate this concern. Nonetheless, the limited mechanical properties and thermal shock resistance of AlN curtail its widespread application. In this study, Y 2 Zr 2 O 7 was introduced as an additive to enhance AlN's properties, and AlN-based composite ceramics were fabricated by employing pressureless sintering. The effects of Y 2 Zr 2 O 7 addition (3–10 wt%) on the mechanical properties and thermal shock resistance of the resulting composites were examined. The findings revealed that the incorporation of 5 wt% Y 2 Zr 2 O 7 (AlN-5YZO) led to the highest relative density and a refined grain structure, resulting in superior mechanical properties. Notably, the flexural strength, fracture toughness, and Vickers hardness of AlN-5YZO reached 322 MPa, 3.70 MPa m1/2, and 13.34 GPa, respectively. Furthermore, the presence of crack branching and crack deflection within the composite ceramics impeded crack propagation, effectively augmenting their thermal shock resistance. AlN-5YZO samples exhibited residual strength retention rates of 91.0 %, 84.2 %, and 76.7 % after 10, 20, and 50 thermal shocks between 1000 and 1600 °C, surpassing those of pure AlN. The findings of this study present promising avenues for advancing crucible materials tailored for high-temperature applications. [ABSTRACT FROM AUTHOR]

a new refractory microstructure with thermal stress buffering gap around aggregates was designed. PVA (Polyvinyl alcohol)-coated MgAl 2 O 4 (MA) aggregates were prepared by spray coating technology. The obtained PVA coated MA aggregates were adopted in MgAl 2 O 4 –C (MA-C) refractories to research its effect on properties of refractories. The results showed that a uniform PVA layer could be coated on the surface of MA aggregates by spraying coating technique. In the heat treatment process, the PVA around MA aggregates was decomposed and leaves gap between aggregates and matrix, which could offset the aggregates expansion. Due to the reducing thermal expansion coefficient, the thermal shock resistance of refractories was significantly improved. The COMR after thermal shock and the residual strength retention rate of the sample with stress buffering gap were 6.02 MPa and 77.87 %, while that of the sample without stress buffering gap were 5.26 MPa and of 60.32 %. [ABSTRACT FROM AUTHOR]

This study introduces a method to reduce the thermal conductivity and boost cement clinker corrosion resistance in sintered magnesia using ZnO-modified additives. Solid-solution modified sintered magnesia was prepared at 1700 °C, and the impact of ZnO on the sintering properties, room-temperature strength, thermophysical properties, and corrosion resistance was assessed. ZnO addition enhanced the densification, grain size, and strength of sintered magnesia due to activated sintering from the ZnO and MgO solid-solution reaction at high temperatures. Additionally, ZnO addition improved the thermal stability and thermal shock resistance of sintered magnesia in a high-temperature environment. However, excessive ZnO led to incomplete diffusion, impeding grain growth and degrading the properties of magnesia. The thermal conductivity significantly decreased compared to the unmodified sample, particularly at 1000 °C with 4 mol% ZnO addition. Moreover, ZnO improved the corrosion resistance due to increased grain size and densification, with 4 mol% ZnO yielding the best results. [ABSTRACT FROM AUTHOR]

Alumina-based multilayer laminates with layers of varied porosities and ceramic fiber reinforcements, which can be achieved by including paper-derived ceramic layers, are interesting candidates for chemically stable and thermal shock resistant materials. In order to investigate the complex sintering behavior of these laminates, the sintering of each alumina layer contained within a laminate, each one with its individual sintering anisotropy and sintering shrinkage, has to be considered separately. For this purpose, sintering curves are determined by dilatometry measurements, serving a consecutive examination by an analytical model. Modeling parameters specific to each layer, are applied in finite-element-type sintering simulations for symmetrical multilayer laminates. Differences in the sintering shrinkages may cause internal stresses at layer interfaces and, in turn, may influence the thermal and mechanical properties of multilayer laminates after sintering. Accordingly, the prediction of developing internal stresses within alumina-based multilayer laminates by the presented sintering simulations is a key aspect of this study. [Display omitted] • Individual laminates sintering dilatometry. • Anisotropic sintering assessment by analytic modeling. • Finite element simulation of multilayer laminates sintering. [ABSTRACT FROM AUTHOR]

Gradient environmental barrier coatings (EBCs) were fabricated via atmospheric plasma spraying to deposit Yb 2 Si 2 O 7 -Yb 2 SiO 5 onto a laser-sculpted SiC substrate, with varying mass ratios. Experimental results reveal that the gradient coating exhibited remarkable integrity, showing no signs of cracking even after exposure to 90% H 2 O-10% O 2 (g) water vapor corrosion at 1300 ℃ for 100 h. Besides, the thickness of the thermally grown oxide (TGO) layer was minimal (18.53 ± 1.08 μm) compared to 75Yb 2 Si 2 O 7 -25Yb 2 SiO 5 single layer EBCs (24.93 ± 1.62 μm) with similar integrity under water vapor environment for 100 h. The superior performance of the gradient coating against water vapor corrosion can be attributed to the outmost layer containing more Yb 2 SiO 5 with excellent vapor corrosion resistance, while the innermost layer primarily comprises Yb 2 Si 2 O 7 , providing significant damage resistance and resilience to thermal shock. These favorable attributes make the gradient coating a promising candidate for EBC application in aerospace. [ABSTRACT FROM AUTHOR]

Flake graphite (FG) poses challenges for incorporation into castables due to its hydrophobic nature. In this paper, a strategy combining liquid-phase shear exfoliation (LPSE) with hydrothermal processing was proposed to produce hydrophilic graphene nanosheet/AlOOH nanofiber (GN/ANF) composite powders to address this issue. Under optimal shear exfoliation conditions, the yield of graphene nanosheets (GNs) reached up to 57%. Following a straightforward hydrothermal treatment, the water contact angle of as-prepared GN/ANF composite powders decreased to 53.1°, compared to 103.6° of the original FG. Benefiting from the hydrophilic properties of the composite powders and the homogeneous dispersion of GNs in MgO castables, the sample containing 0.5 wt% GNs exhibited better high-temperature performance than its counterparts. Relative to the control specimen, the slag corrosion index of the sample containing 0.5 wt% GNs decreased from 0.60 to 0.13, while the thermal shock resistance increased by approximately 2.8 times. • Using the liquid-phase shear exfoliation method, the yield of graphene nanosheets reaches 57.02%. • After hydrothermal treatment, the water contact angle of graphene nanosheet/AlOOH nanofiber composite powders decreases from 103.6° to 53.1°. • Adding 0.5 wt% graphene nanosheets to MgO castables reduces the slag corrosion index from 0.60 to 0.13 and increases thermal shock resistance by about 2.8 times. [ABSTRACT FROM AUTHOR]

The aim is to investigate the effect of critical plasma spraying parameter (CPSP) on the mechanical properties and thermal shock resistance of a novel (Y 0.2 Yb 0.2 Sc 0.2 Gd 0.2 Lu 0.2) 2 Si 2 O 7 high-entropy environmental barrier coating prepared by plasma spraying. Based on a modified Vickers indentation method, the residual stress and fracture toughness of coatings were evaluated, and then the relationship between the CPSP value and thermal shock lifetime of coatings was also established. As a result, the residual compressive stress of (Y 0.2 Yb 0.2 Sc 0.2 Gd 0.2 Lu 0.2) 2 Si 2 O 7 coating is reduced from -(53.24 ± 6.78) MPa to -(17.97 ± 3.04) MPa with the CPSP value decreases from 1.17kW/Lpm to 0.94kW/Lpm, while the corresponding fracture toughness exhibits an increasing tendency. The combination of higher fracture toughness and lower residual stress result in better thermal shock resistance for the coating, and the longest thermal shock lifetime of (136 ± 16) cycles for the coating deposited with a CPSP value of 0.94kW/Lpm is obtained during thermal shock test at 1350 °C. [ABSTRACT FROM AUTHOR]

Reticulated ceramic filters play an important role in the reduction of non-metallic inclusions in molten steel, which can improve the quality of steel products. In this work, periclase-magnesium aluminate spinel ceramic filters with Al 2 O 3 and TiO 2 functional coatings were fabricated by using microporous MgO powder, respectively. The effects of the functional coatings on their microstructure, properties and purification capacity on molten steel were studied. The filter with Al 2 O 3 functional coating exhibited the best mechanical properties owing to the good rheological properties of the coating slurry, as well as the formation of in-situ spinel layer connection between the Al 2 O 3 functional coating and the microporous MgO layer of the filter substrate. Compared with the filters without functional coating or with TiO 2 functional coating, the filter with Al 2 O 3 functional coating made more Al 2 O 3 inclusions deposit on the filter surface by physical adsorption due to the same chemical composition between the functional coating and inclusions, which significantly improved the adsorption capacity of filter for Al 2 O 3 inclusions in molten steel. Overall, the filter with Al 2 O 3 functional coating had the highest cold compressive strength of 1.4 MPa, a residual retention of cold compressive strength after thermal shock of 65.71 % and an efficiency of 36.56 % in reducing the total oxygen content of the steel. [ABSTRACT FROM AUTHOR]

Solar thermal power generation is an important direction of energy utilization, and thermal storage materials are the key to ensure the continuous use of energy. In this paper, forsterite - zirconia composite ceramics were prepared by adding different contents of 3Y–ZrO 2 and their physical properties, phase composition, microstructure thermal shock resistance and thermal physical properties were studied. The results showed that the water absorption, bulk density and bending strength of sample A3 sintered at 1600 °C (59.10 wt% fused magnesia, 40.90 wt% quartz and 30 wt% 3Y–ZrO 2) were 0.35 %, 3.27 g/cm3 and 83.66 MPa, respectively. The crystal phase of sample A3 was forsterite and c-ZrO 2. Mg2+ and Y3+ replace Zr4+, formed oxygen vacancy in the anion position, distort the coordination layer and release some interlayer stress to promote the stability of c-ZrO 2. In the sintering process, the zirconia solid solution existed in the form of second phase, which reduced the growth rate of periclase, facilitated the pore discharge in the sample and promotes sintering. The thermal conductivity of forsterite - zirconia composite ceramics at room temperature was 5.52 W/(m·K). At 1000 °C, the specific heat capacity and heat storage density were 1.09 J/(g·K) and 1062.36 kJ/kg, respectively. The forsterite - zirconia composite ceramic prepared in this study was suitable for high temperature environment, its heat storage capacity was excellent, and it was suitable for high temperature heat storage system. [ABSTRACT FROM AUTHOR]

To promote the application of SiC/SiC in hot-end components in aero-engines, the thermal shock behavior of SiC/SiC and SiC/SiC-EBC were investigated in gas combustion environment between 450 °C and 1200 °C. The tensile strength change, microstructure evolution and thermal cycling performance of samples after 200, 400, 1000 and 2000 cycles were studied respectively to reveal the damage and failure mechanism. Cracking damage induced by thermal stress was the main reason for performance degradation of SiC/SiC after initial thermal cycles, then oxidation/corrosion damage dominated with increasing cycles. The oxidation/corrosion damage to SiC/SiC was effectively inhibited by EBC with almost no reduction in strength. However, the poor crack resistance of SiC/SiC was the main factor affecting its thermal shock performance. Improving the crack resistance or self-healing ability of SiC/SiC and combining it with EBC is considered to be an effective strategy to increase its service lifetime. [ABSTRACT FROM AUTHOR]

Alternative binders offer an avenue for advancing ultra-low-cement and cement-free castables while reducing carbon emissions and energy consumption. In this study, geopolymer binders partially or fully replaced calcium aluminate cement (CAC) in high-alumina castables. The formulations underwent diverse testing, including flowability, physico-thermo-mechanical measurements, and XRD, ATR-FTIR, and SEM analyses. The findings highlighted the feasibility of utilizing geopolymers to craft innovative refractories. The formulation comprising 2.7 wt% CAC and 1.3 wt% geopolymer (AT-3 C-1 G*) exhibited the most successful performance. At 1400 °C, these samples displayed shrinkage of 1.18%, elastic modulus of 135 GPa, flexural strength of 39.1 MPa, and high thermal shock resistance (∆T∼1000 °C). The interaction between CAC and geopolymer inhibited cement hydration while enhancing the geopolymerization process. Moreover, firing the samples at 800–1400 °C led to liquid phase and nepheline formation from the geopolymeric gel, resulting in viscous sintering and improved ceramic densification. These developments produced refractories with remarkable overall performance, surpassing the reference material. [ABSTRACT FROM AUTHOR]

The effect of critical plasma spraying parameters (CPSPs) on phase composition, microstructure and mechanical property of (La 0.2 Nd 0.2 Sm 0.2 Eu 0.2 Gd 0.2) 2 Zr 2 O 7 thick coatings was investigated. After coating deposition, the phase structure of (La 0.2 Nd 0.2 Sm 0.2 Eu 0.2 Gd 0.2) 2 Zr 2 O 7 was transformed from pyrochlore to fluorite in the coating. When the CPSP value increased from 0.83kW/Lpm to 1.17kW/Lpm, the porosity of as-deposited coating was decreased from (16.46 ± 0.65)% to (6.94 ± 0.44)%. As a result, the elastic modulus of the coating was improved from (59.34 ± 2.39) GPa to (79.19 ± 4.78) GPa, and the corresponding micro-hardness was also increased from (2.59 ± 0.30) GPa to (3.39 ± 0.37) GPa. Consequently, the fracture toughness of as-deposited coating was decreased with the increasing CPSP value, while the corresponding residual stress was obtained to be compressive stress and it increased from -(43.00 ± 1.96) MPa to -(70.42 ± 3.89) MPa, indicating that the lower CPSP value was beneficial to reducing the residual compressive stress, which might be in favor of enhancing thermal shock resistance of coating. [ABSTRACT FROM AUTHOR]

Y 2 O 3 /AlN composite films with different thicknesses of AlN interlayer were prepared on CVD diamond by RF magnetron sputtering. The influence of AlN thickness on the microstructure, adhesion strength, film stress, thermal shock resistance and infrared transmittance of the films was investigated by X-ray diffractometer, scanning electron microscopy, scanning probe microscopy, UV–Vis spectrophotometer, Fourier transform infrared spectrometer, scratch tester and 3-D optical surface profiler. The results show that CVD diamond coated with Y 2 O 3 /AlN composite films with different thicknesses of AlN have different degrees of anti-reflective effects in the 8–10 μm infrared band. The adhesion strength and quality of the composite film were improved with the AlN thickness increased, and the anti-reflective and anti-thermal shock of the film showed a trend of first increasing and then decreasing. CVD diamond coated with Y 2 O 3 /AlN composite films with 700 nm AlN interlayer has an average transmittance of 77 % in the 8–10 μm band and a good adhesion between interfaces. It can withstand rapid temperature changes and effectively protect the diamond substrate with little or no degradation of infrared optical properties. [ABSTRACT FROM AUTHOR]

In order to solve the challenge of poor protection of conventional NbSi 2 coatings in high temperature oxidation environments, a new TiB 2 -modified (Nb,Mo,Cr)Si 2 composite ceramic coating was prepared on the surface of Nb521 substrate by triple slurry sintering method. The composite ceramic coating maintained the complete morphology after oxidation at 1600 ℃ for 15 h, due to the oxide layer TiO 2 -(Ti 0.6 Cr 0.2 Nb 0.2)O 2 -SiO 2 formed on the coating surface, which could effectively reduce the volatilization behavior of SiO 2 and prolongue the oxidation life of the coating by wrapping the SiO 2 layer. In addition, the coating successfully withstood 1500 cycles from room temperature to 1600 ℃, due to the fact that CrSi 2 and MoSi 2 significantly modulated the difference in thermal expansion coefficients between the Nb521 substrate and the NbSi 2 coating, making the thermal stress generated during the thermal shock cycle lower than the intrinsic strength of the coating. [ABSTRACT FROM AUTHOR]

Clean energy advances can drive solid heat storage technology. Because of their high-temperature, corrosion, and excellent thermal shock resistance properties, refractory oxides are widely used as solid heat storage materials. However, their applications are limited owing to their poor heat-transfer performance resulting from their multicomponent, multiphase, and complex nature and thus understanding their heat-transfer mechanism will be crucial for their performance optimization. In this study, the thermal properties and mechanisms of corundum, high-alumina, and magnesia bricks were characterized using heat-transfer theories and models. Macroscopic analysis of the bricks revealed that they are all "internal porosity" materials. By comparing the weighting parameter j , the multiphase high-alumina brick shows poor heat-transfer path patency and the measured thermal conductivity is the lowest at 3.55 W m−1 K−1. Microscopic analysis found that in contrast to the thermal conductivity of other materials, the thermal conductivity of high-alumina bricks was significantly affected by phonon intrinsic scattering. Moreover, corundum and magnesia bricks exhibited a wider range of ultimate heat-transfer performance than the high-alumina brick. Hence, the heat-transfer performance of refractory oxide can be enhanced by increasing their particle contact, reducing the negative effects of microcracks, phases, and impurities, and by reducing the number of defects on phonon heat transfer, thereby providing an optimization scheme for improving the heat-transfer performance of the materials. [ABSTRACT FROM AUTHOR]