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This study focuses on enhancing the thermal cycling resistance of multi-layered thermal barrier coatings (TBCs) developed using the atmospheric plasma spraying (APS) method with YSZ/Sm 2 Zr 2 O 7 compositions. Two distinct coating architectures were analyzed: a double-layer system comprising a YSZ intermediate layer sandwiched between a Sm 2 Zr 2 O 7 top coat and a NiCrAlY bond coat, and a functionally graded coating with a gradually varying YSZ/Sm 2 Zr 2 O 7 composition across its thickness. Thermal cycling tests revealed significant delamination, oxide discontinuities, and crack formation in the double-layered systems, which were notably absent in the functionally graded coatings, indicating superior resistance to cyclic thermal fatigue. SEM and EDAX analyses highlighted the formation of craters and a discontinuous oxide scale in the double-layered coatings, while the graded systems exhibited enhanced structural integrity and minimal defect formation. Thermal shock tests further emphasized the advantages of the graded design, revealing prominent phase transformations in all systems. Single-layer Sm 2 Zr 2 O 7 coatings predominantly transformed into cubic Sm 2 Zr 2 O 7 and Sm 2 O 3 , while double-layered systems showed increased monoclinic ZrO 2 and Sm 2 O 3 . In contrast, the graded coatings maintained a high intensity of tetragonal ZrO 2 , coupled with cubic Sm 2 O 3 and monoclinic ZrO 2 , reflecting improved phase stability under thermal shock conditions. These results underscore the potential of functionally graded coatings to outperform conventional designs by mitigating thermal stresses and maintaining structural integrity. Future work will extend these findings by investigating the behavior of these coatings under diverse extreme conditions, including salt spray corrosion, isothermal oxidation, and hot corrosion, to further validate their applicability in high-performance thermal barrier systems.

High entropy alloys (HEA) are frequently employed as catalysts in electrocatalytic hydrogen evolution. However, the traditional high entropy alloy synthesis methods are time-consuming, energy-intensive, and environmentally polluting, which limits their application in the hydrogen evolution reaction (HER). This study leveraged the capabilities of flash Joule heating (FJH) to synthesize carbon-supported high-entropy alloy sulfide nanoparticles (CC-S-HEA) on carbon cloth (CC) with good self-standing properties within 300 ms. The carbon thermal shock generated by the Joule heating could pyrolyze the sulfur source into gas, resulting in numerous pore structures and defects on CC, forming an S-doped carbon substrate (CC-S). Then the S atoms were used to stably anchor the metal atoms on CC-S to form high-density uniformly dispersed HEA particles. The electrochemical test results demonstrated that CC-S-HEA prepared at 60 V flash voltage had HER performance comparable to Pt/C. The density functional theory (DFT) calculation indicated that the S atoms on CC-S accelerated the electron transfer between the carbon substrate and HEA particles. Moreover, the unique electronic structure of CC-S-HEA was beneficial to H* adsorption and promoted catalytic kinetics. The simplicity and versatility of FJH synthesis are of great significance for optimizing the synthesis of HEA and improving the quality of HEA products, which provides a broad application prospect for the synthesis of nanocatalysts with efficient HER performance.

To reveal the thermal shock resistance of double-layer thermal barrier coatings (TBCs), two types of TBCs were prepared via atmospheric plasma spraying, i.e., Gd2Zr2O7/yttria-stabilized zirconia (GZ/YSZ) TBCs and La2Zr2O7 (LZ)/YSZ TBCs, respectively. Subsequently, thermal cycling tests of the two TBCs were conducted at 1100 °C and their thermal shock resistance and failure mechanism were comparatively investigated through experiments and the finite element method. The results showed that the thermal shock failure of the two TBCs occurred inside the top ceramic coating. However, the GZ/YSZ TBCs had longer thermal cycling life. It was the mechanical properties of the top ceramic coating, and the thermal stresses arising from the thermal mismatch between the top ceramic coating and the substrate that determined the thermal cycling life of the two TBCs together. Compared with the LZ layer in the LZ/YSZ TBCs, the GZ layer in the GZ/YSZ TBCs had smaller elastic modulus, larger fracture toughness, and smaller thermal stresses, which led to the higher crack propagation resistance and less spallation tendency of the GZ/YSZ TBCs. Therefore, the GZ/YSZ TBCs exhibited superior thermal shock resistance to the LZ/YSZ TBCs.

A comprehensive understanding of the physico-mechanical behavior of rocks in hot dry rock (HDR) reservoir after different stimulation treatments is essential for the safe and effective exploitation of geothermal energy. In this study, the physico-mechanical properties of high-temperature granite (25–600 °C) subjected to slow cooling, water cooling, and liquid nitrogen (LN2) cooling were experimentally investigated, and the damage evolution and damage mechanism of the rock were discussed from the macro- and microscopic perspectives. According to the experimental results, the increase in thermal treatment temperature aggravates the deterioration of the physico-mechanical properties of granite specimens. It is found that 400 °C is the threshold temperature of the tested granite, after which the physico-mechanical properties of the rock present more prominent changes. Since LN2 can induce a more intense thermal shock within rocks, it has the most significant damage to the specimens compared with other two cooling methods, especially at a higher thermal treatment temperature. Acoustic emission (AE) monitoring can well reflect the failure process and the associated microcrack behavior of the specimens during loading. The results of thin slice analysis indicate that the generation and extension of microcracks are responsible for the macro-properties degradation of rocks. Both grain boundary and intra-grain microcracks are more common near quartz boundaries and inside quartz grains. The results in this study would shed light on performing HDR reservoir stimulations assisted with cryogenic LN2.

In this work, functionally graded lanthanum magnesium hexaluminate (LaMgAl11O19)/yttria-stabilised zirconia (YSZ) thermal barrier coating (FG-TBC), in as-sprayed and laser-glazed conditions, were investigated for their thermal shock resistance and thermal insulation properties. Results were compared with those of a dual-layered coating of LaMgAl11O19 and YSZ (DC-TBC). Thermal shock tests at 1100 °C revealed that the as-sprayed FG-TBC had improved thermal stability, i.e., higher cycle lifetime than the as-sprayed DC-TBC due to its gradient architecture, which minimised stress concentration across its thickness. In contrast, DC-TBC spalled at the interface due to the difference in the coefficient of thermal expansion between the LaMgAl11O19 and YSZ layers. Laser glazing improved cycle lifetimes of both the types of coatings. Microstructural changes, mainly the formation of segmentation cracks in the laser-glazed surfaces, provided strain tolerance during thermal cycles. Infrared rapid heating of the coatings up to 1000 °C showed that the laser-glazed FG-TBC had better thermal insulation capability, as interlamellar pores entrapped gas and constrained heat transfer across its thickness. From the investigation, it is inferred that (i) FG-TBC has better thermal shock resistance and thermal insulation capability than DC-TBC and (ii) laser glazing can significantly enhance the overall thermal performance of the coatings. Laser-glazed FG-TBC provides the best heat management, and has good potential for applications that require effective heat management, such as in gas turbines.

In this work, new double-layer YSZ/La 2 Ce 2 O 7 (LC) + YSZ coatings were developed using air plasma spraying (APS). The surface of the prepared coatings was relatively smooth and consisted of melted and partially melted areas. Their resistance to hot corrosion, CaO-MgO-Al 2 O 3 -SiO 2 (CMAS), and thermal shock were examined. YSZ was added to the upper layer to enhance the lanthanum cerate (La 2 Ce 2 O 7 , LC) properties. During the hot corrosion tests, the corrosion salt reacted with the upper layer, and the CeO 2 phase and new corrosion products were identified. The main phase was LaVO 4 , and the secondary phases were CeVO 4 and YVO 4 . SEM confirmed the formation of new, cuboidal-shaped corrosion products. The infiltration of CMAS led to the formation of additional new products: Ca 4 Mg x Al 4 Si (6-x-γ) O 14 and Ca 2.8 (La x Ce 1-x ). 6 (SiO 4 )O 6-4x . SEM revealed CMAS infiltration through the upper layer in the form of islands. Following the thermal shock resistance tests, the upper layer gradually peeled off, and the coating survived 67 cycles. Possible failure mechanisms were identified, and failure was attributed to the spallation of the upper layer from the surface layer by layer. After all tests, the top layer showed partial spalling and delamination. This was mainly caused by the reaction of corrosive salt or CMAS with the top layer, which changed its composition, leading to the formation and propagation of cracks and, ultimately, the separation of part of the upper layer. Peeling of the upper layer through mainly horizontal cracks was observed after hot corrosion, CMAS and thermal shocks. The NiCrAlY bond coat and YSZ interlayer remained undamaged.

Cordierite diesel particulate filters (DPFs) were prepared using pure cordierite powder with organic binders, sodium silicate aids and pore formers by extrusion technique. The orthogonal test method was adopted to investigate the optimal value of the multi-objective and multi-factor problems. Based on results from statistical analysis, sintering temperature is the most important factor. The optimal parameters for balanced overall performance were determined as a 3 h holding time, 10 wt.% pore former, 12 wt.% sintering aid, and a sintering temperature of 1150 °C, representing a compromise among the individually optimal conditions for porosity, compressive strength, and thermal shock resistance identified by range analysis. The sodium silicate liquid increased and viscosity decreased with the increasing of temperature, which led to the formation of glass phases and the improvement of density. Therefore, with increasing sintering temperature, the porosity and coefficient of thermal expansion decreased. Both the mechanical properties and chemical stability of the prepared samples are strengthened. When the sintering temperature was 1150 °C, the prepared samples with high porosity (56.04%), compressive strength (5.88 MPa), bending strength (13.10 MPa), and low thermal expansion coefficient (CTE, 1.82 × 10 /°C) showed the best comprehensive performance of thermal shock resistance and filtration efficiency. These results demonstrate great potential for DPF applications and provide a reference for the design of other honeycomb ceramics with optimum level of liquid phase.

Porous Ca2Mg2Al28O46 (C2M2A14) ceramics are highly competitive candidates in the field of critical metal filtration due to their attractive non-metallic-inclusions removal capacity. However, the low mechanical strength and inadequate thermal shock resistance (TSR) of these materials restrict their further application. In this work, ZrO2-toughened C2M2A14-based porous ceramics are fabricated by using the polymer sponge replica method. Nano-sized ZrO2 particles derived from nano-ZrO2 sol are beneficial to enhance the mechanical properties and TSR of porous ceramics. The optimized porous C2M2A14 ceramics exhibit robust compressive strength (2.15 MPa), good residual strength ratio (66.4%) and excellent filtration efficiency in the reduction in total oxygen content (68.4%) by adding 3 wt% ZrO2 sol. These excellent comprehensive properties show that as-prepared porous C2M2A14 ceramics are promising candidate materials for application in the field of critical metal filtration.

Yttria-stabilized zirconia (YSZ) fiber composites are highly efficient thermal insulating materials; however, the poor thermal shock resistance limits their versatile applications. In the present study, YSZ fiber was mixed directly with Al2TiO5 fiber, which had an extremely low thermal expansion coefficient, to prepare YSZ−Al 2 TiO 5 (ZAT) fiber composites by compression molding and heat treatment. The minimum thermal expansion coefficient of the prepared ZAT fiber composites was measured to be 7.74×10 −6 K −1 , which was 26% lower than that of the YSZ fiber composites (10.42×10 −6 K −1 ). It was shown that the prepared ZAT fiber composites maintain the integrity after undergoing 51 thermal shock cycles between 1100 °C and room temperature. Whereas, YSZ fiber composites burst immediately after only one thermal shock cycle under the same condition. In addition, the ZAT fiber composites also exhibit considerable mechanical and thermal insulating performance.

Double ceramic layer thermal barrier coatings (DLC-TBCs) are favored for combining the benefits of top and bottom ceramic materials. The thickness ratio of the top and bottom ceramic layers significantly impacts the performance of the DLC-TBCs. In the design process, it is generally desired to balance its thermal insulation properties with a long service life. Therefore, this study establishes a multi-objective parameter optimization design method based on NSGA-II to optimize the thickness of the CeYSZ/Al 2 O 3 DCL-TBCs. Experimental verification of the coating performance was conducted based on the optimization results. Firstly, based on theoretical and numerical models, a quantitative analysis was conducted on the effects of the thickness of each material in the CeYSZ/Al 2 O 3 DCL-TBCs system on thermal insulation and thermal stress. Space parameters were obtained using optimal Latin hypercube sampling, and a radial basis function (RBF) neural network surrogate model was constructed based on the numerical calculation results. Sensitivity analysis was employed to evaluate the impact of the total thickness of the TBCs and the thickness of the Al 2 O 3 ceramic layer on the objective function. Finally, NSGA-II was utilized for optimization. The obtained Pareto optimal solution set was validated, showing that the performance of the CeYSZ 190 μm/Al 2 O 3 120 μm DLC-TBCs satisfied the requirements. Therefore, TBCs of different thicknesses were sprayed and subjected to thermal insulation and thermal shock experiments. The results demonstrated that the optimized TBCs significantly improved service life without compromising thermal insulation, providing a new approach for the subsequent design of DLC-TBCs structures.