To enhance the ablation resistance of C/C composites under ultra-high-temperature and long-duration conditions, a non-embedded reactive melt infiltration technique was employed to fabricate an Hf-Si-based coating-matrix integrated modified C/C composite. Microstructural analysis revealed that the coating and matrix primarily consist of HfC, SiC, and HfSi₂, with strong interfacial bonding formed between them through chemical reactions. Within the materials, the matrix density and composition exhibited a gradient distribution along the infiltration direction. Specifically, regions proximal to the infiltration source were denser and rich in HfC-HfSi₂ phases, whereas distal regions were more porous, with the matrix consisting mainly of SiC and Si-HfSi₂ eutectic structure. The surface coating was continuous and dense, with a uniform thickness of approximately 120 µm. It featured a distinct bilayer architecture composed of an outer SiC layer and an inner HfC-HfSi₂-SiC layer. An in-depth investigation of the reaction mechanism revealed that the HfC-SiC-HfSi₂ coating-matrix integrated structure formed through a synergistic effect of melt infiltration-reaction and vapor permeation-deposition. The composite exhibited exceptional ablation resistance when exposed to an oxyacetylene flame. After ablation tests conducted at 2500 ℃ for 60, 180, 600, and 3540 s, the linear ablation rates were -3.52, -1.35, -0.85, and 0.118 μm/s, respectively. This outstanding performance is attributed to the in-situ formation of a dual-layer oxide barrier. A dense, continuous HfO₂ layer generated from the surface coating works in concert with a multiphase HfO₂-SiO₂-HfSiO₄ oxide layer generated from substrate oxidation. Together, these layers effectively retard inward oxygen diffusion and suppress the oxidative ablation process. This work proposes a viable strategy for designing and fabricating high-performance integrated thermal protection structures.

Continuous fiber-reinforced silicon carbide ceramic matrix composites utilized in hot-section components of high thrust-to-weight ratio aero-engines require protection via thermal/environmental barrier coatings (T/EBCs). To develop novel rare-earth oxide thermal barrier coating materials with low thermal conductivity, compatible thermal expansion coefficients, and excellent high-temperature phase stability, introduction of a high-entropy design concept offers a promising approach and opportunity for composition design and performance optimization. Addressing the challenges of structural modeling and property prediction for complex high-entropy ceramic systems, this study firstly introduces a novel high-entropy ceramic modeling strategy based on the special quasi-random structure (SQS) method. This strategy facilitates rapid prediction of complex ceramic properties while maintaining computational accuracy. Subsequently, crystal structures, elastic properties and thermophysical characteristics of four high-entropy rare-earth oxide materials are predicted and compared by integrating first-principles calculations. This research particularly elucidates regulatory effects and atomic-scale origins of different rare-earth compositions and Hf doping on the material’s low thermal conductivity performance. The research results provide scientific insights and fundamental data for theoretical simulation and material selection design of T/EBCs for aero-engine hot-section components.

Carbon fiber-reinforced carbon aerogel (C/CA) composites are one of the most promising candidates for applications requiring both thermal insulation and load bearing capabilities. The preparation of anti-oxidation coatings on C/CA to address its susceptibility to oxidation is a feasible approach to promote its application in oxidative environments. However, the currently reported coatings on C/CA mainly focus on improving the ablation performance and coating preparation process typically necessitating high-temperature heat treatment. This procedure can increase its thermal conductivity and reduce its thermal insulation ability. In this study, a series of ceramic-resin coatings were fabricated on C/CA through a simple slurry brushing-drying approach at room temperature. The effects of phenolic resin content on the coating structure, residual stress, thermal shock, and oxidation behaviors were investigated. Due to the adhesive properties and curing-induced shrinkage, the PR-7.5 coating (containing 7.5% (in mass) phenolic resin in the slurry) exhibits bonding strength close to fracture strength of the substrate and residual compressive stress of 0.853 GPa, which is beneficial for resisting thermal shock cracking. However, excessive resin content (PR-10.0 containing 10.0% (in mass) phenolic resin in the slurry) induces tensile stress due to uneven curing shrinkage, thereby leading to thermal shock cracking. Meanwhile, oxidation tests reveal significantly reduced weight losses for PR-7.5 (17.46% at 800 ℃/100 min, 8.15% at 1000 ℃/120 min, 3.15% at 1200 ℃/120 min) versus uncoated C/CA’s 44.60% loss at 800 ℃/20 min. This work provides a brand-new and simple approach to improving the anti-oxidation performance of C/CA and expands its application in mild oxidative environments.

As the operating temperature of aero-engine rises, degradation of thermal barrier coatings (TBCs) and environmental barrier coatings (EBCs) on hot-section components affected mainly by infiltration of calcium-magnesium-alumina-silicate (CaO-MgO-AlO_1.5-SiO₂, CMAS) has garnered increasing attention. Rare earth constituents play an essential role in forming corrosion products and subsequent melt penetration when conventional TBCs and EBCs are attacked by CMAS deposits. This study focused on preparation of a series of gadolinium-ytterbium oxides ((Gd_xYb_1-x)₂O₃, x=0, 0.05, 0.10, 0.20, 0.30, 0.50 and 1.00), with particular emphasis on the roles of ytterbium and gadolinium. Their reaction with CMAS deposits was systematically investigated at 1300 ℃ to explore the synergistic mechanism associated with these two rare earth elements. The results indicate that gadolinium cations can efficiently induce the crystallization of products with apatite structure which have a low melt consumption. Conversely, ytterbium cations can induce the formation of products with garnet and silicocarnotite structure which have sluggish kinetics. Furthermore, partitioning of gadolinium and ytterbium ions within corrosion products, along with variation of residual CMAS melt composition, was further analyzed. It is proposed that these two rare earth ions exhibit a synergistic effect within a certain composition range (5%-20% (in mole) of gadolinium content). The optimized ratio of gadolinium and ytterbium within coatings is anticipated to promote apatite crystallization, prevent melt penetration, and modify the sluggish crystallization kinetics of garnet and silicocarnotite, thereby significantly improving the melt consumption. This investigation on synergistic effect of gadolinium and ytterbium cations provides a theoretical support for the anti-CMAS-corrosion composition modification of TBCs/EBCs.

Fabrication of feedstock powders is a critical technology that directly influences the microstructure and performance of plasma-sprayed coatings. Conventional boron thermal reduction methods for synthesizing high-entropy boride powders encounter several limitations such as prolonged processing time, impurity contamination, and inability to obtain spray-ready powders. In this work, an inductive plasma spheroidization (IPS) process was employed to fabricate (Zr_1/4Hf_1/4Ta_1/4Ti_1/4)B₂ high-entropy powders for plasma spraying in contrast to the other two traditional powder preparation routes. The morphology, internal structure, particle size distribution, density, and other fundamental properties of powders were systematically characterized. The effects of different powder fabricating processes on the microstructure and fundamental properties of high-entropy boride powders were systematically investigated, thereby validating the broad applicability of this methodology for synthesizing high-entropy boride powders. The results demonstrate that using commercial micron-sized boride powders as precursors, a hybrid process combining mixing, spray drying, sintering with IPS facilitates the fabrication of high-entropy powders with homogeneous elemental distribution. The resulting powders exhibit spherical morphology, smooth surfaces, high internal density, and high apparent/tap density. Further experiments on synthesizing different high-entropy borides with varied compositions confirm the extensive applicability of this method. The formation mechanism of high-entropy solid solutions is elucidated through first-principles calculations combined with the unique characteristics of IPS process. This work proposes a promising method for fabricating high-entropy ceramic powders suitable for plasma-spray coatings.

Key components of aerospace power systems operating under extreme conditions, such as high loads, elevated temperatures, oxygen-rich environments, and wide-temperature-range alternating thermal shocks, impose stringent requirements on material mechanical properties, thermal stability, and oxidation resistance. Conventional thermally sprayed Al₂O₃ coatings, characterized by high hardness, excellent wear resistance, superior oxidation resistance, and good thermal stability, have been widely applied to aerospace, energy, and mechanical engineering fields. However, these coatings primarily consist of metastable γ-Al₂O₃ as the dominant crystalline phase, which exhibits inferior mechanical and thermal conductivity properties compared to α-Al₂O₃. This limitation hinders their effectiveness under extremely high-load conditions. To address this issue and enhance the overall coating performance, atmospheric plasma spraying (APS) was employed to fabricate Al₂O₃-GdAlO₃ (GAP) amorphous coating with a thickness of approximately 350 µm. The friction and wear behavior, along with the mechanical properties of the coating, were systematically investigated through a designed wear test under a load of 2000 N, a rotational speed of 500 r/min, and a duration of 1 h. Experimental results indicate that due to the high proportion of the amorphous phase and the optimized microstructure, the Al₂O₃-GAP coating exhibits excellent wear resistance and superior crack propagation resistance under high-speed and heavy-load friction conditions, significantly outperforming conventional polycrystalline Al₂O₃ coatings. Furthermore, the Al₂O₃-GAP coating demonstrates a lower and more stable friction coefficient, effectively reducing frictional surface temperature. This mitigates high-temperature oxidation and thermal damage while alleviating stress concentration effects. In summary, the Al₂O₃-GAP amorphous coating demonstrates remarkable advantages under high-load, high-speed friction conditions, providing a high-performance and reliable coating solution for the protection of critical aerospace power system components.

Rare earth silicate environmental barrier coatings (EBCs) are important materials that can be applied to hot sections for the new generation of high thrust-to-weight ratio aero engines. However, oxidation and cracking of the silicon bond layer are significant factors leading to failure during service. Modifying the silicon bond layer has become an important method to extend EBCs’ service life. In this work, Yb₂O₃ was doped in the silicon bond layer to mitigate cracking under high-temperature water vapor conditions, as well as to improve its corrosion resistance. Five kinds of EBC systems (Si-Yb₂O₃)/Yb₂Si₂O₇/Yb₂SiO₅ with different Yb₂O₃ doping (0, 5%, 10%, 15%, 20%, in volume) were prepared on SiC substrates using vacuum plasma spraying technology. Their water-oxygen corrosion behavior was studied, and mechanisms at 1350 ℃ beneath their behavior were revealed. The results indicated that doping an appropriate amount (5%) of Yb₂O₃ into silicon effectively facilitates the reaction with SiO₂ and its subsequent consumption during high-temperature water vapor corrosion. This process reduces the stress variations associated with SiO₂ phase transition (β → α) and inhibits formation of longitudinal cracks in mixed thermal growth oxide (mTGO) layer, thus enhancing structural stability. Furthermore, the reaction product of Yb₂Si₂O₇ exhibits a suitable coefficient of thermal expansion (CTE) and chemical compatibility. Notably, increasing Yb₂O₃ content results in formation of interconnected "skeleton" structure within the bond layer, which may provide a direct pathway for oxidizing substances to permeate into the interior of coating, thereby facilitating corrosion process within the bond layer, and ultimately diminishing the water vapor corrosion resistance of EBC systems.

Integrity and denseness of coatings significantly influence their performance. Scrapping and re-preparation of defective or damaged coatings not only lead to material waste but also prolong preparation time. To address the challenge of cost-effectiveness, repairing the coating to restore its protective capability is obviously essential. However, there is rare literature touched effective repairing method for porous SiC ceramic coatings. In this study, a straightforward and cost-effective gaseous silicon infiltration method was employed to repair defects in porous SiC coating prepared by pack cementation. Comparison experiments on thermal shock and ablation resistance of the coating were carried out before and after repair. Results demonstrated that the repaired coating exhibited robust adhesion to its substrate after 15 thermal cycles from room temperature to 1773 K, with a mass loss rate reduction of 97.05% in contrast to the pack cementation SiC coating. After ablation for 30 s, carbon fibers located in the center area of the repaired coating were successfully coated with SiO₂, without naked exposure or damage. The mass and thickness loss rates were reduced by 97.02% and 67.99%, respectively. All above results indicated that thermal shock and ablation resistance of the repaired coating were enhanced, which can be attributed to the increased densification and the reduction of defects in the repaired coating. Therefore, silicon, introduced through gaseous silicon infiltration, is more easily oxidized at elevated temperature to form SiO₂, which effectively heals defects and obstructs oxygen penetration, thereby preventing further oxidative damage to the substrate. This study provides a novel coating repair strategy with good economy and feasibility, constructs a new approach to effectively repair defects and damages of coatings, and enhances their service stability and durability.

With improvement in service temperature of thermal structural components for the new generation hypersonic aircraft, higher requirements are put forward for the phase stability and ablation resistance of the thermal protection coatings (TPCs). Carrying out high-entropy design for traditional transition metal oxide ZrO₂ and HfO₂ coatings, solid-phase reaction and supersonic atmosphere plasma spraying (SAPS) were applied to prepare (Hf_0.125Zr_0.125Sm_0.25Er_0.25Y_0.25)O_2-δ (M1R3O), (Hf_0.2Zr_0.2Sm_0.2Er_0.2Y_0.2)O_2-δ (M2R3O), (Hf_0.25Zr_0.25Sm_0.167Er_0.167Y_0.167)O_2-δ (M3R3O) high-entropy oxide (HEO) coatings. The effects of rare earth content on phase structure evolution, phase stability and ablative resistance of HEO coatings were investigated. M2R3O coating and M3R3O coating possessed excellent phase stability and ablation resistance, which maintained stable phase structure after ablation by oxygen-acetylene flame with heat flux density of 2.38-2.40 MW/m², without decomposition of solid solution and precipitation of rare earth components. Mass ablation rate and linear ablation rate of M2R3O coating after cyclic ablation for 180 s are 0.01 mg/s and -1.16 μm/s, respectively. Compared with M1R3O coating (0.09 mg/s, -1.34 μm/s) and M3R3O coating (0.02 mg/s, -4.51 μm/s), the reductions of ablation rate are 88.9%, 13.4%, respectively, and 50.0%, 74.3% for M2R3O coatings, respectively, presenting the best ablation resistance. M2R3O coating exhibits excellent ablation resistance due to its high melting point (>2200 ℃) and low thermal conductivity ((1.07±0.09) W/(m·K)), which effectively protects the internal SiC transition layer and C/C composites from oxidation damage, avoiding interface cracking caused by the formation of SiO₂ phase.

In the field of optoelectronic devices, p-type transparent semiconductor materials with controllable electrical properties hold significant application value. CuI, as a representative material, still faces considerable technical challenges in terms of preparation processes and doping control. This study successfully developed a new p-type transparent semiconductor material with adjustable electrical properties through manganese cation doping, offering a new approach for the advancement of transparent electronics. The Cu_1-xMn_xI solid solution film, prepared via reactive magnetron sputtering, exhibits unique performance advantages. Firstly, the material can be fabricated at room temperature while maintaining excellent visible light transparency. Secondly, as the manganese doping concentration (x) increases, the grain size of the film gradually decreases, and pronounced crystal cluster aggregation is observed at higher doping concentrations. X-ray photoelectron spectroscopy analysis reveals that manganese ions in the film exist in a mixed valence state of Mn²⁺ and Mn³⁺. Electrical performance characterization shows that the resistivity of the film can be tuned over two orders of magnitude, ranging from 0.017 to 2.5 Ω·cm, while the hole carrier concentration remains stable at a high order of magnitude of 10¹⁸-10¹⁹ cm^-3. Unlike the n-type doping behavior observed in traditional semiconductors, introduction of high-valent manganese ions does not significantly affect the p-type conductivity of the material. This is likely due to the partially localized electronic state formed when manganese replaces cuprous ions. This discovery suggests that the hole conductivity of CuI semiconductors is not easily affected by high-valent manganese ion doping, enabling a wide range of compositional adjustments while maintaining stable p-type conductivity. This study provides a valuable material basis for the development of CuI-based multifunctional transparent electronic devices.

8% (molar fraction) Y₂O₃ stabilized ZrO₂ (8YSZ) ceramics have important applications in fuel cells, thermal barrier coatings, as well as thermal insulation due to their excellent oxygen ionic conductivity and low thermal conductivity. However, their corrosion resistance to water and their behaviors as thermal insulation or structural material in pressurized water reactors during accidents are not fully understood. This study systematically examined the mass, crystal phase, microstructure, mechanical properties, and solution composition of 8YSZ ceramics over time in a dynamic water environment at 350 ℃/17.4 MPa with 0.3 μg/L dissolved oxygen, aiming to simulate a pressurized water reactor environment. It is found that the mass of 8YSZ ceramics increases firstly and then decreases with corrosion duration time. The mass change is influenced by the surface roughness. The weight gain is attributed to the formation of Zr-OH and Y-OH clusters by the entry of water molecules into the ceramics, whereas the weight loss is caused by the metal cations leaching and the dissolution of grains. Phase analysis demonstrates that the cubic 8YSZ after corrosion does not undergo any phase transformation towards tetragonal or monoclinic phases, which is different from the degradation mechanism of tetragonal or partially stabilized zirconia. Changes in surface and cross-section morphology indicate that water molecules enter the interior of the ceramics along defects or microcracks, producing grain boundary damage and changing the fracture mode in the corrosion-affected region from transgranular to intergranular fracture. Compressive and flexural strengths of this ceramics after corrosion do not change significantly, while the Vicker’s hardness decreases slightly, which are related to the formation of pits in the surface layer. As a consequence, depth of the corrosion pit after 1050 h is only 30.8 μm, and the mass change rate of per unit surface area is -0.108×10^-3 mg∙cm^-2∙h^-1, consolidating excellent water corrosion resistance of 8YSZ ceramic. Therefore, 8YSZ ceramics are promising for thermal insulation or structural materials in pressurized water reactors.

The investigation of novel materials exhibiting exceptional resistance to calcium-magnesium-aluminum- silicate (CMAS) corrosion at temperatures of 1300 ℃ and above has emerged as a pivotal objective in the advancement of environmental barrier coatings for aircraft engines in recent years. In this study, atmospheric plasma spraying (APS) technology was employed to fabricate YAG(Y₃Al₅O₁₂)/Al₂O₃ coatings with eutectic composition, which was acknowledged as a promising material possessing outstanding CMAS corrosion resistance, thereby rendering it suitable for application in environmental barrier coatings. The as-deposited coatings were annealed at 1100, 1300, and 1500 ℃ to obtain different microstructures, and the corrosion resistance as well as mechanism of YAG/Al₂O₃ coatings against CMAS were investigated by comparing the corrosion results after exposure to CMAS at 1300 ℃. The reaction products between YAG/Al₂O₃ coatings and CMAS were found to be garnet-structure solid solution, CaAl₂Si₂O₈, and Ca₂MgSi₂O₇. The nearly continuous distribution of the garnet-structure solid solution layer at the reaction interface between YAG/Al₂O₃ coating annealed at 1100 ℃ and CMAS effectively impedes the diffusion of CMAS corrosion elements. For YAG/Al₂O₃ coating annealed at 1500 ℃, the increase in grain size and decrease in grain boundaries reduce the dissolution rate of the coating. Both of the above can affect the competitive precipitation of various products by influencing the ion transport rate in the corrosion process, and then improve the CMAS corrosion resistance of the coating. Moreover, heat-treatment temperature can tailor grain size, which influences both dissolution-precipitation rate and competitive precipitation of reaction products during CMAS corrosion. These findings provide guidance for selecting appropriate heat-treatment temperature and offer a novel approach to optimize CMAS corrosion resistance of YAG/Al₂O₃ coatings through microstructure optimization.

Environmental barrier coating (EBC) is a key material for high power-to-weight ratio aero engine, which can provide effective protection for the hot end components of ceramic matrix composites, and prevent the erosion of gas and environmental corrosive media. At present, high entropy rare earth disilicates ((xRE_1/x)₂Si₂O₇) are the most promising next-generation environmental barrier coatings. In order to enhance the CMAS corrosion resistance of high entropy rare earth disilicates, a novel high entropy (Y_0.25Yb_0.25Er_0.25Tm_0.25)₂Si₂O₇/RE-Si-Al-O (RE=Yb, Y, and La) multiphase ceramic was designed and prepared. The results show that the RE-Si-Al-O glass phase can not only wrap the ceramic grains, but also exist at the grain boundaries. Moreover, this multiphase ceramics can promote the growth of rare earth disilicate grains, reduce the number of grain boundaries, and decrease the number of diffusion channel of CMAS melt. As the radius of rare earth ion in the RE-Si-Al-O glass phase increases, the glass phase is more prone to react with Ca²⁺ ion in the CMAS melt, generating apatite, reducing the activity of the CMAS melt, inhibiting the erosion of high entropy rare earth disilicate grains by the CMAS molten salt, and thus improving the CMAS corrosion resistance of high entropy rare earth disilicates. After corrosion at 1500 ℃ for 48 h, there is still a residual CMAS layer on the surface of (Y_0.25Yb_0.25Er_0.25Tm_0.25)₂Si₂O₇/La-Si-Al-O multiphase ceramics, indicating that the multiphase ceramics have good resistance to CMAS corrosion. In conclusion, the microstructure design of this multiphase ceramic provides a new approach to improve the long-term application of EBC materials in high-temperature CMAS environments.

The integration of ceramic matrix composites with environmental barrier coatings (CMC-EBC) represents the most promising thermal structural material system in the aerospace field. This paper provides an overview of the advancements in research on the failure mechanisms and numerical models of CMC-EBC. It commences with a concise review of the evolution and primary fabrication techniques of CMC-EBC material system. Subsequently, it summarizes the typical damage modes and failure mechanisms of CMC-EBC under operational conditions, identifying that the interplay between the CMC preform structure, porosity defects, and EBC inner cracks is a critical determinant of the material’s lifespan. However, current mechanistic studies are chiefly focused on the performance evaluation of the coating itself and its susceptibility to environmental factors, disregarding the synergistic effects of the coating and composite architecture during damage progression. This review proceeds with an examination of the history and current status of research on failure simulation and prediction models for CMC-EBC, highlighting issues related to modeling environmental factors and simulating coupled damage evolution. Though much effort has directly developed separate failure models for CMC and EBC, predicting the failure of CMC-EBC components should account for the coupling effects between damage evolution and microstructure. In conclusion, this review offers a perspective on development and service performance prediction methods for CMC-EBC system, which points out that considering the interdependent failure modes of the CMC substrate and EBC is pivotal. Integrated design and analysis of structural and functional aspects are emerging trends in CMC-EBC component research.

In order to improve the ablation resistance of carbon-based materials in elevated-temperature and oxygenated environments, Ti-doped HfB₂-SiC and ZrB₂-SiC composite coatings were prepared on the surface of graphite via a hybrid method involving slurry dipping and reactive infiltration. Phase compositions, microstructures, and element distributions of the composite coatings were studied, and anti-ablation ability of the coating was evaluated at 2300 ℃. Results show that structures of Ti-doped Hf(Zr)B₂-SiC composite coatings are very dense after silicon infiltration. Both HfTiB₂ and ZrTiB₂ ceramic phases are embedded in the coatings, which exhibit no defects and establish robust bonds with the graphite substrates. Residual silicon continuously distributes around Hf(Zr)B₂ and SiC particles. After undergoing ablation at 2300 ℃ for 480 s, the mass ablation rates of HfTiB₂-SiC and ZrTiB₂-SiC composite coating samples are -2.71×10^-3 and -4.20×10^-1 mg/s, respectively, indicating a slight weight gain. The corresponding line ablation rates are 1.88×10^-4 and 3.70×10^-4 μm/s, respectively. Following ablation, a Hf-Ti-Si-O multiphase oxide layer composed of HfTiO₄-HfO₂ as the skeleton and TiO₂-SiO₂ as the filling phase forms on the surface of HfTiB₂-SiC coating. In contrast, a Zr-Ti-Si-O multiphase oxide layer with some micropores, comprising embedded ZrTiO₄ and ZrO₂ phases and a semi-continuous SiO₂ glass phase, develops on the ablative surface of ZrTiB₂-SiC coating. High-melting-point phases, such as HfTiO₄, HfO₂, ZrTiO₄, and ZrO₂, effectively counteract high-temperature flame erosion. Meanwhile, TiO₂ and SiO₂, possessing high-temperature fluidity, can seal the pore defects generated by erosion and thereby preventing oxygen from diffusing into the coatings and substrates. Therefore, the synergy between high-temperature skeletons and filling phases significantly enhances the anti-ablation protection of coatings.

Carbide ultra-high temperature ceramics (UHTCs) have emerged as ideal coating materials for the thermal protection systems of hypersonic vehicles due to their high melting point (>3000 ℃), high hardness, low thermal conductivity, excellent heat resistance, and good chemical stability. This review provides a comprehensive overview of structure and properties of carbide UHTCs, namely TiC, ZrC, HfC, NbC, and TaC. Furthermore, it summarizes recent developments in preparation of carbide UHTC coatings using various methods, including chemical vapor deposition, plasma spraying, and solid-phase reaction. Effects of coating microstructure, composition, structural design, and heat flux on the ablation behavior are analyzed. Data from recent literature corroborate that the added second phase can facilitate formation of complex oxides, generate an oxidation layer during ablation to undergo moderate sintering, protect structural integrity, and enhance oxygen barrier properties. Multi-layer structural designs utilize gradient layering and multi-functional structures, which effectively alleviate thermal stress within the coating, suppress crack propagation, and facilitate synergistic enhancing effects among different layers. Finally, the challenges and opportunities in development of carbide UHTC anti-ablation coatings are prospected.

Rare-earth zirconates (REZs) have attracted attention in the field of thermal barrier materials because they are more resistant to calcium-magnesium-aluminum-silicon oxide (CMAS) corrosion than yttria stabilized zirconia (YSZ). High-entropy design of zirconates is an effective method to enhance CMAS corrosion resistance, but currently the ability of its corrosion resistance still does not meet the growing requirement. In this work, a solid-state reaction technique was used to synthesize high-entropy rare-earth zirconate (HE-REZ) (Y_0.2Gd_0.2Er_0.2Yb_0.2Lu_0.2)₂Zr₂O₇ powder with a single-phased defect fluorite structure, and pressureless sintering (PLS) combined with cold isostatic pressing (CIP) technique was used to efficiently prepare bulk samples. The phase composition, microstructure, element distribution, thermal and mechanical properties were studied, focusing on the CMAS corrosion resistance. According to the results, under the same CMAS corrosion environment at 1300 ℃, the corrosion depth of HE-REZ with a relative density of 98.6% is only 2.6% of 7YSZ and 22.6% of Gd₂Zr₂O₇ (GZO). The synergistic effect of zirconates' chemical inertness and high-entropy materials' sluggish diffusion accounts for this exceptional corrosion resistance. The obtained HE-REZ shows higher hardness and Young's modulus, larger coefficient of linear expansion, and lower thermal conductivity than ever, making its mechanical and thermal properties superior to GZO. All these outcomes demonstrate the good application potential of (Y_0.2Gd_0.2Er_0.2Yb_0.2Lu_0.2)₂Zr₂O₇ in the field of thermal barrier materials.

With the rising of the gas inlet temperature in front of the turbine of aero-engine, ceramic matrix composites (CMCs) have emerged as the preferred matrix material for the new generation of high-temperature components in aero-engine due to their light weight, high strength, oxidation resistance, insensitivity to crack, and excellent temperature durability. However, because of their limited resistance to high temperature water vapor and oxygen erosion, development of thermal spray coating technology for hot-end components of CMCs engines has become an urgent challenge to be overcome. In this paper, based upon changes of material selection strategies and application examples of foreign aero-engines, technical limitations of the employed superalloys + film cooling + thermal barrier coatings (TBCs) for hot-end components of aero-engines were analyzed, and technical advantages of the utilized CMCs + appropriate film cooling + environmental barrier coatings (EBCs) were consolidated. Thermal and environmental barrier coatings (TEBCs) and environmental barrier coatings-abradable sealing coatings (EBCs-ASCs) for CMCs were reviewed on the basis of recent research findings from domestic and oversea scholars. Finally, opportunities and challenges associated with thermal spraying EBCs for higher temperature gas flow were analyzed, and the direction of design and preparation on a certain composition and structure for TEBCs was clarified, among which the focal points of future research endeavors were prospected.