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Low thermal conductivities and high thermal expansion coefficients are desirable for rare-earth zirconate thermal barrier coating materials. Introduction of cation doping and adjustment of the nonstoichiometry are efficient methods for enhancing the thermophysical characteristics of materials. Herein, the thermophysical properties of Yb3+-doped nonstoichiometric gadolinium zirconate ceramic materials were investigated using first-principles calculations and solid-state reaction techniques. As the Yb3+ content increases, additional cations enter the interstitial spaces (for excess Gd3+ gadolinium zirconate) and form vacancy defects (for excess Zr4+ gadolinium zirconate), which serve as phonon scattering centres to decrease the thermal conductivity. When Yb3+ is doped at the same concentration, gadolinium zirconate with excess Zr4+ exhibits a lower thermal conductivity. Specifically, Gd 1.875 Yb 0.25 Zr 2.125 O 7 shows the lowest minimum thermal conductivity of 1.133 W/(m⸱K) (according to the Clark model) and 1.241 W/(m⸱K) (according to the Cahill model). In addition, the experimental results also suggest that the optimal content of Yb3+ is 0.25 excess Zr4+ gadolinium zirconate, which has the lowest intrinsic thermal conductivity of 1.037 W/(m⸱K) at 1300 K. Moreover, the thermal expansion coefficient of the Yb3+-doped excess Gd3+ nonstoichiometric material is greater than that of the doped excess Zr4+ material, this is due to the greater electronegativity difference between Yb3+ and Zr4+ than that between Yb3+ and Gd3+ and the lower binding energy of Gd-O than that of Zr-O. The experimental results and the calculated results are in good agreement. The aim of this work is to enhance the thermophysical characteristics of gadolinium zirconate ceramics for use as thermal barrier coating materials. [ABSTRACT FROM AUTHOR]

Previous results clearly confirmed that the presence of an Al plating layer promotes the development of a dense Al 2 O 3 barrier layer when exposed to high temperatures. This enhances the structural stability and improves the oxidation resistance of the dual ceramic coating. In the work, a continuous study was conducted to investigate the effect of varying Al plating layer thickness on the high-temperature oxidation characteristics of a CoCrNiAlY–YSZ–LMA dual ceramic coating. The results indicate that, compared to samples lacking Al layers, all Al-coated samples exhibit dense surface morphology, effectively inhibiting the permeation of O 2. This results in slower growth of the TGO and minimal elemental diffusion. However, significant differences are observed in structural damage. Al layers of 5 μm and 10 μm thickness show slight local fracture damage and good structural stability. In contrast, the 15 μm Al-coated samples experience more severe structural fracture damage within the YSZ layer, including transverse cracking. These potential oxidation and structural damage mechanisms of the coatings with varying Al plating layer thickness were systematically discussed. [ABSTRACT FROM AUTHOR]

Zircon (ZrSiO 4) is an inexpensive and widely available material with excellent thermal properties that makes it an ideal candidate for thermal barrier coatings. Previous works have demonstrated the feasibility of obtaining coatings with a high retention of zircon by plasma spraying of ZrSiO 4 and ZrSiO 4 /ZrO 2 suspensions. Suspensions of ZrSiO 4 /Al 2 O 3 and ZrSiO 4 /TiO 2 were produced by dispersing a micrometric zircon powder into alumina and titania colloidal sols, optimising their colloidal stability and rheological behaviour. Optimised slurries were plasma sprayed onto metallic substrates, obtaining coatings with the typical morphologies obtained by suspension plasma spraying (SPS). Nanostructured coatings with nanoparticles embedded in the molten matrix were obtained at higher proportions of sprayed colloidal sol. The high retention of ZrSiO 4 in the final coatings and the formation of new crystallographic phases of mullite and zirconium titanate by reaction of the by-products of zircon decomposition (SiO 2 and ZrO 2) and the Al 2 O 3 and TiO 2 colloids was demonstrated. [ABSTRACT FROM AUTHOR]

Molten calcium-magnesium-alumina-silicate (CMAS) corrosion has become a major constraint for the application of YSZ thermal barrier coatings (TBCs). In this paper, Al 2 O 3 and YSZ-Al 2 O 3 protective layers with a thickness of 50 μm were prepared on the surface of 8YSZ TBCs using air plasma spraying technology, and the progressive damage modes of the different TBCs under CMAS exposure were investigated, and the effects of the composition and microstructure of the protective layers on the infiltration and wetting behaviour of CMAS were compared. When the exposure time was shorter, the dense YSZ-Al 2 O 3 had a better impermeability barrier effect. As the interaction time between CMAS and the coating was prolonged, the structure and phase stability of YSZ-Al 2 O 3 were damaged, the thickness was thinned, and Al 2 O 3 had better stability and showed better protective effect. CMAS wettability was mainly related to the roughness of the coating surface, and the wettability was poorer on rough surfaces. [ABSTRACT FROM AUTHOR]

Hafnium-based ceramic with low thermal expansion is suitable for thermal and environmental barrier coating materials. However, the fracture toughness is relatively low. In this work, GdAlO 3 is doped into Gd 2 Hf 2 O 7 , increasing the fracture toughness by 31 %. The increase originates from crack deflecting, crack branching and more tortuous crack route. Meanwhile, GdAlO 3 -Gd 2 Hf 2 O 7 has lower thermal expansion, making it more compatible with environmental barrier coating systems. The thermal conductivity increases from Gd 2 Hf 2 O 7 to GdAlO 3 -Gd 2 Hf 2 O 7 , which can be expected to reduce by controlling the content of GdAlO 3. [ABSTRACT FROM AUTHOR]

This paper is the first to look at the structural, electronic, mechanical, optical, and thermodynamic properties of the ANiX (ASc, Ti, Y, Zr, Hf; XBi, Sn) half‐Heusler (HH) using DFT based first principles method. The lattice parameters that we have calculated are very similar to those obtained in prior investigations with theoretical and experimental data. The positive phonon dispersion curve confirm the dynamical stability of ANiX (ASc, Ti, Y, Zr, Hf; XBi, Sn). The electronic band structure and DOS confirmed that the studied materials ANiX (ASc, Ti, Y, Zr, Hf; XBi, Sn) are direct band gap semiconductors. The investigation also determined significant constants, including dielectric function, absorption, conductivity, reflectivity, refractive index, and loss function. These optical observations unveiled our compounds potential utilization in various electronic and optoelectronic device applications. The elastic constants were used to fulfill the Born criteria, confirming the mechanical stability and ductility of the solids ANiX (ASc, Ti, Y, Zr, Hf; XBi, Sn). The calculated elastic modulus revealed that our studied compounds are elastically anisotropic. Moreover, ANiX (ASc, Ti, Y, Zr, Hf; XBi, Sn) has a very low minimum thermal conductivity (Kmin), and a low Debye temperature (θD), which indicating their appropriateness for utilization in thermal barrier coating (TBC) applications. The Helmholtz free energy (F), internal energy (E), entropy (S), and specific heat capacity (Cv) are determined by calculations derived from the phonon density of states. [ABSTRACT FROM AUTHOR]

Understanding the damage evolution of thermal barrier coatings (TBCs) is crucial for optimizing TBCs systems and predicting service lifetime. This study investigates the correlation between mechanical properties and the thermal cycle lifetime of TBCs with conventional air plasma sprayed (APS) and micro-agglomerated particles embedded (EMAP) plasma sprayed structures, utilizing the Gd 2 Zr 2 O 7 (GZO) and GSc 0.075 Ce 0.3 Z (GSCZ) material systems. The damage evolution and cracking behavior of TBCs with varying material compositions and coating structures are evaluated using a combination of three-point bending tests and digital image correlation (DIC) techniques. Experimental results demonstrate that the thermal cycling lifetime of conventional APS TBCs correlates positively with the fracture toughness of the ceramic layer. Specifically, the conventional APS GSCZ coating with a fracture toughness of 1.12 MPa/m1/2 and the APS GZO coating with a fracture toughness of 0.97 MPa/m1/2 exhibit lifetimes of 34 cycles and 31 cycles, respectively. Moreover, the EMAP structural design exhibits notable advantages in enhancing the thermal cycle lifetime of TBCs across all material systems. DIC results confirm that strain accumulation during interface cracking of EMAP TBCs is effectively mitigated compared to conventional APS TBCs. The loose and porous characteristics of this structure significantly improve the compliance and interface fracture toughness of the TBC system, thereby alleviating TBC failure dominated by interface cracking. [ABSTRACT FROM AUTHOR]

The performance of plasma sprayed thermal barrier coatings (TBCs) is strongly dependent on the quality of the feedstock powders, which usually are fabricated by conventional spray drying and multi-step sintering methods. In this work, a novel supersonic plasma spheroidization technology was employed to fabricate the spherical nanocrystalline Sc 2 O 3 -Y 2 O 3 co-stabilized ZrO 2 (ScYSZ) powder. The deformation process from the irregular powder to the spherical one was stimulated by the COMSOL phase field simulation. The results suggested that the original irregular pyrolysis products of ScYSZ precursors were aggregated into spherical powders by plasma spheroidization technology. The COMSOL simulations verified that the powder changed from irregular particles to spherical ones. The spheroidized ScYSZ particles exclusively consisted of non-transformed t' -ZrO 2 phase and showed good fluidity, smooth surface and high apparent density, which were expected to have a broader application prospect in the field of TBCs and other ceramic coatings. [ABSTRACT FROM AUTHOR]

High-entropy ceramics have potential as thermal barrier coatings (TBCs) and a new way to reduce thermal conductivity. (Gd 0.25 Ho 0.25 Er 0.25 Yb 0.25) 3 NbO 7 (4RE 3 NbO 7) and (Ho 0.33 Er 0.33 Yb 0.33) 3 NbO 7 (3RE 3 NbO 7) rare-earth niobates with disordered defective fluorite structures were synthesized using the solid-phase method. They show prominent phase stability at 1400 °C and excellent chemical compatibility with Al 2 O 3 at 1200 °C. The SEM and EDS results show that the samples have a dense and uniform grain structure, and the average grain size is less than 2 μm. The uniform distributions of rare earth cations further indicate the successful realization of equimolar ratio doping. Compared to yttrium oxide-stabilized zirconia (YSZ) materials, both 4RE 3 NbO 7 and 3RE 3 NbO 7 ceramics have glass-like thermal conductivity, and the thermal conductivity of 4RE 3 NbO 7 ceramics (1.032–1.177W/m·K, 25–800 °C) was lower than that of 3RE 3 NbO 7 ceramics (1.058–1.183W/m·K, 25–800 °C). In addition, 4RE 3 NbO 7 and 3RE 3 NbO 7 exhibited comparable coefficients of thermal expansion (9.78–9.61 × 10−6 K−1, 1200 °C) and enhanced mechanical properties (Hv = 7.14–9.07 GPa, K IC = 2.02–1.62 MPa m1/2). The results of this study motivate a follow-up study on niobate high entropy ceramics with desirable properties. [ABSTRACT FROM AUTHOR]

High‐temperature oxidation (1050°C) of Sr.9(Zr.9Yb.05Y.05)O2.85 (SZYY) thermal barrier coatings (TBCs) by suspension plasma spraying (SPS) and growth behavior of thermally grown oxide (TGO) were investigated. When the TBCs were exposed to high temperature for a period of time (∼5 h), the BC oxidized and TGO inevitably formed between the bond coating (BC) and the ceramic top coating (TC). The high‐temperature oxidation behavior of the BC is generally manifested as the growth of TGO, which has four specific stages as follows: (1) formative oxidation stage (0‒10 h), (2) rapid oxidation stage (10‒50 h), (3) stable oxidation stage (50‒100 h), and (4) complex oxidation stage (100‒200 h). The main component of early TGO is α‐Al2O3. It has a very low oxygen ion diffusivity and provides an excellent diffusion barrier, which has a positive effect on preventing further BC oxidation. However, as the heat treatment time increased, the Al consumption and the formation of a CNS layer (NiO, Co3O4, and spinel) in the BC eventually led to coating failure. The working life of TBCs can be improved by improving the ceramic TC structure and the Al content of BC. SZYY‐TBCs have certain potential application value. [ABSTRACT FROM AUTHOR]

Based on experimental data, this study presents a model of the dynamic growth of a thermally grown oxide (TGO) in thermal barrier coatings (TBCs) during thermal cycling. The model was solved using the finite element method. The thermal stress results of the model were compared with experimental results to verify the accuracy of the model. The stress analysis revealed that the combined effect of radial tensile stress and circumferential compressive stress can lead to the delamination of TBCs in a buckling form, which can induce the formation of cracks in TBCs along the axial direction. This observation was consistent with the conclusions drawn from the experimental results. Crack initiation and propagation result from the action of the maximum shear and radial stresses. In addition, the relationship between buckling failure and microscopic cracks was investigated. Thermal cycling induces radial and circumferential cracks, leading to buckling, delamination, and ultimate coating failure as the radial and circumferential cracks interact at the interface. [ABSTRACT FROM AUTHOR]

The increase in operating temperature contributes to improving the performance and fuel utilization efficiency of gas turbines. However, it also places thermal barrier coatings (TBCs) in a more demanding working environment, requiring higher sintering resistance and better mechanical properties. In the present study, HfO2 was introduced into the dual‐phase LaYbZr2O7 system as a doping oxide to form the LaYb(HfxZr1−x)2O7 system. The research concentrated on its phase composition, mechanical properties, and thermophysical properties. The results show that substituting Hf for Zr does not alter the dual‐phase structure of the system. The mutual inhibition between the two phases and the inherent material‐binding capability of Hf further reduce the grain size compared to pure LYZO. Additionally, the presence of Hf reduces the tendency of Frenkel defect formation and cation migration frequency, effectively inhibiting ion diffusion and thereby suppressing the densification and shrinkage trends of the material. The system retains relatively high hardness, fracture toughness, and low elastic modulus of the LYZO matrix, with a decrease in thermal conductivity and an increase in infrared reflectivity. These results suggest that Hf doping enhances the sintering resistance of LYZO material, making them promising for high‐temperature TBCs. Our study presents a viable approach to enhance the sintering resistance of LYZO, and this methodology can be extrapolated to other rare‐earth zirconates. [ABSTRACT FROM AUTHOR]

Double‐layer thermal barrier coatings are one of the development directions of thermal barrier coatings technology. LaYbZr2O7 (LYZO) has high toughness and low thermal conductivity, making it promising for use as a high‐temperature thermal barrier coating. However, its relatively poor mechanical properties, especially low fracture toughness, limit its further application. Therefore, we prepared a double‐layer coating of LYZO and Y2O3 partially stabilized ZrO2 (YSZ) using atmospheric plasma spraying, with the inner layer being YSZ and the outer layer being LYZO. The results showed that after spraying, LYZO was in the metastable fluorite phase, while YSZ was in the tetragonal phase. LYZO and YSZ had good chemical compatibility, and an interaction layer formed at the interface between them, with its thickness increasing with the sintering time. Eventually, after 100 h of heat treatment, the thickness reached 12 µm. The hardness of the LYZO/YSZ interface increased with the sintering time, reaching a maximum value after sintering at 1300°C for 10 h. When evaluating the interfacial bonding strength using indentation method, the length of cracks caused by indentation significantly decreased with the increase of sintering time. The increase in bonding strength can be attributed to the formation of a reaction layer and the reduction of thermal residual stresses. Raman spectroscopy was used to measure the thermal residual strain at the LYZO/YSZ interface. Unbalanced distribution of thermal residual stress and M phase was observed near the interface. As the sintering time increased, both thermal residual stress and M phase content decreased. In summary, the double‐layer thermal barrier coating of LYZO/YSZ has good potential for development. [ABSTRACT FROM AUTHOR]

Generally, thermal barrier and wear seriously affect flight safety by deforming or disabling the inner surface of the engine and outer surface of the vehicle of supersonic aircraft. In this study, we developed a bimetallic supported composite catalyst coating which can simultaneously eliminate the "thermal barriers" and improve the wear resistance. The bimetal-loaded composite catalysts (Pt-Cu@CeO2-Al2O3) coating was obtained by co-precipitation method. The catalytic cracking for RP-3 and wear resistance of composite catalyst coatings were evaluated via thermal cracking and friction experiments. The simulated catalytic cracking experiment results show that when n(Ce): n(Al) = 1:1, the composite catalyst exhibits the highest catalytic activity, which results from the largest specific surface area and proportion of strong acid centers. Meanwhile, under lower temperature conditions, the gas production rate of RP-3 catalytic cracking is increased by 915% (550 ℃) and 186% (600 ℃) compared with the thermal cracking. Meanwhile, the low frictional coefficient of 0.533 of the catalyst coating also indicates the satisfied wear resistance. This research provides useful information for the creation of a safer flying environment and the extension of the service life of supersonic aircraft. [ABSTRACT FROM AUTHOR]

Thermal barrier coatings (TBCs) reduce the surface temperature of superalloy components but may affect the mechanical properties of the substrate. This study investigates the creep-fatigue behavior of TBC-coated single-crystal superalloys under 1 s, 60 s, and 180 s dwell times. The results indicate that TBCs are beneficial at a 1 s dwell time. The comparison of fracture morphology between coated and uncoated samples showed no change in the failure mechanism due to TBCs under creep-fatigue loading. A creep-fatigue lifetime prediction method based on continuous damage mechanics was also proposed. The predicted results were all within a double dispersion coefficient, showing good agreement with the experimental results. This study provides insights into the durability of TBC-coated single-crystal superalloys under creep-fatigue loading. [ABSTRACT FROM AUTHOR]

Y3NbO7 is regarded as a prospective material for utilization in thermal barrier coating applications, given its low thermal conductivity, high thermal expansion coefficients (TECs), and low oxygen ion conductivity. This study focuses on the dominant mechanisms of thermal properties of Y3-xAxNbO7 (A = Ca, In, Mg, Al; x = 0.05, 0.1) through the introduction of different types of cations. The oxygen ion conductivity of Y3-xAxNbO7 is as low as 2.16 × 10−5 S·cm−1 at 900 °C, which is dominated by contents of oxygen vacancies and electronegativity disorder. Three factors can contribute to reduction in thermal conductivity, including the phonon scattering caused by point defects, disorders in at. wt., ionic radius, and electronegativity, as well as atomic displacement parameters (ADPs). A comparison of the correlation between lattice point defects and thermal conductivity reveals that they are not the primary factor contributing to reduction in thermal conductivity. Conversely, doping elements with larger ADPs have been shown to significantly enhance the intensity of an-harmonic vibrations, thereby increasing TECs to 11.93 × 10−6 K−1 at 1400 °C and reducing thermal conductivity to 1.25 W m−1 K−1 at 25 °C. The effects of ADPs on reducing thermal conductivity overweigh that of lattice point defects in Y3NbO7 ceramics, and both TECs and thermal conductivity are optimized at the same time. This work proposes that large atomic displacements can act as a means of reducing thermal conductivity and increasing TECs for various ceramics. [ABSTRACT FROM AUTHOR]

SiC‐based ceramic matrix composites (CMCs) for turbine engine applications require environmental barrier coatings (EBCs) to protect against water‐vapor induced corrosion. A significant limiting factor of EBC operating lifetime is the formation of a SiO2 thermally grown oxide (TGO) at the EBC–CMC interface at high temperature. Its rapid growth as well as displacive β→α cristobalite phase transformation upon cooling induces strains at this interface, which can result in coating spallation. Recent work has explored upon the use of modifier oxides in EBCs to reduce oxidizing specie transport and possibly stabilize the SiO2 TGO. This work utilizes EBC–glass mixtures to characterize the properties of modifier‐stabilized SiO2 and assess its impact in future EBC systems. [ABSTRACT FROM AUTHOR]

The elucidation of chemical bonding, coupled with an exploration of the correlated dynamics of constituent atoms, is essential for unravelling the underlying mechanism responsible for low lattice thermal conductivity (κL) exhibited by a crystalline solid, which is essential for thermoelectrics and thermal barrier coatings. In this regard, Pauling's third empirical rule, which deals with the cationic repulsion due to proximity in the face or edge shared polyhedra in a crystal structure, can bring about the lattice instability required to suppress the κL. Here, we demonstrate the presence of such instability in a ternary selenide, TlAgSe, leading to a ultra‐low κL of 0.17 W/m.K at 573 K. Our study reveals the instability arising from Ag−Ag repulsion within edge‐shared AgSe4 tetrahedra through investigation of the local structure using synchrotron X‐ray pair distribution function (PDF) analysis and supported by first‐principles density functional theory calculations. We observe correlation between weakening in the Ag and the Tl‐sublattice, providing direct experimental evidence of Pauling's third empirical rule. The correlated rattling of Ag and Tl induces a highly anharmonic lattice and low energy optical phonons, resulting in suppressed sound velocity and ultralow κL in TlAgSe. The electronic origin of soft and anharmonic lattice is the presence of filled antibonding states in the valence band near the Fermi level constructed by Ag(4d)−Se(4p) and Tl(6s)−Se(4p) interactions. This work demonstrates that the evidence of dynamic distortion in a crystal lattice is governed by the third empirical rule given by Pauling, which can act as a potential new strategy for diminishing κL in crystalline solids. [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]

Rare earth zirconate ceramic has been considered as one of the potential thermal barrier coating materials to replace 6–8% YSZ material (6–8% yttrium oxide stabilized zirconia), because of its low thermal conductivity and good high temperature phase stability. However, there is a problem that the coefficient of thermal expansion does not match the matrix. In this paper, rare earth high entropy zirconate ceramic powder with defective fluorite structure was prepared by molten salt synthesis(MSS). The results show that the reaction temperature and the ratio of reactants to molten salt will affect the synthesis effects. With the action of the high entropy effect, the synthesized ceramic powder has low thermal conductivity, improved thermal expansion coefficient and high infrared reflectivity. [ABSTRACT FROM AUTHOR]

A digital process was developed to facilitate additive manufacturing for ceramic materials using digital light processing (DLP). A numerical model that predicts DLP sample properties can be generated from manufacturing inputs to forecast the effect of resin age on mechanical strength of the printed part based on data collected from experiments. Key parameters for printing the green bodies included determining the depth of cure, layer thickness, material composition, and solids loading. Thermogravimetric analyses were used to develop debinding and sintering curves. Debinding is used to remove the volatile organics comprising the photopolymer resin. Sintering is performed after debinding to increase density and mechanical strength of the printed parts. The sintered parts were then subjected to characterization and mechanical testing. The ensemble of data for various DLP-printed ceramic materials were added to a database. A design of experiments can be generated from the manufacturing process defined in the database with selected changeable parameters randomized over a range. Because the database is defined with an architecture to capture manufacturing processes, it can persist as a more generic platform for manufacturing digital twins. This can ease the development of future digital twins and can grow as a common repository for the insights gained from manufacturing research. Creating a digital twin of a DLP system for 3D printing parts enables manufacturers to simulate and assess the impact of resin age on printing parameters and part quality, facilitating optimization, predictive maintenance, and cost reduction. [ABSTRACT FROM AUTHOR]

Yttrium‐stabilized zirconia (YSZ) plays a crucial role in thermal barrier coatings widely used to protect metallic components in gas turbine engines against high‐temperature combustion product gases and harsh environments. The thermal conductivity of these coatings is a critical parameter influencing the gas turbine design, performance, and service life. In this study, a laser temperature gradient method is utilized to measure the thermal conductivity of porous YSZ coatings. The method employs specialized laser energy delivery to create a one‐dimensional temperature gradient through the sample thickness, closely simulating the operational condition. This approach provides an effective, direct means to determine the thermal conductivity of high‐temperature heat‐resistant porous ceramic materials. [ABSTRACT FROM AUTHOR]

Excellent mechanical properties are indispensable for thermal barrier coatings (TBCs), including high hardness and low modulus, as well as excellent creep and wear resistance. This study focuses on nanomechanical properties of RENbO4 (RE = La, Gd, Dy, Y, Yb), and the effects of microstructures on their properties are analyzed. The evolutions of hardness and modulus of RENbO4 are studied based on the changes of RE3+ ionic radius, and the shorter bond lengths lead to the higher hardness and modulus due to the increasing bonding strength. The existence of ferroelastic domains causes the presence of pop out during nanoindentation, which affects the elastic and plastic work. Based on the load‐displacement curves, we further analysis the creep behavior and wear resistance of RENbO4 ceramics, and the results show that these two parameters show a negative correlation. Among the studied RENbO4 ceramics, YbNbO4 exhibits the best mechanical properties, and the used methods in current paper can be employed to screen materials with outstanding properties for various applications. [ABSTRACT FROM AUTHOR]

Phase equilibria in the ZrO2–YO1.5–NbO2.5 system were experimentally studied at 1300°C, and a comparison with the existing ZrO2–YO1.5–TaO2.5 (ZYTO) was conducted. Ternary fluorite phases on the Y:Nb > 1 side extend from binary ZrO2‐YO1.5 to YO1.5–NbO2.5 system, generating a continuous solid solution region. Furthermore, it was observed that three phases of M‐YNbO4, fluorite, and m‐ZrO2 were in equilibrium. On the Y:Nb < 1 side, two three‐phase equilibrium regions were measured, namely M‐YNbO4+m‐ZrO2+O‐Nb2Zr6O17 and h‐Nb2O5+O‐Nb2Zr6O17+M‐YNbO4. The tetragonal YNbO4 and ZrO2 phases both extend nearly along with Y:Nb = 1. The t‐ZrO2 phases with slightly lower stabilizer content were found to transform into their monoclinic polymorph during the cooling process. However, in the ZrO2–YNbO4 subsystem, the tetragonal ZrO2 was nontransformable due to larger YO1.5 and NbO2.5 co‐dopants, and the maximum solubility is about 18.1 mol%. Upon cooling, the tetragonal YNbO4 phase, even with the maximum ZrO2 content, is transformable to monoclinic form. The maximum solubility of ZrO2 in YNbO4 is determined to be about 20.7 mol%. Finally, the high‐temperature liquidus in the ZrO2–YNbO4 system was first determined based on the cooling traces, and a vertical section diagram was proposed for further speculation. A eutectic reaction of Liquid→YNbO4+ZrO2 was discovered, and the eutectic composition and temperature were measured as 39.2ZrO2–29.2YO1.5–31.6NbO2.5 and 1813°C. This study provides the basis for thermodynamic assessment of ZrO2–YO1.5–NbO2.5 and is valuable for the design and development of the ZrO2–YO1.5–NbO2.5‐based ceramic materials. [ABSTRACT FROM AUTHOR]

This study investigates failure mechanisms in a typical thermal barrier coating (TBC) system comprising an EB-PVD columnar top coat, an aluminide bond coat, and a Ni-based single crystal superalloy substrate, simulating gas turbine operating conditions using a burner rig. TBC degradation, initiated by interfacial defects from the LASAT method, was studied during thermal gradient cycling under fast and slow cooling. In-situ optical and infrared imaging, along with ex-situ SEM cross-sectional analysis, monitored failure mechanisms. The Laser Shock for Damage Monitoring (LASDAM) technique provided insights into gradient and cooling rate impacts on columnar TBC damage. Results showed significant effects of cooling rate on delamination and localized failure at blister sites, with LASDAM revealing significant overheating at damage sites. Analysis included full-field temperature and damage assessment, emphasizing blister-driven delamination under severe thermal gradients. Discussion focused on elastic stored energy effects, noting that fast cooling induced transient conditions where reversed temperature gradients increased damage, limiting TBC lifespan. • LASDAM demonstrates simplicity and effectiveness for burner rig conditions. • Multiple points within a given specimen are analyzed under different conditions. • Blister formation induces overheating in gradients configuration. • The damage rate is directly influenced by both cooling rate and thermal gradient. • The local maximum temperature is also considered in our study. [ABSTRACT FROM AUTHOR]

The preparation and realization of highly reliable thermal barrier coatings (TBCs) on the internal surface of complex cavities is a bottleneck problem. Traditional coating methods are difficult to deposit and fulfil service requirements. In this study, a novel structure of YSZ and Ce-doped YSZ (CeYSZ) TBCs was prepared by a newly cathode plasma electrolytic deposition (CPED) technology. The results suggested that both the CPED-YSZ and CPED-CeYSZ coatings exhibited porous cross-linked dendritic structures. Because Ce doping significantly improved the phase stability of tetragonal structure and enhanced thermal insulation temperature during a burner-rig test at 1300 °C, resulting in a threefold increase in the thermal cycling life of the CPED-CeYSZ coating compared to the CPED-YSZ coating. This work provided a new strategy for tailoring multiple rare-earth principal components of high-performance TBCs and depositing them on the inner surface of complex cavities with high aspect ratios. [ABSTRACT FROM AUTHOR]

With the development of marine science and technology, marine construction is entering a new period of modern ocean development and utilization. The scale of marine development is expanding constantly. The lifespan of aircraft engines faces new challenges in marine environments. This paper reviews recent progress in the development of high-temperature coatings for aero-engines designed to resist marine atmospheric corrosion, with a focus on corrosion mechanisms, detection technologies, current research on marine atmospheric corrosion, standards for evaluating coating resistance, and novel advancements in coating materials. [ABSTRACT FROM AUTHOR]

Grit particles remaining on the substrate surface after grit blasting are generally considered to impair the thermal performance of thermal barrier coatings (TBCs). However, the specific mechanisms by which these particles degrade the multilayer structure of TBCs during thermal cycling have not yet been fully elucidated. In this study, the superalloy substrate was grit-blasted using various processing parameters, followed by the deposition of thermal barrier coatings (TBCs) consisting of a metallic bond coat (BC) and a ceramic top coat (TC). After thermal shock tests, local thinning or discontinuities in the thermally grown oxide (TGO) layer were observed in TBCs where large grit particles were embedded at the BC/substrate interface. Moreover, cracks originated at the concave positions of the TGO layer and propagated vertically towards BC; these cracks may be associated with additional stress imposed by the foreign grit particles during thermal cycling. At the BC/substrate interface, crack origins were observed in the vicinity of large grit particles (~50 μm). [ABSTRACT FROM AUTHOR]

With the global energy transition and increasing environmental requirements, hydrogen-mixed gas turbines as a high-efficiency and low-emission energy conversion equipment has been widely concerned. This paper reviews the development status of hydrogen-mixed gas turbines domestically and internationally, analyzes the characteristics of hydrogen combustion in gas turbines, explores the impact of hydrogen combustion on complex components and the application of high-temperature materials, and analyzes the performance requirements for hot-end component materials operating under high temperature, high pressure, and corrosive conditions, as well as the main challenges and potential solutions in current material development. The effects of water vapor and hydrogen embrittlement during hydrogen combustion on gas turbine alloys and thermal barrier coatings are discussed in detail. Water vapor accelerates the oxidation and corrosion of alloys, leading to a decline in mechanical properties. Furthermore, hydrogen embrittlement significantly affects the toughness and durability of alloys, increasing the risk of crack propagation and fracture. In terms of the problems, future research should focus on multi-field coupling simulations and accelerated corrosion tests, considering the factors such as temperature, pressure, and different atmospheres to establish realistic environment simulators to evaluate alloy and coating performances. Additionally, the combined effects of hydrogen and water vapor on high-temperature alloys and thermal barrier coatings should be emphasized. This includes investigating the diffusion mechanisms of hydrogen in alloys, interactions with lattice defects, and the microscopic processes leading to hydrogen embrittlement. Building oxidation models in high-temperature water vapor environments, clarifying the dissociation and adsorption mechanisms of water vapor at high temperatures, the hydroxylation of protective oxide films Al2O3 and Cr2O3, and the growth behavior of non-protective oxides(e.g., spinel) are also essential. [ABSTRACT FROM AUTHOR]

The aircraft engine is considered the "heart" of the aircraft. The development of advanced aircraft engines focuses on achieving a high thrust-to-weight ratio, high efficiency, low fuel consumption, and extended operational life. High-temperature functional coatings, such as thermal barrier coatings (TBCs), thermal/environmental barrier composite coatings (T/EBCs), and high-temperature stealth coatings, are applied to critical hot-end components of aircraft engines. These coatings play a significant role in enhancing the service performance, operational life, safety and reliability of the engine. Taking TBCs, T/EBCs, and high-temperature stealth coatings as examples, this paper provides a systematic overview of recent research progress in the design of high-temperature functional coating materials, coating preparation science and technology, and coating performance evaluation and characterization, both domestically and internationally, with a specific focus on the advancements made at Beihang University. Furthermore, challenges and development trends faced by new high-temperature functional coatings of advanced aircraft engines in the future are also discussed. In the future, the research focus of advanced high-temperature functional coatings will shift toward multifunctional composite coatings, enhanced adaptability to extreme environments, and improved process compatibility. [ABSTRACT FROM AUTHOR]

Drilling cooling holes on the turbine blade is essential for enhancing aero engine performance and to protect it from elevated temperature. So, the objective of this work is to produce micro holes on the thermal barrier coated titanium alloy using a femtosecond laser. An in-depth experimental investigation has been carried out to understand the influence of femtosecond laser parameters, circular and zig-zag scanning modes on geometrical characteristics and surface integrity of the micro holes. It is inferred that better hole circularity and less taper angle are observed for circular scanning method at laser energy density (LED) of 2.04 J/cm2, pulse repetition rate (PRR) of 20 kHz, and scanning speed of 300 mm/s. The surface finish and hole quality are also improved by this method, although at higher LED and PRR the inner hole wall surface degrades because of flaws including microcracks, re-solidified material, and micropores. When compared to circular scanning, the zig-zag scanning strategy reduces the drilling time by 51.87%. Conical spike with micro protrusion and micro trench type microstructure, is noticed for the zig-zag path. In contrast, micropores with micro protrusion type microstructures are obtained for concentric path with minimal surface flaws. [ABSTRACT FROM AUTHOR]

This study investigated the microstructure and tribological performance of TiO 2 coating prepared through the plasma-spraying of TiO 2 on an aluminum alloy (ZL109) surface. Box–Behnken design was employed to calculate the optimal spraying parameters (spraying current: 439 A, spraying voltage: 129 V, and Ar flow rate: 117 m3/h). High-temperature tribological characteristics (T = 120 °C) were examined under varying loads (F = 100 N, 120 N, and 140 N). The scanning electron microscopy and energy-dispersive X-ray spectroscopy analysis results revealed that the coating porosity decreased from 3.31 % to 0.31 % with the increase in the spraying voltage from 120 V to 130 V. Both powder and coating exhibited consistent elemental composition (Ti, O) and phase composition (TiO 2 , TiO, Ti 2 O 3). During the spraying process, part of the powder was oxidized. The average coefficient of friction of the coatings varied from 0.05 to 0.08, and as the load increased, the wear mechanism of the coating changed from abrasion to adhesive wear and oxidation. [ABSTRACT FROM AUTHOR]

The addition of Al 2 O 3 inside thermal barrier coatings (TBCs) is highlighted effective on mitigating TBCs degradation induced by CMAS corrosion. In this study, the cost-effective 20 wt.%Al 2 O 3 -7YSZ/7YSZ double ceramic layer (DCL) TBCs were fabricated and their long-term performance resisting CMAS corrosion was investigated. Significant bending and CMAS infiltration occurred readily for the single layer 7YSZ coatings just after 5 h duration. The top sacrificial Al 2 O 3 -7YSZ layer of DCL coatings greatly constrained coating deflection and CMAS infiltration. This is due to the chemical reaction between alumina splats and CMAS, generating interconnected anorthites for effectively blocking CMAS infiltration and improving resistance to CMAS attack. However, it is highlighted that the role of alumina splats on mitigating CMAS degradation was found different between the short-term corrosion and long-term corrosion. In addition, interfacial delamination/cracking was not observed between the top Al 2 O 3 -7YSZ layer and bottom 7YSZ layer after 100 h CMAS corrosion, demonstrating superior interface integrity and durability. [ABSTRACT FROM AUTHOR]

Boron doped MoSi 2 particles have been envisioned as sacrificial particles for self-healing thermal barrier coatings (TBCs) but their oxidation behaviour is yet not well understood. In this work, oxidation of MoSi 2 based particle is studied in the temperature range of 1050–1200 °C. The oxidation proceeds from a transient to a steady-state oxidation stage. The kinetics during steady-state oxidation is captured with a thermal diffusion-based model. As compared to the oxidation of pure MoSi 2 particles, the addition of boron strongly enhances the silica formation. Also, a finer dispersion of MoB x in the MoSi 2 matrix accelerates the formation of silica. The oxide growth rate constant increases proportional with the boron content of the MoSi 2 particles. This enhanced oxidation is related to the microstructure of the oxide scale. Upon oxidation, boron yields B 2 O 3 , which promptly merge with SiO 2 to form amorphous borosilicate, hindering the formation of crystalline SiO 2. Consequently, the migration of oxygen in the borosilicate oxide scale is faster than in the silica oxide scale on pure MoSi 2 particles. [ABSTRACT FROM AUTHOR]

M-YTaO 4 is one of the most promising candidates for the next-generation thermal barrier coatings. However, the CMAS-induced degradation of M-YTaO 4 is still in dispute. This work comprehensively investigates the CMAS corrosion of M-YTaO 4 at 1300 °C which provides new insights into the corrosion mechanism. CMAS attacks M-YTaO 4 forming a thick recession layer and the main corrosion product is accurately confirmed to be (Ca 2-x Y x)(Ta 2-y-z Mg y Al z)O 7 solid solution. The recession layer presented a small difference in Young's modulus with M-YTaO 4. No delamination cracking occurred during the thermal cycling process indicating good reliability. In addition, grain boundary infiltration of CMAS is first revealed in M-YTaO 4. The results have corrected the misjudgment of the corrosion mechanism and CMAS infiltration process in previous studies which provides guidelines for the design of M-YTaO 4 thermal barrier coatings. [ABSTRACT FROM AUTHOR]

Thermal barrier coatings (TBCs) provide thermal protection for high-temperature components of aero-engines and steam turbines, but are susceptible to failure under thermal cyclic loads. The effective design of interfacial texture is one of the approaches to enhance the lifetime of ceramic TBCs. In this study, four types of interfacial textures were designed on the surface of substrates, and 8YSZ coatings of equal thickness were prepared using atmospheric plasma spraying, and thermal cycling tests were carried out. Meanwhile, the thermal cycle lifetime, microstructure evolution, residual stress, and energy release rate criterion were also studied. The optimal morphology and parameters of the texture are determined. It is found that the lifetime of the concave trapezoidal texture is the longest, with a deflection angle of 67°, diameter of 700 μm, depth of 500 μm, and spacing of 5 mm. This study can provide theoretical guidance for the interfacial texture design of ceramic TBCs. [ABSTRACT FROM AUTHOR]

Thermal barrier coatings, including Al 2 O 3 -doped tetragonal yttria-stabilized zirconia (t-YSZ) coatings are vital in diverse applications. Thermal conductivity is a key property, but prediction often requires some complex experiments. In this study, a novel dual-structure feature extraction coupled with a multi-scale attention fusion network (RCFNet) is introduced for accurate thermal conductivity prediction using electron backscattered diffraction (EBSD) microstructure images. The method requires minimal data, and the result shows high accuracy with a Mean Square Error (MSE) of 0.003 W(m ⋅ k)−1 and an R-squared (R 2) value of 0.81. Furthermore, the model reveals specific correlations between microstructural characteristics and thermal conductivity, facilitating rapid structure selection for specific thermal conductivity. [Display omitted] • New dual-structure, multi-scale fusion for precise thermal conductivity prediction. • Proposed multi-scale attention fusion optimizes data utilization effectively. • Reveals microstructure-performance link in material images. [ABSTRACT FROM AUTHOR]

Gd 2 Zr 2 O 7 thermal barrier coatings (TBCs) were reported to be resistant to calcium-magnesium-aluminum-silicon (CMAS) corrosion, but is still unsatisfactory. In this study, laser surface modification is employed to further improve CMAS resistance of Gd 2 Zr 2 O 7 coatings. The modification layer consists of a columnar microstructure, which is affected by the modification parameters such as pulse width and beam length. CMAS corrosion resistance of the as-fabricated and laser modified Gd 2 Zr 2 O 7 coatings is compared. At 1250 °C for 1 h, a reaction layer forms between the Gd 2 Zr 2 O 7 coating and CMAS which has some ability to suppress molten CMAS penetration. After prolonged corrosion (4 and 10 h), however, the reaction layer continues to thicken until no CMAS remains, which largely consumes the coating thickness and degrades the coating performance. Laser surface modification has solved this problem effectively due to its ability to reduce the melt penetration channels. Hence, laser-modified Gd 2 Zr 2 O 7 coatings have enhanced CMAS resistance. [ABSTRACT FROM AUTHOR]

A novel (Nd 0.2 Sm 0.2 Eu 0.2 La 0.2 Dy 0.2) 2 Gd 0.5 Yb 0.5 TaO 7 high-entropy oxide was successfully prepared through the sol–gel and high-sintering technique. The synthesized powder has a single-lattice structure, and the bulk sample has sole pyrochlore-type lattice. Given the particularity structure and the high concentration of oxygen vacancies caused by ion doping, the (Nd 0.2 Sm 0.2 Eu 0.2 La 0.2 Dy 0.2) 2 Gd 0.5 Yb 0.5 TaO 7 's thermal conductivity (1.385–1.187W·m−1·K−1) is lower than those of (La 1/6 Nd 1/6 Yb 1/6 Y 1/6 Sm 1/6 Lu 1/6) 2 Ce 2 O 7 , Sm 2 Zr 2 O 7 , and Sm 2 Ce 2 O 7. Its excellent phase stability and suitable coefficient of thermal expansion (～10.80 × 10−6 K−1, ～1200 °C) also indicate its potential as candidate oxide for thermal barrier coatings. [ABSTRACT FROM AUTHOR]

Although Hf x Ta 2 O 2 x+ 5 shows great potential as a next-generation thermal barrier coating (TBC) material, the diversity of its potential modulated structures presents challenges in determining their mechanical properties. Hf x Ta 2 O 2 x+ 5 (x = 4, 6, 8) ceramics were successfully fabricated using the sol–gel method. Research on growth kinetics has indicated that grain boundary diffusion is the speed-controlling step. The activation energy increased with a larger modulated structure. In addition, the fracture toughness also increased from 1.98 MPa m1/2 for Hf 4 Ta 2 O 13 to 3.30 MPa m1/2 for Hf 8 Ta 2 O 21. Density functional theory calculations revealed that Hf x Ta 2 O 2 x+ 5 exhibited intrinsic ductility owing to the denser packing of atoms in its larger modulated structure. Thus, the tight-knit chemical bond net may contribute to a large surface energy. The results of this study provide deep insights into the toughening mechanism of modulated structures and pave the way for the design of next-generation TBCs. [ABSTRACT FROM AUTHOR]

Thermal barrier coatings (TBCs) are often applied to base metals exposed to excessive temperatures to protect them from the harsh operating thermal cycle load conditions and to enhance their functionality. For this research, nickel and zirconia was coated over a mild steel substrate by electro-deposition or co-deposition method. While selecting appropriate electro-deposition parameters, this study analyses the convection and conduction heat transfer characteristics and mechanical behaviours of a nickel-zirconia co-deposit over a mild steel substrate. The better-quality deposition is formed with thicknesses of 10 µm and 50 µm. The microstructure and morphological analyses were conducted using scanning electron microscope (SEM). The phase analysis was conducted using Xray diffraction analysis (XRD). The porosity, hardness and wear behaviours were measured as per the American Society for Testing and Materials (ASTM). The results showed that nickel-zirconia coating has better performance. The coating's convection and conduction heat transfer potential are investigated using a specially designed and constructed experimentation apparatus. Compared to an uncoated panel, heat transfer studies on nickel-zirconia coatings demonstrate that nano-coatings with a particle size of about 92 nm show a significant temperature drop with varied coating thicknesses and heat inputs for different heat inputs. [ABSTRACT FROM AUTHOR]

Purpose: The purpose of this study is to investigate the effects of high-temperature oxidation tests and gas thermal shock tests on IC10 simulated components with thermal barrier coatings under different temperatures and oxidation times. Design/methodology/approach: In the high-temperature oxidation test, specimens were oxidized at three different temperatures of 850, 980, and 1,100 °C for durations of 10, 20, 50, 100, 200, and 300 h, respectively. In the gas thermal shock test, specimens were pre-oxidized for 10, 20, 50, and 100 h, followed by a high-temperature gas thermal shock test at 1,100 °C. Findings: In the high-temperature oxidation tests, with increasing oxidation time, the oxidation layer thickened, and the air-film holes diameter decreased. The microstructure of the bond coat transitioned from strip-like to block-like, and internal cracks transformed from numerous and short to larger and deeper. Below the bond coat, a noticeable disappearance layer of strengthening phase appeared, with increasing thickness. The strengthening phase in the substrate transitioned from regular square shapes to circles as temperature increased. In gas thermal shock tests at 1,100 °C, the oxidation weight gain ratio increased with longer pre-oxidation times, whereas the erosion weight loss ratio gradually decreased. Originality/value: The originality and significance of this study lie in its departure from the typical subjects of high-temperature oxidation and thermal shock tests. Unlike common research targets, this study focuses on IC10 simulative specimens with thermal barrier coatings and air-film holes. Furthermore, it investigates the effects of varying temperatures and oxidation durations. [ABSTRACT FROM AUTHOR]

For the temperature monitoring requirements of gas turbine blades, a new infrared temperature measurement probe structure is designed in this paper. Cooling air is used to cool the probe and prevent flue gas flowing into the probe. The computational fluid dynamics method is used to analyze the working process of the temperature probe. Two cases that the optical opening of probe is facing to and on the back of flue gas are considered. The influences of the air inlet total pressure on the pollution protective performance and thermal protective performance of the probe are analyzed. The results show that when the optical opening of probe is facing to flue gas, the pollution protective performance is poorer while the thermal protective performance is better than that when facing to gas. According to the temperature distribution of the probe, three optimization schemes of the probe are proposed: spraying thermal barrier coating on the wall of the probe, drilling film holes at the bottom of the probe, and combining film holes with thermal protective performance. The results show that the probe maximum temperature is reduced by 97, 187 and 328 K by using these three methods, respectively. [ABSTRACT FROM AUTHOR]

LaMgAl 11 O 19 (LMA) with magnetoplumbite structure has emerged as a promising candidate for thermal barrier coating (TBC). However, the inherent high thermal conductivity and relatively low thermal expansion coefficient (TEC) of LMA impose limitations on its further application. In this work, a novel high-entropy hexaluminate (La 0.2 Nd 0.2 Sm 0.2 Eu 0.2 Gd 0.2)MgAl 11 O 19 (HE-LMA) has been designed and prepared to overcome these obstacles. HE-LMA with homogeneous chemical composition distribution possesses excellent phase stability up to 1600°C. Moreover, the TEC of HE-LMA (9.22 × 10−6 K−1 at 1300°C) is larger than that of LMA. The high-entropy strategy effectively decreases the thermal conductivity of HE-LMA (from 3.27 W/(m⋅K) at room temperature to 2.19 W/(m∙K) at 1000°C) in comparison to that of LMA (3.63–2.62 W/(m∙K)). Furthermore, HE-LMA demonstrates higher microhardness and fracture toughness due to the lattice distortion. These results indicate that (La 0.2 Nd 0.2 Sm 0.2 Eu 0.2 Gd 0.2)MgAl 11 O 19 has the potential to be applied as a TBC. [ABSTRACT FROM AUTHOR]

Rare earth niobate Re 3 NbO 7 (Re=Rare earth element) possesses ultra-low thermal conductivity for application as thermal barrier coatings (TBCs). However, Re 3 NbO 7 with large rare earth ion radius (Re La, Nd, Sm) exhibits both low temperature phase transition and poor facture toughness which is detrimental to the durability of the coatings. In this work, an effective method was proposed to solve those problems by doping. Considering the low-temperature phase transition at about 340K, La 3 NbO 7 is selected as representative material. In order to suppress phase transition, Y3+ with relatively smaller ionic radius is used as a doped ion, and (La 1- x Y x) 3 NbO 7 (x = 0.0,0.1,0.3,0.5) were prepared and investigated. It is shown that, low temperature phase transition of La 3 NbO 7 is effectively suppressed due to Y3+ doped. Facture toughness is increased significantly from 0.5 to 2.3 MPa m1/2 with the increase of doping concentration. Furthermore, the Vickers hardness is also improved by doping. Considering the phase stability and ultra-low thermal conductivity, (La 1- x Y x) 3 NbO 7 solid solution (x = 0.5) maybe promising candidates for high temperature thermal insulation materials such as TBCs, thermoelectric materials, etc. [ABSTRACT FROM AUTHOR]

As a thermal barrier coating (TBC) material, 8 wt% yttria-stabilized zirconia (8YSZ) exhibits poor resistance against calcium–magnesium–aluminosilicate (CMAS) corrosion. This is caused by the penetration of molten CMAS glass and the depletion of Y3+, which limits the lifetime of 8YSZ. In this study, a multi-rare-earth-oxide-doped zirconia (15 wt% (Lu 0.2 Yb 0.2 Dy 0.2 Gd 0.2 Y 0.2)–ZrO 2 , denoted as 15LYDGY–SZ) ceramic was prepared to examine its interaction with CMAS. The sluggish diffusion effect and the competition between various dopant elements toward reaction with CMAS effectively slow down the atomic diffusion and limit the transformation of tetragonal phase into monoclinic phase in 15LYDGY–SZ ceramic. Compared with the currently used 8YSZ ceramic, the corrosion resistance of 15LYDGY–SZ to CMAS and its retention rate of fracture toughness after CMAS corrosion are improved. The results show that the multi-rare-earth-oxide-doped zirconia ceramic prepared in this study is a promising candidate material for the development of future TBCs. [ABSTRACT FROM AUTHOR]

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High-temperature conditions are harmful for carbon nanotube-based (CNT-based) composites, as CNTs are susceptible to oxidation. On the other hand, adding CNTs to ceramics with low electrical conductivity, such as 3YSZ, is beneficial because it allows the production of complex-shaped samples with spark plasma sintering (SPS). A shielding coating system may be applied to prevent CNT oxidation. In this work, the 8YSZ (yttria-stabilized zirconia) thermal shielding coating system was deposited by aerosol deposition (AD) to improve the composite's resistance to CNT degradation without the use of bond-coat sublayers. Additionally, the influence of the annealing process on the mechanical properties and microstructure of the composite was evaluated by nanoindentation, scratch tests, scanning electron microscopy (SEM), X-ray diffraction (XRD), flame tests, and light microscopy (LM). Annealing at 1200 °C was the optimal temperature for heat treatment, improving the coating's mechanical strength (the first critical load increased from 0.84 N to 3.69 N) and promoting diffusion bonding between the compacted powder particles and the substrate. The deposited coating of 8YSZ increased the composite's thermal resistance by reducing the substrate's heating rate and preventing the oxidation of CNTs. [ABSTRACT FROM AUTHOR]

In this study, a NiCr/YSZ coating was applied to a γ-TiAl surface using multi-arc ion plating technology to enhance its high-temperature performance and explore the mechanisms of high-temperature oxidation and thermal corrosion. The thermal corrosion properties of the γ-TiAl matrix and NiCr/YSZ coating were investigated at 850 °C and 950 °C using a constant-temperature corrosion test in a 75% Na2SO4 + 25% NaCl mixture. The results indicate that after 100 h, the thermal corrosion weight gain of the coating samples was 70.1 mg/cm2 at 850 °C and 118.2 mg/cm2 at 950 °C. At these temperatures, sulfide formation on the surface increases, leading to a loose and porous surface. After 100 h of high-temperature corrosion at 850 °C, the primary oxidation product on the surface of the coating was tetragonal-ZrO2. At 950 °C, Y2O3, which mainly acts as a stabilizer in YSZ, reacted with Na2SO4, resulting in the continuous consumption of Y2O3. This reaction caused a substantial amount of tetragonal-ZrO2 to transform into monoclinic-ZrO2, altering the volume of the ceramic layer, which induced internal stress, crack propagation, and minor spallation. A continuous and dense internal thermally grown oxide (TGO) layer effectively impeded the diffusion of molten salt substances and oxygen, thereby significantly improving the thermal corrosion resistance of the thermal barrier coating. [ABSTRACT FROM AUTHOR]

Yb-doped Y2O3 stabilized ZrO2 (YbYSZ) coatings, developed through solution precursor plasma spraying (SPPS), are engineered to resist calcium–magnesium–alumino–silicate (CMAS) infiltration by leveraging their unique micro-nano structures. This provides superior anti-wetting properties, crucial for preventing CMAS penetration at high temperatures. The investigation focused on the structural and compositional changes in YbYSZ-SPPS coatings subjected to prolonged thermal exposure at 1300 °C. Results indicate that while the coatings undergo significant sintering, leading to densification and microstructural evolution, the elemental composition and phase stability remain largely intact after up to 8 h of heat treatment. Despite some reduction in CMAS resistance, the coatings maintained their overall protective performance, demonstrating the potential of SPPS coatings for long-term use in high-temperature environments where CMAS infiltration is a concern. These findings contribute to the development of more durable TBCs for advanced thermal protection applications. [ABSTRACT FROM AUTHOR]