The performance of high-power laser-driven white lighting systems is constrained by non-radiative losses from crystallographic defects in color converters. Here, a flux-assisted spray pyrolysis strategy using NaF is developed to enhance crystallinity and suppress defects in LuAG:Ce films. Films with NaF contents of 0-2.0 wt% were synthesized and annealed at 1500 degrees C. With 1.0 wt% NaF, crystallinity reached 93.1% without secondary phases or changes in Ce3 + valence or oxygen-vacancy concentration. The optimized film delivered 2160.9 lm (+25%), lowered operating temperature by 38.8 degrees C under 36 W center dot mm(-2) blue-laser excitation, and increased thermal-quenching activation energy by 13.3% (0.299 eV). Durability tests showed only 9.1% luminous flux degradation after 3600 s at 35 W center dot mm(-2), with stable correlated color temperature and color rendering index. Mechanistic analysis indicates moderate NaF promotes defect-suppressed crystallization, whereas excessive flux degrades luminescence, providing a scalable route to high-performance garnet films for laser lighting.

The performance of high-power laser-driven lighting systems is fundamentally limited by an insufficient understanding of the mechanisms governing heat generation and luminous saturation in color-converting materials. In this study, Ce-doped Lu3Al5O12 (LuAG:Ce) thin films synthesized through spray pyrolysis across a doping range of 0.1-4.0 mol% are systematically investigated to elucidate these effects. Heat generation, resulting from the Stokes shift, is found to scale with both Ce concentration and excitation power density, emerging as a critical factor that constrains luminescence output. At an optimized doping level of 2.5 mol% Ce, the films achieve a luminous flux of 1618.3 lm and exhibit a saturation threshold of 28 W & centerdot;mm(-2) under ambient conditions. Incorporation of water cooling reduces the local laser spot temperature by approximately 42.3 degrees C at the same excitation intensity, effectively raising the saturation threshold to 32 W & centerdot;mm(-2) and increasing luminous flux to 1938.6 lm, representing a 19.8% enhancement. These results demonstrate that nonradiative transitions, arising from thermal quenching, lead to luminous saturation. Collectively, this study clarifies the origins of heat generation and luminous saturation in LuAG:Ce films under high-power laser excitation and underscores the critical roles of Ce doping optimization and heat dissipation in enhancing solid-state lighting performance.

Internal oxidation has been identified as an effective method for enhancing the strength of AgMg alloys. However, the concurrent occurrence of embrittlement remains inadequately understood, thus limiting their broader application. This study investigates the oxidation behavior of AgMg alloys with Mg concentrations ranging from 1 at% to 7 at% at 800 degrees C, revealing a composition-dependent evolution of microstructure and mechanical properties. The oxidation process results in the formation of two distinct zones: a Mg/O solid solution zone (Mg/O SSZ), characterized by similar to 3 nm Mg/O clusters, and an internal oxide band zone (IOBZ), where nanocrystalline MgO stripes emerge at Mg concentrations of 2 at% or higher. The Mg/O SSZ is responsible for substantial strengthening, with surface hardness increasing from 74 HV (as-cast) to 224 HV at 7 at% Mg, and tensile strength rising from less than 50 MPa (pure Ag) to 269 MPa at 1 at% Mg. In contrast, the development of MgO stripes within the IOBZ induces localized stress concentrations at incoherent MgO/Ag interfaces, resulting in embrittlement and a reduction in mechanical performance at higher Mg contents. The oxidation kinetics deviate progressively from Wagner's theory with increasing Mg concentration, as the formation of MgO stripes impedes oxygen transport, decreasing the oxidation rate from 7.83 mu m s-1/2 at 1 at% Mg to 0.69 mu m s-1/2 at 7 at% Mg. These results elucidate a compositionally tunable balance between nanoscale cluster-driven strengthening and oxide stripe-induced embrittlement, providing a mechanistic framework for the design of high-performance AgMg alloys for structural and electronic applications. (sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)Ag-Mg(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic), (sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic), (sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic).(sic)(sic)(sic)(sic)Mg(sic)(sic)(sic)1 at%-7 at%(sic)Ag-Mg(sic)(sic)(sic)(sic)(sic), (sic)(sic)(sic)(sic)(sic)(sic)(sic)800 degrees C(sic)(sic)(sic)(sic)(sic)(sic)(sic), (sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic).(sic)(sic)(sic)(sic), (sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic): (1) Mg/O(sic)(sic)(sic) (Mg/O SSZ), (sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)3 nm(sic)Mg/O(sic)(sic)(sic)(sic); (2) (sic)(sic)(sic)(sic)(sic) (IOBZ) , (sic)Mg(sic)(sic)>= 2 at%(sic)(sic)(sic), (sic)(sic)(sic)(sic)MgO(sic)(sic)(sic)(sic)(sic)(sic)(sic).Mg/O(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic), (sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)74 HV(sic)(sic)(sic)224 HV (7 at% Mg) , (sic)(sic)(sic)(sic)(sic)(sic)Ag(sic)(sic)(sic)50 MPa(sic)(sic)(sic)269 MPa (1 at% Mg), (sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic).(sic)(sic)(sic)(sic), MgO(sic)(sic)(sic)Ag(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic), (sic)(sic)(sic)(sic)(sic)(sic), (sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)Mg(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic).(sic)(sic)Mg(sic)(sic)(sic)(sic), (sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)Wagner(sic)(sic), (sic)(sic)(sic)(sic)(sic)1 at% Mg(sic)(sic)7.83 mu m s-1/2(sic)(sic)7 at% Mg(sic)(sic)0.69 mu m s-1/2, (sic)(sic)(sic)(sic)(sic)MgO(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic).(sic)(sic)(sic)(sic)(sic)(sic)Ag-Mg(sic)(sic)(sic)"(sic)(sic)(sic)(sic)(sic)(sic)-(sic)(sic)(sic)(sic)(sic)(sic)"(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic), (sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic), (sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic).

As the operating temperatures of hot-end components in aerospace engines surpass 1500 degrees C, the heat resistance of traditional nickel-based superalloys becomes severely inadequate. Platinum- and iridium-based precious metal high-temperature alloys have become critical materials owing to their high melting points and excellent oxidation resistance. However, existing alloys also face some challenges: platinum-based (Pt-based) alloys typically lack sufficient high-temperature strength, while iridium-based (Ir-based) alloys exhibit significant room-temperature brittleness and poor machinability. To develop these alloys, this paper provides a systematic review of the latest advances in the strengthening mechanisms and high-temperature properties of platinum- and iridium-based ultra-high-temperature alloys. The synergistic effects of multiple mechanisms are summarized, revealing how multicomponent alloy designs and optimized preparation processes drive the development of these alloys, considering strength and ductility. Furthermore, this review examines their high-temperature mechanical properties and environmental stability at ultra-high temperature, and also concludes their applications. Critically, this review highlights the shift toward computation-driven design, which can effectively bridge the gap between theoretical mechanisms and high-temperature performance. It aims to provide a theoretical foundation for the design and optimization of ultra-high-temperature alloys used in aerospace engines as well as other ultra-high-temperature environments.

The thermal expansion mismatch between sapphire and Ti-6Al-4V (TC4) alloy has traditionally limited the shear strength of ceramic-metal joints to <= 170 MPa. In this study, active brazing with Ag-35.25Cu-1.75Ti (wt%) leads to the formation of a dual-function microstructure, wherein uniformly dispersed submicron Ti3(Cu,Al)3O particles embedded in a ductile Ag-Cu matrix contribute to both Orowan strengthening and reduction in the coefficient of thermal expansion (CTE). Simultaneously, a thin Ti3(Cu,Al)3O reaction layer forms a coherent interface with sapphire. This tailored microstructure results in an unprecedented shear strength of 218.3 MPa, marking a 29% improvement over previous records. By combining fine-particle reinforcement, a coherent reaction layer, and mitigation of residual stresses, this approach offers a promising strategy for developing high-strength ceramic-metal joints. (sic)(sic)(sic)(sic)Ti-6Al-4V(TC4)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(CTE)(sic)(sic),(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic),(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)170 MPa.(sic)(sic)(sic)(sic)(sic)Ag-35.25Cu-1.75Ti (wt%)(sic)(sic)(sic)(sic),(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic):(sic)(sic)(sic)(sic)Ti3(Cu,Al)3O(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)Ag-Cu(sic)(sic)(sic),(sic)(sic)(sic)Orowan(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)CTE; (sic)(sic),(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)Ti3(Cu,Al)3O(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic).(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic),(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)218.3 MPa,(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)29%.(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic),(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic),(sic)(sic)(sic)(sic)(sic)(sic)(sic)/(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic).

ABSTRACT The thermal expansion mismatch between sapphire and Ti‐6Al‐4V (TC4) alloy has traditionally limited the shear strength of ceramic‐metal joints to ≤ 170 MPa. In this study, active brazing with Ag‐35.25Cu‐1.75Ti (wt%) leads to the formation of a dual‐function microstructure, wherein uniformly dispersed submicron Ti 3 (Cu,Al) 3 O particles embedded in a ductile Ag‐Cu matrix contribute to both Orowan strengthening and reduction in the coefficient of thermal expansion (CTE). Simultaneously, a thin Ti 3 (Cu,Al) 3 O reaction layer forms a coherent interface with sapphire. This tailored microstructure results in an unprecedented shear strength of 218.3 MPa, marking a 29% improvement over previous records. By combining fine‐particle reinforcement, a coherent reaction layer, and mitigation of residual stresses, this approach offers a promising strategy for developing high‐strength ceramic‐metal joints.

In pursuit of enhancing the high-temperature service performance of Pt-10Rh alloys, this study focuses on the preparation of two Pt-10Rh-based alloys through the incorporation of reinforcing elements zirconium and zirconium-yttrium. The investigation into the microstructure, mechanical properties and strengthening mechanisms of the alloys involved the utilisation of analytical tools such as an optical metallographic microscopy (OM), X-ray diffraction (XRD), selected area electron diffraction (SAED), energy-dispersive X-ray spectroscopy (EDS) and tensile testing, coupled with first-principle computational analysis methods. The research results indicate the presence of Pt5Y precipitate phase and zirconium yttrium oxides in Pt-10Rh-0.5Zr-0.2Y alloy, but not detected in Pt-10Rh-0.5Zr alloy. It was found that adding a small amount of zirconium and yttrium elements to Pt-10Rh alloy can significantly enhance the mechanical properties at room temperature and 1300 degrees C, especially the composite addition of zirconium and yttrium elements, which can also improve the high-temperature plasticity of the alloy. The strengthening mechanisms of zirconium and yttrium elements on Pt-10Rh alloy are mainly solid solution strengthening and second phase strengthening. The relationship between the mechanical properties of platinum-rhodium based alloys and their valence electron structure was discussed. The zirconium and yttrium reinforced platinum-rhodium based alloy studied in this work can replace Pt-10Rh alloy in certain fields.

In multi-principal refractory alloys (high-entropy alloys, medium-entropy alloys), the presence of the second phase has an important influence on the mechanical properties of the alloys. In this paper, AlxCrTaTi (x = 0, 0.25, 0.5, 1.0) refractory medium-entropy alloys were prepared by vacuum arc melting method, and the microstructure, density, and mechanical properties were investigated. The CrTaTi alloy consists of BCC dendritic and C15 Laves phases, whereas the AlxCrTaTi alloys consist of a two-phase eutectic organization (BCC phase and C14 Laves phase). With the increase of Al content, the content of the second phase increases from 15.97 % to 42.19 %, resulting in an increase in the yield strength of the alloy from 1491 MPa to 2354 MPa at 25 degrees C, and from 253 MPa to 426 MPa at 1000 degrees C. The addition of Al element changes the enthalpy, elemental distribution, and solidification process of the alloy, resulting in the formation of Cr-rich and Ti-rich two-phase eutectic organizations in the alloy. With the increase of Al, the second phase strengthening is the main reason for the enhancement of alloy properties.

The pursuit of Ag-based alloys with both high strength and toughness has posed a longstanding challenge. In this study, we investigated the cluster strengthening and grain refinement toughening mechanisms in fully oxidized AgMgNi alloys, which were internally oxidized at 800 degrees C for 8 h under an oxygen atmosphere. We found that Mg-O clusters contributed to the hardening (138 HV) and strengthening (376.9 MPa) of the AgMg alloy through solid solution strengthening effects, albeit at the expense of ductility. To address this limitation, we introduced Ni nanoparticles into the AgMg alloy, resulting in significant grain refinement within its microstructure. Specifically, the grain size decreased from 67.2 mu m in the oxidized AgMg alloy to below 6.0 mu m in the oxidized AgMgNi alloy containing 0.3 wt% Ni. Consequently, the toughness increased significantly, rising from toughness value of 2177.9 MJ m-3 in the oxidized AgMg alloy to 6186.1 MJ m-3 in the oxidized AgMgNi alloy, representing a remarkable 2.8-fold enhancement. Furthermore, the internally oxidized AgMgNi alloy attained a strength of up to 387.6 MPa, comparable to that of the internally oxidized AgMg alloy, thereby demonstrating the successful realization of concurrent strengthening and toughening. These results collectively offer a novel approach for the design of highperformance alloys through the synergistic combination of cluster strengthening and grain refinement toughening. (c) 2025 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science & Technology.

A novel AgCuTi brazing foil with a unique microstructure was developed, which could achieve strong vacuum brazing of Ti6Al4V (TC4) and sapphire. The brazing foil was composed of Ag solid solution (Ag(s,s)), Cu solid solution (Cu(s,s)), and layered Ti-rich phases, and had a low liquidus temperature of 790 °C and a narrow melting range of 16 °C, facilitating the defect-free joining of TC4 and sapphire. The sapphire/TC4 joint fabricated by using this novel AgCuTi brazing foil exhibited an outstanding average shear strength of up to 132.2 MPa, which was the highest value ever reported. The sapphire/TC4 joint had a characteristic structure, featuring a brazing seam reinforced by TiCu particles and a thin Ti3(Cu,Al)3O reaction layer of about 1.3 μm. The fracture mechanism of the sapphire/TC4 joint was revealed. The crack originated at the brazing seam with TiCu particles, then propagated through the Ti3(Cu,Al)3O reaction layer, detached the reaction layer from the sapphire, and finally penetrated into the sapphire. This study offers valuable insights into the design of active brazing alloys and reliable metal–ceramic bonding.

The strength of Pt-Al superalloys can be effectively improved using a coherent structure composed of a disordered gamma phase and an ordered gamma ' phase. However, gamma '-Pt3Al has a cubic phase only at high temperatures and a tetragonal phase at low temperatures, thus breaking the coherent interface and deteriorating its mechanical properties. Here, high throughput first-principles calculations and rational experiments were conducted to discover novel gamma-gamma ' Pt-Al superalloys. The alloying strategy stabilizes the gamma ' phase through the local charge distortion (LCD) or the local lattice distortion (LLD). Alloying elements, such as, Ti, Hf, and Ta, occupy the Al site in combination with Pt, making the spherical shape of change density in Pt3Al showing obvious directionality, i.e., LCD. Therefore, the stability of the gamma ' phase is proposed at a lower alloying element concentration (3.125 at.%). However, alloying elements near Pt, e.g., Ni, Co, and Ru, tend to occupy the Pt site and induce LLD to stabilize the gamma ' phase at higher alloying element concentration (12.5 at.%). The shape of the change density is similar to that of Pt3Al, and no obvious LCD is found when alloying elements occupy the Pt site. LCD-induced phase stability is observed exclusively at the Al site, whereas LLD-induced phase stability is solely present at the Pt site. The Pt-12Al-6X (X = Hf, Ti, Ta, Cr, and Ni in at.%) alloys were prepared, among which Pt-12Al-6Hf possessed a stable gamma ' phase, a lower lattice misfit between gamma and gamma ', and a higher precipitation strengthening, resulting in its hardness (442.1 H-V) surpassing that of Ni-based superalloys IN718 (413.6 H-V). The gamma ' phase in Pt-12Al-6Hf was characterized by high-resolution transmission electron microscopy, suggesting that the Pt site of the gamma ' phase was occupied by Pt, while the Al site was shared by Pt, Al, and Hf. This is consistent with the calculated results.

Enhancing the ductility of internally oxidized AgMg alloys has posed a longstanding challenge.A new method to achieve simultaneous hardening and toughening of AgMgNi alloys is presented by means of internal oxi-dation.The influence of Ni content on the internal oxida-tion process and the mechanical behavior of AgMgNi alloys is systematically investigated.It is found that Ni addition induces grain refinement by forming nanoscale Ni particles,which act as heterogeneous nucleation sites and inhibit grain growth during internal oxidation.This enhances the plasticity and toughness of the alloys via the Hall-Petch effect.The alloys exhibit a conductivity of～42 MS·m-1 and surface hardness of～HV 125,which are insensitive to the variation of Ni content within 0 wt％-2 wt％.The optimal range of Ni content for achieving the best combination of hardness,strength and toughness is 0.15 wt％-0.3 wt％,corresponding to alloys with a tensile strength above 300 MPa and a toughness surpassing 3300 MJ·m-3.Higher Ni contents reduce the internal oxidation depth(from about 340.6 to about 238.4 μm)and the tensile strength(from about 342.1 to about 230.1 MPa)of the alloys by generating micrometer-sized Ni-rich par-ticles in the matrix,which consume oxygen,obstruct some of the oxygen diffusion channels and impede the oxidation front advancement.The non-oxidized region,which does not benefit from oxidation strengthening,diminishes the overall strength of the alloy.These results reveal the cru-cial role of Ni in regulating the internal oxidation dynamics and microstructure evolution of AgMgNi alloys,and sug-gest a novel approach for designing high-performance alloys with concurrent hardening and toughening.

Lutetium aluminum garnet doped with cerium (LuAG:Ce) thin films have been identified as a promising material for high-power laser-driven lighting applications. In this study, spray pyrolysis we employed to fabricate LuAG:Ce films on sapphire substrates and the impact of film thickness on thermal management and light emission efficiency was investigated. Our results show that, regardless of thickness, LuAG:Ce films exhibit impressive internal quantum efficiencies (IQE) exceeding 83.2

Six rare-earth tantalate high-entropy ceramics of (5RE(.2))Ta3O9 (RE represents any five elements selected from La, Ce, Nd, Sm, Eu, Gd) were designed and prepared by spark plasma sintering process at 1400 degrees C in this study. The (5RE(.2))Ta3O9 ceramics only consist of a single-phase solid solution with perovskite structure. Their relative densities are all above 90%, and the average grain size is in the range of 1.47-2.92 mu m. The thermal conductivity of (5RE(.2))Ta3O9 ceramics is in 2.24-1.90 W m(-1) K-1 (25 degrees C-500 degrees C), which is much lower than that of yttria-stabilized zirconia. In six samples, (La.2Nd.2Sm.2Gd.2Eu.2)Ta3O9 possesses a thermal conductivity of 1.90 W m(-1) K-1, a thermal expansion coefficient of 3.47 x 10(-6) K-1 (500 degrees C), a Vickers hardness of about 7.33 GPa, and a fracture toughness of about 5.20 MPa m(1/2), which are suitable for its application as thermal barrier coatings.

Pt–Ir alloy is potential superalloys used above 1300 °C because of their high strength and creep resistance. However, the ductility of Pt–Ir alloy has rapidly deteriorated with the increase of Ir, resulting in poor machinability. This work quantitatively evaluated the solid solution strengthening (SSS) and grain refinement strengthening (GRS) of Pt–Ir alloy using first-principles calculations combined with experimental characterization. Here, the stretching force constants in the second nearest neighbor region (SFC2nd) of pure Ir (193.7 eV·nm−2) are 3.40 times that of pure Pt (57.0 eV·nm−2), i.e., the interatomic interaction is greatly enhanced with the increase of Ir content, which leads to the decrease of ductility, and modulus misfit plays a dominant role in SSS. Then, the physical mechanisms responsible for the hardness (HV) of Pt–Ir alloy, using the power-law-scaled function of electron work function coupled SSS and GRS, are attributed to the electron redistribution caused by different Ir content. Furthermore, a thorough assessment of the thermodynamic characteristics of Pt–Ir binary alloy was conducted, culminating in development of a mapping model that effectively relates composition, temperature and strength. The results revealed that the compressive strength increases with the Ir content, and the highest strength was observed in Pt0.25Ir0.75. This study provides valuable insights into the Pt–Ir alloy system.

Thermodynamic calculations of Ellingham diagrams and the forming oxides have been performed relevant to the Pt-based alloys Pt82Al12M6 (M = Cr, Hf, Pt, and Ta). The predicted Ellingham diagrams indicate that the elements Hf and Al are easy to oxidize, followed by Ta and Cr, while Pt is extremely difficult to oxidize. Oxidation experiments characterized by X-ray diffraction (XRD) and electron probe micro-analyzers verify the present thermodynamic predictions, showing that the best alloy with superior oxidation resistance is Pt82Al12Cr6, followed by Pt88Al12 due to the formation of the dense and continuous α-Al2O3 scale on the surface of alloys; while the worse alloy is Pt82Al12Hf6 followed by Pt82Al12Ta6 due to drastic internal oxidation and the formation of deleterious HfO2, AlTaO4, and Ta2O5. The present work, combining computations with experimental verifications, provides a fundamental understanding and knowledgebase to develop Pt-based superalloys with superior oxidation resistance that can be used in ultra-high temperatures.

A new kind of Nb-W-C alloy with special microstructure and excellent mechanical property was designed and prepared by CVD subsequent with homogenizing heat treatment. Its microstructure is composed of columnar crystals with specific orientation, needle-like Nb2C second phase and layered structure with Nb/W composition segregation. By analyzing the effect of homogenizing heat treatment on the property and microstructure of the alloy, it was found that the as-deposited layered structure was retained in the microstructure after heat treatment at 1400 degrees C, but disappeared by treated at 1600 degrees C. The layered structure can effectively separate Nb2C and inhibit the size coarsening of Nb2C during carbide formation. During the homogenization process, needle-like carbides can maintain the strengthening effect under the condition of slight grain growth, but excessively high homogenization heat treatment temperature coarsens the grains and carbides, and ultimately weakens the strength of the alloy. The comprehensive strengthening effect of grain refinement and carbide pinning makes the room temperature strength of the sample reach 670 MPa after homogenizing treatment at 1400 degrees C for 6 h, which is about 35-45% higher than the asdeposited Nb-W-C alloy and the existing widely used Nb521 alloy produced by melting-forging-annealing technology.

Rhenium is widely used as functional materials and ultrahigh temperature structural materials due to its excellent physical and mechanical properties. A variety of methods have been applied to prepare rhenium materials, among which chemical vapor deposition (CVD) is one of the main techniques. The reaction type, deposition condition and effect of rhenium by CVD were introduced in the present paper. Then, the deposition dynamics, microstructure characteristics, mechanical properties and typical applications of CVD rhenium were reviewed, and compared with those of powder metallurgical rhenium. Finally, several key issues which need to be solved were put forward, and the research directions and application foreground was prospected.

A series of rare-earth-tantalate high-entropy ceramics ((5RE(0.2))Ta3O9, where RE = five elements chosen from La, Ce, Nd, Sm, Eu and Gd) were prepared by conventional sintering in air at 1500 degrees C for 10 h. The (5RE(0.2))Ta3O9 high-entropy ceramics exhibit an orthogonal structure and sluggish grain growth. No phase transition occurs in the test temperature of 25-1200 degrees C. The thermal conductivities of all (5RE(0.2))Ta3O9 ceramics are in the range of 1.14-1.98 W m(-1) K-1 at a test temperature of 25-500 degrees C, approximately half of that of YSZ. The sample of (Gd0.2Ce0.2Nd0.2Sm0.2Eu0.2)Ta3O9 exhibits a low glass-like thermal conductivity with a value of 1.14 W m(-1) K-1 at 25 degrees C. The thermal expansion coefficient of (5RE(0.2))Ta3O9 ceramics ranges from 5.6 x 10(-6) to 7.8 x 10(-6) K-1 at 25-800 degrees C, and their fracture toughness is high (3.09-6.78 MPa.m(1/2)). The results above show that (5RE(0.2)) Ta3O9 ceramics could be a promising candidate for thermal barrier coatings.

In order to improve the corrosion resistance of tantalum coatings produced by chemical vapor deposition (hereinafter referred to as CVD Ta) in various industrial fields, the effect of the texture on the corrosion behavior was investigated. The microstructure and electrochemical properties of CVD Ta were examined by scanning electron microscopy (SEM), X-ray diffraction (XRD), and electrochemical analysis. The surface energy and work function of the Ta surface were investigated based on first-principles calculations, which were used for the simulations of polarization curves. The SEM analysis revealed that the coatings showed a microscopic pyramid structure. Furthermore, XRD analysis results showed that the coatings mainly exhibited (110), (200), and (211) planes. Electrochemical tests showed that the coatings with a preferential orientation along the (110) plane exhibited the lowest corrosion current density value of 0.009 mA/cm 2 and the corrosion potential value of −0.380 V, which showed the highest quality and corrosion resistance. Further, the first-principles calculation results demonstrated that for these coatings, a highest work function and lowest surface energy result in the weakest chemical activity, which provides a theoretical explanation for the corrosion resistance corresponding to the (110) plane. Based on the results of this work, a method is proposed to regulate Cl 2 flow rate using consistent first-principles theory for the design and selection of Ta coatings that exhibit excellent resistance to anisotropic corrosion.