Phase Structure Research Articles

Effects of Bi2O3–CuO addition on the dielectric properties of MgO–TiO2(w) ceramics sintered at low temperatures

Herein, MgO–12% TiO2(w) ceramics with different contents of Bi2O3–CuO sintering aid were prepared using a solid-state method. The effects of the sintering aid content on the sintering temperature and the dielectric and mechanical properties of the ceramics were studied. The material was characterized using scanning electron microscopy and X-ray diffraction and Precision LCR tester and universal testing machine and Archimedes drainage method. When the Bi2O3–CuO content was less than 9 wt%, the ceramic sample has higher dielectric properties. When the Bi2O3–CuO content was greater than 9 wt%, the dielectric properties will deteriorate. This is because Bi2O3 participates in the chemical reaction between MgO and TiO2, forming a high dielectric loss Bi4Ti3O7 phase. At high temperatures, Cu2+ can easily change valence to Cu+, promoting oxygen vacancies and increasing dielectric loss in ceramic samples. The introduction of Bi2O3–CuO produces new MgTiO3, Mg2TiO4, and Bi4Ti3O12 phases in the sample structure, resulting in a structure in which the MgO grains in the sample are surrounded by the new phases that appear around them. This structure fills the pores, increases density, enhances mechanical properties. The dielectric properties of the ceramics were the when the sintering temperature was 1050 °C, and the Bi2O3–CuO content was 3 wt%. The dielectric constant and dielectric loss were 11.19 and 1.17 × 10−4, respectively. The bending strength of the ceramic sample increased from 138.72 MPa to 179.64 MPa when the Bi2O3–CuO content was increased from 3 wt% to 15 wt%. The Bi2O3–CuO sintering aid enables MgO to be better applied in ceramic substrates.

Fullerene C60 functionalized Sm2O3@Eu2O3 bimetallic oxides core shell Nanocomposites for Zeta potential and energy storage applications

Nanocomposites of Fullerene C60 (FC60) with lanthanide oxides show better energy storage properties compared with any of them alone. In the present research, we have synthesized FC60 (2, 5 and 10 wt%) anchored on Sm2O3@Eu2O3 bimetallic oxides by simple chemical precipitation method. The FC60:Sm2O3@Eu2O3 core shell nanocomposites (NCs) were characterized by XRD (X-ray diffraction), SEM (scanning electron microscopy), EDX (energy dispersive X-ray), UV–visible, XPS (X-ray photoelectron spectroscopy), and BET (Brunauer–Emmett–Teller) analytical methods. XRD studies revealed mixed phase of monoclinic and orthorhombic crystal structure with irregularly scattered small plate/flake like morphology agglomerated and formed as large grains. Electrochemical supercapacitive behaviour of Sm2O3@Eu2O3 bimetallic oxides showed specific capacitance (SCs) of 665.075F/g in 3 M KOH as electrolyte. The SCs of FC60 (5 wt% and 10 wt%):Sm2O3@Eu2O3 electrode material in 3 M KOH solution was found to be 795.92F/g and 1120F/g at a current density of 1 A/g (scan rate of 10 mV/s). FC60 (10 wt%):Sm2O3@Eu2O3 NCs showed excellent capacitive retention of 90.8 % after 10,000 cycles. The Zeta potential (ζ) studies of FC60:Sm2O3@Eu2O3 NCs showed decrease in the mean Zeta potential (ζ) from 34.23 mV to 11.97 mV with decrease in electrophoretic mobility (2.667 to 0.933 (μm cm/Vs)) attributed to the cationic nature of the FC60:Sm2O3@Eu2O3 NCs. The FC60:Sm2O3@Eu2O3 NCs with high cycle stability and charge density can be a better candidate for high energy storage devices, supercapacitor, dielectric related applications.

Dispersion, solid solution, and covalent bond coupled to strengthen K4169/TiAl composite brazed joints: first-principles and experimental perspective

Ni/TiAl composite brazed joints could significantly reduce the aircraft's weight. However, low interfacial adhesion, coarse and brittle-hard intermetallic compounds (IMCs) seriously limited the application of Ni/TiAl composite joints in the next generation of aerospace applications. So enhanced K4169/TiAl composite joints were investigated by vacuum brazed with (Ni53.33Cr20B16.67Si10/Zr25Ti18.75Ta12.5Ni25Cu18.75) composite filler metal (CFM) designed based on cluster-plus-glue-atom model. The shear strength of the joint reached 485 MPa, comparable to the 491 MPa of TiAl substrate. The flat and brittle-hard diffusion reaction layer between Zones I and II was eliminated, simultaneously generating CrB4 dispersion strengthening due to the CFM developed with the interfacial solid-liquid space-time hysteresis effect. In Zones II and III, IMCs all transformed into Niss(Cr,Fe)[0-88], Niss(Ti, Al)[004], and Niss(Zr,Si)[11-2] of circular and oval shapes through isothermal solidification. Meanwhile, the residual stresses and hardness were distributed in reticulated cladding characteristics. Thereby, lattice distortion led to solid solution strengthening and increased plastic toughness through crack termination and bridging mechanisms, which inhibited dislocations from plugging and crack propagation. Various interfaces in Zone Ⅳ were regulated into semi- and coherent interfaces. Ni3(Ti,Al)/(Ni,Ti,Al) and (Ni,Ti,Al)/AlNi2Ti were composed of higher interfacial bonding energy (2.771 J/m2, 2.547 J/m2) and Ni-Ni covalent bonds. Interfacial covalent bonding and large interfacial bonding energy coupling strengthened Zone IV. Consequently, cracks initiated at the (Ni,Ti,Al)[013]/Ti3Al[010] and expanded rapidly into TiAl substrate. Therefore, applying this method to design CFMs and regulate the phase, grain morphology, and interface's fine structure could provide new pathways for dissimilar hard-to-join metals.

Enhanced an eutectic carbide reinforced niobium alloy by optimizing Mo and W alloying elements

Niobium alloys play an indispensable role in aerospace technology. However, traditional niobium alloys has unsatisfactory or high-temperature strength or limited room-temperature. This work introduces Nb2MoxWyC0.25 alloys with strength-plasticity balance by optimizing refractory alloy elements and eutectic carbides drawing on the design concepts of eutectic high-entropy alloys. The influence of Mo and W contents on the microstructure and mechanical properties of the alloys was studied. The Nb2MoxWyC0.25 alloy contain body-centered cubic (BCC) primary phase and eutectic structures composed of BCC and carbide phases with semi-coherent interfaces. Appropriate additions of Mo and W refine the grain size of the primary BCC phase and cause the carbide phase to evolve from Nb2C to NbC. The Nb2Mo0.5W0.5C0.25 hypoeutectic niobium alloy composed of BCC and Nb2C phases with a relatively small lattice mismatch has a room-temperature yield strength of 1.27 ± 0.04 GPa, compressive strength of 2.03 ± 0.06 GPa, and a fracture strain of 17.8 ± 2.2 %. Solid solution strengthening in the BCC phase and second-phase strengthening of the carbide phase simultaneously enhance the alloy. The fine grain strengthening, reduced crack origination at low mismatch interface, and the crack tip by soft BCC at the phase interface improve the plasticity simultaneously. This paper provides a method to improve the room-temperature plasticity and strength of refractory niobium alloys, laying the foundation for the industrial application of refractory niobium alloys.

Grain boundary diffusion in additively manufactured CoCrFeMnNi high-entropy alloys: Impact of non-equilibrium state, temperature and relaxation

Grain boundary diffusion of Ni in the equiatomic CoCrFeMnNi high-entropy alloy, produced by additive manufacturing, is measured using a radiotracer technique in an extended temperature interval of 350 to 703 K. A strongly non-monotonic temperature dependence of the Ni grain boundary diffusion coefficients (with a spectacular retardation of the diffusion rates with increasing temperature) is seen and explained by relaxation of a non-equilibrium state induced by rapid solidification during fabrication. The grain boundary excess energy of the non-equilibrium state of these grain boundaries, as estimated from the diffusion data, is found to be larger than 0.3 J/m2. This corresponds to an increase of about 30% of the interface energy compared to relaxed general high-angle grain boundaries. The temperature-induced evolution of the grain boundary state is analyzed in terms of the concomitant structure evolution, segregation, phase stability and precipitation in the multi-component alloy.

Air-stable manganese-based layered oxide cathode enabled by surface modification and doping strategy for advanced sodium-ion batteries

P2-type layered oxide materials have attracted widespread attention as advanced cathodes for sodium-ion batteries due to their excellent rate potential and attractive cost-effectiveness. However, the unexpected dissolution of transition metal (TM) ions and the annoying Jahn-Teller effect leading to rapid capacity fading and low capacity remain obstacles to their commercial applications. To tackle these handicaps, we introduced a synergistic effect based on surface modification and doping strategies to obtain air-stable sodium carbonate (Na2CO3) protective aluminum (Al)-doped manganese-based layered oxide cathode. The surface Na2CO3 nanolayer is created by converting residual alkali ions, which enhances the air stability of the cathode and scavenges hydrofluoric acid into the fluoride-rich cathode electrolyte interphase layer during cycling, resulting in a steady interfacial interaction. In addition, Al doping causes TMO6-octahedral shrinkage and inhibits structural distortion, thereby affecting structural evolution and phase transition. These findings provide valuable insights into improving the performance of layer oxide cathodes for next-generation low-cost batteries.

Biogenic synthesis and characterization of silver nanoparticles (AgNPs) from aqueous extract of Lepidagathis cristata along with their antibacterial and antineoplastic activity to combat breast cancer cells (MCF-7).

Lepidagathis cristata (L.cristata) plant produces reducing and capping agents; this study utilized microwave-assisted biogenic synthesis to manufacture silver nanoparticles (AgNPs) using this plant. The structure, morphology, and crystallinity phases of prepared nanoparticles (NPs) were characterized by ultraviolet-visible spectroscopy (UV-viz), powder X-ray diffraction (XRD), Fourier-transform infrared (FTIR) spectroscopy, and scanning electron microscopy (SEM). Biologically synthesized AgNPs were treated against pathogenic bacteria species including Escherichia coli (E.coli), Bacillus subtilis (B.subtilis), and Staphylococcus aureus (S.aureus) and its highest zone of inhibition 10 ± 1.45 mm, 10 ± 0.74 mm, and 6 ± 0.43 mm, respectively, at the concentration of 100 μg/mL. The cytotoxic activity of AgNPs against MCF-7 breast cancer cells revealed significant growth inhibition by inhibiting cell viability, inhibitory concentration of 50% (IC50) of NPs observed at 55.76 μg/mL concentration. Finally, our findings concluded that the L.cristata-mediated biosynthesized AgNPs proved its potential antibacterial and neoplastic properties against MCF cells by endorsing the inhibition of cell proliferation especially with low concentration.

Efficient control of automotive emission by Pt-based and Rh-based three-way catalysts: The critical role of phase structure of ceria-zirconia support

Rationally design efficient supports material is essential for heterogeneous catalysts with enhanced activity in many industrial catalytic processes, accordingly a clear understanding of the support effect is necessary. Herein, two ceria-zirconia materials without/with partial κ-Ce2Zr2O8(CZ/κCZ) structure were achieved and then employed as supports for Rh-based and Pt-based three-way catalysts (TWCs), respectively. According to the results of systematic characterizations, it has been manifested that the surface conditions of supports significantly affected the activity and stability of Rh-based and Pt-based catalysts. As κCZ exhibits an intrinsic Zr-rich surface with more oxygen vacancies with respect to CZ, Rh species supported on κCZ mainly occupy the Zr sites over the surface, thus exhibit a more electronic-rich and active state due to the decreased Rh-Ce interfaces, which weakened the undesirable electron transfer from Rh to Ce. As a result, κCZ delivered as an ideal support for improving the performance of Rh-based TWCs effectively. On contrary, comparing with Pt/CZ, more serious sintering of Pt nanoparticles and inferior activity as well as stability have been detected in Pt/κCZ due to the decreased Pt-Ce interfaces, which weakened the anchor effects of the support through Pt-O-Ce bonds. This finding enhances the understanding of support effects for the development of advanced TWCs.

Improved phase prediction of high-entropy alloys assisted by imbalance learning

Predicting phase formation is crucial in novel high-entropy alloys (HEAs) design. Herein, machine learning and imbalance learning algorithms were combined together to improve the phase prediction of HEAs. In this work, an extensive database by collecting experimental data from published literature was constructed, and the key features affecting the phase formation of HEAs were filtered out by performing a three-step feature selection process. Then, extreme gradient boosting (XGB) models were constructed to categorize phase structures of HEAs with high accuracies. Moreover, the Synthetic Minority Oversampling TEchnique (SMOTE) algorithm was employed for data oversampling to address the data imbalance issue. It was found that imbalanced learning significantly improves the phase prediction, particularly for the minority class, without costing the overall prediction accuracy. Finally, a machine learning-base protocol was proposed to integrate established models to classify the phase formation of HEAs into seven phase labels, and its generalization ability was verified. The present work provides a practical approach in predicting phase structures of HEAs and enhances the efficiency in developing advanced HEAs.

Phase compatible surface engineering to boost the cycling stability of single-crystalline Ni-rich cathode for high energy density lithium-ion batteries

Nickel-rich layered oxide is a promising cathode material for the next generation lithium-ion batteries (LIBs) because of its high energy density and cost efficiency. Unfortunately, it suffers from unsatisfying electrochemical performance owing to intrinsic interfacial and structural instability, which limits its application at scale. In this work, a phase compatible TiBO3 coating layer on single crystalline LiNi0.83Co0.11Mn0.06O2 (TBO-SC-NCM) is constructed via modified solid-state chemical reaction. The coating layer serves as a protective screen to mitigate the erosion of organic electrolyte towards TBO-SC-NCM. Furthermore, both titanium ions and boron ions successfully diffuse into the TBO-SC-NCM bulk phase during the annealing process, with titanium ions being uniformly distributed while boron ions accumulating close to the surface. The formation of strong Ti-O bond effectively inhibits the bulk phase structure degradation of TBO-SC-NCM. The near-surface enriched B-O bond greatly stabilizes the surface lattice oxygen at the deeply delithiated state. Additionally, the spread of layer spacing due to the doping of heterogeneous ions ensures the rapid diffusion of Li+, thus improving the rate performance of TBO-SC-NCM. As a h cathode materials.

Strain effects on the structural stability and defect properties of γ-CsPbI3

Black γ phase CsPbI3 exhibits better structure stability at room temperature, making it a compelling candidate for perovskite solar cells. However, the long-term stability remains a challenge due to lattice strain. Here, the lattice structure stability and defect properties of γ-CsPbI3 under biaxial strains on the different planes were investigated by first-principles method. The results show that the tensile strain effectively reduces the PbI6 octahedral tilt to maintain the structural stability and improves the defect formation energies of VI, VPb, VCs and ICs, while the compressive strain can increase the formation energies of IPb and CsPb, hinders the diffusion of VI along the octahedral path and makes the defect level of VI shallower. The biaxial strain on the (001) plane is favourable for decreasing the formation enthalpy difference and maintaining the shallow level of VI to preserve the black phase structure, whereas that on the (100) plane is more beneficial for modulating these properties. This work offers theoretical guidance for applying strain to influence structure stability and suppress defect formation in γ-CsPbI3. Furthermore, it proposes a strategy utilizing lattice strain to modulate the energy levels of defects, thereby facilitating their passivation and enhancing device performance of perovskite photovoltaics.

Dilatonic black holes in dRGT massive gravity

Motivated by high interest in Lorentz invariant massive gravity models known as the dRGT massive gravity, we discuss the dRGT massive gravity including the coupling term between dilaton scalar field and massive graviton, and present static and spherically symmetric solutions of dilatonic black holes in four and higher dimensional spacetime. Later, we investigate phase structure of these black hole solutions, and discover that the dilatonic black hole could possess two horizons, extreme and naked singularity black holes for the suitably parameters values. Calculating the conserved and thermodynamic quantities, we check the validity of the first law of thermodynamics.

Microstructural Evolution and Magnetic Influence Mechanism of Cr in-situ Alloying SLM -formed NiFeMo alloys

NiFeMo is prevalently employed in the field of aerospace and electronic devices owing to its excellent soft magnetic properties. Besides, the incorporation of elements through in-situ alloying presents a novel strategy for performance modulation in Selective Laser Melting (SLM), presenting a novel pathway toward the advancement of soft magnetic materials. In this study, (NiFeMo)100-xCrx alloys (x=0wt.%, 0.5wt.%, 1.0wt.%, 1.5wt.%, 2.0wt.%, 2.5wt.%) were prepared utilizing Cr in-situ alloying SLM. The magnetic properties as well as microstructural characterization were conducted by employing X-ray diffraction (XRD), scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), high-resolution transmission electron microscopy (HRTEM) (Tecnai-G2-F30), and direct current B-H hysteresis curve testing equipment (MATS-2010S). The results indicate that the microstructure of the SLM-formed NiFeMo alloy through in-situ chromium alloying is predominantly characterized by columnar grains growing along the build direction. With an increase in the in-situ alloying ratio of chromium, the lattice parameters of the FCC phase structure of the NiFeMo alloy decrease from 3.582Å to 3.503Å, the average grain size monotonically decreases, and the maximum texture strength monotonically weakens. Furthermore, during the in-situ alloying SLM process, chromium is dissolved into the FCC γ-(Ni, Fe) of the NiFeMo alloy, forming dispersed, chromium-rich precipitates of larger sizes. This leads to a reduction in the intrinsic magnetic properties of the NiFeMo alloy, affecting the exchange coupling interaction between magnetic atoms and the motion of magnetic domains. Compared to the NiFeMo alloy, the saturation magnetization of the (NiFeMo)97.5Cr2.5 alloy is reduced to 0.4685T, and the coercive force is increased to 37.7A/m. However, when the chromium content is 1wt.%, the initial magnetic permeability of the (NiFeMo)99Cr1 alloy is 2.337mH/m, which is an enhancement of 1.9422mH/m compared to the NiFeMo alloy.

Improved comprehensive performance of high entropy rare earth aluminate as T/EBC materials by phase structure regulation

Improved comprehensive performance of high entropy rare earth aluminate as T/EBC materials by phase structure regulation

Bio-inspired self-healing polyurethane system: Mimicking connective tissue with hydrogen-bonding mechanism

Achieving a balance between mechanical strength and self-healing efficiency in self-healing materials is challenging yet crucial. This work introduces PCL-HBU, a polyurethane material designed for the first time to mimic collagen fibers, elastic fibers, and vascular networks of connective tissue, with excellent mechanical properties and self-healing efficiency. Meanwhile, by adjusting the 2-ureido-4-[1H]-pyrimidinone (UPy) and N,N-bis(2-hydroxyethyl)oxamide (BHO) ratio, this work creatively developed PCL-HBU3 with three distinct phase structures: amorphous region, soft segment crystallisation, and hard segment crystallisation, which approach confers excellent mechanical properties to the material. PCL-HBU3 exhibits a tensile strength of 70.0 MPa and elongation at break of 1500 %. It can recover from 600 % elongation within 20 s, achieving 100 % elongation at break self-healing efficiency. Furthermore, the composite conductive material fabricated using PCL-HBU3 as the matrix showcases self-healing abilities and holds promise in motion detection and sound recognition applications.

Atomic resolution scanning transmission electron microscopy at liquid helium temperatures for quantum materials

Fundamental quantum phenomena in condensed matter, ranging from correlated electron systems to quantum information processors, manifest their emergent characteristics and behaviors predominantly at low temperatures. This necessitates the use of liquid helium (LHe) cooling for experimental observation. Atomic resolution scanning transmission electron microscopy combined with LHe cooling (cryo-STEM) provides a powerful characterization technique to probe local atomic structural modulations and their coupling with charge, spin and orbital degrees-of-freedom in quantum materials. However, achieving atomic resolution in cryo-STEM is exceptionally challenging, primarily due to sample drifts arising from temperature changes and noises associated with LHe bubbling, turbulent gas flow, etc. In this work, we demonstrate atomic resolution cryo-STEM imaging at LHe temperatures using a commercial side-entry LHe cooling holder. Firstly, we examine STEM imaging performance as a function of He gas flow rate, identifying two primary noise sources: He-gas pulsing and He-gas bubbling. Secondly, we propose two strategies to achieve low noise conditions for atomic resolution STEM imaging: either by temporarily suppressing He gas flow rate using the needle valve or by acquiring images during the natural warming process. Lastly, we show the applications of image acquisition methods and image processing techniques in investigating structural phase transitions in Cr2Ge2Te6, CuIr2S4, and CrCl3. Our findings represent an advance in the field of atomic resolution electron microscopy imaging for quantum materials and devices at LHe temperatures, which can be applied to other commercial side-entry LHe cooling TEM holders.

Fabricating highly stable and reliable vanadium dioxide thin films: Insights from radio frequency magnetron sputtering

This study establishes an optimization protocol to fabricate a stoichiometric VO2 thin film onto the glass substrate using a single process step in RF magnetron sputtering. An interplay between the substrate temperature and the oxygen-to-argon ratio in process gas is shown to achieve a range of VOx composition (from oxygen-rich to oxygen-deficient phases). The re-sputtering phenomenon is found to be crucial at higher temperature (T ≥ 873 K), leading to a shift in stoichiometry from V2O5 to V2O3. Moreover, a process model for the fabrication of various VOx compounds in thin film form is also established in this study. The crystal structure transformation from M1 to R phase for these VO2 thin films deposited over a range of process conditions is found to be 339 ± 1 K, in close agreement with the reported value for the bulk VO2. In spite of the microstructural variations, these films are found to show consistent phase transition behavior, excellent stability, and reliability in repeated thermal cycles. These films show a semiconductor-to-metal transition, which is correlated to their structural phase transformation temperature. Moreover, this study also establishes a correlation between various external stimuli, widening the usage of this material in a range of applications.

Evolution of static and dynamic magnetic properties of Re/Co/Pt and Pt/Co/Re trilayers with enhanced Dzyaloshinskii-Moriya interaction

The influence of Re layer insertion either at the bottom or top interface of epitaxially grown Pt/Co/Pt heterostructures on their static and dynamic magnetic properties is discussed in terms of their crystalline structure. Magnetic properties were studied as a function of both Re and Co layer thicknesses (dRe and dCo, respectively) in the matrix-like samples with a double-wedge structure, in which the layer thickness gradients were oriented orthogonally. The comprehensive investigations of the changes in coercivity, perpendicular magnetic anisotropy, spin reorientation transition, interfacial Dzyaloshinskii-Moriya interaction (iDMI) and spin wave damping are reported. Two different magnetic phases depending on the Co layer thickness with volume anisotropies (determined without demagnetization term) of KV∼0.25 (low) and KV∼0.75 MJ/m3 (high) were observed. The relation between these phases depends on the stack sequence and thickness of Re inserted layer. For dRe = 0.2 ÷ 0.7 nm deposited as the bottom interface, dCo induced transition at dtr ∼ 2 nm from low to high volume anisotropy phases was observed. Low and high volume anisotropy phases are associated to Co fcc and hcp structural phases. The insertion of half atomic layer of Re had no influence on surface anisotropy but significantly enhanced iDMI above 1 pJ/m and reduced spin wave damping.

Regulations of Thermal Expansion Coefficients of Yb1−xAlxTaO4 for Environmental Barrier Coatings Applications

Environmental barrier coatings (EBCs) are widely used to protect ceramic matrix composites (CMCs, SiCf/SiC, and Al2O3f/Al2O3), and they should have low thermal expansion coefficients (TECs) matching the CMCs and excellent mechanical properties to prolong their lifetime. Current EBC materials have disadvantages of phase transitions and insufficient mechanical properties, which affect their working temperatures and lifetime. It is necessary to develop new oxide EBCs. Ytterbium tantalate (YbTaO4) is a stable and novel EBC material, and we have improved the mechanical properties and TECs of Yb1−xAlxTaO4 (x = 0.05, 0.1, 0.2, 0.3, 0.4, 0.5) ceramics by replacing Yb with Al. XRD, SEM, and EDS are used to verify the crystal and microstructures, and nano-indentation is used to measure the modulus and hardness when changes in TECs are measured within a thermal expansion device. The results show that the phase structure of Yb1−xAlxTaO4 (x = 0.05, 0.1, 0.2, 0.3, 0.4, 0.5) is stable at 25–1400 °C within air atmosphere, and their high-temperature TECs (6.4–8.9 × 10−6 K−1, 1400 °C) are effectively regulated by introductions of different contents of Al, which enlarge their engineering applications for SiCf/SiC and Al2O3f/Al2O3 CMCs. The evolutions of TECs are analyzed from structural characteristics and phase compositions, and the increased TECs make Yb1−xAlxTaO4 potential EBCs for Al2O3 matrixes. Due to the high bonding strength of Al–O bonds, hardness, as well as Young’s modulus, are enhanced with the increasing Al content, with Yb1−xAlxTaO4 (x = 0.05, 0.1, 0.2, 0.3, 0.4, 0.5) having a nano-hardness of 3.7–12.8 GPa and a Young’s modulus of 100.9–236.6 GPa. The TECs of YbTaO4 are successfully regulated to expand their applications, and they match those of Al2O3 and SiC matrixes, as well as displaying improved mechanical properties. This work promotes applications of YbTaO4 as potential EBCs and provides a new way to regulate the TECs of tantalates.

Manufacturing of Ni-Co-Fe-Cr-Al-Ti High-Entropy Alloy Using Directed Energy Deposition and Evaluation of Its Microstructure, Tensile Strength, and Microhardness.

High-entropy alloys (HEAs) have drawn significant attention due to their unique design and superior mechanical properties. Comprising 5-35 at% of five or more elements with similar atomic radii, HEAs exhibit high configurational entropy, resulting in single-phase solid solutions rather than intermetallic compounds. Additive manufacturing (AM), particularly direct energy deposition (DED), is effective for producing HEAs due to its rapid cooling rates, which ensure uniform microstructures and minimize defects. These alloys typically form face-centered cubic (FCC) or body-centered cubic (BCC) structures, contributing to their exceptional strength, hardness, and mechanical performance across various temperatures. However, FCC-structured HEAs often have low yield strengths, posing a challenge for structural applications. In this study, a Ni-Co-Fe-Cr-Al-Ti HEA was manufactured using the DED method. This study proposes that the addition of aluminum and titanium creates a γ + γ' phase structure within a multicomponent FCC-HEA matrix, enhancing the thermal stability and coarsening the resistance and strength. The γ' phase with an ordered FCC structure significantly improves the mechanical properties. Analysis confirmed the presence of the γ + γ' structure and demonstrated the alloy's high tensile strength and microhardness. This approach underscores the potential of AM techniques in advancing HEA production for high-performance applications.