Formation Of Ta Research Articles

Ta'lim Muta'allim: Solutions for Forming the Ta'dzim Attitude of Generation Z Students towards Teachers

This research aims to describe Ta'lim Muta'alim learning in the formation of Ta'dzim attitudes and Ta'dzim attitudes of students towards teachers at Mts Nurul Iman Dempok Grogol Diwek Jombang. The method used in this research is a qualitative method with a case study research design. Data collection techniques in this research were carried out using observation, interviews, and documentation methods. Testing the validity of the data was carried out by extending observations, increasing persistence, triangulation, using reference materials, peer discussions, and member checks. Data analysis techniques use data reduction, data presentation, and verification. This research produces the conclusion (2). The Ta'lim Al-Muta'allim teacher's efforts in forming a student's attitude of ta'dzim towards teachers at MTs Nurul Iman Dempok Jombang were carried out by preparing Expository Learning Strategies (SPE) and Inquiry Learning Strategies (SPI). Using printed learning media based on the Bald Bible and Al-Muta'allim Ta'lim Translation, lecture, deductive, bandongan, and sorogan methods are used. The formation of students' ta'dzim attitudes is carried out using two patterns, namely habituation and modeling. Students' attitude towards teachers at MTs Nurul Iman Dempok Jombang is characterized by respecting knowledge and teachers. Please do not walk in front of the teacher or bend when walking in front of him. Obeying the teacher's orders, namely helping the teacher clean the school environment, reading waqia'ah before Duha prayers, praying Duha prayers in congregation, folding carpets, and participating in activities related to the madrasah's vision and mission. This research provides recommendations to educational institutions and practitioners regarding the potential for developing more effective learning approaches for forming ta'dzim attitudes in Generation Z students.

Electronic structure of Ta2O5 polymorphs: Variation trend of band gap and the role of oxygen vacancies

We provide a systematic study on the electronic structure of a series of Ta2O5 polymorphs using standard density functional theory (DFT) calculations as well as the more accurate many-body perturbation theory within the GW approximation. For the defect-free polymorphs, the variation trend of band gap can be microscopically related to the strength of orbital hybridization, and to the macroscopic bulk formation energy. The presence of oxygen vacancies is found to have profound effects on the electronic properties near the Fermi level, notably the reduction of band gap and gap closure (insulator-to-metal transition). Furthermore, depending on the vacancy sites, the band gap of some defective system may be enlarged with comparison to its defect-free counterpart. Such an anomalous behavior originates from the unexpected formation of Ta–Ta bonds.

Induced degeneration and regeneration in aged muscle reduce tubular aggregates but not muscle function.

Tubular aggregates (TA) are skeletal muscle structures that arise from the progressive accumulation of sarcoplasmic reticulum proteins. Cytoplasmic aggregates in muscle fibers have already been observed in mice and humans, mainly during aging and muscle disease processes. However, the effects of muscle regeneration on TA formation have not yet been reported. This study aimed to investigate the relationship between degeneration/regeneration and TA in aged murine models. We investigated the presence and quantity of TA in old males from two murine models with intense muscle degeneration and regeneration. One murine lineage was a Dmdmdx model of Duchenne muscular dystrophy (n = 6). In the other model, muscle damage was induced by electroporation in C57BL/6J wild-type mice, and analyzed after 5, 15, and 30 days post-electroporation (dpe; n = 15). Regeneration was evaluated based on the quantity of developmental myosin heavy chain (dMyHC)-positive fibers. The frequency of fibers containing TA was higher in aged C57BL/6J (26 ± 8.3%) than in old dystrophic Dmdmdx mice (2.4 ± 2%). Comparing the data from induced degeneration/regeneration in normal mice revealed a reduced proportion of TA-containing fibers after 5 and 30 dpe. Normal aged muscle was able to regenerate and form dMyHC+ fibers, mainly at 5 dpe (0.1 ± 0.1 vs. 16.5 ± 2.6%). However, there was no difference in force or resistance between normal and 30 dpe animals, except for the measurements by the Actimeter device, which showed the worst parameters in the second group. Our results suggest that TA also forms in the Dmdmdx muscle but in smaller amounts. The intense degeneration and regeneration of the old dystrophic model resulted in the generation of new muscle fibers with a lower quantity of TA. Data from electroporated wild-type mice support the idea that muscle regeneration leads to a reduction in the amount of TA. We suggest that TA accumulates in muscle fibers throughout physiological aging and that regeneration leads to the formation of new fibers without these structures. In addition, these new fibers do not confer functional benefits to the muscle.

Fracture‐Resistant and Thermally Insulating Ultrahigh‐Temperature Carbide Foams

Dense ultrahigh‐temperature ceramics (UHTCs) carbides are recognized as potential materials for thermal protection systems (TPS) owing to properties beyond existing structural materials’ capabilities. Recent advances in UHTCs have enabled the development of multiscale porous microstructures. Herein, it is highlighted that the porosity in UHTCs are no longer treated as a defect but as a functional property specifically tailored for thermal insulation. It is a promising solution to design and fabricate bulk UHTC foams via a freeze‐drying (FD) approach followed by calibrated pressureless spark plasma sintering. Herein, monolithic TaC and HfC UHTC foams and their composite show the partial solid–solution formation of (Ta, Hf)C with porosity ≥50%. TaC–HfC foam (≈80–92 N) shows an intermediate load‐bearing capability compared to monolithic TaC (≈120–135 N) and HfC (≈28–35 N) foams, with no evident cracking on the sample surface. The thermal conductivity of partial solid‐solution TaC–HfC foam increases up to fivefold compared to parent UHTC foams. In the results, solid solutions’ efficacy and pores’ unidirectionality in providing thermal insulation to TaC–HfC while maintaining its high‐load bearing capability are illustrated. The developed technique establishes a new paradigm shift in UHTCs, expanding their potential for TPS in extreme environments.

The widening of the solution heat treatment window by the addition of Ru in Ni-based single crystal superalloy

This work investigates the effect of Ru on the solution heat treatment window of the Ni-based single crystal superalloy. The addition of the Ru influences the solidification microstructure and widens the window. The solidification process is established to occur in the sequence of γ (dendrite) → γ + γ' grid eutectic (inter-dendrite) → γ + γ' lamella eutectic (inter-dendrite) → γ' (inter-dendrite). This is followed by the γ → γ + γ' decomposition of the γ dendrite into the common channel-cuboid structure upon cooling. The solvus of γ' and the solidus of the alloy define the window. In alloys containing inter-dendrite eutectic, the window is in principle zero. In this case, only the dynamic window created by homogenization diffusion may allow heat treatment. Adding Ru decreases the elements' partition ratios between the dendrite core and dendrite edge regions. It also promotes the enrichment of Re at the γ/γ' phase interfaces, which helps to refine the γ + γ' channel-cuboid structure and reduce the differences in both the size and volume fraction of the γ' phase between dendrite core and dendrite edge. Ru is found to inhibit the formation of (Ta, X)C carbide. These help widen the solution treatment temperature window of the Ni-based single crystal alloy.

Martensitic transformation and shape memory effect of Ni49.6Ti45.4Ta5 shape memory alloy

NiTiTa shape memory alloys (SMAs) exhibit higher corrosion resistance and much better X-ray visibility in comparison with NiTi SMAs. In this work, the martensitic transformation, microstructure, and shape memory effect (SME) of Ni49.6Ti45.4Ta5 SMA are studied. When solution-treated, the alloy undergoes a single-step B2 ↔ B19′ transformation upon cooling and heating, which is gradually shifted to lower temperatures because of thermal cycling. A martensitic microstructure with well-defined twin variants is observed which is beneficial for SME whereas the formation of (Ta, Ti)2Ni phases may deteriorate it. After an optimal thermomechanical treatment, the maximum recovery strain reaches up to 5.32% under a pre-strain of 7%.

Novel Tri-rutile Ni0.5Ti0.5TaO4 Microwave Dielectric Ceramics: Crystal Structure Chemistry, Raman Vibration Mode, and Chemical Bond Characteristic In-Depth Studies

Here, a novel tri-rutile Ni0.5Ti0.5TaO4 ceramic configuration was first reported, and the sintering features, chemical bond theory, and microwave dielectric properties were systematically explored. Pure Ni0.5Ti0.5TaO4 ceramic with a tri-rutile structure was well sintered at 1275 °C with excellent microwave performance: εr ∼33.06, Q × f ∼14,600 GHz, and τf ∼93.95 ppm/°C. Based on the P–V–L theory, the dielectric constant was mainly affected by the formation of Ta–O bonds (∼62%) due to the larger ionic polarization and bond susceptibility. The experimental dielectric constant (33.06) was comparable to the theoretical calculation (P–V–L: 35.11). The lattice energy was also dominated by the Ta–O bond (∼71%) and the intrinsic loss properties. The τf was also affected by the [M1/M2O6] octahedral distortion. In addition, the relative density, grain size, and packing fraction also played a certain role in the microwave dielectric properties. Insights from the Raman spectroscopy revealed that the A1g mode dominated the Raman vibration at 699.44 cm–1. These results were helpful to provide ideas for novel medium dielectric constant materials and contributed to the miniaturization of microwave electronic devices.

Structural and Mechanical Properties of Fluorine-Containing TaCxNy Thin Films Deposited by Reactive Magnetron Sputtering

TaN thin-film coatings are well known for their good mechanical properties, acceptable toughness, as well as good biocompatibility. However, the friction coefficient of these films is sometimes too high, or the hemocompatibility is poor. The purpose of this study is to reduce the friction coefficient and increase the hydrophobicity of TaN coatings by introducing carbon and fluorine into the coatings. This study has never been conducted by other researchers. Fluorine-containing tantalum carbonitride (i.e., F–TaCxNy) top layers were deposited on TaN/Ta interlayers by reactive sputtering with fixed nitrogen and various hexafluoroethane (C2F6) mass flow rates. During the deposition process, C2F6 gas with various mass flow rates was added. After deposition, these F–TaCxNy multi-layered films were then characterized using XRD, XPS, FTIR, FESEM, WDS, a nano-indenter, a water contact-angle measurement system, and a tribometer. The tribological tests were carried out in the environment with and without humidity. The surface energies of the films were examined with water contact-angle variation. According to structural analysis, TaN phase would transform to TaCxNy with the increase in the C2F6 mass flow rate, which would result in a decrease in the friction coefficient and an increase in hydrophobicity. The films’ hardness (H, increased at most by 20%), elastic modulus (E), and H/E ratio first increased then decreased, most likely due to the increase in relatively soft C–F bonding. According to the results obtained from tribotesting, it was found that an increase in carbon and fluorine contents in the films reduces the friction by more than 30%, and wear rate by more than 50%. More importantly, the effects of moisture on the friction coefficient can be minimized to almost nothing. In a water contact-angle study, the contact angle increased from 60° to 85° with the increase in C2F6 mass flow rates. This evidence illustrated that hemocompatibility of the TaN thin film can be significantly enhanced through the formation of Ta–C and C–Fx bonding. The chemical composition and bonding status of these films, especially the existence of C–Fx bonds, were studied by FTIR and XPS. In sum, with the increased C2F6 mass flow rate, the carbon and fluorine contents in the films increased, while the nitrogen content decreased. The structure, bonding status, and compositions varied accordingly. The tribological behaviors were significantly improved. Furthermore, by carrying out tribotesting in humid air and a dry argon environment, it was confirmed that the greater the fluorine content, the less sensitive the films would be to environment change. This is attributable to the induced lower surface energy and reduced adsorption to water vapor due to the increase in C–Fx bonds. The successfully fabricated and studied F–TaCxNy films could be applied in many areas such as artificial blood vessels, or precision components in an atmospheric or vacuum environment.

Hot corrosion behavior of refractory high entropy alloys in molten chloride salt for concentrating solar power systems

Refractory high entropy alloys have recently attracted widespread attention due to their outstanding mechanical properties at elevated temperatures, making them appealing for concentrating solar power and nuclear energy applications. However, their molten salt corrosion behavior has not been reported, which is critical in evaluating their application merit. Here, the corrosion behavior of two recently developed refractory high entropy alloys, namely TaTiVWZr and HfTaTiVZr, was studied in molten 33NaCl–22KCl–45MgCl2 (wt. %) eutectic salt at 450 °C and 650 °C, using potentiodynamic polarization technique. The results were compared with benchmark alloys, namely 304 stainless steel (SS304) and Inconel 718 (IN718). TaTiVWZr refractory high entropy alloy exhibited an order of magnitude lower corrosion current density (Icorr = 0.7× 10-3 A cm-2) compared to SS304 (Icorr = 9.2 × 10-3 A cm-2) at the higher temperature of 650 °C. The corrosion rate of all the alloys increased with increase in temperature from 450 °C to 650 °C with the exception of TaTiVWZr. The TaTiVWZr alloy showed a corrosion rate of ~ 5 mm/year at 650 °C compared to ~ 110 mm/year for SS304. HfTaTiVZr and IN718 showed comparable corrosion rates in the range of ~ 40 mm/year at 650 °C. The high corrosion resistance of the two refractory high entropy alloys was attributed to a combination of three factors: (i) slower chlorination rate of refractory elements in the molten chloride salt environment driven by thermodynamics, (ii) formation of stable Ta–V and Ta–V–W based complex oxides on their surface, and (iii) Ti/TiCl2 and Zr/ZrCl2 redox couple formation which retarded the depletion of refractory elements. In contrast, the Cr-, Fe-, and Ni-based surface passivation oxides for SS304 and IN718 were less protective in the molten salt environment, particularly at the higher temperature of 650 °C.

Ultra-high-temperature tantalum-hafnium carbonitride ceramics fabricated by combustion synthesis and spark plasma sintering

We report the fabrication of dense single-phase (Ta,Hf)CN carbonitride ceramics using a combination of combustion synthesis (CS) and spark plasma sintering (SPS). The ceramic powder was produced by high-energy ball milling of the reactants (Ta, Hf, C) in different atomic ratios followed by CS of the obtained nanostructured composites in a nitrogen atmosphere. X-ray diffraction analysis of the combustion products revealed the formation of (Ta,Hf)CN with cubic B1 structures as the dominant phases for all investigated compositions. The SPS of the as-synthesized powders allowed both homogenization of the composition and consolidation of the bulk single-phase carbonitride ceramics with a relative density of 98 ± 1 %. Ta25Hf75CN showed the highest hardness (19.4 ± 0.2 GPa) and fracture toughness (5.4 ± 0.4 MPa m1/2) among the investigated composites and excellent oxidation resistance in air.

Nonlithographic Formation of Ta2O5 Nanodimple Arrays Using Electrochemical Anodization and Their Use in Plasmonic Photocatalysis for Enhancement of Local Field and Catalytic Activity.

We demonstrate the formation of Ta2O5 nanodimple arrays on technologically relevant non-native substrates through a simple anodization and annealing process. The anodizing voltage determines the pore diameter (25-60 nm), pore depth (2-9 nm), and rate of anodization (1-2 nm/s of Ta consumed). The formation of Ta dimples after delamination of Ta2O5 nanotubes occurs within a range of voltages from 7 to 40 V. The conversion of dimples from Ta into Ta2O5 changes the morphology of the nanodimples but does not impact dimple ordering. Electron energy loss spectroscopy indicated an electronic band gap of 4.5 eV and a bulk plasmon band with a maximum of 21.5 eV. Gold nanoparticles (Au NPs) were coated on Ta2O5 nanodimple arrays by annealing sputtered Au thin films on Ta nanodimple arrays to simultaneously form Au NPs and convert Ta to Ta2O5. Au NPs produced this way showed a localized surface plasmon resonance maximum at 2.08 eV, red-shifted by ∼0.3 eV from the value in air or on SiO2 substrates. Lumerical simulations suggest a partial embedding of the Au NPs to explain this magnitude of the red shift. The resulting plasmonic heterojunctions exhibited a significantly higher ensemble-averaged local field enhancement than Au NPs on quartz substrates and demonstrated much higher catalytic activity for the plasmon-driven photo-oxidation of p-aminothiophenol to p,p'-dimercaptoazobenzene.

Interaction of components in the system Ta−Fe−P at 1070 K

The interaction of the components in the ternary Ta−Fe−P system was investigated by means of X-ray powder diffraction. The isothermal section of the Ta−Fe−P phase diagram was constructed at 1070 К in the region up to 67 at. % of P for the first time. The samples preparation: synthesis in an arc-furnace for samples with P content less than 35 at. %; samples with P content more than 35 at. % were just sintered at 1070 K; annealing at 1070 K during 800 hours. Phase equilibria were investigated employing X-ray powder and diffraction. The substitutions of Ta by Fe were observed for Ta 3 P, TaP phases, and Fe for Ta in the case of Fe 3 P, Fe 2 P binary compounds. The composition of these solid solutions can be described as: ~α-Ta 3.0 −2.6 Fe 0 −0.4 P (Ті 3 Р-type, space group P 4 2 / n, а =10.150(3)−9.854(4), с =5.012(2)−4.948(2) Å), ~ Ta 0 −0.4 Fe 3.0 −2.6 P (Ni 3 P–type, I -4, a =8.958(2)−9.117(4), c=4.382(1)−4.468(3) Å), Fe 2.0-1.7 Ta 0-0.3 P (Fe 2 P-type, space group P -62 m , а =5.851(1)−6.086(3), с =3.383(1)−3.447(1) Å), Ta 1.00 −0.81 Fe 0 −0.19 P (NbAs-type, space group I 4 1 md, а =3.3184(1)−3.3177(2), с =11.363(3)−11.344(1) Å). The existence of earlier known ternary phosphides Ta 4 FeP (Nb 4 CoSi-type, space group P 4/ mcc , a =6.1070(4), c =4.9829(7) Å) and Ta 1.1 −0.8 Fe 0.9 −1.2 P (TiNiSi-type, space group Pnma , a =6,118(3)−6.087(5), b =3,576(3)−3,583(2), c =6,976(3)−6,949(1) Å) was confirmed. The new ternary compounds TaFe 2 P and Ta 0.89(3) Fe 0.11(3) P 2 were found during the investigation of the Ta−Fe−P system. The crystal structure of these compounds were determined by means of X-ray powder method: TaNi 2 P-type, space group Pnma, a =8.3650(7), b =3.5203(3), c =6.7065(6) Å), R I =0.081, R P = 0.245 for TaFe 2 P; OsGe 2 -type, space group C 2/ m , a = 8.8581(4), b =3.2655(2), c =7.4868(4) Å, b = 119.318(2)°, R I =0.072, R P =0.173 for Ta 0.89(3) Fe 0.11(3) P 2 . The common features of investigated Ta−Fe−P and related Ta− M' −P systems are formation of Ta 1− x M' x P 2 with OsGe 2 -type, wich can be interrupted as quasi-binary compound ТаР 2 , the formation of which is stabilized by third component. Keywords: ternary phosphide, crystal structure, phase equilibria, solid state solution, X-ray diffraction.

Electrochemical behavior of tantalum in ethylene carbonate and aluminum chloride solvate ionic liquid

Abstract To investigate the electrochemical reduction mechanism of Ta(V) in ethylene carbonate and aluminum chloride (EC−AlCl3) solvate ionic liquid, cyclic voltammetry experiments were conducted on a tungsten working electrode. Four reduction peaks were observed in the cyclic voltammogram of the EC−AlCl3−TaCl5 ionic liquid. The reduction peaks at −0.55, −0.72, and −1.12 V (vs Al) were related to the reduction of Ta(V) to tantalum metal by three stages including the formation of Ta(IV) and Ta(III) complex ions. The reduction of Ta(III) to tantalum metal was an irreversible diffusion-controlled reaction with a diffusion coefficient of 3.7×10−7 cm2/s at 323 K, and the diffusion activation energy was 77 kJ/mol. Moreover, the cathode products at 323 K were characterized by scanning electron microscopy, energy-dispersive spectroscopy, and X-ray photoelectron spectroscopy. The results showed that tantalum metal and tantalum oxides were obtained by potentiostatic electrodeposition at −0.8 V for 2 h.

Deposition of TaN Film on Commercial Pure Titanium Disk by Modified Reactive Plasma Sputtering Technique

Background: The new trend of implants is to find materials which accelerate bone formation at bone implant interface and improve Osseo integration to provide immediate or early loading after placement and eliminate waiting period which is uncomfortable and disturbs patients. Titanium as an implant material still need some improvement of surface properties physically and chemically. Tantalum which is gaining more attention as a new metallic biomaterial. Coating layer over implant is an important way for improvement of surface properties of titanium. Plasma used for surface modification, has several advantages such as changing surface topography, increasing surface roughness and in increasing the wettability of the surface. Aim of study: To evaluate the effect of TaN coating by modified plasma sputtering technique of commercially pure titanium disk on wettability, surface roughness, surface chemical composition in comparison to noncoated surface. Materials and methods: Two groups were tested in this study which include non -coated commercial pure titanium disks and coated commercial pure titanium with TaN. Modified reactive plasma sputtering apparatus was used to coat CpTi with TaN at 4, 6 &8, h. Surface characterization by x-ray diffraction (XRD) analysis, scanning electron microscope (SEM), energy dispersive spectroscopy(EDS), contact angle measurement, were carried out for coated and uncoated disks. Results: The result of coating specimen with TaN at times (4,6&8) h showed that 8 h coating time was the best time. And this was according to the results of X-ray diffraction analysis which show a new peak formation of Ta N coated CpTi disk which was not present in non- coated CpTi disk. The results of wettability test for CpTi disk coated with TaN disk was more than wettability of non- coated CpTi disk. Surface Roughness was more and better distributed in CpTi coated with TaN disk than non- coated one which appear clearly in electron microscope.

Sintering Reaction and Pyrolysis Process Analysis of Al/Ta/PTFE

When the Al/Ta/PTFE reactive material was sintered at 360 °C in a vacuum sintering furnace, it was found that the material reacted to form a soft fluffy white substance and carbon black. To explore the reaction process further, powder samples of pure PTFE, Al/PTFE, Ta/PTFE and Al/Ta/PTFE, and molded cylindrical specimens were prepared. A TG-DSC test was carried out on the thermal reaction of four reactive materials, and XRD phase analysis was conducted on the white product, formed by the sintering reaction and the residue of the TG-DSC test sample, based on which of the pyrolysis processes and reaction mechanisms were analyzed. The results show that Ta and PTFE could have a chemical reaction at sintering temperature (360 °C) to form soft and fluffy white material TaF3 and carbon black, which can overflow the surface of the specimen and cause cracking of the specimen, which is tightly pressed. Since no obvious exothermic peak showed up on the TG-DSC curve, the composition of the residue of TG-DSC sample at different temperatures was tested and TaF3 was detected in the residue at 350 °C and 360 °C, indicating that Ta began to react with PTFE at a temperature range of 340–350 °C. According to the chemical properties and product formation of Ta, it could be speculated that the reaction mechanism between Ta and PTFE involves the PTFE decomposing first, then the fluorine-containing gas product reacting with metal Ta. According to the temperature range of the reaction, it is estimated that PTFE starts to decompose before 500 °C, but it is not detected effectively by TG-DSC, and the introduction of Ta could also affect the decomposition process of PTFE.

Fabrication of (Ta,W)C surface gradient layer on Ta-10W alloy by in situ solid-phase diffusion

A novel (Ta,W)C gradient layer was fabricated by in situ solid-phase diffusion on the surface of Ta-10W alloy at 1130 °C for 2, 4, 6, 8, and 10 h. The phase composition and phase distribution of the (Ta,W)C surface gradient layer and the morphologies, grain sizes and crystal structure of the (Ta,W)C particles were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), and transmission electron microscopy (TEM). The nanoindentation hardness, elastic modulus, fracture toughness, and adhesion strength of the (Ta,W)C surface gradient layer were tested by a nanoindenter, Vickers indentation tool, and scratch tester, respectively. The results showed that the phase composition of the (Ta,W)C surface gradient layer was mainly the (Ta,W)C phase and a small amount of the Ta-10W phase. The microstructure exhibited a gradient in the (Ta,W)C grain size that decreased gradually from approximately 920 nm to 100 nm, moving from the surface of the carburized layer to the Ta-10W substrate. Ingrowth of the (Ta,W)C gradient layer was controlled by the diffusion of carbon, and the thickness reached approximately 18 μm when annealed for 10 h. Formation of the (Ta,W)C layer could be attributed to a diffusion-type solid phase transition driven by the diffusion of carbon atoms into the Ta-10W substrate. In addition, moving from the surface of the (Ta,W)C layer to the Ta-10W substrate, the nanoindentation hardness and elastic modulus gradually increased from 25.1 to 28.82 GPa and 500.8 to 537.9 GPa, respectively. The layer exhibited a high surface fracture toughness (4.98 ± 0.31 MPa·m1/2) and excellent layer/substrate adhesion strength. The toughness mechanism of the (Ta,W)C gradient layer was mainly crack deflection, grain bridging and intergranular fracture. In situ solid-phase diffusion offers a new approach for preparing (Ta,W)C surface gradient layer that exhibit high hardness, high toughness and excellent layer/substrate adhesion strength.

High-temperature flexural strength performance of ternary high-entropy carbide consolidated via spark plasma sintering of TaC, ZrC and NbC

The solid solution formation and consolidation of the (Ta,Zr,Nb)C single-phase ceramic made from commercial TaC, ZrC and NbC powders prepared by spark plasma sintering at the temperature of 1920 °C was investigated. Phase analysis and lattice parameter measurements by X-ray diffraction showed multi-stage formation of the single-phase high-entropy-type carbide with the lattice parameter of 4.535 Å. The flexural strength and fracture toughness at room temperature were 460 ± 24 MPa and 2.9 MPa m1/2, respectively. With an increase in temperature, the flexural strength showed an increase up to 1600 °C to 496 ± 44 MPa, then decreased after 1800 °C to 366 ± 46 MPa.

Incorporation of K<sup>+</sup> and Al<sup>3+</sup> during the formation of Ta<sub>3</sub>N<sub>5</sub> with heat-treatment of Ta<sub>2</sub>O<sub>5</sub>–AlN mixtures without flowing ammonia

Incorporation of K<sup>+</sup> and Al<sup>3+</sup> during the formation of Ta<sub>3</sub>N<sub>5</sub> with heat-treatment of Ta<sub>2</sub>O<sub>5</sub>–AlN mixtures without flowing ammonia

Microstructural analysis of Ta-containing NiCoCrAlY bond coats deposited by HVOF on different Ni-based superalloys

The microstructural and chemical evolution after different processing steps of Ta-containing NiCoCrAlY bond coats (BC) sprayed by high velocity oxy-fuel on Ni-base superalloy (SA) substrates, top-coated with 7YSZ and furnace cycled at 1100 °C focusing along the BC/SA interfaces is presented. Three superalloys were selected considering their Ta content relative to that within the BC: a) no Ta in the superalloy composition (IN100) and either b) similar or c) higher Ta content with respect to the BC (M247LC SX and CMSX-4, respectively). The processing conditions were as-sprayed, as-annealed, after EB-PVD deposition of a 7YSZ top coat, and after furnace cyclic tests (1100 °C/120 h). The evolution of chemical composition after the different process steps are presented that include a normalization criteria to a Ni-Al-Cr system, elemental profiles as well as Weibull distribution plots of minor containing elements such as Ti, Ta, Mo, or W at the BC/SA interface. The effect of Ta was activated in some coated substrates by the presence of Ti and C in the superalloy consisting of inward Ta-diffusion, trapping of outward diffusing Ti and the subsequent formation of (Ta, Ti)-rich carbides in the BC avoiding possible segregation effects as titanium oxide in the oxide scale.

Nano-(Ta, Zr)C Precipitates at Multigrain Conjunctions in TaC Ceramic with 10 mol% ZrC and 5 mol% Cu as Sintering Aid

A fully dense TaC ceramic was prepared by hot pressing using 10 mol% ZrC plus 5 mol% Cu as a sintering aid. Formation of (Ta, Zr)C solid solution (ss) by reaction between TaC and ZrC facilitated densification. Addition of Cu refined the microstructure and consequently improved flexural strength of the TaC ceramics. TEM investigation found ubiquitous precipitation of nanocrystallites at multigrain conjunctions. The nanocrystallites were (Ta, Zr)C solid solution with uniform dispersion in an oxygen-rich glassy matrix. Although formation of nanoprecipitates may not much affect the mechanical properties of the TaC ceramic, the structure suggested a new type of nanoceramic worth further research.