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Obtaining accurate lattice thermal conductivity data of LiF under extreme conditions not only provides important reference for performance evaluation, prediction, and control of materials, but also helps to alleviate the significant challenges of precise experimental measurements. The high-temperature phonon properties and lattice thermal conductivity (LTC) of solid LiF were calculated by combining on-the-fly machine learning force fields (MLFFs) with the Green–Kubo method. The introduction of MLFF successfully combines the accuracy of ab initio molecular dynamics with the scalability advantage of classical molecular dynamics. At high temperatures, there is a significant enhancement in the vibrational coupling between the acoustic and optical branches of LiF, as well as resonant effects between Li and F atoms, resulting in strong anharmonicity. Additionally, the main peak of the phonon density of states shows a noticeable redshift compared to the harmonic case. The enhanced coupling of TO and TA modes at high temperature leads to a significant increase in phonon scattering rate. By considering higher-order phonon anharmonicity, the predicted LTC is significantly reduced compared to the results obtained from considering only three-phonon interactions. Along the Hugoniot curve up to 100 GPa (2150 K), the predicted LTC agrees well with the experimental values. These findings demonstrate the crucial role of phonon anharmonicity in promoting phonon scattering. [ABSTRACT FROM AUTHOR]

Five high entropy carbide ceramics, (Hf0.2,Nb0.2,Ta0.2,Ti0.2,Zr0.2)C, (Cr0.2,Hf0.2,Ta0.2,Ti0.2,Zr0.2)C, (Hf0.2,Mo0.2,Ta0.2,Ti0.2,Zr0.2)C, (Hf0.2,Ta0.2,Ti0.2,W0.2,Zr0.2)C, and (Hf0.2,Mo0.2,Ti0.2,W0.2,Zr0.2)C, were synthesized by carbothermal reduction of oxides and direct current sintering. The five high entropy carbide ceramics were determined to be nominally phase-pure with relative densities of more than 98.9% and mean grain sizes of less than 5 μm. Average Vickers hardness values ranged from 19.2 ± 0.4 GPa for (Hf0.2,Nb0.2,Ta0.2,Ti0.2,Zr0.2)C at a load of 2 kgf to 43.5 ± 0.4 GPa for (Hf0.2,Mo0.2,Ti0.2,W0.2,Zr0.2)C at a load of 0.05 kgf. Hardness generally increased with increasing the valence electron concentration and strain as measured by the Williamson–Hall analysis. However, neither correlation was conclusive enough to be a clear indicator of hardness. Instead, it was determined that a combination of effects that includes the valence electron concentration, lattice strain, and grain size all contribute to the hardness of high entropy carbide ceramics. [ABSTRACT FROM AUTHOR]

Alloying heavy metals (HMs) has been an effective method for enhancing the efficiency of spin–orbit torque. In this study, we demonstrate that Pt100−xWx/Pt/Co/Ta multilayers still maintain perpendicular magnetic anisotropy after high-temperature annealing. Doping tungsten (W) into HM platinum (Pt) at the bottom of a Pt/Co/Ta multilayer significantly increases the spin Hall angle (θ S H ) and reduces the critical switching current density (Jc). The harmonic Hall test results show that the θ S H of the Pt88W12 alloy film is approximately 0.29, which is higher than that of the pure Pt film (0.15). The magnetization switching test reveals that the Jc of Pt94W6 alloy film is approximately 4.892 × 106 A/cm2, which is 51.9% lower than that of the pure Pt film. This study offers a valuable method for reducing power consumption and enhancing the efficiency of related application devices. [ABSTRACT FROM AUTHOR]

The giant spin–orbit torque (SOT) generated by topological surface states in topological insulators (TIs) provides an energy-efficient writing method for magnetic memory. In this study, we demonstrate a topological insulator/spin valve (TI/SV) device that operates at room temperature. An ultrathin, high-quality TI (Bi0.5Sb0.5)2Te3 (BST) thin film is epitaxially grown as a functional layer on a (0001)-Al2O3 substrate via molecular beam epitaxy in ultrahigh vacuum. Subsequently, Ta/CoFe/Cu/CoFe/IrMn layers are grown on BST/Al2O3 thin films using magnetron sputtering to form TI/SV devices via a subsequent standard lithography process. The resulting TI/SV devices exhibit a giant magnetoresistance of up to ∼1.1% at room temperature. Additionally, a low switching current density of approximately 1.25 × 105 A cm−2 is achieved, which implies high potential for further reducing the energy consumption of SOT-based devices. The SOT conversion efficiency and charge-spin conversion efficiency of the TI layer are approximately 4.74 × 10−6 Oe A−1 cm2 and 1.33, respectively, as extracted from the SOT-induced shift of the magnetic switching field. Moreover, the switching current density reduces steadily with the device size scaling down. This study can facilitate the realization of energy-efficient magnetic memory devices in the future. [ABSTRACT FROM AUTHOR]

The prospect of creating ferroelectric or high permittivity nanomaterials provides motivation for investigating complex transition metal oxides of the form Ba(Ti, MV)O3, where M = Nb or Ta. Solid state processing typically produces mixtures of crystalline phases, rarely beyond minimally doped Nb/Ta. Using a modified sol-gel method, we prepared single phase nanocrystals of Ba(Ti, M)O3. Compositional and elemental analysis puts the empirical formulas close to BaTi0.5Nb0.5O3−δ and BaTi0.5Ta0.5O3−δ. For both materials, a reversible temperature dependent phase transition (non-centrosymmetric to symmetric) is observed in the Raman spectrum in the region 533–583 K (260–310 °C); for Ba(Ti, Nb)O3, the onset is at 543 K (270 °C); and for Ba(Ti, Ta)O3, the onset is at 533 K (260 °C), which are comparable with 390–393 K (117–120 °C) for bulk BaTiO3. The crystal structure was resolved by examination of the powder x-ray diffraction and atomic pair distribution function (PDF) analysis of synchrotron total scattering data. It was postulated whether the structure adopted at the nanoscale was single or double perovskite. Double perovskites (A2B′B″O6) are characterized by the type and extent of cation ordering, which gives rise to higher symmetry crystal structures. PDF analysis was used to examine all likely candidate structures and to look for evidence of higher symmetry. The feasible phase space that evolves includes the ordered double perovskite structure Ba2(Ti, MV)O6 (M = Nb, Ta) Fm-3m, a disordered cubic structure, as a suitable high temperature analog, Ba(Ti, MV)O3Pm-3m, and an orthorhombic Ba(Ti, MV)O3Amm2, a room temperature structure that presents an unusually high level of lattice displacement, possibly due to octahedral tilting, and indication of a highly polarized crystal. [ABSTRACT FROM AUTHOR]

Extending the storage-recovery model, we propose a new strengthening model, premised on detailed evolution laws for both mobile and immobile dislocations, for metals under moderate to intense loading. These dislocation density evolution laws include the multiplication, storage under the effect of dislocation junctions, release of pinned dislocations, and annihilation by cross-slip. The storage-release description is derived from a simplified depiction of the probability distribution function of the dislocation length in dislocation networks. Although the model requires only few parameters to characterize the evolution of dislocation densities, remarkable agreement is found with available experimental data. From a theoretical study of the long-time behavior of the model, analytical expressions are provided to easily extract most of these parameters from experimental stress–strain curves in the quasi-static regime, whereas the parameter that governs the strength of the release process is adjusted from dynamic tensile tests. Their values so determined for polycrystalline tantalum allow the model to reproduce experimental plate-impact data with a very good match. [ABSTRACT FROM AUTHOR]

We present an IR-PD study of tantalum cluster adsorbate complexes [Tan(N2)m]+, abbreviated (n,m), n = 5–8. We utilize infrared spectroscopy of isolated and size selected clusters as prepared and characterized by a cryogenic tandem ion trap setup, and we augment our experiments with quantum chemical simulations at the level of density functional theory. The cluster adsorbate complexes (n,m) reveal vibrational bands above 2000 cm−1, which indicate end-on coordinated μ1-N2 oscillators, and bands below 2000 cm−1, which indicate side-on μ2-κN:κN,N coordinated ones. We observe a general increase in spectral complexity and an inhomogeneous broadening, mainly towards the red, at certain points of N2 loading m, which originates from an increasingly higher amount of double and triple N2 coordination at Ta sites, eventually at all of them. Other than the small tantalum clusters Tan+, n = 2–4, the IR-PD spectra of the initial N2 adsorbate species (n,1), n = 5–8, provide strong evidence for a lack of spontaneous N2 cleavage. Spontaneous N2 cleavage by Tan+, n = 5–8, seems suppressed. Therefore, the ability of a small Ta cluster to cleave dinitrogen disappears with one more tantalum core atom. The study of stepwise N2 adsorption on size selected Tan+, n = 5–8 clusters revealed adsorption limits m(max) of [Tan(N2)m]+ that are independent of cluster size within this size range. Cryo-adsorption kinetics at 26 K allowed for kinetic fits to consecutive N2 adsorption steps, and the fits revealed significant N2 desorption rates upon higher N2 loads, and the cluster adsorbate complexes eventually reached equilibrium. Some enhanced N2 desorption rates point towards likely adsorbate shell reorganization, and there is also some evidence for the coexistence of isomeric cluster adsorbate complexes. [ABSTRACT FROM AUTHOR]

We investigate small tantalum clusters Tan+, n = 2–4, for their capability to cleave N2 adsorption spontaneously. We utilize infrared photon dissociation (IR-PD) spectroscopy of isolated and size selected clusters under cryogenic conditions within a buffer gas filled ion trap, and we augment our experiments by quantum chemical simulations (at DFT level). All Tan+ clusters, n = 2–4, seem to cleave N2 efficiently. We confirm and extend a previous study under ambient conditions on Ta2+ cluster [Geng et al., Proc. Natl. Acad. Sci. U. S. A. 115, 11680–11687 (2018)]. Our cryo studies and the concomitant DFT simulations of the tantalum trimer Ta3+ suggest cleavage of the first and activation of the second and third N2 molecule across surmountable barriers and along much-involved multidimensional reaction paths. We unravel the underlying reaction processes and the intermediates involved. The study of the N2 adsorbate complexes of Ta4+ presented here extends our earlier study and previously published spectra from (4,m), m = 1–5 [Fries et al., Phys. Chem. Chem. Phys. 23(19), 11345–11354 (2021)], up to m = 12. We confirm the priory published double activation and nitride formation, succeeded by single side-on N2 coordination. Significant red shifts of IR-PD bands from these side-on coordinated μ2-κN:κN,N N2 ligands correlate with the degree of tilting towards the second coordinating Ta center. All subsequently attaching N2 adsorbates onto Ta4+ coordinate in an end-on fashion, and we find clear evidence for co-existence of end-on coordination isomers. The study of stepwise N2 adsorption revealed adsorption limits m(max) of [Tan(N2)m]+ which increase with n, and kinetic fits revealed significant N2 desorption rates upon higher N2 loads. The enhanced absolute rate constants of the very first adsorbate steps kabs(n,0) of the small Ta3+ and Ta4+ clusters independently suggest dissociative N2 adsorption and likely N2 cleavage into Ta nitrides. [ABSTRACT FROM AUTHOR]

We present an IR-PD study of tantalum cluster adsorbate complexes [Tan(N2)m]+, abbreviated (n,m), n = 5–8. We utilize infrared spectroscopy of isolated and size selected clusters as prepared and characterized by a cryogenic tandem ion trap setup, and we augment our experiments with quantum chemical simulations at the level of density functional theory. The cluster adsorbate complexes (n,m) reveal vibrational bands above 2000 cm−1, which indicate end-on coordinated μ1-N2 oscillators, and bands below 2000 cm−1, which indicate side-on μ2-κN:κN,N coordinated ones. We observe a general increase in spectral complexity and an inhomogeneous broadening, mainly towards the red, at certain points of N2 loading m, which originates from an increasingly higher amount of double and triple N2 coordination at Ta sites, eventually at all of them. Other than the small tantalum clusters Tan+, n = 2–4, the IR-PD spectra of the initial N2 adsorbate species (n,1), n = 5–8, provide strong evidence for a lack of spontaneous N2 cleavage. Spontaneous N2 cleavage by Tan+, n = 5–8, seems suppressed. Therefore, the ability of a small Ta cluster to cleave dinitrogen disappears with one more tantalum core atom. The study of stepwise N2 adsorption on size selected Tan+, n = 5–8 clusters revealed adsorption limits m(max) of [Tan(N2)m]+ that are independent of cluster size within this size range. Cryo-adsorption kinetics at 26 K allowed for kinetic fits to consecutive N2 adsorption steps, and the fits revealed significant N2 desorption rates upon higher N2 loads, and the cluster adsorbate complexes eventually reached equilibrium. Some enhanced N2 desorption rates point towards likely adsorbate shell reorganization, and there is also some evidence for the coexistence of isomeric cluster adsorbate complexes. [ABSTRACT FROM AUTHOR]

Heterogenous materials under shock compression can be expected to reach different shock states throughout the material according to local differences in microstructure and the history of wave propagation. Here, a compact, multiple-beam focusing optic assembly is used with high-speed velocimetry to interrogate the shock response of porous tantalum films prepared through thermal-spray deposition. The distribution of particle velocities across a shocked interface is compared to results obtained using a set of defocused interferometric beams that sampled the shock response over larger areas. The two methods produced velocity distributions along the shock plateau with the same mean, while a larger variance was measured with narrower beams. The finding was replicated using three-dimensional, mesoscopically resolved hydrodynamics simulations of solid tantalum with a pore structure mimicking statistical attributes of the material and accounting for radial divergence of the beams, with agreement across several impact velocities. Accounting for pore morphology in the simulations was found to be necessary for replicating the rise time of the shock plateau. The validated simulations were then used to show that while the average velocity along the shock plateau could be determined accurately with only a few interferometric beams, accurately determining the width of the velocity distribution, which here was approximately Gaussian, required a beam dimension much smaller than the spatial correlation lengthscale of the velocity field, here by a factor of ∼30×, with implications for the study of other porous materials. [ABSTRACT FROM AUTHOR]

Nickel-based tungsten carbide composite coatings are extensively utilized on various wear-resistant workpiece surfaces due to their exceptional properties, including high hardness and wear resistance. However, as the WC content increases, uneven structure and susceptibility to cracking of the coating during the forming process are enhanced, thereby impacting its service performance. To address these issues, NiCuBSi/65WC composite coatings with varying tantalum (Ta) contents were fabricated on 42CrMo steel substrates by laser cladding. The influence mechanism of Ta content on the microstructure and wear resistance of the coatings was investigated. The results demonstrate that the addition of tantalum promotes the formation of reinforcement phases such as TaC and W 2 C in the coating. Moreover, with increased Ta content, the edge of WC particle reaction layers in the coating gradually transforms from sawtooth to shorter rod-shaped morphology. Additionally, as the Ta content increases, the dissolution degree of WC particles rises, thereby facilitating the formation of TaC and W 2 C compound carbide. This leads to an enhancement in both the quantity and uniform distribution of carbide reinforced phases within the coating, resulting in an increase in average coating hardness from 482.4 HV 0.2 to 580.1 HV 0.2. When the Ta content reaches 7 wt% in particular, no cracks are observed on the coating surface, and a uniform distribution of carbides is achieved. The relative wear resistance of NiCuBSi/65WC coating with 7 wt% Ta is approximately 2.36 times higher than that without Ta. [ABSTRACT FROM AUTHOR]

Owing to their energy-saving and environmentally friendly characteristics, rare-earth-free ultraviolet-excited green-luminescent materials have garnered significant attention. To improve the luminescence efficiencies of green-luminescent materials, this study synthesized Ta-doped CsV 1-x O 3 green-light-emitting phosphors through a solid-state-reaction method, adopting an optimal Ta doping concentration of 10%. Theoretical calculations and reflection spectra revealed an intrinsic indirect band gap of 2.86 eV for CsV 0.9 Ta 0.1 O 3 , lower than that of CsVO 3 (3.63 eV). Under 365 nm excitation, the as-prepared phosphors exhibited broadband emissions ranging from 400 nm to 700 nm, attributed to the 3T 2 →1A 1 and 3T 1 →1A 1 transitions within VO 4 tetrahedra. Notably, adding Ta5+ ions to CsVO 3 increased its emission intensity by 1.39 times and induced a redshift in its excitation spectrum from 369 to 375 nm. Furthermore, Ta5+ doping significantly distorted the VO 4 tetrahedra and influenced the optical properties of the synthesized phosphors. Specifically, the nearest of Cs–V bond length increased, and weak interactions between V5+ ions and Cs + ions led to a 1.5-fold higher internal quantum efficiency (60.49%) of CsV 0.9 Ta 0.1 O 3 compared to that of CsVO 3. Furthermore, CsV 0.9 Ta 0.1 O 3 demonstrated high thermal stability, retaining 75.57% of its initial intensity even at 140 °C. Overall, these results indicate the potential applicability of CsV 0.9 Ta 0.1 O 3 as a green-emitting phosphor for white-light-emitting diode applications. [ABSTRACT FROM AUTHOR]

Reactive melt infiltration (RMI) is a typical method to produce carbon fiber-reinforced ultra-high temperature ceramic matrix composites (C f /UHTCs), for which the molten Si is a very general and practical infiltrator. High-entropy carbide (HE-carbide) is a newly developed promising matrix phase of C f /UHTCs. Understanding the phase equilibrium relation in the HE-carbide and Si reaction system can provide accurate guidance on designing the RMI process for preparing HE-carbide matrix composites with controlled phases and microstructure. This study systematically investigates W-containing HE-carbide and Si addition reactions at high temperatures. Samples with nominal starting compositions of (Ti 0. 2 Zr 0.2 Hf 0.2 Ta 0. 2 W 0.2)C- x Si (HEC- x Si, x = 2.5, 5 and 10 wt%) are prepared by spark plasma sintering technique at 1500 °C and 1700 °C with an axial pressure of 40 MPa for 10 min. The results show that adding 2.5 wt% or 5 wt% Si removes carbon from the HEC matrix, forming SiC and stable equimolar (Ti 0. 2 Zr 0.2 Hf 0.2 Ta 0. 2 W 0.2)C 1- x phase with carbon deficiency at high temperatures. In contrast, besides the SiC phase, the addition of 10 wt% Si in the HEC matrix may form unstable transient phases of (Ti 0. 2 Zr 0.2 Hf 0.2 Ta 0. 2 W 0.2)C 1- x with supersaturated carbon deficiencies at high temperatures, which finally decomposes into non-equimolar HE-carbide (Ti 0. 2 Zr 0.2 Hf 0.2 Ta 0. 2 W 0.2- y)C 1- z and metal silicide WSi 2 phases. The effects of the HEC and Si reactions on the microstructure evolution of the samples during sintering are discussed. Meanwhile, the mechanical properties of the samples with the reaction resulting microstructure are measured and briefly discussed. [ABSTRACT FROM AUTHOR]

Ultra-high temperature ceramics (UHTCs) are refractory transition-metal carbides, nitrides, and borides with the highest melting temperatures known materials, making them prime candidates for applications in aerospace and hypersonic vehicles. Of the UHTCs, tantalum carbide (TaC) and hafnium carbide (HfC) feature the highest melting temperatures. We investigated the binderless consolidation of HfC/TaC powder blends using Field Assisted Sintering Technology (FAST). Powders consisting of 90/10, 50/50, and 10/90 vol% HfC:TaC were sintered to high densities (>94 %). Bulk and nanomechanical, chemical, and microstructural characterization revealed substantially greater strength, hardness, and stiffness for ternary alloys. Mechanical properties correlated with physiochemical analysis indicated trace oxygen phases, solid-solution strengthening, and nonstoichiometric carbon were the key mechanisms driving the peak property enhancement of the 50 vol% solid-solution sample, despite lower densities. This study provides insight into optimizing the compositional design of HfC-TaC alloys by balancing influences from solid solution strengthening and the thermodynamic effects of oxygen/carbon stoichiometry. [ABSTRACT FROM AUTHOR]

In this study, we utilized the tape-casting method to produce Pb-free (Na 0·52 K 0·4425 Li 0.0375) (Nb 0·8925 Sb 0·07 Ta 0.0375)O 3 + 2 mol% MnCO 3 + y mol% LiF (y = 0 to 3) piezoelectric ceramics. We investigated the impact of LiF sintering in a reduced atmosphere on microstructure, dielectric properties, impedance spectroscopy, and piezoelectric performance. By analyzing the degree of diffuse phase transition, we observed increased density and enhanced long-range order in the sample doped with 1 mol% LiF, which exhibited optimal piezoelectric properties (d 33 = 265 pC/N and k p = 0.437) and a minimal diffusion parameter. Moreover, LiF doping enabled sintering at 1020 °C under low P O2 , facilitating potential co-firing with Cu inner electrodes to further enhance the piezoelectric performance. Using the optimized parameters, we fabricated a cross-type triaxial piezoelectric accelerometer, demonstrating sensitivities of 2.33, 2.44, and 10.6 mV/g along the X, Y, and Z axes, respectively, with a resonance frequency of ∼2600 Hz and frequency range of ∼1300 Hz. This accelerometer holds promise for vibration measurements in low-frequency mechanical systems. [ABSTRACT FROM AUTHOR]

Ti 3 AlC 2 was used as the additive to fabricate a novel (Zr 0 · 2 Ta 0 · 2 Nb 0.2 Hf 0.2 Mo 0.2)B 2 -based (HEBTAC) ceramic using spark plasma sintering at 1900 °C. The as-prepared HEBTAC ceramic sample consists of (Ti, Zr, Hf, Ta, Nb, Mo)B 2 , multiscale (Zr, Hf, Ta, Nb, Mo)C, and Al 2 O 3 phases, which are produced by the decomposition of Ti 3 AlC 2 and subsequent exchange reaction & solid solution reactions during the sintering process. The relative density, hardness, fracture toughness, and flexural strength of the HEBTAC ceramic sample are 99.43 %, 27.92 ± 1.87 GPa, 5.84 ± 0.14 MPa m1/2, and 629 ± 8.7 MPa, respectively, which are even better than the same class of high-entropy diboride ceramics previously published. Solid-solution strengthening, dislocation strengthening and nano-HEC strengthening existed in the ceramic sample contribute to its excellent mechanical properties. The in situ formed Al 2 O 3 and (Zr, Hf, Ta, Nb, Mo)C effectively enhances the toughness of the HEBTAC ceramic sample through the synergistic effect of intrinsic and extrinsic toughening. This study presents a new approach for reactive sintering densification of high-entropy diborides with both high strength and high toughness. [ABSTRACT FROM AUTHOR]

In this study, a dense Ta-based layer with a thickness of 400 nm was fabricated on SS316N bipolar plates (Ta-SS316N) by using a disproportionation reaction of Ta in a K 2 TaF 7 -Ta(powders)-KCl-NaCl molten salt system at 900 °C for 6 h. According to XRD analysis, the Ta-based layer was mainly composed of metallic Ta as well as Ta 2 N 0.86. In the simulated HT-PEMFC cathode environment, the corrosion current density of Ta-SS316N obtained from the potentiodynamicl polarization curves was 0.96 μA/cm2, which meets the 2025 U S. DOE standard. Compared to the SS316N substrate, Ta-SS316N showed two orders of magnitude higher corrosion resistance and nearly 1 V higher self-corrosion potential, with an interfacial contact resistance of 27.5 mΩ∙cm2, accounting for about one-quarter that of SS316N substrate. This provides a low-cost, easy-to-operate method to prepare Ta-based layer on stainless steel bipolar plates used for HT-PEMFC. [ABSTRACT FROM AUTHOR]

This article provides information about Wyoming jade, specifically the two types of rock it is composed of: jadeitite and nephrite. Nephrite is the more common type and is known for its toughness and ability to be carved into delicate shapes. Wyoming jade is found in various mountain ranges in central and eastern Wyoming, particularly in areas where crustal plates have collided. The formation of jade in this region is believed to be a result of hydrothermal fluids interacting with amphiboles and crystallizing rapidly in a tectonically active environment. Detrital jade, or jade float, is also found in alluvial deposits downstream from primary deposits. [Extracted from the article]

Previously, a strategy for doping MIEC perovskites ABO 3-δ with highly charged cations B5+ (Nb, Ta) and B6+ (Mo, W) was developed. The doping strategy is based on the idea that strontium ferrite/cobaltite-based perovskites are ferroelastic, whereas highly charged cations are ferroactive species. An increase in the concentration of the dopant leads to a reduction in the size of the domains of the ferroelastic phase down to the nanoscale. This resulted in the smearing of phase transitions with the formation of the highly conductive glassy state. Tantalum-doped lanthanum-strontium-ferrite perovskite (La 0.6 Sr 0.4 Fe 1-x Ta x O 3-δ , LSFTx) was prepared via solid-state reaction using chemically pure oxide powders of La 2 O 3 , SrCO 3 , Fe 2 O 3 , and Ta 2 O 5 , followed by calcination and sintering up to 1350 °C. The structural and surface properties were examined using X-ray diffraction and a scanning electron microscope. The original oxygen partial pressure relaxation (OPPR) method was used to study the kinetic properties of LSFTx. Continuous equilibrium phase diagram "T – pO 2 – δ" first obtained by oxygen release technique for composition LSFT3.5. Power law dependencies of the kinetic properties on the oxygen partial pressure are presented. [ABSTRACT FROM AUTHOR]

In this study, we investigated the humidity sensing properties of TiO2-based ceramics doped with tantalum pentoxide (Ta2O5) and indium tin oxide (ITO). Pure TiO2, 1%Ta-doped TiO2 (1%TTO), 1%ITO-doped TiO2 (1%ISTO), and 1%(Ta2O5 + ITO) co-doped TiO2 (1%ISTTO) ceramic samples were obtained by sintering at 1200 °C for 3 h. The rutile phase was observed in all samples. The lattice parameters of the single and co-doped samples were larger than those of pure TiO2, confirming the substitution of dopants. Porosity was observed in all ceramics. The mean grain sizes of all doped samples were significantly reduced compared to undoped TiO2. A homogeneous element dispersion was observed in the 1%TTO and 1%ISTTO ceramics, while segregation particles of related In-rich elements was observed in the 1%ISTO ceramic. Giant dielectric properties were not achieved in any samples due to the porosity. Nevertheless, excluding the undoped TiO2, the dielectric properties of all porous ceramics varied significantly with changes in humidity. The 1%ISTTO ceramic demonstrated superior humidity sensing properties, including a low maximum hysteresis error of 3.6% at 102 Hz. In contrast, the 1% TTO and 1% ISTO ceramics showed higher maximum hysteresis errors of 7.2% and 19.8%, respectively. Notably, the response and recovery times were 7.05 ± 0.18 and 2.48 ± 0.39 min, respectively, with good repeatability. This improvement is likely due to the synergistic effect of oxygen vacancies and Ta Ti · defects on the surface, enhancing the humidity sensing properties of the 1% ISTTO ceramic, coupled with its optimal microstructure due to its lowest porosity and grain size. [ABSTRACT FROM AUTHOR]

Full-Heusler alloys with earth-abundant elements exhibit high mechanical strength and favorable electrical transport behavior, but their high intrinsic lattice thermal conductivity limits potential thermoelectric application. Here, the thermoelectric transport properties of Fe-based Full-Heusler Fe2MAl (M = V, Nb, Ta) alloys are comprehensively investigated utilizing density functional theory. The results suggest that Fe2NbAl exhibits exceptionally low lattice thermal conductivity due to low phonon velocities and weakly bound Nb atoms. In Fe2NbAl, the underbonding of the Nb atoms leads large Grüneisen parameters and high anharmonic scattering rates of low-frequency acoustic phonon. Meanwhile, the high band degeneracy and large electrical conductivity lead to a maximum p-type power factor of 255.6 μW·K−2·cm−1 at 900 K. The combination of low lattice thermal conductivity and favorable electrical transport properties leads a maximum p-type dimensionless figure of merit of 1.7. Our work indicates Fe2NbAl, as a low-cost, environmentally friendly, is a potential high-performance p-type thermoelectric material. [ABSTRACT FROM AUTHOR]

A novel Ta/Os heterobimetallic complex, [Ta(CH2tBu)3(μ-H)3OsCp*], 2, is prepared by protonolysis of Ta(CHtBu)(CH2tBu)3 with Cp*OsH5. Treatment of 2 and its iridium analogue [Ta(CH2tBu)3(μ-H)2IrCp*], 1, with CO2 under mild conditions reveal the efficient cleavage of CO2, driven by the formation of a tantalum oxo species in conjunction with CO transfer to the osmium or iridium fragments, to form Cp*Ir(CO)H2 and Cp*Os(CO)H3, respectively. This bimetallic reactivity diverges from more classical CO2 insertion into metal–X (X = metal, hydride, alkyl) bonds. [ABSTRACT FROM AUTHOR]

The photoluminescence properties of f–f emission-type phosphors strongly depend on the electronic structure of the host materials. This study investigated in detail the relationship between the bandgap energy and the photoluminescence properties of Pr3+-activated CaTa2/3Mg1/3O3–CaTaO2N solid solutions. Ca3Ta3−xMgxO6+3xN3−3x (0.00 ≦ x ≦ 1.00) were chosen as the host materials for the approach used herein. The bandgap energy level (Eg) for the Ca3Ta3−xMgxO6+3xN3−3x solid solutions was systematically changed from 2.7 to 5.1 eV by controlling the Mg/Ta and O/N ratios. The photoluminescence excitation and emission control was systematically performed by engineering Eg for the samples. In the excitation spectra, the maximum photoluminescence excitation wavelength shifted to a shorter wavelength according to the Eg expansion. In the emission spectra, the red emission assigned to the 1D2–3H4 levels of Pr3+ in the samples with x = 0.25–0.50 could be excited in near-UV light regions (350 nm) when the Eg in the host materials was adjusted to approximately 3.0 eV. Conversely, several emissions, including a green emission belonging to the 3P0–3H4 levels of Pr3+, were observed when the Eg of the samples with x = 0.75–0.95 became larger than 3.0 eV. The results indicate that the photoluminescence properties of the f–f emission-type phosphors are attributed to the Eg in the host materials. [ABSTRACT FROM AUTHOR]

The study of fracture mechanics is usually within the paradigm of a failure mode that needs to be avoided. However, both in nature and in modern technology, there exist several situations where an ability to fracture is essential. In this work, we consider the problem of machining highly ductile and strain-hardening metals, such as annealed Cu, Al and Ta. These metals are known by the moniker "gummy metals" due to the large forces and poor surface finish associated with machining them. We investigate a chemo-mechanical technique involving adsorption of organic monolayers on the metal surfaces that causes the metals to become relatively brittle. This transition from ductile to brittle results in > 50% drop in the cutting force and an order of magnitude improvement in the surface finish. Molecular dynamics simulations of the phenomenon show the organic monolayers impose a surface stress on the metal surface which results in arresting of the dislocations close to the surface. The results suggest that a deeper understanding of the underlying mechanism has implications in environment-assisted cracking, stress-corrosion cracking and hydrogen embrittlement. [ABSTRACT FROM AUTHOR]

The topological and morphological changes of the (001) surface of single‐crystal (La0.3Sr0.7)(Al0.65Ta0.35)O3 during treatment with high‐purity deionized water (DI) have been investigated by atomic force microscopy and scanning transmission electron microscopy (STEM). Etching by DI treatment at room temperature proceeded mainly in anisotropic etching mode, resulting in rectangular etch pits with {001} inner surfaces forming in the surface. The dominant etching mode changed from anisotropic to isotropic with increasing DI‐treatment temperature, and the lowest surface roughness occurred for DI treatment at 50°C for 60 min. Direct observation of the atomic structure of the surface by STEM showed that the etched surface was the B‐site‐terminated (001) surface after anisotropic etching at 50°C for 60 min, in which the B‐site‐terminated atomic layer was found to maintain the B‐site ordered structure existing in the crystal. This is because DI treatment, which does not require high‐temperature heat treatment of the substrate, suppresses element diffusion, sublimation, and formation of point defects on and in the vicinity of the surface. [ABSTRACT FROM AUTHOR]

The late Neoarchean tonalite – trondhjemite – granodiorite (TTG) and mafic rocks record essential information regarding the early tectonic evolution of the North China Craton, which is crucial for understanding the onset and development of the plate tectonic regime. In this study, we present a comprehensive analysis of petrography, geochronology, and geochemistry of the Guanghua Mélange from the Tonghua area in NE China. The mélange comprises basalt, gabbro, pyroxene diorite, and trondhjemite, and is classified into three groups: basaltic – gabbroic rocks (Group #1), dioritic rocks (Group #2), and trondhjemites (Group #3). Zircon U-Pb analyses indicate that they formed at 2596–2550 Ma, 2531–2515 Ma, and 2502 Ma, respectively, with metamorphism occurring during ~ 2500–2450 Ma. Meanwhile, geochemical data indicate that the calc – alkaline basaltic rocks (Group #1) exhibit slight depletion of Nb or Ta with weakly negative Eu anomalies, suggesting derivation from the lithospheric mantle and formation within a continental arc environment. The pyroxene diorites (Group #2) display similar geochemical characteristics to Group #1, likely formed by partial melting of depleted mantle that underwent sgignificant metasomatism due to variable amounts of slab-derived fluids or melts. The tholeiitic granitoids (Group #3) exhibit strongly fractionated chondrite-normalized REE patterns with high (La/Yb)N and Sr contents, low Y contents, and depletion of Nb, Ta or Ti, resembling adakites generated in arc setting, indicating likely formation through partial melting of subducted oceanic crust. This process was controlled by the initial plate tectonics under a higher geothermal gradient. Consequently, when combined with previous findings, we conclude that an initial subduction of oceanic plate operated in the northeastern North China Craton during the late Neoarchean (>2.55 Ga). Subsequently, it transformed into modern-type plate tectonics during ~ 2.55–2.53 Ga, eventually followed by the continent-continent collision at ~ 2.50–2.45 Ga, resulting in the formation of the Ji – Liao – Ji (Jilin – Liaoning – Hebei) Collision Orogenic Belt. [ABSTRACT FROM AUTHOR]

Phase change materials have issues in the automotive industry and in‐memory computing due to their limited thermal stability and high power consumption. Consequently, numerous studies are conducted to enhance the performance of these materials. Uncertainty persists regarding the effects and mechanisms of various doping on the parent material. In this study, four metallic doping elements are selected, and their effects on Sb2Te3 are meticulously analyzed through experiments and ab initio calculations. The thermal stability of Sb2Te3 has been somewhat enhanced by doping these four elements, with Ta doping having the most impact. According to the ab initio molecular dynamics, this improvement results from the tetrahedral centered In and the increased coordination numbers of Ta, Ti, and Sc. Sc located at the center of the octahedron can accelerate the crystallization process. Ta, in particular, exerts the greatest influence on the migration rates of Sb and Te, resulting in the slowest grain growth rate. Simultaneously, it maximizes the delay in the transition from the cubic phase to the hexagonal phase. These features are beneficial for reducing power consumption. The elucidation of the distinct effects of doping elements sets the stage for phase change memory to adapt to various application scenarios. [ABSTRACT FROM AUTHOR]

According to the mineral phase composition and refractory leaching characteristics of Columbo-tantalite, the main goal of the paper was to investigate mechanism of the oxidation leaching Columbo-tantalite in hydrofluoric acid medium. The oxidation behavior of divalent Fe and divalent Mn in (Fe,Mn)(Nb,Ta)2O6 mineral was determined by electrochemical method. Cyclic voltammetry, Tafel polarization curve, combining with AC impedance, open circuit potential, and other methods were used to study the electrochemical oxidation process and leaching rate of Columbo-tantalite in hydrofluoric acid medium with the concentration of 11 mol/L HF. The result showed that the oxidation peak of 0.3 and 0.6V matched the oxidation of divalent Fe and divalent Mn in (Fe,Mn)(Nb,Ta)2O6 mineral by the method of cyclic voltammetry curve combined with the charge transfer number. The results also showed that the oxidation leaching rate of Nb and Mn increased gradually with the increase of applied oxidation voltage. The maximum oxidation leaching rate was at 0.6 V with current density of 173.1 µA/cm2. Oxidation voltage of 0.6 V corresponds to the oxidation of 25 pct H2O2, and the Nb leaching degree of Columbo-tantalite could reach 95.54 pct at 80 °C. [ABSTRACT FROM AUTHOR]

This paper is to study how to construct Frobenius pairs over a Morita ring Λ = AANBBMA B. Given Frobenius pairs (X,W) and (Y,V) in A-Mod and B-Mod, respectively, we construct Frobenius pairs (XY ,HA(W)⊕ HB(V)) and (Δ(X,Y),TA(W) ⊕TB(V)) in Λ-Mod under some conditions. As an application, we establish a sufficient and necessary condition of Gorenstein projective modules over the Morita ring Λ. [ABSTRACT FROM AUTHOR]

This Letter reports on the processing, mechanical properties, electrochemical performance, and toxicity behavior of a multiprincipal element Ti35Nb30Zr29Mo3Ta3 alloy. The recovered centimeter-sized cubes or parallelepipeds were polished before analysis. It was found that the homogeneity and yield stress of the alloys get increased when higher volumetric energy densities are applied during processing. The synthesized alloys also exhibited a Young modulus closer to those of bones than those usually reported on the conventional orthopedic metals (60–80 GPa for this alloy against 110 and 4–30 GPa for the Ti-6Al-4V and bone, respectively). The electrochemical corrosion assays performed at 25 and 37 °C, in sodium chloride (NaCl, 0.1 M), deoxygenated high glucose Dulbecco's Modified Eagle Medium (DMEM), and deoxygenated DMEM implemented with fetal bovine serum showed corrosion potentials (Ecorr) ranged in the order NaCl(25 °C) ≈ DMEM + PBS(37 °C) > DMEM(37 °C) and impedances much larger in the DMEM and DMEM + PBS media than in NaCl. Finally, pre-osteoblasts cells cultured in the medium conditioned by the alloy did not evidence cytotoxicity effect, because no effects on the cell proliferation and morphology were observed. These data suggest the biocompatibility of this alloy, indicating no acute toxicity, which is a prerequisite for the integration of an alloy as a bioimplant. [ABSTRACT FROM AUTHOR]

Two advanced manufacturing processes, spark plasma sintering (SPS) and selective laser sintering (SLS), have been developed for synthesis of (Zr,Nb,Ta,Ti,W)C compositionally complex carbide (CCC) via reactive sintering of a powder mixture of constitute monocarbides. X‐ray diffraction analysis confirmed that the single‐phase CCC can be formed by both SPS and SLS. While a homogenous microstructure with uniform metal element distributions was developed during SPS, three‐layer microstructures with a thin TiC‐rich layer and two TaC‐rich layers along with a TiO2‐rich surface layer containing W nanoparticles were formed during SLS. In addition, cellular structures with W, Zr, and Ti element segregation and dislocations on cell boundaries were observed in the SLS‐CCC sample, indicating the effect of nonequilibrium conditions on microstructure formation during laser melting followed by rapid cooling and solidification process. Compared to the SPS‐CCC sample, the SLS‐CCC showed enhanced hardness and reduced thermal conductivity, which may be related to their unique cellular structures. [ABSTRACT FROM AUTHOR]

Superconductivity in quasicrystals poses a new challenge in condensed matter physics. We measured the resistance and ac magnetic susceptibility of a Ta1.6Te dodecagonal quasicrystal, which is superconducting below Tc ~ 1 K. We show that the upper critical field increases linearly with a large slope of − 4.4 T/K with decreasing temperature down to 0.04 K, with no tendency to level off. The extrapolated zero-temperature critical field exceeds the Pauli limit by a factor of 2.3. We also observed flux-flow resistance with thermally activated behavior and an irreversibility field that is distinct from the upper critical field. We discuss these peculiarities in terms of the nonuniform superconducting gap and spin-orbit interaction in quasicrystal structures. [ABSTRACT FROM AUTHOR]

Ti/IrO2-Ta2O5 electrodes are extensively utilized in the electrochemical industries such as copper foil production, cathodic protection, and wastewater treatment. However, their performance degrades rapidly under high current densities and severe oxygen evolution conditions. To address this issue, we have developed a composite anode of Ti/Ta-Ti/IrO2-Ta2O5 with a Ta-Ti alloy interlayer deposited on a Ti substrate by double-glow plasma surface alloying, and the IrO2-Ta2O5 surface coating prepared by the traditional thermal decomposition method. This investigation indicates that the electrode with Ta-Ti alloy interlayer reduces the agglomerates of precipitated IrO2 nanoparticles and refines the grain size of IrO2, thereby increasing the number of active sites and enhancing the electrocatalytic activity. Accelerated lifetime tests demonstrate that the Ti/Ta-Ti/IrO2-Ta2O5 electrode exhibits a much higher stability than the Ti/IrO2-Ta2O5 electrode. The significant improvement in electrochemical stability is attributed to the Ta-Ti interlayer, which offers high corrosion resistance and effective protection for the titanium substrate. [ABSTRACT FROM AUTHOR]

The changes in the crystal structure and ferroelectric properties of (Al0.8Sc0.2)N films sandwiched between Pt and TiN electrodes were investigated by subjecting the films to post-heat-treatment at various temperatures up to 600 °C in both H2 and Ar gases. The remanent polarization underwent slight change, whereas the coercive field strengthened by approximately 9% as a result of the post-heat-treatment up to 600 °C irrespective of the atmosphere and electrode material. This change is much smaller than that reported for ferroelectric (Hf,Zr)O2 films as well as for Pb(Zr,Ti)O3 and SrBi2Ta2O9 films for a wide temperature range from 400 to 600 °C and is almost independent of the Pt and TiN electrodes. The high stability of (Al,Sc)N films with both Pt and TiN electrodes under H2 atmosphere is highly promising to stabilize the properties through the device fabrication process. [ABSTRACT FROM AUTHOR]

Radiation detection is being revolutionized by integrating photonic elements into scintillators. In this study, a scalable and cost‐effective method is proposed to achieve tuneable emission enhancement across the visible spectrum by colloidal self‐assembly of photonic crystals on scintillator surfaces. This concept is demonstrated for Eu3+/Tb3+‐doped Gd and Ta oxides. Widely available and affordable colloidal nanospheres of SiO2 or polymethyl methacrylate are self‐assembled on these scintillators. The size of the nanospheres is carefully optimized to match the desired emission lines of Eu3+/Tb3+. The result is homogeneous and closely‐packed structures with clear photonic bandgap in the visible range. Under X‐ray excitation, the scintillators covered with the photonic layers exhibit enhanced light extraction in the direction perpendicular to the surface, compared to isotropic emission in the bare scintillator. Such scintillation directionality, when optically matched with a proper detector, will result in higher efficiency of the overall detection system. Moreover, X‐ray imaging demonstrates an enhancement of 25% in system resolution of the scintillator supplemented with the photonic layer compared to unmodified scintillators. The proposed method is scintillator‐ and nanosphere‐agnostic, thus offering a promising versatile approach for directing the scintillation light toward a photodetector and increasing detection system performance, including high‐resolution imaging applications. [ABSTRACT FROM AUTHOR]

Ta1−xAlxN thin films with 5, 15, and 40 at.% Al addition were co‐deposited by reactive magnetron sputtering and characterized by Rutherford backscattering spectroscopy (RBS), grazing angle X‐ray diffraction (GAXRD), X‐ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), nanohardness, and oxidation tests. GAXRD and XPS analyses showed, regardless of the % Al added, the non‐existence of ternary nitride Ta1−xAlxN, but always as individual binary nitrides, TaN and AlN. Sample TaAlN_15 obtained the highest hardness and H3/E2 values, possibly due to the AlN grains presence, which were efficient in distorting the TaN lattice. All samples failed oxidation tests at 873 K, showing that the Al addition was not efficient in improving this property for tantalum aluminum nitride thin films. [ABSTRACT FROM AUTHOR]

Two inorganic–organic hybrid polyoxotantalates, H4[Na(H2O)5]2[CoII(en)3]2{[CoIII(en)]2(Ta6O19)2}·22H2O (1) and H2K2Na6 (H2O)24{[CoIII(en)]2(Ta6O19)2}·33H2O (2) have been constructed from {[CoIII(en)(Ta6O19)]2}10− ({Co2Ta12}) dimers. Compound 1 has a three-dimensional supramolecular framework with a pcu-type topology. Compound 2 possesses a three-dimensional structure composed of {Co2Ta12} dimers and alkali metal ions (Na+/K+) via coordination bonds. Polyoxotantalates 1 and 2 have been used as active materials for ITO/1/Ag and ITO/2/Ag RRAM devices. These devices exhibit stable non-volatile storage behavior and rewritable resistive switching with high ON/OFF ratios of 1.43 × 103 and 2.17 × 104 for 1-based and 2-based RRAM devices, respectively, and stable cyclic performance during 100-cycle stability tests. This discovery opens up new opportunities for the development of electrical bistability materials. [ABSTRACT FROM AUTHOR]

High entropy silicide (Mo 0.2 Cr 0.2 Ta 0.2 Nb 0.2 W 0.2)Si 2 (named as MeSi 2) coating was successfully prepared on Ta substrate by slurry sintering method. Firstly, precursor powders were initially obtained through mechanical alloying of silicide powders. Then powder slurry was coated on Ta substrate, and then the samples were sintered. For comparison, TaSi 2 coating prepared by halide-activated pack cementation method was synthesized. Subsequently, the static oxidation resistance of both MeSi 2 coating and TaSi 2 coating was examined at 1200 °C, results revealing that the MeSi 2 coating demonstrates an effective protection time of more than 60 h. The protective effect and duration of the MeSi 2 coating on Ta substrate are significantly greater than that of TaSi 2 , indicating an improvement oxidation resistance due to the high entropy effect of the silicide coating. After oxidation, the coating evolved an outer SiO 2 layer, followed by MeSi 2 , Me 5 Si 3 , TaSi 2 , and Ta 5 Si 3 layers. As the oxidation progressed, MeSi 2 gradually transformed into Me 5 Si 3 , leading to a loss of the coating's antioxidant capacity. [ABSTRACT FROM AUTHOR]

[Display omitted] • The refractory oxides of the W-residue formed a harmless slag after smelting with SKW. • Photovoltaic sawing waste was applied as a high-efficient silicothermic reductant. • Heavy metal oxides in W-residue were converted into high-value alloy phase. • An overall recovery rate of valuable metals of 91.7% was achieved. • The synergistic recovery mechanism of two industrial wastes was studied. Solid waste challenges in both the tungsten and photovoltaic industries present significant barriers to achieving carbon neutrality. This study introduces an innovative strategy for the efficient extraction of valuable metals from hazardous tungsten leaching residue (W-residue) by leveraging photovoltaic silicon kerf waste (SKW) as a silicothermic reducing agent. W-residue contains 26.2% valuable metal oxides (WO 3 , CoO, Nb 2 O 5 , and Ta 2 O 5) and other refractory oxides (SiO 2 , TiO 2 , etc.), while micron-sized SKW contains 91.9% Si with a surface oxide layer. The impact of SKW addition on the silicothermic reduction process for valuable metal oxides in W-residue was investigated. Incorporating SKW and Na 2 CO 3 flux enables valuable metal oxides from W-residue to be effectively reduced and enriched as a valuable alloy phase, with unreduced refractory oxides forming a harmless slag phase during the Na 2 O-SiO 2 -TiO 2 slag refining process. This process achieved an overall recovery yield of valuable metals of 91.7%, with individual recovery yields of W, Co, and Nb exceeding 90% with the addition of 8 wt.% SKW. This innovative approach not only achieves high-value recovery from W-residue and utilization of SKW but also minimizes environmental impact through an efficient and eco-friendly recycling pathway. The strategy contributes significantly to the establishment of a resource-efficient circular economy, wherein the recovered high-value alloy phase return to the tungsten supply chain, and the harmless slag phase become raw materials for microcrystalline glass production. [ABSTRACT FROM AUTHOR]

Molten oxide electrolysis is a promising pathway to decarbonize primary metal production. The oxide electrolyte is less hazardous and eco‐toxic than halides (molten salt electrolysis) and, with the use of renewably generated electricity and an inert anode, oxygen is produced as a by‐product instead of CO2. Building fundamental understanding of electrolytic operating windows requires starting with simple chemistries. Here we investigate a simplified binary oxide system as an electrolyte for titanium oxide reduction to metal. The TiO2−Na2O binary system forms a eutectic, reducing the liquidus temperature over a wide composition range. FactSage 8.1 predictions suggested Ti reduction would become favorable over Na reduction for compositions greater than 0.49 mole fraction TiO2. The prediction was validated by the detection of metallic Ti after electrolysis experiments. However, the reduction efficiency was too low (0.24±0.08 % at −0.1 V vs Ti reference electrode) for the TiO2−Na2O system to be a viable industrial electrolyte for Ti production. Scoping for other binary oxide systems was performed for electrolytic production of two critical metals, tantalum and neodymium. Based on TiO2−Na2O system's predicted behavior, candidate binary oxide systems were identified that contained congruently melting line compounds flanked by eutectic reactions from the ACerS‐NIST Phase Equilibria diagrams database. [ABSTRACT FROM AUTHOR]

The photoelectrochemical performance of Ta3N5 photoanodes is strongly impacted by the presence of shallow and deep defects within the bandgap. However, the role of such states in defining stability under operational conditions is not well understood. Here, a highly controllable synthesis approach is used to create homogenous Ta3N5 thin films with tailored defect concentrations to establish the relationship between atomic‐scale point defects and macroscale stability. Reduced oxygen contents increase long‐range structural order but lead to high concentrations of deep‐level states, while higher oxygen contents result in reduced structural order but beneficially passivate deep‐level defects. Despite the different defect properties, the synthesized photoelectrodes degrade similarly under water oxidation conditions due to the formation of a surface oxide layer that blocks interfacial hole injection and accelerates charge recombination. In contrast, under ferrocyanide oxidation conditions, it is found that Ta3N5 films with high oxygen concentrations exhibit long‐term stability, whereas those possessing lower oxygen contents and higher deep‐level defect concentrations rapidly degrade. These results indicate that deep‐level defects result in rapid trapping of photocarriers and surface oxidation but that shallow oxygen donors can be introduced into Ta3N5 to enable kinetic stabilization of the interface. [ABSTRACT FROM AUTHOR]

The photocatalytic performance of high entropy alloy (HEA) and its oxide form (high entropy oxide, HEO) have been evaluated in this study. The HEA, composed of Nb, Ta, Zr, Mo, and W powders, was synthesized through a mechanical alloying process for 120 h. This process was carried out under a high-purity Ar atmosphere to prevent oxidation. Subsequently, the HEA was converted into HEO via a mechano-thermal oxidation method 900 °C for 12 h. The photocatalytic activity of both oxidized and non-oxidized samples was systematically evaluated by degradation of methyl blue (MB) under UV irradiation. Electron dispersive spectroscopy (EDS), X-ray diffraction (XRD), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS) were used to investigate the structural and chemical features of the alloys. Furthermore, BET surface area analysis and Zeta potential measurements were conducted to understand the alloys' surface properties and stability in aqueous solutions. The results showed that the HEA has a remarkable photodegradation performance of around 58.77% which is two times higher than that observed with the HEO. [ABSTRACT FROM AUTHOR]

Variscan granitoids and associated mafic rocks exposed in the External Crystalline Massifs (ECM) of the Western Alps document the Variscan stages from the early Carboniferous collision to the early Permian post-collisional setting. Our study focuses on the Central part of the ECM, synthesizing newly acquired and existing geochronological, whole-rock geochemical and isotopic data. We identified two distinctive magmatic series: (i) high-K calc-alkaline granitoids, which range from magnesian (MgG) to ferro-magnesian (FeMgG) rocks; (ii) ultra-high-K metaluminous (UHKM) rocks ("durbachites"). These series were emplaced roughly simultaneously between ca. 350 and 300 Ma, with two main episodes during the Visean (ca. 348–335 Ma) and the late Carboniferous (305–299 Ma), with a more limited activity in between. A younger Permian event at ca. 280–275 Ma has also been identified in one granitoid pluton. Contemporaneous emplacement of these two series reflects concomitant crustal anatexis and melting of LILE–LREE-rich metasomatized lithospheric mantle. Trace elements and Nd–Sr isotopes reveal significant hybridization between these two magmatic end members, by magma mixing, or assimilation of crystallized mafic ultrapotassic enclaves in the high-K calc-alkaline granitoids. Granitoid composition evolves over time, especially SiO2, Mg#, Sr/Y, La/Yb and Nb/Ta, possibly explained by increasing differentiation of magmas over time, changes in the crust versus mantle sources mass-balance, and decrease in melting pressure due to the orogenic collapse. The εNdi values of both high-K calc-alkaline granitoids and durbachites decreases from [− 3.8; − 2.9] to [− 6.4; − 5.2] between 345 and 320 Ma, possibly indicating an increasing influence of subducted/relaminated crustal material contaminating the lithospheric mantle source. εNdi values then rise to [− 3.7; − 0.5] during the late Carboniferous, possibly due to progressive exhaustion of the enriched mantle source, or advection of the asthenosphere during the post-collisional stage. Possible geodynamic scenario along the central-eastern segment of the Variscan Belt, which may account for the temporal evolution of Variscan magmatism in the External Western Alps. [ABSTRACT FROM AUTHOR]

Evaporation of silicate materials from Earth or its precursors may be important in shaping their primordial compositions represented by undifferentiated meteorites, e.g., enstatite chondrites; however, the conditions under which evaporation occurs and the extent of evaporation-induced elemental and isotope fractionation remain uncertain. Here, we experimentally determine the volatility and isotope fractionation of Si, Mg, Ca, Nb, and Ta during enstatite melt evaporation at 2423–2623 K using a high-temperature conical nozzle levitator. Homogenous glasses are recovered after experiments; then we use EPMA and LA-ICP-MS to measure the elemental compositions, MC-ICP-MS to measure the Si and Mg isotopes, and TIMS to measure the Ca isotopes. Our results show that the evaporation rates of Si are larger than Mg, and the mean vapor/melt isotope fractionation factors (α = Rvapor/Rmelt; R = isotope ratio) are 0.99585 ± 0.00002 for 29Si/28Si and 0.98942 ± 0.00130 for 25Mg/24Mg. However, neither evaporative loss of Ca, Nb, and Ta nor Ca isotope fractionation was observed within analytical uncertainty. In conjunction with previous studies, we find that in an evaporation experiment the saturation degree (partial vapor pressure/equilibrium vapor pressure) of Si (SSi) is larger than SMg when Si is more volatile than Mg, and vice versa. If the Mg/Ca and Si/Ca ratios and isotopes in the bulk silicate Earth are attributed to the evaporation of enstatite chondrite-like precursors, evaporation temperatures >5000 K and SSi < SMg are required. [ABSTRACT FROM AUTHOR]

Thermal and microhabitat resources are two fundamental requirements that affect the life history of any ectotherm. Furthering our understanding of how reptilian species meet these ecological requirements is crucial for assessing the impact of environmental and anthropogenic changes on populations. Here, we explored some fundamental aspects of the thermal and microhabitat ecology of Conopsis biserialis, a small, burrowing, and endemic earthsnake of central Mexico. The study was conducted during the rainy season in a montane site disturbed by rural activities. The mean field body temperature (Tb) of C. biserialis was 26 ± 0.6 ºC. Field Tb did not differ significantly between sex and development stages. However, we found that Tb was positively correlated with substrate, air, and under-rock temperatures (Ts, Ta, and Tr) in the rural microhabitat. Regression analysis showed that substrate and under-rock temperatures (Ts and Tr) were the parameters that best explained Tb variability in the individuals. The temperature and relative humidity under shelter did not differ significantly among shelter types and/or rock sizes. In addition to these thermal traits, earthsnakes selected and utilized six common biotic and physical elements of the rural microhabitat. Most individuals used high proportions of large and medium rocks for sheltering, and these rocks were selected around crop fences and cleared grasslands where the soil can be either covered with low vegetation or bare. Our results suggest that, during the rainy season, individuals of C. biserialis use and select some biotic and structural resources of the rural microhabitats, and were capable of actively regulating their temperature by using shelters with high values of microclimatic homogeneity. [ABSTRACT FROM AUTHOR]

CO oxidation at mild condition is significant for industrial process but still challenging nowadays, especially for the non-noble metal catalysts. The preparation method significant affect the catalytic activity of the catalyst. Comparing with cobalt supported on tantalum oxide prepared by impregnation method, Co/Ta2O5 prepared by deposition–precipitation method with urea in this study has smaller particle size, higher specific surface area and better redox properties, and these features make the catalyst exhibit higher catalytic activity for CO oxidation at mild condition. 90% CO conversion was achieved at 130 ℃, and CO was fully converted at 150 ℃. The XPS and DRIFTs results show that Co/Ta2O5 has more oxygen vacancies, and the absorbed CO will react with oxygen. The study may provide a new thought for the preparation of catalysts with high activity at mild condition. [ABSTRACT FROM AUTHOR]

High-entropy carbide ceramics (HECCs) have demonstrated extraordinary properties and broad application potential. However, the action mechanisms of metallic elements on the properties have not been understood in depth. In this study, the structural stability and the mechanical and thermodynamic properties of (Ti, Hf, Nb, Ta)C HECCs across a broad composition spectrum were systematically analyzed based on the density functional theory and Debye–Grüneisen model. The crystal structure was constructed and validated through experimental testing. The mechanical properties such as elastic moduli, ductility, hardness, and Poisson's and Pugh's ratios were calculated. Furthermore, the temperature dependence of bulk moduli, thermal expansion coefficients, and heat capacities of the HECCs were investigated. To interpret the elastic and toughening mechanisms of non-equiatomic HECCs, the electronic structures were investigated. The results indicate that the HECCs with a single solid solution phase of the FCC rock-salt structure are thermodynamically stable. The HECCs containing higher Nb and Ta contents have greater strength and stiffness, and those containing higher Ti and Hf contents exhibit greater hardness and brittleness than the equiatomic HECC. In addition, non-equiatomic HECCs containing higher Nb and Ta contents have larger bulk moduli and lower linear thermal expansion coefficients, which can be attributed to the stronger covalent interaction among metallic elements and carbon. This study is expected to have an impact on designing ideal HECCs for high-temperature applications under extreme environments. [ABSTRACT FROM AUTHOR]

As the precursor of 2D i -MXene, i -MAX phase appeals lots of exertions on the improvement of its chemical diversity, among which alloying is an effective strategy. Herein, we report on the synthesis of the M-alloyed i -MAX phase (Mo 0.75 M 0.25) 4/3 Er 2/3 GaC (M = Ti, V, Nb, Ta, W). Structure analysis identifies all of them as Cmcm orthorhombic. The corresponding M-alloyed i -MXene, (Mo 0.75 M 0.25) 1.33 CT z (M = Ti, V, Nb, Ta, W), was synthesized by HF etching and shows potential as an electrode for supercapacitors due to its improved charge storage performance and cyclic stability. A volumetric capacitance of 431.7 F g−1 was delivered at the scan rate of 2 mV s−1 for (Mo 0 · 75 V 0.25) 1.33 CT z , and a 94.8% capacitance was retained after 10,000 charge/discharge cycles for (Mo 0 · 75 W 0.25) 1.33 CT z. Modelling was performed to better understand the mechanism improving the electrochemical capacitance and to clarify the i-MXene alloying process. The alloying strategy shows a novel and simple way to control i-MXene's surface termination, which will make it facilitate to use in applications like high-performance supercapacitors. [ABSTRACT FROM AUTHOR]

MSi 2 -type multicomponent silicide coatings were prepared on Nb alloys by spark plasma sintering using mixed powders of Mo, Ta, W, Zr, Ti and Si. The coatings were composed of thick outer layers and thin inner layers (interdiffusion zone). A two-phase structure consisting of C11b (Mo,Ta,W,Ti)Si 2 and C40 (Ti,Ta,Zr)Si 2 was observed in the outer layers of all the coatings sintered for holding times ranging from 15 s to 5 min, but the distribution of these elements in each phase gradually became uniform with increasing holding time. The coatings demonstrated excellent protection during oxidation at 1300 °C for 100 h, and a continuous dense oxide scale mainly composed of ZrSiO 4 and SiO 2 was generated. The alternation of heating and cooling during oxidation caused cracks to appear at the interface between the outer layer and inner layer due to a mismatch of thermal expansion coefficients. However, crack extension was observed only along the inner layer toward the interior due to the multicomponent structure of the outer layer of the coating. The microstructural development and oxidation behavior of the coatings were discussed. [ABSTRACT FROM AUTHOR]