Ta Hf Research Articles

Processing of mineralized microgranite dike for the recovery of niobium, tantalum, and rare earth elements using 1, 2-propyleneglycol extractant

ABSTRACT A number of strategic and economic rare-metal and Rare Earth Elements (REEs)-bearing minerals were recorded in mineralized microgranite dike (MMGD) from Ras Abdah area located in the Northern Eastern Desert of Egypt. Firstly, by sulphuric acid digestion at 300 °C, 3 h, 1/3 ore/Acid ratio, the RE, Nb, and Ta present in the MMGD can be efficiently extracted into the leach solution while Zr, Fe, and Th remained in the unattacked residue. The experimental digestion proved the dissolution of 98.9, 99.2, and 96 % for Nb, Ta, and REEs, respectively. In this study, a novel method was used to selectively recover Nb and Ta content from REEs in the digested concentrate sulphate solution. Solvent extraction using 1, 2-propyleneglycol was applied for the first time to achieve this secondary recovery process. From infrared and 1H-NMR data, the extraction was achieved, and the extractant bonded to Nb and Ta through glycol and alcoholic oxygen atoms. Niobium and Tantalum ions were stripped with water for Ta and 1M HF for Nb, achieving 98.6 and 98.8 % stripping efficiency, respectively. By employing an oxalic acid precipitation technique, a precipitate of extremely pure REEs was extracted from the raffinate solutions.

In-depth S/TEM observation of Ti–Hf and Ta–Hf-doped Nb3Sn layers

In superconducting Nb3Sn layers with coherence lengths of approximately 3 nm, grain boundaries act as effective pinning sites. Thus, grain refinement is an essential issue that directly affects the superconducting critical characteristics of the Nb3Sn layer. In recent years, Hf addition to Nb3Sn wires co-doped with Ta has attracted notable interest as a method that enables grain refinement down to several tens of nm. In-depth characterization of the Nb3Sn grain morphology in Hf-doping is crucially important to correlate the microstructure with the flux pinning characteristics. In this article, the grain morphologies of Ti–Hf and Ta–Hf-doped Nb3Sn layers were clarified by scanning transmission electron microscopy (STEM) and TEM-based automated crystal orientation mapping (ACOM-TEM). STEM/energy dispersive x-ray spectroscopy (EDS) revealed no significant oxide precipitates in our samples. The grain size distribution was attained by ACOM-TEM. Although Hf-doping attained a grain refinement effect in the Nb3Sn layer in both doping cases, the degree of this effect was relatively small for Ti–Hf. Kernel average misorientation analysis by scanning electron microscopy-electron backscattered diffraction unveiled no appreciable difference between the internal strain states of the Nb-alloy parent phases in Ti–Hf and Ta–Hf. One remarkable new finding through STEM/EDS was the presence of a Cu–Hf compound phase in the Nb3Sn layer. The Cu–Hf compound sounds analogous to the Cu–Ti compounds that form when Nb–47Ti with Cu matrix is heat treated. The STEM/EDS maps revealed a larger amount of Cu flow from the Cu–Sn side along the grain boundaries. The large Cu deposition on the grain boundaries might facilitate grain growth in Nb3Sn. Those findings make a novel contribution to the literature as they provide a deep insight into Nb3Sn phase formation via Hf doping.

High strain rate response and mechanical performance of tantalum carbide–hafnium carbide solid solution

Ultra-high temperature ceramics (UHTCs) based on the solid solution TaxHf1-xC have shown great promise as materials for extreme environments (>2500 °C) due to their improved thermo-mechanical properties. However, their dynamic response under high-impact loading remains unknown. In this study, we investigate the dynamic impact behavior and fracturing evolution of TaxHf1-xC samples (with x = 0, 0.2, 0.5, 0.8, and 1) at a strain rate > 103 s-1 using the Split Hopkinson Pressure Bar (SHPB) test. Among the different compositions, Ta0.5Hf0.5C exhibits the highest compressive strength of 1870 MPa, representing a 36% improvement over TaC and 54% over HfC. High frame rate videos and deformation analysis reveal that Ta0.5Hf0.5C, characterized by extensive Ta–Hf bonding, significantly reduces the crack propagation rate by approximately 1435% compared to TaC and 4050% compared to HfC. This effect is attributed to the dislocation pile-ups, nano-twin formation, inter grain twisting exhibited mostly along {111} plane as Hf substitutes Ta in TaxHf1-xC samples. Further, the surface energy is least for {111} plane eliciting the higher probability for bypassing crack propagation along this plane in TaxHf1-xC. The exceptional damage tolerance and improved mechanical properties of Ta0.5Hf0.5C, compared to other solid-solution TaxHf1-xC compositions, make it an extraordinary structural material for hypersonic applications. These findings provide valuable insights into the dynamic behavior of UHTCs and highlight the potential of Ta0.5Hf0.5C as a superior material for extreme environments requiring high-impact resistance.

Critical metals and minerals in the Nordic countries of Europe: diversity of mineralization and green energy potential

Abstract Europe relies mainly on imports of critical raw materials (CRMs) for its industry, not least the vital ones for emerging green energy technologies. Among the main metal and mineral producers in Europe today, the Nordic countries (specifically, Greenland, Norway, Sweden and Finland) share a diverse geology with various deposit types formed over a long geological time span. This has led to large near-future potential with regard to CRM production. Based on current knowledge and datasets, we assess the Nordic geological potential for CRMs that are specifically relevant for green technologies, namely cobalt, graphite, hafnium, lithium, niobium, platinum-group metals, rare earth elements (REEs), silicon, tantalum, titanium and vanadium, describing the most important deposits, their setting and characteristics. Several Nordic CRM resources stand out in a European and even global context, such as the giant REE(–Nb–Ta–Hf) deposits in Greenland, while the REE–Nb–(Hf) deposits at Fen (Norway) and Norra Kärr (Sweden) are very significant for Europe; Finland is the only major cobalt producer, while Norway has very significant graphite and titanium resources and production. Furthermore, Sweden, Finland and Greenland have very large vanadium resources. In addition, we conclude that the Nordic research and exploration potential for most CRMs is large.

APC Nb3Sn superconductors based on internal oxidation of Nb–Ta–Hf alloys

In the last few years, a new type of Nb3Sn superconducting composite, containing a high density of artificial pinning centers (APC) generated via an internal oxidation approach, has demonstrated a significantly superior performance relative to present, state-of-the-art commercial Nb3Sn conductors. This was achieved via the internal oxidation of Nb-4at.%Ta-1at.%Zr alloy. On the other hand, our recent studies have shown that internal oxidation of Nb–Ta–Hf alloys can also lead to dramatic improvements in Nb3Sn performance. In this work we follow up on this latter approach, fabricating a 61-stack APC wire based on the internal oxidation of Nb-4at.%Ta-1at.%Hf alloy, and compare its critical current density (J c) and irreversibility field with APC wires made using Nb-4at.%Ta-1at.%Zr. A second goal of this work was to improve the filamentary design of APC wires in order to improve their wire quality and electromagnetic stability. Our new modifications have led to significantly improved residual resistivity ratio and stability in the conductors, while still keeping non-Cu J c at or above the conductor J c specification required by the proposed Future Circular Collider. Further improvement via optimization of the wire recipe and design is ongoing. Finally, additional work needed to make APC conductors ready for applications in magnets is discussed.

Influence of parent Nb-alloy grain morphology on the layer formation of Nb3Sn and its flux pinning characteristics

The influence of parent Nb-alloy grain morphology on the layer formation of Nb3Sn and its pinning characteristics was clarified using a fundamental method. Nb–Ta–Hf was used in this work, given its high recovery temperature of more than 700 °C, which is higher than the Nb3Sn-phase formation temperature. First, a Cu/Nb–4at%Ta–1at%Hf single-core composite wire (outer: Cu) was prepared. Subsequently, two pieces were cut off, one of which was intermediately annealed at the recrystallization temperature. Thereafter, Sn was attached onto the surface of both the samples by electroplating, and the samples were heat-treated for Nb3Sn layer formation. Evidently, a significantly finer grain morphology appeared on the as-drawn fine parent Nb-alloy layer, leading to a much better pinning force property.

Co-crystals, Salts or Mixtures of Both? The Case of Tenofovir Alafenamide Fumarates.

Tenofovir alafenamide fumarate (TAF) is the newest prodrug of tenofovir that constitutes several drug products used for the treatment of HIV/AIDS. Although the solid-state properties of its predecessor tenofovir disoproxil fumarate have been investigated and described in the literature, there are no data in the scientific literature on the solid state properties of TAF. In our report, we describe the preparation of two novel polymorphs II and III of tenofovir alafenamide monofumarate (TA MF2 and TA MF3). The solid-state structure of these compounds was investigated in parallel to the previously known tenofovir alafenamide monofumarate form I (TA MF1) and tenofovir alafenamide hemifumarate (TA HF). Interestingly, the single-crystal X-ray diffraction of TA HF revealed that this derivative exists as a co-crystal form. In addition, we prepared a crystalline tenofovir alafenamide free base (TA) and its hydrochloride salt (TA HCl), which enabled us to determine the structure of TA MF derivatives using 15N-ssNMR (15N-solid state nuclear magnetic resonance). Surprisingly, we observed that TA MF1 exists as a mixed ionization state complex or pure salt, while TA MF2 and TA MF3 can be obtained as pure co-crystal forms.

Ta-based 413 and 211 MAX phase solid solutions with Hf and Nb

New bulk MAX phase-based ceramics were synthesized in the Ta–Hf–Al–C and Ta–Nb–Al–C systems. Specifically, (Ta1-x,Hfx)4AlC3 and (Ta1-x,Nbx)4AlC3 stoichiometries with x = 0.05, 0.1, 0.15, 0.2, 0.25 were targeted by reactive hot pressing of Ta2H, HfH2, NbH0.89, Al and C powder mixtures at 1550 °C in vacuum. The produced ceramics were characterized in terms of phase composition and microstructure by X-ray diffraction, scanning electron microscopy, electron probe microanalysis and scanning transmission electron microscopy. The investigation confirmed the existence of such M-site solid solutions with low solute concentrations, as predicted by first-principles calculations. These calculations also predicted a linear trend in lattice parameter evolution with increasing Hf concentration, in agreement with the experimental results. In order to increase the low phase purity of the produced ceramics, Sn was added to form (Ta1-x,Hfx)4(Al0.5,Sn0.5)C3 and (Ta1-x,Nbx)4(Al0.5,Sn0.5)C3 double solid solutions, thus resulting in a higher content of the 413 MAX phase compounds in the produced ceramics.

Improved oxidation resistance of CoNiCrAlTaHfY/Co coating on C/C composites by vapor phase surface alloying

Abstract

Understanding the oxidation behavior of Ta–Hf–C ternary ceramics at high temperature

For high-temperature applications, poor oxidation performance of Ta–Hf–C ternary ceramics is an important life-limiting factor. In this work, the oxidation mechanisms of various compositions of Ta–Hf–C ternary ceramics are studied systematically at 1400–1600 °C in air under isothermal conditions for the first time. The oxidation process is demonstrated to be composition dependent: 1TaC–1HfC and 1TaC–3HfC exhibit considerably improved oxidation resistance compared to TaC and HfC individual carbides along with 4TaC–1HfC and 1TaC–4HfC ternary ceramics. The results obtained herein should pave the way to design advanced oxidation-resistant Ta–Hf–C ternary ceramics for high-temperature applications.

Ta, Ti and Hf effects on Nb3Sn high-field performance: temperature-dependent dopant occupancy and failure of Kramer extrapolation

The increasing demand for improving the high-field (16–22 T) performance of Nb3Sn conductors requires a better understanding of the properties of modern wires much closer to irreversibility field, HIrr. In this study we investigated the impact of Ta, Ti and Hf doping on the high-field pinning properties, the upper critical field, Hc2, and HIrr. We found that the pinning force curves of commercial Ti and Ta doped wires at different temperatures do not scale and that the Kramer extrapolation from low field data, typically used by magnet designers to estimate high-field critical current density and magnet operational margins, is not reliable and significantly overestimates the actual HIrr. In contrast, new laboratory scale conductors made with Nb–Ta–Hf alloy have improved high-field Jc performance and, despite contributions by both grain boundary and point defect pinning mechanisms, have more predictable high-field behavior. Using Extended x-ray Absorption Fine Structure spectroscopy, EXAFS, we found that for the commercial Ta and Ti doped conductors, the Ta site occupancy in the A15 structure gradually changes with the heat treatment temperature whereas Ti is always located on the Nb site with clear consequences for Hc2. This work reveals the still limited understanding of what determines Hc2, HIrr and the high-field Jc performance of Nb3Sn and the complexity of optimizing these conductors so that they can reach their full potential for high-field applications.

Prospective SHS composites for high-temperature applications

In this article, a succinct review of the SHS ceramics prospective for the high-temperature applications is provided. Macrokinetic features and mechanisms of combustion and structure formation were studied for the systems Ta–Zr–C, Ta–Hf–C, Zr–Ta–B, Hf–Ta–B, Zr–B–Si–C, Ta–Si–C, Mo–Hf–Si–B, and Zr–Ta–B–Si. Materials were produced by the combination of SHS with hot pressing (HP) and spark plasma sintering (SPS), and their structure and properties were investigated.

Research into the Possibility of Producing Single-Phase Tantalum–Hafnium Carbide by SHS

The influence of mechanical-activation (MA) conditions on the microstructure and phase composition of Ta–Hf–C reaction mixtures and products fabricated from them by self-propagating high-temperature synthesis (SHS) is investigated. The Ta–Hf–C reaction mixtures are mechanically activated in centrifugal planetary mills with various drum revolution rates. It is revealed that an increase in the drum revolution rate from 250 to 900 rpm lowers the heterogeneity scale of the reaction charge, decreases the size of coherent scattering regions of tantalum and hafnium by an order of magnitude, and leads to a rise in the degree of microdeformation of their crystal lattices by a factor of 1.5–2.0. It is established experimentally that it seems impossible to initiate an SHS reaction in the Ta–Hf–C activated mixture at initial temperature T0 < 550 K. The combustion process is implemented only at T0 = 800 K, when the adiabatic combustion temperature reaches 3274 K in mixtures treated with a revolution rate higher than 678 rpm. Single-phase carbide (Ta,Hf)C with lattice parameter a = 0.4487 nm, which corresponds to 18.0 at % dissolved HfC in TaC, is formed from reaction mixtures activated according to optimal regimes. The hafnium oxide content in products does not exceed 1%. The sample structure has high porosity (larger than 30%) and small carbide grain size (smaller than 10 μm), which makes it possible to produce the (Ta,Hf)C powder by milling the SHS product in a ball rotary mill.

Consolidation and characterization of highly dense single‐phase Ta–Hf–C solid solution ceramics

AbstractHerein, Ta–Hf–C solid solution ceramics were consolidated from nano‐scale Ta–Hf–C solid solution powders for the first time. Four different compositions (4TaC–1HfC, 1TaC–1HfC, 1TaC–3HfC, and 1TaC–4HfC) were prepared by hot‐pressed sintering at 2100°C, 70 MPa pressure and a holding time of 30 minutes. The densification, formation of single‐phase solid solution and mechanical properties of the samples were systemically investigated. Relative density &gt;95% was achieved for all four compositions with some improvement when TaC content was increased. And the formation of single‐phase Ta–Hf–C solid solution was strongly demonstrated by phase analysis and crystal measurement using XRD and TEM. A significant improvement of hardness up to ~30 GPa was achieved, which was much higher than that of pure TaC (18.9 GPa) and HfC (22.1 GPa), due to the high densification and solid solution strengthening mechanism.

Gamma and X-ray radiation compatibility of Ti–Ta–Hf–Zr alloys used for coronary stent applications

We have studied the gamma and X-ray radiation compatibility of Ti-based alloys such as Ti–37Ta–26Hf–13Zr-24 (wt%) [Alloy 1], Ti–40Ta–22Hf–11.7Zr-26.3 (wt%) [Alloy 2], Ti–45Ta–18.4Hf–10Zr-26.6 (wt%) [Alloy 3], Ti–50Ta–15Hf–8Zr-27 (wt%) [Alloy 4], Ti–55Ta–12Hf–7Zr-26 (wt%) [Alloy 5], and Ti–60Ta–10Hf–5Zr-25 (wt%) [Alloy 6]. Gamma and X-ray radiation compatibility is studied by evaluating the mass attenuation coefficient, mean free path, HVL, TVL effective atomic number, effective electron density, exposure buildup factor, and relative dose. We have compared these parameters for studied alloys with that of arteries. The alloys Ti–55Ta–12Hf–7Zr-26 and Ti–60Ta–10Hf–5Zr-25 have added properties such as gamma/X-ray radiation compatibility, high elastic admissible strain, high mechanical strength, and excellent biocompatibility. Hence, we may suggest that, among Ti–Ta–Hf–Zr alloys, these alloys are best materials for coronary stent applications.

RESEARCH ON THE POSSIBILITY OF PRODUCING (Ta,Hf)C SINGLE-PHASE TANTALUM-HAFNIUM CARBIDE BY SHS

The paper studies the effect of mechanical activation conditions (MA) on the microstructure and phase composition of Ta–Hf–C reaction mixtures and products derived from them by self-propagating high-temperature synthesis (SHS). The mechanical activation of Ta–Hf-C reaction mixtures was carried out in centrifugal planetary mills with different drum rotation speeds. It was found that an increase in the drum rotation speed from 250 to 900 rpm reduced the heterogeneity scale of the reaction charge, reduced the size of coherent scattering regions of tantalum and hafnium by an order of magnitude, and led to an increase in the strain degree of their crystal lattices by 1,5–2,0 times. It was experimentally established that initiation of the SHS reaction in the activated Ta–Hf–C mixture at an initial temperature Т 0 Т 0 = 800 K only, when the adiabatic combustion temperature reached 3274 K. The single-phase carbide (Ta,Hf)C with a lattice parameter а = 0,44787 nm corresponding to 18,0 at.% of HfC dissolved in TaC, was obtained from reaction mixtures activated under optimal regimes. The content of hafnium oxide in products does not exceed 1 %. The structure of samples is characterized by high porosity (more than 30 %) and a small carbide grain size (less than 10 μm), which made it possible to obtain the (Ta,Hf)C powder by milling the SHS product in a ball mill.

Effects of solution treatment and aging on the microstructure, mechanical properties, and corrosion resistance of a β type Ti–Ta–Hf–Zr alloy

A β type TTHZ alloy (Ti–40Ta–22Hf–11.7Zr) experienced various phase transitions during solution and aging treatments, and the different phases of the alloy significantly influenced its mechanical properties and corrosion behaviour.

Plastic deformation properties of Zr–Nb–Ti–Ta–Hf high-entropy alloys

We have investigated the plastic deformation properties of single-phase Zr–Nb–Ti–Ta–Hf high-entropy alloys from room temperature (RT) up to 300 °C. Uniaxial deformation tests at a constant strain rate of 10−4 s−1 were performed, including incremental tests such as stress relaxations, strain-rate changes, and temperature changes in order to determine the thermodynamic activation parameters of the deformation process. The microstructure of deformed samples was characterized by transmission electron microscopy. The strength of the investigated Zr–Nb–Ti–Ta–Hf phase is not as high as the values frequently reported for high-entropy alloys in other systems. At RT we measure a flow stress of about 850 °C. We find an activation enthalpy of about 1 eV and a stress dependent activation volume between 0.5 and 2 nm3. The measurement of the activation parameters at higher temperatures is affected by structural changes evolving in the material during plastic deformation.

“Grenvillian” intra-plate mafic magmatism in the southwestern Yangtze Block, SW China

Tectonic affinity of Grenvillian magmatism in the South China Block is important for understanding the role of the block in the reconstruction of the Rodinia supercontinent during the Mesoproterozoic. In the southwestern Yangtze Block, South China, late Mesoproterozoic metabasalts occur as layers in the Pudeng Formation of the Julin Group. Most metabasalts are highly metamorphosed to be amphibolites composed of dominantly plagioclase and amphibole with minor Fe–Ti oxides, titanite and apatite. Two metabasalt samples have identical zircon U–Pb ages of ∼1050Ma. These basalts are tholeiitic in compositions and have high and variable TiO2 (1.1–3.2wt.%) and low Mg# values (=Mg/(Mg+Fe2+); 35–60). In the primitive mantle-normalized diagram, they are characterized by enrichments in Th, Nb, Ta and light REE without significant Zr–Hf–Nb–Ta–Ti anomalies. The samples have ɛNd(t) values ranging from −1.4 to +4.0 and their zircon grains have ɛHf(t) values from −1.7 to +11.0. The low Mg# values and Cr (55.1–261ppm) and Ni (13.5–76.5ppm) contents suggest fractional crystallization of olivine and/or clinopyroxene, whereas minor negative Eu anomalies indicates slightly fractional crystallization of plagioclase. High positive ɛNd(t) and ɛHf(t) values suggest derivation of the parental magma from a depleted asthenospheric mantle source. On the other hand, variable ɛNd(t) and ɛHf(t) values and La/Sm and Nb/La ratios are consistent with significant crustal assimilation by the Paleoproterozoic rocks in the region. These samples have high Ti and Ti/V ratios (mostly >40), typical of within-plate basalts. In the Zr–Nb–Y and Th–Ta–Hf diagrams for tectonic discrimination, the samples with least crustal contamination are plotted in the ‘within-plate’ and ‘E-MORB’ fields, indicating an intra-continental rifting setting. In view of subsequent Neoproterozoic arc magmatic activities (950–730Ma) in the region, we suggest that these basalts were likely produced at a rifting basin in a passive margin. Results presented here demonstrate that the Grenville-age magmatism in the southwestern Yangtze Block was not orogenic in origin, thus arguing against the existence of Grenvillian Orogen in the region that was traditionally used to place the South China Block in the central part of the Rodinia supercontinent.

Electronic band structures, dielectric functions and interband transitions of relaxor ferroelectric (1-x) Pb (Sc1/2Ta1/2) O3-xPbHfO3 ceramics: A spectroscopic reflectance study

Electronic band structures and dielectric functions of relaxor ferroelectric (1-x) Pb (Sc1/2Ta1/2) O3-xPbHfO3 (PSTH) ceramics (0⩽x⩽0.2) have been investigated by far-IR–UV reflectance spectra. Based on generalized four-parameter damped oscillators and Tauc–Lorentz dispersion models, the dielectric functions from 0.006 to 6eV have been successfully extracted at room temperature. The status of structural order can be characterized by combining the strength of the Sc–Ta vibrational mode and the dielectric loss in the frequency range of 280–320cm−1. It was found that the electronic structures (which depend closely on the BO6 (B=Sc, Ta Hf) octahedron) are sensitive to the B-site atom concentration. The interband transitions can be clearly demonstrated by the imaginary part of the dielectric function which corresponds to the transition from the O 2p to B-site (Sc, Ta and Hf) d states and Pb 6p states. The two typical transition energies show the opposite trend with increased PbHfO3 composition. Remarkable variations of the B-site order degree and the lattice expansion due to the introduction of PbHfO3 are responsible for modifications of the dielectric function and electronic structures. These results could be crucial for investigating the potential applications of PSTH-based optoelectronic and pyroelectric devices.