Tantalum Powder Research Articles

Mechanism of the local destruction of the amorphous Ta2O5 layer on the surface of a tantalum anode

In the present work, a mechanism of the destruction of amorphous tantalum oxide Ta2O5 on the tantalum anode surface is suggested based on high absorption properties of tantalum. The data of analysis of the morphological peculiarities of the defective areas of the surface layers show that the destruction of the amorphous film occurs due to the growth of a pyramid-shaped defect; the pyramidal defect is not coherent with amorphous surface Ta2O5, and it is not a product of its crystallization. The nucleation and growth of the “pyramid” occurs due to the directed movement of oxygen during the oxidation of the tantalum surface along the grain boundaries to the region of triple junctions of the tantalum matrix with the subsequent local formation of crystalline Ta2O5. The suggested mechanism offig destruction can be realized when high-purity tantalum powders are used.

Sealing of Iatrogenic Distal Coronary Artery Perforation by Liquid Embolization Agent—A Case Report

Percutaneous coronary intervention (PCI) is one of the most commonly performed cardiovascular interventions to treat significant coronary artery stenosis. Although a safe procedure, it carries the risk of complications like coronary artery perforation (CAP), bleeding, stroke, and acute kidney injury rarely resulting in death. The incidence of CAP is 0.84% of all PCI procedures and the incidence is increasing as cardiologists are accepting more and more challenging cases. CAP is caused by a guidewire (GW) or a vessel tear from balloon angioplasty, stenting, or rotational atherectomy. Though the majority of CAPs do not result in cardiac tamponade, some do lead to tamponade and death. The majority of distal wire perforations respond to prolonged balloon inflation, coils, glue, or fat embolization. Herein, we report a case of distal CAP in a 63-year-old woman occurring following left circumflex artery PCI caused by the exiting of coronary GW. The CAP was successfully sealed by the liquid embolization technique using ONYX. First described in 1990, Onyx is an elastic polymer composed of ethylene vinyl alcohol copolymer dissolved in dimethyl sulfoxide and mixed with micronized tantalum powder (Onyx). The Onyx is predominantly used by interventional radiologists while performing neurovascular and peripheral vascular interventions. There were only a few case reports of plugging of CAPs using Onyx. Our case highlights the safety and feasibility of closing distal CAPs using Onyx.

Microstructure, material characteristics and mechanical properties of CoMoNiTa3 medium-entropy alloys through the vacuum hot pressing process

This work fabricated CoMoNiTa3 medium-entropy alloys using the vacuum hot pressing process of powder metallurgy technology. Micron-grade cobalt (6.3 μm), molybdenum (13.2 μm), nickel (2.4 μm) and tantalum powders (25.0 μm) were combined using ball milling. The experiments utilised various hot pressing temperatures (1000, 1050, 1100, and 1150 °C) and hot pressing pressures (20, 35, and 50 MPa) to identify the optimal parameters for CoMoNiTa3 alloys, while simultaneously investigating the differences in microstructures. The experimental results reveal that the optimal hot pressing parameters of this alloy were 1100 °C at 50 MPa for 1 h. The sintering density was enhanced to 9.65 ± 0.01 g cm−3, while the hardness, transverse rupture strength, and flexural modulus reached 85.5 ± 0.1 HRA, 1370.3 ± 90.1 MPa and 168.6 ± 12.7 GPa, respectively. Moreover, the electrical conductivity was 6.53 ± 0.13 × 104 S cm−1. Furthermore, the electron probe microanalyser, electron backscatter diffraction, and transmission electron microscopy results confirmed the face-centred cubic solid solution, Ni3Ta, and μ phases of the CoMoNiTa3 structure, and no preferred grain orientation was found.

Effect of CH4 on plasma spheroidization of tantalum powder

In this work, hydrogenation-dehydrogenation tantalum powder was spheroidized by plasma spheroidization to prepare high purity spherical tantalum powder suitable for use in additive manufacturing. The effects of methane (CH4) in sheath gas on morphology, property and chemical composition of spheroidized tantalum powder were investigated. The spheroidized tantalum powder showed increased spheroidization ratios up to 99.9% by comparison to that of raw powder. Compared to spheroidized tantalum powder obtained in argon (Ar) or Ar + hydrogen atmosphere, a significant reduction in oxygen content from 600 ppm to less than 200 ppm was observed with the addition of CH4. Excessive CH4 addition of 1.5 L/min also caused a sharp increase in carbon content from 250 ppm to 3300 ppm. These findings indicate that the addition of CH4 in spheroidization is an effective way to reduce oxygen content of tantalum powder and expected to be applied to the spheroidization of other powders.

Damage characterisation of tantalum ion source electrodes and reconditioning by wire- and powder-based laser metal deposition

The internal ion source of the Advanced Molecular Image Technologies (AMIT) superconducting cyclotron uses cathodes made of pure tantalum to generate high energy H− ion beams for the production of isotopes for positron emission tomography. During service, the cathodes are impacted by high-energy ions from the plasma. The resulting erosion creates craters that reduce the current density of the extracted beam. The cathodes eventually need to be replaced when the ion source can no longer be activated. This research explores the possibility of repairing the tantalum cathodes used in the AMIT cyclotron through laser metal deposition additive manufacturing. The damaged parts were first characterised by 3D imaging, scanning electron microscopy, and Vickers microhardness to understand the damage mechanisms occurring during service and quantify the extent of the damage. Different repair strategies were then tested employing both high-purity tantalum wire and powder feedstocks and the properties of the reconditioned electrodes were determined. The ability of laser metal deposition to restore the damaged cathodes for use in the AMIT cyclotron has been demonstrated.

Study on the influence of oxygen content evolution on the mechanical properties of tantalum powder fabricated by laser powder bed fusion

In this work, the influence of reuse times on the properties of tantalum powder and its laser powder bed fusion (LPBF) product was investigated. For this purpose, a batch of tantalum powder was reused up to 16 times, and the particle size distribution, flowability, surface topography, and other characteristics of the powder were studied after different reuse times. The mechanical properties of the finished product samples were also tested. Results from the powder reuse showed that the particle size distribution of tantalum powder changed from 30.1 μm to 33.8 μm, and the oxygen content increased from 310 ppm to 450 ppm. The density and fracture strain of tensile specimens decreased from 16.57 g/cm3 to 16.48 g/cm3 and from 37.9% to 11.6%, respectively. The ultimate tensile strength and microhardness decreased after reaching a peak, ranging from 504 MPa to 614 MPa, and 227 HV to 245 HV, respectively. In addition, it was found that the oxides were mainly tantalum pentoxide, along with monovalent and bivalent oxides. The change in tensile properties was likely related to the interstitial solution of oxygen atoms. This study provides a reference for the reusability of LPBF tantalum powder.

Features of Segregation of the Oxide Phase during Sintering of Tantalum Powders with a Large Specific Surface

Features of Segregation of the Oxide Phase during Sintering of Tantalum Powders with a Large Specific Surface

Facile synthesis of nanoscale tantalum powder by electro-deoxidation of Ta2O5

We report a facile approach for the synthesis of nanoscale tantalum powder through the electro-deoxidation of Ta2O5 cathode in molten Na3AlF6-K3AlF6-AlF3. The cathodic process begins with a solid-liquid reaction between Ta2O5 and the electrolyte, resulting in the formation of MxTaO2+xF1-x (M = Na, K) intermediates, which are then electrochemically reduced to tantalum directly. We developed a Ta2O5 cathode with a new porous structure, which contains interconnected microporous, mesoporous and macroporous structures, possessing properties such as high surface area, high pore volume ratios, and excellent accessibility to active sites. This novel cathodic pore structure material enabled the formation of uniform-sized MxTaO2+xF1-x particles with a regular cubic morphology by providing abundant nucleation sites and promoting uniform growth of intermediate. The electrochemical decomposition of these particles and the nucleation, growth mechanisms of tantalum product were also investigated. Our study demonstrates the rational design and synthesis of hierarchically porous cathode materials can facilitate the controllable synthesis of nanoscale metal powders by the FFC process, and may open up new opportunities for the development of other materials with desired morphology and particle size.

Selective Laser Melting Additive Manufactured Tantalum: Effect of Microstructure and Impurities on the Strengthening-Toughing Mechanism.

The balance between the strength and the toughness of pure tantalum (Ta) fabricated with selective laser melting (SLM) additive manufacturing is a major challenge due to the defect generation and affinity for oxygen and nitrogen. This study investigated the effects of energy density and post-vacuum annealing on the relative density and microstructure of SLMed tantalum. The influences of microstructure and impurities on strength and toughness were mainly analyzed. The results indicated that the toughness of SLMed tantalum significantly increased due to a reduction in pore defects and oxygen-nitrogen impurities, with energy density decreasing from 342 J/mm3 to 190 J/mm3. The oxygen impurities mainly stemmed from the gas inclusions of tantalum powders, while nitrogen impurities were mainly from the chemical reaction between the molten liquid tantalum and nitrogen in the atmosphere. The proportion of <110> texture decreased after vacuum-annealing at 1200 °C, while that of the <100> texture increased. Concurrently, the density of dislocations and small-angle grain boundaries significantly decreased while the resistance of the deformation dislocation slip was significantly reduced, enhancing the fractured elongation up to 28% at the expense of 14% tensile strength.

ПОЛУЧЕНИЕ ПОРОШКОВ КАРБИДОВ ТАНТАЛА И НИОБИЯ С ИСПОЛЬЗОВАНИЕМ АЦЕТОНА В КАЧЕСТВЕ ИСТОЧНИКА УГЛЕРОДА

The process of obtaining powders of tantalum and niobium carbides using metal powders of these metals as precursors, and vapors of acetone as a source of carbon has been studied. In the temperature range of 700–850 °C, using magnesium as in situ metal deoxidizers, TaC, Ta2C, and NbC carbide powders were obtained. The specific surface area of the powders is at the level of 8-26 m2/g. The powders are characterized by a mesoporous structure. The average size of crystallites is 10–16 nm.

РАЗРАБОТКИ ИНСТИТУТА ХИМИИ И ТЕХНОЛОГИИ РЕДКИХ ЭЛЕМЕНТОВ И МИНЕРАЛЬНОГО СЫРЬЯ В ОБЛАСТИ ТЕХНОЛОГИИ ТАНТАЛОВЫХ КОНДЕНСАТОРНЫХ ПОРОШКОВ С УДЕЛЬНЫМ ЗАРЯДОМ ОТ 3 000 ДО 120 000 мкКл/Г

The results of research in the field of obtaining tantalum capacitor powders in ICT KSC RAS are presented. The basic technological schemes and original solutions of individual operations included in them for obtaining agglomerated electron-beam (EB) powders with a specific charge 3 000–6 500 C/g, sodium-thermal powders with a specific charge 8 000–70 000 C/g, and magnesium-thermal tantalum powders (specific charge 80 000–120 000 C/g) are considered.

Use of Ethylene Vinyl Copolymer for Embolization Outside the Central Nervous System: A Case Review.

Onyx (ethylene vinyl copolymer; Medtronic, Minneapolis, MN) is a nonadhesive, nonabsorbable, permanent liquid embolic agent. It is Food and Drug Administration (FDA) approved for preoperative embolization of brain arteriovenous malformations (AVMs). Onyx is composed of an ethylene vinyl alcohol (EVOH) copolymer, dimethyl sulfoxide (DMSO), and micronized tantalum powder. Each substance plays a vital part in the overall effectiveness and delivery at embolization. EVOH is the embolic component and DMSO facilitates delivery through the catheter by acting as a solvent. Micronized tantalum powder allows radiographic visualization. Onyx is available in two concentrations: Onyx 18 (6% EVOH) and Onyx 34 (8% EVOH). Onyx 18 has lower viscosity which allows for greater downstream flow from the delivery microcatheter.

Effects of reduction temperature and diluent content on the properties of high-purity tantalum powder prepared using the Hunter process

The Hunter process is predominantly used to manufacture high-purity Ta powder. Among the various physical properties of the Ta powder, its impurity content is particularly crucial. In this study, the process temperature at which a liquid pool of raw material and diluent can be formed and the corresponding amount of diluent were analyzed by performing thermodynamic simulations using FactSage and HSC Chemistry software. Based on the results of the thermodynamic simulations, Ta powder was prepared at process temperatures of 700–800 °C and a specific amount of NaCl at each temperature. Thereafter, the prepared Ta powder was recovered and a post-treatment process was performed to ensure purity. The characteristics of the recovered Ta powder were evaluated according to each process condition by oxygen/nitrogen/hydrogen analysis, scanning electron microscopy/energy-dispersive X-ray spectroscopy, glow discharge-mass spectrometry, and X-ray diffractometry. The synthesized Ta powders were confirmed to exhibit purities >99.95% and oxygen, nitrogen, and hydrogen concentrations of 447, 21, and 10 ppm, respectively. The characterization results indicated that the produced Ta powders were fabricated entirely in a single phase with high purity and recovery rates. Finally, process optimization was achieved for manufacturing high-purity (≥3 N5) Ta powder with controllable impurities.

Development and evaluation of polyacrylamide microspheres loaded with phloretin and tantalum for transcatheter arterial embolization.

Transcatheter arterial embolization is an effective treatment for liver cancer. However, the development of novel embolic agents remains a challenge. In this study, we evaluated polyacrylic acid microspheres loaded with phloretin and tantalum as potential embolic agents for liver cancer treatment. Microspheres were synthesised via emulsion polymerisation and characterised in terms of size, shape, and drug-loading efficiency. Nanosized tantalum powder (0 to 15%) was added to the microspheres as an X-ray blocking agent. The maximum drug-loading capacity of the microspheres was approximately 20 mg g-1. The phloretin-loaded microspheres showed a sustained drug release profile in vitro. The microspheres were also evaluated for their in vivo anticancer efficacy in a rabbit VX2 liver tumour model. In conclusion, polyacrylic acid microspheres loaded with phloretin and tantalum have great potential as novel embolic agents for transcatheter arterial embolization for liver cancer treatment.

Influence of the vacuum hot pressing process on the microstructure, mechanical properties, and material characteristics of CrCoNiTa3 alloys

This research fabricates CrCoNiTa3 alloys using the vacuum hot pressing process, where micron grade chromium (6 μm), cobalt (3 μm), nickel (3 μm) and tantalum (25 μm) powders are mixed by means of ball milling. The experiments utilize various hot pressing temperatures (1000, 1050, 1100, and 1150 °C) and hot pressing pressures (20, 35 and 50 MPa) to determine the optimal hot pressing parameters for CrCoNiTa3 alloys, while simultaneously investigating the differences in microstructures and material characteristics. The results show that the optimal hot pressing parameters of this alloy were 1100 °C at 20 MPa for 1 h. The sintering density was enhanced to 8.34 g cm−3, and the hardness and transverse rupture strength (TRS) reached 72.9 HRA and 2266.1 MPa, respectively. Meanwhile, the electrical conductivity was 1.46 × 103 S cm−1 and the polarization resistance was 1309.1 Ω cm2. Furthermore, the EBSD results confirm that the FCC solid solution and twin of the CrCoNiTa3 crystalline structure, and no preferred grain orientation was found.

Effect of oxygen content of tantalum powders on the characteristics of parts processed by laser powder bed fusion

In this study, spherical tantalum (Ta) powders, having different oxygen contents, were fabricated by a radio frequency plasma spheroidization technique. A laser powder bed fusion (LPBF) technique was then used to consolidate these powders and the effects of different LPBF processing parameters on the densification, microstructure and mechanical properties of parts were investigated. The results indicated that the oxygen content of the used Ta powder has significant influences on the densification, microstructure and the consequent mechanical properties of printed parts. The relative density of the parts printed from the powders with a low oxygen content of ∼150 ppm was insensitive to the applied laser energy density and was higher than the ones prepared from the powders with higher oxygen contents. The grain refinement was observed and the texture in the side-view of the as-built samples changed from {100}∥BD to {111}∥BD with the increase in the oxygen content of the used powders. The microhardness and ultimate tensile strength of samples increased and the ductility of parts decreased with the increase in the oxygen content of the used raw powders. The main fracture mode of the LPBF consolidated Ta samples changed from a typical ductile rupture to the combination of cleavage and ductile rupture modes with the increase of the oxygen content in the processed parts.

On the Synthesis of Tantalum-Carbide Powder by the Reaction of Tantalum with Toluene

The process of obtaining powders of tantalum carbides using a tantalum powder as a precursor and toluene vapors as a carbon source is investigated. Powders of tantalum carbides TaC and Ta2C are obtained in the temperature range of 650–850°C using magnesium as an in situ deoxidizer of tantalum. The specific surface of the powders is at a level of 8–25 m2/g. The average sizes of carbide crystallites are 7–16 nm. The powders are characterized by a mesoporous structure.

High‐temperature reactive synthesis of the Zr–Ta multiboride with a supercomposite structure

AbstractThis study reports the formation of a ceramic composite consisting only of boride phases with an artificially created hierarchical superstructure. Such a composite was formed during the reaction‐driven consolidation process using a mixture of ZrB2, tantalum, and amorphous boron powders. The homogeneity of the reaction among these powders at 1900°C allowed the forming of a highly reproducible and repetitive superstructure where Ta3B4 forms a chain‐like mesh that entraps the ZrB2, ZrB, TaB, and (Zr,Ta)B2 phases. The multiboride ceramic composite exhibited extremely high hardness: 28.6 ± 3.2 or 22.6 ± 0.6 GPa. These were estimated using 98‐ and 196‐N loads, respectively. At 2000°C, the multiboride composite showed a strength of nearly 400 MPa and fractured in an elastic manner at the loading rate of 2.5 mm/min. This level of strength is usually observed for the bulk zirconium diboride at room temperature. The main factors leading to the improvement of the mechanical properties were considered to be the formation of the (Zr,Ta)B2 solid solution as well the composite structure.

Facial Arteriovenous Malformation Embolized Using n-Butyl-2 Cyanoacrylate and Contrast Stasis Rather Than Tantalum Powder with Double Flow Arrest to Prevent Skin Discoloration: A Technical Note

Arteriovenous malformations (AVMs) are congenital errors of vascular morphogenesis that occur during development of the cardiovascular system. Multiple treatment options exist, including coil embolization, Onyx embolization, n-butyl-2 cyanoacrylate, alcohol embolization or sclerotherapy, and open surgical treatments. When the AVM involves superficial regions of the face, head, and neck, it is important to consider cosmetic side effects, such as surgical scarring and skin discoloration. A 23-year-old woman presented with a large, anterior mandibulofacial AVM first identified on computed tomography angiography and confirmed with digital subtraction angiography. The lesion was subsequently embolized using n-butyl-2 cyanoacrylate and contrast stasis for visualization during the procedure, instead of traditional tantalum powder. Flow arrest accompanied by contrast stasis allowed changes in density observed using digital subtraction software, thus avoiding the use of material that might be cosmetically disfiguring. This technique for treatment of superficial AVMs avoids the use of materials that may be seen through or discolor the skin and other soft tissue.

A comprehensive study of tantalum powder preparation for additive manufacturing

In this study, sodium reduced tantalum (Ta) powders were processed by fluidization, jet milling and plasma spheroidization respectively to improve processing performance for additive manufacturing (AM). The morphologies, flowability, chemical compositions, and microstructural evolution of as-processed Ta powders were systematically studied. The flowability of raw Ta powder can be significantly improved by both jet milling (JMed) and plasma spheroidization (PSed). The impurities contents of powders in each process did not significantly change. The homogeneous oxide film and bimodal particle size distribution of PSed powder led to a higher laser absorption and wide printing parameters range as compared to JMed powder. The as-printed Ta components exhibited a good part precision and low hardness due to low oxygen content of both JMed and PSed powders.