Search Results (41)

The objective of this research was to assess the tribological performance and the capacity to withstand low-temperature degradation of alumina-zirconia-tantalum (ZTA) ceramic-metal composites, modified with 0.5 vol.% graphene oxide (GO) under ball (alumina) on disk dry sliding conditions. The studied ceramic and ceramic-metal composites reinforced with 20 vol.% of tantalum particles were prepared using a colloidal mixing and sintered at a temperature of 1500 °C using a spark plasma sintering technique. In contrast to ZTA ceramic, the wear performance of composites with metal particles and graphene oxide was significantly improved, regardless of the chosen load (10 N and 40 N). The results showed an improvement in the friction coefficient of about 20% and 15% at low and high load, respectively. The wear rate was reduced by 2 and 7 times at 10 N and 40 N, respectively. Raman and energy dispersive spectroscopy confirmed that ZTA-Ta-rGO composites exhibited superior wear resistance primarily because a protective tribolayer formed on their surfaces during wear. This layer effectively lubricated the surfaces, leading to a decrease in both friction and the rate of material loss. Furthermore, these composites exhibited excellent resistance to low-temperature degradation. The results obtained will serve as a starting point for future biomedical testing directions, opening up new perspectives for the use of these materials in biomedicine. Full article

High density alumina–zirconia–tantalum ceramic–metal composites with the addition of 0.5 vol.% of graphene oxide were fabricated via a wet processing technique followed by spark plasma sintering. Scanning electron microscopy confirmed the even distribution of metal particles in the composite matrix. The thermal reduction of graphene oxide after consolidation at 1500 °C was proved using Raman spectroscopy. The engineered materials exhibit a fracture resistance of 16 MPa∙m^1/2, which is 30% greater than in the reference ZTA ceramic composites fabricated using the same technology. That increase in fracture toughness could be down to a synergetic interaction mechanism; more specifically, crack trapping, renucleation and blunting, and elongated tantalum particles bridging. In addition to the above-mentioned mechanisms, tetragonal monoclinic phase transformation in zirconia is also an additional source of increased crack resistance in the developed composites. Full article

Titanium has specific uses due to its cost, which is counterbalanced by its extraordinary chemical and physical properties. Submarine hulls and nuclear power plant pipes have been made of titanium since the last century due to its high corrosion resistance, and the aircraft industry has also exploited its remarkable properties, such as lightness and high melting point. Surface modifications by plasma electrolytic oxidation (PEO) may increase its corrosion resistance, roughness and wettability. Furthermore, greater corrosion resistance is a rather attractive property in nuclear power plant pipes, although the increased roughness and wettability are disadvantageous downsides as they favor the attachment of marine organisms. Nonetheless these new features are particularly interesting for biomedical applications. In this study, PEO films were produced on commercially pure titanium substrates using different electrolytes, one of which contains zirconium dioxide and the other consisting of tantalum pentoxide, in addition to a third one composed of a combination of the former two. Scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) analyses were performed in addition to contact angle and roughness measurements, and electrochemical tests were carried out to comparatively characterize the different film compositions. The results revealed that excellent corrosion resistance was achieved by mixing oxides in the electrolyte. Full article

Tantalum is extensively used in inertial confinement fusion research for targets in radiation transport experiments, hohlraums in magnetized fusion experiments, and lining foams for hohlraums to suppress wall motions. To comprehend the physical processes associated with these applications, detailed information regarding the ionization composition and electrical conductivity of tantalum plasma across a wide range of densities and temperatures is essential. In this study, we calculate the densities of ionization species and the electrical conductivity of partially ionized, nonideal tantalum plasma based on a simplified theoretical model that accounts for high ionization states up to the atomic number of the element and the lowering of ionization energies. A comparison of the ionization compositions between tantalum and copper plasmas highlights the significant role of ionization energies in determining species populations. Additionally, the average electron–neutral momentum transfer cross-section significantly influences the electrical conductivity calculations, and calibration with experimental measurements offers a method for estimating this atomic parameter. The impact of electrical conductivity in the intermediate-density range on the laser absorption coefficient is discussed using the Drude model. Full article

This study investigates the microplasma deposition of molten tantalum (Ta) onto a rotating Grade 5 Ti Extra-Low Interstitial (ELI) alloy, producing multilayer film coatings with a porous microstructure. Optimal parameters for microplasma spraying Ta were experimentally determined to improve the surface properties of elbow joint implants. The physical and mechanical properties of the Grade 5 Ti ELI substrate and the Ta-based coating were analyzed. Moreover, mathematical modeling was utilized to determine the optimal parameters for the plasma coating process, including key factors such as spray distance, current, and rotational speed, which were systematically applied across three experimental series. A Ta coating thickness of 250 μm was achieved at 35 A current, 410 mm spray distance, and 7 rpm rotation speed under optimized deposition conditions. The results showed a microhardness increase on the Ta-coated surface, peaking above HV1000 with an average of HV742, while the Ti substrate averaged HV325. Additionally, the XRD patterns revealed the presence of metallic Ta alongside Ta oxides, such as Ta₂O and Ta₂O₅, in the Ta coatings. Full article

Tantalum diffusion layers were fabricated on 316L stainless steel substrates using the double glow plasma surface alloying technology (DGPSAT). The optimization rules of the Fe-Ta diffusion layer under varying alloying times were investigated, focusing on the effects of processing parameters on the phase structure and microstructure. The results indicate that, as the alloying time increases, the surface wrinkled structure in the Fe-Ta alloy layer gradually transforms into a nanoscale acicular α-Ta structure, improving surface roughness and water contact angle. The surface microstructure influenced by the alloying time enhanced mechanical properties significantly, increasing Vickers hardness from 152 HV_0.2 to 970 HV_0.2, improving bonding strength, and reducing the friction coefficient to 0.5. Electrochemical testing showed that the corrosion rate of the tantalum diffusion layer was significantly reduced from 1.04 × 10⁻² mm/a to 2.83 × 10⁻⁴ mm/a, demonstrating the excellent corrosion resistance. The island growth pattern during the formation of alloy layers was simulated by molecular dynamics. Replacing bulk materials with tantalum diffusion layers can economize rare metals, reduce costs, and be of great significant for the special equipment applications in harsh environments. Full article

Rare metals such as lithium and beryllium are strategic mineral resources that play a highly significant role in the national aerospace, defense, and new energy industries. The western Kunlun–Songpan–Ganzi metallogenic belt is an important rare metal metallogenic belt in China that mainly consists of granite–pegmatite-type lithium–beryllium deposits with uncommon beryllium-only deposits. In the Jiulong area on the southeastern edge of this metallogenic belt, several deposits, including the Daqianggou lithium–beryllium, Luomo beryllium, Baitai beryllium, and Shangjigong beryllium deposits, have been identified. Unlike the northern areas of Jiajika, Ke’eryin, Zawulong, and the western regions of Dahongliutan and Bailongshan, this area contains beryllium-only deposits. In this paper, we examine representative beryllium deposits in the Jiulong area, including detailed petrographic observations and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) U-Pb isotope dating of cassiterite and columbite–tantalite, to define the metallogenic age and summarize the spatiotemporal characteristics of the beryllium mineralization in this area. The research results show that the Daqianggou lithium–beryllium deposit is dominated by spodumene and beryl mineralization, while the Luomo and Baitai beryllium deposits primarily feature beryl mineralization. The dating results indicate that the U-Pb ages of the cassiterite and columbite–tantalite in the Daqianggou lithium–beryllium deposit are 157.3 ± 1.7 Ma and 164.1 ± 0.8 Ma, respectively. For the Luomo beryllium deposit, the U-Pb ages of the cassiterite and columbite–tantalite are 156.1 ± 1.5 Ma and 163.3 ± 0.8 Ma, respectively. For the Baitai beryllium deposit, the U-Pb age of the columbite–tantalite is 188.8 ± 1.1 Ma. Therefore, the Jiulong area experienced two pegmatite-type rare metal metallogenic events: a beryllium–niobium–tantalum–molybdenum event at 197~189 Ma and a lithium–beryllium–niobium–tantalum–rubidium event at 164~156 Ma. Based on the reported metallogenic ages, we suggest that the western Kunlun–Songpan–Ganzi rare metal metallogenic belt experienced three rare metal metallogenic events at 210~200 Ma, 200~180 Ma, and 170~150 Ma. Regarding exploration directions, early Yanshanian beryllium mineralization predominates in the Jiulong area along the southeastern edge of the belt, and deep exploration of the early Yanshanian rare metal mineralization within this belt should be strengthened to facilitate new breakthroughs. Full article

In order to enhance the corrosion resistance of tantalum, the double-glow plasma (DGP) metallurgy technique was used to prepare TaC coatings on the tantalum. The morphology, microstructure, and phase constituents of TaC were examined by scanning electron microscopy (SEM) and X-ray diffraction (XRD). Nano-indentation tests were used to evaluate the mechanical properties of the coatings. The specimens were immersed in NaCl-KCl molten salt at 830 °C to evaluate their corrosion resistance. The results showed that the coating prepared by the DGP technique has a thickness of approximately 5 µm, the diffusion layer has a thickness of 2.5 µm, and the nano-indentation hardness is measured to be 17.27 GPa. The high-temperature stable ceramic phase enhances the high-temperature oxidation resistance of pure tantalum (Ta), while the dense corroded surface and oxidation products improve the anti-corrosion property of TaC coatings. Full article

Titanium (Ti) is widely used in structural, maritime, aerospace, and biomedical applications because of its outstanding strength-to-weight ratio, superior corrosion resistance, and excellent biocompatibility. However, the lower surface hardness and inferior wear resistance of the Ti and Ti alloys limit their industrial applications. Coating Ti surfaces can initiate new possibilities to give unique characteristics with significant improvement in the Ti component’s functionality. The current research designed and synthesized titanium nitride (TiN), titanium carbide (TiC), titanium carbonitride (TiCN), tantalum nitride (TaN), and niobium nitride (NbN) ceramic coating layers (400 µm) over a Ti substrate using a spark plasma sintering process (SPS). The coatings on the Ti substrate were compact and consolidated at an SPS temperature of 1500 °C, pressure of 50 MPa, and 5 min of holding time in a controlled argon atmosphere. Microstructure investigation revealed a defect-less coating-substrate interface formation with a transition/diffusion zone ranging from 10 µm to 20 µm. Among all of the ceramic coatings, titanium carbide showed the highest improvement in surface hardness, equal to 1817 ± 25 HV, and the lowest coefficient of friction, equal to 0.28 for NbN. Full article

The aim of this study is to investigate the antibacterial capabilities of different coating durations of three nanoparticle (NP) coatings: molybdenum (Mo), tantalum (Ta), and zinc oxide (ZnO), and their effects on the surface characteristics of 316L stainless steel (SS). The coated substrates underwent characterization utilizing field emission scanning electron microscopy (FE-SEM), energy dispersive X-ray spectrometry (EDX), and X-ray diffractometer (XRD) techniques. The antibacterial efficacy of NPs was evaluated using the agar diffusion method. The FE-SEM and EDX images confirmed the presence of nano-sized particles of Mo, Ta, and ZnO on the surface of the substrates with perfectly symmetrical spheres and a uniform distribution of the NPs. All groups demonstrated antibacterial activity, and the ability to inhibit the growth of Streptococcus mutans and Lactobacillus acidophilus bacteria. The ZnO group had the most potent antibacterial effect, followed by the Mo group, while the Ta group had the least effect. A direct-current (DC) plasma sputtering system was used to produce nano-coatings of high purity that were homogeneous, crack-free and showed no sign of delamination. Bacterial strains exposed to Mo, Ta, and ZnO coated surfaces exhibited a significant loss of viability in a time-dependent manner. The optimum sputtering time to ensure the best antibacterial properties and preserve the resources was 1 hour (h) for Mo, 3 h for Ta and 6 h for ZnO. Full article

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. Full article

We report on the use of an atmospheric pressure, open-air plasma treatment to remove Li₂CO₃ species from the surface of garnet-type tantalum-doped lithium lanthanum zirconium oxide (Li_6.4La₃Zr_1.4Ta_0.6O₁₂, LLZTO) solid-state electrolyte pellets. The Li₂CO₃ layer, which we show forms on the surface of garnets within 3 min of exposure to ambient moisture and CO₂, increases the interface (surface) resistance of LLZTO. The plasma treatment is carried out entirely in ambient and is enabled by use of a custom-built metal shroud that is placed around the plasma nozzle to prevent moisture and CO₂ from reacting with the sample. After the plasma treatment, N₂ compressed gas is flowed through the shroud to cool the sample and prevent atmospheric species from reacting with the LLZTO. We demonstrate that this approach is effective for removing the Li₂CO₃ from the surface of LLZTO. The surface chemistry is characterized with X-ray photoelectron spectroscopy to evaluate the effect of process parameters (plasma exposure time and shroud gas chemistry) on removal of the surface species. We also show that the open-air plasma treatment can significantly reduce the interface resistance. This platform demonstrates a path towards open-air processed solid-state batteries. Full article

Due to their lower cost and good mechanical and corrosion properties, ferrous materials such as stainless steel (SS) are commonly used as bio-materials, mainly as surgical instruments and implants. Surface treatments such as plasma electrolytic oxidation (PEO) can be a valuable tool to increase corrosion resistance and enhance the bio-compatibility of metallic materials. In this scenario, the current study evaluated the effect of electrolyte composition on the surface of SS304 submitted to PEO treatment. The variation in the amount of KOH and Ta(OH)₅ promoted significant changes in the surface characteristics, forming Fe-rich oxide plates, Ta-rich agglomerate particles, and an exposed substrate. The PEO-treated substrates were depleted of some alloying elements (Cr, Ni, and Mn), which, allied to the Ta-enrichment, affected the roughness, wettability, phase stability, micro-hardness, and corrosion resistance. All the PEO treatments presented a phase composition of single γ-Fe instead of a dual α + γ phase from the untreated substrate, which was understood in terms of the Ni_eq-Cr_eq diagram. The corrosion tests indicated that the PEO treatment significantly affected the corrosion parameters, having the presence of a non-uniform oxide layer. The findings show that it is possible to control the chemical and phase composition of SS304 material employing PEO treatment. Full article

In order to enhance the bonding strength between coatings and substrates, argon glow plasma pretreatment with various times was conducted on tantalum substrates, followed by hafnium coating deposition. The coating, consisting of deposition and a diffusion layer with nanocrystalline grains of dimensions ranging from 10 to 20 nm, obtained on the substrate pretreated for 1 h, manifested the optimal structure, with a maximum thickness of approximately 14 μm and the best adhesion performance of approximately 9.5 N. The study found that the pretreatment led to grain refinement at a depth of approximately 150 nm and an increase in the crystal face spacing of substrate and high-energy defects. In addition, the crystal defects and lightly increased surface roughness enhanced the surface energy, while the Ta (200) and Ta (211) crystal faces, which had a lower combination energy and a more stable state with Hf atoms than the Ta (110) crystal face, were considerably increased on pretreated substrates with a decrease in the Ta (110) crystal face. Consequently, coating elements exhibited enhanced diffusion within the substrate, leading to the better formation of a gradient structure, which effectively improved the adhesion of coatings. Further, this study offers an efficacious approach to enhance coating adhesion and provides a deeper understanding of plasma pretreatment. Full article

The demand for orthopedic implants is increasing, driven by a rising number of young patients seeking an active lifestyle post-surgery. This has led to changes in manufacturing requirements. Joint arthroplasty operations are on the rise globally, and recovery times are being reduced by customized endoprostheses that promote better integration. Implants are primarily made from metals and ceramics such as titanium, hydroxyapatite, zirconium, and tantalum. Manufacturing processes, including additive manufacturing and thermal plasma spraying, continue to evolve. These advancements enable the production of tailored porous implants with uniform surface coatings. Coatings made of biocompatible materials are crucial to prevent degradation and enhance biocompatibility, and their composition, porosity, and roughness are actively explored through biocompatibility testing. This review article focuses on the additive manufacturing of orthopedic implants and thermal plasma spraying of biocompatible coatings, discussing their challenges and benefits based on the authors’ experience with selective laser melting and microplasma spraying of metal-ceramic coatings. Full article