Papers by Keyword: Tantalum

Abstract: Tantalum-containing phosphate invert glasses were prepared using a liquid phase method under ambient conditions. In our previous study, the ion-releasing behavior (i.e. chemical durability) of phosphate glasses was controlled by the amount of intermediate oxides. In this work, Ta₂O₅ (intermediate oxide) was used to improve the chemical durability of the glasses. Ta-containing phosphate invert glasses were prepared and their structures were characterized. X-ray diffraction (XRD) patterns of the glasses exhibited broad halos, indicating an amorphous state. The amount of P₂O₅ in the glasses increased with increasing Ta₂O₅ content, while the amount of CaO decreased. The glasses prepared with a nominal P : Ta molar ratio of 2 : 1 showed a value of 1.87 : 1. Thus, almost all the Ta used in the synthesis was contained in the resulting glass. Raman spectra showed bands corresponding to short phosphate units such as ortho-and pyrophosphate, and the P-O-P peak was blue-shifted with increasing Ta₂O₅ content. The P-O-Ta bonds were formed with TaO₄ tetrahedra, as new peaks at 970 cm^-1 (P-O-Ta bonds) and 825 cm^-1 (observed in YTaO₄) were observed. The glasses containing higher amounts of Ta₂O₅ exhibited TaO₆-rich phases, as shown by the Raman band at 630 cm^-1 (Ta-O-Ta bonds) and broad XRD peaks at 2θ = 5 ~ 10°. Therefore, Ta in the phosphate invert glasses prepared by the liquid-phase method crosslinks phosphate units in the form of TaO₄ tetrahedra, and the excess Ta exists in the form of TaO₆ octahedra as a network modifier and/or Ta₂O₅-rich phase.

Abstract: The global production of niobium-microalloyed steels is now a well-established industrial practice. Initially driven by experimental insights into niobium's ability to refine steel microstructures during thermomechanical processing, this technology has become especially prevalent in low-alloy steels. An important aspect of niobium's production is its natural association with tantalum, which often leads to the co-extraction of both elements. This paper investigates the impact of tantalum traces, present as a contaminant in FeNb, on the microstructure and mechanical properties of niobium-microalloyed steels. The study reveals that tantalum's presence leads to further refinement of austenitic grains without negatively affecting the alloys' yield strength. Additionally, this tantalum contamination enhances the steel samples' toughness. By exploring these subtle effects, this study provides new insights into tantalum's influence on microalloyed steels, particularly regarding microstructural refinement and mechanical performance in two specific Nb-microalloyed steel compositions.

Abstract: Laser powder bed fusion (LBPF) is currently the most mature metal additive manufacturing (AM) technology. While it does not have the same flexibility as directed energy deposition techniques to produce compositional gradients, LPBF can still be used to generate bimetallic parts by depositing one metal on a build plate made of another. Here, we print combinations of Ti-6Al-4V with Ta and characterize defects that occur at the interface. We use thermodynamic modeling to explain the formation of keyhole porosity and solidification cracks when Ta is built on a Ti baseplate, and the lack of defects when the materials are reversed. By understanding the mechanisms that lead to defect formation, the methodology demonstrated here can be applied to other material systems to efficiently design bimetallic LPBF processes.

Abstract: The mechanical properties of anodic oxide films of Nb, Ta and Zr were studied by the nanoindentation method. Anomalously high elastic recovery after deformation was observed for oxides with thickness of 20 nm. An analogue of this behavior can be elastic membrane fixed on soft base that does not prevent the membrane from bending. Increase of the oxide thickness to 300 nm reduced the effect associated with the high elasticity of oxide and easy deformation of the soft metal substrate, and was accompanied by an increase in the plastic component of deformation, which is similar to the behavior of ceramic materials with low elastic and significant residual plastic deformation.

Abstract: Titanium (Ti) has been used in metallic implants since the 1950s due to various biocompatible and mechanical properties. However, due to its high Young’s modulus, it has been modified over the years in order to produce a better biomaterial. Tantalum (Ta) has recently emerged as a new potential biomaterial for bone and dental implants. It has been reported to have better corrosion resistance and osteo-regenerative properties as compared to Ti alloys which are most widely used in the bone-implant industry. Currently, Tantalum cannot be widely used yet due to its limited availability, high melting point, and high-cost production. This review paper discusses various manufacturing methods of Tantalum alloys, including conventional and additive manufacturing and also discusses their drawbacks and shortcomings. Recent research includes surface modification of various metals using Tantalum coatings in order to combine bulk material properties of different materials and the porous surface properties of Tantalum. Design modification also plays a crucial role in controlling bulk properties. The porous design does provide a lower density, wider surface area, and more immense specific strength. In addition to improved mechanical properties, a porous design could also escalate the material's biological and permeability properties. With current advancement in additive manufacturing technology, difficulties in processing Tantalum could be resolved. Therefore, Tantalum should be considered as a serious candidate material for future bone and dental implants.

Abstract: The 0.6 mm tantalum sheet was welded under argon atmosphere by Tungsten Inert Gas Welding (TIG) in order to obtain a welded joint with high-quality and high-reliability. Metalloscope, scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDS) were applied to analyze the joint. The results showed that the grain size of the base metal which affected by the welding heat remained the original size or enlarged slightly to 40-70 μm. What’s more, the weld zone was found to be composed of two components with different oxidation degree. And the distribution of these two components was related to the protection atmosphere of the location. The fusion line of the two tantalum sheets was clear which means high welding quality.

Abstract: KENS-II is the second generation of the spallation neutron source at KEK which was operated from December 1, 2000 to March 22, 2006 supplying neutron beam to the neutron spectrometers of material science. The present paper reviews history of the KENS-II from its design to removal together with its performance for the neutron scattering experiments.

Abstract: Ab initio calculations based on the Density Function Theory (DFT) have been performed to study the interaction between helium and helium, helium and vacancy, migration of helium, and the stability of small helium-vacancy clusters in tantalum. The following results are found: (I) The tetrahedral interstitial helium atoms have weak interactions in tantalum, suggesting that no stable covalent bond is formed between this two helium atoms; (II) The stability of small helium-vacancy clusters is investigated. The interstitial helium atom and vacancy to the clusters are found to be positive in almost all case, i.e., all interactions are attractive; (III) The activation energies for a substitutional helium atom migration by the dissociation or vacancy mechanisms are estimated under the irradiation condition.

Abstract: Microstructure and crystallographic texture play an important role in the sputtering target properties. The effect of asymmetric cross rolling (ACR) and deformation strain during ACR on texture homogeneity is not clear. Thus, high-purity tantalum (Ta) plates were ACR to 60% and 87% reduction in thickness. Texture of the rolled Ta sheets in the surface and center layer are characterized via X-ray diffraction (XRD). The XRD results indicate that ACR is effective to weaken the texture gradient existing in the as-received Ta plate. Besides, more homogeneous texture distribution along the thickness can be obtained with the increasing strain during ACR process.

Abstract: The oxidation behaviors of tantalum-tungsten alloy with 10-20% W was investigated between temperature range of 700 to 900 °C exposed in air. The kinetics of Ta-W alloy was determined by TG-DTA, the characteristics of oxides were analyzed by SEM, EDS and XRD. The oxidation tests revealed that the alloys obeyed parabolic kinetic in the initial stage, then translated in linear law. The addition of W has a good effect on the oxidation resistance of Ta-W alloys at experimental temperature. Solid solution of Ta₂O₅ form in case of oxidation product of Ta-10W, Ta-15W alloys, while the complex oxide Ta₂₂W₄O₆₇ form after Ta-20W alloy oxidized. The formation of solid solution and complex oxide impeded the volatilization. The compact oxide film protects the penetration of oxygen in the initial oxidation stage. The large compressive stresses and mismatch of the coefficient of thermal expansion between oxide scale and matrix alloys make the oxides layer be broken, which cause kinetic of oxidization obeying linear law.