Papers by Keyword: Tantalum

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Authors: Wei Cai, Y. Cheng, Y.F. Zheng, Hong Tao Li, Lian Cheng Zhao
Abstract: Ti-50.6 at.% Ni shape memory alloy was coated with tantalum using multi arc ion-plating technique with the aim to increase its radiopacity and biocompatibility. The surface characteristics were investigated by X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). The results of XPS survey spectra show that a thin oxide film are formed inside tantalum coating as a result of natural passivation of Ta in atmosphere. The hemocompatibility was evaluated in vitro by clotting time and platelet adhesion measurement. The results of our study showed that the clotting time of tantalum was higher than that of the TiNi alloys and no sign of accumulation and only slight pseudopodium was observed on the tantalum coatings, suggesting that the tantalum coatings can improve the biocompatibility of TiNi alloy.
Authors: Michael G. Golkovsky, Tatiana V. Zhuravina, Ivan A. Bataev, Anatoliy A. Bataev, Sergey V. Veselov, Vladimir A. Bataev, Elena A. Prikhodko
Abstract: The aim of the work was to clad Ti-Ta-Nb coating on a substrate of pure titanium. Cladding was carried out by non-vacuum electron-beam treatment. As a result a good quality coating thickness of about 2 mm was obtained. Microstructural and microhardness tests were conducted. Dendritic structure and the borders of the former grains of β-phase were revealed. At the microlevel, the coating has a martensitic structure. The average hardness of coating is about 4000 MPa.
Authors: Alexey Ruktuev, Mikhail Golkovski, Vitaly Samoylenko, Pavel Komarov, Ivan Bataev, Anatoly Bataev
Abstract: A method of surface alloying of titanium substrates with tantalum in order to obtain corrosion-resistant layers is described. An electron beam injected into the atmosphere is used as a power source. A powder layer containing a composition of alloying components and a fluxing agent was placed on the surface of a Ti plate. The plate exposed to a scanning beam was moved at a speed of 1cm/sec. The scanning range was 5cm, the scanning frequency was 50 Hz and the beam power was 33.5 kW. To enhance the degree of alloying the coating procedure was repeated up to 4 times. Alloyed layers 2-3 mm thick containing up to 40 wt % Ta were obtained. The rate of corrosion in HNO3 depends on the Ta concentration in the deposited material. It is tens and hundreds times lower than the rate of corrosion of unalloyed titanium for all coatings. Surface deposition by the proposed method can be used to protect internal surfaces of chemical reactors operating in media containing aggressive acids at increased temperatures up to the boiling temperature.
Authors: Yong Cheng
Abstract: Using high-pressure sealed microwave heating method, the WC-Co based cemented carbide samples were digested completely by nitric acid and phosphoric acid (VHNO3: VH3PO4 = 5:1). Then the digestion solution was diluted with water to a constant volume, and directly using inductively coupled plasma atomic emission spectrometry (ICP-OES) determination of the content of 0.005 to 10% Co and 0.005 ~ 1% of Fe, Nb, Ta, V, Cr, Mo and Ni. This paper examine the best digestion conditions, including reagent composition, ratio, and microwave control parameters, etc., then establish a set of microwave digestion and by complex reactions with inorganic reagents to stabilize the high tungsten matrix digestion method, in order to quickly and completely digest the tungsten-cobalt-based samples and avoid the generation of tungsten acid precipitation resulting in the loss of some of the analyte and impact of organic complex agents on the spectral determination. The results showed that: the control parameters of using 5 min to heat the sample to 130 °C and keep for 5 min, then heated to 190 °C in 5 min and keep for 15 min is better to maintain the digestion. By optimizing elemental analysis line, ICP measurement parameters and matrix matching and synchronization of background correction method, the high tungsten matrix effects and spectral interference are eliminated; ensure the detection performance of the method. Background equivalent concentration of 5μg/L (Nb) ~ 18μg/L (Fe), elements of the detection limit of 4μg/L (Nb) ~ 13μg/L (Fe), which used for the determination of impurities in the alloy or elements with the results is RSD <3%, recovery 97.0% ~ 103.5% corresponding with the national standard examination method.
Authors: J. Vacik, Uwe Köster, V. Hnatowicz, J. Cervena, G. Pasold
Abstract: Diffusion of 6Li in the refractory metals Ta and W has been studied using the nondestructive neutron depth profiling technique. The preliminary results point out the complex behavior of 6Li atoms in W and Ta. The experiment showed that the Fickian diffusion is affected by the presence of traps and radiation defects in the sample surface layer. Further experiments and computer simulations of the diffusion process are in progress.
Authors: Chao Yi Chen, Jun Qi Li, Xiong Gang Lu
Abstract: A novel process of solid-oxide-oxygen-ion conducting membrane (SOM) technique has been investigated to produce Ta metal directly from solid Ta2O5 in mixture molten of 55.5MgF2-44.5CaF2 (in wt%). The sintered porous Ta2O5 pellet was employed as the cathode while liquid copper, saturated with graphite powder and encased in a one-end-closed yttria-stabilized-zirconia (YSZ) tube, acted as the anode. An electrolysis potential higher than that in Fray–Farthing–Chen (FFC) Cambridge process could be applied to this process because YSZ membrane blocked the electrolysis of the melts and there was no need for flux to dissolve Ta2O5. The results demonstrated that the electrolytic temperature have played important roles in this electrochemical process. Furthermore, this process can be used to efficiently produce Ta metal without the expensive pre-electrolysis and generation of harmful byproducts.
Authors: Murilo de Oliveira Borges, Gustavo Aristides Santana Martinez, Márcia Regina Baldissera, Geovani Rodrigues, Rosinei Batista Ribeiro, Gilbert Silva
Abstract: Tantalum has characteristics such as excellent ductility, high corrosion resistance, high mechanical strength at high temperatures and high resistance to etching of acids and bases. Its high ductility allows the realization of large reductions without the need for intermediate heat treatment. A process for the production of tantalum wire is drawing. However, when using this process, the high ductility of the tantalum (Ta) metal causes a retention/accumulation of the Ta in the spinneret. Therefore, to be drawn is necessary that the tantalum is encapsulated in a copper tube. In this work was produced a Ta wire by means of rotary forging and drawing process. In the drawing process of the tantalum encapsulated in copper tube, was the appearance of striation on the surface of tantalum, when applied to an area reduction (AR) of approximately 22%. This fact is possibly related to the different sliding systems with consequent formation of non-hydrostatic stress fields at the interface Cu / Ta. After an area reduction (AR) of 94% the Cu was removed from the surface of the wire, through chemical etching, and this wire was drawn up to 0.43mm without retention/accumulation of the Ta in the spinneret.
Authors: Nathalie Bozzolo, S. Jacomet, M. Houillon, B. Gaudout, Roland E. Logé
Abstract: A heating stage as been developed to perform in-situ annealing in a SEM equipped with an EBSD system in order to study recrystallization mechanisms. High temperature treatments could then be performed inside the SEM, up to 1180°C and with high heating-and cooling-rates (~100°C.s-1). Samples were cooled down to room temperature to perform EBSD orientation mapping in between successive short-duration heat-treatments. Microstructure evolution snapshots obtained this way are presented in this paper to show recrystallization in Zircaloy4 and in pure tantalum.
Authors: R.R Ciechonski, Rositza Yakimova, Mikael Syväjärvi, Erik Janzén
Authors: Tian Tian Zheng, Shu Suo Li, Yan Ling Pei, Cheng Ai, Sheng Kai Gong
Abstract: Two kinds of Ni3Al-base SC superalloys, including IC31A (3wt.%Ta) and IC31B (6wt.%Ta) were investigated in the present study by using the differential scanning calorimetry (DSC) and isothermal quenching technology. The results showed that the larger amount of blocky γ′ phases existed in IC31B than that in IC31A. In the solidification process, the primary phase in IC31B was γ′ phases while in alloy IC31A the primary phase was γ phases. Besides, the solidification rate of IC31B in the early stage was lower than that in IC31A.
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