• Journal of Powder Materials
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• v.25 no.5
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• pp.390-394
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• 2018

Metallic tantalum powder is manufactured by reducing tantalum oxide ($Ta_2O_5$) with magnesium gas at 1,073-1,223 K in a reactor under argon gas. The high thermodynamic stability of magnesium oxide makes the reduction reaction from tantalum oxide into tantalum powder possible. The microstructure after the reduction reaction has the form of a mixture of tantalum and magnesium oxide, and the latter could be entirely eliminated by dissolving in weak hydrochloric acid. The powder size in SEM microstructure for the tantalum powder increases after acid leaching in the range of 50-300 nm, and its internal crystallite sizes are observed to be 11.5 to 24.7 nm with increasing reduction temperatures. Moreover, the optimized reduction temperature is found to be 1,173 K as the minimum oxygen concentration is approximately 1.3 wt.%.

• Journal of Powder Materials
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• v.27 no.5
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• pp.373-380
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• 2020

The purpose of this study is to investigate the densification behavior and the corresponding microstructural evolution of tantalum and tantalum-tungsten alloy powders for explosively formed liners. The inherent inhomogeneous microstructures of tantalum manufactured by an ingot metallurgy might degrade the capability of the warhead. Therefore, to overcome such drawbacks, powder metallurgy was incorporated into the near-net shape process in this study. Spark plasma-sintered tantalum and its alloys with finer particle sizes exhibited higher densities and lower grain sizes. However, they were contaminated from the graphite mold during sintering. Higher compaction pressures in die and isostatic compaction techniques also enhanced the sinterability of the tantalum powders; however, a full densification could not be achieved. On the other hand, the powders exhibited full densification after being subjected to hot isostatic pressing over two times. Consequently, it was found that the hot isostatic-pressed tantalum might exhibit a lower grain size and a higher density as compared to those obtained in previous studies.

• Journal of Powder Materials
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• v.15 no.6
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• pp.489-495
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• 2008

Colored tantalum oxy-nitride (TaON) and tantalum nitride ($Ta_{3}N_{5}$) were synthesized by ammonolysis. Oxygen deficient tantalum oxides ($TaO_{1.7}$) were produced by a titration process, using a tantalum chloride ($TaCl_5$) precursor. The stirring speed and the amount of $NH_{4}OH$ were important factors for controling the crystallinity of tantalum oxides. The high crystallinity of tantalum oxides improved the degree of nitridation which was related to the color value. Synthesized powders were characterized by XRD, SEM, TEM and Colorimeter.

• Resources Recycling
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• v.27 no.5
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• pp.30-37
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• 2018

For recylcing of high purity tantalum (Ta) scrap, We investigated manufacture of tantalum powder using hydride-dehydride (HDH) process. Tantalum had excellent properties such as ductile, hardness and high melting point. Usually these properties made difficult to make a powder. In this study, Tantalum powder was manufactured using Tantalum hydride via hydridation. Tantalum hydride was formed at $500^{\circ}C$, 5 hr/$700^{\circ}C$, 3 hr and it is easy to make a tantalum hydride powder because hydrogen in the tantalum act as a defect dislocation and lattice expansion. The powder was pulverized to a size of less than $10{\mu}m$ under a condition of 1300 rpm, 30 min using a ring mill, and tantalum powder with less than 50 ppm hydrogen was prepared through dehydridation in an Ar and low vacuum atmosphere.

• Resources Recycling
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• v.21 no.2
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• pp.59-65
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• 2012

The refining effect of tantalum by electron beam melting(EBM) process for recycling tantalum scraps was investigated in the study. The purity of the tantalum metals refined by EBM was evaluated using glow discharge mass spectrometry (GDMS). From the result of GDMS, most impurities in the tantalum metals were removed by EBM down to a few mass ppm levels. The purity of the refined tantalum scraps was improved up to 5N (99.9991%) from 4 N (99.996%) of the initial tantalum scraps. The amount of metallic impurities in the tantalum was decreased from 30 ppm to 8 ppm. In addition, the gaseous impurities in the tantalum were decreased from 470 ppm to 50 ppm. Therefore a possibility of refining method for recycling tantalum scraps by EBM process was confirmed in this study.

• Journal of information and communication convergence engineering
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• v.8 no.4
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• pp.453-456
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• 2010

Tantalum oxide ($Ta_2O_5$) films are of considerable interest for a range of application, including optical waveguide devices, high temperature resistors, and oxygen sensors. In this paper, we establish an anode oxidation process of tantalum thin film. The voltage drop in the electrolyte is affected not in voltage change but in current change. If the voltage drop in the electrolyte is same with cathode oxidation voltage, the current changes logarithmically in proportion to the voltage drop in interface of tantalum oxide and electrolyte. As a result of the measurement on the electrical property of tantalum oxide thin film, when the thickness of the insulator film is $1500{\AA}$, the breakdown voltage is 350volts and dielectric constant is 29.

• Journal of the Korean Ceramic Society
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• v.46 no.6
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• pp.583-586
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• 2009

The Tantalum nitride has attracted wide at attention as issues related to the toxicity of Cd-related materials. But in the titration process of Ta$Cl_5$ solution with $NH_4$OH, $NH_4$Cl, as a by product, was remained in the prepared Tantalum precursor. The tantalum precursor with $NH_4$Cl was nitrided by ammonolysis. The red color tone of $Ta_3N_5$ was reduced by the residual $NH_4$Cl reduce. Therefore, amorphous Tantalum precursor was prepared by filtering process with as hydrous ethanol to remove the $NH_4$Cl. In the case of using Tantalum precursor without $NH_4$Cl, we successfully synthesized the Tantalum nitride with good red color. The value of red color tone was improved from $a^*$=36.8 to $a^*$=53.0. The synthesized powder was characterized by XRD, SEM, the Nitrogen / Oxygen Determinator, TG-DTA, and the CIE $L^*a^*b^*$ colorimeter.

• Journal of the Korean Society for Heat Treatment
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• v.15 no.1
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• pp.16-20
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• 2002

In conventional metallothermic reduction(MR) for obtaining tantalum powder in batch-type operation, it is difficult to control morphology and location of deposits because the reaction occurs by direct physical contact between reductants and feed materials. On the other hand, a electronically mediated reaction(EMR) is capable to overcome these difficulties through the reaction by electron transfer and have a merit of continuous process. In this study an MR and EMR method has been applied to the production of a tantalum powder by sodium reduction of $K_2TaF_7$. As the reduction temperature increases, the particle size and yield of tantalum powder obtained by MR and EMR method is increased.

• New & Renewable Energy
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• v.9 no.1
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• pp.51-59
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• 2013

Tantalum carbide crystallites which is to be used for $H_2$ fuel cell has been synthesized via a temperature-programmed reduction of $Ta_2O_5$ with pure $CH_4$. The resultant Ta carbide crystallites prepared using two different heating rates and space velocity exhibit the different surface areas. The $O_2$ uptake has a linear relation with surface area, corresponding to an oxygen capacity of $1.36{\times}10^{13}\;O\;cm^{-2}$. Tantalum carbide crystallites are very active for hydrogen production form ammonia decomposition reaction. Tantalum carbides are as much as two orders of magnitude more active than Pt/C catalyst (Engelhard). The highest activity has been observed at a ratio of $C_1/Ta^{{\delta}+}=0.85$, suggesting the presence of electron transfer between metals and carbon in metal carbides.

• Journal of Chest Surgery
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• v.7 no.1
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• pp.67-72
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• 1974

This is a case report of total sternal resection and successful reconstruction of the sternum applying Tantalum plate in multiple myeloma. The patient was a 57 year old male with a tumor located on the middle sternum invading the manubrium and the body of the sternum developing symptoms after a contusion of the anterior sternum. The sternum resected with left and right. from first to sixth costochondral cartilages, and then Tantalum plate was fixed to the all fragments of the ribs with wire sutures. After reconstruction of the sternum applying Tantalum plate, the patient has had good breathing movements of the chest wall and also maintenance of respiratory function was satisfactory. Histopathologically, the tumor was consisted of a tissue of plasma cells, which was identical to multiple myeloma. Postoperative chemotherapy with Endoxan for multiple myeloma was administered. No recurrent symptoms of multiple myeloma could be observed during one year follow up period.