• 산업기술연구
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• 제41권1호
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• pp.25-30
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• 2021

Hydride-dehydride process for efficient recycling of tantalum (Ta) is used for manufacturer of Ta powder. In case of metal powder, Impurities as like nitride, oxygen, hydrogen is decreased of physical properties. For manufacture of Ta powder, control of theses impurities is important. In this study, to decreased of impurities on Ta powder using HDH process optimize dehydride condition. Dehydration behavior of Ta is depended on temperature, time, and atmosphere. Phase transition of Ta hydride is analyzed by X-ray diffraction (XRD). Concentration of hydrogen is decreased with temperature increased. At high temperature, concentration of hydrogen in Ta is similar according to time increased. Size and morphology of powder is not observed after dehydride. Ta powder, which is less than 20 um, concentration of hydrogen under 800 ppm is obtain.

• 한국분말재료학회지
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• 제10권6호
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• pp.395-405
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• 2003

In the conventional metallothermic reduction (MR) process for obtaining tantalum powder in batch-type operation. it is difficult to control morphology and location of deposits. On the other hand, a electronically mediated reaction (EMR) process is capable to overcome these difficulties and has a merit of continuous process, but it has the defect that the reduction yield is poor. MR-EMR combination process is a method that is able to overcome demerits of MR and EMR process. In this study, a MR-EMR combination process has been applied to the production of tantalum powder by sodium reduction of $K_2$TaF$_{7}$. The total charge passed through external circuit and average particle size (FSSS) were increased with increasing reduction temperature. The proportion of fine particle (-325 mesh) was decreased with increasing reduction temperature. The yield was improved from 65% to 74% with increasing reduction temperature. Considering the charge, impurities, morphology, particle size and yield, an reduction temperature of 1,123 K was found to be optimum temperature for MR-EMR combination process.

• 한국재료학회지
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• 제11권12호
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• pp.1052-1056
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• 2001

Pure tantalum powder has been produced by sodium as a reluctant, $K_2TaF_7$as a feed material and KCl/KF as a diluent in an inconel stainless steel bomb by the metallothermic reduction. The influence of experimental variable, such as temperature of reduction on the yield and characteristics of the Ta powder has been studied. As the temperature of the reduction was varied from$ 800{\circ}C~980{\circ}C$, the yield of tantalum powder increased from 41% to 56%. However no appreciable improvement was observed above$920{\circ}C$. The fraction of fine Ta Powder decreased appreciably with the increase of temperature, and particle size was$2~3{\mu}m$at reduction temperature of$920{\circ}C$.Therefore a reduction temperature of$920{\circ}C$was optimally fixed for subsequent runs.

• 한국분말재료학회지
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• 제14권3호
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• pp.190-196
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• 2007

A process known as the MR and EMR combination process is able to overcome the shortcomings of the MR (metallothermic reduction) and EMR (electronically mediated reaction) process. The effects of $K_2TaF_7$ as the raw material, sodium as the reducing agent and KCl/KF as the diluent on the characteristics of tantalum powder are investigated. In this study, a MR-EMR combination process has been employed to tantalum powder on the location of reductant. The excess of reductant were varied from 25, 50 to 75 wt%. The total charge and external circuit decreases as the amount of reductant increases. The average particle size increases with increasing the amount of reductant.

• 한국분말재료학회지
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• 제11권4호
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• pp.333-340
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• 2004

In this study, tantalum powder has been producted by MR-EMR combination process. MR-EMR combination process is a method that is able to improve demerits of MR(metallothermic reduction) and EMR(electronically mediated reaction) process. This study examined the characteristics of powder with the amount of reductant excess using $K_2$TaF$_{7}$ as feed materials, Na as a reductant and KCl/KF as a diluent. In addition, this study examined acid treatment that affect the high purification of powder. The impurities contained in powder was removed in various conditions of acid treatment. The total charge passed through external circuit and average particle size(FSSS) were increased with increasing amount of sodium excess. The proportion of fine particle(-325mesh) was decreased with increasing amount of sodium excess. The yield was improved from 70％ to 76% with increasing amount of sodium excess. Considering the impurities, charge, morphology, particle size and yield, an amount of sodium excess of 10wt% were found to be optimum conditions for MR-EMR combination process.s.

• 한국분말재료학회지
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• 제10권4호
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• pp.255-261
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• 2003

Ultrafine TaC-5%Co composite powders were synthesized by spray conversion process using tantalum oxalate solution and cobalt nitrate hexahydrate(Co($(NO_3)_2$ . 6$H_2O$). The phase of Ta-Co oxide powders had amorphous structures after calcination below 50$0^{\circ}C$ and changed $Ta_2O_5$, $TaO_2$ and $CoTa_2O_6$ phase by heating above $600^{\circ}C$. The calcined Ta-Co oxide powders were spherical agglomerates consisted of ultrafine primary particles <50 nm in size. By carbothermal reaction, the TaC phase began to form from 90$0^{\circ}C$. The complete formation of TaC could be achieved at 105$0^{\circ}C$ for 6 hours. The observed size of TaC-Co composite powders by TEM was smaller than 200 nm.

• 한국재료학회지
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• 제19권7호
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• pp.386-390
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• 2009

Niobium(Nb) and Tantalum(Ta) are rarely found apart in nature and never in the free state. The element niobium amounts to 3% of the crustal abundance. On the whole, the niobium capacitor showed somewhat more unstable characteristics than the commercial tantalum capacitors, but is nonetheless considered applicable as a future substitute for tantalum capacitors. In this study, niobium powder was made from potassium heptafluoroniobite($K_2NbF_7$) by using sodium(Na) as a reductant and KCl and KF as diluents based on the hunter sodiothermic reduction method.,In order to obtain a high surface area niobium powder via the sodiothermic reduction method, a certain amount of diluent, such as alkali metal halides selected from NaCl, KCl, KF and NaF, was added in the raw materials to be reduced. However, if a higher surface area of powder is required, more diluents need to be used in the said method in order to produce niobium powder. But when more diluents are used, the niobium powder will be contaminated with more impurities and the yield will also decreased.

• 한국재료학회지
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• 제12권9호
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• pp.706-711
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• 2002

High-pure tantalum powder was fabricated through Na reduction process and has been produced by using $K_2$TaF$_{7}$, and KCI, KF for raw material and diluent, respectively. A raw material and diluent were charged at the hestalloy bomb by the weight rate of 1:2, 1:1, 1:0.5 and 1:0.25 each other, investigated properties of morphology, chemical composition and yield and particle size after reduced. Ta metal has been achieved by reduction of $K_2$$TaF_{7}$ 500g with 1% sodium in excess of stoichiometric amount in the charge at a reduction temperature of $850^{\circ}C$ for 3hours. According to amount of the diluent, a formation of the powder doesn't have an effect. The diluent prevented the temperature rising caused from the heat of reaction and it maintained the speed of reducing reaction. But in the mixture ratio of raw material and diluent in the 1 : 2 and 1 : 0.25, an oxide and partially not reacted K were detected. As the amount of diluent increased, the size of tantalum powder decreased. According as raw material and the mixture ratio of diluent change from 1:0.25 to 1:2, the size is decreased from 5$\mu\textrm{m}$ to 1$\mu\textrm{m}$, and a particle size distribution which is below 325 mesh in fined powder increases from 71% to 83%. In the case of average size of Tantalum powder which is the mixture ratio (1:0.5), we would get the Ta powder with grain size about 3$\mu\textrm{m}$, which come close to the average size (2~4$\mu\textrm{m}$) of tantalum powder which is used commonly in the present is Ta powder about 3$\mu\textrm{m}$.

• 한국분말재료학회지
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• 제22권1호
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• pp.32-38
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• 2015

The effect of heat treatment environment on the microstructure and properties of tantalum coating layer manufactured by kinetic spraying was examined. Heat treatments are conducted for one hour at $800^{\circ}C$, $900^{\circ}C$, and $1000^{\circ}C$ in two different environments of vacuum and Ar gas. Evaluation of microstructure and physical properties are conducted. High density ${\alpha}$-tantalum single phase coating layer with a porosity of 0.04% and hardness of 550 Hv can be obtained. As heat treatment temperature increases, porosity identically decreases regardless of heat treatment environment (vacuum and Ar gas). Hardness of heat treated coating layer especially in Ar gas environment deceases from 550 Hv to 490 Hv with increasing heat treatment temperature. That in vacuum environment deceases from 550 Hv to 530 Hv. The boundary between particles became vague as heat treatment temperature increases. Oxygen distribution of tantalum coating layer is minute after heat treatment in vacuum environment than Ar gas environment.

• 대한금속재료학회지
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• 제47권6호
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• pp.338-343
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• 2009

The purpose of this study is to make the tantalum powder for solid electrolyte capacitor with SHS (self-propagating high-temperature synthesis) process. Raw materials for manufacturing Ta powder were used $Ta_{2}O_{5}$, Mg and NaCl. While progressing SHS process, $Ta_{2}O_{5}$ powder was reduced by Mg powder. The combustion temperature and velocity were easily controled by the varying mole ratio of NaCl, Mg and initial reaction pressure. In the case of only using NaCl as an inorganic agent, the shape is unagglomerated and has high surface area. whereas we were given the powder which has good net structure by the addition of excessive Mg as a diluent.