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Production of High-Purity Tantalum Metal Powder for Capacitors Using Self-Propagating High-Temperature Synthesis

Lee Yong-Kwan, Sim Jae-Jin, Byeon Jong-Soo, Lee Yong-Tak, Cho Yeong-Woo, Kim Hyun-Chul, Heo Sung-Gue, Lee Kee-Ahn, Seo Seok-Jun, Park Kyoung-Tae

Archives of Metallurgy and Materials

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2021

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Vol. 66, iss. 4

935--939

EN

In this study, high-purity tantalum metal powder was manufactured via self-propagating high-temperature synthesis. During the process, Ta2O5 and Mg were used as the raw material powder and the reducing agent, respectively, and given that combustion rate and reaction temperature are important factors that influence the success of this process, these factors were controlled by adding an excessive mass of the reducing agent (Mg) i.e., above the chemical equivalent, rather than by using a separate diluent. It was confirmed that Ta metal powder manufactured after the process was ultimately manufactured 99.98% high purity Ta metal powder with 0.5 μm particle size. Thus, it was observed that adding the reducing reagent in excess favored the manufacture of high-purity Ta powder that can be applied in capacitors.

2

Effects of ZrO2 and Al2O3 Addition on the Physical Properties of Cu-Mo-Cr Alloy by Liquid Phase Sintering

Cho Yeong-Woo, Sim Jae-Jin, Heo Sung-Gue, Kim Hyun-Chul, Lee Yong-Kwan, Byeon Jong-Soo, Lee Yong-Tak, Lee Kee-Ahn, Seo Seok-Jun, Park Kyoung-Tae

Archives of Metallurgy and Materials

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2021

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Vol. 66, iss. 3

683--687

EN

In this study, the effect of the addition of ZrO2 and Al2O3 ceramic powders to Cu-Mo-Cr alloy was studied by examining the physical properties of the composite material. The ceramic additives were selected based on the thermodynamic stability calculation of the Cu-Mo-Cr alloys. Elemental powders, in the ratio Cu:Mo:Cr = 60:30:10 (wt.%), and approximately 0-1.2 wt.% of ZrO2 and Al2O3 were mixed, and a green compact was formed by pressing the mixture under 186 MPa pressure and sintering at 1250°C for 5 h. The raw powders were evenly dispersed in the mixed powder, as observed by scanning electron microscopy. After sintering, the microstructures, densities, electrical conductivities, and hardness of the composites were evaluated. We found that the addition of ZrO2 and Al2O3 increased the hardness and decreased the electrical conductivity and density of the composites.

3

Fabrication of 4N5 Grade Tantalum Wire from Tantalum Scrap by EBM and Drawing

Yu Ji-Won, Choi Sang-Hoon, Sim Jae-Jin, Lim Jae-Hong, Seo Kyoung-Deok, Hyun Soong-Keon, Kim Tae-Youb, Gu Bon-Woo, Park Kyoung-Tae

Archives of Metallurgy and Materials

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2019

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Vol. 64, iss. 3

935--941

EN

Electron beam melting(EBM) is a useful technique to obtain high-purity metal ingots. It is also used for melting refractory metals such as tantalum, which require melting techniques employing a high-energy heat source. Drawing is a method which is used to convert the ingot into a wire shape. The required thickness of the wire is achieved by drawing the ingot from a drawing die with a hole of similar size. This process is used to achieve high purity tantalum springs, which are an essential component of lithography lamp in semiconductor manufacturing process. Moreover, high-purity tantalum is used in other applications such as sputtering targets for semiconductors. Studies related to recycling of tantalum from these components have not been carried outuntil now. The recycling of tantalum is vital for environmental and economic reasons. In order to obtain high-purity tantalum ingot, in this study impurities contained in the scrap were removed by electron beam melting after pre-treatment using aqua regia. The purity of the ingot was then analyzed to be more than 4N5 (99.995%). Subsequently, drawing was performed using the rod melted by electron beam melting. Owing to continuous drawing, the diameter of the tantalum wire decreased to 0.5 mm from 9 mm. The hardness and oxygen concentration of the tantalum ingot were 149 Hv and less than 300 ppm, respectively, whereas the hardness of the tantalum wire was 232.12 Hv. In conclusion, 4N5 grade tantalum wire was successfully fabricated from tantalum scrap by EBM and drawing techniques. Furthermore, procedure to successfully recycle Tantalum from scraps was established.

4

Electrorefining of Indium Metal From Impure In-Sn Alloy in Fluoride Molten Salt

Lee Hyun-Gyu, Choi Sang-Hoon, Sim Jae-Jin, Lim Jae-Hong, Hyun Soong-Keun, Lee Jong-Hyeon, Park Kyoung-Tae

Archives of Metallurgy and Materials

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2019

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Vol. 64, iss. 3

899--905

EN

In this study, molten salt electrorefining was used to recover indium metal from In-Sn crude metal sourced from indium tin oxide (ITO) scrap. The electrolyte used was a mixture of eutectic LiF-KF salt and InF3 initiator, melted and operated at 700°C. Voltammetric analysis was performed to optimize InF3 content in the electrolyte, and cyclic voltammetry (CV) was used to de-termine the redox potentials of In metal and the electrolyte. The optimum initiator concentration was 7 wt% of InF3 , at which the diffusion coefficients were saturated. The reduction potential was controlled by applying constant current densities of 5, 10, and 15 mA/cm2 using chronopotentiometry (CP) techniques. In metal from the In-Sn crude melt was deposited on the cathode surface and was collected in an alumina crucible.