The Experts below are selected from a list of 24 Experts worldwide ranked by ideXlab platform
Jaesik Yoon - One of the best experts on this subject based on the ideXlab platform.
-
preparation of niobium powders for solid electrolyte capacitors through Hunter Process using metallothermic reduction method
Materials Transactions, 2013Co-Authors: Jaesik Yoon, Jaeyeol Yang, Jimyon Lee, Soonjik HongAbstract:The niobium capacitor shows somewhat more unstable characteristics than the commercial tantalum capacitors, but it will be nonetheless considered as an excellent substitute of tantalum capacitors in the future. In this study, niobium powder is fabricated by metallothermic reduction Process using K2NbF7 as a raw material, KCl and KF as diluents, and Na as a reducing agent. The niobium particle size greatly decreases from 0.7 to 0.2µm as the amount of diluent increases. However, when a higher surface area of niobium powder is desired, more amounts of diluents are used in the said method. The niobium powder morphology and particle sizes are very sensitive to the amount of sodium excess, thus the particle size of niobium powder increases with increases in the amount of sodium excess. When more diluent and sodium are used, the niobium powder is contaminated further by impurities such as Fe, Cr, Ni and others. [doi:10.2320/matertrans.M2012261]
-
The Manufacturing of Niobium Powder by Hunter Process
Surface Review and Letters, 2010Co-Authors: Jaesik YoonAbstract:Niobium powder was fabricated by metallothermic reduction Process using K2NbF7 as the raw material, KCl and KF as the diluents and Na as the reducing agent. The apparatus for the experiment was designed and built specifically for the present study. Varying properties of niobium powder depending on reaction temperature and excess of reducing agent were analyzed. The niobium particle size increased significantly as the reduction temperature increased from 993 to 1093 K. The particle size was fairly uniform at a given reaction temperature, varying from 0.2 μ m to 50 nm depending on the reaction temperature. The yield of niobium powder increased from 58 to 83% with an increase in reaction temperature. The average particle size of niobium powder was improved from 70 nm to 0.2 μ m with the increase in the amount of Na excess. In addition, the yield rate of Nb powder was 82% in the 5% excess sodium.
-
the effect of reduction temperature on the characteristic variation of niobium powder during metallothermic reduction Process
Journal of Korean Powder Metallurgy Institute, 2009Co-Authors: Jaesik Yoon, Sunho Hwang, Youngmi Lee, Byungil KimAbstract:【Niobium powder was made from potassium heptafluoroniobite ( $K_2NbF_7$ ) as the raw material using sodium (Na) as a reducing agent based on the Hunter Process. The apparatus for the experiment was designed and built specifically for the present study. The niobium particle size greatly increased as the reduction temperature increased from $710^{\circ}C$ to $800^{\circ}C$ . The particle size was fairly uniform, varying from $0.09{\mu}m$ to $0.4{\mu}m$ depending on the reduction temperatures. The niobium powder morphology and particle size are very sensitive to a reaction temperature in the metallothermic reduction Process. The yield of niobium powder increased from 55% to 80% with a increasing a reaction temperature.】
-
Making of tantalum powder using the Hunter Process
Metals and Materials International, 2006Co-Authors: Sung-wook Cho, Jaesik Yoon, Gunchoo Shim, Je-shin Park, Joon-su Kim, In-sung Bae, Seong-man JeongAbstract:Tantalum powder was made from potassium heptafluorotantalate (K_2TaF_7) using sodium as a reductant based on the Hunter metallothermic reduction method. The apparatus for the experiment was designed and built specifically for the present study. The tantalum particle size greatly decreased as the reduction temperature decreased from 860 to 740°C. The particle size was fairly uniform, varying from 2–3 μm to submicron sizes depending on the reaction temperature. Holding the reactants for more than 10 minutes after the completion of a sodium feeding caused irregular particle growth, thereby affecting particle size uniformity. It was found to be possible to agglomerate the powder to tens of micrometers in size by a vacuum heat treatment at 1350°C. The formation of Ta_2C during the heat treatment shows that care must be taken to prevent contamination from the furnace environment.
-
THE MANUFACTURING OF NIOBIUM POWDER BY Hunter Process
1Co-Authors: Jaesik YoonAbstract:Niobium powder was fabricated by metallothermic reduction Process using K2NbF7 as the raw material, KCl and KF as the diluents and Na as the reducing agent. The apparatus for the experiment was designed and built specifically for the present study. Varying properties of niobium powder depending on reaction temperature and excess of reducing agent were analyzed. The niobium particle size increased significantly as the reduction temperature increased from 993 to 1093 K. The particle size was fairly uniform at a given reaction temperature, varying from 0.2 μ m to 50 nm depending on the reaction temperature. The yield of niobium powder increased from 58 to 83% with an increase in reaction temperature. The average particle size of niobium powder was improved from 70 nm to 0.2 μ m with the increase in the amount of Na excess. In addition, the yield rate of Nb powder was 82% in the 5% excess sodium.Niobium powder, metallothermic reduction, diluent, reaction temperature, reducing agent, particle size, yield
Peng Fan - One of the best experts on this subject based on the ideXlab platform.
-
a new energy efficient chemical pathway for extracting ti metal from ti minerals
Journal of the American Chemical Society, 2013Co-Authors: Zhigang Zak Fang, Scott Middlemas, Jun Guo, Peng FanAbstract:Titanium is the ninth most abundant element, fourth among common metals, in the Earth’s crust. Apart from some high-value applications in, e.g., the aerospace, biomedicine, and defense industries, the use of titanium in industrial or civilian applications has been extremely limited because of its high embodied energy and high cost. However, employing titanium would significantly reduce energy consumption of mechanical systems such as civilian transportation vehicles, which would have a profound impact on the sustainability of a global economy and the society of the future. The root cause of the high cost of titanium is its very strong affinity for oxygen. Conventional methods for Ti extraction involve several energy-intensive Processes, including upgrading ilmenite ore to Ti-slag and then to synthetic rutile, high-temperature carbo-chlorination to produce TiCl4, and batch reduction of TiCl4 using Mg or Na (Kroll or Hunter Process). This Communication describes a novel chemical pathway for extracting titan...
Soonjik Hong - One of the best experts on this subject based on the ideXlab platform.
-
preparation of niobium powders for solid electrolyte capacitors through Hunter Process using metallothermic reduction method
Materials Transactions, 2013Co-Authors: Jaesik Yoon, Jaeyeol Yang, Jimyon Lee, Soonjik HongAbstract:The niobium capacitor shows somewhat more unstable characteristics than the commercial tantalum capacitors, but it will be nonetheless considered as an excellent substitute of tantalum capacitors in the future. In this study, niobium powder is fabricated by metallothermic reduction Process using K2NbF7 as a raw material, KCl and KF as diluents, and Na as a reducing agent. The niobium particle size greatly decreases from 0.7 to 0.2µm as the amount of diluent increases. However, when a higher surface area of niobium powder is desired, more amounts of diluents are used in the said method. The niobium powder morphology and particle sizes are very sensitive to the amount of sodium excess, thus the particle size of niobium powder increases with increases in the amount of sodium excess. When more diluent and sodium are used, the niobium powder is contaminated further by impurities such as Fe, Cr, Ni and others. [doi:10.2320/matertrans.M2012261]
Byungil Kim - One of the best experts on this subject based on the ideXlab platform.
-
the effect of reduction temperature on the characteristic variation of niobium powder during metallothermic reduction Process
Journal of Korean Powder Metallurgy Institute, 2009Co-Authors: Jaesik Yoon, Sunho Hwang, Youngmi Lee, Byungil KimAbstract:【Niobium powder was made from potassium heptafluoroniobite ( $K_2NbF_7$ ) as the raw material using sodium (Na) as a reducing agent based on the Hunter Process. The apparatus for the experiment was designed and built specifically for the present study. The niobium particle size greatly increased as the reduction temperature increased from $710^{\circ}C$ to $800^{\circ}C$ . The particle size was fairly uniform, varying from $0.09{\mu}m$ to $0.4{\mu}m$ depending on the reduction temperatures. The niobium powder morphology and particle size are very sensitive to a reaction temperature in the metallothermic reduction Process. The yield of niobium powder increased from 55% to 80% with a increasing a reaction temperature.】
Zhigang Zak Fang - One of the best experts on this subject based on the ideXlab platform.
-
a new energy efficient chemical pathway for extracting ti metal from ti minerals
Journal of the American Chemical Society, 2013Co-Authors: Zhigang Zak Fang, Scott Middlemas, Jun Guo, Peng FanAbstract:Titanium is the ninth most abundant element, fourth among common metals, in the Earth’s crust. Apart from some high-value applications in, e.g., the aerospace, biomedicine, and defense industries, the use of titanium in industrial or civilian applications has been extremely limited because of its high embodied energy and high cost. However, employing titanium would significantly reduce energy consumption of mechanical systems such as civilian transportation vehicles, which would have a profound impact on the sustainability of a global economy and the society of the future. The root cause of the high cost of titanium is its very strong affinity for oxygen. Conventional methods for Ti extraction involve several energy-intensive Processes, including upgrading ilmenite ore to Ti-slag and then to synthetic rutile, high-temperature carbo-chlorination to produce TiCl4, and batch reduction of TiCl4 using Mg or Na (Kroll or Hunter Process). This Communication describes a novel chemical pathway for extracting titan...