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Yoon, Jae-sik,Goto, Shoji,Kim, Byung Il The Japan Institute of Metals 2010 MATERIALS TRANSACTIONS Vol.51 No.2
<P>Niobium powder was fabricated by sodiothermic reduction process using K<SUB>2</SUB>NbF<SUB>7</SUB> as the raw materials, 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 μm to 50 nm, depending on the reaction temperature. The yield of niobium powder increased from 58 to 83% with a increasing a reaction temperature. The average particle size of niobium powder is improved from 70 nm to 0.2 μm with a increasing amount of sodium excess. And the yield ratio of Nb powder was 82% in the 5% excess sodium.</P>
Evaluation of Electric Properties for Niobium Capacitors
Jung, Sung Man,Bae, In Sung,Yoon, Jae Sik,Goto, Shoji,Kim, Byung Il The Japan Institute of Metals 2007 MATERIALS TRANSACTIONS Vol.48 No.12
<P>In order to evaluate the applicability of niobium powder, which was manufactured by the external continuous supply method, as a capacitor, the present study measured capacitor performance evaluation factors such as leakage current, permittivity loss (tanδ), capacitance, impedance, equivalent series resistance, etc.Capacitance decreased significantly from 156 μF in electrolyte (wet cap) to 130 μF after carbon (C)/silver (Ag) solution coating, and around 105 μF after aging, falling within the capacity tolerance of tantalum capacitors. If capacitance was converted to CV/g, it was around 81,000 CV/g. Permittivity loss (tanδ) decreased significantly from 12.9% after C/Ag coating to 7.7% after aging, satisfying the general standard level of 10% or less. Leakage current was 2.41 μA after C/Ag coating and 2.93 μA after aging, both less than the standard level of 6.3 μA. As a whole, the niobium capacitor showed somewhat more unstable characteristics than commercial tantalum capacitors but can be considered applicable as a substitute for tantalum capacitors in the future.</P>
용융염 전해질에서 용융탄산염 연료전지 분리재의 고온 특성
박형호,이규택,후등정치 (後藤政治) ( Hyeoung Ho Park,Kyu Taek Lee,Shoji Goto ) 한국공업화학회 1995 공업화학 Vol.6 No.2
본 연구에서는 분리재로 오스테나이트계 스테인레스강 중 310S, 316강을 사용하여 전해질 분위기하에서 분리재의 내식성, 부식거동, 부식산물 형성과정 및 합금원소들의 영향 등을 SEM-EPMA와 X-RD분석을 통해 조사하였다. 내식성은 316강에 비해 310S강이 우수하였으며, 부식 진행과정은 부식산물 형성단계와 부식 억제단계 및 부식 진행단계의 3단계 과정을 경유하였다. 원소들의 거동은 부식산물 형성영역에서는 Fe가, 부식 방어영역에서는 Cr이, 그리고 Ni은 Cr고갈영역과 기지 안쪽에서 부하게 형성되었으며, Mo은 Cr과 같은 거동을 보였다. 부식산물의 형성과정은 부식초기 단계에서는 LiFe_5O_8과 LiFeO₂였으나 최종 안정 부식산물은 LiFeO₂였다. 310S, 316 among the austenitic stainless steel were used as separator material in this study. Corrosion resistance, corrosion behavior, the formation of corrosion products and the effects of alloying elements were examined by the SEM-EPMA and XRD on the separator material at the electrolyte condition. Corrosion resistance of the 310S was higher than that of the 316. Corrosion proceeded via three steps; a formation step of corrosion products, a protection step against corrosion and a advance step of corrosion. From the standpoint of the behavior of the elements in the specimen, Fe, and Cr, Ni were formed richly in the region of corrosion product, in the region of corrosion protection, and at the Cr-depleted zone respectively. Mo showed the same behavior as Cr. With respect to the formation of corrosion products, LiFe_5O_8 and LiFeO₂were the corrosion products at the corrosion initial stage, but LiFeO₂was the final corrosion product.