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Insulation Coating of Fe–Si–Cr Soft Magnetic Powder by Selective Oxidation
Jae‑Young Park,Kwangsuk Park,Bosung Seo,Julien O. Fadonougbo,Tae‑Wook Na,Ki Beom Park,Hyeon‑Tae Im,Nong‑Moon Hwang,Hyung‑Ki Park 대한금속·재료학회 2022 METALS AND MATERIALS International Vol.28 No.7
This study examines the insulation coating technology of Fe–Si–Cr powder via selective oxidation annealing, which oxidizeselements selectively by controlling the oxidation potential. The study calculated the oxidation driving force of Fe, Si, andCr, and conducted a thermodynamic analysis of oxidation and reduction conditions according to temperature and oxidationpotential. Based on the results, a selective oxidation annealing was performed in an atmosphere in which Fe is reduced andonly Si and Cr are selectively oxidized. The oxidation potential was controlled through the partial pressure ratio of hydrogenand water vapor. The XPS analysis results confirmed that a Si and Cr complex oxide layer formed on the powder surfaceafter the selective oxidation annealing. Afterward, withstanding voltages were analyzed to evaluate the insulation property. Then, the withstanding voltage of the powder applying the selective oxidation annealing increased significantly comparedto that of the initial powder. Further analysis showed that the powder annealed in an air atmosphere had a significantly lowersaturation magnetic flux density than the initial powder, while the powder applying the selective oxidation annealing hadonly a slightly reduced saturation magnetic flux density.
Preparation of Nb-silicide based alloy powder by hydrogenation-dehydrogenation reaction
Park, Ki Beom,Park, Jong Min,Choi, Jaeho,Kang, Jang-Won,Lee, Sung Yong,Park, Kwangsuk,Lee, Taeg-Woo,Na, Tae-Wook,Park, Hyung-Ki Elsevier 2018 INTERNATIONAL JOURNAL OF REFRACTORY METALS AND HAR Vol.76 No.-
<P><B>Abstract</B></P> <P>Nb-16Si-25Ti-8Hf-2Cr-2Al alloy powders were prepared by a hydrogenation-dehydrogenation reaction. The Nb alloy ingot, which was prepared by vacuum arc melting, was composed of a (Nb, Ti) solid solution, (Nb, Ti, Hf)<SUB>5</SUB>Si<SUB>3</SUB>, and (Nb, Ti, Hf)<SUB>3</SUB>Si phases. For hydrogenation, the ingot was annealed in the hydrogen atmosphere and it underwent self-crushing. After hydrogenation, the hydrogen concentration increased from 0.003% to 1.30% and the (Nb, Ti) solid solution phase was completely transformed into the (Nb, Ti)H<SUB>2</SUB> hydride phase. The hydrogenated ingot could be easily pulverized by milling due to its brittle nature. For dehydrogenation, the hydrogenated powders were annealed in a vacuum atmosphere, whereby the hydrogen concentration decreased to 0.002% and the (Nb, Ti)H<SUB>2</SUB> hydride phase was transformed back to the (Nb, Ti) solid solution phase. By using this method, Nb alloy powders having sizes less than 20 μm could be easily fabricated.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Nb-silicide based alloy powders were fabricated by a hydrogenation-dehydrogenation reaction. </LI> <LI> Nb-16Si-25Ti-8Hf-2Cr-2Al alloy was composed of (Nb, Ti) solid solution, (Nb, Ti, Hf)<SUB>5</SUB>Si<SUB>3</SUB>, and (Nb, Ti, Hf)<SUB>3</SUB>Si phases. </LI> <LI> The (Nb, Ti) solid solution phase was completely transformed into the brittle (Nb, Ti)H<SUB>2</SUB> hydride phase by hydrogenation. </LI> </UL> </P>
Park, Kwangsuk,Zhang, Qifeng,Xi, Junting,Cao, Guozhong Elsevier 2015 THIN SOLID FILMS - Vol.588 No.-
<P><B>Abstract</B></P> <P>The electron diffusion in the TiO<SUB>2</SUB> aggregate network was enhanced through the addition of TiO<SUB>2</SUB> nanoparticles with preferential filling at the necks between adjacent TiO<SUB>2</SUB> aggregates, which resulted in strengthening the connections, while retaining the porous structure of the TiO<SUB>2</SUB> network. The fortified necks was found to reduce the transport resistance (R<SUB>t</SUB>) by allowing facile transfer of electrons from one aggregate to another, while the scattering effect of the TiO<SUB>2</SUB> aggregate network got weakened with adding the TiO<SUB>2</SUB> nanoparticles as a result of reduction of the light scattering centers such as the necks and gaps between the aggregates. However, due to the increase in surface area as the TiO<SUB>2</SUB> nanoparticles were added, the diminished light scattering effect of the aggregate network was compensated and even the highest performance was achieved when the 10% TiO<SUB>2</SUB> nanoparticle was added into the TiO<SUB>2</SUB> aggregate film, suggesting that widening necks between sub-micrometer sized light scatters such as an aggregate would be a good strategy in achieving further improvement of power conversion efficiency of dye sensitized solar cells through the improved charge transport property.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The added nanoparticles fill the necks preferentially. </LI> <LI> The fortified necks made electron transport in the TiO<SUB>2</SUB> network facilitated. </LI> <LI> Balancing between light scattering and dye uptake should be considered. </LI> </UL> </P>
Park, CheolSoo,Kim, KoKeun,Choi, JongMin,Park, KwangSuk IOP Pub 2007 Physiological measurement Vol.28 No.5
<P>In order to detect minute amounts of glucose in diluted urine, we applied the Raman spectroscopy method. To simulate abnormal diluted urine in a toilet bowl, we diluted normal urine ten-fold with water and added glucose up to 8 mg dl<SUP>−1</SUP>. Data were collected using a low-resolution Raman spectrometer that was preprocessed with the optimizing kernel method. We also applied the neural network algorithm to classify abnormal and normal urine samples according to their glucose concentrations. The kernel optimizing method was very effective in the classification of the tested subjects as it increased the accuracy of classification by 92%. This method suggests the possibility of caring for patients by daily monitoring their urine components in a manner non-invasive to ordinary life.</P>
박창선(Changsun Park),차용훈(Yonghoon Cha),성백섭(Backsub Sung),이석신(Seokshin Lee),배광석(Kwangsuk Bae),최귀현(Kuy syun Choi),김정주(JungjJoo Kim),김남표(Nampyo Kim),박성호(Sungho Park) 한국자동차공학회 2010 한국자동차공학회 부문종합 학술대회 Vol.2010 No.5
Die casting which is extensively known as a necessary technology for lightweight spare parts of automobiles has three central elements of casting equipment, casting technology and die and has had much attention as a technology with the highest coefficient of expansion with increased need of high-quality and high-precision. Therefore, a regulator of LPI automobile receives high internal pressure and works as a central part of the basic fuel supply system according to quality of performance. To produce high-quality casting goods, we need to identify causes of defects and theoretical analyses on physical phenomena occurring in manufacturing. As a result of comparing Types of casting design, it was found that the number of overflow affected flow, flow speed and solidification temperature.