• Journal of Powder Materials
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• v.24 no.2
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• pp.87-95
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• 2017

Lithium silicate, a lithium-ion conducting ceramic, is coated on a layer-structured lithium nickel manganese oxide ($LiNi_{0.7}Mn_{0.3}O_2$). Residual lithium compounds ($Li_2CO_3$ and LiOH) on the surface of the cathode material and $SiO_2$ derived from tetraethylorthosilicate are used as lithium and silicon sources, respectively. Powder X-ray diffraction and scanning electron microscopy with energy-dispersive spectroscopy analyses show that lithium silicate is coated uniformly on the cathode particles. Charge and discharge tests of the samples show that the coating can enhance the rate capability and cycle life performance. The improvements are attributed to the reduced interfacial resistance originating from suppression of solid-electrolyte interface (SEI) formation and dissolution of Ni and Mn due to the coating. An X-ray photoelectron spectroscopy study of the cycled electrodes shows that nickel oxide and manganese oxide particles are formed on the surface of the electrode and that greater decomposition of the electrolyte occurs for the bare sample, which confirms the assumption that SEI formation and Ni and Mn dissolution can be reduced using the coating process.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.11a
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• pp.214-217
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• 2004

숭화법을 이용한 탄화규소(Silicon carbide) 단결정 성장시 사용되는 원료의 상(phase)이 단결정 성장에 미치는 영향을 알아보기 위해 알파형 탄화규소 분말(${\alpha}-SiC$ powder)과 베타형 탄화규소 분말(${\beta}-SiC$ powder)을 각각 사용하였다. 알파형 탄화규소 분말을 사용한 경우에 단결정(single-crystal)을 성장할 수 있었으나, 베타형 탄화규소 분말을 사용하였을 때에는 다결정(poly-crystal)이 성장되었다. 다결정 형성요인에 관한 EPMA 분석결과, 베타형 탄화규소 분말의 탄소에 대한 실리콘의 원소조성비$(N_{Si}/N_C\;=\;1.57)$가 알파형 탄화규소 분말의 경우보다$(N_{Si}/N_C\;=\;0.81)$ 높음을 확인하였다. 따라서 흑연도가니(crucible) 내부의 실리콘 원자가 알파형 탄화규소 분말을 사용하는 경우보다 높은 과포화상태가 되어 종자정 표면에 미세한 실리콘 액적(droplet)이 중착되고 이것으로부터 일정하지 않은 방향성(random orientation)을 갖는 탄화규소 다결정(다양한 방향성을 갖는 다형 포함)이 성장한 것으로 실리콘과 탄소 원소에 대한 EPMA 지도(map) 결과를 통해 확인할 수 있었다.

• Journal of Powder Materials
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• v.30 no.6
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• pp.493-501
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• 2023

This study aimed to develop a solid self-nanoemulsifying drug delivery system (solid-SNEDDS) to enhance the formulation of ketoconazole (KTZ), a BCS Class II drug with poor solubility. Ketoconazole, which is insoluble above pH 3, requires solubilization for effective delivery. This SNEDDS comprises oil, surfactant, and co-surfactant, which spontaneously emulsify in the gastrointestinal tract environment to form nanoemulsions with droplet sizes less than 100 nm. The optimal SNE-vehicle composition of oleic acid, TPGS, and PEG 400 at a 10:80:10 weight ratio was determined based on the smallest droplet size achieved. This composition was used to prepare liquid SNEDDS containing ketoconazole. The droplet size and polydispersity index (PDI) of the resulting liquid SNEDDS were analyzed. Subsequently, solid-SNEDDS was fabricated using a spray-drying method with solidifying carriers such as silicon dioxide, crospovidone, and magnesium alumetasilicate. The physicochemical properties of the solid-SNEDDS were characterized by scanning electron microscopy and powder X-ray diffraction, and its solubility, droplet size, and PDI were evaluated. In particular, the solid-SNEDDS containing ketoconazole and crospovidone in a 2:1 weight ratio exhibited significantly enhanced solubility, highlighting its potential for improved medication adherence and dissolution rates.

• Korean Journal of Materials Research
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• v.23 no.4
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• pp.246-249
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• 2013

Nano-sized ${\beta}$-SiC nanoparticles were synthesized combined with a sol-gel process and a carbothermal process. TEOS and carbon black were used as starting materials for the silicon source and carbon source, respectively. $SiO_2$ nanoparticles were synthesized using a sol-gel technique (Stober process) combined with hydrolysis and condensation. The size of the particles could be controlled by manipulating the relative rates of the hydrolysis and condensation reactions of tetraethyl orthosilicate (TEOS) within the micro-emulsion. The average particle size and morphology of synthesized silicon dioxide was about 100nm and spherical, respectively. The average particles size and morphology of the used carbon black powders was about 20nm and spherical, respectively. The molar ratio of silicon dioxide and carbon black was fixed to 1:3 in the preparation of each combination. $SiO_2$ and carbon black powders were mixed in ethanol and ball-milled for 12 h. After mixing, the slurries were dried at $80^{\circ}C$ in an oven. The dried powder mixtures were placed in alumina crucibles and synthesized in a tube furnace at $1400{\sim}1500^{\circ}C$ for 4 h with a heating rate of $10^{\circ}C$/min under flowing Ar gas (160 cc/min) and furnace cooling down to room temperature. SiC nanoparticles were characterized by XRD, TEM, and SAED. The XRD results showed that high purity beta silicon carbide with excellent crystallinity was synthesized. TEM revealed that the powders are spherical shape nanoparticles with diameters ranging from 15 to 30 nm with a narrow distribution.

• Journal of the Korean Ceramic Society
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• v.41 no.1
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• pp.62-68
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• 2004

In this study, SHS process has been employed to fabricate porous $MoSi_2$ material with electric-resistive heating capability through the control of pore size. The preform for SHS reaction was consisted of molybdenum powder with different sizes and silicon powder with different contained quantity. The size of the $MoSi_2$ particles thus formed was determined by the generated heat of combustion, not by the size of molybdenum powder. However, the pore size of $MoSi_2$ composite was proportional to the particle size of molybdenum powder. that is the coarser the molybdenum powder used, the larget the formed pore size. Based on these results, the porous $MoSi_2$ composite could be fabricated with a desired pore size. By orienting the porous molybdenum disilicide-based material in the form of pore size gradient, porous materials used for filters with improved dirt-holding capacity can be manufactured.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.32 no.5
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• pp.169-174
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• 2022

This study is to verify the feasibility of SiC single crystal growth using recycled SiC powder. The fundamental physical properties such as particle size, shape, composition and impurities of the recycled powder were analyzed, and the sublimation behavior occurring inside the reactor were predicted using the basic data. As a result of comprehensive judgment, the physical properties of the recycled powder were suitable for single crystal growth, and single crystal growth experiments were conducted using this. 100 mm 4H-SiC single crystal ingot with a height of 25 mm was grown without polytype inclusion. In the case of micro-pipe density was 0.02 ea/cm² and resistivity characteristics was 0.015~0.020 ohm·cm², commercial level quality was obtained, but additional analysis related to dislocation density and stacking faults is required for device application.

• Journal of the Korea Organic Resources Recycling Association
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• v.31 no.3
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• pp.15-25
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• 2023

In this study, silicon sludge from semiconductor dicing process is recycled to fabricate silica nanoparticles, which are applied as dispersing materials for electro-responsive (ER) smart fluid. In specific, metal impurities are removed from silicon sludge by acid washing to obtain the high-purity silicon powder. And then, silica nanoparticles are synthesized by facile hydrothermal method employing the silicon powder as reactant material. To control the size of silica nanoparticles, the reaction time of hydrothermal method is varied as 8, 15, 20, and 30 hours are applied to control the size of silica nanoparticles. Sizes of silica nanoparticles are increased proportionally to the reaction time owing to the increased numbers of hydrolysis and condensation reactions. As-synthesized silica nanoparticles are prepared as electro-responsive smart fluids by dispersing into silicon oil. Silica nanoparticles synthesized by 30 hours of hydrothermal reaction (SiO₂-H30) exhibit the highest shear stress of 21.4 Pa under an applied electric field strength of 3.0kV mm^-1. Such enhancement in ER performance of SiO₂-H30 among various silica nanoparticles are attribute to the reinforcing effect originated from the mixed particle size, which allowing the formation of rigid chain-like structures. Accordingly, this study successfully propose a recycling method of silicon sludge to synthesize silica nanoparticles and their derived ER fluids, which may suggest new possibility to ESG management emphasizing the eco-friendliness.

• Korean Journal of Materials Research
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• v.24 no.9
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• pp.502-507
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• 2014

Recently, improvement in the conversion efficiency of silicon-based solar cells has been achieved by decreasing emitter doping concentration, because the lightly doped emitter can effectively prevent the recombination of electrons and holes generated by solar light irradiation. This type of emitter is very thin due to the low doping concentration, thus conductive materials (i.e., silver) used for front electrodes can easily penetrate the emitter during a firing process because of their large diffusivity in silicon. This results in junction leakage currents which might reduce cell efficiencies. In this study, $Al_2O_3$-coated Ag powders were synthesized by an ultrasonic spray pyrolysis method and applied to the conductive materials of the front electrode to control the junction leakage current. The $Al_2O_3$ shell obstructs the Ag diffusion into the emitter during the firing process. The powder is spherical with a core-shell structure and the thickness of the $Al_2O_3$ shell is tens of nanometers. Solar cells were fabricated using pure Ag powders or the $Al_2O_3$-coated Ag powder as front electrode materials, and the conversion efficiency and junction leakage current were compared to investigate the role of the $Al_2O_3$ shell during the firing processes.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.25 no.6
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• pp.239-244
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• 2015

Lead zirconate titanate (PZT) thick films with thickness of $10{\sim}20{\mu}m$ were fabricated on silicon substrate by aerosol deposition method. As-deposited films on silicon were annealed at the temperatures of $700^{\circ}C$. The electrical properties of films deposited by PZT powders were characterized using impedance analyzer and Sawyer-Tower circuit. The PZT powder was prepared by both conventional solid reaction process and sol-gel process. The remanent polarization, coercive field, and dielectric constant of the $10{\mu}m$ thick film with solid reaction process were $20{\mu}C/cm^2$, 30 kV/cm and 1320, respectively. On the other hand, the PZT films by sol-gel process showed a poor dielectric constant of 635. The reason was probably due to the presence of pores produced from organic residue during annealing.

• 한국신재생에너지학회:학술대회논문집
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• 2011.05a
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• pp.187.2-187.2
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• 2011

태양광산업의 value chain중 up-stream쪽인 고순도 실리콘산업은 셀, 모듈, 시스템 쪽에 비하여 영업 이익률이나 부가가치 측면에서 매우 높은 성장성을 현재 보여주고 있으며 최근 원자력산업의 안전성 문제가 대두됨으로 인하여 태양광수요가 전 세계적으로 증대되는 경향을 나타내어 태양광용 실리콘의 수요가 확대됨과 아울러 spot시장에서의 가격 또한 상승하고 있다. 이런 관점에서 잉곳 및 웨이퍼 가공 중에 발생하는 고순도 실리콘 폐기물의 재활용 이 다시 주목받고 있다. 태양전지 웨이퍼(wafer)용 소재는 6N급 이상의 결정질 실리콘 잉곳(ingot)이 주를 이루며, 고효율의 셀을 제조하기 위해서 단결정 실리콘 잉곳이 많이 사용된다. 실리콘 단결정을 육성하는 방법에는 Floating zone 법, Czochralski 법, Bridgeman 법, CVD 등 매우 다양하다. 이 중 Czochralski 법은 전체 생산량의 대부분을 차지하고 있는 방법으로, 용융액에서 결정을 인상하여 ingot을 제작하는 방법이다. 그러나 대량의 전기에너지를 소비하여 제작되는 고순도의 실리콘 단결정 잉곳은 후 가공공정에서 그 절반 이상이 분말(powder) 및 슬러지(sludge)로 폐기되므로, 자원의 재활용 및 환경오염 측면에서 주요과제가 되고 있다. Czochralski 법으로 제작된 ingot의 경우 그 표면이 매끄럽지 못하여, 웨이퍼 단위의 가공 시 형태가 진원이 될 수 있도록 표면을 미리 연마(grinding)하는데, 이때에도 미세 분말이 다량 발생하게 된다. 본 연구에서는 이러한 고순도 단결정 실리콘 ingot의 연마 가공공정에서 발생한 미세 분말을 용해하여 보았다. 진공 챔버(chamber) 내부에 유도가열 코일과 냉도가니로 구성된 장비를 통해 전자기유도가열을 이용하여 실리콘 분말 폐기물을 용해하고, 그 시편을 ICP-MS 및 비저항 측정을 통해 분말 의 특성을 조사하여 재활용 가능성을 검토해 보았다.