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방전플라즈마 소결법으로 제조된 Bismuth Antimony Telluride의 소결온도에 따른 열전특성
이경석,서성호,진상현,유봉영,정영근,Lee, Kyoung-Seok,Seo, Sung-Ho,Jin, Sang-Hyun,Yoo, Bong-Young,Jeong, Young-Keun 한국재료학회 2012 한국재료학회지 Vol.22 No.6
Bismuth antimony telluride (BiSbTe) thermoelectric materials were successfully prepared by a spark plasma sintering process. Crystalline BiSbTe ingots were crushed into small pieces and then attrition milled into fine powders of about 300 nm ~ 2${\mu}m$ size under argon gas. Spark plasma sintering was applied on the BiSbTe powders at 240, 320, and $380^{\circ}C$, respectively, under a pressure of 40 MPa in vacuum. The heating rate was $50^{\circ}C$/min and the holding time at the sintering temperature was 10 min. At all sintering temperatures, high density bulk BiSbTe was successfully obtained. The XRD patterns verify that all samples were well matched with the $Bi_{0.5}Sb_{1.5}Te_{3}$. Seebeck coefficient (S), electric conductivity (${\sigma}$) and thermal conductivity (k) were evaluated in a temperature range of $25{\sim}300^{\circ}C$. The thermoelectric properties of BiSbTe were evaluated by the thermoelectric figure of merit, ZT (ZT = $S^2{\sigma}T$/k). The grain size and electric conductivity of sintered BiSbTe increased as the sintering temperature increased but the thermal conductivity was similar at all sintering temperatures. Grain growth reduced the carrier concentration, because grain growth reduced the grain boundaries, which serve as acceptors. Meanwhile, the carrier mobility was greatly increased and the electric conductivity was also improved. Consequentially, the grains grew with increasing sintering temperature and the figure of merit was improved.
폐전기차 셀분말의 열처리 조건에 따른 선택적 리튬침출 연구
정연재,손성호,박성철,김용환,유봉영,이만승,Jung, Yeon Jae,Son, Seong Ho,Park, Sung Cheol,Kim, Yong Hwan,Yoo, Bong Young,Lee, Man Seung 한국자원리싸이클링학회 2019 資源 리싸이클링 Vol.28 No.6
Recently, the use of lithium ion battery(LIB) has increased. As a result, the price of lithium and the amount spent lithium on ion battery has increased. For this reason, research on recycling lithium in waste LIBs has been conducted1). In this study, the effect of roasting for the selective lithium leaching from the spent LIBs is studied. Chemical transformation is required for selective lithium leaching in NCM LiNi<sub>x</sub>Co<sub>y</sub>Mn<sub>z</sub>O<sub>2</sub>) of the spent LIBs. The carbon in the waste EV cell powder reacts with the oxygen of the oxide at high temperature. After roasting at 550 ~ 850 ℃ in the Air/N<sub>2</sub> atmosphere, the chemical transformation is analysed by XRD. The heat treated powders are leached at a ratio of 1:10 in D.I water for ICP analysis. As a result of XRD analysis, Li<sub>2</sub>CO<sub>3</sub> peak is observed at 700 ℃. After the heat treatment at 850 ℃, a peak of Li<sub>2</sub>O was confirmed because Li<sub>2</sub>CO<sub>3</sub> is decomposed into Li<sub>2</sub>O and CO<sub>2</sub> over 723 ℃. The produced Li<sub>2</sub>O reacted with Al at high temperature to form LiAlO<sub>2</sub>, which does not leach in D.I water, leading to a decrease in lithium leaching ratio. As a result of lithium leaching in water after heat treatment, lithium leaching ratio was the highest after heat treatment at 700 ℃. After the solid-liquid separation, over 45 % of lithium leaching was confirmed by ICP analysis. After evaporation of the leached solution, peak of Li<sub>2</sub>CO<sub>3</sub> was detected by XRD.
플라즈마 전해 산화 공정을 이용한 고 실리콘 알루미늄 합금의 표면 산화막 형성
김용민 ( Yong Min Kim ),황덕영 ( Duck Young Hwang ),이철원 ( Chul Won Lee ),유봉영 ( Bong Young Yoo ),신동혁 ( Dong Hyuk Shin ) 대한금속·재료학회 2010 대한금속·재료학회지 Vol.48 No.1
This study investigated how the surface of Al-12wt.%Si alloy is modified by the plasma electrolytic oxidation process (PEO). The PEO process was performed in an electrolyte with sodium hexametaphosphate as a conducting salt. and the effect of ammonium metavanadate on variations in the morphology of electrochemically generated oxide lavers on the alloy surface was investigated. It is difficult to form a uniform passive oxide layer on Al alloys with a high Si content due to the differences in the oxidation behavior of the silicon-rich phase and the aluminum-rich phase. The oxide layer covered the entire surface of the Al-12wt%Si alloy uniformly when ammonium metavanadate was added to the electrolyte. The oxide laver was confirmed as a mixture of V203 and V2O5 by XPS analysis. In addition, the oxide layer obtained by the PEO process with ammonium metavanadate exhibited a black color. Application of this surface modification method is expected to solve the problem of the lack of uniformity in the coloring of oxide layers caused by different oxidation behaviors during: a surface treatment.
다이아몬드 와이어에 의해 절단된 다결정 실리콘 태양전지의 나노텍스쳐링 및 후속 식각 연구
김명현(Myeong-Hyun Kim),송재원(Jae-Won Song),남윤호(Yoon-Ho Nam),김동형(Dong-Hyung Kim),유시영(Si-Young Yu),문환균(Hwan-Gyun Moon),유봉영(Bong-Young Yoo),이정호(Jung-Ho Lee) 한국표면공학회 2016 한국표면공학회지 Vol.49 No.3
The effects of nanotexturing and post-etching on the reflection and quantum efficiency properties of diamond wire sawn (DWS) multicrystalline silicon (mc-Si) solar cell have been investigated. The chemical solutions, which are acidic etching solution (HF-HNO₃), metal assisted chemical etching (MAC etch) solutions (AgNO₃-HF-DI, HF-H₂O₂-DI) and post-etching solution (diluted KOH at 80℃), were used for micro- and nano-texturing at the surface of diamond wire sawn (DWS) mc-Si wafer. Experiments were performed with various post-etching time conditions in order to determine the optimized etching condition for solar cell. The reflectance of mc-Si wafer texturing with acidic etching solution showed a very high reflectance value of about 30% (w/o anti-reflection coating), which indicates the insufficient light absorption for solar cell. The formation of nano-texture on the surface of mc-Si contributed to the enhancement of light absorption. Also, post-etching time condition of 240 s was found adequate to the nano-texturing of mc-Si due to its high external quantum efficiency of about 30% at short wavelengths and high short circuit current density (Jsc) of 35.4 A/cm².