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코발트 전해채취 시 전착물 순도에 미치는 Pulse-Reverse Current의 영향
한정민 ( Jung Min Han ),이정훈 ( Jung Hoon Lee ),김용환 ( Yong Hwan Kim ),정우창 ( Uoo Chang Jung ),정원섭 ( Won Sub Chung ) 대한금속재료학회 ( 구 대한금속학회 ) 2010 대한금속·재료학회지 Vol.48 No.11
In order to improve the purity on deposit in cobalt electrowining, a fundamental study using Pulse- Reverse Current (PRC) was carried out. Based on a sulfate solution, Cu, Ni, and Fe as impurities were added during cobalt electrowinning. There were four reverse waveforms and frequency conditions from 1 Hz to 10 kHz, and the purity of each condition was compared with the Direct Current (DC) purity. From the results, it was found that the anodic potential induced by reverse current affects selective dissolution of impurities. In this work, the case of the highest reverse peak current density (Ir) with a short reverse time (tr) at 100 Hz showed a higher purity than that of the DC. This PRC condition also showed only a 4% low current efficiency comparable to the DC. We concluded that an optimized PRC for cobalt electrowinning could improve the purity with little loss of current efficiency.
불화칼륨이 첨가된 피로인산구리 도금욕에서 마그네슘합금의 전기도금
이정훈 ( Jung Hoon Lee ),김용환 ( Yong Hwan Kim ),정우창 ( Uoo Chang Jung ),정원섭 ( Won Sub Chung ) 대한금속·재료학회 2010 대한금속·재료학회지 Vol.48 No.3
Direct copper electroplating on Mg alloy AZ31B was carried out in a traditional pyrophosphate copper bath containing potassium fluoride. Electrochemical impedance spectroscopy and polarization methods were used to study the effects of added potassium fluoride on electrochemical behavior. The chemical state of magnesium alloy in the electroplating bath was analyzed by X-ray photoelectron spectroscopy. Adhesion of the copper electroplated layer was also tested. Due to the added potassium fluoride, a magnesium fluoride film was formed in the pyrophosphate copper bath. This fluoride film inhibits dissolution of Mg alloy and enables to electroplate copper directly on it. A dense copper layer was formed on the Mg alloy. Moreover, this copper layer has a good adhesion with Mg alloy substrate.
복사에너지를 이용한 TIM소재의 방열 특성 향상을 위한 연구
황명원,김도형,정우창,정원섭,Hwang, Myungwon,Kim, Dohyung,Jung, Uoo-Chang,Chung, Wonsub 한국표면공학회 2019 한국표면공학회지 Vol.52 No.2
The aim of this study is to quantitatively demonstrate the possibility of heat transfer by thermal radiation by comparing heat transfer by conventional heat transfer and radiation by radiation. 1) The heat transfer was measured by using filler of TIM material with low thermal conductivity (CuS). As a result, heat transfer was easier than ceramic with high thermal conductivity ($Al_2O_3$ and $Si_3N_4$). 2) The reason for this is thought to be that the infrared wave due to radiation of the air diaphragm has moved easily. 3) From the above results, the heat dissipation of the TIM material indicates the possibility of heat transfer by thermal radiation.
Linear Ion Source를 이용한 Anode Voltage 변화에 따른 DLC 박막특성
김왕렬(Wang Ryeol Kim),정우창(Uoo Chang Jung),조형호(Hyung Ho Jo),박민석(Min Suk Park),정원섭(Won Sub Chung) 한국표면공학회 2009 한국표면공학회지 Vol.42 No.4
Diamond-like carbon(DLC) films were deposited by linear ion source(LIS)-physical vapor deposition method changing the anode voltages from 800V to 1800V , and characteristics of the films were investigated using residual stress tester, nano-indentation, micro raman spectroscopy, scratch tester and Field Emission Scanning Electron Microscope(FE-SEM). The results showed that the residual stress and hardness increased with increasing the ion energy up to anode voltage of 1400 V. It was also found that the content of SP³ carbon increased with increasing the anode voltage SP³/SP² ratio through investigation of SP³/SP² ratio by the micro-raman analysis. From these results, it can be concluded that the physical properties of DLC films such as residual stress and hardness are increased with increasing the anode voltage. These results can be explained that 3- dimensional cross-links between carbon atoms and Dangling bond are enhanced and the internal compressive stress also increased with increasing the anode voltage. The optimal anode voltage is considered to be around 1400 V in these experimental conditions.
다이아몬드 입자에 형성된 중간층이 다이아몬드 공구 성능에 미치는 영향
손경식(Kyung-Sik Son),이정훈(Jung-Hoon Lee),최용제(Yong-Je Choi),정우창(Uoo-Chang Jung),정원섭(Won-Sub Chung) 한국표면공학회 2013 한국표면공학회지 Vol.46 No.5
In order to improve the performance of electrodeposited diamond-nickel composite, surface modification of diamond particles was carried out using powder immersion reaction assisted coating (PIRAC). Titanium and chromium were selected as coating elements, which are known as carbide former. With respect to the powder elements, various phases were formed on diamond; metallic Ti and TiC for Ti powder, Cr₃C₂ for Cr powder, and TiC and Cr₃C₂ for Ti-Cr mixed powder. Surface modified diamond particle showed higher specific surface area, especially Ti coating induced considerable increase of specific surface area. The increase of specific surface area suggests increase of surface roughness, and that was confirmed by surface observation using FE-SEM. In addition, wear properties of diamond-nickel composite including surface modified diamonds were improved, and Ti coated diamond showed the highest performance. The wear property of diamondnickel composite is dependent on adhesion strength between diamond particle and nickel layer. Therefore, surface modification of diamond particle by PIRAC increasing surface roughness is effective to improve the properties of diamond-nickel composite.
전해액 중 Sodium silicate의 농도에 따라 양극 산화된 AZ31B 마그네슘 합금 양극 피막의 특성 평가
이동길(Dong-Kil Lee),김용환(Yong-Hwan Kim),박현(Hyun Park),정우창(Uoo-Chang Jung),정원섭(Won-Sub Chung) 한국표면공학회 2009 한국표면공학회지 Vol.42 No.3
Magnesium is one of the lightest metals, and magnesium alloys have excellent physical and mechanical properties such as high stiffness/weight ratios, good castability, good vibration and shock absorption. However their poor corrosion resistance, wear resistance, hardness and so on, have limited their application. To improve these defects, many techniques are developed. Micro arc oxidation(MAO) is a one of the surface treatments under anodic oxidation in which ceramic coating is directly formed on the surface of magnesium alloy. In this study, the characteristics of anodic film were examined after coating the AZ31B magnesium alloy through the MAO process. MAO was carried out in potassium hydroxide, potassium fluoride, and various concentration of sodium silicate in electrolyte. The morphology and chemical composition of the coating layer were characterized by SEM, XRD, EPMA and EDS. The hardness of anodic films was measured by micro-vickers hardness tester. As a result, the morphology and composition of anodic film were changed by concentration of sodium silicate. Thickness and Si composition of anodic film was increased with increasing concentration of sodium silicate in electrolyte. The hardness of anodic film was highly increased when the concentration of sodium silicate was above 40 g/l in electrolyte.
DC 펄스 마그네트론 스퍼터링으로 증착된 TiO₂ 박막의 특성변화에 관한 연구
안은솔(Eunsol An),허성보(Sung-Bo Heo),김규식(Kyu-Sik Kim),정우창(Uoo Chang Jung),박용호(Yong Ho Park),박인욱(In-Wook Park) 한국표면공학회 2015 한국표면공학회지 Vol.48 No.2
This study reports a fabrication of TiO₂ on the surface of dental implants by pulsed d.c. magnetron sputtering from a Ti target. A systematic investigation on the microstructure and mechanical properties of TiO₂ films was carried out with the variation of O₂ contents and substrate temperatures. The effects of deposition parameters on the fabricated structures were investigated by X-ray diffraction (XRD) technique and field emission scanning electron microscope (FE-SEM). Hydrophilic properties were evaluated by measuring water contact angles on the film surface. With increasing O₂ contents up to 40%, surface roughness of TiO₂ film increased while relatively smooth surface was obtained with 50% O₂ contents. Surface roughness and adhesion strength both increased as substrate temperature increased up to 200°C. From these results, hydrophilic and adhesive properties of the present TiO₂ films synthesized with 40% O₂ at 200°C are regarded to be suitable for biocompatible applications.
PC 기판위에 증착된 SiO₂/GZO박막의 전자빔 조사에너지에 따른 특성 변화
허성보(Sung-bo Heo),박민재(Min-jae Park),정우창(Uoo-chang Jung),김대일(Dae-il Kim),차병철(Byung-chul Cha) 한국표면공학회 2014 한국표면공학회지 Vol.47 No.6
Ga-doped ZnO (GZO) single layer and SiO₂/GZO bi-layered films were deposited on Polycarbonate(PC) substrate by radio frequency magnetron sputtering. Influence of the structural, electrical, and optical properties of the films was considered. We have considered the influence of electron irradiation energy of 450 and 900 eV on the stuctural, electrical and optical properties of SiO₂/GZO thin films. The optical transmittance in a visible wave length region increased with the electron irradiation energy. The electrical resistivity of the films were dependent on the electron’s irradiation energy. The SiO₂/GZO films irradiated at 900 eV were showen the lowest resistivity of 7.8 × 10?3 Ωcm. The film which was irradiated by electron at 900 eV shows 84.3% optical transmittance and also shows lower than contact angle of 58o in this study.
과망간산칼륨 용액에서 화학적으로 형성된 AZ31B 마그네슘 합금의 피막 특성평가
김민정(Min Jeong Kim),김형찬(Hyoung Chan Kim),윤석영(Seog Young Yoon),정우창(Uoo Chang Jung) 한국표면공학회 2011 한국표면공학회지 Vol.44 No.2
The films formed on AZ31B magnesium alloy were prepared from alkaline solution composed of potassium permanganate and sodium hydroxide. The immersion tests were carried out at the different concentration of sodium hydroxide and pre-teatment method in 5 minute. The morphology and the phase composition of the film were characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The corrosion behavior of the film in 5.0% NaCl solution was evaluated using potentiodyanmic polarization. Open circuit potential in developing film was examined with time. The thin and transparent film was mainly composed of MgO and Mg(OH)₂. The film with the best corrosion resistance was obtained at 70oC bath temperature, 1.6 M concentration of sodium hydroxide and chemical pre-treatment.