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ZrO<sub>2</sub>-Ag의 복합화 공정에 따른 기계적 특성 및 미세조직 평가
여인철,한재길,강인철,Yeo, In-Chul,Han, Jae-Kil,Kang, In-Cheol 한국분말야금학회 2012 한국분말재료학회지 (KPMI) Vol.19 No.6
This paper introduces an effect of a preparing $ZrO_2$-Ag composite on its mechanical properties and microstructure. In present study, $ZrO_2$-Ag was prepared by reduction-deposition route and wetting dispersive milling method, respectively. Two type of Ag powders (nano Ag and micron Ag size, respectively) were dispersed into $ZrO_2$ powder during wetting dispersive milling in D.I. water. Each sample was sintered at $1450^{\circ}C$ for 2hr in atmosphere, and then several mechanical tests and analysis of microstructure were carried out by bending test, hardness, fracture toughness and fracture surface microstructure. As for microstructure, the Ag coated $ZrO_2$ showed homogeneously dispersed Ag in $ZrO_2$ in where pore defect did not appear. However, $ZrO_2$-nano Ag and $ZrO_2$-micro Ag composite appeared Ag aggregation and its pore defect, which carried out low mechanical property and wide error function value.
유성 볼밀법을 이용한 탄소 도핑 가시광 활성 TiO<sub>2</sub> 광촉매 제조 및 이의 특성 평가
여인철,강인철,Yeo, In-Chul,Kang, In-Cheol 한국분말야금학회 2010 한국분말재료학회지 (KPMI) Vol.17 No.4
A carbon doped $TiO_2$ (C-$TiO_2$) photocatalyst, which shows good photocatalytic activity to Ultraviolet irradiation and visible irradiation, was successfully prepared by co-grinding of $TiO_2$ with ethanol or Activated Carbon(C), followed by heat treatment at $200^{\circ}C$ in air for 60 min. Ethanol and C were used as a representative agent of liquid and solid for carbon doping. Their influence on improving photocatalytic ability and carbon doping degree was studied with degradation of methyl orange and XPS analysis. The product prepared by co-grinding of $TiO_2$ with Ethanol had Ti-C and C-O chemical bonds and showed higher photocatalytic activity than the product prepared by co-grinding of $TiO_2$ with C, where just C-O chemical bond existed. As a result, mechanochemical route is useful to prepare a carbon doped $TiO_2$ photocatalyst activating to visible irradiation, where the solid-liquid operation is more effective than solid-solid operation to obtain a carbon doped $TiO_2$.
가시광 활성 WO<sub>3</sub>-TiO<sub>2</sub> 복합체 광촉매의 제조 및 이의 특성 평가
여인철,강인철,Yeo, In-Chul,Kang, In-Cheol 한국분말야금학회 2013 한국분말재료학회지 (KPMI) Vol.20 No.6
The most general photocatalyst, $TiO_2$ and $WO_3$, are acknowledged to be ineffective in range of visible light. Therefore, many efforts have been directed at improving their activity such as: band-gap narrowing with non-metal element doping and making composites with high specific surface area to effectively separate electrons and holes. In this paper, the method was introduced to prepare a photo-active catalyst to visible irradiation by making a mixture with $TiO_2$ and $WO_3$. In the $TiO_2-WO_3$ composite, $WO_3$ absorbs visible light creating excited electrons and holes while some of the excited electrons move to $TiO_2$ and the holes remain in $WO_3$. This charge separation reduces electron-hole recombination resulting in an enhancement of photocatalytic activity. Added Ag plays the role of electron acceptor, retarding the recombination rate of excited electrons and holes. In making a mixture of $TiO_2-WO_3$ composite, the mixing route affects the photocatalytic activity. The planetary ball-mill method is more effective than magnetic stirring route, owing to a more effective dispersion of aggregated powders. The volume ratio of $TiO_2(4)$ and $WO_3(6)$ shows the most effective photocatalytic activity in the range of visible light in the view point of effective separation of electrons and holes.
여인철,강인철,Yeo, In-Chul,Kang, In-Cheol 한국분말야금학회 2015 한국분말재료학회지 (KPMI) Vol.22 No.1
In this study, the control of microstructure for increasing surface roughness of Al with an electro-chemical reaction and a post treatment is systematically investigated. The Al specimen is electro-chemically treated in an electrolyte. In condition of the post treatment at $100^{\circ}C$ for 10 min, a change of the surface microstructure occur at 50V (5 min), and a oxidized layer is at 400V, to which lead a decreasing surface roughness. The minimum temperature of the post treatment for a change of microstructure is $80^{\circ}C$. Moreover, in the condition of 300V (5 min), the electro-chemical reaction is followed by the post treatment at $100^{\circ}C$, the critical enduring time for the change of microstructure is 3 min. The longer post treatment time leads to the rougher surface. The treated Al specimen demonstrate better heat release ability owing to the higher surface roughness than the non-treated Al.
탄소나노튜브(CNT)의 첨가에 따른 TiO<sub>2</sub>의 광촉매 특성 변화 연구
여인철,강인철,Yeo, In-Chul,Kang, In-Cheol 한국분말야금학회 2016 한국분말재료학회지 (KPMI) Vol.23 No.6
A $TiO_2$/CNT nanohybrid photocatalyst is synthesized via sol-gel route, with titanium (IV) isopropoxide and multi-walled carbon nanotubes (MWCNTs) as the starting materials. The microstructures and phase constitution of the nanohybrid $TiO_2$/CNT (0.005wt%) samples after calcination at $450^{\circ}C$, $550^{\circ}C$ and $650^{\circ}C$ in air are compared with those of pure $TiO_2$ using field-emission scanning electron microscopy and X-ray diffraction, respectively. In addition, the photocatalytic activity of the nanohybrid is compared with that of pure $TiO_2$ with regard to the degradation of methyl orange under visible light irradiation. The $TiO_2$/CNT composite exhibits a fast grain growth and phase transformation during calcination. The nanocomposite shows enhanced photocatalytic activity under visible light irradiation in comparison to pure $TiO_2$ owing to not only better adsorption capability of CNT but also effective electron transfer between $TiO_2$ and CNTs. However, the high calcination temperature of $650^{\circ}C$, regardless of addition of CNT, causes a decrease in photocatalytic activity because of grain growth and phase transformation to rutile. These results such as fast phase transformation to rutile and effective electron transfer are related to carbon doping into $TiO_2$.
대형 LCD 판넬의 표면 검사를 위한 6 자유도 메커니즘의 구조 해석에 관한 연구
여인철,유재명 한국특허학회 2007 특허학연구 : 한국특허학회지 Vol.9 No.1
최근 소형 제품에서만 사용하던 평판 디스플레이의 사용은 대형 TV, 대형 모니터 등과 같은 대형 제품에서도 사용이 늘어나고 있다. 그러나 평판 디스플레이는 제조상의 전기적 신호의 오류나 충격 등으로 디스플레이의 표면에 불량 화소가 발생할 수 있다. 따라서 본 연구에서는 대형 LCD 판넬의 불량화소 검사를 위해 자유롭게 움직일 수 있는 기계 시스템을 제안하고, 제안된 구조를 해석하여 실제 설계에 활용할 수 있는 데이터 획득을 목표로 한다. 제안된 기계 시스템의 구조는 6자유도의 병렬 구조에 기초하며, 크기가 2000×2000[mm]의 판넬을 검사할 수 있도록 한다는 전제로 모델링 한다. 그리고 모델링된 시스템의 각 관절과 링크, 시스템 전체의 변형?강도 등을 FEM 기법을 이용하여 해석한다. 본 연구의 결과를 통해 얻어진 데이터들은 상세 설계 시 중요한 설계 변수들로 활용하여 설계의 오류를 최소화 할 것으로 기대한다. In LCD panel manufacturing process, it is necessary to inspect the panel for bad pixels with the naked eye. If the panel size is large we need auxiliary equipment to move the panel for the inspection. In this study we propose a mechanical system which is the moving a TFT-LCD freely, with parallel mechanism of 6 D.O.F.. And Stress or strain about joint and link of the system are analyzed with FEM method. From the result, we will be expected to minimize the error for design in the future.