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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.
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 $TiO_2$.
MAO(Micro-Arc Oxidation) 공정 중 인가 전압, 반응 시간, 전해액 농도에 따른 알루미늄의 표면 미세조직 평가
여인철,강인철,Yeo, In-Chul,Kang, In-Cheol 한국분말야금학회 2011 한국분말재료학회지 (KPMI) Vol.18 No.6
MAO(Micro-Arc Oxidation) method was used to make $Al_2O_3$ surface on 6063 Al specimen. This study was focused on an influence of voltage, density of electrolyte and a period of treatment on the change of surface microstructure by using SEM(Scanning Electron Microscope), EDS(Energy Dispersive X-ray Spectroscopy). The microstructure shows higher roughness and thicker oxidized layer with increase of voltage and maintaining period of treatment. The density of electrolyte affected a formation of more dense surface and increase of a oxidized layer.
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 $TiO_2$.