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광촉매 TiO<sub>2</sub>의 황산용액에서의 양극산화전압과 도핑이 광촉매 활성에 미치는 영향
이승현,오한준,지충수,Lee, Seung-Hyun,Oh, Han-Jun,Chi, Choong-Soo 한국재료학회 2012 한국재료학회지 Vol.22 No.8
To compare the photocatalytic performances of titania for purification of waste water according to applied voltages and doping, $TiO_2$ films were prepared in a 1.0 M $H_2SO_4$ solution containing $NH_4F$ at different anodic voltages. Chemical bonding states of F-N-codoped $TiO_2$ were analyzed using surface X-ray photoelectron spectroscopy (XPS). The photocatalytic activity of the co-doped $TiO_2$ films was analyzed by the degradation of aniline blue solution. Nanotubes were formed with thicknesses of 200-300 nm for the films anodized at 30 V, but porous morphology was generated with pores of 1-2 ${\mu}m$ for the $TiO_2$ anodized at 180 V. The phenomenon of spark discharge was initiated at about 98 V due to the breakdown of the oxide films in both solutions. XPS analysis revealed the spectra of F1s at 684.3 eV and N1s at 399.8 eV for the $TiO_2$ anodized in the $H_2SO_4-NH_4F$ solution at 180 V, suggesting the incorporation of F and N species during anodization. Dye removal rates for the pure $TiO_2$ anodized at 30 V and 180 V were found to be 14.0% and 38.9%, respectively, in the photocatalytic degradation test of the aniline blue solution for 200 min irradiation; the rates for the F-N-codoped $TiO_2$ anodized at 30 V and 180 V were found to be 21.2% and 65.6%, respectively. From the results of diffuse reflectance absorption spectroscopy (DRS), it was found that the absorption edge of the F-N-codoped $TiO_2$ films shifted toward the visible light region up to 412 nm, indicating that the photocatalytic activity of $TiO_2$ is improved by appropriate doping of F and N by the addition of $NH_4F$.
논문 : 에틸렌 글리콜 용액에서 물 함량에 따른 티타늄 양극산화 나노튜브의 성장거동
이병관 ( Byung Gwan Lee ),이성은 ( Seong Eun Lee ),최진욱 ( Jin Wook Choi ),정용수 ( Yong Soo Jeong ),오한준 ( Han Jun Oh ),이오연 ( Oh Yeon Lee ),지충수 ( Choong Soo Chi ) 대한금속재료학회 ( 구 대한금속학회 ) 2008 대한금속·재료학회지 Vol.46 No.11
TiO2 nanotubes fabricated in aqueous HF-based electrolytes have been generally grown only to about 500nm in length because of the strong dissolubility of HF acid. In this paper, ethylene glycol solution has been applied for increasing the length of the anodic TiO2 nanotubes, and the growth behaviors of the nanotubes according to water contents has been investigated. Anodization of Ti in ethylene glycol+1 wt% NH4F (EG solution) with water additions up to 10 wt% were carried out at the constant voltage of 20 V. The results show that a thin titanium oxide layer is formed in the initial stage and the nanotube structure grows underneath the initial layer. And the length of TiO2 nanotubes decreases with the increasing water content in the solution. It can be ascribed to the locally acidified circumstance around the barrier layer inside the nanopore due to H+ ion originated from water. The XPS for the nanotubes suggests that the spectra of Ti2p and O1s are the major chemical bonding states of the TiO2, and those for F1s, N1s and C1s come from the compound of (NH4)2TiF6.
불소전해용 양극탄소전극의 전극특성에 미치는 첨가 결합제의 영향
안홍주,오한준,지충수,김영철,고영신,Ahn, Hong Joo,Oh, Han Jun,Chi, Choong Soo,Kim, Young Cheul,Ko, Young Shin 대한화학회 2001 대한화학회지 Vol.45 No.5
결합제인 coal tar pitch와 petroleum cokes를 주원료로 결합제 함량을 변화시켜 불소 전해용 탄소 전극을 제조한 후 결합제 함량의 변화가 전극특성에 미치는 영향을 조사하였다. 탄소 전극의 특성 조사는 1mM의 $[Fe$(CN)_6$]^{3-}$/$[Fe$(CN)_6$]^{4-}$가 첨가된 0.5M $K_2SO_4$용액에서의 cyclic voltammogram 거동, 기계적 강도, 그리고 $KF{\cdot}2HF$ 용액에서의 전기화학적 거동을 통하여 평가되었으며 이 결과 40 wt%의 결합제가 첨가된 경우 제일 양호한 전기특성을 나타내었다. 이러한 양호한 전극특성은 탄소전극 표면에 생성된 기공이 적절하게 분포하여 실질적으로 전극의 비표면적을 향상시켰기 때문이다. The carbon electrodes for fluorine electrolysis were prepared from petroleum cokes containing coal tar pitch as binder and the effects of binder contents on electrode properties were investigated. The evaluations were performed by cyclic voltammogram in the 0.5 M $K_2SO_4$ solution with 1 mM $[Fe$(CN)_6$]^{3-}$/$[Fe$(CN)_6$]^{4-}$redox couple, mechanical strength, and electrochemical behaviour in molten $KF{\cdot}2HF$ electrolyte. It was revealed that the carbon anode formed with 40wt% of coal tar pitch as binder has a better electrode properties compared to those of the other carbon anode, which led to the increase in the effective internal surface area due to proper size and distribution of pores on carbon anode.
오한준,장경욱,지충수,Oh, Han Jun,Jang, Kyung Wook,Chi, Choong Soo 대한화학회 1999 대한화학회지 Vol.43 No.1
황산용액에서 제조된 Al양극 산화피막 내부로 여러 주파수의 교류전압을 통하여 1 g/L $KMnO_4$ 용액내에서 Mn금속을 전착시켰다. 이때 Al 산화피막 내부로 전착되는 Mn금속의 변화와 산화피막의 특성변화를 임피던스를 통하여 조사했다. 낮은 교류전압의 주파소로 Mn전착된 피막의 임피던스 스펙트럼은 황산에서 제조된 산화피막의 임피던스 스펙트럼과 차이를 나타냈으며, 특히 등가회로에서는 Mn전착의 영향을 나타내는 파라미터인 저항과 축전용량이 추가로 첨가되었다. 또한 Mn전착은 기공성의 산화피막 내부로 진행되는 것으로 나타났다. 또한 기공성의 산화피막의 경우는 저주파를 부하하여 Mn전착시킬 경우 비전도성의 피막성장에 의해 전하이동저항이 높게 나타났다. 이러한 Al산화피막의 특성은 전도도의 구배를 나타내는 파라미터인 Young 임피던스를 통하여 관찰되었다. The Al oxide layer formed in 1M $H_2SO_4$ solution and the influence of applied frequency for electrodeposition of Mn on Al oxide layer were characterized using by impedance spectroscopy. Mn compounds were electrodeposited at the base of pores during deposition with applied low frequency voltage. For the Mn deposited oxide layer at 6OHz and 5Hz in 1 g/L $KMnO_4$ solution, in equivalent circuit for interpretation, the resistance ($R_2$) and capacitance ($C_2$) were considered to be due to deposition of Mn on base of pore. The electrochemical behavior of barrier layer and porous oxide layer on Al have been characterized by capacitance ($C_b$) and Young capacitance ($C_Y$) in equivalent circuit model.
기공성 알루미나 산화 피막을 이용한 나노 금속화합물의 제조
오한준(Han-Jun Oh),정용수(Yongsoo Jeong),지충수(Choong-Soo Chi) 한국표면공학회 2010 한국표면공학회지 Vol.43 No.5
Porous Al₂O₃ film can be utilized as template for fabrication of nano-structured materials. Porous anodic alumina layer as template was prepared by anodization of aluminum in oxalic acid, and the pore diameter and barrier-type alumina layer can be controlled for proper anodizing parameter by widening process in H₃PO₄ solution. The SiO₂ nanodot and Ni nanowire was fabricated using anodic alumina template and their characteristics were investigated using SEM and TEM with EDS. Especially the growth mechanism of SiO₂ nanodot in alumina membrane compared with thinning of the alumina barrier layer during anodization was also investigated.
오한준(Han-Jun Oh),정용수(Yongsoo Jeong),지충수(Choong-Soo Chi) 한국표면공학회 2010 한국표면공학회지 Vol.43 No.5
For an application as templates of high performance with proper pore size and shape, porous anodic alumina films were prepared by anodization in oxalic acid, and formation behaviors of anodic alumina layer as well as dissolution process in acid solution have been investigated. The surface characteristics on anodic alumina layer were shown to be dependent on the fabrication parameters for anodization. For the dissolution behaviors of anodic alumina, the thickness of the barrier-type alumina layer decreased linearly with the rate of 0.98 ㎚/min in H3PO4 solution at 30℃. The changes of the anodic alumina layers were analyzed by SEM and TEM.
池忠洙,崔秉泳 전북대학교 공업기술연구소 1983 工學硏究 Vol.13 No.-
A study has been made on the transformation behavior of austenite from various initial structure, coarse ferrite+pearlite, fine ferrite+pearlite, tempered martensite in low carbon Mn steels. In order to observe the process of austenite formation, specimens were soaked an 890℃ for 10~300 sec. Experimental results showed as follows ; 1. The rate of austenite transformation is increased in case of smaller grain size of initial structure and at higher heating temperature. Transformation from tempered martensite is faster than that from ferrite+pearlite initial structure. 2. There is incubation period prior to nucleation at the beginning of austenite transformation, ant it is shorter in case of smaller grain size and at higher heating temperature. 3. Nucleation of austenite is observed at ferrite-ferrite boundary and ferrite-pearlite interface. Nuclei of austenite form primarily at pearlite region and grow into ferrite region.
고장력 저합금 실리콘강의 열처리에 따른 마르텐사이트 조직변화와 기계적 성질에 관한 연구
김상주,이후철,지충수 대한금속재료학회(대한금속학회) 1979 대한금속·재료학회지 Vol.17 No.6
저합금 실리콘강에서 규소가 martensite강의 조직에 미치는 영향을 연구하기 위하여 prior austenite 입도를 조절하여 martensite조직을 얻고 소입 및 소려에 따라 강도, 인성 등 기계적 성질과의 관계를 주로 전자현미경을 이용하여 조사하였다. 소입한 상태의 조직은 주로 lath martensite이며 auto-tempered ε-탄화물의 석출이 있었고 300℃의 소려까지 성장이 뚜렷하였으나 400℃부근에서부터 소멸되기 시작했고 세멘타이트의 석출이 시작되었다. 강도와 인성은 packet size와 밀접한 관계가 있으며, 규소가 소려에 따른 강도의 연화현상을 억제하는 것이 분명하였다. Tempered martensite embrittlement는 400℃부근의 소려에서 발생되었고, 이러한 현상은 lath사이의 잔류 austenite가 열적 불안정으로 film형상의 세멘타이트를 석출시키므로써 inter cleavage fracture의 원인이 되는 것 같았다. In the present work, mechanical properties (strength and toughness, etc) of medium carbon silicon steel according to the prior austenite grain size and the change of structures tempered at various temperatures were studied, using primarily electron microscopy. As-quenched martensitic structure consits mainly of packets of laths, and auto-tempered precipitate (ε-carbide) could be also observed within some of laths. ε-carbide was precipitated within laths when tempered at below 300℃, while cementite begins to form first along lath boundaries tempered at 400℃ and develop in spheroidized shape at higher tempering temperature. Packet size was related to yield stress and toughness. And it was apparent for silicon to retard the softening of tempered carbon steel. Tempered martensite embrittlement occurred at around 400℃ tempering and resulted in interlath cleavage of fracture mode. Such a considerable decrease in toughness is thought to be attributed to the formation of cementite in interlath boundaries, since retained austenite in lath boundaries is thermally unstable with respect to tempering temperature.