환원 백색소자인 텅스텐 산화물 적극 계면의 전기화학적 특성 연구

민병철,박인철,주재백,손태원 ( Byoung Chul Min,In Cheol Park,Jeh Beck Ju,Tae Won Sohn ) 한국공업화학회 1995 공업화학 Vol.6 No.5

텅스텐을 열 산화하여 제조한 산화전극과 전자빔 진공 증착기에 의하여 ITO표면에 텅스텐 산화물을 증착시킨 박막전극의 전기화학적 발색 현상을 연구하였다. 두 종류의 전극에 대한 전기화학적 특성 및 용액내 용존 산소와 수소 이온농도의 영향을 순환 전류-전압 측정법, Tafel 분극실험 측정을 통하여 고찰하였다. 산소농도 변화에 따른 cathodic Tafel 분극 특성으로부터 산소 농도의 증가는 발색 반응의 이온교환 전류밀도를 미약하게 증가시키는 반면 Tafel 기울기는 크게 감소시킴을 알 수 있었다. 진공증착 박막 전극에서 발색 반응에 대한 α_°n을 계산하였으며 매우 느린 발색반응속도를 감안하여 완전 비가역이라 가정할 경우 반응에 소모되는 전자수는 0.62로써 박막 텅스텐 산화물의 반응성이 우수한 것을 알 수 있었다. 수소이온농도의 감소시 Tafel 기울기는 일차적으로 감소하였으나 수소이온 농도가 매우 적은 경우에는 반응기구가 다르게 변함을 알 수 있었다. 또한, 주사전자 현미경에 의하여 각 전극의 표면 상태를 조사한 결과 발색-소색의 순환 실험 후의 열 산화 후막 전극에서 심한 균열이, 또한 진공증착 박막 전극의 경우에는 균열에 의한 산화 막의 박리현상이 관찰되었다. X선 회절 분석법에 의하여 열 산화 후막 전극은 결정성을, 진공증착 박막 전극은 비정질성을 지님을 알 수 있었다. The phenomenon of the electrochromism of tungsten oxide films, which were deposited by electron-beam vacuum evaporation on indium tin oxide(ITO) glass and by thermal oxidation of tungsten bulk, was studied in H₂SO₄ solution. The electrochemical characteristics of these two kinds of electrodes were examined by cyclic voltammetry and Tafel polarization method. Considering the effect of dissolved oxygen on the Tafel polarization, the ion exchange current densities were slightly increased, while the catholic Tafel slopes were decreased with an increase of oxygen content. If the coloring process is assumed completely irreversible, the number of electrons or protons consumed in the coloring reaction would be 0.62 as a maximum value. This indicates that the evaporated film used in this study provided the good reactivities for the electrochromic reaction. The Tafel slope was linearly decreased with the decrease of hydrogen ion concentration and the reaction mechanism seems to be changed in a solution with very low hydrogen ion concentration. From the results of SEM, severe and moderate cracks were observed on the surface of thermally oxidized films and evaporated films, respectively. By the analysis of XRD, the structure of thermally oxidized film was identified as polycrystalline, whereas that of evaporated film was amorphous.

자외선에너지를 ( UV - C ) 를 이용한 유기인계 화합물의 분해

민병철,권태무,김병관,김종향 ( Byoung Chul Min,Tae Moo Kyun,Byung Kwan Kim,Jong Hyang Kim ) 한국공업화학회 1997 응용화학 Vol.1 No.1

UV 조사에 의한 방향족오염물의 분해

민병철,김종향,김병관 ( Byoung Chul Min,Jong Hyang Kim,Byung Kwan Kim ) 한국공업화학회 1997 공업화학 Vol.8 No.3

방향족 오염물을 UV산화- 고도산화처리기술로 처리할 때, 여러 가지 반응조건에 따른 분해효율에 대해 고찰하였다. 벤젠 50pmm, 에틸벤젠 150ppm, 크실렌 250ppm을 각각 초기농도로하여 UV조사 하에서 시간변화에 따른 분해실험을 행한 결과, 반응 1시간 후 약 95% 이상의 분해율을 나타내었으나, 톨루엔의 경우에는 43%의 분해율을 보였다. 단일성분이 혼합성분에서 보다 분해가 좋았으며, pH변화에서는 벤젠은 pH변화에 관계없이 분해가 잘되었으며, 에틸벤젠 92%(pH 4.0), 90%(pH 6.4), 91%(pH 10.0), 크실렌 95%(pH 4.0), 90%(pH 6.4), 92%(pH 10.0), 그러나 톨루엔은 80%(pH 4.0), 43%(pH 6.4), 70%(pH 10.0)의 분해율을 나타내었다. 방향족 오염물의 TOC 감소는 에틸벤젠을 제외하고는 유사 1차 반응속도식에 일치하였으며, 이로부터 속도상수를 결정할 수 있었다. Aromatic pollutants(benzene, toluene, ethylbenzene and xylenes) were photodegraded by using a UV oxidation and the rates of degradation were investigated under various reaction conditions. Each of the solution containing 50 ppm benzene, 150 ppm ethylbenzene and 250 ppm xylenes was found UV-photodegraded over 90% in 1 hour of reaction time, wheras the only was 43% of degradation was obtained with 350 ppm toluene solution. A single component solution was more degradable than a mixed component solution and benzene was almost photodegraded at a pH 4.0, 6.4 and 10.0 after reaction time is 1 hr, ehtylbenzene was photodegraded about 92%(pH 4.0), 90%(pH 6.4) and 91%(pH 10.0), xylenes was photodegraded about 95%(pH 4.0), 90%(pH 6.4) and 92%(pH 10.0), but toluene was photodegraded about 80%(pH 40), 43%(pH 6.4) and 70%(pH 10.0), respectively. Kinetics studies show that the rate of decay in TOC(total organic carbon) were pseudo first-order rate except ethylbenzene, and then we could evaluate mineralization rate constants(k) of aromatics.

e - beam 증발법으로 제조된 비정질 WO3 박막과 전해질 계면으로 삽입되는 리튬의 층간 반응에 관한 전기화학적 특성

민병철,손태원,주재백 ( Byoung Chul Min,Tae Won Sohn,Jeh Beck Ju ) 한국공업화학회 1997 공업화학 Vol.8 No.6

본 연구에서는 1M LiClO₄/PC 유기 용액 중에 존재하는 리튬 이온의 층간 반응에 의하여 전기 발색 현상을 나타내는 전자-선 증발법으로 제조된 비정질의 텅스텐 산화물 박막과 전해질 계면에서의 전기화학적 특성들을 연구하기 위하여 음극 Tafel 분극법, 순환 전류-전위법 및 전기량 적정법 등의 전기화학 측정법과 X선 회절 분석법을 이용한 박막의 결정 상태 조사 등이 수행되었다. 특히 다중 순환 전류-전위 곡선으로부터 리튬 이온의 층간 반응은 발색 반응에 대한 인가 과전압이 약 1.0V 이내에서는 안정된 소 · 발색의 가역적 현상을 나타내었으나, 발색 반응에 대한 인가 과전압이 1.5V일 때는 발색 시 삽입된 박막 내부의 리튬이 소색 시 완전히 빠져 나오지 못하여, 박막 내부에 리튬이 축적되는 현상을 나타내었으며, 적은 순환 횟수임에도 불구하고 소 ·발색의 전류 밀도가 감소되는 것이 조사되어 발색에 필요한 인가 과전압의 한계가 존재함을 알 수 있었다. This work was performed to study the characteristics of electrochanical intercalation reactions occurring at the interface between the organic electrolyte and tungsten trioxide thin film (thickness of 4000Å) prepared by e-beam evaporation method as cathodically coloring oxide with regard to the electrochromism by the intercalating reactions of the lithium cation in the 1M LiClO₄/PC organic solution. The characteristics of electrochemical intercalation reactions were investigated by various DC electrochemical methods such as cathodic Tafel polarization test, multiple and the single sweep cyclic voltammetry and the coulometry titrations method. The surfaces of thin films were observed with the patterns of X ray diffraction after the coloring and bleaching reactions. In comparison with the previous results that WO₃ thin film intensely detached from the surface of electrode when the hydrogen cation was intercalated into WO₃ thin film in the O.1N H₂SO₄ aqueous solution, the intercalation reaction of lithium cation into WO₃ thin film in the 1M LiClO₄/PC organic solution was shown that the stable bleaching and coloration was appeared within 1.0V of the applied overpotential. When the overpotential of electrochromic reaction for lithium cation in the 1M LiClO₄/PC organic solution had been applied up to 1.5V, the accumulation phenomenon of lithium in amorphous WO₃ thin film layer occurred because the inserted lithium into amorphous WO₃ thin layer for coloring process was not fully removed from the thin layer to the electrolyte during bleaching process. It was found that there is a limitation of applied overpotential for coloring process by the reduction of the current densities of bleaching and coloration after few number of coloring and bleaching cycles.

e-beam 증발법으로 제조된 비정질 WO₃박막과 전해질 계면으로 삽입되는 리튬의 층간 반응에 관한 전기화학적 특성

민병철,손태원,주재백,Min, Byoung-Chul,Sohn, Tae-Won,Ju, Jeh-Beck 한국공업화학회 1997 공업화학 Vol.8 No.6

본 연구에서는 1M $LiClO_4/PC$ 유기 용액 중에 존재하는 리튬 이온의 층간 반응에 의하여 전기 발색 현상을 나타내는 전자-선 증발법으로 제조된 비정질의 텅스텐 산화물 박막과 전해질 계면에서의 전기화학적 특성들을 연구하기 위하여 음극 Tafel 분극법, 순환 전류-전위법 및 전기량 적정법 등의 전기화학 측정법과 X선 회절 분석법을 이용한 박막의 결정 상태 조사 등이 수행되었다. 특히 다중 순환 전류-전위 곡선으로부터 리튬 이온의 층간 반응은 발색 반응에 대한 인가 과전압이 약 1.0V 이내에서는 안정된 소 발색의 가역적 현상을 나타내었으나, 발색 반응에 대한 인가 과전압이 1.5V일 때는 발색 시 삽입된 박막 내부의 리튬이 소색 시 완전히 빠져 나오지 못하여, 박막 내부에 리튬이 축적되는 현상을 나타내었으며, 적은 순환 횟수임에도 불구하고 소 발색의 전류 밀도가 감소되는 것이 조사되어 발색에 필요한 인가 과전압의 한계가 존재함을 알 수 있었다. This work was performed to study the characteristics of electrochemical intercalation reactions occurring at the interface between the organic electrolyte and tungsten trioxide thin film (thickness of $4000{\AA}$) prepared by e-beam evaporation method as cathodically coloring oxide with regard to the electrochromism by the intercalating reactions of the lithium cation in the 1M $LiClO_4/PC$ organic solution. The characteristics of electrochemical intercalation reactions were investigated by various DC electrochemical methods such as cathodic Tafel polarization test, multiple and the single sweep cyclic voltammetry and the coulomety titrations method. The surfaces of thin films were observed with the patterns of X ray diffraction after the coloring and bleaching reactions. In comparison with the previous results that $WO_3$ thin film intersely detached from the surface of electrode when the hydrogen cation was intercalated into $WO_3$ thin film in the o.1N $H_2SO_4$ aqueous solution, the intercalation reaction of lithium cation into $WO_3$ thin film in the 1M $LiClO_4/PC$ organic solution was shown that the stable bleaching and coloration was appeared within 1.0V of the applied overpotential. When the overpotential of electrochromic reaction for lithium cation in the 1M $LiClO_4/PC$ organic solution had been applied up to 1.5V, the accumulation phenomenon of lithium in amorphous $WO_3$ thin film layer occurred because the inserted lithium into amorphous $WO_3$ thin layer for coloring process was not fully removed from the thin layer to the electrolyte during bleaching process. It was found that there is a limitation of applied overpotential for coloring process by the reduction of the current densities of bleaching and coloration after few number of coloring and bleaching cycles.

실리콘 스핀트로닉스

민병철(Byoung-Chul Min) 한국자기학회 2011 韓國磁氣學會誌 Vol.21 No.2

Semiconductor spintronics is an emerging interdisciplinary technology based on the electron spin degree of freedom, combining the magnetic materials and semiconductors. The spin transistor represents a novel semiconductor device, in which the electron spin is injected, manipulated, and detected, and thereby a memory function and data processing function are enabled in one device. Particularly, the spin transistor based on Silicon, the mainstream semiconductor, might have a significant impact on information technology. This review introduces the major progresses of Silicon spintronics in recent years, and describes the technical issues for the future.

DC 마그네트론 스퍼터링으로 제작된 NiFe 박막에서 Ar 압력이 자기 및 자기저항 성질에 미치는 영향

민병철(Byoung-Chul Min),신성철(Sung-Chul Shin) 한국자기학회 1996 韓國磁氣學會誌 Vol.6 No.2

We have investigated the effects of sputtering Ar gas pressure as well as other deposition conditions on the magnetic and galvano-magnetic properties of NiFe thin films. The films were prepared by dc magnetron sputtering from Ni_(81)Fe_(19) wt.% alloy-target. The microstructures of the films were investigated by TEM, M-H hysteresis loops by VSM, and the composition by ICPS. The columnar structures with crack-like voids were observed in the films deposited at high Ar pressures(≥10 mTorr). These crack-like voids were believed as domain wall pinning sites in magnetization process. So, the coercivity of the film was increased with increasing Ar pressure, while the saturation magnetization was decreased due to decrease of the density. The magnetoresistance was also reduced with increasing Ar pressure, due to increase of the resistivity of film. It was believed that grain boundary scattering and intergranular tunneling made the resistivity of films high.

갑상선 질환에서 표피성장인자 수용체 발현

민병철(Byoung Chul Min),이용진(Yong Jin Lee),차성재(Seong Jae Cha),박용검(Yong Kum Park),지경천(Kyung Chun Chi),임현묵(Hyun Muck Lim),박성일(Sung Il Park),박성준(Sung Jun Park) 대한두경부종양학회 1999 대한두경부 종양학회지 Vol.15 No.2

Objectives: The epidermal growth factor receptor(EGFR) family has been increasingly recognized as an important component in the control of normal cell proliferation and the pathogenesis of cancer. To confirm the usefulness of epidermal growth factor receptor as a tumor marker, we initiated this study. Materials and Methods: EGFR was measured by immunohistochemical staining using EGFR antibody. It was performed on section from paraffin blocks of 65 thyroid tissue including 33 paillary carcinoma, 11 follicular carcinoma, 11 nodular hyperplasia, 5 follicular adenoma and 5 normal thyroid tissue. We evaluated morphologic characteristic of various thyroid neoplasms, and the relationship between EGFR and other prognostic factors in papillary thyroid carcinomas. Results: The expression of EGFR was commonly found in neoplasms of thyroid, with trend for stronger staining in the more malignant tumor(p=0.000). Also the expression of EGFR in papillary thyroid cancer related to tumor characters including tumor size(p=0.042), extent(p=0.024) and prognostic features including AMES scores(p=0.019). The strong EGFR staining in papillary carcinoma was significantly associated with tumor recurrence(p=0.003). Conclusions: EGFR may have a role in the regulation of normal and neoplastic thyroid cell growth. EGFR status may help predict the clinical course of patients with malignant thyroid neoplasms. However, the study of more cases will be needed for significance of the information about the EGFR as an independent prognostic factor.

졸 - 겔법으로 제조된 비정질의 텅스텐 산화물을 박막과 황산 전해질 계면에서 일어나는 수소의 층간 반응에 대한 전기화학적 특성

강태혁,민병철,주재백,손태원,조원일 ( Tae Hyuk Kang,Byoung Chul Min,Jeh Beck Ju,Tae Won Sohn,Won Il Cho ) 한국공업화학회 1996 공업화학 Vol.7 No.6

본 연구에서는 W-IPA(peroxo-polytungstic acid)를 출발 물질로 하는 졸 용액을 ITO(indium tin oxide)가 입혀진 유리판 위에 침적 도포(dip-coating) 방법으로 침적시키고, 이것을 겔화시킨 후에 열처리하여 전기 발색 소자(electrochromic device, ECD)의 텅스텐 산화물 박막 전극을 만들어 이의 전기화학적인 특성을 고찰하였다. 가장 좋은 전기 화학적 특성을 나타내는 조건은 29/10mL(W-IPA/H₂O)졸 용액에 15회 침적 도포하여 230∼240℃의 온도로 최종 열처리 한 텅스텐 산화물 박막 전극이었으며, 침적 횟수의 증가에 따라 산화 텅스텐 박막의 두께는 비례하여 증가하였고, 5회 침적 도포 이후에는 1회 침적 도포시 약 60 두께로 막이 생성됨을 알 수 있었다. 졸-겔법으로 제조된 텅스텐 산화물 박막 전극은X-선 회절 분석에 의하여 비정질 구조, 주사 전자 현미경에 의하여 박막 표면은 균일한 로조사되었다. 다중 순환 전류-전위 주사법에 의하여 작성된 전류-전위 곡선에 의하면 순환 횟수가 수백회 이상임에도 불구하고 소·발색은 뚜렷하게 나타났으나, 더욱 많은 순환 횟수에서는 전해질인 황산 수용액 중에서 텅스텐 산화물 박막의 박리 현상이 일어나 소·발색의 전류 밀도는 차츰 감소하였다. 전위 주사 속도를 변화시키면서 순환 전류-전위 주사법에 의하여 작성된 전류-전위 곡선으로부터 구한 전기화학적 특성 값을 이용하여 반응에 참여하는 수소 이온의 확산 계수를 구할 수 있었다. The peroxo-polytungstic acid was formed by the direct reaction of tungsten powder with the hydrogen peroxide solution. Peroxo-polytungstic powder were prepared by rotary evaporator using the fabricated on to ITO coated glass as substrate by dip-coating method using 2g/10mL(W-IPA/H₂O) sol solution. A substrate was dipped into the sol solution and after a meniscus had settled, the substrate was withdrawn at a constant rate of the 3mm/sec. Thicker layer could be built up by repeated dipping/post-treatment 15 times cycles. The layer dried at the temperature of 65∼70℃ during the withdrawn process, and then tungsten oxides thin film was formed by final heating treatment at the temperature of 230∼240℃ for 30min. A linear relation between the thickness of thin film and the number of dipping/post-treatment cycles for tungsten oxides thin films made by dip-coating was found. The thickness of thin film had 60 after one dipping. From the patterns of XRD, the structure of tungsten oxides thin film identified as amorphous one and from the photographs of SEM, the defects and the moderate cracks were observed on the tungsten oxides thin film, but the homogeneous surface of thin films were mostly appeared. The electrochemical charateristic of the ITO/WO₃ thin film electrode were conformed by the cyclic voltammetry and the cathodic Tafel polarization method. The colaring-bleaching processes were clearly repeated up to several hundreds cycles by multiple cyclic voltammetry, but the dissolved phenomenon of thin film revealed in H₂SO₄ solution was observed due to the decrease of the current densities. The diffusion coefficient was calculated from irreversible Randles-Sevick equation from the data obtained by the cyclic voltammetry with various scan rates.

졸-겔법으로 제조된 비정질의 텅스텐 산화물 박막과 황산 전해질 계면에서 일어나는 수소의 층간 반응에 대한 전기화학적 특성

강태혁,민병철,주재백,손태원,조원일,Kang, Tae-Hyuk,Min, Byoung-Chul,Ju, Jeh-Beck,Sohn, Tae-Won,Cho, Won-Il 한국공업화학회 1996 공업화학 Vol.7 No.6

본 연구에서는 W-IPA(peroxo-polytungstic acid)를 출발 물질로 하는 졸 용액을 ITO(indium tin oxide)가 입혀진 유리판 위에 침적 도포(dip-coating) 방법으로 침적시키고, 이것을 겔화시킨 후에 열처리하여 전기 발색 소자 (electrochromic device, ECD)의 텅스텐 산화물 박막 전극을 만들어 이의 전기화학적인 특성을 고찰하였다. 가장 좋은 전기 화학적 특성을 나타내는 조건은 $2g/10mL(W-IPA/H_2O)$졸 용액에 15회 침적 도포하여 $230{\sim}240^{\circ}C$의 온도로 최종 열처리 한 텅스텐 산화물 박막 전극이었으며, 침적 횟수의 증가에 따라 산화 텅스텐 박막의 두께는 비례하여 증가하였고, 5회 침적 도포 이후에는 1회 침적 도포시 약 $60{\AA}$ 두께로 막이 생성됨을 알 수 있었다. 졸-겔법으로 제조된 텅스텐 산화물 박막 전극은 X-선 회절 분석에 의하여 비정질 구조, 주사 전자 현미경에 의하여 박막 표면은 균일한 것으로 조사되었다. 다중 순환 전류-전위 주사법에 의하여 작성된 전류-전위 곡선에 의하면 순환 횟수가 수백회 이상임에도 불구하고 소 발색은 뚜렷하게 나타났으나, 더욱 많은 순환 횟수에서는 전해질인 황산 수용액 중에서 텅스텐 산화물 박막의 박리 현상이 일어나 소 발색의 전류 밀도는 차츰 감소하였다. 전위 주사 속도를 변화시키면서 순환 전류-전위 주사법에 의하여 작성된 전류-전위 곡선으로부터 구한 전기화학적 특성 값을 이용하여 반응에 참여하는 수소 이온의 확산 계수를 구할 수 있었다. The peroxo-polytungstic acid was formed by the direct reaction of tungsten powder with the hydrogen peroxide solution. Peroxo-polytungstic powder were prepared by rotary evaporator using the fabricated on to ITO coated glass as substrate by dip-coating method using $2g/10mL(W-IPA/H_2O)$ sol solution. A substrate was dipped into the sol solution and after a meniscus had settled, the substrate was withdrawn at a constant rate of the 3mm/sec. Thicker layer could be built up by repeated dipping/post-treatment 15 times cycles. The layers dried at the temperature of $65{\sim}70^{\circ}C$ during the withdrawn process, and then tungsten oxides thin film was formed by final heating treatment at the temperature of $230{\sim}240^{\circ}C$ for 30min. A linear rotation between the thickness of thin film and the number of dipping/post-treatment cycles for tungsten oxides thin films made by dip-coating was found. The thickness of thin film had $60{\AA}$ after one dipping. From the patterns of XRD, the structure of tungsten oxides thin film identified as amorphous one and from the photographs of SEM, the defects and the moderate cracks were observed on the tungsten oxides thin film, but the homogeneous surface of thin films were mostly appeared. The electrochemical characteristic of the $ITO/WO_3$ thin film electrode were confirmed by the cyclic voltammetry and the cathodic Tafel polaization method. The coloring bleaching processes were clearly repeated up to several hundreds cycles by multiple cyclic voltammetry, but the dissolved phenomenon of thin film revealed in $H_2SO_4$ solution was observed due to the decrease of the current densities. The diffusion coefficient was calculated from irreversible Randles-Sevick equation from the data obtained by the cyclic voltammetry with various scan rates.