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Myeongjun Ji,Young-In Lee 한양대학교 세라믹연구소 2021 Journal of Ceramic Processing Research Vol.22 No.4
In this study, Ag-ZnO heterojunction composite nanofibers with an average diameter of about 100 nm and coupled Agnanoparticles with a size of 10 nm were synthesized by facile electrospinning followed by thermal treatment whereby the Agcontent was tuned by controlling the precursor concentration. Rhodamine B (RhB) was employed as a representative dyepollutant to evaluate the ultraviolet (UV) and visible light photocatalytic activity of the pure ZnO and Ag-ZnO compositenanofibers. The photocatalytic activity of 1.5 at% Ag-ZnO nanofibers toward RhB degradation was the greatest,outperforming pure ZnO nanofiber by a factor of more than 5 times. Further increasing the Ag content led to lowerphotocatalytic activity, most likely due to the growth of the Ag nanoparticles. It was found that the enhanced photocatalyticactivity is caused by the heterojunction structure promoting the charge separation of the photogenerated charge carriers, whilethe effect of surface plasmon resonance by the Ag nanoparticles on the photoreactivity is insufficient. The Ag-ZnO nanofibersshow great promise as innovative and highly performing photocatalyst for photocatalytic waste-water treatment.
Ji, Hyung Yong,Parida, Bhaskar,Park, Seungil,Kim, MyeongJun,Peck, Jong Hyeon,Kim, Keunjoo Korea Photovoltaic Society 2013 Current Photovoltaic Research Vol.1 No.1
We investigated the effects of Au eutectic reaction on Si thin film growth by hot wire chemical vapor deposition. Small SiC and Si nano-particles fabricated through a wet etching process were coated and biased at 50 V on micro-textured Si p-n junction solar cells. Au thin film of 10 nm and a Si thin film of 100 nm were then deposited by an electron beam evaporator and hot wire chemical vapor deposition, respectively. The Si and SiC nano-particles and the Au thin film were structurally embedded in Si thin films. However, the Au thin film grew and eventually protruded from the Si thin film in the form of Au silicide nano-balls. This is attributed to the low eutectic bonding temperature ($363^{\circ}C$) of Au with Si, and the process was performed with a substrate that was pre-heated at a temperature of $450^{\circ}C$ during HWCVD. The nano-balls and structures showed various formations depending on the deposited metals and Si surface. Furthermore, the samples of Au nano-balls showed low reflectance due to surface plasmon and quantum confinement effects in a spectra range of short wavelength spectra range.
Hyung Yong Ji,Bhaskar Parida,Seungil Park,MyeongJun Kim,Jong Hyeon Peck,Keunjoo Kim 한국태양광발전학회 2013 Current Photovoltaic Research Vol.1 No.1
We investigated the effects of Au eutectic reaction on Si thin film growth by hot wire chemical vapor deposition. Small SiC and Si nano-particles fabricated through a wet etching process were coated and biased at 50 V on micro-textured Si p?n junction solar cells. Au thin film of 10 nm and a Si thin film of 100 nm were then deposited by an electron beam evaporator and hot wire chemical vapor deposition, respectively. The Si and SiC nano-particles and the Au thin film were structurally embedded in Si thin films. However, the Au thin film grew and eventually protruded from the Si thin film in the form of Au silicide nano?-balls. This is attributed to the low eutectic bonding temperature (363℃) of Au with Si, and the process was performed with a substrate that was pre-heated at a temperature of 450℃ during HWCVD. The nano-balls and structures showed various formations depending on the deposited metals and Si surface. Furthermore, the samples of Au nano-balls showed low reflectance due to surface plasmon and quantum confinement effects in a spectra range of short wavelength spectra range.
HWCVD를 이용한 Amorphous Si 박막 증착공정에서 수소량에 따른 박막성장 특성
박승일(Seungil Park),지형용(Hyung Yong Ji),김명준(MyeongJun Kim),김근주(Keunjoo Kim) 한국태양광발전학회 2013 Current Photovoltaic Research Vol.1 No.1
We investigated the growth mechanism of amorphous-phase Si thin films in order to improve the film characteristics and circumvent photo-degradation effects by implementation of hot-wire chemical vapor deposition. Amorphous silicon thin films grown in a silane/hydrogen mixture can be decomposed by a resistive heat filament. The structural properties were observed by Raman spectroscopy, FTIR, SEM, and TEM. The electrical properties of the films were measured by photo-conductivity, dark-conductivity, and photo-sensitivity. The contents of Si-H and Si-Hn bonds were measured to be 19.79 and 9.96% respectively, at a hydrogen flow rate of 5.5 sccm, respectively. The thin film has photo-sensitivity of 2.2×10<SUP>5</SUP> without a crystalline volume fraction. The catalyst behavior of the hot-wire to decompose the chemical precursors by an electron tunneling effect depends strongly on the hydrogen mixture rate and an amorphous Si thin film is formed from atomic relaxation.
전기방사를 이용하여 합성한 BiVO<sub>4</sub> 나노섬유의 미세구조와 광촉매 특성에 하소 온도가 미치는 영향
지명준,김정현,류철희,고윤택,이영인,Ji, Myeongjun,Kim, Jeong Hyun,Ryu, Cheol-Hui,Ko, Yun Taek,Lee, Young-In 한국분말야금학회 2020 한국분말재료학회지 (KPMI) Vol.27 No.3
Bismuth vanadate (BiVO<sub>4</sub>) is considered a potentially attractive candidate for the visible-light-driven photodegradation of organic pollutants. In an effort to enhance their photocatalytic activities, BiVO<sub>4</sub> nanofibers with controlled microstructures, grain sizes, and crystallinities are successfully prepared by electrospinning followed by a precisely controlled heat treatment. The structural features, morphologies, and photo-absorption performances of the asprepared samples are systematically investigated and can be readily controlled by varying the calcination temperature. From the physicochemical analysis results of the synthesized nanofiber, it is found that the nanofiber calcines at a lower temperature, shows a smaller crystallite size, and lower crystallinity. The photocatalytic degradation of rhodamine-B (RhB) reveals that the photocatalytic activity of the BiVO<sub>4</sub> nanofibers can be improved by a thermal treatment at a relatively low temperature because of the optimization of the conflicting characteristics, crystallinity, crystallite size, and microstructure. The photocatalytic activity of the nanofiber calcined at 350℃ for the degradation of RhB under visible-light irradiation exhibits a greater photocatalytic activity than the nanofibers synthesized at 400℃ and 450℃.
아크 융해로를 이용한 β-Ti<SUB>3</SUB>O<SUB>5</SUB> 및 λ-AlxTi<SUB>3-x</SUB>O<SUB>5</SUB>의 합성
공민식(Minsik Kong),김서희(Seohee Kim),김민재(Min Jae Kim),강명준(Myeongjun Kang),지광철(Gwangcheol Ji),박성욱(Seonguk Park),이지성(Jisung Lee),손영준(Yeongjun Son),박성균(Sungkyun Park),옥종목(Jong Mok Ok) 한국물리학회 2024 새물리 Vol.74 No.1
Ti₃O<SUB>5</SUB> exhibits a metal-insulator transition (MIT) accompanied by a structural change from β- phase to λ-phase at 514 K. During the transition, Ti₃O<SUB>5</SUB> demonstrates significant resistance changes and high thermal energy storage characteristics. To harness the beneficial characteristics of Ti₃O<SUB>5</SUB>, it is essential to develop a growth method that yields homogeneous samples and to control the phase transition temperature. In this study, we successfully synthesized high-quality β-Ti₃O<SUB>5</SUB> and λ-AlxTi₃−xO5 polycrystalline samples using an arc melting method. Furthermore, the structural and physical properties of β-Ti₃O<SUB>5</SUB> and λ-AlxTi₃−xO<SUB>5</SUB> were investigated as a function of the Al doping ratio. Our results suggest that the arc melting method provides an effective way to synthesize high-quality Ti₃O<SUB>5</SUB> and control the transition temperature of the MIT.