• International Journal of Precision Engineering and Manufacturing-Green Technology
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• v.5 no.5
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• pp.643-650
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• 2018

A self-powered electrochromic device was fabricated on an indium tin oxide-polyethylene naphthalate flexible substrate using a dye-sensitized solar cell (DSSC) as a self-harvesting source; the electrochromic device was naturally bleached and operated under outdoor light conditions. The color of the organic electrochromic polymer, poly(3,4-ethylenedioxythiophene) polystyrene sulfonate, was shifted from pale blue to deep blue with an antimony tin oxide film as a charge-balanced material. Electrochromic performance was enhanced by secondary doping using dimethyl sulfoxide. As a result, the device showed stable switching behavior with a high transmittance change difference of 40% at its specific wavelength of 630 nm for 6 hrs. To improve the efficiency of the solar cell, 1.0 wt.% of Ag NWs in the photoanode was applied to the $TiO_2$ photoanode. It resulted in an efficiency of 3.3%, leading to an operating voltage of 0.7 V under xenon lamp conditions. As a result, we built a standalone self-harvesting electrochromic system with the performance of transmittance switching of 29% at 630 nm, by connecting with two solar cells in a device. Thus, a self-harvesting and flexible device was fabricated to operate automatically under the irradiated/dark conditions.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.04b
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• pp.68-71
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• 2004

본 연구는 싱크로트론 방사광의 단색광 (monobeam)을 이용한 영상을 획득하였다. 영상센서로서 CMOS를 사용하였으며 센서 앞단에는 형광체 (phosphor)를 이용하여 방사광에 대한 빛의 신호로서 영상을 획득하였다. 사용된 싱크로트론 방사광의 beam size는 $5mm{\times}2mm$ 이며 ion chamber를 통한 beam intensity 는 $10{\times}10^{-7}$이다. 형광체는 각각 ZnS(Cu:Al), ZnS(Ag,Al), $BiTiO_3$, $Y_2O_2S(Tb)$로서 4가지를 사용하였으며 여기에 사용된 형광체는 기계식 스크린 프린팅 (Screen Printing) 방식으로 직접 제조하였다. 두께는 모두 동일하게 $10{\mu}m$이며 각각에 대한 PL(Photoluminescence)을 측정하여 분석하였다. object로는 물고기와 20linepair를 사용하였으며 CMOS센서를 이용하여 각각의 phosphor에 대하여 영상을 획득하였다. 영상의 평가는 20line pair 영상의 MTF를 이용하였다. 각각의 형광체에 대한 MTF는 5 lp/mm 에서는 0.5650, 0.2150, 0.7890, 0.3840 이며 10 lp/mm 은 0.4500, 0.0900, 0.2510, 0.1500이고 15 lp/mm 는 0.1900, 0.0300, 0.1430, 0.0500이며 마지막으로 20 lp/mm 은 0.0810, 0.004, 0.0500, 0.0320의 MTF 값을 나타내었다. $10{\mu}m$ 두께에 대하여 ZnS(Cu:Al)이 가장 좋은 MTF의 값을 나타내었다.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.32 no.5
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• pp.418-425
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• 2019

A piezoelectric ceramic fiber composite (PCFC) was successfully fabricated using $0.69Pb(Zr_{0.47}Ti_{0.53})O_3-0.31[Pb(Zn_{0.4}Ni_{0.6})_{1/3}Nb_{2/3}]O_3$ (PZT-PZNN) for use in small-scale wind energy harvesters. The PCFC was formed using an epoxy matrix material and an array of Ag/Pd-coated PZT-PZNN piezo-ceramic fibers sandwiched by Cu interdigitated electrode patterned polyethylene terephthalate film. The energy harvesting performance was evaluated in a custom-made wind tunnel while varying the wind speed and resistive load with two types of flutter wind energy harvesters. One had a five-PCFC array vertically clamped with a supporting acrylic rod while the other used the same structure but with a five-PCFC cantilever array. Stainless steel (thickness: $50{\mu}m$) was attached onto one side of the PCFC to form the PZT-PZNN cantilever. The output power, in general, increased with an increase in the wind speed from 2 m/s to 10 m/s for both energy harvesters. The highest output power of $15.1{\mu}W$ at $14k{\Omega}$ was obtained at a wind speed of 10 m/s for the flutter wind energy harvester with the PZT-PZNN cantilever array. The results presented here reveal the strong potential for wind energy harvester applications to supply sustainable power to various IoT micro-devices.

• Korean Journal of Mineralogy and Petrology
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• v.35 no.4
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• pp.469-484
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• 2022

The Janggun Pb-Zn deposit has been known one of the four largest deposits (Yeonhwa, Shinyemi, Uljin) in South Korea. The geology of this deposit consists of Precambrian Weonnam formation, Yulri group, Paleozoic Jangsan formation, Dueumri formation, Janggum limestone formation, Dongsugok formation, Jaesan formation and Mesozoic Dongwhachi formation and Chungyang granite. This Pb-Zn deposit is hydrothermal replacement deposit in Paleozoic Janggum limestone formation. The wallrock alteration that is remarkably recognized with Pb-Zn mineralization at this deposit consists of mainly rhodochrositization and dolomitization with minor of pyritization, sericitization and chloritization. Wallrock alteration is divided into the five zones (Pb-Zn orebody -> rhodochrosite zone -> dolomite zone -> dolomitic limestone zone -> limestone or dolomitic marble) from orebody to wallrock. The white mica from wallrock alteration occurs as fine or medium aggregate associated with Ca-dolomite, Ferroan ankerite, sideroplesite, rutile, apatite, arsenopyrite, pyrite, sphalerite, galena, quartz, chlorite and calcite. The structural formular of white mica from wallrock alteration is (K_0.77-0.62Na_0.03-0.00Ca_0.03-0.00Ba_0.00Sr_0.01)_0.82-0.64(Al_1.72-1.48Mg_0.48-0.20Fe_0.04-0.01Mn_0.03-0.00Ti_0.01-0.00Cr_{0.00As0.01-0.00}Co_0.03-0.00Zn_0.03-0.00Pb_0.05-0.00Ni_0.01-0.00)_2.07-1.92 (Si_3.43-3.33Al_0.67-0.57)_4.00O₁₀(OH_1.94-1.80F_0.20-0.06)_2.00. It indicated that white mica from wallrock alteration has less K, Na and Ca, and more Si than theoretical dioctahedral micas. The white micas from wallrock alteration of Janggun Pb-Zn deposit, Yeonhwa 1 Pb-Zn deposit and Baekjeon Au-Ag deposit, and limestone of Gumoonso area correspond to muscovite and phengite and white mica from wallrock alteration of Dunjeon Au-Ag deposit corresponds to muscovite. Compositional variations in white mica from wallrock alteration of these deposits and limeston of Gumoonso area are caused by mainly phengitic or Tschermark substitution mechanism (Janggun Pb-Zn deposit), mainly phengitic or Tschermark substitution and partly illitic substitution mechanism (Yeonhwa 1 Pb-Zn deposit, Dunjeon Au-Ag deposit and Baekjeon Au-Ag deposit), and mainly phengitic or Tschermark substitution and partly illitic substitution or Na⁺ <-> K⁺ substitution mechanism (Gumoonso area).

• Proceedings of the Korean Vacuum Society Conference
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• 2012.08a
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• pp.151-151
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• 2012

A new plasma process, i.e., the combination of PIII&D and HIPIMS, was developed to implant non-gaseous ions into materials surface. HIPIMS is a special mode of operation of pulsed-DC magnetron sputtering, in which high pulsed DC power exceeding ~1 kW/$cm^2$ of its peak power density is applied to the magnetron sputtering target while the average power density remains manageable to the cooling capacity of the equipment by using a very small duty ratio of operation. Due to the high peak power density applied to the sputtering target, a large fraction of sputtered atoms is ionized. If the negative high voltage pulse applied to the sample stage in PIII&D system is synchronized with the pulsed plasma of sputtered target material by HIPIMS operation, the implantation of non-gaseous ions can be successfully accomplished. The new process has great advantage that thin film deposition and non-gaseous ion implantation along with in-situ film modification can be achieved in a single plasma chamber. Even broader application areas of PIII&D technology are believed to be envisaged by this newly developed process. In one application of non-gaseous plasma immersion ion implantation, Ge ions were implanted into SiO2 thin film at 60 keV to form Ge quantum dots embedded in SiO2 dielectric material. The crystalline Ge quantum dots were shown to be 5~10 nm in size and well dispersed in SiO2 matrix. In another application, Ag ions were implanted into SS-304 substrate to endow the anti-microbial property of the surface. Yet another bio-application was Mg ion implantation into Ti to improve its osteointegration property for bone implants. Catalyst is another promising application field of nongaseous plasma immersion ion implantation because ion implantation results in atomically dispersed catalytic agents with high surface to volume ratio. Pt ions were implanted into the surface of Al2O3 catalytic supporter and its H2 generation property was measured for DME reforming catalyst. In this talk, a newly developed, non-gaseous plasma immersion ion implantation technique and its applications would be shown and discussed.

• Economic and Environmental Geology
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• v.12 no.2
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• pp.79-93
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• 1979

Twenty five samples of the scheelite-powellite series from twelve Korean tungsten deposits of various geologic settings were studied mineralogically and geochemically. Variations in the trace-element contents of the scheelite minerals are considered in relation to geologic settings and mineralogic properties. Scheelites from ore deposits developed in similar geologic settings and under similar physicochemical conditions are characterized by specific combinations of trace elements.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.36 no.4
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• pp.362-368
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• 2023

Multilayered actuators using Pb(Mg_1/3Nb_2/3)O₃-Pb(In_1/2Nb_1/2)O₃-PbTiO₃ (PMN-PIN-PT) crystals have demonstrated excellent properties, but are costly and lack mechanical strength. Textured PMN-PIN-PT ceramics exhibit robust mechanical strength and comparable properties to their single crystals form. However, the development of multilayered actuators using textured PMN-PIN-PT ceramics has not been achieved until now. This study presents the development of a multilayered actuator using textured 0.37PMN-0.29PIN-0.34PT ceramics with an Ag_0.9/Pd_0.1 inner electrode, co-fired at 950℃. A random 0.37PMN-0.29PIN-0.34PT ceramics multilayered actuator was also developed for comparison. The multilayered actuator consisted of 9 ceramic layers (36 ㎛ thickness) with an overall actuator thickness of 0.401 mm. The textured and random 0.37PMN-0.29PIN-0.34PT ceramics-based multilayered actuators achieved displacements of 0.61 ㎛ (0.15% strain) and 0.23 ㎛ (0.057% strain) at a low applied peak voltage of 100 V. These results suggest that the developed multilayered actuator using high-performance textured 0.37PMN-0.29PIN-0.34PT ceramics has the potential to replace expensive single crystal-based actuators cost-effectively.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.08a
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• pp.193-193
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• 2012

In thin film silicon solar cells, p-i-n structure is adopted instead of p/n junction structure as in wafer-based Si solar cells. PECVD is the most widely used thin film deposition process for a-Si:H or ${\mu}c$-Si:H solar cells. Single-chamber PECVD system for a-Si:H solar cell manufacturing has the advantage of lower initial investment and maintenance cost for the equipment. However, in single-chamber PECVD system, doped and intrinsic layers are deposited in one plasma chamber, which inevitably impedes sharp dopant profiles at the interfaces due to the contamination from previous deposition process. The cross-contamination between layers is a serious drawback of single-chamber PECVD system. In this study, a new plasma process to solve the cross-contamination problem in a single-chamber PECVD system was suggested. In order to remove the deposited B inside of the plasma chamber during p-layer deposition, a high RF power was applied right after p-layer deposition with SiH4 gas off, which is then followed by i-layer, n-layer, and Ag top-electrode deposition without vacuum break. In addition to the p-i interface control, various interface control techniques such as FTO-glass pre-annealing in O2 environment to further reduce sheet resistance of FTO-glass, thin layer of TiO2 deposition to prevent H2 plasma reduction of FTO layer, and hydrogen plasma treatment prior to n-layer deposition, etc. were developed. The best initial solar cell efficiency using single-chamber PECVD system of 10.5% for test cell area of 0.2 $cm^2$ could be achieved by adopting various interface control methods.

• KOREAN JOURNAL OF PACKAGING SCIENCE & TECHNOLOGY
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• v.29 no.1
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• pp.15-25
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• 2023

Since the COVID-19 crisis, the use of disposable packaging materials and delivery services, which raise environmental and social issues with waste disposal, has significantly increased. Antimicrobial active packaging has emerged as a viable solution for extending the shelf-life of foods by minimizing microbial growth and decomposition. In this review article, we provide a comprehensive overview of current research trends in antimicrobial active film and coating published over the last five years. First, we introduced various polymer materials such as film and coating that are used in active packaging. Next, various types of antimicrobial (antibacterial, antifungal, and antiviral) packaging including essential oil, extracts, biological material, metal, and nanoparticles were introduced and their activities and mechanisms were discussed. Finally, the current challenges and prospects were discussed. Overall, this review provides insights into the recent advancements in antimicrobial active packaging research and highlights the potential of the technology to enhance food safety and quality.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.11a
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• pp.346-346
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• 2007

압전세라믹 재료는 현재 압전 변압기, actuator, transducer, sensor, speaker 등에 광범위하게 이용이 되고 있다. 이 중에서 압전세라믹 소결체를 이용한 스피커의 제조는 가공이 까다롭고, 대형의 크기로 제작 시 소자가 깨지는 등의 많은 제약을 받고 있으며, 저음 특성이 떨어져 응용 범위가 한정되어 있다. 따라서 최근에는 이러한 단점을 극복하기 위하여 세라믹/고분자 복합체를 이용한 필름 스피커를 제작하고자 시도하고 있다. 이러한 세라믹/고분자 0-3형 압전 복합체를 이용할 경우, 제품의 경량화를 실현할 수 있고, 크기나 환경의 영향을 거의 받지 않으므로, 고기능성 스피커로의 응용에 적합할 것으로 보인다. 따라서 본 연구에서는 PZT계의 세라믹와 PVDF, PVDF-TrFE, Polyester, acrylic resin 등의 여러 고분자 물질과의 복합체를 제조하여 압전특성을 평가하였다. 본 실험은 먼저 $(Pb_{1-a-b}Ba_aCd_b)(Zr_xTi_{1-x})_{1-c-d}(Ni_{1/3}Nb_{2/3})_c(Zn_{1/3}Nb_{2/3})_dO_3$ (이하 PZT라 표기)의 최적화 조성을 선택하여, $1050^{\circ}C$에서 소결된 분말을 48시간 ball milling방법 로 약 $1{\mu}m$ 크기로 분쇄하였다. 고분자 물질들은 알맞은 용제들을 선택하여 녹였다. 그 다음 소결된 PZT분말과 고분자를 50:50, 60:40, 65:35, 70:30등의 무게 분율로 혼합하고, 분산제, 소포제 등을 첨가하여 3단 roll mill을 이용하여 충분히 분산시켜 페이스트 (Paste)를 제조하였다. 제조된 페이스트를 ITO가 코팅된 PET필름 위에 스크린 프린팅 법을 사용하여 인쇄하여 $120^{\circ}C$에서 5분간 건조하였다. 코팅된 복합체의 두께는 약 $80{\mu}m$ 정도로 측정되었다. Ag 페이스트를 이용한 상부 전극 형성에도 스크린 프린팅 법을 적용하였다. 이를 $120^{\circ}C$에서 4 kV/mm의 DC 전계로 분극 공정을 수행한 후 전기적 특성을 평가하였다. 유전특성을 조사하기 위해서 LCR meter (EDC-1620)를 사용하였고, 시편의 결정구조는 XRD (Rigaku; D/MAX-2500H)을 통해 분석하였으며, 전자현미경(SEM)을 이용하여 미세구조를 분석하였다. 압전 전하상수$(d_{33})$ 값은 APC 8000 모델을 이용하여 측정하였다. PZT의 혼합비가 증가할수록 비유전율 및 압전 전하 상수 등의 전기적 특성이 증가되었다. 또 여러 고분자 물질 중에서 PVDF-TrFE 수지가 가장 우수한 특성을 보였다. 이는 PVDF-TrFE 수지가 압전성을 나타내기 때문인 것으로 판단되었다.