• 한국재료학회지
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• 제29권9호
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• pp.553-558
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• 2019

$Cu_2ZnSn(S,Se)_4(CZTSSe)$ thin film solar cells areone of the most promising candidates for photovoltaic devices due to their earth-abundant composition, high absorption coefficient and appropriate band gap. The sputtering process is the main challenge to achieving high efficiency of CZTSSe solar cells for industrialization. In this study, we fabricated CZTSSe absorbers on Mo coated soda lime glass using different pressures during the annealing process. As an environmental strategy, the annealing process is performed with S and Se powder, without any toxic $H_2Se$ and/or $H_2S$ gases. Because CZTSSe thin films have a very narrow stable phase region, it is important to control the condition of the annealing process to achieve high efficiency of the solar cell. To identify the effect of process pressure during the sulfo-selenization, we experiment with varying initial pressure from 600 Torr to 800 Torr. We fabricate a CZTSSe thin film solar cell with 8.24 % efficiency, with 435 mV for open circuit voltage($V_{OC}$) and $36.98mA/cm^2$ for short circuit current density($J_{SC}$), under a highest process pressure of 800 Torr.

• 대한금속재료학회지
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• 제48권4호
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• pp.369-375
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• 2010

Ti-6Al-4V ELI alloy, which is commonly used as a biomaterial, is associated with a high elastic modulus and poor biocompatibility. This alloy presents a variety of problems on several areas. Therefore, the development of good non-toxic biocompatible biomaterials with a low elastic modulus is necessary. Particularly, hydroxyapatite (HA) is an attractive material for human tissue implantation. This material is widely used as artificial bone due to its good biocompatibility and similar composition to human bone. Many scientists have studied the fabrication of HA as a biomaterial. However, applications of bulk HA compact are hindered by the low strength of HA when it is sintered. Therefore, HA has been coated on Ti or Ti alloy to facilitate good bonding between tissue and the HA surface. However, there are many problems when doing this, such as the low bonding strength between HA and Ti due to the different thermal expansion coefficients and mechanical properties. In this study, a Ti-HA composite with a porous surface was successfully fabricated by pulse current activated sintering (PCAS) and a subsequent leaching process.

• Journal of Microbiology and Biotechnology
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• 제31권4호
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• pp.592-600
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• 2021

Probiotics can be processed into a powder, tablet, or capsule form for easy intake. They are exposed to frequent stresses not only during complex processing steps, but also in the human body after intake. For this reason, various coating agents that promote probiotic bacterial stability in the intestinal environment have been developed. Silk fibroin (SF) is a material used in a variety of fields from drug delivery systems to enzyme immobilization and has potential as a coating agent for probiotics. In this study, we investigated this potential by coating probiotic strains with 0.1% or 1% water-soluble calcium (WSC), 1% SF, and 10% trehalose. Under simulated gastrointestinal conditions, cell viability, cell surface hydrophobicity, and cell adhesion to intestinal epithelial cells were then measured. The survival ratio after freeze-drying was highest upon addition of 0.1% WSC. The probiotic bacteria coated with SF showed improved survival by more than 10.0% under simulated gastric conditions and 4.8% under simulated intestinal conditions. Moreover, the cell adhesion to intestinal epithelial cells was elevated by 1.0-36.0%. Our results indicate that SF has positive effects on enhancing the survival and adhesion capacity of bacterial strains under environmental stresses, thus demonstrating its potential as a suitable coating agent to stabilize probiotics throughout processing, packaging, storage and consumption.

• 센서학회지
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• 제32권3호
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• pp.140-146
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• 2023

Water quality is crucial for human health and the environment. Accurate measurement of the quantity of organic carbon in water is essential for water quality evaluation, identification of water pollution sources, and appropriate implementation of water treatment measures. Total organic carbon (TOC) analysis is an important tool for this purpose. Although other methods, such as chemical oxygen demand (COD) and biochemical oxygen demand (BOD) are also used to measure organic carbon in water, they have limitations that make TOC analysis a more favorable option in certain situations. For example, COD requires the use of toxic chemicals, and BOD is time-consuming and can produce inconsistent and unreliable results. In contrast, TOC analysis is rapid and reliable, providing accurate measurements of organic carbon content in water. However, common methods for TOC analysis can be complex and energy-intensive because of the use of high-temperature heaters for liquid-to-gas phase transitions and the use of acid, which present safety risks. This study focuses on a TOC analysis method using TiO₂ photocatalysis, which has several advantages over conventional TOC analysis methods, including its low cost and easy maintenance. For TiO₂, rutile and anatase powders are mixed with an inorganic binder and spray-coated onto a glass fiber substrate. The TiO₂ powder and inorganic binder solutions are adjusted to optimize the photocatalytic reaction performance. The TiO₂ photocatalysis method is a simple and low-power approach to TOC analysis, making it a promising alternative to commonly used TOC analysis methods. This study aims to contribute to the development of more efficient and cost-effective approaches for water quality analysis and management by exploring the effectiveness and reliability of the developed equipment.

• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2000년도 춘계학술강연 및 발표대회 강연 및 발표논문 초록집
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• pp.9-10
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• 2000

An important business-field of world-wide steel-industry is the coating of thin metal-sheets with zinc, zinc-aluminum and aluminum based materials. These products mostly go into automotive industry. in particular for the car-body. into building and construction industry as well as household appliances. Due to mass-production, the processing is done in large continuously operating plants where the mostly cold-rolled metal-strip as the substrate is handled in coils up to 40 tons unwind before and rolled up again after passing the processing plant which includes cleaning, annealing, hot-dip galvanizing / aluminizing and chemical treatment. In the liquid Zn, Zn-AI, AI-Zn and AI-Si bathes a combined action of corrosion and wear under high temperature and high stress onto the transfer components (rolls) accounts for major economic losses. Most critical here are the bearing systems of these rolls operating in the liquid system. Rolls in liquid system can not be avoided as they are needed to transfer the steel-strip into and out of the crucible. Since several years, ceramic roller bearings are tested here [1.2], however, in particular due to uncontrollable Slag-impurities within the hot bath [3], slide bearings are still expected to be of a higher potential [4]. The today's state of the art is the application of slide bearings based on Stellite\ulcorneragainst Stellite which is in general a 50-60 wt% Co-matrix with incorporated Cr- and W-carbides and other composites. Indeed Stellite is used as the bearing-material as of it's chemical properties (does not go into solution), the physical properties in particular with poor lubricating properties are not satisfying at all. To increase the Sliding behavior in the bearing system, about 0.15-0.2 wt% of lead has been added into the hot-bath in the past. Due to environmental regulations. this had to be reduced dramatically_ This together with the heavily increasing production rates expressed by increased velocity of the substrate-steel-band up to 200 m/min and increased tractate power up to 10 tons in modern plants. leads to life times of the bearings of a few up to several days only. To improve this situation. the Mechanical Alloying (MA) TeChnique [5.6.7.8] is used to prOduce advanced Stellite-based bearing materials. A lubricating phase is introduced into Stellite-powder-material by MA, the composite-powder-particles are coated by High Energy Milling (HEM) in order to produce bearing-bushes of approximately 12 kg by Sintering, Liquid Phase Sintering (LPS) and Hot Isostatic Pressing (HIP). The chemical and physical behavior of samples as well as the bearing systems in the hot galvanizing / aluminizing plant are discussed. DependenCies like lubricant material and composite, LPS-binder and composite, particle shape and PM-route with respect to achievable density. (temperature--) shock-reSistibility and corrosive-wear behavior will be described. The materials are characterized by particle size analysis (laser diffraction), scanning electron microscopy and X-ray diffraction. corrosive-wear behavior is determined using a special cylinder-in-bush apparatus (CIBA) as well as field-test in real production condition. Part I of this work describes the initial testing phase where different sample materials are produced, characterized, consolidated and tested in the CIBA under a common AI-Zn-system. The results are discussed and the material-system for the large components to be produced for the field test in real production condition is decided. Outlook: Part II of this work will describe the field test in a hot-dip-galvanizing/aluminizing plant of the mechanically alloyed bearing bushes under aluminum-rich liquid metal. Alter testing, the bushes will be characterized and obtained results with respect to wear. expected lifetime, surface roughness and infiltration will be discussed. Part III of this project will describe a second initial testing phase where the won results of part 1+11 will be transferred to the AI-Si system. Part IV of this project will describe the field test in a hot-dip-aluminizing plant of the mechanically alloyed bearing bushes under aluminum liquid metal. After testing. the bushes will be characterized and obtained results with respect to wear. expected lifetime, surface roughness and infiltration will be discussed.

• 한국작물학회지
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• 제61권1호
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• pp.9-16
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• 2016

벼 직파재배에서 볍씨에 피복재인 지오라이트와 결합재인 수용성규산(25%)으로 혼합 코팅된 "규산코팅볍씨(SCS)"의 활용에 의한 키다리병 억제효과를 구명하고자 서해안 간척지유래토양에서 담수표면직파된 포장시험과 아울러 시험포장에서 발병된 키다리병 이병주를 접종원으로 하여 변온조건(주야 $18{\sim}26^{\circ}C$)과 항온조건($30^{\circ}C$)에서 실내시험으로 수행한 결과는 다음과 같다. 1. 담수직파에서 규산코팅볍씨 처리구는 무코팅볍씨 처리구에서 보다 입모분포상태가 균일하였고 분얼중기경 건물생산량이 13% 증가되었다. 2. 무코팅볍씨 처리구에서는 분얼중기 경부터 키다리병이 발생되어 종자감염을 일으키는 출수기 경에 9.9%의 심한 이병경율을 보인 반면에 규산코팅볍씨 처리구에서는 분얼중기까지 거의 발생이 없다가 출수기 무렵에 0.01%의 극미한 발생으로 99.9%의 방제가를 보였다. 이병주의 줄기마디와 이삭영화 감염부위에서는 전형적인 키다리병균의 소형분생자와 대형분생자 및 균사체 등이 확인되었다. 3. 무코팅볍씨와 규산코팅볍씨를 $30^{\circ}C$ 항온기에 각각 치상하고 시험포장에서 발병된 이병주의 이삭을 2주일간 접종 처리한 결과 무코팅볍씨 처리구의 접종이삭 종자에서는 종자표면에 균총이 형성되었고 종자내에는 소형분생자, 대형분생자 및 균사 발육이 왕성하게 증식된 반면에 규산코팅볍씨 처리구에서는 소형분생자와 균사는 생존하지 못하였고 대형분생자와 균사체 발육은 크게 위축되었다. 이상의 결과로 규산코팅볍씨의 활용으로 직파재배 시 종자소독 없이도 친환경적 키다리병 방제가 가능하며, 향후 종자소독제로의 개발도 가능할 것으로 판단되었다.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2012년도 제43회 하계 정기 학술대회 초록집
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• pp.386-386
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• 2012

For white light emitting diode (LED) applications, it has been reported that Y3Al5O12:Ce3+ (YAG:Ce) in nano-sized phosphor performs better than it does in micro-sized particles. This is because nano-sized YAG:Ce can reduce internal light scattering when coated onto a blue LED surface. Recently, there have been many reports on the synthesis of nano-sized YAG particles using bottom-up method, such as co-precipitation method, sol-gel process, hydrothermal method, solvothermal method, and glycothermal method. However, there has been no report using top-down method. Top-down method has advantages than bottom-up method, such as large scale production and easy control of doping concentration and particle size. Therefore, in this study, nano-sized YAG:Ce phosphors were synthesized by a high energy beads milling process with varying beads size, milling time and milling steps. The beads milling process was performed by Laboratory Mill MINICER with ZrO2 beads. The phase identity and morphology of nano-sized YAG:Ce were characterized by X-ray powder diffraction (XRD) and field-emission scanning electron microscopy (FESEM), respectively. By controlling beads size, milling time and milling steps, we synthesized a size-tunable and uniform nano-sized YAG:Ce phosphors which average diameters were 100, 85 and 40 nm, respectively. After milling, there was no impurity and all of the peaks were in good agreement with YAG (JCPDS No. 33-0040). Luminescence and quantum efficiency (QE) of nano-sized YAG:Ce phosphors were measured by fluorescence spectrometer and QE measuring instrument, respectively. The synthesized YAG:Ce absorbed light efficiently in the visible region of 400-500 nm, and showed single broadband emission peaked at 550 nm with 50% of QE. As a result, by considering above results, high energy beads milling process could be a facile and reproducible synthesis method for nano-sized YAG:Ce phosphors.

• Composites Research
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• 제27권4호
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• pp.146-151
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• 2014

본 연구에서는 분극 전계에 따른 압전 페인트 센서의 특성을 확인하기 위해 충격힘과 분극 전계를 변화시켜 가면서 실험적인 연구를 수행하였다. 페인트 센서 제작을 위해 유연 압전 재료인 $Pb(Ni_{1/3}Nb_{2/3})O_3-Pb(Zr, Ti)O_2$ (PNN-PZT) 파우더와 경화제를 포함하고 있는 에폭시 수지를 중량비 1:1로 혼합 후 몰드를 사용하여 $40{\times}10{\times}1mm^3$ 크기를 같는 시편을 제작 하였다. 이후 시편의 기공을 제거하기 위해 진공 데시케이터를 사용하였다. 분극 작업을 위해 시편의 전극은 실버페이스트를 윗면과 아랫면에 바르고 하루 동안 건조시켜 제작하였다. 분극 작업은 온도는 상온으로, 분극 시간은 30분으로 고정하고 분극 전계를 달리하여 진행되었다. 1 mm의 두께를 갖는 앞전 페인트센서를 제작하여 실험에 사용하였으며, 감도 측정 및 감도 변화는 충격 망치를 사용하여 시편에 충격을 가했을 때 압전 페인트에서 출력되는 전압과 충격 망치에서 출력되는 전압을 측정 후 신호처리 하여 비교하였다. 그 결과 압전 페인트의 민감도에 분극 전계가 미치는 영향에 대해 평가 하였고 그 결과를 기술하였다.

• Journal of Electrical Engineering and Technology
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• 제10권4호
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• pp.1621-1625
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• 2015

Power quality has always been a concern of power engineers. Certainly an argument can be successfully made that most parts of power engineering have the ultimate objective to improve power quality. AC motors were widely used in industrial and domestic applications. Generally, AC motors were of two types: Induction and Synchronous motors. In motor many parameters like different load cycling, switching, working in hot weather and unbalances creates harmonics which creates major reasons for temperature rise of the motors. Due to high peak value of voltage, harmonics can weaken insulation in cables, windings and capacitors and different electronic components. Higher value of harmonics increase the motor current and decrease the power factor which will reduce the life time of the motor and increase the overall rating of all electrical equipments. Harmonics reduction of all the motors in India will save more power. Coating of windings of the motor with nano fillers will reduce the amount of harmonics in the motor. Based on the previous project works, actions were taken to use the enamel filled with various nano fillers for the coating of the windings of the different AC motors. Ball mill method was used to convert the micro particles of Al₂O₃, SiO₂, TiO₂, ZrO₂ and ZnO into nano particles. SEM, TEM and XRD were used to augment the particle size of the powder. The synthesized nano powders were mixed with the enamel by using ultrasonic vibrator. Then the enamel mixed with the nano fillers was coated to the windings of the several AC motors. Harmonics were measured in terms of various indices like THD, VHD, CHD and DIN by using Harmonic analyzer. There are many other measures and indices to describe power quality, but none is applicable in all cases and in many instances, these indices may hide more than they show. Sometimes power quality indices were used as a basis of comparison and standardization. The efficiency of the motors was increased by 5 – 10 %. The thermal withstanding capacity of the motor was increased by 5º to 15º C. The harmonics of the motors were reduced by 10 – 50%.

• 분석과학
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• 제24권4호
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• pp.275-281
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• 2011

세제 제조시설 폐수의 유기물을 틀로 하여 $Al(OH)_3$과 $H_3PO_4$의 반응으로 $AlPO_4$-계 물질을 합성하였다. 소성된 $AlPO_4$-계 물질을 APTMS, 석신산 무수물과 반응시켜 표면을 카르복실기로 바꾸었다. 분말 XRD 결과, 특징적인 $AlPO_4$-계 물질의 패턴을 얻었으며, 물질의 형태는 SEM으로 조사하였고, 작용기는 FT-IR 분석으로 확인하였다. 증류수에 분산시킨 고체의 표면 전위 측정 결과, $AlPO_4-NH_2$는 양의 표면 전하를 갖는 반면, $AlPO_4$-COOH는 음의 표면 전하를 갖는 것으로 나타났다. 합성된 $AlPO_4$-계 물질을 이용하여 수용액에서 유해 중금속의 제거 실험을 수행하였다. 납 이온은 표면에 존재하는 카르복실기와 착물을 형성하며 물질에 흡착되었고, 흡착 분배계수는 91.1 mL/g이었다. 결론적으로 본 연구에서 고찰한 $AlPO_4$-계 물질은 수환경에서 유해 중금속 이온의 제거에 활용될 수 있을 것이다.