최근에 반도체의 식각 및 증착, 금속 및 고분자의 표면처리, 신물질의 합성 등에서 저온플라즈마(low-temperature plasma)가 이용되고 있으며, 공정의 미세화 및 저온화 때문에 응용분야가 점점 더 확대되고 있다. 본 연구는 전분의 인산화 반응에 있어 유전체 장벽 방전(dielectric barrier discharge, DBD) 저온플라즈마를 친환경 반응촉매로서의 적용 가능성을 탐색하는 것이다. 전분의 인산화를 위한 반응혼합물을 제조하기 위해, NaH2PO4와 Na2HPO4를 탈이온수에 용 해시켜 pH를 4, 5, 6으로 조정한 후 일반옥수수전분을 가하여 상온에서 20분 동안 교반하여 50℃에서 수분함량이 10% 미만이 될 때까지 건조하고 분쇄·선별하였다. 제조된 반응혼합물은 DBD 저온플라즈마 장치에 수용하여 밀폐하 고 아르곤(Ar) 가스를 공급하면서 결정된 전압에서 유전체 장벽을 방전시켜 형성된 저온플라즈마 하에서 일정시간 동 안 처리하였다. 전분의 인산화에 대한 DBD 저온플라즈마의 처리조건의 영향을 조사하기 위해 반응혼합물의 pH (4, 5 및 6), 전압(100, 120 및 140 V), 처리시간(10, 20 및 30 min)을 요인으로 하여 Box-Benhken 실험디자인으로부터 17 개의 실험점들을 설계하였다. 실험조건에 따라 처리된 반응혼합물들은 50% 에탄올 수용액으로 세척한 후 신속점도분 석기를 이용하여 페이스팅 점도를 조사하였다. 처리되지 않은 반응혼합물의 페이스팅 점도에 대한 처리된 반응혼합물 의 페이스팅 점도의 변화량을 반응표면분석법을 이용하여 분석하였다. DBD 저온플라즈마 처리는 반응혼합물의 페이 스팅 점도를 무처리 반응혼합물의 페이스팅 점도에 비해 증가시키거나 낮추는 효과를 나타내었다. 따라서 저온플라즈 마 처리를 통해 전분과 인산염 사이의 인산화 반응을 달성할 수 있는 것으로 생각된다.

저온플라즈마(low-temperature plasma)는 미생물의 외벽을 개질시킴으로서 살균효과를 나타낸 것으로 알려져 있다. 본 연구의 목적은 전분과 구연산 사이의 에스테르화에 있어 친환경 반응촉매로서 마이크로웨이브 방전(MW) 저온플 라즈마의 활용가능성을 조사하였다. 일반옥수수전분과 구연산용액(pH 3.5)을 혼합하고 45℃에서 수분함량이 8~10%가 될 때까지 건조하여 반응혼합물을 제조하였다. 구연산은 전분의 건조중량대비 10%와 20% 이었다. 반응혼합물은 N2 및 N2/O2 혼합가스(80:20, v/v)로 치환된 진공상태의 마이크로웨이브 오븐 안에서 마이크로웨이브(900 W)를 발진시켜 형성된 저온플라즈마 하에서 20분 동안 노출되었다. 처리된 반응혼합물은 50% 에탄올 수용액으로 3회 세척하여 전분 과 반응하지 않은 무수구연산을 제거하였다. FT-IR을 이용하여 세척된 반응혼합물의 작용기들을 조사하였을 때, 낮은 강도이지만 1750 cm -1 파장 부근에서 새로운 피크(ester 작용기)가 확인되었다. 따라서 고온, 장시간의 열처리 없이 전 분과 구연산 사이의 에스테르화에 대해 MW 저온플라즈마가 촉매작용하였다. MW 저온플라즈마 처리에 의해 형성된 구연산전분의 표면구조, 몰치환도 및 물리화학적 특성들을 조사하였다. 입자표면이 함몰된 구연산전분 입자들이 빈번 히 관찰되었으나 반응가스 및 구연산 농도에 따른 차이는 구별할 수 없었다. 몰치환도는 0.013~0.015 범위에 있었으며 처리군들 사이에서 통계적으로 유의적인 차이는 없었다. 한편 N2 환경 하에서 형성된 구연산전분은 구연산 농도가 증 가하면서 페이스팅 점도가 생전분에 비해 증가하였으나, N2/O2 혼합가스 환경 하에서 형성된 구연산전분은 생전분에 비해 낮은 페이스팅 점도를 나타내었고 구연산 농도에 따라 차이를 보이지 않았다. 전반적인 결과를 고려할 때, MW 저온플라즈마는 전분의 수산기와 구연산의 카르복실기 사이의 에스테르화를 위한 반응촉매로 잠재력을 보유하고 있 는 것으로 생각된

국내 선식의 유통 안전성 확보를 위한 기초기반연구로 저온플라즈마 처리한 시판 선식의 품질 특성 평가를 진행하 였다. 본 연구에서 사용한 플라즈마 시스템은 서울대학교에서 개발된 컨테이너형 유전격벽 플라즈마로 방전 가스는 공기를 활용하여 0, 5, 10 및 20분간 처리하였고 미생물 감균효과, 색도, 과산화물가 및 관능평가를 국립식량과학원 및 서울대학교에서 공동으로 수행하였다. 일반 호기성 미생물 분석 결과 20분 처리 시 약 1.70 log CFU/g 감소하였으며, Bacillus cereus 및 Escherichia coli O157:H7을 이용한 접종 시험 결과 각각 2.20 및 2.50 log CFU/g 감소하였다. 색도 측정 결과 플라즈마 처리에 의해 명도 값은 증가하였으나 적색도 및 황색도 값은 감소하는 경향을 보였다. 하지만 플 라즈마 처리에 의해 지질 산화가 일어나 관능적 품질이 저하되는 경향을 확인할 수 있었다. 본 연구 결과 공기로 방전 한 저온 플라즈마 기술은 선식의 품질안전성을 개선할 수 있으나, 관능적 식미향상 및 품질개선을 위한 후속연구가 필요하다고 판단된다.

The metal plating industry produces a large amount of wastewater generally containing heavy metals with various chemical compounds; as such, treating the wastewater is both an environmental and an economic challenge. A vacuum evaporation system has been developed to effectively reduce the volume of plating wastewater. However, the gas stream discharged from the distillation unit of the evaporator is often contaminated with high concentrations of odorous compounds such as ammonia and dimethyl disulfide (DMDS). In this study, a non-thermal plasma process operated in wet conditions was applied to remove the odorous compounds, and it showed high removal efficiencies of greater than 99% for ammonia and 95% for DMDS. However, the gas flowrate more substantially affected the efficiency of ammonia removal than the efficiency of DMDS removal, because the higher the gas flowrate, the shorter the contact time between the odorous compound and the mist particles in the wet plasma reactor. The analyses of the maximum removal capacity indicated that the wet non-thermal plasma system was effective for treating the odorous compounds at a loading rate of less than 20 mg/m3/min even though the lowest amount of electrical power was applied. Therefore, the wet-type non-thermal plasma system is expected alleviate to effectively abate the odor problem of the vacuum evaporator used in the treatment of plating wastewater.

Microstructural examination of the Nb-Si-B alloys at Nb-rich compositions is performed. The Nb-rich corner of the Nb-Si-B system is favorable in that the constituent phases are Nb (ductile and tough phase with high melting temperature) and T2 phase (very hard intermetallic compound with favorable oxidation resistance) which are good combination for high temperature structural materials. The samples containing compositions near Nb-rich corner of the Nb- Si-B ternary system are prepared by spark plasma sintering (SPS) process using T2 and Nb powders. T2 bulk phase is made in arc furnace by melting the Nb slug and the Si-B powder compact. The T2 bulk phase was subsequently ballmilled to powders. SPS is performed at 1300oC and 1400oC, depending on the composition, under 30 MPa for 600s, to produce disc-shaped specimen with 15 mm in diameter and 3 mm high. Hardness tests (Rockwell A-scale and micro Vickers) are carried out to estimate the mechanical property.

교류형 플라즈마 디스플레이에서 기입기간 중 방전지연시간을 단축시키기 위하여 공통전극에 추가펄스 인가 하였을 때의 플라즈마 방전이 시뮬레이션 되고 기입 광파형이 측정되었다. AC PDP의 초기화 기간 동안 셀 내부에는 벽전하가 쌓이고 그것들은 기입 기간에 주사와 기입펄스에 의해 기입방전을 트리거링 시키기 위하여 이용되어진다. 그러나 종래에는 공통전극에는 DC 바이어스 전압에 의해 음의 전하는 기입방전에 이용되지 못하므로 방전지연시간 의 단축은 한계가 있다. 만약 주사와 기입전극의 전하뿐만 아니라 공통전극의 음의 전하를 이용한다면 방전지연시간 은 단축될 것이고 이를 확인하기 위하여 기입기간 동안 3 전극에 펄스가 모두 인가될 때, 진공 자외선을 발생시키는 Xe 3P2 의 에너지 상태가 시뮬레이션 되었다. 또한 종래의 구동방법과 공통 전극에 추가 펄스를 인가한 경우에 기입 방전의 광파형의 단축을 각각 측정되었다.

Atmospheric pressure plasma is used in the biological and medical fields. Miniaturization and safety are important in the application of apply atmospheric plasma to bio devices. In this study, we made a small, pocket-sized inverter for the discharge of atmospheric plasma. We used pulse power to control the neutral gas temperature at which the, when plasma was discharged. We used direct current of 5 V of bias(voltage). The output voltage is about 1 to 2 kilo volts the frequency is about 80 kilo hertz. We analyzsed the characteristics of the atmospheric plasma using OES(Optical emission spectroscopy) and the Current-Voltage characteristic of pulse power. By calculating of the current voltage characteristics, we were able to determine that, when the duty ratio increased, the power that actually effects the plasma discharge also increased. To apply atmospheric plasma to human organisms, the temperature is the most important factor, we were able to control the temperature by modulating the pulse power duty ratio. This means we can use atmospheric plasma on the human body or in other areas of the medical field.

Two sintering methods of a pressureless sintering and a spark-plasma sintering are tested to densify the Fe-TiC composite powders which are fabricated by high-energy ball-milling. A powder mixture of Fe and TiC is prepared in a planetary ball mill at a rotation speed of 500 rpm for 1h. Pressureless sintering is performed at 1100, 1200 and 1300oC for 1-3 hours in a tube furnace under flowing argon gas atmosphere. Spark-plasma sintering is carried out under the following condition: sintering temperature of 1050oC, soaking time of 10 min, sintering pressure of 50 MPa, heating rate of 50oC, and in a vacuum of 0.1 Pa. The curves of shrinkage and its derivative (shrinkage rate) are obtained from the data stored automatically during sintering process. The densification behaviors are investigated from the observation of fracture surface and cross-section of the sintered compacts. The pressureless-sintered powder compacts show incomplete densification with a relative denstiy of 86.1% after sintering at 1300oC for 3h. Spark-plasma sintering at 1050oC for 10 min exhibits nearly complete densification of 98.6% relative density under the sintering pressure of 50 MPa.

In this study, ternary compound Max Phase Ti2AlC material was mixed by 3D ball milling as a function of ball milling time. More than 99.5 wt% pure Ti2AlC was synthesized by using spark plasma sintering method at 1000, 1100, 1200, and 1300oC for 60 min. The material characteristics of synthesized samples were examined with relative density, hardness, and electrical conductivity as a function of sintering temperature. The phase composition of bulk was identified by X-ray diffraction. On the basis of FE-SEM result, a terraced structures which consists of several laminated layers were observed. And Ti2AlC bulk material obtained a vickers hardness of 5.1 GPa at the sintering temperature of 1100oC.

SKD11 (ASTM D2) tool steel is a versatile high-carbon, high-chromium, air-hardening tool steel that is characterized by a relatively high attainable hardness and numerous, large, chromium rich alloy carbide in the microstructure. SKD11 tool steel provides an effective combination of wear resistance and toughness, tool performance, price, and a wide variety of product forms. Adding of CNTs increased the performance of mechanical properties more. 1, 3 vol% CNTs was dispersed in SKD11 matrix by mechanical alloying. SKD11 carbon nanocomposite powder was sintered by spark plasma sintering process. FE-SEM, HR-TEM and Raman analysis were carried out for the SKD11 carbon nanocomposites.

High temperature plasma coating technology has been applied to recover damaged aluminum dies from wear by spraying pure aluminum and alumina powder. However, the coated mixed powder layer composed of aluminum and alumina often undergoes a detachment from the substrate, making the coated substrate die unable to maintain its expected life span. In this study, in order to increase the bonding strength between the substrate and the coating layer, a pure aluminum layer was applied as an intermediate bond layer. In order to prepare the specimen with variable bond coating conditions, the bond coat layers with a various gun speed from 10 cm/sec to 30 cm/sec were prepared with coating cycle variations ranging from three to nine cycles. The specimen with a bond coat layer coated with a gun speed of 20 cm/sec and three coating cycles exhibited ~13MPa of adhesion strength, while the specimen without a bond coat layer showed ~6 MPa of adhesion strength. The adhesion strength with a variation of bond coat layer thickness is discussed in terms of coating parameters.

Odor compounds and air-born microorganisms are simultaneously emitted from various aeration processes such as aerobic digestion, food-waste compositing, and carcass decomposition facilities that are biologically-treating wastes with high organic contents. The air streams emitted from these processes commonly contain sulfur-containing odorous compounds such as hydrogen sulfide(H2S) and bacterial bioaerosols. In this study, a wet-plasma method was applied to remove these air-born pollutants and to minimize safety issues. In addition, the effects of a gas retention time and a liquid-gas ratio were evaluated on removal efficiencies in the wet-plasma system. At the gas reaction time of 1.8 seconds and the liquid-gas ratio of 0.05 mLaq/Lg, the removal efficiency of bioaerosol was approximately 75 %, while the removal efficiency of H2S was lower than 20 %, indicating that the gaseous compound was not effectively oxidized by the plasma reaction at the low liquid addition. When the liquid-gas ratio was increased to 0.25 mLaq/Lg, the removal efficiencies of both H2S and bioaerosol increased to greater than 99 %. At the higher liquid-gas ratio, more ozone was generated by the wet-plasma reaction. The ozone generation was significantly affected by the input electrical energy, and it needed to be removed before discharged from the process.

We report the chemical vapor deposition growth characteristics of graphene on various catalytic metal substrates such as Ni, Fe, Ag, Au, and Pt. 50-nm-thick metal films were deposited on SiO2/Si substrates using dc magnetron sputtering. Graphene was synthesized on the metal/SiO2/Si substrates with CH4 gas (1 SCCM) diluted in mixed gases of 10% H2 and 90 % Ar (99 SCCM) using inductively-coupled plasma chemical vapor deposition (ICP-CVD). The highest quality of graphene film was achieved on Ni and Fe substrates at 900˚C and 500 W of ICP power. Ni substrate seemed to be the best catalytic material among the tested materials for graphene growth because it required the lowest growth temperature (600˚C) as well as showing a low ICP power of 200W. Graphene films were successfully grown on Ag, Au, and Pt substrates as well. Graphene was formed on Pt substrate within 2 sec, while graphene film was achieved on Ni substrate over a period of 5 min of growth. These results can be understood as showing the direct CVD growth of graphene with a highly efficient catalytic reaction on the Pt surface.

This study attempted to decompose typical odorous VOCs including toluene, isopropyl alcohol, benzene and acetone using a dielectric barrier discharge plasma in a pilot experiment scale up to 60 m3/min. It utilized oxygen ions(205,000 ions/cm3) and various radicals formed by a plasma generator. Although ozone as a byproduct( approximately 300 ppb) contributes to destroying organic compounds in their gas phase, the residual release could be captured by post manganese filters showing a maximum 30% removal. The present process was more effective for acetone, which is composed of relatively simple molecules, with a 56% decomposition rate. Whilst toluene, benzene and isopropyl alcohol were shown to have of rates of 19%, 37% and 36% respectively.

This study was performed to obtain high conversion efficiency of C7H8 using non-thermal plasma and metal-supported catalyst. Adsorption-desorption characteristics of toluene was performed using 4A type (Zeolite) filled in a concentration reactor. Through this test, it was found that the concentration reactor has 0.020 g/g of adsorption capacity (at ambient temperature and pressure) and 3,600 ppm of desorption property at 150℃ (with in 20 min). In case of developed catalyst, toluene decomposition rate of Pd-AO (Pd coated catalyst) was better than Pd/Cu-AO and Pd/Ag-AO (Pd/Ag composite metal catalyst). Developed non-thermal plasma system was obtained flame amplification effect using injection process of desorbed tolune, and 98% of removal efficiency.

Effect of oxygen content in the ultrafine tungsten powder fabricated by electrical explosion of wire method on the behvior of spark plasma sintering was investigated. The initial oxygen content of 6.5 wt% of as-fabricated tungsten powder was reduced to 2.3 and 0.7 wt% for the powders which were reduction-treated at 400˚C for 2 hour and at 500˚C for 1h in hydrogen atmosphere, respectively. The reduction-treated tungsten powders were spark-plasma sintered at 1200-1600˚C for 100-3600 sec. with applied pressure of 50 MPa under vacuum of 0.133 Pa. Maximun sindered density of 97% relative density was obtained under the condition of 1600˚C for 1h from the tungsten powder with 0.7 wt% oxygen. Sintering activation energy of 95.85kJ/mol-1 was obtained, which is remarkably smaller than the reported ones of 380~460kJ/mol-1 for pressureless sintering of micron-scale tungsten powders.

AC PDP의 부화면 시간동안 기입 방전의 시간지연을 각각 조사하였고 기입방전 마진 범위 내에서 추 가 주사전압의 높이를 변화하여 전체 부화면 시간동안 기입방전 시간을 단축시킨다. 첫번째 초기화 기간 동안 높은 상승 경사파 전압이 주사전극에 인가되어 초기화 방전이 발생하고 셀 내부에서 벽전하를 생성한다. 생성된 벽전하는 기입전압과 더해져서 기입 방전을 일으킨다. 첫 번째 부화면 시간에는 초기화 기간 동안 상승 경사파를 갖는 높은 전압에 의해 벽전하가 많이 존재하므로 첫 번째 기입 방전은 다른 부화면 시간보다 빠르게 형성된다. 한편, 두 번째부터 마지막 부화면 시간까지의 기입 방전 생성시간은 셀 내의 벽전하 소멸에 의하여 점차적으로 늦어진다. 본 연구에서는 각 부화면 시간동안 기입방전의 시간지연을 조사하였고, 부화면 시간의 기입기간 마다 추가 주사전압을 다르게 인가하여 전체 기입방전 지연시간을 단축시키는 방법을 제시한다.