• 한국재료학회지
• /
• 제27권10호
• /
• pp.530-533
• /
• 2017

ZnO micro/nanocrystals with different morphologies were synthesized by thermal evaporation of various zinc source materials in an air atmosphere. Zinc acetate, zinc carbonate and zinc iodide were used as the source materials. No catalysts or substrates were used in the synthesis of the ZnO crystals. The scanning electron microscope(SEM) image showed that the morphology of ZnO crystals was strongly dependent on the source materials, which suggests that source material is one of the key factors in controlling the morphology of the obtained ZnO crystals. Tetrapods, nanogranular shaped crystals, spherical particles and crayon-shaped crystals were obtained using different source materials. The X-ray diffraction(XRD) pattern revealed that the all the ZnO crystals had hexagonal wurtzite crystalline structures. An ultraviolet emission was observed in the cathodoluminescence spectrum of the ZnO crystals prepared via thermal evaporation of Zn powder. However, a strong green emission centered at around 500 nm was observed in the cathodoluminescence spectra of the ZnO crystals prepared using zinc salts as the source materials.

• 한국분무공학회지
• /
• 제24권4호
• /
• pp.203-208
• /
• 2019

In general, the oxi-nitriding method is well known as such a surface treatment way for substantial enhancement in corrosion resistance, even comparable to that of titanium. However, there are still lacks of information on thermal performance of the oxi-nitriding surface being of additional compound layers on the base substrate. Above all, the quantitative measurement of its thermal performance still was not evaluated yet. Thus, the present study experimentally measures the thermal resistance of the oxi-nitriding surface during droplet evaporation and then estimates heat transfer performance with the use of the onedimensional heat transfer model in vertical direction. From the experimental results, it is found that the total evaporation time slightly increased with the thermal resistance caused by the oxi-nitriding layer, showing a maximum difference of approximately 20% with that of the bare surface. Although the heat transfer performance of oxi-nitriding surface became slightly lower than that of the bare surface, the oxi-nitriding surface exhibits much better heat transfer performance compared to titanium.

• 한국연소학회지
• /
• 제21권3호
• /
• pp.7-15
• /
• 2016

The fuel in conventional liquid fuel combustor is atomized by spray method for high efficiency and low emissions. To improve the overall fuel efficiency and lower pollutant emissions in liquid fuel combustion systems, the effective spatial and temporal separation of droplet evaporation from normal spray process is needed. In this paper, the recuperation of high temperature burnt gas for fuel evaporation was proposed to develop a cylindrical premixed combustor. The recuperation process using U shaped tube is effective to evaporate the liquid fuel. The results show that the flame mode is changed into red radiation flame, blue flame and lift off flame with decreasing equivalence ratio as gas fuel combustion mode. In particular, the blue flame is found to be very stable at heating load 9.2 kW and equivalence ratio 0.731. NOx was measured blow 105 ppm ($O_2$ zero base) from equivalence ratio 0.705 to 0.835. CO which is a very important emission index in liquid fuel combustor was observed below 5 ppm ($O_2$ zero base) under the same equivalence region.

• Journal of Astronomy and Space Sciences
• /
• 제19권3호
• /
• pp.181-186
• /
• 2002

We study a role of the proto-accretion disk during the formation of the planetary system, which is motivated with recent X-ray observations. There is an observational correlation of the mass of extrasolar planets with their orbital period, which also shows the minimum orbital period. This is insufficiently accounted for by the selection effect alone. Besides, most of planetary formation theories predict the lower limit of semimajor axes of the planetary orbits around 0.01 AU. While the migration theory involving the accretion disk is the most favorable theory, it causes too fast migration and requires the braking mechanism to halt the planet~0.01 AU. The induced gap in the accretion disk due to the planet and/or the truncated disk are desperately required to stop the planet. We explore the planetary evaporation in the accretion disk as another possible scenario to explain the observational lack of massive close-in planets. We calculate the location where the planet is evaporated when the mass and the radius of the planet are given, and find that the evaporation location is approximately proportional to the mass of the planet as ${m_p}^{-1.3}$ and the radius of the planet as ${r_p}^{1.3}$. Therefore, we conclude that even the standard cool accretion disk becomes marginally hot to make the small planet evaporate at~0.01 AU. We discuss other auxiliary mechanisms which may provide the accretion disk with extra heats other than the viscous friction, which may consequently make a larger planet evaporate.

• 열처리공학회지
• /
• 제14권5호
• /
• pp.292-296
• /
• 2001

In this work, an ultra-high vacuum activated reactive evaporation equipment was built. With reaction of Al and oxygen plasma, $Al_2O_3$ was deposited on the surface of etched Al foil. The chamber was evacuated down to $2{\times}10^{-7}$ torr initially. The Ar and $O_2$ gas introduced into the chamber to maintain $5{\times}10^{-5}$ torr during deposition. Ar gas prevents recombining of the ionized oxygen. Evaporation was maintained by electron beam evaporator continuously. Heating filament and electrode were used in order to generate plasma. The substrate bias of -300V was introduced to accelerate deposition of evaporated Al atoms. The composition and morphology of deposited $Al_2O_3$ films were analyzed by x-ray photoelectron spectroscopy(XPS) and atomic force microscopy (AFM), respectively. The Al oxide was formed on the surface of etched Al foil. According to AFM results, the surface morphology of $Al_2O_3$ film indicates uniform feature. Dielectric characteristic was measured as a function of frequency. Measured withstanding voltage and capacitance were 52V and $24{\mu}F/cm^2$, respectively. The obtained $Al_2O_3$ film shows clean condition without contaminants, which could be adapted to capacitor production.

• 한국신재생에너지학회:학술대회논문집
• /
• 한국신재생에너지학회 2011년도 추계학술대회 초록집
• /
• pp.58.1-58.1
• /
• 2011

CIS(CuInSe2)계 화합물 태양전지는 높은 광흡수계수와 열적 안정성으로 고효율 태양전지 제조가 가능하여 태양전지용 광흡수층으로 매우 이상적이다. 미국 NREL에서는 이러한 CIGS 태양전지를 Co-evaporation 방법으로 제조 20%이상의 에너지 변환 효율을 달성하였다고 보고하였다. CIGS 태양전지의 경우 기존의 유리 기판 대신 유연한 철강 기판을 사용해 태양 전지를 flexible하게 제조 할 수 있다는 장점이 있다. 이러한 flexible 태양전지의 경우 기존의 rigid 태양전지의 적용분야 뿐만 아니라 BIPV, 선박, 장난감, 군용, 자동차등 더욱 더 많은 분야에 활용이 가능하다. 본 연구에서는 기존의 rigid한 기판인 soda lime glass와 flexible 기판인 stainless steel 기판으로 소자를 제조하여 효율을 비교 분석 및 stainless steel 기판의 표면 처리 방법에 따라서 표면 조도의 특성을 분석하여 stainless steel 기판별 효율 특성도 비교 분석 하였다. 후면전극으로는 약 $1{\mu}m$의 Mo를 DC Sputtering 방법을 이용하여 증착하였고, CIGS 광흡수층은 약 $2.5{\mu}m$의 두께로 미국의 NREL과 같은 3 stage 방식을 이용하여 광흡수층을 Co-Evaporation 방법으로 제조하였고, 버퍼층인CdS는 약 50nm의 두께로 CBD 방법으로 제조 하였으며, 창층인 ZnO는 약 500nm 두께로 RF Sputtering 방법으로 제조 하였고, 마지막으로 약 $1{\mu}m$ 두께의 Al 전면전극은 Thermal Evaporation 방법으로 제조 하였다. 소자의 물리적, 전기적 특성을 분석하기위해 FE-SEM, AFM, Solar Cell Simulator 분석을 실시하였다.

• 한국자동차공학회논문집
• /
• 제3권6호
• /
• pp.8-22
• /
• 1995

Three dimensional numerical study of non-evaporating and evaporating spray characteristics was performed in a quiescent and motoring condition of direct injection diesel engine. The calculation parameter was breakup model. The breakup models used were Reitz & Diwakar model and TAB model. The modified k-${\varepsilon}$ turbulence model considering the compressibility effect due to the compression and expansion of piston was used. The calculation results of the spray tip penetration and tip velocity using the TAB model showed similar trends comparing with the experimental data. Although the evaporation rate was not nearly affected with the breakup model at the higher injection pressure, in the low injection case, the evaporation rate result using the TAB model became higher than that of R&D model. The evaporation rate was increased with the injection pressure due to the vigorous interaction with the gas field.

• 한국결정학회지
• /
• 제14권1호
• /
• pp.35-38
• /
• 2003

증기-확산 단백질 결정화의 물-증발 속도를 조절하기 위해서, 간결한 모세관 내의 다중-단계 농도 장착법 (multistep-concentration setting in capillaries) 이 이용되었다. “조절 용액 (regulatory solution)”이라고 일컬어지는 2차 침전 용액이 이용되어, 이 방법으로 다양한 증발 속도 곡선들이 얻어졌다. 이때, 조절 용액은 단백질 용액에 직접적으로 노출되지 않는다. 모델 단백질인 lysozyme의 결정화에 이 그래프들이 적용되었다. 결정 성장은 증발속도에 달려있다는 것을 실험 결과들이 명백하게 보여주었다. 특히나. 단백질 용액의 침전 농도가 어떤 점까지 증가하다가 평형 농도로 줄어드는 decoupling 곡선이 가장 좋은 결정들을 만들어냈다.

• 한국농공학회지
• /
• 제18권4호
• /
• pp.4226-4231
• /
• 1976

The objective of this study is to investigate the characteristics of the concrete mixture and the plastic shrinkage of concrete exposed to a rapid evaporation immediately after placement, and to measure the shringkage rate according to the cement-mixture. Drying of concrete was conducted under a controlled chamber in which the temperature was 36${\pm}$2$^{\circ}C$, the relative humidity 45${\pm}$2%, and the wind velocity 4${\pm}$1m/sec. All of the concrete mo1ds were made to have good workability as 6${\pm}$0.5cm in slump. The results obtained are as follows; 1) The evaporation rate was 3.36kg/$\textrm{km}^2$, 2.98kg/$\textrm{km}^2$ and 2.91kg/$\textrm{km}^2$ respectively for each concretemixtures 365kg, 335kg and 317kg after 5 hour exposure, and the evaporation was measured at all 55∼57% after 2 hours and additional in 10% on after 5 hours exposure. 2) The weight of the concrete were was reduced to 3.0%, 2.6% and 2.4% respectively for each of them. 3) The shrinkage of concrete was 0.87 mm/m, 0.56mm/m and 0.31 mm/m after 5 hour exposure, and the shringkage of concrete was measured at 84%, 59% and 45% after 2 hours and it in 1∼5% after 5 hour exposure and then stopped. 4) A recommendation for good concrete is that the evaporation should be minimized during 2 hours after placement of concrete, if possible.

• 대한전자공학회:학술대회논문집
• /
• 대한전자공학회 2006년도 하계종합학술대회
• /
• pp.569-570
• /
• 2006

Effects of the evaporation rate of MgO films using electron beam were investigated on the MgO properties and the discharge characteristics of the plasma display panel (PDP). The evaporation rate was changed from $3{\AA}$/sec to $15{\AA}$/sec at a substrate temperature of $300^{\circ}C$. MgO properties such as crystal orientation, surface roughness, contact angle, and film structure were inspected using XPS, AFM, drop shape analysis and SEM. We also studied the relation between MgO properties and PDP discharging characteristics. The minimum firing voltage and maximum efficacy were obtained at evaporation rate of $5{\AA}$/sec. In the MgO film deposited at $5{\AA}$/sec, (200) orientation was most intensive and surface roughness was minimum.