• 한국세라믹학회지
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• 제15권2호
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• pp.72-78
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• 1978

The vapor pressure of the high melting point oxides, MgO, $Cr_2O_3$, and $MgCr_2O_4$ were measured over the temperature range 1300 to 175$0^{\circ}C$ under vacuum <$10^{-5}$ torr by the Langmuir and the Knudsen method. The Langmuir vapor pressure was increased with elevating temperature and with increasing porosity of the specimen. The difference between the vapor preseures measured by the Langmuir and the Knudsen method was decreased with elevating temperature and the Langmuir vapor pressure finally reached the Knudsen vapor pressure at the melting point when extrapolated. The vapor pressure of other important oxides with high melting points, i.e., $Al_2O_3$, $ThO_2$, $Yb_2O_3$ and $Y_2O_3$ were cited from the references. The Langmuir and the Knudsen vapor pressure of these oxides also showed the same results, i.e., they showed the same value at their melting points.

• 한국진공학회지
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• 제9권4호
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• pp.394-399
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• 2000

Underlayer의 종류 및 두께가 Al 박막의 texture 및 면저항 변화에 미치는 영향을 연구하였다. Al의 underlayer로는 ionized physical vapor deposition(I-PVD)에 의해 제조된 Ti와 I-PVD Ti 위에 metalorganic chemical vapor deposition(MOCVD)에 의해 제조된 TiN을 적층한 구조가 사용되었으며, 각각에 대해 두께를 변화시키면서 Al 박막의 배향성, 면저항을 조사하고, $400^{\circ}C$, $N_2$분리기에서 열처리하면서 면저항의 변화를 조사하였다. I-PVD Ti만을 Al의 underlayer로 사용한 경우, Ti두께가 5 nm이어도 Al 박막이 우수한 <111> 배향성을 나타내었으나, Al-Ti반응 때문에 열처리 후 Al 배선의 면저항이 크게 상승하였다. I-PVD 와 Al 사이에 MOCVD TiN을 적용함에 의해 Al <111> 배향성의 큰 저하없이 Al-Ti 반응에 의한 면저항의 증가를 억제할 수 있었으며, MOCVD TiN의 두께가 4 nm 이하일 때 특히 우수한 Al <111> 배향성을 나타내었다.

• 한국전기전자재료학회논문지
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• 제33권4호
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• pp.315-320
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• 2020

Methylammonium lead iodide (MAPbI₃) thin films were grown at low temperatures on glass substrates via 3-zone chemical vapor deposition. Lead iodide (PbI₂) and lead bis (dipivaloylmethanate) [Pb(dpm)₂] precursors were used as lead sources. Due to the high sublimation temperature (~400℃) of the PbI₂ precursor, a low substrate temperature could not be constantly maintained. Therefore, MAPbI₃ thin films degraded into the PbI₂ phase. In contrast, for the Pb(dpm)₂ precursor, a substrate temperature of ~120℃ was maintained because the sublimation temperature of Pb(dpm)₂ is as low as 130℃ at a high vapor pressure. As a result, high-quality MAPbI₃ thin films were successfully grown on glass substrates using Pb(dpm)₂. The rms (root-mean-square) roughness of MAPbI₃ thin films formed from Pb(dpm)₂ was as low as ~19.2 nm, while it was ~22.7 nm for those formed using PbI₂. The grain size of the films formed from Pb(dpm)₂ was as large as approximately 350 nm.

• 공업화학
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• 제27권3호
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• pp.335-341
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• 2016

본 연구에서는 지상 및 미소중력환경하에서 물리적 승화법 공정에서의 확산-대류유동에 미치는 불순물의 영향을 이론적으로 $Hg_2Cl_2-I_2$ 시스템에 적용하여 규명하는 것이다. 이론적 해석은 증기상에서 확산-대류 흐름, 열 및 물질전달을 속도 벡터 흐름, 유선, 온도, 농도 분포를 통하여 제시된다. 결정 영역에서의 전체 몰플럭스는 중력가속도와 성분 $I_2$, 불순물에 상당히 민감하게 반응한다. 성분 $I_2$을 증가시켰을 때, 농도 대류효과는 확산-대류 유동흐름을 안정화시키는 경향이 있다. 지상중력가속도의 0.001환경에서는 유동흐름은 1차원포물선의 흐름 구조를 나타내며, 확산지배형태를 보여주고 있다. $10^{-3}$지상중력가속도 이하에서는 대류 영향은 무시할 수 있다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집E
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• pp.51-56
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• 2001

Vapor explosion is one of the most important problems encountered in severe accident management of nuclear power plants. In spite of many efforts, a lot of questions still remain for the fundamental understanding of vapor explosion phenomena. Therefore, KAERI launched a real material experiment called TROI using 20 kg of UO2 and ZrO2 to investigate the vapor explosion phenomena. In addition, a small-scale experiment with molten-tin/water system was performed to quantify the characteristics of vapor explosion and to understand the phenomenology of vapor explosion. A number of instruments were used to measure the physical change occurring during the vapor explosion. In this experiment, the vapor explosion generated by molten fuel water interaction is visualized using high speed camera and the pressure behavior accompanying the explosion is investigated.

• Journal of Korean Society for Atmospheric Environment
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• 제17권E3호
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• pp.101-107
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• 2001

Source profiles were developed for a total of 45 volatile organic compounds (VOC) that can be emitted from gasoline evaporation. The gasoline samples of five major brands (for each season) were blended on the basis of the market share in Seoul area and analyzed by a GC-MS/FID system. In addition, we calculated gasoline evaporative compositions using the Raoult's law from the liquid gasoline compositions. The measured and estimated gasoline vapor compositions agree well each other. As a group, alkanes are the most abundant in the gasoline vapors profiles (77.4% on average), followed by alkenes (19.1%), and aromatics (1.7%). As a specie in gasoline vapor, i-pentane is the most abundant, followed by n-butane, n-pentane, i-butane, trans-and cis-2-butenes, 2-methyl-2-butene, and trans-and cis-2-pentenes . It was also seen that aromatic content was much lower in the vapor phase compositions. From the comparison between experimental and calculated compositions, we identified the fact that once the gasoline vapor composition is reliably constructed entirely from the measured gasoline composition and the Raoult's law calculations, the need for doing separate chemical analyses of the gasoline vapor can be reduced.

• Restorative Dentistry and Endodontics
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• 제10권1호
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• pp.85-92
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• 1984

The aim of this study was to examine the influence of the speed of grinding and coolants on mercury vaporization during amalgam removal. Forty amalgam filled stone dies were stored at $37^{\circ}C$ and 100% relative humidity for 7 days prior to the beginning of the mercury vapor experiment and were divided into 4 different groups; In Group I; Used by high speed without coolant & evacuator during amalgam removal. In Group II; Used by high speed with coolant & evacuator during amalgam removal. In Group III; Used by low speed without coolant & evacuator during amalgam removal. In Group IV; Used by low speed with coolant & evacuator during amalgam removal. The amalgam specimens were removed in a 30-second time period and mercury vapor was collected with membrane filter at 27mm from the site of removal and 45 degree above there. Samples in Group II, IV were removed with coolant spray at a flow rate of 30 ml/min with high-velocity evacuator. Mercury vapor collected membrane filter was analysed by Atomic Absorption Spectrophotometer using cold vapor method. The results were as follows; 1. The mercury vapor levels were obtained all of the Groups. 2. The mercury vapor levels of the Group II, IV (with coolant & evacuator) were less than that of the Group I, III (without coolant & evacuator). 3. The highest mercury vapor level recorded during amalgam removal procedure was Group I (used by high speed without coolant & evacuator) and its record was $0.78{\pm}0.09\;mg/m^3$, which exceed the T.L.V. by 15 times. 4. The mercury vapor level of the Group IV (used by low speed with coolant & evacuator) was more than that of the Group II (used by high speed with coolant & evacuator), but its difference was not significant, statistically. (p > 0.05)

• Applied Science and Convergence Technology
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• 제24권6호
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• pp.262-267
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• 2015

We demonstrate the growth of single-walled carbon nanotubes (SWNTs) using ethylene-based chemical vapor deposition (CVD) and ferritin-induced catalytic particles toward growth temperature reduction. We first optimized the gas composition of $H_2$ and $C_2H_4$ at 500 and 30 sccm, respectively. On a planar $SiO_2$ substrate, high density SWNTs were grown at a minimum temperature of $760^{\circ}C$. In the case of growth using nanoporous templates, many suspended SWNTs were also observed from the samples grown at $760^{\circ}C$; low values of $I_D/I_G$ in the Raman spectra were also obtained. This means that the temperature of $760^{\circ}C$ is sufficient for SWNT growth in ethylene-based CVD and that ethylene is more effective that methane for low temperature growth. Our results provide a recipe for low temperature growth of SWNT; such growth is crucial for SWNT-based applications.

• 방사성폐기물학회지
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• 제8권2호
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• pp.151-158
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• 2010

무에 대한 $I_2$ 증기의 작물체 침적속도와 뿌리 전류계수를 측정하기 위하여 파종 후 29 일에서 53 일 사이에 생육시기별로 작물체를 $I_2$ 증기에 80 분 간 피폭시켰다. 피폭은 오전 중에 투명한 상자 내에서 수행되었다. 침적속도($ms^{-1}$)는 대체로 $1.0{\times}10^{-4}{\sim}2.0{\times}10^{-4}$의 범위로 생육밀도가 높을수록 증가하는 경향이었다. 또한 상대습도가 높을 경우 값이 커진다는 기존 보고와 어느 정도 일치하였다. 본 침적속도는 몇몇 야외 측정치보다 수 십 배 정도 낮았고 이는 주로 피폭상자 내의 낮은 풍속($0.2\;ms^{-1}$ 내외)에 기인하는 것으로 추정되었다. 뿌리 전류계수(작물체 총침적량에 대한 수확시 뿌리 내 함유량의 비)는 다소 보수적으로 계산하여 파종 후 29 일 피폭에서 $1.3{\times}10^{-3}$, 파종 후 53 일 피폭에서는 $5,0{\times}10^{-3}$이었다. 본 실험결과의 이용에 있어서는 기상 조건, 요오드의 물리화학적 형태 등에 유의할 필요가 있다.

• Bulletin of the Korean Chemical Society
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• 제15권1호
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• pp.79-83
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• 1994

The organometallic chemical vapor deposition of single precursors, $[Me_2Al({\mu}-NHR)]_2\;(R=^iPr,\;^tBu)$, for alumininum nitride thin films has been investigated to evaluate their poroperties as potential precursors. In chemical vapor deposition processes the gas phase products scattered from a Ni(100) substrate were analyzed by mass spectrometry and the deposited films were characterized by X-ray photoelectron spectroscopy (XPS). The optimum temperatures for the formation of AlN films have been found to be between 700 K and 800 K. Carbon contamination of the films seems to be attributed mainly to the methyl groups bonded to the aluminum atoms. It is apparent that $^tBu$ group is better than $^iPr$ group as a substituent on the nitrogen atom of the single precursors for the AlN thin film formation.