• Journal of the Korean Institute of Gas
• /
• v.6 no.4 s.18
• /
• pp.8-16
• /
• 2002

Since hydrate has been discovered on the earth, many numbers of experimental studies have been conducted for characterizing the fundamental properties of hydrates, such as equilibrium conditions, thermodynamic properties, structures, kinetics, etc. It is considered naturally occurred hydrates in porous rocks have a great potential as a future of unconventional energy resources, and the investigations of formation and dissociation of hydrates in porous media are required. In this study, an experimental apparatus was designed to perform experiments of hydrates in porous core. With the apparatus developed, firstly, isochoric experiments were conducted to find hydrate equilibrium conditions in porous media, and the results were compared with reference data to verify experimental apparatus and methods in this study. Secondly, experiment of formation was examined by observing the behaviors of pressure and electrical resistance and the effects of initial water saturation on formation were analysed.

• Applied Chemistry for Engineering
• /
• v.18 no.2
• /
• pp.136-141
• /
• 2007

The decomposition of chlorinated methanes including $CCl_4$, $CCl_3H$, and $CCl_2H_2$ was carried out using a thermal plasma process and the characteristics of the process were investigated. The thermal equilibrium composition was analyzed with temperature by Fcatsage program. The decomposition rates at various process parameters including the concentration of reactants, flow rate of carrier gas, and quenching rate, were evaluated, where sufficiently high conversion over 92% was achieved. The generation of main products was strongly influenced by the reaction atmosphere; carbon, chlorine, and hydrogen chloride at neutral condition; carbon dioxide, chlorine, and hydrogen chloride at oxidative condition. The decomposition mechanism was speculated considering the results from Factsage and the identification of generated radicals and ionic species. The main decomposition pathways were found to be dissociative electron attachment and oxidative by radicals formed in a plasma state.

• Applied Chemistry for Engineering
• /
• v.28 no.3
• /
• pp.339-344
• /
• 2017

Reaction characteristics and catalytic activities on reverse water gas shift (RWGS) reaction over $Pt/TiO_2$ catalyst and Pt based catalysts added promoters were investigated. It was confirmed that RWGS reaction activity was affected by the kind of supports and active metals and the $Pt/TiO_2$ catalyst showed the highest catalytic activity. From various inlet $CO_2$ concentration tests and also the evaluation of thermodynamic equilibrium conversion, the catalytic activity of $Pt/TiO_2$ catalyst could be evaluated objectively and it was found to be higher than that of commercial catalysts. The catalytic activity could increase by adding Ca and Na as promoters. The XPS analysis revealed that the catalytic activity is closely correlated with the electron density of surface active sites.

• Journal of the Korean Chemical Society
• /
• v.28 no.4
• /
• pp.231-237
• /
• 1984

The x-values in the nonstoichiometric chemical formulas $YO_{1.5+x}\;and\;HoO_{1.5+x}$, have been measured in the temperature range from 700$^{\circ}$C to 1000$^{\circ}$C under oxygen pressures from $2{\times}l0^{-1}\;to\;1{\times}10^{-6}$ atm by gravimetric method. The observed x-values increase with increasing temperature and oxygen pressure. The enthalpies of formation of excess oxygen in yttrium oxide and holmium oxide decrease with decreasing oxygen pressure and are all positive values representing an endothermic process. The 1/n values calculated from the slopes of the plots of log x vs. log $P_{O2}$ increase with temperature and are positive values which means the higher oxygen pressure dependence at higher temperature. We have examined the nonstoichiometric defect and conduction mechanism from x-values and thermodynamic data.

• Journal of the Korean Chemical Society
• /
• v.59 no.1
• /
• pp.9-17
• /
• 2015

The density functional theory (DFT) calculations on $(H_2O)_n@C_{60}$, (n=1-10) complexes have been performed to elucidate hydrogen interaction between fullerene and water clusters. The optimized geometries, harmonic vibrational frequencies, and binding energies are predicted at various levels of theory. The harmonic vibrational frequencies for the molecules considered in this study show all real numbers implying true minima. We also compare the H-bond interaction between $(H_2O)_n$ and $(H_2O)_n@C_{60}$, (n=1-10) clusters.

• Nuclear Engineering and Technology
• /
• v.28 no.2
• /
• pp.103-117
• /
• 1996

A mathematical model of vapor explosion propagation is presented. The model predict two-dimensional, transient flow fields and energies of the four fluid phases of melt drop, fragmented debris, liquid coolant and vapor coolant by solving a set of governing equations with the relevant constitutive relations. These relations include melt fragmentation, coolant-phase-change, and heat and momentum exchange models. To allow thermodynamic non-equilibrium between the coolant liquid and vapor, an equation of state for oater is uniquely formulated. A multiphase code, TRACER, has been developed based on this mathematical formulation. A set of base calculations for tin/water explosions show that the model predicts the explosion propagation speed and peak pressure in a reasonable degree although the quantitative agreement relies strongly on the parameters in the constitutive relations. A set of calculations for sensitivity studies on these parameters have identified the important initial conditions and relations. These are melt fragmentation rate, momentum exchange function, heat transfer function and coolant phase change model as well as local vapor fractions and fuel fractions.

• Journal of the Korean Applied Science and Technology
• /
• v.37 no.5
• /
• pp.1222-1228
• /
• 2020

The adsorption and ion exchange properties of tin phosphate were studied in an aqueous solution of KCl, varing the pH and metal ion concentration in the solution. The data were explained on the basis of chemical equilibrium. Tin phosphate behaved as an acidic ion exchanger and had an adsorption selectivity toward the bivalent transition metal ions in the following order : Cu⁺² > Co⁺² > Ni⁺². As in the case of a weekly acidic exchanger, the change in hydration of metal ions played the dominant role in determining the selectivity of tin phosphate. In all cases the extent of adsorption increased with an increase in temperature and concentration. The apperance of irregular kinks in the titration curves justified the presence of several exchangeable adsorption sites with different pKa values.

• Proceedings of the Materials Research Society of Korea Conference
• /
• 2010.05a
• /
• pp.6.1-6.1
• /
• 2010

원자층 증착 기술 (Atomic Layer Deposition)은 기판 표면에서 한 원자층의 화학적 흡착 및 탈착을 이용한 nano-scale 박막 증착 기술이기 때문에, 표면 반응제어가 우수하며 박막의 물리적 성질의 재현성이 우수하고, 대면적에서도 균일한 두께의 박막 형성이 가능하며 우수한 계단 도포성을 확보 할 수 있다. 최근 ALD에 의한 박막증착 방법 중 플라즈마를 이용한 ALD 증착 방법에 대한 다양한 연구가 진행되고 있다. 플라즈마는 반응성이 좋은 이온과 라디컬을 생성하여 소스간 반응성을 좋게 하여, 소스 선택의 폭을 넓어지게 하고, 박막의 성질을 좋게 하며, 생산성을 높일 수 있는 장점이 있다. 그러나 플라즈마를 사용함으로써 플라즈마 내에 이온들이 가속되서 박막 증착 중에 기판 및 박막에 손상을 입혀 박막 특성을 열화 시킬 가능성이 있다. 따라서 플라즈마 발생 영역을 기판으로부터 멀리 떨어뜨린 원거리 플라즈마 원자층 공정이 개발 되었다. 이 기술은 플라즈마에서 생성된 ion이 기판이나 박막에 닫기 전에 전자와 재결합 되거나 공정 chamber에서 소멸하여 그 영향을 최소하고 반응성이 좋은 라디칼과의 반응만을 유도하여 향상된 막질을 얻을 수 있도록 하였다. 따라서 이 원거리 플라즈마 원자층 증착기술은 나노 테크놀러지 소자 개발하기 위한 나노 박막 기술에 있어서 그 활용이 점점 확대될 것이다. 그 적용으로써 리모트 플라즈마 원자층 증착 방법을 이용한 고유전 물질 개발이 있다. 반도체 소자의 고집적화 및 고속화가 요구됨에 따라 집적회로의 크기를 혁신적으로 축소하여 스위칭 속도(switching speed)를 증가시키고, 전력손실 (power dissipation)을 줄이려는 시도가 이루어지고 있다. 그 중 하나로 고유전율 절연막은 트렌지스터 소자의 스케일링 과정에 수반하여 커지는 게이트 누설 전류를 억제하기 위한 목적으로 도입되었다. 유전율이 크면 동일한 capacitance를 내는데 필요한 물리적인 두께를 늘릴 수 있어 전자의 tunneling을 억제할 수 있고 전력손실을 줄일 수 있기 때문이다. 이와 같은 고유전율 물질이 게이트 산화막으로 사용되기 위해서 높은 유전상수 열역학적 안정성, 낮은 계면 전하밀도, 낮은 EOT, 전극 물질과의 양립성 등의 특성이 요구되는데, 이에 따라 많은 유전물질에 대한 연구가 진행되었다. 기존 gata oxide를 대체하기 위한 가장 유력한 후보 재료로 주목 받고 있는 high-k 물질들로는 Al2O3, HfO2, ZrO2, La2O3 등이 있다. 본 발표에서는 ALD의 종류에 따른 기술을 소개하고 그 응용으로 고유전율 물질 개발 연구 (고유전율 산화물 박막의 증착, 고유전율 산화물의 열적 안정성 평가, Flatband 매카니즘 규명, 전기적 물리적 특성 분석)에 대해서 발표 하고자 한다.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.3 no.3
• /
• pp.210-215
• /
• 2002

In this study, the computer program called Multi_Cycle, which simulates the steady-state performance (coefficient of performance, capacity, power consumption and etc.) of multi- airconditioning systems using R410A, was developed. In order to validate the simulation program, a series of case studies were carried out. The Multi_Cycle consists of several subroutines for simulating indoor units. outdoor unit, compressor, and expansion devices. and for estimating the thermodynamic and transport properties of the refrigerants and moist air. It would appear to be advantageous to use the Multi_Cycle for a performance analysis when considering various kinds of refrigerants and the complex operating conditions of each unit making up the multi-airconditioner cycle. Moreover, the Multi_Cycle would seem to be useful tool in optimizing a multi-airconditioning system and establishing economical and efficient operating conditions in the multi-airconditioner cycle. In the present study, the Multi_Cycle was programmed with Digital Visual Fortran for the main simulation code and Visual Basic for- the graphic user interface.

• Tunnel and Underground Space
• /
• v.23 no.1
• /
• pp.78-85
• /
• 2013

A primary objective in creating a stratified thermal storage is to maintain the thermodynamic quality of energy, so thermally stratified energy can be extracted at temperatures required for target activities. The separation of the thermal energy in heat stores to layers with different temperatures, i.e., the thermal stratification is a key factor in achieving this objective. This paper introduces different methods that have been proposed to characterize the thermal stratification in heat stores. Specifically, this paper focuses on the methods that can be used to determine the ability of heat stores to promote and maintain stratification during the process of charging, storing and discharging. In addition, based on methods using thermal stratification indices, the degrees of stratification of stored energy in Lyckebo rock cavern in Sweden were compared and the applicability of the methods was investigated.