• Title/Summary/Keyword: Gibbs′ free energy

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Analysis of Thermodynamics in BiSrCaCuO Thin Films Fabricated by Using the i-beam sputtering method (i-beam 스퍼터링 법으로 제작한 BiSrCaCuO 박막의 열역학분석)

  • Kim, Tae-Gon;Park, yong-Pil
    • Journal of the Korea Institute of Information and Communication Engineering
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    • v.11 no.1
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    • pp.89-94
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    • 2007
  • High duality BiSrCaCuO thin films fabricated by using the i-beam sputtering method at various substrate temperatures, $T_{sub}$ and oxidation gas pressures, $pO_3$. The correlation diagrams of the BiSrCaCuO phases with Tsub and $pO_3$ are established in the 2212 and 2223 compositional films. In spite of 2212 compositional sputtering, Bi2201 and Bi2223 as well as Bi2212 phases come out as stable phases depending on $T_{sub}$ and $pO_3$. From these results, the thermodynamic evaluation of ${\Delta}H$ and${\Delta}S$, which are related with Gibbs' free energy change for single Bi2212 or Bi2223 phase, was performed.

Partial Miscibility in Polymer Mixtures from a Viewpoint of the Theory of Flory's Equation of State (Flory의 상태방정식 이론의 관점에서 본 고분자 혼합물에서의 부분혼합도)

  • Jung, Hae-Young
    • Journal of the Korean Chemical Society
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    • v.35 no.6
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    • pp.730-736
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    • 1991
  • In terms of the theory of Flory's Equation of State, the generalized condition for each case of partial miscibilities appearing in the polymer solutions or blends is given. And observing the changes of terms for energies and free volumes in ${\Delta}G_{mix}$ with increasing temperature, their effects on the partial miscibilities are generalized, and the effects of other parameters are also generalized.

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Ab initio and Vibrational Predissociation Studies on Methylammonium-(Water)4 Complex: Evidence for Multiple Cyclic and Non-cyclic Hydrogen-bonded Structures

  • Kim, Kwang-Yon;Han, Woon-Hui;Cho, Ung-In;Lee, Yuan T.;Boo, Doo-Wan
    • Bulletin of the Korean Chemical Society
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    • v.27 no.12
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    • pp.2028-2036
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    • 2006
  • The combined ab initio and vibrational predissociation (VP) spectroscopic studies on methylammonium-$(water)_4$ complex aimed at understanding the hydration behavior of an amphiphilic ion core are described. The ab initio calculations predicted eleven low-energy isomers forming cyclic, tripod, chain, and caged structures, and their relative stabilities, total hydration energies and thermodynamic functions at 298 K and 150 K. The excellent correlation between the observed VP spectra and ab initio spectra for bonded N-H, bonded O-H and free O-H stretches suggested co-existence of five cyclic isomers and two non-cyclic isomers in ion beam at 150 K, consistent with the trends of calculated Gibbs free energies.

Analysis of Thermodynamics for Formation of Single Phase in $Bi_2Sr_2Ca_nCu_{n+1}O_x$ Thin Films ($Bi_2Sr_2Ca_nCu_{n+1}O_x$ 박막의 단상 형성을 위한 열역학 해석)

  • Cheon, Min-Woo;Park, Yong-Pil;Kim, Jeong-Ho
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2003.07b
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    • pp.1208-1211
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    • 2003
  • High quality $Bi_2Sr_2Ca_nCu_{n+1}O_x$ superconducting thin films fabricated by using the evaporation method at various substrate temperatures, $T_{sub}$, and ozone gas pressures, $pO_3$. The correlation diagrams of the $Bi_2Sr_2Ca_nCu_{n+1}O_x$ phases with $T_{sub}$ and $pO_3$ are established in the 2212 and 2223 compositional films. In spite of 2212 compositional sputtering, Bi2201 and Bi2223 as well as Bi2212 phases come out as stable phases depending on $T_{sub}$ and $pO_3$. From these results, the thermodynamic evaluation of ${\Delta}H$ and ${\Delta}S$, which are related with Gibbs' free energy change for single Bi2212 or Bi2223 phase, was performed.

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A Theory of Specific Heat Discontinuity of the Superconducting Crystals by Using the Linear Model for Critical Magnetic Field (임계 자기장 선형 모델을 이용한 초전도 결정의 비열 불연속성 이론)

  • Kim, Cheol-Ho
    • The Journal of the Korea institute of electronic communication sciences
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    • v.13 no.1
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    • pp.23-28
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    • 2018
  • We derive a gap of specific heat discontinuity of superconducting crystals theoretically at the critical temperature $T_{CH}$ as an explicit function of applied magnetic field H by using the thermodynamic relations for Gibbs free energy and the linear model for the critical magnetic field $H_{CT}$. The derived a gap of specific heat discontinuity is compared with experimental results by J. Kacmarcik et al. for superconducting MgCNi3 crystal. Our specific heat gap function well explain the jump up phenomena of the superconducting crystals.

Analysis of Thermodynamics for Single Crystal Formation (단결정 형성을 위한 열역학 분석)

  • Cheon, Min-Woo;Yang, Sung-Ho;Park, Yong-Pil
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2006.04a
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    • pp.70-73
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    • 2006
  • High quality $Bi_2Sr_2Ca_nCu_{n+1}O_x$ superconducting thin films fabricated by using the evaporation method at various substrate temperatures, $T_{sub}$, and ozone gas pressures, $pO_3$. The correlation diagrams of the $Bi_2Sr_2Ca_nCu_{n+1}O_x$ phases with $T_{sub}$ and $pO_3$ are established in the 2212 arid 2223 compositional films. In spite of 2212 compositional sputtering, Bi2201 and Bi2223 as well as Bi2212 phases come out as stable phases depending on $T_{sub}$ and $pO_3$. From these results, the thermodynamic evaluation of ${\Delta}H$ and ${\Delta}S$, which are related with Gibbs' free energy change for single Bi2212 or Bi2223 phase, was performed.

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Precipitation of Rare Earth Chlorides in a LiC-KCl Eutectic Molten Salt (LiCl-KCl 공융염 내에서 희토류염화물들의 침전)

  • Cho, Yung-Zun;Yang, Hee-Chul;Eun, Hee-Chul;Kim, Eung-Ho;Kim, In-Tae
    • Applied Chemistry for Engineering
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    • v.18 no.4
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    • pp.361-365
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    • 2007
  • The precipitation reaction of some rare earth chlorides ($Ce/Nd/GdCl_3$) in a LiCl-KCl molten salt has been carried out by reaction with oxygen. Identification of rare earth precipitates by reaction with oxygen and effects of oxygen sparging time (max. 420 min) and molten salt temperature ($450{\sim}750^{\circ}C$) on conversion were investigated. In this study, regardless of the oxygen sparging time and the molten salt temperature, oxychlorides (REOCl) for $NdCl_3$ and $GdCl_3$, and an oxide ($REO_2$) for $CeCl_3$ are formed as a precipitate, which are identical with the estimation results of Gibbs free energy of reaction (${\Delta}G_r$). The conversion of rare-earth chlorides into insoluble precipitates was described by using a conversion ratio. The conversion ratio increased exponentially with the oxygen sparging time and finally showed asymptotic value, over 0.999 at $750^{\circ}C$ of the molten salt temperature and over 300 min of sparging time conditions. The conversion ratios were increased with the molten salt temperature. In case of $CeCl_3$, when the sparging time exceed 60 min, the values of the conversion ratio were nearly constant over 0.999 in all experimental temperature conditions.

Equilibrium, Kinetic and Thermodynamic Parameter Studies on Adsorption of Allura Red from Aqueous Solution by Granular Activated Carbon (입상활성탄에 의한 수용액으로부터 오로라 레드의 흡착에 대한 평형, 동력학 및 열역학 파라미터에 관한 연구)

  • Lee, Jong-Jib
    • Applied Chemistry for Engineering
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    • v.25 no.4
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    • pp.430-436
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    • 2014
  • Allura Red (AR) is a water-soluble harmful tar-based food colorant (FD & C Red 40). Batch adsorption studies were performed for the removal of AR using bituminous coal based granular activated carbon as adsorbent by varying the operation parameters such as adsorbent dosage, initial concentration, contact time and temperature. Experimental equilibrium adsorption data were analyzed by Langmuir, Freundlich and Temkin isotherms. The equilibrium process was described well by Freundlich isotherm. From determined separation factor ($R_L$), adsorption of AR by granular activated carbon could be employed as effective treatment method. Temkin parameter, B was determined to 1.62~3.288 J/mol indicating a physical adsorption process. By estimation of adsorption rate experimental data, the value of intraparticle diffusion rate constant ($k_m$) increased with the increasing adsorption temperature. The adsorption process were found to confirm to the pseudo second order model with good correlation. Thermodynamic parameters like change of free energy, enthalpy, and entropy were also calculated to predict the nature adsorption in the temperature range of 298~318 K. The negative Gibbs free energy change (${\Delta}G$ = -2.16~-6.55 kJ/mol) and the positive enthalpy change (${\Delta}H$ = + 23.29 kJ/mol) indicated the spontaneous and endothermic nature of the adsorption process, respectively.

Simulation of Rare Earth Elements Removal Behavior in TRU Product Using HSC Chemistry Code (HSC Chemistry 코드를 이용한 TRU 생성물 중의 희토류 원소 제거 거동 모사)

  • Paek, Seungwoo;Lee, Chang Hwa;Yoon, Dalsung;Lee, Sung-Jai
    • Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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    • v.18 no.2
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    • pp.207-215
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    • 2020
  • The feasibility of rare earth (RE) removal process via oxidation reactions with UCl3 was investigated using the HSC Chemistry code to reduce the concentrations of RE in transuranic (TRU) products. The composition and thermodynamic data of TRU and RE elements contained in the reference spent fuel were examined. The reactivity was evaluated by calculating equilibrium data considering oxidation reactions with UCl3. Both RE removal rate and TRU recovery rate were evaluated for the two cases, wherein TRU products with different RE concentrations were used. When TRU products were reacted with UCl3, selective oxidation was driven by the difference in the Gibbs free energy of each element. The calculation results imply that the TRU/RE ratio of the final product can be increased by removing RE elements while maintaining the maximum recovery rate of TRU, which is accomplished by controlling the amount of UCl3 injected. Since the results of this study are based on thermodynamic equilibrium data, there are many limitations to apply to the actual process. However, it is expected to be used as an important data for the process design to supply the TRU product of pyroprocessing to SFR's fuel demanding low RE concentrations.

Physical Property Models and Single Cells Analysis for Solid Oxide Fuel Cell (고체산화물 연료전지를 위한 물성치 모델 및 단전지 해석)

  • Park, Joon-Guen;Kim, Sun-Young;Bae, Joong-Myeon
    • 한국신재생에너지학회:학술대회논문집
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    • 2009.06a
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    • pp.379-381
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    • 2009
  • The simulation model for metal-supported Solid Oxide Fuel Cell(SOFC) is developed in this study. Open circuit voltage is calculated using Nernst equation and Gibbs free energy is required by thermodynamic. The exchange current densities are compared with experimental results since exchange current density is most effective factor for the activation loss. Liu's study is used for the exchange current density of cathode, BSCF, and Koide's result is applied for the exchange current density of anode, Ni/YSZ. For the ohmic loss, ionic conductivity of YSZ is described from Kilner's mode and the data are compared with Wanzenberg's experimental data. Diffusivity is an important factor for the mass transfer through the porous medium. Both binary diffusion and Knudsen diffusion are considered as the diffusion mechanism. For validation, simulation results at this work are compared with our experimental results.

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