• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.08a
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• pp.25-30
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• 2002

The ternary semiconducting compounds of the $A_{4}BX_{6}$(A=Cd, Zn, Hg; B=Si, Sn, Ge; X=S, Se, Te) type exhibit strong fluorescence and high photosensitivity in the visible and near infrared ranges, so these are supposed to be materials applicable to photoelectrical devices. These materials were synthesized and single crystals were first grown by Nitsche, who identified the crystal structure of the single crystals. In this paper. author describe the undoped and $Co^{2+}$-doped $Zn_{4}SnSe_{6}$ single crystals were grown by the chemical transport reaction(CTR) method using iodine of $6mg/cm^{3}$ as a transport agent. For the crystal. growth, the temperature gradient of the CTR furnace was kep at $700^{\circ}C$ for the source aone and at $820^{\circ}C$ for the growth zone for 7-days. It was found from the analysis of x-ray diffraction that undoped and $Co^{2+}$-doped $Zn_{4}SnSe_{6}$ compounds have a monoclinic structure. The optical absorption spectra obtained near the fundamental absorption edge showed that these compounds have a direct energy gaps. These temperature dependence of the optical energy gap were closely investigated over the temperature range 10[K]~300[K]

• The Journal of the Convergence on Culture Technology
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• v.7 no.2
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• pp.389-394
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• 2021

In this work, we study the properties of molecular structure and boundary orbital functions of the DPHMP-AlH and propiophenone and butyrophenone, which are forms of alkoxy-amine-aluminum derivatives. Furthermore, we investigate the effect on the selective reduction of the final products (R), (S)-phenylpropanol and (R), (S)-phenylbutanol by calculating the stereoscopic and thermodynamic parameters of the transition state. Considering the three-dimensional molecular structural stability, the transition status of (S) types DPHMP-AlH and alkylphenone was found to be more stable, resulting in the selective reductions of DPHM-AlH and alkylphenone from this result: (S)-(1)-phenylpropanol and (S)-(1)-phenylbutanol was confirmed that the formation was advantageous.

• Journal of the Korean Applied Science and Technology
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• v.38 no.3
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• pp.832-839
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• 2021

We tried to investigate the effects of substituent position, temperature, and additives such as NaCl and n-butanol on the solubilizations of cresol isomers by tetradecyltrimethylammonium bromide (TTAB), using the UV-Vis spectrophotometric method. The measured solubilization constants (K_s) values for each cresol isomer increased in the order o-cresolo and ∆H^o values for the solubilizations of cresols were all negative values but the ∆S^o values were all positive values within the measured ranges. The values of ∆G^o increased also with increasing the concentration of n-butanol but decreased with increasing the concentration of NaCl. From these facts, we could conclude that both the enthalpy and entropy changes contribute together for the solubilizations of cresols isomers by cationic surfactant of TTAB and they are solubilized in the polar palisade region or at the surface of micelle.

• Analytical Science and Technology
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• v.22 no.2
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• pp.159-165
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• 2009

The thermochromism of fluoran has been examined. The DCF exists as a colorless lactone in aprotic solvents. However, the DCF exists in the form of an equilibrium mixture of a colored zwitter-ion and a colorless lactone in protic solvents. When an acid is added to the solution, the DCF exists an equilibrium mixture as a colorless lactone and a colored cation even in aprotic solvents. In order to understand the interaction between the DCF and the solvent, absorption spectra of the DCF in various solvents were measured. The thermodynamic parameters of the DCF have also been investigated. From the variation of absorbance with temperature, the standard enthalpy changes ${\Delta}H^0$ of the equilibrium between the lactone and the zwitter-ion in various solvents have been determined. The standard enthalpy change ${\Delta}H^0$ is approximately -2.0 kJ/mol in protic solvents. In acidic solution, the standard enthalpy change is measured to be to zero in protic solvents within the experimental error. When the carboxylic group is protonated in acidic solution, a poor interaction between the dye and the solvent is expected.

• Applied Chemistry for Engineering
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• v.35 no.2
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• pp.115-121
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• 2024

This study analyzed the influence of process variables affecting the thermodynamic equilibrium and fluid dynamics of interfaces such as reverse micelle, salt concentration, interfacial tension, and viscosity of fluids to optimize the microencapsulation process using the W1/O/W2 double emulsion method. The process variable with the greatest impact on encapsulation efficiency was found to be the difference in osmotic pressure between the W1 and W2 phases. It was observed that increasing the salt concentration in the W2 phase or decreasing the ascorbic acid concentration in the W1 phase resulted in higher encapsulation efficiency. Additionally, a larger difference in osmotic pressure led to increased damage to the surface of the microparticles, as confirmed by SEM images. The introduction of reverse micelles, which was anticipated to increase encapsulation efficiency, either had a low contribution or even decreased encapsulation efficiency. The yield of microcapsules was expressed as a universal function, applicable to all process conditions or solution compositions. According to this universal function, no further increase in yield was observed beyond the Ca (capillary number) of approximately 20.

• Journal of the Korean Chemical Society
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• v.61 no.1
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• pp.16-24
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• 2017

The adsorption of various atmospheric harmful gases ($CO_x$, $NO_x$, $SO_x$) on graphene-like boron nitride(BN) and aluminum nitride(AlN) sheets was theoretically investigated using density functional theory (DFT) and MP2 methods. The structures were fully optimized at the $B3LYP/6-31G^{**}$ and $CAM-B3LYP/6-31G^{**}$ levels of theory and confirmed to be a local minimum by the calculation of the harmonic vibrational frequencies. The MP2 single-point binding energies were computed at the $CAM-B3LYP/6-31G^{**}$ optimized geometries. Also the zero-point vibrational energy (ZPVE) and 50%-basis set superposition error (BSSE) corrections were included. The adsorptions of gases on the BN sheet were predicted to be a physisorption process and the adsorptions of gases on the AlN sheet were predicted to be a physisorption process for $CO_x$ and $NO_x$ but to be a chemisorption process for $SO_x$.

• Journal of the Korean Chemical Society
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• v.66 no.3
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• pp.185-193
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• 2022

The theoretical investigation has been performed to predict thermodynamic stability, density, detonation velocity, and detonation pressure of energetic salts produced by pairing of nitrogen-rich anions (tetrazine, oxadiazole etc.) and cations (NH₃OH⁺, NH₂NH₃⁺, CH₉N₆⁺, C₂H₆N₅⁺). All possible geometries and the binding energy for the trigger bond of energetic salts have been optimized at the B3LYP/cc-pVDZ level of theory. The detonation velocity and detonation pressure have been calculated using Kamlet-Jacobs equation, while enthalpy has been predicted at the G2MP2 level of theory. The predicted results reveal that the energetic salts including small sized NH₃OH⁺(1) and NH₂NH₃⁺(2) cations increase detonation property. And also the energetic salts including more amino group (-NH₂) such as CH₉N₆⁺(3) cation increase thermodynamic stability. These results provide basic information for the development the high energy density materials (HEDMs).

• Korean Chemical Engineering Research
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• v.55 no.5
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• pp.723-730
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• 2017

The batch experiments by response surface methodology (RSM) have been applied to investigate the influences of operating parameters such as temperature, initial concentration, contact time and adsorbent dosage on 2,4-dichlorophenol (2,4-DCP) adsorption with an activated carbon prepared from waste citrus peel (WCAC). Regression equation formulated for the 2,4-DCP adsorption was represented as a function of response variables. Adequacy of the model was tested by the correlation between experimental and predicted values of the response. A fairly high value of $R^2$ (0.9921) indicated that most of the data variation was explained by the regression model. The significance of independent variables and their interactions were tested by the analysis of variance (ANOVA) and t-test statistics. These results showed that the model used to fit response variables was significant and adequate to represent the relationship between the response and the independent variables. The kinetics and isotherm experiment data can be well described with the pseudo-second order model and the Langmuir isotherm model, respectively. The maximum adsorption capacity of 2,4-DCP on WCAC calculated from the Langmuir isotherm model was 345.49 mg/g. The rate controlling mechanism study revealed that film diffusion and intraparticle diffusion were simultaneously occurring during the adsorption process. The thermodynamic parameters indicated that the adsorption reaction of 2,4-DCP on WCAC was an endothermic and spontaneous process.

• Journal of Korean Society of Environmental Engineers
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• v.38 no.10
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• pp.543-550
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• 2016

Amine-type PP-g-VBC-EDA adsorbent, which possesses anionic exchangeable function, was prepared through photoinduced graft polymerization of vinylbenzyl chloride (VBC) onto polypropylene non-woven fabric and subsequent amination reaction using ethylenediamine (EDA). Adsorption characteristics of anionic nutrients on the PP-g-VBC-EDA adsorbent have been studied by batch adsorption experiments. The equilibrium data well fitted the Langmuir isotherm model, and the maximum monolayer sorption capacity was found to be 59.9 mg/g for $NO_3-N$ and 111.4 mg/g for $PO_4-P$. The adsorption energies were higher than 8 kJ/mol indicating anion-exchange process as the primary adsorption mechanism. The pseudo-second order kinetic model described well the kinetic data and resulted in the activation energy of 9.8-36.7 kJ/mol suggesting that the overall rates of $NO_3-N$ and $PO_4-P$ adsorption are controlled by the chemical process. Thermodynamic parameters such as ${\Delta}G^o$, ${\Delta}H^o$ and ${\Delta}S^o$ indicated that the adsorption nature of PP-g-VBC-EDA for anionic nutrients is spontaneous and exothermic. The PP-g-VBC-EDA could be regenerated by washing with 0.1 N HCl.

• Journal of the Korean Chemical Society
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• v.56 no.5
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• pp.556-562
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• 2012

The critical micelle concentration (CMC) and the counter-ion binding constant (B) for the mixed micellizations of TTAB (tetradecyltrimethylammonium bromide) with other surfactants (DTAB, CTAB, Tween-20, Tween-40, and Tween-80) in aqueous solution of 4-chlorobenzoic acid (0.5 mM) at $25^{\circ}C$ were determined as a function of ${\alpha}_1$ (the overall mole fraction of TTAB) by using the spectrophotometric method and the conductivity method. Various thermodynamic parameters ($X_i$, ${\gamma}_i$, $C_i$, $a_i^M$, ${\beta}$, and ${\Delta}H_{mix}$) were calculated for each mixed surfactant system and compared with the other mixed surfactant systems by means of the equations derived from the nonideal mixed micellar model. The results show that TTAB/DTAB mixed system has a great positive deviation from the ideal mixed micellar model and the other mixed systems have great negative deviations from the ideal mixed model.