• Journal of the Korean Crystal Growth and Crystal Technology
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• v.14 no.4
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• pp.160-168
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• 2004

We investigate the effects of solutal convection on the crystal growth rate in a horizontal configuration for diffusive-convection conditions and purely diffusion conditions achievable in a low gravity environment for a nonlinear thermal gradient. It is concluded that the solutally-driven convection due to the disparity in the molecular weights of the component A $(Hg_2Br_2)$ and B (CO) is stronger than thermally-driven convection for both the nonlinear and the linear thermal profiles, corresponding to $Gr_t= 8.5{\times}10^3,\; Gr_s = 1.05{\times}10^5$. For both solutal and thermal convection processes, the growth rates for the linear thermal profile (conducting walls) are greater than for the nonlinear case. With the temperature humps, there are found to be observed in undersaturation for diffusive-convection processes ranging from $D_{AB}$ = 0.087 to 0.87. For the vertical configurations, the diffusion mode is so much dominated that the growth rate and interfacial distribution is nearly regardless of the gravitational accelerations. Also, the diffusion mode is predominant over the convection for the gravity levels less than 0.1 $g_0$ for the horizontally oriented configuration.

• Analytical Science and Technology
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• v.12 no.2
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• pp.99-104
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• 1999

A stepwise gradient elution with two wavelengths detection was performed for the separation and determination of some anions in saline water. The eight anions such as iodate, bromate, nitrite, bromide, nitrate, chromate, iodide and thiocyanate were successfully separated using AS-7 column and sodium chloride/sodium phosphate buffer solution as an eluant within 40 min. The separation behaviors of anions were studied at various sodium chloride concentrations. The peak shapes of anions of bromate, nitrite, bromide and nitrate gradually broadened as the concentration of sodium chloride increased until 1.0 M in the sample solutions. However, no effect was observed in the peak shapes of chromate, iodide and thiocynate. A good linearity was obtained at the range of ppm(mg/L). The detection limit was proved to be $10-720{\mu}g/L$ for the eight anions with $50{\mu}L$ injection volume. This method was applied to the determination of $Br^-$, ${NO_3}^-$ and $I^-$ in sea water.

• Journal of the Korean Applied Science and Technology
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• v.21 no.1
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• pp.17-23
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• 2004

Silver bromide particles from 50 to 200${\AA}$ in diameter are prepared by mixing two microemulsions contaning the precursor salts $AgNO_3$ and KBr. The microemulsions are composed of AOT(bis(2-ethylhexyl) sodium sulfosuccinate), n-heptane and water. The particle diameters are measured on photomicrographs obtained by transmission electron microscopy. The size of the particles is generally larger than that of the water cores. The influence of both the concentration of precursor salts in the water cores of the microemulsoin and the size of these water cores on the size of the particles has been studied.

• Journal of the Korean Solar Energy Society
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• v.23 no.4
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• pp.45-54
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• 2003

For cooling of double effect absorption heat pump system of solar heating source, analysis of thermodynamic design data has been done to find the property of Libr-water + ethylene Glycol mixture for working fluid by computer simulation. Derived thermodynamic design data, enthalpy based coefficient of performance and flow ratio for possible combinations of operating temperature for water - LiBr and Ethylene Glycol mixture ($H_2O$ : CHO ratio 10:1 by mole) by computer simulation are done. The obtained results, COP and mass flow ratio of the water - lithium bromide - ethylene glycol system, are compared with data for the water-Libr pair solution.

• Journal of the Korean Solar Energy Society
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• v.22 no.4
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• pp.51-61
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• 2002

Analysis of thermodynamic design data of double effect solar absorption heat pump system for heating has been done to find the property of Libr-water + ethylene Glycol mixture for working fluid by computer simulation. Derived thermodynamic design data. enthalpy based coefficient of performance and flow ratio for possible combinations of operating temperature for water - LiBr and Ethylene Glycol mixture (H2O: CHO ratio 10:1 by mole) by computer simulation. The obtained results, COP and mass flow ratio of the water-lithium bromide-ethylene glycol system, are compared with data for the water-Libr pair solution.

• Journal of the Korean Magnetic Resonance Society
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• v.8 no.2
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• pp.86-95
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• 2004

A Cu(I) complex with an asymmetric TTF derivative (CET-EDTTTF) is prepared from the slow-diffusion method using CET-EDTTTF and Cu(I)Br solutions and characterized by X-ray crystallography and EPR spectroscopy. Structural analysis shows Cu(I) ions are tetrahedrally coordinated to two bridging bromides, one terminal bromide, and one S atom from CET-EDTTTF. Detailed geometrical and EPR analysis identified that the dimmer molecule contains [Cu$_2Br_4]^{2-}$ anion between two [CET-EDTTTF]$^+$ radical cations. Single-crystal EPR investigation of the complex reveals that the ganisotropy is unusually big, compared to those of the previously reported TTF+ cation radicals, implying that there is significant contribution of the Cu d-orbital to the HOMO of the complex.

• Bulletin of the Korean Chemical Society
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• v.23 no.2
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• pp.189-194
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• 2002

Two-photon resonant third photon ionization of atomic bromine $(4p^5\;^2P_{3/2}\;and\;^2P_{1/2})$ has been studied using a photoelectron imaging spectroscopy in the wavelength region 250 - 278 nm. The technique has yielded simultaneously both relative branching ratios to the three levels of $Br^+(^3P_2,\;^3P_{0.1}\;and^1D_2)$ with $4p^4$ configuration and the angular distributions of outgoing photoelectrons. The product branching ratios reveal a strong propensity to populate particular levels in many cases. Several pathways have been documented for selective formation of $Br^+(^3P_2)$ and $Br^+(^3P_{0.1})$ ions. In general, the final ion level distributions are dominated by the preservation of the ion core configuration of a resonant excited state. Some deviations from this simple picture are discussed in terms of the configuration interaction of resonant states and the autoionization in the continuum. The photoelectron angular distributions are qualitatively similar for all transitions, with a positive $A_2$ anisotropy coefficient of 1.0-2.0 and negligible $A_4$ in most cases, which suggests that the angular distribution is mainly determined by the single-photon ionization process of a resonant excited state induced from the third photon absorption.

• Analytical Science and Technology
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• v.24 no.5
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• pp.401-405
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• 2011

The efficient removal of bromate ($BrO_3^-$) from aqueous solutions was investigated using activated alumina. Bromate is a disinfection by-product, generally formed by the reaction of ozone and bromide in drinking water during ozonation process. The removal efficiency was about 90% for bromate (500 ng/mL) ion with acidic activated alumina but over 95% with silver or aluminum treated acidic activated alumina without any treatments of neutral water within 1~2 min.

• Journal of the Korean institute of surface engineering
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• v.51 no.1
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• pp.79-85
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• 2018

We systematically investigated the optical properties of sub-micron sized methylammonium lead tribromide ($CH_3NH_3PbBr_3$) cubes in the range of 100 to 700 nm, which were prepared by a surfactant-free precipitation method. We found that despite the strong absorbance, their photoluminescence quantum yield (PLQY) is very low as 0.009~0.011 % for whole range of sizes. Surfactant-free synthesis approach results in nanocubes that has no surface passivating reagents (e.g. surfactants) on their surface. As-prepared particles contain a large number of surface defects that may cause the low PLQY. The role of the surface defects were investigated in their photoluminescence decay process, which can be correlated with the particle size. Larger particles are characterized by a slower decay rate compared to smaller particles due to a large number of surface defects in the smaller particles that trap more excitons in the fluorescence decay process. These experimental results provide new insights into the fundamental relationship between surface state and optical properties.

• Journal of the Korean Chemical Society
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• v.23 no.6
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• pp.368-373
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• 1979

Kinetic studies have been carried out on solvolyses and halide exchanges $(Cl^-,\;Br^-,\;I^-)$ of N,N-dimethyl-, N,N-diethylcarbamoyl chlorides, and solvolyses of N,N-diphenylcarbamoyl chloride. Kinetic results together with simple MO analysis indicated that: (a) N,N-dialkylcarbamoyl chlorides reacted via the $S_N2$ mechanism, while N,N-diphenylcarbamoylchloride reacted via the $S_N1$ mechanism; (b) in chloride exchanges, the bond-breaking appeared to be important, whereas in bromide and iodide exchanges, the bond-formation was shown to be important.