• Applied Chemistry for Engineering
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• v.22 no.3
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• pp.308-311
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• 2011

The reaction mechanism of selective catalytic reduction of NOx over sewage sludge char impregnated with MnOx using $NH_3$ as the reducing agent was investigated. The active Mn phase was shown to be $Mn_3O_4$ from the XRD analysis. Adsorption was the dominant NOx removal mechanism at low temperatures below $150^{\circ}C$ although reduction reaction also contributed partly to the NOx removal at $100{\sim}150^{\circ}C$. The reaction rate constants of NOx removal over non-impregnated and MnOx-impregnated active chars were compared based on experimental results. The MnOx-impregnated char was shown to have a higher reaction rate constant and a higher NOx removal efficiency due to a higher collision coefficient and a lower activation energy. The activation energy for both chars was shown to be relatively low (10~12 kJ/mol) under the experimental conditions of this study.

• Journal of the Korean Ceramic Society
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• v.31 no.4
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• pp.443-447
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• 1994

Compacts of mixed SiO2-Si powder were liquid phase sintered at 145$0^{\circ}C$ for up to 60 min in a hydrogen atmosphere. In contrast to the conventional microstructures of liquid phase sintered materials, the specimens showed that the solid phase of SiO2 formed a matrix while the liquid phase of Si was the dispersed in the solid matrix. The dispersion of liquid Si pockets was attributed to the high wetting angle of liquid Si on solid SiO2. Because of relatively high solubility of SiO2 in liquid Si at 145$0^{\circ}C$, SiO2 particles accommodated their shape via a solution-reprecipitation process. The liquid Si pockets grew by coalescing with their neighbour pockets. In the latter stage of the sintering, plate-shape grains appeared in the liquid Si pockets. The grains were SiO2 phase precipitated from the liquid Si which was oversaturated with oxygen during cooling to room temperature. By the formation and subsequent removal of the gaseous SiO phase due to the reaction between SiO2 and Si, the specimens became porous.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2023.05a
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• pp.99-100
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• 2023

In this study, an approach has been made to understand the effect of encapsulation thickness of the nanoencapsulated PCMs on the phase transition kinetics. Paraffin is encapsulated by silica via single pot polycondensation reaction. Different ratios of silica precursor are chosen to encapsulate paraffin. The obtained encapsulated PCMs are identified as nano sized, as well as with increasing silica precursor, thicker silica encapsulations have been manifested with shrinking core diameter. The synthesized PCMs are characterized using various characterization techniques. Isochronal kinetic studies are done in differential scanning calorimeter (DSC) to understand about their phase transformation behaviors. This study can appreciate the cognition of the large-scale applications of PCMs into the building constructions as well as the fundamental conception on the phase transition kinetics of PCMs can also be amended.

• 한국신재생에너지학회:학술대회논문집
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• 2009.06a
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• pp.134-137
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• 2009

Commercially available elemental powders of Cu, Zn, Sn and Se were employed for crystallizing a stannite-type $Cu_2ZnSnSe_4$ compound by means of solid state reaction. $Cu_2ZnSnSe_4$ reaction chemistry was also modeled based on differential-thermal analysis and X-ray powder diffraction results. It was observed that Se tends to react preferably with Cu to form CuSe and $CuSe_2$ phases at low reaction temperature. The formation of $Cu_5Zn_8$ intermetallic phase was found to be the intermediate reaction path for the binary ZnSe formation. A solid state reaction at $320^{\circ}C$ reacted elemental powderst obinary selenides of CuSe, ZnSe and SnSe completely. The crystallization of $Cu_2ZnSnSe_4$ was was detected to begin at $300^{\circ}C$ and its weight fraction increased with an increase of reaction temperature, which most probably formed from the reaction between $Cu_2SnSe_3$ and ZnSe.

• Korean Chemical Engineering Research
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• v.50 no.6
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• pp.1021-1026
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• 2012

The transient mass transfer in a single droplet system consisting of 1-octanol (continuous phase)/aqueous succinic acid solution (dispersed phase) was investigated in the presence of chemical reaction, which is acid/anion exchange reaction of succinic acid and tri-n-octylamine (TOA). This succinic acid extraction by TOA can be considered to occur at the interface between organic and aqueous phase, that is, heterogeneous reaction system. The basic properties of the system such as viscosity, density, distribution coefficient, terminal velocity of droplet, and diffusion coefficient were measured experimentally or calculated theoretically, and used for theoretical calculation of characteristic parameters of mass transfer later. The effects of succinic acid concentration on the terminal velocity was negligible in the existence of TOA, although the terminal velocity increases with succinic acid concentration in the absence of TOA. On the contrary, the terminal velocity decreases with TOA concentration. While droplets falls through organic phase, the trajectory of droplets is observed to oscillate around its vertical path. A mass trnasfer cell was prepared to monitor the mass transfer behavior in a single droplet and used to measure the mean concentration of succinic acid inside droplet. The results are expressed with dimensionless parameters. Under 50 g/L succinic acid condition, the system with 0.1 mol/kg TOA showed that the molar flux decreases in proportion to the decrease of concentration gradient, while in the case of 0.5 mol/kg TOA Sh increases rapidly with time indicating the molar flux of succinic acid decreases relatively slowly compared to the decrease in concentration gradient.

• Rapid Communication in Photoscience
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• v.3 no.4
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• pp.76-78
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• 2014

Fluorescent nucleic acids were prepared utilizing the polymerase extension (PEX) reaction to incorporate fluorescent molecules. 2'-Deoxyuridine triphosphate (dUTP) derivatives possessing pyrene molecules as fluorophores were synthesized using the aqueous-phase Sonogashira coupling between 5-Iodo-dUTP and acetylene-linked pyrene molecules. The incorporation of the pyrene (Py)-labeled deoxyuridine triphosphates (PyU) into DNA by polymerase was evaluated by polyacrylamide gel electrophoresis, demonstrating that the PyU can work as a good substrate for the PEX reaction. The fluorescent properties of the functionalized DNA prepared by the PEX reaction were characterized by steady-state fluorescence measurements. The Py-conjugated DNA showed typical emission spectra of the pyrene, and the DNA with two pyrene molecules connected to each other by a diethylene glycol linker exhibited a broadened emission attributed to the electronic interaction between the Py molecules.

• Journal of the Korean Society for Heat Treatment
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• v.9 no.4
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• pp.234-242
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• 1996

The direct reaction method has been used for the fabrication of Al-Mg/$Al_2O_3$ functionally gradient materials. It was found that the reaction layer of the Al-Mg/$Al_2O_3$ powder compact at $900^{\circ}C$ under air atmosphere led to the formation of reaction layers with varying ceramic phase contents. As the results of experiments by using the TGA system, the characteristics and growth behavior of the reaction layers were affected by the reaction temperature, the gas flow rate, the Mg contents and the $Al_2O_3$ contents.

• Journal of Korean Society on Water Environment
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• v.23 no.5
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• pp.659-664
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• 2007

The objective of this study is to evaluate the detoxification method for the endocrine disrupting chemicals by manganese oxide. Manganese coated sand and bisphenol-A (BPA) was used as the reactive medium and the contaminant. Results showed that manganese oxide effectively degrades BPA by oxidative coupling reaction. The nonlinear oxidative coupling reaction orders were obtained for BPA and oxide, respectively. The reaction rate of BPA decreased as initial BPA concentration increased, as oxide loading decreased and as pH increased. The higher ionic strength, the higher reaction rate was observed. Divalent cations were adsorbed on the oxide surfaces, resulting in the decreased degradation rate of BPA.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.05b
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• pp.461-464
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• 2005

As the research on the development of the lightweight concrete block by the hydro-thermal synthetic reaction mixed with the calcareous material and bottom ash that is used less among siliceous material, we studied on the physical and chemical characteristics in the changes of hydro-thermal synthetic reaction of lightweight concrete block compounded with the PP fiber to increase flexural toughness and to prevent fragility failure. The results of the experiment are as follow. According to the increase of hydro-thermal synthetic reaction and the fiber content, compressive and flexural strength increased. Despite the changes of the hydro-thermal synthetic reaction time, tobermorite was produced on each of the specimens similarly. However, the phase of tobermorite was changed in accordance with the changes of time. Also, $CaCo_{3}$ appeared on the surface of the 9 hour hardened specimen.

• Journal of Korean Society of Environmental Engineers
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• v.29 no.4
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• pp.412-418
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• 2007

The purpose of this study was to determine the several factors for affecting chlorine disinfection by-products(DBPs) characteristics by reacting chlorine and organic matters in the aquatic phase. The results of this research yield the following specific conclusions: The concentration of trihalomethanes(THMs) was increased with increasing dissolved organic carbon(DOC), and a trend of THMs formation was parabolic with increasing organic matters. Formations of THMs increased straightly for the first 4 hours and the amounts of producted THMs for the 30 minutes were up to $25\sim43%$ in the entire experiment periods(168 hours). When keeping up the concentration of organic matters at constant and changing that of bromide, the quantity of formed THMs did not show distinguished difference with the reaction times. THMs were gradually increased at $4^{\circ}C$ even though a reaction phase was parabolic formation(PF) phase. However, THMs were increased rapidly in the instantaneous formation(IF) phase and then became slowdown in the PF phase between $20\sim35^{\circ}C$. THMs were gradually increased although entering in the PF phase at pH 5. However, THMswere increased rapidly in the IF phase and then became slowdown in the PF phase at pH 7 and pH 9, and these treads were much more clear at pH 9 than at pH 7.