• Journal of Radiation Industry
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• v.4 no.3
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• pp.265-269
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• 2010

Silicon-based non-oxide ceramic carbide fiber is one of the leading candidate ceramic materials for engineering applications because of its excellent mechanical properties at high temperature and good chemical resistance. In this study, polycarbosilane(PCS) and zirconium butoxide were used as a precursor to prepare polyzirconocarbosilane (PZC) fibers. A polymer solution was prepared by dissolving PCS in zirconium butoxide (50/50 wt%). This solution was heated at $250^{\circ}C$ in a nitrogen atmosphere for 2 hour with stirring, and then dried in a vacuum oven for 48 hour. PZC fibers were fabricated using an electrospinning technique. The fibers were irradiated with an electron beam to induce structural crosslinking. Crosslinked PZC fibers were heat treated at $1,300^{\circ}C$ in a nitrogen atmosphere. The microstructures of PZC fibers were examined by SEM. Chemical structures of PZC fibers were examined by FT-IR and XRD. Thermal stability of PZC fibers was investigated by TGA.

• The Korean Journal of Nuclear Medicine
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• v.23 no.1
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• pp.63-69
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• 1989

In order to develop technetium-99m-labelled human albumin microsphere (HAM) for lung scintigraphy, various experimemts such as preparation and fractionation of HAM, establishment of optimal labelling conditions, determination of radiochemical purity, stability test and biodistribution of $^{99m}Tc-HAM$ were carried out. HAM was prepared from the suspension of 1ml aqueous human serum albumin (25%) in 130 ml of olive oil at $130\sim135^{\circ}$ with vigorous stirring. The resulting HAM was fractionated with microsieve to get the desired particle size $(15\sim50\mu)$ and autoclaved for sterilizaiton. The HAM particles were treated with stannous chloride and the pH of the suspension was adjusted to $3.0\sim3.5$ with phosphate buffer. After freeze-drying the contents of single reaction vial containing 5 mg of HAM and 0.2 mg of $SnCl_2$ it was reacted with $Na^{99m}TcO_4$. The labelling yield was higher than 99.5% and the stability of $^{99m}Tc-HAM$ was high enough to maintain 99.1% of radiochemical purity up to 24 hours. Lung and liver uptake in mice was found to be 94% and 0.9%, respectively. Excellent rabbit and human lung scans were also obtained.

• KEPCO Journal on Electric Power and Energy
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• v.2 no.3
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• pp.433-436
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• 2016

In the area of environmental chemistry of power plant, flow analysis of the reactor with built-in impeller is a very important part from the perspective of the improvement of the efficiency of the entire process. As a wide range of methods are being proposed for the analysis of the flow pattern within the reactor, this study analyzed the flow within the reactor according to the baffle structure (height) installed on the internal wall of the reactor in order to improve the reaction efficiency through the inducing of the up and down stirring with the reactor. As the results of the execution of the flow analysis for each of a diverse range of cases by utilizing the Computational Fluid Dynamics (CFD) method, it was possible to confirm that the flow is markdely improved by inducing the up and down stirring among the reactants within the reactor if the baffle is elevated to the level below the water surface. In particular, as the results of the analysis of the general cases in which the baffle is elevated all 4 steps and the cases in which the baffle is elevated only 2 steps, elevating the baffle only 2 steps achieve the same effect as the elevating of the baffle by 4 steps. Therefore, it was possible to expect to improve the efficiency with out the need to increase the use of electric power substantially if the outcomes of this study is applied to the actual sites of power plants in the future.

• Korean Journal of Materials Research
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• v.34 no.7
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• pp.341-354
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• 2024

Today, the principles of green chemistry are being fundamentally applied in the chemical industry, such as the nitrobenzene industry, which is an essential intermediate for various commercial products. Research on the application of response surface methodology (RSM) to optimize nitrobenzene synthesis was conducted using a sulfated silica (SO₄/SiO₂) catalyst and batch microwave reactor. The nitrobenzene synthesis process was carried out according to RSM using a central composite design (CCD) design for three independent variables, consisting of sulfuric acid concentration on the silica (%), stirring time (min), and reaction temperature (℃), and the response variable of nitrobenzene yield (%). The results showed that a three-factorial design using the response surface method could determine the optimum conditions for obtaining nitrobenzene products in a batch microwave reactor. The optimum condition for a nitrobenzene yield of 63.38 % can be obtained at a sulfuric acid concentration on the silica of 91.20 %, stirring time of 140.45 min, and reaction temperature of 58.14 ℃. From the 20 experiments conducted, the SO₄/SiO₂ catalyst showed a selectivity of 100 %, which means that this solid acid catalyst can potentially work well in converting benzene to nitrobenzene.

• Bulletin of the Korean Chemical Society
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• v.34 no.4
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• pp.1195-1198
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• 2013

Nickel hexacyanoferrate supported palladium nanoparticles (Pd-NiHCF NPs) were synthesized and studied for oxygen reduction reactions in direct methanol fuel cell. The NiHCF support was readily synthesized by a comixing of $Ni(OCOCH_3)_2$ and equimolar $K_3[Fe(CN)_6]$ solution into DI water under rigorous stirring. After the preparation of NiHCF support, Pd NPs were loaded on NiHCF via L-ascorbic acid reduction method at $80^{\circ}C$. Pd-NiHCF NPs were electrochemically active for oxygen reduction reaction in 0.1 M $HClO_4$ solution. X-ray absorption near edge structure analysis was conducted to measure the white line intensity of Pd-NiHCF to verify the OH adsorption. As a comparison, carbon supported Pd NPs exhibited same white line intensity. This study provides a general synthetic approach to easily load Pd NPs on porous coordination polymers such as NiHCF and can provide further light to load Pd based alloy NPs on NiHCF framework.

• Journal of Advanced Engineering and Technology
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• v.6 no.2
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• pp.125-129
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• 2013

In the pyrochemcial process of spent nuclear fuel, it is necessary to separate rare earth nuclides from LiCl-KCl eutectic waste salt for radioactive waste reduction. This paper presents the phosphorylation of neodymium chloride in LiCl-KCl-NdCl₃ system using Li₃PO₄-K₃PO₄ as a phosphorylation agent in a chemical reactor with pitched blade impellers. The phosphorylation test was performed changing operation temperature, stirring rate, and amount of phosphorylation agent. Neodymium chloride was effectively converted into neodymium phosphate (NdPO₄). It was confirmed that more than 99 wt% of neodymium can be separated from LiCl-KCl-NdCl₃ system using a phosphorylation method l

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.3 no.1
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• pp.75-84
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• 1993

Copper coating on graphite powders was carried out by cementation process from copper sulfate solution. Effects of operation variables such as copper ion concentration, stirring speed, reaction time and temperature were investigated to obtain optimum conditions for continuous and uniform copper coating on graphite powders. The activation energy of the copper coating process was found to be 3. 59kcal/mole.

• Applied Chemistry for Engineering
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• v.10 no.8
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• pp.1119-1123
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• 1999

In this paper, electrorefining of uranium metal was studied to develop pyrometallurgical processing technology in molten salt system. The reaction between uranium metal and $CdCl_2$ was taken about 3 hours and the uranium metal deposits were obtained in the form of dendrite grown on the cathode surface in every electrotransport experiment. The shapes of dendrite were changed according to the applied voltages. Current efficiency was decreased with the increase of current density. Deposition rate was not changed after 6 hours and its maxium was obtained at $100{\sim}150mA/cm^2$ of current density and about 75 rpm of stirring speed, respectively. Also, the current efficiency was increased with decrease of the pitch of spiral groove curved on cathode.

• Resources Recycling
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• v.24 no.6
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• pp.24-30
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• 2015

The sulfuric acid leaching of ferromanganese dust was studied. The effect of acid concentration, reaction temperature, stirring rate, particle size and solid to liquid ratio on Mn and Fe extraction in the solution were investigated. It was found that the leaching rate of Mn and Fe increased with increasing reaction temperature and sulfuric acid concentration. Examination of data by shrinking core model suggested that the leaching rate is controlled by chemical reaction at the surface of particle. The activation energy for the leaching reaction of Mn and Fe were calculated to be 79.55 kJ/mol and 77.48 kJ/mol, respectively.

• Korean Chemical Engineering Research
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• v.61 no.2
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• pp.322-327
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• 2023

A design of experiments was evaluated in optimizing MOF-5 synthesis for acetylene adsorption. At first, mixture design was used to optimize precursor concentration, terephthalic acid, zinc acetate dihydrate and N,N-dimethylformamide. More specifically, 13 conditions with various molar ratios were designed by extreme vertices design method. After preparing the samples, XRD, N₂ physisorption and SEM analysis were performed for their characterization. Moreover, acetylene adsorption experiments were carried out over the samples under identical conditions. The optimal precursor composition for MOF-5 synthesis was predicted on a molar basis as follows: terephthalic acid : acetate dihydrate : dimethylformamide = 0.1 : 0.4 : 0.5. Thereafter, multi-level factorial design was designated to investigate the effect of synthesis reaction conditions such as temperature, time and stirring speed. By the statistical analysis of 18 samples designed, 4 reaction parameters were determined for additional adsorption experiments. Therefore, MOF-5 prepared under the synthesis time and temperature of 100 ℃ and 12 h, respectively, showed the maximum adsorption capacity of 15.1 mmol/g.