• Clean Technology
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• v.21 no.4
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• pp.271-277
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• 2015

A photocatalyst which mixed by the commercialized P25-TiO₂ and a synthesized Ag_xO was used in an appropriate weight ratio to effectively produce hydrogen gas in this study. The Ag_xOs were synthesized with the conventional sol-gel method, and tetramethylammonium hydroxides were added at the synthesis process in order to stabilize the solutions, and then the solutions were heat-treated at the temperatures of -5, 25, and 50 ℃, resulted to obtain the three types of silver oxides. Physicochemical properties of the synthesized Ag_xOs were identified through X-ray diffraction analysis (XRD), scanning emission microscopy (SEM), ultraviolet-visible spectroscopy, and X-ray photoelectron spectroscopy (XPS). In the photolysis results of water/methanol (weight ratio 1:1) solution, the mixture of P25-TiO₂/Ag_xO exhibited a significantly higher hydrogen gases evolution, compared to that of pure P25-TiO₂. Additionally, the addition of H₂O₂ as an supplement oxidant and in Ag_xO synthesized at 50 ℃ improved the hydrogen production efficiency. In particular, the emitted hydrogen gases reached to 13,000 μmol during 8 hours when a mixed catalyst, Ag_xO of 0.1 g and P25-TiO₂ of 0.9 g, were used.

• Clean Technology
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• v.21 no.1
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• pp.53-61
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• 2015

In this study, we have investigated the kinetics on the char-CO₂ catalytic gasification reaction. Thermogravimetric analysis (TGA) experiments were carried out for char-CO₂ catalytic gasification of an Indonesian Kideco sub-bituminous. Na₂CO₃ and K₂CO₃ were selected as catalysts which were physically mixed with coal. The char-CO₂ catalytic gasification reaction showed a rapid increase of carbon conversion rate at 850 ℃, 60 vol% CO₂, and 7 wt% Na₂CO₃. At the isothermal conditions ranging from 750 ℃ to 900 ℃, the carbon conversion rates increased as the temperature increased. Four kinetic models for gas-solid reaction including the shrinking core model (SCM), random pore model (RPM), volumetric reaction model (VRM), and modified volumetric reaction model (MVRM) were applied to the experimental data against the measured kinetic data. The gasification kinetics were suitably described by the MVRM for the Kideco sub-bituminous. The activation energies for each char mixed with Na₂CO₃ and K₂CO₃ were found 55-71 kJ/mol and 69-87 kJ/mol.

• Clean Technology
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• v.28 no.3
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• pp.232-237
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• 2022

Biorefineries, in which renewable resources are utilized, are an eco-friendly alternative based on biomass feedstocks. Alginic acid, a major component of brown algae, which is a type of marine biomass, is widely used in various industries and can be converted into value-added chemicals such as sugars, sugar alcohols, furans, and organic acids via catalytic hydrothermal decomposition under certain conditions. In this study, ruthenium-supported activated carbon and magnesium oxide were mixed and applied to the depolymerization of alginic acid in a batch reactor. The addition of magnesium oxide as a basic promoter had a strong influence on product distribution. In this heterogeneous catalytic system, the separation and purification processes are also simplified. After the reaction, low molecular weight alcohols and organic acids with 5 or fewer carbons were produced. Specifically, under the optimal reaction conditions of 30 mL of 1 wt% alginic acid aqueous solution, 100 mg of ruthenium-supported activated carbon, 100 mg of magnesium oxide, 210 ℃ of reaction temperature, and 1 h of reaction time, total carbon yields of 29.8% for alcohols and 43.8% for a liquid product were obtained. Hence, it is suggested that this catalytic system results in the enhanced hydrogenolysis of alginic acid to value-added chemicals.

• Korean Chemical Engineering Research
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• v.50 no.5
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• pp.908-912
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• 2012

Lauan sawdust was gasified by steam reforming for hydrogen production from biomass waste. The fixed bed gasification reactor with 1m height and 10.2 cm diameter was utilized for the analysis of temperature and catalysts effect. Steam was injected to the gasification reactor for the steam reforming effect. Lauan sawdust was mixed with potassium carbonate, sodium carbonate, calcium carbonate, sodium carbonate + potassium carbonate and magnesium carbonate + calcium carbonate catalysts of constant mass fraction of 8:2 which was injected to the fixed gasification equipment. The compositions of production gas of gasification reaction were analyzed at the temperature range from $400^{\circ}C$ to $700^{\circ}C$. Fractions of hydrogen, methane and carbon monoxide gas in the production gas increased when catalysts were used. Fractions of hydrogen, methane and carbon monoxide gas were increased with increasing temperature. The highest hydrogen yield was obtained with sodium carbonate catalyst.

• 한국신재생에너지학회:학술대회논문집
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• 2010.06a
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• pp.252.1-252.1
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• 2010

These studies convert to useful electricity from swine wastewater and to treat this wastewater. In order to operate the microbial fuel cell(MFC) for the swine wastewater, the anode volume of MFCs was scaled up with 5L in the vacant condition. Graphite felts and low-priced mesh stainless-less as electrode had mixed up and packed into the anode compartment. The meshed stainless-less electrode could also be acted the collector of electron produced by microorganisms in anode. For a cathode compartment, graphite felt loaded Pt/C catalyst was used. Graphite felt electrode embedded in the anode compartment was punched holds at regular intervals to prevent occurred the channeling phenomenon. The sources of seeding on microbial fuel cell was used a mixture of swine wastewater and anaerobic digestion sludge(1:1). It was enriched within 6 days. Swine wastewater was fed with 53.26 ml/min flow rate. The MFCs produced a current of about 17 mA stably used swine wastewater with $3,167{\pm}80mg/L$. The maximum power density and current density was 680 $mW/m^3$ and 3,770 $mA/m^3$, respectively. From these results it is showed that treatment of swine wastewater synchronizes with electricity generation using modified low priced microbial fuel cell.

• Applied Chemistry for Engineering
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• v.9 no.1
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• pp.89-93
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• 1998

To increase performance of electrodes used in PAFC the new fabrication method was introduced and its characteristics were investigated. In the case of traditional method, electrodes show low performance because of dead catalysts. So new process was investigated to increase the utilization of Pt catalyst. After preparing PTFE/C slurry and Pt/C powder respectively, they were mixed at the ratio of 4:6, 5:5, 6:4, 7:3, 8:2, 9:1 and electrodes were fabricated. In this case of [PTFE/C(6/4):Pt/C(1/9)=5:5], the performance of electrode, $310mA/cm^2$ at 0.7V, was most excellent.

• Progress in Superconductivity
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• v.11 no.1
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• pp.47-51
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• 2009

For many large-scale applications of high-temperature superconducting materials, large critical current density ($J_c$) in high applied magnetic fields are required. A number of methods have been reported to introduce artificial pinning centers in $YBa_2Cu_3O_{7-{\delta}}$ films for enhancement of their $J_c$. We studied the microstructures and characteristic of $YBa_2Cu_3O_{7-{\delta}}$ films fabricated on $SrTiO_3$ (100) substrates with ZnO nanorods as pinning centers. Au catalyst nanoparticles were synthesized on STO substrates with self assembled monolayer to control the number of ZnO nanorods. The density of Au nanoparticles is approximately $240{\sim}260{\mu}m^{-2}$ with diameters of $41{\sim}49nm$. ZnO nanorods were grown on STO by hot-walled PLD with Au nanoparticles. Typical size of ZnO nanorod was around 179 nm in diameter and $2{\sim}6{\mu}m$ in length respectively. YBCO films deposited directly on STO substrates show the c-axis orientation, while YBCO films with ZnO nanorods exhibit any mixed phases without any typical crystal orientation.

• Proceedings of the Materials Research Society of Korea Conference
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• 2003.11a
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• pp.132-132
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• 2003

Second-order nonlinear optical(NLO) materials have been extensively studied for applications in photonic devices, such as frequency doubling and electro-optical(EO) modulation, because of their large optical nonlinearity, excellent processibility, low dielectric constant, and high laser damage thresholds. The poling behaviour of NLO chromophore in organic/inorganic matrixes showed the randomization of poled NLO chromophore in the absence of poling Held. The liquid crystal molecules in a droplet showed a long-range orientational order along a director. Therefore, liquid crystal effects on poling behaviour of NLO chromophore dispersed in organically modified inorganic sol-gel materials were investigated. Using sol-gel process for the development of NLO material has received increasing attention, Organically modifked inorganic NLO sol-Eel materials are obtained via incorporation of the organic NLO active chromophore into an alkoxysilane based inorganic network. One of the most important thing in this works was that tetraethoxysilane(TEOS) and methyltrimathoxysilane(HTMS) were used as precursor followed by hydrolysis and condensation without using any acidic catalyst during the process. The NLO chromophores in the liquid crystal nanodomains were well mixed with I/O hybrid matrix, deposited on transparent ITO-coated glasses. The poling behaviour of liquid crystal effects of NLO chromophore dispersed in I/O hybrid matrix were investigated by UV-vis spectroscopy. Size distribution and morphology of the NLO chromophores doped in the liquid crystal nanodomains dispersed in I/O hybrid matrix were investigated by SEM.

• KEPCO Journal on Electric Power and Energy
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• v.2 no.4
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• pp.589-593
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• 2016

Microbial fuel cell (MFC) can produce electricity from oxidation-reduction of organic and inorganic matters by electrochemically active bacteria as catalyst. Stacked MFCs have been investigated for overcoming low electricity generation of single MFC. In this study, two-typed stacked-MFCs (submerged-flat and stand-falt) were operated according to electrode connection for optimal stacked technology of MFC. In case of submerged-flat MFC with all separator electrode assembly (SEA) sharing anode chamber, MFC with mixed-connection showed more voltage loss than MFC with single-connection method. And MFC stacked in parallel showed better voltage production than MFC stacked in series. In case of stand-flat MFC, voltage loss was bigger when SEAs sharing anodic chamber only were connected in series. Voltage loss was decreased when SEAs parallel connected SEAs sharing anodic chamber were connected in series.

• Journal of Environmental Science International
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• v.23 no.5
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• pp.829-837
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• 2014

Titania-supported chromium oxides with different loadings have been embarked in catalytic oxidation of trichloroethylene (TCE) to inquire association of the formation of crystalline $Cr_2O_3$ with catalytic performances. A better activity in the oxidative TCE decomposition at chosen temperatures was represented when chromium oxides ($CrO_x$) had been dispersed on pure anatase-type $TiO_2$ (DT51D) rather than on phase-mixed and sulfur-contained ones such as P25 and DT51. The extent of TCE oxidation at temperatures below $350^{\circ}C$ was a strong function of $CrO_x$ content in $CrO_x$/DT51D $TiO_2$, and a noticeable point was that the catalyst has two optimal $CrO_x$ loadings in which the lowest $T_{50}$ and $T_{90}$ values were measured for the TCE oxidation. This behavior in the activity with respect to $CrO_x$ amounts could be associated with the formation of crystalline $Cr_2O_3$ on the support surface, that is less active for the oxidation reaction, and an easier mobility of the surface oxygen existing in noncrystalline $CrO_x$ species with higher oxidation states, such as $Cr_2O_8$ and $CrO_3$.