• Journal of Sensor Science and Technology
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• v.4 no.4
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• pp.70-74
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• 1995

We have observed anisotropic anodisation process for porous silicon formation. The starting material was (100) silicon $n/n^{+}/n$ wafer structured by $n^{+}$-diffusion on n-type substrate and by subsequent n-epitaxial growth. After the top n-silicon epitaxial layer was etched to open the porous silicon layer(PSL) anodisation window, anodisation takes place only to $n^{+}$-buried layer. The process of porous silicon formation on (100) sample was anisotropic, which was evident from that the shapes of the reacted porous silicon layer was all squarelike regardless of the shapes of reaction windows. The experimental results show that the PSL anodisation process does not depend on chemical reaction but does on electrical conduction property, which is hole mobility depending on the crystal direction.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.22 no.2
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• pp.644-650
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• 2021

This study characterized the reforming of methane with carbon dioxide, which is a major cause of global warming. The methane decomposition reaction with carbon dioxide was carried out using transition metal catalysts. The reactivity of tin was lower than that of a transition metal, such as nickel and iron. Most of the decomposition reaction occurred in the solid state. The melting point of tin is 505.03 K. Tin reacts in a liquid phase at the reaction temperature and has the advantage of separating carbon produced by the decomposition of methane from the liquid tin catalyst. Therefore, deactivation due to the deposition of carbon in the liquid tin can be prevented. Methane decomposition with carbon dioxide produced carbon monoxide and hydrogen. Ni was used to promote the catalyst performance and enhance the activity of the catalyst and lifetime. In this study, catalysts were synthesized using the excess wet impregnation method. The effect of the reaction temperature, space velocity was measured to calculate the activity of catalysts, such as the activation energy and regeneration of catalysts. The carbon-deposited tin catalyst regeneration temperature was 1023 K. The reactivity was improved using a nickel co-catalyst and a water supply.

• Applied Chemistry for Engineering
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• v.25 no.2
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• pp.161-166
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• 2014

In this study, effects of pyrite ($FeS_2$) particle sizes on the electrochemical characteristics of thermal batteries are investigated using unit cells made of pulverized pyrite by ball-milling. At $450^{\circ}C$ unit cell discharge test, the electrochemical capacity of $1.46{\mu}m$ pyrite-cell largely increases compared to $98.4{\mu}m$ pyrite-cell, and their internal resistances also decrease. These results are attributed to the increase in the active reaction area of pyrite by ball milling. However, at $500^{\circ}C$ unit cell discharge test, a $1.46{\mu}m$ pyrite cell shows lower internal resistance than that of $98.4{\mu}m$ pyrite cell only at Z-phase region ($FeS_2{\rightarrow}Li_3Fe_2S_4$). After that, a $1.46{\mu}m$ pyrite cell shows a decrease in the cell voltage and an rapid increase of the internal resistance in J-phase region ($Li_3Fe_2S_4{\rightarrow}LiFe_2S_4$) is observed compared to those of $98.4{\mu}m$ pyrite cell. It can be concluded that at the higher temperature, the thermally unstable pulverized pyrite is decomposed thermally as well as self discharged, simultaneously, which causes the higher resistance and lower capacity at $500^{\circ}C$ in J-phase than that of $98.4{\mu}m$ pyrite cell.

• Korean Chemical Engineering Research
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• v.48 no.1
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• pp.10-15
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• 2010

Intensive works have been carried out to develop more efficient solid catalysts for biodiesel production from various feedstocks including refined oils and waste fats. Among many catalysts, metal oxides and ion exchange resins are the most intensively studied ones. With regard to metal oxide catalysts, major research activities have focused on the identification of the active compounds and their immobilizing methods on the supports. As metal oxide catalysts have strong thermal stability, they may be used in simultaneous transesterification and esterification of waste fats. However, ion exchange resin catalysts were mainly applied in the esterification of the free fatty acids in waste fats because of their lower thermal stability. For both solid catalysts, further works are needed to make them to be used in commercial process. Especially fast deactivation of the solid catalyst would be the most challenging problem.

• Applied Chemistry for Engineering
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• v.10 no.4
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• pp.515-522
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• 1999

Asymmetric polyetherimide membrane were prepared by phase inversion method, and the effects of NaOH concentration and reaction time on the morphology change of the polyetherimide membranes were studied. The morphology of skin layers varied from dense structure to sphere structure with increasing concentration of modification solution. The thickness of dense layer increased with increasing reaction time. However, when either the concentration of modifying solution was very high or the reaction time was very long, the dense layers of the asymmetric membrane were disappeared. From these results, it was found that the surface morphology of the asymmetric polyetherimide membranes depended strongly on the modification conditions such as concentration of modification solution and reaction time. These results might be explained by the hydrolysis reaction of polyetherimide into polyamic acid by the NaOH solution.

• Korean Chemical Engineering Research
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• v.48 no.5
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• pp.583-588
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• 2010

Esterification of free fatty acid with methanol to biodiesel was investigated in a batch reactor using various solid acid catalysts, such as polymer cation-exchanged resins with sulfuric acid functional group(Amberlyst-15, Dowex 50Wx8), acidic ionic liquids (ILs)-modified silica gels respectively with $-SO_3H$ and $-SO_2Cl$ functional group ($SiO_2-[ASBI][HSO_4]$, $SiO_2-[ASCBI][HSO_4]$) and grafted silica gels respectively with $-SO_3H$ and $-SO_2Cl$ functional group ($SiO_2-R-SO_3H$, $SiO_2-R-SO_2Cl$). The effects of reaction time, temperature, reactant concentration(molar ratio of methanol to oleic acid), and catalyst amount were studied. Allylimidazolium-based ILs on modified silica gels were superior to other tested solid acid catalysts. Especially, the performance of $SiO_2-[ASBI][HSO_4]$ (immobilized by grafting of 3-allyl-1-(4-sulfobutyl)imidazolium hydrogen sulfate on silica gel) was better than that of a widely known Amberlyst-15 catalyst at the same reaction conditions. A high conversion yield of 96% was achieved in the esterification reaction of the simulated cooking oil at 353 K for 2 h. The high catalytic activity of $SiO_2-[ASBI][HSO_4]$ was attributed to the presence of strong Brønsted acid sites from the immobilized functional groups. The catalyst was recovered and the biodiesel product was separated by simple processes such as decantation and filtration.

• Journal of the Korea Society of Computer and Information
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• v.16 no.12
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• pp.167-174
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• 2011

This paper described the estimation methods of CO2 emission of vehicles. The important of energy and environment has emerged in the world, and the field of vehicle's development as well. CO2 was particularly the object of emission-regulation that caused of global warming. There are performance comparison methods by driving mileage, International Panel on Climate Change (IPCC) and chemical equation for the combustion of Octane. We took the measurement by getting data through OBD-II port from vehicle covered 5 km on road. We got the diagnosis information, specific mileage and fuel consumption in this experiment. We are able to expect similar CO2 emission by the methods in the normal speed driving. Also, we can make more realistic approach of CO2 emission by the method of estimation by IPCC and chemical equation for the combustion of Octane in rapid acceleration driving.

• Fire Science and Engineering
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• v.30 no.1
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• pp.31-36
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• 2016

This study investigates the characteristics of thermal decomposition of an epoxy-based intumescent paint using thermogravimetric analysis (TGA) and numerical simulation. A mathematical and numerical model is introduced to describe mass loss profiles of the epoxy-based intumescent coating induced by the thermal decomposition process. The decomposition scheme covers a range of complexity by employing simplified 4-step sequential reactions to describe the simultaneous thermal decomposition processes. The reaction rates are expressed by the Arrhenius law, and reaction parameters are optimized to fit the degradation behavior seen during thermogravimetric (TG) experiments. The experimental results show a major 2-step degradation under nitrogen and a 3-step degradation in an air environment. The experiment also shows that oxygen takes part in the stabilization of the intumescent coating between 200 and $500^{\circ}C$. The simulation results show that the proposed model effectively predicts the experimental mass loss as a function of time except for temperatures above $800^{\circ}C$, which were intentionally not included in the model. The maximum error in the simulation was less than 3%.

• Journal of the Korean Chemical Society
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• v.30 no.4
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• pp.345-351
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• 1986

Monoxo-bridged binuclear molybdenum(V) complex, $[Mo_2O_3\;(bipy)_2\;(NCS)_4]$ in aqueous acetone mixture produces the corresponding dioxo-bridged binuclear molybdenum(V) complex, $MoO_4(bipy)_2(NCS)_2$. The rate of conversion of $[Mo_2O_3(bipy)_2(NCS)_4]$ to $MoO_4(bipy)_2(NCS)_2$ has been measured by spectrophotometric method. The rate of formation of dioxo-bridged binuclear molybdenum(V) complexes with solvent water follows the rate law, rate = k$[Mo_2O_3(bipy)_2(NCS)_4]\;[H_2O]$. The reaction mechanism for the formation of dioxo-bridged complex is discussed. The observed negative volume of activation shows that the complex is strongly attracted to the solvent molecules at transition state.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.22 no.8
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• pp.75-81
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• 2008

Water treatment study employing plasma is thoroughly examined in the following paper. The research using water plasma torch showed superior results in terms of economical and energy efficiency due to the substantial reduction of electric power. A comparison of streamer and arc discharge phenomena taken place in water was put under close scrutiny. Dyeing wastewater exposed to the plasma treatment was sampled and analyzed for relative dissolved ozone concentration, hydrogen peroxide, as well as the color removal efficiency. It was found that streamer discharges is more effective than arc discharge in growth of $H_2O_2$ and $O_3$ by plasma chemical constituents, though plasma torch had small oxidation reagents selectivity. Thus, streamer discharges, due to the efficient plasma-chemical reactions environment, proved to be more efficient compare to the thermal arc plasma loading.