• Bulletin of the Korean Chemical Society
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• v.23 no.12
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• pp.1801-1805
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• 2002

The graphite intercalation compounds(GIC) were prepared by a dry process that led to the intercalation from the direct reaction of gaseous $SO_3$ with flake type graphite. The basal spacing of the GIC was increased from 8.3 ${\AA}$ to 12 in the gallery height. The ejection of interlayer $SO_3$ molecules by the heating for 1 minute at $950^{\circ}C$ resulted in an exfoliated graphite (EG) with surprisingly high expansion in the direction of c-axis. The expansion ratios of the exfoliated graphites were increased greatly between 220 times and 400 times compared to the original graphite particles, and the bulk density was range of 0.0053 to 0.01 $g/cm^3$, depending on reaction time. The pore size distribution of exfoliated graphite was in the range of $10-170{\mu}m$, which exhibites both mesoporosity and macroporosities. This result indicates that the direct reaction of graphite paricles with gaseous $SO_3$ can be proposed as an another route for the exfoliated graphite having excellent physical properties.

• Journal of the Mineralogical Society of Korea
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• v.26 no.2
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• pp.119-127
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• 2013

Borosilicate glass dissolution is an important chemical process that impacts the glass durability as nuclear waste form that may be used for high-level radioactive waste disposal. Experiments reported that the glass dissolution rates are strongly dependent on the bulk composition. Because some relationship exists between glass composition and molecular-structure distribution (e.g., non-bridging oxygen content of $SiO_4$ unit and averaged coordination number of B), the composition-dependent dissolution rates are attributed to the bulk structural changes corresponding to the compositional variation. We examined Na borosilicate glass structures by performing classical molecular dynamics (MD) simulations for four different chemical compositions ($xNa_2O{\cdot}B_2O_3{\cdot}ySiO_2$). Our MD simulations demonstrate that glass surfaces have significantly different chemical compositions and structures from the bulk glasses. Because glass surfaces forming an interface with solution are most likely the first dissolution-reaction occurring areas, the current MD result simply that composition-dependent glass dissolution behaviors should be understood by surface structural change upon the chemical composition change.

• Journal of the Korean Chemical Society
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• v.55 no.1
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• pp.14-18
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• 2011

Esterification of methacrylic acid with ethylene glycol was carried out over Heteropolyacids [HPA: $H_4SiW_{12}O_{40}$ (STA) and $H_3PW_{12}O_{40}$ (PTA)] supported on ZSM-5. For comparison, the same reaction was carried out over unsupported HPA, $H_2SO_4$, $BF_3$ and PTSA. Among the catalysts studied, HPA showed better activity compared to $H_2SO_4$, $BF_3$ and PTSA. Catalytic activity was compared with HPA supported ZSM-5 catalysts. Typical results indicated that 30 wt% PTA supported on ZSM-5 showed nearly the same activity as that of bulk PTA. It was found that the reaction follows first order kinetics with respect to methacrylic acid. The reaction products were identified by $^1H$-NMR and FT-IR.

• Journal of the Korean Society of Combustion
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• v.16 no.4
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• pp.8-15
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• 2011

The present study investigates the combustion phenomena in a sludge incinerator using experimental and numerical method. The temperature and gas concentration were measured at 33 points during operation of the incinerator in order to assess the mixing and combustion characteristics. Numerical simulation was also carried out using a commercial CFD code. Simplified inlet conditions were introduced in oder to predict the bulk solid combustion and the diffusion of the volatile matter released by pyrolysis of sludge. The experimental results showed that the combustion process is extremely inhomogeneous. Large variations were observed in the temperature and gas concentrations in the freeboard of the incinerator due to poor mixing performance between the air and the combustibles, which is caused by massive and bulk generation of volatile matter by fast pyrolysis of sludge particles. The boundary condition of the CFD simulation was found effective in predicting the poor mixing and combustion performance of the reactor.

• Carbon letters
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• v.4 no.4
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• pp.180-184
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• 2003

The role of KOH in the one-stage KOH-activation of rice straws was studied using FTIR, XPS, TGA, and DTG techniques. It was found that at the impregnation, KOH extracts to some extent the lignin component from rice straw and reacts with hydroxyl groups. On heat-treatment, the impregnated KOH facilitates intermolecular condensation reaction on one hand but retards the thermal degradation of cellulose molecules on the other hand. The oxygen-containing surface functional groups newly created by oxidation of KOH may facilitate the bulk, not controlled, consumption of carbon atoms so that the effective porosities may not be able to be developed by the one-stage activation process.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1998.06a
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• pp.371-373
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• 1998

The SmBa$_2$Cu$_3$O$\sub$x/ single crystals were used as seeds to induced YBCO growth in MTG process. As the result, the large bulk oriented YBCO superconductors were prepared with dimension of plane 21mm and 32mm in diameter and 10mm in height. The typical Jc value of the sample is 6.5${\times}$10$^4$A/$\textrm{cm}^2$ and its flux float force is 4.6N/$\textrm{cm}^2$. The oxygen absorption in large bulk textured YBCO samples in pure oxygen was studied at several constant temperatures. It can be divided into two steps: a chemical reaction step and a diffusion step.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1998.06a
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• pp.491-493
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• 1998

The SmBa$_2$Cu$_3$O$\sub$x/ single crystals were used as seeds to induced YBCO growth in MTG process. As the result, the large bulk oriented YBCO superconductors were prepared with dimension of plane 21mm and 32mm in diameter and 10mm in height. The typical Jc value of the sample is 6.5${\times}$10$^4$A/$\textrm{cm}^2$ and its flux float force is 4.6N/$\textrm{cm}^2$. The oxygen absorption in large bulk textured YBCO samples in pure oxygen was studied at several constant temperatures. It can be divided into two steps: a chemical reaction step and a diffusion step.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.321-321
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• 2010

The PEDOT:PSS layer is usually used as hole transporting layer for the polymer bulk heterojunction solar cells. However, the interface between ITO and PEDOT:PSS is not stable and the chemical reaction between ITO and PEDOT can result in degraded device performance. We used the tungsten oxides as a hole transport layer by spin-coating. The $WO_3$ nanoparticles were well dispersed in ammonium hydroxide and deionized water and formed thin layer on the ITO anode. We found that $WO_3$ surface is more hydrophobic than the bare ITO or PEDOT:PSS-coated surfaces. The hydrophobic surfaces promote an ordered growth of P3HT films. A higher degree of P3HT ordering is expected to improve the hole mobility and the lifetime of the device using the tungsten oxide showed better stability compared to the device using the PEDOT:PSS.

• Current Applied Physics
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• v.18 no.11
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• pp.1218-1224
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• 2018

Pressure-dependent structural and morphological changes of two amphibole minerals, tremolite and actinolite, were investigated up to 7.0 GPa using synchrotron X-ray powder diffraction underthree different pressure transmission media (PTM): water (W), $CO_2$ and silicone oil (SI). The elastic response of tremolite and actinolite are found to be dependent on the PTM used. When using water (W) as PTM, tremolite and actinolite show normal volume contractions with bulk moduli of 74(1) and 78(1) GPa, respectively. When using $CO_2$ as PTM, we observe the formation of calcite from tremolite above 3.8(1) GPa, whereas actinolite did not show any carbonation reaction. Under silicone oil PTM, we observe modulated volume contraction behaviors in both samples, compared to water and $CO_2$ PTM, with bulk moduli in the order of 90(1) and 94(4) GPa for tremolite and actinolite, respectively.

• Journal of Industrial and Engineering Chemistry
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• v.67
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• pp.109-122
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• 2018

This work highlights extraction and removal of Lignosulfonate using sunflower oil-Tri-n-octylamine (TOA) system in bulk liquid membrane transport. Maximum extraction and recovery percentages of 92.4% and 75.2% were achieved. Optimum manifold operating conditions were: 4 vol.% TOA, $2{\pm}0.1$ feed phase pH, 300 rpm stirring speed, at $40^{\circ}C$ with 0.2 (M) $Na_2SO_4$ solution. 1:2 (organic/aqueous) and 1:1 (aqueous/aqueous) phase ratios produced best results. Extraction (36.85 kJ/mol) was found to be intermediate controlled and stripping (54.79 kJ/mol) was chemical reaction controlled. Kinetic estimation of data with higher rate constants for stripping vis-${\grave{a}}$-vis extraction showed latter to be rate determining.