• Journal of the Korean Crystal Growth and Crystal Technology
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• v.4 no.3
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• pp.315-324
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• 1994

The effects of impurities of the quartz raw materials on the trasformation of quartz to cristobalite were investigated. As the increase of impurities content, the amount of cristobalite crystal increased, whereas the fusion temperature of quartz and the formation temperature of cristobalite decreased. And the courses of the transformation of quartz to cristobalite were examined. The course of quartz $\rightarrow$ transitional noncrystalline phase $\rightarrow$ melt (T) and quartz $\rightarrow$ transitional noncrystalline phase $\rightarrow$ cristobalite $\rightarrow$ melt (C) were always coexisted on the transformation of quartz. In the case of high purity quartz raw material, the T course was predominant, while in low purity quartz raw material, the C course was predominant. And the calculated density of heat treated sand by the quantitative analysis of quartz and cristobalite phase by XRD is well agreed with the measured density by pycnometer. On the melting proces of quartz glass, the volume expansion of sand at a certain temperature can be estimated with the calculated density data.

• Journal of the Korean Ceramic Society
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• v.39 no.11
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• pp.1028-1034
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• 2002

Spinel/zirconia-glass composites prepared by melt-infiltration were fabricated to investigate the effect of zirconia addition on mechanical and optical properties of the composites. The infiltration distance was parabolic with respect to time as described by the Washburn equation and the penetration rate constant, K, decreased due to the reduction in pore size as the amount of zirconia rose. Although the optimum strength(308 MPa) of the Spinel/zirconia-glass composites was observed when the zirconia was added up to 20 wt%, K and transmittance decreased as the zirconia content rose. In conclusion, it suggested that the positive effect of strength as a result of the addition of zirconia was not effective.

• Journal of the Korean Ceramic Society
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• v.46 no.3
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• pp.271-274
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• 2009

Redox investigation of Sn and S ion was attempted in alkaline earth borosilicate glass melts with only 1 mol% $Na_2O$ by means of Square Wave Voltammetry (SWV). According to voltammograms, there was only one peak due to $Sn^{4+}/Sn^{2+}$ in melt doped with $SnO_2$. The calculated standard enthalpy and entropy of the reduction of $Sn^{4+}$ to $Sn^{2+}$ were 116kJ/mole and 62 J/mol K, respectively. The determined redox ratio, [$Sn^{2+}$] / [$Sn^{4+}$] in the temperature range of $1300{\sim}1600^{\circ}C$ was in $0.4{\sim}2.1$. On the contrary, in the voltammogram of melt doped with $BaSO_4$ there was no peak due to $S^{4+}/S^o$ but shoulder that might be attributed to the adsorption of sulfur at the electrode. The absence of the peak related with $S^{4+}/S^o$ was discussed from the view-point of the thermal decomposition behavior of $BaSO_4$ in the glass batch.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.13 no.3
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• pp.99-104
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• 2003

Alumina/zirconia-glass composites prepared by melt-infiltration were investigated to evaluate the influence of zirconia addition on mechanical and optical properties of the composites and glass penetration kinetics. The infiltration distance was parabolic with respect to time as described by the Washburn equation and the penetration rate constant, K, decreased due to the reduction In pore size as the amount of zirconia rose. The zirconia addition increased lightness ($L^*$) but reduced K, transmittance and color sharpness ($C^*$) It can be concluded that the zirconia addition was not effective to the mechanical properties of the composites due to the increase in porosity even though the toughness of the composites increased when zirconia was added up to 15 wt%.

• Nuclear Engineering and Technology
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• v.54 no.4
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• pp.1206-1212
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• 2022

Cold-crucible induction melting (CCIM) technology has been intensively studied as an advanced vitrification process for the immobilization of highly radioactive waste. This technology uses high-frequency induction to melt a glass matrix and waste, while the outer surface of the crucible is water-cooled, resulting in the formation of a frozen glass layer (skull). In this study, for the fabrication of borosilicate glass waste form, CCIM operation test with 60 kg of glass per batch was conducted using surrogate wastes composed of Cs, Sr, and Nd as a representative of highly radioactive nuclides generated during spent nuclear fuel management. A 60 kg-scale glass waste form was successfully fabricated through melting and draining processes using a CCIM system, and its physicochemical properties were analyzed. In particular, to enhance the controllability and reliability of the draining process, an air-cooling drain control method that can control draining through air-cooling near drain holes was developed, and its validity for draining control was verified. The method can offer controllability on various draining processes, such as molten salt or molten metal draining processes, and can be applied to a process requiring high throughput draining.

• Elastomers and Composites
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• v.54 no.3
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• pp.182-187
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• 2019

To improve the mechanical properties of glass-fiber-reinforced polypropylene (PP) composites through interfacial adhesion control between the PP matrix and glass fiber, the surface of the glass fiber was modified with PP-graft-maleic anhydride (MAPP). Surface modification of the glass fiber was carried out through the well-known hydrolysis-condensation reaction using 3-aminopropyltriethoxy silane, and then subsequently treated with MAPP to produce the desired MAPP-anchored glass fiber (MAPP-a-GF). The glass-fiber-reinforced PP composites were prepared by typical melt-mixing technique. The effect of chemical modification of the glass fiber surface on the mechanical properties of composites was investigated. The resulting mechanical and morphological properties showed improved interfacial adhesion between the MAPP-a-GF and PP matrix in the composites.

• Fibers and Polymers
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• v.4 no.1
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• pp.20-26
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• 2003

The thermal behavior, morphology, ester-interchange reaction of Poly(trimethylene terephthalate) (PTT)/poly(ethylene terephthalate) (PET) melt blends were investigated over the whole composition range(xPTT/(1-x)PET) using a twinscrew Brabender. The melt blends were analyzed by differential scanning calorimetry (DSC), nuclear magnetic resonance spectroscopy ($^{13}{C-NMR}$), and scanning electron microscopy (SEM). Single glass transition temperature ($T_g$) and cold crystallization temperature ($T_cc$) were observed in all melt blends. Melt blends were found to be due to the ester-interchange reaction in PTT/PET blend. Also the randomness of copolymer increases because transesterification between PT and PET increases with increasing blending time This reaction increases homogeneity of the blends and decreases the degree of crystallinity of the melt blends. In PTT-rich blends, mechanical properties decrease with increase of PET content compared with that of pure PTT. And, in PET-rich blends, tensile modulus decreases with increase of PTT content, but tensile strength and elongation is similar to that of pure PET.

• Proceedings of the KAIS Fall Conference
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• 2004.11a
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• pp.96-98
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• 2004

At the previous papers, we showed that K2O-CaO-P2O5 glasses had a solubility in air so that they could be used for glass fertilizer. In this work, we fabricated the Eco-glass fertilizer containing trace elements such as B, Mg, Zn, Fe, Cu, Co, and Mo by a melt-quenching process and the dissolution properties of these glasses were investigated with pH meter and ICP analyzer. In case of the glasses containing the trace elements, effect of trace elements on the dissolutions is not obvious and ignorant the stability of mother glass. Also, the dissolution amounts of each trace elements depend on the mother glass composition and the quantity of each trace element, and mother glasses determined the dissolving velocity of chemical elements.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1994.05a
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• pp.130-132
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• 1994

We fabricated Ag ion exchange glass waveguide. Generally, ion-exchange glass waveguide. are suitable for passive integrated optical components such as directional and star couplers. Its advantages include low loss, ease of fabrication, and low material cost. So, we faricated Ag ion-exchange glass waveguides in AgNO$_3$ melt solution from 2 mole %. And we used Sodalime glass as a substrate in the fabrication process. As the results, we observed multivalent ion-exchange in a typical sodalime glass. Diffusion coefficient and depth are predicted by actual experimental data of Stewart. The exchange rate in silver-ion-exchanged waveguides are compared to the exchange time of waveguide fabrication.

• Polymer(Korea)
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• v.24 no.3
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• pp.333-341
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• 2000

Blends consisting of linear shape polylactic acid and star shape polylactic acid (L-PLLA/S-PLLA) have been prepared by melt and solution blending. The effect of blending method on the thermal properties and crystallization behavior of L-PLLA/S-PLLA blends has been investigated. The molecular weight decrease was revealed both in melt and solution blending. S-PLLA was found to be more stable than L-PLLA in the reduction of molecular weight during the course of blending due to its star shape structure. As a result, broad molecular weight distribution was obtained in solution blending. It was found that melting temperature and glass transition temperature decrease with increasing S-PLLA content. Blending method had large influence on the glass transition temperature of PLLA blends, while less effect on melting temperature. From DSC results, it can be noticed that solution blending is more effective blending method to obtain higher crystallinity than melt blending for S-PLLA and blend with higher S-PLLA content.