• Journal of Korean Society for Atmospheric Environment
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• v.1 no.1
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• pp.99-107
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• 1985

A coated wire ion selective electrode for nitrate (nitrate-CWE_ was constructed using epoxy resin, ion exchanger and plasticizer as a polymer membrane. It's stility, the composition of a polymer membrane, the response characteristics, the selectivity were examined and applied to the environmental analysis. The nitrate-CWE was prepared using a copper wire, wihch was coated with epoxy resin being incorporated with the nitrate ion exchanger and plasticizer. The best composition of the polymer membrane for the nitrate-CWE was obtained by mixing epoxy resin, ion exchanger and plasticizer in the ratio of 2:1:0.4. The potential (56.3$\pm$0.5 mV) of stick form nitrate-CWE in this composition was close to that (59.2 mV) of Nernstian response. The detection limit for nitrate ion were found to the about $6 \times 10^{-5}M$ and the useful pH was 2.5 $\sim$ 10.3. Furthermore, the selectivity of iodide and perchrorate for the nitrage-CWE was also much improved compared with that for a liquid membrane nitrate electrode. The nitrate-CWE was used to determind $NO_x$ in stack gas. The results were in good agreement with those obtained either by electrode method or by the improved NEDA method within a relative error of 4.0%.

• Advanced Composite Materials
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• v.16 no.4
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• pp.269-282
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• 2007

Fully biodegradable high strength composites or 'advanced green composites' were fabricated using yearly renewable soy protein based resins and high strength liquid crystalline cellulose fibers. For comparison, E-glass and aramid ($Kevlar^{(R)}$) fiber reinforced composites were also prepared using the same modified soy protein resins. The modification of soy protein included forming an interpenetrating network-like (IPN-like) resin with mechanical properties comparable to commonly used epoxy resins. The IPN-like soy protein based resin was further reinforced using nano-clay and microfibrillated cellulose. Fiber/resin interfacial shear strength was characterized using microbond method. Tensile and flexural properties of the composites were characterized as per ASTM standards. A comparison of the tensile and flexural properties of the high strength composites made using the three fibers is presented. The results suggest that these green composites have excellent mechanical properties and can be considered for use in primary structural applications. Although significant additional research is needed in this area, it is clear that advanced green composites will some day replace today's advanced composites made using petroleum based fibers and resins. At the end of their life, the fully sustainable 'advanced green composites' can be easily disposed of or composted without harming the environment, in fact, helping it.

• Journal of the Korean Society for Precision Engineering
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• v.30 no.8
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• pp.878-884
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• 2013

Stereolithography can be classified into two main categories according to the cross-sectional shape: scanning type and projection type. Projection stereolithography has significant advantages when making a layer using a single patterned beam, and results in improved speed and accuracy. To implement relatively low-cost projection stereolithography, we developed a system using a commercially available resin, which cures on exposure to visible light. The optimum photoinitiator was investigated, as well as the mixing ratio. The viscosity, shrinkage, curing depth and tensile strength were evaluated through several experiments on fabricated three-dimensional structures, and thus an optimal resin selection system was developed.

• Proceedings of the KIEE Conference
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• 1996.07c
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• pp.1498-1501
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• 1996

To evaluate insulating properties of polyimide thin film on high temperature over $100\;^{\circ}C$, polyimide film were prepared by electrophoretic deposition onto metal surface from nonaqueous emulsion. The emulsion is made by adding a solution of the resin to a precipitant, which is an organic liquid compeltely miscible with the solvent of the organic resin solution, but which does not dissolve the resin. The polyimide film obtained by annealing shows good insulation properties of 5.8 MV/cm at elevated temperature and breakdown strength of the film reveals thickness dependence.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.19 no.7
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• pp.67-73
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• 2020

Shrinkage is inevitable in the curing of resins during the nanoimprint process. The degree of shrinkage that occurs as the resin transforms from a viscous liquid to solid differs depending on the type of resin. However, if the cured material is repeatedly cured using the same material, constant shrinkage can be confirmed. In this study, the pattern of change was observed by repeatedly performing the nanoimprint process using a resin with a constant shrinkage rate. The observed pattern for the change of shape was made using a triangular pyramid-shaped aluminum master mold and a flexible replica mold made from the master. Shrinkage that results from the nanoimprint process occurs linearly in the longitudinal direction of the pattern and can be predicted by simple calculations. The change of the pattern due to shrinkage occurred as expected. If the shrinkage rate remains constant, various patterns can be manufactured with high accuracy by correcting these changes before producing a specific shape. This study confirms that the pattern of the desired angle can be obtained by performing the repeated imprint without having to manufacture a master mold.

• Journal of the Korean Society for Precision Engineering
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• v.15 no.8
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• pp.39-45
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• 1998

In the previous study. the powder casting was attempted as the rapid tooling. The powder casting was the process to cast dry powder into the casting mold transferred from R/P model and infiltrate the liquid binder to solidify the powder. And then, the melted copper was infiltrated to control the shrinkage rate of the final mold Conseqently, the shrinkage rate was under 0.1% through that process. The mechanical characteristic was also excellent. Generally, in the slurry casting, the alumina powder and the water soluble phenol were mainly used. However, the mechanical property of the phenol was not good enough to apply to molds directly. In this study, aluminium powder filled with epoxy is applicated to the slurry casting to solve these problems. The mechanical and thermal properties are better than phenol because the epoxy is the thermosetting resin. We achieved a successful result that the shrinkage rate is shortened about 0.047%. Futhermore, the manufacturing time and cost savings are significant. Finally, we assume that the developing possibility of this process is very optimistic.

• Korean Chemical Engineering Research
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• v.47 no.3
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• pp.303-309
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• 2009

The effects of zeolite type catalysts addition on the thermal decomposition of low density polyethylene(LDPE) and ethylene vinyl acetate(EVA) resin have been studied in a thermal analyzer(TGA, DSC) and a small batch reactor. The zeolite type catalysts tested were natural zeolite, FCC catalyst, used FCC catalyst, and catalyst A. As the results of TGA experiments, addition of antifogging-agent decreased the pyrolysis point to $250^{\circ}C$, but addition of longevity-agent and clay reduced the pyrolysis rate in EVA resin. Addition of the zeolite type catalysts in the LDPE resin increased the pyrolysis rate in the order of catalyst A > used FCC catalyst > natural zeolite > LDPE resin. Addition of the zeolite type catalysts in the EVA resin increased the pyrolysis rate in the order of used FCC catalyst > natural zeolite > catalyst A > EVA resin. In the DSC experiments for LDPE resin, addition of zeolite type catalysts decreased the melting point and the heat of pyrolysis reaction in the order of catalyst A > used FCC catalyst > natural zeolite> LDPE resin. In the batch system experiments, the mixing of natural zeolite enhanced the yield of liquid fuel oil.

• Applied Chemistry for Engineering
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• v.9 no.1
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• pp.66-70
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• 1998

Several liquid crystalline monomers were synthesized and characterized to utilize as new matrix materials of liquid crystal/polymer composite films for display application. Liquid crystalline compounds which have azo group as center link, cyano group at one of the terminal position in common and bromoalkyl(azo(n)), azidoalkyl(AZI(n)), aminoalkyl(ALC(n)) as the terminal group were synthesized and identified respectively by FT-lR, $^1H-NMR$ spectrometer and elemental analysis. All these compounds exhibited nematic liquid crystalline region in the certain temperature range as determined by DSC and polarized optical microscope. These liquid crystalline compounds also showed a typical even-odd effect in both $T_{KN}$ and $T_{NI}$ due to conformational change as the length of terminal alkyl chain, $-(CH_2)n-$. was varied.

• Proceedings of the Korean Radioactive Waste Society Conference
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• 2004.02a
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• pp.12-27
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• 2004

Pretreatment process consisted of submerged hollow-fiber microfiltration(HMF) membrane and spiral-wound nanofiltration(SNF) membrane has been developed by NETEC, KHNP for the purpose of improving the impurities of liquid radioactive waste before entering Selective Ion Exchange System(SIES). The lab-scale combined system was installed at Kori NPP #2 nuclear power plant and demonstration tests using actual liquid radioactive waste were carried out to verify the performance of the combined system. The submerged HMF membrane was adopted for removal of suspended solid in liquid radioactive waste and the SNF membrane was used for removal of particulate radioisotope such as, Ag-l10m and oily waste because ion exchange resin can not remove particulate radioisotopes. The liquid waste in Waste Holdup Tank (WHT) was processed with HMF and SNF membrane, and SIES. The initial SS concentration and total activity of actual waste were 38,000ppb and $1.534{\times}10_{-3}{\mu}Ci/cc$, respectively. The SS concentration and total activity of permeate were 30ppb and lower than LLD(Lower Limit of Detection), respectively.

• ETRI Journal
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• v.41 no.6
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• pp.820-828
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• 2019

A highly reliable conductive adhesive obtained by transient liquid-phase sintering (TLPS) technologies is studied for use in high-power device packaging. TLPS involves the low-temperature reaction of a low-melting metal or alloy with a high-melting metal or alloy to form a reacted metal matrix. For a TLPS material (consisting of Ag-coated Cu, a Sn96.5-Ag3.0-Cu0.5 solder, and a volatile fluxing resin) used herein, the melting temperature of the metal matrix exceeds the bonding temperature. After bonding of the TLPS material, a unique melting peak of TLPS is observed at 356 ℃, consistent with the transient behavior of Ag₃Sn + Cu₆Sn₅ → liquid + Cu₃Sn reported by the National Institute of Standards and Technology. The TLPS material shows superior thermal conductivity as compared with other commercially available Ag pastes under the same specimen preparation conditions. In conclusion, the TLPS material can be a promising candidate for a highly reliable conductive adhesive in power device packaging because remelting of the SAC305 solder, which is widely used in conventional power modules, is not observed.