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        검색결과 2,503

        1921.
        2003.09 KCI 등재 구독 인증기관 무료, 개인회원 유료
        A copolymer 〈HSAs : EA/EMA/2-HEMA/AAEM) which is an acrylic resin containing 70% solid content was synthesized by the reaction of monomers, including ethyl acrylate, ethyl methacrylate, and 2-hydroxyethyl methacrylate with a functional monomer, such as acetoacetoxyethyl methacrylate, which may give improvements in cross-linking density and physical properties of films. The physical properties of prepared acrylic resins, HSA containing AAEM, are as follows : viscosity, 203~550cps ; Mn, 2590~2850 ; and conversion, 82~89%, respectively. It was found from the plotting of Tg versus viscosity and Tg versus molecular weight that viscosity increased with Tg while number averaged molecular weight decreased with increasing Tg.
        4,000원
        1922.
        2003.09 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Electrical properties of carbon filler/PVdF [poly(vinylidene fluoride)] composite were investigated as a funtion of carbon filler/PVdF ratio in the range of 0.2~0.5. Three kinds of comercialzied conductive carbon blacks such as Hiblack 41Y, KE300J, and KE600J, and carbon nanofibers prepared by the catalytic chemical vapor deposition of C2H4 over Ni-Cu catalysts were used as the carbon fillers. The electrical conductivity of carbon filler/PVdF composites were in the range of 0.65 to 13.5 S/cm depending the fillers' electrical conductivity ranging from 5.6 to 23.1 S/cm. Among the carbon fillers used, the KE600J carbon black showed the highest conductivity both in the composite and filler itself because of its high degree of graphitization due to the high-temperature thermal treatment and its high surface area due to the activation treatment.
        4,000원
        1923.
        2003.09 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Poly(oxypropylene-oxyethylene glycol) block copolymer(PBC) oil dispersant, which has low toxicity, high biodegradability, and an excellent dispersion efficiency to crude oils and weathered W/O emulsion was prepared by blending PBC, poly(oxyethylene) oleate, and sorbitan monooleate. The dispersing efficiency was measured by swirling flask method. The PBC oil dispersant had an excellent dispersing efficiency to weathered oil products formed as stable W/O emulsion, and the low toxicity, such as 4000 ppm to Oryzias Latipes(24 hr, TLM), Brine Shrimp Artemia(24 hr, TLM).
        4,000원
        1924.
        2003.09 KCI 등재 구독 인증기관 무료, 개인회원 유료
        In this study, we synthesized p-hexyloxybenzaldehyde(HBA) by using p-hydroxybenzaldehyde and n-hexylchloride. p-dodecylaniline(DDA) prepared by nitration and reduction of dodecylbenzene. The schiff base, p-dodecylbenzylidene-p'-hexyloxyaniline (DBHA) was synthesized by reaction of HBA and DDA. The color of synthetic compound was pale-brown and the yield was 62%. All the synthetic compounds were identified by TLC, FT-IR and iH-NMR.In this study, we synthesized p-hexyloxybenzaldehyde(HBA) by using p-hydroxybenzaldehyde and n-hexylchloride. p-dodecylaniline(DDA) prepared by nitration and reduction of dodecylbenzene. The schiff base, p-dodecylbenzylidene-p'-hexyloxyaniline(DBHA) was synthesized by reaction of HBA and DDA. The color of synthetic compound was pale-brown and the yield was 62%. All the synthetic compounds were identified by TLC, FT-IR and 1H-NMR.
        4,000원
        1926.
        2003.06 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Ultra-thin films of amphiphillic squarylium dye were prepared on the hydrophillic substrate by Langmuir-Blodgett(LB) technique. In this study, the photoelectric properties of a amphiphillic squarylium dye LB film was investigated. The visible light(λ = 684nm ) of xenon lamp was illuminated on the amphiphillic squarylium dye LB films and light absorptivity and photoconductivity were observed. The photoconductivity was nearly constant regardless of nominal layer number. The photoelectric properties of the amphiphillic squarylium dye LB films with bottom electrode showed better than that top electrode.
        4,000원
        1927.
        2003.06 KCI 등재 구독 인증기관 무료, 개인회원 유료
        We have seen the effects of buffer layer in organic light-emitting diodes using poly(N-vinylcarbazole)(PVK). Polymer PVK buffer layer was made using static spin-casting method. Two device structures were made; one is ITO/TPD/Alq3/Al as a reference and the other is ITO/PVK/TPD/Alq3/Al to see the effects of buffer layer in organic light-emitting diodes. Current-voltage characteristics, luminance-voltage characteristics and luminous efficiency were measured with a variation of spin-casting speeds. We have obtained an improvement of luminous efficiency by a factor of two and half when the PVK buffer layer is used.
        3,000원
        1928.
        2003.06 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Fireproofing polyolefin nanocomposite for the application of power distributing panel was prepared by compounding linear low density polyethylene(LLDPE), decabromodiphenyl oxide (DBDPO), Sb2O3 as flame retardant agents, and modified nano clay as filler. The optimized formulation ratio of compounds to prepare the fireproofing polyolefin nanocomposite was obtained. The flame retardant properties for nanocomposite prepared by compounding 22.5 phr of nano clay and 18 phr of DBDPO based on 100 phr of LLDPE were shown that the combustion time. 10~18 s, combustion distance, 12~15 mm and non-melt dropping characteristics. In particular. the content of DBDPO in nanocomposite could be decreased to 18 phr from 40 phr DBDPO for fireproofing composite containing 30 phr of clay. The electrical properties measured from tracking test, had an excellent antitracking properties by not showing the phenomenon of leakage current and sparking.
        4,000원
        1929.
        2003.06 KCI 등재 구독 인증기관 무료, 개인회원 유료
        This paper has applied a simple model to the mass transfer mechanism of Cr(VI) with crownether in a batch-type, supported liquid membrane module. Concentration at pH 3 are as follows : 0.012 kmol/m3≤18-crown-6≤0.036 kmol/m3 and 20 g/m3≤ Cr(VI)≤500 g/m3. The measured values of forward- and backward-reaction rate constants between Cr(VI) and 18-crown-6 were used to simulate the model with the mass conservation equation and associated boundary conditions. Comparison between the experimental and simulated facilitated factor of Cr(VI) transport led to classification of reaction regions.
        4,200원
        1930.
        2003.06 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Electron transfer through an Langmuir-Blodgett(LB) monolayer film sandwiched between metal electrodes. We used an eicosanoic acid material and the material was very famous as a thin film insulating material. Eicosanoic acid monolayer was deposited by Langmuir-Blodgett(LB) technique and a subphase was a CdCl2 solution as a 2×10-4 mol/L. Also we used a bottom electrode as an Al/Al2O3 and a top electrode as a Al and Ti/Al. Here, the Al2O3 on the bottom electrode was deposited by thermal evaporation method. The Al2O3 layer was acted on a tunneling barrier and insulating layer in tunnel diode. It was found that the proper transfer surface pressure for film deposition was 25 mN/m and the limiting area per molecule was about 24 a2/molecule. When the positive and negative bias applied to the molecular device, the behavior shows that a tunnel switching characteristics. This result were analyzed regarding various mechanisms.
        4,000원
        1931.
        2003.06 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Oxidized polyethylene wax is obtained by oxidation of polyethylene wax and it is composed of various chemicals, e.g., fatty acid, alcohol, ketone and ester. The application of oxidized polyethylene wax is determined by the composition of these chemical substances. In this basic study we observed the basic reaction parameters of time, temperature, oxygen concentration and catalysts on the oxidation reaction of low molecular weight polyethylene(PE wax) by analyzing the acid value, physical and chemical properties of oxidized PE wax to develop a new oxidation process. Acid values are increased with temperature increase in the rage of 150℃~180℃ but decreased beyond 190℃. Acid values are also increased with oxygen concentration. As the oxidation reaction proceeds the molecular weight and softening points of oxidation products are decreased by cracking reaction, but the viscosities are increased. To observe the crystallinity of oxidation products SEM experiment was performed. To obtain a high acid-value product in a mild condition, we adopted free radical catalysts and the acid value of the product using catalyst was higher than the product obtained without catalyst in the same reaction condition. The effective initiators were dicumyl peroxide(DCPO), t-butylperoxy-2-ethyl hexanoate(HOPO) and benzoyl peroxide(BPO) having long half-life.
        4,000원
        1932.
        2003.06 KCI 등재 구독 인증기관 무료, 개인회원 유료
        In order to improve the lithium ion battery's performance, the carbon nanofibers were introduced to the anode electrode fabricated with natural graphite particles. The influence of structural adjustment of the particles by the introduction method of carbon nanofibers and the content of carbon nanofibers on the electrical property and charge/discharge characteristics of the electrode were investigated. The electrode fabricated with the mixture of 10 wt% of carbon nanofibers grown separately and 90 wt% of graphite particles showed an excellent discharge capacity of 400 mAh/g and the improved cycle performance. The improved performance could be explained by that the carbon nanofibers shortened and uniformly distributed on the surface of graphite particles by ball milling increased the stability for the intercalation/deintercalation of lithium ion and increased the electrical conductivity due to the closed packing between graphite particles.
        4,200원
        1933.
        2003.06 KCI 등재 구독 인증기관 무료, 개인회원 유료
        The effects of molecular structure on the redox properties of the organic electroluminescent materials (Ir(ppy)3 Ir(m-ppy)3 Ir(p-toly)3) were studied using cyclic voltammetry and spectroscopy. These iridium complexes show reversible oxidation and reduction on the electrode, which produce the symmetric cyclic voltammogram. It indicates that these materials are very stable under repetitive oxidation/reduction cycles. The electrochemically determined ionization potentia/electron affinity values are 5.4OeV/3.02eV for Ir(ppy)3, 5.36eV/2.96eV for Ir(m-ppy)3, and 5.35eV/2.97eV for Ir(p-toly)3 from the SCE(Standard Calomel Electrode). The electrically determined band gaps are 2.38eV (521nm), Ir(ppy)3, 2.4OeV (517nm), Ir(m-ppy)3, and 2.38eV (521nm). Ir(p-toly)3, which are similar with the optical band gaps. The position of methyl group on 2-phenylpyridine (ppy) effects do not influence much on the ionization potential, electron affinity, and band gap of Ir(ppy)3 derivatives.
        4,000원
        1934.
        2003.06 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Silver nanoparticles was synthesized by the method of W/O microemulsions with AOT (bis(2-ethylhexyl) sodium sulfosuccinate). The nucleation particle growth and aggregation was controlled by the droplet exchange process. The intermicellar exchange reaction is varied by changing the AOT and the H2O concentration. The synthesized W/O microemulsions was found to give the nanoparticles, which was confirmed by SEM, TEM, particle-size-analyzer, and UV-spectrometer. The most stable particles was obtained at 0.056 mole AOT solution, and the particle size distribution was found in the range from 27 to 31 nm. The mean particle size was reduced by adding Tween 20 significantly, and distribution was found from 14 to 16 nm. And, It's size was reduced by cosurfactants as toluene and benzyl alcohol. In case of toluene and benzyl alcohol, the range of particle size was found 7~11 nm and 8~12 nm.
        4,000원
        1935.
        2003.06 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Pyrophosphoric modified polyesters (TATBs) were synthesized by polycondensation of adipic acid, trimethylolpropane, 1,4-butanediol, and tetramethylene bis(orthophosphate). Two-component PU flame-retardant coatings (TATBCs) were prepared by blending TATBs with HDI-Biuret. Most of the physical properties of the flame-retardant coatings were comparable to those of non-flame-retardant coatings. Coatings containing 10 and 15wt% 1,4-butanediol, TATBC-10C and TATBC-15C were not flammable in the vertical flame-retardancy test.
        4,000원
        1936.
        2003.06 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Provitamin B5 liquid crystal (PVB5-LC) was the new emulsion system to enhance moisturizing activity on the skin. In this study, it should be mentioned that PVB5-LC could be prepared with the main compound of hydrogenated lecithin (HL) in oil-in water (O/W) emulsion. The key ingredient of humectants was contained 2% of provitamin B5 (PVB5) into the PVB5-LC. The best suitable compositions of PVB5-LC were made from 4.0 wt% of HL, 4.0 wt% of cetostearyl alcohol (CSA) as emulsifier and gelling agent, 3.0 wt% of 1,3-butylene glycol (1,3-BG) and 2.0 wt% of glycerin as moisturizers, 3.0 wt% of cyclomethicone (CMC), 3.0 wt% of isononanoate (ININ), 3.0 wt% of capric/caprylic triglyceride (CCTG), 3.0 wt% of macadamia nut oil (MNO) as emollients. As the analytical result of PVB5-LC, it could know that the distribution range of particle size was 0.14 to 12.37 m level (mean size 3.24 m). It was certified the multi lamellar phase around the droplet of liquid crystal when observed the droplet particles through a polarization microscope. And it clinically was tested the effectiveness of moisturizing activity (in-vivo) compared with control sample (O/W emulsion). The effectiveness of moisturizing activity of PVB5-LC with Skincon-200EX after 6 hours went up 49.0% (p〈0.05, n=20) whereas the effectiveness of moisturizing activity of generally O/W emulsion cream was 25.7% (p〈005, n=20). Also, in case of Comeometer CM-825, the moisturizing activity of PVB5-LC after 6 hours rose 36.6% (p〈0.05, n=20) whereas the effectiveness of moisturizing activity of generally O/W emulsion cream was 10.8%. Therefore, it was known that the effectiveness moisturizing activity of PVB5-LC with HL was remarkably superior compared with O/W emulsion cream.
        4,000원
        1937.
        2003.06 KCI 등재 구독 인증기관 무료, 개인회원 유료
        We studied electrochemical characteristics of Langmuir-Blodgett(LB) films by using cyclic voltammetry with a three-electrode system. An Ag/AgCl as a reference electrode, a platinum wire as a counter electrode and LB film-coated indium tin oxide(ITO) as a working electrode were used to study electrochemical characteristics at a various concentration of NaClO4 solution. LB films were reduced from initial potential to -1350 mV, continuously oxidized to l650mV and returned to the initial point. The scan rate was l00mV/s. The monolayer surface morphology of the LB film have been measured by Atomic Force Microscope(AFM). As a result, We comfirmed that the microscopic properties of LB film by AFM showed the good orientation of momolayer molecules and the thickness of monolayer was 3.5-4.lnm. The cyclic voltammograms(CV) of the ITO-coated glass showed the peak potentials for the reduction-oxidation reation. LB films of 4-octyl-4'-(5-carboxypentamethyleneoxy) azobenzene(8A5H) / L-α-phosphayidyl choline, dilauroyl(DLPC) seemed to be irreversible process caused by only the oxidation current from the cyclic voltammogram. The current of oxidatation increased at cyclic voltammogram by increasing 8A5H density in LB films. The diffusivity(D) of LB films increased with increasing of a 8A5H amount and was inversely proportional to the concentration of NaClO4 solution.
        4,000원
        1938.
        2003.06 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Two-component polyurethane flame retardant coatings (ATTBC) were prepared by blending polyisocyanate (TDI-adduct) with ATTBs mentioned at the previous paper. Most of the physical properties of the flame retardant coatings were comparable to those of non-flame retardant coatings. Especially, the hardness, impact resistance, and accelerated weathering resistance were remarkably improved with the increase of the content of 1,4-butanediol. Coatings containing 10 and 15 wt% 1,4-butanediol, ATTBC-10C and ATTBC-15C, were not flammable in vertical flame-retardancy test. Their char area recorded 1.1~11.6 cm2 in 45˚ eckel burner method.
        4,000원
        1939.
        2003.06 KCI 등재 구독 인증기관 무료, 개인회원 유료
        To prepare alkaline degreasing agents(SADAs), tetrasodium pyrophosphate(TSPP), Na2CO3, Tetronix T-701 (T-701), Na-dioctyl sulfosuccinate(303C), Demol C, and MJU-100A were blended. The prepared degreasing agents were tested with steel specimens and the results were as follows. The degreasing powers of SADA-6(Na2CO3 50g/TSPP 25g/T-701 10g/303C 15g/Demol C 12g/MJU-100A 8g/water 130g mixture) for press-rust preventing oil were 98% and 99% degreasing at 4wt%, 70 ℃ and 90 ℃, respectively; for quenching oil, the degreasing power of SADA-6 was 92% degreasing at 4wt% and 70 ℃. From these results, it was proved that the SADA-6 exhibits a good degreasing power. Foam heights measured immediately after foaming by Ross & Miles method and Ross & Clark method at 6wt% and 60 ℃ were 16mm and 40mm, respectively. SADA-6 was proved a good low foaming degreasing agent.
        4,000원
        1940.
        2003.03 KCI 등재 구독 인증기관 무료, 개인회원 유료
        The impregnated activated carbons were prepared by the incipient wetness method with the contents of KIO3 varied from 1.0~10 wt% as the impregnation material. The specific surface area and micropore volume of the rice hulls activated carbon were 2,600~2,800 m2/g and 1.1~1.4 cc/g, respectively. With increasing the contents of impregnation materials, the surface area and micropore volume decreased by 3~21%. However, The amounts of hydrogen sulfide adsorbed increased by 2.1~2.8 times depending on the impregnation content. The optimum contents of KIO3 were 2.4 wt%. Although the breakthrough time and adsorption capacity of hydrogen sulfide decreased with increasing temperature in the case of the unimpregnated activated carbons, they increased by 1.2~ 3.2 times for the case of the impregnated activated carbons. The optimum aspect ratio(L/D) was 1.0 and the adsorption amount of hydrogen sulfide enhanced with increasing the gas flow rate. The regeneration temperature was determined as 400℃ from the TGA experiment. The adsorption capacity of hydrogen sulfide with the impregnated activated carbon decreased gradually as the regeneration continued. The hydrogen sulfide adsorption amount of the regenerated activated carbon up to 4 times was still higher than that of the unimpregnated activated carbon.
        4,000원