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        검색결과 2,609

        2001.
        2004.03 KCI 등재 구독 인증기관 무료, 개인회원 유료
        The effects of reaction temperature and flow rate of reactants on the methane conversion, product selectivity, product ratio, and carbon deposition were investigated with 13wt% Ni/MgO catalyst. Reaction temperatures were changed from 600 to 850℃, and reactants flow rates were changed from 100 to 200 mL/mim. There were no significant changes in the methane conversion observed in the range of temperatures used. It is possibly stemmed from the nearly total exhaustion of oxygen introduced. The selectiveties of hydrogen and carbon monoxide did not largely depend on the reaction temperature. The selectivities of hydrogen and carbon monoxide were 96 and 90%, respectively. Carbon deposition observed was the smallest at 750℃ and the largest at 850℃. It is found that the proper reaction temperature is 750℃. The best reactant flow rate was 150 ml/min.
        4,000원
        2002.
        2004.03 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Glycosyl acrylate and methacrylate were synthesized by lipase-catalyzed esterification of vinyl acrylate and vinyl methacrylate with β-methyl glucoside in t-butanol as a reaction medium. At the optimum conditions of initial concentration of 150g/l β-methyl glucoside, molar ratio of 1 : 3, 5%(w/v) lipase(Novozym 435) and 50℃, we attained up to 100% conversion for enzymatic glycosylation of vinyl acrylate and vinyl methacrylate by supersaturated solvent process. The polymerizable glycosyl acrylates and methacrylate are expected to have biomedical application as hydrophilic monomers and hydration modifiers to be used for biocdmpatible hydrogel.
        4,000원
        2003.
        2004.03 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Liquid crystalline phases were formed from acylglutamate; polyglyceryl-10 myristate and glycerine mixture and they were used as a base material for preparing an O/W emulsion. When an oil phase is added into the liquid crystalline phases, it was inserted into the dispersed liquid crystal droplets rather than stayed outside the liquid crystals, which can be known by the fact that the size of liquid crystal droplets increases with the increasing oil phase content. Along with the increase in the droplet size, the complex modulus increases from 100 to 350 pascals and the loss angle decreases from 60 to 24 degrees, from which it can be known that the increase in the internal phase volume results in the increase in the elastic property of oil in liquid crystalline-phases (O/LC). When the water phase was lastly added into the O/LC phase, the emulsification occurred to form a O/W emulsion and the averaged particle size of the O/W emulsion changes from 22.5nm to 538nm with the addition of water phase. The results from the droplet size measurements and stability tests under accelerated conditions such as high temperature show that the obtained O/W emulsion is very consistent with time.
        4,000원
        2004.
        2004.03 KCI 등재 구독 인증기관 무료, 개인회원 유료
        New electroluminescent materials based on anthracene chromophore with naphthylethenyl substituent, 9,10-bis(α-naphthylethenyl)anthracene (a-BNA), as well as four kinds of its derivatives were synthesized, and luminescent properties of these materials were investigated. Electrolumineecent(EL) emission band was discussed based on their substituent structure differences. It was found that the emission band strongly depends on the molecular structure of introduced substituent. It can be tuned from 557 nm to 591 nm by changing the substituent structures. On the other hand, the anthracene chromophore with bulky substituent possessed high melting point and they gave stable films through vacuum-sublimation. The double layer EL device of ITO/TPD/emission layer/Mg:Ag was employed, and exhibited efficient orange light originating from emitting materials. EL emission with a maximum luminance was observed in the b-BNA emitting material, : maximum luminance was about 8,060 cd m-2 at an applied voltage of 10 V and current density of 680 mA/cm2. In conclusion, the electroluminescent properties also showed good difference with their substituent structure.
        4,000원
        2005.
        2004.03 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Silver bromide particles from 50 to 200a in diameter are prepared by mixing two microemulsions contaning the precursor salts AgNO3 and KBr. The microemulsions are composed of AOT(bis(2-ethylhexyl) sodium sulfosuccinate), n-heptane and water. The particle diameters are measured on photomicrographs obtained by transmission electron microscopy. The size of the particles is generally larger than that of the water cores. The influence of both the concentration of precursor salts in the water cores of the microemulsoin and the size of these water cores on the size of the particles has been studied.
        4,000원
        2007.
        2003.12 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Water-soluble cutting fluids are used for processing of aluminium materials. This short article describes properties of new additives of water-soluble cutting fluids for aluminium materials. Various Diels-Alder adducts of unsaturated fatty acids with acrylic acid of maleic anhydride were prepared by thermal reactions. Triethanolamine salts of Diels-Alder adducts of dehydrated castor oil fatty acids with acrylic acid or maleic anhydride showed excellent anti-corrosion property of aluminium materals. These thermal adducts showed anti-rust property for cast-iron chips, too.
        4,000원
        2008.
        2003.12 KCI 등재 구독 인증기관 무료, 개인회원 유료
        In this paper, it was studied about the red-sensitive layer. UV-Vis data of the dye at monomeric and J-state were considered with respect to their performance(contrast, speed, density and fog) in photographic emulsion. The sensitizing effect of the dye is found to be strongly structure-dependent. Naphthctbiazolo carbocyanine dye can be used as red sensitizing dye for the spectral sensitization of photographic emulsion.
        4,000원
        2009.
        2003.12 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Zirconium nitride powders were synthesized at a relatively lower temperature using methane as a reducing agent in the nitridation of zircoia. ZrO2 powder was prepared by a sol-gel technique. The resulting sol-gel was centrifuged, and the gel was washed with deionized water. Anhydrous ammonia was used as the nitrogen source and methane was used as the reducing agent. Conversion diagrams show the equilibrium solid phase as a function of reagent concentrations for a specific temperature and gas pressure for the reagent system NH3-ZrO2-CH4. The reagent concentration ranges within which pure ZrN is formed increase with increasing reaction temperature. Low pressure with an excess of hydrogen decreases the reaction temperature at which pure ZrN is formed. Low pressure together with the introduction of excess hydrogen into the reaction system increases Zr and N conversion efficiency and retards C deposition.
        4,000원
        2010.
        2003.12 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Sodium azide (SA) is commonly used as propellant for inflating automatic safety bags and other chemical manufacturing purposes. The investigation of potentially thermal hazard of sodium azide and its mixture with polymers are very important because it can occur an expected traffic accident so we took a experiment s using different scanning calorimeter (DSC) in nitrogen atmosphere. The decomposition temperature were about 350~450℃. We could find not only exothermic reaction was remarkably decreased in mixture s of acrylonitrile-butadiene-styrene (ABS) and polyvinyl chloride (PVC), but also increasing mixed rate of ABS, polyvinyl alcohol (PVA) and polymethyl methacrylate (PMMA) decreased thermal decomposition heat.
        4,000원
        2011.
        2003.12 KCI 등재 구독 인증기관 무료, 개인회원 유료
        BaTiO3, powders were prepared by sol-gel process from different aging time and reaction temperature. Particle shape, size and crystal structure of prepared BaTiO3 powders were analyzed by SEM, XRD and FT-IR. Effect of aging time alternation didn't particularly show up. Spherical nano-sized BaTiO3 powders were obtained from condition more than reaction temperature 55℃, and obtained sintered BaTiO3 powders of tetragonal phase from heat-treatment at 1,100℃.
        4,000원
        2012.
        2003.12 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Organic acid salt of fatty polyamide (DDDT) and acrylate of fatty carbamide (DDTCA) were synthesized as a main component for the softener. O/W type non-ionic softener (NSC) was prepared by blending DDDT and DDTCA with beef tallow, lanolin anhydride. polyoxyethylene(7) stearyl ether, and polyoxyethylene(50) oleyl ether. After treatment of NSC to all cotton fabrics, the physical properties such as tear strength, crease recovery, and flexing abrasion resistance were measured. As a result of the measurement, NSC was proved to be durable non-ionic softener with good softness.
        4,000원
        2013.
        2003.12 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Crosslinked poly(methyl methacrylate) particles from 2.4 to 8.1μm in diameter were prepared by homogenized suspension polymerization. The effect of polymerization parameters such as homogenizing speed, homogenizing time and stabilizer concentration on the particle size were examined. Optical diffusion films were prepared with the crosslinked poly(methyl methacrylate) particles. The effect of film thickness, particle size, and particle size distribution on transmittance and haze of optical diffusion film was examined. Transmittance of optical diffusion film increased with increasing particle size and decreasing film thickness. Haze increased with increasing film thickness and decreasing particle size. We also found the existence of an optimum ratio for optical performance when the mixture of small particle and large particle was used.
        4,000원
        2014.
        2003.12 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Particulate leaching method for the preparation of porous PLLA scaffolds was carried out and especially, the effect of PLLA/CHCl3 solution concentration on the salt leaching rate and the pore structure of PLLA scaffolds were considered. It was found that maintaining lower PLLA/CHCl3 concentration and higher CHCl3 evaporation temperature in the preparation of PLLA/NaCl mixtures resulted in the enhancement of salt leaching rat e and higher porosity. This is understood that those conditions could minimize the formation of dense PLLA layer on the surface of PLLA/NaCl mixture as well as introducing better porosity on the surface. Higher salt leaching temperature accelerated the salt leaching rate but it seems that there is no influence on the porosity of PLLA scaffolds.
        4,000원
        2015.
        2003.12 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Zinc complexes with bis[2-(o-hydroxyphenyl) naphtol [1,2] oxazolato ligands (ZnPBO-4) and its derivatives (ZnPBO-S) were synthesized, and luminescent properties of these materials were investigated. Both the fluorescent emission band and electroluminescent emission band were discussed based on their ligand structure differences. The emission band found that it strongly depends on the molecular structure of introduced ligand. It was tuned from 446 nm to 491 nm by changing the ligand structures. Spreading of the π-conjugation in 2-(o-hydroxyphenyl) group gives rise to a blue shift. The EL properties also showed good consistency with their differences of ligand structure. Bright-blue EL emission with a maximum luminance of 3,100 cd/m2 at 12V, current density, 575 mA/m2 was obtained from the organic light-emitting diodes (OLEDs) using ZnPBO-4 as emitting layer. It was also found that the newly synthesized materials were suitable to be used as emitting materials in organic EL device.
        4,000원
        2016.
        2003.12 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Extraction of Natural Artemisia by using super critical carbon dioxide is operated under 40-50℃ and 200-250 atm, thus, conversion rate is very low as 7wt% while high energy is being wasted. When Natural Artemisia Extract is applied in the control of microbe, concentration and reaction time greatly affected to the growth of microbe. Especially, when refined oil concentration from Natural Artemisia added more than 1,000ppm, staphylococcus aureus and fungi are terminated completely. Thus, it is proven that Natural Artemisia Extract has antimicrobial effect.
        4,000원
        2017.
        2003.12 KCI 등재 구독 인증기관 무료, 개인회원 유료
        The capacity and long life of gel electrolyte batteries is connected with gas recombination producting PbO2 and Pb electrode. We were prepared with phosphoric acid gel electrolyte to know gel characteristics per density to assemble VRLA batteries. We studied by measuring electrolyte dispersion using Brewster-angle microscope(BAM), charge-discharge cycle and electrode structure using scanning election microscope(SEM) per electrolyte density. As a results, phosphoric acid density 1.210 was excellent gel dispersion in sol condition, electrode condition after fifty cycles in this study.
        4,500원
        2018.
        2003.12 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Synthesis gas is produced commercially by a steam reforming process. However, the process is highly endothermic and energy intensive. Thus, this study was conducted to produce synthesis gas by the partial oxidation of methane to cut down the energy cost. Supported Ni catalysts were prepared by the impregnation method. To examine the activity of the catalysts, a differential fixed bed reactor was used, and the reaction was carried out at 750~850℃ and 1 atm. The fresh and used catalysts were characterized by XRD, XPS, TGA and AAS. The highest catalytic activity was obtained with the 13wt% Ni/MgO catalyst, with which methane conversion was 81%, and H2 and CO selectivities were 94% and 93%, respectively. 13wt% Ni/MgO catalyst showed the best MgNiO2 solid solution state, which can explain the highest catalytic activity of the 13wt% Ni/MgO catalyst.
        4,000원
        2019.
        2003.12 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Alkaline powder cleaning agents (APCAs) were prepared by blending of Na2CO3 tetrasodium pyrophosphate (TSPP). sodium orthosilicate (Na-OSi), Na-dioctyl sulfosuccinate (303C), Demol C, and MJU-100A (100A). The physical properties of APCAs tested with steel specimen showed the following results. The cleaning powers of APCA-6 (Na2CO3 250g/TSPP 70g/Na-OSi 40g/303C 60g/Demol C 50g/100A 30g mixture) for press-rust preventing oil was 97% and 98% degreasing at 2wt%, 70℃ and 90℃, respectively; for Quenching oil, the cleaning power of APCA-6 was 95% degreasing at 2wt% and 70℃. From the results, it was ascertained that APCA-6 exhibited a good cleaning power. Also low foaming power tests proved that the APCA-6 maintained good defoaming effect.
        4,000원
        2020.
        2003.12 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Aqueous polyurethane dispersion was synthesized using phosphorus compound which received significant attention for the replacement of halogenated flame retardants. In this study, polyols which have phosphorus moity in their structural unit were synthesized by two-step polycondensation reaction using dimethyl phenylphosphonate, ethylene glycols. adipic acid, and 1,4-butanediol. In the next step, polyurethane dispersion was prepared using these polyols, isophorone diisocyanate with dimethyl propionic acid. The particle size of polyurethane latex was reduced from 347 nm to 240 nm with increasing DMPA content. It was observed that the LOI values of prepared coatings increased from 27% to 35% with increasing phosphorus content.
        4,000원