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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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Journal of Korean Society for Atmospheric Environment
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Korean Society for Atmospheric Environment
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Volume & Issues
Volume 16, Issue 4 - Aug 2000
Volume 16, Issue 6 - Jun 2000
Volume 16, Issue 3 - Jun 2000
Volume 16, Issue 5 - May 2000
Volume 16, Issue 2 - Apr 2000
Volume 16, Issue 1 - Feb 2000
Volume 6, Issue 6 - 00 2000
Volume 6, Issue 5 - 00 2000
Volume 6, Issue 4 - 00 2000
Volume 6, Issue 3 - 00 2000
Volume 16, Issue E - 00 2000
Volume 16, Issue E2 - 00 2000
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Formation of Monodisperse Tio₂ Nanoparticles Generated without HPC Dispersant by Controlling Reaction Method and Temperature
김기도 ; 김희택 ;
Journal of Korean Society for Atmospheric Environment, volume 6, issue 5, 2000, Pages 281~281
Monodiperse TiO？nanoparticles were synthesized from tetracthyl orthotitanate (TEOT) dissolved in ethanol using a semibatch method, shich is easier than a batch process in controlling the size, shape, and size distribution, without the addition of HPC. In this semibatch method, without the addition of HPC. In this semibatch wywtem, the preparation conditions of a low flow rate (1.1 cc/min) and high reaction temperature (70？C) were applied to produce monodiperse nanoparticles. As a result, the smallest size nanoparticles, As a result, the smallest size nanoparticles (？12.7 nm in diameter) with a narrow size distribution were produced. In addition, it was found that the TCOT solution and a high temperature, at shich poing the solubility of the solute increased, thereby decreasing the particle size. In conclusion, at which point the solubility of the solute increased, thereby decreasing the particle size. In conclusion, the efficacy of nanoparticle synthesis was established by controlling the reaction method and temperature.
Catalytic Properties and Characteristics of situ Reduced Cu-ZnO-Al₂O₃ Catalysts
K. S. Rama Rao ; 전기원 ; 선은제 ; 이규완 ;
Journal of Korean Society for Atmospheric Environment, volume 6, issue 5, 2000, Pages 287~287
A Cu-ZnO-Al₂O₃catalyst prepared using the oxalate copocess was subjected to in situ reduction using hydrazine in order to get variable amounts of $Cu^0$, $Cu^+1$, and $Cu^+2$ in the catalyst. The effect of the Cu-oxidation state in the catalyst on its activty clearly indicated that easily reducible $Cu^+2$ species are responsible for creating a high Cu-metal area and thereby a high methanol yield and the presence of $Cu^+1$ crystallites in the fresh catalyst results in an inferior methanol yield. The CO₂ desorbed amounts in the low temperature regions were in line with the Cu-metal area. Therefore, it would appear that the easily reducible CuO sites can adsorb and desorb CO₂ at low temperatures and these common sites are responsible CuO sites can adsorb and desorb CO₂ at low temperatures and these common sites are responsible for creating a Cu-metal area and thereby methanol production from CO₂hydrogenation. However, the presence of ZnO in a poorly crystalline state is active for CO₂hydrogention yet, enhances the RWFS reaction rather methanol formation.
Characterization of Nickel Sulfate Supported on Zirconia and Its Acidic Properties
손종락 ; 박은희 ;
Journal of Korean Society for Atmospheric Environment, volume 6, issue 5, 2000, Pages 297~297
Nickel sulfate supported on zirconia catalysts was prepared by drying the powdered Zr(OH)₄with aqueous solution of nickel sulfate follwed by calcining in air at a high temperature. The characterization of the prepared catalysts was performed using Fourier transform infrared (FTIR), X-ray diffraction (XRD), temperature programmed (TPD), differential scanning calorimetry (DSC), and by the measurement of the surface area. The addition of nickel sulfate to zirconia shifted the phase transition of ZrO₂from amorphous to tetragonal to a higher temperature due to the interaction between nickel sulfate and zirconia, plus the specific surface area and acidity of the catalysts increased in proportion to nickel sulfate content up to 15 wt% fo NiSO₄On the basis of the ZRD, DSC, surface area, and acidity results it was determined that the nickel sulfate monolayer content that covered most of the available zirconia was estimated to be 15 wt% both of NiSO₄. The infrared spectra of the adsorbed ammonia on NiSO₄/ZrO₂showed the presence of both Bronsted and Lewis acid sites on the NiSO₄/ZrO₂surface.
Hydrogenolysis of HCFC-142b over Supported Palladium Catalyst
이경훈 ; 서경원 ; 목영일 ; 박근유 ; 안병성 ;
Journal of Korean Society for Atmospheric Environment, volume 6, issue 5, 2000, Pages 305~305
1,1-Difluoroethane (HFC--152a), 1,1,1-trifluoroethane (HFC -143), and ethae were mainly produced through the hydrogenolysis of 1-chlro-1, 1-difluoroethane (HCFC-142b) over palladium on activated carbon (Pd/C) catalysts. Several types of activated carbon and various methods for the pretreatment of the support were used for impregnating the palladium. Kepending on the method of pretreating the activated carbon base and/or acid, the catalyst activity showed the following trend; 0.5 M NaOH and 0.5 M HCI>0.5 M HNO₃ > 0.5 M HF > non-pretreated carbon. The granular-type catalyst exhibited the highest conversion selectivity to HFC-152a.
Acidic Properties of Ferric Sulfate Supported on Zirconia and Catalytic Activities for Acid Catalysis
손종락 ; 박은희 ;
Journal of Korean Society for Atmospheric Environment, volume 6, issue 5, 2000, Pages 312~312
Ferric sulfate catalysts supported on zirconia were prepared by drying Zr(OH)₄powder with aqueous ferric sulfate solution, followed by calcining in air. The acidity of the catalysts increased in proportion to the ferric sulfate content up to 6 wt% of Fe which ran in parallel with the surface area. Based on the results of the TPD of the ammonia adsorbed on the catalyst. Fe₂(SO₄)₃/ZrO₂ exhibited various acid strengths and the IR spectra of the sample adsorbed with ammonia showed the presence of boht Bronsted and Lewis acid sites. Fe₂(SO₄)₃/ZrO₂ calcined at 650。C with 1.5 wt% fo Fe exhibited the maximum catalytic activities for 2-propanol dehydration and cumene dealkylation.
Functional Relationship between Volume Concentration of Dispersed Phase and Relative Viscosity in a Liquid-Liquid Dispersion and Emulsion
허병기 ; 김종보 ; 이미령 ;
Journal of Korean Society for Atmospheric Environment, volume 6, issue 5, 2000, Pages 318~318
The successive application of Taylor's equation of relative viscosity to a tolueneglycerin dispersion system leads to a mathematical model expressing the function relationship between the relative viscosity of the dispersion, the volume concentration and the drop size destribution. Experimental results of toluene-glycerin dispersions from 5% to 25% of the volume of toluene were tested against the derived equation. The errors between the experimental viscosities and the values calculated by the proposed model ranged from 0.24% to 2.06%. The average error percentage was 1.109% and the maximum error percentage for the system was 2.06%. To validate the proposed model, for various dispersions, published data were applied to the experimental viscosities and the calculated values ranged from 0% to 3.86% depending on the dispersion materials. The same model was also applied to an emulsion system. The predicted viscosities of the emulsions using the model agreed reasonably well with the experimental data giving a maximum error of 4.1%.
Calculation of Electrostatic Potential in the Aqueous Solution with Adsorptive Protein Layers
Journal of Korean Society for Atmospheric Environment, volume 6, issue 5, 2000, Pages 325~325
Protein adsorption in an aqueous solution is known to be strongly controlled by the interacting electrostatic potential energy in the solution phase because protein molecules themselves have electrical charges on their surfaces. Nonetheless, conventional electrostatics, for example the Gouy-Chapman theory, does not account for the existence of adsorbed protein molecules but rather assumes that there is an imaginary charged surface formed by the ions in the solution . However, a realistic calculation of the electrostatic potential experienced by a colloidal particle in an aqueous solution, means that the adsorbed charged molecular surfaces in the solution should be accounted for. Accordinglym, a model was formulated under the postulation of two different layers representing the adsorbed molecular layer and the bulk solution phase. A modified Poisson-Boltzmann equation describing the existence of the two unique electrical layers was solved numerically. The electrostatic potential was then calculated in terms fo the distance from the air-water interface using parameters such as the ionic strength of the solution, molecular charges of the adsorbed region was shown to be concave-shaped, thereby indecating a slower decay fo the potential near the solution interface compared to the drastic decay in the conventional case with an ideal charged surface. The larger thickness of the molecular layer, which exceeded 2 nm, presumably double-layered or larger, led to a lowering of the maximum potential.
Synthesis and Thermal Properties of Poly(phenylene sulfide-co-phenylene sulfide ketone)
박이순 ; 오헌식 ; 이태형 ; 김순학 ; 황진상 ;
Journal of Korean Society for Atmospheric Environment, volume 6, issue 5, 2000, Pages 331~331
Poly(phenylene sulfide-co-phenylen sulfide ketone)s (PPS/SK) were synthesized from ρ-dichorobenzene (DCB)/4.4'-dichlorobenzophenone (DCBP) and ρ-dibromobenzene (DBB)/DCFP monomer pairs using sodium sulfide trihydrate (Na₂S·3H₂O) in N-methyl-2-pyrrolidinone (NMP) solvent. The yield and molecular weight of the PPS/SK copolymers were higher with the DBB/DCBP/Na₂S monomers. The copolymer composition and molecular weight of the PPS/SK copolymers were determined by an elemental (C, H, S) analysis and high temperature (210。C) GPC with 1-chloronaphthalene as an eluent, respectively. The molecular weight of the PPS/SK copolymers showed a maximum value at a feed ratio of [DBB]/[DCBP] = 70/30 mol%. The plot of the $T_g$'s of the PPS/SK copolymers relative to the copolymer content of the DCBP unit imcreased in the PPS/SK copolymers, the Tg of the PPS/SK copolymer also increased in the PPS/SK copolymers exhibited $T_m$'s with all compositions at a 20。C/min scan rate for the DSC measurement. The eutectic point appeared to be 267.2。C with 29.8 mol% DCBP units in the copolymers.
Termal Properties of Liquid-Crystalline Polyurethances Containing Biphenylene Mesogenic Units
Journal of Korean Society for Atmospheric Environment, volume 6, issue 5, 2000, Pages 338~338
A series of thermotropic polyurethanes containing mesogenic units was synthesized by the polyaddition reaction of diisocyanates such as 2,6-toluene diisocyanate (2,6-PDI), 2,5-toluene diioscyanate (2.5-TDI), 2.4-toluene diisocyanate (2,4-TDI), and 1,4-phenlene diisocyanate (1,4-PDI) with 4,4-bis(6-hydroxyhexyloxy) biphenyl (BP6). The polyurethanes, 2,6-TDI/BP6, and 2,4-TDI/BP6, showed liquid crystallinity in the cooling scan under shearing. For example, a para-type 2,5-TDI/BP6 exhibited liquid crystallinity in the temperature range from 200？C to 178？C and a meta-type 2,4-TDI/BP6 exhibited liquid crystallinity in the temperature range from 132？C to 111？C in the cooling scan. The thermal behavior was investigated using differential scanning calorimetry (DSC),polarizing microscopy. and X-ray diffractometry.
Welding and Fracture Characterisitics of ABS/Zeolite Composites
송영욱 ; 조영신 ; 심미자 ; 김상욱 ;
Journal of Korean Society for Atmospheric Environment, volume 6, issue 5, 2000, Pages 343~343
The mechanical properties at the interface of ABS/zeolite composites developed during hot plate welding were investigated using the lap-shear joint method. The self-bonding strength was proportional to one fourth the power of the welding time proposed by the diffusion models. The strength value of the ABS/zeolite system was lower than of neat ABS due to the bad interfacial strength between the ABS and the zeolite, and the obstruction by the natural zeolite for the diffusion of the ABS molecular chains. As regards the fractrue behavior. the welded specimens showed two types of failure, shear failure and tensile failure due to the stress concentration effect. When the lap shear joint samples were silpped by shear stress, plastically deformed ridges, which were the main feature of the welded specimens appeared on the fractrued surface. Stress-shitening by crazing and local drawign was also observed at the edge of the bonded region on the deformed surface.
Kinetic Characterization of Thermal Degradation Process for Commercial Rubbers
김원일 ; 김성득 ; 이승범 ; 홍인권 ;
Journal of Korean Society for Atmospheric Environment, volume 6, issue 5, 2000, Pages 348~348
The kinetic analysis was carried out for the thermal degradation of commercial rubbers such as NR, IR, BR, SBR, 1500, and SBR 1700 with the intention fo establishing a recovery process based on the relation between the process variables and the yield of pyrolytic oil. The activateon energies and reaction orders of NR, IR BR, SBR, 1500, and SBR 1700 were calculated using conventional kinetic models. When considering the effect of the final temperature on thermal degradation, it was shown that the yield of pylytic oil. generally increased with the increase of final temperature. When considering the effect of the heating rate, it was found that the yield of pyrolytic oil. was not consistent for each sample. The pyrolytic oil was analyzed for the components, benzene, toluene, styrene, ethylbenzene, other benzene derivatives and polycyclic compounds using GC-MDS. And it was conisted of about 50 organic compounds. The colorific value of the rubber-derived oil was about 40 kJ/g, high enough to be used as a fuel.