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Hidehiro Kumazawa,Um, Myeong Heon,Lee, Chul Tae 한국공업화학회 1997 Journal of Industrial and Engineering Chemistry Vol.3 No.4
BaTiO₃ fine particles with perovskite structure were synthesized using amorphous TiO₂ at temperatures as low as 300℃ by hydrothermal method. Barium hydroxide and titanium tetraethoxide were used as starting materials. The relationship between the specific dielectric constant of sintered disks and the mean size of synthesized particles has been investigated. The mean size of the BaTiO₃ particles synthesized by hydrothermal reaction for 4 hours was nearly 0.047㎛ while the barium-to-titanium (BT) molar ratio ≥1.2. The specific dielectric constants of sintered BaTiO₃ disks exceeded 6000 with the particle size of 0.10-0.17㎛. It was speculated that the particle size of resulting disks would considerably affect the specific dielectric constant of resulting disks.
Unsteady-State Absorption of CO_2,into w/o Emulsion with Aqueous Alkaline Liquid Droplets
Park, Sang-Wook,Kumazawa, Hidehiro,Sohn, In-Joe 한국화학공학회 2002 Korean Journal of Chemical Engineering Vol.19 No.1
Unsteady-state absorption of CO_2 into w/o emulsion was studied by experimental measurements and prediction from mathematical modeling. Absorption experiments were performed by using a stirred vessel with a flat gasliquid interface under 0.101 MPa and 25℃. Continuous phase was benzene that has larger solubility than water. Dispersed phase was an aqueous solution of NaOH and AMP. The effects of reactant concentration, size of emulsified droplets, volume fraction of continuous phase and stirring speed on the absorption rate of CO_2 were investigated. In the mathematical model, the mechanism of CO_2 absorption into the continuous phase through a gas-liquid interface was described on the basis of the penetration model, while the subsequent absorption/reaction in the dispersed aqueous droplets was modeled by the film model.
GAS ABSORPTION OF CARBON DIOXIDE IN A HOLLOW FIBER CONTAINED LIQUID MEMBRANE ABSORBER
Park, Sang Wook,Kumazawa, Hidehiro,Suh, Dong Soo,Hwang, Kyoung Son 한국화학공학회 1997 Korean Journal of Chemical Engineering Vol.14 No.4
Experiments on the absorption of CO₂ into a hollow fiber contained liquid membrane absorber were performed. The feed gas was a mixture of CO₂ and N₂, absorbent liquid was 2-amino-2-methyl-l-propanol and the hollow fiber was a microporous hydrophobic polytetrafluoroethylene membrane. Outlet concentration of CO₂from the absorber decreased as absorbent concentration increased, gas flow rate increased and were held constant for speed of agitation, but had a maximum value in the range of inlet concentration of CO₂from 5 to 40 mole %. The reaction rate constant obtained for CO₂-amine system was 231 ℓ/㏖·s at 25℃ using a flat stirred vessel, and the membrane-side-mass-transfer coefficient was 1.217 x 10^(-5) ㏖/㎠·s·atm in CO₂/N₂-amine system. A diffusion model based on mass transfer with fast-reaction was proposed to predict the performance of the absorber.
Kim, Hee Taik,Bae, Seong Youl,Kumazawa, Hidehiro 한국화학공학회 1994 Korean Journal of Chemical Engineering Vol.11 No.3
The modified dual-mole mobility model for permeation of a gas in glassy polymer membranes was combined with the extended dual-mode sorption model to take account of the plasticization effect of sorbed gas molecules on both sorption and diffusion processes. The combined model was further simplified by the introduction of a concentration of the mobile gas species. However, the observed pressure dependence of mean permeability coefficients of carbon dioxide in methylmethacrylate-n-butyl acrylate copolymer and polymethylmethacrylate films at 30℃ and also that of oxygen in a polycarbonate film at 50℃ and 60℃ showed that a plasticization action of sorbed gas species has an influence on the diffusion process rather than on the sorption process, that is, were simulated by the modified dual-mode mobility model combined with the conventional dual-mode sorption model.
Plasticization of Chitosan Membrane for Pervaporation of Aqueous Ethanol Solution
Kim, Hee Taik,Bae, Seong Youl,Kumazawa, Hidehiro,Won, Jang Mook,Ha, Baik Hyun 한국화학공학회 1996 NICE Vol.14 No.4
The process of pervaporation in which two components diffuse through a nonporous polymer membrane was modelled when one of the penetrants can exert a plasticization action to the membrane material. There at a phenomenological model was employed for describing the plasticization effect on the diffusivities for penetrants in the membrane. The sorption equilibria and permeation fluxes for aqueous ethanol solutions in a chitosan membrane were measured, and the permeation fluxes for water were compared with those predicted by the proposed model. The concentration of sorbed water was linear with its weight fraction (x_A) in the feed solution, whereas the permeation flux of water was affected by the plasticization action of sorbed water to the polymer. This plasticization effect on the diffusion process can be simulated in terms of the proposed phenomenological model.
Seong Youl Bae,Hee Taik Kim,Hidehiro Kumazawa 한국화학공학회 1994 NICE Vol.12 No.5
N/A The modified dual-mode mobility model for permeation of a gas in glassy polymer membranes was combined with the extended dual-mode sorption model to take account of the plasticization effect of sorbed gas molecules on both sorption and diffusion processed. The combined model was further simplified by the introduction of a concentration of the mobile gas species. However, the observed pressure dependence of mean permeability coefficients of carbon dioxide in methylmethacry date butylacrylate copolymer and polymethylmethacry late films at 30℃ and also that of oxygen in a polycarbonate film at 51℃ and 60℃ showed that a plasticization action of sorbed gas species has an influence on the diffusion process rather than on the sorption process, that is, were simulated by the modified dual-mode mobility model combined with the conventional dual-mode sorption model.