• Journal of Powder Materials
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• v.19 no.4
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• pp.278-284
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• 2012

$Al_2O_3$ foam is an important engineering material because of its exceptional high-temperature stability, low thermal conductivity, good wear resistance, and stability in hostile chemical environment. In this work, $Al_2O_3$ foams were designed to control the microstructure, porosity, and cell size by varying different parameters such as the amount of amphiphile, solid loading, and stirring speed. Particle stabilized direct foaming technique was used and the $Al_2O_3$ particles were partially hydrophobized upon the adsorption of valeric acid on particles surface. The foam stability was drastically improved when these particles were irreversibly adsorbed at the air/water interface. However, there is still considerable ambiguity with regard to the effect of process parameters on the microstructure of particle-stabilized foam. In this study, the $Al_2O_3$ foam with open and closed-cell structure, cell size ranging from $20{\mu}m$ to $300{\mu}m$ having single strut wall and porosity from 75% to 93% were successfully fabricated by sintering at $1600^{\circ}C$ for 2 h in air.

• Applied Chemistry for Engineering
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• v.10 no.8
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• pp.1119-1123
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• 1999

In this paper, electrorefining of uranium metal was studied to develop pyrometallurgical processing technology in molten salt system. The reaction between uranium metal and $CdCl_2$ was taken about 3 hours and the uranium metal deposits were obtained in the form of dendrite grown on the cathode surface in every electrotransport experiment. The shapes of dendrite were changed according to the applied voltages. Current efficiency was decreased with the increase of current density. Deposition rate was not changed after 6 hours and its maxium was obtained at $100{\sim}150mA/cm^2$ of current density and about 75 rpm of stirring speed, respectively. Also, the current efficiency was increased with decrease of the pitch of spiral groove curved on cathode.

• Applied Chemistry for Engineering
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• v.9 no.4
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• pp.591-594
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• 1998

Biodegradable microsphere containing bovine serum albumine (BSA) as a model drug were prepared with the microgel based on poly(caprolactone diol) by a modified solvent evaporation method. The influence of the stirring speed, the concentration of microgel and the mixing rate but increased with increasing the concentration of microgel in methylene chloride. The biodegradability of microsphere in 100 unit/mL of lipase solution was investigated. A lot of small pores appeared on the surface of microsphere after 3 hours of incubation time and the pores and cracks were developed with increasing the incubation time and microsphere lost their own shape after 36 hours of incubation time.

• Proceedings of the Korean Institute of Resources Recycling Conference
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• 2003.10a
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• pp.116-121
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• 2003

In this study, the thermal degradation process has been investigated at various reaction temperature$(350{\sim}400^{\circ}C)$ and times$(30{\sim}120\;min)$ in order to recycle waste plastic films as solid state wax. Waste plastic films were easily melted by adding a small amount of waxes. The effects of wax addition and nitrogen flow rate on their thermal degradation properties were investigated. FT-IR, GPC and viscometer were used to analyze properties of the solid wax including the structure, molicular weight distribution and melt viscosity. The average molecular weight of solid wax was decreased with increasing the reaction time, temperature and amount of wax added, Also, the viscosity of solid wax decreased with increasing the stirring speed at a constant reaction temperature and time, and its viscosity got close to zero above $390^{\circ}C$.

• Fibers and Polymers
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• v.3 no.4
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• pp.159-168
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• 2002

Polyurethane foams were produced by using a homogenizer as a mixing equipment. Effects of stirring speed on the foam structure were investigated with SEM observations. Variation of the bubble size, density of the foam, compressive strength, and thermal conductivity were studied. A hybrid foam consisting of polyurethane foam and commercial polystyrene foam is produced. Mechanical and thermal properties of the hybrid foam were compared with those of pure polyurethane foam. Advancement of flow front during mold filling was observed by using a digital camcorder. Four types of mold geometry were used for mold filling experiments. Flow during mold filling was analyzed by using a two-dimensional control volume finite element method. Variation of foam density with respect to time was experimentally measured. Creeping flow, uniform density, uniform conversion, and uniform temperature were assumed for the numerical simulation. It was assumed for the numerical analysis that the cavity has thin planar geometry and the viscosity is constant. The theoretical predictions were compared with the experimental results and showed good agreement.

• Membrane and Water Treatment
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• v.6 no.4
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• pp.277-292
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• 2015

The extraction of lactic acid by an emulsion liquid membrane (ELM), in batch and continuous mode, has been reported. On the basis of preliminary experiments, the optimum composition of the organic phase (membrane) is determined. When the SPan 80 is used as surfactant, the emulsion breakage exceeds 50%, but only 10% is obtained when the ECA4360 is used. The effects of surfactant, carrier and solute concentrations, phase volume ratio, and stirring speed on the extraction yield were examined and optimized. Surfactant, carrier and diluent used were ECA4360, trilaurylamine (TLA) and dodecane, respectively; 2-ethylhexane-1,3-diol (EHD) is used as a co-surfactant. Under optimal conditions, emulsion breaking is very low and the swelling is kept at its lowest level. Under the pH conditions of fermentation medium, the extraction yield is lower. A mixer-settler continuous system was used for testing these conditions. The residence time, the number of extraction stages and the stability of the emulsion were studied and optimized. The extraction yield obtained exceeds 90%.

• Membrane and Water Treatment
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• v.10 no.2
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• pp.127-137
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• 2019

The D2EHPA/TBP co-extractants immobilized PolyHIPE membrane can be used for the selective separation of Mn (II) from Co (II). By solvent-nonsolvent method, D2EHPA/TBP co-extractants can be effectively immobilized into PolyHIPE membrane. The pore structure of PolyHIPE membrane and the presence of TBP enhance the stability of immobilized co-extractants. The optimal operating conditions for the separation of Mn (II) and Co (II) are feeding phase at pH 5.5, sulfuric acid concentration in the stripping phase of about 50 g/L and stirring speed at 400 rpm. The D2EHPA/TBP co-extractants ratio of 5:1 shows synergetic effect on Mn/Co separation factor about 22.74. The removal rate and recovery rate of Mn (II) is about 98.4 and 97.1%, respectively, while for Co (II) the transport efficiency is insignificant. The kinetic study of Mn (II) transport shows that high initial flux, $J_f^o=80.1({\mu}mol/m^2s)$, and maxima stripping flux, $J_s^{max}=20.8({\mu}mol/m^2s)$, can be achieved with D2EHPA/TBP co-extractants immobilized PolyHIPE membrane. The stability and reusability study shows that the membrane can maintain a long term performance with high efficiency. High purity of Co (II) and Mn (II) can be recovered from the feeding phase and stripping phase, respectively.

• Applied Chemistry for Engineering
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• v.22 no.4
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• pp.444-446
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• 2011

Nanosized polystyrene (PS) particles with the narrow size distribution were synthesized from styrene monomer at the presence of the surfactant (polyvinylpyrrolidone, PVP), the solvent of 95 % alcohol, and the initiator of benzoyl peroxide (BPO). Since the emulsion polymerization method was applied, many factors could have effects on the size of PS particles during polymeric process. Aside from the concentration of monomer, surfactant and initiator, the factors such as the stirring speed and the ultrasonic radiation were mainly studied. By adjusting the radiating time, PS particles with their size of about 400 nm were synthesized.

• Advances in nano research
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• v.11 no.6
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• pp.667-678
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• 2021

Multiwalled carbon nanotubes (MWCNTs) were first oxidized (O-CNTs) to introduce carboxylic group and then further functionalized (F-CNTs) with m-phenylenediamine, which was confirmed by FTIR and SEM. It was used as an effective adsorbent for the adsorptive removal of diclofenac drug from water. Under optimum conditions of pH 6, stirring speed 600 rpm, the maximum adsorption capacity obtained was 532 mg g^-1 which is superior to the values reported in literature. The adsorption was quite rapid as 25 mg L^-1 drug solution was adsorbed in only 3 minutes of contact time with 10 mg of adsorbent dose. The adsorption kinetics and isotherms were studied using various models to evaluate the adsorption process. The results showed that the data best fit in kinetics pseudo-second order and Langmuir isotherm model. Furthermore, the oxidized and functionalized MWCNTs were applied on gram-negative Escherichia coli and gram-positive Staphylococcus aureus using agar disc diffusion assay to validate their anti-microbial activity. Results were unique as both oxidized and functionalized MWCNTs were equally active against both E. coli and S. aureus. The newly synthesized F-CNTs have great potential in water treatment, with their dual action of removing drug and pathogens from water, makes it potential applicant to save environment.

• Korean Chemical Engineering Research
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• v.61 no.2
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• pp.322-327
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• 2023

A design of experiments was evaluated in optimizing MOF-5 synthesis for acetylene adsorption. At first, mixture design was used to optimize precursor concentration, terephthalic acid, zinc acetate dihydrate and N,N-dimethylformamide. More specifically, 13 conditions with various molar ratios were designed by extreme vertices design method. After preparing the samples, XRD, N₂ physisorption and SEM analysis were performed for their characterization. Moreover, acetylene adsorption experiments were carried out over the samples under identical conditions. The optimal precursor composition for MOF-5 synthesis was predicted on a molar basis as follows: terephthalic acid : acetate dihydrate : dimethylformamide = 0.1 : 0.4 : 0.5. Thereafter, multi-level factorial design was designated to investigate the effect of synthesis reaction conditions such as temperature, time and stirring speed. By the statistical analysis of 18 samples designed, 4 reaction parameters were determined for additional adsorption experiments. Therefore, MOF-5 prepared under the synthesis time and temperature of 100 ℃ and 12 h, respectively, showed the maximum adsorption capacity of 15.1 mmol/g.