• Applied Chemistry for Engineering
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• v.21 no.5
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• pp.495-499
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• 2010

To develop chemical and biosensors, this paper studies sensing characteristics of bulk carbon nanotube (CNT) electrodes by means of their electrical impedance properties due to their large surface area and excellence chemical absorptivity. The sensors were fabricated in the form of film and nano web style by using composite process for mass production. The bulk composite electrodes were fabricated with singlewall and multi-wall carbon nanotubes based on host polymers such as Nafion and PAN, using a solution-casting and an electrospinning technique. The resistance and the capacitance of electrodes were measured with LCR meter under the various amounts of buffer solution to study the electrical impedance change properties of them. On the experimental of sensor electrode, impedance characteristics of the composite electrode are affected by its host polymer and nanofiller and its sensing response showed saturated result after applying some amounts of buffer solution for test chemical. Especially, the capacitance values showed drastic changes while the resistance values only changed within few percent range. It is deduced that the ions in the solution penetrated and diffused into the electrodes surface changed the electrical properties of the electrodes much like a doping effect.

• Journal of Korea Foundry Society
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• v.22 no.1
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• pp.42-48
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• 2002

Effects of coating treatment of metallic Cu, Ni-P film on $SiC_p$, for $SiC_p$/iron aluminide composites were studied. Porous hybrid preforms were fabricated by reactive sintering after mixing the coated $SiC_p$, Fe and Al powders. Then the final composites were manufactured by squeeze casting after pouring AC4C Al alloy melts in preforms. The change of reactive temperature, density, microstructure of the preforms and microstructure of the composites were investigated. The exprimental results were summarized as follows. The thickness of Cu and Ni-P metallic layer formed on $SiC_p$ by electroless plating method were about $0.5{\mu}m$ and coated uniformly. There was no remakable change in the ignition temperature with variation of the mixing ratio of Fe and Al powder while in the case of coated $SiC_p$ it was lower about $20^{\circ}C$ than in the non-coated $SiC_p$. The maximum reaction temperature increased with increasing Al contents, but decreased with increasing $SiC_p$ contents. Expansion ratio of preform after reactive sintering increased with amount of Cu coated $SiC_p$. In the case of Fe-70at.%Al, the expansion ratio was about 7% up to 8wt.% of $SiC_p$, addition but further addition of $SiC_p$, increased the ratio significantly. And in the case of Fe-50 and 60at.%Al, it was about 20% up to 16wt.% of $SiC_p$ addition and about 28% in 24wt.% of $SiC_p$, addition. The microstructures of compounds showed that the grains became finer as amount of $SiC_p$, and mixing ratio of iron powder increased and the shape of compounds was changed gradually from irregular to spheroidal.

• Korean Chemical Engineering Research
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• v.51 no.5
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• pp.622-627
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• 2013

Colloidal silica is used in various industrial products such as chemical mechanical polishing slurry for planarization of silicon and sapphire wafer, organic-inorganic hybrid coatings, binder of investment casting, etc. An accurate determination of particle size and dispersion stability of silica sol is demanded because it has a strong influence on surface of wafer, film of coatings or bulks having mechanical, chemical and optical properties. The study herein is discussed on the effect of measurement results of average particle size, sol viscosity and electrophoretic mobility of particle according to the volume fraction of eight types of silica sol with different size and surface properties of silica particles which are presented by the manufacturer. The measured particle size and the mobility of these sol were changed by volume fraction or particle size due to highly active surface of silica particle and change of concentration of counter ion by dilution of silica sol. While in case the measured sizes of small particles less than 60 nm are increased with increasing volume fraction, the measured sizes of larger particles than 60 nm are slightly decreased. The mobility of small particle such as 12 nm are decreased with increase of viscosity. However, the mobility of 100 nm particles under 0.048 volume fraction are increased with increasing volume fraction and then decreased over higher volume fraction.

• Journal of the Korea institute for structural maintenance and inspection
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• v.17 no.5
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• pp.67-76
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• 2013

In this study, the inhibitive effect of electrochemical treatment subjected to fresh and hardened concrete and literature reviews in terms of the treatment were performed. In hardened concrete, chloride ions are mixed during casting to destroy the passivity of steel, and then the current was provided for 2 weeks with 250, 500 and $750mA/m^2$. After completion of electrochemical treatment, the extraction of chloride ions was quantified and repassivation of steel was observed. Simultaneously, the equated levels of current density for 2 weeks were applied to fresh concrete. Steel-concrete interface in concrete was observed by BSE image analysis and the concrete properties in terms of the diffusivity of chloride ions and the resistance of steel corrosion was measured. As the result, electrochemical treatment is very effectiveness to rehabilitate the passive film on the steel surface and 63-73% of chloride ions in concrete were extracted by the treatment. As the treatment was applied to fresh concrete, the resistance of steel corrosion was improved due to the densification of $Ca(OH)_2$ layers in the vicinity of steel. However, an increase in the current density resulted in an increase in surface chloride content of concrete.

• Korean Journal of Food Science and Technology
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• v.37 no.3
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• pp.405-411
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• 2005

Chitosan, second largest biomass after cellulose on earth, has potential for use as functional food package due to its antibacterial activity. However, due to high melting temperature of chitosan, chitosan films have been made by casting method. Because gelatin has relatively low molting temperature depending upon amount of plasticizer added, it was added to chitosan to produce commercially feasible film. The objective of the current study was to determine optimum blend ratio and amount of chitosan/gelatin blend solutions against antibacterial activities for extruder resin. Gram-positive bacteria (Bacillus cereus ATCC 14579 and Listeria monocytogenes ATCC 15313) and -negative bacteria (Escherichia coli ATCC 25922 and Salmonella enteritidis IFO 3313) were used. Paper (8 mm) diffusion and optical density methods were used to evaluate effect of different blending ratio solutions on the inhibition of bacterial growth. Measured clear none size ranged from 8 mm to 18.07 mm in paper diffusion test. For B. cereus, E. coli, and S. enteritidis, addition of $50\;{\mu}L$ blend solution (chitosan/gelatin = 2/8: 0.3 mg) resulted in clear zone on paper disc. In L. monocytogenes, inhibition effect was observed with 0.6 mg chitosan (chitosan/gelatin=4/6). Minimum inhibitory concentration (MIC) values of B. cerues, L. monocytogenes, E. coli, and S. enteritidis with addition of chitosan were 0.1461, 0.2419, 0.0980, and 0.0490 mg/mL, respectively, These results indicate possibility of producing commercially feasible film with addition of optimum chitosan/gelatin amount.

• Progress in Medical Physics
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• v.16 no.2
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• pp.82-88
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• 2005

In this study, the physical compensator made with the high density material, Cerrobend, and the electronic compensator realized by the movement of a dynamic multileaf collimator were analyzed in order to verify the properness of a design function in the commercial RTP (radiation treatment planning) system, Eclipse. The CT images of a phantom composed of the regions of five different thickness were acquired and the proper compensator which can make homogeneous dose distribution at the reference depth was designed in the RTP. The frame for the casting of Cerrobend compensator was made with a computerized automatic styrofoam cutting device and the Millennium MLC-120 was used for the electronic compensator. All the dose values and isodose distributions were measured with a radiographic EDR2 film. The deviation of a dose distribution was $\pm0.99 cGy\;and\;\pm1.82cGy$ in each case of a Cerrobend compensator and a electronic compensator compared with a $\pm13.93 cGy$ deviation in an open beam condition. Which showed the proper function of the designed compensators in the view point of a homogeneous dose distribution. When the absolute dose value was analyzed, the Cerrobend compensator showed a $+3.83\%$ error and the electronic compensator showed a $-4.37\%$ error in comparison with a dose value which was calculated in the RTP. These errors can be admtted as an reasonable results that approve the accuracy of the compensator design in the RTP considering the error in the process of the manufacturing of the Cerrobend compensator and the limitation of a film in the absolute dosimetry.