• Journal of the Korean Electrochemical Society
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• v.4 no.3
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• pp.109-112
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• 2001

An activated carbon paste electrode was modified with the N-Hydroxysuccinimide(NHS) layer and applied to determine the dopamine in the presence of an excess ascorbic acid using square-wave voltammetry. The electrochemical properties of the modified electrode were examined in the solution containing dopamine/ascorbic acid using cyclic voltammetry(CV): the separation between the oxidation peaks of dopamine and ascorbic acid was largely dependent on the pH of the sample solution and became maximum at pH 4.0. Hence, the square-wave voltammetric determination of dopamine was carried out in a pH 4.0, 100mM phosphate buffer saline(PBS) containing 140mM NaCl. The detection limit and response slop were improved from $1.0{\mu}M\;to\;5.0\times10^{-2}{\mu}M\;and\;from\;0.93{\mu}A/{\mu}M\;to\;6.1{\mu}A/{\mu}M$, respectively, upon modification of the electrode surface by NHS.

• Journal of the Korean Chemical Society
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• v.37 no.8
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• pp.723-729
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• 1993

Cu(II) ion-responsive chemically modifed electrodes (CMEs) were constructed by incorporating 1-(2-pyridylazo)-2-naphthol (PAN) into a conventional carbon-paste mixture of graphite powder and Nujol oil. Cu(II) ion was chemically deposited on the surface of the PAN-chemically modified electrode in the absence of an applied potential by immersion of the electrode in a buffer solution (pH 3.2) containing Cu(II) ion, and then reduced at a constant potential in 0.1 M KNO$_3$. And a well-defined voltammetric peak could be obtained by scanning the potential to the positive direction. The electrode surface could be regenerated with exposure to acid solution and reused for the determination of Cu(II) ion. In 5 deposition / measurement / regeneration cycles, the response could be reproduced with 6.1${\%}$ relative standard deviation. In case of using the differential pulse voltammetry, the calibration curve for Cu(II) was linear over the range of 2.0 ${times}$ 10$^{-7}$ ∼ 1.0 ${times}$ 10$^{-6}$ M. And the detection limit was 6.0 ${times}$ 10$^{-8}$ M. Studies of the effect of diverse ions showed that Co, Ni, Zn, Pb, Mg and Ag ions added 10 times more than Cu(II) ion did not influence on the determination of Cu(II) ion, except EDTA and oxalate ions.

• Journal of the Microelectronics and Packaging Society
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• v.25 no.4
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• pp.123-128
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• 2018

Effect of activators in flux on the printability and wettability of a solder paste was evaluated in this study. The activators in this study were dicarboxylic acids, which were oxalic acid (n = 0), malonic acid (n = 1), succinic acid (n = 2), glutaric acid (n = 3), adipic acid (n = 4), and pimelic acid (n = 5). When the solder pastes were observed with a SMT scope, solder with glutaric acid showed clean and shiny surface when it was melted. Slump ratio of the solder pastes was low when the carbon numbers of the dicarboxylic acid were 1-3. Spreadability was high when the carbon number was over 2. Zero cross time of wetting balance test was under 1 sec when the carbon number was over 3. When activator was oxalic acid or malonic acid, zero cross time was over 1 sec and maximum wetting force was low. Fluxes with the oxalic acid and malonic acid showed decomposition at the temperature close to melting point. Among the dicarboxylic acids, glutaric acid provided excellent slump, spreadability, and wettability.

• Journal of the Korean Electrochemical Society
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• v.13 no.1
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• pp.50-56
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• 2010

The multi-wall carbon nano-tube composite mixed with carbon paste electrode presented more sensitive and selective amperometric signals in the oxidation of glucose than general screen-printed carbon electrodes(SPCEs). Redox mediators to transport electrodes from enzyme to electrodes are very important part in the biosensor. A novel osmium redox complex was synthesized by the coordinating pyridine group containing primary amines which were electrochemically immobilized onto the MWCNT-SPCEs surface. Electrochemical studies of osmium complexes were investigated by cyclic voltammetry, chronoamperometry. The surface coverage of osmium complexes on the modified carbon nano-tube electrodes were significantly increased at 100 time (${\tau}_0=2.0\;{\times}\;10^{-9}\;mole/cm^2$) compared to that of the unmodified carbon electrodes. It's practical application of the glucose biosensor demonstrated that it shows good linear response to the glucose concentration in the range of 0-10 mM.

• Korean Journal of Materials Research
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• v.14 no.11
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• pp.807-812
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• 2004

The uniformity of emission mage and field emission properties of carbon nanotube(CNT) cathodes dependence on CNT particle dispersion were investigated for field emission displays. We used multi-walled carbon nanotubes (MWNTs) synthesized by CVD method as the field emitter materials. CNT dispersion in CNT ink was carried out by ultrasonication and shaking methods. According to CNT dispersion conditions, the uniformity of emission image and field emission properties of CNT cathodes were greatly affected. The smaller particles of filler materials and CNT powders provide the better properties of the CNT cathodes.

• Journal of Information Display
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• v.7 no.2
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• pp.22-25
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• 2006

This paper presents heating process for obtaining standing carbon nanotube emitters to improve field-emission properties from the screen-printed multiwalled carbon nanotube (MWCNT) films. In an atmosphere with optimum combination of nitrogen and air for heat treatment of CNT films, the CNT emitters can be made to protrude from the surface. This allows for high emission current and the formation of very uniform emission sites without special surface treatment. The morphological change of the CNT film by this technique has eliminated additional processing steps, such as surface treatment which may result in secondary contamination and damage to the film. Despite its simplicity the process provides high reproducibility in emission current density which makes the films suitable for practical applications.

• Advances in concrete construction
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• v.11 no.5
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• pp.367-374
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• 2021

The present study investigated the effect of the combined carbonation and steam curing on the physicochemical properties and CO₂ uptake of the Portland cement concrete. Four different curing regimes were adopted during the initial 10 h of curing to evaluate the potential of carbonation curing as an alternative to conventional steam curing in the precast concrete industry from environmental and practical viewpoints. Four combinations of carbonation and steam curing conditions were applied as curing regimes to the samples at an early age. The test results indicated that the samples treated with the combined carbonation and steam curing exhibited higher early strength development compared to the other samples, signifying that carbonation curing can reduce the production time of precast concrete. Furthermore, the CO₂ uptake capacity of the samples was calculated and found to be as high as 18% with respect to the mass of the paste samples. Hence, the simultaneous utilization of steam and CO₂ for the fabrication of precast concrete members has the potential to make precast concrete greener and more cost-effective.

• Journal of the Korean Chemical Society
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• v.51 no.3
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• pp.291-297
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• 2007

• KCI Concrete Journal
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• v.12 no.1
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• pp.79-89
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• 2000

This research developed an accelerated curing processe for cellulose fiber reinforced cement composites using vigorous reaction between carbon dioxide and cement paste. A wet-processed cellulose fiber reinforced cement system was considered. Carbonation curing was used to complement conventional accelerated curing. The parametric study followed by optimization investigation indicated that the carbonation curing can enhance the productivity and energy efficiency of manufacturing cellulose fiber reinforced cement composites. This also adds environmental benefits to the technical and economical advantages of the technology.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2021.11a
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• pp.135-136
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• 2021

This study investigated the use of different amounts of eggshell powder (ESP), namely 5%, 10%, and 15% by weight, as a substitute for Ordinary Portland Cement. The results show that its flowability and 28-day compressive strength. Meanwhile the carbon dioxide emission was though sustainable assessment analyzed It was concluded that ESP replacement level of around 5% provides the best performance to reduces environmental pollution.