• Journal of Electrochemical Science and Technology
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• v.13 no.3
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• pp.390-397
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• 2022

The use of microwaves as the energy source for synthesis and sintering of ceramics offers substantial advantages compared to conventional gas-fired and electric resistance furnaces. Benefits include much shorter processing times and reaching the sintering temperature more quickly, resulting in superior final product quality. Most oxide ceramics poorly interact with microwave irradiation at low temperatures; thus, a more complex setup including a susceptor is needed, which makes the whole process very complicated. This investigation pursued a new approach, which enabled us to use microwave irradiation directly in poorly coupled oxides. In many solid-state electrochemical devices, the support is either metal or can be reduced to metal. Metal powders in the support can act as an internal susceptor and heat the entire cell. Then sufficient interaction of microwave irradiation and ceramic material can occur as the sample temperature increases. This microwave heating and exothermic reaction of oxidation of the support can sinter the ceramic very efficiently without any external susceptor. In this study, yttria stabilized zirconia (YSZ) and a Ni-YSZ cermet support were used as an example. The cermet was used as the support, and a YSZ electrolyte was coated and sintered directly using microwave irradiation without the use of any susceptor. The results were compared to a similar cell prepared using a conventional electric furnace. The leakage test and full cell power measurement results revealed a fully leak-free electrolyte. Scanning electron microscopy and density measurements show that microwave sintered samples have lower open porosity in the electrode support than conventional heat treatment. This technique offers an efficient way to directly use microwave irradiation to sinter thin film ceramics without a susceptor.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.353.2-353.2
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• 2016

We studied electrochemical detection of Botulinum neurotoxin, Vaccinia virus, and Streptococcus Pneumoniae based on nanogap device. Target bio substances were employed as representative targets of protein, virus, and bacteria, respectively. Redox current generated by ferri/ferrocyanide as an electroactive probe was enhanced according to gap distance which was controlled by surface-catalyzed chemical deposition. We found that enhanced electrochemical signal leads more sensitive signal changes according to selective interaction of target and its complementary elements on the electrode or gap area. In case of Botulinum neurotoxin, the redox signal showed a time-dependent increase due to cleavage of the immobilized peptide which blocked redox cycling. Redox cycling was also hindered by Vaccinia virus and Streptococcus Pneumoniae which were selectively immobilized in the gap area.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.18 no.7
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• pp.605-609
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• 2005

Chemical mechanical polishing (CMP) of Ni was performed by the various ratios of four kinds of oxidizers and an addition of alumina powders as an abrasive in each slurry with the different oxidizers. Moreover, the interaction between the Ni and the each oxidizer was discussed by potentiodynamic polarization measurement, in order to compare the effects of Ni-CMP and electrochemical characteristics on the Ni with the different oxidizers. As an experimental result, the removal rate of Ni reached a maximum at 1 $vol\%$ of $H_2O_2$. Also the removal rates of Ni increased with the audition of alumina abrasives in each slurry. The potentiodynamic polarization of Ni under dynamic condition showed a significant difference in electrochemical behavior by addition of $H_2O_2$ in solutions. Ni showed the perfect passivation behavior in solution without $H_2O_2$ under potentiodynamic polarization condition, while active dissolution dominates in solution with the addition of $H_2O_2$. The results indicate that the surface chemistry and electrochemical characteristics of Ni play an important role in controlling the polishing behavior of Ni.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.07b
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• pp.918-921
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• 2003

The electrochemical behavior of vilogen self-assembled monolayer has been investigated with QCM, which has been known as ng order mass detector. The self-assembly process of viologen was monitored using resonant frequency(${\Delta}F$) and resonant resistance(R). The QCM measurements indicated a mass adsorption for viologen assembling on the gold surface with a frequency change about 300, 135 Hz and calculated its surface coverage($\Gamma$) to be $5.02{\times}10^{-9}$ and $1.64{\times}10^{-9}mol/cm^2$. Also a reversible redox process was observed and analyzed with an ionic interaction at the Viologen/solution interface using ${\Delta}F$.

• 한국전기화학회:학술대회논문집
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• 2003.11a
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• pp.141-151
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• 2003

The electrochemical activity of the olivine type $LiMPO_4$ (M=transition metals) cathodes strongly depends on various factors, e.g., the transition metal element M, perturbative doping of the supervalent cations into Li site, composite formation with conductive additives, state of charge/discharge, and particle size and its geometries, etc. This is, therefore, an important issue of interdisciplinary between electrochemistry and solid state science towards practical applications. In order to shed light on this interesting but complicated issue with the transport properties and crystallographic aspects, systematic discussion will be made with the review of our recent publications; (1) first principle derivation of the electronic structures, (2) crystallographic mapping of the selected solid solutions, (3) quantitative elucidation of the electron-lattice interaction, (4) spectroscopic detection of the local environment with Mossbauer and EXAFS, (5) synthetic optimization of the electrode composite, and (6) electrochemical evaluation of the reaction kinetics, particularly on M = Fe, Mn.

• Korean Chemical Engineering Research
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• v.55 no.4
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• pp.483-489
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• 2017

The loss of the sulfur cathode material through dissolution of the polysulfide into electrolyte causes a significant capacity reduction of the lithium-sulfur cell during the charge-discharge reaction, thereby debilitating the electrochemical performance of the cell. We addressed this problem by using a chemical and physical approach called reduction of polysulfide dissolution through direct coating functional inorganic (graphene oxide) or organic layer (polyethylene oxide) on electrode, since the deposition of external functional layer can chemically interact with polysulfide and physically prevent the leakage of lithium polysulfide out of the electrode. Through this approach, we obtained a composite electrode for a lithium-sulfur battery (sulfur: 60%) coated with uniform and thin external functional layers where the thin external layer was coated on the electrode by solution coating and drying by a subsequent heat treatment at low temperature (${\sim}80^{\circ}C$). The external functional layer, such as inorganic or organic layer, not only alleviates the dissolution of the polysulfide electrolyte during the charging/discharging through physical layer formation, but also makes a chemical interaction between the polysulfide and the functional layer. As-formed lithium-sulfur battery exhibits stable cycling electrochemical performance during charging and discharging at a reversible capacity of 700~1187 mAh/g at 0.1 C (1 C = 1675 mA/g) for 30 cycles or more.

• Bulletin of the Korean Chemical Society
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• v.34 no.4
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• pp.1065-1069
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• 2013

A highly sensitive electrochemical detection method for bisphenol A (BPA) has been developed by using multi-walled carbon nanotube (CNT)-doped titania-Nafion composite modified glassy carbon (GC) electrode. The CNT-titania-Nafion/GC electrode exhibited excellent electrocatalytic activity towards BPA. Therefore, the CNT-titania-Nafion/GC electrode showed improved voltammetric responses for BPA compared to that obtained with bare GC electrode. In addition, cetyltrimethylammonium bromide (CTAB), a cationic surfactant, was added into the BPA sample solution in order to accumulate BPA through hydrophobic interaction between CTAB and BPA. The CNT-titania-Nafion/GC electrode gave a linear response ($r^2$ = 0.999) for BPA from $1.0{\times}10^{-8}$ M to $5.0{\times}10^{-6}$ M with a detection limit of $9.0{\times}10^{-10}$ M (S/N = 3). The modified electrode showed good selectivity against interfering species and also exhibited good reproducibility. The present electrochemical sensor based on the CNT-titania-Nafion/GC electrode was applied to the determination of BPA in food package samples.

• Journal of Surface Science and Engineering
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• v.56 no.1
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• pp.40-54
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• 2023

In this work, we synthesized a novel electrochemical sensing materials based on tetracarboxylic copper phthalocyanine (TcCuPtc) conjugated PANI (TcCuPtc@PANI). The synthesized materials were employed to modify the screen-printed carbon electrode (SPCE) for the selective sensing of 4-nitrophenol. The TcCuPtc was conjugated with conducting polymer of PANI through the electrostatic interaction and π-π electron conjugation, the polymer film of PANI to inhibit the leakage of TcCuPtc from the surface of the electrode. The prepared TcCuPtc@PANI were characterized and confirmed by scanning electron microscopy (SEM) with EDX, ATR-IR, UV-vis absorption spectroscopy, cyclic voltammetry, and differential pulse voltammetry techniques. The prepared TcCuPtc@PANI/SPCE showed an excellent electrocatalytic sensing of 4-NP in the linear concentrations from 3 to 500 nM with a LOD of 0.03 nM and a sensitivity of 8.8294 ㎂/nM cm^-2. However, the prepared TcCuPtc@PANI/SPCE showed selective sensing of 4-NP in the presence of other interfering species. The practical applicability of the TcCuPtc@PANI/SPCE was employed for the sensing of 4-NP in different water samples by standard addition method and showed satisfactory recovery results.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.05b
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• pp.21-23
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• 2002

In this paper, the electrochemical behavior of Viologen self assembly monolayer has been investigated with QCM, which has been known as nano-gram order mass detector. The self assemvly process of Viologen was monitored using resonant frequency $({\Delta}F)$ and resonant resistance(R). QCM measurements indicated a mass adsorption for Viologen assembling on the gold sufrace with a frequency change about 135[Hz] and calculated its surface coverage($\Gamma$) to be $3.5273{\times}10^{-9}[mol/cm^{2}]$. Also reversible redox process was observed and analyzed with ionic interaction at the Viologen/solution interface using ${\Delta}F$.

• Journal of the Korean Electrochemical Society
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• v.12 no.3
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• pp.234-238
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• 2009

In the excitation spectra of $YNbO_4$ : $Eu^{3+}$, the charge transfer (CT) band around 270 nm due to $[NbO_4]^{3-}$$-Eu^{3+}$ interaction and sharp excitation peaks by f-f transition of $Eu^{3+}$ strongly appeared simultaneously. CT band depended on the structural properties of powders, showing the red-shift with increasing the crystallinity, while the f-f transition peaks were independent of the crystallinity. For $YNb_{1-x}Ta_xO_4$ : $Eu^{3+}$ (x = 0.05.0.2), $[TaO_4]^{3-}$. configuration was locally constructed, leading to the blue-shift in CT band and the decrease in the red emission intensity with increasing the Ta content.