• Proceedings of the Korean Society of Precision Engineering Conference
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• 2001.04a
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• pp.942-945
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• 2001

Pulse electrochemical micromachining offers significant improvements in dimensional accuracy as compared with conventional electrochemical machining. One primary issue in pulse electrochemical micromachining is to identify and control machining depth as well as interelectrode gap size. This paper presents an identification method for the machining depth by in-process analysis of machining current and interelectrode gap size. The inter electrode gap characteristics, including pulse current, effective volumetric electrochemical equivalent and electrolyte conductivity variations, are analysed based on the model and experiments.

• Journal of Electrochemical Science and Technology
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• v.11 no.1
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• pp.1-13
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• 2020

As research on secondary batteries becomes important, interest in analytical methods to examine the condition of secondary batteries is also increasing. Among these methods, the electrochemical impedance spectroscopy (EIS) method is one of the most attractive diagnostic techniques due to its convenience, quickness, accuracy, and low cost. However, since the obtained spectra are complicated signals representing several impedance elements, it is necessary to understand the whole electrochemical environment for a meaningful analysis. Based on the understanding of the whole system, the circuit elements constituting the cell can be obtained through construction of a physically sound circuit model. Therefore, this mini-review will explain how to construct a physically sound circuit model according to the characteristics of the battery cell system and then introduce the relationship between the obtained resistances of the bulk (R_b), charge transfer reaction (R_ct), interface layer (R_SEI), diffusion process (W) and battery characteristics, such as the state of charge (SOC), temperature, and state of health (SOH).

• Journal of the Korean Electrochemical Society
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• v.2 no.1
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• pp.13-16
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• 1999

A mathematical analysis of bipolar electrode reactor model for complex electrochemical reactions could estimate total current from time-concentration data, which coincided well with experimental total current data. Thus behaviour of bipolar electrode reactor could be described by a proposed simulation model. This paper demonstrates how such a model can be used a useful tool in the design for pilot plant experimentation.

• Analytical Science and Technology
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• v.8 no.3
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• pp.383-389
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• 1995

A new approach for the measurement of the surface coverages of monomolecular films fabricated by spontaneous adsorption of thiol compounds on gold is described. It is based on the mass change measurement with EQCM for the reductive electrochemical desorption of thiol in aqueous KOH solution. The results were compared with that of charge calculation during electrochemical desorption. The surface coverage value for eicosanethiol agrees with that obtained by charge calculation of electrochemical reduction as well as that expected from a geometrical model of the compact monolayer.

• Transactions of the Korean hydrogen and new energy society
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• v.24 no.5
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• pp.401-412
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• 2013

The paper is to study on the simulation of the micro/macroscale thermo-electrochemical model of a single cell of anode-supported SOFC with direct internal reforming. The coupled heat and mass transport, electrochemical and reforming reactions, and fluid flow were simultaneously simulated based on mass, energy, charge conservation. The micro/macroscale model first calculates the detailed electrochemical and direct internal reforming processes in porous electrodes based on the comprehensive microscale model and then solve the macroscale processes such as heat and mass transport, and fluid flow in SOFCs with assumption of fully-developed flow in gas channel. The simulation results evaluate the overall performance by analyzing distributions of mole fraction, current density, temperature and microstructural design in co/counter flow configurations.

• 한국전기화학회:학술대회논문집
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• 2002.07a
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• pp.147-150
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• 2002

• 한국신재생에너지학회:학술대회논문집
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• 2008.10a
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• pp.63-66
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• 2008

This study presents 0-dimensional model for solid oxide fuel cells(SOFCs). The physics of the cell and the simplifying assumptions are presented, and only hydrogen participates in the electrochemical reaction. The electrical potential is predicted using this model. The Butler-Volmer equation is used to describe the activation polarization and the exchange current density is changed according to the partial pressure of reactants and the temperature. The electrical conductivities of electrodes and an electrolyte are calculated for the ohmic polarization. Material characteristics and temperature affect those factors. Analysis of concentration polarization based on transport of gaseous species through porous electrodes is incorporated in this model. Both binary diffusion and Knudsen diffusion are considered as the diffusion mechanism. For validation, simulation results at this work are compared with our experimental results and numerical results by other researchers.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2011.06a
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• pp.991-992
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• 2011

• Journal of the Korean Electrochemical Society
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• v.3 no.2
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• pp.76-80
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• 2000

Electrochemical oxidation of ethanol has been studied at nickel and $RuO_2-modified$ nickel electrodes in 1 M KOH using electrochemical impedance spectroscopy. Equivalent circuits have been worked out from simulation of impedance data to model oxidation of ethanol as well as the passivation of the electrode. The charge-transfer resistances for oxidation of these electrodes became smaller in the presence of ethanol than in its absence. The nickel substrate facilitated ethanol oxidation at $RuO_2-modified$ nickel electrodes. We also describe the Performance of nanosized electrocatalysts of the same composition in comparison to those of the bulk electrodes. The nanosized electrodes were obtained by electrode-positing the alloy from complexed form of these metal ions with fourth and fifth generation polyamidoamine dendrimers.

• Journal of the Korean Society for Precision Engineering
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• v.28 no.11
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• pp.1251-1258
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• 2011

With the help of nanoscale materials like carbon nanotube (CNT), there is the potential to develop new actuators that will provide higher work per cycle than previous actuator technologies, and generate much higher mechanical strength. In this study, the electrochemical actuation characteristics of nano carbon materials were experimentally studied to develop electrochemical actuators. The electrochemical actuators were composed of aqueous NaCl electrolyte and their actuating electrodes were made of multi-walled carbon nanotube (MWCNT)/polystyrene composite and graphene respectably. Actuation is proportional to charging transfer rate, and the electrolysis with an AC voltage input has very complex characteristics. To quantify the actuation property, the strain responses and output model were studied based on electrochemical effects between the nano carbon films and the electrolyte.