<b>Effect of Electrochemical Conditions on Material Removal Rate in Electrochemical Oxidation Assisted Machining</b>

Nam, Eunseok,Lee, Chan-Young,Min, Jaehong,Lee, Sang Jo,Min, Byung-Kwon Electrochemical Society 2017 Journal of the Electrochemical Society Vol.164 No.2

<P>Recently, a new process for machining glassy carbon using electrochemical oxidation has been introduced. The process is effective in reducing cracks on the machined surface of glassy carbon, unlike conventional mechanical processes. This paper proposes a method for increasing the electrochemical oxidation rate in this process by applying a high overvoltage to improve the material removal rate. Suitable electrochemical conditions for applying high overvoltage were investigated. Experiments were conducted by varying the electrochemical conditions, including high overvoltage, to compare the material removal rates. The results showed that the material removal rate could be increased by using a high overvoltage. (C) 2017 The Electrochemical Society. All rights reserved.</P>

Investigation of the Electrochemical Behavior of Ytterbium Cations in LiCl-KCl Melt Using Spectro-Electrochemical Methods

Bae, Sang-Eun,Kim, Dae-Hyeon,Lee, Na-Ri,Park, Tae-Hong,Kim, Jong-Yun The Electrochemical Society 2016 Journal of the Electrochemical Society Vol.163 No.2

<P>Electrochemical behavior of ytterbium cations in a LiCl-KCl melt was investigated by electrochemical and UV-VIS absorption spectroscopy methods. In the LiCl-KCl melt, ytterbium exists with divalent and trivalent oxidation states. The electrochemical results showed that the electrochemical reactions of the Yb2+/3+ are reversible and controlled by their diffusion rates. UV-VIS absorption spectroscopy results indicate that the Yb2+ and Yb3+ ions in the LiCl-KCl melt have a few strong absorption bands below 400 nm. Additionally, the molar absorptivities of these electronic transitions of Yb2+ and Yb3+ in LiCl-KCl melt are reported. (C) 2015 The Electrochemical Society.</P>

Methodological Consideration on the Prediction of Electrochemical Mechanical Polishing Process Parameters by Monitoring of Electrochemical Characteristics of Copper Surface

Seo, Yong-Jin The Korean Electrochemical Society 2020 Journal of electrochemical science and technology Vol.11 No.4

The removal characteristics of copper (Cu) from electrochemical surface by voltage-activated reaction were reviewed to assess the applicability of electrochemical-mechanical polishing (ECMP) process in three types of electrolytes, such as HNO₃, KNO₃ and NaNO₃. Electrochemical surface conditions such as active, passive, transient and trans-passive states were monitored from its current-voltage (I-V) characteristic curves obtained by linear sweep voltammetry (LSV) method. In addition, the oxidation and reduction process of the Cu surface by repetitive input of positive and negative voltages were evaluated from the I-V curve obtained using the cyclic voltammetry (CV) method. Finally, the X-ray diffraction (XRD) patterns and energy dispersive spectroscopy (EDS) analyses were used to observe the structural surface states of a Cu electrode. The electrochemical analyses proposed in this study will help to accurately control the material removal rate (MRR) from the actual ECMP process because they are a good methodology for predicting optimal electrochemical process parameters such as current density, operating voltage, and operating time before performing the ECMP process.

Electrochemical Behavior of Aromatic Compounds on Nanoporous Gold Electrode

Quynh, Bui Thi Phuong,Byun, Ji Young,Kim, Sang Hoon The Electrochemical Society 2018 Journal of the Electrochemical Society Vol.165 No.10

<P>This study aimed at investigating the electrochemical behavior of benzene and its substituted derivatives on nanoporous gold and assessing the possibility of utilizing this electrode as a platform for simultaneous detection of different aromatic compounds. Cyclic voltammetric studies were performed with benzene, hydroquinone, catechol, phenol, 2-aminophenol, 2-chlorophenol as well as their mixtures on the nanoporous gold prepared from dealloying of AuxSi1-x films. The nanoporous structure was found to provide enhanced electro-oxidation of hydroquinone, catechol, phenol, 2-aminophenol and 2-chlorophenol and remarkable fouling resistance in the electro-oxidation of phenol and 2-aminophenol compared to the compact and flat gold electrode. Interestingly, oxidation potentials of these aromatics appear to be affected significantly by the attachment of functional groups to the benzene ring. Based on the onset oxidation potentials, the easiness of oxidation at nanoporous gold was found to follow the order: hydroquinone > catechol > 2-aminophenol > 2-chlorophenol, phenol > benzene. Moreover, nanoporous gold was found to be advantageous over nanoporous platinum for potential application in simultaneous analysis employing voltammetric techniques as it could offer discernable peak potential separation in the electro-oxidation of the different aromatics. (C) 2018 The Electrochemical Society.</P>

Electrochemical Response of Al₂O₃-MoO₂-TiO₂ Oxide Films Formed on 6061 Al Alloy by Plasma Electrolytic Oxidation

Kaseem, Mosab,Ko, Young Gun The Electrochemical Society 2016 Journal of the Electrochemical Society Vol.163 No.9

<P>The purpose of this study is to investigate the electrochemical response of Al2O3-MoO2-TiO2 oxide films fabricated on 6061 Al alloy by plasma electrolytic oxidation (PEO). The coatings were fabricated under alternating current conditions using an alkalinesilicate- molybdate electrolyte with TiO2, and the results were compared to those without TiO2. Microstructure observations revealed that when TiO2 was added to the electrolyte, the average size and area fraction of the micro-pores of the oxide layer coated in the electrolyte incorporating TiO2 were respectively smaller. The results of potentiodynamic polarization test in 3.5 wt% NaCl solution clearly indicated that the corrosion resistance of the oxide films was significantly improved by the incorporation of TiO2 particles. High corrosion resistance of the Al2O3-MoO2-TiO2 oxide films was also revealed by impedance tests and analyzed in relation to the equivalent circuit model. (C) 2016 The Electrochemical Society. All rights reserved.</P>

Tris(pentafluorophenyl)silane as a Solid Electrolyte Interphase (SEI)-Forming Agent for Graphite Electrodes

Lee, Tae Jin,Lee, Jeong Beom,Yoon, Taeho,Park, Hosang,Jurng, Sunhyung,Kim, Daesoo,Jung, Jiwon,Soon, Jiyong,Ryu, Ji Heon,Lee, Kyu Tae,Oh, Seung M. The Electrochemical Society 2017 Journal of the Electrochemical Society Vol.164 No.9

<P>Tris(pentafluorophenyl) silane (TPFPS) is examined as a solid electrolyte interphase (SEI)-forming agent for a graphite electrode. The surface film (SEI layer) generated from a conventional carbonate-based electrolyte (TPFPS-free) is so poorly passivating that continued reductive electrolyte decomposition and concomitant film deposition are employed to increase its thickness. Thus, the electrode develops more sluggish kinetics. An electrochemical quartz crystal microbalance (EQCM) study demonstrates that TPFPS is preferentially electroreduced before the organic carbonate solvents on the copper electrode, as predicted from ab initio calculations. Preferential electroreduction of TPFPS over the carbonate-based electrolyte is also observed after first lithiation of the graphite electrode. This gives a more compact and evenly covered SEI layer. The passivating ability of the resulting SEI layer is so high that additional electrolyte decomposition/film deposition is greatly suppressed. Consequently, both Li/graphite half-cell and graphite/LiCoO2 full-cell show higher Coulombic efficiency and better capacity retention in the TPFPS-added electrolyte. (C) 2017 The Electrochemical Society. All rights reserved.</P>

Effects of Zr⁴⁺ Doping on the Electrochemical Characteristics of Li₂FeP₂O₇/C in Lithium Ion Batteries

Ryu, Da-Jeong,Lee, Seong-Hun,Ryu, Kwang-Sun Electrochemical Society 2017 Journal of the Electrochemical Society Vol.164 No.13

<P>Using splash combustion synthesis, Zr4+-doped Li2Fe1-xZrx/2P2O7/C (x = 0, 0.01, 0.02, 0.03, and 0.04) composites were successfully synthesized in order to increase the redox voltage and c-rate performance. X-ray diffraction (XRD) patterns indicated that the successfully obtained Li2Fe1-xZrx/2P2O7/C had a monoclinic structure. The results indicated that the zirconium atoms within the Zr4+-doped system do not change the lattice structure of Li2FeP2O7, but do enlarge the lattice volume. During the de-intercalation and intercalation of lithium ions, the doped zirconium atoms protect the Li2FeP2O7 structure from spontaneous structural rearrangement, which can lower the reaction potential. Among the various samples, Li2Fe0.97Zr0.015P2O7/C exhibited excellent rate and cycling performance. We investigated the electrochemical performance and lithium ionic diffusion coefficient by using three electrochemical perturbation methods: cyclic voltammetry (CV), galvanostatic intermittent titration technique (GITT), and potentiostatic intermittent titration technique (PITT). Li2Fe0.97Zr0.015P2O7/C exhibited relatively good electrochemical performance in comparison with Li2FeP2O7/C. We further investigated the lithium ion diffusion behavior by using CV, GITT, and PITT. Li2Fe0.97Zr0.015P2O7/C demonstrated more rapid ionic diffusion than Li2FeP2O7/C did due to its higher diffusion coefficient value. Therefore, these ionic kinetic studies were helpful to understand the enhanced electrochemical performance. (C) 2017 The Electrochemical Society. All rights reserved.</P>

Polymer-Assisted Solution Processing of TiO₂ Thin Films for Resistive-Switching Random Access Memory

Vishwanath, Sujaya Kumar,Jeon, Sanghun,Kim, Jihoon Electrochemical Society 2017 Journal of the Electrochemical Society Vol.164 No.2

<P>In this study, we present a polymer-assisted solution (PAS) process to prepare TiO2 electrolyte layers for resistive-switching random access memory (ReRAM). The PAS process utilizes the stability of metal-polymer complexes in the coating solution to form uniform and dense films. In addition, the viscosity of the PAS coating solution can easily be adapted for any currently used coating technique. The electrochemical-metallization-based (ECM-based) ReRAM devices were prepared by spin-coating the PAS coating solution on an indium tin oxide (ITO) glass substrate that is used as the bottom electrode. Cu was deposited on the PAS-TiO2 electrolyte as an electrochemically active metal electrode used as the top electrode. The ECM-based ReRAM with the PAS-TiO2 electrolyte layer demonstrated bipolar resistive-switching behavior with a memory window wider than 13, cycle endurance over 500 cycles, and retention time longer than 10(4) s. Analysis of the conduction mechanism in high and low resistive states indicates that the resistive switching is attributed to the formation and rupture of Cu conducting filaments (CFs) in the PAS-TiO2 electrolyte layer. (C) 2016 The Electrochemical Society. All rights reserved.</P>

Enhanced Electrocatalytic Activity of Cu₂S-Polyaniline Heterostructure Counter Electrode for Quantum Dot-Sensitized Solar Cells

Vijayakumar, Elayappan,Quy, Vu Hong Vinh,Kwon, JongMyeong,Chae, Jiyoung,Kim, Jae-Hong,Kang, Soon-Hyung,Kim, Hyunsoo,Ahn, Kwang-Soon Electrochemical Society 2017 Journal of the Electrochemical Society Vol.164 No.12

<P>The Cu2S-Polyaniline (Cu-P) counter electrode (CE) was prepared by electropolymerization of polyaniline (PANI) on a FTO/Cu2S film. The surface morphology and crystallinity of the counter electrode were examined. The FTO/Cu-P CE provided significantly enhanced electrochemical activity and a faster charge transfer rate compared to the platinum (Pt), Cu2S, PANI, and PANI-Cu2S (P-Cu) CEs because of the synergistic effect between the high carrier mobility of PANI and the good electrocatalytic activity of Cu2S on the polysulfide electrolyte. Besides, the FTO/Cu-P CE exhibited excellent electrochemical stability, due to the strong interaction between the metal particles and electronegative nitrogen of PANI. The quantum dot-sensitized solar cell (QDSSC) with the FTO/Cu-P heterostructure CE exhibited a higher energy conversion efficiency (4.12%) than those with Pt (1.85%), Cu2S (3.71%), PANI (0.77%), and PANI-Cu2S (P-Cu) (1.01%) CEs. (C) 2017 The Electrochemical Society. All rights reserved.</P>

Fabrication of Pr-PVP-Co-Doped NanoTiO₂ Film on Titanium Matrix with Outstanding Electrocatalytic Reduction Activity for Oxalic Acid

Song, Wenliang,Zhang, Yu,Jin, Hua,Kim, Mi-Ra,Kim, Seok,Kim, Il Electrochemical Society 2017 Journal of the Electrochemical Society Vol.164 No.9

<P>A highly active and stable praseodymium-polyvinylpyrrolidone (Pr-PVP)-co-doped nanoTiO(2) film/titanium matrix was successfully fabricated for the electrocatalytic reduction of oxalic acid. The structure, morphology, and electro catalytic activity of the assynthesized Pr-PVP-doped nanoTiO(2) film on a titanium matrix surface was studied with X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, cyclic voltammetry, and electrochemical impedance spectroscopy. The electro catalytic properties were assessed by studying the electro reduction of oxalic acid on Pr-PVP-co-doped nanoTiO(2) film electrodes. The results showed a high yield of glyoxylic acid (82.6%) and a high current efficiency (81%) with galvanostatic preparative reduction. Based on the results, Pr-PVP-modified nanoTiO(2) film has a large electrochemical active surface area and small charge transfer resistance. The good electro catalytic performance of Ti/Pr-PVP-nano TiO2 makes it promising for use as an electrode in the electro catalytic reduction of oxalic acid. (C) 2017 The Electrochemical Society. All rights reserved.</P>