• Bulletin of the Korean Chemical Society
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• 제30권6호
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• pp.1341-1348
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• 2009

Electrocatalytic oxidation of two anti-inflammatory drugs (Mefenamic acid and Indomethacin) was investigated on a cobalt hydroxide modified glassy carbon (CHM-GC) electrode in alkaline solution. The process of oxidation and its kinetics were established by using cyclic voltammetry and chronoamperometry techniques as well as steady state polarization measurements. Voltammetric studies indicated that in the presence of under study drugs, the anodic peak current of low-valence cobalt species increased, followed by a decrease in the corresponding cathodic current. This result indicates that the drugs were oxidized via cobalt hydroxide species immobilized on the electrode surface via an E$\acute{C}$ mechanism. A mechanism based on the electrochemical generation of Co (IV) active sites and their subsequent consumption by the drugs in question was also investigated. The constants rate of the catalytic oxidation of the drugs and the electron-transfer coefficients reported.

• Bulletin of the Korean Chemical Society
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• 제19권7호
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• pp.754-760
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• 1998

It was found that the adsorption of a cobalt(III) complex with a macrocyclic ligand, C-meso-5,7,7,12,14,14-hexamethyl-1,4,8,11-tetraazacyclotetradecane (hmc), was induced on a glassy carbon electrode by heavily oxidizing the electrode surface. Adsorption properties are discussed. The glassy carbon electrode with the adsorbed complex was employed to see the catalytic activities for the electro-reduction of O2. In the presence of oxygen, reduction of (hmc)Co3+ showed two cathodic waves in cyclic voltammetry. Compared to the edge plane graphite electrode at which two cathodic waves were also observed in a previous study, catalytic reduction of O2 occurred in the potential region of the first wave while it happened in the second wave region with the other electrode. A rotating disk electrode after the same treatment was employed to study the mechanism of the O2 reduction and two-electron reduction of O2 was observed. The difference from the previous results was explained by the different reactivity of the (hmc)CoOOH2+ intermediate, which is produced after the two electron reduction of (hmc)Co3+ in the presence of O2.

• Journal of Electrochemical Science and Technology
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• 제7권4호
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• pp.277-285
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• 2016

There is a growing demand for simple, cost-effective, and accurate analytical tools to determine the concentrations of biological and environmental compounds. In this study, a stable electroactive thin film of cobalt hexacyanoferrate (Cohcf) was prepared as an in situ chemical precipitant using electrostatic adsorption of $Co^{2+}$ on a silicate sol-gel matrix (SSG)-modified indium tin oxide electrode pre-adsorbed with $[Fe(CN)_6]^{3-}$ ions. The modified electrode was characterized by scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and electrochemical techniques. Electrocatalytic oxidation of hydrazine on the modified electrode was studied. An electrochemical sensor for hydrazine was constructed on the SSG-Cohcf-modified electrode. The oxidation peak currents showed a linear relationship with the hydrazine concentration. This study provides insight into the in situ growth and stability behavior of Cohcf nanostructures and has implications for the design and development of advanced electrode materials for fuel cells and sensor applications.

• 대한기계학회논문집A
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• 제26권2호
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• pp.322-328
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• 2002

In wire-electrical discharge machining (W-EDM), the dielectric plays an important role as the working fluid. It affects the material removal rate and the properties of the machined surface. This paper deals with the effects of the electrical conductivity of dielectric and cobalt percentage of sintered carbides on the machining characteristics and the machined surface integrities with deionized water as dielectric. A series of experiments have been performed on sintered carbides having different cobalt contents. Experimental results show that a higher cobalt content of WC decreases the metal removal rate and worsens the surface quality. Lower electrical conductivity of the dielectric results in a higher metal removal rate as the gap between wire electrode and workpiece reduced. Especially, the surface integrities of rough-cut workpiece, wire electrode, and debris were analyzed also through scanning electron microscopy(SEM) and surface roughness tester. By energy dispersive spectrometry(EDS), it is confirmed that micro cracks and some of electrode material are found on the workpiece surface.

• 대한화학회지
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• 제37권4호
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• pp.462-469
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• 1993

Cofacial bis-cobalt tetraphenylporphyrin 유도체 화합물들이 수식된 유리질 탄소 전극과 microelectrode에서 순환 전압 전류법 및 시간 전류법에 의해 산소의 환원 반응을 조사하였다. Microelectrode를 사용하여 시간-전류법에 의해 얻은 전자수 n값들은 유리질 탄소 전극을 사용하여 순환 전압 전류법들에 의해 얻은 결과들과 다소 다른 값으로 나타났다. 알카리성 용액에서 monomer인 cobalt tetraphenylporphyrin 화합물이 수식된 전극에서 산소의 호나원 반응 경로는 중간 생성물인 $H_2O_2$로 가는 2 전자반응으로 진행되었고, dimer인 cofacial bis-cobalt tetraphenylporphyrin 유도체 화합물들이 수식된 전극에서는 최종 생성물인 $H_2O$로 가는 4 전자 반응으로 진행되었다. 이와 같은 산소의 환원 반응은 전체적으로 비가역적으로 확산 지배적인 반응으로 주어졌다.

• The Korean Journal of Ceramics
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• 제4권1호
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• pp.43-46
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• 1998

We have investigated the formation and thermal stability of cobalt aluminide(CoAl) thin films on GaAs. In order to obtain cobalt-aluminide thin films, we deposited a multilayer of Co/Al on GaAs, and subsequently annealed the samples at 80$0^{\circ}C$ for 30 min. After annealing, single-phase cobalt aluminide was produced showing a flat and uniform interface with GaAs. which indicates that cobalt aluminide (CoAl) is thermally stable with GaAs. In addition, the adherence and mechanical properties of the as-deposited, and annealed Co/Al multilayer structure on GaAs are compatible with those required for device fabrication processes. The electrical property of the CoAl/GaAs contact shows rectifying characteristics, indicating that the diodes were usable as rectifying gate electrodes.

• 자원리싸이클링
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• 제8권3호
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• pp.18-25
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• 1999

화학제염이나 전지화학제염을 통해 발생된 방사성 폐액을 정화처리할 수 있는 새로운 방법으로, 다공성 활성탄소섬유(ACF)상에서 폐액중 코발트이온의 전기적 흡·탈착에 대한 연구를 수행하였다. 회전원판 전극을 사용하여 순환전압전류법으로 전기이중층 충전만이 발생하는 전위 영역을 조사하였다. ACF 전극을 사용한 회분식 전기흡착 실험결과, 음의 전위 가용은 저위 미가용 시의 흡착에 비해 코발트이온의 흡착을 증가시켰다. 또한 흡착된 코발트 이온은 역전된 가용전위에 의해 용액으로 용출되었으며 이와 동시에 탄소체 전극이 재생되어, 전기흡착 공정의 가역성을 확인 할 수 있었다.

• 대한화학회지
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• 제61권6호
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• pp.320-327
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• 2017

Borate 완충용액에서 Co의 부동화 피막의 생성과정(growth kinetics)과 부동화 피막의 전기적 성질을 변전위법, 대 시간 전류법 그리고 단일 주파수 전기화학적 임피던스 측정법으로 조사하였다. 불안정 부동화가 일어나는 낮은 전극전위에서 생성되는 Co의 부동화 피막 $Co(OH)_2$와 CoO로 구성되었으며, 전극전위가 증가하면 산화피막의 조성이 $Co_3O_4$, CoOOH로 변화되었다. 또한 산화피막의 조성은 전극전위와 산화시간에 따라 변하였다. 이 때 생성되는 산화피막은 Mott-Schottky 식이 적용되는 p-형 반도체 성질을 보였다.

• Journal of information and communication convergence engineering
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• 제1권3호
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• pp.129-132
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• 2003

In this paper, cobalt (Co)-electrode FBAR devices fabricated on seven-layered Bragg Reflectors are presented along with their resonance characteristics. ZnO films are used as the resonating material in FBAR devices where the Co electrode is 3000${\AA}$ thick. All processes are preformed in an RF magnetron sputtering system. As a result of characterization, the resonance characteristics are observed to depend strongly on the quality of ZnO film and Bragg Reflectors. In addition, the FBAR devices with W/$SiO_2$ reflectors show good resonance characteristics in term of return loss and quality-factor (Q-factor).

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집C
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• pp.64-70
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• 2001

This work deals with the electrical conductivity of dielectric and cobalt percentage on output parameters such as metal removal rate and surface roughness value of sintered carbides cut by wire-electrical discharge machining (W-EDM). To obtain a precise workpiece with good quality, some extra repetitive finish cuts along the rough cutting contour are necessary. Experimental results show that increases of cobalt amount in carbides affects the metal removal rate and worsens the surface quality as a greater quantity of solidified metal deposits on the eroded surface. Lower electrical conductivity of the dielectric results in a higher metal removal rate as the gap between wire electrode and workpiece reduced. Especially, the surface characteristics of rough-cut workpiece and wire electrode were analyzed too. To obtain a good surface equality without cracks, 4 finish-cuts were necessary by reducing the electrical energy and the offset value.