• The Korean Journal of Ceramics
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• 제4권2호
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• pp.103-113
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• 1998

By using a gas-tight electrochemical cell, we can perform high-temperature coulometric titration and measure electronic transport properties to determine the elecronic defect structure of metal oxides. This technique reduces the time and expense required for conventional thermogravimetric measurements. The components of the gas-tight coulometric titration cell are an oxygen sensor, Pt/yttria stabilitized zirconia(YSZ)/Pt, and an encapsulated metal oxide sample. Based on cell design, both transport and thermodynamic measurements can be performed over a wide range of oxygen partial pressure ($pO_2=10^{-35}$ to 1 atm). This paper describes the high-temperature gas-tight electrochemical cells used to determine electronic defect structures and transport properties for pure and doped-oxide systems, such as YSZ, doped and pure ceria $(Ca-CeO_2 \;and\; CeO_2)$, copper oxides and copper-oxide-based ceramic superconductors, transition metal oxides, $SrFeCo_{0.5}O_x,\; and \;BaTiO_2$.

• Structural Engineering and Mechanics
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• 제52권5호
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• pp.957-969
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• 2014

Among severe plastic deformation methods, groove pressing is one of the prominent techniques for producing ultra-fine grained sheet materials. This process consists of imposing repetitive severe plastic deformation on the plate or sheet metals through alternate pressing. In the current study, a 2 mm pure Cu sheet has been subjected to repetitive shear deformation up to two passes. Hardness and tensile yield and ultimate stress were obtained after groove pressing. Fracture toughness tests have been performed and compared for three conditions of sheet material namely as received (initial annealed state), after one and two passes of groove pressing. Results of experiments indicate that a decrease in the values of fracture toughness attains as the number of constrained groove pressing (CGP) passes increase.

• 한국정밀공학회지
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• 제29권12호
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• pp.1346-1350
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• 2012

Contact wire is one of the most important components supplying electricity to railroad cars. At the beginning of the research on contact wire, wear problem caused by friction between contact wire and pantograph was considered even more important issue for the failure of contact wire. However, since several fatigue fractures were reported from Shinkansen in Japan, fatigue fracture has become another important issue for the failure of contact wire. Despite of its importance, standard of the fatigue test of contact wire has not been established yet. Thus, fatigue characteristics of contact wire is very difficult issue to evaluate quantitatively. Hence, in this study, test method simulating operating conditions of contact wire by Minsung Kang and etc. is used to evaluate the fatigue characteristics of copper alloy contact wire. Also, test results is compared with the result of Minsung Kang's research on pure copper contact wire.

• Journal of Electrochemical Science and Technology
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• 제8권2호
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• pp.124-132
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• 2017

The performance of electrolytic processes using copper and catalyzed electrodes for enhanced nutrient removal with various catalyzers and combinations of electrodes was evaluated. The catalyzed electrodes removed more ammonia nitrogen than the copper electrode, but higher ammonia removal was achieved using a Pt/Ti anode. On the other hand, electrolysis using the Pt/Cu anode consumed less energy and cost less. During electroreduction, nitrate was better removed by a pair of copper electrodes than by the catalyzed electrodes. During electrolysis of synthetic wastewater, ammonia removal not only increased owing to direct oxidation at the anode, but was also influenced by indirect oxidation at the cathode. Platinum-coated copper and titanium cathodes actively produced oxidizers and thus removed more ammonia than a pure metal cathode. Although phosphorus was removable irrespective of the type of catalyzer, electrocoagulation using the copper electrode achieved complete removal of phosphorus in a period of less than 10 min.

• 자원리싸이클링
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• 제6권3호
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• pp.9-14
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• 1997

염산계 에칭폐액으로부터 추출제로 Alamine336(Tri-n-octylamine)을 이용하여 용매추출법에 의해 구리를 회수하기 위한 연구를 행하였다. 주요 실험변수로는 염산농도 및 염소이온농도, 추출제의 농도, 유기상과 수용액상(폐액상)의 상비 등 구리이온의 추출에 영향을 미칠 수 있는 인자들에 대하여 실험을 하엿는데, 이 실험결과 추출제의 농도 및 상비가 구리의 추출에 큰영향을 미침을 알 수 있었고 또한 수용액상의 염산 및 염소이온의 농도가 증가할수록 구리의 추출률이 증가하였다. 한편 McCabe-Thiele diagram으로부터 구리성분의 연속추출공정에 필요한 이론적인 추출단수를 결정하였다. 유기상으로 추출된 구리성분은 탈거제로 물($H_2$O)을 사용함으로써 효율적으로 탈거가 가능하였고 탈거제의 온도가 증가할수록 구리성분의 탈거율은 증가하였다.

• 소성∙가공
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• 제16권5호통권95호
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• pp.360-363
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• 2007

Microstructure and microhardness of metallic powders of pure copper were studied after high pressure torsion(HPT) processing with 10 turns of die rotation and high pressure of 6 GPa. The grain size of copper decreases drastically after HPT and reaches nanometer size ranges. During HPT, the hardness of consolidates of copper powders increases with increasing the temperature of HPT processing. Examinations of the fracture surfaces indicated evidence of ductile fracture. The results proved that HPT of copper powders has a beneficial effect for homogeneous deformation with reducing grain size.

• 상하수도학회지
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• 제13권1호
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• pp.140-145
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• 1999

This study was carried out a investigate the effect of chemical cleaning of corrosion product in cooling system made of copper and copper alloy as basic material and used cooling water as pure water. We studied chemical cleaning condition that minimizes the influence on basic material by means of EDTA solution so as to eliminate the slurry in cooling system. As a result, we found that the main components of sludge in cooling system produced by corrosion of copper were $Cu_2O$, CuO, Cu, and Fe. The optimum condition of chemical cleaning was 400 ppm EDTA solution at $60^{\circ}C$.

• International Journal of Railway
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• 제3권1호
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• pp.19-27
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• 2010

In the present study, the electrical sliding wear and corrosion resistance of pure copper (Cu) and six age-hardened copper alloys (CuCr, CuZr, CuCrZr, CuNiSiCr, CuBe and CuBeNi) were investigated by a pin-on-disc tribometer and electrochemical measurement. Various copper-based alloys in the form of cylindrical pin were forced to slide against a counterface stainless steel disc in air under unlubricated condition at a sliding velocity of 31 km/h under normal load up to 20 N with and without electric current. The worn surface of and wear debris from the specimens were studied by scanning electron microscopy. Both mechanical wear and electrical arc erosion were the wear mechanisms for the alloys worn at 50 A. Owing to its good electrical conductivity, high wear and corrosion resistance, CuCrZr is a promising candidate as the overhead catenary material for electric traction systems.

• Journal of Magnetics
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• 제10권3호
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• pp.118-121
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• 2005

We have investigated the magnetic properties of electroplated thin Cu/Co multilayers by using electrolytes made of copper sulphate and cobalt sulphate and by applying alternating plating voltage. While the multilayers plated with pure electrolyte showed superparamagnetism, those plated with organic additives showed ferromagnetic behavior. These changes are attributed to the so-called 'self-annealing' effect and reduction of grain size caused by the organic additives.

• Membrane and Water Treatment
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• 제9권6호
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• pp.481-487
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• 2018

Membrane clogging or fouling of the membrane caused by organic, inorganic, and biological on the surface is one of the main obstacles to achieve high flux over a long period of the membrane filtration process. So researchers have been many attempts to reduce membrane fouling and found that there is a close relationship between membrane surface hydrophilicity and membrane fouling, such that the same conditions, a greater hydrophilicity were less prone to fouling. Nanotechnology in the past decade is provided numerous opportunities to examine the effects of metal nanoparticles on the both hydrophilic and antibacterial properties of the membrane. In the present study the improvement of hydrophilic and antimicrobial properties of the membrane was evaluated by adding nanoparticles of titanium dioxide and copper oxide. For this purpose, 4% copper oxide and titanium dioxide nanoparticles with a ratio of 0, 30, 50, and 70% of copper oxide added to the polymeric membrane and compare to the pure polymeric membrane. Comparison experiments were performed on E. coli PTCC1998 in two ways disc and tube and also to evaluate membrane hydrophilic by measuring the contact angle and diameter of pores and analysis point SEM has been made. The results show that the membrane-containing nanoparticle has antibacterial properties and its impact by increasing the percentage of copper oxide nanoparticles increases.