• 대한화학회지
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• 제57권3호
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• pp.316-321
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• 2013

Electrocoagulation (EC) technique is applied for the treatment of wastewater containing heavy metals ions such as nickle (Ni), lead (Pb) and cadmium (Cd) by using sacrificial anodes corrode to release active coagulant flocs usually aluminium or iron cations into the solution. During electrolytic reactions hydrogen gas evolve at the cathode. All the experiments were carried out in Batch mode. The tank was filled with synthetic wastewater containing heavy metals and efficiency of electro-coagulation in combination with aluminum and iron electrodes were investigated for removal of such metals. Several parameters, such as contact time, pH, electro-coagulant concentration, and current density were optimized to achieve maximum removal efficiency (%). The concentrations of heavy metals were determined by using Atomic Absorption Spectroscopy (AAS). It is found that the electro-coagulation process has potential to be utilized for the cost-effective removal of heavy metals from wastewater specially using iron electrodes in terms of high removal efficiencies and operating cost.

• Membrane and Water Treatment
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• 제6권1호
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• pp.43-52
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• 2015

A small-scale electro-dialysis system was constructed for domestic use. It is composed of six compartments in which five special polystyrene ionic membranes are housed. A series of experiments on the transport of sodium and chloride ions through polystyrene membranes was performed and the effects of electric current and voltage on the pH of water were investigated. This electrodialyser could reduce the NaCl content to an acceptable level (5307 mg/L) when water containing 9945 mg/L of sodium chloride is fed to the electrodialyser. The reduction was by the action of direct current 60 mA/100 mA when a 15 V / 20 V potential is maintained across the membrane. The results showed that the pH of the treated water attained a value in the range of 7-8, with the chloride concentration of 5307 mg/L when the voltage was in the range of 20 volts. This was achieved when two of the small-scale electro-dialysers were placed in series and the solutions from the respective compartments were mixed. This is considered useful because this complies to the requirement of drinking water standard both in terms of chloride and pH. Therefore, this type electrodialyserhas the potential for domestic uses in isolated houses where potable water supply is not available.

• Bulletin of the Korean Chemical Society
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• 제35권6호
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• pp.1806-1808
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• 2014

We report the successful preparation of gold nanoparticles (Au NPs) using a novel electroreduction process, which is simple, fast, and environmentally friendly (toxic chemicals such as strong reducing agents are not required). Our process allows for the mass production of Au NPs and adequate particle size control. The Au NPs prepared show high biocompatibility and are non-toxic to healthy human cells. By applying radio-frequency (RF) ablation, we monitored the electro-hyperthermia effect of the Au NPs at different RFs. The Au NPs exhibit a fast increase in temperature to $55^{\circ}C$ within 5 min during the application of an RF of 13 MHz. This temperature rise is sufficient to promote apoptosis through thermal stress. Our work suggests that the selective Au NP-mediated electro-hyperthermia therapy for tumor cells under an RF of 13 MHz has great potential as a clinical treatment for specific tumor ablation.

• Journal of Advanced Marine Engineering and Technology
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• 제24권6호
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• pp.70-77
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• 2000

In this paper, the effect of solution and age heat treatment to the corrosion behavior for the Ti-6Al-4V alloy were studied by cyclic polarization methods. Ti-6Al-4V was solution heat treated at $1,066^{\circ}C$ and $966^{\circ}C$ for 5 hours, and followed by age heat treated at $650^{\circ}C$, $600^{\circ}C$ and $550^{\circ}C$ with 1, 2, 4, 8 and 16 hours under vacuum environment. Test solution was 3.5% NaCl with temperature $25^{\circ}C$. The obtained results were as follows: 1. Base metal was exhibited higher electrical charge than that of solution and aged material. With decrease of solution-treatment temperature from 1066 to $966^{\circ}C$, the electrical charge was increased due to softening of micro structure. 2. The corrosion resistance of specimen that solution treated at $966^{\circ}C$ for 5 hours and age heat treated at 650, 660 and $550^{\circ}C$ were increased with increase of aging time to 4, 8 and 16 hours respectively, and then decreased. 3. In case of 316L stainless steel, measured charge and corrosion potential was 0.0627 coulomb and -614 mV respectively. Corrosion resistance of Ti-6Al-4V was higher than that of 316L.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2008년도 추계학술대회 논문집 Vol.21
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• pp.412-412
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• 2008

ENIG(Electroless Nickel Immersion Gold)is a surface treatment method that is used most widely at fine pitch's SMT and BGA packaging process. ENIG has good diffusion barrier of Ni against solder and good wettability due to Au finish. But when the discoloration occurred on the Au finish of ENIG, some key characteristics related to the quality and reliability of PCB such as bondability, solderability and electrical flowing of packaging process could be deteriorated. In this paper, we have performed the water dip test ($88^{\circ}C$ purified water) which accelerates the galvanic corrosion of Ni diffused from the Ni-P layer. That is, the excessive oxidation of the Ni layer could result in non-wetting of the solder because the flux may not be able to remove excessive oxides. Though Au discoloration have been reported to be caused by Ni oxides in many literature, it is still open to verify and discuss The microstructures and chemical compositions have been investigated using FE-SEM, TEM, FIB, EDS and XPS. As a result, authors have found that the Au discoloration in ENIG type is severely caused by the oxidation of the Ni and the mechanism of Au discoloration can be confirmed through the experiment result of water dip test.

• 한국세라믹학회지
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• 제39권8호
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• pp.711-714
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• 2002

The Ce, Mn: $LiTaO_3$ crystals were grown by Czochralski method in congruent ${\varphi}$3＂ $LiTaO_3$ single crystal growing conditions. Concentrations of Ce and Mn in melt were respectively 0.1 mole%. As-grown crystals were red, transparent and the grown crystals were tested with oxidation/reduction treatment for clor and other properties. Influence of Ce and Mn dopants on $LiTaO_3$ crystal properties was discussed. And the nonlinear optical properties of the Ce, Mn: $LiTaO_3$ crystal are being studied.

• Environmental Engineering Research
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• 제19권4호
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• pp.395-399
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• 2014

Operation characteristics of the sequencing batch reactor (SBR) process with electro-flotation (EF) as a solid liquid separation method (EF-SBR) were investigated. EF-SBR process showed excellent solid-liquid separation performance which enabled to separate biosolids from liquid phase within 30 min and to extend cyclic reaction time. Although influent organic loading rate was increased stepwise from 5 to 15 g COD/day, food to microorganisms (F/M) ratio could be maintained about 0.3 g COD/g VSS/day in EF-SBR because biomass concentration could be easily controlled at desired level by EF. However, it was impossible to increase biomass concentration at the same level in control SBR (C-SBR) process because solid-liquid separation by gravity settling showed a limitation at higher mixed liquor suspended solids (MLSS) concentration with 60 min of settling time. Total chemical oxygen demand (TCOD) removal efficiency of EF-SBR process was not decreased although influent organic loading rate became 3 times higher than initial value. However, it was seriously deteriorated in C-SBR process after increasing the rate over 10 g COD/day, which was accounted for insufficient organic removal by relatively higher food to microorganisms (F/M) ratio as well as biosolids wash-out by a limitation of gravity sedimentation.

• Journal of Advanced Marine Engineering and Technology
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• 제23권6호
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• pp.806-813
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• 1999

The effect of Post-Weld Heat Treatment(PWHT) of SS400 Steel was investigated with parameters such as micro vickers hardness corrosion potential polarization behaviors galvanic current Al anode generating current Al anode weight loss etc. Hardness of each parts(HAZ, BM, WM)by PWHT is lower than that of each parts by Non Post-Weld Heat Treatment(NPWHT) However hardness of WM of HAZ part was the highest among those three parts and HAZ area were also acted as cathode without any case of heat treatment. Potential difference between each three parts by PWHT was also smaller compared to NPWHT. Therefore it is suggested that Corrosion resistance property is increased by PWHT. However both Al anode generating current and anode weight loss was also decreased by PWHT compared to NPWHT when SS400 steel is cathodically protected by Al anode.

• 한국전기전자재료학회논문지
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• 제15권10호
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• pp.883-888
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• 2002

SiC direct bonding technology is very attractive for both SiCOI(SiC-on-insulator) electric devices and SiC-MEMS(micro electro mechanical system) fields because of its application possibility in harsh environments. This paper presents pre-bonding techniques with variation of HF pre-treatment conditions for SiC wafer direct bonding using PECVD(plasma enhanced chemical vapor deposition) oxide. The PECYD oxide was characterized by XPS(X-ray photoelectron spectrometer) and AFM(atomic force microscopy). The characteristics of the bonded sample were measured under different bonding conditions of HF concentration and an applied pressure. The bonding strength was evaluated by the tensile strength method. The bonded interface was analyzed by using SEM(scanning electron microscope). Components existed in the interlayer were analyzed by using FT-IR(fourier transform infrared spectroscopy). The bonding strength was varied with HF pre-treatment conditions before the pre-bonding in the range of 5.3 kgf/cm$^2$to 15.5 kgf/cm$^2$.

• KEPCO Journal on Electric Power and Energy
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• 제1권1호
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• pp.151-156
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• 2015

In order to improve the properties of high-temperature superconducting wire for superconducting cable system, we optimized the electro-polishing (EP), ion-beam assisted deposition (IBAD), superconducting (SC) layer, and baking (heat) treatment. The buffer layer was deposited on electro-polished substrate with RMS roughness ($R_{RMS}$) less than 5 nm. The IBAD process was carried out at $V_{beam}$: 1100 V and $V_{accel}$: 850 V that resulted in highly crystalline film of $LaMnO_3$. Chemical composition of SC layer is key to higher critical current, and we found that composition can be determined by surface color of SC layer. We adopt a proprietary contorl system based on RGB analysis of the surface and achieved critical current of 150 A/4 mm-width. The proposed baking treatment resulted in decreasing of about 10% of fraction defects.