• Journal of the Korean Chemical Society
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• v.17 no.4
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• pp.306-313
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• 1973

With the intention of obtaining technical data for the industrial production of ${\gamma}-MnO_2$ for dry cell depolarizer by electrolytic oxidation of acidic manganese sulfate solution made from domestic rhodochrosite, optimum conditions of ore leaching, purification of leached solution and electrolytic oxidation of divalent manganes to tetravalent were investigated using simulated micro pilot plant having a production capacity of 4 kg of $MnSO_4$ per day. The nature and quality of the products were investigated by means of chemical analysis, DTA, X-ray diffraction and electron microscopy. The cell activity of $MnO_2$were examined by cell discharging character measurements. The optimum electrolysis conditions were as follow: Temperature of the electrolyte, above $90^{\circ}C$; current density, 0.7${\sim}A/dm^2$; anode materials, graphite or lead ; concentration of electrolyte, $MnSO_4 50{\sim}150g/l $ g/l and $H_2SO_4/MnSO_4 = 0.15{\sim}0.25$. Under the best condition the current efficiency was 99% and the products were almost pure ${\gamma}-MnO_2$. The cell discharging character were good and almost the same as that of regular grade commercial electrolytic manganese dioxide.

• Journal of the Korean Electrochemical Society
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• v.9 no.3
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• pp.107-112
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• 2006

Si-C composites were prepared by the carbonization of silicon powder covered by polyaniline(PAn). Physical and electrochemical properties of the Si-C composites were characterized by the particle size analysis, X-ray diffraction technique, scanning electron microscope, and electrochemical test of battery. The average particle size of the Si was increased by the coating of PAn and somewhat reduced by the carbonization to give silicone-carbon composites. XRD analysis' results were confirmed co-existence of crystalline silicon and amorphous-like carbon. SEM photos showed that the silicon particle were well covered with carbonacious materials depend on the PAn content. Si-C|Li cells were fabricated using the Si-C composites and were tested using the galvanostatic charge-discharge test. Si-C|Li cells gave better electrochemical properties than that of Si|Li cell. Si-C|Li cell using the Si-C from HCl undoped PAn Precursor showed better electrochemical properties than that from HCl doped PAn Precursor. Using the electrolyte containing FEC as an additive, the initial discharge capacity was increased. After that the galvanostatic charge-discharge test with the GISOC(gradual increasing of the state of charge) condition was carried out. Si-C(Si:PAn:50:50 wt. ratio)|Li cell showed 414 mAh/g of the reversible specific capacity, 75.7% of IIE(initial intercalation efficiency), 35.4 mAh/g of IICs(surface irreversible specific capacity).

• Resources Recycling
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• v.25 no.1
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• pp.24-30
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• 2016

The study to obtain tantalum concentration from electronic components (ECs) on Printed circuit board assembly (PCBA) of laptop was conducted. Electronic components on laptop PCBA were detached from boards by using self-developed experimental apparatus. The detached electronic components were sieved and 93.2 wt.% of tantalum capacitors were concentrated from the size interval from 2.80 mm to 6.35 mm. The tantalum capacitors were pulverized by hammer mill and electrodes (anode and cathode) were removed from the grinding products by using magnetic separators under the magnetic force of 300 Gauss. Finally, tantalum concentrate was concentrated from the magnetic separator products by using Knelson concentrator, and the maximum efficiency of 76.9% was achieved under the operating condition of bowl rotating speed of 200 rpm, and fluidizing water flowrate of 7 L/min. The grade and recovery of Ta concentrate under the condition were 81.1% and 78.8%, respectively.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.100-101
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• 2012

The plasma damage free and room temperature processedthin film deposition technology is essential for realization of various next generation organic microelectronic devices such as flexible AMOLED display, flexible OLED lighting, and organic photovoltaic cells because characteristics of fragile organic materials in the plasma process and low glass transition temperatures (Tg) of polymer substrate. In case of directly deposition of metal oxide thin films (including transparent conductive oxide (TCO) and amorphous oxide semiconductor (AOS)) on the organic layers, plasma damages against to the organic materials is fatal. This damage is believed to be originated mainly from high energy energetic particles during the sputtering process such as negative oxygen ions, reflected neutrals by reflection of plasma background gas at the target surface, sputtered atoms, bulk plasma ions, and secondary electrons. To solve this problem, we developed the NBAS (Neutral Beam Assisted Sputtering) process as a plasma damage free and room temperature processed sputtering technology. As a result, electro-optical properties of NBAS processed ITO thin film showed resistivity of $4.0{\times}10^{-4}{\Omega}{\cdot}m$ and high transmittance (>90% at 550 nm) with nano- crystalline structure at room temperature process. Furthermore, in the experiment result of directly deposition of TCO top anode on the inverted structure OLED cell, it is verified that NBAS TCO deposition process does not damages to the underlying organic layers. In case of deposition of transparent conductive oxide (TCO) thin film on the plastic polymer substrate, the room temperature processed sputtering coating of high quality TCO thin film is required. During the sputtering process with higher density plasma, the energetic particles contribute self supplying of activation & crystallization energy without any additional heating and post-annealing and forminga high quality TCO thin film. However, negative oxygen ions which generated from sputteringtarget surface by electron attachment are accelerated to high energy by induced cathode self-bias. Thus the high energy negative oxygen ions can lead to critical physical bombardment damages to forming oxide thin film and this effect does not recover in room temperature process without post thermal annealing. To salve the inherent limitation of plasma sputtering, we have been developed the Magnetic Field Shielded Sputtering (MFSS) process as the high quality oxide thin film deposition process at room temperature. The MFSS process is effectively eliminate or suppress the negative oxygen ions bombardment damage by the plasma limiter which composed permanent magnet array. As a result, electro-optical properties of MFSS processed ITO thin film (resistivity $3.9{\times}10^{-4}{\Omega}{\cdot}cm$, transmittance 95% at 550 nm) have approachedthose of a high temperature DC magnetron sputtering (DMS) ITO thin film were. Also, AOS (a-IGZO) TFTs fabricated by MFSS process without higher temperature post annealing showed very comparable electrical performance with those by DMS process with $400^{\circ}C$ post annealing. They are important to note that the bombardment of a negative oxygen ion which is accelerated by dc self-bias during rf sputtering could degrade the electrical performance of ITO electrodes and a-IGZO TFTs. Finally, we found that reduction of damage from the high energy negative oxygen ions bombardment drives improvement of crystalline structure in the ITO thin film and suppression of the sub-gab states in a-IGZO semiconductor thin film. For realization of organic flexible electronic devices based on plastic substrates, gas barrier coatings are required to prevent the permeation of water and oxygen because organic materials are highly susceptible to water and oxygen. In particular, high efficiency flexible AMOLEDs needs an extremely low water vapor transition rate (WVTR) of $1{\times}10^{-6}gm^{-2}day^{-1}$. The key factor in high quality inorganic gas barrier formation for achieving the very low WVTR required (under ${\sim}10^{-6}gm^{-2}day^{-1}$) is the suppression of nano-sized defect sites and gas diffusion pathways among the grain boundaries. For formation of high quality single inorganic gas barrier layer, we developed high density nano-structured Al2O3 single gas barrier layer usinga NBAS process. The NBAS process can continuously change crystalline structures from an amorphous phase to a nano- crystalline phase with various grain sizes in a single inorganic thin film. As a result, the water vapor transmission rates (WVTR) of the NBAS processed $Al_2O_3$ gas barrier film have improved order of magnitude compared with that of conventional $Al_2O_3$ layers made by the RF magnetron sputteringprocess under the same sputtering conditions; the WVTR of the NBAS processed $Al_2O_3$ gas barrier film was about $5{\times}10^{-6}g/m^2/day$ by just single layer.

• Journal of the Korean Electrochemical Society
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• v.10 no.1
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• pp.25-30
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• 2007

Proton exchange membrane fuel cell(PEMFC) performance could be affected by various factors such as cell temperature, total pressure, partial pressure of reactants and relative humidity. Hydrogen ion is combined with water to form hydronium ion [$H_3O^+$] and pass through membrane resulting electricity generation. Cooling system is needed to remove heat and other uses on large scale fuel cell. In case that collant conductivity is increased, fuel cell performance could be decreased because produced electricity could be leaked through coolant. In this study, triple distilled water(TDW) and antifreeze solution containing ethylene glycol was used to observe resistance change. Resistance of TDW was taken 28 days to reach preset value, and effect on fuel cell operation was not observed. Resistance of antifreeze solution was not reached to preset value up to 48 days, but performance failure occurred presumably caused by bipolar plate junction resulting stoppage resistance experiment. Generally PEMFC humidification is performed near-saturated operating conditions at various temperatures and pressures, but non-humidifying condition could be applied in small scale fuel cell to improve efficiency and reduce system cost. However, it was difficult to operate large scale fuel cell without humidifying, especially higher than $50{\sim}60^{\circ}C$. In case of small flux such as 0.78 L/min, temperature difference between inlet and outlet was occurred larger than other cases resulting performance decrease. Non-humidifying performance experiments were done at various cell temperature. When both of anode and cathode humidification were removed, cell performance was strongly depended on cell operating temperature.