• Journal of the Microelectronics and Packaging Society
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• v.19 no.4
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• pp.65-69
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• 2012

Composite coating can be manufactured during the electroplating with the bath containing a suspension of particles: ceramic, polymer, nanopowders. Improvement of hardness, wear resistance, corrosion resistance and lubrication properties are well-known advantage of composite coating. In this study, nano $TiO_2$ powder dispersed Ni composite plating was investigated. The improvement of surface hardness and photo decomposition effects can be expected in this coating. Zeta potential was measured with pH. The effect of ultrasonication time and types of ultrasonicator were studied to minimize the agglomeration of $TiO_2$ nanopowders in the electrolyte. Optimum conditions for nano $TiO_2$ dispersed Ni composite coating were $40mA/cm^2$ of current density, pH 3.5, and $50^{\circ}C$. At these conditions, $TiO_2$ nanoparticles contents in the Ni deposit was 15-20 at.%.

• Transactions of the Korean hydrogen and new energy society
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• v.7 no.1
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• pp.29-37
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• 1996

Alkaline water electrolysis has been commercialized as the only large-scale method for a long time to produce hydrogen and the technology is superior to other methods such as photochemical, thermochemical water splitting, and thermal decomposition method in view of efficiency and related technical problem. However, such conventional electrolyzer do not have high electric efficiency and productivity to apply to large scale hydrogen production for energy or chemical feedstocks. Solid polymer electrolyte water electrolysis using a perfluorocation exchange membrane as an $H^+$ ion conductor is considered to be a promising method, because of capability for operating at high current densities and low cell voltages. So, this is a good technology for the storage of electricity generated by photovoltaic power plants, wind generators and other energy conversion systems. One of the most important R&D topics in electrolyser is how to minimize cell voltage and maximize current density in order to increase the productivity of the electrolyzer. A commercialized technology is the hot press method which the film type electrocatalyst is hot-pressed to soild polymer membrane in order to eliminate the contact resistance. Various technologies, electrocatalyst formed over Nafion membrane surface by means of nonelectrolytic plating process, porous sintered metal(titanium powder) or titanium mesh coated with electrocatalyst, have been studied for preparation of membrane-electrocatalyst composites. In this study some experiments have been conducted at a solid polymer electrolyte water electrolyzer, which consisted of single cell stack with an electrode area of $25cm^2$ in a unipolar arrangement using titanium mesh coated with electrocatalyst.

• Proceedings of the Korean Society of Marine Engineers Conference
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• 2005.11a
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• pp.196-197
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• 2005

Cathodic protection is one of the successful ways to prevent corrosion of steel structures in marine environments. The unique feature of cathodic protection in seawater is the formation of calcareous deposits on cathodic metal surface. The formation principles of calcareous deposit seawater had been known for a long time. That is, cathodic reduction reactions associated with cathodic protection in seawater generate $OH^-$ at the metal surface in accordance with the formular ; 1/2 $O_2$ + $H_2O$ + $2e^-$ $2OH^-$ and $2H_2O$ + $2e^-$ ${\rightarrow}$ $H_2$ + $2OH^-$. These reactions increase the pH at the metal / seawater interface. The high pH causes precipitation of $Mg(OH)_2$ and $CaCO_3$ in accordance with the formular ; $Mg^{2+}$ + $2(OH)^-$ ${\rightarrow}$ $Mg(OH)_2$ and $Ca^{2+}$ + $HCO_3^-$ + $OH^-$ ${\rightarrow}$ $H_2O$ + $CaCO_3$. These are typically the main compounds in calcareous deposits. It obviously has several advantages compared to the conventional coatings, since the environment-friendly calcareous deposit coating is formed by the elements($Mg^{2+}$, $Ca^{2+}$) naturally present in seawater. In this study, environmental friendly calcareous deposit films were prepared on steel plates by electro plating technic in natural seawater. The influence of current density on composition ratio, structure and morphology of the coated films were investigated by scanning electron microscopy formation process of calcareous deposits films in natural seawater. And we confirmed the properties of all the films can be improved greatly by controlling the material structure and morphology with effective use of the electroplating method in natural seawater.

• Journal of the Korean institute of surface engineering
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• v.41 no.4
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• pp.147-155
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• 2008

The dental orthodontic wire provides a good combination of strength, corrosion resistance and moderate cost. The purpose of this study was to investigate the effects of TiN and ZrN coating on corrosion resistance and physical property of orthodontic wire using various instruments. Wires(round type and rectangular type) were used, respectively, for experiment. Ion plating was carried out for wire using Ti and Zr coating materials with nitrogen gas. Ion plated surface of each specimen was observed with field emission scanning electron microscopy(FE-SEM), energy dispersive X-ray spectroscopy(EDS), atomic force microscopy(AFM), vickers hardness tester, and electrochemical tester. The surface of TiN and ZrN coated wire was more smooth than that of other kinds of non-coated wire. TiN and ZrN coated surface showed higher hardness than that of non-coated surface. The corrosion potential of the TiN coated wire was comparatively high. The current density of TiN coated wire was smaller than that of non-coated wire in 0.9% NaCl solution. Pit nucleated at scratch of wire. The pitting corrosion resistance $|E_{pit}-E_{rep}|$ increased in the order of ZrN coated(300 mV), TiN coated(120 mV) and non-coated wire(0 mV).

• Journal of Plant Biotechnology
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• v.30 no.4
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• pp.359-363
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• 2003

Mass propagation of tulip tree (Liriodendron tulipifera L) via somatic embryogenesis was successfully achieved with immature samaras collected from adult trees. Embryogenic tissues were induced by culturing them samaras on 1/2 LM medium (Litvay's) containing 2,4-D and BA. Somatic embryos developed from the embryogenic tissues and germinated to normal plants (emblings) upon transfer onto the same medium containing either AgNO$_3$ or activated charcoal. So far, several factors appeared to influence both the induction of embryogenic tissues and germination of the embryos into plants. These include the collection time of samaras for the induction of embryogenic tissue, sucrose level in the culture medium, the level of both AgNO$_3$ and activated charcoal, and plating density of somatic embryos on germination medium for maturation and germination of somatic embryos into plantlets.

• Korean Journal of Environmental Agriculture
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• v.31 no.1
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• pp.68-74
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• 2012

BACKGROUND: Some microorganisms extant in nature have ability to suppress various plant pathogens, and also can promote plant growth. Thus microorganisms are such great source of antimicrobial agents to develop antagonistic microorganism production and eco-friendly crop management. We isolated the microorganisms in various eco-friendly formulations. The suppressive abilities against plant pathogens have been characterized in vitro level. METHODS AND RESULTS: The indigenous microorganisms have been isolated from Cooked rice, Black sugar, Rice Bran, and Red clay using dilution plating method. Population of bacteria and fungi were above 107 in the all formulations. We isolated and pure cultured the microorganisms based on morphological characteristics. Three major plant pathogens (Fusarium oxysporum, Rhizoctonia solani, Phytophthora capsici) have been used to select antagonistic microorganisms. Total 20 bacteria and 9 fungi showed the pathogen growth suppression ability in vitro condition. The selected microorganisms were identified by ITS sequence similarity. CONCLUSION: All tested eco-friendly formulations contained high-density of the microorganisms. Among the isolated microorganisms, Bacillus spp. and Streptomyces spp. showed the most effective antifungal activity against the plant pathogens such as F. oxysporum, R. solani, and P. capsici. Among the selected fungi Trichoderma sp. demonstrated antifungal activity. Our results suggest that the currently adapted eco-friendly formulations might useful for sustain agricultural system.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2013.05a
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• pp.62-62
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• 2013

Magnesium alloys exhibit many attractive properties such as low density, high strength/weight ratio, high thermal conductivity, very good electromagnetic features and good recyclability. However, most commercial magnesium alloys require protective coatings because of their poor corrosion resistance. Attempts have been made to improve the corrosion resistance of the Mg alloys by surface treatments, such as chemical conversion coatings, anodizing, plating and metal coatings. Among them, chemical conversion coatings are regarded as one of the most effective and cheapest ways to prevent corrosion of Mg alloys. In this study, the effects of various $Zn^{2+}$ concentrations and pH levels on the formation of zinc phosphate conversion coatings (ZPCCs) on AZ31 magnesium alloy were investigated, and corrosion resistances of the coated samples were evaluated by immersion test and potentiodynamic polarization experiment. The corrosion resistance of the coated AZ31 samples was found to increase with increasing $Zn^{2+}$ concentration and the lowest corrosion rate was obtained for the samples coated at pH of 3.07, independent of $Zn^{2+}$ concentration. The best coatings on AZ31 were obtained at [$Zn^{2+}$] = 0.068 M and pH 3.07. At the conditions of [$Zn^{2+}$] = 0.068 M and pH 3.07, the formation and growth processes of ZPCCs on AZ31 Mg alloy are divided into four stages: formation of a dense layer, precipitation of fine crystals on the dense layer, growths of the inner and outer layers, and reorganization of outer crystalline layer.

• Journal of the Microelectronics and Packaging Society
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• v.14 no.1
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• pp.55-60
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• 2007

The codeposition behavior of submicron sized diamond with nickel from nickel electrolytes has been investigated. Electroplating of diamond dispersed nickel composites was carried out on a rotating disk electrode (RDE). The effects of current type and current density on the electrodeposited Ni-diamond composite coating were investigated. The effects of surfactants on the composite coating were also investigated. The hardness of coating was measured with varying electroplating conditions using Micro Vickers. As diamond was incorporated into the coating, the hardness of coating as well as the wear resistance was improved. The hardness of the coating was increased as much as 100% and the wear resistance was improved as much as 27%. The hardness of composite coating layer increased slightly at the diamond content of above 20 gpl.

• Journal of Microbiology and Biotechnology
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• v.13 no.4
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• pp.509-516
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• 2003

A model system for the immnunochemical detection of Escherichia coli O157:H7 using a combined immunomagnetic separation (IMS) and test-strip liposome immunoassay (LIA) procedure was developed. Immunomagnetic beads coated with anti-E. coli O157 IgG antibodies were used to separate the E. coli O157 (including the H7 serotype) from culture. Immunoliposomes, whose surface was conjugated to goat anti-E. coli O157:H7 IgG and which encapsulated the marker dye, sulforhodamine B, were used as a detection label. The test strip, onto which antibodies to goat IgG were immobilized, was the immunosensor capturing immunoliposomes that did not bind to E. coli O157:H7 on the immunomagnetic bead-E. coli O157:H7 complexes. In experiments, pure cell culture suspensions of $10^5 E.$ coli O157:H7 organisms per ml produced a measurable signal inhibition, whereas a weak yet detectable signal inhibition occurred with $10^3CFU/ml$. The inhibition signals increased, when the incubation time for IMS was extended to 90 min and higher IgG-tag density (0.4mol%) was used on the liposomes. With 0.2 and 0.4mol% IgG-tagged liposomes, the IMS-LIA procedure showed more improved signal inhibitions than those of a direct (no IMS) LIA. The combined assay, which measures the instantaneous signal from immunoliposomes, can be completed within 90 min, making it significantly faster than conventional plating methods and enzyme-linked immunosorbent assay (ELISA). Accordingly, it is quite feasible to use the combined immunoassay format of IMS and dye-loaded immunoliposomes for the detection of E. coli O157:H7.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2011.10a
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• pp.903-906
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• 2011

The electroplating and electro-less plating methods have been applied for the high density chip interconnect of the Copper Pillar Tin Bump (CPTB) preparation. The CPTB was prepared, which had been electroplated about $100{\mu}m$ pitch of copper layer firstly, and then the Tin layer was deposited on the copper pillar surface to protect the oxidation of it. It was also very important to get uniform thickness of electroplated copper layer, though it was difficult and sensitive. In order to control the thickness distribution, it was examined that the current separating disk of Insulating Gate with a hole in the center was installed between electrodes. The current flows through the center hole of the Insulating Gate in the cylindrical electroplating bath and the other parts were blocked to protect current flowing. The main current flowed through the center hole of the Insulating Gate directly to the opposite electrode of wafer disk. As the results, it was verified that the copper layer was thick in the center part of wafer disk with distribution of thinner to the outer part toward edge.