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The MIC(Microbiologically Influenced Corrosion) of lower deck steel plates in double hull VLCC(Very Large Crude Oil Carrier) cargo tanks has been focused because of severe localized corrosion. Recently, ship companies have reported that TMCP(Thermomechanical Control Process) steel plates have been showed more severe localized corrosion than conventional rolled steels. In order to elucidate the MIC resistance of TMCP steels by comparison with conventional rolled steels and normalized steels in environments of double hull VLCC cargo oil tanks, various measurements and corrosion tests were performed such as measurements of polarization curves, immersion tests in bacteria culture medium. All results revealed that three types of steels have almost the same corrosion resistance in bacteria culture medium. Three kinds of steel exhibit almost the same polarization behavior and the corrosion rate. The movement of the open-circuit potential first towards more negative values and later to more positive values is a phenomenon common to all kinds of specimens. This phenomenon resulted from an initial stimulation of the anodes by sulphide ions produced by the bacteria from the reduction of sulphate ions in the medium, followed by the formation of an insoluble partly protective film of ferrous sulphide on the surface of the electrode. The effect of SRB (Sulphate Reducing Bacteria) is clearly showed in the cathodic polarization curve. When the SRB is in a condition of rapid growth, there is a strong cathodic depolarization. However, as the sulphate is depleted and reaction products accumulate, the activity of the bacteria declines and the cathodic polarization curve returns the same form as in the inoculated culture.

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The purpose of the present investigation was to study the stress corrosion cracking (SCC) properties of environmentally friendly Bi-brasses in Mattsson`s solution (0.05M copper sulfate and 0.5M ammonium sulfate, pH 7.4) at room temperature. Three unleaded brasses with Bi content ranging from 1 to 3 wt% and a conventional leaded brass for comparison were investigated. The effect of Bi on SCC of unleaded brasses was studied through polarization test, electrochemical impedance spectroscopy (EIS), scanning electron microscopy (SEM, energy dispersive spectroscopy (EDS) and slow-strain-rate test (SSRT). Potentiodynamic polarization studies indicated that the corrosion resistance of Bi-containing brasses was improved as the content of Bi, which showed a passivating characteristic in Mattsson`s solution, increased. The Pb- and Bi-containing brasses presented an inductive behavior on impedance data in low frequency region at the open-circuit potential (OCP). Such behavior could be attributed to the adsorption process on the alloy surface. The observed dezincified layers after SSRT should be particularly good initiators of SCC as they could induce tensile stress. As the content of Bi increased, the thickness of dezincified layer and the volume fraction of preferentially attacked Β phase decreased, therefore, SCC resistance of the Bi-containing brasses was improved.

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Effects of Sn content on the corrosion behavior of Zr-xSn (x=0.2.0 wt.%) binary alloys were investigated through the corrosion test at 360℃ in pure water and LiOH solution containing 2.2, 30, 70 and 220 ppm Li. Corrosion behavior of Zr-xSn binary alloys was found to be highly dependent on Sn content and test environment. Corrosion resistance decreased with Sn content in pure water, but it increased with Sn content in LiOH solution. In the case of oxidation in pure water, Sn was thought to play an important role in transformation of grain morphology from columnar grain to equiaxed grain and of crystal structure from tetragonal to monoclinic. In the case of oxidation in LiOH solution, however, the porous equiaxed grain with monoclinic structure was mainly observed in the oxide of low Sn alloys and the columnar grain with tetragonal structure in the oxide of high Sn alloys, which showed the superior corrosion resistance. From the results obtained, it is suggested that the stability of columnar grain with tetragonal structure was maintained in high Sn alloys because the Li diffusion in oxide was effectively inhibited by Sn.

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Effects of Nb contents and test temperature on the corrosion behavior of Zr-xNb (x = 0-0.6 wt.%) binary alloys were investigated. A corrosion test was performed at 300℃, 360℃, 400℃, 450℃ and 500℃. The best corrosion resistance was observed for Zr-0.lNb at 300℃, Zr-0.2Nb at 360℃ and 400℃ and Zr-0.3Nb at 450℃ and 500℃. Nb-containing precipitates were found in the alloys containing more than 0.4 wt.% Nb before the corrosion test. After corrosion test at 400℃ for 1000 hours, however, Nb-containing precipitates were found in the alloys containing more than 0.3 wt.% Nb suggesting that Nb solubility changed with the test temperature. The superior corrosion resistance was obtained when the Nb content decreased to equilibrium solubility due to the precipitation of the supersaturated Nb in α matrix. It can be concluded that the corrosion resistance of Zr-Nb binary alloys is considerably dependant on the Nb content in α matrix and the best corrosion resistance is achieved with the Nb content of equilibrium solubility.

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The thermosonic bonding was investigated as a fluxless solder bump flip chip bonding method. The 100 ㎛-diameter Sn-3.5 mass%Ag solder bumps were formed on test flip chip by laser ball bonding process. The test flip chips were bonded to a TSM-coated glass substrate using thermosonic bonding method at different temperature, bonding load and ultrasonic power. The die shear strength was evaluated and fracture surfaces were examined with SEM. The Sn-3.5Ag solder flip chip bonding was possible at lower temperature than the melting point of the solder. The die shear strength increased with increasing bonding temperature, bonding load, and ultrasonic power. However, at excessive bonding load condition over 1.0 N/bump, the die shear strength decreased due to the fracture at UBM/ Si-chip interface. The bump height decreased with increasing bonding load but did not change with ultrasonic power.

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Recarbonization experiments of lime produced from rotary kiln had been performed to improve the hydration resistance of lime in the air. From recarbonization and hydration experiments, it was found that the amount of hydrated lime was greatly reduced by coating the surface of lime with CaCO_3 of about 6 wt%. The effect of reaction temperature and partial pressure of carbon dioxide on the recarbonization rate of lime was investigated by a thermogravimetric analysis method. Rate equation for the recarbonization of lime was derived from the thermogravimetric data at various temperatures.

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The Nano-sized Fe particles were successfully synthesized by Chemical Vapor Condensation (CVC) process using the precursor of iron pentacarbonyl (Fe(CO)_5) as a source. The influence of CVC parameters on the formation of nanoparticle, the microstructure and magnetic properties was studied. The synthesized nanoparticles consisted of the core-shell type structure with nearly spherical shape and 5-13 ㎚ in mean size. Average particle size increased with increasing the decomposition temperature. The size distribution became wider and asymetric with increase of particle size. The lattice parameter of metallic core increased with decreasing the particle size. This could be explained by the coherency relationship between the Fe core and Fe_3O_4 oxide shell. With change of particle size and core microstructure, the magnetic state of Fe nanoparticle was changed from ferromagnetism to superaparamagnetism.

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