• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.14 no.7
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• pp.533-538
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• 2001

The barrier height is found to increase from 0.25 to 0.690 eV for Schottky contacts on n-InGaAs using deposition of Ag on a substrate cooled to 77K(LT). Surface analysis leads to an interface model for the LT diode in which there are oxide compounds of In:O and As:O between the metal and semiconductor, leading to behavior as a metal-insulator-semiconductor diode. The metal film deposited t LT has a finer and more uniform structure, as revealed by scanning electron microscopy and in situ metal layer resistance measurement. This increased uniformity is an additional reason for the barrier height improvement. In contrast, the diodes formed at room temperature exhibit poorer performance due to an unpassivated surface and non-uniform metal coverage on a microscopic level.

• Journal of the Korean Society for Precision Engineering
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• v.3 no.3
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• pp.13-21
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• 1986

Turning property of metal is affected by the cutting condition, tool geome- try and cutting material. But the turning property of welded material is not welknown. Welded structures usually contain nonhomogeneity, defects and resi- dual stresses due to differential contraction between welded metal and base metal. In this paper, authors conducted the experimental test on the turning property, by changing turning condition and welding electrodes of the welded specimens. The results obtained in these experimental tests are as follows; (1) Within the limit of this experimental test, the cutting force of the weld zone is bigger than that of base metal, and this phenomena is caused by the different mechanical property of the weld zone. The range of the variation of cutting force in the weld zone is caused by the nonhomogeneity of the weld zone, respectively. (2) The surface roughness follows the general characteristic of the effect of cutting condition on the surface roughness and the surface roughness of the weld zone shows coarse surface comparing with that of the base metal. (3) The specimen welded by the electrode E4301, shows worse cutting property than that of E4361 and E4313.

• Corrosion Science and Technology
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• v.10 no.1
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• pp.24-29
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• 2011

The greatest purpose of chromate treatment is to improve anti-corrosion by stabilizing a metal surface. Because metal surface forms a compound by absorbing oxygen or water in the air by being generally unstable, it is necessary to improve anti-corrosion of the metal by forming the metal surface with a stable film. When considering the economical efficiency and requirements together because the film of the metal surface treated with chromate has good anti-corrosion and the stability also in the air by being compact and strong, Chromate treatment has been used most up to the electronics industry from the auto industry. However, these days, because hexavalent chromium is both a toxic agent to be able to cause cancers and deadly poisonous environmental pollutant, the strong legal controls on its use is being imposed all over the world. Because of this reason, a new anti-corrosion method is being required. Also, by users' various demands, the passivations that have recently been developed require various characteristics such as conductivity, chemical resistance, alkali cleaning resistance as well as anti-corrosion. We could confirm the results such as excellent anti-corrosion compared to chromate, conductivity, chemical resistance and detergent resistance as the result of analysis of various characteristics of the galvannealed sheet steels coated with Cr-Free solution developed in this research.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.08a
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• pp.317.2-317.2
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• 2013

Ultrathin oxide encapsulated metal-oxide hybrid nanocatalysts have been fabricated by a soft chemical and facile route. First, SiO2 nanoparticles of 25~30 nm size have been synthesized by modified Stobber's method followed by amine functionalization. Metal nanoparticles (Ru, Rh, Pt) capped with polymer/citrate have been deposited on functionalized SiO2 and finally an ultrathin layer of TiO2 coated on surface which prevents sintering and provides high thermal stability while maximizing the metal-oxide interface for higher catalytic activity. TEM studies confirmed that 2.5 nm sized metal nanoparticles are well dispersed and distributed throughout the surface of 25 nm SiO2 nanoparticles with a 3-4 nm TiO2 ultrathin layer. The metal nanoparticles are still well exposed to outer surface, being enabled for surface characterization and catalytic activity. Even after calcination at $600^{\circ}C$, the structure and morphology of hybrid nanocatalysts remain intact confirm the high thermal stability. XPS spectra of hybrid nanocatalyst suggest the metallic states as well as their corresponding oxide states. The catalytic activity has been evaluated for high temperature CO oxidation reaction as well as photocatalytic H2 generation under solar simulation. The design of hybrid structure, high thermal stability, and better exposure of metal active sites are the key parameters for the high catalytic activity. The maximization of metal-TiO2 interface interaction has the great role in photocatalytic H2 production.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.7 no.1
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• pp.34-40
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• 1998

Conductive metal matrix composite(MMC) material of 30% silicon carbide particulated based on aluminum matrix was machined by die sinking electrical discharge machining(EDM) process according to different current and duty factor for reverse polarity of electrode. Material removal rate(MRR) was examined by process under various operation conditions. The surface morphology was evaluated by surface roughness parameter and scanning electron microscopy(SEM) research. The MRR was suddenly increased over 11 ampere of current, and it was slightly changed over 0.3 of duty factor. The maximum surface roughness of EDMed surface was affected by the duty factor. The SEM photograghs of EDMed surface showed wide recast distribution region of melting materials as increased of current and duty factor.

• Transactions of Materials Processing
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• v.14 no.8 s.80
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• pp.668-674
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• 2005

In sheet metal forming, drawbeads are often used to control uneven material flow which may cause deffets such as wrinkles, fractures, surface distortion and springback. Appropriate setting and adjusting of the drawbead force is one of the most important parameters in sheet forming process control. Therefore in this study, drawbead friction test with circular shape bead was performed at various sheets, lubricants(dry, three kinds of lubricants having different viscosities), bead materials and surface treatments of bead surface. The results obtained by drawbead friction test show that the friction and drawing characteristics of deforming panels were mainly influenced by strength of sheet, viscosity of lubricant and hardness of bead surface.

• Journal of Microbiology and Biotechnology
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• v.12 no.6
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• pp.878-881
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• 2002

The goal of the current research was to assess the influence of the growth rate of Nocardia amarae on its overall metal binding capacity. Batch sorption isotherms for cadmium (Cd), copper (Cu), and nickel (Ni) showed that Nocardia cells harvested from chemostat cultures at a dilution rate of $0.33d^-1$ had a significantly higher metal sorption capacity than cells grown at 0.5 and $1d^-1$. The cell surface area estimated using a dye technique indicated that pure N. amarae cells grown at a lower growth rate had a significantly more specific surface area than cells harvested from a higher growth rate operation. Accordingly, this difference in the specific surface area seemed to indicate that the higher metal sorption capacity of the slowly growing Nocardia cells was due to their higher specific surface area.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1997.03a
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• pp.140-143
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• 1997

The present study is concerned with the hydrostatic extrusion process of copper-clad aluminium bar to investigate the basic flow characteristics. Considering the bonding mechanism of bi-metal contact surface as cold pressure welding, the normal pressure and the contact surface expansion are selected as process parameters governing the bonding condition. The critical pressure required for the bonding at the interface is obtained by solving a "local extrusion" using a slip line meyhod. A viscoplastic finite element method is used to analyze the steady state extrusion process. The boundary profile of bi-metal rod is predicted by tracking a particle path adjacent to interface surface. The variations of contact surface area and the normal pressure along the interface profile are predicted and compared to those by experiments.

• Journal of Powder Materials
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• v.14 no.6
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• pp.391-398
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• 2007

The surface roughness of Al, Ag and Ni nano-powders which were prepared by pulsed wire evaporation method was quantified based upon the fractal theory. The surface fractal dimensions of metal nano-powders were determined from the linear relationship between In $V/V_{mono}$ and Inln ($P^o/P$) using multi-layer gas adsorption theory. Moreover, the fractal surface image was realized by computer simulation. The relationship between preparation condition and surface characteristics of metal nano-powders was discussed in detail.

• Journal of the Semiconductor & Display Technology
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• v.18 no.3
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• pp.105-109
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• 2019

Plasmons have conductive properties using the effect of amplifying magnetic and electric fields around metal particles. The collective movement of free electrons in metal particles induces and produces the generation of plasmon. Because the plasmon is concentrated on the surface of the nanoparticles, it is also called the surface plasmon. The polarizing effect of plasma on the surface is similar to the principle of surface currents occurring in insulators. In this study, it was found the conditions under which plasma is produced in SiOC insulators and studied the electrical properties of SiOC insulators that are improved in conductivity by plasmons. Due to the heat treatment temperature of thin film, plasma formation was shown differently, metal particles were used with normal aluminium, SiOC thin films were treated with heat at 60 degrees, conductivity was improved dramatically, and heat treatment at higher temperatures was found to be less conductivity.