• Journal of the Korean Chemical Society
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• v.56 no.4
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• pp.448-458
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• 2012

In order to develop alloy resistance in aggressive sulphat ion, the corrosion behavior of metallic glasses $Ni_{92{\cdot}3}Si_{4.5}B_{32}$, $Ni_{82,3}Cr_7Fe_3Si_{4.5}B_{3.2}$ and $Ni_{75.5}Cr_{13}Fe_{4.2}Si_{4.5}B_{2.8}$ (at %) at different concentrations of $H_2SO_4$ solutions was examined by electrochemical methods and Scanning Electron Microscope (SEM) and X-ray Photoelectron Microscopy (XPS) analyses. The corrosion kinetics and passivation behavior was studied. A direct proportion was observed between the corrosion rate and acid concentration in the case of $Ni_{92{\cdot}3}Si_{4.5}B_{32}$ and $Ni_{75.5}Cr_{13}Fe_{4.2}Si_{4.5}B_{2.8}$ alloys. Critical concentration was observed in the case of $Ni_{82,3}Cr_7Fe_3Si_{4.5}B_{3.2}$ alloy. The influence of the alloying element is reflected in the increasing resistance of the protective film. XPS analysis confirms that the protection film on the $Ni_{92{\cdot}3}Si_{4.5}B_{32}$ alloy was NiS which is less protective than that formed on Cr containing alloys. The corrosion rate of $Ni_{82,3}Cr_7Fe_3Si_{4.5}B_{3.2}$ and $Ni_{75.5}Cr_{13}Fe_{4.2}Si_{4.5}B_{2.8}$. alloys containing 7% and 13% Cr are $7.90-26.1{\times}10^{-3}$ mm/y which is lower about 43-54 times of the alloy $Ni_{92{\cdot}3}Si_{4.5}B_{32}$ (free of Cr). The high resistance of $Ni_{75.5}Cr_{13}Fe_{4.2}Si_{4.5}B_{2.8}$ alloy at the very aggressive media may due to thicker passive film of $Cr_2O_3$ which hydrated to hydrated chromium oxyhydroxide.

• Elastomers and Composites
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• v.40 no.1
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• pp.12-21
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• 2005

In this work, magnesium carbonate and calcium hydroxide as metallic crosslinking agent were added to chlorosulfonated polyethylene rubber (CSM) emulsion to enhance the mechanical properties of emulsion film such as tensile strength, elongation at break, and tear strength and crosslinking density, thermal features, and surface energy were also investigated. Crosslinking density of the CSM emulsion film with increasing the amount of magnesium carbonate and calcium hydroxide increased, leading to the enhancement of water resistance. It was shown that compared with calcium hydroxide, magnesium carbonate had a little higher crosslinking density and $T_g$ value. The surface energy and mechanical characteristics of the CSM emulsion film, however, showed somewhat different behaviors. The highest surface energy, tensile strength, and tear strength were observed when 0.75% for magnesium carbonate and 1.0% for calcium hydroxide were added respectively. Therefore, it can be concluded that as metallic crosslinking agent to improve water resistance and mechanical properties of the CSM emulsion, magnesium carbonate is more preferable to calcium hydroxide.

• Proceedings of the Materials Research Society of Korea Conference
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• 2011.10a
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• pp.25.1-25.1
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• 2011

Over the past few decades, metallic nanoparticles (NPs) have been of great interest due to their unique mesoscopic properties which distinguish them from those of bulk metals; such as lowered melting points, greater versatility that allows for more ease of processability, and tunable optical and mechanical properties. Due to these unique properties, potential opportunities are seen for applications that incorporate nanomaterials into optical and electronic devices. Specifically, the development of metallic NPs has gained significant interest within the electronics field and technological community as a whole. In this study, gold (Au) pads for surface finish in electronic package were developed by inkjet printing of Au NPs. The microstructures of inkjet-printed Au film were investigated by various thermal treatment conditions. The film showed the grain growth as well as bonding between NPs. The film became denser with pore elimination when NPs were sintered under gas flows of $N_2$-bubbled through formic acid ($FA/N_2$) and $N_2$, which resulted in improvement of electrical conductance. The resistivity of film was 4.79 ${\mu}{\Omega}$-cm, about twice of bulk value. From organic anlayses of FTIR, Raman spectroscopy, and TGA, the amount of organic residue in the film was 0.43% which meant considerable removal of the solvent or organic capping molecules. The solder ball shear test was adopted for solderability and shear strength value was 820 gf (1 gf=9.81 mN) on average. This shear strength is good enough to substitute the inkjet-printed Au nanoparticulate film for electroplating in electronic package.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1997.11a
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• pp.202-205
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• 1997

We investigated grain boundary effect for terrestrial applications of solar cell\ulcorner with low cost, large area, and high efficiency. Grain boundaries are known as potential barriers and recombination centers for the photo-generated charge carriers, which make it difficult to achieve a high efficiency cell. To reduce these effects of grain boundaries, we investigated various influencing factors such as thermal treatments, various grid patterns, selective wet etchings for grain boundaries, buried contact metallizations along grain boundaries, and use of metallic thin films. From the various grid patterns we learned that the series resistance of solar cell reduced open circuit voltage and consequently decreased the cell efficiency. This paper describes the effect of various grid patterns and the employment of metallic thin films for a top electrode.

• Journal of Sensor Science and Technology
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• v.32 no.4
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• pp.252-256
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• 2023

A one-step method for nanoscale patterning of silver ionic ink on a substrate is developed using a microscale, elastic mold deformation. This method yields unique micro/nanoscale metallic structures that differ from those produced using the original molds. The linewidth of these metallic structures is significantly reduced (approximately 10 times) through the sidewall deformation of the original mold cavity on a thin liquid film, as verified by finite element analysis. The process facilitates the fabrication of various, isolated and complex micro/nanoscale metallic structures with negligible residual layers at low cost and high throughput. These structures can be utilized for various applications, including optoelectronics, wearable sensors, and metaverse-related devices. Our approach offers a promising tool for manipulation and fabrication of micro/nanoscale structures of various functional materials.

• Proceedings of the SAREK Conference
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• 2008.06a
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• pp.1128-1133
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• 2008

Drying process in the thin film layer of sludge with the thickness less than a few millimeters has been investigated using the simple one-dimensional model. Thin film drying is usually used to dry the viscous materials like sewage sludge. The thin film layer of sludge is dried on the metallic surface through which thermal energy is supplied to the layer during drying. In order to solve the equations, the mass transfer rate on the drying surface should be determined. The mass flux of evaporated water vapor on the surface is estimated with the formulation given in the literature. The effect of heating temperature, film thickness, and air velocity on drying has been examined to figure out the drying characteristics of the sludge layer.

• Bulletin of the Korean Chemical Society
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• v.33 no.4
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• pp.1177-1182
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• 2012

The corrosion resistance of 316L stainless steel coated with NiO-YSZ (Ni added yttria stabilized zirconia) was examined in a proton exchange membrane fuel cell (PEMFC) environment. The NiO-YSZ coating was carried out using a sol-gel dip coating method, and the corrosion resistance and interfacial contact resistance (ICR) were determined by the composition and morphology of the NiO-YSZ film. The corrosion resistance increased with increasing Ni content in the NiO-YSZ film, but rapid corrosion was observed when the YSZ film contained more than 15 wt % Ni due to surface cracks. The polarization resistance was improved by several orders of magnitude when 316L stainless steel was coated with a 15 wt % NiO-YSZ film compared to bare 316L. The ICR of the NiO-YSZ film was decreased to that of bare 316L when the YSZ film contained 25 wt % NiO, suggesting the possible application of NiO-YSZ coated stainless steel for a bipolar plate.

• Journal of the Korean Ceramic Society
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• v.31 no.12
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• pp.1529-1535
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• 1994

Electrical conduction mechanisms of RuO2-based thick film resistors were investigated with frequency depandence on AC conductivity. Electrical conduction mechanisms of lower resistivity system (100{{{{ OMEGA }}/sq) sintered at 600~90$0^{\circ}C$ were all metallic conduction mechanism. In case of higher resistivity (10K{{{{ OMEGA }}/sq) system, the electrical conduction mechanisms were very depenent on sintering temperature. When sintering temperature was $600^{\circ}C$, the electrical conduction mechamism was ionic, and as increasing the sintering temperature, the electrical conduction mechanism was changed from ionic to hopping conduction mechanism.

• Proceedings of the SAREK Conference
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• 2009.06a
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• pp.1326-1331
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• 2009

Drying process in the cylindrical thin film layer of sludge with the thickness less than a few millimeters has been investigated. Thin film drying is specially designed and used to dry the viscous materials like sewage sludge. The thin film layer of sludge is dried on the metallic cylindrical surface through which thermal energy is supplied to the layer during drying. The wall temperature is assumed to be constant during drying in the present study for the simplification. In order to solve the equations, the mass transfer rate on the drying surface should be determined. The mass flux of evaporated water vapor on the surface is estimated with the formulation given in the literature. The effect of some physical parameters on drying has been examined to figure out the drying characteristics of the sludge layer.

• Journal of the Semiconductor & Display Technology
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• v.2 no.4
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• pp.31-35
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• 2003

We present a formation technique of thin film heater for heat transfer components. Thin film structures of Cr-Si have been prepared on top of alumina substrates by magnetron sputtering. More samples of Mo thin films were prepared on silicon oxide and silicon nitride substrates by electron beam evaporation technology. The electrical properties of the thin film structures were measured up to the temperature of $500^{\circ}C$. The thickness of the thin films was ranged to about 1 um, and a post annealing up to $900^{\circ}C$ was carried out to achieve more reliable film structures. In measurements of temperature coefficient of resistance (TCR), chrome-rich films show the metallic properties; whereas silicon-rich films do the semiconductor properties. Optimal composition between Cr and Si was obtained as 1 : 2, and there is 20% change or less of surface resistance from room temperature to $500^{\circ}C$. Scanning electron microscopy (SEM) and Auger electron spectroscopy (AES) were used for the material analysis of the thin films.