• Composites Research
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• v.24 no.5
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• pp.17-22
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• 2011

Recently transparent electrodes using carbon nanotube (CNT) have been studied actively to replace conventional ITO. In this work, CNT or ITO coated poly(ethylene terephthalate) (PET) were prepared by controlling the surfaces since the cohesion degree depends upon drying conditions. As transparent electrode application, 3 drying temperatures were set as 20, 80, and $120^{\circ}C$ to produce the change of surface properties. Interfacial durability and electrical properties of prepared transparent electrodes were evaluated by electrical resistance measurement. Surface change with changing drying temperature was observed by FE-SEM, whereas the transparency change was measured by UV-spectroscopy. The electronic properties of nanoparticle coated surface were evaluated using cyclic voltametry method upon the surface change with controlled drying temperature. Durability of CNT coated surfaces was better than ITO coated ease. As drying temperature increased, better coated surface was prepared due to improved cohesion among nanoparticles, which resulted in increased electrical properties.

• Korean Chemical Engineering Research
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• v.50 no.5
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• pp.929-932
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• 2012

Novel platform technology has been developed to replace the photolithography used currently for manufacturing semiconductors and display devices. As a substrate, plastics, especially polycarbonates, have been considered for future application such as flexible display. Other plastics, i.e. polyimide, polyetheretherketon, and polyethersulfone developed for the substrate at this moment, are available for photolithography due to their high glass transition temperature, instead of high price. After thin polystyrene film was coated on the polycarbonate substrate, microstructure of the film was formed with polydimethylsiloxane template over the glass transition temperature of the polystyrene. The surface of the structure was treated with potassium permanganate and octadecyltrimethoxysilane so that the surface became hydrophobic. After this surface treatment, the nanoparticles dispersed in aqueous solution were aligned in the structure followed by evaporation of the DI water. Without the treatment, the nanoparticles were placed on the undesired region of the structure. Therefore, the interfacial interaction was also utilized for the nanoparticle alignment. The surface was analyzed using X-ray photoelectron spectrometer. The evaporation of the solvent occurred after several drops of the solution where the hydrophilic nanoparticles were dispersed. During the evaporation, the alignment was precisely guided by the physical structure and the interfacial interaction. The alignment was applied to the electric device.

• Composites Research
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• v.35 no.2
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• pp.80-85
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• 2022

This work presents an experiment study to evaluate the nanoparticle adhesion and surface hydrophobicity characteristics of Teflon-polyurethane top coat depending on the number of multi-wall carbon nanotube (MWCNT) coatings, which is a carbon-based hydrophobic particle. In order to measure the adhesion between the nanoparticles and the top coat, adhesion pull-off test was performed with different MWCNT oxidation times. Static contact angle and roughness measurements were carried out to characterize the surface hydrophobic behavior. Through the roughness evaluation, it was confirmed that the carbon nanotubes were wetted in the Teflon-polyurethane top coat, and the degree carbon nanotube wetting was confirmed through a USB-microscope. As a result, it was found that the larger the degree of wetting, the better the adhesion. From the experimental results, as the hydrophobicity of Teflon-polyurethane increased, the adhesive propertydecreased with the number of coatings. It was possible to improve the adhesive force and determine the number of coatings of carbon nanotubes with optimized hydrophobicity.

• Tribology and Lubricants
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• v.33 no.6
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• pp.245-250
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• 2017

In this work, we examine pure water and water with nanoparticles to investigate water lubrication characteristics and the effect of nanoparticles as lubricant additives for different substrates. We test carbon-based coatings and metals such as high-speed steel and stainless steel in pure deionized (DI) water and DI water with nanoparticles. We investigate water lubrication characteristics and the effect of nanoparticles based on the friction coefficient and wear rate for different substrates. The investigation reveals that nanoparticles enhance the friction and wear properties of high-speed steel and stainless steel. The friction coefficient and wear rate of both high-speed steel and stainless steel decreases in DI water with nanoparticles compared with the results in pure DI water. The presence of nanoparticles in water show good lubricating effect at the contact area for both high-speed steel and stainless steel. However, for carbon-based coatings, nanoparticles do not improve friction and wear properties. Rather, the friction coefficient and wear rate increases with an increase in the concentration of nanoparticles in case of water lubrication. Because carbon-based coatings already have good tribological properties in a water environment, nanoparticles in water do not contribute toward improving the friction and wear properties of carbon-based coatings.

• Journal of the Microelectronics and Packaging Society
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• v.20 no.2
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• pp.39-46
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• 2013

In this paper, organic solar cells(OSCs) based on bulk-heterojunction structures were fabricated by spin coating method using polymer P3HT and fullerene PCBM as a photoactive layer. The fabricated OSCs had a simple glass/ITO/PEDOT:PSS/P3HT:PCBM/Al structures. The photoactive layer of mixed P3HT:PCBM was formed with 1:1 weight ratio. The hole transport layer(HTL) was used conducting polymer PEDOT:PSS concentration with gold nanoparticles. The annealing temperature and concentration of nanoparticles in HTL were verified to improve the OSC characterization. The percentage of gold nanoparticles in HTL were 0.5 wt% and 1.0 wt%, and the surface morphology, electrical properties and absorption intensities were investigated. The devices were 0.5 wt%, and the highest 3.1% of the powder conversion efficiency(PCE), 10.2 $mA/cm^2$ of the maximum short circuit current density($J_{SC}$), 0.535V of the open circuit voltage($V_{OC}$) and 55.8% of the fill factor(F.F) could be obtained when the nanoparticle concertration was 0.5 wt%. The annealing temperature of HTL was $110^{\circ}C$, $130^{\circ}C$, $150^{\circ}C$ in vacuum oven and measured the absorption intensities, surface morphology, crystallinity and electrical properties were investigated. The best property was obtained in HTL annealed at $130^{\circ}C$ for gold nanoparticles of 0.5 wt%, showing that $J_{SC}$, $V_{OC}$, F.F and PCE were about 12.0 $mA/cm^2$, 0.525V, 64.2% and 4.0%, respectively.

• Applied Chemistry for Engineering
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• v.27 no.1
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• pp.68-73
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• 2016

Silver nanoparticles were prepared by chemical reduction-protection method using 1-decanoic acid and tri-n-octylphosphine as surfactants, and using $NaBH_4$ as a reducing agent. The silver nanoparticles were also studied for their formation, structure, morphology and size using UV-Visible spectroscopy, XRD, TEM and SEM. Further the viscosity of the silver paste and the surface resistance of the silver metal film produced by screen coating onto a PET film were investigated. Well dispersed and quasispherical silver nanoparticles with the size of 10-200 nm were obtained under the optimal molar ratio of $NaBH_4/AgNO_3=1:5$. The surface resistance of silver metal film coated on the PET film made with the silver nanoparticles under the optimal molar ratio showed a minal value of $41{\mu}{\Omega}/cm^2$.

• Journal of the Microelectronics and Packaging Society
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• v.29 no.1
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• pp.55-59
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• 2022

In this paper, we compared the electric field and absorptance of nano particles in nanostructures by amplifying the electric field around the nanoparticles through plasmon resonance and comparing the structure that can increase the absorptance with the nanostructure by using the Finite Different Time Domain (FDTD) simulation. In addition, the width of the nanostructure was adjusted to 240 nm ~ 300 nm, and the light absorptance rate was higher as the gap between the particles was short. In addition, a study was conducted on the formation of nanoparticles and nanostructures on the surface through UV imprint. In order to form particles in the structure, the nano particles were first arranged in the mold used for the fabrication of the structure using spray coating, and then fabricated through UV imprinting. The nanostructure and particles were formed together by scanning electron microscopy.

• Journal of the Korean institute of surface engineering
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• v.56 no.4
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• pp.233-242
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• 2023

In recent years, energy-management studies in buildings have proven useful for energy savings. Typically, during heating and cooling, the energy from a given building is lost through its windows. Generally, to block the entry of ultraviolet (UV) and infrared (IR) rays, thin films of deposited metals or metal oxides are used, and the blocking of UV and IR rays by these thin films depends on the materials deposited on them. Therefore, by controlling the thicknesses and densities of the thin films, improving the transmittance of visible light and the blocking of heat rays such as UV and IR may be possible. Such improvements can be realized not only by changing the two-dimensional thin films but also by altering the zero-dimensional (0-D) nanostructures deposited on the films. In this study, 0-D nanoparticles were synthesized using a sol -gel procedure. The synthesized nanoparticles were deposited as deep coatings on polymer and glass substrates. Through spectral analysis in the UV-visible (vis) region, thin-film layers of deposited zinc oxide nanoparticles blocked >95 % of UV rays. For high transmittance in the visible-light region and low transmittance in the IR and UV regions, hybrid multiple layers of silica nanoparticles, zinc oxide particles, and fluorine-doped tin oxide nanoparticles were formed on glass and polymer substrates. Spectrophotometry in the UV-vis-near-IR regions revealed that the substrates prevented heat loss well. The glass and polymer substrates achieved transmittance values of 80 % in the visible-light region, 50 % to 60 % in the IR region, and 90 % in the UV region.

• Journal of the Microelectronics and Packaging Society
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• v.22 no.3
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• pp.25-30
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• 2015

SAC-coated Cu specimens were fabricated by novel pad finish process using a phenomenon that metal nanoparticles less than 20 nm in diameter melted at a temperature lower than the melting point of bulk metal, and their wettabilities were evaluated. The thickness of SAC305 layer coated at low temperature of $160^{\circ}C$ using SAC305 ink was extremely thin as the level of several nanometers. It was analyzed by Auger electron spectroscopy that $Cu_6Sn_5$ intermetallic layer with a thickness of 10~100 nm and $Cu_3Sn$ intermetallic layer with a thickness of 50~150 nm were sequentially formed under the SAC305 coating layer. The thickness of formed intermetallic layers was thicker in electroplated Cu than rolled Cu, which attributed to improved surface roughness in the electroplated Cu. The improved surface roughness induces the contact, melting, and reaction of a larger number of SAC305 nanoparticles per the unit area of Cu specimen. In the wetting angle test using SAC305 solder balls, the Cu coated with SAC305 through the low temperature process presented evidently low wetting angles than those in non-coated Cu, indicating that only a few nanometer-thick SAC305 coating layer on Cu could also cause the enhancement of wettability.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.4
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• pp.20-25
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• 2020

As nanoscience and nanotechnology advance, techniques for selective pattern growth have attracted significant attention. Silica nanoparticles (NPs) are used as a promising nanomaterials for bio-labeling, bio-imaging, and bio-sensing. In this study, silica NPs were synthesized by a sol-gel process using a modified Stöber method. In addition, the selective pattern growth of silica NPs was achieved by the surface functionalization of the substrate using a micro-contact printing technique of a hydrophobic treatment. The particle size of the as-synthesized silica NPs and morphology of selective pattern growth of silica NPs were characterized by FE-SEM. The contact angle by surface functionalization of the substrate was investigated using a contact angle analyzer. As a result, silica NPs were not observed on the hydrophobic surface of the OTS solution treatment, which was coated by spin coating. In contrast, the silica NPs were well coated on the hydrophilic surface after the KOH solution treatment. FE-SEM confirmed the selective pattern growth of silica NPs on a hydrophilic surface, which was functionalized using the micro-contact printing technique. If the characteristics of the selective pattern growth of silica NPs can be applied to dye-doped silica NPs, they will find applications in the bio imaging, and bio sensing fields.