• Korean Journal of Metals and Materials
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• v.49 no.10
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• pp.811-817
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• 2011

In this study, we have investigated the role of a metal oxide hole injection layer (HIL) between an Indium Tin Oxide (ITO) electrode and an organic hole transporting layer (HTL) in organic light emitting diodes (OLEDs). Nickel Oxide films were deposited at different deposition times of 0 to 60 seconds, thus leading to a thickness from 0 to 15 nm on ITO/glass substrates. To study the influence of NiO film thickness on the properties of OLEDs, the relationships between NiO/ITO morphology and surface properties have been studied by UV-visible spectroscopy measurements and AFM microscopy. The dependences of the I-V-L properties on the thickness of the NiO layers were examined. Comparing these with devices without an NiO buffer layer, turn-on voltage and luminance have been obviously improved by using the NiO buffer layer with a thickness smaller than 10 nm in OLEDs. Moreover, the efficiency of the device ITO/NiO (< 5 nm)/NPB/$Alq_3$/ LiF/Al has increased two times at the same operation voltage (8V). Insertion of a thin NiO layer between the ITO and HTL enhances the hole injection, which can increase the device efficiency and decrease the turn-on voltage, while also decreasing the interface roughness.

• Steel and Composite Structures
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• v.46 no.1
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• pp.15-31
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• 2023

Organic solar cells utilized natural polymers to convert solar energy to electricity. The demands for green energy production and less disposal of toxic materials make them one of the interesting candidates for replacing conventional solar cells. However, the different aspects of their properties including mechanical strength and stability are not well recognized. Therefore, in the present study, we aim to explore the chaotic responses of these organic solar cells. In doing so, a specific type of organic solar cell constructed from layers of material with different thicknesses is considered to obtain vibrational and chaotic responses under different boundaries and initial conditions. A square plate structure is examined with first-order shear deformation theory to acquire the displacement field in the laminated structure. The bounding between different layers is considered to be perfect with no sliding and separation. On the other hand, nonlocal elasticity theory is engaged in incorporating the structural effects of the organic material into calculations. Hamilton's principle is adopted to obtain governing equations with regard to boundary conditions and mechanical loadings. The extracted equations of motion were solved using the perturbation method and differential quadrature approach. The results demonstrated the significant effect of relative glass layer thickness on the chaotic behavior of the structure with higher relative thickness leading to less chaotic responses. Moreover, a comprehensive parameter study is presented to examine the effects of nonlocality and relative thicknesses on the natural frequency of square organic solar cell structure.

• Journal of the Korean Ceramic Society
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• v.46 no.5
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• pp.447-451
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• 2009

Continuous SiC fiber-reinforced SiC composites ($SiC_f$/SiC) were fabricated by electrophoretic deposition (EPD). Nine types of slurries with different powder contents, binder resin amounts and slurry pH were deposited on Tyranno$^{TM}$-SA fabrics by EPD at 135 V for ten minutes to determine the optimal conditions. Further EPD using the optimum slurry conditions was performed on fabrics with four different pyrolitic carbon (PyC) thicknesses. The density of the hot-pressed composites decreased with increasing PyC thickness due to the difficulty of infiltrating the slurry into the narrow gaps between the fibers. On the other hand, the mechanical strength increased with increasing PyC thickness despite the decrease in density, which was explained by the enhanced crack deflection with increasing PyC thickness. The $SiC_f$/SiC composites showed the highest density and flexural strength of 94% and 342 MPa, respectively, showing EPD as a feasible method for dense $SiC_f$/SiC fabrication.

• Journal of the Korean Society of Safety
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• v.11 no.3
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• pp.33-43
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• 1996

In this paper, collapse test of thin-walled structures, which are widely used in the vehicle members is carried out to observe the dependence of cross-sectional forms and materials on the absorbed energy in the viewpoint of crashworthiness. Also, specimens consist of two kinds (Al, CFRP) with various thickness. Comparisons of circular specimens are made to find characteristics of the different specimens on the absorption ability according to specimen thickness and materials.

• Journal of Welding and Joining
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• v.22 no.2
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• pp.38-45
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• 2004

Ultrasonic signals transmitted through adhesively bonded plates were used to evaluate parameters related to attenuation and frequency in the adhesively bonded joint. The kinds of bonding materials with a different bonding thickness of constant pressure were used. And ultrasonic diagnosis was evaluated by p-wave sensor of 10MHz. FFT has been performed to determine bond-layer parameters such as effective thickness and frequency for adhesively bonded joint of A16061 plates in comparison with measured to theoretical ratios. When variable thickness exists, the ultrasonic spectrum was changed the frequency wave. The more materials thickness and the higher the frequency, the larger shift was observed. Measured ratios for cases of bond thickness and variety bonding materials are then used to determine bond parameters. The results show that the technique can be applied to the characterization of adhesively bonded joint.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.11a
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• pp.345-345
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• 2007

ZnS/$Na_3AlF_6$/ZnS/Cu multi-layered thin film were simulated by EMP. EMP is a comprehensive software package for the design and analysis of optical thin film. ZnS and $Na_3AlF_6$ was selected as a high refractive index material and low refractive index material And Cu was selected as mid reflective material. Optical properties including color effect were systematically studied in terms of different low refractive index materials thickness. $Na_3AlF_6$ were changed 0.25, 0.5, 0.75, $1.0{\lambda}$. The thin film showed $0.25{\lambda}$ : blue, purple / $0.5{\lambda}$ : yellow $0.75{\lambda}$ : blue, purple, red / $1.0{\lambda}$ : yellow, green, blue, purple. It was becaused by different optical thickness of $Na_3AlF_6$. The maximum of optical interference by refractive layer.

• Journal of Adhesion and Interface
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• v.11 no.3
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• pp.120-125
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• 2010

UV-curable acrylic Pressure-sensitive adhesives (Acrylic PSAs) are used in many different parts in the world. A wafer manufacture process which is based on semiconductor industry is one thing. We have used acrylic PSAs whose thickness is different from $20{\mu}m$ to $30{\mu}m$ in wafer manufacture process so far. But as wafers become more thinner, acrylic PSAs are supposed to satisfy the requirements such as proper adhesion performance. The main purpose of this research is studying proper adhesion performance and UV-curing behavior of UV-curable acrylic PSAs with very thin thickness and then determining optimized conditions to raise the efficiency of thin wafer production. Acrylic PSAs contain 2-Ethylhexyl Acrylate (2-EHA), Acrylic Acid (AA) and Butyl Acrylate (BA). Ethyl acetate (EtAc) is used as solvent. The acrylic PSAs are obtained using solvent polymerization. Thickness of UV-curable acrylic PSAs is different from $10{\sim}30{\mu}m$. By peel strength and probe tack, adhesion performance and UV curing behavior of acrylic PSA are concerned.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2004.10a
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• pp.23-26
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• 2004

Ag/Ni multilayers with different bilayer thickness between 3 and 100 nm produced by DC magnetron puttering have been studied by cross-sectional TEM and nanoindentation. The micrograph shows perfect layered structure with sharp interfaces between Ag and Ni layers. Absolute hardness is calculated as a reference value to compare hardness of specimens regardless of indent depth. A hardness enhancement of nearly $100\%$ over the rule-of-mixtures values, calculated from the measured hardness of single Ag and Ni thin films, is observed. The hardness increases with decreasing bilayer thickness until 8nm. This enhancement shows a good agreement with Hall-Petch relation using grain size (one half of the bilayer thickness) confined within a layer. The deformation behavior can be explained by dislocation pile-up in smaller grains.

• Korean Journal of Metals and Materials
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• v.49 no.5
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• pp.367-373
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• 2011

This paper studies the experimental method that uses the homogeneous precipitation method to prepare mica flakes coated with anatase-type titania pearlescent pigment with urea as precipitant. The optimum technology parameters, the chemical composition, the microstructure, and the color property of resulting pigments are discussed. The coating principle of mica coated titania with various coating thickness is analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy(TEM) and tested by spectrophotometer analysis. The colored nanocrystalline pigments with different morphology and coating thickness 45-170 nm were prepared by homogeneous precipitation treatment of $TiOSO_4$(titanum oxysulfate) aqueous solutions. Characterizations on the pigments show that the pearlescent effects of the pigments depend mainly on mica size, thickness of the metal oxide deposit, its chemical composition, and crystal structure.

• Korean Journal of Materials Research
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• v.29 no.7
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• pp.443-450
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• 2019

Thermal management is a critical issue for the development of high-performance electronic devices. In this paper, thermal conductivity values of mild steel and stainless steel(STS) are measured by light flash analysis(LFA) and dynamic thermal interface material(DynTIM) Tester. The shapes of samples for thermal property measurement are disc type with a diameter of 12.6 mm. For samples with different thickness, the thermal diffusivity and thermal conductivity are measured by LFA. For identical samples, the thermal resistance($R_{th}$) and thermal conductivity are measured using a DynTIM Tester. The thermal conductivity of samples with different thicknesses, measured by LFA, show similar values in a range of 5 %. However, the thermal conductivity of samples measured by DynTIM Tester show widely scattered values according to the application of thermal grease. When we use the thermal grease to remove air gaps, the thermal conductivity of samples measured by DynTIM Tester is larger than that measured by LFA. But, when we did not use thermal grease, the thermal conductivity of samples measured by DynTIM Tester is smaller than that measured by LFA. For the DynTIM Tester results, we also find that the slope of the graph of thermal resistance vs. thickness is affected by the usage of thermal grease. From this, we are able to conclude that the wide scattering of thermal conductivity for samples measured with the DynTIM Tester is caused by the change of slope in the graph of thermal resistance-thickness.