• Korean Journal of Materials Research
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• v.18 no.3
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• pp.117-122
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• 2008

Micro-sized bumps on a multi-layered build-up PCB were fabricated by pulse-reverse copper electroplating. The values of the current density and brightener content for the electroplating were optimized for suitable performance with maximum efficiency. The micro-bumps thus electroplated were characterized using a range of analytical tools that included an optical microscope, a scanning electron microscope, an atomic force microscope and a hydraulic bulge tester. The optical microscope and scanning electron microscope analyses results showed that the uniformity of the electroplating was viable in the current density range of $2-4\;A/dm^2$; however, the uniformity was slightly degraded as the current density increased. To study the effect of the brightener concentration, the concentration was varied from zero to 1.2 ml/L. The optimum concentration for micro-bump electroplating was found to be 0.6 ml/L based on an examination of the electroplating properties, including the roughness, yield strength and grain size.

• Proceedings of the Korean Magnestics Society Conference
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• 2005.12a
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• pp.154-155
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• 2005

Multi-layer film of $MgO/(FePt-B)_{50nm}/ MgO$ was deposited on Si(100) substrates by RF magnetron sputtering. The boron chips were uniformly placed oil tile FePt target. The boron content of thin film was found to be about 5, 10, 15, 25 and $33 at\%$ by using a CAMECA SX-51 wavelength dispersive spectroscopy (WDX). It is observed that X-ray diffraction patterns of FePt-B film by post-annealing exhibited a transformation from disordered fcc structure to ordered $Ll_0$ phase with fct structure from around $400^{\circ}C$. By adding B, annealing temperature for ordering is about $200^{\circ}C$ lower than that of pure FePt. This remarkable decrease of the annealing temperature is closely related to the high diffusivities of Fe and Pt associated with the defects caused by movements of B atoms. The maximum coercivity(Hc) for FePt films was found to be ${\~}$13 kOe after annealing at $600^{\circ}C$ for 1hr.

• Korean Journal of Plant Resources
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• v.22 no.6
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• pp.584-591
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• 2009

Adventitious root culture was established in the Jawahar variety of Withania somnifera using MS basal medium supplemented with 0.5 (mg/l) IAA and 2.0 (mg/l) IBA. Root tips from germinated seedlings, MS0 maintained plants and adventitious roots were maintained in suspension medium (1/2 MS basal medium supplemented with 3% sucrose) for a period of 1 to 6 months. The weight gain in roots was noted and the withanolides were extracted from the dry roots using solvents petroleum ether, 50% ethanol and chloroform. The withanolides in the chloroform fractions of all root samples analyzed were compared using thin layer chromatographic analysis. Withanolide content in adventitious root sample was found to be superior compared to other roots at any given point of time during the 6month growth period.HPLC analysis of in vitro adventitious roots showed the presence of a new compound.

• Proceedings of the Membrane Society of Korea Conference
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• 2005.11a
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• pp.133-147
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• 2005

In order to investigate applicability for 2,2,2-trifluoroethyl methacrylate (TFEMA) produced by esterification of 2,2,2-trifluoroethanol(TFEA) and methacrylic acid(MA) using pervaporation membrane, poly(vinyl alcohol) (PVA) composite membranes were prepared with glutaraldehyde(GA) onto porous polyethersulfone(PES) support. The degree of crosslinking and thickness of PVA coating layer were analyzed by swelling test and SEM(scanning electron microscopy), respectively. Pervaporation test was done with two feed mixures; TFEA/water, MA/water. The pervaporation data were obtained as a function of content of crosslinking agent, feed composition, and operating temperature, respectively. In case of TFEA-water(90/10 wt%) feed mixture at $80^{\circ}C$, the optimized membrane showed the high permeation flux of 1.5 $kg/m^2hr$ and separation factor of 320. In case of MA-water(90/10 wt%) feed mixture, the membranealso showed high permeation flux of 2.3 $kg/m^2hr$ and separation factor of 740 in same conditions.

• Journal of the Korean Society of Safety
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• v.13 no.3
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• pp.102-111
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• 1998

This study was concerned with the development of a heavy duty rust-converting agent, the function of which is to form metal complex coatings, containing vinyl halide-acrylic terpolymer emulsion, defoamer, emulsifying agent, glass flakes, chelating agent such as gallotannic acid, gallic acid, and pyrogallic acid, and other additives. The resulted emulsion products(Sample No.1~No.5) were characterized through test either in the forms of emulsions, which include Viscosity, Penetration rate, Acidity and Film drying rate test, or in the forms of coated layer on rusty steel substrates by FT-IR, which include hardness, gloss, salt spray, adhesion and flame retardant test. The test results are as follows ; Penetration rate(0.1~0.4 mm/min), Solid content(70%), Acidity (pH 1.8~2.0), Specific gravity(1.30~1.35), Film drying rate(108min, RH 40% ; 150min, RH 80%), Gloss(83~92, incident angle $60^{\circ}$; 88~97, incident angle $85^{\circ}$), Pencil hardness(4H~5H), Adhesion (100/100), Salt spray test(>720Hr), LOI(%) value(38%), Vertical burning test(UL 94-v-l). According to the various performance of specimens show above, the evaluation of the availability of this heavy duty rust-converting agent can be concluded that all the samples(No.1~No.5) are capable of being used in the field of chemical plant and in the hazard areas of fire and explosion potential. It was observed that the properties of sample No.2, especially gloss and hardness, were much better than that of the other samples.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.11a
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• pp.341-345
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• 2001

In this study, nano-sized powders of SiO$_2$-0∼15mo1%B$_2$O$_3$ composition were prepared by sol-gel processing method using TEOS(Tetra ethyl ortho silicate) and H$_3$BO$_3$ solution. The powders were tape-cast on High silicate glass sheet(HSG) substrate and sintered to form a layer of undercladding for the planar light wave module. During the sol-gel processing, H$_2$O/Si mole ratio were varied to modify the size of the powders in a range from 600 to 75nm. The dispersion of the powder was modified by changing the pH of the slurry. Sintering temperature of the tape was observed to decrease with the size of the powder and the B$_2$O$_3$ content in the powder. When the silica powders of 75∼125nm in diameter containing 15mo1% B$_2$O$_3$ were used, 98 TD% was obtained at 1250$^{\circ}C$, which is approximately 300$^{\circ}C$ reduction in sintering temperature compared with micrometer-sized powders.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.29 no.6
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• pp.376-379
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• 2016

In this paper, the efficiency improvement of the heterojunction with intrinsic thin layer (HIT) solar cells is obtained by optimization process of p-type a-SiC:H as emitter. The optoelectronic of p-type a-SiC:H layers including the optical band-gap and conductivity under the methane gas content variation is conducted in detail. A significant increase in the Jsc by $1mA/cm^2$ and Voc by 30 mV are attributed to enhanced photon-absorption due to broader band-gap of p-a-SiC:H and reduced band-offsets at p-side interface, respectively of HIT solar cells.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.31 no.4
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• pp.238-243
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• 2018

A nanofiber was fabricated with carbon nanotubes for transparent electrodes. It was prepared with a composite solution of bio-molecules polycaprolactone (PCL) and multiwalled carbon nanotubes (MWCNTs) by electrospinning on a glass substrate, following which its electrical characteristics were investigated. The content of MWCNTs was varied during electrospinning, while that of PCL was fixed. Further, a nanometer-thick thin film of silver was deposited on the nanofiber layer using a thermal evaporator to improve the electrical characteristics; the sheet resistance significantly reduced after this deposition. The results showed that this carbon nanotube nanofiber has potential applications in biotechnology and as a flexible transparent display material.

• Journal of Surface Science and Engineering
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• v.27 no.4
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• pp.193-206
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• 1994

A wear behavior of electroless (Ni-P-X, X: SiC, $Al_2O_3$, Diamond) composite coating layers, formed under various conditions on commerical grade low carbon steel, has been investigated using Taber abrasion tester and scanning electron microscope. Several factors, which are type of particles, co-deposited content, particle size, distribution of particles and heat-treatment, influenced the wear resistance. The wear resistance of the composited coating layers after heat-treatment at $400^{\circ}C$ for 1 hr was increased 70 times with diamond, 15 times with SiC and 8 times with $Al_2O_3$, compared with the electroless nickel plating layer without heat-treatment.

• Journal of Surface Science and Engineering
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• v.34 no.2
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• pp.125-134
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• 2001

($Ti_{1-x}$ $Cr_{x}$ )N coatings were deposited by an ion-plating method in a reactor with two separate metal sources, Ti and Cr. Ti was evaporated using an electron beam, while Cr evaporation was carried out by resistant heating. The Ti and Cr concentrations in the coatings were controlled by the Ti and Cr evaporation ratio. The coating hardness increased with increasing the Cr content(x) and showed a maximum value of 6,000 HK at around x=0.8. The critical load of the coatings, measured by the scratch test, was around 30 N. The wear resistance properties of the ($Ti_{1-x}$$Cr_{ x}$)N coatings were evaluated using a CSEM pin-on-disk type tribometer. A Cr-steel ball as well as a SiC ball, which had hardness values of 590 HK and 2,600 HK respectively, were used as the pin. After the wear test, the surface morphology, roughness and the concentration of the coatings were investigated, with the main focus being on the effect of wear debris and the transferred layer on the wear behavior.