• Journal of Welding and Joining
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• v.20 no.1
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• pp.47-54
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• 2002

Powder type Ag system insert metals were manufactured by ball milling process. The variables of milling process such as milling media, revolution speed and powder/ball weight ratio were constant except the milling time. The milling times were selected for 24, 48 and 72 hours. The insert metals made by milling process were evaluated by performing scanning electron microscope, x-ray and DSC(differential scanning calorimetry) analysis, and further in terms of wettability test. The selected insert metals that have the good characteristics compared to commercial insert metals were applied to make the brazed joints of the steel/steel and the steel/WC superhard particles. The characterizations of those brazed joints were also conducted by microstructural observations, shear tensile tests and microhardness measurements. The results indicated that milling time of 48 hours for making powder type insert metals was the best condition showing the small amount of oxides residue, low wetting angle and stable microstructure. The brazed joints that applied the 48 hours milled insert metal were very sound condition indicating the shear tensile value of $2.29{\times}102$ MPa and the microhardness of 138VHN. Further, the amount of the porosity was appeared to be lower than that of the commercial insert metals.

• Korean Journal of Metals and Materials
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• v.50 no.8
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• pp.557-562
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• 2012

Self-organized ruthenium (Ru) dots were fabricated by $400^{\circ}C$ RTA (rapid thermal annealing) and ALD (atomic layer deposition). The dots were produced under the $400^{\circ}C$ RTA conditions for 10, 30 and 60 seconds on all Si(100)/200 nm-SiO2, glass, and glass/fluorine-doped tin oxide (FTO) substrates. Electrical sheet resistance, and surface microstructure were examined using a 4-point probe and FE-SEM (field emission scanning electron microscopy). Ru dots were observed when a 30 nm-Ru layer on a Si(100)/200 nm-SiO2 substrate was annealed for 10, 30 and 60 seconds, whereas the dots were only observed on a glass substrate when a 50 nm-Ru layer was annealed on glass. For a glass/FTO substrate, RTA <30 seconds was needed for 30 nm Ru thick films. Those dots can increase the effective surface area for silicon and glass substrates by up to 5-44%, and by 300% for the FTO substrate with a < $20^{\circ}$ wetting angle.

• Proceedings of the SAREK Conference
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• 2006.06a
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• pp.621-626
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• 2006

Regenerative evaporative cooling is known as an environment-friendly and energy efficient cooling method. A regenerative evaporative cooler (REC) consisting of dry and wet channels is able to cool down the air stream below the inlet wet-bulb temperature. In the regenerative evaporative cooler, the cooling effect is achieved by redirecting a portion of the air flown out of the dry channel into the wet channel and spraying water onto the redirected air. In this study, a horizontal regenerative cooler is considered. In the horizontal regenerative cooler, the flow direction of evaporating water has a right angle to the flow direction of supply air. This difference was investigated with visualization technique and simplified 2-module performance test was done in a thermo-environment chamber. Optimum design configuration is changed due to the wet channel which are easily fully covered with evaporating water and block the air flow inside the channel. Applying the optimized fin configuration design with the highly wetting surface treatment, a regenerative evaporative cooler was fabricated and tested to Identify the cooling performance improvement and operation characteristics. From the experimental results at the intake condition of $32^{\circ}C$ and 50% RH, the supply temperature was measured to be around $23.4^{\circ}C$. The cooling effectiveness based on the inlet dewpoint temperature was evaluated 73% which is almost close to the design expectation.

• Corrosion Science and Technology
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• v.22 no.3
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• pp.193-200
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• 2023

Titanium alloy (grade-4) is commonly used in industrial and medical applications. To improve its corrosion resistance and biocompatibility for medical use, it is necessary to form a titanium oxide film. In this study, the morphology of the oxide film formed by anodizing Ti-grade 4 using different electrolytes was analyzed. Wetting properties before and after surface modification with SAM coating were also observed. Electrolytes used were categorized as A, B, and C. Electrolyte A consisted of 0.3 M oxalic acid and ethylene glycol. Electrolyte B consisted of 0.1 M NH₄F and 0.1 M H₂O in ethylene glycol. Electrolyte C consisted of 0.07 M NH₄F and 1 M H₂O in ethylene glycol. Samples B and C exhibited a porous structure, while sample A formed a thickest oxide film with a droplet-like structure. AFM analysis and contact angle measurements showed that sample A with the highest roughness exhibited the best hydrophilicity. After surface modification with SAM coating, it displayed superior hydrophobicity. Despite having the thickest oxide film, sample A showed the lowest insulation resistance due to its irregular structure. On the other hand, sample C with a thick and regular porous oxide film demonstrated the highest insulation resistance.

• 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 Korean Vacuum Society
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• v.16 no.2
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• pp.79-90
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• 2007

Prototype of $800{\ell}$ vacuum web coater (Vic Mama) consisting of ion source with low energy less than 250 eV for high speed surface modification and 4 magnetron sputter cathodes was designed and constructed. Its performance was evaluated through fabricating the adhesiveless flexible copper clad laminate (FCCL). Pumping speed was monitored in both upper noncoating zone pumped down by 2 turbo pumps with 2000 l/sec pumping speed and lower surface modification and sputter zone vacuumed by turbo pumps with 450 1/sec and 1300 1/sec pumping speed respectively. Ion current density, plasma density, and uniformity of ion beam current were measured using Faraday cup and the distribution of magnetic field and erosion efficiency of sputter target were also investigated. With the irradiation of ion beams on polyimide (Kapton-E, $38{\mu}m$) at different fluences, the change of wetting angle of the deionized water to polyimide surface and those of surface chemical bonding were analyzed by wetting anglometer and x-ray photoelectron spectroscopy. After investigating the deposition rate of Ni-Cr tie layer and Cu layer was investigated with the variations of roll speed and input power to sputter cathode. FCCL fabricated by sputter and electrodeposition method and characterized in terms of the peel strength, thermal and chemical stability.

• Korean Journal of Soil Science and Fertilizer
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• v.28 no.3
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• pp.249-255
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• 1995

This study was conducted to investigate the effects of some soil conditioners, such as polyacrylamide(PAM), polyvinylalcohol(PVA) and Bitumen emulsion, on aggregate formation and stability, wetting angle, sorptivity and penetrability of the soil with different textures : sand, sandy loam, loam and clay loam. A pot experiment was carried out to find out the effect of treatment on the germination and growth of lettuce with three textures : sand, sandy loam and silt loam. Soil aggregates larger than 2mm in untreated soils at dry condition were naught in sand, 45% in sandy loam, 80% in loam and 90% in clay loam. Treatments of soil conditioners tended to increase the occurrence of soil aggregate larger than 2mm, which were 20~25% in sand, 55~75% sandy loam, but not affected greatly aggragate occurence in loam and clay loam. The aggregate instability was decreased by the soil conditioner treatment. The wetting angles of the soils were greatly changed by hydrophobic of Bitumen, but those were changed slightly by PVA and PAM application. The sorptivity and penetrability data indicated that the effects of different materials on these parameters differed depending upon soil texture. Application of PVA and PAM were no effect exceptive in sand. Application of Bitumen revealed that water movement was not showed in all soils. The germination rate, root weight and top plant weight of lettuce were increased in all soils by PAM treatment as compared to untreated soils. Particularly the greater effect was occurred in sand soil than in sandy loam and silt loam. PAM increased greatly the moisture content and air phase of soils.

• 한국생물공학회:학술대회논문집
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• 2003.10a
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• pp.428-433
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• 2003

We measured the effect of wettability of six MPSs for RGP(rigid gas permeable) lens. The used MPSs(multipurpose solutions) were OPTI-SOAK(ALCON), SOLO care hard(CIBA Vision), Total care(ALLERGAN), Simplicity(BOSTON), Wetting and Soaking Sol.(Bausch & Lomb) and Aquas-multi(Saehan). These MPSs keeps hydrophilic property of lens surface and increase the effect of cleaning or increase the effect of preservative effect. To compare with the effect of wettability we followed the way of contact angle measurement which was general way to measure wettability and compared lens which was conducted by each MPS made by different companies. As a control, 0.9% NaCl solution and artificial tears were used. The degree of the effect of wettability was decided by contact angle. It is hydrophilic property nearby $0^{\circ}$ of contact angle and it is closed by hydrophobic property as it increases. The results showed that every lens was nearby hydrophilic property within $25\;^{\circ}-36\;^{\circ}$. Also, it was differed by various factors. The surface tension showed various differences between 19.8 and 31.3 mN/m. In the viscosity, MPSs represented the highest viscosity between $4^{\circ}C$ and $20^{\circ}C$. It was much higher than compared with the viscosity of soft lens MPS. This experiment could be used to grasping the interaction between solutions used to MPS and the natural endowments of lens and to considering the relations of different factors effecting the wettability.

• International Journal of Automotive Technology
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• v.5 no.4
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• pp.221-238
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• 2004

Wall interactions of direct injection spray were investigated using laser-sheet imaging, shadowgraphy, wetted footprint and phase Doppler interferometry techniques. A narrow-cone high-pressure swirl injector is used to inject iso-octane fuel onto a plate, which has three different impact angles inside a pressurized chamber. Heated air and plate conditions were compared with unheated cases. Injection interval was also varied in the heated case to compare dry- and wet- wall impingement behaviors. High-speed macroscopic Mie-scattering images showed that presence of wall and air temperature has only minor effect on the bulk spray structure and penetration speed for the narrow-cone injector tested. The overall bulk motions of the spray plume and its spatial position at a given time are basically unaffected until a few millimeters before impacting the wall. The surface properties of the impact surface, such as the temperature, the presence of a preexisting liquid film also have a small effect on the amount of wetting or the wetted footprint; however, they have strong influence on what occurs just after impact or after a film is formed. The shadowgraph in particular shows that the plate temperature has a significant effect on vapor phase propagation. Generally, 10-20% faster horizontal vapor phase propagation is observed along the wall at elevated temperature condition. For impingement onto a preexisting film, more splash and evaporation were also observed. Contrary to some preconceptions, there is no significant splashing and droplet rebounding from surfaces that are interposed in the path of the DI gasoline spray, especially for the oblique impact angle cases. There also appears to be a dense spray front consists of large sac spray droplets in the oblique impact angle cases. The bulk of the spray is not impacted on the surface, but rather is deflected by it The microscopic details as depicted by phase Doppler measurements show that the outcome of the droplet impaction events can be significantly influenced. Only droplets at the spray front have high enough Weber numbers for wall impact to wet, splash or rebound. Using the sign of vertical velocity, the time-resolved downward droplets and upward droplets are compared. The Weber number of upward moving droplets, which seldom exceeds unity, also decreases as the impact angle decreases, as the droplets tend to impact less and move along the wall in the deflected spray plume.

• Journal of the Korean Vacuum Society
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• v.7 no.3
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• pp.221-228
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• 1998

Enhancement of adhesion between polymer films and metal films are obtained by forming the hydrophilic functional groups on the polymer surfaces by ion assisted reaction which uses ion beam in reactive gas environments. In ion assisted reaction, ion dose, blown gas flow rate and ion energy were changed from $5\times 10^{14}$ to $1\times 10^{17}\textrm{ions/cm}^2$, from 0 to 8 sccm, and 0.3 to 1.2 kV, respectively. Wetting angle of water on polymer films modified by $ Ar^+$ ion without blowing oxygen decreases to ~$40^{\circ}$. Contact angle of water on polymer films modified by $ Ar^+$ ion with blowing oxygen decreases to ~$20^{\circ}$, and the surface free energy increases to ~70 dyne/$\textrm{cm}^2$. However, contact angle of water on polytetraflouroethylene (PTFE) modified by ion assisted reaction increases with ion dose. The adhesion strength of metal film deposited on the polymer surface was investigated. In the case of the metal film deposited on the untreated polymers, the metal films are detached from the polymer surface. While, In the case of the metal film deposited on the polymers treated by ion assisted reaction, the metal films are strongly adhere to the polymer surfaces.