• Journal of the Korean institute of surface engineering
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• v.50 no.5
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• pp.360-365
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• 2017

In this study, ion release and biocompatibility of sintered Ni-Cr-Ti alloy for dental prosthodontics have been researched by corrosion and cell culture test. The microstructures of the alloys were observed by optical microscope, and corrosion behavior was investigated using potentiostat (Model PARSTAT 2273, EG&G, USA). Cell culture was carried out using hGf cell in DMEM (Welgene Inc., South Korea) supplemented with 10% fetal bovine serum (FBS) (Welgene Inc., South Korea) and antibiotic antimycotic solution (Welgene Inc., South Korea). After corrosion and cell culture test, surface morphologies were observed by field-emission scanning electron microscopy. For wettability behaviors, contact angles were measured by wettability test. As the content of Ti increased, the number of pit decreased and the corrosion resistance was improved from anodic polarization test, also, polarization resistance of samples containing Ti remarkably improved as compared with the alloy not containing Ti. The sintered alloy showed a low contact angle due to the pores formed on the surface. The addition of Ti element showed that the cell survival rate was better than that of the control group.

• Journal of ILASS-Korea
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• v.12 no.4
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• pp.198-203
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• 2007

In the present work, surface wetting effect on spread-splash regime and transition criterion of the water and ethanol droplets impacting an unheated dry wall has been experimentally investigated. The droplet was directed on a polished STS plate and a glass slide, and the impinging behavior was visualized and recorded using a CCD camera. Droplet diameter and velocity approaching the wall were measured as well. The critical Sommerfeld number representing the spread-splash boundary for the ethanol droplet impinging on the substrates turned out to be smaller compared to that for the water droplet impinging on the substrates with the surface roughness condition remained unchanged. The shift of the transition boundary is considered to be due to the effect of the surface wettability represented by static contact angle and surface tension of droplet.

• Elastomers and Composites
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• v.54 no.4
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• pp.359-367
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• 2019

Poly(2-hydroxyethyl methacrylate) (PHEMA) hydrogels modified with various co-monomers, such as N-vinyl pyrrolidone (NVP), glycidyl methacrylate (GMA), and glycerol monomethacrylate (GMMA), were prepared to investigate the effect of adding a co-monomer on the water contents, surface wettability, and tensile modulus. These polymers were synthesized by thermal- and photo-polymerization in the presence of azobisisobutyronitrile (AIBN) and diphenyl(2,4,6-trimethylbenzoyl)-phosphineoxide (TPO) as the initiators. The characteristics of the hydrogels were analyzed via FTIR and UV/Vis spectroscopies, contact angle measurements, and tensile modulus measurements with UTM. Regarding the properties of water in the hydrogels, the ratio between free to bound water was investigated using differential scanning calorimetry (DSC). The effects of adding the co-monomers on the water content, surface wettability, and tensile modulus for soft contact lenses were also investigated. In the case of p(HEMA-co-NVP) hydrogels, the increase in the equilibrium water content (EWC) was primarily due to the increase in the bound water content. For p(HEMA-co-GMMA) hydrogels, an increase in free water content was the main reason for the increased EWC. In contrast, in the case of p(HEMA-co-GMA) hydrogels, a decrease in bound water content was observed to be the main factor that reduced the EWC. Photo-polymerized PHEMA hydrogels showed enhanced surface wettability and tensile modulus as compared to those produced via thermal polymerization.

• Proceedings of the Korean Vacuum Society Conference
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• 1999.07a
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• pp.204-204
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• 1999

The plasma source ion implantation(PSII) technique which is a method using high negative voltage pulse in plasma system has the potential to change the surface properties of polymer. PSII technique increase the surface free energy by introducing polar functional groups on the surface so that it improves reactivity, hydrophilicity, adhension, biocompatability, etc. However, the mobility of polymer chains enables the modified surface layers to adapt their composition to interfacial force. This hydrophobic recovery interrupts the stability of modified surfaces to keep for the long time. In this study, poly(methyl methacrylate)(PMMA), poly(2-hydroxyethyl methacrylate)(PHEMA), and polu(2-hydroxypropyl methacylate)(PHPMA) for contact lens application, were modified to improve the wettability with PSII technique and were investigated the surface stabilities. Polymer film was prepared with solution casting(3 wt.% solution) and was annealed at 11$0^{\circ}C$ under vacuum oven to remove solvent completely and to eliminate physical ageing. The thickness of the film measured by scanning electron microscopy (SEM) and surface profilometer was about 10${\mu}{\textrm}{m}$. Polymers were treated with different kinds of gases, pulse frequency, pulse with, pulse voltage, and treatment time. Even though PMMA, PHEMA, and PHPMA have similar repeat unit structure, the optimal treatment conditions and the tendency to hydrophobic recovery were different. PHPMA, more hydrophilic polymer than PMMA and PHEMA showd better wettability and stability after mild treatment. Surface tensions were obtained by water and diiodomethane contact angle measurements to monitor the relation between hydrophobic recovery and polymer structure. Different ion species in plasma change the polar component and dispersion component of polymer surface. For better wettability surface, the increase of polar component was a dominant factor. We also characterized modified polymer surfaces using x-ray photoelectron spectroscopy(XPS), secondary ion mass spectrometry(SIMS), Fourier Transform infrared spectroscopy(FT-IR), and SEM.

• Journal of the Korean Society of Safety
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• v.33 no.1
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• pp.41-46
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• 2018

Experiments were carried out the phenomenal observation on effect of corona treated hotmelt laminating film in process of manufacture by 2 kinds of rolling speed and electric power variatons. Surface treatment by corona which is exposure of film surface to electron of ion bombardment, rather than mere exposure to active species, like atomic oxygen or ozone, can enhance adhesion by removing contaminant, electret, roughening surface, and introducing reactive chemical group. Reactive neutrals, ions, electron and photons generated during the corona treatment interact simultaneously with polymers to alter surface chemical composition, wettability, and thus film adhesion. However, it is highly recommended that extensive chains scission is avoided because it can lead to side-effect by forming sticky matter, resulting in dropouts. This paper reviews principles of surface preparation of polypropylene substrate by corona discharging. In addition, the experimental section provides a description of parameter optimization on corona discharging treatment and its side-effect. Experimental results are discussed in terms of surface wetting as determined by contact angle and SEM measurements. When the rolling speed of the film decreased from 1.666 [m / sec] to 0.083 [m / sec], contact angle decreased from $80[^{\circ}]$ to $64[^{\circ}]$, and the wettability was greatly improved. As the supply power increased from 0.4 [kVA] to 2 [kVA] at the corona discharge surface treatment, the contact angle decreased from $77[^{\circ}]$ to $65[^{\circ}]$, and the wettability was greatly improved.

• Textile Coloration and Finishing
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• v.13 no.1
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• pp.18-22
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• 2001

Effects of cationic surfactants old the wetting behavior of the DMDHEU treated cotton fibers were investigated using a technique based on the Wilhelmy principle. The results indicated that Interactions between the fiber and water ill the interface make contributions to wettability of the cotton fiber surface because of reorientation of polar groups at the interface. The effects of types and concentration of cationic surfactant on the wettability of both control and durable press(DP) finished cotton fiber are discussed. Below and near the critical micelle concentration(cmc), the adsorption of hexadecyltrimethylammoniumbromide(HTAB) on the control fiber makes the fiber surface more hydrophobic. Near and above the cmc of octadecyltrimethylammouniumbromide(OTAB) , the decrease in advancing contact angles indicates that the control cotton surface became hydrophilic. By the adsorption of both HTAB and OTAB onto the fiber surface, the hydrophobicity of the DP finished fiber surface became mere hydrophilic.

• Nuclear Engineering and Technology
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• v.43 no.3
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• pp.205-216
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• 2011

Recently, many research studies have investigated the enormous critical heat flux (CHF) enhancement caused by nanofluids during pool boiling and flow boiling. One of the main reasons for this enhancement is nanoparticle deposition on the heated surface. However, in real applications, nanofluids create many problems when used as working fluids because of sedimentation and aggregation. Therefore, artificial surfaces on silicon and metal have been developed to create an effect similar to that of nanoparticle deposition. These modified surfaces have proved capable of greatly increasing the CHF during pool boiling, and good results have also been observed during flow boiling. In this study, we demonstrate that the wetting ability of a surface, i.e., wettability, and the liquid spreading ability (hydrophilic surface property), are key parameters for increasing the CHF during both pool and flow boiling. We also demonstrate that when the fuel surface in nuclear power plants is modified in a similar manner, it has the same effect, producing a large CHF enhancement.

• Interaction and multiscale mechanics
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• v.5 no.4
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• pp.399-405
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• 2012

A dissipative particle dynamics (DPD) simulation was presented to analyze surface wettability and contact angles of a droplet on a solid platform. The many-body DPD, capable of modeling vapor-liquid coexistence, was used to resolve the vapor-liquid interface of a droplet. We found a constant density inside a droplet with a transition along the droplet boundary where the density decreased rapidly. The contact angle of a droplet was extracted from the isosurfaces of the density generated by the marching cube and a spline interpolation of 2D cutting planes of the isosurfaces. A wide range of contact angles from $55^{\circ}$ to $165^{\circ}$ predicted by the normalized parameter ($|A_{SL}|/B_{SL}$) were reported. Droplet with the parameters $|A_{SL}|>5.84B{_{SL}}^{0.297}$ was found to be hydrophilic. If $|A_{SL}|$ was much smaller than $5.84B{_{SL}}^{0.297}$, the droplet was found to be superhydrophobic.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.05c
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• pp.31-35
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• 2002

It is hard to expect excellent electrical, mechanical and chemical properties from most of the composite materials presently used as insulators due to insufficient wettability property caused by the difference of interfacial properties between the matrix material and the reinforcer. Therefore, various interfacial coupling agents have been developed to improve the interfacial properties of composite materials. But if the wettable coupling agents are used outdoor for a long time, change in quality takes place in the coupling agents themselves, bringing about deterioration of the properties of the composite materials. In this study, composite materials were put to dry interfacial treatment by use of plasma technology. It has been presented that the optimum parameters for the best wettability of the samples at the time of generation of plasma were oxygen atmosphere, 0.1 torr of system pressure, 100 W of discharge power, and 3 minutes of discharge time. Also, the surface resistance rate and dielectric property were improved.

• Journal of the Microelectronics and Packaging Society
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• v.24 no.2
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• pp.1-9
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• 2017

Recently, there has been a continuous researches on solders having sophisticated and improved performance due to demand for high-density and miniaturization of electronics, and development of solder for automotive electronics which can be used in harsh environment. When developing a new solder alloy, there is a wettability of solder on substrate for things to consider, and the wetting balance test is one of the methods for measuring that one. In this paper, the wetting balance test is introduced, and the calculus of the surface tension of solder and the contact angle between solder and substrate using wetting curve obtained is introduced too. In detail, the principle and test method of the wetting balance test, the introduction of the parameters with important meaning in the wetting curve, the method of calculating the contact angle as well as the surface tension of the solder using the shape of the solder meniscus.