• Journal of Dental Rehabilitation and Applied Science
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• v.32 no.4
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• pp.263-273
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• 2016

In the implant prosthetic procedure, the soft tissue reaction was varied with the material and surface treatment of the abutment. It may be the cause of the peri-implantitis, and hence it can affect the long-term prognosis of the implant prosthesis. Titania and zirconia abutment presented superior biocompatibility and stable soft tissue reaction, while gold alloy abutment showed unfavorable reaction sometimes. A soft tissue reaction can be differed by the surface characteristics even in the same material type. Because rougher surface induces a bacterial attachment, the part contacting a soft tissue should have smooth surface. Additional surface treatment can enhance the cellular response without increasing bacterial attachment. Repeated removal and insertion of the abutment and the shape of the abutment may affect the soft tissue reaction, also. Ultrasonic cleaning and argon plasma cleaning are effective way to clean the retained micro-dust on the customized abutment.

• Journal of the Korean Chemical Society
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• v.50 no.2
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• pp.163-177
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• 2006

Alpha Nickel hydroxide samples have been synthesized by electrodeposition on platinum and nickel substrates at current densities of 1, 5, 6, 7 and 10 mAcm？2 at a controlled temperature of 30.00 oC from Ni(NO3)2 bath. Platinum substrate shows a tendency to incorporate less nitrate ions with increase in current density thus producing less hydroxy-deficient nickel hydroxide layers. On the whole the interlayer distance (d003) is found to be inversely proportional to the amount of nitrate ions incorporated in-between the lattice. For the first time we have observed a decrease in lattice spacing with increase in concentration of intercalant (anions) and the reason for lattice contraction is attributed to the columbic attractive forces exerted by the oppositely charged nitrate ion and positively charged slabs. The Infrared spectra of the samples with expanded interlayers show two types of OH vibrations corresponding to hydrogen bonded and non-hydrogen bonded OH groups whereas the contracted interlayers show only hydrogen-boded OH groups. Although the faradaic efficiency is found to increase with increase in applied current there is a local minimum at 6.0 mAcm？2 current density on both platinum and nickel substrates. In this manuscript, GC-MS data is provided which clearly demonstrates the electrodeposited nickel hydroxide sample to consist of huge amount of carbonate ions although the electrolyte solution in nickel nitrate.

• Journal of the Korean Magnetics Society
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• v.16 no.2
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• pp.140-143
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• 2006

Single crystalline $CoFe_2O_4$ thin films on (100) MgO substrates were fabricated using a rf magnetron sputtering method. The deposited films were investigated for their crystallization by X-ray diffraction, Rutherford back-scattering spectroscopy and field emission scanning electron microscopy. When a cobalt ferrite film was deposited at the substrate temperature of $600^{\circ}C$, squared grains of about 200 nm were uniformly distributed in the film. However, the grains became irregular and their sizes also varied from 30 to 150 nm when the substrate temperature was $700^{\circ}C$. Hysteresis loops of a film deposited at $600^{\circ}C$ showed that the magnetically easy axis of the film was perpendicular to the substrate surface. Except for the squareness ratio, magnetic properties of the cobalt ferrite films grown by the present rf sputtering method were as good as those of the films prepared by a laser ablation method: The in-plane and perpendicular coercivities were 283 and 6800 Oe, respectively. As the thickness of the deposited film increased twice, the saturation magnetization became double but the coercivity remained unchanged. However, deposition of the Co ferrite films with a higher rf powder decreased the squareness ratio and the perpendicular coercivity of the films.

• Journal of the Korean Vacuum Society
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• v.19 no.2
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• pp.81-90
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• 2010

We introduce a novel and versatile approach for preparing self-assembled nanoporous multilayered films with antireflective properties. Protonated polystyrene-block-poly (4-vinylpyrine) (PS-b-P4VP) and anionic polystyrene-block-poly (acrylic acid) (PS-b-PAA) block copolymer micelles (BCM) were used as building blocks for the layer-by-layer assembly of BCM multilayer films. BCM film growth is governed by electrostatic and hydrogen-bonding interactions between the oppositely BCMs. Both film porosity and film thickness are dependent upon the charge density of the micelles, with the porosity of the film controlled by the solution pH and the molecular weight (Mw) of the constituents. PS7K-b-P4VP28K/PS2K-b-PAA8K films prepared at pH 4 (for PS7K-b-P4VP28K) and pH 6 (for PS2K-b-PAA8K) are highly nanoporous and antireflective. In contrast, PS7K-b-P4VP28K/PS2K-b-PAA8K films assembled at pH 4/4 show a relatively dense surface morphology due to the decreased charge density of PS2K-b-PAA8K. Films formed from BCMs with increased PS block and decreased hydrophilic block (P4VP or PAA) size (e.g., PS36K-b-P4VP12K/PS16K-b-PAA4K at pH 4/4) were also nanoporous. Furthermore, we demonstrate that the nanostructured electrochemical sensors based on patterning methods show the electrochemical activities. Anionic poly(styrene sulfonate) (PSS) layers were selectively and uniformly deposited onto the catalase (CAT)-coated surface using the micro-contact printing method. The pH-induced charge reversal of catalase can provide the selective deposition of consecutive PE multilayers onto patterned PSS layers by causing the electrostatic repulsion between next PE layer and catalase. Based on this patterning method, the hybrid patterned multilayers composed of platinum nanoparticles (PtNP) and catalase were prepared and then their electrochemical properties were investigated from sensing $H_2O_2$ and NO gas. This study was based on the papers reported by our group. (J. Am. Chem. Soc. 128, 9935 (2006); Adv. Mater. 19, 4364 (2007); Electro. Mater. Lett. 3, 163 (2007)).

• Korean Journal of Food Science and Technology
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• v.35 no.4
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• pp.610-616
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• 2003

Five oats and 17 barley cultivars were ground, sieved (105, 210, 300, 425, 600 ${\mu}m$) and we have analyzed the ${\beta}-glucan$ contents to obtain grain fractions. The milling yields ranged $65.1{\sim}89.7%$ for barley and $53.4{\sim}73.5%$ for oat cultivars. Total ${\beta}-glucan$ contents of barley and oats become higher than those of the flour increasing the particle size. The soluble and insoluble ${\beta}-glucan$ contents of them were especially higher in medium and coarse particle size fractions. The contents of total, soluble and insoluble ${\beta}-glucan$ of barley were 1.5, 1.7 and 2.0 times higher than the whole flour before sieving and these content of oats were 2.1, 1.6 and 2.0 times, respectively. In this study, larger particle size would enrich the ${\beta}-glucan$ and it is desirable to consider the best particle size range to enrich the ${\beta}-glucan$ level, the water-solubility of the ${\beta}-glucan$ as well as cereal varieties.

• Journal of the Korean Recycled Construction Resources Institute
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• v.4 no.2
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• pp.90-96
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• 2009

The high rising building construction makes increasing the requirement of high strength concrete. Especially, the workability analysis is related with dispersion of admixture such as SF for improving strength and FA, BS for reducing construction cost and improving durability of Ultra High Strength Concrete which has over 100 MPa of compressive strength is very important. Precisely, decreases dispersion because of lumping situation of each admixture and it causes the workability of admixture is decreased. Therefore, the workability of cement paste is tested for analyze effects of pre-mixed cement for solving those problems with it to this research. The summary of the results are like below. First of all, OBS is increasing workability more than OFS. This result causes that the glassy surface of BS in the OBS is increasing workability and the absorption of admixture of FA in the OFS is decreasing workability. In the case of mixing methods, pre-mixing method is increasing workability more than normal one. This result shows that the normal mixing method is bad dispersion of binders. The other side, the pre-mixing method is good. Furthermore, depending on the mixing time, according to the increasing mixing time such as 30, 60, and 120 seconds, the dispersion of binders and workability turns better.

• Korean Chemical Engineering Research
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• v.48 no.2
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• pp.218-223
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• 2010

The zinc oxide thin film, which can be applied as the gas sensor of a semiconductor type, was grown on the silicon substrate by CFR(continuous flow reaction) method in this study. The growth property and the electrical property of the zinc oxide thin films synthesized by CFR method were also investigated. Zinc acetate solutions of 0.005~0.02 M were used as the precursor for the preparation of zinc oxide thin films. The size of ZnO particles consisted on the zinc oxide thin film increased not only with increasing concentration of precursor, but also the thickness of thin film increased. The growth rate of zinc oxide thin film by CFR method was proportionably depend on the concentration of precursor and the uniform ZnO thin film was prepared when zinc acetate of 0.01 M is used as the precursor. The charged currents on the zinc oxide thin films were obtained as its electrical property by I-V meter, and increased agree with increasing the thickness of zinc oxide thin film. Thus, it was concluded that the charged current on the zinc oxide thin film can be controlled with changing concentration of precursor solution in CFR method. The charged currents on the zinc oxide thin films also decreased when ZnO thin film is exposed under hydrogen sulfide of 500 ppmv at $300^{\circ}C$ for 5 min. From these results, it could be confirmed that the zinc oxide thin film prepared by CFR method can be used for the detection of sulfur compounds.

• Journal of the Korean Electrochemical Society
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• v.16 no.3
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• pp.129-137
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• 2013

From the cooked-rice as a raw material, activated carbons throughout a hydrothermal synthesis and vacuum soak of KOH for chemical activation were obtained. Activated carbon electrodes for electric double layer supercapacitors were prepared and electrochemical characteristics were examined. Including the specific surface area by BET method and pore size distribution by NLDFT method, physical properties of activated carbons were investigated by means of SEM, EDS, XRD, and TG analyses. Cycle voltammetry and AC-impedance measurements were conducted to confirm the electrochemical characteristics for the electrodes. From hydrothermal synthesis, $5{\sim}7{\mu}m$ diameters of spherical carbons were obtained. After the activation at $800^{\circ}C$, it was notable for the activated carbon to be the specific surface $1631.8cm^2/g$, pore size distribution in 0.9~2.1 nm, and micro-pore volume $0.6154cm^3/g$. As electrochemical characteristics of the activated carbon electrode in 6M KOH electrolyte, it was confirmed that the specific capacitances of 236, 194, and 137 F/g at the scan rate of 5, 100, and 500 mV/s respectively were exhibited and 91.2% of initial capacitance after 100,000 cycles at 200 mV/s was maintained.

• Journal of the Korean Ceramic Society
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• v.39 no.9
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• pp.846-850
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• 2002

A PMN-PT-BT/Ag composite was prepared by surface modification with MgO sol with hoping to suppress silver's migration during sintering. The mixture of PbO, $N_2O_5,\;TiO_2\;with\;Mg(NO_3)_2$ instead of MgO was ball milled, the solvent was removed and then the dried powders were calcined at 950$^{\circ}C$/1h. The calcined powder were treated with 3.0 mol% $Ag_2O$ and 1.0 wt% MgO sol and calcined at 550$^{\circ}C$/1h. The dielectrics sintered at 1000$^{\circ}C$/4h under a flowing oxygen showed the density of 7.84g/$cm^3$, the room temperature dielectric constant of 18400, the dielectric loss of 2.4%, the specific resistivity of $0.24{\times}10^{12}{\Omega}{\cdot}cm$. It also showed the bending strength of $120.7{\pm}11.26$ MPa and the fracture toughness of $0.87{\pm}0.002\;MPam^{1/2}$ which were comparable to commercial PZT. The microstructure sonsisted of grains of ∼4${\mu}m$. SEM and SIMS analysis showed that Ag grew as ∼1${\mu}m$ and excess MgO as ∼0.5${\mu}m$.

• Journal of the Microelectronics and Packaging Society
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• v.23 no.3
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• pp.57-61
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• 2016

In order to protect the solar cells from the moisture and oxygen, we evaluated the electrical and optical properties for the $Cu(In,Ga)Se_2$ (CIGS) solar cells which were prepared by the spray coating method. Generally, the EVA (ethylene-vinyl acetate) films are laminated to protect the CIGS flexible solar cells, which results in a high cost process due to complicated devices. In this study, we tried to prepare the protection layers of the flexible CIGS flexible solar cells by using spray coating method instead of conventional laminating films in order to reduce the device weight as well as the process time. The CIGS solar cells with spray coating method showed an enhanced efficiency than the before treated sample (2.77% to 2.93%) and relatively proper water vapor transmission rate of the solar cells about 62.891 gm/[$m^2-day$].