• Bulletin of the Korean Chemical Society
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• v.30 no.2
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• pp.319-322
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• 2009

Gel polymer electrolytes were prepared by immersing a porous poly(vinylidene fluoride-co-hexafluoropropylene) membrane in an electrolyte solution containing small amounts of polymerizable additive (3,4-ethylenedioxythiophene, thiophene, biphenyl). The organic additives were electrochemically oxidized to form conductive polymer films on the electrode at high potential. With the gel polymer electrolytes containing different organic additive, lithium-ion polymer cells composed of carbon anode and LiCo$O_2$ cathode were assembled and their cycling performances were evaluated. Adding small amounts of thiophene or 3,4-ethylenedioxythiophene to the gel polymer electrolyte was found to reduce the charge transfer resistance in the cell and it thus exhibited less capacity fading and better high rate performance.

• Korean Journal of Materials Research
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• v.25 no.10
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• pp.509-515
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• 2015

MAO ceramic coatings were prepared on AZ61 magnesium alloy for various processing times ranging from 5 to 60 min, in an electrolyte solution based on silicate-fluoride. The mechanical, electrochemical and, microstructural properties and the phase compositions of the coating layers were investigated. In this work, unlike previous studies, coatings with high amounts of the $Mag_2SiO_4$ phase were formed which contained small amounts of MgO and $MgF_2$ at a processing condition of 30 min. A microstructural analysis revealed that the porosity of the coatings was reduced considerably with an increase in the processing time, together with a change in the pore geometry from an irregular to a spherical shape. Potentiodynamic polarization and mechanical testing results showed that the coatings acquired after a processing time of 30 min were superior to all of the others.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.26 no.7
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• pp.550-554
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• 2013

Carbon nanotubes (CNT) / polyvinylidene fluoride (PVDF) piezoelectric composite films for nanogenerator devices were fabricated by spray coating method. When the CNT/PVDF mixture solution passes through the spray nozzle with small diameter by the compressed nitrogen gas, electric charges are generated in the liquid by a triboelectric effect. Then randomly distributed ${\beta}$ phase PVDF film could be re-oriented by the electric field resulting from the accumulated electrical charges, and might be resulted in extremely one-directionally aligned ${\beta}$ phase PVDF film without additional electric field for poling. X-ray diffraction patterns were used to investigate crystal structure of the CNT/PVDF composite films. It was confirmed that they revealed extremely large portion of the ${\beta}$ phase PVDF crystalline in the film. Therefore we could obtain the poled CNT/PVDF piezoelectric composite films by the spray coating method without additional poling process.

• Journal of the korean academy of Pediatric Dentistry
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• v.43 no.4
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• pp.391-400
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• 2016

The purpose of this study was to evaluate the difference of remineralization effects of various anti-cariogenic toothpastes on artificial carious lesions in primary and permanent teeth using quantitative light-induced fluorescence-digital (QLF-D) system. Sound human primary (n = 48) and permanent teeth (n = 48) were randomly divided into following groups : control group (Group 1), fluoride toothpaste (Group 2), functionalized tricalcium phosphate (fTCP) + fluoride toothpaste (Group 3), and casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) toothpaste (Group 4). Specimens were prepared by exposure in a demineralizing solution and then treated using the different toothpastes twice daily during 14 days. All specimens were analyzed with the QLF-D system. QLF data analysis indicated three different toothpastes showed significant remineralizing effects compared to Group 1 in both primary and permanent teeth. Also, the remineralizing effects in Group 3 and 4 were significantly higher than in Group 2. This study suggested that the toothpastes containing fTCP + fluoride and CPP-ACP have the significant anti-cariogenic effects on enamel demineralization in both primary and permanent teeth, and QLF-D is an useful device to assess the incipient carious lesion and remineralization effects of the anti-cariogenic materials quantitatively. Therefore, clinicians can consider the QLF-D system for the evaluation of demineralization and remineralization in primary and permanent teeth.

• Journal of the korean academy of Pediatric Dentistry
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• v.34 no.2
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• pp.183-191
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• 2007

Through out the world dental caries seems to be decreased as it is difficult to make an accurate diagnosis for dental caries. The traditional diagnostic method which is probing and x-ray taking has many limitations to diagnose the early caries, so there were recommendations for the needs of new equipments such as laser fluorescence(LF), digital imaging fiber-optic trans-illumination(DIFOTI), and quantitative light fluorescence (QLF) which were developed from various study results. Also confocal laser scanning microscopy(CLSM) and ultrasonics are used for research progression. This study is to evaluate whether it is possible to monitor accurately for remineralization amount of enamel surface early caries using DIFOTI or LF After inducing artificial caries to bovine teeth to 10 participants remineralization was enhanced by 0 ppm and 500 ppm fluoride mouth rinse solution for 3 weeks. Then they were cross sectioned and analyzed using gold standard of the lesion depth measured by CLSM. The following results were obtained: 1. The measured percentage of light intensity(luminosity ratio) by DIFOTI increased with remineralization period, and showed significant reverse correlation with lesion depth measured by CLSM (p<0.01). 2. The measurement of laser fluorescence increased with remineralization period, and showed significant correlation with lesion depth measured by CLSM (p<0.01). 3. To the result for CLSM, 500 ppm fluoride mouth rinse group showed rapid rate for decreased tendency of lesion depth than 0 ppm fluoride mouth rinse group. In conclusion DIFOTI system was used to measure accurately for the remineralization amount of early surface caries, it is a very useful equipment to detect precisely the changes for early enamel caries remineralization during treatments.

• Journal of the korean academy of Pediatric Dentistry
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• v.35 no.3
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• pp.446-455
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• 2008

The aim of this study was to evaluate the effect of fluoride varnish application on enamel decalcification. Eighty bovine enamel blocks divided randomly into 4 groups. Group I is the control group. Group II was treated with the APF gel and washed after 4 minutes. Group III and IV was treated with Fluor $Protector^{(R)}$ and $CavityShield^{TM}$ and washed after 1 minutes. Decalcification were created by placing all specimen into artificial acidic solution(pH 4.0). Then the optical density of the lesions were measured by visible light fluorescence and the lesion depths were measured. The results were : 1. The optical density of group II was higher than group I but lower than group III, IV(p<0.05) and there was no difference between group III, IV(p>0.05) at 48 hours. 2. The optical density of group IV was highest at 72 hours(p<0.05). 3. Mean lesion depths were $205.36{\pm}42.85{\mu}m$ and $210.81{\pm}44.60{\mu}m$ in group I, II but no significant difference between two groups(p>0.05). 4. Mean lesion depths were $80.03{\pm}21.66{\mu}m$ and $77.46{\pm}27.72{\mu}m$ in group III, IV but no significant difference between two groups(p>0.05). Fluoride varnish treatment resulted in a significant reduction in lesion depth compared with APF gel. Fluor $Protector^{(R)}$ and $CavityShield^{TM}$ provided the similar effect.

• Applied Chemistry for Engineering
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• v.29 no.4
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• pp.479-483
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• 2018

Our group reported the thermal decomposition of R-22 ($CHClF_2$) refrigerants by nitrogen thermal plasma in previous studies. However, it was proposed that the wastewater generated from the end part of the process contains high concentration of fluoride ion which is a component of R-22. The additional post-treatment process to neutralize the $F^-$ ions in the wastewater was investigated in this study. The wastewater generated through the decomposition of R-22 with the same procedure in the previous work was treated using the neutralizer, $Ca(OH)_2$, and the atmospheric pressure plasma jet (APPJ) independently as a post-treatment process. Wastewater samples were collected directly after the treatment for ion-chromatography analysis to trace the change of the concentration of $F^-$ ion in the wastewater. The fluoride concentration in the wastewater showed the highest value when the single water was used as a neutralizer, and the concentration of fluoride in the wastewater was dramatically reduced when the post-treatments were performed.

• Journal of the korean academy of Pediatric Dentistry
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• v.46 no.3
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• pp.293-300
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• 2019

As a common side effect of fixed orthodontic treatment, demineralization of the enamel adjacent to the bracket and band occurs in patients with poor oral hygiene. The purpose of this study was to investigate what is the most effective method to prevent demineralization around the fixed orthodontic appliance among various methods using fluoride. 80 extracted bovine incisors with a healthy surface were classified into four groups as experimental materials: (Group I) Control group, (Group II) V $varnish^{TM}$, (Group III) Tooth Mousse $Plus^{(R)}$, (Group IV) $Vanish^{TM}$ XT. After treatment for each group, mineral loss and Vickers surface microhardness were measured at 0, 30, 60 and 90 days after demineralization in artificial carious solution. Mineral loss was the lowest in group IV, followed by group II and group III, which showed a significant difference. The surface microhardness was the lowest in group IV, followed by group II and group III, which showed a significant difference. Through this study, group IV showed the best effect to prevent enamel demineralization around the bracket. Group III showed significant prevention of enamel demineralization compared with the control group, but the effect was less than that of the other groups.

• Journal of the Korean Wood Science and Technology
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• v.32 no.2
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• pp.82-89
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• 2004

Two kinds of chemicals (RNF-3 and RNF-4) with high anti-mold effectiveness against stored fungi causing fungal discoloration was selected from among the six kinds of fluoride-based chemicals in the preceding study. In this study, the anti-mold test using 16 species fungi isolated from the softwood lumbers which were fungal discolored and field test in the sawmill was carried out to prove the feasibility for practical using of selected chemicals.For the isolated fungi, the RNF-3 consist of F and Cu showed high mycelial growth control in the PDA medium and fungicidal effectiveness in the japanese red pine (Pinus densiflora), korean pine (Pinus koraiensis) and radiata pine (Pinus radiata) when the concentration was 2% or more. However the RNF-4 consist of F only was not effective compared with RNF-3 because of mycelial growth in the PDA medium and wood treated with 2% or more chemical solution. The RNF-3 also showed a strong anti-mold effectiveness because there was no fungal discoloration for the radiata pine boards treated by 2% and 10 min. soaking in the field test. These results mean that RNF-3 can be used as domestic anti-stain chemicals for prevention of fungal discoloration of the softwood lumber

• Membrane Journal
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• v.25 no.1
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• pp.67-74
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• 2015

In this study the nanofiber was prepared by electrospinning method with polyvinylidene fluoride (PVdF) and a completely dispersed solution of graphene oxide (GO) in the mixed solvent of dimethylformamide (DMF) and acetone. The $0.4{\mu}m$ pore size microfiltration flat membrane was made by increasing layers of the PVdF/GO composite nanofiber. Also, transmembrane pressure (TMP) was measured in order to evaluate fouling of the PVdF/GO composite membrane which was introduced GO reducing biological fouling with the intrinsic antibacterial characteristics. The permeate experiments were carried out simultaneously for the PVdF/GO and commercialized CPVC (chlorinated polyvinyl chloride) flat membranes with $0.01m^2$ effective area in the activated sludge solution of MLSS 4,500 mg/L. TMP of PVdF/GO membrane decreased up to 79% lower than that of CPVC for $10L/m^2{\cdot}h$ permeate flux without air supply. Also, for the case of run/stop operational mode, TMP of PVdF/GO membrane decreased up to 69% lower than that of CPVC for $10L/m^2{\cdot}h$.