• YAKHAK HOEJI
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• v.3 no.1
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• pp.51-55
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• 1957

It has been suggested that the fluorine content of crude sea salt may have special value in the prevention of tooth decay, by A.E.Schaefer and J/H/.Shaw. Shaw calculated that if crude sea salt containing about 40 ppm of fluorine were used, the consumption of 26-44 grams of the salt per day for each prison would be sufficient for the prevention of tooth decay. He also suggested that this level of salt consumption is actually quite common among many population in the far and near east. In order to examine the fluorine contents of sea salt in Korea, several kinds of solar-evaporating salt and pan-evaporating salt were studied. The experimental results may be summarized as follows; 1. Fluorine contents of 9 kinds of solar-evaporating salt ranged from 3.8 to 15.0 ppm and the average was 7.52 $\pm$ 3.89 ppm. 2. Fluorine contents of 7 kinds of pan-evaporating salt ranged from 2.5 to 7.1 ppm. 3. The more the salt is refined, the less becomes the fluorine content. 4. Even the crudest sea salt can not contain about 40 ppm of fluorine. 5. Statistically, daily consumption of sea slat for each person in Korea is 28 grams.

• Bulletin of the Korean Chemical Society
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• v.24 no.7
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• pp.981-985
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• 2003

Fluorine-19 NMR solution measurements have been made for various phenyl-fluorinated iron porphyrin complexes. Large chemical shifts for phenyl fluorine signals of iron(III) and iron(II) are observed, and these signals are sensitive to electronic structure. The chemical shift differences in ortho-phenyl fluorine signals between high-spin ferric and low-spin ferric tetrakis(pentafluorophenyl)porphyrins are approximately 40 ppm, whereas the differences are approximately 7 ppm between high- and low-spin states of ferrous tetrakis(pentafluorophenyl)porphyrin complexes. Analysis of fluorine-19 isotropic shifts for the iron(III) tetrakis(pentafluorophenyl) porphyrin using fluorine-19 NMR indicates there is a sizable contact contribution at the ortho-phenyl fluorine ring position. Large phenyl fluorine-19 NMR chemical shift values, which are sensitive to the oxidation and spin states, can be utilized for identification of the solution electronic structures of iron(III) and iron(II) porphyrin complexes.

• Journal of the Korean Vacuum Society
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• v.5 no.4
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• pp.327-332
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• 1996

In this study, the effects of $WSi_x$, thickness and fluorine concentration in tungsten polycide gate structure on gate oxide were investigated. As $WSi_x$, thickness increases, gate oxide thickness increases with fluorine incorporation in gate oxide, and time-to-breakdown($T_{BD,50%}$) of oxide decreases. The stress change with $WSi_x$ thickness was also examined. But it is understood that the dominant factor to degrade gate oxide properties is not the stress but the fluorine, incorporated during $WSi_x$ deposition, diffused into $WSiO_2$ after heat treatment. In order to understand the effect of fluorine diffusion into oxidem fluorine ion implanted gates were compared. The thickness variation and $T_{BD,50%}$ of gate oxide is saturated over 600 $\AA$ thickness of $WSi_x$. The TEM and SIMS studies show the microstructure less than 600 $\AA$ thickness is dense and flat in surface. However, over 600$\AA$, the microstructure of $WSi_x$ is divided into two parts: upper porous phase with rugged surface and lower dense phase with smmoth interface. And this upper phase is transformed into oxygen rich crystalline phase after annealing, and the fluorine is captured in this layer. Therefore, the fluorine diffusion into the gate oxide is saturated.

• Journal of Korean Society on Water Environment
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• v.23 no.3
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• pp.371-376
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• 2007

The features of precipitating reaction of fluorine have been examined under several aquatic conditions by employing calcium ion as a precipitant. Based on MINTEQ program, fluorine was found to exist in the forms of $H_2F_2$ and HF in strong acidic environment and change into $F^-$ with increasing pH. In the experimental condition, the precipitating reaction of fluorine progressed rapidly within a few minutes after the reaction started and reached its equilibrium in 10 minutes. As the addition of precipitant was increased, removal of fluorine by the formation of precipitate was promoted and its was also enhanced by the rise of pH. The precipitating reaction of fluorine was impeded when its initial concentration was low and X-ray analysis showed that the crystalline structure of precipitate was mainly $CaF_2$ with partly NaF. Coexisting phosphate in solution influenced the fluorine removal by impeding the precipitate formation and similar effect was found when metallic ion such as $Zn^{2+}$ was present with fluorine.

• Journal of the Korean Magnetic Resonance Society
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• v.17 no.2
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• pp.81-85
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• 2013

Various fluorine-containing materials are used in electronic devices like LCD display panels and Li-ion batteries. The structural conformation of fluorine in fluorinated materials is an important contributing factor that influences the chemical and physical properties. The conformation can be changed by heat and stress during manufacture or use. Understanding the conformational changes is critical for understanding the performance and durability of electronic devices. Solid-state NMR spectroscopy could be widely used for the analysis of various fluorine-containing materials for electronic devices. However, conventional CPMAS probes cannot be used for in-situ analysis of fluorine-containing electronic devices like LCD panels and Li-ion batteries. In this paper, we show the design, construction, and optimization of a $^{19}F-^{13}C$ double-resonance solid-state NMR probe for a 400MHz wide-bore magnet with a flat square coil for in-situ analysis of fluorine-containing electronic devices without observing fluorine background signals. This custom-built probe does not show any fluorine background signals, and can have higher efficiency for lossy samples.

• Bulletin of the Korean Chemical Society
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• v.13 no.2
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• pp.131-135
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• 1992

High-Tc superconducting materials, $HoBa_2Cu_3O_{7-x}F_y$ with $0.0{\leq}y{\leq}0.5$, were synthesized by ceramic method and studied by X-ray diffraction, thermogravimetric analysis, differential thermal analysis, scanning electron microscopy and resistivity measurement. From the X-ray diffraction data, it was found that the samples had only single phase of which lattice volumes were decreased in proportional to the amount of fluorine, which indicated that the relatively small fluorine atoms are effectively substituted for the oxygen sites. Also, an anomalous phenomenon appeared that the peak intensities of (001) planes were greatly increased as fluorine contents increased. SEM photographs revealed that the grain sizes were enlarged progressively with fluorine contents. This fact could be explained along with DTA & TGA data that the incorporation of fluorine gave rise to lowering the melting point. Tc decreased as the incorporation of fluorine content increased. This implies that the superconducting electrons are perturbed due to the substitution of electronegative fluorine atom.

• The Journal of the Korea Contents Association
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• v.15 no.11
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• pp.329-337
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• 2015

Fluorine is an element that promotes dental caries preventive effect at proper concentration level, but may have significantly undesirable impact on dental caries if correct information of fluorine is not recognized. Therefore, this study is intended to evaluate fluorine awareness among the adults in their 20s and analyze oral health conditions based on such awareness in order to promote dental caries preventive effect and convey correct knowledge of fluorine. For this study, 82 adult men and 102 adult women in their 20s, all of whom lived in Daegu, Gyeongsangbuk-do, were surveyed from May 1, 2014 to June 30 of the same year, along with oral health examination to evaluate their oral health conditions. The results of the analysis showed that 19.46% of respondents answered "No" to the question related to awareness towards the use of fluorine in DT rate dental clinic based on the degree of fluorine awareness, which was higher than 11.10% who answered "Yes"(p<.05). Moreover, 18.32%of respondents answered "No" to the question related to whether they were checking the label indicating the fluorine content in product, which was the highest rate, suggesting that the rate was higher when there was stronger tendency to avoid reading the precaution notice (p<.05). In addition, 71.98% of respondents answered "Yes" to the question associated with the awareness to the use of fluorine in FT rate dental clinic based on the fluorine awareness, which was higher than 49.04% of respondents who answered "No" (p<.05). This study is meaningful in that it provides basic data for the implementation of fluorine prevention projects in the period ahead by determining the effect of fluorine awareness on oral health conditions. Based on aforesaid results, both educational and promotional activities need to be carried out vigorously to help raise fluorine awareness.

• Journal of environmental and Sanitary engineering
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• v.15 no.2
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• pp.41-48
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• 2000

In this study, we have investigated the effect of the various operating conditions on the removal fluorine in the rinsed water for the semiconductor industry by using electrolysis process. The removal efficiency of fluorine was irrelevant to initial pH, and carbon anode was high-level treatment in the effect of various electrodes. Fluorine included in the wastewater is treated by the addition of a Ca(OH)2, removal efficiency of electrolysis was increased about 40%. Besides the removal efficiency of fluorine was increased as the current density was increased and this treatment system could reduce both the total sludge and running costs. The feasibility of the electrochemical treatment to the fluorine containing wastewater was verified from this study.

• Journal of Electrochemical Science and Technology
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• v.6 no.4
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• pp.116-120
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• 2015

Lithium diffusivity of fluorine-free and -doped tin-nickel (Sn-Ni) film model electrodes with improved interfacial (solid electrolyte interphase (SEI)) stability has been determined, utilizing variable rate cyclic voltammetry (CV). The method for interfacial stabilization comprises fluorine-doping on the electrode together with the use of electrolyte including fluorinated ethylene carbonate (FEC) solvent and trimethyl phosphite additive. It is found that lithium diffusivity of Sn is largely dependent on the fluorine-doping on the Sn-Ni electrode and interfacial stability. Lithium diffusivity of fluorine-doped electrode is one order higher than that of fluorine-free electrode, which is ascribed to the enhanced electrical conductivity and interfacial stabilization effect.

• Journal of Information Display
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• v.1 no.1
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• pp.25-28
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• 2000

We propose a new in-situ fluorine passivation of poly-Si TFTs using excimer laser annealing to reduce the trap state density and improve reliability significantly. To investigate the effect of an in-situ fluorine passivation, we have fabricated fluorine-passivated p-channel poly-Si TFTs and examined their electrical characteristics and stability. A new in-situ fluorine passivation brought about an improvement in electrical characteristic. Such improvement is due to the formation of stronger Si-F bonds than Si-H bonds in poly-Si channel and $SiO_2$/Poly-Si interface.