• Journal of the Korean Wood Science and Technology
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• 제36권2호
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• pp.73-78
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• 2008

Inorganic chemical treated wood was prepared by impregnation of calcium or magnesium chloride ($CaCl_2$ or $MgCl_2$) solution and immersion in saturated solution of ammonium fluoride ($NH_4F$) as a reactant in order to make an introduction of a refractory fluorides with fungicidal and insecticidal effects in wood. The weight percent gains (WPGs) were increased with increase in concentration of calcium chloride or magnesium chloride solution, and were higher in treatment with calcium chloride than with magnesium chloride. Inorganic substances were produced mainly in the lumina of tracheides. These substances were proved to be the calcium fluoride or magnesium fluoride by the energy dispersive X-ray analyzer in conjunction with a scanning electron microscope (SEM-EDX). The treated wood showed good decay resistance because the weight losses were hardly occurred by the test fungi such as Tyromyces palustris and Trametes versicolor. The fire resistance effect was superior to the treated wood compared with that of the untreated wood.

• 대한금속재료학회지
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• 제48권3호
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• pp.218-224
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• 2010

Direct copper electroplating on Mg alloy AZ31B was carried out in a traditional pyrophosphate copper bath containing potassium fluoride. Electrochemical impedance spectroscopy and polarization methods were used to study the effects of added potassium fluoride on electrochemical behavior. The chemical state of magnesium alloy in the electroplating bath was analyzed by X-ray photoelectron spectroscopy. Adhesion of the copper electroplated layer was also tested. Due to the added potassium fluoride, a magnesium fluoride film was formed in the pyrophosphate copper bath. This fluoride film inhibits dissolution of Mg alloy and enables to electroplate copper directly on it. A dense copper layer was formed on the Mg alloy. Moreover, this copper layer has a good adhesion with Mg alloy substrate.

• Asian-Australasian Journal of Animal Sciences
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• 제17권12호
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• pp.1695-1699
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• 2004

The antioxidant enzymes, lipid peroxidation and free radicals assessment were made of the effects of selenium, copper and magnesium on bovine endemic fluorosis under high fluoride, low selenium and low copper productive conditions. Thirty-two beef cattle were selected from high fluoride area, and randomly divided into four groups with eight cattle each as follows: (1) high fluoride control group (HFC); (2) supplemented group with 0.25 mg/kg selenium (HFSe); (3) supplemented group with 15 mg/kg copper (HFCu) and (4) supplemented group with 0.25 mg/kg selenium+15 mg/kg copper+1 mg/kg magnesium (HFSeCuMg) per day for 83 days. Moreover, eight beef cattle were selected from non-high fluoride area as normal control group. Blood samples were collected from cattle on 0 d, 30 d and 83 d respectively, to analyze the enzyme activities and concentration of GSH-px, CAT, SOD, MDA and free radicals. The results showed that the contents of free radicals and MDA in HFC group were significantly higher, and the whole blood GSH-px, CAT, erythrocyte SOD activities were lower than the normal control group. Free radicals, metabolic imbalance and antioxidant disorder therefore, play an important role in fluorosis. However, GSH-px, CAT and SOD activities in HFSe group and HFSeCuMg group at 30 d and 83 d were markedly higher than the same groups at the 0 d and the HFC group at the same time. Likewise, there was a corresponding reduction in the contents of free radicals and MDA. These findings indicated that supplementation with selenium, copper and magnesium elevated high fluoride bovine antioxidant enzymes, and decreased MDA and free radicals contents. But, the activities of supplementation selenium group did not increase until day 83. These results demonstrated that fluorosis was associated with lower serum Se and Cu levels than in the control, and it was therefore concluded that fluorosis is associated with decreased serum levels of these minerals. Long-term high fluoride intake under productive condition enhances oxidative stress in the blood, thereby disturbing the antioxidant defense of cattle. Increased oxidative stress could be one of the mediating factors in the pathogenesis of toxic manifestations of fluoride. It is benefical for high fluoride cattle supplemented with proper selenium, copper and magnesium to increase fluoride excretion and obtain the protective impact of the activity of oxidative enzymes, and to decrease lipid peroxidation and free radicals contents.

• 한국환경보건학회지
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• 제29권2호
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• pp.38-44
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• 2003

This study was performed to investigate the levels of fluoride (F), calcium (Ca), and magnesium (Mg) in water samples taken from five reservoirs or direct sources on a stream used for agricultural or domestic water in the Iksan and Wanjoo areas, Jeon-buk, Korea, and to find a possible link between Ca or Mg and fluoride in water sources in theses areas. The samples were collected by the recommendation methods of the World Health Organization and analyzed by the recommendations of the Japanese Standard Methods. Statistical analyses were performed by the analysis of variance and correlation analysis. The F levels in water samples wire 0.80~2.53 ppm. In four sampling sites the water fluoride levels exceeded 1 ppm. which if the recommended level for fluorosis/caries control. The Ca levels in water samples were 6.82~12.98 ppm, and the Mg levels were 0.30~1.97 ppm, which are lower compared with the natural levels of water sources previously reported by other investigators. This study showed a positive correlation between Ca and Mg (r= 0.8779. p<0.01) and a negative correlation between F and Ca (r=-0.6974, p<0.05) and also between F and Mg (r=-0.5581) in the water samples. However, the study did not find remarkable relationships in fluoride levels between sampling sites. These results support the fact that there were epidemics of dental fluorosis in this area. The lack of significant positive correlations in fluoride levels between sampling sites suggests that there may be some pathways for the transfer of the metal to the water through other environmental media besides the water course. Long-term epidemiological studies are needed on the relationship between high F together with low Ca and Mg levels in the water, and total human health in this community. There should alto be a long-term monitoring of the water quality in this area.

• 한국농공학회논문집
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• 제55권3호
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• pp.35-40
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• 2013

The present study was conducted to investigate the adsorption potential of red mud for fluoride removal. Different operation parameters such as the effect of contact time, initial concentration, pH, competing anions, seawater, adsorbent dose amount, and adsorbent mixture were studied. Nearly 3 hr was required to reach sorption equilibrium. Equilibrium sorption data were described well by Langmuir model and the maximum adsorption capacity of red mud was 5.28 mg/g. The fluoride adsorption at pH 3 was higher than in the pH range 5-9. The presence of anions such as sulfate, nitrate, phosphate, and bicarbonate had no significant effect on fluoride adsorption onto red mud. The fluoride removal by red mud was greater in seawater than deionized water, resulting from the presence of calcium and magnesium ion in seawater. The use of red mud alone was more effective for the removal of fluoride than mixing red mud with other industrial waste such as oyster shells, lime stone, and steel slag. This study showed that red mud has a potential application in the remediation of fluoride contaminated soil and groundwater.

• Environmental Analysis Health and Toxicology
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• 제13권1_2호
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• pp.19-26
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• 1998

In Korea, fluoride was first introduced into the drinking water of residents of Jinhae, KyungNam in 1981 for the prevention of dental caries. Ever since, growing numbers of communities favor fluoridation. The mechanism of F prevention of tooth decay is well known: fluoride ions substitute for hydroxyl ions in hydroxyapatite of hard tissues, which result in crystal perfection, with consequent reduction in dental caries. Soluble fluorides such as sodium fluoride are almost completely absorbed from the gastrointestinal tract. However, the presence of divalent or trivalent cations such as aluminum, magnesium, and calcium that can complex with F can reduce the degree of absorption. In U.S.A., over 7000 communities are now adding F to their drinking water. However, some portion of population oppose fluoridation, voicing both concern about the safety of fluoridation as well as for personal choice. Thus, This paper reviews the interaction of fluoride and cations as well as fluoride and suggests possible problems associated with fluoridation, a controversial issue.

• Nuclear Engineering and Technology
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• 제53권6호
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• pp.1931-1938
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• 2021

Uranium ingot is produced by metallothermic reduction of uranium tetrafluoride using magnesium or calcium as reductant. Presence of oxygen containing compounds viz. uranyl fluoride and uranium oxide in the starting uranium fluoride has a significant effect on the firing time, final temperature of the charge, slag-metal separation and hence the metal recovery. As reported in the literature, the maximum tolerable limit for uranyl fluoride in the UF₄ is 2.5 wt% and limit for uranium oxide content is in the range 2-3 wt%. No theoretical or experimental basis is available till date for these limits. Analyses have been carried out in this study to understand the effect of UO₂F₂ concentration in the starting fluoride on the final temperature of the products and thus the reduction characteristics. UF₄ having uranyl fluoride concentration, less than as well as more than 2.5 wt%, have been investigated. Thermodynamic calculations have been carried out to arrive at a general expression for the final temperature attained by the products during calciothermic reduction of UF₄. Finally, an upper limit for the oxygen containing impurities has been estimated using the CaO-CaF₂ phase diagram.

• 대한소아치과학회지
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• 제36권3호
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• pp.404-411
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• 2009

생수 내에는 많은 미네랄이 포함하고 있으며, 이 중 칼슘, 나트륨, 칼륨, 마그네슘, 불소는 생수통에 반드시 표기해야 할 무기물이다. 칼슘, 마그네슘, 불소와 같은 무기물은 치아형성에 관여하며, 적절하게 섭취시 치아우식증을 예방할 수 있다. 현행 먹는 샘물 수질기준에 따르면 무해무기물질인 칼슘과 마그네슘에 대한 기준치는 없으며, 유해무기물질인 불소와 같은 무기물은 2 mgF/L 이하로 규정하고 있다. 본 연구는 국내에서 판매되고 있는 생수 15종을 대상으로 칼슘, 마그네슘, 불소의 농도를 측정하였고, 생수 내 무기물 함량의 표기 여부 및 무기물 농도를 비교, 검토하여 다음과 같은 결론을 얻었다. 1. 15개의 생수 중 1개의 생수를 제외하고 모두 칼슘함량을 표기하였다. 평균 칼슘농도는 34.68${\pm}$31.84 mg/L, 최대 128.91${\pm}$1.85 mg/L, 최소 2.0${\pm}$0.02 mg/L이었다. 2. 15개의 생수 중 2개의 생수를 제외하고 모두 마그네슘 함량을 표기하였다. 평균 마그네슘 농도는 9.22${\pm}$11.06 mg/L, 최대 30.43${\pm}$0.75 mg/L, 최소 0.0 mg/L이었다. 3. 15개의 생수 중 4개의 생수를 제외하고 모두 불소 함량을 표기하였다. 평균 불소 농도는 0.25${\pm}$0.33 mg/L, 최대 1.13${\pm}$0.04 mg/L, 최소 0.01${\pm}$0.03 mg/L이었다. 모두 생수는 현행 먹는 샘물 기준치인 2 mg F/L이하에는 만족시켰다.

• 한국표면공학회:학술대회논문집
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• 한국표면공학회 2016년도 추계학술대회 논문집
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• pp.124.2-124.2
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• 2016

Corrosion resistance and adhesion of electro-paint (E-paint) with fluoride conversion coating (FCC) on AZ31 Mg alloy were studied. Corrosion resistance and adhesion were studied as a function of FCC-treatment time and concentration of FCC-bath. Aqueous hydrogen fluoride (HF) solutions, with concentrations ranging from 0.5 M to 5 M, were used to form FCC on chemically polished AZ31 Mg alloy samples for six different times; 10, 30, 60, 90, 120, and 180s. The results from salt spray test (SST) showed that corrosion resistance of E-paint appeared to decrease with increasing FCC treatment times in low concentration FCC baths. The number of blisters formed on the FCC-treated samples increased with increasing FCC treatment time of more than 1 min in low concentration (0.5 M to 1 M) solutions. On the other hand, samples treated in the 5 M HF solution for 120s showed no delamination or blistering even after 1200h of SST.

• 한국표면공학회지
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• 제49권5호
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• pp.395-400
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• 2016

This article reports improved corrosion resistance and adhesion of electro-paint (E-paint) with fluoride conversion coating (FCC) on AZ31 Mg alloy for the first time. These improvements were observed in comparison to chemically polished samples with no chemical conversion coating and samples with cerium conversion coatings (CeCC). FCCs were prepared in a hydrofluoric acid (HF) solution for four different times; 10, 30, 60, and 120 s. The colour of the samples changed from light gold to brown with increasing immersion time, indicating the formation of thicker FCC coatings with increasing immersion time. The adhesion of the E-paint on FCC-coated AZ31 Mg alloy was tested after 500 h of immersion in deionized (DI) water. Salt spray test (SST) results revealed delamination of E-paint on the chemically polished sample, severe blistering on the samples with CeCC, but no delamination and no blistering on the samples with FCC.