• Journal of the Korean Ceramic Society
• /
• v.41 no.10 s.269
• /
• pp.749-755
• /
• 2004

Fluosilicic acid ($H_2SiF_6$) is recovered as aqueous solution which absorbs $SiF_4$ produced from the manufacturing of industrial-graded $H_3PO_4$ or HF. Generally, fluosilicate salts prepared by the reaction between $H_2SiF_6$ and metal salts. Addition of fluosilicate salts to cement endows odd properties through unique chemical reaction with the fresh and hardened cement. In this study, two-component fluosilicate salt based chemical admixtures (MZ) of $4\%,\;6\%$, and $8\%$ concentration were prepared by the reaction of $H_2SiF_6$ ($25\pm2\%$) and metal salts. The effect of concentration of MZ at a constant adding ratio on the hydration and watertightness of cement were investigated respectively. In a cement containing MZ, metal fluorides such as $CaF_2$ and soluble silica by hydrolysis were newly formed during hydration. The total porosity of the hardened cement was lower in the presence of U because of packing role of metal fluoride and pozzolanic reaction of soluble $SiO_2$. Consequently, the watertightness of the hardened paste containing MZ was more improved than non-added (plain) due to an odd hydration between cement and MZ.

• Journal of the Korea Concrete Institute
• /
• v.17 no.5 s.89
• /
• pp.769-774
• /
• 2005

Fluosilicic acid(H2SiF6) is recovered as an aqueous solution which absorbs $SiF_4$ produced from the manufacturing of industrial-graded H3PO4 or HF. Generally, fluosilicates are the salts produced by the reaction of H2SiF6 and metal salts. Addition of fluosilicates to cement endows odd properties through unique chemical reaction with the fresh and hardened cement. This study was performed to know mechanical properties and watertightness using fluosilicates based composite made from fluosilicates and other compounds. Mix proportions for experiments were modulated at 0.45 of water to cement ratio and $0.0-2.0\%$ of adding ratio of fluosilicates based composite. Evaluation for mechanical properties of concrete was conducted to know fresh state of concrete, hardening state of concrete, and watertightness. Evaluation for watertightness of concrete was carried out permeability, absorption test and porosity analysis. In addition. Scanning Electron Microscopy(SEM) and Energy Dispersive X-Ray(EDX) used for investigating micro-structure and atomic component distributed in hardened concrete. It is ascertained that characteristics of mechanical properties and watertightness was more improved than non-added because of packing role of fluosilicates based composite and pozzolanic reaction of soluble $SiO_2$. Also, concrete added fluosilicates based composite had a tendency to delay setting time and only $0.5\%$ addition of fluosilicates based composite delayed 150 minutes compared with non-added.

• Journal of Korean Society of Water and Wastewater
• /
• v.17 no.4
• /
• pp.510-518
• /
• 2003

The fluoride work management of water supply conveyance has been recommending by the WHO to prevent of tooth decay. Fluoridation of public water supplies has been practiced since 1945. The present approximately 67 countries reported community water fluoridation benefiting many cities. At our country, Fluoridation began in 1981 in Chongiu and Jinhea. In 2002, approximately 40 cities have large populations consuming fluoridated water. But Chongiu stopped fluoridation water works. Few public health measures have been accorded greater clinical and laboratory research, epidemiological study, clinical trials, and public attention than has water fluoridation. In this study, chemical analysis of Sodium Silicofluoride and Fluoride Feed Equipment analyzed. And this study proposed to Fluoride concentration experimental (lab. and field exp.), economics analysis, prevention effect. This study can be decided on the concentration of fluoride injection in Water Fluoridation. Hereafter, this study will be useful in safety and economics of Water Fluoridation in the future.

• Biomolecules & Therapeutics
• /
• v.8 no.2
• /
• pp.179-183
• /
• 2000

To determine biosafety of fluorosilicic acid as a source of fluoride, we carried out acute toxicity and general pharmacological studies using mouse. Fluorosilicic acid had little effects on general behavior, pain response, convulsion, skeletal muscle function and intestinal mobility as compared to controls. It had either little adverse effects on alkaline phosphatase and collagen levels in osteoblast cells. This study supports the safety of fluorosilicic acid in animals.

• Korean Journal of Soil Science and Fertilizer
• /
• v.14 no.3
• /
• pp.163-168
• /
• 1981

The studies were carried out to examine the effect of soil improvement agents, such as lime, wollastonite and phosphate, in reducing the damage caused by hydrogen fluoride gas to the vegetative growth of rice. The yield loss, damage rate of the plant leaves, the fluoride and silicate concentrations of the plants were measured. The results obtained are summarized as follows : 1. Of various levels of added lime and wollastonite, the best were found to be neutralized lime plus lime 150kg/10a, and wollastonite 150kg/10a. 2. Added fluoride increased the fluoride content of the plant and the damage rate of the plant leaves, and the yield was greatly decreased. 3. The silicate concentration at harvesting period was also increased by high amounts of fluoride in the plant during vegetative growth. 4. Increasing the amount of added lime increased the watersoluble silicate concentration in the soil. The silicate content of the plant showed the same tendency.

• Journal of the Korean Vacuum Society
• /
• v.20 no.5
• /
• pp.374-380
• /
• 2011

Carbon coils could be synthesized on nickel catalyst layer-deposited silicon oxide substrate using $C_2H_2$ and $H_2$ as source gases and $SF_6$ as an additive gas under thermal chemical vapor deposition system. The characteristics (formation density and morphology) of as-grown carbon coils according to the injection stage of $SF_6$ gas incorporation were investigated. A continuous injecting of $SF_6$ gas flow could give rise to many types of carbon coils-related geometries, namely linear tub, micro-sized coil, nano-sized coil, and wave-like nano-sized coil. However, the limitation of the geometry as the nano-sized geometries of carbon coils could be achieved by the incorporation of $SF_6$ in a short time (1 min) during the initial deposition stage. A delayed injection of a short time $SF_6$ gas flow can deteriorate the limitation of the geometries. It confirms that the injection time and its starting point of $SF_6$ gas flow would be very important to determine the geometries of carbon coils.

• Korean Journal of Soil Science and Fertilizer
• /
• v.14 no.3
• /
• pp.157-162
• /
• 1981

The studies we re carried out to examine the effect of soil improvement agents, such as lime, wollastonite and phosphate, in reducing the damage caused by hydrogen fluoride gas to the vegetative growth of rice. The yield loss, damage rate of the plant leaves, the fluoride of the plants were measured. The results obtained are summarized as follows : 1. The best results were obtained a treatment of lime and wollastonite. 2. The rice yield was not significantly increased by the soil improvement agents. 3. The fluoride content of the plants was positively correlated with yield loss and damage rate during vegetative growth.

• Journal of the Korean Vacuum Society
• /
• v.21 no.3
• /
• pp.178-184
• /
• 2012

Carbon coils could be synthesized on nickel catalyst layer-deposited silicon oxide substrate using $C_2H_2$ and $H_2$ as source gases and $SF_6$ as an additive gas under thermal chemical vapor deposition system. The characteristics (formation density and morphology) of as-grown carbon coils were investigated as functions of additive gas flow rate and the cycling on/off modulation of $C_2H_2/SF_6$ flows. Even in the lowest $SF_6$ flow rate (5 sccm) in this work, the cycling on/off modulation injection of $SF_6$ flow for 2 minutes could give rise to the formation of nanosized carbon coils, whereas the continuous injection of $SF_6$ flow for 5 minutes could not give rise to the carbon coils formation. With increasing $SF_6$ flow rates from 5 to 30 sccm, the cycling on/off modulation injection of $SF_6$ flow confines the geometry for the carbon coils to the nanosized ones. Fluorine's role of $SF_6$ during the reaction was regarded as the main cause for the confinement of carbon coils geometries to the nano-sized ones.

• Journal of the Korea Concrete Institute
• /
• v.18 no.1 s.91
• /
• pp.57-64
• /
• 2006

The crack presented in concrete structures causes a structural defect, the durability decrease, and external damages etc. Therefore, it is necessary to improve durability through the effort to control the crack. Fluosilicic acid($H_2SiF_6$) is recovered as aqueous solution which absorbs $SiF_4$ produced from the manufacturing of industrial-graded $H_3PO_4$ or HF. Generally, fluosilicates prepared by the reaction between $H_2SiF_6$ and metal salts. Addition of fluosilicates to cement endows odd properties through unique chemical reaction with the fresh and hardened cement. Mix proportions for experiment were modulated at 0.45 of water to cement ratio and $0.0{\sim}2.0%$ of adding ratio of fluosilicate salt based inorganic compound. To evaluate correlation of concrete strength and adding ratio of fluosilicate salt based inorganic compound, the tests were performed about design strength(21, 24, 27 MPa) with 0.5% of adding ratio of fluosilicate salt based inorganic compound. Applications of fluosilicate salt based inorganic compound to reduce cracks resulted from plastic and drying shrinkage, to improve durability are presented in this paper. Durability was evaluated as neutralization, chloride ion penetration depth, freezing thawing resistant tests and weight loss according reinforcement corrosion. It is ascertained that the concrete added fluosilicate salt based inorganic compound showed m ability to reduce the total area and maximum crack width significantly as compared non-added concrete. In addition, the durability of concrete improved because of resistance to crack and watertightness by packing role of fluosilicate salt based inorganic compound obtained and pozzolanic reaction of soluble $SiO_2$ than non-added concrete.

• Proceedings of the Korean Institute of Surface Engineering Conference
• /
• 2016.11a
• /
• pp.175-175
• /
• 2016

Sn도금액은 강산에서는 $Sn^{2+}$, 강알칼리에서는 $Sn^{4+}$석출이 안정하다. 중성영역은 도금액에 $Sn^{2+}$침전을 방지하기 위하여 착화제가 필요하다. 기록에 남아 있는 가장 오래된 Sn도금은 1856년 Gore가 4가의 주석산염을 사용한 알칼리성용액이다. 그 후 50~60년 사이에 2가의 염화주석($SnCl_2$)과 KOH에 Cyan 등의 착화제를 첨가한 도금액이 발표되었다. 최초의 실용적인 알칼리주석용액은 1931년 Oplinger의 4가 주석산 염으로서, $CH_3COONa$를 완충제로 사용하였고, $Sn^{2+}$을 산화시키기 위하여 과산화물이나 과 붕산염을 첨가하였다. 알칼리성 Sn용액은 Natrium용액과 Kalium용액이 있지만, Kalium염이 용해성이 좋고, Sn농도를 높여 전류밀도를 높일 수 있다. 알칼리성용액은 도금속도가 산성용액의 1/2로 되고, 음극효율도 80~90% 정도 낮아, 두꺼운 피막이나 생산성을 중시하는 부품에는 적합하지 않다. 초기의 산성용액은 Sn의 정련목적으로 사용되었고, Pb정련에 사용된 Fluor규산용액에 Gelatine을 첨가하였다. Mathers는 Cresol산을 첨가하여 미량의 Cresol포화용액을 사용하여 고속으로 두껍게 석출시킬 수 있었다. 독일의 Schloetter도 다양한 방향족 술폰산으로써 반 광택피막을 실현하였다. 산성Sn도금액은 첨가제에 어떠한 유기화합물을 사용하는가는 도금장치나 석출상태로써 결정할 수 있다. Hothersall과 Bradshaw는 Cresol술폰산을 첨가하여 도금액 안정성 향상을 발견했다. Cresol술폰산은 $Sn^{2+}$의 안정제이며, Gelatine은 분산제기능을 한다. 붕 불화용액은 Sn농도를 높일 수 있고, $2{\sim}12A/dm^2$의 고 전류밀도의 도금이 가능하다. 1937년 Schloetter가 개발하여 미국의 제철회사에서 사용되었다. Sn-Ni도금은 Ni도금보다도 뛰어난 내식성이 있기 때문에 자전거, 자동차부품에 사용되고 있다. 실용도금액은 1951년 Parkinson이 발표한 HBF/HCL용액이다. $SnCl_2$산성용액에서 표준전위는 -0.136V인데 비하여, Ni이온의 표준전위는 -0.25V이다. HF용액에서는 불화물이온이 $Sn^{2+}$의 석출전위를 (-)방향으로 이동시켜서 합금석출이 가능하다. Sn-Co도금은 Cr도금의 색조에 가깝고, 장식목적으로 사용된다. Cr도금 대체용으로 사용된다. 내마모성이나 내식성은 Cr도금보다도 떨어지기 때문에 장식목적에 한정된다. 1953년 Parkinson은 Sn-Ni도금연구에서 동일한 용액조성으로부터 Co 30%를 석출시켰다. Sn-Zn도금은 방식도금으로서 자동차부품에 많이 사용되고 있다. Sn과 Zn의 표준전위는 서로 멀리 떨어져 있기 때문에 산성용액에서는 공석될 수 없다. 1980년대에 들면서, 방식Cd(Cadmium)도금의 독성 때문에 Sn-Zn도금을 재인식 하게 되었다. 1957년 Vaid 등이 No Cyan도금액을 발표했다. 그 후 러시아의 연구자가 안정한 도금액을 연구하였고, Srivastava와 Muckergee가 1976년에 종합하였다.