• Applied Chemistry for Engineering
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• v.22 no.5
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• pp.467-472
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• 2011

This study investigated illite/polypropylene (PP) composite filament formation via melt-spinning and evaluated their physical properties to prepare functional fibers using natural materials. When composite filaments were formed, the composite filaments exhibited smaller fiber diameters compared to that of neat PP filament because of the lubricant effect of illite induced by its layered structure. Moreover, fluorination effect increased interfacial affinity and dispersion in the polymer, resulting in smaller diameter of fluorinated illite/PP composite filament, which was 2/3 of the neat PP filament diameter. Addition of raw and fluorinated illite improved thermal stability of illite/PP composite filament. Raw illite/PP composite filament cannot be used for a practical application, because it broke during drawing process, whereas the fluorinated illite/PP composite filament can be used for a practical application, because it exhibited similar tensile strength of the neat PP filament and 50% increased modulus. Even with improved illite/PP interfacial affinity and illite dispersion in the polymer, illite/PP composite filament formed microcomposite, because non-expandable illite had strongly bound layers, resulting in only a little illite exfoliation and PP intercalation into illite.

• Journal of the korean academy of Pediatric Dentistry
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• v.48 no.4
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• pp.367-375
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• 2021

This study evaluated the fluoride release of alkasite restorative material (ARM) and giomer penetrating the dentin adhesive layer. Twenty specimens were prepared for each restorative material, and dentin adhesive with uniform thickness was applied to half of them. The prepared specimens were placed in a polyethylene tube containing 2.0 mL of deionized water and deposited in a 37.0℃ water bath for the study duration. The amount of fluoride release was measured on the 1^st, 3^rd, 7^th, 14^th, 21^st, and 28^th days after deposition. The dentin adhesive applied to the ARM and giomer could not completely block the fluoride release; however, it significantly reduced its amount. The cumulative amount of fluoride release of the ARM after 28 days was higher than that of the giomer regardless of the application of dentin adhesive.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.08a
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• pp.295-295
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• 2012

염소와 불소 혼합가스와 펄스 직류 전원 플라즈마를 이용하여 GaAs/$Al_{0.2}Ga_{0.8}As$의 선택적 식각을 연구하였다. 식각 주요 공정 변수는 혼합 플라즈마에서 불소 가스의 유량(0~50%) 이었다. 다른 공정 조건은 공정 압력, 펄스 파워, 펄스 주파수, 리버스 시간이 이 있다. 저진공(~100 mTorr) 플라즈마에 대한 연구로 한정하여 기계적 펌프만을 사용하여 공정을 진행하였다. 오실로스코프(Oscilloscope) 데이터에 의하면 가스의 조성 변화에도 척에 걸리는 입력 전압과 전류가 거의 변화가 없었다. $BCl_3/SF_6$플라즈마에서 $SF_6$가스가 10%의 조성에서 GaAs와 $Al_{0.2}Ga_{0.8}As$의 식각 선택비가 약 50:1로 우수한 결과를 나타내었다. 혼합 플라즈마에서 $SF_6$가스의 증가는 GaAs의 식각율과 선택도를 감소시켰다. 그리고 불소 성분 가스의 조성비가 일정량 이상일 경우에는 GaAs와 $Al_{0.2}Ga_{0.8}As$가 거의 식각되지 않았다. 위의 결과들을 종합적으로 보면 펄스 직류 전원 $BCl_3/SF_6$플라즈마에서 불소의 조성비는 GaAs의 선택적 식각에서 중요한 역할을 함을 알 수 있었다.

• Journal of the Korean earth science society
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• v.23 no.6
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• pp.486-493
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• 2002

Hydrogeochemical characteristics of groundwater from a limestone and granite area were studied in the Hwanggangri district, where important fluorite ore deposits are distributed. The geochemical properties of groundwater from limestone and granite are commonly characterized as Ca$^{2+}$-HCO$_3\;^-$ and (Ca$^{2+}$+Na$^+$)-HCO$_3\;^-$ type, respectively. Groundwater, contaminated by mine drainage water from the neighboring ore deposits, has not been observed yet. However, fluoride in groundwater exceeding the drinking water permission level is found in the wells located in a Cretaceous granite area. The concentrations of F in the groundwater show a positive relationship with the values of Na, HCO$_3$, Li and pH. This may suggest that the groundwater come from the decomposition of fluoride-bearing silicate minerals within highly differentiated granitic rocks.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2005.04a
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• pp.90-93
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• 2005

경상남도 합천군과 창녕군 생활용수 지하수 관정 개발시 지하수 굴착공종으로부터 얻어진 구간별 지층자료와 대수층 수질 자료를 획득하여 이용하는 방법을 연구하였다. 지층정보를 파악하기 위하여 지하수공 굴착심도 10m마다 슬라임을 채취하였으며, 대수층 관통시에 지하수 시료를 구간별로 채수하여 전기전도도 및 수질시료를 분석하였다. 경도가 높은 지역의 경우, 음용수 수질기준치에 적합한 지하수를 개발하기 위해서 대수층별 전기전도도를 분석측정하여 경도를 간접적으로 파악함으로써 지하수 굴착심도 결정에 이용하였다. 그리고 대수층 구간별 불소 농도를 파악하였으며, 불소 농도가 높은 대수층 구간에서는 하부대수층 메움 등을 실시하였다. 대수층의 수질검사결과에서 기준치를 초과하는 우려 인자들(불소, 경도, 증발잔류물, 질산성 질소, 철, 알루미늄, 아연 등)에 대한 수질기준 초과 가능성을 대비한 양수시험 모니터링을 설계함으로써 지하수공의 수질 특성 파악이 가능하였다. 양수시험과정에서 탁도가 시간에 따라 기준치 이하까지 감소하는 일반적인 경향과 기준치 이상에서 더 이상 감소하지 않는 경향에 대한 원인을 분석할 수 있었다.

• Journal of the Korean Ceramic Society
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• v.37 no.11
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• pp.1105-1113
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• 2000

Bioglass 조성 중 45S5 (46.1SiO$_2$.24.4$Na_2$O.26.9CaO.2.6P$_2$O$_{5}$ : 몰비)를 기본 조성으로 하여 46P4 (46.2SiO$_2$.49.5CaO.4.3P$_2$O$_{5}$ : 몰비), 46SF (46.1SiO$_2$24.4$Na_2$O.16.1CaO.2.6P$_2$O$_{5}$.10.8CaF : 몰비) 그리고 55SF (55.1SiO$_2$.9.2$Na_2$O.27.8CaO.3.4P$_2$O$_{5}$.4.5CaF : 몰비)를 제조하여 tris-완충용액 및 유사 생체용액(simulated body fluid)에서 반응시킨 후 생체활성유리의 표면에 생성되는 아파타이트 결정형에 관하여 연구하였다. 45S5 유리를 tris-완충용액에 반응시켰을 경우 6시간 반응시부터 수산화 아파타이트가 생성되었으나 유사 생체용액에 반응시켰을 경우에는 24시간까지도 수산화 아파타이트 결정이 생성되지 못하고 비정질 상태의 칼슘 인산염만 형성되었다. tris-완충용액에 각 조성의 유리를 200시간 반응시킨 경우 불소를 함유하지 않은 유리에서는 잎사귀 모양의 수산화 아파타이트가, 불소를 함유한 유리에서는 구상의 플루오르 아파타이트가 형성되었다. 그러나 유사 생체용액에 각 조성의 유리를 200시간 반응시켰을 경우 불소를 함유하지 않은 유리에서는 누에고치형의 수산화 아파타이트가 형성되었고 불소를 함유한 유리에서는 무정형의 칼슘 인산염이 생성되었다.

• Applied Biological Chemistry
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• v.41 no.7
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• pp.550-555
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• 1998

For fluoro-quinolone carboxylic acid derivatives, one bond carbon-fluorine coupling constants are ranged from 249 Hz to 257 Hz regardless of positions. But geminal and vicinal carbon-fluorine coupling constants vary according to positions, namely, geminal coupling constants are ranged from 6 Hz to 23 Hz, and vicinal coupling constants are ranged from 1.9 Hz to 7 Hz. In cases of proton-fluorine couplings, three bond coupling constants are ranged from 9 Hz to 10.3 Hz, and four bond coupling constants ate ranged from 6 Hz to 8.3 Hz.

• Analytical Science and Technology
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• v.27 no.3
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• pp.167-171
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• 2014

Hydrofluoric acid (HF), a typical inorganic acid, has been used in the industry for its various usage and classified as the toxic compound, because it can cause the pneumonia and pulmonary edema when it was exposed to respiratory organs. The official environmental analytical method for fluorine and its compound in waste has not been developed. For this reason, we have faced some problem to treat the contaminated wastes by the HF leakage from industrial process. In this study, prepared for analytical method for combustible waste (crop, trees, etc.) generated from HF leaking accident and to be applied as the official analytical method for fluorine contaminated waste when the fluorine and its compound will be regulated as a hazardous material by the waste management law later.

• Journal of Korean Society of Environmental Engineers
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• v.35 no.11
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• pp.803-808
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• 2013

The purpose of this study was performed to investigate the optimum conditions of pH, concrete sludge, seed dosage, mixing intensity, operation time in treating fluoride-containing wastewater as $CaF_2$ using the ready-mixed concrete sludge. Considering fluoride removal, water content, that pH 6, concrete sludge dosage of 10 g/L, Seed dosage ($CaF_2$) of 2 g/L, mixing intensity of 100 rpm and operation time of 60 min were found to be optimum. Correspondingly, removal of fluoride and water content was about 85% and 64%, respectively. Increase in amount of seed dosage did not affect fluoride removal efficiency. but the result that the water content is decreased was shown up in occuring the solid-liquid separation well.

• Polymer(Korea)
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• v.34 no.5
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• pp.464-468
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• 2010

In this study, a vinylbenzyl chloride (VBC) monomer was successfully grafted onto the several fluoropolymer films including poly(tetrafluoroethylene-co-hexafluoropropylene) (FEP), poly(tetrafluoroethylene-co-perfluoropropylvinyl ether) (PFA), and poly(ethylene-co-tetrafluoroethylene) (ETFE) films by using a simultaneous irradiation method. The results indicated that PVBC graft polymer can be easily grafted onto the ETFE film than other fluorinated films under the same irradiation condition. The grafted films were characterized by using FTIR, TGA, and SEM-EDS instruments. The elongation at the breaking of the grafted films was found to decrease with an increase of degree of grafting (DOG). The PVBC-grafted ETFE films were found to have better mechanical properties than other PVBC-grafted fluorinated films.