• 한국자기학회지
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• 제21권5호
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• pp.157-162
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• 2011

황산제일철/황산제이철의 몰비와 침전제 종류(NaOH, $NH_4OH$)를 변화시켜 공침법으로 $Fe_3O_4$를 합성하였다. 합성한 분말의 특성을 평가한 결과 모든 실험조건(황산제일철/황산제이철의 몰비와 침전제의 종류)에서 단일상의 나노 크기 $Fe_3O_4$가 생성 되었다. NaOH를 침전제로 사용한 경우에 $NH_4OH$를 침전제로 사용한 경우보다 입자크기가 작고, 좁은 입도분포를 나타내었다. 동일한 침전제를 사용할 경우에는 혼합 황산철(황산제일철/황산제이철)의 몰비가 증가할수록 입자크기와 결정자 크기가 증가하였으며 입도 분포는 넓어졌다. 모든 실험조건에서 합성된 $Fe_3O_4$ 분말은 초상자성을 나타내었으며 침전제로 $NH_4OH$를 사용하고 혼합 황산철의 몰비를 2.5로 하였을 때 가장 높은 포화자화 값 72 emu/g을 갖는 $Fe_3O_4$를 합성할 수 있었다.

• 한국지하수토양환경학회지:지하수토양환경
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• 제27권4호
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• pp.49-62
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• 2022

The magnesium and iron-based layered double hydroxide (Mg-Fe LDH) was synthesized by the co-precipitation process and the bead type LDH (BLDH, 5~6 mm in diameter) was manufactured by using the Mg-Fe LDH and the starch as a binder. To evaluate the feasibility of the BLDH as the As stabilizer in the soil, various experiments were performed and the As stabilization efficiency of the BLDH was compared to that of powdered type LDH (PLDH, <149 ㎛ in diameter). For the As sorption batch experiment, the As sorption efficiency of both of the PLDH and the BLDH showed higher than 99%. For the stabilization experiment with soil, the As extraction reducing efficiency of the PLDH was higher than 87%, and for the BLDH, it was higher than 80%, suggesting that the BLDH has similar the feasibility of As stabilization for the contaminated soil, compared to the PLDH. From the continuous column experiments, when more than 7% BLDH was added into the soil, the As stabilization efficiency of the column maintained at over 91% for 7 pore volume flushing (simulating about 21 months of rainfall) and slowly decreased down to 64% after that time (to 36 months) under the non-equilibrium conditions. Results suggested that more than 7% of BLDH added in As-contaminated soil could be enough to stabilize As in soil for a long time. The main As fixation mechanisms on the LDH were also identified through the X-ray fluorescence (XRF), the X-ray diffraction (XRD), and the Fourier transform infrared (FT-IR) analyses. Results showed that the LDH has enough of an external surface adsorption capacity and an anion exchange capability at the interlayer spaces. Results of SEM/EDS and BET analyses also supported that the Mg-Fe LDH used in this study has sufficient porous structures and outer surfaces to fix the As. The reduction of carbonate (CO₃^2-) and sulfate (SO₄^2-) anions in the LDH after the reaction between As and the LDH was observed through the FT-IR, the XRF, and the XRD analyses, suggesting that the exchange of some of these anions with the arsenate (H₂AsO₄^- or HAsO₄^2-) occurs at the LDH interlayers during the stabilization process in soil.

• Restorative Dentistry and Endodontics
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• 제39권2호
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• pp.89-94
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• 2014

Objectives: The aim of this study was to evaluate the cytotoxicity, setting time and compressive strength of MTA and two novel tricalcium silicate-based endodontic materials, Bioaggregate (BA) and Biodentine (BD). Materials and Methods: Cytotoxicity was evaluated by using a 2,3-bis(2-methoxy-4-nitro-5-sulfophenyl)-5-((phenylamino)carbonyl)-2H-tetrazolium hydroxide (XTT) assay. Measurements of 9 heavy metals (arsenic, cadmium, chromium, copper, iron, lead, manganese, nickel, and zinc) were performed by inductively coupled plasma-mass spectrometry (ICP-MS) of leachates obtained by soaking the materials in distilled water. Setting time and compressive strength tests were performed following ISO requirements. Results: BA had comparable cell viability to MTA, whereas the cell viability of BD was significantly lower than that of MTA. The ICP-MS analysis revealed that BD released significantly higher amount of 5 heavy metals (arsenic, copper, iron, manganese, and zinc) than MTA and BA. The setting time of BD was significantly shorter than that of MTA and BA, and the compressive strength of BA was significantly lower than that of MTA and BD. Conclusions: BA and BD were biocompatible, and they did not show any cytotoxic effects on human periodontal ligament fibroblasts. BA showed comparable cytotoxicity to MTA but inferior physical properties. BD had somewhat higher cytotoxicity but superior physical properties than MTA.

• 자원환경지질
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• 제42권5호
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• pp.487-494
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• 2009

본 연구에서는 무산소 환경에서 As(III)로 대체된 자철석으로의 침전 가능성을 확인하기 위하여 Fe(II)와 As(V)의 반응을 통한 As(V)의 As(III)로의 환원 여부를 조사하였다. Fe(II)와 As(V)가 용액상으로 존재하는 균질조건에서의 환원반응 실험은 pH에 따른 영향을 알아보기 위해 수행되었고, 주어진 pH 조건(3.0~7.3)에서 용해된 Fe(II)에 의한 As(V)의 As(III)로의 환원반응은 일어나지 않았다. 균질조건에서의 환원반응 실험결과와 유사하게 침철석을 이용한 불균질조건에서의 환원반응 실험에서도 침철석에 흡착된 Fe(II)에 의한 As(V)의 환원반응은 일어나지 않았다. 또한 Fe(II)의 산화에 미치는 As(V)의 영향에 대한 회분식 실험결과, As(V)가 Fe(II)의 산화반응을 저해하는 영향을 주었고 균질한 조건에서보다 불균질한 조건에서 As(V)의 영향이 명확하게 나타난 것으로 사료된다. 이런 결과들은 무산소 및 지하 환경에서 Fe(II)와 공존할 때, As(V)는 안정한 상태로 존재함을 시사한다.

• 헤리티지:역사와 과학
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• 제45권1호
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• pp.86-101
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• 2012

운주사 원형다층석탑의 주요 구성암석은 암편질응회암과 유문암질 각력응회암으로 담녹색 및 회색을 띠며 원마도가 불량한 암편을 함유하고 있다. 암편질응회암은 유리질 기질과 은미정질의 장석과 석영이 보이고 미정질 결정들이 나타난다. 유문암질 각력응회암에서는 장석 및 불투명 광물로 이루어진 기질에 석영과 장석이 반정으로 관찰된다. 석탑의 모든 부재에는 먼지, 박리박락, 공동, 탈락, 균열이 발달되어 있으며, 적외선 열화상 촬영 결과 부분적으로 내부 공극이 상당히 진행되어 박리를 유발하고 있는 상태이다. 또한 서측과 북측의 3층 이상 옥개석 상부에서는 회색, 녹색, 황갈색 등의 다양한 지의류 및 선태류들이 높은 점유율을 보인다. 기단부와 옥개석에는 산화망간, 산화철 및 수산화철 등의 무기오염물에 의한 변색이 나타난다. 석탑 부재의 화학적 풍화지수(CIA)와 풍화잠재지수(WPI)를 산출한 결과, 각각 55.69, 1.12로 상당히 풍화가 진행되었으며 초음파속도는 평균 2,892m/s, 풍화도지수와 일축압축강도는 각각 0.4k, $1,096kg/cm^3$로 암석의 강도와 내구성이 약화된 상태이다.

• 대한핵의학회지
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• 제7권2호
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• pp.27-34
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• 1973

Pulmonary perfusion scan with radioactive $^{113m}In$-iron hydroxide particle was performed in the 25 cases of heart disease which had been diagnosed by cardiac catheterization prior to surgery from July, 1972 to July, 1973 at the Department of Radiology and Nuclear Medicine, Yonsei Medical College. It consists of 7 mitral stenosis, 2 mitral insufficiency, 1 aortic insufficiency, 3 atrial septal defect, 5 ventricular septal defect, 2 patent ductus arteriosus, 1 transposition of great vessel and 4 Tetralogy of Fallot. Findings of pulmonary perfusion scan in relation to hemodynamic data of cardiac catheterization were examined. 1) Out of 10 cases of acquired valvular heart disease, In 6 cases of mitral stenosis and 1 case of aortic insufficiency, radioactivity was increased at both upper lung. This finding is noted when pulmonary wedge or venous pressure was elevated above 22 mmHg and arterial systolic pressure above 33 mmHg. 2) Out of 15 cases of congenital heart disease. In almost all cases of atrial septal defect and ventricular septal defect except 2 cases, radioactivity was even at both entire lung. In 2 cases of patent ductus arteriosus, radioactivity was decreased especially at the left lung. It is observed that in acyanotic congenital heart disease, radioactivity of lung is not related with pulmonary arterial pressure. In 3 cases of Tetralogy of Fallot, radioactivity was even at both entire lung and in 2 of them, extrapulmonary radioactivity of liver or kidney which depends on size of defect and volume of right to left shunt reversible, was noted.

• 분석과학
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• 제13권3호
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• pp.297-303
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• 2000

저니토 시료 중의 미량 Cd, Cu, Pb, Ni, Zn 등의 분석을 위해 동위원소희석 질량분석법을 이용하였다. 시료는 마이크로파 혼합산(질산, 불산, 과염소산) 분해법을 이용하여 용해하였다. Ammonium pyrrolidenedithiocarbamate(APDC) 용매 추출법을 이용하여 알칼리 및 알칼리 토금속을 분리한 다음 Pb를 측정하고, 나머지 원소들은 이 용액에 $NH_4OH$ 첨가 후 원심 분리하여 Fe, Sn, Ti 등을 제거한 다음 측정하였다. 측정원소의 회수율은 다소 떨어지나 동중원소 방해를 일으키는 매질원소를 효율적으로 제거할 수 있었다. 2종의 저니토 인증표준물질 중의 미량원소 분석에 이 방법을 적용한 결과 인증값과 잘 일치하는 측정 결과를 얻을 수 있었다.

• Environmental Engineering Research
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• 제10권5호
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• pp.205-212
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• 2005

The study was conducted to investigate the removal of heavy metals by using Hydroxyapatite(HAp) made from waste oyster shells and wastewater with high concentration of phosphorus. The maximum calcium concentration for the production of HAp in this study was released up to 361 mg/L at pH of 3 by elution experiments. When the pH was at adjusted 6, the maximum calcium released concentration was 41 mg/L. During the elution experiment, most of the calcium was released within 60 minutes. This reaction occurred at both pH levels of 3 and 6. The result of the XRD analysis for the HAp product used in this study shows the main constituent was HAp, as well as OCP. The pH was 8.6. As the temperature increased, the main constituent did not vary, however its structure was crystallized. When the pH was maintained at 3, the removal efficiency decreased as the heavy metal concentration increased. The order of removal efficiency was as follows: $Fe^{2+}$(92%), $Pb^{2+}$(92%) > $Cu^{2+}$(20%) > $Cd^{2+}$(0%). Most of these products were dissolved and did not produce sludge in the course of heavy metals removal. As the heavy metal concentration increased at pH of 6, the removal efficiency increased. The removal efficiencies in all heavy metals were over 80%. From the analysis of the sludge after reaction with heavy metals, the HAp was detected and the OCP peak was not observed. Moreover, lead ion was observed at the peaks of lead-Apatite and lead oxidant. In the case of cadmium, copper and iron ions, hydroxide forms of each ion were also detected.

• 한국재료학회지
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• 제21권4호
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• pp.225-231
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• 2011

The effect of ferrous/ferric molar ratio on the formation of nano-sized magnetite particles was investigated by a co-precipitation method. Ferrous sulfate and ferric sulfate were used as iron sources and sodium hydroxide was used as a precipitant. In this experiment, the variables were the ferrous/ferric molar ratio (1.0, 1.25, 2.5 and 5.0) and the equivalent ratio (0.10, 0.25, 0.50, 0.75, 1.0, 2.0 and 3.0), while the reaction temperature ($25^{\circ}C$) and reaction time (30 min.) were fixed. Argon gas was flowed during the reactions to prevent the $Fe^{2+}$ from oxidizing in the air. Single-phase magnetite was synthesized when the equivalent ratio was above 2.0 with the ferrous/ferric molar ratios. However, goethite and magnetite were synthesized when the equivalent ratio was 1.0. The crystallinity of magnetite increased as the equivalent ratio increased up to 3.0. The crystallite size (5.6 to 11.6 nm), median particle size (15.4 to 19.5 nm), and saturation magnetization (43 to 71 $emu.g^{-1}$) changed depending on the ferrous/ferric molar ratio. The highest saturation magnetization (71 $emu.g^{-1}$) was obtained when the equivalent ratio was 3.0 and the ferrous/ferric molar ratio was 2.5.

• Composites Research
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• 제30권1호
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• pp.41-45
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• 2017

Magnetite nanoparticles were synthesized by adding an ammonium hydroxide to a mixed solution of iron (II) and (III) chlorides. A silicon surfactant of ${\alpha},{\omega}$-(3-aminopropyl)polydimethylsiloxane was adsorbed on the particles as dispersant and a polydimethylsiloxane polymer was used to prepare ferrofluids of silicone oil base. Fluorinated surfactants of anionic ammoniated perfluoroalkyl sulfonamide and nonionic fluoroaliphatic polymeric esters were applied to the particles and a perfluoropolyether was used to prepare ferrofluids of fluorine oil base. The experimental conditions were used for preparing the ferrofluids with concentrations of 200, 300 and 400 mg/mL, and density, magnetization and viscosity of the products were characterized. The density values increased in proportion to the concentration, indicating 1.11-1.27 g/mL for silicone-oil-based fluids and 1.95-2.10 g/mL for fluorine-oil-based fluids in the range of 200-400 mg/mL. The saturation magnetization of the silicone-oil-based and fluorine-oil-based fluids indicated 14.7, 24.4, and 30.7 mT and 15.8, 23.3, and 33.7 mT for 200, 300, and 400 mg/mL, respectively, depending on the content of magnetic particles in the fluid. The viscosity of the silicone-oil-based ferrofluids was highly stable compared to that of the fluorine-oil-based with increasing temperatures. The ferrofluids are usually applied to seals and speakers with the silicone base and to seals with the fluorine base.