• Advances in nano research
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• 제2권2호
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• pp.89-98
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• 2014

A novel and simple method for the synthesis of nano-magnetite particles is disclosed. In the novel procedure, $Fe^{2+}$ is the only source of metal cation. Carboxymethylcellulose (CMC) is used as the structure directing agent. The phase analysis of the nano-particles was performed using XRD and electron diffraction techniques. Size and morphology analysis was performed using light scattering and TEM techniques. The effect of $NH_4OH$ solution (32 wt. %) at different CMC concentrations on the size distribution of the final magnetite powders is studied. An optimal base concentration exists for each CMC concentration leading to minimal agglomeration. There exists a minimum CMC concentration (0.0016 wt. %), lower than that no magnetite forms. It is shown that using the new method, it is possible to immobilize a lipase enzyme (Candida Rugosa) with immobilization efficiency larger than 98 % with a loading more than 3 times the reported value in the literature. The latter phenomenon is explained based on the agglomerate state of the nano-particles in the liquid phase.

• 한국분말재료학회지
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• 제15권2호
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• pp.148-155
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• 2008

Nano magnetite particles have been prepared by two step reaction consisting of urea hydrolysis and ammonia addition at certain ranges of pH. Three different concentrations of aqueous solution of ferric ($Fe^{3+}$) and ferrous ($Fe^{2+}$) chloride (0.3 M-0.6 M, and 0.9 M) were mixed with 4 M urea solution and heated to induce the urea hydrolysis. Upon reaching at a certain pre-determined pH (around 4.7), 1 M ammonia solution were poured into the heated reaction vessels. In order to understand the relationship between the concentration of the starting solution and the final size of magnetite, in-situ pH measurements and quenching experiments were simultaneous conducted. The changes in the concentration of starting solution resulted in the difference of the threshold time for pH uprise, from I hour to 3 hours, during which the akaganeite (${\beta}$-FeOOH) particles nucleated and grew. Through the quenching experiment, it was confirmed that controlling the size of ${\beta}$-FeOOH and the attaining a proper driving force for the reaction of ${\beta}$-FeOOH and $Fe^{2+}$ ion to give $Fe_3O_4$ are important process variables for the synthesis of uniform magnetite nanoparticles.

• 한국재료학회지
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• 제22권7호
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• pp.362-367
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• 2012

Magnetite nanoparticles(NPs) have been the subject of much interest by researchers owing to their potential use as magnetic carriers in drug targeting and as a tumor treatment in cases of hyperthermia. However, magnetite nanoparticles with 10 nm in diameter easily aggregate and thus create large secondary particles. To disperse magnetite nanoparticles, this study proposes the infiltration of magnetite nanoparticles into hybrid silica aerogels. The feasible dispersion of magnetite is necessary to target tumor cells and to treat hyperthermia. Magnetite NPs have been synthesized by coprecipitation, hydrothermal and thermal decomposition methods. In particular, monodisperse magnetite NPs are known to be produced by the thermal decomposition of iron oleate. In this study, we thermally decomposed iron acetylacetonate in the presence of oleic acid, oleylamine and 1,2 hexadecanediol. We also attempted to disperse magnetite NPs within a mesoporous aerogels. Methyltriethoxysilicate(MTEOS)-based hybrid silica aerogels were synthesized by a supercritical drying method. To incorporate the magnetite nanoparticles into the hybrid aerogels, we devised two methods: adding the synthesized aerogel into a magnetite precursor solution followed by nucleation and crystal growth within the pores of the aerogels, and the infiltration of magnetite nanoparticles synthesized beforehand into aerogel matrices by immersing the aerogels in a magnetite nanoparticle colloid solution. An analysis using a vibrating sample magnetometer showed that approximately 20% of the magnetite nanoparticles were well dispersed in the aerogels. The composite samples showed that heating under an inductive magnetic field to a temperature of $45^{\circ}C$ is possible.

• Advances in nano research
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• 제6권1호
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• pp.1-19
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• 2018

Iron oxide nanoparticles excite researcher interest in biomedical applications due to their low cost, biocompatibility and superparamagnetism properties. Magnetic iron oxide especially magnetite ($Fe_3O_4$) possessed a superparamagnetic behaviour at certain nanosize which beneficial for drug and gene delivery, diagnosis and imaging. The properties of nanoparticles mainly depend on their synthesis procedure. There has been a massive effort in developing the best synthetic strategies to yield appropriate physico-chemical properties namely co-precipitation, thermal decomposition, microemulsions, hydrothermal and sol-gel. In this review, it is discovered that magnetite nanoparticles are best yielded by co-precipitation method owing to their simplicity and large production. However, its magnetic saturation is within range of 70-80 emu/g which is lower than thermal decomposition and hydrothermal methods (80-90 emu/g) at 100 nm. Dimension wise, less than 100 nm is produced by co-precipitation method at $70^{\circ}C-80^{\circ}C$ while thermal decomposition and hydrothermal methods could produce less than 50 nm but at very high temperature ranging between $200^{\circ}C$ and $300^{\circ}C$. Thus, co-precipitation is the optimum method for pre-compliance magnetite nanoparticles preparation (e.g., 100 nm is fit enough for biomedical applications) since thermal decomposition and hydrothermal required more sophisticated facilities.

• 한국지하수토양환경학회지:지하수토양환경
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• 제28권4호
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• pp.1-5
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• 2023

In the fabrication of magnetic adsorbent by incorporating iron species on base materials with layered structure, there can be a potential loss of adsorption capacity from the penetration of dissolved iron species into the structure. This work newly synthesized a magnetic adsorbent by incorporating nano magnetite and glucose into layered metal sulfide via hydrothermal treatment, and tested the removal efficiencies of cesium ions (Cs⁺) by the adsorbents fabricated under different conditions (final temperature and glucose mass ratio). As a result, the optimal fabrication condition was found to be mass ratio of 1 (layered metal sulfide): 0.1 (nano magnetite): 0.4 (glucose) and final temperature of 160℃. As-prepared adsorbent possessed good adsorption ability of Cs⁺ (54.8 mg/g) without a significant loss of adsorption capacity from attaching glucose and nano magnetite onto the surface.

• 자원환경지질
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• 제45권2호
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• pp.195-204
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• 2012

미생물에 의한 광물합성은 지화학적 순환 및 미생물의 독성에 대한 저항기작을 위해 주로 연구되어져 왔으나 본 논문에서는 NanoFermentation을 통한 경제적, 친환경적, 저에너지, 대량생산이 가능한 나노입자 크기의 자철석 합성연구를 소개하고 또한 초상자성(Superparamagnetism)과 준강자성(Ferrimagnetism)을 결정짓는 입자크기에 대한 조절인자를 살펴보고자 한다. NanoFermentation을 통한 자철석의 합성 시 입자 크기의 조절 인자는 선택된 미생물 종 및 배양 온도, 배양액의 화학적 조성, 배양기간, 치환된 원소의 조성 및 함량, 자철석 전조물질(Precursor)의 형태, 반응 부피의 증가 및 자철석 전조물질의 농도와 같은 조건들의 조합에 의해 결정되어지며 주로 핵형성 및 결정 성장의 균형에 의해 조절된다. 생광물화 작용을 통한 무기재료의 합성 연구는 앞서 언급한 지표에서의 원소의 순환 및 미생물 생리학적 측면뿐만 아니라 최종 산물인 나노입자의 대량 생산을 통해 재료학적 응용 분야에도 많은 파급 효과가 예상된다.

• 한국재료학회지
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• 제25권11호
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• pp.612-615
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• 2015

In this work, on-site corrosion behavior of heat resistant tubes of T91, used as components of a superheater in a power plant for up to 25,762 h, has been investigated using scanning electron microscopy(SEM), energy dispersive X-ray spectroscopy (EDS), and electron backscattered diffraction(EBSD), with the objectives of studying the composition, phase distribution, and evolution during service. A multi-layer structure of oxide scale was found on both the steamside and the fireside of the tube surface; the phase distribution was in the order of hematite/magnetite/spinel from the outer to the inner matrix on the steamside, and in the order of slag/magnetite/spinel from the outer to the inner matrix on the fireside. The magnetite layer was found to be rich in pores and cracks. The absence of a hematite layer on the fireside was considered to be due to the low oxygen partial pressure in the corrosion environment. The thicknesses of the hematite and of the slag-deposit layer were found to exhibit no significant change with the increase of the service time.

• 한국자기학회:학술대회 개요집
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• 한국자기학회 2008년도 Asian Magnetics Conference
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• pp.161.2-161.2
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• 2008

• Membrane and Water Treatment
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• 제8권1호
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• pp.51-71
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• 2017

Antimicrobial polyethersulfone ultrafiltration membranes containing zerovalent iron ($Fe^0$) and magnetite ($Fe_3O_4$) nanoparticles were synthesized via phase inversion method using polyethersulfone (PES) as membrane material and nano-iron as nanoparticle materials. Zerovalent iron nanoparticles (nZVI) were prepared by the reduction of iron ions with borohydride applying an inert atmosphere by using $N_2$ gases. The magnetite nanoparticles (nMag) were prepared via co-precipitation method by adding a base to an aqueous mixture of $Fe^{3+}$ and $Fe^{2+}$ salts. The synthesized nanoparticles were characterized by scanning electron microscopy, X-ray powder diffraction, and dynamic light scattering analysis. Moreover, the properties of the synthesized membranes were characterized by scanning electron microscopy energy dispersive X-ray spectroscopy and atomic force microscopy. The PES membranes containing the nZVI or nMag were examined for antimicrobial characteristics. Moreover, amount of iron run away from the PES composite membranes during the dead-end filtration were tested. The results showed that the permeation flux of the composite membranes was higher than the pristine PES membrane. The membranes containing nano-iron showed good antibacterial activity against gram-negative bacteria (Escherichia coli). The composite membranes can be successfully used for the domestic wastewater filtration to reduce membrane biofouling.

• 한국지구물리탐사학회:학술대회논문집
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• 한국지구물리탐사학회 2009년도 학술대회 초록집
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• pp.107-109
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• 2009

미세자기학은 분자구조 단위에서 (Micromagnetic modeling) 자성 광물의자화 획득 및 자화 소멸을 연구하는 학문으로 행성지질학적으로 흥미있는 자성 광물의 자화 상태를 수치해석으로 풀어내는 학문이다. 자기이력곡선 분석은 시료를 파괴하거나 가열하지 않고 빠르고 정확하게 자성 광물의 종류 및 크기를 식별할수 있다. 정6면체 형태의 합성자철석이 아닌 자연산에 존재하는 8면체 형태의 모델을 택해야 기존의 실험 결과를 더 잘 설명함을 알아내었다. 특히 8면체의 경우 120 nm 이상의 크기에서 magnetic coercivity와 magnetic remanence가 더욱 안정적이고 커짐을 알아냈다.