• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09a
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• pp.482-483
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• 2006

Synthesis of iron nanopowder by room-temperature electrochemical reduction process of ${\alpha}-Fe_2O_3$ nanopowder was investigated in terms of phase evolution and microstructure. As process variables, reduction time and applied voltage were changed in the range of $1{\sim}20$ h and $30{\sim}40$ V, respectively. From XRD analyses, it was found that volume of Fe phase increased with increasing reduction time and applied voltage, respectively. The crystallite size of Fe phase in all powder samples was less than 30 nm, implying that particle growth was inhibited by the reaction at room temperature. Based on the distinct equilibrium shape of crystalline particle, phase composition of nanoparticles was identified by TEM observation.

• Journal of Magnetics
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• v.9 no.3
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• pp.83-85
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• 2004

Magnetic nanoparticles have been investigated for use as biomedical purposes for several years. For biomedical applications the use of particles that present superparamagnetic behavior at room temperature is preferred [1-4]. To control the magnetic materials by magnetic field is essential locate particle to the suitable destination on feeding by injection. In order to use them properly, the particles should be nano size. However there are many difficulties in applications, because there is lack of identifications in nano magnetic properties. In our studies, structural and magnetic properties of iron oxide nanoparticles were investigated by XRD, VSM, TEM, and Mossbauer spectroscopy. At 13 K, hyperfine fields of ${\gamma}-Fe_2O_3$ were 516 kOe and 490 kOe, that of $Fe_3O_4$ were 517 kOe and 482 kOe. The saturation magnetizations were 21.42 emu/g and 39.42 emu/g. The particle size of powders is 5～19 nm.

• Journal of Powder Materials
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• v.14 no.1 s.60
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• pp.19-25
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• 2007

This study was focused on the optimization of low-pressure ultrasonic spraying process for synthesis of pure ${\gamma}-Fe_2O_3$ nanoparticles. As process variables, pressure in the reactor, precursor concentration, and reaction temperature were changed in order to control the chemical and microstructural properties of iron oxide nanoparticles including crystal phase, mean particle size and particle size distribution. X-ray diffraction (XRD) and transmission electron microscopy (TEM) studies revealed that pure ${\gamma}-Fe_2O_3$ nanoparticles with narrow particle size distribution of 5-15 nm were successfully synthesized from iron pentacarbonyl ($Fe(CO)_{5}$) in hexane under 30 mbar with precursor concentrations of 0.1M and 0.2M, at temperatures over $800^{\circ}C$. Also magnetic properties, coercivity ($H_c$) and saturation magnetization ($M_s$) were reported in terms of the microstructure of particles based on the results from vibration sampling magnetometer (VSM).

• Textile Coloration and Finishing
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• v.15 no.5
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• pp.327-332
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• 2003

In this study, the polyurethane microcapsules for non-aqueous dyeing containing iron oxide and disperse dyes were prepared by in-situ polymerization method using hexamethylene diisocyanate(HDI) with ethylene glycol(EG). And the size, shape, and particle size distribution of microcapsules prepared were investigated. The size and shape of microcapsule were observed by optical microscope and scanning elecron microscope. The particle size distribution was analyzed by particle size analyzer. The microcapsule size and its distribution were largely effected by the existance of surface active agent in the system. When a surfactant did not exist in the system, the size distribution of microcapsules prepared was much uneven. By adding a surfactant, this phenomenon was disappeared. And the size of microcapsule was also effeced by the hydrophobicity of core material(disperse dye). It was considered due to the difference of dispersity of core materials. And the size of microcapsule prepared was inversely proportional to the stirring speed.

• Proceedings of the Korean Ceranic Society Conference
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• 2003.04a
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• pp.33.2-33
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• 2003

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09a
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• pp.173-174
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• 2006

X-ray analysis on iron ores and reduced iron powders revealed that the main acid-insoluble substances were hexagonal and tetragonal quartz, another substances were sillimanite, alumina-silicate, an unnamed zeolite, all contained Si and Al. Their particle size was in the range of $3{\sim}7\;{\mu}m$. Statistics analysis showed that the AIC for high-grade magnetite powder was $(0.130{\pm}0.010)%$) during the latest five months. The predicting value for reduced iron powder should be 0.179%. However, the testing value for reduced iron powder was $(0.192{\pm}0.014)%$. The limited difference of 0.013% might imply rare pollution coming from the reduction and milling processes. The most important step for control AIC should be the separation process of iron ore powders.

• Environmental Engineering Research
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• v.10 no.4
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• pp.174-180
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• 2005

Nano-sized iron was synthesized using borohydride reduction of $Fe^{3+}$ in aqueous solution. A wide range of synthesis conditions including varying concentrations of reagents, reagent feeding rate, and solution pH was applied in an aqueous system under anaerobic condition. The reactivity of nano-sized iron from each synthesis was evaluated by reacting the iron with TCE in batch systems. Evidence obtained from this study suggest the reactivity of iron is strongly dependent on the synthesis solution pH. The iron reactivity increased as solution pH decreased. More rapid TCE reduction was observed for iron samples synthesized from higher initial $Fe^{3+}$ concentration, which resulted in lower solution pH during the synthesis reaction. Faster feeding of $BH_4^-$ solution to the $Fe^{3+}$ solution resulted in lower synthesis solution pH and the resultant iron samples gave higher TCE reduction rate. Lowering the pH of the solution after completion of the synthesis reaction significantly increased reactivity of iron. It is presumed that the increase in the reactivity of iron synthesized at lower pH is due to less precipitation of iron (hydr)oxides or less surface passivation of iron.

• Advances in nano research
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• v.3 no.3
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• pp.169-176
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• 2015

Iron nanoparticles were made by using the modified coprecipitation technique. Usually the characteristics of synthesised particles depend upon the process parameters such as the ratio of the iron ions, the pH of the solution, the molar concentration of base used, type of reactants and temperature. A modified coprecipitation method was adopted in this study. A magnetic stirrer was used for mixing and the morphology and nature of particles were observed after synthesis. Nanoparticles were characterised through XRD. Obtained nanoparticles showed the formation of magnetite and maghemite under citric acid and oxalic acid as stabilisers respectively. The size of nanoparticle was greatly affected by the use of different types of stabilisers. Results show that citric acid greatly reduced the obtained particle size. Particle size as small as 13 nm was obtained in this study. The effects of different kinds of nucleating agents were also observed and two different types of nucleating agents were used i.e. potassium hydroxide (KOH) and copper chloride ($CuCl_2$). Results show that the use of nucleating agent in general pushes the growth phase of nanoparticles towards the end of coprecipitation reaction. The particles obtained after addition of nucleating agent were greater in size than particles obtained by not utilising any nucleating agent. These particles have found widespread use in medical sciences, energy conservation and electronic sensing technology.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.11 no.4
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• pp.176-179
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• 2001

Iron oxide powders were prepared under high temperature (up to $175^{\circ}C$) and pressure conditions( up to 129 pasi) by precipitation from metal nitrates with aqueous potassium hydroxide. Various types of iron oxide powders were obtained at different conditions. The size and the shape of the particles can be controlled as afunction of starting solution pH. The average particles size of the synthesized iron oxide powders increased, the particle shapes of the powders became fibrous, and the crystalline phase of the powder changes from iron oxide to iron hydroxide with increasing solution pH. The effects of synthesis parameters are discussed.

• Elastomers and Composites
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• v.47 no.2
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• pp.168-173
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• 2012

Polystyrene-polyimide core-shell microsphere was prepared by dispersion polymerization using poly(amic acid) as the stabilizer. Iron oxide was formed at the microsphere by thermal decomposition of iron pentacarbonyl impregnated in the microsphere. The magnetic polystyrene-polyimide microsphere was monodisperse and the size was about 500 nm. The magnetic polystyrene-polyimide microsphere had 40% of iron oxide, which was identified as $Fe_3O_4$ by X-ray diffraction.