• Journal of Powder Materials
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• v.17 no.4
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• pp.263-269
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• 2010

Hexagonal barium ferrite ($BaFe_{12}O_{19}$) nano-particles have been successfully fabricated by spraypylorysis process. $BaFe_{12}O_{19}$ precursor solutions were synthesized by self-assembly method. Diethyleneamine (DEA) surfactant was used to fabricate the micelle structure of Ba-DEA complex under various DEA concentrations. $BaFe_{12}O_{19}$ powders were synthesized with addition of Fe ions to Ba-DEA complex and then fabricated $BaFe_{12}O_{19}$ powders by spray-pyrolysis process at the temperature range of $800{\sim}1000^{\circ}C$. The molar ratio of Ba/DEA and heat-treatment temperatures significantly affected the magnetic properties and morphology of $BaFe_{12}O_{19}$ powders. $BaFe_{12}O_{19}$ powders synthesized with Ba/DEA molar ratio of 1 and heat-treated at $900^{\circ}C$ showed the coercive forces (iHc) of 4.2 kOe with average crystal size of about 100 nm.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.30 no.12
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• pp.782-787
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• 2017

There is growing interest in power inductors in which metal soft magnetic powder and epoxy resin are combined. In this field, the process technology for increasing the packing density of magnetic particles in an injection molding process is very important. However, little research has been reported in this regard. In order to improve the packing density, we investigated and compared the sedimentation heights of pastes for three types of soft magnetic alloy powders as a function of the mixing ratios and the type of resin used. Experimental results showed that the packing density was the highest (71.74%) when the mixing ratio was 80 : 16 : 4 (Sendust : Fe-S : CIP) according to the particle size using an SE-4125 resin. In addition, the packing density was found to be inversely related to the layer separation distance. As a result, it was confirmed that the dispersion of solid particles in the paste was important for curing; however, the duration of the curing process can greatly affect the packing density of the final composite.

• Journal of the Korean Ceramic Society
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• v.41 no.9
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• pp.670-676
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• 2004

The synthesis of highly concentrated silver nano sol assisted by polymeric dispersant (polyelectrolytes) for inkjet method was studied. The silver nano sol was prepared with AgNO$_3$, polyelectrolytes (HS5468cf ; polyacrylic ammonium salt), and reducing agent. The polyelectrolytes play an important role in formation of complex composed of Ag$\^$+/ion and carboxyl group (COO$\^$-/), result in preparation of highly dispersed silver nano particles. The optimization of added amount of polyelectrolytes, and concentration of silver nano sol was studied. The silver nanoparticles were evaluated by XRD, particle size/zeta potential analyzer and FE-TEM. The silver nanoparticles with the range of 10 nm in diameter were produced. The concentration of batch-synthesized silver nano sol was possible up to 40 wt%.

• Advances in nano research
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• v.6 no.1
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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.

• Journal of Hydrogen and New Energy
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• v.22 no.4
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• pp.504-511
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• 2011

Nano-sized Sn powder was prepared by pulsed wire evaporation method. The Sn powder and carbon black were charged in jar and ball milled. The milling time was varied with 10 min., 1h, 2h, and 4h, respectively. The milled powders were dried and the shape and size were observed by FE-SEM. Nano-sized Sn powders were plastic-deformed and agglomerated by impact force of balls and heat generated during the SPEX milling. The agglomerated Sn powder also consisted of many nano-sized particles. Initial discharge capacities of milled Sn electrode powders with carbon powder were milled for 10 min., 1h, 2h, and 4h were 787, 829, 827, and 816 mAh/g, respectively. After 5 cycle, discharge capacities of Sn electrode powders with carbon powder milled for 10 min., 1h, 2h, and 4h decreased as 271, 331, 351, and 287 mAh/g, respectively. Because Sn electrode powders milled for 2h constist of uniform and fine size, the cyclability of coin cell made of this powders is better than others.

• Journal of Environmental Impact Assessment
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• v.30 no.4
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• pp.247-257
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• 2021

In this work, Iron Nano-Particles Impregnated BioChar/bead (INPBC/bead) soil amendment was developed to increase biochar's reactivity to As in soil and preventing possible wind loss. Prior to preparation of INPBC/bead, INPBC was produced utilizing lignocellulosic biomass and Fe(III) solution in a hydrothermal method, followed by a calcination process. Then, the bead type amendment, INPBC/bead was produced by cross-linking reaction of alginate with INPBC. FT-IR, XRD, BET, and SEM-EDS analyses were utilized to characterize the as-synthesised materials. The particle size range of INPBC/bead was 1-4 mm, and different oxygen-containing functional groups and Fe3O4 crystalline phase were produced on the surface of INPBC/bead, according to the characterization results. The soil cultivation test was carried out in order to assess the stabilization performance of INPBC/bead utilizing As and Pb-contaminated soil obtained from an abandoned mining location in South Korea. After 4 weeks of culture, TCLP and SPLP extraction tests were performed to assess the stabilization efficacy of the amendment. The TCLP and SPLP findings revealed that raising the application ratio improved stabilizing efficiency. The As stabilization efficiency was determined to be 81.56 % based on SPLP test findings for a 5% in (w/w) INPBC/bead treatment, and the content of Pb in extracts was reduced to the limit of detection. According to the findings of this study, INPBC/bead that can maintain pH of origin soil and minimize wind loss might be a potential amendment for soil polluted with As and heavy metals.

• Polymer(Korea)
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• v.33 no.5
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• pp.452-457
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• 2009

Hybrid nanomaterials consisting of multi-walled carbon nanotube(MWNT) and/or PEDOT of conductive polymer were prepared in this study. In the presence of catalyst and ligand, the MWNT-Br compound prepared by the successive surface treatment reaction was mixed with MMA to initiate the atom transfer radical polymerization process. PMMA was covalently linked to the surface of MWNT for the formation of MWNT/PMMA nanocomposites. The EDOT and oxidant were added in the aqueous emulsion of PS produced via a miniemulsion polymerization process and then it proceeded to carry out the oxidative chemical polymerization of EDOT for the preparation of PEDOT/PS nanoparticles with the core-shell structure. The aqueous dispersion of PEDOT:poly(styrene sulfonate) (PSS) was mixed with the silica particles treated with a silane compound and thus PEDOT:PSS-clad silica nanoparticles were prepared by the surface chemistry reaction. The hybrid nanomaterials were analyzed by using TEM, FE-SEM, TGA, EDX, UV, and FT-IR.

• Journal of the Korean Vacuum Society
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• v.17 no.6
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• pp.576-581
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• 2008

High-quality double-walled carbon nanotubes (DWNTs) were synthesized without defects and amorphous carbonaceous particles by catalytic decomposition method at $800^{\circ}C$ in high yield. As-synthesized carbon materials almost consist of DWNT bundles with a diameter 12 - 20 nm.. The DWNTs rope have uniform diameter about 2 - 5 um and length up to several tens micrometer. DWNTs is inner tube diameter 0.9 - 1.5 nm and outer tube 1.6 - 2.2 nm. We investigate the crystallinity of DWNTs by TEM and Raman spectroscopy. We also found that the Fe-Mo bimetallic catalyst was active as a very efficient catalyst for the synthesis of DWNTs with the catalyst decomposition method. Our results also indicate that Tetra Hydro Furan (THF) is a very ideal carbon source for the synthesis of DWNTs.

• Journal of Magnetics
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• v.19 no.3
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• pp.210-214
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• 2014

The effects of manganese substitution on the crystallographic and magnetic properties of Li-Zn-Cu ferrite, $Li_{0.5}Zn_{0.2}Cu_{0.4}Mn_xFe_{2.1-x}O_4$ ($0.0{\leq}x{\leq}0.8$), were investigated. Ferrites were synthesized via a conventional ceramic method. We confirmed the formation of crystallized particles using X-ray diffraction, field emission scanning electron microscopy and $M{\ddot{o}}ssbauer$ spectroscopy. All of the samples showed a single phase with a spinel structure, and the lattice constants linearly decreased as the substituted manganese content increased, and the particle size of the samples also somewhat decreased as the doped manganese content increased. All the $M{\ddot{o}}ssbauer$ spectra can be fitted with two Zeeman sextets, which are the typical spinel ferrite spectra of $Fe^{3+}$ with A- and B-sites, and one doublet. The cation distribution was determined from the variation of the $M{\ddot{o}}ssbauer$ parameters and of the absorption area ratio. The magnetic behavior of the samples showed that an increase in manganese content led to a decrease in the saturation magnetization, whereas the coercivity was nearly constant throughout. The maximum saturation magnetization was 73.35 emu/g at x = 0.0 in $Li_{0.5}Zn_{0.2}Cu_{0.4}Mn_xFe_{2.1-x}O_4$.

• Bulletin of the Korean Chemical Society
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• v.29 no.4
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• pp.799-804
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• 2008

An amphiphilic diacetylene compound was deposited on the surface of nano sized magnetite particles ($Fe_3O_4$) using a self-assembly method. The diacetylene molecular assembly formed on the surface of nanoparticle was subjected to photopolymerization. This resulted in the formation of a polymeric assembly on the surface of the nanoparticles in which the adjacent diacetylene molecules were connected through conjugated covalent networks. The presence of immobilized polymer species on the surface of nanoparticles is expected to protect them from agglomeration and ripening, thereby stabilizing their physical properties. In this work, $Fe_3O_4$ nanoparticles were prepared by chemical coprecipitation method and the diacetylene molecule 10,12- pentacosadiynoic acid (PCDA) was anchored to the surface of $Fe_3O_4$ nanoparticles through its carboxylate head group. Irradiation of UV light on the nanoparticles containing immobilized diacetylenes resulted in the formation of a polymeric assembly. Presence of diacetylene molecules on the surface of nanoparticles was confirmed by X-ray photoelectron spectroscopy and FT-IR measurements. Photopolymerization of the diacetylene assembly was detected by UV-Visible spectroscopy. Magnetic properties of the nanoparticles coated with polymeric assembly were investigated with SQUID and magnetic hysteresis showed superparamagnetic behaviors. The results put forward a simple and effective method for achieving polymer coating on the surface of magnetic nanoparticle.