• Journal of the Korean Magnetics Society
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• v.16 no.3
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• pp.163-167
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• 2006

Ultrasonic irradiation in a solution during the chemical reaction may accelerate the rate of the reaction and the crystallization at low temperature. We have synthesized nanometer sized magnetite particles using coprecipitation method, sonochemical method without surfactant, and sonochemical method with surfactant, in order to investigate the effect of ultrasonic irradiation and surfactant on the coprecipitates of metal ions. The size of the magnetite nanoparticles prepared by coprecipitation method, and sonochemical method without surfactant showed broad distributions. But we got uniform nanoparticles using a sonochemical method with oleic acid. The average size of the particles can be controlled by the ratio $R=[H_2O]/[surfactant]$. The size of the magnetite nanoparticles prepared by this method showed narrow distributions. We have characterized the nanoparticles using an X-ray diffraction (XRD), a superconducting quantum interference device (SQUID), and atomic force microscope (AFM). The size and distribution of the magnetite nanoparticles were measured by dynamic light scattering (DLS) method.

• Journal of Powder Materials
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• v.22 no.1
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• pp.39-45
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• 2015

In this study, cobalt nanopowder is fabricated by sonochemical polyol synthesis and magnetic separation method. First, sonochemical polyol synthesis is carried out at $220^{\circ}C$ for up to 120 minutes in diethylene glycol ($C_4H_{10}O_3$). As a result, when sonochemical polyol synthesis is performed for 50 minutes, most of the cobalt precursor ($Co(OH)_2$) is reduced to spherical cobalt nanopowder of approximately 100 nm. In particular, aggregation and growth of cobalt particles are effectively suppressed as compared to common polyol synthesis. Furthermore, in order to obtain finer cobalt nanopowder, magnetic separation method using magnetic property of cobalt is introduced at an early reduction stage of sonochemical polyol synthesis when cobalt and cobalt precursor coexist. Finally, spherical cobalt nanopowder having an average particle size of 22 nm is successfully separated.

• Journal of Korean Society on Water Environment
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• v.18 no.3
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• pp.271-282
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• 2002

The sonochemical process has been applied as a treatment method to investigate its effect on the decomposition of humic substances (HS). The reaction kinetics and mechanisms in the process of sonochemical treatment for humic substances in wastewater have also been discussed. It was observed that the metal ions such Fe(II) and Mn(II) showed catalytic effects, while Al(III), Ca(II), and Mg(II) had inhibitory effects on the decomposition of humic substances in sonochemical reaction with hydrogen peroxide. Experimental results also showed factors such as hydrogen peroxide dose affected the formation of disinfection by-products. Two trihalomethanes, chloroform and dichlorobromomethane were formed as major disinfection by-products during chlorination. The depolymerization and the radical reaction of HS radicals appear to occur simultaneously. The final step of the reaction is the conversion of organic acids to carbon dioxide.

• Environmental Sciences Bulletin of The Korean Environmental Sciences Society
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• v.10 no.S_3
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• pp.127-137
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• 2001

The sonochemical Process has been applied as a treatment method and was investigated its effect on the decomposition of humic substances(HS). The reaction kinetics and mechanisms in the Process of sonochemical treatment for humic substances(HS) in wastewater have also been discussed. It was observed that the metal ions such as Fe(II) and Mn(II) showed catalytic effects, while Al(III), Ca(II), and Mg(II) had inhibitory effects on the decomposition of humic substances in sonochemical reaction with hydrogen peroxide. Experimental results also showed factors such as hydrogen peroxide dose affected the formation of disinfection by-products. Two trihalomethanes, chloroform and dichlorobromomethane were formed as major disinfection by-products during chlorination. The mechanism of radical reaction is controlled by an oxidation process. The radicals are so reactive that most of them are consumed by HS radicals and hydroxyl radicals can be acted on organic solutes by hydroxyl addition, hydrogen abstraction, and electron transfer. The depolymerization and the radical reaction of HS radicals appear to occur simultaneously. The final steps of the reaction are the conversion of organic acids to carbon dioxide.

• Proceedings of the Materials Research Society of Korea Conference
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• 2005.05a
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• pp.198-198
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• 2005

• Journal of the Korean Ceramic Society
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• v.52 no.6
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• pp.489-496
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• 2015

In this study, novel $Ag_2Se$ sensitized $TiO_2$ nanocomposites were prepared by facile sonochemical assisted synthesis method. The as-prepared products were characterized by X-ray diffraction (XRD), Scanning electron microscopy (SEM) with energy dispersive X-ray (EDX) analysis, transmission electron microscopy (TEM), and N2 adsorption BET analysis. The as-prepared $Ag_2Se/TiO_2$ nanocomposites simultaneously possessed great adsorptivity for organic dyes and efficient charge separation properties. In the decolorization of rhodamine B, a significant enhancement in the reaction rate was observed for the $Ag_2Se/TiO_2$ nanocomposite compared to the cases of using pure P25 or $TiO_2$. The sonocatalysis activity was higher due to the greater formation of reactive radicals, as well as to the increase of the active surface area of the $Ag_2Se/TiO_2$ nanocomposite.

• Journal of Magnetics
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• v.14 no.3
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• pp.124-128
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• 2009

Magnetic nanoparticles were synthesized by using the sonochemical method with oleic acid as a surfactant. The average size of the magnetite nanoparticles was controlled by varying the ratio R=[$H_2O$]/[surfactant] in the range of 2 to 9 nm. To prepare chitosan-coated magnetite nanoparticles, chitosan solution was added to a magnetite colloid suspension under ultrasonication at room temperature for 20 min. The chitosan-coated magnetite nanoparticles were characterized by several techniques. Atomic force microscopy (AFM) was used to image the chitosan-coated nanoparticles. Magnetic hysteresis measurement was performed by using a superconducting quantum interference device (SQUID) magnetometer to investigate the magnetic properties of the magnetite nanoparticles and the chitosan-coated magnetite nanoparticles. The SQUID measurements revealed the superparamagnetism of both nanoparticles. The T1- and T2-weighted MR images of these chitosan-coated magnetite colloidal suspensions were obtained with a 4.7 T magnetic resonance imaging (MRI) system. The chitosancoated magnetite colloidal suspensions exhibited enhanced MRI contrasts in vitro.

• Journal of Soil and Groundwater Environment
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• v.22 no.5
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• pp.40-47
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• 2017

The effects of ultrasound in heterogeneous system were investigated in three kinds of ultrasonic systems including a bath-type system (System #1), a double-bath-type system (System #2), and a double-bath-type system partly filled with glass beads (System #3). The ultrasound energy and its attenuation were quantified using calorimetry and the sound pressure measurement method. The sonochemical effects mainly involved in radical oxidation reactions were quantified using KI dosimetry. It was found that ultrasound energy was significantly attenuated in System #2 and #3 due to the presence of solid materials such as a submerged stainless steel reactor and glass beads. However, in spite of low ultrasound energy status, sonochemical oxidation reactions occurred more violently due to the presence of glass beads in System #3. In addition, calorimetry was more adequate to estimate the total energy status of ultrasound in sonoreactors compared to the sound pressure measurement method.

• Journal of Magnetics
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• v.15 no.3
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• pp.112-115
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• 2010

We have investigated a surfactant-assisted sonochemical approach to produce monodisperse $Fe_3O_4$ nanoparticles (NPs). The non-ionic surfactant Igepal CO-520 (Poly(oxyethylene)(5) nonylphenyl ether) has been used for the preparation of NPs and the effects on the NP size, size distribution, and magnetic properties have been studied. The $Fe_3O_4$ NPs were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), and vibrating sample magnetometry (VSM). The results reveal that the NPs prepared by a Igepal CO-520-assisted sonochemical method exhibit a narrow range of size distributions and a high monodispersity compared to the NPs from the conventional sonochemical method. The analysis of NPs prepared in the presence of the surfactant suggested that it could be used not only as a protector to prevent the oxidation of Fe (II), but also as a controller to vary the size of the NPs.

• Proceedings of the Korean Magnestics Society Conference
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• 2003.06a
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• pp.82-83
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• 2003