• Bulletin of the Korean Chemical Society
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• v.22 no.10
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• pp.1111-1119
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• 2001

• Journal of the Korean Chemical Society
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• v.33 no.3
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• pp.326-331
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• 1989

Superconducting fiber of high Tc $YBa_2Cu_3O_{7-{\sigma}}$ was successfully prepared by the sol-gel method. The stoichiometric mixture of Y, Ba and Cu nitrates was dissolved in water, to which citric acid solution was added. Then ammonium hydroxide was added to the mixture in order to increase the pH to a value between 5.8 and 6.2. The mixture was heated carefully to form a homogeneous colloid sol at 358 K. The solution was viscous enough to draw a long gel fiber, which was then heated at 1223K for 8 hrs. under oxygen partial pressure of $Po_2$ = 1 atm., cooled slowly and annealed at 723K for 13 hrs.. The reacted superconducting sample maintained a fiber form with some shrinkage of its volume. The superconducting transition temperatures (Tc, onset and Tc, offset) of $YBa_2Cu_3O_{7-{\sigma}}$ have been determined to be approximately 95K and 82K, respectively. The superconducting phase was also confirmed by Meissner effect at liquid nitrogen boiling temperature.

• 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 the Korean Magnetics Society
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• v.16 no.4
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• pp.221-227
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• 2006

We have synthesized uniform nanometer sized magnetite particles using chemical coprecipitation technique through a sonochemical method with surfactant such as oleic acid. Magnetite phase nanoparticles could be observed from X-ray diffraction. Magnetite nanoparticles is surface phase morphology and biopolymer-microspheres for Application Medical. Magnetite nanoparticles coated biopolymer. Atomic Force Microscope (AFM) was used to image the coated nanoparticles. Magnetic colloid suspensions containing particles with sodium oleate, chitosan and $\beta$-glucan have been prepared. The morphology of the magnetic biopolymer microsphere particles were characterized using optical microscope. Magnetic hysteresis measurement were performed using a superconducting quantum interference device (SQUID) magnetometer at room temperature to investigate the magnetic properties of the biopolymer microspheres and magnetite coated biopolymer including magnetite nanoparticles. Magnetic Resonance (MR) imaging was used to investigate biopolymer coated nanoparticles and biopolymer microspheres.

• Journal of the Korean Magnetics Society
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• v.16 no.1
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• pp.66-70
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• 2006

Magnetite nanoparticles, which have been extensively used in many fields, were encapsulated with a natural polymer, chitosan, to improve their biocompatibility. We have synthesized magnetite $(Fe_3C_4)$ nanoparticles using chemical coprecipitation technique with sodium oleate as surfactant. Nanoparticle size can be varied from 1.2 to 7.4nm by controlling the sodium oleate concentration. Magnetite phase nanoparticles could be observed from X-ray diffraction. Magnetic colloid suspensions containing particles with sodium oleate and chitosan have been prepared. High magnetic property chitosan-microsphere particles were prepared from oleate-coated magnetite suspension using spray method. The surftce, and tile morphology of the magnetic chitosan microsphere particles were characterized using optical microscope and scanning electron microscope. Magnetic hysteresis measurement were performed using a superconducting quantum interference device (SQUID) magnetometer at room temperature to investigate the magnetic properties of the chitosan microspheres including magnetite nanoparticles. The SQUID measurements revealed superparamagnetism of nanoparticles.

• Journal of the Korean Magnetics Society
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• v.16 no.1
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• pp.102-106
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• 2006

Magnetic nanoparticles can be used for a variety of biomedical applications. They can be used in the targeted delivery of therapeutic agents in vivo, in the hyperthermic treatment of cancers. in magnetic resonance (MR) imaging as contrast agents and in the biomagnetic separations of biomolecules. We have synthesized magnetite $(Fe_3O_4)$ nanoparticles using chemical coprecipitation technique with sodium oleate as surfactant. Nanoparticle size can be varied from 2 to 8nm by controlling the sodium oleate concentration. Magnetite phase nanoparticles could be observed from X-ray diffraction. Magnetic colloid suspensions containing particles with sodium oleate and chitosan have been prepared. Nanoparticles, both oleate-coated and chitosan-coated, have been characterized by several techniques. Atomic farce microscope (AFM) was used to image the coated nanoparticles. Magnetic hysteresis measurement were performed using a superconducting quantum interference device (SQUID) magnetometer at room temperature to investigate the magnetic properties of the magnetite nanoparticles. The SQUID measurements revealed superparamagnetism of nanoparticles.