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초상자성 코발트 페라이트 나노입자에 대한 자화 및 자기엔트로피 변화
안양규(Yangkyu Ahn),최은정(Eun Jung Choi) 한국자기학회 2008 韓國磁氣學會誌 Vol.18 No.2
In order to the magnetization and magnetic entropy change for superparamagnetic ferrite nanoparticles, ultrafine cobalt ferrite particles were synthesized using a mircoemulsion method. The peak of X-ray diffraction pattern corresponds to a cubic spinel structure with the lattice constant 8.40Å. The average particle size, determined from X-ray diffraction line-broadening using Scherrer's, is 7.9 ㎚. The maximal magnetizations measured at 5 and 300 K are 24.3 emu/g and 17.2 emu/g, respectively. Superparamagnetic behavior of the sample is confirmed by the coincidence of the M vs. H/T plots at various temperatures. According to the thermodynamic theory, magnetic entropy change decreases with increasing temperature.
조준희(Jun Hee Cho),고상길(Sang Gil Ko),안양규(Yangkyu Ahn),송기창(Ki-Chang Song),최은정(Eun Jung Choi) 한국자기학회 2006 韓國磁氣學會誌 Vol.16 No.3
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 = [H₂O]/[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.
생분해성 고분자(PLGA)로 캡슐화한 Magnetite 나노입자의 제조
이호석(Ho Seok Lee),정일엽(Il Yeop Choung),송기창(Ki Chang Song),안양규(Yangkyu Ahn),최은정(Eun Chung Choi) 한국자기학회 2006 韓國磁氣學會誌 Vol.16 No.1
Magnetite nanoparticles encapsulated with biodegradable polymer [poly(D,L-lactide-co-glycolide), PLGA] were prepared by an emulsification-diffusion method. To investigate the effect of type of organic solvents on the mean particle sizes of obtained composite particles, different organic solvents [ethyl acetate (EA), propylene carbonate (PC) and acetone (ACE)] were used with a stabilizer [didodecyl dimethyl ammonium bromide (DMAB)]. The particle size of nanoparticles was observed by the dynamic light scattering method. When EA and PC as partially water-soluble solvents were used, small composite nanoparticles below 80 ㎚ were obtained, while large composite nanoparticles above 330 ㎚ were prepared for ACE as a fully water-soluble solvent.
의학적 응용을 위한 생체 고분자로 피복 된 자성 나노 입자와 미소구체의 제조
고상길(Sang Gil Ko),조준희(Jun Hee Cho),안양규(Yangkyu Ahn),송기창(Ki-Chang Song),최은정(Eun Jung Choi) 한국자기학회 2006 韓國磁氣學會誌 Vol.16 No.4
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 β-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.
조준희(Jun Hee Cho),고상길(Sang Gil Ko),안양규(Yangkyu Ahn),송기창(Ki-Chang Song),최은정(Eun Jung Choi) 한국자기학회 2006 韓國磁氣學會誌 Vol.16 No.1
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 (Fe₃O₄) nanoparticles using chemical coprecipitation technique with sodium oleate as surfactant. Nanoparticle size can be varied from 2 to 8 ㎚ 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 force 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.
조준희(Jun Hee Cho),고상길(Sang Kil Ko),이환(Hwan Lee),안양규(Yangkyu Ahn),송기창(Ki Chang Song),최은정(Eun Jung Choi) 한국자기학회 2006 韓國磁氣學會誌 Vol.16 No.1
In order to investigate the dependence of the particle size on the cation distribution in the spinel structure, Mossbauer spectra were taken in the presence of an external magnetic field for the magnetic nanoparticles prepared by using a microemulsion method. The crystals are found to have a cubic structure. The results show that as the particle sizes decrease, Fe³+ ions migrate from the octahedral site to tetrahedral site.
나노 크기의 마그네타이트 입자를 이용한 자성 키토산 미소구체의 제조
고상길(Sang Gil Ko),조준희(Jun Hee Cho),안양규(Yangkyu Ahn),송기창(Ki-Chang Song),최은정(Eun Jung Choi) 한국자기학회 2006 韓國磁氣學會誌 Vol.16 No.1
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 (Fe₃O₄) nanoparticles using chemical coprecipitation technique with sodium oleate as surfactant. Nanoparticle size can be varied from 1.2 to 7.4 ㎚ 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 oleatecoated magnetite suspension using spray method. The surface, and the 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.
안양규,김인회 建陽大學校 1997 建陽論叢 Vol.- No.5
Properties of colloidal suspension of magnetic fluids for a speaker damper have been investigated by means of transmission electron microscopy, infrared spectroscopy, mass spectrometry and other chemical techniques. The magnetic particles are made of magnetite and coated with oleic acid. The diameters of magnetic particles without surfactants obtained 6 nm to 20 nm. One of three samples has an average grain size of 11nm, and the others have 15nm. The IR and GC/MS data analysis indicates that the fine magnetic particles coated with oleic acid are suspended in a mixed organic carrier. The oil carrier is consist of the mixed long chained hydrocarbon compounds such as spindle oil. The most significant observation was that two samples of three magnetic fluids have small quantities of hevy oils to increase viscosity ; the one has Vanlube 81 and the other have 28-nor-17beta(H)-Hopane and (E)-4-(2', 6', 6' - Trimethy-1'-cyclohexen-1'-yl)-3-peten-2-one.
Magnetization study of nanosize CoFe₂O₄particles prepared by a microemulsion method
Ahn, Yangkyu,Choi, Eun Jung 建陽大學校 2000 建陽論叢 Vol.- No.8
Nanosize CoFe₂O₄particles prepared by a microemulsion method have been investigated by X-ray diffractometry, transmission electron microscopy and SQUID magnetometry. All peaks of X-ray diffraction patterns correspond to a cubic spinel structure with the lattice constant a0=8.397Å. The average size of the particles, determined by transmission electron microscopy, is 49 Å. The coercivity and the maximal magnetization measured at 5 K in an applied magnetic field of 50 kOe is 15.1 kOe and 15.2 emu/g, respectively. In the same field of 50 kOe, the measured blocking temperature is about 35 K. Superparamagnetic behavior of these particles at room temperature is confirmed by the coincidence of the magnetization (M) versus an applied magnetic field(H/T) plots for different temperatures.