Visualization of Magnetic Domains in Electrical Steel Using High-Resolution Dark-Field Imaging

김영주,김종열,Daniel Seth Hussey,Oh Youl Kwon,이승욱 대한금속·재료학회 2019 대한금속·재료학회지 Vol.57 No.6

Electrical steel is a soft magnetic steel material used in electric devices such as transformers and motors. The performance of these electric devices is primarily related to the magnetic properties of electrical steel, and the assessment of the magnetic properties of electrical steel has been considered an important topic. We use neutron grating interferometry, which is an imaging technique for visualizing the magnetic domain of electrical steel as the evaluation of magnetic properties. The dark-field image provided by neutron grating interferometry shows a sensitive contrast with respect to the magnetic domain of electrical steel due to the small angle neutron scattering generated at the domain wall. The Talbot-Lau interferometer was installed, and the feasibility test of high-resolution dark-field imaging was conducted at cold neutron imaging beamline of the NIST Center for Neutron Research. The dark-field image of electrical steel was compared with the magnetic domain image observed by the Bitter pattern based on the magnetic powder method to prove the validity of neutron grating interferometry. The dark-field image visualizes the magnetic domains of electrical steel, more detailed domain walls regardless of laser-irradiated lines than Bitter pattern result.

Electrical Properties of a High Tc Superconductor for Renewed Electric Power Energy

Sang-Heon Lee 대한전기학회 2006 Journal of Electrical Engineering & Technology Vol.1 No.3

Effects of Ag₂O doping on the electromagnetic properties in the BiSrCaCuO superconductor. The electromagnetic properties of doped and undoped Ag₂O in the BiSrCaCuO superconductor were evaluated to investigate the contribution of the pinning centers. It was confirmed experimentally that a larger amount of magnetic flux was trapped in the Ag₂O doped sample than in the undoped one, indicating that the pinning centers of magnetic flux are related closely to the occurrence of the magnetic effect. We have fabricated superconductor ceramics by the chemical process. A high Tc superconductor with a nominal composition of Bi₂Sr₂Ca₂Cu₃Oy was prepared by the organic metal salts method. Experimental results suggest that the intermediate phase formed before the formation of the superconductor phase may be the most important factor. The relation between electromagnetic properties of Bi HTS and the external applied magnetic field was studied. The electrical resistance of the superconductor was increased by the application of the external magnetic field. But the increase in the electrical resistance continues even after the removal of the magnetic field. The reason is as follows; the magnetic flux due to the external magnetic field penetrates through the superconductor and the penetrated magnetic flux is trapped after the removal of the magnetic flux. During the sintering, doped Ag₂O was converted to Ag particles that were finely dispersed in superconductor samples. It is considered that the area where normal conduction takes place increases by adding Ag₂O and the magnetic flux penetrating through the sample increases. The results suggested that Ag₂O acts to amplify pinning centers of magnetic flux, contributing to the occurrence of the electromagnetic properties.

Electrical Properties of a High Tc Superconductor for Renewed Electric Power Energy

Lee Sang-Heon The Korean Institute of Electrical Engineers 2006 Journal of Electrical Engineering & Technology Vol.1 No.3

Effects of $Ag_2O$ doping on the electromagnetic properties in the BiSrCaCuO superconductor. The electromagnetic properties of doped and undoped $Ag_2O$ in the BiSrCaCuO superconductor were evaluated to investigate the contribution of the pinning centers. It was confirmed experimentally that a larger amount of magnetic flux was trapped in the $Ag_2O$ doped sample than in the undoped one, indicating that the pinning centers of magnetic flux are related closely to the occurrence of the magnetic effect. We have fabricated superconductor ceramics by the chemical process. A high Tc superconductor with a nominal composition of $Bi_2Sr_2Ca_2Cu_3O_y$ was prepared by the organic metal salts method. Experimental results suggest that the intermediate phase formed before the formation of the superconductor phase may be the most important factor. The relation between electromagnetic properties of Bi HTS and the external applied magnetic field was studied. The electrical resistance of the superconductor was increased by the application of the external magnetic field. But the increase in the electrical resistance continues even after the removal of the magnetic field. The reason is as follows; the magnetic flux due to the external magnetic field penetrates through the superconductor and the penetrated magnetic flux is trapped after the removal of the magnetic flux. During the sintering, doped $Ag_2O$ was converted to Ag particles that were finely dispersed in superconductor samples. It is considered that the area where normal conduction takes place increases by adding $Ag_2O$ and the magnetic flux penetrating through the sample increases. The results suggested that $Ag_2O$ acts to amplify pinning centers of magnetic flux, contributing to the occurrence of the electromagnetic properties.

Epitaxial Growth and Electric/Magnetic Properties of a Magneto-electric Cr2O3 Thin Film

Takeshi Yokota,Izuna Tsuboi,Manabu Gomi 한국물리학회 2016 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.68 No.1

We have investigated the epitaxial growth and the electric/magnetic properties of magnetoelectric material: a Cr2O3 thin film. The epitaxial growth mode of Cr2O3 was changed from 2- to 3- dimensional at a temperature around 500 C. Although Cr2O3 is antiferromagnetic, the epitaxial Cr2O3 showed ferromagnetic hysteresis. Because the magnetic behavior showed perpendicular anisotropy, the epitaxial compressive stress is responsible for the ferromagnetic behavior. The film also showed a polarization change even with the application of a small magnetic field. This revealed that the epitaxial stress could affect the magneto-electric properties of Cr2O3.

Investigation of microwave absorbing properties for magnetic nanofiber of polystyrenee-polyvinylpyrrolidone

Seyed Hossein Hosseini,Mahsa Sadeghi 한국물리학회 2014 Current Applied Physics Vol.14 No.7

Aligned magnetic blend of polystyreneepolyvinylpyrrolidone (PSePVP) nanofibers were prepared by this method. First, polystyreneepolyvinylpyrrolidone (PSePVP) blend solution in THF was synthesized. Then magnetic of PSePVPeFe3O4epolyethylene glycol (PEG) was prepared by masking method. Finally, magnetic nanofiber of PSePVPeFe3O4ePEG was prepared by electrospinning method, too. An electric potential difference of 25 kV was applied between the collector and a syringe tip, and the distance between the collector and the tip was 13 cm. Fe3O4 is exhibit various magnetic properties of which the complex permeability and the permittivity, in particular, are important in determining their high frequency characteristics. The magnetic oxide particles and nanofiber of nanometer size were characterized by TEM and SEM respectively. The thermal properties of nanofibers were determined by TGA and DSC. The magnetic characterization of the fibers was also performed by VSM and AFM techniques. On the other hand, nanofiber with diameters ranging from 30 to 40 nm, showing at room temperature, coercive field values of around 25 kV and saturation magnetization was 1.1 emu/g. Microwave reflection loss of the sample was tested at 8e12 GHz microwave frequencies and the results showed that magnetic nanofiber possessed the microwave absorbing properties.

Enhancing the electrical, optical, and magnetic characteristics of DNA thin films through Mn²⁺ fortification

Kesama, Mallikarjuna Reddy,Yun, Byung Kil,Dugasani, Sreekantha Reddy,Jung, Jong Hoon,Park, Sung Ha Elsevier 2018 Colloids and Surfaces B Vol.167 No.-

<P><B>Abstract</B></P> <P>DNA is one of the most propitious biomaterials for use in nanoscience and nanotechnology because of its exceptional characteristics, <I>i.e.</I> self-assembly and sequence-programmability. In this study, we fabricate sequence-designed double-crossover (DX) DNA lattices and naturally available salmon DNA (SDNA) thin films modified with the transition metal ion Mn<SUP>2+</SUP>. Phase transition of DX DNA lattices from crystalline to amorphous form controlled by varying the concentration of Mn<SUP>2+</SUP> is discussed and a critical transition concentration ([Mn<SUP>2+</SUP>]<SUB>C</SUB>) is estimated. In addition, the electrical, optical, and magnetic properties of Mn<SUP>2+</SUP>-modified SDNA thin films including current, absorbance, photoluminescence, the X-ray photoelectron spectrum, and magnetization are studied to understand their conductivity, binding modes, energy transfer characteristics, chemical composition, and magnetism. Interestingly, the physical values such as the maximum current and photoluminescence, and the minimum absorbance, occur at around [Mn<SUP>2+</SUP>]<SUB>C</SUB> =4 mM, which may be due to the optimal incorporation of Mn<SUP>2+</SUP> into the SDNA. The magnetization and susceptibility of SDNA thin films with Mn<SUP>2+</SUP>, served as magnetic dipoles, are studied under different temperature and magnetic field. The magnetization of SDNA thin films with [Mn<SUP>2+</SUP>]<SUB>C</SUB> shows an S-shaped curve, indicating ferromagnetism.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Magnetic ions (Mn2+) intercalated into the DNA thin films have been received significant attention. </LI> <LI> DNA lattices and DNA thin films modified with Mn2+ are fabricated. </LI> <LI> Phase transition of DNA lattices from crystalline to amorphous form controlled by the concentration of Mn2+ is discussed. </LI> <LI> The electrical, optical, and magnetic properties of Mn2+-modified SDNA thin films are studied. </LI> <LI> Due to the optimal incorporation, enhanced physical values occur at around critical concentration of Mn2+. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

고에너지효율 연자성 복합 분말 소재의 연구개발 동향

김휘준(HwiJun Kim) 한국자기학회 2011 韓國磁氣學會誌 Vol.21 No.2

The use of soft magnetic materials have been increasing in the various industrial fields according to the increasing demand for high performance, automatic, miniaturing equipments in the recent our life. In this study, we investigated the effect of factors on the core loss and magnetic properties of electrical steel and soft magnetic composites. Furthermore, we reviewed the major efforts to reduce the core loss and improve the soft magnetic properties in the two main soft magnetic materials. Domain purification which results from reduced density of defects in cleaner electrical steels is combined with large grains to reduce hysteresis loss. The reduced thickness and the high electrical conductivity reduce the eddy current component of loss. Furthermore, the coating applied to the surface of electrical steel and texture control lead to improve high permeability and low core loss. There is an increasing interest in soft magnetic composite materials because of the demand for miniaturization of cores for power electronic applications. The SMC materials have a broad range of potential applications due to the possibility of true 3-D electromagnetic design and higher frequency operation. Grain size, sintering temperature, and the degree of porosity need to be carefully controlled in order to optimize structure-sensitive properties such as maximum permeability and low coercive force. The insulating coating on the powder particles in SMCs eliminates particle-toparticle eddy current paths hence minimizing eddy current losses, but it reduces the permeability and to a small extent the saturation magnetization. The combination of new chemical composition with optimum powder manufacturing processes will be able to result in improving the magnetic properties in soft magnetic composite materials, too.

Magnetic-field-tuned Insulator to Conductor Transition in Magnetorheological Suspension

Xiongbo Yang,Yuhuan Jiang,Yuehua Huang,Ruizhen Xu,Hongguang Piao,Gaomeng Jia,Xinyu Tan 한국자기학회 2014 Journal of Magnetics Vol.19 No.4

Magnetorheological suspensions (MRSs) are smart materials that have the potential to revolutionize several industrial sectors because of their special rheological behaviors. In this paper, MRS, based on carbonyl iron (CI) microparticles that were dispersed in silicone oil with oleic acid, were prepared. We showed that the electroconductibility of MRS was significantly influenced by the intensity of the external magnetic field that was applied. The resistance value can vary from infinite to below 300 Ω after applying an external magnetic field. The results indicated that this MRS had the property of magnetic-field-tuned insulator to conductor transition. This system has potential applications in controllable MRS electrical devices.

Tetragonal-structural changes influenced the magnetic and ferroelectric properties of (Y, Fe)-codoped BaTiO3 ceramics

Choi Y.J.,Kim S.W.,Phan T.L.,Lee B.W.,Yang D.S. 한국물리학회 2023 Current Applied Physics Vol.53 No.-

We present a detailed study on the structural characterization, electronic structure, and magnetic/electric-polarization properties of Ba1-xYxTi1-xFexO3 (BYxTFxO, x = 0–0.1) ceramic samples. These samples mainly crystalized in a tetragonal structure, and a small amount of a YFeO3-related secondary phase constituted as x ≥ 0.08. With increasing x, the lattice constant a increases while c decreases. Such structural changes reduce rapidly the intensity of characteristic Raman modes. Magnetization data have proved all BYxTFxO samples exhibiting ferromagnetism at room temperature. Both the saturation magnetization and coercivity tend to increase with increasing x. This is ascribed to an enhanced exchange interaction between Fe3+ ions, and the YFeO3-phase formation. Herein, the Fe3+ presence has been confirmed upon analyzing X-ray absorption spectra. Though all the samples exhibit ferroelectricity, the electric-polarization slightly decreases with increasing x. This is associated with an increased symmetry due to the changes in the lattice parameters towards the cubic structure.

Synthesis and Characterization of Magnetic of Ni/ABS Nanocomposites by Electrical Explosion of Wire in Liquid and Solution Blending Methods

Minh-Thuyet Nguyen,Hong-Hai Nguyen,김원주,김호윤,김진천 대한금속·재료학회 2017 METALS AND MATERIALS International Vol.23 No.2

Nanomaterials have attracted great attention from chemists, physicists and materials scientists because oftheir application benefits and special properties. Thermoplastics have been used in many applications suchas molding of non-electrical components, conducting, magnetic field and 3D printing. Nanocomposites areknown as a material which blends the best properties of components, a high performance material exhibitsunusual property combinations and unique design possibilities. In this research, we focused to investigate andreport primary results in the synthesis of magnetic nanocomposites based on acrylonitrile butadiene styrene(ABS), which are useful and important thermoplastics. Nickel nanopowder was prepared by electrical explosionof wire in a liquid were used as magnetic component. The composites were prepared by following steps, firstthe obtained Ni nanopowders were incorporated into the ABS matrix via a solution blending method (drop-casting),and then the solvent was evaporated. The characterizations of obtaining composites were analyzed byfield emission scanning electron microscopy, X-Ray Diffraction analysis and vibrating sample magnetometer.