Sung yong An

Nano-scale Inter-lamellar Structure of Metal Powder Composites for High Performance Power Inductor and Motor Applications

The unique nano-scale inter-lamellar microstructure and unparalleled heat treatment process give our developed metal powder composite its outstanding magnetic property for power inductor & motor applications. Compared to the conventional polycrystalline Fe or amorphous Fe-Cr-Si-B alloys, our unique designed interlamellar microstructure strongly decreases the intra-particle eddy current loss at high frequencies by blocking the mutual eddy currents. The combination of optimum permeability, magnetic flux and extremely low core loss makes this powder composite suitable for high frequency applications well above 10 MHz. Moreover, it can be also possible to SMC core for high speed motor applications in order to increase the motor efficiency by decreasing the core loss.

The effect of precursor types on the magnetic properties of Y-type hexa-ferrite composite

With magnetic composite including uniform magnetic particles, we expect to realize good high-frequency soft magnetic properties. We produced needle-like (α-FeOOH) nanoparticles with nearly uniform diameter and length of 20 and 500 nm. Zn-doped Y-type hexa-ferrite samples were prepared by solid state reaction method using the uniform goethite and non-uniform hematite (Fe2O3) with size of <1 μm, respectively. The micrographs observed by scanning electron microscopy show that more uniform hexagonal plates are observed in ZYG-sample (Zn-doped Y-type hexa-ferrite prepared with non-uniform hematite) than in ZYH-sample (Zn-doped Y-type hexa-ferrite prepared with uniform goethite). The permeability (μ′) and loss tangent (δ) at 2 GHz are 2.31 and 0.07 in ZYG-sample and 2.0 and 0.07 in ZYH sample, respectively. We can observe that permeability and loss tangent are strongly related to the particle size and uniformity based on the nucleation, growth, and two magnetizing mechanisms: spin rotation and domain wall motio...

M-Zn (M = Sb, V, and Nb) Substituted Strontium Hexaferrites with Enhanced Saturation Magnetization for Permanent Magnet Applications

M-Zn (M = Sb, V, Nb) substituted M-type strontium hexaferrites were prepared by a ceramic method. The phase composition, morphology and magnetic properties were studied by x-ray diffractometry, scanning electron microscopy and vibrating sample magnetometry. Saturation magnetization increases with a substitution up to 75.0 emu/g (2.5 % higher compared to unsubstituted hexaferrite) and then decreases with a further substitution. A coercive field of substituted hexaferrite powders with highest saturation magnetization is more than 3 kOe. Substituted strontium hexaferrite powders prepared in this work are a rare example of high M S compositions without doping rare-earth elements and would be a promising candidate for a permanent magnet application.

Synthesis and Magnetic Properties of LiFeO2 Powders by a Sol-Gel Method

Ordered LiFeO2 powders were prepared by the sol-gel method. The crystal structures were measured by X-ray diffraction (XRD). Thermal analysis such as thermogravimetry analysis (TGA) and differential thermal analysis (DTA) were performed on the dried powder obtained from the LiFeO2 precursor solution. The particle morphology of the samples was observed using a scanning electron microscope (SEM). Magnetic properties were measured using a vibrating sample magnetometer (VSM). Mossbauer spectra of 57Fe at room temperature for LiFeO2 powders are shown paramagnetic behavior as demonstrated by the single quadrupole doublet with zero hyperfine fields.