A5066098785- Magnetic Properties and Synthesis of Ferrites
- Multiferroics and related materials
- Magnetic and transport properties of perovskites and related materials
- Advanced Condensed Matter Physics
- Iron oxide chemistry and applications
- Advancements in Battery Materials
- Magnetic properties of thin films
- Magneto-Optical Properties and Applications
- Magnetic Properties of Alloys
- ZnO doping and properties
- Rare-earth and actinide compounds
- Magnetic Properties and Applications
- Electromagnetic wave absorption materials
- Advanced Battery Materials and Technologies
- Characterization and Applications of Magnetic Nanoparticles
- Metallic Glasses and Amorphous Alloys
- Copper-based nanomaterials and applications
- Electronic and Structural Properties of Oxides
- Crystal Structures and Properties
- Transition Metal Oxide Nanomaterials
- Iron-based superconductors research
- High-pressure geophysics and materials
- Ferroelectric and Piezoelectric Materials
- Catalysts for Methane Reforming
- Pigment Synthesis and Properties
Kookmin University
2015-2024
Korea University
2012
Samsung (South Korea)
2006-2011
Bar-Ilan University
2007
University of Stuttgart
2007
Central Electrochemical Research Institute
2007
Konkuk University
2005
Korea Institute of Science and Technology
2004
Johns Hopkins University
1988
Yonsei University
1975-1982
Iron-nitrogen on carbon (Fe-N/C) catalysts have emerged as promising nonprecious metal (NPMCs) for oxygen reduction reaction (ORR) in energy conversion and storage devices. It has been widely suggested that an active site structure Fe-N/C contains Fe-Nx coordination. However, the preparation of high-performance mostly involves a high-temperature pyrolysis step, which generates not only catalytically sites, but also less large iron-based particles. Herein, we report general...
Easy preparation of iron oxide nanoparticles [5- and 11-nm maghemite (γ-Fe2O3) 19-nm magnetite (Fe3O4)] by thermal decomposition Fe(CO)5 in the presence residual oxygen system consecutive aeration were investigated TEM/HRTEM, XRD, Mössbauer spectroscopy. Also, magnetic properties studied SQUID magnetometer optical microscopy. It was suggested that intermediate (before aeration) formed competing processes oxidation crystal growth after Fe(CO)5. At room temperature, aerated 5-nm particles...
New iron-based mixed-polyanion compounds Li(x)Na(4-x)Fe(3)(PO(4))(2)(P(2)O(7)) (x = 0-3) were synthesized, and their crystal structures determined. The new contained three-dimensional (3D)sodium/lithium paths supported by P(2)O(7) pillars in the crystal. First principles calculations identified complex 3D with activation barriers revealed them as fast ionic conductors. reversible electrode operation was found both Li Na cells capacities of one-electron reaction per Fe atom, 140 129 mAh...
Abstract Although layered double hydroxides (LDHs) are extensively investigated for oxygen electrocatalysis, their development is hampered by limited active sites and sluggish reaction kinetics. Here, sulfur mismatch substitution of NiFe–LDH (S–LDH) demonstrated, which in‐situ deposited on nitrogen‐doped graphene (S–LDH/NG). This atomic‐level incorporation leads to the construction tailored topological microstructure modulated electronic structure improved catalytic activity durability...
Thin films with cobalt ferrite layers on thermally oxidized silicon wafers were fabricated by a sol-gel method. Magnetic and structural properties of the investigated an x-ray diffractometer, vibrating sample magnetometer atomic force microscopy. The crystallization temperature for Co thin was determined using Mössbauer spectroscopy. annealed at above 450 °C have only single phase spinel structure without any preferred crystallite orientation. Their rms surface roughness is less than 3 nm...
A novel Fe<sub>5</sub>C<sub>2</sub>@C catalyst bearing small iron carbide particles ∼10 nm in diameter was prepared using a simple thermal treatment of oxalate dihydrate cubes, employed high-temperature Fischer–Tropsch synthesis.
Fischer–Tropsch synthesis (FTS) was carried out over precipitated iron-based catalysts activated by syngas (H2 + CO) with different amounts of CO2 (0%, 20%, 33%, and 50%). The activation using CO2-containing significantly suppressed the production undesired products, CH4 C2–C4 hydrocarbons, but facilitated valuable C5+ hydrocarbons. In particular, in case C19+ target products low-temperature FTS (⩽280 °C), both selectivity productivity showed a great increase an increased inlet content...
Highly activated K-doped Hägg-carbide/charcoal nanocatalyst at K/Fe = 0.075 showed the highest FTY value, best hydrocarbon yield, and a good gasoline selectivity for high-temperature Fischer–Tropsch reaction.
Co–Ti substituted M-type hexagonal barium ferrite nanoparticles BaFe12−2xCoxTixO19 (0⩽x⩽1.0) have been prepared by a sol-gel method. Magnetic and structural properties of the powders were characterized with Mössbauer spectroscopy, vibrating sample magnetometer, x-ray diffraction (XRD), thermogravimetry (TG), differential thermal analysis (DTA). The decomposition amorphous hydroxides in dried precipitate continued until 570 °C, according to TG-DTA analysis. result XRD measurements shows that...
CuFe2O4−xNiO (x = 1, 5, 10, and 20 wt %) nanocomposites have been successfully prepared by a simple combustion method using urea−nitrate precursors. The samples were sintered at different temperatures, namely 600, 800, 1000, 1100 °C, for 5 h to enhance the compound formation phase purity, studied means of XRD patterns. Then °C sample was further characterized its structural (EXAFS, XANES, FT-IR, UV–vis), morphological (SEM, TEM, HRTEM, SAED), electrical (ac conductivity, dielectric constant,...
Ultrafine Co0.9Mn0.1Fe2O4 particles are fabricated by a sol–gel method. Magnetic and structural properties of powders investigated with x-ray diffraction, vibrating samples magnetometer, Mössbauer spectroscopy. Co–Mn ferrite which were fired at above 673 K have only single phase spinel structure behave ferrimagnetically. Powders annealed typical the paramagnetic ferrimagnetic nature, simultaneously. The formation nanocrystallized is confirmed when 623 K. magnetic behavior 823 shows that an...
Although complex metal oxides with tailored compositions are increasingly in demand for applications advanced technologies, their preparation by solution-based routes, which typically low cost and easy to scale up, is challenging. Here, we report high-entropy layered double hydroxides (HE-LDHs) having as precursors oxides. Furthermore, reveal that the ionic radii key factors determining incorporation of cations into hydroxide layers, can contain up 10 different kinds simultaneously a cation...
Ni–Co ferrite has been studied with Mössbauer spectroscopy and x-ray diffraction. The crystal structure for this system is spinel, the lattice constant in accord Vegard’s law. spectra consist of two six-line patterns corresponding to Fe3+ at tetrahedral (A) octahedral (B) sites. Néel temperature increases linearly Ni concentration, suggesting superexchange interacion Ni–O–Fe link stronger than that Co–O–Fe link. It found Debye temperatures A B sites CoFe2O4 NiFe2O4 are be θA=734 K, θB=248...
The amorphous state of ferromagnetic ${\mathrm{Fe}}_{75.4}$${\mathrm{B}}_{14.2}$${\mathrm{Si}}_{10.4}$ and its crystalline phases after crystallization have been studied by M\"ossbauer spectroscopy magnetic-moment measurements. average hyperfine field ${H}_{\mathrm{hf}}(T)$ the shows a temperature dependence...
Piezoelectric and ferrimagnetic AFeO3 (A=Ga,Al) samples have been prepared by various annealing conditions then their hyperfine structures investigated x-ray diffraction Mössbauer spectroscopy. From the analysis of patterns Rietveld refinement method, crystal structure was found to be an orthorhombic (Pc21n,Pna21) with four different cation sites which are labeled A1 A2 (predominantly occupied gallium aluminum ions) Fe1 Fe2 Fe ion). The is not changed between samples, but occupancies ions in...
Y-type barium hexaferrite is attractive material for various applications, such as high frequency antennas and RF devices, because of its interesting magnetic properties. Especially, Ni substituted Y- type hexaferrites have higher ordering temperature than other Y-type. We investigated macroscopic microscopic properties hexaferrite. Ba2Co2−xNixFe12O22 (x = 0, 0.5, 1.0, 1.5, 2.0) samples are prepared by solid-state reaction method studied X-ray diffraction (XRD), vibrating sample...