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    Wyświetlanie 1-5 z 5
    Tytuł:
    Effect of Deformation Temperature on the Magnetic Properties of PrFeB Alloy Fabricated by Gas Atomization
    Autorzy:
    Cho, Ju-Young
    Song, Myung-Suk
    Choa, Yong-Ho
    Kim, Taek-Soo
    Powiązania:
    https://bibliotekanauki.pl/articles/2049154.pdf
    Data publikacji:
    2021
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    PrFeB alloy
    gas atomization
    plastic deformation
    rolling
    REFeB magnet
    Opis:
    To form the fine micro-structures, the Pr17Fe78B5 magnet powders were produced in the optimized gas atomization conditions and it was investigated that the formation of the textures, microstructures, and the changes in the magnetic properties with increasing the deformation temperatures and rolling directions. Due to the rapid cooling system than the casting process, the homogenous microstructures were composed of the Pr-rich and Pr2Fe14B without any oxides and α-Fe and enables grain refinement. The pore ratios were 2.87, 1.42, and 0.22% at the deformation temperatures of 600, 700, 800°C, respectively in the rolled samples to align the c-axis which is the magnetic easy axis. Because Pr-rich phase cannot flow into the pore with a liquid state at low temperature, the improvement of pore densification was gradually observed with increasing deformation temperature. To confirm the magnetic decoupling effects of Pr2Fe14B phases by Pr-rich phases, the magnetic properties were investigated in rolled samples produced at the deformation temperature of 800°C. Although the remanent field is slightly decreased by 30%, the coercivity fields increased by about 2 times than that previous casted ingot. It is suggested that the gas atomization method can be suitable for fabricating grain refined and pure PrFeB magnets, and the plastic deformation conditions and rolling directions are a critical role to manipulate microstructure and magnetic properties.
    Źródło:
    Archives of Metallurgy and Materials; 2021, 66, 4; 955-958
    1733-3490
    Pojawia się w:
    Archives of Metallurgy and Materials
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Effect of Powder Size on the Microstructure and Magnetic Properties of Nd-Fe-B Magnet Alloy
    Autorzy:
    Cho, Ju-Young
    Abbas, Sardar Farhat
    Choa, Yong-Ho
    Kim, Taek-Soo
    Powiązania:
    https://bibliotekanauki.pl/articles/353634.pdf
    Data publikacji:
    2019
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    Nd-Fe-B
    gas atomization
    powder size
    crystal orientation
    hot deformation
    Opis:
    Rare earth Nd-Fe-B, a widely used magnet composition, was synthesized in a shape of powders using gas atomization, a rapid solidification based process. The microstructure and properties were investigated in accordance with solidification rate and densification. Detailed microstructural characterization was performed by using scanning electron microscope (SEM) and the structural properties were measured by using X-ray diffraction. Iron in the form of α-Fe phase was observed in powder of about 30 μm. It was expected that fraction of Nd2 Fe14 B phase increased rapidly with decrease in powder size, on the other hand that of α-Fe phase was decreased. Nd-rich phase diffused from grain boundary to particle boundary after hot deformation due to capillary action. The coercivity of the alloy decreased with increase in powder size. After hot deformation, Nd2 Fe14 B phase tend to align to c-axis.
    Źródło:
    Archives of Metallurgy and Materials; 2019, 64, 2; 623-626
    1733-3490
    Pojawia się w:
    Archives of Metallurgy and Materials
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Effect of Temperature on the Plastic Deformability of Gas Atomized NdFeB Anisotropic Magnets
    Autorzy:
    Cho, Ju-Young
    Choa, Yong-Ho
    Nam, Sun-Woo
    Rasheed, Mohammad Zarar
    Kim, Taek-Soo
    Powiązania:
    https://bibliotekanauki.pl/articles/351923.pdf
    Data publikacji:
    2020
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    NdFeB permanent magnet
    stoichiometric composition
    gas atomization
    plastic deformability
    crystal orientation
    Opis:
    NdFeB anisotropic sintered permanent magnets are typically fabricated by strip casting or melt spinning. In this study, the plastic deformability of an NdFeB alloy was investigated to study the possibility of fabricating anisotropic sintered magnets using gas atomized powders. The results show that the stoichiometric composition Nd12Fe82B6 softens at high temperatures. The aspect ratio and orientation factor of Nd12Fe82B6 billets after plastic deformation were found to increase with increasing plastic deformation temperature, particularly above 800°C. This confirms that softening at high temperatures can lead to plastic deformation of Nd2Fe14B hard magnetic phases.
    Źródło:
    Archives of Metallurgy and Materials; 2020, 65, 4; 1293-1296
    1733-3490
    Pojawia się w:
    Archives of Metallurgy and Materials
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Morphology Control of One-Dimensional Gallium Nitride Nanostructures by Modulating the Crystallinity of Sacrificial Gallium Oxide Templates
    Autorzy:
    Ko, Yun Taek
    Park, Mijeong
    Park, Jingyeong
    Moon, Jaeyun
    Choa, Yong-Ho
    Lee, Young-In
    Powiązania:
    https://bibliotekanauki.pl/articles/2049246.pdf
    Data publikacji:
    2021
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    GaN
    nanofiber
    nanotube
    electrospinning
    chemical transformation
    Opis:
    In this study, we demonstrated a method of controllably synthesizing one-dimensional nanostructures having a dense or a hollow structure using fibrous sacrificial templates with tunable crystallinity. The fibrous Ga2O3 templates were prepared by calcining the polymer/gallium precursor nanofiber synthesized by an electrospinning process, and their crystallinity was varied by controlling the calcination temperature from 500°C to 900°C. GaN nanostructures were transformed by nitriding the Ga2O3 nanofibers using NH3 gas. All of the transformed GaN nanostructures maintained a one-dimensional structure well and exhibited a diameter of about 50 nm, but their morphology was clearly distinguished according to the crystallinity of the templates. When the templates having a relatively low crystallinity were used, the transformed GaN showed a hollow nanostructure, and as the crystallinity increased, GaN was converted into a denser nanostructure. This morphological difference can be explained as being caused by the difference in the diffusion rate of Ga depending on the crystallinity of Ga2O3 during the conversion from Ga2O3 to GaN. It is expected that this technique will make possible the tubular nanostructure synthesis of nitride functional nanomaterials.
    Źródło:
    Archives of Metallurgy and Materials; 2021, 66, 3; 709-712
    1733-3490
    Pojawia się w:
    Archives of Metallurgy and Materials
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Control of Nd-Fe-B Morphology as Function of the PVP Concentration Using Electrospinning Process
    Autorzy:
    Eom, Nu Si A.
    Haq, Muhammad Aneeq
    Lee, Jimin
    Lim, Kyoung Mook
    Kim, Taek-Soo
    Choa, Yong-Ho
    Kim, Bum Sung
    Powiązania:
    https://bibliotekanauki.pl/articles/351180.pdf
    Data publikacji:
    2020
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    Nd2Fe14B
    1-D magnet fiber
    electrospinning
    magnet properties
    morphology
    Opis:
    In this study, we demonstrate a facile and cost-effective way to synthesize Nd-Fe-B of various shapes such as powders, rods and fibers using electrospinning, heat-treatment and washing procedures. Initially Nd-Fe-B fibers were fabricated using electrospinning. The as-spun Nd-Fe-B fibers had diameters ranging 489 to 630 nm depending on the PVP concentration in reaction solutions. The different morphologies of the Nd2Fe14B magnetic materials were related to the difference in thickness of the as-spun fibers. The relationships between the as-spun fiber thickness, the final morphology, and magnetic properties were briefly elucidated. The intrinsic coercivity of Nd2Fe14B changed with the change in morphology from powder (3908 Oe) to fiber (4622 Oe). This work demonstrates the effect of the Nd-Fe-B magnetic properties with morphology and can be extended to the experimental design of other magnetic materials.
    Źródło:
    Archives of Metallurgy and Materials; 2020, 65, 3; 993-996
    1733-3490
    Pojawia się w:
    Archives of Metallurgy and Materials
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
      Wyświetlanie 1-5 z 5

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