• Title/Summary/Keyword: fcc 상변태

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Characterization of FePtN Nano-particles Synthesized by Thermal Decomposition and Mixed-gas Nitrification (열분해법과 혼합가스 질화법으로 합성한 FePtN 나노 입자의 특성)

  • Oh, Young Woo
    • Journal of the Korean Magnetics Society
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    • v.26 no.4
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    • pp.129-132
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    • 2016
  • The effect of thermal-nitrification on L1o transfomation in nano-sized FePt particles was studied. As-synthesized FePt nanoparticles by thermal decomposition method have fcc structured phase and their Hc and Ms were 247.34 Oe and 27.308 emu/g, respectively. According to the XRD analysis, phase transformation from fcc (face centered cubic) to fct (face centered tetragonal) structure was revealed by heating under $NH_3+H_2$ mixed-gas atmosphere. Also a slight shift of each (111) peak indicated phase transformation from fcc to fct structure. Hc and Ms of fct FePtN were 1058.2 Oe and 32.718 emu/g, respectively. The nano-sized FePtN magnetic particles synthesized by thermal decomposition method and mixed-gas nitrification are expected for advanced applications such as high density magnetic recording media and biomedical materials.

New Magnetic Phases of Fe-N and Mn-Al Alloys Produced by Mechanochemical Milling (기계적 밀링 및 화학적 추출법에 의해 제조한 Fe-N 및 Mn-Al계의 새로운 자성재료)

  • Kyu-Jin Kim;Tae-Hwan Noh;Kenji Suzuki
    • Journal of the Korean Magnetics Society
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    • v.4 no.4
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    • pp.347-354
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    • 1994
  • The structural change and magnetic properties of mechanically milled Fe-N and Mn-Al alloy powders have been investigated by XRD, TEM, VSM, $M\"{o}ssbauer$ spectroscopy and inelastic neutron scattering measurements. During milling of ${\gamma}'-Fe_{4}N$ powders, and fcc ${\gamma}'-Fe_{4}N$ phase is transformed to a bct ${\alpha}'-Fe(N)$ phase by stress-induced martensitic transformation, being accompanied by an initial increase in saturation magnetization. During annealing the bct ${\alpha}'-Fe(N)$ nanocrystalline phase which is obtained by mechanical grinding for a long time, an ${\alpha}'-Fe_{16}N_{2}$ phase partially appears as an intermediate phase at 673~773 K, causing an increase in saturation magnetization. During milling of Mn-45, 70 and 85 at.% Al mixed powders, Al atoms are partially solubilized into an ${\alpha}-Mn$ phase. The Al supersaturated ${\alpha}-Mn-type$ phases change from paramagnetic to ferromagnetic : the saturation magnetization is 11 emu/g for the as-milled Mn-70 at.% Al powders. Moreover, by removing almost all Al atoms from the as-milled Mn-85 at.% Al powders using chemical leaching, the saturation magnetization increases up to 36 emu/g. The above bct ${\alpha}'-Fe(N)$ and ferromagnetic ${\alpha}-Mn$ type alloys are the magnetic materials found for the first time, by using the present mechanochemical process.

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The Processing and Characterization of Sol-Gel Derived Ferroelectric PMN Powders and Thin Films (졸-겔법에 의한 강유전성 PMN 분말 및 박막의 제조와 특성)

  • Hwang, Jin-Myeong;Jang, Jun-Yeong;Eun, Hui-Tae
    • Korean Journal of Materials Research
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    • v.8 no.12
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    • pp.1138-1145
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    • 1998
  • The sliding wear behavior of Ni-base hardfacing alloy, Deloro 50, was investigated at the contact stresses of 15ksi and 30ksi under the various wear environments. In air at room temperature, Deloro 50 showed lower wear resistance than Stellite 6 even at 15ksi due to the occurrence of severe adhesive wear. This seems to be caused by the lower hardness and work- hardening rate of Deloro 50 than those of Stellite 6. In water at room temperature, Deloro 50 showed as good wear resistance as Stellite 6 at 15ksi. It was considered to be due to that water could effectively prevent metal to metal contact through contacting asperities. However, Deloro 50 showed severe adhesive wear at 30ksi in water at room temperature. It seems to be that the water could not suppress adhesion wear at 30ksi. At $300^{\circ}C$ in air, Deloro 50 exhibited higher wear resistance than Stellite 6 even at 30ksi. It was considered that the oxide glaze layers formed on wear surface during sliding, effectively prevented direct metal-to-metal contacts.

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Effect of Wear Environments on the High Stress Sliding Wear Behavior of Ni-base Deloro 50 Alloy (Ni계 Deloro 50합금의 고하중 Sliding 마모거동에 미치는 마모환경의 영향)

  • Choi, Jin-Ho;Choi, Se-Jong;Kim, Jun-Gi;Kim, Yong-Deog;Kim, Hak-Soo;Mun, Ju-Hyun;Baek, Ha-Chung;Lee, Duck-Hyun;Kim, Seon-Jin
    • Korean Journal of Materials Research
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    • v.8 no.12
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    • pp.1115-1120
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    • 1998
  • The sliding wear behavior of Ni-base hardfacing alloy, Deloro 50, was investigated at the contact stresses of 15ksi and 30ksi under the various wear environments. In air at room temperature, Deloro 50 showed lower wear resistance than Stellite 6 even at 15ksi due to the occurrence of severe adhesive wear. This seems to be caused by the lower hardness and work- hardening rate of Deloro 50 than those of Stellite 6. In water at room temperature, Deloro 50 showed as good wear resistance as Stellite 6 at 15ksi. It was considered to be due to that water could effectively prevent metal to metal contact through contacting asperities. However, Deloro 50 showed severe adhesive wear at 30ksi in water at room temperature. It seems to be that the water could not suppress adhesion wear at 30ksi. At $300^{\circ}C$ in air, Deloro 50 exhibited higher wear resistance than Stellite 6 even at 30ksi. It was considered that the oxide glaze layers formed on wear surface during sliding, effectively prevented direct metal-to-metal contacts.

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A Transmission Electron Microscopy Study on the Crystallization Behavior of In-Sb-Te Thin Films (In-Sb-Te 박막의 결정화 거동에 관한 투과전자현미경 연구)

  • Kim, Chung-Soo;Kim, Eun-Tae;Lee, Jeong-Yong;Kim, Yong-Tae
    • Applied Microscopy
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    • v.38 no.4
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    • pp.279-284
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    • 2008
  • The phase change materials have been extensively used as an optical rewritable data storage media utilizing their phase change properties. Recently, the phase change materials have been spotlighted for the application of non-volatile memory device, such as the phase change random access memory. In this work, we have investigated the crystallization behavior and microstructure analysis of In-Sb-Te (IST) thin films deposited by RF magnetron sputtering. Transmission electron microscopy measurement was carried out after the annealing at $300^{\circ}C$, $350^{\circ}C$, $400^{\circ}C$ and $450^{\circ}C$ for 5 min. It was observed that InSb phases change into $In_3SbTe_2$ phases and InTe phases as the temperature increases. It was found that the thickness of thin films was decreased and the grain size was increased by the bright field transmission electron microscopy (BF TEM) images and the selected area electron diffraction (SAED) patterns. In a high resolution transmission electron microscopy (HRTEM) study, it shows that $350^{\circ}C$-annealed InSb phases have {111} facet because the surface energy of a {111} close-packed plane is the lowest in FCC crystals. When the film was heated up to $400^{\circ}C$, $In_3SbTe_2$ grains have coherent micro-twins with {111} mirror plane, and they are healed annealing at $450^{\circ}C$. From the HRTEM, InTe phase separation was occurred in this stage. It can be found that $In_3SbTe_2$ forms in the crystallization process as composition of the film near stoichiometric composition, while InTe phase separation may take place as the composition deviates from $In_3SbTe_2$.