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  • 1
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 87 (2000), S. 8658-8665 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The microstructures of a Nd8Fe76.5Co8B6Nb1Cu0.5 nanocomposite magnet have been investigated by transmission electron microscopy and three-dimensional atom probe microanalysis. The ribbon prepared by the single roller melt-spinning process under an optimal cooling rate was partially crystallized, being composed of α-Fe, Nd2Fe14B, and the intergranular amorphous phase. The volume fraction of the Nd2Fe14B phase increases by annealing at 740 °C for 3 min, but a small amount of amorphous phase remains in the intergranular region. Atom probe results show Nb and B are significantly enriched in the remaining amorphous phase, which would be the reason for the high thermal stability of the remaining amorphous phase. Cu atoms are dissolved in the Nd2Fe14B phase during solidification, and they do not have much influence on the microstructural evolution. © 2000 American Institute of Physics.
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  • 2
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 83 (1998), S. 7769-7775 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Partitioning of Co and Ga atoms in nanocrystalline Nd4.5Fe73B18.5Co3Ga1 at various stages of crystallization has been studied by atom probe field ion microscopy. In the early stage of crystallization, Co and Ga atoms are rejected from primary particles of the soft magnetic Fe3B phase and partitioned to the amorphous matrix phase. These atoms are enriched at the Fe3B/amorphous interfaces in this stage. Three crystalline phases (Fe3B, Nd2Fe23B3, and Nd2Fe14B) are present in the fully crystallized state, and Ga partitions preferentially only to the Nd2Fe14B phase. In a fully crystallized Fe3B/Nd2Fe14B nanocomposite with optimum magnetic hardness, Co and Ga atoms are partitioned to the Nd2Fe14B phase, and evidence for a slight enrichment of Ga atoms at the Nd2Fe14B/Fe3B interface has been found. Based on these results, the role of Ga and Co additions for improved hard magnetic properties is discussed. © 1998 American Institute of Physics.
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  • 3
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 90 (2001), S. 4708-4716 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The microstructure and magnetic property relationship in L10 ordered FePt–Al–O and FePt–Ag granular thin films have been studied. As-sputtered FePt–Al–O films, composed of isolated fine spherical FePt particles of ∼2 nm diameter with a disordered face-centered-cubic (fcc) structure, exhibit superparamagnetism. Annealing above 650 °C induces a transformation from a disordered fcc structure to ordered L10 phase and the films become magnetically hard. The microstructures of these films change greatly depending on the film compositions and annealing conditions, which are correlated with the magnetic properties. It was found that FePt particles smaller than 5 nm do not order at 500 °C, while the continuous FePt film orders perfectly at the same temperature, suggesting that the ordering temperature, Tc, decreases significantly when the particle size becomes less than 5 nm. In the FePt–Ag granular thin film, when the Ag composition is around 50 at. %, high coercivity (∼10 kOe) and fine uniform microstructure are obtained by annealing the films at 550 °C for 1 h. The changes in the magnetic properties of these granular films are discussed based on microstructural observation results. © 2001 American Institute of Physics.
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  • 4
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 77 (2000), S. 1102-1104 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The formation of an icosahedral phase during crystallization of Zr–Pd binary amorphous alloys is reported. The icosahedral phase forms in the nanocrystalline state with a grain size of about 10 nm as a metastable transient phase during the transformation from an amorphous to a crystalline state in Zr70Pd30 and Zr65Pd35 alloys. The amorphous phase coexists with the nanoquasicrystalline phase before complete crystallization to Zr2Pd occurs. © 2000 American Institute of Physics.
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  • 5
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 76 (2000), S. 55-57 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The present letter reports the formation of the icosahedral phase during crystallization of amorphous Zr65−xCu27.5Al7.5Ox (x=0.43% and 0.82%) alloys. Three-dimensional atom probe studies have revealed that the quasicrystalline phase is enriched in oxygen. This, together with the fact that no icosahedral phase forms at low oxygen level (0.14%), clearly establishes that the quasicrystalline phase in Zr-based metallic glasses is stabilized by oxygen. © 2000 American Institute of Physics.
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  • 6
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 4501-4505 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Polycrystalline Fe-Mo-Si-B alloys with grain sizes of 15–200 nm were synthesized via crystallization of the amorphous alloy. Positron lifetime results show that there are two existing types of interfacial defects in nanocrystalline Fe-Mo-Si-B alloys, namely free-volume-sized defects and nanovoids. The free-volume-sized defect shows almost no change in size or density during grain growth, and has a mean lifetime smaller than that of its amorphous counterpart as a result of structural relaxation in the process of crystallization. However, abnormal changes in size and density of nanovoids with grain growth were noticed. It is of great interest that the variations of intermediate lifetime τ2 and intensity ratio I1/I2 with the average grain size D¯ are exactly compatible with those of microhardness. A lower density of nanovoids corresponds to a larger microhardness in the case of the present alloy system.
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  • 7
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 85 (1999), S. 2448-2450 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Minor addition of Cu to Nd4.5Fe77B18.5 melt-spun alloy is effective on reducing the grain size of the Fe3B/Nd2Fe14B nanocomposite permanent magnet produced via the crystallization route from the amorphous phase, thereby improving hard magnetic properties. Three-dimensional atom probe and transmission electron microscopy observations have shown that Cu clusters with a number density of ∼1024 m−3 is formed prior to the nucleation event of the Fe3B primary crystal. In the nucleation and growth stage of the Fe3B primary crystals, Cu clusters are in direct contact with the primary particles, suggesting that Cu clusters serve as heterogeneous nucleation sites for the Fe3B primary particles, thereby increasing the number density of the particles.© 1999 American Institute of Physics.
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  • 8
    Electronic Resource
    Electronic Resource
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 27 (1994), S. 96-102 
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: The microstructure of natural magnetite found in the Panzhihua mountain in China was studied by means of high-resolution transmission electron microscopy (HRTEM). Electron diffraction patterns show lattice modulations along the [110] direction of wüstite co-existing with magnetite. Such a one-dimensional superstructure, with a lattice parameter of 2.6a0, is the characteristic feature of an incommensurate structure. It is related to the nonstoichiometric phase P′ of Fe0.920O that results from a deficiency of Fe atoms in the wüstite. The structural images exhibit the intergrowth of the magnetite matrix and the wüstite. The wavelike ultra-fine structure in wüstite suggests that the superstructure is possibly coincident with the displacive lattice modulation. Basal and nonbasal domains, which result from the random distribution of Fe atoms during the initial stage of nucleation of magnetite during the geological aging of wüstite, are also revealed in the structural images and are discussed on the basis of the structure of magnetite.
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Journal of materials science 14 (1995), S. 1536-1540 
    ISSN: 1573-4811
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Journal of materials science 32 (1997), S. 2501-2507 
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The microstructures of zirconia reinforced with silicon carbide fibres prepared by the sol–gel process have been examined using a transmission electron microscope. The characteristic feature of highly oriented grains of monoclinic zirconia, with its unique b-axis as well as c-axis of the tetragonal structure nearly all parallel to the hot pressing plane, shows the formation of matrix texture. Twinning in the monoclinic phase was well developed and highly dominated by twinning with the (1 0 0) plane as the interface. Alternative twinning with the interfaces parallel to the (0 0 1) plane has also been revealed and a possible model was suggested based upon the basic structure to be coincident with the [1 0 0] rotation twinning. Strong intergrowth of the tetragonal and monoclinic phases was frequently found and the orientation relationship was determined. The possible orientation variants resulting from the tetragonal to monoclinic phase transformation were proposed based upon such orientations of the lattices. Two of them with the misorientation angle of 9°15′ and 80°45′, respectively, were also found to coexist with the two kinds of twinning. Such texture configuration may have a close relation to the improvement of toughness.
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