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  • 1
    Electronic Resource
    Electronic Resource
    TEM observation of DO3 structure in Fe3 Al alloy with Mn addition (1999)
    Springer
    Journal of materials science 34 (1999), S. 1025-1030 
    Details
    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 structures of DO3 Fe-28Al-1.5Mn alloy, including ordering degree, superdislocation, APD and APB, were investigated by TEM. The results showed that addition of manganese into DO3 Fe3Al could not change the ordered type of the alloy, but could reduce APD size and then reduce ordering degree of the alloy. The fourfold superdislocations were retarded in DO3 Fe3Al alloy after Mn addition. Undeformed alloy with Mn has mainly twofold superdislocations. As deformation increases, the twofold superdislocations slip and decompose into unit dislocations, and unit dislocations slip and slip cross, leading to better ductility. The deformation mechanism of DO3 Fe-28Al-1.5Mn alloy was controlled at first by twofold superdislocation and at last by unit superdislocation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1004591927568
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  • 2
    Electronic Resource
    Electronic Resource
    Thermally assisted resonant quantum tunneling of magnetization in Fe8 clusters (1999)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 85 (1999), S. 5633-5635 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Magnetic ac susceptibility of randomly arranged crystallites (powder sample) and well-oriented Fe8 crystallites has been measured as a function of applied magnetic field, temperature, and frequency. The Fe8 clusters, made of eight iron ions and with formula [(tacn)6Fe8O2(OH)12]8+, have a ground state S=10. From the magnetization data M(H) with the dc field, H, applied parallel and perpendicular to the easy axis of the aligned sample and χ″(T) data for different frequencies, the anisotropy field Han∼5 T and energy barrier U/kB=26.9 K were obtained. Peaks in the curves of χ′(H) were clearly observed at fields Hn=nH0, with n=0,±1 for powder sample where H0=2.4 kOe; and n=0, ±1, ±2, for an oriented sample where H0=2.2 kOe. These peaks appearing at Hn=nH0 in the curves of χ′(H) can be well described by the thermally assisted resonant quantum tunneling of magnetization. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.369823
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  • 3
    Electronic Resource
    Electronic Resource
    Transient reconnection caused by the impact and switch-off of a transverse shear flow (1999)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 6 (1999), S. 2393-2400 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: It is supposed that local and transient reconnection in the plasma boundary layer can be caused by the impact and switch-off of a single directional transverse shear flow. MHD (magnetohydrodynamic) simulation is used to investigate the reconnection processes in the two cases. It is found that if the inflow is homogeneous, it does not cause reconnection; if the inflow is shearing flow, no matter how great the shear of the flow is, it may cause reconnection either during impacting period or after stop impacting. It is pointed out that the sudden stop of external force may be an important triggering mechanism of energy transformation and reconnection in the plasma boundary layer region. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.873510
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  • 4
    Electronic Resource
    Electronic Resource
    Brillouin scattering from acoustic excitations in TiN films on high speed steel—A stiffening system (1999)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 86 (1999), S. 311-317 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Brillouin scattering measurements are presented of surface acoustic waves in TiN films of various thicknesses on high speed steel. Because of its relatively high elastic moduli as compared with those of steel, TiN has a stiffening effect on the surface, causing the surface acoustic wave (SAW) to increase in velocity, merge into the bulk wave continuum, and become a pseudo-SAW. In the limit of large film thickness this pseudo-SAW evolves into the Rayleigh wave for TiN. A Green's function method, invoking the surface ripple mechanism for the inelastic scattering of light, is used to calculate the Brillouin spectrum for scattering from these surface acoustic modes, and reveals details of the acoustic excitations of stiffening thin films not previously appreciated. A comparison between the measured and calculated dispersion relation for TiN thicknesses ranging from 20 to 4180 nm reveals that the elastic moduli of the thicker films are close to those of bulk TiN, but the effective elastic moduli of the thinner films are found to decrease with reducing film thickness. This conclusion is reinforced by backscattering measurements of Brillouin spectra at incident angles between 50° and 80° for a film thickness of 350 nm. Compositional variations at the interface have been investigated using x-ray photoelectron spectroscopy in an effort to understand this reduction in the elastic constants. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.370730
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  • 5
    Electronic Resource
    Electronic Resource
    Giant magnetoimpedance of glass-covered amorphous microwires of Co–Mn–Si–B and Co–Si–B (1999)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 85 (1999), S. 4445-4447 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A study of magnetic hysteresis and giant magnetoimpedance (GMI) in amorphous glass-covered Co–Si–B and Co–Mn–Si–B wires is presented. The wires, about 10 μm in diameter, were obtained by a glass-coated melt spinning technique. Samples with positive magnetostriction (MS) have a rectangular bistable hysteresis loop. A smooth hysteresis loop is observed for wires with nearly zero MS. When the MS is negative, almost no hysteresis is observed. The GMI was measured in the frequency range between 20 Hz and 30 MHz. The shapes of the impedance versus field curves are qualitatively similar to each other for both positive and zero MS samples. The impedance is maximum at zero field, and decreases sharply in the range of 10–20 Oe. For the negative MS wires, when the driving current is small, the impedance is maximum at a finite external field. The position of the maximum approaches zero with increasing current. The contributions of the moment rotation and domain wall motion in the three cases are discussed. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.370369
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  • 6
    Electronic Resource
    Electronic Resource
    Hetero- and homoepitaxial Nd3+-doped LaF3 thin films grown by molecular beam epitaxy: A spectroscopic study (1999)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 86 (1999), S. 3699-3704 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Hetero- and homoepitaxial Nd3+-doped LaF3 thin films have been grown by molecular beam epitaxy. Two different orientations of CaF2 substrates, (111) and (110), have been used for the heteroepitaxial structures. High-resolution emission and excitation spectra as well as the decay time of the emission have been measured. The spectroscopic measurements demonstrate that one Nd3+ site is present in the LaF3 layers grown on CaF2(111) substrates but two slightly different Nd3+ centers are resolved in the films on CaF2(110) substrates. One Nd3+ site has been found in the homoepitaxial sample. Slight differences are observed between the centers found in the LaF3 layers and the one observed in the Nd3+-doped LaF3 bulk crystal. For the homoepitaxial layer, the linewidths are similar to those of the bulk crystals, whereas for the heteroepitaxial layers, a broadening is observed. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.371281
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  • 7
    Electronic Resource
    Electronic Resource
    Characterization of GaAs/AlGaAs heterojunction bipolar transistor devices using photoreflectance and photoluminescence (1999)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 86 (1999), S. 6160-6163 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Photoreflectance (PR) and photoluminescence (PL) techniques were used to characterize the AlGaAs/GaAs heterojunction bipolar transistor (HBT) wafers grown by molecular beam epitaxy (MBE). The line shape of the PR GaAs signal is closely related to the cleanliness of the MBE system. The Franz–Keldysh oscillations of the GaAs signal become sharper, well defined, and the oscillation amplitude increases slightly as the MBE system is cleaned up. The dc current gain of the HBT devices was observed to increase accordingly. The origin for this correlation is discussed. The PL spectra of the HBT device wafers indicate that the intensity of the free-to-bound transition corresponding to the donor to valence band becomes strong in high gain device wafers. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.371669
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  • 8
    Electronic Resource
    Electronic Resource
    First principles modeling of magnetic random access memory devices (invited) (1999)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 85 (1999), S. 5834-5839 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Giant magnetoresistance (GMR) and spin-dependent tunneling may be used to make magnetic random access memory devices. We have applied first-principles based electronic structure techniques to understand these effects and in the case of GMR to model the transport properties of the devices. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.369933
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  • 9
    Electronic Resource
    Electronic Resource
    Optical mapping of fluid density interfaces: Concepts and implementations (1996)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 67 (1996), S. 1858-1868 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Several ideas of color encoding for surface slope measurements are systematically explored and reviewed to develop a new set of fundamental concepts. It is shown that different systems, such as shadowgraphs, Schlieren optics, and our water surface gradient detectors, can also be universally described through the concepts of sun glitter functions, incident light-source encoding, and observer encoding. These concepts provide a more precise way of mathematically formulating and physically interpreting the flow visualization images, thereby providing quantitative results. It is this new system of concepts that uncover the quantitative potential of these optical methods. The measurement abilities of various existing optical systems are thus enhanced from qualitative observation or visualization to the well-defined quantitative measurement. This is a critical step forward. The concepts can also be further extended to measure fluid flows with multiple density layers or flows with continuous density variations. As an example of implementation, the method of measuring a water-surface gradient is extended into a reflective approach of detecting small changes of surface slope at an air–water interface. In this process, fluid surface slopes (surface gradients) are first optically mapped into color space. An array of lenses is used to transform the rays of an optical light source into a series of colored parallel light beams by passing the light through a group of two-dimensional color palettes at the focal planes of the lens array. This system of parallel light beams is used to illuminate a free surface of water. The reflected rays from the free surface are captured by a charge-coupled device color camera located above the surface. The slopes are derived from the color images after the calibration, and surface elevations are obtained by integrating the slopes. This technique is then applied to observe free-surface deformations caused by near-surface turbulence interacting with the free surface. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1146990
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  • 10
    Electronic Resource
    Electronic Resource
    Design of solid/liquid–liquid/solid trilayer systems for the measurement of diffusion coefficients in liquid metals (1998)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 69 (1998), S. 3002-3005 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A new method for investigation of diffusion processes in liquid metals with solid/liquid–liquid/solid trilayer systems is described. The design of this kind of trilayers enables diffusion processes with no effects from gravity-induced convection and Maragoni-convection conditions. The Ta/Zn–Sn/Si trilayers were prepared and the interdiffusion of liquid zinc and tin at 500 °C was investigated. The interdiffusion coefficients range from 1.0×10−4 to 2.8×10−4 mm2/s, which are less than previous values measured by capillary reservoir technique under 1 g environment where various kinds of convection exist. It is the removing of disturbances of these kinds of convection that brings about the precise interdiffusion coefficients in liquid metals. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1149047
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