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  • EDP Sciences  (18)
  • American Institute of Physics (AIP)  (16)
  • Copernicus  (16)
  • 1
    Electronic Resource
    Electronic Resource
    Liquid metal expulsion during laser irradiation (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 72 (1992), S. 3317-3322 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: During laser assisted materials processing such as welding, cutting, drilling, or surface alloying, the processing conditions are adjusted to either achieve or avoid liquid metal expulsion. Currently, there is no theoretical model to determine, from fundamental principles, the operating conditions for the initiation of liquid metal expulsion during laser irradiation. Processing conditions necessary for the initiation of liquid metal expulsion during pulsed laser irradiation have been investigated experimentally and theoretically. Lead, titanium, and stainless steel samples were irradiated by single and multiple pulses of varying pulse durations to investigate conditions for liquid metal expulsion. It is demonstrated that using theoretically computed transient spatial temperature profiles, and by balancing surface tension and recoil forces, the conditions for the initiation of liquid metal expulsion can be determined.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.351452
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  • 2
    Electronic Resource
    Electronic Resource
    Electron-beam-irradiation effects in bulk YBa2Cu3O7−x (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 3167-3171 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Irradiation effects on thin foils of bulk YBa2Cu3O7−x have been studied in a transmission electron microscope using 100-, 150-, 200-, 250-, and 300-keV electrons at 83 and 300 K. The disordering of the oxygen atoms and vacancies in the O(4) and O(5) sites in the Cu-O planes during irradiation was monitored by measuring the splitting of the (11¯0) diffraction spots in the [001] diffraction pattern. The results show that YBa2Cu3O7−x is insensitive to 100-keV electron irradiation. Irradiation by higher-energy electrons leads to irradiation-induced oxygen disordering of the oxygen atoms and vacancies, mainly by single displacement events. The excellent fit of the data to a disordering model suggests that the displacement threshold energy for oxygen in YBa2Cu3O7−x is around 18 eV and that irradiation-assisted oxygen reordering occurs in YBa2Cu3O7−x at 300 K, but not at 83 K.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.348586
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  • 3
    Electronic Resource
    Electronic Resource
    Probing laser induced metal vaporization by gas dynamics and liquid pool transport phenomena (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 70 (1991), S. 1313-1319 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: During laser beam welding of many important engineering alloys, an appreciable amount of alloying element vaporization takes place from the weld pool surface. As a consequence, the composition of the solidified weld pool is often significantly different from that of the alloy being welded. Currently there is no comprehensive theoretical model to predict, from first principles, laser induced metal vaporization rates and the resulting weld pool composition changes. The weld pool heat transfer and fluid flow phenomena have been coupled with the velocity distribution functions of the gas molecules at various locations above the weld pool to determine the rates of the laser induced element vaporization for pure metals. The procedure allows for calculations of the condensation flux based on the equations of conservation of mass, momentum and energy in both the vapor and the liquid phases. Computed values of the rates of vaporization of pure metals were found to be in good agreement with the corresponding experimentally determined values. The synthesis of the principles of gas dynamics and weld pool transport phenomena can serve as a basis for weld metal composition control.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.350358
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  • 4
    Electronic Resource
    Electronic Resource
    Absorption and photoluminescence spectra of the diluted magnetic semiconductor Ga1−xFexSb (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 88 (2000), S. 924-926 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Bulk growth of the III–V diluted magnetic semiconductor, Ga1−xFexSb is reported for different iron concentrations. Room-temperature optical absorption coefficient measurements were performed. The dependence of the band gap Eg on the Fe concentration was studied. The band gap decreased with increasing x, and the variation was observed to follow a nonlinear trend. Photoluminescence (PL) measurements at 18 K were also carried out. The PL spectra showed a clear peak shift due to incorporation of Fe in the lattice, thus agreeing with the optical absorption results. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.373756
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  • 5
    Electronic Resource
    Electronic Resource
    Magneto-impedance effect in soft magnetic tubes (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 87 (2000), S. 4807-4809 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Soft magnetic crystalline alloys have been fabricated in a tube form by electrodepositing magnetic FeNi and FeNi–Al2O3 onto W fibers with a diameter of 25 μm. Fine Al2O3 particles have also been incorporated into the magnetic matrix to improve mechanical properties. As-prepared materials are not magnetically soft. With heat treatment, the magnetic properties of these composites are similar to commercial bulk soft FeNi alloys. A giant magnetoimpedance value as large as 190% has been found in as-prepared FeNi-W with a magnetic layer thickness of 20 μm. This value is comparable to GMI observed in amorphous magnetic wires. Experiments also show that GMI values decrease when the Al2O3 content increases in a range from 0 to 7.0 at. %. This behavior is due to the increase in electrical resistivity and magnetic permeability of the samples that modifies the skin effect. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.373166
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  • 6
    Electronic Resource
    Electronic Resource
    Pinning effect of the grain boundaries on magnetic domain wall in FeCo-based magnetic alloys (1999)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 85 (1999), S. 6655-6659 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have studied the dynamics of grain growth and the pinning effect of grain boundaries on magnetic domain walls in FeCo soft magnetic alloys. It has been found that grain growth takes place at temperatures above 600 °C. The activation energy for grain growth in a disordered state at 820 °C is about 57.4±0.5 kcal/mole. The effect of grain size on magnetic properties has been singled out by keeping the same ordering parameter (S=0 and 0.88) for all samples studied. Microstructural characterization and magnetic measurements indicate that the grain size significantly affects the magnetic coercivity. A linear relationship between the coercivity and the reciprocal of the grain size has been universally found regardless of the heat-treatment histories. Lorenz microscopic observation demonstrates that grain boundaries act as pinning sites for the magnetic domain wall movement. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.370175
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  • 7
    Electronic Resource
    Electronic Resource
    Audio-frequency discharge cleaning system for the SINP tokamak using single turn primary (1994)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 65 (1994), S. 135-139 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Taking advantage of the iron core of the Saha Institute of Nuclear Physics (SINP) tokamak, a single turn primary coil was used to generate low power ohmically excited audio-frequency hydrogen plasma to clean the SINP tokamak vacuum vessel of adsorbed gases. This scheme allowed us to easily use available low voltage power transistors and other existing power supply components to generate audio-frequency voltage. Using this scheme the discharge cleaning system was tested successfully in a short period of 2–3 months. The system has been utilized to carry out initial discharge cleaning of the vessel as well as daily cleaning to achieve full designed parameters of our tokamak.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1144785
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  • 8
    Electronic Resource
    Electronic Resource
    Modeling of O-18 tracer distribution during "double oxidation'' experiments for inward growing scales (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 78 (1995), S. 2060-2069 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Quantitative modeling of oxygen tracer (18O) concentration profiles obtained during double oxidation experiments has been carried out. An existing model in the literature, involving combined grain-boundary and lattice diffusion of oxygen with exchange, has been extended to cases where the grain size of the oxide is allowed to vary over its thickness. The model predicts tracer profiles in the entire oxide for the case of scale growth by inward oxygen diffusion. A computer program has been developed along with a graphical user interface for easy generation and visualization of simulated tracer profiles. The sensitivity of the simulated profiles to variations in volume (Dv) and grain-boundary (Db) diffusivities of oxygen in the oxide scale as well as the oxide grain-size variation have been studied. The results indicate that the normalized tracer profiles are sensitive to variations in Db, although to a lesser extent as compared to similar variations in Dv. Also, incorporation of variable grain size leads to profiles very different from those obtained from a constant oxide grain-size assumption. The computer program has been used to fit an experimental profile reported in the literature to obtain values of Dv and Db. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.360718
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  • 9
    Electronic Resource
    Electronic Resource
    Dependence of crystalline orientation on film thickness in laser-ablated YBa2Cu3O7−δ on LaAlO3 (1991)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 58 (1991), S. 871-873 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The microstructure of YBa2Cu3O7−δ thin films deposited on (001)LaAlO3 substrates by a laser ablation process has been investigated by scanning electron microscopy, x-ray diffraction, and cross-sectional transmission electron microscopy. Adjacent to the substrate, the film is entirely oriented with the c-axis perpendicular to the surface. At a thickness of about 0.4 μm, the occurrence of 90° boundaries brings about a transition to grains with their c-axes parallel to the surface (aligned along the [100] and [010] directions of the pseudocubic LaAlO3 substrate). This transition is discussed in terms of the crystal growth anisotropy and the retained strain that may precipitate the transition.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.104491
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  • 10
    Electronic Resource
    Electronic Resource
    Phase separation and ordering in InGaN alloys grown by molecular beam epitaxy (1998)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 84 (1998), S. 1389-1395 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In this study, we investigated phase separation and long-range atomic ordering phenomena in InGaN alloys produced by molecular beam epitaxy. Films grown at substrate temperatures of 700–750 °C with indium concentration higher than 35% showed phase separation, in good agreement with thermodynamic predictions for spinodal decomposition. Films grown at lower substrate temperatures (650–675 °C) revealed compositional inhomogeneity when the indium content was larger than 25%. These films, upon annealing to 725 °C, underwent phase separation, similar to those grown at the same temperature. The InGaN films also exhibited long-range atomic ordering. The ordering parameter was found to increase with the growth rate of the films, consistent with the notion that ordering is induced at the growth surface. The ordered phase was found to be stable up to annealing temperatures of 725 °C. A competition between ordering and phase separation has been observed, suggesting that the driving force for both phenomena is lattice strain in the alloy. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.368251
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