The Experts below are selected from a list of 237 Experts worldwide ranked by ideXlab platform

M E Mchenry - One of the best experts on this subject based on the ideXlab platform.

  • the effect of distributed exchange parameters on magnetocaloric refrigeration capacity in amorphous and nanocomposite materials
    Journal of Applied Physics, 2012
    Co-Authors: Nicholas J Jones, Huseyin Ucar, J J Ipus, M E Mchenry, D E Laughlin
    Abstract:

    The temperature dependent magnetization of nanocomposite alloys has been fit with a modified Handrich-Kobe equation with an asymmetric exchange fluctuation parameter combined with the Arrott-Noakes equation. The two equations of state are combined to calculate the entropy change in the magnetocaloric effect associated with the ferromagnetic to paramagnetic phase transformation. The complete fit for the M(T) of (Fe70Ni30)88Zr7B4Cu nanocomposite powder is accomplished by combining the two theories. We investigate the broadening of the second-order transition arising from asymmetric exchange parameters and resulting from the fluctuations of Interatomic Spacing found in an amorphous matrix and the asymmetric dependence of exchange energy on Interatomic Spacing. The magnetic entropy curve revealed extra broadening with a refrigeration capacity (RC) value of 135 J/kg at 5 T, which is comparable to (Fe76Cr8-xMoxCu1B15) ribbons, which have a RC value of 180 J/kg for the same applied field. Broadening of the magne...

  • The effect of distributed exchange parameters on magnetocaloric refrigeration capacity in amorphous and nanocomposite materials
    Journal of Applied Physics, 2012
    Co-Authors: Nicholas J Jones, Huseyin Ucar, J J Ipus, M E Mchenry, D E Laughlin
    Abstract:

    The temperature dependent magnetization of nanocomposite alloys has been fit with a modified Handrich-Kobe equation with an asymmetric exchange fluctuation parameter combined with the Arrott-Noakes equation. The two equations of state are combined to calculate the entropy change in the magnetocaloric effect associated with the ferromagnetic to paramagnetic phase transformation. The complete fit for the M(T) of (Fe70Ni30)88Zr7B4Cu nanocomposite powder is accomplished by combining the two theories. We investigate the broadening of the second-order transition arising from asymmetric exchange parameters and resulting from the fluctuations of Interatomic Spacing found in an amorphous matrix and the asymmetric dependence of exchange energy on Interatomic Spacing. The magnetic entropy curve revealed extra broadening with a refrigeration capacity (RC) value of 135 J/kg at 5 T, which is comparable to (Fe76Cr8-xMoxCu1B15) ribbons, which have a RC value of 180 J/kg for the same applied field. Broadening of the magnetic entropy can lead to larger RC values and a wider working temperature range, making nanocomposite alloys promising for magnetocaloric applications

  • Magnetic and thermal properties of amorphous Al-Gd-TM (TM=Fe, Cu) alloys
    Journal of Materials Science, 1993
    Co-Authors: R. A. Dunlap, V. Srinivas, G. Beydaghyan, M E Mchenry
    Abstract:

    Amorphous aluminium-transition metal-rare earth alloys (Al-RE-TM) with compositions Al_65Gd_15Cu_20 and Al_1 Gd_1 Fe_1 have been prepared by melt spinning. X-ray diffraction studies show the average Interatomic Spacing in these alloys to be about 7% greater than in fcc aluminium and about 20% greater than in amorphous Al-TM-Si alloys. Thermal analysis measurements of the Al_65Gd_15Cu_20 and Al_1 Gd_1 Fe_1 alloys show the crystallization temperatures to be 647 and 945 K, respectively. Magnetization studies show Al_65Gd_15Cu_20 to be paramagnetic with a localized gadolinium moment of 8.0 ± 0.2 μ_B. Al_1 Gd_1 Fe_1 shows ferromagnetic behaviour, with T _c=275 K and a saturation magnetization of 124 e.m.u. g^−1. A room-temperature ^57Fe Mössbauer spectrum of Al_1 Gd_1 Fe_1 shows a well-defined quadrupole doublet with a mean splitting of about 0.4 mm s^−1. At 77 K, the Mössbauer spectrum shows a well-resolved sextet, corresponding to a mean iron hyperfine field of 96 kOe.

Quncheng Fan - One of the best experts on this subject based on the ideXlab platform.

  • A new method of calculating Interatomic Spacing: the equal-ratio method
    Journal of Applied Crystallography, 2019
    Co-Authors: Quncheng Fan
    Abstract:

    Based on a simple principle of analytical geometry, a new equal-ratio method has been developed to calculate the Interatomic Spacing of crystal structures. If an atom (x2, y2, z2) or its equi-position atom (e + x2, f + y2, g + z2) (e, f and g are integers) is located at the 1/r ≤ 1 of one Interatomic Spacing period d′[uvw] on the [uvw] atomic row passing through the atom (x1, y1, z1), the distance between the two atoms can be calculated by the formula d[uvw](1/r) = d′[uvw]/r, where d′[uvw] = (u2a2 + v2b2 + w2c2 + 2uvabcosγ + 2vwbccosα + 2uwaccosβ)1/2 is the interlattice point Spacing of the corresponding primary lattice of the crystal structure, 1/r is the Interatomic Spacing coefficient, and r is equal to the reciprocal of the common factor of (x2 − x1), (y2 − y1) and (z2 − z1). The reliability and advantages (no auxiliary view is required, suitable for arbitrary directions and for all crystal structures) of the equal-ratio method have been examined by calculations for the β-cristobalite SiO2 structure and Cu3Au I superstructure as well as face-centred cubic, body-centred cubic and hexagonal close-packed structures.

Douglas A. Keszler - One of the best experts on this subject based on the ideXlab platform.

  • Effects of Oxygen Incorporation on the Physical Properties of Amorphous Metal Thin Films
    The Journal of Physical Chemistry C, 2014
    Co-Authors: Sean Muir, E. William Cowell, Wei Wang, John F. Wager, Douglas A. Keszler
    Abstract:

    Incorporated oxygen is known to affect amorphous metal thin film (AMTF) mechanical properties, but comparatively little is known about how it affects their structural characteristics and electrical transport properties. In this study, AMTFs are produced by using sputter deposition. Chemical composition, average Interatomic Spacing, surface roughness, and electrical transport properties are examined using electron probe microanalysis (EPMA), X-ray diffraction (XRD), atomic force microscopy (AFM), spectroscopic ellipsometry (SE), and variable-temperature resistivity. ZrCuAlNi amorphous metal thin films exhibit a temperature dependence that is characteristic of d-electron conduction and electrical resistivity that increases substantially with increasing oxygen content. TiAl and ZrCuB are found to be sp-electron conductors with electrical resistivity that decreases with increasing oxygen content. The surface roughness of all films increases with oxygen content, whereas Interatomic Spacing is relatively insens...

  • Effects of Oxygen Incorporation on the Physical Properties of Amorphous Metal Thin Films
    2014
    Co-Authors: Sean W. Muir, Wei Wang, John F. Wager, William E. Cowell, Douglas A. Keszler
    Abstract:

    Incorporated oxygen is known to affect amorphous metal thin film (AMTF) mechanical properties, but comparatively little is known about how it affects their structural characteristics and electrical transport properties. In this study, AMTFs are produced by using sputter deposition. Chemical composition, average Interatomic Spacing, surface roughness, and electrical transport properties are examined using electron probe microanalysis (EPMA), X-ray diffraction (XRD), atomic force microscopy (AFM), spectroscopic ellipsometry (SE), and variable-temperature resistivity. ZrCuAlNi amorphous metal thin films exhibit a temperature dependence that is characteristic of d-electron conduction and electrical resistivity that increases substantially with increasing oxygen content. TiAl and ZrCuB are found to be sp-electron conductors with electrical resistivity that decreases with increasing oxygen content. The surface roughness of all films increases with oxygen content, whereas Interatomic Spacing is relatively insensitive to incorporated oxygen content. The relationships among amorphous metal composition, structural characteristics, and electrical transport properties are discussed

Michael Wulff - One of the best experts on this subject based on the ideXlab platform.

  • Visualizing photochemical dynamics in solution through picosecond x-ray scattering.
    Physical review letters, 2001
    Co-Authors: Richard Neutze, Remco Wouts, Simone Techert, Jan Davidsson, Menhard Kocsis, Adam Kirrander, Friedrich Schotte, Michael Wulff
    Abstract:

    A photoexcited state of molecular iodine in solution is observed using diffuse x-ray scattering at a synchrotron source. The measured changes in the diffuse scattering profile were consistent with earlier models of iodine’s photodissociation and geminate recombination reaction, for which the recombined AA 0 state has a 0.4 A greater Interatomic Spacing than the resting state and has a lifetime of 500 ps in CH2Cl2. This technique should find application in the study of increasingly complicated photochemical systems which undergo structural rearrangements following rapid photolysis.

Christophe Blancard - One of the best experts on this subject based on the ideXlab platform.

  • Resistivity saturation in warm dense matter
    Physical review. E Statistical nonlinear and soft matter physics, 2015
    Co-Authors: Gérald Faussurier, Christophe Blancard
    Abstract:

    Electrical resistivity is shown to saturate in solid-density aluminum in the warm dense matter regime. Calculations are done using the average-atom model SCAALP and the finite-temperature Ziman-Evans formula for electrical resistivity. The mean free path is estimated using the Drude law. This mean free path is shown to present a minimum of the order of the Interatomic Spacing.