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Full-Text Articles in Physics

Second Order Phase Transition Temperature Of Single Crystals Of Gd5si1.3ge2.7 And Gd5si1.4ge2.6, Ravi L. Hadimani, Yevgen Melikhov, Deborah L. Schlagel, Thomas A. Lograsso, Kevin W. Dennis, R. William Mccallum, David C. Jiles Jan 2015

Second Order Phase Transition Temperature Of Single Crystals Of Gd5si1.3ge2.7 And Gd5si1.4ge2.6, Ravi L. Hadimani, Yevgen Melikhov, Deborah L. Schlagel, Thomas A. Lograsso, Kevin W. Dennis, R. William Mccallum, David C. Jiles

Electrical and Computer Engineering Publications

Gd5(Six Ge 1−x)4 has mixed phases in the composition range 0.32 < x < 0.41, which have not been widely studied. In this paper, we have synthesized and indexed single crystal samples of Gd5Si1.3 Ge 2.7 and Gd5Si1.4 Ge 2.6. We have investigated the first order and second orderphase transition temperatures of these samples using magnetic moment vs. temperature andmagnetic moment vs. magnetic field at different temperatures. We have used a modified Arrott plot technique that was developed and reported by us previously to determine the “hidden” second order phase transition temperature of the orthorhombic II phase.


Multi-Channel Polarized Thermal Emitter, Jae-Hwang Lee, Kai-Ming Ho, Kristen P. Constant Jul 2013

Multi-Channel Polarized Thermal Emitter, Jae-Hwang Lee, Kai-Ming Ho, Kristen P. Constant

Iowa State University Patents

A multi-channel polarized thermal emitter (PTE) is presented. The multi-channelPTE can emit polarized thermal radiation without using a polarizer at normal emergence. The multi-channel PTE consists of two layers of metallic gratings on a monolithic and homogeneous metallic plate. It can be fabricated by a low-cost soft lithography technique called two-polymer microtransfer molding. The spectral positions of the mid-infrared (MIR) radiation peaks can be tuned by changing the periodicity of the gratings and the spectral separation between peaks are tuned by changing the mutual angle between the orientations of the two gratings.


Spatially Resolved Distribution Function And The Medium-Range Order In Metallic Liquid And Glass, X. W. Fang, Cai-Zhuang Wang, S. G. Hao, Matthew J. Kramer, Yongxin Yao, Mikhail I. Mendelev, Z. J. Ding, Ralph E. Napolitano, Kai-Ming Ho Dec 2011

Spatially Resolved Distribution Function And The Medium-Range Order In Metallic Liquid And Glass, X. W. Fang, Cai-Zhuang Wang, S. G. Hao, Matthew J. Kramer, Yongxin Yao, Mikhail I. Mendelev, Z. J. Ding, Ralph E. Napolitano, Kai-Ming Ho

Materials Science and Engineering Publications

The structural description of disordered systems has been a longstanding challenge in physical science. We propose an atomic cluster alignment method to reveal the development of three-dimensional topological ordering in a metallic liquid as it undercools to form a glass. By analyzing molecular dynamic (MD) simulation trajectories of a Cu64.5Zr35.5 alloy, we show that medium-range order (MRO) develops in the liquid as it approaches the glass transition. Specifically, around Cu sites, we observe “Bergman triacontahedron” packing (icosahedron, dodecahedron and icosahedron) that extends out to the fourth shell, forming an interpenetrating backbone network in the glass. The discovery of ...


Electrical Transport In Amorphous Semiconducting Almgb14 Films, Y. Tian, G. Li, Joseph Shinar, N. L. Wang, Bruce A. Cook, James W. Anderegg, Alan P. Constant, Alan Mark Russell, J. E. Snyder Aug 2004

Electrical Transport In Amorphous Semiconducting Almgb14 Films, Y. Tian, G. Li, Joseph Shinar, N. L. Wang, Bruce A. Cook, James W. Anderegg, Alan P. Constant, Alan Mark Russell, J. E. Snyder

Materials Science and Engineering Publications

The electrical transport properties of semiconducting AlMgB14films deposited at room temperature and 573K are reported in this letter. The as-deposited films are amorphous, and they exhibit high n-type electrical conductivity, which is believed to stem from the conduction electrons donated by Al, Mg, and/or Fe impurities in these films. The film deposited at 573K is less conductive than the room-temperature-deposited film. This is attributed to the nature of donor or trap states in the band gap related to the different deposition temperatures.


Method Of Making Active Magnetic Refrigerant, Colossal Magnetostriction And Giant Magnetoresistive Materials Based On Gd-Si-Ge Alloys, Karl A. Gschneidner Jr., Alexandra O. Pecharsky, Vitalij K. Pecharsky Jul 2003

Method Of Making Active Magnetic Refrigerant, Colossal Magnetostriction And Giant Magnetoresistive Materials Based On Gd-Si-Ge Alloys, Karl A. Gschneidner Jr., Alexandra O. Pecharsky, Vitalij K. Pecharsky

Iowa State University Patents

Method of making an active magnetic refrigerant represented by Gd5(SixGe1−x)4alloy for 0≦x≦1.0 comprising placing amounts of the commercially pure Gd, Si,and Ge charge components in a crucible, heating the charge contents under subambient pressure to a melting temperature of the alloy for a time sufficient to homogenize the alloy and oxidize carbon with oxygen present in the Gd charge component to reduce carbon, rapidly solidifying the alloy in the crucible, and heat treating the solidified alloy at a temperature below the melting temperature for a time effective to ...


The Resistivity And Microstructure Of Heavily Drawn Cu‐Nb Alloys, J. D. Verhoeven, H. L. Downing, L. Scott Chumbley, E. D. Gibson Jan 1989

The Resistivity And Microstructure Of Heavily Drawn Cu‐Nb Alloys, J. D. Verhoeven, H. L. Downing, L. Scott Chumbley, E. D. Gibson

Materials Science and Engineering Publications

A combined resistivitytransmission electron microscopy(TEM) study has been done on heavily drawn Cu‐20 vol % Nb alloys (so‐called i n s i t u alloys). The results show that electron scattering at Cu‐Nb interfaces makes the major contribution to resistivity in heavily drawn wire. The dislocation contribution is small and constant at deformation strains greater than around 4, apparently as a result of dynamic recovery/recrystallization of the Cu matrix which occurs during room‐temperature drawing. Results of this study and other recent TEM dislocation studies indicate that the dislocation density in heavily drawn Cu‐20 vol ...


An Electron Channeling Study Of Polycrystalline Yba2cu3o X, J. D. Verhoeven, E. D. Gibson, L. Scott Chumbley, R. William Mccallum, H. H. Baker Jul 1988

An Electron Channeling Study Of Polycrystalline Yba2cu3o X, J. D. Verhoeven, E. D. Gibson, L. Scott Chumbley, R. William Mccallum, H. H. Baker

Materials Science and Engineering Publications

An electron channeling study has been done on large grained YBa2Cu3O x samples. Selected area channeling patterns (SACP) were used to examine several dozen grains on electropolished surfaces and it was demonstrated that (a) the twin planes observed in polarized optical light microscopy lie parallel to {110} crystal planes, and (b) the long flat sides of high aspect ratio grains are formed by basal planes, and the shorter sides are formed by either (010), (100), or {110} planes. A majority of the large grains examined were found to contain subgrains, misaligned by 0.5°–1° and ...


Possible Twin-Boundary Effect Upon The Properties Of High-Tc Superconductors, M. M. Fang, Vladimir G. Kogan, Douglas K. Finnemore, J. R. Clem, L. Scott Chumbley, D. K. Farrell Feb 1988

Possible Twin-Boundary Effect Upon The Properties Of High-Tc Superconductors, M. M. Fang, Vladimir G. Kogan, Douglas K. Finnemore, J. R. Clem, L. Scott Chumbley, D. K. Farrell

Materials Science and Engineering Publications

We have studied the field at which superconductivity nucleates in grain-aligned samples of Y1Ba2Cu3O7-δ very close to the transition temperature Tc. For the field parallel to the c axis and for temperatures within 2 K of Tc, the nucleation field is found to vary as (1-T/Tc)1/2. The data suggest that superconductivity localized near twin boundaries may exist at temperatures close to Tc. .AE


Secondary Electron Emission Due To Positive Ion Bombardment, John W. Murdock, Glenn H. Miller Jun 1955

Secondary Electron Emission Due To Positive Ion Bombardment, John W. Murdock, Glenn H. Miller

Ames Laboratory ISC Technical Reports

Stray electrons were produced in the Ames Laboratory linear accelerator by the ion beam striking the target and various other parts of the accelerator. This experiment was done to determine if the stray electrons from parts of the accelerator other than the target could be reduced by using construction materials other than brass. Measurements of the number of electrons produced from several materials, however, indicated that there is no particular advantage in using other materials in place of brass.


Thermal Conductivity Of Metals At High Temperatures, Paul H. Sidles, G. C. Danielson Dec 1951

Thermal Conductivity Of Metals At High Temperatures, Paul H. Sidles, G. C. Danielson

Ames Laboratory ISC Technical Reports

A new method of measuring thermal diffusivity and hence thermal conductivity of metals is suggested. Like previously reported dynamic methods, this method uses a heat source, whose temperature varies sinusoidally located at one end of an effectively infinite rod. Unlike these methods only one period of the heat wave is required to eliminate the unknown coefficient determining the heat lost by radiation since both velocity and amplitude decrement of the heat wave are measured. The new method is faster in taking data and simpler in computation. The thermoelectric potentials from two thermojunctions are amplified and plotted on a Brown "Electronic ...