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Articles 1 - 10 of 10
Full-Text Articles in Physical Sciences and Mathematics
Electronic Structure Of Thallium Filled Skutterudites Studied By X-Ray Absorption And Mössbauer Spectroscopy, Gary J. Long, Bernard M. Mahieu, Brian C. Sales, Raphäel P. Hermann, Fernande Grandjean
Electronic Structure Of Thallium Filled Skutterudites Studied By X-Ray Absorption And Mössbauer Spectroscopy, Gary J. Long, Bernard M. Mahieu, Brian C. Sales, Raphäel P. Hermann, Fernande Grandjean
Chemistry Faculty Research & Creative Works
The electronic structure of the three sites in the thallium filled skutterudites was studied. Two series of thallium filled skutterudites were formed because thallium has a formal valence of +1 and iron or tin must replace some of the cobalt or antimony respectively, to maintain charge neutrality. Large atomic mean-square displacements were observed for the thallium filling atoms and it helps to produce the large thermal resistivity observed for these skutterudites.
Superfluidity In The Solar Interior: Implications For Solar Eruptions And Climate, Oliver Manuel, Barry W. Ninham, Stig Friberg
Superfluidity In The Solar Interior: Implications For Solar Eruptions And Climate, Oliver Manuel, Barry W. Ninham, Stig Friberg
Chemistry Faculty Research & Creative Works
Efforts to understand unusual weather or abrupt changes in climate have been plagued by deficiencies of the standard solar model (SSM) [1]. Although it assumes that our primary source of energy began as a homogeneous ball of hydrogen (H) with a steady, well-behaved H-fusion reactor at its core, observations instead reveal a very heterogeneous, dynamic Sun. As examples, the upward acceleration and departure of H+ ions from the surface of the quiet Sun and abrupt climatic changes, including geomagnetic reversals and periodic magnetic storms that eject material from the solar surface are not explained by the SSM. The present …
Polarized Neutron Diffraction And Mössbauer Spectral Study Of Short-Range Magnetic Correlations In The Ferrimagnetic Layered Compounds (Pph₄) [FeIiFeIii(Ox)₃] And (Nbu₄) [FeIiFeIii(Ox)₃], Simon G. Carling, Dirk W. Visser, Dimitri Hautot, Ian D. Watts, Peter Day, Jürgen Ensling, Phillip Gütlich, Gary J. Long, Fernande Grandjean
Polarized Neutron Diffraction And Mössbauer Spectral Study Of Short-Range Magnetic Correlations In The Ferrimagnetic Layered Compounds (Pph₄) [FeIiFeIii(Ox)₃] And (Nbu₄) [FeIiFeIii(Ox)₃], Simon G. Carling, Dirk W. Visser, Dimitri Hautot, Ian D. Watts, Peter Day, Jürgen Ensling, Phillip Gütlich, Gary J. Long, Fernande Grandjean
Chemistry Faculty Research & Creative Works
Short-range antiferromagnetic correlations have been studied in the layered compounds (PPh4) [FeIIFeIII(ox)3] and (NBu4) [FeIIFeIII(ox)3] by neutron polarization analysis and Mössbauer spectroscopy. Polarized neutron diffraction profiles obtained between 2 and 50 K on (d20-Pph4) [FeIIFeIII(ox)3] show no magnetic Bragg scattering; the lack of such scattering indicates the absence of long-range magnetic order. However, a broad asymmetric feature observed at a Q of ca. 0.8 Å-1 is attributed to two-dimensional short-range magnetic correlations, which …
Morphologic And Magnetic Properties Of Pd₁₀₀₋ₓfeₓ Nanoparticles Prepared By Ultrasound Assisted Electrochemistry, Maribel Guzman, Jean Luc Delplancke, Gary J. Long, Jacques P. Delwiche, Marie Jeanne Hubin-Franskin, Fernande Grandjean
Morphologic And Magnetic Properties Of Pd₁₀₀₋ₓfeₓ Nanoparticles Prepared By Ultrasound Assisted Electrochemistry, Maribel Guzman, Jean Luc Delplancke, Gary J. Long, Jacques P. Delwiche, Marie Jeanne Hubin-Franskin, Fernande Grandjean
Chemistry Faculty Research & Creative Works
Nanopowdered alloys of Pd100-xFex, with x=4, 6, 8, and 12, have been prepared by ultrasound assisted electrochemistry. The composition of the individual particles, as determined by x-ray fluorescence, and the bulk composition, as determined by atomic absorption, are in agreement within experimental error. Transmission electron microscopy indicates that the nanopowders consist of agglomerates of small grains with a radius of approximately 5 nm, a radius which is confirmed by the broadening of the reflections in the x-ray powder diffraction patterns. X-ray fluorescence analysis of individual grains indicates a homogeneous distribution of palladium and iron throughout the …
The Relationship Between Magnetic Interactions And Near Neighbor Interatomic Distances In The Transition Metal Sublattice Of R(Mn/Fe)₆A₆(R=Nd Or Sm, A=Ge Or Sn), G. K. Marasinghe, J. Han, William Joseph James, William B. Yelon, Naushad Ali
The Relationship Between Magnetic Interactions And Near Neighbor Interatomic Distances In The Transition Metal Sublattice Of R(Mn/Fe)₆A₆(R=Nd Or Sm, A=Ge Or Sn), G. K. Marasinghe, J. Han, William Joseph James, William B. Yelon, Naushad Ali
Chemistry Faculty Research & Creative Works
The magnetic and crystallographic structures of R(Fe/Mn)6A6 (R=Nd or Sm and A = Ge or Sn) intermetallics have been investigated using x-ray and neutron diffraction techniques and superconducting quantum interference device magnetic measurements. For both stannides (A = Sn) and germanides (A = Ge), the lattice contracts with increasing iron content. In the case of the stannides, substitution of manganese by iron enhances the saturation magnetization and Curie temperature at low iron concentrations (x ≤2 ) suggesting the presence of an extremely rare occurrence, positive coupling between iron and manganese magnetic moments. In contrast, the magnetic properties …
A New Layered Iron Fluorophosphates, Amitava Choudhury
A New Layered Iron Fluorophosphates, Amitava Choudhury
Chemistry Faculty Research & Creative Works
A new iron fluorophosphate of the composition, [C6N4H21] [Fe2F2(HPO4)3][H2PO4]·2H2O, I. has been prepared by the hydrothermal route. This compound contains iron fluorophosphate layers and the H2PO4- anions are present in the interlayer space along with the protonated amine and water molecules. The compound crystallizes in the monoclinic space group P21/c. (a = 13.4422(10) Å, b = 9.7320(10) Å, c = 18.3123(3) Å, ? = 92.1480°, V = 2393.92(5) Å3, Z = 4, …
A Mössbauer Spectral Study Of The Magnetic Properties Of Ho₂Fe₁₇ And Ho₂Fe₁₇D₃.₈, Gary J. Long, Olivier Isnard, Fernande Grandjean
A Mössbauer Spectral Study Of The Magnetic Properties Of Ho₂Fe₁₇ And Ho₂Fe₁₇D₃.₈, Gary J. Long, Olivier Isnard, Fernande Grandjean
Chemistry Faculty Research & Creative Works
The Mössbauer spectra of Ho2Fe17 and Ho2Fe17D3.8 have been measured between 4.2 and 295 K and analyzed with a model which takes into account both the disordered nonstoichiometric hexagonal Th2Ni17-like structure and the basal orientation of the iron magnetic moments. The isomer shifts of the five crystallographically inequivalent iron sites in both Ho2Fe17 and Ho2Fe17D3.8 follow the sequence of Wigner-Seitz cell volumes and their temperature dependence follows the typical second-order Doppler shift. An increase in the weighted average isomer shift …
Magnetic And Mössbauer Spectral Evidence For The Suppression Of The Magnetic Spin Reorientation In Tm₂Fe₁₇ By Deuterium, Fernande Grandjean, Olivier Isnard, Gary J. Long
Magnetic And Mössbauer Spectral Evidence For The Suppression Of The Magnetic Spin Reorientation In Tm₂Fe₁₇ By Deuterium, Fernande Grandjean, Olivier Isnard, Gary J. Long
Chemistry Faculty Research & Creative Works
The structural and magnetic properties of Tm2Fe17 and Tm2Fe17D3.2 are investigated by means of x-ray-diffraction, thermal, and ac magnetic susceptibility measurements, and iron-57 Mössbauer spectroscopy. Both compounds crystallize in a hexagonal P63/mmc space group with a Th2Ni17-like structure. Deuterium insertion into Tm2Fe17 induces large increases in the unit-cell volume, the saturation magnetization, and the ordering temperature. The unit-cell expansion is anisotropic, with a larger increase in the a lattice parameter than the c lattice parameter. A spin reorientation is observed at 90 K …
Thermogravimetric Studies Of Pmma On Silica, Bing Zhang, Frank D. Blum
Thermogravimetric Studies Of Pmma On Silica, Bing Zhang, Frank D. Blum
Chemistry Faculty Research & Creative Works
The thermal degradation of poly(methyl methacrylate) (PMMA) has been studied extensively. It is well accepted that the degradation process is a radical chain reaction involving initiation, depropagation, transfer, and termination reactions. In the degradation process, the factors having observable effects on the decomposition behavior include molecular mass, polydispersity, tacticity, and sample dimensions. The effects of tacticity on the degradation behavior of PMMA were investigated by Kashiwagi et al., Jellinek et al. And Chiamtore et al. The results indicated that both isotactic and syndiotactic PMMA have similar decomposition pathways and activation energies. Isotactic PMMA will decompose at a slightly lower temperature …
Effect Of Polymer-Surface Mobility On Adhesion In Poly(Methyl Methacrylate)-Tape System, Bhavesh C. Gandhi, Frank D. Blum, Lokeswarappa R. Dharani
Effect Of Polymer-Surface Mobility On Adhesion In Poly(Methyl Methacrylate)-Tape System, Bhavesh C. Gandhi, Frank D. Blum, Lokeswarappa R. Dharani
Chemistry Faculty Research & Creative Works
The interaction between two polymer layers, especially adhesion between them, plays an important role in polymer processing and other applications. Detailed knowledge of the molecular structure and dynamics of polymer interfaces, and how they relate to macroscopic mechanical properties, should help designers construct more functional systems. Unfortunately, there have been few studies where both molecular and macroscopic studies have been performed on similar systems. In previous studies from our group, we have probed the dynamics of poly(methyl acrylate) (PMA) and thermal behavior of poly(methyl methacrylate) (PMMA) on silica. These studies helped us paint a picture for strongly bound molecules on …