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991.
A number of samples of sodium phosphate glasses doped with Cd/Co or Ag chlorides were prepared and characterized by X-ray diffraction, IR spectral, ion transport and DSC studies. It was found from DSC studies that the glass transition temperature (T
g) and crystallization temperature (T
c) values increased with the increasing concentrations of the dopants Cd/ or Co chlorides. However, the T
g and T
c values were found to decrease when the AgCl was taken as the dopant and the following sequence is observed: T
g(CoCl2)>T
g(CdCl2)> T
g(AgCl) T
c(CoCl2)>T
c(CdCl2)>T
c(AgCl) These results have been discussed and explained on the basis of changes in the structure of sodium phosphate glassy matrix by the addition of different cations as dopants.The authors are thankful to Prof. M. L. Srivastava, Head, Department of Chemistry, D. D. U. Gorakhpur University, Gorakhpur, and Prof. Suresh Chandra, Department of Physics, B. H. U. Varanasi for providing necessary laboratory facilities and help in carrying out the present work. The financial support from the Department of Science and Technology and University Grants Commission, New Delhi is also gratefully acknowledged. 相似文献
992.
F. Krzakala O.C. Martin 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,28(2):199-208
We address the problem of chaotic temperature dependence in disordered glassy systems at equilibrium by following states of
a random-energy random-entropy model in temperature; of particular interest are the crossings of the free-energies of these
states. We find that this model exhibits strong, weak or no temperature chaos depending on the value of an exponent. This
allows us to write a general criterion for temperature chaos in disordered systems, predicting the presence of temperature
chaos in the Sherrington-Kirkpatrick and Edwards-Anderson spin glass models, albeit when the number of spins is large enough.
The absence of chaos for smaller systems may justify why it is difficult to observe chaos with current simulations. We also
illustrate our findings by studying temperature chaos in the naıve mean field equations for the Edwards-Anderson spin glass.
Received 27 March 2002 Published online 19 July 2002 相似文献
993.
The adsorption of thiophene on clean Al(1 1 1) at 90 and 130 K has been studied with X-ray and ultraviolet photoelectron spectroscopy (XPS and UPS) and work function measurements. Relatively weak chemisorption compared to adsorption on transition metals is indicated by minor changes in the valence spectrum in progressing from monolayer to multilayer thiophene, a modest work function change of −0.50 eV due to saturation dosing, and return of the work function and valence spectrum to that of clean Al(1 1 1) upon annealing at 210 K. The complementary experiment in which aluminum is thermally deposited on multilayer thiophene condensed on gold at 130 K has also been performed. XPS peak area analysis shows that metal doses less than 14×1015 atoms/cm2 result in penetration through the physisorbed thiophene, but higher doses lead to the gradual build up of metal throughout the organic layer. Persistence of the thiophene UPS valence features for metal doses of 50×1015 atoms/cm2 is consistent with penetration and aluminum island formation. For aluminum deposition on thiophene, charge transfer from aluminum is evidenced by metal-induced low binding energy components in the C 1s and S 2p spectra at 282.6 and 162.5 eV, respectively, and a shift in the Al 2p spectrum of 0.5 eV to higher binding energy compared to metallic aluminum. UPS also indicates progression of the frontier orbital toward the Fermi level as aluminum is deposited. 相似文献
994.
IR absorption spectra of As-Se glasses have been studied over a wide range of compositions. Various two-phonon, multiphonon
(combination tones) and impurity absorptions have been identified. Compositional variation of relative band intensities has
been explained in terms of the chemically ordered network model. 相似文献
995.
We investigate photostructural transformations in glassy Ge–S films by the method of luminescence and Raman scattering of light. The appearance of a new shortwave band in the luminescence spectra of sulfurenriched Ge–S specimens as a result of irradiation by a He–Cdlaser light and subsequent relaxation is discussed. To explain the results obtained, a model of photostructural transformations is invoked, in which the decisive role is assigned to solitary electrons of the chalcogen atoms. 相似文献
996.
Drábik M. Kozák T. Ležal D. Poulain M. Kalužný J. 《Journal of Thermal Analysis and Calorimetry》2002,67(1):223-227
The present study shows the dependence of the temperature of glass transition — T
g upon the presence and quantity of doping Pr atoms. Substantial effect of the form — chemical nature of compound from which the doping atoms are incorporated into the glass has been displayed as well. With the increase of the content of sulfidic form T
g values approach the level of undoped glasses. Thus, if the studied glasses are doped by sulfidic form, bonded areas atoms of Pr so atoms of S. Glasses doped by halogenous source of Pr behave differently; the shift of the T
g value does not change with the amount of the dopand, displaying the anion deficiency of glass stoichiometry in studied interval of halogenous dopands. Generally, a very slight non-stability of the glass against the oxidation in temperature region of glass transition is observed.This revised version was published online in November 2005 with corrections to the Cover Date. 相似文献
997.
Electrical resistivityρ(T) of spin glasses within the framework of Mookerjee and Chowdhury’s percolation model where there is a distribution of relaxation
times (drt) is calculated.ρ(T) thus calculated is in better qualitative agreement with experimental results than that in the single relaxation time model. 相似文献
998.
Dmitry?PanchenkoEmail author Michel?Talagrand 《Probability Theory and Related Fields》2004,130(3):319-336
In an important recent paper, [2], S. Franz and M. Leone prove rigorous lower bounds for the free energy of the diluted p-spin model and the K-sat model at any temperature. We show that the results for these two models are consequences of a single general principle. Our calculations are significantly simpler than those of [2], even in the replica-symmetric case.Supported by NSF grantRevised version: 30 December 2003 相似文献
999.
1000.
Shamshad A. Khan Zishan H. Khan M. Zulfequar M. Husain 《Physica B: Condensed Matter》2007,400(1-2):180-184
The kinetics of crystallization in Se80Te20−xPbx (x=0, 2, 6 and 10) glasses is studied by non-isothermal method using differential scanning calorimetry (DSC). DSC is performed at different heating rates of 5, 10, 15 and 20 K/min. The values of glass transition and crystallization temperatures are found to be composition and heating-rate dependent. From the heating-rate dependence of the glass transition and crystallization temperatures, the activation energy of crystallization (ΔEc) and order parameter (n) are calculated. 相似文献