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921.
T. Yoshinari 《Phase Transitions》2013,86(1-4):89-93
Abstract A new absorption band has been found at 5.10 eV in (C n H2n + 1NH3)2CdCl4: n = 1, 2, 3 in addition to the absorption bands of CdCl2 whose electronic structure resembles the former crystals. The energy of the additional peak shifts with temperature by as much as 0.38 eV from 5.10eV at room temperature (RT) to 5.48 eV at liquid nitrogen temperature. This large peak shift is attributed to a structural phase transition between these two temperatures. A new type of electron center has been found in these crystals (M = Cd, Mn; n = 1, 2, 3) irradiated with X-rays at 15 K in addition to the Cl2 ?. This shows optical absorption bands (IR bands) in the infrared region of 10 ~ 20 kcm ?1. The IR bands are assigned to an electron center where an electron is trapped at an ammonium site in the neighborhood of a Cl? vacancy. 相似文献
922.
Characterization of porous materials by small-angle scattering has been extensively pursued for several years now as the pores
are often of mesoscopic size and compatible with the length scale accessible by the technique using both neutrons and X-rays
as probing radiation. With the availability of ultra small-angle scattering instruments, one can investigate porous materials
in the sub-micron length scale. Because of the increased accessible length scale vis-a-vis the multiple scattering effect,
conventional data analysis procedures based on single scattering approximation quite often fail. The limitation of conventional
data analysis procedures is also pronounced in the case of thick samples and long wavelength of the probing radiation. Effect
of multiple scattering is manifested by broadening the scattering profile. Sample thickness for some technologically important
materials is often significantly high, as the experimental samples have to replicate all its essential properties in the bulk
material. Larger wavelength of the probing radiation is used in some cases to access large length scale and also to minimize
the effect of double Bragg reflections. 相似文献
923.
Alba P. Santo Mariaelena Fedi Lorenzo Giuntini Pier Andrea Mandò Mirko Massi Francesco Taccetti 《Mikrochimica acta》2006,155(1-2):263-267
The external microbeam facility at the 3 MV Tandetron accelerator of the LABEC Laboratory of INFN in Florence has been used
to determine, by PIXE, major, minor and trace element abundances of minerals and groundmass in the lavas from the active Nyiragongo
Volcano (Democratic Republic of Congo), which is well known for its lava lake intra-crateric activity [e.g. 1, 2]. During
the last eruption of this volcano (January, 2002), two main flows entered the Goma town producing major devastation, forcing
the rapid exodus of about 300,000 people and causing the death of 150 persons [3]. After this eruption, the interest of the
scientific community on this volcanic area suddenly increased. In this respect, determination of major and trace element abundances
in mineral phases and groundmass of lavas may allow to constrain the evolution of magma within the volcanic system from a
quantitative view point, thus helping to better understand the way this volcano works.
PIXE measurements have been performed in a two-detector setup that makes it possible to simultaneously detect and quantify
all elements from Na to the heaviest ones; possible compositional zoning effects in the crystals can also be reliably measured
thanks to the good space resolution of the microbeam facility (better than 10 μm) and to the possibility of performing one-
and bi-dimensional scans over the areas of interest. Concentration maps of all elements can be obtained, both on-line and
a posteriori: the data are collected with a list-mode acquisition system, which allows the distribution of any detected element to be
reconstructed after completing the scan. 相似文献
924.
Sabina Ronneteg Marck-Willem Lumey Richard Dronskowski Rolf Berger 《Journal of magnetism and magnetic materials》2006
Various solid solutions TlCo2−xMexSe2 (Me=Fe, Ni and Cu) have been investigated by neutron powder diffraction, supplemented by magnetometry. The incommensurate spin-helix running along the c-axis in tetragonal TlCo2Se2 prevails for low concentrations of copper and iron but changes pitch. In the copper case, only cobalt carries a magnetic moment. On nickel substitution, however, collinear antiferromagnetic coupling between the ferromagnetic layers occurs. The magnetic moment distribution between the two transition metals in the solid solution TlCo2−xNixSe2 was tentatively probed with first principle calculations on fictive ordered TlCoNiSe2, modelled by two types of superstructures. Also the ternary mother compounds, Pauli paramagnetic TlNi2Se2 and antiferromagnetic TlCo2Se2, were investigated with the same LMTO method. 相似文献
925.
Layered hydroxides crystallize in a hexagonal structure and incorporate a number of different types of structural disorders
as an exigency of anisotropic bonding. Structural disorder contributes to the non-uniform broadening of lines in the powder
X-ray diffraction pattern. Common among the disorders are stacking faults, which broaden theh0ℓ/0kℓ reflections. Interstratification selectively broadens the 00l reflections and turbostratic disorder broadens the 0kℓ reflections. The line broadening caused by structural disorder has to be discounted before estimates of particle size are
made by applying the Scherrer formula.
Dedicated to Prof J Gopalakrishnan on his 62nd birthday. 相似文献
926.
Min Wei 《Journal of solid state chemistry》2004,177(7):2534-2541
Layered double hydroxides, novel anionic clay, meet the first requirement as inorganic matrices for encapsulating functional drugs or biomolecules with negative charge in aqueous media. In this study, naproxen has been intercalated into Mg-Al layered double hydroxide by the methods of ion exchange. The structure and composition of the intercalated material have been studied by X-ray diffraction (XRD), UV-vis spectroscopy and inductively coupled plasma emission spectroscopy. A schematic model has been proposed. Furthermore, in situ Fourier transform infrared spectroscopy, in situ high-temperature XRD, and thermogravimetry (TG) have been used to characterize the thermal decomposition of the hybrid material. It has been found that the thermal stability of the intercalated naproxen is significantly enhanced compared with the pure form before intercalation, which suggests that this drug-inorganic layered material may have prospective application as the basis of a novel drug delivery system. 相似文献
927.
Photoluminescence (PL) measurement has been made on P-doped p-GaS. The 2.35 and 2.12 eV emission bands are observed in the PL spectrum of P-doped sample at 77 K. The temperature dependence of full-width at half-maximum and the shape of the PL spectrum of the 2.12 eV emission band are characterized by the recombination mechanism of the configurational coordinate model. It is found that the 2.12 eV emission band is related to the complex center of vacancy and acceptor due to P atoms. It is found from the presence of the complex center that the P-doped samples include a high concentration of defects or defect complexes. 相似文献
928.
This work is concerned with the determination of the effective behavior of sequentially laminated composites with nonlinear behavior of the constituting phases. An exact expression for the effective stress energy potential of two-dimensional and incompressible composites is introduced. This allows to determine the stress energy potential of a rank-N sequentially laminated composite with arbitrary volume fractions and lamination directions of the core laminates in terms of an N-dimensional optimization problem.
Stress energy potentials for sequentially laminated composites with pure power-law behavior of the phases are determined. It is demonstrated that as the rank of the lamination becomes large the behaviors of certain families of sequentially laminated composite tend to be isotropic. Particulate composites with both, stiffer and softer inclusions are considered. The behaviors of these almost isotropic composites are, respectively, softer and stiffer than the corresponding second-order estimates recently introduced by Ponte Castañeda (1996). 相似文献
929.
Zhi Hua WANG Min CAI Shu Jun WANG 《中国化学快报》2006,17(6):809-812
As a novel type builder for phosphate-free detergent1,2, layered crystal sodium disilicate has many advantages over other builders for phosphate detergents. The raw material of layered crystal sodium disilicate is sodium silicate. Because of the effects o… 相似文献
930.
Everson Kandare Dongyan Wang Jeanne M. Hossenlopp 《Polymer Degradation and Stability》2006,91(8):1781-1790
Composites of poly(vinyl ester) (PVE) with copper hydroxy dodecyl sulfate (CHDS) were prepared by thermal curing. The efficiency of the additive, CHDS, in reducing flammability is demonstrated via cone calorimetry and thermogravimetric analysis (TGA). The addition of 1-10% by mass of the CHDS additive resulted in significant increments in char formation (∼4-11%) from thermogravimetric analysis (TGA). Incorporation of the CHDS into the polymer matrix at these low concentrations leads to substantial reductions in the total heat release (∼20-30%) but no significant change in the peak heat release rate. The composite materials generally ignite more quickly, however, the flame extinguishes faster for the composites relative to the virgin polymer. X-ray diffraction (XRD) and infrared spectroscopic analyses of the residues collected at various stages during thermal decomposition of the composites, suggest the participation of copper-containing species in promoting enhanced thermal stability of PVE. 相似文献