Materials Literature
按标题、摘要、年份、主题和来源检索公开元数据。结果保留作者、摘要、分类与原始来源链接。
We present valence and core-level photoemission measurements from vacuum-fractured, single-crystal barium titanate. These results resolve contradictory measurements in the literature which have employed other methods of sample surface preparation. The valence-shell electronic structure is compared with previously publ…
The atomic and electronic structures of microtubules of graphitic carbon have been investigated by ab initio molecular dynamics. Fully optimized atomic structures of two microtubules, a reflection symmetric and a chiral, are found to differ little from their ideal, graphite-derived geometries. Both are semiconductors…
We report here results from experiments on low-frequency Raman scattering from CdS microcrystals of various sizes embedded in a germanium dioxide glass matrix. We observed peaks in the low-frequency region in the tail parts of the Rayleigh lines and we found that the frequencies of these peaks were proportional to the…
Abstract The cure of a liquid dicyanate ester monomer, which reacts to form a high‐ T g (≈200°C) polycyanurate network, has been investigated using differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR), and a dynamic mechanical technique, torsional braid analysis (TBA). The monomer is…
The administration of drugs directly into the central nervous system using polymers as drug carriers may improve the treatment of malignant brain tumors. In this study, the effect of the interstitial, localized delivery of 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU) incorporated into controlled release polymers implan…
Polyaniline (PANI) films of superior homogeneity can be prepared by using functionalized protonic acids to protonate the polymer and simultaneously induce solubility, in the conducting form, in common organic solvents. The results of measurements of the temperature dependence and magnetic-field dependence of the condu…
Nanometer-size semiconductor particles coated with another semiconductor can exhibit unusual and interesting phenomena associated with the redistribution of the electron and hole wave functions. Using the band offsets and effective masses, the overlap of the electron and hole wave functions can be altered by changing…
The electronic structure of coaxial, graphene double-layer tubules is predicted for various combinations of metallic and insulating constituent inner and outer monolayers, depending on the diameter and chirality of the tubule. For the examples chosen, some of the energy bands of the inner and outer tubules are coupled…
The electronic structure of nanocrystalline Si which shows visible photoluminescence is calculated using the density-functional approach for finite structures. Except for geometry this is the same theory as for first-principles band structures of semiconductors and other solids. Our results for clusters ranging up to…
A homogeneous system for the selective, catalytic oxidation of methane to methanol via methyl bisulfate is reported. The net reaction catalyzed by mercuric ions, Hg(II), is the oxidation of methane by concentrated sulfuric acid to produce methyl bisulfate, water, and sulfur dioxide. The reaction is efficient. At a met…
Single-domain microcrystals of LaC(2) encapsulated within nanoscale polyhedral carbon particles have been synthesized in a carbon arc. Typical particle sizes are on the order of 20 to 40 nanometers. The stoichiometry and phase of the La-containing crystals have been assigned from characteristic lattice spacings observ…
The reaction between methane and oxygen over platinum and rhodium surfaces in metalcoated ceramic monoliths can be made to produce mostly hydrogen and carbon monoxide (greater than 90% selectivity for both) with almost complete conversion of methane and oxygen at reaction times as short as 10(-3) seconds. This process…
The dielectric constants of a series of hydrothermally grown berlinite crystals containing increasing amounts of H 2 O were determined using a two-terminal method and empirically determined edge corrections with kappa 11 T ranging from 4.67 to 4.86 and kappa 33 T from 4.54 to 4.76. The extrapolated values for 'dry' be…
The reversible photoisomerization of azobenzene derivatives is known for its anisotropic properties. We study the dichroism and the anisotropy induced by a linearly polarized pump in DR1 doped PMMA films and in a copolymer of PMMA and DR1. We demonstrate the competition of three processes, the angular hole burning (AH…
The range of optical and thermal properties offered by Nd-doped phosphate glasses allows these materials to service a variety of laser applications. For example, the high extraction efficiency, low non-linear index and superb optical quality render Nd:phosphate glasses suitable for large-scale fusion laser technology.…
Proton induced absorption over the 350 nm to 2500 nm spectral region and the growth of that absorption with increasing dosage was determined for four glasses (Schott glasses FK3, SF57, IRG7, and Corning Glass Works fused silica 7940). For FK3 and SF57 we can compare the proton induced absorption with x- ray induced ab…
The structural model of fluoride phosphate glasses can be described as Al(F,O)<SUB>6</SUB>-octahedral chains bonding by mono- and diphosphate groups and cations. Proofs are given of Raman and NMR spectroscopy. These glasses posses special optical properties making them attractive candidates for application in high per…
Stable nematic director fields of liquid crystals confined to cylindrical cavities which enforce homogeneous concentric anchoring depend on the competition between azimuthal and polar molecular anchoring strengths and the surface elastic constant ${\mathit{K}}_{24}$. Deuterium nuclear-magnetic-resonance line shapes of…
The soft potential model (an extension of the tunneling model to include soft localized vibrations) is shown to describe the anomalous features of the specific heat ${\mathit{C}}_{\mathit{P}}$ and the thermal conductivity of glasses over the entire low-temperature range, up to an including the peak in ${\mathit{C}}_{\…
Abstract Three‐ and four‐element mechanical analogues are commonly used to describe viscoelastic behavior in creep (deformation under constant force or stress) but not in stress relaxation (stress response after a suddenly imposed, constant strain). Mathematical models of the mechanical analogues in stress–relaxation…