Materials Literature
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The rheological properties of colloidal suspensions of spheres and rods have been studied using dissipative particle dynamics (DPD). We have measured the viscosity as a function of shear rate and volume fraction of the suspended particles. The viscosity of a 30 vol% suspension of spheres displays characteristic shear-…
Amorphous Si/SiO2 superlattices with 100–525 periods and a 2–3 nm periodicity were deposited by radio frequency magnetron sputtering onto silicon and quartz substrates. All samples exhibited visible photoluminescence (PL) at room temperature and the PL peak wavelength shifted towards shorter wavelengths with decreasin…
We report Monte Carlo simulations that show both vapor-liquid and closed-loop liquid-liquid equilibrium in a pure substance, for a model fluid that forms orientation-dependent intermolecular bonds. This is the first time that direct evidence of liquid-liquid immiscibility in a pure fluid has been found using exact met…
One of the most serious forms of damage that occurs during the integration of Pt/PZT/Pt ferroelectric capacitors [where PZT is Pb(ZrxTi1−x)O3] is the disappearance of polarization hysteresis characteristics during the passivation process. The hydrogen content of the atmosphere during this process affects the ferroelec…
Scanning force microscopy has been used to perform a comparative nanoscale study of domain structures and switching behavior of Pb(ZrxTi1−x)O3 (PZT) thin films integrated into heterostructures with different electrodes. The study revealed a significant difference between polarization state of as-deposited PZT films on…
We provide a systematic test of empirical theories of covalent bonding in solids using an exact procedure to invert ab initio cohesive energy curves. By considering multiple structures of the same material, it is possible for the first time to test competing angular functions, expose inconsistencies in the basic assum…
Some recent progress in the study of liquid foams is reviewed in outline. Calculations of foam conductivity are presented, which further improve upon the approximation recently proposed by us, in accounting for the nonlinearity in the dependence of conductivity on liquid fraction.
Slow sublimation of the dithiadiazolyl radical 1 yields crystals of a new polymorph 1β (orthorhombic, space group Fdd2). Below 36 K this new phase exhibits a spontaneous magnetic moment, which is described in terms of canted antiferromagnetism.
We design three-phase composites having maximum thermal expansion, zero thermal expansion, or negative thermal expansion using a numerical topology optimization method. It is shown that composites with effective negative thermal expansion can be obtained by mixing two phases of positive thermal expansions with a void…
We report on the fabrication of a new class of trilayer epitaxial thin film devices based on the doped perovskite manganates La–Ca–Mn–O and La–Sr–Mn–O. We show that large resistance changes, up to a factor of 2, can be induced by a moderate applied magnetic field below 200 Oe in these trilayers supporting current-perp…
A computational approach is presented to obtain energy-minimized structures in glassy materials. This approach, the activation-relaxation technique (ART), achieves its efficiency by focusing on significant changes in the microscopic structure (events). The application of ART is illustrated with two examples: the struc…
The x-ray line profiles of an ultrafine grained copper crystal, produced by equal-channel angular pressing, were measured by a special high resolution diffractometer with negligible instrumental line broadening. The analysis of the line breadths and the Fourier coefficients have shown that taking into account the cont…
The variation of photoemission from negative electron affinity semiconductor surface with the position of the surface Fermi level is theoretically studied. Resonance maxima both in photoyield and surface recombination rate (when the depth and the width of the quantum well in the band bending region (BBR) are close to…
X-ray photoelectron spectroscopy (XPS) is a well established surface analytical technique capable of giving elemental and chemical state information for nearly all elements. Recent improvements in the sensitivity of the method have made spatially resolved XPS a viable technique with, at present, a resolution of 5-30 μ…
Dynamic susceptibility and electrical resistance of thin films of ${\mathrm{Cd}}_{1\mathrm{\ensuremath{-}}\mathit{x}}$${\mathrm{Mn}}_{\mathit{x}}$Te (0\ensuremath{\leqslant}X\ensuremath{\leqslant}0.6) deposited on Corning 7059 glass substrates at a 650-K substrate temperature were studied in the 20--300-K temperature…
beta-Azafulvenones 16 and 33 were generated from 14 or 18 and 31 or 37, respectively, and directly observed by IR spectroscopy. These heterocyclic ketenes tetramerize to the macrocycles 20 and 34.
Graft copolymerization of methyl methacrylate onto curdlan was first investigated. In the graft copolymerization initiated by ammonium persulfate (APS) in DMSO under a homogeneous condition, the resulting graft copolymers had low molecular weights and low grafting percentages. However, the initiation by APS in water g…
We have used the photoacoustic technique in an open photoacoustic cell configuration to measure the thermal diffusivity of conducting polypyrrole films. The samples were obtained by electrochemical deposition from solutions of pyrrole dissolved in 0.08 M p-toluene sulfonic acid and their thicknesses were in the 50–125…
The crystal structures of H2SO4 and (H3O)(HSO4) have been refined with good accuracy (R = 0.027 and 0.033, respectively) making a discussion of hydrogen bonding now possible. In sulfuric acid the S—O and S—OH distances are 1.426 (1) and 1.537 (1) Å, respectively, and the structure is characterized by layers of hydroge…
A model is presented to explain the transition of the angular distribution of valence-band photoelectrons from the low-energy regime, characterized by emission only along the Mahan cones, to the high-energy regime, characterized by emission patterns very similar to those of core-level photoelectron diffraction. The tw…