Materials Literature
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We demonstrate a fully analytical method for calculations of excited state static and dynamic polarizabilities. From the double residues of a single reference state cubic response function all excited state polarizabilities can be determined. The method forms also a basis for calculations of excited state hyperpolariz…
Resistivity, susceptibility, and specific heat measurements on the new layered superconductors ${\mathrm{Y}}_{2}{\mathrm{C}}_{2}{\mathrm{I}}_{2}$ and ${\mathrm{Y}}_{2}{\mathrm{C}}_{2}{\mathrm{Br}}_{2}$ have been performed to characterize their superconducting state. Our experiments indicate bulk superconductivity with…
A hybrid technique is reported, which combines magnetron sputtering and pulsed laser ablation to produce plasma fluxes intersected on a substrate surface to form metal, ceramic and diamond-like materials. Deposition of crystalline Ti, TixCy, TiCN, and amorphous diamond-like carbon films at low temperatures by the new…
Self-consistent field theory is used to study the phase behavior of melts of semiflexible diblock copolymers. Repulsion between the incompatible blocks leads to microphase separation, while anisotropic external fields and interactions between polymers induce liquid-crystalline phases. Considering symmetric diblocks wi…
Carbon nanotubes have been synthesized by heat treating the polymer at 400 °C in air which was obtained by polyesterification between citric acid and ethylene glycol. Transmission electron micrographs and an electron diffraction pattern showed the formation of carbon nanotubes. The diameter of the tubes ranged from 5…
Results on a lanthanum-modified, lead zirconate-titanate have revealed (1) pressure-induced crossover from normal ferroelectric- (nFE-) to-relaxor (R) behavior; (2) the continuous evolution of the dynamics of the relaxation process; (3) a spontaneous R-to-nFE transition at a temperature well below the dynamic glass te…
A molecular model of network-forming liquids has been formulated in terms of a lattice fluid in which bond formation depends strongly on molecular orientations and local density. The model has been solved in the zeroth- and first-order approximations for molecular and bond geometries similar to water or silica. Result…
Dielectric spectroscopy up to 370 GHz has been performed on supercooled glycerol for temperatures between 250 and 330 K. The high-frequency dielectric loss, ${\ensuremath{\varepsilon}}^{\ensuremath{'}\ensuremath{'}}$, has been investigated by coherent-source submillimeter-wave spectroscopy. Special attention is given…
The optical properties of the linear chain compound bis-(tetramethyltetraselenafulvalene)hexafluoro-phosphate, (TMTSF${)}_{2}$P${\mathrm{F}}_{6}$, were examined in an extremely wide frequency range in the metallic state, above the spin density wave transition ( $T>12\mathrm{K}$). Parallel to the chains the conducti…
A simple lattice model describing the recombination dynamics in visible-light-emitting porous silicon is presented. In the model, each occupied lattice site represents a Si crystal of nanometre size. The disordered structure of porous silicon is modelled by modified random percolation networks in two and three dimensi…
It is shown that unique defect thermodynamics and transport properties result for oxides of a few nanometers crystallite size. Fully-dense CeO2−x polycrystals of ∼10 nm grain size were synthesized, and their electrical properties compared with those of samples coarsened from the same material. The nanocrystals showed…
Raman shifts of Si nanocrystals versus size were studied theoretically by a bond polarizability model. Zero-dimensional spheres and one-dimensional columns were considered. The relation between the Raman shift and the size for Si spheres and columns was established, from which the size of Si nanocrystals can be obtain…
Nickel ferrite nanoparticles exhibit anomalous magnetic properties at low temperatures: low magnetization with a large differential susceptibility at high fields, hysteresis loops which are open up to 160 kOe, time-dependent magnetization in 70 kOe applied field, and shifted hysteresis loops after field cooling. We pr…
We study {{\rm C}$_{60}$} with the use of Thomas-Fermi theory. A spherical shell model is invoked to treat the nuclear potential, where the nuclear and core charges are smeared out into a shell of constant surface charge density. The valence electron distribution and the electrostatic potential are efficiently compute…
Aromatic polyesters, prepared by the reaction of aromatic dicarboxylic acids and 1,4-butanediol, were used to improve the toughness of bisphenol-A diglycidyl ether epoxy resin cured with p,p′-diaminodiphenyl sulfone. These polyesters contained poly(butylene phthalate)s (PBP), poly(butylene phthalate-co-butylene isopht…
The influence of thermal history on the properties of commercial P(3HB-co-12%-3HV) was studied. Thermogravimetric analysis and differential scanning calorimetry revealed that the plasticizer evaporated at 140°C or higher. The loss of plasticizer during thermal treatment at 170 and 180°C resulted in a slight increase o…
This article studies the influence of the heating rate and sample weight on the thermal decomposition of polystyrene (first-order kinetics). For this purpose, the kinetic parameters (i.e., frequency factor and activation energy), variables at the maximum decomposition rate (such as conversion, reaction rate, and tempe…
Microporous polypropylene sheets were prepared as follows. First, polypropylene pellet-containing CaCO3 filler was extruded to prepare base sheets, which were then biaxially stretched. The draft effect at the extrusion process was studied in relation to some properties of the resultant microporous polypropylene sheets…
Data on the tensile yield behavior of poly(vinyl chloride) (PVC), reported in the literature, are interpreted in terms of a model involving a cooperative movement of several independent structural units, all with the same activation enthalpy. This analysis leads to physical parameters such as the internal stress, acti…
Wood is an inexpensive filler that reduces the overall cost of polymer composites, with loss in some properties (e.g., ultimate strength, elongation, and water sorption often suffer with the addition of fillers) and a gain in others (e.g., Young modulus increment, reduced weight with respect to inorganic fillers, redu…