Materials Literature
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Computer Program Abstracts The category Computer Program Abstracts provides a rapid means of communicating up-to-date information concerning both new programs or systems and significant updates to existing ones. Following normal submission, a Computer Program Abstract will be reviewed by one or two members of the IUCr…
This article deals with the characterization of the structural changes induced by uniaxial extension in the amorphous phase of an ethylene/butene copolymer. Volume change measurements indicate a reversible densification relevant to a strain-induced organization in the amorphous phase. The dynamic mechanical behavior s…
The fundamental results of the Coupling Model, i.e . crossover from independent relaxation at short-times to slowed down cooperative relaxation at a temperature independent time t c, are represented by three equations. They are shown to be in accord with experimental data in molecular glass formers, glass-forming, gla…
Poly(OxyMethylene) (POM) and its miscible blends were studied by multifrequency A.C. dielectric and thermally stimulated currents (TSC). The blends contained small amounts of either poly(vinyl phenol), which is a high glass transition (Tg) diluent, or a styrene-co-hydroxy styrene oligomeric low Tg diluent. The variati…
We describe an original QSPR model called the EVM model (Energy, Volume, Mass) to calculate the glass transition temperature (Tg) of aliphatic acrylate and methacrylate homopolymers using classical molecular mechanics and dynamics. The latter was used to calculate an energy density function related to the cylindrical…
The novel polyetherethersulfone (PES-C) prepared from phenol-phthalein in our institute is an amorphous, rigid, tough material with good mechanical properties over a wide temperature range. To improve its water vapor permeability for the application of gas drying, the PES-C was sulfonated with concentrated sulfuric ac…
The miscibility of polycarbonate PC and poly(butylene terephthalate) PBT is controversially discussed in the literature. Partial miscibility has been generally found in melt blends of the two polymers. However, in solution cast blends they were found to be immiscible. It is known that the transesterification takes pla…
A series of polyesters were synthesized by the bulk polycondensations of the respective combinations of two difuranic diesters, i.e., bis(5-(methoxycarbonyl)-2-furyl)methane (4a) and 1,1-bis(5-(methoxycarbonyl)-2-furyl)ethane (4b), with two 1,4 : 3,6-dianhydrohexitols [1,4 : 3,6-dianhydro-D-glucitol (1) and 1,4 : 3,6-…
The results of the studies of the structure and properties of non-crystalline (liquid and amorphous) oxide systems obtained using computer simulation methods are summarised. The models of simple oxides, homologous series of non-crystalline oxides and of binary and multi-component oxide systems are considered. The resu…
In nature, supercooled liquids play an important role in areas as diverse as volcanoes and hibernating animals. From a technological standpoint, supercooled liquids are linked intimately to processes ranging from the development of new materials to the storage of nuclear waste. It is also becoming increasingly evident…
Polyaniline, synthesized by using potassium dichromate as the oxidant, was doped with iodine in order to increase its electrical conductivity. The iodine-doped polyanilines attained a conductivity of 1.83 × 10−3 S/cm, which was about eight orders of magnitude greater than that of intrinsic polyaniline. The iodine-dope…
The kinetics of the isothermal polymerization of acrylic acid were determined utilizing 1H-NMR spectroscopy. The polymerization rate was observed to depend approximately on the \documentclass{article}\pagestyle{empty}\begin{document}$ \frac{3}{2} $\end{document} power of monomer and the \documentclass{article}\pagesty…
It has been revealed using microlensing that a considerable part, possibly more than half, of the dark matter in the halo of our Galaxy consists of objects with a mass spectrum ranging from 0.05 to 0.8 of the solar mass. What is the nature of these objects? There exist two hypotheses. According to one, these are Jupit…
In ab initio calculations of electronic structures, total energies, and forces, it is convenient and often even necessary to employ a broadening of the occupation numbers. If done carefully, this improves the accuracy of the calculated electron densities and total energies and stabilizes the convergence of the iterati…
An analytical theory is presented for the damping of low-frequency adsorbate vibrations via resonant coupling to the substrate phonons. The system is treated classically, with the substrate modeled as a semi-infinite elastic continuum and the adsorbate overlayer modeled as an array of point masses connected to the sur…
We calculate the electronic structure of nm scale InP islands embedded in $Ga_{0.51}In_{0.49}P$. The calculations are done in the envelope approximation and include the effects of strain, piezoelectric polarization, and mixing among 6 valence bands. The electrons are confined within the entire island, while the holes…
The structure of the complex perovskite (PFT), which belongs, according to the literature, to the ferroic species , has been refined by single-crystal and powder x-ray diffraction at room temperature, i.e. within the range of stability of the cubic phase. Attention has been paid to the possible presence of tetragonal…
Cathodoluminescent phosphors excited at low voltages and high current densities often exhibit brightness saturation due to ground state depletion. A two-level model can be used to show that the luminance and saturation behavior of low voltage phosphors can be greatly improved by choosing phosphors with an activator de…
phosphors find applications in dosimetry of ionizing radiations. Phosphors having Dy or Tm activators are high-sensitivity thermoluminescence dosimetry materials, while the phosphors with Eu or Sm activators are the proposed materials for radio-photoluminescence dosimetry. Mechanisms of several processes related to va…
A confocal Raman spectroscopy was used to measure intrinsic stress distribution on the growth surface within individual grains of chemical-vapor-deposited diamond film. Polarization analysis of the Raman line shape revealed that even in high quality (2.8 cm−1 linewidth), free-standing film of 0.6 mm thickness, small r…