Materials Literature
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CaF 2 :RE and CaSO 4 :RE are important phosphors. The phosphors corresponding to RE identical to Dy and Tm find applications in thermoluminescence dosimetry using ionizing radiations. Although these phosphors have been in use for several years, the mechanism of thermoluminescence in these phosphors is not well underst…
Computer simulations of Fe 3+ electron paramagnetic resonance spectra at X (9.5 GHz) and Q (34 GHz) bands in the alkali borate glass Li 2 O-2B 2 O 3 doped with Fe 2 O 3 have been carried out using an approach based on the eigenfield method applied to the 'rhombic' spin Hamiltonian, which contains only the Zeeman and q…
Single-shell nanotubes of carbon were produced by vapor-phase condensation on highly oriented pyrolytic graphite (HOPG). Atomic-resolution images were obtained using a scanning tunneling microscope (STM). The nanotubes are 1 nm wide and up to 20 nm long. The atomic structure of a zigzag configured tube is identified.…
The growth energetics of carbon nanotubes during arc discharge conditions are investigated. Ab initio molecular dynamics calcualtions show that the electric field alone cannot stabilize the growth of open metallic tubes. The addition of atoms and small clusters to tubes were studied using realistic atomic potentials.…
Abstract Various segmented block copolyetheramides based on nylon 6 and polyoxypropylene (POP) were synthesized by melt polymerization of caprolactam (CPL) and polyoxypropylene diamines (POPD) as a function of the size and content of POPD. As the content of POPD in the feed increased, the IR absorption band at 1110 cm…
Data on the synthesis and properties of various types of polyarylates, including cardo-, self-coloured, self-protecting, carbaborane-containing, stereoregular, and block-polyarylates, etc., are examined and surveyed. It is shown that polyarylates represent a promising class of polymers with a valuable set of propertie…
Abstract Solubility of methyl cellulose (MC) depends on the degree of substitution (DS), the average degree of polymerization (DP), and the distribution of methoxyl groups. Of these, the DS appears to be the most important. The DS of the MC depends on the conditions of preparation. The conditions studied in this work…
Porous silicon has received considerable attention for its potential as a silicon-based visible light emitter. In this letter we introduce the lateral photovoltaic effect in porous silicon and show its origin in amphoteric dangling bond traps at the porous silicon surface, which also play a role in the light-induced p…
We demonstrate that long random copolymers (monomer fraction $f=0.48$) can be more effective than a long symmetric block copolymer in strengthening interfaces between immiscible homopolymers. The effectiveness of the random copolymer is inferred to result from each random copolymer crossing the interface multiple time…
We calculated and analyzed for the first time the local atomic stress distributions and the elastic constants of realistic amorphous carbon networks. We found that there is always softening of the elastic constants of these isotropic systems, even in the case of nearly tetrahedral coordinations. The local stresses pla…
The shielding efficiency of various intrinsically conducting polymers (ICPs) as a function of their intrinsic properties (conductivity and dielectric constant), thickness, and temperature is determined. Two types of shielding, reflection and absorption, by ICPs are discussed. The high shielding efficiencies of highly…
ABSTRACT The most common remedy which is applied to solve mineral scaling problems in water producing North Sea fields is the scale inhibitor "squeeze" process. The central objective of this treatment is to maintain a sufficiently high level (typically, 2-50 ppm) of inhibitor in the produced water to prevent scale for…
Nitrogen-substituted graphite thin films were prepared by chemical vapor deposition (CVD) using pyrrole as a starting material. Ni was used as the substrate material whose temperature was kept in the range 700–1000 °C. The interlayer spacing of these films, determined by x-ray diffraction, was close to that of single-…
Freely suspended smectic-$C$ films, 2, 3, and 4 layers in thickness, of the achiral compound ${\mathrm{C}}_{7}{\mathrm{F}}_{15}{\mathrm{CH}}_{2}\mathrm{O}\ensuremath{-}\ensuremath{\varphi}\ensuremath{-}\mathrm{C}\mathrm{O}\mathrm{O}\ensuremath{-}\ensuremath{\varphi}\ensuremath{-}\mathrm{O}{\mathrm{C}}_{6}{\mathrm{H}}_…
Using high-resolution low-energy electron diffraction we studied in situ low-temperature molecular-beam epitaxial growth of Si/Si(111). At $\ensuremath{\sim}275 \ifmmode^\circ\else\textdegree\fi{}\mathrm{C}$ and a deposition rate of $\ensuremath{\sim}7$ bilayers/min, a roughening evolution occurs after an initial tran…
Abstract Liquid crystalline triheptyl cellulose (THC) was synthesized directly from cellulose acetate and heptyl bromide with dimethyl sulfoxide as a single‐component solvent. Synthetic conditions were studied with respect to reaction temperature, time, and yield. The molecular structure and liquid crystalline charact…
The crystal structure and the lattice dynamics of the ordered gamma -ZrD phase were studied by means of neutron diffraction and inelastic neutron scattering (INS). It was found that the actual structure of the gamma phase is orthorhombic, space group Cccm, rather than tetragonal as previously believed. The one-phonon…
Abstract This article deals with the preparation and morphological characterization of porous materials obtained by freezing and lyophilizing silk fibroin solutions. When an aqueous silk solution is frozen at different temperatures (−18, −45, and −80°C), the average pore size decreases with lowering of the freezing te…
We report on neutron scattering observations of the fast picosecond relaxation in two amorphous polycarbonates. Contrary to previous experience, one already observes these fast relaxations far below the glass transition, at temperatures where they cannot be related to the flow process. An explanation in terms of low-b…
Hydrogenated amorphous silicon nitride (a-SiNx:H) films have been fabricated by plasma-enhanced chemical vapor deposition at temperatures ranging from 50 to 250 °C. It is found that as soon as the samples are taken out from the reaction chamber and exposed to the atmosphere, the a-SiNx:H films start to oxide. The oxid…