Materials Literature
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We report on our observation of the formation of permanent holographic gratings induced in nematic liquid crystals doped with carbon nanotubes by the simultaneous action of both a spatially modulated light and dc electric field. Properties of these irreversible gratings were investigated with a normally incident laser…
Abstract Three raw samples of Fe-rich smectites from Gafsa (Jebels Shemsi and Hammadi, Tunisia) have been characterized by different techniques which indicate that they contain (15 – 20%) illite, probably interstratified and to a lesser extent they also contain kaolinite, calcite, quartz and Fe oxides. These samples p…
For the first time, time-resolved emission and excitation spectra, as well as decay kinetics of luminescence of CsCl : Tl single crystals have been measured at 10 K under excitation in the 4–20 eV energy range. The results obtained confirm the earlier conclusion that the emission spectrum of the main thallium centres…
It is shown that high-temperature treatment of self-poled lead zirconate-titanate films containing an excess of lead oxide, followed by prolonged storage at room temperature, results in a charge redistribution in the near-electrode regions of ferroelectric films. Such heat treatment destroys, as a rule, the self-poled…
From heat capacity measurements performed in the 5-350 K temperature range at 0- and 5-Tesla applied magnetic field on the intermetallic compounds Gd/sub 7/Pd/sub 3/ and Gd/sub 7/Pd/sub 2/Ni, and on the eutectic between Gd and Gd/sub 7/Pd/sub 3/ with composition Gd/sub 76/Pd/sub 24/, the main magnetocaloric properties…
Abstract. The physical mechanisms responsible for the wide variation of metallic color within a single species, Plateumaris sericea, were investigated by the structural observations and the spectral analysis of the reflected light. The surface of elytra consisted of epicuticle and exocuticle, both having high and low…
Abstract The equilibrium solubility of CsCl‐CeCl 3 ‐HCl (11%)‐H 2 O quaternary system at 25 °C has been determined by the physic‐chemical analysis method, and the phase diagram was plotted. Two new double salts 3CsCl · CeCl 3 · 3H 2 O and CsCl · CeCl 3 · 4H 2 O obtained from the complicated system were identified and…
Abstract Photochromic reactions of some substituted 2-hydroxychalcones [3-(2-hydroxyphenyl)-1-phenyl-2-propen-1-ones] have been studied in solid hydrogel matrices. The results demonstrated good reversibilities for the chalcone-flavylium interconversion. Thus, in an agar-gel matrix the coloration-decoloration could be…
We report the fabrication of thin films perforated by high aspect ratio helical or chevron pores by an extension of the glancing angle deposition (GLAD) technique. The perforated films were created by transferring the nanostructure of a GLAD template film into target materials such as polymers and spin-on-glasses and…
Two compounds of EuII with benzo-18-crown-6, triaqua(benzo-18-crown-6)europium(II) diperchlorate (1) and triaqua(benzo-18-crown-6)europium(II) perchlorate hydrate benzo-18-crown-6 solvate (2), were synthesized by electrochemical reduction. The coordination environment of the metal cation in both cases contains six O a…
The reaction of N-(4-n-alkoxysalicylidene)-4′-n-alkylanilines with freshly prepared lanthanide salts leads to mesomorphic terbium and dysprosium complexes exhibiting the smectic A phase.
The matrix Δ suggested by Berreman for optically active crystals of various symmetry classes has been calculated with the use of the Mathematica-4.1 package. It is shown that the eigenvalues of this matrix are the refractive indices, whereas its eigenvectors determine the polarization states of eigenwaves propagating…
Abstract. Colloidal crystals are the suspensions in which colloidal particles distribute regularly as atoms and molecules do in metals and protein crystals. Giant colloidal crystals invented by the authors emit brilliant iridescent light by the Bragg diffraction and are quite beautiful. In this article recent works in…
By solid state reaction two new layered perovskites have been synthesized related to the Ruddlesden-Popper family, K2La2/3Ta2O7 and Li2La2/3Ta2O7, with La partial occupancy of the 12-coordinated site. The structures of K2La2/3Ta2O7 and Li2La2/3Ta2O7are respectively determined by powder X-ray diffraction and by single…
Abstract The electroactive copolymer of poly(acryloyl chloride) (PAC) and polypyrrole (PPy) can be synthesized by electrochemical polymerization using a polymer precursor which contains a pyrrole moiety in its side chain. Poly(acryloyl pyrrole) (PAP) was synthesized chemically with acryloyl chloride and potassium pyrr…
A one‐dimensional nonisothermal model has been developed for the “rapid carbothermal reduction” synthesis of fine silicon carbide powders. Intrinsic reaction and self‐diffusion kinetics are identified through simulation of the model and comparison to experimental results. The reaction rate follows a shrinking‐core mec…
Hydrogen-induced degradation in Pb(ZrxTi1−x)O3 (PZT) thin film capacitors is investigated in terms of three process parameters, such as electrode structures (Pt/PZT/Pt and Ir/IrO2/PZT/Pt/IrO2), Zr/Ti compositional ratios (60/40, 53/47, 40/60, 30/70), and the domain poling states (±5 V). It was found that the hydrogen-…
A comparative study is made of the copper corrosion rate and corrosion products originated by acetic and formic acid vapours at 40%, 80% and 100% relative humidity (RH) using gravimetric, scanning electron microscopy, X-ray powder diffraction and X-ray photoelectron spectroscopy techniques. Five acetic and formic acid…
There is much interest in developing industrial processes to manufacture extruded polystyrene foam that do not involve ozone depleting blowing agents. A popular alternate candidate is HFC-134a. It has a zero ozone depletion factor and is nearer in chemical structure to standard blowing agents (CFC-22 and HCFC-142b) th…
Nonoriented electrical steels have been cut using pulsed or continuous-laser techniques and mechanical cutting has been used as a reference. The corresponding states of internal stresses at the cut edges have been systematically investigated by X-ray diffraction, for both laser and mechanical cut samples. The characte…