Materials Literature
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We present a model for the propagation of optical beams in a nematic droplet. For a low intensity electromagnetic field, we first derive an analytical asymptotic expression for the configuration of a nematic droplet that satisfies hard-anchoring, bipolar boundary conditions. Then, from Maxwell's equation, we find the…
This paper discusses how the luminescence-excitation method affects the spectral content of the emission in ZnS: Mn single crystals. It shows that the nearest neighborhood of the Mn 2+ ions is associated with the elementary emission bands having maxima at the wavelengths λ m =557, 578, 600, 616, and 638±2 nm in zinc s…
Grain‐boundary sliding and grain interlocking of two‐phase ceramics during creep are examined on the basis of the Dryden–Kucerovsky–Wilkinson–Watt theory. That theory is extended to the plane–strain creep deformation of model arrays of square and hexagonal grains embedded in a continuous grain‐boundary melt phase to d…
The Mössbauer spectra of a series of rhombohedral Tb2Fe17−xSix solid solutions, with x equal to 0, 1, 2, and 3, have been measured as a function of temperature. Although the spectra of Tb2Fe17 change substantially upon cooling from 295 to 85 K, it has been possible to fit them with a consistent seven sextet model corr…
Abstract This report re-examines the technical basis for the AET as presented inPCA Research Department Bulletin RX45 as well as more recent research. Thefocus is on the potential for disruptive expansions caused by crystallineMgO in portland cements hydrated under various conditions, including the AET.Much of the dat…
Using an oriented single crystal, Raman and infrared vibrational spectra have been measured for phenakite, Be 2 SiO 4 . The results have been interpreted on the grounds of Born−von Karman rigid-ion lattice-dynamical calculations, using empirical potentials derived from fitting the vibrational frequencies of a group of…
Magnetostriction λ∥(H) and field-induced phase transitions were studied in the single crystal of La1−xSrxMnO3 (x=0, 0.05, 0.1, and 0.175) in the pulsed magnetic fields up to 230 kOe. Anomalies in the λ∥(H) curves were revealed at 200 kOe in the LaMnO3, which were identified with the spin-reorientation AyFz→AzFy in the…
Electrical properties of defect structure in Ni-doped (Ba 1- x Sr x )TiO 3 ceramics were studied by means of electron spin resonance (ESR), thermally stimulated current (TSC), dielectric and conduction measurements. A set of experimental results revealed that the nickel cations were located on the B-site of the perovs…
Abstract The crystal structure of the ternary Co 2 NiAl 9 (Y 2 phase in the Co–Ni–Al system) has been solved by single crystal methods. Despite the expectation, the Y 2 structure cannot be considered as a possible approximative structure for decagonal/icosahedral phases because of the small size of the structural segm…
Thermoelectric power measurements have been made on macroporous (pore width >500 Å°) porous silicon samples prepared by an anodic dissolution technique. The sign of thermopower is found to be negative indicating that conduction takes place due to electrons in the conduction band. The conduction mechanism is fou…
Two different approaches to hysteresis modeling are compared using a common ground based on energy relations, defined in terms of dissipated and stored energy. Using the Preisach model and assuming that magnetization is mainly due to domain-wall motion, one can derive the expression of magnetization along a major loop…
La 0.7 Sr 0.3 Mn 1−x Ru x O 3 , 0⩽x⩽0.2 samples were prepared both in bulk and thin film formed using pulsed laser deposition. Magnetization measurements of bulk samples indicate a marginal decrease in Tc from 366 to 335 K up to 15% Ru substitution in Mn site. X-ray diffraction of the 〈100〉 oriented epitaxial films in…
The reactions of O(1D) atoms with fluorides have been investigated by time-resolved laser magnetic resonance (LMR). O(1D) atoms were produced by the dissociation of ozone with an excimer laser (KrF, 248 nm). By monitoring Cl atoms (when HCl or Cl2 is added) or FO radicals, the rate constants for total removal of O(1D)…
Quantitative texture analysis, which included calculation of the orientation distribution function, was used to demonstrate textures in hot‐pressed and subsequently annealed silicon carbide (SiC). The results indicated that the hot pressing and annealing could produce strong textures in SiC. Grain rotation during hot…
Two superstructures of the TTB type (tetragonal tungsten bronze) exist in the system Nb 2 O 5 /WO 3 . They are caused by an ordered arrangement of pentagonal tunnels filled with metal–oxygen strings. Besides the well known 4:9 phase (Nb 8 W 9 O 47 ), which has a tripled b axis, evidence for a new orthorhombic structur…
To understand the mechanism behind the pitch change during the transient planar to the planar state transition of a cholesteric liquid crystal (while it is relaxing from the homeotropic state to the planar state), we studied a more controlled situation of pitch change in a thermochromic liquid crystal. We studied the…
Oxiranes, such as glycidyl phenyl ether (GPE) and benzyl glycidate (BG), were copolymerized with succinic anhydride (SA) by lipase at a temperature between 60 and 80°C to yield the corresponding polyesters bearing carboxyl or phenyl groups. Bulk polymerization, especially at the temperature of 80°C, and preferably usi…
We report here the results of the synthesis of soluble polymers derived from 3,4- ethylenedioxythiophene. Starting from a 3,4-ethylene dioxythiophene monomer functionalized by an hydroxymethyl group, we synthesized several monomers bearing different side groups. The influence of alkyl chain length of side groups was s…
The synthesis and structural characterization of the novel [MnIII,IV2O2(N,Nbispicen)2](ClO4)3·CH3CN complex employing the tetradentate ligand N,Nbispicen = N,N-bis(2-pyridylmethyl)-1,2-diaminoethane are reported. Magnetic properties were determined and show that the ground state is a spin doublet. This can be quantita…
The effect of prepolymer structure on the electro-optic properties of polymer dispersed liquid crystals (PDLCs) prepared from UV-cured polyurethane acrylates (PUAs) has been studied. Among four types of films with different soft-segment structure, polypropylene glycol (PPG)- and polytetramethyl ether glycol (PTMG)-bas…