Materials Literature
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Abstract Laser excitation studies of CaF 2 crystals doped with 0.01 to 10% Ho 3+ using the second harmonic wavelength 532 nm of a pulsed Nd: YAG laser are carried out. Three fluorescence bands belonging to the 5 F 4 , 5 S 2 → 5 I 8 , 5 F 4 , 5 S 2 → 5 I 7 and 5 F 5 → 5 I 8 transitions are detected. Fluorescence lifeti…
The experimental tools, that is frequency-dependent conductivity and quasi-elastic neutron scattering, are briefly outlined. Spectra are then presented, and the dynamic information is read from them. As a result, the elementary steps of translational motion of ions in solids can be described on atomic scales of space…
The performances of triangular groove photoresist gratings used in transmission are studied in the visible and near-infrared regions with the electromagnetic theory. The mounting considered here associates triangular groove gratings on the hypotenuse face of a right-angle prism in a configuration, usually called a gri…
Phonon dispersion in solids is usually calculated starting from model interaction potentials. In this paper, we discuss an approach for calculating phonon energies in a crystalline solid close to melting, using the density-functional theory of freezing. This theory uses the (measured or calculated) direct correlation…
Abstract 5-Methoxy-3-methyl-6′-nitrospirobenzoselenazolinobenzopyrans have been newly prepared and their reversible structure changes induced by light were characterized by spectroscopic studies. Their stable colored-forms were identified as 5-methoxy-3-methylbenzoselenazolenium-2-trans-(5′-nitrostyryl-2′-oxide) being…
Abstract The passivity of copper in NaOH and borate buffer solutions containing chloride, bromide and fluoride ions was studied by using cyclic voltammetry and potentiostatic current transient measurements. At scan rates ≥ 20 mVs −1 , the addition of halide ions does not nearly affect the cyclic voltammograms in the a…
Dry friction is introduced into the Landau-Lifshitz equations. Numerical simulations show sustained motions or transitions to rest in a critical state. Hysteresis and Barkhausen noise can be modeled with simple structures. Dry friction in the Landau-Lifshitz equation can be a useful element in the modeling of ferromag…
In a combined photoelectron-vibrational spectroscopic study of the chemistry of formic acid interaction with A1(111) surfaces the influence of temperature, surface oxidation and coadsorption with water have been investigated. At the clean surface adsorption at low temperatures leads to deprotonation and on warming to…
Work function topography maps of a heterogeneous oxide surface were produced by a scanning Kelvin probe. The specimens studied were anodically grown films on polycrystalline titanium. The defect densities in this oxide vary from one metal grain to another, and this is responsible for the variation of work function wit…
Abstract Raman scattering and calorimetric measurements are used to study the ferro‐paraelastic phase transition undergone by [N(CH 3 ) 4 ] 2 ZnBr 4 at 287.19 K. The knowledge of its vibrational spectrum, together with the available elastic and thermal expansion data, allow to obtain the specific heat of the phase tra…
The corrosion of aluminosilicate refractories by molten aluminum, such as in melting and holding furnaces, generally leads to the formation of an alumina deposit on the refractory. In the presence of alkalies and under a reducing atmosphere the extent of corrosion is increased. This could be related to the transformat…
The diatom Chaetoceros coarctatus has been studied by light (LM) and electron microscopy (SEM, TEM), from preserved plankton samples collected in the Gulf of California and off the Pacific coast of Baja California. Observations include the finding of a number of rimoportulae in a single valve (terminal or intercalary)…
The structure of friction open-end yarns made with a much modified DREF 3 friction spinning unit with replaced suction rolls and equipped with a comber roll assembly from a Platt 881 rotor spinning unit was studied and found to be dissimilar to that of ring spun yarns. Migration theory, as it is known in ring spinning…
We studied phase transitions in an antiferroelectric liquid crystal TFMHPOBC (C 8 H 17 O-&benzf;-&benzf;-COO-&benzf;- * CH(CF 3 )C 6 H 13 ) by means of dielectric measurements and microscopic observations. Both a Goldstone mode and a soft mode were observed in the SmC * phase, but only a soft mode in the S…
peer reviewed
The high-field magnetization process in the (${\mathrm{Nd}}_{1\mathrm{\ensuremath{-}}\mathit{x}}$${\mathrm{Dy}}_{\mathit{x}}$${)}_{2}$${\mathrm{Fe}}_{14}$B system has been investigated using single crystals with x=0, 0.125, 0.2, 0.33, 0.47, 0.6, and 1. Magnetization measurements were performed using steady magnetic fi…
Abstract The synthesis of a block copolymer with polystyrene (PS) and polycarbonate (PC) segments is described. It is produced by anionic polymerization of the styrene and endcapping with a hydroxyl group followed by subsequent reaction with phosgene and bisphenol‐A. The polystyrene/polycarbonate block copolymer was u…
The Al composition of AlGaAs has been determined by four methods: high-resolution transmission electron microscopy (HRTEM), reflection high-energy electron diffraction (RHEED), photoluminescence (PL), and double-crystal x-ray diffraction (DCXRD). HRTEM is direct and the most accurate method because it does not involve…
Domain wall processes (domain wall configuration, propagation, and collapse) in magnetostrictive amorphous wires of the composition Fe/sub 77.5/Si/sub 7.5/B/sub 15/ were investigated. The wires were held under tensile stress (up to 1700 MPa in the case of as-quenched). The domain wall length and normal mobility (or da…
This paper describes an attempt at a theoretical study of large-scale tensile defor mation of plain woven fabrics. The basis of the investigation is to use a more realistic approximation of nonlinear yarn bending behavior for both the undeformed fabric state and the stress analysis than has been used by most previous…