Materials Literature
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The positive temperature coefficient of resistivity (PTCR) behavior of semiconductive BaTiO 3 is well explained by the Heywang model, which predicts the resistivity behavior above the Curie point based on the acceptor state density at the grain boundaries, the charge carrier density, and the energy gap, E s , between…
Machine learning (ML) is transforming all areas of science. The complex and time-consuming calculations in molecular simulations are particularly suitable for an ML revolution and have already been profoundly affected by the application of existing ML ...Read More
The spectroscopic properties of octahedrally coordinated ${\mathrm{Ni}}^{2+}$ ions in ${\mathrm{Gd}}_{3}$${\mathrm{Ga}}_{5}$${\mathrm{O}}_{12}$ garnet are described with a five-parameter model in the framework of the adiabatic approximation. The effect of spin-orbit coupling on the vibronic potentials due to the fully…
Based on experience gained from processing samples from the Cenozoic basins of south-west Ecuador, a composite procedure for the processing of fossil diatoms from lithified or partially consolidated sediments is presented. The procedure is divided into four stages: (I) initial sample breakdown. (II) cemented rock brea…
The movement of dislocations in response to a finite-amplitude shear stress is treated as a quantum-mechanical process in which the dislocations tunnel through the lattice potential barriers and transit into adjacent potential wells. For simple potential barriers, the predicted dislocation velocity and macroscopic pla…
Highly-dense spherical particles of thorium-based oxides, ThO2 and (Th, U)O2, prepared by the sol-gel method were subjected to dissolution with nitric acid containing 0–0.05 mol/l NaF at high temperatures above 120°C. The dissolution rate depended upon temperature, fluoride concentration and UO2 content. High-temperat…
The new compound [VO(H2O)5][Cu2(bipym)2(H2O)(SO4)3]·7H2O 1(bipym = 2,2′-bipyrimidine) has been synthesised and its crystal structure determined by single-crystal X-ray diffraction [monoclinic, space group P21/c, a= 9.944(3), b= 13.928(6), c= 26.275(6)Å, β= 99.59(2)° and Z= 4]. Its structure consists of anionic alterna…
Abstract Accuracy, or how well a measurement conforms to the true value of a parameter, is important in XRD analyses in three primary areas, 1) 26 position or d-spacing; 2) peak shape; and 3) intensity. Instrumental factors affecting accuracy include zero-point, axial-divergence, and specimen- displacement errors, ste…
The effects of heat treatments of the industrial type: 8 h hold times at temperatures comprised between 600°C and lOOO’C, on the structural, mechanical and corrosion resistance characteristics of weld alloy 625 have been studied. During the heat treatments, the mean concentration ratios of Nb, MO, Si, Cr, Ni and Fe el…
The efficiency of additives against photoageing of poly(vinyl chloride) was evaluated by means of a combination of spectroscopic and chromatographic methods. IR and UV-VIS spectroscopy reveal the formation of chemical groups (such as carbonyl or polyene) that are characteristic products of the early stages of photodeg…
Thin-slice accelerated aging methodologies have not been ag gressively pursued because of concerns about the reliability and applicability of the results. The use of gases such as helium, nitrogen and carbon dioxide, which diffuse rapidly and are only sparingly soluble in the polymer, may be used to obtain a diffu sio…
A number of new DMIT derivatives have been synthesized and their structures have been determined. Among them only chiral BNPT-DTO has significant powder SHG efficiency which varies strongly with the crystal growth solvent and the crystalline temperature; this corresponds to its variability in molecular configuration.…
A rigorous numerical simulation of imaging in an optical scanning microscope is described. The sample is assumed to be a perfectly conducting one-dimensional surface-relief object. The approach is capable of taking into account multiple interactions between the illuminating field and the surface and is also valid for…
The complexation of zinc and magnesium complexes of tetra(3,5-di-tert-butylphenyl)porphyrin with 3′,5′-di-tert-butyl-2-stilbazole is reversibly photoswitchable by UV and visible light via trans–cis isomerization of the stilbazole.
Abstract
Adhesion durability of dc magnetron sputtered tantalum to in situ radio frequency (rf) plasma treated biphenyl tetracarboxylic acid dianhydride–para phenylene diamine (BPDA-PDA) polyimide films was determined as a function of repeated 400 °C thermal exposure cycles and 85 °C/80% temperature/humidity (T/H) exposures. r…
Abstract Surface treatments are applied to magnesium parts primarily to improve their appearance and corrosion resistance. Mechanical and chemical cleaning methods are used singly or in combination, depending on the specific application and product involved to ensure repetitive reliability. This article focuses on mec…
A new method for measuring the magnetostriction of silicon steel sheet using a laser Doppler velocimeter has been developed. This method has the following advantages: (a) non-contact measurement, (b) better resolution (less than 4/spl times/10/sup -8/ m under the condition that the error is within 1%) than conventiona…
A thin cylindrical shell under general thermal and mechanical shocks is considered. The fields of displacements and temperature are assumed to be coupled through a system of dynamic thermoelastic equations. The method of solution is based on Galerkin finite element and Kantorouich approximation for space and time doma…
The photophysics of polyimides and several N-arylphthalimide model compounds has been investigated as part of an effort to understand the factors that control the oxidative photodegradation of these materials. Substituents that increase the donor-acceptor (D-A) character of both polymers and models cause an enhancemen…