Materials Literature
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The structural evolution and magnetic properties of nanostructured copper ferrite, CuFe 2 O 4 , have been investigated by x-ray diffraction, Mössbauer spectroscopy, and magnetization measurements. Nanometre-sized CuFe 2 O 4 particles with a partially inverted spinel structure were synthesized by high-energy ball milli…
The solid solutions La 2 Ni 1–x Fe x O 4+δ (x = 0.02 and 0.10), La 1.9 Sr 0.1 Ni 1 – x Fe x O 4 + δ (x = 0.02 and 0.10) and La 2 Ni 0.88 Fe 0.02 Cu 0.10 O 4+δ with the tetragonal K 2 NiF 4 -type structure were prepared by a standard ceramic technique. The thermal expansion coefficients of the ceramic materials, calcul…
The reconstruction of layered double hydroxides with the hydrotalcite-like structure from material previously calcined at increasing temperatures has been studied. Both the calcination temperature and the time the samples spent equilibrating with a controlled water vapour pressure have been considered. The crystallini…
The crystal structures of a large number of silica polytypes ( - and -quartz, - and -cristobalite, -tridymite, keatite, coesite and stishovite) have been studied using density functional theory, both in the local density approximation and including generalized-gradient corrections to the exchange-correlation functiona…
Magnetic and microwave absorbing properties have been investigated in the M-type barium ferrites (BaFe/sub 12-2x/A/sub x/Co/sub x/O/sub 19/) with planar magnetic anisotropy. For the tetravalent A ions, Ti/sup 4+/ and Ru/sup 4+/ are chosen and the samples are prepared by a conventional ceramic processing technique. At…
We present numerical simulations which support the formal asymptotic analysis relating a multiorder parameter Allen--Cahn system to a multiphase interface problem with curvature-dependent evolution of the interfaces and angle conditions at triple junctions. Within the gradient energy of the Allen--Cahn system, the nor…
Beside normal cyclization/ring-opening photochromic reactions, a side reaction to produce a photostable by-product took place when 1,2-bis(2-methyl-5-phenyl-3-thienyl)perfluorocyclopentene was irradiated in deaerated hexane with ultraviolet light.
Amorphous silver nanoparticles of ca. 20 nm size have been prepared by the sonochemical reduction of an aqueous silver nitrate solution in an atmosphere of argon-hydrogen. The silver nanoparticles have been characterized by TEM, X-ray diffraction, absorption spectroscopy, differential scanning calorimetry and EPR spec…
Polarized neutron scattering has been used to determine the changes in the distribution of unpaired electrons which take place in the martensitic transition in Ni 2 MnGa. Ni 2 MnGa is a ferromagnetic Heusler alloy which undergoes a reversible transition at about 220 K from a high temperature cubic phase to a low tempe…
A chemical precipitation method has been used for the synthesis of ZnO nanoparticles with controlled morphology. The precursor powders were prepared using several precipitation reagents and using ammonium carbamate as a precipitating reagent led to unusual rod-shape morphology. The precursor was decomposed by heating…
We study the aging of a colloidal glass, which is obtained for extremely low volume fractions due to strong electrostatic repulsions, leading to the formation of a "Wigner glass". During the aging, a new crossover between a complete and incomplete decay of the correlation function is observed, accompanied by an increa…
Polythiophenes are a very versatile class of conjugated polymers. Substituted polythiophenes can be tailored for various applications by designing the side groups to give the polymer different desired properties. Our work on preparing polythiophenes designed to have high stability in the doped state is described. We a…
The electronic structure of zinc aluminate (ZnAl 2 O 4 ) and that of zinc gallate (ZnGa 2 O 4 ) were studied by the self-consistent tight-binding linearized muffin-tin orbital method with the atomic sphere approximation. The calculated results predict these zinc-based spinel oxides to be direct-gap materials. The dire…
For amorphous ruthenium, the current‐voltage characteristics of cyclic voltammetric (CV) curves depended strongly on the voltage scan rate. At high voltage scan rates, asymmetrical reduction and oxidation current behavior was obtained. The specific capacitance decreased with increasing voltage scan rate. The composite…
A general formulation for the analysis of complex Bravais crystals using atomic energy functionals embedded within a finite element framework is presented. The method uses atomistic potentials to determine the constitutive response of the system. Unlike traditional finite element methods, the nonlinear elastic effects…
Nanocomposites containing silicon and titanium nitride were synthesized by high‐energy mechanical milling. The process results in very fine Si particles distributed homogeneously inside the TiN matrix. Si / TiN nanocomposites synthesized using different experimental conditions were evaluated for their electrochemical…
We consider a fully practical finite element approximation of the Cahn--Hilliard equation with degenerate mobility $$ \textstyle \frac{\partial u}{\partial t}= \del .(\,b(u)\, \del (-\gamma\lap u+\Psi'(u))) , $$ where $b(\cdot)\geq 0$ is a diffusional mobility and $\Psi(\cdot)$ is a homogeneous free energy. In additio…
For the first time, the time dependence of the amount of O2 evolved in the reaction of Fe2+ with H2O2 (the Fenton reaction) was measured by following the decrease of the total [Fe3+] formed upon quenching the reaction mixture with an excess of a strongly acidic solution of Fe2+. The disappearance of Fe2+ in the reacti…
Conventionally, the aragonite polymorph of CaCO3 possesses a ‘needle-like’ morphology. Aragonite crystals with unconventional morphologies, like ‘cauliflower’ and ‘flake’, have been synthesised by combining aqueous solutions of CaCl2 and Na2CO3 under ambient reaction conditions. The unambiguous characterisation of the…
Aluminium-incorporated SBA mesoporous materials have been obtained for the first time by direct synthesis; the resulting materials retain the hexagonal order and physical properties of purely siliceous SBA-15 and present higher catalytic activities in the cumene cracking reaction than AlMCM-41 materials.