Materials Literature
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The magnetization, magnetoresistance and elastic properties of Sm 0.56 (Sr 0.44- x Me x )- MnO 3 (Me = Ba, Cd, Ca) have been investigated. It is established that Sm 0.56 Sr 0.44 MnO 3 exhibits a metamagnetic behaviour as well as anomalous elastic properties in a wide range of temperatures above the Curie point T C = 1…
Extending the Debye approach for studying the specific heat of a crystal to a quasicrystal, this study gives the formula of the specific heat of a one-dimensional hexagonal quasicrystal.
The ceramics of new solid solutions of Ag 1- x Na x NbO 3 (ANN) have been sintered for the whole concentration range. Low frequency dielectric investigations (120-800 K) and DTA investigations (290-600 K) revealed a series of phase transitions. Two predominant aspects of the Na substitution have been found. The first…
Core-corona structures of poly(ethyleneoxide)/polybutadiene (PEO/PB) block copolymer micelles are directly resolved for the first time by examining rapidly vitrified samples by transmission electron microscopy at liquid nitrogen temperature (Cryo-TEM). Spherical micelles form at higher PEO/PB block volume ratio; cylin…
The hydrolytic properties of the novel biodegradable thermosensitive poly(organophosphazenes) with methoxypoly(ethylene glycol) (MPEG) and amino acid esters as side groups have been studied by means of gel permeation chromatography and 31 P and 1 H NMR spectroscopy and by identification of the hydrolysis products. The…
The synthesis of Co 5 (OH) 8 (C 7 H 15 CO 2 ) 2 ·4H 2 O, Co 5 (OH) 8 (O 2 CC 6 H 12 CO 2 )·5H 2 O, Co 5 (OH) 8 (C 12 H 25 SO 4 ) 2 ·(3H 2 O·2NH 3 ), and Co 5 (OH) 8 (C 2 N 3 ) 2 ·6H 2 O, their characterization by electron microscopy, XRD, TGA, IR, UV−vis, and XANES, and their magnetic properties are reported. They bel…
A novel poly(vinyl alcohol) (PVA) degradation pathway was demonstrated such that the hydroxy group of PVA was first dehydrogenated into the corresponding carbonyl group to form the β-hydroxy ketone moiety which was followed by the aldolase-type cleavage to produce the methyl ketone and the aldehyde terminals by the PV…
Small-angle neutron scattering (SANS) studies indicate that oil-in-water microemulsions, consisting of aqueous HCl, the nonionic block copolymer surfactant Pluronic P123 (poly(ethylene oxide)- block -poly(propylene oxide)- block -poly(ethylene oxide), EO 20 −PO 70 −EO 20, M av = 5800), 1,3,5-trimethylbenzene (TMB, oil…
Poly(amidoamine) (PAMAM) dendrimers can be used as a polymeric template/stabilizer/reservoir to prepare stable gold−dendrimer nanocomposites by reducing PAMAM−tetrachloroaurate polysalts using hydrazine. In the gold−dendrimer nanocomposite, the presence of elemental gold is indicated by its characteristic plasmon abso…
Dielectric insulator materials containing nanometer-scale closed-cell pores with low dielectric constants ( k < 2.2), good mechanical properties, and high dielectric breakdown strengths are required for future semiconductor devices. In this paper we present a novel method for preparing nanoporous polyorganosilicate fi…
Powder neutron diffraction has been used to pinpoint the nature of the ferroelectric-paraelectric phase transition in Bi 4 Ti 3 O 12 . Below T c (675 °C) the structure has been refined in orthorhombic space group B 2 cb [at 25 °C a = 5.4444(1) Å, b = 5.4086(1) Å, c = 32.8425(6) Å; at 650 °C a = 5.46183(5) Å, b = 5.448…
A theoretical investigation is made of the dispersion characteristics of plasmons in a two-dimensional periodic system of semiconductor (dielectric) cylinders embedded in a dielectric (semiconductor) background. We consider both square and hexagonal arrangements and calculate extensive band structures for plasmons usi…
We discuss the possibility that, besides roughening, a vicinal surface could display preroughening (PR), and consider the possible mechanisms for its promotion. Within the framework of a terrace-step-kink model, it turns out that a PR transition is possible, and could be induced by a short-range repulsion between para…
We report results of density-functional theory calculations on the structural, magnetic, and electronic properties of (1x1)-structures of Co on Cu(001) for coverages up to two monolayers. In particular we discuss the tendency towards phase separation in Co islands and the possibility of segregation of Cu on top of the…
The order parameters of the magnetic, charge and structural orders at half-doped manganites are identified. A corresponding Landau theory of the phase transitions is formulated. Many structural and thermodynamical behaviors are accounted for and clarified within the framework. In particular, the theory provides a unif…
We propose that a specific spatial configuration of lattice sites that energetically favor {\it 3+} or {\it 4+} Mn ions in moderately doped manganites constitutes approximately a spatially random two-energy-level system. Such an effect results in a mechanism of metal-insulator transitions that appears to be different…
The methods of thermogravimetric analysis (TGA) and differential scanning calorimettry (DSC) have been used to study the thermal decomposition of ammonium perchlorate (AP). TGA curves obtained under both isothermal and nonisothermal conditions show a characteristic slowdown at the extents of conversion, α = 0.30−0.35.…
Power plant piping operating at elevated temperatures is subject to several types of service aging-related degradation, such as softening, spheroidization, embrittlement, and creep. When cracks are found in these components, weld repair is often employed to ensure continued operation. The efficacy of the weld repairs…
Controlled, reversible electrochemical promotion (EP) of a base metal catalyst has been demonstrated for the first time. Electropumping of Na from a β‘ ‘ alumina solid electrolyte to a Cu film catalyst results in large improvements in both activity and selectivity of the latter. In the catalytic reduction of NO by CO,…
Exocyclic tris(bidentate) ligands attached to a cyclotriphosphazene skeleton have been prepared and characterized. The cobalt complexes of the ligand have an unusual structure and demonstrate CoIII/CoII equilibrium over a wide temperature range.