Materials Literature
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A numerical model is developed describing the very fast process of microstructure evolution under the common action of nucleation and diffusional growth of minority phase droplets during cooling of a hypermonotectic alloy through the miscibility gap. The model is validated comparing it with an analytical solution obta…
We report measurements of microwave loss in micron-size powders of the manganites La0.7Ba0.3MnO3 and La0.7Sr0.3MnO3, as functions of temperature and magnetic field. At zero field, the loss increases rapidly as the temperature is lowered below a frequency-dependent temperature T*. The more exciting observation is that…
A finite‐element model is developed and implemented on a massively parallel supercomputer to study the viscous sintering of a three‐dimensional (3‐D) configuration of three particles. Model development is described, implementation is discussed, and calculations are compared with benchmark results for a two‐dimensional…
Dodecavanadate rings of trans-edge-sharing VO5 square pyramids capped on each side by a square-shaped [B16O32(OH)4]20- polyborate unit form doughnut-shaped [V12B32O76(OH)8]12- clusters in the unprecedented polyoxovanadium borate compound (H3O)12[(VO)12{B16O32(OH)4}2]·28H2O (1). The [V12B18O76- (OH)8]12- clusters in 1…
Reviews the inherent advantages, i.e. design flexibility and processing, of manufacturing piezoelectric ceramics and composites with numerous architectures via rapid prototyping techniques. Reports on processing in which piezoelectric ceramics and composites with novel and conventional designs were fabricated using ra…
Equilibrium constants for the chemisorption reactions of molecular nitrogen with nickel clusters Nin have been determined as a function of temperature for n=19 to 71. Van’t Hoff analysis of the data yields standard-state changes in reaction enthalpy and entropy. These changes are related to what is known about nickel…
Electrical properties of semiconducting ZnO( n )‐CuO( p ) ceramic composites with varying composition were investigated. The electrical conductivity increased with increasing CuO volume fraction between 1 to 95 mol%. Impedance response showed three semicircles, indicating three resistive elements contributing to the t…
Supramolecular hydrogen-bonded networks have been prepared by self-assembly of a chiral bifunctional H-bond acceptor and achiral trifunctional H-bond donors. A stilbazole dimer, (R)-1,2-bis{4-\[2-(4-pyridyl)ethenyl]phenoxy}propane (1) has been synthesized for use as a chiral component for cholesteric networks. Compoun…
Symmetric polydisperse (Mw = 23 × 104, Mw/Mn = 2.84) and monodisperse (Mw = 21 × 104, Mw/Mn < 1.05) polystyrene (PS), and asymmetric polydisperse PS/poly(2,6-dimethyl 1,4-phenylene oxide) (PPO) interfaces have been bonded in the vicinity of the glass transition temperature (Tg) of PS. In a lap-shear joint geometry, st…
We report an electrically conducting polyaniline–poly(acrylic acid) blend coatings prepared by mixing the emeraldine base (EB) form of polyaniline (PANI) and poly(acrylic acid) (PAA) aqueous solution. The samples show a moderate electrical conductivity σ. If they are immersed in an HCl aqueous solution, the conductivi…
Abstract Percolation, positive temperature coefficient (PTC), and negative temperature co‐efficient (NTC) in carbon black‐filled HDPE composites, were studied by measuring AC electrical properties. An equivalent single parallel circuit model, which consists of a resistor and a capacitor, was adapted to explain the dis…
We propose a mechanism for $A$-type antiferromagnetism in orthorhombic ${\mathrm{LaMnO}}_{3}$, compatible with the large Jahn-Teller splitting inferred from structural data. Orbital ordering resulting from Jahn-Teller distortions effectively leads to layered ordering (antiferromagnetic in the $c$ axis and ferromagneti…
The magnesium, nickel, copper, zinc and vanadium metalloporphyrins from octaethylporphyrin, etioporphyrin I and tetraphenylporphyrin were characterized using electrospray ionization mass spectrometry (ESI-MS). The ion abundance of each of the porphyrins present in binary mixtures was monitored as a function of the por…
In order to evaluate the quantitative cavitation-erosion resistance of materials, a pressure-detector-installed specimen was developed, which can measure both the impact load produced by cavitation bubble collapse and the volume loss simultaneously. Test specimens (pressure-detection rod) used were nine kinds of metal…
The method of ab initio molecular dynamics, based on finite temperature density functional theory, is used to simulate laser heating of graphite. We find that a sufficiently high concentration of excited electrons dramatically weakens the covalent bond. As a result the system undergoes an ultrafast melting transition…
The stepwise synthesis and characterization of a family of selectively metalated 1,2-bis[5-(2,3,7,8,12,13,17,18-octaethylporphyrinyl)]ethenes is described. These compounds are distinct from most of the previously reported bisporphyrin systems which possessed rigid linking groups or multiple strapping units, and their…
A theoretical framework for the temporal behavior of photoinduced anisotropy in liquid-crystalline azobenzene side-chain polyesters is constructed. The domain structure of the material is taken into account and intermolecular interactions are included through a mean-field description. Photoinduced trans↔cis isomerizat…
The electrical and mechanical properties of piezoelectric lead zirconate titanate (PZT) ceramics are strongly influenced by domain‐wall motion, which can be tailored via the substitution of ions within the perovskite structure. Different domain mobilities are achieved by lead and/or oxygen vacancies, according to the…
We have determined the alignment of a Gay-Berne model liquid crystal near a graphite surface using Monte Carlo computer simulations. We find in this regime, where adsorption is dominating with respect to the intermolecular interactions, a discontinuous change in anchoring from planar to normal on going from the first…
We study the onset of sidebranching of growth cells in directional solidification of impure succinonitrile. Care is taken to obtain uniform cell spacing over large distances in order to use this variable as a true control parameter. Two sidebranching modes referring to different crystalline orientations are observed a…