Materials Literature
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The crystal structures of dilithium, disodium and diammonium terephthalate (1,4-benzenedicarboxylate) have been solved ab initio using Monte Carlo simulated annealing techniques, and refined using synchrotron powder data. The structures of dipotassium terephthalate, potassium hydrogen terephthalate and ammonium hydrog…
Abstract. Volcanic ash soils are generally recognized as soils with excellent and stable physical properties. Here we characterized the porosity and water properties of volcanic ash Andosols and Nitisols from Guadeloupe in contrasting banana systems: (1) perennial crop without mechanization, (2) mechanized and regular…
We present a theory of the melting of elements as a dislocation-mediated phase transition. We model dislocations near the melt as noninteracting closed loops on a lattice. In this framework we derive simple expressions for the melting temperature and latent heat of fusion that depend on the dislocation density at melt…
Metastable tetragonal ZrO 2 phase has been observed in ZrO 2 –SiO 2 binary oxides prepared by the sol–gel method. There are many studies concerning the causes of ZrO 2 tetragonal stabilization in binary oxides such as Y 3 O 2 –ZrO 2 , MgO–ZrO 2 , or CaO–ZrO 2 . In these binary oxides, oxygen vacancies cause changes or…
The viability of conjugated polymer thin film electrooptical devices and sensors depends strongly on high quantum efficiency thin films with excellent charge and exciton mobilities.1,2 The brightness of electroluminescent devices depends on the charge transport and emission efficiency, and energy migration to low ener…
Several recent studies of phthalocyanines and porphyrins as materials in emerging technologies are reviewed here. Emphasis is placed on the use of these materials as components in building materials where the symmetry, optical and electrical properties of the molecule are important. Aggregates or polymers of these mol…
ADVERTISEMENT RETURN TO ISSUEPREVCommunication to the...Communication to the EditorNEXTSupramolecular Self-Assembly of Three-Dimensional Nanostructures and Microstructures: Microcapsules from Electroactive and Photoactive Rod−Coil−Rod Triblock CopolymersX. Linda Chen and Samson A. JenekheView Author Information Depart…
Recent progress in antimicrobial dendrimers is reviewed. Both specific interactions and non-specific interactions can be utilized to design multifunctional (polyvalent) antimicrobial agents, which might be more potent than their mono-functional counterparts. Dendrimers or hyperbranched polymers can also be used to des…
The temperature dependence of the thermopower $(S)$ for ${\mathrm{La}}_{1\ensuremath{-}x}{A}_{x}{\mathrm{MnO}}_{3}$ $(\mathrm{A}\phantom{\rule{0ex}{0ex}}=\mathrm{Sr},$ Ba, Pb, and Ca) perovskites has been investigated systematically as a function of doping $(x)$ in order to determine the role of several scattering mec…
The adsorption of CO on a 4.7% Cu/Al 2 O 3 catalyst either reduced or oxidized is studied using the FTIR spectra recorded at adsorption temperatures T a in the range 298−740 K and with two constant partial pressures P a (10 3 and 10 4 Pa). On the reduced solid and at T a = 300 K a single IR band is detected at 2092 cm…
Optical properties of epitaxial ZnO layers have been studied in the spectral region from 1.5 to 5.4 eV using four-zone null spectroscopic ellipsometry. An existing model dielectric function based on excitonic structure near direct band gap has been improved by including a high-energy absorption term. Surface layer, co…
Rapid construction of nanoarchitectures of high dimension and complexity is what these authors aim to achieve using core–shell tecto-(dendrimers). Self-assembly of the core-dendrimer tectons followed by amide bond formation to attach the shell-dendrimer tectons (see Figure) allows the construction of dendrimers so lar…
Volume‐phase holographic (VPH) gratings show great potential as an alternative dispersing element to the classical surface‐relief (SR) gratings presently used in most astronomical spectrographs. We present an introduction to this technology and give the results of an evaluation of three different VPH gratings: a 300 l…
Following the intriguing report about catalysis by corrole metal complexes, we present now the syntheses and characterization of the cobalt(III), rhodium(III), and iron(IV) tris(pentafluorophenyl)corrole, including the X-ray structures of the last two.
The structure of a microporous carbon prepared by the carbonization of sucrose was examined using high-resolution electron microscopy. It was found to be disordered and isotropic and primarily made up of tightly curved individual carbon layers, enclosing pores typically about 1nm in size. Completely closed carbon part…
The third known polymorph of silicon nitride, which is cubic and was only recently discovered, has been prepared from two further, different precursors—Si2N2(NH) and a-Si3N4—in a high-pressure, high-temperature synthesis using multi-anvil presses. The synthesis and characterization of the products is described, which…
Woven Hi‐Nicalon™‐reinforced melt‐infiltrated SiC‐matrix composites were tested under tensile stress‐rupture conditions in air at intermediate temperatures. A comprehensive examination of the damage state and the fiber properties at failure was performed. Modal acoustic emission analysis was used to monitor damage dur…
Space charge observation is becoming the most widely used technique to evaluate polymeric materials for dc insulation applications, particularly HV cables. However, quantities are still lacking that can help to summarize and interpret the huge amount of data resulting from space charge measurements, and that also are…
A large number of carboxylic groups were introduced onto chitosan by grafting with poly(acrylic acid) as an efficient way of modification. The reactions were carried out in a homogeneous aqueous phase by using potassium persulfate and ferrous ammonium sulfate as the combined redox initiator system. The efficiency of g…
The ac conductivity resulting from ion motion in glasses displays a power-law frequency dependence characterized by an exponent $n<1.$ Recently, it was suggested that this exponent depends upon the dimensionality of the local cation conduction space, such that n decreases with decreasing dimensionality. Here, I rep…