Materials Literature
按标题、摘要、年份、主题和来源检索公开元数据。结果保留作者、摘要、分类与原始来源链接。
Abstract Octabromotetraphenylporphyrin adopts a severe saddle-shaped distorted structure owing to the steric crowding of heavy bromine substituents. The rate enhancement of porphyrin metalation reaction is primarily due to the nonplanarity of the ring while the electronic effect diminishes the affinity of the porphyri…
The preparation and the conversion in ceramics of the precursor cross‐linked copolysilazane (CPSZ) of formula (ViSiHNH) x (MeSiHNH) y have been summarized in Part I. Part II will examine the evolution and the thermal behavior of CPSZ at high temperatures under argon atmosphere. Gaseous phase, graphite or alumina cruci…
ZnO varistors with and without ZnO crystalline seeds have been prepared through conventional ceramic processing. Their electrical nonuniformity has been carefully examined using microcontact measurements of single grain boundaries, current‐voltage ( I‐V ) characteristics, and dielectric temperature spectra of bulk sam…
Corrosion of prestressing steel in concrete has become a major technological problem in highways, buildings, and pipeline structures. While cathodic protection is recognized as an appropriate technique to mitigate corrosion of reinforcing steel in concrete, the possibility of environmental cracking (hydrogen embrittle…
Abstract Development of crystallinity in NEW‐TPI semicrystalline polyimide has been studied using differential scanning calorimetry (DSC), wide (WAXS), and small angle X‐ray scattering (SAXS). Crystallinity of the fully imidized powder, pellet, or film processed NEW‐TPI can occur from the melt, and depends upon the ho…
The basic properties of conducting polymers which can be coloured by reversible electrochemical doping processes, are briefly described. The application of these materials for the development of optical devices of technological importance, such as electrochromic displays and windows, is also illustrated and discussed.
Arthrobacter sp. strain NO-18 was first isolated from soil as a bacterium which could degrade the sodium acrylate oligomer and utilize it as the sole source of carbon. When 0.2% (wt/wt) oligomer was added to the culture medium, the acrylate oligomer was found to be degraded by 70 to 80% in 2 weeks, using gel permeatio…
The kinetic equations are formulated and solved to describe a first-order phase transition initiated by diffusion of particles from the surface into the bulk. The scenario of phase transformation is assumed to involve the following three stages. At first, the particles diffuse in the bulk almost freely because the gra…
Cd1−xMnxSe microcrystallites have been successfully prepared by rf sputtering in SiO2 matrix glass. Optical absorption edge shows high energy shifts of 20–550 meV to the high energy as compared to its position in bulk crystals; these shifts are interpreted as evidence for exciton confinement in the microcrystallites.…
A number of products are promoted for the purpose of regenerating used frying oils. These materials are referred to as “active” filter aids. They are purported to adsorb polar compounds, which are the products of oil degradation, and to retain them for removal by filtration. To evaluate some of these materials, portio…
Ideal random AB copolymers with degree of polymerization N are mixtures of N+1 types of chains with different compositions (fractions fi of A monomers). Conditions for single phase and multiphase equilibria are studied using Flory–Huggins free energy of mixing with χ representing the A–B interaction parameter. The spi…
Displacement of coordinated 1,5-cyclooctadiene or norbornadiene from suitable precursors has given a series of hapto1-C-bonded organoplatinum(II) complexes containing 1,4,7-trithiacyclononane (9S3), i.e. PtRR'(9S3) [R = R' = Me(l), Et(2), CH2CMe3(3), CH2SiMe3(4), Ph(5); R = Me, R' = CH2SiMe3(6); R = C1, R' = CH2SiMe3(…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTGas phase metal chalcogenide cluster ions: a new cobalt-sulfur [CoxSy]- series up to [Co38S24]- and two iron-sulfur [FexSy]- seriesJohn El Nakat, Keith J. Fisher, Ian G. Dance, and Gary D. WillettCite this: Inorg. Chem. 1993, 32, 10, 1931–1940Publication Date (Print):May 1,…
Abstract SnO2 showed catalytic activity for the selective reduction of NO with hydrocarbons (C2H4, C3H8, and CH4) in the presence of excess oxygen, and the activity was not so much decreased even after heat treatments in dry air at 900 °C as well as in humid air at 800 °C. These results show that SnO2 is an active and…
Vertex-sharing tetrahedral ZnO4 and triangular BO3 subunits form a three-dimensional network of intersecting channels in Zn4O(BO3)2 a new molecular sieve not belonging to the aluminosilicates. The ab initio structure determination was possible with X-ray powder data; the picture on the right shows the view along [100].
The early stages of Pt electrodeposition (0.675-0.620 V vs RHE) on highly oriented pyrolytic graphite (HOPG) from chloroplatinic acid at 25 °C have been studied by ex-situ STM and SEM imaging complemented with electrochemical data. Nucleation and 3D growth of Pt initiate at HOPG surface defects. Large Pt agglomerates…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTSynthesis of cationic metalloporphyrin precursors related to the design of DNA cleaversChristiane Casas, Bernadette Saint-Jalmes, Christophe Loup, C. Jeffrey Lacey, and Bernard MeunierCite this: J. Org. Chem. 1993, 58, 10, 2913–2917Publication Date (Print):May 1, 1993Publica…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTSynthesis and characterization of nanophase Group 6 metal (M) and metal carbide (M2C) powders by chemical reduction methodsD. Zeng and M. J. Hampden-SmithCite this: Chem. Mater. 1993, 5, 5, 681–689Publication Date (Print):May 1, 1993Publication History Published online1 May…
It is shown on a specific example that fractal boundary conditions drastically alter the properties of wave excitations in space. The low-frequency part of the vibration spectrum of a finite-range fractal drum is computed using an analogy between the Helmoltz equation and the diffusion equation. The irregularity of th…
Trapping effects of dopant ions on the chemical diffusion due to valence changes of the impurity ions (association with electronic charge carriers) and/or due to association with ionic defects are considered. It is shown that the chemical or ambipolar diffusion coefficient may be substantially changed and may even be…