Materials Literature
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Liquid crystals and polymer glasses can be formed into orientationally ordered materials by raising the temperature of the material to a temperature at which molecular motion is greatly enhanced, applying an external aligning field, and then cooling with the field applied. The resulting material exhibits second-order…
Heteropolyanions are polymeric oxoanions which are formed by the condensation of more than two different oxoanions [Eq. (1)l. Polyanions consisting of one kind of oxoanion are called isopolyanions [Eq. (2)]. Acidic elements such as Mo, W, V, Nb, and Ta are present as oxoanions in aqueous solutions and polymerize to fo…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTStructural-electronic relationships in inorganic solids: powder neutron diffraction studies of the rutile and anatase polymorphs of titanium dioxide at 15 and 295 KJeremy K. Burdett, Timothy Hughbanks, Gordon J. Miller, James W. Richardson Jr., and Joseph V. SmithCite this:…
Two competing types of thermal reactions of monomers of different classes, namely oligomerisation and polymerisation, are examined. The characteristics of the formation of the initiating radicals and of low-molecular-weight products (dimers and trimers) and of the inhibition of the thermal polymerisation by radical ac…
The most significant feature in the transition from the quasicrystalline to the amorphous state is the loss of long-range bond-orientational order. Disclinations are candidates for elementary excitations which destroy angular correlations. Generalizing the topological defect classification, we investigate point singul…
Temporal oscillations in the specular beam of reflection high-energy electron diffraction (RHEED) provide the primary method of monitoring growth by molecular-beam epitaxy. We develop a model to investigate the origin of these oscillations with which, by monitoring the step density of a growing sample, we are able to…
Abstract The emission of weak visible chemiluminescence (CL) during the cure of a tetraglycidyl 4,4′‐diaminodiphenyl methane (TGDDM)‐based epoxy resin, with three different concentrations of 4,4′‐diaminodiphenylsulfone (DDS) has been studied at 135°C. Spectral analysis indicates that the CL originates from trace oxida…
Abstract Complete conversion of the crystal form in cotton fibers to cellulose IV (cell IV cotton) was obtained by heat treatment of ethylamine‐treated cotton cellulose in either saturated steam or formamide. Degradation of the fibers was not extensive during the conversion process; oxidative damage appeared to have b…
Abstract Triphenylchloromethane and p ‐toluenesulfonyl chloride were reacted with chopped or powdered cellulose, with and without premercerization, to form trityl–cellulose ethers or tosyl–cellulose esters. Powdered and premercerized cellulose samples were more readily derivatized. Differential scanning calorimetric (…
Abstract The effect of the physical aging of ethylene ionomers was studied for the samples with the acid content of 5.4 mol%, and the degree of neutralization, 0%, 60% Na, 60% Zn, and 90% Zn. The information about the crystal and the cluster part of the physically aged ionomers was obtained by differential scanning ca…
Abstract A comprehensive examination of the die‐drawing behavior of polypropylene has been carried out, examining the effects of draw temperature, haul‐off speed, and initial billet size. A range of oriented products was obtained and characterized, primarily by the determination of Young's modulus at room temperature,…
Abstract The reaction of EPR with dicumyl peroxide at 180°C or t ‐butyl perbenzoate at 140°C resulted in the formation of a fraction insoluble in cyclohexane at 22°C. The presence of maleic anhydride (MAH) in the EPR‐peroxide reaction mixture increased the amount of insoluble polymer, whose concentration decreased as…
Abstract The influence of macroscopic dimensions, heat treatment, and polymer morphology on the chemical degradation of poly(glycolic acid) (PGA) fibers and pellets was examined in media of different pH values by monitoring the sample mass, dimensions, crystallinity, mechanical strength, and surface character. The deg…
The role of the secondary structure in the folding mechanism of dihydrofolate reductase from Escherichia coli was probed by studying the effects of amino acid replacements in two alpha helices and two strands of the central beta sheet on the folding and stability. The effects on stability could be qualitatively unders…
Polyacrylonitrile films have been spin cast and pyrolyzed to produce thin (500–1500 Å) carbon films. These films have higher electrical conductivities than films produced by other methods at similar temperatures. The conductivity can be varied by at least four orders of magnitude by changing the pyrolysis temperature.…
The kinetic parameters and emission spectra of TL induced by X-irradiation at RT are studied in two feldspars: albite (Naalsi3O8) and microcline (KAlsi3O8). Peaks with activation energies of ≈ 0.70, 0.82, ≈ 1.05, 1.17, and 1.24 eV are found for both crystals while in albite there are three additional peaks (of 0.60, 0…
The chemical potential of oxygen in nonstoichiometric ceria, CeO2−x, was measured versus composition x (10−4 ≤x ≤10−2) and temperature (823≤T≤1073 K) using a novel solid electrochemical cell, utilizing yttrium stabilized zirconia. The composition of CeO2−x was varied by coulometric titration. The O2 chemical potential…
The properties of thin gelatin films sensitized with a dye (methylene blue) when used as a holographic material are discussed. On illumination the excited dye molecule changes its structure giving a colorless molecule. The higher rate of bleaching and therefore the higher diffraction efficiency of the developed phase…
Numerical experiments have been performed with use of a fairly realistic model for polyethylene which has enabled the effects of anharmonicity, temperature, and positional disorder on the thermal conductivity to be investigated. It has been shown that the classical conductivity may be substantially increased by both i…
The electronic and structural properties of graphite have been determined in the local-density approximation with our precise total-energy full-potential linearized augmented-plane-wave method. We confirm the presence of a low-lying unoccupied ${\ensuremath{\Gamma}}_{1}^{+}$ interlayer state, which is of importance fo…