Materials Literature
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The possibility of large scale mobility of flexible linear macromolecules is discussed with examples of quantitative studies of crystallization and melting kinetics, the segregation of complete molecules on crystallization and the direct observation of molecular diffusion.
Abstract Detailed results of the overall thermal degradation of poly(butylene terephthalate) are reported. Laser microprobe analysis and dynamic mass spectrometric techniques were used to identify the primary volatile degradation products and initial pyrolysis reactions that control polymer degradation. A complex mult…
Reaction of tetrasodium tetrathiafulvalene-tetrathiolate with transition metal salts leads to the formation of tetrathiafulvalene-metal bisdithiolene oligomers which in the case of the nickel derivative possesses unusually high conductivity (ca. 30 Ω–1 cm–1).
A. Keller, Faraday Discuss. Chem. Soc., 1979, 68, 145 DOI: 10.1039/DC9796800145
Zinc tetraphenylporphine shows fairly weak fluorescence and phosphorescence but intense, long-lived triplet absorption. Benzo-1,4-quinone quenches the singlet and triplet excited states of ZnTPP and the quenching probability increases with increased polarity of the solvent. Quenching leads to formation of a complex wh…
Some of the earliest investigations concluded that the basic mechanisms of fatigue in composites and fatigue in homogeneous materials differ greatly. Instead of the initiation and propagation of a fatigue crack traditionally identified with homogeneous materials, fatigue in composites consists of various combinations…
Vibrational spectra of α-P2W18O62 6− and of the two isomers α1 and α2-P2W17O61 10− are reported and discussed by comparison with those of PW12O40 3−. With given assumptions, calculations of force constants for the PO4tetrahedra are carried out. The location of the holes in the structures of α1 and α2-P2W17 are inferre…
In this paper, the Rayleigh hypothesis in the theory of reflection by a grating is investigated analytically. Conditions are derived under which the Rayleigh hypothesis is rigorously valid. A procedure is presented that enables the validity of the Rayleigh hypothesis to be checked for a grating whose profile can be de…
The crystal and molecular structures of the β-polymorphic forms of phthalocyaninatomanganese(II), [Mn(pc)], and phthalocyaninatocobalt(II), [Co(pc)], have been determined by single-crystal X-ray diffraction methods at 295 K, and also at 116 K in the case of [Mn(pc)]. Crystals are of the monoclinic β-polymorph type, sp…
Rates of relaxation of polymer chains of high molecular weight preclude extensive configurational rearrangements of long range in the process of crystallization from a melt. Analyses of neutron scattering functions for deuterated polyethylene and polypropylene chains dispersed with the corresponding protonated host in…
The principles of forming metastable solids by rapid melt quenching are reviewed with primary emphasis on the growth of crystals into melts and glasses. Experience is reviewed which indicates that the rate of growth of crystals in pure metal melts may be limited only by the impingement frequency of atoms from the melt…
Examines the evolution of this new scientific discipline. Deals with selected solid (engineering) materials while also describing asbestos, asphalt, natural gas, cellulose, wood, reeds, lignin, paper, liquid crystals, spinels, coal tar, and coal gas and petroleum. Considers such recent materials as glassy metals, sial…
A promising alternative for hydrogen storage is storage as a metal hydride. The properties and applications of those systems which have proven or potential utility as hydrogen storage compounds are summarized. Specific systems discussed are magnesium alloy hydrides, iron-titanium alloys, titanium-chromium alloys, and…
It is shown that the “reptation” process proposed by de Gennes allows molecules to be reeled from the melt onto the crystal surface with chain folding by the force associated with crystallization at a rate that is comparable with that demanded by the observed crystallization kinetics for polyethylene fractions n= numb…
In the course of experiments using the Freedericksz transition on a planar nematic film in a magnetic field perpendicular to the limiting plates, we have observed the transient existence of a periodic roll structure very similar to published observations by Carr, and apparently similar to Williams domains. The present…
Neutron scattering experiments have been performed with n-alkane and polyethylene (PE) samples crystallized from melt and solution. Differences between different conformation models are most pronounced in the short-range order region covered by intermediate angle neutron scattering (IANS) experiments. The angular rang…
Alterations of the concentrations of certain components in a lyotropic nematic mesophase may change the sign of the anisotropy of its magnetic susceptibility, Δχ. We report here : 1) the determination of the sign of Δχ by optical observation of the textures in the presence of a magnetic field, 2) the results of an X-r…
Description This volume covers six subject areas: microstructure, fracture of thermal reactor materials, primary damage production and irradiation creep simulation, dosimetry and damage function analysis, mechanical properties and creep.
Abstract Melt blends of polycarbonate and poly(ethylene terephthalate) were prepared and examined for their transitional behavior by thermal analysis and dynamic mechanical testing. A single T g was observed for compositions containing more than 60%–70% PET by weight while compositions below this range showed two glas…
The effect of pretreatment temperature on the u.v. photo-adsorption of O2 on TiO2 has been studied by e.p.r. Different oxygen species are found if the sample is completely hydroxylated or strongly dehydroxylated, this being related to two different photo-adsorption mechanisms. O2H· and V-centres are found for the hydr…