Thermal degradation of polyvinyl chloride
Abstract
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Processus de photoluminescence dans les oxydes et les orthovanadates de terres rares polycristallins activés par l'ion Bi3+
On analyse les propriétés de fluorescence de l'ion Bi3+ incorporé dans les oxydes et orthovanadates de terres rares LnVO4 (Ln = Sc, Y, Gd), La2O 3 et Ln2O3 (Ln = Sc, Lu, Y, Gd). Les transitions électroniques responsables de l'absorption et de l'émission sont attribuées aux niveaux de l'ion libre du premier état excité…
Transport Properties of Silver Beta Alumina
The total electrical conductivity and the electronic conductivity in silver beta alumina have been determined between 23° and 800°C over a wide range of oxygen partial pressure using a‐c and d‐c techniques. The ionic transference number was found to be very close to unity under all conditions. Comparison of these meas…
Interlayer complexes in layer silicates. The structure of water in lamellar ionic solutions
The stretching vibrations of water (H2O, HDO and D2O) in montmorillonite, hectorite, saponite and vermiculite are split into two components, similar to those seen in perchlorate solutions. Examination of lower hydrates and pyridine complexes of the layer silicates shows that the higher frequency component corresponds…
Nuclear spin relaxation and self-diffusion in the binary system, dimethylsulphoxide (DMSO)+ water
Spin-lattice (T1) and, where appropriate, tranverse (T2) relaxation times are reported for the protons in DMSO + water mixtures over a range of temperature and composition. Self-diffusion coefficients are also measured. A minimum in T1 for a d6-DMSO + H2O sample enables rotational correlation times for water molecules…
Liquid bridges between cylinders, in a torus, and between spheres
Abstract The stability of a capillary liquid bridge of given volume between two small, solid, equal, separated spheres is investigated by formulating and treating a minimum energy problem in the calculus of variations and by experiment. A conjecture is made that in the case of two solutions one and only one is minimiz…
Thermogravi metric Study of the Oxidation of ZrB[sub 2] in the Temperature Range of 800° to 1500°C
A thermogravimetric system is described for the determination of the total oxygen consumption, sample weight‐change, and vaporization rate during the oxidation of . The results show an increasing deviation from parabolic kinetics with increasing temperature at 250 mm oxygen pressure. The following equation is used to…
Identification of oxygen species adsorbed on reduced titanium dioxide
The nature of oxygen adsorbed on slightly reduced TiO2 has been investigated using oxygen enriched with 17O2. On anatase, the oxygen adsorbs as O–2 with a hyperfine splitting Axx about g3 of 77 G; no structure could be resolved for Ayy and Azz. On rutile, oxygen adsorbs as O–2 on two sites of different thermal stabili…
Conduction in polythene with strong electric fields and the effect of prestressing on the electric strength
There has been speculation in the past about the extent to which space charge formed by the flow of prebreakdown current affects the electric strength of polythene. In the present work, conduction and absorption-current measurements up to about half the breakdown field have given clear evidence of space-charge effects…
Interdiffusion in the Al–Cu System
Interdiffusion in the aluminum-copper system was investigated in the temperature range of 400° to 535°C with diffusion couples of pure aluminum and copper metals.In the aluminum-copper equilibrium phase diagram there are five intermediate phases in this temperature range, namely γ2, δ, ζ2, η2 and θ. Electron probe mic…
Extended Debye theory for dielectric relaxations in nematic liquid crystals
A theory of orientation polarization in nematic liquid crystals is developed for a molecular dipole moment parallel to the long axis of the molecule. The theory is essentially an extension of the Debye model for normal polar liquids to take into account the strong intermolecular potential which is responsible for the…
Intergranular Corrosion of Austenitic Stainless Steel
The well‐known susceptibility of austenitic stainless steels to intergranular corrosion after heat‐treatment in the temperature range of 550°–800°C ( i.e. , "sensitization") has long been attributed to depletion of Cr from regions of the alloy matrix adjacent to grain boundaries in which had precipitated. Those region…
A HYPOTHESIS CONCERNING SILICA AND THE FRESHWATER PLANKTONIC DIATOMS1
The literature was examined to relate ambient silica concentrations to numerical dominance of specific freshwater planktonic diatoms. Mean silica concentrations (mg/liter) during dominance are: Stephanodiscus astraea, 0.6; Tabellaria flocculosa asterionelloides, 0.9; Asterionella formosa, 1.7; Melosira granulata, 13.4…
The Use of Metalorganics in the Preparation of Semiconductor Materials
Abstract not Available.
Hydrodynamic instabilities of nematic liquid crystals under A. C. electric fields
We present an extension of the Helfrich theory of hydrodynamic instabilities to the case of alternating electric fields. The electrohydrodynamic effects are described by two coupled equations for the charge density (q) and the local curvature of the molecular alignment (ψ). The relaxation time for q is the dielectric…
On the Elastic Theory of Uniaxial Liquid Crystals
Simple derivations of the elastic theory of liquid crystals with uniaxial molecular order are given using a molecular Cauchy-like approach and a more general phenomenological approach. In a second-order approximation, both methods lead to the same expression for the elastic energy density, except for the existence of…
The Growth of Single Crystals
Abstract not Available.
Measurement of Sodium Ion Transport in Beta Alumina Using Reversible Solid Electrodes
The ionic conductivity of the solid electrolyte NaAl11O17 has been measured from − 150 to + 820°C using a novel nonpolarizing solid electrode, reversible to sodium ions. The resistivity at 25°C was found to be 72 Ω-cm, the lowest value reported for any ionically conducting oxide ceramic. The enthalpy of motion is 3.79…
Structural aspects of co-ordinated nitrate groups
C. C. Addison, N. Logan, S. C. Wallwork and C. D. Garner, Q. Rev. Chem. Soc., 1971, 25, 289 DOI: 10.1039/QR9712500289
Elements of polymer degradation
A survey of the degradation of polymer structures through thermal, oxidative, radiative, mechanical, chemical and biological means is presented. Examples, data and equations are largely based on synthetic polymer analyses, but the essential theories of polymer degradation are presented. -- AATA