Materials Literature
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Abstract This paper presents a rigorous new theory of differential thermal analysis, taking account of the temperature gradient in the sample. From this consideration, a new quantitative method is proposed, where a solid-cell holder of low thermal conductivity is set between a sample cell and a metal block, and a ther…
The fluorescence of unactivated and rare-earth-activated materials of the type Ln2WO6, Ln2MoO6, and Y2W1−xMoxO6 (0≤x≤0.1) has been studied. From the experiments on unactivated materials it follows that energy transfer from tungstate to tungstate or mobyldate group takes place, whereas there is no transfer from molybda…
Abstract The structure of polypropylene crystallized at pressures up to 5000 atm. has been studied. Upon slow cooling from the melt at 320 atm., the γ modification, previously found only in low molecular weight and stereoblock fractions, begins to appear in small amounts in addition to the normal α monoclinic form. As…
Glass transition temperatures of a very wide molecular-weight range of ethylene oxide polymers were measured by mechanical loss and by broadline NMR. Starting at about −95°C for ethylene glycol, the glass transition rises to a maximum of −17° for molecular weight 6000 and then drops off to −53° for polymers with molec…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTPhosphonitrilic Compounds. VII. High Molecular Weight Poly(diaminophosphazenes)H. R. Allcock and R. L. KugelCite this: Inorg. Chem. 1966, 5, 10, 1716–1718Publication Date (Print):October 1, 1966Publication History Published online1 May 2002Published inissue 1 October 1966htt…
Microstructure of spherulites of the monoclinic modification of isotactic polypropylene has been studied in thin films by transmission electron microscopy and electron diffraction. Centers of spherulites are found to consist invariably of complex arrays of intercrossing lamellae. Radiating from the central regions are…
Abstract Thermal conversion rates of the polyamic acid derived from pyromellitic dianhydride and 4,4′‐diaminodiphenyl ether are presented. Formation of the imide ring proceeds by fast and slow first‐order processes. Tertiary amines give ring closures faster by a factor of 10 than the free acid. The enhancement is an a…
Fluorescence yields of solutions of several chelates of europium and terbium have been measured: (a) upon excitation in the ligand absorption bands and (b) upon selective excitation to individual upper levels of the rare-earth ion. Yields with upper-ion-level excitation are lower than when the emitting level is excite…
Variational principles have been applied to aggregates of randomly oriented pure-phase polycrystals having tetragonal symmetry. The bounds of the effective elastic moduli obtained in this way show a substantial improvement over the bounds obtained by means of the Voigt and Reuss assumptions. The Hill average is found…
Four rules are proposed to explain the photoluminescent efficiency of Eu3+-activated oxides: (a) uv absorbing groups in the host lattice should be nearest neighbors in the crystal structure to have sufficient wavefunction overlap; (b) the emission spectrum of the absorbing group should overlap the absorption spectrum…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTPhosphonitrilic Compounds. VI. High Molecular Weight Poly(alkoxy- and aryloxyphosphazenes)H. R. Allcock, R. L. Kugel, and K. J. ValanCite this: Inorg. Chem. 1966, 5, 10, 1709–1715Publication Date (Print):October 1, 1966Publication History Published online1 May 2002Published…
Machine learning (ML) is transforming all areas of science. The complex and time-consuming calculations in molecular simulations are particularly suitable for an ML revolution and have already been profoundly affected by the application of existing ML ...Read More
The detailed movement of a dislocation line through a random array of point obstacles in the glide plane has been examined, using a digital computer, on the basis of the line tension approximation. The breakaway criterion at each obstacle is a critical angle between the arms of the dislocation, corresponding to a crit…
The solubility of stibnite ( Sb(2)S(3)) was measured at 25 degrees C and 1 atmosphere in solutions ranging from 0.45 to 7.16 percent Na(2)S by weight. Sb(2)S(3): Na(2)S mole ratios of saturated solutions range from 0.238 to 0.403. Stibnite solubility increases at an increasing rate with rising Na(2)S concentration. Th…
Single crystals of potassium chloride were grown from aqueous solutions under carefully controlled conditions of supersaturation, agitation, and impurity lead chloride concentration. The growth rate of the (100) face was determined. It was found that PbCl2 concentrations as low as 10−8 moles PbCl2/mole KCl decreased t…
Equilibrium constants have been measured for the following displacement reactions between copper(II) and zinc(II) with hematoporphyrin IX.[Formula: see text]Preliminary measurements have also been made for the reactions of Mn(II) and Co(II) with hematoporphyrin IX in glacial acetic acid solutions.
The X-band electron paramagnetic resonance spectra of Cu+ + ions doped into amorphous, tetragonal, and hexagonal GeO2 have been observed at 295°K. Optical absorption and reflection data for, respectively, the doped glass and polycrystalline samples were also obtained. From the experimental results, the symmetry of the…
The radical ions SO4− and S2O3−, trapped in γ-irradiated K2SO4 and Na2S2O3·5H2O crystals, respectively, have been identified by their ESR spectra. In the preceding paper molecular orbital calculations were described the results of which predict a ···1t163t262a1, 2A1 (symmetry Td) configuration for SO4− and a ···5e45a1…
The Raman and infrared spectra of the aluminate ions in alkaline solutions have been measured. Two ionic species, one predominant from pH 8 to pH 12 and the other predominant above pH 13, may be identified from the spectra. At intermediate pH's both forms are present. The selection rules and the polarization of the li…
The radial and longitudinal development of electron-photon showers has been measured in copper and lead at 1 GeV. A new technique using the thermoluminescent property of LiF has been employed to measure energy deposition. The resultant radial distributions and transition curves show good agreement with Monte Carlo cal…