Materials Literature
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The problem of surface diffusion-controlled whisker growth is considered in a moving frame of reference. In addition, diffusive exchange with the substrate, a problem not treated heretofore, is considered. The results are compared with experiment and with prior treatments of whisker growth. The possibility of occurren…
The absorption and fluorescence spectra of Eu3+ in single crystals of Y2O3 have been observed and analyzed. The intermediate-coupling free-ion energy levels for Eu3+, including the effects of the 46 singlet states of the 4f6 configuration, are presented for all levels appearing below 41 000 cm—1. The results obtained…
I have touched upon the great variety of crystal forms and dendritic forms in nature, have discussed the essential physics involved in the generation of these forms during either constrained or unconstrained crystal growth, and have shown how this knowledge helps in the classification of this seemingly infinite variet…
Abstract : Evidence is presented that the atomic arrangement of high-pressure FeVO4 is similar to that of ambientpressure FeNbO4. Evidence is presented in the form of comparing the indexing of high-pressure FeVO4 and the disordered wolframite FeNbO4, which indicates that FeVO4 crystallizes in the disordered wolframite…
In contrast to the extensive studies performed on AgBr and AgC1 l i t t le effort has been made to unders tand the nature of s t ructural disorder in AgI, CuC], CuBr and CuI. This is p r imar i ly a consequence of the comparat ive s t ructural s impl ic i ty of AgC1 and AgBr, as Table 1 i l lustrates. In t r ins ic th…
The structure of a synthetic iron mica, KFe~+(Fea+Sia)O10(OH)~, determined from visually estimated intensities, shows very slight departure from Pabst's idealized biotite structure. The sextuple cell formerly used to describe micas accounts for the observed twinning.
The lactic dehydrogenase of a strain of Streptococcus bovis specifically requires fructose-1,6-diphosphate for activity. Phosphate or fructose-1-6-diphosphate prevents inactivation of the dehydrogenase, but phosphate and other compounds cannot be substituted for the fructose-1,6-diphosphate required for activity. Lact…
Abstract The shear mechanical impedance of six polydimethylsiloxane liquids of viscosity grades ranging from 100 to 100000 cS has been measured over the frequency range 10 kc/s to 78 Mc/s, and at temperatures from –50 to +50 °C. It was found possible to reduce the experimental data for each liquid to give a single cur…
The diffusion of radioactive Cr, Mn, Fe, Co, Ni, Cu, and Nb tracers in bcc gamma uranium has been measured from 780 to 1080\ifmmode^\circ\else\textdegree\fi{}C, using the thin-layer sectioning technique. The Arrhenius plots are curved at low temperatures; the curvature is not due to diffusion along grain boundaries or…
The magnetic structure of Co${\mathrm{Cl}}_{2}$\ifmmode\cdot\else\textperiodcentered\fi{}2${\mathrm{H}}_{2}$O has been investigated by means of single-crystal magnetic susceptibility and proton nuclear magnetic resonance (NMR) measurements. A transition to a two-sublattice antiferromagnetic structure with large uniaxi…
A new electron-phonon interaction characteristic of layer structures is described. Depending on the strength of the coupling between electron and lattice, this interaction, which involves short-range forces, leads to free or self-trapped charge carriers. The theoretical findings are compared with the experimentally de…
The evidence for, and the factors determining, the formation of metal-to-metal (m-m) bonds in transition metal oxides, sulphides, halides, and related complexes are discussed. It is proposed that when metals of high preferred valence state are constrained to low formal oxidation states, m-m bonds will form to allow th…
Magnesium oxysulfate, 3Mg (OH h MgSO., 81-120, was preci pi tated from metastable aqueous solutions of MgO in M gSO.. The co mpound form s in solutions containing 12 percent or more of JVIgSO., .and ,remains unchanged in solutions containing 10 percen t MgSO., but at lower concentratIons IS converted to Mg(OHh. Magnes…
Abstract The cyclopolymerization of methacrylic anhydride at 36.6°C. produces a polymer whose structure has been examined by infrared spectrometry and bromometric analysis. This polymer contains mainly hexaatomic rings of the A type (absorption bands at 1800 and 1760 cm. −1 ) and open anhydride units with unsaturated…
Kinetic studies of the early stages of the oxidation of pure iron, initiated at a clean metal surface, have been carried out at a pressure of 76 mm Hg absolute, and isothermally in the range 700–900°c, using a constant pressure-differential gas apparatus. The duration of each isothermal study has been restricted to th…
The magnetoelastic behaviour of antiferromagnetic substances possessing a helical spin system has been investigated. It is shown that all magnetoelastic phenomena arise from two distinct effects, termed the anisotropy and exchange magnetostrictions. Equations governing the magnetostriction of single and polycrystals a…
Abstract There are wide discrepancies in the literature values for the heat of fusion (Δ H u ) of isotactic polypropylene. A study was therefore made of the variables affecting Δ H u as determined by differential thermal analysis. The results of this study show Δ H u for 100% “crystalline” polypropylene to be 2400 cal…
It is shown that a dc electric field can generate continuous oscillations of current in a CdS crystal provided a region of higher resistivity exists near the positive electrode of the sample. Frequency measurement reveals the existence of two kinds of periods. One corresponds to a round-trip of sound waves in the samp…
Abstract The reaction rates for the uncatalyzed as well as the dibutyltin dilaurate‐catalyzed reactions between polyether polyols and tolylene diisocyanate (80/20 mixture of 2,4 and 2,6 isomers) are reported. Titration and infrared absorption methods were used for the determination of the residual isocyanate content,…
The hea t of combustion of a luminum carbi de (Al, 0 3) in oxyge n was m eas ured by mea ns of bomb calorimetry. The solid produ ct of t he co mbust ion cons ist ed of alpha a luminum oxi de a nd a nother crystalline form of a lumina, whi ch was characterized as delta alumi na . The h eats of combustion wer e correcte…