Materials Literature
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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…
Torque and susceptibility measurements with well annealed and chemically polished crystals of CoO were made down to 90°K. When cooled through the Néel point of 20°C with a temperature gradient along one of the cubic principal axes, the crystals yielded torque and susceptibility curves that are attributable to nearly u…
Birefringence patterns in antiferromagnetic NiO crystals were investigated with the orthoscope and conoscope methods using a polarizing microscope. A new birefringence pattern (p-domain pattern), which differs from usual twin domain patterns in NiO crystals, was found within a crystallographically single domain in rat…
The transformation from one resistance state to another by glasses in the system As‐Te‐I is discussed and a model is postulated. The anomalous behavior of the electrical properties of glasses in this system is shown to result from thermal breakdown of the dielectric during which reversible glass‐to‐crystal phase trans…
A study has been made of the morphology of fractionated linear polyethylene crystallized from solution in n-alkanes. Crystals have been found whose habits, though markedly different from any described in this polymer, are similar to, and provide useful models for, the radial crystalline units in melt-grown spherulites…
Monatomic and alternating diatomic chains, with nearest neighbour harmonic interactions, are considered; in each case the force constants are governed by a probability distribution function which is continuous and bounded in a well-defined region and zero elsewhere. It is shown that the lattice modes are, in general,…
The ranges of electrons in evaporated films of aluminium, copper, silver and gold have been measured for incident energies E 0 between 5 and 20 keV. From electron transmission measurements the maximum range and the extrapolated range were determined. Energy loss measurements gave the mean range and the Thomson-Whiddin…
Abstract X‐ray diagrams of different samples of nylon passed over a hot‐plate held at different temperatures show that the observed effect depends on the type of nylon used. Clear evidence consistent with the melting of the core of the nylon is obtained for monofilament.
This article describes work carried out in UKAEA laboratories to examine the possibility of using protective coatings on cadmium plate—such as that used to protect mild steel—in order to prevent or minimise corrosion due to hostile organic vapours. The degree of attack by vapours of acetic, formic, butyric and propion…
In FeTiO 3 , CoTiO 3 and NiTiO 3 the dominant magnetic exchange interactions are held to be of super-superexchange type, using two oxygens or one oxygen and one diamagnetic Ti 4+ ion between the pairs of paramagnetic cations. In order to explain the antiferromagnetic ordering of manganese spins in the same layer in Mn…