Materials Literature
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The degree of normal segregation, occurring during directional (normal) freezing in a transverse magnetic field of 34 000 oersteds, has been determined for aluminium–copper alloys solidified for rates of [Formula: see text] to 4 inches per hour. For ingots in the composition range 0.5% < %Cu < 4.5%, solidified a…
Liquid crystal mixtures were sandwiched between two transparent electrodes on glass and a direct or alternating potential was applied. The light scattering property of the liquid crystal changes upon application of voltage, the intensity varying from 1 to 10% of that scattered by a MgO diffuse surface. The maximum inc…
Étude spectrophotométrique de l'absorption bleue et violette de Cu2O aux températures de l'azote et de l'hélium liquides. On a pu évaluer le facteur d'intensité d'oscillateur des raies bleues et violettes et attribuer le spectre à des transitions excitoniques de première classe.
Abstract The photoconductivity and carrier mobilities of synthetic crystals of realgar (As 4 S 4 ) have been investigated. A sharp increase in the photoresponse at short wavelengths is attributed to an energy gap of (2.40 ± 0.05) eV. An additional weak peak in the photoresponse at 600 nm is due to free hole formation…
Abstract The anisotropy field strength H K is measured in thin nickel and 81/19 nickel‐iron films immediately after deposition and during subsequent systematic annealing in external magnetic fields. These measurements are performed with the films kept in ultra high vacuum using a planar Hall effect method. An analysis…
Abstract The thermally induced solid‐state polymerization of 66 nylon was investigated. It was found that the rate‐controlling step in the process is chemical reaction. A mechanism of the form, rate = kt n was shown to hold. The reaction rate constant was found to be k = 1.53 × 10 10 exp [ − 12,960/ RT ]. Units of k a…
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Abstract Es werden experimentelle Ergebnisse über die thermischen und strahleninduzierten Phasenumwandlungen sowie über die Verschiebung der Umwandlungstemperaturen zwischen den Raum‐ und Hochtemperaturphasen von BaTiO 3 , PbZrO 3 und PbTiO 3 bekanntgegeben. Es wurden vorwiegend röntgenographische und kalorimetrische…
Thermal conductivities were measured for extensively characterized magnesia, alumina, and zirconia powders. Thermal conductivities of the powders in dry air at atmospheric pressure were determined at volume fractions solid varying from 0.49 to 0.70 as a function of temperature from about 100° to about 850°C. Particle-…
The reactions of cobalt(II) chloride with hydrazine, monomethylhydrazine, and 1,1-dimethylhydrazine have been studied under various conditions and the magnetic and spectral properties of the resulting complexes used for stereochemical identification. Six-co-ordinate complexes are formed by hydrazine and monomethylhydr…
One of the most exciting current fields of research is that of biomedical polymers: the replacement of various complex biological materials in the body with less complex synthetic polymers, designed to perform the function of the natural material. These may range from relatively simple “artificial” parts (such as vasc…
Abstract The absorption spectra and the magnetic moments of Co 2+ , Ni 2+ , and Cu 2+ in alkali borate glasses of various compositions and in halide‐containing glasses have been explained from the point of view of the ligand field theory. Spectra and magnetic moments are highly dependent on the composition of the base…
The standard enthalpy change of the reaction AOH(g)→A(g)+OH(g) has been measured in H2+O2+N2 flames for all alkali metals A through a procedure based upon the third law. Values obtained for ΔH°° are 101±2, 77±4, 81±2, 83±2 and 91±3 kcal/mole for A = Li, Na, K, Rb and Cs respectively.
Abstract In der vorliegenden Arbeit wird aus dem elektronenmikroskopischen Beugungskontrast von Stapelfehlerdipolen in verformten kubisch‐flächenzentrierten Metallen die spezifische Stapelfehlerenergie bestimmt. Der elektronenmikroskopische Beugungskontrast von Stapelfehlerdipolen wurde in Abhängigkeit von der Geometr…
The reaction between finely divided SiO2 and SiC at 1270–1430°C was studied. The reaction scheme proposed is: 2SiC+SiO2= 3Sia+2COa 2Sia+CO = SiOa+SiC Sia+SiO2= 2SiOa Sia, SiOa, COa= Sig, SiOg COg. During the first 2–6% of reaction, Si volatilizes; thereafter primarily SiO and CO volatilize. Only the upper layers of th…
Large dislocation loops on the basal plane and rows of prismatic dislocation loops are both observed in quenched magnesium specimens. It was found that by altering the environment in the quenching furnace either type of dislocation defect could be made to predominate. A mechanism for the production of rows of punched…
Copper produces two emission bands in all and all phosphors. Both bands shift monotonically to lower or higher quantum energies, if the Zn/Cd ratio is varied, so that their differences to the also varying energy of the band gap remain constant. In contrast, the positions of the emission bands in , , and depend relativ…
The magnetic susceptibilities of four iron(III) and five ruthenium(III) compounds, all with the low-spin configuration t52g, have been measured in the range 80–300°K. The data are compared with the theory for a 2T2g ground term in the presence of a low-symmetry ligand-field component, and including electron delocalisa…
Pure zinc oxide is active at 200°C in the catalysis of the oxidation of carbon monoxide. Oxygen appears to be adsorbed in an ionic as well as a non-ionic form, while carbon monoxide and carbon dioxide are adsorbed essentially in non-ionic forms. Two surface sites, probably Zn+ ions, are required to fix O2 and also CO2…
In this review a qualitative description is given of the various types of exchange interactions which might be present in metals and insulators and which might lead to co-operative interactions - particularly ferromagnetism. The theory of spin waves is then described and this is extended to include non-linear and temp…