Materials Literature
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Summary The linear strain hardening observed after the easy glide region in face-centred cubic single crystals at sufficiently low temperature is explained by assuming that all the Frank-Read sources of the active slip system are in action, and form small active slip planes bounded on all four sides by Cottrell barrie…
Silver migration may be defined as a process by which silver, when in contact with insulating materials under electrical potential, is removed ionically from its initial location, and is redeposited as metal at some other location. This process requires adsorption of water on the insulation surface. Silver is unique i…
Experience with the scanning electron microscope has shown that there are fields of application where this instrument has distinct advantages over the conventional transmission microscope (with or without replicas) and the reflexion electron microscope. For example, there are specimens which are too thick to be viewed…
Summary The present paper treats in some detail the various mechanisms by which lattice defects are formed by moving dislocations. Particular attention is paid to the role of thermal energy in these processes and to the special features of extended dislocations in metals with low stacking fault energies. The results a…
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Este método, que mide la retracción total de morteros de resinas al pasar de la forma plástica al estado completamente curado, puede ser útil para predecir la retracción máxima de dichos morteros.
Se indican las normas prácticas que se han de seguir al llevar a cabo el curado eléctrico del hormigón.
Se ha conseguido que la cocción con carbón pulverizado sea económica gracias a un nuevo modelo de parrilla. Un nuevo procedimiento de cocción con granulación y recubrimiento de los gránulos mediante una capa exenta de carbón, permite reducir considerablemente las pérdidas de CO del horno vertical.
Se destaca, tomando como base numerosas determinaciones, la importancia, en el plan industrial, de la estructura granulométrica de las arcillas, como factor principal que determina la actitud de una arcilla para preparar un determinado producto.
A treatment is given of the hysteresis loops of dilute mixtures of various sizes of ferromagnetic particles. Three ranges of particle size are considered: very small particles called ``super-paramagnetic'' which are single domain and equilibrate resulting from thermal vibrations, single domain particles which are larg…
Co mpositional proximity to a morphotropic t ransformation between two ferroelectric solid-s olution phases seems to yie ld ceramic transducers having desirable properties over a wide range of te mperature. Examples of t his phenomenon were observed in the systems PbTi03-PbZr03, PbTi03-PbO:Sn02, PbTi03-PbZr03-PbO:SnO"…
Abstract Previous theoretical work by Stoner & Wohlfarth (1948) on the magnetic properties of single domain ferromagnetic particles is extended to take some account of the interaction between the particles. Earlier theoretical considerations of the interaction problem are critically discussed (§2), and the experim…
Abstract The method described previously for measuring the energy stored in cold-worked metals has now been applied to nickel and arsenical copper as well as to pure copper. Torsion, tension and compression have been used as methods of deformation, and the heating rates were 2, 4 and 6° C/min. For all these materials,…
The theory of the magnetic susceptibility of graphite is presented in terms of a three-dimensional Wallace electron energy band structure. The experimentally observed variation with temperature is explained in a satisfactory manner, provided the interplane resonance integral occurring in the band approximation is give…
The superconducting transition temperatures of alloys between zirconium and VIIIth column elements are substantially higher than those of zirconium. The same is true for zirconium-gold alloys. This observation confirms a rule previously established about the height of transition temperatures.
The neutron diffraction data of Shull et al. on the powder specimens of MnO, FeO, CoO, etc., are re-examined. It is found that except for FeO the observed Debye-Scherrer patterns may be produced by a number of magnetic moment arrangements with the same antiparallel coupling among the moments on the next nearest neighb…
A mechanism is suggested for the nonradiative quenching of excited states of simple impurity centers, namely a crossover to the ground electronic state of the center immediately after excitation and before thermal equilibrium has had time to come about. It is proposed that this mechanism is responsible for the absence…
The symmetry properties of the one-electron energy bands of a crystal of the zinc blende structure are studied by means of group theory. This is done both with and without the inclusion of spin-orbit coupling. The character tables and compatability tables are obtained for the various irreducible representations of the…