Materials Literature
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An experimental study is described of the formation and growth of gas bubbles in crosslinked elastomers. A critical condition for bubble formation is found to hold in most cases: The gas supersaturation pressure must exceed 5G/2, where G is the shear modulus of the elastomer. The kinetics of bubble growth are shown to…
An empirical equation is developed for the prediction of total penetration distance of a projectile in many natural earth targets. Development of this equation was based on approximately 160 full-scale penetration tests into a variety of targets, including rock, gypsite, permafrost, ice, desert alluvium, silt, sand an…
The geometry of the deformation produced by the climb of edge dislocations is defined and the conditions are determined under which dislocation climb, by itself or in conjunction with glide, can produce a general change of shape. The results are important in understanding the high-temperature deformation (T > 0.5Tm) o…
The contribution to the electrical resistivity caused by grain boundaries has been measured in polycrystalline specimens of high purity copper and various grades of high purity aluminium. The specific grain boundary resistivity appeared to be independent of the impurity content, depended to a small extent on the tempe…
Using mass spectroscopic and ultrahigh vacuum techniques, solution and diffusion of hydrogen in tungsten was investigated for pressures between 600 and 10−8 Torr and temperatures between 1100 and 2400 K. Solubility and diffusion constants are derived from degassing rates of a solid cylinder which was pre-loaded with h…
A simple phenomenological constitutive equation for porous materials is proposed, which allows a detailed description of irreversible compaction behavior at low pressures and reduces to the correct Hugoniot description at high pressures. The theory is compared to some existing data on Hugoniots of porous aluminum and…
The transition metal dichalcogenides are about 60 in number. Two-thirds of these assume layer structures. Crystals of such materials can be cleaved down to less than 1000 Å and are then transparent in the region of direct band-to-band transitions. The transmission spectra of the family have been correlated group by gr…
The most recent achievements in the study of the degradation and the stabilsation of polyorganosiloxanes, including those containing other atoms in the chain, are surveyed. The effect of polymer structure on their thermal stability is examined, and the part played by catalytic impurities in developing processes of the…
The structure and the chemical properties of polymeric radicals having their free valency on a carbon atom in the main chain are surveyed. Most of the information on radicals in solid polymers has been obtained by electron spin resonance. The first part of the review gives a detailed analysis of the hyperfine structur…
Abstract It has been widely thought that the use of wavefunctions with full electronic correlation would involve integrals of 3N dimensions, where N is the number of electrons. Here it is shown that by a method similar to that of variation theory a set of equations which determine the orbitals and correlation function…
Abstract A novel expression is presented from which kinetic parameters, activation energy (E) and reaction order (n), may be estimated from a single DTA thermogram. A simpler version of this expression was presented by P ILOYAN . The two expressions are compared and the limitations of the P ILOYAN equation are mention…
The metal-semiconductor transition in ${\mathrm{V}}_{2}$${\mathrm{O}}_{3}$ is found to be suppressed above 26 kbar which corresponds to a volume compression of 0.9%. The temperature and volume dependence of the resistivity of the metallic phase is consistent with semimetallic behavior and a pressure-dependent band ove…
The contrast between phases in pyrex glass was heightened for viewing in the electron microscope by exchanging silver ions for sodium ions in the glass. The scale of phase separation in pyrex was foud to be about 30 angstroms; sample of commercial soda-lime glass, prepared in the same way, showed no phase separtion.
Abstract The problem of accommodation of constrained deformation by slip and twinning has been analysed. The analysis is based on Taylor’s least work hypothesis. In this analysis, the operative combination of slip and twinning systems is found by minimizing the orientation factor M = (∑isi+α∑iti)/ε, where si and ti ar…
Soap bubbles of long life (over 2 years) and large size (over 60 centimeters in diameter, 100 liters volume) have been produced from bubble solutions improved by the addition of water-soluble synthetic organic polymers such as polyvinyl alcohol or polyoxyethylene. The natural life can be defined as the time it takes f…
Single crystals of strontium oxide have been additively colored by heating them in strontium vapor at pressures from 0.35 to above 42 Torr in a range of temperature from 1391 to 1618\ifmmode^\circ\else\textdegree\fi{}C. An asymmetric optical absorption band was observed at room temperature which peaked at 2.50 eV and…
Magnetic property of CrSb 2 having marcasite structure was investigated by means of magnetic, X-ray and neutron diffractions, specific heat and electrical resistivity measurements. The magnetic susceptibility of CrSb 2 showed a maximum at about 550°K and it seems to be antiferromagnetic with a negative paramagnetic Cu…
The luminescence spectra of various polymers and solid-model compounds induced by 1-MeV electrons are reported and interpreted. The presence of enhanced triplet emission and absence of singlet emission from poly(p-xylene), poly(monochloro-p-xylene), and the model compound dibenzyl are interpreted on the basis of a mol…
Electrical resistivities as a function of temperature (−130° to 25°C) were determined on single crystals of cerium hydride ranging in composition from CeH1.94–CeH2.85. Measurements were performed in an inert-atmosphere dry box using the four-point probe technique. Cerium hydride exhibited metallic behavior in the rang…
Single crystals of Ni2+-doped spinel were made by using a large solar furnace in our laboratory, and their absorption spectra were measured in near-infrared, visible, and ultraviolet regions. The observed bands were analyzed according to the crystal-field theory in which the spin–orbit coupling was taken into account,…