Materials Literature
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The high strength potential of single‐phase mullite was investigated under compressive stress‐strain and creep testing conditions at 1400° and 1500°C. In single‐crystal experiments, no plastic deformation and, hence, no dislocation glide was observed. Polycrystalline mullite was deformed via the Nabarro‐Herring mechan…
Linear thermal expansion measurements have been carried out from 6 to 340 K on a high-purity silicon sample using a linear absolute capacitance dilatometer. The accuracy of the measurements varies from ±0.01×10−8 K−1 at the lowest temperatures to ±0.1×10−8 K−1 or 0.1%, whichever is greater, near room temperature, and…
Abstract This paper surveys the basic aspects of physical aging. It shows that aging i s a general and important phenomenon found in all organic and inorganic glasses and in some metals as well. Moreover, the behavior of all these materials is very similar. It further shows that aging cannot be ignored in the testing…
Abstract The free‐volume theory describing diffusion in polymer–solvent systems is reexamined. Calculation of the specific free volume for such systems is discussed, and equations are presented for the determination of the self‐diffusion coefficients of the polymer and the solvent. Conditions under which the mutual di…
Recent advances in the investigation of polyurethanes are surveyed. Considerable attention is paid to copolyurethanes based on multicomponent initial constituents, which may exhibit thermoplastic or thermoelastoplastic properties depending on the distribution of the components in the chain and the length of the glycol…
My high-resolution studies of the bound-exciton luminescence in Ga-doped Si reveal a triplet structure. Also, I report for the first time bound multiexciton complexes associated with Ga, which are similar to those previously reported for Si doped with P, Li, and and B. In the case of Ga, however, the $m=2$ bound-multi…
Abstract An extensive examination of the cathodoluminescent emissions from natural diamonds has been performed with due regard to their inhomogeneity, correlating cathodoluminescence properties point-by-point with the local crystal lattice texture and imperfection content as revealed by other topographic techniques (i…
Abstract Caprolactam has been polymerised by sodium hydride in the presence of isocyanate terminated polymers. The latter participate in the initiation reaction and allow the preparation of materials where the prepolymer can amount to 50% of the product. There is evidence that block copolymers are formed, and the prop…
The ratio of the radial diffusion coefficient to mobility D r / mu exp has been measured for the first time in five gases at high E/N (ratio of electric field to gas number density). The range of E/N was as follows: helium 3<or=E/N<or=847 Td; argon 8<or=E/N<or=1271 Td; air 14<or=E/N<or=1412 Td; methane 14<or=E/N<or=56…
Effecls of chro mium, moly'bdenum and vanadium on slJheroidi z alion of carbides in 0.8 0 a carbon sleel b)' slow cooling annealing have been invesligaled.
The effect oj boron on the transformation oj 10w-carbon-!-mo!),bdCllum steels has been investigated by means oj dilatomelly and microstructural observations.The steels containing boron below 30 ppm exhibits the largest hardenability in the case oj austenitization at 930°C, but the hal-denability is reduced by austmiti…
The low-temperature thermal conductivity of three type-II $a$ diamonds irradiated with 0.75-MeV electrons at room temperature and one irradiated at 77 K was found to be reduced and is characteristic of phonon scattering by large aggregates: the conductivity changing from Rayleigh scattering at the lowest temperatures…
The theory of the angularly dependent photoemission from a semi-infinite crystal as a one-step process is briefly reviewed, starting from the formulas of Adawi and using surface-matched wave functions in both upper and lower states and absorption in the upper state. We derive conditions under which the three-step mode…
A systematic perturbation theory is developed to study the interaction of electromagnetic waves at rough dielectric surfaces. The Ewald-Oseen extinction theorem is used as the basis of the perturbation theory. Explicit expressions for both first-order and second-order fields (in terms of the surface roughness paramete…
In previous publications we reported on the optical properties of aggregated metal systems, where the metal particles were assumed to be free-electron type with damping, and where they were assumed to be dispersed in a dielectric medium with a varying index of refraction. The main results were the shift of bulk and su…
We report measurements of C${\mathrm{O}}_{2}$ photodesorption and associated surface-conductivity changes in ZnO. The measurements show a one-to-one correspondence between the rates of those two quantities. The rates of both C${\mathrm{O}}_{2}$ photodesorption and surface-conductivity changes are initially fast, becom…
Polarized spectra of evaporated thin films of ${\mathrm{As}}_{2}$${\mathrm{S}}_{3}$ glass have been recorded before and after annealing at the glass transition temperature and compared with the corresponding spectrum of the bulk glass. The spectra of virgin films consist of several sharp molecular bands superposed on…
Mid-gap optical absorption and electron spin resonance (ESR) attributed to optically induced localized paramagnetic states have been studied in several chalcogenide glasses and amorphous arsenic for $T\ensuremath{\le}80$ K. The observation of these optically induced metastable paramagnetic centers provides the most di…
A method is proposed for estimating the free energy of cation vacancy migration in alkali halides with NaCl structure from macroscopic parameters. It is based on the calculation of the electrical and the dilatation work during the migration of the cation. The dilatation work can be calculated from the elastic constant…
The infrared reflectivity of reduced rutile $\mathrm{Ti}{\mathrm{O}}_{2\ensuremath{-}x}$ at room temperature is reported at departures $x$ from stoichiometry varying from ${10}^{\ensuremath{-}3}$ to 5 \ifmmode\times\else\texttimes\fi{} ${10}^{\ensuremath{-}2}$. The electron carriers resulting from the lattice defects…