Materials Literature
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ESR measurements on X-irradiated undoped CaSO 4 single crystals at 77K reveal two related radiation damage centres. Step annealing measurements suggest a connection between these centres and the thermoluminescent glow peaks at approximately 395 and 465K. An analysis of the g-values (centre I: g x =2.006, g y =2.0091 a…
The stiffness constants of a nematic liquid crystal are calculated for the situation of perfect orientational order with the aid of a model of distributed harmonic forces. Both attractive and repulsive forces are taken as distributed along the molecules, and thus are only important for the parts of two molecules that…
A novel geometry in which it is possible to do x-ray diffraction from a horizontal surface of fluids is applied to liquid crystals. A large-diameter drop of octyloxycyanobiphenyl (8OCB) on a glass plate treated for homeotropic alignment yields perfect alignment of the smectic-$A$ layers at the top surface over an area…
Abstract Isothermal crystallization of polypropylene in two temperature steps has been investigated by means of polarizing optical microscopy. On the edges of growing β‐spherulites a β → α modification change is observed when the temperature is raised beyond 140°C. The growth rate of the β‐modification exceeds that of…
Physical-chemical conditions of synthesis are found and trigonal GdF3-CaF2 crystals with Nd3+ ions are grown using the Bridgman technique. Detailed investigations are made of their spectroscopic intensity characteristics. Intermanifold luminescence branching ratios from the 4F3/2 state and transition cross-sections ar…
Variable range hopping conductivity (i.e. resistivity proportional to exp T−1/4) has been observed in Al implanted sapphire. The conductivity of these implanted layers was studied as a function of implanted doses.
We consider the interaction of electrons in unfilled shells of an ion substituted as an impurity in an insulating host crystal with their self-fields induced through polarizable ligands. All orders of the interaction (dipole, quadrupole, etc.) are considered, thereby extending previous treatments that included induced…
Absorption spectra of Pr3+ and Nd3+ diluted in LuPO4 and YPO4 crystals have been measured from 4000 to 30 000 cm−1, at liquid He and N2 temperatures. Fluorescence was observed for Pr3+ and Nd3+ in YPO4, and Zeeman spectra were obtained in the visible region. The transitions were assigned and fit to a semiempirical Ham…
The chelating agents EDTA, o-phenanthroline, nitrilotriacetic acid (NTA), ethylenediamine-bis(o-hydroxyphenylacetic acid) (EDDA) or dimethylglyoxime prevented the expression of hydrogenase activity in batch cultures of nitrogen-fixing Azotobacter chroococcum, but did not inhibit preformed enzyme. The inhibition was re…
Some important statistical properties of the self-avoiding freely jointed ring-polymer model are studied. Using dynamic Monte Carlo techniques, which yield proper ring configurations, the probability distribution function Pn(r) of intrachain distances, the bond correlation function 〈u0u0+n〉 and related quantities as m…
High-resolution electron-energy-loss spectra are reported which describe the oxidation of Al(111) surfaces. The initial stage of oxidation is characterized by both surface and subsurface atomic oxygen. The surface oxygen phase is unstable and converts to subsurface oxygen at room temperature. No evidence of molecular…
Results of the temperature-dependent Raman spectra of graphite-bromine intercalation compounds are reported in the temperature range $290<T<380$ K. Of particular importance is the first observation of phase transitions in intercalated graphite using the Raman scattering technique, including (1) a commensurate-in…
The magnetoresistance of pure graphite has been measured at low temperatures down to 0.48 K, under a steady magnetic field up to 28.5 T with the use of a hybrid magnet. A striking anomaly in the magnetoresistance was found at fields above 22 T. The fact that the critical field of the anomaly has a strong temperature d…
Optical absorption and fluorescence spectra of the Kramers ions Ce3+, Sm3+, Dy3+, and Yb3+ in the C2 sites of Y2O3 are reported. A crystal-field analysis of these data and previously reported data for Nd3+ and Er3+ is performed that is based on a Hamiltonian of C2 point-group symmetry, including J-mixing effects. A be…
A theory of the tetramethyltetraselenafulvalene (TMTSF) salts and their sulfur analogs is developed. It is shown that the phase diagram is controlled by electron-electron umklapp scattering. The theory accounts for differences between the sulfur and selenium series, and the absence of Peierls transitions. Predictions…
(110), (100) and (111) single crystals of silver were cleaned by argon ion bombardment and annealing in ultra-high vacuum, the chemical purity and atomic arrangement of the surfaces being monitored by Auger electron spectroscopy and low-energy electron diffraction. The work functions of the crystals, determined photoe…
Abstract Conditions have been defined for applying polyimide coatings onto the silicon wafer as passivation and/or dielectric. Processing variables studied included the critical areas of adhesion, cure cycle and thermostability. Aminosilane was shown to be effective adhesion promoter. The rate of imidization was follo…
Theoretical calculations are presented which show that the enhancement predicted by the particle plasmon model of surface-enhanced Raman scattering is limited by radiation damping. The damping becomes more severe as particle size increases, while the enhancement produced by small particles is limited by surface scatte…
Previously pressurized (pre-pressurized) fuel rod tests recently performed in the Nuclear Safety Research Reactor (NSRR) investigate the effects of initial internal pressure on fuel rod behavior during reactivity initiated accident (RIA) conditions. A single PWR type fuel rod was contained within a waterfilled, ambien…
The remarkable electromechanical propertithe PZT-type piezoelectric ceramics approach presently to their saturation. Now it is necessary to research solid solutions which are not based on the Pb(Zr,Ti)03 system