Materials Literature
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In order to gain some insight into the nature of the interactions in TTF-TCNQ (tetrathiafulvalene-tetracyanoquinodimethane), we compare the magnitude of the observed magnetic susceptibility $\ensuremath{\chi}$ with the predictions of two simple models. First we consider a tight-binding band of noninteracting electrons…
An alternative formulation of the generalized van der Waals theory of nematic liquid crystals is presented and discussed briefly. The derivation is considerably more straightforward than that of Gelbart and Baron and is closely analogous to the usual derivation of the van der Waals equation of state.
The glass transition temperatures (Tg) of binary mixtures of the lower normal alkanols with several aprotic Lewis bases have been measured as a function of composition. The initial molar slope (IMS) at the pure alcohol end of the curve of Tg against mole fraction of base was accurately determined for each base. A rela…
Relationships between the molecular dimensions of polymers adsorbed on solid surfaces and the ’’hydrodynamic thickness’’ obtained by viscosimetry or flow rates through capillaries are derived by solving the corresponding Navier–Stokes equation. An exponential density distribution of polymer segments in the vicinity of…
Bound and excited negative ion states of gaseous 7,7,8,8-tetracyanoquinodimethan (TCNQ) are studied from experiments involving collisions of electrons and fast cesium beams with TCNQ. The electron affinity of TCNQ is measured to be 2.8+0.05−0.3 eV by the collisional ionization technique. TCNQ attaches electrons with e…
In this paper, a theoretical analysis of secondary electron emission in the nearly-free-electron (NFE) metals is presented. Restricting ourselves to excitation of secondary electrons (SE's) from the valence (or conduction) band only, we investigate the roles played by screened electron-electron scattering and by volum…
The measurement of vibrational Raman depolarization ratios has been used to study molecular orientational order in uniaxial single domain nematic and smectic liquid crystal samples. This technique is demonstrated to obtain the same microscopic order parameter 〈P2〉=1/2 〈3 cos2ϑ−1〉, where ϑ is the angle between a molecu…
The exponential absorption edge in amorphous semiconductors is discussed in relation to the Mott-Street model (Phys. Rev. Lett., vol.35, p.1293 (1975)) for chalcogenide glasses. It is shown that the absorption of a photon leads to neutralization of a donor-acceptor pair. The concentration of such pairs is exponentiall…
The subgroups that arise in phase transitions from a high-symmetry phase are characterized as those subgroups that are maximal with respect to the property of acting trivially on a given non-zero subspace U i of the representation space M i of a given irreducible representation T i of H. In the case of subgroups of fi…
For pt.I see ibid., vol.10, no.7, p.1035 (1977). The electron swarm parameters for the steady-state Townsend, pulsed Townsend and time-of-flight experiments are calculated using a Boltzmann equation for argon at E/N values from 85 to 566 Td, when electron impact ionization is appreciable. The results suggest that the…
The simultaneous high-energy-resolution and high-angular-resolution (15 meV, 0.8\ifmmode^\circ\else\textdegree\fi{}) measurements of the (00) beam diffracted from W(001) near 45\ifmmode^\circ\else\textdegree\fi{} incident angles are reported. Apart from the well-known surface-state resonance previously identified, new…
Abstract Rayon yarns grafted with poly(ethyl acrylate) become highly elastic following decrystallization in aqueous zinc chloride solutions. An increase in temperature speeds up the decrystallization rate but does not have a substantial effect on the ultimate elongation properties of the grafted fiber. Increasing the…
Describes an image convertor, Phototitus, consisting of a photoconductor deposited on an electrooptical dielectric crystal. The electron microscope beam incident on the photoconductor creates electron-hole pairs which modulate the transparency of the electro-optical dielectric crystal by means of the Pockels effect. T…
A high-voltage electron microscope has been used to study displacement damage at 600°C in graphite. Small defect clusters were observed for incident electron energies above 150 keV, indicating a threshold energy of 34 ± 2eV for atomic displacement along the c-axis.
This paper reports measurements of the magnetostriction in both single-crystal SmCo5 and in the liquid-phase sintered (LPS) SmCo5 permanent magnet material at fields up to μoH=21 T. By using a strain-gauge technique the changes in length in different crystallographic directions were measured as a function of the field…
Abstract Regular copolyoxamides were prepared from diamine‐oxamides and aliphatic diacid chlorides by interfacial and solution polymerization. Interfacial polymerization is preferred with diamineoxamides where the diamine portion has two to six methylene groups and the diamine‐oxamides are readily soluble in water. Re…
Abstract Antiplasticization, defined as an increase in glassy modulus of polymers upon dilution with low molecular weight compounds, was studied for highly crosslinked epoxy resins. A series of oligomers with average molecular weight 500–4000 was incorporated with epoxy resins for elucidating the effect of their molec…
The first single crystals of As 2 O 5 have now been obtained by annealing amorphous As 2 O 5 under oxygen excess pressure and with careful exclusion of moisture. They were suitable for X‐ray structure analysis.
The optical spectra of (NEt/sub 4/)/sub 2/UI/sub 6/ and (NEt/sub 4/)/sub 2/UF/sub 6/ are presented and analyzed. With these data the electrostatic, spin-orbit, and crystalline field parameters have been obtained for the series of octahedral compounds UX/sub 6//sup 2 -/ (X = F, Cl, Br, I). The Slater parameter F/sup 2/…
Design details and measured performance are presented for a laboratory gas gun with a novel rectangular bore. Projectiles weighing 0.5 g have been accelerated to 300 m s -1 . This design eliminates axial rotation of the projectile which is possible in a cylindrical-bore gun, and provides important advantages in some i…