Materials Literature
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A physical picture of the smectic $C$ phase is proposed in which the molecules rotate freely about their long axes in the smectic $A$ phase and this rotation is frozen out in the smectic $C$ phase. This picture is in contrast with the accepted view that the long axis of the molecules is normal to the smectic planes in…
A new analysis of polarization curves in the non-Tafel region in the vicinity of the corrosion potential is described which allows calculation of the polarization resistance (Rp) and the Tafel slopes (ba and bc). From these data instantaneous corrosion rates are calculated. Experimental data for the system Fe/1N H2SO4…
The exact renormalization-group approach of Wilson is used to study the critical behavior for $T>{T}_{c}$, $H=0$, and small $\ensuremath{\epsilon}>0$, of an isotropic ferromagnetic system in $d=4\ensuremath{-}\ensuremath{\epsilon}$ dimensions, with exchange and dipolar interactions between $d$-component spins. N…
A method is described for producing thin, hydrophilic support films for electron microscopy. These films have a well defined composition and can be made as thin as 10–15 Å. An application is described in which these hydrophilic films are used as ultrathin ``windows'' for frozen, aqueous specimens.
The emission, excitation and reflection spectra at 300, 80 and 15 K were obtained. The blue emission at 442 mµ was observed for CaS:Sb 3+ as well as the well-known yellow-green emission at 540 mµ. In the excitation or reflection spectra, A , B and C bands were found for all phosphors of Ca(S:Se):Sb 3+ investigated. Th…
By measuring the conductivity of stannic oxide crystals as a function of oxygen partial pressure at elevated temperatures, it is shown that the dominant native defect in SnO2 is a doubly ionizable oxygen vacancy. Both donor levels of this defect, the first 30 meV deep and the second 150 meV deep, are identified and a…
Abstract The reversibility of the reaction CaCO 3 ⇌ CaO+CO 2 has been examined through a large number of cycles (up to 40), mainly at 866 °C. The decomposition to the oxide is always 100% but the reactivity of the oxide so formed to carbon dioxide falls off markedly after a rapid initial reaction. There is a large inc…
The kinetic theory of the rate of growth G and the initial lamellar thickness lg* of chain-folded crystals is extended so that it is applicable at high undercoolings. Attention is centered on the details of how the first step element and the first fold are put down on the substrate. A parameter φ that varies between z…
A theory of yielding of glassy polymers by thermally-activated production of local molecular kinks is described. It is possible to obtain the activation free enthalpy of this process by modeling the intermolecular energy barrier as resulting from the stress fields of two equal and opposite closely spaced wedge disclin…
The short-range stresses of the hexagonal screw dislocation boundary, of the straight tilt boundary, and of a zig-zag tilt boundary are computed. These are found to be quite complicated geometrically. They are of comparable magnitude in all three cases but smaller for the straight tilt boundary than for the zig-zag bo…
Tantalum borate (TaBO4) has the zircon structure with unusual coordination for the cations: Ta5+ in eight- and B3+ in four-coordination. The infrared and Raman spectrum is reported and discussed. The symmetrical and asymmetrical BO5−4 valence stretching lies at much lower energy than usually observed in borates. A com…
High-pressure treated titanium and zirconium have been investigated by means of transmission electron microscopy. The specimens consisted mainly of retained ω-phase, while in some regions α-phase platelets were observed. Two crystallographically nonequivalent sets of matrices of correspondence between the α- and ω-pha…
The second-order Raman-scattering spectra of KCl, KBr, KI, RbCl, RbBr, and RbI have been recorded at 300, 90, and 23 K. A symmetry analysis for reducing phonon pairs into irreducible representations has been employed, in conjuction with a knowledge of the one-phonon densities of states derived from neutron-diffraction…
Current noise measurements at high current densities have been applied to the detection of constrictions in thin-film metallization. Potentially open metal films due to scratches, notching, improper step coverage, etc., are easily detected. The noise level, in the absence of such defects, appears to be an indicator of…
Photoemission experiments have been performed on amorphous and crystalline films of Se and Te using photon excitation energies of 1486.6 ($\mathrm{Al}K\ensuremath{\alpha}$), 40.8, and 21.2 eV (He II and He I). From these experiments we have determined the densities of valence states, the binding energies of the core l…
The diffuse scattering of x rays ($\mathrm{Cu}{K}_{\ensuremath{\alpha}l}$) from single crystals of aluminum has been investigated after low-temperature electron irradiation (defect concentrations 3 \ifmmode\times\else\texttimes\fi{} ${10}^{\ensuremath{-}4}$ and 5 \ifmmode\times\else\texttimes\fi{} ${10}^{\ensuremath{-…
The $\stackrel{\ensuremath{\rightarrow}}{\mathrm{k}}\ensuremath{\approx}0$ phonon spectra of the layer crystals GaSe, GaS, and their solid solutions are presented. All phonon bands in GaSe (${D}_{3h}$ symmetry) and GaS (${D}_{6h}$ symmetry) are assigned and good agreement prevails between experimental results and grou…
Linear-combination-of-atomic-orbitals-molecular-orbitals cluster calculations using the extended H\"uckel theory are carried out for the interstitial carbon in the diamond lattice. The results suggest that the interstitial configuration is not the tetrahedral or hexagonal site, as has been previously assumed, but is i…
A simplified model is introduced to study the temperature dependence of the index of refraction $n$ in the transparent regime of crystals. The dielectric susceptibility is written as a sum of an electronic contribution due to band-to-band transitions and a lattice contribution, viewed as due to a single mode ${\ensure…
We have investigated the phase behavior of 35 N -(p -alkoxybenzylidene)-p -n -alkylaniline compounds, CnH2n + 1O–φ–CHN–φ–CmH2m + 1′ with n values ranging from 1 to 7 and m from 4 to 8 by means of thermal microscopy and differential scanning calorimetry. We report transition energies and entropies in addition to transi…