Materials Literature
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Sharp luminescence lines from indirect-free-exciton decay are observed in selenium. These permit for the first time an unambiguous identification of the indirect gap. A unique feature of the band structure and symmetry is the existence of two almost degenerate types of excitons with different wave vectors, leading to…
Neutron scattering gives information on molecular conformations in solid solutions of polymers of one isotope in another. Results on crystals of polyethylene grown from solution show a molecular dimension (in the form of a radius of gyration) that is almost invariant with the length of the chain. It is proposed that c…
Experimental results on the deformation of silicon crystals reported in a foregoing paper are discussed on the basis of a model and a hypothesis so far proposed. The dependence of the upper and the lower yield stresses on the temperature and the strain-rate can be described reasonably well by the model of Haasen et al…
The infrared reflectivity minimum in the transverse-longitudinal band gap of the ${\ensuremath{\nu}}_{3}({E}_{u})$ mode of NaN${\mathrm{O}}_{3}$ cannot be described by the usual damped-harmonic-oscillator model of the dielectric constant if only one resonance is assumed. A comparison of the single-crystal infrared ref…
Abstract Cotton fabric was subjected to thermal treatment for durations ranging from 0.5 to 5 min at a temperature range of 160°C. In comparison with the untreated cotton, the copper number (measure of the aldehyde content) decreased after heating cotton for up to 3 min at 160°, 180°, and 190°C but increased when heat…
An analysis is carried out of the effects produced by the possibly strong electric dipolar coupling between intracell dielectric response and intercell hopping response in a simple model of thermally activated ionic conductivity. The results suggest the presence of two marked effects. The first is an enhancement of th…
Tantalum single crystals of the four orientations (100), (110), (111), and (112) have been irradiated with electrons in the energy range 1.0-1.7 MeV. A special irradiation procedure has been used which enables us to distinguish between subthreshold and intrinsic defects. The threshold energy for atomic displacement is…
The oscillatory magnetothermal effect has been used to study the Fermi surface of niobium-doped strontium titanate at low temperatures. Several de Haas-van Alphen frequencies were identified in the (011) crystallographic plane and compared with the predictions of various theoretical models of the conduction band. The…
Abstract Melt blends of polycarbonate with Kodel, a homopolyester formed from 1,4‐cyclohexanedimethanol and terephthalic acid, and with Kodar, a copolyester formed by replacing some of the terephthalic acid with isophthalic acid, were prepared and their transitional behavior were examined by thermal analysis and dynam…
Abstract Polycarbonate blends with poly(ε‐caprolactone) were prepared by both melt‐blending and solution‐blending techniques, and the properties of these blends were studied by thermal analytical and dynamic mechanical testing methods. Each blend composition was found to have a single glass transition temperature, and…
Coherent acoustic echoes are generated in fused silica glass at very low temperatures by a sequence of short acoustic pulses that interact with the intrinsic two-level configurational systems of the glass. Coherent effects are observable below $T\ensuremath{\approx}100$ mK, where the two-level-system phase memory time…
Single crystals of $n$-${\mathrm{Bi}}_{2}$${\mathrm{Se}}_{3}$ were prepared with free-carrier concentration $N$ in the range $5\ifmmode\times\else\texttimes\fi{}{10}^{18}<N<2\ifmmode\times\else\texttimes\fi{}{10}^{20}$ ${\mathrm{cm}}^{\ensuremath{-}3}$. Results of the measurements of infrared reflectance, Seebec…
We show that a suitable electron paramagnetic resonance experiment can discriminate sufficiently against the predominantly harmonic fluctuations characterizing a system undergoing a displacive phase transition, that a cluster-induced order-disorder component of the local behavior is exposed. We find evidence that, at…
The dissolution of iron from carbon steel in aqueous H 2 S solutions has been studied as a function of time and temperature at 0.1 MPa H 2 S pressure using the rotating disc technique. The iron sulfide film formed on the disc surface has been identified by X-ray diffraction analysis. The solubility and dissolution rat…
The random-network model for amorphous alloys proposed by White has been developed for some Se-based amorphous semiconductors (Ge-Se, As-Se, and Se-As-Ge) annealed or irradiated with light. The model suggests that the photobleaching and the photodarkening in these systems may be due to change in the number of bonds. A…
The results of Raman scattering and infrared reflectivity studies of the mixed-valence ternary sulphide ${\mathrm{Sn}}^{\mathrm{II}}$${\mathrm{Sn}}^{\mathrm{IV}}$${\mathrm{S}}_{3}$ are presented. The infrared-active phonon frequencies and the dielectric constants for all the principal directions have been determined.…
The near-band-edge optical properties of a series of 15 crystals including the two binary compounds GaSe and GaTe have been investigated in great detail at 300, 77, and 1.6\ifmmode^\circ\else\textdegree\fi{}K. The absorption spectra at 77 and 1.6\ifmmode^\circ\else\textdegree\fi{} K show well-resolved excitonic struct…
Abstract The influence of shearing history on the viscoelastic properties of low‐density polyethylene (LDPE) is investigated. Swelling of extrudates from a melt indexer is measured for monitoring the variation in viscoelasticity. Continuous shearing of molten LDPE reduces the swelling ratio. The reduction is not due t…
Abstract A low molecular weight poly(ester urea), poly(L‐phenylalanine/ethylene glycol/1,6‐diisocyanatohexane), and a model diester diurea, dimethyldiphenylalaninehexamethylenediruea, were synthesized and found to be hydrolyzed by α‐chymotrypsin solutions at pH 7.8. After ten‐day exposure to 0.1 mg/ml enzyme solution…
Spectral, kinetic, and relative quantum intensity measurements are reported for a series of ${\mathrm{Y}}_{3}$${\mathrm{Al}}_{5}$${\mathrm{O}}_{12}$ (YAlG) crystals, both nominally undoped and activated by ${\mathrm{Ce}}^{3+}$ and ${\mathrm{Tb}}^{3+}$. The undoped crystal shows a complex emission band in the near uv w…