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Normalización del cemento. Características químicas: Algunos comentarios sobre los métodos de ensayo
El Pliego de Prescripciones Técnicas Generales para la Recepción de Cementos (RC-75), Decreto 1.064/1975 de 23 de mayo de 1975, publicado en los B.O.E. núms. 206 y 207, de fechas 28 y 29 de agosto, respectivamente, del mismo año, incluye la clasificación de los cementos, las prescripciones relativas a las característi…
Charge neutralisation of insulating surfaces in the SEM by gas ionisation
A theory is presented in which the elimination of charging artefacts on uncoated insulating surfaces in the scanning electron microscope by a low-pressure ambient gas is taken to be due to ionisation of the gas. Curves of ion current against ionising field calculated from a model of gas neutralisation give good agreem…
Propagation of partially polarized light through anisotropic media with or without depolarization: A differential 4 × 4 matrix calculus
We extend the scope of the Mueller calculus to parallel that established by Jones for his calculus. We find that the Stokes vector S of a light beam that propagates through a linear depolarizing anisotropic medium obeys the first-order linear differential equation dS/dz = mS, where z is the distance traveled along the…
Conducting polymers: Halogen doped polyacetylene
A study of the electrical conductivity of the halogen doped transpolyacetylene system, (CH)x, is reported. When films of trans- (CH)x are exposed to chlorine, bromine, or iodine vapor, uptake of halogen occurs; and the conductivity increases markedly, over eleven orders of magnitude in the case of iodine. The behavior…
Raman spectrum of anatase, TiO2
Abstract Raman spectra of anatase have been observed in natural and synthetic crystals. Both crystals show the same spectral features. The Raman band occurring at 516 cm −1 at room temperature is split into two peaks centred at 519 cm −1 and 513 cm −1 at low temperature (73 K). The six Raman active fundamentals predic…
Elements of X-ray Diffraction
B D Cullity London: Addison-Wesley 1978 pp xii + 555 price £16.50 This is the second edition of a book concerned with the theory and application of x-ray diffraction to polycrystalline materials in particular. The first edition is an established text for many metallurgists, physicists and chemists interested in orient…
Heat of transport in solids. III. Computer simulation of vacancy in an FCC crystal
For pt.II see ibid., vol.10, p.3051 (1977). Uses computer simulation to study the evolution of the time-dependent energy current J(t) for a vacancy in a model FCC system. In view of the problems arising in the thermal-equilibrium calculation of J(t), the simulation is performed at zero temperature, using the augments…
Electronic band structure and bonding in transition metal layered dichalcogenides by atomic orbital methods
It is shown that the main features of the electronic structure of transition metal layered dichalcogenides can be calculated in a simple ab initio atomic orbital framework. Examples from Groups IV, V and VI of the transition series are considered.
An X-ray photoelectron spectroscopic study of the interaction of oxygen and nitric oxide with aluminium
Abstract The interaction of oxygen and nitric oxide with clean aluminium surfaces has been investigated by X-ray photoelectron spectroscopy. Studies have been in the main confined to the temperature range 80–290 K and pressure range 10-6–10-2 Pa. The Al(2p) level is shown to exhibit a shifted component at a binding en…
A comparison between microsectioning studies of low-temperature self-diffusion in silver
A comparison is made between various microsectioning techniques for radiotracer studies of self-diffusion in silver. Previous investigations by various groups were made with the help of chemical and electrochemical microsectioning techniques. In the present work ion-beam sputtering is applied to the sectioning of silv…
Traps and emission centres in thermoluminescent ZrO2
The thermoluminescence (TL) of heated amorphous ZrO2, doped by Ti, Th, U, Nb, Dy, excited by 253.7 nm or X-radiation is investigated. Six main peaks are observed at 100, 135, 190, 245, 285, and 385 K and their activation energies determined by four methods. It is shown that most traps obey Curie's model, and that the…
Optica absorption spectrum of x-irradiated CaF2:Co
Optical-absorption spectra of Ca${\mathrm{F}}_{2}$: Co x-irradiated at 80 and 300 K are reported. Room-temperature x-irradiated crystals show five bands with peaks at 250, 295, 545, 715, and 780 nm which are associated with a Co-related defect. Irradiation at 80 K produces some bands at 240, 280, and 535 nm which are…
Diffraction gratings for color filtering in the zero diffraction order
Phase gratings with deep rectangular grooves have been successfully used in the zero diffraction order as transmission color filters. They form the basis of the ZOD microimage system for recording color images as surface-relief structures. ZOD images can be inexpensively replicated by hot embossing in a transparent sh…
Theoretical study of lithium graphite. II. Spatial distribution of valence electrons
Based on band-structure calculations presented in part I, the valence charge density of Li${\mathrm{C}}_{6}$ is evaluated and presented in contour diagrams and iinear plots. The hybridization of the Li $2s$ states with the bands of graphite is studied and quantified in terms of the Li contact density. It is found that…
Optical properties of single crystals of some rare-earth trifluorides, 5-34 eV
The reflectances of single crystals of the trifluorides of La, Ce, Pr, Nd, Dy, and of polycrystalline Gd${\mathrm{F}}_{3}$ were measured in the 10-34-eV region, along with 5-9-eV transmission measurements on films of these materials. Localized $4f\ensuremath{\rightarrow}5d$, $6s$ transitions on the rare-earth ions giv…
Influence of pressure and temperature on phonons in molecular chalcogenides: CrystallineAs4S4andS4N4
In molecular solids, vibrational frequencies can be profoundly affected (shifted by > 50%) by relatively modest hydrostatic pressures. We have carried out an extensive Raman-scattering investigation of the influence of pressure and temperature on a large number of phonons in two inversely related chalcogenide molec…
Two-band model for NbSe3(Ohmic regime)
The charge-density-wave (CDW) linear-chain metal Nb${\mathrm{Se}}_{3}$ shows striking non-Ohmic behavior when the applied electric field exceeds \ensuremath{\sim} 0.1 V/cm. Hall effect, transverse magnetoresistance, conductivity anisotropy, and Shubnikov-de Haas measurements using sufficiently low current densities to…
Lattice modes in ferroelectric perovskites. III. Soft modes in BaTiO3
We report careful right-angle Raman measurements, in the tetragonal phase of BaTi${\mathrm{O}}_{3}$, of the lowest overdamped "soft" $E(\mathrm{TO})$ mode. The measurements are from 22\ifmmode^\circ\else\textdegree\fi{}C to the tetragonal-to-cubic phase transition, which occurs at ${T}_{c}=135\ifmmode^\circ\else\textd…
Electronic structure of pendant-group polymers: Molecular-ion states and dielectric properties of poly(2-vinyl pyridine)
A spectroscopic characterization of poly(2-vinyl pyridine) is presented for the purpose of utilizing this material as a test case to examine the validity of a new theory of the electronic structure of saturated-chain pendant-group polymers. In this theory, which we refer to as the molecular-ion model, low-energy elect…