Materials Literature
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The spectra of methane adsorbed at low temperature in NaA zeolite show two strong effects of the field existing in the cavities: (i) the appearance of the ν1 forbidden band which increases when decreasing the temperature and (ii) the splitting of the ν3 degenerate band. The variation with T of its components lead to t…
The two-fluid theory of phonon transport and thermal conductivity recently proposed by the author is refined, with the major source of error identified as the previous neglect of the subset of normal processes called NN processes. A correction is provided for these processes, which are mainly those of phonon splitting…
A microscopic model of the effective deactivation of the ZnS visible photoluminescence by iron impurities is presented. It is shown that strong photoionization (${\mathrm{Fe}}^{2+}$\ensuremath{\rightarrow}${\mathrm{Fe}}^{3+}$) absorption enables an effective transfer of energy between centers active in luminescence pr…
Overall rate constants for the removal of N2(A,v) by O2 and O were measured at 298 K in a rapidly pumped flow reactor using laser-induced fluorescence (LIF) detection of N2(A,v) by excitation in the first positive system of N2, B(3πg)←A(3Σ+u). O atoms were generated in microwave discharges of pure O2 prepared by therm…
Conformational and displacive molecular defects in even-numbered paraffins ${\mathrm{C}}_{\mathrm{n}}$${\mathrm{H}}_{2\mathrm{n}+2}$, with 22\ensuremath{\le}n\ensuremath{\le}28, are studied as a function of temperature by means of small-angle x-ray diffraction. The amplitude of the molecular longitudinal motion in the…
The process of growing large diameter single crystals of Al2O3:Ti3+ by vertical solidification of the melt is described, and some of the problems in producing high-optical quality material are discussed. The characterization of the distribution and valance state of titanium ions was performed by x-ray techniques and l…
A model for describing a new kind of order in amorphous covalently-bonded networks is described. We introduce the concept of ``propagated short-range order'' (SRO), which expresses the idea that SRO about a particular atom can constrain the form of SRO around neighboring atoms. Propagated SRO can be achieved by applyi…
M r = 223.19, orthorhombic, Pbcm , a = 5.8931 (1), b = 5. 4904 (1), c = 4.7528 (1) A, V = 153.78 (1) A 3 , Z = 4, D x = 9.640 g cm -3 , lambda = 1.893 A, mu = 0. 210 cm -1 , F(000) = 608 fm 2 , T = 295 K, R wp = 0.0846 for 2623 step intensities, R B = 0.0182 for 98 reflections. The structure consists of sheets 2.71 A…
Surface-state occurrence on low-index faces of metals is analyzed with use of a combination of elementary multiple-reflection theory and elementary nearly-free-electron (NFE) theory. Five NFE gaps on Cu are considered in detail, three associated with the bulk L gap at \ensuremath{\Gamma}\ifmmode\bar\else\textasciimacr…
Explicit formulas for the calculation of stress are presented based on the stress theorem and the local-density-functional approximation. Norm-conserving pseudopotentials are applied in a plane-wave basis for calculations on the semiconductors Si, Ge, and GaAs. Besides the lattice constants and bulk moduli, complete s…
Optical and electrical properties of transparent conductive oxide films of undoped and doped SnO 2 and In 2 O 3 prepared using the pyrolysis spray method were studied. The optical constants extracted from transmittance and reflectance measurements between 0.25 and 3 mu m are interpreted to give values of the direct al…
The optical energy gap of amorphous Se powder has been determined by a photo-acoustic method and has been found to be 1.99+or-0.02 eV. On annealing, the gap decreases linearly as a function of annealing temperature towards that of the crystalline selenium.
A number of organic materials have been observed to possess very large intrinsic nonlinear optical susceptibilities. Second and third order susceptibilities have been measured to be larger than any inorganic materials. These large susceptibilities as well as potentially very fast switching times arise from certain cha…
Measurement by a vibrating capacitor probe of the variation with temperature of the surface potential of freshly cleaved surfaces of sodium chloride single crystals confirm the basic characteristics predicted by point defect theory: negative potentials at low temperature, positive potentials at high temperature, and a…
Abstract The phenomenon of scale formation has been experienced by generations of different races whenever water has been used. It was formed in Roman aqueducts and canals and is also found in the present day in the most modern oil production operations. The most commonly found scales in this industry are the carbonat…
Abstract Many real, exothermic systems involve more than one simultaneous reaction. In part I of this series (Boddington, T., Gray, P. & Wake, G. C. Proc. R. Soc. Lond. A 393, 85 (1984)) a simple, unifying approach to the behaviour of such multi-reaction systems was proposed. It built on a communal activation ener…
The temperature-composition phase diagram of the ${\mathrm{Ni}}_{1\ensuremath{-}x}{\mathrm{Pt}}_{x}$ system was determined by x-ray diffraction and in situ high-temperature measurements of electrical resistivity. The Curie temperatures were also determined for both disordered and ordered alloys. Our results provide di…
Polystyrene chains in solution have been crosslinked by $\ensuremath{\gamma}$ irradiation. The gelation reaction has been stopped at various stages before the gel point and the size distribution function has been measured. We show that the distribution functions obey a simple scaling law.
There is a possibility that the phase separation process is coupled with other ordering processes such as crystallization. New types of phase separation behavior during the crystallization process in polymer blends with phase diagram are presented probably for the first time. Two different types of nonequilibrium phen…
A new processing scheme suitable for commercial production has been developed so that the Fe-28Cr-10.5Co magnet alloy can be used as a replacement for high cobalt Vicalloy (52Co-38Fe-10V) in thin strip (1-2mil) permanent magnet applications, offering the advantages of lower cost, lower cobalt content, improved rust re…