Materials Literature
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Microcrystalline diamond has been formed on silicon or molybdenum substrates by vapor deposition from a geseous mixture of methane and hydrogen. Cubo-octahedral or multiply-twinned crystals were obtained. The structure of the deposits was identified by electron diffraction and Raman scattering.
The critical exponent γ in the relation between the dielectric constant and temperature (1/ε—1/εm = C'-1x (T—Tm)γ) has been determined precisely for relaxor ferroelectrlics Pb(Mg1/3Nb2/3)O3, Pb(Zn1/3 Nb2/3)O3 and a related solid solution 0.88Pb (Zn1/3 Nb2/3)O3-0. I2PbT103, as well as for normal ferroelectrics BaTiO3 a…
Sulphur concretes have been used for low-cost housing in developing countries and have potential for various other applications. Field trials have been conducted of sulphur-based curbs and gutters, sewer pipes, median barriers, linings for acid containers and road bases. Recent research has been concentrated on stress…
Abstract Electrochemical techniques were used to identify alloys having adequate localized (pit and crevice) corrosion resistance in a 121°C (250°F) - 3.5 MPa (500 psi) CO2 - 11 wt. % NaCl environment. Various molybdenum alloyed iron and nickel base type materials and a titanium alloy were found to be resistant. Concu…
Abstract The erosion behavior of candidate steel alloys for liquid-solid particle slurry service in coal conversion equipment was determined over a range of testing conditions. It was determined that relative erosion reistance of the carbon, low alloy, chromium, and austenitic steels tested could not be readily relate…
The Raman spectrum of lithium diborate (Li 2 B 4 O 7 ) has been recorded for the first time. After correction for polarisation leakthrough, the spectrum is consistent with group theoretical predictions. No anomaly is seen in the Raman spectrum from 100 to 400K or in the low-frequency dielectric constant from 150 to 35…
On the Depolymerization of Poly‐( R )‐3‐hydroxy‐butanoate ( PHB ) From cell‐free PHB or from dried cells of Alcaligenes eutrophus H 16 , which had been grown in an aqueous fructose solution, enantiomerically pure methyl, ethyl, butyl or β‐methoxyethyl ( R )‐3‐hydroxy‐butanoates are obtained in yields ranging from 75–9…
Abstract Corrosion control planning should begin before any well is drilled. The means of controlling corrosion in oil and gas wells are outlined in some detail in this paper. Primary cause of corrosion of metals is contact of metal with corrosive gases in well fluids in the presence of liquid water. Corrosion can be…
The impression creep behaviour of zinc is studied in the range 300 to 500 K and the results are compared with the data from conventional creep tests. The steady-state impression velocity is found to exhibit the same stress and temperature dependence as in conventional tensile creep with the same power law stress expon…
A model for the electronic and geometric structure of the non-bridging oxygen defect center in fused silica is presented. The structure of the center is determined by the dynamic Jahn-Teller effect, which appears as a forming of an additional oxygen-oxygen bond between the non-bridging oxygen atom and another oxygen a…
As2(SO4)3 belongs to the monoclinic system, space group P2~/c, with a = 9.389 (3), b = 5.255 (2), c = 19.355 (6) .i, fl = 91.88 (2) °, V = 954.5 A, 3, Z = 4, D,, = 3.00 (5), D x = 3.05 Mg m -~. The structure has been solved at 293 K with 1922 independent reflexions (2 = 0 .7107/ i , 0 < 32 °) and refined to a weighted…
Expressions for the relaxation rates for three-phonon "resonant" processes are obtained for the first time. It is also demonstrated that the contribution of such processes can be as high as 30% of the phonon resistivity of Ge at high temperatures. Because of the different temperature dependence from the nonresonant pr…
Additional transitions which appear in the absorption and luminescence spectra of heavily doped (\ensuremath{\sim} 1 at.%) Li${\mathrm{Ga}}_{5}$${\mathrm{O}}_{8}$:${\mathrm{Cr}}^{3+}$ originate on nearest-neighbor Cr-Cr ion systems. By analyzing these spectra at different temperatures, values are obtained for the exch…
The electron spin resonance and polarized optical absorption spectra of V4+ have been studied in single crystals of ZrSiO4, HfSiO4, ThSiO4, and ThGeO4, each having the zircon structure. The principal values of g and A in ZrSiO4 and HfSiO4 are found to be anomalous and significantly different from those of ThSiO4 and T…
A thermodynamics is introduced for fluids subjected to a constant shear. The theory is based primarily on the results of computer simulations using the technique of homogeneous shear nonequilibrium molecular dynamics applied to a system of 108 Lennard-Jones particles. It is supported qualitatively by the results of se…
A statistical theory of nematic systems has been developed for semiflexible polymers on the basis of a new wormlike model of chain statistics. This wormlike chain model closely represents the short-range statistics of real chains and allows the evaluation of the orientation-dependent configurational partition function…
From sets of adsorption isotherms, critical temperatures of two-dimensional condensation have been determined for the first monolayer of Ar, Kr, or Xe adsorbed on a number of lamellar dihalides. Once properly scaled by the critical temperature of the bulk adsorbate, their value appears to be strikingly correlated to t…
Crystal field parameters (Bkq) were obtained for the REOBr:Eu3+ series (RE = Y, La, Gd) and LaOI:Eu3+ from the analysis of fluorescence spectra. The sets of five nonzero Bkq parameters for the C4v symmetry reproduce the experimental 7FJ Stark level schemes within a few cm−1. The Racah (E0–3) and spin–orbit (ζ) paramet…
Electronic energy-band calculations have been performed for the KMg${\mathrm{F}}_{3}$ crystal by using the method of linear combinations of atomic orbitals with a self-consistent-field procedure. The basis set consists of 124 Bloch sums formed by atomic wave functions and single Gaussians. The wave functions of the va…
The dynamic behavior of atoms in bulk amorphous silica SiO2 has been investigated by using the molecular dynamics computer simulation technique to generate the frequency spectrum. A modified Born–Mayer–Huggins equation was used as the interatomic potential function. Due to the covalency of the Si–O bond, the ability o…