Materials Literature
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The numerical fitting of an analytical function representing electron density profile at a jellium surface to the one tabulated by Lang and Kohn is presented. The two sets of parameters entering the electron density profile is proposed. The first one is obtained by purely numerical fitting, and the second one is calcu…
<div class="htmlview paragraph">The need to reduce the weight of automobiles has favored the widespread use of aluminum in automotive ventilation and cooling systems. Space, weight restrictions, the need for increased thermal efficiency, and recycling legislation have all contributed to new designs for heat exch…
Abstract X-ray diffraction (XRD), Mössbauer spectroscopy (MS), and magnetization (SQUID) data are reported for a “pyrrhotite-like” compound ( δ -FeSe), belonging to the central portion of the Fe-Se system. The δ -phase(s) extends compositionally over a range of around Fe 0.94 Se-Fe 0.86 Se at 870 K, but narrows around…
Effect of high pressure on the crystal structure of rhombohedral NaNO3 was investigated by X-ray diffraction of single crystals mounted in a miniature diamond-anvil cell on synchrotron radiation source. Diffraction intensity measurements were made at three pressures across a suggested transition pressure 4.3 GPa. No c…
High pressure X-ray diffraction study was carried out on a graphite to investigate its compressibility as well as any possible phase transition to the hexagonal diamond structure at room temperature. Energy dispersive X-ray diffraction method was introduced using a Mao-Bell type diamond anvil cell with Synchrotron Rad…
Experimental and observational evidence is reviewed for the mechanisms and kinetics of antiphase domain coarsening in silicate minerals. The expected rate law has the form (domain size)n ≈ annealing time, but the ideal value of n=2 has been observed in only one of three cases. Values of n≈8 or 10 are interpreted as im…
The kinetics of the hydrogen absorption and desorption behaviour of a NdFeB sintered magnet is studied. Hydrogenation at temperatures above 200/spl deg/C is used to crumble the Nd-enriched phase. The grains of Nd/sub 2/Fe/sub 14/B phase remain undamaged. Hydrogen desorption occurs in several stages and is complete at…
Magnetic properties, microstructure and intercrystalline segregation of antimony were examined on 2.4 wt.% Si steels containing 0.005 to 0.047 wt.% Sb. The measured reduction of the total core losses in steels containing 0.040 and 0.047 wt.% Sb has various values for chosen variants of pre-annealing at 500/spl deg/C a…
A natural olivine sample from a mantle peridotite xenolith has been studied by in situ high-temperature powder diffraction. The structure has been successfully refined from powder data at three temperatures (25, 600, and 800 °C) using the Rietveld method. The study shows that the full-profile technique is well suited…
The individual Co site contributions to the magnetocrystalline anisotropy in RCo5, RCo4 B and R3Co11B4 compounds have been studied. An analysis is given of the room temperature anisotropy constants of these compounds by using a model of Streever. The values of the rare earth-transition metal exchange coupling JRco/kB…
Abstract Polybenzimidazole (PBI) and polysulfone (PS) do not form miscible blends; however, the tensile properties of the polymer blend in fibers, and the fiber process window, are strongly dependent on the presence of LiCl. The addition of LiCl opens the molecular chains and reduces dope viscosity. As a result, LiCl…
The X-ray powder diffraction pattern of hydrated lithium monoborate LiB(OH) 4 , sometimes formulated LiBO 2 ·2H 2 O, has been obtained. Refinements of indexed reflections yielded the following parameters: a = 9.1732(7)Å, b = 7.9622(6)Å, c = 8.5354(8)Å, space group Pbca, Z = 8, D x = 1.827, D m = 1.83 g/cm 3 . The Smit…
Around 200 kg of (Pu0.55 U0.45)C fuel pellets of relatively low density (86 ± 2% theoretical density) would be used as a driver fuel in the second core of the Fast Breeder Test Reactor in India. The current paper summarizes the production experience of the initial 15 kg of these fuel pellets following the “vacuum carb…
Abstract The use of electron donor–electron acceptor groups to enhance miscibility in polymer blends has been investigated, using the immiscible binary pair polystyrene and polyisoprene as the basic materials. These polymers have been modified by copolymerization with monomers that are either donor or acceptor groups.…
Glucose isomerase from Streptomyces murinus has been crystallized in space group P4(1)2(1)2, cell dimensions a = b = 137.65 and c = 132.20 A. One dimer of the tetrametric molecule is found per asymmetric unit. An initial structure solution was obtained by the molecular replacement method. The crystallographic refineme…
Abstract A model for a twin consisting of two domains is proposed for a new pseudo-hexagonal modification of high-density boron nitride. A structure refinement based on high resolution diffraction data taken with 0.5 Å synchrotron radiation resulted in R factors below 0.015 for each domain. The refinement against detw…
Total photon mass attenuation of six multielement shielding materials (concrete, plaster of paris, quick lime, black cement, white cement, and silica) is measured in the 123- to 1250-keV energy range. The experimental results are analyzed in terms of cross sections, effective atomic numbers, and electron densities. Co…
Polyethylene and polyvinyl chloride pellets were introduced into concrete to improve its neutron attenuation characteristics while several types of heavy coarse aggregates were used to improve its gamma ray attenuation properties. Neutron and gamma ray attenuation were studied in concrete samples containing coarse agg…
<div class="htmlview paragraph">The effect of small amounts of silicate on coolant performance has been studied. The corrosion protection provided by different coolant technologies was evaluated for different silicate contents. This work includes results from electrochemical tests and static and dynamic heat-rej…
We show that transmission-mode perpendicular incidence ellipsometry, which yields the trivial values Psi =45 degrees , Delta =0 for an isotropic thin film, can be used to provide useful data during the vacuum deposition of anisotropic coatings. Thus the number of quarter-wave film thicknesses necessary for a quarter-w…