1,158 research outputs found
High pressure synthesis of FeO-ZnO solid solutions with rock salt structure: in situ X-ray diffraction studies
X-ray diffraction with synchrotron radiation has been used for the first time
to study chemical interaction in the FeO-ZnO system at 4.8 GPa and temperatures
up to 1300 K. Above 750 K, the chemical reaction between FeO and ZnO has been
observed that resulted in the formation of rock salt (rs) Fe1-xZnxO solid
solutions (0.3 \leq x \leq 0.85). The lattice parameters of these solid
solutions have been in situ measured as a function of temperature under
pressure, and corresponding thermal expansion coefficients have been
calculated.Comment: 9 pages, 2 figures, 1 tabl
Blistering Failure of Elastic Coatings with Applications to Corrosion Resistance
A variety of polymeric surfaces, such as anti-corrosion coatings and
polymer-modified asphalts, are prone to blistering when exposed to moisture and
air. As water and oxygen diffuse through the material, dissolved species are
produced, which generate osmotic pressure that deforms and debonds the
coating.These mechanisms are experimentally well-supported; however,
comprehensive macroscopic models capable of predicting the formation osmotic
blisters, without extensive data-fitting, is scant. Here, we develop a general
mathematical theory of blistering and apply it to the failure of anti-corrosion
coatings on carbon steel. The model is able to predict the irreversible,
nonlinear blister growth dynamics, which eventually reaches a stable state,
ruptures, or undergoes runaway delamination, depending on the mechanical and
adhesion properties of the coating. For runaway delamination, the theory
predicts a critical delamination length, beyond which unstable corrosion-driven
growth occurs. The model is able to fit multiple sets of blister growth data
with no fitting parameters. Corrosion experiments are also performed to observe
undercoat rusting on carbon steel, which yielded trends comparable with model
predictions. The theory is used to define three dimensionless numbers which can
be used for engineering design of elastic coatings capable of resisting visible
deformation, rupture, and delamination.Comment: 29 pages, 11 figures, submitted to Electrochimica Acta (under review
Role of electric charge in shaping equilibrium configurations of fluid tori encircling black holes
Astrophysical fluids may acquire non-zero electrical charge because of strong
irradiation or charge separation in a magnetic field. In this case,
electromagnetic and gravitational forces may act together and produce new
equilibrium configurations, which are different from the uncharged ones.
Following our previous studies of charged test particles and uncharged perfect
fluid tori encircling compact objects, we introduce here a simple test model of
a charged perfect fluid torus in strong gravitational and electromagnetic
fields. In contrast to ideal magnetohydrodynamic models, we consider here the
opposite limit of negligible conductivity, where the charges are tied
completely to the moving matter. This is an extreme limiting case which can
provide a useful reference against which to compare subsequent more complicated
astrophysically-motivated calculations. To clearly demonstrate the features of
our model, we construct three-dimensional axisymmetric charged toroidal
configurations around Reissner-Nordstr\"om black holes and compare them with
equivalent configurations of electrically neutral tori.Comment: 14 pages, 7 figure
Varying the flexibility of the aromatic backbone in half sandwich rhodium(III) dithiolato complexes : a synthetic, spectroscopic and structural investigation
A series of rhodium(III) half sandwich complexes of the type [Cp*Rh(PMe3)(S—R—S)]; S—R—S = naphthalene-1,8-dithiolate, acenaphthene-5,6-dithiolate, [1,1′-biphenyl]-2,2′-dithiolate and [2,2′-binaphthalene]-1,1′-dithiolate are reported. In the case of [2,2′-binaphthalene]-1,1′-dithiolate this represents an infrequent example of a metal complex containing this ligand. All the complexes have been fully characterised using multinuclear NMR spectroscopy and single crystal X-ray diffraction. The single crystal X-ray structure of the starting material [Cp*Rh(PMe3)Br2] ( 1 ) is also reported for the first time.Publisher PDFPeer reviewe
Single crystal X-ray structural features of aromatic compounds having a pentafluorosulfuranyl (SF5) functional group
The authors are grateful to the University of St Andrews for financial support.Nine pentafluorosulfuranyl (SF5)-containing aromatic compounds have been characterized crystallographically. The SF5 group has an umbrella geometry, and the sulfur atom in the SF5 group is in an approximately octahedral coordination environment. All S-F bond lengths [1.572(3) to 1.618(3) Å] are very similar and the C-S-Fax bond angles [178.94(14) to 180°] are very close to each other. The angle of two adjacent Feq is approximate to 90°. The intramolecular and intermolecular interactions such as Caryl-H···Feq, Caryl-H···O/N/F/Cl interactions, and π-stacking interactions play a very important role in their three-dimension packing frameworks.PostprintPostprintPeer reviewe
Equatorial circular orbits in the Kerr-de Sitter spacetimes
Equatorial motion of test particles in the Kerr-de Sitter spacetimes is
considered. Circular orbits are determined, their properties are discussed for
both the black-hole and naked-singularity spacetimes, and their relevance for
thin accretion discs is established.Comment: 24 pages, 19 figures, REVTeX
Sterically restricted tin phosphines, stabilized by weak intramolecular donor-acceptor interactions
Funding: Engineering and Physical Sciences Research Council (EPSRC)Four related sterically restricted pen-substituted acenaphthenes have been prepared containing mixed tin phosphorus moieties in the proximal 5,6-positions (Acenap[SnR3][(PPr2)-Pr-i]; Acenap = acenaphthene-5,6-diyl; R-3 = Ph-3 (1), Ph2Cl (2), Me2Cl (3), Bu2Cl (4)). The degree of intramolecular P-Sn bonding within the series was investigated by X-ray crystallography, solution and solid-state NMR spectroscopy, and density functional theory (DFT/B3LYP/SBKJC/PCM) calculations. All members of the series adopt a conformation such that the phosphorus lone pair is located directly opposite the tin center, promoting an intramolecular donor acceptor P -> Sn type interaction. The extent of covalent bonding between Sn and P is found to be much greater in triorganotin chlorides 2-4 in comparison with the triphenyl derivative 1. Coordination of a highly electronegative chlorine atom naturally increases the Lewis acidity of the tin center, enhancing the Ip(P)-sigma*(Sn-Y) donor acceptor 3c-4e type interaction, as indicated by conspicuously short Sn-P peri distances and significant (1)J(P-31,Sn-119) spin spin coupling constants (SSCCs) in the range 740-754 Hz. Evidence supporting the presence of this interaction was also found in solid-state NMR spectra of some of the compounds which exhibit an indirect spin spin coupling on the same order of magnitude as observed in solution. DFT calculations confirm the increased covalent bonding between P and Sn in 2-4, with notable WBIs of ca. 0.35 obtained, in comparison to 0.1 in 1.PostprintPeer reviewe
On the ground state energy scaling in quasi-rung-dimerized spin ladders
On the basis of periodic boundary conditions we study perturbatively a large
N asymptotics (N is the number of rungs) for the ground state energy density
and gas parameter of a spin ladder with slightly destroyed rung-dimerization.
Exactly rung-dimerized spin ladder is treated as the reference model. Explicit
perturbative formulas are obtained for three special classes of spin ladders.Comment: 4 page
Constrained phosphine chalcogenide selenoethers supported by peri-substitution
A series of phosphorus and selenium peri-substituted acenaphthene species with the phosphino group oxidized by O, S, and Se has been isolated and fully characterized, including by single-crystal X-ray diffraction. The P(V) and Se(II) systems showed fluxional behavior in solution due to the presence of two major rotamers, as evidenced with solution NMR spectroscopy. Using Variable-Temperature NMR (VT NMR) and supported by DFT (Density Functional Theory) calculations and solid-state NMR, the major rotamers in the solid and in solution were identified. All compounds showed a loss of the through-space JPSe coupling observed in the unoxidized P(III) and Se(II) systems due to the sequestration of the lone pair of the phosphine, which has been previously identified as the major contributor to the coupling pathway.Publisher PDFPeer reviewe
(Decacarbonyl)(1-isopropyl-2-phenyl-1,2,5,6-tetrahydroacenaphtho [5,6-cd][1,2]diphosphole)ditungsten(0) : Molbank
A binuclear tungsten(0) complex with an asymmetric bridging 1,2-diphosphole ligand was prepared by the photolysis of tungsten hexacarbonyl in the presence of 1-isopropyl-2-phenyl-1,2,5,6-tetrahydroacenaphtho [5,6-cd][1,2]diphosphole. The tungsten complex 1 was characterized by high resolution mass spectrometry, multinuclear NMR spectroscopy (1H, 13C, 31P), and elemental microanalysis. The structure of the trans isomer was resolved by single crystal X-ray diffraction, showing a slight elongation of the P−P bond upon coordination to the W(CO)5 groups.Publisher PDFPeer reviewe
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