Chapter 5. Charge densities from X-ray diffraction data
M. A. Spackman, Annu. Rep. Prog. Chem., Sect. C: Phys. Chem., 1998, 94, 177 DOI: 10.1039/PC094177
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Ecology of siliceous sponges - Application to the environmental interpretation of the Upper Jurassic sponge facies (Oxfodian) from Spain.
the major factors controtling [he morphological and taxonomie composition of siliceous sponge faunas are sedimentation rate and nutrient supply. In seawater bacteria are most abundant in the upper par[ of [he water column. Towards greater depths bacteria disappear gradually. The bathymetric distribution of filter-feed…
Atomistic simulation of the effects of calcium and strontium defects on the surface structure and stability of BaSO4
BaSO4 (baryte), SrSO4 (celestine) and CaSO4 (anhydrite) were studied using atomistic simulation techniques and their equilibrium morphologies determined from the calculated surface energies. Monolayer and bilayer growth of strontium sulfate or calcium sulfate on barium sulfate were modelled and the calculated surface…
The crosslinking mechanism in gamma irradiation of polyarylsulfone: evidence for Y-links
Measurements of molecular weights, soluble fractions and examination of NMR spectra of bisphenol-A polysulfone, after gamma irradiation in vacuum at 150°C were used to elucidate the mechanism of crosslinking. Excellent agreement was obtained between G(S) and G(X) determined from measurements above and below the gel do…
Porous Silicon Physics and Device Applications: A Status Report
Silicon, an indirect gap semiconductor, can emit light with 10% efficiency at room temperature, provided that it is in the form of low-dimensional (quantum dots or wires) nanostructures. Porous silicon is the best known example of such nanostructures. The luminescence mechanisms and the relationship between bandgap en…
Crystal structures of di-tin-hexa(seleno)hypodiphosphate, Sn2P2Se6, in the ferroelectric and paraelectric phase
Abstract The crystal and molecular structure of Sn 2 P 2 Se 6 in the low temperature ferroelectric phase is determined by single crystal X-ray diffraction techniques. These results are compared with the crystal structure of the same compound in the paraelectric phase, which was redetermined at room temperature. In bot…
Characterization of Ni/TiO2 catalysts prepared by successive adsorption–reduction of Ni2+ ions
Three Ni/TiO2 samples have been synthesized by impregnation (sample Ni-i-Ti), adsorption of Ni2+ ions from alkaline media on TiO2 (sample Ni-1-Ti) and on reduced Ni-1-Ti (sample Ni-2-Ti). The samples have been characterized by TPR, IR spectroscopy of adsorbed CO and X-ray diffraction. Impregnation leads to a less homo…
Recognition of 1,2-diazines by a bidentate Lewis acid
Dimeric ortho-phenyleneindium bromide 1 shows a higher affinity for 1,2-diazines than for 1,3- and 1,4-diazines; as shown by the X-ray crystal structure analysis of the host–guest complex 3 the observed selectivity results from subtle structural variation which can bring the indium p orbitals to converge.
Universality and its origins at the amorphous solidification transition
Systems undergoing an equilibrium phase transition from a liquid state to an amorphous solid state exhibit certain universal characteristics. Chief among these are the fraction of particles that are randomly localized and the scaling functions that describe the order parameter and (equivalently) the statistical distri…
Synthesis, X-ray crystal structure and spectroscopic characterization of the new dithiolene [Pd(Et2timdt)2] and of its adduct with molecular diiodine [Pd(Et2timdt)2]·I2·CHCl3 (Et2timdt = monoanion of 1,3-diethylimidazolidine-2,4,5-trithione)
The first Pd dithiolene [Pd(Et2timdt)2] 4a belonging to the new class of metal dithiolenes deriving from the R12timdt (R12timdt = monoanion of 1,3-dialkylimidazolidine-2,4,5-trithione) ligand has been characterised by X-ray crystal structure determination on a single crystal [monoclinic, space group P21/n, a = 9.545(2…
Effects of Hydrogen Peroxide on Intergranular Stress Corrosion Cracking of Stainless Steel in High Temperature Water, (I) Effects of Hydrogen Peroxide on Electrochemical Corrosion Potential of Stainless Steel.
In order to determine effects of hydrogen peroxide on stress corrosion cracking of structural materials in the primary cooling systems of boiling water reactors, a high temperature high pressure water loop with controlled hydrogen peroxide concentrations and lower possible oxygen concentrations has been fabricated. Te…
Developments in Marine Corrosion
The diversity of subjects involved in marine corrosion and fouling processes are evident in the approaches and techniques described in this book. An improvized understanding of biologically influenced corrosion and fouling processes is essential to the development of better corrosion protection systems, and this book…
Space charge formation in water-treed insulation
Observations of the space charge distribution around water trees are reviewed, and the nature of water trees analyzed from those results is discussed. It was concluded that at least two mechanisms are responsible for the formation of space charges. One is interfacial polarization due to the high conductivity of a tree…
Stoichiometry control of SiOC ceramics by siloxane polymer functionality
The guidelines, or empirical rules, previously described in the literature to estimate ceramic compositions from preceramic polymer compositions have been refined and quantified. Thermogravimetric and residual gas analyses of the pyrolysis of organosilsesquioxane polymers have identified the organic degradation produc…
Oxygen Position and Bond Lengths from Lattice Parameters in Tetragonal Zirconias
A survey of the available data on the oxygen positions in various tetragonal zirconias reveals a simple, approximate relationship between the departure of the oxygen from the position it would have in the ideal fluorite structure, and the tetragonality ( c/a ) of the material. This relationship can be understood on th…
Phase Behavior of Polystyrene/Polybutadiene and Polystyrene/Hydrogenated Polybutadiene Mixtures: Effect of the Microstructure of Polybutadiene
The effect of the microstructure on the phase behavior of mixtures of polybutadiene (PB) and poly(ethylene- co -1-butene) (PEB) with polystyrene (PS) has been investigated. A series of PBs with 1,2-addition content ranging from 7 to 93% were synthesized by anionic polymerization, and a portion of each was subsequently…
Thermotropic properties of monosubstituted ferrocene derivatives bearing bidentateN-benzoyl-N′-arylthiourea ligands—novel building blocks for heterometallic liquid crystal systems
Ferrocene-based derivatives such as 4-{3-[4-(octyloxy)benzoyl]thioureido}phenyl 4-ferrocenylbenzoate and other higher homologues (n=12,16 and 18; n=length of alkoxy chain) were prepared by reacting 4-alkoxybenzoyl isothiocyanates with the corresponding amines containing the ferrocenyl moiety. Their mesomorphic propert…
RISULTATI DI MISURE DI STANDARD DI MINERALI E DI VETRI NATURALI IN MICROANALISI A DISPERSIONE DI ENERGIA
EDS analysis on standard samples of minerals and glasses. In this paper is reported the setting up of a EDS microanalitic system present at the laboratory of elec tron microscopy and microanalysis at the Dipartimento di Scienze della Terra of Pisa University. Pure element inten sity factors for the standardless softwa…
Contrast mechanism of negatively charged insulators in scanning electron microscope
The main features of negatively charged images are: bright regions are always accompanied by a dark region, which corresponds to the region above connecting lines in LSI, and dark regions seem to encroach the bright region. These features are explained by a new model, which contains redistribution and multiplication o…
Phosphaniminato-Komplexe Seltener Erden. Synthese und Kristallstrukturen von [M2(C5H5)3(NPPh3)3] · 3 C7H8 mit M = Y, Dy und Er. Magnetische Eigenschaften von [Dy2(C5H5)3(NPPh3)3] · 3 C7H8
Die Titelverbindungen werden durch Reaktion der Cyclopentadienidchloride [M(C5H5)2Cl]2 mit LiNPPh3 in siedendem Toluol hergestellt und durch Kristallstrukturanalysen charakterisiert. Alle drei Verbindungen kristallisieren isotyp miteinander in der orthorhombischen Raumgruppe Pbca mit Z = 8. Zwei der drei Phosphanimina…