Neutron Diffraction and Raman Studies of the Incorporation of Sulfate in Silicate Glasses.

The oxidation state, coordination, and local environment of sulfur in alkali silicate (RO-SiO; R = Na, Li) and alkali/alkaline-earth silicate (NaO-MO-SiO; M = Ca, Ba) glasses have been investigated using neutron diffraction and Raman spectroscopy. With analyses of both the individual total neutron correlation functions and suitable doped-undoped differences, the S-O bonds and (O-O) correlations were clearly isolated from the other overlapping correlations due to Si-O and (O-O) distances in the SiO tetrahedra and the modifier-oxygen (R-O and M-O) distances. Clear evidence was obtained that the sulfur is present as SO groups, confirmed by the observation in the Raman spectra of the symmetric S-O stretch mode of SO groups.

In vitro cellular testing of strontium/calcium substituted phosphate glass discs and microspheres shows potential for bone regeneration.

Phosphate-based glasses (PBGs) are ideal materials for regenerative medicine strategies because their composition, degradation rates, and ion release profiles can easily be controlled. Strontium has previously been found to simultaneously affect bone resorption and deposition. Therefore, by combining the inherent properties of resorbable PBG and therapeutic activity of strontium, these glasses could be used as a delivery device of therapeutic factors for the treatment of orthopaedic diseases such as osteoporosis.

Multicomposition EPSR: Toward Transferable Potentials To Model Chalcogenide Glass Structures.

The structure of xAsSe-(1 - x)AsS glasses, where x = 1.000, 0.667, 0.

Correlating structure with non-linear optical properties in xAs40Se60·(1-x)As40S60 glasses.

A series of xAs40Se60·(100 - x)As40S60 glasses, where x = 0, 25, 33, 50, 67, 75 and 100 mol% As40Se60, has been studied using neutron and X-ray total scattering, Raman spectroscopy and (77)Se MAS-NMR. The results are presented with measurements of non-linear refractive indices, n2, and densities. There is no evidence for the formation of homopolar bonds in these glasses, but neutron correlation functions suggest that there is a non-random distribution of sulfur and selenium atoms in sulfur-rich glasses.

Local and average structure in zinc cyanide: toward an understanding of the atomistic origin of negative thermal expansion.

Neutron diffraction at 11.4 and 295 K and solid-state (67)Zn NMR are used to determine both the local and the average structures in the disordered, negative thermal expansion (NTE) material, Zn(CN)2. Solid-state NMR not only confirms that there is head-to-tail disorder of the C≡N groups present in the solid, but yields information about the relative abundances of the different Zn(CN)4–n(NC)n tetrahedral species, which do not follow a simple binomial distribution.

Characterisation of phosphate coacervates for potential biomedical applications.

In this study, amorphous (Na2O)x(CaO)0.50- x(P2O5)0.50·yH2O (where x = ~0.

Structures of uncharacterised polymorphs of gallium oxide from total neutron diffraction.

A structural investigation is reported of polymorphs of Ga(2)O(3) that, despite much interest in their properties, have hitherto remained uncharacterised due to structural disorder. The most crystalline sample yet reported of γ-Ga(2)O(3) was prepared by solvothermal oxidation of gallium metal in ethanolamine. Structure refinement using the Rietveld method reveals γ-Ga(2)O(3) has a defect Fd3m spinel structure, while pair distribution function analysis shows that the short-range structure is better modelled with local F43m symmetry.

A structural investigation of the alkali metal site distribution within bioactive glass using neutron diffraction and multinuclear solid state NMR.

The atomic-scale structure of Bioglass and the effect of substituting lithium for sodium within these glasses have been investigated using neutron diffraction and solid state magic angle spinning (MAS) NMR. Applying an effective isomorphic substitution difference function to the neutron diffraction data has enabled the Na-O and Li-O nearest-neighbour correlations to be isolated from the overlapping Ca-O, O-(P)-O and O-(Si)-O correlations. These results reveal that Na and Li behave in a similar manner within the glassy matrix and do not disrupt the short range order of the network former.

Structure and properties of an amorphous metal-organic framework.

ZIF-4, a metal-organic framework (MOF) with a zeolitic structure, undergoes a crystal-amorphous transition on heating to 300 degrees C. The amorphous form, which we term a-ZIF, is recoverable to ambient conditions or may be converted to a dense crystalline phase of the same composition by heating to 400 degrees C. Neutron and x-ray total scattering data collected during the amorphization process are used as a basis for reverse Monte Carlo refinement of an atomistic model of the structure of a-ZIF.