Patterns of chaos: fractal statistics and the oscillatory chemistry of zircon

The compositional dependence of the first sharp diffraction peaks (FSDPs) of lithium, sodium and potassium silicate glasses were studied by calculating the neutron static structure factors. The advantage of using molecular dynamics simulations is that the contributions of partial structure factors to the FSDPs can be easily determined and provides the basis for detailed analysis. Examination of the correlations of the FSDP with the short and medium range structure reveal that the position and the shape of FSDP strongly depend on the type and concentration of alkali oxide in alkali silicate glasses. The characteristic repeating distances and the characteristic correlation lengths both decrease with increasing alkali oxide concentration indicating a decrease in the intermediate range order. In the lithium silicate glasses, the characteristic correlation length increases with lithium oxide concentration that is anomalous in that the trend is opposite to the other alkali silicate glasses. This anomaly is explained by the high field strength of lithium ions that increases the intermediate range order of the silicon oxygen network.

Compositional dependence of the first sharp diffraction peaks in alkali silicate glasses: A molecular dynamics study

An exhaustive review of compositional and thermal extents of miscibility gaps in 41 binary silicate systems permits identification of three groups of cations exhibiting different immiscibility behaviours. The first group comprises network-modifier cations with an ionic radius larger than about 87.2 pm. They have coordination numbers equal to, or higher than, 5 and their miscibility gap size increases linearly with increasing ionic potential. The second group involves cations with an ionic radius larger than 26 pm and smaller than about 87.2 pm (in octahedral coordination). They have at least two coordination numbers: the first one is always 4 and the other 5 (or more). For this reason they are called amphoteric. Their miscibility gap sizes do not increase linearly with an increase of the ionic potential, but follow curves. The third group includes cations with variable crystal field stabilization energies. They are characterized by larger miscibility gap sizes than expected when they are compared with cations with similar ionic radii despite the fact that some of them (e.g. Cr3+) may behave as an amphoteric element because their ionic radii in octahedral coordination are smaller than about 87.2 pm. The origin of phase separation in binary silicate systems is due to coulombic repulsions between poorly screened cations bounded by bridging oxygen strongly polarized towards the silicon, and by non-bridging oxygen.

The nature of phase separation in binary oxide melts and glasses. I. Silicate systems

Strontium substitution has been found to have a beneficial effect on tissue growth in traditional bioglasses. In this paper, we have studied the effect of SrO/CaO substitution on the structure of 4...

Effect of Strontium Substitution on the Structure of 45S5 Bioglasses

A study of the interaction of strontium ions in aqueous solution with the surfaces of calcite and kaolinite

The invention concerns reinforcing glass fibres whereof the composition comprises the following constituents, within the limits defined as follows expressed in weight percentages: 58 to 62 % SiO2, 10 to 16 % Al2O3, more than 18 % CaO, more than 1.5 % MgO, less than 28 % CaO + MgO, less than 2 % Na2O + K2O + Li2O, less than 1.5 % TiO2, less than 0.5 % Fe2O3, less than 2 % B2O3, less than 2 % F2; said composition further comprising 1 % of other constituent(s) and comprising more than 0.5 % of at least three F2, B2O3, Li2O constituents. Said glass fibres have a composition providing excellent compromise between its cost and its fibre drawing capability.

Glass yarn for reinforcing organic and/ or inorganic materials

Medium range order around cations in silicate glasses

The environment around Sr in silicate and aluminosilicate glass has been studied by neutron and anomalous x-ray diffraction and reverse Monte Carlo modeling. The first Sr-O distances are smaller in the silicate glass than in the aluminosilicate glass, which can be related to the different structural role of the element in the glass structure. We found Sr-Sr distances at about 4 and 7 \AA{} in both glasses, which implies a nonhomogeneous spatial distribution.

Environment around strontium in silicate and aluminosilicate glasses

Anomalous wide angle X-ray scattering (AWAXS) is used to investigate the short and medium range order in Sr silicate and Sr aluminosilicate glasses. Strong SrSr correlations at 4 A are found in the silicate glass, whereas they are much weaker in the presence of aluminium. The first SrO distance and coordination number and further SrSr distances in the silicate glass are consistent with edge sharing octahedra. The SrAl correlations cannot be exactly determined, but the role of charge compensator imposed on the Sr by tetrahedral Al3+ rapidly reduces the order found in the silicate glass.

Anomalous wide angle X-ray scattering study of strontium silicate and aluminosilicate glasses

Neutron scattering data have been obtained for a strontium- and a barium-containing silicate glass and a strontium aluminosilicate glass. These data are compared with previously published anomalous wide-angle X-ray scattering data for the Sr-containing glasses. Features in the diffraction data at the smaller scattering vectors, Q , are compared with simulated X-ray and neutron diffraction patterns for compositionally similar crystals. Peaks are found at Q s close to the `first sharp diffraction peaks' of the glasses and have a cation–cation dependence. We suggest that this correspondence shows that the smaller Q features in the glasses have similar structural origins to those in the scattering data for the crystals with the same composition and therefore that the medium-range structures and cation–cation arrangements in the glasses are similar too.

Sophie Creux

Papers

Glass yarn for reinforcing organic and/ or inorganic materials

Medium range order around cations in silicate glasses

Environment around strontium in silicate and aluminosilicate glasses

Anomalous wide angle X-ray scattering study of strontium silicate and aluminosilicate glasses

Comparison of the low-Q features in diffraction data for silicate glasses and crystals containing Sr or Ba