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The aim of this work was to synthesise novel strontium containing glass-ceramics based on the apatite-wollastonite system. Parent glasses were formed via the melt quench route with strontium being substituted for calcium according to: 35.4SiO2•7.1P2O5•0.4CaF2•7.1MgO• (49.9-X)CaO•XSrO, where X = 6.2, 12.5, 18.7 or 24.9. Glass frits were ground and sieved and size distribution shown to be constant. Successful substitution of strontium into the parent glass was confirmed with energy dispersive x-ray (EDX) analysis, x-ray diffraction (XRD) and density measurements Glass rods were successfully cast for all the compositions tested. The x-ray attenuation of the material increased with increasing strontium substitution in line with theoretical values. Differential scanning calorimetry (DSC) revealed two major exotherms, TP1 and TP2. TP1 moved to lower temperatures with increasing strontium substitution while TP2 moved to higher temperatures. XRD and Rietveld refinement identified TP1 as corresponding to fluorapatite and TP2 as to wollastonite, both phases took in strontium following substitution. Pseudowollastonite formed at higher strontium contents. The weight percentage of wollastonite decreased with increasing strontium substitution. Scanning electron microscopy (SEM) and EDX revealed the bulk morphology and composition of the material’s phases. Porous scaffolds were formed by sintering the parent glasses in carbon moulds. Increasing strontium substitution shifted sintering from a solid state mechanism towards liquid phase resulting in a loss of porosity. In all but the highest substitution, the flexural strength decreased with increasing strontium. Simulated body fluid (SBF) testing indicated an increase in solution pH with increasing strontium substitution and a shift in the ability of the material to form a surface apatite layer. Human bone mesenchymal stem cells (hMSCs) were able to attach, expand and differentiate on the materials. Strontium doping was shown to significantly affect the osteogenic capacity of apatite-wollastonite glass-ceramic.

Grain growth has been investigated in high purity uranium dioxide and in uranium dioxide containing a number of additives. High purity UO[2]F[2] powder was chosen as the source material for the fine UO[2] powder needed to produce the specimens for this work. Ammonium diuranate was precipitated from a solution of UO[2]F[2] using ammonia. Using a solution coating technique, quantities of ammonium diuranate were doped with various additives: Cr, Ni, La, Mo, and Al. The ADU was reduced to UO[2] by heating for two hours in dry hydrogen at 500°C. The resulting powder had a surface area of 18-20 m[2]/g. The UO[2] powder was cold pressed into pellets weighing 0.5g each and these were sintered at 1400°C in wet hydrogen. The water content of the hydrogen was not sufficient to cause deviation from stoichiometry. Completely pore free specimens were obtained. The surfaces of the specimens were then ground and polished flat suitable for microscopic examination because thermal etching was relied on to reveal grain boundaries. Grain growth experiments were performed at temperatures between 1400 and 1800°C, the majority however, were at 1500, 1600 or 1700°C. A multianneal technique on two specimens provided all the data for each experiment. Grain size measurements were made on photomicrographs of the specimen surfaces. Spectrographic analysis was carried out on the specimens at the end of the runs. These revealed that excessive evaporation of the dopant compounds had occurred in most cases resulting in lower dopant concentrations than were intended and also in contamination of each batch of UO[2] with dopants used for the previous experiments. The experimental results showed that the behaviour of the undoped UO[2] was controlled by the residual impurities of which iron and silicon were the most abundant. The molybdenum doped material showed results typical of a material containing inert second phase particles. The lanthanum doped materials behaviour indicated that solute drag was occurring. The activation energy for grain growth in this material was 40 kcal/mole. The Cr, Ni, and Al doped specimens all showed different grain growth exponents at different temperatures indicating that the rate controlling process changed with temperature. Exaggerated grain growth occurred in Cr and La doped specimens. It was concluded that impurity effects on grain growth are dependent on the concentration, the mobility and the energy of interaction of the impurity with the grain boundaries.

This study established the fundamental relationships between slag chemistry and reaction kinetics of sodium carbonate-activated slag. The application of the smart chemical addition CLDH for sodium carbonate-activated slag based on the understanding of slag chemistry, has not only made the sodium carbonate activator a plausible option for implementation, but more of a better option with performance advantages. The knowledge developed in this study about the ionic interaction between chlorides and individual reaction product filled in gaps in literature, and becomes a useful tool whose usage is not limited to tailing of sodium carbonate-activated slag, but also for optimising mix design of all types of AAS for achieving better performance.