Papers by Author: A. van Riessen

Abstract: Foaming methods to reduce the density of geopolymers were investigated as low density geopolymers are increasingly being reported in the literature to be effective in improving the insulating properties. However, there is no consistency in foaming methods and as such this study was performed to compare different foaming agents in order to better understand their effect on the properties of geopolymers. In particular, a surfactant and hydrogen peroxide were used individually and in combination to ensure a homogeneous pore distribution in the slurry. Physical and microstructural properties of the hardened low density geopolymers are presented and discussed. The behaviour under fire conditions of fibre reinforced and foamed geopolymer samples will also be presented in order to appreciate the suitability of geopolymer composite in high temperature applications.

Abstract: This paper reports development of a production method to produce a composite material that is biocompatible, with high mechanical strength and resilience. The chemical precipitation conditions necessary for the production of synthetic hydroxyapatite (HAp) were determined and include pH, temperature and rate of reaction. A gas phase purification method was optimised to remove the soot impurity from the nanotubes, with transmission electron microscopy showing the preservation of the carbon nanotubes. Subsequent development of chemical and physical reinforcement techniques to produce a HAp + carbon nanotube composite material have been trialled. Hot isostatically pressed samples showed excellent densification and strength.

Abstract: This paper reports neutron diffraction data and its analysis that characterise a biocompatible hydroxyapatite composite material. The neutron data has elucidated the crystal structure, and enabled the positions of the hydrogen atoms to be determined. The data also shows the improvement of crystallinity during the heat treatment process. An extension of the work involved looking at a hydroxyapatite – carbon nanotube composite material, and neutron diffraction has shown that the retention of the carbon nanotubes in the composite material has been successful. The nanotubes have had no affect on the hydroxyapatite structure.