Glass - Back to the Future!

Presenting Author:
Jamila Almuhamadi

article posted 21 March 2016

Jamila Almuhamadi gained her BSc degree in dental technology in 2005 from the school of dentistry, University of Zawia, Libya and then worked as a lecturer assistant in the department of prosthodontics from 2006-2008. In September 2010, she obtained her MSc degree in dental technology from Barts and the London School of Dentistry, Queen Mary University.

In September 2015, she was awarded a PhD degree in dental bioceramics from QMUL. Her PhD project focused on the development of novel glasses and glass-ceramics based on diopside solid solutions and the characterisation of their physical-mechanical, structural and microstructural properties. The intention was to produce high strength diopside glass-ceramics suitable for restorative dentistry.

She then worked for six months as a postdoctoral researcher on the characterisation of novel leucite glass-ceramics for dental applications and the work was funded by Schottlander dental company.

Investigations into the structure–property relationships
in CaMgSi2O6–NaAlSi2O6 glasses

Jamila Almuhamadi*, Natalia Karpukhina & Mike Cattell
Queen Mary University of London

Aluminosilicate glasses often have unique chemical and physical properties. The interpretation of such properties requires an understanding of the structural behaviour in glasses, which vary as a function of their initial chemical compositions. In this paper, a series of glass compositions based on the pseudobinary system of CaMgSi2O6–NaAlSi2O6 with increasing Na2O and Al2O3 content were studied. Glasses were synthesised via a melt-quench route, ground and re-melted to ensure homogeneity.

Glasses were processed into powders with different particles size and characterised using X-ray diffraction, dilatometry and solid state-NMR. The crystallisation mechanism and its kinetics for the glasses were studied using differential scanning calorimetry (DSC). The density of the glasses was measured using Archimede’s principle and their oxygen densities were calculated from the bulk density values. The refractive index of glasses was measured using the Becke line method.

Both XRD and NMR results confirmed the amorphous nature of the glasses. The initial diopside based glass gave a higher glass transition of 720°C than all other formulations. As a result of increasing Na+/Al3+ substitution, a drop in the glass transition and dilatometric softening temperatures and an increase in the crystallisation temperatures were seen across the series.

The thermal expansion coefficient was in a range of (8.11-8.36×10-6/K, 100-400°C). The glass/oxygen densities and the refractive indices of the glasses were found to decrease linearly with increasing Na2O and Al2O3. The studied glasses showed signs of both surface and bulk crystallisation mechanism. A reduction in the activation energies of the glasses was found at a higher substitution.