Essential material properties of bioactive silicate glasses and the implementation of topographical features

Pföss, Barbara Sophie; Conradt, Reinhard (Thesis advisor); Boccaccini, Aldo R. (Thesis advisor); Roos, Christian Hans-Georg (Thesis advisor)

Aachen (2019)
Dissertation / PhD Thesis

Dissertation, Rheinisch-Westfälische Technische Hochschule Aachen, 2019

Abstract

A phase theoretical approach forms the basis for a thermodynamic description of bioactive glasses. Both the dissolution behavior and crystallization characteristics are discussed in detail as fundamental material properties with the intention to join theoretical concepts with experimental results. To describe the dissolution of bioactive glasses, the Gibbs energy of hydration is calculated and linked with kinetic models, taking notice of equilibrium conditions as well as reaction rates. Diffusion coefficients of alkali and alkaline earth elements leaching from the glass and the reaction rate of network dissolution are determined experimentally. Tammann-curves are calculated, modeling the nucleation rate and crystal growth velocity of individual phases from a multi component glass and by using this infor- mation, TTT-curves for each single phase are obtained. The calculations are set in context and agree with experimental data from thermal analysis, X-ray diffraction and microscopy. Besides the characterization of essential material properties, the implementation of a cast surface topography is a further objective. A mold with 15 μm deep grooves is filled with glass melt to successfully mirror the surface features to the glass surface. During form filling the interaction of parameters such as wetting, mainly determined by the mold material, and the viscosity of the melt regulate to what extend a topography can be mimicked from one surface to another.

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