Synthesis of nature-inspired graded Li2Si2O5 crystalline architectures as dental CAD/CAM glass-ceramics

• Applicant: Dr. Julia Lubauer
• Subject Area: Glass, Ceramics and Derived Composites ; Dentistry, Oral Surgery
• Term: since 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 546265228

Here we seize on gained knowledge on mechanical principals governing the structure-property relationship in biological structural materials, e.g. hierarchical arrangement, high aspect-ratio of microstructural elements, local and bulk microstructural alignment, gradient orientation, etc., to apply on the conceptualization of partially crystallized glasses with more nature-like structures aiming for corresponding mechanical improvements. This project will focus on the synthesis and processing parameters of lithium disilicate glasses that show a gradient crystallinity for application in CAD/CAM machining. Specifically, we will concentrate on tailoring the crystallization stage so to induce a thermal gradient in the glass monolith. For that, we will focus on two strategies: Thermal Insulation (TI) and Electric Field (EF) -assisted crystallization. We will work on developing a process for thermal insulating the glass using low thermal diffusivity templates during the nucleation/crystallization heat-treatments, thus controlling the density of nuclei formation and crystal growth in respect to the direction of thermal gradient. For that, several materials and geometrical iterations of insulating ceramic templates will be investigated in order to generate different thermal gradient in the pre-casted glass. Likewise, the parameters of the second annealing heat-treatment for crystal growth will be evaluated to determine the most effective program to induce the most mechanically promising crystal size/aspect ratio and interlocking. Parallel to that, we will develop the novel Electric Field-assisted crystallization process so to attain a gradient thermal gradient within our samples. Both strategies will be guided by feedback from Finite Element simulations. The resulting material is aimed to present a double gradient of phase-separated glass transitioning into a gradient crystallized glass-ceramic. Promising samples from successful synthesis/fabrication protocols will be fully characterized in terms of microstructure, phase content and mechanical properties. Key mechanical behaviors such as gradient strength, fracture toughness and R-curve behavior will be used to demonstrate the success in creating a gradient architecture.

• DFG Programme: Research Grants
• International Connection: Brazil
• Co-Investigators: Privatdozent Renan Belli, Ph.D.; Professorin Kerstin Galler, Ph.D.; Professor Dr.-Ing. Ulrich Lohbauer
• Cooperation Partner: Dr. João Vitor Campos