研究目的
Investigating the interaction between glass and ceramic phases with a running crack and the mechanisms by which propagation is hindered or altered in lithium disilicate glass-ceramics.
研究成果
Cracks propagate in glass-ceramics in a dramatically different manner as compared to the precursor parent glass. In glassy samples, clean crack branching seems to be triggered by multiple cavitation events ahead of the crack tip, while in glass-ceramics counterpart crack propagates by microcracks at multiple glass-nanocrystal interface sites, clean nanocrystal cleavage along certain crystalline plane, and even secondary cracks due to the percolation of multiple microcracks. All these additional crack characteristics facilitate energy dissipation during crack propagation, which makes glass-ceramics generally tougher than glasses.
研究不足
The microstructure of generated glass-ceramics samples is falling short of capturing real experimental ones due to the various limitations in atomistic simulations. Additionally, the algorithm for inserting nanocrystals is technically extremely challenging to make samples with very high nanocrystal volume fraction given the current simulation setting.
1：Experimental Design and Method Selection:
Molecular dynamics simulations were conducted to study crack propagation in lithium disilicate glass-ceramics. The simulations focused on samples with various distributions and configurations of LS2 nanocrystals.
2：Sample Selection and Data Sources:
Glass-ceramics samples were prepared by supercooled liquid quenching to form as-melt glass, substituting certain glass regions with pre-made crystalline nanocrystals, and healing the interface by heating up the sample to elevated temperature and cooling down again.
3：List of Experimental Equipment and Materials:
LAMMPS was used for all simulations with a timestep of 2 fs. OVITO was used to visualize simulation results and conduct atomic shear strain analysis. Pedone force field was used to capture short-range interactions for both lithium disilicate crystal and glass.
4：Experimental Procedures and Operational Workflow:
Crack propagation was achieved by loading the sample in the x direction with an engineering strain rate of 0.2 ns-1 while fixing the dimension in the y direction.
5：2 ns-1 while fixing the dimension in the y direction.
Data Analysis Methods:
5. Data Analysis Methods: Atomic shear strain analysis was conducted to study the deformation maps for glass and glass-ceramics samples.
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