Molecular dynamics investigation of the fracture mechanism of a glass‐ceramic containing cleavable crystals

Abstract

In this study on a novel glass‐ceramic containing hexagonal CaAl2Si2O8 crystals embedded in a SiO2–Al2O3–CaO glass, we used molecular dynamics simulations to unravel the toughening mechanism of the partially crystallized composite material. The crystalline phase is composed of alternate layers of SiO4/AlO4 tetrahedra and calcium ions. After careful modeling of crystals embedded in the glass matrix, we conducted crack propagation simulations using single‐notched models. We found that: (a) when a crack propagates parallel to the cleavable calcium layer, the glass‐ceramic breaks in a brittle way since the crack passes through the fragile interlayer promptly, (b) the stiffer SiO4/AlO4 oxide layer can inhibit crack propagation, and the crack is thus deflected to the interface between the crystal and the glass matrix; and (c) a calcium layer present between the glass matrix and the edge of the CaAl2Si2O8 crystal is more fragile than those inside the crystal, indicating that cracks prefer to travel along the glass‐crystal interface. These theoretical simulations successfully demonstrated that the anisotropy and the fragile feature of the crystals lead to microcrack toughening of the glass‐ceramic. In addition, we discuss deformation anisotropy in the microscale by constructing a larger model that includes randomly orientated multiple CaAl2Si2O8 crystals.

Higher Toughness of Metal-nanoparticle-implanted Sodalime Silicate Glass with Increased Ductility

“…Because the modulus of metal is larger than that of glass matrix, the resultant SLG with lower modulus with larger deformation should be attributed to ductility due to metal particles which takes place when the load exceeds the yield strength. This toughening mechanism is distinguishable to the other hybrid glass system such as glass with phase-separation, and glass ceramics 28,29 because they increase fracture surface to impede total breakage. It is also largely different in scale from glass with nanoductility 30 induced by disconnecting bonds of network atoms either by introducing alkali ions or disconnecting bonds by electron beam irradiation.…”

Mechanical Properties of CaO–Al2O3–SiO2 Glass-Ceramics Precipitating Hexagonal CaAl2Si2O8 Crystals

“…In this study, the microcracks induced by Vickers indentation were nondestructively observed for the first time (Figure 6). Our previous observation by SEM, as well as a theoretical approach using molecular dynamics simulation, indicated that the microcracks tend to travel in a glass-crystal interface [24,44]. Because the gap between two parallel microcracks and the size of the microcrack planes observed in Figure 6c agreed with the typical thickness and size of the hexagonal crystals, it is suggested that the microcracks in Figure 6c rendered the hexagonal crystal; hence, many microcracks were induced depending on the distribution of the hexagonal crystals around the imprint of the Vickers indentation.…”

Improved empirical force field for multicomponent oxide glasses and crystals

“…PMMCS potentials make use of the Morse function for short-range interactions whose parameters were fitted to structural and elastic properties of various oxide and silicate crystals. The availability of parameters for many cation-oxygen pairs and its ability to predict the mechanical properties fairly accurately have made it a very popular choice for the study not only of multicomponent oxide glasses but also crystalline materials and oxide nanoparticles [21][22][23][24][25][26][27][28][29].…”