Brittle–ductile transition and toughening of silica glass via Ni nanoparticle incorporation at a small volume fraction

The brittleness of glass significantly limits its application, and an effective solution is to impart ductility to it. In this study, Ni nanoparticles of different sizes were dispersed in SiO ₂ glass to investigate the effect of the particle size on the ductility of glass. Ni nanoparticles (0.5 vol. %) of two sizes (average particle sizes: 119 and 30 nm) were precipitated in the SiO ₂ glass by sintering on Ni nanoparticle-dispersed SiO ₂ glass powder. The fracture toughness obtained by microcantilever beam tests was significantly enhanced from 0.71 MPam ^1/2 for unmodified glass to 1.02 and 2.03 MPa m ^1/2 , respectively, for the glass samples incorporated with small (30 nm) and larger Ni nanoparticles (119 nm). The fracture surface energy increased significantly with the dispersion of the Ni nanoparticles in the glass matrix, despite their small volume fraction (0.5 vol. %). Moreover, a cup–cone structure indicative of ductile fracture was formed in the glass containing large Ni nanoparticles, whereas the glass dispersed with smaller Ni nanoparticles exhibited brittle fracture. These results indicate large stress dissipation in the former owing to its ductility. A theoretical approach based on the generation and movement of dislocations was employed to rationalize the particle-size-dependent fracture characteristics of the metal-particle-incorporated glass. Thus, we developed a cost-effective method to significantly enhance the fracture toughness of glass by imparting ductility via the dispersion of a small amount of metallic nanoparticles.