Research ArticleMATERIALS SCIENCE

Picosecond amorphization of SiO2 stishovite under tension

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Science Advances  12 May 2017:
Vol. 3, no. 5, e1602339
DOI: 10.1126/sciadv.1602339

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Abstract

It is extremely difficult to realize two conflicting properties—high hardness and toughness—in one material. Nano-polycrystalline stishovite, recently synthesized from Earth-abundant silica glass, proved to be a super-hard, ultra-tough material, which could provide sustainable supply of high-performance ceramics. Our quantum molecular dynamics simulations show that stishovite amorphizes rapidly on the order of picosecond under tension in front of a crack tip. We find a displacive amorphization mechanism that only involves short-distance collective motions of atoms, thereby facilitating the rapid transformation. The two-step amorphization pathway involves an intermediate state akin to experimentally suggested “high-density glass polymorphs” before eventually transforming to normal glass. The rapid amorphization can catch up with, screen, and self-heal a fast-moving crack. This new concept of fast amorphization toughening likely operates in other pressure-synthesized hard solids.

Keywords
  • Amorphization
  • toughening
  • nano-polycrystal
  • stishovite
  • high-density glass
  • quantum molecular dynamics

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