Ultrastrong Translucent Glass Ceramic with Nanocrystalline, Biomimetic Structure.

Abstract

Transparent/translucent glass ceramics (GCs) have broad applications in biomedicine, armor, energy, and constructions. However, GCs with improved optical properties typically suffer from impaired mechanical properties, compared to traditional sintered full-ceramics. We present a method of obtaining high-strength, translucent GCs by preparing ZrO₂-SiO₂ nanocrystalline glass ceramics (NCGCs) with a microstructure of monocrystalline ZrO₂ nanoparticles (NPs), embedded in an amorphous SiO₂ matrix. The ZrO₂-SiO₂ NCGC with a composition of 65%ZrO/35%SiO₂ (molar ratio, 65Zr) achieved an average flexural strength of 1 GPa. This is one of the highest flexural strength values ever reported for GCs. ZrO₂ NPs bond strongly with SiO₂ matrix due to the formation of a thin (2-3 nm) amorphous Zr/Si interfacial layer between the ZrO₂ NPs and SiO₂ matrix. The diffusion of Si atoms into the ZrO₂ NPs forms a Zr-O-Si superlattice. Electron tomography results show that some of the ZrO₂ NPs are connected in one direction, forming in situ ZrO₂ nanofibers (with length of ∼500 nm), and that the ZrO₂ nanofibers are stacked in an ordered way in all three dimensions. The nanoarchitecture of the ZrO₂ nanofibers mimics the architecture of mineralized collagen fibril in cortical bone. Strong interface bonding enables efficient load transfer from the SiO₂ matrix to the 3D nanoarchitecture built by ZrO₂ nanofibers and NPs, and the 3D nanoarchitecture carries the majority of the external load. These two factors synergistically contribute to the high strength of the 65Zr NCGC. This study deepens our fundamental understanding of the microstructure-mechanical strength relationship, which could guide the design and manufacture of other high-strength, translucent GCs.