Nature-inspired design of strong, tough glass-ceramics
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Introduction Ever since the discovery of glass-ceramics by Stookey in the 1950s,1 there have been widespread applications for this unique class of materials.2–5 Glass-ceramics are generally defined as microcrystalline solids formed by controlled nucleation and crystallization of glass.5,6 The ability to use high-speed glassforming processes (e.g., pressing, blowing, rolling, floating) to manufacture glass-ceramics provides a unique advantage over conventional ceramics. Nowadays, the quest for more damage-resistant engineering materials is driving the development of high-performance materials with exceptional mechanical properties. Glassceramics with high strength and toughness are in demand for medical, structural, and consumer electronics markets.3 The properties of glass-ceramics strongly depend on both composition and microstructure. The bulk glass composition controls the ability for glass melting, forming, and the potential phase assemblage after ceramming (heat treatment), while the design of microstructure is crucial for key mechanical and optical properties.6,7 The microstructure is controlled through optimization of the heat-treatment cycle of the precursor glass. This article presents an overview of current developments in the creation of glass-ceramics with the requisite structure and properties, with a focus on their body strength. First, we
provide an overview of the composition, microstructure, and mechanical properties that have been reported in glass-ceramics. The section titled “Nature-inspired toughening” contains a detailed analysis of the approaches used to produce high strength and high toughness with inspirations from biological and geological materials. We conclude with recommendations for future directions in the development of glass-ceramics with unique structure and properties.
Composition–microstructure–mechanical properties An extremely broad range of glass-ceramic compositions has been reported in the literature. The ability to form a glass and to control its crystallization through internal nucleation is generally required for a glass-ceramic composition. However, the phase assemblage and microstructure are restricted to those metastable crystals that can form from glass. The majority of reported glass-ceramic compositions are based on silica-containing glasses and can be divided into three groups: silicates, aluminosilicates, and fluosilicates. Table I provides a summary of the typical compositions and properties in these three glass-ceramic families.6–10 Figure 1 shows microstructures of silicates (lithium disilicate),11 aluminosilicates (β-spodumene),10 and fluosilicates
Qiang Fu, Corning Incorporated, USA; [email protected] George H. Beall, Corning Incorporated, USA; [email protected] Charlene M. Smith, Corning Incorporated, USA; [email protected] doi:10.1557/mrs.2017.31
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