Bioinspired nacre-like alumina with a bulk-metallic glass-forming alloy as a compliant phase

Amy Wat,Daniel Kiener,Takehiko Ishikawa,Antoni P Tomsia,Chae Woo Ryu,Je In Lee,Bernd Gludovatz,Andreas Meyer,Eun Soo Park,Julianna Schmitz,Jinyeon Kim,Markus Alfreider,Robert O Ritchie

doi:10.1038/s41467-019-08753-6

Abstract

Bioinspired ceramics with micron-scale ceramic “bricks” bonded by a metallic “mortar” are projected to result in higher strength and toughness ceramics, but their processing is challenging as metals do not typically wet ceramics. To resolve this issue, we made alumina structures using rapid pressureless infiltration of a zirconium-based bulk-metallic glass mortar that reactively wets the surface of freeze-cast alumina preforms. The mechanical properties of the resulting Al2O3 with a glass-forming compliant-phase change with infiltration temperature and ceramic content, leading to a trade-off between flexural strength (varying from 89 to 800 MPa) and fracture toughness (varying from 4 to more than 9 MPa·m½). The high toughness levels are attributed to brick pull-out and crack deflection along the ceramic/metal interfaces. Since these mechanisms are enabled by interfacial failure rather than failure within the metallic mortar, the potential for optimizing these bioinspired materials for damage tolerance has still not been fully realized.

Highlights

Bioinspired ceramics with micron-scale ceramic “bricks” bonded by a metallic “mortar” are projected to result in higher strength and toughness ceramics, but their processing is challenging as metals do not typically wet ceramics
To overcome the issues associated with infiltrating a metal into a ceramic scaffold, we have employed the concept of reactive wetting by utilizing a Zr-based bulkmetallic glass (BMG) as the infiltrating phase
We discuss below the features of our processing procedures to create these materials, our associated attempts at tailoring the ceramic–metal interfaces, and how these factors can result in enhanced damage-tolerant properties in nacre-like structural ceramics

Summary

Introduction

Bioinspired ceramics with micron-scale ceramic “bricks” bonded by a metallic “mortar” are projected to result in higher strength and toughness ceramics, but their processing is challenging as metals do not typically wet ceramics To resolve this issue, we made alumina structures using rapid pressureless infiltration of a zirconium-based bulk-metallic glass mortar that reactively wets the surface of freeze-cast alumina preforms. The high toughness levels are attributed to brick pull-out and crack deflection along the ceramic/metal interfaces Since these mechanisms are enabled by interfacial failure rather than failure within the metallic mortar, the potential for optimizing these bioinspired materials for damage tolerance has still not been fully realized. There have been comprehensive review papers on various experiments to freeze-cast[21] or to use other methods[22,23] to create such nacre-like ceramics

Methods

Results

Conclusion