China develops greener ‘seashell’ glass

Chinese scientists develop new glass inspired by seashell with unparalleled strength and thermal insulation properties

The structure of nacre, also known as mother-of-pearl, is a natural composite found in the inner layer of mollusk shells such as abalone and pearl oysters. Nacre has a unique brick-and-mortar arrangement that consists of alternating layers of brittle calcium carbonate (aragonite) tablets and organic matrix, primarily composed of proteins and polysaccharides.

The remarkable characteristic of nacre lies in its hierarchical structure at multiple length scales. At the nanoscale, the aragonite tablets have a thickness of a few hundred nanometers and a diameter of a few micrometers. These tablets are stacked in a staggered pattern, with each tablet interlocking with its neighboring tablets through organic layers. The organic matrix acts as a glue, providing cohesion and interlocking between the tablets.

The combination of the aragonite tablets and the organic matrix gives nacre its exceptional mechanical properties. The brick-and-mortar arrangement provides structural reinforcement, preventing crack propagation and increasing toughness. When subjected to external forces, such as tensile or impact loads, the tablets slide on one another over large volumes, triggering viscoelastic responses (to stretch and bounce back when forces are applied to them) in the organic matrix and interlocking between tablets. This behavior allows nacre to dissipate a significant amount of mechanical energy, making it highly resistant to fracture and impact.

The nacre structure has inspired the design of glass composites because of its exceptional mechanical properties. By incorporating the brick-and-mortar arrangement and interlocking mechanism, glass composites can enhance their impact resistance and toughness.

The nacre-inspired SSG/glass composite (NSG) offers a revolutionary solution for enhancing the performance of glass materials. The SSG material, derived from silly putty, possesses unique mechanical properties that make it highly resistant to impact. Its energy dissipation capabilities increase with higher strain rates, allowing it to effectively absorb and dissipate energy during impact events.

The researchers discovered that the nacre-inspired structure in the composite promotes deformation within the SSG core when subjected to impact. The combination of the structure and SSG material makes the composite much better at resisting impacts, even at different speeds.

Moreover, the NSG composite also exhibits excellent thermal insulation properties. The nacre-inspired structure has a special way of conducting heat that varies depending on the direction. This, combined with the SSG core’s ability to resist heat flow, makes the composite really good at insulating against temperature changes from the outside.

The applications of this technology are vast. Imagine windows that provide exceptional thermal insulation, reducing heating and cooling costs in buildings. Electronic devices could be protected from mechanical shocks and impacts, ensuring their durability. The lightweight and transparent nature of the NSG composite also opens up possibilities for its use in various engineering fields.

This bioinspired material demonstrates how nature-inspired designs can lead to innovative solutions with real-world applications. The research, conducted by a team of eight scientists led by Professor Kaijin Wu and Professor Yong Ni, has been published in the journal Advanced Materials. While the technology is still in the research stage and requires further refinement, it holds great promise for transforming the way we use glass in everyday life. As this technology progresses, we can look forward to a future where glass materials offer enhanced functionality, durability, and safety, making our everyday lives more comfortable and secure.

Source: The China AcademyScience Express, March 4, 2024.

Research paper: Advanced Materials, 16 January 2024. Xiao Zhang et al, ‘Simultaneous Enhancement of Thermal Insulation and Impact Resistance in Transparent Bulk Composites’.