White graphene makes ceramics multifunctional

phys.org | 1/11/2018 | Staff
bab_ohhbab_ohh (Posted by) Level 3
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A little hBN in ceramics could give them outstanding properties, according to a Rice University scientist.

Rouzbeh Shahsavari, an assistant professor of civil and environmental engineering, suggested the incorporation of ultrathin hexagonal boron nitride (hBN) sheets between layers of calcium-silicates would make an interesting bilayer crystal with multifunctional properties. These could be suitable for construction and refractory materials and applications in the nuclear industry, oil and gas, aerospace and other areas that require high-performance composites.

Materials - Radiation - Shahsavari - Calculations - Calcium-silicates

Combining the materials would make a ceramic that's not only tough and durable but resistant to heat and radiation. By Shahsavari's calculations, calcium-silicates with inserted layers of two-dimensional hBN could be hardened enough to serve as shielding in nuclear applications like power plants.

The research appears in the American Chemical Society journal ACS Applied Materials and Interfaces.

HBN - Graphene - Graphene - Hexagons - Plane

Two-dimensional hBN is nicknamed white graphene and looks like graphene from above, with linked hexagons forming an ultrathin plane. But hBN differs from graphene as it consists of alternating boron and nitrogen, rather than carbon, atoms.

"This work shows the possibility of material reinforcement at the smallest possible dimension, the basal plane of ceramics," Shahsavari said. "This results in a bilayer crystal where hBN is an integral part of the system as opposed to conventional reinforcing fillers that are loosely connected to the host material.

High-level - Study - Stability - Property - Enhancement

"Our high-level study shows energetic stability and significant property enhancement owing to the covalent bonding, charge transfer and orbital mixing between hBN and calcium silicates," he said.

The form of ceramic the lab studied, known as tobermorite, tends to self-assemble in layers of calcium and oxygen held together by silicate chains as it dries into hardened cement. Shahsavari's molecular-scale study showed that hBN mixes well with tobermorite, slips into the spaces between the layers as the boron and oxygen atoms bind and buckles the flat hBN sheets.

Buckling

This accordion-like buckling is...
(Excerpt) Read more at: phys.org
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