Anomalous properties of spark plasma sintered boron nitride solids

TL;DR

This study demonstrates that spark plasma sintering of hexagonal boron nitride creates high-density solids with enhanced mechanical, dielectric, thermal, and radiation shielding properties due to induced structural modifications.

Contribution

It introduces a scalable method for synthesizing high-density crystalline h-BN with unique structural features that improve its functional properties.

Findings

High-density crystalline h-BN achieved via SPS

Induction of non-basal plane crystallinity and layer twisting

Enhanced mechanical, dielectric, thermal, and radiation shielding properties

Abstract

Hexagonal boron nitride (h-BN) is a brittle ceramic with a layered structure, however, recent experiments have suggested that inter-layer structural engineering could be key to new structural and functional properties. Here we report the scalable bulk synthesis of high-density crystalline h-BN solids, by using high-temperature spark plasma sintering (SPS) of h-BN powders, which show high values of mechanical strength, ductility, dielectric constant, thermal conductivity, and exceptional neutron radiation shielding capability. Through exhaustive characterizations we reveal that SPS induces non-basal plane crystallinity, twisting of layers, and facilitates inter-grain fusion with a high degree of in-plane alignment across macroscale dimensions, resulting in near-theoretical density and improved properties. Our findings highlight the importance of material design, via new approaches such as layer twisting and interlayer interconnections, to create novel ceramics with properties that could go beyond their intrinsic limits.