Atomic insights on mechanical and piezoelectric properties of BNNTs and BNNTs/PDMS nanocomposites

Abstract

This study introduced a molecular dynamic (MD)-based numerical model to evaluate the mechanical and piezoelectric behavior of boron nitride nanotubes (BNNTs) and their composites, alongside a strategy to modulate mechanical and piezoelectric properties of their composite by controlling BNNTs defects. First, effects of BNNTs diameter and vacancy defects on their mechanical and piezoelectric properties were investigated, revealing the relationship between the defect orientation, symmetry, and electromechanical response. Subsequently, a Monte Carlo random number algorithm was applied to construct the coupling model of BNNTs/polydimethylsiloxane (PDMS) nanocomposites, enabling theoretical predictions of composite's mechanical and piezoelectric properties. Specifically, both the Young's modulus and piezoelectric coefficient (e33) of BNNTs decreased as their diameter increased. The vacancy defects had a complex effect on electromechanical properties of BNNTs. An increase in the number of defect atoms, dispersed vacancy defects, and circumferential defects significantly reduced the strength of BNNTs, whereas B atomic vacancies, symmetrical defects, and circumferential defects enhanced their piezoelectric performance. For BNNTs/PDMS composites, a larger BNNTs diameter and a moderate number of vacancy defects improved the interfacial bonding, which enhanced the Young's modulus and e33 values of composites. The BNNTs composites with circumferential defects exhibited higher mechanical strength than those with axial defects. These findings provided valuable insights into optimizing BNNTs diameter, defect management, and interfacial characteristics for designing high-performance piezoelectric nanocomposites for next-generation flexible devices.