Nanotwinning and amorphization of boron suboxide

Abstract

Recently, researchers discovered that in contrast to isolated twins, periodic twins with nanoscale spacing can dramatically improve mechanical properties. Ceramics engineers now seek to incorporate this “nanotwinning” into icosahedral solids because of their high strength, high stability, and low mass density. In this manuscript, we assert that boron suboxide, while far less studied than boron carbide (i.e., the most popular icosahedral solid), possesses higher propensity for nanotwinning and higher theoretical promise. For boron suboxide, the influence of processing on twin spacing is explored through mechanical testing and transmission electron microscopy. Quantum-mechanical simulations are then performed to suggest a critical twin spacing that would maximize performance and to show how to track experimental nanotwinning with x-ray diffraction. Finally, transmission electron microscopy and Raman spectroscopy show that amorphization, the localized loss of crystallinity, drives mechanical failure in ways unique to boron suboxide.