Neutron radiation induced transmutation of boron to lithium in aluminum-boron nitride composite

Lightweight materials are essential for applications in harsh environments, such as space explorations, where materials must exhibit exceptional durability and resistance to radiation damage for both humans and equipment. Boron nitride nanoplatelets (BNNPs) serve as a reinforcement in metals offering superior radiation shielding along with excellent thermal and mechanical properties for extreme environments. In this work fully dense Al-BNNP composites are fabricated by solid-state friction stir welding (FSW). The neutron mass absorption coefficient of the FSW Al-BNNP composite was measured at 0.136 cm 2 /g, significantly higher than the 0.06 cm 2 /g of its counterpart FSW aluminum. This remarkable neutron shielding effectiveness is attributed to the transmutation of the 10 B isotope of BNNP to Li and He. This neutron capture mechanism was experimentally investigated at the atomic scale by atom probe tomography (APT). Notably, Al-BNNP composites demonstrate great potential as multi-functional materials for future space explorations, from spacecraft assemblies to rocket fuel tanks, benefiting from their high strength, low weight, and superior radiation shielding. • The Al-BNNP composite fabricated by friction stir welding (FSW) exhibited a neutron absorption rate of 0.136 cm 2 /g, more than twice that of aluminum, making it ideal for space applications. • BNNP reinforcement during FSW refined grain structure and improved isotropy, enhancing material strength and durability. • The remarkable neutron shielding effectiveness is attributed to the transmutation of the 10 B isotope to lithium (Li) and helium (He). • The transmutation was investigated at an atomic scale using atom probe tomography for the first time, offering new insights into the neutron capture mechanism and its potential applications in space technology.