Simultaneous exfoliation and functionalization of high-aspect-ratio boron nitride nanosheets and their application in composite membranes for fire-warning systems

This study aims to develop a highly sensitive fire-warning material by synergistically combining graphene oxide (GO) with boron nitride (hBN), renowned for its exceptional thermal conductivity and flame retardancy. Urea and water were employed as precursors to exfoliate and functionalize hBN via a semi-solid-state stone-milling method, yielding amino-functionalized boron nitride nanosheets (BNNS-NH2) possessing a high aspect ratio. Subsequently, BNNS-NH2 was assembled with GO through a layer-by-layer assembly approach to fabricate a BNNS/GO composite membrane. Fire-warning tests were conducted on the composite membrane, unveiling an impressively short fire response time of only 0.2 s and an extended duration of up to 52 s, thus demonstrating its exceptional sensitivity and long-lasting fire-warning performance. Upon exposure to fire, the GO layer within the composite membrane underwent thermal reduction, leading to the formation of electrically conductive reduced graphene oxide (RGO). The high thermal conductivity of the BNNS layer, coupled with strong interfacial bonding, facilitated rapid heat propagation throughout the composite membrane, thereby promoting the thermal reduction reaction of GO and enhancing the response speed. Furthermore, the outstanding flame retardancy of BNNS contributed to the material's persistent fire-warning performance.