Flash soldering of boron nitride nanosheets for all-ceramic films

The assembly of boron nitride nanosheets (BNNSs) into strong, flexible thin films capable of withstanding extreme conditions, such as high/low working temperatures and corrosive environments, holds immense promise for numerous applications. However, BNNSs are difficult to assemble and sinter to achieve the dense thin film structure observed in graphene thin films. We report the rapid fabrication of dense BNNS all-ceramic films (BACFs) in 30 s by combining the fabrication strategies for 2D and ceramic materials. In this process, densely arranged and highly oriented BNNSs are flash soldered into a monolith achieved by precisely controlled ultrafast sintering. This fusion of BNNS leads to an ultrahigh in-plane thermal conductivity of 134.5 W·m−1·K−1, which was among the highest values for BNNS films (mostly ≤ 70 W·m−1·K−1). The as-prepared BACF exhibits the combined advantages of sintered ceramics (durability, stability, acid-alkali resistance) and 2D material films such as flexibility and shock resistance, which is important for practical uses but rarely found in existing ceramics. It also has excellent cooling performance, dielectric properties, and good thermal stability, which is promising for demanding thermal management applications in emerging technologies.