Super-thermal insulating and high-strength ceramic film assembled by Si₃N₄ nanowire-BN nanosheet dual-phase intertwined structure

In the thriving fields of thermal management fields, ceramic films with superior thermal insulation and excellent mechanical properties are in high demand. Nevertheless, the fabrication of ceramic films that combine both mechanical performance and low thermal conductivity remains highly challenging. Herein, we report a dual-phase Si₃N₄ nanowire-boron nitride (BN) nanosheet (SNB) with an intertwined structure, where BN nanosheets are firmly intertwined on the surface of Si₃N₄ nanowires. The results demonstrate that the SNB film possesses exceptional mechanical properties, with a tensile strength of 5.25 MPa, representing a 127% improvement over the Si₃N₄ nanowire film (SN) without BN nanosheets incorporation. Simultaneously, benefiting from the interface and cross-linking nodes formed between Si₃N₄ nanowires and BN nanosheets, the thermal conductivity of the SNB film is as low as 0.043 W·m^–1·K^–1, marking a 23% reduction compared to the SN film without BN nanosheets. Furthermore, the all-ceramic component characteristic endows the SNB film with high temperature resistance up to 1200 °C. The combination of high strength, low thermal conductivity, and high-temperature resistance enables the SNB film a promising candidate for applications in high temperature environments.