In situ growth of single crystal Si3N4 nanowire foam with good wave-transparency and heat insulation performance

The radome of high Mach number aircraft requires a bearing material that is light weight, capable of wave transmissivity, and has excellent high temperature stability. In this regard, silicon nitride (Si3N4) nanomaterials, especially porous macroscopic structures formed by them (such as Si3N4 nanowire foam), are promising candidates. However, there have been no studies on the various Si3N4 nanofoams. In this study, a carbon template was used with a simple and reliable in situ synthesis method to prepare Si3N4 single crystal nanowire foam with a cross-linking structure between nanowires. High purity Si3N4 nanowires have the characteristics of low density (8.9 mg/cm3) and high foam volume fraction (17.35%). The nanowires can be distributed spontaneously and uniformly in three-dimensional space. The elasticity of this foam is mainly a result of the high aspect ratio of the nanowires and the large amount of large size pores in the structure. In addition, the foam has an ultralow dielectric constant, good wave transmissivity, and excellent thermal insulation and high-temperature stability. All of these characteristics are related to the special pore structure and intrinsic single crystal structure of the nanowire foam. Thus, Si3N4 nanowire foam is a transparent material with heat insulation, wave-transparency, and high temperature resistance, and has special application prospects.