Synthesis of multifunctional foam-like isotropic high volume fraction SiC nanowires preform via a simple method

Lightweight, pure, foam-like and macro-structured ceramic nanowires preform with a certain structural strength and good electromagnetic functional performance can be used as the skeleton of new isotropic ceramic matrix composites (CMCs) to improve its comprehensive performance. With this aim, silicon carbide (SiC) nanomaterials are promising candidates. However, little is studied at present regarding pure SiC nanowires as the preform for structural and functional CMCs. In this study, an isotropic SiC nanowire preform with a cross-linked structure among the nanowires was designed and prepared via an in-situ synthesis method, based on the carbon template. As prepared SiC nanowires with high purity can spontaneously and uniformly distribute in three dimensions. Furthermore, the crystallinity, and volume fraction of the nanowires preform can be flexibly adjusted. SiC nanowires preform has a low-density (0.1 g cm⁻³) and rigid structure, which can be attributed to high-volume fraction (26.05%) of nanowires and the crossing and connection among nanowires. Importantly, owing to its unique structure, the maximum stress of the SiC nanowires preform reaches 34 KPa. The prepared SiC nanowire preform achieved full absorption in the X-band, and the specific microwave absorption performance exceeded 45.18 dB cm⁻² g⁻¹. The preform exhibits also excellent thermal stability and thermal insulation performance. These make it a particularly promising preform of CMCs combining structure and functional performance.