Enhanced ablation resistance of phenolic composites through the construction of a sea-island nanostructured char layer via in-situ catalytic graphitization of incorporated Salen-Ni complex

Abstract

Phenolic resin (PR) are widely used as ablative thermal protection systems for aerospace applications. However, it remains a challenge to improve the ablation resistance of phenolic composites by designing the structures of char layer via a facile approach. In this paper, a Salen-Ni complex (CL) modified boron phenolic composite (CLBPR) was designed with low concentrations of Ni (0.05–0.45 wt%). The chemically incorporated Salen-Ni structures enabled the uniform distribution of Ni element, and the enhancement of graphitization degree of char layer through the significant catalytic effect. XPS, XRD, RAMAN and TEM analyses showed that the metallic Ni nanoparticles arising from Salen-Ni structures could effectively catalyze the ablated char layer to generate various type of graphitic nanostructures, and construct a sea-island nanostructured char layer during ablation. Furthermore, we found that the inlaid graphitic phases formed through Solid-Liquid-Solid mechanism in amorphous carbon (AC) can hinder the growth of defects, while improve the graphitization degree of char layer. The results demonstrated that the linear and mass ablation rates of CLBPR were reduced by 128.9% and 32.6% compared to the counterpart at 4 MW/m2. This research will provide some inspirations more or less for the development of more advanced polymer-matrix ablative composites in the future.