In-situ growth of carbon nanotubes for fabrication of surface-enhanced thin-walled carbon/carbon composites

Carbon nanotubes (CNTs) were in-situ grown in the shallow surface of carbon/carbon (C/C) composites with a bulk density of 0.7-0.8 g/cm³, and then they were further densified by pyrocarbon (PyC). After that, a novel CNT-induced C/C composite (CNT-C/C) with a reinforced surface layer was prepared. Since CNTs optimized the spatial nucleation of PyC in the surface layer greatly, a porous isotropic layer with a lower coefficient of thermal expansion was obtained, alleviating the thermal contraction and inducing a compressive stress surface layer after cooling. This structure can effectively resist the initiation and propagation of cracks and improve the mechanical properties of C/C composites. The flexural strength, modulus, and fracture toughness of surface layer enhanced CNT-C/C increase by 53.7%, 13%, and 31.6% than that of the baseline, respectively.