Surface coating on carbon nanofibers with alumina precursor by different synthesis routes

Alumina-reinforced carbon nanofiber nanocomposites were prepared using different routes; powders mixture, colloidal route and sol–gel process followed by spark plasma sintering (SPS). CNFs/xAl2O3 (x = 10–50 vol.%) were prepared through nanopowders mixing in a high-energy attrition milling. The main limitations in the preparation of this kind of nanocomposites are related to the difficulty in obtaining materials with a homogeneous distribution of both phases and the different chemical nature of CNFs and Al2O3, which causes poor interaction between them. A surface coating of CNFs by wet chemical routes with an alumina precursor is proposed as a very effective way to improve the interaction between CNFs and Al2O3. An improvement of 50% in fracture strength was found for similar nanocomposite compositions when the surface coating was used. The improved mechanical properties of these nanocomposites are caused by stronger interaction between the CNFs and Al2O3.