A SiC-ZrB2-ZrC coating toughened by electrophoretically-deposited SiC nanowires to protect C/C composites against thermal shock and oxidation

A SiC nanowire-toughened SiC-ZrB2-ZrC coating was prepared on SiC-Si-coated carbon/carbon composites by a three-step process of pack cementation, electrophoretic deposition and pack cementation. The introduction of nanowires improved the oxidation resistance of SiC-ZrB2-ZrC coating, whose mass loss decreased from 4.49% to 0.27% after isothermal oxidation at 1500 °C for 210.5 h. Meanwhile, the thermal shock resistance of coating was improved significantly by introducing the nanowires, whose mass loss decreased from 11.13% to 0.52% after 30 thermal cycles between 1500 °C and room temperature. The nanowires could effectively alleviate the thermal stress generated from thermal shock and increase the toughness of coating, resulting in the decrease of crack sizes. Similar with the chemical vapor deposited SiC nanowires, the electrophoretically-deposited SiC nanowires could play positive role in enhancing the oxidation and thermal shock resistance of coating, attributing to the toughening mechanism including bridging and pullout of nanowires. As a fast and controllable technique, electrophoretic deposition of SiC nanowires could provide a more practical method to toughen coatings, which might have a broader prospect in practical applications.