Improvement of mechanical property and ablation resistance of carbon/carbon composites by adding nano-diamond particles

In order to improve mechanical property and ablation resistance of carbon/carbon (C/C) composites, nano-diamond particles were introduced into carbon fiber preforms by vacuum ultrasonic treatment. These particles could enhance the fiber/matrix interfacial bonding owing to the pinning effect and could contribute to the crack deflection. The flexural strength could be increased by 111.5% for composites modified with the optimal concentration of ethanol/diamond dispersion, compared with those without diamond. Such enhanced interfacial bonding is also beneficial to resist the mechanical denudation under the oxyacetylene torch; meanwhile, the oxidative erosion of C/C composites could be reduced since diamond particles increase their thermal conductivity, causing the mass and linear ablation rates decreased by 61.5% and 54.6% respectively. With excessive particles added, the fiber pull-out would be blocked due to over-strengthened bonding and cracks could not propagate along the interfaces, decreasing flexural strength of the composites; the structural defects including pores and micro-cracks are produced excessively, which would be exposed to the flame and play a negative role on the anti-ablation performance.