Effect of B2O3 Doping and Phosphate Impregnation on Oxidation Resistance and Mechanical Properties of Mesocarbon Microbead Composites

Mesocarbon microbead/carbon nanotubes (MCMB/CNTs) composites were modified by adding B2O3 powders and phosphate impregnation and the MCMB/CNTs were prepared using in-situ thermal polymerization. The morphology, flexural strength and oxidation resistance behavior were studied using scanning electron microscope (SEM), three-point bending tests, thermo gravimetric analysis (TG) and isothermal oxidation method. The results show that the oxidation resistance and flexural strength of the composites are enhanced with proper amount of B2O3. When the ratio of B2O3 is beyond 2%, the flexural strength of the sample begins to decrease. The sample with 2% B2O3 impegnated with phosphate reachs the highest flexural strength of 66 MPa, and the initial mass loss temperature of the samples is 520 degrees C. After isothermal oxidation at 500 degrees C for 60 min, the mass loss and the flexural strength of the sample are 5% and 50.3 MPa, respectively.