The effect of ball-milling time on the oxidation behavior of boron doped graphites

Boron doped graphites were fabricated by a ballmilling dispersion method. The oxidation behavior of B4C/C composite materials with various milling time at temperatures up to 1?400?℃ was analyzed by the TG/DTA technique and surface morphologies of the composites after isothermal oxidation at 800?℃ and 1?000?℃ were examined by scanning electron microscopy. The results indicated that doped graphite with fine boron carbide prepared by a ballmilling dispersion method for 50?h had excellent oxidation resistance with selfprotection at 1?000?℃. A general model and mechanism for selfprotection against oxidation of such materials was proposed. A possible reason is that a uniform dispersion of fine B4C could rapidly form a continuous and uniform B2O3 film covering on the surface of the sample during oxidation, which effectively inhibited the diffusion of oxygen into the interior of the carbon substrates.