球磨时间对硼掺杂石墨材料抗氧化行为的影响

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

通过球磨分散方法制备了掺杂细颗粒碳化硼石墨材料。采用热分析仪考察了经不同球磨时间制备的复合材料在室温至1400℃温度范围内的抗氧化行为;利用扫描电镜分析了样品在800℃和1000℃恒温氧化后的表面形貌。研究结果表明:经球磨50h制备的细颗粒碳化硼掺杂石墨材料在1000℃氧化时,有优良的自愈合抗氧化性能。其抗氧化机理为:均匀分散的细颗粒B4C可以在氧化时迅速形成连续的、均匀的保护膜覆盖在基体表面,从而有效地抑制氧气进入和基体反应。

Boron doped graphites were fabricated by a ball-milling dispersion method. The oxidation behavior of B4C/C composite materials with various milling time at temperatures up to 1400degreesC was analyzed by the TG/DTA technique and surface morphologies of the composites after isothermal oxidation at 800 degreesC and 1000 degreesC 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 1000 degreesC. 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 B4C could rapidly form a continuous and uniform B2O3 film covering on the surface of the sample during oxidation, which effectively inhibited the diffusion of oxygen into the interior of the carbon substrates.