炭黑含量对短纤维增强反应烧结碳化硅结构与性能的影响

Effect of Carbon Black on the Microstructure and Mechanical Behaviors of Reaction Bonded Silicon Carbide Ceramics Reinforced by Chopped Fiber

以短碳纤维为增强体改性反应烧结碳化硅陶瓷,研究了炭黑含量对短纤维增强反应烧结碳化硅陶瓷结构与性能的影响。随着炭黑含量的增加反应烧结碳化硅的体积密度增加、游离硅含量降低。炭黑含量为12%(质量分数)、短纤维含量为30vol%时材料的断裂韧性达到5.5 MPa·m1/2;但炭黑含量过高时炭黑在浆料中的均匀性降低,烧结体中的缺陷增加。热分析表明反应烧结碳化硅复合材料的热膨胀系数随炭黑含量的增加略有提高,因此应限制炭黑的加入量。

Reaction bonded silicon carbide(RBSC) is a typical structural ceramic due to the high hardness, high stiffness and excellent resistance to wear, and is becoming the first candidate of the next-generation reflection mirror. In this study, random chopped carbon fiber was introduced to improve mechanical behaviors of RBSC ceramics. The effect of carbon black on the microstructure and mechanical behaviors was investigated. With the increase of carbon black, the relative density is increased and the content of silicon is reduced. At the carbon black fraction of 12wt% and fiber fraction of 30vol%, the fracture toughness reaches the peak value of 5.5 MPa·m^(1/2). However, the microstructure defects increase because of the non-uniform dispersion of carbon black in the slurry. Thermal analysis indicates that the coefficient of thermal expansion is increased with the increase of carbon black, and thus the content of carbon black should be limited in considering of the thermal stability in the field of reflection mirror.