碳化硅晶须改性反应烧结碳化硅陶瓷的显微结构及性能

Microstructure and Mechanical Behavior of Reaction Bonded Silicon Carbide Ceramics Modified with SiC Whisker

以碳化硅晶须为增强体、碳化硅--碳为基体制备晶须增强反应烧结碳化硅复合材料,研究了碳化硅晶须、碳含量对复合材料显微结构与性能的影响。结果表明:碳化硅晶须经高温反应烧结后仍保持表面的竹节结构,且晶须增强体与反应烧结碳化硅基体间形成适中的界面结合强度;材料断口处有明显的晶须拔出,当碳黑含量为6%(质量分数)时,随着晶须含量的增加,材料的抗弯强度从200MPa提高到310MPa(晶须含量15%),当碳黑含量为18%时,随着晶须含量的增加,材料断裂韧性从3.3MPa·m1/2提高到4.3MPa·m1/2;碳化硅晶须含量过高时,晶须的"搭桥"效应导致材料中含有较多的游离硅,限制了材料力学性能进一步提高;微氧化处理使材料表面形成致密、均匀的氧化膜,可显著提高反应烧结碳化硅的抗弯强度和断裂韧性。

A composite of reaction bonded silicon carbide(RBSC)reinforced with silicon carbide whisker was prepared.The effects of the whisker and carbon on the microstructure and mechanical behavior were investigated.The whisker maintains the burl profile on the surface after reactive sintering.Some whisker pullouts occur on the fracture surface,indicating an appropriate bonding strength between the whisker and the RBSC matrix.For the composite with 6%(mass fraction)of carbon,the flexural strength increases from 200 MPa to 310 MPa at a whisker fraction of 15%,and for the composite with 18% of carbon,the fracture toughness increases from 3.3MPa·m1/2 to 4.3MPa·m1/2 at a whisker fraction of 20%.Some pores in the green body appear when the whisker fraction further increases due to the bridging effect of whisker,giving rise to residual silicon in the sintered body.A protective film is formed on the material surface due to mild oxidation in ambient air.The flexural strength and fracture toughness both are improved in the presence of this film.