ZrB_2-SiC陶瓷材料的力学性能研究

STUDY ON PROPERTIES OF ZrB_2-SiC CERAMICS

为适应新型防热材料的要求,采用热压烧结工艺制备了氧化钇和氧化镧掺杂ZrB2-SiC陶瓷材料,分析了氧化钇和氧化镧对陶瓷材料室温/高温力学性能的影响,探讨了稀土氧化物掺杂ZrB2-SiC陶瓷材料的增强增韧机制。结果表明,随氧化钇含量的提高,材料的致密度和维氏硬度增加,而弯曲强度和断裂韧性先是升高然后下降。在氧化钇掺量体积分数为3%时获得最大强度和断裂韧性。氧化镧对原材料比较敏感,杂质比较多的情况下,强度明显下降,原材料纯度较高时,掺杂体积分数5%氧化镧可以获得较高的致密度、抗弯强度和断裂韧性。弯曲强度的提高主要来源于晶粒细化、均匀化和致密化,断裂韧性的提高主要是裂纹偏转数量的增加消耗裂纹扩展能量而引起的。

ZrB2-SiC composites added with rare earth oxides Y2O3 and La2O3 were prepared by hot- pressing for the requirement of thermal protection materials. The effects of Y2O3 and La2O3 addition on the room and high temperature mechanical properties were studied in detail using modem analyzing and testing methods. Mechanical experimental results show that the relative density and Vickness hardness increase, while flexural strength and fracture toughness increase firstly and then decrease with the increasing of Y203 volume fraction. The maximum flexural strength and fracture toughness are obtained for composite with 3 vol% Y2O3. The flexural strength of ZrB2-SiC-La2O3 composites decreases obviously when the purity content is high. However, with high purity raw materials, the relative density, strength and toughness are improved by adding 5 vol% La2O3. The smaU and uniform of grain size as weil as high relative density are contributed to the high flexural strength, while increasing of crack propagating can consume more crack energy thus leading to the improvement of fracture toughness.