【作者】 于萍；

【导师】 周玉；

【作者基本信息】 哈尔滨工业大学 ， 材料学， 2010， 硕士

【摘要】 本文以C_f、SiC_f、熔石英粉、SiC_w等为原料,采用真空热压烧结工艺制备了SiC_f（w）-C_f/SiO₂陶瓷基复合材料。采用XRD、SEM、TEM等分析手段和三点弯曲、单边缺口梁法等试验方法,研究了在复合材料10vol%C_f/SiO₂基础上,进一步引入SiC_f、同时引入SiC_f和SiC_w时,其含量变化对SiC_f（w）-C_f/SiO₂陶瓷基复合材料力学、热学及抗热震性能的影响规律。结果表明,所加SiC_f含量分别为0vol%、5vol%、10vol%、15vol%时,其致密度和抗弯强度呈降低-增加-降低的趋势变化,而断裂韧性和断裂功先不断增加后降低。其中,5vol%SiC_f-C_f/SiO₂复合材料中熔石英发生大量析晶,析晶量约42%,析出产物为α-方石英。而10vol%SiC_f-C_f/SiO₂复合材料的综合力学性能最好,抗弯强度、断裂韧性和断裂功分别为97.9MPa、2.15MPa·m1/2、287.2J/m2,弹性模量为46.3GPa。引入SiC_f后,复合材料的热导率随着SiC_f含量的增加而增加,材料的热膨胀系数先增加后下降。材料具有优良的抗热震性能,经过T=1100℃热震之后,材料的最低残余强度保持率为58.8%。在5vol%SiC_f-C_f/SiO₂中加入5vol%SiC_w以及在10vol%SiC_f-C_f/SiO₂的复合材料中加入10vol%SiC_w时,复合材料中熔石英的析晶量大大降低。并且材料的抗弯强度、断裂韧性、断裂功都明显增加。由于SiC_w具有较高的模量,因此加入晶须后复合材料的弹性模量明显增加。加入SiC_w后,复合材料的热膨胀系数降低,热导率增加,经过T=1100℃热震之后,材料的最低残余强度保持率为56.5%。通过对复合材料的断裂行为的分析发现,本实验所制备的复合材料的断裂方式均为伪塑性断裂。更多还原

【Abstract】 SiC_f（w）-C_f/SiO₂ composites were fabricated by vacuum hot-pressing using carbon fiber, silicon carbide fiber, fused silica powder and silicon carbide whisker as raw materials. The effect of SiC_f and SiC_w amounts on mechanical, thermal properties and thermal shock resistance of the 10vol%C_f/SiO₂ composites is studied by means of XRD, SEM, TEM as well as three point bending and single edge notched beam bending tests.Results show that density and bending strength of composites exhibited a tendency of drop-increase-drop while fracture toughness and work of fracture increased first then drop with the increase of SiC_f content. Theα-cristobalite formed as a result of crystallization of fused silica was detected in 5vol%SiC_f-C_f/SiO₂ composites and its content was up to 42%. The 10vol%SiC_f-C_f/SiO₂ composites show the best mechanical properties with bending strength, fracture roughness and work of fracture were 97.9MPa, 2.15MPa·m^1/2, and 287.2J/m², respectively.The thermal conductivity increased with an increased addition of SiC_f content, and the thermal expansion coefficient increased and then decreased. The composites show good thermal shock resistance, after a thermal shock, underΔT=1100℃, with the minimum residual strength retention of 58.8%.The content of crystallized fused SiO₂ was dropped dramatically, and the bending strength, fracture roughness and work of fracture were increase obviously after 5vol%SiC_w was added in 5vol%SiC_f-C_f/SiO₂ and 10vol%SiC_w was added in 10vol%SiC_f-C_f/SiO₂. The elastic modulus of the composites was increased remarkably due to the high modulus of the SiC_w..Thermal expansion coefficient of composite was decreased while the thermal conductivity was increased after whisker was added in. And the composites minimum residual strength retention was 56.5% after a thermal shock with△T=1100℃.Investigation on the fractured behaviors of composites, it was found that fracture occurred in the composites was pseudo-plastic fracture, instead of elastic catastrophic fracture.更多还原