【作者】 杜红娜；

【导师】 周万城；

【作者基本信息】 西北工业大学 ， 材料加工工程， 2006， 硕士

【摘要】 C／C-SiC复合材料，即碳纤维增强碳-碳化硅双基体陶瓷基复合材料，具有密度低、抗氧化性好、耐腐蚀、良好的摩擦磨损性能等优点，是一种能满足高温使用的新型高温结构材料和功能材料。本文采用先驱体裂解浸渍的方法制备了一系列C／C-SiC复合材料，研究了浸渍液浓度、浸渍次数、预制体密度对制得的材料的密度的影响，并分析了对最终制得的复合材料的力学性能的影响，同时对材料的热物理性能也进行了简要的分析。本文得到的主要的结论如下： 从试验过程的静力学及动力学分析可知，为了使浸渍更加容易，应该使得浸渍液与预制体之间涧湿良好，采用表面张力大及粘度较小的浸渍液，选择孔隙度较大的预制体。通过理论分析和试验结果的分析可以看出，计算出的先驱体致密化模型能够较准确的反映出复合材料的密度与浸渍次数和浸渍液浓度的关系。 聚碳硅烷的热分解反应主要发生在300℃到1000℃，而分解出的无定形态SiC转换为碳化硅晶体的过程则发生在1000℃到1300℃阶段。聚碳硅烷的裂解产率为60％左右，裂解产物主要为碳化硅。 在相同的浸渍循环次数的情况下，对不同的预制体以及浸渍液浓度来说，当浸渍液浓度为50％时，试样最终密度最大。复合材料的弯曲强度随着裂解温度的升高而增加，1400℃制得的复合材料的强度最低，断裂韧性则为在1500℃时最低，而在1600℃制得的复合材料的综合性能最佳。 在浸渍液浓度为50％，裂解温度为1600℃的条件下，预制体密度为1.21g／cm³的材料性能最好，预制体密度为1.51g／cm³的复合材料性能最差。 加压浸渍制得的复合材料的致密度比真空浸渍的要高，能够有效的提高C／C-SiC复合材料的力学性能。当预制体密度为0.80g／cm³，C／C-SiC复合材料的密度为1.95g／cm³时，复合材料的弯曲强度达到323MPa，剪切强度为33.45MPa，断裂韧性为14.37MPa·m^1／2。 预制体的分次沉积导致试样出现二次断裂的形貌。浸渍裂解制备的复合材料中存在大量气孔，大部分存在于纤维束之间或两束纤维的交叉处，这些气孔的存在在一定程度上降低复合材料的韧性。 材料的致密度越大，则复合材料的孔隙越小，导热系数越大。制得的材料的更多还原

【Abstract】 C/C-SiC composites, carbon fiber reinforced cabon silicon carbide binary matrix composites, is a new high temperature structure and function materials, having the characteristics of low density, excellent oxidation resistance, corrosion resistance and good friction properties. In this study, C/C-SiC composites are prepared by precursor infiltration pyrolysis, and the influence of infiltration concentration, times and preform densities on C/C-SiC composites’ densities and mechanical properties are studied. Thermal behaviores of C/C-SiC composites are also analyzed in brief. The conclusions are shown as the following:Analysis of statics and dynamics of test shows that the liquid with large surface tension and small viscosity and preform with large porosity should be selected for achieving good wetting effect, which could make the infiltration easier. The theory and experiment result indicates that the precursor condensation model could explain the relation of the density of composites to cycle times and maceration extract concentration much exactly.The decomposition of Polycarbosilane mainly occurs between 300 and 1000℃. and the amorphous SiC from the decomposition of polycarbosilane will crystallize into SiC crystal at 1000-1300℃. The productivity from polycarbosilane is 60%, and SiC is the mainly product.When the cycle times are the same, the density of sample nearly all achieve to the maximum for different preform densities when the maceration extract concentration is 50%, no matter how different the perform densities are. The flexural strength of the composites increases as the decomposition temperature, and the composites prepared in1600℃ have the best over-all properties.When maceration extract concentration is 50%, decomposition temperature is 1600℃, the properties of composites with preform density of 1.21 g/cm³are the best, while those with perform density of 1.51 g/cm³ are the worst.The composites using pressed infiltration have higher densities than that using vacuum infiltration. Pressed infiltration can enhance the mechanics properties of the C/C-SiC composites effectively. When preform density is 0.80 g/cm³, the final density , flexural strength, shearing strength, and the fracture toughness of the C/C-SiC composite reaches to 1.95 g/cm³, 323 MPa, 33.45 MPa, and 14.37 MPa·m^1/2,更多还原