【摘要】 采用液相渗积工艺制备了三维SiO₂/SiO₂复合材料,对该材料的致密化以及力学性能、热物理性能、烧蚀性能和断口显微形貌进行了研究与分析,并着重研究了纤维体积含量及热处理温度对复合材料抗弯强度的影响。研究表明:该复合材料具有较好的力学性能和优良的抗烧蚀性能,随着纤维体积含量的提高,复合材料的抗弯强度随之提高。当纤维体积分数为50％,热处理温度为700℃时,复合材料显示出最高的抗弯强度（78 MPa）。在烧蚀过程中无分层和剥离现象,表面光滑平整,耐烧蚀速率为0.17 mm/s。通过加入非离子型表面活性剂,极大地改善了料浆的渗积性能,提高了复合材料的致密化程度,复合材料的密度高达1.65 g/cm³。复合材料的断面显微观察表明,材料的增韧机制是基体与纤维界面的脱粘和纤维的拔出吸收了大量的能量,使得该材料具有较高的强度,并具有非脆性断裂的特征。更多还原

【Abstract】 Silica fiber preform reinforced fused silica composites were fabricated by repeated vacuum-assisted Hquid-phase infiltration. The-mechanical properties, thermal properties and ablative properties of the samples were evaluated. Flexural test was conducted to investigate the effect of silica fiber content and treatraent temperature on the flexural strength of the three-dimen-sional SiO2 composite. Experimental results show that the SiOz composites not only have good mechanical properties but also have excellent ablative performance. The flexural strength is increased with the increment of silica fiber content and decreased with the increment of treatment temperature. When the volume fraction of silica fiber content is 50% and treatment temperature is 700℃, the flexural strength of the composite reach to the maximum value (78 MPa). By adding the cyclohexanone sur-factant the infiltration property can be much improved, resulting in the increase of densification of SiO2 composite. The density of SiO2 composite is up to 1. 65 g/cm3. The fracture surfaces of the flexural specimens observed by SEM show that the pseudo-plasticity and toughening mechanisms of the composites are caused by the absorption of much fracture energy by the interface debonding and fiber pulling-out.更多还原