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以聚丙烯腈预氧化纤维为先驱纤维,使其在真空烧结过程中原位转化生成碳纤维来增韧氧化铝陶瓷材料.利用热重–差热分析和X射线衍射研究了聚丙烯腈预氧化纤维的相结构和化学结构以确定制备复合材料的升温烧结工艺,并探讨了加压方式和聚丙烯腈预氧化纤维含量对复合材料组织结构和性能的影响.研究发现聚丙烯腈预氧化纤维在差热曲线上444℃左右的放热峰和X射线衍射图谱中17左右的衍射峰是由预氧化阶段残留的未充分氧化的聚丙烯腈分子引起的;而1073℃左右的吸热峰和25.5左右的衍射峰说明预氧化纤维在加热烧结过程中已开始向碳纤维转变.热压烧结制备的复合材料的力学性能明显优于无压烧结.随着聚丙烯腈预氧化纤维含量的增加,复合材料的密度和显微硬度降低,而断裂韧性则先升高后降低,当聚丙烯腈预氧化纤维体积分数为20%时,复合材料的断裂韧性最大,达9.39MPa.m1/2,说明原位碳纤维的生成提高了复合材料的断裂韧性,其增韧机制主要为纤维拔出和脱黏.
The polyacrylonitrile pre-oxidized fiber was taken as the precursor fiber, which was transformed into carbon fiber in-situ during vacuum sintering to toughen the alumina ceramic material.Thermogravimetric-differential thermal analysis and X-ray diffraction were used to study the properties of polyacrylonitrile preoxidation fiber Phase structure and chemical structure of the composites to determine the temperature-rising sintering process of the composites, and discuss the influence of the pressurization method and the content of polyacrylonitrile pre-oxidized fibers on the microstructure and properties of the composites. The exothermic peak at about 444 ° C and the diffraction peak around 17 in the X-ray diffraction pattern are caused by insufficiently oxidized polyacrylonitrile molecules remaining in the pre-oxidation stage. The endothermic peak at about 1073 ° C and about 25.5 The diffraction peaks indicate that the pre-oxidized fibers have started to transform into carbon fibers during the heating and sintering process.The mechanical properties of the composites prepared by hot-pressing sintering are obviously better than that of the non-pressure sintering.With the increase of polyacrylonitrile pre-oxidized fibers, the density of composites And the microhardness decreased, while the fracture toughness first increased and then decreased. When the volume fraction of polyacrylonitrile pre-oxidized fiber was 20%, the fracture of composite Greatest, of 9.39MPa.m1 / 2, generated in situ described carbon fibers improves the fracture toughness of the composite, the toughening mechanism mainly fiber debonding and pull.