加张烧结下连续氧化铝纤维的组织结构演变规律

Microstructure evolution of continuous alumina fiber under tensile sintering

采用溶胶凝胶干法纺丝-高温烧结的方法制备连续氧化铝纤维,在对前驱体纤维进行预烧结和高温烧结时,利用自行设计搭建的加张烧结装置对纤维施加轴向张力,通过对氧化铝纤维的形貌、成分及组织结构进行表征,并与自由烧结(不加张力)的纤维进行对比,研究张力对烧结过程中氧化铝纤维的热分解、相变、组织结构演变以及性能的影响。结果表明:施加张力可显著提高预烧结纤维和烧结纤维的平直度,促进前驱体纤维中残留物质的分解和脱除;加张烧结可抑制纤维的轴向收缩,加大径向收缩,并促进γ-AlO向α-AlO转变;加张烧结还能改善纤维的晶粒形貌与孔洞分布,促进晶粒生长与晶间孔洞的收缩脱除,促进纤维致密化。相对于自由烧结,施加0.9 MPa轴向张力使得1500℃烧结3 min的氧化铝纤维平均抗拉强度从0.35 GPa提高到1.16 GPa,提高231%。

Continuous alumina fibers were prepared using sol-gel dry spinning-high temperature sintering method.During the pre-sintering and high-temperature sintering of the precursor fibers,the self-designed tensioning sintering device was used to apply axial tension to the fibers.The effects of tension on the thermal decomposition,phase transformation,structural evolution and properties of alumina fibers during the sintering process were investigated by characterizing the morphology,composition and structure of alumina fibers and comparing with the fibers sintered freely(without tension).The results show that the application of tension during sintering can significantly increase the straightness of pre-sintered and sintered fibers,and promote the decomposition and removal of residues in precursor fibers.Tensile sintering can inhibit the axial shrinkage of fibers,increase the radial shrinkage,and promote the transformation ofγ-AlOtoα-AlO.Tensile sintering can also improve the grain morphology and pore distribution of fibers,promote grain growth and shrinkage,and removal of intergranular pores,and promote the densification of fibers.Compared with free sintering,the application of 0.9 MPa axial tension during sintering increases the average tensile strength of alumina fibers sintered at 1500℃for 3 min by 231%,from 0.35 GPa to 1.16 GPa.