Abstract:

Phenolic aerogel/carbon fiber composites with different microstructures have been prepared by sol-gel polymerization of phenolic resin and curing agent. The particle size and pore size of phenolic aerogel in the composites were controlled by changing the amount of curing agent. It was found that the particle size of the aerogels could be decreased from 368 nm to 54 nm with the decrease of the curing agent amount, corresponding to the decrease of average pore size from 5 μm to 230 nm. Furthermore, the properties of composites were strongly depended on the microstructure of aerogel, in which the mechanical strength and ablation property increased while the thermal conductivity decreased with nanoparticle size decreasing. The composites with the minimized particle size had a low density of 0.27 g·cm^-3, a high bending strength of 8.9 MPa and a low room-temperature thermal conductivity of 0.065 W·m^-1·K^-1. Under the oxyacetylene ablation conditions of 2000℃ for 30 s, its mass/linear ablation rate were 0.0081 g·s^-1 and 0.0204 mm·s^-1, respectively. By regulating the nanostructure of material, it can effectively improve the mechanics, heat insulation and ablation performance of the material to meet the needs of high performance thermal protection applications.

Key words: composites, nanostructure, particle, thermal protection, phenolic aerogels

摘要：

以酚醛树脂为前体、碳纤维针刺预制体为增强体，采用溶胶-凝胶、常压干燥方法制备得到纳米孔酚醛气凝胶/碳纤维复合材料。在不改变材料密度的条件下，通过调节固化剂的用量来调控酚醛气凝胶的纳米颗粒尺寸及孔隙结构，改变气凝胶颗粒在碳纤维针刺预制体中的填充状态，制备出不同微观结构的复合材料。研究表明：随着固化剂用量的减少，气凝胶的颗粒粒径逐渐变小，平均孔径在230 nm~5μm范围内可调；与碳纤维复合后，随着气凝胶颗粒的减小，复合材料的力学性能逐渐提升、热导率逐渐降低、烧蚀性能明显提高。优化后的PAC复合材料具有极低的密度（0.27 g·cm^-3）、高弯曲强度（8.9 MPa）、较低的热导率（0.065 W·m^-1·K^-1）；在2000℃、30 s的中等热流烧蚀条件下，质量烧蚀率为0.0081 g·s^-1、线烧蚀率为0.0204 mm·s^-1。通过调控材料的纳米结构，能够有效地提升材料的力学、隔热以及烧蚀性能，满足高性能热防护应用需求。

关键词: 复合材料, 纳米结构, 粒子, 热防护, 酚醛气凝胶