Liu Lanfang, Li Liangjun, Hu Yijie, Feng Junzong, Jiang Yonggang, Feng Jian
Science and Technology on Advanced Ceramic Fibers and Composites Laboratory, College of Aerospace Science and Engineering, National University of Defense Technology, Changsha 410073, China.
Gels. 2024 Sep 24;10(10):613. doi: 10.3390/gels10100613.
Fiber-reinforced aerogel composites are widely used for thermal protection. The properties of the fibers play a critical role in determining the structure and properties of the final aerogel composite. However, the effects of the fiber's characteristics on the structure and properties of the aerogel composite have rarely been studied. Herein, we prepared quartz fiber felt-reinforced silica-polybenzoxazine aerogel composite (QF/PBSAs) with different fiber diameters using a simple copolymerization process with the ambient pressure drying method. The reasons for the effects of fiber diameter on the structure and properties of the aerogel composites were investigated. The results showed that the pore structure of the aerogel composites was affected by the fiber diameter, which led to significant changes in the mechanical behavior and thermal insulation performance. At room temperature, pore structure and density were found to be the main factors influencing the thermal conductivity of the composites. At elevated temperatures, the radiative thermal conductivity (λr) plays a dominant role, and reducing the fiber diameter suppressed λr, thus decreasing the thermal conductivity. When the QF/PBSAs were exposed to a 1200 °C butane flame, the PBS aerogel was pyrolyzed, and the pyrolysis gas carried away a large amount of heat and formed a thermal barrier in the interfacial layer, at which time λr and the pyrolysis of the PBS aerogel jointly determined the backside temperature of the composites. The results of this study can provide valuable guidance for the application of polybenzoxazine aerogel composites in the field of thermal protection.
纤维增强气凝胶复合材料被广泛用于热防护。纤维的性能在决定最终气凝胶复合材料的结构和性能方面起着关键作用。然而，纤维特性对气凝胶复合材料结构和性能的影响鲜有研究。在此，我们采用简单的共聚工艺结合常压干燥法制备了具有不同纤维直径的石英纤维毡增强二氧化硅-聚苯并恶嗪气凝胶复合材料（QF/PBSAs）。研究了纤维直径对气凝胶复合材料结构和性能产生影响的原因。结果表明，气凝胶复合材料的孔隙结构受纤维直径影响，这导致了力学行为和隔热性能的显著变化。在室温下，孔隙结构和密度是影响复合材料热导率的主要因素。在高温下，辐射热导率（λr）起主导作用，减小纤维直径可抑制λr，从而降低热导率。当QF/PBSAs暴露于1200℃的丁烷火焰中时，PBS气凝胶发生热解，热解气体带走大量热量并在界面层形成热障，此时λr和气凝胶的热解共同决定了复合材料的背面温度。本研究结果可为聚苯并恶嗪气凝胶复合材料在热防护领域的应用提供有价值的指导。
