聚酰亚胺(PI)气凝胶在航空航天中具有多种应用,国防,军工,和轨道交通设备。本文报道了一系列超轻量级,高弹性,高强度,低热导率,冰模板法制备的高阻燃rGO/PI纳米复合气凝胶。冻结过程(单向冻结和随机冻结)的影响,化学成分,和环境温度(-196-200°C)对形态,机械,系统研究了气凝胶的热性能。结果表明,单向气凝胶具有各向异性的力学性能和热性能。水平方向的压缩显示出高弹性,高抗疲劳性,和优越的隔热。同时,在垂直方向,它表现出高强度(PI-G-9达到14MPa)。在水平方向上进行10,000次压缩循环后(在50%应变下),单向PI-G-5气凝胶仍保留90.32%的高度保留率,和78.5%的应力保留,并表现出较低的稳定能量损失系数(22.11%)。它还具有低热导率(32.8mWm-1K-1),并通过在200°C下保持30分钟而表现出良好的隔热性能。有趣的是,气凝胶的弹性随着温度的降低而增强,在液氮中压缩时,高度回收率高达100%。更重要的是,rGO/PI气凝胶可以在很宽的温度范围(-196-200°C)内使用,并且具有43.3%至48.1%的高极限氧指数(LOI)。因此,这项工作可以提供一个可行的方法来设计隔热和阻燃保护材料具有优良的机械性能,适用于恶劣的环境。
Polyimide (PI) aerogels have various applications in aerospace, national defense, military industry, and rail transit equipment. This paper reports a series of ultra-lightweight, high elasticity, high strength, low thermal conductivity, and high flame retardant rGO/PI nanocomposite aerogels prepared by the ice templating method. The effects of freezing processes (unidirectional freezing and random freezing), chemical composition, and environmental temperature (-196-200 °C) on the morphology, mechanical, and thermal properties of the aerogels were systematically studied. The results indicated that unidirectional aerogels exhibit anisotropic mechanical properties and thermal performance. Compression in the horizontal direction showed high elasticity, high fatigue resistance, and superior thermal insulation. Meanwhile, in the vertical direction, it demonstrated high strength (PI-G-9 reaching 14 MPa). After 10,000 cycles of compression in the horizontal direction (at 50 % strain), the unidirectional PI-G-5 aerogel still retains 90.32 % height retention, and 78.5 % stress retention, and exhibited a low stable energy loss coefficient (22.11 %). It also possessed a low thermal conductivity (32.8 mW m-1 K-1) and demonstrated good thermal insulation performance by sustaining at 200 °C for 30 min. Interestingly, the elasticity of the aerogels was enhanced with decreasing temperatures, achieving a height recovery rate of up to 100 % when compressed in liquid nitrogen. More importantly, the rGO/PI aerogels could be utilized over a wide temperature range (-196-200 °C) and had a high limiting oxygen index (LOI) ranging from 43.3 to 48.1 %. Therefore, this work may provide a viable approach for designing thermal insulation and flame-retardant protective materials with excellent mechanical properties that are suitable for harsh environments.