干燥方式对高氯酸铵/石墨烯复合材料的结构和热分解行为的影响

通过溶胶-凝胶法制备了石墨烯水凝胶, 并将其与高氯酸铵(AP)复合, 然后分别采用自然干燥、冷冻干燥和超临界CO₂干燥三种干燥方式制备了AP/石墨烯复合材料, 并通过扫描电镜(SEM)、元素分析、X射线衍射(XRD)、差示扫描量热仪(DSC)和热重-红外联用技术(TG-FTIR)研究了不同干燥方式对其结构和热分解行为的影响. 结果表明, 干燥方式对AP/石墨烯复合材料的形貌具有明显影响, 其中通过超临界CO₂干燥制备的AP/石墨烯复合材料基本能保持与石墨烯气凝胶相似的外观和多孔结构. 通过自然干燥、冷冻干燥和超临界CO₂干燥制备的AP/石墨烯复合材料中AP的质量分数分别为89.97%、92.41%和94.40%, 其中通过超临界CO₂干燥制备的复合材料中AP的粒径尺寸为69 nm. DSC测试结果表明, 石墨烯对AP的热分解过程具有明显的促进作用, 能使AP的低温分解过程大大减弱, 高温分解峰温明显降低. 三种干燥方式相比, 通过超临界CO₂干燥制备的AP/石墨烯复合材料中石墨烯的促进作用最明显. 与纯AP相比, 其高温分解峰温降低了83.7℃, 表观分解热提高到2110 J·g^-1. TG-FTIR分析结果表明, AP/石墨烯复合材料的热分解过程中, AP分解产生的氧化性产物与石墨烯发生了氧化反应, 生成了CO₂.

Effect of Drying Methods on the Structure and Thermal Decomposition Behavior of Ammonium Perchlorate/Graphene Composites

Graphene hydrogels were prepared by the sol-gel method, and then used to prepare ammonium perchlorate (AP)/graphene composites by the incorporation of AP. The composites were dried naturally in air, freeze-dried, or dried with supercritical CO₂. Scanning electron microscopy (SEM), elemental analyses (EA), and X-ray diffraction (XRD) were used to characterize the structure of the AP/graphene composites dried using different methods. Furthermore, the thermal decomposition behavior of the AP/graphene composites was investigated by differential scanning calorimetry (DSC) and thermogravimetric analysis/infrared spectroscopy (TG-FTIR). Drying method had an obvious influence on the morphology of the AP/graphene composites; only the AP/graphene composites dried with supercritical CO₂ showed similar three-dimensional networks and porous structure to graphene aerogels. Elemental analyses revealed that the AP contents in the AP/graphene composites prepared by drying naturally, freeze-drying, and supercritical CO₂ drying were 89.97%, 92.41%, and 94.40%, respectively. XRD results showed that AP was dispersed homogeneously on the nanoscale in the AP/graphene composites dried with supercritical CO₂ and the average particle diameter of AP was about 69 nm. DSC and TG-FTIR analyses indicated that graphene could promote the thermal decomposition of AP, particularly for the sample dried with supercritical CO₂. Independent of drying method, the low-temperature decomposition of the as-prepared AP/graphene composites was not observed and the high-temperature decomposition was accelerated. Compared to the other two drying methods, graphene in the AP/graphene composites dried with supercritical CO₂ showed most obvious promoting effects. The high-temperature decomposition temperature of the AP/graphene composites dried with supercritical CO₂ decreased by 83.7 ℃ compared with that of pure AP, and the total heat release reached 2110 J·g^-1. Moreover, graphene also took part in the oxidation reactions with oxidizing products, which was confirmed by the generation of CO₂.