聚丙烯腈/石墨烯纳米复合材料：迈向下一代碳纤维
Polyacrylonitrile/Graphene Nanocomposite: Towards the Next Generation of Carbon Fibers
摘要：
碳纤维（CF）是未来汽车轻量化的关键解决方案，由于其强度与重量比，可提高燃油效率并减少排放。然而，目前占主导地位的PAN基CF的高成本阻碍了它们的应用。使用低成本的替代前体可以克服这一问题。不幸的是，衍生自更便宜的单组分前体的低成本CF遭受差的机械性能。通过添加纳米添加剂来开发复合碳纤维对于低成本碳纤维是非常有前途的。因此，在整个碳纤维生产过程中，碳化条件的影响和聚合物/添加剂的转化机制的基本理解是至关重要的，以开发低成本的碳纤维。在这项工作中，我们已经证明了碳化温度如何影响PAN/石墨烯CF的性能，通过执行一系列的ReaxFF为基础的分子动力学模拟。我们发现，石墨烯边缘以及氮和氧官能团具有催化作用，并作为石墨结构生长的种子。我们的MD模拟揭示了将石墨烯添加到PAN前体中修饰了CF中的全碳元环，并增强了碳化中6元碳环的排列，这导致与PAN基CF相比具有优异的机械性能。这些ReaxFF仿真结果验证了实验的结构和机械特性。有趣的是，机械表征表明，与在1500 ℃下热处理的PAN基CF相比，在1250 ℃下热处理的PAN/石墨烯CF的强度增加了90.9%，杨氏模量增加了101.9%。PAN/石墨烯CF在较低碳化温度下的优异机械性能提供了通过降低碳化温度来节省能源和降低成本的途径，并且可以为低成本CF的开发提供关键见解。
英文摘要：
Carbon Fibers (CFs) are the key solution for the future lightweight vehicle with enhanced fuel efficiency and reduced emissions owing to their ultrahigh strength to weight ratio. However, the high cost of the current dominant PAN-based CFs hinders their application. The use of low-cost alternative precursors may overcome this issue. Unfortunately, low-cost CFs derived from cheaper single component precursors suffer from poor mechanical properties. Developing composite CFs by adding nanoadditives is very promising for low-cost CFs. Therefore, a fundamental understanding of carbonization condition impacts and polymer/additives conversion mechanisms during whole CF production are essential to develop low-cost CFs. In this work, we have demonstrated how the carbonization temperature affects the PAN/graphene CFs properties by performing a series of ReaxFF based molecular dynamics simulations. We found that graphene edges along with the nitrogen and oxygen functional groups have a catalytic role and act as seeds for the graphitic structure growth. Our MD simulations unveil that the addition of the graphene to PAN precursor modifies all-carbon membered rings in CFs and enhances the alignments of 6-member carbon rings in carbonization which leads to superior mechanical properties compare to PAN-based CFs. These ReaxFF simulation results are validates by experimental structural and mechanical characterizations. Interestingly, mechanical characterizations indicate that PAN/graphene CFs carbonized at 1250 C demonstrate 90.9% increase in strength and 101.9% enhancement in Young's modulus compare to the PAN-based CFs carbonized at 1500 C. The superior mechanical properties of PAN/graphene CFs at lower carbonization temperatures offers a path to both energy savings and cost reduction by decreasing the carbonization temperature and could provide key insights for the development of low-cost CFs.
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