Mao Qian, Rajabpour Siavash, Talkhoncheh Mahdi Khajeh, Zhu Jiadeng, Kowalik Malgorzata, van Duin Adri C T
Department of Mechanical Engineering, The Pennsylvania State University, University Park, PA, 16802, USA.
Department of Chemical Engineering, The Pennsylvania State University, University Park, PA, 16802, USA.
Nanoscale. 2022 May 5;14(17):6357-6372. doi: 10.1039/d2nr00203e.
Blending polyacrylonitrile (PAN) with plastic wastes and bio-based polymers provides a convenient and inexpensive method to realize cost-effective carbon fiber (CF) precursors. In this work, PAN-based blend precursors are investigated using ReaxFF reactive molecular dynamics simulations with respect to the formation of all-carbon rings, the evolutions of oxygen-containing and nitrogen-containing species, and the migration of carbon atoms to form turbostratic graphene. From these simulations, we identify that PAN/cellulose (CL) blend manifests the highest carbon yield and the most substantial all-carbon ring formation. This ReaxFF-based finding is confirmed by Raman and TEM experiments indicating high crystallinity for PAN/CL-derived blend CFs. We trace the pathway of gasification and carbonization of PAN/CL to elaborate the mechanism of the formation of all-carbon ring networks. We discover that the acetals of CL can catalyze the cyclization of the blend precursor, allowing for the search for CL derivatives or the other kinds of bio-based polymers with similar functionalities as alternative blends. In addition, we examine the structural characteristics using the carbon-carbon (C-C) radial distribution functions, C-C bond length distributions, and C atom ratios for the four representative precursors, , PAN, oxidized PAN, PAN/nylon 6,6, and PAN/CL. Our simulation results show the most extensive all-carbon ring cluster and graphitic structure growths for PAN/CL. Therefore, we propose PAN/CL as a cost-effective alternative CF precursor, since (a) CL is naturally abundant and eco-friendly for production, (b) the blend precursor PAN/CL does not require oxidation treatment, (c) PAN/CL has a high carbon yield with substantial all-carbon ring formation, and (d) PAN/CL based CFs potentially provide a mechanical property enhancement.
将聚丙烯腈（PAN）与塑料废料和生物基聚合物混合，为实现具有成本效益的碳纤维（CF）前驱体提供了一种便捷且廉价的方法。在这项工作中，使用ReaxFF反应分子动力学模拟研究了基于PAN的共混前驱体，涉及全碳环的形成、含氧和含氮物种的演变以及碳原子迁移以形成乱层石墨烯。通过这些模拟，我们发现PAN/纤维素（CL）共混物表现出最高的碳产率和最大量的全碳环形成。基于ReaxFF的这一发现得到了拉曼和透射电镜实验的证实，这些实验表明PAN/CL衍生的共混CF具有高结晶度。我们追踪了PAN/CL的气化和碳化途径，以阐述全碳环网络的形成机制。我们发现CL的缩醛可以催化共混前驱体的环化，从而有助于寻找CL衍生物或其他具有类似功能的生物基聚合物作为替代共混物。此外，我们使用碳 - 碳（C - C）径向分布函数、C - C键长分布以及四种代表性前驱体（PAN、氧化PAN、PAN/尼龙6,6和PAN/CL）的C原子比来研究结构特征。我们的模拟结果表明PAN/CL具有最广泛的全碳环簇和石墨结构生长。因此，我们提出PAN/CL作为一种具有成本效益的替代CF前驱体，原因如下：（a）CL天然丰富且生产过程对环境友好；（b）共混前驱体PAN/CL不需要氧化处理；（c）PAN/CL具有高碳产率和大量全碳环形成；（d）基于PAN/CL的CF可能提供机械性能增强。
