Peng Qing, Han Liang, Lian Jie, Wen Xiaodong, Liu Sheng, Chen Zhongfang, Koratkar Nikhil, De Suvranu
Department of Mechanical, Aerospace and Nuclear Engineering, Rensselaer Polytechnic Institute, Troy, NY 12180, USA.
Phys Chem Chem Phys. 2015 Jul 15;17(29):19484-90. doi: 10.1039/c5cp02986d.
Oxidation is a major cause for the degradation of materials including graphene, where epoxidation (forming the C-O-C bond) is very common. In addition, graphene oxide, in which the epoxy group is one of the two major functional groups (the other is hydroxy), is an important precursor material used for the bulk synthesis of graphene sheets. Information about the mechanical stabilities, non-linear elastic properties, and elastic limits under various strain components is invaluable for application of these nanomaterials. Here, we investigate the mechanical properties of the epoxidized graphene in ordered graphene oxide, namely C6O1, C6O2, and C6O3, representing the carbon : oxygen ratios of 6 : 1, 3 : 1, and 2 : 1, respectively, using first-principles calculations within the framework of density functional theory. We predict a reduction of Young's modulus of graphene by a factor of 20%, 23%, and 27% for C6O1, C6O2, and C6O3, respectively, indicating a monotonic degradation with respect to epoxidation. However, there is no clear trend for Poisson's ratio, implying that the local atomic configurations are dominant over oxygen concentrations in determining the Poisson ratio. Our computed high order elastic constants are good for the design of graphene oxide based flexible transparent electronics.
氧化是包括石墨烯在内的材料降解的主要原因，其中环氧化（形成C-O-C键）非常普遍。此外，氧化石墨烯是用于大规模合成石墨烯片的重要前驱体材料，环氧基团是其两个主要官能团之一（另一个是羟基）。了解这些纳米材料在各种应变分量下的机械稳定性、非线性弹性特性和弹性极限对于其应用具有重要价值。在此，我们在密度泛函理论框架内使用第一性原理计算，研究了有序氧化石墨烯（即C6O1、C6O2和C6O3，分别代表碳与氧的比例为6∶1、3∶1和2∶1）中环氧化石墨烯的力学性能。我们预测，对于C6O1、C6O2和C6O3，石墨烯的杨氏模量分别降低20%、23%和27%，这表明随着环氧化程度的增加，杨氏模量呈单调下降趋势。然而，泊松比没有明显的变化趋势，这意味着在确定泊松比时，局部原子构型比氧浓度起主导作用。我们计算得到的高阶弹性常数有利于基于氧化石墨烯的柔性透明电子器件的设计。
