石墨烯/聚乙烯复合材料致密区间密度变化的分子动力学模拟

Molecular dynamics simulation of density variation in compact region of graphene/polyethylene composites

石墨烯增强复合材料的性能受到粘结界面,致密区间等多种因素的影响。如果没有考虑到这些因素的影响,在分析石墨烯增强复合材料时可能会导致错误的结果。本文采用分子动力学模拟的方法进行石墨烯/聚乙烯复合材料致密区间密度变化的分析。首先对聚乙烯晶胞进行分子动力学计算,得到的聚乙烯晶胞密度为0.95 g/cm3,与聚乙烯实际密度吻合,然后运用该计算步骤进行石墨烯/聚乙烯复合材料的分子动力学模拟,最后通过切片的方法得出聚乙烯基体密度的变化趋势。模拟计算结果表明,石墨烯/聚乙烯复合材料的聚乙烯基体在石墨烯的作用下出现了致密的现象,在石墨烯两侧存在对称的致密区间,并且在石墨烯和聚乙烯之间存在范德华(Van der Waals)间隙,间隙的厚度为0.28 nm。致密区间中,远离石墨烯的聚乙烯密度为0.95 g/cm3,与常温常压下聚乙烯的密度一致;接近石墨烯的聚乙烯的密度出现1.5 g/cm3的峰值,是常温常压下聚乙烯密度的1.6倍。

The properties of graphene reinforced composites are affected by many factors,such as bonding interface,compact region and so on.If these factors are not taken into account,the analysis of graphene reinforced composites may lead to errors in results.Molecular dynamics simulationwas used to analyze the density variationin compact region of graphene/polyethylene composites.The molecular dynamics of polyethylene cell was calculated firstly.The obtained density of polyethylene cell was 0.95 g/cm3and was in agreement with the actual density of polyethylene.And then the procedures of polyethylene’s simulation were applied to the molecular dynamics simulation of graphene/polyethylene composites.The density variationtrend of compact regioncould be obtained by slicing.The simulationresults showed that a compact phenomenon appearedin the polyethylene matrix of graphene/polyethylene composites by the effect of the graphene,so that there were symmetrical compact regions on both sides of graphene.Besides,there wasVan der Waals(vdW)gap between graphene and polyethylene and its thickness was 0.28 nm.In compact region,the density of the polyethylene far away from the graphene was 0.95 g/cm3 and in agreement withthe density of the polyethylene under normal temperature and pressure.The peak density of the polyethylene appeared in the place which wasnear the graphene and its value was 1.5 g/cm3.The peak density was 1.6 times of that of the polyethylene density under normal temperature and pressure.