Density functional theory for molecular orientation of hard rod fluids in hard slits

A density functional theory (DFT) is used to investigate molecular orientation of hard rod fluids in a hard slit. The DFT approach combines a modified fundamental measure theory (MFMT) for excluded-volume effect with the first order thermodynamics perturbation theory for chain connectivity. In the DFT approach, the intra-molecular bonding orientation function is introduced. We consider the effects of molecular length (i.e. aspect ratio of rod) and packing fraction on the orientations of hard rod fluids and flexible chains. For the flexible chains, the chain length has no significant effect while the packing fraction shows slight effect on the molecular orientation distribution. In contrast, for the hard rod fluids, the chain length determines the molecular orientation distribution, while the packing fraction has no significant effect on the molecular orientation distribution. By making a comparison between molecular orientations of the flexible chain and the hard rod fluid, we find that the molecular stiffness distinctly affects the molecular orientation. In addition, partitioning coefficient indicates that the longer rodlike molecule is more difficult to enter the confined phase, especially at low bulk packing fractions.     

富勒烯在聚乙烯薄膜中的分散性研究

利用分子动力学方法,对纳米富勒烯/聚乙烯复合薄膜体系进行了模拟,分析了薄膜的空间限制作用、挤压作用以及薄膜变形速率对纳米粒子在聚乙烯薄膜中分散性的影响.结果表明,纳米复合薄膜的空间限制作用阻碍了纳米富勒烯的分散;对薄膜施加单向压力,纳米粒子受到的挤压作用可以促进纳米富勒烯的分散;在挤压变形量相同的条件下,薄膜变形的速率越小,纳米富勒烯的分散效果越好.当薄膜变形速率减小到一定程度时,富勒烯的分散效果能够接近其与聚合物本体进行复合的情形.     

高取向度碳纤维原丝制备工艺研究进展

碳纤维原丝的性能好坏在很大程度上决定着碳纤维的最终性能。缺陷少、细旦化、高取向、高纯化等是高性能原丝的基本要求。其中原丝的取向度在很大程度上决定了碳纤维在预氧化、碳化过程中形成的类石墨片层的取向结构，这会影响碳纤维最终的强度和模量，所以制备出高取向的碳纤维原丝具有重大意义。本文聚焦于高取向碳纤维原丝制备工艺，首先分析了高取向原丝的重要性，然后在原丝制备工艺上将纺丝方法以及牵伸工艺对取向度的影响进行总结分析，同时介绍了微积分纳米层叠法和高取向复合纤维原丝的制备工艺，指出优质的初生纤维以及具有稳定化取向排列的原丝是制备高取向碳纤维原丝的关键，以期对提升原丝的取向度进而提升碳纤维性能的研究有所贡献。