Nanoscale Structural Rearrangement and Strain Softening in Ultra-Pure Nanotube Membranes

单壁碳纳米管薄膜在需要柔性导电涂层的应用中显示出相当大的前景，纳米管-纳米管接触的变形机制最终决定了这种薄膜的强度和耐久性。电子类型可以通过接触纳米管之间的范德华相互作用的性质对这些接触的强度产生重大影响。在这项基金支持的工作中，我们将纳米管分离成金属和半导体部分，并将它们组装成柔性聚合物表面的原始膜。应变引起的结构变化将在广泛的长度范围内使用不同的测量技术进行研究。为了解释这些测量结果，我们将使用二维刚性杆网络中具有可调节摩擦和可调节相互作用势的纳米级变形的粗粒度分子动力学模拟。这些模拟使我们能够在广泛的实验相关参数范围内模拟网络弹性的各向异性变化，为控制柔性纳米管薄膜力学的局部结构变化提供关键的见解。这项工作的更广泛影响可以在商业部门和课堂上找到。所获得的见解将导致纳米管薄膜的机械性能和耐用性的改进，并在光伏器件和燃料电池膜中出现应用。大学生参与研究是本研究的重要组成部分。我们的团队在指导本科生（包括女性和少数族裔）方面有着良好的记录，通过具有挑战性的研究项目，最终在领先的科学期刊上发表论文。我们获得的见解也将直接纳入NDSU材料与纳米技术的研究生和本科课程，这是一个新成立的跨学科项目，涵盖物理系，机械工程系，土木工程系和涂料与聚合物材料系。

Thin films of single-walled carbon nanotubes show considerable promise for applications that require flexible conductive coatings, and the deformation mechanics of nanotube-nanotube contacts is what ultimately dictates the strength and durability of such films. Electronic type can have a significant impact on the strength of these contacts through the nature of the van der Waals interactions between contacted nanotubes. In work supported by this grant, we are separating nanotubes into metallic and semiconducting fractions and assembling them as pristine membranes on flexible polymer surfaces. Strain-induced structural changes will be investigated over a broad range of length scales using a diverse set of measurement techniques. To interpret these measurements, we will use coarse-grained molecular dynamics simulations of nanoscale deformation in two-dimensional rigid-rod networks with adjustable friction and tunable interaction potentials. These simulations allow us to model anisotropic changes in network elasticity over a wide range of experimentally relevant parameters, providing critical insight into the local structural changes that govern the mechanics of flexible nanotube films.The broader impact of this work can be found in both the commercial sector and the classroom. The insight gained will lead to improvements in the mechanical performance and durability of nanotube films, with emerging applications in photovoltaic devices and fuel-cell membranes. Undergraduate research participation is a significant part of this research. Our group has an established record of mentoring undergraduates, including women and under-represented minorities, through challenging research projects that culminate in publications in leading scientific journals. The insight we gain will also be directly incorporated into the graduate and undergraduate curriculum in Materials and Nanotechnology at NDSU, a newly established interdisciplinary program that spans the departments of Physics, Mechanical Engineering, Civil Engineering, and Coatings & Polymeric Materials.