Ultrasound Alignment of Carbon Nanotubes in a Polymer Medium for Additive Manufacturing of Nanocomposite Materials

聚合物纳米复合材料是用纳米级填充材料增强聚合物基体材料。特别是，与传统材料相比，定向碳纳米管增强的聚合物纳米复合材料由于其在碳纳米管定向方向上具有更高的强度-重量比和刚度-重量比而受到关注。在聚合物基体材料中排列碳纳米管有几种方法，包括拉伸、切片和基于电场和磁场的技术。然而，这些方法在效率和可伸缩性方面受到限制。该奖项支持使用超声波在聚合物材料中以可扩展的方式排列碳纳米管的基础研究。研究结果可能使超声定向自组装与立体光刻增材制造工艺相结合，以制造具有排列碳纳米管的工程聚合物纳米复合材料。这些材料的机械性能可以媲美或超过最先进的轻质材料，可用于广泛的应用，包括航空航天，汽车和基础设施。本研究的目的是建立碳纳米管在光聚合物基质中的排列与超声定向自组装技术的操作参数之间的关系。为了实现这一目标，将采用实验方法。利用表面活性剂和超声技术将碳纳米管分散在液态光聚合物中，并利用超声定向自组装技术在光聚合物中形成排列整齐的碳纳米管线状图案。光聚合物随后将使用立体光刻增材制造工艺固化成矩形试样。超声定向自组装技术的以下工作参数将改变：超声波频率为0.19至2.00 MHz，超声波驱动电压幅值为10至40伏，光聚合物层厚度为100至500微米，碳纳米管长度为10至100微米，碳纳米管重量分数为0.01至1%。碳纳米管在固化光聚合物基体中的排列将使用一套表征工具来确定，包括扫描电子显微镜、电子计算机断层扫描和x射线计算机断层扫描。此外，碳纳米管的排列将使用Hermans取向因子和半最大全宽度技术进行量化。

Polymer nanocomposite materials consist of a polymer matrix material reinforced with a nanoscale filler material. In particular, polymer nanocomposite materials reinforced with aligned carbon nanotubes are of interest due to their potentially higher strength-to-weight and stiffness-to-weight ratios in the direction of the carbon nanotube alignment, compared to traditional materials. Several methods exist to align carbon nanotubes in a polymer matrix material, including stretching, slicing, and techniques based on electric and magnetic fields. However, these methods are limited in terms of efficiency and scalability. This award supports fundamental research on using ultrasound waves to align carbon nanotubes in a polymer material in a scalable fashion. Research results can potentially enable integrating ultrasound directed self-assembly with a stereolithography additive manufacturing process to fabricate engineered polymer nanocomposite materials with aligned carbon nanotubes. These materials can exhibit mechanical performance that may rival or exceed that of state-of-the-art lightweight materials, and can be used in a wide range of applications, including aerospace, automobile, and infrastructure. The objective of this research is to establish the relationship between alignment of the carbon nanotubes in the photopolymer matrix and operating parameters of the ultrasound directed self-assembly technique. An experimental approach will be followed to achieve this objective. Carbon nanotubes will be dispersed in liquid photopolymer using surfactant and sonication, and ultrasound directed self-assembly will be used to create line patterns of aligned carbon nanotubes within the photopolymer. The photopolymer will subsequently be cured into a rectangular specimen using a stereolithography additive manufacturing process. The following operating parameters of the ultrasound directed self-assembly technique will be varied: ultrasound wave frequency from 0.19 to 2.00 MHz, ultrasound wave driving voltage amplitude from 10 to 40 Volt peak-to-peak, the photopolymer layer thickness from 100 to 500 micrometer, carbon nanotube length from 10 to 100 micrometer, and carbon nanotube weight fraction from 0.01 to 1 weight percent. The alignment of the carbon nanotubes in the cured photopolymer matrix will be determined using a suite of characterization tools that include scanning electron microscopy, electron computed tomography, and X-ray computed tomography. Furthermore, the alignment of the carbon nanotubes will be quantified using the Hermans' orientation factor and the full-width at half maximum techniques.