Nanomanufacturing and Production Scale-up of Long Carbon Nanotube Arrays for Advanced Applications

碳纳米管（CNT）因其优异的机械、电学和光学性能而受到广泛关注。由于长排列碳纳米管在纳米医学、航空航天、电子和许多其他领域的潜在应用，人们对其进行了大量的研究。从理论上讲，这种长碳纳米管阵列可以纺成比任何现有纤维都更坚固、更轻的纤维，这将在轻量化和高强度材料的开发方面带来革命性的进步。然而，合成长碳纳米管阵列仍然存在许多限制。最近，UC（辛辛那提大学）的研究人员开发了一种用于定向生长的新型复合催化剂，并成功地生产出了文献报道中最长的碳纳米管阵列（11.5毫米及以上）。这种“黑棉”的长度是纺线的最佳长度。该项目包括密集的研究工作，以满足工业对大量长纳米管的需求，扩大培育过程的规模，并开发工业“大规模生产”纳米管所需的制造工具和方法。UC新的纳米管合成实验室和“洁净室”使这些目标可以实现。该项目的直接目标是开发一种在直径为10厘米的衬底上合成长碳纳米管（CNT）阵列的技术，并证明将纳米管阵列的生产规模扩大到更大的衬底的潜力。该方法将基于一种新型催化剂的实现，该催化剂提供定制的催化活性、适中的生长温度和增加的反应性生长侧数。此外，还将使用一种优化的化学气相沉积（CVD）工艺来生长厘米长的碳纳米管。大面积衬底的制备将采用不同的薄膜沉积技术，这些技术已在工业环境中得到了成功的验证。一系列精心策划的实验将依次优化纳米管合成中涉及的不同变量，包括当前催化剂的组成。阵列生产的扩大将包括：(1)确定在10厘米尺寸的单晶硅衬底上沉积催化剂的最佳参数，(2)在更大的衬底上使用优化的催化剂沉积和CVD生长，以及(3)评估降低每厘米碳纳米管阵列制造成本的方法。该项目的预期结果是在美国产生纳米级制造的突破。纳米管材料发展的进步将对所有工程和生命科学学科产生巨大的连锁反应。加州大学的研究人员已经花了四年的时间来开发衬底加工程序，以生产长纳米管的密集阵列。他们还将与CVD设备公司和北卡罗来纳理工大学合作，优化衬底制备和扩大纳米管生产规模。碳纳米管阵列最重要的应用之一是将纳米管旋转成纤维，用于先进的复合材料。纺丝将由Industrial Nano， Inc.开发。UC将生产大面积、长纳米管阵列，作为“黑棉”商品，用于纺丝。拟议活动的广泛影响将是通过提供生产大宗商品规模的长碳纳米管的技术，推动美国经济向前发展，这将有助于开发超轻质导电线，以取代复合材料中的微纤维。这将在许多产品中得到应用，包括波音787等飞机、太空电梯、飞机发动机和运动器材。由于碳纳米管阵列优异的导热性，另一个将受益于本研究的现有领域与高密度电子芯片和电路的成功散热有关。该项目的教育活动包括在新兴纳米技术的跨学科领域培训学生，并将纳米结构材料工程和制造纳入课程，为纳米技术时代的未来劳动力提供支持。

Carbon Nanotubes (CNT) are of great interest because of their outstanding mechanical, electrical, and optical properties. Intense research efforts have been undertaken to synthesize long aligned CNT because of their potential applications in nanomedicine, aerospace, electronics and many other areas. The long CNT arrays can be spun into fibers that are in theory stronger and lighter than any existing fibers, which will engender revolutionary advances in the development of lightweight and high-strength materials. Nevertheless, many limitations to synthesize long CNT arrays still remain. Recently, UC (University of Cincinnati) researchers developed a novel composite catalyst for oriented growth and succeeded to produce the longest CNT arrays (11.5 mm and above) reported in the literature. The length of this "black cotton" is optimal for spinning threads. The project includes intense research efforts to meet industry demand for large quantities of long nanotubes, to scale up the cultivated process, and to develop the manufacturing tools and methods that industry needs to "mass produce" nanotubes. The UC new nanotube synthesis lab and "clean room" makes these goals achievable. The immediate objectives of this project are to develop a technique to synthesize long carbon nanotube (CNT) arrays on 10 cm diameter substrates, and to demonstrate the potential to scale-up production of nanotube arrays to larger substrates. The approach that will be taken is based on the implementation of a novel catalyst that provides tailored catalytic activity, moderate growth temperature, and an increased number of reactive growth sides. In addition, an optimized Chemical Vapor Deposition (CVD) process for growth of centimeter long CNT will be used. The large area substrate preparation will be handled by employing different thin film deposition techniques which are successfully proven in industrial environment. A series of carefully planned experiments will be performed to sequentially optimize different variables involved in nanotube synthesis, including the current catalyst composition. Scale-up of array production will involve: (i) determining the optimal parameters for catalyst deposition on 10 cm size single crystal Si substrates, (ii) employing the optimized catalyst deposition and CVD growth on larger substrates, and (iii) evaluating methods to reduce manufacturing cost per squire cm of CNT array. The expected outcome of the project is to produce a breakthrough in nanoscale manufacturing in the US. Advances in the development of nanotube materials will have a tremendous rippling effect across all engineering and life sciences disciplines. The UC researchers have been working for four years to develop substrate processing procedures to produce dense arrays of long nanotubes. They will also work with CVD Equipment Corp. and North Carolina A&T SU to optimize substrate preparation and scale up nanotube production. One of the most important CNT array applications is to spin the nanotubes into fibers for use in advanced composite materials. The spinning will be developed by Industrial Nano, Inc. UC will produce large area, long nanotube arrays as a "black cotton" commodity for spinning into threads. The broad impact of the proposed activities will be to kick the US economy forward by providing technology to produce commodity scale quantities of long carbon nanotubes that will enable development of ultra lightweight electrically conductive threads to replace micro fibers in composites. This will have applications in many products including aircraft such as the Boeing 787, the space elevator, aircraft engines, and sporting equipment. Another exiting field that will benefit from this research is related to successful heat dissipation from high density electronic chips and circuits, because of the excellent thermal conductivity of the CNT arrays.The educational activity of this project involves training students in the interdisciplinary area of the emerging nanotechnology, and integrating nanostructured materials engineering and manufacturing into the curriculum to provide the future work force in the nanotechnology age.