Synthesis of Multiwalled Carbon Nanocoils and their Foundational Property

碳纳米线圈有望成为高性能纳米机电系统和电磁波吸波材料的重要组成部分。在本研究中，我们研究了碳纳米管生长的催化剂和工艺，以控制碳纳米管的生长。此外，还对碳纳米管的力学性能进行了研究。用于碳纳米管生长的催化剂1)催化剂颗粒的制备我们使用三个等离子弧枪的组合来制备催化剂，这些催化剂是逐层沉积或均匀混合的状态沉积在一个衬底上的。用原子力显微镜和透射电子显微镜对催化剂的详细结构进行了研究。在700℃的热处理过程中，所有的元素都混合在一起，形成了催化剂颗粒，两种情况下都是逐层或混合的。相反，通过改变一种底物可以大大提高碳纳米管的产率。这表明制备催化剂颗粒的表面相互作用对CNCs的生长是非常关键的。电学和力学性能1)导电性和剪切模数碳纳米管的导电率与劣质碳纳米管相当。为了研究剪切模量，我们分别测量了悬臂碳纳米管的共振频率随长度的变化关系，并将实验结果与有限元计算结果进行了比较。实验测得碳纳米管的剪切模量和Q因子分别为~50GP_a和~100。2)结构变化研究表明，经~1000℃的热处理后，碳纳米管的剪切模量和Q因数均有很大提高，但仍保持了碳纳米管的原始形状。这表明，所制备的碳纳米管的低剪切模量和低Q因子源于碳纳米管内部的吸附或缺陷。

Carbon nanocoils (CNCs) are expected to be one of components for high performance nano-electromechanical systems and electromagnetic wave absorbers. In this study, we have investigated catalysts and processes for the growth of CNCs to control the growth of CNCs. Furthermore, mechanical properties of CNCs were also investigated.1. Catalyst for CNCs Growth1) Preparation of Catalyst particleWe have used a combination of three plasma arc guns to prepare the catalysts, which were deposited layer-by-layer or well mixed states on a substrate. Detailed structures of catalysts were investigated by AFM and TEM. All of elements were mixed during the annealing process at 700℃ and were formed catalyst particles for both cases gayer-by-layer or mixed).2).High Yield Synthesis of CNCsYield of CNCs were slightly changed by changing the process conditions. On the contrary, yield of CNCs were greatly improved by changing a kind of substrates. This indicates that the surface interaction for making the catalyst particle is very crucial for the growth of CNCs.2. Electrical and Mechanical Properties1) Conductivity and Shear ModulusConductivities of CNCs were comparable to those of poor carbon nanotubes. To investigate the shear moduli, we have measured the length dependence of the resonant frequency of cantilevered CNCs individually and compared the experimental results with computed values obtained by a finite element method. The share moduli and Q factor for the as prepared CNCs were estimated to be〜50 GP_a and〜100, respectively.2) Structural Change by AnnealingIt was revealed that the shear moduli and Q factors of CNCs were much improved by annealing at〜1000℃, where the original shapes of CNCs were remained. This implies that low shear modulus and low Q factor for as-prepared CNCs originate from the adsorbate or defects inside the CNCs.