Materials World Network: Novel Catalyst Systems for Carbon Nanotube (CNT) Synthesis and their Underlying Mechanisms

利用纳米粒子催化剂和催化膜的化学气相沉积(CVD)技术已被证明是合成碳纳米结构(如纳米管和石墨烯)的通用和有效的方法。化学气相沉积使人们能够对这些结构进行广泛的研究，并为其在集成电路、能量存储、透明导体、热管理表面、分级复合材料、传感器、药物输送和仿生方面的应用开辟了道路。尽管取得了这些成功，但催化CVD的详细机制仍然知之甚少，CVD过程缺乏确定性控制，特别是关于CNT手性的控制。常见的催化剂，如镍和铁，在其金属状态下是活性的，因此在CVD所需的高温下容易粗化和载体相互作用。我们最近证明，纳米颗粒氧化锆在中等温度下催化碳纳米管的生长，因此它既不会还原成金属，也不会形成碳化物。氧化物的低反应性和有限的重组预示着对CVD过程的高水平控制。我们建议研究一系列氧化物作为CVD催化剂。我们计划利用原位X射线光电子能谱和环境透射电子显微镜来探索石墨烯的形成和纳米管成核的机理(S)。我们将分析氧化物辅助的碳纳米管化学气相沉积的手性选择性，并探索在氧化物薄膜上大面积石墨烯化学气相沉积的可能性。

Chemical vapor deposition (CVD) techniques employing nano-particulate catalysts and catalyst films have proven to be versatile and effective methods for synthesizing carbon nanostructures, such as nanotubes (CNTs) and graphene. CVD enabled extensive investigation of these structures as well as opened routes towards their application in integrated circuits, energy storage, transparent conductors, thermal management surfaces, hierarchical composites, sensors, drug delivery and biomimetics. Despite these successes, the detailed mechanisms of catalytic CVD remain poorly understood and the CVD process lacks deterministic control, in particular regarding CNT chirality. Common catalysts, such as Ni and Fe, are active in their metallic state and hence are prone to coarsening and support interactions at the elevated temperatures required for CVD. We recently demonstrated that nano-particulate zirconia catalyses CNT growth at moderate temperatures, whereby it neither reduces to a metal nor forms a carbide. The low reactivity and limited restructuring of oxides promise a high level of control for the CVD process. We propose to study a range of oxides as CVD catalysts. We plan to use in-situ X-ray photoemission spectroscopy and environmental transmission electron microscopy to explore the mechanism(s) of graphene formation and nanotube nucleation on pre-treated oxide films and size-selected oxide nanoparticles. We will analyse the chiral selectivity of oxide-assisted CNT CVD and explore the possibility of large area graphene CVD on oxide films.