中文摘要
碳纳米管的结构决定其性质和选择性应用，有意识地调控碳纳米管的结构具有重要意义，这有赖于对其形成机理的充分认识。碳纳米管通常是在金属催化作用下生长，而科学界一直对此催化作用机理缺乏清楚的认识。金属常被认为是唯一的催化组元，完全忽视了金属催化过程中可能的碳自身的作用。最近，我们提出并实验验证了气-气过程中碳纳米管的"颗粒-线-管"逐级进化机理。在这一新的认识基础上，本项目着重针对一些重要问题进行了深入研究：对浮游化学气相沉积和气-固化学气相沉积过程的研究，进一步证实了"颗粒-线-管"进化机制的普适性；确认了金属催化碳纳米管形成过程中碳的自作用；在该机理的指导下成功地将碳纳米颗粒转化为碳纳米管，形成了无金属催化剂固相合成碳纳米管的新技术途径；通过引入氮元素和氯元素，控制性合成出碳纳米管和石墨烯；从热力学和动力学控制的角度初步提出了化学气相沉积过程中各种碳纳米结构的进化关系图。以上研究结果进一步深化了对化学气相沉积过程中碳纳米管形成机制的认识，并且一些新的实验结果为更深入地洞察碳纳米管催化形成机制及不同碳纳米结构的形成过程提供了新的信息，同时在技术上探索了对碳纳米管进行结构调变的可能性。
英文摘要
It is very important to modulate the strucutre of carbon nanotubes (CNTs) since the properties and applications of CNTs are determined by their structures. Achieving this goal depends on fully understanding of the formation mechanism of CNTs. CNTs is generally catalyzed by metal catalysts, but it is still lack of a clear perspective of the metal-catalytic growth mechanism up to now. For the metal-catalytic growth mechanism, metals were considered as the only active component, the functions of carbon which possibly exists during the metal-catalytic synthesis process of CNTs was completely neglected. Recently, we have proposed and experimentally proved that in a gas-gas synthesis process, CNT formation follows a "particle-wire-tube" (PWT) stepwise evolution mechanism. Based on this new knowledge, the research project focuses mainly on several key issues: studies on the floating chemical vapor deposition (CVD) and gas-solid CVD processes further confirmed that the PWT evolution mechanism is gnerally applicable to CNT formation in CVD processes; the functions of carbon were identified in the metal-catalytic process; with the PWT mechanism as theoretical guidance, carbon nanoparticles (CNPs) were successfully transformed into CNTs, providing a new technical approach to synthsize CNTs through solid-phase transformation without using metal catalysts; CNTs and graphenes were controllably synthesized through introducing nitrogen and chlorine elements; preliminary relationships of different carbon nanostructures were proposed on the basis of their formation kinetics and thermodynamics. These results give us an indepth understanding of the CNT formation mechanism in CVD processes. Moreover, some new experimental phenomena prove new information to discern the formation mechanism of CNTs and other carbon nanostructures. Meanwhile, the feasibility of modulating structures of CNTs was technically explored.
结题摘要
碳纳米管的结构决定其性质和选择性应用，有意识地调控碳纳米管的结构具有重要意义，这有赖于对其形成机理的充分认识。碳纳米管通常是在金属催化作用下生长，而科学界一直对此催化作用机理缺乏清楚的认识。金属常被认为是唯一的催化组元，完全忽视了金属催化过程中可能的碳自身的作用。最近，我们提出并实验验证了气-气过程中碳纳米管的"颗粒-线-管"逐级进化机理。在这一新的认识基础上，本项目着重针对一些重要问题进行了深入研究：对浮游化学气相沉积和气-固化学气相沉积过程的研究，进一步证实了"颗粒-线-管"进化机制的普适性；确认了金属催化碳纳米管形成过程中碳的自作用；在该机理的指导下成功地将碳纳米颗粒转化为碳纳米管，形成了无金属催化剂固相合成碳纳米管的新技术途径；通过引入氮元素和氯元素，控制性合成出碳纳米管和石墨烯；从热力学和动力学控制的角度初步提出了化学气相沉积过程中各种碳纳米结构的进化关系图。以上研究结果进一步深化了对化学气相沉积过程中碳纳米管形成机制的认识，并且一些新的实验结果为更深入地洞察碳纳米管催化形成机制及不同碳纳米结构的形成过程提供了新的信息，同时在技术上探索了对碳纳米管进行结构调变的可能性。