高压下碳纳米管限域分子体系的结构相变及其超硬相研究

Design and synthesis of new sp3-hybridized carbon allotropes with desired structure and property has always been one of the most important topics in condensed matter physics and materials science. However, achieving the novel high-pressure carbon phase which can be preserved back to ambient conditions remains a great challenge. In this proposal, we investigate the high-pressure behaviors of the confined systems of carbon nanotubes acted as building block and featured by the easy formation of the polymerization reaction and the interlinked structures under high pressure due to the confinement effect and the flexible carbon bonds. Combining in situ high pressure Raman spectroscopy with synchrotron X-ray diffraction, we aim to obtain the structural evolution process, study the effect of the dimension and shape of confined molecules on the structural transition, and reveal the phase transformation mechanism under extreme conditions. Also, we focus on the formation of pressure-induced superhard carbon phases recovered back to ambient conditions in these one-dimensional confined compounds. Based on the theoretical simulations, we will resolve the crystal structures, study the mechanical and electrical properties, and establish the evolution path of superhard phase driven by pressure. These findings not only can help us understand deeply their various properties and reveal the mechanism of phase transformation for nanoconfined molecular system, but also provide a new strategy to construct the novel carbon structures with desired properties.

制备具有新型结构和优异性能的非金刚石相、全sp3杂化成键的新型碳材料一直是凝聚态物理和材料科学研究领域的前沿课题，而实现高压相的sp3碳材料截获至常压条件仍是本领域的难题和挑战。针对以上问题，本项目利用碳纳米管限域全碳分子体系因纳米限域效应和碳元素灵活的成键类型在高压下易于产生聚合和共价键连行为的特点，以此作为初始碳源开展高压及高温高压研究。拟采用高压原位拉曼散射、同步辐射X射线衍射等实验方法，研究填充分子尺寸和形状对限域体系在极端条件下相变行为的影响，揭示纳米限域条件下压致聚合规律及相变机制，寻找新型sp3超硬碳相形成的条件及稳定结构，并截获至常压。结合理论计算确定新相的结构，研究其力学和电学等特性，理清结构与性质之间的关系，揭示高压相变的物理图像。本项目的开展将加深碳纳米管限域体系作为基本构筑单元全新的物理相变规律和新奇物理特性的认识，为获得新型功能碳材料提供思路。

碳的高压研究中，初始碳材料的高压相变及其高压相保留至常压条件下是困扰学术界的难题。针对以上问题，本项目提出设计碳纳米管限域分子复合结构体系为前驱体，利用高压技术结合限域效应协同作用，获得了限域于碳纳米管内一维碳链在高压下的结构相变的物理机制和带隙演化规律，澄清了前人关于一维碳链高压下结构变化的争议；利用激光加热碳纳米管阵列前驱体实验上合成了金刚石/石墨复合结构材料，为新型功能碳材料的制备提供思路；此外，结合晶体结构预测软件和第一性原理计算，预测了几种稳定的且硬度媲美金刚石的全sp3杂化超硬碳结构；进一步将研究拓展到零维荧光碳纳米点，采用纳米限域策略，实现了荧光增强且室温保留的碳纳米点材料，为设计构筑新型刺激响应发光材料开辟了新途径。在项目资助下，共发表国内外SCI论文15篇，包括本专业领域专业权威期刊Nano Letter （1篇），Light: Science Applications （1篇），Advanced Science（1篇），Nano Research（1篇），Carbon （3篇）和Journal of Physical Chemistry Letters （1篇），申请国家发明专利3项。