Controllable Synthesis,Characterization, And Growth Mechanism Of High-Temperature One-Dimensional Nanomaterials In Si-C-N-W System

To apply high-temperature1-D nanostructures in the high-temperature structural materials, it is necessary to explore large-scale synthesis methods. For this reason, it is important to prepare1-D nanostructures with controllable and tunable properties, and study the microstructure and performance relationship.In this study, we have studied several high-temperature1-D nanostructures (Si3N4, SiC, amorphous CNT, and W) in Si-C-N-W system. In Chapter3, we studied the growth mechanism of W-catalyzed Si3N4nanowires via self-propagating high-temperature synthesis process (SHS), and found how W affects the morphology and structure of Si3N4nanowires. Finally we studied the elastic bending modulus of single Si3N4nanowires by in-situ TEM technology. In Chapter4, we prepared SiC nanowires in large scale by SHS process in Si-C-N system, and studied the catalyst effect of W and Ti, and found how PTFE affects the phase, morphology, microstructure, yields of SiC nanowires. Similarly, we also studied the elastic bending modulus of single SiC nanowires by in-situ TEM technology. In this chapter we reported a novel growth mechanism of W catalyzed SiC nanowires in Si-C-N system by HRTEM and EELS techniques, named "Intermediate template directed SiC nanowire growth in Si-C-N systems". Furthermore, we have confirmed the VLS growth mechanism of Ti catalyzed SiC nanowires in this system. In Chapter5, tunable amorphous CNT were prepared in large-scale by vacuum heating process. By adjusting the heating rate, amorphous CNT with different aspect ratios were prepared. We studied the growth mechanism of tunable amorphous CNT, and studied the crystallization behavior of amorphous CNT at high temperature. In Chapter6, W nanowires were prepared by using amorphous CNT as template, we studied the growth mechanism of this template assisted W nanowires...