Synthesis of Carbon Nanotubes and its Applications in Composites and Field Emission Light

Abstract

Two processes, the floating catalyst chemical vapor deposition (CVD) process and the rapid heating and cooling (RHC) process, were adopted for synthesizing single walled carbon nanotubes (SWNTs) and multi-walled carbon nanotubes (MWNTs). Batch production of SWNTs and MWNTs with the diameters of 0.8~1.5 nm and 15~40 nm, respectively, were prepared using the floating catalytic chemical vapor deposition (CCVD) process. The production rate is 70±20 mg every 10 minutes. The as-synthesized carbon nanotubes (CNTs) were used for fabricating carbon nanotubes reinforced composites and field emitter for lighting. On the study of nano-composites, around 70% enhancement of tensile strength was detected when 1.5 wt% MWNTs in the form of network structure were introduced to the phenolic matrix. Comparisons on the mechanical properties of the composites reinforced with the network MWNTs and SWNTs were made. Microstructures of the MWNTs and SWNTs were studied by Field Emission Scanning Electron Microscope (FESEM) and High Resolution Transmission Electron Microscope (HRTEM). In the RHC process for fabricating the device for lighting, the carbon nanotube array was grown on a silicon substrate which was pre-coated with a catalyst thin film. The synthesis process was performed in a thermal CVD chamber equipped with a rapid heating apparatus. The as-synthesized CNT array was then transferred onto the substrate which was coated with silver paste. After heat treatment, field emission properties of the CNT-based cathode were tested, high current density of 35 mA/cm2 and low turn-on voltage of 0.65 V/μm were achieved in this work.