Event Information
Synthesis and Mechanistic Study of Carbon Nanotubes by Chemical Vapor Deposition Methods
- Abstract:
Chemical vapor deposition (CVD) is a versatile method for materials preparation. Materials from films to nanostructures can be obtained by tuning the parameters of CVD method. In the field of one-dimensional nanostructure, CVD is the most extensively employed method. This defense presentation is focused on synthesis of carbon nanotubes (CNTs) by CVD method as well as the growth mechanism.
The presentation consists of three parts of work. The first and second parts are focused on the synthesis of bulk CNTs with less impurity. In the first part, synthesis of few-walled carbon nanotube (FWNTs) with ethanol as carbon source is explored. It is proved that addition of methanol to ethanol increases the purity of raw FWNT materials. Methanol acts as “carbonaceous impurities remover” to remove impurities deposit on MgO support and hinders the formation of such impurities during FWNTs growth. In the second part, double-walled carbon nanotubes (DWNTs) with high purity and small size distribution have synthesized with FeSi2 as catalyst. In FeSi2, iron is dispersed at atomic scale, thus it is possible to provide uniform iron particles for CNT growth. In the third part, a two-stage growth model for the growth of SWNTs is proposed, which may explain the low yield of SWNT growth in some early results. In this model, growth of SWNTs is divided into two stages, which are nucleation and growth stage. These two stages need different carbon feeding rate. To obtain high yield of SWNTs, different carbon feeding gases should be applied to different stages.
Ph.D. Defense Examination Seminar
Student Exams Seminar