Numerical Simulation Of The Chemical Vapor Deposition Process Of Carbon Nanotubes

Carbon nanotubes(CNTs) have been widely used in many fields owing to unique electron transport, mechanics, and gas adsorption properties. The main technology for the mass production of carbon nanotubes is the chemical vapor deposition(CVD) technique. Many process parameters have important effects on the deposition rate, making the CVD process much more complex. Optimizing and improving the CVD process by the traditional method of trial and error are often expensive and time consuming. An important optimization step is modeling of the growth, where computer simulations can be used to achieve a deeper understanding of the deposition process, making development faster and less expensive and showing important guide significance to the experimental study.A complete two-dimensional(2D) model for the growth of CNTs in the horizontal hot-wall reactor is presented, incorporating flow, heat transfer, mass transfer, gas chemistry and surface chemistry. The commercially fluid dynamics(CFD) is used to simulate the CVD process of CNTs for analyzing the process of acquiring the initial carbon source. The influences of different reaction conditions and the composition of the internal structure of the Nozzle CVD reactor on the carbon deposition rate are discussed. The following conclusions can be drawn from the present study:(1) The carbon deposition rates at different inlet gas velocities of the CVD reactor is analyzed. The results show that with the increase of the inlet gas velocities, the carbon deposit growth rate at each stage is different. The carbon deposition increases significantly as the inlet gas velocity is increased from 0 to 5m/s, and then it changes slightly with the further increase of the velocity.(2) The carbon deposition rates at different temperature of the CVD reactor is analyzed. The result shows that as the selection of optimum reaction temperature is determined by the product of the amount of carbon deposition and conversion rate of the carbon nanotubes by comparing the change of the reaction temperature and the conversion rate of carbon nanotubes under different temperature.(3) The change of gas supply as well as the inlet gas temperature of the CVD reactor have influence on the carbon deposition rate in the process of reaction which is analyzed. The results show that the carbon deposition rate increases with the increase of gas supply as well as the inlet gas temperature, and the carbon deposit growth rate is similar at each stage.(4) The impact on the carbon deposition rate is analyzed in the process of reaction with the structure of the Nozzle CVD reactor. The results show that has little effect on the mass fraction of species distribution in the reactor without nozzle, but the chip has a certain influence on the species distribution in the reactor with nozzle, the chip can increase the efficiency of deposition in the reactor with nozzle. It can be concluded from the simulation results that both of the nozzle and chip will promote the carbon deposition rate in a reactor. The effect of the height of the chip on the carbon deposition rates is also analyzed. The results show that with the increase of the height of the chip, the carbon deposit growth rate at each stage is different. The carbon deposition increases significantly when the height of the chip is less than half of the diameter, and then it changes slightly with the further increase of the height of the chip.