Synthesis Of Vertically Oriented Carbon Nanotubes Array On Vermiculite Substrate

Vertically arranged nitrogen-doped carbon nanotube arrays(VA-NCNTs)have attracted much attention,which have wide applications in many fields.However,the efficient synthesis of VA-NCNTs has always been a challenge.In this thesis,a simple method for obtaining high-quality VA-NCNTs between vermiculite layers using horizontal chemical vapor deposition(CVD)is proposed.We use layered compound vermiculite as a catalyst carrier,iron and molybdenum active metals are evenly distributed between the vermiculite layers,and melamine as a single carbon and nitrogen source to synthesize nitrogen-doped carbon nanotube array with relatively uniform length and diameter in one step.In details,it can be divided into two parts:1.The catalyst is the key parameter for the preparation of carbon nanotubes.It is very important to understand the influence of the process parameters of the catalyst preparation on the carbon product.This study proved that the catalyst active metal loading and the catalyst calcination temperature are the key parameters that affect the morphology and quality of carbon nanotube arrays.Scanning electron microscopy(SEM)images show that the optimum ratio of catalyst support and transition metal loading is 5:1 The metal loading directly affects the number of active sites of the catalyst,while the firing temperature affects the interlayer spacing of the vermiculite layer and the length of the carbon nanotube array,the optimal calcination temperature of the catalyst for the growth of the carbon nanotube array at 800°C.2.Through high temperature decomposition of nitrogen-rich melamine,under the catalysis of Fe/Mo/vermiculite catalyst,horizontal chemical vapor deposition method is used to synthesize nitrogen-doped carbon nanotube arrays perpendicular to the vermiculite layer.The influence of temperature on the morphology and quality of carbon nanotube array fibers is explored by changing the growth temperature.The results show that during the CVD synthesis process,VA-NCNTs are very sensitive to temperature changes,and in our experiment the optimal growth temperature is 800°C.At this temperature,the length and diameter of VA-NCNTs are relatively uniform.In addition,the arrangement of CNTs,Diameter,nitrogen content and type of nitrogen function can all be modified by temperature.This work helps to study the influence of growth temperature on the morphology of the prepared CNTs and provides a potential method for the controlled mass production of oriented NCNTs.