Investigation On The Catalyst Activity For The Growth Of Carbon Nanocoils And The Highly Efficient Synthesis Of CNCs With Small Coil Diameter

Carbon nanocoils (CNCs), as a new kind of three-dimensional carbon nano-materials, have outstanding electrical and mechanical properties, and excellent field emission characteristics. Because of these properties, CNCs have many potential applications, such as nanosprings,electron guns for flat panel field emission displays, electromagnetic wave absorbers and micro-sensors, etc. So far, highly efficient synthesis of CNCs was developed. However, since the as-grown normal CNC is larger than100nm, their graphitz is low, which limited their application. Hence, the multi-wall CNCs (MCNCs) should be synthitized, but large scale growth of MCNCs is difficult such as low production rate.We have investigated the relationship between the catalyst and the growth of CNCs. It is found that with the increase of deposition time the yield of CNCs gradually increased, while their growth rate decreased exponentially. The short reaction time would lead to the growth of CNCs with smaller coil diameters, however, CNCs with larger coil diameters are increased gradually after a long-time reaction. The Fe-Sn-O catalyst particles are not uniform in sizes. It is considered that CNCs with smaller/larger coil diameters can be synthesized from the smaller/larger catalyst particles. A further fitting of the growth curve indicates that the as-prepared catalyst particles have different activities. It can be inferred that catalyst particles with different sizes have different catalytic activities. The smaller catalyst particles have a higher activity but a shorter lifetime, and the coil diameter of CNCs synthetized from it is smaller.We also developed the method for high efficent synthesis of CNCs with small coil diameter. We limit the size of catalyst particles by using different substrate and find the optimized method for preparing the catalyst. It’s found that the porous silicon substrate can distribute catalyst particles uniformly. Silicon nanowire are also used as the substrate, however, most of the product are CNTs with line diameter from10to30nm. We prepare catalyst particles by spin-coating and sputtering in order to get smaller catalyst particles. And it’s found that the yeild of CNCs with small coil diameter by spin-coating method is random. However, the yeild of CNCs with small coil diameter is high,when we prepare the catalyst by sputtering Fe and Sn with particular arrangement.