Feedstock and byproduct diffusion in the root growth of aligned CNT arrays was discussed in this work. A non-dimensional modulus was proposed to differentiate catalyst-decay controlled growth deceleration from diffusion controlled one. It was found t
hat aligned MWNT arrays are usually free of feedstock diffusion while SWNT arrays are usually facing strong diffusion limit. The present method can also be utilized to predict the maximum length that CNT forest can grow in certain CVD process.
A novel strategy for the large scale and continuous production of aligned carbon nanotube arrays using millimeter-diameter spheres as growth substrates is reported. The present technique is more productive than the conventional process on flat wafers
because of the higher available growth surface and the good fluidity of the spherical substrates. It can be adapted for the industrial production and application of aligned carbon nanotube arrays with lengths up to millimeter.
By sequential feeding of catalyst materials, it is revealed that the active growth sites are at the bottom of the carbon nanotubes (CNTs), and that catalyst particles are constantly encapsulated into nanotubes from the bottom. This gives a better ins
ight into the mechanism of CNT formation and on ways to control the growth process. CNTs encapsulated with different materials should enable the study of their electronic or magnetic properties, with potential applications as building blocks for nanoelectronics and as fillers in composites for electromagenetic shielding.
