Catalyst nanoparticle growth dynamics and their influence on product morphology in a CVD process for continuous carbon nanotube synthesis

Abstract

Extrapolating the properties of individual CNTs into macro-scale CNT materials using a continuous and cost effective process offers enormous potential for a variety of applications.The floating catalyst chemical vapor deposition (FCCVD) method discussed in this paper bridges the gap between generating nano-and macro-scale CNT material and has already been adopted by industry for exploitation. A deep understanding of the phenomena occurring within the FCCVD reactor is thereby key to producing the desired CNT product and successfully scaling up the process further. This paper correlates information on decomposition of reactants, axial catalyst nanoparticle dynamics and the morphology of the resultant CNTs and shows how these are strongly related to the temperature and chemical availability within the reactor. For the first time, in-situ measurements of catalyst particle size distributions coupled with reactant decomposition profiles and a detailed axial SEM study of formed CNT materials reveal specific domains that have important implications for scale-up.A novel observation is the formation, disappearance and reformation of catalyst nanoparticles along the reactor axis, caused by their evaporation and re-condensation and mapping of different CNT morphologies as a result of this process.

Agglomeration Dynamics of 1D Materials: Gas‐Phase Collision Rates of Nanotubes and Nanorods

“…An application of the collision kernel for rigid 1D materials is the process of self-assembled aerogel formation within a CNT reactor, which is of significant academic and industrial interest. [18,19,42,43] Despite the large number of studies on the nanotube aerogel process, [60] the lack of known collision rates between the nanotubes has hindered quantitative understanding of the bundle formation process, a precursor to aerogel formation. Figure 5a shows the production of nanotubes and resulting self-assembled aerogel formation within a continuous gas-phase chemical vapor deposition reactor.…”

“…Quantifying the range of collision kernels β ij in gas‐phase systems consisting of 1D materials gives new insights into the spontaneous formation of aerogels from 1D materials. These results are broadly applicable to all natural and anthropogenic 1D materials of similar geometries undergoing gas‐phase collisions . As such, we employ the term nanotube generally to represent 1D materials that may consist of nanorods, nanotubes, or chain‐like agglomerates with an axial length to diameter ratio > 10:1.…”

“…These results are broadly applicable to all natural and anthropogenic 1D materials of similar geometries undergoing gas-phase collisions. [19,42,43] As such, we employ the term nanotube generally to represent 1D materials that may consist of nanorods, nanotubes, or chain-like agglomerates with an axial length to diameter ratio > 10:1.…”

Effect of Hydrogen Concentration on the Growth of Carbon Nanotube Arrays for Gecko-Inspired Adhesive Applications

“…Presently, catalytic chemical vapor deposition (CVD) is the main preparation method for obtaining carbon nanotubes due to its many advantages such as simple processing, low technical cost, and high degrees of control and scalability [22,23]. The mechanism of CNT growth through CVD methods has been studied [24][25][26][27][28][29].…”

Quantitative and Controllable Growth of Carbon Nanotubes on Silicon Carbide Particles Via Chemical Vapor Deposition

“…And this method, without the damage of CNT, has been recognized to be more convenient than those methods mentioned above [12,13]. But until now, researches still focus on the matrix powder to disperse nanotubes, and then to fabricate composites directly, such as CNT/Al 2 O 3 , CNT/Al and CNT/Cu composite [14][15][16].…”