scaled-up synthesis; reacting flow modeling; vertically aligned carbon nanotube; catalyst size matching; temperature gradient chemical vapor deposition
Celebi Kemal, Yang Ning, Cole Matthew T., Teo Kenneth B. K., Park Hyung Gyu (2016), Graphene Synthesis by Chemical Vapor Deposition on Copper, in Aliofkhazraei Mahmood , Gervasoni Juana L. , Ozkan Cengiz S. , Mitura Stanislaw , Ali Nasar, Milne William I (ed.), CRC Press, N.A., 225.
Buchheim Jakob, Wyss Roman M., Kim Chang-Min, Deng Mengmeng, Park Hyung Gyu (2016), Novel Graphene Membranes - Theory and Application, in Singh Rajindar, Hankins Nick (ed.), Elsvier, N.A., 371.
Vertically aligned carbon nanotubes (VA-CNTs) pose an excellent opportunity stemming from the properties of one-dimensional graphitic nanotubes, individual and collective, which opens new avenues to the carbon nanotube applications. To fulfill the demands of various target applications, much of the current research has focused on the efficient and controlled synthesis of the carbon nanotube forests, understanding and tailoring many aspects of the growth and characterizing the properties of the resultant structures. We have prepare independent studies on the control of acetylene-based precursor thermal rearrangement and catalyst size matching with the substrate asperities, for the diameter-controlled VA-CNT growth. The chemical vapor deposition (CVD) approach we take bases its unique controllability on the use of dual heaters that can generate temperature gradient in the carbon precursor gas mixture between gas injector and catalysts. This single-chamber setup allowed for various reactions of acetylene thermal rearrangement right atop the catalysts, without potential loss of benign yet shortly living intermediate species. Thereby, we could see potential of controlling the VA-CNT growth rate (efficiency) with additionally possible wall number tailoring, on the thick (20 nm) catalyst system. Independently, catalyst size matching with the substrate asperities showed great feasibility for the CNT diameter control by achieving sub-2-nm diameter control in the millimeter-long VA-CNT with no use of moisture or any other additive.Here, we propose the one-chamber method of enhancing the growth efficiency and diameter control, a method we named temperature gradient (TG) CVD. A systematic study is prepared for probing the VA-CNT growth behavior on sub-1-nm Fe and Fe-Mo catalyst systems in the TG CVD parametric window. Catalyst size matching will be carefully studied to extend the envelope of the method. Reacting flow modeling incorporating more than 200 possible reactions will be carried out in order to probe the gas-phase pyrolysis, well known yet difficult to measure, in a highly cost-effective way. Obtained data and simulation results will allow us to create new knowledge on the diameter-selective VA-CNT growth via the single-chamber TG CVD. We will finally apply this knowledge to the scaled-up synthesis of VA-CNTs up to 10 centimeters in substrate dimension. Success of our project will lend the combined methods of TG CVD and catalyst size matching immediate adaptability to industrial applications in need of VA-CNTs with tailored morphology and properties.