| AVS 58th Annual International Symposium and Exhibition | |
| Nanometer-scale Science and Technology Division | Thursday Sessions |
| Session NS-ThM |
| Session: | Molecular Assembly and Devices |
| Presenter: | Kyung Lee, The University of Texas at Dallas |
| Authors: | K.H. Lee, The University of Texas at Dallas D. Burk, The University of Texas at Dallas L.J. Overzet, The University of Texas at Dallas G.S. Lee, The University of Texas at Dallas |
| Correspondent: | Click to Email |
Spin-capable multi-walled carbon nanotube (MWCNT) forests that can form webs, sheets, and yarns provide a promising means for advancing various technologies [1-4]. The important factors enabling the growth of the spin-capable forests are still not well understood. Growing spin-capable CNT forests depends on several growth factors such as the catalyst film thickness, the growth temperature, and the carrier and reactant gases [5-9]. Other factors still remain to be investigated more thoroughly. These include the flow rate (or ratio) of the reactant gas, the reactant gas species, and the pressure.
Herein we show how both the spinning capability and morphology of MWCNT forests are changed significantly by controlling the acetylene (C2H2) concentration and the thermal ramp rate. The acetylene gas flow is varied in the range of 0.25 ~ 7.5 % in volume. The MWCNTs grown at C2H2 concentrations between 1.5 ~ 3.5 % are well-aligned and are spin-capable. The well-aligned forests have higher areal density and shorter distances between the CNTs caused by strong Van der Waals interactions. CNTs grown at C2H2 concentrations under 1.5 % or over 3.5 % are curled and have random orientation. The resulting forests have reduced areal density and have poor spinnability. The thermal ramp rate is varied from 30 oC/min to 70 oC/min. Only the CNT forests grown with 50 oC/min condition are well-aligned and spinnable due to high areal density and closer spacing between adjacent CNTs. This condition alone results in Fe nanoparticles which have the proper size and density to produce spin-capable CNT forests.
Figure 1 shows SEM images and picture of spin-capable CNTs grown at 1.5 vol.% of acetylene and 50 oC/min on 70kΩ/sq Fe film at 780oC for 5min with mixture of He, H2, and C2H2. The spinnable CNTs of 330 µm have good alignment which is dependent on the ability to form ribbons. From a 1 × 1 cm substrate, the CNTs can form a 4 m length sheet.
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