{"id":1149,"date":"2010-07-01T14:29:06","date_gmt":"2010-07-01T18:29:06","guid":{"rendered":"https:\/\/wpmu2.mit.local\/?p=1149"},"modified":"2010-07-01T14:34:57","modified_gmt":"2010-07-01T18:34:57","slug":"1149","status":"publish","type":"post","link":"https:\/\/wpmu2.mit.local\/1149\/","title":{"rendered":"Growth and Characterization of Carbon Nanotube Carpets for Electrochemical Applications"},"content":{"rendered":"

Improvements in electrochemical devices for energy storage, such as in Li-ion batteries and ultracapacitors, are being aggressively investigated due to demand for small and lightweight batteries with high energy densities and capacitors for high power.\u00a0 There are many benefits to fabricating nanostructured electrodes for these devices [1<\/a>]<\/sup>.\u00a0 Carbon nanotube (CNT) arrays show immense promise as electrodes due to the high aspect ratios, electrical conductivity, and mechanical rigidity of CNTs.<\/p>\n

Carbon nanotubes are typically grown using transition metal catalysts, such as Fe.\u00a0 The catalyst morphology has a direct influence on the resulting nanotube diameter and areal density. We have demonstrated control of catalyst coarsening by changing the time of the introduction of H2<\/sub> during CVD growth for nanotubes grown on insulating substrates [2<\/a>]<\/sup>.\u00a0 This technique allows the modulation of tube properties and carpet morphology.\u00a0 Additionally, we have demonstrated low-temperature growth on conductive substrates, enabled by gas preheating [3<\/a>]<\/sup> and rapid sample insertion into the growth zone in concert with an appropriate catalyst-substrate combination [4<\/a>]<\/sup>.\u00a0 An example of crystalline tubes grown on conductive substrates is shown in Figure 1.<\/p>\n

In order to explore the effect of nanotube carpet density on electrochemical device performance, we mechanically densify nanotube carpets using a technique developed by Wardle et al. [5<\/a>]<\/sup>.\u00a0 This densification process is performed on CNTs grown on insulating substrates requiring the development of a process for transferring nanotubes to conductive substrates as illustrated in Figure 2.\u00a0 In addition to investigating densified nanotube carpets, we also plan to explore composite electrode structures for Li-ion batteries composed of CNT-supported nanoparticle Li intercalation materials.<\/p>\n\n\t\t