Bio-Inspired Method to Improve the Carbon Nanotube Adhesion Strength Onto Substrates

A bio-inspired method involving the deposition of a carbon nanolayer after the growth of carbon nanotubes (CNTs) to improve the CNT adhesion onto substrate is proposed. CNTs were synthesized on micro-spherical alumina particles by a liquid injection chemical vapor deposition (CVD) process. Carbon nanolayers were deposited in a controlled way using the same CVD setup under different conditions. Thermogravimetric analysis, electron energy loss and Raman spectroscopies indicated that the deposited carbon shell was highly oriented and could be assimilated to graphite or few layer graphene being less-ordered than the structure of the as-grown CNTs. Electron microscopy observations showed that the CNT roots were embedded within the deposited carbon shell on the substrate. The CNT adhesion onto the substrate was investigated by both sonication in buffer solution and three-roll milling composite processing. Results revealed that the amount of CNTs remaining after each test obviously increased for the carbon shielded samples. This was a significant improvement of adhesion compared to preparations not undergoing carbon deposition after CNT growth, where almost no CNTs remained. The effect of the carbon shell on the bulk electrical conductivity was also examined and discussed.