Joining cross-stacked carbon nanotube architecture with covalent bonding
R Li and WB Gong and QA He and QW Li and WB Lu and WJ Zhu, APPLIED PHYSICS LETTERS, 110, 183101 (2017).
Carbon nanotubes (CNTs) have superior mechanical properties that make them highly attractive for high performance bulk structures such as CNT fibers and films; however, the weak wan der Waals interaction between CNTs gives degraded strength and modulus, forming covalent bonding between CNTs which is considered to be highly promising but remains a considerable challenge due to the inert nature of the carbon surface. An appropriate electron-beam, as yet, has been used to introduce covalent bonding but limited to CNT bundles. Here, we used a spinnable CNT array to form a cross-stacked CNT architecture first, a bulk film, and proved that sp(3) covalent bonding can be directly formed between cross-stacked CNTs under high pressure at appropriate temperatures via a laser heated diamond anvil cell method. The Raman spectrum and molecular dynamic simulations were used to probe and interpret the bonding formation process, respectively. It was found that under 30 GPa with the temperature of 765-1345 K, sp(3) covalent bonding was mainly formed in the cross-stacked region. We anticipate that the formation of sp(3) covalent bonding between CNTs under high pressure could offer a general pathway to enhance the performance of nano-carbon based materials.
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