Engineering news
Researchers from several Russian universities have collaborated to demonstrate that an ultra-strong material can be produced by ‘fusing’ multi-wall carbon nanotubes (MWCNTs) together, the findings published in Applied Physics Letters.
Carbon nanotubes have a wide range of commercial applications due to their mechanical, thermal and conduction properties. They are used in batteries and accumulators, tablet and smartphone touch screens, solar cells, antistatic coatings, and composite frames in electronics.
A material of that kind is strong enough to endure very harsh conditions, making it useful for applications such as the aerospace industry, according to the researchers.
The authors of the paper performed a series of experiments to study the effect of high pressure on MWCNTs. A shear diamond anvil cell (SDAC) was used for the pressure treatment of the nanotubes. The experiments were performed at pressures of up to 55 GPa, which is 500 times the water pressure at the bottom of the Mariana Trench. The cell consists of two diamonds, between which samples of a material can be compressed. The sample is subjected to pressure that has both a hydrostatic and a shear component, meaning the stress is applied both at a normal and parallel to its surface.
Computer simulations showed that the two types of stress affect the structure in different ways. The hydrostatic pressure component alters the geometry of the nanotube walls in a complex manner, whereas the shear stress component connects them to the neighbouring carbon tubes by means of covalent bonding as a result of the structural rearrangements on their outer surfaces. The inner concentric nanotubes retain their structure by shrinking under pressure and restoring their shape once the pressure is released.
Professor Mikhail Y. Popov of the Department of Molecular and Chemical Physics at MIPT, and head of the Laboratory of Functional Nanomaterials at TISNCM, said: “These connections between the nanotubes only affect the structure of the outer walls, whereas the inner layers remain intact. This allows us to retain the remarkable durability of the original nanotubes.”
This study demonstrates the possibility of covalent intertube bonding giving rise to polymerised multi-wall nanotubes, that can be cheaper to produce than their single-wall counterparts.
The researchers involved were from the Moscow Institute of Physics and Technology (MIPT), Technological Institute for Superhard and Novel Carbon Materials (TISNCM), Lomonosov Moscow State University (MSU), and the National University of Science and Technology MISiS.