Effects of compressive strains on electrical conductivities of a macroscale carbon nanotube block

Abstract

A macroscopic block ͑ϳ9 mm 3 ͒ of aligned carbon nanotubes ͑CNTs͒ was grown by chemical vapor deposition and its simultaneous electrical conductivity and compressive strain responses were measured parallel and perpendicular to the CNT alignment. The block exhibits elastic moduli of 0.9 and 1.6 MPa for compressive strain of Ͻ20% in parallel and perpendicular configurations, respectively. The electrical conductivity increases with increasing compressive strain in both configurations. The reversible electrical conductivity and compressive strain responses of block is attributed to elastic bending of CNTs. These excellent properties of CNT block can be used in compressive strain sensing applications.

Multiscale Mass-Spring Models of Carbon Nanotube Arrays Accounting for Mullins-like Behavior and Permanent Deformation

“…We already noted that the assumption (A1) introduced in section 2.2 implies that the phases (a) and (b) of the microscopic response ( Figure 2 It is known, however, that real CNT foams exhibit a gradient in density along the height of the tubes, which typically increases from the base to the top (e.g., [29,18]); and Mullins-like behavior characterized by different stiffness during loading and unloading [21]. In particular, the density gradient typically induces bottom-totop increasing local buckling loads and progressive tube collapse starting from the bottom [6,18].…”

Strain sensing using a multiwalled carbon nanotube film

“…Pushparaj et al [10] discovered the fully recoverable electrical conductivity and compressive strain relationship by conducting compressive tests on a macroscopic MWCNT block. Zhang et al [11] studied the strain-sensing capabilities of MWCNT/ polycarbonate composites.…”

Visible iridescence from self-assembled periodic rippling in vertically aligned carbon nanotube forests

“…1͑a͒, which appear similar to previous reports. [2][3][4][5][6][7][8][9][10] Here, ripples form spontaneously during growth, likely due to a growth rate difference between different nanotubes in the forest, 3,4 which in turn causes a compressive strain that bends the nanotubes. It is known that growing nanotubes exert a mechanical force, 7 which likely causes the compressive strain.…”

“…The presence of strain is also suggested by the ripples generated by intentional compression of forests. [7][8][9][10] The periodic nature of the ripples is likely due to the balance between the stiffness of the nanotubes that resists bending and the van der Waals interaction between nanotubes. The van der Waals interaction is also responsible for the long range synchronization of the amplitude and the wavelength.…”

“…[2][3][4][5][6] Ripples can also be obtained by compressing a forest along the axis of the nanotubes, either during growth, 7 or postgrowth. [8][9][10] Iridescence from periodic arrangements of individual vertically aligned multiwalled nanotubes on a substrate [11][12][13] and periodic arrangements forests on a substrate 14 has previously been observed. Here, it is the rippled structure of the forest itself that causes the iridescence, not their arrangement on the substrate.…”