Abstract
Imogolite nanotubes (INTs) display a range of useful properties and provide an ideal material system to study the assembly of nanomaterials into macroscopic fibers. A method of wet spinning pure, binder-free imogolite fibers has been developed using double-walled germanium imogolite nanotubes. The nanotube aspect ratio can be controlled during the initial synthesis and is critical to the spinning process. Fibers made from short nanotubes (<100 nm) have very low gel strengths, while dopes with longer nanotubes (500–1000 nm) are readily spinnable. The tensile behavior of the resulting imogolite nanotube fibers is strongly influenced by relative humidity (RH), with a modulus of 30 GPa at 10% RH compared to 2.8 GPa at 85% RH, as well as a change in failure mode. This result highlights the importance of inter-nanotube interactions in such assemblies and provides a useful strategy for further exploration. Interestingly, in the absence of a matrix phase, a degree of misorientation appears to improve load transfer between the individual INTs within the porous fiber, likely due to an increase in the number of interparticle contacts. Imogolite nanotubes are an appealing analogue to other nanotube fiber systems, and it is hoped that learnings from this system can also be used to improve carbon nanotube fibers.
Highlights
Nanotubes and nanorods are promising candidates for producing high-performance fibers due to their excellent intrinsic mechanical properties and compatible one-dimensional morphology
Most studies have focused on carbon nanotube (CNT)-based fibers, using both dry and wet spinning methods;[1−4] fiber properties have typically been improved by increasing the aspect ratio and alignment of the nanotubes
Www.acsami.org ratio rods, the load can be supported by mechanical interlocking, which occurs through a jamming transition when the number of independent contacts per rod exceeds a critical value of around 10.55,56 This mechanism of load transfer has been observed in systems across a variety of length scales including bird nests, bamboo skewers, and colloidal gels.[57−59] As the number of contacts between rigid rods increases with increased misorientation,[60] it is expected that jamming occurs more frequently in the less aligned Imogolite nanotubes (INTs) fibers and leads to more efficient stress transfer within the fiber and a higher modulus
Summary
Nanotubes and nanorods are promising candidates for producing high-performance fibers due to their excellent intrinsic mechanical properties and compatible one-dimensional morphology. Ratio rods, the load can be supported by mechanical interlocking, which occurs through a jamming transition when the number of independent contacts per rod exceeds a critical value of around 10.55,56 This mechanism of load transfer has been observed in systems across a variety of length scales including bird nests, bamboo skewers, and colloidal gels.[57−59] As the number of contacts between rigid rods increases with increased misorientation,[60] it is expected that jamming occurs more frequently in the less aligned INT fibers and leads to more efficient stress transfer within the fiber and a higher modulus The deformation of these fibers may be considered as analogous to the shear of granular assemblies of frictional rigid rods. With a composite matrix,[28] a more conventional increase in mechanical properties with alignment can be anticipated
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