Macromol. Mater. Eng. 8/2017

Campo, Eva M.; Yates, Douglas M.; Berson, Benjamin; Rojas, Wudmir Y.; Winter, A. Douglas; Ananth, M.V.; Santiago-Avilés, Jorge J.; Terentjev, E. M.

doi:10.1002/mame.201770025

Cited by 3 publications

(3 citation statements)

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“…This has enabled the assembly of hierarchical structures in simple dry post drawing, and thus produces fibers with mechanical properties comparable to nature. Investigating fiber microstructure using a combination of 2D focused ion beam/scanning electron microscopy (FIB/SEM), [ 12 ] secondary electron hyperspectral imaging (SEHI), [ 13 ] and synchrotron ptychographic X‐ray computed tomography [ 14 ] confirming a previous hypothesis of a progressive stress‐induced phase transition in silks which enables structure development through gelation, fibrillation, and consolidation. [ 15 ]…”

Section: Introductionmentioning

confidence: 72%

Carbon Nanotubes Facilitate Silk Hierarchical Assembly by Dry Drawing

Wan,

Farr,

et al. 2024

Small Structures

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Biologically derived hierarchical structural materials not only boast energy‐efficient processing but also exhibit impressive mechanical performance. Silk stands as the gold standard in hierarchical fiber production, leveraging a unique combination of advantages. Nevertheless, the artificial replication of silk poses technical challenges related to precision processing and comprehensive molecular control. To address such issues, this study investigates the hierarchical assembly of solid regenerated silk in an air atmosphere, facilitated by the incorporation of carbon nanotube (CNT) seeding. Results obtained highlight that this CNT seeding facilitates multiscale structure development in response to post‐spin tensile stress. Such CNT bridged structure assembly bypasses some natural processing control variables (pH, ions) and the necessary solvent immersed state for conventional silk post‐drawing. Combining secondary electron hyperspectral imaging and 3D synchrotron X‐ray ptychotomography, this study reports silk protein conversion from a disordered as‐spun state to a longitudinal orientated semi‐crystalline nano structure during drawing. The development of microscale structure during the drawing process is attributed to the presence of CNTs, yielding mechanical properties comparable to, and frequently surpassing, those exhibited by native fibers. These findings collectively propose a framework for exploring novel processing routes and offer a practical means controlling self‐assembly in silk materials.

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Section: Introductionmentioning

confidence: 72%

Carbon Nanotubes Facilitate Silk Hierarchical Assembly by Dry Drawing

Wan,

Farr,

et al. 2024

Small Structures

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“…Electron tomography is undoubtedly the most pertinent technique able to perform a three-dimensional analysis of polymer / CNT microstructures. Few electron tomography studies dealt with the characterization of polymer / CNT nanocomposites [9,10,11,12,13]. To our knowledge, only Natarajan et al [14] reported a quantitative analysis of the tomograms and related the evolution of several morphological parameters with the CNT volume fraction in epoxy-based nanocomposites.…”

Section: Introductionmentioning

confidence: 99%

Quantitative analysis of grafted CNT dispersion and of their stiffening of polyurethane (PU)

Jomaa

Roiban

Dhungana

et al. 2019

Composites Science and Technology

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Electroactive devices are developed for energy conversion purposes. In particular, polyurethanes (PU) are lightweight and flexible materials, which have demonstrated their ability to convert electrical energy into mechanical energy (actuation by electrostriction) and vice-versa (energy harvesting). It has been shown that energy conversion efficiency can be increased by incorporating carbon nanotubes (CNTs) into a PU matrix. The counterpart of this improvement is the stiffness increase, which in turn limits the electrostriction efficiency. On the other hand, it is well known that CNTs are hardly dispersed in a polymeric matrix, and that the interfacial adhesion strength is generally poor. One solution to improve both dispersion and adhesion consists in grafting polymeric chains onto the CNT surfaces. As most of the works dedicated to improve material electroactivity are mainly empirical, this work aims to (i) better characterize these material microstructures by electron tomography, through the measurement of the CNT tortuosity, the CNT-CNT minimum distance and the number of their contacts, and (ii) and to predict their mechanical stiffness from these microstructural data. From electron microscopy observations of the studied materials, CNTs can be assumed to be composed of successive stiff rods of measured length and orientation, linked together by flexible kinks. Their mechanical stiffening effect in PU is, simply and in an original way, evaluated using the classical analytical equations derived by Halpin and Kardos, accounting for the microstructural parameters determined by electron tomography. It appears clearly that, due to their tortuosity and despite their ultra-high longitudinal stiffness, CNTs only poorly stiffen soft matrices. Fully stretching 10 m long nanotubes increases the composite modulus by almost 10 for a fraction of only 2 vol.%.

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“…Improved applications also need more sophisticated and efficient characterization and analysis tools for nanofibrous materials to be designed and developed. A relevant example is provided by multimodal focused ion beam imaging, which is used for tomographic reconstruction and phase‐separation analysis of blends and carbon nanotubes in electrospun composites . The polymer stretching behaviour during electrospinning is similarly important, being at the base of the stretched conformation of macromolecules along the longitudinal axis of nanofibers.…”

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confidence: 99%