Quantitative nanoscopy: Tackling sampling limitations in (S)TEM imaging of polymers and composites

Gnanasekaran, Karthikeyan; Snel, Rcq Roderick; Friedrich, Heiner

doi:10.1016/j.ultramic.2015.10.004

Cited by 14 publications

(17 citation statements)

References 37 publications

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“…An assignment of the bright and dark stripes to either the benzene rings close to the cation binding site or the alkyl backbone could not be established. When imaging the striping pattern throughout the film, the smectic C orientation proposed in Figure B1 is clearly visible (Figure S8 and Movie S1, Supporting Information) …”

Section: Resultsmentioning

confidence: 99%

Nanohybrid Materials with Tunable Birefringence via Cation Exchange in Polymer Films

Oosterlaken

Rijt

et al. 2019

Adv Funct Materials

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In this work, a nanohybrid material based on a freestanding polymeric liquid crystal network capable of postmodification via cation exchange to tune birefringence is proposed. The smectic liquid crystal films can be infiltrated with a variety of cations, thereby changing the refractive indices (n e and n o ) and the effective birefringence (Δn) of the nanohybrid material, with reversible cation infiltration occurring within minutes. Birefringence could be tuned between values of 0.06 and 0.19, depending on the cation infiltrated into the network. Upon infiltration, a decrease in the smectic layer spacing is found with layer contraction independent of the induced change in birefringence. Potential applications are in the field of specialty optical devices, such as flexible, retunable reflective filters.

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Section: Resultsmentioning

confidence: 99%

Nanohybrid Materials with Tunable Birefringence via Cation Exchange in Polymer Films

Oosterlaken

Rijt

et al. 2019

Adv Funct Materials

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“…Analysis of 3D CNT networks presents unique challenges as they are sensitive to the electron beam and have very low contrast, especially when imaging thick TEM specimens that are required to analyze a representative volume of randomly ordered materials . To overcome these difficulties and to quantify the network topology, i.e., packing density, CNT–CNT contacts, and connectivity, which determine the final conductivity of the CNT network we employed electron tomography combined with model‐based image analysis.…”

Section: Resultsmentioning

confidence: 99%

A Unified View on Nanoscale Packing, Connectivity, and Conductivity of CNT Networks

Gnanasekaran

Grimaldi

With

et al. 2019

Adv Funct Materials

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The design of functional structures from primary building blocks requires a thorough understanding of how size, shape, and particle-particle interactions steer the assembly process. Specifically, for electrically conductive networks build from carbon nanotubes (CNTs) combining macroscopic characterization and simulations shows that the achievable conductivity is mainly governed by CNT aspect ratio, length dispersity and attractive interactions. However, a direct link between the actual 3D network topology that leads to the observed electrical conductivity has not been established yet due to a lack in nanoscale experimental approaches. Here it is shown experimentally for randomly packed (jammed) CNT networks that the CNT aspect ratio determines, as theoretically predicted, the contact number per CNT which in turn scales linearly with the resulting electrical conductivity of the CNT network. Furthermore, nanoscale packing density, contact areas, contact distribution in random and nonrandom configurations, and least resistance pathways are quantified. The results illustrate how complex nanoscale networks can be imaged and quantified in 3D to understand and model their functional properties in a bottom-up fashion.

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“…Xie et al [33] reviewed studies related to alignment of CNTs in a matrix, especially using force and magnetic fields, electrospinning and procedures involving liquid crystals. More recently, K. Gnanasekaran et al [15] quantified TEM images of spincoated latex/CNT composite films and could evidence CNT alignment along the spin-coating direction, providing that the measurements are carried out on large enough areas. In our case, the film was cast on glass using a Doctor Blade Film Applicator.…”

Section: Quantification and Control Of The Cnt Dispersion Statementioning

confidence: 99%

“…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. Alternatively, 2D images have been used to quantify the CNT orientation [15,16] or the mean distance between neighboring CNTs [17]. Although they could provide nice agreements with experimental data, the methods used could contain artifacts due to the use of 2D projections of a 3D volume.…”

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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Quantitative nanoscopy: Tackling sampling limitations in (S)TEM imaging of polymers and composites

Cited by 14 publications

References 37 publications

Nanohybrid Materials with Tunable Birefringence via Cation Exchange in Polymer Films

Nanohybrid Materials with Tunable Birefringence via Cation Exchange in Polymer Films

A Unified View on Nanoscale Packing, Connectivity, and Conductivity of CNT Networks

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

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