MXene/Carbon Nanotube Composite Yarn for Energy Storage and Electromagnetic Interference Shielding

Carbon Nanotube (CNT) yarns have gained increased attention in structural health monitoring due to their multifunctional properties. They exhibit a unique change in their resistivity when subjected to mechanical strain. This piezoresistive response can be tapped for sensing purposes. The objective of this study is to determine experimentally the piezoresistive response of CNT yarns that are embedded in a medium while subjected to tension, and compare it with that of the free or unconstrained CNT yarns. The constraint is achieved by embedding the CNT yarns in epoxy to produce coated CNT yarns and fiber monocomposite beams. Tensile tests were performed on the coated yarn while the monocomposites were subjected to both uniaxial and bending tests. The curves of the constrained CNT yarns are fairly linear and produce higher gauge factors than that of the free CNT yarn. Consequently, the piezoresistivity of the constrained CNT yarns is higher than that of the unconstrained CNT yarns. This difference between them may be explained by the lack of the effective slippage, fiber unraveling and subsequently, Poisson’s effect of the CNT yarn when integrated in the polymer. The composite samples tested under bending showed a higher gauge factor than under uniaxial tension. CNT yarns that were dipcoated in the polymer showed high fiber impregnation due to the yarns porous structure. However, they also showed improved strength, more linearity and higher piezoresistive response but lower strain to failure when compared to the uncoated CNT yarn.

Yarn supercapacitors are promising power sources for flexible electronic applications that require conventional fabric-like durability and wearer comfort. Carbon nanotube (CNT) yarn is an attractive choice for constructing yarn supercapacitors used in wearable textiles because of its high strength and flexibility. However, low capacitance and energy density limits the use of pure CNT yarn in wearable high-energy density devices. Here, transitional metal oxide pseudocapacitive materials NiO and Co3 O4 are deposited on as-spun CNT yarn surface using a simple electrodeposition process. The Co3 O4 deposited on the CNT yarn surface forms a uniform hybridized CNT@Co3 O4 layer. The two-ply supercapacitors formed from the CNT@Co3 O4 composite yarns display excellent electrochemical properties with very high capacitance of 52.6 mF cm(-2) and energy density of 1.10 μWh cm(-2) . The high performance two-ply CNT@Co3 O4 yarn supercapacitors are mechanically and electrochemically robust to meet the high performance requirements of power sources for wearable electronics.

Carbon nanotube (CNT) yarns are fiber-like materials that exhibit excellent mechanical, electrical and thermal properties. More importantly, they exhibit a piezoresistive response that can be tapped for sensing purposes. The objective of this study is to determine experimentally the piezoresistive response of CNT yarns that are embedded in a polymeric medium while subjected to either tension or compression, and compare it with that of the free or unconstrained CNT yarns. The rationale is the need to know the piezoresistive response of the CNT yarn while in a medium, which provides a lateral constraint to the CNT yarn, thus mimicking the response of integrated CNT yarn sensors. The experimental program includes the fabrication of samples and their electromechanical characterization. The CNT yarns are integrated in polymeric beams and subjected to four-point bending, allowing the determination of their response under tension and compression. The electromechanical data from a combined Inductance–Capacitance–Resistance (LCR) device and a mechanical testing system were used to determine the piezoresistive response of the CNT yarns. At a strain rate of 0.006 min−1, the gauge factor obtained under tension for a maximum strain of 0.1% is ~29.3 which is higher than ~21.2 obtained under compression. The CNT yarn sensor exhibited strain rate dependence with a gauge factor of approximately 23.0 at 0.006 min−1, in comparison to 19.0 and 1.3, which were obtained at 0.0005 min−1 and 0.003 min−1, respectively. There is a difference of up to two orders of magnitude in the sensitivity of the constrained CNT yarn under bending with respect to that of the free CNT yarn under uniaxial tension. However, the difference becomes smaller when the constrained CNT yarn was tested under uniaxial tension. This data and information will be used for future modeling efforts and to study the phenomena that occur when CNT yarns are integrated in polymeric and composite materials and structures.

This paper presents a study on the skin effect-related AC resistance of macroscopic scale carbon nanotube (CNT) yarn. The range of interest frequency in this study is up to 10 MHz which is considered conventional high-frequency power converters operating range. AC resistance of both CNT yarn and copper (Cu) wires are measured by impedance analyzer for the small-signal frequency-response. The 1-turn core-less layout of inductors made of both CNT yarn and Cu wire are implemented to eliminate the proximity effect and magnetic core. The measurement results are compared with the theoretical model results based on Bessel-Kelvin function. The results show that the increasing rate of AC resistance in CNT yarn is lower than in Cu wire as frequency increases so that it causes lower CNT yarn resistance at higher frequencies. It was found that the Cu wire measurement result follows the theoretical model whereas CNT yarn does not. Therefore, a new skin effect related AC resistance correction factor for CNT yarn is introduced. To verify the same trends in large signal level of current, conduction losses for both CNT yarn and Cu wire are tested as an inductor component in a power converter circuit working like a large signal generator. The losses were collected and presented for the same frequency range (between 1 and 10 MHz). The results show less losses with CNT yarn inductor. Finally, another CNT yarn-based inductor was constructed and tested in around 200 W power converter circuit. The results show 91.72% of high efficiency at 3.125 MHz switching frequency. The study shows that, for power converter circuits working in the range higher than 1 MHz, the CNT yarns are reasonable to replace Cu wires due to the lower skin effect- related losses.

Recent rapid advancements related to enhancing the material properties of carbon nanotube (CNT) yarns, which are composed of twisted nanoscale CNTs, have opened new possibilities for their application as reinforcing agents in composite materials. In this study, the failure behaviors of CNT yarns were examined in a polymer matrix environment under tensile loading using synchrotron radiation X-ray computed tomography (CT) and polarized light microscopy. Double-yarn fragmentation specimens, composed of two closely positioned CNT yarns embedded in parallel, were employed to examine the failure interactions between the CNT yarns. X-ray CT observations revealed that the fracture surfaces of the CNT yarns exhibited a high degree of irregularity, with cracks propagating into the surrounding matrix and some extending into the yarn bodies, thereby suggesting that the failure of CNT yarns involves both breakage and slippage of the CNTs. The investigation of yarn–yarn failure interactions revealed that ∼70% of the fractures observed in the CNT yarns occurred as coordinated fractures, which was clearly higher than the ∼20% observed without such interactions. This finding demonstrates that the failure behaviors of CNT yarns in the polymer matrix environment are governed by yarn–yarn interactions rather than by the statistical strength distributions of the yarns. These results provide valuable insights for researchers in the field of composite materials, ultimately promoting further advancements in the development of strength prediction models based on the actual failure behaviors of CNT yarns in the polymer matrix environment. • Failure of CNT yarns involves both breakage and slippage within a polymer matrix • Upon breakage, CNT yarn likely causes the premature fracture of neighboring yarns • Polymer matrix cause a unique CNT yarn failure, unlike in standard ambient conditions • Yarn–yarn interaction is a key mechanism in CNT yarn-polymer composites

Coiled structures made from polymer and Carbon Nanotube (CNT) yarns are used as artificial muscles, stretchable conductors, and energy harvesters. The purpose of this work is to present our latest understanding of the mechanical behavior of these CNT-based structures. CNT yarns are fabricated by inserting twists in sheets spun from CNT forests. Over twisting the CNT yarns results in coiled CNT yarns, similar to a spring where the spring radius is comparable to the diameter of the CNT yarn. In this study, we explain the development and validation of a viscoelastic model, to capture damping and hysteresis in CNT yarns under quasi-static and dynamic loads. Confirmation of linear viscoelastic behavior of CNT yarns can lead us to the development of a model for coiled CNT yarns. Coiled CNT yarns, on the other hand, show a complex non-linear viscoelastic behavior. Possible mechanisms responsible for this non-linear behavior are discussed.

How to overcome the electrical conductivity limitation of carbon nanotube yarns drawn from carbon nanotube arrays

Effect of twist on the electromechanical properties of carbon nanotube yarns

Carbon nanotube (CNT) yarns (CNTYs) are porous fibers with a myriad of applications based on their electrical response. This study presents an electrical finite element model of the cross section of CNTYs, comprising smaller hierarchical elements (CNT bundles) arranged in a hexagonal pattern. The model captures the most relevant mechanisms explaining the effect of porosity and resin infiltration on the electrical conductivity of the CNTY and reproduces experimental data. The porosity is generated with a random algorithm that avoids void clustering. The model assists in explaining factors that modify the electrical resistivity of the CNTY when a liquid polymer infiltrates it. The model suggests that the electrical resistivity of the CNTY increases in a sigmoidal fashion with increased porosity, with the highest electrical sensitivity occurring between 40% and 60% porosity. The experimental findings on the porosity effect are better reproduced if the bundle diameter concomitantly changes with the yarn's porosity. The CNTY's electrical resistivity strongly depends on the electrical resistivity of the infiltrating liquid and on the extent of infiltration. The outer 20–30% CNTY radius is the most sensitive to infiltration. High electrical sensitivity is predicted during the first polymerization stages of a thermosetting polymer resin infiltrating the CNTY.

Simulation of mechanical response of carbon nanotube yarns under uniaxial tensile loading

While individual carbon nanotubes (CNTs) are known as one of the strongest fibers ever known, even the strongest fabricated macroscale CNT yarns and fibers are still significantly weaker than individual nanotubes. The loss in mechanical properties is mainly because the deformation mechanism of CNT fibers is highly governed by the weak shear strength corresponding to sliding of nanotubes on each other. Adding polymer coating to the bundles, and twisting the CNT yarns to enhance the intertube interactions are both efficient methods to improve the mechanical properties of macroscale yarns. Here, we perform molecular dynamics (MD) simulations to unravel the unknown deformation mechanism in the intertube polymer chains and also local deformations of the CNTs at the atomistic scale. Our results show that the lateral pressure can have both beneficial and adverse effects on shear strength of polymer coated CNTs, depending on the local deformations at the atomistic scale. In this paper we also introduce a bottom-up bridging strategy between a full atomistic model and a coarse-grained (CG) model. Our trained CG model is capable of incorporating the atomistic scale local deformations of each CNT to the larger scale collect behavior of bundles, which enables the model to accurately predict the effect of lateral pressure on larger CNT bundles and yarns. The developed multiscale CG model is implemented to study the effect of lateral pressure on the shear strength of straight polymer coated CNT yarns, and also the effect of twisting on the pull-out force of bundles in spun CNT yarns.

The modeling and demonstration of large stroke, high energy density and high power density torsional springs based on carbon nanotube (CNT) yarns is reported, as well as their application as energy-storing actuators for regenerative braking systems. An originally untwisted CNT yarn is cyclically loaded and unloaded in torsion, with the maximum rotation angle increasing incrementally until failure. The measured average extractable energy density values are 2.9 kJ kg−1 ± 1.2 kJ kg−1 and 3.4 kJ kg−1 ± 0.4 kJ kg−1 for 1-ply CNT yarns and 2-ply CNT yarns, respectively. Additionally, a regenerative braking system is demonstrated to capture the kinetic energy of a wheel and store it as elastic energy in twisted CNT yarns. When the yarn’s twist is released, the stored energy reaccelerates the wheel. The measured energy and mean power densities of the CNT yarns in the simple regenerative braking setup are on average 3.3 kJ kg−1 and 0.67 kW kg−1, respectively, with maximum measured values of up to 4.7 kJ kg−1 and 1.2 kW kg−1, respectively. A slightly lower energy density of up to 1.2 kJ kg−1 and a 0.29 kW kg−1 mean power density are measured for CNT yarns in a more complex setup that mimics a unidirectional rotating regenerative braking mechanism.

Nanostructural characterization of carbon nanotube yarn high-strengthened by joule heating

first_page settings Order Article Reprints Font Type: Arial Georgia Verdana Font Size: Aa Aa Aa Line Spacing:    Column Width:    Background: Open AccessAbstract Structural Health Monitoring Using Carbon Nanotube Yarns: Sensing Concept and Applications in Composites † by Jandro L. Abot Department of Mechanical Engineering, The Catholic University of America, Washington, DC 20064, USA † Presented at the 5th International Symposium on Sensor Science (I3S 2017), Barcelona, Spain, 27–29 September 2017. Proceedings 2017, 1(8), 852; https://doi.org/10.3390/proceedings1080852 Published: 4 December 2017 (This article belongs to the Proceedings of Proceedings of the 5th International Symposium on Sensor Science (I3S 2017)) Download Download PDF Download PDF with Cover Download XML Versions Notes Non-destructive evaluation and structural health monitoring techniques can provide frequent or immediate feedback of the condition of a structure including potential damage. However, these techniques cannot detect initiating damage in composite materials with high compaction or multifaceted construction. More critically, they are unable to achieve damage detection without altering the microstructure of the composite material. An alternative method of strain monitoring and damage detection that may offer the advantages of structural health monitoring without their drawbacks consists of using piezoresistive-based carbon nanotube (CNT) yarns integrated in polymers and composite materials. The concept is that the CNT yarns form a continuous sensor circuit and their inherent piezoresistive sensitivity detects strain within the host material through resistance measurements without adding much weight or altering the integrity of the host material. This presentation includes a summary of the piezoresistive response of CNT yarns and the concept and latest experimental results on damage detection in laminated polymeric composite materials and distributed and localized strain measurement. Experimental results also show the ability of a combination of different yarn sensors to detect the exact location and extent of delamination in real time. CNT yarn sensors may provide an adaptive, practical, and sensitive structural health monitoring technique. © 2017 by the author. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/). Share and Cite MDPI and ACS Style Abot, J.L. Structural Health Monitoring Using Carbon Nanotube Yarns: Sensing Concept and Applications in Composites. Proceedings 2017, 1, 852. https://doi.org/10.3390/proceedings1080852 AMA Style Abot JL. Structural Health Monitoring Using Carbon Nanotube Yarns: Sensing Concept and Applications in Composites. Proceedings. 2017; 1(8):852. https://doi.org/10.3390/proceedings1080852 Chicago/Turabian Style Abot, Jandro L. 2017. "Structural Health Monitoring Using Carbon Nanotube Yarns: Sensing Concept and Applications in Composites" Proceedings 1, no. 8: 852. https://doi.org/10.3390/proceedings1080852 Find Other Styles Note that from the first issue of 2016, MDPI journals use article numbers instead of page numbers. See further details here. Article Metrics No No Article Access Statistics Multiple requests from the same IP address are counted as one view.

Morphology-dependent load transfer governs the strength and failure mechanism of carbon nanotube yarns