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Novel Applications of Carbon Nanotube-Based Materials
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Novel Applications of Carbon Nanotube-Based Materials

A topical collection in C (ISSN 2311-5629). This collection belongs to the section "Carbon Materials and Carbon Allotropes".

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Editor

Prof. Dr. Jandro L. Abot

E-Mail Website
Guest Editor
Department of Mechanical Engineering, The Catholic University of America, Washington, DC 20064, USA
Interests: experimental stress mechanics; polymeric composite materials; carbon nanotube fibers; integrated and distributed structural health monitoring in composite materials; piezoresistive sensors
Special Issues, Collections and Topics in MDPI journals

Topical Collection Information

Dear colleagues,

Carbon nanotubes are quasi-one-dimensional structures of rolled graphene, a one atomic layer of graphite that is the allotrope of sp2 carbon. Carbon nanotubes have outstanding mechanical, electrical, thermal, and optical properties due to that unique atomic structure. In addition, they exhibit large aspect ratios and high surface areas that enable unique electrochemical properties and potential for dispersion in matrices. Structures and assemblies of carbon nanotubes such as arrays or forests, fibers, ribbons, and other two- or three-dimensional structures will exhibit at least one dimension in the microscale and thus enable their use in a wider variety of applications. This Special Issue is specifically dedicated to novel and conceptual applications of carbon nanotube structures and materials based on carbon nanotubes. Applications include sensing via piezoresistive, piezo-impedance, thermoresistive, chemoresistive and electrochemical, magnetoresistive or piezoelectric approaches; electronics including transistors, cooling, field emission, photodection or data transmission; chemical, biological and medical; catalysis; energy and gas storage; filters and membranes; fiber, fabrics, or reinforcements; probing; and others. Papers may be based on experimental, numerical, or analytical studies. Entirely novel applications may include the rationale and a theoretical section.

Kind regards,
Prof. Dr. Jandro L. Abot
Guest Editor

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Keywords

  • carbon nanotube
  • carbon nanotube structures
  • experimental
  • modeling
  • concepts
  • applications

Published Papers (19 papers)

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2024

Jump to: 2023, 2022, 2021

19 pages, 2186 KiB  
Review
Recent Advances in Carbon Nanotube Technology: Bridging the Gap from Fundamental Science to Wide Applications
by Zhizhi Tao, Yuqiong Zhao, Ying Wang and Guojie Zhang
C 2024, 10(3), 69; https://doi.org/10.3390/c10030069 - 6 Aug 2024
Viewed by 1171
Abstract
Carbon nanotubes, as carbon allotropes distinguished by their intricate structures and exceptional physicochemical properties, have demonstrated substantial progress in recent years across diverse domains, including energy production, chemical synthesis, and environmental preservation. They exhibit notable attributes such as high thermal stability, superior adsorption [...] Read more.
Carbon nanotubes, as carbon allotropes distinguished by their intricate structures and exceptional physicochemical properties, have demonstrated substantial progress in recent years across diverse domains, including energy production, chemical synthesis, and environmental preservation. They exhibit notable attributes such as high thermal stability, superior adsorption capacity, and a substantial specific surface area, rendering them superb catalyst supports. Particularly in electrochemical energy storage, CNTs are extensively employed in supercapacitor electrodes owing to their elevated electrical conductivity, mechanical robustness, and electrocatalytic prowess, which facilitate significant energy storage capabilities. Their intricate pore architecture and reactive sites make functionalized carbon nanotubes well suited for synthesizing composite materials with diverse components, which are ideal for sequestering carbon dioxide from both atmospheric and indoor environments. This review presents a comprehensive examination of carbon nanotube synthesis methodologies, encompassing chemical vapor deposition, arc discharge, and laser ablation, and evaluates their impacts on the structural and functional properties of carbon nanotubes. Furthermore, this article underscores the applications of carbon nanotubes in fields such as fuel cells, photocatalysis, ammonia synthesis, dry methane reforming, Fischer–Tropsch synthesis, and supercapacitors. Despite the considerable potential of carbon nanotubes, their manufacturing processes remain intricate and costly, impeding large-scale industrial production. This review concludes by addressing the challenges in fabricating carbon nanotube composites and outlining future development prospects. Full article
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Full article ">Figure 1
<p>Schematic diagram of ion sputtering-assisted chemical vapor deposition method [<a href="#B26-carbon-10-00069" class="html-bibr">26</a>].</p> Full article ">Figure 2
<p>Schematic diagram of FeNi-NCNT/DrGO synthesis [<a href="#B43-carbon-10-00069" class="html-bibr">43</a>].</p> Full article ">Figure 3
<p>A schematic diagram of the preparation of an artificial vesicular structure photocatalyst [<a href="#B47-carbon-10-00069" class="html-bibr">47</a>].</p> Full article ">Figure 4
<p>Schematic diagram of Mo/BCN-catalyzed ammonia synthesis mechanism [<a href="#B51-carbon-10-00069" class="html-bibr">51</a>].</p> Full article ">Figure 5
<p>A schematic diagram of the modified light-Fenton method [<a href="#B59-carbon-10-00069" class="html-bibr">59</a>].</p> Full article ">Figure 6
<p>FTIR spectra of MWCNTs, f-MWCNTs, CS, and CS-grafted MWCNTs [<a href="#B82-carbon-10-00069" class="html-bibr">82</a>]. Notes: Cs: chitosan.</p> Full article ">
25 pages, 15545 KiB  
Article
Pristine and Coated Carbon Nanotube Sheets—Characterization and Potential Applications
by Prakash Giri, Irwin Gill, Morgan Swensgard, Alexandra Kaiser, Audrey Rust, Brian Stuparyk, Andrew Fisher, Justice Williams, Katie Renoit, Eleanor Kreeb, Corentin Lavenan and Mark J. Schulz
C 2024, 10(1), 17; https://doi.org/10.3390/c10010017 - 9 Feb 2024
Viewed by 1937
Abstract
A carbon nanotube (CNT) sheet is a nonwoven fabric that is being evaluated for use in different textile applications. Several properties of pristine CNT sheets and CNT sheets coated with a polysilazane sealant and coating were measured and compared in the paper. The [...] Read more.
A carbon nanotube (CNT) sheet is a nonwoven fabric that is being evaluated for use in different textile applications. Several properties of pristine CNT sheets and CNT sheets coated with a polysilazane sealant and coating were measured and compared in the paper. The polysilazane coating is used to reduce the shedding of CNT fibers from the sheet when the sheet is in contact with surfaces. Most fabrics show some shedding of fibers during the washing or abrasion of the fabric. This study showed that the coating reduces the shedding of fibers from CNT fabric. The coating also increased the flame resistance of the fabric. The pristine and coated sheets both have low strength but high strain to failure. The pristine and coated CNT sheet densities are 0.48 g/cc and 0.65 g/cc, respectively. The pristine CNT sheet is approximately 27 μ thick. The coated sheet is approximately 24 μ thick. The coating may have densified the sheet, making it thinner. The thickness of the compliant sheets was difficult to measure and is a source of error in the properties. Characterization results are given in this paper. The results are for comparison purposes and not to establish material properties data. Possible applications for CNT sheets are briefly discussed. Full article
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Full article ">Figure 1
<p>CNT sheet characterization. (<b>a</b>) Polysilazane-coated CNT sheet under an optical microscope at 15×. Polysilazane-coated CNT sheets have a smooth surface. Also, polysilazane-coated CNT sheet SEM image and EDAX chart are shown. (<b>b</b>) Pristine CNTs with the nonwoven bundles of CNTs visible at 15× magnification. Pristine CNT sheet SEM image and EDAX chart are also shown. The SEM is at 20,000× magnification.</p> Full article ">Figure 1 Cont.
<p>CNT sheet characterization. (<b>a</b>) Polysilazane-coated CNT sheet under an optical microscope at 15×. Polysilazane-coated CNT sheets have a smooth surface. Also, polysilazane-coated CNT sheet SEM image and EDAX chart are shown. (<b>b</b>) Pristine CNTs with the nonwoven bundles of CNTs visible at 15× magnification. Pristine CNT sheet SEM image and EDAX chart are also shown. The SEM is at 20,000× magnification.</p> Full article ">Figure 2
<p>Instruments for measuring the size of the sheets. (<b>a</b>) Vernier caliper, where force on the adjustment wheel changes the thickness reading, using multiple folds of fabric to increase accuracy of measurement, versus the (<b>b</b>) Hitachi TM3000 Tabletop scanning electron microscope (SEM).</p> Full article ">Figure 3
<p>Measuring the thickness of CNT sheet using a benchtop electron microscope. (<b>a</b>) The average thickness of the pristine CNT sheet was 27.3 μ. (<b>b</b>) The average thickness of the polysilazane-coated CNT sheet was 24.1 μ.</p> Full article ">Figure 4
<p>Flame testing polysilazane samples. (<b>a</b>,<b>b</b>) Flame applied to two samples. (<b>c</b>) Sample after flame was removed. (<b>d</b>) 11 mm tear in polysilazane-coated sample after flame testing.</p> Full article ">Figure 5
<p>Measuring electrical sheet resistance of CNT sheet using a non-contact eddy current meter.</p> Full article ">Figure 6
<p>Preparing the CNT samples for tensile testing. (<b>a</b>) Oxford Lasers Micro Machining System. (<b>b</b>) Laser cutting of CNT sheet sample. (<b>c</b>) Paper frame is used to support the CNT tensile specimen just for mounting into the tensile test machine. The paper is cut after the sample is mounted into the Instron machine. (<b>d</b>) Benchtop Instron tensile test machine for measuring the strength of small-sized samples. The Instron machine is Model 5948.</p> Full article ">Figure 7
<p>Pristine CNT sample testing. (<b>a</b>) Along direction D1. (<b>b</b>) Along direction D2.</p> Full article ">Figure 8
<p>Polysilazane-coated CNT sample testing. (<b>a</b>) Along direction D1. (<b>b</b>) Along direction D2.</p> Full article ">Figure 9
<p>Raman graphs. (<b>a</b>) Raman spectrometer. (<b>b</b>) Pristine CNT plot. (<b>c</b>) Polysilazane-coated CNT plot.</p> Full article ">Figure 10
<p>CNT samples handling testing. (<b>a</b>) Polysilazane-coated CNT sheet’s folding action. (<b>b</b>) Pristine sheet’s folding action. (<b>c</b>) Surface after polysilazane-coated CNT contact on scotch tape, showing release of fibers only in one location which is roughly 1% of the area of the CNT fabric. (<b>d</b>) Surface after pristine CNT contact on scotch tape, showing release of fibers in 14 locations which is roughly 14% of the area of the CNT fabric.</p> Full article ">Figure 11
<p>CNT sheet samples used for density measurement. (<b>a</b>) Pristine. (<b>b</b>) Polysilazane-coated.</p> Full article ">Figure 12
<p>Hydrophobicity testing. (<b>a</b>) Pristine CNT sheet with water droplet. (<b>b</b>) Pristine CNT sheet with oil droplet. (<b>c</b>) Coated CNT sheet with water droplet. (<b>d</b>) Coated CNT sheet with oil droplet.</p> Full article ">Figure 13
<p>Alkali metal battery material with pristine CNT sheet. (<b>a</b>) Sodium CNT piece dropped into water in beaker. Sodium burns on the one-sided CNT fabric in water. The CNT was torn by burning but was intact. The flash burning was completed in about one second. (<b>b</b>) Sodium covered with two-sided CNT fabric is impermeable to water and does not react with water.</p> Full article ">Figure 14
<p>Illustration of a possible actuating textile. The device components are a nitinol SMA wire coil connected to a polysilazane-coated CNT sheet (with Cu strips at the ends) that is connected to a restoring spring. A 12 V power supply powers the SMA wire. The actuating textile may be useful for soft actuation, robotics, and technical or smart textiles. The CNT sheet tightens and displaces based on the stiffness of the bias spring and the length and stiffness of the SMA wire coil. (<b>a</b>) Before actuation (SMA spring is extended in the cold condition). (<b>b</b>) After actuation (SMA spring is heated and retracted). The resistance of the multi-layer CNT sheet is 2 ohms, allowing it to conduct electricity in the smart material. <a href="#app1-carbon-10-00017" class="html-app">Supplementary Materials Video S3</a>: Sample of SMA CNT actuator is a video of the actuation.</p> Full article ">Figure 15
<p>Electromagnetic shielding of incoming and outgoing electromagnetic waves can be achieved by surrounding electronics with electrically conductive laminated polysilazane-coated CNT sheet (outer nonconductive fabrics (blue) enclose the polysilazane-coated CNT sheet (black). As an example, a cell phone can be wrapped in three layers (75 μ thick in total, not including the thickness of the insulating outer fabrics) of polysilazane-coated CNT sheets. The phone disconnects from a call when wrapped with this sheet. The CNT sheet should always be laminated with electrically insulating sheets to add strength and prevent electrical contact of the CNT sheet.</p> Full article ">Figure 16
<p>Force-sensing resistors (FSR) [<a href="#B36-carbon-10-00017" class="html-bibr">36</a>]. (<b>a</b>) Different commercial shape sensors [<a href="#B36-carbon-10-00017" class="html-bibr">36</a>] that can be integrated with CNT fabric. (<b>b</b>) Long force-sensing resistor integrated with CNT–silicone sheet produced at UC Nanoworld Labs [<a href="#B3-carbon-10-00017" class="html-bibr">3</a>]. The resistor can detect transverse force being applied to the CNT fabric at any location along the center of the CNT sheet. (<b>c</b>) EMI can be reduced using polysilazane-coated CNT sheet. The sheet must have protective outer fabric layers that are strong and electrically insulating for safety.</p> Full article ">Figure 17
<p>CNT sheet integrated within fiberglass prepreg samples for a test high-temperature composite. Six layers of high-temperature prepreg [<a href="#B39-carbon-10-00017" class="html-bibr">39</a>] with CNT sheet are used to form a high-temperature composite.</p> Full article ">
19 pages, 7449 KiB  
Article
Continuous Reactive-Roll-to-Roll Growth of Carbon Nanotubes for Fog Water Harvesting Applications
by Jean-Luc Meunier, Jeanne Ouellet, Kaustubh Basu, Alessio Aufoujal, Richard Boudreault and Jason Robert Tavares
C 2024, 10(1), 9; https://doi.org/10.3390/c10010009 - 9 Jan 2024
Viewed by 2053
Abstract
A simple method is presented for the continuous generation of carbon nanotube forests stably anchored on stainless-steel surfaces using a reactive-roll-to-roll (RR2R) configuration. No addition of catalyst nanoparticles is required for the CNT-forest generation; the stainless-steel substrate itself is tuned to generate the [...] Read more.
A simple method is presented for the continuous generation of carbon nanotube forests stably anchored on stainless-steel surfaces using a reactive-roll-to-roll (RR2R) configuration. No addition of catalyst nanoparticles is required for the CNT-forest generation; the stainless-steel substrate itself is tuned to generate the catalytic growth sites. The process enables very large surfaces covered with CNT forests to have individual CNT roots anchored to the metallic ground through primary bonds. Fog water harvesting is demonstrated and tested as one potential application using long CNT-covered wires. The RR2R is performed in the gas phase; no solution processing of CNT suspensions is used, contrary to usual R2R CNT-based technologies. Full or partial CNT-forest coverage provides tuning of the ratio and shape of hydrophobic and hydrophilic zones on the surface. This enables the optimization of fog water harvesters for droplet capture through the hydrophobic CNT forest and water removal from the hydrophilic SS surface. Water recovery tests using small harp-type harvesters with CNT-forest generate water capture of up to 2.2 g/cm2·h under ultrasound-generated fog flow. The strong CNT root anchoring on the stainless-steel surfaces provides opportunities for (i) robustness and easy transport of the composite structure and (ii) chemical functionalization and/or nanoparticle decoration of the structures, and it opens the road for a series of applications on large-scale surfaces, including fog harvesting. Full article
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<p>Droplet dynamic through (<b>a</b>) fine-meshed grid, (<b>b</b>) coarse-meshed grid, (<b>c</b>) fine harp, and (<b>d</b>) coarse harp [<a href="#B33-carbon-10-00009" class="html-bibr">33</a>]. Reprinted with permission from Shi W. et al. [<a href="#B30-carbon-10-00009" class="html-bibr">30</a>].</p> Full article ">Figure 2
<p>(<b>a</b>): SS surface after 5-min etching in HCl acid, detailed surface structure, and scale bar of 1 μm. (<b>b</b>): Detailed SS surface structure after 5-min etching in HCl acid followed by 30 min recrystallization heat treatment at 850 °C and scale bar of 500 nm. Reprinted with permission from [<a href="#B32-carbon-10-00009" class="html-bibr">32</a>].</p> Full article ">Figure 3
<p>(<b>a</b>) Schematic of the tube furnace showing the RR2R configuration with both spools and gas supply located outside of the hot zone of the furnace. The wire velocity over various tests varies from 0 (static) to a maximum speed of 9.32 × 10<sup>−4</sup> m/s. (<b>b</b>) General view of the experimental setup used for the continuous RR2R CNT-forest generation. 1. C<sub>2</sub>H<sub>2</sub> cylinder, 2. argon cylinder, 3. gas flowmeter, 4. gas inlet, 5. manipulation chambers, 6. tubular furnace, 7. temperature controller, 8. quartz tube, 9. stepping motor, 10. O<sub>2</sub> analyzer, 11. motor controller, and 12. gas exit.</p> Full article ">Figure 4
<p>Summary of the various processing steps for the growth of CNT forest structures on the SS wire in a typical static mode, with indication of the time scales and temperatures involved (see color code). These steps follow the initial material preparation steps based on acid etching and ultrasonic cleaning.</p> Full article ">Figure 5
<p>SEM images of the two mesh surfaces employed for constructing the mesh fog harvester: (<b>a</b>) bare SS mesh, (<b>b</b>) CNT forest on the SS base mesh, (<b>c</b>) high-resolution image of the CNT forest on the SS + CNT forest mesh observed in (<b>b</b>).</p> Full article ">Figure 6
<p>Temperature profile on the axis of the tubular reactor for two different temperature set points of the furnace. The dotted lines (<b>a</b>) and (<b>d</b>) represent the two extremities of the tube furnace, while dotted lines (<b>b</b>) and (<b>c</b>) correspond to the ends of the heating elements of the oven.</p> Full article ">Figure 7
<p>SEM images of the CNT growth in static (V<sub>wire</sub> = 0 m/s) RR2R geometry for two gas conditions: (<b>A</b>) 5 min C<sub>2</sub>H<sub>2</sub> and 10 min Ar, (<b>B</b>) 10 min C<sub>2</sub>H<sub>2</sub> and 0 min Ar.</p> Full article ">Figure 8
<p>SEM micrograph examples of static and dynamic RR2R experiments. Wire speed in dynamic experiments indicated in both cm/min and in time (min) within the CNT nucleation/growth zone (NGZ). The (<b>a</b>–<b>c</b>) sequence: (<b>a</b>): Bare SS wire before RR2R treatment. (<b>b</b>) Static experiment: No HCl pre-treatment, with recrystallization step, growth using 5 min C<sub>2</sub>H<sub>2</sub> at 700 °C and 5 min in argon; partial growth leaving large zones of uncovered SS wire surface when using no acid surface treatment. (<b>c</b>) Static experiment: 2 min HCl pre-treatment, with other conditions same as in (<b>b</b>); well-dispersed and high-density islands of CNT coverage on the SS wire. (<b>d</b>–<b>f</b>) Dynamic growth sequences at 700 °C. (<b>d</b>,<b>e</b>): Wire speed of 5.59 cm/min (5 min in NGZ). (<b>d</b>) is an enlargement of the circle in (<b>e</b>); (<b>f</b>): wire speed of 2.8 cm/min (10 min in NGZ). (<b>g</b>,<b>h</b>) dynamic growth sequences at 725 °C: wire speed of 5.59 cm/min (5 min in NGZ).</p> Full article ">Figure 9
<p>(<b>A</b>) Experimental harp-type fog harvester made of a SS wire (1) having ~3 m in length, with and without CNT-forest coverage, and two SS bolts (2) of type 10–32 pitch. (<b>B</b>) Fog harvester setup.</p> Full article ">Figure 10
<p>Water droplet size distribution observed on the bare SS wires (<b>left</b>) and on SS wires with partial CNT coverage (<b>right</b>).</p> Full article ">Figure 11
<p>Water collection rates for various harp-based fog harvesters and for harvesters based on a grid configuration.</p> Full article ">

2023

Jump to: 2024, 2022, 2021

21 pages, 8435 KiB  
Article
Synthesis and Processing of Near Infrared—Activated Vitrimer Nanocomposite Films Modified with β-Hydroxyester-Functionalized Multi-Walled Carbon Nanotubes
by Tomás E. Byrne Prudente, Diandra Mauro, Julieta Puig, Facundo I. Altuna, Tatiana Da Ros and Cristina E. Hoppe
C 2023, 9(4), 119; https://doi.org/10.3390/c9040119 - 8 Dec 2023
Cited by 1 | Viewed by 1905
Abstract
Films of a vitrimer based on the reaction between diglycidylether of bisphenol A and glutaric acid in the presence of 1-methylimidazole were processed using a solvent-based technique. The curing schedule was divided into two steps: first, a soluble linear polymer was formed through [...] Read more.
Films of a vitrimer based on the reaction between diglycidylether of bisphenol A and glutaric acid in the presence of 1-methylimidazole were processed using a solvent-based technique. The curing schedule was divided into two steps: first, a soluble linear polymer was formed through the reaction of the diacid and the diepoxide, and then the crosslinking was induced at a higher temperature via transesterification reactions. This epoxy–acid vitrimer was modified with multi-walled carbon nanotubes (MWCNTs) functionalized with β-hydroxyesters, produced by a robust and straightforward strategy based on a two-phase reaction between oxidized MWCNTs and phenylglycidylether. Nanocomposite vitrimer films were obtained by drop casting a dispersion of the functionalized MWCNTs in the linear polymer/cyclohexanone solution, followed by a thermal treatment. A high degree of dispersion of the carbon nanostructures was attained thanks to the β-hydroxyester functionalization when compared with oxidized MWCNTs. Nanocomposite films showed a significant photothermal effect (reaching 200 °C or above in 30 s) upon NIR light irradiation (850 nm) from a single LED (500 mW/cm2). The released heat was used to activate the shape memory effect and weld and heal the vitrimer matrix, proving the success of this easy strategy for the generation of remotely activated carbon-based vitrimer nanocomposites. Full article
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<p>FT-MIR spectrum of the polymer obtained after 1 h of bulk polymerization at 100 °C. Insets depict selected regions (marked with a dashed square) showing the bands associated with epoxy (915 cm<sup>−1</sup>), carboxylic acid (1710 cm<sup>−1</sup>), and ester groups (1734 cm<sup>−1</sup>).</p> Full article ">Figure 2
<p>Evolution of the epoxy conversion followed by the decrease in the epoxy NIR peak centered at 4532 cm<sup>−1</sup>.</p> Full article ">Figure 3
<p>Storage (G’; full symbols) and loss (G’’; empty symbols) shear moduli and damping factor (tan δ; dashed and full lines) for DGEBA-GA-1MI polymer before and after the step at 160 °C for 2 h.</p> Full article ">Figure 4
<p>Stress relaxation of the DGEBA-GA-1MI network at 160 °C.</p> Full article ">Figure 5
<p>Optical images of the vitrimer films prepared by dip coating from 10 wt% solutions in DMF of the polymer obtained after 1 h of reaction at 100 °C.</p> Full article ">Figure 6
<p>(<b>a</b>) Optical images of aqueous dispersions of <span class="html-italic">p</span>-MWCNTs (<b>left</b>) and <span class="html-italic">ox</span>-MWCNTs (<b>right</b>). (<b>b</b>) TEM images of <span class="html-italic">p</span>-MWCNTs ((<b>top</b>), scale bar = 200 nm) and <span class="html-italic">ox</span>-MWCNTs ((<b>bottom</b>), scale bar = 50 nm).</p> Full article ">Figure 7
<p>Optical image of <span class="html-italic">ox</span>-MWCNTs (0.5 wt%) in the unreacted epoxy/acid formulation (<b>left</b>). Optical micrograph of <span class="html-italic">ox</span>-MWCNTs (0.5 wt%) in the films obtained from solutions of the thermoplastic polymer (inset: optical image) (<b>right</b>). The scale bar is 100 µm.</p> Full article ">Figure 8
<p>FTIR spectra of oxidized and functionalized MWCNTs.</p> Full article ">Figure 9
<p>TGA thermograms of pristine, oxidized, and functionalized MWCNTs.</p> Full article ">Figure 10
<p>Raman spectra and I<sub>D</sub>/I<sub>G</sub> values for <span class="html-italic">p</span>-MWCNTs, <span class="html-italic">ox</span>-MWCNTs, and <span class="html-italic">f</span>-MWCNTs.</p> Full article ">Figure 11
<p>TOM images of nanocomposite vitrimers with 1.2 wt% of <span class="html-italic">ox</span>-MWCNTs (<b>a</b>) and 1.2 wt% of <span class="html-italic">f</span>-MWCNTs (<b>b</b>) casted onto glass slides. The bar is 100 µm. Insets show an optical image of the coatings produced by the irregular dropping of the solution on glass slides, followed by evaporation and thermal treatment at 160 °C. (<b>c</b>) Optical image of the nanocomposite immersed in DMF for a prolonged time.</p> Full article ">Figure 12
<p>DSC thermograms of nanocomposites with different contents of <span class="html-italic">f</span>-MWCNTs.</p> Full article ">Figure 13
<p>Temperature increase of the samples with different wt% of <span class="html-italic">f</span>-MWCNTs irradiated with a LED lamp in the NIR region (λ = 850 nm, 500 mW/cm<sup>2</sup>).</p> Full article ">Figure 14
<p>Optical images showing the NIR-activated shape memory effect (<b>a</b>) and welding of two films via irradiation (<b>b</b>).</p> Full article ">Figure 15
<p>(<b>a</b>) TOM images (scale bar = 100 μm) and (<b>b</b>) profilometry scans of the film damaged with a needle and healed after 10 min of irradiation with the infrared LED.</p> Full article ">Figure 16
<p>(<b>a</b>) TOM images (scale bar = 100 μm) and (<b>b</b>) profilometry scans of the film damaged with a cutter and healed after 10 min of irradiation with the infrared LED.</p> Full article ">Figure 17
<p>Reprocessing of the DGEBA-GA-1MI/<span class="html-italic">f</span>-MWCNTs nanocomposites for 2 h at 160 °C.</p> Full article ">Scheme 1
<p>Chemical structures of DGEBA, GA, 1MI, TPP, and PGE.</p> Full article ">Scheme 2
<p>(<b>a</b>) Formation of the linear poly β-hydroxyester through the epoxy–acid addition catalyzed by 1MI; (<b>b</b>) transesterification reactions leading to the formation of covalent crosslinks.</p> Full article ">Scheme 3
<p>Reaction of a carboxylic acid group with the epoxy group of the PGE leading to a β-hydroxyester functional group.</p> Full article ">
19 pages, 9149 KiB  
Article
Development of CNT-Based Nanocomposites with Ohmic Heating Capability towards Self-Healing Applications in Extrusion-Based 3D Printing Technologies
by Niki Loura, Eleni Gkartzou, Aikaterini-Flora Trompeta, Georgios Konstantopoulos, Panagiotis A. Klonos, Apostolos Kyritsis and Costas A. Charitidis
C 2023, 9(4), 111; https://doi.org/10.3390/c9040111 - 17 Nov 2023
Cited by 2 | Viewed by 1903
Abstract
In the present study, a series of carbon-based nanocomposites based on recycled thermoplastic polyurethane (TPU) matrix and MWCNT fillers synthesized in a laboratory environment were prepared at various loadings and assessed in terms of their functional thermal, dielectric, and rheological properties, as well [...] Read more.
In the present study, a series of carbon-based nanocomposites based on recycled thermoplastic polyurethane (TPU) matrix and MWCNT fillers synthesized in a laboratory environment were prepared at various loadings and assessed in terms of their functional thermal, dielectric, and rheological properties, as well as their ohmic heating capability, for self-healing applications in extrusion-based 3D printing technologies. The synthesis of nanomaterials focused on the production of two different types of carbon nanotubes (CNTs) via the chemical vapor deposition (CVD) method. A comparative assessment and benchmarking were conducted with nanocomposite filaments obtained from commercial nanomaterials and masterbatches with MWCNTs. For all the polymer nanocomposites, samples were prepared at additive contents up to 15 wt.% and filament feedstock was produced via the melt-extrusion process for 3D printing; these were previously characterized by rheological tests. The measurements of thermal and electrical conductivity resulted in a selected composition with promising ohmic heating capability. As a preliminary assessment of the self-healing ability of the above samples, artificial cracks were introduced on the surface of the samples and SEM analysis took place at the crack location before and after applying voltage as a measure of the effectiveness of the material remelting due to the Joule effect. Results indicate a promising material response with a partial restoration of artificial cracks. Full article
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Full article ">Figure 1
<p>A schematic diagram following from the raw materials to the filament production.</p> Full article ">Figure 2
<p>Schematic workflow diagram following from the filament to characterization techniques.</p> Full article ">Figure 3
<p>SEM micrographs of (<b>a</b>,<b>b</b>) MWCNTs_csCVD and (<b>c</b>,<b>d</b>) MWCNTs_cfCVD_bp.</p> Full article ">Figure 4
<p>XRD of (<b>a</b>) MWCNTs_csCVD and (<b>b</b>) MWCNTs_cfCVD_bp.</p> Full article ">Figure 5
<p>Raman spectra of (<b>a</b>) MWCNTs_csCVD and (<b>b</b>) MWCNTs_cfCVD_bp.</p> Full article ">Figure 6
<p>Variation in the storage modulus (G′), loss modulus (G″), and complex viscosity (|η*|) as a function of angular frequency (rad/s) at 240 °C. (<b>a</b>) Comparative plot of complex viscosity for 1 wt.% and 10 wt.% nanoparticle contents; (<b>b</b>) comparative plot of storage and loss modulus for 1 wt.% nanoparticle content; (<b>c</b>) comparative plot of storage and loss modulus for 10 wt.% nanoparticle content.</p> Full article ">Figure 6 Cont.
<p>Variation in the storage modulus (G′), loss modulus (G″), and complex viscosity (|η*|) as a function of angular frequency (rad/s) at 240 °C. (<b>a</b>) Comparative plot of complex viscosity for 1 wt.% and 10 wt.% nanoparticle contents; (<b>b</b>) comparative plot of storage and loss modulus for 1 wt.% nanoparticle content; (<b>c</b>) comparative plot of storage and loss modulus for 10 wt.% nanoparticle content.</p> Full article ">Figure 7
<p>Thermal conductivity measurements of the produced 3D-printed nanocomposites. The measurement error is within 3% when the measured sample has a thermal conductivity ranging from 0.005 W/(m K) to 500 W/(m K).</p> Full article ">Figure 8
<p>Variation in the conductivity (σ′) and as a function of frequency (Hz); (<b>a</b>) comparative plot of rTPU/MTPU_1001 and rTPU/MWCNTs_csCVD 3D-printed specimens and (<b>b</b>) comparative plot of specimens produced via injection moulding and 3D printing at 15 wt.% nanofiller content.</p> Full article ">Figure 9
<p>Current intensity versus source voltage plots for mTPU_1001_10wt filaments.</p> Full article ">Figure 10
<p>SEM micrographs of mTPU_1001_10wt nanocomposite (<b>a</b>) in the initial state, (<b>b</b>) after heating with the Joule effect.</p> Full article ">
14 pages, 3633 KiB  
Article
Effect of Multi-Walled Carbon Nanotubes on the Mechanical and Thermal Properties of Curauá Natural-Fiber-Reinforced Composites
by Jorge S. S. Neto, Daniel K. K. Cavalcanti, Luiz E. da Cunha Ferro, Henrique F. M. de Queiroz, Ricardo A. A. Aguiar and Mariana D. Banea
C 2023, 9(4), 102; https://doi.org/10.3390/c9040102 - 3 Nov 2023
Cited by 3 | Viewed by 1805
Abstract
The main objective of this research centered on investigating the effect of the addition of multi-walled carbon nanotubes (MWCNTs) on the mechanical and thermal properties of curauá-fiber-reinforced composites. The MWCNTs were added either to the fiber surface or into the resin matrix as [...] Read more.
The main objective of this research centered on investigating the effect of the addition of multi-walled carbon nanotubes (MWCNTs) on the mechanical and thermal properties of curauá-fiber-reinforced composites. The MWCNTs were added either to the fiber surface or into the resin matrix as the second reinforcing phase. The MWCNT-modified curauá fibers as well as raw fibers were characterized using a single-fiber tensile test, TGA, and FTIR analysis. Further, different composite samples, namely, pure curauá, (curauá + MWCNTs) + resin and curauá+ (resin + MWCNTs), were manufactured via compression molding and tested to determine their mechanical and thermal properties. Scanning electron microscopy (SEM) analysis was used to examine the surfaces of the tested fibers. It was found that the addition of MWCNTs to the curauá fibers resulted in positive effects (an enhancement in properties was found for the MWCNT-modified fibers and their composites). The addition of MWCNTs also increased the thermal stability of the natural fibers and composites. Full article
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<p>Schematic of the process of coating curauá fibers with MWCNTs.</p> Full article ">Figure 2
<p>FTIR spectra of Curauá fiber and MWCNT-modified Curauá fiber.</p> Full article ">Figure 3
<p>Thermogravimetric analysis data for the curauá fiber: (<b>a</b>) TG curves; (<b>b</b>) DTG curves.</p> Full article ">Figure 4
<p>Tensile data on natural fiber as a function of MWCNT coating: (<b>a</b>) tensile strength and (<b>b</b>) Young’s modulus.</p> Full article ">Figure 5
<p>Thermogravimetric analysis data for the curauá fiber composite: (<b>a</b>) TG curves; (<b>b</b>) DTG curves.</p> Full article ">Figure 6
<p>Representative tensile stress–strain curves of the composite specimens.</p> Full article ">Figure 7
<p>Representative flexural stress–strain curves of the curauá fiber composite specimens.</p> Full article ">Figure 8
<p>Average flexural properties as a function of reinforcement methods: (<b>a</b>) flexural strength and (<b>b</b>) flexural modulus.</p> Full article ">Figure 9
<p>Representative SEM images of the fiber morphology: (<b>a</b>) curauá fiber and (<b>b</b>) MWCNT-modified curauá fiber.</p> Full article ">Figure 10
<p>Representative MWCNT-modified curauá composite fiber failure.</p> Full article ">
13 pages, 4235 KiB  
Article
Piezoresistive Response of Carbon Nanotube Yarn Monofilament Composites under Axial Compression
by Iriana Garcia Guerra, Tannaz Tayyarian, Omar Rodríguez-Uicab and Jandro L. Abot
C 2023, 9(4), 89; https://doi.org/10.3390/c9040089 - 25 Sep 2023
Cited by 1 | Viewed by 1464
Abstract
The hierarchical structure and microscale dimensions of carbon nanotube yarns (CNTYs) make them great candidates for the development of integrated sensing applications. The change in the electrical resistance of CNTYs due to mechanical strain, known as piezoresistivity, is the principal mechanism in strain [...] Read more.
The hierarchical structure and microscale dimensions of carbon nanotube yarns (CNTYs) make them great candidates for the development of integrated sensing applications. The change in the electrical resistance of CNTYs due to mechanical strain, known as piezoresistivity, is the principal mechanism in strain sensing using CNTYs. While the axial tensile properties of CNTYs have been studied widely, studies on the axial piezoresistive response of CNTYS under compression have been limited due to the complexities associated with the nature of the experiments involving subjecting a slender fiber to compression loading in its axial direction. In this study, the piezoresistive response of a single CNTY embedded into a polymeric resin (CNTY monofilament composite) was investigated under axial compression. The results suggest that the CNTY exhibits a strong piezoresistive response in the axial direction with sensitivity or gauge factor values in the order of 0.4–0.5 for CNTY monofilament composites. The piezoresistive response of the CNTY monofilament composites under compression was compared to that under tension and it was observed that the sensitivity appears to be slightly lower under compression. The potential change in sensitivity between the freestanding CNTY and the CNTY monofilament composite under compression is still unknown. Knowing the axial piezoresistive response of the CNTYs under both tension and compression will enable their use in sensing applications where the yarn undergoes compression including those in aerospace and marine structures, and civil or energy infrastructure. Full article
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<p>Scanning Electron Microscopy images of CNTY: (<b>a</b>) 5000×; (<b>b</b>) 50,000× (<span class="html-italic">images were taken by MIRA3 TESCAN</span>).</p> Full article ">Figure 2
<p>Schematic view of the CNTY monofilament composite specimen instrumented with strain gauge.</p> Full article ">Figure 3
<p>Schematic of experimental setup for mechanical and electrical measurements.</p> Full article ">Figure 4
<p>CNTY monofilament composite under axial compression at a strain rate of 0.04 min<sup>−1</sup>: (<b>a</b>) Relative change of electrical resistance and strain versus time; (<b>b</b>) Relative change of electrical resistance versus strain.</p> Full article ">Figure 5
<p>Relative change of electrical resistance and strain versus time of CNTY monofilament composites under axial compression at strain rates of: (<b>a</b>) 0.02 min<sup>−1</sup>; (<b>b</b>) 0.2 min<sup>−1</sup>; (<b>c</b>) 0.4 min<sup>−1</sup>; (<b>d</b>) 0.6 min<sup>−1</sup>. <span class="html-italic">In each instance, the maximum compressive load reached 2000 N (stress of 12.4 MPa) and reached 0 at the conclusion of the unloading period.</span></p> Full article ">Figure 6
<p>Relative change of resistance-strain of CNTY monofilament composites under loading-unloading cycles at strain rates of: (<b>a</b>) 0.02 min<sup>−1</sup>; (<b>b</b>) 0.2 min<sup>−1</sup>; (<b>c</b>) 0.4 min<sup>−1</sup>; (<b>d</b>) 0.6 min<sup>−1</sup>.</p> Full article ">Figure 7
<p>Schematic of the experimental parameters used for piezoresistive analysis.</p> Full article ">Figure 8
<p>Stress-strain curve of CNTY monofilament composite under compressive loading cycle (second cycle).</p> Full article ">Figure 9
<p>Scanning Electron Microscopy (SEM) images of the CNTY monofilament composite cross-section at: (<b>a</b>) 4000×; (<b>b</b>) 15,000× (<span class="html-italic">images were taken by MIRA3 TESCAN)</span> [<a href="#B24-carbon-09-00089" class="html-bibr">24</a>].</p> Full article ">Figure 10
<p>Relative change of electrical resistance and strain versus time of CNTY monofilament composite under axial tension at a strain rate: (<b>a</b>) 0.01 min<sup>−1</sup>; (<b>b</b>) 0.05 min<sup>−1</sup>.</p> Full article ">Figure 11
<p>Relative change of electrical resistance versus strain of CNTY monofilament composites under loading-unloading cycle (fifth cycle) at strain rate: (<b>a</b>) 0.01 min<sup>−1</sup>; (<b>b</b>) 0.05 min<sup>−1</sup>.</p> Full article ">
22 pages, 6143 KiB  
Article
Membranes of Multiwall Carbon Nanotubes in Chitosan–Starch with Mechanical and Compositional Properties Useful in Li-Ion Batteries
by Yoxkin Estévez-Martínez, Enrique Quiroga-González, Erick Cuevas-Yañez, Sergio Durón-Torres, Daniel Alaníz-Lumbreras, Elizabeth Chavira-Martínez, Rubén Posada-Gómez, Jeremias Bravo-Tapia and Víctor Castaño-Meneses
C 2023, 9(3), 87; https://doi.org/10.3390/c9030087 - 8 Sep 2023
Cited by 2 | Viewed by 1783
Abstract
This work reports on membranes of a combination of chitosan–starch with lithium-modified multiwall carbon nanotubes. One of the most important contributions of this article is the functionalization of the surface of multiwall carbon nanotubes by means of an accessible technique that allows for [...] Read more.
This work reports on membranes of a combination of chitosan–starch with lithium-modified multiwall carbon nanotubes. One of the most important contributions of this article is the functionalization of the surface of multiwall carbon nanotubes by means of an accessible technique that allows for high grafting yields of lithium and their incorporation into a polymeric matrix. The natural compounds chitosan and starch were used as a support to embed the nanotubes, forming membranes with good mechanical stability. A thorough characterization via Raman, infrared and X-ray photoelectron spectroscopies, transmission and scanning electron microscopies and dynamic mechanical analysis is presented here, as well as electrochemical characterization. The composition, structure and mechanical stability of the membranes make them viable candidates to be used as anodes sustainable Li-ion batteries. Full article
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Full article ">Figure 1
<p>Schematic of the fabrication process of the different modifications to the carbon nanotubes and the synthesis of the chitosan–starch matrix and the different nanocomposites.</p> Full article ">Figure 2
<p>FTIR of different modifications of multiwall carbon nanotubes: raw (<span class="html-italic">MWNTs</span>), oxidized (<span class="html-italic">MWOHs</span>) and lithium-modified (R<span class="html-italic">Li</span> and S<span class="html-italic">Li</span>).</p> Full article ">Figure 3
<p>Raman spectra of different modifications of multiwall carbon nanotubes: raw (<span class="html-italic">MWNTs</span>), oxidized (<span class="html-italic">MWOHs</span>) and lithium-modified (R<span class="html-italic">Li</span> and S<span class="html-italic">Li</span>). The most significant bands (G’, G and D) are marked.</p> Full article ">Figure 4
<p>XPS spectra of <span class="html-italic">C</span>1<span class="html-italic">s</span>, <span class="html-italic">O</span>1<span class="html-italic">s</span> bands of <span class="html-italic">MWNTs</span>, <span class="html-italic">MWOHs</span>, R<span class="html-italic">Li</span> and S<span class="html-italic">Li</span> samples and <span class="html-italic">Li</span>1<span class="html-italic">s</span> band for <span class="html-italic">RLi</span> and <span class="html-italic">SLi</span> samples.</p> Full article ">Figure 5
<p>HRTEM (<b>left</b>) and FFT patterns (<b>right</b>) of multiwall carbon nanotubes (<span class="html-italic">MWNTs</span>) in different sections (1 and 2).</p> Full article ">Figure 6
<p>HRTEM (<b>left</b>) and FFT patterns (<b>right</b>) of oxidized multiwall carbon nanotubes (<span class="html-italic">MWOHs</span>) in different sections (1 and 2).</p> Full article ">Figure 7
<p>HRTEM (<b>left</b>) and ED patterns (<b>right</b>) of R<span class="html-italic">Li</span> and S<span class="html-italic">Li</span>.</p> Full article ">Figure 8
<p>Storage modulus (E’) at different temperatures via dynamic mechanical analysis (DMA). The dashed lines and arrows indicate reference temperatures used for the discussion.</p> Full article ">Figure 9
<p>FTIR of starch (St), chitosan (Ch) and chitosan–starch (<span class="html-italic">ChSt</span>).</p> Full article ">Figure 10
<p>Scanning electron microscopy (SEM) of the surface (S) and cross-section (C) of biopolymer chitosan–starch (<span class="html-italic">ChSt</span>) with <span class="html-italic">MWNTs</span> and <span class="html-italic">MWOHs</span> reinforced.</p> Full article ">Figure 11
<p>Device for electrochemical characterization.</p> Full article ">Figure 12
<p>Cyclic voltammograms of membranes of (<b>a</b>) MWOHs and (<b>b</b>) RLi. The assembly of <a href="#carbon-09-00087-f011" class="html-fig">Figure 11</a> was used for the experiments. The red continuous arrows indicate processes of aluminum oxidation and dissolution, while the dashed arrows indicate processes of Li-Al alloying/de-alloying.</p> Full article ">Figure 13
<p>Impedance spectroscopy spectra of the assembly of <a href="#carbon-09-00087-f011" class="html-fig">Figure 11</a> using membranes of MWOHs and RLi.</p> Full article ">
16 pages, 10060 KiB  
Article
Lightweight Copper–Carbon Nanotube Core–Shell Composite Fiber for Power Cable Application
by Kavitha Mulackampilly Joseph, Kyle Brittingham, Vamsi Krishna Reddy Kondapalli, Mahnoosh Khosravifar, Ayush Arun Raut, Brett David Karsten, Hunter J. Kasparian, Nhat Phan, Arun Kamath, Amjad S. Almansour, Maricela Lizcano, Diana Santiago, David Mast and Vesselin Shanov
C 2023, 9(2), 43; https://doi.org/10.3390/c9020043 - 24 Apr 2023
Cited by 3 | Viewed by 3608
Abstract
The substitution of traditional copper power transmission cables with lightweight copper–carbon nanotube (Cu–CNT) composite fibers is critical for reducing the weight, fuel consumption, and CO2 emissions of automobiles and aircrafts. Such a replacement will also allow for lowering the transmission power loss [...] Read more.
The substitution of traditional copper power transmission cables with lightweight copper–carbon nanotube (Cu–CNT) composite fibers is critical for reducing the weight, fuel consumption, and CO2 emissions of automobiles and aircrafts. Such a replacement will also allow for lowering the transmission power loss in copper cables resulting in a decrease in coal and gas consumption, and ultimately diminishing the carbon footprint. In this work, we created a lightweight Cu–CNT composite fiber through a multistep scalable process, including spinning, densification, functionalization, and double-layer copper deposition. The characterization and testing of the fabricated fiber included surface morphology, electrical conductivity, mechanical strength, crystallinity, and ampacity (current density). The electrical conductivity of the resultant composite fiber was measured to be 0.5 × 106 S/m with an ampacity of 0.18 × 105 A/cm2. The copper-coated CNT fibers were 16 times lighter and 2.7 times stronger than copper wire, as they revealed a gravimetric density of 0.4 g/cm3 and a mechanical strength of 0.68 GPa, suggesting a great potential in future applications as lightweight power transmission cables. Full article
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Full article ">Figure 1
<p>Schematic of CNT array synthesis and CNT fiber spinning process. (<b>a</b>) Growth of vertically aligned CNT array on a catalyst-sputtered substrate by CVD process. (<b>b</b>) Spinning of CNT fiber from the vertically aligned CNT array by pulling and twisting. Reproduced with permission from [<a href="#B25-carbon-09-00043" class="html-bibr">25</a>,<a href="#B26-carbon-09-00043" class="html-bibr">26</a>].</p> Full article ">Figure 2
<p>Densification setup. (<b>a</b>) Supply bobbin. (<b>b</b>) Acrylic die hole. (<b>c</b>) Solvent bath. (<b>d</b>) Hot plate. (<b>e</b>) Thermometer. (<b>f</b>) Teflon rods. (<b>g</b>) CNT fiber. (<b>h</b>) Collecting bobbin.</p> Full article ">Figure 3
<p>Schematic of continuous oxygen functionalization process by tubular plasma head setup. (Reproduced with permission from [<a href="#B34-carbon-09-00043" class="html-bibr">34</a>]).</p> Full article ">Figure 4
<p>Schematic for continuous copper electrodeposition on CNT fiber.</p> Full article ">Figure 5
<p>Simplified block diagram of current density testing setup.</p> Full article ">Figure 6
<p>Characterization of CNT fiber. (<b>a</b>–<b>d</b>) SEM images of pristine and densified fiber at different magnifications. (<b>e</b>) Cross-sectional SEM image of densified CNT fiber at (<b>e</b>) low magnification and (<b>f</b>) high magnification. (<b>g</b>) Mechanical stress–strain plots of CNT fibers. (<b>h</b>) I–V plots of CNT fibers obtained with four-probe measurements.</p> Full article ">Figure 7
<p>Morphology (SEM images) of metal-coated CNT fiber with higher magnification images in the inset. (<b>a</b>) Pd–CNT fiber. (<b>b</b>) Pd–CNT–Cu (1st coated layer). (<b>c</b>) Pd–CNT–Cu (2nd coated layer). (<b>d</b>) Annealed Pd–CNT–Cu fiber. (<b>e</b>) FIB of Cu–CNT fiber at low and (<b>f</b>) high magnification showing the thickness of the coated copper shell.</p> Full article ">Figure 7 Cont.
<p>Morphology (SEM images) of metal-coated CNT fiber with higher magnification images in the inset. (<b>a</b>) Pd–CNT fiber. (<b>b</b>) Pd–CNT–Cu (1st coated layer). (<b>c</b>) Pd–CNT–Cu (2nd coated layer). (<b>d</b>) Annealed Pd–CNT–Cu fiber. (<b>e</b>) FIB of Cu–CNT fiber at low and (<b>f</b>) high magnification showing the thickness of the coated copper shell.</p> Full article ">Figure 8
<p>XRD of pristine CNT and Cu–CNT composite.</p> Full article ">Figure 9
<p>Mechanical (<b>a</b>), electrical (<b>b</b>), and (<b>c</b>) property comparison between pristine CNT, densified CNT, copper-coated CNT, and annealed copper-coated CNT fibers.</p> Full article ">Figure 9 Cont.
<p>Mechanical (<b>a</b>), electrical (<b>b</b>), and (<b>c</b>) property comparison between pristine CNT, densified CNT, copper-coated CNT, and annealed copper-coated CNT fibers.</p> Full article ">Figure 10
<p>(<b>a</b>) Comparison of the average current density for various samples. (<b>b</b>) SEM image of the burnout sample. (Inset high magnification image).</p> Full article ">Figure 10 Cont.
<p>(<b>a</b>) Comparison of the average current density for various samples. (<b>b</b>) SEM image of the burnout sample. (Inset high magnification image).</p> Full article ">
15 pages, 2833 KiB  
Article
Nanocomposites Produced with the Addition of Carbon Nanotubes Dispersed on the Surface of Cement Particles Using Different Non-Aqueous Media
by Vanessa Vilela Rocha, Bruno Athaíde Bacelar, Isabela Domingues Coelho and Péter Ludvig
C 2023, 9(1), 36; https://doi.org/10.3390/c9010036 - 22 Mar 2023
Cited by 1 | Viewed by 1854
Abstract
The inclusion of carbon nanotubes (CNTs) in cementitious composites has been studied due to their electrical, thermal, and mechanical enhancing properties. Considering the hydrophobic characteristics of CNTs, these nanomaterials need to be well dispersed in the aqueous media in which they are inserted [...] Read more.
The inclusion of carbon nanotubes (CNTs) in cementitious composites has been studied due to their electrical, thermal, and mechanical enhancing properties. Considering the hydrophobic characteristics of CNTs, these nanomaterials need to be well dispersed in the aqueous media in which they are inserted to guarantee those gains. Among the methods applied to produce such composites is the dispersion of CNTs on the surface of anhydrous cement particles using non-aqueous suspensions such as acetone, ethanol, or isopropanol. Even though those non-aqueous media have been individually studied by researchers, comparisons of the efficiency of CNTs dispersion was not found in the literature. Therefore, as a novelty, the present article aims to analyze the influence of the addition of the multi-walled CNTs dispersed in the cited three types of non-aqueous suspensions on the cement paste’s electrical and mechanical properties. Pastes containing 0%, 0.5%, and 1.0% of CNTs were prepared on the surface of anhydrous cement particles using a pre-dispersion technique based on simultaneous sonication and mechanical agitation in the three cited media. Tests to determine electric-volumetric resistivity, compressive strength, and splitting tensile strength were performed. It was observed that acetone dispersion decreases the cement paste’s electrical resistivity, even without the addition of CNTs. The cementitious composites with CNTs demonstrated increased mechanical strength (both compressive and tensile) using all three dispersion media. Statistical analysis (analysis of variance—ANOVA—and Tukey’s Test) was performed to evaluate the significance of the results. Full article
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<p>MEV and TEM images of CNTs used.</p> Full article ">Figure 2
<p>Characterization of dimensions and purity information of the CNTs, provided by the supplier.</p> Full article ">Figure 3
<p>Flowchart of the dispersion process of the CNTs in the anhydrous cement particles in a non-aqueous suspension [<a href="#B25-carbon-09-00036" class="html-bibr">25</a>].</p> Full article ">Figure 4
<p>Experimental setup of the electric-volumetric resistivity test.</p> Full article ">Figure 5
<p>Splitting tensile strength test setup.</p> Full article ">Figure 6
<p>Results of the electrical-volumetric resistivity.</p> Full article ">Figure 7
<p>Results of the compressive strength tests.</p> Full article ">Figure 8
<p>Results of splitting tensile strength tests.</p> Full article ">
13 pages, 5491 KiB  
Article
Highly Selective Detection of Hydrogen Sulfide by Simple Cu-CNTs Nanocomposites
by Nahida Musayeva, Hadiya Khalilova, Bakhtiyar Izzatov, Giovanna Trevisi, Shahla Ahmadova and Muhammad Alizada
C 2023, 9(1), 25; https://doi.org/10.3390/c9010025 - 24 Feb 2023
Cited by 4 | Viewed by 1920
Abstract
The presented work is devoted to the preparation of nanocomposites based on multiwall carbon nanotubes (MWCNTs) and copper (Cu) nanoparticles by a simple chemical method, and to study their sensing properties to hydrogen sulfide (H2S) gas. The Cu decorated multiwall carbon [...] Read more.
The presented work is devoted to the preparation of nanocomposites based on multiwall carbon nanotubes (MWCNTs) and copper (Cu) nanoparticles by a simple chemical method, and to study their sensing properties to hydrogen sulfide (H2S) gas. The Cu decorated multiwall carbon nanotubes (MWCNTs/Cu) were prepared by the deposition of very thin Cu layers on the pristine and functionalized multiwall carbon nanotubes (f-MWCNTs) using both physical (electron beam evaporation (EBE)) and chemical (electrochemical deposition) methods. MWCNTs/Cu prepared in the two above-mentioned ways, their sensing properties were studied, and the results were comparatively analyzed. The effect of the chemical functionalization of MWCNTs by oxygen-containing groups on the sensing properties of these f-MWCNT/Cu nanocomposites has been investigated. All the prepared sensors demonstrated high sensitivity and selectivity to H2S in the air at room temperature. The f-MWCNT/Cu structure obtained by the chemical method demonstrated about 5 times (~400%) higher sensitivity (∆R/R0) to H2S gas compared to the similar structure obtained by the physical method. The temperature effect on sensory characteristics (response and self-recovery time) of the f-MWCNTs/Cu structure was also studied. Full article
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<p>Sensor structure (<b>left</b>) and I-V characteristics of the Ag-f-MWCNTs/Cu-Ag structures (<b>right</b>).</p> Full article ">Figure 2
<p>Sensor testing system.</p> Full article ">Figure 3
<p>SEM images of pristine (<b>left</b>) and functionalized (<b>right</b>) MWCNTs.</p> Full article ">Figure 4
<p>SEM images of f-MWCNTs/Cu nanocomposite obtained by (<b>a</b>) physical and (<b>b</b>) chemical methods; (<b>c</b>) higher magnification of (<b>b</b>).</p> Full article ">Figure 5
<p>Raman spectra of the samples: 1—pristine MWCNTs, 2—MWCNTs/Cu (physical method), 3—f-MWCNTs, 4—f-MWCNTs/Cu (physical method), and 5—f-MWCNTs (chemical method) with calculated I(D)/I(G) relation.</p> Full article ">Figure 6
<p>Sensitivity of the f-MWCNTs/Cu nanocomposites prepared by physical and chemical deposition methods.</p> Full article ">Figure 7
<p>Selectivity of the sensors, prepared by (<b>a</b>) physical and (<b>b</b>) chemical methods.</p> Full article ">Figure 8
<p>Temperature dependence of the sensitivity of f-MWCNTs/Cu structure.</p> Full article ">Figure 9
<p>SEM image of MWCNT/Cu (<b>left</b>); high resolution SEM image (<b>right</b>).</p> Full article ">Figure 10
<p>Sensitivity diagram of the MWCNTs/Cu and f-MWCNTs/Cu structures obtained by the physical method (in the H<sub>2</sub>S medium).</p> Full article ">Figure 11
<p>SEM image of f-MWCNTs/Cu nanocomposite obtained by the chemical method.</p> Full article ">
18 pages, 3322 KiB  
Article
Physical Processes Occurring in Dispersed Media with Carbon Nanomaterials under the Influence of Ultrasonification
by Svetlana Obukhova and Evgenii Korolev
C 2023, 9(1), 18; https://doi.org/10.3390/c9010018 - 31 Jan 2023
Cited by 1 | Viewed by 1769
Abstract
The up-to-date carbon nanoparticle application in materials science and composites is mostly represented by controlling of different methods of structure formation including incorporation of nanomaterials or nano-modifiers. The efficiency of such methods depends on disagglomeration and the distribution degree of the carbon nanoparticle [...] Read more.
The up-to-date carbon nanoparticle application in materials science and composites is mostly represented by controlling of different methods of structure formation including incorporation of nanomaterials or nano-modifiers. The efficiency of such methods depends on disagglomeration and the distribution degree of the carbon nanoparticle within a dispersion medium, which are critical parameters to produce a composite with improved performance. At the same time, common approaches such as a surface activation or using surfactants do not guarantee a homogeneous dispersion of carbon nanoparticles. This research reports on a theoretical analysis of physical processes which take place during the ultrasonic treatment which is a widely used method for dispersion of nanomaterials. The experimental data demonstrate an efficiency of the proposed method and prove the theoretical assumptions. The theoretical analysis performed in this study can be applied to implement and scale-up the process using sonicators. It was established that ultrasonic treatment has a more intensive effect in an organic hydrocarbon medium. So, in industrial oil, the heating rate from ultrasonification is 20 °C/min, in residual selective purification extract, it is 33 °C/min. For aqueous systems, the heating rate from ultrasonification is significantly lower and amounts to 2 °C /min for suspensions with Sulfanol and 11 °C/min for suspensions with ViscoCrete 2100. It was established that in the studied dispersed systems (aqueous solutions with surfactants and organic medium), there is no directly proportional dependence of the amount of heating of suspensions on the duration of ultrasound dispersion (USD), which is caused by ultrasonic dispersion not under adiabatic conditions, as well as the dependence of absorption coefficient of ultrasonic energy for dispersed systems on parameters of system structure. Full article
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<p>Schematic depiction of the structure of multilayer polyhedral nanoparticles.</p> Full article ">Figure 2
<p>The structure of CNPLUS.</p> Full article ">Figure 3
<p>The structure of MWCNTS.</p> Full article ">Figure 4
<p>The structure of MWCNT-MD.</p> Full article ">Figure 5
<p>The flow chart of the research approach.</p> Full article ">Figure 6
<p>Dependence of solution (for each concentration in range) temperatures on the duration of USD: (<b>a</b>) aqueous (MFN and Sulfanol); (<b>b</b>) aqueous (CNPLUS and ViscoCrete 2100); (<b>c</b>) organic (MWCNT and industrial oil); (<b>d</b>) organic (MWCNT-MD and RSPE).</p> Full article ">Figure 7
<p>Change in the average particle size from the duration of the USD: (<b>a</b>) aqueous (MFN and Sulfanol); (<b>b</b>) aqueous (CNPLUS and ViscoCrete 2100); (<b>c</b>) organic (MWCNT and industrial oil); (<b>d</b>) organic (MWCNT-MD and RSPE).</p> Full article ">Figure 8
<p>Change in the particle content &lt;100 nm from the duration of the USD: (<b>a</b>) aqueous (MFN and Sulfanol); (<b>b</b>) aqueous (CNPLUS and ViscoCrete 2100); (<b>c</b>) organic (MWCNT and industrial oil); (<b>d</b>) organic (MWCNT-MD and RSPE).</p> Full article ">Figure 9
<p>The energy dependence of the interaction between particles on their distance. U—energy of interaction between particles; <span class="html-italic">R</span><sub>1</sub>—distance of the nearest potential holes (near coagulation); <span class="html-italic">R</span><sub>2</sub>—distance of the farther potential holes (distant coagulation).</p> Full article ">Figure 10
<p>The effect of CNPLUS content on the strength parameters of concrete mortar: (<b>a</b>) compressive strength; (<b>b</b>) tensile strength during bending.</p> Full article ">

2022

Jump to: 2024, 2023, 2021

27 pages, 2922 KiB  
Article
Applicability and Limitations of Ru’s Formulation for Vibration Modelling of Double-Walled Carbon Nanotubes
by Matteo Strozzi
C 2022, 8(4), 59; https://doi.org/10.3390/c8040059 - 2 Nov 2022
Cited by 1 | Viewed by 1624
Abstract
In this paper, a comparison is conducted between two different formulations of the van der Waals interaction coefficient between layers, as applied to the vibrations of double-walled carbon nanotubes (DWCNTs); specifically, the evaluation of the natural frequencies is achieved through Ru’s and He’s [...] Read more.
In this paper, a comparison is conducted between two different formulations of the van der Waals interaction coefficient between layers, as applied to the vibrations of double-walled carbon nanotubes (DWCNTs); specifically, the evaluation of the natural frequencies is achieved through Ru’s and He’s formulations. The actual discrete DWCNT is modelled by means of a couple of concentric equivalent continuous thin cylindrical shells, where Donnell shell theory is adopted to obtain strain-displacement relationships. In order to take into account the chirality effect of DWCNT, an anisotropic elastic shell model is considered. Simply supported boundary conditions are imposed and the Rayleigh–Ritz method is used to obtain approximate natural frequencies and mode shapes. A parametric analysis considering different values of diameters and numbers of waves along longitudinal and circumferential directions is performed by adopting Ru’s and He’s formulations. From the comparisons, it is evident that Ru’s formulation provides unsatisfactory results for relatively low values of diameters and relatively high numbers of circumferential waves with respect to the more accurate He’s formulation. This behaviour is observed for every number of longitudinal half-waves. Therefore, Ru’s formulation cannot be used for the vibration modelling of DWCNTs in a large range of diameters and wavenumbers. Full article
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<p>Continuum modelling of a DWCNT. (<b>a</b>) Actual discrete DWCNT; (<b>b</b>) geometry of the equivalent continuous thin circular cylindrical shell; (<b>c</b>) cross-section of the surface of the equivalent continuous shell.</p> Full article ">Figure 2
<p>Schematic illustration of a <math display="inline"><semantics> <mrow> <mrow> <mo>(</mo> <mrow> <mi>r</mi> <mo>,</mo> <mi>s</mi> </mrow> <mo>)</mo> </mrow> </mrow> </semantics></math> single-walled carbon nanotube. (<b>a</b>) Global structure with a zoom of a single representative atom; (<b>b</b>) side view of the local structure; (<b>c</b>) top view of the local structure. Reprinted with permission from Ref. [<a href="#B22-carbon-08-00059" class="html-bibr">22</a>], 2006, The Royal Society.</p> Full article ">Figure 3
<p>Effect of the inner radius <span class="html-italic">R</span><sub>1</sub> (10<sup>−9</sup> m) on the value of van der Waals interaction coefficient <span class="html-italic">c</span> (10<sup>20</sup> N/m<sup>3</sup>) of the DWCNT of <a href="#carbon-08-00059-t001" class="html-table">Table 1</a>. Comparison between Ru’s (38) and He’s (39) formulations.</p> Full article ">Figure 4
<p>Percentage differences between the highest radial natural frequencies of the simply supported DWCNT of <a href="#carbon-08-00059-t001" class="html-table">Table 1</a> with inner radius <span class="html-italic">R</span><sub>1</sub> = 0.5 nm and aspect ratio <span class="html-italic">L</span>/<span class="html-italic">R</span><sub>2</sub> = 10 from Ru’s (38) and He’s (39) formulations. Donnell shell theory. Anisotropic elastic shell model. Number of longitudinal half-waves <span class="html-italic">m</span>. Number of circumferential waves <span class="html-italic">n</span>.</p> Full article ">Figure 5
<p>Percentage differences between the highest radial natural frequencies of the simply supported DWCNT of <a href="#carbon-08-00059-t001" class="html-table">Table 1</a> with inner radius <span class="html-italic">R</span><sub>1</sub> = 1 nm and aspect ratio <span class="html-italic">L</span>/<span class="html-italic">R</span><sub>2</sub> = 10 from Ru’s (38) and He’s (39) formulations. Donnell shell theory. Anisotropic elastic shell model. Number of longitudinal half-waves <span class="html-italic">m</span>. Number of circumferential waves <span class="html-italic">n</span>.</p> Full article ">Figure 6
<p>Percentage differences between the highest radial natural frequencies of the simply supported DWCNT of <a href="#carbon-08-00059-t001" class="html-table">Table 1</a> with inner radius <span class="html-italic">R</span><sub>1</sub> = 2 nm and aspect ratio <span class="html-italic">L</span>/<span class="html-italic">R</span><sub>2</sub> = 10 from Ru’s (38) and He’s (39) formulations. Donnell shell theory. Anisotropic elastic shell model. Number of longitudinal half-waves <span class="html-italic">m</span>. Number of circumferential waves <span class="html-italic">n</span>.</p> Full article ">Figure 7
<p>Percentage differences between the highest radial natural frequencies of the simply supported DWCNT of <a href="#carbon-08-00059-t001" class="html-table">Table 1</a> with inner radius <span class="html-italic">R</span><sub>1</sub> = 5 nm and aspect ratio <span class="html-italic">L</span>/<span class="html-italic">R</span><sub>2</sub> = 10 from Ru’s (38) and He’s (39) formulations. Donnell shell theory. Anisotropic elastic shell model. Number of longitudinal half-waves <span class="html-italic">m</span>. Number of circumferential waves <span class="html-italic">n</span>.</p> Full article ">Figure 8
<p>Percentage differences between the highest radial natural frequencies of the simply supported DWCNT of <a href="#carbon-08-00059-t001" class="html-table">Table 1</a> with inner radius <span class="html-italic">R</span><sub>1</sub> = 10 nm and aspect ratio <span class="html-italic">L</span>/<span class="html-italic">R</span><sub>2</sub> = 10 from Ru’s (38) and He’s (39) formulations. Donnell shell theory. Anisotropic elastic shell model. Number of longitudinal half-waves <span class="html-italic">m</span>. Number of circumferential waves <span class="html-italic">n</span>.</p> Full article ">Figure 9
<p>Percentage differences between the highest radial natural frequencies obtained via Ru’s (38) and He’s (39) formulations (He as reference). Donnell shell theory. Anisotropic elastic model. Simply supported DWCNT of <a href="#carbon-08-00059-t001" class="html-table">Table 1</a> with <span class="html-italic">m</span> = 1 longitudinal half-wave and aspect ratio <span class="html-italic">L</span>/<span class="html-italic">R</span><sub>2</sub> = 10. Inner radius <span class="html-italic">R</span><sub>1</sub>. Number of circumferential waves <span class="html-italic">n</span>.</p> Full article ">Figure 10
<p>Percentage differences between the highest radial natural frequencies obtained via isotropic and anisotropic elastic shell models (anisotropic model as reference). Donnell shell theory. He’s formulation (39). Simply supported DWCNT of <a href="#carbon-08-00059-t001" class="html-table">Table 1</a> and <a href="#carbon-08-00059-t002" class="html-table">Table 2</a> with aspect ratio <span class="html-italic">L</span>/<span class="html-italic">R</span><sub>2</sub> = 10 and <span class="html-italic">n</span> = 2. Inner radius <span class="html-italic">R</span><sub>1</sub>. Number of longitudinal half-waves <span class="html-italic">m</span>.</p> Full article ">
11 pages, 5260 KiB  
Article
Stability of Carboxyl-Functionalized Carbon Nanotubes in Simulated Cement Pore Solution and Its Effect on the Compressive Strength and Porosity of Cement-Based Nanocomposites
by Laura Silvestro, Geannina Terezinha Dos Santos Lima, Artur Spat Ruviaro and Philippe Jean Paul Gleize
C 2022, 8(3), 39; https://doi.org/10.3390/c8030039 - 19 Jul 2022
Cited by 5 | Viewed by 2538
Abstract
The application of carbon nanotubes to produce cementitious composites has been extensively researched. However, the dispersion of this nanomaterial remains a technical limitation for its use. Thus, initially, this study assessed the stability of carboxyl-functionalized CNT on aqueous suspensions and simulated cement pore [...] Read more.
The application of carbon nanotubes to produce cementitious composites has been extensively researched. However, the dispersion of this nanomaterial remains a technical limitation for its use. Thus, initially, this study assessed the stability of carboxyl-functionalized CNT on aqueous suspensions and simulated cement pore solution for 6 h through UV–visible spectroscopy. Subsequently, a CNT content of 0.1% by cement weight was incorporated into the cement pastes, and the compressive strength after 7, 14, 28, and 91 days was evaluated. In addition, the porosity of the CNT cementitious composites at 28 days of hydration was investigated by mercury intrusion porosimetry (MIP), and the microstructure was evaluated via scanning electron microscopy (SEM). The simulated cement pore solution’s alkaline environment affects the CNT stability, progressively reducing the dispersed CNT concentration over time. CNT reduced the cementitious matrix pores < 50 nm by 8.5%; however, it resulted in an increase of 4.5% in pores > 50 nm. Thus, CNT incorporation did not significantly affect the compressive strength of cement pastes. SEM results also suggested a high porosity of CNT cementitious composites. The CNT agglomeration trend in an alkaline environment affected the CNT performance in cement-based nanocomposites. Full article
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<p>SEM image of CNTs at 100,000× magnification.</p> Full article ">Figure 2
<p>Correlation between absorbance at 253 nm and CNT concentration.</p> Full article ">Figure 3
<p>Stability of CNT dispersions in water and simulated cementitious pore solution after 6 h.</p> Full article ">Figure 4
<p>Compressive strength of cement pastes after 7, 14, 28, and 91 days.</p> Full article ">Figure 5
<p>Cumulative pore volume (<b>a</b>) and pore size distribution (<b>b</b>) of cement pastes after 28 days.</p> Full article ">Figure 6
<p>SEM images of cement pastes after 28 days: (<b>a</b>) 0.0% CNT and (<b>b</b>) 0.1% CNT (1000× magnification).</p> Full article ">
17 pages, 5184 KiB  
Article
Digital Synthesis of Realistically Clustered Carbon Nanotubes
by Bryan T. Susi and Jay F. Tu
C 2022, 8(3), 34; https://doi.org/10.3390/c8030034 - 22 Jun 2022
Cited by 4 | Viewed by 2791
Abstract
A computational approach for creating realistically structured carbon nanotubes is presented to enable more accurate and impactful multi-scale modeling and simulation techniques for nanotube research. Much of the published literature to date involving computational modeling of carbon nanotubes simplifies their structure as being [...] Read more.
A computational approach for creating realistically structured carbon nanotubes is presented to enable more accurate and impactful multi-scale modeling and simulation techniques for nanotube research. Much of the published literature to date involving computational modeling of carbon nanotubes simplifies their structure as being long and straight, and often existing as isolated individual nanotubes. However, imagery of nanotubes has shown over several decades that nanotubes agglomerate together and exhibit looping and curvature due both to inter- and intra-nanotube attraction. The research presented in this paper leverages multi-scale simulations consisting of a simple bead-spring model for initial nanotube relaxation followed by a differential geometry approach to create an atomic representation of carbon nanotubes, and then finalized with molecular dynamics simulations using the Tersoff potential model for carbon that allows dynamic bonding and cleavage. The result is atomically accurate representations of carbon nanotubes that exist as single nanotubes, or as clusters of multiple nanotubes. The presented approach is demonstrated using (5,5) single-walled carbon nanotubes. The synthesized nanotubes are shown to relax into the curving and looping structures observed in transmission or scanning electron microscopy, but also exhibit nano-scale defects due to buckling, crimping, and twisting that are resolved during the molecular dynamics simulations. These features locally compromise the desired strength characteristics of nanotubes and therefore the presented procedure will enable more accurate modeling and simulation of nanotubes in subsequent research by representing them less as the theoretically straight and independent entities, but as realistically imperfect. Full article
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<p>(<b>a</b>) A straight section of an atomically resolved (5,5) singled-walled carbon nanotube, and (<b>b</b>) a simplified coarse-grained model based on [<a href="#B21-carbon-08-00034" class="html-bibr">21</a>] that serves as the coarsest representation of the presented hierarchical modeling approach.</p> Full article ">Figure 2
<p>(<b>a</b>) Orthographic view of a small section of a (5,5) SWNT, (<b>b</b>) Isolated view of two levels of concentric carbon rings that form a unit cell, colored by individual ring, and (<b>c</b>) View down the central axis of this straight example SWNT, where the central axis is denoted by the cross symbol.</p> Full article ">Figure 3
<p>A three-dimensional space curve (red line) with consistently oriented finite frames along the curve. The red line is representative of the coarse-grained nanotube’s central axis and the consistency in the finite frames defined by planes spanned by vectors <math display="inline"><semantics> <mover accent="true"> <mi>N</mi> <mo>¯</mo> </mover> </semantics></math> and <math display="inline"><semantics> <mover accent="true"> <mi>B</mi> <mo>¯</mo> </mover> </semantics></math> normal to the curve’s tangent vector <math display="inline"><semantics> <mover accent="true"> <mi>T</mi> <mo>¯</mo> </mover> </semantics></math> is required to enforce the appropriate rotations and re-orientations of the atomic carbon rings for building the atomistic nanotubes.</p> Full article ">Figure 4
<p>(<b>a</b>) Example of a cluster of random walk realizations for <span class="html-italic">N</span> = 10 nanotubes of varying lengths sampled from specifications provided by Carbon Solutions Inc. [<a href="#B35-carbon-08-00034" class="html-bibr">35</a>]. (<b>b</b>) Highly maligned and energetically unfavorable configuration shown in the magnified section.</p> Full article ">Figure 5
<p>(<b>a</b>) TEM image from Liu et al. [<a href="#B19-carbon-08-00034" class="html-bibr">19</a>] (<b>b</b>) slice of the relaxed coarse-grained configuration from the present research, and (<b>c</b>) the energy relaxation from the canonical MD simulation of the bead spring filament system showing convergence in kinetic and potential energies.</p> Full article ">Figure 6
<p>(<b>a</b>) Images of 4 carbon nanotubes differentiated by color from a large cluster on the order of 100 nm and (<b>b</b>) a close-up view of one representative loop to show atomistic resolution.</p> Full article ">Figure 7
<p>100 nm cluster of 10 relaxed atomically resolved carbon nanotubes (<b>e</b>) with insets (<b>a</b>–<b>d</b>) showing greater detail from different locations in the cluster. Different colors denote individual carbon nanotubes.</p> Full article ">Figure 8
<p>Transient records of the average kinetic (red, right axis) and average potential energy (black, left axis) for the 5-stage relaxation of the 100 nm cluster of 10 atomically resolved carbon nanotubes where the ensemble is noted graphically in concurrence with <a href="#carbon-08-00034-t003" class="html-table">Table 3</a>.</p> Full article ">Figure 9
<p>Atomically resolved nanotubes exhibit features and interactions coarse-grained models under-represent. Examples shown here include (<b>a</b>) nanotube fracture, (<b>b</b>) bending-buckling, and (<b>c</b>) fusing.</p> Full article ">
9 pages, 1751 KiB  
Article
Plasma-Enhanced Carbon Nanotube Fiber Cathode for Li-S Batteries
by Yanbo Fang, Yu-Yun Hsieh, Mahnoosh Khosravifar, Paa Kwasi Adusei, Sathya Narayan Kanakaraj, Bely Stockman, Vamsi Krishna Reddy Kondapalli and Vesselin Shanov
C 2022, 8(2), 30; https://doi.org/10.3390/c8020030 - 22 May 2022
Viewed by 3119
Abstract
Fiber-shaped batteries have attracted much interest in the last few years. However, a major challenge for this type of battery is their relatively low energy density. Here, we present a freestanding, flexible CNT fiber with high electrical conductivity and applied oxygen plasma-functionalization, which [...] Read more.
Fiber-shaped batteries have attracted much interest in the last few years. However, a major challenge for this type of battery is their relatively low energy density. Here, we present a freestanding, flexible CNT fiber with high electrical conductivity and applied oxygen plasma-functionalization, which was successfully employed to serve as an effective cathode for Li-S batteries. The electrochemical results obtained from the conducted battery tests showed a decent rate capability and cyclic stability. The cathode delivered a capacity of 1019 mAh g−1 at 0.1 C. It accommodated a high sulfur loading of 73% and maintained 47% of the initial capacity after 300 cycles. The demonstrated performance of the fiber cathode provides new insights for the designing and fabrication of high energy density fiber-shaped batteries. Full article
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<p>Low magnification SEM images of (<b>a</b>) OCNT-S, (<b>b</b>) CNT-S. High magnification SEM images of (<b>c</b>) OCNT-S, (<b>d</b>) CNT-S. The scale bars in the SEM images for (<b>a</b>,<b>b</b>) are 20 µm, and for (<b>c</b>,<b>d</b>) are 5 µm. (<b>e</b>) X-ray CT images of OCNT-S in XY slice. (<b>f</b>) X-ray CT images of OCNT-S in YZ slice. Scare bars for both (<b>e</b>,<b>f</b>) are 10 µm. (<b>g</b>) TGA curves for OCNT-S and CNT-S. (<b>h</b>) Raman spectra of CNT, OCNT, and OCNT-S, where characteristic peaks of sulfur were observed for CNT-S. The I<sub>D</sub>/I<sub>G</sub> ratios in all these samples are indicated. (<b>i</b>) Tensile stress vs. strain plot of pristine CNT and OCNT-S, respectively.</p> Full article ">Figure 1 Cont.
<p>Low magnification SEM images of (<b>a</b>) OCNT-S, (<b>b</b>) CNT-S. High magnification SEM images of (<b>c</b>) OCNT-S, (<b>d</b>) CNT-S. The scale bars in the SEM images for (<b>a</b>,<b>b</b>) are 20 µm, and for (<b>c</b>,<b>d</b>) are 5 µm. (<b>e</b>) X-ray CT images of OCNT-S in XY slice. (<b>f</b>) X-ray CT images of OCNT-S in YZ slice. Scare bars for both (<b>e</b>,<b>f</b>) are 10 µm. (<b>g</b>) TGA curves for OCNT-S and CNT-S. (<b>h</b>) Raman spectra of CNT, OCNT, and OCNT-S, where characteristic peaks of sulfur were observed for CNT-S. The I<sub>D</sub>/I<sub>G</sub> ratios in all these samples are indicated. (<b>i</b>) Tensile stress vs. strain plot of pristine CNT and OCNT-S, respectively.</p> Full article ">Figure 2
<p>(<b>a</b>) Rate capability of Li-S cells with CNT-S and OCNT-S cathodes up to 2 C. (<b>b</b>) Discharge/charge profiles in the second cycle of Li-S cells with CNT-S and OCNT-S cathodes at a current density of 0.2 C.</p> Full article ">Figure 3
<p>(<b>a</b>) Cycling performance of Li-S cells assembled with CNT-S and OCNT-S as cathodes at a current density of 0.1 C. (<b>b</b>) EIS spectra of the CNT-S and OCNT-S after 3 cycles and after 300 cycles.</p> Full article ">
18 pages, 1793 KiB  
Article
Engineering of Nanostructured Carbon Catalyst Supports for the Continuous Reduction of Bromate in Drinking Water
by João M. Cunha Bessa da Costa, José R. Monteiro Barbosa, João Restivo, Carla A. Orge, Anabela Nogueira, Sérgio Castro-Silva, Manuel F. Ribeiro Pereira and Olívia S. Gonçalves Pinto Soares
C 2022, 8(2), 21; https://doi.org/10.3390/c8020021 - 22 Mar 2022
Cited by 3 | Viewed by 3641
Abstract
Recent works in the development of nanostructured catalysts for bromate reduction in drinking water under hydrogen have highlighted the importance of the properties of the metallic phase support in their overall performance. Since most works in catalyst development are carried out in powder [...] Read more.
Recent works in the development of nanostructured catalysts for bromate reduction in drinking water under hydrogen have highlighted the importance of the properties of the metallic phase support in their overall performance. Since most works in catalyst development are carried out in powder form, there is an overlooked gap in the correlation between catalyst support properties and performance in typical continuous applications such as fixed bed reactors. In this work, it is shown that the mechanical modification of commercially available carbon nanotubes, one of the most promising supports, can significantly enhance the activity of the catalytic system when tested in a stirred tank reactor, but upon transition to a fixed bed reactor, the formation of preferential pathways for the liquid flow and high pressure drops were observed. This effect could be minimized by the addition of an inert filler to increase the bed porosity; however, the improvement in catalytic performance when compared with the as-received support material was not retained. The operation of the continuous catalytic system was then optimized using a 1 wt.% Pd catalyst supported on the as-received carbon nanotubes. Effluent and hydrogen flow rates as well as catalyst loadings were systematically optimized to find an efficient set of parameters for the operation of the system, regarding its catalytic performance, capacity to treat large effluent flows, and minimization of catalyst and hydrogen requirements. Experiments carried out in the presence of distilled water as a reaction medium demonstrate that bromate can be efficiently removed from the liquid phase, whereas when using a real water matrix, a tendency for the deactivation of the catalyst over time was more apparent throughout 200 flow passages over the catalytic bed, which was mostly attributed to the competitive adsorption of inorganic matter on the catalyst active centers, or the formation of mineral deposits blocking access to the catalyst. Full article
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<p>Schematic representation of the reactor system used for reduction of bromate in continuous mode.</p> Full article ">Figure 2
<p>Dimensionless bromate concentration during semi-batch hydrogen reduction over 1 wt.% Pd catalysts on different carbon supports. (H<sub>2</sub> = 50 cm<sup>3</sup> min<sup>−1</sup>, C<sub>0</sub> (BrO<sub>3</sub><sup>−</sup>) = 200 ppb, 0.125 g<sub>CAT</sub> L<sup>−1</sup>).</p> Full article ">Figure 3
<p>Bromate concentration (ppb) during continuous hydrogen reduction over the catalysts 1 wt.% Pd/MWCNT-O, 1 wt.% Pd/MWCNT@N and 1 wt.% Pd/MWCNT-BM mixed with 0.500 mm carborundum under H<sub>2</sub>. (Q = 5 mL min<sup>−1</sup>, 200 mg<sub>CAT</sub>, H<sub>2</sub> = 50 cm<sup>3</sup> min<sup>−1</sup>, C (BrO<sub>3</sub><sup>−</sup>) = 200 ppb).</p> Full article ">Figure 4
<p>Bromate concentration (ppb) during continuous hydrogen reduction over the catalyst 1 wt.% Pd/MWCNT-O mixed with 0.500 mm carborundum under different H<sub>2</sub> flow rates. (Q = 5 mL min<sup>−1</sup>, 200 mg<sub>CAT</sub>, C (BrO<sub>3</sub><sup>−</sup>) = 200 ppb).</p> Full article ">Figure 5
<p>Bromate concentration (ppb) during continuous hydrogen reduction over the catalyst 1 wt.% Pd/MWCNT-O mixed with 0.500 mm carborundum under H<sub>2</sub> using different feed flow rates of water containing bromate. (200 mg<sub>CAT</sub>, H<sub>2</sub> = 50 cm<sup>3</sup> min<sup>−1</sup>, C (BrO<sub>3</sub><sup>-</sup>) = 200 ppb).</p> Full article ">Figure 6
<p>Bromate concentration (ppb) during continuous hydrogen reduction using different catalyst loadings of 1 wt.% Pd/MWCNT-O mixed with 0.500 mm carborundum under H<sub>2</sub>. (Q = 5 mL min<sup>−1</sup>, H<sub>2</sub> = 50 cm<sup>3</sup> min<sup>−1</sup>, C (BrO<sub>3</sub><sup>−</sup>) = 200 ppb).</p> Full article ">Figure 7
<p>Dimensionless bromate concentration during semi-batch hydrogen reduction over the catalyst 1 wt.% Pd/MWCNT-BM using different types of water. (H<sub>2</sub> = 50 cm<sup>3</sup> min<sup>−1</sup>, C<sub>0</sub> (BrO<sub>3</sub><sup>−</sup>) = 200 ppb, 0.125 g<sub>CAT</sub> L<sup>−1</sup>).</p> Full article ">Figure 8
<p>Bromate concentration (ppb) during continuous hydrogen reduction over the catalyst 1 wt.% Pd/MWCNT-O mixed with 0.500 mm carborundum under H<sub>2</sub> using distilled water and water from a water treatment plant. (Q = 7.8 mL min<sup>−1</sup>, 200 mg<sub>CAT</sub>, H<sub>2</sub> = 12.5 cm<sup>3</sup> min<sup>−1</sup>, C (BrO<sub>3</sub><sup>−</sup>) = 200 ppb).</p> Full article ">
9 pages, 3449 KiB  
Article
From Waste Plastics to Carbon Nanotube Audio Cables
by Varun Shenoy Gangoli, Tim Yick, Fang Bian and Alvin Orbaek White
C 2022, 8(1), 9; https://doi.org/10.3390/c8010009 - 25 Jan 2022
Cited by 3 | Viewed by 4592
Abstract
Carbon nanotubes (CNTs) have long been at the forefront of materials research, with applications ranging from composites for increased tensile strength in construction and sports equipment to transistor switches and solar cell electrodes in energy applications. There remains untapped potential still when it [...] Read more.
Carbon nanotubes (CNTs) have long been at the forefront of materials research, with applications ranging from composites for increased tensile strength in construction and sports equipment to transistor switches and solar cell electrodes in energy applications. There remains untapped potential still when it comes to energy and data transmission, with our group having previously demonstrated a working ethernet cable composed of CNT fibers. Material composition, electrical resistance, and electrical capacitance all play a strong role in the making of high-quality microphone and headphone cables, and the work herein describes the formation of a proof-of-concept CNT audio cable. Testing was done compared to commercial cables, with frequency response measurements performed for further objective testing. The results show performance is on par with commercial cables, and the CNTs being grown from waste plastics as a carbon source further adds to the value proposition, while also being environmentally friendly. Full article
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<p>Example CNT/Cu audio cable manufactured using CNTs grown from polystyrene as the carbon source in the middle (black wiring) and copper wiring (red wiring) on either side to complete the circuit from one 3.5 mm stereo jack plug to another.</p> Full article ">Figure 2
<p>Custom set of artificial ears manufactured with soft silicone earmolds on either side and two IEC711 occluded ear simulators to measure the frequency response of headphones. There are both XLR and 3.5 mm microphone outputs to aid in the same.</p> Full article ">Figure 3
<p>Scanning electron microscopy of MWCNTs produced using polystyrene dissolved in toluene as the carbon source and ferrocene as a source of iron catalyst. Residual catalyst and amorphous carbon impurities are present here, although the vast majority of the product remains CNTs.</p> Full article ">Figure 4
<p>Resonant Raman spectroscopy of MWCNTs was recorded using (<b>a</b>) 633 nm and (<b>b</b>) 785 nm lasers.</p> Full article ">Figure 5
<p>(<b>a</b>) Control setup for the frequency response measurement of the HiFiMAN Arya headphones using commercial copper headphone and microphone cables and (<b>b</b>) the setup using the CNT/Cu audio cable as the headphone cable along with the same commercial microphone cable.</p> Full article ">Figure 6
<p>The frequency response of the HiFiMAN Arya headphones (right channel, averaged over three measurements) using a commercial headphone cable compared to the CNT/Cu cable as the headphone cable. Both are within error margins once the volume is matched.</p> Full article ">Figure 7
<p>(<b>a</b>) Control setup for frequency response measurement of the HiFiMAN Arya headphones using commercial copper headphone and microphone cables and (<b>b</b>) the setup using the CNT/Cu audio cable as the microphone cable along with the same commercial headphone cable from before.</p> Full article ">Figure 8
<p>The frequency response of the HiFiMAN Arya headphones (right channel, averaged over three measurements) using a commercial microphone cable compared to the CNT/Cu cable as the replacement microphone cable.</p> Full article ">

2021

Jump to: 2024, 2023, 2022

11 pages, 1944 KiB  
Article
Prediction of the Near-Infrared Absorption Spectrum of Single-Walled Carbon Nanotubes Using a Bayesian Regularized Back Propagation Neural Network Model
by Takao Onishi, Yuji Matsukawa, Yuto Yamazaki and Daisuke Miyashiro
C 2021, 7(4), 80; https://doi.org/10.3390/c7040080 - 25 Nov 2021
Cited by 1 | Viewed by 2944
Abstract
DNA-wrapped single-walled carbon nanotubes (DNA-SWCNTs) in stable dispersion are expected to be used as biosensors in the future, because they have the property of absorption of light in the near infrared (NIR) region, which is safe for the human body. However, this practical [...] Read more.
DNA-wrapped single-walled carbon nanotubes (DNA-SWCNTs) in stable dispersion are expected to be used as biosensors in the future, because they have the property of absorption of light in the near infrared (NIR) region, which is safe for the human body. However, this practical application requires the understanding of the DNA-SWCNTs’ detailed response characteristics. The purpose of this study is to predict, in detail, the response characteristics of the absorption spectra that result when the antioxidant catechin is added to oxidized DNA-SWCNTs, from a small amount of experimental data. Therefore, in the present study, we predicted the characteristics of the absorption spectra of DNA-SWCNTs using the Bayesian regularization backpropagation neural network (BRBPNN) model. The BRBPNN model was trained with the catechin concentration and initial absorption peaks as inputs and the absorption spectra after catechin addition as outputs. The accuracy of the predicted absorption peaks and wavelengths after the addition of catechin, as predicted by the BRBPNN model, was within 1% of the error of the experimental data. By inputting the catechin concentrations under hundreds of conditions into this BRBPNN model, we were able to obtain detailed prediction curves for the absorption peaks. This method has the potential to help to reduce the experimental costs and improve the efficiency of investigating the properties of high-cost materials such as SWCNTs. Full article
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Full article ">Figure 1
<p>Typical reaction example of experimental data targeted by the BRBPNN model. Blue line of step 1 is NIR spectrum in the initial state of DNA-SWCNTs. Red line is NIR spectrum with H<sub>2</sub>O<sub>2</sub> added to the initial state. Green line is NIR spectrum with catechin added in step 2.</p> Full article ">Figure 2
<p>Overview of the learned BRBPNN model. Initial (8,4)/(9,4) peak absorption and catechin concentration are used as input data I, II, and NIR spectra after catechin addition in (iii) state as output data.</p> Full article ">Figure 3
<p>Comparison of the results of prediction data and verification data in the spectrum waveform after catechin addition for each catechin concentration.</p> Full article ">Figure 4
<p>(<b>a</b>) Comparison of prediction data and verification data of absorption peak of (8,4)/(9,4) DNA-SWCNTs. (<b>b</b>) Comparison of prediction data and verification data of peak wavelength of (8,4)/(9,4) DNA-SWCNTs. Each value is expressed as mean ± standard deviation.</p> Full article ">Figure 5
<p>Prediction results of (8,4)/(9/4) absorption peaks for catechin concentration input using BRBPNN: The blue circles represent the BRBPNN model’s output from learned data. The orange circles represent the BRBPNN model’s outputs when the learned excluding the catechin 1.5 μg/mL. The light blue circles represent the BRBPNN model’s output when learned excluded the catechin 0.075 μg/mL. The green squares, black lines and gray dotted lines represent the validation data, the power approximation lines and the polynomial approximation lines (quadratic) for them, respectively.</p> Full article ">
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