Nanotube-based Composites Research Articles

Modulating the Doping Effect for Carbon Nanotube-Based Thermoelectric Composites by Radical-Containing Naphthalene Diimides

Modulating the Doping Effect for Carbon Nanotube-Based Thermoelectric Composites by Radical-Containing Naphthalene Diimides

Development of Lightweight and Flexible Electromagnetic Shielding Materials using Carbon Nanotube-based Composites

Development of Lightweight and Flexible Electromagnetic Shielding Materials using Carbon Nanotube-based Composites

Vertically Oriented Carbon Nanotube-Based Composites for Thermal Management

Vertically Oriented Carbon Nanotube-Based Composites for Thermal Management

3D printable carbon nanotubes-based composites with reconfigurable shapes and properties

In this work, we developed an efficient approach to fabricating composites of carbon nanotubes (CNT) with shape reconfiguration ability and Joule heating behavior by incorporating the direct ink writing (DIW) technique. Our 3D printable ink consisted of a high concentration of CNT stabilized by polyvinylpyrrolidone (PVP) in an aqueous polyvinyl alcohol (PVA) solution. The rheology of the ink was tuned by the amounts of CNT and PVP. The printed objects underwent the freeze-thaw process to form weak hydrogels induced by the crystallization of PVA. Subsequently, the hydrogels were immersed in a deep eutectic solvent (DES) bath consisting of choline chloride and glycerol. This process replaced the water in the hydrogels with DES and led to mechanically tough DES/CNT gels. We utilized the high stretchability of DES/CNT gel to achieve complex geometries that would be challenging to accomplish solely with DIW. After reshaping the DES/CNT gels, the target shape was fixed by further solvent exchange with ethanol and drying. The final CNT composites showed a high electric conductivity of up to 33.94 S/m and exhibited remarkable Joule heating performance using a low applied voltage (5 V). Additionally, we successfully achieved a spatial variation of mechanical stiffness, electrical conductivity, and Joule heating across the printed objects by a selective solvent removal process. In short, this work expands the scope of possible shapes and properties of CNT-based composites.

Continuous Biopotential Monitoring via Carbon Nanotubes Paper Composites (CPC) for Sustainable Health Analysis.

Skin-based wearable devices have gained significant attention due to advancements in soft materials and thin-film technologies. Nevertheless, traditional wearable electronics often entail expensive and intricate manufacturing processes and rely on metal-based substrates that are susceptible to corrosion and lack flexibility. In response to these challenges, this paper has emerged with an alternative substrate for wearable electrodes due to its cost-effectiveness and scalability in manufacturing. Paper-based electrodes offer an attractive solution with their inherent properties of high breathability, flexibility, biocompatibility, and tunability. In this study, we introduce carbon nanotube-based paper composites (CPC) electrodes designed for the continuous detection of biopotential signals, such as electrooculography (EOG), electrocardiogram (ECG), and electroencephalogram (EEG). To prevent direct skin contact with carbon nanotubes, we apply various packaging materials, including polydimethylsiloxane (PDMS), Eco-flex, polyimide (PI), and polyurethane (PU). We conduct a comparative analysis of their signal-to-noise ratios in comparison to conventional gel electrodes. Our system demonstrates real-time biopotential monitoring for continuous health tracking, utilizing CPC in conjunction with a portable data acquisition system. The collected data are analyzed to provide accurate heart rates, respiratory rates, and heart rate variability metrics. Additionally, we explore the feasibility using CPC for sleep monitoring by collecting EEG signals.

Enhancing electromagnetic properties through carbon Nanotube-Based polymer composites

In this study, electromagnetic [EM] wave-absorbing property material was fabricated from a polymer composite material with [0°/90°]s fiber orientation and Multiwall Carbon Nanotubes (MWCNTs) as filler materials, and with a Perfect Electric Conducting (PEC) material. The experiments are conducted for the composites with PEC-coated and non-PEC-coated materials, using a Vector Network Analyzer by X-band in the frequency range of 8.2 to 12.4 GHz. The characteristics like EM properties and microwave (MW) absorbing properties were calculated in terms of permeability, permittivity, and reflection losses. In addition, mechanical, thermal, and morphological analysis was also performed. The EM absorbing properties were found to be strong for the composites at 5 % reinforcement and for PEC-coated specimens, i.e., −38.69 dB at 10.5 GHz. A similar trend was followed for both mechanical and thermal properties. The CRITIC analysis was performed for these experimental data of EM, mechanical, and thermal properties. By this analysis, the weight percentages were calculated, which defines the sequence order in which the fabricated composites are capable of sustaining all properties. The highest weight percentage obtained for the weight loss parameter (thermal property) was 16.3 %, and the lowest percentage obtained for thermal degradation was 9.7 %.

Effects of carbon nanotubes-based composites on the corrosion protection and mechanical properties of polymer coating in chloride environment

Carbon nanotubes (CNTs) possess excellent mechanical, thermal, electrical, electrochemical and optical properties. The combination of tungsten disulphide (WS2) and 3-aminopropyltriethoxysilane (APTES) with carbon nanotubes (CNTs) has improved the anticorrosive and mechanical capabilities of poly(p-phenylenediamine) (PpPD) coatings. Scanning electron microscopy/energy dispersive X-ray analysis (SEM/EDX), Transmission electron microscopy (TEM), Thermogravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS), and X-Ray diffraction (XRD) techniques were used to characterize the composites such as APTES/CNTs, CNTs/WS2, and APTES/CNTs-WS2. As a result, the dielectric constant of PpPD was raised by 82 times at 102 Hz with the addition of just 0.6% APTES/CNTs-WS2. The APTES/CNTs-WS2 composite demonstrate improved anticorrosive and mechanical performance of the PpPD coating, according to electrochemical methods and mechanical testing. With a water contact angle (WCA) of 157°, this material is highly hydrophobic. Additionally, the PpPD-APTES/CNTs-WS2 was discovered to have significantly stronger resistance (17989 kΩ.cm2) than pure PpPD (101 kΩ.cm2), as well as significantly higher microhardness and tensile strength. The structure of the PpPD-APTES/CNTs-WS2 nanocomposite plays major role in enhancing the mechanical and anticorrosion properties. As a result, the PpPD-APTES/CNTs-WS2 nanocomposite may be used as a covering for solar panel frames.

Irregularity molecular descriptors of VC5C7[m,n] and HC5C7[m,n] nanotubes

Scientific organizations are creating carbon nanotube-based composites like VC5C7[m,n] and HC5C7[m,n], which indicate significant response against voltage. Imbalance-based irregularity indices determine the degree of irregularity of a certain molecular structure and, as a result, determine the properties of a molecular substance. In this article, we aim to compute irregularity indices of two nanotubes, VC5C7[m,n] and HC5C7[m,n]. We produce formulas for the irregularity of these two nanotubes, which are functions depending on the parameters of the structure m and n. We compare our results graphically and conclude that VC5C7[m,n] is more irregular than HC5C7[m,n].

High-resolution and electrically conductive three-dimensional printing of carbon nanotube-based polymer composites enabled by solution intercalation

Incorporating multi-walled carbon nanotubes (MWCNT) as conductive nanofillers is attractive for improving electrical conductivity of 3D-printed photocurable polymers. However, poor dispersion of MWCNT in the resin significantly degrades electrical conductivity and dimensional accuracy. Herein, the rational strategy for promoting dispersion employing a solution intercalation method is presented, thereby contributing to high electrical conductivity and dimensional accuracy in stereolithography process. For the mask-image-projection-based stereolithography, optimal dispersion and corresponding curing conditions (e.g., UV dose) of the MWCNT-incorporated resin were investigated with respect to various concentration. Commercial polyurethane-based resin was used as a matrix mixed with varying MWCNT concentrations of up to 0.6 wt%; an electrical conductivity of 0.071 S/m was achieved while maintaining a high dimensional accuracy verified with the International Tolerance (IT) grade. Quantitative comparison of the dimensional accuracy using standardized benchmark artifact could prove the effectiveness of the developed methods on the 3D printing quality. Complex 3D metamaterial structures and micro-to-macro sized capacitive sensors have been fabricated to demonstrate their fine quality in terms of the conductivity and physical dimension. This work can highly improve the 3D-printing qualities in the nanocomposites with high concentration fillers, thereby extending their applications to multi-functional/multi-scale structures, such as metamaterials, sensing components, and mechanical interfaces.

Multi-walled carbon nanotube supported manganese selenide as a highly active bifunctional OER and ORR electrocatalyst

A manganese selenide and multiwalled carbon nanotube-based composite shows promising bifunctional electrocatalytic activity for the oxygen evolution and oxygen reduction reactions with superior stability and lower overpotential for both OER and ORR.

Development of Multi-Scale Carbon Nanofiber and Nanotube-Based Cementitious Composites for Reliable Sensing of Tensile Stresses

In this work, multi-scale cementitious composites containing short carbon fibers (CFs) and carbon nanofibers (CNFs)/multi-walled carbon nanotubes (MWCNTs) were studied for their tensile stress sensing properties. CF-based composites were prepared by mixing 0.25, 0.5 and 0.75 wt.% CFs (of cement) with water using magnetic stirring and Pluronic F-127 surfactant and adding the mixture to the cement paste. In multi-scale composites, CNFs/MWCNTs (0.1 and 0.15 wt.% of cement) were dispersed in water using Pluronic F-127 and ultrasonication and CFs were then added before mixing with the cement paste. All composites showed a reversible change in the electrical resistivity with tensile loading; the electrical resistivity increased and decreased with the increase and decrease in the tensile load/stress, respectively. Although CF-based composites showed the highest stress sensitivity among all specimens at 0.25% CF content, the fractional change in resistivity (FCR) did not show a linear correlation with the tensile load/stress. On the contrary, multi-scale composites containing CNFs (0.15% CNFs with 0.75% CFs) and MWCNTs (0.1% MWCNTs with 0.5% CFs) showed good stress sensitivity, along with a linear correlation between FCR and tensile load/stress. Stress sensitivities of 6.36 and 11.82%/MPa were obtained for the best CNF and MWCNT-based multi-scale composite sensors, respectively.

New Developments in Carbon-Based Nanomaterials for Automotive Brake Pad Applications and Future Challenges

The proper functioning of automotive brake pads is of utmost importance to ensure the safety of passengers. Therefore, brake pad materials must be chosen with utmost precision and care to ensure their optimal functioning for long durations. Through a thorough literature review, it is found that the materials used currently for this purpose pose multiple discrepancies. Therefore, it is imperative to shift our focus towards nanomaterials, as they are one of the essential novel materials in this field. This study discusses the multiple constituents used in commercial brake pads, their role in improving and stabilizing their operation, and their desired properties to achieve optimal functioning. Parallelly, this study also reviews some of the potential organic and carbon nanomaterials that could prove to provide tough competition to currently utilized materials for brake pad applications. From this review, the major future commercial brake pad materials obtained include the likes of banana peel powder, crab shell powder, coconut fibers, stark corn fibers, metal oxide composites, metal nitride composites, multiwalled carbon nanotubes, and hybrid nanocomposites. These materials are studied on the basis of their performance under high-frictional force applications and analyzed by considering their mechanical, chemical, thermal, and tribological properties. Carbon nanotube-based composites showed improved tribological and braking performances making them more attractive than the materials in commercially available brake pads. In addition to these, the effects of usage of such nanomaterials on the environment and health are reviewed, in order to understand the feasibility of utilization of nanomaterials in automotive brake pad applications. From this analysis, this work suggests that there are a variety of nanomaterials that prove to be capable of automotive brake pad applications and, with further research and technological developments, would prove to be an asset to the automotive brake pad industry.

Investigation of tetracycline removal from aqueous solutions using halloysite/chitosan nanocomposites and halloysite nanotubes/alginate hydrogel beads

In this study, halloysite nanotube-based composites were synthesized using chitosan and alginate biopolymers. The removal of tetracycline from aqueous solutions containing the tetracycline antibiotic with these composites was examined in batch-stirred vessels.The characterization of halloysite/chitosan nanocomposites and alginate hydrogel beads filled with halloysite nanotubes was performed using FTIR, BET, XRD and compared with their pure states. To examine the surface morphology, the SEM images of alginate hydrogel beads filled with halloysite nanotubes and TEM images of halloysite/chitosan nanocomposites were obtained.The tetracycline adsorption of halloysite/chitosan nanocomposites and halloysite/alginate hydrogel beads was investigated as a function of the medium pH, initial tetracycline concentration, the amount of sorbent, and the ratio of the components forming the composite to each other by mass. The tetracycline adsorption capacity and efficiency of the composites were compared with the adsorption systems in which pure halloysite nanotubes, chitosan nanoparticles and alginate beads were used as a sorbent alone. The fit of tetracycline adsorption of halloysite nanotubes, halloysite/chitosan nanocomposites, and halloysite/alginate hydrogel beads to the Langmuir and Freundlich adsorption models was investigated. To evaluate adsorption kinetics of tetracycline on halloysite based nanocomposites, the fit to the pseudo-first-order kinetic model and pseudo-second-order kinetic model was investigated.The removal of tetracyclines in different chemical forms from medical wastewater in a wide pH range can be ensured by using halloysite nanotubes alone or in composite forms. Halloysite-based composite structures have been shown to be effective in the removal of tetracyclines by the adsorption method.

Resistive Response of Carbon Nanotube-Based Composites Subjected to Water Aging.

This work aimed to monitor, through the changes in electrical resistance, the evolution of the mechanical properties due to aging caused by water sorption in carbon nanotube-based epoxy composites. The epoxy/CNT nanocomposites were prepared by dispersing the filler in the precursor through the ultra-sonication process and mixing the hardener by mechanical stirring. After an evaluation of the electrical properties, detected through a two-probe electrical measurement method, of nanocomposites at different percentages by weight of the filler (0.025, 0.05, 0.1, 0.3, 0.5, and 1.0), a concentration (0.1% by weight), close to that of the electrical percolation threshold, was chosen to evaluate the resistive response. This specific concentration was selected in order to obtain maximized values of the variation detected for the changes in the electrical resistance resulting from phenomena of structural relaxations/rearrangements due to water absorption. In particular, the electrical conductivity value switched from 8.2 × 10−14 S/m for the unfilled epoxy resin to 6.3 × 10−2 S/m for carbon nanotube-based epoxy composite at 0.1% by weight of the nanofiller. The water sorption caused a reduction in the mechanical properties (storage modulus and tan δ) due to swelling and plasticization phenomena, which caused the structural reorganization of the conductive interparticle contacts in the matrix with a consequent variation in the electrical resistance of the material. The found ‘non-Fickian’ water diffusion behavior was very similar to the variation in the electrical resistance with time. This last correlation allows the association of the measurement of the electrical resistance with the quantity of absorbed water and, therefore, with the aging of the material to water absorption, through the sensitivity factor (β). The resistive nature of the composite can be used to monitor the amount of water absorption and the changes in the structure of the material subject to water aging.

Multifunctional Leather Surface Design by Using Carbon Nanotube-Based Composites.

This paper deals with original research in smart leather surface design for the development of multifunctional properties by using multi-walled carbon nanotube (MWCNT)-based nanocomposites. The conductive properties were demonstrated for both sheepskin and bovine leather surfaces for 0.5% MWCNTs in finishing nanocompositions with prospects for new material design intended for flexible electronics or multifunctional leathers. The photocatalytic properties of bovine leather surface treated with 0.5% MWCNTs were shown against an olive oil stain after visible light exposure and were attributed to reactive oxygen species generation and supported by contact angle measurements in dynamic conditions. The volatile organic compounds’ decomposition and antibacterial tests confirmed the self-cleaning experimental conclusions. Ultraviolet protection factor had excellent values for leather surfaces treated with multi-walled carbon nanotube and the fastness resistance tests showed improved performance compared to control samples. Scanning electron microscopy with energy dispersive X-ray (SEM-EDX), X-ray photoelectron spectroscopy (XPS), and attenuated total reflection-Fourier transform infrared (ATR-FTIR) spectroscopy analysis confirmed the influence of different leather surfaces on MWCNT dispersion with an effect on nanoparticle reactivity and efficiency in self-cleaning properties. Multifunctional leather surfaces were designed and demonstrated through MWCNT-based nanocomposite use under conventional finishing conditions.

Combined effect of N-methyl pyrrolidone and ferrocene derivatives on thermoelectric performance of n-type single-wall carbon nanotube-based composites

Organic/single-walled carbon nanotube (SWCNT) composites as thermoelectric (TE) materials have been developed rapidly in recent years; however, research on n-type organic/SWCNTs is relatively lagging, and their performance needs to be further improved. In this work, three low-cost organometallic complexes (OMCs) with reducing abilities, including ferrocene (FeCp2), FeCp2 with an acetenyl group (EtFc) to extend the conjugation degree, and FeCp2 with a (dimethylamino)methyl group (FcMA) to increase the electron-donating ability, were developed to enhance the TE properties of n-type SWCNT-based composites. In addition, the effect of solvents was also studied, and it was determined that a synergistic effect of N-methyl pyrrolidone (NMP) and ferrocene derivatives occurred in enhancing the n-type properties. Among the three OMCs, SWCNT/FcMA prepared from NMP displayed the highest TE performance, indicating that the ferrocene and (dimethylamino)methyl group can also form synergistic effects. When the mass ratio of the SWCNTs and FcMA was 1:7, the highest power factor of 567.54 ± 27.18 μW m−1 K−2 at room temperature was achieved, which is among the state-of-the-art n-type SWCNT/organic molecule-based TE materials in literature. A combination of field emission scanning electron microscopy and photoelectron spectroscopy indicated that the electrons could be transferred from NMP, FeCp2 and its derivatives to SWCNTs, leading to an upshift in the Fermi level and an increase in conductivity. Moreover, a TE device containing five p (SWCNTs) − n (SWCNT/FcMA) junctions was assembled, and an open-circuit voltage of 22.7 mV with an output power of 0.75 µW at a temperature difference of 54.1 K was achieved. These results showed that OMCs possess promising applications in future n-type carbon nanotube-based TE materials.

The physical fundamentals of the electrical conductivity in nanotube-based composites

In this article, we show that the classical theories of percolation, continuum percolation, and effective medium theory can account for all the features of electrical conductivity dependence on the content of the fibrous filler in composites in which the conducting particles are nanotubes, nanofibers, and nanowires. We show this by applying the corresponding concepts of the percolation nodes–links–blobs model, the excluded volume and the effective local conductance. In particular, in contrast with ad hoc or empirical evaluations of others, our analysis accounts simultaneously and quantitatively for the variety of values of the percolation thresholds, the electrical conductivity exponent, and the conductivity prefactor in all those systems. Our approach, therefore, provides a well-based theoretical physical framework for a comprehensive understanding of the electrical conductivity in those composites.

Mussel-inspired fabrication of halloysite nanotube-based magnetic composites as catalysts for highly efficient degradation of organic dyes

In this work, heterogeneous catalysts based on halloysite nanotubes (HNTs) were fabricated through mussel-inspired chemistry that could be used in situ to generate Fe3O4 nanoparticles on HNTs. HNT-based magnetic composites (HNTs@PDA-MNPs) were examined as catalysts for the Fenton reaction. The characterization results demonstrated that Fe3O4 nanoparticles could be well-dispersed on HNTs with polydopamine (PDA) as the linkage. Various experimental parameters, such as the concentrations of HNTs@PDA-MNPs and H2O2, reaction temperature and solution pH, of the degradation efficiencies were investigated in detail. The results demonstrated that the degradation efficiencies of methylene blue were greater than 97% under optimized conditions. Moreover, HNTs@PDA-MNPs also exhibited excellent degradation efficiencies for other organic dyes (such as rhodamine B, methyl orange, and Congo red). Electron spin-resonance spectroscopy suggested that free radicals such as •OH and •O2− were generated during the Fenton reaction, which could destroy the structure of the organic dyes. Taken together, a biomimetic method based on the self-polymerization of dopamine and the in situ generation of Fe3O4 nanoparticles on HNTs is developed for the fabrication of HNTs@PDA-MNP composites, which exhibit excellent degradation efficiencies towards different organic dyes through the Fenton reaction. This method can also be extended for the preparation of other multifunctional composites with potential for different applications.

Large-Area Carbon Nanotube-Based Flexible Composites for Ultra-Wide Range Pressure Sensing and Spatial Pressure Mapping.

Flexible pressure sensors are of broad interest for applications including human-machine interfaces, wearable electronics, and object/motion detection. However, complexities associated with constituent materials, fabrication processes, sensing mechanisms, and hardwiring often hinder the large-scale applications of using high performance pressure sensors reported in the literature. Here we demonstrate a large-area, highly flexible, conformable, and mechanically robust pressure sensor using a silicone elastomer with an embedded nonwoven textile carrier coated with carbon nanotubes. The selected silicone polymer allows through-thickness deformability of the sensor while the high modulus textile carrier ensures in-plane stiffness and stability. The sensor has an initial electrical conductivity of 4.4 ± 0.38 S/m and is fabricated using a straightforward dip coating and polymer infusion process and can be easily scaled-up for large-scale applications. On the basis of its hierarchical composite structure, this piezoresistive pressure sensor possesses extremely high resilience under compression, a repeatable monotonic positive pressure correlation, and an ultrawide elastic working range (5.5 ± 0.5 MPa) that can be segmentally linearized. A true two-dimensional modality for spatial pressure mapping is realized by utilizing electrical impedance tomography (EIT) and demonstrated to yield conductivity maps that can estimate the location, shape, and amplitude of both localized and distributed pressure with simple contact areas.

Wet-Chemical Assembly of 2D Nanomaterials into Lightweight, Microtube-Shaped, and Macroscopic 3D Networks.

Despite tremendous efforts toward fabrication of three-dimensional macrostructures of two-dimensional (2D) materials, the existing approaches still lack sufficient control over microscopic (morphology, porosity, pore size) and macroscopic (shape, size) properties of the resulting structures. In this work, a facile fabrication method for the wet-chemical assembly of carbon 2D nanomaterials into macroscopic networks of interconnected, hollow microtubes is introduced. As demonstrated for electrochemically exfoliated graphene, graphene oxide, and reduced graphene oxide, the approach allows for the preparation of highly porous (> 99.9%) and lightweight (<2 mg cm–3) aeromaterials with tailored porosity and pore size as well as tailorable shape and size. The unique tubelike morphology with high aspect ratio enables ultralow-percolation-threshold graphene composites (0.03 S m–1, 0.05 vol%) which even outperform most of the carbon nanotube-based composites, as well as highly conductive aeronetworks (8 S m–1, 4 mg cm–3). On top of that, long-term compression cycling of the aeronetworks demonstrates remarkable mechanical stability over 10 000 cycles, even though no chemical cross-linking is employed. The developed strategy could pave the way for fabrication of various macrostructures of 2D nanomaterials with defined shape, size, as well as micro- and nanostructure, crucial for numerous applications such as batteries, supercapacitors, and filters.