Carbon Nanotubes Content Research Articles

Structural modification of CNT-C xerogel through synthesis parameters

This study focuses on the synthesis of porous carbonaceous structures by drying resorcinol-formaldehyde (RF) gels under ambient conditions and then carbonizing them in an inert atmosphere. This avoids the expensive drying processes like supercritical drying or freeze drying. However, drying under ambient conditions does cause structural shrinkage and a reduction in porosity and specific surface area. Therefore, the goal of this study was to compensate for these structural degradations by adjusting other synthesis and process parameters, such as solvent exchange, drying condition, content of water, catalyst, and CNT in the gel. In the present study, different organic solvents such as t-butanol, ethanol, and acetone were used to replace the water in the hydrogels at a certain R/F molar ratio (1:2). The experimental results showed that t-butanol, with its low surface tension, resulted in a structure with a high specific surface area and pore volume. Regarding the catalyst dosage, by changing the R/C molar ratio between 71 and 849, the best structural properties were obtained using R/C∼200. Increasing the water content from 15 to 30 mL led to a decrease in specific surface area and pore volume. Drying the gel at an oven temperature of 85 °C resulted in the highest specific surface area, pore volume, and mean pore diameter. Increasing the dosage of carbon nanotubes (CNTs) in the range of 20–150 mg led to an increase in total pore volume and mean pore diameter. The results of this work can be a step forward towards the industrialization of these materials in various applications.

Study on the key influencing factors of KOH-catalyzed coal pyrolysis for direct preparation of carbon nanotubes

The environmental pollution and greenhouse gas emission caused by the traditional utilization of coal such as combustion, coking and gasification are becoming increasingly apparent. Green and environmentally friendly coal utilization technology is an effective way to solve this problem. In this study, high-value carbon nanotubes (CNTs) were directly prepared from coal by catalytic pyrolysis with low KOH content. It was found that when the KOH additive amount was 50 wt%, the influence of three main factors on the preparation of CNTs was as follows: pyrolysis temperature＞residence time＞heating rate. Pyrolysis temperature of 900 °C, heating rate of 15 °C/min, and residence time of 60 min were the best combination of KOH-catalyzed coal pyrolysis to prepare CNTs, and the content of CNTs in the corresponding sample was 10.01 wt%. This study has a specific contributes to the high-value transformation and utilization of coal resources and the preparation of CNTs.

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.

Behavior of Spin Probe TEMPO in Composites Based on Polypropylene with Different Content of Single-Wall Carbon Nanotubes

Behavior of Spin Probe TEMPO in Composites Based on Polypropylene with Different Content of Single-Wall Carbon Nanotubes

Effect of boramidic acid modified carbon nanotubes on neurological, morphological and physiological responses of zebrafish (Danio rerio) embryos and larvae

This study aimed to determine the potential toxicological effects of carbon nanotubes (CNTs), their modifications with ethylenediamine (ED) and boric acid (BA) on aquatic organisms. Specifically, the research focused on the morphological, physiological, and histopathological-immuno-histochemical responses in zebrafish (Danio rerio) embryos and larvae, via applying different concentrations of CNTs, CNT-ED, and CNT-ED-BA (Control, 5, 10, and 20 mg/L).The results indicated that 20 mg/L CNT nanoparticles were toxic to zebrafish larvae, with mortality rates increasing with CNT and CNT-ED concentrations, reaching 36.7 % at the highest CNT concentration. The highest dose caused considerable degeneration, necrosis, DNA damage, and apoptosis, as evidenced by histopathological and immunohistochemical tests. In contrast, despite their high concentration, CNT-ED-BA nanoparticles exhibited low toxicity. Behavioral studies revealed that CNT and CNT-ED nanoparticles had a more significant impact on sensory-motor functions compared to CNT-ED-BA nanoparticles. These findings suggest that modifying the nanosurface with boric acid, resulting in boramidic acid, can reduce the toxicity induced by CNT and CNT-ED.

Understanding interfacial dynamics: Hydrostatic pressure-induced sono-dispersion of carbon nanotubes

Homogeneously dispersing carbon nanotubes (CNTs) is crucial for minimizing agglomeration issues commonly encountered in commercially available CNTs samples, thereby enhancing their unique mechanical, electrical, thermal, and optical properties. In this study, we propose an alternative hydrostatic pressure-driven dispersion approach to effectively disperse CNTs and assess the impact of hydrostatic pressure on CNTs dispersion in deionized water (DIW). Our results demonstrate that ultrasonic treatment under a hydrostatic pressure of 0.1 MPa enables the achievement of a high concentration of multi-walled carbon nanotubes (MWCNTs) at approximately 4.23 mg/ml, significantly surpassing concentrations reported in recent studies (∼1.9 mg/ml). Thin buckypaper generated from these solutions exhibit exceptional electrical conductivity (∼4938 S/m). Numerical modeling demonstrates that the shock wave induced by bubble implosion is significantly enhanced, reaching 80 MPa under hydrostatic pressure, markedly higher than atmospheric pressure in previous studies (∼1.6 MPa). This enhancement leads to a twofold improvement in dispersion efficiency. For the first time, we reveal the underlying mechanism of nanobubbles (NBs) in dispersion stability. Our experimental results show a significant increase in the generation of NBs resulting from ultrasonic bubble collapse under hydrostatic pressure. This phenomenon plays a crucial role in the long-term stabilization of dispersion, which we observed over several months. The presence of negatively charged hydroxyl groups on the interface of the NBs is identified as a key factor in this stabilization process. The hydrostatic pressure-driven dispersion approach presented is essential for the large-scale dispersion of CNTs and other nanomaterials.

Structural Design of Multifunctional PET Non‐woven Fabric with Porous Dual‐Network for Infrared Stealth, Flame Retardant, and Electromagnetic Interference Shielding

With rapid advances in electronic and communication technology, electromagnetic interference and other problems are becoming increasingly prominent. Thus, electromagnetic interference shielding materials have recently garnered extensive attention. In this study, a multi‐walled carbon nanotube/polyurethane/non‐woven electromagnetic shielding material (CPNW) is developed using impregnation and nonsolvent‐induced‐phase separation techniques. Utilizing a three‐dimensional nonwoven network as the substrate, the “nonwoven fabric‐polyurethane‐carbon nanotube” composite is impregnated and cured via the non‐solvent‐induced‐phase separation method, resulting in a distinctive porous dual‐network structure that ensures robust interfacial bonding between carbon nanotubes, nonwoven fabric, and polyurethane. At a carbon nanotube content of 10% (based on the mass of nonwoven fabric), CPNW exhibited an electromagnetic interference shielding effectiveness of 28.8 dB, a thermal conductivity of 0.127 W m−1 K−1, and a burning time of 1 min and 15 s, demonstrating outstanding electromagnetic shielding, flame retardant, and infrared stealth capabilities. Overall, this study laid a theoretical groundwork for the development of multifunctional non‐woven electromagnetic shielding materials with widespread application potential in aerospace, military, artificial intelligence, and wearable electronics.

Piezoresistive properties for soft structures using hybrid CCB/CNT-based natural rubber latex composites

This study explores the development of flexible sensors for soft structures. Conductive carbon black (CCB) and carbon nanotubes (CNT) were incorporated into a natural rubber (NR) matrix using glutaraldehyde (GA) as a curing system. The sensor properties of latex-NR composites with 20 phr of CCB, including variations of CNT content (0.5 to 3 phr), were examined. Increasing CNT content beyond 0.5 phr decreased tensile strength and elongation at break, but improved sensitivity and gauge factor (GF). Additionally, applying a voltage over 5 V caused a joule heating of the latex-NR composite strip elements. When integrated onto a soft tendon-based TPU bending actuator, higher CNT content reduced electrical signal drift during cyclic bending, enhancing long-term monitoring. This research highlights the potential of CCB/CNT-based latex-NR composites for soft structure applications, including soft robotics and health monitoring.

Machine learning approach to predict the mechanical properties of cementitious materials containing carbon nanotubes

This research explores the use of machine learning to predict the mechanical properties of cementitious materials enhanced with carbon nanotubes (CNTs). Specifically, the study focuses on estimating the elastic modulus and flexural strength of these novel composite materials, with the potential to significantly impact the construction industry. Seven key variables were analyzed including water-to-cement ratio, sand-to-cement ratio, curing age, CNT aspect ratio, CNT content, surfactant-to-CNT ratio, and sonication time. Artificial neural network, support vector regression, and histogram gradient boosting, were used to predict these mechanical properties. Furthermore, a user-friendly formula was extracted from the neural network model. Each model performance was evaluated, revealing the neural network to be the most effective for predicting the elastic modulus. However, the histogram gradient boosting model outperformed all others in predicting flexural strength. These findings highlight the effectiveness of the employed techniques, in accurately predicting the properties of CNT-enhanced cementitious materials. Additionally, extracting formulas from the neural network provides valuable insights into the interplay between input parameters and mechanical properties.

Assessment of effective electrical conductivity in spherocylindrical carbon nanotube composites incorporating intrinsic properties of CNTs and interphase layer

This study introduces an analytical model using mean-field theory to estimate the effective electrical conductivity in composites of spherocylindrical carbon nanotubes (CNTs). The model adjusts the interphase layer's thickness and conductivity based on CNT concentration, affecting the electrical tunneling effect, and incorporates the properties of both CNTs and the interphase layer. Validated through detailed comparisons with experimental data, the model accurately predicts the electrical conductivities of polymer-CNT composites (PCNTs). Mean Squared Error analysis highlights its enhanced precision and superiority over traditional cylindrical CNT models. The model also explores how CNT dimensions, intrinsic conductivity, tunneling distance, potential barrier height, and variations in interphase thickness and conductivity influence electrical conductivity and percolation thresholds. This analytical model improves accuracy in predicting PCNT electrical conductivity and provides critical insights for designing and optimizing conductive polymer nanocomposites.

Conductive NR/PMMA-RAFT-CNT-rGO composites and their morphological, mechanical, and electrical properties

This study reports the synthesis of poly(methyl methacrylate) (PMMA)-carbon nanotube (CNT)-reduced graphene oxide (rGO) emulsions via reversible addition-fragmentation chain-transfer (RAFT)-mediated surfactant-free emulsion polymerization using a hydrophilic chain transfer agent. The rGO was prepared by the modified Hummers method and reduced with L-ascorbic acid. The effects of the CNT:rGO ratios and CNT and rGO contents on the conversion and stability of emulsion were investigated. Increasing the CNT and rGO contents from 1 to 4 wt% decreased the monomer conversion, while all the samples remained as colloidal dispersions. The morphology of PMMA-CNT-rGO composites showed the incorporated arrangement of a linear CNT portion connected with the rGO sheet dependent on the CNT:rGO ratio. Various PMMA-CNT-rGO filled natural rubber (NR) cast films were prepared. The NR/PMMA-CNT-rGO composite film with a 1 wt% filler loading at a CNT:rGO ratio of 1:1 presented a quite high modulus value (3.08 MPa) and sufficient intrinsic electrical conductivity (1.36 S/m) due to its strong filler-matrix interaction. Thus, the PMMA-RAFT-CNT-rGO composites at a very low filler content can be used as an effective reinforcement to enhance the mechanical and electrical properties of NR films with a high compatibility between the fillers and NR matrix.

Effects of carbon nanotubes and carbon fibers on the properties of ultra-high performance concrete for offshore wind power generation

Ultra-high performance concrete (UHPC), as one of the most eye-catching building materials, has been the subject of extensive research by scholars. On this basis, to expand the application of UHPC for offshore wind turbine towers in complex marine environments, three different fiber materials - copper-plated microfibre steel fibers, carbon fibers, and carbon nanotubes (CNTs) - have been selected for the study of the possibilities of further improving the mechanical properties of UHPC. This study focused on understanding the impact of various fiber combinations and dosages on the flowability, compressive strength, flexural strength, and tensile strength of UHPC. Our findings indicate that carbon fiber, when present at a concentration of up to 0.5%, the effect on the fluidity of UHPC is only about 1.05%. However, the addition of CNTs significantly diminishes the flowability of UHPC, with a consistent decrease observed as the CNT content increases. Notably, when carbon fiber and CNTs are used in combination, the maximum reduction in flowability reaches 7.8%. Furthermore, as the dosage of these fibers increases, the compressive strength, flexural strength, and tensile strength of UHPC all demonstrate a positive trend of improvement. It is observed that the optimal performance is achieved when both carbon fiber and CNTs are present. In particular, carbon fiber exhibits a more profound impact on enhancing compressive strength and flexural strength, when carbon fibers were doped by volume at 0.5%, the compressive and flexural strengths were increased by 6.7% and 11.7%, respectively, compared to the control group, while carbon nanotubes increased the tensile strength by 7.4% at lower dosage. These findings highlight the potential of fiber combinations to optimize UHPC’s mechanical properties for various engineering applications..

High‐performance electromagnetic shielding composite materials based on carbon nanotubes and Sandwich laminate structures

AbstractCarbon fiber‐reinforced composite materials exhibit excellent mechanical and electromagnetic shielding capabilities. However, they have some drawbacks, such as high cost and significant reflection losses. In order to address these shortcomings, this study set out to design a sandwich‐structured composite material and produce a composite material designed for electromagnetic shielding using Vacuum Assisted Resin Transfer Molding (VARTM) technology. This composite material promotes the “absorption‐reflection‐reabsorption” process of electromagnetic waves, significantly enhancing its shielding effectiveness, achieving up to 59.4 dB of shielding effect in the 8.2–12.4 GHz (X‐band) range. The study also employed carbon nanotubes (CNTs) matrix doping to modify the composite material, significantly reducing reflection losses. When the amount of carbon nanotubes added reaches 0.6 wt%, the overall SE can be increased by 18%. Additionally, the introduction of CNTs significantly improves the flexural strength and tensile strength of the composite material; at a 0.6 wt% CNT content, the average tensile strength increased from 526.4 to 600.9 MPa, indicating good interfacial interactions between CNTs and epoxy resin. This work provides valuable insights for the preparation of high‐performance electromagnetic shielding materials, with profound theoretical and practical significance.Highlights Observations through SEM and CT scanning techniques reveal that Vacuum Assisted Resin Transfer Molding (VARTM) technology facilitates strong interlayer bonding between carbon fibers, glass fibers, and copper wires, alongside effective epoxy resin adhesion, thus enhancing the mechanical properties. The sandwich structure's impedance mismatch characteristic facilitates an efficient “absorption‐reflection‐reabsorption” process of electromagnetic waves. Additionally, the incorporation of Carbon Nanotubes (CNTs) enhances the absorption mechanism, reducing reflection losses. Incorporating CNTs further boosts both flexural and tensile strengths, attributed to improved interfacial interactions inhibiting crack formation.

Improving Signal Transmission Quality of Wind Turbine Pitch Slip Ring With Copper Matrix Composites

Abstract To improve the signal transmission quality, copper matrix composites added with different contents of carbon nanotubes (CNTs) and molybdenum disulfide (MoS2) were prepared. The electrical and tribological properties of composites were studied. A new parameter, the correlation dimension of electrical noise, was proposed to quantitatively characterize the stability of signal transmission. Copper matrix composites added with reasonable amount of CNTs and MoS2 can effectively reduce the values and fluctuations of friction coefficient and improve the wear resistance, efficiency, and stability of the signal transmission. Tribo-films are generated on the surface of composites. The contents of CNTs and MoS2 affect the stability of tribo-film and further affect the signal transmission quality. 0.5 wt% CNTs and 15 wt% MoS2 can make good synergistic effects on improving the signal transmission quality of composites. The results provide good guidance to improve the signal transmission quality of wind pitch slip rings.

Mechanical properties of carbon nanotube (CNT) reinforced polymers using electron‐deficient aromatics as additives

AbstractIn initial experiments the effects of aromatic model substances on carbon nanotube (CNT) dispersions in dimethylformamide (DMF) were investigated. Electron‐deficient aromatics interact strongly with CNTs, causing increased agglomeration and sedimentation. Conversely, electron‐donating aromatics stabilize CNT dispersions in DMF. Polymers with electron‐deficient aromatics, such as polydinitrostyrene (PDNS), exhibit a concentration‐dependent effect: low concentrations lead to stabilization of dispersions, while higher concentrations lead to sedimentation. This suggests that such polymers can enhance attraction between the matrix of CNT‐reinforced polymers as well as stabilize the dispersed CNTs. Polycarbonate, modified with polydinitrocarbonate (PDNC) and reinforced with CNTs showed improved mechanical properties. The addition of 6 wt.% CNTs and 6 wt.% PDNC resulted in a notable improvement with a 22% increase in tensile strength, a 29% increase in flexural strength, a 39% increase in Young's modulus and a 47% increase in flexural modulus. This enhancement resulted in an overall mechanical performance comparable to the high‐performance polymer polyetherimide. However, there must be noted, that the addition of PDNC increases the CNT particle size, which can negatively affect mechanical properties. The results highlight the additive's dual role in enhancing adhesive interactions while potentially increasing CNT agglomerate sizes.Highlights Interactions of CNTs dispersed in DMF and various aromatics were investigated. Polydinitrocarbonate (PDNC) was synthesized as a new additive for CNT‐composites. Polycarbonate/CNT‐composites were obtained using extrusion. Test specimens with CNT contents up to 6 wt.% were obtained. Mechanical properties of polycarbonate reached the level of polyetherimide.

The effect of CNT grafting on the mechanical properties of the UHMWPE fiber/HDPE composite

In order to improve the mechanical properties of the ultra‐high molecular weight polyethylene (UHMWPE) fiber‐reinforced high‐density polyethylene (HDPE) composite, carbon nanotube (CNT) was grafted on the UHMWPE fiber. The UHMWPE fiber/HDPE composite was prepared by injection molding process, and the effects of CNT contents on the mechanical properties of composite materials were studied. The results show that the mass fraction of CNT will significantly affect the mechanical properties of the composite. When the CNT content is 4 wt%, the tensile strength, tensile modulus, flexural strength, flexural modulus, and impact strength of the UHMWPE fiber/treated CNT/HDPE composite increased compared to the UHMWPE fiber/CNT/HDPE composite and UHMWPE fiber/HDPE composite. When the CNT content is 4 wt%, the above‐mentioned performance is the best. Pull‐out and fracture, bridging effect, and crack deflection effect are the main mechanisms of CNTs in UHMWPE fiber/HDPE composites. This study provides new insights into the interface design of UHMWPE fiber/HDPE composites and paves the way for their further development.

270 MHz passively mode-locked Er-doped fiber laser using single walled carbon nanotube polymer film.

We demonstrated a short-cavity mode-locked erbium-doped fiber laser based on single walled carbon nanotube polymer composite film saturable absorber with a maximum fundamental repetition rate of 270.5 MHz. To the best of our knowledge, this is the highest fundamental repetition rate among mode-locked erbium-doped ring fiber lasers based on nanomaterial polymer composite films. Samples with non-saturable loss range from 13.2% to 60% and modulation depth from 1.63% to 7.08% are prepared by controlling carbon nanotube concentration and film thickness. We systematically investigate the impacts of saturable absorbers on mode-locking repetition rate. Our results show that when the laser repetition rate continuously increases from 15.45 MHz to 270.5 MHz, samples with higher non-saturable loss will push forward the mode-locking threshold and eventually lose mode-locking. In addition, the increased modulation depth will enhance the pulse shaping ability and result in a shorter pulse. Our results may help for high repetition rate mode-locked fiber laser design and improve the laser characteristics. The demonstrated laser may support applications such as frequency comb, etc.

Effect of Carbon Nanotubes on Chloride Diffusion, Strength, and Microstructure of Ultra-High Performance Concrete.

This study delved into the integration of carbon nanotubes (CNTs) in Ultra-High Performance Concrete (UHPC), exploring aspects such as mechanical properties, microstructure analysis, accelerated chloride penetration, and life service prediction. A dispersed CNT solution (0.025 to 0.075 wt%) was employed, along with a superplasticizer, to ensure high flowability in the UHPC slurry. In addition, the combination of high-strength functional artificial lightweight aggregate (ALA) and micro hollow spheres (MHS) was utilized as a replacement for fine aggregate to not only reduce the weight of the concrete but also to increase its mechanical performance. Experimental findings unveiled that an increased concentration of CNT in CNT1 (0.025%) and CNT2 (0.05%) blends led to a marginal improvement in compressive strength compared to the control mix. Conversely, the CNT3 (0.075%) mixture exhibited a reduction in compressive strength with a rising CNT content as an admixture. SEM analysis depicted that the heightened concentration of CNTs as an admixture induced the formation of nanoscale bridges within the concrete matrix. Ponding test results indicated that, for all samples, the effective chloride transport coefficient remained below the standard limitation of 1.00 × 10-12 m2/s, signifying acceptable performance in the ponding test for all samples. The life service prediction outcomes affirmed that, across various environmental scenarios, CNT1 and CNT2 mixtures consistently demonstrated superior performance compared to all other mixtures.

Research on the deformation law of ultra-thin fiber metal laminates under the synergistic effect of nano-reinforcement and scale effect

At present, titanium alloy/carbon fiber reinforced polymer (TA1/CFRP) laminates, representing the latest fourth generation of fiber metal laminates (FMLs), are predominantly applied in the field of aerospace. The miniaturization of traditional FMLs in thickness or plane size to the micron level for the study of structural properties of ultra-thin laminates will further expand the application of FMLs in the field of micro-devices. Given that carbon nanotubes have a strengthening mechanism in polymers. However, most existing studies have focused on the effect of carbon nanotubes on the properties of macro-scale FMLs, while the enhancement mechanism of the interfacial and mechanical properties of ultra-thin micro-scale FMLs has not been studied, leaving the mechanism still unclear. Based on this, this paper explores the interfacial deformation mode, damage fracture and performance enhancement mechanism of the ultra-thin TA1/CFRP laminates by comparing the parameters of tensile strength and elongation under quasi-static conditions and different process parameters of multi-walled carbon nanotubes content, test temperature, geometry size and grain size. Meanwhile, the correlation law between high-speed tension and quasi-static tension is determined, a 29.3 % increase in tensile strength as the strain rate rises from 0.001 s−1 to 100 s−1, yielding the basic deformation law of ultra-thin FMLs.

Carbon nanotube as a conductive rheological modifier for carbon fiber-reinforced epoxy 3D printing inks

Rheological modifiers enable direct ink writing of polymers with low viscosity such as epoxy without requiring light or heat. Modifiers that conduct electrons and phonons impart multifunctional properties to 3D printed polymers. Here, we report the development of printable nanocomposite inks comprised of epoxy, carbon fibers (CFs), and carbon nanotubes (CNTs) to achieve excellent mechanical properties and multifunctionality via high electrical conductivity required for next-generation light weight aerospace, electronics, and energy applications. CF and CNT concentrations of 8.5 and 1.7 wt%, respectively, render the material shear-thinning with a high yield stress, hence printable and self-supporting after being printed. An average electrical conductivity of 10−2 S/cm and thermal conductivity of 0.3 W/m.K were measured for the 3D-printed multi-layer structures. Furthermore, tensile modulus, tensile strength, flexural modulus, and flexural strength were measured to be 5.8, 0.08, 6.0, and 0.1 GPa, respectively. Compared with other 3D printed conductive polymer nanocomposites with reported electrical conductivity and elastic modulus, the structures here have the highest specific elastic modulus. They also possess the highest electrical conductivity among the 3D printed polymeric composites of carbon nanomaterials with an elastic modulus above 1 GPa. This is due to the outstanding combination of CNTs, CFs, and epoxy. The results expand the range of polymer properties for multifunctional applications.