Carbon Nanotubes Research Articles

Enhancing Electrochemical Performance of Si@CNT Anode by Integrating SrTiO3 Material for High-Capacity Lithium-Ion Batteries

Silicon (Si) has attracted worldwide attention for its ultrahigh theoretical storage capacity (4200 mA h g−1), low mass density (2.33 g cm−3), low operating potential (0.4 V vs. Li/Li+), abundant reserves, environmentally benign nature, and low cost. It is a promising high-energy-density anode material for next-generation lithium-ion batteries (LIBs), offering a replacement for graphite anodes owing to the escalating energy demands in booming automobile and energy storage applications. Unfortunately, the commercialization of silicon anodes is stringently hindered by large volume expansion during lithiation–delithiation, the unstable and detrimental growth of electrode/electrolyte interface layers, sluggish Li-ion diffusion, poor rate performance, and inherently low ion/electron conductivity. These present major safety challenges lead to quick capacity degradation in LIBs. Herein, we present the synergistic effects of nanostructured silicon and SrTiO3 (STO) for use as anodes in Li-ion batteries. Si and STO nanoparticles were incorporated into a multiwalled carbon nanotube (CNT) matrix using a planetary ball-milling process. The mechanical stress resulting from the expansion of Si was transferred via the CNT matrix to the STO. We discovered that the introduction of STO can improve the electrochemical performance of Si/CNT nanocomposite anodes. Experimental measurements and electrochemical impedance spectroscopy provide evidence for the enhanced mobility of Li-ions facilitated by STO. Hence, incorporating STO into the Si@CNT anode yields promising results, exhibiting a high initial Coulombic efficiency of approximately 85%, a reversible specific capacity of ~800 mA h g−1 after 100 cycles at 100 mA g−1, and a high-rate capability of 1400 mA g−1 with a capacity of 800 mA h g−1. Interestingly, it exhibits a capacity of 350 mAh g−1 after 1000 lithiation and delithiation cycles at a high rate of 600 mA hg−1. This result unveils and sheds light on the design of a scalable method for manufacturing Si anodes for next-generation LIBs.

Oxidative Catalytic Depolymerization of Lignin into Value-Added Monophenols by Carbon Nanotube-Supported Cu-Based Catalysts

Lignin valorisation into chemicals and fuels is of great importance in addressing energy challenges and advancing biorefining in a sustainable manner. In this study, on the basis of the high microwave absorption performance of carbon nanotubes (CNTs), a series of copper-oxide-loaded CNT catalysts (CuO/CNT) were developed to facilitate the oxidative depolymerization of lignin under microwave heating. This catalyst can promote the activation of hydrogen peroxide and air, effectively generating a range of reactive oxygen species (ROS). Through the application of electron paramagnetic resonance techniques, these ROS generated under different oxidation conditions were detected to elucidate the oxidation mechanism. The results demonstrate that the •OH and O2•− play a crucial role in the formation of aldehyde and ketone products through the cleavage of lignin Cβ-O and Cα-Cβ bonds. We further evaluated the catalytic performance of the CuO/CNT catalysts with three typical lignin feedstocks to determine their applicability for lignin biorefinery. The bio-enzymatic lignin produced a 13.9% monophenol yield at 200 °C for 20 min under microwave heating, which was higher than the 7% yield via hydrothermal heating conversion. The selectivity of G-/H-/S-type products was slightly affected, while lignin substrate had a noticeable effect on the selective production. Overall, this study explored the structural characteristics of CuO/CNT catalysts and their implications for lignin conversion and offered an efficient oxidation approach that holds promise for sustainable biorefining practices.

Synergistic plasma and platinum catalysts interactions in CO2 reforming of propane at room temperature: The role of supports

This study investigates the synergistic impact of plasma and catalyst in a hybrid non-thermal plasma system integrated with 1 wt% Pt catalysts supported on diverse catalyst supports (γ-Al2O3, SBA-15, HZSM-5, CeO2, TiO2, and multi-wall carbon nanotube (CNT)) at ambient conditions in dry reforming of propane (DRP). To optimize the reaction, the impact of in-situ plasma reduction time was investigated over the Pt/Al2O3 catalyst at varying durations before the DRP reaction. The most favorable catalytic performance was observed at a reduction time of 60 min due to having the highest surface area (284 m2/g), which might result in smaller Pt particle size, and the effective reduction of oxidation states to Pt0. A comparison of reduction sources also revealed that the plasma-reduced catalyst outperformed the other, which was attributed to the agglomeration of Pt active sites during the thermal reduction process. The chemo-physical properties of different catalysts directly affected the plasma characteristics and catalytic performance. Pt/Al2O3 exhibited the highest performance, attributed to having the smallest mean Pt particle size (0.94 nm) and highest discharge power (13.97 W), effective capacitance (1.41 nF), and charge transfer (0.34 μC) during DRP reaction, leading to a 13 % and 15 % increase in CO2 and C3H8 conversions, respectively, compared to plasma-only mode. The catalytic performance showed that the synergy of catalysts with higher basic sites and plasma characteristics, along with smaller Pt particle size, resulted in high reactant conversion and syngas selectivity. Binary HRTEM images also indicated the presence of more soft carbon (coke) in the pore channels of the spent Pt/HZSM-5 catalyst than in spent Pt/Al2O3.

Damage sensing in multi-functional nanocomposite polymer bonded energetics with embedded multi-walled carbon nanotube sensing networks

Abstract This experimental investigation evaluates the strain and damage sensing abilities of multi-walled carbon nanotube (MWCNT) networks embedded in the binder phase of polymer-bonded energetics (PBEs). PBEs are a special class of particulate composite materials that consist of energetic crystals bound by a polymer matrix, wherein the polymer matrix serves to maintain the composite’s shape and form. The structural health monitoring (SHM) approach presented in this work exploits the piezoresistive properties of the distributed MWCNT networks. Major challenges faced during such implementation include the low binder concentrations of PBEs, the presence of conductive/non-conductive particulate phases, the high degree of heterogeneity in the PBE microstructure, and achieving the optimal MWCNT dispersion. In this study, ammonium perchlorate (AP) crystals as the oxidizer, Aluminum grains as the metallic fuel, and Polydimethylsiloxane (PDMS) as the binder are used as the constituents for fabricating PBEs. To study the effect of each constituent on the MWCNT network’s SHM abilities, various materials systems are comprehensively studied: MWCNT/PDMS materials are first evaluated to study the binder’s electromechanical response, followed by AP/MWCNT/PDMS to assess the impact of AP addition, and finally, AP/AL/MWCNT/PDMS to evaluate the impact of adding conductive aluminum grains. Compression samples (ASTM D695) were fabricated and subjected to monotonic compression. Electrical resistance is recorded in conjunction with the mechanical test via an LCR meter. Gauge factors relating to the change in normalized resistance to applied strain are calculated to quantify the electromechanical response. MWCNT dispersions and mechanical failure modes are analyzed via scanning electron microscopy imaging of the fracture surfaces. Correlations between the electrical behavior in response to the mechanical behavior are presented, and possible mechanisms that influence the electromechanical behavior are discussed. The results presented herein demonstrate the successful ability of MWCNT networks as SHM sensors capable of real-time strain and damage assessment of PBEs.

Dynamic Tracking of Biological Processes Using Near-Infrared Fluorescent Single-Walled Carbon Nanotubes.

Biological processes are characterized by dynamic and elaborate temporal patterns driven by the interplay of genes, proteins, and cellular components that are crucial for adaptation to changing environments. This complexity spans from molecular to organismal scales, necessitating their real-time monitoring and tracking to unravel the active processes that fuel living systems and enable early disease detection, personalized medicine, and drug development. Single-walled carbon nanotubes (SWCNTs), with their unique physicochemical and optical properties, have emerged as promising tools for real-time tracking of such processes. This perspective highlights the key properties of SWCNTs that make them ideal for such monitoring. Subsequently, it surveys studies utilizing SWCNTs to track dynamic biological phenomena across hierarchical levels─from molecules to cells, tissues, organs, and whole organisms─acknowledging their pivotal role in advancing this field. Finally, the review outlines challenges and future directions, aiming to expand the frontier of real-time biological monitoring using SWCNTs, contributing to deeper insights and novel applications in biomedicine.

Scalable Layered Heterogeneous Hydrogel Fibers with Strain-Induced Crystallization for Tough, Resilient, and Highly Conductive Soft Bioelectronics.

The advancement of soft bioelectronics hinges critically on the electromechanical properties of hydrogels. Despite ongoing research into diverse material and structural strategies to enhance these properties, producing hydrogels that are simultaneously tough, resilient, and highly conductive for long-term, dynamic physiological monitoring remains a formidable challenge. Here, a strategy utilizing scalable layered heterogeneous hydrogel fibers (LHHFs) is introduced that enables synergistic electromechanical modulation of hydrogels. High toughness (1.4MJ m-3) and resilience (over 92% recovery from 200% strain) of LHHFs are achieved through a damage-free toughening mechanism that involves dense long-chain entanglements and reversible strain-induced crystallization of sodium polyacrylate. The unique symmetrical layered structure of LHHFs, featuring distinct electrical and mechanical functional layers, facilitates the mixing of multi-walled carbon nanotubes to significantly enhance electrical conductivity (192.7 S m-1) without compromising toughness and resilience. Furthermore, high-performance LHHF capacitive iontronic strain/pressure sensors and epidermal electrodes are developed, capable of accurately and stably capturing biomechanical and bioelectrical signals from the human body under long-term, dynamic conditions. The LHHF offers a promising route for developing hydrogels with uniquely integrated electromechanical attributes, advancing practical wearable healthcare applications.

Development and evaluation of cable-less heating mats utilizing low-power carbon nanotube planar heaters

We aimed to develop a low-power heating mat based on a carbon nanotube (CNT) planar heater and verify its performance by utilizing the heating element. The cell samples were manufactured, and their electrical and thermal properties were evaluated to conduct heating tests. The developed CNT planar heater was tested in four ways, namely heating one cell individually and heating two/three/four cells simultaneously. When operating multiple cells, the resistance decreased, and the power increased. The temperature averaged 37°C even when multiple cells were operating, and the power consumption per unit area was at a similar level. In addition, a prototype heating vest was fabricated using the cells, and a performance comparison was conducted with a third-party heating vest product. The heating efficiency was more than twice as high as that of the third-party product, and the heating area was more than twice as large. Prototype heating pads were made using the cells and compared with two other third-party samples that are heated by thermal wires, and the developed prototype was found to have a heating efficiency more than 20% higher than the other samples, with the lowest temperature deviation. The CNT planar heater developed in this study can be realized in various shapes without wires and can be used safely. It is economical because it can be set to the appropriate temperature in the desired area with a controller, and it is eco-friendly because it prevents mold growth by emitting far-infrared radiation.

Automating Trace Detection and Chemical Purity Analysis of Carbon Nanotube Mixtures by Non-Negative Matrix Factorization of Spatial Raman Scattering Hyperspectra

Carbon nanotubes come in different species having different properties. So, it is useful to develop automated ways to quantify species purities and trace impurity content. Spatially scanned Raman spectra make hyperspectral data sets that can be used to discriminate between species and determine purities, and their analysis can be automated. A promising analytical machine learning approach is non-negative matrix factorization, which is a multivariate algorithm well adapted to hyperspectral Raman scattering data sets, and, significantly, available in open source. We prepare samples from different concentrations of pure nanotubes and acquire spatially scanned Raman scattering hyperspectra. We compare the known concentrations of the source dispersions to those determined from hyperspectra acquired from deposited materials on substrates. Here, we demonstrate and deal with several metrological issues: We show that the stability of the focusing conditions is critical. We show that if there are strong peaks that are not significant, normalization is helpful. We show that this approach compares favorably to the “best case” situation where the spectra are factored into a priori known library spectra. Scans of around 100 data points provided good bounds on concentrations down to about the parts per thousand level. Using more than one laser wavelength, so that different species are brought into resonance with each laser should enable higher relative purity measurements. However, there is an important consideration if the difference in laser energies is less than or comparable to the phonon energy. Overall, this approach is promising for the determination of chemical purity of carbon nanotubes and could be generalized to other chemical mixtures.

Laser Surface Alloying of 7075 Aluminum Alloy with Cr, SiC, and Carbon Nanotube Powders

Laser Surface Alloying of 7075 Aluminum Alloy with Cr, SiC, and Carbon Nanotube Powders

The improved viscoelastic properties of long‐length carbon nanotubes reinforced polyamide‐6 composites

AbstractThe semi‐crystallinity, thermoplasticity, high toughness, and light weight of polyamide‐6 (PA6) when reinforced with carbon nanotubes (CNTs) provide outstanding physical properties to the nanocomposites by combining the physical properties of both components. The processing difficulties arising due to the high toughness and abrasion resistance of PA6 and the agglomeration of in‐house synthesized long‐length CNTs can be tackled by melt‐mixing the components inside a twin‐screw extruder with a back‐flow channel. The 0.1–7 parts per hundred ratios (phr) of CNTs reinforced PA6 composites were characterized for their viscoelastic properties through oscillatory rheometry and dynamic mechanical analysis (DMA) at fixed operating conditions. The outcomes showed continuous shiftings in storage and loss modulus values with increasing reinforcements along with a viscoelastic transition at 3 phr CNTs reinforcements observed in DMA. A 19°C rise in glass transition temperature (Tg) was observed in DMA with 0.1 phr CNTs reinforcement, which showed further improvements with increasing CNTs content. The interactions among PA6 and CNTs were further confirmed by X‐ray diffraction (XRD) and Raman spectroscopy curves. These nanocomposites promise mechanical applications in the equipments of automobiles, aerospace, defense, biomedical, bio‐sensors, etc.Highlights Viscoelastic properties study for CNTs/PA6 composites Uniform intermixing of CNTs within PA6 via extrusion with back‐flow channel Detailed analysis of rheometry and DMA of the composites CNTs‐PA6 interactions estimated from rising intensity peaks in Raman spectra and X‐ray diffraction (XRD) Potential candidates for components in automobiles, aircraft, biomedicals, and sports industry

A Three-Dimensional Modeling Approach for Carbon Nanotubes Filled Polymers Utilizing the Modified Nearest Neighbor Algorithm.

Carbon nanotubes (CNTs) are extensively utilized in the fabrication of high-performance composites due to their exceptional mechanical, electrical, and thermal characteristics. To investigate the mechanical properties of CNTs filled polymers accurately and effectively, a 3D modeling approach that incorporates the microstructural attributes of CNTs was introduced. Initially, a representative volume element model was constructed utilizing the modified nearest neighbor algorithm. During the modeling phase, a corresponding interference judgment method was suggested, taking into account the potential positional relationships among the CNTs. Subsequently, stress-strain curves of the model under various loading conditions were derived through finite element analysis employing the volume averaging technique. To validate the efficacy of the modeling approach, the stress within a CNT/epoxy resin composite with varying volume fractions under different axial strains was computed. The resulting stress-strain curves were in good agreement with experimental data from the existing literature. Hence, the modeling method proposed in this study provides a more precise representation of the random distribution of CNTs in the matrix. Furthermore, it is applicable to a broader range of aspect ratios, thereby enabling the CNT simulation model to more closely align with real-world models.

Extremely Fast Wicking Self‐Layered Interpenetrating Network Hydrogel for Rapid All Day Collection of Atmospheric Water

AbstractHygroscopic salt hydrogel photothermal composites and related technology are a promising pathway for water harvesting. However, due to the overly cumbersome preparation process, the distribution of the surface photothermal layer is difficult to control and the photothermal efficiency is low. In this paper, a method is proposed to greatly simplify the preparation process of photothermal layer hydrogels and improve their atmospheric water harvesting performance by constructing temperature‐sensitive interpenetrating networks. Due to the decomposition of some reversible hydrated structures in the network during heating and warming, carbon nanotubes move autonomously to form a layered structure with a photothermal effect on the upper surface, which can return to its original state after cooling and remain stable at room temperature or under solar illumination. Compared with hydrogels with general layered structure or overall distribution of photothermal materials, agar/GG/PAM/CNT hydrogel has faster moisture adsorption efficiency and higher desorption efficiency, and during the 24 h continuous sorption–desorption cycle is capable of achieving high water yield of 2.57 Lwater kgsorbents−1 day−1, superior to most recent hydrogel adsorbents. Simplifying the preparation process while maintaining high efficiency, while greatly improving photothermal performance, paves the way for cost‐effective mass production applications for a wide range of hygroscopic salt‐hydrogel photothermal composites.

Multiwalled carbon nanotubes decorated ɛ-MnO2 nanoflowers cathode with oxygen defect for aqueous zinc-ion batteries

As a potential cathode for aqueous zinc-ion batteries, the low electrical conductivity and poor electrochemical kinetics of MnO2 limit its further development and application. Herein, multiwalled carbon nanotubes decorated MnO2 nanoflowers with hexagonal structure (ɛ-MnO2/MWCNTs) were synthesized by one-step co-precipitation method. The ɛ-MnO2/MWCNTs inherit the advantages of highly conductive MWCNTs and nanostructured MnO2, thus showing excellent zinc-ion storage capacity. The ɛ-MnO2/MWCNTs display high invertible capacity of 335.6 mAh/g at 0.2 A/g after 150 cycles, and long-term capacity of 115.7 mAh/g at 2.0 A/g after 4000 cycles. The results of kinetics tests further reveal that the MWCNTs decoration can reduce polarization of MnO2 and accelerate its reaction kinetics. Thanks to these merits, the ɛ-MnO2/MWCNTs hold great potential for high performance eco-friendly batteries cathode material.

Enhanced Mechanical Properties of Ni3Al Composites Reinforced with Single-Walled and Multi-Walled Carbon Nanotubes: An Atomistic Modeling Study

In this study, the mechanical properties of a Ni3Al matrix composite reinforced with single-walled carbon nanotubes (SWCNTs) and multi-walled carbon nanotubes (MWCNTs) were investigated using atomistic modeling. The analysis focused on the behavior of the composite under uniaxial tensile strain across a range of temperatures (100–900[Formula: see text]K). The results demonstrated that the incorporation of any type of carbon nanotubes (CNTs) significantly enhanced Young’s modulus, yield strength, and tensile strength of the Ni3Al matrix. Notably, the reinforcement with MWCNTs resulted in superior mechanical properties compared to SWCNTs. Additionally, an increase in temperature led to a reduction in Young’s modulus for all composite samples. Among the tested configurations, the composite reinforced with MWCNTs exhibited the highest tensile modulus and yield strength, outperforming both the SWCNT-reinforced composite and the unreinforced Ni3Al crystal. These findings underscore the potential of MWCNTs as effective reinforcements in improving the mechanical performance of Ni3Al-based composites, especially at elevated temperatures.

A first-principles adsorption study of functionalized carbon, boron nitride, silicon carbon nanotubes with ifosfamide as vehicles for drug delivery: Thermal analysis

We investigated the adsorption of ifosfamide (IFS) on the outer surface of zigzag (10, 0) carbon nanotubes (CNT), boron nitride nanotubes (BNNT), and silicon carbon nanotubes (SiCNT), using density functional theory (DFT) calculations at the PBE-D3 level in a water solvent phase. Based on zero-point corrected binding energies (Ebin), IFS exhibits chemisorption through its O-head and Cl-head on CNT (−1.05 eV) compared to BNNT (−0.93 eV), characterized by covalent interaction. In contrast, IFS undergoes physisorption via its O-head on SiCNT with binding energy of −0.68 eV as the most stable model this interaction is driven by electrostatic forces. The formation of complexes between the drug and nanotubes is influenced by charge transfer dynamics. Our thermodynamic analysis demonstrates the Gibbs free energy (ΔG) and enthalpy energy (ΔH) for all models are exothermic and spontaneous. The observed decrease in binding energy for BNNT and CNT correlates with changes in their energy gap, dipole moment, and charge transfer upon IFS adsorption. Notably, SiCNT exhibits a different response with a significant energy gap change leading to an increase in dipole moment and charge transfer. These findings suggest that these nanotubes demonstrate promising sensitivity to the presence of IFS and could be explored as potential drug delivery systems for this drug.

Bifunctional fluorine doped Ru/RuO2 clusters with dynamic electron modification and strong metal-support interaction boost proton exchange membrane water electrolyzer

The sluggish kinetics and inherent instability over the Ru/RuO2 clusters are still enormous challenges in proton exchange membrane (PEM) water electrolyzer. Herein, we innovatively report synergistic modulation of dynamic electron modification and strong metal-support interaction (SMSI) to activate and stabilize bifunctional fluorine doped Ru/RuO2 clusters anchored on carbon nanotube (CNT), thus achieving efficient and stable acidic overall water splitting. Theoretical and experimental studies found that surface metal-fluorine modification layer could dynamically regulate the interfacial electronic environment to stabilize and activate multiple active Ru species; and the SMSI between Ru/RuO2 cluster and CNT maintains stable electronic environment for dynamic electron modification and avoids migrating or shedding of active species in acidic environment. Therefore, the PEM electrolyzer assembled with optimal F5.5-Ru/RuO2@CNT can operate stably for 100 h at a high current density of 100 mA cm−2, which is the first time that bifunctional Ru-based nanocatalysts applied to PEM device at a high current density.

Carbon nanotubes as heterogeneous catalysts for the multicomponent reaction synthesis of heterocycles

Carbon nanotubes as heterogeneous catalysts for the multicomponent reaction synthesis of heterocycles

Collapse of G+/G- bands, modification of Breit–Wigner–Fano signals and structural amorphization in single wall carbon nanotube networks under great excess of sulfur

The identification of superconductivity and ferromagnetic to superconductive transitions in sulfur-modified carbons has recently attracted an important attention. Additional work is however needed to better understand the structural modification of the graphitic interfaces in presence of sulfur. Here we report on an advanced methodology which involves soaking of large amounts (in the order of 500 mg) of sulfur through several annealing cycles into bundles comprising of hollow single-wall/few-wall carbon nanotubes (SWCNTs). TEM, HRTEM, XRD and Raman spectroscopy characterization analyses reveal the presence of structural amorphization of the SWCNTs, with dramatic impact on the intensity of the G+ and a progressive vanishing of the G- signal-contribution. We demonstrate the presence of high sulfur content by employing both point and mapping energy dispersive X-rays (EDX maps) acquisitions, with high local quantities of sulfur in the order of 16 %. Interestingly, a complex variation in the contribution of the Breit-Wigner-Fano (BWF) band, with appearance of extra D, G+ and C-S band-contributions, is revealed by deconvolution-analyses. The appearance of these structural features is a clear indicator of structural amorphization of the CNTs, with consequential formation of C-S hybrid structures, which we analyze systematically with the aid of energy dispersive X-ray spectrum mapping and Raman point/mapping spectroscopy approaches.

Novel Eco‐Friendly Electrode: Copper Nanoparticle‐Doped MWCNTs for Green Electro‐Organic Synthesis of 1,2,3‐Triazoles With ChCl/Urea as a Solvent and Cocatalyst

ABSTRACTMeticulous electrode design is pivotal in advancing greener and more sustainable electro‐organic synthesis practices. In this research, our team designed and synthesized a copper‐doped electrode on multiwalled carbon nanotubes (MWCNTs) and characterized it using Fourier transform infrared spectroscopy (FT‐IR), scanning electron microscopy (SEM), energy‐dispersive X‐ray spectroscopy (EDS), thermogravimetric analysis (TGA), Brunauer–Emmett–Teller (BET) analysis, X‐ray diffraction (XRD) analysis, X‐ray photoelectron spectroscopy (XPS), and cyclic voltammetry (CV) analysis. Subsequently, this electrode was utilized as a catalyst at the electrode surface, serving as a cathode in electro‐oxidation reactions in the presence of phenylacetylene, sodium azide (NaN3), and benzyl halide for the production of 1,2,3‐triazole derivatives under ambient temperature, within a 30‐min reaction time, and at atmospheric pressure, achieving an efficiency level ranging from good to excellent, specifically between 88% and 96%. The synthesized 1,2,3‐triazole derivatives were identified using proton nuclear magnetic resonance (1H NMR) spectroscopy, CHN elemental analysis, and melting point. In this paper, choline chloride/urea deep eutectic solvents (DES) serve multiple roles in the reaction mechanism. They function as solvents and co‐catalysts, generate weak bases, and provide numerous advantages in green chemistry. These advantages include low toxicity, reduced environmental risks, improved atom economy, and non‐volatility, making them safer alternatives to traditional organic solvents.

Research progress of carbon nanotubes as anode materials for lithium-ion batteries: a mini review

Research progress of carbon nanotubes as anode materials for lithium-ion batteries: a mini review