CNT Aerogels Research Articles

Achieving efficient electromagnetic absorption in multifunctional carbon nanotube aerogels by manipulating radialized network structure

The rapid advancements in communication technology have greatly propelled the widespread applications of artificial intelligence (AI). While AI technology facilitates society, it also brings the unavoidable electromagnetic hazards and the issue of disposal of electronic plastic wastes. So, utilizing electronic plastic wastes to constructing carbon-based electromagnetic wave (EMW) absorption materials, are highly promising. However, how to use CNTs from plastic wastes to build good EMW absorption performance aerogels is a critical challenge. In this work, highly porous and well-interconnected network aerogels constructed by radialized CNT arrays are rationally designed under the guidance of grave-to-cradle strategy, exhibiting altered impedance matching and multiple EMW attenuation methods. Theoretical calculations suggest that a well-designed heterojunction interface structure can enhance the conductivity and interface polarization of CNTAs. The CNT aerogels (CNTAs) realize broad absorption bandwidth covering 8.48 GHz with a minimum reflection loss of −59.5 dB. Moreover, the radialized arrays network of CNTAs also endows it with electromagnetic protection, thermal management, self-cleaning, and air purification functions. These inspiring achievements of multifunctional CNTA-2 provides new help for the safe and stable promotion of the AI era.

Mechanical and sensing properties of three-dimensional, high-strength superflexible CMC/SA/MXene/CNT aerogels

The CSMC aerogel, with a 3D isotropic porous structure supported by 2D faces in X, Y and Z dimensions, shows 148.78 kPa compressive strength at 80% strain. As a sensor, it has high sensitivity (GF = 7.6, S = 894.8 kPa−1) and durability (10 000 cycles).

Porosity control of CNT aerogel and its conversion to CNT fiber in floating catalyst chemical vapour deposition

Porosity control of CNT aerogel and its conversion to CNT fiber in floating catalyst chemical vapour deposition

Ultra-fast detection and monitoring of cancerous volatile organic compounds in environment using graphene oxide modified CNT aerogel hybrid gas sensor

Ultra-fast detection of cancerous volatile organic compounds (VOCs) by carbon nanotube aerogel (CNT aerogel)-graphene oxide (GO) hybrid network has been studied in this paper. VOCs, especially non-polar compounds are difficult to detect due to their low electronegativity. A homogenous GO solution was drop cast on CNT aerogel film, both developed in-house, to obtain the CNT aerogel-GO composite. The CNT aerogel contains multi-directional porous CNT webs providing a stable and compact platform for GO adsorption. The loading concentration of GO and O/C ratios were optimized to obtain a highly sensitive CNT aerogel-GO hybrid sensor. The hybrid sensor could detect a range of non-polar VOCs like benzene, hexane, toluene, cyclohexane, and chlorobenzene with a limit of detection around 70 ppb. The optimized CNT aerogel-GO hybrid sensor showed 3 times better sensing performance than the bare CNT aerogel sensor. The principal component analysis (PCA) plot showed discrimination in all the VOCs as they all were distinct and spread over all four quadrants, indicating highly selective behavior of the sensor. Chemical and structural analysis by X-ray photoelectron spectroscopy and Raman spectrum showed that the oxygen loading could change the sp2 structure, making it ideal for sensing applications. The electron micrography images confirm the uniformity of the GO layer on the CNT aerogel. It is concluded that the concomitant formation of the CNT-GO junction can achieve better interaction and charge transfer during hybrid sensor fabrication. Subsequently, a sensitive, fast and durable CNT aerogel-GO hybrid sensor can be obtained for detection and continuous monitoring of cancerous VOCs.

RuCo alloys anchoring on hierarchical oxidized CNT architectures with boosted catalytic activity for water splitting

Exploring cost-competitive electrocatalysts with enhanced catalytic activity is important for producing clean energy via water-splitting, including hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). Herein, RuCo alloy nanoparticles uniformly anchoring on oxidized carbon nanotube architectures (RuCo-OCA) have been constructed via ozonation, freeze-drying and thermal activation methods. RuCo-OCA exhibits excellent catalytic HER and OER performance. To reach a current density of 10 mA cm−2, RuCo-OCA requires low overpotential of 42 and 258 mV for HER and OER with the Tafel slope of 32.8 and 65.9 mV dec−1 in 1 M KOH, respectively. Meanwhile, RuCo-OCA shows negligible change of current density after chronoamperometry test for 10 h with low charge transfer resistance of 15.9 and 96 Ω for HER and OER. Furthermore, the symmetric RuCu-OCA||RuCu-OCA electrolyzer shows superior water-spitting performance to Pt/C/||RuO2 electrolyzer with a potential of 1.56 V at 10 mA cm−2. The excellent electrocatalytic performance of RuCo-OCA can be attributed to the hierarchical structure of oxidized CNT aerogel for the improved reaction kinetics and the formation of RuCo alloys with the modified electronic structure and adsorbability of intermediates. Meanwhile, the boosted active sites have been probed by density function theory. The coupling of RuCo alloys with conductive oxidized CNT aerogel can provide a new strategy to further expedite the electrocatalytic efficiency and activity of catalysts for water splitting.

Effect of O/N doping in CNT aerogel film on their nucleic acid hybridization detection ability as electrochemical impedance biosensor

An emerging material CNT aerogel, mitigating nano-level properties of CNT into macro level, has been synthesized using scalable floating catalyst chemical vapor deposition and doped with oxygen/nitrogen via plasma treatment. The dopant leads to formation of a strong space charge layer due to the high surface wetting effect, which is unfavorable for DNA hybridization detection. Bare CNT aerogel showed best sequence selectivity for the detection of DNA hybridization. The present study showed existence of a critical trade-off between doping and presence of huge hydrophilic functional groups on CNT aerogel surface is detrimental for electrochemical impedance bio sensing performance.

Tailoring surface properties with O/N doping in CNT aerogel film to obtain sensitive and selective sensor for volatile organic compounds detection

Volatile organic compounds (VOCs), listed as toxins/hazardous air pollutants are harmful to human health, and challenges associated with VOCs detection are selectivity of sensors. An emerging material CNT aerogel can offer selective and sensitive detection capabilities of VOCs. The CNT aerogel sensor has been synthesized using scalable floating catalyst chemical vapor deposition and doped with oxygen/nitrogen via plasma treatment. The oxygen/ nitrogen doping was introduced to simultaneously manage defect creation, functional group generation, enhance surface chemistry to obtain superior analyte molecule detection. The surface and functional characterization confirm that plasma treatment introduces oxygen/nitrogen doping in individual CNT uniformly throughout the film without disturbing the mechanical integrity of standalone CNT aerogel film. The bare, oxygen and nitrogen-doped CNT aerogel sensors can detect the polar compounds acetone, ethanol, methanol, as well as non-polar compound benzene in the concentration range of 2–100 ppm. The nitrogen-doped CNT aerogel sensor showed the highest sensitivity, selectivity, response (~ 5 fold increase in comparison to bare) with a limit of detection of 50 ppb. Hence, the present study showed the existence of a critical trade-off between doping and sensing performance of CNT aerogel, and enabling proper composition in CNT aerogel, a sensor with significant performance can be fabricated.

Highly conductive CNT aerogel synthesizedviaan inert FC-CVD technique: a step towards a greener approach

The accumulation of hydrogen gas molecules generatedin situas a byproduct of chemical reactions enhances the reducing ambient conditions of the otherwise inert FC-CVD reactor which improves the quality of the CNTs.

One Step Fabrication of Aligned Carbon Nanotube Sheet via FC‐CVD Technique

The rising need for lightweight and strong mechanical structures has contributed significantly towards the development of CNT macrostructures; however, the interplay of parameters and their discontinuous synthesis have obstructed their delivery to commercial level. Herein, floating catalyst chemical vapor deposition technique (FC‐CVD) has been employed for the fabrication of 90 cm long CNT sheet via continuous production of CNT aerogel. High degree of graphitization, thermal stability and purity have been indicated by Raman spectroscopy (IG/ID = 10.03), thermogravimetric analysis, and SEM studies. Continuous winding of CNT aerogel has increased the alignment into the sample which resulted into high electrical conductivity value of 21400 S/m. Furthermore, the alignment has been quantified by calculating optical anisotropic ratio via polarized Raman technique and conductivity anisotropic ratio κ‖ /κ⊥ which were calculated to be 4.63 and 3.4, respectively, and show reasonable agreement. These findings indicate that a well correlation of synthesis parameters results in highly aligned CNT sheet structure in a single step.

Ultra-Fast Detection and Monitoring of Cancerous Volatile Organic Compounds in Environment Using Graphene Oxide Modified CNT Aerogel Hybrid Gas Sensor

Ultra-Fast Detection and Monitoring of Cancerous Volatile Organic Compounds in Environment Using Graphene Oxide Modified CNT Aerogel Hybrid Gas Sensor

High-performance asymmetric supercapacitors of advanced double ion-buffering reservoirs based on battery-type hierarchical flower-like Co3O4-GC microspheres and 3D holey graphene aerogels

We have prepared 2D macromolecular brushes of G>N-PEGm nanosheets and CNT>N-PEGm from the Graphene and CNTs with methoxypolyethylene glycol (mPEG) via Nitrene Chemistry, respectively. Owing to a typical solvothermal method, the hierarchical flower-like spheres of Co3O4-G>N-PEGm-CNT>N-PEGm (Co3O4-GC) ternary composites have been synthetized, which present honeycomb-like structures as “ion-buffering reservoir” and substantial ion-diffusion channels in the ultrathin 2–4 nm Co3O4 nanosheets. And as typical battery-type positive electrode materials, a high capacity of Co3O4-GC can be calculated up to 173.3 mAh g−1 at 0.5 A g−1 (the specific capacitance can be achieved to 1783 F g−1). On the other hand, 3D holey reduced graphene oxide and carboxylic CNT aerogels (HRGOCNTc, denoted as HRGC) formed with holey graphene and the acid-modified CNTc are summarized as 282.3 Fg−1 (78.4 mAh g−1) at 0.5 A g−1, demonstrating excellent long cycling performance. The advanced double “ion-buffering reservoirs” of asymmetric supercapacitors Co3O4-GC//3D HRGC energy devices are further fabricated based on advanced battery-type Co3O4-GC as positive electrode and 3D HRGC aerogels as negative electrode, meanwhile the asymmetric devices with excellent electrochemical performance also exhibit 42.6 Wh kg−1 at power densities of 775 W kg−1 and 81.1% capacitance maintained after 10,000 cycles for energy-storage and energy-conversion potential application.

Direct synthesis of carbon nanotube aerogel using floating catalyst chemical vapor deposition: effect of gas flow rate

Carbon nanotube aerogel (CNT aerogel) was synthesized through the catalytic decomposition of toluene in the mixture of ferrocene and thiophene through floating catalyst chemical vapor deposition method. This study described the effect of (Ar and H2) carrier gas flow rate on the quality and yield of CNT aerogel. Results indicated that the flow rate of the gas was an important parameter which helped in determining the yield and quality of the CNTs. The CNTs are multiwalled with its diameter decreased when the H2 flow rate was increased. Scanning electron microscopy indicated the average diameter of ≈ 31, 30, 27, 26, 18, and 15 nm when the H2 flow rate was increased from 400, 450, 500, 550, 600, 650 sccm, respectively. Furthermore, elemental analysis with energy dispersion spectrum for CNT aerogel produced at 600 sccm resulted in a 96.22 wt% carbons along with 3.78 wt% iron in the CNT aerogel sample. Results indicated that a hydrogen flow rate of 600 sccm produced high yield and good CNTs morphology.

Utilization of waste engine oil for carbon nanotube aerogel production using floating catalyst chemical vapor deposition

The floating catalyst chemical vapor deposition (FCCVD) approach has been successfully employed in offering a continuous single-step process to the synthesis of carbon nanotubes aerogel (CNT aerogel) in terms of the industrial scale. Industrial applications require selecting a carbon source that is abundant, cost-effective and environment-friendly. Thus, waste engine oil (WEO) is preferably employed as a carbon source involving the production of CNT aerogel. In this research study, the catalytic decomposition of the WEO was employed to synthesize CNT aerogel. First, fractional distillation of WEO was achieved resulted in five (5) fractions. As per analysis is performed via GC-MS, low molecular weight hydrocarbons could be efficiently separated, which is required for catalyst dissolving. As per CNS analysis, each fraction was found to contain >69% carbon, <0.1% sulfur and <0.3% nitrogen. The FCCVD method was employed to synthesize CNT aerogel via a WEO fraction 1 mixed along with ferrocene catalyst at a temperature of 1150 °C. It was found that the product’s MWCNTs were associated with 86.74% purity and 496% carbon deposition yield. The aerogel was found to possess a mesopore distribution of 142.9 m2 g−1 as its specific surface area, 39.079 nm as average pore diameter and 1.3964 cm3 g−1 as total pore volume. The CNTs tend to assemble randomly as well as get entangled to form a 3-D structure.

Rational and wide-range tuning of CNT aerogel conductors with multifunctionalities.

Different from conventional conductors, elastic 3D nanoarchitectured conductors have shown promise in developing various flexible devices. However, rational design and control of their microstructures to achieve desired physicochemical properties is challenging and lacks comprehensive and profound investigation. In this study, we report an interesting quantitative correlation between density and physical properties when highly porous CNT aerogels are densified, enabling a wide-range tuning of CNT 3D networked structures with different functions. Upon densification by compressing the original thickness of a CNT aerogel by 100 fold, a linear double-logarithmic structure-property relationship in terms of both thickness and density is witnessed, with the resultant density increased by a factor of 100 from 3 to 286 mg cm-3, Young's modulus by 20 times (5.0-105 kPa), electrical conductivity by 400 times (0.4-163 s cm-1), and thermal conductivity by 140 times (0.048-6.7 W m-1 K-1). It can be thus inferred that the CNT aerogel can be regulated with desired mechanical, electrical and thermal properties in a quantitative manner over a wide range, making it promising as a multifunctional aerogel conductor. As a proof, two pieces of CNT aerogel conductors tailored with high conductivity and low thermal conductivity are employed to fabricate a flexible TE device using a simple all-carbon design, which yields a typical power density of 27.5 μW cm-2 and stable outputs under various deformations, demonstrating a potential strategy for design and fabrication of low-cost, flexible and portable power-generation devices.

Aerogel sheet of carbon nanotubes decorated with palladium nanoparticles for hydrogen gas sensing

In the development of hydrogen sensors, it is required to meet the demands of both high sensor performance as well as the ease of fabrication for mass production. For this purpose we proposed a chemiresistive hydrogen sensors based on an aerogel sheet of carbon nanotubes decorated with palladium nanoparticles (CNT/Pd sheet). The fabrication process is straightforward that a dry-spun CNT aerogel sheet is suspended between concentric electrodes followed by depositing Pd nanoparticles on CNT sheets by thermal evaporation. The present CNT/Pd sheet sensors can detect hydrogen at concentrations as low as 2 ppm at room temperature with a detection range from 2 to 1000 ppm. The aerogel nature of CNT/Pd sheet contributes to low detection limit and broad detection range of the CNT/Pd sensor. Relations between hydrogen concentration and sensor response and response time, and the effects of temperature on sensor performance were investigated.

Anisotropic compressive properties of porous CNT/SiC composites produced by direct matrix infiltration of CNT aerogel

AbstractCarbon nanotube‐reinforced silicon carbide composites (CNT/SiC) produced by direct infiltration of matrix into a porous CNT arrays have been demonstrated to possess a unique microstructure and excellent micro‐mechanical properties. However, the thickness of the array preforms is usually very small, typically less than 2 mm. Therefore, fabrication of macroscopic CNT/SiC composites by chemical vapor infiltration (CVI) process requires that the nanoscale fillers could form macroscopic architectures with an open pore network. Here, this study reports an experimental strategy for the fabrication of SiC matrix composites reinforced by CNT based on an ice‐segregation‐induced self‐assembly (ISISA) technique. Macroscopic CNT aerogel with well‐defined macroporous network was produced by ISISA technique and was subsequently infiltrated by SiC in a CVI reactor. After five CVI cycles, the porosity of as‐fabricated composites was 11.6±0.3% and the machined specimens exhibited lamellar structure with parallel lamellaes intersected at discrete angles. By observed, there are in fact five different representative anisotropic macrostructures, the compressive strengths of these five different loading modes with respect to lamella orientation were 933±55, 619±34, 200±45, 199±21, and 297±41 MPa, respectively, and the failure mechanisms were attributed to the anisotropic nature of the macrostructures. Energy dissipation toughening mechanism at the nanoscale such as CNT pull‐out was observed and the phase composition of the fabricated materials included β‐SiC, CNT, and SiO2.

A rGO–CNT aerogel covalently bonded with a nitrogen-rich polymer as a polysulfide adsorptive cathode for high sulfur loading lithium sulfur batteries

A covalently bonded polyethylenimine–rGO–MWCNT composite achieves outstanding performance at an ultra-high sulfur loading of up to 18 mg cm−2.

Silicon-Carbon Nanotube Aerogel Core-Shell Nanostructures for Lithium-Ion Batteries with Long-Cycle Life and High Capacity

Silicon anode for lithium ion battery (LiB) has been attracted considerable attention due to providing theoretical capacity up to about 10 times higher than that of conventional graphite. However, huge volume expansion during the cycle cause crack in the silicon, resulting in degradation of cycling performance and eventual failure. Moreover, low electrical conductivity and unstable solid electrolyte interface (SEI) layer aroused from repeated changes in volume still block the next step forward to commercialization of silicon material. Herein we demonstrate Si-carbon nanotube (CNT) aerogel core-shell nanostructure for LiB via freeze casting followed by RF magnetron sputtering process, exhibiting improved capacity retention as compared to Si only samples while 1,000 times of electrochemical cycle. The freeze casted CNT aerogel as 3D porous scaffold structures could provide buffer volume expansion/shrinkage of Si lattice upon cycling and increase electrical conductivity. In addition, the CNT aerogel could maintain the conducting network between pulverized Si materials during cycling. For this reason, after 1,000 charge/discharge cycles with high current densities (4.0 A g-1), Si@CNT aerogel anode yielded a high specific capacity of 1439 mAh g-1 with low capacity fade. Our approach could be applied to other LiB materials that go through large volume changes, and also affords promising potential for high performance energy applications.

Graphene–carbon nanotube aerogel as an ultra-light, compressible and recyclable highly efficient absorbent for oil and dyes

Ultra-light graphene–CNT aerogels were successfully synthesized by a one-step hydrothermal method and exhibited excellent adsorption capacity to oil and dyes as well as reusability.

Face‐to‐Face Contact and Open‐Void Coinvolved Si/C Nanohybrids Lithium‐Ion Battery Anodes with Extremely Long Cycle Life

To develop high‐performance anode materials of lithium‐ion batteries (LIBs) instead of commercial graphite for practical applications, herein, a layer of silicon has been well‐anchored onto a 3D graphene/carbon nanotube (CNT) aerogels (CAs) framework with face‐to‐face contact and balanced open void by a simple chemical vapor deposition strategy. The engineered contact interface between CAs and Si creates high‐efficiency channels for the rapid electrons and lithium ions transport, and meanwhile, the balanced open‐void allows the free expansion of Si during cycling while maintaining high structural integrity due to the robust mechanical strength of 3D CAs framework. As a consequence, the as‐synthesized Si/CAs nanohybrids are highly stable anode materials for LIBs with a high reversible discharge capacity (1498 mAh g−1 at 200 mA g−1) and excellent rate capability (462 mAh g−1 at 10 000 mA g−1), which is much better than Si/graphene‐CNTs‐mixture (51 mAh g−1 at 10 000 mA g−1). More significantly, it is found that the Si/CAs nanohybrids display no obvious capacity decline even after 2000 cycles at a high current density of 10 000 mA g−1. The present Si/CAs nanohybrids are one of the most stable Si‐based anode materials ever reported for LIBs to date.