Nanotube Aerogels Research Articles

CNTs/PVA Composite Aerogel for Efficient Microwave and Acoustic Absorption

The lightweight three-dimensional (3D) carbon nanotubes (CNTs) aerogel has garnered significant interest due to their exceptional characteristics, including high porosity, large specific surface area, and a 3D conductive network. These characteristics make it as a promising candidate for various applications in microwave absorption. However, to construct a multifunctional framework, that can swiftly adapt to complex real-world environments, remains a large challenge. In this study, we fabricated a multifunctional CNTs/polyvinyl alcohol composite aerogel (CPA). Integrating polyvinyl alcohol (PVA) into CNTs aerogel could effectively prevent CNTs aggregation, thus obtaining the remarkable electromagnetic absorption, acoustic, mechanical, and thermal properties. The minimum reflection loss (RL) of CPA achieved an outstanding value of -39.77 dB, measured with a thickness of 2 mm. In addition, CPA showed excellent sound absorption performance, with the highest sound absorption coefficient (SAC) of 0.981. Sound transmission loss (STL) could be improved by adjusting the ratio of CPA, the improvement of STL was 5-8 dB at the mid-high frequencies. Finally, CPA also exhibited excellent thermal insulation performance with the lowest thermal conductivity of 0.0297 W/m·k. The multifunctional capabilities of CPA position it as a highly promising material for various applications, such as microwave absorption, noise reduction, and heat preservation.

Atomic regulation strategies of dual-metal single-atom catalytic sites supported on 3D N-doped carbon nanotube aerogels for boosting oxygen reduction and zinc-air battery

Dual-metal single-atom catalysts (DSAs) exhibit excellent electrocatalytic properties, holding great promise in energy conversion and storage fields. Their rational design and synthesis are realized by optimizing the types of supporting substrate or regulating the coordination microenvironment. Herein, FeCo DSAs supported on N-doped carbon nanotube aerogels (FeCo DSAs/N-CNAs) were facilely fabricated by a glucose-assisted atomic regulation pyrolysis approach. The morphology and structure were characterized by a series of techniques. The influences of the pyrolysis temperature and types of the metal precursors were carefully investigated, coupled by elaborating the formation mechanism. The resulting FeCo DSAs/N-CNAs catalyst shows a positive onset potential (Eonset = 1.075 V) and half-wave potential (E1/2 = 0.907 V) for oxygen reduction reaction (ORR) in a 0.1 M KOH solution, outperforming those of commercial Pt/C. The obtained catalyst is further exploited for establishing rechargeable Zn-air battery, which shows a larger peak power density of 86.7 mW cm−2 and a longer cycle stability over 144 h. These findings identify low-cost FeCo DSAs/N-CNAs as promising electrocatalysts for advanced rechargeable Zn-air batteries.

Porous Carbonaceous Aerogels Composed of Multiscale Carbon-Based Units for High-Performance Microwave Absorption.

Structural engineering is definitely a promising and effective approach to develop excellent microwave absorbing materials with quantities of advantages. Especially, when carbon materials act as the constituents, the fabricated absorbers are available to gain more prominent absorption performance. However, extra high conductivities and the widespread aggregations and stacking of low-dimensional carbon materials always detrimentally affect the impedance matching and weaken the attenuation capacity, inevitably confining their further absorption applications. Herein, by introducing the amorphous chiral carbon nanocoils to overcome the challenges and achieve the strategies of structure optimization and multicomponent recombination, the reduced graphene oxide/carbon nanocoil/carbon nanotube aerogels were successfully synthesized by a successive hydrothermal method and freeze-drying strategy. The as-obtained aerogels possess a porous architecture that contribute to the extraordinary impedance matching and multiple reflections, which integrate the multifarious dielectric loss mechanisms of diverse carbon materials simultaneously. Benefiting from the tricomponent synergistic effect, the ultralight aerogels reach an outstanding microwave absorption property with an extremely low filler content of only 6 wt %. This work provides a helpful approach to design hierarchical absorbers consisted by multidimensional carbon materials for fantastic microwave absorption.

High-speed and scalable combustion fabrication of ultralight carbon nanotube aerogels below air density

In this study, we introduce a fast, scalable method to fabricate ultralight carbon nanotube (CNT) aerogels with a bulk density (ρ) lower than air, using a combustion process. Typical fabrication methods for ultralight nanocarbon aerogels (ρ ≤ 1.0 mg cm−3) often involve intricate steps, such as high-temperature annealing and thermal reduction. These processes are time-consuming and pose scalability challenges. Here, we propose a high-speed fabrication process for ultralight CNT aerogels by combusting cellulose nanofibers (CNF) as a sacrificial template. The combustion process for CNT/CNF composite aerogels in an open environment takes only a few seconds, and the fabricated CNT aerogels with a lower-than-air density (ρ ≥ 0.48 mg cm−3) have high light absorption and good thermal and mechanical stability. We further illustrate the capability of these ultralight CNT aerogels to achieve levitation upon heating like a hot air balloon. Ultralight CNT aerogels capable of levitation by heating, fabricated by our fast and scalable method, hold the potential to replace traditional motor-driven unmanned aerial vehicles and conventional stratospheric platforms, such as high-altitude balloons, with sunlight-driven materials.

RGO/CNTs/PEDOT: PSS ternary composites with enhanced thermoelectric properties

Graphene oxide/ carbon nanotubes (GO/CNTs) aerogels were prepared by adjusting the proportion of GO and CNTs, the corresponding reduced graphene oxide/CNTs (rGO/CNTs) aerogels were obtained by thermal reduction. Then, poly (3,4-ethylenedioxythiophene): polystyrene sulfonic acid (PEDOT: PSS) was compounded with rGO/CNTs aerogels at a mass ratio of 1:1 to prepare rGO/CNTs/PEDOT: PSS (GCP) composites. Structural analyses revealed the strong π-π interaction between rGO/CNTs and PEDOT: PSS, which leads to the formation of ordered regions. Porous structures of rGO/CNTs aerogels act as conductive network skeleton to promote carrier transport in GCP composites, and the electrical conductivity of GCP composites improves effectively. The optimal electrical conductivity and Seebeck coefficient of GCP5 were 1788.11 S cm−1 and 15.87 μV K−1 respectively. The maximum power factor and ZT merit of GCP5 achieved to 45.03 μW m−1 K−2 and 2.65 × 10−2 at room temperature, which was almost 43 and 17 times than that of PEDOT: PSS.

Flexible, Thermally Stable, and Ultralightweight Polyimide-CNT Aerogel Composite Films for Energy Storage Applications.

Polyimide (PI) aerogels are promising in various fields of application, ranging from thermal insulators to aerospace. However, they are typically in the form of a bulk monolith, which suffers from a lack of conformability and drapability. Moreover, their electrical conductivity is limited, and they mainly display an insulative behavior. These shortcomings can limit the applications of PI aerogels in energy storage systems, which require ultralightweight flexible conductive films, which at the same time offer high thermal stability, ultralow density, and high surface area. To overcome these obstacles, the present study reports the fabrication of PI-carbon nanotube (PI-CNT) aerogel composite films with varying CNT content prepared through a sol-gel preparation method, followed by a supercritical drying procedure. Compared to pristine PI aerogels, which displayed a large shrinkage and density of 18.3% and 0.12 g cm-3, respectively, the incorporation of only 5 wt % CNTs resulted in a significant reduction of both shrinkage and density to only 11.5% and 0.10 g cm-3, respectively. This suggests the importance of CNTs in improving the dimensional stability of aerogels and creating a robust network. Further characterizations showed that incorporation of 5 wt % CNTs also resulted in the highest pore volume (1.25 cm3 g-1), highest surface area (324 m2 g-1), highest real permittivity (80), highest electrical conductivity (3 × 10-1 S m-1), and ultrahigh service temperature (575 °C). It was also shown that the aerogel films can withstand a large degree of bending, can be twisted, and can be fully rolled with no obvious cracks propagated in the structure. The combined outstanding properties of the developed aerogel composite films make them promising potential candidates for supercapacitor electrodes. Therefore, the electrochemical performance of the devices based on aerogel electrodes was further studied. The device demonstrated a high energy density of 2.6 Wh kg-1 at a power density of 303.8 W kg-1. The total capacitance after 5000 cycles was 91.8% of the initial capacitance, which indicated excellent stability and durability of the device. Overall, this work provides a facile yet effective methodology for the development of high-performance aerogel materials for energy storage applications.

Devisable pore structures and tunable thermal management properties of aerogels composed of carbon nanotubes and cellulose nanofibers with various aspect ratios

The anisotropic cellulose nanofiber (CNF)/carbon nanotube (CNT) aerogels hold a great promise in directional applications due to their distinct xylem-like aligned penetrating pore structures. The aspect ratio of CNF plays a crucial role in the pore structures of aerogels, directly dominating the final macroscopic properties of materials. Herein, three types of CNF with different aspect ratios were extracted through the 2,2,6,6-tetrmethylpiperidine-1-oxyl radical (TEMPO) oxidation process by changing the doses of oxidant. The corresponding anisotropic CNF/CNT aerogels were prepared by the unidirectional freeze-drying method and then their pore morphologies and properties were investigated in detail. The resulting aerogel with the shortest aspect ratio of CNF exhibited the densest porous structure, thereby obtaining the highest compressive strength of 110 kPa and elastic modulus of 383 kPa, while that containing the longest CNF possessed the highest thermal conductivity coefficient of 0.17 W m−1 K−1 and the worst thermal insulation. This research explored the relationship between the properties of the CNF/CNT aerogels and devisable pore structures caused by various aspect ratios of CNF, thus providing a new insight into the development of CNF/CNT aerogels with tunable performances.

High-efficient adsorption for versatile adsorbates by elastic reduced graphene oxide/Fe3O4 magnetic aerogels mediated by carbon nanotubes

Fabrication of highly elastic three-dimensional aerogel adsorbents with outstanding adsorption capacities is a long pursuit for the treatment of industrial contaminated water. In this work, a magnetic reduced graphene oxide (rGO)/Fe3O4/carbon nanotubes (CNTs) aerogel material was constructed by the electrostatic attraction between the negatively charged GO and positively charged CNTs following a one-pot water bath treatment. The as-synthesized aerogel demonstrated high compressive stress (28.4 kPa) and lower density (24.11 mg/cm3) with exceptional adsorption capacities for versatile adsorbates which are attributed to CNTs and magnetic Fe3O4 nanoparticles. The effect of pH, initial concentration of adsorbates (dyes, Cd (ІІ) ions, organic solvents, and pump oil), content of CNTs and cyclic times on the adsorption capacities of the aerogel were investigated in detail. Furthermore, from simulation, the adsorption kinetics, and thermodynamics of the aerogel for adsorbates were more satisfied by endothermic quasi-second-order kinetic model with characteristic physical adsorption. Thus, the optimized rGO/Fe3O4/CNTs-10 aerogel adsorbent can be used as a powerful and versatile tool to deal with contaminated industrial or domestic wastewater.

A Highly Porous and Flexible Carbon Nanotube Array Coated with Gold Nanoparticles: Application in Non‐Enzymatic Ultrasensitive Detection and Monitoring of Blood/Saliva Glucose

AbstractFlexible, reusable, and ultrasensitive glucose sensors are the need of the hour for advanced health monitoring, specifically for economical diabetes management in low‐income countries. Here, we demonstrate an ultra‐sensitive, and extremely lightweight non‐enzymatic glucose sensor based on gold nanoparticles sputtered carbon nanotube aerogel film (Au‐CNT), which is flexible, durable, reusable, and portable. The flexible Au‐CNT aerogel non‐enzymatic glucose sensor showed remarkable sensitivity of 779 μA mM−1 cm−2, a wide linear range of 0.1 mM to 6 mM and a limit of detection (LoD) of 1.47 μM. The sensitivity of our sensor is highest among literature‐reported carbon nanomaterials‐based flexible glucose sensors for selective detection of glucose in blood serum/saliva samples. The Au‐CNT aerogel shows the potential application as practical non‐invasive and invasive self‐monitoring glucose sensor. Therefore, highly sensitive and paper‐thin Au‐CNT electrode is a promising candidate for future commercial robust flexible and wearable biosensor applications.

MXene/CNTs/Aramid Aerogels for Electromagnetic Interference Shielding and Joule Heating

It is a considerable challenge to develop a composite material with ultra-light and high electromagnetic interference (EMI) shielding efficiency for the next generation of electronic equipment. MXenes have received extensive attention in composite aerogel EMI shielding due to their abundant surface groups and ultra-high conductivity. However, the poor mechanical properties make them difficult to apply on a large scale. Here, we demonstrate a simple method to construct ultra-light conductive Ti3C2Tx MXene/aramid nanofibers (ANFs)/carbon nanotubes (CNTs) aerogels with a “sandwich” structure. CNTs and MXene absorb and reflect electromagnetic waves, while ANF aerogel provides good mechanical strength. Our composite aerogels with an extra-high EMI shielding efficiency of up to 69.0 dB at the X-band, despite their thickness and density being only 2 mm and 0.0428 g/cm3, respectively. At the same time, the composite aerogel with a low 0.0488 W/(m·K) thermal conductivity shows extraordinary flame resistance, heat preservation, and insulation ability. Besides, MXene/ANFs/CNTs aerogel can reach 104 °C in 3 s under an 8 V voltage and shows long-term Joule heating stability. This work provides a forward-looking idea for building multifunctional EMI shielding materials. The obtained aerogels have potential applications in aerospace, portable electronic devices, and defense industries.

Metal decorated carbon nanotube aerogels from sodium polyacrylate crosslinking by divalent ions

Metal decorated carbon nanotube aerogels from sodium polyacrylate crosslinking by divalent ions

Fabricating Flexible Strain Sensor with Direct Writing Graphene/Carbon Nanotube Aerogel

Flexible strain sensor has wide applications in wearable devices and human–computer interaction. These sensors exhibit a flexible performance, which makes the structure of the device adapt to a wide range of application scenarios. This work proposes a low-cost and accurate direct writing method to fabricate a three-dimensional graphene/carbon nanotube strain sensor by using prepared printing ink with good dispersion, extruding ordered lamellae, and controlling porous aerogel structure. The morphology of the prepared three-dimensional porous aerogel was controlled with the ice template method. The strain sensor could be obtained by encapsulating the PDMS precursor, which shows high stretchability with a sensitivity of 18.55 at a 20% tensile strain. It offers good stability after 900 times of repeated stretching under 20% strain. This study of fabricating flexible strain sensors could provide a facile and effective way to apply intelligent packaging and wearable electronic devices.

Ultra-Low-Density Carbon Nanotube Aerogel Film for Fast and Sensitive Bolometric Sensing.

In various applications, infrared (IR) detectors with quick responses and high sensitivity at room temperature are essential. This work synthesizes carbon nanotube aerogel films (CAFs) with an ultra-low density of 1.33 mg cm-3. Transient electrothermal (TET) technology is used to characterize the thermal and electrical transport of CAFs in the temperature range of 320 to 10 K. CAF has record-low thermal conductivity (2.5 mW m-1 K-1 at 320 K) and thermal diffusivity (2.24 × 10-6 m2 s-1 at 320 K) in vacuum. The TCR of CAF is -0.11%/K at 295 K, which is 57% higher than that of the MWCNT films. In addition, the comprehensive bolometric performance of carbon nanotube aerogels is tested and analyzed, including the photothermal response, resistivity responsivity, and response time to lasers of a broad spectrum from ultraviolet to near-infrared. The relative responsivity of CAF to lasers of different wavelengths is found to be consistent. The response time of CAF with 200 μm suspended length is measured to be as short as 2.95-3.03 ms (framing rate of 330-339 per second). In addition, the resistive response of the CAF sample to a blackbody radiator and the radiation of the human hand also shows good sensitivity and repeatability. These results demonstrate the promising application of CAF as a sensitive and fast-response uncooled bolometer.

Hierarchical lamellar single-walled carbon nanotube aerogel interlayers for stable lithium-sulfur batteries with high-sulfur-loading

Lithium-sulfur (Li-S) battery has been recognized as a new energy storage device with broad prospects because of its satisfactory specific capacity and theoretical energy density. Nevertheless, the shuttle effect of polysulfides seriously hinders the real applications of high-sulfur-loaded Li-S batteries. To remove the hurdle, hierarchical lamellar single-walled carbon nanotube aerogels (SWCNTAs) are herein fabricated and applied as multifunctional interlayers in Li-S batteries, which exhibit an initial area-specific capacity as high as 7.1 mAh cm−2 at a sulfur loading of 8.02 mg cm−2. The introduced SWCNTA interlayers can lower the internal resistance and suppress the shuttling of polysulfides by a layer-by-layer physical blocking mechanism. Moreover, owing to the super wettability of SWCNTAs, electrolytes with a dosage of 10 μL mg−1 could effectively wet and infiltrate the interlayers, rendering the lean-electrolyte Li-S batteries a high specific capacity of 559 mAh g−1 at a sulfur loading of 10.35 mg cm−2 after 60 cycles. This work presents an example for rationally designing the interlayers structures for high-sulfur loading batteries, which paves a stepping stone for the future commercialization of Li-S batteries.

Bioinspired Cellular Single-Walled Carbon Nanotube Aerogels with Temperature-Invariant Elasticity and Fatigue Resistance for Potential Energy Dissipation

Elastic and fatigue-resistant materials with a wide service temperature range are extremely needed in the crash cushion, automobile safety, and personal protective equipment. By combining radial freeze casting with carbon welding, single-walled carbon nanotube aerogels (SWCNTAs) with cellular structures are fabricated from a facile, scalable sol–gel method. The prepared SWCNTAs show a negative Poisson’s ratio and high energy loss efficiency under the uniaxial compressive strain. Furthermore, the SWCNTAs exhibit both outstanding fatigue resistance with negligible plastic deformation even after 105 compressive cycles and superior elasticity ranging from −100 to 300 °C in air, making the aerogels viable candidates for energy dissipation in extreme environments.

Defect-Induced Adsorption Switching (p- to n- Type) in Conducting Bare Carbon Nanotube Film for the Development of Highly Sensitive and Flexible Chemiresistive-Based Methanol and NO2 Sensor.

Lightweight and flexible gas sensors are essentially required for the fast detection of toxic gases to pass on the early warning to deter accident situations caused by gas leakage. In view of this, we have fabricated a thin paper-like free-standing, flexible, and sensitive carbon nanotube (CNT) aerogel gas sensor. The CNT aerogel film synthesized by the floating catalyst chemical vapor deposition method consists of a tiny network of long CNTs and ∼20% amorphous carbon. The pores and defect density of the CNT aerogel film were tuned by heating at 700 °C to obtain a sensor film, which showed excellent sensitivity for toxic NO2 and methanol gas in the concentration range of 1-100 ppm with a remarkable limit of detection ∼90 ppb. This sensor has consistently responded to toxic gas even after bending and crumpling the film. Moreover, the film heat-treated at 900 °C showed a lower response with opposite sensing characteristics due to switching of the semiconductor nature of the CNT aerogel film to n-type from p-type. The annealing temperature-based adsorption switching can be related to a type of carbon defect in the CNT aerogel film. Therefore, the developed free-standing, highly sensitive, and flexible CNT aerogel sensor paves the way for a reliable, robust, and switchable toxic gas sensor.

Aero Graphene in Modern Aircraft & UAV

The paper focuses on aero graphene and carbon nanotube (CNT) aerogel which will use in aircraft such as battery, engine, pitot probe, wings, fuselage, plane front glass which will also protect the aircraft from rain and wind because of the buoyant force. There are several ways to make aero graphene, but the most common approach includes reducing a precursor graphene oxide solution to make a graphene hydrogel. Through freeze-drying, any solvent is removed from the pores and replaced with air. A new method for producing aero graphene has emerged: 3-D printing. This is a significant scientific achievement. It creates a resin by diffusing graphene in a gel. The graphene resin can be cured into a solid and then dried in a furnace using UV LED light. Aero-graphene coating into the fuselage, wings and front glasses of the cockpit will give a great impact on the next-generation aircraft. Making an aircraft with aero-graphene will give the aircraft a strong and light skeleton.

Biodegradable, conductive, moisture-proof, and dielectric enhanced cellulose-based triboelectric nanogenerator for self-powered human-machine interface sensing

With the rapid development of sensors and triboelectric nanogenerators (TENGs), multifunctional self-powered sensors have received extensive attention. In this study, we prepare cellulose carbon nanotubes aerogel TENG (CCA-TENG) with high output, moisture-proof, simplified structure, and biodegradability for ambient energy harvesting and self-powered sensing. The cellulose carbon nanotubes aerogel (CCA) can be used not only acts as a tribolayer, but also as an electrode, with the characteristics of a 3D porous structure, high specific surface area, and dielectric enhancement. CCA-TENG exhibits improved output performance due to the advantages of the enhanced dielectric constant and 3D porous structure. Since regenerated cellulose is a dense polymer, it still keeps high output performance under high humidity. More importantly, CCA-TENG can be rapidly degraded in cellulase, and the output performance of the CCA-TENG prepared from recycled CNTs reaches 91.04% output of the original TENG. This study demonstrates the preparation, degradation, and reuse of CCA-TENGs and their applications, providing new avenues for high-performance, moisture-proof, and ambient self-powered systems.

Facile Synthesis of Vertically Arranged CNTs for Efficient Solar-Driven Interfacial Water Evaporation.

Solar-driven evaporation of water is a sustainable and promising technology for addressing the crisis of clean water. Herein, novel vertically arranged carbon nanotube (V-CNT) aerogels with a tree branch structure is facilely synthesized through an ice templating method. The V-CNT-based photothermal evaporator exhibits efficient broadband light trapping and super-hydrophilicity. Owing to the unique structure and ultrafast water transportation, a high evaporation rate of 3.26 kg m-2 h-1 was achieved by the three-dimensional V-CNT-based evaporator under a solar illumination of 1 kW m-2. More significantly, the V-CNT shows excellent recycling stability and salt-resistant performance in seawater and may provide a novel strategy to the practical sustainable technique of water purification applications.

Polypyrrole coated carbon nanotube aerogel composite phase change materials with enhanced thermal conductivity, high solar-/electro- thermal energy conversion and storage

Phase change materials (PCMs) have been widely investigated as promising thermal management materials due to their high thermal storage capacity, satisfactory heat transfer rate and multi-responsive energy conversion and storage characteristics. In this work, a shape-stabilized solar-/electro- responsive thermal energy capture and storage system is proposed involving polypyrrole (PPy)-deposited carbon nanotubes (CNT) heterogeneous porous aerogel as a supporting matrix and the paraffin wax (PW) as a PCM. The composite PCMs obtained via integration of PW into aerogel supports present a relatively high thermal storage density of 160.9 J/g and outstanding phase transition stability even after 100 heating–cooling cycles. Furthermore, great enhancement of thermal conductivity (0.64 W/m−1·K−1, 2.56 times that of PW) is achieved in the composite PCMs by inducing PPy coating as a binder in the gap between CNTs. The mechanism of heat transport enhancement is explored by molecular dynamics simulation. It concludes that the in-situ polymerization of PPy through the vapor deposition method on the CNT aerogels effectively builds additional thermal transfer channels and enhances the heat transport between CNT by coordinating the carbon atom vibration. Herein, this reported stratagem may shed light on preparing composite PCMs with high thermal conductivity and multi-energy utilization functions.