Carbon Nanotube Aerogels Research Articles

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.

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.

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

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.

Construction of multi-dimensional NiCo/C/CNT/rGO aerogel by MOF derivative for efficient microwave absorption

The development of high-performance microwave absorption materials is currently imperative in order to solve the problem of electromagnetic pollution. Herein, we successfully obtained a multi-dimensional graphene-based aerogel (NiCo/C/CNT/rGO aerogel) decorated with one-dimensional carbon nanotubes (CNTs) and metal-organic framework (MOF) derivatives. The introduction of rGO aerogel significantly modifies the phase composition (NiCo/C/CNT and rGO) and hierarchical structure (1D CNT, 3D NiCo/C/CNT and rGO aerogel) of the composite, resulting in a multi-dimensional gradient, defects, heterogeneous interfaces, and superior microwave absorption properties. The optimum electromagnetic wave absorption performance of −58.8 dB is achieved at a filler loading of 20 wt%, with a thickness of 1.8 mm and an effective absorption bandwidth of 7.6 GHz, covering the entire Ku-band. The excellent electromagnetic wave absorption performance can be attributed to the synergistic effect of impedance matching, electromagnetic attenuation capability, unique multi-dimensional porous structure, abundant defects and interfaces. In summary, the present work provides a novel approach for the synthesis of multi-dimensional lightweight magnetic/dielectric microwave absorbers.

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.

DNA aerogels and DNA-wrapped CNT aerogels for neuromorphic applications.

Nucleic acids are programmable materials that can self-assemble into defined or stochastic three-dimensional network architectures. Various attributes of self-assembled, cross-linked Deoxyribonucleic acid (DNA) hydrogels have recently been investigated, including their mechanical properties and potential biomedical functions. Herein, for the first time, we describe the successful construction of pure DNA aerogels and DNA-wrapped carbon nanotube (CNT) composite (DNA-CNT) aerogels via a single-step freeze-drying of the respective hydrogels. These aerogels reveal highly porous and randomly branched structures with low density. The electrical properties of pure DNA aerogel mimic that of a simple capacitor; in contrast, the DNA-CNT aerogel displays a fascinating resistive switching behavior in response to an applied bias voltage sweep reminiscent of a volatile memristor. We believe these novel aerogels can serve as a platform for developing complex biomimetic devices for a wide range of applications, including real-time computation, neuromorphic computing, biochemical sensing, and biodegradable functional implants. More importantly, insight obtained here on self-assembling DNA to create aerogels will pave the way to construct novel aerogel-based material platforms from DNA coated or wrapped functional entities.

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.

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.

Ultralight Single‐Walled Carbon Nanotube Aerogels for Low‐Frequency Sound Absorption

In the article number 2200357 Tomonaga Ueno, and co-workers report an ultralight single-walled carbon nanotube (SWCNT) aerogel for low-frequency sound absorption, with a hierarchical porous structure and a high-modulus framework. The Biot–Johnson–Champoux–Allard model indicates the significant effect of the high elastic modulus of the SWCNT aerogel on the low-frequency sound absorption.

Organic aerogel as electro‐catalytic support in low‐temperature fuel cell

Fuel cells have been developed efficiently in recent years as a secure and high-energy conversion technology. The innovation in electrocatalysis focuses on initiatives to minimize or replace Pt electrodes used. As an alternative, organic aerogel materials are normally used as electrodes in low temperature fuel cells due to their high electronic conducting and electrocatalytic characteristics. These are usually characterized by fundamental functional elements of strong covalent C-C bonds from organic precursors. This review will mainly focus on organic aerogel nanomaterials related to carbon aerogels, carbon nanotube aerogels, and graphene aerogels as electrocatalytic supports by surface modification or structural features in catalysis. In contrast, organic aerogel materials prove to be durable, economical, and active electrocatalysts that can provide outstanding electrocatalytic efficiency in low temperature fuel cell applications. Last, this paper recaps the challenges faced in current fuel cell applications and the use of organic aerogel materials to address these challenges.

A facile approach to cellulose/multi-walled carbon nanotube gels—Structure, formation process and adsorption to methylene blue

In view of the deficiencies in the preparation of cellulose gels, such as, cumbersome process, harsh conditions, high consumption of chemicals, secondary pollution caused by side reactions, this work reports a facile approach to make cellulose/multi-walled carbon nanotube (MWCNTs) hydrogels and aerogels via mixing cellulose with N,N′-methylene bisacrylamide (MBA) and MWCNTs in NaOH/urea/H2O aqueous solution. The gels were revealed to be formed by an addition reaction between the double bonds of MBA and the hydroxyl groups of cellulose and the intermolecular interactions between cellulose and MWCNTs. The preparation process can be realized at room temperature and atmospheric pressure without the intervention of ultrasonic dispersion, catalyst and initiator. The gelation time, puncture strength and water retention ability of the hydrogels were investigated. Results showed that, compared with pure cellulose hydrogel, cellulose/MWNCTs hydrogels have obviously shorter sol-gel transition time (124–129.2 min), higher puncture strength (29.6022–34.2854 KPa) and water retention ability (274.2619–301.7291 g/g). Cellulose/MWCNTs aerogels possessed three dimensional network with macroporous structure (about 500 μm), low density (0.00546–0.00557 g/cm3), high porosity (99.6360–99.6426 %), good thermal stability (242 °C) and certain absorbency to methylene blue (233.2901–242.1122 mg/g).

Succulent‐Inspired Ultraflexible and Multifunctional Carbon Aerogel for High‐Performing Strain Sensing and Thermal Management

AbstractPorous carbon materials have exhibited many superior characteristics with extensive applications. To adequately exert their advantages at macroscale, the mechanical property plays a critical role to ensure the structural stability and functionality. Porous carbon monoliths overcome brittleness by endowing compressive superelasticity but are still plagued by poor toughness, easily suffering from the tensile, bending, or torsional fracture. Here, inspired by the biostructure of succulent plants, graphene aerogel is used to mimic the hydrenchyma tissue, carbon nanotube aerogel film as the epidermis, and graphene oxide ethanol solution as the hemicellulose binder to make ultraflexible carbon aerogels (UCAGs), addressing the critical and bottleneck issue between mechanics and functionality. The UCAGs feature a sequence of robust mechanical properties simultaneously, including compressive strain up to 99.5%, tensile strength up to 460 kPa, bending and torsional angle up to 180°. This ultraflexible aerogel is exploited for large‐deformable, and high‐sensitive strain sensor with extended working temperature (−196 to 400 °C), as well as lightweight thermal regulator with record‐high switch ratio (500:1). The high‐performance structures of this type establish a set of fundamental considerations in structural design of inorganic aerogels for a wide spectrum of applications.