Compressible Carbon Research Articles

Blade-Coated Porous 3D Carbon Composite Electrodes Coupled with Multiscale Interfaces for Highly Sensitive All-Paper Pressure Sensors

HighlightsA blade-coated composite paste, composed of a compressible 3D carbon skeleton, PEDOT:PSS, and CNTs, can naturally dry to form a porous electrode on paper with a micro- and nano-structured surface.The all-paper pressure sensor demonstrated an ultrahigh sensitivity of 1014 kPa−1, a wide responsive range up to 300 kPa, and an ultralow operating voltage of 0.01 V.The sensor showcased superior detection capability, ranging from subtle wrist pulses and robust finger taps to large-area spatial force.

Application of Compressible Carbon in Cement to Mitigate Cement Pore Pressure Reduction and Improve Cement Bonding

Summary A quality cement job is essential to ensure long-term zonal isolation in oil/gas and carbon storage wells. This may be affected by the cement hydration process, during which water is consumed, causing pore pressure reduction and shrinkage, which increases the risk of fluid/gas invasion, formation of microannuli, and even the risk of shear bond strength reduction. In this paper, we present the application of compressible carbon (CC) particles as a cement additive to mitigate cement pore pressure reduction and improve zonal isolation. We designed cement formulations with CC and evaluated them using API standard tests and industry-wide recognized tests to ensure they met functional requirements for well cementing, such as mixability, thickening time, rheology, compressive strength development, fluid loss, and free water. The concept is as follows: When cement is pumped into an annulus, the CC particles will compress under hydrostatic pressure. When the cement is hydrating, the CC will expand to mitigate the pore pressure reduction. To validate the proof of concept, we developed a benchtop high-pressure, high-temperature setup and a pilot-scale test setup. A cement formulation with 9% CC by volume was found to be stable and have controllable performance properties such as thickening time, fluid loss, and free water. We also designed and tested a control slurry without CC for comparison. Both the benchtop and pilot-scale tests demonstrated that adding CC into the cement formulation mitigated the pore pressure reduction during cement hydration. This may reduce the risk of fluid/gas invasion that could result in migration in the set cement. Comparing the cement containing carbon with the control system without carbon, the gas permeability was reduced. The bond strength obtained from shear bond tests improved significantly, which may reduce the risk of debonding and be an indication of the reduction of shrinkage. In addition, a better hydraulic seal was found in one test, but further investigation is needed. Similar mechanical properties such as compressive strength were measured for both cements with and without CC. The data showed that adding CC does not have a negative impact on the hardened cement properties. In fact, adding CC decreased Poisson’s ratio slightly. In this paper, we present the results of proof-of-concept testing for the novel application of CC in cement to improve zonal isolation by mitigating pore pressure reduction. We also present new benchtop and pilot-scale experimental setups to measure pore pressure changes during cement hydration.

Tissue‐derived highly compressible anisotropic carbon aerogels with aligned fibrous matrices for solid‐state rechargeable zinc‐cobalt‐air hybrid batteries

AbstractThe rising demand for wearable zinc‐air batteries encounters challenges in balancing electrochemical performance and mechanical resilience. Elastic carbon aerogels in air cathodes necessitate a metal content constraint of less than 3 wt.%, adversely impacting catalytic activity optimization. This study presents a novel fabrication method for fibrous carbon aerogels with high compressive resilience and extraordinary catalytic performance. An external layer of graphene shells and carbon nanotubes integrated onto the fibrous carbon matrix mitigates metallic species diffusion. This confinement ensures exceptional bi‐catalytic activity for oxygen‐involved redox reactions without compromising ultra‐elasticity. With high cobalt content in the aerogel cathode, it exhibits minimal voltage gaps during charge–discharge cycles, showcasing unique zinc‐cobalt‐air hybrid battery characteristics. It sustains exceptional elasticity in repeated testing, achieving approximately 79.2% round‐trip efficiency over a 60‐h cycle test, underscoring its potential as a wearable energy storage device.image

Highly Compressible, Light-Weight and robust Nitrogen-Doped graphene composite aerogel for sensitive pressure sensors

The demand for compressible multifunctional carbon aerogels with reliable mechanical properties and high response sensitivity has increased in the competitive smart electronics era. This study presents a novel nitrogen-doped graphene composite aerogel that exhibits exceptional robustness, elasticity, and lightweight characteristics. The synthesis involves combining dispersions of Graphene Oxide (GO), Dopamine (DA), and Polyaniline (PANI), followed by chemical reduction, crosslinking at 90 °C, freeze-drying, and thermal annealing. The incorporation of flexible DA with the graphene sheet enhances the composite gel’s toughness, while the π-π stacking interaction between PANI and the graphene sheet strengthens the aerogel framework. The resulting composite aerogel, named GDPA demonstrates outstanding strength, toughness, and compressibility due to the combined effects of DA and PANI. Furthermore, GDPA is assembled into a pressure sensor that exhibits excellent compressive cycle stability. The sensor achieves a low detection limit of 0 Pa and a wide detection range of 0 to 25.48 kPa, surpassing the performance of most previously reported graphene-based aerogels. The remarkable properties of GDPA suggest its immense potential for application in healthcare detection, wearable electronics, and intelligent packaging.

Role of graded microstructure and electrolyte distribution in electrochemical capacitance of compressible three-dimensional carbon nanotubes-polymer foam based supercapacitor

Three-dimensional microstructure of carbon materials has a prime importance in supercapacitor for energy storage. Carbon nanotubes (CNT) provide microstructurally porous structure via entangled nodes that dynamically changes with the uniaxial compression. A unique graded CNT-polymer based three-dimensional compressible cellular foam is used as an electrode material for the solid-state supercapacitor. A direct correlation was established between the applied strain and resulting electrochemical capacitance when the foam electrode was soaked and unsoaked in the electrolyte. In a novel finding, unsoaked electrodes revealed in an extraordinary enhancement of ∼1216% in gravimetric capacitance measured at a uniaxial strain of 80% and to no surprise, the electrochemical capacitance of electrolyte-soaked electrodes remained nearly invariant from its uncompressed state. The response of electrochemical capacitance under compression is also observed varying with the mode of compression i.e. quasi-static versus pre-compressed state to a targeted strain. The role of graded microstructure during uniaxial compression was verified by using as-grown CNT mat for the electrodes of a supercapacitor. The results demonstrated a dominating contribution of dynamic variation in the density of nodes in the compressed CNT mat. The impact of macroscopic variation on the response of electrochemical capacitance of a compressed cellular CNT-polymer foam was further understood using the separators of varying pore sizes. Our results pave the way to engineer the three-dimensional compressible cellular structures for extraordinarily large energy storage capacity.

Super-assembled compressible carbon frameworks featuring enriched heteroatom defect sites for flexible Zn–air batteries

Flexible Zn–air batteries (FZABs) exhibit low cost and inherent safety and have potential for application in wearable electronic devices. Nevertheless, balancing the high energy density and flexibility of the self-supported electrodes in FZABs is still a challenge. Herein, we develop a novel superassembly strategy for the preparation of N, S-codoped porous carbon frameworks (NS@CFs) as cathodes in FZABs. Benefiting from the abundant heteroatom defect sites, NS@CF exhibits excellent electrocatalytic performance for the oxygen reduction reaction (ORR), including high electrochemical activity and long-term stability. When used as the cathode in a liquid flowing ZAB, NS@CF exhibited a power density of 221 mW cm−2 and achieved a 60% improvement over Pt/C-based ZABs. This new ZAB exhibited a high specific capacity of 792 mA h gZn−1, excellent long-term durability and cycling stability, which is superior to those of ZABs assembled with commercial Pt/C cathodes. In addition, the flexible NS@CF with directional channels can be used as independent air cathodes for FZABs, where it provides small charge/discharge voltage gaps, a power density of 49 mW cm−2 and outstanding cycling stability. This work provides a novel strategy for designing and fabricating highly efficient integrated electrodes for flexible and wearable electrochemical devices.

Cicada-Wing-Inspired Highly Sensitive Tactile Sensors Based on Elastic Carbon Foam with Nanotextured Surfaces.

Electronic devices with tactile and pressure-sensing capabilities are becoming increasingly popular in the automatic industry, human motion/health monitoring, and artificial intelligence applications. Inspired by the natural nanotopography of the cicada wing, we propose here a straightforward strategy to fabricate a highly sensitive tactile sensor through nanotexturing of erected polyaniline (PANI) nanoneedles on a conductive and elastic three-dimensional (3D) carbon skeleton. The robust and compressible carbon networks offer a resilient and conducting matrix to catering complex scenarios; the biomimetic PANI nanoneedles firmly and densely anchored on a 3D carbon skeleton provide intimate electrical contact under subtle deformation. As a result, a piezoresistive tactile sensor with ultrahigh sensitivity (33.52 kPa-1), fast response/recovery abilities (97/111 ms), and reproducible sensing performance (2500 cycles) is developed, which is capable of distinguishing motions in a wide pressure range from 4.66 Pa to 60 kPa, detecting spatial pressure distribution, and monitoring various gestures in a wireless manner. These excellent performances demonstrate the great potential of nature-inspired tactile sensors for practical human motion monitoring and artificial intelligence applications.

Multifunctional Flexible Pressure Sensor Based on a Cellulose Fiber-Derived Hierarchical Carbon Aerogel

Flexible pressure sensors have attracted widespread attention in recent years due to their potential applications for health monitoring and human–machine interfaces. However, the fabrication of environmentally friendly and well-performing pressure sensors using biobased materials remains a great challenge. Herein, a compressible carbon aerogel was prepared by sequential microfibrillation, periodate oxidization, and tannic acid (TA) cross-linking of cellulose fibers (CFs) followed by freeze-drying the as-prepared CF suspension and high-temperature pyrolysis of the obtained CF aerogel. The microfibrillation endows the carbon aerogel with a hierarchical structure, which improves the bonding strength and compressibility of the carbon aerogel. Periodate oxidation and TA cross-linking improved the mechanical properties of the carbon aerogel, while pyrolysis endowed the carbon aerogel with excellent conductivity, enabling the carbon aerogel to be a good pressure-sensing material. When assembled into a pressure sensor, the sensor shows a high sensitivity of 4 kPa–1, a fast response/recovery time of 32/30 ms, a low-pressure detection limit of 0.8 Pa, and good stability and excellent reproducibility (3000 cycles at 0.5 kPa). Moreover, the pressure sensor can be used to accurately monitor various human activities and also spatially resolve pressure variations when integrated into a sensor array. The pressure sensor also responds linearly to increased temperature and humidity. These results suggest that this hierarchical carbon aerogel-based pressure sensor has great potential for application as a multifunctional sensor.

A resilient and lightweight cellulose/graphene oxide/polymer-derived multifunctional carbon aerogel generated from Pickering emulsion toward a wearable pressure sensor.

In the new era of competitive smart electronics, the development of compressible multifunctional carbon aerogels is highly needed, but still faces enormous challenges. Here we demonstrate a robust strategy to fabricate multifunctional carbon aerogel via freeze-drying of cellulose nanofibers (CNF) and graphene oxide (GO) co-stabilized Pickering emulsion gel followed by high-temperature annealing. The resulting carbon aerogel exhibits tunable mechanical, hydrophilic and hydrophobic properties due to varying the elemental composition and the pyrolysis of introduced polymers. The carbon aerogel is resilient against high compression strain up to 99% and has ultralow density (1.82mg/cm3). The CNF/GO/acrylonitrile butadiene styrene-derived carbon aerogel (CRA)-based sensor has shown desirable sensitivity (17.65kPa-1), ultralow detection limit of pressure (60Pa), and fast responsive time (130ms), which is capable of detecting human activity, identifying spatial pressure distribution, and communicating with smartphones via Wi-Fi. Moreover, the carbon aerogel reveals effective thermal insulation and photothermal conversion performance. These results suggest the great potentials for developing lightweight and compressible carbon aerogels with multiple functions to meet various applications.

Carbon Nanocoils/Carbon Foam as the Dynamically Frequency‐Tunable Microwave Absorbers with an Ultrawide Tuning Range and Absorption Bandwidth

AbstractThe absorption frequency of conventional microwave absorbing materials (MAMs) is hardly tuned in operando, while such dynamic frequency regulation of MAMs is of great significance to meet the high demands of modern radars and intelligent electron devices. Here, an ingenious frequency‐tuning strategy by means of the pressure variations is developed by fabricating highly compressible carbon nanocoils/carbon foam (CNCs/CF) as a dynamically frequency‐tunable microwave absorber. Through adjusting the compression strain, the absorption bandwidth of CNCs/CF can be precisely tuned from S‐band (2−4 GHz) to Ku‐band (12−18 GHz). The adjustable effective absorption bandwidth is as wide as 15.4 GHz, which covers 96% of the entire microwave frequency. Under 10% compression strain, CNCs/CF shows an attractive bandwidth of 9.0 GHz and a strong reflection loss of −64.6 dB. Furthermore, the CNCs/CF also exhibit a good thermal insulation, strong hydrophobicity, and strain‐sensitive conductivity, endowing them with fascinating functions of heat insulation and self‐cleaning. The method of utilizing an external pressure to dynamically adjust the absorption frequencies of CNCs/CF is demonstrated for the first time, which opens an avenue for the applications of dynamically frequency‐tunable MAMs with an ultrawide adjusting range and absorption bandwidth.

Compressible, superelastic and fatigue resistant carbon nanofiber aerogels derived from bacterial cellulose for multifunctional piezoresistive sensors

Carbon aerogels have been widely exploited for wearable piezoresistive sensing thanks to their fascinating properties such as ultralow density, high electrical conductivity, superelasticity, and fatigue resistance, but to date, maintain high mechanical performances and high sensitivity in a wide pressure range still remains a huge challenge for carbon aerogels based piezoresistive sensors. Herein, we propose a simple but efficient morphology-maintained carbonization strategy by tailoring the pyrolysis chemistry of BC to fabricate superelastic and fatigue-resistant carbon nanofiber aerogels. Bacterial cellulose hydrogels are fabricated as nanofiber aerogels with a 3D-interconnected honeycomb-like structure by unidirectional freeze-drying technology, while the rational introduction of (NH 4 ) 2 SO 4 significantly inhibits the shrinkage and deformation of bacterial cellulose nanofiber aerogels during the carbonization process, enabling the retention of the 3D-interconnected honeycomb-like structure after carbonization. The as-prepared carbon nanofiber aerogels (CNFAs) exhibit exceptional mechanical performances of high compressibility (up to 99% strain), superelasticity (∼97.4%, 500 cycles at 90% compression), and fatigue resistance (up to 10 000 cycles). Moreover, the CNFAs derived sensor possesses a high sensitivity (5.66 kPa −1 ) at a wide pressure range (0–28 kPa), and a fast response time (∼100 ms), enabling the CNFAs-based sensor to monitor signals of the human body, spatial pressure, and voice recognition. These fascinating attributes make the CNFAs highly attractive for flexible wearable devices. • Biomass-based carbon nanofiber aerogels were designed for Multifunctional sensors. • The carbon nanofiber aerogel reveals a 3D-interconnected honeycomb-like structure. • Superior compressibility and fatigue resistance surpasses other carbon aerogels. • The carbon nanofiber aerogel possesses a high sensitivity at a wide pressure range.

Iron-Adjustable Compressible Elastic Chitosan-Derived Carbon Aerogel with Wide-Range Linear Sensitivity and Super Sensing Performances for Wearable Piezoresistive Sensors

Iron-Adjustable Compressible Elastic Chitosan-Derived Carbon Aerogel with Wide-Range Linear Sensitivity and Super Sensing Performances for Wearable Piezoresistive Sensors

The porous spongy nest structure compressible anode fabricated by gas forming technique toward high performance lithium ions batteries

The state-of-the-art electronics promote the development of flexible and deformable batteries, which rely on design of advanced structure batteries and fabrication of suitable electrode materials. The current flexible electronics are generally limited by rigidity and nondeformable electrodes. Herein, this work reports an exceeding compressible spongy carbon nanofibers composite anode which was fabricated by electrospinning and gas-forming techniques. The abundant macro/micro porous and loss structure of spongy layers enable the composite electrode exhibited compressible capability and faster ions infiltration ability. And the nest morphology of spongy carbon nanofibers network promised stable conductivity and superior cycling performance of self-standing anodes. The compressible SnO2@spongy carbon nanofibers and SiO2@spongy carbon nanofibers self-standing anode exhibited outstanding cycling ability before 300 cycles under compressed state, with a capacity of 350 and 398 mA h g−1, respectively. Notably, the stress and strain of compressible spongy composite electrode are 370 kPa and 92%, separately, with recovery ability. The compressible spongy anode is highly recommended for flexible electrochemical energy storage devices and the novel gas-forming technique is a potential method for fabrication of multi morphology electrode.

Interfacial Assembly of Compressible Carbon Aerogels Featuring Oxygen Reduction Reaction Property for Rechargeable and Flexible Zn-Air Batteries

Interfacial Assembly of Compressible Carbon Aerogels Featuring Oxygen Reduction Reaction Property for Rechargeable and Flexible Zn-Air Batteries

Hardened wood as a renewable alternative to steel and plastic

Hardened wood as a renewable alternative to steel and plastic

Enhancing the Mechanical Performance of Reduced Graphene Oxide Aerogel with Cellulose Nanofibers

AbstractUltralight, highly compressible and superelastic carbon materials hold great promise in wearable and flexible electronic devices, but the fabrication remains to be a challenge because of the brittleness nature of carbon. Herein, a carbon aerogel with ultralow density yet high mechanical performance is successfully fabricated from graphene oxide (GO) liquid crystal stabilized bubbles with the enhancement of cellulose nanofiber (CNF). The incorporation of CNF into reduced graphene oxide (rGO) nanosheets enhances the interaction among rGO nanosheets through welding effect, which restricts the slip of rGO nanosheets and the detachment among microspheres, leading to a significant improvement on mechanical properties. The as‐prepared carbon aerogel with tightly packaged cell‐wall architecture displays ultrahigh compressibility (up to 99% strain) and elasticity (90.1% stress retention and 99.0% height retention after 10000 cycles at 50% strain), which are superior to those of the present bubble‐templated carbon aerogels and many other carbon materials through various methods. The structural feature leads to rapid and stable current response and high sensitivity to external strain and pressure, allowing the carbon aerogel to detect very small pressure and various human motions from finger bending to pulse. These advantages make the carbon aerogel promising for flexible electronic devices.

Mechanically Flexible Carbon Aerogel with Wavy Layers and Springboard Elastic Supporting Structure for Selective Oil/Organic Solvent Recovery.

Even though compressible carbon aerogels are widely studied for oil/organic solvent recovery, it is challenging to simultaneously achieve excellent mechanical performance and recovery efficiency due to the brittleness of the carbon skeleton. Here a novel strategy is proposed to efficiently fabricate a 3D elastic reduced graphene oxide (RGO)-cross-linked carbon aerogel. Notably, cellulose nanocrystals (CNCs) isolated from plant pulp act as an essential component, and prehydrolysis liquor (PHL), an industrial byproduct in the plant pulping process, serves as the adhesion promoter to achieve enhancement of the strength and flexibility of the carbon aerogel. For the first time, all components (pulp and PHL) of the tree were fully exploited to design a carbon aerogel. The formation of wavy carbon layers with springboard elastic supporting microstructure enables mechanical stretch and shrink as well as avoids interfacial collapse during compression. Benefiting from the unique wavy layer structure and strong interaction, the carbon aerogels are ultralight (4.98 mg cm-3) and exhibit supercompression (undergoing extreme strain of 95%) and superelasticity (about 100% height retention after 500 cycles at a strain of 50%). Particularly, the carbon aerogel can selectively and quickly adsorb various oily contaminants, exhibiting high oil/organic solvents absorption capacity (reaches up to 276 g g-1 for carbon tetrachloride) and good recyclability. Finally, practical applications of the carbon aerogel in oil-cleanup and pollution-remediation devices are exhibited. Hence, this versatile and robust functionalized carbon aerogel has promising potential in oil cleanup and pollution remediation.

Compressible Carbon Sponges from Delignified Wood for Fast Cleanup and Enhanced Recovery of Crude Oil Spills by Joule Heat and Photothermal Effect

AbstractFast and efficient cleanup of crude oil spills is still a global challenge because most of the crude oils are highly viscous and lowly fluid. Herein, a kind of polydimethylsiloxane‐decorated wood carbon sponges (PDMS@WCS) with desirable compressibility and hydrophobicity for the fast adsorption and enhanced recovery of crude oil via the promotion of Joule‐heating and photothermal effect is reported. Moreover, the PDMS@WCS can be compressed and released at a constant strain of 50% for over times without structural damage due to the protection of PDMS coating. Thus, the adsorbed crude oil can be facilely excluded from PDMS@WCS under external pressure to show enhanced recovery.

Dry-pressed lithium nickel cobalt manganese oxide (NCM) cathodes enabled by holey graphene host

There is an increasing demand for electric vehicle batteries with higher energy densities that can be manufactured with low cost utilizing environmentally friendly processes. Lithium nickel cobalt manganese oxides (NCM), such as LiNi0.5Co0.2Mn0.3O2 (NCM523), are commonly used in commercial lithium ion batteries for electric vehicle applications. These cathodes are typically fabricated using environmentally hazardous, energy intensive, and time-consuming solvent-based slurry casting processes. Polymeric binders, also required for cathode preparation, add weight and can undergo parasitic reactions during battery cycling. Here we report a facile, solvent-free, binder-free, and rapid cold-press electrode fabrication process to prepare high mass loading NCM cathodes within minutes. This process is enabled by the use of holey graphene, a unique lightweight, compressible carbon nanomaterial that serves as both a binder and an electrically conductive matrix. NCM cathodes fabricated by this method are stable and exhibit good active material utilization. A significant advantage for the dry-press process is that the electrode mass loadings can be readily increased simply by adding more composite powder to the compression molding die, resulting in improved areal capacities that are attractive for applications requiring high energy per unit footprint.

Construction of shape-memory carbon foam composites for adjustable EMI shielding under self-fixable mechanical deformation

The design and fabrication of novel electromagnetic interference (EMI) shielding materials with the capability of realizing convenient performance regulation under self-fixable mechanical deformation is becoming an urgent challenge due to the increasingly complex application conditions. To alleviate this problem, the composite construction that consisted of compressible carbon foam (CF) and shape-memory polymer coating was proposed, and the demo samples were fabricated by coating trans-l,4-polyisoprene (TPI)-MXene layer onto compressible wood-derived CF with multilayer microstructure. The resultant composites (thickness: ~2–10 mm, density: ~150 mg/cm3) with enhanced shielding effectiveness (SE) of ~25.3–44.7 dB could not only adjust their SE value by changing their compressive strains, but also possess excellent thermally/electrically stimulated shape-memory behaviors that can be easily deformed and recovered as being heated and fix a temporary shape at low temperature, thereby realizing convenient SE regulation under self-fixable mechanical deformation. Moreover, based on different initial SE performance and compression conditions, the EMI SE of the composites can also be tuned within effective SE range of >20 dB, or switched between >20 and <20 dB, exhibiting smart function-tunable or function-switchable feature, which provides a promising platform for developing novel EMI shields for smart electromagnetic response applications.