Conductivity Of Carbon Nanotubes Research Articles

Breathable and Wearable Strain Sensors Based on Synergistic Conductive Carbon Nanotubes/Cotton Fabrics for Multi-directional Motion Detection.

Flexible strain-sensitive sensors have been receiving intensive attention in many aspects ranging from human motion capture to health-related signal monitoring. However, the fabric strain sensor with multi-directional sensing capability, besides having a wide strain range and high response sensitivity, is still very challenging and deserves further exploration. Here, we have prepared a wearable cotton fabric strain sensor uniformly decorated with single-walled carbon nanotubes through a facile solution process. The unique hierarchical architecture of the cotton fabric woven from twisted yarns combined with the conductive carbon nanotube network endows the fabric strain sensors with attractive performance, including low detection limit, large workable strain range, fascinating stability and durability, excellent direction-dependent strain response, and good air permeability. The strain sensor without polymer encapsulation can not only monitor subtle and large multi-directional motions but also fit well to the human body with satisfactory comfort, demonstrating its potential application in wearable electronics and intelligent clothing.

Progress on carbon nanotube filled polymer-based thermal conductive composites

<p indent="0mm">In the 5G era, the effective thermal management has become more demanding due to the ever-rising integration of electronic devices. High thermal conductivity materials play a crucial role in the field of thermal management, for example, thermal interface materials (TIMs) are used to fill the gap between the electronic chip and the heat sink to improve thermal transfer. In recent years, polymers have become a popular choice for thermal conductive materials because of their light, economical and excellent insulation and processability. To improve the thermal conductivity of materials, inorganic fillers with high thermal conductivity are generally composited with polymers. With the merits of high thermal conductivity, desirable chemical stability, carbon nanotubes (CNTs) are considered to have broad application potential in thermal conductive composites. Simple composition methods failed to increase thermal conductivity of composite materials to expected levels due to the large interfacial thermal resistance between CNTs and polymers and the disorderly distribution of CNTs in polymers. Therefore, reasonable design of polymer composites filled with CNTs is the key to achieving high thermal conductivity. This review mainly introduces the application of CNTs in thermal conductive polymer composites. Based on the existing theoretical research on thermal conductivity of composites and the application of molecular dynamics, more feasible strategies for improving the thermal conductivity of polymer composites filled with CNTs have been proposed. The approaches that improve the thermal conductivity of composites are mainly introduced from three aspects. (1) The intrinsic thermal conductivity of CNTs is an important factor affecting the thermal conductivity of polymer-based composites. CNTs and their macroscopic bulk materials both have excellent thermal conductivity. However, the thermal conductivity test results of the macroscopic materials of CNTs (such as CNTs fibers, arrays, and films) showed that the thermal conductivity of the macroscopic materials of CNTs was much smaller than that of single CNTs due to impurities, defects and inter-tube contact thermal resistance. Studies have shown that purification of CNTs and reduction of intertubular contact thermal resistance can improve the intrinsic thermal conductivity of CNTs. (2) From a microscopic perspective, phonons, the quantized energy of lattice vibration, are the main mechanism of heat conduction in most carbon fillers and polymers. Phonon scattering occurs in the process of phonon transfer, including the scattering between phonons and the scattering at the interface caused by defects and impurities, resulting in thermal resistance. The bonding strength of fillers and polymer interfaces are the crucial factors affecting the transmission of phonons. Hence, the thermal conductivity of composites could be effectively enhanced by surface treatment of CNTs, including covalent functionalization and non-covalent functionalization. Studies have shown that the functionalization can enhance the interfacial interaction between CNTs and polymers, while improving the dispersion of CNTs in polymers. (3) According to the thermal conduction network theory, the key to improving the thermal conductivity is whether the fillers can form a large number of continuous thermal conduction paths in the polymers and maintain a stable existence. However, high CNTs content usually affects the comprehensive properties of composites. To solve this problem, the arrangement and distribution of CNTs in the polymer should be improved to construct more heat conduction pathways, which can achieve high thermal conductivity at a low filling content. Here we introduce some effective methods, including the synergy effect, field orientation and the construction of 3D network structures. In this review, the characteristics and improvement effects of different technical approaches are summarized, which provides a reference for the research and application of CNT-filled polymer-based composites with high thermal conductivity. Finally, the future development prospects of carbon nanomaterial-filled polymer composites are discussed from perspectives of theoretical research, experimental design and engineering application.

Binder-free 3D hierarchical Bi Nanosheet/CNTs arrays anode for full sodium-ion battery with high voltage above 4 V

Aiming to the repetitively large volume change and the inevitably loss of volumetric capacity of bismuth (Bi) based sodium-ion battery (SIB) during cycling, a binder-free Bi anode based on one-step electrochemical co-deposited three-dimensional Bi nanosheets and conductive carbon nanotube networks (Bi NS/CNTs) was developed. Compared with the sole Bi anode achieved via the same strategy, the co-deposition of 3D hierarchical Bi nanosheet/CNTs arrays manifests the strong interfacial adhesion and accommodates the volume change upon sodium alloying/dealloying. Such structural feature endows the Bi NS/CNTs anode a long-term cycling stability (383.72 mAh g−1 at 0.1 A g−1 after 200 cycles, 311.68 mAh g−1 at 1 A g−1 after 1000 cycles) and a good rate performance. A full SIB assembled with Bi NS/CNTs anode and Na3(VOPO4)2F@rGO cathode shows a high operating voltage (above 4 V) and a high energy density of 221.99 Wh kg−1, which outperforms many reported Bi-based analogues. This work may open a new opportunity for developing efficient SIB with high energy and good practicability.

From waste to wealth: Crumb rubber@carbon nanotube/Fe3O4 composites towards highly effective electromagnetic microwave absorption with wide bandwidth

The reuse of the waste crumb rubber (CR) is of great significance to alleviate the increasingly serious black pollution problem. Herein, low-cost electromagnetic microwave absorption (EMA) CR composites assisted by conductive carbon nanotubes (CNTs) and magnetic Fe3O4 are fabricated with the aid of microwave. The effects of the addition of CNTs and Fe3O4 on the structure and morphology, and EMA properties of the CR@CNT/Fe3O4 composite are evaluated in detail. The resulted composite can exhibit a superior minimum reflection loss (RLmin) of −60.46 dB at 14.19 GHz with a thickness of 2.3 mm, and a wide effective absorption bandwidth of 5.5 GHz (11.2–16.7 GHz) due to the synergy effect of coordinated dielectric and magnetic losses, good interface impedance matching, and internal multiple reflections. This composite recycling from waste tire rubber is expected to become a potential candidate as a low-cost microwave absorber for reducing electromagnetic and black pollution.

Hard Carbon Microsphere with Built-In Electron Transport Channels as a High-Performance Anode for Sodium-Ion Batteries

Hard carbon is one of the most promising candidate materials as the anode for sodium-ion batteries (SIBs). In this work, we developed an effective strategy to homogenize highly conductive carbon nanotubes (CNTs) into a hard carbon microsphere (e-HC) to construct electron transport channels to improve the performance of hard carbon. The material featured a wrinkled hard carbon microsphere with built-in electron transport channels. Although the optimization made no significant changes in the particle size and the graphitization state for the hard carbon, the electrochemical performance was greatly improved in comparison with the pure hard carbon material without CNTs (HC). The increase in the electric and ionic conductivity was identified. The electrochemical measurements showed that the e-HC electrode delivered a reversible capacity of 335.6 mAh g−1 at 0.05 mA g−1, which was higher than that of the HC electrode (304.1 mAh g−1 at 0.05 mA g−1). The as-synthesized e-HC material exhibited a higher rate performance and a better cycle life than the HC material. The correlated mechanism for the enhancement was proposed in this study. The e-HC material can be used as a feasible anode for SIBs.

Nanocomposite electrodes using highly conductive sub-millimetre-long single-walled carbon nanotubes pasted with PEDOT:PSS and high-performance actuators

We describe new nanocomposite electrodes and actuators using highly conductive single-walled carbon nanotubes (<1 mm in length) fabricated using the ‘super-growth’ method (SG-SWCNT) pasted with poly(3,4-ethylenedioxythiophene):poly(4-styrenesulfonate) (PEDOT:PSS) and combined with electrostatic double-layer capacitors (EDLCs) and faradaic capacitors (FCs). The electromechanical/chemical properties of the SG-SWCNT/PEDOT:PSS/ionic liquid (IL) electrode and actuator were compared with those of the SG-SWCNT/IL electrode and actuator. The SG-SWCNT/PEDOT:PSS/EMI[C(CN)3] electrode (volume resistivity; 4.26 Ω cm, surface resistivity; 0.55 Ω/sq. and conductivity; 235 S/cm) was a more conductive electrode than the equivalent SG-SWCNT/EMI[C(CN)3] electrodes (36.0 Ω cm, 2.37 Ω/sq. and 28.0 S/cm). This is thought to be a result of the synergy between SG-SWCNT and PEDOT:PSS. The maximum strain of the SG-SWCNT/PEDOT:PSS/EMI[B(CN)4] actuator ranged from 0.39% to 1.88%, which is approximately 1.6–7.5 times larger than that of the SG-SWCNT/EMI[B(CN)4] actuator. The actions of the hybrid actuators differed from those of the SG-SWCNT/IL actuators, which function only as EDLC units. A kinetic model featuring double-layer charging successfully simulated the frequency-dependent displacement responses of both types of actuators. The use of a PEDOT:PSS polymer promotes higher conductivity, specific capacitance, and strain, which is thought to originate in synergy between SG-SWCNT and PEDOT:PSS. Thus, flexible robust films that exploit this synergy are likely to be useful as actuator components in energy conversion and wearable devices.

A Hygroscopic Janus Heterojunction for Continuous Moisture-Triggered Electricity Generators.

Moisture-triggered electricity generator (MEG) harvesting energy from the ubiquity of atmospheric moisture is one of the promising potential candidates for renewable power demand. However, MEG device performance is strongly dependent on the moisture concentration, which results in its large fluctuation of the electrical output. Here, a Janus heterojunction MEG device consisting of nanostructured silicon and hygroscopic polyelectrolyte incorporating hydrophilic carbon nanotube mesh is proposed to enable ambient moisture harvesting and continuous stable electrical output delivery. The nanostructured silicon with a large surface/volume ratio provides strong coupling interaction with water molecules for charge generation. A polyelectrolyte of polydiallyl dimethylammonium chloride (PDDA) can facilitate charge selective transporting and enhance the effectiveness of moisture-absorbing in an arid environment simultaneously. The conductive, porous, and hydrophilic carbon nanotube mesh allows water to be ripped through as well as the generated charges being collected timely. As such, any generated charge carriers in the Janus heterojunction can be efficiently swept toward their respective electrodes, because of the device asymmetric contact. A MEG device continuously delivers an open-circuit voltage of 1.0 V, short-circuit current density of 8.2 μA/cm2, and output power density of 2.2 μW/cm2 under an ambient environment (60% relative humidity, 25 °C), which is a record value over the previously reported values. Furthermore, the infrared thermal measurements also reveal that the moisture-triggered electricity generation power is likely ascribed to surrounding thermal energy collected by the MEG device. Our results provide an insightful rationale for the design of device structure and understanding of the working mechanism of MEG, which is of great importance to promote the efficient electricity conversion induced by moisture in the atmosphere.

Multidefect N-Nb2 O5- x @CNTs Incorporated into Capillary Transport Framework for Li+ /Na+ Storage.

As an ion-embedded material with small strain and low transport energy barrier, the limited ion transport rate and conductivity of niobium pentaoxide (Nb2 O5 ) are the main factors limiting its application in lithium/sodium storage systems. In this work, the microsphere composites (N-Nb2 O5- x @CNTs) are prepared by combining Nb2 O5 , rich in nitrogen doping and vacancy defects, with carbon nanotubes (CNTs) penetrating the bulk phase. With the capillary effect, CNTs can enable the rapid electrolyte infiltration into the microspheres, thus shorting the Li+ /Na+ transport path. In addition, CNTs also hinder the direct contact between the electrolyte and Nb2 O5 , and inhibit the irreversible reaction. Meanwhile, nitrogen doping and oxygen vacancy defects reduce the energy barrier of Li+ /Na+ transport, and improve their transport rate, proved by density functional theory. Highly conductive CNTs and unpaired electrons from defects also ameliorate the insulation property of Nb2 O5 . Therefore, N-Nb2 O5- x @CNTs display good electrochemical performance in both Li/Na half-cell and Li/Na hybrid capacitors. Interestingly, kilogram-scale microsphere composites can be produced in laboratory conditions by using industrial grade raw materials, implying its potential for practical application.

Preparation of carbon nanotubes‐hollow Co 9 S 8 composite and its use in separator modification for lithium‐sulfur battery

Lithium-sulfur batteries (LSBs) have received numerous studies because of their advantages of high specific capacity, low cost of the sulfur element and so on. However, there are several obstacles restricting the commercial use of LSBs, including low conductance of sulfur, volume expansion effect of the positive sulfur electrode and serious shuttle effect of soluble lithium polysulfides. In this work, a composite of carbon nanotubes (CNTs) and hollow Co9S8 (CNTs/Co9S8) is synthesized via ZIF-67 as a template and is applied on the surface of the PE separator for LSBs. Benefited from the excellent conductance of CNTs as well as the adsorption and catalysis properties of polar hollow Co9S8, the cell with the CNTs/Co9S8 composite functional separator delivered the discharge capacity of 977.6 and remained 456 mAh g−1 after 500 loops at a current density of 0.5 C, corresponding to a low attenuation rate of only 0.1% per cycle, as well as excellent rate properties. Even at high areal mass loading of active sulfur, LSBs exhibited excellent long-term cycling stability at various current rates. In addition, the Li dendrites were remarkably restrained, which further enhanced the safety of batteries. This paper provides an effective and newfangled approach with modified separators coating composite materials of carbon species and structural sulfide to inhibit the shuttle of intermediate polysulfides and further enhance the utility of LSBs in the future.

Water‐resistant conductive organogels with sensation and actuation functions for artificial neuro‐sensory muscular systems

AbstractThe development of functional flexible conductive materials can significantly contribute to the improvement of intelligent human–computer integration. However, it is a challenge to endow human–machine interface with perception and response actuation simultaneously. Herein, a customizable and multifunctional electronic conductive organogel is proposed by combining conductive carbon nanotube (CNT) clusters and flexible adhesive organogels. The conductive CNT cluster layers generated on the surface of organogels equip the resulting organogel‐based conductors with considerable quasi‐superhydrophobicity and increase their potential applicability as highly sensitive stress and strain sensors. In particular, this quasi‐superhydrophobicity is insensitive to tensile strain. Based on customizable conductive networks and entropy‐driven organogel actuation, the conductive organogels can sense various strain and stress signals and imitate natural organisms with muscle actuation and neurofeedback. This strategy for preparing electronic conductors can enhance the rational design of soft robotics and artificial intelligence devices, facilitating further progress of human‐like intelligent systems.

Layer-by-Layer Assembly of CeO2-x@C-rGO Nanocomposites and CNTs as a Multifunctional Separator Coating for Highly Stable Lithium-Sulfur Batteries.

Commercialization of high-energy Li-S batteries is greatly restricted by their unsatisfactory cycle retention and poor cycling life originated from the notorious "shuttling effect" of lithium polysulfides. Modification of a commercial separator with a functional coating layer is a facile and efficient strategy beyond nanostructured composite cathodes for suppressing polysulfide shuttling. Herein, a multilayered functional CeO2-x@C-rGO/CNT separator was successfully achieved by alternately depositing conductive carbon nanotubes (CNTs) and synthetic CeO2-x@C-rGO onto the surface of the commercial separator. The cooperation of multiple components including Ce-MOF-derived CeO2-x@C, rGO, and CNTs enables the as-built CeO2-x@C-rGO/CNT separator to perform multifunctions from the separator surface: (i) to hinder the diffusion of polysulfide species through physical blocking or chemical adsorption, (ii) to accelerate the sluggish redox reactions of sulfur species, and (iii) to enhance the conductivity for sulfur re-activation and efficient utilization. Serving as a multilayer and powerful barrier, the CeO2-x@C-rGO/CNT separator greatly constrains and reutilizes the polysulfide species. Thus, the Li-S battery assembled with the CeO2-x@C-rGO/CNT separator demonstrates an excellent combination of capacity, rate capability, and cycling performances (an initial capacity of 1107 mA h g-1 with a low decay rate of 0.060% per cycle over 500 cycles at 1 C, 651 mA h g-1 at 5 C) together with remarkably mitigated self-discharge and anode corrosion. This work provides guidelines for functional separator design as well as rare-earth material applications for Li-S batteries and other energy storage systems.

Asymmetric Neutral‐alkaline Microbial Electrolysis Cells for Hydrogen Production

AbstractThe development of highly efficient cathodes for hydrogen production that can operate in a suitable pH condition is a daunting challenge in microbial electrolysis cells (MECs). Herein, an asymmetric neutral‐alkaline double‐chamber microbial electrolysis cells (AMECs) by using conventional carbon brush with microorganism attached as neutral anode and the Ru/CNTs electrode as alkaline cathode, respectively, was proposed. To implement this, a hybrid with ruthenium nanoparticles loaded on conductive carbon nanotubes (Ru/CNTs) was prepared by a reduction deposition method, which exhibited comparable electrocatalytic performance to the expensive benchmark Pt/C catalysts for hydrogen evolution reaction (HER). Compared to the traditional MECs running in symmetric neutral electrolyte, the as‐developed AMEC displayed a higher current density of 17.13 A m−2 and hydrogen production rate of 0.167 m3 m−2 d−1. The present AMEC provides an energy‐saving and cost‐effective process technology for electrolysis H2 generation.

Enhancing anaerobic methane production in integrated floating-film activated sludge system filled with novel MWCNTs-modified carriers

Conductive materials can enhance anaerobic methane production by accelerating interspecies electron transfer between electroactive bacteria and methanogens. However, the daily loss or less specific surface area of small/big size of conductive materials always limits their application in anaerobic digestion. In this study, the conductive multi-walled carbon nanotubes (MWCNTs) (15 wt% and 20 wt%) were mixed with high-density polyethylene (HDPE) and novel conductive suspended carriers were prepared. Results showed the conductivity of the novel conductive suspended carriers increased by 1–2 orders of magnitude comparing with HDPE carriers, as well as the attached biomass improved from 3.93 g/m2 (HDPE carriers) to 5.82 g/m2 (15 wt% MWCNTs-modified carriers) and 6.67 g/m2 (20 wt% MWCNTs-modified carriers). Integrated floating-film activated sludge (IFFAS) filled with MWCNT-modified carriers showed significant advantages in chemical oxygen demand (COD) removal (removal efficiency increased by 3.6–37.2%) and methanogenic performance (cumulative methane increased by 12.28–62.91%) compared with the control reactor filled with conventional HDPE carriers when treating sodium propionate wastewater at the organic loading rates (OLR) of 11.3–26.3 kg COD/(m³∙d). SEM images and high-throughput sequencing results proved potential direct interspecies electron transfer (DIET) had been established successfully on the MWCNTs-modified carriers. The syntrophic electroactive bacteria (Geobacter, Thauera) and Methanotrix were enriched by 2.28–4.58% and 9.41–16.80% respectively owning to the addition of novel conductive carriers. This study proved IFFAS process filled with novel MWCNTs-modified suspended carriers showed great potential in establishing DIET to enhance anaerobic digestion in practical application.

Boosting Li-CO2 battery performances by creating holey structure on CNT cathodes

Li-CO2 batteries have attracted more and more attention because of their high theoretical energy density and promising CO2 capture capacity. However, irreversible formation of Li2CO3 during discharging causes a high overpotential, short cycling life, and poor rate capability. To enable Li-CO2 batteries stable and rechargeable operation, the development of high-efficiency catalysts for CO2 reduction and Li2CO3 decomposition is highly desired. Herein, holey carbon nanotubes (CNTs) are developed as the cathode catalysts for the rechargeable Li-CO2 batteries. Benefiting from abundant defects for enhancing CO2 reduction/evolution reactions and holey structures for storing more discharge products, and combining advantage of high conductivity of CNTs for rapid electron transport, the as-prepared Li-CO2 batteries with holey CNTs exhibited a low overpotential of 1.18 V at 50 mA g−1. More importantly, the batteries delivered an ultrahigh discharge capacity of 17,500 mA h g−1 and long-time stability over 1500 h at 100 mA g−1. This study unlocks new avenues to develop high-efficiency cathode catalysts for high-performance metal-CO2 batteries and beyond.

Hierarchically nanostructured carbon nanotube/polyimide/mesoporous Fe2O3 nanocomposite for organic-inorganic lithium-ion battery anode

Integrating organic multiple-carbonyl polymers and inorganic mesoporous metal oxides on highly conductive carbon nanotubes is a promising strategy to manufacture high-performance lithium-ion battery anodes; however, developing multicomponent nanocomposites with a hierarchical architecture still remain challenging. Herein, we design and produce hierarchically nanostructured carbon nanotube (CNT)/polyimide (PI)/mesoporous Fe 2 O 3 (meso-Fe 2 O 3 /PI/CNT) ternary nanocomposite materials via a sequential assembly and high-temperature dehydration strategy, aiming to fabricate flexible PI-supported meso-Fe 2 O 3 stacked on a conductive CNT supporting skeleton. By controlling the linear PI mainchain through the comonomer composition, different PI assemblies can grow on the surface of CNT to anchor meso-Fe 2 O 3 nanoparticles as well as alleviate the structural strain resulting from the volume expansion of meso-Fe 2 O 3 in its phase conversion reaction. Considering the porosity and cavity, the mesoporous Fe 2 O 3 architecture can not only buffer its volume expansion but also accommodate a large number of electrolytes to promote Li + transport. In addition, the hierarchical architecture endows the meso-Fe 2 O 3 /PI/CNT nanocomposite materials with a high structural stability during the electrochemical process. Benefiting from these structural advantages, Li-ion batteries assembled with meso-Fe 2 O 3 /PI-EDA/CNT electrodes deliver high capacities of 708.9, 608.2, and 454.5 mAh g −1 at 0.1, 0.3, and 0.5 A g −1 , respectively. Even at a high current density of 1 A g −1 , a discharge capacity of 95.6 mAh g −1 is still obtained after 3000 cycles. This work provides a promising route to integrate multiple-carbonyl polymers and mesoporous metal oxides with the aim of developing multicomponent organic-inorganic composite anode for Li-ion battery. • Hierarchically tubular organic-inorganic nanocomposite anode from self-assembly-assisted fabrication technique is reported. • Polyimide assemblies with controllable architecture for organic anode material and strain buffer interlayer. • Fe 2 O 3 nanoparticle with mesoporous structures for inorganic anode material. • The organic-inorganic nanocomposite anode shows desirable lithium-ion battery performance.

Intermittent direct joule heating of membrane surface for seawater desalination by air gap membrane distillation

Air gap membrane distillation (AGMD) is a low-temperature separation process applied commonly to desalination of (hyper)saline feeds. The low energy efficiency of heating the bulk feed solution to drive vapor transport in MD must be addressed through novel materials and techniques. In this work, we introduce the concept of intermittent electrical heating at the membrane surface using electrically conductive carbon nanotube structure (CNS) films pressed on commercial polypropylene (PP) membranes. First, the Joule heating effect was optimized by varying the mass loading of the CNS layer between 1.4 and 4.2 mg cm −2 . The effect of mass loading on porosity, electrical properties and cross-sectional morphology of the CNS layer was also investigated. Electrical conductivity of CNS films increases with increasing CNS mass loading. A CNS loading of 1.4 mg cm −2 yielded the highest electrical resistance, which translated into higher Joule heat generation, and highest steady-state temperature in response to applied current. When an alternating current of 2 A was passed through the CNS films in air, the maximum surface temperature achieved was 184 °C, 126 °C and 100 °C at CNS loadings of 1.4 mg cm −2 , 2.8 mg cm −2 and 4.2 mg cm −2 , respectively. Maximum surface temperature and spatial temperature distribution of CNS films were verified using a steady-state thermal-electric simulation. CNS films exhibited rapid thermal cycling between on and off states, due to their low thermal mass, with low thermal time constants for both heating and cooling. CNS film with a loading of 1.4 mg cm −2 was then pressed onto a commercial PP membrane and applied to AGMD for seawater desalination, with the conductive layer in direct contact with the feed solution. Intermittent heating was carried out by passing a current of 2 A for 10 min at 20 min intervals, for 10 cycles. Feed outlet temperature increased by > 9 °C during each cycle, which improved average permeate flux by 78%. While specific thermal energy consumption increased by 34%, a 25% enhancement was found in GOR, indicative of higher thermal energy efficiency. We have demonstrated the effectiveness of intermittent membrane surface heating for simultaneous performance enhancement and improved energy efficiency for seawater desalination using MD. • Direct surface heating applied to lab-scale air gap membrane distillation system for seawater desalination. • Carbon nanotube nanostructures coated onto hydrophobic membrane to enable Joule heating. • Intermittent application of electrical field improves GOR by 25% and productivity by 78%. • Long-term application of high-grade electrical energy not required.

Flexible temperature sensor based on RGO/CNTs@PBT melting blown nonwoven fabric

The flexible smart wearable device with low cost and high performance is highly desired but rather challenging. In this work, a wearable temperature sensor was developed by integrating the polybutylene terephthalate melt-blown nonwoven fabric (PBT NW) with reduced graphene oxide (rGO) and carbon nanotubes (CNTs) via a simple mechanical ultrasonication method. The microstructures of the rGO/CNTs@PBT NW sensor were investigated by FT-IR, XRD, and SEM techniques, and the thermal and mechanical properties of this sensor were systematically analyzed. The conductive rGO and CNTs could be tightly fixed to the surface of PBT NW. Compared with original PBT NW, the tensile properties of rGO/CNTs@PBT NW sensor were improved. The results of sensing performance tests showed that the prepared temperature sensor had high sensitivity (−0.737% °C−1) and linearity (R2 =0.98) with a resolution of 0.1 °C between 25 °C and 45 °C, a long-term stability and good circularity indicating that our sensor can meet the monitoring requirement of real-time human body temperature. In addition, this sensor could also be used to monitor human respiratory rate. Our study may provide a new idea for the fabrication of the flexible temperature sensor with nonwoven substratefor monitoring the human body and environment temperature.

Enhanced Joule heating performance of flexible transparent conductive double-walled carbon nanotube films on sparked Ag nanoparticles

A hybrid flexible and transparent heater based on double-walled carbon nanotubes (DWCNTs) and silver nanoparticles (AgNPs) is fabricated on a polyethylene terephthalate substrate via facile spray-coating and spark-depositing techniques, respectively. The AgNPs are simply prepared by electrically sparking pure Ag wires in ambient environment with no vacuum system required. The optical, electrical and electrothermal properties of the hybrid AgNP/DWCNT and simple DWCNT film devices are investigated. The results show that the hybrid film heaters exhibit superior electrothermal performances to the DWCNT film heaters, as having higher maximum temperatures at the same applied voltages, as well as faster thermal heating and cooling responses. The simple DWCNT heater with optical transmittance of 72.7% at a wavelength of 550 nm reaches the maximum temperature of 95.0 °C, whereas the hybrid AgNP/DWCNT heater with optical transmittance of 64.0% reaches higher maximum temperature of 118.6 °C, as electrically supplied at 8 V. Furthermore, the mechanical flexibility of the hybrid and DWCNT film heaters is studied with different folding directions, and a little deviation in their electronic conduction is observed, while still performing good heating temperature after a bending test. This simple hybrid film heater demonstrates the efficient electrothermal performances, which can be utilized as a flexible and transparent heating device in various practical applications.

A general tape-coating strategy to construct multifunctional superhydrophobic surfaces with self-adhesion, self-healing, and conductivity on various substrates

Recently, integrating multifunctionality into superhydrophobic surfaces is becoming a tendency to meet the complexity of substrates and practical applications. However, the types of multifunctional superhydrophobic surfaces are limited and effectively constructing superhydrophobic surfaces on random substrates especially with special materials, environments, or shape is still a challenge. Herein, a tape-strategy to obtain superhydrophobic surfaces with special properties just by a simple pasting process is reported. In detail, multifunctional superhydrophobic tape is achieved through the method of spraying the superhydrophobic conductive carbon nanotubes on polyurethane (PU) coating, which could conveniently manufacture the superhydrophobic surfaces on various solid substrates (Al, CF/EP, polyimide, and glass). Depending on the proper crosslinking density of PU, existing of disulfide-bond, and uniform distribution carbon nanotubes, the obtained tape endows the solid surfaces with the multifunctional performance of superhydrophobicity, desirable self-adhesive/self-healing properties as well as conductivity. Moreover, the tap could fabricate arbitrary patterns by a simple pasting and heating process, which is adaptable for various shapes or substrates. Generally, this work provides new sights for fabricating multifunctional superhydrophobic surfaces, and the tap would have promising potential in electromagnetic stealth cloth, various multifunctional sensors, the motion monitoring, or other applications in future.

Effect of pyrolysis carbon black and carbon nanotubes on properties of natural rubber conductive composites

AbstractCarbon based materials with excellent conductivity such as conductive carbon black, graphene, and carbon nanotubes (CNTs) are often used in the preparation of conductive polymer composites. Pyrolysis carbon black, as a recycled material of waste rubber, can be used as a substitute for other carbon black in some fields, which can greatly reduce the production cost and promote reuse of used rubber. In this article, pyrolysis carbon black is mixed with CNT and added to natural rubber by mechanical blending method to get the composite material. The synergistic effect of pyrolysis carbon black and CNT, 3D network structure and formation of conductive network are investigated, and the properties of composites are analyzed. The results show that the 3D “grape cluster” network structure formed by the synergistic action of the pyrolysis carbon black and CNT, which led to the improvement of the curing properties and mechanical properties of the composites, increase the Payne effect, decrease the dispersion of the filler, and significant reduction the volume resistivity of the composites. With the increasing of CNT content, the variation of the properties of the composites changed and stabilized. In general, when 40 phr pyrolysis carbon black and 4 phr CNT are mixed into rubber matrix, the composite has the best comprehensive performance, and the volume resistivity is 9.25E5. Our results provide new thoughts in preparing natural rubber conductive composites. By adding highly CNT and inexpensive pyrolysis carbon black, the problem of easy aggregation of a single filler is overcome, which is more economical than adding two highly conductive fillers, and the process is simpler and time‐saving compared to the modified solution. More studies need to be done in order to reveal the effects of pyrolysis carbon black in practical conductive composites.