Carbon Nanotube Composite Films Research Articles

Enhanced Thermoelectric Properties of Stable n-Type Ferrocene Derivatives-Doped Polyethylenimine/Single-Walled Carbon Nanotube Composite Films.

Preparing stable n-type flexible single-walled carbon nanotube (SWCNT)-based thermoelectric films with high thermoelectric (TE) performance is desirable for self-powering wearable electronics but remains a challenge. Here, the interface regulation and thermoelectric enhancement mechanism of ferrocene derivatives on polyethylenimine/single-walled carbon nanotube (PEI/SWCNT) composite films have been explored by doping ferrocene derivatives (f-Fc-OH) into PEI/SWCNT films. The results show that the introduction of f-Fc-OH leads to the formation of "thorn" structures on the surfaces of SWCNT bundles via hydrophilic and hydrophobic interactions, the generated energy-filtering effect improves the thermoelectric properties of the PEI/SWCNT film, and the f-Fc-OH-doped PEI/SWCNT (f-Fc-OH/PEI/SWCNT) achieves the highest room-temperature power factor of 182.22 ± 8.60 μW m-1 K-2 with a Seebeck coefficient of -64.28 ± 0.96 μV K-1 and the corresponding ZT value of 4.69 × 10-3. The Seebeck coefficient retention ratio of the f-Fc-OH/PEI/SWCNT nearly remained 68% after being exposed to air for 3672 h, while the PEI/SWCNT film changed from n-type to p-type after being exposed to air for about 432 h. In addition, the temperature-dependent thermoelectric properties show that the f-Fc-OH/PEI/SWCNT achieves a high power factor of 334.57 μW m-1 K-2 at 353 K. Finally, a flexible TE module consisting of seven pairs of p-n junctions is assembled using the optimum composite film, which produces an open-circuit voltage of 42 mV and a maximum output power of 4.32 μW at a temperature gradient of 60 K. Therefore, this work provides guidance for preparing stable n-type SWCNT-based composite films with enhanced thermoelectric properties, which have potential applications in flexible generators and wearable electronic devices.

Sandwich-Structured Carbon Nanotube Composite Films for Multifunctional Sensing and Electrothermal Application.

Electro-conductive films with excellent flexibility and thermal behavior have great potential in the fields of wearable electronics, artificial muscle, and soft robotics. Herein, we report a super-elastic and electro-conductive composite film with a sandwich structure. The composite film was constructed by spraying Polyvinyl alcohol (PVA) polymers onto a buckled conductive carbon nanotube-polydimethylsiloxane (CNTs-PDMS) composite film. In this system, the PVA and PDMS provide water sensing and stretchability, while the coiled CNT film offers sufficient conductivity. Notably, the composite film possesses high stretchability (205%), exceptional compression sensing ability, humility sensing ability, and remarkable electrical stability under various deformations. The produced CNT composite film exhibited deformation (bending/twisting) and high electro-heating performance (108 °C) at a low driving voltage of 2 V. The developed CNT composite film, together with its exceptional sensing and electrothermal performance, provides the material with promising prospects for practical applications in wearable electronics.

Structural optimization of ion storage layer for highly stable electrochromic devices based on polythiophene derivative films

Due to their rich color, fast switching speed and high coloration efficiency, polymer-based electrochromic devices (ECDs) have broad application prospects in various fields such as smart windows, anti-glare rearview mirrors, displays and adaptive camouflage. However, the preparation of highly stable polymer-based ECDs is still a great challenge. Herein, we present a simple and efficient strategy to construct the poly (3,4-ethylenedioxythiophene) (PEDOT)-multi-walled carbon nanotubes (MWCNTs) composite film or PEDOT/MWCNTs bilayer film, which serves as ion storage layer. The ECDs are assembled with poly (3-hexylthiophene) (P3HT) as EC layer due to its good EC behavior. The P3HT film was prepared by potentiostatic deposition, and the PEDOT, PEDOT-MWCNTs and PEDOT/MWCNTs films were obtained by spray-coating technology. We investigated the structure, morphology and electrochemical performance of P3HT, PEDOT, PEDOT-MWCNTs and PEDOT/MWCNTs films, and EC properties of devices. The results indicate that the rough and porous P3HT film consists of many nanoparticles. Compared with PEDOT-MWCNTs composite film, the PEDOT/MWCNTs film is more loose and porous, where PEDOT nanoparticles and some PEDOT nanosheets are coated on a three-dimensional skeleton film of MWCNTs. These films possess good electrochemical performance. The ECD based on P3HT and PEDOT/MWCNTs films achieves an optical contrast of 38 % and coloration efficiency of 375 cm2/C, exhibiting good cyclic stability (retaining 92 % of initial optical contrast after 2000 cycles). Its coloration time and bleaching time are 0.60 and 1.83 s, respectively. This study suggests that structural optimization of ion storage layer might be a facile strategy for fabricating highly stable polymer-based ECDs.

Enhanced Thermoelectric Properties of Exfoliated BN Nanosheets/Single-Walled Carbon Nanotube Composite Films for Applications in Flexible Electronics

Enhanced Thermoelectric Properties of Exfoliated BN Nanosheets/Single-Walled Carbon Nanotube Composite Films for Applications in Flexible Electronics

Construction of flexible carbon nanotube film/PA66 composite with high dynamic mechanical properties

Carbon nanotube (CNT) has potential application in many fields owing to its excellent properties, but the weak Van der Waals forces between randomly arranged tube bundles limit their mechanical properties. In this paper, CNT films were prepared by floating catalyst chemical vapor deposition (FCCVD), whereas PA66 resin was introduced via impregnation and hot press curing in order to further improve the mechanical tensile properties and environmental resistance of the films. The results demonstrate that the tensile properties of PA66-impregnated CNT film are significantly improved. When the mass fraction of PA66 is 1 %, the composite film exhibits the best tensile properties under quasi-static conditions, with a tensile strength of 528 MPa and an energy absorption (EA) value of 109.5 MJ/m3. Plus, at the high strain rate of 2900 s−1, the strength and EA of CNT film/PA66 composite can reach 534 MPa and 107 MJ/m3, respectively. The results in present research can provide a feasible and effective strategy for the design of CNT composite film with high mechanical tolerance which will broaden the application field to a large extent.

Flexible conductive polymer composite film with sandwich-like structure for ultra-efficient and high-stability electromagnetic interference shielding

Flexible electromagnetic interference (EMI) shielding films with the merits of light-weight, flexibility, and high EMI shielding performance are the essential materials for the consumer electronics and communication products. Herein, we construct a hybrid conductive network based on the electrospinning thermoplastic polyurethane (TPU) film loaded with different dimensional conductive fillers, including 0D FeCl3, 1D carbon nanotube (CNT) and 2D graphene nanosheet (GN) to achieve a flexible, light-weight, and ultra-efficient EMI shielding composite film. In specific, the electrospinning porous TPU film is firstly anchored by CNTs assisted by ultrasound to generate the porous TPU/CNT film. Thereafter, the as-prepared porous TPU/CNT film is loaded a GN/CNT/FeCl3 layer by vacuum-assisted filtration to generate a double-layer GN/CNT/FeCl3@TPU/CNT film. Finally, another porous TPU/CNT film is sealed onto the GN/CNT/FeCl3@TPU/CNT film by hot-pressing, which fabricates a sandwiched TPU/CNT@GN/CNT/FeCl3@TPU/CNT composite film. It is interesting to note that the composite film possesses the ultrahigh EMI shielding value (56.0 dB at 10.0 GHz) in the X-band (8.2–12.4 GHz) with high flexibility, excellent mechanical properties, long-term durability (acid-base environment resistance and stability after 1000 bends), as well as high thermal conductivity (6.53 W/(m.K)). This work proposes a simple but efficiency strategy to design the flexible EMI shielding film with ultra-high performance and outstanding durability.

Oxygenated moiety enhanced thermal stabilization, mechanical, and thermomechanical performance of polyacrylonitrile/single wall carbon nanotubes films

AbstractThermo‐oxidative stabilization of polyacrylonitrile (PAN)‐copolymer and PAN/single‐walled carbon nanotube (SWCNT) composite films were studied in the presence of oxygenated entities which may act as an internal oxygen supplier. The oxygenated moiety exhibited dual behavior, enhancing the stabilization efficiency of PAN while also improving the dispersion of SWCNT. The addition of oxygenated moiety treated SWCNT to PAN resulted in a significant reduction in activation energy from 118 kJ/mol to 99 kJ/mol, owing to a more stable oxidation reaction. Thermogravimetric analysis showed weight loss due to stabilization, and polymer chain degradation was lower in treated SWCNT composite films, resulting in an approximate 6% increase in residual weight. Mechanical testing showed a significant increase in tensile strength to 54.15 MPa and tensile modulus to 2.53 GPa with elongation at break of 13.2%, which is attributed to the enhanced interfacial shear strength resulting from the improved dispersion of oxygenated moiety‐treated nanotubes. Furthermore, thermomechanical analysis studies showed improvement in dimension stability with oxygenated moiety treated SWCNT composite films, attributed to better dispersion and increased interfacial strength between the polymer and filler.Highlights Oxygenated entities stabilize PAN and improve SWCNT dispersion. Activation energy was reduced from 118 to 99 kJ/mol with Tween‐80. Residual weight increased by 6% with treated SWCNT in TGA. Improved tensile strength (54.14 MPa), modulus (2.53 GPa) with modified SWCNT. Dimension stability is enhanced by interfacial strength with modified SWCNT.

Characterization and radiation shielding efficiency of MWCNT/shape memory ternary blend composite films

In this study, the structural, X-ray and gamma-ray, and neutron shielding properties of shape memory ternary blend/multi-walled carbon nanotube (MWCNT) composite films were investigated. The composition of the composite films was defined as (100-x) poly (ε-caprolactone) (PCL):polyethylene glycol (PEG):polyvinyl chloride (PVC) + xMWCNT, where x = 0, 1, 3, 5% (mole percentage). The ternary blend/MWCNT composite films were characterized using Attenuated Total Reflectance Infrared Spectroscopy (ATR-IR), Thermogravimetric Analysis (TGA), Differential Scanning Calorimetry (DSC), X-ray Diffraction (XRD), and Scanning Electron Microscopy (SEM). Thermal results showed that the degradation temperatures of composite materials with two degradation curves increased with increasing MWCNT percentage. The appearance of the MWCNT signal along with the characteristic polymer signals in the XRD pattern may be evidence that MWCNT is homogeneously distributed in the polymer blend. The mass attenuation coefficients (MAC), half-value layer (HVL), mean free path (MFP), and effective atomic numbers (Z_eff) of the composite films were experimentally measured over an energy range of 8.04–383.85 keV. Additionally, the equivalent dose rates for fast neutrons were measured, and the exposure buildup factor (EBF) and fast neutron removal cross-section (Σ_R) were theoretically calculated. The proton and alpha shielding parameters of the ternary blend/MWCNT composite films were determined, revealing that the inclusion of higher amounts of MWCNTs in the composite structure significantly improved capability of the films in shielding against radiation and neutrons.

In situ Preparation of SiOx/Carbon Nanotube Composite Films with Excellent Mechanical and Electrochemical Properties as an Anode Material for Lithium‐Ion Batteries

Silicon monoxide (SiOx) has become one of the most promising anode materials for next‐generation lithium‐ion batteries (LIBs) due to its high theoretical capacity. However, the inherent low electrical conductivity and large volume change during lithiation/delithiation processes hinder its practical applications. Here, a novel and facile strategy is designed to prepare SiOx/carbon nanotube (CNT) composite films in one step by using a method involving floating catalytic chemical vapor deposition (FCCVD). That is, SiOx particles and CNTs form at high temperature and winded directly on a drum to give rise to a film in an open air environment. The composite film is made up of a 3D CNT network with SiOx particles uniformly embedded. The as‐prepared composite film not only has a tensile strength of 78 MPa and elongation at break of 52%, but also exhibits a high specific capacity of 966.4 mA h g−1 after 120 cycles at the current density of 0.1 A g−1 and a good rate capacity of 448.7 mA h g−1 at the current density of 2 A g−1 when used as an anode material for LIBs. The results from the in‐situ preparation and resultant composite suggest a new route for developing high‐performance anode materials for LIBs.

Flexible piezoelectric sensor based on polyvinylidene fluoride/polyacrylonitrile/carboxy-terminated multi-walled carbon nanotube composite films for human motion monitoring

Flexible piezoelectric devices have attracted much attention in the fields of intelligent devices and biomedicine because of their high sensitivity, stability, and flexibility. In this paper, a multifunctional flexible pressure sensor was prepared by adding polyacrylonitrile (PAN) and carboxylic-terminated multi-walled carbon nanotubes (c-MWCNTs) with polyvinylidene difluoride (PVDF) as the substrate. The β-phase content of PVDF/PAN blended fibers compounded with c-MWCNT was up to 95%. At the same time, when PAN was added, the mechanical properties of the composite fibers were constantly improved. The results show that the polymer blending method can improve the comprehensive properties of PVDF composite. The flexible sensor prepared from the PVDF/PAN/c-MWCNT composite film has an output voltage of 2.1 V and a current of 7 μA. The addition of c-MWCNT can largely improve the sensitivity of the sensor (4.19 V N−1). The sensor is attached to the finger and shows good output performance under different degrees of bending of the finger. The maximum output voltage of the sensor is 0.4 V, 0.56 V and 1.15 V when the finger bending angle is 30°, 60°, and 90°, respectively. Moreover, the developed piezoelectric sensor can monitor large-scale movements of various parts of the human body. Therefore, this composite material shows potential in areas such as motion monitoring and energy storage devices.

Bacterial cellulose/multi-walled carbon nanotube composite films for moist-electric energy harvesting

Generation of renewable and clean electricity energy from ubiquitous moisture for the power supply of portable electronic devices has become one of the most promising energy collection methods. However, the modest electrical output and transient power supply characteristics of existing moist-electric generator (MEG) severely limit its commercial application, leading to an urgent demand of developing a MEG with high electrical output and continuous power generation capacity. In this work, it is demonstrated that a flexible bacterial cellulose (BC)/Multi-walled carbon nanotube (MWCNT) double-layer (BM-dl) film prepared by vacuum filtration can maintain the moisture concentration difference in the film MEG. Unlike previous studies on cellulose based MEG, BM-dl film has a heterogeneous structure, resulting in a maximum output power density of 0.163 μW/cm2, an extreme voltage of 0.84 V, and current of 2.21 μA at RH = 90 %. BM-dl MEG can generate a voltage of 0.55 V continuously for 45 h in a natural environment (RH = 63–77 %, T = 26–27 °C), which is in a leading level among existing reported cellulose-based MEGs. In summary, this study provides new ideas for innovative design of MEG, which is highly competitive in terms of energy supply for the Internet of Things and wearable devices.

High thermal conductivity regenerated cellulose/carboxylated carbon nanotubes composite films with semi-insulating properties prepared via ionic coordination and hydrothermal synthesis of zinc oxide

With the rapid development of miniaturization and integration of electronic products, its heat dissipation has become the focus of research. In order to improve the heat dissipation efficiency of electronic components, flexible thermal conduction materials are constantly studied. Cellulose has good flexibility and load capacity, which is often used in the preparation of thermal conduction materials. In this paper, carboxylated multi-walled carbon nanotubes (C-MWCNTs) were modified by metal ion coordination and hydrothermal synthesis of zinc oxide (ZnO) to prepare semi-insulating thermal conduction fillers, which were dispersed into regenerated cellulose (RC) to cast to be composite films. The results show that the two modification methods can reduce the probability of phonon scattering and block the electron transport path, so as to improve the thermal conductivity (TC) and electrical insulation properties of the composite films. Especially for the RC/C-MWCNTs@ZnO composite films, when the total filler content is 20 wt%, the in-plane TC can reach 11.89 ± 0.19 (W/(m·K)), and the surface electrical resistivity (ρs) is (5.24 ± 0.17) × 106 Ω. Compared with the RC/C-MWCNTs composite films, the in-plane TC and ρs of the RC/C-MWCNTs@ZnO composites films are increased by about 94.92 % and 555 %, respectively. Therefore, the developed RC-based composite film has broad application prospects in thermal management.

Dual Capacitive Behavior of Hollow Porous Gold Nanoparticle/Multi-Walled Carbon Nanotube Composite Films as Anode and Cathode Electrode Materials for Supercapacitors

Dual Capacitive Behavior of Hollow Porous Gold Nanoparticle/Multi-Walled Carbon Nanotube Composite Films as Anode and Cathode Electrode Materials for Supercapacitors

A V2O5/MWCNTs composite thin film gas sensor for the fast detection of ammonia

In the present study, we develop a new ammonia gas sensor by using sol-gel method and post annealing process. The structure, morphology, and composition of the gas sensor have been characterized by SEM, XRD, XPS, and Raman. The results prove that the V2O5/MWCNTs (multi-walled carbon nanotubes) composite thin film was successfully deposited on alumina substrate. By comparing the responses of the gas sensor to ammonia gas at different temperatures, we find out that the sensor shows good response and excellent response time to ammonia gas at 200 ℃. At this temperature, the sensor exhibits a response of 20% for 100 ppm of ammonia gas with a response time of only 8 s. We find its response time is better than that of ammonia sensors based on single V2O5 or MWCNTs materials. The outstanding sensitivity and unique response curve can be mainly attributed to the semiconductor properties of the two materials and the formation of P-N heterojunction at their interface.

The fabrication of MnO2 nanoparticles/multi-walled carbon nanotubes composite modified electrode for electrochemical sensing of ascorbic acid

Herein, an electrochemical ascorbic acid (AA) sensor was fabricated based on the MnO2/multi-walled carbon nanotubes (MWNTs-COOH) composite film modified glassy carbon electrode (GCE). The scanning electron microscopy (SEM) was used to characterize the morphologies of MnO2/MWNTs-COOH composite film. The MnO2/MWNTs-COOH/GCE was employed to detect AA by cyclic voltammetry (CV) and differential pulse voltammetry (DPV). The experiment test results showed that the proposed electrode exhibited an obvious electrocatalytic ability to the oxidation of AA. The DPV was employed to analyze AA in 0.1 M PBS (pH=7.0), the oxidation peak current of AA displayed a good linear relationship with the logarithm of the concentration of AA in the range of 1.0 × 10−6 - 1.0 × 10−4 mol/L, the detection limit was 2.7 × 10−7 mol/L (S/N = 3). Additionally, the results indicated that the constructed method possessed high selectivity, long-term stability and excellent reproducibility, and successfully used to detect AA in water samples with satisfactory results.

Low-density polyethylene-multi-walled carbon nanotube nanocomposite membranes with enhanced conductivity for highly sensitive vapor sensing

A facile technique was reported for fabricating high conductivity and improved strength of linear low-density polyethylene/multi-walled carbon nanotubes (LLDPE/MWNTs) composite films by the ultrasonication anchoring technique and compression molding treatment. Thermal property, mechanical property, electrical conductivity, microstructures, optical property, and organic vapor sensing behaviors of the MWNTs/LLDPE composite films were studied. The MWNTs are uniformly anchored onto the surface of LLDPE matrix, and the conductive networks are easily formed by the ultrasonication anchoring technique. After compression molding treatment, the incorporation of MWNTs causes an easier formation of LLDPE extended-chain, which is wrapped around of MWNTs shish. The MWNTs/LLDPE composite films exhibit an excellent conductivity of 2.79 × 105 Ω∙cm with 0.15 wt % MWNTs. Meanwhile, the tensile strength of the composite films reaches 18.9 MPa. Interestingly, the transparency is not significantly reduced. The sensitivity and reproducibility of vapor sensing behaviors have been demonstrated during immersion-drying runs toward two representative solvents, i.e., acetone and xylene. This work opens up a new direction for the conductivity optimization of MWNTs/LLDPE composite films with a broad prospect in the field of vapor sensor.

High-performance carbon-based nanomaterial composites for ultrafast lasers based on stretch processing

Carbon-based nanomaterials, and specifically carbon nanotube and graphene, have been widely used as saturable absorber (SA) in ultrafast fiber laser. However, the performance of these SAs is limited due to the low damage threshold or self-starting capability. In our work, we have proposed a novel and straightforward method for enhancing the optical performance of polyvinyl alcohol-based carbon nanotube and graphene composite film. By mechanical stretching the composite films, the damage threshold of carbon nanotube-based SA and the self-starting capability of graphene-based SA can be obviously improved. The distinct nonlinear optical properties of carbon nanotube and graphene are analyzed, and the mode-locking performance is compared. Our finding provides a new insight and experimental basis for the development of high-performance carbon-based nanomaterial mode locker for ultrafast fiber lasers.

Spray deposited carbon nanotube embedded ZnO as an electrons transport layer in inverted organic solar cells

In this report, the synthesis and characterization of ZnO and carbon nanotube (CNT) embedded ZnO composite thin films are presented. The obtained ZnO and CNT composite ZnO thin films are used as an electron transport layer (ETL) for bulk heterojunction (BHJ) inverted organic solar cell (IOSC) with the architecture of ITO/ZnO:CNT/PTB7:PC71BM/MoO3/Ag. Both ZnO and CNT composite ZnO thin films exhibited a highly preferred c-axis oriented (002) diffraction peak and the peak position is shifted toward a lower angle after embedding CNT into the ZnO matrix. The transmittance slightly decreases after CNT is embedded into the ZnO matrix. Completely wrapped CNT with the ZnO was confirmed by Scanning electron microscope (SEM) measurement. The resistivity of ZnO decreased from 2.02 × 10−2 to 5.61 × 10−3 Ω-cm and mobility increased from 4.30 to 15.24 cm2/V-s after adding CNT into the ZnO matrix. CNT composite ZnO thin film surface is found to be hydrophobic, providing good interfacial contact with the BHJ layer resulting to improve fill factor (FF) of IOSC. The performance of IOSC with CNT composite ZnO ETL layer was significantly improved with a power conversion efficiency of 6.76%, open circuit voltage (VOC) of 700 mV, short circuit current density (JSC) of 20.05 mA/cm2 and FF of 48.17%, respectively.

High-performance g-C3N4 coated single-walled carbon nanotube composite films for flexible thermoelectric generators

Thermoelectric (TE) devices consisting of p-type and n-type single-walled carbon nanotubes (SWCNTs) based films, which can gather waste heat and turn it into electrical power, show potential application in supplying power for wearable electronic devices. In this study, graphitic carbon nitride (g-C3N4) has been prepared by high temperature pyrolysis of melamine and confirmed by scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), and X-ray diffraction pattern (XRD), respectively. Then the prepared g-C3N4 is composited with SWCNTs via mechanical mixing and vacuum-filtering method to obtain free-standing flexible g-C3N4/SWCNT thermoelectric composite films. The results demonstrate that g-C3N4 is efficiently covered on the surface of SWCNTs via interfacial π-π interaction, and g-C3N4 layer with several nanometers coated on SWCNTs simultaneously improves the electrical conductivity (σ) and the Seebeck coefficient (S) of g-C3N4/SWCNT. At a mass ratio of 2.5 % for g-C3N4/SWCNT, an optimal power factor value of 163.0 ± 1.0 μW m−1 K−2 is obtained for g-C3N4/SWCNT with the σ of 702.6 ± 1.6 S cm−1 and the S of 48.2 ± 0.2 μV K−1 at room temperature. Finally, a self-powering TE device composed of three pairs of p-n junctions is manufactured, and the actual output power is about 1.13 μW at the temperature difference of 50 K. As a result, this study offers a straightforward way to enhance the thermoelectric performance of single-walled carbon nanotubes, which can be utilized in flexible power generators.

Correction: Facile preparation of OHB-T–carbon nanotube composite films for modification of the electrical and optical properties

Correction: Facile preparation of OHB-T–carbon nanotube composite films for modification of the electrical and optical properties