Single-walled carbon nanotube incorporated novel three phase carbon/epoxy composite with enhanced properties

In the present work, single-walled carbon nanotubes were dispersed within the matrix of carbon fabric reinforced epoxy composites in order to develop novel three phase carbon/epoxy/single-walled carbon nanotube composites. A combination of ultrasonication and high speed mechanical stirring at 2000 rpm was used to uniformly disperse carbon nanotubes in the epoxy resin. The state of carbon nanotube dispersion in the epoxy resin and within the nanocomposites was characterized with the help of optical microscopy and atomic force microscopy. Pure carbon/epoxy and three phase composites were characterized for mechanical properties (tensile and compressive) as well as for thermal and electrical conductivity. Fracture surfaces of composites after tensile test were also studied in order to investigate the effect of dispersed carbon nanotubes on the failure behavior of composites. Dispersion of only 0.1 wt% nanotubes in the matrix led to improvements of 95% in Young's modulus, 31% in tensile strength, 76% in compressive modulus and 41% in compressive strength of carbon/epoxy composites. In addition to that, electrical and thermal conductivity also improved significantly with addition of carbon nanotubes.     

Activated carbon–carbon nanotube composite porous film for supercapacitor applications

Activated carbon/carbon nanotube composite electrodes have been assembled and tested in organic electrolyte (NEt₄BF₄ 1.5 M in acetonitrile). The performances of such cells have been compared with pure activated carbon-based electrodes. CNTs content of 15 wt.% seems to be a good compromise between power and energy, with a cell series resistance of 0.6 Ω cm² and an active material capacitance as high as 88 F g⁻¹.     

Ultrathin ZnS nanosheet/carbon nanotube hybrid electrode for high-performance flexible all-solid-state supercapacitor

Flexible and easily reconfigurable supercapacitors show great promise for application in wearable electronics.In this study,multiwall C nanotubes (CNTs) decorated with hierarchical ultrathin zinc sulfide (ZnS) nanosheets (ZnS@CNT) are synthesized via a facile method.The resulting ZnS@CNT electrode,which delivers a high specific capacitance of 347.3 F·g-1 and an excellent cycling stability,can function as a high-performance electrode for a flexible all-solid-state supercapacitor using a polymer gel electrolyte.Our device exhibits a remarkable specific capacitance of 159.6 F·g-1,a high energy density of 22.3 W·h·kg-1 and a power density of 5 kW·kg-1.It also has high electrochemical performance even under bending or twisting.The all-solid-state supercapacitors can be easily integrated in series to power different commercial light-emitting diodes without an external bias voltage.     

Hydrothermal synthesis of carbon nanotube/cubic Fe3O4 nanocomposite for enhanced performance supercapacitor electrode material

Carbon nanotube/Fe₃O₄ (CNT/Fe₃O₄) nanocomposite with well-dispersed Fe₃O₄ nano-cubes inlaid on the surfaces of carbon nanotubes, was synthesized through an easy and efficient hydrothermal method. The electrochemical behaviors of the nanocomposite were analyzed by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and chronopotentiometry in 6 M KOH electrolyte. Results demonstrated that CNT as the supporting material could significantly improve the supercapacitor (SC) performance of the CNT/Fe₃O₄ composite. Comparing with pure Fe₃O₄, the resulting composite exhibited improved specific capacitances of 117.2 F/g at 10 mA/cm² (3 times than that of pure Fe₃O₄), excellent cyclic stability and a maximum energy density of 16.2 Wh/kg. The much improved electrochemical performances could be attributed to the good conductivity of CNTs as well as the anchored Fe₃O₄ particles on the CNTs.     

Integrating carbon nanotube into activated carbon matrix for improving the performance of supercapacitor

A method of in situ integrating carbon nanotubes (CNTs) into activated carbon (AC) matrix was developed to improve the performance of AC as a supercapacitor electrode. Glucose solution containing pre-dispersed CNTs was hydrothermally carbonized to be a char-like intermediate product, and finally converted into a “tube-in-AC” structure by the chemical activation using KOH. The “tube-in-AC” composite had oxygen content of 12.98 wt%, specific surface area of 1626 m²/g and 90% of 1–2 nm micropores. It exhibited capacitance of 378 F/g in the aqueous KOH electrolyte and excellent cyclibility under high current, that is, the capacitance only decreased 4.6% after 2000 cycles at scanning rate of 100 mV/s. These performances of “tube-in-AC” electrode are better than those of commercial AC electrodes, post-mixed with CNTs or carbon black.     

Fabrication horizontal aligned MoO2/single-walled carbon nanotube nanowires for electrochemical supercapacitor

The horizontally aligned MoO₂/single-walled carbon nanotube (MoO₂/SWNT) composite has been prepared by electrochemically induced deposition method which utilizes the good electronic conductivity of SWNTs as supporting material to deposit MoO₂. The morphology and crystal structure of the composite were investigated by X-ray photoelectron spectroscopy and scanning electron microscopy, respectively. The capacitive properties of the MoO₂/SWNT composites have been investigated by cyclic voltammetry (CV). A specific capacitance (based on MoO₂) as high as 597 F g^− 1 is obtained at a scan rate of 10 mV s^− 1 in 0.1 M Na₂SO₄ aqueous solution. Additionally, the MoO₂/SWNT composites electrode shows excellent long-term cycle stability (only 2.5% decrease of the specific capacitance is observed after 600 CV cycles).     

Preparation of carbon nanotube/copper/carbon fiber hierarchical composites by electrophoretic deposition for enhanced thermal conductivity and interfacial properties

A facile electrophoretic deposition method was proposed to deposit copper (Cu) and carbon nanotubes (CNTs) on the surface of carbon fiber (CF) to improve the thermal conductivity and interfacial properties of carbon fiber-reinforced polymer (CFRP) composites. Surface morphologies, crystallographic properties, thermal conductivity, interlaminar shear strength (ILSS) and element distribution of the composites were characterized by scanning electron microscopy (SEM), X-ray diffraction, thermal constant analysis, short-beam bending tests and SEM energy-dispersive X-ray diffractometer (SEM–EDX), respectively. The results indicate that the presence of Cu and CNTs generated networks and bridges with each other, which produced continuous heat conduction pathways and significantly enhanced both the specific surface area and roughness of the fiber surface. These pathways obviously promoted an improvement in the thermal and interfacial properties. The thermal conductivity and ILSS of the CNTs–Cu–CF/epoxy composites increased by 292 and 39.5%, respectively, compared with CF/epoxy composites. Therefore, this method is anticipated to be utilized in the future fabrication of multifunctional CFRP composites.     

Gas ionization sensors with carbon nanotube/nickel field emitters

Gas ionization sensors based on the field emission properties of the carbon nanotube/nickel (CNT/Ni) field emitters were first developed in this work. It is found that the breakdown electric field (E(b)) slightly decreases from 2.2 V/microm to 1.9 V/microm as the pressure of H2 gas increases from 0.5 Torr to 100 Torr. On the contrary, E(b) obviously increases from 2.9 V/microm to 6.5 V/microm as O2 gas pressure increases from 0.5 Torr to 100 Torr. This may be explained by the depression of the electron emission that caused by the adsorption of the O2 gas on the CNT emitters. The Raman spectra of the CNT/Ni emitters also show that more defects were generated on the CNTs after O2 gas sensing. The Joule heating effect under high current density as performing H2 sensing was also observed. These effects may contribute the pressure dependence on the breakdown electric field of the CNT/Ni gas ionization sensors.     

Three-dimensional heterostructured MnO2/graphene/carbon nanotube composite on Ni foam for binder-free supercapacitor electrode

In this article, three-dimensional (3D) heterostructured of MnO₂/graphene/carbon nanotube (CNT) composites were synthesized by electrochemical deposition (ELD)-electrophoretic deposition (EPD) and subsequently chemical vapour deposition (CVD) methods. MnO₂/graphene/CNT composites were directly used as binder-free electrodes to investigate the electrochemical performance. To design a novel electrode material with high specific area and excellent electrochemical property, the Ni foam was chosen as the substrate, which could provide a 3D skeleton extremely enhancing the specific surface area and limiting the huge volume change of the active materials. The experimental results indicated that the specific capacitance of MnO₂/graphene/CNT composite was up to 377.1 F g^?1 at the scan speed of 200 mV s^?1 with a measured energy density of 75.4 Wh kg^?1. The 3D hybrid structures also exhibited superior long cycling life with close to 90% specific capacitance retained after 500 cycles.     

Microwave-irradiated novel mesoporous nickel oxide carbon nanocomposite electrodes for supercapacitor application

Journal of Materials Science: Materials in Electronics - The present work accentuates the aspects of electrochemical analysis determined by cyclic voltammeter (CV), especially enhancement in...     

Structure and properties of multi-walled carbon nanotube porous sheets with enhanced elongation

In this article, multi-walled carbon nanotubes (MWNTs)/dodecyl benzene sulfonic acid (DBSA) porous sheet networks (PSNs) of enhanced extensibility were developed and characterized. The MWNT/DBSA networks possess failure strains of 8–12 %, markedly higher than the literature reported values of 0.5–4 %. The networks were prepared through micro-filtration of highly dispersed MWNT in DBSA aqueous solutions. The DBSA molecule has two functions: In the dispersion stage, DBSA functions as a dispersant leading to the establishment of stable individually dispersed MWNT, and in the MWNT porous sheet, the presence of DBSA within the nanotubes’ network creates a lubrication-like effect, enhancing the networks’ extensibility. In fact, it was found that DBSA is assembled in two modes within the nanotubes’ network: a fraction which is strongly adsorbed onto the CNT surface, and another fraction entrapped within the network as a DBSA/water solution. It should be noted that the composition of these systems is stable under ambient room temperature conditions. Comparison of MWNT networks prepared from the MWNT/DBSA dispersions and from the same but coagulated before filtration has shown superiority of the non-coagulated systems in relation to structure and mechanical properties. The prepared MWNT/DBSA PSNs of enhanced extensibility were developed without any modification by polymers, and they are characterized by high electrical conductivity and nano-porosity.     

Pt-modified carbon nanotube networked layers for enhanced gas microsensors

Carbon nanotubes (CNTs) networked films have been grown by chemical vapor deposition (CVD) technology onto miniaturized low-cost alumina substrates, coated by nanosized Co-catalyst for growing CNTs, to perform chemical detection of toxic gasses (NO₂ and NH₃), greenhouse gasses (CO₂ and CH₄) and domestic safety gasses (CO and C₂H₅OH) at an operating sensor temperature of 120 °C. The morphology and structure of the CNTs networks have been characterized by scanning electron microscopy (SEM). A dense network of bundles of multiple tubes consisting of multi-walled carbon nanostructures appears with a maximum length of 1-5 μm and single-tube diameter varying in the range of 5-40 nm. Surface modifications of the CNTs networks with sputtered Platinum (Pt) nanoclusters, at tuned loading of 8, 15 and 30 nm, provide higher sensitivity for significantly enhanced gas detection compared to un-decorated CNTs. This could be caused by a spillover of the targeted gas molecules onto Pt-catalyst surface with a chemical gating into CNTs layers. The measured electrical conductance of the functionalized CNTs upon exposures of a given oxidizing and reducing gas is modulated by a charge transfer model with p-type semiconducting characteristics. The effect of activated carbons as chemical filters to reduce the influence of the domestic interfering alcohols on CO gas detection has been studied. Functionalized CNT gas sensors exhibited better performances compared to unmodified CNTs, making them highly promising candidates for functional applications of gas control and alarms.     

Model-based design of low-temperature carbon nanotube synthesis via catalytic oxidation for supercapacitor application

Novel electrochemical double layer capacitors with carbon nanotube (CNT) electrode, often referred to as supercapacitors, have a potential to bridge a power and energy gap between traditional dielectric capacitors and chemical batteries. However, their future is uncertain because current fabrication technologies involve difficult-to-control post-growth manipulations of CNTs. This paper addresses this problem by introducing model-based design of low-temperature CNT synthesis that is suitable for in-situ fabrication of CNT-based supercapacitor electrode. The insight to the surface kinetics during low-temperature CNT synthesis via catalytic oxidation was obtained via coupled Molecular Dynamics and Quantum Semiempirical Hamiltonian simulations. It was determined that the presence of oxygen on the surface of catalyst increases, by several times, the time necessary for the decomposition of hydrocarbons as well as shifts the reaction zone from the surface of catalyst to the catalyst underlayer. Theoretical trends were confirmed by CNT growth experiments. A contact between conducting CNTs and zinc oxide binding layer was analyzed in detail since its properties strongly affect the performance of CNT electrode. It was demonstrated that the formed CNT-zinc oxide interface was free from unbonded oxygen atoms and/or clusters of zinc atoms and was weakly affected by defects in CNTs.     

Nanostructured SnS/carbon composite for supercapacitor

Net-like nanostructured SnS/carbon composite was prepared by heating mixture of SnS nanoparticles and resorcinol-formaldehyde sol at 650 °C. The morphology and structure of prepared SnS and SnS/carbon composite were studied by transmission electron microscopy (TEM) and X-ray diffraction (XRD). Electrochemical investigation indicated that SnS/carbon composite presented superior electrochemical performances than pristine SnS. SnS/carbon composite had better capacitive response in cyclic voltammetry and could deliver larger specific capacitance of 36.16 F/g in galvanostatical charge-discharge process. Net-like structure of SnS/carbon composite and good conductivity of carbon were considered to be responsible for its preferable electrochemical performances.     

过渡金属/活性炭电极的电容性能研究

选用微孔和中孔活性炭采用浸渍法负载金属离子,考察在水性电解质中用于超级电容器的活性炭复合电极的电化学性能,探讨活性炭在负载前后的放电容量变化情况.采用低温氮吸附和直流恒流循环实验考察活性炭复合电极的孔结构及电容性能.研究表明:金属Cu、Mn具有比较明显的准电容效应,Co、Ni可提高中孔活性炭的放电容量,而金属Mo、Fe和Y的准电容效应不显著;中孔活性炭负载金属的作用明显强于微孔活性炭;中孔活性炭负载金属Cu时,放电容量随负载量的增加而上升.     

Electrohydrodynamic 3D printing of orderly carbon/nickel composite network as supercapacitor electrodes

Electrohydrodynamic(EHD)3D printing of carbon-based materials in the form of orderly networks can have various applications.In this work,microscale carbon/nickel(C-Ni)composite electrodes with con-trolled porosity have been utilized in electrochemical energy storage of supercapacitors.Polyacrylonitrile(PAN)was chosen as the basic material for its excellent carbonization performance and EHD print-ing property.Nickel nitrate(Ni(NO3)2)was incorporated to form Ni nanoparticles which can improve the conductivity and the capacitance performance of the electrode.Well-aligned PAN-Ni(NO3)2 com-posite structures have been fabricated and carbonized as C-Ni electrodes with the typical diameter of 9.2±2.1 μm.The porosity of the as-prepared C-Ni electrode can be controlled during the EHD process.Electrochemical results show the C-Ni network electrode has achieved a 2.3 times higher areal specific capacitance and 1.7 times higher mass specific capacitance than those of a spin-coated electrode.As such,this process offers a facile and scalable strategy for the fabrication of orderly carbon-based conductive structures for various applications such as energy storage devices and printable electronics.