Macroscopic self standing SWCNT fibers as efficient electron emitters with very high emission current for robust cold cathodes

A novel of self-standing nanotube-based cold cathode is described. The electron emitter is a single macroscopic fibre spun from neat single wall carbon nanotubes and consists of an ensemble of nanotube bundles held together by van der Waals forces. Field emission measurements carried out using two different types of apparatus demonstrated the long working life of the realised cathode. The system is able to emit at very high current densities, up to 13 A/cm2, and shows very low values of both turn on and threshold field, 0.12 V/lm and 0.21 V/lm, respectively. Such easy to handle self-standing electron sources assure good performances and represent an enabling technology for a scalable production of cold cathodes. 2012 Elsevier Ltd. All rights reserved. 1. Introduction Due to a unique combination of properties, including high electrical and thermal conductivity, and high mechanical/ chemical/thermal stability, carbon nanotubes (CNTs) have been recognised as ideal candidate materials for application in microelectronics [1]. Moreover, the high aspect ratio characterising this intriguing material makes possible to significantly strengthen electric fields into the vicinity of nanotubes tips

Transport mechanism in granular Ni deposited on carbon nanotubes fibers

We investigate the transport properties of granular nickel electrodeposited on carbon nanotube fibers by measuring the electrical resistance and the current voltage characteristics as a function of the temperature. The bare fiber is governed by a three-dimensional variable range hopping transport mechanism, however, a semiconducting to metallic transition is observed after the Ni deposition as a consequence of the evolution from weak to strong coupling between the deposited nickel grains. The experimental results indicate that the charge transport in the Ni-coated fiber develops from hopping governed by the Coulomb blockade in the case of small grains dimensions to a metallic electron phonon interaction mechanism for large grains dimensions. Tunneling enhanced by thermal fluctuation is responsible for the transport in the intermediate conductivity range. The role of the fiber and the effects due to the magnetic nature of the nickel grains are also discussed

Strong, Light, Multifunctional Fibers of Carbon Nanotubes with Ultrahigh Conductivity

Broader applications of carbon nanotubes to real-world problems have largely gone unfulfilled because of difficult material synthesis and laborious processing. We report high-performance multifunctional carbon nanotube (CNT) fibers that combine the specific strength, stiffness, and thermal conductivity of carbon fibers with the specific electrical conductivity of metals. These fibers consist of bulk-grown CNTs and are produced by high-throughput wet spinning, the same process used to produce high-performance industrial fibers. These scalable CNT fibers are positioned for high-value applications, such as aerospace electronics and field emission, and can evolve into engineered materials with broad long-term impact, from consumer electronics to long-range power transmission

Zinc Phthalocyanine−Graphene Hybrid Material for Energy Conversion: Synthesis, Characterization, Photophysics and Photoelectrochemical Cell Preparation

Graphene exfoliation upon tip sonication in o-­‐DCB was accomplished. Then, covalent grafting of (2-­‐ aminoethoxy)(tri-­‐tert-­‐butyl) zinc phthalocyanine (ZnPc), to exfoliated graphene sheets was achieved. The newly formed ZnPc-­‐graphene hybrid material was found soluble in common organic solvents without any precipitation for several weeks. Application of diverse spectroscopic techniques verified the successful formation of ZnPc-­‐graphene hybrid materi-­‐ al, while thermogravimetric analysis revealed the amount of ZnPc loading onto graphene. Microscopy analysis based on AFM and TEM was applied to probe the morphological characteristics and to investigate the exfoliation of graphene sheets. Efficient fluorescence quenching of ZnPc in the ZnPc-­‐graphene hybrid material suggested that photoinduced events occur from the photoexcited ZnPc to exfoliated graphene. The dynamics of the photoinduced electron transfer was evaluated by femtosecond transient absorption spectroscopy, thus, revealing the formation of transient species such as ZnPc+ yielding the charge-­‐separated state ZnPc•+–graphene•–. Finally, the ZnPc-­‐graphene hybrid material was integrated into a photoactive electrode of an optical transparent electrode (OTE) cast with nanostructured SnO2 films (OTE/SnO2), which exhibited sta le and reproducible photocurrent responses and the incident photon-­‐to-­‐current conversion efficien-­‐ cy was determine

Aligned carbon nanotube–epoxy composites: the effect of nanotube organization on strength, stiffness, and toughness

10.1007/s10853-016-0228-6Journal of Materials Science512210005-1002

Stage Transitions in Graphite Intercalation Compounds: Role of the Graphite Structure

© 2019 American Chemical Society. Despite intensive and long-lasting research on graphite intercalation compounds (GIC), the mechanism of the stage transitions remains unclear. Using optical and Raman microscopy, we perform direct real-time monitoring of stage transitions in H2SO4-GICs made from highly oriented pyrolitic graphite (HOPG). We observe that stage transitions in HOPG-based GICs occur very differently from those in GICs made from the natural flake graphite. During the stage-2 to stage-1 transition, formation of the stage-2 phase begins nearly simultaneously over the entire graphite surface that is exposed to the media. We attribute this concerted transition to the movement of the small intercalant portions toward the points of attraction, thus growing continuous islands. During the reverse process, the stage-1 to stage-2 transition begins strictly from the edges of the graphite sample and propagates toward the center of the graphite sample. The deintercalation front is discontinuous; the selected micrometer-sized domains of the graphite surface deintercalate preferentially to release the strain that had been induced by the intercalation. The intercalant dynamics in the two-dimensional (2D) graphite galleries, occurring at the speed > 240 μm/s, has fast kinetics. The initial intercalation process is different from the rest of the reintercalation cycles. The difference in the mechanisms of the stage transitions in natural flake graphite-based GICs and in the HOPG-based GICs exemplifies the role of the graphite structure for the intercalant dynamics in 2D graphite galleries

Stage Transitions in Graphite Intercalation Compounds: Role of the Graphite Structure

© 2019 American Chemical Society. Despite intensive and long-lasting research on graphite intercalation compounds (GIC), the mechanism of the stage transitions remains unclear. Using optical and Raman microscopy, we perform direct real-time monitoring of stage transitions in H2SO4-GICs made from highly oriented pyrolitic graphite (HOPG). We observe that stage transitions in HOPG-based GICs occur very differently from those in GICs made from the natural flake graphite. During the stage-2 to stage-1 transition, formation of the stage-2 phase begins nearly simultaneously over the entire graphite surface that is exposed to the media. We attribute this concerted transition to the movement of the small intercalant portions toward the points of attraction, thus growing continuous islands. During the reverse process, the stage-1 to stage-2 transition begins strictly from the edges of the graphite sample and propagates toward the center of the graphite sample. The deintercalation front is discontinuous; the selected micrometer-sized domains of the graphite surface deintercalate preferentially to release the strain that had been induced by the intercalation. The intercalant dynamics in the two-dimensional (2D) graphite galleries, occurring at the speed > 240 μm/s, has fast kinetics. The initial intercalation process is different from the rest of the reintercalation cycles. The difference in the mechanisms of the stage transitions in natural flake graphite-based GICs and in the HOPG-based GICs exemplifies the role of the graphite structure for the intercalant dynamics in 2D graphite galleries