Search

We demonstrate a unique strategy to fabricate highly transparent and flexible field electron emitters (FEEs) based on combined carbon nanostructures, i.e., conical nanocarbon structures (CNCSs) and single-walled carbon nanotubes (SWNTs). The combined structure was prepared by spray coating of 1,2-dichloroethane (DCE) dispersed SWNTs onto neon ion (Ne+) irradiation induced CNCSs on nafion substrate. The field emission (FE) property of SWCNTs on both flat nafion and CNCSs surfaces increased with increasing the SWCNTs amount. The best FE result was attained for the highest amount of SWCNTs on the CNCSs substrate. This kind of collective structures is found to be effective emitters on transparent and flexible ion-irradiated nafion substrate. Moreover, the combined carbon nanostructures showed improved transparency and emission performance compared to the individual nanostructures. The FE properties of 0.5 ml SWCNTs solution on CNCSs surfaces were equal to those of 1.5 ml SWCNTs solution on flat nafion surface. The hybrid structure based emitters (CNCSs and SWCNTs) produced by this method are lower-cost cathode materials than hybrid structures of SWCNTs and flat nafion. Thus the combined nanostructures of SWCNTs/CNCSs might have huge prospects for the fabrication of efficient transparent and flexible FEEs and their broad application in next-generation portable display devices. (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]

An efficient cathode material with high transparency (93%) based on conducting polymer poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) and single wall carbon nanotubes (SWCNTs) has been developed for the fabrication of highly transparent and flexible field electron emitters (FEE). This kind of material showed superior field emission (FE) performance with very high current density (10-3A/cm2) at very low electric field. The FE performance of the hybrid materials was dramatically improved compared to either SWCNTs and PEDOT:PSS. Thus the hybrid structures of conducting polymer and SWCNTs might be a good choice for use as a cathode material to enhance the FE performance and for potential application in future portable displays. (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]

In this work, the potential of utilizing a waste latex-based precursor (i.e., natural rubber glove (NRG)) as a carbon source for carbon nanotube (CNT) fabrication via chemical vapor deposition has been demonstrated. Gas chromatography-mass spectroscopy (GC-MS) analysis reveals that the separation of the lightweight hydrocarbon chain from the heavier long chain differs in hydrocarbon contents in the NRG fraction (NRG-L). Both solid NRG (NRG-S) and NRG-L samples contain >63% carbon, <0.6% sulfur and <0.08% nitrogen content, respectively, as per carbon-nitrogen-sulfur (CNS) analysis. Growth of CNTs on the samples was confirmed by Raman spectra, SEM and TEM images, whereby it was shown that NRG-S is better than NRG-L in terms of synthesized CNTs yield percentage with similar quality. The optimum vaporization and reaction temperatures were 350 and 800 °C, respectively, considering the balance of good yield percentage (26.7%) and quality of CNTs (ID/IG = 0.84 ± 0.08, diameter ≈ 122 nm) produced. Thus, utilization of waste NRG as a candidate for carbon feedstock to produce value-added CNTs products could be a significant approach for eco-technology. [ABSTRACT FROM AUTHOR]

Single-walled carbon nanotubes (SWNTs) have been used successfully to fabricate highly transparent and flexible field emission displays (FEDs). Field emission measurements indicated that SWNTs films have great potential to work as building blocks for next generation transparent and flexible FEDs. [ABSTRACT FROM AUTHOR]

Novel glass-ceramic composites with optical bandgap tunability were synthesised. Zinc silicate powder (ZS) was mixed with multi-walled carbon nanotubes (MWCNTs) at various mass fractions (0, 1, 2, and 3 wt %), followed by argon sintering. X-ray diffraction (XRD) analysis revealed the structural change from an amorphous ZS phase to a crystalline willemite phase (Zn 2 SiO 4) by adding MWCNTs, and the largest crystallite size was obtained for ZS with 2.0 wt% MWCNTs. Although the agglomeration of ZS and MWCNTs was observed by field emission scanning electron microscopy (FESEM), there was no chemical interaction between ZS and MWCNTs as confirmed by Fourier transform infrared spectroscopy (FTIR). MWCNTs enhanced the crystallisation, which led to the green emission of Zn 2 SiO 4 blue-shifting from 572 nm to 557 nm. The narrowed optical bandgap of Zn 2 SiO 4 was attributed to the MWCNT-induced exciton localised between the valence band and conduction band of Zn 2 SiO 4. The bandgap tuning effect of MWCNTs potentially paved new ways to mass fabricate zinc silicate-based semiconductors with desirable optical bandgap energy E g , which significantly benefits the sensor and laser-related industry. [ABSTRACT FROM AUTHOR]

Materials with ideal thermal dissipation can prevent electronic devices from overheating and sustaining internal damage. However, obtaining passive heat sink materials with a well-distributed thermal transport network remained challenging. In this study, carbon nanotubes (CNTs) reinforced zinc silicate (Zn 2 SiO 4) composites (CNTs/ZS) were fabricated via colloidal processing and pressureless sintering. The CNTs was first dispersed in 1,2,3,4-tetrahydronapathalene (C 10 H 12) through sonication, before composite-mixing and densification with zinc silicate ceramic. It revealed that the dispersed CNTs simultaneously improved the mechanical and thermal properties of the composites, along with reducing relative density. The Vickers hardness, thermal diffusivity, and thermal conductivity of the optimized composite containing 1.0 wt% CNTs increased by 42%, 179%, and 537%, respectively, compared to the pristine ZS. The SEM observation on the 1.0 wt% CNTs/ZS composite surface determined that the area fraction of the CNTs inclusions was approximately 60%, which was advantageous for phonon propagation and electron transmission path. The combined effect of the phonon and electron transmission path outperformed the polycrystalline-induced Umklapp scattering and porosity-induced phonon-pore scattering, which were identified as obstacles to the heat-transfer process. Thus, this CNTs reinforcement through colloidal processing can be a strategy for designing of efficient silicate-based heatsink candidates in optoelectronic applications. [Display omitted] • Low density CNTs/ZS composite exhibited higher surface hardness than bare ZS composite. • ZS ceramic with 1.0 wt% CNTs reinforcement improved the thermal diffusivity from 0.25 to 0.70 mm2s-1. • Carbon nanotubes (CNTs) was well-dispersed in tetralin before composite-mixing with ZS ceramic. • High resolution XPS spectra reveal the formation of Si–C bonding in the composite. [ABSTRACT FROM AUTHOR]

In this work, we utilize Joule heating to convert Pt-embedded amorphous carbon nanofiber (CNF) to multiwall carbon nanotube (CNT) in a transmission electron microscope (TEM). The transformation process of Pt-embedded amorphous CNF to multiwall CNT and nano-soldering process using Pt encapsulated CNT was investigated in TEM in detail. Molten Pt-encapsulated inside CNF and CNT always flowed towards the anode, proving electromigration to be the dominant force over thermal migration. Controllable electromigration of Pt was utilized to connect the Pt-included CNT to another CNT, thus forming a seamlessly welded CNT structure. Further, two separate CNF were brought together to form Y-contact which was transformed into Y-junction CNT structure by controlled electromigration of Pt. Changes in morphology and electrical property during CNT formation and nano-soldering were probed in real time with high resolution TEM. Our method provides a procedure for the position control synthesis of CNT and its nano-soldering which can be an important step for future development of a CNT based nanoelectrical circuit. [ABSTRACT FROM AUTHOR]

Carbon nanotubes (CNTs) as fillers in ceramic matrix composites have been widely explored to enhance the thermal properties due to its excellent thermal transport mechanism. Zinc silicate (ZS) is a crystalline ceramic with good fluorescence properties but low thermal diffusivity and effusivity. The introduction of CNTs into ZS is a good approach to improve the thermal transport parameters of the ceramic. Carbon nanotubes/zinc silicate (CNTs/ZS) composites with various CNTs mass fractions, ranging from 0 to 3.0 wt%, were fabricated using a combination of powder processing and pressureless sintering. The measured surface hardness, alternating current (AC) conductivity and thermal diffusivity of CNTs-free ZS composites are 285 HV, 2.31 × 10−7 Sm−1, and 0.25 mm2s−1, respectively. Paradoxically, the composite's surface hardness and thermal diffusivity decreased by 90.3 % and 72.1 %, respectively, when 3.0 wt% CNTs were added, while the AC conductivity increased by 105 times. The reduced bulk density and the high degree of phonon scattering in grain boundaries led to a reduction in surface hardness and thermal diffusivity. In addition, the micro-morphology observations revealed that the CNTs aggregation rate increased proportionally with the CNTs mass fraction. The CNTs aggregation formed a soft phase at the composite's surface and a phonon scattering site, which further degraded the material's mechanical and thermal properties. The enhanced AC conductivity of the composites was attributable to the introduction of an efficient free electron flow path formed by the CNTs network. The combination technique of powder processing and pressureless sintering provided a fabrication route to prepare the CNTs/ZS composite with minimal complexity and expense. Through this fabrication method, the results allowed the CNTs-ceramic research path to be navigated in the better direction and served the scientific community in the development of micro-optoelectronic and passive heat sinks. [Display omitted] • Carbon atom, from scratch-off CNTs, diffused into the zinc silicate composite and enlarged the crystal volume. • The AC conductivity of CNTs incorporated zinc silicate increased greatly due to the introduction of electron conductive path. • The surface mechanical and thermal performance drop due to the high degree of CNTs aggregation and pore formation. [ABSTRACT FROM AUTHOR]

Abstract: Synthesis of transfer-free high quality graphene on an arbitrary substrate by metal assisted graphitization with control carbon diffusion process has lot of significance for device applications. Here, we demonstrate the synthesis of monolayer graphene using common triblock co-polymer (EOnPOmEOn) as carbon source by solid phase reaction. In the synthesis process, we used Ni and NiO thin film as catalyst and carbon diffusion barrier, respectively on the top of polymer deposited SiO2/Si substrate. The long carbon chain of triblock co-polymer pluronic F127(EO106PO70EO106) can be graphitized in presence of Ni layer, where carbon diffusion to the top surface is controlled by NiO thin layer. The effects of carbon diffusion, thickness of polymer layer and annealing process are studied to obtain high quality monolayer graphene. Our findings reveal that the NiO/Ni stacked, thickness of polymer layer and reaction process in H2 atmosphere strongly influence the quality of synthesized graphene. [Copyright &y& Elsevier]

Abstract: We present both thermal and electrical conduction properties of vertically aligned carbon nanotubes (VACNTs), synthesized by the water-assisted chemical vapor deposition method using Fe–Ti–O nanoparticles as catalyst. Thermal diffusivity and electrical resistance of VACNTs have been measured by the laser flash method and direct-current four-terminal method, respectively. The VACNTs are found to have thermal diffusivities of the same order as isotropic graphite and the electrical characteristics of semiconductors. The electrical resistance shows a T −1/4 temperature dependence, which implies that the conduction of electrons is dominated by 3D Mott variable range hopping. [Copyright &y& Elsevier]

Abstract: Single carbon nanotube (CNT) has exceptional electrical and mechanical properties. And CNT fiber is an interesting application because it can become the wire which is more excellent than exiting one. Some groups reported the fabrication of CNT fiber spun from vertically aligned CNTs forest (VACNF), but mechanism of spinning has not clear yet. In this paper, we present the optimum parameters for spinnable VACNF via the difference between spinnable and unspinnable VACNF. [Copyright &y& Elsevier]