Carbon Nanotube Networks Reinforced by Silver Nanowires with Improved Optical Transparency and Conductivity (original) (raw)
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2014
There is a large promise for thermophones in high power sonar arrays, flexible loudspeakers and noise cancellation devices. The freestanding aerogel-like carbon nanotube sheet as a thermoacoustic (TA) heat source demonstrates so far the best performance. However, the limited accessibility of large size free standing carbon nanotube sheets and other even more exotic materials published recently, hampers the field. I present here new alternative materials for TA heat source with high energy conversion efficiency, additional functionalities, environmentally friendly and cost effective production technologies. I discuss the TA performance of alternative nanoscale materials and compare their spectral and power dependencies of sound pressure in air. The study presented here focuses on engineering of thermal gradients in the vicinity of nanostructures and subsequent heat dissipation processes from the interior of encapsulated thermoacoustic projectors. Applications of TA projectors for hig...
ACS Nano, 2012
Ultrathin (thicknessnm) electrically conducting membranes can be used as electrodes for sensors, actuators, optical devices, fuel cells, scaffolds for assembling nanoparticles, and separation of biological macromolecules.1-6 Various approaches have been suggested for the fabrication of free-standing nanomembranes based on organic polymers and/or inorganic materials: spin-casting of films,7 layer-by-layer assembly of polyelectrolyte multilayers,8 cross-linking of self-assembled monolayers,9 and assembly of triblock copolymers.10,11 Loading materials such as gold nanoparticles12 or carbon nanotubes13 make membranes robust and electrically conductive. However, these methods are often time-consuming and have some limitations in terms of achievable electrical and electrochemical membrane performance as well as scaleup. Alternative approaches are needed for the preparation of mechanically robust, free-standing, conductive nanomembranes that could be easily manufactured. ABSTRACT We report mechanically robust, electrically conductive, free-standing, and transparent hybrid nanomembranes made of densified carbon nanotube sheets that were coated with poly (3,4-ethylenedioxythiophene) using vapor phase polymerization and their performance as supercapacitors. The hybrid nanomembranes with thickness of ∼66 nm and low areal density of ARTICLE
Scientific Reports
Two-dimensional networks made of metal nanowires are excellent paradigms for the experimental observation of electrical percolation caused by continuous jackstraw-like physical pathways. Such systems became very interesting as alternative material in transparent electrodes, which are fundamental components in display devices. This work presents the experimental characterization of low-haze and ultra-transparent electrodes based on silver nanowires. The films are created by dipcoating, a feasible and scalable liquid film coating technique. We have found dominant alignment of the silver nanowires in withdrawal direction. The impact of this structural anisotropy on electrical anisotropy becomes more pronounced for low area coverage. The rod alignment does not influence the technical usability of the films as significant electrical anisotropy occurs only at optical transmission higher than 99 %. For films with lower transmission, electrical anisotropy becomes negligible. In addition to the experimental work, we have carried out computational studies in order to explain our findings further and compare them to our experiments and previous literature. This paper presents the first experimental observation of electrical anisotropy in two-dimensional silver nanowire networks close at the percolation threshold. Alternative materials for transparent conductive films (transparent electrodes) in displays and touch panels have sparked huge interest during the past years 1-3. The use of the conventional material indium tin oxide (ITO) demands high process temperatures and expensive indium mining. Moreover, it cannot be used within a bendable device due to its brittleness. Frequently discussed alternative materials are graphene 4,5 , carbon nanotube (CNT) networks 6,7 and networks of metallic nanowires 8-10 , especially silver nanowires (AgNWs). With regard to optoelectrical performance, AgNWs are superior to the other alternative materials 11. Industrial requirements for transparent electrodes are often referred as sheet resistance R s < 100 Ω/sq and optical transmission T > 90% 12-14. Multiple works have shown that such performance is achieved easily 9,15,16. However, AgNW films appear hazy, which does not match today's quality standards in display industry. Haze increases with area coverage and wire diameter. We have previously shown that only networks made of rather thin AgNWs (diameter d = 31 nm) with area coverage that corresponds to T > 97% exhibit acceptable low haze 11,17. For d = 25 nm we observe the same requirements (Fig. S2, supporting information). In case of such ultra-transparent films, sufficient conductivity (R s < 100 Ω/sq) can only be achieved by using AgNWs with very high aspect ratio and amongst hundreds of papers on transparent AgNW films, only three works achieve this requirement 11,18,19. AgNW films are usually prepared by liquid film coating. Among other liquid film coating techniques such as Meyer rod coating, knife coating and slot die coating, dip-coating is a self-metered coating technique and the liquid film is created by withdrawing the substrate from an ethanolic AgNW dispersion (Fig. 1a). After evaporation of the ethanol, the AgNWs create a continuous two-dimensional network that allows electrical conductivity. It is
Nanotube aerogel sheet flutter for actuation, power generation, and infrasound detection
Scientific reports, 2014
Electromagnetic induction (EMI) is a mechanism of classical physics that can be utilized to convert mechanical energy to electrical energy or electrical to mechanical energy. This mechanism has not been exploited fully because of lack of a material with a sufficiently low force constant. We here show that carbon nanotube (CNT) aerogel sheets can exploit EMI to provide mechanical actuation at very low applied voltages, to harvest mechanical energy from small air pressure fluctuations, and to detect infrasound at inaudible frequencies below 20 Hz. Using conformal deposition of 100 nm thick aluminum coatings on the nanotubes in the sheets, mechanical actuation can be obtained by applying millivolts, as compared with the thousand volts needed to achieve giant-stroke electrostatic actuation of carbon nanotube aerogel sheets. Device simplicity and performance suggest possible applications as an energy harvester of low energy air fluctuations and as a sensor for infrasound frequencies.
Recent Progress on Electrochemical Capacitors Based on Carbon Nanotubes
Carbon Nanotubes - Recent Progress
This review is focused on the theoretical and practical aspects of electrochemical c a p a c i t o r sb a s e do nc a r b o nn a n o t u b e s .I np articular, recent improvements in the capacitance properties of the systems are discussed. In the first part, the charge storage mechanisms of the electrochemical capacitors are briefly described. The next part of the review is devoted to the capacitance properties of pristine single-and multi-walled carbon nanotubes. The major portion of the review is focused on the capacitance properties of modified carbon nanotubes. The electrochemical properties of nanotubes with boron, nitrogen, and other atoms incorporated into the carbon network structure as well as nanotubes modified with different functional groups are discussed. Special attention is paid to the composites of carbon nanotubes and conducting polymers, transition metal oxides, carbon nanostructures, and carbon gels. In all cases, the influences of different parameters such as porosity, structure of the electroactive layer, conductivity of the layer, nature of the heteroatoms, solvent and supporting electrolyte on the capacitance performance of hybrid materials are discussed. Finally, the capacitance properties of different systems containing carbon nanotubes are compared and summarized.
Polymer Reviews, 2019
Interference and chaos among different electromagnetic signals become the prime challenge of the current era which relies on wireless communication. Effective shielding of electromagnetic interference (EMI) waves with advanced materials thus emerges as major research field to prevent cross-talking among electronic devices. This article reviews the current research status of polymer-based EMI shielding materials with a particular focus on a high-performance hybrid with diverse nanomaterials filler. Compatibility and synergist of polymer host with filler materials have been illuminated in this article. Developments of polymer-based EMI hybrid with carboneous, metallic, magnetic and nano/micro materials have been summarized in detail. Emphasis has been given to discuss the role of nano/micro materials size and shape, their electronic, mechanical, chemical properties in tuning the EMI shielding effectiveness (EMI SE) of polymer hybrid. A specific correlation of surface chemical modification/doping of filler materials with EMI SE of their polymer hybrid have been summarized. In the last section, future research direction has been proposed to overcome the existing technological bottlenecks to realize most advanced EMI shielding materials for future use. ARTICLE HISTORY
Energies
The urge to develop high-speed data transfer technologies for futuristic electronic and communication devices has led to more incidents of serious electromagnetic interference and pollution. Over the past decade, there has been burgeoning research interests to design and fabricate high-performance porous EM shields to tackle this undesired phenomenon. Polymer nanocomposite foams and aerogels offer robust, flexible and lightweight architectures with tunable microwave absorption properties and are foreseen as potential candidates to mitigate electromagnetic pollution. This review covers various strategies adopted to fabricate 3D porous nanocomposites using conductive nanoinclusions with suitable polymer matrices, such as elastomers, thermoplastics, bioplastics, conducting polymers, polyurethanes, polyimides and nanocellulose. Special emphasis has been placed on novel 2D materials such as MXenes, that are envisaged to be the future of microwave-absorbing materials for next-generation e...
Soft Bioelectronics Based on Nanomaterials
Chemical Reviews, 2021
Recent advances in nanostructured materials and unconventional device designs have transformed the bioelectronics from a rigid and bulky form into a soft and ultrathin form and brought enormous advantages to the bioelectronics. For example, mechanical deformability of the soft bioelectronics and thus its conformal contact onto soft curved organs such as brain, heart, and skin have allowed researchers to measure high-quality biosignals, deliver real-time feedback treatments, and lower long-term side-effects in vivo. Here, we review various materials, fabrication methods, and device strategies for flexible and stretchable electronics, especially focusing on soft biointegrated electronics using nanomaterials and their composites. First, we summarize top-down material processing and bottomup synthesis methods of various nanomaterials. Next, we discuss state-of-the-art technologies for intrinsically stretchable nanocomposites composed of nanostructured materials incorporated in elastomers or hydrogels. We also briefly discuss unconventional device design strategies for soft bioelectronics. Then individual device components for soft bioelectronics, such as biosensing, data storage, display, therapeutic stimulation, and power supply devices, are introduced. Afterward, representative application examples of the soft bioelectronics are described. A brief summary with a discussion on remaining challenges concludes the review.