Encapsulated thermoacoustic projector based on freestanding carbon nanotube film

A suspended nanotube film (or films) producing sound by means of the thermoacoustic (TA) effect is encapsulated between two plates, at least one of which vibrates, to enhance sound generation efficiency and protect the film. To avoid the oxidation of carbon nanotubes at elevated temperatures and reduce the thermal inertia of surrounding medium the enclosure is filled with inert gas (preferably with high heat capacity ratio, γ=Cp/Cv, and low heat capacity, Cp). To generate sound directly as the first harmonic of applied audio signal without use of an energy consuming dc biasing, an audio signal modulated carrier frequency at much higher frequency is used to provide power input. Various other inventive means are described to provide enhanced projected sound intensity, increased projector efficiency, and lengthened projector life, like the use of infrared reflecting coatings and particles on the projector plates, non-parallel sheet alignment in sheet stacks, and cooling means on one projector side.Board of Regents, University of Texas Syste

Carbon nanotube foils for electron stripping in tandem accelerators

Author Posting. © Elsevier B.V., 2007. This is the author's version of the work. It is posted here by permission of Elsevier B.V. for personal use, not for redistribution. The definitive version was published in Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms 261 (2007): 44-48, doi:10.1016/j.nimb.2007.03.023.Carbon nanotube technology has rapidly advanced in recent years, making it possible to create meter-long, ~4 cm wide films of multi-walled tubes of less than 3 μg/cm2 areal density in a bench top open-air procedure [1]. The physical properties of individual carbon nanotubes have been well established, equaling or surpassing electrical and thermal conductivity and mechanical strength of most other materials, graphite in particular. The handling and transport of such nanotube films, dry-mounted self-supporting on metal frames with several cm2 of open area, is problem-free: the aerogel films having a volumetric density of about 1.5 mg/cm3 survived the trip by car and air from Dallas to Oak Ridge without blemish. In this paper we will present the results of first tests of these nanotube films as electron stripper media in a tandem accelerator. The tests were performed in the Model 25 URC tandem [2] of the Holifield Radioactive Ion Beam Facility (HRIBF) at Oak Ridge National Laboratory. We will discuss the performance of nanotube films in comparison with chemical vapor deposition and laser-ablated carbon foils.This work was supported by a grant from the “Cecil H. and Ida M. Green Technology Innovation Awards” program of the Woods Hole Oceanographic Institution and in part by the U.S. National Science Foundation through Cooperative Agreement 82899613 and the Robert A. Welch Foundation grant AT-0029

Carbon nanotube electroactive polymer materials: opportunities and challenges

Carbon nanotubes (CNTs) with macroscopically ordered structures (e.g., aligned or patterned mats, fibers, and sheets) and associated large surface areas have proven promising as new CNT electroactive polymer materials (CNT-EAPs) for the development of advanced chemical and biological sensors. The functionalization of CNTs with many biological species to gain specific surface characteristics and to facilitate electron transfer to and from them for chemical- and bio-sensing applications is an area of intense research activity. Mechanical actuation generated by CNT-EAPs is another exciting electroactive function provided by these versatile materials. Controlled mechanical deformation for actuation has been demonstrated in CNT mats, fibers, sheets, and individual nanotubes. This article summarizes the current status and technological challenges for the development of electrochemical sensors and electromechanical actuators based on carbon nanotube electroactive materials

Multifunctional Characteristics of Carbon Nanotube (CNT) Yarn Composites

By forming composite structures with Carbon Nanotube (CNT) yarns we achieve materials capable of measuring strain and composite structures with increased mechanical strength. The CNT yarns used are of the 2-ply and 4-ply variety with the yarns having diameters of about 15-30 micrometers. The strain sensing characteristics of the yarns are investigated on test beams with the yarns arranged in a bridge configuration. Additionally, the strain sensing properties are also investigated on yarns embedded on the surface of a flexible membrane. Initial mechanical strength tests also show an increase in the modulus of elasticity of the composite materials while incurring a weight penalty of less than one-percent. Also presented are initial temperature characterizations of the yarns

Simple and strong: twisted silver painted nylon artificial muscle actuated by Joule heating

Highly oriented nylon and polyethylene fibres shrink in length when heated and expand in diameter. By twisting and then coiling monofilaments of these materials to form helical springs, the anisotropic thermal expansion has recently been shown to enable tensile actuation of up to 49% upon heating. Joule heating, by passing a current through a conductive coating on the surface of the filament, is a convenient method of controlling actuation. In previously reported work this has been done using highly flexible carbon nanotube sheets or commercially available silver coated fibres. In this work silver paint is used as the Joule heating element at the surface of the muscle. Up to 29% linear actuation is observed with energy and power densities reaching 840 kJ m[superscript -3] (528 J kg[superscript -1]) and 1.1 kW kg[superscript -1] (operating at 0.1 Hz, 4% strain, 1.4 kg load). This simple coating method is readily accessible and can be applied to any polymer filament. Effective use of this technique relies on uniform coating to avoid temperature gradients

Stimulated emission and lasing in π-conjugated polymer films, microstructures and opal photonic crystals

SPIE's International Symposium on Optical Science, Engineering, and Instrumentation, 1999, Denver, CO, United StatesZ. Valy Vardeny, Sergey V. Frolov, Douglas Chinn, Maxim N. Shkunov, Werner Gellermann, Katsumi Yoshino, Akihiko Fujii, Richard V. Gregory, Ray H. Baughman, and Anvar A. Zakhidov "Stimulated emission and lasing in π-conjugated polymer films, microstructures, and opal photonic crystals", Proc. SPIE 3797, Organic Light-Emitting Materials and Devices III, (17 December 1999). DOI: https://doi.org/10.1117/12.37269

Hybrid nanomembranes for high power and high energy density supercapacitors and their yarn application

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 scale-up. Alternative approaches are needed for the preparation of mechanically robust, free-standing, conductive nanomembranes that could be easily manufactured