Showing papers by "Anvar A. Zakhidov published in 2005"

Strong, Transparent, Multifunctional, Carbon Nanotube Sheets

Abstract: Individual carbon nanotubes are like minute bits of string, and many trillions of these invisible strings must be assembled to make useful macroscopic articles. We demonstrated such assembly at rates above 7 meters per minute by cooperatively rotating carbon nanotubes in vertically oriented nanotube arrays (forests) and made 5-centimeter-wide, meter-long transparent sheets. These self-supporting nanotube sheets are initially formed as a highly anisotropic electronically conducting aerogel that can be densified into strong sheets that are as thin as 50 nanometers. The measured gravimetric strength of orthogonally oriented sheet arrays exceeds that of sheets of high-strength steel. These nanotube sheets have been used in laboratory demonstrations for the microwave bonding of plastics and for making transparent, highly elastomeric electrodes; planar sources of polarized broad-band radiation; conducting appliques; and flexible organic light-emitting diodes.

Nonlinear surface waves at the interfaces of left-handed electromagnetic media.

Abstract: We report the existence of families of nonlinear TE-polarized surface waves propagating along the interface between different conventional and left-handed electromagnetic media as well as between two left-handed media. Both nonlinear/nonlinear and linear/nonlinear interfaces are considered. The constraints for the mode existence are identified and the energy flow associated with the surface modes is calculated.

Method and apparatus for transferring an array of oriented carbon nanotubes

Abstract: The present invention provides a method and apparatus for transferring an array of oriented carbon nanotubes from a first surface to a second surface by providing the array of oriented carbon nanotubes on the first surface within a vacuum chamber, providing the second surface within the vacuum chamber separate from the first surface, and applying an electric potential between the first surface and the second surface such that the array of oriented carbon nanotubes are sublimed from the first surface and re-deposited on the second surface.

Nanocomposite solar cells based on conjugated polymer/ PbSe quantum dot

Abstract: We report a novel type of nanocomposite of conjugated polymer (regio-regular polythiophene) with infrared-sensitive, PbSe quantum dots (QD), which have size-tunable lowest-energy absorption bands between 0.3 and 1 eV. Thin film devices show very good diode characteristics and sizable photovoltaic response with an open circuit voltage, Voc , of ~ 0.3-0.4 V and short circuit current density, J sc , of ~ 0.2mA/cm 2 , which is significantly higher than recently reported in PbS QD-based devices. This is the evidence of a quite efficient photoinduced charge transfer between the polymer and QD, with infrared sensitivity. Photocurrent under reverse bias is significantly enhanced to J ph ~ 1 mA/cm 2 indicating that the polythiophene/PbSe QD system can be used as effective infrared photodetectors. Detailed spectroscopic studies of photoresponse over a wide spectral range are presented. Quenching of photoluminescence by PbSe QDs has also been studied to gain more understanding of energy and charge transfer in this system.

Theory of the nonlinear all-optical logical gates based on PBG structures

Abstract: In our work, we show that photonic bandgap (PBG) systems containing nonlinear insertions are of interest for possible applications as the all-optical adders and logical gates Two principal schemes of an all-optical adder based on the combined 1D-3D PBG materials containing optically nonlinear layers are discussed Due to the electromagnetic spectra nonlinear dependence on the light signal intensity, the reflection properties of the system change significantly for chosen operation frequencies The photonic structure behavior with changing intensity is investigated for a few systems consisting of a periodically layered structure covered with an optically nonlinear material and a 3D opal PBG structure The latter plays the role of a motherboard controlling and directing the signals after the logical transformation Theoretical estimations of the adder cell parameters are made for Si/SiO/sub 2/ and GaAs/AlAs photonic crystals covered with layers made from nonlinear doped glasses The ideology of angular signal processing is developed It is shown that the angular-frequency diagram contains extremely sensitive areas inside the total reflection range, where the weak nonlinearity leads to dramatic change in light reflection and transmission Both solitary local modes and pure band modes are considered For 256-digit capacity the adder body has to consist of 32768 cells connecting by optical channels in the both schemes In summary, we discuss some general problems of "all-optical" signal processing, mechanisms of nonlinear signal transformation and the optical negative differential resistance areas existence, heating, energy losses and energy redistribution channels and geometry factors

Electrochromic Adaptive Infrared Camouflage

Abstract: : The goal of this research program was to create a technology for artificially programmable infrared emissivity of surfaces. As an example, this would permit a vehicle, or a person to blend into its surroundings, and become invisible to an infrared camera. A great deal has been accomplished in this research program, that will help convert this technology into a practical reality. The main technical objective is the controlled reduction of infrared emissivity. An emissivity reduction not an increase is desired, since objects of interest are generally hotter than their surroundings. The tunability of emissivity is made possible by electrochromics. Today, electrochromics is becoming a common technology that is used, for example, in self-dimming rear view mirrors in automobiles. Electrochromic materials change their color by undergoing an electronic transition of some form. In the most common type the electronic transformation is induced electro-chemically in special polymeric materials. In effect this is a type of electrochemical doping, with the material thereby undergoing a transition from an insulator to a metal, with the corresponding changes in color.

Flipping Carbon Nanotubes to Continuously Produce Strong, Transparent, Multifunctional Sheets

Abstract: We demonstrate carbon nanotube assembly by cooperatively rotating carbon nanotubes in vertically-oriented nanotube arrays (forests) and make 5-centimeter-wide, meter-long transparent sheets These self-supporting nanotube sheets are initially formed as a highly anisotropic electronically conducting aerogel that can be densified into strong sheets that are as thin as 50 nanometers The measured gravimetric strength of orthogonally oriented sheet arrays exceeds that of high strength steel sheetCopyright © 2005 by ASME