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Search Publications by: Jan Obrzut (Fed)

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Displaying 51 - 75 of 113

Flexure-induced structural and electronic changes in polymer supported membranes of length purified single-wall carbon nanotubes

February 22, 2011
Author(s)
John M. Harris, Ganjigunte R. Iyer, Daneesh O. Simien, Jeffrey Fagan, JiYeon Huh, Jun Y. Chung, Steven Hudson, Jan Obrzut, Jack F. Douglas, Christopher Stafford, Erik K. Hobbie
Thin membranes of length purified single-wall carbon nanotubes (SWCNTs) are uniaxially compressed by depositing them on prestretched polymer substrates. Upon release of the strain, the topography, microstructure and conductivity of the films are

Carbon Nanotubes: Measuring Dispersion and Length

August 26, 2010
Author(s)
Jeffrey A. Fagan, Barry J. Bauer, Erik K. Hobbie, Matthew Becker, Angela R. Hight Walker, Jeffrey R. Simpson, Jae H. Chun, Jan Obrzut, Vardhan Bajpai, Frederick R. Phelan Jr., Daneesh O. Simien, JiYeon Huh, Kalman D. Migler
Advanced technological uses of single-wall carbon nanotubes (SWCNTs) rely on the production of single length and chirality populations that are currently only available through liquid phase post processing. The foundation of all of these processing steps

Separation and Characterization of Double Wall Carbon Nanotube Sub-Populations

July 8, 2010
Author(s)
JiYeon Huh, Angela R. Hight Walker, Hyun W. Ro, Jan Obrzut, Jeffrey Fagan
We present the separation of surfactant encapsulated double wall carbon nanotubes (DWCNTs) synthesized by the high pressure carbon monoxide decomposition (HiPco) process by length and electronic characteristics using density gradient ultracentrifugation

Wrinkling and Strain Softening in Single-Wall Carbon Nanotube Membranes

March 26, 2010
Author(s)
Erik K. Hobbie, Daneesh O. Simien, Jeffrey A. Fagan, JiYeon Huh, Jun Y. Chung, Steven D. Hudson, Jan Obrzut, Jack F. Douglas, Christopher M. Stafford
Ultrathin layers of single-wall carbon nanotubes (SWCNTs) show considerable promise for applications ranging from fuel-cell membranes and biochemical sensors to bioactive films and transparent electrodes. The high conductivity and extreme anisotropy of

Electrical Conductivity and Relaxation in Poly(3-hexylthiophene)

November 25, 2009
Author(s)
Jan Obrzut, Kirt A. Page
ABSTRACT: We studied the complex conductivity of regio-regular poly(3-hexylthiophene) (P3HT) in the temperature range between 193K to 333 K (-80 C to 60 C) and in the frequency range from the direct current (DC) to 12 GHz. The identified relaxation process

Microscale Polymer-Nanotube Composites

July 2, 2009
Author(s)
Erik K. Hobbie, Jeffrey A. Fagan, Jan Obrzut, Steven D. Hudson
Microscopic polymer colloids with an interfacial coating of purified single-wall carbon nanotubes (SWCNTs) have been synthesized from length and type sorted SWCNTs. Aqueous SWNCT suspensions sorted through density-gradient ultracentrifugation are used to

Transparency and conductivity of carbon nanotube networks

March 18, 2009
Author(s)
Jan Obrzut
The conductivity of films made of nanotubes longer than 200 nm closely follows the percolation theory for two-dimensional (2D) networks. The scaling universal exponents describing the percolation transition from an insulating to conducting state with

Processing Phase Diagram of Melt-Dispersed Carbon-Nanotubes

October 16, 2008
Author(s)
Erik K. Hobbie, Jan Obrzut, H Wang, E A. Grulke, D J. Fry
We measure the processing 'phase diagram' of a model carbon-nanotube polymer melt composite in the parameter space of concentration, shear stress, and confinement. With decreasing strain rate, we observe a hierarchy of flow-induced structure, from flow

Relationship between dispersion metric and properties of PMMA/SWNT nanocomposites

June 13, 2007
Author(s)
Takashi Kashiwagi, Jeffrey Fagan, Jack F. Douglas, Kazuya Yamamoto, N. Alan Heckert, Stefan D. Leigh, Jan Obrzut, Fangming Du, Minfang Mu, Sheng Lin-Gibson, K Winey, R Haggenmueller
Particle spatial dispersion is a crucial characteristic of polymer composite materials and this property is recognized as especially important innanocomposite materials due to the general tendency of nanoparticles to aggregate under processing conditions

Measurement of Complex Impedance of Individual Metallic Carbon Nanotubes

May 3, 2007
Author(s)
Jan Obrzut, Kalman D. Migler, L F. Dong, J Jiao
We describe impedance measurements of individual single wall carbon nanotubes (CNTs) in the frequency range of 40 Hz to 100 MHz. The extracted CNT capacitance of 4 10-14 F/mm, is independent of the total resistance, however the CCNT value is larger than

I-NEMI 2007 Organic and Printed Electronics Roadmap

April 2, 2007
Author(s)
Jan Obrzut, Regis J. Kline, Eric K. Lin, David J. Gundlach, Daniel Gamota
This roadmap provides an overview of the most critical technologies necessary for commercial launch and market diffusion of organic & printed electronics based products. To the best of our knowledge, this roadmap is the first of its kind and as such should

Measurement of Materials Dielectric Properties

September 4, 2006
Author(s)
Jan Obrzut
Dielectric materials are the building blocks of functional electronic circuits, capacitors, gate dielectrics, transmission lines, and are essential as electrical insulators for power distribution. Molecular solids, organic polymer resins, ceramic glasses

Nonlinear charge transport in semiconducting polythiophene

May 23, 2006
Author(s)
Jan Obrzut
We measured the complex impedance and nonlinear conductivity for regioregular poly(3-hexylthiophene) (P3HT) by recording and analyzing AC waveforms at their fundamental frequency and at higher order harmonic frequencies. We used 50 µm thick films of P3HT

TDR Permittivity Measurements of Dielectric Films

May 15, 2006
Author(s)
Jan Obrzut, R Nozaki
We have developed a time-domain reflectometry (TDR) technique to measure the dielectric permittivity of film specimens. The test specimen consists of a planar capacitor terminating coaxial waveguide. The complex permittivity is obtained from analysis of

Broadband Permittivity Measurements of High Dielectric Constant Films

March 1, 2006
Author(s)
Jan Obrzut, Nozaki R. AnopchenkoA
Our investigation concerns measuring broadband dielectric permittivity and loss tangent of thin film high dielectric constant (high-k) dielectric materials at microwave frequencies. The measurements are made in an APC-7 coaxial configuration where the test

Dielectric Study of the Anti-Plasticization of Trehalose by Glycerol

January 1, 2006
Author(s)
A Anopchenko, Tatiana Psurek, David L. VanderHart, Jack F. Douglas, Jan Obrzut
Recent measurements have suggested that the antiplasticizing effect of glycerol on trehalose can significantly increase the preservation times of proteins stored in this type of preservative formulation. In order to better understand the physical origin of