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Full-Text Articles in Physical Sciences and Mathematics
High-Temperature Fiber Matrices: Electrospinning And Rare-Earth Modification, W. Kataphinan, R. Teye-Mensah, Edward A. Evans, R. D. Ramsier, D. H. Reneker, D. J. Smith
High-Temperature Fiber Matrices: Electrospinning And Rare-Earth Modification, W. Kataphinan, R. Teye-Mensah, Edward A. Evans, R. D. Ramsier, D. H. Reneker, D. J. Smith
Edward A Evans
We demonstrate the production of nonwoven mats of high-temperature organic and inorganic fibers by electrospinning. Specifically, glass/ceramic (tetraethylorthosilicate-SiO) and fire-blanket (polydiphenoxyphosphazene-PDPP) precursors are electrospun, and the resulting fibers are characterized by scanning electron microscopy, thermogravimetric analysis, and infrared (IR) spectroscopy. We find that the SiO fibers are smaller in diameter and more uniform than the PDPP fibers, and stable to higher temperatures. We also coat these fiber systems with several rare-earth nitrates, and find that these coatings can be used to selectively modify the near-IR spectra of the fibers. This work extends the use of electrospinning into two new classes …
Modeling And Simulation Of Coating Growth On Nanofibers, J. Wilder, C. B. Clemons, K. L. Kreider, G. W. Young, Edward A. Evans, G. Zhang
Modeling And Simulation Of Coating Growth On Nanofibers, J. Wilder, C. B. Clemons, K. L. Kreider, G. W. Young, Edward A. Evans, G. Zhang
Edward A Evans
This work presents modeling and simulation results of a procedure to coat nanofibers and core-clad nanostructures with thin film materials using plasma enhanced physical vapor deposition. In the experimental effort that motivates the modeling, electrospun polymer nanofibers are coated with metallic materials under different operating conditions to observe changes in the coating morphology. The modeling effort focuses on linking simple models at the reactor, nanofiber, and atomic levels to form a comprehensive model. Numerical simulations that link the concentration field with the evolution of the coating free surface predict that as the Damkohler number is increased the coating morphology changes …
Poly(Meta-Phenylene Isophthalamide) Nanofibers: Coating And Post Processing, Wenxia Liu, Matthew Graham, Edward A. Evans, Darrell H. Reneker
Poly(Meta-Phenylene Isophthalamide) Nanofibers: Coating And Post Processing, Wenxia Liu, Matthew Graham, Edward A. Evans, Darrell H. Reneker
Edward A Evans
Electrospun nanofibers have applications in the areas of filtration, composites; biomaterials, and electronics. Controlling the surface properties of these nanofibers is important for many applications. Nanofibers can also be used as unique substrates for observing the growth of deposited films and creating nanoscale structures. In this work, electrospun poly(meta-phenylene isophthalamide) (MPD-I) nanofibers were used as substrates for creating nanoscale structures out of carbon-based materials and metals. MPD-I was used because it can be electrospun into nanofibers with diameters smaller than 10 nm and it has good thermal stability. MPD-I nanofibers were coated with carbon, copper, and aluminum using plasma enhanced …
Synthesis And Characterization Of Erbia Doped Metal Oxide Nanofibers For Applications In The Rmophotovoltaics, E. T. Bender, R. Wang, M. T. Aljarrah, Edward A. Evans, R. D. Ramsier
Synthesis And Characterization Of Erbia Doped Metal Oxide Nanofibers For Applications In The Rmophotovoltaics, E. T. Bender, R. Wang, M. T. Aljarrah, Edward A. Evans, R. D. Ramsier
Edward A Evans
Titania (TiO2) nanofibers doped with erbia (Er2O3) have been synthesized by electrospinning mixtures of polymers, titanium-containing materials, and erbia particles. These electrospun nanofibers are subsequently annealed at temperatures of 800, 900, 1000, and 1050 degrees C to remove the organics and leave behind the metal oxides. The crystal structure and optical properties of the metal oxides depend on the annealing temperature, and we characterize these nanofibers using x-ray diffraction and Fourier transform infrared spectroscopy (FTIR). An Er2Ti2O7 phase is formed in an amount which depends on the annealing temperature, and relationships between the nature of FTIR spectra and the relative …
Spm Oxidation And Parallel Writing On Zirconium Nitride Thin Films, N. Farkas, J. R. Comer, G. Zhang, Edward A. Evans, R. D. Ramsier, J. A. Dagata
Spm Oxidation And Parallel Writing On Zirconium Nitride Thin Films, N. Farkas, J. R. Comer, G. Zhang, Edward A. Evans, R. D. Ramsier, J. A. Dagata
Edward A Evans
Systematic investigation of the SPM oxidation process of sputter-deposited ZrN thin films is reported. During the intrinsic part of the oxidation, the density of the oxide increases until the total oxide thickness is approximately twice the feature height. Further oxide growth is sustainable as the system undergoes plastic flow followed by delamination from the ZrN-silicon interface keeping the oxide density constant. ZrN exhibits superdiffusive oxidation kinetics in these single tip SPM studies. We extend this work to the fabrication of parallel oxide patterns 70 nm in height covering areas in the square centimeter range. This simple, quick, and well-controlled parallel …
Multiscale Modeling, Simulations, And Experiments Of Coating Growth On Nanofibers. Part I. Sputtering, A. Buldum, I. Busuladzic, C. B. Clemons, L. H, Dill, K. L. Kreider, G. W. Young, Edward A. Evans, G. Zhang, S. I. Hariharan, W. Kiefer
Multiscale Modeling, Simulations, And Experiments Of Coating Growth On Nanofibers. Part I. Sputtering, A. Buldum, I. Busuladzic, C. B. Clemons, L. H, Dill, K. L. Kreider, G. W. Young, Edward A. Evans, G. Zhang, S. I. Hariharan, W. Kiefer
Edward A Evans
This paper is Part I of an integrated experimental/modeling investigation of a procedure to coat nanofibers and core-clad nanostructures with thin-film materials using plasma-enhanced physical vapor deposition. In the experimental effort, electrospun polymer nanofibers are coated with aluminum under varying operating conditions to observe changes in the coating morphology. This procedure begins with the sputtering of the coating material from a target. This paper focuses on the sputtering process and transport of the sputtered material through the reactor. The interrelationships among the processing factors for the sputtering and transport are investigated from a detailed modeling approach that describes the salient …
Local Oxidation Of Metal And Metal Nitride Films, N Farkas, J. C. Tokash, G. Zhang, Edward A. Evans, R. D. Ramsier, J. A. Dagata
Local Oxidation Of Metal And Metal Nitride Films, N Farkas, J. C. Tokash, G. Zhang, Edward A. Evans, R. D. Ramsier, J. A. Dagata
Edward A Evans
Oxide growth on sputter-deposited thin films is studied on the local scale by atomic force microscope (AFM)-assisted lithography. We investigate the group IV reactive metals Zr, Hf, Ti, and their nitrides.-The nitrogen content of the deposition plasma affects the film crystal structure and electrical resistivity, which in turn alter the local oxidation rates. Mass transport plays an important role, producing features with heights ranging from a few nanometers up to hundreds of nanometers. The heights of the largest features are one to two orders of magnitude greater than observed in other material systems, and the growth is well controlled. We …
Multiscale Modeling, Simulations, And Experiments Of Coating Growth On Nanofibers. Part Ii. Deposition, A. Buldum, C. B. Clemons, L. H. Dill, K. L. Kreider, G. W. Young, X. Zheng, Edward A. Evans, G. Zhang, S. I. Hariharan
Multiscale Modeling, Simulations, And Experiments Of Coating Growth On Nanofibers. Part Ii. Deposition, A. Buldum, C. B. Clemons, L. H. Dill, K. L. Kreider, G. W. Young, X. Zheng, Edward A. Evans, G. Zhang, S. I. Hariharan
Edward A Evans
This work is Part II of an integrated experimental/modeling investigation of a procedure to coat nanofibers and core-clad nanostructures with thin-film materials using plasma-enhanced physical vapor deposition. In the experimental effort, electrospun polymer nanofibers are coated with aluminum materials under different operating conditions to observe changes in the coating morphology. This procedure begins with the sputtering of the coating material from a target. Part I [J. Appl. Phys. 98, 044303 (2005)] focused on the sputtering aspect and transport of the sputtered material through the reactor. That reactor level model determines the concentration field of the coating material. This field serves …
Nanoscale Oxidation Of Zirconium Surfaces: Kinetics And Mechanisms, N. Farkas, G. Zhang, Edward A. Evans, R. D. Ramsier, J. A. Dagata
Nanoscale Oxidation Of Zirconium Surfaces: Kinetics And Mechanisms, N. Farkas, G. Zhang, Edward A. Evans, R. D. Ramsier, J. A. Dagata
Edward A Evans
We show that atomic force microscope-induced oxide features can be formed reproducibly on both Zr and ZrN surfaces, and that the growth rate decreases rapidly with increasing time. There is an increase in oxide-feature height with humidity for both systems, and an approximately linear dependence of the height of the structures on the applied voltage for all films for short exposure times. As the anodization time increases, only the thinnest (6 nm) films show a large enhancement in oxide-feature height, demonstrating the role of the film/substrate interface. Under the same conditions, the height of features grown on ZrN films is …
Parallel Writing On Zirconium Nitride Thin Films By Local Oxidation Nanolithography, N. Farkas, J. Comer, G. Zhang, Edward Evans, R. Ramsier, S. Wight, J. Dagata
Parallel Writing On Zirconium Nitride Thin Films By Local Oxidation Nanolithography, N. Farkas, J. Comer, G. Zhang, Edward Evans, R. Ramsier, S. Wight, J. Dagata
Edward A Evans
Parallel pattern transfer of submicrometer-scale oxide features onto zirconium nitride thin films is reported. The oxidation reaction was verified by Auger microprobe analysis and secondary ion mass spectrometry. Oxide features of similar to70 nm in height can be formed and selectively etched in a dilute aqueous hydrogen fluoride solution. This provides an interesting route to potential new applications for high-melting point, biocompatible surfaces that possess small feature sizes with controlled geometries. (C) 2004 American Institute of Physics.
Modeling, Simulation, And Experiments Of Coating Growth On Nanofibers, C. B. Clemons, P. Hamrick, J. Heminger, K. L. Kreider, G. W. Young, A. Buldum, Edward A. Evans, G. Zhang
Modeling, Simulation, And Experiments Of Coating Growth On Nanofibers, C. B. Clemons, P. Hamrick, J. Heminger, K. L. Kreider, G. W. Young, A. Buldum, Edward A. Evans, G. Zhang
Edward A Evans
This work is a comparison of modeling and simulation results with experiments for an integrated experimental/modeling investigation of a procedure to coat nanofibers and core-clad nanostructures with thin film materials using plasma enhanced physical vapor deposition. In the experimental effort, electrospun polymer nanofibers are coated with metallic materials under different operating conditions to observe changes in the coating morphology. The modeling effort focuses on linking simple models at the reactor level, nanofiber level and atomic level to form a comprehensive model. The comprehensive model leads to the definition of an evolution equation for the coating free surface around an isolated …
Characterization Of Zirconium Nitride Films Sputter Deposited With An Extensive Range Of Nitrogen Flow Rates, N. Farkas, G. Zhang, R. D. Ramsier, Edward A. Evans, J. A. Dagata
Characterization Of Zirconium Nitride Films Sputter Deposited With An Extensive Range Of Nitrogen Flow Rates, N. Farkas, G. Zhang, R. D. Ramsier, Edward A. Evans, J. A. Dagata
Edward A Evans
ZrNx films are deposited by rf magnetron sputtering using a wide range of nitrogen flow rates to control film properties. Scanned probe microscope (SPM) oxidation is presented as a complimentary characterization tool to x-ray diffraction, colorimetric, and four point probe analyses. The SPM oxidation behavior of the ZrNx films is related to their structural, optical, and electrical properties. Whereas stoichiometric ZrN films have applications as protective and/or decorative coatings, ZrNx films sputtered with higher nitrogen flow rates have potential applications in devices where arrays of high aspect ratio nanostructures would be useful. (C) 2008 American Vacuum Society.
High-Voltage Parallel Writing On Iron Nitride Thin Films, N. Farkas, J. Ehrman, Edward Evans, R. Ramsier, J. Dagata
High-Voltage Parallel Writing On Iron Nitride Thin Films, N. Farkas, J. Ehrman, Edward Evans, R. Ramsier, J. Dagata
Edward A Evans
We report large area patterning of sputter-deposited FeN thin films by a high-voltage parallel writing technique that was recently developed to modify ZrN surfaces. Systematically patterned 15-100-nm-thick FeN films consisting of features with well-defined sizes and shapes are obtained by applying high dc voltages between a stamp and the samples. During the process the oxide dissolves, exposing the substrate beneath. This controlled breakdown eliminates the need for any postexposure etching. The single-step imprinting method presented here provides an emerging route to fabricate isolated FeN geometrical structures on silicon substrates for magnetic applications. (c) 2006 American Vacuum Society.