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Articles 1 - 30 of 726
Full-Text Articles in Engineering
Tribological Performance Of Hybrid Filtered Arc-Magnetron Coatings: Part I: Coating Deposition Process And Basic Coating Properties Characterization, Vladimir Gorokovsky, Chris Bowman, Paul Gannon, David Vanvorous, Andrey Voevodin, Adam Rutkowski, Christopher Muratore, Richard Smith, Asghar Kayani, David Gelles, Vaithiyalingam Shutthanandan, Boris Trusov
Tribological Performance Of Hybrid Filtered Arc-Magnetron Coatings: Part I: Coating Deposition Process And Basic Coating Properties Characterization, Vladimir Gorokovsky, Chris Bowman, Paul Gannon, David Vanvorous, Andrey Voevodin, Adam Rutkowski, Christopher Muratore, Richard Smith, Asghar Kayani, David Gelles, Vaithiyalingam Shutthanandan, Boris Trusov
Christopher Muratore
Aircraft propulsion applications require low-friction and wear resistant surfaces that operate under high contact loads in severe environments. Recent research on supertough and low friction nanocomposite coatings produced with hybrid plasma deposition processes was demonstrated to have a high potential for such demanding applications. However, industrially scalable hybrid plasma technologies are needed for their commercial realization. The Large area Filtered Arc Deposition (LAFAD) process provides atomically smooth coatings at high deposition rates over large surface areas. The LAFAD technology allows functionally graded, multilayer, super-lattice and nanocomposite architectures of multi-elemental coatings via electro-magnetic mixing of two plasma flows composed of different …
Progress In The Development Of Adaptive Nitride-Based Coatings For High Temperature Tribological Applications, Samir Aouadi, Brandon Luster, Punit Kohli, Christopher Muratore, Andrey Voevodin
Progress In The Development Of Adaptive Nitride-Based Coatings For High Temperature Tribological Applications, Samir Aouadi, Brandon Luster, Punit Kohli, Christopher Muratore, Andrey Voevodin
Christopher Muratore
Adaptive tribological coatings were recently developed as a new class of smart materials that were designed to adjust their surface chemical composition and structure as a function of changes in the working environment to minimize friction coefficient and wear between contact surfaces. This paper provides an overview of the current research developments in this field, including: (1) Chameleon nanocomposite coatings which are produced by depositing a multi-phase structure whereby some of the phases provide mechanical strength and others are lubricious; (2) Micro- and nano-textured coatings which consist of hard nitride films with highly ordered micropores and nanopores that are subsequently …
Plasma Enhanced Surface Treatments Using Electron Beam-Generated Plasmas, Darrin Leonhardt, Christopher Muratore, Scott Walton, Robert Meger
Plasma Enhanced Surface Treatments Using Electron Beam-Generated Plasmas, Darrin Leonhardt, Christopher Muratore, Scott Walton, Robert Meger
Christopher Muratore
NRL has developed a ‘large area plasma processing system’ (LAPPS) utilizing a high energy (∼2 keV) modulated electron beam to drive the plasma ionization. This system has been shown to be (1) efficient at producing plasma in any gas composition, (2) capable of producing low temperature plasma electrons (9–1012 cm−3) and (3) scalable to large area (square meters). In this work, the progress of a number of applications using LAPPS is discussed. Nitride growth in stainless steel was investigated, which demonstrated high rates (up to 20 μm/h1/2) at low temperatures (≤462 °C). Complementary mass spectrometry …
Molybdenum Disulfide As A Lubricant And Catalyst In Adaptive Nanocomposite Coatings, Christopher Muratore, Andrey Voevodin
Molybdenum Disulfide As A Lubricant And Catalyst In Adaptive Nanocomposite Coatings, Christopher Muratore, Andrey Voevodin
Christopher Muratore
Nanocomposite YSZ–Ag–Mo–MoS2 coatings with different MoS2 additions (0–100 at.%) were deposited with a hybrid pulsed laser/magnetron sputtering/filtered cathodic arc process. Wear testing was performed from 25 to 700 °C for each of the coatings. Electron microscopy and other characterization techniques were used to examine the surfaces and wear tracks of the coatings and to determine the mechanisms resulting in the measured tribological properties. Adaptive coatings containing 8 at.% MoS2demonstrated a friction coefficient of 0.2 throughout the temperature range examined here, compared to 0.4 for YSZ–Ag–Mo with no MoS2. Characterization of the YSZ–Ag–Mo–8% MoS2 …
In Situ Studies Of Tic1−X N X Hard Coating Tribology, Marisa Rebelo De Figueiredo, Christopher Muratore, Robert Franz, Richard Chromik, Kathryn Wahl, Andrey Voevodin, Michel O'Sullivan, Markus Lechthaler, Christian Mitterer
In Situ Studies Of Tic1−X N X Hard Coating Tribology, Marisa Rebelo De Figueiredo, Christopher Muratore, Robert Franz, Richard Chromik, Kathryn Wahl, Andrey Voevodin, Michel O'Sullivan, Markus Lechthaler, Christian Mitterer
Christopher Muratore
TiC1−x N x hard coatings present time-dependent tribological behavior with an initial running-in period (500–2000 cycles) marked by an elevated friction coefficient, followed by >10000 cycles with low-friction and wear at room temperature (RT) in ambient air. The mechanisms behind this behavior are not completely understood. Tribological tests performed at RT and at different relative humidity (RH) levels revealed that a minimum value between 15 and 25% RH is needed to trigger the low-friction regime at a sliding speed of 100 mm s−1. By in situ observations of transfer film growth, it could be observed that third body material …
Adaptive Nanocomposite Coatings With A Titanium Nitride Diffusion Barrier Mask For High-Temperature Tribological Applications, Christopher Muratore, Jianjun Hu, Andrey Voevodin
Adaptive Nanocomposite Coatings With A Titanium Nitride Diffusion Barrier Mask For High-Temperature Tribological Applications, Christopher Muratore, Jianjun Hu, Andrey Voevodin
Christopher Muratore
Adaptive nanocomposite coatings that demonstrate low friction throughout broad ranges of temperature, wear, humidity and other environments are currently in development. One effective temperature adaptation mechanism at temperatures ≤ 500 °C is diffusion of noble metal to the coating surface, providing a low shear strength interface at the friction contact supported by a hard surface underneath. To prolong the wear lifetime of chameleon coatings relying upon this mechanism for low friction, a coating architecture incorporating a diffusion barrier mask to inhibit noble metal diffusion was employed. The diffusion barrier-capped coating provided lubrication at 500 °C over ten times longer than …
A Simultaneous Increase In The Thermal And Electrical Transport In Carbon Nanotube Yarns Induced By Inter-Tube Metallic Welding, Sabyasachi Ganguli, Amber Reed, Chaminda Jayasinghe, Joe Sprengard, Ajit Roy, Andrey Voevodin, Christopher Muratore
A Simultaneous Increase In The Thermal And Electrical Transport In Carbon Nanotube Yarns Induced By Inter-Tube Metallic Welding, Sabyasachi Ganguli, Amber Reed, Chaminda Jayasinghe, Joe Sprengard, Ajit Roy, Andrey Voevodin, Christopher Muratore
Christopher Muratore
Vertically aligned arrays of multiwall carbon nanotubes (MWCNT) were decorated with gold (Au) nanoparticles of different diameter and areal densities and spun into yarns. The melting point of Au nanoparticles determined by differential scanning calorimetry was approximately 260 °C, well below the oxidation temperature of carbon. A continuous yarn was formed while pulling out a bundle of CNTs from the metalized CNT array. Relatively low temperature (300 °C) thermal processing of the metalized yarn resulted in a 30% improvement in thermal conductivity, 40% increase in electrical conductivity and a 4× increase in elastic modulus. Cross-sections of the yarn were examined …
Control Of Plasma Flux Composition Incident On Tin Films During Reactive Magnetron Sputtering And The Effect On Film Microstructure, Christopher Muratore, Scott Walton, D. Leonhardt, Richard Fernsler
Control Of Plasma Flux Composition Incident On Tin Films During Reactive Magnetron Sputtering And The Effect On Film Microstructure, Christopher Muratore, Scott Walton, D. Leonhardt, Richard Fernsler
Christopher Muratore
A hybrid plasma enhanced physical vapor deposition (PEPVD) system consisting of an unbalanced dc magnetron and a pulsed electron beam-produced plasma was used to deposit reactively sputteredtitanium nitride thin films. The system allowed for control of the magnitudes of the ion and neutral flux, in addition to the type of nitrogen ions (atomic or molecular) that comprised the flux. For all deposition experiments, the magnitude of the ion flux incident on the substrate was held constant, but the composition of the total flux was varied. X-ray diffraction and atomic force microscopy showed that crystallographic texture and surface morphology of the …
Temporally And Spatially Resolved Plasma Spectroscopy In Pulsed Laser Deposition Of Ultra-Thin Boron Nitride Films, Nicholas Glavin, Christopher Muratore, Michael Jespersen, Jianjun Hu, Timothy Fisher, Andrey Voevodin
Temporally And Spatially Resolved Plasma Spectroscopy In Pulsed Laser Deposition Of Ultra-Thin Boron Nitride Films, Nicholas Glavin, Christopher Muratore, Michael Jespersen, Jianjun Hu, Timothy Fisher, Andrey Voevodin
Christopher Muratore
Physical vapor deposition (PVD) has recently been investigated as a viable, alternative growth technique for two-dimensional materials with multiple benefits over other vapor deposition synthesis methods. The high kinetic energies and chemical reactivities of the condensing species formed from PVD processes can facilitate growth over large areas and at reduced substrate temperatures. In this study, chemistry, kinetic energies, time of flight data, and spatial distributions within a PVD plasma plume ablated from aboron nitride (BN) target by a KrF laser at different pressures of nitrogen gas were investigated. Time resolved spectroscopy and wavelength specific imaging were used to identify and …
Control Of Plasma Flux Composition Incident On Tin Films During Reactive Magnetron Sputtering And The Effect On Film Microstructure, Christopher Muratore, Scott Walton, D. Leonhardt, Richard Fernsler
Control Of Plasma Flux Composition Incident On Tin Films During Reactive Magnetron Sputtering And The Effect On Film Microstructure, Christopher Muratore, Scott Walton, D. Leonhardt, Richard Fernsler
Christopher Muratore
A hybrid plasma enhanced physical vapor deposition (PEPVD) system consisting of an unbalanced dc magnetron and a pulsed electron beam-produced plasma was used to deposit reactively sputteredtitanium nitride thin films. The system allowed for control of the magnitudes of the ion and neutral flux, in addition to the type of nitrogen ions (atomic or molecular) that comprised the flux. For all deposition experiments, the magnitude of the ion flux incident on the substrate was held constant, but the composition of the total flux was varied. X-ray diffraction and atomic force microscopy showed that crystallographic texture and surface morphology of the …
Cross-Plane Thermal Properties Of Transition Metal Dichalcogenides, Christopher Muratore, Vikas Varshney, Jaime Gengler, Jianjun Hu, John Bultman, Timothy Smith, Patrick Shamberger, Bo Qiu, Xiulin Ruan, Ajit Roy, Andrey Voevodin
Cross-Plane Thermal Properties Of Transition Metal Dichalcogenides, Christopher Muratore, Vikas Varshney, Jaime Gengler, Jianjun Hu, John Bultman, Timothy Smith, Patrick Shamberger, Bo Qiu, Xiulin Ruan, Ajit Roy, Andrey Voevodin
Christopher Muratore
In this work, we explore the thermal properties of hexagonal transition metal dichalcogenide compounds with different average atomic masses but equivalent microstructures. Thermal conductivity values of sputtered thin films were compared to bulk crystals. The comparison revealed a >10 fold reduction in thin film thermal conductivity. Structural analysis of the films revealed a turbostratic structure with domain sizes on the order of 5–10 nm. Estimates of phonon scattering lengths at domain boundaries based on computationally derived group velocities were consistent with the observed film microstructure, and accounted for the reduction in thermal conductivity compared to values for bulk crystals.
Ftir Studies Of Ionic Interactions In Blends, Robert Weiss
Ftir Studies Of Ionic Interactions In Blends, Robert Weiss
Robert Weiss
No abstract provided.
Supercritical Carbon Dioxide Aided Preparation Of Conductive Polyurethane-Polypyrrole Composites, Robert Weiss
Supercritical Carbon Dioxide Aided Preparation Of Conductive Polyurethane-Polypyrrole Composites, Robert Weiss
Robert Weiss
Conductive polyurethane (PU) foams were prepared using a two-step procedure. First, PU foams were impregnated with the oxidant I2 from a scCO2 solution. Subsequently, the foams were subjected to pyrrole vapor, which polymerized within the foam in the presence of the oxidant. The reduced form of iodine as a result of the oxidative polymerization of pyrrole functions as a dopant. The conductivities of the foams ranged from 10−7 to 10−2 S/cm and the foams were flexible and not brittle. The concentration of conductive polypyrrole, i.e. the PPy–I2 charge-transfer complex, needed to achieve a conductivity of 10−4–10−3 S/cm was about 22% …
Supercritical Carbon Dioxide Aided Preparation Of Conductive Polyurethane-Polypyrrole Composites, Robert Weiss
Supercritical Carbon Dioxide Aided Preparation Of Conductive Polyurethane-Polypyrrole Composites, Robert Weiss
Robert Weiss
Conductive polyurethane (PU) foams were prepared using a two-step procedure. First, PU foams were impregnated with the oxidant I2 from a scCO2 solution. Subsequently, the foams were subjected to pyrrole vapor, which polymerized within the foam in the presence of the oxidant. The reduced form of iodine as a result of the oxidative polymerization of pyrrole functions as a dopant. The conductivities of the foams ranged from 10−7 to 10−2 S/cm and the foams were flexible and not brittle. The concentration of conductive polypyrrole, i.e. the PPy–I2 charge-transfer complex, needed to achieve a conductivity of 10−4–10−3 S/cm was about 22% …
Tissue Specific Shrna Delivery: A Novel Approach For Gene Therapy In Cancer, Shilenath Ghatak, Viacent Hascall, Franklin Berger, Maria Penas, Celestia Davis, Esmaiel Jabbari, Xuezhong He, James Norris, Yujing Dan, Roger Markwaid, Suniti Misra
Tissue Specific Shrna Delivery: A Novel Approach For Gene Therapy In Cancer, Shilenath Ghatak, Viacent Hascall, Franklin Berger, Maria Penas, Celestia Davis, Esmaiel Jabbari, Xuezhong He, James Norris, Yujing Dan, Roger Markwaid, Suniti Misra
Esmaiel Jabbari
No abstract provided.
Release Characteristics Of A Model Plasmid Dna Encapsulated In Biodegradable Poly(Ethylene Glycol Fumarate)/Acrylamide Hydrogel Microspheres, Esmaiel Jabbari
Release Characteristics Of A Model Plasmid Dna Encapsulated In Biodegradable Poly(Ethylene Glycol Fumarate)/Acrylamide Hydrogel Microspheres, Esmaiel Jabbari
Esmaiel Jabbari
No abstract provided.
Mapping The Concentration Profile At The Poly(Vinyl Chloride)/Poly(Ethyl Methacrylate) Interface, Esmaiel Jabbari, Nikolaos Peppas
Mapping The Concentration Profile At The Poly(Vinyl Chloride)/Poly(Ethyl Methacrylate) Interface, Esmaiel Jabbari, Nikolaos Peppas
Esmaiel Jabbari
No abstract provided.
Temperature Effects On Interdiffusion At Glassy/Rubbery Interfaces, Esmaiel Jabbari, Nikolaos Peppas
Temperature Effects On Interdiffusion At Glassy/Rubbery Interfaces, Esmaiel Jabbari, Nikolaos Peppas
Esmaiel Jabbari
No abstract provided.
Molecular Weight And Polydispersity Effects On Interdiffusion At The Interface Between Polystyrene And Poly(Vinyl Methyl Ether), Esmaiel Jabbari, Nikolaos Peppas
Molecular Weight And Polydispersity Effects On Interdiffusion At The Interface Between Polystyrene And Poly(Vinyl Methyl Ether), Esmaiel Jabbari, Nikolaos Peppas
Esmaiel Jabbari
No abstract provided.
Evidence Of Mucoadhesion By Chain Interpenetration At A Poly (Acrylic Acid)/Mucin Interface Using Atr-Ftir Spectroscopy, Esmaiel Jabbari, Natalie Wisniewski, Nikolaos Peppas
Evidence Of Mucoadhesion By Chain Interpenetration At A Poly (Acrylic Acid)/Mucin Interface Using Atr-Ftir Spectroscopy, Esmaiel Jabbari, Natalie Wisniewski, Nikolaos Peppas
Esmaiel Jabbari
No abstract provided.
Quantitative Measurement Of Interdiffusion At Polymer–Polymer Interfaces With Tem/Eds And Eels, Esmaiel Jabbari, Nikolaos Peppas
Quantitative Measurement Of Interdiffusion At Polymer–Polymer Interfaces With Tem/Eds And Eels, Esmaiel Jabbari, Nikolaos Peppas
Esmaiel Jabbari
No abstract provided.
Comparison Of Interdiffusion At Polystyrene–Poly(Vinyl Methyl Ether) And Polystyrene–Poly(Isobutyl Vinyl Ether) Interfaces, Esmaiel Jabbari, Nikolaos Peppas
Comparison Of Interdiffusion At Polystyrene–Poly(Vinyl Methyl Ether) And Polystyrene–Poly(Isobutyl Vinyl Ether) Interfaces, Esmaiel Jabbari, Nikolaos Peppas
Esmaiel Jabbari
No abstract provided.
Morphology And Structure Of Microcapsules Prepared By Interfacial Polycondensation Of Methylene Bis(Phenyl Isocyanate) With Hexamethylene Diamine, Esmaiel Jabbari
Morphology And Structure Of Microcapsules Prepared By Interfacial Polycondensation Of Methylene Bis(Phenyl Isocyanate) With Hexamethylene Diamine, Esmaiel Jabbari
Esmaiel Jabbari
No abstract provided.
Preliminary Study Of Synthesis Gas Production Using The Electrofuel Concept, João Gomes
Preliminary Study Of Synthesis Gas Production Using The Electrofuel Concept, João Gomes
João F Gomes
This paper describes preliminary work on the generation of synthesis gas from water electrolysis using graphite electrodes without the separation of the generated gases. This is an innovative process, that has no similar work been done earlier. Preliminary tests allowed to establish correlations between the applied current to the electrolyser and flow rate and composition of the generated syngas, as well as a characterisation of generated carbon nanoparticles. The obtained syngas can further be used to produce synthetic liquid fuels, for example, methane, methanol or DME (dimethyl ether) in a catalytic reactor, in further stages of a present ongoing project, …
Development Of Miscible Blends Of Bisphenol-A Polycarbonate And Sulfonated Polystyrene Ionomers From Intrapolymer Repulsive Interactions, Robert Weiss
Robert Weiss
Differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FTIR) were used to characterize the phase behavior and interactions of blends of the free acid derivative and lithium and sodium salts of lightly sulfonated polystyrene (MSPS) with Bisphenol A polycarbonate (PC). The blends exhibited upper critical solution temperature (UCST) phase behavior and a miscibility window with respect to the sulfonation level. At a fixed blend composition, a minimum in the cloud point temperature occurs at the sulfonation level marking the middle of the miscibility window. The miscibility window depended on the sulfonate cation used. No interactions involving either the carbonate …
Rheological Behavior Of Liquid Crystalline Polymer/Polymer Blends, Robert Weiss
Rheological Behavior Of Liquid Crystalline Polymer/Polymer Blends, Robert Weiss
Robert Weiss
This paper reviews the literature on the rheological behavior of liquid crystalline polymer/polymer blends. The advantages of blending a LCP with a thermoplastic polymer is that the LCP serves as a processing aid and can also form a reinforcing phase. Rheology plays an important role in determining the morphology and hence the mechanical properties of these blends. This review also discusses the slow behavior of neat liquid crystalline polymers.
Synthesis And Thermal Properties Of Telechelic Poly(Lactic Acid) Ionomers, Robert Weiss
Synthesis And Thermal Properties Of Telechelic Poly(Lactic Acid) Ionomers, Robert Weiss
Robert Weiss
Telechelic poly(lactic acid) (PLA) ionomers were synthesized using a chemical recycling process. A transesterification reaction between a commercial PLA and 2-hydroxyethyl methacrylate or ethylene glycol was used to produce a hydroxy-terminated PLA. The hydroxy-terminated PLA was then reacted with itaconic anhydride to produce terminal carboxylic acid groups, which were neutralized with appropriate metal acetates to produce Na-, Li-, K-, Zn-, Ca- and Y-ω- and α,ω-telechelic PLA ionomers. 1H NMR spectroscopy was used to confirm the presence of the itaconic acid end-groups and FTIR spectroscopy was used to quantify the extent of neutralization. The addition of the ionic groups increased the …
Sulfonated Polystyrene Ionomers Prepared By Emulsion Copolymerization Of Styrene And Sodium Styrene Sulfonate, Robert Weiss
Sulfonated Polystyrene Ionomers Prepared By Emulsion Copolymerization Of Styrene And Sodium Styrene Sulfonate, Robert Weiss
Robert Weiss
Sulfonated polystyrene (S–PS), which is of considerable scientific and technological interest, has been traditionally prepared by the sulfonation of preformed polystyrene. This report describes the preparation and properties of S–PS prepared by emulsion copolymerization of styrene and sodium styrene sulfonate. S–PS prepared by copolymerization gave solubility, solution behavior and thermal characteristics that are consistent with an ionomeric structure. The solubility characteristics indicated some chain-to-chain sulfonate heterogeneity. Thermal analysis studies indicated that the glass transition does not increase with increasing sulfonate content. This is contrary to what has been observed for S–PS prepared by sulfonation and suggests that the S–PS prepared …
New Design Of Shape Memory Polymers: Mixtures Of An Elastomeric Ionomer And Low Molar Mass Fatty Acids And Their Salts, Robert Weiss
New Design Of Shape Memory Polymers: Mixtures Of An Elastomeric Ionomer And Low Molar Mass Fatty Acids And Their Salts, Robert Weiss
Robert Weiss
No abstract provided.
Development Of An Ionomer Tracer For Extruder Residence Time Distribution Experiments, Robert Weiss
Development Of An Ionomer Tracer For Extruder Residence Time Distribution Experiments, Robert Weiss
Robert Weiss
A polymeric tracer was developed from the tributylamine salt of lightly sulfonated polystyrene. The residence time distribution (RTD) measured for the extrusion of polystyrene with this tracer was compared with that measured using conventional particulate tracers, In general, the particulate tracers had a longer mean residence time and a broader RTD, which were attributed to increased mixing of the particulates.