Other Materials Science and Engineering Commons^™

Limited Thermal Conductance Of Metal-Carbon Interfaces, Jaime J. Gengler, Sergei V. Shenogin, John E. Bultman, Ajit K. Roy, Andrey A. Voevodin, Christopher Muratore

Chemical and Materials Engineering Faculty Publications

The thermal conductance for a series of metal-graphite interfaces has been experimentally measured with time-domain thermoreflectance (TDTR). For metals with Debye temperatures up to ∼400 K, a linear relationship exists with the thermal conductance values. For metals with Debye temperatures in excess of ∼400 K, the measured metal-graphite thermal conductance values remain constant near 60 MW m−2 K−1. Titanium showed slightly higher conductance than aluminum, despite the closeness of atomic mass and Debye temperature for the two metals. Surface analysis was used to identify the presence of titaniumcarbide at the interface in contrast to the aluminum and gold-carbon interfaces (with …

Design Mixers To Minimize Effects Of Erosion And Corrosion Erosion, Julian B. Fasano, Eric E. Janz, Kevin J. Myers

Chemical and Materials Engineering Faculty Publications

A thorough review of the major parameters that affect solid-liquid slurry wear on impellers and techniques for minimizing wear is presented. These major parameters include (i) chemical environment, (ii) hardness of solids, (iii) density of solids, (iv) percent solids, (v) shape of solids, (vi) fluid regime (turbulent, transitional, or laminar), (vii) hardness of the mixer's wetted parts, (viii) hydraulic efficiency of the impeller (kinetic energy dissipation rates near the impeller blades), (ix) impact velocity, and (x) impact frequency. Techniques for minimizing the wear on impellers cover the choice of impeller, size and speed of the impeller, alloy selection, and surface …

Giant Magnetostriction In Annealed Co1-XFeX Thin-Films, Dwight Hunter, Will Osborn, Ke Wang, Nataliya Kazantseva, Jason R. Hattrick-Simpers, Richard Suchoski, Ryota Takahashi, Marcus L. Young, Apurva Mehta, Leonid A. Bendersky, Same E. Lofland, Manfred Wuttig, Ichiro Takeuchi

Faculty Publications

Chemical and structural heterogeneity and the resulting interaction of coexisting phases can lead to extraordinary behaviours in oxides, as observed in piezoelectric materials at morphotropic phase boundaries and relaxor ferroelectrics. However, such phenomena are rare in metallic alloys. Here we show that, by tuning the presence of structural heterogeneity in textured Co_1−xFe_x thin films, effective magnetostriction λeff as large as 260 p.p.m. can be achieved at low-saturation field of ~10 mT. Assuming λ100 is the dominant component, this number translates to an upper limit of magnetostriction ofλ100≈5λeff >1,000 p.p.m. Microstructural analyses …

Electrostatic Quadrupole Plasma Mass Spectrometer Measurements During Thin Film Depositions Using Simultaneous Matrix Assisted Pulsed Laser Evaporation And Magnetron Sputtering, Chad N. Hunter, Michael H. Check, Christopher Muratore, Andrey A. Voevodin

Chemical and Materials Engineering Faculty Publications

A hybrid plasma deposition process, combining matrix assisted pulsed laser evaporation (MAPLE) of carbon nanopearls (CNPs) with magnetron sputtering of gold was investigated for growth of composite films, where 100 nm sized CNPs were encapsulated into a gold matrix. Composition and morphology of such composite films was characterized with x-ray photoelectron spectroscopy, scanning electron microscopy, and transmission electron microscopy (TEM) analysis. Carbondeposits on a gold magnetron sputter target and carbon impurities in the gold matrices of depositedfilms were observed while codepositing from gold and frozen toluene-CNP MAPLE targets in pure argon. Electrostatic quadrupole plasma analysis was used to determine that …

Chameleon Coatings: Adaptive Surfaces To Reduce Friction And Wear In Extreme Environments, Christopher Muratore, Andrey A. Voevodin

Chemical and Materials Engineering Faculty Publications

Adaptive nanocomposite coating materials that automatically and reversibly adjust their surface composition and morphology via multiple mechanisms are a promising development for the reduction of friction and wear over broad ranges of ambient conditions encountered in aerospace applications, such as cycling of temperature and atmospheric composition. Materials selection for these composites is based on extensive study of interactions occurring between solid lubricants and their surroundings, especially with novel in situ surface characterization techniques used to identify adaptive behavior on size scales ranging from 10−10 to 10−4 m. Recent insights on operative solid-lubricant mechanisms and their dependency upon the ambient environment …

Thermal Damage Approach Of Concrete: Application To Specimens Subjected To Combined Compressive And High Temperature Loads, Abdellah Menou, Ghassan Mounajed, Hocine Boussa, Christian La Borderie, Khalid Lafdi

Chemical and Materials Engineering Faculty Publications

Within the framework of study of concrete structures subjected to fire, .a theoretical and experimental work was conducted. The aim of this study was to investigate and to model the damage mechanisms of concrete after their exposure to high temperatures. The multiphase Digital Concrete Model as well as the damage model, MOD EV, which were both implemented on the finiteelem~ rit software package, SYMPHONIE, were used simμltaneously to assess the thermal damage of the concrete. In order to validate the thermal damage model, an experimental investigation was performed. The mechanical characteristics of 5 cementitious materials, which included cement paste, mortar, …

Effect Of Carbon Nanofiber-Matrix Adhesion On Polymeric Nanocomposite Properties—Part Ii, Khalid Lafdi, William Fox, Matthew Matzek, Emel Yildiz

Chemical and Materials Engineering Faculty Publications

A successful integration of two independent phases with good adhesion is imperative for effective translation of superior carbon nanofiber filler properties into a physically superior carbon nanocomposite. Carbon nanofibers were subjected to electrochemical oxidation in 0.1 M nitric acid for varying times.

The strength of adhesion between the nanofiber and an epoxy matrix was characterized by flexural strength and modulus. The surface functional groups formed and their concentration of nanofibers showed a dependence on the degree of oxidation. The addition of chemical functional groups on the nanofiber surface allows them to physically and chemically adhere to the continuous resin matrix. …

Carbon Nanoadditives To Enhance Latent Energy Storage Of Phase Change Materials, Shadab Shaikh, Khalid Lafdi, Kevin P. Hallinan

Chemical and Materials Engineering Faculty Publications

Latent energy storage capacity was analyzed for a system consisting of carbon nanoparticlesdopedphase changematerials (PCMs). Three types of samples were prepared by doping shell wax with single wall carbon nanotubes(SWCNTs), multiwall CNTs, and carbon nanofibers. Differential scanning calorimetry was used to measure the latent heat of fusion. The measured values of latent heat for all the samples showed a good enhancement over the latent heat of pure wax. A maximum enhancement of approximately 13% was observed for the wax/SWCNT composite corresponding to 1% loading of SWCNT. The change in latent heat was modeled by using an approximation for the intermolecular …

Nitrogen And Hydrogen Plasma Treatments Of Multiwalled Carbon Nanotubes, John G. Jones, A. R. Waite, Christopher Muratore, Andrey A. Voevodin

Chemical and Materials Engineering Faculty Publications

This article investigates plasma treatment of vertically aligned multiwall carbon nanotube (CNT) films in different plasma environments for modification of surface chemistry and morphology. The surfaces of the CNTs were functionalized with a pulsed dc plasma treatment, where the power was directly applied to the nanotube film in low pressure argon/nitrogen and argon/hydrogen backgrounds. Optical emission spectroscopy was used to detect atomic and molecular excitations in the gas mixtures as well as in pure gases in the vicinity of the CNT films. In situx-ray photoelectron spectroscopy was performed on the treated samples to examine CNT surface chemistry after treatment. …

Enhanced Dielectric Properties In Single Crystal-Like Bifeo3 Thin Films Grown By Flux-Mediated Epitaxy, S.-H. Lim, M. Murakami, J. H. Yang, S.-Y. Young, Jason R. Hattrick-Simpers, M. Wuttig, L. G. Salamanca-Riba, I. Takeuchi

Faculty Publications

We have fabricated single crystal-like BiFeO₃ (BFO) thin films by flux-mediated epitaxy using pulsed laser deposition(PLD). The Bi–Cu–O flux composition and its thickness were optimized using composition spread, thickness gradient, and temperature gradient libraries. The optimized BFO thin films grown with this technique showed larger grain size of ∼2μm and higher dielectric constant in the range of 260–340 than those for standard PLD grown films. In addition, the leakage current density of the films was reduced by two orders of magnitude compared to that of standard PLD grown films.

Signaling Pathways Activated By Interleukin-2 And Interluekin-4 Receptors Mediate T Lymphocyte Clonal Expansion, Kristen K. Comfort

Chemical and Materials Engineering Faculty Publications

Cells sense and respond to chemical and physical stimuli through signal transduction pathways, which mediate cell proliferation, differentiation, migration, and survival. The cytokines interleukin-2 (IL-2) and interleukin-4 (IL-4) are key regulators of the adaptive immune system, particularly influencing the clonal expansion and differentiation of T cells. At least in culture, both synergistic and antagonistic effects of IL-2 and IL-4 co-stimulation have been reported; the antagonism, when observed, is thought to arise from the utilization of a common subunit shared by IL-2 and IL-4 receptors. We have sought to characterize IL-2 and IL-4 signaling at the level of intracellular pathways activated …

Thermal Conductivity Improvement In Carbon Nanoparticle Doped Pao Oil: An Experimental Study, Shadab Shaikh, Khalid Lafdi, Rengasamy Ponnappan

Chemical and Materials Engineering Faculty Publications

The present work involves a study on the thermal conductivity of nanoparticle-oil suspensions for three types of nanoparticles, namely, carbon nanotubes(CNTs), exfoliated graphite (EXG), and heat treated nanofibers (HTT) with PAO oil as the base fluid. To accomplish the above task, an experimental analysis is performed using a modern light flash technique (LFA 447) for measuring the thermal conductivity of the three types of nanofluids, for different loading of nanoparticles.

The experimental results show a similar trend as observed in literature for nanofluids with a maximum enhancement of approximately 161% obtained for the CNT-PAO oil suspension. The overall percent enhancements …

Experimental Study On The Influence Of Foam Porosity And Pore Size On The Melting Of Phase Change Materials, Khalid Lafdi, Osama Mesalam Mesalhy, Shadab Shaikh

Chemical and Materials Engineering Faculty Publications

Experimental study was carried out to study the phase change heat transfer within a composite of phase change material (PCM) infiltrated high thermal conductivity foam. An experimental setup was built to measure the temperature profiles and capture the melting evolution of the PCM inside aluminum foams. Aluminum foams were used as the porous material, and low melting temperature paraffin wax was used as the PCM. It was observed from the results that the system parameters of the wax/foam composite had a significant influence on its heat transfer behavior.

By using higher porosity aluminum foam, the steady-state temperature was reached faster …

Effect Of Carbon Nanofiber Heat Treatment On Physical Properties Of Polymeric Nanocomposites—Part I, Khalid Lafdi, William Fox, Matthew Matzek, Emel Yildiz

Chemical and Materials Engineering Faculty Publications

The definition of a nanocomposite material has broadened significantly to encompass a large variety of systems made of dissimilar components and mixed at the nanometer scale. The properties of nanocomposite materials also depend on the morphology, crystallinity, and interfacial characteristics of the individual constituents. In the current work, vapor-grown carbon nanofibers were subjected to varying heat-treatment temperatures.

The strength of adhesion between the nanofiber and an epoxy (thermoset) matrix was characterized by the flexural strength and modulus. Heat treatment to 1800C∘ demonstrated maximum improvement in mechanical properties over that of the neat resin, while heat-treatment to higher temperatures demonstrated a …

Interfacial And Capillary Pressure Effects On The Thermal Performance Of Wax/Foam Composites, Mohammad Rajab Almajali, Khalid Lafdi, Shadab Shaikh

Chemical and Materials Engineering Faculty Publications

A numerical investigation study was performed to study the phase change behavior of wax/foam composite encapsulated in an aluminum casing. Two types of foam materials, namely, aluminum and carbon, were infiltrated with paraffin wax. The progress of melt interface and temperature distribution within the encapsulated composite was analyzed using computational fluid dynamics software (CFD). A two-energy equation model was implemented in the CFD software through the use of user-defined function (UDF). Interfacial effects influencing the heat transfer process at the casing-composite junction and between the wax-foam surfaces within the composite were addressed through the use of separate UDF. In addition, …

Oxygen Plasma Treatment And Deposition Of Cnx On A Fluorinated Polymer Matrix Composite For Improved Erosion Resistance, Christopher Muratore, Andras Korenyi-Both, John E. Bultman, A. R. Waite, John G. Jones, T. M. Storage, Andrey A. Voevodin

Chemical and Materials Engineering Faculty Publications

The use of polymer matrix composites in aerospace propulsion applications is currently limited by insufficient resistance to erosion by abrasive media. Erosion resistant coatings may provide necessary protection; however, adhesion to many high temperature polymer matrix composite (PMC) materials is poor. A low pressure oxygen plasma treatment process was developed to improve adhesion of CNx coatings to a carbon reinforced, fluorinated polymer matrix composite. Fullerene-like CNx was selected as an erosion resistant coating for its high hardness-to-elastic modulus ratio and elastic resilience which were expected to reduce erosion from media incident at different angles (normal or glancing) relative to the …

The Microstructure And Grain Size Of Jet Electroplated Copper Films In Damascene Trench Features, Andrew Tzanavaras, Gregory Young, Stacy H. Gleixner

Faculty Publications

The brightening additive level and dc current density of electroplating baths are two parameters that affect the gap-filling capability and the degree of impurity incorporation in electroplated copper films. Additive incorporation can inhibit grain growth during the room temperature recrystallization process and therefore affect the final grain size. This investigation explores the grain size and microstructure of dc jet-electroplated copper films in 0.35 and 0.50μm Damascene trenches as a function of current density and brightening additive level after first receiving a high-temperature anneal. Unlike a previous study that explored these variables in blanket Cu films [ J. Electrochem. Soc. , …

Intracellular Signaling Networks In The Immune Response: Pathways Activated By Interleukin-2 And-4 Receptors And Their Roles In T Cell Proliferation, Kristen K. Comfort

Chemical and Materials Engineering Faculty Publications

Cells sense and respond to chemical and physical stimuli through signal transduction pathways, which mediate cell proliferation, differentiation, migration, and survival. The cytokines interleukin-2 (IL-2) and interleukin-4 (IL-4) are key regulators of the adaptive immune system, particularly influencing the clonal expansion and differentiation of T cells. At least in culture, both synergistic and antagonistic effects of IL-2 and -4 co-stimulation have been reported; the antagonism, when observed, is thought to arise from the utilization of a common subunit shared by IL-2 and IL-4 receptors. We have sought to characterize IL-2 and IL-4 signaling at the level of intracellular pathways activated …

Control Of Plasma Flux Composition Incident On Tin Films During Reactive Magnetron Sputtering And The Effect On Film Microstructure, Christopher Muratore, Scott G. Walton, Darrin Leonhardt, Richard F. Fernsler

Chemical and Materials Engineering Faculty Publications

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 sputtered titanium 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 Grain Size And Microstructure Of Jet-Electroplated Damascene Copper Films, Stacy H. Gleixner, Andrew Tzanavaras, Gregory Young

Faculty Publications

Electroplated damascene copper is rapidly replacing aluminum-copper alloys for on-chip interconnect metallization in advanced ultralarge scale integrated (ULSI) semiconductor devices. In addition to a high degree of (111) crystallographic texture, large defect-free grains are desired to enhance the performance and reliability of copper interconnects in such devices. The brightening additive level and dc current density of electroplating baths are two parameters that affect the process gap-filling capability and the degree of additive incorporation in these copper films. Additive incorporation can inhibit grain growth during the room-temperature recrystallization process and therefore affect the final grain size in electroplated copper films. This …

Etching With Electron Beam Generated Plasmas, D. Leonhardt, Scott G. Walton, Christopher Muratore, Richard F. Fernsler, R. A. Meger

Chemical and Materials Engineering Faculty Publications

A modulated electron beam generated plasma has been used to dry etch standard photoresist materials and silicon. Oxygen–argon mixtures were used to etch organic resist material and sulfur hexafluoride mixed with argon or oxygen was used for the silicon etching. Etch rates and anisotropy were determined with respect to gas compositions, incident ion energy (from an applied rf bias) and plasma duty factor. For 1818 negative resist and i-line resists the removal rate increased nearly linearly with ion energy (up to 220 nm/min at 100 eV), with reasonable anisotropic pattern transfer above 50 eV. Little change in etch rate was …

Effect Of Plasma Flux Composition On The Nitriding Rate Of Stainless Steel, Christopher Muratore, Scott G. Walton, D. Leonhardt, Richard F. Fernsler, David D. Blackwell, R. A. Meger

Chemical and Materials Engineering Faculty Publications

The total ion flux and nitriding rate for stainless steel specimens exposed to a modulated electron beam generated argon-nitrogen plasma were measured as a function of distance from the electron beam axis. The total ion flux decreased linearly with distance, but the nitriding rate increased under certain conditions, contrary to other ion flux/nitriding rate comparisons published in the literature. Variation in ion flux composition with distance was explored with a mass spectrometer and energy analyzer as a possible explanation for the anomalous nitriding rate response to ion flux magnitude. A transition in ion flux composition from mostly N2 1 to …

Exploration Of Artificial Multiferroic Thin-Film Heterostructures Using Composition Spreads, K.-S. Chang, M. A. Aronova, C.-L. Lin, M. Murakami, M.-H. Yu, Jason R. Hattrick-Simpers, O. O. Famodu, S. Y. Lee, R. Ramesh, M. Wuttig, I. Takeuchi, C. Gao, L. A. Bendersky

Faculty Publications

We have fabricated a series of composition spreads consisting of ferroelectric BaTiO₃ and piezomagnetic CoFe₂O₄ layers of varying thicknesses modulated at nanometer level in order to explore artificial magnetoelectricthin-film heterostructures. Scanning microwavemicroscopy and scanning superconducting quantum interference device microscopy were used to map the dielectric and magnetic properties as a function of continuously changing average composition across the spreads, respectively. Compositions in the middle of the spreads were found to exhibit ferromagnetism while displaying a dielectric constant as high as ≈120.

Development Of A Curved Layer Lom Process For Monolithic Ceramics And Ceramic Matrix Composites, Donald A. Klosterman, Richard P. Chartoff, Nora R. Osborne, George A. Graves, Allan Lightman, Gyoowan Han, Akos Bezewredi, Stan Rodrigues, Sung Pak, Gary Kalmanovich, Leon Dodin, Song Tu

Chemical and Materials Engineering Faculty Publications

A novel rapid prototyping technology incorporating a curved layer building style was developed. The new process, based on Laminated Object Manufacturing (LOM), was designed for efficient fabrication of curved layer structures made from ceramics and fiber reinforced composites. A new LOM machine was created, referred to as Curved Layer LOM. This new machine uses ceramic tapes and fiber prepregs as feedstocks and fabricates curved structures on a curved-layer by curved-layer basis. The output of the process is a three dimensional "green" ceramic that is capable of being processed to a seamless, fully dense ceramic using traditional techniques. A detailed description …

Derivation Of An Analytical Model To Calculate Junction Depth In Hgcdte Photodiodes, Stacy H. Gleixner, H. G. Robinson, C. R. Helms

Faculty Publications

Presents an enhanced analytical model to calculate junction depth and Hg interstitial profile during n-on-p junction formation in HgCdTe photodiodes. Detailed information on the enhanced model; Function of the model; Information on HgCdTe; Detailed information on how the model was obtained.