Bulletin of the American Physical Society
2006 73rd Annual Meeting of the Southeastern Section of the APS
Thursday–Saturday, November 9–11, 2006; Williamsburg, Virginia
Session HC: Materials II |
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Chair: Chris Hughes, James Madison University Room: Williamsburg Hospitality House Yorktown |
Friday, November 10, 2006 10:15AM - 10:27AM |
HC.00001: Probing Chemicurrent Production in Ultrathin Film Schottky Diode Devices using Hyperthermal Energy Ion Beams. Matthew Ray, Chad Sosolik We are investigating the interactions of hyperthermal energy ions with ultrathin film Schottky diode devices, probing the role of ion-surface impact events and charge transfer on chemicurrent production. Chemicurrents are a fundamental ``chemical current'' that arises from electron-hole pair production at a diode surface. To date, these currents have been explored only for thermal energy gas-surface impacts. Using a UHV beamline to produce well-collimated monoenergetic noble gas and alkali-metal beams from 10 eV to 10 keV, we have the unique flexibility to probe our in-house designed diode devices with a wide range of incident species, energies, and charge states. Preliminary results are presented and discussed in the context of basic gas-surface energy transfer processes. [Preview Abstract] |
Friday, November 10, 2006 10:27AM - 10:39AM |
HC.00002: The modification of nanocomposite hybrid polymer surfaces by exposure to oxygen containing plasmas Ashley Figueiredo, Katherine Zimmermann, Brian Augustine, Chris Hughes, Charles Chusuei The wetting properties of the surfaces of the nanocomposite hybrid polymer poly[(propylmethacryl-heptaisobutyl- polyhedral oligomeric silsequioxane)-co-(methylmethacrylate)] (POSS-PMMA)has been studied before and after exposure to plasmas containing oxygen. The contact angle of water droplets on the surface showed a substantial decrease after plasma exposure indicating an increase in the hydrophilicity of the surface. A model was developed in which the plasma preferentially removed organic material including both the PMMA backbone and isobutyl groups from the corners of the POSS cages leaving behind a surface characterized by the silicon oxide-like POSS material. Measurements of surface concentrations of oxygen, silicon, and carbon by x-ray photoelectron spectroscopy (XPS) showed an increase in the amount of oxygen and silicon compared to carbon and the appropriate chemical shifts were observed in the XPS data to support the model of Si-O enrichment on the surface. Variable angle spectroscopic ellipsometry (VASE) and atomic force microscopy (AFM) measurements also supported the model and these results will be presented. [Preview Abstract] |
Friday, November 10, 2006 10:39AM - 10:51AM |
HC.00003: Nuclear Magnetic Resonance Chemical Shift Calculation of Bulk Crystalline Materials Daniel Pechkis, Eric Walter, Henry Krakauer Recent $^{17}$O nuclear magnetic resonance (NMR) measurements for PZT solid solutions have given a new understanding of the local structure within this material. Due to the low signal to noise ratio in the experimental spectrum, some ambiguities in these data remain. The experimental results may be clarified by first principles density functional theory (DFT) calculations of the NMR properties. NMR is an excellent tool for studying short range chemical order in crystalline solid state systems. The electric field gradient experienced by quadrupole nuclei indicate the local symmetry of a crystallographic site. While the isotropic chemical shifts felt by the nuclei indicate the number of distinct crystallographic sites. The shift tensor shows the orientation of the nuclei with respect to the externally applied magnetic field. The tensor also indicates the variations in shielding by the electronic environment in response to an applied magnetic field. Our recent DFT $^{17}$O chemical shift results of PZT will be presented. [Preview Abstract] |
Friday, November 10, 2006 10:51AM - 11:03AM |
HC.00004: Development and Testing of MEAM Potential for Al-Mg Alloys Bohumir Jelinek, Sungho Kim, Jeffery Houze, Seong-Gon Kim, Mark Horstemeyer, Michael Baskes A MEAM potential for Al-Mg alloys was developed based on the elastic and structural properties determined from ab-initio calculations. Transferability of the new potential was tested by comparing various bulk, surface, and point defect properties with ab-initio simulations. Volume-energy dependence of Al and Mg in fcc, hcp, bcc and simple cubic crystal structures from MEAM and ab-initio simulations was determined. Heat of formation for Al-Mg crystals with several different stoichiometries and structures was calculated using both methods. Surface formation, stacking faults, and adsorption energies were also compared. For point defects calculations, a close agreement of vacancy formation energies, interstitial and substitutional point defect energies was found. [Preview Abstract] |
Friday, November 10, 2006 11:03AM - 11:15AM |
HC.00005: Thigtness Compound Climatic Test - Q$_{C}$ Mariana Cornelia Butnaru This method determinate the suitabilty of materials components, finised products and others to stressful conditions like: cold, heat, UV and IR radiations {\ldots} others. Generally, the thigtness is testing in lab environmental conditions. But some materials, components or finised products are used transported or/and deposited in special climatic conditions. So when we test thighness we must mimic the environmental factors of aging. The samples are same elastomers of general use (used for gaskets). The rubber was studied using IR measurements. We studied the structural changes which appear due to the climatic factors on samples of N50 rubber. The elastomer was cooled and irradiated with UV radiation. Due to cooling a new spectral band at 1443 cm $^{-1}$ appears, and also the intensity of spectral band from 1432 cm $^{-1}$ decreases. The most important structural changes, due to the degradation action of the ultraviolet radiations, appear after 10 hours of the action of the aging factor. The rubber was also studied with photoacoustic technique. An important decrease of thermal diffusity with the number of climatic cycles (aging factor - cold) and the UV irradiations dose was observed for N50 type samples. We assume that a variety of structural changes have been produced. This kind of elastomer is not a resistent one to stressful conditions. The results proved that thigtness compound method Q$_{C}$, works, is a very imortant one and must be applied. [Preview Abstract] |
Friday, November 10, 2006 11:15AM - 11:27AM |
HC.00006: Solitary Wave Behavior in Grains in One Dimension Corey Kim I observed the propagation of stress from one grain to the next when stacked in a vertical column.~ The grains that were used are made of a photoelastic material, which allows instantaneous visual evidence of the amount of stress at each point of each grain.~ An impulse was applied to the top of the granular system in the form of a plexiglas rod which was allowed to drop in free fall onto the grains.~ The process is recorded with a high-speed camera, capturing about three to six frames where the stress is still in the process of traveling through the observed grains. Based on the pictures taken, it is possible to quantify the force at each grain, and to model the stress propagation as a wave.~ I explored the theory that the stress travels as a solitary wave, which is said to have a constant velocity that is proportional to the amplitude.~ In this case, amplitude was controlled by the initial height of the impulse-applying rod. \newline [Preview Abstract] |
Friday, November 10, 2006 11:27AM - 11:39AM |
HC.00007: The Effect of Nanoscopic Bubbles on the Viscosity of Fluids at a Solid-Liquid Interface Jonathan M. Jones It has been suggested that gaseous nanobubbles formed at solid-fluid interfaces may be responsible for a reduced interfacial viscosity at those surface boundaries. Here, we present measurements of the changing interfacial viscosity using both hydrophilic (Au, and SiO2) and hydrophobic (octadecanethiol self assembled monolayers (SAMs) on Au) at the interface of a coated gold electrode submerged in seltzer water, sonicated DI water, and DI water distilled in a vacuum chamber. We monitor changes in the resonant frequency of our quartz oscillator, and from the frequency measurements we can determine the viscosity. By acquiring movies of bubble formation on the QCM surface in seltzer water and correlating these movies with the measurements of the QCM frequency, we see that the measured viscosity of the seltzer water is decreased due to the presence of bubbles on the gold electrode. As the seltzer water goes flat with increasing time, the measured viscosity increases, approaching the viscosity of water as expected. We suggest similar behavior occurs with nanobubbles, and present data for DI water which has been distilled to varying degrees. On the hydrophobic surfaces, the bubbles form more readily, which results in a reduced interfacial viscosity as compared to the hydrophilic surfaces. [Preview Abstract] |
Friday, November 10, 2006 11:39AM - 11:51AM |
HC.00008: Shear Strength and Microstructure of Sn-3Ag-0.5Cu Solder Joints Sylvester Ekpenuma, Min He, Viola Acoff Sn-Ag-Cu based solders have been studied extensively as they show great promise for use in electronics assembly and packaging industry as alternatives to Sn-Pb based solders. As a further test of the reliability of these solders, the shear strength of single lap shear Sn-Ag-Cu solder joints was investigated. The microstructures of the solder joints and the fracture surfaces were examined using SEM. [Preview Abstract] |
Friday, November 10, 2006 11:51AM - 12:03PM |
HC.00009: A novel method for the fabrication of microfluidic devices by photopolymerization of polymethylmethacrylate Jacob Forstater, Brian Augustine, Chris Hughes We have developed a new technique for the rapid fabrication of structures useful for microfluidic devices called micromolding by photopolymerization in capillaries ($\mu $-PIC). The technique involves the replication of features from a silicon master in which features on the order of tens to hundreds of microns have been formed by crystallographic etching. The negative of the features is then transferred to a sheet of polymethylmethacrylate (PMMA) by placing the PMMA sheet over the silicon master and injecting a solution of methylmethacrylate monomer with a benzoin methyl ether photoinitiator. This solution is drawn between the PMMA and the silicon by capillary action forming a liquid layer that is no more than a few hundred microns thick. This liquid is then polymerized by exposure to ultraviolet light for less than a half hour. The features transferred in this manner have nearly identical surface structure and roughness. Analysis of these surfaces and structures by atomic force microscopy and scanning electron microscopy will be presented. [Preview Abstract] |
Friday, November 10, 2006 12:03PM - 12:15PM |
HC.00010: Osmotic Pressure: Conceptions \& Misconceptions from Pfeffer, to Van't Hoff, to Einstein, to Fermi, to the Present Theodore R. Reiff A phenomenological approach to understanding osmotic pressure in terms of competing effects of solute-solvent, solute-solute, and solvent-solvent interactions helps to avoid the misconceptions about osmotic pressure that were held by Van't Hoff, Einstein, Fermi, and many others. It also provides a better understanding of the concept of ``negative'' osmotic pressure and its role in explaining water of crystallization, gel syneresis, and in biological tissue aging and pathological states. Negative osmotic pressure may be conceptualized as due to a transient metastable state wherein the chemical potential of solvent is temporally increased above that of pure solvent in the standard state. Measureable changes in differential osmotic pressure-volume relationships of osmotic systems are readily related to differential changes in solvent chemical potential and number of mols of solvent in a system. [Preview Abstract] |
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