bluuebunny/crossref_metadata_2025_split huggingface dataset:
Plasma Torch Production of Ti-Al Nanoparticles
Authors: Phillips Jonathan , Cheng Lili , Luhrs Claudia , Zea Hugo , Courtney Matthew , Hanson Caleb 
Published: April 2011

ABSTRACTUsing the Aerosol-through-Plasma (A-T-P) technique high surface area (from 100 to 203 m2/gm) bi-cationic (Ti-Al) oxide particles of a range of stoichiometries were produced that showed remarkable resistance to sintering. Specifically, we found that homogeneous nanoparticles with surface areas greater than 150 m2/gm were produced at all stoichiometries. In particular, for particles with a Ti:Al ratio of 1:3 a surface area of just over 200 m2/gm was measured using the BET method. The most significant characteristic of these particles was that their sinter resistance was far superior to that of TiAl particles produced using any other method. For example, A-T-P generated particles retained >70% of their surface area even after sintering at 1000 C for five hours. In contrast, particles made using all other methods lost virtually all of their surface area after an 800 C treatment.
Tridimensional Microstructures of C-SWNT Reinforced Polymer Nanocomposite by Means of a Microfluidic Infiltration Approach
Authors: Lebel Louis Laberge , Aissa Brahim , Khakani My Ali El , Therriault Daniel 
Published: April 2011

ABSTRACTThree-dimensional (3D) microstructures of single walled carbon nanotube (C-SWNT)/polymer nanocomposite are fabricated by the infiltration of 3D microfluidic networks. The microfluidic network was first fabricated by direct-write assembly which consists of the robotised deposition of fugitive ink filaments on an epoxy substrate to form a 3D microstructured network. After encapsulation of the deposited structure with an epoxy resin, the fugitive ink was removed by heating, resulting in a 3D network of microchannels. This microfluidic network is then infiltrated by a ultraviolet (UV) -curable polymer loaded with C-SWNTs. The C-SWNTs were produced by the UV-laser ablation method, physico-chemically purified and dispersed in a polymer matrix using ultrasonic treatment in dichloromethane. The C-SWNTs were characterized by means of high-resolution scanning electron microscopy and microRaman spectroscopy. The infiltrated nanocomposite (i.e., the C-SWNT reinforced polymer) is then cured under UV exposure and post-cured. The manufactured 3D microstructures were rectangular sandwich beams having an epoxy core and unidirectional nanocomposite fibers placed parallel to the beam axis, on both sides of the core. Flexural mechanical tests were performed on empty, pure resin and nanocomposite microfluidic beams using a dynamic mechanical analyzer. The achieved nanocomposite beams were found to show an increase of 5% in the storage modulus and more than 50% increase in the loss modulus, under 30°C compared to the pure resin beams. The nanocomposite infiltration of microfluidic networks is shown to be a promising approach to achieve 3D microstructures of reinforced nanocomposites.
Effect of Functionalization on the Crystallization Behavior of MWNT-PBT Nanocomposites
Authors: Mago Gaurav , Velasco-Santos Carlos , Martinez-Hernandez Ana L. , Kalyon Dilhan M. , Fisher Frank T. 
Published: April 2011

ABSTRACTThere is tremendous interest in using low loadings of multiwalled carbon nanotubes (MWNTs) to enhance the multifunctional properties of polymers, with functionalization often pursued to increase the dispersion and effective reinforcement of MWNTs within the polymer. In our interest to understand the effect of MWNT functionalization on Poly (butylene terephthalate) (PBT) crystallization kinetics, morphology and mechanical properties, nanocomposites were fabricated with both as-received and carboxyl group (-COOH) functionalized MWNTs. Initial results indicate as-received and functionalized nanotubes alter the crystallization temperature and crystal size for quiescent samples. In addition, isothermal crystallization studies using an Advanced Rheometric Expansion System (ARES) show that the addition of MWNTs increases the rate of PBT crystallization. However, functionalization was found to decrease the rate of nanocomposite crystallization as compared to nanocomposites samples prepared using pristine MWNTs, suggesting that nanotube functionalization weakens the nucleation effect observed in the nanocomposite samples. These results suggest that semicrystalline polymer nanocomposite crystallization kinetics and morphology can be significantly influenced by nanoparticle functionalization and chemistry. Further study of how these changes impact the rheological and multifunctional properties of semicrystalline nanocomposite systems are ongoing.
Nano-dispersed Particulate Ceramics in Poly-Lactide-Co-Glycolide Composites Improve Implantable Bone Substitute Properties
Authors: Liu Huinan , Webster Thomas J. 
Published: April 2011

ABSTRACTMetallic materials widely used in orthopedic applications have much stronger mechanical properties (such as elastic modulus) than natural bone, which can weaken the newly formed bone interface due to stress-shielding. Because natural bone is under continuous physiological stresses (such as compression, tension, torsion, and/or bending), the mechanical properties of orthopedic implant materials should closely match those of living bone. This is necessary to minimize stress and strain imbalances during physiological loading conditions which will lead to implant failure. The objective of the present study was to characterize the mechanical properties of PLGA with well-dispersed nanophase titania. The dispersion of titania in PLGA was controlled by sonication and was characterized by field emission scanning electron microscopy and image analysis. For this purpose, two major stresses (compression and tension) that natural bone experiences under physiological loading conditions were characterized using an Instron Material Testing System. The results showed that nano-dispersed titania particles in PLGA increased the compressive and tensile modulus of such scaffolds compared to pure PLGA scaffolds and the more agglomerated ceramics in PLGA scaffolds. The mechanisms behind these results were also speculated. Since the predominant feature of nano-particles lies in their ultra-fine dimension, a large fraction of filler atoms can reside at the PLGA-ceramic interface which can lead to a stronger interfacial interaction, but only if the nano-particles are well dispersed at the nanometer level in the surrounding polymer matrix. As the interfacial PLGA-ceramic structure plays a critical role in determining the mechanical properties of composites, nano-composites with a great number of smaller interfaces could be expected to provide unusual properties, and the shortcomings induced by the heterogeneity of conventional (or micron) particle filled composites would also be avoided. Therefore, coupled with prior studies demonstrating greater osteoblast functions, the combination of PLGA with a strong and biocompatible well-dispersed nano-ceramic phase may provide better candidate materials for orthopedic applications.
Growth and Characterization of a Combinatorial Array of Mixed-Phase Magnesium-Aluminum Thin-Film Alloys
Authors: Olk Charles , Haddad Daad B. 
Published: April 2011

ABSTRACTCombinatorial gradient-controlled sputter deposition has been employed to produce a library of 100 separate thin films with a wide range of Mg-Al alloy compositions. We have successfully isolated the â (Mg17Al12) phase in polycrystalline films for investigation. The presence of the â phase has been found to be desirable for increasing corrosion resistance; however, in structural components under tensile loading and/or at elevated temperatures, the â phase precipitates undergo coarsening which induces poor creep behavior in several common alloys. We have also synthesized amorphous Mg-Al and mixed-phase compositions as identified by X-ray diffraction measurements. Details of the growth procedure as well as structural and compositional characterization are presented.
Investigation of Phase Transition in Stacked Ge-Chalcogenide/SnTe Phase-change Memory Films
Authors: Bai Feiming , Gupta Surendra , Devasia Archana , Kurinec Santosh , Davis Morgan , Campbell Kris A 
Published: April 2011

ABSTRACTPhase transitions in stacked GeTe/SnTe and Ge2Se3/SnTe thin layers for potential phase-change memory applications have been investigated by X-ray diffraction using a two-dimensional area detector system. The as-deposited underlying GeTe or Ge2Se3 layer is amorphous, whereas the top SnTe layer is crystalline. In the GeTe/SnTe stack, the crystallization of GeTe phase occurs near 170°C, and upon further heating, the GeTe phase disappears, followed by the formation of rocksalt-structured GexSn1−xTe solid solution. In the Ge2Se3/SnTe stack, the phase transition starts with the separation of a SnSe phase due to the migration of Sn ions into the Ge2Se3 layer. SnSe is believed to facilitate the crystallization of Ge2Se3-SnTe solid solution at ∼360°C, which is much lower than the crystallization temperature of Ge2Se3, therefore consuming less power during the phase transition.
Polymer Composites with Oriented Magnetic Nanowires as Fillers
Authors: Sun Li , Keshoju Kusuma 
Published: April 2011

ABSTRACTMetallic nickel nanowires with excellent physical properties have been introduced into polydimethylsiloxane matrix to form polymer nanocomposites. Nanowires were synthesized by template-assisted electrochemical deposition. By utilizing ferromagnetic nickel nanowires, small external magnetic field can be used to control their alignment and distribution during composite synthesis. Unlike dielectrophoresis, optical tweezers, and microfluidic flow control, magnetic manipulation provides a cost-effective, non-contact, and versatile approach to control nanostructured materials in fluids over a large area. Polydimethylsiloxane composites with nanowires arranged in longitudinal, transverse, and random orientations with respect to the applied load direction were studied. Tensile tests showed that the composites with longitudinal arrangement have higher elastic modulus and tensile strength than the other composite samples. Experimentally obtained elastic modulus values were compared with the prediction of classical Halpin-Tsai model. Metallic nickel nanowires with excellent physical properties have been introduced into polydimethylsiloxane matrix to form polymer nanocomposites. Nanowires were synthesized by template-assisted electrochemical deposition. By utilizing ferromagnetic nickel nanowires, small external magnetic field can be used to control their alignment and distribution during composite synthesis. Unlike dielectrophoresis, optical tweezers, and microfluidic flow control, magnetic manipulation provides a cost-effective, non-contact, and versatile approach to control nanostructured materials in fluids over a large area. Polydimethylsiloxane composites with nanowires arranged in longitudinal, transverse, and random orientations with respect to the applied load direction were studied. Tensile tests showed that the composites with longitudinal arrangement have higher elastic modulus and tensile strength than the other composite samples. Experimentally obtained elastic modulus values were compared with the prediction of classical Halpin-Tsai model.
Ion Beam Induced Surface Modulations from Nano to Pico: Optimizing Deposition During Erosion and Erosion During Deposition
Authors: MoberlyChan Warren John , Schalek Richard 
Published: April 2011

ABSTRACTIon beams of sufficient energy to erode a surface can lead to surface modulations that depend on the ion beam, the material surface it impinges, and extrinsic parameters such as temperature and geometric boundary conditions. Focused Ion Beam technology both enables site-specific placement of these modulations and expedites research through fast, high dose and small efficient use of material. The DualBeam (FIB/SEM) enablesin situmetrology, with movies observing ripple formation, wave motion, and the influence of line defects. Nanostructures (ripples of >400nm wavelength to dots spaced <40nm) naturally grow from atomically flat surfaces during erosion, however, a steady state size may or may not be achieved as a consequence of numerous controlled parameters: temperature, angle, energy, crystallography. Geometric factors, which can be easily invoked using a FIB, enable a controlled component of deposition (and/or redeposition) to occur during erosion, and conversely allow a component of etching to be incurred during (ion-beam assisted) deposition. High angles of ion beam inclination commonly lead to “rougher” surfaces, however, the extreme case of 90.0° etching enables deposition of organized structures 1000 times smaller than the aforementioned, video-recorded nanostructures. Orientation and position of these picostructures (naturally quantized by their atomic spacings) may be controlled by the same parameters as for nanostructures (e.g. ion inclination and imposed boundary conditions, which are flexibly regulated by FIB). Judicious control of angles during FIB-CVD growth stimulates erosion with directionality that produces surface modulations akin to those observed for sputtering. Just as a diamond surface roughens from 1-D ripples to 2-D steps with increasing angle of ion sputtering, so do ripples and steps appear on carbon-grown surfaces with increase in angle of FIB-CVD. Ion beam processing has been a stalwart of the microelectronics industry, is now a vital tool for research of self-organizing nanostructures, and promises to be a focus for future picotechnology.
Self-Organized Swelling of a Metal-Capped Polymer Thin Bilayer
Authors: Kwon S. Joon , Park Jae-Gwan 
Published: April 2011

ABSTRACTSelf-organized swelling of a metal-polymer bilayer directed by a corrugated mold was reported. The corrugated pattern by the elastomeric mold was observed from the earlier stages of swelling. The temporal evolution of the self-organized pattern was analyzed theoretically, and the experimental data were well matched with the analysis. The maximum harmonic number for the corrugated wave number was also analyzed. With a relatively large line width, irregular self-organized patterns were observed.
Nanohole and Nanopillar Arrays on GaAs and GaSb Using Nanosphere Lithography and Bromine Ion Beam Assisted Etching
Authors: Qian Xifeng , Li Jin , Goodhue William D. 
Published: April 2011

ABSTRACTNanosphere lithography (NSL) has been successfully used to nanopattern silicon and glass substrate surfaces using a spin process in conjunction with the chemical functionalized polystyrene nanospheres. Here, we report for the first time the formation of periodic arrays of nanohole and nanopillar on GaAs and GaSb substrates using a combination of NSL, electron beam (E-Beam) evaporation and Bromine Ion Beam Assisted Etching (Br-IBAE). When 250 nm diameter nanospheres were used as a template or mask, periodic arrays of approximate 55 nm hexagonal nanoholes and 39 nm hexagonal nanopillars were obtained from double-layer nanosphere templates, while arrays of approximate 65nm triangular nanohole and 53nm triangular nanopillar were obtained from single-layer nanosphere templates. The high uniformity of these nanohole and nanopillar arrays demonstrates the technique¡¦s potential for applications in the fabrication of novel high performance opto- and electronic devices in the important GaAs and GaSb III-V direct bandgap semiconductors.
Monitoring nanoprobe diffusion in osmotically-stressed hydrogels
Authors: Boukari Hacene , de Silva Candida , Nossal Ralph , Horkay Ferenc 
Published: April 2011

ABSTRACTWe have developed an optical chamber for studying the effect of swelling or shrinking of a gel on the translational diffusion of fluorescent nanoprobes embedded in the gel. On one side of the chamber, the gel is in contact with a hydrating or dehydrating polymeric solution through a porous membrane, allowing control of the rate of hydration or dehydration of the gel. On the other side, a laser beam is focused into the gel to excite the fluorescence of the nanoprobes, which is continuously monitored to reveal possible structural changes of the stressed gel. Using fluorescence correlation spectroscopy we measure correlation functions of the nanoprobes at various times following the contact of the gel with the hydrating or dehydrating solution, and determine changes of both the average concentration and the apparent diffusion time of the nanoprobes as the gel is shrinking or swelling. We have tested the chamber using the fluorophore, TAMRA (MW = 430 Da), embedded in a poly(vinyl-alcohol) gel that is being dehydrated by a solution of poly(vinyl-pyrrolidone) (28% w/w). As expected TAMRA moves slower as the gel shrinks. However, the changes in the diffusion time of TAMRA as a function of the PVA concentration of the shrinking gel appear to be different than those measured on TAMRA diffusing in PVA gels prepared at different PVA concentrations but with the same cross-link density.
Analytical Approach to Quantifying the Non-Affine Behavior of Fiber Networks
Authors: Hatami-Marbini Hamed , Picu Catalin 
Published: April 2011

ABSTRACTFiber networks deform nonaffinely due to their inhomogeneous structure. The degree of nonaffinity depends on many factors such as the spatial distribution and properties of fibers, the nature of the applied load, the type of joints and the length scale of observation. The “homogenized” response on given scale depends on the non-affine mechanics on all sub-scales. Here, a method is developed to map the non-affine mechanics of a regular network with a large density of defects into an equivalent continuum, which is then used to determine the homogenized elastic properties of the network. This semi-analytic method establishes a relationship between the structure of the network and its overall elastic properties. Furthermore, we develop a method to quantify the nonaffine strains in a random network and use it to study the dependence of the degree of non-affinity to the scale of observation as well as the dependence on the network architecture.
Electrical Impedance Analysis of Phospholipid Bilayer Membranes for Enabling Engineering Design of Bio-based Devices
Authors: Sarles Stephen A. , Sundaresan Vishnu B. , Leo Donald J. 
Published: April 2011

ABSTRACTRecent research at Virginia Tech have shown that active transporter proteins reconstituted into suspended bilayer lipid membranes (BLMs) formed across an array of pores in synthetic substrates can convert chemical energy available in adenosine triphosphate (ATP) into electricity. Experimental results from this work show that this system—called BioCell—is capable of 1.7μW of electrical power per square centimeter of BLM area and per 15μL of ATPase enzyme. In support of such a system, the lipid membrane, as host to active biological proteins and channels, must be formed evenly across a porous substrate, remain stable and yet fluid-like for protein folding and activation, and provide sufficient electrical insulation. We report on the formation and characterization using electrical impedance spectroscopy (EIS) of BLMs formed across two types of porous substrates: polycarbonate filters and single-aperture silicon substrates. Equivalent electrical circuits describing the lipid membranes and their supporting substrates are approximated to fit the measured responses. The results show that BLMs formed in some but not all of the 400nm pores of the filters, while the formation of BLMs on the single-aperture silicon substrates was much more consistent.
Electrostatic Field Calculations for Electrophoresis Using Surfaces
Authors: Ramasamy Perumal Radha , Elmaghrabi Raafat M , Halada Gary 
Published: April 2011

ABSTRACTThe distribution of electric field in and near the surface of the electrophoretic cell determines the motion of proteins in the buffer and along the surface. This is a complicated problem, influenced by buffer ion concentration, electrode configuration, and surface and substrate conductivities. Steady state calculations approximating the experimental geometry were made for different arrangements of electrodes using MAFIA (Computer Simulation Technologies) program and ESTAT programs. Electric field distributions in both conducting surfaces like ITO (Indium Tin Oxide) (Kevley Technologies), gold and aluminum and non conducting surfaces were studied. In order to measure the EOF of the buffer neutrally charged fluorescent Poly-Styrene beads of 1 μm diameter were included in the buffer and imaged using confocal microscope. It was observed that the electric filed was highly modified by various factors like the conducting nature of the surface, position of the electrodes, salt concentration in the buffer and distance from the separation surface.
Effects of Changes in Structural Hydration of Multiphasic Heterogeneous Calcium Phosphate Powders Created via Auto-Ignition Combustion Synthesis
Authors: Vollmer Nina Louise , Burkes Douglas , Moore John , Ayers Reed 
Published: April 2011

ABSTRACTCalcium phosphate (CaP) materials are commonly used in bone tissue engineering applications since they closely resemble the chemistry of bone and teeth. The inorganic component of mineralized tissue is multiphasic in nature-thus to better replicate those tissues, CaP materials should also be multiphasic. Combustion synthesis is a process that creates multiphasic CaP (HCaP) with low energy input over a relatively short time. The structure and chemistry of HCaP synthesized via auto-ignition combustion synthesis (AICS) varies greatly with respect to structural hydration. Product hydration was accomplished by modifying hydrogen and oxygen content in the combustion reaction by changing the amount of fuel, urea [ ] pre-reaction, and heating or sintering products post-reaction. The reaction equation for this specific system is given below. Calcium nitrate [ ], and ammonium nitrate [ ] are the components that form HCaP. Urea acts as an ignition source and fuel. Changes in the amount of urea dictate the amount of excess hydrogen to form water within the reaction. Excess products formed include water, carbon dioxide, and nitrogen. Salts of the reactants were mixed with 10 milliliters of de-ionized water in a Pyrex beaker, heated on a hot plate for 20 minutes or until the reactants began to foam, and then placed in a muffle furnace at 1000°C until the foam ignited in a combustion reaction. This was noted by the progression of a combustion wave throughout the foam. Post-AICS, products were heated at 105°C for 8 hours and 24 hours and massed to determine water content of the product. Subsequently, the products were sintered at 1000°C for 8 hours and massed again. The primary products formed using AICS are hydroxyapatite (HA), á-tricalcium calcium phosphate (TCP) and hydrated forms of tricalcium phosphate (HTCP). During low temperature heating, 105°C, water content decreases as time increases and the products began to densify. Initial results indicate that surface porosity decreases during the powder densification. XRD shows that peak intensity increases after low temperature heating, indicating an increase in crystallinity and grain orientation. XRD confirms that both crystalline and amorphous phases occur in the hydroxyapatite (HA), á-TCP and HTCP products. The amount of structural hydration has an effect on CaP, and these effects are noted by an increase in density and decrease in porosity as structurally bound water is removed from the system. Future research will be dedicated to determining hydration ratio (amount of urea in the reaction to the amount of water within the products) and a Ca:P ratio that result in optimal powder porosity, ductility and grain size generating a multiphasic HCaP implant biomaterial that accurately replicates natural bony tissue.