bluuebunny/crossref_metadata_2025 huggingface dataset:
Atomic Ordering in Nano-layered FePt: Multiscale Monte Carlo Simulation
Authors: Kozubski Rafal , Kozlowski Miroslaw , Wrobel Jan , Wejrzanowski Tomasz , Kurzydlowski Krzysztof J , Goyhenex Christine , Pierron-Bohnes Veronique , Rennhofer Marcus , Malinov Savko
Published: March 2010

Combined nano- and mesoscale simulation of chemical ordering kinetics in nano-layered L10 AB binary system was performed. In the nano- (atomistic) scale Monte Carlo (MC) technique with vacancy mechanism of atomic migration was implemented with diverse system models. The mesoscale microstructure evolution was, in turn, modeled by means of MC procedure simulating antiphase boundary (APB) motion as controlled by APB energies evaluated within the nano-scale simulations. The study addressed FePt thin layers considered as a material for ultra-high density magnetic storage media and revealed metastability of the L10 c-variant superstructure with monoatomic planes parallel to the (001) free surface and off-plane easy magnetization. The layers, initially perfectly ordered in the L10 c-variant, showed homogenous disordering running in parallel with a spontaneous re-orientation of the monoatomic planes into a mosaic-microstructure composed of L10 a- and b-variant domains with (100)- and (010)-type monoatomic planes, respectively. The domains nucleated heterogeneously on the Fe free surface of the layer, grew discontinuously inwards its volume and finally relaxed generating an equilibrium microstructure of the system. Two �atomistic-scale� processes: (i) homogenous disordering and (ii) nucleation of the L10 a- and b-variant domains showed characteristic time scales. The same was observed for the meso-scale processes: (i) heterogeneous L10 variant domain growth and (ii) domain microstructure relaxation. The above phenomena modelled within the present study by means of multiscale MC simulations have recently been observed experimentally in epitaxially deposited thin films of FePt.
An Interactive Desktop Computer Program for Simulating Nanometer Scale Surface Pattern Formation
Authors: Wang Michael
Published: March 2010

Nanometer-scale patterns may form as one or more chemical components deposit on a solid substrate. This self-assembly process can be described by a set of nonlinear integral-differential diffusion equations accounting for two opposing factors: phase separation to minimizing Gibb's free energy in individual surface phases and reduction in phase boundaries to minimize surface energy created by phase separation. I here present a desktop computer program that allows us to interactively simulate self-assembly of nanometer-scale surface patterns. In particular, this program provides a convenient tool for studying the effects of temperature variations and preexisting patterns on the self-assembly process. Computer simulations show that an increase in temperature may enlarge pattern sizes and can eventually lead to the disappearance of the patterns.
Molecular dynamics simulation of ds-DNA on a gold surface at low surface coverage
Authors: Lee One-Sun , Schatz George C.
Published: March 2010

Molecular dynamics methods have been used to study the conformation of ds-DNA on a gold surface for low surface coverage at the atomistic level. Each ds-DNA strand, which is attached to the [111] surface of gold with a -S(CH2)6- linker, is found to be nearly perpendicular to the surface and maintaining the Watson-Crick B-DNA conformation. The tilt angle between the ds-DNA and an axis normal to the gold surface is 7.3 (+/-) 2.2 degree. The concentration of counterions around the ds-DNA is increased by a factor of 1.8 relative to the bulk, which is significantly lower than in our previous simulations of ds-DNA at high surface coverage.
Density-Functional Analysis on Vacancy Orbital and its Elastic Response of Silicon
Authors: Ogawa Takafumi , Tsuruta Kenji , Iyetomi Hiroshi , Kaneta Hiroshi Yamada , Goto Terutaka
Published: March 2010

Recent experiments on ultrasonic measurements of non-doped and boron-doped silicon indicate that vacancies in crystalline silicon can be detected through the elastic softening at low temperature. This is attributed to enhanced response of electronic quadrupole localized at the vacancies to the elastic strain. In the present work, the electronic quadrupole moment of the vacancy orbital in silicon and their strain susceptibility are evaluated quantitatively by using the density-functional method. We show the orbital of gap state is localized around vacancy but extended over several neighbors. The effect of applied magnetic field on the vacancy orbital and its multipole structures are also investigated. We find that the results obtained from these calculations are consistent with the ultrasonic experiments.
InGaAs/GaAsSb Heterostructures: Aluminum-Free Intersubband Devices
Authors: Nobile Michele , Strasser Gottfried , Detz Hermann , Mujagic Elvis , Andrews Aaron , Klang Pavel , Schrenk Werner
Published: March 2010

An experimental study on mid-infrared intersubband absorption in InGaAs/GaAsSb multiple quantum wells grown lattice-matched to InP substrates by molecular beam epitaxy is presented. Intersubband absorption in a broad wavelength region (5.8 - 11.6 μm) is observed in multiple quantum well samples with well widths ranging between 4.5 and 12 nm. A conduction band offset at the InGaAs/GaAsSb heterointerface of 360 meV gives an excellent agreement between the theoretically calculated ISB transition energies and the Fourier-transform infrared spectroscopy measurements over the whole range of well widths under investigation. Two kinds of intersubband devices based on the InGaAs/GaAsSb material system are presented: a quantum well infrared photodetector operating at a wavelength of 5.6μm and an aluminum-free quantum cascade laser. The presented quantum cascade laser emits at a wavelength of 11.3 μm, with a threshold current density of 1.7 kA/cm2 at 78 K.
MESFETs on H-terminated Single Crystal Diamond
Authors: Calvani Paolo , Rossi Maria Cristina , Conte Gennaro , Carta Stefano , Giovine Ennio , Pasciuto Benedetto , Limiti Ernesto , Cappelluti Federica , Ralchenko Victor , Bolshakov A. , Sharonov G.
Published: March 2010

Epitaxial diamond films were deposited on polished single crystal Ib type HPHT diamond plates of (100) orientation by microwave CVD. The epilayers were used for the fabrication of surface channel MESFET structures having sub-micrometer gate length in the range 200-800 nm. Realized devices show maximum drain current and trasconductance values of about 190 mA/mm and 80 mS/mm, respectively, for MESFETs having 200 nm gate length. RF performance evaluation gave cut off frequency of about 14 GHz and maximum oscillation frequency of more than 26 GHz for the same device geometry.
RF Power Performance Evaluation of Surface Channel Diamond MESFET
Authors: Rossi Maria Cristina , Calvani Paolo , Conte Gennaro , Camarchia Vittorio , Cappelluti Federica , Ghione Giovanni , Pasciuto Benedetto , Limiti Ernesto , Dominijanni Donatella , Giovine Ennio
Published: March 2010

Large-signal radiofrequency performances of surface channel diamond MESFET fabricated on hydrogenated polycrystalline diamond are investigated. The adopted device structure is a typical coplanar two-finger gate layout, characterized in DC by an accumulation-like behavior with threshold voltage Vt ∼ 0-0.5 V and maximum DC drain current of 120 mA/mm. The best radiofrequency performances (in terms of fT and fmax) were obtained close to the threshold voltage. Realized devices are analyzed in standard class A operation, at an operating frequency of 2 GHz. The MESFET devices show a linear power gain of 8 dB and approximately 0.2 Wmm RF output power with 22% power added efficiency. An output power density of about 0.8 W/mm can be then extrapolated at 1 GHz, showing the potential of surface channel MESFET technology on polycrystalline diamond for microwave power devices.
Nanodiamonds Particles as Additives in Lubricants
Authors: Michail Ivanov G. , S Pavlyshko V. , Ivanov D. M. , Petrov Igor , McGuire Gary , Shenderova Olga
Published: March 2010

In the current work we report results of tribological testing of stable colloidal dispersions of detonation nanodiamond (DND) and polytetrafluoroethylene (PTFE) in mineral oil based greases as well as in polyalphaolefin (PAO) oil. Testing has been performed on these formula-tions using ring-on-ring, shaft/bushing and four ball test techniques. The test results demon-strated significant improvements for tribological characteristics (friction coefficient, extreme pressure failure load and diameter of wear spot) for certain formulations. A strong synergistic effect when using a combination of DND/PTFE additives was observed by a sharp decrease of friction coefficient. It was also demonstrated that using DND with smaller aggregate size (10nm versus 150nm) resulted in better lubricating performance of PAO-based composition.
Substitutionally-Functionalized vs Metallicity-Selected Single-Walled Carbon Nanotubes: A High Energy Spectroscopy Viewpoint
Authors: Ayala Paola , Kramberger Christian , Miyata Yasumitsu , De Blauwe Katrien , Shiozawa Hidetsugu , Follath Rolf , Kataura Hiromichi , Pichler Thomas
Published: March 2010

The unique one-dimensional electronic and optical properties attributed to single-walled carbon nanotubes (SWCNTs) are mainly related to the peculiar local arrangement of sp2 hybridised carbon atoms. This structural configuration gives raise to interesting features, which can be identified with various spectroscopic techniques. In the case of SWCNTs, high energy spectroscopy methods represent effective key tools to analyse the modifications of the underlying basic correlation effects in the bonding environment, the charge transfer between functionalized nanotubes, and on-wall doping. More specifically, in this article we review the shape of the C1s photoemission (PES) response related to the density of states (DOS) of the valence band (VB) in SWCNTs and its changes upon on-wall functionalization and metallicity-sorting. In the last, the progress in the identification of changes in the site selective valence-band electronic structure is clarified in detail.
Synthesis of High Quality Few Layer Graphene Sheets in Large Quantities by Radio Frequency Chemical Vapor Deposition
Authors: Dervishi Enkeleda , Li Zhongrui , Watanabe Fumiya , Shyaka Jimmy , Biswas Abhijit , Courte Aurelie , Umwungeri Jean Luc , Biris Alexandru R. , Biris Alexandru S.
Published: March 2010

This work reports a low-cost method for large scale production of high quality graphene via radio-frequency chemical vapor deposition. High quantities of graphene were successfully synthesized on the Fe-Co/MgO (2.5:2.5:95 wt.%) catalytic system utilizing acetylene as a hydrocarbon source at 1000 °C. The as-produced graphene sheets were purified in a single step by washing with a diluted hydrochloric acid solution under sonication. Next, they were thoroughly characterized by microscopy, spectroscopy, and X-Ray diffraction. Advanced transmission electron microscopy and atomic force microscopy analyses have indicated the formation of 3-5 layered graphene nanosheets. Thorough analyses by Raman spectroscopy were also performed demonstrating the presence of high quality and few-layer graphene samples. This low cost and highly reproducible method may be applied in a straightforward way to produce large quantities of graphene for various advanced applications.
CNTFET Gas Sensors Using SWCNT Mats: Method for Low-cost Fabrication, Solution to Improve Selectivity, Experimental Results using Interfering Agents
Authors: Bondavalli Paolo , Gorintin Louis , Legagneux Pierre , Pribat Didier , Caillier Laurent , Simonato Jean-Pierre
Published: March 2010

The first paper showing the great potentiality of Carbon Nanotubes Field Effect transistors (CNTFETs) for gas sensing applications was published in 2000 [1]. It has been demonstrated that the performances of this kind of sensors are extremely interesting: a sensitivity of around 100ppt (e.g. for NO2 [2]) has been achieved in 2003 and several techniques to improve selectivity have been tested with very promising results [2]. The main issues that have not allowed, up to now, these devices to strike more largely the market of sensors, have been the lack of an industrial method to obtain low-cost devices, a demonstration of their selectivity in relevant environments and finally a deeper study on the effect of humidity and the possible solutions to reduce it. This contribution deals with CNTFETs based sensors fabricated using air-brush technique deposition on large surfaces. Compared to our last contribution [3], we have optimized the air-brush technique in order to obtain high performances transistors (Log(Ion)/Log(Ioff) ∼ 5/6) with highly reproducible characteristics : this is a key point for the industrial exploitation. We have developed a machine which allows us the dynamic deposition on heated substrates of the SWCNT solutions, improving dramatically the uniformity of the SWCNT mats. We have performed tests using different solvents that could be adapted as a function of the substrates (e.g. flexible substrates). Moreover these transistors have been achieved using different metal electrodes (patented approach [4]) in order to improve selectivity. Results of tests using NO2, NH3 with concentrations between ∼ 1ppm and 10ppm will be shown during the meeting.
A Figure of Merit for Transparent Conducting Nanotube Films
Authors: Pekker Aron , Kamaras Katalin , Nemes Norbert , Garcia-Hernandez Mar
Published: March 2010

We propose a wavelength-dependent figure of merit for transparent conducting nanotube networks, composed of the sheet resistance and the optical density. We argue that this would be more useful than previous suggestions, because it relies on more realistic assumptions regarding the optical parameters of real nanotubes.
Electrically Conductive CNT/PTFE Composite Film for Corrosion Resistant Coating on Bipolar Plate of Fuel Cell
Authors: Show Yoshiyuki , Takahashi K. , Nishimura R. , Kohara K. , Fukami Y. , Murata H.
Published: March 2010

Composite film of carbon nanotube (CNT) and polytetrafluoroethylene (PTFE) was formed with despersion fluid of CNT and PTFE. The film showed high electrical conductivity in the range of 5-13S/cm. This conductive film was applied on the stainless steel bipolar plate for the polymer electrolyte membrane fuel cell (PEMFC) as anticorrosion film. This coating decreased the contact resistance between the surface of bipolar plate and the membrane electrode assembly (MEA) of the PEMFC. Therefore, the output power of the fuel cell was increased by 1.6 times.
Catalyst-Free GaN Nanowire Nucleation: Correlation of Temperature-Dependent Nanowire Orientation and Growth Matrix Changes
Authors: McElroy Kaylee , Ayres Virginia M , Bieler Thomas R. , Jacobs Benjamin W , Crimp Martin A
Published: March 2010

Growth orientation and type of internal structures are both observed to change abruptly as a function of growth temperature in catalyst free growth of gallium nitride nanowires. In the present work, corresponding temperature-dependent changes in the growth matrix substrate that can affect the availability of nucleation sites and influence the reactivity of constituent adatom materials in catalyst-free nanowire growth are investigated. The influence of Ga vapor pressure and an abrupt change in the availability of single versus molecular adatom constituents is identified as a possible controlling parameter.
Shape Control and Emission-wavelength Extension of InP-based InAsSb Nanostructures
Authors: Lei Wen , Tan H. H. , Jagadish C.
Published: March 2010

This paper presents a study on the shape control and emission wavelength extension of InP-based InAsSb nanostructures. InGaAs buffer, combined with low growth temperature and medium V/III ratio, provides an effective approach to fabricate InAsSb QDs. By using InGaAsSb sandwich layer to serve as both strain reducing layer and metamorphic buffer layer, the emission wavelength of InAsSb QDs can be extended well beyond 2um, which is very useful for their application as mid-infrared emitters.
Mid-infrared Electroluminescence from Surface Plasmon Coupled InAs Quantum Dots
Authors: Passmore Brandon , Adams David , Ribaudo Troy , Wasserman Dan , Lyon Stephen , Shaner Eric
Published: March 2010

The mid-infrared spontaneous emission from intersubband energy transitions in self-assembled InAs quantum dots is demonstrated with plasmonic top contact output couplers. Electrically pumped devices having subwavelength meshes designed to exhibit extraordinary optical transmission from 9 – 12 μm are measured and compared to a reference device with an open area contact. From additional patterning on the top contact, the signal-to-noise ratio was 4 times greater than the reference device. Beyond simply filtering the emission spectra of the quantum dot material, an emission null is observed which we link to the dots being in the near field region of the plasmonic coupler.
Fascinating World of Nanomaterials, Applications and Technology Hurdles in Commercial Production
Authors: Hullavarad Shiva , Hullavarad Nilima
Published: March 2010

Nanoparticles, nanowires, nanorods and other kinds of nanostructures have been of great interest to scientific field. Semiconducting nanowires have attracted much attention due to the fact that reduced dimensional confinement of electrons, holes and photons make them particularly attractive as potential building blocks for nanoscale optoelectronic devices, highly quantum efficient lasers and non-linear optical converters. It is generally accepted that the low dimensional structures (where the size in one direction is equivalent to or smaller than the de Broglie wavelength) are useful materials for investigating the dependence of electrical and thermal transport or mechanical properties on the dimensionality and quantum confinement. Nanomaterials also play an important role as functional units in fabricating the electromechanical devices. Semiconductor nanostructures of different materials and shapes are investigated due to their size dependent electronic properties observable at dimensions comparable to or less than Bohr radius of exciton in these materials. Especially various oxides and sulphides have generated interests in variety of applications. In this paper, the recent progress in various nanostructures, paradigms in implementation and technology hurdles in implementing nanostructures are discussed
Moving Nanotechnology Toward the Market: Business Strategy and IP Management in the Value Chain
Authors: Giordani Sara
Published: March 2010

The idea that nanotechnologies have the potential to transform different industry sectors and impact on various market segments is receiving large support and contributions from international economic organisations’ reports, research institutions’ newsletters, academics’ and management scholars’ papers and consulting firms’ articles.
The patent landscape, with its burgeoning number of patent filings, and the patent offices worldwide reporting on the increasing number of patent applications in the nanotechnology field, appear as complementary indicators of this trend. As nanosciences research and engineering efforts made feasible the attractive promise of closing the gap between research and industrialization, research outcomes and applications were protected for exclusive exploitation via patent filing and patent portfolio building.
Different Cell Responses on Biologically Inspired Nano-coatings for Orthopedic Applications
Authors: Zhang Lijie , Hemraz Usha D. , Fenniri Hicham , Webster Thomas J
Published: March 2010

Various bone defects, caused by trauma, disease or age-related degeneration, represent a crucial clinical problem all over the world. However, traditional implant materials may cause many complications after surgeries, leading to intense patient pain. Thus, the objective of this in vitro study was to develop a biologically inspired coating on conventional titanium with materials that possess biomimetic nanostructured architectures and favorable surface chemistry. Specifically, self-assembled rosette nanotubes (RNTs) functionalized with various osteogenic peptides and amino acids (such as lysine-arginine-serine-arginine (KRSR), arginine-glycine-aspartic acid (RGD) and lysine (K)) were designed as coatings. Results revealed excellent cytocompatibility properties of these RNTs towards enhancing osteoblast (bone forming cell) and endothelial cell adhesion. In particular, KRSR and RGD functionalized RNTs coated on titanium promoted the greatest osteoblast densities when compared to uncoated titanium. In addition, the KRSR functionalized RNTs selectively improved osteoblast adhesion but not endothelial cell adhesion when coated on titanium. From this study, it can be speculated that the biologically inspired nanotubular structure and osteogenic surface chemistry of RNTs altered the surface properties of titanium to transform it into a more favorable environment for orthopedic applications.
The Impact of Substrate Topography on Cell Filopodia Extension and Cell Spreading
Authors: Yang Lei , Stout David Andrew , Liang Amy , Webster Thomas J
Published: March 2010

Recent research has found that cell spreading on materials affects cell functions, including proliferation and differentiation. Also, cell spreading is related to filopodia extension which has been shown to be dependent on substrate topography. To better understand this correlation, live-cell imaging was used here to investigate osteoblast (bone forming cell) filopodia extension and cell spreading on two different kinds of diamond. Nanocrystalline diamond (NCD) and submicron crystalline diamond (SMCD) were fabricated to possess similar surface chemistry but different topographies, consisting of nanoscale spherical grains in NCD and submicron polyhedral grains in SMCD. The filopodia extension and cell expansion results showed that cells on nanoscale topographies had faster filopodia extension and greater expansion area than on submicron topographies. Results indicated that substrate topography has an impact on cell filopodia extension and cell spreading, and NCD promoted filopodia extension and cell expansion better than SMCD.
Nanoengineering of Immune Cell Function
Authors: Shen Keyue , Milone Michael C , Dustin Michael L. , Kam Lance Cameron
Published: March 2010

T lymphocytes are a key regulatory component of the adaptive immune system. Understanding how the micro- and nano-scale details of the extracellular environment influence T cell activation may have wide impact on the use of T cells for therapeutic purposes. In this article, we examine how the micro- and nano-scale presentation of ligands to cell surface receptors, including microscale organization and nanoscale mobility, influences the activation of T cells. We extend these studies to include the role of cell-generated forces, and the rigidity of the microenvironment, on T cell activation. These approaches enable delivery of defined signals to T cells, a step toward understanding the cell-cell communication in the immune system, and developing micro/nano- and material- engineered systems for tailoring immune responses for adoptive T cell therapies.
Air Independent Fuel Cells Utilizing Borohydride and Hydrogen Peroxide
Authors: Urian Richard Craig
Published: March 2010

The US Navy continues to pursue electrochemical power sources with high energy density for low rate, long endurance air independent, undersea applications. The use of borohydride and hydrogen peroxide as fuel and oxidant sources offer several different fuel cell configurations; each with their own advantages and technical challenges.

The direct electro-oxidation and electro-reduction of sodium borohydride and hydrogen peroxide is conceptually a simple system. In the fuel cell configuration where Nafion 115 is used and both electrolyte solutions are allowed to have a pH >8, high efficiencies (>70%) can be maintained with careful control of the concentration of reactants in the flowing electrolyte, choice of catalyst and electrode architecture. The onset of borate precipitation is offset by diffusion of water created by the osmotic pressure between anode and cathode.

The direct liquid/liquid system has the potential to be a “2V” system if the pH of the hydrogen peroxide catholyte is maintained at a pH<1. In order to make this a viable system for Naval applications, the amount of acid used in the catholyte to establish the desired pH needs to be minimized. The key enabling technology is the development of a suitable anion exchange membrane. The characteristics of the anion membrane are: 1) conduct hydroxides generated at the cathode to the anode in order to minimize its concentration buildup in the catholyte solution and to maintain the desired pH.<1, 2) minimize hydrogen peroxide cross-over and 3) afford high ionic conductivity.

Efforts are currently underway to improve the understanding of the reaction mechanism of borohydride at the catalyst surface and to identify membranes with higher ionic conductivity. These efforts have been identified as critical paths for the successful development of a liquid/liquid borohydride/hydrogen peroxide fuel cell.
Scanning Force Microscopy Study of Phase Segregation in Fuel Cell Membrane Materials as a Function of Solvent Polarity and Relative Humidity
Authors: Hawley Marilyn , Kim Yu Seung , Hjelm Rex P.
Published: March 2010

Scanning force microscopy (SFM) phase imaging provides a powerful method for directly studying and comparing phase segregation in fuel cell membrane materials due to different preparation and under different temperature and humidity exposures. In this work, we explored two parameters that can influence phase segregation: the properties of the solvents used in casting membrane films and how these solvents alter phase segregation after exposure to boiling water as a function of time. SFM was used under ambient conditions to image phase segregation in Nafion samples prepared using five different solvents. Samples were then subjected to water vapor maintained at 100°C for periods ranging from 30 minutes to three hours and re-imaged using the same phase imaging conditions. SFM shows what appears to be an increase in phase segregation as a function of solvent polarity that changes as a function of water exposure.
Effects of Different Carbon Nanotube Supported Catalysts on Methanol and Ethanol Electro-Oxidation
Authors: Sanganna Gari Raghavendar Reddy , Li Zhou , Dong Lifeng
Published: March 2010

In this work, Pt and Pt-Ru nanoparticles were synthesized on both single-walled carbon nanotubes (SWCNTs) and multi-walled carbon nanotubes (MWCNTs). Effects of different nanotube supports on electrocatalytic activity of Pt and Pt-Ru nanoparticles for methanol and ethanol oxidations were investigated using cyclic voltammetry and electrochemical impedance spectroscopy. In comparison to MWCNTs, SWCNT supported Pt and Pt-Ru catalysts demonstrate better electrocatalytic activities in terms of forward peak current density, the ratio of forward peak current density to reverse peak current density, and charge transfer resistance. This study indicates that SWCNTs can serve as effective catalyst supports for both direct methanol and ethanol fuel cells.
PdCo Nanoparticles Formation at HOPG and High Surface Area Carbon Support Vulcan XC-72R
Authors: Arroyo-Ramirez Lisandra , Miras Haralampos N , Raptis Raphael G , Cabrera Carlos Raul
Published: March 2010

Thermal reduction of PdCo molecular precursors may lead to the controlled production of nanoparticles on high surface area carbon supports that can be used as methanol tolerant oxygen reduction catalysts for direct methanol fuel cells (DMFC). Following this concept, a single molecular precursor source was used for the synthesis of bimetallic nanoparticles on highly oriented pyrolytic graphite (HOPG) and Vulcan (VC) carbon supports. Nanostructural formation of palladium-cobalt on highly ordered pyrolytic graphite (HOPG) was study by AFM, SEM and voltammetry. The relative humidity during precursor deposition was used to control the rings self-formation on HOPG surfaces. Palladium and palladium-cobalt nanoparticles were also formed on high surface area carbon support (Vulcan XC-72R) by thermal reduction and characterized by TEM. The Pd/VC and PdCo/VC nanoparticles were tested for the oxygen reduction reaction (ORR) with and without methanol. The Pd-based catalysts have ORR activity and high methanol tolerance.
Green Synthesis of Platinum-encapsulated Nickel Nanocatalyst and Its Microstructure Evaluation
Authors: Medina-Ramirez Iliana , Pan Xu-Bin , Bashir Sajid , Liu Jingbo Louise
Published: March 2010

Platinum (Pt) is the most efficient and highly utilized electrocatalsyt; however its high cost hinders its widespread use as a stand-alone catalyst. To remedy this problem, a nickel (Ni) encapsulated by Pt (NiⓔPt) nanocatalyst was fabricated using a cost-effective green colloidal method. The NiⓔPt nanoparticles (NPs) were then characterized using transmission electron microscope (TEM) equipped with X-ray energy dispersive spectroscopy (EDS), and X-ray powder diffraction (XRD) to determine the particle size distribution, morphology, elemental composition, and crystalline phase structure. The surface energetic was also measured using ZetaPALS™ to identify the stability of the colloidal suspension.
Investigation of Interaction of Hydrogen with Defects in Zirconia
Authors: Melikhova Oksana , Kuriplach Jan , Cizek Jakub , Prochazka Ivan , Brauer Gerhard , Anwand Wolfgang
Published: March 2010

In the present work we study theoretically hydrogen incorporated into several positions in the zirconia cubic and tetragonal lattices. These are positions in the interstitial space and in the zirconium vacancy (VZr). We examine the structure of such configurations and for VZr-related defects we also calculate selected positron characteristics in order to assess their capability of trapping positrons. It is shown that hydrogen atoms do not prefer to stay in the center of the largest interstitial space nor of VZr and they rather tend to create bonds with neighboring oxygen atoms. The positron lifetime of the VZr+1H complex is shorter than that for non-decorated VZr and positron trapping in VZr+1H complexes could, in principle, explain experimental lifetime data.
SURFACE SEGREGATION STUDIES OF SOFC CATHODES: COMBINING SOFT X-RAYS AND ELECTROCHEMICAL IMPEDENCE SPECTROSCOPY
Authors: Miara Lincoln , Piper Louis , Davis Jacob Nathan , Saraf Laxmikant , Kaspar Tiffany , Basu Soumendra , Smith Kevin E. , Pal Uday B. , Gopalan Srikanth
Published: March 2010

A system to grow heteroepitaxial thin-films of solid oxide fuel cell (SOFC) cathodes on single crystal substrates was developed. The cathode composition investigated was 20% strontium-doped lanthanum manganite (LSM) grown by pulsed laser deposition (PLD) on single crystal (111) yttria-stabilized zirconia (YSZ) substrates. By combining electrochemical impedance spectroscopy (EIS) with x-ray photoemission spectroscopy (XPS) and x-ray absorption spectroscopy XAS measurements, we conclude that electrically driven cation migration away from the two-phase gas-cathode interface results in improved electrochemical performance. Our results provide support to the premise that the removal of surface passivating phases containing Sr2+ and Mn2+, which readily form at elevated temperatures even in O2 atmospheric pressures, is responsible for the improved cathodic performance upon application of a bias.
Liquid Encapsulation by Bonding-in-Liquid Technique
Authors: Okayama Yoshiyuki , Nakahara Keijiro , Ninomiya Takeshi , Matsumoto Yasuaki , Miki Norihisa
Published: March 2010

We propose and demonstrate Bonding-in-Solution Technique (BiST) for encapsulation of liquid in MEMS devices. Liquid encapsulation enables innovative MEMS devices with various functions, such as hydraulic displacement amplification and scanning mirrors. Interfusion of air bubbles and leakage of the encapsulated liquid must be averted not to deteriorate device performances. Several liquid encapsulation processes have been proposed, such as parylene deposition and polymer thermal bonding. However, they involve vacuum and/or thermal processes and cannot be applied to volatile liquids. In BiST, two structural layers are passively aligned and brought into contact in solution, where the encapsulation cavities are uniformly filled up with the liquid without air bubbles. A UV-curable resin is used as an adhesive that does not require heat or vacuum environment but UV to bond the two layers. The detail processes of BiST are (a)UV-curable adhesive resin is coated onto the bonding surface of a structural layer. The layer contains not only encapsulating cavities but also concave-shaped structures for the following passive alignment. (b) The other layer with convex-shaped structures is brought into contact in solution, when the two layers are passively aligned by matching concave and convex structures. (c) UV light is irradiated and the two layers are permanently bonded while the contact is maintained by the jig. We successfully achieved encapsulation of DI water and glycerin in PDMS and silicon structural layers. No liquid remains in the bonding interface. Since conventional aligners are not applicable to BiST, we experimentally evaluated the accuracy of the passive alignment process in solution that makes use of matching concave and convex structures. We used a PDMS layer with cylinders (concave) and a silicon layer with cavities (convex) to evaluate the alignment in BiST. The height and depth of the cylinders and cavities are designed such that the PDMS cylinders elastically deform when the two layers are brought into contact. The elastic averaging enables the passive alignment of the two layers. We investigated the bonding accuracy with respect to the number of pairs of concave/convex structures and the height of PDMS cylinders while in contact. The bonding accuracy improved as the number of pairs increased while the height of PDMS cylinders did not show a correlation. The alignment accuracy of 5μm in BiST was achieved with 12 pairs of the concave/convex structures. The ultimate goal of our research is to develop innovative MEMS devices with encapsulated liquid, such as a hydraulic displacement amplification mechanism applicable to a tactile display. Glycerin was encapsulated by largely-deformable-PDMS thin membranes and silicon cavities by using BiST. The displacement at the input was successfully amplified at the output associated with the ratio of the cross-sectional areas.
Extreme Phonon Softening in Laser-excited Bismuth – Towards an Inverse Peierls-transition
Authors: Lu Wei , Nicoul Matthieu , Shymanovich Uladzimir , Tarsevitch Alexander , Kammler Martin , Horn-von Hoegen Michael , von der Linde Dietrich , Sokolowski-Tinten Klaus
Published: March 2010

Large amplitude coherent optical phonons have been investigated in laser-excited Bismuth by means of femtosecond time-resolved X-ray diffraction. For absorbed laser fluences above 2 mJ/cm2, the experimental data reveal an extreme softening of the excited A1g-mode down to frequencies of about 1 THz, only 1/3 of the unperturbed A1g-frequency. At even stronger excitation the measured diffraction signals no longer exhibit an oscillatory behavior presenting strong indication that upon intense laser-excitation the Peierls-distortion, which defines the equilibrium structure of Bismuth, can be transiently reversed.
Ultrafast Tuning of Magnetization Precession and Magnetic Anisotropy in Thin Iron Films
Authors: Carpene Ettore , Mancini Eduardo , Dazzi Daniela , Dallera Claudia , Puppin Ezio , De Silvestri Sandro
Published: March 2010

We have developed an experimental set-up based on time-resolved Magneto-Optical Kerr Effect (MOKE) that allows to retrieve the vectorial magnetization dynamics in thin films with sub-picosecond resolution. This method has been exploited to measure the variations of the magnetization (modulus and orientation) induced by an ultrashort laser pulse. The initial demagnetization is established at the electronic level within a few hundreds of femtoseconds through electron-magnon excitations. The subsequent dynamics is characterized by a precessional motion on the 100 picosecond time-scale, around an effective, time-dependent field. Following the full dynamics of the magnetization, we have unambiguously determined the temporal evolution of the magneto-crystalline anisotropy, providing the clear experimental evidence that the precession is triggered by the rapid, optically-induced misalignment between the magnetization vector and the effective field. This method provides a simple and widely applicable way to study both magnetization and anisotropy in the sub-picosecond regime and therefore to unravel the mechanisms underlying the ultrafast evolution of the spin order in magnetic media.
Using a Low Cost Indentation Apparatus for the Study of Mechanical Properties of Thermoinsulating Materials and its Utilization in the Laboratory Practice of Students
Authors: Tsihouridis Charilaos A. , Polatoglou Hariton M.
Published: March 2010

In the present work we describe an experimental apparatus of very low cost , aiming at the experimental study of the mechanical properties of solid materials, using the method of indentation. The measurements allow, through a simple analysis, the quantitative determination of the materials' hardness and bulk modulus. A very important class of commonly used materials, namely thermoinsulating materials, is proposed for a case study. The method can furthermore be used to demonstrate the elastic and the plastic behavior of materials. The educational exploitation of the specific apparatus at a technical high school class in Larissa (Greece) and at a university physics students' laboratory practice on the subject of mechanical properties of materials are also described. The responses of the students on the whole process, and specifically on observations related to the pedagogical-educational aspects (active participation, challenge of interest, easiness of measurements, easiness of processing experimental data), as well as related to metrological aspects (uncertainty of measurements), were very positive and are also presented and discussed.
Academic/Industrial/NSF Collaborations at the IBM Almaden Research Center-Benefits from Dr. Marni Goldman's Involvement
Authors: Wade Charles G. , Miller Dolores C. , Black Kristin , Frank Curtis , Pesek Joseph
Published: March 2010

College undergraduate and high school teacher internships are significant factors in materials science education. Traditionally, NSF-supported internships are done in academia. The NSF-supported academic/industrial internship programs involving Stanford University, San Jose University and the IBM Almaden Research Center extend the impact by the inclusion of an industrial research component. Internships through San Jose State University have existed since 1994 under a variety of NSF grants, most recently with NSF-REU support for undergraduate internships. Internships through Stanford university have existed since 1995 through an NSF Materials Research Science and Engineering Center, the “Center for Polymer Interfaces and Macromolecular Interfaces” (CPIMA). In these programs, the interns become members of an existing research group for 10 weeks and have their own project under a mentor. The interns attend a weekly seminar series on industrial research frontiers, a career day, a Graduate Record Examination workshop, a graduate school workshop, and tours of industrial research labs. Every participant presents a poster at an internal technical meeting at IBM at the end of the summer. For the industrial internships at IBM, the research is publishable but closely related to a technical area important to IBM. While the undergraduate and teacher internship programs are the major components of educational outreach of CPIMA, many other projects have been pursued, including public science, programs with local high schools, and science outreach to local community colleges. Dr. Marni Goldman was the Director of Educational Outreach for CPIMA from 2000 until her death in 2007, and she started many of the educational projects and programs. She was especially interested in diversity and initiated an internship program for students who are disabled. The programs will be reviewed and her contributions emphasized.
Introduction of Role Playing to a Research Ethics Module for the Undergraduate
Authors: Miller Dolores C. , Houle Frances A. , Stemwedel Janet , Pesek Joseph , Wade Charles
Published: March 2010

As part of the NSF supported SUMMIT (San Jose State University/IBM Almaden Research Center collaboration) REU and CPIMA (Stanford University/Almaden) SURE undergraduate internship programs we have developed a workshop that emphasizes the scientific community's dependence on ethical behavior for its success and advancement at this nascent stage of a scientific career. We have successfully introduced open-ended role playing based on recent real life ethics cases as reported in the scientific news to a foundation presentation based on the APS Ethics and Professional Conduct Guidelines for Physicists. The goal is to foster discussion of complex cases and their effects not only on the protagonists but on the scientific community.
A Novel Route for Preparation of Transparent and Superhydrophobic Silica Aerogels
Authors: Wu Guo-you , Cheng Xuan , Yu Yu-xi , Zhang Ying
Published: March 2010

Silica aerogels were synthesized via sol-gel processing followed by a two-step surface modification and ambient pressure drying, using methyltrimethoxysilane (MTMS) and trimethylchlorosilane (TMCS)/ethanol/n-hexane as surface modification agents. The transparent silica aerogels possessed the porosities, densities and specific surface areas in the range of 87.7–92.3%, 0.27–0.17 g·cm-3 and 852–1005 m2·g-1, respectively. The SEM and HRTEM analysis revealed the three-dimensional nanoporous structure of the silica aerogels. The presence of –CH3 functional groups on the surface of silica particles as indicated by the FTIR spectra was further confirmed by two visible exothermic peaks at 310 and 450–500 °C from the DTA curve. In addition, the silica aerogels were superhydrophobic with the contact angle as high as 160°.
Marrow Stromal Cell Reponse to Fiber-Reinforced Laminated Nanocomposites
Authors: Ma Junyu , Xu Weijie , Jabbari Esmaiel
Published: March 2010

Current biomaterials as a scaffold for bone regeneration are limited by the extent of degradation concurrent with bone formation, mechanical strength, and the extent of osteogenic differentiation of marrow stromal cells migrating from the surrounding tissues. In this project, a novel laminated nanocomposite scaffold is fabricated, consisting of poly (L-lactide ethylene oxide fumarate) (PLEOF) hydrogel reinforced with poly (L-lactide acid) (PLLA) electrospun nanofibers and hydroxyapatite (HA) nanoparticles. The laminated nanocomposites were fabricated by dry-hand lay up technique followed by compression molding and thermal crosslinking. The laminated nanocomposites were evaluated with respect to mechanical strength and osteogenic differentiation of marrow stromal (BMS) cells. Laminates showed modulus values much higher than that of hydrogel or fiber. The effect of laminated nanocomposites on osteogenic differentiation of BMS cells was determined in terms of ALPase activity and calcium content. Our results demonstrate that grafting RGD peptide to a PLEOF/HA hydrogel reinforced with PLLA nanofibers synergistically enhances osteogenic differentiation of BMS cells.
Terminal phosphate group influence on DNA - TiO2 nanoparticle interactions
Authors: Rice Zachary , Cady Nathaniel C , Bergkvist Magnus
Published: March 2010

Immobilization of DNA/RNA, onto various metal and metal oxide surfaces is of great importance for the development of future microarray, gene mapping, DNA sequencing, nanoparticle targeting, and sensor applications. Attachment of DNA to solid interfaces typically occurs through either electrostatic interactions or covalent bonds to functional groups introduced to nucleic acid termini. Previously, we and others have demonstrated that alkanephosphates and terminal phosphate groups present on nucleic acids play an important role in the interaction with group IV metal oxides such as zirconium and hafnium, providing a stable linkage to the surface. Titanium dioxide (TiO2), which is frequently employed in various nanoscale applications, belongs to the same group and similar interactions with phosphate are expected. Various adsorption studies have demonstrated binding of nucleic acids to TiO2 surfaces, although the influence of terminal phosphate versus electrostatic interaction (via the DNA/RNA backbone) on the surface interaction is unclear. The research presented here investigates the effect of nucleic acid length, presence of terminal phosphates, and differences between dsDNA and ssDNA on their binding to TiO2 nanoparticles. TiO2 nanoparticles (20 nm) were used to study the adsorption of Lambda DNA (˜48 kbp), and shorter (21 bp) ssDNA and dsDNA oligonucleotides with and without a 5’ phosphate group. Initial adsorption of DNA to nanoparticles was calculated via UV absorption. Results showed that all types of nucleic acids (Lamda DNA, ssDNA and dsDNA) initially bind to nanoparticles, independent of molecular weight single/double strandedness, or phosphorylation state. The total amount of DNA initially adsorbed to nanoparticles (ng/particle) differs between ssDNA and dsDNA, as well as the length of the DNA used. These results show that nucleic acid interactions with TiO2 nanoparticles are not dependent upon the presence of a terminal phosphate group. These results provide valuable data for future applications based on DNA-nanoparticle constructs including nanoelectronics, photovoltaics, and biotemplated synthesis of semiconducting materials.
A Novel Bioactive Ceramic Coating for Improved Fixation of Orthopedic Implant
Authors: El-Ghannam Ahmed , . Aniket
Published: March 2010

Electrophoretic deposition (EPD) coating of medical grade Ti-6Al-4V substrate with a novel silica-calcium phosphate nano-composite (SCPC) in the particle size range 50 nm-5 μm has been described. The influence of EPD parameters and thermal treatment on the coating homogeneity, thickness and adhesion strength has been studied. SEM analyses showed that EPD carried out in 5% (w/v) SCPC/ethanol suspension at 50 V produced a homogeneous coating on passivated Ti alloy discs. Tensile tests carried out to evaluate the adhesion strength at the ceramic/metal interface showed that the SCPC coating layer developed adhesion strength of 47 ± 4 MPa with Ti alloy after thermal treatment at 800 °C for 1 hr. SEM – EDX analyses of the fracture surface revealed that the presence of SCPC layer on the surface of the Ti alloy indicating high interfacial stability. Upon immersion of the SCPC-coated Ti alloy substrate in PBS, a surface biological hydroxyapatite layer was deposited suggesting bone bonding ability. The successful coating of SCPC on the Ti-6Al-4V has the potential to stimulate rapid fixation and lower stress shielding by enhancing the bone bonding ability of the implant.
Biomimetic Nanostructured Surfaces with Designer Mechanics and Geometry for Broad Applications
Authors: Epstein Alexander K , Aizenberg Joanna
Published: March 2010

A powerful fabrication platform for a wide range of biomimetic, high-aspect-ratio nanostructured surfaces is introduced. The principles of soft lithography are extended into a double-mold replication process, whereby a master topography is mapped onto an elastomeric inverse mold and replicated in arbitrary multiple material and stiffness gradients, and an array of modified geometries. Control of geometry via deformation of the inverse mold and control of stiffness via prepolymer mixing are discussed. New capabilities enabled by our approach include biomimetic actuation/sensor arrays with programmable biases, precisely tunable mechanical and geometric properties for optical or wetting applications, and flexible curved substrates. Indeed, flexibly anchored ciliary high-aspect-ratio nanostructures are now possible, and a proof-of-principle is described.