bluuebunny/crossref_metadata_2025 huggingface dataset:
Surface-Enhanced Infrared Absorption and Raman Scattering of Adsorbate Molecules on Self-assembled Au Nanorods
Authors: Tay Li-Lin , Hulse John , Rowell Nelson , Fraser Jeff , Huang Ping-Ji
Published: September 2011

The localized surface plasmon resonance (LSPR) is a collective oscillation of conduction electrons confined in metal nanostructures and is largely responsible for surface enhanced spectroscopies. Surface enhanced Raman scattering (SERS) is the best known and most widely applied example of such a surface enhanced spectroscopy. Although closely related and complementary to SERS, surface enhanced infrared absorption (SEIRA) spectroscopy requires more careful engineering of the LSPR of metal nanostructures so that the resonance is within the mid-infrared region. In this study, we demonstrate the use of gold nanorods (Au NR) as a suitable substrate capable of sustaining strong SEIRA spectroscopy. Adsorbate saturated Au NR typically exhibit Fano-type resonances in their SEIRA spectra obtained using reflectance FTIR. Such line asymmetry occurs due to the coupling of the relatively sharp molecular vibrations to the broad continuum of the LSPR resonance of the aggregated Au NR.
Development of the Grain Size Distribution During the Crystallization of an Amorphous Solid
Authors: Bill Andreas , Bergmann Ralf B.
Published: September 2011

We present an overview of the theory developed over the last few years to describe the crystallization of amorphous solids. The microstructure of the crystallizing solid is described in terms of the grain size distribution (GSD). We propose a partial differential equation that captures the physics of crystallization in random nucleation and growth processes. The analytic description is derived for isotropic and anisotropic growth rates and allows for the analysis of different stages of crystallization, from early to full crystallization. We show how the timedependence of effective nucleation and growth rates affect the final distribution. In particular, we demonstrate that for cases described by the Kolmogorov-Avrami-Mehl-Johnson (KAMJ) model applicable to a large class of crystallization processes a lognormal type distribution is obtained at full crystallization. The application of the theory to the crystallization of silicon thin films is discussed.
Computational Study of the Electronic Performance of Cross-Plane Superlattice Peltier Devices
Authors: Jeong Changwook , Klimeck Gerhard , Lundstrom Mark
Published: September 2011

We use a state-of-the-art non-equilibrium quantum transport simulation code, NEMO-1D, to address the device physics and performance benchmarking of cross-plane superlattice Peltier coolers. Our findings show quantitatively how barriers in cross-plane superlattices degrade the electrical performance, i.e. power factor. The performance of an In0.53Ga0.47As/In0.52Al0.48As cross-plane SL Peltier cooler is lower than that of either a bulk In0.53Ga0.47As or bulk In0.52Al0.48As device, mainly due to quantum mechanical effects. We find that a cross-plane SL device has a Seebeck coefficient vs. conductance tradeoff that is no better than that of a bulk device. The effects of tunneling and phase coherence between multi barriers are examined. It is shown that tunneling, SL contacts, and coherency only produce oscillatory behavior of Seebeck coefficient vs. conductance without a significant gain in PF. The overall TE device performance is, therefore, a compromise between the enhanced Seebeck coefficient and degraded conductance.
Thermoelectric Properties of Carbon Nanotubes Added n-type CoSb3 Compound
Authors: Itoh Takashi , Tachikawa Masashi
Published: September 2011

Cobalt triantimonide compounds are well known as materials with good thermoelectric properties over temperature range of 550-900 K. For further improving thermoelectric performance, reduction of thermal conductivity is required. In this study, we attempted to disperse carbon nanotubes (CNTs) homogeneously into the n-type CoSb3 compound for lowering lattice thermal conductivity by the phonon scattering. Powders of Co, Ni, Sb and Te were blended with molar ratios of n-type Co0.92Ni0.08Sb2.96Te0.04 compound, and the compound was synthesized through a pulse discharge sintering (PDS) process. After coarsely grinding the synthesized compound, CNTs were mixed with the compound powder at different mass% (0, 0.01, 0.05 and 0.1 mass%). Then, the mixture was mechanically ground with a planetary ball milling equipment. The ground composite powder was compacted and sintered by PDS. Thermoelectric properties (Seebeck coefficient, electrical resistivity and thermal conductivity) of the sintered samples were measured. It was confirmed that the fibrous CNTs existed homogeneously in the compound matrix. The absolute value of Seebeck coefficient slightly decreased with increase of CNT content. The minimum thermal conductivity was obtained at addition of 0.01mass%CNT, and the electrical resistivity was a little increased with CNT content. The maximum ZT of 0.98 was achieved at 853 K in the 0.01mass%CNT-added sample.
Novel Lead Telluride Based Thermoelectric Materials
Authors: Wu Chun-I , Girard Steven N. , Sootsman Joe , Timm Edward , Case Eldon D. , Kanatzidis Mercouri G. , Schock Harold , Chung Duck Young , Hogan Timothy P.
Published: September 2011

PbTe-PbS materials are promising for thermoelectric power generation applications. For the composition of (Pb0.95Sn0.05Te)0.92(PbS)0.08 nanostructuring from nucleation and growth and spinodal decomposition has been reported along with thermal conductivity of approximately 1.1 W/m·K at 650 K [1]. Based on temperature-dependent measurements of electrical conductivity, thermopower, and thermal conductivity, the thermoelectric figure of merit, ZT, are ~1.5 at 650 K for cast ingots.

To develop larger quantities of material for device fabrication, advancement in the synthesis, processing and production of (Pb0.95Sn0.05Te)0.92(PbS)0.08 is necessary. Powder processing of samples is a well-known technique for increasing sample strength, and uniformity. In this presentation, we show sample fabrication and processing details of pulsed electric current sintering (PECS) processed (Pb0.95Sn0.05Te)0.92(PbS)0.08 materials and their thermoelectric properties along with the latest advancements in the preparation of these materials.
Polyethyleneimine Functionalized ZnO Quantum Dots and their Binding Interaction with Bovine Serum Albumin Protein
Authors: Joshi Prachi , Chakraborti Soumyananda , Chakrabarti Pinak , Singh Surinder P. , Ansari Z. A. , Shanker Virendra
Published: September 2011

Water stable fluorescent ZnO quantum dots (QDs) have been synthesized by wet chemical route in presence of hydrophilic capping agent polyethyleneimine (PEI) as stabilizing agent. The binding interaction of prepared ZnO QDs is studied with bovine serum albumin (BSA) protein. X-ray diffraction measurement reveals hexagonal wurtzite structure of as synthesized ZnO QDs with an average size 4-6 nm, determined using Scherer’s equation and confirmed by transmission electron microscopy (TEM). The ZnO/PEI QDs exhibit strong yellow-green emission centered at 555 nm (2.23 eV). The interaction between BSA and ZnO/PEI QDs has been studied by using spectroscopic and calorimetric methods. Static mode of tryptophan quenching in BSA by ZnO/PEI QDs indicates that a ground state complex formation is taking place between ZnO/PEI and BSA, where, the week interactions (hydrogen bonding and hydrophobic interaction) are contributing towards the stability of the complex.
Patterning Nanomaterials on Fragile Micromachined Structures using Electron Beam Lithography
Authors: Das Kaushik , Hubert Pascal , Vengallatore Srikar
Published: September 2011

Integration of nanomaterials (in the form of quantum dots, nanotubes, nanowires, nanocrystalline thin films, and nanocomposite films) with micromachined structures and devices has the potential to enable the development of microelectromechanical systems (MEMS) with enhanced functionality and improved performance. Here, we present a fabrication approach that combines spray-coating of electron beam resist with direct-write electron beam lithography to pattern nanomaterials on fragile micromachined components. Polymers and metallic structures in the form of arrays of holes, concentric circles, and arrays of lines, with critical dimensions ranging from 135 nm to 500 nm, were patterned directly on various micromachined structures including commercial metal-coated silicon microcantilevers used for atomic force microscopy, and commercial plate-mode SiC/AlN microresonators used for sensing.
Decreased Attachment of Bacteria to Lubricin Coated Intraocular Lenses
Authors: Aninwene George E. , Taylor Erik , Mei Amy , Jay Gregory D. , Webster Thomas J.
Published: September 2011

Lubricin is an amphiphilic glycoprotein that is found in the synovial fluid [1]. This protein holds promise as an anti-biofouling agent. This study investigated lubricin’s ability to prevent bacterial attachment and proliferation on intraocular lenses. The findings from this study indicated that lubricin is able to reduce the attachment of Staphylococcus aureus to poly (methyl methacrylate) intraocular lens. Lubricin coatings were confirmed on the surfaces after a 2 hour soak by changes in surface energy. Also, lubricin reduced bacterial proliferation.
Study Abroad Experiences in the Developing World: Opportunities and Challenges
Authors: LeSar Richard A. , Bryden Kenneth M.
Published: September 2011

Over the past three years the Departments of Materials Science and Engineering and Mechanical Engineering at Iowa State University have conducted a study-abroad course for ISU undergraduates in a small, isolated, village in the country of Mali, in western, sub-Saharan Africa. Most, if not all, of the people in the village live under conditions that the World Bank refers to as extreme poverty. The focus of the course is on the development of sustainable technologies that are appropriate for the people in this village and villages similar to it. Our goal is to offer students a chance to develop such technologies, in the end changing how they view engineering and their role as engineers. One of the challenges of the course is how to integrate this high value off-campus experience into the on-campus curriculum. To do this we have linked two on-campus sustainable engineering courses (sustainable engineering systems and appropriate technology design) with this study abroad course. In this paper, we discuss the course in more detail, with a focus on an assessment of how well we are meeting our objectives. We shall also discuss the challenges of holding such a course and will offer some advice for those who may wish to venture along the same path.
Mechanism of hole inlet closure in shape transformation of hole arrays on Si(001) substrates by hydrogen annealing
Authors: Hiruta Reiko , Kuribayashi Hitoshi , Sudoh Koichi , Shimizu Ryosuke
Published: September 2011

We investigated the process of the hole inlet closure in surface-diffusion-driven transformation of arrays of high-aspect-ratio holes on Si(001) substrates. The inlet gradually shrinks while keeping the circular shape because of lateral bulging of the inlet surface. We observed complicated top view morphologies reflecting the four-fold symmetry of the Si(001) surface on the inlet surface. Large {111} and {113} facets are formed in the four equivalent azimuths of the [110], while corrugated patterns arise in the four equivalent azimuths of the [100]. Atomic force microscopy observations reveal that the corrugated pattern is composed of three types of small facets, namely, {110} and two {113} in relation of the mirror symmetry. The corrugated pattern formation is due to the geometrical restriction that there is no stable facet between (001) and (010) in the [010] azimuth. The observed morphological evolution is interpreted as surface-diffusion-driven transformation under constraint of the anisotropic surface energy of Si.
SU8 / modified MWNT composite for piezoresistive sensor application
Authors: Ray Prasenjit , Seena V. , Khare Rupesh A. , Bhattacharyya Arup R. , Apte Prakash R. , Rao Ramgopal
Published: September 2011

SU-8 is being increasingly used as a compliant structural material for MEMS applications due to its interesting properties such as lower Young’s modulus and higher mechanical and thermal stability. One of the popular classes of MEMS devices is a piezoresitive microcantilever. Ultra-sensitive polymer composite cantilevers made up of SU-8 as a structural layer and 10% carbon Black in SU8 as a piezoresistive layer with lower Young’s modulus and higher gauge factor have been reported recently by our group. Higher electrical conductivity at lower concentration of conductive filler is of increased interest. Here we report a novel composite with purified multiwall carbon nanotubes (MWNT) in SU8 as a piezoresistor. MWNT were modified with octadecyl triphenyl phosphonium bromide (OTPB) in order to achieve debundled MWNT. A microcantilever device with integrated MWNT/SU-8 composite has been fabricated and characterized.
Team-based Interdisciplinary Materials Research using Image Processing
Authors: Garofano Jacquelynn , Sadowski Thomas , DaPonte John , Broadbridge Christine
Published: September 2011

There is an acute and well-documented need for image processing of microscopy data in materials science regarding, for example, the characterization of the structure/property relationship of a given materials system. In our work, image processing has been used as a framework for conducting interdisciplinary team-based research that effectively integrates programs within the Center for Research on Interface Structures and Phenomena (CRISP) Materials Research Science and Engineering Center (MRSEC), e.g. research experiences for undergraduates (REU), teachers (RET) and high school fellowships. This research resulted from a five-year long collaboration between CRISP and the Physics and Computer Science Departments at Southern Connecticut State University (SCSU). This paper will focus on the implementation of team-based research experiences as a vehicle for interdisciplinary science and education. Representative results of several of the studies are presented and discussed.
Growth and characterization of transition-metal and rare-earth doped III-nitride semiconductors for spintronics
Authors: Asahi H. , Hasegawa S. , Zhou Y.K. , Emura S.
Published: September 2011

Transition metal (Cr) and rare-earth (Dd, Dy) doped III-nitride semiconductor bulk layers and superlattice (SL) structures are grown on sapphire (0001) substrates and GaN (0001) templates by plasma-assisted molecular-beam epitaxy. For the GaGdN/GaN and InGaGdN/GaN SL and Si co-doped samples, enhancement of magnetization and magnetic moment are observed, suggesting the carrier-mediated ferromagnetism. Low temperature growth of GaGdN can increase the Gd concentration and magnetization. Results for the Dy-doped GaN as well as the GaCrN/AlN/GaCrN tunnel magneto-resistance (TMR) diodes are also described.
Conductive Nano-brush Synthesized by Physical Grafting of Conducting Polymers on Carbon Nanotube
Authors: Purohit Kaushalkumar , Mirville Maureen , Yang Sze C. , Shukla Arun , Chalivendra Vijaya B.
Published: September 2011

We report a novel method for synthesizing electrically conductive nano-brush (CNB) by physical grafting of organic conducting polymers on carbon nano tubes (CNT). The objective for this synthesis is to produce nano tubes having a CNT stem coated with flexible electronic conducting polymers. The nano-brush is to be blended into common polymers (e.g. epoxy, polyurethane, and poly(vinyl alcohol)) to form electrically conductive composite material. The flexible organic conducting polymer in CNB is a potentially sensitive electronic probe for mechanically induced nano-deformation of the composite because it is molecularly entangled with the host polymers. The electrical networks of CNB embedded in polymeric composites are potentially useful as in situ sensors for monitoring material deformation with an unprecedented level of sensitivity. The composite material is “smart” in the sense that it self-reports the structural “health” before load induced material failure.

Our method for grafting conducting polymer does not require chemical reactions with the surface atoms of the carbon nano tube. We used physical adsorption to graft electronic conducting polymer to CNT. We first synthesized a water-soluble electronic conducting polymer which is a molecular complex between poly(acrylic acid) and polyaniline. The CNT solid were dispersed and un-bundled by sonnication in the conducting polymer solution. Due to the high affinity between CNT and the conducting polymer, the surface of CNT can be fully covered with the conducting polymer. The experimental data is consistent with a structure of nano brush with high density of conducting polymers grafted on the CNT surface.
Monte Carlo Simulations of the Exchange Bias Effect in Heusler Ni50Mn37.5Sb12.5 Alloys Using Real Unit Cell
Authors: Buchelnikov Vasiliy D. , Taranenko Ivan A. , Sokolovskiy Vladimir V. , Taskaev Sergey V. , Zagrebin Mikhail A. , Entel Peter
Published: September 2011

In present work we propose a theoretical model for investigation of the exchange bias effect in Ni50Mn37.5Sb12.5 alloy. In the model, we use a three-dimensional cubic lattice with periodic boundary conditions. Also we take into account the magnetic interactions between atoms in 1st, 2nd and 3rd coordination spheres and the ferromagnetic and antiferromagnetic anisotropy terms. It is shown that the obtained theoretical temperature dependence of the exchange bias field for Ni50Mn37.5Sb12.5 alloy is close to the experimental data.
Layered and Functionally Graded Nanocomposite Thin Films with Unique Mechanical Properties
Authors: Farias Stephen L. , Breysse Patrick C. , Chien Chai-Ling , Cammarata Robert C.
Published: September 2011

A novel electrochemical deposition method for manufacturing functionally graded, oxide-dispersion strengthened metal matrix nanocomposites will be presented. Using a rotating disk electrode and depositing from an electrolyte containing a suspension of oxide nanoparticles, metal-ceramic nanocomposites have been produced. This method leads to precise control over the volume fraction of the oxide in the nanocomposite and allows for the manufacturing of compositionally uniform, periodically layered, or functionally graded structures. In the higher order structures the composition variation can be finely tuned with nanometer resolution, and the characteristic microstructural length scale (e.g., individual layer thickness) can range from microns up to millimeters. Using indentation methods, the nanocomposites are shown to display enhanced and tunable mechanical properties.
Phase diagrams of Ni2+xMn1-xGa Heusler alloys from Hubbard Hamiltonian with account of Jahn-Teller effect
Authors: Zagrebin Mikhail A. , Buchelnikov Vasiliy D. , Taskaev Sergey V. , Fedulova Natal’ya Yu.
Published: September 2011

In this work a microscopic Hamiltonian is investigated using the Hubbard model for a ferromagnet with two degenerate bands, taking into account the Jahn-Teller effect. A macroscopic free energy is obtained from the microscopic Hubbard Hamiltonian. All free energy coefficients depend on microscopic parameters: temperature T and composition x. As a result of analytical minimization of free energy, phase diagrams are numerically constructed. It is shown that at certain values of parameters on the phase diagrams there are thermodynamic paths which correspond to experimentally observed sequences of phase transitions. Using density of states spectra for different compositions x the T-x phase diagram is numerically constructed. This phase diagram can theoretically explain experimentally observed behavior of the temperatures of phase transitions.
Engineering Elephants: Introducing Young Children to Engineering
Authors: Hunt Emily M. , Pantoya Michelle L. , Reeves Abbye M.
Published: September 2011

In this study, the authors focused on children from 2-8 years of age and asked the simple question: what do engineers do? The number one response was: “I don’t know”, the number two response was “they drive a train.” While children are very familiar with professionals such as doctors, teachers, nurses, firefighters and policemen, they are rarely introduced to engineers. With this motivation, the authors developed a novel children’s book on engineering: Engineering Elephants. This book is an outreach tool that introduces children to the dynamic world of engineering design through roller coasters, fireworks, and a plethora of other exciting adventures. The book teaches children about relevant topics such as nanotechnology, renewable energy, and prosthetics by engaging them through an interactive journey of an elephant and his questioning of the world around him. The text was strategically developed using the language of science (asking questions) and introducing vocabulary relevant to science and math using a lyrical pattern. This presentation will highlight the development of this book as an instructional aid but also detail the response of various age groups to engineering activities presented as a companion to this book. In particular, an elementary school district in West Texas designed a 4-5th grade 3-week summer school curriculum around this book. Results from this study will have an impact on future generations by inspiring them to consider the exciting profession of engineering at an early age.
CVD Growth of Graphene on Three Types of Epitaxial Metal Films on Sapphire Substrate
Authors: Nozawa Katsuya , Matsukawa Nozomu , Toyoda Kenji , Yoshii Shigeo
Published: September 2011

Graphene growth by chemical vapor deposition (CVD) was studied on three types of epitaxial metal films with different crystal structures on sapphire. Nickel (face-centered-cubic: fcc), Ru (hexagonal-closed-pack: hcp), and Co (fcc at temperature for graphene growth and hcp at R.T.) were deposited on c-face sapphire substrates and annealed in a furnace for solid phase epitaxial growth. Graphene layers were grown by CVD with methane gas on the epitaxial metal film. The graphene layer uniformity was consistent with the structural simplicity of the metal film. The Ru sample had a single domain in the metal film and the highest graphene uniformity. The Co sample had a very complex crystal structure in the metal film and the poorest uniformity in graphene. The Ni sample had two types of stacking domains in the metal film and the graphene layer was uniform on each domain, but inhomogeneity was observed at domain boundaries.
Nanoindentation Characterization of PECVD Silicon Nitride on Silicon Subjected to Mechanical Fatigue Loading
Authors: Huang Z-K , Ou K-S , Chen K-S
Published: September 2011

In this work, the mechanical properties of PECVD silicon nitride deposited on silicon substrates by two different processing conditions were investigated. Indentation method was primary used for qualitatively examining the effect of process conditions to the achieved mechanical properties. The experimental results indicated that the residual stress, fracture toughness and interfacial strength, as well as the fatigue crack propagation were strongly depended on the processing conditions such as deposition temperatures and chamber pressures. Preliminary results indicated that the specimen deposited at a lower temperature and a lower pressure exhibited a much less residual tensile stress and a better interface strength. On the other hand, it was found that RTA could enhance the interfacial strength but the generated high tensile strength could actually reduce the equivalent toughness and leads to structural reliability concerns. In summary, the characterization results should be possible to provide useful information for correlating the mechanical reliability with the processing parameters for future structural design optimization and for improving the structural integrity of PECVD silicon nitride films for MEMS and IC fabrication.
On the carbo-thermal reduction of silica for carbon nano-fibre formation via CVD
Authors: Bachmatiuk Alicja , Börrnert Felix , Ibrahim Imad , Büchner Bernd , Rümmeli Mark H.
Published: September 2011

The formation of carbon nanostructures using silica nanoparticles from quartz substrates as a catalyst in an aerosol assisted chemical vapor deposition process was examined. The silica particles are reduced to silicon carbide via a carbothermal reduction process. The recyclability of the explored quartz substrates is also presented. The addition of triethyl borate improves the efficiency of the carbothermal reduction process and carbon nanotubes formation. Moreover, the addition of hydrogen during the chemical vapor deposition leads to the helical carbon nanostructures formation.
Hole or Electron Doped C60Polymer Using Free Electron Laser Irradiation
Authors: Iwata Nobuyuki , Koide Daiki , Katou Syouta , Ikeda Eri , Yamamoto Hiroshi
Published: September 2011

Polymerized C60 crystals were grown using the free electron laser (FEL) irradiation. In order to promote the polymerization degree, hole or electron was doped in the C60 crystals grown by the liquid-liquid interfacial precipitation (LLIP) method to eliminate the degradation by oxidation. The specimen grown with the I2 dissolved butylalcohol (BTA, CH3(CH2)3OH) and the C60 saturationo-xylene solution, subsequently pressed at 7GPa, showed only Ag(2)-derived mode at 1456 cm-1 after the FEL irradiation. The specimen belonged to so-calledFphase, which is not obtained by the typical photo-induced polymerization process. It was noted that the FEL irradiation for polymerization of C60 was quite useful.
Comparison of Epitaxial Graphene on Si-face and C-face 6H-SiC
Authors: Mou Shin , Boeckl J. J. , Grazulis L. , Claflin B. , Lu Weijie , Park J. H. , Mitchel W. C.
Published: September 2011

We present atomic force microscopy (AFM), Hall-effect measurement, and Raman spectroscopy results from graphene films on 6H-SiC (0001) and (000-1) faces (Si-face and C-face, respectively) produced by radiative heating in a high vacuum furnace chamber through thermal decomposition. We observe that the formation of graphene on the two faces of SiC is different in terms of the surface morphology, graphene thickness, Hall mobility, and Raman spectra. In general, graphene films on the SiC C-face are thicker with higher mobilities than those grown on the Si-face.
Growth of diameter-modulated single-walled carbon nanotubes through instant temperature modulation in laser-assisted chemical vapor deposition
Authors: Mahjouri-Samani M. , Zhou Y. S. , Xiong W. , Gao Y. , Mitchell M. , Lu Y. F.
Published: September 2011

The diameter of individual single-walled carbon nanotubes (SWNTs) was successfully modulated along their axes by instant temperature control in a laser-assisted chemical vapor deposition (LCVD) process. SWNTs were grown using different temperature profiles to investigate the effects of temperature variation on their growth. Due to the inverse relationship between SWNT diameter and growth temperature, SWNTs with ascending diameters were obtained by reducing the LCVD temperature from high to low. The diameter-modulated SWNTs were grown across a pair of Mo electrodes to form field-effect transistors (FETs) for investigation of their electronic transport properties. Fabricated devices demonstrated properties similar to Schottky diodes, implying different bandgap structures at the ends of the SWNTs. Raman spectroscopy, transmission electron microscopy, and electronic transport characteristics were studied to investigate the influence of temperature variation on the structural and electronic characteristics of SWNTs.
Thermal, Chemical and Radiation Treatment Influence on Hydrogen Adsorption Capability in Single Wall Carbon Nanotubes
Authors: Obolensky Michail , Kravchenko Andrew , Beletsky Vladimir , Petrusenko Yuri , Borysenko Valeriy , Lavrynenko Sergey , Basteev Andrew , Bazyma Leonid
Published: September 2011

The raw single wall carbon nanotubes (SWCNT) were chemically and thermally treated and then milled in ball mill. After this SWCNT were irradiated by electron beam with energy 2.3 MeV up to fluence 1014 e-/cm2 at room temperature. Then SWCNT were saturated with hydrogen at pressure 5 bar and quenching down to the temperature 78 K. The sorption capability was measured by means of mass-spectroscopy and volumetric methods. The double increasing of mass hydrogen content in electron bombarded SWCNT was showed comparatively with non-irradiated samples.
Residual Stress in Sputtered Silicon Oxycarbide Thin Films
Authors: Du Ping , Lin I-Kuan , Yan Yunfei , Zhang Xin
Published: September 2011

Silicon carbide (SiC) has received increasing attention on the integration of microelectro-mechanical system (MEMS) due to its excellent mechanical and chemical stability at elevated temperatures. However, the deposition process of SiC thin films tends to induce relative large residual stress. In this work, the relative low stress material silicon oxide was added into SiC by RF magnetron co-sputtering to form silicon oxycarbide (SiOC) composite films. The composition of the films was characterized by Energy dispersive X-ray (EDX) analysis. The Young’s modulus and hardness of the films were measured by nanoindentation technique. The influence of oxygen/carbon ratio and rapid thermal annealing (RTA) temperature on the residual stress of the composite films was investigated by film-substrate curvature measurement using the Stoney’s equation. By choosing the appropriate composition and post processing, a film with relative low residual stress could be obtained.
Poly Lactic-Co-Glycolic Acid Carbon Nanofiber Composite for Enhancing Cardiomyocyte Function
Authors: Stout David A. , Yoo Jennie , Webster Thomas J.
Published: September 2011

The objective of the present in vitro research was to determine cardiomyocyte function on poly lactic-co-glycolic acid (50:50 (PLA:PGA); PLGA) with greater amounts of carbon nanofibers (CNFs) and variations in CNF size, for myocardial tissue engineering applications. The addition of CNFs would increase conductivity and strength of pure PLGA. For this reason, different PLGA: CNF ratios (100:0, 75:25, 50:50, 25:75, 0:100 wt.%) were created and conductivity and cytocompatibility properties with human cardiomyocytes were determined. Results showed that PLGA:CNF materials were conductive and that conductivity increased with greater amounts of PLGA added, from 0 S.m-1 for 100:0 wt.% (pure PLGA) to 5.5x10-3 S.m-1 for 0:100 wt.% (pure CNFs) material. Furthermore, results indicated that cardiomyocyte density increased with greater amounts of CNFs of 200nm in diameter in PLGA (up to 25:75 wt.% , PLGA:CNFs). This study, thus, provided an alternative conductive scaffold using nanotechnology which should be further explored for cardiovascular applications.
Vesicular Lipid Nanoparticles (Liposomes) for the Treatment of Medical Device Infections
Authors: Taylor Erik , Kaviratna Anubhav , Banerjee Rinti , Webster Thomas J.
Published: September 2011

Liposomes (a phospholipid bi-layer which can be formulated to contain drugs or other reagents) composed of endogenous phospholipid dipalmitoylphosphatidylcholine (DPPC) in combination with dioleoylphosphatidylethanolamine (DOPE), lauric acid, and silver sulfadiazine were made into vesicular nanoparticles in this study using an optimized extrusion technique. Liposomes were then tested for antibacterial activity against a range of bacteria species including Pseudomonas aeruginosa, Staphylococcus aureus, Escherichia coli, and Bacillus subtilis (all are relevant human pathogens known to infect implants) and were also challenged to prevent the growth of adherent biofilms (a robust slimy extracellular matrix) through an in vitro assay relevant to device related infections. It was found that all liposomes reduced bacterial growth, and, most importantly, liposomes containing DPPC and DOPE reduced biofilm formation better than the commercially available antibiotic silver sulfadiazine. These results indicated for the first time that such liposomes might be a better approach to prevent device related infections.
Antibacterial zinc oxide nanoparticles in polymer biomaterial composites
Authors: Seil Justin T. , Webster Thomas J.
Published: September 2011

Particulate zinc oxide (ZnO) is a known antibacterial agent. Studies have shown that reducing the size of ZnO particles to nanoscale dimensions further enhances their antibacterial properties. Polymers, like all biomaterials, run the risk of harboring bacteria which may produce an antibiotic-resistant biofilm. The addition of ZnO nanoparticles, to form a composite material, may reduce undesirable bacteria activity. The purpose of the present in vitro study was to investigate the antibacterial properties of ZnO nanoparticles when incorporated into a polymer biomaterial. Staphylococcus aureus were seeded at a known cell density onto coverslips coated in a film of polyvinyl chloride (PVC) with varying concentrations of ZnO nanoparticles. Samples were cultured for 24 or 72 h. Methods of analysis, including optical density readings and crystal violet staining, indicated a reduced presence of biofilm on ZnO nanoparticle and polymer composites compared to polymer control. Live/dead assays provided images to confirm reduced presence of active bacteria on samples with zinc oxide nanoparticles. Development of this technology may improve biomaterial effectiveness for applications, such as endotracheal tubes and implanted biomaterials, which are prone to bacterial infection.
A Picowatt Energy Harvester
Authors: Evans Joe , Smits Johannes , Montross Carl , Salazar Gerald
Published: September 2011

The authors describe an energy harvester circuit fabricated with integrated thin ferroelectric film capacitors on a silicon substrate. The harvesting mechanism is a folded double-beam cantilever with proof masses at both end points. Interdigitated electrode capacitors are located at the three points on the folded cantilever that are expected to experience maximum bending moment and should produce up to 5V as a function of external vibration. The die has the dimensions of 1.6mm on a side and is designed to be mounted in a TO-18 package transistor-style package. Due to its small size, the self-contained piezoelectric MEMs device should produce 50 picowatts in a 1g vibration environment while occupying little space.
Structure Control of Bioactive Titanate Nanomesh Layers Fabricated on Laser Irradiated Ti-based Bulk Metallic Glass using Hydrothermal-Electrochemical Method
Authors: Maruyama Sayaka , Sugiyama Naota , Yoshimura Masahiro , Shinonaga Togo , Tsukamoto Masahiro , Abe Nobuyuki , Wada Takeshi , Wang Xinmin , Inoue Akihisa , Okada Kiyoshi , Matsushita Nobuhiro
Published: September 2011

The surface of Ti-based bulk metallic glass (BMG) was irradiated by the femto-second laser and microgrooves were formed on the surface. The titanate nanomesh layers were fabricated on the micro-grooved BMG surface by hydrothermal-electrochemical (H-E) treatment changing the conditions of the concentration of electrolyte solution (0 and 5 M) and applying current density (0-200 mA/cm2). The bone-inducing capacity of the samples with different H-E treatment was confirmed by soaking them in a simulated body fluid for 12 days. The H-E treatment in higher concentration 5 M NaOH aq. and applying higher current density above 0.5 mA/cm2exhibited excellent bioactivity inducing large hydroxyapatite crystallites.
Laser Treatment of Organic Thin Film Solar Cells
Authors: Clair Maurice , Scholz Christian , Keiper Bernd , Haenel Jens
Published: September 2011

In the last years more and more effort has been put into the development of thin-film organic solar cells using conductive and semi-conductive polymers. A great advantage of these polymers is the possibility to deposit them in high throughput print and coating processes. This feature provides huge potential for future production of low cost photovoltaics. While TCO layers form the transparent front contact, polymers are used for the buildup of the active layer and the design of the interface between active layer and front contact. The polymer materials have to be patterned in order to allow for a row connection of the solar cell work (typically by structured deposition, e.g. printing). In addition the bulk hetero junction (BHJ) of the active layer consisting of poly(3-hexylthiophene):phenyl-C61-butyric acid methyl ester (P3HT:PCBM) requires an annealing step to optimize the layers structure and therewith the efficiency of the solar cell (typically by thermal treatment, e.g. oven). 3D-Micromac used ultra-short pulsed lasers to evaluate the applicability of various wavelengths for the selective ablation of the BHJ consisting of P3HT:PCBM on top of a Poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate) (PEDOT:PSS) and indium tin oxide (ITO) film system on glass substrates. The process of laser annealing was investigated using a short-pulsed laser with a wavelength close to the absorption maxima of the BHJ.
Fe-42%Ni austenitic alloy as a novel substrate for flexible electronics
Authors: Ma Xiaoxiao , Khan Shahrukh A. , Choi Nackbong , Hatalis Miltiadis , Robinson Mark
Published: September 2011

We report Fe-42%Ni as a novel high-performance substrate for a-IGZO TFT fabrication after evaluating 8 different metals for chemical compatibility, mechanical flexing and dimensional stability. Excellent flexibility and rollability indicates that Fe-42%Ni would be a good choice as flexible substrate for R2R process. Pre-annealing process for stabilizing the substrate is studied and applied to the Fe-42%Ni foil before TFT fabrication. Staggered bottom gate a-IGZO TFTs which were fabricated on this substrate have field effect mobility of 12 cm2/V.s, threshold voltage of 2V, sub-threshold swing of 0.6V/decade and on/off current ratio exceeding 107.
Size Dependent Particle Toxicity in Drosophila
Authors: Gorth Deborah J , Rand David M , Webster Thomas J
Published: September 2011

Nanotechnology, or the use of materials with one dimension less than 100nm, offers the ability to change particle reactivity by simply changing their size. This novel property of nanomaterials is used to create more effective medical treatments for cancer, tissue engineering and regenerative medicine, but the influence of nanoparticle size on environmental toxicity has not been thoroughly addressed to date. This study examines the influence of the size of silver particles on drosophila egg development by exposing their eggs to particle concentrations ranging from 10ppm-100 ppm of silver. Size, chemistry and agglomeration of the silver particles are evaluated using transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and dynamic light scattering (DLS). This analysis confirmes individual silver particle size in the ranges of 20-30nm, 100nm and 500-1,200 nm with similar chemistry. DLS and TEM data also indicates agglomeration in water; with the TEM images showing individual particles in the correct size range, but the DLS z-average sizes of the silver nanoparticle are 782 ± 379 nm for the 20-30nm silver nanoparticles, 693 ± 114 nm for the 100nm silver nanoparticles and 508 ± 32 nm for the 500-1,200nm silver particles. Most importantly, here we show significantly more drosophila egg toxicity when exposed to larger, non-nanometer, silver particles. Upon exposure to silver nanoparticles sized 20-30nm, drosophila eggs do not exhibit a statistically significant (p<0.05) decrease in their likelihood to pupate, but eggs exposed to larger silver particles (500-1,200nm) are 91% (±18%) less likely to pupate. Exposure to silver nanoparticles reduces the percentage of pupa able to emerge as adults. At 10ppm of silver particle exposure, only 57% (± 48) of the pupa exposed to 20-30nm silver particles become adults whereas 89% (±25) of the control group becoem adults and 94%(±52) and 91%(±19) of the 500-1,200nm and 100nm group, respectively, reached adulthood. In this manner, this paper provides evidence that nanoscale silver particles (<100nm) are less toxic to drosophila eggs than conventional (>100nm) sized silver particles.
Refractive Index memory effect of ferroelectric materials by domain control
Authors: INOUE Kazuhiko , MORITA Takeshi
Published: September 2011

Ferroelectric electro-optics materials are widely studied for optical applications, such as optical switches, optical scanners, and optical shutters. However, conventional operation of those devices requires a continuous external electrical field. On the other hand, our group proposes an optical property memory effect by controlling domain structure as either full-polarized or depolarized state using asymmetric voltage operation. The optical property memory effect can keep its optical value, such as refractive index and light transmittance without any external electrical field. In this study, it was confirmed that the refractive index state had two stable values depending on domain conditions. This memory effect should be useful for innovative optical switch or scanner in the future.
Ionization of decaborane with controlled hydrogen content by charge transfer from ambient gas
Authors: Ohishi Yuji , Kimura Kaoru , Yamaguchi Masaaki , Uchida Noriyuki , Kanayama Toshihiko
Published: September 2011

We present the ionization of decaborane (B10H14) and formation of hydrogen- and boron-contents-controlled B10-yHx+ through the charge transfer from ambient gas ion to decaborane molecules in an external quadrupole static attraction ion trap. The charge transfer energy is estimated from the experimentally observed products. PBE0/6-311+G(d)//B3LYP/6-31G(d) level of DFT calculations are conducted to investigate the mechanism of charge transfer from ambient gas ion. The calculation of the difference of ionization energies and mismatch of orbital energies between decaborane and ambient gas reveals the mechanism of ionization.
Ionic mobility in Nasicon-type LiMIV2(PO4)3 materials followed by 7Li NMR spectroscopy.
Authors: Arbi K. , Sobrados I. , Hoelzel M. , Kuhn A. , Garcia-Alvarado F. , Sanz J.
Published: September 2011

Lithium mobility in LiM2(PO4)3 compounds, with M= Ge, Ti, Sn, Zr and Hf, has been investigated by 7Li Nuclear Magnetic Resonance (NMR) spectroscopy in the temperature range 100-500 K. From the analysis of 7Li NMR quadrupole interactions (CQ and η parameters), Li sites occupancy and exchange processes between structural sites have been studied. Below 250K, Li ions are preferentially located at M1 sites in rhombohedral phases, but occupy M12 sites in triclinic ones. At increasing temperatures, Li mobility has been deduced from spin-spin () and spin-lattice relaxation () rates. In this analysis, the presence of two relaxation mechanisms in plots has been associated with departures of conductivity from the Arrhenius behavior. At high temperatures, residence times at M12−T11−T11−T1 and M12 sites become similar and conductivity significantly increase. This superionic state can be achieved by enlarged order-disorder transformations in rhombohedral phases, or by sharp first order transitions in triclinic ones. Results described in the LiTi2(PO4)3 sample have been compared with those obtained in rhombohedral Li1+xTi2-xAlx(PO4)3 and LiTi2-xZrx(PO4)3 series showing respectively higher and lower conductivities. In the case of Li1.2Ti1.8Al0.2(PO4)3, displaying the highest reported conductivity, NMR results are discussed in relation with those obtained by Neutron Diffraction (ND) and Impedance Spectroscopy (IS). Diffusion coefficients determined by NMR Pulse Field Gradient (PFG) technique are similar to those deduced from Impedance Spectroscopy and NMR relaxation data.
New Insight into Electrochemical Differences in Cycling Behaviors of a Lithium-ion Battery Cell Between the Ethylene Carbonate- and Propylene Carbonate-Based Electrolytes
Authors: Tasaki Ken , Goldberg Alexander , Liang Jian-Jie , Winter Martin
Published: September 2011

Density functional theory (DFT) calculations and classical molecular dynamics (MD) simulations have been performed to gain insight into the difference in cycling behaviors between the ethylene carbonate (EC)-based and the propylene carbonate (PC)-based electrolytes in lithium-ion battery cells. DFT calculations for the ternary graphite intercalation compounds (Li+(S)iCn: S=EC or PC), in which the solvated lithium ion Li+(S)i (i=1~3) was inserted into a graphite cell, suggested that Li+(EC)iCn was more stable than Li+(PC)iCn in general. Furthermore, Li+(PC)3Cn was found to be energetically unfavorable, while Li+(PC)2Cn was stable, relative to their corresponding Li+(PC)i in the bulk electrolyte. The calculations also revealed severe structural distortions of the PC molecule in Li+(PC)3Cn, suggesting a rapid kinetic effect on PC decomposition reactions, as compared to decompositions of EC. In addition, MD simulations were carried out to examine the solvation structures at a high salt concentration: 2.45 mo kg-1. The results showed that the solvation structure was significantly interrupted by the counter anions, having a smaller solvation number than that at a lower salt concentration (0.83 mol kg-1). We propose that at high salt concentrations, the lithium desolvation may be facilitated due to the increased contact ion pairs, so that a stable ternary GIC with less solvent molecules can be formed without the destruction of graphite particles, followed by solid-electrolyte-interface film formation reactions. The results from both DFT calculations and MD simulations are consistent with the recent experimental observations.
Thermoelectric Materials Discovery Using Combinatorial Chemistry
Authors: Amani Matin , Tougas Ian , Gregory Otto J.
Published: September 2011

Transparent conducting oxides have been previously investigated for both bulk and thin film thermoelectric applications, and have shown promising results due to their thermal stability and electrical conductivity. Alloys of two or more transparent conducting oxides have been deposited using pulsed laser deposition (PLD) and combinatorial sputtering, and the resulting films were optimized for optical applications. In this study, thermoelectric materials were prepared by co-sputtering techniques, whereby a chemical gradient was formed across an alumina substrate that was patterned using photolithography to form hundreds of micro-thermocouples. The systems indium tin oxide (ITO), indium zinc oxide (IZO), and zinc tin oxide (ZTO) were investigated for this purpose and the resulting combinatorial libraries were rapidly screened to establish room temperature resistivity, Seebeck coefficient, and power factor as functions of both composition and heat treatment, in nitrogen and air ambients. Due to their chemical stability, oxidation resistance, and large Seebeck coefficients relative to metal thermocouples, these materials are ideal for temperature measurement or energy harvesting in harsh environments such as gas turbine engines.
Optoelectronic characterization of morphology-controlled zinc oxide nanowires
Authors: Kuo Shou-Yi , Lai Fang-I , Wang Chun-Chieh , Lin Woei-Tyng
Published: September 2011

In this paper, we report the characterization of vertically aligned ZnO nanowire (NW) arrays synthesized by metal-catalyzed chemical vapor deposition. The growth mechanism of ZnO NWs may be related to vapor-solid-nucleation. Morphological, structural, optical and field emission characteristics can be modified by varying the growth time. For growth time reaches 120 min, the length and the diameter of ZnO NWs are 1.5 μm and 350 nm, and they also show preferential growth orientation along the c-axis. Moreover, strong alignment and uniform distribution of ZnO NWs can effectively enhance the antireflection to reach the average reflectance of 5.7% in the visible region as well. Field emission measurement indicated that the growth time play an important role in density- and morphology-controlled ZnO NWs, and thus ZnO NWs are expected to be used in versatile optoelectronic devices.