bluuebunny/crossref_metadata_2025_split huggingface dataset:
Characterization on the Electrical Properties of PDMS Nanocomposites by Conducting Polymer Nanowires
Authors: Du Ping , Lin Xi , Zhang Xin 
Published: April 2011

ABSTRACTPolydimethylsiloxane (PDMS) is one of the most used materials in bio-applications. However, previous works were mainly focus on the mechanical aspect. In this paper we presented a practical and efficient approach to enhance the electrical properties of PDMS by using conducting polymer nanowires (CPNWs). The nanowires were synthesized using template method and added in PDMS to form nanocomposites. The dielectric constants of the composites were characterized by impedance measurements, and the dielectric relaxation behavior and the volume fraction of CPNWs was investigated. Based on the percolation theory a much lower threshold (5.3 vol%) was achieved.
Development of Bacterial Cellulose Nanocomposites
Authors: Benson Roberto , O’Neill Hugh M. , Evans B.R. , Hutchens S. , Stephens C.P. , Hammonds R. 
Published: April 2011

ABSTRACTThe development of synthetic materials with inherent bone properties would allow the safe restoration of bone function and reduce current risks associated with the use of grafts. This study investigated the development of bacterial cellulose–hydroxyapatite composite (CdHA-BC) as a potential bone substitute material. Composites of bacterial cellulose (BC) and oxidized, degradable, cellulose (OBC) were mineralized by sequential incubation in calcium chloride and aqueous sodium phosphate to form a calcium deficient hydroxyapatite (CdHA). The CdHA produced in BC and OBC is similar in morphology and chemistry to the hydroxyapatite found in natural bone. The formation of CdHA is supported by XRD, and EDS results. The CdHA-BC and CdHA-OBC composites degrade in a simulated aqueous physiological environment.
Self-Assembled Nano-Needles of Polyaniline, Efficient Structures in Controlling Electrical Conductivity
Authors: Ibrahim Michael I. , Bassil Maria J. , Demirci Umit B. , El Haj Moussa Georges , El Tahchi Mario R. , Miele Philippe 
Published: April 2011

ABSTRACTPolyaniline (PANI) is one of the most interesting conducting polymers with a wide and controllable conductivity range, synthesized easily via chemical or electrical route, stable chemically and environmentally, having high absorption in the visible range and high mobility of charge carriers. Under different conditions, PANI morphology can be controlled yielding to the creation of nano-tubes, belts, rods, fibers and particles.In this study, the chemical oxidative polymerization which consists of mixing aniline hydrochloride (A-HCl) with ammonium peroxydisulfate (APS) was used to synthesize HCl doped PANI. Fixing the weight ratio A-HCl/APS defined by the IUPAC while varying their quantities leads to the formation of PANI nanoparticles with variable diameters. In addition, PANI nano-needles of 60 nm average diameter at the center are also obtained. Different methods are used to investigate of 1-D morphologies. The electrical conductivity of bulk PANI pellets is measured using the four-point probe technique. The absorption in the visible range of PANI particles and nano-needles is determined by UV-Vis spectroscopy. XRD analysis was performed to study the effect of PANI particle size and morphology on the crystallinity of the powder. Such structures could be used in hybrid solar cells for higher conversion efficiencies.
Photo-polymerizable gold nanorods / methyl methacrylate composite for plasmonic optical application
Authors: Masui Kyoko , Shoji Satoru , Duan Xuan-Ming , Kawata Satoshi 
Published: April 2011

ABSTRACTWe prepared a photo-polymerizable compound of Au nanorods and methyl methacrylate (MMA). An irradiation of ultraviolet (UV) light onto the compound induces photo-polymerization of MMA, resulting in a formation of an Au nanorods/PMMA composite. Au nanorods were synthesized by seed-mediated growth method in aqueous solution. Hydrophobically functionalized Au nanorods were dispersed into MMA with a small amount of photosensitizer and initiator. We investigated the stability and the uniformity of the dispersion of Au nanorods during the photo-polymerization process through VIS-NIR absorption spectroscopy. We also demonstrated the use of the compound for two-photon micro/nanolithography.
Rheological Behavior of Nanoclay Containing Nanofluids
Authors: Munro Jeffrey C. , Rao YuanQiao 
Published: April 2011

ABSTRACTA synthetic hectorite nanoclay, Laponite®, with a disc shape (20 – 30 nm in diameter and 1 nm in thickness) was used as a model nanoparticle to prepare dispersions in water and different organic solvents. Although up to 20 wt% of nanoclay can be dispersed in water to form a low-viscosity stable colloidal sol, dispersions in organic solvents behave differently. The effect of the dielectric constant of the medium on the viscosity of the dispersion was studied systematically using two series of water-organic solvent miscible blends. Changes in the rheological behavior of the dispersions suggest that the dielectric constant of the organic solvent is a determining factor in the sol-gel transition of a nanoclay-containing nanofluid.
Image Analysis Optimization for Quantifying Nanoparticle Dispersions in Polymer-based Nanocomposites Using Transmission Electron Microscopy (TEM)
Authors: Badami Anand S. , Beach Mark W. , Wood Stewart P. , Rozeveld Steven J. , Heeschen William A. 
Published: April 2011

ABSTRACTWhen comparing large numbers of TEM micrographs of insoluble additives in polymer-based nanocomposite systems, the ability to determine or estimate the dispersion quality (i.e. uniformity of size and/or spatial distribution) is often difficult. The objective of this study was to develop a method to quantify dispersions observed in TEM micrographs that enables both a numerical “ranking” to be assigned to individual dispersions as well as tabulation a multitude of images acquired over time. Several methods were reviewed and applied to a set of TEM dispersion images of an insoluble additive in polystyrene. Projected area diameter, particle area, and Euclidean distance between particle centroids were chosen from all the particle size distribution and spatial distribution parameters present in the literature, but none successfully yielded a quantitative indicator of dispersion quality for the micrographs. In contrast, generating cumulative volume percent curves for each sample appeared to be a preferred method of quantifying and comparing dispersions in TEM micrographs. The volume diameter values obtained by this method can be used for “ranking” and tabulation of dispersion quality and account for both “good” additive dispersions (i.e. those with small domains of a narrow size range around 1 μm or less) and “bad” additive dispersions (i.e. those with non-uniform domains ranging in size by several microns or more). As a result, the numerical values generated by this method can be used to quantitatively determine correlations between the dispersion quality of nanoparticles in polymer-based nanocomposite materials and various macroscale physical and/or performance properties of such materials. This method’s precision was statistically determined to decrease with increasing particle size and be heavily dependent on representative sampling.
Conjugated Polymer:TiO2 Nanocomposite Solar Cells Based on P3HT Nanoparticles
Authors: Venkatraman B. Harihara , Kokil Akshay , Satapathi Soumitra , Kumar Jayant , Venkataraman* Dhandapani 
Published: April 2011

ABSTRACTThere is widespread interest in developing efficient solar cells derived from conjugated polymers and TiO2. The conjugated polymer can act as a light harvesting dye as well as a hole transport material, and can potentially replace both the ruthenium dye and the I3-/I- couple in the DSSCs. Herein, we report a novel and facile approach of using conjugated polymer nanoparticles to make conjugated polymer:TiO2 nanocomposite based solar cell. Nanoparticles from poly(3-hexylthiophene) (P3HT) were made using mini-emulsion technique. In this work we report on incorporation of these P3HT nanoparticles into nanoporous titania. Device characteristics made using P3HT nanoparticle sensitized solar cells were measured. These devices showed a short-circuit current density (Jsc) of 0.207 mA/cm2, open-circuit voltage (Voc) of 0.62 V and 0.07% (η) efficiency.
Stochastic Models of Epitaxial Growth
Authors: Margetis Dionisios , Patrone Paul N. , Einstein T. L. 
Published: April 2011

ABSTRACTWe study theoretical aspects of step fluctuations on vicinal surfaces by adding conservative white noise to the Burton-Cabrera-Frank model in one spatial dimension. We consider material deposition from above, as well as entropic and elastic-dipole step repulsions. Two approaches are discussed: (i) the linearization of stochastic equations when fluctuations are small, which captures correlations; and (ii) a mean field approach, which leaves out correlations but captures nonlinearities. Comparisons to kinetic Monte-Carlo simulations are presented.
Nanostructured Broad Band Infrared Absorber
Authors: Corrigan Timothy D. , Park Dong Hun , Drew Dennis , Phaneuf Ray 
Published: April 2011

ABSTRACTWe describe a near perfect broad band absorber based on a laterally nanostructured multilayer material. We present calculations of the structure that demonstrates over 99% absorption of the 500 K black body spectrum. We also show the ability to manufacture an anti-reflective layer using a nanostructured metamaterial which allows us to tailor the index of refraction using effective medium theory. The absorber can be adapted for use in any frequency range and any source type. These materials may have applications in energy harvesting and scattered light control.
Carbon-based Materials as Key-enabler for “More Than Moore”
Authors: Kreupl Franz 
Published: April 2011

ABSTRACTCarbon-based materials like nanotubes and graphene are heavily investigated as future transistor devices and in interconnect applications. While much of the interest has been devoted to the device aspects in competition to conventional transistors, the paper here will focus on some less known applications of pyrolytically deposited carbon. Proposed and demonstrated are applications in capacitors, gate materials, through-silicon vias, novel non-volatile memories, carbon-silicon Schottky diodes and sensors.
Pt/TiO2/Ti Metal-Insulator-Metal Tunnel Diodes for Rectification in an Energy Harvesting System
Authors: Chin Matthew , Nichols Barbara , Osgood Richard , Kilpatrick Stephen , Dubey Madan , Dhar Nibir 
Published: April 2011

ABSTRACTMethods for extracting or harvesting energy from the surrounding battlefield environment are of great importance to the United States Army. Scavenging energy from local environments reduces the required energy and weight transported to the theater. Micro- and nano-scale metal-insulator-metal (MIM) tunnel diodes are being developed to provide half-wave rectification as part of a “rectenna” energy harvesting system, which includes a radiation-collecting antenna, a rectifying MIM tunnel diode, and a storage capacitor. In this work, high-frequency MIM tunnel diodes for power rectification were designed, fabricated and characterized. Planar Pt/TiO2/Ti stacks are being fabricated to create a diode with highly asymmetric I-V characteristics that has a very low threshold voltage. The metals were chosen for their high work function difference, and the insulator was chosen for its barrier height, its compatibility with Ti, and its availability. The energy band diagram and the I-V characteristics were modeled to determine the feasibility of the Pt/TiO2/Ti material system for use as a rectifier diode in a rectenna system. Metals and insulator thin films were deposited onto silicon dioxide/silicon substrates. Pillars with lateral dimensions ranging from 20 μm x 20 μm up to 100 μm x 100 μm were fabricated. The dielectric thickness of the MIM diode was varied from 5 nm up to 50 nm to determine the optimal thickness for quantum tunneling. I-V measurements were taken using an electrical characterization system to confirm a non-linear, asymmetric response on a survey of devices fabricated with varying areas. Preliminary results exhibit asymmetric I-V characteristics with threshold voltages of less than 700 mV.
Fracture Transfer of Vertical Semiconductor Pillar Arrays to Low Cost Arbitrary Substrates for Flexible Energy Device Applications
Authors: VJ Logeeswaran , Ombaba Matthew , Islam M.Saif 
Published: April 2011

ABSTRACTIn this paper, we demonstrate a heterogeneous integration technique that preserves the integrity, order, shape, and fidelity of vertically aligned single-crystal semiconductor micro- and nano- pillars by harvesting and transferring them from a single crystal substrate to a low-cost carrier substrate. The mechanism of the transfer technique exploits a combination of vertical embossing and lateral fracturing of the crystalline pillars with the assistance of a spin-coated polymer layer on a carrier substrate as well as facilitating multilayer process device integration. Specifically, the novel use of a water soluble adhesive polymer from MasterBond that acts simultaneously as a mechanical transfer polymer and as a sacrificial harvest layer further expands the versatility of this approach. Arrays of vertical micropillars of average height ~15)μm and diameter ~1.5μm on a die silicon substrate of 5mm x 5mm were fabricated via transformative top-down approaches (DRIE) on a single crystal silicon substrate and then transferred to a different target carrier substrate using the adhesive polymer assisted bendingfracturing process. The adhesive polymer is odorless, non-conducting, easy to process, spincoatable, optically transparent, resistant to heat, high mechanical strength and easily cures at room temperature. The original pillar wafers may be used repeatedly after polishing for generating more devices and are minimally consumed. Low contact resistances are formed for electrical addressing using metals and conducting thermoplastics of Ag nanoparticles. This heterogeneous integration technique potentially offers enhanced photon semiconductor interactions, while enabling multimaterial integration such as silicon with compound semiconductors (InP, GaAs etc.) for applications, including high speed electronics, low-cost and flexible electronics, displays, tactile sensors, and energy conversion systems.
Multiparameter Imaging and Understanding the Role of the Tip - Atomic Resolution Images of Rutile TiO2 (110)
Authors: O’Brien S. J. , Ozgur Ozer H. , Cross G. L. W. , Pethica J. B. 
Published: April 2011

ABSTRACTA major challenge for scanned probe microscopy is to identify structures and chemical species on a surface, which have not already been inferred from other analytical techniques. Progress is impeded by the fact that in general the structure and composition of the tip atom is not known. To illustrate some of the issues involved, we report simultaneous scanning tunneling microscopy/atomic force microscopy (STM/AFM) of the TiO2 (110) surface. The use of small amplitudes enabled the simultaneous acquisition of force gradient and barrier height images during standard STM imaging. Surprisingly, we find most STM images exhibit a corrugation contrast inverse to that usually reported in the literature. However, regardless of the contrast in STM, force gradient images always showed greater attraction over O rows. Barrier height images also show this consistency, always being greater over O rows. This supports the theoretical model of the electronic structure of the surface, but shows that the tip structure and interaction cannot be ignored in modeling STM images. We conclude that there is a fine balance between topography and local density of states (LDOS) in STM imaging of this surface; which of them dominates the STM image is determined by the tip. Simultaneous multi-parameter imaging is useful in interpreting images reliably, particularly on multi-component surfaces.
Permeability of Polymer/Clay Nanocomposites
Authors: Choudalakis Georgios A. , Gotsis Alexandros D. 
Published: April 2011

ABSTRACTBecause of their large interfacial area, the presence of nanoplatelets in the polymeric matrix decelerates the process of diffusion of gases through the material. The particles are impermeable barriers to the diffusing molecules, forcing them to follow complicated paths, increasing, thus, the diffusion length. The barrier properties of the nanocomposites depend on the properties of the polymeric matrix, the volume fraction of the nanoplatelets, their aspect ratio, their orientation, and their interactions with the matrix. The mobility of the molecules is hindered by the crystallinity but it is facilitated by the free volume within the material. The size and shape of the free volume holes in the polymer affect, thus, the rate of diffusion. Interactions between the nanoparticles and the matrix may lower the barrier properties because they may increase the free volume in the material. The estimation of free volume in the nanocomposite is important for the proper choice of components and the manufacturing of nanocomposite coatings with optimum barrier properties. Detailed information about the diffusion mechanisms at atomic and molecular levels can be obtained using the approach of free volume.
Observation Of Real-Time Thin Film Evolution Using Microcantilever Sensors
Authors: Schilowitz Alan M. , Yablon Dalia G. 
Published: April 2011

ABSTRACTAdsorption and desorption kinetics of thin film formation on metal surfaces has been directly monitored in real-time by optically measuring the deflection of activated atomic force microscope microcantilevers. Microcantilever deflection is caused by stress generated during the formation of an adsorbate layer on one side of the microcantilever. In this work, rapid adsorption of carboxylic acid in hydrocarbon solvent onto a gold surface was directly observed as a compressive stress developed on the microcantilever substrate. Upon exposure to alkylthiol, acid desorbed and was displaced by alkylthiol; this process was continuously monitored in real-time. Experiments suggest that some film organization and intermolecular interaction are required before substantial surface stress can be detected.
X-Ray Study of Strained and Strain Balanced Superlattice Materials
Authors: Johnson Natee , Choa Ruth , Cheng Liwei , Choa Fow-Sen 
Published: April 2011

ABSTRACTNano-scale superlattice (SL) based devices, such as quantum cascade lasers QCLs, have recently become very important due to their capability to identify toxic and explosive chemicals. In manufacturing these Mid-IR photonic devices, atomic-level scanning tunneling microscopes (STM) and transmission electron microscopes (TEM) have been used to characterize the growth quality of superlattice wafers. However, these methods yield observations that are localized and cannot view the entire structure and even now we have not been able to correlate these measured crystal lattice images with device performance. The x-ray scanning technique has greater likelihood of success given that it can observe not only the localized, but also the entire superlattice structure. By extracting special features and key parameters in x-ray diffraction (XRD) patterns, the epitaxial quality of QCL superlattices can be evaluated and correlated to the performance of fabricated QCL devices. We can then differentiate and classify different grades of wafers before starting device fabrication and testing.Such an example of the usefulness of XRD can be found with strain-balanced superlattices, such as InGaAs/InAlAs, where there is notable decrease in laser performance after relaxation. It can also be found with type-II InAs/GaSb strained layer superlattice, which is currently the best candidate for room temperature mid-IR detectors and focal plane arrays. Experimentally measured x-ray patterns are compared to simulation results and problem sources are identified.
In-situ TEM Observation of Formation-Retraction-Fracture Experiment of Liquid-Like Silicon Nanocontact
Authors: Ishida Tadashi , Kakushima Kuniyuki , Fujita Hiroyuki 
Published: April 2011

ABSTRACTWe have examined the change of mechanical characteristics of silicon nanocontacts with and without the pre-treatment by flowing current through the contact. The silicon nanocontact formed between silicon tips by a mechanical contact was quickly deformed during its tensile test under a transmission electron microscope, after applying over 100 μA at a high bias voltage around 15 V between tips for a short duration. In the tensile experiment, the diameter of the nanocontact easily decreased from the initial diameter of 98 nm to 30 nm and the length increased from 11 nm to 66 nm. At 30 nm in diameter, it was suddenly fractured without further elongation and became round tips with smooth surfaces. According to the close observation, the silicon nanocontact seemed amorphous. In the retraction process of the silicon nanocontact, steps moved along the surface from the neck of the nanocontact to the tip side at the speed of 7.0 nm/s. Nano-scaled round step propagations were repeated from the neck to the tip. The step propagation caused the fast thinning of the nanocontact. On the other hand, the silicon nanocontact formed at 1 V in bias voltage was gradually thinned from 42.5 nm to 1.6 nm in diameter and elongated from 2.9 nm to 61.9 nm in length. From the comparison of silicon nanocontacts with and without the pre-treatment, the silicon nanocontact after flowing substantial current showed quick deformation and had different mechanical characteristics from the silicon nanocontact without the pre-treatment.
Crosslinked Organic/Inorganic Hybrid Proton Exchange Polymeric Membranes
Authors: Di Vona Maria Luisa , Marani Debora , D'Ottavi Cadia , Trombetta Marcella , Traversa Enrico , Beurroies Isabelle , Knauth Philippe , Licoccia Silvia 
Published: April 2011

ABSTRACTA general, efficient and experimentally simple method for the synthesis of covalently crosslinked class II hybrid polymers based on PolyEtherEtherKetone (PEEK) with a high degree of sulfonation (DS = 0.8) was performed. The synthetic strategy foreseen two steps: the first one, direct sulfonation, led to the introduction of sulfonic acid groups and to the formation of sulfone bridges among repeat units. The second step, lithiation and silylation, led to the formation of covalent bonds between the organic backbone and Si(OH)3 moieties. The materials were characterized by 1H NMR Spectroscopy, ATR/FTIR Spectroscopy, Thermogravimetric Analysis (TGA) and Mass Spectrometry. Preliminary proton conduction measurements in dry conditions were performed. The introduction of silicon groups in the system improved thermal stability.
Preparation of Nano-Sized Doped Ceria for SOFC Anodes
Authors: Kobayashi Jumpei , Takamura Hitoshi , Kamegawa Atsunori , Okada Masuo 
Published: April 2011

ABSTRACTNano-particles of Pr and Mn-doped ceria have been prepared by mixing nitrate solutions and hexamethylenetetramine as an oxidizing agent, and their thermal stability has been investigated. The particle size was evaluated by means of XRD, BET and dynamic light scattering techniques. The particle size of Pr and Mn-doped ceria was found to be approximately 3 nm as prepared. Even though the particle size of doped ceria increases with increasing annealing temperature, the size of less than 15 nm was kept after annealing at 873 K for 10 h. On the other hand, the lattice constant of nano-sized ceria, for example 0.544 nm for 3 nm-size particles, decreases and reaches to the value of bulk material (0.541 nm) as annealing temperature increases. This suggests that the valence state of cerium and the amount of oxygen vacancies strongly depend on the particle size.