bluuebunny/crossref_metadata_2025_split huggingface dataset:
Nature of High Critical Current Density in Epitaxial Films of HTS YBCO Cuprate and Coated Conductors
Authors: Pan Vladimir M. , Cherpak Yuriy V. , Pashitskii Ernst A. , Semenov Aleksey V. 
Published: April 2011

ABSTRACTCurrently a problem of crystal defects nanoengineering for pinning enhancement is extensively studied. A number of efforts were done to realize nanodot-like and particulate-dispersive pins to enhance pinning and critical current density in high-Tc cuprate films and coating. Sometimes some effect of Jc enhancement was achieved. However it is important to comprehend mechanisms of such an enhancement. It is known the ensemble of random point-like pins with size ro of order of coherence length, xab(T), can provide Jc(77 K) not to exceed 5§¹104 A/cm2. Estimations give the maximum pinning force of about for linear extended defects (if ). Here eo is the characteristic vortex energy. A model of vortex pinning and supercurrent limitation is developed and discussed on the base of measurements and analysis of magnetic feld and angle dependencies of Jc(H,¦È) in epitaxial c-oriented YBa2Cu3O7-δ (YBCO) films measured by the four-probe transport current technique, low-frequency ac magnetic susceptibility and SQUID magnetometry. Films nanostructure is studied by SEM, TEM, HREM and X-ray diffractometry. Rows of growth-induced out-of-plane edge dislocations (EDs), forming low angle subboundaries (LABs), are shown to play a key role in achievement of the highest critical current density Jc ¡Ý 2 106 A/cm2 at 77 K. The model takes into account the transparency of LABs for supercurrent as well as the pinning of vortex lattice on a network of LABs. Films defect structure parameters, such as a domain size distribution and a mean misorientation angle, are extracted from Jc(H||c)-curves as well as from X-ray diffraction data. Evolution of angle dependencies Jc(¦È) with H is shown to be consistent with the model, supposing dominant pinning on EDs. Strongly pinned vortices parallel to the c-axis exist in strongly tilted magnetic felds up to threshold feld Hp. Below Hp the magnetic induction within a film obeys a simple relation B = Hcos¦È. This feature is shown to explain the absence of the maximum in Jc(¦È)-plot, expecting at H||c in low applied feld. A peak-effect in Jc(H||ab)-dependencies and an angular hysteresis of Jc(¦È) observed in intermediate feld range, are discussed in terms of film thickness, surface quality and orientation of the applied feld. The effects observed are found to be consistent with the developed model. To our mind any nano-, micro- and macro-interfaces, emerging within films or coatings at the deposition process (e.g., nanodot-like and particulate dispersive inclusions) being coherently connected with a YBCO-matrix serve as a source of formation of a multitude of additional dislocations and as a result can promote the essential Jc-enhancement.
Strain Dependent Transport and Mechanical Characteristics of High-current and High-Strength Type Ag/Bi2223 Composite Superconductors
Authors: Adam Malik Idries , Osamura Kozo 
Published: April 2011

ABSTRACTTensile strain dependence of electromechanical characteristics of high-current, (Hic) and high-strength, (Hs) type Ag/Bi2223 composite tapes measured at room temperature, RT and 77K is investigated. Mechanical strength of composites revealed strain-hardening signature in Bi2223 filaments due to plastic strain above the elastic limit. Critical current, Ic maintained constant value up to the elastic limit then decreased slowly before finally dropped to about 10% at 0.19% and 0.39% strain, signaling a three-stage limitation. Microstructure observations and electromechanical response of the composites suggest that a limited longitudinal, transverse, interfacial, granular and transgranular microcracks formed during gradual imposition of strain hardening in Bi2223 filaments may be responsible for the slow reduction of Ic in the medium mechanical stage.
Dispersion of Single Walled Carbon Nanotubes by Self Assembly of Polymers
Authors: Dhullipudi Ramasudhakar Babu , Lvov Yuri M , Dobbins Tabbetha A 
Published: April 2011

ABSTRACTDispersion and stability of single walled nanotubes (SWNT) is one of the inhibiting factors affecting their tailorability for various electronic, chemical and mechanical applications . The realization of these applications depends on dispersing the SWNTs in aqueous media by inducing high forces of repulsion among the nanotubes. Steric repulsions are induced to the nanotubes by attaching polyelectrolytes, like poly styrene sulfonate (PSS) and poly allyl amine hydrochloride (PAH). In this work, Self Assembly technique is employed to attach polyelectrolytes, and thereby enhance the dispersion of SWNTs in aqueous media. The steric forces produced by the attached polyelectrolytes overcome the high van der waals force of attraction between the nanotubes and aid in the nanotubes dispersion. Characterization of the dispersions with UV-Vis Spectrophotometric method in kinetic mode revealed that nanotubes treated at pH 3 are seen to be more stable than the ones treated at pH 7. The effect of pH of the polyelectrolyte solutions in the assembly and its consequence on dispersion stability is also studied with zeta potential measurements. The morphology of the films produced by drying the nanotubes in vacuum on a silicon substrate is characterized by field emission scanning electron microscopy (FESEM).
Carbon Nanotube Micro-Opto-Mechanical Grippers
Authors: Lu Shaoxin , Liu Ye , Shao Ning , Panchapakesan Balaji 
Published: April 2011

ABSTRACTWe report the integration of single wall carbon nanotube ensembles into micro-mechanical systems to realize a new carbon nanotube micro-optomechanical system (CNT-MOMS). CNT-MOM grippers were fabricated with CMOS compatible techniques involving nanotube film formation, wafer bonding, photo-lithography, plasma etching and dry release. MOM-grippers displacement of ∼24μm was obtained from a gripper of 430μm in length under infra-red laser stimulus and continuous operation of more than 100,000 cycles was acquired. The optical power consumption of the gripper operation was estimated to be as small as ∼240μW. This study is a good example of how nano-materials could be integrated into CMOS compatible techniques for applications in high performance MEMS and nanoscale actuation technologies.
Effect of Solvent Concentration to the Preparation of Polystyrene Nanoparticles Using Polyelectrolyte Block Copolymer
Authors: Edwin Garcia Doronila , Choi Youngjin , Moon Hyeongmin , Jung Bumsuk 
Published: April 2011

ABSTRACTParticles of sizes within the nano region have attracted many applications in different fields of science. In this study, the self assembly property in a selective solvent of block copolymers has been used for the preparation of polystyrene nanospheres. Sulfonated Styrene-Butadiene-Styrene (SSBS) tri block copolymer was used as a polymeric surfactant for synthesis of uniformly sized polystyrene nanoparticles using emulsion polymerization. The effects of initiator, monomer and block copolymer concentration to the molecular weight distribution and size distribution were investigated. Uniformly sized nanoparticles with a polydispersity index of 1.004 and diameter of 112.9nm was verified by Dynamic Light Scattering (DLS) and Scanning Electron Microscopy (SEM), respectively. Using a mixed continuous phase solution of water and methanol, it was found out that the particle size decreased relative to the increase of methanol added to the reaction solution. Associating behavior of the polyelectrolyte block copolymer in the binary solvent environment regarding size of micelle formed was reflected on the properties of the nanospheres. Nanoparticles prepared with greater methanol concentration were observed to be less than 100 nm. Size distribution was also observed to be narrower in proportion to MeOH concentration.
Polymer Nanofibers Containing Isolated and Aligned Single Wall Carbon Nanotubes
Authors: Young Robert , Eichhorn Stephen , Kannan Prabhakaran 
Published: April 2011

ABSTRACTElectrospinning has been used to prepare poly(vinyl alcohol) (PVA) nanofibers, with diameters ranging from 1 micron down to 20 nm, that contain dispersions of isolated, well-aligned, single wall carbon nanotubes (SWNTs). The nanofibers were characterized by Raman spectroscopy and single radial breathing modes (RBMs) were found for the SWNTs in the nanofibers indicating debundling of the original SWNT ropes. Moreover a split G' band for some nanotubes and the results of polarized Raman spectroscopy were consistent with the presence of isolated SWNTs, highly aligned along the nanofiber axes.
Conducting polymer fibers of polyaniline doped with camphorsulfonic acid
Authors: Khan Saima Naz , Khan Aurangzeb , Kordesch Martin E. 
Published: April 2011

ABSTRACTElectrically conducting fibers of polyaniline doped with Camphorsulfonic acid PAn.HCSA in the Polyethylene Oxide (PEO) matrix were prepared using the non-mechanical electrospinning technique. The morphology of the fibers was studied using the scanning electron microscope (SEM) and Transmission electron microscope (TEM), showing a uniform thickness along the fiber length. The fibers had a diameter ranging from 800nm to 2μm. The electrical conductivity of the non-woven fibrous mat and the cast film was measured using the four-point probe method, for different concentrations of Pan.HCSA in the blend. Some possible factors affecting the electrical conductivity of the fibers/films were discussed.
Fabrication of Polymeric Capsules Enclosing Eletrophoretic Particle Dispersion
Authors: Qiao Ru , Zhang Xiao Li , Qiu Ri , Li Yan , Kang Young Soo 
Published: April 2011

ABSTRACTPoly(urea-formaldehyde) capsules enclosing electrophoretic particle dispersion were formed by carrying out an in-situ polymerization reaction in an oil-in-water emulsion. The internal dispersion was composed of pigment particles Yellow-14 modified by charge control agent to have superior electrophoresis velocity and the mixture of tetrachloroethylene and sec-butylbenzene, using Span 80 as the stabilizer and emulsifier. FE-SEM, TEM, and optical microscope (OM) were performed to investigate on the capsule size and surface morphology. Contact angle measurements showed that UF prepolymer deposited at the o/w interface to form hollow capsules only when the interfacial tension is large enough.
A Comparative Study of the Structure/Property Relationships of Langmuir-Blodgett and Spin-Cast Films of an Amphiphilic, Regioregular Polythiophene Polymer
Authors: Mattu Jusroop , Johansson Thomas , Holdcroft Steven , Leach Gary W. 
Published: April 2011

ABSTRACTThe effects of structural conformation and order on materials properties and reactivity in thin films of an amphiphilic, regioregular polythiophene π-conjugated polymer (πCP) derivative are presented. Thin films deposited by the Langmuir Blodgett technique provide highly ordered anisotropic films compared to those deposited by spin cast methods. Large differences in both the thermal reactivity and physical properties of the films are observed.
Electrical and Microstructural Changes of β-PVDF under Different Processing Conditions by Scanning Force Microscopy
Authors: Nunes J. Serrado , Sencadas V. , Wu A. , Kholkin A. L. , Vilarinho P. M. , Lanceros-Méndez S. 
Published: April 2011

ABSTRACTPoly vinylidene fluoride (PVDF) has been widely investigated due to its important pyro- and piezoelectric properties. These properties have found various applications, especially as sensor and actuators. The existence and optimization of these properties is intimately related with the fraction of the polymer in the crystalline phase, its structure, microstructure and orientation. All of these in turn heavily depend on the processing conditions. PVDF is a semi-crystalline polymer which shows polymorphism and is commonly crystallized in non-polar crystalline α-phase. The piezo- and pyroelectric properties mainly depend on the β-phase, so that increasing β-phase content has always been of great concern in this field.β-phase can be obtained by mechanical stretching of α-phase films at a given temperature or directly from solution. Conversion of α into β-phase takes place at stretching temperatures below 100 °C, at a stretch ratio of about 3–5. Nevertheless the achieved amount of β-phase in the crystalline fraction of the material is never 100%. In the films obtained from solution, 100% beta phase films can be achieved in either a porous or non-porous form. The degree of crystallinity is also larger for the samples obtained from solution.This work is mainly devoted to the study of the variations in the topological morphology and piezoelectric domain response of PVDF prepared by the aforementioned methods by scanning force microscopy in a piezo-response mode.
Melt Crystallization of Nanocomposites of Poly(Vinylidene Fluoride) with OMS
Authors: Ince-Gunduz Bedriye Seyhan , Amare Debeshu , Alpern Robert , Cebe Peggy , Crawford Jennifer , Dolan Breanna , Jones Stacey , Kobylarz Ryan , Reveley Matthew 
Published: April 2011

ABSTRACTIn our previous work [1] we investigated the impact of cold-crystallization on the structure of nanocomposites of PVDF with Lucentite STN™ OMS and observed the crossover composition in which the crystallographic beta phase dominated over alpha phase. Here, melt crystallization of PVDF/OMS nanocomposites was studied in the range of 0 to 1.0 wt% of OMS. In crystallization from melt, a decrease in crystallinity index occurs as a result of an increase in OMS. While beta phase fraction increased with an increase of OMS content in the range of interest, the amount of alpha crystals was found to be dominant even at high OMS compositions. At 1.0 wt% of OMS, beta crystals had reached at most 30% of the total crystallinity. Polarizing optical microscopy (POM) studies showed smaller, less birefringent spherulites with higher melting temperature compared to alpha spherulites appeared with OMS addition. Growth rate of these weakly birefringent spherulites is smaller than that of the strongly birefringent alpha spherulites. The increase in size and amount of the weakly birefringent spherulites with an increase of OMS and their higher melting point suggests these spherulites may be in the beta crystallographic phase.
Dynamic Behavior Investigation of the Piezoelectric PVDF for Flexible Fingerprint
Authors: Chang Wen-Yang , Cheng Ying-Hui , Liu Shu-Yuan , Hu Ying-Chiang , Lin Yu-Cheng 
Published: April 2011

ABSTRACTThe paper reported a novel flexible concept for acquiring the fingerprint that based on the piezoelectric PVDF (polyvinylidene fluoride) was integrated into the flexible polyimide substrate to form the fingerprint. In this study, it focused on the array PVDF fabrication and dynamic control circuit to read pressure signal for fingerprint identification. The fabrication of PVDF powder was melt at 180°C, pressed under 2 tons and subsequently quenched at 10°C/min to form the PVDF films. Next the PVDF films were put into the oven at different temperatures for 40 minutes to stretch 4 times from its original length. As for the dynamic control, the sensing circuit was presented two parts, one is charge amplifier and the other is capacitance detect by using frequency oscillator. We demonstrated that the dynamic pressure measurement of PVDF could achieve fingerprint acquisition. Experimental results showed the response speed of sensing is as fast as 5 ms. Therefore, the aim of this study is to speed up the technology for promoting the flexible fingerprint.
Ionic Polymer Conductor Nano-Composites as Distributed Nanosensors, Nanoactuators and Artificial Muscles - A Review
Authors: Shahinpoor Mohsen 
Published: April 2011

ABSTRACTBasic recent results, properties and characteristics of ionic polymer conductor nano-composites (IPCNC) as biomimetic distributed nanosensors, nanoactuators and artificial muscles are briefly discussed in this paper. Some fundamental considerations on biomimetic distributed nanosensing and nanoactuation are first presented and then expanded to cover some recent advances in manufacturing techniques, force optimization, 3-D fabrication of IPMC's, recent modeling and simulations, sensing and transduction and product development. This paper also covers some recent industrial and medical applications including a multi-fingered grippers (macro, micro, nano), biomimetic robotic fish and caudal fin actuators, diaphragm micropump, multi-string musical instruments, linear actuators made with IPMNC's, IPMNC-based data glove and attire, IPMNC-based heart compression/assist devices and systems, wing flapping flying system made with IPMNC's and a host of others.
PLD Growth of CNTs using a Nanostuctured Ni Buffer Layer: Dependence of H2 partial Pressure
Authors: Chandran Maneesh , Kant K. Mohan , Rama N. , Rao M.S. Ramachandra 
Published: April 2011

ABSTRACTThe effect of hydrogen partial pressure on the growth of CNT thin films using on-axis PLD has been studied. Using nickel as buffer layer, carbon nanotubes can be produced with good yield in Hydrogen atmosphere. We have found strong visible-near infrared (NIR) photoluminescence (PL) from carbon nanotube thin films synthesized under various hydrogen partial pressures. The present result shows that bright, narrow PL from CNTs can be obtained without any post growth processing.
Use of High Surface Area TiO2 Nanosheet in Dye-sensitized Solar Cell
Authors: Pavasupree Sorapong , Ngamsinlapasathian Supachai , Suzuki Yoshikazu , Yoshikawa Susumu 
Published: April 2011

ABSTRACTHigh surface area nanosheet TiO2 with mesoporous structure were synthesized by hydrothermal method at 130 °C for 12 h. The samples characterized by XRD, SEM, TEM, SAED, and BET surface area. The nanosheet structure was slightly curved and approximately 50-100 nm in width and several nanometers in thickness. The as-synthesized nanosheet TiO2 had average pore diameter about 3-4 nm. The BET surface area and pore volume of the sample were about 642 m2/g and 0.774 cm3/g, respectively. The solar energy conversion efficiency (η) of the cell using nanorods/nanoparticles TiO2 (from the nanosheet calcined at 450 °C for 2 h) with mesoporous structure was about 7.08 % with Jsc of 16.35 mA/cm2, Voc of 0.703 V and ff of 0.627; while η of the cell using P-25 reached 5.82 % with Jsc of 12.74 mA/cm2, Voc of 0.704V and ff of 0.649.
Design, Fabrication and Testing of a Novel Gas Sensor utilizing Vertically Aligned Zinc Oxide Nanowire Arrays
Authors: Parthangal Prahalad , Cavicchi Richard , Zachariah Michael 
Published: April 2011

ABSTRACTWe report on a novel, non-destructive, in-situ approach toward connecting and electrically contacting vertically aligned zinc oxide nanowire arrays using conductive gold nanoparticles. A chemical gas-sensing device was constructed and tested using this nano-architecture. Well-aligned, single-crystalline zinc oxide nanowires were grown through a direct thermal evaporation process at 550 °C on gold catalyst layers. Electrical contact to the top of the NW array was established by creating a contiguous nanoparticle film through electrostatic attachment of conductive gold nanoparticles exclusively onto the tips of nanowires. The gas-sensing device fabricated through this approach was found to be sensitive to both reducing (methanol) and oxidizing (nitrous oxides) gases. This assembly approach is amenable to any array of one-dimensional nanostructures for which a top contact electrode is needed.
Mechanoluminescence Studies upon Single Nanoparticles by AFM-photomeasurement System
Authors: Terasaki Nao , Sakai Kazufumi , Koga Toshiaki , Li Chengzhou , Imai Yusuke , Yamada Hiroshi , Adachi Yoshio , Nishikubo Keiko , Xu Chao-Nan 
Published: April 2011

ABSTRACTWe successfully measured the mechanoluminesence (ML) from a single ML nanoparticle at the first time. In order to measure the weak light emission from a single nanoparticle induced by applying a micro force, we developed an AFM-based new apparatus with a photomultiplier. Interestingly, the emission (ML) intensity from a nanoparticle was approximately proportional to the load, the phenomena is similar to the macroscopic ML emission properties.
Endothelial Cell Adhesion on Highly Controllable Compared to Random Nanostructured Titanium Surface Features
Authors: Lu Jing , Webster Thomas J. 
Published: April 2011

ABSTRACTThe application of vascular stents using conventional metals is limited because the implantation process will cause significant injury to the vascular wall and endothelium, resulting in neointima hyperplasia and then the development of long-term restenosis. The objective of this in vitro study was to investigate endothelial cell function (especially their adhesion behavior) on highly controllable nanostructured surface features. Considering the importance of the endothelium and its properties, highly controllable nanostructured surface features of titanium (a popular vascular stent metal) were created using E-beam evaporation to promote endothelialization and to control the direction of endothelial cells on vascular stents. Endothelial cells are aligned with blood flow naturally in the body. In this manner, the present in vitro study provides much promise for the use of nanotechnology for improving metals for vascular stent applications.
Importance of Nanosensors: Feynman's Vision and the Birth of Nanotechnology
Authors: Devreese Jozef T. 
Published: April 2011

ABSTRACTIn his visionary 1959 lecture at Caltech, Feynman envisaged the potential of the ability to manipulate matter at the atomic scale. I discuss implementations of Feynman's vision in the field of nanosensors and perspectives of its further development and applications.
Stimuli-Responsive Hydrogels Based on the Genetically Engineered Proteins: Actuation, Drug Delivery and Mechanical Characterization
Authors: Moschou Elizabeth A. , Chopra Nitin , Khatwani Santoshkumar L. , Ehrick Jason D. , Deo Sapna K. , Bachas Leonidas G. , Daunert Sylvia 
Published: April 2011

ABSTRACTHerein, we describe a biomimetic approach aimed at the development of synthetic biohybrid materials inspired by nature's sensing and actuating mechanism of action. The biomaterials are based on the incorporation of the hinge-motion binding protein calmodulin (CaM) and its low affinity ligand phenothiazine (TAPP) within the bulk of an acrylamide hydrogel network, which is accomplished through covalent binding. At the initial state and in the presence of Ca2+ ions, CaM interacts with TAPP creating chemical (non-covalent) cross-links within the bulk of the hydrogel, forcing the material to assume a constrictive configuration. Upon the removal of Ca2+, CaM releases TAPP, breaking the non-covalent cross-links within the bulk of the hydrogel and letting the material relax into a swollen state. The same type of effect is observed when a higher affinity ligand for CaM, like chlorpromazine (CPZ), is employed. In the presence of CPZ, the protein releases TAPP and binds CPZ, allowing the biomaterial to swell into a relaxed state. This swelling response of the biomaterial is reversible, and is directly related to the levels of CPZ used. The sensing and subsequent actuating mechanism of the CaM-based stimuli-sensitive hydrogels makes them suitable for a variety of applications, including sensing, mechanical actuation, high-throughput screening, and drug delivery. Additionally, it is shown that the CaM-based stimuli-sensitive hydrogels developed present unique mechanical properties, suitable for integration within microfluidics and MEMS structures. It is envisioned that these biomaterials will find a number of applications in a variety of fields, including drug delivery.