bluuebunny/crossref_metadata_2025_split huggingface dataset:
Determination of Coherency Strain Fields Around Coherent Particles in Ni-Al Alloys by HREM and CBED
Authors: Calderon H. A. , Calzado L. , Kisielowski C. , Wang C. Y. , Kilaas R. 
Published: April 2011

AbstractQuantitative evaluation of coherency strains around particles in the alloy Ni-12 at.% Al has been performed by means of high resolution electron microscopy (HREM) and convergent bean electron diffraction (CBED). Evaluation of the elastic strain fields around particles can give insight into the elastic interaction between particles during their coarsening mechanism and especially for the late stages where the elastic energy becomes particularly important. Typically, particles form spatial arrangements after long aging times. In the case of fcc-type structures, they align along the <001> soft elastic directions and form groups of many particles. HREM has been used to acquire images including the particle matrix interface. The selected zone axis is [001]. The quantitative analysis to determine the positions of the intensity maxima and the subsequent evaluation of the lattice parameters, is made by using the software Darip. Two different directions with respect to the particle matrix interface (parallel and perpendicular) are considered for the evaluation. These measurements are compared to determinations made by means of quantitative evaluation based on calibrated CBED patterns taken from similar regions of the samples.
On the Raman Spectrum of Nanobundles of Single Wall Carbon Nanotubes
Authors: Alvarez L. , Righi A. , Rols S. , Anglaret E. , Sauvajol J.L. 
Published: April 2011

ABSTRACTRaman scattering is used to study the structure and electronic properties of bundles of single wall carbon nanotubes. A relation between the tube diameter and the radial breathing mode frequency is derived by combining a description of the covalent bonds inside each nanotube via force constant model with a pair-potential approach to deal with the van der Waals interaction between nanotubes. In the framework of this approach a good agreement is evidenced between the diameter distribution derived from the A1g radial breathing mode frequencies and the one obtained from the analysis of the neutron diffraction spectrum. On the other hand, an investigation of the intermediate frequency range (600-1100 cm-1) of the Raman spectrum is reported. A dependence of the frequency of the modes with the excitation energy is clearly evidenced and assigned to a mode coupling.
Direct Observation of Intercalant and Catalyst Particle in Single Wall Carbon Nanotubes
Authors: Fan X. , Dickey E. C. , Eklund P. , Williams K. , Grigorian L. , Puretzky A , Geohegan D. , Buczko R. , Pantelides S. T. , Pennycook S. J. 
Published: April 2011

ABSTRACTThe Z-contrast scanning transmission electron microscopy (STEM) imaging technique has been used to study dopant atoms and catalyst particles in single wall carbon nanotubes (SWNT). Iodine and bromine have been doped respectively in arc-grown SWNTs. We have directly observed the dopant sites and distributions. Both dopants appear to be incorporated linearly within the SWNT bundles. SWNT were also grown by pulsed laser ablation with mixed Ni and Co catalyst, and the size and distribution of catalytic particles was studied. By using Z-contrast imaging, we found that the size distribution of the catalyst particles varied over a large range, but even the smallest were larger than the diameter of an individual SWNT. Furthermore, electron energy loss spectroscopy (EELS) is used to determine the composition of individual nanocatalyst particles, and were found to consist of a uniform alloy of Co and Ni.
Electron Field Emission Characterization of Nanocrystalline Diamond Thin Film Cold Cathode Devices
Authors: Weiss B. L. , Badzian A. , Pilione L. , Badzian T. , Drawl W. , Morell G. 
Published: April 2011

ABSTRACTElectron field emission measurements have been performed on thin film cold cathode materials grown, on molybdenum, by a modified MPACVD diamond process. Specifically the modification is due to the addition of nitrogen and oxygen, in varying ratios, during the diamond growth phase. Characterization using Raman spectroscopy shows features at 1190, 1330 and 1550 cm−1. A simple triode device was fabricated for electron emission characterization. KAPTON® film is used as the insulating layer and a Mo mesh is used as the extraction gate electrode. The collector is an indium tin oxide (ITO) coated glass plate which is positively biased with respect to the gate electrode. Field emission characteristics have shown current measurements of greater than I microamp for fields of 40 V/micron. Gate currents are typically 1000 times greater than the emitted current. Issues currently being addressed include improvement in the total emitted current, current stability and device failure. We also present field emission measurements on diamond films grown by HFCVD.
Structure and Photoluminescence of Hydrogenated Amorphous Carbon Films Produced by Using Aromatic Hydrocarbon Source
Authors: Xu Jun , Ma Tianfu , Li Wei , Wang Li , Li Zhifeng , Chen Kunji 
Published: April 2011

ABSTRACTThe organic carbon source –xylene(C6H6-C2H4), was used to fabricate a-C:H films in plasma enhanced chemical vapor deposition system. The structures and bonding configurations were characterized and compared with that of conventional methane-based samples by using Fourier Transform Infrared spectroscopy and Raman scattering technique. Strong room temperature luminescence in blue-green light range was found and the PL feature was quite different from that of methane-based a-C:H films.
Intrinsic Stress Measurements in CVD Diamond Films
Authors: Yu Jin , Kim J.G. , Sohn Y. C. , Lee Y. S. 
Published: April 2011

ABSTRACTDiamond films were grown over Si substrate at 1253K by the hot filament chemical vapor deposition method using CH4/H2 gas mixture, and intrinsic stresses in the film were deduced from the ex-situ curvature measurements. In order to account for the creep deformation of the Si substrate, an elastic/plastic stress and strain analysis were conducted. Results showed that intrinsic stresses were generally several times larger than the average film stresses and always positive increasing with the film thickness. For the film thickness larger than 10μm, stress relaxation by creep of the substrate became significant, and must be considered for the accurate assessment of the film stress in diamond. Later, an analysis based on the grain growth accounted for the development of intrinsic stresses reasonably well
Ultra-High Strain Response of Elastomeric Polymer Dielectrics
Authors: Kornbluh Roy , Pelrine Ronald , Joseph Jose , Pei Qibing , Chiba Seiki 
Published: April 2011

AbstractThe strain response of dielectric elastomers sandwiched between compliant electrodes was studied. These electroactive polymer artificial muscle (EPAM) materials show excellent overall performance and appear more attractive than many competing actuator technologies. Based on the available data, the actuation mechanism is due to the free charge interaction of the compliant electrodes, enhanced by the dielectric properties of the elastomer (Maxwell stress). Strains over 200%, actuation pressures up to 8 MPa, and energy densities up to 3.4 J/cm3have been demonstrated with silicone rubber and acrylic elastomers. Response time is rapid, and the potential efficiency is high. The fabrication of EPAM actuators can be simple and low cost. A wide range of small devices have been made, to demonstrate the potential of the technology and reveal more about performance and fabrication issues. These devices include bending beam actuators for scanners and clamps, diaphragm actuators for pumps and valves, stretched-film actuators for electro-optics, and bow actuators for muscle-like actuators for small robots and other micro machines.
On the Nature of Heterogeneity in Vacuum Deposited Polyaniline Films
Authors: Ivanov V. F. , Nekrasov A. A. , Cheberyako K. V. , Gribkova O. L. , Vannikov A. V. 
Published: April 2011

AbstractHeterogeneity of polyaniline and other conductive polymers in intermediate oxidation states is fundamental problem of physics and chemistry of these ones. Usually only advanced methods may be used for immediate detection of the heterogeneity in the molecular scale range. For the first time we have observed the process of the heterogeneous net-like structure formation in macroscopic scale under the oxidation of the evaporated polyaniline films by aqueous HNO3. and other oxidative agents. Formation of heterogeneous structure is explained in terms of nonequilibrium thermodynamic and chemical kinetics.
Biochemical Synthesis and Unusual Conformational Switching of a Molecular Complex of Polyaniline and DNA
Authors: Nagarajan Ramaswamy , Tripathy Sukant K. , Kumar Jayant , Samuelson Lynne A. , Bruno Ferdinando F. 
Published: April 2011

AbstractPolyaniline (Pani) is one of the most interesting conducting polymers because of its promising electrical properties and unique redox tunability. Recently a new template assisted, enzymatic synthetic approach has been developed which yields a water-soluble and conducting complex of polyaniline and the template used. The mild reaction conditions in this approach allow for the utilization of delicate biological systems as template materials, such as DNA. Here we report the extension of this enzymatic approach to the synthesis of Pani on a DNA matrix. DNA serves as a suitable template for complexation and formation of conducting polyaniline. The redox behavior of Pani induces reversible conformational change in the secondary structure of DNA. Circular dichroism results suggest that the secondary structure of the DNA may be reversibly switched through manipulation of the redox state of the polyaniline.
Modified Constitutive Equation of Superplasticity Including Grain Growth Rate
Authors: Miyazaki H. , Iseki T. , Yano T. 
Published: April 2011

AbstractSuperplastic behavior associated with grain growth in ceramics at high temperature is predicted by using a modified constitutive equation for superplasticity that incorporates the rate of grain growth. The equation reveals that there is an optimum deformation conditions – i.e., the strain rate and deformation temperature - so that ceramics have low flow stress when the grain growth is significant. The equation provides an explanation of increased flow stress for liquid-phase-sintered SiC in the slow-strain-rate region or higher-temperature region in which grain growth plays an important role.
Computer Simulation of Grain Boundary Character in a Superplastic Aluminum Alloy
Authors: McNelley T.R. , Peréz-Prado M.T. 
Published: April 2011

AbstractHigh-angle grain boundaries are generally deemed necessary for superplasticity in metals. In polycrystalline materials the grain boundary character must be described in terms of a probability distribution rather than by a single parameter, and little has been reported on the relationship between this distribution and fine-grain superplasticity. For aluminum alloys that exhibit continuous recrystallization the results of computer-aided electron backscatter diffraction analysis have shown that bimodal grain boundary disorientation distributions are present in as-processed material and persist during subsequent annealing. Such distributions may be simulated by computer methods based on a model of the microstructure which assumes that deformation banding occurs during deformation processing. High-angle boundaries (≥30°) develop in association with deformation banding while boundaries of lower disorientation (<30°) develop by dislocation reaction within the bands. Improved understanding of the grain boundary types associated with various microstructural transformation mechanisms will aid the design of processes to produce superplastic microstructures.
Cavitation Behavior of Coarse-Grained Al-4.5Mg Alloy Exhibiting Superplastic-Like Elongation
Authors: Iwasaki H. , Mori T. , Hosokawa H. , Tagata T. , Mabuchi M. , Higashi K. 
Published: April 2011

AbstractCavitation behaviors related to ferrous primary crystals have been investigated at a temperature of 653 K and a strain rate of 10−3/s for Al-4.5%Mg-0.05%Fe and Al-4.5%Mg-0.2%Fe alloys which have a grain size of 50;Lm. The alloys constantly exhibited a large elongation-to-failure above 300% at the temperature of 653 K and strain rate of 10−3/s. Cavitation was increased by increasing the iron content. Most cavities were nucleated at the interface between the ferrous primary crystal and matrix and elongated parallel to the tensile direction. The experimental critical diameter of the primary crystal, above which cavity is nucleated, was 1.5 µm at the grain boundary and 0.5µm at grain interior, which were very close to double the critical diffusion length.
Intelligent Gels
Authors: Osada Yoshihito , Gong Jian Ping , Narita Tetsuharu 
Published: April 2011

AbstractWe reported an electro-driven chemomechanical hydrogel showing quick responses with worm-like motility. The principle of the motion is based on the molecular assembly reaction of cationic surfactant and negatively charged hydrogel. And direction of complexation accompanying gel contraction is controlled by changing the polarity of the applied electric field. Both thermodynamics and kinetics of surfactant binding and diffusion are investigated experimentally and theoretically. We also reported shape memory hydrogel by order-disorder transition of alkyl side chain, and some examples od friction of hydrogels showing that frictional behaviors of hydorgels do not conform to Amonton's law.
Electrical Properties and Power Considerations of a Piezoelectric Actuator
Authors: Jordan T. , Ounaies Z. , Tripp J. , Tcheng P. 
Published: April 2011

AbstractThis paper assesses the electrical characteristics of piezoelectric wafers for use in aeronautical applications such as active noise control in aircraft. Determination of capacitive behavior and power consumption is necessary to optimize the system configuration and to design efficient driving electronics. Empirical relations are developed from experimental data to predict the capacitance and loss tangent of a PZT5A ceramic as nonlinear functions of both applied peak voltage and driving frequency. Power consumed by the PZT is the rate of energy required to excite the piezoelectric system along with power dissipated due to dielectric loss and mechanical and structural damping. Overall power consumption is thus quantified as a function of peak applied voltage and driving frequency. It was demonstrated that by incorporating the variation of capacitance and power loss with voltage and frequency, satisfactory estimates of power requirements can be obtained. These relations allow general guidelines in selection and application of piezoelectric actuators and driving electronics for active control applications.
High-Temperature Thermoelectric Properties of Silicon Boride Ceramics as a Smart Material
Authors: Takashima Noriyuki , Azuma Yasuo , Matsushita Jun-Ichi 
Published: April 2011

AbstractSeveral silicon boride phases such as SiB4, SiB6, SiB6-x, SiB6+x, and Si11B31, were previously reported. Among them, SiB6has proved to be a potentially useful material because of its excellent electrical conductivity, high degree of hardness, moderate melting point, and low specific gravity. The sintering conditions and thermoelectric properties of silicon boride (SiB6) ceramics produced by hot pressing were investigated in order to determine the suitability of this material for high-temperature thermoelectric applications as a smart material. The relative density increased with increasing sintering temperature. With a sintering temperature of 1923 K, a sintered body having a relative density of more than 99% was obtained. X-ray diffraction analysis showed no crystalline phase other than SiB6 in the sintered body. The specimens were prepared for measurement of the electrical conductivity and Seebeck coefficient by the D.C. four-terminal method. The thermal conductivity of SiB6 was obtained by calculation from the thermal diffusivity and specific heat capacity of the specimen. The electrical conductivity of SiB6 increased with increasing temperature. The electrical conductivity of the polycrystalline SiB6 (99% dense) was 0.5 to 1.1 × 103 S/m at 298 to 1273 K. The thermal conductivity decreased with increasing temperature in the range of room temperature to 1273 K. The thermal conductivity was 9.1 to 2.5 W/mK in the range of room temperature to 1273 K. The Seebeck coefficient of SiB6 increased with increasing temperature. The Seebeck coefficient of SiB6 was 140 × 10−6 V/K at 1273 K. The figure of merit Z of SiB6 increased with increasing temperature. The Z of SiB6 reached 8.1 × 10−6/K at 1273 K. The ZT value is useful to evaluate the ability of thermoelectric materials. The ZT value reached 0.01 at 1273 K. Based on the results, SiB6 showed very good thermoelectric material characteristics at high temperature.
Force Capability of a Planar Peristaltic Terfenol-D Motor
Authors: Gerver M. J. , Goldie J. H. , Kim Won-Jong , Kiley Jerome , Swenbeck J. R. 
Published: April 2011

AbstractA magnetostrictive peristaltic motor, similar to an INCHWORM® motor, was designed, built, and tested, using Terfenol-D® as the active element. Unlike the Kiesewetter motor, which uses a rod of Terfenol-D in a closely fitting cylindrical channel, in our design the Terfenol-D is in the form of a flat slab, held between two spring-loaded plates. With this configuration the motor is not affected by wear of the Terfenol-D surface. In order to avoid eddy currents, we used laminated Terfenol-D. Operating at 1600 Hz with a peak field of 430 oersteds, the speed at no load was observed to be 12 mm/sec, which is 65% of the theoretical value (the peak strain times the peristaltic phase velocity), probably because the surface flatness of the Terfenol-D slab was only a few times smaller than the height of the peristaltic bumps. The measured stalling force was 90 newtons, corresponding to 350 kPa load stress in the Terfenol-D, only 3.5% of the peak strain times the stiffness of the Terfenol-D. This force was in almost exact agreement with a model which took into account the force from the spring-loaded plates (needed to avoid slippage), the transverse stiffness of the Terfenol-D slab, and the finite bending stiffness of the stator. The model can be used to design optimized motors with improved force capability. We tried using composite Terfenol-D, consisting of Terfenol-D particles in an epoxy binder, but the speed and stalling force were lower, perhaps because it did not have a very uniform distribution of particles, and was not machined as flat as the laminated Terfenol-D. The motor was driven by a specially designed 3-phase power inverter and digital controller, and the large reactive power inherent in this kind of motor was reduced by putting it in series with resonant capacitors.
The Design of Organic Gelators Based on a Family of Bis-Ureas
Authors: Meléndez Rosa E. , Carn Andrew J. , Sada Kazuki , Hamilton Andrew D. 
Published: April 2011

AbstractThe use of organic molecules as gelators in certain organic solvents has been the target of recent research in materials science. The types of structures formed in the gel matrix have potential applications as porous solids that can be used as absorbents or in catalysis. We will present and discuss the organogelation properties of a family of bis-ureas. Studies presented will include a molecule structure activity relationship, thermodynamic properties, comparison to x-ray crystallographic data and potential functionalization of the gels formed by this class of compounds
Fluxless Microjoining by Au-In-Ni Isothermal Solidification
Authors: Waelti M. , Schneeberger N. , Brand O. , Baltes H. 
Published: April 2011

AbstractA reliable, fluxless microjoining technique based on isothermal solidification is reported. The Au-In-Ni system has been chosen for bonding, because gold is often applied for wafer bumping, and Ni is commonly used for substrate plating. To demonstrate the potential of this microjoining scheme, optical filter have been directly attached to a smart CMOS thermoelectric IR system. Since further packaging of the microsystem includes SMT assembly, the bond has to withstand subsequent SnPb reflow-soldering.The influence of bonding time and temperature on the bond was investigated. Phase formation and transformation were analyzed by light and scanning electron microscopy (SEM). Bonding performed at temperatures below 200°C remained stable even after multiple soldering cycles with peak temperatures of 235°C. The shear strength of the bonds was found to be more than 70 MPa. Long term stability was confirmed by extended anneal at 160°C. The method is generally well suited for processes involving sequences of joining steps, and for bonds demanding high strength and high thermal stability at low bonding temperature.
Deposition and Characterization of In-Situ Boron Doped Polycrystalline Silicon Films for Microelectromechanical Systems Applications
Authors: McMahon J. J. , McMahon J. J. , Melzak J. M. , Zorman C. A. , Chung J. , Mehregany M. 
Published: April 2011

AbstractIn an effort to develop thick, p-type polycrystalline silicon (polysilicon) films for microelectromechanical systems (MEMS) applications, in-situ boron-doped polysilicon films were deposited by a single-step APCVD process at susceptor temperatures ranging from 700°C to 955°C. The process produces boron-doped films at a deposition rate of 73 nm/min at 955°C. Spreading resistance measurements show that the boron doping level is constant at 2 × 1019 /cm3 throughout the thickness of the films. Doped films deposited at the low temperatures exhibit compressive stress as high as 666 Mpa; however films deposited at 955°C exhibited stress as low as 130 MPa. TEM and XRD show that the microstructure strongly depends on the deposition conditions. Surface micromachined, singly clamped cantilevers and strain gauges were successfully fabricated and used to characterize the residual stress of 5.0 µm-thick doped films deposited at a susceptor temperature of 955°C.
Maskless Patterning and Structuring on Ultra-Hard Film Materials
Authors: Park J.K. , Ayres V.M. , Asmussen J. , Mukherjee K. 
Published: April 2011

AbstractUltra-hard film materials such as chemical vapor deposited (CVD) diamond are uniquely qualified for applications where superior tribological and electronic properties are required. Patterning of the film materials is essential to produce functional micro devices. Conventional lithography-based chemical etching is difficult or impossible on the ultra-hard diamond film materials, which have a high chemical resistance. Investigations on maskless patterning of the CVD diamond film are presented. Focused excimer laser pulses are used for dry etching on the film materials, and a micro computer numerical control (micro-CNC) stage is used for patterned translation of a target. The laser ablation of CVD diamond is observed to set up relationships among the processing parameters, such as the gas processing environments, the laser energy fluence and the number of laser pulses. The extent of the ablation-induced plasma is observed by time integrated image capturing. A cell-patterned structure, fabricated by the innovative maskless process, is presented for discussion.