bluuebunny/crossref_metadata_2025_split huggingface dataset:
Structural and Mechanical Properties of Diamond-Like Carbon Films Prepared by Pulsed Laser Deposition With Varying Laser Intensity
Authors: Bonelli M. , Ferrari A. C. , Fioravanti A. P. , Miotello A. , Ossi P. M. 
Published: April 2011

ABSTRACTDiamond-like carbon (DLC) films have been prepared by pulsed laser deposition (PLD) (wavelength 248 nm), ablating highly oriented pyrolytic graphite (HOPG) at room temperature in a vacuum of 10−2Pa, at fluences between 0.5 and 35 Jcm−2. Films have been deposited on Si(100) with and without a SiC interlayer. Structural analysis, such as visible and UV Raman, Infrared and Electron Energy Loss (EEL) spectroscopies show that the films are hydrogen-free and undergo a transition, from mainly disordered graphitic to up to 80% tetrahedral amorphous carbon (ta-C), above a laser threshold fluence of 5 J cm−2. The measured residual stresses of as deposited ta-C films do not exceed 2 GPa. Scratch tests show excellent adhesion properties. Low friction coefficients (0.05-0.1) have been measured in ambient humidity. Nanoindentation indicates that film hardness is as high as 70 GPa
Interaction of Oxygen with Nanophase Carbons Investigated by Electron Spin Resonance Spectroscopy
Authors: Manivannan A. , Punnoose A. , Seehra M.S. 
Published: April 2011

ABSTRACTInteraction of oxygen with three commercial activated carbons (GX203, P1400 and MEED50 supplied by PICA USA Inc., with BET surface areas of 1000, 1150 and 2000 m2/g respectively) is investigated using 9 GHz electron spin resonance (ESR) spectroscopy. All three carbons give a single ESR line with g = 2.0028(3), but the linewidth ΔH and the spin concentration Ns, are strongly affected by exposure to oxygen. The ESR parameters (g, ΔH, Ns) are measured for different partial pressures of oxygen. For the highly evacuated samples, δH ≃ 1.2 Oe and Ns≃ 1019/gm and these results are interpreted in terms of uncompensated surface dangling bonds. Oxygen exposure broadens the line and reduces Ns, in direct relation to the surface areas of the carbons and the effect is reversible. Possible effects of the paramagnetic oxygen on dangling bonds are discussed.
Tribochemistry of ZDOL Decomposition on Carbon Overcoats in Ultra-High Vacuum (UHV)
Authors: Bhatia C.S. , Chen C.-Y. , Fong W. , Bogy D.B. 
Published: April 2011

ABSTRACTTribochemical studies of the effect of lubricant bonding on the tribology of the head/disk interface (HDI) were conducted using hydrogenated (CHx) carbon disk samples coated with perfluoropolyether ZDOL lubricant. The studies involved drag tests with uncoated and carbon-coated A1203-TiC sliders and also thermal desorption experiments in an ultra-high vacuum (UHV) tribochamber. We observed that a larger mobile lubricant portion significantly enhances the wear durability of the (head/disk interface) HDI by providing a reservoir to constantly replenish the lubricant displaced in the wear track during drag tests. In the thermal desorption tests we observed two distinct temperatures of desorption. The mobile ZDOL layer is desorbed at the lower thermal desorption temperature and the residual bonded ZDOL layer is desorbed at the higher thermal desorption temperature. We also observed that the hydrogen evolution from CHx overcoats initiates lubricant catalytic decomposition with uncoated A1203/TiC sliders, forming CF3 (69) and C2F5(119). The generation of Hydroflouric acid (HF) during thermal desorption experiments provides the formation mechanism of Lewis acid, which is the necessary component for catalytic reaction causing Z-DOL lube degradation
Electrical and Electrochemical Properties of a-C:N:H Films
Authors: Pleskov Yu.V. , Krotova M.D. , Polyakov V.I. , Khomich A.V. , Rukovishnikov A.I. , Druz B.L. , Zaritskiy I. 
Published: April 2011

ABSTRACTElectrochemical impedance in H2SO4solutions and kinetics of redox reactions in the Fe(CN)63-/4-system were studied on amorphous nitrogenated diamond-like carbon (a-C:N:H) thin-film electrodes. Parameters of point defects (trapping centers) were also measured by the Deep Level Transient Spectroscopy techniques. The films have been fabricated onp- andi-type silicon and quartz substrates, using direct ion beam deposition from an RF inductively coupled N2+ CH4plasma source. The increase in N2/CH4ratio in the gas mixture lead to a decrease in the electrical resistivity and optical bandgap of the films from 3×1010to 5×106Ω cm and from 1.3 to 0.6 eV, respectively. Simultaneously, the concentration of electrically active point defects increased significantly and the charge transfer at the a-C:N:H film/redox electrolyte interface was facilitated
Non-Electrical Poling in Novel Ferroelectric Polymers
Authors: Tasaka S. , Furutani O. , Inagaki N. 
Published: April 2011

AbstractNon-electrical poling was proposed in novel ferroelectric polymers including such as polythioureas, polycyanophenylenesulfides, and polyvinyfluorides. This poling method utilizing the cooperativity of molecular dipoles can be called “surface energy poling” and takes agvantage of the energy difference inthe top and bottom surface of apolar aggregate (dipole glass) to form a remanent polarization. A ferroelectric polymer film sandwiched between a metal with higher surface energy and PTFE film with lower surface energy were heated to Tp=Tc (glass tramsition temperature or ferroelectric transition) × 1.2 and cooled slowly to room temperature. In the thin films less than 10μm, we observed the remanent polarization which gives a large pyroand piezo-electric constant as well as that obtained by electrical poling. This poling is effective for homogenious structures such as amophous ferroelectric polymers.
Challenges to the Transition to the Practical Application of IPMC as Artificial-Muscle Actuators
Authors: Bar-Cohen Y. , Leary S. , Yavrouian A. , Oguro K. , Tadokoro S. , Harrison J. , Smith J. , Su J. 
Published: April 2011

AbstractIn recent years, electroactive polymers (EAP) materials have gained recognition as potential actuators with unique capabilities having the closest performance resemblance to biological muscles. Ion-exchange membrane metallic composites (IPMC) are one of the EAP materials with such a potential. The strong bending that is induced by IPMC offers attractive actuation for the construction of various mechanisms. Examples of applications that were conceived and investigated for planetary tasks include a gripper and wiper. The development of the wiper for dust removal from the window of a miniature rover, planned for launch to an asteroid, is the subject of this reported study. The application of EAP in space conditions is posing great challenge due to the harsh operating conditions that are involved and the critical need for robustness and durability. The various issues that can affect the application of IPMC were examined including operation in vacuum, low temperatures, and the effect of the electromechanical and ionic characteristics of IPMC on its actuation capability. The authors introduced highly efficient IPMC materials, mechanical modeling, unique elements and protective coatings in an effort to enhance the applicability of IPMC as an actuator of a planetary dust-wiper. Results showed that the IPMC technology is not ready yet for practical implementation due to residual deformation that is introduced under DC activation and the difficulty to protect the material ionic content over the needed 3-years durability. Further studies are under way to overcome these obstacles and other EAP materials are also being considered as alternative bending actuators.
Conduction Behavior of Doped Polyaniline Under High Current Density and the Performance of an all Polymer Electromechanical System
Authors: Xu Haisheng , Bharti V. , Cheng Z.-Y. , Zhang Q. M. 
Published: April 2011

AbstractIn many device applications, such as electro-acoustic transducers and actuators based on high strain electroactive polymers, there are many advantages to utilize conductive polymers as electrodes. However, in these applications, a high electric power usually is required which translates to high voltage and high current in the system. Hence, the maximum current density which a conducting polymer can carry is of great interest and importance. In this paper, the conduction behavior at high current density of doped polyaniline(PANI) is reported. It was found that the current density deviates strongly from the ohmic relation with the electric field in high current density region and a saturation of the current density was observed. The maximum current density Jm observed is proportional to the conductivity of the samples and for PANI doped with HCSA, Jm can reach as high as 1200 A/cm2. Making use of the conducting polymer as the electrodes for the electrostrictive P(VDF-TrFE) copolymer, an all-polymer electromechanical system was fabricated. The all-polymer films exhibit similar or larger electric field induced strain responses than those from films with gold electrodes, presumably due to reduced mechanical clamping from the electrodes. In addition, the all-polymer system also exhibits comparable dielectric and polarization properties to those of gold-electroded P(VDF-TrFE) films in a wide temperature (from −50°C to 120°C) and frequency range (from 1Hz to 1MHz). These results demonstrate that polyaniline can be used for many electro-acoustic devices and provide improved performance.
Effect of the Pore Formation on the Solution Flow through Acrylamide Gel
Authors: Tamagawa H. , Popovic S. , Taya M. 
Published: April 2011

AbstractA simple synthesis method of porous acrylamide gel is proposed. Pore formation in gel body is dominated by the amount of polymerization initiator, accelerator and gelation temperature. We investigated the influence of these factors on the number and the size of pores. Gelation temperature control is the easiest and the most effective way to create a number of large pores in a gel body. We also investigated the pore volume fraction dependence of solution flow through the gels. Solution flow rate was found to be promoted with the increase of pore volume fraction.
Computer Controlled Pulsed Pecvd Reactor for Laboratory Scale Deposition of Plasma Polymerized Thin Films
Authors: Pedrow P. D. , Shepsis L. V. , Mahalingam R. , Osman M. A. 
Published: April 2011

AbstractA pulsed PECVD reactor has been successfully constructed for laboratory scale studies of plasma polymerized thin films. A computer control system based on National Instrument's LABVIEW software controls power supply sequence, feed injection, and introduction of RF energy. An optical fiber and a photo diode allow the user to monitor the emitted light for each pulse. A fast ionization gauge is used to characterize the pressure evolution over time, subsequent to acetylene gas injection. Substrates with diameter as large as 10 cm can be accommodated within the reactor. Both aniline liquid and acetylene gas have been used as reactor feed. The deposited plasma-polymerized films were characterized using AFM and SEM. Electrical conductivity of plasma polymerized acetylene film was also measured
Role of Vacancies and Solute Atoms on Grain Boundary Sliding
Authors: Vetrano J.S. , Henager C.H. , Simonen E.P. 
Published: April 2011

AbstractIt is necessary for grain boundary dislocations to slide and climb during the grain boundary sliding process that dominates fine-grained superplastic deformation. The process of climb requires either an influx of vacancies to the grain boundary plane or a local generation of vacancies. Transmission electron microscopy (TEM) observations of grain boundaries in superplastically deformed Al-Mg-Mn alloys quenched under load from the deformation temperature have revealed the presence of nano-scale cavities resulting from a localized supersaturation of vacancies at the grain boundary. Compositional measurements along interfaces have also shown an effect of solute atoms on the local structure. This is shown to result from a coupling of vacancy and solute atom flows during deformation and quenching. Calculations of the localized vacancy concentration indicate that the supersaturation along the grain boundary can be as much as a factor often. The effects of the local supersaturation and solute atom movement on deformation rates and cavity nucleation and growth will be discussed.
On the Relationship Between Grain Boundary Sliding and Intragranular Slip During Superplastic Deformation
Authors: Sheikh-Ali A. D. , Szpunar J. A. , Garmestani H. 
Published: April 2011

AbstractThis paper examines grain boundary sliding under the conditions of plastic strain incompatibility that is the most frequent case in polycrystalline materials. Two components of grain boundary sliding: dependent and independent on intragranular slip are distinguished. Theoretical estimate of a ratio between slip induced sliding and intragranular slip is obtained. It is concluded that slip and sliding are rather independent than interrelated processes.
High-Strain Rate Superplasticity in Three Contrasting Fine Grained Aluminum Alloys
Authors: Todd R.I. , Kim J.S. , Zahid G.H. , Prangnell P.B. 
Published: April 2011

AbstractThe superplastic properties and microstructures of three contrasting fine grained aluminium alloys were investigated. These included (i) a powder metallurgy MMC, (ii) a severely deformed spray cast alloy, and (iii) the Zn-22%Al eutectoid alloy. The results showed some differences in the details of behaviour between the alloys. One of these was the presence of true work hardening, associated with dislocation activity, in the MMC, and its absence in the microduplex Zn-Al eutectoid alloy. In addition, the powder route MMC had the high threshold stress (up to 10MPa) commonly encountered in such materials, whereas this was not the case with the cast and severely deformed alloy, indicating that the threshold stress was associated with the presence of ceramic particles in the MMC (oxide + reinforcement). In all the alloys, however, the m value tended to increase with temperature, and this led to a corresponding increase in elongation with temperature until the microstructure became destabilised. In the two predominantly single phase alloys studied this destabilisation corresponded to the solvus temperature. The constantly changing m value indicates that there is no unique value of this parameter. The same was found to be true of the grain size exponent, p. The direct interpretation of apparent activation energies in terms of simple physical processes should be made with care in the light of the present results, as (i) the microstructures of two of the alloys were found to change continuously and significantly with small changes in temperature, and (ii) the fact that m is a function of temperature necessarily implies that the apparent activation energy is a function of stress.
Routes to Develop Fine-Grained Magnesium Alloys and Composites for High-Strain Rate Superplasticity
Authors: Mukai Toshiji , Watanabe Hiroyuki , Nieh T. G. , Higashi Kenji 
Published: April 2011

AbstractSuperplastic properties of magnesium alloys and their composites were reviewed with a special emphasis on the achievement of high strain rate superplastic forming. The role of grain size on superplastic deformation mechanisms was particularly addressed. Commercial Mg-Al-Zn alloys and a ZK60-based composite are used as model materials to illustrate the underlining principles leading to the observation of high strain rate superplasticity. In this paper, experimental results from several processing routes, including thermomechanical processing, severe plastic deformation, and extrusion of machined chips and rapidly solidified powders, are presented. High strain rate superplasticity (HSRS) is demonstrated in ZK60-based composites.
SPD Processing and Superplasticity in Ultrafine-Grained Alloys
Authors: Valiev R.Z. , Islamgaliev R.K. 
Published: April 2011

AbstractSevere plastic deformation (SPD), for example by intense plastic straining under high pressure, is an innovative technique for producing ultrafine-grained (UFG) metals and alloys. The SPD fabricated UFG structures can lead to enhanced superplasticity, which, however, depends strongly on processing parameters. The present paper focuses on examples of attaining enhanced superplasticity in several alloys, subjected to SPD and considers the relationship between processing – UFG structures – superplastic properties in SPD produced materials.
“Monolithic Shape Memory Alloy Actuators”: A New Concept for Developing Smart Micro-Devices
Authors: Bellouard Y. , Lehnert T. , Sidler T. , Gotrhardt R. , Clavel R. 
Published: April 2011

AbstractIn micro-robotics and for micro-systems, one cannot simply scale down conventional actuators. Specific difficulties like friction forces between parts and the assembly have to be considered carefully and need a special design strategy adapted to this “micro-world”. Shape Memory Alloys (SMA) have strong potential in micro actuators. So far, most of SMA devices used the SMA material as a part of a mechanical system, which raised several problems when scaling down. In this paper, a concept of monolithic SMA micro-devices, which consists in considering the SMA as a mechanical system by itself, is presented. Several applications are shown to illustrate this concept.
Hypersonic and Dielectric Studies of Relaxor Ferroelectric Single Crystal
Authors: Tu Chi-Shun , Schmiidt V.H. , Yeh C.-H. , Chen L.-F. , Tsai C.-L. 
Published: April 2011

AbstractBoth the longitudinal (LA) Brillouin back-scattering spectra and dielectric permittivity along the [001] direction have been measured as a function of temperature for a relaxor ferroelectric single crystal (PbMg1/3Nb2/3O3)0.68(PbTiO3)0.32 (PMN-32%PT). A sharp ferroelectric phase transition (which is associated with a Landau-Khalatnikov-like phonon damping maximum) was observed near 445 K. As temperature increases, a diffuse phase transition was detected near 280 K. In addition, the nature of the thermal hysteresis for the dielectric permittivity confirms that these transitions (near 280 and 445 K for heating procedure) are diffuse first-order and first-order, It respectively. The dielectric data prove the existence of an electric dipolar relaxation process below 300 K.
On Magnetostrictive Transducer Applications
Authors: Flatau Alison B. , Dapino Marcelo J. , Calkins Frederick T. 
Published: April 2011

AbstractThis paper provides an overview of magnetostrictive transducer technology. The bi-directional coupling between the magnetic and mechanical states of a magnetostrictive material provides a transduction mechanism that can be used both for actuation and sensing. The current interest in design of adaptive smart structures, coupled with the advent of materials that exhibit high sensor figures of merit, such as Metglas and giant magnetostrictive materials such as Terfenol-D has lead to a renewed interest in the engineering of optimized magnetostrictive transducer designs. A survey of recent applications for giant magnetostrictive materials as both sensors and actuators and their use in smart structure applications will be presented along with a brief discussion of some pertinent device design issues. Examples of magnetostrictive actuation used to produce displacements, force and acoustic waves are summarized. Magnetostrictive sensor configurations that measure motion, stress or force, torque, magnetic fields and target characteristics are discussed. A very brief look at transducer modeling and experimental results is included and schematics of a number of actuator and sensor configurations are presented.
Loss Mechanisms in Piezoelectrics
Authors: Uchino K. , Zheng J. , Chen Y.H. , Du X. , Hirose S. , Takahashi S. 
Published: April 2011

AbstractLosses in piezoelectrics are considered in general to have three different mechanisms; dielectric, mechanical and piezoelectric losses. This paper deals with the phenomenology of losses, first, then how to measure these losses separately in experiments.
Modeling and Experiments for Deformation Under Load in Ni-Mn-Ga Ferromagnetic Shape Memory Alloy
Authors: Murray S. J. , Allen S. M. , O'Handley R. C. 
Published: April 2011

AbstractA simple model is proposed to relate strain, stress, field and anisotropy in a ferromagnetic shape memory alloy (FSMA) and experiments were performed to test the validity of the model. The model is presented as applied to the case of orthogonal field and load in a NiMn-Ga FSMA. The model predicts threshold-type strain behavior as field changes at constant load or as load changes with constant field. The measured behavior of strain with stress at constant field approximated the predictions of the model. Field-induced strain remained constant at about 6% with the addition of stress until such a stress was applied that the mechanical energy overcame the anisotropy of the sample and the strain was reduced to 0. The model's predictions of critical strain behavior with applied field at constant stress were qualitatively accurate at some stress levels, but under-predicted the field necessary to produce strain.
Microstructural Effects on Piezoelectric Cracking
Authors: Fulton C.C. , Gao H. 
Published: April 2011

AbstractThe successful development of smart structures using piezoelectric sensors and actuators depends on a thorough characterization of the mechanical limits of these materials. However, fundamental discrepancies between theoretical predictions and empirical observations of their cracking behavior hinder attempts to provide appropriate design guidelines. The complex microstructure of a piezoelectric ceramic leads to severe nonlinear effects at the crack tip, motivating a physics-based investigation of the fracture mechanics. Specifically, the switching and saturation that occur at the level of individual polar domains require a multiscale viewpoint in order to evaluate the conditions which control crack advance. We introduce a model for domain switching based on discrete electric dipoles superimposed on a homogeneous medium with the macroscopic material properties. Each dipole then represents the deviation of a given domain's polarization vector from the linear constitutive law. Within this framework, we develop a relationship between the apparent loads applied to a cracked sample and the local energetic forces driving the crack. Shrinking the length scale down to the crack tip reveals a “singularity conversion”, from the apparent combination of stress and electrical intensity factors to purely mechanical effective opening forces. Using the energy release rate derived from these local stress singularities to predict the dependence of failure load on applied electric field, we are able to reproduce the trends observed in the laboratory.