bluuebunny/crossref_metadata_2025_split huggingface dataset:
Change in Activation Volume for Plastic Deformation of Zr-based Bulk Metallic Glass following Annealing
Authors: Puthoff Jonathan B. , Stone Donald S. , Cao Hongbo , Voyles Paul M. 
Published: April 2011

AbstractWe performed nanoindentation creep experiments on the bulk metallic glass Zr54Cu38Al8 in an effort to measure the scale of the individual deformation events responsible for plastic deformation. From a nanoindentation creep experiment, we can determine V*, the activation volume, which we interpret as the volume of a shear transformation zone (STZ) multiplied by the shear strain undergone by the STZ during thermal activation. For the as-cast alloy hardness, H, is 5.33 ± 0.06 GPa, and V* is 87 ± 5 Å3. The alloy was then annealed near Tg for 24 hr and retested. No crystallization occurred during annealing as verified by XRD and TEM. Following annealing H increased to 7.36 ± 0.08 GPa and V* increased to 160 ± 10 Å3. We interpret the change in V* as arising from an increase in the number of atoms involved in the STZ.
Geometry-sensitive plasticity of a monolithic bulk metallic glass
Authors: Wu WenFei , Li Yi 
Published: April 2011

AbstractWe report a strong geometry-dependence of compressive plasticity in a Zr-based bulk metallic glass (BMG). With a standard orthogonal geometry, the Zr-based BMG typically fractured at a plastic strain less than 2%. However, by modifying the sample geometry while maintaining the sample aspect ratio, a large apparent compressive plastic strain over 10% was achieved consistently. These results present a new method on arresting the catastrophic failure of the glassy alloys and offer ways for BMGs in engineering applications.
Phase Stability of Crystalline and Amorphous Phases and Formation of Nanostructure in Zr-Pd and Zr-Pt Alloys Under Electron Irradiation
Authors: Umakoshi Yukichi , Nagase Takeshi , Hosokawa Takashi 
Published: April 2011

AbstractElectron irradiation induced phase transition behavior of Zr-Pd and Zr-Pt alloys was investigated focusing on phase selection in crystallization by thermal annealing and electron irradiation. Nano quasi-crystalline (QC) phase was formed by thermal crystallization in Zr66.7Pd33.3 and Zr80Pt20 alloys, while nano two-type f.c.c. super-saturated solid solutions were formed by irradiation induced crystallization at 298K. In Zr66.7Pt33.3 alloy, polycrystalline Zr5Pt3 and Zr9Pt11 phases transformed to two-type f.c.c. nano-crystalline phase through an amorphous state by crystal-to-amorphous-to-crystal (C-A-C) transition during electron irradiation. Nano-composite phase composed of f.c.c. super-saturated solid solution and residual amorphous phase was stable rather than an amorphous single phase, thermal equilibrium crystalline phase and quasi-crystalline phase under 2.0MV electron irradiation at 298K, resulting in the formation of nano-composite structure by irradiation induced amorphization and crystallization.
Effect of Hydrostatic Pressure on Indentation Modulus
Authors: Mook William M. , Gerberich W. W. 
Published: April 2011

AbstractThe high pressures generated at a contact during nanoindentation have a quantifiable effect on the measured indentation modulus. This effect can be accounted for by invoking a Murnaghan equation of state-based analysis where the measured indentation modulus is a function of the hydrostatic component of the stress state which is generated beneath the indenter tip. This approach has implications pertinent to a range of mechanical characterization techniques that include instrumented indentation and quantitative atomic force microscopy (AFM) since these techniques traditionally consider only zero-pressure modulus values during data interpretation. To demonstrate the validity of this approach, the indentation modulus of four materials (fused quartz, sapphire, rutile and silicon) is evaluated using a 1 μm radius conospherical diamond tip to maximum contact depths of 30 nm. The tip area function is independently determined via AFM while the unloading stiffness from the load-displacement data is determined using standard Oliver-Pharr analysis.
Mechanical Properties of 3C-SiC Films for MEMS Applications
Authors: Reddy Jayadeep Deva , Volinsky Alex A. , Frewin Christopher L. , Locke Chris , Saddow Stephen E. 
Published: April 2011

AbstractThere is a technological need for hard thin films with high elastic modulus and fracture toughness. Silicon carbide (SiC) fulfills such requirements for a variety of applications at high temperatures and for high-wear MEMS. A detailed study of the mechanical properties of single crystal and polycrystalline 3C-SiC films grown on Si substrates was performed by means of nanoindentation using a Berkovich diamond tip. The thickness of both the single and polycrystalline SiC films was around 1-2 μm. Under indentation loads below 500 μN both films exhibit Hertzian elastic contact without plastic deformation. The polycrystalline SiC films have an elastic modulus of 457 GPa and hardness of 33.5 GPa, while the single crystalline SiC films elastic modulus and hardness were measured to be 433 GPa and 31.2 GPa, respectively. These results indicate that polycrystalline SiC thin films are more attractive for MEMS applications when compared with the single crystal 3C-SiC, which is promising since growing single crystal 3C-SiC films is more challenging.
Theory of Lubrication due to Poly-Electrolyte Polymer Brushes
Authors: Sokoloff Jeffrey B. 
Published: April 2011

AbstractIt is shown using a method based on the mean field theory of Miklavic Marcelja that it should be possible for osmotic pressure due to the counterions associated with the two polyelectrolyte polymer brush coated surfaces to support a reasonable load (i.e., about 105Pa) with the brushes held sufficiently far apart to prevent entanglement of polymers belonging to the two brushes, thus avoiding what is likely to be the dominant mechanisms for static and dry friction.
PLASTICITY CHARACTERISTICS OBTAINED THROUGH INSTRUMENTAL INDENTATION
Authors: Milman Yuliy , Dub Sergey , Golubenko Alex 
Published: April 2011

AbstractThe nanohardness and microhardness testing of crystalline materials with different types of interatomic bonds and different crystal structures was performed with Berkovich indenter.The plasticity characteristics for crystalline materials with different types of interatomic bonds and different crystalline structures were determined by microindentation and by nanoindentation. The relation between these characteristics and parameters of material (Meyer hardness, Young's modulus and Poisson's ratio) was assigned. Plasticity characteristic may be used for characterization of mechanical behavior of materials which are brittle at standard mechanical tests and for coatings.
Tip-Induced Calcite Single Crystal Nanowear
Authors: Gunda Ramakrishna , Volinsky Alex A. 
Published: April 2011

AbstractWear behavior of freshly cleaved single crystal calcite (CaCO3) was investigated by continuous scanning using the Hysitron Triboindenter in ambient environment as a function of scanning frequency (1 Hz – 3 Hz) and contact load (2 µN – 8 µN). At lower loads below 4 µN, initiation of the ripples takes place at the bottom of the surface slope, which continue to propagate up the slope as scanning progresses. The orientation of these ripple structures is perpendicular to the long scan direction. As the number of scans increases, ripples become fully developed, and their height and periodicity increase with the number of scans. At 6 µN normal load, tip-induced wear occurs as the tip begins removing the ripple structures with increased number of scan cycles. As the contact load increased further, ripples did not initiate and only tip-induced wear occurred on the surface, and saturated after 20 scans. At 1 Hz frequency wear takes place as material slides towards the scan edges when the tip moves back and forth. Material removal rate increased with contact load and it is observed that the number of scans required to create a new surface is inversely proportional to the contact load. Possible mechanisms responsible for the formation of ripples at higher frequencies are attributed to the slope of the surface, piezo hysteresis, system dynamics, or a combination of effects. The wear regime is due to abrasive wear. Single crystal calcite hardness of 2.8±0.3 GPa and elastic modulus of 75±4.9 GPa were measured using nanoindentation and used to determine the wear mode.
Determination of Residual Stress and Yield Stress Simultaneously by Indentation Method with Dual Indenters
Authors: Baoxing Xu , Wang Xinmei , Yue Zhufeng 
Published: April 2011

AbstractIn general, the method of obtaining residual stress from indentation test requires calculating the contact area of indenter and indented material, and also needs to know yield stress of indented material in advance. In this work, the dimensional analysis of indentation loading curve was first analyzed, and then a reverse numerical procedure was explored to show a possibility of determining residual stress and yield stress of materials simultaneously from indentation test. Besides, the calculation of contact area can be also avoided.
Haasen Plot Activation Analysis of Constant-Force Indentation Creep in FCC Systems
Authors: Bhakhri Vineet , Klassen Robert J. 
Published: April 2011

AbstractAn analysis of the length-scale and temperature dependence of Haasen plots obtained from constant-force nano- and micro-indentation creep tests performed are reported here. The operative deformation mechanism for all the systems studied involved dislocation glide limited by dislocation-dislocation interactions. Our findings illustrate the potential usefulness of Haasen plot activation analysis for interpreting data from constant-force pyramidal indentation creep tests.
Magnetic-Field-Induced Strain of Fe-based Ferromagnetic Shape-Memory Alloy in a Pulsed Magnetic Field
Authors: Sakon Takuo , Fukuda Takashi , Nojiri Hiroyuki , Kakeshita Tomoyuki 
Published: April 2011

AbstractThe magnetic field-induced strain (MFIS) of the martensite metallic compound Fe3Pt were studied in a pulsed magnetic field using the capacitance method at low temperatures down to 4.2 K in a martensitic phase, which is much lower than the martensitic transformation temperature TM = 85 K. After zero field cooling, pulse magnetic field with the maximum frequency of 160 Hz was applied parallel to [001]p axis. Large MFIS has been measured. The value of the MFIS is ΔL/L = −1.7 %. When the magnetic field was decreased, the recovery of the strain was observed. At the 2nd shot, the strain of about 0.6 % was observed. It means that MFIS occurs even in short-pulse magnetic fields.
Optimization of the Geometry of the MEMS Electrothermal Actuator to Maximize In-Plane Tip Deflection
Authors: Kolesar Edward S. , Htun Thiri , Least Brandon , Tippey Jeffrey , Michalik John 
Published: April 2011

AbstractSeveral microactuator technologies have been investigated for positioning individual elements in large-scale microelectromechanical systems (MEMS). Electrostatic, magnetostatic, piezoelectric and thermal expansion represent the most common modes of microactuator operation. This investigation optimized the geometry of the asymmetrical electrothermal actuator to maximize its in-plane deflection characteristics. The MEMS polysilicon surface micromachined electrothermal actuator uses resistive (Joule) heating to generate differential thermal expansion and movement. In this investigation, a 3-D model of the electrothermal actuator was designed, and its geometry was optimized using the finite-element analysis (FEA) capabilities of the ANSYS computer program. The electrothermal actuator's geometry was systematically varied to establish optimum values of several critical geometrical ratios that maximize tip deflection. The value of the ratio of the length of the flexure component relative to the length of the hot arm was discovered to be the most sensitive geometrical parameter ratio that maximizes tip deflection.
The Effect of Hydrophobic Patterning on Micromolding of Aqueous-Derived Silk Structures
Authors: Tsioris Konstantinos , White Robert D , Kaplan David L , Wong Peter Y 
Published: April 2011

AbstractA novel micromolding approach was developed to process liquid biopolymers with high aqueous solvent contents (>90% water). Specifically silk fibroin was cast into a well-defined scaffold-like structure for potential tissue engineering applications. A method was developed to pattern the hydrophilicity and hydrophobicity of the polydimethylsiloxane (PDMS) mold surfaces. The water based biopolymer solution could then be directly applied to the desired regions on the cast surface. The variations in degree of hydrophilicity and hydrophobicity on the PDMS surfaces were quantified through contact angle measurements and compared to the outcome of the molded silk structures. Through this method free-standing structures (vs. relief surface-patterning) could be fabricated.
Design and Fabrication of an Optical-MEMS Sensor
Authors: Mathur Vaibhav , Li Jin , Goodhue William D. 
Published: April 2011

AbstractA novel optical-MEMS sensor based on the AlGaAs material system is designed and fabricated. The device consists of micro-beam waveguides butt-coupled with their ends separated by approximately 2 to 4 µm. The device works on the principle that when acoustically driven by an external source, the waveguides misalign, leading to coupling loss. The device design parameters were determined using FEM (Finite Element Method) modeling. The dielectric waveguide beams were designed for single mode propagation at 785 nm and longer wavelengths. A combination of dry and wet etching process followed by precision laser cutting was used to fabricate the suspended beams. Beams ranging from 100 µm to 400 µm with fundamental frequencies of 50 KHz to 200 KHz were successfully fabricated. Initial uncut waveguide test results will be discussed along with the plan for characterizing the devices using an acoustically coupled piezoelectric driver. These devices may be utilized for vibration sensing, or optical intensity modulation.
Excimer Laser Induced Patterning of PSZT and PLZT Flms
Authors: Leech Patrick William , Holland Anthony S 
Published: April 2011

AbstractThe patterning of strontium-doped lead zirconium titanate (PSZT) and lanthanum-doped lead zirconium titanate (PLZT) films has been examined using excimer laser radiation. Both types of film were deposited by rf magnetron sputtering using in-situ heating and a controlled cooling rate in order to obtain the perovskite-oriented phase. The depth of laser ablation in both PSZT and PLZT films showed a logarithmic dependence on fluence. The threshold fluence required to initiate ablation was ∼1.25 mJ/cm2 for PLZT and ∼1.87 mJ/cm2 for PSZT films. The ablation rate of PLZT films was slightly higher than that of PSZT films over the range of fluence (10-150 J/cm2) and increased linearly with number of pulses. The higher ablation rate of PLZT films has been attributed to the finer grainsize (160-200 nm) than in the PSZT films (1.0-1.2 µm).
High Temperature Annealing Studies on the Piezoelectric Properties of Thin Aluminum Nitride Films
Authors: Farrell R. , Pagán V. R. , Kabulski A. , Kuchibhatla Sridhar , Harman J. , Kasarla K. R. , Rodak L. E. , Hensel J. , Famouri P. , Korakakis D. 
Published: April 2011

AbstractA Rapid Thermal Annealing (RTA) system was used to anneal sputtered and MOVPE-grown Aluminum Nitride (AlN) thin films at temperatures up to 1000°C in ambient and controlled environments. According to Energy Dispersive X-Ray Analysis (EDAX), the films annealed in an ambient environment rapidly oxidize after five minutes at 1000°C. Below 1000°C the films oxidized linearly as a function of annealing temperature which is consistent with what has been reported in literature [1]. Laser Doppler Vibrometry (LDV) was used to measure the piezoelectric coefficient, d33, of these films. Films annealed in an ambient environment had a weak piezoelectric response indicating that oxidation on the surface of the film reduces the value of d33. A high temperature furnace has been built that is capable of taking in-situ measurements of the piezoelectric response of AlN films. In-situ d33 measurements are recorded up to 300°C for both sputtered and MOVPE-grown AlN thin films. The measured piezoelectric response appears to increase with temperature up to 300°C possibly due to stress in the film.
Influence of Materials on the Performance Limits of Microactuators
Authors: Srinivasan Prasanna , Spearing S. Mark 
Published: April 2011

AbstractThe selection of actuators at the micro-scale requires an understanding of the performance limits of different actuation mechanisms governed by the optimal selection of materials. This paper presents the results of analyses for elastic bi-material actuators based on simple beam theory and lumped parameter thermal models. Comparisons are made among commonly employed actuation schemes (electro-thermal, piezoelectric and shape memory) at micro scales and promising candidate materials are identified. Polymeric films on Si subjected to electro-thermal heating are optimal candidates for high displacement, low frequency devices while ferroelectric thin films of Pb-based ceramics on Si/ DLC are optimal for high force, high frequency devices. The ability to achieve ∼10 kHz at scales < 100μm make electro-thermal actuators competitive with piezoelectric actuators considering the low work/volume obtained in piezoelectric actuation (∼ 10−8J.m−3.mV−2). Although shape memory alloy (SMA) actuators such as Ni-Ti on Si deliver larger work (∼ 1 J.m−3K−2) than electro-thermal actuators at relatively low frequencies (∼ 1 kHz), the critical scale associated with the cessation of the shape memory effect forms the bounding limit for the actuator design. The built-in compressive stress levels (∼ 1GPa) in thin films of Si and DLC could be exploited for realizing a high performance actuator by electro-thermal buckling.
Systematic Characterization of DRIE-Based Fabrication Process of Silicon Microneedles
Authors: Held Jochen , Gaspar Joao , Ruther Patrick , Hagner Matthias , Cismak Andreas , Heilmann Andreas , Paul Oliver 
Published: April 2011

AbstractThis paper reports on the systematic characterization of a deep reactive ion etching based process for the fabrication of silicon microneedles. The possibility of using such microneedles as protruding microelectrodes enabling to electroporate adherently growing cells and to record intracellular potentials motivated the systematic analysis of the influence of etching parameters on the needle shape. The microneedles are fabricated using dry etching of silicon performed in three steps. A first isotropic step defines the tip of the needle. Next, an anisotropic etch increases the height of the needle. Finally, an isotropic etch step thins the microneedles and sharpens their tip. In total, 13 process parameters characterizing this etching sequence are varied systematically. Microneedles with diameters in the sub-micron range and heights below 10 µm are obtained. The resulting geometry of the fabricated microneedles is extracted from scanning electron micrographs of focused ion beam cross sections. The process analysis is based on design-of-experiment methods to find the dominant etch parameters. The dependence of the needle profiles on process settings are presented and interpolation procedures of the geometry with processing conditions are proposed and discussed.
Enhanced Phonon Scattering in Oxide Superlattices to Improve Laser Induced Thermoelectric Voltages
Authors: Habermeier Hanns-Ulrich , Zhang Peng Xiang , Zhang Hui 
Published: April 2011

AbstractOptimizing the figure of merit for thermoelectric applications, ZT = S2σ2T/κ is currently at the core of materials oriented research in thermoelectricity. Here, one promising approach is to reduce ther thermal conductivity without sacrificing the electrical conductivity. Constructing superlattices of structurally compatible materials is one way to accomplish this goal. We report an enhanced laser induced thermoelectric voltage (LITV) effect observed in (YBa2Cu3O7/La1-xPbxMnO3)n multilayer thin films for the first time. Two groups of multilayer thin films grown on vicinal cut LaAlO3 substrates were prepared by pulsed laser deposition technique. The first group were grown on different substrates vicinal cut at different angles, and were used for checking the mechanism of the induced voltages. The second group samples were made at different period number n and for studying the number dependence of the peak values of LITV. The substrate angle dependence proved that this is a thermoelectric effect [1]. It was found that the LITV signals were enhanced significantly for these multilayer thin films comparing with the single layer ones. It is natural that the conductivity is going to be anisotropic due to the layered structure, and the same holds for the Seebeck coefficients. The enlarged Seebeck anisotropy will lead to higher induced voltages. Another possible reason is the reduced thermal conductivity in the layered structure. The maximum enhancement of LITV signals takes place at period number of 7, which seems in agreement with the prediction of minimum thermal conductivity in superlattices by Simkin and Mahan.
3-Dimensional Al2O3 Fiber Networks using Low Temperature Atomic Layer Deposition on a Cotton Template
Authors: Hojo Daisuke , Hyde G. Kevin , Spagnola Joseph , Parsons Gregory N 
Published: April 2011

ABSTRACTMicro-scale woven structures were replicated 3 dimensionally by conformal coating onto natural woven cotton using a binary reaction of trimethylaluminum and water at 100°C. Even after the woven cotton was removed at 450°C, the woven structures completely remained. Results demonstrate the capability of ALD to penetrate into the complex 3D network structure of natural woven cotton to form uniform coating at low temperature and give insight into general understanding of methodology to translate deposition processes from 2D surface to a 3D network to obtain a uniform coating throughout the sample network bulk. It also shows the possibility of replication of micro-scale structures from highly conformal coatings to give the unique synthesis root of hollow structures.
Functionalised Nanostructured Polyaniline – A New Substrate for Building Adaptive Sensing Surfaces
Authors: Lahiff Emer , Bell Steven , Diamond Dermot 
Published: April 2011

ABSTRACTA new method for covalently binding side-chains to the surface of solution based conducting polymer nanostructures is introduced in this paper. Modification of the structures is achieved by convenient reflux in the presence of a nucleophile, and post-functionalization purification is subsequently carried out by centrifugation. The entire process is easily scalable and hence suitable for bulk production of functionalized nanomaterials. In particular we focus on the modification of polyaniline nanofibres which can be synthesized by interfacial polymerization. Mercaptoundecanoic acid side-chains are attached to the polymer nanostructures, with the intrinsic nano-morphology of the material being maintained during the process. The modified PAni nanofibres provide a template for the attachment of other specific functional groups which could be used to target a particular species.