bluuebunny/crossref_metadata_2025 huggingface dataset:
Crystalline, Glassy and Molten Electrolytes: Conductivity Spectra and Model Consdderations
Authors: Funke K.
Published: April 2011

Conductivity spectra of crystalline, glassy and molten electrolytes are presented and discussed. The spectra cover fourteen decades on the frequency scale as well as wide temperature ranges. In some crystalline ion conductors, the translational and vibrational contributions to the conductivity are well separated on the frequency scale. This is not observed in glasses and melts. In these cases, the vibrational components can, however, often be removed from the total spectra, yielding the translational component. We find that in crystalline, glassy, and molten electrolytes the conductivity caused by translational motion of the ions exhibits plateaux at both low and high frequencies, with a dispersive regime in between. The dispersive sections of the conductivity isotherms always cover a triangular area in a log-log plot of conductivity times temperature versus frequency. For an interpretation, the jump relaxation model turns out to be appropriate for crystalline electrolytes. The existence of different kinds of site is typical of glasses. For fragile molten electrolytes, a simple semimicroscopic model is presented which explains the experimental findings including the Vogel-Fulcher-Tammann temperature dependence of the dc conductivity.
Proteins and Glasses
Authors: Frauenfelder Hans
Published: April 2011

The structure, the energy landscape, and the dynamics of proteins and glasses are similar. Both types of systems display characteristic nonexponential time dependencies of relaxation phenomena. Experiments suggest that both, proteins and glasses, are heterogeneous and that this fact causes the observed time dependence. This result is discussed in terms of the rough energy landscape characteristic of complex systems.
Liquid and Glassy State Polyamorphism in the System Y2O3-Al2O3
Authors: McMillan Paul F. , Ho Chung , Aasland Siv , Yeganeh-Haeri Amir , Weber Richard
Published: April 2011

During a recent study of supercooled liquids in the system Y2O3-Al2O3, a first-order phase transition between two liquid phases with the same composition, but different structure and density, was observed to occur. The transition occurred close to the glass transformation of the two liquids, so that both phases were quenched to metastably coexisting glasses. We report further studies on the liquids and glasses in this system, prepared by rapid (roller) quenching and by containerless levitation techniques.
2D Lattices on Substrates with Randomly Distributed Pinning Centers: A Possible Scaling Law for Domain Sizes
Authors: Sen Surajit , Cai Zhi-Xiong , Schummer J.
Published: April 2011

We consider 2D lattices which are disordered by an external field, in this case by a dense, random distribution of attractive pinning centers of an underlying substrate. The preferred configuration of the 2D system with screened-Coulomb two-body interactions and a fixed number of particles is a triangular lattice configuration. The pinning centers strongly affect the triangular lattice configuration. By keeping the location and the density of the pinning centers fixed, we study the effects of pinning strength on the structural properties of the lattice. We find that the strongly disordered lattice prefers to form irregular domains of size s which are composed entirely of topological defects. The distribution of sizes of these domains, D(s) suggest that s−τ for sufficiently large s. Our results are consistent with τ ≥ 2 in the solid phase and τ < 2 in the liquid phase. We present a general argument in support of our findings and suggest that the physics which dictates the structure of 2D lattices on substrates with randomly distributed pinning centers is the same as that for a broad range of problems in which an external field strongly influences the behavior of an interacting physical system.
Dielectric Spectroscopy at High Frequencies on Glass Forming Liquids
Authors: Lunkenhemer P. , Pimenov A. , Dressel M. , Gorshunov B. , Schneider U. , Schiener B. , Böhmer R. , Loedl A.
Published: April 2011

Dielectric spectroscopy up to 950 GHz has been performed on various glass formers as glycerol, propylene-carbonate, and Salol. Special attention is given to the dielectric loss, ε″, in the crossover regime from the a-relaxation to the far-infrared (FIR) response where it can be directly compared to the dynamic susceptibilities obtained by neutron and light scattering techniques. We observe a minimum in ε″(ν) at high frequencies which cannot be explained by a simple transition from a-relaxation peak to the FIR bands but has to be attributed to additional fast processes. In all materials investigated, ε″(ν) increases significantly sublinear above the minimum. The ratio of the intensity of the α-process and the fast process as determined from our dielectric experiments is significantly higher compared to the results from the scattering experiments.
Spectral Characterization and Excited-State Interactions Between Rare Earth Ions Doped in Borosilicate and Sol-Gel Glasses: Energy Transfer Up-Conversion in the Pr-Sm System
Authors: Assefa Z. , Haire R. G. , Stump N. A.
Published: April 2011

Spectroscopie properties of selected 4f-elements in a sol-gel and two high temperature silicate based glasses are reported. In particular, the spectral properties of the Eu3+ ion have been used to probe the local coordination environment of the f-elements in these glass matrices. Luminescence studies of the high temperature glasses indicated that the electric dipole allowed f-f transitions dominate the spectra which suggests that the local symmetry around the 4f-ions is low. Temperature-dependent spectroscopie studies of the sol-gel glasses indicated that the f-elements retain a “solution-like” environment prior to thermal processing. After heat treatment, an increase in the emission intensities of the electric-dipole transitions is accompanied by a concomitant decrease in the magnetic-dipole allowed transitions. Moreover, excited state interactions has also been observed in the high temperature glasses that contain certain multiple f-elements. In Pr-Sm systems, exclusive excitation of the Sm3+ ion with a 514 nm argon ion laser line provides a higher-energy emission band (ca. 490 nm) from the Pr3+ ion (3P0 → 3H4) transition. This energy up-conversion is attributed to energy transfer from the 6H13/2 level of the Sm3+ ion to the 3Hg6 state of the Pr3+ ion. Following a second photon absorption, the Pr3+ ion is excited to the emitting 3P0level.
Relaxation Processes and the Mixed Alkali Effect in Alkali Metasilicate Glasses
Authors: Habasaki J. , Okada I. , Hiwatari Y.
Published: April 2011

A molecular dynamics simulation (MD) of lithium metasilicate (Li2SiO3) and related mixed alkali system (LiKSiO3) has been performed. Changes in the mean squared displacement and the corresponding clear two-step (β and α1) relaxations in a density correlation function have been observed at 700 K (self-part) for each ion in Li2SiO3 following an exponential decay by vibrational motion in a simulation up to 300 ps (run I). The mean squared displacement of the atoms shows the change in the slope at ca. 300 ps when the simulation is extended up to 1 ns (run II). Here we call the slowest relaxation (ca. 300 ps∼) the α2 region.

Oscillation, which is clearer for O and Si than for Li, is found in the second (β-relaxation) region of the function, which is attributed to the so called “boson peak”. Both the β-relaxation and the boson peak are found to be due to the correlated motion.

The slower relaxation (α1-relaxation) can be fitted to a stretched exponential form and the origin of this type of decay is confirmed to be waiting time distribution of jump motions. The back-correlated jumps also decrease the decay rate.

Components A and B in α1 and α2 regions for Li ion are analyzed, where the Li ion of component A is located within the first neighboring sites and that of component B moves longer than the nearest neighbor distances by cooperative jump motion. The component B shows accelerated dynamics larger than t-linear ones (∼ t1.77) in the region 50–300 ps, and the dynamics can be characterized as Lévy flight.

We have found that the contribution of the cooperative jumps decreases in the mixed alkali glass. This explains the maximum of the Haven ratio accompanied with the mixed alkali effect.
Quantitative Analysis of Segregation to Grain Boundaries in Steels
Authors: Garratt-Reed A. J. , Cliff G. , Lorimer G. W. , Pilkington R.
Published: April 2011

Grain boundary segregation of phosphorous in model reactor steels has been measured using EDX Spectroscopy in the FEG-STEM. The results have been compared with Auger spectroscopy measurements made on similar materials. The results were in excellent agreement.
Transmission Electron Microscopy (TEM) Studies of Interfaces in TiB2-ZrO2 Composites
Authors: Stemmer S. , Vleugels J. , Van Der Biest O.
Published: April 2011

TEM studies of the microstructure and of chemical reactions at interfaces in TiB2-ZrO2 composites are presented. Samples with 70 vol% of Y2O3-stabilized ZrO sintered at 1700 °C showed reaction zones around the TiB2 grains, that consisted of a solid-solution of TiO2 and ZrO2(Y2O3). In addition, nontransformable, tetragonal t'-ZrO2 was observed in these samples. In contrast, the interphase boundaries in composites sintered at 1450 °C contained no reaction products, and the ZrO2 matrix consisted of small, transformable tetragonal grains, as required for transformation toughening of the composites.
Modification of Fracture Energy of Niobium/sapphire Interface By Impurity Doping
Authors: Ji Hong , Was Gary S. , Wayne Jones J. , Moody Neville R.
Published: April 2011

The effect of interface composition on the fracture energy and fracture toughness of the niobium/sapphire system was studied. Niobium films with thickness of 100 nm were deposited on (0001) sapphire substrates by physical vapor deposition (PVD). The interface was doped with silver to reduce the interfacial cohesion. The amount of silver ranged from less than 2.1 monolayers to 6.4 monolayers as measured by Rutherford backscattering spectrometer (RBS). The microscratch test was used in determining the interfacial fracture energy and the interfacial fracture toughness. Both interfacial fracture energy Gc and fracture toughness Kc decrease non-linearly with the amount of silver, and level off for samples with larger silver thickness ( > 4.2 monolayers). The values of interfacial fracture energy range from 3.43 J/m2 - 9.20 J/m2 for the sample doped with 2.1 monolayer silver (sample B) to 0.05 J/m2 - 0.5 J/m2 for samples with silver levels above 4.2 monolayers (samples D and E). The corresponding fracture toughnesses are 0.80 MPa-m½ - 1.29 MPa-m½ for sample B and 0.09 MPa-m½ - 0.30 MPa-m½ for samples D and E.
The Influence of Film-Substrate and Internal Interfaces on the Strength and Ductility of <001> Oriented B2 NiAl-Based Alloys
Authors: Misra A. , Kim J. T. , Gibala R.
Published: April 2011

The effects of surface films and second phase interfaces on the room temperature ductility of <001> oriented β (B2) NiAl-based alloys were investigated. Significant reduction in flow stress and enhancement in plasticity, as compared to the monolithic β phase, were seen in both film-coated and ductile γ (fcc)/γ' (Ll2) second-phase-containing alloys. The constrained deformation at the film/substrate and interphase interfaces was effective in nucleating mobile a<100> dislocations in the β phase even though the loading axis was approximately parallel to <001>. For the case of film-coated NiAl single crystals deformed in compression, a micro-kinking model is proposed to explain the propagation of a<001> dislocations generated at the film/substrate interface. For multiphase β/γ+γ' alloys where 10–12% tensile ductility was observed, the role of crystallographic orientation relationships in promoting slip transfer is highlighted. In these multiphase alloys, the intrinsic tensile ductility of β phase by {011}<100> slip when deformed approximately along the <001>β orientation is explained using lattice rotation concepts.
Improvement of Abrasive Wear Resistance by Whisker Reinforcement in Alumina Ceramics
Authors: Iwasa Mikio
Published: April 2011

Alumina based composite ceramics with silicon carbide whisker were fabricated by hot-press sintering. Their abrasive or erosive wear properties were measured by abrasive waterjet method and micro-sandblast method, and the results were compared with those of normally sintered engineering ceramics. In the case of normal impact of abrasive waterjet, where micro-fracture may be the mam wear mechanism, the whisker composite showed considerable improvement of wear properties because of its higher toughness. In the case of low angle impact, where cutting is the mam wear mechanism, only a small improvement were observed by a small addition of whisker (5wt%SiC), but larger addition (30wt%SiC) resulted in higher wear. No effect of whisker was observed with the micro-sandblast method, perhaps because of its rather mild abrasive conditions.
Static Simulation of the Effect of Alkalline Metal Impurities on the Bonding of Al Atoms at the Grain Boundaries of Aluminum
Authors: Tu Geng , Itoh Akira , Kyuno Kentaro , Yamamoto Ryoichi
Published: April 2011

Unlike the iron based alloys, the embrittlement behavior of aluminum based alloys due to impuri ty segregation at the grain boundaries have not previously studied. Recently, experiments were performed on the Al-Mg alloys and it was found that more than 0.6ppm Na impurity atoms will cause embrittlement of these alloys. In the present study, we have created aluminum clusters containing about 20 atoms based on the structure of tilt grain boundries and then performed the first-principle calculations on these clusters with or without alkalline metal impurity atom(Li, Na, K,). The overlap populations between aluminum atoms were calculated so as to find the effect of impurity atoms on the bonding between aluminum atoms. Na impurity atom was found to weaken the bonding between the aluminum atoms around it.
Effect of α/β Interfaces on Creep Behavior of Single Colony Titanium Alloys at Room Temperature
Authors: Suri S. , Hou Vincent D. -H. , Neeraj T. , Scott J. M. , Mills M. J.
Published: April 2011

Creep occurs in two phase α/β Ti alloys at room temperature and at stresses below the yield strength. Creep strains in the Widmanstatten structure are affected by colony size and by sliding at the α/β interfaces. This paper reports the results of an investigation on single colony crystals of a near a Ti alloy to understand the dependence of creep on the orientation of the α/β interface and the operative slip system. Associated mechanisms of slip transfer across the α/β interface and possible interface sliding are investigated and the results obtained are presented.
Study of Dynamic Embrittlement in Alloy Bicrystals
Authors: Muthiah R. G. , Pfaendtner J. A. , McMahon C. J. , Lejcek P. , Paidar V.
Published: April 2011

In a kinetic model [1] for the phenomenon of dynamic embrittlement, the cracking rate is predicted to be proportional to the diffusivity of the embrittling species along the grain boundary. To test this model, bicrystals of Cu-Sn and Fe-Si with Σ5 symmetrical tilt boundaries are used in which tin and sulfur, respectively, are the embrittling elements. The diffusivities parallel and perpendicular to the tilt axis are expected to be different, therefore the crack growth rates in these two directions should vary in the same ratio as the diffusivities.

Preliminary measurements of crack growth rate along the [100] direction in the Cu-Sn alloy bicrystal are presented. The cracking occurred by decohesion along the grain boundary with almost no observable plasticity. The steady state crack growth was found to be approximately 10∼6 m/sec.
Interface Synthesis By UHV Deposition/Diffusion Bonding
Authors: Kim M. J. , Cox M. J. , Xu J.
Published: April 2011

An ultra high vacuum (UHV) deposition/bonding system has been constructed that can produce planar interfaces from a wide array of materials. The interfaces in this system can be synthesized in-situ by UHV diffusion bonding of two substrates with or without various interfacial layers. Substrate surfaces can be heat treated, sputter cleaned and characterized in-situ prior to deposition and/or bonding. Interfacial layers can be deposited by e-beam evaporation and/or sputter deposition in any layered or alloyed combination. After deposition, the two substrates are bonded in UHV, by the application of heat and pressure.

This synthesis procedure permits systematic variation and control of interface morphology and chemistry. Integrity of the bonded interface as well as the microstructure and chemistry are examined by cross-sectional analytical transmission electron microscopy. In this study, stainless steel and single and polycrystalline alumina were used as substrate materials to produce interfaces with and without Ti and Cu interlayers.
Hydrogenation and Magnetic Properties of Pd/Co Multilayers
Authors: Suzuki A. , Kyuno K. , Akiba E. , Manago T. , Miyajima H. , Yamamoto R.
Published: April 2011

The magnetic properties of sputtered Pd/Co multilaysers in hydrogen atmospheres were studied. The x-ray diffraction(XRD) patterns in hydrogen atmospheres showed that the lattice expansion of hydrogenated Pd decreased with decreasing thickness of Pd layers, which is reminiscent of nano-crystalline Pd. Perpendicular magnetic anisotropy(PMA) and saturation magnetization were reduced by the hydrogénation. The interface anisotropy energy per unit area, Ks, and volume anisotropy energy per unit volume, Kv are discussed. These results suggest that interface magnetic anisotropy between Pd and Co layers is suppressed by hydrogenation.
Boron Nitride Coatings on Silicon Carbide Whiskers
Authors: Brown Steven , Partch Richard
Published: April 2011

Boron nitride thin films have been produced on silicon carbide whiskers (SiCw) by a novel processing method. A polydivinylbenzene (PDVB) coating was formed in situ on the whisker surface which was subsequently thermally degraded creating a highly porous carbon layer. The total available pore volume of the carbon layer/ SiCw system (SiCwC) was varied by controlling the quantity of PDVB adsorbed. Next, anhydrous sodium borate was mixed with the SiCwC, and upon heating, the precursor melted and absorbed into the porous carbon layer followed by nitridation with anhydrous ammonia. Under certain reaction conditions, silicon oxynitride was also produced as a sublayer. The amount of the latter can be controlled by varying the reaction temperature and time. Control over the thickness of the BN film was achieved by varying the amount of the carbonized polymer layer in proportion to the quantity of sodium borate.
Tem Characterization of Highly Oriented Diamond Films on (001) Silicon Synthesized by Bias Enhanced Nucleation Technique
Authors: Jeon Seung-Joon , Chawla Arun Kumar , Baik Young-Joon , Sung Changmo
Published: April 2011

Highly oriented diamond films were deposited on a (001) silicon substrate by bias enhanced MPCVD technique. Three-dimensional TEM characterizations were carried out to understand the nucleation and growth mechanism of diamond grains. The surface morphology, defects, and misorientations of diamond films were compared as a function of synthesizing temperatures and thickness of the films. From our experimental results the texture formation mechanism of diamond films is discussed.
Metal Oxide and Metal Carbide Thin Film Coatings on Large Spherical Particles
Authors: Stephenson Richard C. , Partch Richard E.
Published: April 2011

Synthesis and characterization of titanium and zirconium oxide and carbide thin films (1–25 μm) on spherical substrates is reported. Hydrolysis of an appropriate metal alkoxide precursor in aqueous acid yields the amorphous metal oxide coating. Thermal treatment can produce the highly crystalline phases of the oxides or, in the presence of a carbon containing reducing gas, the metal carbide. Scanning electron microscopy and x-ray diffraction have been used to study the surface morphology and the crystallographic structure of the coating films. Morphological characteristics strongly depend on the acid species and acid strength used during hydrolysis. The thickness of the film is also governed by control of the acid hydrolysis step.
Interface Characterization and Delamination Mechanism of c-BN Film
Authors: Kim Ig-Hyeon , Sung Changmo , Lee Sang-Ro , Seo Young-Woon
Published: April 2011

Cubic boron nitride films were prepared by helicon wave plasma CVD process on (100) Si. The growth and delamination mechanism of c-BN film was investigated with FT-IR spectroscopy and transmission electron microscopy. The film deposited under the intense impact of energetic ions is usually delaminated from the substrate after deposition. It is found that moisture in the air, surface roughness of the film and substrate, as well as severe compressive stresses in the film are the primary contributors to film delamination. An aqueous oxidation was verified by EDXS analysis, which generate local stress by volume expansion at the crack region in the c-BN layer. From the experimental results and ??? observation a model for the delamination mechanism of c-BN film is suggested. Based on the delamination mechanism, several kinds of remedies such as post annealing and post N2plasma treatment were carried out for improving the adhesion.
Residual Stress Effects on the Fracture of Tantalum Nitride Films
Authors: Moody N. R. , Hwang R. Q. , Angelo J. E. , Venkataraman S. , Gerberich W. W.
Published: April 2011

In this study, continuous microscratch testing was used to determine the effects of compressive residual stresses on the fracture of thin tantalum nitride films. The films were sputter deposited at room temperature onto single crystal sapphire substrates to a thickness of 600 nm. Some films were left in the as-deposited condition while the remaining films were vacuum annealed at 300°C. The only discernible change in structure was a surface rearrangement of atoms into parallel arrays of striations on the vacuum annealed samples revealing a high compressive residual stress in the films. These stresses had a strong effect on fracture as shown by the as-deposited films which buckled readily during scratch tests forming uniform-width and circular blisters while the vacuum annealed films exhibited a much lower susceptibility to fracture. Application of mechanics-based models for film buckling defined the levels of compressive residual stress and their effect on interfacial fracture.
Residual Stresses in Single and Multilayer Composite Diamond Coatings
Authors: Jagannadham K. , Watkims T. R. , Narayan J.
Published: April 2011

Residual stresses were measured in different types of diamond coatings deposited onto molybdenum substrates by hot filament chemical vapor deposition. The types of coatings examined include a continuous single layer diamond coating and a continuous multilayer diamond composite coating with an aluminum nitride embedding layer. The stresses were determined by X-ray diffraction and Raman spectroscopy and compared.
Interface Shear Strength and Fracture Behavior of NiAl/Metal Laminates
Authors: Fox M. R. , Pickard S. , Ghosh A. K.
Published: April 2011

Mechanical response of interfaces between intermetallic matrices and ductile reinforcements is of considerable interest in intermetallic matrix composite design. A new approach has been developed to study crack initiation at a planar bimaterial interface by loading one of the adjoining phases in compression. A primarily Mode II stress state with different degrees of superimposed tensile and compressive loading develops at the interface as predicted by FEM analysis. This test method has been used to study NiAl/Mo and NiAl/Cr interfaces in model laminates.
Interfacial Characterization of Mosi2+ X Sic Composite Thin Films on Molybdenum Substrates
Authors: Govindarajan S. , Moore J. J. , Ohno T. R. , Disam J.
Published: April 2011

A novel coating architecture is being examined for enhancing the high temperature, oxidation resistance of molybdenum. The coating incorporates a thin, composite film of MoSi2+1.96 mole fraction SiC in order to match the coefficients of thermal expansion between the molybdenum substrate and the coating. Since the as-deposited composite film is amorphous in nature, a diffusion anneal treatment is carried out at 1000°C to achieve crystallization of the film. In this paper, a detailed examination of the Mo-MoSi2+1.96 SiC interface will be presented. The microstructural features of the composite films will be discussed based on electron microscopy, auger electron spectroscopy (AES), and X-ray diffraction analysis. Finally, a novel diffusion barrier layer for minimizing silicon and carbon diffusion from the coating to the substrate will be discussed.
Active Stiffening of Composite Materials by Embedded Shape-Memory-Alloy Fibres
Authors: Bidaux J.-E. , Månson J.-A. E. , Gotthardt R.
Published: April 2011

The use of shape-memory-alloy (SMA) fibres to actively changethe stiffness of a composite beam is investigated on a model system composed of an epoxy matrix with a series of embedded pre-strained NiTi fibres. Stiffness changes are detected through shifts in the natural vibration frequency of the beam. When electrically heated, the pre-strained NiTi fibres undergo a phase transformation. Since the shape recovery associated with the transformation is restrained by the constraints of both the matrix and the clamping device, a force is generated. This force leads to an increase in the natural vibration frequency of the composite beam. Depending on the degree of fibre pre-strain, either ordinary martensite, R-phase or a mixture of the two can be stress-induced. It is found that the R-phase gives rise to the largest change in vibration frequency for a given temperature increase and the most reversible behaviour. Its low transformation strain is also more favourable for fibre-matrix adhesion. The effect of stress relaxation in the polymer matrix on the composite response is discussed.
Mechanical Properties of NiTi-TiC Shape-Memory Composites
Authors: Dunand D. C. , Fukami-Ushiro K. L. , Mari D. , Roberts J. A. , Bourke M. A.
Published: April 2011

This paper reviews recent work on the mechanical behavior of martensitic NiTi composites reinforced with 10–20 vol.% TiC particulates. The behavior of the composites is compared to that of unreinforced NiTi, so as to elucidate the effect of mismatch due to matrix transformation, thermal expansion, twinning or slip, in the presence of purely elastic particles. The twinning and subsequent thermal recovery of deformed composites, measured both macroscopically (by compressive testing and by dilatometry) and microscopically (by neutron diffraction), are summarized.
A Study of Ta2O5 for use as High Temperature Piezoelectric Sensors
Authors: Jooste B. R. , Viljoen H. J.
Published: April 2011

Acoustic sensors which can function at high temperatures have important potential uses. In this work we report on the deposition, characterization and qualitative assessment of piezoelectric behaviour of orthorhombic Ta2O5• It is shown that orthorhombic Ta2O5 belongs to the class 2mm. XRD analysis of films annealed for 1 min., 10 min. and 1 hr at 800°C and 900°C reveal the formation of (0 0 1), (1 10 0) and (1 11 0) orientations at 800 °C, but the (1 10 0) increases at the expense of the other two as the annealing period is extended. At 900°C the dominant orientations are (1 10 0) and (2 9 0). The piezoelectric effect is significantly stronger after annealing and the stronger piezoelectric effect does not correlate with the presence of (1 10 0) and (2 9 0) so much as with the absence of (0 0 1) and (1 11 0).
Laser Irradiation Effect on Saw Properties of Layered Structure of Oxide/Piezoelectric Substrate
Authors: Ichikawa Yo , Kitagawa Masatoshi , Setsune Kentaro , Kawashima Syun-ichiro
Published: April 2011

Using surface acoustic wave (SAW) propagating in the layered structure of oxide/piezoelectric substrate, a responsibility of the oxide thin films for the laser irradiation has been investigated. Amorphous Ti-O, Si-O and Si-X-O, where X is other metal elements, films were formed on the surface of the SAW device composed of quartz or LiTaO3 substrate and several hundred Al electrode fingers for oscillating and detecting the SAW. A KrF excimer laser with 248nm in wavelength was used for the irradiation. The center frequency of the SAW devices was immediately decreased by the irradiation of the laser pulses. Although the response to the irradiation was reversible for lower laser energy, the change of the center frequency was irreversible for the laser energy density higher than 20mJ/cm2. It is considered that the response appeared in the frequency shift is generated by a change of an elastic stiffness of the films lowered by an absorption of the laser energy.
High Sensitive Strain Microsensor based on Dielectric Matrix with Metal Nanoparticles
Authors: Konovalov I. A. , Fedorovich R. D. , Nepijko S. A. , Viduta L. V.
Published: April 2011

A dielectric matrix, containing metal nanoparticles with interparticle spacings of 1–2 nm, is a system with tunnel mechanism of electrical conductivity. Its electrical resistance is very sensitive to deforming of matrix because it leads to changes in spaces between particles and as a result the potential barrier transperancy is varied.

Different metals (Mo, Cr, Ta, Au, Pt, Bi, Al) and their films morphology structure were studied in order to get high sensitive strain sensors. Metal nanoparticles were deposited on elastic dielectric substrates. Strain coefficients were measured for a wide range of strains and temperatures. Variation of matrix structure gives possibilities to produce strain sensors with high electrical resistance and weak temperature dependence. The matrix with Au nanoparticles was found to have maximum strain coefficient (>100). These sensors can be manufactured in the miniature scale (sensitive area around 1 micron or less).
The Influence of Hafnium Content, Cold Work, and Heat Treatment on the R-Phase Transformation of Niti Based Shape Memory Alloys
Authors: Zhang Chen , Thoma Paul E. , Zee Ralph H.
Published: April 2011

The R-phase transformation of a Ti-rich NiTi shape memory alloy (SMA) and two ternary SMAs having the compositions Ni49Ti51-XHfx with lat% and 3at% Hf, has been investigated. The influence of cold work (CW) and heat treatment (HT) on the R-phase transformation is analyzed thermally using Differential Scanning Calorimetry (DSC). Results show that the R-phase transformation depends on the SMA composition as well as the CW and HT conditions in a complex manner. For example, the formation of R-phase upon cooling from austenite (A) is increasingly suppressed with the substitution of Hf for Ti. For the ternary SMA with 3at% Hf, the A→R and R→A transformations are observed only at relatively large amounts of CW (above approximately 40%) and at a high HT temperature (450°C). DSC results also show that for the Ti-rich NiTi and the ternary SMA containing lat% Hf, the A→R and R→A transformation temperatures (TTs) are insensitive to cold work at a HT temperature of 450°C. However, at a lower HT temperature of 350°C, the TTs are found to decrease with increasing CW. For a given CW, the A→R and R→A transformations decrease with decreasing HT temperature and the effect is greatest at high CW (>50%) conditions. An effort is made to identify the factors responsible for the observed behavior in the R-phase transformation.
A Theory of Shape-Memory Thin Films with Applications
Authors: Bhattacharya K. , James R. D.
Published: April 2011

Shape-memory alloys have the largest energy output per unit volume per cycle of known actuator systems [1]. Unfortunately, they are temperature activated and hence, their frequency is limited in bulk specimens. However, this is overcome in thin films; and hence shape-memory alloys are ideal actuator materials in micromachines[l]. The heart of the shape-memory effect lies in a martensitic phase transformation and the resulting microstructure. It is well-known that microstructure can be significantly different in thin films as compared to bulk materials. In this paper, we report on a theory of single crystal martensitic this films. We show that single crystal films of shape memory material offer interesting possibilities for producing very large deformations, at small scales.
Smart Piezoelectric PZT Microcantilevers with Inherent Sensing and Actuating Abilities for AFM and LFM
Authors: Lee C. , Itoh T. , Chu J. , Ohashi T. , Maeda R. , Schroth A. , Suga T.
Published: April 2011

Novel designs of the force sensing components for an atomic force microscope (AFM) and lateral force microscope (LFM) have been proposed in this study. By using PZT thin layers, a smart structure that can perform force sensing and feedback actuation at the same time is applied to the AFM. Clear images can be derived by an AFM equipped with this smart structure. A structure of two parallel PZT bars integrated on a SiO2 free standing cantilever has shown potential for operation in an LFM, because a difference in the piezoelectric charge outputs from these two beams will be induced by frictional force when the cantilever end quasi-staticly contacts with the sample surface in dynamic scanning across the surface.
Phase Transformations and Crystallography of Twins in Martensite in Ti-Pd Alloys
Authors: Nishida M. , Morizono Y. , Kijima H. , Ikeya A. , Iwashita H. , Hiraga K.
Published: April 2011

Phase transformations and crystallography of twins in near-equiatomic Ti-Pd alloys have been studied. In the first half we have found that the transformation temperature decreases with decreasing the Pd contents and the successive transformations take place in the Ti-rich alloys. While the transformation temperature is nearly constant with the composition and a single transformation takes place in the equiatomic and Pd-rich alloys. The solubility limit of TiPd compound in Ti-rich side is extended to about 55 at%Ti at 900°C and abruptly decreased with decreasing temperature. In the latter half we have found three twinning modes, i.e., {111} Type I, <121> Type II and {101} compound twins, in the martensite. The {111} Type I and <121> Type II twinnings which are conjugate to each other coexist in the same variant. The {111} Type I twins are dominantly observed and the <121> Type II twins are less frequently observed. The former twinning is considered to be a lattice invariant shear. There is no martensite variant consisting wholly of the <121> Type II twins throughout the present observation. The <121> Type II twinning is considered to be a deformation twin due to the elastic interaction during the transformation. The {101} compound twinning is also considered to be a deformation twin, since the twin has an isolated fashion in the martensite variant. The boundary structure of the above three twinning modes was also discussed on the basis of lattice image.
Shape Memory Effect and Pseudoelasticity in Ti-40%Ni-10%Cu (At.%) Single Crystals
Authors: Chumlyakov Yu.I. , Kireeva I. V. , Zuev Yu.I. , Lyisyuk A. G.
Published: April 2011

The dependence of shape memory effect (SME) and pseudoelasticity (PE) on crystal orientation and on sign of applied stresses (tension/compression) has been investigated on Ti-40%Ni-10%Cu (at.%) single crystals. It have been shown that both SME and PE depend on an orientation and an applied stress sign. Asymmetry effects were found at deformation in high-temperature B2 phase and in the range of stress-induced martensite transformations.
Nonthermoelastic and Thermoelastic Martensitic Transformation Behavior Characterized by Acoustic Emission in An Fe-Pt Alloy
Authors: Ohtsuka H. , Takashima K. , Olson G. B.
Published: April 2011

Acoustic emission (AE) signals generated during the martensitic transformation in an Fe-24at%Pt alloy with various ordering treatments have been measured, and the AE parameters have been correlated with phase transformation events. AE events are generated during cooling of specimens, which is the first detection of the AE events associated with the martensitic transformation in Fe-Pt alloys. In all specimens, AE events were observed at higher temperature than the Ms temperatures determined by electrical resistivity measurement. AE events started to increase abruptly for the weakly ordered specimen with decreasing temperature. In contrast, AE events increased gradually for the highly ordered specimen with decreasing temperature. This is consistent with the nature of the transformation behavior in this alloy. The critical defect size of weakly ordered and highly ordered specimens were calculated using Ms temperature determined by AE technique. Results obtained in this investigation strongly suggests that the AE technique is useful for analysis of transformation kinetics in this alloy.
The Effect of Reverse Transformation on Recovery • Recrystallization Process in Ti-Pd-Ni High Temperature Shape Memory Alloys
Authors: Xu Ya , Otsuka Kazuhiro , Ueki Tatsuhiko , Mitose Kengo
Published: April 2011

The effect of martensitic reverse transformation on recovery • recrystallization process in cold rolled Ti-Pd-Ni high temperature shape memory alloys has been investigated systematically by flash heating treatment, micro-Vickers hardness test, differential scanning calorimetry and transmission electron microscopy. It was found that the temperatures of softening in hardness after flash heating treatments agree well with the reverse transformation temperatures in the present alloys, and most of the softening occurs within 60 seconds when annealing temperature is raised to above the reverse transformation temperature. We conclude that the recovery • recrystallization process is controlled by the reverse transformation. The reasons are considered based on the large difference in atomic diffusion rate in the parent phase and in the martensite.
Microstructures and Mechanical Properties of 6061 Al Matrix Smart Composite Containing TiNi Shape Memory Fiber
Authors: Lee J. H. , Hamada K. , Miziuuchia K. , Taya M. , Inoue K.
Published: April 2011

6061 Al-matrix composite with TiNi shape memory fiber as reinforcement has been fabricated by vacuum hot pressing to investigate the microstructure and mechanical properties. The yield stress of this composite increases with increasing amount of prestrain, and it also depends on the volume fraction of fiber and heat treatment. The smartness of the composite is given due to the shape memory effect of the TiNi fiber which generates compressive residual stresses in the matrix material when heated after being prestrained. Microstructual observations have revealed that interfacial reactions occur between the matrix and fiber, creating two intermetallic layers. The flow strength of the composite at elevated temperatures is significantly higher than that of the matrix alloy without TiNi fiber.
Fabrication of Piezoelectric Sensors for Biomedical Applications
Authors: Hussajn Iqbal , Kumar Ashok , Mangiaracina A. , Perlaky S. C. , Mccombs S. C. , Zhong F. , Weimer J. J. , Sanderson L.
Published: April 2011

Biosensors are a special class of chemical sensors that take advantage of the high selectivity and sensitivity of biologically active material. We are currently investigating the characteristics of various deposited electrode coatings (Au and Pt) on 10 MHz quartz crystals using the sputtering method. We are also investigating the effect of magnetic behavior (by intermixing Fe and Ni with electrodes) on the binding nature of antigen with the substrate. A change in mass occurs due to the binding of antigens and antibodies on the surface of the thin film coating. The frequency change as a result of a change in mass makes it possible to use these crystals as biological sensor devices. This paper describes the construction of antibody-based piezoelectric crystals capable of detecting mycobacterial antigens in diluted cultures of attenuated M. tuberculosis. The microstructural features of these crystals have been studied using scanning electron microscopy (SEM) and atomic force microscopy (AFM) techniques. The crystallographic properties have been characterized using the X-ray diffraction (XRD) method. The long term objective of this research is to develop a rapid quantitative method of analysis for the diagnosis of tuberculosis (TB) and other infections caused by mycobacteria, using biosensor technology.
The Application of High Energy Density Transducer Materials to Smart Systems
Authors: Lindberg J. F.
Published: April 2011

Recent NUWC research efforts in the field of high power sonar transducers designed to produce high acoustic outputs over significant bandwidths while being of minimal size and weight have been aided by advances in the continuing development of several new high energy density transducer drive materials. Both Terfenol-D, a rare earth magnetostrictive material, and lead magnesium niobate, a relaxor ferroelectric, have demonstrated a tenfold increase in field-limited energy density over a typical very hard lead zirconate titanate (i.e., Clevite PZT-8) piezoelectric ceramic. The Center's focus is to double the demonstrated performance of each material and to address such issues as hysteresis reduction in the magnetostrictive material and coupling coefficient improvements in the electrostrictive materials. Poly (vinylidene fluoride-trifluoroethylene) can also be considered a high energy density material because of its excellent energy density and its broad bandwidth possibilities. The application of these material technologies, either separately or as hybrid composites, to smart material design will be detailed.
Theory and Applications of Large Stroke Terfenol-D® Actuators
Authors: Gerver M. J. , Berry J. R. , Dozor D. M. , Goldie J. H. , Ilmonen R. T. , Leary K. , Nimblett F. E. , Roderick R. , Swenbeck J. R.
Published: April 2011

Traditionally, control algorithms for Terfenol-D® magnetostrictive actuators have modelled the strain as a linear function of magnetic field and stress, but nonlinearity becomes important for strains of more than a few hundred parts per million (ppm), and for many applications even the maximum strain, about 1500 ppm, is inadequate. Larger strokes can be obtained by various types of stroke amplifiers, by resonant operation, or by inchworming. Previously, SatCon successfully used a 10:1 lever arm stroke amplifier in a helicopter flap actuator [1]. Current projects include a water pump using a hydraulic stroke amplifier, which potentially could be more compact and efficient than a lever arm amplifier, and linear and rotary inchworm motors for robotics. In all these designs, satisfactory performance requires careful attention to machining tolerances and to making the mechanisms and housing stiff enough or compliant enough. A model for inchworm motors has been developed, including finite load and resonant effects. Nonlinear control algorithms will be discussed, applicable to arbitrarily large Terfenol-D® strains, stresses, and magnetic fields.
Application of Smart Materials to Wireless ID Tags and Remote Sensors
Authors: Fletcher Richard , Levitan Jeremy A. , Rosenberg Joel , Gershenfeld Neil
Published: April 2011

Material structures having an electromagnetic or magnetomechanical resonance can be excited or detected remotely using an antenna. Incorporating smart materials into such structures provides new opportunities to encode ID and sensor information in the electromagnetic signature of the “tag.” In this way, it is possible to create tags which not only have a unique ID but which can also respond to local changes in their environment (e. g. force, temperature, light, etc.). This principle forms the basis for a low-cost wireless ID and wireless sensor technology which has many potential applications in manufacturing, inventory control, security, surveillance, and new human-computer interfaces. As a means of illustrating this concept, two simple examples are given: a force sensor incorporating a piezoelectric polymer and a relative position sensor which incorporates a magnetoelastic amorphous metal ribbon.
Giant Magnetostrictive Multilayer Thin Film Transducers
Authors: Quandt E. , Ludwig A.
Published: April 2011

Magnetostrictive multilayer films which combine exchange coupled giant magnetostrictive materials (amorphous Tb0.4Fe0.6) and materials with large polarizations (Fe or Fe0.5Co0.5) were prepared by dc or rf magnetron sputtering using a rotary turn-table technique in a stop-and-go mode. The magnetic properties of TbFe/Fe and TbFe/FeCo multilayers were investigated in relation to the layer thicknesses and the annealing temperatures. Giant magnetoelastic coupling coefficients (or magnetostrictions) are achieved at low fields, due to the magnetic polarization enhancement in such multilayers. Saturation magnetoelastic coupling coefficients of 20 MPa at 20 mT in the case of TbFe/Fe and of 28 MPa at 20 mT in the case of TbFe/FeCo were achieved. These high low-field magnetoelastic coupling coeffients and the possibility to engineer the material's properties by layer thickness variation are considered to be important features for applications of these films as thin film transducers in microsystems.
Effect of Noble Metals on Selective Detection of LPG Based on SnO2
Authors: Phani A. Ratna , Pelino M.
Published: April 2011

The present investigation deals with the electrical response of noble metal doped SnO2 to improve the selectivity for Liquid Petroleum Gas (LPG) in the presence of CO and CH4. Addition of small amounts of nobel metals (Pd, Pt and Rh) to the base material SnO2 is carried out by co-precipitation method. X-ray diffraction and X-ray photoelectron spectroscopy studies are carried out to find out the crystalline phase and chemical composition of the SnO2. The sensor element has been tested for cross selectivity to reducing gases by measuring sensitivity versus sintering temperatures and sensitivity versus operating temperatures. The sensor elements with the composition of Pd (1.5 wt%) andPt (1.5 wt%) in the base material SnO2 sintered at 800°C showed high sensitivity towards LPG at an operating temperature of 350°C suggestingthe possibility to utilize the sensor for the detection of LPG.
Size Distributions of Fluid Membrane Vesicles Far From Equilibrium
Authors: Golubović Leonardo , Golubović Mirjana
Published: April 2011

We investigate nonequilibrium behavior of a polydisperse ensemble of fluid membrane vesicles by means of a diffusive Boltzmann transport equation which, incorporates vesicle diffusion and the reactions between vesicles. This approach is used to study the time evolution of the size distribution of an initially monodisperse vesicle ensemble and its interesting properties such as the internal aqueous, encapsulated volume. We investigate various nonequilibrium paths such ensembles may follow during the equilibration process.
Vector Lattice Model of Amphiphilic Mixtures: Interfacial Behavior
Authors: Buzano C. , Evangelista L. R. , Pelizzola A.
Published: April 2011

The interfaces between the water-rich, oil-rich and disordered phases of a balanced ternary mixture of oil, water and amphiphile are studied, on the basis of a vector lattice model, by means of an exact partial integration and a local mean field approximation. The phase diagram exhibits a water/oil-rich phase, structured (ordered bicontinuous and lamellar) phases and a disordered phase with a microemulsion region. The interfacial tension and profiles at oil/water/disordered phase coexistence are calculated and the possibility of a wetting transition is discussed.
An Avoidance Model for Short-Range Order Induced by Soft Repulsions in Systems of Rigid Rods
Authors: Han Jining , Herzfeld Judith
Published: April 2011

The effects of soft repulsions on hard particle systems are calculated using an avoidance model which improves upon the simple mean field approximation. The method not only yields a better free energy, but also gives an estimate for the short-range positional order induced by soft repulsions. The results indicate little short-range order for isotropically oriented rods. However, for parallel rods short-range order increases to significant levels as the particle axial ratio increases.