bluuebunny/crossref_metadata_2025 huggingface dataset:
Preparation and Properties of
Poly(Phenyleneterephthalamide)-Silica Ceramers With Interphase Bonding From
Aminophenyltrimethoxysilane
Authors: Ahmad Z. , Wang S. , Mark J. E.
Published: April 2011

Poly(phenyleneterephthalamide) chains having carbonyl chloride end groups
were prepared by reacting a mixture of m- and
p--phenylene diamines with terephthaloyl chloride, and
were then end-capped with aminophenyl-trimethoxysilane. The polymer thus
prepared was used to synthesize a hybrid material in which it was chemically
bonded to a silica network produced in-situ by hydrolyzing
tetramethoxysilane. Films prepared from this hybrid material were yellow but
transparent, and quite tough. The transparency of the films and their
mechanical strength were considerably improved relative to the corresponding
systems in which the inorganic network was not bonded to the organic phase.
Tensile strength was found to increase initially with addition of silica but
then to decrease rapidly with further additions. Elongation at rupture also
decreased after an initial small increase. A systematic increase in the
tensile modulus and hardness with increase in the silica content and a
decrease in water absorption were also observed. SEM analysis showed that
the silica particle size depends on the silica content, and was 0.5 μm or
less. These transparent ceramers were found to withstand tensile stresses
the order of 175 MPa and had thermal decomposition temperatures around 460 -
475 ° C, and could thus be very useful in engineering applications at high
temperatures.
Electron Spin Resonance (Esr) Study of VO2+ Doped
Germanium Dioxide Synthesized Via the Sol-Gel Process
Authors: Mendez-Vivar Juan , Arroyo R.
Published: April 2011

VOSO4.3H2O was used as doping agent to prepare
GeO2 xerogels, via the sol-gel process. Samples were analyzed
by Thermal Gravimetric Analysis (TGA), Differential Thermal Analysis, (DTA),
Diffuse reflectance (UV-Vis) spectroscopy and electron spin resonance (ESR).
Study of thermally treated samples was done. VO2+ were found in
V2O5 at 350 °C. VO2+ ions were
incorporated to the GeO2 network after thermal treatment at 700
°C. From the results we propose that VO2+ acts as crystal former
in these samples.
Wet-Chemical Processing of Tin-Doped Indium Oxide
Layers
Authors: Van Bommel Mark J. , Bernards Tom N.M. , Talen Wim
Published: April 2011

For industrial applications the wet-chemical deposition of tin-doped indium
oxide (ITO) layers would be favourable, especially at low temperatures.

It is shown that conductive transparent films can be made by spinning
solutions which contain alkoxide precursors of indium and tin. The
hydrolysis conditions of these alkoxides are varied using different water to
indiumalkoxide ratios and different hydrolysis times. It is shown that when
processed at low temperatures, the hydrolysis of these alkoxides has a
severe influence on the electrical properties of the layers. A decrease in
resistance as a function of time is observed for ITO layers which are stored
at room temperature in an ambient atmosphere. Annealing at 350°C in forming
gas further reduces the resistance of the ITO layers.
Doped Silicon Carbonitride: Synthesis, Characterization and
Properties
Authors: Bill J. , Friess M. , Aldinger F. , Riedel R.
Published: April 2011

We report on an alternative route to quaternary ceramics which can be
prepared by polycocondensation of commercially available polysilazanes with
the appropriate alkyl amides (M(NRR')X with M = B or P and
subsequent pyrolysis in argon atmosphere at 1000°C. Ceramic monoliths are
obtained if the modified polysilazane is crosslinked at 400°C for 3 h. After
ball-milling, sieving and cold isostatic pressing the green body is directly
pyrolysed to the appropriate monolith. The obtained material is amorphous to
X-ray-diffraction. Investigations by electron spectroscopie imaging (ESI) in
TEM indicate a homogeneous distribution of the elements M, Si, C and N (M =
B, P) within a resolution of 2 nm. Upon annealing at elevated tempertures in
a nitrogen atmosphere crystallization of the appropriate thermodynamically
stable phases occurs around 1400°C yielding a micro/nano-, nano/nano- or
micro/microcrystalline microstructure with design-tailored properties
depending on the element M.
Polymer-Derived Micro-Nano-Structured Si3N4/SiC-CompositeS
Authors: Greiner Axel , Bill Joachim , Riedel Ralf
Published: April 2011

Micro-nano-structured Si3N4/SiC-composites were prepared by liquid phase sintering of either amorphous, polymer derived Si-C-N powder or SiC1+xcoated OC-Si3N4 powder, followed by gas pressure sintering. The obtained microstructures were investigated by scanning and transmission electron microscopy (SEM, TEM). Nanosized SiC inclusions embedded in microcrystalline Si3N4 grains were analysed by elemental mapping with electron spectroscopie imaging (ESI).
Studies on SiBN(C)-ceramics: Oxidation- and Crystallization
Behavior Lead the Way to Applications
Authors: Baldus H.-P. , Passing G.
Published: April 2011

The thermal stability of amorphous borosilicon nitride
(Si3B3N7) and borosilicon carbonitride
(SiBN3C) between 1000°C and 2000oC both in air and
under inert conditions is reported. Both materials are derived from
polymerization and subsequent pyrolysis of a “single source” precursor. On
heating in vacuum or nitrogen SiBN3C remains amorphous up to lCWC
whereas Si3B3N7 crystallizes at about
1800°C under these conditions. At about 2000^ the SiBN(C)-materials
decompose into SiC, BN, B4C and N2.

Oxidation studies performed by TEM- and SEM-investigations of oxidized
borosilicon carbonitride grains reveal that an interlayer consisting of B,
N, and only little O is formed between the oxide scale on the surface and
the inner bulk material. The interlayer does not disappear at temperatures
above 1450°C in contrast to the Si2N20-interiayer
observed on oxidized silicon nitride. The oxidation kinetics of the new
ceramics are established in the range from 1000°C to 1600°C indicating a
very high oxidation resistance. Possible applications as matrix materials as
well as materials for fibers and coatings are discussed.
Preparation Of Pt/Al2O3 Catalysts By
Sol-Gel Process And Its Application To Uranyl Ion Reduction
Authors: Deptuia A. , Łada W. , Olczak T. , Di Bartolomeo A.
Published: April 2011

Various kinds of active alumina supports were obtained in the following
steps: (1) preparation of alumina sols by extraction of nitrates with
Primene JMT from aluminium nitrate solution, (2) gelation to spherical
particles (with diameter < 100 μm) by extraction of water from sol
emulsion in 2-ethyl -1-hexanol, (3) sometimes conversion of NO3− stabilized gel to OH− form by reaction with ammonia,
(4) calcination of gels to γ-Al2O3 with specific
surface area >100 m2/g at 500°C . The powders were then
impregnated with chloroplatinic acid and recalcined at 500°C. Catalysts were
also prepared by direct gelation of alumina sol containing hydroplatinic
acid followed by steps (3) and (4). Pt/Al2O3 catalysts
were used for reduction of 1M UO2(NO3-0.5M HCOOH
solution with hydrogen at atmospheric pressure. The course of the reduction
was controlled analytically and by measuring the U(VI)/U(IV) redox
potential. It was concluded that the catalysts obtained by impregnation of
supports prepared from nitrate stabilized gels exhibit the best activity and
stability.
Preparation and Processing of Monodisperse Colloidal
Silica-Cadmium sulfide nanocomposites
Authors: Chang Song-Yuan , Liu Lei , Asher Sanford A.
Published: April 2011

A novel synthetic methodology has been developed for preparing monodisperse
colloidal silica-cadmium sulfide nanocomposite spheres in the 50 – 300 nm
size regime. This methodology uses water-in-oil microemulsions as the
reaction medium. Monosize silica colloids are first produced by the
controlled hydrolysis of tetraethyl orthosilicate in the micro water
droplets of the microemulsion. Cadmium sulfide quantum dots are incorporated
into the silica colloids during synthesis by the introductions of
Cd2+ and S2- microemulsions. Various morphologies
of the nanocomposite are fabricated by controlling the heterogeneous
coagulation of CdS and SiO2. Unique high surface area silica
particles can be prepared when nitric acid etches out the CdS and leaves
behind topologically defined voids. The CdS nanocomposites are new materials
useful for non-linear optics, while the high surface area silica particles
should have novel applications in areas such as catalysis.
Self-Connected Cds Nanocrystals as Precursors for Anisotropic
Semiconducting Films
Authors: Chemseddine A.
Published: April 2011

Monosized and anisotropically capped CdS nanocrystals have the property to
self-connect into a polymeric material. The viscosity of this fibrous
material can be adjusted to fabricate texturized and homogeneous coatings.
These films can be thermally converted into pure CdS films. Based on the
size dependent band gap of this semiconductor, the absorbance of the film
can be fine-tuned through the size of the particle-precursor or by
controlling the film heat treatment. The evolution of the film nanostructure
with temperature was investigated by optical absorption, DTA, SEM and X-ray
diffraction techniques.
Preparation of Sol-Gel Coatings by Electrophoretic
Deposition
Authors: Hirashima Hiroshi , Obu Yusuke , Nagai Takayuki , Imai Hiroaki
Published: April 2011

Thin films of ZrO2 and lead zirconate-titanate, PZT, about 100 to
1000 nm in thickness, were prepared by electrophoretic deposition from
transparent sols obtained by hydrolysis of metal alkoxides. Stainless steel
plates and Pt-coated glass plates were used as substrates/electrodes. The
applied field was up to 20 V/cm. The refractive indices of as dried films
were higher than those of dip-coated films. High temperature oxidation of
stainless steel plates was suppressed by the ZrO2 coatings.
Uniformity of the chemical composition of the as-dried PZT films, determined
by Auger electron spectroscopy, was better than the dip-coated PZT
films.
Ionic Properties of Hydrogenated and Fluorinated Fullerenes
Authors: Hettich R.L. , Jin C. , Britt P.F. , Tuinman A.A. , Compton R.N.
Published: April 2011

The ionization potentials (IP) and electron affinities (EA) for a number of hydrogenated and fluorinated derivatives of C60 and C70 have been determined using the charge exchange “bracketing” technique. Samples of C60Hx and C70Hy were prepared by direct solid phase hydrogenation (x=2-18, y=2-30) or platinum oxide catalytic hydrogen reduction (x=36, y=36). The IP's for C60H2-18 are between 6.75 and 7.53 eV for even x<10 and lower than 6.75 for odd x<10. The EAs for C60F44,46,48, and C70F52,54 were “bracketed” to be 4.0 ± 0.25 eV. The highly fluorinated chiral C3h molecule C60F48 was observed to directly attach two electrons in the gas phase to produce C60F482- and C60F462− + F2−. Studies of the metastable decompositions and collision-induced dissociation of C60F482− showed fluorine atom and F2 loss, but no loss of an electron. In addition, the C60F48,46,442− dianions do not charge exchange with molecules possessing high electron affinities, including the neutral parent compound, C60F482− (EA = 4.06 eV). The remarkable stability of C60F482− to the removal of an excess electron is attributed to a long-range Coulomb barrier which is built from the bound state for the two electrons near the molecule and the electron-electron Coulomb repulsion between the two at large distance.
Characterization of Pulsed Supersonic Cvd System For Diamond Growth
Authors: Ohlberg Douglas A. A. , Ren James , Williams R.Stanley
Published: April 2011

An ultra-high vacuum chemical vapor deposition system using pulsed, supersonic jets of halogenated hydrocarbon precursors has been constructed with the intention of growing diamond thin films. Experimental results from this system should determine whether the hyperthermal activation of precursors improves the carbon incorporation efficiency of film growth. The jets, produced by commercially available pulsed valves, were characterized with a fast ionization gauge. Parameters such as valve backing pressure and the pulse width were varied to optimize material flux and avoid the formation of boundary layers above the substrate that could reduce the kinetic energy of the precursors.
Optical Characterization and Modeling of Amorphous Hydrogenated Carbon Films
Authors: McGahan William A. , Woollam John A.
Published: April 2011

Amorphous hydrogenated carbon (a-C:H) thin films are of great importance in a number of industrial applications due to their hardness, chemical stability, and optical transparency. In many applications, the thickness of the a-C:H film and/or its optical properties are critical for the performance of the complete structure, and, as a result, a means of measuring these quantities is important. In this work we review the use of spectroscopic ellipsometry and transmission measurements for the estimation of the thickness and optical constants of thin a-C:H films. Spectra are shown for films exhibiting Tauc effective bandgaps ranging from 0 - 2.3 eV. The films were prepared by magnetron sputtering and plasma CVD on both silicon and glass substrates. The general energy dependence of the a-C:H optical constants is discussed in terms of the absorption processes which occur in the film.
Structure and Electronic Properties of Diamond-Like Amorphous Carbon
Authors: Wang C. Z. , Ho K. M.
Published: April 2011

Amorphous carbon networks generated by quenching high-density liquid from hightemperature using a tight-binding molecular dynamics method are found to be dominated by tetrahedral bonding sites. The overall structural and electronic properties of these networks resemble those observed in experimental diamond-like amorphous carbon films produced by the mass-selected ion beam deposition technique. Our study shows that bonding and antibonding of π states associated with pairs and quartets of threefold “defected-atoms” embedded in the fourfold matrix yield a band gap of about 2 eV.
Structure and Performance of Carbon Aerogel Electrodes
Authors: Pekala R.W. , Mayer S.T. , Poco J.F. , Kaschmitier J.L.
Published: April 2011

The chemistry and physics of small clusters of atoms (1-100 nm) has received considerable attention in recent years because these assemblies often have properties between the molecular and bulk solid-state limits. The different properties can be explained in terms of the large fraction of atoms that are at the surface of a cluster as compared to the interior. Although the synthesis and properties of metal and semiconductor clusters, metallocarbohedrenes, fullerenes, and nanotubes are the subject of extensive investigations, little attention has been paid to cluster-assembled porous materials. This oversight is of particular interest to us since we believe that aerogels are one of the few monolithic materials presently available where the benefits of cluster assembly can be demonstrated. In particular, the unique optical, thermal, acoustic, mechanical, and electrical properties of aerogels are directly related to their nanostructure, which is composed of interconnected particles (3-30 nrm) with small interstitial pores (< 50 nm). This structure leads to extremely high surface areas (400-1100 m2/g) with a large fraction of the atoms covering the surface of the interconnected particles. As a result of these structural features, carbon aerogels are finding applications as electrodes in supercapacitors with high energy and power densities.
Growth, Structure and Stress of DC Magnetron Sputtered TiB2 Thin Films
Authors: Deng H. , Chen J. , Inturi R. B. , Barnard J. A.
Published: April 2011

TiB2 is a very hard refractory compound that strongly resists erosion and shows metallic luster and good electrical conductivity. It has potential applications in protective coating systems. This paper investigates the microstructure and stresses of as-deposited TiB2 thin films ranging from 2000 °A to 4000 °A thick produced by dc magnetron sputtering as a function of sputtering power and Ar pressure. Three power levels: 100, 400, 600 W, and four pressures: 3, 5, 8, and 12 mTorr were used. X-ray diffraction studies indicate that two types of crystalline structure are formed: a randomly oriented fine crystalline structure and a coarser grained (001) textured structure, depending on the sputtering power and pressure. As-deposited stresses at different powers all show a transition from compression to tension as the Ar pressure increases. The relationship between the processing parameters, microstructure and residual stresses is discussed. The effects of the deposition power and pressure on the residual stress transition of TiB2 thin films are clearly mapped out by 3-D and contour maps.
Tunability of Intrinsic Stress in Siox Dielectric Films Formed by Molecular Beam Deposition
Authors: Chand Naresh , Kola R. R. , Osenbach J. W. , Tsang W. T.
Published: April 2011

Silicon monoxide (SiO) formed by molecular beam deposition (MBD) has many attractive optical, electrical, mechanical, and chemical properties which make it a suitable dielectric for many semiconductor device applications. It can be thermally evaporated at a much lower temperature than Si, SiO2 or Si3 N4 and it condenses on cooler surfaces in uniform and adherent stoichiometric SiO (x = 1) films when evaporated in high vacuum. At low deposition rates and at high pressures of oxygen, SiOx (1 ≤ x ≤ 2) films result. This allows variation of refractive index, stress and other properties of SiOx with x. In general, the SiO (x = l) films are under tensile stress <100 MPa which is significantly lower than that observed in other dielectric films. Slight introduction of oxygen during deposition reduces the tensile stress; at an O2 pressure of 5 × 10−7 Torr and above, the films are in compression. This allows the tunability of stress in SiOx films and deposition of films essentially free from stress. Furthermore, both Si and SiO have similar values of the linear thermal expansion coefficient (average values between 23 °C and 350°C: 3.37 × 10−6°C−1 and 2.7 × 10−6°C−1, respectively). As a result, SiOx/Si films develop little thermal stress during thermal cycling.
Stacking Fault Tetrahedra Formation During Growth of Si1-xGex Strained Layers on 〈111〉 Oriented Si Substrates: Tem Observations and Defect Modeling
Authors: Howard David J. , Bower Allan F. , Paine David C.
Published: April 2011

We report the observation of stacking fault tetrahedra (SFT) in strained Si1-xGex layers grown via rapid thermal CVD on (111) Si substrates. It is shown that these defects provide a mechanism for strain relief in films strained in compression due the presence of bounding edge-type stair rod partials whose Burgers vectors lie parallel to the strained layer interface. Cross section and plan view TEM were used to characterize this defect structure in epilayers (30 to 650nm thick) of Si1-xGex (0 < xGe < 0.27) grown on 〈111〉 oriented Si wafers. Stacking fault tetrahedra were observed only in alloys in the compositional range xGe ≥ 0.13 and only when growth proceeded on the 〈111〉 surface. A critical strain energy model that identifies conditions for the stable growth of stacking fault tetrahedra in a strained layer is presented. The model was based on conventional strain energy considerations where the energy of the stacking fault area plus the bounding dislocation network (including dislocation interactions but neglecting the free surface) was balanced against the strain energy released by the introduction of the defect. In addition, a formation mechanism consistent with these observations is described that involves the dissociation of Frank partial dislocation loops bounding stacking faults lying in the growth plane.
Misfit Strain Relief Beyond the Critical Thickness Using Curvature Measurements and in Situ Characterization of the Magneto-Optic Kerr Effect
Authors: Inglefield H. E. , Bochi G. , Ballentine C. A. , O’Handley R. C. , Thompson C. V.
Published: April 2011

Epitaxial misfit has been characterized in Ni/Cu/Si (100) as a function of Ni film thickness using wafer curvature measurements. This strain can be related to measurements of magnetic anisotropy made in the deposition system using the magneto-optic Kerr effect. Films were deposited using molecular beam epitaxy (MBE) with varying Ni epilayer thickness between 10 and 1000Å. The change in wafer curvature due to misfit strain was measured using optical interferometry and the strain was calculated using Stoney’s equation. Transmission electron microscopy was used to characterize misfit dislocations at the Ni/Cu interface. It has been determined that misfit strain can have a very strong effect on magnetic anisotropy, particularly in the regime between the critical thickness and complete misfit accommodation, where strain has been found to decrease significantly as a function of film thickness. A critical strain has been determined at which a transition in the direction of magnetization easy axis from perpendicular to the film to in the film plane occurs. This discovery allows the use of Kerr effect measurements to characterize misfit strain in situ.
Nanoindentation of Epitaxial Films: A Study of Pop-in Events
Authors: Mann A. B. , Pethica J. B. , Nix W. D. , Tomiya S.
Published: April 2011

Discontinuities in nanoindentation loading curves are frequently observed in ceramic materials. These normally occur at fairly random loads and displacements, probably due to the random distance of pre-existing defects from the indent location. Here we report the observation of reproducible, sudden indent-depth changes which occur over a very narrow distribution of depths and loads, for GaAs and a range of related epitaxial layer systems. The surface preparation and material defect density have a significant influence. Different tip geometries have been used to gain insights into the deformation processes which cause these discontinuities.
Mechanical Properties and Microstructure of Cu/Cu-Ni And Cu/Ag Multilayer thin Films
Authors: Krzanowski James E. , Duggan Peter
Published: April 2011

The mechanical properties of thin-film Cu/Cu-Ni and Cu/Ag multilayers are examined in this study. Films were prepared by magnetron sputter deposition onto cleaved NaCl substrates. The use of a computer-controlled deposition system enabled the multilayer interface width to be varied, as well as the multilayer amplitude and bilayer thickness. The Cu/Cu-Ni multilayers had the form of (001) oriented single crystal films, but for Cu-Ag multilayers only polycrystalline films could be obtained in the (001) orientation. For Cu/Cu-15%Ni multilayers, the tensile strengths were measured and observed to increase with decreasing interface width at constant wavelength. Tensile strengths were also found to increase with increasing composition modulation amplitude. For films with constant interface width but bilayer thicknesses ranging from 10 to 60 nm, the tensile strength was relatively constant. The results are consistent with previous theoretical treatments, particularly the theory of modulus hardening.
In-Situ Electromigration Stressing in Transmission Electron Microscopy for Al-Cu Interconnects
Authors: Shih W. C. , Greer A.L.
Published: April 2011

Unpassivated 2.1 μm wide Al-4wt%Cu interconnects with near-bamboo grain structure, are electromigration-tested to failure in-situ in transmission electron microscopy. Early stress-induced voids stop growing and are not fatal. Hillocking is associated with precipitates, fatal voiding with copper depletion. Electromigration-induced voids form at the upstream end of inclined grain boundaries. Healing events are analysed and it is shown that open-circuit failure can occur when the proximity of grain boundaries impairs the stress-driven healing.
A Method for Analyzing the Critical Adhesion Energy of Thin Film Coatings
Authors: McGarry Frederick J. , Shaffer Edward O.
Published: April 2011

The edge delamination test (EDT) measures the energy required to cause a thin film, under biaxial tensile stress, to debond from a rigid substrate. Circular holes are etched through the films and if the stress is large enough, stable debond rings grow radially around the holes. A finite element analysis is used to find the applied strain-energy release rate as a function of debond crack length, hole radius and side-wall angle. However, the analysis may not be widely available, so, we present tables of reduced debond energy val ues, Gr, to facilitate the use of the EDT. With observed EDT results, Gr is extrapolated from the tables and then the critical debond energy is calculated by multiplying Gr by the maximum strain energy. Also, we have fit Gr with a semi-empirical equation, which is in good agreement over a broad range of geometries.
In-Situ Fluorescence Strain Sensing of the Stress in Interconnects
Authors: Wen Q. , Ma Q. , Clarke D. R.
Published: April 2011

An optical fluorescence method is introduced for determining the localized stresses in passivated aluminum lines on sapphire substrates containing a thin epitaxial ruby film at the AI/AI2O3 interface. The method is based on the piezo-spectroscopic properties of the ruby film, which acts as an in situ sensor. By focusing a laser beam through the sapphire substrate and onto the bottom of an aluminum line, the fluorescence from the ruby sensor can be excited and collected through an optical microscope. The frequency shift of the fluorescence lines is proportional to the stress in the aluminum line. To illustrate our observations two sets of measurements are presented: the spatial variation perpendicular to an interconnect line; and the temperature dependence on heating upto the deposition temperature of the SiN used to passivate the interconnects.
Time Dependent Indentation Testing At Non-Ambient Temperatures Utilizing the High Temperature Mechanical Properties Microprobe
Authors: Lucas B. N. , Oliver W. C.
Published: April 2011

Time dependent indentation data for pure indium from -100 °C to 75 °C is presented. The properties reported include hardness, indentation strain rate, stress exponent and apparent activation energy for creep. These properties were measured using a depth-sensing indentation system capable of performing experiments between -100 °C and 300 °C in ultra-high vacuum. In addition, by employing laser interferometric techniques, this system can obtain displacement data with time constants as low as 50 ns. This allows the investigation of the material response to very fast stress changes over an extremely wide range of strain rates. The adverse and beneficial dynamic effects of step-loading the indenter into the surface of the material will be discussed. Initial results obtained from this type of experiment show that it is possible to obtain energy dissipation or damping information from the material being studied.
Nanomechanical Response of Materials and Thin Film Systems: Finite Element Simulation
Authors: Syed Asif S.A. , Derby B. , Roberts S.G.
Published: April 2011

Finite element simulation of the nanoindentation process has been carried out to investigate the nanomechanical response of materials and thin film systems. The influence of the geometry of the indenter, friction between the indenter and the surface, and pre-stress in the film, on the nanomechanical response have all been investigated. The effect of pile-up on the contact area calculation and the problems which occur with the commonly used methods in calculating the contact area have been studied. Results shows considerable error in calculating the contact area which depends on the indentation conditions used for the simulation. Simulation results suggest, that the influence of residual stress on hardness response is material sensitive.
Ion Beam Mixing of Titanium Overlayers with Hydroxyapatite Substrates
Authors: Levine Timothy E. , Nastasi Michael , Alford T. L. , Suchicital Carlos , Russell Stephen , Luptak Karen , Pizziconi Vincent , Mayer James W.
Published: April 2011

The mixing of titanium overlayers with hydroxyapatite (HA) substrates via ion irradiation has been demonstrated. Analysis via secondary ion mass spectroscopy (SIMS) indicates an interfacial broadening of titanium and calcium of the implanted sample compared to that of the unimplanted sample. Attendant to the observed ion beam mixing of titanium into the HA, the oxygen signal of the titanium overlayer increases as a result of ion irradiation. It is supposed that this change is evident of diffusion through the metal layer and possibly from titania formation at the free surface and perovskite formation at the film/substrate interface. This possibility is consistent with thermodynamic predictions. Additionally, the force required to separate the film from the substrate increased as a result of ion irradiation, validating the continued study of ion beam processing of Ti/HA systems towards the improvement of long term fixation of implant devices.
Effects of Interlayers on the Scratch Adhesion Performance of Ultra-Thin Films of Copper and Gold on Silicon Substrates
Authors: McAdams S. D. , Tsui T. Y. , Oliver W. C. , Pharr G. M.
Published: April 2011

Scratch testing has long been used to assess the adhesion of a film to its substrate. As film thicknesses have decreased, the need for greater precision and sensitivity in the scratch testing apparatus has increased. To this end, a nanoindenter was modified to make finely controlled, low-load scratches. Scratches at various loads and two orientations of a Berkovich scratching diamond were made in films of 100 nm of gold and 200 nm of copper, each on single crystal silicon. For each film type, samples with no interlayer, with an SiO2 interlayer, and with a TiW on SiO2 interlayer were tested. The scratch morphology was found to vary in a regular way with load, diamond orientation and interlayer material.
On the Use of Electrostrictive Actuators in Recovering the Optical Performance of the Hubble Space Telescope
Authors: Fanson James L.
Published: April 2011

This paper describes the development of a space qualified active mirror—the Articulating Fold Mirror—which forms part of the scheme for recovering the optical performance of the Hubble Space Telescope. Three Articulating Fold Mirrors are incorporated into the optical train of the Jet Propulsion Laboratory's Wide Field and Planetary Camera-2, which was installed into Hubble by astronauts in December, 1993. Each Articulating Fold Mirror utilizes six electrostrictive ceramic multilayer actuators to precisely position a mirror in tip and tilt in order to correct the spherical aberration of the Hubble Space Telescope's primary mirror. Flight qualification aspects of the electrostrictive actuators are described. Pre- and postrepair images from the Wide Field and Planetary Camera, showing the effect of the optical correction, are presented.
Optical Non-Invasive Evaluation of Ferroelectric Films/Memory Capacitors
Authors: Thakoor Sarita , Thakoor A. P. , Cross L. Eric
Published: April 2011

NON-INVASIVE photoresponse (photocurrent/voltage, reflectance and transmittance) from ferroelectric thin films and memory capacitors, with its strong dependence not only on the remanent polarization, but also on the film microstructure, crystal orientation, and nature of the interfaces (state of formation/degradation, etc.) offers an excellent “tool” for probing the ferroelectric capacitors at virtually any stage of fabrication, including on-line quality control. In fact, simultaneous measurement of spectral photoresponse and spectral reflectance, as a distinctive signature of the device probed, is an ideal, high speed, non-invasive means of evaluation for such thin films at high spatial resolution (∼ 100 nm) using beam scanning. This paper discusses three aspects of such evaluation. First, the spectral transmittance of the film as a direct function of the microstructure, second, the use of band-gap illumination (365 nm) to condition a fatigued capacitor; and third, the optical E field interaction with the ferroelectric capacitor, yielding a high speed photoresponse which is related to the remanent polarization and the operational history (status of internal fields) of the ferroelectric capacitor. Combined, these different kinds of photoresponses provide a good signature of the device quality.
Study of Boundary Free Tb-Dy-Fe Magnetostrictive Materials
Authors: Li Qiang , Chang Y.L. , Ouyang Shixi , Yuan R.Z.
Published: April 2011

As a promising candidate of advanced smart materials Tb-Dy-Fe system has been studied for many years. It is well known that the boundaries (which exist in polycrystal and grain oriented crystals of magnetostrictive materials) heavily hinder the motion of domain walls. Therefore to eliminating those boundaries will improve their magnetostrictive behaviors to a large extent. A single crystal growth method (which is called: growth with magnetic levitation cold crucible in CZ technique) has been successfully developed in our lab. since a few years ago. Now bulk cubic Laves phase RFe2 TbxDy1-xFe1.95–2.0 single crystals with boundary free structure can be prepared. Studies have been focused on comparing the performances of polycrystal, grains oriented crystal with a single crystal of the same composition. Some results indicate that λs and d33 performed by the single crystal are much higher than the two former materials under the same conditions.
Electrically-Induced Strains in Sn-Modified Lead Zirconate Titanate
Authors: Li Jie-Fang , Dai Xunhu , Forst Donald , Viehland Dwight
Published: April 2011

Incommensuate antiferroelectric tin-modified lead zirconate titanate ceramics, PbNb0.02[(Zr1−x,Snx)1−yTiy]0.98O3, have been studied by Sawyer-Tower polarization and electrically-induced strain (ε-E) techniques. Sawyer-Tower polarization studies revealed antiferroelectric-ferroelectric (AFE-FE) P-E loops. Investigations then revealed that the electrically-induced strain associated with the AFE-FE transformation was not realized until field strengths significantly above that required for polarization saturation. It is believed that the electrically-induced strain is decoupled from the polarization due to AFEFE switching by the modulation of the phase of a <110> incommensurate structure. At field strengths above saturation, the commensurate rhombohedral ferroelectric state is believed to be induced from an incommensurate orthorhombic ferroelectric, and the electrically-induced strain is then realized.
Electro-Mechanical Properties of PbZrO3-PbTiO3 -Pb(Mn1/3Sb2/3)O3 Ceramics Under Vibration-Level Change
Authors: Takahashi Sadayuki , Sasaki Yasuhiro , Hirose Seiji , Uchino Kenji
Published: April 2011

Electro-mechanical properties in the pseudo-ternary solid solution system of PbZrO3-PbTiO3- Pb(Mn1/3Sb2/3)O3 piezoelectric ceramics were studied by changing the vibration- level using a constant current / velocity driving method. The vibration velocity is proportional to the driving electric field under a relatively low field. The velocity, however, deviates from a linear relationship as electric field increases and converges on a certain value.

The increase of the vibration-level is accompanied by a large amount of heat generation as well, and this heat generation sets a practical upper limit of the vibration-level. The heat generation is caused by a dissipated-vibration-energy which is represented as a function of vibration velocity and the constants depending on the materials and transducers.

In these pseudo-ternary solid solution ceramics, the compositional ratio which shows excellent electro-mechanical properties under a relatively low vibration-level does not necessarily coincide with the compositional ratio which is excellent under a relatively high vibration-level.
Magnetostrictive Damping to Reduce Noise and Vibrations
Authors: Karimi A. , Giauque P. H. , Martin J. L.
Published: April 2011

The magnetomechanical damping capacity of cast and thermally sprayed Fe-Cr based alloys has been investigated using free and forced vibration techniques. The coatings were deposited using a vacuum plasma spraying method and the cast alloys were prepared in a high frequency furnace under an argon atmosphere. Three laboratory devices including a torsion pendulum, a resonant bar and a cantilever were used to cover a wide range of frequencies and amplitudes varying between f = 1Hz to 10 kHz, and ε = 10−6to 10−3. The damping capacity of the plasma sprayed coatings was found to be comparable to that of cast alloys. Appropriate heat treatments improved the damping capacity of both coatings and cast alloys by several times. The variation of the loss factor as function of the vibration amplitude showed a maximum, but versus frequency exhibited a slightly monotonous character. The magnetic domains were observed using the magneto-optical Kerr effect and their modification under heat treatments was associated with different values of the damping capacities.
Effects of the Multilayer Structure on the Responsivity of Pyroelectric Thin Film Detectors
Authors: Jianguo Zhu , Dingquan Xiao , Zhenghong Qian , Wen Zhang , Siaosong Du
Published: April 2011

Pyroelectric thin film detectors have advantages of wavelength independent sensitivity, room temperature operation and direct incorporation with integrated circuit amplifiers. Pyroelectric thin films with good quality have be prepared by many advanced thin film technologies [1-2]. The responsivity of pyroelectric thin film detectors is dependent on the thermal properties of the substrate, on which pyroelectric thin film detectors are prepared. The heat conduction in the detectors was investigated using the one-dimensional heat flow equation and the expressions describing the detectors performance were derived for pyroelectric thin films detectors with multilayer structure. The numerical simulation showed that the pyroelectric thin film detectors need effective heat isolation. If the air gap could be the heat isolation layer, which is between the bottom electrode and substrate, the iesponsivity of detectors would be higher than that of detectors which have no heat isolation in certain modulation frequency range.
Recent Developments in High Temperature Shape Memory Alloys
Authors: Beyer Jeno , Mulder Jan.H.
Published: April 2011

The functional properties of Shape Memory Alloys (SMA's) are used succesfully at present in a variety of industrial and medical applications. The use of these materials in smart structures is now emerging in the field of aeronautic/space technology. Many applications require higher operating temperatures than available to date, or higher cooling rates and/or a higher number of cycles. For this purpose the properties and fabricability of commercial alloys as Ni-Ti-(X), Cu-Al-Ni or Cu-Zn-Al are being adjusted and improved. Other feasible alloys are being developed. The research and development is directed towards the control of the stress, strain, temperature and time dependence of shape memory properties for a stable in-service behaviour. In this paper the various approaches taken up in recent years by academic and industrial laboratories for developing high temperature SMA's are reviewed.
Development of NiAI(B2)-Base Shape Memory Alloys
Authors: Kainuma R. , Ono N. , Ishida K.
Published: April 2011

The basic concept underlying the alloy design and microstructural control method utilised in developing a new type ofβ(B2)+ γ (A1) two-phase ductile shape memory alloy in the Ni-Al base systems is briefly reviewed. The characteristic features of the shape memory effect (SME) in the Ni-Al-Fe and Ni-Al-Fe-Mn alloys are reported with particular reference to the transformation and deformation temperatures, the volume fractions of theγphase, the morphology of theβ + γstructure and the effect of cycling. Training by cycling treatment has a significant effect on the degree of shape recovery and pseudo-elasticity in theβ + γtwo-phase alloys. These duplexβ + γalloys also exhibit a combination of relatively high damping capacity and high yield strength. It is emphasized that these alloys could be expected to fill the need for a new group of shape memory alloys which operate at elevated temperatures over 100°C.
The Effects of La on Rapidly Solidified Al – 66 at.% NI
Authors: Sun Baode , Zhou Yaohe , Lin Hul , Lin Dongllang
Published: April 2011

This paper investigates the microstructure and ductility of Al - 66 at.% Ni by means of melt spinning technology combined with La microalloying. It shows that the Al - 66 at.% Ni without La exhibits coarse equiaxed martensite grains with Ni3Al precipitating at the grain boundaries (GBs). An addition of 0.05 wt.% La suppresses the precipitation of Ni3Al and a microstructure of complete martensite is obtained. When the amount of La is 0.2∼0.8 wt.%, a “supersaturated” single phase of B2 structure NiAl results. The elongation of Al - 66 at.% Ni without La is only 0.8%. When 0.05, 0.2, and 0.8 (wt.%) La are added to the alloy, their elongations can be as high as 2.6, 3.0, and 3.2% respectively. This shows that the elongation increases with increasing La content. The microstructural morphology and the ductility enhancement mechanism are discussed.
A Dye-Dispersed Liquid Crystal Smart Reflector
Authors: Chang Ching-Chao , Lonberg Franklin , Meyer Robert B.
Published: April 2011

We report a liquid crystal smart reflector, consisting of a cholesteric liquid crystal doped with dye. Light entering the liquid crystal is absorbed by the dye, generating heat which raises the average temperature of the liquid crystal. This in turn changes the pitch length of the cholesteric liquid crystal, causing an increase in its reflectivity, and thus reducing the amount of light absorbed by the dye molecules. A negative feedback stabilized condition is reached, in which the reflectivity is proportional to the incident light intensity. This effect is demonstrated both theoretically and experimentally.
Site Preference of Ternary Additions in Ni3Si
Authors: Sluiter M. , Kawazoe Y.
Published: April 2011

The site preference of Al and elements in the 3rd row of the periodic table in Ni3Si was studied in a systematic way by using electronic structure calculations based on the local density approximation. Alloying elements in this intermetallic may occupy exclusively the Ni or Si sublattices, or may exhibit no particular site preference. By performing the calculations both for spin-polarized and non-spin-polarized cases, it was found that magnetism affects the computed site substitution behavior of Mn, Fe, and Co in Ni3Si. In the case of Fe, e.g., a preference for the Ni sublattice is computed when magnetic effects are ignored, but when magnetic effects are accounted for it is found that Fe has no significant site preference Specific trends regarding the site preference across the transition metal series are shown and discussed.
Theoretical and Experimental Studies on the C15 Intermetallic Compound NbCr2
Authors: Chu F. , Thoma D. J. , He Y. , Mitchell T. E. , Chen S. P. , Petepezki J. H.
Published: April 2011

The electronic structure and total energy of the C15 NbCr2 phase have been calculated using the linear muffin-tin orbital (LMTO) method with the atomic sphere approximation (ASA). The total energy vs. volume curve, band structure, density of states and Fermi surface were obtained. The calculated results were used to examine several features of the C15 phase, including the elastic properties, phase formation and stability, and solubility range of the C15 phase. The theoretical results are compared to experimental studies on NbCr2 For example, the elastic moduli, phase stability, and homogeneity range have been determined with a variety of experimental techniques. Comparison of the experimental and theoretical results will be discussed.
Observation of Precipitation of the Intermetallic Phase Mg17Al12 In Mg-Al Alloys By 25Mg and 27Al Nmr
Authors: Bastow T. J. , Smith M.E.
Published: April 2011

The strength of the lightweight Mg(Al) alloys with Al concentration less than 10 wt% is due to controlled precipitation of the intermetallic phase Mg17Al12. This phase and its solid solution host have been characterised by 25Mg and 27Al NMR in terms of Knight shifts and nuclear quadrupole interactions for the distinguishable Mg and Al sites.
Alloying Effect on the Environmental Embrittlement of Ni3(Si,Ti) Alloys
Authors: Ma C. L. , Takasugi T. , Hanada S.
Published: April 2011

The effect of additions of chromium, manganese and iron on environmental embrittlement of the Ni3(Si,Ti) alloy is investigated by room temperature tensile tests in various kind of atmospheres (vacuum, air, distilled water and H2 gas) and at various strain rates. The observed tensile elongation and the associated fracture mode are very much dependent on atmospheres and strain rates. It is shown that additions of these transition elements to the Ni3(Si,Ti) alloy are effective in reducing the embrittlement particularly in air and distilled water, and their magnitude of reducing the embrittlement decreased in the order, chromium, manganese and iron. However, additions of these transition elements are only slightly effective in reducing the embrittlement in H2 gas. The beneficial effect of additions of these transition elements on environmental embrittlement of the Ni3(Si,Ti) alloy is discussed, based on some possible mechanisms.
Atomic Ordering and Lattice Site Location in Cubic (L12) Al3Ti-Based Alloys
Authors: Kim S. M. , Kogachi M. , Kameyama A. , Morris D. G.
Published: April 2011

Neutron powder diffraction measurements have been carried out on cubic Al3TiX compounds (X = Cu, Cr, Mn, Fe and Ni) as a function of temperature from room temperature to 1200°C. The data were analysed by the Rietveld method in order to determine the ordering and lattice site location of the constituent atoms. All these intermetallic compounds were found to be highly ordered at room temperature, and a significant increase in disorder at higher temperatures was observed only in alloys containing Cr and Cu.
Disordering and Reordering Kinetics of a Fe–40A1 B2 Alloy
Authors: Gialanella S. , Baró M. D. , Lutterotti L. , Suriñach S.
Published: April 2011

The ordered structure of Fe–40A1 B2 powders was completely disordered by high energy ball-milling. The defect structures of the powders disordered to different extents were characterized using X-Ray diffraction. A significant lattice expansion was observed, which we tried to relate to the high concentration of point defects introduced into the material as a consequence of milling.

A complete reordering was accomplished by heating up the specimens under an inert Ar atmosphere. We followed the kinetics of the disorder to order transformation by Differential Scanning Calorimetry and Thermogravimetric Magnetic Measurements. The two techniques allowed us to identify the temperature range and the apparent activation energy of the process. As expected, a decrease in the magnetic moment of the originally disordered powders as a consequence of the reordering treatments was also observed.
Screw Dipoles Acting as Strong Locks in Ni3Al
Authors: Karnthaler H. P. , Rentenberger C. , Yu H.
Published: April 2011

Single crystalline specimens of L12 ordered binary Ni3A1 and Ni3(A1,B) with single slip [123] and multiple slip [001] orientations were deformed in compression within the anomalous temperature regime. In all cases the TEM investigations show that dipoles of locked screws are a dominant feature of the dislocation structure. This is of special interest since screw dipoles are not observed in disordered fee structures. The results indicate that screws interact and form long sessile dipoles even when their height is much larger (= factor of 10) than that given by the passing stress. The minimum height of the screw dipoles is about 16±4 nm and seems to be given when the interaction stress corresponds to the saturation stress. In the dipoles the locked screws are very difficult to unlock since the external stress is screened to a large extent. Therefore the deformation has to occur by the movement of edge segments. It is suggested that based on this exhaustion of the screws steady state conditions do not always apply on a local scale.