bluuebunny/crossref_metadata_2025 huggingface dataset:
Monophasic Pre-Mullite Gels Prepared by a Nonhydrolytic
Process
Authors: Acosta Sylvie , Corriu Robert J.P. , Leclercq Dominique , Mutin P. Hubert , Vioux Andre
Published: April 2011

A nonhydrolytic sol-gel route to aluminosilicates is proposed which avoids
the problems associated with different hydrolysis rates for the precursors.
Two pre-mullite gels (Al2O3/SiO2=3/2) were
prepared in two different ways. The conversion to mullite was studied as a
probe for chemical homogeneity. The results indicate that a monophasic
precursor (i.e. homogeneous at the atomic level) may be easily obtained by
etherolysis of a mixture of SiCl4 and AlCl3.
Sol-Gel Synthesis of Protoenstatite
Authors: Jones Steven A. , Burlitch James M.
Published: April 2011

Protoenstatite, a high-temperature polymorph of enstatite
(MgSiO3), is generally not stable at room temperature, and is
difficult to synthesize. Using a recently developed, hydrogen
peroxide-assisted, sol-gel synthesis, protoenstatite was synthesized in a
form that was stable at room temperature. Its crystallization was strongly
dependent on processing conditions, particularly on the manner in which the
xerogel was formed and fired. Xerogels prepared by evaporation, sprav-drying
and freeze-drying were compared by XRD, HTXRD, BET, TG/DTA, and
29Si NMR methods. When samples were prepared by evaporation or
spray-drying, the result was a mixture of polymorphs. Only the freeze-dried
precursor yielded protoenstatite at a lower temperature and within a shorter
time than any previously reported.
Electrochemical Synthesis and Characterization of
NaCuO2
Authors: Roberts Gerald L. , Kauzlarich Susan M.
Published: April 2011

NaCuO2 has been prepared via electrodeposition from a sodium
hydroxide/potassium hydroxide melt and characterized by single crystal and
powder X-ray diffraction, magnetic susceptibility, and resistivity. Clusters
of blue-black plate-like and needle crystals are grown at positive
potentials on a platinum anode with a platinum or a zirconium crucible
serving as the cathode and a platinum reference electrode. Details of the
electrochemical procedure are described, along with a cyclic voltammogram.
NaCuO2 exhibits temperature independent paramagnetism over the
temperature range 30 – 300 K. Its room temperature resistivity is greater
than 106 Ω-cm.
Properties and Characterization of Porous Material Prepared by
Hydrothermal Treatment of Kaolin
Authors: Malla Prakash B. , Arrington-Webb Lee Ann
Published: April 2011

A kaolin was hydrothermally treated with various amounts of NaOH and KOH at
150°C for 15 min to chemically aggregate the kaolin plates in a structured
configuration. X-ray powder diffraction analysis indicated that kaolin was
the only crystalline phase present. Chemical analyses showed that about 0.25
- 1.1 % Na2O and 1.2 - 5.0 % K2O were trapped in the
solid phase depending on the reaction conditions. Mercury porosimetry
indicated a highly porous nature with pore volumes of 0.3 - 1.4 ml/g and
median pore sizes of 0.06 - 0.3 μm. Scanning electron micrographs showed
that the aggregation was achieved by surface modification and random
association (edge to edge and face to edge, face to face) of the particles.
Measurement of light scattering coefficient of the coating showed an
increase of ∼350% in scattering compared to that of the precursor kaolin.
These materials are useful in imparting highly opacifying properties to
paper and paint. They are also potentially useful as catalysts, catalyst
supports, and in other applications which demand a high light scattering
ability and macroporous nature.
Microporous Alumino-Silicate Gels Synthesized by Sol-Gel
Method
Authors: Chu L. , Yaluris G. , Zeltner W. A. , Anderson M. A.
Published: April 2011

Microporous alumino-silicate gels were prepared by the sol-gel method. The
Al cations were incorporated into these systems by mixing an aluminum
nitrate solution into silica water based sols under controlled pH
conditions. The micro structure as well as the form of the products are
influenced by the amount of Al additives. Al cations have significant
effects on the properties of silica sols and gels. The alumino-silicate gel
has micro porosity with surface area as high as 300 m2/g even
after calcining at 900 °C for one hour. Strong negative charge is found on
these alumino-silicate surfaces in aqueous solution indicating the Al
cations have been substituted isomorphically into the Si sites in the
framework of silica.
CdSe Nanocrystals Formation in Silica Sonogels
Authors: Hummel Daniele C. , Torriani Iris L. , Ramos Aline Y. , Craievich Aldo F. , De La Rosa-Fox Nicolas , Esquivias Luis
Published: April 2011

Host-matrix gels were prepared by hydrolysis of TEOS with the addition of
cadmium nitrate, formamide as DCCA (drying control chemical additive) and
submitted to a preselected dose of high power ultrasound. The impregnation
of the dry “sonogel” with KSeCN solution under vacuum conditions promoted
the formation of the CdSe nanocrystals and enhanced the mechanical
properties of the matrix. A transparent red xerogel was obtained and
characterized by optical spectroscopy, TEM and SAXS measurements. The
results support a structural model of a porous matrix containing CdSe
nanocrystals exhibiting a bimodal size distribution that depends on the Se
content of the impregnating solutions. The blue shift of the optical
absorption bands reveal the quantum-size confinement effects of CdSe
nanocrystals.
Morphology of TiO2 Aerogels
Authors: Zhu Zhu , Tomkiewicz Micha
Published: April 2011

The morphology of titanium dioxide aerogel was studied using a variety of
complementary techniques that include: nitrogen adsorption, Small-Angle
Neutron Scattering (SANS), scanning and transmission electron microscopies
(SEM/TEM) and X-ray diffraction. Since these techniques sense different
components of the microstructure, global parametrization should coalesce the
results into a uniform framework.
Nano Sized Pd Particles In A SiO2 Matrix By Sol-Gel
Processing
Authors: Burkhart T. , Mennig M. , Schmidt H. , Licciulli A.
Published: April 2011

Pd colloid containing Ormocers (organically
modified ceramics) have
been prepared from Pd amino complexes of the type
Pd[NH2CH2CH2NH(CH2)3Si(OMe)3]2ac2
by hydrolysis and condensation (sol-gel reaction) of the silane together
with Si(OEt)4 and
Si(OEt)3(CH2)3OCH2CHCH2O.
The amino complex formation is necessary to avoid spontaneous reduction and
uncontrolled colloid formations in the liquid phase. This synthesis route
leads to Pd colloid containing powders and coatings on glass. By thermal
curing (temperatures up to 500 °C) using different atmospheric conditions
(N2, Ar, H2/N2) brown to deep black
coatings on glass with transmission values from 80 to 0 % can be obtained.
The average particle size can be controlled by varying the molar ratio of
the used Pd salt (Pd(ac)2) and the aminosilane.
Sol-Gel Processing and Structure Development of Lead Titanate
Particles
Authors: Wright John S. , Francis Lorraine Falter
Published: April 2011

Spherical particles of lead titanate, PbTiO3, (PT) were prepared
from partially hydrolyzed alkoxide solutions modified with benzoic acid.
Modified and aged alkoxide solutions were added dropwise to isopropyl
alcohol, forming particles (0.2 to 1.0 μm in diameter). FTIR spectroscopy
results demonstrate chelation of the PT alkoxide which prevented the
formation of an extended gel network. Diffuse reflectance FTIR (DRIFT)
spectra indicate the benzoate ligands are present until 450°C; TGA results
show significant weight loss at 450°C. PT particles crystallize into the
perovskite phase at =450°C, as determined by DTA and XRD. The relatively low
crystallization temperature may be due to the effect of benzoate ligands on
amorphous structure and presence of internal surfaces.
Clay-Polymer Nanocomposites: Polyether and Polyimide
Systems
Authors: Pinnavaia Thomas J. , Lan Tie , Kaviratna Padmananda D. , Wang Muh S.
Published: April 2011

A new type of clay-polyether nanocomposite has been prepared by the
self-polymerization of diglycidyl ether of bisphenol A in the galleries of
acidic alkylammonium ion exchanged forms of montmorillonite. The acid
catalyzed intragallery polymerization process leads to the spontaneous
exfoliation to the 10Å-thick clay layers. Intra- and extragallery
polymerization processes are distinguishable by DSC.

Clay-polyimide hybrid composites have also been prepared by the
intercalation of polyamic acid in montmorillonites and subsequent thermal
conversion to polyimide. In contrast to the completely exfoliated
clay-polyether system, the polyimide system contain regularly intercalated
clay aggregates in the polymer matrix. Although regular face-face clay layer
aggregation is extensive, the clay-polyimide hybrid composite films exhibit
greatly improved CO2 barrier properties.
New Routes to Silicic Acid Containing Inorganic-Organic Hybrid
Precursors and Polymers
Authors: Hoebbel D. , Endres K. , Reinert T. , Schmidt H.
Published: April 2011

In view of the outstanding role that silicic acids (sa.) play in inorganic
materials a survey will be presented regarding the possibilities of the
integration of sa. in organic matrices via chemical reactions. The objective
is to combine the advantageous properties of the silicic acid with those of
the organic compounds in order to generate novel materials. The reactions of
silicic acids with organic molecules, as studied by 29Si NMR
spectroscopy, are described using the silicic acid
H8Si8O20 with a defined double four-ring
structure as an example. By silylation of the hydrophilic
H8Si8O20 its functional organophilic
derivatives were synthesized. The s.a. derivatives with epoxy-, alkoxy-,
HSi-, ketoester or unsaturated groups are capable of condensation,
polymerization, complexation or additive reactions leading to reactive
inorganic-organic precursors or polymers with the defined silicic acid unit.
The synthesis and structure of the following s.a. containing precursors and
polymers will be reported, (a) inorganic-organic polymers with a high
content of silanol groups, (b) microporous polymers free of silanol groups
and (c) metal (Al, Zr) alkoxide complexes attached to defined silicic acid
units. The model reactions of the double four-ring silicic acid derivatives
can be transferred to technical silicic acid solutions prepared
from water glass. The presented reaction pathways are a basis
for the preparation of a great variety of new inorganic-organic compounds
with tailor-made structures and properties which can be used for highly
homogeneous and stoichiometric materials.
Synthesis and Characterization of Semiconductor Nanop
Articulates
Authors: Herron Norman , Wang Ying
Published: April 2011

Semiconductor nanoparticulates are important materials bridging the gap in
size and electronic properties between molecular species and bulk materials.
Synthetic approaches to producing controlled sized clusters of this sort
will be described, covering physical encapsulation in zeolites or porous
glass and extending to discrete syntheses using surface terminating
reagents. The optical properties of the resultant materials will be
described in detail and the structural topology of the clusters elucidated
by combined powder and single crystal diffraction. Thermal transformations
of these clusters into bulk materials will be tracked and the processing
possibilities explored for the production of polycrystalline films and
polymer/semiconductor composites. Photoconductivity in the latter composites
will be described.
Synthesis and Properties of Ytterbium Doped C60
Authors: Irons Stephen H , Klavins P. , Liu J.Z. , Lan M.D. , Shelton R.N. , Song K. , Kauzlarich S.M.
Published: April 2011

Ytterbium doped C60 (YbxC60) has been synthesized through the use of a liquid ammonia intercalation route. This allows for precise control of the stoichiometric composition. Magnetization data were taken in fields up to 1 Tesla and temperatures between 5 and 300 K on samples with 1≤X≤5. We find the ytterbium introduces significant anisotropies into the system which give rise to long time magnetic relaxation effects that persist to high temperatures. We suggest the existence of an amorphous structure to explain the results.
Vapor-Phase Grown Bundles of Carbon Nanotubes
Authors: Ge Maohui , Sattler Klaus
Published: April 2011

We have produced bundles of nanotubes by vapor-phase condensation of carbon on highly-oriented pyrolytic graphite (HOPG). The bundles are found to have widths between 15 nm and 50 nm, and up to 200 nm long. They are composed of concentric tubules with 2-4 nm in diameter. Atomic resolution STM images reveal their graphitic surface structure.
Low Temperature Diamond Growth With CF4 Addition in A Hot Filament Reactor
Authors: Corat Evaldo. J. , Trava-Airoldi V. J. , Leite Nélia F. , Peña Angel F.V. , Baranauskas Vítor
Published: April 2011

In this work we show that the addition of a small amount of CF4 to a regular CH4 -H2 gas mixture allows diamond growth at lower temperatures with reasonable growth rates. We used a hot filament assisted reactor and observed diamond growth with a substrate temperature as low as 390 ଌ. We present a comparative study for the growth dependence on substrate temperature with and without CF4 addition in the gas mixture. The growth rate is measured by post growth weighting with a micro balance. Raman spectroscopy, SEM and AFM images show the good quality of the films grown at low temperatures when CF4 is added to the feeding gas.
The Growth of Amorphous CuxTi1-x Films: Relationship Between Intrinsic Stresses and Microstructure Observed by STM
Authors: Von Hülsen U. , Geyer U. , Dina S. , von Minnigerode G.
Published: April 2011

The evolution of the surface topography of thin amorphous Cu-Ti films during the film growth is investigated by scanning tunneling microscopy. The films begin to grow with smooth surfaces until the film thickness reaches a critical value. Then, within a small thickness interval, a grainy microstructure of the film develops which looks very similar to the microstructure of polycrystalline films. Measurements of the intrinsic macroscopic stress in these films during the film growth show compressive stresses in the early growth stages. Then a change to tensile stresses accompanies the change in the surface topography within the same thickness interval. Both, the surface topography and the intrinsic stresses, are always correlated and depend on the deposition temperature and on the film composition. We discuss implications of these observations on the origin of macroscopic intrinsic tensile stresses in amorphous transition metal films.
Potential Limitations of Conventional Photomasks Due to Inherent Internal Stress - the Need for an Alternative Opaque Layer
Authors: Cairns James A. , Liu Chi-Wing , Hourd Andrew C. , Keatch Robert P. , Lawrenson Brian
Published: April 2011

Conventional photomasks consisting of chromium films on fused silica or glass substrates are widely used. However, it is becoming apparent that interfacial stress between the chromium and the transparent substrate, as well as the need for wet chemical processing for pattern production, will ultimately limit a photomask’s ability to be patterned reproducibly. An alternative approach is to chose an opaque layer which exhibits minimum interfacial stress with respect to the substrate while having the ability of being patterned by fluorocarbon gas plasma processing.

This work describes the use of silicon/germanium as an alternative opaque layer, which can be deposited uniformly by co-sputtering and patterned by fluorocarbon reactive ion etching. The suitability of the material in terms of interfacial stress is demonstrated by the use of microfabricated silicon dioxide cantilever structures. In addition, the influence of Si/Ge ratio on optical properties, the plasma processing performance, and chemical compatibility with the rest of the photomask making process is described.
Metallic thin Films on Ceramic Substrates: Stress-Enhanced Intermixing and Spinel Formation
Authors: Pirouz P. , Ikuhara Y. , Flynn C. P.
Published: April 2011

Multilayers of vanadium and MgO with different layer thicknesses were grown by molecular beam epitaxy (MBE) and the V/MgO and MgO/V interfaces were investigated by cross-sectional high resolution electron microscopy (HREM). For the smallest layer thickness of 5 nm, the vanadium and MgO films were coherent with each other and no misfit dislocations were observed. For the larger layer thicknesses of 10 nm and 50 nm, the vanadium surface exhibited undulations, and for the largest thickness, interdiffusion had occurred between the MgO film and the underlying V substrate and an interfacial spinel phase had formed. These observations are discussed in terms of the morphological instabilities of the strained vanadium film as it grows on the MgO substrate.
A Study on the Strain and Microstructure in SiGe Film Grown on Si(001) Substrate by MBE
Authors: Cho Kyoung-Ik , Nahm Sahn , Kim Sang-Gi , Lee Seung-Chang , Kim Kyung-Soo , Park Sin-Chong
Published: April 2011

Si/Si0.8Ge0.2/Si(001) structures were grown at various growth temperatures (250 ∼ 760 °C) using molecular beam epitaxy, and the variation of strain and microstructure of the film was investigated using double crystal X-ray diffractometry and transmission electron microscopy. SiGe films with good single crystallinity were obtained at the growth temperatures of 440 ∼ 600 °C. For the samples grown below 350 °C, an amorphous SiGe film was developed over the SiGe single crystalline layer with a jagged amorphous/crystalline (a/c) interface, and many defects such as stacking faults and microtwins were formed below the a/c interface. Dislocations were developed through out the films for the samples grown above 680 °C. In addition, for the samples grown below 680 °C, the amount of in-plane strain of the SiGe film was found to be about − 8×l0−3 without strain relaxation. However, the SiGe films grown at 760 °C have small in-plain strain of − 4×l0−3 and large strain relaxation of 50%.
Calculation of the (GaAs)m(AlAs)n Superlattice Piezoelectric Constants
Authors: Mirovitskii Vadim. Yu.
Published: April 2011

A new method for calculation of superlattice (SL) piezoelectric properties is proposed. It is used for derivation of the piezoelectric constants of ultrathin [001] oriented (GaAs)m(AlAs)n SL. These SL are formally considered to result from complete ordering Ga (Al) atoms over a-positions of a hypothetical initial structure of a bulk mixed crystal of (GaxAl1-x)As with x=m/(m+n). This viewpoint allows us to develop a method which is close to the Landau phenomenological theory of second- order phase transitions and which is intended for calculation of the SL crystal-lophysical constants. It is shown that a nontrivial term has much significance in changing one of the piezoelectric constants, γz,xy, when the initial structure is transformed into a SL. This term is composed of coefficients at three translational invariants (Dzyaloshinskii invariants) in the expansion of the thermodynamic potential of the “ordering” system in a power series of the order parameter components. The values of these coefficients must be obtained from microscopic calculations which take account of spatial correlations in Ga(Al) atomic distribution. Specific calculations are carried out for a SL with m+n=3.
Effect of Annealing on High Frequency Viscoelastic Waves in Spincoated Polymer thin Films
Authors: Dutcher J. R. , Wang Z. , Neal B. J. , Copeland T. , Stevens J. R.
Published: April 2011

We present a study of the effect of elevated temperatures on the high frequency viscoelastic waves guided by thin films of poly(styrene) [PS] and poly(methyl methacrylate) [PMMA]. The films, which are spincoated onto Si(OOl) wafers, have thicknesses h ˜ 1000 Å. The frequencies and linewidths of the film-guided waves were measured using Brillouin light scattering (BLS). In both PS and PMMA, we observed guided waves for temperatures above the glass transition temperature Tg of the polymers, however, the damping of the waves for temperatures above Tg was significantly higher for PS. We observed no significant (< 1 %) difference between room temperature guided-wave frequencies for films annealed at temperatures below and above Tg for PS, and a slight (4 %) increase in the wave frequency for PMMA following annealing at a temperature above Tg. The heating effects due to the focussing of the laser beam on the film surface are quite small (˜ 16°C/100 mW laser power).
Temperature Dependence of Residual Stresses and Stress Relaxation in Blanket Films of Various Thicknesses
Authors: Clarke A. P. , Langelaan G. , Saimoto S.
Published: April 2011

A rapid method to measure residual strains using x-rays during continuous temperature ramping has been developed whereby resolution of ±5xl0-5 can be attained with 2θ scans of about one minute using low index reflections. The method was used to make residual stress measurements during temperature cycling at heating rates of 2 to 15°C/min with interrupted stress relaxations at 235°C and 130°C on pure Al blanket films of 0.24μm, 0.58μm and 1.01 μm thicknesses. The results are consistent with the notion that surface sources are activated by the back stress of misfit dislocations.
Maskless Single-Sided Wet Etching Process for the Fabrication of Ultra-Low Distortion Polyimide Membranes
Authors: Schattenburg M. L. , Fuentes R. I. , Czernienko G. , Fleming R. C. , Porter J.
Published: April 2011

A process for volume production of ultra-low distortion (<200 ppm), thin polyimide membranes on silicon wafers was developed using the RotoEtch™ dynamic fluid confinement tool. A critical advantage of the process is that it exposes the sample to the etching solution over a selected area on one side only, without contacting, wetting, or otherwise contaminating the front surface. This unique feature allows the etching away of a circular portion (over 40 mm diameter) of the backside of a patterned silicon wafer to form a freestanding thin polyimide membrane (<1 μim thick). The polyimide film is patterned prior to wet etching with a sub-micron period grating (200 nm period). The resulting distortion of the grating on the freestanding membrane is less than 200 ppm over the entire membrane area. This process seems ideally suited for instances—like the one above—when immersion, contacting, or contamination of one side of the sample would be impossible or impractical. It also allows backetching finished micro-structures that would otherwise be disturbed or destroyed by immersion in the fluid. Finally, it speeds up the fabrication of freestanding films since it does not require masking or any other form of front-side protection or backside lithographic steps. In this paper we report on a silicon through-etch process based on an HF:HNO3 acid mixture which typically forms membranes in only 10–20 minutes. Since polyimide easily distorts due to excessive heat or mechanical strain, the etching process needs to be carefully controlled. This process is also ideal for forming large membranes of other HF:HNO3-inert materials such as silicon carbide or diamond.
Instability Analysis of Strained Interfaces Via a Discrete Atom Method
Authors: Lee Jong K.
Published: April 2011

The morphological instability of an epitaxially-strained, thin film is studied by means of a discrete atom method in a dislocation-free, two-dimensional crystal. The instability of the film-substrate interface is also examined in conjunction with the migration of the free surface. The results show that a mobile film-substrate interface can accelerate merger between the two surfaces, and anisotropic effects facilitate island formation. In addition, the instability of a curved interface is discussed with the results on the morphological evolution of coherent precipitates. A circular, soft precipitate in an isotropic matrix undergoes a series of shape transitions before reaching its equilibrium shape. As in the strained thin film case, transition begins with interfacial waves induced by the coherency strain. The waves then develop small lobes, which coarsen into a lower density of larger lobes. The larger lobes eventually coarsen as the equilibrium shape is approached. Anisotropic effects suppress some of the interfacial waves.
Indentation at the Nanometer Scale on Ultra Thin Films of Diamond-Like Carbon
Authors: Bec Sandrine , Tonck André , Loubet Jean-Luc
Published: April 2011

Ultra thin films (50 nm and 180 nm) of amorphous diamond-like carbon on a silicon substrate produced by laser ablation are tested by nanoindentation with a new instrument deriving from a Surface Force Apparatus. Quasi-static measurements of the load and dynamic measurements of the contact stiffness are continuously and simultaneously recorded versus the penetration depth. Scanning lines on the tested surface before and after indentation are made by means of tangential displacement of the diamond indenter on the surface.

The tests are conducted with maximum loads from 50 μN to 2500 μN, which correspond to maximum indentation depths between 7 nm and 70 nm. The indentation curves show near elastic recovery but scanning lines and/or topographic images on the surfaces show detectable plastic prints. Despite the extremely small residual indentation depths for these ultra thin films, we show how the hardness value we calculate from the indentation curves with an elastoplastic theory is in good agreement with the hardness value we calculate from the indentation print profile. The determination of the Young's modulus, even at the smallest indentation depths, must take into account the mechanical properties of the substrate. The determination of both values, hardness and elastic modulus, also requires a calibration procedure for the geometry of the tip and knowledge of the piling-up effect.

We find that the apparent hardness and the apparent Young's modulus of the tested diamondlike films are high. They are underestimated in comparison with the real values. A rough correction which overestimates the Young’s modulus gives higher values than those of natural diamond.
Indentation behavior of a Brittle Film/Brittle Substrate Composite
Authors: Czarnik C. M. , Gibala R. , Baron O. , Nastasi M. , Jervis T. R.
Published: April 2011

Surface-film induced plasticity caused by the generation of dislocations at the film-substrate interface has been demonstrated previously for bcc metals and B2 ordered alloys deformed at low homologous temperatures. More recently, we have observed similar effects at elevated temperatures for ZrO2-coated MoSi2, which also demonstrates a film-induced reduction in hardness for microhardness tests over 25°C - 1300°C. In this investigation, 120 nm - 480 nm thick ZrO2 films were deposited on (001) single crystal MoSi2 by electron beam deposition. These composites were used to characterize the film-induced softening of MoSi2 at room temperature, where both MoSi2 and ZrO2 are brittle. Indents were made through the film into the substrate at 0.5 kgf loads using Vickers and Knoop indenters. Atomic Force Microscopy was employed to measure the geometry of Knoop indents after load removal, and to compare the results to the loaded indentation shapes. Increasing film thickness reduces the length of radial cracks in the substrate and lowers the composite hardness. The film also changes the relative amounts of deformation associated with material pileup at the surface near the edges of the indent, suggesting a change in deformation mechanism from pileup around the indenter edges to deformation by dislocation motion in the bulk.
Nanoindentation and Nanoscratching of Hard Coating Materials for Magnetic Disks
Authors: Tsui T. Y. , Pharr G. M. , Oliver W. C. , Chung Y. W. , Cutiongco E. C. , Bhatia C. S. , White R. L. , Rhoades R. L. , Gorbatkin S. M.
Published: April 2011

Nanoindentation and nanoscratching experiments have been performed to assess the mechanical and tribological behavior of three thin film materials with potential application as wear resistant coatings for magnetic disk storage: (1) hydrogenated-carbon (CHx); (2) nitrogenated-carbon (CNx); and (3) boron suboxide (BOx). The hardness and elastic modulus were measured using nanoindentation. Ultra-low load nanoscratching tests were performed to assess the relative scratch resistance of the films and measure their friction coefficients. The mechanical and tribological performance of the three materials are discussed and compared.
Dislocation Emission at Surfaces
Authors: Beltz G. E. , Freund L. B.
Published: April 2011

An exact expression for the elastic energy associated with a semicircular shear dislocation loop emanating from a free surface, such as that of a stressed thin film, is derived (within continuum dislocation theory) and compared with earlier approximations. The energy required to activate a semicircular dislocation loop into its unstable “saddle-point” configuration is then re-calculated, based on the modified expression for the self-energy. It is found that the shear stress necessary to emit a loop, as a function of temperature, is almost 50% less than earlier estimates. The effects of ledges on the surface, as well as loop geometry, are discussed. The principal drawback to this type of calculation is pointed out, namely, that the critical radius of an incipient dislocation loop can be on the order of one atomic spacing, which is too small for a continuum theory to be valid.
Fabrication of Thick, Sol Gel Pzt Films: Applications to Macroscopic Piezoelectric Devices
Authors: Barrow D.A. , Petroff T.E. , Sayer M.
Published: April 2011

Lead zirconate titanate (PZT) films of up to 60 μm in thickness have been fabricated on a wide variety of substrates using a new sol gel process. The dielectric properties (∈ = 900), ferroelectric (Ec = 16 kV/cm and Pr = 35 μC/cm 2) and piezoelectric properties are comparable to bulk values. The characteristic Curie point of these films is at 420 °C. Piezoelectric actuators have been developed by depositing thick PZT films on both planar and coaxial substrates. Stainless steel cantilevers and optical fibres coated with a PZT film exhibit flexure mode resonant vibrations observable with the naked eye. A low frequency in-line fibre optic modulator has been developed using a PZT coated optical fibre. The high frequency resonance of a 60 μm film on a aluminum substrate has been observed.
Magnetomechanical Properties of Circumferentially Field-Annealed Metglas® 2605SC Cylinders
Authors: Restorff J. B. , Wun-Fogle M. , Clark A. E. , Luu Thu-Van T.
Published: April 2011

We have measured the magnetomechanical coupling coefficient of Metglas®2605SC (Fe81B13.5C2) ribbons that were annealed into 1.27 and 0.8 cm diameter cylinders. Lengths ranged from 0.6 to 5 cm. A novel furnace was constructed in which a cylindrical magnetic field was supplied by a current carrying copper rod. During the annealing, a 300 A current created a circumferential field of more than 6400 A/m. Annealing temperatures ranged from 380 to 420 ºC. Large shifts in both the optimum bias field and the coupling coefficient as a function of length and diameter were found due to demagnetizing effects. Impedance vs. frequency measurements show large numbers of modes, some of which are field dependent. Effective coupling coefficientsof the lowest order longitudinal mode were calculated from impedance measurements by using k2 = 1-f2r/f2a, where fr, and fa. are the resonant and antiresonant frequencies respectively. Coupling coefficients for 5 cm long cylinders were as high as 0.58. When the demagnetizing factor is taken into account, we find material coupling coefficients as high as 0.89.
Magnetostrictive Methods of Detecting Torque from Case-Hardened Steel Shafts
Authors: Sasada Ichiro
Published: April 2011

This paper begins with a review of the current problems associated with the application of conventional magnetic-head-type shaft torque sensors. These sensors were first proposedin 1954. Newly developed low-profile magnetic heads for torque sensors which address the problems of the older type of sensors are then presented. The torque sensor which uses the lowprofile pick-up heads is described in detail. Experimental results showing the basicperformance of the torque sensor with carburized nickel chromium molybdenum steel shafts (SNCM 420 in JIS) are then described. In this combination of the heads and the shaft, thehysteresis of the inputoutput relationship is generally small and shows that the direction of traversal around the hysteresis loop changes as the amplitude of the excitation current changes. It is shown that an optimum operating condition exists for the torque sensorin which the hysteresis achieves a minimum value yet the sensitivity remains high. In a particular combination studied in this paper, the optimum excitation current was 0.3 A at the excitation frequency 60 kHz, where the total power loss at the pick-up heads was 0.37W. Under this operating condition, the hysteresis was extremely small, and the linearity was better than 0.6%.
High Precision Actuator with Tb0.27Dy0.73Fe1.95 Single Crystal
Authors: Li Qiang , Chang Y.L. , Ouyang Shixi , Huang X.H.
Published: April 2011

It has been proved that the saturation magnetostrictive constant λs of Tb0.2 7Dy0.73Fe1.95 single crystal is greater than the polycrystal and grains oriented crystal with the terfenol compositions, especially for its large linear magnetostrictive strain. Th0.27Dy0.73Fel.95 single crystal also can produce large force and fast, precision motion at high efficiency and power levels. A proto-type micro positioning actuator with the single crystal was designed inour lab. The structure and performances are discussed in this paper.
Ultrasonic Appucations Using Magnetostrictive Smart Materials
Authors: Hansen T. Toby , Ghorayeb Solomon R.
Published: April 2011

Many of the innovations in ultrasonic technology make use of modem smart alloys and materials. As a result, the theory and application of ultrasonic energy have become extremely important in various disciplines such as ultrasonic surgery, deaning and imaging. However, despite the fact that most of these ultrasonic devices are based on widely known materials, there remains a class of materials which have not been fully explored as potential active components in ultrasonic designs. In this paper, the giant magnetostrictive smart material, ETREMA TERFENOL-D®, is discussed to illustrate its potential for such applications. Frequency analysis, reliability and advantages of ultrasonic mechanisms using ETREMA TERFENOL-D® are also shown for a general broadband ultrasonic device. Frequencies between 1 kHz and 30 kHz were obtained for these applications.
Dynamic Shear Characterization in a Magnetostrictive Rare Earth - Iron Alloy
Authors: Bouchilloux Philippe , Lhermet Nicolas , Claeyssen Frank
Published: April 2011

A previous study about the power limits of the magnetostrictive alloy called Terfenol-D, using a device biased by coils, showed the intrinsic superiority of this material compared to piezoelectric ceramics when used in high power sonar transducers. This fact was confirmed by another study where giant dynamic peak-to-peak deformations of 3500 ppm were measured with a transducer biased by permanent magnets.

Experience shows that the longitudinal functioning of magnetostrictive transducers is sometimes disrupted by interference caused by ‘flexure’ in the magnetostrictive rods. In fact, due to the shape of the rods, the flexure effects are strongly coupled to shear. Characterization of shear in Terfenol-D under conditions of magnetic bias and prestress is then necessary to control those effects. This was made possible by using a simple and original device that was designed totally with Computer Aided Design programs.
A Facility For Evaluation of Actuators Based on Giant Magnetostrictive Materials
Authors: Tiberg H. , Engdahl G.
Published: April 2011

The recent development of actuators based on giant magnetostrictive materials in for instance hydroacoustic transducers has caused an increase in output forces from the drive elements used. The high stress levels make testing of the actuators with well defined mechanical loads difficult. The need for standards and improved evaluation methods has therefore become evident.

Based on experiences from earlier test facilities a new set-up has been designed with the intention to obtain

- higher resonance frequency

- facilitated assembly of test objects

- increased operating forces

- flexible choice of mechanical loads

- computer controlled measurement procedure

- controllable environmental conditions, for instance temperature.

In order to achieve the specifications, the test rig involves hydraulics for prestressing and clamping of the test object and the mechanical load. A method of mechanically disconnecting the prestress device from the fixture gives lower mass to stiffness ratio in the fixture and therefore a better high frequency performance.

The presented test rig is considered to have the prerequisites of serving as a platform for future evaluation and standardization of actuators.
Carbon Fiber Reinforced Concrete as an Intrinsically Smart Concrete for Damage Assessment During Dynamic Loading
Authors: Chen Pu-Woei , Chung D.D.L.
Published: April 2011

Concrete containing short carbon fibers (0.2-0.5 vol.%) was found to be an intrinsically smart concrete that can sense elastic and inelastic deformation, and fracture. The signal provided is the change in electrical resistance, which is reversible for elastic deformation and irreversible for inelastic deformation and fracture. The presence of electrically conducting short fibers is necessary for the concrete to sense elastic or inelastic deformation, but the sensing of fracture does not require fibers. The fibers serve to bridge the cracks and provide a conduction path. The resistance increase is due to conducting fiber pull-out in the elastic regime, conducting fiber breakage in the inelastic regime, and crack propagation at fracture.
Magnetic and Magnetoelastic Properties of Highly Magnetostrictive Amorphous Films with TbFe-FeB-TbFe Sandwich Structure
Authors: Igari T. , Ishii S. , Inoue M. , Fujii T.
Published: April 2011

Amorphous Tb40Fe60-Fe80B20-Tb40Fe60 sandwich films were prepared by multitarget rf magnetron co-sputtering. Their magnetization and magnetostriction were studied to examine whether magnetic softening of the amorphous TbFe films could be achieved without loosing their giant magnetostriction by introducing the simple sandwich structure. The results revealed that a considerably soft in-plane magnetization (coercive force H≈ 6Oe and the squareness ratio Mr/Ms≈ 0.8) and a huge magnetostriction (λ >500ppm) could be obtained in the sandwich films at room temperature, provided that the thickness of the FeB interlayer was within the range of 10% to 40% of the total film thickness (1 μm).
Engineering Considerations in the Application of NiTiHf and NiAI as Practical High-Temperature Shape Memory Alloys
Authors: Russell Scott M. , Sczerzenie Frank
Published: April 2011

NiTiHf and NiAI have shown the potential for development as high temperature shape memory alloys with transformation temperatures of 150°C or higher. However, various engineering considerations must be addressed before these systems can be used as practical high temperature shape memory alloys. These considerations include: fabricability, phase stability, mechanical stability, and cost. NiTiHf is attractive from a cost standpoint, although its fabricability must still be demonstrated on larger heats of material. The phase stability and mechanical stability of NiTiHf are unknown. NiAl requires great improvements in both fabricability and phase stability. The mechanical stability and costs for producing NiAI shape memory alloys are still unclear.
Smart Damping Treatment for Flexible Structure
Authors: Chen Q. , Levy C.
Published: April 2011

The mathematical model of a flexible cantilever beam with a constrained viscoelastic layer and shape memory alloy layer called smart damping treatment (SDT) is presented. It is shown that a change of the elastic modulus of the shape memory alloy layer will affect the system loss factor and resonance frequency. The recovery stress of the SMA layer leads to an inhomogeneity in the governing differential equation. The recovery stress also functions as an excitation to the system. The effects of the different parameters found in the analysis are discussed in the paper.
Shape Memory Properties of an Iron Modified Nickel Aluminide Alloy
Authors: Horton J. A. , Liu C. T. , George E. P.
Published: April 2011

The ordered intermetallic NiAl with aluminum levels near 36% undergoes a B2 to martensite transformation. Shape memory alloys based on NiAl+Fe have the potential for transition temperatures of greater than 150°C. While binary alloys appear inherently brittle, alloying with iron and boron results in two phase alloys with L12and B2 phases and with about 7% room temperature tensile ductility. These alloys show a two-way shape memory effect over a range of transition temperatures with austenite peak temperature, Ap, between 100 to 200'C based on composition. Unfortunately, the B2 phase and its low temperature body centered tetragonal martensitic form are not stable and both can transform to Ni5Al3with a loss in ductility. These alloys with a constant tensile load show a two way shape recovery of up to 0.6% during temperature cycling between 100 and 200°C. A thorough survey of the shape memory properties of one such alloy with a composition of Ni-25.5 Al-16 Fe-0. 12 B (at.%) as a function of prior cold work, tensile loading and other training steps is presented. Nanoindentation was used to independently measure the mechanical properties of the two phases.
Review of Environmental Effects in Intermetallics
Authors: George E. P. , Liu C. T.
Published: April 2011

The recent progress made in our understanding of the phenomenology and mechanisms of environmental embrittlement in ordered intermetallics is reviewed by considering two model alloy systems of the L12and B2 crystal classes (Ni3Al and FeAl). The poor ductility commonly encountered when these alloys are tensile tested in ambient air is due mainly to environmental embrittlement, in the absence of which, both alloys are now known to be quite ductile. Both H2O and H2, at levels found in ordinary ambient air, are found to cause environmental embrittlement, with the former usually more deleterious. In the case of H2O, the micromechanism involves reaction with the intermetallic to form an oxide (or hydroxide) and simultaneous generation of atomic hydrogen which then enters the metal and causes embrittlement. In the case of H2, on the other hand, atomic hydrogen is generated as a result of the dissociation of physisorbed hydrogen molecules on the intermetallic surfaces. Consistent with the proposed embrittlement mechanism, ductility is found to increase with decreasing amounts of H2O (or H2) in the test environment, increasing strain rate, and decreasing (or increasing) temperature. Environmental embrittlement in Ni3Al (and other L12alloys) occurs predominantly intergranularly, whereas in FeAl (and other B2 alloys) it can also occur transgranularly—presumably because diffusion of hydrogen is fast enough through the bulk in the more open B2 structure but only so along grain boundaries in the L12structure. Microalloying with B, which segregates strongly to the grain boundaries, can overcome environmental embrittlement in L12alloys, but not in B2 alloys; in the latter, alloying additions probably have to be added at significantly higher (macroalloy) levels to affect the bulk properties. In neither alloy is environmental embrittlement the sole source of brittleness: depending on the alloy stoichiometry, and grain boundary character, a given grain boundary may be intrinsically weaker (or stronger) than the bulk, thereby influencing overall ductility.
Effect of Surface Treatment on the Formation of Oxygen Enriched Brittle Layer in A Ti3A1-Nb Alloy
Authors: Zhang B. , Wan X. , Li D. , Wang J. , Wang H. , Chen W. R.
Published: April 2011

Effect of surface treatment on the formation of oxygen enriched brittle layer in a Ti3Al-Nb alloy was investigated. The results show that a mixed Ti2N and TiN layer was formed at the surface by the titanium nitride vapor deposit treatment, and this titanium nitride layer makes it possible to suppress the formation of the oxygen enriched brittle layer during thermal exposure. An Al2O3 film was formed at the surface of the alloy, when the surface treatment was conducted under a low partial pressure oxygen atmosphere. However, such surface treatment is not able to depress the formation of the oxygen enriched brittle layer during thermal exposure, due to the higher affinity of α2 phase for oxygen as well as the higher diffusivity of titanium in Al2O3.
Microstructure of the Intermetallic Compounds Al3(Ti1-XMx)
Authors: Kita K. , Itoh G. , Kanno M.
Published: April 2011

An attempt was made to change the crystal structure of the intermetallic compound Al3Ti from DO22 to Ll2, by replacing Ti with several alloying elements. The alloying elements chosen in this study were Sc, Er and Lu with which Al forms intermetallic compounds having LI, structure. Ingots weighing about 50g of Al3(Ti1-xMx) — M represents alloying element and the x value is 0, 0.25 or 0.5 — were melted in an argon plasma arc furnace. X-ray diffraction, energy dispersive spectroscopy and scanning electron and optical microscopy were carried out to examine the microstructurc in relation to the kind and amount of alloying elements. Microstructural observation revealed the occurrence of an Ll2 phase in all M bearing alloys. Compression tests were also carried out to assess the ductility of these alloys. The results showed that the Sc alloying is effective to increase the room temperature ductility of Al3Ti.
New Gas Atomizing Technique for Nb3Al Intermetallic Alloy
Authors: Murahashi Noriaki , Kohmoto Hiroaki , Kohno Tohru
Published: April 2011

Plasma-Melt-Gas-Atomizing (PMGA) technique has been developed to produce rapidly solidified powders of intermetallic alloys for ultra-high temperature structural applications. Using this technique, rapidly solidified Nb3Al powders have been produced. These powders consist mainly of supersaturated solid solution of Al in Nb (A2), while the conventional cast structure consists of ordered A 15, and may be a good source for most powder metallurgical applications. Furthermore, a unique technique to control the powder size distribution is currently under development. In-situ measurement method of the atomized powder size distribution has been examined by using phase Doppler particle analyzer to control final powder size distribution by the feedback from the in-situ measurement data to the control system of the Plasma-Melt-Gas-Atomizer.
The Mechanics of Cross-Slip in L12Alloys
Authors: Saada Georges , Shi Xiaoli , VeyssiÈre Lem Patrick
Published: April 2011

Relationships between the microstructural organization in Ll2alloys and the flow stress anomaly are discussed. Attention is paid to the origin of friction on the cube plane, to the stability of Kear-Wilsdorf (KW) locks and to the fine structure of kinks. The difficulty of dislocation multiplication and the easiness of their annihilation are outlined. Directions for a future model of the flow stress anomaly based on a close analysis of the microstructure are given.
The Influence of Mo on the Physical and Mechanical Properties of Single Crystalline Nial
Authors: Hu J. , Levit V. , Kaufmann M. J.
Published: April 2011

The room and elevated temperature (300°C and 600°C) tensile properties of single crystalline NiAl with and without molybdenum additions have been investigated. It is shown that 0.2at% molybdenum has a considerable influence on the mechanical properties of NiAl and this influence is sensitive to heat treatment. At room temperature, the ductility of the Mo-doped alloy was higher than the binary NiAl after appropriate heat treatment. Furthermore, the elongations observed are highest at 300°C and are related to greater uniformity of deformation.