bluuebunny/crossref_metadata_2025 huggingface dataset:
In-Situ Spectroscopic Ellipsometry for the Control of Si based Thin Multi-Layers Grown by UHV-CVD
Authors: Glowacki F. , Larre A. , Ferrieu F. , Campidelli Y. , Bensahel D.
Published: April 2011

In-situ Spectroscopic Ellipsometry as a function of time is used to follow the growth of Si/SiGe Multi Quantum Well (MQW) structures. It provides both the starting surface control and the growth parameters understanding (thickness, growth rate, Ge content). Si and SiGe optical data were recorded at different temperatures on individual Si and SiGe layers. Using the measured indices and the known thicknesses of the layers, the experimental MQW data are fitted without adjustable parameters.
Luminescent Properties of Rapid Thermal Oxidized Porous Silicon
Authors: Ramm Peter , Steiner Peter , Kozlowski Frank , FrOschle Barbara , Lang Walter
Published: April 2011

We present an investigation on the photo and electroluminescence of rapidly thermally oxidized porous silicon.
Control of Long-Lived Gas Emissions From Semiconductor Processing Equipment
Authors: Mocella Michael T.
Published: April 2011

Certain perfluorocompounds (PFCs) - including CF4, C2F6, SF6, and NF3 - are widely used in gas phase thin film processing applications such as dry etching and CVD chamber cleaning. Through a combination of long atmospheric lifetimes and high infrared absorption cross sections, many PFCs have high global warming potentials (GWPs). Abatement of PFC emissions from semiconductor applications is consistent with existing and developing international, national, and industrial policies for the control of greenhouse gas emissions. For PFC applications in the semiconductor industry, there exist a number of promising options for emissions control. These options include destruction (comprising combustion, plasma, and chemical-thermal routes), recovery, and process replacement.
The Role of Microelectronic Integration In Environmental Control: A Perspective
Authors: Bhattacharyya Arup
Published: April 2011

The paper discusses the potential of silicon-based integration of disciplines of microelectronics, microoptics, and micromechanics, (MEOM), to achieve sensor-based smart subsystems for pervasive environmental applications. The author proposes a federally-focused initiative to establish an R & D institute to expedite progress and achieve global industrial leadership.
Evidence of Modifications of Micellar Interface In Sol-Gel
Glass
Authors: Catuara Christina M. , Lin Chhiu-Tsu
Published: April 2011

A new sol-gel procedure using micellar solutions has been developed to
immobilize local anesthetic drugs in optically transparent glass. Dibucaine
was selected as a direct emission probe at 77 K for determining the forms of
the anesthetic drug (free base, monoprotonated, and/or diprotonated) and its
location (hydrophobic core, interfacial layer or hydrophilic region) in
micelles. The photophysical properties of local anesthetics obtained in gels
are compared to those in solutions. During the gelation stage, the
predominant drug species was identified as free base dibucaine embedded in
the hydrophobic core of neutral as well as charged micelles. This
observation suggests that the micellar interface was modified by the large
hydrophilic gel surface during the gelation stage. The modified micellar
interface allows an increase in the partition of free base dibucaine into
the hydrophobic region. At the xerogel stage, however, the collapse of
micellar structure provides a direct interaction of dibucaine with the
acidic gel surface, leading to a formation of diprotonated dibucaine. The
results are discussed in terms of molecular basis of pharmacological
implications such as drug delivery, release, and transport under
microencapsulation conditions.
Optical Sol-Gel Materials Based on Binding and Catalysis by
Biomolecules
Authors: Zink Jeffrey I. , Dunn Bruce , Yamanaka Stacey , Lan Esther , Valentine J. S. , Chung K. E.
Published: April 2011

The proteins copper-zinc Superoxide dismutase (CuZnSOD), cytochrome c,
myoglobin, hemoglobin, and bacterio-rhodopsin are encapsulated in stable,
optically transparent, porous, silica glass matrices prepared by the sol-gel
method such that the biomolecules retain their characteristic reactivities
and spectroscopic properties. The resulting glasses allow transport of small
molecules into and out of the glasses at reasonable rates but retain the
protein molecules within their pores. The transparency of the glasses
enables the chemical reactions of the immobilized proteins to be monitored
by means of changes in their visible absorption spectra. Silica glasses
containing the immobilized proteins have similar reactivities and
spectroscopic properties to those found for the proteins in solution. The
enzymes glucose oxidase and peroxidase were also encapsulated in transparent
silica glass matrices. Upon exposure to glucose solutions, a colored glass
is formed that can be used as the active element in a solid state optically
based glucose sensor. Likewise, gels containing oxalate oxidase and
peroxidase exhibit spectroscopic changes upon exposure to aqueous solutions
containing oxalic acid.
Liquid-Mix Synthesis of Oxide Powders and Thin Films Using A
Starch-Based Polymer
Authors: Tai Lone-Wen F. , Anderson Harlan U.
Published: April 2011

A commercially available water-soluble starch derivative was used as the
sole organic precursor in the Liquid-Mix synthesis of mixed-cation oxide
powders and thin films. The acidified polymer (by nitric acid) was able to
complex metal ions through the carboxylate ligands. Loosely agglomerated
fine powders as well as dense thin films of complex oxides have been
prepared using the same type of polymer. Oxide powders of Cr-doped lanthanum
aluminate and yttrium aluminum garnet both crystallized in a single step,
without forming any intermediate or second phases, when the amorphous resin
intermediates were calcined at 650°C and 750°C for 2 hours, respectively. It
was demonstrated that nitric acid could effectively reduce the viscosity of
the polymer-nitrate solution to make it suitable for spin coating process.
Dense thin films of Y(8 mol%)-doped ZrO2 were formed on Si and
A12O3 substrates by spin coating the polymeric
solution and heating at temperatures below 1000°C.
Evidence of Hexa-Coordination CcP Immobilized in Sol-Gel Glass
Authors: Meuret Les B. , Catuara C. M. , Mahloudji A. M. , Lin C. T.
Published: April 2011

Absorption spectra of Cytochrome c Peroxidase (CcP) in phosphate buffer at pH 6.5 were recorded from 700 to 250 nm. The CcP solution was then encapsulated in sol-gel derived glass. The absorption spectra of CcP in xerogels were compared to those in buffer solutions. An increase in absorptivity at the Soret maximum, a decrease between 360 and 380 nm, and a spectral shift of the charge-transfer band from 645 to 620 nm was observed for CcP in gel matrix as compared to those in solution. Those spectral observations indicate a change in the coordination of the iron porphyrin ring in CcP from penta-coordinated in solutions to hexa-coordinated in gels. The oxidant H2O2, reductant Na2S2O4, and inhibitors NaF and KN3were allowed to diffuse through the porous glass, to react or to complex with the encapsulated CcP in sol-gel glass. The results show that H2O2and S2O42-lead to a change of oxidation state from Fe(III) to Fe(IV) and to Fe(II), respectively. Moreover, F-results in an enhancement of high-spin CcP, and N3- promotes a spin state change to a low-spin CcP. For CcP in xerogels, the chemical changes caused by inhibitors were found to be reversible when washed with deionized water. The possible applications of CcP immobilized xerogels in chemical and biochemical sensor technologies are discussed.
The Detection of Hexavalent Chromium by Organically Doped
Sol-Gels
Authors: Wong Phillip W. , Mackenzie John D.
Published: April 2011

The sol-gel process can be used to produce porous inorganic matrices that
are doped with organic molecules. These doped gels can be used as a
quantitative method for the spectrophotometric determination of trace
concentrations of metallic ions. For the detection of hexavalent chromium,
malachite green was used as the dopant. Preliminary results indicate
concentrations on the order of 5 ppb are detectable using this method.
New Routes to Nanocomposite Materials
Authors: Hunt Arlon J. , Cao Wanqing
Published: April 2011

New composite materials were prepared by using aerogel as a matrix for gas
phase decomposition. Various gases were infiltrated into the open pore
aerogel structure which were subsequently decomposed thermally by the
catalytic action of the aerogel. Composites of silica aerogel with carbon,
silicon, iron, and iron oxides were prepared. The method is applicable to a
wide range of new composite materials. Materials produced this way contain
nanometer-sized deposits that can give rise to size induced quantum
effects.
Synthesis of Wc-Co Nanocomposites Using Polymer as Carbon
Source
Authors: Manthiram A. , Zhu Y. T.
Published: April 2011

Ceramic-metal composites such as WC-Co are attractive for cutting-tool
applications as they have high hardness, chemical inertness and resistance
to heat. The properties and performance of these composites can be enhanced
by keeping the size of the components on a nanometer scale. Synthesis of
WC-Co nanocomposites generally involves gas-phase carburization. We have
developed a novel approach in which a polymer precursor such as
polyacrylonitrile serves as an in situ source for carbon.
The WC-Co nanocomposites formed are characterized by x-ray diffraction and
electron microscopy. The synthesis and processing conditions such as firing
temperature, time and atmosphere play a critical role in obtaining
phase-pure products.
Conversion of Polymers of Methyl- And Vinylsilane To Sic
Ceramics
Authors: Hurwitz Frances I. , Kacik Terrance A. , Bu Xin-Ya , Masnovi John , Heimann Paula J. , Beyene Kassahun
Published: April 2011

Poly(methylsilane) and poly(vinylsilane) were synthesized using a titanocene
catalyst, and their pyrolytic conversion to ceramics was followed using a
combination of thermal analysis and infrared spectroscopy. The two polymers
have distinctly different backbone structures, as determined by
29Si NMR; methylsilane polymerizes to a polysilane, while
vinylsilane polymers have a predominately polycarbosilane backbone, with
some polysilane structure as well. The pyrolysis path and char yield were
dependent primarily on backbone structure, with little influence of polymer
molecular weight. The majority of the weight loss on conversion occurs below
650 °C, although bond rearrangement continues to 1400 °C. Poly(vinylsilane)
produced a C-rich Si-C ceramic in which the carbon was dispersed on a
sufficiently fine level to show resistance to oxidation on heating in air to
1400 °C.
Factors Affecting Strength of Agglomerates Formed During Spray
Drying of Nanophase Powders
Authors: Maskara A. , Smith D.M.
Published: April 2011

Nanosized silica particles dispersed in various solvents were spray dried
and the change in size distribution, agglomerate strength, and strength
distribution was determined. The effect of solvent surface tension, pH, and
particle surface chemistry on strength of agglomerates formed during spray
drying was studied for particle sizes between 15 and 500 nm. Alcohol/water
mixtures having different surface tension, and water at different pH levels,
were employed to separate the effects of capillary pressure and surface
hydroxyl condensation reactions. The agglomerate strength was determined
using an ultrasonic measurement technique. The particle size was determined
using sedimentation. The strength and strength distribution of agglomerates
was found to depend on the solvent surface tension, solubility (pH), and
primary particle size.
Study of Molecular Precursors of Group iv Metal Oxides by
Tga-Ftir Coupling
Authors: Poncelet Olivier , Guilment Jean , Truchet Sylvie
Published: April 2011

Halogenoalkoxides are promising molecular precursors useable in sol-gel
technology. They exhibit a lower sensitivity towards hydrolysis than common
alkoxides and so appear to be easier to handle. Some data about the
structure of titanium chloroalkoxides, pure and with the addition of a
controlled amount of water, were obtained using FT-Raman, while the effect
of thermal treatment under nitrogen or oxygen was studied using TGA-IR
coupling. Finally the oxide products were characterized by Raman and by
ED-XRMA, proving mat chloroalkoxides could be used as molecular precursors
of oxide by sol-gel process. We showed that TGA-FTIR coupling is a powerful
tool in order to study a thermal treatment and could be used to optimize
it.
Glass-Ceramics In The Systems La-Pb-Mn-B-O And
La-Pb-Mn-Te-O
Authors: Gattef E. , Staneva A. , Dimitriev Y.
Published: April 2011

Compositions from the systems Pb-Mn-B-O and Pb-Mn-Te-0 are used to
synthesize glass-ceramics obtained by solid state reactions and from
supercooled melts. By casting on a metal plate or by quenching with the aid
of twin rollers the melts are cooling. The glass-crystalline materials are
obtained after heating glasses from the combination of
PbO-MnO-B203 and PbO-MnO-TeO2 with the
addition of La203 from 10 to 50 wt.% and the formation
of the crystalline phases is determined.
Soft Hydrothermal Synthesis of New Microporous Materials Based
on Phosphate-Like Species
Authors: Beltran D. , Marcos M. D. , Amoros P. , Roca M. , Beltran A.
Published: April 2011

Factors controlling hydrothermal synthetic procedures are not well
understood. A good knowledge of the solution chemistry of precursor species
is the best reference for the design of rational procedures. Examples of the
predictive character of simple models in order to rationalize complex
syntheses are discussed in detail.
Preparation of Centimeter-Sized Zeolite Crystals by Hydrothermal
Seeded Growth
Authors: Klemperer Walter G. , Marquart Todd A.
Published: April 2011

Centimeter-sized crystals of pyridine dodecasil 3C (all silica zeolite
ZSM-39) have been prepared using hydrothermal seeded growth techniques and
characterized by differential scanning calorimetry, nuclear magnetic
resonance, optical microscopy and powder X-ray diffraction.
Dsc Study in Situ on Copolymerization of C60with Paracyclophane
Authors: Huang Shaoming , Yu Xuhai , Yang Changzheng
Published: April 2011

Copolymerization of C60with paracyclophane at high temperature was investigated by DSC in situ. Situ DSC profiles of mixed solids with different mole ratio of C60/paracyclophane(2:1, 1:1; 1:2; 1:4; 1:10) were determined. Experimental results show that C60first dissolves in melting paracyclophane (280-330°C) then reacts with paracyclophane at 400-520°C. Copolymerization reaction is a stepwise and continued process. The reaction does not take place when the temperature is lower than 400 °C. The ratio of C60/paracyclophane affects the copolymerization process which is the reaction of C60with p-xylylenediradical and also affects the structure of the resulting product. Semi-quantitative analysis of DSC profiles indicates every C60molecule reacts with about 4-5 paracyclophane molecules to form crosslinking elastic copolymer. The structure of the copolymer may be like starburst dendrimer polymer. The copolymer was also characterized by IR, UV-VIS, and ESR.
Electronic Properties of C58Bn Fullerenes
Authors: Esfarjani Keivan , Gu Bing-Lin , Maruyama Yutaka , Ohno Kaoru , Kawazoe Yoshiyuki
Published: April 2011

Recent studies of electronic structure of solid fullerenes have revealed many interesting properties of these systems. In the present paper, the effects of substitution of carbon atoms by nitrogen and/or boron. We have modified our C60 fcc band-structure program to calculate the electronic properties of the C58BN fcc crystal, where we adopt the mixed-basis approach in which the Is, 2s, and 2p orbitals in addition to about 2000 plane waves are included. The band structure and the charge density distribution are calculated for the first time. When B and N are substituted in places of two C atoms sharing a double bond in C60, we found that there is no donor nor accepter level, and no net charge transfer between B and N. This character is considerably different from the boron-substituted fullerenes.
Growth Phenomena of Carbon Nanotubes Produced by Arc-Discharge
Authors: Zhou Dan , Seraphin Supapan , Wang Su
Published: April 2011

Based on the high resolution TEM observations, we report here on the nonconcentric growth phenomena of carbon nanotubes from the arc-discharge. We also report on a novel form of carbon nanoclusters - the strings of carbon nanobeads - produced by the catalytic arc-discharge with Ni as the catalyst, and on the bundles of single-walled carbon nanotubes, synthesized with YC2 as the catalyst, growing radially out from YC2 particles.
Photoluminescence by Hydrogenated Carbon Solids in Interstellar Space
Authors: Witt Adolf N.
Published: April 2011

We review the observational evidence for the widespread existence of hydrogenated carbon dust in astronomical environments. Photoluminescence by such materials appears strongly enhanced in regions where additional hydrogenation becomes possible, e.g. through the photodissociation of abundant molecular hydrogen. Recent laboratory experiments have demonstrated that rehydrogenation of previously annealed hydrogenated amorphous carbon (HAC) does indeed restore the photoluminescence, and furthermore, hydrogenation of pure amorphous carbon leads to characteristic HAC photoluminescence, which can be further enhanced by UV irradiation. Present evidence suggests that hydrogenated amorphous carbon may represent a significant fraction of the interstellar dust mass in the Milky Way Galaxy.
Special C44 Isomers
Authors: White C.T. , Lyons M. , Brenner D.W. , Mintmire J.W. , Robertson D.H. , Mowrey R.C. , Dunlap B.I.
Published: April 2011

O'Keefe, Ross, and Baronavski, using laser vaporization of graphite and time-of-flight mass spectrometric detection have observed enhanced abundances of C+N cluster ions not only for n=50 and 60 but also for N = 44. Stimulated by this experimental result we have carried out a search for unusually stable C44 fullerene isomers. In this search, all possible 87 fullerene isomers of C44 were first generated and then classified according to the number of bonds, p, shared by abutting pentagons. We found that for C44 the minimum value of p is 8 and that there are only two C44 fullerenes with this value of p. Self-consistent geometry optimized calculations at the AM1 level show that these two special C44 fullerene isomers—although differing from one another by only about 0.1 eV in total energy—are over 1.0 eV more stable than any of the other possible 85 fullerene isomers of C44. These self-consistent-field calculations not only single out these two C44 fullerenes for special attention, but also further confirm the instability of abutting pentagons for lower fullerenes (those fullerenes with less than 60 carbon atoms).
A Photoluminescence Detected Magnetic Resonance (PLDMR) Study of C70 Films, Glasses and Photopolymerized and Oxidized Fullerenes
Authors: Lane P. A. , Shinar J.
Published: April 2011

The X-band PLDMR of C70 films and C70 molecules isolated in a toluene/polystyrene glass matrix (C70:T/PS) is described. The PLDMR of C70:T/PS strikingly differs from that observed in C60:T/PS due to much longer triplet lifetimes. The PLDMR of C70 films indicates that the delocalized triplet is distorted by intermolecular interactions and shows a half-field resonance due to triplet-triplet fusion. In addition, a broader powder pattern and a narrow enhancing line at g=2.0029 are observed. The former is attributed to a localized triplet exciton of size similar to a 5- or 6-membered ring. The latter is believed to result from enhanced polaron recombination. The PLDMR of oxidized and photopolymerized films quenches the localized triplet and reveals the possibility of an even more delocalized exciton.
Synthesis, Characterization and Properties of Ionic Metal—Fullerene Adducts
Authors: Huang Shaoming , Yang Changzheng , Yu Xuehai
Published: April 2011

Ionic metal-fullerene adducts C60M ( M = Li+, Mg2+, Ca2+, Sr2+, Ba2+, Fe3+, Co2+, Ni2+, Cu2+, Zn2+, Cd2+, Hg2+, A13+ Ag+, Ce3+ ) are synthesized by reaction of watersoluble C60Lin with metal salt. 13C NMR of C60Li in D20 gives a sharp peak at 171.44 ppm which is much higher than the chemical shift of C60 in benzene ( 142.98 ppm ). Elemental analysis suggests the state of C60 in the adducts is C605-. ESR spectra of the adducts show a strong narrow peak at 9=2.001. UV-Vis and IR spectra of those adducts are completely different from those of C60. Magnetic measurement indicates that C60Li, C60Ce are antiferromagnetism and C60Fe adducts is ferromagnetism in the range of 150–300 K. But C60Fe adduct becomes paramagnetism when temperature is lower than 150 K. Mossbauer spectroscopy indicates Fe3+ in C60Fe adduct is Fe3+ (I.S.=0.30 mm/s, Q.S.=0.67 mm/s). The experimental results strongly suggest that C605- is a stable single free radical polyanion of fullerene which is a weak acid radical and possesses the similar properties with general inorganic anion. This is the first report on the synthesis and properties of air-stable and water-soluble polyanion of fullerene( C605-). A method for preparing metal-fullerene adducts has been developed, and many unusual properties of the adducts are found.
Nucleation Enhancement and Growth Of Diamond Films Using An Enclosed Combustion Flame
Authors: Morrison P. W. , Somashekhar A. , Glass J. T. , Prater J. T.
Published: April 2011

This research investigates the growth of diamond thin films using an enclosed oxyacetylene torch. Using statistical experimental design, we have systematically explored the parameter space to construct maps of nucleation density, film quality, and growth rate as functions of growth conditions. The deposition process is divided into nucleation enhancement and growth, and each step is optimized separately. In the study of the nucleation enhancement, we vary R = O2/C2H2, substrate-flame distance (z), and pretreatment time and determine the nucleation density and nucleation uniformity using electron microscopy. For the growth study, the variables are R, z, and substrate temperature, and we employ two different Raman scattering measurements to assess film quality. In one case, we determine a quality ratio β = diamond peak/(diamond peak + nondiamond peak); the second indicator is the luminescence determined from the baseline of the spectrum. In the growth study, the best film quality is comparable to the best films grown in an atmospheric flame in which R is cycled. We also find that the growth rate is a factor of 10 less than in the atmospheric flame.
Relationship Between Crystal Structure, Internal Stress and Properties in the Naturally Occurring Supportless Thin Films of Chrysotile Asbestos
Authors: Denes Georges , Le Van Mao R. , Vaillancourt A.
Published: April 2011

Chrysotile asbestos (empirical formula: Mg3Si2O7.2H2O, structural formula: Mg3Si2O5(OH)4) crystallizes in a sheet structure so thin that it is equivalent to a thin film that has no support. The magnesium ions are too large to fit comfortably in their octahedral sites, the size of which is determined by the network of SiO4 tetrahedra. The squeezing of the magnesium ions in sites that are too tight forces the thin layers to bend and coil around themselves. The bending of the unit-cells results in the presence of an enormous amount of highly directional stress, which has been analyzed by X-ray diffraction. The carcinogenic properties of chrysotile asbestos are a direct consequence of this stress.
Dependence of Stress on Background Pressure in Sputtered Mo/Si Multilayer Films
Authors: Windt David L. , Brown W. L. , Volkert C. A. , Waskiewicz W. K.
Published: April 2011

We have measured the stress in Mo/Si multilayer films deposited by magnetron sputtering, using the wafer-curvature technique, and find a strong dependence on background pressure. For multilayers containing 40 bilayers of ˜4.3 nm Si layers and ˜2.6 nm Mo layers, the stress increases from approximately −280 MPa (compressive) to −450 MPa as the background pressure in the deposition chamber (i.e., measured just prior to deposition) decreases from 1.0 } 10−5 to 6.0 } 10−8 torr. For multilayers of the same period but with thicker Mo layers, the dependence on background pressure is even stronger. X-ray (λ = 0.154 nm) diffraction measurements reveal a slight increase in interfacial roughness for films deposited at high background pressure. Atomic concentrations of incorporated oxygen and carbon, measured with Auger electron spectroscopy, were found to be less than ˜0.5 at.% for all samples. However, the average hydrogen concentration, as determined from forward-recoil-scattering measurements, was found to vary from ˜0.3 at.% to ˜1.6 at.%, increasing with both background pressure and Mo layer thickness. We discuss possible mechanisms for the observed dependence of film stress on background pressure, including gas incorporation and the affect of residual gas atoms on adatom mobility.
Mechanical Properties of Alumina Films Sputtered Over Steps
Authors: Ross C. A. , Barrese J. J.
Published: April 2011

The properties of sputtered films are strongly affected by the topography of the underlying substrate, due to the dependence of film growth and resputtering yield on the angle of incidence of the sputtered material and other species from the plasma. Thick r.f.-sputtered alumina films were deposited with different levels of substrate bias onto substrates into which parallel grooves had been cut. The alumina sputtered in the vicinity of the grooves forms well-defined regions with a lower incorporated argon content than the alumina sputtered onto the planar parts of the substrate. The ratio of compressive stress perpendicular to the grooves compared to the stress parallel to the grooves varies from 0.85 at zero substrate bias and 0.5 at biases of -50V and -100V. Comparing with finite element simulations, these ratios suggest that in the biased samples, the material near the steps has a lower level of compressive intrinsic stress than exists in the planar material. Nanoindentation was used to measure the modulus and hardness of the material near the steps and on the planar areas of the substrate. The alumina has an indentation modulus of 150 – 200 GPa and a hardness of 8 – 10 GPa, depending on its proximity to the grooves and on the substrate bias.
Mechanical Properties of Sputter-Deposited Nb5Si3 Film and Nb5Si3/Nb Microlaminates
Authors: Rawal S. P. , Swanson G. M. , Moshier W. C. , Misra M. S.
Published: April 2011

Monolithic Nb5Si3 films and microlaminates consisting of alternating, equally thick layers of Nb and Nb5Si3 were synthesized by magnetron sputtering. Thick monolithic Nb5Si3 films (25,000 nm) were deposited on a sapphire substrate to set process parameters and evaluate the microstructure and mechanical properties of as-deposited crystalline films. Nb5Si3/Nb micro-laminates with modulation wavelengths (i.e., bilayer thickness) of 40 and 200 nm were deposited on Nb substrates. Mechanical properties (elastic modulus, microhardness, compressive yield strength) of the films and microlaminates were studied using the nanoindentation method and Vickers microhardness. Mechanical property test results are presented.
AFM/SEM Study of Thermally Induced Hillock Coalescence
Authors: Chaiken J. , Goodisman Jerry , Villarica R. M. , Beasock J. V. , Walsh L. H.
Published: April 2011

The growth of hillocks and voids in metal films was studied. The applicability of a model involving fractals and kinetic equations was examined on the basis of whether there is independent justification for using scaling arguments in the model and whether there is reason to connect the evolution of hillocks with that of voids. Hillocks and voids were found to be self-similar across about three orders of magnitude of variation in spatial scale with the same fractal dimension. Voids and hillocks were found to have the same fractal dimension whether studied using atomic force microscopy (AFM) or scanning electron microscopy (SEM). The parameters obtained from these fractal analyses demonstrate quantitative internal consistency with an earlier time dependent study of thermal annealing effects on hillock distributions. Remarkably, area-perimeter data obtained from either a long-time study of a single void or a spatial average of a large number of different voids both yield quantitatively identical results.
Stress Evolution Kinetics in Ultra Thin Sputtered Au Films
Authors: Su Quanmin , Bailly Cecile , Wuttig Manfred , Corcoran Sean , Sieradzki Karl
Published: April 2011

The stress and microstructure of a thin film evolve in time if the deposition is interrupted or terminated. To establish the parameters which control the kinetics of both processes, ultra thin Au layers were sputter deposited on Si membranes and the stress evolution was monitored by a vibrating membrane technique. The evolution of the surface morphology was studied by scanning tunnelling microscopy. Aging after the termination of each deposition causes stress evolution towards higher tension which, around ambient temperature, follows an exponential law with a characteristic relaxation time of the order of tenths of seconds. This time was found to depend strongly on the accumulated film thickness as well as the surface morphology. The intrinsic stress of the depositing layer increases with the coverage of the film on the substrate. Scanning Tunnelling Microscopy shows that the film grows in a Volmer-Weber mode and that the average stress reaches a sharp maximum as the film become continuous.
Elastic Modulus and Hardness as Derived from Nanoindentation of Ni And Mo Films Prepared by Ion Beam Assisted Deposition
Authors: Wroblewski A. , Chechenin N. , BØttiger J. , Chevallier J. , Karpe N. , Krog J. P.
Published: April 2011

Using ion beam assisted deposition, 1.5–2.2 μm thick molybdenum and nickel films were prepared on silicon substrates. Some films were found to be strongly textured. By changing the rate of Ar+ bombardment during the deposition, the resulting in-plane film stresses could be changed from being strongly tensile to strongly compressive. Using nanoindentation, the hardness and elastic modulus were measured for all films, but no major influence of the film stress or different textures could be found. The elastic modulus of the Ni films was found to be close to its polycrystalline bulk value, and that of Mo was found to be about 70% of its polycrystalline bulk value.
Dielectric Fracture Leading to Metallic Connections by Laser Heating
Authors: Bernstein J. B.
Published: April 2011

Laser programmed connections between adjacent lines on the same level of metallization have been developed as a means to achieve high density linking for customization in programmable gate arrays and for additive redundancy in restructurable integrated circuits. The resistances of the connections were approximately 1Ω and the overlaying passivation remained in tact. Links were formed by focusing a pulsed laser between two adjacent lines of metal, one of which was connected to a lower level of metal through a contact via. The mechanism of link formation appears to be a fissure contained within planarized passivation due to the stress of thermal expansion of the metallization with molten aluminum filling the crack.
Practical and Fundamental Studies of Nanocrystalline Composite Thin Films
Authors: Cheng Yang-Tse , Qiu Boqin , Tung Simon , Blanchard J. P. , Drew G.
Published: April 2011

Nanocrytslline composite films of Ag-Mo and Ag-Ni have been made by a co-deposition technique in UHV. The structure and composition have been studied by x-ray diffraction (XRD), transmission electron microscopy (TEM), and electron probe microanalysis (EPMA). For practical applications, the friction coefficient and wear rate were measured using a pin-on-plate machine for Ag-Mo composites deposited on steel. For fundamental studies, the hardness of the Ag-Ni composites deposited on oxidized Si wafers was measured using a nanoindenter. Experiments show that (1) reduction of friction and wear rate can be achieved using these nanocomposite coatings and (2) the hardness of the nanocomposites depends on the grain size. As the grain size of the Ag decreases from 100 to 10 nm, the hardness increases about 4 times.
Magnetostrictive Motor Development
Authors: Teter Joseph P. , Miesner John E.
Published: April 2011

This paper reviews the history and present state of magnetostrictive devices capable of controlled motion over large linear distances. Magnetostriction imparts the most force perunit weight of any technology however, the successful development of practical devices requires a multi-disciplinary effort involving materials science, magnetics, innovative mechanical design, electrical power engineering, and system control engineering. Advances todate have included demonstrations linear motors capable of 115 Newtons of force at 2.54 centimeters/second.
Low Temperature Magnetic Behavior of Ni-Fe-Al-B Shape Memory Alloys: Magnetic Susceptibility and Mössbauer Spectra.
Authors: Marquina V. , JimÉnez M. , Marquina M.L. , Ridaura R. , Aburto S. , GÓmez R. , Escudero R. , Morales F. , RÍos-Jara D.
Published: April 2011

Magnetic susceptibility measurements and Mössbauer spectra (MS) were performed on a series of NixFeyAlzB shape memory ribbons obtained by a melt spinning technique. The MS at room temperature show quadrupole splittings of two iron sites. At low temperatures (T<120 K) relaxed magnetic spectra begin to develop and, in one of the samples, a complete resolved magnetic spectrum at 13 K was observed. The overall magnetic susceptibility curves show non Curie-Weiss type behavior with peaks at around 60 K and 35 K. These curves also show magnetic hysteresis in the up-down temperature cycle used during the measurements. We relate our observations with a structural change occurring at temperatures between room temperature and 260 K, a second one around 200 K, and with the developing of spin-glass behavior at low temperatures, when the magnetic influences of Fe and Ni atoms almost compensate each other.
Deformation of Adaptive Heterophase Crystal
Authors: Roytburd Alexander L. , Slutsker Julia
Published: April 2011

A crystal which can be in two possible phase states is considered. During tensile extension the crystal is deformed elastically. After a certain amount of elastic strain a phase transformation begins. For each fixed level of strain an equilibrium mesostructure is established, which corresponds to a minimum in the free energy of the crystal. The equilibrium mesostructure consists of plane, parallel layers of a product phase separated by layers of an initial phase. The product phase itself consists of two or more different domains (twins) forming plane, parallel alternations. The volume fractions of the phases and of different twin components in the product phase are functions of strain and temperature. Above a critical temperature the product phase is a single domain (untwinned). The stress-strain curve which reflects the evolution of the equilibrium mesostructure is calculated. For deformation under a strain control the calculated equilibrium stress-strain curve has a section with negative slope that corresponds to a negative Young's modulus. If deformation proceeds under stress control, hysteretic stress-strain curves on loading and unloading will result from a section with negative slope.
A Modified Transmission Line Approach to The Analysis of Superconducting Microwave Resonators
Authors: Goff Edward D. , Weber Robert J.
Published: April 2011

A technique for modeling a superconductor contacted piezoelectric microwave resonator is presented. A transmission line method of modeling the superconductor as a two fluid model is shown to agree with the London penetration depth, and is modeled to take into account the superconductor to normal transition. By including both the normal conductor effects along with the superconductor effects, crystal quality can be factored into this model using an analytical approximation. A two dimensional model for the superconductor, applying experimental results from Y1Ba2Cu3O7−x for circuit elements, is analyzed. The superconducting layer is modeled as an electrical circuit in combination with an acoustical circuit to model its effect on a piezoelectric resonator. The acoustical equivalent of the superconductor including mass loading effects and terminations are taken into account in the Mason model acoustical equivalent circuit.
Pressure-Sensitive Microvalves Made from Polymer Brushes
Authors: Sevick E.M. , Williams D.R.M.
Published: April 2011

We describe a novel microvalve, constructed from polymer chains end-grafted onto opposing surfaces of a narrow slit. The assembly of polymer chains acts as both sensor and valve for microflow control and bypasses the need to construct an external feedback mechanism. This microflow control results from densely grafted chains which repel one another and stretch away from the surface, forming a brush which acts as an elastic and impenetrable layer. The height of a sheared brush increases or decreases depending upon solvent quality, i.e the layer can show a negative Poission's ratio. The discharge through the brushlined conduit is a non-linear function of pressure enabling different modes of valve operation. For brushes which extend moderately into the inter-slit region the valve assembly maintains constant discharge over a wide range of pressure. For brushes which extend far into the inter-slit region the valve assembly cuts off flow above a critical pressure, limiting the maximum discharge.
High Temperature X-Ray Diffraction Study of the Effect of Nb and Si on Oxidation behavior of Ti3Al Alloy
Authors: Qiu Guohua , Wu Jiansheng , Zhang Lanting , Lin Dongliang
Published: April 2011

A disadvantage to the application of Ti3Al is its poor high temperature oxidation resistance. It is found that the element Nb or(and) Si can greatly reduce the oxidation rate of Ti3A1. A hot stage in situ X-ray diffractometer was used to determine the formation sequence of the oxide layers. At 800°C, TiO2 as well as Al2O3 was detected on the surface of binary Ti3Al at the beginning of the oxidation process. The addition of 5 at % Si to Ti3Al alloy did not favor the formation of an A12O3 layer. On the contrary, it inhibited the onset of Al2O3 to nearly 20 hours from the start of the oxidation process at the temperature of 800°C. The Nb addition also did not promote the formation of Al2O3. TiO2 formed first on the surface of Ti3Al-11 at % Nb alloy while TiN and TiAl formed consequently. Al2O3 was further delayed to 20 hours from the beginning of the oxidation process. When the Nb addition increased to 15 at %, however, TiN and TiAl were not found. It is suggested that the favorable effect of Nb and Si to the oxidation resistance of Ti3Al alloy is not due to their promotion of A12O3 layer, but probably due to some other mechanisms, such as the formation of TiN which serves as a diffusion barrier and decreases porosity in the TiO2 layer.
Alloying of Cubic Alloys Based on Al3Ti: Phase Instabilities and the Control of Fault Energies
Authors: Morris David G. , Lerf Reto , Leboeuf Mireille
Published: April 2011

Alloys based on Al3Ti with the ordered L12 structure show slight ductility when the Ti content is near 25% and about 8% of Mn or Cr is present as ternary addition. Such materials are relatively soft due to the easy movement of APB-dissociated superdislocations but remain almost completely brittle. While the precise reasons for such brittleness are not clear, it seems reasonable to consider that alloying to lower fault energies may soften the material and enhance ductility. In the present study, new alloys are selected on the basis of electronic structure calculations using the discrete variational cluster method, and the ordered state, mechanical behaviour, and dislocation and fault characteristics examined.

The alloys examined were based on the Al-26%Ti-8%Mn composition, with lower Ti and Mn contents, in an attempt to maintain a single-phase matrix and weaker, less-directional bonding and lower fault energies. In addition, for some alloys, Al was partially substituted by Mg.

The single-phase region of the L12 Al-Ti-Mn phase is very small and second phases such as DO22 and complex AlxMn can appear which lead to hardening and strain ageing, much as Al2Ti does in more Ti-rich alloys. Mg substitution is limited to a few percent before a Mg-rich phase appears and the alloys examined are complex mixtures of this, the L12 phase, and γTiAl. The dislocation structures observed after deformation are examined to determine fault energies, and it is shown that these values can be rationalised in terms of the structural instabilities of the matrix phases and the secondary phases produced.
Effects of Processing on the Mechanical Properties and Oxidation behavior of Al2Ti
Authors: Ma John C. , Benci John E. , Feist Thomas P.
Published: April 2011

Al2Ti is a promising material for use in elevated temperature structural applications. It has a lower density than Ti3Al and TiAl. We have previously shown that the compressive yield strength of Al2Ti is higher than that of similarly processed TiAl and Al3Ti between room temperature and 900°C. In this study, two additional processing methods were utilized to produce the material: uniaxial hot pressing of rapidly solidified powder and hot forging of cast ingots. Effects of hot forging or annealing of as-cast Al2Ti on the microhardness and load for crack initiation were studied. The microhardness and crack initiation load were also used to compare powder processed material consolidated either by hot pressing or hot isostatic pressing. The oxidation behavior of as-cast, cast & hot isostatically pressed (cast & hip’ed), and powder processed & hip’ed (PP) Al2Ti was also investigated. The oxidation tests were performed in air at 815°C and 982°C for 100 hr. PP Al2Ti exhibited the lowest weight gain and as-cast exhibited the highest. Al2Ti shows superior oxidation resistance compared to Ti3Al- and TiAl- based alloys tested under similar conditions and shows comparable oxidation resistance to Al3Ti at 800°C. SEM/EDS was used to study the morphological development of the oxide scale and to identify the chemical constituents present in the various layers of the scale.
Study of The Microstructure and Oxidation of NbSi2 Base Alloys
Authors: Pitman S.H. , Tsakiropoulos P.
Published: April 2011

The microstructures of arc melted ingots and melt spun ribbons of NbSi2 and NbSi2-(8,20 at%)Cr alloys are discussed. Rapid quenching from the melt refined the grain size of the alloys by two orders of magnitude and suppressed the formation of Nb5Si3 in Zone A of the binary alloy ribbons. In the ternary alloy ingots and ribbons formation of the Nb5Si3 was suppressed, and the C40 NbSi2 and CrSi2 and orthorhombic Nb2Si6Cr3 phases were formed. Zone A was not formed in the ribbons of the ternary alloys. The microhardness of these phases and the oxidation behaviour of the alloys up to 1350°C in air and an Ar atmosphere are discussed. NbSi2 did not form a protective silica layer on oxidation. Instead a mixed oxide scale of silica and α-Nb2O5 formed which cracked during growth of the oxide and hindered protection of the alloy. It is shown that the addition of Cr modifies the oxide to a duplex oxide of SiO2 and Cr2O3 and that the underlying matrix becomes depleted in Cr. Pest oxidation at 750°C was suppressed in Nb-60Si-20Cr.
Experimental And Theoretical Studies On The C15 Intermetallic Compounds MV2 (M=Zr, Hf AND Ta): Elasticity And Phase Stability
Authors: Chu F. , Mitchell T. E. , Chen S. P. , Šob M. , Siegl R. , Pope D. P.
Published: April 2011

The phase stability of C15 HfV2 was studied by specific heat measurements. The elastic constants of C15 HfV2 were measured by the resonant ultrasound spectroscopy. Total energy and electronic structure of CI5 intermetallic compounds MV2 (M=Zr, Hf and Ta) were calculated using the linear muffin tin orbital (LMTO) method. The band structures at the X-point near the Fermi level were used to understand the anomalous shear moduli of HfV2 and ZrV2. It was found that the double degeneracy with a linear dispersion relation of electronic levels at the X-point near the Fermi surface is mainly responsible for the C15 anomalous elasticity at high temperatures. The density of states at the Fermi level and the geometry of the Fermi surface were used to explain the low temperature phase instability of C15 HfV2 and ZrV2 and the stability of C15 TaV2. The relationship between the anomalous elasticity and structural instability of C15 HfV2 and ZrV2 were also studied.
Effect of Heat Treatment at 1150°C on Creep-Rupture Properties of a Fe3Al-Based Alloy
Authors: McKamey C. G. , Marrero-Santos Y. , Maziasz P. J.
Published: April 2011

The effects of heat treatment at 1150°C on the creep-rupture properties of a Fe3Al-based alloy were studied. Tests were conducted in air using various test temperatures and stresses. By plotting the data to a power-law equation, the activation energy for creep was determined to be approximately 150 kcal/mole and the creep exponent to be about 8. Optical metallography and scanning electron microscopy of ruptured specimens indicated that failure occurred in a ductile manner by microvoid coalescence at grain boundaries and triple points. Analytical electron microscopy was used to study characteristics of the microstructure and to identify Zr-rich precipitates that formed during heat treatment or creep testing. These precipitates were found to provide strengthening by pinning dislocations and grain boundaries.
The Influence of Iron on the Physical and Mechanical Properties of β-Nial
Authors: Lim Y. J. , Hong K. T. , Levit V. , Kaufmann M. J.
Published: April 2011

The influence of iron on the the microstructure and properties of B2 NiAl has been investigated using electrical resistivity, magnetic susceptibility, microhardness and transmission electron microscopy. The resistivity data suggest that quenched-in vacancies (1) enhance iron rearrangement at low temperatures (600–800 K) and (2) annihilate above 800 K. These effects depend strongly on Ni/Al ratio and are greatest for Ni/Al=1. It is also shown that these data correlate directly with the results obtained using the other experimental techniques.
Assessment of Microalloying Effects on the High Temperature Fatigue Behavior of NiAl
Authors: Noebe R. D. , Lerch B. A. , Bhanu K. , Rao Sankara
Published: April 2011

Binary NiAl suffers from a lack of strength and poor creep properties at and above 1000 K. Poor creep resistance in turn affects low cycle fatigue (LCF) lives at low strain ranges due to the additional interactions of creep damage. One approach for improving these properties involves microalloying with either Zr or N. As an integral part of a much larger alloying program the low cycle fatigue behavior of Zr and N doped nickel aluminides produced by extrusion of prealloyed powders has been investigated. Strain controlled LCF tests were performed in air at 1000 K. The influence of these microalloying additions on the fatigue life and cyclic stress response of polycrystalline NiAl are discussed.
Microstructure and Mechanical Properties of Ni3Al-Based Alloy/Tic Composites
Authors: Yin W. M. , Guo J. T. , Wang S. H. , Li H. , Tan M. H. , Lai W. H.
Published: April 2011

The microstructure and mechanical properties of Ni3Al-based composites reinforced with TiC particles have been investigated. The composites, which contained 2, 6, 10 vol.%TiC particulate reinforcement, were fabricated by solidification processing method. The matrix alloy selected for this study was the advanced nickel-aluminide (Ni-16Al-8Cr-1Zr-0.8Mo-0.04B at.%).The optical micrographs revealed that the carbides in the composites distributed uniformly in the martix and appeared as fairly equiaxed particles. SEM observation showed that the interface between TiC and matrix is quite smooth, sharp and free of any phase. The test results indicated that the hardness was increased with increasing volume fraction of TiC particles at ambient temperature, and the composites exhibited higher hardness after 1100°C × 8h heat treatment. The yield strength has been improved due to reinforcement by the TiC particles at ambient and elevated temperature, but their ductility was reduced obviously. From SEM fractography, it could be seen that tensile failure occurred at the matrix / particulate interface.