bluuebunny/crossref_metadata_2025 huggingface dataset:
Mechanical Reliability of Z5u Multilayer Capacitors
Authors: Mchenry Kelly D. , Koepke Barry G.
Published: March 2011

Dynamic fatigue experiments were performed on Z5U multilayer capacitors in an attempt to correlate microflaw fracture behavior due to intrinsic processing defects within the material with predictions of fracture behavior based on macrocrack fracture mechanics determinations. A direct correlation between microflaw fracture behavior and predictions based upon macrocrack fracture mechanics techniques was not observable due to the wide size range of processing defects. A systematic post-mortem examination of fracture surfaces was used to identify fracture origins and sort individual test specimens into groups with equivalent flaw sizes. The correlation between microflaw and macrocrack fracture behavior became more “sorting” the dynamic fatigue data into groups withm oereq uoibvvailoeunst aflfatwer sizes.
Adhesion Behavior of PIQ to Si/SiO2 Surfaces
Authors: de Hodgins O. C. , Uhlmann D. R. , Tesoro G. C. , Angilello J.
Published: March 2011

The present paper reports the results of an investigation of the adhesion characteristics of PIQ13, an isoindaloquin-azolinedione-modified polyimide, to silicon wafers. The wafers were used both untreated and pretreated with a layer of CVD SiO2. Also investigated was the adhesion behavior of a condensation-type polyimide, P15878. A comparison is made between the behavior of the PIQ with two different coupling agents, an aluminum chelate (Coupler 3) and γ-aminopropyltriethoxy silane (A-1100). Superior adhesion performance of the A-1100 is indicated; and with A-1100, the adhesion of the two resins is similar.
Copper Interactions in Thick Film Multilayer Ceramics: Dielectric Blushing and Performance
Authors: Button D. P. , Siuta V. P.
Published: March 2011

As the popularity of copper metallizations grows in ceramic-based electronic applications, an understanding of copper-ceramic interactions during firing assumes greater technological importance. Copper metallizations often interact with thick film microcircuit dielectrics during the firing of multilayer interconnects to yield rosy discoloration, or so-called blushing or staining of this insulating ceramic. In the conventional filled-glass dielectrics studied here, blushing is concentrated at special interfaces over Cu conductors where submicron Cu precipitates are localized. Several firing strategies which improve binder burnout can be employed using standard belt furnaces to depress, if not prevent, this precipitation. A multistage blushing mechanism is proposed that is dominated by the reduction of Cu ions in the ceramic by carbonaceous products formed when firing dielectric compositions under non-oxidizing conditions. Dielectric glass composition also plays an important role with respect to solid state Cu ion interdiffusion. Theoretical and experimental analyses show that materials interactions responsible for blushing in conventionally-processed CMS (copper multilayer system) microcircuits degrade neither dielectric performance nor reliability. Microcircuit dielectrics metallized by Cu compare favorably to noble metal systems including gold, an accepted military standard. CMS dielectrics exhibit high activation barriers for ionic conductivity, and an absence of shorting due to solid state diffusion during high temperature/ high bias testing.
Monolithic Multicomponents Ceramic (MMC) Substrate
Authors: Utsumi Kazuaki , Shimada Yuzo , Takamizawa Hideo
Published: March 2011

New monolithic multicomponents ceramic (MMC) substrates were made using a glass-ceramic material, low firing high dielectric constant ceramic material, metal oxide resistance materials, piezoelectric ceramic material and metal conductors. In the MMC substrate, many passive components, such as capacitors, resistors and wiring conductors can be included. In addition, designed-space can be formed in the substrate with new designed-space forming technology.

The new MMC substrates have the following excellent characteristics.

1)

A wide range of capacitors can be formed in the substrate.(10pF˜3μF).

2)

A wide range of resistors can be formed in the substrate.(10Ω/π∼1MΩ/π).

3)

A plurality of resistor and capacitor elements can be three-dimensionally constructed in the substrate.

4)

Designed-space can be formed in the substrate.

5)

Miniaturization and cost reduction can be accomplished in the substrate.

The MMC substrates were applied to voltage controlled crystal oscillators (VCXO), CR active filters, memory cards for personal computers, AC thin film electroluminescent (AC TFEL) devices and drop-on demand ink jet heads.

These devices using MMC substrate showed good electrical propeties and achieved miniaturization, multifunction and cost reduction. The new monolithic multicomponent ceramic substrate can be applied to many kinds of hybrid microcircuits and electronic components and devices.
Deformation Properties of a Lead-Tin (95–5) Solder
Authors: Stone D. , Wilson H. , Subrahmanyan R. , Li Che-Yu
Published: March 2011

Consecutive load relaxation tests are performed on a 95 Pb-5 Sn specimen near room temperature, then at 69 ° C and 1°C. The initial relaxation runs at room temperature show evidence of static recovery, which diminishes after a number of load relaxations have been performed. Evidence of grain boundary sliding is also found. The specimen hardens slowly at 69°C, as manifested by successive load relaxation data falling at lower strain rates. At 1°C, the material slowly softens. These temperature effects are believed to result from a dislocation-solute interaction involving tin atoms in the lead matrix.
Low Permittivity SiO2/Void Nanocomposite Films
Authors: Das Amitabh , Messier R. , Gururaja T. R. , Cross L. E.
Published: March 2011

A novel approach for preparing porous SiO2 thin films by sputter deposi-tion is being developed. The porosity is introduced to reduce the dielectric permittivity of the film to less than 3 for potential use in packaging high speed VLSIs. In the first approach, amorphous silicon is initially deposited to produce a columnar structure with a thickness of 25μm, followed by etching and thermal oxidation to result in closely spaced SiO2 pillars. Capping the structure by a thin film (0.1μm), silica gel layer provides the support for strip line traces. In the second approach, porous SiO2 films are prepared by reactive sputtering. The dielectric properties of the sputter deposited SiO2 films are presented.
Phase Equilibria in Complex Solder Systems
Authors: Notis M. R. , Tarby S. K. , Cawley T.
Published: March 2011

Ternary solder alloys have come into wide use in chip bonding, printed circuit board connection, and in ceramic package sealing applications. Little is known concerning phase equilibria in many of these systems. Methods for predicting phase equilibria in the ternary (Pb+Sn)+Ag system using CAD (computer aided design) are described, and a predicted value for the ternary eutectic temperature is compared with values obtained by differential scanning calorimetry (DSC) for this system.
Dielectric Properties of Sol - Gel Silica Glasses
Authors: Chandrashekhar G. V. , Shafer M. W.
Published: March 2011

Dielectric properties have been measured for a series of porous and fully densified silica glasses, prepared by the sol-gel technique starting from Si-methoxide or Si-fume. The results for the partially densified glasses do not show any preferred orientation for porosity. When fully densified (˜2.25 gms/cc) without any prior treatment of the gels, they have dielectric constants of ≥ 6.5 and loss factors of 0.002 at 1 MHz, compared to values of 3.8 and <0.001 for commercial fused silica. There is no corresponding anomaly in the d.c. resistivity. Elemental carbon present to the extent of 400–500 ppm is likely to be the main cause for this enhanced dielectric constant. Extensive cleaning of the gels prior to densification to remove this carbon were not completely successful pointing to the difficulty in preparing high purity, low dielectric constant glasses via the organic sol-gel route at least in the bulk form.
Synthesis, Structure and Applications of TiO2 Gels
Authors: Livage J.
Published: March 2011

TiO2 gels are usually obtained through hydrolysis of titanium alkoxides. Chemical additives can however react with the precursor at a molecular level and therefore modify the hydrolysis-condensation reactions. Several examples will be described :acetic acid, acetylacetone or Cr(acac)3. The whole sol-gel process is followed all the way from the precursors to the gel and each step is characterized by spectroscopic experiments (Infra-red, N.M.R, E.S.R.). Some electronic properties of TiO2 gels are then described. Chemical addi-tives allow an optimization of thý sol-gel process according to each speci-fic applications : electrochromic display devices, photoanodes or photoche-mical reactions.
Crystallization of Oxide Films Derived from Metallo-Organic Precursors
Authors: Chen K. C. , Janah A. , Mackenzie J. D.
Published: March 2011

Ferroelectric lead zirconate titanate and ferrimagnetic nickel ferrite films were prepared by dip-coating of metal organic solutions. In the amorphous state, both films were porous, with specific porous surface areas on the order of tens of square meters. Crystallization temperatures were in the range of 400 – 500°C. The crystallization kinetics of the porous films and powders of both compounds have been studied by using non-isothermal DSC and isothermal XRD. The kinetic parameters were empirically described by the Johnson-Mehl-Avrami transformation equation α = 1 - exp(-Ktn). The order of reaction (n) of PZT film is approximately 1 but that of the powder is 2, and their activation energies are 80 and 70 kcal/mole, respectively. It was found that the PZT film crystallizes more easily than the powder at the same temperature. The nickel ferrite film and powder, on the other hand, have similar n values ranging from 0.6 to 0.7, with activation energies of 20 and 35 kcal/mole, respectively. The possible mechanisms were also briefly discussed.
Patterned Macrovoids for Dielectric Constant Control of High Frequency Circuit Substrates
Authors: Kahn M. , Kriese B.
Published: March 2011

Fugitive ink and tape technology permit the inclusion of flat voids at predetermined locations in ceramic microcircuit substrates. Calculations show that critical stray capacitances can be reduced by as much as 65% and the propagation delay of microstrip transmission lines by 30% and more. The selectivity of the void location permits the retention of the full thermal conductance of the substrate under heat dissipating elements.
Ultra-Low Dielectric Permitfivity Ceramics and Composites for Packaging Applications
Authors: Cross L. E. , Gururaja T. R.
Published: March 2011

To accomplish the interconnect systems which will be required in the next generation of very high speed Ga:As digital ICs, it will be necessary to use strip line techniques for signal traces which must be deposited over very low permittivity dielectric substration. Materials with relative dielectric permittivities k 〈 3.0 and very low loss tangent up to microwave frequencies will be required. For ceramic systems such values are impossible to achieve in single phase monoliths, and composite approaches are required. Techniques for processing ceramic insulators which permit the introduction of controlled pore structures are discussed. The introduction of pores degrades some other desirable properties of the ceramic such as mechanical strength and thermal conductivity so that control of both scale and location of pores is desirable.

Materials investigated include sol-gel processed silica films and monoliths, reactively sputtered silica, etched glass compositions and Macro-Defect-Free (MDF) cements.
Fracture Behavior of Ceramics Used in Multilayer Capacitors
Authors: Baker Theresa L. , Freiman Stephen W.
Published: March 2011

This study involved the determination of the effects of composition and microstructure on the fracture toughness and susceptibility to environmentally enhanced crack growth of several ceramic materials used in multilayer capacitors. Indentation-fracture procedures were used to measure KIC as well as to assess the possible effects of internal stresses on the fracture behavior of these materials and to correlate dielectric aging phenomena with strength. The environmentally enhanced crack growth behavior of these materials was determined by conducting dynamic fatigue tests in water.
Residual Stresses and Damage in Multilayer Ceramic/Metal Packages
Authors: Evans A. G. , Hsueh C. H.
Published: March 2011

Multilayer ceramic/metal modules are subject to stresses that develop both upon co-sintering and upon cooling. The sources and magnitudes of these stresses are described and discussed. The co-sintering induced stresses derive from densification-rate mismatch and can be analyzed in terms of constitutive laws that describe the densification and creep of partially dense ceramic and metal bodies. Cooling induced stresses are associated with thermal contraction mismatch and are strongly influenced by the plastic flow laws for porous metals. Typical stresses produced during co-sintering and cooling are calculated and techniques for minimizing such stresses are discussed and analyzed. Mechanical damage, manifest as brittle cracks and creep cracks, are also described and analyzed. Critical values of material parameters that exclude extensive crack damage are then emphasized, based on models of crack propagation.
Studies of Critical Phenomena and Phase Transition with SANS and DKD in the Polymerblend PVME-PSD
Authors: Schwahn D. , Mortensen K. , Yee-Madeira H.
Published: March 2011

Critical behaviour of PSD-PVME polymer blends are presented. Spinodal and binodal transition temperatures have been determined by the use of a SANS-camera, and non-meanfield characteristics have been observed close to the critical point. A dynamic decomposition study has been performed by the use of a neutron double crystal diffraction.
SANS Studies of the Configurations of Single Chains in Heterogeneous Block Copolymers
Authors: Berney C. V. , Cheng P. , Kofinas P. , Cohen R. E.
Published: March 2011

Small-angle neutron scattering studies of polystyrene-polybutadiene diblock copolymers of spherical morphology are discussed, with emphasis on the effect of this morphology on the spatial organization of the polymer chains. Three particular cases are examined: (i) the distribution within the matrix of added (matrix) homopolymer, (ii) the distribution within the spherical microdomains of added (microdomain) homopolymer, and (iii) isotopic effects occurring in the B domains when a B-deuterated diblock SBd is blended with a normal sample SB. Deviations from ideal mixing are found in all three cases.
Neutron Scattering from Charged Polymer Latices
Authors: Hayter John B.
Published: March 2011

Aqueous suspensions of charged polymer latex particles exhibit several forms of ordered structure, the particular form depending on the size, number density and charge of the latex particles, and on the ionic strength of the aqueous medium. At low ionic strength, the inter-particle potential may become sufficiently long-ranged to generate crystalline order, which usually shows bcc symmetry at low density and becomes fcc above about 3% volume fraction of latex in the system. As the ionic strength increases, the crystalline structure melts, and ordered liquid structures develop. Light scattering may be used to study these structures at low density, but at higher density, where the opacity of the suspensions renders optical techniques intractable, neutron scattering must be used.

This paper will review some of the recent small-angle neutron scattering experiments on polymer latex suspensions, in the light of new theoretical methods which permit in situ analysis of the particle size and charge. The discussion will also encompass new experimental methods for studying latex structures under dynamic shear conditions.
Local Aspects of Non-Elastic Deformation in Atactic Glassy Polystyrene
Authors: Coulon G. , Lefebvre J. M. , Rawiso M.
Published: March 2011

Atactic glassy polystyrene has been deformed by shear banding. The influence of the macroscopic shear stress down to a scale smaller than the dimensions of the macromolecules has been investigated by small-angle neutron scattering. The chemical resolution has been improved by using isotopic labelling on different parts of the monomer unit. The analysis of the experimental scattering curves has been made according to the thin thread model with a superimposed thickness. On the other hand, the contrast variation method has been applied in order to determine both the structure factor of the phenyl rings and that of the backbone part of the chain. This allows us to precise the influence of non-elastic deformation on the local structure of the chain.
Coil Relaxation in Uniaxially Deformed Polymer Melt
Authors: Mortensen Kell , Kramer Ole , Batsberg Walther , Fetters L. J.
Published: March 2011

SANS studies on the relaxation of an amorphous polymer melt is reported. Just after the uniaxial elongation the chains deform affinely. Shortly thereafter the SANS results give evidence of chain contraction. Some randomization is observed long before the reptation time is reached.
Real Time Small Angle X-Ray Scattering Measurements of Hips and ABS During Tensile Impact
Authors: Bubeck Robert A. , Blazy Joseph A. , Kramer Edward J. , Buckley Donald J. , Brown Hugh R.
Published: March 2011

One of the basic problems in the field of mechanical properties of polymers is the observation of the sequence of deformation events and the changes in microstructure associated with them during deformation at relatively high rates. Typically, well characterized polymer-samples are subjected to mechanical impact, and then various microscopy techniques are used to determine the deformation events (i.e., crazing, shear banding, cavitation) post mortem. Real time small angle X-ray scattering (RTSAXS) techniques, however, make possible the direct observation of scattering from crazes and voids while the deformation is in process. In this paper we report RTSAXS measurements, performed using intense synchrotron X-ray radiation, from a high impact polystyrene (HIPS) and an acrylonitrile butadiene styrene (ABS) copolymer during tensile impact. At a deformation rate of 4.2 cm/sec, (100 in./min), the ABS was found to absorb over ten times the impact energy of a HIPS sample. RTSAXS studies indicated: (1) that the ABS has a larger average craze fibril diameter than the HIPS (12.2nm vs. 8.7nm), (2) that localized shear occurs before crazing in the ABS, and (3) that the ABS sample generated 3.8 times the craze volume compared to the HIPS. The increase in craze volume alone, however, does not account for the greater toughness of the ABS, indicating the importance of the contribution of localized shear deformation to impact behavior.
The use of Small-Angle Neutron Scattering Techniques for the Study of Polymer Miscibility and Deformation
Authors: Stein Richard S.
Published: March 2011

The scattered amplitude from a collection of objects, each small as compared with the wavelength of the radiation, is given by
Temperature Dependence of Stress Relaxation at the Copper/Polyimide Interface
Authors: Chen S. T. , Yang C. H. , Tong H. M. , Ho P. S.
Published: March 2011

A Cu/polyimide thin film couple prepared on a thin quartz reed has been used to study interfacial stress relaxation during thermal cycling between room temperature and 400 °C. The polyimide thickness varies from 0 (no polyimide at all) to 10.5μm while the Cu thickness was fixed at 0.53μm. The average copper film stress has been calculated from the curvature of the quartz reed. The information clarifies the relation between the polyimide thickness and the average Cu film stress. The Cu/polyimide interfacial morphology after thermal cycling has also been examined using the cross sectional TEM technique. The results suggest that the interfacial stress is partially released through the deformation of polyimide near the Cu/polyimide interface.
Molecular Theory of Strength
Authors: Kausch Henning H.
Published: March 2011

Polymer strength depends on the nature of the constituting elements and their mechanical, thermal, and otherwise physical, but also chemical interaction. Some of these mechanisms are discussed in this paper; special attention is given to disentanglement and chain scission.
Computer Simulation of Stress-Strain Behavior in Polymeric Materials
Authors: Cook Robert
Published: March 2011

We have developed a model of polymeric materials which includes many of the features of condensed-phase polymer chain dynamics, central among them chain relaxation by conformational motion. The model consists of a number of chains of particles which are connected by bonds with double-welled potentials to approximate the energetics of conformational motion. Interactions between particles on adjacent chains are modeled by shortrange repulsive potentials. We have examined the stress-strain behavior of the model using molecular dynamics simulations and find qualitative agreement with the observed experimental behavior of polymeric materials.
Pre-Yield Strain Hardening in Thermoplastics
Authors: Martin David C.
Published: March 2011

Successive stress relaxation testing was used to investigate the strain hardening of polypropylene and polystyrene in the stage of deformation before yielding. By combining this information with that of a stress relaxation test it was possible to measure the change in flow stress with plastic strain or “workhardening” parameter K. K has been associated with the nucleation of “defects” of some sort which slow down the kinetics of the deformation process.

Both polymers were found to strain harden in this deformation region. In polystyrene, the amount of time need to relax through a fixed stress increment reached a plateau at a point corresponding with visible crazing in the gage section of the sample. The workhardening parameter K was determined and found to decrease with stress. By plotting the rate of change of flow stress with total strain plots were obtained which avoided the use of strain, an ill-defined parameter in materials which change state during deformation. From these plots it was seen that polystyrene exhibits a well-defined linear region at small strain whereas polypropylene deviates from linearity immediately. Hardening of polystyrene was observed even in the linear response regime.
Reptation Analysis of Interdiffusing Chromophore-Labeled Polymers
Authors: Merrill W. W. , Tirrell M. , Prager S.
Published: March 2011

Understanding the dynamics of the microscopic mixing of polymer across an interface is crucial in determining the dependence of the fracture yield stress on healing time, and on the dynamics of polymer blending. Previous theoretical analyses of healing by Prager, Tirrell and Adolf [1,2,3] and Kim and Wool [4] have been helpful in interpreting the results of crack healing experiments. These models have asserted strict reptation dynamics and then postulated simple relationships between microstructure and fracture stress. The underlying microstructure can be probed directly by fluorescence measurements on interdiffusing chromophore-labeled polymers.
Small Angle Neutron Scattering Study of Micellization of a Charged Copolymer in Aqueous Solutions
Authors: Shih L. B. , Luccas M. H. , Chen S. H. , Lin T. L.
Published: March 2011

We present an asymototic analysis of small angle neutron scattering data of a comb-shaped charged copolymer, poly (1-octadecene-co-maleic anhydride), in D20. It is shown that at full ionization, the coRolymer self-asso iate to form cylindrical shape micelles with a radius 26Å and length 101 Å. The number of repeating units per micelle is calculated to be 200 and the hydration number 15 per repeating unit. The dimension of the cylinder remains approximately constant over the concentration range studied.
Application of SAS to Bulk Amorphous Polymers, Block Copolymers and Polymer Blends
Authors: Roe R. J.
Published: March 2011

This article discusses the application of small-angle neutron and X-ray scattering techniques to the study of bulk amorphous polymers, block copolymers and polymer blends. The subject matter discussed include density fluctuation in single component amorphous polymers, concentration fluctuation in compatible polymer blends and its interpretation in terms of the random phase approximation theory, analysis of the scattering from incompatible polymer blends as developed by Porod, determination of the phase boundary thickness, order-disorder transition in block copolymer, interpretation of the scattering from disordered block copolymer systems by means of the random phase approximation theory, characterization of ordered block copolymer structure, and the study of block copolymer micelles.
The Modeling of Rapidly Solidified Powders
Authors: Patterson R. J.
Published: March 2011

In the past several years, rapid solification technology has been extended from the realm of splats and foils to powders. This paper surveys several of the models that have been developed for such powders and considers their comparison with experimental results.
Nickel Base Metallic Glass Powders for Application as Plasma Sprayed Coatings
Authors: Panchanathan V. , Billerica N. , Tsai C.L. , Whang S.
Published: March 2011

New nickel rich alloys containing molybdenum and chromium prepared as metallic powders are reported. Using standard plasma spray techniques, these powders (−170 mesh) can be deposited onto metallic substrates as dense, well bonded coatings having predominantly glassy structure. Such coatings exhibit high structural strength, hardness and good corrosion resistance in various corrosive media.
Casting of Laminated Ribbon using a Modified Melt-Spinning Technique
Authors: Raman R. V. , Witt A. F.
Published: March 2011

Laminated metal-metal and metal-semiconductor ribbons have been prepared by a modified melt-spinning technique. Characterization studies have been carried out on laminated Sn-Zn, Ge-Al, InSb-CuZr and some other materials. Characteristics of these ribbons and their potential applications will be described.
Comparison of the Quench Rates Attained in Gas Atomized Powders and Melt-Spun Ribbons of Co and Ni Base Superalloys : Influence on Resulting Microstructures
Authors: Duflos F. , Stohr J.F.
Published: March 2011

The cooling rates during solidification of gas atomized Stellite 6 (S6) powders range from 103 K/s to 106 K/s for 400μm to 10 μm diameter powder particles respectively. The microstructures vary from equiaxed type in the coarser particles to fully dendritic, cellular and microcrystalline in the finer particles. In the case of melt spun ribbons, the variations in freezing rate along a cross section of the ribbon produce a change in the microstructure from microcrystalline at cooling rates greater than 107 K/s to cellular and finally dendritic at rates on the order of 106 K/s.
Cooling Rates and Fine Microstructures of Rsr and Argon Atomized Superalloy Powders
Authors: Cosandey F. , Kissinger R.D. , Tien J.K.
Published: March 2011

Superalloy powders of an IN 792 plus Hf type alloy produced from Rapid Solidification (RSR) and Argon Atomized process (AA) techniques are analyzed and compared according to particle size. Characterization of powders include surface and interior morphology, particle size and void distribution, cooling microstructures, microcrystallinity, microsegretation and especially dendrite arm spacing and cooling rates. It is found that, for the alloy studied, RSR cooling rates are a factor of only two to four greater than those for AA, regardless of particle size.
Microsegregation of an Aluminum and Magnesium Alloy at High Solidification Rates
Authors: Masur L.J. , Burke J.T. , Kattamis T.Z. , Flemings M.C.
Published: March 2011

Results are presented of an on-going study of structure and solute redistribution in ribbon cast Al-Cu and Mg-Zn alloys. Regions found in these ribbons are (1) an apparently chemically homogeneous coarse-grained zone adjacent the chill, (2) a transition cellular region, and (3) a dendritic zone, usually equiaxed. In both alloys, structure in the equiaxed region becomes coarser with increasing distance from the chill. In Mg-Zn alloys, the amount of nonequilibrium second phase increases essentially linearly with distance in the cellular and dendritic regions. Scanning transmission electron microscopy can accurately measure solute distribution across rapidly solidified cells or dendrites, but the possibility of surface compositional changes during specimen preparation must be recognized.
Microstructures of Glassy and Metastable Crystalline Phases Formed From FE-C- Ternary Alloys
Authors: Hornbogen Erhard , Schmidt Ingo
Published: March 2011

Fe-C-base alloys were rapidly cooled from the liquid and then reheated from ambient temperature. In addition to the transitional elements (V,Cr,Mo,W), B was added as third element to substitute C. A systematic approach to the understanding of phases and microstructures, which form under these conditions is the purpose of this work. This includes the considerations of forming ability and thermal stability of metallic glasses. Three aspects require attention: a) absolute stability of the glass phase, b) relative stability i.e. the difference of Free Energy between the amorphous and particular crystalline phases, c) kinetic stability based on the rate and mechanisms of crystallization reactionsincluding the rate determing diffusion process. Light and electron microscopy and electron diffraction were used for the analysis of the structure of the alloys.
The Variation of Magnetic Properties of Fe-Based Amorphous Alloys Along the Ribbon Length
Authors: Sato Takashi , Ozawa Tsutomu , Yamada Toshio , Matsumoto Ryutaro
Published: March 2011

The variation of ac magnetic properties along the length of melt-spun Fe-based amorphous ribbons was examined in relation to the variations of the roller surface temperature and the ribbon thickness. The results indicated that the lengthwise variation of magnetic properties strongly depends both on the roller surface temperature and the ribbon thickness. The critical cooling rates at which core loss begins to increase were determined from the relationship between core loss and cooling rate. For ribbons cast at lower cooling rate than critical cooling rate, the finedomain patterns were usually observed on the free surface. From the disappearance of the fine-domain pattern and the remarkable decrease of core loss by removal of the surface layers, it is ascertained that the surface layers deteriorate magnetic properties.
Thermodynamic Properties of Dilute Solutions of Hydrogen in Glassy PD.80SI.20
Authors: Finocchiaro R.S. , Tsai C.L. , Giessen B.C.
Published: March 2011

Equilibrium vapor pressures of dilute solutions of hydrogen in glassy Pd.80Si.20 have been measured from 10–90°C and at hydrogen pressures P of 1–100 torr. Under these conditions the ratio of hydrogen to alloy, x as determined by a volumetric method, reaches a maximum value of 0.0070. Over this range of x, the system exhibits a positive deviation from Sieverts' Law; isotherms were analyzed in terms of Lacher's modified statistical mechanical theory of hydrogen in palladium. The data were used to calculate relative partial molar enthalpies, excess entropies, and excess free energies for the formation of the solid solutions. The thermodynamic properties were found to vary with hydrogen content over the composition range studied.
Catalytic Hydrogenation with Amorphous and Crystalline Pd8 0Si2 0
Authors: Giessen Bill C. , Mahmoud Sabri S. , Forsyth David A. , Hediger Markus
Published: March 2011

Several metallic glasses in the form of ribbons were screened for activity as hydrogenation catalysts. Pd80Si20 and (Ni50Fe50)80B20 showed activity in reducing cyclohexene. Pd 80 Si20 was further examined for differences between the glassy and crystalline phases in the selectivity shown during hydrogenation reactions of n-hexenes, phenylethyne, α-pinene, and cyclododecene. No significant differences were found for catalytic selectivity in regard to cis-trans isomerization, double bond migration, and stereochemistry of addition under the reaction conditions used. Minor differences were observed in hydrogen-deuterium exchange.
Microstructures of Rapidly Solidified Fe-Al-Zr Alloys
Authors: Patel A. N. , Vassamillet L. F. , Clauer A. H.
Published: March 2011

Rapidly quenched short fibers of Fe–8Al and Fe– 8Al–XZr (X = 0.1, 0.2, 0.4, and 1) alloys were produced by the Pendant Drop Melt Extraction Process, (PDME) to explore the feasibility of producing intermediate temperature, oxidation resistant iron base alloys. The fibers had a diameter of 20 to 50 μm and ranged in length from 2–5 mm. The cooling rate was insufficient to retain zirconium in solution in the Zr-containing alloys, resulting in precipitates of the type Fex(Zr,Al) having differing compositions at the grain boundaries and within the matrix. No precipitates were observed in the FeAl alloys. The precipitates were uniform in distribution and size (nominally 0.1 to 0.3 μm diameter). Grain boundary precipitation and precipitate size both decreased with decreasing Zr contents.
Mechanical Properties of (Fe100−XMX)83B17 Metallic Glasses
Authors: Hunger Gerhard , Mordike Barry L.
Published: March 2011

The mechanical properties hardness, tensile strength and fracture toughness of (Fe100−x Mx )83B17 glasses were measured for different alloying con en s and heat treatments. In the as quenched state the hardness is influenced mainly by changes in the metal-metalloid bonding. The fracture toughness is dependent on the alloying elements as well as the actual state of the glass. Heat treatment of the glass thus hardly influences the hardness whereas the toughness decreases strongly and significant changes in the fracture surface occur. Calorimetric observations suggest that structural relaxation is the primary reason for this behaviour although some effect of annealing out of internal stresses must be present.
Rapid Solidification Of Steels
Authors: Cantor Brian
Published: March 2011

This paper reviews some fundamental aspects of the rapid solidification of iron-based alloys and commercial steels, concentrating on heat flow during cooling, the thermodynamics and kinetics of solidification, post-solidification solid state phase transformations, and the effect of these processes on the resulting steel microstructures.
Ostwald Ripening in Two Phase Mixtures With Application to Rapid Solidification
Authors: Voorhees P. W. , Glicksman M. E.
Published: March 2011

Rapid solidification invariably results in fine-scale microstructures with concomitant fine-scale segregation. These microstructures, which are produced relatively far from equilibrium, have large. specific surface energies and tend to coarsen rapidly. Experiments were carried out on highly supercooled bulk specimens of elemental P4 in which the average temperature of rapidly solidified 2-phase mixtures was accurately monitored over time. A continuous rise in temperature toward the bulk melting point is always measured, independent of the volume fraction of solid produced at recalescence. New theoretical work outlined here shows that this temperature rise can be associated with the Ostwald ripening of the as-solidified solid-plusliquid mixture. The new theory permits calculation of coarsening rates after recalescence and the distribution of dendritic particle sizes as a function of time. Implications for establishing limiting dendritic particle sizes are discussed.
FCC and BCC Solidification Products in a Rapidly Solidified Austenitic Steel.
Authors: Kelly Thomas F. , Vander Sande John B. , Cohen Morris
Published: March 2011

The microstructures and local composition variations in centrifugally atomized high-sulfur stainless steel powder are investigated. Both fcc and bcc are found to be primary solidification phases in the as-solidified powder of this nominally austenitic steel where the smaller powder particles (≲ 70 micron diameter) tend to be bcc.Cellular solidification structures, with sulfide precipitates (100 to 200 nm diameter in size) at the cell walls, are observed in both fcc and bcc particles. The bcc structure, however, has many small sulfide precipitates (10 to 20 nm diameter) in the cell interior with few larger sulfide precipitates at the cell walls. The small precipitates, observed only in the bcc structures, form on cooling from a supersaturated solid solution that results from reduced solute partitioning during solidification. Partitioning of chromium and nickel is minimal in these cellular structures. A non-cellular bcc structure is also observed with small sulfide precipitates throughoutthe entire structure. This non-cellular bcc structure results from smooth-front massive solidification. Analysis of the nucleation process for solidification indicates that a transition from fcc nucleation to bcc nucleation occurs with increasing wetting angle in heterogeneous nucleation. Thus bcc should nucleate in the smaller droplets of a liquid dispersion where catalytic surfaces of low potentcy (large wetting angle) tend to be the only heterogeneous nucleants available.
Superconducting Properties and Flux Pinning in Liquid Quenched Nb-Ga Alloys
Authors: Clemente Gregory B. , Habbal F. , Bevk J.
Published: March 2011

Nb75−xGa25+xtapes (1≤ x ≤ 6) were prepared by liquid quenching technique in an argon atmosphere. The transition temperature Tc, upper critical field Hc2 and critical current density Jc were measured in both as-quenched and annealed samples. The values of Tc (onset) ranged from 16.5 to 18.0K in the asquenched samples and increased upon annealing up to 20.0 K. Similar increase was also observed in the values of Hc2 (4.2 K) from ∼190 kOe to values higher than the attainable field of 220 kOe. For annealed samples near stoichiometric composition, Hc2 was estimated to be higher than 300 kOe. The critical current densities of these tapes are relatively low [Jc (4.2 K) ≤ 2 × 104A/cm2] compared to other melt-quenched A-15 compounds. Flux pinning force, FP, does not obey a single scaling law. The existence of two peaks in FP at low temperatures and of only one peak at 13.4 K for 1 ≤ x ≤ 4 is discussed in terms of the microstructural characteristics of the samples.
Structure/Property Relationships and Applications of Rapidly Solidified Aluminum Alloys
Authors: Adam C. M.
Published: March 2011

During the last five years Pratt & Whitney Aircraft has developed rapid solidification powder metallurgy and consolidation techniques to produce advanced aluminum alloys. A centrifugal rotary atomization device with forced high velocity helium convective cooling has been developed to pilot-plant stage, to produce aluminum alloys of novel compositions for advanced gas turbine engine applications. Rapidly solidified aluminum alloys solidify as spherical droplets up to 100 μm diameter with cooling rates of 105 — 106 K/sec, and demonstrate new microstructural features which have been exploited to develop elevated temperature mechanical properties. Alloys have been developed for 400 — 500°F fan and compressor applications that have traditionally used titanium alloys, and this paper reviews the microstructural evolution of rapidly solidified structures during thermomechanical processing.
Microstructure and Properties of Fine Grained Supersaturated Fe-C Alloys
Authors: Mordike B. L. , Bergmann H. W.
Published: March 2011

Rapidly quenched tapes of Fe-C-X alloys (X=Cr, Mn,Ni, Co, Al, Si) were produced by melt spinning. The hardness, ductility, grain size and micro and lattice structure were determined. The system Fe 2.1C 13 Cr was chosen for further study. The transformation (isothermal and continious) characteristics were determined for the as quenched and reaustinitized states. The results can be presented in the form of TTT diagrams and hardness measurements
Surface Alloying of Iron Alloys by Laser Beam Melting
Authors: Mordike Barry L. , Bergmann Hans W.
Published: March 2011

The surface heat treatment of iron alloys using high power lasers is reported. The essential features e.g. epitaxial growth, homogeneity etc. are discussed. The results are tabulated for the technically important alloys. The possibilities of laser hardening are demonstrated by four examples.
Production and Properties of Amorphous Layers on Metal Substrates by Laser and Electron Beam Melting
Authors: Bergmann H.W. , Mordike B.L.
Published: March 2011

Various techniques of laser glazing are presented. Rules are given for the choise of systems which are suitable for producing amorphous surface layers. Methods of demonstrating the existence of a truly amorphous layer are discussed. Two examples are given: I) electron beam glazing of Ni-Nb coated single crystals 2) laser beam glazing of Fe-B coated Fe-Cr-C cold working steel.
Laser Surface Treatment of Aerospace Steels
Authors: Christodoulou G. , Henry P. , Steen W.M. , West D.R.F.
Published: March 2011

An investigation is reported of the laser surface melting of four alloy steels with carbon contents ranging up to 1 wt%. Studies were made of the profiles, microstructures and hardnesses of zones produced using a laser power of 1.7 kW and a range of traverse speeds and beam diameters. The observed zone profiles were correlated with calculations from a three-dimensional, moving source, heat transfer model. In the high carbon steels, the shallow laser melted zones contained substantial amounts of retained austenite.
Solidification Mechanism of Highly Undercooled Metal Alloys
Authors: Shiohara Yuh , Chu Men G. , Macisaac David G. , Flemings Merton C.
Published: March 2011

This paper describes the results of experiments on metal droplet undercooling, and presents a preliminary analysis of the structures obtained. Work was conducted with Sn-25wt%Pb and Ni-34wt%Sn alloys. To achieve the required high degrees of undercooling, emulsification treatments were utilized following techniques described by Perepezko and co-workers.

Experiments show the fraction of supersaturated primary phase is found to be a function of the amount of undercooling, as is the fineness of the structures. The solidification behavior of the tin-lead droplets during recalescence was analyzed using three different hypotheses; 1) solid forming throughout recalescence is of the maximumthermodynamically stable composition, 2) partitionless solidification below the “To” temperature, and solid forming thereafter is of the maximum thermodynamically stable composition, and 3) partitionless solidification below the “To” temperature with solid forming thereafter that is of the maximum thermodynamically metastable composition that is possible.
Formation and Stability of Extended Solid Solutions Made by Rapid Quenching from the Melt
Authors: Jones Howard
Published: March 2011

Extension of solid solubility by rapid quenching from the melt (RQM) enormously increases scope for alloy development in metals such as aluminium for which solid solubility is particularly limited under equilibrium conditions. The present contribution reviews mainly recent work concerned with matching of experimental observations with predictions affecting:

(1)

conditions for solidification without change in composition

(2)

temperatures and modes of deconposition on subsequent heating

(3)

hardening effects as-quenched and on heat treatment.

The significance of such findings for bulk production and consolidation of wrought products for engineering applications is briefly discussed.
Relation Between the Chemical Short-Range Order in Liquid and Amorphous Alloys
Authors: Wagneri C.N.J. , Ruppersberg H.
Published: March 2011

Recent advances in both diffraction theory and experiment have led to the determination of the topological and chemical short-range order in liquid alloys and metallic glasses. In binary alloys, three partial interference functions (or partial structure factors) must be determined to evaluate the Warren chemical short-range order parameter α. Examples of recent attempts to determine α in binary liquid and glassy alloys are given. In most glasses, studied so far, evidence exists for the occurrence of unlike nearest neighbor ordering which must be present in the liquid state.
Origin of Defects in MOCVD Growth of GaP on Silicon
Authors: Blakeslee A.E. , Al-Jassim M.M. , Asher S.E.
Published: March 2011

We have studied the nucleation, annealing and growth of GaP on Si substrates. Our findings are very similar to those reported for GaAs/Si. That is, dislocation density after I μm of growth is usually about 108 cm−2 surface morphology is best when a multi-temperature growth process is used and is dependent on the substrate orientation; antiphase domain density is minimized by misorienting the substrates. This commonality of results leads us to conclude that the elimination of interfacial contamination is more important in achieving good epitaxial growth of III-V compounds on Si than is the overcoming of lattice mismatch. In support of this hypothesis we present SIMS data revealing up to 2% of interfacial carbon and TEM observations of an amorphous interfacial phase. The carbon comes from the organometallic source and, we believe, reacts with the Si to form amorphous SiC, which disrupts the coalescence of GaP grains and produces lattice defects.
Epitaxial Growth of GaAs on 4-Inch Diameter Silicon Substrates by OMCVD.
Authors: Salerno Jack P. , Lee J. W. , McCullough R. E. , Gale R. P.
Published: March 2011

GaAs epitaxial layers grown on Si substrates up to 4 inches in diameter by OMCVD are characterized with respect to the materials parameters important for their application for device and circuit manufacturing. The layers are characterized using commercial flatness and surface quality measurement instrumentation, x-ray diffraction, Schottky diode
characteristics, and photoluminescence. The 4-inch diameter GaAs epilayers are a singleoriented phase and are of comparable quality to GaAs epilayers grown on smaller diameter Si substrates.
Characterization of Dislocations in GaAs Grown on Si and Ge
Authors: Cho N.-H. , Mckernan S. , Carter C. B. , De Cooman B. C. , Wagner K.
Published: March 2011

Dislocations are produced at the interface between epilayers and the substrate when there is a lattice mismatch. When GaAs is grown on Ge substrates, these dislocations can propagate into the epilayers. They can then interact with one another or with antiphase boundaries which are generated when the polar-material is grown on a non-polar materials.The interactions between these defects have been investigated using the weak-beam imaging technique of transmission electron microscopy. Possible interactions between the misfit dislocations and heterojunctions were examined in a specially prepared layer structure model of GaAs-AlxGal−xAs.
MO-CVD GaAs Grown by Direct Deposition on Si
Authors: Vernon S. M. , Pearton S. J. , Gibson J. M. , Caruso R. , Abernathy C. R. , Short K. T. , Stavola Michael , Haven V. E. , Jacobson D. C.
Published: March 2011

GaAs layers were grown directly on misoriented (2° off (100)→[011]) Si substrates by Metalorganic Chemical Vapor Deposition. The threading dislocation density at the surface of 4 μm thick layers was typically 108cm−2, as determined by both preferential etching and transmission electron microscopy. Rapid thermal annealing (900°C, 10s) improved the crystalline quality of the GaAs near the heterointerface while allowing no detectable Si diffusion into this layer. Two deep electron traps were observed in the undoped GaAs, but were present at a low concentration (∼ 1013 cm−3 ). The (400) x-ray diffraction peak width from the GaAs was significantly reduced with increasing GaAs layer thickness, indicating improved material quality. This is supported by Si implant activation data, which shows higher net donor activity in thicker layers.