bluuebunny/crossref_metadata_2025 huggingface dataset:
Optical Interconnects for High Performance Data Processing Systems
Authors: Crow John D.
Published: March 2011

The interconnection of many processors in order to increase the computing power of the ensemble is a growing theme in the data processing industry [1]. These processors may be within modules on a common board, on seperate boards within a common frame, or in seperate frames distributed in a room or building. A key element of this “computer complex” is the network which allows efficient data transfers. These data processing networks are differentiated from data communications networks by a demand for fast data transfer, so that the processors and memory at the nodes can interact in times measured in about 1–1000 machine cycles. Machine cycle times might be from tens to hundreds of nanoseconds, and the amount of data transferred might be measured in Kilobytes [2]. This implies both a fast and a high bandwidth technology for implementing these interconnections, as well as a limited link distance. The VLSI IC technology and associated dense electrical chip packaging which has made such powerful computing nodes possible, also implies a requirement for dense packaging of the optical link adapter, for compatability [3]. The multiprocessor complex has very high requirements on reliability, leading to low tolerance for component failure or erroneous data transmission. Eight year life, with failure rates less than 0.01%/Khr, and link bit error rates less than 1 in 1015 are not uncommon requirements [4]. The performance and cost of these networks are often determined by the wiring technology chosen, specifically the electronics and opto-electronics of the interfaces at the network's nodes. Optical interconnections are potentially attractive for this application, but the requirements on optical, electrical and associated packaging technologies are significantly different than the technology which has been developed for the data communications applications. [4, 5].
Optical Waveguides in the Computer Environment a Packaging Perspective
Authors: Oprysko Modest M.
Published: March 2011

Fiber optics has had a major impact on the technology of the telecommunications industry but has made little impact on the computer industry. One reason for this is the incompatability of present day optoelectronic component packaging technology with the needs of the computer industry. This problem is most evident in high-performance computer packaging.
Organic Die Coat Materials for Plastic Packages
Authors: Padmanabhan R.
Published: March 2011

The role of organic materials in electronic packages is constantly being expanded. A fairly recent application is the use of these materials for encapsulating high lead count IC dice, like TAB chips that are bonded directly to the board or housed in plastic packages. Since these packages are non-hermetic, some special constraints are placed in the selection of these die coat materials. Reliability issues that have to be addressed include compatibility with the underlying dielectric medium, chemical resistance, low moisture absorption, corrosion protection and resistance to thermal stresses. This paper discusses some of these concerns and reviews the suitability of different categories of die coat materials for this application.
Leaching Characteristics of Fly Ash after Four Years of Natural Weathering
Authors: Andrade A. , Coenegracht Y. M. A , Hollman G. G. , Janssen-Jurkovicova M. , Pietersen H. S. , Vriend S. P. , Schuiling R. D.
Published: March 2011

The natural weathering process of fly ashes was studied in artificial fly ash beds. The ashes were previously classified according to their total alkali content into acid, neutral and alkaline. After 4 years the effects of weathering are minor. The formation of concretions due to local cementation by calcite is observed in alkaline fly ash. Small brown pellets, highly enriched in some heavy metals, are present in the acid fly ash beds. Under natural conditions leaching is mainly confined to the alkaline fly ash. Elements which are leached most are sulphur and some alkalis as well as minor amounts of some trace elements.

Shake- and column experiments of the weathered fly ashes with acids of pH 1 and 4, the latter also in combination with complexing agents, were carried out in order to check if the natural leaching process may be accelerated artificially. Strong acids (pH= 1) were most effective, but relatively large quantities of major elements were also leached. Experiments with the weak acids, combined with complexing agents, resulted in leaching percentages which did not significantly differ from experiments without these agents. This indicates that a major part of the elements are present in an immobile form; because of the use of sulphuric acid, it is likely that they are in some cases precipitated as sulphates (e.g. barium, calcium).
The Practitioners View of Fly Ash Utilisation
Authors: Mills Ronald H.
Published: March 2011

Partial substitution of Portland cement (PC) with fly ash (FA) offers the practitioner expanded scope for optimal utilisation of materials. This method requires careful evaluation of the resulting blended cement beyond the basic age-strength relationship. For the construction practitioner, workability, rate of strength gain, and inherent variability are major factors in meeting strength requirements and determining costs. A blend may be characterised by a mass efficiency factor which is the mass ratio of PC to FAwhich will yield the same target strength at fixed maturity and workability. Alternatively, the maturity efficiency factor may be determined as the ratio of log maturity values for the cements to reach a given target strength. Both efficiency factors incorporate important economic parameters of interest to the practitioner.

Because of its glassy character, FA attracts calcium hydroxide as well as sodium and potassium ions released into solution by the PC component. The risk of alkali-aggregate reaction may therefore be reduced. This characteristic may prove to be of such over-riding importance that a new approach to mix design may become necessary. The essence of such an approach would be the provision of sufficient FA to absorb reactive species released by the PC. This might involve increased PC+FA and water, with concomitant reduction in aggregate and in fineness modulus.

Dimensional changes such as shrinkage and creep affect the distribution of load between steel and concrete in columns, the deflection of beams and slabs, and cracking where displacements are restrained. In the case of PC concrete, both creep and shrinkage depend on the volume ratio of hydration products and the movement of pore water caused by drying and by mechanical load. In general the magnitude of creep and shrinkage varies with Vp, the volume proportion of cement paste, and reduces with wo*. Part substitution of PC with FA generally results in increase of Vp, but this is compensated by decrease in wo*. The nature of the hydration products varies with PCiFA ratio, and thus quantities such as the internal surface area, the hydraulic mean radius of pores and the effective modulus—the ratio of stress to total strain—must be evaluated.

In general the data required by the practitioner is not available in the literature and he must have recourse to ad hoc tests in order to establish basic workability-time-temperature-strength data. This is, potentially, a fruitful area of research.
Performance of a Fly Ash Stabilized Pavement
Authors: Laguros Joakim G. , Hayes Curt
Published: March 2011

An expansive shale roadbase, stabilized with a Class C (high-calcium) fly ash received an 11–inch full–depth asphaltic concrete surface layer and the highway was opened to traffic six years ago. Periodic sampling and visual observations indicate that the performance of the pavement test sections are above average.

Analyses of field samples showed that fly ash was effective in ameliorating the texture and plasticity of the shale and imparting strength to it on a long term basis. Pavement deflections and the extent of cracking have not increased beyond acceptable levels during the six year period.

X-ray diffraction studies show a reduction of the areas under the peaks and the SEM observations reveal a dense degree of packing and reduction of the void areas. These modifications occur during the first two years of service and any changes beyond that period appear to be minor.
Evaluating the Use of Ponded Fly Ash in a Roadway Base Course
Authors: Hunsucker David Q. , Graves R. Clark
Published: March 2011

This paper summarizes findings of laboratory and field trial evaluations of ponded fly ash used as a component in a stabilized aggregate base course. Ponded fly ash is the fine portion of pond ash which is a by-product of a coal burning process and is disposed by sluicing to a disposal pond.

Three stabilized aggregate base mixtures containing various proportions of dense graded aggregate, ponded fly ash, and hydrated lime were evaluated in the laboratory relative to maximum dry density, optimum moisture content, unconfined compressive strength, and static chord modulus of elasticity. The mixture that was selected for field trial evaluation had the highest unconfined compressive strength and consisted of 84% dense graded aggregate, 11% ponded fly ash, and 5% hydrated lime.

A 750 foot section of a 22 foot wide roadway was constructed in May 1988. Approximately 88 tons of ponded fly ash were utilized in constructing the experimental base. Prior to construction, in-place California Bearing Ratio tests, moisture content determinations and Road Rater deflection tests were performed on the prepared subgrade. The stabilized aggregate base was placed in one 8 inch lift. During construction, relative compaction and moisture content of the base material were monitored by means of nuclear devices. Post construction evaluations included Road Rater deflection tests and coring to obtain samples for laboratory evaluation.

To date, the section containing the stabilized aggregate base is performing very well in comparison to the conventionally paved section.
Environmental Assessment of Botitom Ash and Fly Ash Used in Road Stabilization
Authors: Atalay Asmare , Laguros Joakim G.
Published: March 2011

Fly ash and bottom ash are being used extensively for stabilization of roads. Unpaved county roads in rural areas are often being resurfaced with bottom ash to improve their stability. A preliminary, uncontrolled examination was conducted to assess the environmental problems that may result from the use of fly ash and bottom ash on highways. To do this, soil, plant and run–off water samples were collected from county roads and highways in Oklahoma that were constructed using either of the two ash forms. These samples were analyzed for fourteen elements of which eight are under the USEPA regulation list of priority pollutants for solid waste and drinking water. The results indicated that the allowable limits for six out of the eight elements were exceeded in the run-off water samples. Compared with the control, fly ash, bottom ash, coal and soil-core samples all contained significantly higher levels of all elements; however, except for barium all were below the regulatory levels. The concentrations of As, Sb, Pb, Ni, Se, and TI in the run-off water samples are high enough to be of concern, although they are below the allowable limits for drinking water. These six elements are found at much higher levels in the fly ash and bottom ash than in the input coal. More Ba is released into the run–off water when the roads were under heavy traffic. Although there was no visual damage observed on the collected plant samples, much higher than normal levels of most metals, were obtained in the tissues.
Analysis of Coal Fly Ash by Bulk and Surface Characterization Techniques
Authors: Bellotto M. , Boni C. , Caridi A. , Cereda E. , Chemelli C. , Marcazzan G. M. Braga , Parmigiani F. , Scagliotiti M. , Bellagamba B.
Published: March 2011

The application of different characterization techniques to the study of coal fly ash formation and of its behaviour in particulate control devices is discussed. Particle Induced X-ray Emission (PIXE) and Proton Induced Gamma-ray Emission (PIGE) are used for bulk elemental analyses, while X-Ray Photoelectron and Auger Spectroscopies are used for surface elemental analyses. Structural characterization is carried out by powder X-Ray Diffraction and Raman Microfocus Spectroscopy. The effect of different collection efficiencies of electrostatic precipitators on emitted fly ash characteristics is addressed. Furthermore size fractionated fly ash is analyzed to investigate the mechanisms of particle growth.
Microstructure, Mass Transport and Densification of Slag Cement Pastes
Authors: Feng Q. L. , Glasser F. P.
Published: March 2011

The kinetics and mechanism of the hydration reactions in slag cements were explored in blends containing either 40 or 50 wt% ground granulated blast furnace slag, made to a water:solid ratio of either 0.50 or 0.60 and aged 7d to 885d at 20°C. The microstructure of the slag rapidly differentiates into zonal structures. Analytical electron microscopy has been used to analyze the composition and indirectly determine the mineralogy of the zones. It is shown that considerable chemical matter is transported out of the slag grains, resulting in porosification of the former slag grains and densification of the cement hydrate matrix. This is supported by mass balance calculations. The driving force for these migrations is accounted for by the existence of a chemical potential gradient of water; hydrophyllic species such as Ca, Si, etc. migrate into regions of high chemical potential for water. The densification of the phase matrix is probably responsible for the low permeabilities of matured slag-cement blends.
A Statistical Investigation on Particle to Particle Variation of Fly Ash Using SEM-AIA-EDAX Technique.
Authors: Barta L. E. , VÁmos G. , Toqan M. A. , Teare J. D. , BeÉr J. M. , Sarofim A. F.
Published: March 2011

Due to the particle to particle variation of coal mineral properties and random coalescence of mineral particles during coal burnout, fly ash particle properties change from particle to particle. The variations of particle properties (e.g. SiO2 content, viscosity) can be mathematically described by random variables. Since bulk analysis of fly ash gives only the mean values of chosen random variables, it is considered insufficient to describe the fly ash behavior either in boiler slagging/fouling or in different concrete structures. SEM-AIA-EDAX technique was used to supply raw data for estimating the distribution functions of particle size and chemical compounds in Texas lignite minerals and fly ash and Eagle Butte fly ash. To determine the volume based size distributions of these samples from their area-based size distributions, Abelian transformation was used. To estimate the distribution functions of CaO and SiO2 contents of the samples, particle area fractions were used. The confidence limits were also calculated for the estimated parameters. By determining the distribution functions of particle viscosity and chemical composition, it was shown that in the case of Texas lignite the coal burnout does not cause significant changes in the mineral matter properties. It was observed that the properties of fly ash depended solely on the mineral matter properties. However, in the Eagle Butte case the coal burnout has a major effect on the fly ash size distribution and its chemical composition.
Macro-Defect-Free Cement: A Review
Authors: Young J. Francis
Published: March 2011

Cement-based materials have been traditionally formed by casting. The amount of water used in the casting process determines the porosity of the hardened material. The water requirements, and the tendency for cement grains to agglomerate, result in hardened cement paste having high porosity and a wide range of pore sizes. Consequently, such materials are not very strong and contain critical flaws whose dimensions are of the order of 0.1 mm. Although improvements in particle packing and particle dispersion to reduce porosity have resulted in significant increases in strength, such materials are still very brittle and have relatively low tensile and flexural strengths.
The Chemistry Of MDF Cements Produced From Polyacrylamide-Cement-Water Pastes
Authors: Silsbee M. R. , Roy D. M. , Adair J. H.
Published: March 2011

It is becoming more generally accepted that the role of the polymers in these MDF (macro-defect-free) cement systems is more complex than simply acting as a processing aid or a filler. The polymer interacts in some way with the cations released from the cement to form a metal cross-linked polymer gel. Studies on complex formation in polymer gels have shown that there is often an unusual specificity in the ions, resulting in the highest degree of complexation. In addition, gel formation often occurs only within a narrow pH regime. Hence, the results shown here will attempt to examine the effects of altering the cement chemistry on strength development in calcium silicate-based systems.
Alkali Activated Slag And Portland/Slag Ultrafine Cement
Authors: Clarke William J. , Helal Maan
Published: March 2011

Ultrafine Alkali Activated Slag (AAS) and Portland/Slag (P/S) cements have been commercially available in the United States for 2 and 5 years, respectively. Ultrafine cements have been the subject of research at Northwestern University for 6 years.

Particle size of the ultrafine slag cement is characterized by 98% passing at 7 microns and a D50 at 3 microns in contrast to the ultrafine portland/slag cement which has 98% passing at 10 microns and a D50 at 4 microns.

The chemical composition of the slag used in these cements is 35% SiO2, 16% Al2O3, and 43% CaO. The composition of the portland/slag cement, which is a 25/75 blend, is therefore between the bulk composition of portland cement and the slag.

Both of the ultrafine cements permeate fine sands when formulated at high
water-to-cement ratios. Viscosity plays an important part in the permeation mechanism, and both cements exhibit viscosities below 10 cps at water-to-cement ratios of 2. This low viscosity is obtained through the use of superplasticizing with naphthalene sulfonate and acrylic acid polymers.

Applications of the ultrafine cements include dam grout curtain rehabilitation, consolidation grouting, and nuclear and hazardous waste containment. One hundred and twenty metric tonnes of the portland/slag cement have been used for hazardous waste containment at Niagara Falls, New York.
Low-Temperature (<300°C) Phosphate Ceramics from Reactive Aluminas
Authors: Silsbee M. R. , Steinke R. A. , Roy D. M. , Agrawal D. K. , Roy R.
Published: March 2011

Reactive aluminas, including rapidly calcined gibbsites, offer exciting potential for forming ceramic materials at low temperatures. New x-ray amorphous aluminas will react with water at room temperatures to form compacts with 10–50 MPa tensile strengths, via viscous slurries. The cementious behavior of these materials has been examined. The results of TGA, x-ray diffraction, SEM, mechanical properties, and other characterization techniques, as applied to these systems, will be discussed.
High-Temperature Processing and Applications of Silica-Modified Portland Cement CBC Composites
Authors: Wise Sean , Kevan R.
Published: March 2011

Silica-modified portland cement-based Chemically Bonded Composites (CBCs) have been prepared and cured to elevated temperatures. It has been found that when cementitious composites with calcium-to-silica (C/S) ratios of 0.83 are thoroughly hydrated through hydrothermal curing, followed by careful dehydration, mortars of exceptional strength are produced. The bulk of this strength is maintained to over 600°C. X-ray diffraction studies of binder samples dried at 200°C and 500°C show only slight differences in mineral product contents. Above 600°C, a drop in strength is noted, and a substantial portion of the binder converts to wollastonite. Even so, these CBC composites retain as much as 40% of their peak compressive strength to temperatures up to 800°C. Applications of these materials in high-temperature industrial processes are presented.
Temperature Dependence of Stress for Copper, Copper-Silver and Copper-Tin Films
Authors: Haynes Richard
Published: March 2011

1. Introduction

In VLSI processing and other applications such as printed circuit boards thin films of copper, usually used as conductors, undergo thermal cycling. This thermal cycling can cause loss of adhesion and mechanical failures thus decreasing reliability of the devices[l–7]. Understanding thermally induced stress due to mismatch of thermal expansion may assist in generating designs, processes and material replacement for increased reliability. This paper reports studies of the temperature dependence of stresses for plated and sputtered copper and plated copper-silver and copper-tin alloys. Studies of thermally annealed plated copper and copper-tin alloys are also reported.
Mechanical Properties of Carbon-Implanted Niobium
Authors: Zinkle S. J. , Huang J. S.
Published: March 2011

Polycrystalline niobium specimens were implanted with either 200 keV carbon ions or a combination of 50, 100, and 200 keV carbon ions to peak concentrations of 0.6 to 50 at. %. Microindentation techniques were used to measure the hardness and elastic modulus of the implanted layer. Both the hardness (H) and modulus (E) showed dramatic increases due to the carbon implantation. The measured peak hardness and modulus following uniform implantation with 16 at. % C were 15× and 3× that of niobium, respectively, which is comparable to the literature values for NbC. The peak hardness and modulus for the implanted specimens were observed at an indent depth of ˜40 nm, which is about one-eighth of the depth of the implanted carbon layer. The decrease in the indentation mechanical properties at deeper indent depths is due to the interaction of long-ranging strain fields underneath the indenter with the niobium substrate.
The Hardness and Elastic Modulus of TiN Films as Determined by Ultra-Low Load Indentation
Authors: O'Hern M. E. , Oliver W. C. , McHargue C. J. , Rickerby D. S. , Bull S. J.
Published: March 2011

The mechanical properties of a series of titanium nitride films on stainless steel substrates have been evaluated using an indentation technique with a mechanical properties microprobe (MPM). The MPM makes possible measurement of film properties without contribution by the substrate material. The titanium nitride films were deposited with a PVD technique known as sputter ion plating (SIP). Deposition substrate bias was varied from 0 to −120 V, while keeping other deposition parameters constant. With increasing negative substrate bias, dramatic increases in hardness and elastic modulus have been observed.
Measurement of Stress Relaxation in Thin Aluminum Metallizations by Continuous Indentation and X-Ray Techniques
Authors: Korhonen M. A. , LaFontaine W. R. , Paszkiet C. A. , Black R. D. , Li Che-Yu
Published: March 2011

Thin aluminum films deposited on silicon substrates are representative of materials systems used in integrated circuit technology. Large stresses in such systems usually arise from thermal expansion mismatch between the thin film and the substrate, and constitute an important reliability concern.

X-ray and continuous indentation testing were used to measure post-heat treatment stresses in a 0.3 μm thick aluminum film on a silicon substrate. The sample was heat treated at 450°C for one hour in an inert atmosphere, after which the stress relaxation was followed as a function of time. The stress data gathered by the two techniques agree very closely during a time span of about 100 hours.
Deflection Shapes Due to Intrinsic Stress in Thin Films
Authors: Masters Christine B. , Salamon N. J. , Fahnline D. E.
Published: March 2011

The curvatures of thin film/substrate systems are obtained for a nonlinear plate deflection model using a Galerkin minimization procedure proposed by Hyer. A fifth order polynomial involving the curvatures is given. The results show that the linear models of Stoney and Brenner and Senderoff apply only at low stress states and that stable and unstable configurations develop at higher stresses even for isotropic systems.
Mechanical Properties of Carbon Films for Thin Film Disks
Authors: White Richard L. , Doerner Mary F. , Walker George W.
Published: March 2011

Carbon overcoat films are used extensively in thin film disk applications to provide wear resistance. A nano-indentation technique and wafer curvature measurements have been used to study the mechanical properties of carbon films sputtered under various processing conditions. Specifically, the effects of substrate/target spacing, power, pressure, and substrate bias have been studied for films sputtered in an argon plasma. The relationship of these properties to contact start-stop performance of hydrocarbon lubricated disks is further described. The frictional performance during the test can be related to film hardness, while the durability can be affected by the residual film stress.
Experiments on, and a Two-Component Model for, the Behavior of Water Nano-Films on Metals
Authors: Gao Chao , Kuhlmann-Wilsdorf D.
Published: March 2011

By means of the hoop apparatus, contact resistance and coefficient of friction of fiber bundles on a solid substrate have been determined in air at different humidities. The results can be explained by a two-component model, comprising (i) a double molecular layer of adsorbed water at contact spots and (ii) a zone about each contact spot within which excess adsorbed moisture which has been squeezed out from the load-bearing area bypasses the spot.
Hard Coatings
Authors: Bull S. J. , Rickerby D. S.
Published: March 2011

Thin ceramic coatings have been used in tribological applications for some time because their high defect densities and small grain size leads to a very hard, wear-resistant surface. However it is not sufficient to look at properties such as hardness in isolation when considering the selection of a coating for a given engineering application as other properties such as residual stress or adhesion may be equally important. In fact it is central to the continued development of advanced coating technologies to understand the inter-relationship between the important properties of the coating/substrate system (residual stress, hardness, adhesion etc.) and coating microstructure particularly as this can be controlled to a certain extent by the choice of deposition technology and processing parameters. By using PVD titanium nitride as an example, this paper reviews the potential for microstructural control using current physical vapour deposition (PVD) processes and shows how the microstructure of the coating is important in dictating its mechanical properties. These properties and others which still need to be measured are discussed and the potential for designing with coatings assessed in the light of current understanding.
Photoreflectance Characterization of Silicon Films on Insulator
Authors: Giordana Adriana , Glosser R. , Pellegrino Joseph G. , Qadri S. , Twigg M. E. , Richmond E. D. , Joyner Keith , Pollack Gordon
Published: March 2011

Photoreflectance (PR) was used to study crystalline quality and stress in silicon films on insulator. The position and amplitude of the 3.4 eV PR silicon structure was monitored for both MBE silicon on sapphire (SOS) and SIMOX structures. The SOS film thicknesses ranged from 6 to 4000 nm. The shift in energy of the 3.4 eV structure from its bulk position is dependent on the sample thickness and on the strain in the films. In the SIMOX case, the amplitude of the 3.4 eV PR signal provided information about the crystalline quality of the top silicon layer for a set of six samples, each one removed at a different step of a process involving three implantation-anneal cycles. In this case the PR signal appeared to deteriorate with the each cycle undergone by the samples. Further investigations are needed to resolve the discrepancy bet ween these SOS results and the ones obtained in an earlier set of measurements.
A Vibrational Technique for Stress Measurement in Films
Authors: Jagota A. , Mazur S. , Farrisf R. J.
Published: March 2011

This paper presents a new technique for the measument of stress in films based on the classical theory of membrane vibrations. The specimens for vibrational analysis are prepared by removing a circular or square piece of the substrate far from any edge of the film (this operation preserves the state of stress in the film). The specimen is mechanically excited by random noise and its natural frequencies are peaks in the measured response of the membrane. The natural frequencies increase as the square root of stress in the film. The only material parameter needed to determine stress from the natural frequency is the density of the film. The technique has been used to measure stress in two different systems: urethane cured epoxies and silver films under different environmental conditions (temperature and humidity).
The In-Situ Measurement of Biaxial Modulus and Residual Stress of Multi-Layer Polymeric Thin Films
Authors: Lin Pinyen , Senturia Stephen D.
Published: March 2011

Polymeric coatings have been used in many ways from automobile paints to package coatings for integrated circuits. It is important to understand the mechanical properties of coatings in order to ensure fulfilling their designed functions. To measure these properties, in situ measurement techniques are desirable since these techniques measure the mechanical properties of coatings in the presence of the correct residual stress. In addition, the coatings most commonly used are multi-layer structures, a fact which increases the difficulty of the mechanical analysis. At present, the in situ mechanical behavior of multi-layer coatings has not been well characterized, and very few researchers have reported a satisfactory way to analyze multi-layer problems.
Analysis of Stress Variations in Epitaxial Films Using Cathodoluminescence Microscopy and Spectroscopy
Authors: Yacobi B. G. , Sheldon P.
Published: March 2011

This paper presents experimental results of a new application of cathodoluminescence microscopy in the analysis of stress variations in epitaxial layers. Cathodoluminescence microscopy and spectroscopy techniques, in conjunction with the known behavior of the optical transitions in the presence of stress, can be effectively used for both the qualitative and quantitative analyses of spatial variations of stress in epitaxial films.
Non-Destructive Assessment of Thin Film Stresses and Crystal Qualify of Silicon on Insulator Materials with Raman Spectroscopy
Authors: Wolf Ingrid De , Vanhellemont Jan , Maes Herman E.
Published: March 2011

Micro Raman spectroscopy (RS) is used to study the crystalline quality and the stresses in the thin superficial silicon layer of Silicon-On-Insulator (SO) materials. Results are presented for SIMOX (Separation by IMplanted OXygen) and ZMR (Zone Melt Recrystallized) substrates. Both as implanted and annealed SIMOX structures are investigated. The results from the as implanted structures are correlated with spectroscopic ellipsometry (SE) and cross-section transmission electron microscopy (TEM) analyses on the same material. Residual stress in ZMR substrates is studied in low- and high temperature gradient regions.
Stresses in Amorphous Gd-Fe Alloy Thin Films Deposited by Magnetron Sputtering
Authors: Zhou Zhi-Feng , Zhou Qi-Gang , Fan Yu-Dian
Published: March 2011

Amorphous Gd-Fe alloy thin films were made by D.C. planar magnetron sputtering under various deposition conditions (e.g., film thickness, composition, working pressure of Ar, negative bias voltage and deposition rate). The stress, the film composition and the content of entrapped Ar in the films were measured respectively. The experimental results showed that in this case the working pressure of Ar and the negative bias voltage did not change the composition of the films, and the stresses were all compressive except for the films deposited in a very high working pressure of Ar. The origin of the compressive stress can be attributed to the atomic peening effect produced by fast neutral working gas atoms rebounded from the sputtering target. The magnitude of the compressive stress depends not only on the amount of Ar atoms incorporated in the films but also on the film microstructure such as the packing density.
The Representation of Thermodynamic Properties in Multicomponent Alloys
Authors: Ansara I.
Published: March 2011

In addition to theoretical models which have been developped to interpret the interactions in metallic systems, polynomials of different types have been used to represent the thermodynamic properties of solution phases. Ternary and higher order systems have been described by adding the properties of the limiting binary systems, using various summation methods ; interaction parameters specific to the multicomponent systems can be derived from sufficiently precise experimental measurements.
Mathematical Representation of Size and Electronic Factors
Authors: Brewer Leo
Published: March 2011

The relative sizes of the atoms and their electronic configurations are important factors in determining the thermodynamic properties of metallic phases. The regular solution model provides for an asymmetric excess Gibbs energy when there is a size difference, but the actual degree of asymmetry does not correspond to crystallographic sizes. This is due in part to the effect of electronic configurations upon the asymmetry of the Gibbs energy. The Hume–Rothery Rules indicate that the bcc, hcp, and ccp structures are associated with characteristic outer–shell electron per atom concentrations. The electronic factors require modification of the usual definition of internal pressure as used in the regular solution theory. Rather than using the energy of vaporization to the ground atomic state, the energy of vaporization to the valence state atom, which has the same electronic configuration as in the condensed state, is a more appropriate measure of the degree of cohesion and the internal pressure. The problems of providing mathematical expressions that accomodate the contributions of internal pressure, electronic factors, and size factors are discussed.
Coherent Phase Diagrams in the Cluster Variation Approximation
Authors: De Fontaine Didier
Published: March 2011

Coherent phase diagrams are defined as pertaining to equilibria between phases which differ from one another merely by the distribution of different types of atoms on fixed crystallographic sites. Resulting ordered structures must then all be superstructures of one parent lattice, and corresponding phase diagrams are isomorphous to those of the Ising model with non–vanishing magnetic field. Rather complex phase diagrams can then be obtained from a single free energy functional by means of the cluster variation method. Calculated phase diagrams will be shown for the case of the fcc parent lattice with various positive and negative ratios of the values of second-to-first-neighbor pair interactions, this ratio being the only parameter which enters the calculation. Results will be compared to those of Monte Carlo calculations. The possibility of performing these first-principle calculations of coherent phase diagrams will be briefly touched upon.
Phase Stability in Rapidly Solidified Iron and Nickelrease Alloys
Authors: Wood John
Published: March 2011

The structure of a large ranqe of model steels and high speed steels after rapid solidification are described in terms of the effect of processing conditions and alloy content. General lessons are deduced for these structures regarding the stability of austenite, ferrite, ′ and ɛ martensite, and excess carbon concentrations in rapidly solidified steels and these are compared with other workers' results. Some preliminary data regarding the structure of model nickel alloys are presented in order to shed light on previously described structures of nickel superalloys.
Hydrogen Solubility in Pd100-xSix Metallic Classes and the Phase Diagram of Pd-Si-H Glasses
Authors: Finocchiaro R. S. , Tsai C. L. , Giessen B. C.
Published: March 2011

The hydrogen solubility of glassy Pdl00-xSix alloys with 14≤x≤22 has been measured in the temperature range of 10°C to 90°C and the hydrogen partial pressure range of 0 to 100 torr. The absorption of hydrogen in these glassy alloys is exothermic and Sieverts' law is not observed. An isothermal-isobaric ternary phase diagram showing the change of hydrogen solubility with silicon concentration is given. A preliminary analysis suggests that the hydrogen solubility is related to the atomic structure of the metallic glasses.
Metallic Glass Formation Diagrams
Authors: Giessen B. C. , Whang S. H.
Published: March 2011

The ability to predict ready glass formation (RGF) in binary alloy systems upon rapid cooling of the melt is of value both theoretically and practically. Two-dimensional maps show promise as a means of associating RGF with two system parameters which must have a combination of favorable values. In this paper, two types of glass formation diagrams are reviewed. One of these, the ΔH-r/R plot, is based on fundamental parameters which can, in principle, be derived from elemental quantities for each binary alloy system. The second type of diagram, the temperature-composition map, uses two equilibrium phase diagram features, namely reduced liquidus temperatures and reduced eutectic compositions to predict RGF. Both approaches are compared for binary alloys of Zr. The temperature-composition plot approach can be extended to predict qualitatively the RGF composition range of a given alloy system.
Effects of Coherency Constraints on Phase Equilibria
Authors: Cahn J. W. , LarchÉ F. C.
Published: March 2011

In many solid-state phase changes, atoms in a crystal rearrange themselves to form several phases differing in composition and order, while retaining the topology of the original crystal [l]. Although the crystal is distorted, the individual sites that atoms occupy and the lattice can still be identified with equivalent positions in an undistorted crystal. An equilibrium with respect to atom rearrangement, keeping the crystal intact, is called a coherent equilibrium. Such an equilibrium has been observed and its properties can be computed [1–3]. Coherent equilibrium is usually compared with an incoherent phase equilibrium in which each of the same phases form separate crystals that do not interact elastically with the other phases, but exchange atoms. For large enough particles, coherent equilibrium is metastable with respect to incoherent equilibrium, and loss of coherency is a spontaneous process.
Superconductivity and Magnetic Order: Low Temperature Phase Diagrams
Authors: Brian Maple M.
Published: March 2011

Recent experiments on magnetically-ordered ternary and pseudoternary rare earth superconductors are briefly reviewed. Superconductivity has been found to coexist with antiferromagnetic order, but to be destroyed by the onset of ferromagnetic order at a second transition temperature Tc2∼TM, where TM is the Curie temperature. In antiferromagnetic superconductors, the antiferromagnetic order modifies superconducting properties such as the curve of the upper critical magnetic field versus temperature. In ferromagnetic superconductors, a long wavelength (∼ 102 Å sinusoidally modulated magnetic state develops in the superconducting state as a result of the superconducting-ferromagnetic interactions. The interplay of superconductivity and competing magnetic interactions in pseudoternary rare earth systems produces complex and interesting low temperature phase diagrams.
Phase Diagrams Under Irradiation
Authors: Russell K. C.
Published: March 2011

The high intensity irradiation environments produced by advanced fast fission and proposed fusion reactors, high voltage electron microscopes, and heavy ion accelerators add a new and exciting dimension to materials science. Typical irradiations of alloys in these devices introduce the order of 108 J/mol displacement energy in the form of vacancy-interstitial (Frenkel) pairs. Although most of this energy is disspiated as heat during Frenkel pair recombination, significant amounts may be harnessed to produce microstructural change, hence changes in the phase diagram. This extended abstract discusses the various atomistic mechanisms available to convert irradiation energy to microstructural change and cites selected experimental observations where the various mechanisms are operative. An extensive, critical review of phase stability under irradiation is in press [1].
Phase Equilibria at 1173K in the Ni-Ti-Al System
Authors: Liang W.W. , Nash P.
Published: March 2011

In a recent review of the published literature on this system it was concluded that there is a lack of experimental data in this system particularly in regions of the system with less than 75 atomic per cent of each one of the components (1). In order to provide some consistent data over a substantial range of composition an experimental determination of the phase equilibria at 1173K and from 0–50 atomic % Al is being carried out. The main experimental technique being used is quantitative electron microprobe analysis (JEOL 733) by wavelength dispersive x-ray spectrometry. In addition, x-ray diffraction is being used to establish the structures of phases present and optical metallography of cast structures to determine the fields of primary crystallization. In addition to establishing the phase equilibria at this temperature the composition range for the existence of the AlNi2Ti phase is being determined. The results thus far are compared with previous experimental data and calculated isothermal sections (2).
Cu-Pb-Sn Ternary System: Low Cu Additions to Pb-Sn- Binary System
Authors: Marcotte V. C. , Schroder K.
Published: March 2011

A portion of the Cu-Pb-Sn ternary diagram was determined experimentally. The investigation was concentrated on the high Pb corner and, to a lesser extent of alloys from Sn to the binary Pb-Sn eutectic. The experimental techniques used were thermal analysis, metallography, and electron microprobe analysis. A new technique for determining liquidus temperatures was used. For the high Pb region the proposed ternary eutectic at 0.06 Cu 0.02% SnPb (all compositions are in weight %) was not observed. For most alloys the primary crystallization phase was Cu3Sn. It was shown that Cu6Sn5 exists in the solid state; for high Sn alloys, it was observed that the addition of Pb reduced the decomposition temperature of Cu6Sn5. A ternary eutectic reaction near the binary Pb-Sn eutectic was confirmed, and the temperature of the ternary eutectic was 1°K below that of the binary eutectic. Liquidus temperatures as well as other reactions detected by thermal analysis will be presented.
Monotectic Alloy Solidification - Determination of the Liquidus Surface in the System Succinnonitrile-Ethanol-Glycerol
Authors: Grugel Richard N. , Hellawell A.
Published: March 2011

The microstructure of alloys undergoing a monotectic reaction, Liquid I ⇆ Solid I + Liquid II, is related to the height of the liquid miscibility gap, upper consolute temperature, TC, relative to that of the monotectic horizontal at TM. It has been shown in the system Cu-Pb-Al that a transition in microstructure occurs as the temperature interval, Tc-TM, changes with composition. In order to observe the structural change directly in a transparent material, it has been necessary to determine the liquidus surface for the system succinnonitrile(S)-ethanol(E)-glycerol(G). In this system monotectic reactions in the binary S-E and S-G systems are joined by a monovariant valley and a structural transition occurs at approximately 85.6 wt. % S, 7.5 wt. % E, 6.9 wt. % G, at a ratio of 48:52 = G:E.
Alloy Chemical Comparison of the Refractory Metal - Noble Metal Phase Diagrams T5-T10 (T5 = V, Nb, Ta; T10 = Pd, Pt)
Authors: Waterstrat R. , Giessen B.C.
Published: March 2011

The six T5-Tl0 metal alloy phase diagrams containing Pd or Pt have now all been established. The alloy phases occurring in these systems are tabulated and reviewed here with respect to their structures.
Lattice Energy Functions for Prediction of Structural Properties of Alloy Phases
Authors: Machlin Eugene S.
Published: March 2011

Lattice energy functions have been used to predict various properties. The energies and volumes of formation of alloy phases, as well as the relative stabilities of competing phases are provided by a model based on Mie type interatomic potentials. The elastic constants of alloy phases are treated using a model sensitive to the quadrupole distortion of a repulsion spheroid. The properties of defects are treated using a model based on both a volume dependent contribution and an interatomic potential contribution to the lattice energy. Good predictability is obtained for all three types of lattice energy functions in their respective applications.
Structural Maps and Parameters Important to Alloy Phase Stability
Authors: Watson R. E. , Bennett L. H.
Published: March 2011

Alloy properties are often summarized on two-dimensional maps. For instance, Darken and Gurry related the terminal solubilities of alloy systems to two coordinates (the differences in electronegativities and in atomic radii of the alloy constituents). Maps are considered here which correlate the structures in which the compounds form as well as providing some indication of whether a compound forms at some given composition in the first place. This class of map involves one coordinate which is the difference in an atomic parameter (here it will be taken to be the electronegativity) while the other is an average (in this case the d band hole count). This contrasts with Darken Gurry maps and Giessen's maps related to glass-forming ability (elsewhere in this volume) where both coordinates are differences. The situation for 50/50 transition metal alloys is reviewed and results are presented for systems off 50/50 composition.
Sic Reinforced-Mosi2 Alloy Matrix Composites
Authors: Petrovic J. J. , Honnell R. E. , Vasudevan A. K.
Published: March 2011

MoSi2 based composites possess significant potential as high temperature structural materials. The present investigation constitutes an initial study of the fabrication and properties of MoSi2/silicide alloys and SiC particle reinforced-MoSi2 /silicide alloy matrix composites. Alloying disilicides (WSi2, Nb5Si2, Ta5Si2 ) and trisilicides (Mo5 Si3, W5Si3, Nb5Si3, Ta5Si3, Ti5Si3 ) were examined. Results indicated that at the 50/50 mole % alloying level, MoSi2 formed solid solutions with the alloying disilicides. Reaction of the MoSi2 /TaSi2 alloy with SiC was observed. An initial assessment of 50/50 mole % disilicide alloy oxidation behavior suggested an oxidation resistance inferior to that of pure MoSi2.
Microstructures and Mechanical Properties of NiAl+Mo In-Situ Eutectic Composites
Authors: Subramanian P. R. , Mendiratta M. G. , Miracle D. B. , Dimiduk D. M.
Published: March 2011

The quasibinary NiAI-Mo system exhibits a large two-phase field between NiAl and the terminal (Mo) solid solution, and offers the potential for producing in-situ eutectic composites for high-temperature structural applications. The phase stability of this composite system was experimentally evaluated, following long-term exposures at elevated temperatures. Bend strengths as a function of temperature and room-temperature fracture toughness data are presented for selected NiA1-Mo alloys, together with results from fractography observations.
On the Flow and Creep Strength of Power Law Materials Containing Rigid Reinforcements
Authors: He Ming Y.
Published: March 2011

Investigation of the flow properties of materials containing rigid reinforcements has been prompted by various technological challenges concerned with high specific strength composites. The materials of interest range from metallic materials such as Al alloys, to ceramic materials such as Si3N4 and also include the intermetallics: TiAl and MoSi2. The reinforcements are typically A12O3 and SiC. The strengths of interest may be the flow strength at ambient temperature or the creep strength. The present analysis constitutes an attempt to provide estimates of either the flow or creep strength for matrices that exhibit power law deformation.