bluuebunny/crossref_metadata_2025_split huggingface dataset:
Diamond-Like Films as Optical and Protective Coatings
Authors: Gupta D. Das , Demichelis F. , Spagnolo R. , Tagliaferro A. 
Published: March 2011

ABSTRACTFilms of amorphous carbon (a-C) and hydrogenated amorphous carbon (a-C:H) are deposited by R.F. Magnetron Sputtering and Sputter Assisted Plasma CVD respectively and their properties are compared. It is found that high optical gap, high resistivity a-C can be obtained, so indicating a large amount of sp 3 bonded C atoms. For this reason attention was mainly focused on a-C and possible application were considered.
Measurement of Interface Strength by Laser Pulse induced Spallation
Authors: Gupta V. , Argon A. S. 
Published: March 2011

ABSTRACTThe strength of planar interfaces between a substrate and a thin coating (1–2 µm) can be measured quite effectively by a laser spallation technique. In this technique a laser pulse of a high energy and a predetermined length is converted into a pressure pulse of a critical amplitude and width that is sent through the substrate toward the free surface with the coating. The compressive pressure pulse is reflected into a tension pulse from the free surface of the coating and loads the coating/substrate interface in tension. The laser flux is tuned to a threshold level at which the interface comes apart. The critical stress amplitude that accomplishes the removal of the coating is determined from a computer simulation process. The simulation itself is verified by means of a piezoelectric crystal probe which is capable of mapping out the profile of the stress pulse generated by the laser pulse.
Compressive Stresses, Buckling and Spalling of Tungsten LPD Films
Authors: Borer Aidan , Derby Brian 
Published: March 2011

ABSTRACTVery large compressive stresses have been measured in thin LPD tungsten films. These stresses are responsible for the extensive buckling of the films. Buckling occurs over a wide range of radii and is accompanied by random spalling over the same range. The large compressive stresses are thought to be oxidation induced. The pattern of random buckle spalling does not fit the specific spalling criteria proposed by other workers. These criteria are examined and a further explanation for the spalling behaviour of these films proposed
Cracking and Delamination of Vapour-Deposited Tantalum Films
Authors: Fisher R. M. , Duan J. Z. , Liu J. B. 
Published: March 2011

ABSTRACTTantalum films begin to crack and spall during vapour deposition on glass at a thickness of 180 nm. Islands and ribbons, 10 – 30 µm in size, delaminate by crack growth along the Ta/glass interface for several gIm after which the crack penetrates into the glass to a depth of 0.5–1 µm and complete spalling occurs. X-ray diffraction showed that about 50 % of the original bct, β-tantalum, phase had transformed to the bcc α-Ta phase. When Ta was deposited on glass that was first covered with 52 nm of copper, spalling was observed to begin at a thickness of 105 nm. In this case, the film first cracks and then peels along the Cu/glass interface and curls into scrolls indicating the presence of a small stress gradient. X-ray diffraction of the asdeposited film, and electron diffraction of ion-milled flakes, showed that Ta films deposited on Cu-coated glass almost completely transform to bcc α-Ta. The critical thickness for delamination along the Cu/glass interface is about 1/2 that for cracking in the glass substrate when an intermediate layer of Cu is not present. All of the above findings are in good agreement with previous observations on Cr films.
Indentation Fracture of Brittle Materials
Authors: Lucas Barry N. , Oliver W. C. , Wert J. J. 
Published: March 2011

ABSTRACTThe response of four transparent materials, soda-lime glass, fused silica, single crystal (0001) A12O3, and Y2O3-ZrO2, to contact by a sharp indenter has been studied. Insitu observation and continuous monitoring of the load and displacement throughout the test allowed the indentation fracture sequence of the transparent materials to be characterized and also permitted the effects of these fracture events on the corresponding load displacement curves to be noted. It was found that if the cracks produced during indentation grew discontinuously, they manifested themselves in discontinuities in displacement on the corresponding load-displacement curve.
Properties of a Submicron-Honeycomb thin film
Authors: Furneaux R. C. , Crompton J. S. , Fitchett D. J. 
Published: March 2011

ABSTRACTA method has been developed of separating the porous film produced by anodizing aluminium from its substrate. Such films have a honeycomb morphology with pores that open at both surfaces. They are composed of essentially anhydrous alumina doped with acid anion from the anodizing electrolyte, and are electron diffraction insensitive. A geometrical model has been developed that describes how the pore morphology is determined by the anodizing voltage. Using this model, expressions are derived that relate cell dimensions to voltage-determined parameters and bulk properties such as porosity.The flexural modulus and tensile strength of honeycombs have been modelled by considering bending moments experienced by the cell walls. Thus, the properties were expressed in terms of cell dimensions. Here, the anodic film and honeycomb models are combined. These are used to analyze the mechanical properties of the films as determined by the anodizing parameters. A critical crack size is predicted and compared with the results of microstructural examinations. Good agreement is shown. Assumptions behind these findings and the implications arising are discussed.
Mechanical Properties of Multilayered Copper-Nickel thin films Measured by Indentation Techniques
Authors: Schlesinger T. E. , Cammarata R. C. , Kim C. , Qadri S. B. , Edelstein A. S. 
Published: March 2011

ABSTRACTArtificially multilayered copper/nickel thin films with bilayer repeat lengths between 1.6 and 12 nm were produced by ion beam sputtering. The mechanical properties of these films were investigated by low load microhardness and nanoindentation (force versus depth) techniques. It was found that none of the films displayed bilayer repeat length dependent enhanced elastic behavior (the supermodulus effect) as measured during unloading in the nanoindenter. However, enhancements in hardness, as measured by both the nanoindenter and the low load microhardness tester, were observed in films with small bilayer repeat lengths. These measurements displayed a Hall-Petch-type relationship, using the individual layer thickness (equal to half the bilayer repeat length) as the characteristic “grain size.” This hardness behavior can be understood in terms of a mechanism involving dislocation pinning at the interfaces analogous to the mechanism of grain boundary hardening.
Structural Dependence of the Elastic Constants of Polymeric Langmuir-Blodgett Films Studied Using Brillouin Scattering
Authors: Lee Sukmock , Dutcher J. R. , Hillebrands B. , Stegeman G. I. , Knoll W. , Duda G. , Wegner G. , Nizzoli F. 
Published: March 2011

ABSTRACTWe have used Brillouin scattering to study the dependence of the elastic constants of uniaxial polymeric Langmuir-Blodgett thin films on the thickness of the polymeric molecule monolayers. With increasing monolayer thickness, an overall decrease in the elastic constants and an increase in the refractive index n33 was observed.
Thermodynamic Factors in the Extension of Solid Solubility in Al-Based Alloys
Authors: Murray Joanne L. 
Published: March 2011

ABSTRACTStable and metastable equilibrium diagrams and To curves are calculated for the Al-based binary systems Al-Ga, Al-Ge, Al-Fe, Al-Mg, and Al-Si. Extended solid solubilities and metastable phases have been produced by rapid solidification for each of these systems, and the calculations are compared to experimental observations.
Thermal Cycling and Amorphous-Cyrstalline Transition in the Amorphous C60-Zr40 Alloy System
Authors: Otooni M. A. 
Published: March 2011

ABSTRACTThe transition behavior of the amorphous Cu60Zr40 alloy system during its transition to crystallinity by thermal cycling has been studied. A Differential Scanning Calorimeter (Perkin-Elmer model DSC-2) was used to record, in situ, the onset of thermal evolution of the sample during the course of transition. Analysis of DSC tracings reveal that: a. Transition occurs at a lower temperature than those transformed without thermal cycling, b. The amplitude of the exothermic rise decreases proportionally with increasing numbers of the thermal cycles and c. Details of the profile of the DSC tracing, i.e., the width of the exothermic rise and the presence of the secondary exotherm, are quite different from those transformed without thermal cycling. Preliminary high resolution electron microscopy of thermally cycled samples indicate random distribution of copper-rich precipitates at the early stages of cycling and their coalescence during the final stage of crystallization. For large number of cycles, however, the induced strains from thermal cycles contributes to the image contrast of the quenched solid thus allowing the assessment of the proposed atomic level stresses and strains, via technique of high resolution electron microscopy.
The Au–Pb Phase Diagram
Authors: Evans Dain S , Prince Alan 
Published: March 2011

ABSTRACTThe Au–Pb system has been redetermined using dta, metallography and X-ray techniques. The compounds Au2 Pb, AuPb2 and AuPb3 are generated by peritectic reactions at 434° , 253° and 221.5°C respectively. AuPb3 and Pb form a eutectic at 84.8 at% Pb and 212°C. It is confirmed that Au2 Pb is stable down to at least 200°C.
Relative Solubility Trends in Transition-Metal Alloys
Authors: Goodman D. A. , Bennett L. H. , Watson R. E. 
Published: March 2011

ABSTRACTThe prediction of terminal solubilities for a given metal solute and solvent is a formidable problem, and it remains a major unsolved question in metallurgy. In this paper we describe the relative solubilities of the transition metals in one another. After discussing the problem of defining an appropriate measure of solubility for the transition-metal alloys which have any intermediate phases, we present a map of relative solubilities for the transition metals. From this map, we delineate the trend which occurs. Both the Engel-Brewer theory and d-band transition-metal alloy theory are consistent with this trend.
The Atom as the Building Block in Crystal: The Use of Electron Charge-Density Data Base for Calculating Structural Properties of Metals
Authors: Krasko Genrich L. 
Published: March 2011

ABSTRACTWe suggest a new method of calculating structural properties of metals. The method utilizes the data base of “firstprinciple” charge-density distributions in pure metals accumulated in recent years. If, for a metal, the solution to the Schrodinger equation within the atomic cell is known, the electron charge-density distribution in an orbitrary point of the crystal may be “reconstructed” within the framework of a model. Using the Density-Functional Formalism and the virial theorem, the total energy of the crystal may be found in terms of an effective interatomic potential. The latter may be used for the calculating of other structural properties, such as phonon spectra and elastic moduli. The extension of this method to alloys is briefly discussed.
Solidification Processing of NbCr2 Alloys
Authors: Thoma D. J. , Perepezko J. H. 
Published: March 2011

AbstractMicrostructural development in alloys bordering the NbCr2 Laves phase composition has been evaluated following solidification processing. With splat quenching of binary alloys, rapid solidification has yielded supersaturation of both Nb-rich and Cr-rich primary solid solutions as well as some solubility extension of the C15 phase during cooling as compared to as-cast structures. Ternary additions of Ti are soluble in NbCr2 along the pseudobinary NbCr2-TiCr2 section for C15 structures and completely miscible in bcc Nb and Cr solutions. In the rapid freezing of splats, modest Ti additions to NbCr2 enhance the development of an extended bcc solution during freezing and the supersaturation of the C15 phase during solid-state cooling. In the solid state, the C14–C15 transformation of the Laves phase is suppressed partially in arc-cast ingots and more completely at high cooling rates. Upon heating, thermal analysis has revealed that the retained C14 phase undergoes a decomposition sequence with at least two stages, possibly involving polytypes and associated faulting, to the stable C15 structure. The microstructural options developed by solidification processing, solid state transformations, and alloying have been observed to modify the brittle behavior of the as-cast structures.
The Effects of Cooling Rate Upon Xdt m TiAl Weld Microstructure
Authors: Robertson Erica , Hill Mary Ann , Schwarz Ricardo B. 
Published: March 2011

AbstractFusion zone microstructures of an electron beam (EB) welded XDt m Ti–48at%Al + 6.5 vol% TiB2 alloy revealed plate-like precipitates which were absent in the base metal. The volume fraction of this phase increased with increasing cooling rate and correlated with increased weld cracking frequency. To determine whether this phase was a product of solidification from the melt or a product of a solid-state transformation, the microstructures of the welds were compared to those of samples cycled in a Gleeble 1500/20 Thermal-Mechanical Test System which was programmed to simulate the solid-state portion of the weld cooling rates (as predicted by a Rosenthal analysis). The microstructures were characterized by X-ray diffraction, optical and by scanning electron microscopy. The plate-like phase found in the weld microstructures was identified as TiB2 occurring upon rapid solidification of the melted weld metal.
Microstructure and Mechanical Bevavior of Ni3Al-Matrix Composites
Authors: Brennan P. C. , Kao W. H. , Jeng S. M. , Yang J.-M. 
Published: March 2011

AbstractAn aluminum oxide particulate-reinforced nickel-aluminide composite was fabricated by vacuum hot pressing and hot extrusion. Room temperature three point bend tests were conducted after 1 and 100 h at 1000 °C. The composite exhibited a decrease in yield strength from 772 to 517 MPa after 100 h while the ultimate fracture stress decreased from 1174 to 998 MPa. The strain to failure increased from 4.6% to 6.0% after the same exposure. Saphikon single crystal Al2O3 fibers were used to demonstrate the materials' compatibility. The fracture surfaces of the failed composites indicated ductile failures in the matrix and decohesion between the particles and matrix.
Creep Behavior and Microstructure of XD™ Titanium Aluminide
Authors: Feng C. R. , Smith H. H. , Michel D. J. , Crowe C. R. 
Published: March 2011

AbstractThe creep behavior of extruded XD™ Ti-47at%Al/7.5v%TiB2 composite was investigated together with extruded Ti-46at%Al alloy. Prior to creep testing, both materials received a duplex heat-treatment at 1200°C for 16h plus 900°C for 8h. The creep tests were conducted at 69, 103 and 138MPa at 760°C in air. The microstructures of both materials prior to and after the creep testing were examined by TEM. The microstructures suggest that the formation of the TiAl/Ti3Al two-phase lamellar structure was the predominant creep mechanism.
Structure/Property Comparisons in Particulate and Short Fiber γ-Based Titanium Aluminide Composites
Authors: Kampe S. L. , Clarke J. A. , Christodoulou L. 
Published: March 2011

AbstractThe effect of matrix microstructure on the mechanical properties of two model XD™ titanium aluminide composites containing 7 volume percent of either particulate (TiB2) or short-fiber ((Ti,Nb)By) reinforcement has been evaluated. Subsequent to wrought-processing via isothermal forging, heat treatments were performed to produce either a fully equiaxed or fully lamellar matrix microstructure. The synergism between matrix microstructure and reinforcement type has been evaluated for ambient-temperature tensile ductility and fracture toughness, and 800°C tensile strength and creep rate. Results indicate that overall composite performance is strongly dependent on reinforcement shape, the extent of which depends on the morphology of the matrix microstructure.
Microstructure and Interface Behavior in Diffusion Bonded Ni3Al+B Matrices Containing Continuous Al2O3 Fibers.
Authors: Lee C. , Grummon D. S. , Gottstein G. 
Published: March 2011

AbstractDiffusion bonding is a well known method for fabricating metal matrix composites with continuous fiber reinforcements. However. little data yet exist regarding optimum processing conditions for production of such composites using intermetallic matrices. In this study, diffusion bonded couples were made from boron doped nickel aluminide slabs (vacuum arc remelted alloy IC-15 ) into which small numbers of continuous fibers of α-A12O3 were laid up. Diffusion bonding was carried out in vacuum at stresses between 20 and 50 MPa for 2 to 8 hours at 1273K to 1553K. The specimens were then fractured in uniaxial tension at room temperature and the microstructures and fracture surfaces examined. Preliminary data from optical and scanning electron microscopy showed complete metallurgical bonding of the IC-15 slabs occurred only when process temperatures exceeded 1533K. At these temperatures a 2-hour processing time resulted in considerable grain growth in both the matrix and in the fibers. Occasional fiber fracture was also found to have occurred during the bonding cycle. Auger electron spectroscopy revealed little interdiffusion between fiber and matrix after 2 hours at 1553K and no apparent fiber-matrix reaction zones were detected for any of the process conditions studied.
Cyclic Oxidation Resistance of a Reaction Milled Nial-AlN Composite
Authors: Lowell Carl E. , Barrett Charles A. , Whittenberger J. Daniel 
Published: March 2011

AbstractBased upon recent mechanical property tests a NiAl-AlN composite produced by cryomilling has very attractive high temperature strength. This paper focuses on the oxidation resistance of the NiAl-AlN composite at 1473 and 1573 K as compared to that of Ni-47Al-0.15Zr, one of the most oxidation resistant intermetallics. The results of cyclic oxidation tests show that the NiAl-AlN composite has excellent properties although not quite as good as those of Ni-47Al-0.15Zr. The onset of failure of the NiAl-AlN was unique in that it was not accompanied by a change in scale composition from alumina to less protective oxides. Failure in the composite appears to be related to the entrapment of AlN particles within the alumina scale.
Ductile Phase Toughening of MoSi2-Chemical Compatibility and Fracture Toughness
Authors: Xiao L. , Kim Y. S. , Abbaschian Reza 
Published: March 2011

AbstractChemical compatibility between oxide coated Nb filament reinforcements and MoSi2 was investigated. It was determined that ZrO2, Al2O3, and mullite coatings were chemically compatible with both Nb and MoSi2. Comparison between coated and uncoated filaments indicated that the coatings reduced the thickness of the interaction zone. The fracture toughness of the Nb filament reinforced composites showed an increase, while W filament reinforced composite showed a decrease, in the toughness compared to that of the matrix. The results are discussed in terms of the mismatches in the coefficients of thermal expansion and the bonding characteristics of the reinforcement/matrix interface.
Oxidation of Powder Processed NbAl3 Matrix Composites
Authors: Korinko Paul S. , Duquette D. J. 
Published: March 2011

AbstractNiobium aluminide based composites fabricated by powder metallurgy techniques were tested for oxidation resistance between 1000 and 1400°C. The oxidation rate of these materials was improved over conventionally cast or pack aluminized NbAl3. The inclusion of oxide dispersoids decreased the rate constant by an order of magnitude at 1000°C compared to monolithic NbAl3 and to a value of the same order of magnitude as NiAl at 1170°C. The most heavily reinforced material studied had a rate constant an order of magnitude greater than NiAl at 1400°C.The oxide scale was generally adherent and compact but contained oxide nodules.
Interface Modification for Fiber-Reinforced Titanium Aluminide Composites
Authors: Boss Daniel E. , Yang J. M. 
Published: March 2011

AbstractCandidate diffusion barrier coatings were applied to aluminum oxide and silicon carbide fibers, and consolidated in a gamma titanium aluminide alloy. Interfacial coatings of titanium carbide and titanium diboride were applied to the fibers using chemical vapor deposition, while calcium oxide coatings were applied from a solution. Sections of these specimens were vacuum encapsulated in quartz tubing and heat treated for 50 hours at 1100°C. The thermochemical stability of the fibers was evaluated using energy dispersive x-ray spectroscopy to compare the fiber-matrix interface of the specimens before and after heat treatment. Both the as-manufactured and the coated aluminum oxide fibers showed no discernable interaction with the titanium aluminide matrix. Titanium diboride effectively prevented the silicon carbide fiber from reaction with the matrix. The silicon carbide fiber which was coated with titanium carbide showed significant reaction between the fiber and the coating after heat treatment.
Effect of Thermomechanical Treatments on Solidification Inhomogeneity in Ingot Metallurgy Gammtait Anium Aluminides
Authors: Bryant J. D. , Semiatin S. L. , Maisano J. R. , Winter D. T. , Barrett A. R. H. 
Published: March 2011

AbstractThe addition of titanium diboride to near gamma titanium aluminides has been effective in reducing the initial grain size formed on solidification from the melt. Despite this refinement, however, significant constitutional inhomogeneity may be found due to segregation of alloying elements and reinforcement phases during solidification. The dendritic solidification of several XD'T alloys was studied to assess the extent of this segregation. Quantitative elemental analysis of dendritic and interdendritic regions indicates that a substantial chemical gradient is developed in aluminum and ternary alloying elements. The extent of chemical and reinforcement segregation and its relationship to overall aluminum content in the alloys is discussed. In a study to determine thermomechanical processing steps required to eliminate the casting inhomogeneity, homogenization heat treatments and isothermal forging were performed and the effect on microstructure determined. Remnant dendritic cell structures were seen to persist despite high-temperature heat treatments and mechanical working.
Synthesis and Characterization of Cellular SiO2 Materials by Foaming Sol Gels
Authors: Covino Josephine , Gehris Allen P. 
Published: March 2011

AbstractA variety of cellular SiO2 materials have been synthesized using a foaming sol-gel process and their properties have been characterized. The process uses the rapid viscosity change during gelation to stabilize the structure of a foamed silica sol. It was found that the properties of these cellular materials are determined by method used. For example, the porosity and strength of these porous oxides depend on method of agitation and addition of Freon during the foaming process.Density measurements, viscosity measurements as a function of pH, optical characterization, x-ray crystallography, ultimate compressive strength, dielectric constant measurements and thermal diffusivity were used to characterize these porous SiO2 materials. This paper will discuss the synthetic processes used to develop the porous silicas and properties of these materials.