bluuebunny/crossref_metadata_2025_split huggingface dataset:
Ni-Mo-Cr-B Alloys: Corrosion Resistant Amorphous Hardfacing Coatings
Authors: Das S. K. , Norin E. M. , Bye R. L. 
Published: March 2011

ABSTRACTA series of rapidly solidified Ni-Mo-Cr-B alloys have been investigated for possible application as corrosion resistant hardfacing coatings. As-cast amorphous ribbons were pulverized to powder, which was subsequently applied to a substrate by plasma spraying. The coatings are substantially amorphous, as revealed by x-ray diffraction and transmission electron microscopy. They exhibit ∼95% of theoretical density and exhibit good corrosion and wear resistances, superior to those of many commercially available hardfacing coatings.
Short Range Ordering-Disordering in an FeNiB Metallic Glass
Authors: Kursumovic A. 
Published: March 2011

ABSTRACTLow temperature relaxation of Fe40Ni40B20 glassy samples was monitored by DSC, velocity of sound and creep recovery measurements. The as-quenched samples exhibited very pronounced exothermic reactions in the temperature region prior to crystallization. Reversible changes were found during subsequent heat treatmentof preannealed glassy material having exothermic and endothermic heat flow during ordering and disordering respectively. Results were found to be in agreement with velocity of sound and creep recovery changes, found earlier , having activation energy for these reversible changes around 160 kJ/mole.
Comparison of Microstructure and Properties Obtained by Different Solidification Techniques
Authors: Bergmann H. W. , Barton G. , Mordike B. L. , Fritsch H. U. 
Published: March 2011

ABSTRACTThe processes responsible for solidification, e.g., nucleation and growth, are influenced to various extents by the currently employed quenching techniques. The microstructures produced by these techniques are discussed and compared.
Microstructures of Rapidly Solidified Aluminum Alloys
Authors: Zindel J.W. , Stanley J.T. , Field R.D. , Fraser H.L. 
Published: March 2011

ABSTRACTAn investigation was performed to study the origin and stability of microstructures in rapidly solidified aluminum alloys. Al-Ni and Al-Fe base alloys were rapidly solidified by means of laser surface melting and melt spinning techniques. Microstructures were studied using optical and transmission electron microscopy. The effect of microstructure on mechanical properties was also studied using microhardness measurements. The origin of the observed microstructural constituents will be explained in terms of features of the metastable phase diagram. The effect of ternary additions on stability will also be considered.
Rapid Solidification Microstructures and Precipitation in AL-Mn Alloys
Authors: Schaefer R. J. , Shechtman D. , Biancaniello F. S. 
Published: March 2011

ABSTRACTRapidly solidified Al containing up to to 15 wt.% Mn was prepared by melt spinning. The alloys were examined by TEM and X-ray diffraction in the as-spun condition and after annealing at 450°C. Four precipitate phases were detected, and their growth kinetics were correlated to subgrain structures in the Al matrix.
Rapid Solidification of an Aluminum-Neodymium Alloy
Authors: Savage S. J. , Froes F. H. 
Published: March 2011

ABSTRACTA rationale for rapid solidification processing of aluminum-lanthanide alloys is given, and preliminary results of microstructural studies on an aluminum-neodymium alloy are presented. Three distinct types of microstructure are seen in the as-cast rapidly solidified material, which are still evident after heat treatment at 350°C for 1 hour. Microhardness measurements indicate each microstructure has a different response to isochronal heat treatments.
Microstructural Analysis of Rapid Solidification and Undercooling in the Al-Ge System
Authors: Kaufman M.J. , Fraser H.L. 
Published: March 2011

ABSTRACTSubmicron powders, amorphous films and melt spun ribbons of various Al-Ge alloys have been analyzed to determine the relative roles of undercooling and cooling rate in the production of non-equilibrium structures. All analyses were performed in transmission electron microscopes equipped with energy dispersive x-ray spectrometers. The submicron powders, produced by electro-hydrodynamic atomization, were analyzed in their as-received condition and then annealed and/or melted using the electron beam as a local heating source. Once molten, the liquid droplets were undercooled at different cooling rates by varying the rate of beam obstruction. In this manner, a number of different microstructures were produced. These included metastable crystalline phases and mixed amorphous/crystalline structures. By combining this technique with a microscope heating stage, it was possible to carry out controlled dynamic undercooling experiments and determine phase selection as a function of undercooling and composition. The amorphous films were rapidly heated with the electron beam in the microscope and metastable as well as stable phases were produced. The results of these complementary analyses will be compared and discussed with reference to current models and theories of rapid solidification.
Microstructures of Rapidly Solidified Titanium-Eutectoid Former Alloys
Authors: Krishnamurthy S. , Vogt R. G. , Eylon D. , Froes F. H. 
Published: March 2011

ABSTRACTTitanium-base binary alloys containing eutectoid forming additions such as Fe, Si, W, and Cr were rapidly solidified by pendant drop melt extraction, melt spinning, and “hammer and anvil” techniques. The materials obtained were fibers, ribbons, and splats, respectively. The microstructures of these rapidly solidified materials were analyzed by optical microscopy, SEM, and TEM. The fibers showed fine microstructures near the quenched side, but less homogeneous and coarser microstructures were observed away from this side. Similar variations were observed between the edge and the center of splats. The results of this microstructural characterization are discussed, and a comparison made between microstructures obtained by the different rapid solidification methods used.
Comparison of Rapidly Solidified Nickel Base Superalloys Prepared by Melt Spinning and Plasma Deposition
Authors: Taub A.I. , Jackson M.R. , Huang S.C. , Hall E.L. 
Published: March 2011

ABSTRACTThe microstructure and yield strength of two nickel base superalloys prepared by melt spinning and plasma deposition are compared in the as-solidified condition and after annealing. The results support the interpretation of the yield strengths obtained by tensile testing melt spun ribbon as representative of the values obtained for bulk specimens with equivalent microstructures. The effectiveness of grain size strengthening in a nickel base superalloy is also examined. The Hall-Petch relation appears to be obeyed, with a slope k = .77±.15 MPa−m1/2.
A Microstruciure Investigation on Rapidly Solidified Ni3Al Containing Boron
Authors: Ciiang K.M. , Huang S.C. , Taub A.I. 
Published: March 2011

ABSTRACTA small amount of boron addition in rapidly solidified Ni3Al has been found to yield remarkable improvements in bolh room-temperature strength and ductility. In this study, the microstructure of melt-spun Ni3Al ribbons with various boron modifications ranging from 0 to 6.0 at% was investigated in detail by using transmission electron microscopy. All alloy compositions studied reveal a completely ordered fcc L12matrix phase, in which polygonized dislocation networks and subgrain boundaries are observed. The boron-free Ni3Al contains a dispersion of an Al-rich martensitic phase consisting of alternate twins. The boron addition tends to suppress the formation of the martensitic phase, but excessive boron (≥ 2.0 at%) causes the precipitation of M23B6type borides.
Microstructure of Rapidly Solidified Cu-Fe Alloys
Authors: Köster Uwe , Caesar Christoph 
Published: March 2011

ABSTRACTRapidly solidified ribbons of Cu-Fe alloys with iron contents up to 20 at.−% have been prepared by melt-spinning. Optical and electron microscopy as well as x-ray and electron diffraction techniques were used to characterize quantitatively the microstructure, i.e., grain size and shape, solubility of iron, lattice parameter, volume fraction and distribution of precipitated iron-particles, etc.Whereas the free surfaces of melt-spun Cu-Fe ribbons have been found to be very smooth, the contact surfaces usually consist of isolated areas of good thermal contact with small equiaxed grains separated by bands without contact during casting and therefore poor heat transfer. The cross sections of the ribbons generally exhibit a strong anisotropy in their microstructure: very fine crystals adjacent to the contact surface develop into narrow columnar grains, generally significantly elongated and extending across the whole section. The average columnar width of the grains has been found to decrease significantly with increasing iron content. Precipitation of iron not only depends on the iron content but also on the distance from the contact surface.
The Effect of Quenching Variables on the Transformation Characteristics of Some Rsp Shape-Memory Alloys
Authors: Wood J.V. 
Published: March 2011

ABSTRACTRibbons of a Cu-Al-Ni shape memory alloy have been rapidly solidified by planar flow casting. Attempts have been made to vary casting and secondary quench conditions in order to identify the predominant process variable in determining the subsequent β1↔γ1′ transformation temperatures. By varying wheel speed, wheel material and secondary quenching rate it is concluded that the large excess vacancy concentration has most influence on the as cast ribbon, but that after subsequent heat treatment, the grain size dominates.
Monte Carlo Simulations of Film Profile Evolution During Nonplanar CVD Processes
Authors: Coronell Daniel G. , Jensen Klavs F. 
Published: March 2011

ABSTRACTA Monte Carlo simulation approach has been developed to model transport and film profile evolution for rarefied gas flows during nonplanar CVD over trenches and contact holes. A systematic study of the effect of various parameters on the film conformality including intermolecular collisions, reactant sticking coefficient and feature geometry is reported.
X-Ray Grazing Angle Scattering and Fluorescence Studies of Interfacial Microstructures in Si1-xGex/Si Multilayers
Authors: Ming Z. H. , Krol A. , Soo Y. L. , Kao Y. H. , Park J. S. , Wang K. L. 
Published: March 2011

ABSTRACTAngular dependence of grazing incidence x-ray scattering and Ge fluorescence yield were measured for the heterostructures of Si1-xGex/Si and the inverted bilayer Si/Si1-xGex as well as two 10-period superlattices. Interfacial roughness, correlation of height fluctuations between interfaces and Ge density profiles in the multilayers were investigated.
Interface Roughness, Composition, and Alloying of Low-Order ALAS/GAAS Superlattices Studied by X-Ray Diffraction
Authors: Miller W. R. , Pellegrino Joseph G. , Comas James 
Published: March 2011

ABSTRACTLow-order, monolayer by monolayer (1×1) AlAs/GaAs superlattices grown by MBE using different growth techniques have been studied by X-ray diffractometry. High-resolution multiple-crystal diffractometry was used to study diffraction features near the [004] peaks due to the substrate and epilayers. Using this technique, we have investigated the effect of growth techniques on the strain and tilt of the superlattices. High-resolution X-ray diffraction (HRXRD) results suggest that the sample grown by migration-enhanced epitaxy (MEE) is more highly strained and has more tilt than the same superlattice sample grown using the interrupted growth (IG) technique.
Growth Morphologies of Steps on Vicinal Surfaces in Molecular-Beam Epitaxy
Authors: Xiao Rong-Fu 
Published: March 2011

ABSTRACTA Monte Carlo model has been used to study growth morphologies of steps on vicinal surfaces in molecular-beam epitaxy. The model accounts for molecule attachment, detachment, and surface diffusion. Through variation of surface temperature, impingement rate of source molecules, and the orientation of vicinal surface, we have explored the surface diffusion and the conditions under which two dimensional nucleation (2DN) growth and step flow (SF) growth occur. We have found optimum growth windows for 2DN growth and SF growth. For SF growth we have found that morphological stabilitity of steps are closely dependent on their step height. Steps with multi-molecular-layers are seen to be less stable than single-layer steps in a surface diffusion field, due to a decrease in the attachment of growth units from the upper terrace.
Stepped Surfaces and Internal Film Microstructures
Authors: Chernov A. A. 
Published: March 2011

It is known since long ago that “birth defects” of crystals appearing during their nucleation and growth may hardly be eliminated by further “education,” like heat treatment. Even less hope, if any, exists for fabricating fancy device structures unless we use detailed techniques of crystal growth, techniques based on interfacial processes, and determine the real defect structure of the crystal or film.These practical issues encourage those who are excited by the goal to penetrate into processes at solid surfaces and should encourage those who make decisions on funding this research.In what follows I emphasize selected general issues that seem to be hot today and that have been addressed at Symposium B of the 1992 Fall MRS Meeting. Of course, the selection is a matter of taste.
Phases and Phase Transitions in the First Few Layers of Methane, Argon and Krypton Adsorbed on Graphite
Authors: Goodstein David , Day P. , LaMadrid M. , Lysek M. 
Published: March 2011

ABSTRACTThe equilibrium phase diagrams of monolayers of many substances adsorbed on graphite have long been studied as examples of 2-dimensional (2D) matter. One typically observes 2D gas and liquid phases, and solid phases that may be commensurate or incommensurate with the substrate lattice. Many experimental techniques have been used, but thermodynamic measurements are generally the most useful for tracing out phase boundaries.Recent advances in technique have made it possible to use thermodynamic measurements to study the phase diagrams of the second and higher layers, up to the fifth or sixth. These advances include ultra high resolution scanning calorimetry, and a detailed understanding of the role of capillary condensation in corners and pores of the graphite foam substrate. We find a rich array of phases and phase transitions in multilayer methane, argon and krypton. The second and third layers typically have distinct 2D gas, liquid and solid phases evidenced by 2D triple points and critical points. We observe phase transitions between solid phases that are commensurate and incommensurate with the layer below. We also observe melting of the first layer at higher temperatures, even when one to five additional layers are adsorbed on top of it.In argon and krypton, but not in methane, a strange new phenomenon is observed at temperatures above the gas-liquid critical point of the nth layer for n> 3. Below that temperature, nthlayer gas coexists with a condensed nth layer. At some temperature above it, a new coexistence region is observed in which a partial nth layer coexists with a partial n + 1st layer. This behavior is thought to be evidence for a theoretically predicted phase transition of the bulk interface, called the preroughening transition.
Morphology of Monolayer Films Observed by Photoelectron and Low-Energy-Electron Microscopy
Authors: Mundschau M. , Bauer E. , Świech W. 
Published: March 2011

ABSTRACTMany of the fundamentals of epitaxial growth, long predicted by theories of crystal growth, have been seen during the molecular beam epitaxial growth of monolayer films. In general, high temperatures and low deposition flux favor nucleation at atomic steps. The opposite extreme of low temperature and high flux favors island nucleation in terraces, and steps play little role. For intermediate conditions a wide variety of growth morphology is seen. High temperatures and high flux have been seen to produce two-dimensional dendritic growth. Atomic steps on substrates have been observed to migrate during sublimation. Pinning of steps during migration gives rise to complex atomic step and terrace structures and a distribution of terrace widths. For terraces wider than the diffusion length of adsorbed atoms, nucleation of islands is favored in the terraces, whereas narrow terraces favor nucleation at the atomic steps. For a constant substrate temperature and deposition flux, morphology can vary profoundly depending upon local terrace width. Complex structures in monolayer films are produced during sublimation. These include lockeime or hole nuclei which are one atomic step deep. Steps are seen to oscillate during step flow apparently due to considerable mass transport between steps and terraces.
Defect-Mediated Growth of YBa2Cu3O7-δ Films
Authors: Schlom D. G. , Anselmetti D. , Bednorz J. G. , Gerber Ch. , Mannhar J. 
Published: March 2011

ABSTRACTThe evolution of the surface microstructure of sputtered c-axis oriented epitaxial YBa2Cu3O7-δ films has been monitored by scanning tunneling microscopy (STM). The results indicate that growth is dominated by the incorporation of depositing species at defect sites. These defect sites, which provide energetically favorable positions for accommodating the arriving species, are at ledges—either along growth spirals emanating from screw dislocations, or due to the closely spaced surface steps arising from the macroscopic tilt of the substrate. If the substrate is misoriented sufficiently, the depositing species may diffuse to and be accommodated by these surface steps, without the supersaturation on the terraces attaining a high enough level for two-dimensional nucleation to occur. Under these conditions, growth occurs by step propagation. Otherwise, a high density of screw dislocations (≈109 cm-2) is nucleated during the initial stages of growth, which provides a continual supply of ledge incorporation sites in the vicinity of the depositing species. The surface evolution reported appears to be an intrinsic feature of c-axis oriented YBa2Cu3O7-δ films for a wide range of growth conditions, irrespective of the substrate material or vapor phase deposition method.
Irreversible Island Formation During Deposition: Island Size and Separation Distributions
Authors: Bartelt M. C. , Tringides M. C. , Evans J. W. 
Published: March 2011

ABSTRACTWe present precise simulation results for a simplified model of irreversible nucleation and growth of islands during deposition. We characterize the scaling of the island and adatom densities, the complete island size distribution, and the adatom-island and island-island separation distributions, with the ratio of diffusion to deposition rates (for fixed coverages,θ<1). We also make some comparisons with rate equation predictions.
Microstructural Evolution During Epitaxial Growth of Chemically Derived Ba2YCu307-x. Thin Films
Authors: Mclntyre Paul C. , Cima Michael J. 
Published: March 2011

ABSTRACTMicrostructure development in thin films of Ba2YCu3O7-x (BYC) synthesized on (001) LaA1O3 using an ex situ process was characterized by TEM and STEM examination of specimens quenched from different points in the growth heat treatment. The microchemistry of the growing oxide films was characterized by EDS in STEM. Phase development was also studied by X-ray diffraction. Several investigators have suggested that growth of BYC during ex situ processing occurs by nucleation and growth of BYC into an amorphous precursor film. Our observations indicate that this process involves growth into a substantially crystalline matrix. X-ray diffraction was used to identify three phases, BaF2, BaCuO2, and CuO, which are present prior to BYC nucleation. Nucleation of both c-axis normal and a-axis normal BYC occurred at approximately 760°C during rapid heating to 830°C in the growth heat treatment. Rapid growth of the c-axis normal material parallel to the substrate surface caused this orientation to become dominant in the fully converted films. Chemical microanalysis of the quenched films suggests that the BYC grows into an overlying layer that, after quenching, is composed of relatively large (25–100 nm diameter) yttrium- and copper-rich particles in a nanocrystalline barium-rich matrix.
Epitaxial Growth in Large Lattice Mismatch Systems: Characteristics of Domain Epitaxy
Authors: Zheleva Tsvetanka S. , Jagannadham K. , Narayan J. 
Published: March 2011

ABSTRACTThe characteristics of epitaxial growth in large lattice mismatch TiN/Si and TiN/GaAs systems are analyzed. The epitaxial growth in these large mismatch systems is modelled in terms of various energy contributions to the epilayer. The new mode of growth, defined as domain epitaxial growth in these high mismatch systems is maintained by the formation of misfit dislocations at repeated intervals. The epitaxial relationship within the domain consists of n interplanar distances of the overlayer film closely matching with m interplanar distances of the substrate, where m and n are integers. The interfacial energy is found to be a very important term in determining the orientation relationships. The results of the model calculations are compared with the experimental observations.
Evaluation and Control of Plastic Deformation in GaAs Film on Si Substrate by Means of Crystal Plasticity Analysis
Authors: Ohashi Tetsuya 
Published: March 2011

ABSTRACTDislocation accumulation in patterned gallium-arsenide film, which is deposited on silicon substrate and cooled down from the deposition to room temperature, is numerically simulated under a continuum mechanics approximation. A new approach to suppression of dislocation accumulation is proposed where selective growth of the film and partial doping of impurities into it are combined. The results show the possibility to keep the surface region of the film almost dislocation free.
Strain Distribution in Heterolayers with low Misfit as Revealed by Convergent Beam Illumination Methods
Authors: Ljjleental-Weber Zuzanna , Kaneyama T. , Terauchi M. , Tanaka M. 
Published: March 2011

ABSTRACTConvergent beam electron diffraction (CBED) was applied to the local measurement of lattice parameter across a strained interface with small mismatch. GaAs layers grown at low temperature with excess As (with 0.15% misfit) on a GaAs substrate were chosen for these studies. Tetragonal distortion was detected in the layer up to 0.5μm from the interface. With an increase of the layer thickness lowering of the symmetry of these CBED patterns was observed. This lowering of symmetry is most probably due to saturation of As solubility and the strain build into these layer.
In-situ X-ray Measurements of the Initial Epitaxy of Fe(001) Films on MgO(001)
Authors: Lairson Bruce M. , Payne A. P. , Brennan S. , Rensing N. M. , Daniels B. J. , Clemens B. M. 
Published: March 2011

ABSTRACTWe have studied die evolution of the lattice parameter of epitaxial Fe(001) on MgO(001) vs. thickness between 1 and 200 monolayers using Grazing Incidence X-ray Scattering. We show that an interaction exists between the islanded film and the substrate, which allows the film to be incommensurate, even when the islands are too small to allow full dislocations to exist. For the conditions studied, the Fe lattice parameter increases toward the MgO lattice parameter with increasing thickness in the 1–10 monolayer coverage regime, and then relaxes back toward the bulk Fe lattice parameter at greater thicknesses. We employ a model for the interaction between film islands and the substrate which explains large changes in the lattice parameter of the Fe in the 1–10 monolayer thickness range. Relaxation at larger thicknesses is described by continuum elasticity theory.