bluuebunny/crossref_metadata_2025_split huggingface dataset:
Some Fundamental Considerations During Rapid Solidification Processing
Authors: Laxmanan V. 
Published: March 2011

ABSTRACTThree estimates of the solidification rates required to obtain a fully homogeneous structure during rapid solidification processing (RSP) have been made. One is given by the “absolute stability” criterion and another obtained from a new analysis for dendritic solidification. The third estimate, also derived from the above analysis, requires that “hypercooled” conditions be maintained after nucleation. A mechanism for the formation of “featureless” segregation-free zones during melt spinning and atomization processes is suggested and expressions for the critical cooling rate and thermal gradient required to produce such structures have been obtained.
Corrosion Behavior of Rapidly Solidified Fe-Ti-P Alloys With Cu, Cr, and B Additions
Authors: Shastry C. R. , Latanision R. M. , Townsend H. E. 
Published: March 2011

ABSTRACTRapidly solidified ribbons of Fe67Ti13P(20-x)Bx (x= 0, 7, 20 a/o) and Fe(85-y)Ti l5Py (y=5, 10 a/o) alloys were produced by melt spinning, and their structure and anodic polarization behavior were examined by x-ray diffraction and potentio-dynamic polarization measurements in deaerated 1 N H2SO4, respectively. The only alloy that developed an amorphous structure on rapid solidification, Fe67Ti13B20, exhibited poor corrosion resistance, whereas crystalline alloys with 10 a/o or more P exhibited a tendency to passivate during anodic polarization. Substituting Cr for Ti led to significant improvement in corrosion resistance and promoted development of glassy structures in Fe67(TiCr)13P13B7 compositions. No such improvements were observed when Cu was substituted for Ti. It is concluded that alloy composition is more important than degree of crystallinity in determining corrosion resistance.
Studies of Relaxation of Metallic Glasses by Dilatometry and Density Measurements
Authors: Cahn R.W. , Pratten N.A. , Scott M.G. , Sinning H.R. , Leonardsson L. 
Published: March 2011

ABSTRACTHigh-precision density measurements on coldrolled Pd77.5Cu6Si16.5 glass rods before and after relaxation anneals showed that 30 – 40% rolling leads to a density reduction of ∼0.14%, recoverable on subsequent annealing below Tg. This change is about half of the density increase attainable by recovery-annealing the as-quenched glass.Density changes in Fe40Ni40B20 glass ribbon, resulting from recovery-annealing, were studied indirectly by measuring isothermal length changes through dilatometry of foil sandwiches. The experimental conditions for reliable isothermal dilatometry, using a commercial instrument, are outlined. It was found that the kinetics of length change in the longitudinal and transverse directions were quite different, being faster in the former. Prolonged recovery-annealing prior to dilatometry removed this difference. The intermediate stage of each isotherm followed loqt kinetics.Experiments were performed with Fe40Ni40B20, Ni64Zr36 and Cu66Ti34 to search for a reversible component of length change during cyclic isothermal holds at two temperatures. Such a component probably exists but is extremely small, less than 1% of the limiting irreversible length change.The implications of the various findings are discussed in the light of recent literature.
Glassy Pd-Y-Si Alloys and Their Relaxation and Crystallization Kinetics
Authors: Gao Y.Q. , Giessen B.C. 
Published: March 2011

ABSTRACTPd-Y-Si glasses with a Si content as low as 9 at.% were produced by hammer and anvil quenching, the reduction of the Si concentration from a minimum value of 14 at.% in binary Pd-Si alloys was due to the synergistic effect of the addition of Y. The glass forming composition region is reported.The alloy Pd2Y,Si, was studied in detail. The change of the microhardness upon isothermal annealing was investigated. Isothermal and non-isothermal heating experiments yielded activation energies of 52 and 53 kcal/mol (218 and 222 kJ/mol) in good agreement with each other and an Avrami exponent n = 3.7 was found.
Measurement Of Precipitate Nucleation Times In Molten Metals By Pulsed Surface Melting
Authors: Follstaedt D.M. , Picraux S.T. , Peercy P.S. , Knapp J.A. , Wampler W.R. 
Published: March 2011

ABSTRACTThe short melt duration resulting from pulsed laser and electron beam surface melting of ion-implanted metals has been used to measure precipitate nucleation times of compounds within the melt. We have examined the phases present in several alloy systems with TEM and used calculated thermal histories to place limits on the time required for nucleation of the following compounds: AlSb (5–25 ns), Al3Ni (≳ 750 ns)Al3Ni2 (≳ 950 ns) and AlNi (< 1000 ns), all in molten Al, and TiC (≲ 100 ns) in molten Fe. The compounds observed after our rapid solidification have relatively simple, cubic structures and melt congruently, while those predicted but not observed have more complex structures and decompose peritectically.
Phase Decomposition in Cu-Ti Metallic Glass
Authors: Shull R. D. , Singhal S. P. , Mozer B. , Maeland A. 
Published: March 2011

ABSTRACTA metallic glass ribbon of Cu55Ti45 prepared by melt spinning was examined by x-ray, neutron, and electron diffraction, by small angle neutron diffraction (SANS), transmission electron microscopy (TEM), and by differential thermal analysis (DTA). In the liquid quenched condition large angle diffraction data (both x-ray and neutron) show the broad banded structure typical of the amorphous state. The SANS data, however, exhibit highly anisotropic patterns arising from the phase decomposition during solidification. Ribbons annealed below the glass transition temperature (Tg ) produced neutron diffraction patterns of materials with the same amorphous structure combined with a new short range order; and the SANS patterns retained the asymmetry of the as-quenched material. Ribbons annealed above the crystallization temperature (Tc) show both isotropic and anisotropic contributions to the SANS patterns. Formation of the equilibrium TiCu phase occurs directly from the metallic glass at Tc. The equilibrium Ti3Cu4 phase, however, forms from the TiCu phase at slightly higher temperatures.
Some Aspects Of The Rapid Solidification Of Light Alloys
Authors: Jones H. 
Published: March 2011

ABSTRACTThe engineering light metals, especially aluminium and magnesium, exhibit limitations in alloying behaviour and performance that identify them as particular targets for development via rapid solidification. The present contribution reviews recent work in the author's group aimed at advancing understanding of both alloying and processing, including:(1) parametric mapping as a guide to extension of phase fields(2) prediction and application of observed characterisation of binary and ternary extended solid solutions(3) optimisation and control of conditions during rapid solidification and consolidation,
Cooling Rate Effects on Ti-6A1-4V and Beta III Titanium Alloys
Authors: Broderick T. F. , Froes F. H. , Jackson A. G. 
Published: March 2011

ABSTRACTThe titanium alloys Ti-6A1-4V and Ti-11.5Mo-6.0Zr-4.5Sn (Beta III) were produced at cooling rates of 103°C/sec and 105°C/sec using the Rotating Electrode Process (REP), and the Electron Beam Splat Quenching (EBSQ) process, respectively. Material from both alloys examined in the as-produced, heat treated, and vacuum hot pressed (VHP) conditions exhibited an order of magnitude decrease in beta grain size with increasing cooling rate (~135 μm and 7 μm in the Ti-6A1-4V alloy; ~40 μm and 2–4 μm in the Beta III alloy), and a difference in aging response between REP powder and EBSQ flakes. After heat treatment the Ti-6A1-4V developed an alpha morphology which was lenticular in REP powder and equiaxed in EBSQ flakes. Three possible mechanisms are proposed to explain this change involving an increased dislocation density and a tendency for grain boundary allotriomorphic alpha in the EBSQ case. Heat treatment of the Ti-11.5Mo-6.0Zr-4.5Sn materials showed a change in the location of alpha precipitation from interdendritic to grain boundary in going from REP to EBSQ. It is suggested that this change may relate to the decreased solute redistribution which occurs in the more rapidly cooled material.
Rapidly Solidified Ti Alloys Containing Metalloids and Rare Earth Metals— Their Microstructure and Mechanical Properties
Authors: Chi C.S. , Whang S.H. 
Published: March 2011

ABSTRACTRapidly solidified (RS) Ti alloys containing novel additives were prepared by splat quenching and melt spinning techniques. Microstructures of the as-quenched and heat-treated alloys were studied by electron microscopies. The results show that microstructural refinement and precipitation reaction are universal phenomena in all RS Ti alloys. A significant difference in second phase coarsening was observed between metalloid-origin precipitates and those of rare earth-origin. The precipitates in a Ti-Al-La(Ce) were identified predominantly as rare earth-Al compounds. Exce llent stability for rare earth-origin precipitates was found.Except for a carbon-containing alloy (700 ° C), age hardening behavior is a universal phenomenon in all RS Ti alloys with additives. A significant strength increase (hardness) in the RS alloy was noted at both room and elevated temperatures.
Thermal Stability of Precipitates in a Rapidly Quenched Ti-Al-Si Alloy
Authors: Wrang S.H. , Lu Y.Z. , Giessen B.C. 
Published: March 2011

ABSTRACTOstwald ripening of precipitates in rapidly solidified Ti- 5A1-2Si (wt.%) has been studied by TEM. Results show that particle coarsening at 700 and 800°C is controlled by volume diffusion. Diffusion coefficients of Si in a-Ti were found to be ˜7.5 × 10−13 cm2/sec at 700°C and ˜1.2 × 10−11 cm2 /sec at 800°C.At these temperatures, microstructural refinement due to rapid quenching had no noticeable effect on the coarsening mechanism for the RS Ti-5A1-2Si alloy.
Rapidly Solidified Microstructures in a Ti-22 Wt% Fe Alloy
Authors: Baeslack III W. A. , Weeter L. , Krishnamurthy S. , Smith P. , Froes F. H. 
Published: March 2011

ABSTRACTRapidly-solidified microstructures were produced in aTi-22 wt% Fe alloy by laser surface melting, melt extraction, melt spinning and splat cooling. Increased cooling rates during solidification promoted increasingly finer beta grain sizes ranging from approximately 75 microns in a laser melt to 0.5 to 2.0 microns for splats. Beta grain morphologiesw ere generally equiaxed, although epitaxially-nucleated columnar grains were observed at the pool-substrate interface for laser melts. Fitting of the equiaxed beta grain size data to a λ0 = Boε−n0 power relationship for homogenous nucleation and isotropic growth resulted in Bo = 3 × 104 and no = 0.62. The refinement of dendrite structure with increasing cooling rate was also documented for laser melts. Dendrite spacing versus cooling rate data were fitted to a similar general power relationship and resulted in B1 = 45 and n1 = 0.34.
Mechanical Properties of Nickel Base Metastable Solid Solutions with Large Size Mismatch
Authors: Tsai C.L. , Giessen B.C. 
Published: March 2011

ABSTRACTNi-based stable and metastable solid solutions with T3 and T4 transition metals have been prepared by rapid liquid quenching. The microhardnesses of these alloys show a substantial increase (by a factor of 4 to 5) that scales with their size mismatch as well as the solute concentration. It was found that the microhardness increase, ΔH, can be fitted well to the theoretical equation: ΔHv = K μ (cη)4/v3 where μ is the solvent shear modulus, c is the solute concentration and η is the size mismatch. The constant K for Ni base solid solutions is ~85.
Glass Forming Ability in Transition Metal Films at 1010 K/s
Authors: Von Allmen M. , Affolter K. 
Published: March 2011

ABSTRACTGlass formation by ns and ps laser quenching is investigated for the systems Au-Ti, Co-Ti, Cr-Ti and Zr-Ti. Glassy phases are found in all but the last system. These results (as well as earlier ones) show little correlation with published rules to predict glass forming ability, but are consistent with the kinetic analysis presented. Simple Physical parameters related to glass forming ability are discussed. Comparison with results for Cr-Ti allows a determination of the nucleation time-lag.
Microroughness at the Si/SiO2 Interface from Pre-Oxidation Annealing, Measured Using Quantum Oscillations in Fowler-Nordheim Tunneling Currents
Authors: Poler J. C. , McKay K. K. , Irene E. A. 
Published: March 2011

ABSTRACTAs design rules shrink to conform with ULSI device dimensions, gate dielectrics for MOSFET structures are required to be scaled to even thinner proportions. Upon scaling the gate oxides below ∼60Å some properties of the device, such as interface roughness, that are negligible for thicker films become critical and must be evaluated. Microroughness at the interface of ultrathin MOS capacitors has been shown to degrade these devices.We are studying the interfacial region of ∼50Å SiO2 on Si using the quantum oscillations in Fowler-Nordheim tunneling currents. The oscillations are sensitive to the electron potential and abruptness of the film and its interfaces. In particular, inelastic scattering and/or thickness inhomogeneities in the film will reduce the amplitude of the oscillations. We are using the amplitude of the oscillations to examine the degree of microroughness at the interface that results from a pre-oxidation high temperature anneal in an inert ambient containing various amounts of H2O. Preliminary AFM imaging has shown correlations supporting our microroughness interpretation of the quantum oscillation amplitudes.
Afm Studies of Surface Roughness of Borophosphosilicate Glass (BPSG) Films and Their Impact on Defect Detection Capability for Sub Micron Vlsi Technology
Authors: Rojhantalab H. , Moinpour M. , Peter N. , Dass M.L.A. , Hough W. , Natter R. , Moghadam F. 
Published: March 2011

ABSTRACTChemically vapor deposited borophosphosilicate glass (BPSG) has been widely used in microelectronic device fabrication as interlayer dielectric film due to its excellent planarization, gettering and flow properties. With device geometry reducing to sub micron levels, there is an increasingly greater emphasis on detection and elimination of sub micron defects particularly on deposited film. In this paper, we report on the evaluation and characterization of the surface roughness of BPSG films of various thicknesses and film compositions deposited on Si substrates using the Atomic Force Microscopy (AFM). The effects of high temperature densification process on the surface roughness are presented. The defect detection capabilities of conventional laser-based particle counters with respect to the surface roughness of BPSG films are investigated.
A Tem Study of Step Morphology on the Non-Uhv Heat-Treated MgO (100) Surface
Authors: King Simon , Barry Carter C. 
Published: March 2011

ABSTRACTPreliminary results from a study of the morphology of the MgO (100) surface after chemical etching followed by heat-treatment in air are presented. Contrast arising from the surface-steps so formed is found to be strongly dependent on the deviation parameter, suggesting that many of the step-faces are not perpendicular to the (100) foil plane but are, instead, often rather shallowly inclined.
A Theoretical Study of Amorphous-Crystalline Transition in Si [111] MBE Growth
Authors: Venkatasubramanian R. , Dorsey Donald L. , Das S. G. 
Published: March 2011

ABSTRACTThe amorphous crystalline transition temperature for Si MBE growth is higher for [111] growth than for [100] growth. The mechanism for the growth of amorphous Si in [111] growth is thought to be due to the possibility of of direct formation of stacking faults on the [111] surface. To investigate this mechanism, a kinetic model describing the amorphous-crystalline transition in low temperature Si [111] MBE growth is proposed. The model allows Si atoms to incorporate at three types of sites: A, B and C where A is the triply covalent bonded correct diamond site, B is the triply covalent bonded wrong hep site and C is the singly covalent bonded wrong site. The model allows for the migration of atoms from a wrong site to a nearest neighbor correct site through Arrhenius type rate equations. The migration from B → A is assumed 1000 times weaker than the reverse migration process. Similarly migrations from C → A are assumed 106 time stronger than the reverse migration. All possible migrations are considered with different rates. At the high temperature, the model will allow the growth of a perfect diamond cubic structure with correct ordering of layers AaBbCc etc. A stochastic model describing the above kinetic model is developed based on the master equation approach and random distribution approximation. The low temperature MBE growth of Si [111] is investigated using this model. The results of the model are compared with existing experimental work [1]. The results are in good agreement. The study shows that the kinetics of the site correcting migration process well describes the observed amorphous-crystalline transition in [111] Si MBE growth.
Interface Formation and Thin Film Properties of an Incompatible Polymer System
Authors: Guckenbiehl B. , Stamm M. , Springer T. 
Published: March 2011

ABSTRACTThe polymer blend system of deuterated polystyrene (PSd) and the statistical copolymer poly(styrene-co-para-bromo-styrene) (PBrxS) is partially compatible or incompatible depending on the degree of bromination x. The width of the interface in a bilayer system can thus be controlled in a wide range by an adjustment of x. This is demonstrated in neutron reflectivity experiments where the interfacial width is measured with an accuracy better than lnm. The interface width depends strongly on compatibility as expressed by the Flory-Huggins interaction parameter x- Results are compared with current theories.
Ge Segregation and Surface Roughening During Si Growth on Ge(001)2×l by Gas-Source Molecular Beam Epitaxy from Si2H6
Authors: Tsu R. , Lin D.-S. , Greene J. E. , Chiang T.-C. 
Published: March 2011

ABSTRACTSurface morphological and compositional evolution during the initial stages of Si growth on Ge(001)2×1 by cyclic gas-source molecular-beam epitaxy (GSMBE) from Si2H6 has been investigated using in-situ reflection high-energy electron diffraction (RHEED), Auger electron spectroscopy (AES), electron energy-loss spectroscopy (EELS), and scanning tunneling microscopy (STM). At 550 °C, single-step-height island growth was observed for nominal Si deposition thicknesses tsi up to ≃ 1.5 ML. The islands were essentially pure Ge which segregated to the surface as H was desorbed. At higher tsi, the Ge coverage decreased, the surface roughened, and two-dimensional multi-layer island growth was observed for tSi up to ≃8 ML above which three-dimensional island growth was obtained. For thick layers (t S: 75 ML), no Ge was detected at the surface.
Orientational and Microstructural Evolution During Epitaxial Growth of Cu on Si(001) by Sputter Deposition
Authors: Hashim I. , Park B. , Atwater H. A. 
Published: March 2011

ABSTRACTEpitaxial Cu thin films have been grown on H-terminated Si(OOl) substrates at room temperature by D.C. ion-beam sputter deposition in ultrahigh vacuum. The development of orientation and microstructure during epitaxial growth from the initial stages of Cu growth up to Cu thicknesses of few hundred nm has been investigated. Analysis by in-situ reflection high energy electron diffraction, thin film x-ray diffraction, and plan-view and cross-sectional transmission electron microscopy indicates that the films are well textured with Cu(001)∥ Si(001) and Cu[100]∥ Si[110]. Interestingly, it is found that a distribution of orientations occurs at the early stages of Cu epitaxy on Si(001) surface, and that a (001) texture emerges gradually with increasing Cu thickness. The effect of silicide formation and deposition conditions on the crystalline quality of Cu epitaxy is also discussed.
Epitaxial Influence of Textured Conducting Metal Oxide Templates on Electrodeposited Ag(Ag3O4)2N03
Authors: Breyfogle Bryan E. , Phillips Richard J. 
Published: March 2011

ABSTRACTThe conducting oxysalt Ag(Ag3O4)2NO3 has been electrodeposited onto highly oriented conducting oxides of Tl2 03 and Pb0.8Tl0.2O1.9. T12O3 was grown in a [100] texture while the Pb0.8Tl0.2O1.9 was grown with two different thickness-dependent textures of [110] and [210]. The orientation of the Ag(Ag3O4)2NO3 crystals with respect to the substrate surface was determined by x-ray diffraction. The face-centered-cubic Ag(Ag3O4)2N03 crystals deposited on body-centered-cubic T12 03 and face-centered-cubic Pb0.8Tl0.2O1.9 followed the orientation of these prelayers. However, Ag(Ag3O4)2N03 which was electrodeposited onto polycrystalline 430 stainless steel had a nearly random orientation. The lattice mismatch is 6.6% between T12 03 and Ag(Ag3O4)2N03, and it is 7.8% between Ag(Ag3O4)2N03 and the doubled unit cell of Pb0.8Tl0.2Ol.9.
Defect Anisotropy in Movpe CdTe/GaAs
Authors: Cheng T. T. , Aindow M. , Jones I. P. , Hails J. E. , Williams D. J. , Astles M. G. 
Published: March 2011

ABSTRACTA cross-sectional TEM study of the defect structure in CdTe buffer layers grown on 2°-off (001) GaAs substrates by MOVPE is presented. The nature and distribution of defects in the buffer layers are shown to be highly anisotropic. Images obtained with the beam direction parallel to [110] show that high densities of stacking faults are present on one of the two equivalent (111} planes, whereas those obtained with the beam direction parallel to [110] show subgrain boundaries perpendicular to the interface. HREM images of the interfacial region along these two directions show a pronounced difference in the character of the misfit dislocations with b = a/2 <110>. Those with line directions parallel to [110] are all edge (90°) dislocations whilst the orthogonal set are an intimate mixture of edge and mixed character (60°) dislocations. This anisotropy is attributed to the combined effects of substrate off-cut and the formation of high aspect ratio island nuclei, giving differences in misfit accommodation.
Amplification of Misorientation of Ge Films on Si (100) During Ion-Assisted Molecular Beam Epitaxy
Authors: Tsai Cho-Jen , Atwater Harry A. 
Published: March 2011

ABSTRACTWe have observed significant increases in the misorientation of Ge films on Si (001) grown by ion-assisted molecular beam epitaxy. The misorientation between the Ge films and Si substrates was found to be a function of the ion-to-atom flux ratio and growth temperature. The parametric dependence of the misorientation on the growth conditions suggests that defects generated by low energy ion bombardment are responsible for the observed increase in misorientation. The amplification of misorientation produced by concurrent low energy ion bombardment during epitaxial growth was attributed to an increase in the fraction of misfit strain accommodated by threading dislocations.
Structural Characterization of GaP/GaAs/GaP Heterostructure by TEM
Authors: Aragón G. , Molina S. I. , García R. 
Published: March 2011

ABSTRACTThe defect structure in a GaP/GaAs/GaP heterostructure deposited on a (001) GaAs substrate with a GaAs buffer layer has been characterized by cross sectional TEM. The buffer layer presents dislocations and (α-δ)-fringe contrast parallel to (001) interface plane. HREM study reveals uniformly distributed amorphous capsules in the first GaP/GaAs buffer layer interface. The dominant defects are microtwins which are propagated into the overall heterostructure. Microtwin density is different in the GaP and GaAs layers.The different stress signs may explain the density difference.