bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Effect of Heat Treatment on the Microstructure and Properties of FeAl+Cr
Authors: Munroe P. R. , Kong C. H. 
Published: April 2011

ABSTRACTMicrostructural studies were performed on an alloy of composition Fe45Cr5Al50 heat treated at 950°C and oil-quenched and then given isothermal annealing treatments for times up to 200 hours at either 400°C or 500°C. The observed microstructures were correlated with variations in hardness during isothermal annealing. It was deduced that the thermal vacancies retained following the initial heat treatment are removed relatively rapidly from the lattice, which leads to an initial drop in hardness. However, during prolonged annealing, the coarsening of bothFeAl2 particles and a disordered a(Fe,Cr) phase leads to further softening. It was also deduced that the chromium atoms, which remain in solution, are effective solute strengtheners. The a(Fe,Cr) phase, which is coherent with the B2 matrix, appears to coarsen by a ledge growth mechanism.
A Model for the Yield Strength Anomaly in FeAl
Authors: Baker I. , George E. P. 
Published: April 2011

ABSTRACTA phenomenological model is used to explain the yield strength anomaly in FeAl. The model incorporates hardening by thermal vacancies at intermediate temperatures, and dislocation creep at elevated temperatures. Since the vacancy concentration increases exponentially with increasing temperature, the model predicts an exponential increase in strength with increasing temperature. This increasing strength is terminated by the onset of dislocation creep. The model captures the experimentally-observed strain rate dependency of the yield stress at high temperatures, and yields an activation enthalpy for vacancy formation which is in excellent agreement with a previously measured value [1].
Examination of Dislocation Structures Near Crack TIP Region of B2 NiAl Alloys
Authors: Ng B-C. , Simkin B. , Crimp M. A. 
Published: April 2011

ABSTRACTThe structure and distribution of dislocations in the region of crack tips and crack edges have been examined in single crystal stoichiometric B2 NiAl using electron channeling contrast imaging (ECCI). ECCI, which allows examination of near surface substructural crystalline defects in bulk specimens, has been carried out for undeformed as well as in-situ deformed 4-point bend specimens. Images of dislocations at crack tips and along the crack fracture surfaces have been studied. Observations have been correlated with variations in thermal treatment corresponding with brittle and toughened conditions. A higher dislocation density was observed over a larger region in front of crack tips for the toughened materials as compared to brittle material.
Practical Design of Ni3Al with High Hot Workability
Authors: Wang Yinmin , Lin Dongliang , Zhang Yun 
Published: April 2011

ABSTRACTFrom our previous work, Ni3Al polycrystals with combined addition of magnesium and silicon kept high values of compressive strain at rupture (CSR) when the strain rate rose. In order to further improve hot workability of Ni3Al, 7.9wt.% Cr was added. The compressive tests showed that 30%∼40% CSR values of the alloy had been kept in a wide temperature range of 1173K-1373K at strain rates of 10-2sec-1 and 10-2sec-1 in contrast with 15%∼25% CSR values of the alloy without Cr addition.In practical hot rolling process, at initial deformation temperature of 1373K, strain rate of 1.0 sec-1 and by controlling reduction within 10∼15% each rolling pass, Ni3Al ingots were successfully hot-rolled into polycrystals with different deformations, the maximum of which was 55%. The deformed alloys had manifestly enhanced mechanical properties shown by tensile tests.The dislocation configurations of deformed alloys have been investigated by using transmission electron microscope(TEM).
Plastic Deformation of Mo(Si,Al)2 Single Crystals with the C40 Structure
Authors: Moriwaki M. , Ito K. , Inui H. , Yamaguchi M. 
Published: April 2011

ABSTRACTThe deformation behavior of single crystals of Mo(Si,Al)2 with the C40 structure has been studied as a function of crystal orientation and Al content in the temperature range from room temperature to 1500°C in compression. Plastic flow is possible only above 1100°C for orientations where slip along <1120> on (0001) is operative and no other slip systems are observed over whole temperature range investigated. The critical resolved shear stress for basal slip decreases rapidly with increasing temperature and the Schmid law is valid. Basal slip appears to occur through a synchroshear mechanism, in which a-dislocations (b=1/3<1120>) dissociate into two synchro-partial dislocations with the identical Burgers vector(b*1/6<1120>) and each synchro-partial further dissociates into two partials on two adjacent planes.
Preparation, Structure and Mechanical Properties of RuAl and (Ru,Ni)Al Alloys
Authors: Sabariz A. L. R. , Taylor G. 
Published: April 2011

ABSTRACTThe intermetallic compound, RuAl with B2 CsCl type structure, has been shown to possess room-temperature toughness and plasticity. NiAl also forms a B2 compound and it is claimed that a pseudo-binary compound, (Ru,Ni)Al, may be formed because the difference in lattice parameter between the two binary phases is slight. In this work a study has been made of the mechanical properties of some polycrystalline compounds, across the RuAl-(Ru,Ni)Al pseudo-binary, prepared from high-purity elemental powders. Compressive yield stresses were measured between room-temperature and 900°C, and the mechanisms of plastic flow are discussed in relation to the dislocation structures observed by TEM. Hot-microhardness tests were made to provide an indication of the effect of solid-solution hardening.
The Effect of Aluminum on the Formation of Orthorhombic Plates in the Nb-Ti-Al Ternary System
Authors: Hoelzer D. T. , Ebrahimi F. 
Published: April 2011

ABSTRACTTransmission electron microscopy (TEM) was used to study the phase transformation in an alloy containing 33Ti-27Nb-40Al (at.%). The results showed that the BCC β phase was present at high temperatures, which ordered to the B2 phase, and finally was martensitically transformed to a plate microstructure during quenching. The plates possessed an orthorhombic crystal structure and a substructure that consisted of both coarse and fine anti-phase domain boundaries (APDBs). These APDBs were consistent with three sublattices that were derived from the inherited site occupancy of the B2 matrix and a subsequent disorder to order transition. The CBED analysis of the plates showed that the site occupancy of this orthorhombic phase was consistent with the Al2NbTi stoichiometry with Al occupying the 8g, Nb the 4c1, and Ti the 4c2 Wyckoff sites.
Development Of Miscible Blends From Intrapolymer Repulsive Interactions: Polycarbonate/Polystyrene Ionomers
Authors: Xie R. , Weiss R. A. 
Published: April 2011

ABSTRACTThe phase behavior of blends of zinc sulfonated polystyrene (ZnSPS) and bisphenol-A polycarbonate (PC) was studied as a function of the sulfonation level and the molecular weight of the ZnSPS ionomer. The system exhibits upper critical solution temperature (UCST) behavior. The cloud point temperatures increased with increasing ZnSPS molecular weight and decreased with increasing sulfonation level. No strong interactions between ZnSPS and PC were detected by FTIR. The composition dependence of the glass transition temperatures of the miscible blends exhibited negative deviation from linear additi vity, which is consistent with no or weak interactions between ZnSPS and PC. Miscibility is believed to arise from strong repulsive interactions between the charged and uncharged species on the ionomer chain.
Thermal Characterization of a Microlayered Polycarbonate/Polymethyl Methacrylate Composite
Authors: Hsieh Alex J. , Gutierrez Alex W. 
Published: April 2011

ABSTRACTThermal behavior of a coextruded microlayer composite with 388 alternating layers of polycarbonate and polymethyl methacrylate (PMMA) was investigated using differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA). Two distinct glass transition temperatures were observed with DSC for the coextruded composite, however both were shifted very slightly towards each other, compared to the glass transition temperatures of the pure components, indicating limited miscibility. Adhesion between the alternating microlayers appeared to be very good; delamination did not occur after the microlayer composite was subjected to a high speed impact test. Adhesion is attributed to limited miscibility since little mixing resulted from the laminar flow which was required in the coextrusion process. DMA results revealed an additional damping peak, which was not observed with DSC, at a temperature between the glass transitions of the two components. This intermediate transition peak is more sensitive to change in frequency compared to the response for the individual pure components.
Microchemical Studies of Tuyeres and Refractory Materials used by Phoenicians and Punics at Tharros (Sardinia, Italy)
Authors: Ingo G.M. , Acquaro E. , Manfred L-I. , Bultrini G. , Chiozzini G. , Veroli C. 
Published: April 2011

ABSTRACTA large amount of smelting slags, tuyeres and curved refractory materials used during pyrometallurgical activities have been found at Tharros (western-Sardinia, Italy) during an excavation stratigraphically related to the Phoenician-Punic period (VI-IV BC). The microchemical structure of the vitrified end of tuyeres and of the thick fragments of the smelting furnaces, has been studied by means of scanning electron microscopy (SEM) with energy dispersive X-ray analysis (EDS). The results indicate that these materials can be associated with an iron smelting process. Furthermore, the temperature and duration of the smelting process has been estimated from the study of vitrification process and penetration depth of vitrification of the tips of some tuyeres combined with the study of pieces of clay taken from a unverified fragment of a tuyere and subjected to different thermal treatments under reducing atmosphere.
Incipient Maya Burnt-Lime Technology: Characterization and Chronological Variations in Preclassic Plaster, Stucco and Mortar at Nakbe, Guatemala
Authors: Hansen Eric F. , Rodriguez-Navarro Carlos , Hansen Richard D. 
Published: April 2011

ABSTRACTPatterned technological behaviors in the production and use of burnt-lime products can be characterized using optical microscopy and image analysis of pétrographie thin-sections to determine the texture (supplemented by X-ray diffraction analysis). Variations in technological styles have been identified in 21 samples from the ancient Maya site of Nakbe, Petén, Guatemala dating to the Middle Preclassic (1,000 B. C. - 300 B. C.) and Late Preclassic (300 B. C. - 150 A. D.) periods. Middle Preclassic floors exhibit a chaotic texture with a highly random aggregate particle size. Late Preclassic modeled stucco or painted fragments have a well-sorted texture with a low acid-insoluble content (<2%). Load -bearing mortar dating from the early Late Preclassic has a matrix with a high acid insoluble content (>15%), the major phases being quartz (-10%) and clays (∼5%). The variations correlate both with the time of occurrence and the function of the end-product. These issues of construction methods and levels of technology contribute data to aid our understanding of cultural development in this area at a critical time when the Maya were formulating power structures.
On-Site Non-Destructive MID-IR Spectroscopy of Plastics in Museum Objects Using a Portable Ftir Spectrometer with Fiber Optic Probe
Authors: Scott Williams R. 
Published: April 2011

ABSTRACTThe easy determination of the chemical composition of the plastic components of museum objects has been identified as a critical requirement for the proper preservation and treatment of museum objects with plastic components. To date, chemical identification has been done by wet chemical spot tests applied directly on the object, or by spot tests or instrumental techniques such as IR spectroscopy on samples excised from objects. These methods are not satisfactory. Spot tests are neither comprehensive nor unambiguous, and instrumental techniques are not convenient since the instruments are generally located in analytical laboratories remote from the museum collections. This paper describes the use of a portable FTIR spectrometer with a fiber optic sampling probe to acquire mid-IR reflectance spectra from plastics in museum objects. The technique is non-destructive and is performed on-site at the museum collection. Results will be described with an emphasis on the practicalities of transporting the spectrometer and accessories, and collecting and interpreting spectra.
Principal Component Analysis of Spectral Data: A Contribution to the Knowledge of the Materials Constituting Works of Art
Authors: Bacci M. , Baronti S. , Casini A. , Lotti F. , Picollo M. , Porcinai S. 
Published: April 2011

ABSTRACTThe use of totally non-destructive techniques such as image spectroscopy for diagnosing paintings makes it possible to obtain a large amount of spectral data that provides information concerning the composition of works of art. Here, we stress how statistical treatments, such as principal component analysis (PCA), applied to 2-D data, can contribute to a better knowledge of the work of art itself and of the distribution of the materials that constitute it.Laboratory tests, as well as applications to actual paintings, will be presented and discussed.
The Evolution Process of the Ancient Chinese Yaozhou Porcelain
Authors: Leung P. L. , Hongjie Luo , Jiazhi Li , Stokes Michael J. 
Published: April 2011

ABSTRACTThe chemical composition (body and glaze) of over thirty Yaozhou porcelain fragments are determined by X-ray fluorescence (XRF) analysis. Statistical analysis of these results combined with data already published indicate that the full evolution process of Yaozhou porcelain can be divided into four stages. Each stage exhibits a characteristic composition determined by the raw materials and batch composition used to produce the porcelain bodies and glazes. Almost all of Yaozhou celadon and white ware glazes belong predominantly to the CaO-type glaze (or lime glaze), but the glazes of the Song Dynasty (A.D. 960–1280) and later periods have higher K2O content and less CaO than the earlier periods.
AB Initio Pseudopotential Calculations of Dopant Diffusion in SI
Authors: Zhu Jing 
Published: April 2011

ABSTRACTThe ab initio pseudopotential method is used to study transient-enhanced-diffusion (TED) related processes. The electronic degrees of freedom are included explicitly, together with the fully self-consistent treatment of the electron charge density. A large supercell and a fine k-point mesh are used to ensure numerical convergence. Such method has been demonstrated to give quantitative description of defect energetics. We will show that boron diffusion is significantly enhanced in the presence of the Si interstitial due to the substantial lowering of the migrational barrier through a kick-out mechanism. The resulting mobile boron can also be trapped by another substitutional boron, forming an immobile and electrically inactive two-boron pair. Similarly, carbon diffusion is also enhanced significantly due to the pairing with Si interstitiels. However, carbon binds to Si interstitials much more strongly than boron does, taking away most Si interstitials from boron at sufficiently large carbon concentration, which causes the suppression of the boron TED. We will also show that Fermi level effect plays an important role in both Si intersititial and boron diffusion.
Atomistic Model of Transient Enhanced Diffusion and Clustering of Boron In Silicon
Authors: Pelaz L. , Gilmer G. H. , Jaraiz M. , Gossmann H.-J. , Rafferty C. S. , Eaglesham D. J. , Poate J. M. 
Published: April 2011

ABSTRACTAn atomistic model for B implantation, diffusion and clustering is presented. The model embodies the usual mechanism of Si self-interstitial diffusion and B kick-out and also includes the formation of immobile precursors of B clusters prior to the onset of transient enhanced diffusion. These immobile complexes, such as BI2 (a B atom with two Si self-interstitials) form during implantation or in the very early stages of annealing, when the Si interstitial concentration is very high. They then act as nucleation centers for the formation of B-rich clusters during annealing. This model explains and predicts the behavior of B under a wide variety of implantation and annealing conditions.
Defect Reduction and Improved Device Performance using Rapid Isothermal Diffusion in Silicon
Authors: Vedula L. , Singh R. , Ratakonda D. , Rohatgi A. , Narayanan S. 
Published: April 2011

ABSTRACTQuantum photoeffects associated with photons of wavelength less than 0.8 micron lead to higher bulk and surface diffusion coefficients. We have exploited this fundamental property in designing rapid isothermal processing (RIP) systems for shallow junction formation in silicon. A detailed comparative study of diffusion, metallization and CVD with and without high energy photons has been carried out. The results show that microscopic defects, cycle time and processing temperature is lower than what can be achieved byconventional methods is realized by using photons in the ultra violet (UV) and vacuum ultra violet (VUV) spectrum.
Diffusion and Self-Gettering of Nickel in Float Zone Silicon Wafers
Authors: Gay N. , Martinuzzi S. 
Published: April 2011

ABSTRACTExternal gettering techniques trap removed impurities in regions of a semiconductor which contain defects or in which the solubility is enhanced like in phosphorus diffused layers or in Al-Si alloy. If a fast diffuser like nickel is used in place of Al to obtain an alloy or a compound close to the surface, contamination and decontamination can occur resulting of the indiffusion and removal of nickel atoms. P type FZ samples were partly covered by nickel (nickel òn part 1 and not on part 2) and then annealed at 950°C for 1h.As expected, after nickel indiffusion the diffusion length of minority carriers decreases but the values are always higher in part 1 than in part 2. Scanning infrared microscopy detects precipitates in part 2 and not in part 1. The results are explained assuming that the nickel-silicon compound formed at the surface serves as a diffusion source as well as an external self-gettering region.
Oxygen Stabilization of Damage Induced by Mev Ion Implantation
Authors: Jain Amitabh , Mercer Doug 
Published: April 2011

ABSTRACTAs devices are scaled down and their performance is enhanced, the role of oxygen in silicon remains critical. The precipitation of oxygen away from the device region leads to desirable gettering of deleterious impurities and is a useful technique. In the device region, however, oxygen has recently been shown to take part in the annealing of dopant implants and segregate to damaged regions. This may result in the stabilization of damage structures and the attraction of unwanted impurities to sensitive regions of the device. In this work we examine these phenomena and their potential impact on device performance. For example, oxygen has been observed to segregate at two positions following a 1000°C, one hour anneal of a 2 MeV, 3.5×1015/cm2phosphorus implant into CZ p-Si. The oxygen concentration is greatly enhanced above its initial level of 1018O/cm3, both in the end-of-range region and at approximately half that depth, near the peak of the predicted damage profile. Iron deliberately introduced at the surface prior to annealing, getters out strongly at these locations No significant redistribution of carbon can be detected. The results assume significance in view of the increasing use of high energy implantation for both epi-layer replacement and retrograde well formation.
Microstructure of c-BN Films Deposited by IBAD: IR and Hrem Analyses
Authors: Ilias S. , Pascallon J. , Stambouli V. , Bouchier D. , Nouet G. 
Published: April 2011

ABSTRACTThe in-depth distribution of phases in c-BN films deposited by Ion Beam Assisted Deposition (IBAD) at two different ion energy values (300 and 600 eV) was investigated using the quantitative IR transmission measurements and the HREM technique. Whatever the value of the studied ion energies, the characteristic layered morphology of c-BN film is observed including the interfacial sp2 zone between the substrate and the c-BN volume. In the case of 600 eV ion energy, this interfacial zone is less well-defined in comparison with 300 eV ion energy and the corresponding thickness is more important. Furthermore, the h-BN phase is more diluted within the c-BN film volume showing that the purest phase concentration of c-BN is found for the lowest ion energy, i.e. 300 eV.
The Spreading of a Void on a Facet During Electromigration
Authors: Chu X. , Bauer T C. L. , Mullinst T W. W. , Klinger L. M. 
Published: April 2011

ABSTRACTA void of cross sectional area A may spread perpendicular to the applied electric field Ea during electromigration because its leading surface develops a facet whose advance is limited by the supply of steps. If the facet is immobile (no step source) and the remaining surface is free to move, and if EaA is less than a threshold value, then the void assumes a stationary elongated shape dictated by a balance between capillarity and electric field. If EaA exceeds the threshold value, however, a balance is no longer possible, and the void spreads along the facet without arrest. If the facet has limited mobility, a balance is possible for all values of EaA, resulting in an elongated moving steady-state shape. The treatment simplifies the void shape as rectangular but preserves the essential features of capillarity and surface electromigration. We argue that the motion of a facet on a void along the outward normal requires defects (e.g. intersecting screw dislocations) that act as step sources since homogeneous nucleation of steps on the facet is expected to be negligible. Since voids in fine-line interconnects are often observed to be partially faceted, restricted void motion and resultant spreading which depend sensitively on crystallographic features, such as defect structure and grain orientation, may indeed limit the lifetime of fine-line interconnects in electronic devices.
Turnover of Texture in low rate Sputter-Deposited Nanocrystalline Molybdenum Films
Authors: Drüsedau Tilo P. , Klabunde Frank , Lohmann Mirko , Hempel Thomas , Bläsing Jurgen 
Published: April 2011

ABSTRACTThe crystallite size and orientation in molybdenum films prepared by magnetron sputtering at a low rate of typical 1 Å/s and a pressure of 0.45 Pa was investigated by X-ray diffraction and texture analysis. The surface topography was studied using atomic force microscopy. Increasing the film thickness from 20 nm to 3 μm, the films show a turnover from a (110) fiber texture to a (211) mosaic-like texture. In the early state of growth (20 nm thickness) the development of dome-like structures on the surface is observed. The number of these structures increases with film thickness, whereas their size is weakly influenced. The effect of texture turnover is reduced by increasing the deposition rate by a factor of six, and it is absent for samples mounted above the center of the magnetron source. The effect of texture turnover is related to the bombardment of the films with high energetic argon neutrals resulting from backscattering at the target under oblique angle and causing resputtering. Due to the narrow angular distribution of the reflected argon, bombardment of the substrate plane is inhomogeneous and only significant for regions close to the erosion zone of the magnetron.