bluuebunny/crossref_metadata_2025_split huggingface dataset:
Luminescence Properties of Pulsed Laser Deposited Eu:Y2O3 Thin Film Phosphors on Sapphire Substrates
Authors: Cho K.G. , Kumar D. , Holloway P. H. , Singh R. K. 
Published: April 2011

AbstractEu:Y2O3 phosphor films were deposited on (0001) sapphire substrates using 248 nm KrF pulse laser to investigate microstructure-property correlations. A slow film growth (60 nm/min) process results in predominantly (222) orientation while a fast film growth (170 nm/min) process results in predominantly (400) orientation of Eu:Y2O3 film. With an increase in film thickness from 0.6μm to 1.2μm, a 300% increase in brightness has been achieved from Eu:Y2O3 films. An increase in substrate temperature during deposition from 700°C to 800°C resulted in ~40% brighter films. Improvement in brightness from Eu:Y2O3 films with the film thickness may be attributed to an increase in roughness while that from substrate temperature may be attributed to a combined effect of increased roughness and improved crystallinity.
Vacancy Mobility in Nickel Aluminide Versus Composition
Authors: Bai Bin , Fan Jiawen , Collins Gary S. 
Published: April 2011

ABSTRACTThe fractional concentration of Ni-vacancies in NiAl at high temperature has been determined for compositions between 50 and 53 at.% Ni from measurements using perturbed angular correlation of gamma rays (PAC). The vacancies were detected by quadrupole interactions induced at nearby 111In/Cd impurity probes present on the Al sublattice in high dilution. One set of measurements was made at high temperature. A second set made after rapid quenching exhibited an enhancement of Ni-vacancy site fractions that is attributed to diffusion and trapping of vacancies during quenching. The composition dependence of the enhancement was analyzed assuming that the enhancement is proportional to the root-mean-square diffusion length during quenching. The experimental dependence on composition is found to be consistent with bulk diffusion data. The methodology developed clarifies how local environments of impurity probes are modified during rapid quenching. In addition, it is shown that there is an enormous increase in the mobility of vacancies with increasing deviation of the composition from stoichiometry. Diffusion mechanisms that can explain the data trends are discussed.
Determination of the thermodynamic factor for the B2 FeAl phase from X-ray diffuse scattering data
Authors: Liubich Vlad , Dorfman Simon , Fuks David , Mehrert Helmut 
Published: April 2011

ABSTRACTThe interdiffusion coefficient is related via the modified Darken equation to the tracer diffusivities of the constituents. The thermodynamic factor Φ entering the Darken equation for the interdiffusion coefficient is expressed in terms of the energy parameters which describe the ordering process in the binary alloy. Our calculations for Fe-Al alloys yield the dependence of Φ on the long-range order parameter. These calculations are performed with the parameters extracted from diffuse X-ray scattering data on FeAl.
Properties of Iron Atoms at Grain Boundaries in Fe and Fe72Al28
Authors: Schneeweiss O. , Turek I. , Čermák J. , Lejček P. 
Published: April 2011

ABSTRACTLocation of diffused 57Co atoms in single crystals, bicrystals and polycrystals of pure iron and Fe72Al28alloy were investigated by means of emission Mössbauer spectroscopy. To interpret the results, first principles calculations of iron atom magnetic moments and hyper-fine field were carried out. From comparison of M6ssbauer spectra of single crystals with those of bicrystals and polycrystals, an information about grain boundary positions occupied by diffusing atoms is obtained. It is shown that about 5% of the diffusing atoms at the {112} grain boundary of iron are located at the positions either having impurity atoms in the nearest neighbourhood or characterized by larger atomic spacing in comparison with the bulk. In the Fe72Al28 a dominating portion of diffusing atoms have different surrounding than in grain volume. An enrichment of grain boundaries by aluminum could explain their hyperfine parameters.
Defect formation at internal interfaces and grain boundaries of cold-rolled Fe and Ni during heavy ion irradiation
Authors: Aggarwal G. , Sen P. 
Published: April 2011

ABSTRACTInstabilities arise out of dynamic events and can lead to nonequilibrium (self-organization) processes. Ion irradiation is by nature a nonequilibrium process and hence formation of structures, metastable or otherwise is to be expected. Recently, it has been theoretically predicted that metals under ion irradiation can lead to dissipative structure formation arising out of radiation damage and their subsequent annealing. The possibility of direct observation of such structures in metals, under irradiation, is however reduced due to nonavailability of a large concentration of defects (mainly point defects) at any point of time. In this experimental presentation we show that this can be overcome through the involvement of microstructural imperfections which rearrange during irradiation. Employing microstructurally impure specimens of Fe and Ni, it is shown that heavy ions dissipate their electronic energy to modify atomic arrangements at the microstructure. The increased concentration of defects (atomic rearrangements), amenable to statistical decay is shown to produce structures in the 4-probe resistivity measurements which we assign to dissipative structure formation.
Diffusion in Metals, Quasicrystals, and Intermetallic Compounds
Authors: Mehrer H. , Zumkley Th. , Eggersmann M. , Galler R. , Salamon M. 
Published: April 2011

ABSTRACTIn this paper recent developments of diffusion in three related areas will be reviewed: The first part is devoted to self- and solute diffusion in metals with particular emphasis on Al. Contrary to most other metallic solvents, diffusion of transition elements in Al is anomalous in several respects: diffusion is very slow, activation enthalpies, pre-exponential factors and activation volumes are unusually high. By contrast, non-transition elements in Al show more or less normal solute diffusion behaviour. The anomalous behaviour is attributed to a strong repulsive interaction between transition metal solutes and vacancies. Ab-initio calculations could help to understand this well-documented diffusion problem in detail.In the second part very recent diffusion studies on single crystals of the Al-base quasicrystalline intermetallic compound Al-Pd-Mn will be discussed. Diffusion of Zn, Ge, Mn, Fe, Co, Pd and Au has been studied by various groups. At least in the high-temperature regime diffusion in the quasicrystal – despite some differences in detail – shows striking similarities to diffusion in Al, for which a vacancy-type mechanism is generally accepted. The activation volumes of +0.67 and +0.74 atomic volumes measured for Mn- and Zn-diffusion in Al-Pd-Mn strongly favour a vacancy mechanism as well. For the low temperature regime of Pd and Au diffusion the possibility of a phason-related mechanism is discussed.The third part deals with recent investigations of iron-aluminides and iron-silicides for which Fe self-diffusion and diffusion of selected foreign elements (Ge in Fe–Si, In and Zn in Fe–Al) has been investigated. There is no doubt that vacancies mediate the diffusion process. Within this general mechanism a number of factors like the crystal structure, the state of order, the composition, and the type of bonding have strong influence on diffusion. Such factors are discussed also in connection with results from positron annihilation and M6ssbauer spectroscopy.
Self and Impurity Diffusion in Icosahedral Al-Pd-Mn Quasicrystals
Authors: Sprengel W. , Nakajima H. , Lograsso T.A. 
Published: April 2011

ABSTRACTDiffusivities of Cr in icosahedral quasicrystals of Al-Pd-Mn system have been measured by the radioactive tracer method in combination with a precision grinding technique. The temperature dependence of the diffusivities follows the Arrhenius equation in the investigated temperature range from 850 to 1107 K. The activation energy Q = 235.5 ± 7.8 kJmol-1 and pre-exponential factor D0 = 1.2 × 10-2 m2s-1 were evaluated. The diffusion behavior is discussed in terms of a vacancy diffusion mechanism.
Self-Diffusion in Isotopically Controlled Heterostructures of Elemental and Compound Semiconductors
Authors: Bracht H. , Haller E. E. , Eberl K. , Cardona M. , Clark-Phelps R. 
Published: April 2011

ABSTRACTWe report self-diffusion studies of silicon between 855 and 1388°C in highly enriched epitaxial 28Si layers. Diffusion profiles of 30Si and 29Si are determined with high resolution secondary ion mass spectrometry (SIMS). The temperature dependence of the Si self-diffusion coefficients is accurately described with an activation enthalpy of 4.76 eV and a pre-exponential factor of 560 cm2s-1. The single activation enthalpy indicates that Si self-interstitials dominate self-diffusion over the whole temperature range investigated. Self- and interdiffusion in buried Al71GaAs/Al69GaAs/71GaAs isotope heterostructures with different Al composition is measured between 800 and 1160°C. Ga self-diffusion in AlGaAs and interdiffusion of Al and Ga at the AlGaAs/GaAs interface show that Ga diffusion decreases with increasing Al composition and that the interdiffusion coefficient depends linearly on Al concentration. Furthermore Al is found to diffuse more rapidly into GaAs than Ga diffuses in GaAs. The temperature dependence of Ga and Al diffusion in GaAs and of Ga diffusion in AlGaAs is described by a single activation enthalpy in the range of 3.6±0.1 eV, but by different pre-exponential factors. Differences found for Ga and Al diffusion in GaAs and for Ga diffusion in AlGaAs with different Al concentrations are discussed.
Ionic Conductivity Study on the New High Oxide Conducting Perovskite LaGaO3
Authors: Kiruthika G.V.M. , Varadaraju U.V. 
Published: April 2011

ABSTRACTOxide ion conductivity studies have been done on the Lanthanum Gallate based compounds. Yttrium substitution at the Ga site has been attempted to increase the unit cell size. Single phase was obtained for limited Y substituion i.e., La0.9Sr0.1Ga0.7Y0.1Mg0.2O3-x. It is found that the activation energy for the oxide ion conductivity has decreased for this composition. Based on the tolerance factor and B-site radius values, the migration energies were obtained for the LaGaO3 based perovskites. It is observed that migration energy has been significantly reduced upon substitution at the B-site. Absence of an enhancement in the conductivity with Yttrium substitution could be due to the vaccancy ordering inhibiting the oxide ion migration.
Enhancement of Ionic Diffusion by Microwave-Field-Induced Ponderomotive Forces at Physical Interfaces
Authors: Booske J. H. , Cooper R. F. , Freeman S. A. , Binger K. R. 
Published: April 2011

ABSTRACTNumerous observations have been reported in the literature of enhanced mass transport and solid-state reaction rates during microwave heating or processing of a variety of ceramic, glass, and polymer materials. Recent research reveals that these phenomena are probably the result of a previously-unknown driving force for ionic mass transport. The driving force--termed a “ponderomotive” (mass-moving) force--results from the application of intense, high-frequency electric fields near physical interfaces (e.g., free surfaces, grain boundaries). Experiments, theory, and numerical simulations all demonstrate that this driving force can influence solid state reaction kinetics by enhancing mass transport rates.
A Controlled Solid State Diffusion Process to form Cermet Anodes for Solid Oxide Fuel Cells
Authors: Tang Eric Z. , Ivey Douglas G. , Etsell Thomas H. 
Published: April 2011

ABSTRACTThe interfacing of thin film vapor deposition technologies and solid state electrochemistry has led to the recent development of polarized electrochemical vapor deposition (PEVD). In this study, PEVD was applied to deposit a thin layer of yttria stabilized zirconia (YSZ) over a porous metallic electrode to form the cermet anode of a solid oxide fuel cell (SOFC). During PEVD, oxygen ions are transported through the solid electrolyte of an SOFC under an electrical potential gradient provided by an external dc source. At the metallic electrode (anode) surface, oxygen ions react electrochemically with ZrCl4and YCl3 in the vapor phase to deposit YSZ. The growth of YSZ resembles the mechanisms illustrated in Wagner's tarnishing theory. However, modification has been made to the initial growth of YSZ at both electronically and ionically shorted paths along the metallic electrode and solid electrolyte surfaces, respectively. The initial experimental results in the present study showed that PEVD is capable of depositing a thin layer of YSZ on a porous metallic electrode to form a cermet anode. This layer not only provides a continuous ionic conducting path in the anode to reduce the overpotential loss, but also protects the metallic electrode from further sintering, vapor loss and poisoning in the harsh SOFC operating conditions.
Mobility of Self-Interstitial Clusters in FE and CU
Authors: Osetsky Yu.N. , Serra A. , Priego V. 
Published: April 2011

ABSTRACTMolecular dynamics (MD) simulation has been used to study the thermally activated mobility of clusters of self-interstitial atoms (SIAs) in Fe and Cu. Such clusters are formed in metals during irradiation with energetical particles and, according to the cascade production bias model, they play an important role in the microstructure evolution of metals under irradiation. An extensive simulation of clusters from 2 to 30 interstitials has been carried out for the temperature range ≍360-1200K using long-range interatomic pair potentials. The results show that clusters bigger than two SIAs are one-dimensionally mobile. Di-interstitials have two migration mechanisms depending on the temperature. At low temperature the mechanism is one-dimensional whereas at high temperature the probability of rotation and three-dimensional migration increases. It was found that in both metals the effective migration energy of clusters estimated via their jump frequency does not depend on the cluster size, although the cluster jump frequency decreases as the cluster size increases. The mechanism of cluster migration and problems of the treatment of one-dimensional mobility are discussed.
Simulations of Defect and Diffusion Properties in The Interstitial CU-C Solid Solutions
Authors: Ellis D.E. , Mundim K.C. , Fuks D. , Dorfman S. , Berner A. 
Published: April 2011

ABSTRACTHRSEM analyses of copper/graphite interfaces are presented, showing a narrow solid solution zone. Atomistic simulations in the framework of the Generalized Simulated Annealing approach lead to very reasonable relaxed geometries around carbon interstitials and vacancy complexes of a Cu host, and for a Cu/graphite interface. Embedded Cluster Density Functional results indicate a charge transfer of ~1 e to carbon, mostly from the first neighbor shell, in all relaxed environments studied.
Comparison of Release Profiles of Various Growth Factors from Biodegradable Carriers
Authors: Tabata Y. , Yamamoto M. , Ikada Y. 
Published: April 2011

AbstractA biodegradable hydrogel was prepared by glutaraldehyde crosslinking of acidic gelatin with an isoelectric point (IEP) of 5.0 as a carrier to release basic growth factors on the basis of polyion complexation. Basic fibroblast growth factor (bFGF), transforming growth factor β1 (TGF-β1), and bone morphogenetic protein-2 (BMP-2) were sorbed from their aqueous solution into the dried gelatin hydrogels to prepare respective growth factor-incorporating hydrogels. Under an in vitro non-degradation condition, approximately 20 % of incorporated bFGF and TGF-β1 was released from the hydrogels within initial 40 min, followed by no further release, whereas a large initial release of BMP-2 was observed. After subcutaneous implantation of the gelatin hydrogels incorporating 125I-labeled growth factor in the mouse back, the remaining radioactivity was measured to estimate the in vivo release profile of growth factors. Incorporation into gelatin hydrogels enabled bFGF and TGF-β1 to retain in the body for about 15 days and the retention period well correlated with that of the gelatin hydrogel. Taken together, it is likely that the growth factors ionically complexed with acidic gelatin were released in vivo as a result of hydrogel biodegradation. On the contrary, basic BMP-2 did not ionically interact with acidic gelatin, resulting in no sustained released by the present biodegradable carrier system.
A New Approach to Cartilage Tissue Engineering Using Human Dermal Fibroblasts Seeded on Three-Dimensional Polymer Scaffolds
Authors: Nicoll S. B. , Wedrychowska A. , Smith N. R. , Bhatnagar R. S. 
Published: April 2011

AbstractCurrent methods for correcting articular cartilage defects are limited by a scarcity of cartilage cells. Here we describe a novel method for the conversion of human dermal fibroblasts to chondrocyte-like cells and the potential application of this methodology to cartilage tissue engineering. Human neonatal foreskin fibroblasts were seeded on two-dimensional, tissue culture polystyrene (TCPS) in high density micromass cultures in the presence of staurosporine (50-200 nM), a protein kinase C (PKC) inhibitor, and lactic acid (40 mM) to induce functional hypoxia. Dermal fibroblasts were similarly cultured on three-dimensional polymer scaffolds composed of a non-woven polyglycolic acid (PGA) fiber mesh reinforced in a dilute solution of poly(L-lactic acid) (PLLA). At 24 hours, northern analysis revealed a staurosporine dose-dependent increase in aggrecan core protein expression in lactate-treated micromass cultures on TCPS, while type I collagen gene expression was virtually abolished in all cultures supplemented with staurosporine. The cells in these cultures displayed a rounded, cobblestone-shaped morphology typical of differentiated chondrocytes (most pronounced at 200 n.M staurosporine and 40 mM lactate), and were organized into nodules which stained positively with Alcian blue. When seeded on PGA/PLLA matrices under identical conditions as described for TCPS, a chondrocyte-like morphology was observed in cultures treated with lactate and staurosporine in contrast to the flattened sheets of fibroblast-like cells seen in untreated controls. Taken together, the above findings suggest that staurosporine treatment coupled with high density micromass culture in the presence of lactate induces chondrogenic differentiation in human dermal fibroblasts, and that these cells may be used in concert with three-dimensional polymer scaffolds for the repair of articular cartilage lesions.
Materials Designed to Control and Examine The Function of Single Cells
Authors: Thomas C.H. , Lhoest J.B. , Castner D.G. , Mcfarland C.D. , Healy K.E. 
Published: April 2011

AbstractStress levels imparted on a cell have been shown to alter cell organization and function, presumably as a result of morphological cues affecting cytoskeletal organization. Materials with spatially resolved surface chemistry were designed to isolate individual mammalian cells to determine the influence of projected area on cell proliferation and cytoskeletal organization. Surfaces were fabricated using a photolithographic process resulting in islands of cell binding N-(2-aminoethyl)-3-aminopropyl-trimethoxysilane (EDS) separated by a non-adhesive interpenetrating polymer network [poly acrylamide-co-ethylene glycol; P(AAm-co-EG)]. The surfaces contained over 3800 adhesive islands/cm2, allowing for isolation of single cells with projected areas ranging from 100µm2to 10,000µm2. These surfaces provide a useful tool for researching how cell morphology and mechanical forces affect cell function.
Impact of Silicon Wafer Material on Dislocation Generation in Local Oxidation
Authors: Peidous I. V. , Sundaresan R. , Quek E. , Leung Y. K. , Beh M. 
Published: April 2011

ABSTRACTCrystalline quality of locally oxidized silicon wafers has been studied. Wafers from different supply sources were found to be differently susceptible to stress-induced dislocation generation, although they had been produced to the same specification. On the basis of the analysis of a depth distribution of the dislocations, critical resolved shear stress of dislocation movement in the bulk areas of the wafers was determined. It varied from about 1.65 to 5.12 MPa and correlated positively to the surface defect density. The results show that uncontrollable variations of bulk silicon properties may significantly influence the stress-induced defect nucleation on the surface of wafers during processing.
Ultra Shallow Junction Formation by Cluster Ion Implantation
Authors: Matsuo Jiro , Aoki Takaaki , Goto Ken-ichi , Sugii Toshihiro , Yamada Isao 
Published: April 2011

ABSTRACTImplantation of B cluster ions into Si using decaborane (B10H14) has been demonstrated. SIMS measurements show that the depth distribution of boron atoms implanted with a monomer ion is exactly matched by that of boron atoms implanted from decaborane ions, if the cluster ion has an order of magnitude larger acceleration energy. According to the Langmuir-Child equation, two orders of magnitude larger space-charge limited ion beam current is possible when decaborane ions are used. Implanted boron atoms from decaborane ions are electrically activated after annealing. Junction depth of the implanted layer with 3 keV decaborane ions is approximately 20nm after annealing at 900°C. Molecular dynamic caluculations show that implantation efficency of boron monomer ions and decaborane ions are the same. However, the number of displaced silicon atoms per implanted boron atom from a decaborane ion impact is 4 times larger than that by boron monomer impact so that a heavily damaged region is created near the impact zone by decaborane ion penetration.
Formation of Subthreshold Defects in Erbium Implanted Silicon
Authors: Flink C. , Mui S. , Gottschalk H. , Palm J. , Weber E. R. 
Published: April 2011

ABSTRACTIn this work we present the first quantitative approach to model subthreshold defects. Using cross-sectional Transmission Electron Microscopy (XTEM) and Convergent Beam Electron Diffraction (CBED), we studied subthreshold defects in Cz-silicon that followed a deep implantation of erbium, and their interaction with co-implantations. The analyzed Frank loops show an increasing size by a factor of five with increasing depth in the wafer. The ratios of the number of condensed silicon atoms to the implant doses support a “+0.4 model” for the erbium and a “+0.07 model” for the oxygen as a co-implant. Our results indicate that a “push away” mechanism produces the excess silicon atoms in the case of interstitial implant atoms. The observed loop size depth distributions helped to reveal the condensation mechanism of subthreshold defects. This mechanism is described by the relaxation of excess silicon atoms on primary defect clusters. The decreasing concentration profiles of the primary defect clusters together with the high diffusivity of silicon interstitials results in a number of condensed silicon atoms per loop that increases with the depth in the wafer.