bluuebunny/crossref_metadata_2025_split huggingface dataset:
Agglomerate-Free Silica-Tin Oxide Particles
Authors: Gellermann Carsten , Wolter Herbert , Storch Werner 
Published: April 2011

ABSTRACTMonodisperse silica-tin oxide particles of the core-shell type were prepared via a sol-gel process without formation of agglomerates. After synthesis of silica cores the surface was coated with tin oxide by controlled hydrolysis and condensation of tin(IV) tertiary butoxide. Particle properties were characterized by electron microscopy, dynamic light scattering, N2-sorption (BET), zeta potential and X-ray fluorescence analysis. As a consequence of the variable content of tin oxide numerous possible applications arise, for example introducing X-ray opacity in dental filling materials. In order to use such particles as fillers, an additional surface functionalization with 3-methacryloxypropyltrimethoxysilane was created matching the C=C-functional groups of the polymer resins, e.g. ORMOCER*s. Characterization methods such as diffuse reflectance infrared Fourier transform spectroscopy and elemental analysis were used to confirm the surface coverage.
Electrically Assisted Aerosol Reactors using Ring Electrodes
Authors: Briesen H. , Fuhrmann A. , Pratsinis S. E. 
Published: April 2011

ABSTRACTNanostructured materials have distinctly different properties than the bulk because the number of atoms or molecules on their surface is comparable to that inside the particles creating a number of new materials and applications. Despite this potential for nanoparticles, very few practical applications have been developed because of the current high cost of these materials ($100/lb). On the other hand, flame aerosol reactors are routinely used for inexpensive production (∼$1/lb) of submicron sized commodities such as carbon blacks, pigmentary titania, fumed silica and preforms for optical fibers in telecommunications. Flame technology can be used also for synthesis of nanoparticles with precisely controlled characteristics. In these reactors, gas mixing is used to widely control the primary particle size and crystallinity of product powders while electric fields can be used to narrowly control the primary, and aggregate particle size and crystallinity. Here the application of axial electrical fields on a silica producing flame using hexamethyldisiloxane (HMDS) as precursor is presented. Experiments varying the precursor delivery rate corresponding to total production rates of 10, 20 and 30 g/h are presented. Electric fields decreased the particle size by electrostatic dispersion and repulsion of charged particles and by the reduced particle residence time inside the flame.
Physical Characterization of Zirconium Doped Zinc Oxide Thin Firms Deposited by Spray Pyrolysis
Authors: Maldonado A. , Acosta D.R. , De La Luz Olvera M. , Castanedo R. , Torres G. , Ortega J.Cañetas , Asomoza R. 
Published: April 2011

ABSTRACTZinc oxide thin films doped with zirconium were prepared from solutions with doping material dispersed at several concentrations and using the spray pyrolysis technique.The films were deposited over sodocalcic glasses at different substrate temperatures. Effects of doping material concentration and substrate temperatures on electrical, optical, structural and morphological film properties are presented. Results show an evolution in morphology and grains size as the doping concentration is increased. Preferential growth in the (002) orientation was detected for each thin film from X ray diffractograms.
Novel Hollow Powder Porous Structures
Authors: Sypeck David J. , Parrish Phillip A. , Wadley Haydn N.G. 
Published: April 2011

ABSTRACTRecent finite element calculations [1] indicate that structures constructed from partially compacted hollow spheres exhibit a greater stiffness and strength than many other cellular structures at comparable density. It has been observed that gas atomization of metallic powders often leads to entrapment of the flow field gas [2]. The resulting hollow powders are an unwanted by-product in the sense that they lead to porosity and future sites of defect in solid parts. Here a method is developed to separate the hollow powders according to their size, shape and density. They are then consolidated to a porous structure. Examples of this are given for both a titanium alloy and a nickel-base superalloy. The compressive mechanical properties are measured and compared to those of other porous structures.
Superplastic Foaming of Titanium and Ti-6Al-4V
Authors: Dunand D. C. , Teisen J. 
Published: April 2011

ABSTRACTSolid-state foaming of metals can be achieved by hot-isostatic pressing of powders in presence of argon followed by expansion of the resulting high-pressure argon bubbles at ambient pressure and elevated temperature. This foaming technique was first demonstrated by Kearns et al. [1] for Ti-6Al-4V, but is limited by its low creep rate and ductility, which lead to early cell wall fracture. We address these issues by performing the foaming step under superplastic conditions. Rather than using microstructural superplasticity (requiring fine grains which are difficult to achieve in porous powder-metallurgy materials), we used transformation superplasticity, which occurs at all grain sizes by biasing with a deviatoric stress (from the pore pressure) of internal stresses (from the allotropic mismatch during thermal cycling about the allotropic temperature range). As compared to control experiments performed under isothermal creep conditions, superplastic foaming under temperature cycling of unalloyed titanium and alloyed Ti-6Al-4V led to a significantly higher pore volume fraction and higher foaming rate.
Lightweight Products with Metal Foam - Properties and Methods of Processing
Authors: Neugebauer R. , Brdunlich H. , Wagner U. 
Published: April 2011

ABSTRACTThe aim of future production technology is the economic application of lightweight components with improved property profiles.Demands for weight reduction made by both the automotive industry and the machine-building industry can be met through selective utilization of metal foam composite _ structures. To that end, basic investigations into material behavior and the machineability of metal foam composites are necessary.The presentation will submit an overview of the properties and processing parameters of selected composites based on an analysis of industrial requirements. The development of analytical models of the process mechanics will contribute to the creation of preconditions for a numerical simulation of selected processes. Innovative applications and the potential for future use of metal foam composites in lightweight construction will be shown as well.Finally, results from projects of the Fraunhofer-Institut für Werkzeugmaschinen und Umformtechnik together with industrial companies in Saxony will be presented.
Influence of Imperfections on Effective Properties of Cellular Solids
Authors: Grenestedt Joachim L. 
Published: April 2011

ABSTRACTThe mechanical properties of cellular solids, or solid foams, is affected by “imperfections” such as wavy distortions of cell walls, variations in cell wall thickness, non-uniform cell shape, etc. The present paper is focused mainly on elastic stiffnesses of closed cell cellular solids. A “perfect” model is first discussed and shown to predict the behavior of PVC foams well. However, this model over-estimates the stiffnesses of aluminum foams. The relatively poor properties of the aluminum foam are believed to be caused by imperfections in the cells. The main body of the paper focuses on modeling different kinds of imperfections, and analyzing their impact on foam properties.
A Continuum Plasticity Model for the Constitutive Behaviour of Foamed Metals
Authors: Miller Ronald E. , Hutchinson John W. 
Published: April 2011

ABSTRACTA yield surface is proposed that can be fit to the plastic flow properties of a broad class of solids which exhibit plastic compressibility and different yield points in tension and compression. The yield surface is proposed to describe cellular solids, including foamed metals, and designed to be fit to three simple experimental results: (1) the compressive stress-strain response (including densification), (2) the difference between the tensile and compressive yield points and (3) the degree of compressibility of the foam, as measured by the lateral expansion during a uniaxial compression test. The model is implemented using finite elements and used to study the effects of plastic compressibility on two problems: the compression of a doubly notched specimen and indentation by a spherical indenter.
Elastic Properties of Porous Structural Ceramics Produced by Plasma-Spraying
Authors: Wanner A. 
Published: April 2011

ABSTRACTThis study focuses on the relationship between porosity and elastic stiffness of structural ceramic materials produced by plasma-spraying. Mg-AI-spinel was chosen as a model material and studied in as-sprayed condition as well as upon annealing to increasingly higher temperatures up to 1650°C. The detailed analysis of the stiffness and mass density evolution offers a deep insight into the initial microstructural state of the material and into the morphological changes that occur upon heat treatment.
High Cycle Fatigue Properties of Aluminium Foams
Authors: Zettl B. E. , Stanzl-Tschegg S. E. , Gradinger R. , Degischer H. P. 
Published: April 2011

ABSTRACTFatigue lifetime measurements have been performed on foamed Al-Mg-Si wrought alloys and Al-Si cast alloys in the high cycle range using an ultrasonic resonance testing method. The porous structure of the material is described by quantitative image analysis of optical micrographs and non destructively by X-ray computer tomography. The static mechanical properties as determined by tensile, compression and bending tests in earlier studies are used for material characterisation in this paper. The evaluation of the stress strain curves is specified for porous structures to obtain the stiffness and the plateau strength. The influence of the surface skin on the mechanical properties as well as on oscillation behaviour during lifetime measurements was studied.
RTP Temperature Measurements Using Si Grating Prepared by Laser Ablation for Large Diameter Wafer Applications
Authors: Liu C. W. , Lee M. H. , Chao C. Y. , Chen C. Y. , Yang C. C. , Chang Y. 
Published: April 2011

ABSTRACTAlthough a resolution of 1 °C of the grating temperature measurements has been demonstrated in RTP process[l], the conventional etching process to fabricate gratings on large diameter wafers makes it impractical for the production purpose. We, therefore, used the laser ablation technique to fabricate such Si gratings without any lithography and etching process. To increase the sensitivity of measurements, a large-angle diffracted beam was used by optimizing the incident angle and the grating period. As a result, an improvement of sensitivity could be obtained. The Si gratings were fabricated by the interference of two high power laser beams with the wavelength of 266 nm. The grating period was determined by interference condition, and could be varied from 180 to 550 nm, which would be beneficial to increase the measurement sensitivity. HeNe laser was used as the light source to measure the thermal expansion of grating periods for the temperature measurements. The temperature measurement of Si wafer from room temperature to 800 °C was demonstrated.
Novel Applications of Rapid Thermal Chemical Vapor Deposition for Nanoscale MOSFET’s
Authors: Sturm J. C. , Yang M. , Chang C. L. , Carroll M. S. 
Published: April 2011

ABSTRACTIn this paper we examine several applications of Rapid Thermal Chemical Vapor Deposition (RTCVD) for the fabrication of sub-100 rum MOSFET's. Vertical dual-gated MOSFET’s are used as a test vehicle to implement FET's of very short channel length. To realize such devices, the ability of epitaxial Si1-x-y, GexCy layers for suppressing the thermal diffusion, transient enhanced diffusion, and oxidation enhanced diffusion of boron both in the Si1-x-y, GexCy and in nearby Si layers is very useful Novel gate electrodes deposited by RTCVD also showed the ability to greatly reduce boron penetration in ptype polycrystalline gates for p-channel FET’s.
Comparison of the Performance of Single Wafer and Batch Systems for Identical Processes
Authors: Claasen T. , Van Driel R. , Hasper A. , Radelaar S. 
Published: April 2011

ABSTRACTWe compare single wafer systems, conventional batch systems and fast ramp batch systems in terms of throughput, cycle time and cost per wafer for four different processes. Comparison is based on dynamic fab simulations done with proprietary software package. The results show that vertical furnaces are the best choice in terms of throughput and cost per wafer for those processes for which both a single wafer and a batch process exist. Fast ramp furnaces are an attractive option to conventional batch furnaces in case a shorter cycle time is needed. Single Wafer systems show a substantially lower cycle time, but a higher cost per wafer. These additional costs might be justified by short cycle times in e.g. ASIC's manufacturing and in product development.
Chemical Ordering Along the Growth Direction in Epitaxial [0002] Co1−xRux Alloy Thin Films
Authors: Ersen O. , Bouzidi L. , Pierron-Bohnes V. , Cadeville M.C. 
Published: April 2011

AbstractThe occurrence of metastable long range order (LRO) along the growth direction with a periodicity twice that of a disordered alloy is now a well established result in epitaxial hcp [0002] Co-Ru and Co-Pt alloy thin films. We first present a review of previous results obtained in Co-rich Co1−xRux alloy thin films (x = 0.25) prepared at various growth temperatures (TG) and the diffusive model developed to account for the observed behavior. This model which takes into account the competition between surface and bulk interactions and surface and bulk diffusion during the growth time reproduces the TG dependence of the LRO parameter (η) and of the lattice constants. Then we present new results on the occurrence of this LRO in Co1−xRux films for higher Ru concentrations (0.22 ≤ x ≤ 0.78) prepared at the optimal temperature for the occurrence of this LRO (570-595 K). Chemical ordering is observed over the whole explored concentration range and it is found to be in agreement with results obtained in a previous series prepared at 610 K with lower Ru content. The LRO parameter deduced from the difference in composition between two successive planes normalized with respect to the concentration of the minonty element displays a nearly symmetric dependence with concentration characterized by a maximum around x = 0.2 and a minimum around the equiatomic composition. These results are qualitatively discussed in terms of a balance between the different energetic contributions to the surface segregation that arise from the release of the elastic energy and the difference in the wetting energy of each element. The important role played by the quality of the substrate in determining the value of η is outlined.
Coarsening Simulations of Two-Dimensional Islands on Solid Surfaces
Authors: Metiu H. , Mattsson T. R. , Mills G. 
Published: April 2011

AbstractUsing simulations, we have studied the coarsening of an ensemble of atom-high two-dimensional islands on a square lattice. The parameters are chosen to represent metal-on-metal homogeneous epitaxy. We study first the elementary processes controlling coarsening: the evaporation of atoms from islands of various sizes and the migration of these islands due to material transport along their edges. The information obtained from these preliminary studies is used to produce a very efficient simulation of coarsening. This allows us to study how coarsening modifies the number of islands, the distribution of their sizes, and the positions of the islands on the surface.
Cosegregation-Induced Epitaxial Growth of Two- and Three-Dimensional Compounds on Multicomponent Alloy Surfaces
Authors: Clauberg E. , Dziakova A. , Eltester B. , Hammer L. , Hüning B. , Kottcke M. , Müller C. , Rath C. , Uebing C. , Heinz K. 
Published: April 2011

AbstractIn this contribution the cosegregation-induced epitaxial growth of two- and three-dimensional chromium nitrides on ferritic Fe-15%Cr-N(100) (CN= 30 wt-ppm) single crystal surfaces will be discussed. The two-dimensional CrN surface compound is stable between 600 and 720°C. From the (1 × 1) LEED pattern it is inferred that the surface compound is epitaxial to the bcc(100) alloy surface. XPD and LEED-IV investigations have revealed that this surface compound consists of a single CrN compound layer plus an additional subsurface chromium layer with a huge interlayer expansion between both layers. The CrN surface precipitate formed at temperaturesT< 600°C is also epitaxially arranged on the bcc(100) substrate surface. Its structure corresponds to the rocksalt structure, i.e. the structure of the well-known bulk CrN. Starting from a sputter cleaned alloy surface the growth of the epitaxial CrN surface precipitate proceeds via the two-dimensional CrN surface nitride. After completion of this two-dimensional CrN layer the nucleation and growth of the three-dimensional CrN surface precipitate takes place.
Energetics of Fullerene Clusters
Authors: Rotkin Slava V. , Suris Robert A. 
Published: April 2011

AbstractA new phenomenological model for calculation of formation energy of carbon nano-clusters of definite shape is proposed. The model uses only three energetic parameters: two first, Ec and ω5, being determined from comparison with experimental data, results of computer simulation for various carbon nano clusters, and the last one is dangling bond energy. Eb Energies of formation of carbon clusters shaped as cylinder, sphere, icosahedral polyhedra, capsule, were calculated in frame of unified phenomenological approach, which allows to judge relative energetical stability of these clusters.
The Influence of Anisotropic Grain Boundary Energy on Triple Junction Morphology and Grain Growth
Authors: King Alexander H. 
Published: April 2011

AbstractWe consider some examples of triple junction equilibration in the presence of grain boundary energy anisotropy. It is shown that the presence of one or two cusp-trapped grain boundaries can reduce the restrictions upon the dihedral angles formed with the remaining (isotropic) boundaries This allows for a reduction in the average grain boundary curvature, and thus in the driving force for grain boundary migration.
Calculation of Residual Stress in F-Doped Depressed Inner Cladding (DIC) Fiber
Authors: Park Y. W. , Oh K. , Paek U. C. , Kurkjian C. R. 
Published: April 2011

AbstractThe analytic calculation and the measurement of thermal stresses have been performed for concentric three layered structures of a fiber-core, inner, and outer cladding. Especially the effects of F-doped inner cladding on the residual stress have been parametrically studied.
Magnetosensitive Ni-Coated Optical Fibers
Authors: Biriukov A. S. , Belovolov M. I. , Bogatyrjov V. A. , Dianov E. M. , Lebedev V. F. , Sysolyatin A. A. , Khitun A. G. 
Published: April 2011

AbstractWe report, for the first time, optical fibers coated with Ni by the freezing technique. Ni-coated fibers demonstrate acceptable mechanical strength and effects related to magnetoactivity of the coating. Mechanical and optical characteristics of Ni-coated fibers along with their promising applications are discussed.
Near Defect Free GaN Substrates
Authors: Porowski S. 
Published: April 2011

AbstractThe current status of GaN crystallization under high nitrogen pressure will be presented. Both conductive and semi-insulating GaN crystals will be characterized.In particular the influence of Mg on the growth mechanisms will be discussed. The influence of Mg doping on morphology of Mg-doped crystals grown under pressure and Mg-doped homoepitaxial layers will be shown. It will be also shown that the addition of about I at.% of Mg into the solution improves significantly the structural quality of crystals reducing dislocation density at least by 3 orders of magnitude comparing to the crystals grown without an intentional doping. As it was estimated by selective wet etching and transmission electron microscopy the dislocation densities in the Mg-doped GaN is as low as 10 cm-1. The introduction of Mg also lowers the optical absorption coefficients for energies below fundamental edge by 2 to 3 orders of magnitude what is explained by disappearance of defect related states in the gap.The procedures for preparation of atomically flat epi-ready (000 1 ) surfaces without subsurface damage will be described. It will be shown that high quality homoepitaxial layers growing by monoatomic steps are possible on these substrates.
Doping of Aigan Alloys
Authors: Walle Chris G. Van de , Stampfl C. , Neugebauer J. , McCluskey M. D. , Johnson N. M. 
Published: April 2011

AbstractNitride-based device structures for electronic and optoelectronic applications usually incorporate layers of AlxGal-xN, and n- and p-type doping of these alloys is typically required. Experimental results indicate that doping efficiencies in AlxGal-xN are lower than in GaN. We address the cause of these doping difficulties, based on results from first-principles density-functional-pseudopotential calculations. For n-type doping we will discuss doping with oxygen, the most common unintentional donor, and with silicon. For oxygen, a DX transition occurs which converts the shallow donor into a negatively charged deep level. We present experimental evidence that oxygen is a DX center in AlxGal-xN for x>∼0.3. For p-type doping, we find that compensation by nitrogen vacancies becomes increasingly important as the Al content is increased. We also find that the ionization energy of the Mg acceptor increases with alloy composition x. To address the limitations on p-type doping we have performed a comprehensive investigation of alternative acceptor impurities; none of the candidates exhibits characteristics that surpass those of Mg in all respects.
Structural Study of GaN(As,P) Layers Grown on (0001) GaN by Gas Source Molecular Beam Epitaxy
Authors: Seong Tae-Yeon , Bae In-Tae , Zhao Y. , Tub C.W. 
Published: April 2011

AbstractTransmission electron microscope (TEM) and transmission electron diffraction (TED) examination has been performed to investigate microstructural properties of gas source molecular beam epitaxial GaN(As,P) layers grown on (0001) GaN/sapphire at temperatures in the range 500–760 °C. As for the GaNAs, we report the observation of ordering with a space group P3ml in the layer grown at 730 °C. The layers grown at temperatures below 600 °C are polycrystalline, whist the 730°C GaNAs layer has epitaxial relation to the GaN substrate. It is also shown that the GaNAs layers experience a structural change from a zinc-blende phase to a wurtzite phase, as the growth temperature increases. As for the GaNP, it is shown that the layers grown at temperatures ≤ 600 °C experience phase separation resulting in a mixture of GaN-rich and GaP-rich GaNP with zinc-blende structure. However, the layers grown at temperatures ≥ 730 °C are found to be binary zinc-blende GaN(P) single crystalline materials. The layers grown at temperatures ≥ 730 °C consist of two types of micro-domains, i.e., GaN(P)1 and GaN(P)11; the former having twin relation to the latter.