bluuebunny/crossref_metadata_2025_split huggingface dataset:
Deformation Microstructure Under Nanoindentations in Cu Using 3D X-Ray Structural Microscopy
Authors: Yang Wenge , Larson B. C. , Pharr G. M. , Lepienski C. P. , Ice G. E. , Budai J. D. , Tischler J. Z. , Liu Wenjun 
Published: April 2011

ABSTRACTWe have used a recently developed x-ray structural microscopy technique to make nondestructive, submicron-resolution measurements of the deformation microstructure below a 100mN maximum load Berkovich nanoindent in single crystal Cu. Direct observations of plastic deformation under the indent were obtained using a ∼0.5 μm polychromatic microbeam and diffracted beam depth profiling to make micron-resolution spatially-resolved x-ray Laue diffraction measurements. The local lattice rotations underneath the nanoindent were found to be heterogeneous in nature as revealed by geometrically necessary dislocation (GND) densities determined for positions along lines beneath a flat indent face and under the sharp Berkovich indent blade edges. Measurements of the local rotation-axes and misorientation-angles along these lines are discussed in terms of crystallographic slip systems.
Activation volume analysis of plastic deformation in fcc materials using nanoindentation
Authors: Elmustafa A. A. , Tambwe M. F. , Stone D. S. 
Published: April 2011

ABSTRACTActivation volumes for plastic deformation of fcc metals are measured using nanoindentation. Materials include bulk, polycrystalline aluminum and α-brass, and sputtered copper and nickel thin films on silicon substrates. From a hardness measurement, V* is defined as 9kBT/∂H/∂ln , where H is the hardness and is a representative strain rate beneath the indenter. Data obtained using nanoindentation are consistent with those obtained using more conventional experiments based on uniaxial loading.
Fracture Behavior of Thin Film PZT on Silicon Mems and Membranes
Authors: Olson A. L. , Skinner J. L. , Bahr D. F. , Richards C. D. , Richards R. F. 
Published: April 2011

ABSTRACTThis research focuses on identifying the fracture mechanism in thin film silicon membranes and PZT on silicon composite structures under static and dynamic loading conditions. Square silicon membranes with a 3mm side-length and thickness between 1.5 and 3.0μm, with and without 1.5μm of PZT, were pressurized to failure while laser interferometry was used to determine the maximum strain at failure. The strain at fracture of silicon membranes, initiating from the sharp corner radius inside the micromachined cavity, was improved from 0.37% to 0.8% by an isotropic etch of the sharp corner. Fracture of PZT on silicon membranes, tested at the mechanical resonant frequency suggested that fracture initiates in the blanket PZT layers under reversed bending. Etching the PZT from high strain regions along the membrane surface improved the strain at failure of the composite device by 40%.
Frictional behavior of C60 monolayer films on graphite (HOPG)
Authors: Okita S. , Matsumuro A. , Miura K. 
Published: April 2011

ABSTRACTThe frictional behavior of a C60 monolayer film between graphite substrates is studied using a homebuilt surface force apparatus. The mean frictional force from the C60 monolayers is estimated to be approximately 2mN, which is one-fifth that of C60 thin films. The C60 monolayer films exhibit a low frictional force of 2mN up to one hundred scans under a normal stress of 8MPa, which indicates that the C60 monolayer film is highly promising for use as a lubricant. Key words, C60 monolayer film, Lubrication, Mechanical properties, Micromachines
Effects of Large Load and Shear Rate Variations on the Friction of a Branched Hydrocarbon Liquid
Authors: Gourdon Delphine , Israelachvili Jacob 
Published: April 2011

ABSTRACTShear measurements were performed on mica surfaces with molecularly thin films of squalane confined between them. Squalane is a branched hydrocarbon liquid that can be in the liquid, glassy or liquid-crystalline state under confinement. The friction forces, especially the transitions between smooth and intermittent (e.g., stick-slip) sliding, were measured over a wide range of applied loads and sliding velocities. The results reveal that, depending on the conditions, qualitatively different behavior can arise in the same system. These include both abrupt and continuous transitions, short and very long transient effects, and chaotic or saw-tooth stick-slip. The differences between these branched and simpler molecules are compared, and the results are analyzed in terms of rate-and-state models traditionally used in the analysis of seismic phenomena.
Synthesis and Characterization of Magnetic Polymeric Nanospheres for Biomedical Applications
Authors: Kim D. K. , Mikhaylova M. , Toprak M. , Guyou A. , Jeong Y. K. , Muhammed M. 
Published: April 2011

ABSTRACTEntrapment of proteins in biodegradable nanospheres has been widely investigated as a technique to produce sustained release formulations for protein or anti-cancer drugs administration. Amphiphilic PLLA-mPEG diblock copolymer was prepared by ring opening polymerization (ROP) to form polymeric nanoparticles with a core-shell structure. The main encapsulation technique done is a water-in-oil-in-water (w/o/w) solvent evaporation technique. Here, protein was encapsulated using a newly developed water-in-oil emulsion-solvent diffusion technique. This technique leads to the formation of an emulsion combined with the immediate precipitation of the PLLA-mPEG. This phenomenon is caused by the diffusion of the polymer solvent to an external organic phase.
Cross-linked Chitosan and Poly(allyl amine) Thin Films
Authors: Schauer Caroline L. , Schoen Paul E. , Ligler Frances S. 
Published: April 2011

ABSTRACTThe alternation of chitin layers with various compounds allows nature to create novel materials with selective refractive properties. Various organisms employ layered materials for survival; for example, in butterflies such materials cause the apparent disappearance and reappearance during flight to evade predators. The selective light refraction is achieved through control of the thickness and index of refraction of the multiple layers. With the ultimate goal of reproducing these layers, thin single films of chitosan, the soluble form of chitin, and poly(allyl amine) have been prepared and their optical properties analyzed. Ellipsometry, reflectance IR, reflectance spectroscopy, SEM and software modeling were used to characterize these films. Possible applications for optical layered materials range from medical diagnostics to environmental monitoring.
Novel Macro and Meso Porous Materials Prepared from Miscible Polysulfone/Polyimide Blends
Authors: Ding Yong , Bikson Benjamin 
Published: April 2011

ABSTRACTNovel macro and meso porous polysulfone materials were prepared from miscible blends of polysulfones with a phenylindane containing polyimide by chemically decomposing the polyimide phase with a dilute hydrazine solution in methanol. The polyether sulfone meso porous membranes are transparent films, with uniform pore sizes in the range of 30 nm. On the other hand, bisphenol A polysulfone based porous materials are opaque with pore sizes in the range of 200 nm.
Ferrimagnetic Membranes for Separation of Paramagnetic and Diamagnetic Species
Authors: Gwak Jihye , Ayral André , Rouessac Vincent , Cot Louis , Grenier Jean-Claude , Jang Eue-Soon , Choy Jin-Ho 
Published: April 2011

ABSTRACTFor using as separative membranes based on magnetic selectivity, nanoporous ferrimagnetic membranes of maghemite (γ-Fe2O3) and cobalt ferrite (Fe2CoO4) were prepared by the sol-gel route from ferrofluid colloidal solutions. Their magnetic properties were examined by superconductor quantum interference device (SQUID), and their structures and porous textures were studied by X-ray diffraction (XRD), scanning electron microscopy (SEM) and nitrogen adsorption-desorption analyses. O2-N2 adsorption and air separation experiments were carried out in order to evidence magnetic interactions in static and dynamic conditions, respectively. A small effect of an external magnetic field on the selectivity of these membranes was observed.
Study of the effect of morphology of nanoporous carbon membranes on permselectivity
Authors: Rajagopalan Ramakrishnan , Foley Henry C. 
Published: April 2011

ABSTRACTThe present work is aimed at developing uniform nanoporous carbon membranes on porous stainless steel supports. Thin layers of polyfurfuryl alcohol are applied on the stainless steel supports using spin coating method. Nanoporous carbon is obtained by pyrolyzing polyfurfuryl alcohol films under inert atmosphere. Uniform nanoporous carbon membranes were obtained by repeated spin coating and pyrolysis of polyfurfuryl alcohol on the stainless steel supports. The morphology of the membranes was examined using Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM). It was shown that there is direct correlation between the morphology and the selectivity of the membranes. SEM and AFM show the presence of globular domains during the formation of carbon membranes. The selectivity increased with the decrease in the size of the globules. It was also shown that the annealing of the membrane affected both the morphology and the selectivity of the membrane.
Pervaporation and Vapor Permeation Characteristics of a Porous SiO2-ZrO2 Membrane for Separation of Organic Solvents/Water Mixtures
Authors: Asaeda Masashi , Tasaka Yasuhumi 
Published: April 2011

ABSTRACTThe sol-gel techniques were applied to fabricate some improved porous SiO2-ZrO2(50%) membranes for separation of organic solvents/water mixtures by pervaporation and vapor permeation methods at the normal boiling points of mixtures such as iso-propanol(IPA)/water and 1-propanol /water mixtures. The porous SiO2-ZrO2 membranes were found quite stable even at a high water content in the feed mixtures. They showed quite large pervaporation fluxes more than 450moles/(m2h) at 73mol% of IPA in the feed, for example, while the water flux for vapor phase separation at the same conditions was around 250mol/(m2h). The separation characteristics of organic chemicals/water mixtures by pervaporation and the vapor permeation methods are largely different in many points. Especially in this work separation by vapor permeation has been studied to compare with that of pervaporation taking into account the vapor-liquid equilibrium characteristics of the mixtures.
Selective Deposition of Pd on Porous Alumina Support Using Supercritical CO2
Authors: Matsukata Masahiko , Nishizuka Takashi , Sekine Yasushi , Kikuchi Eiichi 
Published: April 2011

ABSTRACTA Pd/α-Al2O3 composite membrane was prepared on a porous α-Al2O3 disk via the thermal decomposition of bis(hexafluoroacetylacetonato)Pd(II), Pd(hfac)2. Pd(hfac)2 was dissolved in supercritical CO2 at 303 K, supplied to the substrate, and thermally decomposed at 403 and 443 K. The decomposition of Pd(hfac)2 at 443 K resulted in a sufficient pore filling of substrate with Pd as well as the formation of a thin Pd top layer. The hydrogen flux through this membrane was about 1.7 times than that of a electro-less plating Pd membrane with about 20 μm thick. Hydrogen permeation was governed by the solution-diffusion mechanism which gave a high separation selectivity.
Biocompatibility of Modified Polyetheretherketone (Peek-Wc) Membranes: Human Plasma Adsorption
Authors: Bartolo Loredana De , Gugliuzza Annarosa , Cirillo Beatrice , Morelli Sabrina , Drioli Enrico 
Published: April 2011

ABSTRACTPolymeric membranes are widely used in biomedical field for bioartificial organs, medical devices and disposable clinical apparatus. Clinical utilization of blood-contacting devices requires the development of biomaterials with improved blood compatibility. The aim of this work was the exploration of a potential biocompatible membrane derived from a modified polyetheretherketone such as PEEK-WC. The surface affinity of this membrane to human plasma and plasmatic proteins such as albumin, fibrinogen and immunoglobulin G was compared to that of some commercial membranes. Changes with time of the membrane interfacial properties were evaluated by means of contact angle measurements using human protein solutions and human plasma. The extent of plasma protein adsorption on all investigated membranes was measured by comparing the behavior of the different polymer surfaces when contacting the three plasmatic proteins.
Modelling Flocculated Cell Suspensions using a Population Balance Approach: Applications to Microfiltration
Authors: Ranil Wickramasinghe S. , Han Binbing , Akeprathumchai Saengchai , Qian Xianghong 
Published: April 2011

ABSTRACTExperimental results for flocculation of yeast and CHO cells using cationic polyelectrolytes are presented. These results suggest the existence of a self-similar floc size distribution. The experimentally determined floc size distributions have been modelled using a population balance approach. For flocculated yeast suspensions, the variation of the floc volume fraction with dimensionless particle diameter is predicted by the population balance model assuming a binary fragment distribution function. However, for CHO cell flocs, the floc volume fraction is predicted using a log normal fragment distribution function. Since the efficiency of unit operations such as microfiltration may be improved by flocculation of the feed suspension characterization of the particle size distribution is of great importance.
Elastomeric and nanoporous membranes via Langmuir Blodgett transfer of cross-linked monolayers
Authors: Xu Hui , Heger Robert , Mallwitz Frank , Blankenhagel Marita , Peyratout Claire , Goedel Werner. A. 
Published: April 2011

ABSTRACTNanometer thin membranes with considerable application potential in micro mechanics and materials science can be prepared by transferring cross-linked monomolecular layers of polyisoprenes or polyisobutenes with ionic head groups from the water surface to solid substrates with holes. Especially if monolayers of low glass transition polymers are cross-linked, elastomeric membranes are obtained, which might find application in micro mechanical devices like membrane valves and pumps. Incorporation of hydrophobised colloids leads to composite membranes, which can be converted into porous membranes via removal of the colloids.
Structurally Composite Membranes of Titanium Oxide and Titanium Phosphorus Oxide for Proton Conduction at Intermediate Temperatures
Authors: Tsuru Toshinori , Yagi Yasuhito , Kinoshita Yosuke , Yoshioka Tomohisa , Asada Masashi 
Published: April 2011

ABSTRACTComposite membranes of titanium oxide and phosphorus oxide (TiP) were prepared by the sol-gel method and evaluated for use as proton conductive materials at intermediate temperatures. Titanium phosphorus oxide sol solutions were prepared by the hydrolysis of titanium isopropoxide (TTIP) using hydrochloric acid as a catalyst in isopropanol solutions, and the addition of an appropriate amount of phosphoric acid (H3PO4). A new concept for structurally composite membranes is proposed for proton conductive membranes. A composite membrane, Ti/TiP, where the pores of a porous titanium oxide layer are filled with titanium phosphorus oxide, was found to be effective for high electrical conductivity as well as mechanical strength. Electrical conductivities as high as 0.1 and 0.06 S cm−1 at 100 and 300 °C, respectively, under a partial pressure of water of 50 kPa, was achieved for the Ti/ TiP membranes.
Critical Evaluation of Macroscopic Theories for Multi-Component Diffusion in Ideal Langmuir Sorbents
Authors: Benes Nieck E. , Verweij Henk 
Published: April 2011

ABSTRACTMaterials research involves many areas for which a proper understanding of multi-component mass transport is essential. Examples include sintering and transport-limited reaction in syntheses. In addition, materials may be principally designed for direct manipulation of mass transport, as in membrane materials. Macroscopic descriptions for mass transport are available, but physical interpretation of related transport parameters is generally not straightforward and often relies on microscopic considerations. We will show that, even for diffusion in a simple ideal Langmuir type lattice, macroscopic theories should be used with caution. Differences in mobilities of dissimilar species can set off percolation behavior, causing the flux of the more mobile species to vanish. Such behavior is, for instance, observed for zeolite membranes and cannot be predicted by commonly accepted macroscopic transport theories. Correlations between successive movements of molecules cause a decrease in the self-diffusion coefficient, DS. For non-equilibrium transport it can be shown that correlation effects in most cases disappear in which case non-equilibrium transport becomes related to the component diffusion coefficient D, instead of the smaller DS.
Some Defect Types in Intermetallics and their Consequences
Authors: Cahn Robert W. 
Published: April 2011

ABSTRACTThis short introductory overview focuses on point defects and their practical implications, on antiphase domains, and also on a feature that is not always perceived as a defect – imperfect long-range order. All these defect types have consequences for mechanical behavior of various kinds; imperfect LRO also affects the superconducting behavior of A15s. Other unfamiliar defects in intermetallics, to be outlined, include ‘rattling atoms’ in certain thermoelectric materials. Geometry and dynamics of dislocations in intermetallics are left to other contributors.
Point Defect Mechanisms in Deformation and Phase Transformation of Titanium Aluminide Alloys
Authors: Appel Fritz , Paul Jonathan D.H. , Fröbel Ulrich 
Published: April 2011

ABSTRACTPoint defects in intermetallic compounds are subjected to significant constraints due to the directional bonding, long-range order and off-stoichiometric deviation of the materials. This leads to a variety of defects with distinct differences in morphology, concentration and mobility. In the present study the implications of these defect characteristics on the mechanical properties of two-phase titanium aluminide alloys will be investigated. The major areas of the study are: (i) deformation induced point defects that contribute to work hardening; (ii) dislocation locking due to the formation of defect atmospheres; (iii) transport processes involved in phase transformation and recrystallization occurring during long-term creep. The applied methods include mechanical testing, static strain aging and structural characterisation by high resolution electron microscopy.
A Revised Jogged-Screw Model For Creep Of Equiaxed γ-TiAl: Identification Of The Key Substructural Parameters.
Authors: Karthikeyan Subramanian , Viswanathan Gopal B. , Mills Michael J. 
Published: April 2011

ABSTRACTA modification of the classic jogged-screw model has been previously adopted to explain observations of 1/2[110]-type jogged-screw dislocations in equiaxed Ti-48Al under creep conditions. The aim of this study has been to verify and validate the parameters and functional dependencies that have been assumed in that model. The original solution has been reformulated to take into account the finite length of the moving jog. This is a better approximation of the tall jog. The substructural model parameters have been further investigated in light of the Finite Length Moving Line (FLML) source approximation. The original model assumes that the critical jog height (beyond which the jog is not dragged) is inversely proportional to the applied stress. By accounting for the fact that there are three competing mechanisms (jog dragging, dipole dragging, dipole bypass) possible, we can arrive at a modified critical jog height. The critical jog height was found to be more strongly stress dependent than assumed previously. The original model assumes the jog spacing to be invariant over the stress range. However, dynamic simulation using a line tension model has shown that the jog spacing is inversely proportional to the applied stress. This has also been confirmed by TEM measurements of jog spacings over a range of stresses. Taylor's expression assumed previously to provide the dependence of dislocation density on the applied stress, has now been confirmed by actual dislocation density measurements. Combining all of these parameters and dependencies, derived both from experiment and theory, leads to an excellent prediction of creep rates and stress exponents.
Creep Properties of a High Niobium Containing γ-TiAl Alloy Sheet Material
Authors: Bartels A. , Bystrzanowski S. , Gerling R. , Schimansky F.-P. , Kestler H. , Weller M. , Clemens H. 
Published: April 2011

ABSTRACTIn this study Ti-46Al-9Nb (at%) sheet material processed by a powder metallurgical route was examined. Subsequent to hot rolling the sheets were subjected to a stress-relief treatment at 1273K for 3 hours. During this heat treatment a fine-grained near gamma microstructure has been formed. 100 hours tensile creep tests under constant load were carried out at 700°C in rolling direction, transverse direction as well as 45° direction. Using the method of load changes a stress exponent of 4.1 was determined. Furthermore, the apparent activation energy was determined in the temperature range of 715 – 775°C. Both stress exponent and activation energy suggest that diffusion assisted dislocation climb is the dominant creep mode. A comparison of these results with those of so-called conventional or so-called “2nd generation” γ-TiAl based alloys, e.g. Ti-46.5Al-4(Cr,Nb,Ta,B) (at%) and Ti-47Al-4(Cr,Mn,Nb,Si,B) (at%), indicates a significantly better creep resistance and a higher activation energy of the high Nb containing alloy. Additionally, internal friction experiments were conducted in order to analyze the deformation behavior under very small strains at elevated temperatures.
Interface Structure and Energy Calculations for Carbide Precipitates in γ-TiAl
Authors: Benedek R. , Seidman D. N. , Woodward C. 
Published: April 2011

ABSTRACTTernary carbide precipitates improve the high-temperature creep strength of 2-phase TiAl alloys. The perovskite (P-type) Ti3AlC nucleates at relatively low temperatures (750 deg. C), whereas hexagonal (H-type) Ti2AlC precipitates occur at somewhat higher temperatures. Calculations are performed, based on first- principles-local-density-functional theory, of the interface structure and energy of these two carbides with a 7-TiAl matrix. Calculations are first done on coherent interfaces, and approximate corrections are then made for the effect of misfit. The perovskite is known to form needle-shaped precipitates oriented along the c-axis of the host. Our calculations yield a relatively low energy for the (100) perovskite-host interface, which is a favorable orientation owing to its low misfit, and because the terminating carbide layer for the coherent interface is pseudomorphic with the host. Predictions are given for the critical thickness for coherence and the critical nucleation size for a P-type precipitate. Calculations for interfaces of H-type platelets with the host show a much larger interface energy than that for the P-type precipitate.
Oxygen induced chemical ordering and ultrafine lamellar structure formation in a Ti-48 at. % Al alloy
Authors: Lefebvre Williams , Loiseau Annick , Menand Alain 
Published: April 2011

ABSTRACTInfluence of oxygen on the microstructure development of a Ti-48 at. % Al alloy has been investigated by means of transmission electron microscopy and 1D atom probe. Oxygen is found to significantly increase the temperature of the α → α2 chemical ordering reaction. As a consequence, above a critical oxygen content, the α → α2 transformation is substituted to the α → γm massive transformation when the Ti-48 Al alloy is quenched from the single a-phase field. In such a case, our pervious work has shown that the alloy exhibits a fully (α2 + γ) ultrafine lamellar structure. The present work gives a complete description of the ultrafine lamellar structure formation which, in opposition to the classical lamellar structure formation, involves an intragranular nucleation and growth of the γ phase within the α2 matrix.