bluuebunny/crossref_metadata_2025_split huggingface dataset:
In-situ electrical characterization of Si during nanoindentation
Authors: Bradby J. E. , Williams J. S. , Swain M. V. 
Published: April 2011

ABSTRACTA novel in-situ electrical characterization technique is used to study the deformation behavior of silicon during nanoindentation. The method involved the formation of a Schottky contact on high resistivity epitaxial Si that is converted to an ohmic contact when Si transforms from the familiar semiconducting Si-I to a metallic Si-II phase. This behavior leads to substantial changes in the current measured across the sample. The Si conductivity used (epitaxial 5 Ωcm on 6 × 10-3 Ωcm) provides particular sensitivity to the onset of a phase transformation directly under the indenter. On unloading, a reverse transformation from ohmic to Schottky contact was observed. This configuration was used to correlate the observed changes in the electronic properties with features in nanoindentation load-unload curves. The onset of the transformation to the metallic phase was observed to occur during loading using both spherical and Berkovich indenters. Interestingly, the onset of the transformation was detected before the observed discontinuity on loading (the so-called ‘pop-in’ event). This observation is consistent with our previous suggestion that the pop-in event is a result of the onset of flow of the ductile metallic phase beyond the constraint of the indenter. These changes were consistently observed after repeated indentation on the same position in the sample, indicating that small volumes of Si-III and Si-XII crystalline phases as well as amorphous Si (a-Si), which form on unloading, can transform back to the metallic Si-II phase on reloading. A strong decrease in the measured electrical current across the sample occurred as soon as the unloading cycle commenced and prior to the observation of the pop-out event. Overall, these in-situ measurements have provided much insight into pressure-induced transformation in Si under nanoindentation.
Monitoring Faceting on Ceramic Surfaces
Authors: Gilliss Shelley R. , Altay Arzu , Reisterer Jessica , Ravishankar N. , Barry Carter C. 
Published: April 2011

ABSTRACTFaceting is the transformation of a planar surface into two or more surfaces of lower energy. Metal, semiconductor and ceramic surfaces can all undergo faceting. The evolution of facets formed on the m-plane (1010) of alumina has been monitored using atomic-force microscopy (AFM). When heat-treated, the (1010) surface reconstructs into a hill-and-valley morphology. The present study investigates the manner in which facets originally form and grow to cover a surface. A gravity-loaded indenter (load of 25 grams) was used to mark a 25 μm × 25 μm square area on as-received, polished alumina specimens. An initial heat-treatment of 1400°C for 10 minutes is carried out to initiate faceting. With the indents as guides the same area can be identified and imaged after each subsequent heat-treatment. The morphology of the facets can be described as being comprised of a “simple” and “complex” surface. The simple surface corresponds to the (1102) plane which is stable over the course of heat treatments, whereas the complex surface gradually transforms to a lower energy surface after several heat treatments and acts as a nucleation site for new facet growth.
“Incompressible” pore effect on the mechanical behavior of Low-K dielectric films
Authors: Volinsky Alex A. , Palacio Manuel-Luis B. , Gerberich William W. 
Published: April 2011

ABSTRACTNew Low-K dielectric constant materials development is underway. Introducing porosity is one of the ways to lower the dielectric constant. Those are typically spin coated organic filled glasses. The pore size is on the order of a several nanometers and pore introduction compromises mechanical properties of low-K thin films, especially fracture toughness, as these materials are typically brittle.In our previous studies we have evaluated different low-K dielectric constant materials in terms of their mechanical properties using nanoindentation. It was interesting to see that for a large range of various porous low-K materials the modulus-to-hardness ratio was constant. It was also found that the indenter contact is mostly elastic, as the loading and unloading portions of the load-displacement curve did not show any hysteresis, following indentation depth to the 3/2 power load dependence. Based on these results current analysis explains the observed constant modulus-to-hardness ratio.The paper also describes the “incompressible” pore effect. As a particle gets smaller, the yield stress increases due to the Hall-Petch effect, but for the nanometer-size particles there are also high surface energy contributions that prevent is from deforming plastically. The same approach can be applied for a nanometer size pore elastic deformation, thus we call it an “incompressible” pore concept.
Influence of Average Free Volume Element Size on the Transport of Gases Through Polymers With Equivalent Total Free Volumes
Authors: Wilks Broderick R. , Chung Won J. , Ludovice Peter J. , Rezac Mary E. , Meakin Pavla , Hill Anita J. 
Published: April 2011

ABSTRACTThe permeability coefficients of gases through glassy polymers have been correlated with the fractional free volume (FFV) of the polymers. In general, polymers with high fractional free volumes have high permeabilities while those with low FFV have low permeabilities. This observation is valid for many, but not all materials. This study evaluates the impact of the average size of a free volume element on the permeability of gases through the polymer.Evaluation of the influence of average free volume element size is only possible by employing model systems in which the chemistry and the total free volume are essentially equivalent. In this study, two stereochemical forms of a methyl-substituted polynorbornene were employed. The isomers are chemically equivalent, with similar total free volumes (0.181 versus 0.188). The average defect size was probed using positron annihilation lifetime spectroscopy. The ortho-positronium lifetimes were measured and it was determined that the difference between the two isomers was approximately 10% with the lower-FFV isomer having the larger average lifetime. For simplicity, the two isomers will be termed Pd and Ni (in reference to the catalysts used in their preparation). The Pd isomer has a slightly lower FFV, but larger average defect size. The Ni isomer has a higher FFV, but smaller average defect size.Transport evaluation indicates that the Pd-isomer has gas permeabilities two to three times those of the Ni-isomer. In depth analysis indicates that the increase in permeability is a result of an increase in both the diffusivity of gases through the polymer and gas solubility.
Preparation and Characterization of Porous Collagen Membranes on Silicon
Authors: Lepak Lori A. , Richards Troy , Guillen Nancy , Caggana Michelle , Turner James N. , Spencer Michael G. 
Published: April 2011

ABSTRACTAdvances in biotechnology in the past decade have raised the possibility of fabricating biocompatible, porous membranes for molecular sieving and dialysis separations of particles sized 20–50 nm or less. As a prerequisite for such applications, we demonstrate that thin films (∼ 400 nm) of monomeric bovine dermal collagen spin-deposited on a silicon substrate are patternable using standard semiconductor microlithographic processing techniques. Patterning via liftoff has reliably produced square features as small as 10–25 μm laterally, and 50 nm thick, in initial experiments.HVEM (high vacuum electron microscope) images of these collagen membranes have revealed typical pore sizes ranging from 1–100 nm. Through-membrane diffusion of chromophores spanning this size range was quantified via UV/vis spectrometry. These studies revealed that a 400 nm thick collagen membrane crosslinked with 0.02% glutaraldehyde rejected detectable quantities of methyl orange dye (MW 327) for at least 48 hours, while a 100 nm thick layer admitted methyl orange in under 30 minutes. DNA has been demonstrated to pass through a 100 nm thick collagen layer more slowly than through a bare through-etched control wafer.
Ordered 3D Hexagonal Mesoporous Silica Membranes: Synthesis and Characterization
Authors: Klotz Michaela , Besson Sophie , Ricolleau Christian , Bosc Florence , Ayral André 
Published: April 2011

ABSTRACTA ceramic membrane with an ordered mesoporous top layer has been developed. The active layer possesses a close-packed hexagonal network of spherical pores. Results on permeation of helium and argon through the membrane are presented and correlated with the structural and textural properties of the top layer. New insights are given on the porosity of this close-packed hexagonal structure.
Fibrin Free and Aqueous Humor Penetration Modified Membrane With ArF Excimer Laser for Glaucoma Implant
Authors: Sato Yuji , Parel Jean. Marie , Murahara Masataka 
Published: April 2011

ABSTRACTThe hydrophilic group was substituted with separation distance of 100μm in a porous poly-tetrafluoroethylene (PTFE) membrane by ArF laser irradiation. With the micro domain structure of hydrophilic and hydrophobic groups in the porous PTFE, the membrane was modified to be fibrin and fat- free. Furthermore, the differential osmotic pressure was controlled freely by changing the density of the hydrophilic group into the porous PTFE. As a result, we developed the glaucoma implant membrane that is free from fibrin and fat and inhibits the graft rejection in the human body.
Electric Field Mediated Ion Transport Through Charged Mesoporous Membranes
Authors: Schmuhl Riaan , Samuel de Lint W. B. , Keizer Klaas , van den Berg Albert , ten Elshof Johan E. 
Published: April 2011

ABSTRACTThe transport of ions from aqueous solutions through a stacked Au/α-Al2O3/γ-Al2O3/Au membrane under the influence of a dc potential difference is reported. The membrane shows high cation permselectivity at ionic strengths of ∼10-3 M at pH 4.3–6.5, which is associated with a combination of anion adsorption and double-layer overlap inside the pores of the γ-alumina layer. The cation flux can be controlled by ionic strength, dc potential difference and pH.
Exploring specimen size effects in plastic deformation of Ni3(Al, Ta)
Authors: Uchic Michael D. , Dimiduk Dennis M. , Florando Jeffrey N. , Nix William D. 
Published: April 2011

ABSTRACTIn this paper we present a mechanical test methodology to explore specimen size effects in Ni3Al, where the overall test sample dimensions artificially limit the volume for substructure evolution and hence the availability of jogs/kinks along individual dislocation lines. The test methodology consists of using Focused Ion Beam milling to micromachine cylindrical compression samples that have diameters ranging from 5 to 20 microns into the surface of a bulk sample, which is followed by nanoindentation using a flat-ended tip to measure the mechanical properties of the microsamples in uniaxial compression. The initial test results show that there is a strong increase in the flow stress with decreasing sample size, although misfit between the flat indenter tip and the top surface of the compression samples complicates complete interpretation of the mechanical test results at this time.
Optimization of Mo-Si-B Intermetallics
Authors: Schneibel Joachim H. , Tortorelli Peter F. , Kramer Matthew J. , Thom Andrew J. , Kruzic Jamie J. , Ritchie Robert O. 
Published: April 2011

ABSTRACTMo-Si-B intermetallics consisting of the phases Mo3Si, Mo5SiB2, and α-Mo (Mo solid solution) can be designed to exhibit some degree of oxidation resistance, fracture toughness, and creep strength, but not necessarily all of these at the same time. For example, microstructures that enhance the oxidation resistance are typically associated with low fracture toughness. Examples will be given illustrating the oxidation resistance, fracture toughness, and creep strength of Mo-Si-B intermetallics as a function of their phase volume fractions as well as the topology and length scale of their microstructures. Microstructures containing either individual α-Mo particles or a continuous α-Mo matrix will be described. The examples provide possible ways to control the composition and microstructure of Mo-Si-B alloys such as to optimize the desired balance of properties.
Microscopic and Quantitative Investigations on PST Ti-Al / Ti Reaction Diffusion Couples
Authors: Pan Ling , Luzzi David E. 
Published: April 2011

ABSTRACTInterdiffusion in multi-phase diffusion couples of polycrystalline Ti and polysynthetically twinned (PST) Ti-49.3 at.% Al, with the diffusion direction parallel to the lamellar planes, is investigated in the temperature range 973 – 1173 K. A reaction zone (RZ) of the a2-Ti3Al phase forms between the end materials and exhibits deeper penetration in the a2 lamellae than in the primary g lamellae. The mass balance and the lamellar thickness across the RZ / PST interface are believed to be the major factors that lead to the different behaviors in the penetration depth of the RZ. Direct measurements of the RZ thickness reveal a parabolic growth of the RZ, indicating a diffusion-controlled growth macroscopically. Concentration profiles from the Ti, through the RZ, into the PST g and a2 lamellae are measured by x-ray spectroscopy in a transmission electron microscope. Deviations from a diffusion-controlled composition profile indicate some extent of interface-controlled growth. Plateaus are seen in the concentration profiles in the RZ adjacent to the RZ/PST interface, extending through most of the deeply penetrated well region. The interfacial energy and strain energy are possible reasons for the plateaus. The interdiffusion coefficients are found to be largely independent of composition with a temperature dependence that obeys the Arrhenius relationship.
Numerical Simulations of Coarsening of Lamellar Structures: Applications to metallic alloys
Authors: El-Khozondar Rifa J. , El-Khozondar Hala J. 
Published: April 2011

ABSTRACTUnderstanding the microstructural evolution in metallic alloys helps to control their properties and improve their performance in industrial applications. The emphasis of our study is the coarsening mechanisms of lamellar structures.Coarsening of lamellar structure is modeled numerically using Monte Carlo Potts method. The initial microstructure consists of alternating lamellae of phase A and phase B with the spacing proportional to their volume fraction. Faults are introduced to the lamellae to induce instability in the system. We find that an isotropic lamellar structure degenerates via edge spheroidization and termination migration into nearly equiaxed grains with a diameter which is 2 to 3 times larger than the original lamellar spacing. The duration of this process is comparable with the time it would take Ostwald ripening to produce grains of the same size. Eventually grain growth reaches the asymptotic regime of coarsening described by a power-law function of time. Lamellae with anisotropic grain boundaries coarsen more slowly and via discontinuous coarsening mechanism. This produces larger grains upon degeneration of lamellae. Discontinuous coarsening was observed in lamellar alloys as well as termination migration.
Effect of Antiphase Domain Boundaries on Prism Slip in Ti3Al Single Crystals
Authors: Koizumi Y. , Minamino Y. , Tsuji N. , Nakano T. , Umakoshi Y. 
Published: April 2011

ABSTRACTEffect of antiphase domain boundaries (APDBs) on yielding and dislocation structure were investigated in Ti3Al single crystals oriented for prism slip. The yield stress greatly depended on the size of antiphase domains (APDs). The yield stress of Ti3Al with the average APD size of 35nm was about six times higher than that of Ti3Al without APDB. Single dislocations (isolated superpartial dislocations) were observed in the deformed Ti3Al single crystal with APD sizes smaller than 100nm, while superdislocation pairs were observed in those with larger APDs. The mechanism of the interaction between the prism dislocations and APDBs is discussed.
Nanoporous Behavior Induced by Excess Vacancy Clustering in Rapidly-Solidified B2 FeAl Ribbons
Authors: Haraguchi Tomohide , Yoshimi Kyosuke , Yoo Man H. , Kato Hidemi , Hanada Shuji , Inoue Akihisa 
Published: April 2011

ABSTRACTRapidly solidified ribbons of B2-ordered Fe-40, 45 and 50mol%Al were produced by a conventional single-roll melt-spinning method. The lattice parameters of as-spun ribbons are fully restored by annealing at 723 K for 24 h. This suggests that large numbers of supersaturated thermal vacancies are removed by the heat treatment. After the heat treatment, it is found that clustering of the supersaturated vacancies leads to a large number of pores that have a few hundreds nm or less in diameter near the surfaces, thus creating nanoporous surfaces. DSC measurements show irreversible exothermic peaks due to vacancy clustering. Vacancy complexes such as dislocations and pores are also observed inside the ribbons by TEM. The volume fraction of the overall vacancy complexes shows Al concentration dependence, demonstrating that defect structure formed by clustering of the excess vacancies is controllable by changing Al concentration in rapidly solidified FeAl ribbons.
Effect of Additives on the Phase Equilibria Related to the E21-Fe3AlC Intermetalic Compound with Carbon Atom at the Interstitial Site
Authors: Ishii Hiroaki , Miura Seiji , Mohri Tetsuo 
Published: April 2011

ABSTRACTThe structure of E21 is a derivative of L12 structure with an interstitial carbon in the body center or the octahedral interstitial site. In the Fe-Al-C ternary system E21-Fe3AlC intermetallic is known to precipitate in γ-austenite alloys. For the high temperature application, the stability of microstructure is a key issue and the control of the lattice misfit is essential. By adding some elements to Fe-Al-C alloys, the lattice constant can be controlled, and enhancement of the stability of γ-austenite + E21-Fe3AlC two phase structure is expected. In this study, phase stability and lattice parameter of E21 phase in the (Fe-Mn)-(Al-M)-C system (M=Si, Ge) are investigated. In both systems, no significant changes in microstructures were observed within the composition range of concern. The lattice constant of E21-Fe3AlC phase, however, does not show decrease with the addition of Si or Ge. This result is different from what was expected. By WDS analysis, it was revealed that Si tends to distribute mainly in γ phase, and Ge concentrates in E21-Fe3AlC phase. It was found that the lattice constants of E21 phases are very close to those of L12 structure estimated from the atomic radii of constituent elements which are evaluated from those in binary alloys and compounds. The distribution behavior of Si and Ge can be related to tolerance factor which strongly affects the stability of phases.
Plastic Deformation Behavior of Ni3X(X=Nb, Ti, Sn) Type HCP-Based Intermetallics with the Geometrically Close-Packed Structure
Authors: Hagihara Koji , Nakano Takayoshi , Umakoshi Yukichi 
Published: April 2011

ABSTBACTIn this paper, our recent results on the plastic deformation behaviors of Ni3X-type hcp-based GCP compounds, such as D0a-Ni3Nb, D019-Ni3Sn and D024-Ni3Ti, are summarized. The similarity and difference of their plastic behavior are discussed focusing on the correlation with the characteristic features of their crystal structures. The criterion for the occurrence of yield stress anomaly (YSA) by slip on the basal plane is also discussed.
Ordering and disordering in anisotropic L10-FePd
Authors: Kulovits A. , Soffa W. A. , Püschl W. , Pfeiler W. 
Published: April 2011

ABSTRACTNearly equiatomic FePd (Fe-52at.%Pd) alloys have been deformed by cold-rolling to 60% thickness reduction. Ordering and disordering was studied during isochronal and isothermal annealing by residual resistometry (REST) in the deformed as well as in the recrystallized state. In both cases a first order phase transition with a broad thermal hysteresis is observed. Resistivity values corresponding to thermal equilibrium of LRO-states, however, result lower in the deformed case. This is interpreted as a consequence of internal stresses leading to a preference of one variant of ordered domains and consequently to a higher degree of LRO.A detailed study by an isothermal small-step annealing treatment yields two counteracting exponential processes during order-order relaxation with an activation energy of 2.7eV and 2.4eV, respectively.
Phase Stability and Mechanical Properties of Ti(Ni, Ru) Alloys
Authors: Tsuji Masahiro , Hosoda Hideki , Wakashima Kenji , Yamabe-Mitarai Yoko 
Published: April 2011

ABSTRACTEffects of ruthenium (Ru) substitution on constituent phases, phase transformation temperatures and mechanical properties were investigated for Ti-Ni shape memory alloys. Ti50Ni50-XRuX alloys with Ru contents (X) from 0mol% (binary TiNi) to 50mol% (binary TiRu) were systematically prepared by Ar arc-melting followed by hot-forging at temperatures from 1173K to 1673K depending on chemical composition. Phase stability was assessed by DSC (differential scanning calorimetry), XRD (X-ray diffractometry) and TEM (transmission electron microscopy). Mechanical properties were investigated using hardness and tensile tests at room temperature. With increasing Ru content, it was found that the lattice parameter of B2 phase increases, the martensitic transformation temperature slightly decreases, and the melting temperature increases monotonously. Besides, R-phase appears for Ti-Ni alloys containing 3mol% and 20mol%Ru but no diffusionless phase transformation is seen in Ti-Ni alloy containing 5mol%Ru. Vickers hardness shows the maximum at an intermediate composition (HV1030 at 30mol%Ru); this suggests that large solid solution hardening is caused by Ru substitution for the Ni-sites in TiNi.
The Influence of Irradiation Parameters on the Behavior of Martensitic Titanium Nickel Thin Films
Authors: LaGrange Thomas B. , Grummon David S. , Gotthardt Rolf 
Published: April 2011

ABSTRACTIn view of a planar processing technique to develop a micro-actuator, irradiation experiments on plastically deformed martensitic TiNi thin films were performed using 5 MeV Ni++, with various fluences and temperatures, to study the dependence of microstructure and transformation characteristics on irradiation parameters. TEM observation and X-ray diffraction spectra show that irradiation resulted in a sharply defined continuous amorphous matrix, extending to the projected ion range, that contained both monoclinic and body centered cubic nanocrystals. The irradiation mechanisms and films' temperature-displacement are discussed in terms of the observed microstructure.
Crystal Structure and Morphology of Hydrogen Absorbing Alloys with BCC Structure
Authors: E. Akiba , H. Enoki , Y. Nakamura 
Published: April 2011

ABSTRACTHydrogen absorbing alloys with BCC (body centered cubic) structure such as Ti-V-Mn, Ti-V-Cr and Ti-V-Cr-Mn systems were proposed and named as “Laves phase related BCC solid solution” by Akiba in 1993. Since our reports, many researchers have developed BCC hydrogen absorbing alloys. These alloys have higher hydrogen capacity (about 2.8 mass% at present) than conventional intermetallic compounds. Many efforts have been made to increase hydrogen capacity of the alloys but fundamental studies were a few. Crystal structure and morphology of the BCC alloys that are keys to understand BCC hydrogen absorbing alloys are reviewed.