bluuebunny/crossref_metadata_2025 huggingface dataset:
Top Electrode Area Dependence on Displacement Property of Lead Zirconate Titanate Films Prepared by Chemical Solution Deposition Process
Authors: Iijima Takashi , Ito Sachiko , Matsuda Hirofumi
Published: April 2011

Effects on ferroelectric and piezoelectric properties of top-electrode diameter variance from 80 to 8 μm were investigated using an AFM probing system connected with a ferroelectric test system with bipolar and unipolar signals at 5 Hz. The Pt and 1.2-μm-thick PZT layers were etched off to prepare Pt top electrode etched samples or Pt/PZT stack etched samples. In the case of bipolar measurement, the top electrode diameter did not affect ferroelectric properties, while the maximum displacement of the butterfly-shaped hysteresis curve, related with piezoelectric response, increased with decreasing top-electrode diameter. On the other hand, the longitudinal piezoelectric constant, AFM d33, calculated from the strain curve slope at 5 Hz, +5 V, increased with decreasing top-electrode diameter. The average value of the Pt/PZT stack-etched AFM d33 almost equals that of Pt-etched AFM d33. Average AFM d33 of the 8-μm-diameter Pt-etched and Pt/PZT stack-etched samples are 129 and 135 pm/V, respectively.
PMN-PT thin films: Electromechanical behaviour, polarisability and microstructure
Authors: Donnelly N. J. , Catalan G. , Morros C. , Bowman R. M. , Gregg J. M. , Kighelman Zian , Damjanovic Dragan , Setter Nava
Published: April 2011

Thin film capacitor structures of Pb(Mg1/3Nb2/3)O3 (PMN) - PbTiO3 (PT) were fabricated using pulsed laser deposition (PLD) on MgO{100} substrates using (La1/2,Sr1/2)CoO3 (LSCO) as a lower electrode. Crystallographic and dielectric characterisation confirmed perovskite relaxor-like behaviour. Measurements of the electrostrictive coefficients by in-situ X-ray diffraction, piezo-response atomic force microscopy and three point bending experiments showed both Q11 and Q13 to be comparable to accepted values for single crystals. However, for a given field, the electric field-induced strain in the thin films was much less than that of single crystal. This was clearly intimately linked to poor thin film polarisability. Previous work had shown sol-gel PMN-PT films to have significantly greater permittivities than PLD films, and a TEM investigation was undertaken to see if functional differences could be related to differences in microstructure, and hence if the functional and electromechanical properties of PLD films could be improved by attempting to replicate sol-gel microstructures.
Positive Temperature Coefficient of Resistance in MOCVD (Ba0.75Sr0.25)Ti1+yO3+z Films
Authors: Saha S. , Kaufman D. Y. , Streiffer S. K. , Erck R. A. , Auciello O.
Published: April 2011

The leakage and dielectric properties of a thickness series (90–480 nm) of {100} fiber-textured MOCVD (Ba0.75Sr0.25)Ti1+yO3+z (BST) thin films on Pt/SiO2/Si were investigated. The temperature and voltage dependence of the permittivity were consistent with previous observations, where thinner films demonstrated a suppressed temperature and electric field response that transitioned to a more bulk-like response with increasing film thickness. The current-voltage characteristics showed two distinct regimes. At low fields the current displayed weak field dependence and a monotonic increase with increasing temperature. In contrast, positive temperature coefficient of resistance (PTCR) was observed in the high-field leakage current behavior. The PTCR behavior was more pronounced for thicker BST films. Factors contributing to the observed PTCR effect are outlined and contrasted with the description for bulk BaTiO3 ceramics.
Hardness and modulus of CrNx coatings
Authors: Janssen G. C. A. M. , Hoy R. , Kamminga J.-D.
Published: April 2011

Two series of CrNx coatings have been deposited in an industrial PVD set-up. It is shown that for an increased ion bombardment on the growing film the hardness (H) and Young's modulus (E) are independent on composition. For these hard coatings the elastic strain to failure or plasticity limit (H/E) is 0.11. The coating fails long before it is stretched to its plasticity limit. Deformation of the coating by 1% already leads to crack formation. It is argued that the cause of this failure is the low work of fracture of the coating combined with flaws in the coating.
Microindentation of Coarse-Grained Polycrystalline α-Brass
Authors: Zhang Nian , Xie Changjin , Tong Wei
Published: April 2011

Effects of the indent depth, the distance between the indent and the grain boundary, grain sizes, and crystallographic orientations on the microhardness of annealed coarse-grained polycrystalline α-brass were investigated using a Vickers indenter with indents much smaller than the α-brass grains (ranging from 80 μm to 550 μm). It is found that the microhardness of α-brass crystals shows a strong dependence on the indentation depth when it is smaller than 5 μm and a very weak dependence on both the distance between the indent and the grain boundary and the grain size when the indentation depth is about 5 μm and more. No significant dependence of the microhardness on the crystallographic orientations was observed in the fourteen grains of different orientations studied in this investigation.
Processing and Characterization of CVD c-BN Films and c-BN/Diamond Bilayers
Authors: Yang Tien-Syh , Cheng Jong-Bin , Wong Ming-Show
Published: April 2011

The paper reports the syntheses of c-BN films by the reaction of B2H6 and NH3 in the hydrogen and argon mixture using microwave plasma-assisted chemical vapor deposition (MPCVD). The effects of NH3/B2H6 ratios, hydrogen addition, pulsed-DC substrate-bias voltage and diamond as bufferlayer on the formation of c-BN were investigated. As-grown films are characterized by FTIR, grazing-incidence XRD, and SEM. The NH3/ B2H6 = 3 was selected to obtain a better crystallized BN films with moderate deposition rate. When the hydrogen content was at 85 vol.% in the gas mixture and the substrate bias at −200 V, the maximum c-BN content about 65 % was obtained. However, the film was easily cracked in a few hours. The film deposited at lower substrate biasing of −100 V could preserve for a few days without peeling off, although it had lower c-BN content about 40 %. Nanocrystalline diamond film, deposited from 1 vol.% CH4/Ar plasma, as bufferlayer can promote the heteroepitaxial growth of c-BN, resulting in 80 % c-BN content. The c-BN/diamond bilayer were adherent with a total thickness of 1.2 μm.
Nanoindentation induced crack morphologies in nanostructured hard thin films
Authors: Karimi A. , Santana A. E. , Cselle T. , Morstein M.
Published: April 2011

Crack formation in hard thin films and the influence of nanostructuring on nucleation and propagation of different crack types were studied using TiAlSiN-based multicomponent nitrides. Thin films of about 2 μm thickness were deposited onto tungsten carbide-cobalt substrates using cathodic arc PVD method. By rotation of samples and changing deposition parameters and chemical composition of target materials, various nanostructured thin films were obtained including: nanocomposite films made of nanocrystallites about 10–30 nm, chemically modulated layers with the bilayer thickness at the range of 10 nm, iso-structured TiAlN/TiAlSiN multilayers with variable bilayer thickness, and finally monolithic single layer with columnar structures of different size. Depth sensing nanoindentation was used to measure hardness and modulus of thin films and to activate several failure modes in order to provide an estimation of the fracture toughness and interfacial fracture energies. Morphology of cracks mainly consist of successive microcracks nucleated at the contact edge periodically under stretching tensile stress upon displacement of indenter. These cracks are almost straight, parallel to each other, regularly distributed at the contact site in fine structure films. They appear discontinuous and irregular in coarse columnar monolithic and in multilyers with larger bilayer periods. The annular cracks appear at greater loads due to tensile peaks caused by bending stresses generated from the substrate depression and coating deflection. These can be accompanied by the interface fracture and delamination. The radial cracks emanating from the corner of indenter appear in high stress films and extend to the neighbouring zones of the contact area. In addition to geometrical cracks, nanoscale cracks frequently appear around the contact area leading to the formation of small discontinuities on the load-displacement curves.
Ion-Assisted Adhesion Treatments for MoS2-Metal Alloy Solid Lubricating Coatings
Authors: Savan Alan , Spassov Vladislav , Gerbig Yvonne , Haefke Henry , Munnik Frans , Mikhailov Serguei
Published: April 2011

Adhesion layers are well-known to significantly improve the lifetime of MoS2-based solid lubricants. Typically, adhesion layers are “optimized” based on a phenomenological tests and then their deposition parameters are held fixed while the functional coating is studied. Here we examine the adhesion layer itself, while holding an MoS2 layer constant. In particular, the critical interfaces between the adhesion layer and the substrate, and between the adhesion layer and functional coating are regarded. MoS2-metal solid lubricant is chosen as the functional layer because it is a relatively brittle material whose performance is significantly affected by the quality and type of adhesion treatments. Substrate surface sputter cleaning was done by cathodic arc evaporation with different arc energies and substrate bias voltages. In addition to sputter etching of any surface oxides or other contaminants, some level of shallow implantation might be expected. The more usual surface preparation technique of argon plasma sputter etching was also used for comparison. Chromium and titanium were tested as adhesion layer materials. The adhesion layer thickness and deposition pressure were varied. Rutherford backscattering spectroscopy (RBS) and transmission electron microscopy (TEM) were used to analyze the adhesion layers and their interfaces with the substrates and with the MoS2-metal coatings. Ballon-disk tribometer sliding wear tests were made to assess changes in solid lubricant performance coming from variations in the adhesion layer. Scratch test characterizations were made to further evaluate adhesion layer performance.
Towards the Industrialization of Superhard Nanocrystalline Composites for High Speed and Dry Machining
Authors: Jilek Mojmir , Holubar Pavel , Veprek-Heijman Maritza G. J. , Veprek Stan
Published: April 2011

Novel superhard wear resistant nanocomposite coatings nc-(Ti1-xAlx)N/a-Si3N4 for advanced machining tools were developed and introduced into large scale industrial production within a relatively short time. We describe the development of the coating technology based on vacuum arc evaporation from a specially designed cylindrical cathode and, as a result of that development, the improvement of the properties and machining performance of the coatings.
Plasma-Enhanced Chemical Vapor Deposition of High Quality Cubic BN Films with an Intermediate Layer of Turbostratic BN Thinner than 3 nm
Authors: Yang Hangsheng , Iwamoto Chihiro , Yoshida Toyonobu
Published: April 2011

Cubic boron nitride (cBN) thin films were deposited on silicon wafers by low-pressure inductively coupled plasma-enhanced chemical vapor deposition (ICP-CVD). By using special substrate pre-treatment processes including positive biasing treatment in H2 plasma or 1200 K pre-heating in H2 atmosphere followed by an N2 plasma treatment, turbostratic BN (tBN) intermediate layer was revealed to directly grow on Si substrates without an initial amorphous layer. The thickness of the tBN transition layer can be reduced to less than 3 nm.
Properties of Molybdenum Nitride Thin Film Deposited by Reactive Sputter Deposition
Authors: Wang Yimin , Seok Jin W. , Lin Ray Y.
Published: April 2011

Molybdenum nitride thin film was deposited on silicon wafer with the reactive sputter deposition. γ-Mo2N thin film was obtained with nitrogen content in sputtering gas varying from 10% to 30%. An amorphous structure was observed in the thin film deposited at 50% nitrogen. Crystallinity of Mo-N thin film decreased as the total sputtering gas pressure increased. SEM examinations showed that the surface morphology of Mo-N thin films varies with the nitrogen content in the sputtering gas. The sheet resistivity of as deposited thin film increases with increasing nitrogen content in sputtering gas. The amorphous thin film deposited at 50% nitrogen survived 700°C/5min thermal annealing without obvious crystallization but failed after 800°C/5min thermal annealing, in which the crystalline γ-Mo2N and h-MoSi2 phases were observed. Sheet resistivity measurement showed a decrease in thin film resistivity with increasing thermal annealing temperatures.
Kinetic and Surface Mechanisms to Growth of Hexagonal Boron Nitride
Authors: Barreto Patrícia R. R. , Kull Alan E. , Cappelli Mark A.
Published: April 2011

A mechanism is presented for the gas-phase chemistry and surface reactions describing the growth of boron nitride films. The gas phase mechanism includes 33 species and 216 elementary reactions. Rate parameters for 117 elementary reactions were obtained from published experimental/theoretical data and those for the other 99 were determined using transition state theory. The mechanism examined here is an extension and update of a previous mechanism that contained 26 species and 67 elementary reactions. Standard reaction flux/pathway and gradient sensitivity analysis techniques are used to identify important reaction pathways. The calculations were handled through the use of the ChemKin software package. The model was applied to the growth of hexagonal boron nitride in an arcjet plasma source operating on mixture of BF3, H2 and N2. From the growth rate and experimental conditions for such reactors, this work demonstrates that species with mole fractions in the range of 1 × 10-10 − 2 × 10-4 (easily generated by gas-phase conditions) can account for the measured growth rate. A comparison of the predicted mole fractions of the gas-phase species present for the experimental residence times with those required to account for the measured film growth rates allows us to identify possible growth precursors. At the experimental settings, it is found that the residence time of the reacting species does not allow the flow to reach the chemical equilibrium, and that many radicals other than the source gases can account for the measured BN growth rate. The gas-phase is shown to be removed from thermodynamic equilibrium. For comparison, the equilibrium mole fractions were also calculated using an available equilibrium chemistry solver, STANJAN. Growth rates of 10-9 to 10-6 kg m-1 s-1 were measured for a wide range of H2, BF3 and NF3 flux. Both the finite-rate kinetics and equilibrium calculations confirm the importance of added hydrogen to facilitate boron nitride condensation from the gas phase. A simple surface mechanism with 7 steps is proposed with rate constants chosen to best fit the experimental growth kinetics. The results of the model, with surface rate coefficients determined from analogous gas-phase reactions, tuned slightly to agree with the experimental growth rates for BFx, x = 1, 2 or 3, as the rate-limiting growth precursor. It is also shown that the hydrogen atom has a great influence in the growth rate and that fluorine atom etches the hBN films.
Using of SILD technology for surface modification of SnO2 films for gas sensor applications
Authors: Korotcenkov G. , Macsanov V. , Boris Y. , Brinzari V. , Tolstoy V. , Schwank J. , Morante J.
Published: April 2011

The possibilities of SILD (successive ionic layer deposition) technology for modification of surface properties of nano-scaled SnO2 films for gas sensor applications were studied and are discussed in this article. Samples of SnO2 with thickness ranging from 30–40 nm were deposited by spray pyrolysis from SnCl4-water solutions. Nano-clusters of Pd and Ag, deposited by the SILD method were applied for surface modification. PdCl2 and AgNO3 were used as precursors for Pd and Ag deposition on the SnO2 surface.

It was found that the method of surface modification by SILD can be used for improving both the sensitivity and the rate of gas response of SnO2-based gas sensors to CO and H2. At the same time, the presence of Pd and Ag clusters on the surface of SnO2 depresses the gas response to ozone.
Thermal and Mass Balance in Reactive Thermal Processing of Nickel Aluminide Coatings on Steel Substrates
Authors: Alaeddine Tarek , Ranganathan Rajesh , Ando Teiichi , Doumanidis Charalabos C. , Wong Peter Y.
Published: April 2011

Nickel aluminide coatings were produced on steel substrates by reactive thermal processing of pre-plated precursor layers of nickel and aluminum using plasma arc as the heat source. Controlled rapid heating melted the outer aluminum layer, which then dissolved nickel to facilitate the nucleation and growth of a nickel aluminide. The resultant coating microstructures varied from a duplex or triplex structure, consisting of either NiAl3and a eutectic; Ni2Al3, NiAl3and a eutectic; to a fully monolithic Ni2Al3structure, with the latter resulting at high heat input rates and/or low heat-source traverse rates. The temperature of the reaction layer was simulated for the experimental conditions by a numerical model based on Green's function analysis. The nickel concentration at the liquid-solid interface just before any nickel aluminide nucleation was calculated by assuming local equilibrium interface conditions between the liquid layer and the fcc nickel-rich solution. The depth of nickel dissolution, which consequently determines the extent of nickel aluminide growth, was also predicted by the model. Numerical results of the nickel dissolution compared well with experimental observations.
Nanostructured DLC-Ag Composites for Biomedical Applications
Authors: Narayan R. J. , Wang H. , Tiwari A.
Published: April 2011

We have synthesized novel diamondlike carbon coatings with silver nanoparticles embedded into the DLC film. The size of silver nanoparticles that are confined into layered structures has been varied from 5 nm to 50 nm using an ingenious pulsed laser deposition technique. The size of nanoparticles was found to be remarkably uniform within 15%. We have characterized these samples using high-resolution cross-section TEM and STEM-Z contrast techniques, electron energy loss spectroscopy (EELS), Raman, nanohardness, adhesion, and biocompatibility measurements. In the STEM-Z, where the contrast is proportional to atomic number2, we have obtained the details of the atomic structure of silver particles. We have correlated the microstructure with hardness and adhesion properties. The EELS was used in conjunction with STEM-Z to obtain sp3/sp2 bonding ratio. This ratio was compared with Raman result to provide an average bulk value. The role of silver nanoparticles is surmised to provide a reservoir of electrons for antimicrobial activity on the surface, as revealed by our biocompatibility tests.
Mechanical properties of pulsed laser-deposited hydroxyapatite thin films for applications in biomedical implants
Authors: Kim Hyunbin , Vohra Yogesh K. , Lacefield William R. , Camata Renato P.
Published: April 2011

We have obtained nanostructured hydroxyapatite thin films on titanium alloy substrates by pulsed laser deposition. Deposition was carried out using a KrF excimer laser (248 nm) with the energy density of 4 – 7 J/cm2 at substrate temperatures in the 550°C - 650°C range. The crystallinity of the coatings was probed by X-ray diffraction. Phase transitions from hydroxyapatite to other calcium phosphate compounds were observed with varying the substrate temperature during the growth process. Scanning electron microscopy revealed thin films made up of partially sintered nanoscale grains. The average size of nanoscale grains increased significantly with film thickness, suggesting a growth mechanism involving the coalescence of nanoscale grains. As the laser energy density increases, the hydroxyapatite crystallites in the coatings are oriented preferentially along the c-axis perpendicular to the substrate. Mechanical properties of the highly c-axis oriented coatings such as hardness and Young's modulus were studied by using nanoindentation technique.
In-situ electrical characterization of Si during nanoindentation
Authors: Bradby J. E. , Williams J. S. , Swain M. V.
Published: April 2011

A 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

Faceting 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

New 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.
Asymmetric membranes with controlled morphology from modified polyetheretherketone (PEEKWC): preparation and characterization.
Authors: Buonomenna M. G. , Figoli A. , Jansen J. C. , Davoli M. , Drioli E.
Published: April 2011

Asymmetric membranes were prepared from modified poly(ether ether ketone), PEEKWC, by the nonsolvent induced phase separation (NIPS) technique. The influence of the type of solvent and polymer concentration in the casting solution on the morphology, bubble point and on the gas and water transport properties of the membranes were studied.
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

The 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

Advances 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

A 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

The 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

The 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

In 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

Mo-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

Interdiffusion 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

Understanding 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

Effect 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

Rapidly 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

The 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

ABSTBACT

In 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

Nearly 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

Effects 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

In 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

Hydrogen 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.
Hydrogen Storage in Titanium-Magnesium-Nickel Mixtures
Authors: Lomness Janice K. , Hampton Michael D. , Giannuzzi Lucille A.
Published: April 2011

The hydrogen interaction properties of mechanically alloyed mixtures of Ti, Mg, and Ni have been shown to be strongly dependent on the time and energy of ball milling. Mixtures ball milled at a ball to powder ratio (by mass) of 20:1 were able to absorb 3–4 wt% hydrogen. Mixtures ball milled at a ball to powder ratio of 70:1 were able to absorb up to 11 wt% hydrogen. The dependence of hydrogen uptake on ball milling time and energy is shown to be related to the microstructural morphology of the ball milled powders. The original Mg powder particles were heavily deformed by the ball milling process and contained nano-sized inclusions of both Ti and Ni at the surface. The higher energy ball milled samples showed a more refined microstructure and a greater hydrogen capacity. In addition, there was an inverse relationship between the amount of hydrogen uptake and the size of inclusions at the surface of the particles.
Soft X-Ray Emission and Resonant Inelastic X-Ray Scattering Studies of Transition Metal Oxides.
Authors: Smith Kevin E. , McGuinness Cormac , Downes James , Ryan Philip , Fu Dongfeng , Hulbert Steven L. , Honig J.M. , Egdell Russel
Published: April 2011

This paper discusses the application of soft x-ray emission and resonant inelastic x-ray scattering as probes of the electronic structure of transition metal oxides. The results of studies on the narrow gap insulator CdO, and the Mott-Hubbard oxide Cr-doped V2O3, are reported. The O 2p valence band partial density of states for CdO has been measured, and emission due to the hybridization of the O 2p valence band states with Cd 4d shallow core level has been observed. For Cr-doped V2O3, the temperature induced metal-insulator transition in samples with 1.5% Cr was observed using soft x-ray emission, and both charge transfer and dipole forbidden d-d excitations were observed using resonant inelastic x-ray scattering.
Rules for Understanding and Designing Novel Molecule-Based Rare-Earth Magnetic Compounds
Authors: Roy Lindsay E. , Hughbanks Timothy
Published: April 2011

Results of SDFT calculations were used to construct and check features of a generally applicable qualitative approach to understanding magnetic coupling in rare-earth-rich compounds. Using fragments based on structures of metal-rich lanthanide compounds, we have investigated molecular and low-dimensional extended structures, including Gd3I6(OPH3)12, Gd6I12Co(OPH3)6, and Gd2Cl3. Open-d-shell clusters facilitate strong ferromagnetic coupling whereas in the closed-d-shell systems prefer antiferromagnetic coupling. The f-d exchange interaction, mediated by spin polarization of both filled and partially-filled metal-metal bonding orbitals, was described for the model system Gd3I6(OPH3)12n+ using basic perturbation methods. This method has been successful for predicting the magnetic ground state for models of Gd[Gd6I12Fe] and Gd2Cl3.
Synthesis of [Ca2(Co1-xCux)2O4] yCoO2 Single Crystals and Their Intrinsic Properties
Authors: Suzuki M. , Horii S. , Sano M. , Fujie K. , Otzschi K. , Shimoyama J. , Kishio K.
Published: April 2011

Thin plate-like [Ca2(Co1-xCux)2O4] y CoO2 single crystals were successfully grown by the flux method using SrCl2 solvent. The largest crystal size was approximately 3 × 3 × 0.01 mm3. The copper concentrations, x, in the crystals were found to be depending on each crystal, suggesting a certain solid-solution range of copper in the present system. The obtained crystal showed low resistivity (∼4.3mQcm) and high Seebeck coefficient (∼160μVK-1) at 300K. The crystal showed anisotropic magnetization with larger magnetization under H ∥ c. Irreversible magnetization behavior below ∼90K was also found under H ∥ c.