TiAl polysynthetically twinned (PST) crystals were deformed under plane strain condition, in which the anisotropic macroscopic deformation of PST crystals is restricted with a channel die, in order to clarify the deformation behavior of TiAl/Ti3Al lamellar structure under constraint conditions. TEM analysis of deformation modes together with the Taylor analysis reveals that all TiAl orientation variants deform to yield the relaxed-constraint-type plastic strain, where three shear strain components are not zero for each TiAl variant but are macroscopically compensated to zero by the existence of twin-related TiAl lamellae at the early stage of deformation. The Taylor analysis assuming the relaxed constraint conditions is found to be adaptable for predicting the operative deformation modes in TiAl at the early stage of deformation and also for correlating quantitatively the stress-strain behavior of PST crystals under external constraint with those under the unconstraint condition.

We report transport measurements of superconducting amorphous W-based nanodeposits fabricated by focused-ion-beam-induced-deposition (FIBID) technique using W(CO)6 as the gas precursor. We have found that nanowires with width down to ˜100 nm can be grown by FIBID, maintaining the relatively high TC of �5.2 K shown by wider nanodeposits. The critical current found in these nanowires is in the range of 0.8 mA/?m2 at 2 K. At that temperature the critical field HC2 is found to be ?8 T. As previously shown by STM measurements [I. Guillam�n et al., New Journal of Physics 10, 093005 (2008)], these nanodeposits closely follow the BCS theory and are very stable under ambient conditions. All these features pave the way for a wide range of applications of these FIBID W-based nanowires in the field of Nanotechnology.

Cell encapsulation has been broadly investigated as a technology to provide immunoprotection for transplanted endocrine cells. Here we develop a new fabrication method that allows for rapid, homogenous microencapsulation of insulin-secreting cells with varying microscale geometries and asymmetrically modified surfaces. Micromolding systems were developed using polypropylene mesh, and the mesh material/surface properties associated with efficient encapsulation were identified. Cells encapsulated using these methods maintain desirable viability and preserve their ability to proliferate and secrete insulin in a glucose-responsive manner. This new cell encapsulation approach enables a practical route to an inexpensive and convenient process for the generation of cell-laden microcapsules without requiring any specialized equipment or microfabrication process.

We applied a new type of flow-through test method using micro-reactor consisting of a simple test apparatus with compact size to measurement of the dissolution rate of a Japanese type of simulated waste glass (P0798 glass). In this test method, a solution flows through a micro-channel (20 mm length, 2 mm width, 0.16 mm depth) in contact with a face of coupon shaped glass specimen, and the output solution is retrieved at certain intervals to be analyzed for determination of the glass dissolution rate. By using this test method the initial dissolution rate of glass matrix or forward dissolution rate was measured as a function of pH (3 to 11) and temperature (25°C to 90°C). The present test results indicated that the initial dissolution rate has ‘V-shaped’ pH dependence, and the effect of pH on the dissolution rate decreases with increase in temperature similar to the results measured by using the Single-pass flow-through (SPFT) method. The present test results also indicated that the dissolution of B is controlled by diffusion process and that of Si is controlled by surface reaction process.

The effects of defects caused by Cu chemical-mechanical polishing (CMP) on time-dependent dielectric breakdown (TDDB) in a damascene structure incorporating a low-k interlevel dielectric layer were investigated experimentally. Comb line capacitor structures were prepared with one of three types of defects (rough Cu surface corrosion, Cu depletion, or crevice corrosion) and stressed at 3.2 to 6.2 MV/cm at 140°C. The first two defects had an insignificant effect on the TDDB characteristics while crevice corrosion at the edges of wires significantly degraded them. Investigation of the effects of Cu oxidation during post-CMP cleaning on the TDDB characteristics revealed that the formation of a non-uniform oxide layer accompanying deionized water rinsing was due to the dissolution of Cu oxide during the post-CMP cleaning process. When a barrier metal slurry containing a soluble inhibitor was used, non-uniform oxide formation on the Cu surfaces during post-CMP cleaning degraded the TDDB characteristics. These results demonstrate the importance of uniform Cu oxidation during post-CMP cleaning for improving the TDDB characteristics.

The heat transfer coefficients of porous copper fabricated by the lost carbonate sintering (LCS) process with porosity range from 57% to 82% and pore size from 150 to 1500 μm have been experimentally determined in this study. The sample was attached to the heat plate and assembled into a forced convection system using water as the coolant. The effectiveness of the heat removal from the heat plate through the porous copper-water system was tested under different water flow rates from 0.3 to 2.0 L/min and an input heat flux of 1.3 MW/m2. Porosity has a large effect on the heat transfer performance and the optimum porosity was found to be around 62%. Pore size has a much less effect on the heat transfer performance compared to porosity. High water flow rates enhanced the heat transfer performance for all the samples.

Radiation damage effects in ceramics, e.g., nuclear waste forms, transmutation targets, and inert matrix fuels, may have important implications for the physical and chemical stability of these materials as the cumulative radiation dose increases over time. A key aspect of scientific research in this area is the ability to understand the fundamental damage mechanisms through the combination of experimental and atomistic modelling techniques. In this paper, we review some of the lessons learned from the significant body of data now available for pyrochlore-defect fluorite based materials, followed by an illustration of the advantages of working on simple compounds with well established interatomic potentials. We conclude the paper with a description of radiation damage processes in the LaxSr1-1.5xTiO3 defect perovskites, a system that includes phase transformations, short-range order effects, and complex defect behavior.

Nanocrystals of zinc oxides have demonstrated to be very important materials for several applications in many fields, particularly in catalysis. Nanocrystalline zinc peroxide (ZnO2), which is a precursor of zinc oxide (ZnO), has been prepared by means of a hydrothermal process from zinc acetate dehydrates. On the other hand, it is of great interest to have a detailed structural characterization, in order to correlate it with the catalytic properties of the synthesized material. In this work, some results are presented about the nanostructure of the prepared zinc peroxide. By using X-ray diffraction followed of a pattern refinement by the Rietveld techniques, refined average cell parameters and crystallite size were calculated and, from these refined values, crystallite morphology was simulated in an averaged manner. With the aim to get a more complete characterization, besides these results, some micrographs of the crystalline structure of ZnO2, observed by TEM, were also included in this work.

In this work, europium implanted InGaN/GaN SL with a fixed well/barrier thickness ratio grown by metal-organic chemical-vapor deposition (MOCVD) on GaN/(0001) sapphire substrate were investigated. The as-grown and Eu ion implanted InGaN/GaN SLs were annealed at different temperatures ranging from 600°C to 950°C in nitrogen ambient. The quality of the SL interfaces in undoped and implanted structures has been investigated by X-ray diffraction (XRD) at room temperature. The characteristic satellite peaks of SLs were measured for the (0002) reflection up to the second order in the symmetric Bragg geometry. The XRD simulation spectrum of the as-grown SL agrees well with the experimental results. The simulation results show x=0.06 atomic percent the InGaN well sub-layers, with thicknesses of 2.4 and 3.3 nm for single InGaN well and GaN barrier, respectively. It was observed that annealing of the undoped SL does not significantly affect the interfacial quality of the superstructure, whereas, the Eu ion implanted InGaN/GaN SL undergo partial induced degradation. Annealing the implanted SLs shows a gradual improvement of the multilayer periodicity and a reduction of the induced degradation with increasing the annealing temperature as indicated by the XRD spectra.

We have recently reported a solid-state, mass-quantity transformation from V2O5 powders to nanorods via a two-step approach [1]. In this paper we present detailed investigation of the growth process using x-ray diffraction, scanning/transmission electron microscopy and electron spin resonance. The growth of nanorods at intermediate stages has been examined. Oxidation, surface energy minimization and surface diffusion play important roles in the growth mechanism.

Oxygen potentials of (Th0.7Ce0.3)O2-x were experimentally determined by means of thermogravimetric analysis as a function of non-stoichiometry at 1173 and 1273 K. Oxygen potentials of (Th0.7Ce0.3)O2-x at each temperature increased with increase of oxygen to metal (O/M) ratio (=2-x) and steep increases of the oxygen potentials when approaching O/M ratio = 2 were observed. These characteristics are typical for non-stoichiometric fluorite-type actinide dioxides. The oxygen potentials of (Th0.7Ce0.3)O2-x were similar to those of CeOO2-x when they were plotted as a function of average Ce valence.

Electroluminescence images gained from Cu(In,Ga)Se2 mini-modules under different voltage bias conditions are investigated. The mini-modules of area 20 × 20 cm2 with 42 cells exhibit typically 10-20 localized shunts. The consequences of these shunts on the performance of the individual cells and of the entire module are analyzed quantitatively by evaluating the electroluminescence images. Our evaluation method uses the fact that the electroluminescence intensity at each position in each cell within the module depends on the actual voltage drop over the junction at this specific location. Thus, the analysis of the electroluminescence intensity allows us to reconstruct the current/voltage characteristics of all individual cells in the module. In addition, we provide first simulations using a distributed diode network model to quantitatively explain the experimental results.

We studied photoluminescent properties and luminescent decay dynamics in Si quantum dots (QDs) produced by Si implantation in SiO2, and their modification by the application of an implantation mask. Silicon quantum dots were prepared by ion implantation, followed by high temperature annealing leading to nanocrystal nucleation and growth. The mask was prepared by spin-coating silica microspheres to achieve laterally-selective implantation, to control QD size and separation. Transmission electron microscopy (TEM) images were obtained to verify the diameter of the quantum dots. We observe a noticeable peak shift and narrowing in the photoluminescence spectra with the application of the implantation mask. Observed maxima in the photoluminescence spectra are compared with a quantum field theoretical model using an infinite confining 1D potential for Si quantum dots. We comment on the role of excitation transfer by observing a change in the dispersion exponent of the luminescent decay dynamics due to the mask.

Purification of diamond nanopowder (DNP) was conducted in a less-destructive mild polyphosphoric acid (PPA)/phosphorous pentoxide (P2O5). The wide-angle X-ray diffraction (XRD) showed that the intensity of the characteristic diamond d-spacing (111) at 2.07 Å from purified DNP (PDNP) was fairly increased compared to pristine DNP, indicating that significant amount of carbonaceous impurities were removed. Chemical modification of pristine DNP and PDNP with 4-ethylbenzoic acid was carried out to afford 4-ethylbenzoyl-functionalized DNP (EBA-g-DNP) and PDNP (EBA-g-PDNP). The morphologies of EBA-g-DNP and EBA-g-PDNP from scanning electron microscopy (SEM) were further affirmed the feasibility of chemical modification. The results suggested that the reaction condition was indeed viable for the one-pot purification and functionalization of DNP. The resultant functionalized DNP could be useful for nanoscale additives. Hence, EBA-g-DNP and EBA-g-PDNP was brominated by using N-bromosuccinimide (NBS). The resultant N-brominated DNP and PDNP could be used as initiator for the atom transfer radical polymerization (ATRP) to introduce many polymers onto the surface of functionalized DNP and PDNP.

A novel, first-principle theoretical approach and synergetic computational methods designed to predict electronic and magnetic transport properties of strongly spatially inhomogeneous systems, including small quantum dots and wires (QDs and QWs, respectively), and molecules, have been developed recently. This approach is based on a many-body quantum theoretical formalism - a projection operator method due to Zubarev and Tserkovnikov (ZT) - formulated in terms of the equilibrium, two-time temperature Green functions (or TTGFs). There are several significant advantages of this approach, as compared to traditional non-equilibrium two-time thermodynamic and field-theoretical Green's function (NGF) methods that are currently used to study electronic and magnetic transport properties of strongly spatially inhomogeneous systems. In particular, the TTGFs are directly related to experimentally assessable microscopic charge, spin and microcurrent densities.

In the work reported here the TTGF-based approach has been used to derive a fundamental, yet tractable expression for the space-time Fourier transform of the tensor of quasi-local refraction indices (TRI) from the first principles. The TTGFs necessary to predict TRI can be calculated using quantum statistical mechanical means, modeling and simulations, and experimental data. Applications of the theoretical predictions for TRI open new prospects in materials design. In particular, the derived theoretical expression for TRI can be used to guide experimental synthesis of structured materials and systems with both direction- and position-dependent indices of refraction in desirable frequency ranges.

Natural materials such as bone, shell, tendon and the attachment system of gecko exhibit multi-scale hierarchical structures. Here we summarize some recent studies on an idealized self-similar hierarchical model of bone and bone-like materials, and discuss mechanical principles of self-similar hierarchy, in particular to show how the characteristic length, aspect ratio and density at each hierarchical level can be selected to achieve flaw tolerance and superior stiffness and toughness across scale.Tel.: (401) 863-2626; Email address:

Three-dimensional electron diffraction data was collected with our recently developed module for automated diffraction tomography and used to solve inorganic as well as organic crystal structures ab initio. The diffraction data, which covers nearly the full relevant reciprocal space, was collected in the standard nano electron diffraction mode as well as in combination with the precession technique and was subsequently processed with a newly developed automated diffraction analysis and processing software package. Non-precessed data turned out to be sufficient for ab initio structure solution by direct methods for simple crystal structures only, while precessed data allowed structure solution and refinement in all of the studied cases.

The present paper deals with surface enhanced Raman scattering (SERS) study of an organic dye Alizarin Red on colloidal silver nanoparticles. The colloidal solution of nanoparticles is synthesized by pulsed laser ablation of silver rod in pure deionized water using focused out put of 1064nm wavelength of Nd:YAG laser having 35mJ/ pulse energy. Sodium chloride is used as aggregating agents. It is observed that SERS enhancement factor varies strongly depending on concentration of used aggregating agent (especially on the concentration of Cl- ions). These changes in SERS efficiency of colloid are reflected through changes on the absorption spectra. The possible mechanism of SERS is also discussed.

Considering the desirable effects of doping CdTe with heavy elements like Bi, we have grown a Cadmium Zinc Telluride (Zn=10%) ingot with Bi (doping levels ∼1014 to 1015 at/cm3) as the heavy element dopant for use as a room temperature radiation detector, using the Bridgman method. In-spite of a high bulk resitivity (∼1010?cm), and the ability to hold high electric field (>2000 V/cm), these lightly doped crystals had a poor spectral resolution for the Co-57 photo peaks and ??e measurements were so low that these measurement were not reliable. Thermo electric effect spectroscopy (TEES) and thermally stimulated current (TSC) experiments on samples C and F (single crystals close to the tip and the heel of the ingot respectively) have revealed various defect levels in the band gap. Among these defect levels, we have identified and characterized two Bi-related deep levels namely a deep donor level L5 (thermal ionization energy: 0.33[5] to 0.39[5] eV and trap cross-section: 7.1[5] × 10-17 to 2.54 [5] × 10-16 cm2), and a deep acceptor level L8 (thermal ionization energy of 0.82 [5] eV and trap cross-section of 2.59 [5] × 10-12 cm2). These levels were responsible for the observed high electrical resistivity (∼1010 ?*cm) in the CdZnTe samples. From a comparison to studies on Bi doped CdTe samples, level L8 was tentatively associated with the (0/-) transition of (BiCd- - OTe) complex, however is still under study. Since these defect levels also act as trapping centers for charge carriers, in spite of the semi-insulating behavior the samples are poor radiation detectors.

In the present work we study theoretically hydrogen incorporated into several positions in the zirconia cubic and tetragonal lattices. These are positions in the interstitial space and in the zirconium vacancy (V Zr). We examine the structure of such configurations and for V Zr-related defects we also calculate selected positron characteristics in order to assess their capability of trapping positrons. It is shown that hydrogen atoms do not prefer to stay in the center of the largest interstitial space nor of V Zr and they rather tend to create bonds with neighboring oxygen atoms. The positron lifetime of the VZr+1H complex is shorter than that for non-decorated V Zr and positron trapping in V Zr+1H complexes could, in principle, explain experimental lifetime data.