In this work, the effect of structural characteristics of organomodified clays on the dispersion degree, mechanical and rheological properties of the nanocomposites PP-EP/EVA/nanoclay has been studied. The studied effects were: degree of chemical modification of the clay, length of substitute groups on the surfactant, and the steric effect caused by surfactant structure. The characterization techniques used were Wide Angle X-ray Diffraction (WAXD), Scanning Transmission Electron Microscopy (STEM), Dynamic Mechanical Analysis (DMA), Tensile Test and Capillary Rheometry. Cloisite 6A, 15A and 20A were used to evaluate the first effect. Better intercalation-exfoliation and mechanical properties were obtained when the clay with lower content of surfactant was used (C20A), these results were attributed to a higher saturation of the system. In order to study the second effect, Cloisite 20A and Cloisite 25A were employed. It was found that the bigger initial intergallery space between these nanoclay’s caused by the longer chains in Cloisite 20A, allows the formation of a structure with better intercalated-exfoliated structure. This was confirmed with the observed increase in mechanical properties. Finally, the third effect was studied with Cloisite 10A and 15A. It was clearly seen that only with Cloisite 15A was possible to obtain an intercalated-exfoliated structure. This was attributed to a major steric effect when using C10A than with 15A.

Fulfilling the need for reproducible Quantum Dots (QDs) with certain spectroscopic features, high stability and luminescence we have established synthetic routes for the production of CdSe core as well as CdSe/shell particles in a continuous flow (cf) system. Our method features the deviation between nucleation and growth in two different parts of the system to mimic the well-known and often-used hot injection method for the synthesis of nanoparticles in organic solvents.

We have investigated the effect of temperature annealing on bilayer heterojunction solar cells based on poly[9,9’-hexyl-fluorene-alt-bithiophene] as active layer. Film morphology for different temperature annealing was probed by atomic force microscopy (AFM) and the values of roughness range from 0.59 up to 2.15 nm. The best photovoltaic performance was found for devices with active layer annealed at 200°C with power conversion efficiency (η) of 2.8 % while devices without annealing presented only 0.4%. This performance enhancement is attributed to the reduction of traps and increased hole mobility after the thermal annealing.

The mechanical properties of individual electrospun polystyrene fibers with sub-micron diameters were measured using a combination of atomic force microscopy (AFM) and scanning electron microscopy (SEM). The strain to failure of the electrospun fibers was observed to increase as the fiber diameter decreased. This size dependent mechanical behavior in individual electrospun polystyrene fibers indicates a suppression of localized failure and a shift away from crazing that is dominant in bulk samples.

There have been reports of improvements in the thermoelectric figure of merit through the use of nanostructured materials to suppress the lattice thermal conductivity. Here, we report on a fundamental study of the combined effects of defect planes and surface scattering on phonon transport and thermoelectric properties of defect-engineered InAs nanowires. A microfabricated device is employed to measure the thermal conductivity and thermopower of individual suspended indium arsenide nanowires grown by metal organic vapor phase epitaxy. The four-probe measurement device consists of platinum resistance thermometers and electrodes patterned on two adjacent SiNx membranes. A nanowire was suspended between the two membranes, and electrical contact between the nanowire and the platinum electrodes was made with the evaporation of a Ni/Pd film through a shadow mask. The exposed back side of the device substrate allows for characterization of the crystal structure of the suspended nanowire with transmission electron microscopy (TEM) following measurement. The 100-200 nm diameter zincblende (ZB) InAs nanowire samples were grown with randomly spaced twin defects, stacking faults, or phases boundaries perpendicular to the nanowire growth direction, as revealed by transmission electron microscopy (TEM) analysis. Compared to single-crystal ZB InAs nanowires with a similar lateral dimension, the thermal conductivity of the defect-engineered nanowires is reduced by fifty percent at room temperature.

Diamond-like carbon (DLC) films as a new strain-capping material with compressive stress up to 12GPa for strained silicon technology were fabricated by filtered cathodic vacuum arc (FCVA) deposition system. The films’ compositions and bonding structures were characterized using multi-wavelength Raman spectroscopy. The relationship between intrinsic stress and G peak dispersion of the films’ Raman spectra were discussed. The results showed that the bias voltage applied to substrate during deposition determines films’ sp3 bonding content and intrinsic stress. Process compatibility of the DLC films with standard CMOS technology was confirmed by using WDXRF measurement. Also diffusion behavior of carbon atoms in DLC films with copper and silicon was studied with a Cu(200nm)/DLC(40nm)/silicon multilayer structure annealed at 500℃ in N2 atmosphere for an hour. At last, stress induced on silicon surface by DLC strips was characterized using surface sensitive UV-Raman spectroscopy. The results showed that DLC films with extremely high compressive stress have potential application in future CMOS strain engineering.

The effect of the electron blocking layer on the performance of white organic light-emitting diodes is studied. A variation of the material influences not only the carrier transport, but also the light distribution from the different emitters. Highest external quantum efficiency is reached for the material with the worst electrical properties, while highest luminous efficacy is obtained for the material with the best transport characteristics.

Biofilms are a common cause of persistent infections on medical devices as they are easy to form and hard to treat. Selenium and its compounds are considered to be a novel material for a wide range of applications including anticancer applications and antibacterial applications. The objective of this study was to coat selenium nanoparticles on the surface of polycarbonate medical devices and examine their effectiveness at preventing biofilm formation. The results of this in vitro study showed that the selenium coating significantly inhibited Staphylococcus aureus growth on the surface of polycarbonate after 24 hours. Thus, this study suggests that coating polymers with nanostructured selenium is a fast and effective way to reduce bacteria functions leading to medical device infections.

In this paper, I discuss the basis for the following recommendations for the development of standards and regulations for the long-term disposal of spent nuclear fuel and high-level nuclear waste in a geologic repository:

• • The standard and supporting regulations for the licensing of a geologic repository should be generic - applicable to all potential sites. These standards and regulations should be finalized prior to the site-selection process.

• • Site-selection should be based on a set of common-sense criteria [1]. If during site characterization process it is discovered that the site does not meet the technical criteria, the site should be abandoned. These criteria should not only consider the characteristics of the site, but should also include careful consideration of the degree to which a site can be analyzed. Unnecessary complexity may jeopardize the confidence in the analysis of a suitable site.

• • The standard must acknowledge and adapt its structure and standard-of-proof to the fact that there are two time-scales of interest: the human time-scale that extends to some thousands of years and the geologic time-scale that extends to many hundreds of thousands of years. Reasonable and robust containment at both time scales is possible, but the type of analysis and standard-of-proof will be different for each.

• • Because there are two time-scales and because the types of “proof” for each are very different, the total system analysis of performance, reduced to a single numerical estimate of risk at some very distant time, should be abandoned. The standard should not require scientists and engineers to complete an analysis that is at its best opaque and at its worst not believable.

Cathode reaction on overpack corrosion in the geological repository environments of radioactive waste was identified from corrosion experiments of carbon steel specimens. Carbon steel specimens were encapsulated in degassed glass ampoules with various solutions which were prepared by distilled water degassed by Ar gas bubbling, and set in a thermostatic bath for several weeks. In the X-ray diffraction and X-ray photochemical spectroscopy, crystalline Fe3O4 and Fe2(OH)2CO3, and amorphous Fe(OH)2 were mainly detected on specimens which were immersed into distilled water, high concentration of sodium hydrogen carbonate solution, and low concentration of sodium hydrogen carbonate solution and sodium sulfate solution, respectively. Only hydrogen gas was detected in a gas phase analysis, indicating that hydrogen generation reaction was the dominant cathode reaction in the anoxic condition expected in geological repository environments.

Cement-based materials used in the construction of the repository for high/low level radioactive wastes may produce a highly alkaline calcium-rich groundwater (plume). The Ca ions react with soluble silicic acid, depositing calcium-silicate-hydrate (CSH) gel on the surfaces of the groundwater flow-paths and decreasing the permeability of the bedrock. Such a decrement of permeability may play a role in retarding the migration of radionuclides. In this study, the deposition behavior in a fracture was experimentally examined by using a micro flow-cell consisting of silicon plate (including a slit (60 mm×5 mm, or 60 mm×2 mm)) and granite-chip. The initial equivalent-aperture based on the square law was estimated in the range of 26 μm to 45 μm from the flow test of pure water.

In the experiments, a Ca(OH)2 solution of 6.36 mM (pH: 12.2 to12.5, including NaOH) was continuously injected into the flow system at a constant flow rate of 1 or 2 ml/h. The solution flowed on the surface of the granite-chip. In this study, we prepared two kinds of chips that differed in the treatment of the surface. One chip was roughly ground with #2000 sandpaper (hereinafter referred to as rough surface) and another was polished to mirror-like surface. As a result, on the rough surface the deposits of CSH gel appeared along flow-channels across mineral grain-boundaries, while the deposits on the mirror-like surface were relatively uniform. Furthermore, the permeability in the case of rough surface became smaller than that in the case of mirror-like surface, showing the repeats of rapid decrement and increment due to the relatively large roughness of the surface. In order to estimate the decrement degrees of permeability, a simple, one-dimensional mathematical model is proposed in this study.

The drive to reduce the thickness of solar cells is putting ever greater demands on light-trapping techniques. Techniques are required to improve absorption of light within the semiconductor, while not adversely affecting the electrical properties of the device. Conventional diffraction gratings can scatter visible and near-infrared photons into large angles, which get trapped in the silicon layer by total internal reflection. However, diffraction gratings typically have large feature sizes and so increase the overall surface area of a solar cell compared to the planar case. A periodic arrangement of metal nanoparticles acts as a diffraction grating, but an over-coated semiconductor will have a similar surface area to a planar layer due a combination of a low particle height and low surface coverage.

Random arrays of identical metal nanoparticles feature Lorentzian scattering peaks that can be tuned by modifying the size and shape of the particle. Periodic arrays have much more complicated scattering peaks, due to the enhancement and suppression of scattering at different wavelengths caused by the constructive and destructive interference between each nanoparticle. In effect the scattering spectrum of the individual nanoparticle is modified by the diffractive orders of the array, and so both parameters must be optimized together.

We have studied periodic arrays of metal nanoparticles fabricated using electron-beam lithography, and characterised their reflectance properties. The optical properties of the fabricated arrays were found to be in good agreement with finite-difference time-domain (FDTD) simulations. Au and Al nanoparticles are found to have a strong scattering effect and Al nanoparticles are also shown to exhibit an anti-reflection effect in combination with scattering. This work is focused on verifying that FDTD simulations can accurately model metal nanoparticle arrays and then extending the simulations to determine the previously unknown transmittance characteristics of metal nanoparticle arrays on silicon.

Results for a radiolysis model sensitivity study of radiolytically produced H2O2 are presented as they relate to Spent (or Used) Light Water Reactor uranium oxide (UO2) nuclear fuel (UNF) oxidation in a low oxygen environment. The model builds on previous reaction kinetic studies to represent the radiolytic processes occurring at the nuclear fuel surface. Hydrogen peroxide (H2O2) is the dominant oxidant for spent nuclear fuel in an O2-depleted water environment. The most sensitive parameters have been identified with respect to predictions under typical conditions. As compared with the full model with about 100 reactions, it was found that only 30 to 40 of the reactions are required to determine [H2O2] to one part in 10–5 and to preserve most of the predictions for major species. This allows a systematic approach for model simplification and offers guidance in designing experiments for validation.

Epitaxial Fe-Te-Se thin films were deposited by pulsed laser deposition at 250 ~ 600 °C on SrTiO3 (100, STO), MgO (100), LaAlO3 (100, LAO) and CaF2 (100) single crystal substrates. Best superconducting film was grown on CaF2: T c onset = 20.0 K and T c 0 = 16.18 K with T dep = 300 °C, 45000 pulses, 3 Hz. The critical current density J c at 4.2 K was 0.41×106A/cm2 at 0 T and 0.23×106 A/cm2 at 9 T. Angular dependence of J c showed broad c-axis correlated peak when B ≥ 3 T.

The mechanism leading to RT ferromagnetism in Gd-doped GaN is not agreed upon, despite many experimental and theoretical reports. Oxygen impurities have been proposed as a possible contributor to ferromagnetic behavior in GaN:Gd films. In this report, GaN:Gd thin films grown by MOCVD using two different metalorganic Gd precursors are examined. The two precursors are (TMHD)3Gd, which contains oxygen, and Cp3Gd, which does not. The films have been characterized by XRD, VSM, and EDS. EDS measurements indicate that the TMHD3Gd samples contain oxygen, while the Cp3Gd samples do not, and VSM scans show that the TMHD3Gd samples exhibit much higher magnetic moments than the Cp3Gd samples, supporting the theory that oxygen enhances the ferromagnetic behavior of GaN:Gd.

The structures and energies of stoichiometric and oxygen-deficient monoclinic HfO2 were calculated using density functional theory. The electronic interactions in HfO2 were calculated using the LDA+U and GGA+U formalisms, where on-site Coulomb corrections were applied to the 5d electrons of hafnium (Ud ) and the 2p electrons of oxygen (Up ). Properties calculated using these techniques are compared to results obtained from LDA, GGA, hybrid functionals, and experiment. Ultimately, we show that LDA+Ud +Up and GGA+Ud +Up calculations of HfO2’s electronic and structural properties achieve a level of accuracy on par with much more computationally demanding hybrid functional techniques, such as PBE0 and HSE06.

Graphite that had been ball-milled for 10 h in 3 bar hydrogen, was then mixed with lithium borohydride (2:1 molar ratio of graphite to LiBH4) and milled for a further 2 h. This resulted in a significantly enhanced the hydrogen desorption properties: compared with the pure hydrogenated milled graphite, added LiBH4 lowered the desorption temperature by 170°C, to 230°C, and increase the hydrogen desorption from 5.6 to 9.3 wt%, heating to 500°C. There was no detectable methane generation in the desorption gas.

This investigation is on alternative cementitious materials of low cost, energy and environmental emissions. Portland cement (PC) was replaced by different types of calcium sulphate (hemihydrate HH, or anhydrite AN), fly ash (PFA) and cupola slag (CS) from an iron foundry. Pastes of blends of (HH or AN) – CS – PC and (HH or AN) – PFA – PC were characterized. The compositions varied within the ranges of 0 – 35% PC, 15 – 80% HH or AN, 10 – 80% CS and 10 – 80% PFA. The water/solids ratio was kept at 0.45 for HH blends and 0.37 for those of AN. The pastes were cured in dry and for some time under water. Selected blends of CS were repeated with blast furnace slag (BFS) for comparison. CS showed better results over PFA and less than BFS, perhaps as derived from its chemical composition, phase configuration and physical characteristics. These and other results of microstructural characterization will be discussed. This work is part of a broader research on the development of alternative environment friendly hydraulic composite cements of Portland cement highly replaced by calcium sulphate and industrial byproducts.

Mg–Si thin films were fabricated on glass, Si(100), Si(111), and polycrystalline Al2O3 substrates by radio-frequency (RF) magnetron sputtering deposition using an elemental composite target composed of Si chips on a Mg disk. The effect of deposition conditions such as the composition ratio of Mg/Si in the target area, substrate temperature, and the type of substrate on the thin film deposition was investigated. By controlling the deposition conditions, pure-phase Mg2Si polycrystalline films were successfully fabricated at room temperature. The crystalline orientation of the films was strongly influenced by the Mg/Si elemental composition ratio in the targets as well as by the surface roughness and porosity of the substrate. The electron concentration and mobility of nondoped Mg2Si films were 2.2 × 1016 cm-3 and 2.0 cm2/Vs, respectively. The electron concentration of Mg2Si films was drastically increased by impurity doping with Al and Bi.

Nanostructure templates fabrication from P(S-b-MMA) thin films requires precise control of interfacial energies to achieve perpendicular orientation of microdomains to the substrate surface and can be obtained by modifying the oxide layer on silicon with a covalently anchored hydroxyl-terminated random copolymer P(S-r-MMA) termed a “neutral brush”. This commonly employed method enables precise fine-tuning of interfacial energies, but involves a lengthy process, requires starting materials that are commercially available but expensive, and results in a relatively thick under layer that can interfere with subsequent surface processing. We report here the microphase separation behaviour of an asymmetric P(S-b-MMA) diblock copolymer on electronic substrates modified with ethylene glycol (EG) self-assembled monolayer (SAM) as alternative to standard random copolymer brush. The diblock copolymer films deposited on EG SAMs upon thermal annealing spontaneously generates features with sub-lithographic resolution and pitch with perpendicular orientation. Selective etching provides a rapid route for the generation of PS template structures as the PMMA domains are etched at a faster rate. These templates can subsequently be used as etch masks to generate nanoscale features. We use state of the art lithography to generate sub-μm features and within these generate nm sized copolymer templates. Graphoepitaxy method proved a successful approach for the alignment of the microphase separated structures. This method of EG SAM driven self-0assembly provides a simple, rapid, yet tuneable approach for surface neutralization and nanofabrication technique for creating high density nanoscale features for the nanoelectronic industry.