TiO2 films with poly crystal were electrodeposited on conductive substrate (NESA glass, approximately 10Ω/□, Asahi glass Co. Ltd.) from the titanium potassium oxalate dehydrate aqueous solution containing hydroxylamine adjusted pH 9 with KOH aq. at 333k. The peak corresponded to Ti3+ion into these TiO2 film was not observed by using X-ray photoelectron spectroscopy (XPS). The photocatalysis of TiO2 film increased with a decrease of cathodic potential. In particular, TiO2 film obtained at cathodic potential of -1.3V, had the higher photocatalysis than that of other potential.

Various metal fluoride crystals were subjected to electron beam irradiation at 200 and 300 kV using transmission electron microscopy in order to study in-situ fabrication of 3D metal nanostructures. Lithium fluoride, cobalt fluoride and aluminum fluoride salt fragments were chemically reduced and transformed by the electron beam to the corresponding metals. Using live video recording we observe that LiF crystals decompose in a unique way different to all other metal-halides. Li diffuses rapidly out of the salt crystal and covers its surface and the surrounding C-support film to many microns distance, where at random positions nucleation, growth and annihilation of Li nanorods and some nanospheres is observable. Decomposition of CoF2 also involves non-local synthesis of Co nanoparticles, mostly facetted, however, these are stable, without annihiliation, and their positioning seems to follow some degree of self-organisation. AlF3 transforms locally to Al grains inside the irradiated area only, and grain growth occurs to sizes proportional to the beam intensity. Findings are discussed in terms of displacement energy differences between the materials.

Surface plasmon enhanced InAs/GaAs quantum dot solar cells are reported. Light trapping by metallic nanostructures offers the potential to realize high efficient quantum dot based intermediate band solar cells. Both Au and Ag nanoparticles spherical metal nanoparticles are synthesized by the salt reduction method. The large area coupling of metal nanoparticles and quantum dot solar cell surface is carried out by using 1,3-propanedithiol as linker molecules. The conversion efficiency of the solar cells has been increased from 9.5% to 11.6% after deposition of Au nanoparticles and from 9.5 to 10.9% after incorporating Ag nanoparticles. The conversion efficiency enhancement is mainly as a result of improved photocurrent due to enhanced forward scattering from the plasmonic nanostructures.

Single walled carbon nanotubes (SWNTs) possess unique structural and functional properties. Their ability to be functionalized with different biomolecules makes them excellent candidates for biomedical applications like targeted drug delivery and cancer diagnostics. However, prior to use in therapeutic applications, biocompatibility of SWNTs needs to be thoroughly investigated. Blood is a living tissue and contains cells which can potentially interact with SWNTs during the drug delivery process. The interaction of leukocytes in blood with the SWNTs can provide information regarding the immune response of the host to the nanotubes. Here, we evaluated the acute immune response of leukocytes in blood to SWNTs via (a) direct interaction, due to the presence of SWNTs in circulation and (b) indirect interaction, due to the presentation of SWNTs to leukocytes via antigen presenting cells. These SWNTs were non-covalently functionalized with single stranded DNA (ss-DNA) that acts as a surfactant for suspending SWNTs in aqueous solutions and also serves as a backbone for attaching and transporting different biomolecules. Isolation of cells from blood was done using density gradient centrifugation. Early activation markers were used to study the activation of different leukocyte subpopulations and any activation results in changes of these markers. Flow cytometry was done to analyze the different subpopulations. Results of our study demonstrated that ss-DNA functionalized SWNTs do not elicit an immune response from leukocytes in blood via direct or indirect interaction. This intensive study demonstrates the biocompatibility of single walled carbon nanotubes and paves the way for their safe use in drug delivery and cancer therapeutics without cytotoxicity.

This investigation deals with the production process and the characterization of ceramic materials consisting of magnetic particles in an insulating matrix. Composites made of magnetite particles (Fe3O4 or MgFe2O4) in a wüstite or magnesiowüstite matrix (FexO or Mg1-xFexO), respectively, have been produced by means of mechanical milling and spark plasma sintering. As-milled powders have a nanocrystalline structure in both systems. As a function of milling time, low energy milling gives rise to an increasingly higher volume fraction of wüstite in the FexO-Fe3O4 system while it promotes increasing amounts of magnesiowüstite (MgxFe1-xO). Sintering is performed from 673 to 1273 K in vacuum. Sintering at low temperatures allows retention of nanosized grains containing a fine dispersion of magnetic particles in a wüstite and magnesiowüstite matrix. Measurement of magnetic properties reflects the constitution of the sintered samples and the effect of grain size. It also allows determination of the transformation sequence both during mechanical milling and sintering

We simulate the thermodynamics and kinetics of the drift/diffusion of oxygen vacancy defects in rutile TiO2, using the density-functional based tight-binding (DFTB) method. Both static and dynamic simulations have been performed. Results indicate that DFTB is well suited to examine the dynamic behavior of oxygen vacancies in TiO2. Detailed analysis shows, that strong model size dependence in relative diffusion barrier heights between different diffusion processes requires great care in defect diffusion simulations in TiO2. Thermodynamic results on the influence of an external electric field show that, due to the large dielectric constant, the coulomb driving force on oxygen vacancy diffusion is very small. Dynamic simulation of the influence of electric fields on the diffusion requires the use of advanced molecular dynamics acceleration schemes.

This work studies the performance of sputtered bismuth films as disposable working electrodes for stripping voltammetry. The electrodes were produced by coating a glass substrate with a bismuth film using DC magnetron sputtering under different conditions of power and time. The Bi-based sensors were characterized by X-ray diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy and scanning electron microscopy. Electrochemical evaluation included linear sweep voltammetry using different buffer solution and pHs to observe the effect of the deposition conditions and thickness on the potential window accessible for stripping analysis. Subsequently, the electrodes were tested for the detection of low concentrations of trace metals (Cd(II) and Pb(II)) by square wave anodic stripping voltammetry (SWASV). Clear and reproducible stripping peaks were observed for trace concentrations in the 50 - 450 ppb range of the target analytes. The detection limit of the Bi electrodes were quantitatively estimated from the analyses of SWASV, demonstrating that even using simple sensor geometry, detection limits in the 14-20 ppb range could be obtained. The reproducibility of the measurements is good (relative standard deviations about 4%) after 10 consecutive measurements which define the maximum number of times that the sensor can be used.

The structural integrity of nuclear fuel cladding is affected by the precipitation of hydrides during operation, which may embrittle the cladding. The aim of this work is to obtain the mechanical and fracture properties of the cladding as a function of the hydrogen content and testing temperature. To this end, the embrittlement caused by circumferential hydrides was simulated on unirradiated fuel cladding samples in the laboratory. The structural integrity of the cladding was assessed at different temperatures (20, 135 and 300ºC), by using the ring compression test. The mechanical properties and the fracture energy were calculated from the experimental load vs. displacement curves, by means of a finite element model which incorporates the cohesive crack model.

We study the effect of the spacing between electrodes in very high frequency plasma enhanced chemical vapor deposition on the properties of microcrystalline silicon films and their related n-i-psolar cells. We vary the spacing from 0.2 to 1.0 cm to deposit microcrystalline silicon at 67.8 MHz while maintaining other growth parameters. The spacing between the electrodes significantly changes the plasma conditions, which govern film precursor chemistry as well as introduce etching and ion bombardment to the film; thereby, influencing nucleation and growth of the microcrystalline Si films. The resulting films were characterized by UV-Vis spectrometry, atomic force microscopy, X-ray diffraction, and transmission electron microscopy. We found that deposition rate decreases, while surface roughness and short circuit current density increase with smaller spacing.

Tb doped gadolinium fluoride nanophosphors embedded in an aluminosilicate glass matrix is reported for X-ray imaging applications. The nanocomposite scintillators were prepared by a melt-quench method followed by annealing. The GdF3:Tb nanophosphors precipitated within the oxide glass matrix during the processing and their luminescence and scintillation properties were investigated.

To perform a safety assessment for the geological disposal of radioactive waste, it is important to understand the response characteristics of the disposal system. In this study, approximate analytical solutions for steady-state nuclide releases from the engineered barrier system (EBS) of a repository were derived for an orthogonal one-dimensional diffusion model. In these approximate analytical solutions, inventory depletion, decay during migration and the influence of groundwater flow in the excavation damaged zone (EDZ) were considered. These solutions were simplified by the Taylor theorem in order to clearly represent the response characteristics of the EBS. The validity of these solutions was shown by comparison with numerical solutions. The response characteristics of the EBS are useful for identifying target values for important parameters that would have the effect of improving the robustness of system safety. The robustness of the geological disposal system and the reliability of the safety assessment can thus potentially be improved using the approximate analytical solutions.

Temperature dependent optical properties of RF-sputtered c-axis oriented ZnO:N thin film have been investigated. Surface Plasmon modes are excited at the metal-dielectric interface in the Kretschmann-Reather configuration using prism coupling technique. Effect of ZnO:N thin film deposited over Prism-Au structure on the SPR reflectance is studied over a wide range of temperature from 300–500 K at 633 nm wavelength. The value of dielectric constant of ZnO:N film obtained by fitting the experimentally obtained data with the theoretically generated SPR curve at the optical frequency is found to increase linearly with temperature. The increase in dielectric constant (4.03 to 4.11) with increase in temperature from 300 K to 500 K indicates a promising application of the system as an efficient low-cost temperature sensor.

Neutron detection scintillators based on rare-earth activated transparent glass and glass-ceramics are reported. Ce3+ doped gadolinium halides in 6 LiF modified aluminosilicate glass matrices were synthesized by a melt-quench method followed by annealing. Their optical properties and alpha, neutron scintillation performance were investigated and compared to conventional 6 Li-based scintillating glass.

Vertically oriented, highly dense ZnO nanowires (NWs) array was successfully grown on both glass and silicon substrates using hydrothermal technique. A systematic study was carried out to investigate the effects of growth parameters including growth time and thickness of ZnO seed layer on the quality of ZnO NWs in terms of their homogeneity and orientation in the vertical direction. The diameter as well as the length of grown ZnO NWs was found to be closely dependent on the thickness of the pre-coated ZnO seed layer. The structures of ZnO NWs and electron-beam evaporated AgGa0.5In0.5Se2 (AGIS) thin film have been characterized by X-ray diffraction measurements and optical properties were measured by transmission measurement. The optic band gap of AGIS thin film was found to be almost optimum (1.56 eV) to match the abundant part of solar cell spectrum. AGIS thin film was deposited on the synthesized ZnO NWs to form p-n heterojunction based inorganic solar cell, which exhibited photovoltaic behavior with a power conversion efficiency of 0.37 % under A.M (1.5) illumination.

The feasibility of the fabrication of tungsten based nuclear fuel cermets via Spark Plasma Sintering (SPS) is investigated in this work. CeO2 is used to simulate fuel loadings of UO2 or Mixed-Oxide (MOX) fuels within tungsten-based cermets due to the similar properties of these materials. This study shows that after a short time sintering, greater than 90 % density can be achieved, which is suitable to possess good strength as well as the ability to contain fission products. The mechanical properties and the densities of the samples are also investigated as functions of the applied pressures during the sintering.

By using aberration corrected scanning transmission electron microscopy we have found no small scale lateral In composition fluctuations exist in the In0.15Ga0.85N active region of a light emitting diode. Images were acquired at 2% of the electron dose known to create electron beam damage, so the acquired images reflect the intrinsic structure of the InGaN active region. Position averaged convergent beam electron diffraction reveals the local sample thickness where images were acquired is 4.8 nm, eliminating the possibility that the absence of composition variation was observed due to projection through a thick sample. In addition, 2-3 atomic layer steps were observed in the top surface of In0.08Ga0.92N layers and the In0.15Ga0.85N active layers, providing a possible mechanism for lateral carrier confinement.

Natural and synthetic hydroxyapatite (HA) scaffolds for potentialload-bearing bone implants were fabricated by two methods. The naturalscaffolds were formed by heating bovine cancellous bone at 1325°C, whichremoved the organic and sintered the HA. The synthetic scaffolds wereprepared by freeze-casting HA powders, using different solid loadings (20–35vol.%) and cooling rates (1–10°C/min). Both types of scaffolds wereinfiltrated with polymethylmethacrylate (PMMA). The porosity, pore size, andcompressive mechanical properties of the natural and synthetic scaffoldswere investigated and compared to that of natural cortical and cancellousbone. Prior to infiltration, the sintered cancellous scaffolds exhibitedpore sizes of 100 – 300 μm, a strength of 0.4 – 9.7 MPa, and a Young’smodulus of 0.1 – 1.2 GPa. The freeze-casted scaffolds had pore sizes of 10 –50 μm, strengths of 0.7 – 95.1 MPa, and Young’s moduli of 0.1 –19.2 GPa.When infiltrated with PMMA, the cancellous bone- PMMA composite showed astrength of 55 MPa and a Young’s modulus of 4.5 GPa. Preliminary data forthe synthetic HA-PMMA composite showed a strength of 42 MPa and a modulus of0.8 GPa.

We introduce a technique to permit x-ray absorption spectroscopy studies focusing on individual phase-change (Ge2Sb2Te5) memory cells in fully integrated PC-RAM structures. Devices were investigated employing an x-ray nanobeam of only about 300 nm diameter, which could be fully contained within the spatial extent of the active area within a single device cell and enabled us to investigate individual devices without interference from non-switching material surrounding the area of interest. By monitoring the fluorescence signals of tungsten and germanium at a photon energy corresponding to the Ge K-edge absorption edge white line position, we were successful in producing 2D area maps of the active cell region, which clearly show the imbedded tungsten heater element and the switched region of the phase change material. Additionally, position dependent changes in the phase change material could be traced by taking an array of XANES spectra at the Ge K-edge on and in the vicinity of individual devices.