Laves-type intermetallic phases have been observed to be the dominant phases in a series of alloy compositions being designed for the immobilization of technetium in a metallic waste form. The dominant metals in the alloy compositions were Fe-Mo and Fe-Mo-Zr. The alloy composition, Fe-Mo-Zr, also contained Pd, Zr, Cr, and Ni. Both non-radioactive rhenium-containing and radioactive technetium-bearing alloy compositions were investigated. In the Fe-Mo series, the phases observed were Fe2Mo (C14 Laves phase) and ferrite in agreement with predictions. Both Tc and Re resided predominantly in the Laves phases. In the Fe-Mo-Zr system, the phases included hexagonal C14 with the composition (Fe,Cr)2Mo, cubic C15 phase with a (Fe,Ni)2Zr composition, and the hcp phase Pd2Zr. The observation of these phases was in agreement with predictions. Re was found in the C14 intermetallic, (Fe,Cr)2Mo. Technetium was also observed to be partitioned preferentially into the (Fe,Cr)2Mo phase; however, this phase exhibited a cubic structure consistent with the C15 structural type. The composition of Laves phases is influenced by both the atomic size and electro-negativity of the constituent elements. The long-term release behavior of technetium under nuclear waste disposal conditions may be more dependent on the corrosion characteristics of these individual Laves phases containing Tc than the other metallic phases.

A calcium phosphate ceramic waste-form has been developed at AWE for the immobilisation of chloride containing wastes arising from the pyrochemical reprocessing of plutonium. In order to determine the long term durability of the waste-form, aging trials have been carried out at PNNL. Ceramics were prepared using Pu-239 and -238, these were characterised by PXRD at regular intervals and Single Pass Flow Through (SPFT) tests after approximately 5 yrs.

While XRD indicated some loss of crystallinity in the Pu-238 samples after exposure to 2.8 x 1018 α decays, SPFT tests indicated that accelerated aging had not had a detrimental effect on the durability of Pu-238 samples compared to Pu-239 waste-forms.

The corrosion behavior of simulated spent nuclear fuel (SIMFUEL) was investigated using electrochemical impedance spectroscopy and solution chemistry analyses. The SIMFUEL was exposed to aerated solutions of NaCl+NaHCO3 with and without calcium (Ca) and silicate. Two SIMFUEL compositions were studied, representing spent nuclear fuel (SNF) corresponding to 3 or 6 at % burnup in terms of fission product equivalents of surrogate elements. For all tested cases, the polarization resistance increased with increased immersion time, indicating possible blocking effects due to accumulation of corrosion products on the SIMFUEL surface. The potential-pH diagram suggests formation of schoepite that may cause the increase in the polarization resistance. The addition of Ca and silicate produced no measureable change in the polarization resistance measured at the corrosion potential. The dissolution rate ranged from 1 to 3 mg/m2-day, which is similar to the range of dissolution rates for SIMFUEL and SNF reported in the literature for comparable conditions. SIMFUEL burnup did not have a major effect on the dissolution rate. Analysis of the solution chemistry shows that uranium is the dominant element dissolved in the posttest solutions, and the dissolution rates calculated from uranium (U) concentrations are consistent with the dissolution rates obtained from impedance measurements. Simulated-fission product elements (i.e., barium, molybdenum, strontium, and zirconium) dissolved from the SIMFUEL electrode at a relatively high rate. Sorption test results indicated significant sorption of U onto the oxide formed on stainless steel. Electrochemical methods were found to be effective for measuring the uranium dissolution rate in real time.

Material like PET {polyethylene terephthalate (C10H8O4)n} are usually thrown away present in glasses of refreshments, water bottles between others which are hard to be degraded. However, this material can be recycled and used to acquire nanostructures. During this investigation the objective was to obtain nanoparticles and carbon based nanostructures from the polymer type PET by means of microwave irradiation at the temperature of 260°C at normal pressure and at 600 psi in the presence of acids, ethylene glycol and by means of calcinations. The obtained nanoparticles of ultrananocrystalline diamonds were studied by means of scanning electron microscopy (SEM), high-resolution transmission electron microscopy (TEM), and Raman spectroscopy.

The capability of tuning the functional properties of nanosize TiO2 nanoparticles (NPs) by suitable control of surface chemistry, phase stability and crystal size plays a key role on their safe use and enhanced efficacy in actual and envisioned applications, including nanomedicine, environmental remediation, and food safety, among others. On this basis, any attempt to develop a size-controlled synthesis method and an efficient surface treatment protocol becomes indispensable. Accordingly, we have synthesized TiO2 NPs via a modified aqueous processing route using HNO3 as a catalyst and polyvinylpyrrolidone as particle size controller and a dispersing agent. The NPs surface was treated by using Ethylenediamine (EDA) as a source for amine species. Bare and amine-treated TiO2 NPs were characterized by X-ray diffraction (XRD) and FTIR spectroscopy. The photocatalytic activity of TiO2 NPs was assessed by irradiating an aqueous solution of Methylene Blue (MB) dye containing different amounts of the NPs. XRD analyses evidenced the formation of two phases of crystalline TiO2 with an average crystallite size estimated at 15.3 nm. Bare and amine-treated TiO2 NPs exhibited significant activity under UV light illumination (365 nm). Bare NPs exhibited a dye photo degradation capability of about 38.02% with particle concentration of 0.5 g/l while amine-treated NPs reported 66.18% dye photo degradation capability with particle concentration of 0.5 g/l.

The dye-sensitized solar cells (DSSC) are a technological and economical alternative to conventional p-n junction solar cells. The DSSC is composed of a transparent conducting electrode (SnO2:F) coated by a porous, nanocrystalline film of n-ZnO to which dye molecules are attached, an organic electrolyte containing a reduction-oxidation couple, and finally a counter-electrode (glass/SnO2:F) coated by a thin film of platinum. The most efficient dyes for DSSCs are based on Ruthenium polypyridyl complexes, related to the high absorption coefficient in the entire visible range and the efficient injection of electrons into the conduction band of ZnO. However, the ruthenium polypyridyl complex contains a heavy metal of relatively high cost, and synthetic routes are complicated with low yields. Moreover, natural dyes in addition to their availability, are cost-effective, non-toxic and biodegradable materials, and can be extracted by simple procedures. In this paper we report the extraction of natural dyes from the stems of mangrove (D1) and tinto (D2) trees as well as from walnut (D3) shell. First, it was necessary to dehydrate the materials, after which extraction was performed using ethanol, water and sodium hydroxide solution. The dyes were characterized using UV-visible and infrared spectroscopy. The analysis of the infrared spectra shows an intense and broad band related to OH bond stretching vibration at 3393, 3442 and 3390 cm-1 for the mangrove tree, tinto tree and walnut shell, respectively. At 1051, 1123 and 1050 cm-1, there was a very strong absorption due to the stretching vibration of CO group, for the mangrove tree, tinto tree and walnut shell, respectively. These results indicate that the functional group for bonding to the ZnO is -OH for these dyes. The results of the U-Vis spectroscopy show that the strongest absorption in the visible region is provided by dyes of the tinto and mangrove trees. The current - voltage curve of a preliminary ZnO-DSSC sensitized with the natural dye of the mangrove tree bark is presented.

Understanding electron transfer in molecular systems is important, especially in the context of molecular electronics. With the desire to incorporate biological molecules in molecular electronic devices, there is a need to establish the relative importance of the various factors like the environment and the molecular structure (DNA sequence) on the electrical conduction. There has been much debate about mechanisms of electron transfer in biological molecules. We have conducted a systematic study of electron conduction across DNA molecular segments using the non-equilibrium Green function (NEGF) method. The Hamiltonian matrix elements were determined within the framework of the Extended Hückel Approximation. In considering (CG) base pair sequences, we find that the conductance decreases with segment length and that the substitution of (AT) base-pairs also reduces the conductance. When the DNA segments are in aqueous solution, the conductance is found to almost double in magnitude.

Living neuronal cells present active mechanical structures which evolve with cellular growth and changes in the cell microenvironment. Detailed knowledge of various mechanical parameters such as cell stiffness or adhesion forces and traction stresses generated during axonal extension is essential for understanding the mechanisms that control neuronal growth, development and repair. Here we present a combined Atomic Force Microscopy (AFM)/Fluorescence Microscopy approach for obtaining systematic, high-resolution elasticity and fluorescent maps for live neuronal cells. This approach allows us to simultaneously image and apply controllable forces to neurons, and also to monitor the real time dynamics of the cell cytoskeleton. We measure how the stiffness of neurons changes both during axonal growth and upon chemical modification of the cell, and identify the cytoskeletal components most responsible for the changes in cellular elasticity. This is accomplished by identifying cellular components with unique elastic signatures, and tracking those components over time within healthy cells or within cells treated to disrupt selective components.

A new type of counter-electrode based on platinum (Pt) nanoclusters has been introduced for semi-transparent dye-sensitized solar cells (DSSCs). This electrode is fabricated using a drop coating method where Pt nanoparticles dispersed in an acetone solvent are applied on a heated indium tin oxide (ITO) coated glass substrate. Scanning Electron Microscope (SEM) and Atomic Force Microscope (AFM) images suggest that the Pt nanoparticles form a nanoporous structure with a large surface area while the distribution of Pt appears to be uniform on the surface of the ITO layer. UV/visible/near infrared transmittance spectroscopy showed that the Pt/ITO/glass electrode is highly transparent with a maximum transparency of 80% at 550 nm.

In this work a survey of possible optical stimulation processes in irradiated KCl:Eu with a focusing on photo-transfer thermoluminescence (PTTL) effects are shown. For different wavelengths in the range from 180 to 800 nm a cycle of measurements was performed, each comprising of a TL measurement after light irradiation, a TL measurement after beta irradiation for reference purposes and a PTTL measurement. The latter was obtained by applying first a beta irradiation, then a partial readout up to a certain end temperature followed by a monochromatic light irradiation of a specific wavelength and finally a TL measurement. This procedure was repeated for different partial readout end temperatures. From the results the existence of at least four different photo-transfer processes, induced by 310, 245 and 550 nm light are deduced. The photo transfer process induced by an approximate value of 245 nm produced a TL glow peak not seen before in beta or light induced TL. Furthermore it was observed that some of the TL peaks created by light of 240 and 260 nm were strongly sensitized after a beta irradiation and a partial readout.

Kinetics of the microstructural evolution in ZnO and NiO black powder mixture during prolonged mechanical processing (MP) was investigated by Scanning electron microscopy (SEM), Laser Particle Sizer (LPS), X-ray diffraction, electron paramagnetic resonance (EPR), infrared absorption (FTIR) and UV-Visible diffuse reflection methods.

Solutions of individual, unbroken single-walled carbon nanotubes in organic solvent were fabricated in a reductive dissolution process. Transparent conductive films deposited from these organic inks gave a significantly higher conductivity to absorptivity ratio than those cast from an aqueous dispersion of carbon nanotubes. For example, films from the organic ink have achieved a sheet resistance of 250 Ω/□ with transmittance of 92% at 550 nm wavelength, compared to 76% transmittance for a 250 Ω/□ film from the aqueous dispersion. The promise of these films as transparent electrodes has been demonstrated by their incorporation into organic solar cells with power conversion efficiency of 2.3%, comparable to that of solar cells produced using indium tin oxide transparent electrodes.

Periodic hybrid-exchange density functional theory (DFT) simulations are used to develop a predictive model of the structure of water on the rutile TiO2(110) surface (Θ ≤ 1 ML). A description of the adsorbed species is given: dissociated water molecules and either mixed or dissociative dimers. The behaviour of the adsorbates is rationalised by considering both direct intermolecular and surface-mediated interactions. Some of these results are then compared with those from water adsorption on the rutile SnO2(110) sur- face, isostructural to TiO2(110). Lastly, the electronic structure of the surface in contact with monolayer water (Θ = 1 ML) reveals the contributions of adsorbate states involved in the photocatalytic reaction that controls the water oxidation process.

The development of suitable waste forms for waste produced by generation IV reactors is of critical concern for future operations. To date no accepted disposal route for Tri-Structural Isotropic (TRISO) High Temperature Reactor (HTR) fuel exists. Alumino-borosilicate glass has been studied for its ability to encapsulate TRISO particle fuels. This glass was selected for its high aqueous durability. Encapsulation was achieved by cold pressing and sintering of glass powders mixed with HTR fuel. Sintering profiles capable of eliminating interconnected porosity in the composites were developed. The chemical compatibility and wetting of the glass matrix with the fuel were analysed along with the aqueous durability of the sintered glass matrix. Composites sintered under a controlled atmosphere produced unfractured monoliths with minimal chemical interaction between the glass and the TRISO particles. The Product Consistency Test (PCT) durability assessment indicated the sintered alumino-borosilicate glass was approximately an order of magnitude more durable than an equivalent R7T7 borosilicate glass. These results suggest sintered alumino-borosilicate glass-TRISO particle composites may provide a potential disposal route for spent TRISO particle fuel.

A nanopatternable oligomeric PDMS layer has been first verified as a nano-adhesive for its intrinsic transferability and universal adhesiveness. Utilizing the well-established PDMS surface modification and bonding techniques, we have been able to form irreversible bonding between a wide range of substrate pairs, representing ones within and across different material categories, including metals, ceramics, thermoset, and thermoplastic polymers. The anisotropic conductivity of the PDMS oligomer nano-adhesive has been investigated, which allows specific and excellent directional conductivity between bonded electrodes without risk of electrical shorts across different contacts.

Anodic oxide formation and chemical and electrochemical etching of n-Si(111) have been investigated in alkaline media. Due to the complexity of the processes, the investigation has been restricted to the initial phase where a transitory anodic photocurrent peak is observed slightly positive from the open circuit potential (ocp). In-system photoelectron spectroscopy, performed at the U 49/2 beamline at Bessy, shows sub-monolayer silicon surface oxidation and remnant H-termination, indicating island-type oxide formation. Scanning probe microscopy shows the formation of macropores with 300-500 nm diameter and an average depth of 5-8 nm. The discussion comprises chemical and electrochemical dissolution mechanisms and routes to development of nanoemitter fuel generating devices.

Tungsten is one the most important material for both plasma facing and structural applications in current designs for advanced divertors. Recent work has shown that composites can be manufactured from nanostructured tungsten foils which show significantly higher toughness than monolithic tungsten, but there is no data on the radiation resistance of such materials. In this study W-5 wt% Re foil in both an as rolled and annealed condition was implanted with 2MeV W+ ions to two damage levels, 0.07 and 0.4 dpa. The change in hardness was measured using nanoindentation. An increase in hardness was seen in both materials at both damage levels, with more hardening seen for the 0.4 dpa implanted samples. However the increase in hardness due to ion implantation was 2.6 times higher in the annealed material as compared to the as rolled material. This is due to the smaller grain size and higher dislocation density providing more sinks for the irradiation produced defects in the as rolled material as compared to the annealed material. Thus showing that unannealed tungsten foils are superior for use in applications in which they will see significant levels of radiation damage.

We present a detailed study carried out on oxide buffer layers grown by Metal-Organic Decomposition (MOD) on metallic substrates for YBa2Cu3O7-x (YBCO) coated conductor applications. Precursor solutions have been made starting from acetates or pentanedionates and characterized by means of Differential Scanning Calorimetry (DSC) and Thermogravimetric (TG) analyses coupled with Fourier Transform Infra-Red spectroscopy (FT-IR). Thin buffer layers have been grown by spin-coating on Ni-5at.%W substrates. X-ray diffraction spectra (XRD), Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM) have been employed in order to optimize buffer layers in terms of film microstructure and surface quality, with the final aims of producing a suitable template for YBCO growth. It will be shown that the optimization of the recrystallization process can lead to high quality buffer layer allowing the growth of YBCO films showing good superconductive properties.

Silicatein is general catalyst for synthesis of silica structure in siliceous sponges. However, the advent of biomimetic silicification by this recombinant version is limited by its poor yield. To overcome this limitation, we employed a cathepsin L as an alternative to silicatein. Cathepsin L has high sequence identity and similarity with silicatein alpha except cysteine other than serine residues at the active site. Here, we expressed recombinant hypothetical cathepsin-like protein (CAT) from Nematostella vectensis, displaying not only protease activity but also silica condensing activity. To increase the silica forming activity, some residues including cysteine in active site were changed into silicatein conserved residues. The mutant silicatein-like cathepsin (SLC) revealed increased protein stability in comparison with that of CAT when expressed in E. coli. The silica forming activity of SLC was comparable to that of SIL. SLC produced silica particles of size less than 50 nm which were increased to 200∼300 nm in the presence of a structure-directing agent, Triton X-100. Protein immobilization by SLC-mediated silicification was performed using bovine carbonic anhydrase under ambient conditions. Immobilized protein retained its enzymatic activity for a longer time and was reused up to several times. In conclusion, CAT from Nematostella vectensis was evolved to a more soluble and available biosilica forming protein that can be applied for various silica-based materials.

We report a method for stress measurement and analysis in silicon oxide thin films using optical interference. Effects of design and fabrication on stress have been studied by fabricating submicron-thick slabs of oxide anchored at one end and extending over a reflective surface. Optical interference occurs between reflections from the surface and the oxide slab, giving rise to light and dark fringes that may be imaged with a microscope. Analysis of the interference pattern at different wavelengths gives the radius of curvature and means of stress mapping. The accuracy exceeds non-interferometric profilometry using optical or confocal microscopes, and it can be more quantitative than scanning electron microscopy. This nondestructive profilometry method can aid the stress optimization of silicon oxide or other transparent thin films to achieve specific mechanical characteristics in MEMS devices.