A new hybrid material system that consists of ceria attached silica nanoparticles has been developed. Because of the versatile properties of silica and antioxidant properties of ceria nanoparticles, this material system is ideally suited for biomedical applications. The silica particles of size ∼50nm were synthesized by the Stöber synthesis method and ceria nanoparticles of size ∼2-3nm was attached to the silica surface using a hetrocoagulation method. The presence of silanol groups on the surface of silica particles mediated homogenous nucleation of ceria which were attached to silica surface by Si-O-Ce bonding. The formations of silica-ceria hybrid nanostructures were characterized by X-photoelectron spectroscopy (XPS) and high resolution transmission electron microscopy (HRTEM). The HRTEM image confirms the formation of individual crystallites of ceria nanoparticles attached to the silica surface. The XPS analysis indicates that ceria nanoparticles are chemically bonded to surface of silica and possess mixture of +3 and +4 chemical states.

An effective strategy to produce thermo-responsive islands-in-the-sea hydrogel nanofibres was developed using a single needle electrospinning setup. The produced hydrogel nanofibre mats not only showed excellent temperature response and high response speed, but also showed nanostructured surfaces.

We report the synthesis of polycrystalline films of La1-xCaxMnO3 in Si (111) by Polymer Assisted Deposition (PAD). An aqueous solution polyethyleneimine (PEI) and different metal ions stabilized with EDTA, was spin coated on hydrophilized Si substrates and subsequently annealed under different atmospheres. Homogeneous, dense polycrystalline films are obtained at optimized conditions of 950 ºC under flowing O2. The morphology and magnetic properties of the samples are compared with films obtained by Pulsed Laser Deposition.

Ba0.75Sr0.25AlSi2O8 (SBAS) - Al2O3 composites, with SBAS/Al2O3 weight ratios of: (a) 90/10, (b) 70/30, and (c) 50/50, are in situ synthesized by reactive sintering at 900-1500°C/5h. The effect of mechanical activation of the precursor mixtures for 0, 4 or 8h in an attrition milling device on the microstructure and phase composition of the composites is studied. Only SBAS and Al2O3 phases are obtained at 1300-1500°C, independently of milling time. In general, the relative proportion of the desirable monoclinic SBAS (Celsian) phase increases in the materials with increasing milling time and sintering temperature, which is enhanced by their SrO content. The promotion of surface nucleation of the undesirable hexagonal SBAS (Hexacelsian) phase by mechanical activation results in a maximum Hexacelsian to Celsian conversion fraction of only 81.4%, obtained for composition 2 milled for 8h and sintered at 1500°C/5h. Under these synthesis conditions, an increment in the amount and size of the Al2O3 particles in the composites is detrimental for the Hexacelsian to Celsian conversion.

We investigated the anisotropic g tensors of nine kinds of organic semiconductor molecules in the cationic state by density functional theory (DFT) calculations. Large anisotropy was obtained in sulfur-containing molecules because of the large spin-orbit coupling at the sulfur atoms. The calculated g values were validated by electron spin resonance (ESR) experiments for the cation radicals in solution.

Ceramics based on the general compositions CaLnXNbO7 (where Ln = La, Nd and Sm, and X=Zr and Sn) have been prepared, and irradiated with 1 MeV Kr ions at the IVEM-TANDEM user facility. The radiation tolerance of these materials has been found to be less than Zr and Hf equivalents. The results also suggest that the amorphisation cross section for these materials is related to the Ln component, and is similar to those observed for Zr and Hf equivalents.

Effect of high-pressure water vapor (HPV) annealing is discussed from density of state (DOS) by capacitance–voltage (C–V) method and ΔV FB by the cyclic C–V measurement. The DOS of HPV samples were smaller than that of conventional atmosphere (AT) annealing around conduction band minimum (E c). The ΔV FB of HPV samples were also smaller than that of AT. This suggests that HPV annealing is an effective method to decrease electron trap density as compared with AT condition. Especially, HPV 0.5 MPa sample was lower electron trap density and more stable than the other pressure HPV samples. Therefore, it is considered that the HPV in 0.5 MPa is the most promising condition. In addition, we succeeded in demonstrating the analysis of trap density in thin film by C–V method and cyclic C–V measurement.

The temperature dependent resistance R(T) and thermopower S(T) of sintered single wall carbon nanotubes (SWCNT) and magnesium diboride (MgB2) composites containing 5wt%, 10wt%, and 15wt% of SWCNTs have been measured and compared to their pure counterparts. The thermopower of both MgB2 (in the normal state) and SWCNT remain positive over the entire temperature range (10K to 300K) with room temperature values being ∼ 8μV/K and 57μV/K, respectively. The thermopower of the sintered composites decreased with decreasing temperature and switched from positive to negative near 70K. The superconducting critical temperature (Tc) of the samples ranges from 38K-41K. The room-temperature resistance ratio (RRR) is seen to depend on the sample composition. The temperature width (ΔT) is observed to increase with increasing SWCNT concentration. The normal state resistance data were fitted with the generalized Block-Grüneisen function obtaining Debye temperature of ∼ 900K.

Corrosion mechanisms take place at the extreme surface of materials before spreading in the bulk. In this way, in situ surface characterization techniques as scanning probe microscopy (Scanning Tunneling Microscopy (STM) and Atomic Force Microscopy (AFM)) allow the observations of the very initial reaction steps.

To achieve that goal, an environmental cell has been designed ; it is able to integrate either an atomic force microscope (AFM) or a scanning tunneling microscope (STM). This cell can resist to internal pressures ranging from 10-5 to 20 atm. Heterogeneous “solid – gas” reactions that only occur with pressures above several atmospheres, can then be studied. This could be achieved by following the topographical evolution of samples reacting with gaseous species. Identification of the surface defects at the origin of corrosive attacks as well as proposition of reaction mechanisms will be describe in future works.

The present work shows first in situ measurements that validate this new and unique experimental “HP-AFM” (High Pressure Atomic Force Microscope). The impact of the atmosphere’s composition as well as the pressure values on the topographical measurements recorded by the AFM system is especially studied.

In this way, a calibration standard is used to detect a potential working drift of the AFM system (scanner head displacements, optical detection …) that could lead to eventual distortions of pictures recorded and misinterpretation of observations. This sample has been studied under several experimental conditions and the results have shown an identical behaviour of the AFM used ex situ and in situ under Ar or He up to 1.5 atm as well as a good stability during long recording acquisitions (up to 90 min) necessary for kinetic studies.

Ion-exchange resins are used for purification of radioactive liquid waste from nuclear reactors. After exhaustion, resins become intermediate level radioactive waste to be managed. They have to be immobilized before being stored to improve the leach resistance of the waste matrix and to maintain mechanical stability for safety requirements. The immobilized resins are thus contained in steel drums that can undergo internal corrosion depending on the presence of certain contaminants. This work shows an study of the corrosion susceptibility of steel drums in contact with cemented ion-exchange resins with different types and contents of aggressive species. Results show that the corrosion depth of the steel drums after a period of 300 years (foreseen life-span of the radioactive waste disposal facility), in the most unfavorable case (high chloride contamination), will be considerably lower than the thickness of the wall of the drums.

Combining interdisciplinary fields of nonlinear optics, dynamic holography, and photoelectrical phenomena, we developed the optical measurement technologies for monitoring the spatial and temporal non-equilibrium carrier dynamics in wide bandgap semiconductors at wide range of excitations (1015 to 1020 cm-3) and temperatures (10 to 800 K).

We explored advantages of non-resonant optical nonlinearities, based on a short laser pulse induced refractive or absorption index modulation (Δn and Δk) by free excess carriers. This approach, based on a direct correlation between the electrical and optical processes, opened a possibility to analyze dynamics of electrical phenomena in “all-optical” way, i.e. without electrical contacts.

Carrier diffusion and recombination processes have been investigated in various wide band gap materials - differently grown GaN, SiC, and diamonds - and their key electrical parameters determined, as carrier lifetime, diffusion coefficient, diffusion length and their dependences on temperature and injected carrier density. The studies provided deeper insight into nonradiative and radiative recombination processes in GaN crystals, revealed diffusion-driven long nonradiative carrier lifetimes in bulk GaN and SiC, disclosed impact of delocalization in InGaN layers, and suggested a trap-assisted Auger recombination in highly-excited InN. Injection and temperature dependent diffusivity revealed a strong contribution of carrier-carrier scattering in diamond and bandgap renormalization in SiC.

We obtained interestingly-shaped ZnS nanocrystals in oleylamine solution and characterized their structures using HR-TEM and HAADF tomography. These interesting nanocrystals had a conical head rather than the frequently-reported pyramidal one. The cone consisted of not only low-energy planes but high Miller-index planes. In addition, we three-dimensionally and crystallographically investigated the particle growth of these nanocrystals by the same method.

Pulsed Electron Deposition (PED) is an attractive alternative to Pulsed Laser Deposition (PLD) for growing high temperature superconductor thin films because of its relatively low cost. In this study, YBa2Cu3O7-δ(YBCO) thin film has been fabricated on silicon substrates by Pulsed Electron Deposition technique. SrTiO3 (STO) as a buffer layer has been grown between Si substrate and YBCO superconducting layer. The crystalline structures of STO/Si and YBCO/STO/Si films have been investigated by x-ray diffraction (XRD). The surface morphology and microstructure of YBCO/STO/Si thin film have been characterized with atomic force microscope (AFM) and scanning electron microscope (SEM). From the θ-2θ XRD analysis of YBCO thin films, (00l) diffraction peaks are obtained indicating they have a poor c-axis oriented structure. SEM analysis shows that the surfaces of films are crack-free, but they have some particulates. On AFM images, the droplets are clearly observed leading to a roughly surface.

In this research, we describe the electrospinning processing of polylactic acid (PLA) and the influence of silver nanoparticles on the morphology and microstructure of produced non woven membranes thus produced. The PLA was electrospun from a chloroform solution and a filamentary and granular morphology was obtained, the filaments having an average diameter of 1.25 μm, When silver nanoparticles (of ca. 12 nm size) were incorporated, the filaments diameter was reduced to an average of 0.65 μm, and the density of beads was also reduced. The membranes were rather amorphous, as revealed by X-ray scattering, presumably due to the quenching process associated with the electrospinning process. Water contact angle measurements showed that silver nanoparticles induced significant hidrophobicity in the membranes as neat PLA membrane had a contact angle of 54° and PLA/Ag membrane exhibited an angle of 115°.

Ni-Cr-Mo alloys offer an outstanding corrosion resistance in a wide variety of highly corrosive environments. Alloys 625, C-22, C-22HS and HYBRID-BC1 are considered among candidates as engineered barriers of nuclear repositories. The objective of the present work was to assess the effect of temperature on the crevice corrosion resistance of these alloys. The crevice corrosion repassivation potential (ER,CREV) of the tested alloys was determined by the Potentiodynamic-Galvanostatic-Potentiodynamic (PD-GS-PD) method. Alloy HYBRID-BC1 was the most resistant to chloride-induced crevice corrosion, followed by alloys C-22HS, C-22 and 625. ER,CREV showed a linear decrease with temperature. There is a temperature above which ER,CREV does not decrease anymore, reaching a minimum value. This ER,CREV value is a strong parameter for assessing the localized corrosion susceptibility of a material in a long term timescale, since it is independent of temperature, chloride concentration and geometrical variables such as crevicing mechanism, crevice gap and type of crevice former.

This paper reports on electrochemical hydrogen oxidation at atomically smooth single crystal surfaces. These surfaces are considered as planar models for (bi)metallic nanoparticles that are commonly used as catalytically active electrode materials in low-temperature fuel cells. These samples are prepared in ultrahigh vacuum but are characterized under conditions of enhanced mass transport in hydrogen saturated electrolyte. The two examples shown in this paper are Ru(0001) with or without an atomically thin layer of Pt. The Pt thin layer turns out to be more active than pure Ru(0001) by three orders of magnitude and also more active than bulk Pt electrodes. We show that those findings agree very well with predictions based on density functional theory in combination with a simple kinetic model.

Deep boreholes have been proposed for many decades as an option for permanent disposal of high-level radioactive waste and spent nuclear fuel. Disposal concepts are straightforward, and generally call for drilling boreholes to a depth of four to five kilometers (or more) into crystalline basement rocks. Waste is placed in the lower portion of the hole, and the upper several kilometers of the hole are sealed to provide effective isolation from the biosphere. The potential for excellent long-term performance has been recognized in many previous studies. This paper reports updated results of what is believed to be the first quantitative analysis of releases from a hypothetical disposal borehole repository using the same performance assessment methodology applied to mined geologic repositories for high-level radioactive waste. Analyses begin with a preliminary consideration of a comprehensive list of potentially relevant features, events, and processes (FEPs) and the identification of those FEPs that appear to be most likely to affect long-term performance in deep boreholes. The release pathway selected for preliminary performance assessment modeling is thermally-driven flow and radionuclide transport upwards from the emplacement zone through the borehole seals or the surrounding annulus of disturbed rock. Estimated radionuclide releases from deep borehole disposal of spent nuclear fuel, and the annual radiation doses to hypothetical future humans associated with those releases, are extremely small, indicating that deep boreholes may be a viable alternative to mined repositories for disposal of both high-level radioactive waste and spent nuclear fuel.

In this work, we demonstrated the growth of three dimensional graphene/carbon nanotubes hybrid carbon nanostructures on metal foam through a one-step chemical vapor deposition (CVD). The as-grown three dimensional carbon nanostructure foams can be potentially used as the electrodes of energy storage devices such as supercapacitors and batteries. During the CVD process, the carbon nanostructures are grown on highly porous nickel foam to form a high surface area 3-D carbon nanostructure by introducing a mixture precursor gases (H2, C2H2). The surface morphology was investigated by scanning electron microscopy (SEM) and the results demonstrated relatively homogeneous and densely packed 3-D carbon nanostructure. The quality was characterized by Raman spectroscopy. To further increase the capacitive capability the supercapacitors were fabricated based on the electrodes of carbon nanostructure foam and cyclic voltammetry, charge-discharge, and electrochemical impedance spectroscopy (EIS) were conducted to determine their performance.