A T-Jump/Time-of-Flight Mass Spectrometer (T-Jump/TOFMS) is used to probe the decomposition of several aminotetrazole containing energetic materials under very high heating rates of 105-106 K/s. Subtle differences between materials in functional group placement and anion composition allow for further understanding of the decomposition pathway of the tetrazole structure and various anions. Two decomposition pathways for the tetrazole ring are observed, which result in the primary formation of HN3 or N2. Further analysis is performed using a rapid-heating μ-DSC device, which revealed lower activation energies than previously reported.

Electroless (chemical) copper deposition, followed by electrolytic (galvanic) copper deposition, is used to construct electrical interconnects for electronic components on insulating substrate materials. As smooth substrates, such as glass or flexible materials like polyimide or polyethylene terephthalate, are used increasingly, achieving the required level of adhesion becomes more difficult. The film strain is one key variable that influences film adhesion. Standard X-ray diffraction based strain analysis was adapted for in situ strain monitoring during and after wet-chemical copper deposition. The results show that adding nickel suppresses an initial compressive strain that frequently appears in Ni-free baths. Adding ruthenium complexes to a standardized electroless copper formulation gradually shifts the strain from tensile to compressive. Spontaneous recrystallization at room temperature was monitored in detail for films obtained by direct current galvanic copper plating.

A combinatory approach of Step-and-Flash Imprint Lithography (SFIL) and Metal-Assisted Chemical Etching (MacEtch) was used to generate near perfectly-ordered, high aspect ratio silicon nanowires (SiNWs) on 4" silicon wafers. The ordering and shapes of SiNWs depends only on the SFIL nanoimprinting mould used, thereby enabling arbitary SiNW patterns not possible with nanosphere and interference lithography (IL) to be generated. Very densely packed SiNWs with periodicity finer than that permitted by conventional photolithography can be produced. The height of SiNWs is, in turn, controlled by the etching duration. However, it was found that very high aspect ratio SiNWs tend to be bent during processing. Hexagonal arrays of SiNW with circular and hexagonal cross-sections of dimensions 200nm and less were produced using pillar and pore patterned SFIL moulds. In summary, this approach allows highlyordered SiNWs to be fabricated on a wafer-level basis suitable for semiconductor device manufacturing.

To assess the long-term behavior of spent fuel in alkaline conditions representative for the Belgian Supercontainer design, static and dynamic dissolution tests were performed with depleted and Pu-doped UO2 , simulating medium burn-up UOX fuels of different fuel ages. The experiments were performed under argon atmosphere at 25 – 30°C in cement waters in the pH range 11.7 – 13.5 and at different SA/V ratios. This paper presents the observed UO2 matrix dissolution rates based on the (238U or 233U) release, and proposes a selection of reference dissolution rates for performance assessment. We demonstrate that the dissolution rates at high pH are equivalent to the dissolution rates reported in the literature for neutral pH conditions. The α-activity threshold below which radiolytical fuel oxidation becomes negligible, seems to be close to the threshold reported for anoxic media at neutral pH.

In the present global environmental context, it becomes more and more critical to find efficient solutions to lower our energy consumption on one hand, and to produce energy from clean renewable sources on the other hand. Consequently, research efforts on materials for energy applications are intensifying.

The present work aims at developing optoelectrical components usable for both energy saving (light emitting diodes) and renewable energy production (solar cells) by fabricating p-n heterojunctions based on a single semiconductor, titanium dioxide. TiO2 is indeed a very promising candidate: it is chemically and physically stable under irradiation, transparent to visible and near-infrared light (Eg= 3 – 3.5 eV), presents photocatalytic activity, is non-toxic and low cost, which permits to envisage its large scale use.

In the present paper, the proposed architecture for both solar cells and LEDs is original as well as common for both applications: a three-dimensional architecture based on an anodic alumina nanoporous membrane which serves as nanomask for TiO2 growth in order to enlarge the effective surface of the components. TiO2is synthesized by Atomic Layer Deposition (ALD), a technique particularly well adapted to the deposition of ultrathin films (from one monolayer to few tens of nanometers) on 3D porous substrates patterned with high aspect ratio nanopores.

In this work, the capacity of synthesizing 3D nanostructures is demonstrated. TiO2ultrathin films (10 to 100 nm) were grown by ALD on flat, micropatterned, microporous and nanoporous anodic alumina membranes (AAM) substrates. The films were highly conformal, as confirmed by SEM and TEM imaging. Both EDS and XPS analyses validated the dioxide film stoichiometry.

Dye type solar cells, especially those incorporating low cost dyes suffer from a very narrow photo-response wavelength range. Motivated by natural photosynthesis research, energy relay dyes (ERDs) appear to offer a possibility to broaden the dye-cell spectral response. In-turn photovoltaic cells can be an extremely sensitive tool for investigation of dye ERD photochemistry. Sensitive Chlorophyll based dye-type solar cells were prepared from purified natural Chlorophyll A. The importance of Chlorophyll purity is discussed as well as the use of purified Chlorophyll A in combination with ERD’s. . Results shed light on many interesting phenomenon including the nature of purified Chlorophyll A excitation and absorption. Importantly, it was found by this work that the ERD architecture when combined with a photosensitizer do not appear to having greater absorption in the infrared region of the spectrum than the ERD alone indicating a lack of cooperative absorption.

Tb and Yb co-doped oxyfluoride glasses were fabricated in a lithium-lanthanum-aluminosilicate matrix by a melt-quench technique. Glass-ceramics were obtained by appropriate heat treatment of the as-prepared glasses. Visible to near-infrared down-conversion quantum cutting was studied for samples with different thermal annealing temperatures and time. Laser light at 488 nm was used to excite Tb3+ ions while Yb3+ ions were excited by energy transfer from the excited Tb3+ ions. Near-infrared emission at 940 – 1020 nm was observed. It has been found that the emission at 940 – 1020 nm increased significantly from the glass-ceramic compared to that of the as-prepared glass. This result suggests that the energy-transfer efficiency increases in glass-ceramics compared to that in glass. A significant portion of rare-earth ions may be incorporated inside LaF3 nanoparticles (NPs) in the glass-ceramic. Because the Yb3+ emission at 940 – 1020 nm is matched well with the band gap of crystalline Si, the quantum cutting effect may have its potential application in silicon-based solar cells.

We present a joint experimental and theoretical study dedicated to analyze the properties of Boron-Nitride (BN) nanotubes. First, multi-walled boron-nitride (MWBN) nanotubes were prepared by means of a modified electric arc discharge technique using boron-nitride powder. In a first stage, the BN powder was subjected to a ball milling process for about 100 hours in an atmosphere of ammonia. Later on, BN nanoparticle formation took place after the preparation of a pressed pellet at 300 °C to 25 kPa which was sintered in a furnace at approximately 1000 °C in nitrogen atmosphere for 15 hrs. The pellets were subsequently incorporated to the electrical arc discharge set up to obtain the MWBN nanotubes. The as-prepared MWBN nanotubes samples were characterized by scanning electron microscope, X-ray photoelectron spectroscopy, and micro RAMAN spectroscopy. Second, and in order to understand the measured data, extensive density functional theory calculations were performed. We present low energy atomic configurations for model finite-length armchair, zigzag, and chiral single-walled BN nanotubes, as well as for two-dimensional BN sheets. We calculate the vibrational spectra and the optical gap of each one of our considered structures and reveal how precise details of the local atomic environment can be revealed. Finally, we consider BN nanotubes functionalized with NH2, glycine and S-H molecules. We present the structural characteristics of the adsorbed configurations, charge transfer effects, and the electronic behavior. We conclude by underlining the crucial role played by molecular functionalization in order to tune the properties of these kinds of systems.

Cu-doped ZnO film in nanowire structure is synthesized by a closed space flux sublimation and periodic oxidation method at ∼300°C over Si substrate. Oxidative process controlled selfcatalytic VLS mechanism is proposed for the film growth. X-ray diffraction pattern establishes that Cu-doped ZnO nanowires retain the crystallite structure of the wurtzite ZnO. TEM studies indicate single crystal character of the Cu-doped ZnO nanowires. Optical absorption analysis of Cu-doped ZnO nanowires defines two direct energy band gaps. The low energy band gap at 3.2eV is intrinsic to the Cu-doped ZnO material. The higher energy band gap at 3.5eV is attributed to the nanosize, mediated by strong forward scattering of light from the nanowires. Sharp photoluminescence in Cu-doped ZnO corresponding to near bandgap free exciton emission is observed and a redshift of ∼0.07 eV is consistent with the effect of Cu-doping. The visible emission band in both ZnO and Cu-doped ZnO shows a broad green emission band with Cu-substitution shifting the maximum visible luminescence towards the higher energy side.

To demonstrate the effects of particle size and alloying on hydrogen adsorption on metals, we explore stable configurations of Pd-Pt alloy using a 55-atom cubo-octahedron. Via first-principles based cluster expansion method, we obtained groundstate configurations and show how their hydrogen adsorption energies change with Pd-Pt composition. Comparison with surface adsorption energies further shows the effect of particle size.

Thin films of zirconium oxide (ZrOx) and hafnium oxide (HfOx) were rf sputtered onto fused silica substrates in an oxygen rich argon environment. Pure zirconium and hafnium targets were used, and the oxygen partial pressure was varied to control the oxygen stoichiometry. Measurement of the EPR characteristics of the ZrOx films indicated two peaks corresponding to two orientations of the magnetic field. This anisotropic response suggested the films were polycrystalline with a preferred orientation. This was confirmed by XRD pole figures. The measured g-values for the ZrOx films were less than the free-spin g-value, indicating the defects corresponded to electron traps. It was further shown that the lower the oxygen partial pressure during deposition, the larger the EPR response, strongly suggesting the traps correspond to oxygen vacancies in ZrOx. Hafnium oxide thin films were also characterized by EPR. The EPR measurements indicated the presence of a single resonance peak, suggesting these films were polycrystalline without a preferred orientation or amorphous. XRD measurements confirmed that the HfOx films were amorphous. The g-value for these films was greater than that the free-spin value, indicating the presence of possibly self-trapped oxygen hole centers. These results will be discussed in the context of prior experimental and theoretical work on these systems.

The breaking strength that can withstand solder is known as resistance welding, low resistance welding will cause a failure of the weld. This study optimized the effect of the main variables in a welding steel proceess on the mechanical propierties of the steel like the resistance welding. The main variables studied were electrode, machine, post induction, and dotted pressure. The factors that have the most influence in the resistance welding are the post induction, and the combination of post induction and the raw material.The statistical model used for the evaluation process was an analysis of variance (ANOVA) in a full crossing factorial design 2k with a second order of interaction.

Bismuth ferrite (BiFeO3) is a magnetoelectric, multiferroic material with coexisting ferroelectric and magnetic orderings. It is considered as a candidate for the next generation of ferroelectric random-access memory devices because BiFeO3, in contrast to industrial ferroelectrics used today, does not contain the toxic element lead. Furthermore, its polarization values are higher than those of lead-based ferroelectrics. The magnitude of the polarization of a BiFeO3 film is dependent on its orientation and is related to the domain structure. This contribution presents and discusses the preparation of epitaxial BiFeO3 (BFO) thin films grown on SrRuO3/SrTiO3 substrates by pulsed laser deposition (PLD) and their characterization, especially by piezo force microscopy (PFM) and atomic force acoustic microscopy (AFAM). The thickness of an individual BFO film varies between 100 and 200 nm. The epitaxial nature of films in the crystallographic (100), (110), and (111) directions was confirmed by x-ray diffraction (XRD). Thin SrRuO3 layers, also prepared by PLD, were used as bottom electrode for the ferroelectric hysteresis measurements. Low frequency PFM measurements showed a monodomain structure for the as-grown (110) and (111) oriented samples. In BFO (100) films, different polarization variants were observed by ultrasonic piezo force microscopy (UPFM). The domain structure is reproduced from minimization of the electrostatic and elastic energies. Switching experiments using standard PFM as well as UPFM were carried out on the three samples with the objective of testing the coercive field and domain stability. The AFAM technique was used to map the elastic properties of the BFO thin-films at the micro- and nanoscale.

Nanocomposite Bi2Te3 based alloys are attractive for their potentially high thermoelectric figure-of-merit (ZT) around room temperature. The nano-scale structural features embedded in the matrix provide more scattering of phonons and can thus reduce the lattice thermal conductivity. To further take advantage of such nanocomposite structures, we focus on the development of nanocrystalline Bi(Sb)Te(Se) powders by high energy cryogenic mechanical alloying followed by an optimized hot pressing process. This approach is shown to successfully produce Bi(Sb)Te(Se) alloy powders with grain size averaging about 9 nm for n-type BiTe(Se) and about 16 nm for p-type Bi(Sb)Te respectively. This cryogenic process offers much less milling time and prevents thermally activated contamination or imperfections from being introduced during the milling process. The nanocrystalline powders are then compacted at optimized pressures and temperatures to achieve full density compactions and preserve the grain sizes effectively. The resulting nano-bulk materials have optimal Seebeck coefficients and are expected to have improved ZT. Thermoelectric properties and microstructure studies by X-ray diffraction and transmission electron microscopy will also be presented and discussed.

The work presented is devoted to study the mechanisms and kinetics of plastic deformation of bcc and fcc metals and alloys under shock-wave loading (strain rates > 105 s-1). To study the behavior of metals under conditions described the two scale approach is developed. It comprises molecular dynamics (MD) calculations of dislocation mobility and dislocations nucleation rate and continuum mechanics model with equations for description of elastoplastic deformation, kinetics and dynamics of dislocations.

Dislocation velocities as functions of applied shear stress are calculated from MD in a wide temperature range up to the melting point. Velocity-dependent drag coefficient is introduced to approximate the data obtained.

The influence of Guinier–Preston (GP) zones on dislocation motion is analyzed. The results obtained are used to evaluate temperature dependence of dynamic flow stress and the evolution of dislocations subsystem under shock loading. Data on the attenuation of the elastic precursor and rare surface velocity profiles calculated for Al are in good agreement with the experiments. Simulation of the free surface velocity profiles during shock-wave loading of AlCu alloys is carried out.

We report on the formation of hierarchical nanostructures of Au, Pt, Fe2O3 and PdO2 using a hybrid technique combining laser interference patterning (LIP) and block copolymer phase separation (BCPS). By varying the loading time of the block copolymer with metallic salts and the laser interference technique, different types of hierarchical square, triangular, linear and circular arrays can be formed. Such a robust method can be applied to other metallic and ceramic materials and has potential for use in the large-scale production of nano-catalysts, photonics, optoelectronics, MEMS devices and bio-sensors.

It has been found that the blue light emission of LED is remarkably enhanced by using optical window of CaF2 disk doped with Eu2O3. The CaF2 crystals doped with Eu2O3 strongly absorb UV light with 330~420nm optical wavelength as a cutting filter. Instead, CaF2 crystals emit 420~425nm wavelength visible light. As a result, the UV light shifts to a light of around 420nm wavelength, and the LED light emission intensity markedly increases. In our experiments, the UV components were absorbed, while, around 420nm emitting light has been strengthened by more than 30%. The FWHM value is improved by around 30%.

Nuclear graphite components are produced from polycrystalline artificial graphite manufactured from binder and filler coke material with approximately 20% porosity. During the operational lifetime of a nuclear reactor the graphite moderator is subjected to fast neutron irradiation which contributes to changes in material and physical properties such as thermal expansion co-efficient, young’s modulus and dimensional change. These changes are directly driven by irradiation induced changes to the crystal structure as reflected through the bulk microstructure. Therefore it is important that irradiation changes and there implications on component property changes are understood. Work carried out under the FP7 CARBOWASTE consortium under work package three is underway to characterize both structural and radiological damage in graphite. This study examines a range of irradiated graphite samples removed from the British Experimental Pile Zero (BEPO) reactor. Raman spectroscopy and Transmission Electron Microscopy (TEM) have been used to compare the effect of increased irradiation Fluence on graphite microstructure. Irradiation induced crystal defects and changes in crystallite size are observed using TEM and related to Raman Spectroscopy, comparisons are also made to virgin nuclear grade graphite.

A three-dimensional (3D) carbon nanotube (CNT) resistor network computational model was developed to investigate the electrical conductivity, and current and thermal flow in polymer composites with randomly dispersed CNTs. A search algorithm was developed to determine conductive paths for 3D CNT arrangements and to account for electron tunneling effects. By coupling Maxwell specialized finite-element (FE) formulation with Fermi-based tunneling resistance, specialized FE techniques were then used to obtain current density evolution for different CNT/polymer dispersions and tunneling distances. These computational approaches address the limitations of percolation theories that are used to estimate electrical conductivity of CNTs. The predictions indicate that tunneling distance significantly affects 3D electrical conductivity and thermal distributions.