Cladding tubes of water-cooled nuclear reactors are usually made of Zircaloy and are an important retaining element for radionuclides present in the fuel both during predisposal activities such as reloading of fuel assemblies from interim storage casks to final disposal casks and during final disposal in the case of canister breaching. However, cladding integrity is affected by various processes during reactor operation and beyond, e.g. fuel cladding chemical interaction and fission product precipitation onto the inner cladding surface. Using experimental and modelling methods, the radionuclide inventory of an irradiated Zircaloy-4 plenum section is analyzed. Quantities of 235/238U, 237Np, 238/239/240/241/242Pu, 241/243Am, 243/244Cm besides 14C, 55Fe, 125Sb, 154Eu, and 134/137Cs were (radio-)chemically determined in digested Zircaloy-4 subsamples. Measured inventories of activation products in the Zr-alloy are in good agreement with calculated values. However, amounts of actinides and fission products exceed the calculated inventory by factor ∼57 (minor actinides and non-volatile fission products) and ∼114 (137Cs). Excess of minor actinides and part of enhanced Cs inventory originate from fuel residues deposited on the inner cladding surface during fuel rod fabrication, whereas vast amount of cesium is volatilized from subjacent fuel pellets and transported to the plenum.

Environmental atomic force microscopy (AFM) study of brush macromolecules, polymer blends and bitumen was performed with regular and Quick Scan imaging. Condensation of different vapors on sample surface has induced swelling of hydrophilic domains that helps recognizing the components of heterogeneous compounds. High-resolution imaging of brush macromolecules was achieved in ethyl acetate vapor. Fast monitoring of aggregation/spreading of brush macromolecules revealed dynamics of conformational changes and molecular motion.

We applied NiSi2 as an electrode for thermoelectric modules because NiSi2 has high electric conductivity and is expected to suppress the inter-diffusion of Si from MgSi2 and higher manganese silicide (HMS). The thermal expansion coefficient of NiSi2 is close to that of Mg2Si but differs from that of HMS. Therefore, to reduce thermal stress, we tried to insert a buffer layer consisting of HMS and NiSi2 for the interface between the HMS sintered body and the NiSi2 electrode. The NiSi2 was prepared by using spark plasma sintering (SPS) equipment. NiSi2 electrodes and gradients were formed and connected with the HMS by SPS treatment. Crack-free bonding was achieved by inserting gradients consisting of HMS and NiSi2. The inserted composite buffer layer reduced interface stress and interface resistance between HMS and NiSi2.

Epoxy is widely used as structural adhesive for bonded material systems in aerospace, construction, microelectronics and other industrial applications. In order to achieve better performance, carbon nanotubes are often applied as reinforced additives due to the extraordinary mechanical properties. The resulting carbon nanotube-reinforced epoxy has presented enhancement in the bonding strength and durability during long-term sustained loading. However, the bonded material systems in reality usually suffer from different ambient environments, especially varying temperature conditions. The evaluation of temperature effect on creep responses at the interface between epoxy adhesive and substrate becomes an essential issue. The investigation is conducted using molecular dynamics simulations to study the interfacial creep behavior in the bilayer system containing carbon nanotube-reinforced epoxy and silica substrate. The simulation results show the atomistic movement at the interface region under constant loading at various temperature levels, and indicate the improved properties with the addition of carbon nanotubes in epoxy matrix. The study enriches the understanding of temperature effect on the interfacial creep behavior at the atomic level, and provides promising predictions and guidelines for the design of composite materials in long-term applications.

Shale formations are considered by a number of countries as the most suitable media to dispose of high-level radioactive waste. This is mainly due to the impermeable, self-sealing, chemical reducing, and sorption properties that tend to retard radionuclide migration. However, shale formations can also contain highly connected fault zones with permeabilities that can differ of several orders of magnitudes with respect to the undeformed host rock. The objective of this work is to use the 14C-PMMA autoradiography method combined with SEM-EDS measurements to understand the porosity variations in and around fault gouges and to define their relationship to mechano-chemical processes. The studied samples were taken from a low permeability shale in a small-scale vertical strike-slip fault at the Tournemire underground research laboratory. Results display significant variations in porosity and mineralogy along the studied gouge zone due to polyphased tectonics and paleo-fluid circulations.

Catalytic activity of conducting polymers in biofuel cells has been studied in comparison with the performance of Pt-black (Pt-B). The cells were direct and passive type with structure of biofuel/anode catalyst/Nafion®/cathode catalyst/air. Conducting polymers of polyaniline, polypyrrole and poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT*PSS) were examined for the anode and cathode catalysts. L-ascorbic acid was used as the biofuel, and the Nafion® was served as a proton transfer membrane. In the standard Pt-B anode/Pt-B cathode cell, the typical Voc (open circuit voltage) = 0.52 V, ISC (short circuit current) = 8 mA/cm2 and the Pmax (maximum power density) of approximately 0.8 mW/cm2 were obtained. In a cell with catalysts of PEDOT*PSS anode/Pt-B cathode, Voc = 0.55 V and the maximum power density of 1.2 mW/cm2 were obtained, which were larger than that of the standard Pt-B/Pt-B cell. Polyaniline and Polypyrrole were also found to be a potential candidate for catalysts in biofuel cells.

Pb-based organometal halide perovskite solar cells have passed the threshold of 20 % power conversion efficiency (PCE). However, the main issues hampering commercialization are toxic Pb contained in these cells and their instability in ambient air. Therefore, great attention is devoted to replace Pb by Sn or Bi, which are less harmful and - in the case of Bi - also expected to yield enhanced stability. In literature, the most efficient hybrid organic-inorganic methylammonium bismuth iodide (MBI) perovskite solar cells reach PCE up to 0.2 %. In this work, we present spin-coated MBI perovskite solar cells and highlight the impact of the concentration of the perovskite solution on the layer morphology and photovoltaic (PV) characteristics. The solar cells exhibit open-circuit voltages of 0.73 V, which is the highest value published for this type of solar cell. The PCE increases from 0.004 % directly after processing to 0.17 % after 48 h of storage in air. 300 h after exposure to air, the cells still yield 56 % of their peak PCE and 84 % of their maximum open-circuit voltage.

Sodalites have been investigated experimentally for the capture and long-term containment of 129I, a significant and hazardous waste product of the nuclear fuel cycle. Sodalites are zeolite-type structures commonly occurring in nature in alkaline igneous rocks and having the prototype formula Na8(AlSiO4)6Cl2. The crystal structure is based around β-cages consisting of corner-sharing SiO4 and AlO4 tetrahedra. In the centre of the β-cage is an anion X. Iodine captured by sodalites sits in the centre of the β-cages as iodide anions. Silver iodide (AgI) plays an important role in the capture and subsequent processing of 129I in the nuclear fuel cycle. Using ab initio density functional theory (DFT) modelling, we investigate the energetics and feasibility of iodine capture and containment in mixed cation sodalites Na8-xAgx(AlSiO4)6I2, and compare the results with experimental observations.

Interest in active metamaterial (MM) devices has recently increased due to their potential for tunable, switchable, and scalable optical responses. More specifically, a dynamic, on-chip MM polarizer has applications ranging from material characterization to sensing without the need for cumbersome external filters. This work demonstrates efforts to optimize MM devices for dynamic polarization filtering by combining elements from split-ring resonators, wire-pairs, and fishnet patterns. The polarization grid has been designed to operate under an applied voltage with simulated on/off ratios of 75% and dynamic polarization selectivity of 70%. Samples have been fabricated using epitaxial GaAs on sapphire with various n-type doping concentrations to approximate electrical tuning.

Organolead iodide perovskites, CH3NH3PbI3, have attracted the attention of researchers around the world due to their optical and electrical properties. Their main characteristics include, direct band-gap (1.4 to 3.0 eV), large absorption coefficient in the visible spectrum, long carrier diffusion length and ambipolar charge transport. Aside that, perovskite thin films can be produced with low cost and are compatible with large-scale manufacture. Perovskite thin films have been synthesized mainly by spin-coating technique and thermal evaporation, which can be executed in one or two steps. Aiming to increase the light absorption, nanostructured perovskite thin films are also under intense study, since the nanostructures can absorb more light than a flat film. Thus, in this work, we reported the synthesis of perovskite (CH3NH3PbI3) nanorods by means of conversion of lead sulphide quantum dots (PbSQD). The perovskite nanorods were grown by exposing the PbSQD to a highly concentrated iodine atmosphere and then dipping the resulting film in methylammonium iodide (CH3NH3I) solution. The first step converts completely the PbSQD into lead iodide (PbI2) nanowires, ≈50 µm long and ≈200 nm diameter, through substitution of sulphur by iodine atoms and subsequent aggregation of the particles. The later step converts the PbI2 nanowires in perovskite nonorods (≈5 µm long and ≈400 nm diameter). The perovskite nanorods present a regular geometry along all its length. A preferential alignment of nanorods to the substrate plane was observed. The preliminary results show that we can control the size of nanorods through exposition time of PbSQD to iodine, which change the size of PbI2 nanowire as well. The conversion process was studied by x-ray diffraction, optical absorption, photoluminescence and scanning electron microscopy.

Recently, Plasma Assisted Atomic Layer Deposition Technique will easily control the thickness and the composition of semiconductor films. The radical generated by using the plasma techniques, gave the decrease of the defect into the semiconductor films. In this investigation, the relationship between microwave plasma power, nitrogen gas flow rate and concentration of generated nitrogen radical, was evaluated. At the first, Plasma emission spectrum at microwave plasma power (0 to 400W) was measured using a mixed 200sccm argon gas and 10sccm nitrogen gas. Next, the plasma emission spectrum was measured in the mixing of nitrogen gas flow rate (0 to 40sccm) with 200sccm argon gas flow rate. At that time, the microwave plasma power was set to 200W. Nitrogen radical spectrum were identified from all the emission spectrum, and the nitrogen radical intensity was calculated. As a result, the nitrogen radical intensity became the largest at 200sccm argon gas flow rate and 10sccm nitrogen gas flow rate. In addition, the nitrogen radical intensity increased in proportion to the microwave plasma power. The concentration of generated nitrogen radical could be controlled by changing the microwave plasma power and the nitrogen gas flow rate. Mentioned above, nitride thin films will be obtained on Si Substrates by microwave generated remote plasma assisted atomic layer deposition technique.

Polycrystalline materials’ mechanical properties and failure modes depend on many factors that include diffusion and segregation of different alloying elements and solutes as well as the structure of its grain boundaries (GBs). Segregated solute atoms to GB can alter the properties of steel alloys. Some of these elements lead to enhancing the strength of steel, on the other hand others can degrade the toughness of steel significantly. It is well known that carbon increases the cohesion at grain boundary. While the presence of hydrogen in steel have a drastic effects including blistering, flaking and embrittlement of steel. In practice during forming processes, the coincidence site lattice (CSL) GBs are experiencing deviations from their ideal configurations. Consequently, this will change the atomic structural integrity by superposition of sub-boundary dislocation networks on the ideal CSL interfaces. For this study, the ideal ∑3 (112) structure and its angular deviations in BCC iron within the range of Brandon criterion are studied comprehensively using molecular statics simulations. The GB and free surface segregation energies of carbon and hydrogen atoms will be quantified. Rice-Wang model is used to assess the strengthening/embrittlement impact variation over the deviation angles.

Polarization-dependent absorption spectra of two functionalized derivatives of fluorinated anthradithiophene, diF TES-ADT and diF TDMS-ADT, were studied in the crystal phase using a Holstein-like Hamiltonian. For both molecules, the primary contribution to the lowest energy absorption was found to be the S0-S1 excitonic transition perturbed by an intermolecular coupling of 15 meV for both TES and TDMS. A secondary contribution, consistent with that from charge-transfer states, was also found. Additionally, absorption spectra were analysed when crystals were placed inside of optical microcavities formed by two metal mirrors. Cavities exhibited a primary absorption peak determined to be an enhanced absorption from the lowest-energy S0-S1 transition.

Thin film tin sulphide (SnS) was deposited on to molybdenum (Mo) substrates using metal organic chemical vapor deposition at 470°C using tetraethyltin and ditertiarybutylsulfide as precursors. In situ mass spectroscopy was used to study the exhaust gas species downstream of the reaction zone. The precursor vapor carrier gas was either nitrogen or hydrogen, thin film SnS only forming when the latter was used. Mass spectroscopy determined that hydrogen sulfide was being produced and playing a critical role in the vapor phase reaction process and adsorption of tin and sulfur on to the Mo surface. As-grown grain sizes were determined by scanning electron microscopy and were observed to be large averaging around 2 microns across. X-ray diffraction showed the films to be single phase SnS without any parasitic Sn2S3 or SnS2 phases, with a small amount of MoS2 also being detected.

Several reports have shown band-gap tuning in TMDs, from indirect band gap in the bulk material to a direct gap in single layer due to the absence of interlayer coupling. This unique property stems from the modified electronic states. The phononic properties are extremely modified as well, due to layered effect and quantum size effect. There are several reports on layered effect; however, reports on the confined phonon states in these structures are limited. Thus, we present a preliminary studies of the confined phonon states in TMDs (WS2 and MoS2) quantum dots, and elucidate on the evolution of the phonon lineshape with diameter using a phenomenological model with an envelop function that truncates the phonon wave at the surface of the quantum dot. Furthermore, we delineate the layered effect from the quantum size effect in the phonon lineshape of WS2 and MoS2.

Flexible sensors are fundamental components of flexible electronics allowing a great number of applications from compliant robots to biomonitoring devices. The present work developed a carbohydrate-based elastomer (CBE) which possesses flexibility and tunable properties to meet the requirements of several sensing applications. Specifically, CBE was engineered to have high elasticity and sensing capabilities to humidity, stress and strain, enabling possible applications for monitoring physiological and external mechanical stimuli. These sensing capabilities of CBE were also adjustable to meet the requirements of applications such as electronic skin and wearable electronics.

The main functions of the dynamic cantilever calibrator (DCC), which are related to characterization of AFM probes and instruments, are demonstrated on a variety of probes. The resonant frequency, Q-factor and spring constant of the rectangular and V-shaped probes were evaluated by thermal tune method. The inverse optical sensitivity and optical beam deflection noise, which define performance of AFM microscopes, were extracted from DCC data. Peculiarities of thermal tune studies and the use of DCC for advanced applications are discussed.

This paper presents experimental results on the synthesis of boron rich diamond-like carbon phases (BCx) obtained by high pressure sintering (s-BCx) and pulsed laser deposition (PLD-BCx). It has been shown that sintering of a mixture of a powder of micro-diamonds with a powder of boron in the toroid type high pressure device leads to the creation of s-BCx phase with a low resistivity, and high elastic moduli. The PLD-BCx film found to be rigid with the resistivity as low as that of best conductive boron–doped diamond films. It indicates that the presence of B atoms in a laser plasma leads to the formation of sp3 bonds in the material in the process of chemical sputtering. The combination of unique characteristics can be achieved by changing the ratio B/C.

Alginate is a hydrogel polymer commonly used in multiple drug delivery and cellular tissue transplantation applications. Tunability, gel formation, and stabilization properties of this biopolymer contributes to a better controlled and prolonged release of encapsulated drugs as well as the ability to provide immunoisolation to transplanted cells. One commonly used application of this biopolymer is pancreatic islet transplantation, as a promising approach of providing insulin to type 1 diabetics. The encapsulant alginate provides passage to nutrients, glucose and oxygen and allows the insulin to diffuse while blocking immunoglobulins. In this study, a hydrogel encapsulator is designed and used to fabricate spherical alginate microcapsules. These capsules are then incubated in either a calcium chloride solution typical used to polymerize alginate or a physiological media formulated to mimic in vivo conditions. The diffusion of different molecular weight particles tagged with spectrally distinct fluorescent molecules into the microspheres is observed using confocal laser microscopy. We characterize changes in diffusional characteristics of these molecules within alginate spheres as a function of incubation duration. We estimate diffusion coefficients (D) from fluorescence image series and observe a notable increase in capsule permeability once incubated in physiological media. Our strategy can serve as quantitative method to analyze structural changes in hydrogels.

To improve conversion efficiency of silicon nanowire (SiNW) solar cells, it is very important to reduce the surface recombination rate on the surface of SiNWs, since SiNWs have a large surface area. We tried to cover SiNWs with aluminum oxide (Al2O3) and titanium oxide (TiO2) by atomic layer deposition (ALD), since Al2O3 grown by ALD provides an excellent level of surface passivation on silicon wafers and TiO2 has a higher refractive index than Al2O3, leading to the reduction of surface reflectance. The effective minority carrier lifetime in SiNW arrays embedded in a TiO2/Al2O3 stack layer of 94 μsec was obtained, which was comparable to an Al2O3 single layer. The surface reflectance of SiNW solar cells was drastically decreased below around 5% in all of the wavelength range using the Al2O3/TiO2/Al2O3 stack layer. Heterojunction SiNW solar cells with the structure of ITO/p-type hydrogenated amorphous silicon (a-Si:H)/n-type SiNWs embedded in Al2O3 and TiO2 stack layer for passivation/n-type a-Si:H/back electrode was fabricated, and a typical rectifying property and open-circuit voltage of 356 mV were successfully obtained.