Transparent conducting cadmium tin oxide (CTO) thin films were obtained from a mixture of CdO and SnO2 precursor solutions by the dip-coating sol-gel technique. The thin films studied in this work were made with 7 coats (∼200 nm) on corning glass and quartz substrates. Each coating was deposited at a withdrawal speed of 2 cm/min, dried at 100°C for 1 hour and then sintered at 550°C for 1 hour in air. In order to decrease the resistivity values of the films, these were annealed in a vacuum atmosphere and another set of films were annealed in an Ar/CdS atmosphere. The annealing temperatures (Ta) were 450°C, 500°C and 550°C, as well as 600°C and 650°C, when corning glass and quartz substrates were used, respectively. X-Ray diffraction (XRD) patterns of the films annealed in a vacuum showed that there is only the presence of CTO crystals for 450°C≤ Ta ≤ 600°C and CTO+SnO2 crystals for Ta=650°C. The films annealed in Ar/CdS atmosphere were only constituted of CTO crystals independent of the Ta. The minimum resistivity value obtained was ∼4 x 10-4 Ωcm (Rsheet= 20 Ω/□) for the films deposited on quartz and annealed at Ta=600°C under an Ar/CdS atmosphere. The films deposited on quartz showed the higher optical transmission (∼90%) with respect to the films deposited on corning glass substrates (∼85%) in the Uv-vis region. For their optical and electrical characteristics, these films are good candidates as transparent electrodes in solar cells.

The nucleation, growth and coarsening of carbides is investigated in high niobium containing TiAl alloys by diffraction and transmission electron microscopy. Higher carbon content increases the dissolution temperature of carbides. The solubility of carbon is much higher in a γ/α2-phase alloy than in the γ phase alone. Hereby no significant influence of Nb on carbon solubility is found. Crystallographic defects as grain boundaries and dislocations promote carbide nucleation which results in a carbide precipitation sequence starting first at grain boundaries, then at dislocations and only later in the γ matrix away from crystallographic defects. The consumption of carbon by grain boundary carbides or neighboring α2 grains also generates a precipitate free zone in γ grains near the grain boundary.

Helium embrittlement poses a great threat to materials used in both fusion and fissionreactor systems due to (n,α) transmutation reactions. Because of this, materials capable of moderating the helium content reaching grain boundaries and voids must be developed and improved to prevent catastrophic failure of reactor materials. Nanostructured ferritic alloys (NFAs) have shown great promise in preventing helium embrittlement due to the large number density of nanoscale precipitates acting as trapping sites for helium clusters and helium bubbles. In this study, we present density functional theory calculations on the interaction of helium with nanoscale precipitates found in NFAs as a preliminary study to furthering our understanding of the energetic mechanisms causing the precipitates to act as trapping sites for helium.

The density-functional-theory model for plutonium metal is shown to be consistent with recent magnetic measurements that suggest anti-ferromagnetism in Pu-Ga alloys at low temperatures. The theoretical model predicts a stabilization of the face-centered-cubic (fcc, δ) form of plutonium in an anti-ferromagnetic configuration when alloyed with gallium. The ordered magnetic phase occurs because Ga removes the mechanical instability that exists for unalloyed δ-Pu. The cause of the Ga-induced stabilization is a combination of a lowering of the band (kinetic) and electrostatic (Coulomb) energies for the cubic relative to the tetragonal phase.

The release of radionuclides measured during washing cycles of spent nuclear fuel samples in a series of experiments using different solutions are analyzed with respect to the fission products Cs, Sr, and Tc and the actinides U, Pu, and Am. Based on the concentrations of the dissolved radionuclides, their release rates are evaluated in terms of fraction of inventory in the aquatic phase per day. The application of this information on the fast/instant radionuclide release fraction (IRF) is discussed and following issues are addressed: Duration of the wash steps, solution chemistry, and radionuclide sorption onto surface of the experimental vessels. Data for the IRF are given and the correlation between the mobilization of the various elements is analyzed.

Here we introduce a highly stretchable Printed Circuit Board (PCB) inter-connection technology achieved through the combination of flexibility allowed by the silver nanowire (AgNW)-based electrode and stretchability provided by the meander-shaped substrate. Horseshoe-shaped elastic material, polydimethylsiloxane, is used as a substrate of the AgNW conductors for relaxed stress concentration. Continuously maintained 2-D percolation of stretchable AgNW networks overcomes the usage restrictions with ordinary rigid Printed Circuit Board (PCB). The horseshoe-shaped inter-connection is physically reliable with repeated stretching/releasing processes and maintains its conductivity under tensile strains up to 20 %, allowing the durable and stretchable PCB inter-connecting applications.

ZnO nanowire (NW) arrays were examined with Transmission Electron Microscopy (TEM) in cross-section after preparation by Focused Ion Beam (FIB) milling. This technique revealed that ZnO nanowires grown using a Au catalyzed vapor technique typically have Au particles at the NW tips, and also randomly dispersed across the base crystal growth that joins adjacent NWs. It is shown the adjacent NWs and the combined base growth is one crystal structure which can be used as a back electrical contact making fabrication of vertical array devices possible. However, the base growth displays detrimental features such as embedded Au particles and lattice defects which can affect the electrical output through depletion regions and scattering centers. In an effort to overcome these problems we investigate a growth method that is nucleated through a minor alteration of the a-plane sapphire surface roughness via a weak chemical etch. Observations of various stages of the growth show the growth nucleates as separate nanoislands that grow in c-plane alignment with Sapphire (1-210), and as growth continues these islands meet and form a polycrystalline film. Further growth initiates nanowire growth and the formation of a single crystal base layer and NW structure that can cover several square millimeter’s. This allows high quality arrays that are relatively free from defects to be formed without any metals contamination and ready for further device processing.

This paper reports on the development of a new type of low cost artificial aggregates based on granulated reactive silica (AAGS) for application in lightweight concrete. The functional principle of AAGS is based on the formation of polysilicate solutions under heat treatment (up to 80 °C) and migration of these solutions into the porous space of concrete under the thermal gradients, resulting in strengthening of inter-porous space. Developed AAGSs are based on low cost local raw materials, which may contain different amounts of amorphous silica. The activity coefficient (AC) and amorphous silica content are used to evaluate the performance of raw materials by suggested accelerated method.

Silica components with different genesis are investigated and ranked according to their AC. It is found out that chemogenic and biogenic siliceous rocks with a low degree of diagenetic transformations, which are mostly represented by CT-opals (a low-temperature nanoscale modification of tridymite and crystobalite, such as diatomite, tripoli and opoka) are the most highly active raw materials for AAGS. All tested siliceous materials including natural and artificial components are divided into three groups: highly active (with AC of 51–100%), active (with AC of 21–50 %) and low-active (with AC of 5–20 %). Based on theoretical and experimental studies, the requirements for AAGS raw materials are developed.

Optical properties of Si nanowire arrays (SiNWs) prepared on p-doped Si(111) and Si(100) substrates are studied. The SiNWs were synthesized by self-assembly electroless metal deposition nanoelectrochemistry in an ionic silver HF solution through selective etching. Total reflectance (R t) and total diffuse reflectance (R dt) of SiNWs change drastically in comparison to polished Si. To understand these changes diffuse reflectance (R d) with polarized incident light was studied. For samples prepared on Si(111), the wavelength integrated R d (wIRd) shows maxima at certain angle of incidence θ and it does not depend on light polarization. Moreover, R dt of SiNWs prepared on Si(111) can be modeled as an ensemble of diffuse reflectors. For samples prepared on Si(100) wIRd increases with θ, being greater when the light electric field is parallel to the plane of incidence. Also, R d spectra show structures due to interference effects. For these reasons SiNWs prepared on Si(100) can be considered as a thin film whose refractive index depends on light polarization.

Melting of Direct Reduced Iron (DRI) pellets in Electric Arc Furnaces (EAF) in steelmaking production is a common practice worldwide. Mathematical models are proper tools to study the phenomena involved in melting DRI. In this work we develop a mathematical model to predict melting kinetics of DRI in a liquid slag bath. The model is successfully validated against experimental results and it is used to develop a process analysis to estimate the effects of DRI size, stirring conditions, and temperatures of the bath and pellet on the melting kinetics of DRI.

The advance in Electron Backscatter Diffraction known as High Resolution EBSD has permitted the strain tensor components and neighbour disorientation measurements to be mapped at resolutions better than 2 parts in 10000. Following earlier research into this technique which was focused on verifying the sensitivity and accuracy of the measurements, recent studies have involved investigations on semiconductor and metallic polycrystalline materials. In particular observations of localized regions where residual strains exceeded the macroscopic yield stress have been thoroughly investigated to eliminate experimental error as a possible explanation. No such cause was found. Strain measurements on polycrystalline steels in uniaxial tension and during thermal stress relieving thermal treatment have also been carried out. Maps of the strain distribution during elastic loading and early stages of plastic flow showed hot spots of high strain as in the static tests but overall the measured elastic strain was equal to the applied strain.

Graphene is a strong contender as a material to replace indium tin oxide as the transparent conductor of choice for electronic applications due to its exceptional electrical and optical properties. In this work, we present a study of graphene oxide (GO) films produced by inkjet-printing. The printed GO films are reduced using hydriodic acid (HI) and acetic acid vapour at low temperature. The reduced GO (rGO) films displayed good optical and electrical properties with a sheet resistance 6.8 kΩ/□ at a transmittance of 80%. In addition, we show that the conductivity of rGO films is related to both the size of individual GO sheets in the ink and the thickness of printed films. The rGO films using large size GO sheets displayed a thickness-independent conductivity of ∼ 4 × 104 S/m, while the rGO films using small size GO sheets showed a thickness-independent conductivity of ∼ 1.7 × 104 S/m. These properties are comparable to graphene films produced by solvent exfoliation. In summary, we demonstrate a scalable and potentially low-cost technique to produce rGO transparent films and a route to improve the conductivity of rGO films by controlling size of GO sheets in the ink.

Many theoretical predictions have suggested that the confined length scales and increased interface density of various nanostructured materials may result in desired thermal, mechanical, and radiation properties. An important aspect of this for next generation nuclear reactors is understanding the change in swelling resulting from helium evolution in tungsten alloys, as a function of grain size and grain boundary type. This study investigated this using a new ion irradiation transmission electron microscope (TEM) facility that has been developed at Sandia National Laboratories and is capable of ion implanting helium at energies up to 20 keV. It was demonstrated in this feasibility study that helium could be implanted into an ultrafine grained tungsten TEM sample produced by severe plastic deformation. The size and density of the helium bubbles formed during the experiment appear nearly constant; while the larger voids formed appear to be dependent on the local microstructure. Future work is underway to both optimize the facility, as well as better understand the evolution of ultrafine grained tungsten resulting from both helium implantation and displacement damage.

We have employed a semicontinuum model to investigate the effect of tensile strain on thermal properties of graphene. Analytical expressions derived by Nihira and Iwata for phonon dispersion relations and vibrational density of states are employed, based on the semicontinuum model proposed by Komatsu and Nagamiya. The thermal conductivity is computed within the framework of Callaway’s effective relaxation time theory. It is found that thermal properties of graphene are quite sensitive to tensile strain. In the presence of tensile strain, the specific heat increases but the thermal conductivity decreases.

Pioneer works on nanocomposites were focused in carbon nanofibers or nanotubes dispersed in epoxy matrix, a viscous liquid facilitating the compounding stage. The interest in developing new composites aimed for biomedical applications led us to design new nanocomposites based in biodegradable polymers with demonstrated biological performance.

We report herein the development of micro-nano composites by extruding poly(butylene succinate) (PBS) microfibers with two different diameters, 200 and 500 µm, reinforced with electrospun chitosan nanofibers. Analysis of the microfibers showed high levels of alignment of the reinforcing phase and excellent distribution of the nanofibers in the composite. Its geometry facilitates the development of orthotropy, maximizing the reinforcement in the axial fiber main axis.

The biodegradable microfiber composites show an outstanding improvement of mechanical properties and of the kinetics of biodegradation, with very small fractions (0.05 and 0.1 wt.%) of electrospun chitosan nanofibers reinforcement. The high surface area-to-volume ratio of electrospun nanofibers combined with the increased water uptake capability of chitosan justify the accelerated kinetics of biodegradation of the composite as compared with the unfilled synthetic polymer.

The focus of this work is on back contact improvement for sputtered CZTS thin film solar cells. Three methods have been investigated including a thin Ag coating, a thin ZnO coating on the Mo back contact and rapid thermal annealing of the back contact. All of these methods have been found to reduce defects such as voids as well as secondary phases at the back contact region and inhibit the formation of MoS2. Consequently all the mothods effectively enhances Voc, Jsc, FF and therefore efficiency significantly.

The catalytic activity of disordered binary alloy metal surfaces is investigated for the oxygen reduction reaction (ORR) by generating free energy diagrams and performing calculations on d-band centers of alloys. The disorder was simulated using virtual crystal approximation; then, based on periodic, self-consistent density functional theory (DFT) methods, we calculated adsorption energies of reaction intermediates. Alternative pathway for ORR mechanism, involving proton/electron transfer to adsorbed oxygen and hydroxyl, is considered. The methodology was applied to (111) surface of PdxCu1-x disordered binary alloys, with different values of x concentration. This study found that at the ORR equilibrium potential of 1.23 V, the reactivity of all surfaces is shown to be limited by the rate of OH removal from the surface. Among the surfaces studied, the surface of Pd0.80Cu0.20 shows the highest reactivity and is more active than other non-Pt alloys. These results are in excellent agreement with earlier experimental and theoretical work.

Three types of silica materials with different morphology, specifically SiO2 hollow microspheres, mesoporous silica, and silica aerogel were tested as potential precursors for synthesis of silicon nano- and meso-structures that resemble the original morphology of the precursors. In the optimized magnesium thermal reduction process, magnesium vapor was delivered to silica surface through a stainless steel mesh placed on top of a zirconia boat filled with silica precursor. This approach allowed for better control of silicon nanostructure formation by minimizing reaction by-products that can affect performance of lithium ion battery anode. Material morphological properties of the reduced silica precursors are discussed in terms of X-ray diffraction, BET, BJH pore size distribution, Raman spectroscopy, and TGA.