Comparative studies have been carried out on the performance of the photovoltaic devices with dissimilar shapes of the InN nanostructures fabricated on p-Si (100). The devices fabricated with the nanodots show a superior performance compared to the devices fabricated with the nanorods. The discussions have been carried out on the superior junction property, larger effective junction area and inherent random pyramidal topographical texture of the cell fabricated with nanodots. Such single junction devices exhibit a promising fill factor and external quantum efficiency of 38% and 27%, respectively, under concentrated AM1.5 illumination.

A process-oriented stress modeling methodology is developed to investigate the stress evolution during the silicon interposer packaging process. An FEM based 3D TCAD simulator is used to perform the process steps to construct the silicon interposer stack in sequential order. These steps include TSV fabrication for passive silicon interposer, micro-bumping and reflow process for integrating active dies and passive interposer, C4-bumping and reflow for interposer BT-substrate stacking, and epoxy mold curing for interposer encapsulation. Stress simulations are carried out for each process step to obtain accurate stress evolution history. To resolve micron features within millimeter structures, the modeling strategy employs symmetry conditions, and equivalent materials for regions away from structure features of interest. The detailed structure includes 3x3 arrays of microbumps, TSV arrays, and C4-bumps with multiple material layers at the stack corner. Important design parameters include interposer thickness and edge clearance. For different silicon interposer configurations critical stresses in the outmost microbump and C4-bump are analyzed and compared. The reliability implications are discussed.

The container is the only absolute barrier in the multi-barrier system that forms the basis of all nuclear waste disposal strategies. The selection of an appropriate container material is therefore of utmost importance. Some of the factors that underlay the choice of container material are discussed, ranging from the properties of the near-field and host rock to the desired or expected containment period.

There has been a trend towards the specification of container materials that will corrode actively under repository conditions, such as copper and carbon steel. Passive materials, such as titanium and nickel alloys and the various stainless steels, have found less acceptance and the reasons for this emphasis on active materials are also discussed.

In selecting an appropriate container material, it is essential to understand the nature of the corrosive environment and how it evolves over time. The evolution of environmental conditions will also cause the corrosion behaviour of the container to change with time. For repositories in saturated environments, it will be argued that passive alloys can provide long container lifetimes without some of the disadvantages of some active materials such as gas generation and other adverse impacts on other barriers.

Finally, areas of future development and areas requiring additional study will be discussed.

Growth stresses in amorphous SiO2 scales formed during SiC fiber oxidation were calculated. A numerical method using Deal-Grove oxidation kinetics and shear-stress dependent SiO2 viscosity was used. Initial compressive stresses in SiO2 of ∼25 GPa from the 2.2× oxidation volume expansion rapidly relaxes. At >1200°C, viscous flow of amorphous SiO2 further relaxes stress to negligible levels. At 700° - 900°C, axial and hoop stress at the GPa level persist in SiO2 near the SiC-SiO2 interface. Radial expansion of the scale causes hoop stress to become tensile, and axial stresses are driven to tensile values by the Poisson effect. These tensile stresses can be >1 GPa for thick scales formed at lower temperatures on surfaces with high curvature. Approximate analytical expressions for growth stress are discussed. Effects of viscosity variation as well as other assumptions and limitations of the calculation method are discussed.

The growth of thin and ultra-thin titanium dioxide layers was investigated. Oxide films were grown by galvanostatic and potentiodynamic anodisation of evaporated titanium layers on conductive substrates. It is shown that thin-film oxidation differs significantly from anodic oxidation of solid foils or plates, due to the sudden stop of anodisation process before complete oxidation of the thick films. Depending on the pH value and the potential sweep rate, the effective defect density and the dielectric constant of the anodized layers vary from 3·1019 cm-3 to 1020 cm-3and from 16 to 27, respectively, whereas the electrolyte temperature plays only a minor role.

Irradiating a planar silicon surface with femtosecond laser pulses under a sulfuric atmosphere creates first a structured surface featuring cones of up to 20 microns in height, and second a 0.1 – 1 μ m thick layer of multi-crystalline silicon on theses cones containing up to 1 at.% sulfur acting as n-type dopant. Further, the sulfur establishes energy states within the band gap of silicon allowing for the absorption of infrared (IR) light with energies below the band gap energy of silicon. This black silicon process is distinguished by the fact that only one single laser process is required to tailor three material characteristics in on step: the surface structure, the doping and the light absorption. In this work we study structural and optical material characteristics of black silicon. For the first time this work presents properties of black silicon processed with shaped femtosecond laser pulses. Finally, black silicon substrate is used as substrate for manufacturing a black silicon solar cell with a femtosecond laser pulse formed sulfur emitter. For such a black silicon solar cell we achieved a record efficiency of η =4.5%

Hierarchically porous materials are of interest in a wide range of applications. If the materials are electronic or ionic conductors such materials are of interest as electrodes for use in fuel cells, flow batteries, electrocatalysis, and pseudo/supercapacitors. We have demonstrated the synthesis of hierarchically porous carbon, metal and metal oxide monoliths. Hierarchically porous silica with porosity at three length scales: 0.5-30 micrometer, 200-500 nm, and 3-8 nm, is used as a template to form these materials. The porosity of the silica template is produced by spinodal decomposition (0.5-30 micrometer), particle agglomeration (200-500 nm) and addition of surfactant or block copolymer (3-8 nm). Nanocasting: replication of all or part of the structure via one of a number of chemical replication techniques has been used to produce the carbon, metal oxide and metal replicas. The final surface areas of the materials can be as high as 1200 m2/g for carbon replicas, and >300 m2/g for metals and metal oxides. The use of the nanocasting technique allows for formation of materials that are compositionally or spatially heterogeneous.

We report here results on the synthesis and characterization of hierarchically porous monoliths of carbon and, nickel and the use of some of these monoliths in catalysis and electrochemical capacitors.

We present a first principles study of the electronic and magnetic properties of Fe-based pnicitdes superconductors as a function of pressure and doping. We show that the magnetic phase and a local magnetic moment persists at doping level quite larger than what found in experiments and the pressure phase diagram consists of a paramagnetic, antiferromagnetic and non-magnetic phases.

Although this result calls for the inclusion of long-wavelength or local fluctuations of iron magnetic moment and non-hydrostatic pressure effects, in order to improve the theoretical description of real experimental conditions, recent photoemission experiments[1] reconcile these DFT results, showing a local magnetic moment on Fe site different from zero in the paramagnetic, antiferromagnetic and the superconducting phase.

In this work the microstructures of star acrylated poly(ethyleneglycol-co-lactide) (SPELA) with different LA:EG ratios in the aqueoussolution have been simulated via Dissipative Particle Dynamics (DPD)approach at the mesoscale. The system components were coarse-grained intodifferent beads (set of atoms) which moved according to the Newton’sequations of motion integrated via a modified Velocity-Verlet algorithm. Theforce acting on each bead, in a specific cutoff distance (rc),was divided into a conservative force (FC), random force (FR), dissipativeforce (FD), bond force (FS) and bond angle force (FE). The repulsionparameters of the conservative force (αij) were calculated fromthe solubility parameter of the beads, each of which were extracted from anatomistic molecular dynamics simulation (MD). Simulations showed theformation of micelles with lactide and acrylate beads occupied the core andhydrophilic ethylene oxide segments extending through the water to form thecorona. The micelles showed an increasing trend in size and decreasing trendin number density with increase in LA:EG ratio. Results showed that theacrylate density decreased from the center of the micelles to the coresurface although the overall amount of acrylates increased due to theincrease in volume. Furthermore, the running integration number ofacrylate-water beads showed decreasing accessibility of acrylates to waterwith increasing PLA volume fraction.

We have employed first-principles density-functional calculations to study the electronic characteristics of graphene functionalized by metal-bis-arene and metal-carbonyl molecules. It is shown that functionalization with M-bis-arene (M(C6H6)@gr, M=Ti, V, Cr, Mn, Fe) molecules leads to an opening in the band gap of graphene (up to 0.81eV for the Cr derivative), and functionalization with M-carbonyl (M(CX)3@gr, X=O,N; M= Cr, Mn, Fe, Co) up to one 1eV for M=Cr and X=O, and therefore transforms graphene from a semi-metal to a semiconductor. The band gap induced by attachment of a metal atom topped by a functionalizing group is attributed to modification of π-conjugation and depends on the concentration of functionalizing molecules, metal’s and moiety’s electronic structure. This approach offers a means of tailoring the band structure of graphene and potentially its applications for future electronic devices.

Short-chain oligomers of aniline are attractive semi-metallic materials for applications as organic electrodes or hole-transporting layers in organic photovoltaics. However, conventionally processed oligoanilines are often amorphous, which limits their conductivities and carrier transport mobilities. Here, we report a simple solvent-exchange method that can render a variety of oligoanilines and their derivatives into crystals of different shapes and dimensions, including 1-D fibers and wires, 2-D ribbons, and 3-D plates, hollow spheres, porous sheets, and flower-like structures. Dopant ions are also simultaneously incorporated into the crystals during self-assembly, allowing them to become conducting. Mechanistic studies suggest that the higher order crystals arise from the most primitive nanofibrillar morphology via hierarchical assembly, providing insights into a general approach to control organic crystal morphologies. Selected area electron diffraction studies reveal their single crystalline nature.

Since the 1970s there has been a steady increase in research on candidate ceramic and glass-ceramics for immobilisation of HLW and ILW, both from the aspects of crystal-chemical design and processing technology. The variety of ceramics and glass-ceramics designed for different types of HLW and ILW will be presented, notably those which are problematic for vitrification. Several of these materials are optimally processed by hot isostatic pressing (HIP), a technology which can consolidate calcined intermediate-level and high-level nuclear waste. Thus we are targeting such wastes for development of alternative waste forms. The essential process steps during the HIP cycle will be outlined. Effective consolidation of a wide variety of tailored glass-ceramic and ceramic waste forms has been demonstrated. The principal advantages of the HIP technology include negligible offgas during the high temperature consolidation step, relatively small footprint, and high waste/volume loadings. While it can be argued that the “nuclear waste problem” is essentially solved technically, at least with current regulatory guidelines, different perceptions of the “best” waste form and processing method for a given waste, together with the general current lack of agreed locations for final repositories, or even interim storage sites, create uncertainties.

We have developed a microfluidic sensor to measure the electrical coupling through gap junctions across a 2D sheet of cultured Normal Rat Kidney cells. The chip is based on a tri-stream laminar flow with conductive solutions on either end and a nonconductive solution in the middle stream. When an electrical voltage is applied, the current can only pass through the cell sheet, thereby enabling us to measure the electrical coupling of gap junctions between cells. Using this sensor we have measured the effect of 2-aminoethoxydiphenyl borate (2-APB) on Cx43 channels. We show that 2-APB reversibly inhibits electrical coupling of Cx43 in NRK cells. Moreover, we screened other potential candidates to block Cx43, 1-Heptanol and GsMTx-4, and examined their effects on Cx43 gap junctions.

Emerging phase-change electrical memory technologies rely on the fast amorphous to crystalline transition, which is usually characterized by an ‘S-shape’ current-voltage curve. We investigate the possibility that electric field induced nucleation may play a dominant role in defining this characteristic electrical switching behavior. We derive quantitative crystallization maps to study the kinetics of the amorphous to crystalline transition in the presence of electric field contribution to the free energy and we investigate how the prediction of the electric field induced nucleation model is affected by material properties such as enthalpy and relative electric permittivity.

The effects of temperature and moisture on the resistive switching characteristics of oxide-based atomic switches were investigated to reveal their switching mechanism. The observed temperature variations of the SET voltages can be qualitatively explained by the classical nucleation theory. The moisture absorption in oxides results in the formation of a hydrogen-bond network at grain boundaries, and metal ions are likely to migrate along the grain boundaries. Depending on the strength of hydrogen bonds in oxides, the atomic switches exhibit a different switching behavior to ambient conditions.

Electrical transport and microstructure of interfaces between nm-thick films of various perovskite oxides grown by pulsed laser deposition (PLD) on TiO2- terminated SrTiO3 (STO) substrates are compared. LaAlO3/STO and KTaO3/STO interfaces become quasi-2DEG after a critical film thickness of 4 unit cell layers. The conductivity survives long anneals in oxygen atmosphere. LaMnO3/STO interfaces remain insulating for all film thicknesses and NdGaO3/STO interfaces are conducting but the conductivity is eliminated after oxygen annealing. Medium-energy ion spectroscopy and scanning transmission electron microscopy detect cationic intermixing within several atomic layers from the interface in all studied interfaces. Our results indicate that the electrical reconstruction in the polar oxide interfaces is a complex combination of different mechanisms, and oxygen vacancies play an important role.

Lead is an engineering material used mainly in the manufacturing of lead-acid batteries for the automotive industry. Lead recovery from exhausted batteries is carried out by the pyrometallurgical route by injecting sulfur the powder reagent through a lance into the lead bath. In this work a mathematical simulation was carried out on the copper drossing process with the software COMSOL 3.4. A kinetic study of the injection process of the lance-kettle system was carried out. The copper concentration profiles were obtained according with the injection rate of the particles. The best conditions for the copper drossing process were an injection rate of 3.31 m/s at 380°C. The modeling results were validated with experimental results obtaining good agreement.

This work shows current research on lithic raw material used by the ancient Maya of Toniná. The core of the city of Toniná lies on a steep-sided hill of calcareous sandstones from the shallow marine deposits dated as Oligocene, in the Chiapas Highlands of Southern Mexico. Results of paleontological fieldwork in Toniná show several biostrome sediments mound-like with tabular bafflestones and large coquina flagstones, which are sheet-like rocks enriched with fossil mollusk shells, corals, encrusted organisms, and calcareous debris. The people of Toniná intentionally selected and carved these rocks for use as building blocks and bricks on floors, walls, and stairways. At least two coquina flagstones measuring about 1.90 m long were identified in an archeological context most likely associated with carved stelae. Also non-marine carbonate rocks such as a crudely banded travertine and spongy calcareous tufa from recent sediments of freshwater environments surrounding Toniná were used by the Maya as a raw material on walls, columns, reliefs and murals base.

Results of the chemical, mineralogical and micromorphological analysis on plaster and bedding mortars from the walls of Toniná display a slightly interbedded lime of sparry calcite cemented in a highly porous groundmass with silt-to pebble-size of calcareous and siliciclastic rock-crushed aggregates, sand, and soil remains. Lime fabric reveals enclosing quartz grains, granular calcite crystals, and carbonaceous inclusions which may suggest that the lime has been made from a burnt grain-rich limestone with fibrous cement and porous microfabric. WDX analysis in lime lumps of plaster reveal an average amount of 1.37 wt% MgO associated with a limestone source ranging from regular to a magnesium-enriched limestone (1 to 2 wt %). XRF detect a strontium-rich level in the calcite matrix of plaster which is as high as that of fossil shells, tufa, and coquina. Finally, XRD shows that the mean amount of calcite in plaster is 95 wt% and lower amount (2-2.5w%) of siliciclastic minerals: quartz and albite. In contrast, calcite in mortar ranges less than 90.1 wt%. The concentrations of non-carbonate minerals, such as quartz and albite, are higher than those in plaster because mortar incorporates more siliciclastic rock remains, sand and clay.

A 1/6th gas–stirred water physical model of a 140 ton steel ladle is used to evaluate mixing in air–water and air–water–oil systems to model argon–steel and argon–steel–slag systems respectively. Thickness of the slag layer is kept constant at 0.004 m. The effect of the gas flow rate (7, 17, and 37 l/min), plug position (0, 1/3, ½, and 2/3 of the ladle radius, R), and number of plugs (1, 2, and 3) on mixing time is also analyzed in this work. Gas is injected at the bottom of the ladle under several plug configurations varying both position and number of plugs. Chemical uniformity of 95% is selected as mixing criterion. Mixing times are experimentally determined when a tracer is suddenly injected into the ladle and the model is instrumented with a pH meter to track the time evolution of the tracer concentration (NaOH 1 M solution) in a given location inside the ladle. Process conditions for best mixing in both water–gas and water-gas–slag systems are: a single plug located at 2/3 of the ladle radius with a gas flow rate of 17 l/min.