Amorphous oxide semiconductors (AOS) are promising candidate materials for thin film transistors in display devices, but one major challenge for mass application is their instability under illumination. In this work, a theoretical method for analyzing transient photoconductivity response in such AOS thin films is reviewed, namely the continuous multi-exponential model. This model can deduce a continuous distribution of decay time constants representing activation energy levels in an AOS, and is shown to reliably reproduce a model of density of states (DOS) of mid-gap traps assumed to be responsible for the transient photoconductivity. Provided the data collection time is sufficiently long, the continuous multi-exponential model was verified to reconstruct the modeled continuous DOS spectrum, thus providing a powerful tool to analyze photoresponse in AOS. This method has the advantage that no prior assumptions about the form of the density of states are needed, but the drawback that long data collection times are required for the transient to be fully relaxed.

2-, 4-, 6- and 8-arm star amphiphilic block copolymers were prepared with the branching point located in the hydrophobic core composed of poly(propylene sulfide) (PPS); poly(ethylene glycol) (PEG) pendant chains completed the macromolecular structure. The level of branching influenced the rigidity of the PPS core and of the overall macromolecule, with the Mark-Houwink parameter a gradually approaching the value typical of globules for 6 and 8 arms. A binary behavior (linear vs. branched) was noticed for the kinetics of oxidation by H2O2 and the stability of the colloidal aggregates formed in water: irrespective of the number of arms, all branched polymers showed a slower response (to oxidation) and a more stable hydrophobic domains (a critical micellar concentration < 0.01 mg/mL).

Monoclinic Cu2SnS3 was made by solution based processing of the precursor metals after which the samples are annealed in a sulphur environment. XRD and Raman spectra shows that the monoclinic phase was synthesised. One sample was further etched in KCN and HCl to remove possible secondary phases. Transmission spectra show that the material has two optical transitions and in conjunction with reflection data absorption spectra were calculated. The two optical transitions are determined to be 0.91 and 0.98 for the unetched sample and 0.90 and 0.95 eV for the etched sample. The values of the optical transitions are within the error the same and thus etching does not affect the values of these optical transitions. Photoluminescence spectra map show only one luminescence peak with a maximum at 0.95 eV, which is consistent with the values found by absorption spectra. This in combination with the Raman spectra and XRD indicates that the sample contains only one polymorph of Cu2SnS3, which is monoclinic. Therefore the two optical transitions are intrinsic to monoclinic Cu2SnS3.

This work presents results on the prediction of the molecular weight distributions (MWD) of chain growth polymerization using conventional software and hardware tools. The investigation focuses on two kinds of polymerization processes: free radical batch and continuous polymerization processes with application to low density polyethylene synthesis (LDPE); and coordination polymerization via metallocenes with application to high density polyethylene synthesis (HDPE). For both processes, kinetic models, consisting of sets of differential equations describing the dynamic behavior of all the chemical species in the reaction media, are presented. From these sets is possible to obtain the molecular weight distribution of the polymer1,2,4

Strategies for the simulation of the polymerization models were developed and results of these simulations are presented. On the free radical polymerization case, the next results are highlighted: i) It was confirmed that the chain transfer to polymer step produces strong asymmetries on the MWD as well as a high polydispersity index; ii) It’s possible to calculate the MWD in the CSTR process through a simulation strategy that permits the decoupling of the live and dead chains populations. On the metallocene polymerization case, it was demonstrated that the coordination standard model represents well the system experimentally studied and it can be employed to directly calculate the molecular weight distribution.

These results confirm the idea that the complete MWD can be directly calculated with conventional hardware and software tools.

In order to better understand the micrometer-scale structure of rock and its transport properties which arise from it, seven monomineral samples from two sites (Olkiluoto and Sievi, Finland) were studied with micro- and nanotomography and scanning electron microscopy. From the veined gneiss of Olkiluoto we studied biotite, potassium feldspar, plagioclase (composition of oligoclase) and cordierite, and from Sievi tonalite biotite and two grains of plagioclase (albite). These minerals were the main minerals of these samples. Samples were carefully separated and selected using heavy liquid separation and stereomicroscopy, their three dimensional structure was imaged using X-ray tomography, and their precise mineral composition was determined using scanning electron microscopy and energy-dispersive X-ray spectroscopy (SEM/EDS). The micrometer-scale mineral structure of these samples was observed together with their pores and fissures, and alteration effects were identified whenever applicable. Nanotomography combined with SEM analysis was concluded to be a good tool for analyzing effects of alteration in monomineral samples.

A complete understanding of radioactive waste glass interactions with near-field materials is essential for appropriate nuclear waste repository performance assessment. In many geologic repository designs, Fe is present both in the natural environment and in the containers that will hold the waste glasses. In this paper we discuss investigations of the alteration of International Simple Glass (ISG) in the presence of Fe0 foil and hematite (Fe2O3). Based on solid analysis, ISG alteration is more pronounced in the presence of Fe0 than with hematite. Additionally, typical glass corrosion is observed for distances of 5 mm between Fe materials and ISG, but incorporation of Fe in the alteration layer is only observed for systems exhibiting full contact between Fe0 material and ISG. Solution analysis results indicate that diatomaceous earth minimizes corrosion to a larger extent than fumed silica does when present with iron and ISG.

Tin oxide aerogels were synthesized using the epoxide-assisted technique and characterized with X-ray diffraction, diffusive reflectance spectroscopy, particle-induced X-ray emission and scanning electron microscopy. Our results indicate that the material is electrically semi-insulating as the result of oxygen vacancies that appear as fixed charges at the bottom of the conduction band. A modification of the technique with the addition of hydrogen peroxide is proposed to reduce the levels of defects and enhance the optical transparency of the material.

Covalent integration of inorganic nanoparticles into polymer matrices leads to a homogenization of their distribution and enhances the structural properties. Here, we report on a thermally-controlled reversible shape-memory effect (R-SME) of magnetic nanocomposites under stress-controlled conditions. The magnetic nanocomposites consisted of an oligo(ω-pentadecalactone) (OPDL) matrix with covalently integrated or physically added magnetic nanoparticles (MNP). The R-SME of these materials was based on crystallization-induced elongation (CIE) and melting-induced contraction (MIC) under a constant stress in thermomechanical experiments. Furthermore, the adjustability of the recovery stress in magnetic nanocomposites as a function of MNP content was investigated. A slight increase in the recovery stress from 0.9 MPa for pure OPDL network to 1.2 MPa for H-NC containing 9 wt% of covalently integrated MNP was observed.

The need for higher energy density batteries has spawned recent renewed interest in alternatives to lithium ion batteries, including multivalent chemistries that theoretically can provide twice the volumetric capacity if two electrons can be transferred per intercalating ion. Initial investigations of these chemistries have been limited to date by the lack of understanding of the compatibility between intercalation electrode materials, electrolytes, and current collectors. This work describes the utilization of hybrid cells to evaluate multivalent cathodes, consisting of high surface area carbon anodes and multivalent nonaqueous electrolytes that are compatible with oxide intercalation electrodes. In particular, electrolyte and current collector compatibility was investigated, and it was found that the carbon and active material play an important role in determining the compatibility of PF6-based multivalent electrolytes with carbon-based current collectors. Through the exploration of electrolytes that are compatible with the cathode, new cell chemistries and configurations can be developed, including a magnesium-ion battery with two intercalation host electrodes, which may expand the known Mg-based systems beyond the present state of the art sulfide-based cathodes with organohalide-magnesium based electrolytes.

In the present work was used Dynamical Mechanical Analysis (DMA) to study the magnesium alloy Mg AZ31-B, in plate form with a thickness of 2.5 mm. The plates were processed using Equal Channel Angular Sheet Drawing (ECASD), which is a severe plastic deformation technique, which allows imposing strain without dimensional changes to a metal plate, at room temperature with an angle of 135°. The obtained results show dependence between the storage modulus (M’), temperature and frequency used on the tests. The greater M’ values were obtained at the lower temperatures and at the higher frequency used. However, at lower frequencies M’ response is not affected by the used frequencies. At the higher temperatures there is an M’ reduction, which promotes the material deformation.

Under controlled irradiation of low energy carbon ions, photoluminescence (PL) study of InAs quantum dots prepared with different capping structures (GaAs and InAlGaAs) was carried out. Samples were investigated by varying implantation energy from 15 keV to 50 keV with fluence ranging between 3 × 1011ions/cm2 and 8 × 1011 ions/cm2. For fixed fluence of 4 × 1011ions/cm2, low temperature PL showed enhancement in a certain range of energy, along with a blue shift in the PL peak wavelength. In contrast, with varying fluence at fixed implantation energy of 50 keV, PL enhancement was not significant, rather a drop in PL intensity was noted at higher fluence from 5 × 1011 to 8 × 1011 ions/cm2. Moreover, carbon ion implantation caused a blue shift in the PL emission peak for both energy and fluence variations. PL intensity suppression was possibly caused by the formation of non-radiative recombination centers (NRCs) near the capping layer, while the corresponding blue shift might be attributed to stress generation in the capping layer due to implantation. As-grown and implanted InAlGaAs capped samples did not exhibit much variation in full width at half maxima of PL spectra; however, significant variation was observed for the GaAs capped sample. These results validate that InAlGaAs-capped QDs are more immune to ion implantation.

We have investigated the transport properties of topological insulator based on single-crystal Bi0.83Sb0.17 nanowires. The single-crystal nanowire samples in the diameter range 200 nm – 1.1 μm were prepared by the high frequency liquid phase casting in a glass capillary using an improved Ulitovsky technique; they were cylindrical single-crystals with (1011) orientation along the wire axis. In this orientation, the wire axis makes an angle of 19.5o with the bisector axis C 1 in the bisector-trigonal plane. Bi0.83Sb0.17 is a narrow gap semiconductor with energy gap at L point of Brillouin zone ΔE= 21 meV. In accordance with the measurements of the temperature dependence of the resistivity of the samples resistance increases with decreasing temperature, but at low temperatures decrease in the resistance is observed. This effect, decrease in the resistance, is a clear manifestation of the interesting properties of topological insulators - the presence on its surface of a highly conducting zone. The Arrhenius plot of resistance R in samples with diameter d=1.1 µm and d=200 nm indicates a thermal activation behavior with an activation gap ΔE= 21 and 35 meV, respectively, which proves the presence of the quantum size effect in these samples. We found that in the range of diameter 1100 nm - 200 nm when the diameter decreases the energy gap is growing as 1/d. We have investigated magnetoresistance of Bi0.83Sb0.17 nanowires at various magnetic field orientations. From the temperature dependences of Shubnikov de Haas oscillation amplitude for different orientation of magnetic field we have calculated the cyclotron mass m c and Dingle temperature T D for longitudinal and transverse (B||C 3 and B||C 2 ) directions of magnetic fields, which equal 1.96*10-2m 0 , 9.8 K, 8.5*10-3m 0 , 9.4 K and 1.5*10-1m 0 , 2.8 K respectively. The observed effects are discussed.

We use the combinatorial sputter technique to simultaneously sputter HfO2 and Al2O3 targets to obtain a film of HfxAl1-xOy of specific compositions. The effect of oxide thickness, oxide composition (i.e. Hf:Al ratio) and oxygen gettering layer thickness on DC sweep based resistive switching performance of RRAM is investigated. The oxide thickness primarily affects forming voltage and causes the memory window to increase for the thinnest oxide (6 nm, other thicknesses – 12 nm, 18 nm). The composition of oxide has a non-linear effect on the memory window (high to low resistance ratio) and variability of resistance states whereas the variability of set voltage improves significantly for ternary oxide compared to individual binary oxides. Finally, electrode interlayer for oxygen-gettering is also critical where a thin Ti layer of 1.5nm maintains the memory window but reduces variability in HRS, LRS, reduces Vset and Vreset and improves the variability in Vset.

In this contribution, we report progress in the preparation of superconducting materials made by Spark Plasma Sintering (SPS). On the one hand, the fabrication process was optimized in order to improve the texturing of Bi2Ca2Sr2CuO8 superconductor ceramics. The new process is referred to as “Spark Plasma Texturing” (SPT). During SPT, the bulk material is free to deform itself. As a result, an inter-grain preferential crystallographic orientation is generated, while materials processed by conventional SPS are usually quasi-isotropic. The crystallographic orientation causes a strong anisotropy in the magnetic properties of the Bi2Ca2Sr2CuO8 bulk.

On the other hand, superconducting MgB2 discs were consolidated using the rapid SPS process. MgB2 has not been yet been seriously considered as a superconductor that could be used for magnetic levitation. Here we present trapped field measurements as a function of the distance to the superconductor and field cooled levitation force measurements that suggests that it presents interesting characteristics for this application.