Ambipolar organic thin-film transistors (OTFTs) have been used to study the transport of charge carriers in bulk heterojunction (BHJ) organic photovoltaic devices. Active layers of phase separated blend of poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl C61-butyric acid methyl ester (PCBM), have been chosen due to their use in performance BHJ organic photovoltaic devices as well as ease of device fabrication. A method for determining recombination rate after exciton dissociation and measurement of excess carrier lifetime has been reported by studying drain current behavior which yields carrier mobility, conductivity, and carrier concentration both in dark and AM1.5g illumination. Channel-length dependent measurements of the photocurrent show that significant recombination of separated charge carriers begins to occur at lengths greater than 10 μm. A recombination rate ofcm-3 s-1 and a carrier lifetime of ≥ 8.8 ms has been calculated.

The waste management process of the French nuclear spent fuels is managed by a new vitrification conditioning step. High level radioactive borosilicate glasses are melted by induction in a cold crucible to accommodate a wide range of minor actinides and fission products. Among the fission products, platinoids precipitate in the form of (Pd-Te, Ru-Rh, Ru) metallic particles in the glass. The microstructure of these phases can affect the physicochemical properties of the melt during the vitrification process. To predict the thermodynamic properties of these alloys in the glass, a database is being developed on the Pd-Rh-Ru-Te system using the Calphad method. The binary (Pd-Te, Pd-Ru, Ru-Te) and ternary (Pd-Te-Ru) systems have been modelled. The Pd-Te-Ru ternary system built by extrapolation from the binaries enables to calculate ternary isothermal sections and thermodynamic properties of the platinoid phases between 873 K and 1573 K. Solidification paths are also calculated for Pd-Te alloys representative for those observed in the glasses. The phase composition at equilibrium and the Ru solubility limit in Pd-Te alloys are also calculated.

In this work, an Al-bronze alloy is reinforced with TiC through reaction of the alloy melt with methane gas. The resultant alloy is then centrifugally cast in cylindrical molds. It is found that the surface at the inner diameter of the cast contained in-situ produced TiC as well as Fe-rich inclusions. Metallographic observations using optical and scanning electron microscopy confirmed the presence of TiC particles (30 % volume), alpha and beta grains including iron precipitates. Cylindrical pins are machined from the inner surface and tested under various conditions in a three pin on disk Falex machine. Pins are tested under a constant load of 2.86 MPa and friction and wear rates are determined from measurements of weight losses versus wear lengths. It is found that under the applied load the reinforced material exhibits high friction and relatively low wear when compared with the unreinforced material. Apparently, under these conditions the TiC particles become abrasive particles thus contributing to wear of the steel counter-face through three body abrasive wear.

X-ray photoelectron spectroscopy has been used to characterize a sample of UO2 grown on an underlying substrate of Uranium. Both AlKα (1487 eV) and MgKα (1254 eV) emission were utilized as the excitation.

Many challenges remain in the effort to realize the exceptional properties of carbon nanotubes (CNT) in composite materials. Here, we report on electrically conductive composites fabricated via infiltration of CNT-based aerogels. The ultra low-density, high conductivity, and extraordinary robustness of the CNT aerogels make them ideal scaffolds around which to create conductive composites. Infiltrating the aerogels with various insulating materials (e.g. epoxy and silica) resulted in composites with electrical conductivities over 1 Scm-1 with as little as 1 vol% nanotube content. The electrical conductivity observed in the composites was remarkably close to that of the CNT scaffold in all cases.

CoSb3 is known as a skutterudite compound that could exhibit high thermoelectric figure of merit. However, the thermal conductivity of CoSb3 is relatively high. In order to enhance the thermoelectric performance of this compound, we tried to reduce the thermal conductivity of CoSb3 by substitution of Rh for Co and by Tl-filling into the voids. The polycrystalline samples of (Co,Rh)Sb3 and Tl-filled CoSb3 were prepared and the thermoelectric properties such as the Seebeck coefficient, electrical resistivity, and thermal conductivity were measured in the temperature range from room temperature to 750 K. The Rh substitution for Co reduced the lattice thermal conductivity, due to the alloy scattering effect. The minimum value of the lattice thermal conductivity was 4 Wm-1K-1 at 750 K obtained for (Co0.7Rh0.3)Sb3. Also the lattice thermal conductivity rapidly decreased with increasing the Tl-filling ratio. T10.25Co4Sb12 exhibited the best ZT values; the maximum ZT was 0.9 obtained at 600 K.

In this paper, individual Ge nano island on top of a silicon dioxide layer of thermally grown on a n+ type doped silicon (001) substrate have been studied. The charging ability of an individual Ge island was evaluated by EFM two-pass lift mode measurement. Such Ge nano island becomes an iso-potential and behaves as a conductive material after being charged. These charges were directly injected and were trapped homogenous in the isolated Ge island. It is also shown that the dominant charge decay mechanism during discharging of nc-Ge is related to the leakage of these trapped charges. Further more, the retention time of these trapped charges was evaluated and the electrostatic force was also studied by using different tip bias during scan. Such a study should be very useful to the Ge-nc in memory applications.

Polypeptide sequences have an inherent tendency to self-assemble into filamentous nanostructures commonly known as amyloid fibrils. Such self-assembly is used in nature to generate a variety of functional materials ranging from protective coatings in bacteria to catalytic scaffolds in mammals. The aberrant self-assembly of misfolded peptides and proteins is also, however, implicated in a range of disease states including neurodegenerative conditions such as Alzheimer's and Parkinson's diseases. It is increasingly evident that the intrinsic material properties of these structures are crucial for understanding the thermodynamics and kinetics of the pathological deposition of proteins, particularly as the mechanical fragmentation of aggregates enhances the rate of protein deposition by exposing new fibril ends which can promote further growth. We discuss here recent advances in physical techniques that are able to characterise the hierarchical self-assembly of misfolded protein molecules and define their properties.

In this study, the temperature map distribution in the Sn3.0Ag0.5Cu solder bump with Cu column under current stressing is directly examined using infrared microscopy. It is the radiance changes between the different materials of the surface that cause the unreasonable temperature map distribution. By coating a thin layer of black optical paint which is in order to eliminate the radiance changes, we got the corrected temperature map distribution. Under a current stress of 1.15 × 104 A/cm2 at 100℃C, the hot-spot temperature is 132.2℃ which surpasses the average Cu column temperature of 129.7℃C and the average solder bump temperature of 127.4 ℃. Thermomigration in solder may still occur under a large current stressing.

We present growth of vertically aligned carbon nanotube (VCNT) on metal substrates such as Cu foils, Inconel 600 and stainless steel (SUS316L) using thermal chemical vapor deposition (TCVD) in order to get a low contact resistance at interface between CNT and substrates for future applications. The temperature range for VCNT growth was 700-775 °C and mixtures of acetylene, argon and hydrogen were used as processing gas. The tube length was controlled by growth time and temperature. Finally, we successfully grew the VCNT on Cu foils over 1 cm2 and confirmed the excellent electrical conductance which can be directly used as anodic electrode in lithium ion battery. On the other hand, the growth of VCNT on Inconel 600 or SUS316L sheets was carried out as purchased. These tubes are expected to be useful for field emission devices.

Shockley-type Stacking faults (SSF) in hexagonal Silicon Carbide polytypes have received considerable attention in recent years since it has been found that these defects are responsible for the degradation of forward I-V characteristics in p-i-n diodes. In order to extend the knowledge on these kind of defects and theoretically support experimental findings (specifically, photoluminescence spectral analysis), we have determined the Kohn-Sham electronic band structures, along the closed path Γ-M-K-Γ, using density functional theory. We have also determined the energies of the SSFs with respect to the perfect crystal finding that the (35) and (44) SSFs have unexpectedly low formation energies, for this reason we could expect these two defects to be easily generated/expanded either during the growth or post-growth process steps.

We investigated the impact of doping group III elements (Al, Ga, In and Tl) on the electronic structure of PbTe by first principles calculations. The impurity-induced defect level changes with respect to the charge state of the impurity. We find that among the four elements, Tl is the best candidate for the enhancement of thermoelectric efficiency, consistent with the experimental data.

The extended defects, such as dislocations and in-grown stacking faults (IGSFs), in 4H-SiC epilayers have been detected and visualized by a non-destructive method, the micro photoluminescence (μ-PL) intensity mapping method, at room temperature. The one-to-one correspondence between the extended defects and the μ-PL mapping contrast has been successfully obtained. A threading dislocation corresponds to a dark circle with the reduced intensity in the μ-PL mapping image performed at 390 nm, while a basal plane dislocation dissociates into a single Shockley SF during the measurements. Three kinds of IGSFs have been identified in the samples. Each kind of IGSF shows the distinct PL emission located at 460 nm, 480 nm, and 500 nm, respectively. The shapes and distributions of IGSFs have also been profiled by μ-PL intensity mapping.

A low copper reactor pressure vessel steel was characterised by atom probe tomography after neutron irradiation at different fluences. The specimens were irradiated within the frame of the Surveillance Program of a production reactor. Roughly spherical clusters enriched in nickel, manganese, silicon and, in a lesser extent, phosphorus and copper were observed at all fluences. The chemical composition of these clusters shows no evolution with fluence, as well as their diameter, close to 3 nm. Their number density increases linearly with the neutron fluence. A continuous segregation of the elements found in the clusters is also observed along dislocation lines, with similar enrichments.

Polymer nanocomposite gratings with a 363 nm period and a 12 nm step height were replicated using a glass master in a rapid, low-pressure imprint process. The composite materials were based on a UV-curable acrylated hyperbranched polymer and nanosized SiO2 particles. The influence of particle fraction up to 25 vol%, process pressure and UV intensity on the grating geometry was analyzed using atomic force microscopy. The period of the grating was found to be identical to that of the glass master for all investigated conditions. It was shown that the gel point of the nanocomposite was an important factor that determined the stability as well as the dimensions of the imprinted structure. However, a distortion of the grating was observed with increasing fraction of SiO2, which was correlated to the increased internal stress of the composite. Wavelength interrogated optical sensors were produced by depositing a high refractive index TiO2 layer on the composite gratings. The laser signal strength of the polymer sensors was equal to that of the reference high precision glass sensor with 10-12 g/mm2 sensitivity. The strength was lower for the nanocomposites due to propagation losses argued to result from residual porosity.

Ionic transport in electrolyte membranes limits performance in both battery and fuel cell membranes. The problems have been well known for years, sometimes decades, but empirical progress in solving them has been slow. The focus here is on studies to improve understanding of transport mechanisms, which despite extensive study, remain in dispute in several important cases. For lithium transport in polymer membranes, I will review simulation work by ourselves and others, and contend that the original qualitative picture by Ratner and coworkers is confirmed in many respects by recent work. It means, however, that the fundamental difficulty is that the transport is controlled by torsion forces in the hydrocarbon backbone which are extremely difficult to manipulate experimentally. Turning to possibly promising additives, I review recent work on proton and lithium transport in ionic liquids, on which promising experimental results have been reported. The data, both from simulation and experiment, indicate nontrivial collective effects in the transport properties which need to be sorted out to control these systems. In the case of proton transport, we report results suggesting that high mobilities occur in acid-ionic mixtures with a common anion in mixtures near phase separation.

Shape memory polymers (SMPs) are increasingly being considered for use in minimally invasive medical devices. For safe deployment of implanted devices it is important to be able to precisely control the actuation temperature of the device. In this study we report the effect of varying monomer composition on the glass transitions/actuation temperatures (Tg) of novel low density shape memory foams. The foams were based on hexamethylenediisocyanate (HDI), triethanolamine (TEA) and tetrakis (2-hydroxyl propyl) ethylenediamine (HPED), and were produced via a combination of chemical and physical blowing process. The process for post-foaming cleaning was also varied. Foams were characterized by DSC, DMA, and for shape memory. No clear trends were observed for foam samples without cleaning, and this was attributed to process chemicals acting as plasticizers. In foams cleaned via washing and/or sonication, the Tg was observed to decrease for compositions that were higher in the TEA content. Also, no change in shape memory behavior was observed for varying compositions. This work demonstrates the ability to tailor actuation transition temperature while maintaining shape memory behavior for low density foams suitable for aneurysm treatment.

Few-layer hexagonal boron nitride (h-BN) nanosheets were produced by using super-short-pulse laser produced plasma deposition techniques. Scanning electron microscopy, Energy dispersive x-ray spectroscopy, and micro-Raman spectroscopy were used to explore the morphologies, elemental concentrations and bond structures of the few-layer h-BN nanosheets. High-quality transparent few-layer h-BN nanosheet with the width up to more than 6 μm, and length more than 20 μm were successfully obtained. The change in contrast suggests that the number of atomic layers varies over the area. A comparative study between the obtained few-layer h-BN nanosheets and the previously synthesized few-layer graphene were also conducted in order to further investigate the properties of the promising 2-Dimention (2D) nanomaterials. Our results suggest that the development h-BN nanosheets has the potential to revolutionize the understanding of 2-D nanomaterials with delocalized electronsheralding a transformative technology with dramatic future implications.

We report on the growth and properties of novel amorphous Silicon (a-Si:H) p-i-n devices prepared using chemical annealing with argon gas. The i layer in the p-i-n devices was grown using a layer by layer approach, where the growth of a very thin a-Si:H layer (7-30 angstroms) grown using a silane:argon mixture was followed by chemical anneal by argon ions. Repeated cycling of such growth/anneal cycles was used to produce the desired total thickness of the i layer. The thickness of the a-Si layer, and duration of the anneal time, were varied systematically. Pressure and power of the plasma discharge were also systematically varied. It was found that a thin a-Si layer, <10 angstroms, and low pressures which led to relatively high ion flux on the surface, gave rise to a significantly smaller bandgap in the device, as indicated by a significant lateral shift in the quantum efficiency vs. photon energy curve to lower energies. The smallest Tauc gap observed was in the range of 1.62 eV. Corresponding to this smaller bandgap, the current in the solar cell increased, and the voltage decreased. The Urbach energies of the valence band tail were also measured in the device, using the quantum efficiency vs. energy curve, and found to be in the range of45 meV, indicating high quality devices. Too much ion bombardment led to an increase in Urbach energy, and an increase in defect density in the material. Raman spectra of the device i layer indicated an amorphous structure. When hydrogen was added to argon during the annealing cycle, some materials turned microcrystalline, as indicated by the Raman spectrum, and confirmed using x-ray diffraction.