Much has been reported on the excellent performance of the Eu2+ activated SrI2-scintillator in spectroscopic applications, like the high light yield (97 660 ph/MeV) and good energy resolution (2.7% FWHM at 662 keV). The exploitation of these properties for other application fields is limited by the hygroscopic nature of the SrI2. Single crystal scintillating screens exhibit high spatial resolution, this combined with the high density, high effective atomic number, and the high light yield of the SrI2 could be used for high resolution X-ray imaging.

Some of the questions we tried to answer in this work are the following: owing to the excellent performance of the SrI2-scintillator in spectroscopic applications, how would it perform in X-ray imaging applications. X-ray images are described based on their (spatial) resolution and contrast, how would they look like when recorded using the SrI2-scintillator detector.

First a packaging technique was developed that protected the hygroscopic screens during the measurements. Our results show a high resolution of the images obtained with thin SrI2-scintillator screens both in 2D radiography and 3D tomography measurements. With these results, we think that the SrI2-scinitillator is not only a candidate for spectroscopic applications, but also for high resolution X-ray imaging purposes.

Eutectic fibers consisting of an ordered arrangement of LiF fibrils inside a LiREF4 matrix (RE = Y, Gd) can be grown with the micro-pulling-down method at sufficiently large pulling rate exceeding 120 mm/h. The distance between individual fibrils could be scaled down to 1 µm at 300 mm/h pulling. LiF-LiYF4 has stronger tendency to form facetted eutectic colonies than LiF-LiGdF4, explained by the larger entropy of melting of the former.

We report on the direct synthesis of multi-layer boron nitride nanosheets (BNNSs) and their electron microscopic characterization. The synthesis process is carried out by irradiating hexagonal boron nitride (h-BN) target using short laser pulses. Scanning electron microscopy showed large area (≈50×50 μm2) flat layers of BNNSs transparent to the electron beam. Low magnification transmission electron microscope (TEM) is used to characterize different areas of nanosheets. TEM revealed that each individual nanosheet is composed of several layers. High resolution TEM (HRTEM) measurements confirmed the layered structure. HRTEM analysis of the edge of a nanosheet showed 10 layers from which we obtained the thickness (3.3nm) of an individual nanosheet. Selected area electron diffraction pattern indicated polycrystalline structure of nanosheets. Raman spectroscopy clearly identified E2g vibrational mode related to h-BN.

Polyurethanes are widely used, from medical devices to electrical materials to consumer goods. These materials have chemical stability issues which impact the mechanical stability. Infrared micro spectroscopy has been used to study polyurethane degradation, but due to experimental limitations, samples examined were no smaller than approximately 15 microns on a side. Because of the complex chemistry of urethanes, chemical examination of the material on a much higher spatial resolution scale would be valuable.

A relatively new technique, Attenuated Total Reflection Fourier Transform Infrared Spectrochemical MicroImaging has been used to examine degraded polyester urethanes. Rather than using a single-element detector, a two dimensional array detector generates thousands of spectra simultaneously. In addition, a germanium prism generates a magnification effect; resulting in a significantly higher spatial resolution. The net output of the analysis is a hypercube of high resolution infrared spectra showing urethane degradation progression on a much smaller spatial scale than was previously possible.

Nanostructuring has been the foremost approach to the manufacture of high-performance thermoelectric materials for nearly a decade. This study explores a novel nanostructuring technique, attrition-enhanced nanocomposite synthesis, in maximum indium-filled, iron-substituted cobalt antimonide skutterudites. In0.3Fe0.8Co3.2Sb12 was synthesized and subjected to varying degrees of mechanical attrition (via ball milling). These samples exhibited increased indium precipitation coincident with the duration of mechanical attrition. Indium readily diffused through the skutterudite crystal structure and rapidly precipitated forming 20-50 nm-sized indium-rich inclusions during sintering.

In this work, composites consisting of the Al 2024 matrix reinforced with β-Al3Mg2 particles have been produced by powder metallurgy with the aim of increasing the strength of the matrix and, at the same time, reducing the density of the material. The β-Al3Mg2 phase represents an ideal candidate as reinforcement in lightweight composites due to its low density and high-temperature strength. The β-Al3Mg2 reinforcement remarkably improves the mechanical properties of the 2024 matrix. In particular, the composite with 20 vol.% reinforcement display yield and compressive strengths exceeding that of the unreinforced matrix by about 120 and 180 MPa, while retaining appreciable plastic deformation of about 30 %. The strength of the material is further increased for the samples with 30 and 40 vol.% of β-Al3Mg2 phase, however, the composites show reduced plastic deformation of 11 and 4.5 %. Furthermore, the addition of the low-density β-Al3Mg2 particles decreases the density of the materials below that of the unreinforced 2024 matrix, considerably increasing the specific strength of the composites.

Microstructural variations of directionally-solidified (DS) MoSi2/Mo5Si3 eutectic composites caused by ternary additions of V, Cr, Nb, Ta and W were investigated. Ternary addition of relatively large amount of V resulted in the apparent modification of the morphology as well as the macroscopic inclination angle of one type of the interfaces extending nearly along the growth direction in the DS ingots. Ternary addition of Cr was found to change the microstructures of the DS ingots from a cellular-type with coarse boundary regions to a plate-like cellular-type with increasing the amount of the ternary addition. No significant change of scriptlamellar morphology was observed for the DS ingots containing Nb, Ta and W irrespective of the amount of the ternary addition.

The unrestrained combustion of fossil fuels has resulted in vast pollution at the local scale throughout the world, while contributing to global warming at a rate that seriously threatens the stability of many of the world's ecosystems. Solar photovoltaic (PV) technology is a clean, sustainable and renewable energy conversion technology that can help meet the energy demands of the world’s growing population. Although PV technology is mature with commercial modules obtaining over 20% conversion efficiency there remains considerable opportunities to improve performance. The nearly global access to the solar resource coupled to nanotechnology innovation-driven decreases in the costs of PV, provides a path for a renewable energy source to significantly reduce the adverse anthropogenic impacts of energy use by replacing fossil fuels. This study explores several approaches to improving indium gallium nitride-based PV efficiency with nanotechnology: optical enhancement, microstructural optimization for electronic material quality and increasing the spectral response via bandgap engineering. The results showing multibandgap engineering with InGaN and impediments to widespread deployment and commercialization are discussed including technical viability, intellectual property laws and licensing, material resource scarcities, and economics. Future work is outlined and conclusions are drawn to overcome these limitations and improve PV device performance using methods that can scale to the necessary terawatt level.

In this work, the thermoelectric properties of Se-doped Bi2Te3 are examined using first-principles density functional theory and semi-classical Boltzmann transport theory. Placing a single Se atom on the 3a Wyckoff position lowers the unit cell energy by approximately 3.6 eV, compared to the 6c Te position. The electronic structure of Bi2Te3 has minor changes upon Se doping. At carrier concentration of 1019 cm-3, the optimal thermopower, S, is obtained as 207 and 220 μV/K for n-type and p-type doping, respectively. Unlike the thermopower, the power factor, S 2 σ/τ, is highly anisotropic for the in-plane and cross-plane conduction. At carrier concentrations of 1019 cm-3, the best power factor is predicted to be around 1.05 and 1.4×1011 W/m·s·K2 for n-type and p-type doping, respectively.

In this paper, a novel set of macros with line/space width from 128nm/128nm, 64nm/64nm to 32nm/32nm was designed and installed on 20nm technology-node hardware. The pitch-dependent pad erosion post Cu CMP was studied by atomic-force microscopy (AFM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) quantitatively on these macros. Two methods were investigated to reduce the difference between pitch- and density-induced CMP non-uniformity. The first is using new scheme of partial Cu plating process followed by SiCNH insulator deposition and then CMP. The second is through the selection of slurries and pads. Both results are discussed in this paper.

The properties of superconductors at the extreme limits of dimensionality are of fundamental interest. The interface of LaAlO3 and SrTiO3 hosts a quasi-two-dimensional superconductor below Tc≈200 mK. Here we report superconductivity in nanowire-shaped structures created at the LaAlO3/SrTiO3 interface using conductive atomic force microscope lithography. Nanowire cross-sections are small compared to the superconducting coherence length in LaAlO3/SrTiO3 (w <<ξSC∼100 nm), placing them in the quasi-1D regime. The ability to “write” fully superconducting nanostructures on an insulating LaAlO3/SrTiO3 “canvas” opens possibilities for the development of new families of superconducting nanoelectronics. Four-terminal transport measurements suggest that in some devices both the normal and superconducting states are confined to a single quantum channel.

Anodically formed TiO2 nanotube arrays composed of the anatase phase with periodically modulated diameters (PMTiNTs) are excellent photocatalysts for the sunlight-driven transformation of carbon dioxide into hydrocarbons. Exploiting the full potential of this nanoarchitecture for CO2 photoreduction requires integration with metal nanoparticles that function as catalytic promoters for multistep electron transfer reactions. We studied the effect of different metallic and bimetallic nanoparticles on the rate of generation of light hydrocarbons by the photoreduction of CO2. All the metal nanoparticles were loaded on to the TiO2nanotubes using the technique of photodeposition, which standardized the coating process and enabled examination purely of the effect of different metals. Photodeposition was used not only due to its simplicity but also because it enabled us to engineer very fine coatings possessing excellent uniformity and depth penetration into the nanotubes. The best performing co-catalysts were found to be CuPt (atomic ratio of 0.33:0.67), Pt and NiPt (1:2), which when loaded onto the PMTiNTs yielded total hydrocarbon generation rates of 3.5, 0.85 and 0.8 mL g-1 hr-1 respectively. The time required to form PMTiNTs was reduced by a factor of 160 by using a recently reported recipe based on fluoride ion bearing electrolyte containing lactic acid. PMTiNTs formed using the ultrafast growth lactic acid-based electrolytes exhibited similar photocatalytic properties to samples obtained more slowly using conventional ethylene glycol-based electrolytes.

Recently, there has been much interest in the creation of 3D networks of nanowires. One possible way to do this is to encase the nanowires inside transparent polymer matrices since there is also a demand for obtaining conducting transparent composites. If the filler of the composite is made from a strongly conducting material, the degree of connectivity of the networked nanowires can be tested by measuring its conductivity. Though much work has been done with ITO (Tin-doped indium oxide), little has been done with the chemically similar, but cheaper, ATO (Antimony-doped tin oxide). In this study, ATO nanoparticles were added into a polystyrene matrix and simultaneously pressed and heated so that a 3D network of the nanoparticles would form. The effecti veness of the conducting pseudo-nanowire networks was measured as the concentration of ATO in polystyrene was varied. Another variable utilized was the temperature at which the samples were pressed. The optical transmittance of the composites was also measured in order to quantify their transparency. It was found that, once the nanowire networks had percolated at a concentration of about 1.25 PHR, the conductivity and, consequently, the coherence of the networks increased at a decreasing rate as the concentration was increased. The effect of the pressing temperature was complex and required many additional sets of specimens to understand. Samples pressed at the highest temperature had the least coherent networks, as the polystyrene became too fluid and disrupted the ATO networks while at lower temperatures the opposite occurred. The optical transmittance dropped sharply as the concentration of ATO reached and surpassed 1.0 PHR. Nanowire networks were, indeed, formed through this process using these materials, but use as a conducting transparent composite in the visible range is unlikely as the percolation threshold occurs at a concentration greater than that of the optical transmittance drop, creating a trade-off between conductivity and transparency. The resistivity did drop as much as six orders of magnitude and may be useful for other applications.

Ordered arrays of crystalline complex oxides nanostructures were synthesized onto single crystal insulating substrates using aqueous polyvinyl alcohol based electron beam resist precursors. The irradiated zones are insoluble in water (negative-tone resist) due to the electron induced cross linking of polyvinyl alcohol. The subsequent high temperature treatment of the developed precursor samples leads to the formation of ordered arrays of nanodots for low irradiation doses. For high irradiation dosages, epitaxially and oriented nanowires are obtained. These same precursors were shown to be nanoimprintable on single crystal substrates. This allows for future dual processing of a single precursor film gaining nano-structuration from both electron beam and nanoimprint lithography methods.

Molecular dynamics (MD) simulations are carried out to understand the mechanisms of damage production and recovery near grain boundaries in β-SiC under neutron irradiation. Our investigations show that the damage generated by radiation is reduced by the presence of a ∑9{122}[110] tilt grain boundary. Directional displacements which are averaged over an isoconfigurational ensemble are used to characterize the statistical nature of atomic mobility near the grain boundary.

Photonics Integrated Circuits (PICs) are being applied by the telecommunications industry as transceivers for fibre optic networks. The core component of a typical PIC is the laser array and these devices can have relatively low operating temperatures (15°C - 25°C) with a tight operating range (±0.1K). To accommodate such a specification, a thermal control system is required that can change the cooling rate through feedback. The power density of next generation PICs is at such a level to demand novel thermal management architectures including developments such as near source liquid cooling. In order to control the thermal performance of fluidic devices, effective methods for varying the rate of coolant are an essential component. Consequently, micro-valve structures are required, ideally involving passive actuation to meet stringent reliability standards. One solution to this challenge is to exploit the phase-change driven shape memory effect of the NiTi Shape Memory Alloy (SMA). A micro-valve could be developed from the NiTi SMA, thermally coupled to the laser array component in order to work passively to regulate the flow of coolant in a micro-channel. Such a valve would have to be intrinsically reliable, and the goal of this paper is to investigate the conditions that will affect this reliability. The objective of the work is to investigate the mechanical properties relevant to the design of a passive NiTi SMA micro-valve, with a focus on the formation of stress-induced Martensite bands. It is not understood why these bands form on a plane inclined at ∼55° to the axis of loading and in this paper theory is presented that suggests a reasoning for this. A plate sample of NiTi was tested in uni-axial tension and Digital Image Correlation (DIC) used to analyse the strain fields across the surface of the sample. The DIC results revealed areas of high stress concentrations occurring in bands inclined on average 53.86° to the axis of loading. The theory and experimental observations are in agreement with the literature but to validate the theory the crystal texture needs to be analysed in the stress concentration regions. This paper provides valuable insight into the mechanical behaviour of a passive NiTi SMA micro-valve subjected to a sufficient pressure to form stress-induced Martensite.

Cu nanoparticles capped with fatty acids and amines were developed as low-temperature sintering materials. The fatty acids and amines used were decanoic acid + decyl amine (C10) and oleic acid + oleyl amine (C18), respectively. The synthesized Cu nanoparticles were analyzed using X-ray diffraction, transmission electron microscopy, and thermogravimetric and differential thermal analysis. Because both of the capping layers could be decomposed at temperatures lower than 300°C even under an inert atmosphere, bonding and sintering experiments could be carried out in the absence of oxygen to prevent the oxidation of the Cu nanoparticles. The sintered structures were observed using scanning electron microscopy. The shear strengths of Cu plates bonded using the C18 Cu nanoparticles were larger than those of plates bonded using the C10 Cu nanoparticles. At 300°C, the strength was higher than 30 MPa, and of the same order as ordinary high-temperature solders, even though the processing temperature was low. The resistivity of a film sintered using the C18 Cu nanoparticles was 12 μΩcm at 300°C, which was lower than the values reported in previous studies.

The mechanism for the gelation reaction of colloidal silica, Si(OH)4 +Si(OH)3 (O)- ----> Si2O8H5- + H2O, by an anionic pathway was investigated using density functional theory(DFT). Using transition state theory, the rate constants were obtained by analyzing the potential energy surface at the reactants, saddle point, and the products. In addition, reaction rate constants were investigated in the presence of ammonium chloride (NH4Cl) and sodium chloride (NaCl). These salts act as catalysts to induce gelation by destabilizing the double layer of colloidal silica to allow for Van der Waal interactions. Furthermore, it was observed that ammonium chloride plays an important role by initiating a hydride transfer allowing the reaction to proceed from the second transition state to the final product.

A series of laser pump, x-ray probe experiments show that above band gap photoexcitation can generate a large out-of-plane strain in multiferroic BiFeO3 thin films. The strain decays in a time scale that is the same as the photo-induced carriers measured in an optical transient absorption spectroscopy experiment. We attribute the strain to the piezoelectric effect due to screening of the depolarization field by laser induced carriers. A strong film thickness dependence of strain and carrier relaxation is also observed, revealing the role of the carrier transport in determining the structural and carrier dynamics in complex oxide thin films.