Neutron detection scintillators based on rare-earth activated transparent glass and glass-ceramics are reported. Ce3+ doped gadolinium halides in 6 LiF modified aluminosilicate glass matrices were synthesized by a melt-quench method followed by annealing. Their optical properties and alpha, neutron scintillation performance were investigated and compared to conventional 6 Li-based scintillating glass.

Vertically oriented, highly dense ZnO nanowires (NWs) array was successfully grown on both glass and silicon substrates using hydrothermal technique. A systematic study was carried out to investigate the effects of growth parameters including growth time and thickness of ZnO seed layer on the quality of ZnO NWs in terms of their homogeneity and orientation in the vertical direction. The diameter as well as the length of grown ZnO NWs was found to be closely dependent on the thickness of the pre-coated ZnO seed layer. The structures of ZnO NWs and electron-beam evaporated AgGa0.5In0.5Se2 (AGIS) thin film have been characterized by X-ray diffraction measurements and optical properties were measured by transmission measurement. The optic band gap of AGIS thin film was found to be almost optimum (1.56 eV) to match the abundant part of solar cell spectrum. AGIS thin film was deposited on the synthesized ZnO NWs to form p-n heterojunction based inorganic solar cell, which exhibited photovoltaic behavior with a power conversion efficiency of 0.37 % under A.M (1.5) illumination.

The feasibility of the fabrication of tungsten based nuclear fuel cermets via Spark Plasma Sintering (SPS) is investigated in this work. CeO2 is used to simulate fuel loadings of UO2 or Mixed-Oxide (MOX) fuels within tungsten-based cermets due to the similar properties of these materials. This study shows that after a short time sintering, greater than 90 % density can be achieved, which is suitable to possess good strength as well as the ability to contain fission products. The mechanical properties and the densities of the samples are also investigated as functions of the applied pressures during the sintering.

By using aberration corrected scanning transmission electron microscopy we have found no small scale lateral In composition fluctuations exist in the In0.15Ga0.85N active region of a light emitting diode. Images were acquired at 2% of the electron dose known to create electron beam damage, so the acquired images reflect the intrinsic structure of the InGaN active region. Position averaged convergent beam electron diffraction reveals the local sample thickness where images were acquired is 4.8 nm, eliminating the possibility that the absence of composition variation was observed due to projection through a thick sample. In addition, 2-3 atomic layer steps were observed in the top surface of In0.08Ga0.92N layers and the In0.15Ga0.85N active layers, providing a possible mechanism for lateral carrier confinement.

Natural and synthetic hydroxyapatite (HA) scaffolds for potentialload-bearing bone implants were fabricated by two methods. The naturalscaffolds were formed by heating bovine cancellous bone at 1325°C, whichremoved the organic and sintered the HA. The synthetic scaffolds wereprepared by freeze-casting HA powders, using different solid loadings (20–35vol.%) and cooling rates (1–10°C/min). Both types of scaffolds wereinfiltrated with polymethylmethacrylate (PMMA). The porosity, pore size, andcompressive mechanical properties of the natural and synthetic scaffoldswere investigated and compared to that of natural cortical and cancellousbone. Prior to infiltration, the sintered cancellous scaffolds exhibitedpore sizes of 100 – 300 μm, a strength of 0.4 – 9.7 MPa, and a Young’smodulus of 0.1 – 1.2 GPa. The freeze-casted scaffolds had pore sizes of 10 –50 μm, strengths of 0.7 – 95.1 MPa, and Young’s moduli of 0.1 –19.2 GPa.When infiltrated with PMMA, the cancellous bone- PMMA composite showed astrength of 55 MPa and a Young’s modulus of 4.5 GPa. Preliminary data forthe synthetic HA-PMMA composite showed a strength of 42 MPa and a modulus of0.8 GPa.

We introduce a technique to permit x-ray absorption spectroscopy studies focusing on individual phase-change (Ge2Sb2Te5) memory cells in fully integrated PC-RAM structures. Devices were investigated employing an x-ray nanobeam of only about 300 nm diameter, which could be fully contained within the spatial extent of the active area within a single device cell and enabled us to investigate individual devices without interference from non-switching material surrounding the area of interest. By monitoring the fluorescence signals of tungsten and germanium at a photon energy corresponding to the Ge K-edge absorption edge white line position, we were successful in producing 2D area maps of the active cell region, which clearly show the imbedded tungsten heater element and the switched region of the phase change material. Additionally, position dependent changes in the phase change material could be traced by taking an array of XANES spectra at the Ge K-edge on and in the vicinity of individual devices.

Trivalent rare earth ions in crystalline or fiber hosts are among the most successful of laser materials, but new dopant-host combinations and more detailed understanding of existing materials continue to be needed. This paper presents a few examples from the work of our team at the Army Research Laboratory, highlighting the interrelation between spectroscopic properties and laser behavior. It focuses on bulk solids, though rare-earth-doped fiber lasers are also extremely important. One system discussed is Nd:YAG, particularly concentration quenching in heavily doped ceramic YAG. Spectroscopic properties of Yb:Y2O3 and Yb:Sc2O3 help to elucidate their laser performance. Spectra indicate that Er:YAG is more promising than Er:Sc2O3 for room temperature laser operation, but that the reverse is true for operation at and somewhat above liquid nitrogen temperature.

GaZnO and GaZnON thin films were deposited on both Si (100) and c-axis oriented sapphire substratesby RF co-sputtering of ZnO target and Ga2O3tablets in Ar/O2 and Ar/N2, respectively, by changing the number of Ga2O3tablets (NGa2O3) placed on the ZnO target in the range of 0 to 16.They were subsequently annealed in N2 at 800 °C and then, some of the samples formed by Ar/O2-sputtering were subjected to NH3 treatment at 650 °C for nitridation. XRD measurements revealed that the c-axis lattice parameter calculated from the ZnO (002) peak for GaZnON film son Si (100) was remarkably larger than for GaZnO films on Si (100). Moreover, ZnO (002) was observed up to NGa2O3=16 for GaZnON films formed on sapphire, while no XRD peaks were observed above NGa2O3=8 for GaZnON films on Si(100). Optical band-gap ofGaZnO and GaZnON films became wider from 3.34to 3.67 eVand from 3.21to 3.40 eV, respectively, with increasing NGa2O3 from 0 to 16. Photoluminescence spectra of GaZnO films showed band-to-band emission at 380nm, while those of GaZnON films exhibited broad and weak peaks centered at 550 nm and 647nm.

The equilibrium geometry and electronic structure of graphene deposited on a multilayer hexagonal boron nitride (h-BN) substrate has been investigated using the density functional and pseudopotential theories. We found that the energy band gap for the interface between a monolayer graphene (MLG) and a monolayer BN (MLBN) lies between 47 and 62 meV, depending on the relative orientations of the layers. In the most energetically stable configuration the binding energy is found to be approximately 40 meV per C atom. Slightly away from the Dirac point, the dispersion curve is linear, with the electron speed almost identical to that for isolated graphene. The dispersion relation becomes reasonably quadratic for the interface between MLG and 4-layer-BN, with a relative effective mass of 0.0047. While the MLG/MLBN superlattice is metallic, the thinnest armchair nanoribbon of MLG/MLBN interface is semiconducting with a gap of 1.84 eV.

In order to develop a novel proton conductive membrane for proton exchange membrane fuel cell (PEMFC), a poly(vinyl di-fluoride) (PVDF) matrix was irradiated with swift heavy ions (SHI) to obtain radically active cylindrical latent tracks in the polymer film. Styrene was then radiografted and further sulfonated into these irradiated cylindrical regions, leading to sulfonated polystyrene (PVDF-g-PSSA) domains within PVDF. The role of the grafting degree and fluence of irradiation of the PVDF matrix on PVDF-g-PSSA membranes properties (chemical composition, ion exchange capacity) was investigated. Then, a membrane-electrode assembly (MEA) was prepared and fuel cell tests have been performed. Our results clearly show that PVDF-g-PSSA membranes with a grafting degree of about 140%, obtained after irradiation at a fluence of 1010 ions/cm2, exhibit good conductivity values but their durability is limited to about 70 h. Decreasing the fluence leads to membranes with lower grafting yield but with fuel cell performances closer to those of 140% grafted PVDF-g-PSSA membrane and improved mechanical properties. Then, ion track grafting technique is a promising technique to obtain PEM with a good trade-off between proton conductivity and mechanical properties.

Pb(Zr0.53Ti0.47)O3 (PZT) films have been fabricated on stainless steel substrates by a Polyvinylpirrolidone (PVP) modified sol-gel route. The single layer of about 0.26 μm was achieved by using the PVP-modified PZT sol, and Crack-free PZT films with thickness of up to 2.37 μm were fabricated by repeating the deposition process. The variations in crystallite orientation, microstructure, dielectric and ferroelectric properties of PZT films were investigated as a function of film thickness. Our results indicate that PZT films prepared on stainless steel substrates maintain good dielectric and ferroelectric properties.

Transport properties of polymer nanocomposites become increasingly important for range applications with many outstanding questions remaining. Thermal conductivity is especially important in applications like temperature sensing and packaging. We chose isotactic PolyPropylene (iPP) as one of the most widely used polymers and created nano-colloidal dispersions at different weight percent concentration of carbon nanotubes (CNTs). We oriented the thin-film samples using melt-shear at 200°C and 1Hz in a Linkam microscope shearing hot stage. Thermal conductivity measurements were performed at room temperature on two iPP/CNT sheared thin-film samples (1% and 5% CNT content) both parallel and perpendicular to the shear direction as well as a pure iPP sheared thin-film, prepared using the same process. Our findings indicate that the CNTs enhance kappa by 12% for the 1% CNT sample and 35% by the 5% CNT sample compared to that measured for pure iPP. Additionally, the CNTs under shear induce a novel anisotropy to the thermal conductivity in iPP/CNTs nano-composites. We introduce an approach to extract the shear induced orientational order of thermal conductivity by the dispersed CNTs.

We report on a multiplexed, ratiometric method that can confidently distinguish between cancerous and non-cancerous epithelial prostate cells in vitro, as demonstrated by a double blind experiment. The technique is based on bright SERRS biotags (SBTs) infused with unique Raman reporter molecules, and carrying cell-specific peptides. Two sets of SERRS biotags were used. One targets the neuropilin-1 (NRP) receptors of cancer cells through the RPARPAR peptide. The other functions as a positive control (PC) and binds to both non-cancerous and cancer cells through the HIV derived TAT peptide. Averaging the SERRS signal over a given cell yielded an NRP/PC ratio from which a robust quantitative measure of the overexpression of the NRP-1 by the cancer cell line was extracted. The use of a local, on-cell reference produces quantitative, statistically robust measures of overexpression independent of such sources of uncertainty such as variations in the location of the focal plane, the local cell concentration and turbidity.

Magnetically separable and reusable core-shell CoFe2O4-ZnO photocatalyst nanospheres were prepared via hydrothermal synthesis technique using glucose derived carbon nanospheres as template. The morphology and phase of core-shell hybrid structure of CoFe2O4-ZnO was assessed via TEM, and XRD. The UV-vis photocatalytic activity of the composite was assessed via measuring the degradation rate of modeled pollutant methylene blue in water. The magnetic composite showed high UV photocatalytic activity for the degradation of methylene blue. The photocatalytic activity was found to be ZnO shell thickness dependent. Thicker ZnO shells lead to higher rate of photocatalytic activity. Hybrid nanospheres recovered using external magnetic field demonstrated good repeatability of photocatalytic activity. These results promise the reusability of hybrid nanospheres for photocatalytic activity.

We have developed a cluster-eliminating filter which reduces amount of amorphous silicon nanoparticles (clusters) incorporated into a-Si:H films. We have applied the filter to fabricate a-Si:H Schottky solar cells. The cells show a high initial fill factor FF=0.563 and a high stabilized value after light soaking FF=0.552 which light-induced degradation was quite low value of 1.95 %.

To date, there are a strikingly growing number of patients who need variousorthopedic implants. However, traditional orthopedic implants face manycomplications such as infection and implant loosening which may lead toimplant failures. Conventional metal implants such as titanium were chosenfor orthopedic applications mainly based on their excellent mechanicalproperties and biological inertness. Since natural bone matrix is nanometerin dimension, it is desirable to design a biologically inspirednanostructured coating that can turn conventional inert titanium surfacesinto biomimetic active interfaces, thus enhance bone cell adhesion andosseointegration. For this purpose, we designed a biomimetic nanostructuredcoating based on nanocrystalline hydroxyapatites (nHA) and single wallcarbon nanotubes (SWCNTs). Specifically, nHA with good crystallinity andbiomimetic dimensions were prepared via a wet chemistry method andhydrothermal treatment; and the SWCNTs were synthesized via an arc plasmamethod with or without magnetic fields. TEM images showed that thehydrothermally treated nHA possessed regular rod-like nanocrystals andbiomimetic nanostructure. In addition, the length of SWCNTs can besignificantly increased under external magnetic fields when compared tonanotubes produced without magnetic fields. More importantly, our resultsshowed that the above nHA and SWCNTs nanomaterials can greatly promoteosteoblast (bone-forming cell) adhesion on titanium in vitro, thus holding great promise to improve osseointegrationand lengthen the lifetime of current orthopedic implants.

Solid-electrolyte interphase (SEI) regions play a critical role in stabilizing lithium batteries, but little is known about the detailed mechanism of growth and formation. We have developed a novel method for in situ study of the interfacial regions of SEI layers, using an interface-selective nonlinear vibrational spectroscopy method termed femtosecond broadband multiplex vibrational sum-frequency generation spectroscopy (SFG) and a lithium battery electrochemical cell with optical access. SFG has high sensitivity and high selectivity needed to study vibrational transitions of molecular species during the SEI growth. SFG is most sensitive to interfacial regions, so with SFG we ignore the bulk electrolyte and focus on interface regions just a few molecules thick. During SEI growth there are two such interfaces, the electrode-SEI interface and the electrolyte SEI interface. We will present results obtained using a lithium battery and model materials relevant to Li batteries, where during successive cycles of charge and discharge we selectively probe the structural evolution of these two interfaces on Au, Cu and carbon.

We report the fabrication and characterisation of the first graphene ring micro electrodes, formed by dip coating fibre optics with subsequently reduced graphite oxide. The behaviour of the so-formed Graphene RIng Micro Electrodes (GRIMEs) is studied using the ferricyanide probe redox system while electrode thicknesses is assessed using established electrochemical methods. A ring electrode of ∼73 nm thickness is produced on 220 μm diameter fibre optics, corresponding to an inner to outer radius ratio of >0.999, so allowing for use of extant analytical descriptions of very thin ring micro electrodes in data analysis. GRIMEs are highly reliable (current response invariant over >3000 scans) with the microring design allowing for efficient use of electrochemically active graphene edge sites. Further, the associated nA scale currents neatly obviate issues relating to the high resistivity of undoped graphene. Thus, the use of graphene in ring micro electrodes improves the reliability of existing micro electrode designs and expands the range of use of graphene-based electrochemical devices.

Intermetallic compounds containing actinide ions exhibit a broad spectrum of different physical phenomena at low temperatures. The latter include heavy quasiparticles, unconventional superconductivity and various forms of magnetic ordering. The complex and sometimes enigmatic properties of these compounds derive from the strong correlations among the 5f electrons. Previous model calculations suggested that the intra-atomic Hund’s rule-type correlations may lead to partial localization which is reflected e. g. in the co-existence of itinerant 5f-derived heavy quasiparticles and local magnetic excitations. The conjectured "dual nature" of 5f electrons which is closely related to the question of the 5f valence of the actinide ions is not directly probed by ground state properties and the low-energy excitations. Here we present microscopic calculations for core-level spectroscopy emphasizing the consequences of strong intra-atomic correlations of the 5f shell.

Polymers and polymer nanocomposites have been studied under conditions of extremely high heating rates. Traditionally, these materials have been examined by the flammability research community using methods which have heating rates on the order of 10 degrees C/min. In this study, we have examined how polypropylene-nanoclay (montmorillonite) and polypropylene-carbon nanotube nanocomposites behave subjected to heating rates on the order of one million degrees C/min when irradiated with a 1064 nm Nd-YAG variable pulse millisecond laser. Time-resolved temperature data and mass loss data was collected for each sample as well as post-mortem surface characterization using spectroscopy and electron microscopy. The analysis shows that the nanospecies are effective in providing a protective barrier that decreases the amount of degradation and mass loss to the underlying polymer material. The effect is clearly seen after irradiating with a single pulse and multiple pulses. A comparison between the performance of the nanoclay and carbon nanotube composites is given.