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The copper precursor N,N'-diisopropylacetamidinate has been decomposed at low temperature (80-110°C) in a liquid process under a moderate H2 pressure. Depending on the choice of the solvent, the process leads to a colloidal solution of well controlled copper nanoparticles or the deposition of composite Cu-SiO2 films on the surfaces. The latter layer is highly adhesive to silica surface, behaves as an active seed layer for electroless copper deposition and allows a conformal covering inside deep trenches.
Although AgSbTe2 exhibits excellent thermoelectric properties, the single phase is unstable and second phases such as Ag2Te and Sb2Te3 are easy to precipitate. In the present study, we tried to stabilize the AgSbTe2 phase by adding a small amount of another phase. Here we chose Pb0.16Ge0.84Te as the adding phase because the crystal structure and the lattice parameter were completely the same as those of AgSbTe2. The samples of (Ag0.5Sb0.5Te1-x(Pb0.16Ge0.84Te)x (x = 0, 0.01, 0.02, 0.05, and 0.1) were prepared and the phase stability and the thermoelectric properties were examined. The AgSbTe2 phase was stabilized in the samples of x = 0.01 and 0.02. All the samples exhibited large thermoelectric figure of merit.
In this work the synthesis and mechanical characterization of a polymer matrix composite is reported. An epoxy resin is used as matrix with addition of starch and coconut fibers as reinforcement. Vickers hardness and impact tests are used for mechanical characterization. Starch is used to promote degradability of the polymer matrix with clear benefits for the environment. Natural fibers have been used for reinforcing the composite materials. Natural fibers have several advantages such as price, low density and relatively high mechanical properties, they are also biodegradable and non abrasive In this investigation, the composite material samples are fabricated with epoxy resin, 5, 10, 15 wt % of starch and 5, 10 wt % of coconut fibers with the help of silicon molds which have the dimensions and geometry according to ASTM Standards for make Impact and Vickers hardness tests. The obtained results show that increases in the amount of coconut fibers cause an enhancement of the mechanical properties of the material, due to a good adhesion between the polymeric matrix and the natural fibers.
Recently nanostructured bulk silicon and silicon-germanium have achieved large increases in the thermoelectric figure of merit (ZT). The ZT enhancement is attributed to a significant reduction in the lattice thermal conductivity while maintaining relatively high carrier mobility. Silicon-based thermoelectric devices are attractive due to their low-toxicity, thermal stability, low density, relative abundance and low cost of production. Although significant enhancements in ZT have been achieved using the nanostructuring route, additional decoupling of the thermal and electric transport terms is still necessary in order for silicon-based materials to be viable for thermoelectric applications such as waste heat recovery or radioisotope thermoelectric generators. It is theorized that additional increases in ZT could be achieved by forming composites with nanostructured inert inclusions to further scatter the heat-carrying phonons. Here we present the impact of insulating and conductive nanoparticle composites on ZT. The nanostructured composites are formed via ball milling and high pressure sintering of the nanoparticles. The thermoelectric properties and microstructure of the silicon-based composites are discussed.
Beaded fibers and/or uniform, smooth-surface fibers of conductive polymers with the average diameters ranging in nanometers to sub-micrometers were fabricated by electrospinning of a mixture of poly(3-hexylthiophene) (P3HT) and polyvinylpyrrolidone (PVP) in a mixed solvent of chlorobenzene and methanol. After the removal of PVP from as-spun fibers by Soxhlet extraction, pure P3HT fibers were obtained as a spindle-like with groove-like morphological appearance which may be widely applicable for some specific applications, such as photovoltaic cells, thin film transistors, and light emitting diodes. Optical properties, including UV absorption and photoluminescence (PL) of fibers were investigated. As-spun fibers showed relatively higher conjugation length and different chain distribution, in comparison with the cast film.
Through-silicon via (TSV) 3-D packaging and integration present many new opportunities and challenges for metals CMP applications. For front-side TSV polishing, challenges include the removal of large amounts of copper overburden, dishing control during copper clearing steps, and removal of large amounts of barrier metal and dielectric layers while still maintaining control over topography and defectivity. Additionally, the choice of barrier material can have significant impact on polishing in terms of the mechanical reliability regarding adhesion between the barrier metal and underlying dielectric layers. This paper will address many of these challenges with an emphasis on innovative technologies for superior process and endpoint controls, such as real-time profile control for thick copper films up to 6μm or more in thickness and automatic endpoint controls for barrier removal and dielectric stopping. The paper will also discuss some salient challenges for back-side TSV polishing, including the handling and polishing of bonded wafer pairs and strategies to minimize handling and polishing damage to the potentially fragile thinned device wafer. Additionally, the development of slurries with highly tunable copper-to-dielectric selectivity will be critical for enabling a wide range of final topographies, depending on requirements for subsequent bonding steps.
The performance of the thermoelectric devices and materials is shown by a dimensionless figure of merit, ZT = S2σT/K, where S is the Seebeck coefficient, σ is the electrical conductivity, T is the absolute temperature and K is the thermal conductivity. ZT can be increased by increasing S, increasing σ or decreasing K. We have prepared 100 alternating nanolayered films of SiO2/SiO2+CoSb3 using the ion beam assisted deposition (IBAD). The 5 MeV Si ions bombardments have been performed using the AAMU Pelletron ion beam accelerator to make quantum clusters in the nanolayered superlattice films at the three different fluences to decrease the cross plane thermal conductivity, increase the cross plane Seebeck coefficient and cross plane electrical conductivity. We have characterized 100 alternating nanolayered films of SiO2/SiO2+CoSb3 before and after Si ion bombardments as we measured the cross-plane Seebeck coefficient, the cross-plane electrical conductivity, and the cross-plane thermal conductivity for three different fluences.
Ce-containing MCM-41 mesoporous materials with large surface area and ordered pore structure system have been possible to be synthesized through a surfactant-assisted approach. The textural properties and structural regularity of the materials varied with the Si/Ce molar ratio. It is found that the band at 970 cm-1 in the FTIR spectrum of the Ce-MCM-41 mesoporous materials might be used as an indicator of the formation of the Ce-O-Si bond and its intensity as a measure of a degree of cerium ion substitution in the framework of Si-MCM-41. When Ni was loaded on the Ce-MCM-41 support, the Ni/Ce-MCM-41 catalysts show high catalytic activity which has strong temperature dependence. The methane conversion over these catalysts reached 60-75 % with a 100 % selectivity towards hydrogen.
The influence of stress on the phase change behaviour of Ge2Sb2Te5 encapsulated by ZnS-SiO2 and TiN is investigated using temperature dependent Extended X-ray Asbsorption Fines Structure and Ellipsometry to determine the crystallisation temperature. The encapsulation material surrounding the Ge2Sb2Te5 has an increasingly dominant effect on the material's ability to change phase and can cause a profound increase in its crystallization temperature. We have experimentally shown that the increased crystallization temperature originates from compressive stress exerted from the encapsulation material. By minimizing the stress we have maintained the bulk crystallization temperature in Ge2Sb2Te5 films just 2 nm thick.
Templated growth for the fabrication of semiconductor nanostructures such as quantum dots and lattice-mismatched structures has been employed in this study. Self assembly of block copolymers (BCP) has been exploited to create a regular array of nanoscale patterns on a substrate to generate the growth template. These patterned templates were used for the selective area growth of pseudomorphic quantum dots, allowing for precise control over the dot size and spatial distribution. Strain relaxation in lattice-mismatched structures grown past the pseudomorphic limit was also studied. Analysis of the grown structures suggests that this approach using block copolymer templating followed by selective growth can be used for defect reduction in lattice-mismatched materials.
CuInSe2 (CIS) is commercially processed using energy intensive vacuum processes such as sputtering and thermal evaporation followed by thermal annealing. In order to reduce the cost of fabricating CIS photovoltaic absorber layers we need fast and cheap processing methods. We have investigated the use of non-vacuum electrochemical deposition (ED) followed by ultra violet pulsed laser annealing (UV-PLA). We report here on the results of ns pulsed KrF irradiation of ED CIS films and ED CIS films which were first annealed in a Se atmosphere.
Tungsten (W)-substituted SBT ceramics [SrBi2(Ta1-xWx)2O9; 0.0 ≤ x ≤ 0.20] were synthesized by solid state reaction method using different sintering temperatures (1100 οC, 1150 οC, 1200 οC and 1250 οC). W substitution is found to significantly affect the electrical properties of SBT, including dielectric permittivity, Curie temperature, and ferroelectricity. Dielectric constant (εr) and the Curie temperature (Tc) increase with increasing W content. The dielectric loss reduces significantly with increase in W concentration. The maximum Tc of ~ 390 οC is observed in the sample with x = 0.20 as compared to ~ 320 οC for the pure sample when sintered at 1200 οC. The peak ε increases from ~ 270 in the sample with x = 0.0 to ~ 700 for the composition with x = 0.20, when sintered at 1200 οC. All the tungsten-substituted ceramics have higher 2Pr than that in the pristine sample. The maximum 2Pr (~25 μC/cm2) is obtained in composition with x = 0.05 sintered at 1200 οC. These effects have been interpreted based on the model of the recovery of oxygen vacancies upon W substitution. Such compositions with low loss and high Pr values should be excellent materials for highly stable ferroelectric memory devices.
Fabrication of all-solid-state Li battery has been strongly required to overcome safety issue of present Li battery. One of promising structures for ceramics electrolyte in all-solid-state battery is 2-layered structure composed of 3 dimensionally ordered macroporous layer (3DOM) and dense layer. In this study, we prepared LLT ceramics electrolyte with the 2-layered structure by suspension filtration method. Thicknesses of the dense and the porous layers were about 17 and 111 μm, respectively. The porous layer involved uniform pores of 1.8 μm in diameter. An electrochemical property of LiMn2O4/2-layered LLT composite, prepared by impregnation of precursor sol for LiMn2O4 into the pores followed by calcination, was tested. A rechargeable behavior of the composite electrode was clearly observed. From this result, it can be said that the composite can work as rechargeable battery. The discharge capacity of the composite was 27 mA h g-1.
Both SnO2 and SnO2:Ag thin films were fabricated by the sol-gel process and dip-coating technique. SnCl4•5H2O was used as a precursor of tin to prepare a 0.2M solution with 2-methoxyethanol and monoethanolamine as solvents. From AgNO3 a 0.012M solution in ethanol was prepared, from where the Ag was used as catalyst, which was incorporated superficially to SnO2 film grown on soda-lime substrate. Two series of samples (A and B) about 150 and 300 nm in thickness were prepared and studied. Several layers of Ag as catalyst on the surface of SnO2 films were applied. The films were characterized in structure (RXD), morphology (SEM and AFM) and EDX, electrical and optical properties (UV-vis). The sensing properties of films to the propane at, 0, 1, 5, 50, 100, 200, 300, 400 and 500 ppm gas concentrations were tested in sensors operating at 23, 100, 200 and 300°C. Results for a selection of sensors are presented in this paper.
The electrical resistance change of amorphous SixTe100-x (x: 10-23) films during heating was investigated by a two-point probe method. The SixTe100-x films showed two-stage crystallization processes. The film was firstly crystallized to Te and subsequently crystallized to Si2Te3 with an electrical resistance drop. The first crystallization temperature Tx1st slightly increased with increasing Si content, while the second crystallization temperature Tx2nd was independent on the composition and was a constant temperature of 310 °C. In all films, the electrical resistance once increased in the temperature range from 250 to 295 °C before the crystallization of the Si2Te3. This temporal resistance increase could be explained by considering a formation of high-resistivity Si-rich amorphous phase.
The authors prepared a near-UV to red wavelength conversion thick film containing 38.8 wt% of YVO4:Bi3+,Eu3+ nanoparticles of 10.8 ± 1.6 nm in size. This nanoparticle film shows a high transparency in the visible region, e.g., the transmittance at 619 nm is ∼ 96% irrespective of the film thickness. The photoluminescence intensity at 619 nm corresponding to the f-f transition of Eu3+ for this nanoparticle film increases with increasing the film thickness up to 400 μm, whereas that of the film containing micron-sized particles reaches the maximum at the film thickness of ∼ 40 μm. On the other hand, YVO4:Bi3+,Eu3+ nanoparticles have a sufficient photostability for practical use over 15 years outside, as confirmed by the light fastness test. These results suggest that the transparent film of YVO4:Bi3+,Eu3+ nanoparticles are potentially applicable to the spectral convertor for photovoltaic cells from the aspects of low light-scattering loss and high photostability.
Indium Tin Oxide (ITO) films were deposited by RF sputtering onto glass and quartz substrates with no external heating. An ITO target containing 10 wt% SnO2 was used for the deposition in a Kurt Lesker PVD75 system, in an atmosphere of 50% O2 + 50% Ar. Post-deposition heat treatments were done on these coatings at 150°C, 300°C and 450°C in an atmosphere of commercial air or argon. The effects of these heat treatments on the microstructure and the properties of the films were evaluated using atomic force microscopy, resistivity measurements, and UV-visible absorption spectroscopy. The heat treatments were observed to significantly affect the properties such as transmittance in the visible region, optical band gap and the electrical resistivity of the films. The main differences are caused by the differences in thermal expansion coefficient of the substrates as compared to the sputtered ITO films.
Radiogenic iodine is one of the more difficult fission products to capture and immobilize during the reprocessing of spent nuclear fuel.
However, for metallic fuels reprocessed by electrometallurgical treatment, it is believed that the majority of fission-product iodine is retained during the various processing steps. Spent fuel from the Experimental Breeder Reactor II (EBR-II) at the Idaho National Laboratory (INL) is being treated by a combination of electrochemical and pyrometallurgical methods to deactivate the bond sodium of the fuel, recover uranium, and immobilize fission products for disposal. This paper discusses the progress of various strategies and experiments to confirm the expected retention of iodine during the electrometallurgical treatment of EBR-II spent fuel. This includes surveys of previous observations and measurements, and the direct measurement of iodine from various process samples. Current measurements are aimed at iodine determination in the bond sodium and plenum regions of the fuel, refined iodine measurements in electrorefiner salt, and the retention of iodine during waste form production.
Electrospray ionization quadrupole ion trap mass spectrometry of the ammonium lanthanide(III) phosphomolybdate complex (NH4)11Ce(III)(PMo11O39)2 has been conducted revealing the Ce-POM complexes H2Ce(III)P2Mo22O753- and Ce(III)PMo11O382- as the primary Ce species in 10 mM solutions. From the complex isotopic fingerprints produced through the assembly of multiple molybdenum atoms, a transition metal with seven naturally occurring isotopes, the identities of larger ions were confirmed via successive collision induced dissociation (CID) studies of the gas phase ions. The result of these CID studies was the production of smaller ions with reduced molybdenum content, allowing for comparison between calculated and experimental isotopic distributions. CID studies also provided insights into favored fragmentation pathways. These studies provide a basis to explore speciation and ESI behavior of actinide cluster complexes.