Behavior of Zinc Incorporation into Fuel Deposits in Borated and Lithiated Water with Dissolved Zinc.

The objective of this study was to investigate the behavior of zinc incorporation into newly forming fuel deposits and pre-formed deposits in a simulated pressurized water reactor coolant including 1000 ppm of boron and 2 ppm of lithium at 328 °C. Zinc was incorporated into fuel deposits that were being newly nucleated and grown on nuclear fuel cladding tubes in a zinc-containing coolant. The zinc incorporation resulted in a decrease in the lattice constant of the deposits, which was attributed to the decrease in larger iron content and the corresponding incorporation of smaller zinc in the deposits. However, zinc incorporation was not found, even after the fuel deposits pre-formed before zinc addition were subsequently exposed to the 60 ppb of zinc coolant for 500 h.

Fabrication and photovoltaic properties of heterostructured TiO2 nanowires.

One-dimensional heterostructured TiO2 nanowires were successfully fabricated by an electrospinning technique and modified by hydrolysis. We investigated their structure, morphology, chemical composition, and optical properties by using the X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and UV-vis spectroscopy. In the case of the photovoltaic performance, the short-circuit current density and cell efficiency of the DSSCs employing single TiO2 nanowires and heterostructured TiO2 nanowires improve from 6.90 to 11.38 mA/cm2 and from 2.56 to 4.29%, respectively. The results show that the photoconversion efficiency of the heterostructured TiO2 nanowires could be improved by more than approximately 67% compared to that of the single TiO2 nanowires because of the enhanced specific surface area that facilitates dye adsorption.

Field modulation in Na-incorporated Cu(In,Ga)Se2 (CIGS) polycrystalline films influenced by alloy-hardening and pair-annihilation probabilities.

The influence of Na on Cu(In,Ga)Se2 (CIGS) solar cells was investigated. A gradient profile of the Na in the CIGS absorber layer can induce an electric field modulation and significantly strengthen the back surface field effect. This field modulation originates from a grain growth model introduced by a combination of alloy-hardening and pair-annihilation probabilities, wherein the Cu supply and Na diffusion together screen the driving force of the grain boundary motion (GBM) by alloy hardening, which indicates a specific GBM pinning by Cu and Na. The pair annihilation between the ubiquitously evolving GBMs has a coincident probability with the alloy-hardening event.PACS: 88. 40. H-, 81. 10. Aj, 81. 40. Cd.

Probing the lithium ion storage properties of positively and negatively carved silicon.

Here, we report Si pillar and well arrays as tailored electrode materials for advanced Li ion storage devices. The well-ordered and periodic morphologies were formed on a Si electrode thin film via laser interference lithography followed by a dry etch process. Two different patterns of negatively or positively carved Si electrodes exhibited highly improved cycle performance as a consequence of the enlarged surface area and the nanoscale pattern effects. The Si well arrays showed the highest energy density, rate capability, and cycling retention among the prepared Si electrodes. This tailored electrode platform demonstrates that these design principles could be applied to future developments in Si electrodes.

Copper nanofiber-networked cobalt oxide composites for high performance Li-ion batteries.

We prepared a composite electrode structure consisting of copper nanofiber-networked cobalt oxide (CuNFs@CoOx). The copper nanofibers (CuNFs) were fabricated on a substrate with formation of a network structure, which may have potential for improving electron percolation and retarding film deformation during the discharging/charging process over the electroactive cobalt oxide. Compared to bare CoOxthin-film (CoOxTF) electrodes, the CuNFs@CoOxelectrodes exhibited a significant enhancement of rate performance by at least six-fold at an input current density of 3C-rate. Such enhanced Li-ion storage performance may be associated with modified electrode structure at the nanoscale, improved charge transfer, and facile stress relaxation from the embedded CuNF network. Consequently, the CuNFs@CoOxcomposite structure demonstrated here can be used as a promising high-performance electrode for Li-ion batteries.

Structural and electrochemical properties of Ag nano-dots combined amorphous Si electrodes for thin-film lithium rechargeable batteries.

We have one-pot fabricated Si-based nanocomposite electrodes containing Ag nano-dots for thin-film Li rechargeable batteries by a co-sputtering method. The structural and electrochemical properties of the Si/Ag nanocomposite electrodes are investigated via transmission electron microscopy (TEM), field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), and cycler. The TEM and XRD results show that crystalline Ag nano-dots (approximately 5-9 in size) are well-dispersed within an amorpohous Si matrix. It is shown that the Si/Ag nanocomposite electrode shows much better structural stability than the Si only sample. It is also shown that the Si/Ag nanocomposite electrode shows superior capacity retention compared to the Si only electrode. The results indicate that the presence of the Ag nano-dots is important minimizing the formation of cracks in the electrode, so leading to the better life-time for thin-film Li rechargeable batteries.

Porous networks of CdSe nanocrystal chains from ultrafine Cd(OH)2 nanowires and their composite materials.

Long ultrathin Cd(OH)(2) nanowires have been selectively grown on silica colloids in a basic aqueous condition. The Cd(OH)(2) nanowires could be detached from the surface of the silica colloids by simply applying ultrasonication and then transformed into isolated CdSe nanocrystal chains. When the transformation into CdSe was conducted without detaching the Cd(OH)(2) nanowires, nanoporous CdSe shells composed of wire-like nanocrystal chains were produced. The good solubility of the Cd(OH)(2) nanowires in both hydrophilic and hydrophobic solvents facilitated the formation of composites with quantum dots, magnetic particles, organic molecules, and polymers. Embedding premade quantum dots possessed broad light absorption range and enhanced photoluminescence. Large amount of superparamagnetic particles endowed a fast magnetic response in addition to the fluorescence. Composites of organic/nanocrystal chains were readily fabricated by employing the electrostatic attraction between the positively charged Cd(OH)(2) nanowires and negatively charged polymers or small molecules.

Fabrication and optical properties of conjugated polymer composited multi-arrays of TiO2 nanowires via sequential electrospinning.

We report here a simple method of fabricating multi-layered architectures of cross-aligned inorganic nanowires via sequential electrospinning method equipped with a newly devised collector that is able to prepare aligned inorganic nanowires. The multi-layers of aligned TiO2 nanowires can be deposited in a proportional increment of weight with collecting time and reveal a large reduction of electrical resistance by at least 30% compared to a randomly collected TiO2 nanowire structure. The solar cell performance of the cross-aligned TiO2 nanowire layers composited with a conjugated polymer of poly[2-methoxy, 5-(2'-ethyl-hexyloxy)-1,4-phenylenevinylene] (MEH-PPV) is significantly enhanced by 70% or greater in the organic-inorganic hybrid photovoltaic devices than that fabricated with the randomly-collected TiO2 nanowire photoanode.

Patterned array of nanoparticles on substrates via contact printing method with CNTs/AAO stamp.

Patterned arrays of Fe oxide nanoparticles were transferred via contact printing method on a substrate surface using carbon nanotubes embedded in anodic aluminum oxide (CNTs/AAO) as a stamp, in which vertically aligned CNTs in hexagonally patterned array was first fabricated by chemical vapor deposition into the AAO, followed by a partial chemical etching to expose the CNTs from the AAO. Fe precursor inked CNTs stamp was contact-printed on a Pt-coated Si substrate, and after heat treatment at 200 degrees C, patterned array of Fe oxide nanoparticles with ca. 80 nm of diameter and ca. 120 nm of inter-distance between the nanoparticles was consequently obtained.

Size controlled nickel oxide nanoparticles on carbon nanotubes for supercapacitor electrode.

We have synthesized supercapacitor electrodes fashioned of NiO(x)/multiwalled carbon nanotubes (MWNTs), in which the controlled NiO(x) nanoparticles were prepared via a simple colloidal method and supported on the MWNTs. The sizes of the NiO(x) nanoparticles on MWNTs were systematically varied from 4 to 14 nm at a fixed metal loading of 20 wt% by changing sintering temperature in a controlled manner. The maximum specific capacitance of the NiO(x)/MWNTs was measured to be ca. 215 F per unit gram of NiO(x)/MWNTs by cyclic voltammetry (CV) in an aqueous 1 M KOH electrolyte, demonstrating that the specific capacitance of the MWNTs-supported nanosize NiO(x) is strongly dependent on the dispersion and size of the nanoparticles for the supercapacitor performance.

Ta2O5-Incorporated WO3 nanocomposite film for improved electrochromic performance in an acidic condition.

We report electrochromic and electrochemical properties of a WO3-Ta2O5 nanocomposite electrode that was fabricated from co-sputtering. Transmission electron microscopy (TEM) images of the WO3-Ta20 nanocomposite electrode revealed that morphology of the WO3 film was changed by incorporation of Ta2O5 nanoparticles, and their chemical states were confirmed to be W6+ and Ta5+ oxides from X-ray photoelectron spectroscopy (XPS). The introduction of Ta2O5 to the WO3 film played a role in alleviating surface roughness increase during continuous potential cycling; whereas the surface roughness of the WO3 film was increased from ca. 3.0 nm to ca. 13.4 nm after 400 cycles, the roughness increase on the WO3-Ta2O5 was significantly reduced to 4.2 nm after 400 cycles, as investigated by atomic force microscopy (AFM). This improvement of the stability by adding Ta2O5 may be responsible for the enhanced electrochemical and optical properties over long-term cycling with the WO3-Ta2O5 nanocomposite electrode.