42 research outputs found
Enhanced Radiation Tolerance in Sputtered Cu/V Multilayers
No full textHigh energy particle (neutron, proton and He ions) irradiation to materials
typically leads to deteriorating properties, including void swelling, blistering,
embrittlement, fracture and exfoliation of surfaces. This dissertation examines size
dependent radiation damage in nanostructured metallic multilayers synthesized by the
magnetron sputtering technique at room temperature. It reveals the roles of interface in
achieving enhanced radiation tolerance in metallic materials. The microstructure and
mechanical properties of as-deposited Cu/V multilayer films are systemically
investigated, providing the basis for studying radiation damage mechanisms.
Sputter-deposited Cu/V multilayers are subjected to helium (He) ion irradiation at
room temperature with a peak dose of 6 displacements per atom (dpa). The average
helium bubble density and lattice expansion induced by radiation decrease significantly
with decreasing h, where h is individual layer thickness. The magnitude of radiation
hardening decreases with decreasing h, and becomes negligible when h is 2.5 nm or
less. The interactions between interfaces and radiation induced point defects and the
evolution of microstructurs and mechanical behavior are discussed. This study indicates that nearly immiscible Cu/V interfaces spaced a few nm apart can effectively reduce the
concentration of radiation induced point defects.
Dose dependent radiation damage at room temperature in these Cu/V multilayers
is systematically investigated with a peak dose in the range of 1-12 dpa. Peak bubble
density increases with increasing dose, but it is much lower in Cu/V 2.5 nm multilayers
than that in Cu/V 50 nm specimens. A similar radiation hardening trend is observed in
multilayers irradiated at different fluences. Radiation hardening increases with dose and
seems to reach saturation at a peak dose of 6 dpa. Negligible hardening for fine ( h less than/equal to 2.5
nm) multilayers is observed at all dose levels.
Thermal stability of Cu/V multilayers is revealed by in situ annealing inside a
transmission electron microscope. During isothermal annealing at 600 degrees C grain boundary
grooving occurs across layer interfaces in Cu/V 50 nm specimens, whereas Cu/V 5 nm
multilayers appear rather stable. Annealing of Cu/V multilayers at 400 degrees C leads to
hardening of multilayers, whereas softening occurs in Cu/V multilayers annealed at 600
degrees C. The evolution of mechanical properties during annealing is correlated to the
degradation of the layer interface and the consequent reduction of interface resistance to
the transmission of single dislocation
Study of epitaxial thin films of YBa2Cu3O7-[delta] on silicon with different buffer layers
No full textpublished_or_final_versionabstractPhysicsMasterMaster of Philosoph
Fabrication of Cu2ZnSnS4 Thin Films from Ball-Milled Nanoparticle inks under Various Annealing Temperatures
No full textCu2ZnSnS4 (CZTS) has been recognized as a promising thin-film absorber material of chalcopyrite-related solar cells. A two-stage method for fabricating CZTS films using CZTS nanoparticles was developed. Nanocrystal inks fabricated by a ball-milling method was utilized to °C deposit CZTS precursors by spin-coating approach. The CZTS precursors were annealed in the sulfur atmosphere under different annealing temperatures ranging from 550 °C to 650 °C. Influences of annealing temperature on grain growth, composition, crystallinity, and photovoltaic properties of CZTS films were characterized. With the increase of annealing temperature, grain growth was enhanced, while the sulfur atomic ratio fist increased then decreased. The crystallinity of the films was significantly improved after the annealing, and the obvious peak of the secondary phase of ZnS, were observed from the X-ray diffraction results, when the annealing temperature increased to 625 °C. However, the secondary phase was not detected from the surface Raman spectrum. Through comparing the Raman spectrum of different areas of the CZTS film, secondary phases of ZnS and SnS were observed, indicating the decomposition of CZTS films, due to the high temperature. The highest conversion efficiency of 7.5% was obtained when the annealing temperature was 600 °C
In-Depth Characterization of Secondary Phases in Cu2ZnSnS4 Film and Its Application to Solar Cells
No full textSecondary phases are common in Cu2ZnSnS4 (CZTS) thin films, which can be fatal to the performance of solar cell devices fabricated from this material. They are difficult to detect by X-Ray diffraction (XRD) because of the weak peak in spectra compared with the CZTS layer. Herein, it was found that in-depth elemental distribution by a secondary ion mass spectroscopy method illustrated uniform film composition in the bulk with slight fluctuation between different grains. X-ray photoelectron spectroscopy (XPS) measurement was conducted after sputtering the layer with different depths. An Auger electron spectrum with Auger parameter were used to check the chemical states of elements and examine the distribution of secondary phases in the CZTS films. Secondary phases of CuS, ZnS and SnS were detected at the surface of the CZTS film within a 50-nm thickness while no secondary phases were discovered in the bulk. The solar cell fabricated with the as-grown CZTS films showed a conversion efficiency of 2.1% (Voc: 514.3 mV, Jsc: 10.4 mA/cm2, FF: 39.3%) with an area of 0.2 cm2 under a 100 mW/cm2 illumination. After a 50-nm sputtering on the CZTS film, the conversion efficiency of the solar cell was improved to 6.2% (Voc: 634.0 mV, Jsc: 17.3 mA/cm2, FF: 56.9%)
Fabrication of Cu2ZnSnS4 (CZTS) Nanoparticle Inks for Growth of CZTS Films for Solar Cells
No full textCu2ZnSnS4 (CZTS) is a promising candidate material for photovoltaic applications; hence, ecofriendly methods are required to fabricate CZTS films. In this work, we fabricated CZTS nanocrystal inks by a wet ball milling method, with the use of only nontoxic solvents, followed by filtration. We performed centrifugation to screen the as-milled CZTS and obtain nanocrystals. The distribution of CZTS nanoparticles during centrifugation was examined and nanocrystal inks were obtained after the final centrifugal treatment. The as-fabricated CZTS nanocrystal inks were used to deposit CZTS precursors with precisely controlled CZTS films by a spin-coating method followed by a rapid high pressure sulfur annealing method. Both the grain growth and crystallinity of the CZTS films were promoted and the composition was adjusted from S poor to S-rich by the annealing. XRD and Raman characterization showed no secondary phases in the annealed film, the absence of the detrimental phases. A solar cell efficiency of 6.2% (open circuit voltage: Voc = 633.3 mV, short circuit current: Jsc = 17.6 mA/cm2, and fill factor: FF = 55.8%) with an area of 0.2 cm2 was achieved based on the annealed CZTS film as the absorber layer
Study on the performance of Tungsten-Titanium alloy film as a diffusion barrier for iron in a flexible CIGS solar cell
No full textA Tungsten-Titanium (W-Ti) diffusion barrier was prepared on an iron (Fe) substrate by means of magnetron sputtering with subsequent annealing at different temperatures. Rutherford Backscattering Spectrometry (RBS) was used to analyze the Fe distribution in the W-Ti layer. The diffusion constant D-0 = 3.4 x 10(-16) m(2)/s and the activation energy Q = 43 kJ/mol of the Fe diffusing in the W-Ti layer were subsequently calculated based on Fick's Second Law. The results demonstrated that a 291 nm-thick W-Ti barrier layer can be used to block Fe from diffusing into a CIGS solar cell for 20 years at a work temperature of 308 K (35 degrees C). (C) 2015 Elsevier Ltd. All rights reserved.Key Laboratory for Advanced Materials Processing Technology, Ministry of Education, P. R. China; State Key Laboratory of New Ceramics and Fine Processing, P. R. ChinaSCI(E)[email protected]
Irradiation effects on multilayered W/ZrO2 film under 4 MeV Au ions
No full textIrradiation induced structural changes in multilayered W/ZrO2 nanocomposites with periodic bilayer thicknesses of (7/14 nm) and (70/140 nm) were investigated following Au+ ion irradiation. The samples were irradiated by 4 MeV Au ions with fluences ranging from 6 x 10(14) to 1 x 10(16) ions/cm(2). The immiscible W/ZrO2 interfaces remained unchanged without intermixing of the layers upon the irradiation. No voids were observed in the samples with different periodic layer thicknesses. The XRD and XTEM studies reveal thickness dependent microstructural changes in the samples. W and ZrO2 grains in the thinner (7/14 nm) bilayer sample exhibit significant resistance to grain growth compared to the thicker (70/140 nm) bilayer sample as well as a W monolayer film. The high fraction of flat interfaces as well as grain boundaries in multilayer films plays a role in suppressing ion irradiation-induced grain growth and void formation. (C) 2014 Elsevier B.V. All rights reserved.Materials Science, MultidisciplinaryNuclear Science & TechnologyMining & Mineral ProcessingSCI(E)[email protected]
A general polymer-assisted solution approach to grow transition metal oxide nanostructures directly on nickel foam as anodes for Li-ion batteries
No full textCobalt oxide nanostructures have been successfully grown on nickel foam by a facile polymer-assisted chemical solution method for lithium-ion battery anodes. The carbon left from the decomposition of polymers is an effective binder between the metal oxides and nickel foam. As compared to the metal oxide powder prepared in a conventional way by using polymer binder and carbon black, these one-step direct growth electrodes showed much better Li storage properties with high capacities, stable cyclability, and rate capability: Co3O4 on nickel foam gave a capacity of 900 mAh g(-1), at a current density of 1 A g(-1) and 600 mAh g(-1) at 4 A g(-1). The good performances of these electrodes could be attributed to intimate contact between the active material and nickel foam, the porosity of the current collector, and the network structure of the active materials. This general method could also be applied to other transition metal oxides. (C) 2013 Elsevier B.V. All rights reserved.http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000323628100075&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=8e1609b174ce4e31116a60747a720701ElectrochemistryEnergy & FuelsSCI(E)EI8ARTICLE604-60924
Bismuth oxide: a new lithium-ion battery anode
No full textBismuth oxide directly grown on nickel foam (p-Bi2O3/Ni) was prepared by a facile polymer-assisted solution approach and was used directly as a lithium-ion battery anode for the first time. The Bi2O3 particles were covered with thin carbon layers, forming network-like sheets on the surface of the Ni foam. The binder-free p-Bi2O3/Ni shows superior electrochemical properties with a capacity of 668 mA h g(-1) at a current density of 800 mA g(-1), which is much higher than that of commercial Bi2O3 powder (c-Bi2O3) and Bi2O3 powder prepared by the polymer-assisted solution method (p-Bi2O3). The good performance of p-Bi2O3/Ni can be attributed to higher volumetric utilization efficiency, better connection of active materials to the current collector, and shorter lithium ion diffusion path.http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000324553400016&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=8e1609b174ce4e31116a60747a720701Chemistry, PhysicalEnergy & FuelsMaterials Science, MultidisciplinarySCI(E)EIPubMed13ARTICLE3912123-12127
High electrocatalytic performance inspired by crystalline/amorphous interface in PtPb nanoplate
No full textA novel structure with a crystalline/amorphous interface in a two-dimensional PtPb nanoplate enhances the electrocatalytic activity of the nanocatalyst.</p
