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Results for “ZINC OXIDE”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

Robust passivation of CdSeTe based solar cells using reactively sputtered magnesium zinc oxide

Magnesium zinc oxide (MZO, Mg x Zn 1-x O) is a leading emitter for CdTe-based solar cells due to its transparency and the ability to tune its conduction band offset with the absorber. Devices employing alloyed cadmium selenide telluride (CST, CdSe y Te 1-y ) absorbers achieved high efficiency (>19%) using MZO deposited by reactive sputtering over a broad composition range (3.68–3.92 eV, x: 0.20–0.35). Minimal differences in implied and measured open circuit voltage indicate that the contacts are well passivated and highly selective across the spectrum of MZO employed. Device performance insensitivity to MZO composition, which is not observed in CdTe devices, is attributed to the formation of an oxygenated interface layer. Se volatility creates a group VI deficiency at the interface that drives O migration from the MZO into the absorber. This introduces conductivity in the emitter not present in its as-deposited state, contributing to the exceptional performance observed. It is shown that the quality of device passivation depends on the oxidation state of the as-deposited MZO such that intelligent control and management of the reactive sputtering process is required.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Effects of humic acid on the interactions between zinc oxide nanoparticles and bacterial biofilms

The effects of humic acid (HA) on interactions between ZnO nanoparticles (ZnO NPs) and Pseudomonas putida KT2440 biofilms at different maturity stages were investigated. Three stages of biofilm development were identified according to bacterial adenosine triphosphate (ATP) activity associated with biofilm development process. In the initial biofilm stage 1, the ATP content of bacteria was reduced by more than 90% when biofilms were exposed to ZnO NPs. However, in the mature biofilm stages 2 and 3, the ATP content was only slightly decreased. Biofilms at stage 3 exhibited less susceptibility to ZnO NPs than biofilms at stage 2. These results suggest that more mature biofilms have a significantly higher tolerance to ZnO NPs compared to young biofilms. In addition, biofilms with intact extracellular poly-meric substances (EPS) showed higher tolerance to ZnO NPs than those without EPS, indicating that EPS play a key role in alleviating the toxic effects of ZnO NPs. In both pure ZnO NPs and ZnO-HA mixtures, dissolved Zn 2+ originating from the NPs significantly contributed to the overall toxicity. The presence of HA dramatically decreased the toxicity of ZnO NPs due to the binding of Zn 2+ on HA. The combined results from this work suggest that the biofilm maturity stages and environmental constituents (such as humic acid) are important factors to consider when evaluating potential risks of NPs to ecological systems.

Ouyang, Kai↗
DOE OSTI2018

Effective photocatalytic removal of different dye stuffs using green synthesized zinc oxide nanogranules

Highlights: • Zinc oxide nanoparticles (ZnO-NPs) synthesized by a green strategy using lemon juice and ethylene glycol. • Physicochemical studies confess the formation of hexagonal wurtzite ZnO nanaogranules with some honed faces. • Direct band gap energy obtained for ZnO nano granules was 3.15 eV. • ZnO nano granules act as good catalyst for the photo degradation of methylene blue, congo red, and rhodamine B under UV-light irradiation. - Abstract: Zinc oxide nanoparticles (ZnO-NPs) obtained by a green synthetic strategy using lemon juice and ethylene glycol. The material was characterized using the techniques UV–vis spectroscopy, FTIR spectroscopy, X-ray diffraction analysis, FESEM, EDAX and HRTEM. Diffraction patterns and TEM micrographs confess the formation of hexagonal wurtzite ZnO nanaogranules with some honed faces and having an average size of 49.16 nm. The developed ZnO-NPs was tested for the photocatalytic degradation of Methylene Blue, Congo Red and Rhodamine B target dyes under UV irradiation and found to have remarkable activity.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2022

Entrapped Molecule‐Like Europium‐Oxide Clusters in Zinc Oxide with Nearly Unaffected Host Structure

Abstract Nanocrystalline ZnO sponges doped with 5 mol% EuO 1.5 are obtained by heating metal–salt complex based precursor pastes at 200–900 °C for 3 min. X‐ray diffraction, transmission electron microscopy, and extended X‐ray absorption fine structure (EXAFS) show that phase separation into ZnO:Eu and c ‐Eu 2 O 3 takes place upon heating at 700 °C or higher. The unit cell of the clean oxide made at 600 °C shows only ≈0.4% volume increase versus undoped ZnO, and EXAFS shows a ZnO local structure that is little affected by the Eu‐doping and an average Eu 3+ ion coordination number of ≈5.2. Comparisons of 23 density functional theory‐generated structures having differently sized Eu‐oxide clusters embedded in ZnO identify three structures with four or eight Eu atoms as the most energetically favorable. These clusters exhibit the smallest volume increase compared to undoped ZnO and Eu coordination numbers of 5.2–5.5, all in excellent agreement with experimental data. ZnO defect states are crucial for efficient Eu 3+ excitation, while c ‐Eu 2 O 3 phase separation results in loss of the characteristic Eu 3+ photoluminescence. The formation of molecule‐like Eu‐oxide clusters, entrapped in ZnO, proposed here, may help in understanding the nature of the unexpected high doping levels of lanthanide ions in ZnO that occur virtually without significant change in ZnO unit cell dimensions.

36 MATERIALS SCIENCE↗
DOE OSTI2019

A Kinetic Model for Dissolution of Zinc Oxide Powder Obtained from Waste Alkaline Batteries in Sodium Hydroxide Solutions

The determination of individual dissolution behaviors of zinc and manganese in waste alkaline battery powders is an important subject from the points of the leaching yield, design of leaching reactor, and separation and recovery steps of hydrometallurgical process. In the current study, we investigated the dissolution kinetics of zinc oxide powder. Zinc oxide was obtained from waste alkaline batteries, and sodium hydroxide solutions were used as solvent. In the experiments, the effects of solution concentration, reaction temperature, stirring speed, solid-to-liquid ratio, and particle size on the dissolution of zinc oxide were investigated. It was demonstrated that the dissolution increased with the increasing concentration, reaction temperature, and stirring speed, and with the decreasing solid-to-liquid ratio and particle size. In consequence of the kinetic analysis performed, it was found that the dissolution kinetics of zinc powder obeyed the Avrami model. Activation energy for the process was determined to be 19.42 kJ/mol. Zinc ions in the resulting solution after dissolution process was recovered in the form of hydroxy-carbonate product by precipitation method. Zinc oxide was produced by isothermal decomposition of hydroxy-carbonate product.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Effect of Deposition Temperature on the Tribology of MOCVD Zinc Oxide Thin Films Tested under Dry Contact

Zinc oxide has justifiably been attracting attention in several fields, and the relatively new field of tribology is not left out. Aside from its already extensively researched and documented applications in materials science, semiconductor and electronics industry, zinc oxide nanoparticles and thin films appear to be gaining fast grounds as tribological materials, thereby justifying a zealous approach in further exploring their inherent properties in this area. In this work, zinc oxide thin films were deposited by MOCVD (metal-organic chemical vapour deposition) on soda lime glass andAISI304L stainless steel plates at temperatures of 300°C, 330°C, 360°C, 390°C and 420°C respectively, using anhydrous zinc acetate as the precursor. The carrier gas was air with a flow rate of 2.5 dm 3 min -1 at atmospheric pressure, and deposition time of 2 hours each. The thickness and tribological properties of the thin films produced were thereafter investigated. The thickness was measured by RBS (Rutherford backscattering spectroscopy) using a 1.7 MeV Tandem Accelerator, and the friction and wear properties were tested with a HFRR (high frequency reciprocating rig) under dry contact conditions, Olympus BH-2 Optical Microscope, and ADE Phase Shift MicroXam Optical Surface Profiler. The thickness was found to decrease with increasing deposition temperature, although for the 300°C deposition temperature there appeared to be a bloated thickness, which is attributable to such factors as incomplete precursor decomposition, turbulence in precursor flow, and energy straggling during RBS measurement. The friction tests highlighted coefficients of friction which were relatively low at the onset of the tests, but thereafter rapidly increased, owing possibly to temperature rise, attendant rapid oxidation and aided abrasion by worn debris. The average coefficient of friction of each test was computed, and the outcome (0.33 – 0.43) for all of them was a material still good enough for use in reducing friction at nanolevel, even with worn out matter and increased working temperature, with no noticeable trend regarding their varied deposition temperatures. Microscope and profilometer profiles vividly showed wear scars with material removal and material transfer. The average wear scar diameters as well as the wear volumes were compiled for both the test balls and the thin films. The result showed a largely correlated trend in the wear scar diameters and the wear volumes, and the thin film deposited at 330°C was the coating with the least wear scars, material removal cum transfer on the test ball and sample. This result is attributed to the enhanced thickness of the sample over the others, apart from sample X1 earlier reported to have a problem in its thickness. As a result, this temperature is therefore recommended as the optimum deposition temperature for the best tribologically applicable zinc oxide thin films, using zinc acetate precursor by MOCVD.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Structural, optical and photocatalytic properties of zinc oxides obtained from spent alkaline batteries

Highlights: • Zinc oxides were synthetized using spent alkaline batteries as raw materials. • Both prepared samples present the wurzite structure and exhibits good optical properties. • The decrease in lattice parameters and the narrow band gap are associated with the formation of oxygen vacancies. • Recovered zinc oxides were active for photodegradation of methylene blue by UV irradiation. • The photocatalytic was correlates to the bulk/surface defects ratio. - Abstract: The structural, optical and photocatalytic properties of two zinc oxides prepared from spent alkaline batteries were analysed. After leaching the anode of alkaline batteries, zinc was precipitated from the leachate liquor by introducing oxalic acid (O-ZnO) or sodium carbonate (C-ZnO). The structure of ZnO samples were analysed by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), S{sub BET}, DRS-UV-vis spectroscopy and positron annihilation lifetime spectroscopy (PALS). Both oxides present the ZnO wurzite structure and similar morphology. C-ZnO presents a cell lower lattice parameters and bang gap energy (2.99 eV) than O-ZnO (3.05 eV), possibly due to higher concentration of oxygen vacancies. The photocatalytic activity in the degradation of methylene blue (MB) of O-ZnO (achieving 70% MB degradation at 90 min) was superior to C-ZnO, due to its higher surface area and degree of crystallinity and lower bulk/surface defects ratio.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Morphological and spectroscopic studies on the vertically aligned zinc oxide nanorods grown on low and high temperature deposited seed layer

Vertically aligned zinc oxide nanorods were grown on low and high temperature deposited aluminium doped zinc oxide seed layer by hydrothermal method and annealed to improve crystallinity. The morphology of the seed layer and the grown nanorods were studied by field emission scanning electron microscopy characterization technique. The properties of the zinc oxide nanorods were analyzed using laser spectroscopic studies. Resonant Raman spectroscopy reveals the unique increase in the A{sub 1}(LO) mode of vibration with increase in count. The luminescence property of the nanorods was studied with photoluminescence spectrometer. The vertically aligned zinc oxide nanorods show, the very high band edge emission in the ultraviolet region of the electromagnetic spectrum.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Zinc oxide based sorbent and process for preparing same

Zinc oxide-based sorbents, and processes for preparing and using them are provided, wherein the sorbents are preferably used to remove one or more reduced sulfur species from gas streams. The sorbents contain an active zinc component, optionally in combination with one or more promoter components and/or one or more substantially inert components. The active zinc component is a two-phase material, consisting essentially of a zinc oxide (ZnO) phase and a zinc aluminate (ZnAl 2 O 4 ) phase. Each of the two phases is characterized by a relatively small crystallite size of typically less than about 50 nm (500 Angstroms). Preferably the sorbents are prepared by using an alkali metal base to convert a precursor mixture, containing a precipitated zinc oxide precursor and a precipitated aluminum oxide precursor, to the two-phase, active zinc oxide containing component, with the resulting sorbent having a sodium level within a desired range.

Shen, Jian-Ping↗
DOE OSTI2025

Fabrication of nanoporous doped metal oxide coatings via selective infiltration of a block copolymer template: The case of Al-doped zinc oxide

Conductive nanoporous conformal coatings are important for various applications including touchscreens, displays, and electrochromic windows, though design of such coating with controlled porosity and composition remains challenging. We propose a sequential infiltration synthesis (SIS) method for the fabrication of nanoporous conductive aluminum-doped zinc oxide (AZO) films by infiltrating block copolymer (BCP) templates, specifically polystyrene-block-polyvinyl pyridine (PS-b-P4VP), with diethyl zinc and trimethyl aluminum precursors. Tunability of both porosity and electrical conductivity is achieved by precisely controlling the swelling behavior of the polymer templates and adjusting the number of SIS cycles. Further, our results reveal that porosity levels can reach up to 80 %, with resistivity as low as ~7.83 Ωcm. Using conductive atomic force microscopy (C-AFM) and Hall effect measurements, we show that lower concentrations of aluminum doping relative to zinc (around 1: 17) results in higher conductivity of the AZO films. Additionally, AZO is based on zinc oxide (ZnO) which is cost-efficient, abundant and less toxic than commonly used transparent conductive oxides such as indium tin oxide (ITO) and fluorine-doped tin oxide (FTO). Therefore, this novel approach opens new possibilities for creating highly porous, conformal, conductive AZO coatings with customizable porosity and composition, making them ideal candidates for diverse optoelectronic applications.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Analysis of the Structural Evolution of Zinc Oxide Powders Obtained by Mechanical High-Energy Grinding

Zinc oxide powders made by mechanical high-energy grinding have been investigated using the methods of scanning electron microscopy, thermal nitrogen desorption, and Raman spectroscopy of infrared Fourier spectroscopy. Their structural evolution, including reduction of the average size of crystallites, increase in specific surface area, as well as changes in the number and ratio of adsorption centers, has been demonstrated. The data on the reconstruction of the surface of zinc oxide powders and multiple bond breaking in near-surface areas resulting from long-term dispersion have been presented.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

Backward-Diode Heterostructure Based on a Zinc-Oxide Nanoarray Formed by Pulsed Electrodeposition and a Cooper-Iodide Film Grown by the SILAR Method

A heterostructure promising for designing a backward diode is formed from a zinc-oxide nanorod array and a nanostructured copper-iodide film. The effect of modes of successive ionic layer adsorption and reaction (SILAR) deposition and the subsequent iodization of CuI films on smooth glass, mica, and fluorine-doped tin oxide (FTO) substrates and on the surface of electrodeposited nanostructured zinc-oxide arrays on the film structure and electrical and optical properties is investigated. A connection between the observed variations in the structure and properties of this material and intrinsic and iodination-induced point defects is established. It is found that the cause and condition for creating a backward-diode heterostructure based on a zinc-oxide nanoarray formed by pulsed electrodeposition and a copper-iodide film grown by the SILAR method is the formation of a p{sup +}-CuI degenerate semiconductor by the excessive iodination of layers of this nanostructured material through its developed surface. The n-ZnO/p{sup +}-CuI barrier heterostructure, which is fabricated for the first time, has the I–V characteristic of a backward diode, the curvature factor of which (γ = 12 V{sup –1}) confirms its high Q factor.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Formation of Zinc-Oxide Nanorods by the Precipitation Method

Zinc oxide (ZnO) rod-shaped nanoparticles are produced by the precipitation method upon the hydrolysis of zinc-nitrate hexahydrate (Zn(NO{sub 3}){sub 2} · 6H{sub 2}O) in the presence of hexamethylenetetramine (C{sub 6}H{sub 12}N{sub 4}). The effect of various parameters on the ZnO-nanorod size and shape is shown. The ZnO nanopowders produced are studied by scanning electron microscopy and X-ray diffraction analysis. The adhesive and mechanical properties of samples containing ZnO nanoparticles and microparticles as additions are studied.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Study of the photodegradation of brilliant green on mechanically activated powders of zinc oxide

A study of the photocatalytic activity of commercial and mechanically activated zinc oxide powders has been carried out based on the example of the decomposition of Brilliant Green. The goal of this work was to study the effect of the grinding time (0, 1, 3, 5, and 7 min) on the structure of zinc oxide and its photocatalytic activity under visible and ultraviolet (UV) radiation. It has been found that, when UV radiation is used, the constant of the dye oxidation rate for samples activated for 1 min increases compared with unactivated powders, whereas further mechanical activation leads to a decrease in the photocatalytic activity. When using visible radiation, samples activated for 1 min showed the minimum photocatalytic activity and further mechanical activation led to an increase in the efficiency of photocatalysis.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗