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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 667 records · Page 37
All sourcesNASA NTRSDOE OSTI
DOE OSTI2019

Prospect of Thermal Shock Induced Healing of Lithium Dendrite

Dendritic growth plagues the development of rechargeable lithium metal anodes. Recently, it has been reported that self-heating of the cell provides a mitigation strategy for suppressing dendrites. In order to study this phenomenon, we extend our recently developed nonlinear phase-field model to incorporate an energy balance equation allowing a full thermally coupled electrodeposition model using the open-source software package MOOSE. In this study, we consider the interplay between ionic transport and electrochemical reaction rate as a function of temperature and explore the possibility of using thermal shock induced dendrite suppression. We discover that, depending on the electrochemical reaction barrier and ionic diffusion barrier, self-heating could accelerate (larger reaction barrier) or decelerate (larger diffusion barrier) dendrite formation. Given that the electrolyte constituents can be used to tune both barriers, this study could provide an important avenue to exploit the self-heating effect favorably through electrolyte engineering.

25 ENERGY STORAGE↗
DOE OSTI2025

Using Electrochemistry to Benchmark, Understand, and Develop Noble Metal Nanoparticle Syntheses

The complex chemical nature of metal nanoparticle synthesis presents obstacles for the mechanistic understanding of nanoparticle growth and predictive synthesis design, despite significant progress in this area. Real-time characterization of the chemical processes that take place throughout nanoparticle growth will enable progress toward addressing outstanding challenges in metal nanoparticle synthesis, such as mitigating synthetic reproducibility issues, defining chemical mechanisms that direct nanoparticle growth, and designing synthetic conditions for previously unachievable combinations of nanoparticle shape and composition. In this Perspective, we present open-circuit potential (OCP) measurements as an in situ, real-time method for characterizing chemical changes during nanoparticle growth and discuss the method’s strengths in comparison to and in combination with other characterization techniques. We propose the use of OCP measurements as benchmarks for troubleshooting irreproducibility and streamlining synthetic optimization. Finally, we explore possibilities for using the increased parameter space accessible by electrodeposition to accelerate the development of shape-selective nanoparticle syntheses.

benchmarking↗
DOE OSTI2025

Tuning the Selectivity of Carboxylic Acid–Based Eutectic Solvents for the Dissolution and Electrochemical Separation of Metal Oxides

Extracting metals from natural resources and recovering from waste materials with less-hazardous solvents is essential for sustainable technological advancements. The commonly employed method utilizes harsh chemicals for metal dissolution and the ensuing separation. Here, in this study, we examined the potential of eutectic solvents (types III and IV) as alternative media for the selective dissolution of metals and metal oxides and their subsequent electrochemical separation. Notably, type III eutectics composed of betaine:acetic acid and triazole:lactic acid exhibited excellent solubility for cobalt oxide (24.1 g·L –1 ) and copper oxide (30.5 g·L –1 ), respectively. In comparison, the type IV eutectic mixture of Ca(NO 3 ) 2 ·4H 2 O:acetic acid demonstrated the highest conductivity and lowest viscosity with solubility for both copper oxide (6.1 g·L –1 ) and metallic copper (5.4 g·L –1 from a used electronic circuit). Using a Ca(NO 3 ) 2 ·4H 2 O:acetic acid mixture, copper was selectively dissolved from a waste printed circuit board and subsequently electrodeposited onto a nickel electrode. These findings highlight the tunability of DESs for the selective recovery of metals from electronic waste, offering a promising approach for sustainable metal recycling and resource recovery.

electrodeposition↗
DOE OSTI2015

Composite WO 3 /TiO 2 nanostructures for high electrochromic activity

A composite material consisting of TiO 2 nanotubes (NT) with WO 3 electrodeposited on its surface has been fabricated, detached from its Ti substrate, and attached to a fluorine-doped tin oxide (FTO) film on glass for application to electrochromic (EC) reactions. Several adhesion layers were tested, finding that a paste of TiO 2 made from commercially available TiO 2 nanoparticles creates an interface for the TiO 2 NT film to attach to the FTO glass, which is conductive and does not cause solution-phase ions in an electrolyte to bind irreversibly with the material. The effect of NT length and WO 3 concentration on the EC performance were studied. As a result, the composite WO 3 /TiO 2 nanostructures showed higher ion storage capacity, better stability, enhanced EC contrast, and longer memory time compared with the pure WO 3 and TiO 2 materials

36 MATERIALS SCIENCE↗
DOE OSTI2013

Characterization and modeling of a ZnO nanowire ultraviolet photodetector with graphene transparent contact

We report the demonstration of a ZnO nanowire ultraviolet photodetector with a top transparent electrode made of a few-layered graphene sheet. The nanowires have been synthesized using a low-cost electrodeposition method. The detector is shown to be visible-blind and to present a responsivity larger than 10{sup 4} A/W in the near ultraviolet range thanks to a high photoconductive gain in ZnO nanowires. The device exhibits a peak responsivity at 370 nm wavelength and shows a sub bandgap response down to 415 nm explained by an Urbach tail with a characteristic energy of 83 meV. The temporal response of the detector and the power dependence are discussed. A model of the photoconductive mechanism is proposed showing that the main process responsible for the photoconductive gain is the modulation of the conducting surface due to the variation of the surface depletion layer and not the reduction of recombination efficiency stemming from the electron-hole spatial separation. The gain is predicted to decrease at high incident power due to the flattening of the lateral band bending in agreement with experimental data.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2014

Silver nanoplates with ground or metastable structures obtained from template-free two-phase aqueous/organic synthesis

Silver has unique electrical, catalytic, and plasmonic characteristics and has been widely sought for fabrication of nanostructures. The properties of silver nanostructures are intimately coupled to the structure of silver crystals. Two crystal structures are known for silver: the stable (ground) state cubic face centered 3C-Ag structure and the metastable hexagonal 4H-Ag structure. Recently, Chackraborty et al. [J. Phys.: Condens. Matter 23, 325401 (2011)] discovered a low density, highly reactive metastable hexagonal 2H-Ag structure accessible during electrodeposition of silver nanowires in porous anodic alumina templates. This 2H-Ag structure has enhanced electrical and catalytic characteristics. In the present work we report template-free synthesis of silver nanoplates with the metastable 2H-Ag crystal structure, which appears together with the ground 3C-Ag and the metastable 4H-Ag structures in a two-phase solution synthesis with citric acid as the capping agent. The capacity of citric acid to stabilize both the stable and the metastable structures is explained by its preferential binding to the close packed facets of Ag crystals, which are the (111) planes for 3C-Ag and the (0001) planes for 4H-Ag and 2H-Ag. Nanoplate morphology and structure are characterized using scanning electron microscopy, X-ray diffraction, and transmission electron microscopy. The synthesized nanoplates have thickness from 15 to 17 nm and edge length from 1 to 10 μm. Transmission electron microscopy selected area electron diffraction is used to uniquely identify and distinguish between nanoplates with 2H-Ag or 4H-Ag or 3C-Ag structures.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2014

Electrochemically deposited BiTe-based nanowires for thermoelectric applications

Nanostructured materials systems such as thin-films and nanowires (NWs) are promising for thermoelectric power generation and refrigeration compared to traditional counterparts in bulk, due to their enhanced thermoelectric figures-of-merit. BiTe and its derivative compounds, in particular, are well-known for their near-room temperature thermoelectric performance. In this work, both the binary and ternary BiTe-based nanowires namely, BiTe and BiSbTe, were synthesized using template-assisted electrodeposition. Diameters of the nanowires were controlled by the pore sizes of the anodised alumina (AAO) templates used. Systematic study on the compositional change as a function of applied potential was carried out via Linear Sweep Voltanmetry (LSV). Chemical compositions of the nanowires were studied using Energy Dispersive X-ray Spectrometry (EDXS) and their microstructures evaluated using diffraction and imaging techniques. Results from chemical analysis on the nanowires indicated that while the Sb content in BiSbTe nanowires increased with more negative deposition potentials, the formation of Te{sup 0} and Bi{sub 2}Te{sub 3} were favorable at more positive potentials.

36 MATERIALS SCIENCE↗
DOE OSTI2014

Fabrication of single crystalline, uniaxial single domain Co nanowire arrays with high coercivity

Whilst Co nanorods with high coercivity were synthesized during recent years, they did not achieve the same results as for Co nanowires embedded in solid templates. In the present work, Co nanowire arrays (NWAs) with high coercivity were successfully fabricated in porous aluminum oxide template under optimum conditions by using pulsed ac electrodeposition technique. Magnetic properties and crystalline characteristics of the nanowires were investigated by hysteresis loop measurements, first-order reversal curve (FORC) analysis, X-ray diffraction (XRD), and selected area electron diffraction (SAED) patterns. Hysteresis loop measurements showed high coercivity of about 4.8 kOe at room temperature together with optimum squareness of 1, resulting in an increase of the previous maximum coercivity for Co NWAs up to 45%. XRD and SAED patterns revealed a single crystalline texture along the [0002] direction, indicating the large magnetocrystalline anisotropy. On the other hand, FORC analysis confirmed a single domain structure for the Co NWAs. In addition, the reversal mechanism of the single crystalline, single domain Co NWAs was studied which resulted in the fixed easy axis with a coherent rotation. Accordingly, these nanowires might offer promising applications in high density bit patterned media and low power logic devices.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2014

Templated fabrication and characterization of SiO{sub 2} nanotube covered Fe nanowires

In this study, Fe nanowires coated with SiO{sub 2} nanotubes have been synthesized by electrodeposition method using anodic alumina oxide template. Before growing Fe nanowires, 6–8 nm thick SiO{sub 2} nanotubes are grown inside the template using a “surface sol-gel” technique. The nanotube structures were characterized by field emission scanning electron microscopy and energy dispersive x-ray spectroscopy. Magnetic properties of the SiO{sub 2} insulated Fe nanowires inside the membrane are characterized by superconducting quantum interference device. Coercivities of around 120 Oe with field parallel to the nanowire axis and 240 Oe with field perpendicular the nanowire axis are observed at room temperature. These values are comparable to Fe nanowires without insulating layer in membrane. The magnetic hysteresis loop suggests that the SiO{sub 2} insulated nanowires have uniaxial magnetic anisotropy with the easy axis magnetization direction along the nanowire arrays due to their large shape anisotropy.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2014

Structural and magnetic characterization of as-prepared and annealed FeCoCu nanowire arrays in ordered anodic aluminum oxide templates

Herein, we report on the preparation, structure, and magnetic characterization of FeCoCu nanowire arrays grown by DC electrodeposition inside self-assembled ordered nanopores of anodic aluminum oxide templates. A systematic study of their structure has been performed both in as-prepared samples and after annealing in the temperature range up to 800 °C, although particular attention has been paid to annealing at 700 °C after which maximum magnetic hardening is achieved. The obtained nanowires have a diameter of 40 nm and their Fe{sub 0.28}Co{sub 0.67}Cu{sub 0.05} composition was confirmed by energy dispersive X-ray spectroscopy (EDS). Focused ion-beam lamellas of two samples (as-prepared and annealed at 700 °C) were prepared for their imaging in the high-resolution transmission electron microscopy (HRTEM) perpendicularly to the electron beam, where the obtained EDS compositional mappings show a homogeneous distribution of the elements. X-ray diffraction analysis, and selected area electron diffraction (SAED) patterns confirm that nanowires exhibit a bcc cubic structure (space group Im-3m). In addition, bright-dark field images show that the nanowires have a polycrystalline structure that remains essentially the same after annealing, but some modifications were observed: (i) an overall increase and sharpening of recrystallized grains, and (ii) an apparent shrinkage of the nanowires diameter. Obtained SAED patterns also show strong textured components with determined <111> and <112> crystalline directions parallel to the wires growth direction. The presence of both directions was also confirmed in the HRTEM images doing Fourier transform analyses. Magnetic measurements show strong magnetic anisotropy with magnetization easy axis parallel to the nanowires in as-prepared and annealed samples. The magnetic properties are tuned by suitable thermal treatments so that, maximum enhanced coercivity (∼2.7 kOe) and normalized remanence (∼0.91 Ms) values are achieved after annealing at temperature of 700 °C. The contribution of the changes in the crystalline structure, induced by the heat treatment, to the magnetic hardening of the FeCoCu nanowires is discussed.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2014

Nano-/micro metallic wire synthesis on Si substrate and their characterization

Nano-/micro wires of copper are grown on semiconducting Si substrate using the template method. It involves the irradiation of 8 um thick polymeric layer coated on Si with150 MeV Ni ion beam at a fluence of 2E8. Later, by using the simple technique of electrodeposition, copper nano-/micro wires were grown via template synthesis. Synthesized wires were morphologically characterized using SEM and electrical characterization was carried out by finding I-V plot.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2014

Off-axis electron holography of ferromagnetic multilayer nanowires

We have used electron holography to investigate the local magnetic behavior of isolated ferromagnetic nanowires (NWs) in their remanent states. The NWs consisted of periodic magnetic layers of soft, high-saturation magnetization CoFeB alloys, and non-magnetic layers of Cu. All NWs were fabricated by pulsed-potential electrodeposition in nanoporous alumina membranes. The NW composition and layer thicknesses were measured using scanning transmission electron microscopy and energy dispersive spectroscopy. The magnetization of individual NWs depended upon the thicknesses of the layers and the direction of an external magnetic field, which had been applied in situ. When the CoFeB was thicker than the diameter (50 nm), magnetization was axial for all external field directions, while thinner layers could be randomized via a perpendicular field. In some cases, magnetization inside the wire was detected at an angle with respect to the axis of the wires. In thinner Cu/CoFeB (<10 nm each) multilayer, magnetic field vortices were detected, associated with opposing magnetization in neighbouring layers. The measured crystallinity, compositions, and layer thicknesses of individual NWs were found to be significantly different from those predicted from calibration growths based on uniform composition NWs. In particular, a significant fraction of Cu (up to 50 at. %) was present in the CoFeB layers such that the measured magnetic induction was lower than expected. These results will be used to better understand previously measured effective anisotropy fields of similar NW arrays.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2014

Oxygen-vacancy-induced room-temperature magnetization in lamellar V{sub 2}O{sub 5} thin films

In this work, we study the local atomic and electronic structures as well as oxygen-vacancy-induced magnetic properties of electrodeposited V{sub 2}O{sub 5} films. Unlike stoichiometric V{sub 2}O{sub 5}, which is a diamagnetic lamellar semiconductor, our oxygen-defective V{sub 2}O{sub 5} films are ferromagnetic at room-temperature and their saturation magnetization decreases with air exposure time. X-ray absorption spectroscopy was used to monitor the aging effect on these films, revealing that freshly-made samples exhibit only local crystalline order, whereas the aged ones undoubtedly show an enhancement of crystallinity and coordination symmetry. The mean number of oxygen atoms around V tends to increase, indicating a decrease of oxygen vacancies with time. Concurrently with the decrease of oxygen vacancies, a loss of saturation magnetization is also observed. Hence, it can be concluded that the ferromagnetism of the V{sub 2}O{sub 5} films originates from a vacancy-induced mechanism, confirming the universality of this class of ferromagnetism.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2014

Circular single domains in hemispherical Permalloy nanoclusters

We have studied ferromagnetic Permalloy clusters obtained by electrodeposition on n-type silicon. Magnetization measurements reveal hysteresis loops almost independent on temperature and very similar in shape to those obtained in nanodisks with diameter bigger than 150 nm. The spin configuration for the ground state, obtained by micromagnetic simulation, shows topological vortices with random chirality and polarization. This behavior in the small diameter clusters (∼80 nm) is attributed to the Dzyaloshinskii-Moriya interaction that arises in its hemispherical geometries. This magnetization behavior can be utilized to explain the magnetoresistance measured with magnetic field in plane and out of sample plane.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2015

Development of vertically aligned ZnO-nanowires scintillators for high spatial resolution x-ray imaging

Newly designed scintillator of (0001)-oriented ZnO vertical nanowires (vnws) for X-ray imaging was prepared on a Ga-doped ZnO/soda-lime glass by electrodeposition, and the light emission feature was estimated in a synchrotron radiation facility. The ZnO-vnws scintillator revealed a strong light emission and improved resolution on CMOS image compared with that for the ZnO-layer scintillator, although the light emission performance was deteriorated in comparison to the Lu{sub 3}Al{sub 5}O{sub 12:}Ce{sup 3+}. The light emission property closely related to the nanostructure and the resultant photoluminescence characteristic.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2015

Heterojunction metal-oxide-metal Au-Fe{sub 3}O{sub 4}-Au single nanowire device for spintronics

In this report, we present the synthesis of heterojunction magnetite nanowires in alumina template and describe magnetic and electrical properties from a single nanowire device for spintronics applications. Heterojunction Au-Fe-Au nanowire arrays were electrodeposited in porous aluminum oxide templates, and an extensive and controlled heat treatment process converted Fe segment to nanocrystalline cubic magnetite phase with well-defined Au-Fe{sub 3}O{sub 4} interfaces as confirmed by the transmission electron microscopy. Magnetic measurements revealed Verwey transition shoulder around 120 K and a room temperature coercive field of 90 Oe. Current–voltage (I-V) characteristics of a single Au-Fe{sub 3}O{sub 4}-Au nanowire have exhibited Ohmic behavior. Anomalous positive magnetoresistance of about 0.5% is observed on a single nanowire, which is attributed to the high spin polarization in nanowire device with pure Fe{sub 3}O{sub 4} phase and nanocontact barrier. This work demonstrates the ability to preserve the pristine Fe{sub 3}O{sub 4} and well defined electrode contact metal (Au)–magnetite interface, which helps in attaining high spin polarized current.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2015

Influence of controlled surface oxidation on the magnetic anisotropy of Co ultrathin films

We studied the influence of controlled surface-limited oxidation of electrodeposited epitaxial Co(0001)/Au(111) films on their magnetic anisotropy energy using real time in situ magneto optical Kerr effect and density functional theory (DFT) calculations. We investigated the Co first electrochemical oxidation step which we demonstrate to be completely reversible and determined the structure of this oxide layer. We show that the interface magnetic anisotropy of the Co film increases by 0.36 erg/cm{sup 2} upon Co surface oxidation. We performed DFT calculations to determine the different surface structures in a wide potential range as well as the charge transfer at the Co surface. Our results suggest that the magnetic anisotropy change is correlated with a positive charge increase of 0.54 e{sup −} for the Co surface atom upon oxidation.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2015

Development and characterisation of Ni-Si{sub 3}N{sub 4} nanocomposites

Nickel–Si{sub 3}N{sub 4} composites were generated by means of pulse-reverse (PR) electrodeposition technique. The corrosion rate was calculated for the composites by electrochemical methods such as polarisation and impedance methods. Composites were characterised by scanning electron microscope (SEM) and X-ray diffractometer (XRD) to evaluate their microstructures. Coatings obtained by PR method shows more corrosion resistance than DC generated coatings.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗