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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 163 records · Page 9
All sourcesNASA NTRSDOE OSTI
DOE OSTI2018

Preparation and Property Research of Perfluoropolyether Oil-Based Ferrofluid

In this study, perfluoropolyether oil-based ferrofluid was prepared to satisfy special demands in applications which are too harsh to conventional ferrofluids. Fe{sub 3}O{sub 4} magnetic nanoparticles were synthesized by co-precipitation and modified by perfluoropolyether carboxylic acid surfactant in the atmosphere without protective gas. Perfluoropolyether oil-based ferrofluid was prepared with modified nanoparticles and perfluoropolyether by high-energy ball milling. Properties of ferrofluid fabricated were verified through a series of experiments. Ferrofluid stability was tested by interval point-density method; the average density change is merely 0.0077 g/ml, and change rate is 0.37% after 500 days. Saturation magnetization is 582.46 Gs, much larger than the other four ferrofluids. The average volatility rate is 7.4985*10{sup − 5} g/h/cm{sup 2} at 80 °C after 260 h. Viscosity increases to 1825.7 mPa⋅ s under − 20 °C and still have mobility at − 40 °C. The ferrofluid can resist air blast for 8 h under 200 °C without oxidation or decomposition. Perfluoropolyether oil-based ferrofluid cannot be damaged by water or organic solvents. In addition, the ferrofluid can survive in pH = 1 acid or pH = 14 alkali at least 279 days without corrosion.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

Synthesis, Spectroscopy, and Magnetic Characterizations of PVP-Assisted Nanoscale Particle

Inverse spinel ferrite of nonmagnetic metal-doped ferro-ferric oxide was synthesized by co-precipitation technique, and its characterizations have been performed by XRD, FTIR, TEM, EDX, VSM, and EPR. XRD figures show the prepared samples in their cubic phase and that their crystallite faces vary from 5.57 to 18.47 nm. FTIR spectra of the as-synthesized samples were performed in the range of 400 and 4000 cm{sup −1} and annealed at 600 {sup ∘}C. The TEM revealed that the syllable construction of the nanoscale particles was agglomerated in their crystalline sample. From VSM study, the sample obtained has a doublet pattern, and ferromagnetic performance was observed from the samples. From EPR spectra, the line shape and the g values obtained for the samples conformed to superparamagnetic resonance due to Mg{sup + 2} ions with a stoichiometric composition. These typical magnetic hypnotic specifications are used for various sensing applications.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

Spin State of Cobalt and Electrical Transport Mechanism in MgCo{sub 2}O{sub 4} System

MgCo{sub 2}O{sub 4} samples were synthesized by inverse co-precipitation method. The formation of a single-phase spinel structure was confirmed by X-ray diffraction measurements and Fourier-transform infrared spectroscopy. The samples crystallized in a face-centered cubic structure with Fd-3m space group as revealed from the Rietveld refinement of X-ray diffraction data. Magnetic measurements carried out in a broad temperature range of 5–300 K showed antiferromagnetic to paramagnetic phase transition (Neel temperature) observed at 101 K. Magnetic susceptibility data fitted using the Curie Weiss law and effective Bohr magnetic moment (μ{sub eff}) for Co atoms was determined. Calculated μ{sub eff} comes out to be 3.05 μ{sub B}. These results were correlated to the spin states of Co{sup 3+} atoms. A small hysteresis in the field-dependent magnetization MH loop taken at 5 K indicates the existence of weak ferromagnetism in this system. The electrical resistivity measurement in the temperature range 77–750 K displayed the semiconducting-like behavior for this system.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

Synthesis and Characterization of NiFe{sub 2}O{sub 4} Nanoparticles for the Enhancement of Direct Sunlight Photocatalytic Degradation of Methyl Orange

The current investigation shows the simple and direct sunlight-mediated photocatalytic degradation of methyl orange dye by quasi globular NiFe{sub 2}O{sub 4} nanocrystals synthesized from the high-temperature chemical co-precipitation method. The experiment was carried out under direct sunlight which shows significant degradation results lead to the practical possibility of heterogeneous photocatalysis towards environmental remediation. The as-synthesized quasi globular NiFe{sub 2}O{sub 4} nanocrystals also were characterized by well-known analytical measurements of their structural, morphological, bonding, surface area, band gap and magnetic properties prior to the photocatalytic experiments. The presence of active free radicals formed during the photocatalytic reaction was confirmed from the EPR signals recorded for the solution containing the photocatalyst and dye solution, and accordingly, the photocatalytic degradation mechanism was discussed.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

Structural and Magnetic Characteristics of Ferroxplana Co{sub 2}Y Nanoferrites Synthesized via Two Chemical Routes

Barium Y-type hexaferrite Ba{sub 2}Co{sub 2}Fe{sub 12}O{sub 22} nanopowders have been purposefully tailored using two different chemical wet methods, namely sol-gel auto-combustion (SGA) and co-precipitation (CP) routes. The impact of the pre-annealing and the annealing temperature of the formed precursors synthesized using two strategies on the structural, microstructure, and magnetic properties was investigated using x-ray diffraction (XRD), scanning electron microscopic (SEM), Fourier transform infrared spectroscopy (FT-IR), and vibrating sample magnetometer (VSM). For instance, well-defined Ba{sub 2}Co{sub 2}Fe{sub 12}O{sub 22} hexagonal plate-like particles was observed using SGA and CP routes for the precursors pre-annealed at 600 {sup ∘}C for 4 h and then annealed at low temperature 1000 {sup ∘}C for 2 h. The magnetic properties measured at room temperature evinced that hexaferrite Co{sub 2}Y particles have ferromagnetic characteristics. Good magnetic properties involving saturation magnetization (M{sub s}) of 23.64 and 24.37 emu/g and the coercivity (H{sub c}) of 417.76 and 280.92 Oe were accomplished for the samples pre-annealed at 600 {sup ∘}C for 4 h and then annealed at 1000 {sup ∘}C for 2 h for SGA and CP methods, respectively.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2019

Preparation and Thermophysical Investigations of CoFe{sub 2}O{sub 4}-based Nanofluid: a Potential Heat Transfer Agent

Cobalt ferrite nanoparticles were synthesized by employing chemical co-precipitation technique. The structure, morphology, elemental composition, and magnetization studies of cobalt ferrite nanoparticles were carried by XRD, FE-SEM, EDS, and VSM techniques, respectively. Rietveld refined XRD pattern exhibited the single-phase cubic spinel structure with Fd-3m space group. FE-SEM images indicated some agglomeration of spherical grains which can be attributed to high surface energy and magnetic interactions. Presence of peaks of respective elements (Co, Fe, and O) in EDS spectrum showed formation of CoFe{sub 2}O{sub 4}. The M–H loop recorded at 300 K revealed superparamagnetic behavior and explained by fine particles size. The blocking temperature of the CoFe{sub 2}O{sub 4}nanoparticles from FC-ZFC curve was found to be 144 K. Cobalt ferrite–ethylene glycol nanofluids of various concentrations 0.0–1.0% in steps of 0.2% were prepared by ultrasonically assisted two-step technique. Thermophysical parameters such as thermal conductivity, specific heat, viscosity, and density were investigated as a function of both volume fraction and temperature. The experimental and theoretical value of each sample was correlated. The thermal conductivity was significantly enhanced with an increase in volume fraction and temperature.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Infrared Spectroscopic Study of Magnetic Behavior of Dysprosium Doped Magnetite Nanoparticles

Dysprosium doped magnetite (Fe{sub 3−x}Dy{sub x}O{sub 4} with x = 0.0–0.1) nanoparticles have been synthesized using the co-precipitation method. Magnetic characterization using vibrating sample magnetometer (VSM) has revealed an enhancement in the saturation magnetization with Dy{sup 3+} doping. The occupancy of the dopant ions in magnetite lattice has been probed using Fourier transform infrared spectroscopy (FTIR). The shifting of ν{sub 2} (Fe–O) band at 452 cm{sup − 1} for undoped samples to 443 cm{sup − 1} for dysprosium-doped samples is indicative of occupancy of dysprosium at the octahedral site. X-ray diffraction (XRD) patterns have been used to calculate the strain and lattice constant. The strain is found to increase with doping level and attained a maximum value for the x = 0.03. This increase in the strain can be attributed to occupancy of large diameter Dy{sup 3+} ions at the octahedral site of spinel structure of the magnetite lattice.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2019

Physical Properties of Mn{sub 2}O{sub 3} Nanoparticles Synthesized by Co-precipitation Method at Different pH Values

Mn{sub 2}O{sub 3} nanoparticles were synthesized at different pH values ranging from 10 to 13 by co-precipitation technique. The characterization of all samples were completed by X-ray diffraction (XRD), transmission electron microscopy (TEM), energy-dispersive X-ray (EDX), thermogravimetric analysis (TGA), Fourier transform infrared (FTIR), ultraviolet-absorption spectroscopy (UV), Raman spectroscopy, and M–H loop measurements. The XRD spectra show that the structure of Mn{sub 2}O{sub 3} is cubic, and the lattice parameter a decreases as pH increases. Crystalline size, determined from TEM and XRD analyses, decreases as pH increases. TGA curves show that a mass loss is significantly affected as pH increases, indicating the decomposition of organic species besides the oxidation of Mn{sub 2}O{sub 3} to Mn{sub 3}O{sub 4}. FTIR spectra indicate that the absorption peaks at 593.73 and 519.09 cm{sup − 11} referred to the stretching vibration of Mn–O and Mn–O–Mn bonds during the synthesis of Mn{sub 2}O{sub 3} nanoparticles. UV-visible spectroscopy is measured in the range 250–800 nm and showed a deviation to the lower wavelength in addition to an increase in the band-gap energy (E{sub g}) values from 1.012 to 1.370 eV is obtained. Raman spectra shows a slight deviation to the left which is conversely proportional to the crystalline size. M–H loops for the prepared samples were measured and the results of retentivity (M{sub s}) and coercivity (H{sub c}) were discussed.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2019

Effect of Synthesis Approaches and Morphological Properties on Dielectric Enhancement and Microwave Absorption of Fe{sub 3}O{sub 4}/PANI Nanocomposites

In the present work, Fe{sub 3}O{sub 4} spherical (Fe{sub 3}O{sub 4}-cop) and raspberry-like (Fe{sub 3}O{sub 4}-hyd) nanoparticles were synthesized via co-precipitation and hydrothermal routes, respectively. Fe{sub 3}O{sub 4}/polyaniline (PANI) nanocomposites were prepared by in situ oxidative polymerization of aniline monomer in the presence of the Fe{sub 3}O{sub 4} materials. Characterization of the nanocomposites by XRD, FT-IR, FESEM, and TEM techniques revealed a core/shell structure for Fe{sub 3}O{sub 4}-hyd/PANI, unlike the PANI blocks with embedded Fe{sub 3}O{sub 4} and γ-Fe{sub 2}O{sub 3} observed in Fe{sub 3}O{sub 4}-cop/PANI composites. The larger and pure magnetite nanoparticles produced with the hydrothermal process and the respective nanocomposite with PANI possess higher magnetization and coercivity values, according to the magnetic investigation with VSM. Moreover, according to the electromagnetic characterization in the X-band, the Fe{sub 3}O{sub 4}-hyd/PANI nanocomposite exhibits the highest complex permittivity level, as a consequence of increased interfacial polarization in the Fe{sub 3}O{sub 4}-hyd/PANI system. On this account, reflection loss measurements have shown the superior microwave absorption capability of Fe{sub 3}O{sub 4}-hyd/PANI composite, compared with Fe{sub 3}O{sub 4}-cop/PANI, with a measured maximum of −31.28 dB at 8.5 GHz for 3.5 mm layer thickness.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2019

Effect of Zn Concentration on the Structure, Morphology, and Magnetic Behavior of Ni{sub 1 − x}Zn{sub x}Fe{sub 2}O{sub 4} Ferrofluid

In this work, we investigated the effect of doping zinc ions onto nickel ferrite upon the structure, morphology, and magnetic properties of Ni{sub 1 − x}Zn{sub x}Fe{sub 2}O{sub 4} ferrite nanoparticles (x = 0, 0.25, and 0.75) prepared via co-precipitation method. X-ray diffraction analysis showed the presence of the most intense peak corresponding to the (311) crystallographic orientation of NiFe{sub 2}O{sub 4} cubic spinel phase, and the crystallite size obtained from Scherrer formula increased from 6.8 to 11.2 nm when the Zn concentration increases from x = 0 to x = 0.75. Fourier transform infrared spectroscopy analysis confirmed the presence of a prominent band associated to the vibrations of metal ions, as a feature of spinel ferrite phase formation, observing that their band positions were very sensitive to Zn doping concentration. Transmission electron microscopy studies allowed to determinate that for all Zn concentrations, the particle sizes are around 15 nm. The magnetic properties were studied by using the vibrating sample magnetometer at room temperature. The results reveal superparamagnetic behavior determined by the shape of the hysteresis loop, presenting decreased coercive magnetic field and increased saturation magnetization, with increased zinc concentration. Additionally, from field cooling and zero field cooling curves, we can observe the typical behavior of the blocking process assembly of superparamagnetic nanoparticles. Alternate current susceptibility measurements show that the blocking temperature is frequency dependent and shifts toward higher temperatures by increasing the frequency, a characteristic of superparamagnetic, and glassy systems. Furthermore, τ{sub 0}, related to the jump attempt frequency of the magnetic moment of the nanoparticle between the opposite directions of the magnetization easy axis, is in the range of 2 × 10{sup −10} and 7 × 10{sup −13} s for the three different Zn concentrations, which agrees with characteristic of non-interacting superparamagnetic systems.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Structural and Electrical Dependence in Zn-Doped Li-Ferrite Nanostructures

Zinc-doped lithium ferrite nanoparticles with general formula Li{sub 0.46}Zn{sub 0.04}Fe{sub 2.5}O{sub 4} were prepared by Co-precipitation method and their thin films were grown by spin coating method. X-ray diffraction (XRD) confirmed the spinel structure of the synthesized samples. Fine morphology of the films was obtained by controlling the parameters. AC electrical properties including dielectric constant (έ), dielectric loss tangent (tanδ), AC electrical conductivity (σ{sub ac}), and impedance (Z) were studied as a function of frequency at different temperatures and at 1 MHz frequency in a temperature range of 40–500 °C. Dielectric constant, dielectric loss tangent, and ac electrical conductivity showed the decreasing trend with increase in temperature while opposite trend was observed for impedance. Zinc-doped Li-ferrite has better absorption properties in the studied frequency and temperature range as compared to that of Li-ferrites.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2019

Structural, Optical, Dielectric, and Magnetic Characteristics of Nd Ions Substituted BaFe{sub 11}(Sn{sub 0.5}Mg{sub 0.5}){sub x}O{sub 19} M-Type Hexaferrite via Co-precipitation

Nanoparticles (NPs) of barium hexaferrite were synthesized by a chemical co-precipitation technique in an aqueous solution with a nominal composition of BaFe{sub 11}(Sn{sub 0.5}Mg{sub 0.5}){sub 1−x}Nd{sub x}O{sub 19} (x = 0, 0.5, 1). XRD and FTIR analyses were performed to study the crystal structure of the magnetic powders (MPs) in order to obtain details on the hexaferrite structure. Grain morphology and elemental composition were assessed by SEM and EDS, respectively, and nano-sized hexagonal platelet-like structures in all MPs were demonstrated. All of the structural parameters such as “a”, “c”, V{sub (cell)} and D{sub x} have been altered with successful incorporation of Nd into hexagonal lattices, thereby the band gap E{sub g} first increased x ≤ 0.5 then decreased up to x = 1 (i.e., drawn via a Tauc plot) from 1.53–1.82 eV. The measurements of dielectric properties depict relaxation behavior at higher frequencies. The dielectric measurements increase with increased hexaferrite. Furthermore, the magnetic properties of all MPs were examined by VSM at room temperature (RT). The saturation magnetization (M{sub s}), remnant magnetization (M{sub r}), and coercivity (H{sub c}) were linearly decreased by the SnMg content, whereas an increasing trend appeared with the additional Nd content. However, the squareness ratio increased with an increase in the content (x). These outcomes make this substitution an excellent candidate for multiple applications such as optical, electrical-based devices, circulators, and recording materials. .

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2019

Investigation of Electrical and Magnetic Properties of La{sup 3+} Substituted M-Type Ba–Ni Nano-Ferrites

In this paper, La{sup 3+} substituted M-type Ba–Ni hexaferrite nanoparticles having composition Ba{sub 0.8}Ni{sub 0.2}Fe{sub 12-x}La{sub x}O{sub 19} (x = 0, 0.2, 0.4, 0.6, and 0.8) were prepared by co-precipitation route. The phase of the grown NPs was confirmed using X-ray diffraction analysis and results reveal the growth of M-type hexaferrite NPs as a major phase. The energy dispersive X-ray spectroscopy (EDX) was employed to determine the elemental composition of prepared samples. The FTIR spectra of synthesized samples confirm the bond formation of M-type hexaferrites. The optical bandgap was determined by UV-Vis spectroscopy and the results exhibit an increase in optical bandgap with decreasing crystallite size. The vibrating sample magnetometry (VSM) technique was used to analyze the effect of dopant on the magnetic properties like coercivity, saturation magnetization, and remanence of the synthesized samples. The electrical resistivity was measured by two probe method and it was observed that the activation energy shows a decreasing trend with increase in La content. The highly resistive nature of prepared nano ferrites indicates the potential to use these ferrites for high-frequency applications.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2025

LABQ3: Bayesian method for quantification of mineral compositions and nano-scale elemental mapping of 3D synchrotron XCT data

Quantitative analysis of mineral compositions is essential in understanding geochemical, mineralogical and environmental processes. Fine-resolution 3D imaging is widely done using synchrotron X-ray computed tomography (XCT), but existing analyses are limited to visualization and segmentation. This paper presents a new method, Linear Attenuation Bayesian Quantitative 3D-mapper (LABQ3), based on the linearity of X-ray attenuation with respect to elemental concentrations. To address the random variability in attenuation measurements, LABQ3 employs Bayesian decision theory to minimize classification error, using reference attenuation distributions from scans of pure mineral standards. To demonstrate LABQ3 and test its performance, we studied precipitated carbonate samples. XCT scans were done at multiple energies using the transmission X-ray microscope (TXM) at beamline 32-ID-C of the Advanced Photon Source at Argonne National Laboratory. The reconstructed 3D images have a voxel size of 20 nm. Analyses revealed rich nano-scale compositional heterogeneity within individual particles. A mixture of calcium and cadmium produced an overall stoichiometric composition of (Ca 0.78 ,Cd 0.22 )CO 3 , with some voxels containing nearly pure CdCO 3 . The addition of zinc led to an overall stoichiometric composition of 33% Ca, 28% Cd, 39% Zn, with a nearly pure CaCO 3 core and compositional zonation through the rim. These compositional gradients are related to temporal sequences of carbonate mineral formation where Cd precipitated at the beginning in (Ca,Cd)CO 3 , while Cd and Zn precipitated at the end in (Ca, Cd,Zn)CO 3 . Results differ from bulk analyses using Inductively Coupled Plasma-Mass Spectrometry (ICP-MS), showing that LABQ3 provides particle-specific insights. LABQ3 distinguishes itself by quantifying chemical compositions along a continuum, making it different from XCT analyses based on segmentation. LABQ3 allows simultaneous acquisition of morphology and chemical composition in 3D, facilitating the interpretation of chemical gradients of trace elements, quantification of solid solution compositions, inferences about temporal sequences of mineral precipitation, and addressing other concerns about solid-phase chemistry.

58 GEOSCIENCES↗
DOE OSTI2018

Photocatalytic inactivation of Vibrio fischeri using Fe2O3-TiO2-based nanoparticles

Highlights: • A marine bacterium (Vibrio fisheri) was examined as biofilm forming microorganism. • The inactivation of bacteria was performed in saline and nutrient growth media. • The performance of five TiO{sub 2} based photocatalysts was investigated. • Effective inactivation of bacteria was achieved by visible light driven photocatalysts. Biofouling is a major problem in water membrane processes, especially in seawater reverse osmosis plants. Inactivation of Vibrio fischeri (a well-known marine bacterium forming biofilm) through photocatalysis via visible light was investigated in this work using active Fe{sub 2}O{sub 3}-TiO{sub 2} nanoparticles. Five Fe{sub 2}O{sub 3}-TiO{sub 2} photocatalysts with different weight percentage of Fe{sub 2}O{sub 3} (0–5 wt%) were synthesized using an ultrasonic-assisted co-precipitation method. The photocatalysts were characterized by powder X-ray diffraction (XRD), BET surface area, transmission electron Æ (TEM) plus selected area electron diffraction (SAED) patterns, scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX) and diffuse-reflectance spectroscopy (DRS). Based on the design of experiments, the synthesized photocatalysts were tested for inactivation of V. fischeri under visible light irradiation at different temperatures (25–35 °C) and different photocatalyst dosage (0.1–2 g/L). The photocatalytic microbial inactivation experiments were performed in artificial seawater appropriate for growth of the marine bacterium. The results revealed that the highest inactivation efficiency of V. fischeri was achieved when 1 g/L of 2.5 wt% Fe{sub 2}O{sub 3}-TiO{sub 2} were used, at 35 °C. Photocatalytic inactivation of microorganisms using visible light-driven Fe{sub 2}O{sub 3}-TiO{sub 2} photocatalysts, could introduce an innovative green method in pretreatment units of reverse osmosis plants to control the membrane biofouling.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2026

Influence of aluminum source and Ni/Al ratio in a batch stirred tank reactor on the structure, morphology, and electrochemical performance of Ni-rich NMA cathodes

Here, the structural, morphological, and electrochemical performance of Ni-rich LiNi 0.9 Mn 0.05 Al 0.05 O 2 (955NMA) and LiNi 0.85 Mn 0.05 Al 0.1 O 2 (85,510) cathodes strongly depends on the properties of their hydroxide precursors. Ni-Mn-Al hydroxide precursors were synthesized through controlled co-precipitation in a batch stirred tank reactor, where pH, reaction time, metal-ion feed rate, aluminum source, and aluminum concentration were systematically varied to tailor particle morphology, phase composition, and dopant distribution. Two aluminum sources, aluminum nitrate and sodium aluminate produced two distinct hydroxide precursors NMA(OH) 2 -1 and NMA(OH) 2 -2, which were lithiated to form LiNMA1 (Li 0.992 [Ni 0.905 Mn 0.049 Al 0.046 ]O 2 ) and LiNMA2 (Li 0.990 [Ni 0.850 Mn 0.047 Al 0.103 ]O 2 ). Structural and compositional analyses revealed that aluminum incorporation and phase formation in Ni–Mn–Al hydroxides are governed by local supersaturation and interfacial growth kinetics. Rapid dilute aluminum addition produced aluminum-free β-phase hydroxides, intermediate conditions generated mixed α/β phases, whereas slow concentrated dosing enabled uniform aluminum incorporation and stabilization of the β-phase structure. LiNMA1 delivers a high initial discharge capacity of 223 mAhg −1 but significant capacity fading with 67% retention after 100 cycles, associated with structural instability. In contrast, LiNMA2 delivers a lower initial capacity 172 mAhg −1 yet excellent cycling stability 91% retention, attributed to improved TM–O framework stability and reduced cation disorder.

Capacity↗
DOE OSTI2018

Room temperature magnetic ordering and analysis by bound magnetic polaron model of Yb3+ doped nanocrystalline zinc oxide (Zn0.98Yb0.02O)

Highlights: • ZnO and Yb doped ZnO are synthesized by co-precipitation method. • Rietvelt anlysis of XRD patterns confirms the complete substitution of Yb{sup 3+} in ZnO. • Vacancy and defect mediated RTFM is introduced in doped ZnO. • BMP model successfully analyze the magnetic property of Zn{sub 0.98}Yb{sub 0.02}O. - Abstract: Nanocrystalline ZnO and Yb-doped ZnO (Zn{sub 0.98}Yb{sub 0.02}O) are prepared by simple co-precipitation method. The pure crystallographic phases of ZnO and Zn{sub 0.98}Yb{sub 0.02}O are confirmed by Rietveld analyses of XRD patterns. Raman and photoluminescence spectra recorded at room temperature (RT) indicates that lattice defects and oxygen vacancy in Zn{sub 0.98}Yb{sub 0.02}O is more than that of ZnO. Magnetic measurements of ZnO and Zn{sub 0.98}Yb{sub 0.02}O are carried out from 300 to 5 K. Ferromagnetic ordering is observed in Zn{sub 0.98}Yb{sub 0.02}O at RT and the strength of the ordering increases with the lowering of temperature. Ferromagnetism of Zn{sub 0.98}Yb{sub 0.02}O is attributed to the oxygen vacancy introduced by annealing in vacuum. Magnetization vs. temperature curve is well fitted by the combination of 3D spin wave and Curie-Weiss law, which suggest simultaneous presence of para- and ferro-magnetic phases in Zn{sub 0.98}Yb{sub 0.02}O. Ferromagnetic ordering is successfully explained by vacancy mediated bound-magnetic polaron model.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

Nanoparticles-constructed spinel ZnFe2O4 anode material with superior lithium storage performance boosted by pseudocapacitance

Highlights: • Nanoparticles-constructed ZnFe{sub 2}O{sub 4} was fabricated by co-precipitation method. • The ZnFe{sub 2}O{sub 4} sample shows excellent high rate capability and cycling stability. • The lithium storage mechanism was analyzed by CV and EIS measurements. • Pseudocapacitive effect has a significant contribution to the total stored charge. - Abstract: The practical application of ZnFe{sub 2}O{sub 4} in lithium ion batteries (LIBs) is severely hampered by its fast capacity fading and poor rate performance. To overcome these issues, herein, ZnFe{sub 2}O{sub 4} powders consist of aggregated nanoparticles (50∼100 nm) with porosity were prepared by a facile co-precipitation method and subsequent thermal decomposition. When used as anode material for LIBs, the ZnFe{sub 2}O{sub 4} sample delivers capacities of 920, 820, 650, 485, and 421 mA h g{sup −1} at current densities of 0.5, 1, 3, 7, and 10 A g{sup −1}, respectively. Moreover, the sample can maintain a capacity of 814 mA h g{sup −1} even after 300 cycles at the current density of 1 A g{sup −1}, implying an excellent rate capability and cycling stability. Cyclic voltammetry analysis reveals that both diffusion-controlled lithium storage and surface pseudocapacitive lithium storage contribute to the total stored charge of ZnFe{sub 2}O{sub 4}, which boosts the high rate capability and superior cycling stability of the ZnFe{sub 2}O{sub 4}.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗