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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 1,063 records · Page 59
All sourcesNASA NTRSDOE OSTI
DOE OSTI2018

An Investigation on the Optical Band Gap and Ac Conductivity of Mn-Zn Nanoferrites

In this paper, the behaviour of the optical band gap and ac conductivity of Mn-Zn nanoferrites with the variation of the Zn concentration is reported. It was observed that in spite of a slight increase in the optical band gap, ac conductivity increases with the increase in Zn concentration. The observed behaviour has been explained in terms of the dominating factor which plays a key role in determining its properties. Optical band gap has a strong dependence on the crystallite size while the ac conductivity depends on the availability of the charge carriers for conduction and applied frequency. With the variation in Zn concentration, the above-mentioned important factors change which affect both the properties. A comparative examination of the optical band gap and ac conductivity of the prepared samples clearly gives support to the hopping of the charge carriers as the conduction mechanism in ferrites.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2017

Facile Synthesis of Magnetically Recyclable Fe{sub 2}O{sub 3}–MFe{sub 2}O{sub 4} Photocatalyst from Saprolite-Limonite Laterite Leach Liquors

Photocatalyst degradation is an effective and environment-friendly method for dye pollution. Magnetically recyclable Fe{sub 2}O{sub 3}–MFe{sub 2}O{sub 4} composites were successfully synthesized from laterite leach liquors by a simple coprecipitation-calcination method. The as-prepared samples were characterized by x-ray diffraction (XRD), physical property measurement system (PPMS), and UV-Vis. The results show that the Fe{sub 2}O{sub 3}–MFe{sub 2}O{sub 4} composites can be easily recycled from the solution due to the magnetic properties. Photodegradation experiments results indicated that the degradation rate of rhodamine B (RhB) solution were found to be about 90.0% for the composites, and the degradation rate were still more than 80.0% after being reused for five times. The heterostructure between the Fe{sub 2}O{sub 3} and MFe{sub 2}O{sub 4} effectively enhanced the separation of electron hole pairs, facilitating the photocatalysis process. This paper provided a facile pathway for comprehensive utilization of laterite leach liquor to synthesize magnetically recyclable Fe{sub 2}O{sub 3}–MFe{sub 2}O{sub 4} with enhanced photocatalyst performance.

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

Critical Behavior and Size Dependence of Magnetic Entropy Changes on La{sub 0.6}Sr{sub 0.4}MnO{sub 3} Manganite

In this work, nano and micro scales of La{sub 0.6}Sr{sub 0.4}MnO{sub 3} ceramics are prepared by sol-gel and solid-state reaction methods. In order to investigate the dependency of the magnetic properties on the size variation of as-prepared samples, their magnetic entropy change (ΔS{sub M}) at different magnetic fields and temperatures are fitted by Lorentz universal function. The obtained results confirmed the size impression on magneto-caloric properties, in spite of proving significant influence on some parameters related to the refrigeration system.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

Effect of the Milling Conditions on the Properties of ZnO Doped with Fe

(Zn{sub 0.9}Fe{sub 0.1})O powders were produced with different ball to powder weight ratios (BPR) by ball milling of ZnO and Fe elemental powders. The BPR used were 15:1, 20:1, 25:1, and 30:1. The prepared samples were studied by x-ray diffraction (XRD), vibrating sample magnetometer (VSM), and Mössbauer spectroscopy (MS). The XRD patterns showed a zinc oxide (ZnO) single phase with wurtzite structure, except for the 15:1 ratio, which exhibits an additionally bcc structure associated to α-Fe. The mean crystallite sizes were found to be around 100 Å. The Mössbauer spectra were fitted using two doublets, associated to the incorporation of Fe ions into the ZnO lattice, which correspond to the Fe{sup 3+} and Fe{sup 2+} oxidation states except for the 15:1 ratio, for which an additional sextet was necessary to obtain a good fit, this sextet was associated to segregated Fe into the sample. The increase of the BPR allowed that all Fe penetrated into the ZnO matrix. The magnetization measurement using VSM reveals that the system exhibits ferromagnetic behavior at room temperature. For sample with BPR 15:1, the ferromagnetism is due to the segregated Fe, and for higher BPRs, from 20:1 up to 30:1, we propose that their ferromagnetism is due to the percolation of polarons. These polarons appear due to the oxygen vacancies (detected by XRD) which are occupied by electrons, which appear in the charge balance. Exchange interaction between the electron spins located in the vacancies or holes and those of the magnetic impurities (Fe atoms) leads to the formation of bound magnetic polarons, which percolate, producing in this way magnetic behavior.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

Comparing the Effects of Nb, Pb, Y, and La Replacement on the Structural, Electrical, and Magnetic Characteristics of Bi-Based Superconductors

In this study, the effects of Pb, Nb, La, and Y replacements were investigated on Bi-based superconducting materials. In preparing the samples, we used a method called solid-state reaction method. The patterns of the X-ray diffraction of all samples indicated presence of Bi-2212 and Bi-2223 phases. The results obtained from XRD revealed that with increase of the melting point of substation elements, the Bi-2223 phase decreased while the Bi-2212 phase and impurity phases of samples grew. From the electrical resistivity measurements using the four-probe method, it was found that sample A with Pb and sample B with La replacements had the maximum and minimum critical temperatures of 111.4 and 81.6 K, respectively. Based on hysteresis loop (M–H) measurement using Bean’s model, estimation of critical current density (J{sub c}) showed that sample A with Pb and sample B with La substitution had the maximum and minimum values respectively. These results may be due to the melting point of these elements with values of 888, 1512, 2315, and 2425 {sup ∘}C for PbO, Nb{sub 2}O{sub 5}, La{sub 2}O{sub 3}, and Y{sub 2}O{sub 3}, respectively. These elements were replaced by Bi{sub 2}O{sub 3} with a melting point of 817 {sup ∘} C. Further, the samples were prepared at the temperature of 845 {sup ∘}C. It seems at this temperature, these elements not only dissolve within the main matrix and participate in the formation of the Bi-2212 phase during the sintering process but they also participate in the development of the variety of the impurity phases as confirmed by XRD results.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2019

Effect of Cysteine Substitutions on the Structural and Magnetic Properties of Fe{sub 3}O{sub 4}–Cysteine/RGO and Fe{sub 3}O{sub 4}/RGO–Cysteine Nanocomposites

We synthesized by electrostatic self-assembly route in basic solution Fe{sub 3}O{sub 4}–cysteine/RGO and Fe{sub 3}O{sub 4}/RGO–cysteine nanocomposites. In this method, electrostatic interaction was created via negatively charged surface of the reduced graphene oxide and reduced graphene oxide–cysteine sheets and positively charged surface of the Fe{sub 3}O{sub 4} and Fe{sub 3}O{sub 4}–Cys nanoparticles in aqueous solution. The structural and magnetic properties of the prepared samples were analyzed by x-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, transmission electron microscopy (TEM), and vibrating sample magnetometer (VSM), respectively. The dependences of magnetization as a function of applied field using a vibrating sample magnetometer exhibit S-like curves, indicating a magnetic hysteresis behavior for all samples. It clearly showed that, the nanocomposites showed a reduction of saturation magnetization to the Fe{sub 3}O{sub 4} nanoparticles.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2019

Microstructure and Magnetic Properties of Ba{sub 0.95}Y{sub 0.05}Fe{sub 12−x}Co{sub x}O{sub 19} Hexaferrites

Magnetoplumbite-type (M-type) barium ferrites doped with different Y–Co doping content Ba{sub 0.95}Y{sub 0.05}Fe{sub 12−x}Co{sub x}O{sub 19} (x = 0, 0.1, 0.2, 0.3, 0.4, and 0.5) were successfully prepared by ceramic process and investigated in this paper for the first time. X-ray diffraction were used to analyze the phase of the prepared sample. The scanning electron microscopy (SEM) was used to measure the morphology, and magnetic properties were measured by vibrating sample magnetometer (VSM). The results of XRD show that the single phase of M-type barium ferrites was obtained with the increase of Co content (x), but α-Fe{sub 2}O{sub 3} occurred when x exceeds 0.3. The SEM results exhibit the uniform plane hexagonal structures of M-type ferrites with all range of Co doping content. VSM results display that magnetization (M{sub s}) and coercivity (H{sub c}) show the same tendency that their values first increase and then decrease with the increase of Co content.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Enhanced Magneto-optical and Antibacterial Studies of Bi{sub 1−x}Mg{sub x}FeO{sub 3} (0.0 ≤ x ≤ 0.15)) Nanoparticles

Mg-doped BiFeO{sub 3} (Bi{sub 1−x}Mg{sub x}FeO{sub 3} (0.00 ≤ x ≤ 0.15)) nanoparticles (NPs) have been successfully prepared by simple solution combustion method using urea as fuel. The obtained product was sintered at 550 °C for 2 h to get pure-phase formation. The as-prepared samples were characterized by powder X-ray diffraction (XRD), Fourier transform infrared (FT-IR), field emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray spectroscopy (EDX), transmission electron microscope (TEM), ultraviolet–visible (UV-Vis) absorption, photoluminescence (PL) spectra, and vibrating sample magnetometer (VSM) analysis. Powder XRD study revealed that all products exhibit rhombohedral structure with pure-phase formation. The average crystallite size of the samples decreased from 56.25 to 46.15 nm with increasing the concentration of Mg (x = 0.00, 0.05, 0.10, and 0.15). Surface morphology of the samples were analyzed by FE-SEM and TEM micrograph techniques, and the grain distribution was not quite homogeneous and observed agglomeration of the particles, which is mainly due to the magnetic interaction among them. EDX analysis confirmed the presence of Bi, Fe, O, and Mg elements without any form of impurity peak in all products. PL spectra shows a high intense peak at 464 nm, which is attributed to blue emission. The saturation magnetization is enhanced with increasing Mg doping level at RT. Antibacterial activity of Bi{sub 1−x}Mg{sub x}FeO{sub 3} NPs was found to be enhanced with increase in Mg doping concentration as it causes a reduction in the grain size of the samples.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2019

Chemical, Morphological, Structural, Optical, and Magnetic Properties of Transition Metal Titanium (Ti)-Doped LaFeO{sub 3} Nanoparticles

In the present work, pure and transition metal titanium (Ti)-doped LaFe{sub 1−x}Ti{sub x}O{sub 3}(x = 0.0, 0.2, 0.4, and 0.6) nanoparticles have been successfully synthesized by hydrothermal synthesis technique for various molar ratios of 0.2, 0.4, and 0.6. The prepared samples were grinned and annealed in furnace at 600 {sup ∘}C/4 h. The X-ray diffraction (XRD) analysis confirms the phase orthorhombic formation of LaFeO{sub 3} and Ti-doped LaFeO{sub 3}. The stoichiometric analysis was performed through energy-dispersive X-ray studies (EDX). The micro-structural features of surface morphology were examined by field emission scanning electron microscopy (FESEM). Further, surface nanocrystalline of the titanium (Ti)-doped LaFe{sub 1−x}Ti{sub x}O{sub 3} was also investigated through high-resolution transmission electron microscopic (TEM) analysis. The enhancement of room temperature magnetization value has been observed from the M–H curve which is measured using vibrating sample magnetometer (VSM).The weak ferromagnetic behavior was observed from hysteresis loop. From hysteresis loop, saturation takes place when the applied magnetic field intensity is 15 kO{sub e}.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2019

Structural, Optical, Magnetic, and Dielectric Properties of Cr{sup 3+} Substituted Cobalt Aluminate Nanoparticles

The present study investigates the influence of Cr{sup 3+} substitution on structural, optical, dielectric, and magnetic properties of cobalt aluminates in the aluminates series CoAl{sub 2-x}Cr{sub x}O{sub 4}, 0.00 ≤ x ≤ 0.20. These series of nanoparticles are effectively synthesized using the co-precipitation method. The cubic spinel aluminate structure is confirmed by X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopic measurements. Transmission electron microscopy (TEM) analysis shows the formation of spherical nanoparticles, which are homogeneous in shape and size. The optical properties of the prepared samples have been investigated by means of optical absorbance spectra. The optical band gap E{sub opt}{sup i} and Urbach energy E{sub u} are estimated. At room temperature, the magnetization of undoped CoAl{sub 2}O{sub 4} reveals a weak ferromagnetic behavior. This ferromagnetism is increased for the sample with x = 0.05, and the samples with higher Cr{sup 3+} content have a tendency to be superparamagnetic on account of the formation of single-domain particles as a consequence of small particle size. Real part of dielectric constant (ε{sup ′}), dielectric loss (tanδ), ac conductivity (σ{sub ac}), real part of impedance (Z{sup ′}), and imaginary part of impedance (Z{sup ″}) are analyzed as a function of frequency and Cr{sup 3+} content. The results show that the dielectric loss (tanδ), dielectric permittivity (ε{sup ′}), and ac conductivity (σ{sub ac}) decrease with the increase in Cr{sup 3+} content, x = 0.05, and then increase with a further increase in Cr{sup 3+} content. The increase in these parameters has been explained on the basis of the hopping mechanism. From the Cole–Cole diagram, the value of the relaxation time τ can be calculated and it has been found to increase with increasing the Cr{sup 3+} content. Actually, a high dielectric constant makes these materials good for energy storage at high frequencies.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2019

Investigation to the Structural, Optical, and Magnetic Properties of Synthesized Ni-Doped Anatase Nanoparticles: Essential Role of Treatment in Hydrogen on Long-Range Ferromagnetic Order

Nanocomposite powders of anatase TiO{sub 2} doped with Ni ions (TiO{sub 2}:Ni) were synthesized by facile thermal co-decomposition of a mixture of metals complexes. The X-ray diffraction (XRD) analyses using the Rietveld method confirm the formation of almost single nanocrystalline anatase structure. Anatase TiO{sub 2} incorporated with Ni ions (TiO{sub 2}:Ni) illustrated the formation of a substitutional solid solutions (SSS). The diffuse reflection spectroscopy (DRS) method used to study the optical properties of the prepared samples revealed a redshift associated with Ni doping and hydrogenation, which is explained by the creation of point defects including O-vacancies. This study showed the essential importance of hydrogenation process in order to create or boost room-temperature ferromagnetism (RT-FM). The magnetic measurements indicated that anatase TiO{sub 2} doped with 4.8 mol% Ni produce a magnetic saturation of 0.84 emu/g, which is a remarkable result compared with that related to the similar studies on doped TiO{sub 2}.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2019

Effects of Mg Substitution on the Structural and Magnetic Properties of Ni{sub 0.2}Mg{sub x}Co{sub 0.8−x}Fe{sub 2}O{sub 4} Nanoparticle Ferrites

Sol-gel auto-combustion is a method of preparing ferrite by combining combustion with chemical gel. In this study, Ni-Mg-Co ferrite powders are prepared by coprecipitation method, and the nanocrystals of Ni{sub 0.2}Mg{sub x}Co{sub 0.8−x}Fe{sub 2}O{sub 4} are successfully synthesized. The structure and magnetic properties of undoped and Mg-substituted Ni-Co ferrite nanoparticles are systematically investigated. The methods used to characterize the prepared samples are X-ray diffraction (XRD) analysis, Fourier transform infrared spectroscopy (FTIR), and Vibrating sample magnetometry (VSM). The synthesized samples are confirmed by XRD analysis to form a single-phase cubic spinel structure with crystals between 48 and 50 nm. With the increase of Mg ion concentration, the lattice constant decreases. The results of FTIR spectroscopy indicated that a spinel structure was formed. Transmission electron microscopy (TEM) images show spherical cubic microcrystals in the samples. EDX analysis confirms that the synthesized ferrite is pure phase structure, and Mg{sup 2+} is successfully replaced. With the increase of Mg{sup 2+} ion content, the saturation magnetization and remanent magnetization decreased from 70.16 to 39.77 emu/g and 36.40 to 20.20 emu/g at room temperature, respectively. Meanwhile, the coercivity decreases from 1032.16 to 378.50 Oe by increasing Mg{sup 2+} concentration. This also indicates that the Mg-substituted Ni-Co nano-ferrite has a low magnetic of multi-ferric material. The increasing of peak height of dM/dH at H{sub m} indicates that the cubic spinel structure sample has good crystallinity and magnetic stability.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2019

Critical Properties of Perovskite Manganese Oxides Pr{sub 1−x}Ba{sub x}MnO{sub 3}

The critical properties of polycrystalline Pr{sub 1−x}Ba{sub x}MnO{sub 3} (x = 0.13 and 0.23) samples prepared by using a standard ceramic fabrication method were investigated. Pr{sub 1−x}Ba{sub x}MnO{sub 3} exhibited a second-order magnetic transition. As per the modified Arrott plot method and double logarithmic M-μ{sub 0}H curve, the critical exponents (CE) were calculated as β = 0.459 ± 0.03, γ = 1.346 ± 0.02, δ = 4.32 ± 0.04, and T{sub C} ≈ 130 K, for x = 0.13, and β = 0.424 ± 0.03, γ = 1.362 ± 0.02, δ = 4.19. ± 0.03, and T{sub C} ≈ 163 K, for x = 0.23. To confirm the reliability of such CE values, the M (H) data of Pr{sub 1−x}Ba{sub x}MnO{sub 3} were checked by the scaling equation M(H, t) = |t|{sup β}f{sub ±}(H/|t|{sup β + γ}), where t=(T/(T{sub C}))−1 refers to the reduced temperature, f{sub ±} is the scaling function above (+)/below (−) T{sub C}. The β values for Pr{sub 1−x}Ba{sub x}MnO{sub 3} (x = 0.13 and 0.23) are between β = 0.365 (3D Heisenberg exponent) and β = 0.5 (mean-field exponent), whereas γ values are fairly close to γ = 1.386. This reveals long- and short-range order coexisting in Pr{sub 1−x}Ba{sub x}MnO{sub 3}.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2016

Rapid method for the determination of 226Ra in hydraulic fracturing wastewater samples

A new method that rapidly preconcentrates and measures 226 Ra from hydraulic fracturing wastewater samples was developed in the Savannah River Environmental Laboratory. The method improves the quality of 226 Ra measurements using gamma spectrometry by providing up to 100x preconcentration of 226 Ra from this difficult sample matrix, which contains very high levels of calcium, barium, strontium, magnesium and sodium. The high chemical yield, typically 80-90%, facilitates a low detection limit, important for lower level samples, and indicates method ruggedness. Ba-133 tracer is used to determine chemical yield and correct for geometry-related counting issues. The 226 Ra sample preparation takes < 2 hours.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2018

Physical characterization of uranium oxide pellets and powder applied in the Nuclear Forensics International Technical Working Group Collaborative Materials Exercise 4

Physical characterization is one of the most broad and important categories of techniques to apply in a nuclear forensic examination. Physical characterization techniques vary from simple weighing and dimensional measurements to complex sample preparation and scanning electron microscopy-electron backscatter diffraction analysis. This paper reports on the physical characterization conducted by several international laboratories participating in the fourth Collaborative Materials Exercise, organized by the Nuclear Forensics International Technical Working Group. Methods include a range of physical measurements, microscopy-based observations, and profilometry. In conclusion, the value of these results for addressing key investigative questions concerning two uranium dioxide pellets and a uranium dioxide powder is discussed.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2022

Total Mercury Analysis of Radioactive Waste Containing Multiple Mercury Species

In this work, a direct mercury analyzer (DMA) was used to analyze total mercury in radioactive waste samples containing methylmercury and other forms of mercury including Hg o (elemental) together with inorganic ionic mercury species and complexes. These samples were also analyzed using Cold Vapor Atomic Absorption Spectroscopy (CVAAS) and/or Inductively Coupled Plasma Mass Spectroscopy (ICMS). Comparative statistical evaluation of the results from spike solutions/simulants, liquid radioactive waste samples, and interlaboratory performance test samples demonstrated that the various methods generated accurate and/or equivalent total mercury data and equivalent precision (2σ ± < 20%). Triplicate total mercury analysis of an exemplar radioactive waste resulted in an average value of 54.1 mg/L (as Hg) using CVAAS, 55.1 mg/L using ICPMS and 56.0 mg/L using DMA. A primary advantage of the DMA in a radioactive environment is avoiding multi-step, labor-intensive, time-consuming and waste-producing sample preparation protocols needed for CVAAS and ICPMS. DMA was determined to be the preferred method for measuring total mercury in the Savannah River National Laboratory (SRNL) radioanalytical laboratory based on analytical performance combined with ease of use in a radiological containment unit.

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEA↗
DOE OSTI2025

Sample screening of uranium ore concentrates using portable spectrophotometers: investigating the correlation between visible colors and chemical signatures

A research collaboration between the Japan Atomic Energy Agency and the Department of Energy’s National Nuclear Security Administration examined nuclear forensic signatures and analytical methods for tracing the origins of uranium ore concentrates (UOCs). Here, this study focuses on utilizing portable spectrophotometers capable of reflectance measurements in the visible light spectrum as a potential rapid screening tool for nuclear forensics analysis. Unlike laboratory-based near-infrared spectroscopy or digital image analysis, this research investigated the potential to correlate visible color measurements with key nuclear forensics signatures using seven types of UOC samples with known origins and three UOC certified reference materials. Results demonstrated that distinct color groups, quantified using CIELAB values, correlated with major uranium compounds. Furthermore, the findings indicated that trace elements can influence the UOC colors, providing additional insights into material characteristics. Although this approach requires further validation across a broader range of UOC species, this study demonstrated that simple colorimetric analysis using visible spectrophotometry, which does not require complex sample preparation or data processing, can serve as a practical and novel rapid tool for preliminary screening and attribution in nuclear forensics investigations.

and nuclear chemistry↗