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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 307 records · Page 17
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Magneto-structural and induction heating properties of MFe2O4 (M?=?Co, Mn, Zn) MNPs for magnetic particle hyperthermia application

The thermal decomposition approach was used for the synthesis of MFe2O4 magnetic nanoparticles (MNPs) by substituting M as Co, Mn, and Zn. The obtained MNPs were characterized for magneto-structural properties using X-Ray diffraction patterns, FTIR, Raman and Mossbauer spectroscopy techniques which confirm the formation of phase pure cubic spinel ferrite with space group Fd3m and five Raman active modes. The size, morphology, and compositional analysis was performed using HRTEM and EDX where the size of MNPs was found to be less than 10 nm that attains superparamagnetism. The magnetic hyperthermia performance of obtained MNPs was evaluated by induction heating experiments at magnetic field range 13.3 to 26.7 kAm-1. The specific absorption rate (SAR) and intrinsic loss power (ILP) values were determined at different magnetic fields within the human tolerable range and correlated with magneto-structural properties to evaluate its potential for possible magnetic particle hyperthermia therapy.

Magnetic nanoparticles, complex-decomposition, mag↗
DOE OSTI2015

Synthesis, characterization and thermodynamic study of carbon dioxide adsorption on akaganéite

A mixture of akaganeite nanoparticles and sodium salts was synthesized and modi fied, first by washing, and then by Li exchange. The structural characterization of the produced materials was performed with: powder X-ray diffraction, scanning electron microscopy, energy dispersive X-ray analysis, thermogravimetric analysis, diffuse reflectance infrared Fourier transform spectrometry, Mossbauer spectros- € copy and magnetization measurements. Additionally low pressure nitrogen and high pressure carbon dioxide adsorption experiments were performed. The sum of the characterization information made possible to conclude that the produced akaganeite phases crystallized in a structure exhibiting the symmetry of the I2/m space group, where the measured equivalent spherical diameter of the akaganeite crystallites yielded 9 nm, as well, the tested phases exhibited a standard behaviour under heating and displayed a superparamagnetic behaviour. Finally the high pressure carbon dioxide adsorption experiments demonstrated a pressure-responsive framework opening event due to a structural transformation of the adsorbent framework induced by the guest molecules. This fact opens new applications for akaganeite as a high pressure adsorbent.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2014

Modified release from lipid bilayer coated mesoporous silica nanoparticles using PEO–PPO–PEO triblock copolymers [Modified release from lipid bilayer coated mesoporous silica nanoparticles using PEO PPO PEO triblock copolymers]

Triblock copolymers comprised of poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (PEO-PPO-PEO, or trade name Pluronic) interact with lipid bilayers to increase their permeability. Here we demonstrate a novel application of Pluronic L61 and L64 as modification agents in tailoring the release rate of a molecular indicator species from 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) bilayer-coated superparamagnetic Fe 3 O 4 /mesoporous silica coreshell nanoparticles. Lastly, we show there is a direct relationship between Pluronic concentration and the indicator molecule release, suggesting Pluronic may be useful for the controlled release of drugs from lipid bilayer-coated carriers.

36 MATERIALS SCIENCE↗
DOE OSTI2014

Characterization of Magnetic NiFe Nanoparticles with Controlled Bimetallic Composition

The exploration of the magnetic properties of bimetallic alloy nanoparticles for various technological applications requires the ability to control the morphology, composition, and surface properties. In this report, we describe new findings of an investigation of the morphology and composition of NiFe alloy nanoparticles synthesized under controlled conditions. The controllability over the bimetallic composition has been demonstrated by the observation of an approximate linear relationship between the composition in the nanoparticles and in the synthetic feeding. The morphology of the NiFe nanoparticles is consistent with an fcc-type alloy, with the lattice strain increasing linearly with the iron content in the nanoparticles. The alloy nanoparticles exhibit remarkable resistance to air oxidation in comparison with Ni or Fe particles. The thermal stability and the magnetic properties of the as-synthesized alloy nanoparticles are shown to depend on the composition. The alloy nanoparticles have also be sown to display low saturation magnetization and coercivity values in comparison with the Ni nanoparticles, in line with the superparamagnetic characteristic. These findings have important implications for the design of stable and controllable magnetic nanoparticles for various technological applications.

Environmental Molecular Sciences Laboratory↗
DOE OSTI2015

Magnetic study of M-type Ru–Ti doped strontium hexaferrite nanocrystalline particles

We carried out a systematic study on the effect of the substitution of Ti2+ and Ru4+ ions for Fe3+ ions on the structural and magnetic properties of the strontium ferrite SrFe12-2xRuxTixO19 nanoparticles with (0 <= x <= 0: 3), using x-ray diffraction, Quantum Design PPMS-9 magnetometry, and electrical resistivity. A clear irreversibility between the zero-field-cooled and field-cooled curves was observed below room temperature and the zero-field-cooled magnetization curves displayed a broad peak at a temperature TM. These results were discussed within the framework of random particle assembly model and associated with the magnetic domain wall motion. The resistivity data showed some kind of a transition from insulator to perfect insulator around TM. The high-temperature magnetization measurements exhibited sharp peaks just below T-c indicating a superparamagnetic behavior. With Ru-Ti substitution, the saturation magnetization at 5 K showed small variations were it slightly increased with increasing x up to 0.2, and then decrease for x = 0.3, while the coercivity decreased monotonically, recording a reduction of about 78% at x = 0.3. These results were discussed in light of the cationic distributions based on the results of the structural refinements.

Alsmadi, A. M.↗
DOE OSTI2013

CoxC nanorod magnets: Highly magnetocrystalline anisotropy with lower Curie temperature for potential applications

Magnetic CoxC nanorods with larger magnetocrystalline anisotropy of 5 x 10(5) J/m(3) as well as larger coercivity and lower Curie temperature are introduced. The particles have an average diameter of 8 nm and shows three different magnetic behaviors. The sample shows ferromagnetism up to 400 K, superparamagnetism at temperature > 400 K and <T-C (465 K) and paramagnetism above 465 K. Such different behaviors open the door for various applications such as permanent magnets, magnetic sensors and contract agent for magnetic resonance imaging. (c) 2013 Elsevier B.V. All rights reserved.

El-Gendy, AA↗
DOE OSTI2016

Synthesis and characterization of Gd-doped magnetite nanoparticles

There has been rising interest in the synthesis of magnetite nanoparticles due to their importance in biomedical and technological applications. Tunable magnetic properties of magnetite nanoparticles to meet specific requirements will greatly expand the spectrum of applications. Tremendous efforts have been devoted to studying and controlling the size, shape and magnetic properties of magnetite nanoparticles. We investigate gadolinium (Gd) doping to influence the growth process as well as magnetic properties of magnetite nanocrystals via a simple co-precipitation method under mild conditions in aqueous media. Gd doping was found to affect the growth process leading to synthesis of controllable particle sizes under the conditions tested (0–10 at% Gd 3+ ). Typically, undoped and 5 at% Gd-doped magnetite nanoparticles were found to have crystal sizes of about 18 and 44 nm, respectively, supported by X-ray diffraction and transmission electron microscopy. These results showed that Gd-doped nanoparticles retained the magnetite crystal structure, with Gd 3+ randomly incorporated in the crystal lattice, probably in the octahedral sites. The composition of 5 at% Gd-doped magnetite was Fe (3-x) Gd x O 4 (x=0.085±0.002), as determined by inductively coupled plasma mass spectrometry. 5 at% Gd-doped nanoparticles exhibited ferrimagnetic properties with small coercivity (~65 Oe) and slightly decreased magnetization at 260 K in contrast to the undoped, superparamagnetic magnetite nanoparticles. Templation by the bacterial biomineralization protein Mms6 did not appear to affect the growth of the Gd-doped magnetite particles synthesized by this method.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Relationship between nanostructure-magnetic property induced by temperature for iron oxide nanoparticles in vacuum, Ar and O 2 environments

It is known that superparamagnetic magnetite (Fe 3 O 4 ) nanoparticles (NPs) become ferromagnetic under Si 2+ ion irradiation due to particle size growth and microstructure evolution; it has been proposed that this feature could be used for in situ high temperature (up to 500 °C) radiation monitoring in the core of nuclear reactors. Herein, magnetite NPs synthesized by a nanocluster deposition system are heated to 800 °C in three different environments (argon, oxygen and vacuum), and nanostructure-magnetic property correlations are investigated by vibrating sample magnetometry, scanning electron microscopy, and X-ray diffraction. Magnetization of the NPs is increased due to the sintering and overall size growth by the agglomeration of the particles, while the morphology remains nearly unchanged up to 800 °C, with the one anomaly that zerovalent Fe appeared due to the reduction of the Fe 3 O 4 at 800 °C in vacuum. In argon and oxygen at high-temperature, antiferromagnetic hematite is created, which causes a reduction of the magnetization, and abrupt growth of particle size above 500 °C.

36 MATERIALS SCIENCE↗
DOE OSTI2013

Synthesis and characterization of magnetite nanoparticles coated with lauric acid

Understanding the process of synthesis of magnetic nanoparticles is important for its implementation in in vitro and in vivo studies. In this work we report the synthesis of magnetic nanoparticles made from ferrous oxide through coprecipitation chemical process. The nanostructured material was coated with lauric acid and dispersed in aqueous medium containing surfactant that yielded a stable colloidal suspension. The characterization of magnetic nanoparticles with distinct physico-chemical configurations is fundamental for biomedical applications. Therefore magnetic nanoparticles were characterized in terms of their morphology by means of TEM and DLS, which showed a polydispersed set of spherical nanoparticles (average diameter of ca. 9 nm) as a result of the protocol. The structural properties were characterized by using X-ray diffraction (XRD). XRD pattern showed the presence of peaks corresponding to the spinel phase of magnetite (Fe{sub 3}O{sub 4}). The relaxivities r{sub 2} and r{sub 2}* values were determined from the transverse relaxation times T{sub 2} and T{sub 2}* at 3 T. Magnetic characterization was performed using SQUID and FMR, which evidenced the superparamagnetic properties of the nanoparticles. Thermal characterization using DSC showed exothermic events associated with the oxidation of magnetite to maghemite. - Highlights: • Synthesis of magnetic nanoparticles coated with lauric acid • Characterization of magnetic nanoparticles • Morphological, structural, magnetic, calorimetric and relaxometric characterization.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Bioinspired aligned magnetic features in aerogels for humidity sensing

Many natural plant tissues, such as pinecones, utilize structures to transduce changes in humidity into movement or strain. These often employ layered structures with aligned features in order to create differential stress across the material as different portions swell at different rates. Here, by replicating these types of structures in synthetic materials we can create structures that respond to humidity in a similar manner. Taking these aligned features as inspiration, silica aerogels with tailored humidity reactive properties were created. This behavior was achieved by creating aligned features in these aerogels using a Helmholtz coil to produce a uniform magnetic field that aligned ferrofluid droplets into chains and needle like features. These magnetite-based structures were shown to retain their superparamagnetic properties, allowing them to easily be removed from the aerogels, leaving a large number of aligned channels. Aerogels with the removed needles experienced significantly different strains than both unmodified aerogels and aerogels with the aligned features still in place. Aerogels with these tunable aligned features could be used in humidity sensors that can transduce changes in humidity into strain and could be used in applications such as volatile organic compound capture.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2013

Investigations on the temperature dependent electrical and magnetic properties of NiTiO{sub 3} by molten salt synthesis

Highlights: ► NiTiO{sub 3} particles were synthesized by simple molten salt technique. ► The single phase compound formation was confirmed through XRD analysis. ► The detailed impedance properties of NiTiO{sub 3} were studied at elevated temperature. ► The conductance spectra were fitted using Jonscher Power Law. ► Low temperature magnetization behaviour was explained by core shell model. - Abstract: Submicron-sized NiTiO{sub 3} particles were successfully synthesized by simple molten salt method. The phase purity and crystal structure was confirmed through X-ray diffraction. The characteristics bands of Ni-O and Ti-O were identified using Fourier Transform Infra-red spectrum. The SEM and TEM images shows that the particles are lying in the range of 150–300 nm and selected area electron diffraction pattern (SAED) infers the single crystalline nature of NiTiO{sub 3}. The impedance spectra elucidate the grain interior conducting mechanism and semi-conducting nature of NiTiO{sub 3} at elevated temperatures. The frequency dependent conductance spectra were found to obey Jonscher's power law and a maximum value of conductivity observed was 2 × 10{sup −5} S cm{sup −1} at 520 °C. The magnetic susceptibility measurement infers the antiferromagnetic behavior with the Neel temperature (T{sub N}) of 14.9 K. The increase in coercivity below T{sub N} reveals the coexistence of antiferromagnetic with superparamagnetic behavior. B–H curve represents the first order phase transition from antiferromagnetic to ferromagnetic transition.

36 MATERIALS SCIENCE↗
DOE OSTI2013

Simple polyol route to synthesize heptanoic acid coated magnetite (Fe{sub 3}O{sub 4}) nanoparticles

Highlights: ► Heptanoic acid@Fe{sub 3}O{sub 4} nanocomposite has been prepared via simple polyol. ► Heptanoic acid used as both surfactant and solvents. ► Magneto polymer composite with adjustable Ea has a potential usage as functional composites. - Abstract: Magnetite (Fe{sub 3}O{sub 4}) nanoparticles were prepared via polyol method by using FeCl{sub 2} as only source of iron. As-prepared samples were characterized by powder X-ray diffractometer (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), thermal gravimetric analyzer (TGA) and vibrating sample magnetometer (VSM). Crystalline phase was identified as Fe{sub 3}O{sub 4} and the crystallite sizes were calculated as 19.1 ± 1.1 and 22 ± 1.3 nm for uncalcinated and calcinated products from X-ray line profile fitting. The capping of heptanoic acid around Fe{sub 3}O{sub 4} nanoparticles was confirmed by FT-IR spectroscopy, the interaction being via bridging oxygen's of the carboxylate and the nanoparticle surface and also by TG analysis. VSM measurements showed that both samples exhibited typical superparamagnetic behavior at room temperature with different Ms values. The ε′ decreases with increasing frequency for both composites and permeability has almost same values for all temperatures at higher frequencies. As synthesized and calcinated samples conductivity increase linearly with the temperature.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Enhanced effect of geldanamycin nanocomposite against breast cancer cells growing in vitro and as xenograft with vanquished normal cell toxicity

Despite enormous advances in remedies developed for breast cancer, an effective therapeutic strategy by targeting malignant cells with the least normal tissue toxicity is yet to be developed. Hsp90 is considered to be an important therapeutic target to inhibit cell proliferation. Geldanamycin (GDM), a potent inhibitor of Hsp90 was withdrawn from clinical trials due to its undesirable hepatotoxicity. We report a superparamagnetic iron oxide (SPION) based polymeric nanocomposite of GDM augmenting anticancer competence with decreased hepatic toxicity. The particle size of nanocomposite was ascertained to be 76 ± 10 nm with acceptable stability. A comparative dose dependent in vitro validation of cytotoxicity showed an enhanced cellular damage and necrosis in breast cancer (MCF-7) cell line at a low dose of 5.49 nM (in GDM nanocomposite) in contrast to 20 nM of pure GDM, while normal breast epithelial cells (MCF-10A) were least affected. Besides, in vivo study (in breast cancer xenografts) substantiated 2.7 fold delay in tumor progression mediated by redundancy in the downstream functions of p-Akt and MAPK-Erk leading to apoptosis with negligible hepatotoxicity. Pure GDM disrupted the function and morphology of liver with lesser therapeutic efficacy than the GDM nanocomposite. These findings deduce that GDM based polymeric magnetite nanocomposite play a vital role in efficacious therapy while vanquishing normal cells and hepatic toxicity and thereby promising it to be reinstated in clinics. - Highlights: • GDM nanocomposite shows selective cell kill of cancerous breast cells. • Nanocomposite delays the growth of tumor in comparison to pure GDM treatment. • GDM promotes apoptosis by down-regulation of p-Akt and MAPK-Erk. • GDM nanocomposite nullifies the hepatotoxicity generally exhibited by pure GDM.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2015

Selective Metal Exsolution in BaFe 2-y My(PO 4 ) 2 (M = Co 2+ , Ni 2+ ) Solid Solutions

The 2D-Ising ferromagnetic phase BaFe 2+ 2 (PO 4 ) 2 shows exsolution of up to one-third of its iron content (giving BaFe 3+ 1.33 (PO 4 ) 2 ) under mild oxidation conditions, leading to nanosized Fe 2 O 3 exsolved clusters. Here we have prepared BaFe 2–y My(PO 4 ) 2 (M = Co 2+ , Ni 2+ ; y = 0, 0.5, 1, 1.5) solid solutions to investigate the feasibility and selectivity of metal exsolution in these mixed metallic systems. For all the compounds, after 600 °C thermal treatment in air, a complete oxidation of Fe 2+ to Fe 3+ leaves stable M 2+ ions, as verified by 57 Fe Mössbauer spectroscopy, TGA, TEM, microprobe, and XANES. Furthermore, the size of the nanometric α-Fe 2 O 3 clusters coating the main phase strongly depends on the y M metal concentration. For M-rich phases the iron diffusion is hampered so that a significant fraction of superparamagnetic α-Fe2O3 particles (100% for BaFe 0.5–x Co 1.5 (PO 4 ) 2 ) was detected even at 78 K. Although Ni 2+ and Co 2+ ions tend to block Fe diffusion, the crystal structure of BaFe 0.67 Co 1 (PO 4 ) 2 demonstrates a fully ordered rearrangement of Fe 3+ and Co 2+ ions after Fe exsolution. We found that the magnetic behaviors of the Fe-depleted materials are mostly dominated by antiferromagnetic exchange, while Co 2+ -rich compounds show metamagnetic transitions reminiscent of the BaCo 2 (PO 4 ) 2 soft helicoidal magnet.

Alcover, Ignacio Blazquez↗
DOE OSTI2015

Dynamic Structural Changes of SiO₂ Supported Pt-Ni Bimetallic Catalysts over Redox Treatments Revealed by NMR and EPR

SiO 2 supported Pt-Ni bimetallic catalysts with different nickel loadings were prepared and their structural changes after redox treatments were studied by XRD, NMR, and EPR. It is found that the paramagnetic Ni species are mainly located on the surface of silica lattice. The relaxation of detected 29 Si nuclei in our samples is mainly governed by a spin-diffusion mechanism. The paramagnetic effects are reflected in the spin-lattice relaxation of Q 4 species, with the oxidized samples presenting faster relaxation rates than the corresponding reduced ones. Meanwhile the Q 3 species, which are in close contact with the paramagnetic nickel ions, are “spectrally invisible”. In reducing atmosphere Ni gradually diffuses into Pt NPs to form PtNi alloys. While under oxidization treatment, the alloyed Ni atoms migrate outward from the core of Pt NPs and are oxidized. The main EPR spectrum results from reduced nickel species, and the reduced samples show stronger EPR signal than the corresponding oxidized ones. However, in the reduced samples, the superparamagnetic or ferromagnetic metallic Ni particles were inside the PtNi NPs, making their influence on the 29 Si relaxation in the SiO 2 support weaker than the oxidized samples.

Environmental Molecular Sciences Laboratory↗
DOE OSTI2018

Temperature-dependent Structural and Spectroscopic Studies of (Bi 1– x Fe x )FeO 3

We report on temperature-dependent structural and spectroscopic features of (Bi 1–x Fe x )FeO 3 perovskite for x = 0.15 and 0.25. Samples were synthesized by heating quantum crystalline precursors obtained by the polyol method. Crystal structures of each composition were obtained from in-house X-ray, synchrotron X-ray, and time-of-flight neutron powder diffraction data Rietveld refinements. Partial replacement of the Bi site by the Fe 3+ cation significantly changes the crystal physicochemical properties, such as thermal expansion, polyhedral distortion, Debye temperature, and vibrational and magnetic properties. Whereas BiFeO 3 is multiferroic, both Bi 0.85 Fe 0.15 FeO 3 and Bi 0.75 Fe 0.25 FeO 3 are found to be superparamagnetic, as observed by temperature-dependent Mössbauer and SQUID measurements. Lattice thermal expansion was modeled using the Debye–Einstein-anharmonicity approach. Debye temperatures obtained from the mean-squared atomic displacement parameter and lattice thermal expansion are compared. Furthermore, temperature dependence of selective Raman modes is also analyzed.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2016

Dynamic Assembly of Magnetic Colloidal Vortices

Magnetic colloids in external time-dependent fields are subject to complex induced many-body interactions governing their self-assembly into a variety of equilibrium and out-of-equilibrium structures such as chains, networks, suspended membranes, and colloidal foams. Here, we report experiments, simulations, and theory probing the dynamic assembly of superparamagnetic colloids in precessing external magnetic fields. Within a range of field frequencies, we observe dynamic large-scale structures such as ordered phases composed of precessing chains, ribbons, and rotating fluidic vortices. We show that the structure formation is inherently coupled to the buildup of torque, which originates from internal relaxation of induced dipoles and from transient correlations among the particles as a result of short-lived chain formation. We discuss in detail the physical properties of the vortex phase and demonstrate its potential in particle-coating applications.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Magnetic Field-Driven Convection for Directed Surface Patterning of Colloids

Drying sessile droplets is a promising route to transform colloidal dispersions into surface coatings, which are widely used in material design and biochemical detection. However, directing the assembly of the particles within drying droplets and achieving surface patterns beyond the well-known coffee-ring formation remain a challenge. Here, we present a new principle of directing the assembly of nonmagnetic colloidal particles dispersed in a magnetic fluid and generating unusual surface patterns. We use the ability of ferrofluids to change phases with the application of magnetic fields to program the assembly of nonmagnetic microparticles present in drying sessile droplets. We show that in the absence of external magnetic field, the superparamagnetic nanoparticles in the magnetic fluid are spontaneously transported to the droplet edge because of solvent evaporation. This nanoparticle transport leads to the formation of nanoparticle-rich edge and nanoparticle-depleted center of the drying droplet. Upon the application of a uniform external magnetic field, the asymmetry in the magnetic nanoparticle distribution drives a magnetostatic convection and finger-like instability from the droplet edge to the center. This magnetic microconvection from droplet edge-to-center reverses the particle transport from center-to-edge, well-known for drying droplets in the absence of external field. We use this magnetostatic microconvection to assemble secondary nonmagnetic microspheres in droplets, overwriting ring formation and direct their assembly into four distinct kinetically stable states. As a result, the method presented here offers an active control over the colloidal assembly achieved by drying sessile droplets and thus enables a new route for fabricating complex patterns and functional surface coating.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗