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1

Evolution of clay mineral assemblages in the Tinguiririca geothermal field, Andean Cordillera of central Chile: an XRD and HRTEM-AEM study  

NASA Astrophysics Data System (ADS)

HRTEM textural evidence shows that clay minerals in the Tinguiririca geothermal field (Andean Cordillera, central Chile) are the result of direct alteration of former volcanic glass and minerals by hydrothermal fluids at similar temperatures to the present day. They show the classical pattern of diagenetic transformation from smectite at the top to illite at the bottom, with the progressive formation of corrensite and chlorite. The high fluid/rock ratio, disposability of necessary cations and absence of previous detrital phyllosilicates allow the consideration of this area as a natural laboratory to establish the extreme ideal conditions for very low-T reactions. Transformations from smectite to R1 illite-smectite (I-S) and from these to R3 mixed-layers occur respectively at 80-120 °C and 125-180 °C. In spite of ideal genetic conditions, the new-formed minerals show all the defective character and lack of textural and chemical equilibrium previously described in the literature for diagenetic and hydrothermal low-temperature assemblages. Chemistry of smectite-illite phases evolves basically through a diminution of the pyrophyllitic component toward a theoretical muscovite (Si4 + + ? -> Al3 ++ K+). However, a second chemical vector (Si4 ++ Mg2 + ? Al3 ++ Al3 +), that is, decreasing of the tschermack component, also contributes to the evolution toward the less Si-more Al rich muscovite in relation to the original smectite. Residual Mg (and Fe) from the latter reaction is consumed in the genesis of chloritic phases. Nevertheless, as a consequence of the lack of chemical equilibrium (probably because of the short time-scale of the geothermal alteration processes), the composition of clay minerals is highly heterogeneous at the level of a single sample. Consequently, the respective fields of smectite, R1 I-S and R3 I-S overlap each other, making the distinction among these three phases impossible based exclusively on chemical data.

Vázquez, M.; Nieto, F.; Morata, D.; Droguett, B.; Carrillo-Rosua, F. J.; Morales, S.

2014-08-01

2

Size distribution of magnetic iron oxide nanoparticles using Warren-Averbach XRD analysis  

NASA Astrophysics Data System (ADS)

We use the Fourier transform based Warren-Averbach (WA) analysis to separate the contributions of X-ray diffraction (XRD) profile broadening due to crystallite size and microstrain for magnetic iron oxide nanoparticles. The profile shape of the column length distribution, obtained from WA analysis, is used to analyze the shape of the magnetic iron oxide nanoparticles. From the column length distribution, the crystallite size and its distribution are estimated for these nanoparticles which are compared with size distribution obtained from dynamic light scattering measurements. The crystallite size and size distribution of crystallites obtained from WA analysis are explained based on the experimental parameters employed in preparation of these magnetic iron oxide nanoparticles. The variation of volume weighted diameter (Dv, from WA analysis) with saturation magnetization (Ms) fits well to a core shell model wherein it is known that Ms=Mbulk(1-6g/Dv) with Mbulk as bulk magnetization of iron oxide and g as magnetic shell disorder thickness.

Mahadevan, S.; Behera, S. P.; Gnanaprakash, G.; Jayakumar, T.; Philip, J.; Rao, B. P. C.

2012-07-01

3

Magnetic composites from minerals: study of the iron phases in clay and diatomite using Mössbauer spectroscopy, magnetic measurements and XRD  

NASA Astrophysics Data System (ADS)

Magnetic particles as matrix for enzyme immobilization have been used and due to the enzymatic derivative can be easily removed from the reaction mixture by a magnetic field. This work presents a study about the synthesis and characterization of iron phases into magnetic montmorillonite clay (mMMT) and magnetic diatomaceous earth (mDE) by 57Fe Mössbauer spectroscopy (MS), magnetic measurements and X-ray diffraction (XRD). Also these magnetic materials were assessed as matrices for the immobilization of invertase via covalent binding. Mössbauer spectra of the magnetic composites performed at 4.2 K showed a mixture of magnetite and maghemite about equal proportion in the mMMT, and a pure magnetite phase in the sample mDE. These results were verified using XRD. The residual specific activity of the immobilized invertase on mMMT and mDE were 83 % and 92.5 %, respectively. Thus, both magnetic composites showed to be promising matrices for covalent immobilization of invertase.

Cabrera, M.; Maciel, J. C.; Quispe-Marcatoma, J.; Pandey, B.; Neri, D. F. M.; Soria, F.; Baggio-Saitovitch, E.; de Carvalho, L. B.

2014-01-01

4

IEEE TRANSACTIONS ON MAGNETICS, VOL. 45, NO. 10, OCTOBER 2009 4861 NSOM/HRTEM Characterization of Biologically Derived  

E-print Network

microscopy, magnetooptic Kerr effect, magnetotactic bacteria, magnetospirillum gryphiswaldense, nanomagnets of nanomagnets by these bacteria occurs at very mild conditions (at room temperature and atmospheric pressure­optic Kerr effect (MOKE). The NSOM-MOKE image clearly shows the magnetization of the nano- magnets, while

Mittal, Aditya

5

EXAFS and SR-XRD study on Mn occupations in Zn 1-xMn xO diluted magnetic semiconductors  

NASA Astrophysics Data System (ADS)

Mn-doped ZnO films were prepared by radio frequency (RF) magnetron sputtering on sapphire substrate. Mn content was determined by proton induced X-ray emission (PIXE). Only Mn, no other magnetic impurities such as Fe, Co and Ni were observed. Also, no precipitates such as MnO, Mn 3O 4 and other secondary phases or Mn clusters, were found by SR-XRD, even in Mn-doped content up to 11 at.%. EXAFS analyses showed that Mn atoms were incorporated into ZnO crystal lattice by occupying the sites of zinc atoms.

Li, M.; Zhang, B.; Wang, J. Z.; Shi, L. Q.; Cheng, H. S.; Wang, Y. Z.; Lv, H. Y.; Yang, T. Y.; Wen, W.; Hu, F. C.

2011-11-01

6

Composition, structure and layer charge distribution in K-bentonite illite/smectite clays: Evidence from HRTEM  

SciTech Connect

Fourteen illite/smectite (I/S) clays separated from lower Paleozoic K-bentonites have been studied by XRD, XRF, HRTEM, and alkylamonium ion exchange. The samples represent the full range of commonly occurring I/S compositions in diagenetic K-bentonites. Chemical analysis and XRD data show that the increases in the amount of tetrahedral Al[sup +3] for Si[sup +4] substitution and the amount of fixed-K, are the principle factors controlling the increases in the proportion of illite layers and the degree of ordering in I/S. Extrapolation of the chemical data indicates: (1) a constant fixed-K content of 0.75 per illite layer (half cell); and (2) a montmorillonitic and a phengitic end-member compositions, respectively, for smectite and illite. The magnitude and distribution of layer charge of expandable component of I/S determined by alkylammonium ion exchange is characteristic of smectite in I/S with 15--100% expandability, confirming the two-component nature of I/S in this range. The layer charge data both from XRD and HRTEM for alkylammonium ion-exchanged I/S with < 15% expandability suggest a vermiculitic, rather than a smectitic charge for the expandable interlayers. The HRTEM data demonstrate that the postulated fundamental particles are the result of disintegration of larger I/S crystals. The data is consistent with a layer-by-layer transformation mechanism in which randomly distributed high-, intermediate-, and low-charged interlayers of a precursor smectite preferentially incorporate K[sup +] ions in response to an increasingly negative tetrahedral charge. A neoformation process involving dissolution of smectite and reprecipitation of illite is unlikely because such a mechanism requires precipitation of illite particles with surface charges significantly higher than that of a smectite.

Cetin, K.; Huff, W.D. (Univ. of Cincinnati, OH (United States). Dept. of Geology)

1992-01-01

7

Fe@Ag core–shell nanoparticles with both sensitive plasmonic properties and tunable magnetism  

Microsoft Academic Search

Monodisperse Fe@Ag core–shell nanoparticles with relatively uniform Fe cores and Ag shells have been successfully fabricated by a seed mediated method in a two-step reducing process, and then characterized by electron microscopy techniques (HRTEM, EDX), X-ray diffraction (XRD), UV–vis spectroscopy?and magnetometry. The results demonstrate unique optical and magnetic properties for Fe@Ag core–shell nanoparticles. The surface plasmon resonance of Fe@Ag core–shell

Liying Lu; Wentao Zhang; Dong Wang; Xiaoguang Xu; Jun Miao; Yong Jiang

2010-01-01

8

HRTEM Study of Diesel Soot Collected from Diesel Particulate Filters  

SciTech Connect

HRTEM study of several soot samples collected on Diesel Particulate Filters (DPF) under conditions relevant to practical applications of DPF technology, revealed nano-structure, to our knowledge, not reported previously for diesel soot. In particular, some of the primary particles were found to have hollow interior, and the outer shell exhibiting evidence of graphitization, with a higher crystallinity compared to the non-hollowed particles. The percentage of such particles varied between different soot samples and tentatively appeared to be related to the oxidation history of the sample. Remarkably, similar effect was not reproduced for a carbon black sample, Printex-U, suggesting that propensity to such oxidation-induced graphitization is related to the original nano-structure of the particle. These initial observations were independently confirmed for the same set of soot samples by two different HRTEM facilities, at NASA-Glenn and PNNL.

Vander Wal, Randy L.; Yezerets, Aleksey; Currier, Neal; Kim, Do Heui; Wang, Chong M.

2007-01-01

9

HRTEM and EELS studies of nanoscale structured electronic materials  

NASA Astrophysics Data System (ADS)

This thesis focuses on the growth and structure of a number of nanoscale structured electronic materials characterized using HRTEM and EELS. Both rare earth silicide nanostructures self-assembled on Si(001) and sputtered GMR multilayers have been studied by characterizing their crystal structures, interfacial epitaxy, interfacial chemical nature, and electronic nature, which provide fundamental insights into material behavior at the nanometer scale. High aspect ratio nanowires and nanosized islands have been observed to self-assemble on Si(001) for both the Gd and Tm silicide systems. HRTEM results show that Gd silicide nanostructures exhibit either the hexagonal GdSi 2-x or the orthorhombic GdSi2 crystal structures, with lattice parameters consistent with the bulk phases. In the case of Tm, the observed nanostructures are likewise either hexagonal or orthorhombic. The hexagonal phase has lattice parameters consistent with the bulk, while the orthorhombic does not. For both systems, bi-phasic silicide structures were observed, which may reflect a mechanism for strain accommodation at the interface with the substrate. In the case of Gd, the phase with lower strain lies at the substrate. For the case of Tm, the relative mismatches of the two phases predicted from bulk silicide lattice parameters disagree with that derived from measured lattice constants, and it is a relaxed orthorhombic phase at the interface that appears to have the lowest mismatch with the substrate. EELS studies were carried out to compare the electronic structures of metallic Gd, thin film Gd silicide, and Gd oxide in bulk phases and Gd silicide nanostructures. The results from the three bulk phases are similar, while the intensity ratio of M5:M4 in the GdSi2 nanostructures varies from the bulk, which may suggest that a slightly different spin state exists in the silicide nanostructures. As-sputtered and annealed F(Co, or Py)/Al multilayers have been studied using HRTEM and EELS. Although the interfacial intensity profiles from EELS spectrum images suggest some limited intermixing exists in the F/Al interfacial regions, both HRTEM and diffraction studies show no obvious intermediate phase formation. In particular, the annealing treatments do not significantly alter the multilayer structures. In contrast, intermediate phase formation has been observed in both Cu/Al multilayers and Cu/Al regions in spin valves. Tetragonal Al2Cu and bcc AlCu3 are formed in the Cu(8nm)/Al(10nm) multilayers, while Al2Cu and fcc Cu are formed in the Cu(5nm)/Al(3nm) multilayers. For Cu/Al/Cu layers in the spin-valves, evidence of Al2 Cu and AlCu3 phase formation in the annealed spin-valve with the 30nm Al layer was found, while Al2Cu and Cu were observed in the as-sputtered spin-vale with the 10nm Al layer. These results are discussed in terms of the balance between interfacial and plume free energies in order to rationalize the formation of non-equilibrium structures.

Zhang, Jiaming

10

Ceramic/metal nanocomposites by lyophilization: Processing and HRTEM study  

SciTech Connect

Highlights: Black-Right-Pointing-Pointer A cryogenic route has been used to obtain ceramic/metal nanostructured powders. Black-Right-Pointing-Pointer The powders present good homogeneity and dispersion of metal. Black-Right-Pointing-Pointer The metal nanoparticle size distributions are centred in 17-35 nm. Black-Right-Pointing-Pointer Both phases, ceramic and metal, present a high degree of crystallinity. Black-Right-Pointing-Pointer Good metal/ceramic interfaces due to epitaxial growth, studied by HRTEM. -- Abstract: This work describes a wet-processing route based on spray-freezing and subsequent lyophilization designed to obtain nanostructured ceramic/metal powders. Starting from the ceramic powder and the corresponding metal salt, a water-based suspension is sprayed on liquid nitrogen. The frozen powders are subsequently freeze-dried, calcined and reduced. The material was analyzed using X-ray diffraction analysis at all stages. High resolution transmission electron microscopy studies showed a uniform distribution of metal nanoparticles on the ceramic grain surfaces, good interfaces and high crystallinity, with an average metal particle size in the nanometric range.

Gutierrez-Gonzalez, C.F. [Centro de Investigacion en Nanomateriales y Nanotecnologia (CINN), Consejo Superior de Investigaciones Cientificas - CSIC - Universidad de Oviedo - UO - Principado de Asturias - PA, Parque Tecnologico de Asturias, 33428 Llanera (Spain)] [Centro de Investigacion en Nanomateriales y Nanotecnologia (CINN), Consejo Superior de Investigaciones Cientificas - CSIC - Universidad de Oviedo - UO - Principado de Asturias - PA, Parque Tecnologico de Asturias, 33428 Llanera (Spain); Agouram, S. [Department of Applied Physics and Electromagnetism, Universitat de Valencia, 46100 Burjassot (Spain)] [Department of Applied Physics and Electromagnetism, Universitat de Valencia, 46100 Burjassot (Spain); Torrecillas, R. [Centro de Investigacion en Nanomateriales y Nanotecnologia (CINN), Consejo Superior de Investigaciones Cientificas - CSIC - Universidad de Oviedo -UO - Principado de Asturias- PA, Parque Tecnologico de Asturias, 33428 Llanera (Spain)] [Centro de Investigacion en Nanomateriales y Nanotecnologia (CINN), Consejo Superior de Investigaciones Cientificas - CSIC - Universidad de Oviedo -UO - Principado de Asturias- PA, Parque Tecnologico de Asturias, 33428 Llanera (Spain); Moya, J.S. [Instituto de Ciencia de Materiales de Madrid, Consejo Superior de Investigaciones Cientificas (ICMM-CSIC), Cantoblanco, 28049 Madrid (Spain)] [Instituto de Ciencia de Materiales de Madrid, Consejo Superior de Investigaciones Cientificas (ICMM-CSIC), Cantoblanco, 28049 Madrid (Spain); Lopez-Esteban, S., E-mail: s.lopez@cinn.es [Centro de Investigacion en Nanomateriales y Nanotecnologia (CINN), Consejo Superior de Investigaciones Cientificas - CSIC - Universidad de Oviedo - UO - Principado de Asturias - PA, Parque Tecnologico de Asturias, 33428 Llanera (Spain)

2012-02-15

11

Investigation of Local Structures and Magnetism in (Y, Co) codoped CeO2 Nanoparticles  

NASA Astrophysics Data System (ADS)

Nanocrystals of (Y, Co) codoped CeO2 with different Y concentration prepared by a Polyol method were studied by X-ray diffraction (XRD), high-resolution transmission electron microscopy (HR-TEM), Raman spectroscopy, x-ray absorption fine structures (XAFS), and superconducting quantum interference device (SQUID) techniques to monitor the structural and magnetic variations of the samples. As revealed by the XRD data, all nanocrystal samples under investigation have similar average particle size. The concentration of O vacancies in the samples was found to increase with Y doping level as indicated by the Raman spectroscopy and XAFS data. Such increase of O vacancies is also accompanied by enhanced ferromagnetism as observed by SQUID measurements. Our experimental results demonstrate clear correlation between magnetism and O vacancies induced by Y doping and therefore are consistent with the bound magnetic polaron model.

Wu, T. S.; Li, H. D.; Chen, Y. W.; Chen, S. F.; Chang, S. L.; Soo, Y. L.

2013-03-01

12

A HRTEM/EDX approach to identification of the source of dust particles on urban tree leaves  

NASA Astrophysics Data System (ADS)

Dust on tree leaves in the urban area of Hangzhou, China, was analyzed in terms of heavy metal contents and magnetic properties. Morphological and chemical composition of the dust particles were analyzed using a high resolution transmission electron microscope equipped with an energy-dispersive X-ray analyzer (HRTEM/EDX). Results indicated that the dusts contained high concentrations of Cd (mean 2.62), Cu (63.7), Zn (535.9) and Pb (150.9 mg kg -1). Magnetic susceptibility of the dusts was in a range of (16-856) × 10 -8 m 3 kg -1. It was shown that the dusts close to industrial area and busy road intersection had higher heavy metal contents and magnetic susceptibility. The dusts showed a strong positive inter-correlation for the concentrations of Fe, Mn, Cr, Zn, Pb, and Cu in addition to magnetic susceptibility, which suggests that the dusts had a common source for the heavy metals and magnetic carriers. We found that the dust particles were composed mainly of Fe-rich near-spherical, plate and agglomerate particles, and Ca-rich, S-rich and silicate particles, and that iron oxide spherules (0.2-0.5 ?m in diameter) and larger iron-bearing particles were the magnetic carriers. Ca in the dusts was present in the forms of CaCO 3 and CaCO 3/CaSO 4 internal mixture. The Fe-rich, Ca-rich and S-rich particles in dusts could be directly related to nearby polluting activities, such as coal combustion, traffic emission and industrial activity. The identification of the main sources of dusts on tree leaves can help in controlling the polluting sources in urban areas. The close correlation between magnetic susceptibility and heavy metal concentration makes it possible to use the magnetic technique as a non-destructive and time-efficient tool for biomonitoring of the atmospheric dust pollutants.

Lu, S. G.; Zheng, Y. W.; Bai, S. Q.

13

HRTEM study of zircon from Eliseev anorthosite complex, Antarctica  

SciTech Connect

Zircon-bearing rocks of this study are metamorphic oxide-apatite gabbronorites (OAGN) from the Eliseev Anorthosite Complex, Wohlthat-Massif, East Antarctica. These unusual rocks are strongly enriched in accessory minerals apatite: <10 vol.%; zircon: < 1 vol.. Three steps in the evolution of these rocks are distinguished: a magnetic formation, followed by a granulite facies metamorphism and finally a tectonomagmatic overprint. The zircon crystals of this study are brown colored, up to 12 mm in length and up to 3 mm wide. Petrological investigations show that zircon has formed during the granulite facies event. Optical microscopy and cathodoluminiscence microscopy reveal a rhythmic zoning and many microcracks. The concentrations of uranium and thorium are low (U: 34-89 ppm and Th: 3-9 ppm). The radiation damage by radioactive decay of U and Th is expected to be minor due to the low uranium and thorium content. The investigations were carried out in a Philips CM200 transmission electron microscope. Analytical electron microscopy was performed by energy dispersive analysis (EDAX).

Wirth, R.; Kaempf, H. [GeoForschungsZentrum Potsdam (Germany); Hoehndorf, A. [Bundesanstalt fuer Geowissenschaften und Rohstoffe, Hannover (Germany)

1996-12-31

14

Magnetic photocatalysts with a p-n junction: Fe3O4 nanoparticle and FeWO4 nanowire heterostructures.  

PubMed

Magnetic n-type semiconductor Fe3O4 nanoparticle and p-type semiconductor FeWO4 nanowire heterostructures were successfully synthesized without any surfactants or templates via a facile one-step hydrothermal process at 160 °C. The heterojunction structure and morphology were characterized by X-ray powder diffraction (XRD), transmission electron microscopy (TEM) and high-resolution transmission electron microscopy (HRTEM). Magnetic measurements indicated the coexistence of ferrimagnetic behavior of Fe3O4 and weak antiferromagnetic behavior of FeWO4. The degradation of methylene blue (MB) under UV-Visible light irradiation was studied as a model experiment to evaluate the catalytic activity of the Fe3O4/FeWO4 heterostructure p-n junctions. The decomposition efficiency was 97.1% after one hour UV-Visible irradiation. This magnetic photocatalyst can be easily recovered from the solution using a permanent magnet and redispersed by removing the magnet. PMID:25201551

Cao, Xuan; Chen, Yan; Jiao, Shihui; Fang, Zhenxing; Xu, Man; Liu, Xu; Li, Lu; Pang, Guangsheng; Feng, Shouhua

2014-10-01

15

ZnFe 2O 4 nanoparticles for ferrofluids: A combined XANES and XRD study  

Microsoft Academic Search

A soft-chemistry method is used to synthesize zinc ferrite nanoparticles to prepare a magnetic fluid. We investigate here their internal structure by X-ray Absorption Near Edge Spectroscopy (XANES) and X-Ray Diffraction (XRD). A cross analysis of XANES and Rietveld refinement of XRD spectra shows non-equilibrium site occupancy with respect to bulk zinc ferrite, suggesting a cation redistribution that enhances the

J. A. Gomes; G. M. Azevedo; J. Depeyrot; J. Mestnik-Filho; G. J. da Silva; F. A. Tourinho; R. Perzynski

2011-01-01

16

HRTEM of microcrystalline opal in chert and porcelanite from the Monterey Formation, California  

Microsoft Academic Search

Microcrystalline opal was investigated using low-dose transmission electron microscopy (TEM) methods to identify microstructural characteristics and possible phase-transformation mechanisms that accommodate silica diagenesis. High-resolution TEM (HRTEM) revealed that microcrystalline opal in opal-CT chert (>90 wt% silica) and opal-CT porcelanite (50-90 wt% silica) from the Miocene Monterey Formation of California displays various amounts of structural disorder and coherent and incoherent lamellar

S. L. Cady; H.-R. WENK; K. H. Downing

1996-01-01

17

Microstructure and thermodynamics of zirconolite- and pyrochlore-dominated synroc samples: HRTEM and AEM investigation  

NASA Astrophysics Data System (ADS)

Scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), and analytical electron microscopy (AEM) studies have been conducted on samples crystallized from melts with a composition of zirconolite {(Ca0.9Gd0.1)Zr(Ti1.9Al0.1)2O7} and CaCeTi2O7. The formation of a whole suite of Synroc phases (zirconia, ZrTiO4, zirconolite, perovskite, and rutile) has been observed.

Xu, Huifang; Wang, Yifeng

2000-07-01

18

Characterization of illuminated manuscripts by laboratory-made portable XRD and micro-XRD systems.  

PubMed

Illuminated Arabic manuscripts have been studied, employing two laboratory-made X-ray diffraction (XRD) systems developed recently in the C2RMF laboratory. The validity of the micro-XRD and XRD portable systems for the study of this type of artworks has been demonstrated. A common observation in all the analyses is the presence of calcite and rutile; also, hematite, goethite, cinnabar, brass, anatase and barite were detected in the various colours. Differences between the results obtained by both techniques due to acquisition mode are discussed. In addition, other techniques such as X-ray fluorescence (XRF) and micro-Raman were used for the complete characterization of the manuscripts. PMID:19685044

Duran, A; Perez-Rodriguez, J L; Espejo, T; Franquelo, M L; Castaing, J; Walter, P

2009-12-01

19

Synthesis, characterization and magnetic properties of hematite (?-Fe2O3) nanoparticles on polysaccharide templates and their antibacterial activity  

NASA Astrophysics Data System (ADS)

The present study is to synthesize iron oxide nanoparticles on different polysaccharide templates calcined at controlled temperature, characterizing them for spectroscopic and magnetic studies leading to evaluate their antibacterial property. The synthesized iron oxide nanoparticles were characterized by X-ray diffractometer (XRD), Fourier transform infrared spectroscopy, high resolution scanning electron microscopy (HRSEM), high resolution transmission electron microscopy (HRTEM) and vibrating sample magnetometer. The iron oxide nanoparticles were tested for antibacterial activity against gram-positive and gram-negative bacterial species. The XRD confirms the crystalline nature of iron oxide nanoparticles with the mean crystallite size of 10 nm. The functional groups of the synthesized iron oxide nanoparticles were 547, 543 and 544 cm-1 characterizing the Fe-O and the broad bands at 3,398, 3,439 and 3,427 cm-1 were attributed to the stretching vibrations of hydroxyl group absorbed by iron oxide nanoparticles. HRTEM analyses revealed that the average particle size of the hematite nanoparticles are about 85, 92 and 77 nm for AF, DF and GF, respectively, which was a coincident with the results obtained from the HRSEM analysis. Magnetic measurement exhibited ferromagnetic behavior of the ?-Fe2O3 at the room temperature with higher coercivity of H C = 2,303, 2,333 and 1,019 Oe for AF, DF and GF, respectively. Antibacterial test showed the inhibition against Aeromonas hydrophila and Escherichia coli with significant antagonistic activity.

Rafi, M. Mohamed; Ahmed, K. Syed Zameer; Nazeer, K. Prem; Siva Kumar, D.; Thamilselvan, M.

2014-08-01

20

Atom by atom: HRTEM insights into inorganic nanotubes and fullerene-like structures  

PubMed Central

The characterization of nanostructures down to the atomic scale is essential to understand some physical properties. Such a characterization is possible today using direct imaging methods such as aberration-corrected high-resolution transmission electron microscopy (HRTEM), when iteratively backed by advanced modeling produced by theoretical structure calculations and image calculations. Aberration-corrected HRTEM is therefore extremely useful for investigating low-dimensional structures, such as inorganic fullerene-like particles and inorganic nanotubes. The atomic arrangement in these nanostructures can lead to new insights into the growth mechanism or physical properties, where imminent commercial applications are unfolding. This article will focus on two structures that are symmetric and reproducible. The first structure that will be dealt with is the smallest stable symmetric closed-cage structure in the inorganic system, a MoS2 nanooctahedron. It is investigated by means of aberration-corrected microscopy which allowed validating the suggested DFTB-MD model. It will be shown that structures diverging from the energetically most stable structures are present in the laser ablated soot and that the alignment of the different shells is parallel, unlike the bulk material where the alignment is antiparallel. These findings correspond well with the high-energy synthetic route and they provide more insight into the growth mechanism. The second structure studied is WS2 nanotubes, which have already been shown to have a unique structure with very desirable mechanical properties. The joint HRTEM study combined with modeling reveals new information regarding the chirality of the different shells and provides a better understanding of their growth mechanism. PMID:18838681

Sadan, Maya Bar; Houben, Lothar; Enyashin, Andrey N.; Seifert, Gotthard; Tenne, Reshef

2008-01-01

21

HRTEM Study of yttrium oxide particles in ODS steels for fusion reactor application  

Microsoft Academic Search

An oxide dispersion strengthened ferritic-martensitic steel with yttrium oxide (Y2O3) was produced by mechanical alloying and hot isostatic pressing techniques for high-performance structures of fusion energy devices. The structure of the nanometer-sized Y2O3 particles analysed by HRTEM shows a strong correlation of its crystallographic orientation with the alloy lattice. The orientation correlations [110]YO?[111]FeCr and (11?1?)YO?(11?0)FeCr were found. The strong orientation

M. Klimiankou; R. Lindau; A. Möslang

2003-01-01

22

Swelling of ion-irradiated 3C-SiC characterized by synchrotron radiation based XRD and TEM  

NASA Astrophysics Data System (ADS)

An experimental technique was established to characterize irradiation-induced volume swelling through a combined utilization of synchrotron radiation-based X-ray diffraction (XRD) and transmission electron microscopy (TEM). 3C-SiC specimens were irradiated by Si2+ ions (5 MeV) with fluences up to 5 × 1017 ion/cm2 at 1000 °C. In order to avoid the accumulation of implanted Si ions in the SiC layer, specific thicknesses of the epitaxy layer and implanted ion energy were chosen. Unresolvable black spot defects were studied by TEM, and the average size and density were calculated. XRD radial scan results of surface (0 0 2), (1 1 1), (0 2 2), (1 1 3), and (2 0 0) including peak shift and asymmetry peak broadening were observed. Different interplanar spacing information of single crystal SiC can be obtained from this XRD measurement method, making it possible to investigate the lattice expansion and volume swelling more precisely. While TEM provided a direct visualization of the microstructures and the interplanar spacing was measured from HRTEM images. It is suggested that irradiation induced point defects and compressive stress from the Si substrate were the cause of anisotropic (a = b < c) volume swelling of irradiated 3C-SiC in this study.

Lin, Yan-Ru; Ho, Chun-Yu; Chuang, Wei-Tsung; Ku, Ching-Shun; Kai, Ji-Jung

2014-12-01

23

Synthesis, Characterization and Studies on Optical, Dielectric and Magnetic Properties of undoped and Cobalt doped Nanocrystalline Bismuth Ferrite  

NASA Astrophysics Data System (ADS)

Multiferroic perovskite nanocrystalline Bismuth ferrite (BFO) and Co doped Bismuth ferrite are synthesized by chemical route annealed at 500, 550 and 600 °C. XRD studies revealed the phases formed during synthesis while crystallite size is calculated in the range of 15.4-55 nm by Scherrer's formula from the identified XRD major peaks. The FTIR spectra of undoped BFO sample synthesized at 500, 550 and 600 °C exhibits clear presence of peaks at 554 cm-1 confirms the existence of Bi-O, Fe-O stretching and bending behavior of two different M-O co-ordination using Shimadzu-8400S Spectroscopy. The microstructure, lattice image and interplanar spacing are obtained by HRTEM analysis. The particle sizes are also measured from HRTEM while the chemistry is verified by energy dispersive x-ray analysis (EDX) (Oxford Instruments, INCA). Dielectric properties are observed for both undoped and Co doped samples. The band gap energy is measured by UV-VIS characterization using Tauc equation. Magnetic measurements are carried out using Physical Properties Measurement systems.

Sarkar, K.; Mukherjee, Soumya; Mukherjee, S.; Mitra, M. K.

2014-09-01

24

Synthesis, Characterization and Studies on Optical, Dielectric and Magnetic Properties of undoped and Cobalt doped Nanocrystalline Bismuth Ferrite  

NASA Astrophysics Data System (ADS)

Multiferroic perovskite nanocrystalline Bismuth ferrite (BFO) and Co doped Bismuth ferrite are synthesized by chemical route annealed at 500, 550 and 600 °C. XRD studies revealed the phases formed during synthesis while crystallite size is calculated in the range of 15.4-55 nm by Scherrer's formula from the identified XRD major peaks. The FTIR spectra of undoped BFO sample synthesized at 500, 550 and 600 °C exhibits clear presence of peaks at 554 cm-1 confirms the existence of Bi-O, Fe-O stretching and bending behavior of two different M-O co-ordination using Shimadzu-8400S Spectroscopy. The microstructure, lattice image and interplanar spacing are obtained by HRTEM analysis. The particle sizes are also measured from HRTEM while the chemistry is verified by energy dispersive x-ray analysis (EDX) (Oxford Instruments, INCA). Dielectric properties are observed for both undoped and Co doped samples. The band gap energy is measured by UV-VIS characterization using Tauc equation. Magnetic measurements are carried out using Physical Properties Measurement systems.

Sarkar, K.; Mukherjee, Soumya; Mukherjee, S.; Mitra, M. K.

2014-10-01

25

In-situ synthesis of magnetic (NiFe{sub 2}O{sub 4}/CuO/FeO) nanocomposites  

SciTech Connect

In-situ synthesis of magnetic nanocomposites with (NiFe{sub 2}O{sub 4}/CuO/FeO) crystal phases has been done using a sol-gel method by taking a non-stoichiometric composition of the precursors. The average particle size of the nanocomposites was calculated using X-ray diffraction (XRD) and high resolution tunneling electron microscope (HR-TEM) and it turns out to be {approx}20 nm. The vibrating sample magnetometer (VSM) measurements demonstrate the ferromagnetic nature of the nanocomposites. The synthesized nanocomposite was used to prepare magnetic fluid using tetramethylammonium hydroxide as a surfactant and its stability in the solution was also discussed. -- Graphical abstract: Magnetic nanocomposites containing (NiFe{sub 2}O{sub 4}/CuO/FeO) phases having particle size {approx}17 nm were synthesized by a sol-gel method. The synthesized nanocomposites exhibit ferromagnetic nature with small value of coercivity.

Srivastava, Manish [Department of Physics, Motilal Nehru National Institute of Technology, Allahabad 211004 (India); Ojha, Animesh K., E-mail: animesh_r1776@rediffmail.co [School of Engineering and Science, Jacobs University, 28759 Bremen (Germany); Chaubey, S. [Department of Physics, Motilal Nehru National Institute of Technology, Allahabad 211004 (India); Singh, Jay [Department of Chemistry, Motilal Nehru National Institute of Technology, Allahabad 211004 (India)

2010-11-15

26

Microstructure and magnetic studies of the Fe-Nd-Al magnets  

NASA Astrophysics Data System (ADS)

Ribbons of the Fe53Nd37Al10 alloy with different rolling rates were prepared by the melt spinning method. The magnetic properties, phase composition and microstructure of the ribbons were systematically investigated by vibrating sample magnetometer (VSM), differential scanning calorimeter (DSC), X-ray diffraction (XRD), scanning electron microscope (SEM), focused ion beam (FIB) and high resolution transmission electron microscope (HRTEM). The micrograph shows that the ribbon melt-spun at 5 m s-1 is composed of Nd2Fe17 phase with approximately 5 ?m in size and some clusters of 5 nm in diameter in the amorphous matrix, while no obviously crystallized phase is detected in the sample melt-spun at 20 m s-1. Both of the ribbons melt-spun at 5 m s-1 and 20 m s-1 show hard magnetic properties at room temperature, but they exhibit different magnetic properties at low temperature. The hard magnetic property of the ribbon melt-spun at 5 m s-1 would be due to the exchange coupling interactions and pinning effect. However, the magnetism of the sample melt-spun at 20 m s-1 would be contributed to the pinning effect.

Bai, Q.; Wang, J.; Hao, Y. F.; He, J. M.; Xu, H.; Xia, S.

2014-04-01

27

TEM and HRTEM of Soot-in-oil particles and agglomerates from internal combustion engines  

NASA Astrophysics Data System (ADS)

Over time, the performance of lubricating oil in a diesel engine is affected by the build-up of carbon soot produced by the combustion process. TEM and HRTEM are commonly used to investigate the characteristics of individual and agglomerated particles from diesel exhaust, to understand the structure and distribution of the carbon sheets in the primary particles and the nanostructure morphology. However, high resolution imaging of soot-in-oil is more challenging, as mineral oil is a contaminant for the electron microscope and leads to instability under the electron beam. In this work we compare solvent extraction and centrifugation techniques for removing the mineral oil contaminant, and the effect on particle size distribution.

Fay, M. W.; La Rocca, A.; Shayler, P. J.

2014-06-01

28

Synthesis and Characterization of Zinc Ferrite by XRD, Vsm and Electron Spin Resonance Techniques  

NASA Astrophysics Data System (ADS)

In this report, the synthesis of zinc ferrite (ZnFe2O4) by co-precipitation method has been presented along with its subsequent characterization by using X-ray diffraction (XRD), vibrating sample magnetometer (VSM) and electron spin resonance (ESR) techniques. The obtained XRD results of as-synthesized sample indicates the cubic spinel phase formation, which was confirmed from the XRD data of the above calcined sample at 1000°C. By using VSM, a complex magnetic structure was observed with substantial change on calcined sample. The ESR result of zinc ferrite sample studied at room temperature was found to be significantly different from that of the low temperature results, especially after heat-treatment.

Nayak, Pranaba K.; Jothiramalingam, R.

2013-02-01

29

Magnetic photocatalysts with a p-n junction: Fe3O4 nanoparticle and FeWO4 nanowire heterostructures  

NASA Astrophysics Data System (ADS)

Magnetic n-type semiconductor Fe3O4 nanoparticle and p-type semiconductor FeWO4 nanowire heterostructures were successfully synthesized without any surfactants or templates via a facile one-step hydrothermal process at 160 °C. The heterojunction structure and morphology were characterized by X-ray powder diffraction (XRD), transmission electron microscopy (TEM) and high-resolution transmission electron microscopy (HRTEM). Magnetic measurements indicated the coexistence of ferrimagnetic behavior of Fe3O4 and weak antiferromagnetic behavior of FeWO4. The degradation of methylene blue (MB) under UV-Visible light irradiation was studied as a model experiment to evaluate the catalytic activity of the Fe3O4/FeWO4 heterostructure p-n junctions. The decomposition efficiency was 97.1% after one hour UV-Visible irradiation. This magnetic photocatalyst can be easily recovered from the solution using a permanent magnet and redispersed by removing the magnet.Magnetic n-type semiconductor Fe3O4 nanoparticle and p-type semiconductor FeWO4 nanowire heterostructures were successfully synthesized without any surfactants or templates via a facile one-step hydrothermal process at 160 °C. The heterojunction structure and morphology were characterized by X-ray powder diffraction (XRD), transmission electron microscopy (TEM) and high-resolution transmission electron microscopy (HRTEM). Magnetic measurements indicated the coexistence of ferrimagnetic behavior of Fe3O4 and weak antiferromagnetic behavior of FeWO4. The degradation of methylene blue (MB) under UV-Visible light irradiation was studied as a model experiment to evaluate the catalytic activity of the Fe3O4/FeWO4 heterostructure p-n junctions. The decomposition efficiency was 97.1% after one hour UV-Visible irradiation. This magnetic photocatalyst can be easily recovered from the solution using a permanent magnet and redispersed by removing the magnet. Electronic supplementary information (ESI) available: The equation used to calculate the energy band gap, XRD data of the products with various pH values, the SEM image of Fe3O4/FeWO4, and the TEM image of FeWO4 nanowires. See DOI: 10.1039/c4nr03729d

Cao, Xuan; Chen, Yan; Jiao, Shihui; Fang, Zhenxing; Xu, Man; Liu, Xu; Li, Lu; Pang, Guangsheng; Feng, Shouhua

2014-10-01

30

Characterization of neoformed illite from hydrothermal experiments at 250 C and P{sub v,soln}: An HRTEM/ATEM study  

SciTech Connect

Solid products from hydrothermal experiments conducted at 250 C and P{sub v,soln} were characterized by powder X-ray diffraction (XRD) and ATEM/HRTEM. Experiments were conducted with muscovite, kaolinite, and quartz or amorphous silica in 2M KCl solutions for 43 to 176 d. Post-experiment solution compositions lie either within the illite(0.88 K) stability field or on the illite(0.88 K)-kaolinite or illite(0.88 K)-diaspore univariant boundaries in log (a{sub K}{sup +}/a{sub H}{sup +}) vs. log a{sub H{sub 4}SiO{sub 4}} activity space. Transmission electron microscopy (TEM) observations of muscovite grain edges reveal the neoformation of illite crystals with a range of compositions (ATEM) from 0.31 to 0.89 K/O{sub 10}(OH){sub 2}. The range of K-contents appears to narrow toward 0.88 K/O{sub 10}(OH){sub 2} with increased experiment duration. HRTEM suggests the presence of 2 to 11 layer fundamental particles composed of illitic layers with 10 A periodicity. Fundamental particle thicknesses increase toward an average of 8 layers/particle with increased experiment duration. In the longer duration experiments, fundamental particle thicknesses were normally distributed about thicknesses of 4 and 8 layers, whereas fundamental particles with thicknesses <4 layers were common in a shorter duration experiment. The compositions and structure of the illites are consistent with the multiphase model, which states that the smectite-to-illite transition occurs through the step-wise formation of solubility-controlling phases consisting of fundamental particles with thicknesses of 1, 2, 4, and {le}8 layers. The increase in K-content and fundamental particle thickness with the extent of reaction suggests that the illite crystals underwent a prograde reaction culminating in the formation of end-member illite [0.88 K/O{sub 10}(OH){sub 2}]. This reaction, in conjunction with the previously observed, retrograde reaction from muscovite to end-member illite, demonstrates the stability of end-member illite in the system K{sub 2}O-Al{sub 2}O{sub 3}-SiO{sub 2}H{sub 2}O at 250 C.

Yates, D.M.; Rosenberg, P.E. [Washington State Univ., Pullman, WA (United States). Dept. of Geology

1998-11-01

31

HRTEM Study of Oxide Nanoparticles in K3-ODS Ferritic Steel Developed for Radiation Tolerance  

SciTech Connect

Crystal and interfacial structures of oxide nanoparticles and radiation damage in 16Cr-4.5Al-0.3Ti-2W-0.37 Y{sub 2}O{sub 3} ODS ferritic steel have been examined using high-resolution transmission electron microscopy (HRTEM) techniques. Oxide nanoparticles with a complex-oxide core and an amorphous shell were frequently observed. The crystal structure of complex-oxide core is identified to be mainly monoclinic Y{sub 4}Al{sub 2}O{sub 9} (YAM) oxide compound. Orientation relationships between the oxide and the matrix are found to be dependent on the particle size. Large particles (> 20 nm) tend to be incoherent and have a spherical shape, whereas small particles (< 10 nm) tend to be coherent or semi-coherent and have a faceted interface. The observations of partially amorphous nanoparticles and multiple crystalline domains formed within a nanoparticle lead us to propose a three-stage mechanism to rationalize the formation of oxide nanoparticles containing core/shell structures in as-fabricated ODS steels. Effects of nanoparticle size and density on cavity formation induced by (Fe{sup 8+} + He{sup +}) dual-beam irradiation are briefly addressed.

Hsiung, L; Fluss, M; Tumey, S; Kuntz, J; El-Dasher, B; Wall, M; Choi, W; Kimura, A; Willaime, F; Serruys, Y

2009-11-02

32

TEM and HRTEM studies of ball milled 6061 aluminium alloy powder with Zr addition.  

PubMed

The effect of mechanical alloying on the microstructure of atomized 6061 aluminium alloy powder and 6061 powder with a zirconium addition was studied in the work. The atomized 6061 aluminium alloy powder and 6061 powder with addition of 2 wt.% Zr were milled in a planetary ball mill and investigated using X-ray diffraction measurements, conventional and high-resolution electron microscopy (TEM/HRTEM) and high-angle annular dark field scanning transmission electron microscopy combined with energy dispersive X-ray microanalysis. An increase of stresses was observed in milled powders after the refinement of crystallites beyond 100 nm. In the powder with zirconium addition, some part of the Zr atoms diffused in aluminium forming a solid solution containing up to 0.5 wt.% Zr. The remaining was found to form Zr-rich particles containing up to 88 wt.% Zr and were identified as face centred cubic (fcc) phase with lattice constant a= 0.48 nm. That fcc phase partially transformed into the L1(2) ordered phase. Eighty-hour milling brought an increase of microhardness (measured with Vickers method) from about 50 HV (168 MPa) for the initial 6061 powder to about 170 HV (552 MPa). The addition of zirconium had no influence on the microhardness. PMID:20500426

Lity?ska-Dobrzy?ska, L; Dutkiewicz, J; Maziarz, W; Rogal, ?

2010-03-01

33

Structure, magnetic and dielectric properties of nanocrystalline Se-xFe  

NASA Astrophysics Data System (ADS)

Nanocrystalline Se-xFe (x = 3 and 5 wt%) samples were prepared by solid state reaction. XRD revealed the presence of two phases; FeSe2 and Se. HRTEM showed the epitaxial growth of FeSe2 on Se. The magnetization measurements showed ferromagnetic behavior above room temperature for sample with x = 5 wt%. The a.c. conductivity for x = 3 wt% follows the overlapping large polaron tunneling model, while for (x = 5 wt%) sample it follows the correlated barrier hoping model. The temperature dependence of the dielectric measurements revealed an anomaly above room temperature for (x = 5 wt%) sample, while it appeared at room temperature for (x = 3 wt%) sample.

EL-Sayed, Karimat; Mohamed, Mohamed Bakr; Heiba, Z. K.; Al-Nabriss, A. R.

2014-11-01

34

Magnetic silica spheres with large nanopores for nucleic acid adsorption and cellular uptake.  

PubMed

Template assisted fabrication of magnetic silica nanospheres with large nanopores (MSNLP) and their adsorption and delivery of nucleic acids are reported in this paper. Silica spheres with controlled particle diameter (~400 nm) and large nanopore size (13-24 nm) are prepared by using Brij56 as a template of mesopore, enabling incorporation of magnetic nanocrystals into the particles under mild neutral synthesis conditions. High resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), and field-dependent magnetisation measurements confirm that the magnetic nanocrystals have been encapsulated into the silica spheres. The saturation magnetisation values of the resulted magnetic-silica nanocomposites are tunable by adjusting the amount of Fe(3)O(4) magnetic nanocrystals used in the synthesis process. The nitrogen sorption analysis reveals that mesopores with large pore size exist in the silica matrix. After functionalisation of the silica surface with poly-(l-lysine) (PLL), the nanoparticles show strong adsorption capacity (q(m) ranging from 10 to 22.5 ?g/mg) for CpG DNA. We have further demonstrated successful delivery of miRNA into rat proximal tubular epithelial cells, facilitated by efficient cellular uptake of the nanocomposites. This work provides a convenient strategy to prepare MSNLP which can offer a versatile platform for biological applications such as simultaneous drug delivery and magnetic resonance imagining under external magnetic field. PMID:22019119

Liu, Jian; Wang, Bo; Hartono, Sandy Budi; Liu, Tingting; Kantharidis, Phillip; Middelberg, Anton P J; Lu, Gao Qing Max; He, Lizhong; Qiao, Shi Zhang

2012-01-01

35

HRTEM study of track evolution in 120-MeV U irradiated Gd2Ti2O7  

SciTech Connect

High resolution Scanning Transmission Electron Microscopy (HRTEM) experiments were performed on Gd2Ti2O7 pyrochlores irradiated with 120-MeV U ions. A judicious choice of irradiation energy, sample preparation (using Focused Ion Beam) and analytical technique (HRTEM) allowed us to visualize the complete evolution of tracks from the surface of samples down to depths exceeding the projected range of irradiating ions. Such features as variation of track diameters, changes in track directions and discontinuous segments of tracks were clearly documented at various depths. By using two different STEM imaging modes: High- and Low-Angle Annular Dark Field imaging (HAADF and LAADF), it was possible to observe the layered structure of tracks composed of an amorphous core surrounded by a strained crystalline envelope.

Jozwik Biala, Iwona; Jagielski, Jacek K.; Thome, Lionel; Arey, Bruce W.; Kovarik, Libor; Sattonay, G.; Debelle, A.; Monnet, I.

2012-09-01

36

HRTEM image contrast and atomistic microstructures of long-period ordered Al-rich TiAl alloys.  

PubMed

Long-period superstructures formed in off-stoichiometric L 1(0)-TiAl alloys were investigated by high-resolution transmission electron microscopy (HRTEM). The HRTEM analysis combined with multislice simulation and image processing was carried out to clarify atomistic microstructures of Al5Ti3 and h-Al2Ti ordered states and a short-range ordered (SRO) state in Ti-62.5 at.% Al alloys. Aluminium atoms in the (002) Ti layers form square-, lean rhombus- and fat rhombus-type ordered clusters in the SRO state. The ordered clusters are in contact with each other and form microdomains of various long-period superstructures. The ordered clusters are tiled periodically in a long range to form Al5Ti3 or h-Al2Ti domains and characteristic antiphase boundary structures. PMID:15077893

Hata, Satoshi; Higuchi, Kiyoshi; Mitate, Toshitsugu; Itakura, Masaru; Tomokiyo, Yoshitsugu; Kuwano, Noriyuki; Nakano, Takayoshi; Nagasawa, Yosuke; Umakoshi, Yukichi

2004-01-01

37

Chemical characterization of soot particles emitted by Wood-Burning Cook Stoves: A XPS and HRTEM study  

NASA Astrophysics Data System (ADS)

The morphology, microstructure, chemical composition, and electronic structure of soot particles emitted directly from biofuel cook stoves have been studied by high resolution transmission electron microscopy (HRTEM) and X-ray photoelectron spectroscopy (XPS). In order to obtain freshly emitted soot particles, copper grids for Transmission Electron Microscope (TEM) were placed on the last two of an 8-stages MOUDI cascade impactor. The analysis of HRTEM micrographs revealed the nanostructure and the particle size of soot chain. Additionally, the morphology of soot particles was analyzed calculating the border-based fractal dimension (Df). Particles sampled on the first heating stage exhibit complex shapes with high values of Df, which are present as aggregates formed by carbon ceno-spheres. The XPS survey spectrum for soot particles shows that the main particle composition is carbon. We also observed differences in the carbon/oxygen (C/O) ratio of the particles, which probably depends on the combustion process efficiency of each cook-stove analyzed. The XPS C-1s spectra show carbon with two peaks that correspond to sp2 and sp3 hybridization. Also, real-time absorption (?a) and scattering (?s) coefficients of the particles emitted by cook stoves were measured. The trend in ?a and ?s indicate that the cooking process has two important combustion stages which varied in its flaming strength, being vigorous in the first stage and soft in the second one.

Carabali, Giovanni; Peralta, Oscar; Castro, Telma; Torres, Ricardo; Ruiz, Gerardo; Molina, Luisa; Saavedra, Isabel

2014-05-01

38

Earliest stages of crystal growth in a silicate glass containing titanium and zirconium as nucleating elements — HRTEM and XAS study  

NASA Astrophysics Data System (ADS)

The earliest stages of crystallization have been studied for a SiO 2-Al 2O 3-Li 2O glass-ceramics containing a few percent of titanium and zirconium as nucleating elements. After heat treatments at temperatures ranging between T=750°C and T=860°C, the growth process has been studied by combining HRTEM (high resolution transmission electron microscopy) and XAS (X-ray absorption spectrometry). A fine phase separation has been found in the parent glass (? 7 nm in size) independent of the presence of the nucleating elements. From HRTEM, the earliest crystalline phase has been definitely stated as being TiZrO 4. The incorporation of titanium atoms into TiZrO 4 crystals is correlated with a change of their coordinance from 4 to 6, directly evidenced in XAS spectra by the "prepeak" analysis at titanium K-edge. The crystallization of the aluminosilicate occurs after full precipitation of TiZrO 4. In glass ceramics, the number of aluminosilicate and TiZrO 4 crystals per unit volume are nearly equal, in good agreement with heterogeneous nucleation of the silicate solid solution on TiZrO 4 crystals. For samples heat treated at 750°C and 780°C, the number of TiZrO 4 crystallites is constant for a given temperature. These crystallites grow until the matrix becomes free of zirconium atoms. Their growth activation energy has been found to be 400±50 kJ/mol.

Ramos, A.; Gandais, M.

1990-03-01

39

Anomalous magnetic behavior of La0.6Sr0.4MnO3 nano-tubes constituted with 3-12 nm particles  

NASA Astrophysics Data System (ADS)

Uniform La0.6Sr0.4MnO3 (LSMO) nanotubes of an average diameter 180 nm were synthesized by a modified sol-gel method employing nanochannel porous anodic alumina templates. The nanotubes were characterized chemically and structurally by XRD, SEM, EDX, and TEM. Postannealed (700 °C for 1 h hour) nanotubes were found to be polycrystalline from XRD and SAED studies. To get further insight into the nanotube structure, HRTEM studies were done, which revealed that obtained LSMO nanotubes were structurally constituted with nanoparticles of 3-12 nm size. These constituent nanoparticles were randomly aligned and self-knitted to build the nanotube wall. Investigation of magnetic properties at this structured nanoscale revealed remarkable irreversibility between the zero field cooling (ZFC) and field cooling (FC) magnetization curves accompanied with a peak in the ZFC curve indicating spin-glass-like behavior. Structural defects and compositional variations at surfaces and grain-boundaries of constituent nanoparticles might be responsible for this anomalous magnetic behavior.

Banerjee, Nirupam; Krupanidhi, S. B.

2013-05-01

40

An introduction to XRD using the MSA Crystal Structure Database  

NSDL National Science Digital Library

This is a variant on a traditional mineralogy XRD lab with a few twists: 1. Rather than use "black box" search software or IPCC cards, the lab outlines a procedure for students to identify their patterns using the MSA online database with the following benefits: a. This allows the flexibility to have students do this work alone or in groups, in lab or on their own time. This can be an advantage at institutions where the XRD is not as accessible for individual student use as we might like. b. Identifying the powder pattern requires trial and error and thinking about the data, rather than simply putting faith in a search/match routine. Students have to exercise judgement as they proceed. 2. I use samples that students have already characterized by other means. Recently I have chosen samples that students have identified in optical labs. In particular we have a Mn-rich tourmaline sample with no pleochroism that students routinely identify as apatite. By revisiting the same sample in the XRD lab students are able to test and revise hypotheses they have made using other means. This also provides them with an important filter in finding matches for their pattern, and make the job more tractable. 3. Samples should be chosen that are of relatively high symmetry to make estimating unit cell dimensions feasible. Students can use reference books to relate unit cell dimensions to solid solutions. The lab could be extended to use a statistical treatment of the unit cell dimensions determined from different peaks.

Page, Zeb

41

Photoluminescence Spectra and Magnetic Properties of Hydrothermally Synthesized MnO2 Nanorods  

NASA Astrophysics Data System (ADS)

In this paper, single crystalline tetragonal MnO2 nanorods have been synthesized by a simple hydrothermal method using MnSO4? H2O and Na2S2O8 as precursors. The crystalline phase, morphology, particle sizes and component of the as-prepared nanomaterial were characterized by employing X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SAED) and energy-dispersive X-ray spectroscopy (EDS). The photoluminescence (PL) emission spectrum of MnO2 nanorods at room temperature exhibited a strong ultraviolet (UV) emission band at 380 nm, a prominent blue emission peak at 453 nm as well as a weak defect related green emission at 553 nm. Magnetization (M) as a function of applied magnetic field (H) curve showed that MnO2 nanowires exhibited a superparamagnetic behavior at room temperature which shows the promise of synthesized MnO2 nanorods for applications in ferrofluids and the contrast agents for magnetic resonance imaging. The magnetization versus temperature curve of the as-obtained MnO2 nanorods shows that the Néel transition temperature is 94 K.

Toufiq, Arbab Mohammad; Wang, Fengping; Javed, Qurat-Ul-Ain; Li, Quanshui; Li, Yan

2013-10-01

42

4-D XRD for strain in many grains using triangulation  

SciTech Connect

Determination of the strains in a polycrystalline materialusing 4-D XRD reveals sub-grain and grain-to-grain behavior as a functionof stress. Here 4-D XRD involves an experimental procedure usingpolychromatic micro-beam X-radiation (micro-Laue) to characterizepolycrystalline materials in spatial location as well as with increasingstress. The in-situ tensile loading experiment measured strain in a modelaluminum-sapphire metal matrix composite using the Advanced Light Source,Beam-line 7.3.3. Micro-Laue resolves individual grains in thepolycrystalline matrix. Results obtained from a list of grains sorted bycrystallographic orientation depict the strain states within and amongindividual grains. Locating the grain positions in the planeperpendicular to the incident beam is trivial. However, determining theexact location of grains within a 3-D space is challenging. Determiningthe depth of the grains within the matrix (along the beam direction)involved a triangulation method tracing individual rays that producespots on the CCD back to the point of origin. Triangulation wasexperimentally implemented by simulating a 3-D detector capturingmultiple diffraction images while increasing the camera to sampledistance. Hence by observing the intersection of rays from multiple spotsbelonging to the corresponding grain, depth is calculated. Depthresolution is a function of the number of images collected, grain to beamsize ratio, and the pixel resolution of the CCD. The 4DXRD methodprovides grain morphologies, strain behavior of each grain, andinteractions of the matrix grains with each other and the centrallylocated single crystal fiber.

Bale, Hrishikesh A.; Hanan, Jay C.; Tamura, Nobumichi

2006-12-31

43

Porosity investigation of compacted bentonite using XRD profile modeling.  

PubMed

Many countries intend to use compacted bentonite as a barrier in their deep geological repositories for nuclear waste. In order to describe and predict hydraulic conductivity or radionuclide transport through the bentonite barrier, fundamental understanding of the microstructure of compacted bentonite is needed. This study examined the interlayer swelling and overall microstructure of Wyoming Bentonite MX-80 and the corresponding homo-ionic Na(+) and Ca(2+) forms, using XRD with samples saturated under confined swelling conditions and free swelling conditions. For the samples saturated under confined conditions, the interparticle, or so-called free or external porosity was estimated by comparing the experimental interlayer distances obtained from one-dimensional XRD profile fitting against the maximum interlayer distances possible for the corresponding water content. The results showed that interlayer porosity dominated total porosity, irrespective of water content, and that the interparticle porosity was lower than previously reported in the literature. At compactions relevant for the saturated bentonite barrier (1.4-1.8 g/cm(3)), the interparticle porosity was estimated to ?3%. PMID:22192342

Holmboe, Michael; Wold, Susanna; Jonsson, Mats

2012-02-01

44

Magnetic composite BiOCl-SrFe12O19: a novel p-n type heterojunction with enhanced photocatalytic activity.  

PubMed

The magnetic composite BiOCl-SrFe12O19, a novel p-n type heterojunction was synthesized by hydrolysis with a medium temperature sintering method. The microstructure and magnetic properties of the prepared material were characterized by FTIR, XRD, SEM, TEM, HRTEM, SAED, and VSM. The results showed the [001] facet of BiOCl with high photocatalytic activity was exposed in the BiOCl-SrFe12O19. The heterostructured BiOCl-SrFe12O19 had better magnetic properties, contributing to its reuse and improvement in photocatalysis. Moreover, the composite was blessed with excellent photocatalytic activity and stability. In the BiOCl-SrFe12O19 system, SrFe12O19 not only inhibited the growth of BiOCl along the [001] direction to enhance the exposure of the [001] wafer, but also acted as a sensitizer absorbing light irradiation. The magnetic field generated from SrFe12O19 made BiOCl, under light irradiation, produce more photo-induced electrons and holes and simultaneously hampered their recombination. For the first time we propose the possible mechanism of how to enhance photocatalytic activity by a magnetic field effect originating from the magnetic photocatalyst itself. PMID:24297101

Xie, Taiping; Xu, Longjun; Liu, Chenglun; Yang, Jun; Wang, Mei

2014-02-01

45

A Combined XRD/XRF Instrument for Lunar Resource Assessment  

NASA Technical Reports Server (NTRS)

Robotic surface missions to the Moon should be capable of measuring mineral as well as chemical abundances in regolith samples. Although much is already known about the lunar regolith, our data are far from comprehensive. Most of the regolith samples returned to Earth for analysis had lost the upper surface, or it was intermixed with deeper regolith. This upper surface is the part of the regolith most recently exposed to the solar wind; as such it will be important to resource assessment. In addition, it may be far easier to mine and process the uppermost few centimeters of regolith over a broad area than to engage in deep excavation of a smaller area. The most direct means of analyzing the regolith surface will be by studies in situ. In addition, the analysis of the impact-origin regolith surfaces, the Fe-rich glasses of mare pyroclastic deposits, are of resource interest, but are inadequately known; none of the extensive surface-exposed pyroclastic deposits of the Moon have been systematically sampled, although we know something about such deposits from the Apollo 17 site. Because of the potential importance of pyroclastic deposits, methods to quantify glass as well as mineral abundances will be important to resource evaluation. Combined x ray diffraction (XRD) and x ray fluorescence (XRF) analysis will address many resource characterization problems on the Moon. XRF methods are valuable for obtaining full major-element abundances with high precision. Such data, collected in parallel with quantitative mineralogy, permit unambiguous determination of both mineral and chemical abundances where concentrations are high enough to be of resource grade. Collection of both XRD and XRF data from a single sample provides simultaneous chemical and mineralogic information. These data can be used to correlate quantitative chemistry and mineralogy as a set of simultaneous linear equations, the solution of which can lead to full characterization of the sample. The use of Rietveld methods for XRD data analysis can provide a powerful tool for quantitative mineralogy and for obtaining crystallographic data on complex minerals.

Vaniman, D. T.; Bish, D. L.; Chipera, S. J.; Blacic, J. D.

1992-01-01

46

Effect of calcination temperature on microstructure and magnetic properties of Ni0.5Zn0.25Cu0.25 Fe2O4 nanoparticles synthesized by sol-gel method  

NASA Astrophysics Data System (ADS)

This paper examines the effect of calcination process on the structural and magnetic properties material nanostructure composite of Ni0?5Zn0?25Cu0.25 Fe2O4 ferrites. The samples were successfully prepared by sol-gel method at different calcination temperature, which are 600°C, 700°C, 800°C and 900°C. Morphological investigation, average crystallite size and microstructure of the material were examined by using X-ray diffraction (XRD) and confirmed by high resolution transmission electron microscope (HRTEM) and field emission scanning electron microscope (FESEM). The effects of calcination temperature on the magnetic properties were calculated by using vibrating sample magnetometer (VSM). The XRD result shows single-phase cubic spinel structure with interval average size 5.9-38 nm, and grain size microstructure of the material was increasing with temperature increases. The highest magnetization saturation was reached at a temperature 800°C with value 53.89 emu/g, and the value coercive force (Hc) was inversely with the grain size.

Pransisco, Prengki; Shafie, Afza; Guan, Beh Hoe

2014-10-01

47

Magnetic properties of MBE-grown Zn1-xCrxTe  

NASA Astrophysics Data System (ADS)

We have grown Zn1-xCrxTe films by molecular-beam-epitaxy (MBE) and investigated their magnetic properties with variation of Cr concentrations (x) between 0.01-0.08. Systematic increase of the lattice constant was observed by XRD only up to around x = 0.02. Measurements of the magnetizations M-H reveal that ferromagnetic transition occurs in the films at low temperatures. The transition temperature (TC) which was estimated from Arrott-plots increased with Cr concentration up to about 100 K for x = 0.08. However, the temperature dependence of the magnetization M-T shows different curves below TC for field-cooled (FC) and zero-field-cooled (ZFC) processes. Moreover, their paramagnetic Curie temperatures (), estimated from the higher temperature M-T curves, are different from and much higher than TC. These behaviours could be attributed to the superparamagnetism in the films. Indeed, many defects such as stacking faults are observed in the sample with x = 0.08 through HRTEM. It could give rise to the distribution of the Cr concentrations and/or the presence of precipitates including Cr.

Ozaki, N.; Nishizawa, N.; Nam, K.-T.; Kuroda, S.; Takita, K.

2004-03-01

48

Interface characterization of XUV multilayer reflectors using HRTEM (high-resolution transmission electron microscopy) and x-ray and XUV reflectance  

Microsoft Academic Search

We have examined the structure of XUV multilayer coatings using high-resolution transmission electron microscopy (HRTEM). Using a variety of techniques, we have measured the interface widths and the interface topography from the digitized TEM images, and have compared these results to x-ray and XUV reflectance measurements. We find that the structural parameters measured from the TEM images and those deduced

D. L. Windt; R. Hull; W. K. Waskiewicz; J. B. Kortright

1990-01-01

49

Determining the molecular weight distribution of Pocahontas No. 3 low-volatile bituminous coal utilizing HRTEM and laser desorption ionization mass spectra data  

Microsoft Academic Search

Knowledge of the molecular weight distribution is important for rationalizing coal behavior. While many analytical approaches generate average data, inclusion of coal’s inherent structural diversity would improve molecular representations of coal and their usefulness. The molecular weight distribution of Pocahontas No. 3 coal was estimated based on a new approach coupling HRTEM lattice fringe image data and laser desorption ionization

Jonathan P. Mathews; Victor Fernandez-Also; A. Daniel Jones; Harold H. Schobert

2010-01-01

50

Practical aspects of the use of the X(2) holder for HRTEM-quality TEM sample preparation by FIB.  

PubMed

The X(2) holder enables the effective production of thin, electron transparent samples for high-resolution transmission electron microscopy (HRTEM). Improvements to the X(2) holder for high-quality transmission electron microscopy (TEM) sample preparation are presented in this paper. We discuss the influence of backscattered electrons (BSE) from the sample holder in determining the lamella thickness in situ and demonstrate that a significant improvement in thickness determination can be achieved by comparatively simple means using the relative BSE intensity. We show (using Monte Carlo simulations) that by taking into account the finite collection angle of the electron backscatter detector, an approximately 20% underestimation of the lamella thickness in a silicon sample can be avoided. However, a correct thickness determination for light-element lamellas still remains a problem with the backscatter method; we introduce a more accurate method using the energy dispersive X-ray spectroscopy (EDX) signal for in situ thickness determination. Finally, we demonstrate how to produce a thin lamella with a nearly damage-free surface using the X(2) holder in combination with sub-kV polishing in the Fischione Instruments? NanoMill(®) TEM specimen preparation system. PMID:25194827

van Mierlo, Willem; Geiger, Dorin; Robins, Alan; Stumpf, Matthias; Ray, Mary Louise; Fischione, Paul; Kaiser, Ute

2014-12-01

51

Coaxial-Electrospun Magnetic Core-Shell Fe@TiSi Nanofibers for the Rapid Purification of Typical Dye Wastewater.  

PubMed

Magnetic mesoporous ?-Fe2O3@Ti0.9Si0.1O2 (abbreviated as Fe@TiSi) core-shell nanofibers were prepared using sol-gel chemistry combined with coaxial-electrospinning technology by adjusting the inner and outer feed ratios. The properties of these novel core-shell nanofibers were characterized by SEM, HRTEM, XRD, FTIR, BET, XPS, and UV-vis spectra. To evaluate the chemical properties of the nanofibers for cleaning typical organic wastewater, methylene blue (MB) was used as a target organic pollutant and was cleaned under irradiation with sunlight and visible light. The Fe@TiSi hierarchical nanofibers composed of a 1:10 feed ratio displayed a mesoporous structure and showed the highest photocatalytic activity for the degradation of MB in water. Furthermore, 86.8% and 71.1% of the MB, which was added at an original concentration of 1 mg/L, was removed after 60 min of irradiation with sunlight and visible light in the presence of Fe@TiSi at a concentration of 0.2 g/L, and 100% of the MB was removed after 75 min. It is very important that the magnetic nanofibers could be recycled rapidly with an outside magnet, and the actual water treatment process was easy to achieve. Moreover, the mechanism of MB degradation by Fe@TiSi core-shell nanofibers was proposed. PMID:25226354

Zhan, Sihui; Zhu, Dandan; Ren, Guangyuan; Shen, Zhiqiang; Qiu, Mingying; Yang, Shanshan; Yu, Hongbing; Li, Yi

2014-10-01

52

Interplay of bulk and surface on the magnetic properties of low temperature synthesized nanocrystalline cubic Cu1-xZnxFe2O4 (x=0.00, 0.02, 0.04 and 0.08)  

NASA Astrophysics Data System (ADS)

Synthesis of Cu1-xZnxFe2O4, (x=0.00, 0.02, 0.04 and 0.08) nanoparticles by a low-temperature combustion method is achieved and its structural and magnetic characterizations are performed. X-ray powder diffraction (XRD) study and high resolution transmission electron microscope (HRTEM) images confirm the formation of single cubic phase of nanocrystalline copper ferrite. The inter-planar spacing (d) and particle size increases with increasing Zn content. Cation distribution of mixed spinel Cu1-xZnxFe2O4 nanoparticles are estimated by Fourier transformed infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS) and further verified by 57Fe Mo¨ssbauer spectroscopy. Detailed magnetic properties are studied by means of Field Cooled (FC) - Zero Field Cooled (ZFC) magnetization measurements and hysteresis loops at various temperatures by the physical property measurement system (PPMS). A transition from superparamagnetic state to ferrimagnetic state is observed as the Zn concentration increases in Cu1-xZnxFe2O4 nanoparticles. The temperature dependence of intrinsic magnetic parameters, i.e., coercivity (HC), saturation magnetization (MS), effective anisotropy constant (Keff) and paramagnetic susceptibility (?p) of Cu1-xZnxFe2O4 reveals the existence of low-temperature spin-glass-like state, which is more prominent for smaller particles and starts to disappear with increasing Zn concentration.

Chatterjee, Biplab K.; Dey, Abhishek; Ghosh, Chandan K.; Chattopadhyay, Kalyan K.

2014-10-01

53

Magnetism  

NSDL National Science Digital Library

This webpage is part of the University Corporation for Atmospheric Research (UCAR) Windows to the Universe program. It describes the nature and configuration of magnetic fields, which are the result of moving electric charges, including how they cause magnetic objects to orient themselves along the direction of the magnetic force points, which are illustrated as lines. Magnetic field lines by convention point outwards at the north magnetic pole and inward at the south magnetic pole. The site features text, scientific illustrations and an animation. Text and vocabulary are selectable for the beginning, intermediate, or advanced reader.

Team, University C.

2007-12-12

54

Crystal structure of La{sub 0.4}Sr{sub 0.6}CoO{sub 2.71} investigated by TEM and XRD  

SciTech Connect

The structure of the oxygen-deficient perovskite La{sub 0.4}Sr{sub 0.6}CoO{sub 3-{delta}} ({delta}=0.29) was investigated by transmission electron microscopy (TEM) and X-ray powder diffraction (XRD). Domains between 50 and 250 nm in size were observed in the electron microscope. Weak superstructure reflections were found with both X-ray and electron diffraction. Investigations of these superstructure reflections by selected area electron diffraction (SAED) and convergent beam electron diffraction (CBED) showed that the domains in a crystal are orientated in a 90 deg. relationship. High-resolution transmission electron microscopy (HRTEM) images from the domain boundary also revealed a 90 deg. orientation dependency. Using the symmetry of CBED patterns, the point group 4/mmm was determined. By comparing reflections from the SAED pattern with possible reflections, the space group I4/mmm (No. 139) could be isolated and finally the crystal structure was refined by Rietveld refinement. - Graphical abstract: Two adjacent domains show different orientation of the c-axis of the tetragonal unit cell in the according convergent beam electron diffraction patterns.

Gspan, C. [Institute for Electron Microscopy and Fine Structure Research, Graz University of Technology, Steyrergasse 17, A-8010 Graz (Austria); Centre for Electron Microscopy Graz, Steyrergasse 17, A-8010 Graz (Austria)], E-mail: christian.gspan@felmi-zfe.at; Grogger, W. [Institute for Electron Microscopy and Fine Structure Research, Graz University of Technology, Steyrergasse 17, A-8010 Graz (Austria); Centre for Electron Microscopy Graz, Steyrergasse 17, A-8010 Graz (Austria); Bitschnau, B. [Institute of Physical and Theoretical Chemistry, Graz University of Technology, Technikerstrasse 4, A-8010 Graz (Austria); Bucher, E.; Sitte, W. [Department of General, Analytical and Physical Chemistry, University of Leoben, Franz-Josef-Strasse 18, A-8700 Leoben (Austria); Hofer, F. [Institute for Electron Microscopy and Fine Structure Research, Graz University of Technology, Steyrergasse 17, A-8010 Graz (Austria); Centre for Electron Microscopy Graz, Steyrergasse 17, A-8010 Graz (Austria)

2008-11-15

55

Structural and magnetic properties of pristine and Fe-doped NiO nanoparticles synthesized by the co-precipitation method  

SciTech Connect

Highlights: ? The prepared samples were characterized by XRD, TEM, HR-TEM techniques. ? Magnetic properties of the samples were compared. ? Surface spins frozen at lower temperatures resulted a spin glass. ? The samples show enhancement of coercivity with decreased temperature. -- Abstract: Ni{sub 1?x}Fe{sub x}O (x = 0 and 0.03) nanoparticles are synthesized by a chemical route. XRD and TEM measurements confirm phase purity and crystallinity of the nanoparticles. Fe substitution in NiO reduces considerably the average particle size of the nanoparticles. The pristine NiO sample with size 14 nm and Fe-substituted sample having size 7 nm show room temperature ferromagnetism. The pristine NiO having 31 nm size and Fe-substituted sample with size 25 nm are found to be antiferromagnetic. The M–H and M–T behavior of the pristine and Fe-doped samples are explained with a core–shell model with an antiferromagnetic core and a ferromagnetic shell. The disordered spins at the shell give rise to a spin-glass like frozen state below 10 K. The obtained room temperature ferromagnetism in the pristine and Fe-doped NiO has been attributed to particle size effect.

Mishra, A.K. [UGC-DAE Consortium for Scientific Research, Kolkata Centre, III/LB-8, Bidhannagar, Kolkata 70098 (India)] [UGC-DAE Consortium for Scientific Research, Kolkata Centre, III/LB-8, Bidhannagar, Kolkata 70098 (India); Bandyopadhyay, S. [Department of Physics, University College of Science, 92, A P C Road, Kolkata 700009 (India)] [Department of Physics, University College of Science, 92, A P C Road, Kolkata 700009 (India); Das, D., E-mail: ddas@alpha.iuc.res.in [UGC-DAE Consortium for Scientific Research, Kolkata Centre, III/LB-8, Bidhannagar, Kolkata 70098 (India)

2012-09-15

56

Novel Sample-handling Approach for XRD Analysis with Minimal Sample Preparation  

NASA Technical Reports Server (NTRS)

Sample preparation and sample handling are among the most critical operations associated with X-ray diffraction (XRD) analysis. These operations require attention in a laboratory environment, but they become a major constraint in the deployment of XRD instruments for robotic planetary exploration. We are developing a novel sample handling system that dramatically relaxes the constraints on sample preparation by allowing characterization of coarse-grained material that would normally be impossible to analyze with conventional powder-XRD techniques.

Sarrazin, P.; Chipera, S.; Bish, D.; Blake, D.; Feldman, S.; Vaniman, D.; Bryson, C.

2004-01-01

57

Determination of size distributions in nanosized powders by TEM, XRD, and SAXS  

Microsoft Academic Search

Crystallite size distributions and particle size distributions were determined by transmissions electron microscopy (TEM), X-ray powder diffraction (XRD), and small-angle X-ray scattering (SAXS) for three commercially available TiO2 powders (P25, UV100, and TiO2_5?nm) and one SSEC produced powder (SSEC78). The theoretical Guinier model was fitted to the experimental obtained XRD data and compared to analytical expressions. Modeling of the XRD

H. Jensen; J. H. Pedersen; J. E. Jørgensen; J. Skov Pedersen; K. D. Joensen; S. B. Iversen; E. G. Søgaard

2006-01-01

58

Magnetism  

NSDL National Science Digital Library

This radio broadcast discusses the history of magnetism from the time of its discovery by an apocryphal Greek sheperd until the late 16th century and the work of William Gilbert. There is also discussion of who pioneered the study of magnetism, what theories they constructed from its curious abilities, and how the power of the magnet was brought out of the realm of magic and into the service of science. The broadcast concludes with a discussion of why magnetism is still mysterious and how the modern search for the single magnetic pole, or magnetic monopole, could provide a fundamental unit of magnetism, essential for ultimate explanation. The broadcast is 41 minutes and 45 seconds in length.

2010-10-27

59

Equilibrium and kinetic studies on acid dye Acid Red 88 adsorption by magnetic ZnFe2O4 spinel ferrite nanoparticles.  

PubMed

A magnetic ZnFe2O4 (MNZnFe) was synthesized by microwave assisted hydrothermal method and was used as an adsorbent for the removal of acid dye Acid Red 88 (AR88) from aqueous solution. The effects of various parameters such as initial AR88 concentration (10-56 mg L(-1)), pH solution (3.2-10.7), and temperature (20-60°C) were investigated. Prepared magnetic ZnFe2O4 was characterized by XRD, SEM, HRTEM, ICP-AES, BET, FTIR, and measurements of the magnetic susceptibility. The experimental data were analyzed by the Langmuir and Freundlich models of adsorption. Equilibrium data fitted well with the Langmuir model. Pseudo-first-order and pseudo-second-order kinetic models and intraparticle diffusion model were used to examine the adsorption kinetic data. The adsorption kinetics was found to follow the pseudo-second-order kinetic model. Thermodynamics parameters, ?G°, ?H° and ?S°, indicate that the adsorption of AR88 onto MNZnFe was spontaneous and exothermic in nature. PMID:23506747

Konicki, Wojciech; Sibera, Daniel; Mijowska, Ewa; Lendzion-Bielu?, Zofia; Narkiewicz, Urszula

2013-05-15

60

Nanoscale chemical and structural study of Co-based FEBID structures by STEM-EELS and HRTEM  

PubMed Central

Nanolithography techniques in a scanning electron microscope/focused ion beam are very attractive tools for a number of synthetic processes, including the fabrication of ferromagnetic nano-objects, with potential applications in magnetic storage or magnetic sensing. One of the most versatile techniques is the focused electron beam induced deposition, an efficient method for the production of magnetic structures highly resolved at the nanometric scale. In this work, this method has been applied to the controlled growth of magnetic nanostructures using Co2(CO)8. The chemical and structural properties of these deposits have been studied by electron energy loss spectroscopy and high-resolution transmission electron microscopy at the nanometric scale. The obtained results allow us to correlate the chemical and structural properties with the functionality of these magnetic nanostructures. PMID:22085532

2011-01-01

61

Magnetism  

NSDL National Science Digital Library

This overview of magnetism provides a brief history prior to 1600 and continues with the work of William Gilbert, Hans Christian Oersted, and Andre-Marie Ampere in describing and exploring the magnetosphere and learning the role that electric current plays in producing magnetism. Magnetic field lines are then discussed, citing the work of Michael Faraday. The work of James Clerk Maxwell and Heinrich Hertz is mentioned in a discussion of the relationship of light waves and radio waves as part of the electromagnetic spectrum.

Stern, David

62

Interface characterization of XUV multilayer reflectors using HRTEM (high-resolution transmission electron microscopy) and x-ray and XUV reflectance  

SciTech Connect

We have examined the structure of XUV multilayer coatings using high-resolution transmission electron microscopy (HRTEM). Using a variety of techniques, we have measured the interface widths and the interface topography from the digitized TEM images, and have compared these results to x-ray and XUV reflectance measurements. We find that the structural parameters measured from the TEM images and those deduced from reflectance are consistent in light of the probable systematic errors associated with the measurement and interpretation techniques. 14 refs., 12 figs., 1 tab.

Windt, D.L.; Hull, R.; Waskiewicz, W.K.; Kortright, J.B.

1990-07-01

63

The mineralogy and chemistry analyser (MARS-XRD) for the ExoMars 2018 mission  

NASA Astrophysics Data System (ADS)

The Mineralogy and Chemistry Analyser (MARSXRD) is a miniaturised X-ray diffraction and fluorescence (XRD/XRF) spectrometer aimed to the mineralogical characterisation of Martian rocks. Simultaneously, MARS-XRD is able to acquire the diffraction pattern for mineralogical phases identification and the X-ray fluorescence spectrum for the chemical species, providing a complete rock characterization. The X-ray diffractometer (XRD) is the routine instrument used in every Earth Science laboratory to provide the mineralogical composition of rocks. XRD produces unequivocal results because it is based on the recognition of the geometrical properties of the crystal lattice. This kind of investigation is an extremely useful tool to define the textural and petro-mineralogical characteristics of the Martian rocks or soils and provide information on the past Martian environment conditions related to life. The analytic range we plan to cover includes all the silicate minerals, from clays or other phyllosilicates characterised by high interplanar lattice distance, to oxide and carbonates or evaporates (mainly sulphates). This rock spectrum is what we expect to be the target for exobiological exploration. These data will be integrated with those obtained by elemental analysis, in order to determine the exact elemental chemistry characterization of rock components. As mineralogy can be unambiguously derived from XRD analysis, it is probably our most powerful tool for distinguishing targets of biologic importance. In summary, the main scientific objectives of the proposed XRD/XRF instrument, Mars-XRD, are: - In situ determination of the mineral paragenesis of rock samples; - The characterization of the origin of rock samples; - Determination of alteration processes; - Understanding the exobiological potential of the samples. The hardware is developed by the Thales Alenia Space Italia with an important contribution of the Univ. of Leicester for the detection system.

Marinangeli, L.; Hutchinson, I. B.; Stevoli, A.; Adami, G.; Ambrosi, R.; Amils, R.; Assis Fernandes, V.; Baliva, A.; Basilevsky, A. T.; Benedix, G.; Bland, P.; Böttger, A. J.; Bridges, J.; Caprarelli, G.; Cressey, G.; Critani, F.; D'Alessandro, N.; Delhez, R.; Domeneghetti, C.; Fernandez-Remolar, D.; Filippone, R.; Fioretti, A. M.; Garcia Ruiz, J. M.; Gilmore, M.; Hansford, G. M.; Iezzi, G.; Ingley, R.; Ivanov, M.; Marseguerra, G.; Moroz, L.; Pelliciari, C.; Petrinca, P.; Piluso, E.; Pompilio, L.; Sykes, J.; Westall, F.

2011-10-01

64

Improved magnetic and ferroelectric properties of Sc and Ti codoped multiferroic nano BiFeO? prepared via sonochemical synthesis.  

PubMed

The room temperature multiferroic properties of bulk BiFeO3 are not exciting enough for its application in devices. Here, we report the sonochemical synthesis of scandium and titanium codoped BiFeO3 nanoparticles which exhibit improved magnetic and ferroelectric properties at room temperature. The nanoparticles have been checked for phase purity and composition using powder X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDX) and X-ray photoelectron spectroscopy (XPS). The size and morphology of the nanoparticles have been confirmed using scanning electron microscopy (SEM), and both low and high resolution transmission electron microscopy (TEM/HRTEM). The breaking of the spin cycloid due to the smaller size and slight structural distortion caused by the doping has been found to be instrumental for the enhancement of multiferroic properties. The electrical polarization increases significantly in the case of BiFe(0.925)Sc(0.05)Ti(0.025)O3 nanoparticles. A marked reduction in the leakage current was seen compared to undoped BiFeO3. Magnetoelectric coupling was also observed in the BiFe(0.925)Sc(0.05)Ti(0.025)O3 sample. Our results demonstrate that codoping with Sc and Ti ions is an effective way to rectify and enhance the multiferroic nature of BiFeO3. PMID:24705584

Dutta, Dimple P; Mandal, B P; Mukadam, M D; Yusuf, S M; Tyagi, A K

2014-06-01

65

Manganese Based Oxidative Technologies For Water/Wastewater Treatment  

E-print Network

and structural properties of ferrites. These laboratory prepared catalysts were thoroughly characterized using XRD, SEM, TEM, HR-TEM, and BET. Their magnetic properties have also been studied. These manganese ferrites offer the potential to enhance hydroxyl...

Desai, Ishan

2013-08-27

66

Response Time Measurements of the NIF DANTE XRD-31 X-Ray Diodes (Pre-print)  

SciTech Connect

The XRD-31 is a fast, windowless X-ray vacuum photodiode developed by EG&G. It is currently the primary fast X-ray detector used to diagnose the X-rays on NIF and OMEGA on the multichannel DANTE spectrometer. The XRD-31 has a dynamic range of less than 1e-12 amps to more than 10 amps. A technique is described to measure the impulse response of the diodes to a 150 fs pulse of 200 nm laser light and a method to calculate the “risetime” for a square pulse and compare it with the computed electron transit time from the photocathode to the anode. Measured response time for 5 XRD-31s assembled in early 2004 was 149.7 ps +-2.75 ps.

Don Pellinen and Michael Griffin

2009-01-23

67

Data acquisition and control software for XRD beamline at Indus-2  

NASA Astrophysics Data System (ADS)

X-ray diffraction (XRD) beamline is under commissioning on Indus-2 synchrotron radiation facility. The experimental setup of XRD beamline consists of a six-circle diffractometer and various detector systems such as scintillation detector, ionization chamber and image plate. The diffractometer can be controlled via EIA232 serial interface or Ethernet. Standard data acquisition software with a graphical user interface has been developed using LabVIEW. A firm safety and error handling scheme is implemented for failsafe operation of the experimental station. This paper describes in detail the data acquisition and control software for the experimental station.

Kane, Sanjeev R.; Garg, C. K.; Sinha, A. K.

2010-06-01

68

Synthesis and characterization of 3D Cu0.45Mn0.55O2 nanoflowers with novel photoluminescence and magnetic properties  

NASA Astrophysics Data System (ADS)

In this paper, three-dimensional (3D) Cu0.45Mn0.55O2 nanoflowers self-assembled by interconnecting dense stacked single-crystalline nanoplates have been prepared using the template-free hydrothermal growth method. The morphology, phase structure and composition of the as-prepared nanomaterial were characterized by X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM) with selected area electron diffraction (SAED) and energy-dispersive X-ray spectroscopy (EDX). FESEM and TEM analyses show that the size of 3D Cu0.45Mn0.55O2 nanoflowers is in the range of 1-1.5 ?m and the thickness of interconnected nanoplates is about 40 nm on the average. The photoluminescence (PL) spectra of the as-prepared Cu0.45Mn0.55O2 nanostructures at room temperature exhibits prominent emission bands located in red-violet spectral region. Moreover, magnetic investigations revealed the weak ferromagnetic behavior of the as-prepared Cu0.45Mn0.55O2 nanoflowers and reported for the first time using vibrating sample magnetometer (VSM).

Toufiq, Arbab Mohammad; Wang, Fengping; Javed, Qurat-Ul-Ain; Li, Quanshui; Li, Yan

2014-04-01

69

Highly ordered magnetic mesoporous silicas for effective elimination of carbon monoxide  

SciTech Connect

Catalysts based on crystalline nanoparticles of Fe metal supported on mesoporous silica have been developed. The synthetic process involves hydrogen reduction processing for high abundant Fe metal nanoparticles within the mesopores, in which impregnated Fe salt in the inner nanopores of mesoporous silica is thermally treated under hydrogen at 500 Degree-Sign C. Detailed characterization was achieved by XRD, XPS, BET, and HR-TEM techniques. The catalytic efficiency was demonstrated as a function of the used amounts and reaction time. The results show that more than 90% of the carbon monoxide was eliminated at room temperature during a period 80 min with 0.5 g of catalyst. - Graphical abstract: Strategy for the preparation of highly abundant Fe nanoparticle embedded MS catalyst by hydrogen reduction process and HR-TEM images of cross-sectional and top view. Highlights: Black-Right-Pointing-Pointer MS based heterogeneous catalyst with Fe nanoparticles were demonstrated for CO elimination. Black-Right-Pointing-Pointer Highly Fe nanoparticle embedded MS catalyst prepared by hydrogen reduction process. Black-Right-Pointing-Pointer Systematic characterization was achieved by XRD, XPS, BET, and HR-TEM analyses. Black-Right-Pointing-Pointer More than 90% of the CO was eliminated at RT during 80 min with 0.5 g of catalyst.

Lee, Jiho [Korea Institute of Ceramic Engineering and Technology, Seoul 153-801 (Korea, Republic of); Department of Chemistry, Inha University, Incheon 402-751 (Korea, Republic of); Ho Chang, Jeong, E-mail: jhchang@kicet.re.kr [Korea Institute of Ceramic Engineering and Technology, Seoul 153-801 (Korea, Republic of)

2012-04-15

70

Understanding changes in cellulose crystalline structure of lignocellulosic biomass during ionic liquid pretreatment by XRD.  

PubMed

X-ray diffraction (XRD) was used to understand the interactions of cellulose in lignocellulosic biomass with ionic liquids (ILs). The experiment was designed in such a way that the process of swelling and solubilization of crystalline cellulose in plant cell walls was followed by XRD. Three different feedstocks, switchgrass, corn stover and rice husk, were pretreated using 1-butyl-3-methylimidazolium acetate ([C4mim][OAc]) at temperatures of 50-130°C for 6h. At a 5 wt.% biomass loading, increasing pretreatment temperature led to a drop in biomass crystallinity index (CrI), which was due to swelling of crystalline cellulose. After most of the crystalline cellulose was swollen with IL molecules, a low-order structure was found in the pretreated samples. Upon further increasing temperature, cellulose II structure started to form in the pretreated biomass samples as a result of solubilization of cellulose in [C4mim][OAc] and subsequent regeneration. PMID:24269347

Zhang, Jiafu; Wang, Yixun; Zhang, Liye; Zhang, Ruihong; Liu, Guangqing; Cheng, Gang

2014-01-01

71

TEM, XRD and nanoindentation characterization of Xenon ion irradiation damage in austenitic stainless steels  

NASA Astrophysics Data System (ADS)

Cross-sectional and bulk specimens of a 20% cold-worked 316 austenitic stainless steel (CW 316 SS) has been characterized by TEM, XRD and nanoindentation to determine the microstructural evolution and mechanical property changes of 316 SS after irradiation with 7 MeV Xe26+ ions. TEM results reveal the presence of dislocation loops with a number density of approximately 3 × 1022 m-3 and sizes between 3 to 10 nm due to the collapse of vacancy rich cores inside displacement cascades. Peak broadening observed in XRD diffraction patters reveal systematic changes to lattice parameters due to irradiation. The calculated indentation values in irradiated 316 SS were found to be much higher in comparison to the unirradiated specimen, indicating the dose dependent effect of irradiation on hardness. The relationship between irradiation induced microstructural evolution and the changes to the mechanical properties of CW 316 SS are discussed in the context of fluence and irradiation temperature.

Huang, H. F.; Li, J. J.; Li, D. H.; Liu, R. D.; Lei, G. H.; Huang, Q.; Yan, L.

2014-11-01

72

3QMAS of three aluminum polycations: space group consistency between NMR and XRD  

Microsoft Academic Search

Three aluminum polycations, Al13?-Keggin Johansson-type, Al13 Mögel-type and Al30 ?-Taulelle-type have been measured by 27Al solid state NMR, using MAS and 3QMAS spectroscopies. The number of inequivalent aluminum obtained by these high resolution NMR experiments leads to a comparison with their respective XRD results obtained on single crystal. In all three cases, the inequivalent sites measured by NMR and deduced

L. Allouche; C. Huguenard; F. Taulelle

2001-01-01

73

Study on Decomposition of Goethite/siderite in Thermal Modification Through XRD, SEM and Tga Measurements  

NASA Astrophysics Data System (ADS)

The decomposition of goethite and goethite/siderite concentrates into hematite with thermal modification was studied through the measurements of X-ray diffraction (XRD), scanning electronic microscope (SEM) and thermal gravimetric analysis (TGA). The experimental results showed that goethite decomposed into hematite directly at around 300°C without any intermediate phase and the decomposition of siderite completed at 500°C. Nanoscale granular structures were observed in the thermally treated products. It deserves highlighting that the decomposition processes proceeded from surfaces into bulks.

Song, Shaoxian; Jia, Feifei; Peng, Changsheng

2014-01-01

74

In-Situ Cold Temperature XRD of Calcium Phosphate Produced From Organic Phosphoric Acid  

NASA Astrophysics Data System (ADS)

In this study, we synthesized calcium phosphate from an organic phosphoric acid, diethylhexyl phosphoric acid (DEHPA) and calcium hydroxide solution. The reaction involves a sol-gel process with a whitish gel formed. In-situ XRD analysis was then performed on the sample from room temperature to -140° C. At room the XRD diffractogram shows the sample as an amorphous material and as the temperature was further lowered sharp peaks begins to form indicating that the material had becomes crystalline. The peaks were identified to be that calcium hydrogen phosphate (Ca(H2PO4)2) and this indicates that there is no hydroxyl group removal during the cooling process. The relative crystallinity values obtained for the different cooling temperatures show a slow exponential increase on the initial cooling of 0 to -100° C and at further cooling temperatures resulted fast and linear process. Also unlike the in-situ XRD analysis performs at high temperature no phase transformation occurred at this low temperature.

Yusoff, M. S. Meor; Paulus, Wilfred; Muslimin, Masliana

2010-01-01

75

Effect of detrital muscovite on illite crystallinity measurement by x-ray diffraction (XRD)  

SciTech Connect

Illite crystallinity measurement by XRD can determine shale geothermometry and be used to map anchimetamorphic or diagenetic zones. A problem occurs in accuracy of XRD peak measurement because detrital muscovite from higher temperature source rocks constitutes a small percentage in many shales. The (001) XRD peaks coincide for diagenetic illite and detrital muscovite. The muscovite peak is very sharp, whereas the illite peak becomes sharper with increasing diagenetic grade. Thermal history, detrital muscovite, and sample preparation techniques will affect illite crystallinity measurements. Natural and artificially mixed samples can be used to show this effect quantitatively. Pegmatitic muscovite ground to clay size simulates this detrital component. When mixed with clay fractions from illitic shales, the induced error becomes insignificant for shales with a high-temperature history. Small detrital muscovite fractions adversely affect determination of lower diagenetic grades. Separation techniques that presume the coarser detrital fraction can be removed are not effective for siliceous shales, which must be ground. Calcareous and organic-rich shales may require disaggregation by chemical treatment, which may alter illite peak sharpness. Shales with 1 to 7% detrital muscovite showed higher illite crystallinity on x-ray diffractograms if the coarser fraction was not removed. At trace amounts of muscovite, the difference was negligible . By accurately estimating detrital percentages, a decision may be made to abandon tedious separation procedures. A correction factor may also be applied to crystallinity measurements to allow for the amount of detrital muscovite.

Gundy, L.

1987-08-01

76

XRD, Photoluminescence and Optical Absorption Investigations of Cobalt-doped ZnO  

NASA Astrophysics Data System (ADS)

Zn1-xCoxO (with x = 0, 0.01, 0.10 and 0.20) were synthesized by solid-state reaction method sintered at 600° C for 12 hours. The samples were studied by X-ray diffraction (XRD), optical absorption (UV-Vis) and Photoluminescence (PL). Structural analysis by Rietveld method using XRD showed that the peaks of secondary phase Co3O4 with a cubic structure were visible in the high-doped sample (x = 0.1, 0.2), besides the main peaks of wurtzite-like structure the same as that of ZnO. Shift of the XRD peaks proved the incorporation of Co2+ into the ZnO lattice. The band gap energy decreased from 3.18 to 3.14 eV with the increasing of cobalt concentration. PL spectra at room temperature showed the blue emission with the peak around 412 nm. In addition, the intensity of the blue emission decreased upon increasing the Co concentration, which indicated their high structural, defects and optical quality in the ZnO.

Sujinnapram, Supphadate; Onreabroy, Wandee; Nantawisarakul, Tuangrak

2009-07-01

77

HRTEM Study of Oxide Nanoparticles in 16Cr-4Al-2W-0.3Ti-0.3Y2O3 ODS Steel  

SciTech Connect

Crystal and interfacial structures of oxide nanoparticles in 16Cr-4Al-2W-0.3Ti-0.3Y{sub 2}O{sub 3} ODS ferritic steel have been examined using high-resolution transmission electron microscopy (HRTEM) techniques. Oxide nanoparticles with a complex-oxide core and an amorphous shell were frequently observed. The crystal structure of complex-oxide core is identified to be mainly monoclinic Y{sub 4}Al{sub 2}O{sub 9} (YAM) oxide compound. Orientation relationships between the oxide and matrix are found to be dependent on the particle size. Large particles (> 20 nm) tend to be incoherent and have a spherical shape, whereas small particles (< 10 nm) tend to be coherent or semi-coherent and have a faceted interface. The observations of partially amorphous nanoparticles lead us to propose three-stage mechanisms to rationalize the formation of oxide nanoparticles containing core/shell structures in as-fabricated ODS steels.

Hsiung, L; Fluss, M; Wall, M; Kimura, A

2009-11-18

78

[Analysis of XRD spectral characteristics of soil clay mineral in two typical cultivated soils].  

PubMed

The present paper took black soil and chernozem, the typical cultivated soil in major grain producing area of Northeast, as the study object, and determinated the soil particle composition characteristics of two cultivated soils under the same climate and location. Then XRD was used to study the composition and difference of clay mineral in two kinds of soil and the evolutionary mechanism was explored. The results showed that the two kinds of soil particles were composed mainly of the sand, followed by clay and silt. When the particle accumulation rate reached 50%, the central particle size was in the 15-130 microm interval. Except for black soil profile of Shengli Xiang, the content of clay showed converse sequence to the central particle in two soils. Clay accumulated under upper layer (18.82%) in black soil profile while under caliche layer (17.41%) in chernozem profile. Clay content was the least in parent material horizon except in black profile of Quanyanling. Analysis of clay XRD atlas showed that the difference lied in not only the strength of diffraction peak, but also in the mineral composition. The main contents of black soil and chernozem were both 2 : 1 clay, the composition of black soil was smectite/illite mixed layer-illite-vermiculite and that of chernozem was S/I mixture-illite-montmorillonite, and both of them contained little kaolinite, chlorite, quartz and other primary mineral. This paper used XRD to determine the characteristics of clay minerals comprehensively, and analyzed two kinds of typical cultivated soil comparatively, and it was a new perspective of soil minerals study. PMID:25269317

Zhang, Zhi-Dan; Luo, Xiang-Li; Jiang, Hai-Chao; Li, Qiao; Shen, Cong-Ying; Liu, Hang; Zhou, Ya-Juan; Zhao, Lan-Po; Wang, Ji-Hong

2014-07-01

79

Spectral studies of 2-pyrazoline derivatives: structural elucidation through single crystal XRD and DFT calculations.  

PubMed

A series of biologically active N-thiocarbamoyl pyrazoline derivatives have been synthesized using anhydrous potassium carbonate as the catalyst. All the synthesized compounds were characterized by FT-IR, (1)H NMR, (13)C NMR spectral studies, LCMS, CHN Analysis and X-ray diffraction analysis (compound 7). In order to supplement the XRD parameters, molecular modelling was carried out by Gaussian 03W. From the optimized structure, the energy, dipolemoment and HOMO-LUMO energies of all the systems were calculated. PMID:24457935

Chinnaraja, D; Rajalakshmi, R; Srinivasan, T; Velmurugan, D; Jayabharathi, J

2014-04-24

80

Titanium dioxide (TiO2) Nanoparticles XRD Analyses: An Insight  

E-print Network

This work reports aspect related to nano-sized particles of tetragonal anatase phase Titania. This approach is simple, faster, Eco-friendly, cost effective and suitable for large scale production. X-Ray Diffraction studies analyze particles size. It is found to be 74 nm and specific surface area is 19.16m2g-1. Morphology index (MI) derived from FWHM of XRD data explains the interrelationship of particle size and specific surface area. It is observed that MI has direct relationship with particle size and an inverse relationship with specific surface area. This work throws some light on and helps in the production line of Titania nano-particles.

Theivasanthi, T

2013-01-01

81

Characterization of Nanoporous Ceramic Materials Using Combined XRD, XPS and PAL Spectroscopy  

Microsoft Academic Search

\\u000a Some functional nanoporous materials such as dielectric magnesium aluminate MgAl2O4 ceramics with spinel structure are widely used for environment humidity sensors. It is established that functionality of\\u000a these humidity-sensitive ceramics depends on their microstructural peculiarities concerning mainly of phase composition. This\\u000a work is aimed to investigate a microstructure of sintered nanoporous magnesium aluminate materials using combined X-ray diffractometry\\u000a (XRD), high-resolution

Halyna Klym

82

XRD and EPR structural investigation of some zinc borate glasses doped with iron ions  

NASA Astrophysics Data System (ADS)

Glasses in the system xFe2O3·(100-x) [45ZnO·55B2O3] (0?x?10 mol%) have been prepared by melting at 1200 °C and rapidly cooling at room temperature. The obtained samples were submitted to an additional thermal treatment at 570 °C for 12 h in order to relax the glass structure as well as to improve the local order. The as cast and heat treated samples were investigated using X-ray diffraction (XRD) and electron paramagnetic resonance (EPR) measurements. The XRD patterns of all the studied samples show their vitreous nature. Structural modifications occurring in the heat treated samples compared to the untreated ones have been pointed out. EPR spectra of untreated and heat treated samples revealed resonance absorptions centered at g?2.0, g?4.3 and g?6.4. The compositional variation of the line intensity and linewidth of the absorptions from g?4.3 and g?2.0 have been interpreted in terms of the variation in the concentration of the Fe3+ ions and the interaction between the iron ions. The EPR spectra of the untreated samples containing 5 mol% Fe2O3 have been studied at different temperatures (110-290 K). The line intensity of the resonance signals decreases with increase in temperature whereas the linewidth is found to be independent of temperature. It was also found that the temperature variation of reciprocal line intensity obeys the Boltzmann law.

Stefan, Razvan; Pascuta, Petru; Popa, Adriana; Raita, Oana; Indrea, Emil; Culea, Eugen

2012-02-01

83

Structural characterization of Chloride Salt of conducting polyaniline obtained by XRD, SAXD, SAXS and SEM  

NASA Astrophysics Data System (ADS)

Emeraldine-salt polyaniline form (ES-PANI) was chemically synthesized using hydrochloric acid at time synthesis ranging from 0.5 to 48 h and characterized by X-ray diffraction (XRD), LeBail fit, Small-angle X-ray diffraction (SAXD), Small-angle X-ray Scattering (SAXS) and Scanning Electron Microscopy (SEM). Crystallinity and crystal data (a = 5.7122, b = 17.8393, c = 22.8027, ? = 83.1575, ? = 84.6971 and ? = 88.4419) were obtained by XRD and showed that the crystallinity did not vary with the time synthesis. LeBail fit revealed that the crystallites were very small lamellae with global average size around 39 Å. By SAXS it was obtained the particle Radius of Giration (Rg) of 320 Å. The maximum particle size (Dmax) of 650 Å was obtained from the pair-distance distribution function (p(r)). SEM images showed a fiber morphology formed by interconnected non homogeneous nanospheres. Electrical conductivity of the samples was in ˜1.84 × 10-4 S/cm.

Sanches, E. A.; Soares, J. C.; Mafud, A. C.; Fernandes, E. G. R.; Leite, F. L.; Mascarenhas, Y. P.

2013-03-01

84

[Research on reducing mold flux's radiative heat transfer based on FTIR and XRD].  

PubMed

The mold fluxes samples containing transition metal oxides TiO2 were designed based on the composition of commercial mold fluxes in continuous casting of steel, and the relation between radiative heat transfer and the content of TiO2 was obtained through FTIR spectrum analysis and XRD analysis. The result of FTIR analysis indicates that TiO2 has a great negative effect on infrared transmittance of flux samples in the wavelength range of 1-6 microm. The result of XRD analysis indicates that crystallization of cuspidine was restrained with addition of TiO2, and CaTiO3 and other phases were found in the samples. The decrease in cuspidine phase is beneficial to strand lubrication in the mold. Radiation heat flux from the strand to the mold was calculated using a radiative heat transfer model concluded in previous study. Addition of TiO2 was found to result in a remarkable decrease in radiation heat flux for both glassy and crystalline samples, and the heat flux tended to decrease with increasing TiO2, with the maximal decrease reaching 30%. As a result of great refraction and scatter at surface and grain boundaries of samples, the negative effect of crystalline samples was much larger than that of the glassy ones. PMID:19445198

Diao, Jiang; Xie, Bing

2009-02-01

85

Hydrometallurgical Extraction of Zinc and Copper A 57Fe-Mössbauer and XRD Approach  

NASA Astrophysics Data System (ADS)

The most commonly used route in the hydrometallurgical extraction of zinc and copper from a sulphide ore is the concentrate roast leach electro winning process. In the present investigation a zinc copper ore from the Maranda mine, located in the Murchison Greenstone Belt, South Africa, containing sphalerite (ZnS) and chalcopyrite (CuFeS2), was studied. The 57Fe-Mössbauer spectrum of the concentrate yielded pyrite, chalcopyrite and clinochlore, consistent with XRD data. Optimal roasting conditions were found to be 900°C for 3 h and the calcine produced contained according to X-ray diffractometry equal amounts of franklinite (ZnFe2O4) and zinc oxide (ZnO) and half the amount of willemite (Zn2SiO4). The Mössbauer spectrum showed predominantly franklinite (59%), hematite (6%) and other Zn- or Cu-depleted ferrites (35%). The latter could not be detected by XRD analyses as peak overlapping with other species occurred. Leaching was done with HCl, H2SO4 and HNO3, to determine which process would result in maximum recovery of Zn and Cu. More than 80% of both were recovered by using either one of the three techniques. From the residue of the leaching, the Fe-compounds were precipitated and <1% of the Zn and Cu was not recovered.

Mulaba-Bafubiandi, A. F.; Waanders, F. B.

2005-02-01

86

XRD and FTIR structural investigation of gadolinium-zinc-borate glass ceramics  

SciTech Connect

X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy measurements have been employed to investigate the (Gd{sub 2}O{sub 3}){sub x}?(B{sub 2}O{sub 3}){sub (60?x)}?(ZnO){sub 40} glass ceramics system, with 0 ? x ? 15 mol%. After heat treatment applied at 860 °C for 2 h, some structural changes were observed and new crystalline phases appeared in the structure of the samples. In these glass ceramics four crystalline phases were identified using powder diffraction files (PDF 2), namely ZnB{sub 4}O{sub 7}, Zn{sub 4}O(B{sub 6}O{sub 12}), Zn{sub 3}(BO{sub 3}){sub 2} and GdBO{sub 3}. From the XRD data, the average unit-cell parameter and the quantitative ratio of the crystallographic phases in the studied samples were evaluated. FTIR data revealed that the BO{sub 3}, BO{sub 4} and ZnO{sub 4} are the main structural units of these glass ceramics network. The compositional dependence of the different structural units which appear in the studied samples was followed.

Borodi, G. [National Institute for Research and Development of Isotopic and Molecular Technologies, 65-103 Donath, 400293 Cluj-Napoca (Romania)] [National Institute for Research and Development of Isotopic and Molecular Technologies, 65-103 Donath, 400293 Cluj-Napoca (Romania); Pascuta, P.; Dan, V.; Pop, V. [Technical University, 28 Memorandumului, 400114 Cluj-Napoca (Romania)] [Technical University, 28 Memorandumului, 400114 Cluj-Napoca (Romania); Stefan, R. [Agricultural Science and Veterinary Medicine University, 3-5 Calea Manastur, 400372 Cluj-Napoca (Romania)] [Agricultural Science and Veterinary Medicine University, 3-5 Calea Manastur, 400372 Cluj-Napoca (Romania); Radulescu, D. [University of Medicine and Pharmacy Iuliu Hatieganu, 8 Victor Babes, 400012 Cluj-Napoca (Romania)] [University of Medicine and Pharmacy Iuliu Hatieganu, 8 Victor Babes, 400012 Cluj-Napoca (Romania)

2013-11-13

87

Powder XRD and dielectric studies of gel grown calcium pyrophosphate crystals  

NASA Astrophysics Data System (ADS)

Formation of calcium pyrophosphate dihydrate (CPPD) crystals in soft tissues such as cartilage, meniscus and synovial tissue leads to CPPD deposition diseases. The appearance of these crystals in the synovial fluid can give rise to an acute arthritic attack with pain and inflammation of the joints, a condition called pseudo-gout. The growth of CPP crystals has been carried out, in the present study, using the single diffusion gel growth technique, which can broadly mimic in vitro the condition in soft tissues. The crystals were characterized by different techniques. The FTIR study revealed the presence of various functional groups. Powder XRD study was also carried out to verify the crystal structure. The dielectric study was carried out at room temperature by applying field of different frequency from 500 Hz to 1 MHz. The dielectric constant, dielectric loss and a.c. resistivity decreased as frequency increased, whereas the a.c. conductivity increased as frequency increased.

Parekh, Bharat; Parikh, Ketan; Joshi, Mihir

2013-06-01

88

Studying Cellulose Fiber Structure by SEM, XRD, NMR and Acid Hydrolysis  

SciTech Connect

Cotton linters were partially hydrolyzed in dilute acid and the morphology of remaining macrofibrils studied with Scanning Electron Microscopy (SEM) under various magnifications. The crystal region (microfibril bundles) in the macrofibrils was not altered by hydrolysis, and only amorphous cellulose was hydrolyzed and leached out from the macrofibrils. The diameter of microfibril bundles was 20-30 nm after the amorphous cellulose was removed by hydrolysis. XRD experiments confirm the unaltered diameter of the microfibrils after hydrolysis. The strong stability of these microfibril bundles in hydrolysis limits both the total sugar monomer yield and the size of nano particles or rods produced in hydrolysis. The large surface potential on the remaining microfibril bundles drives the agglomeration of macrofibrils.

Zhao, Haibo; Kwak, Ja Hun; Zhang, Z. Conrad; Brown, Heather M.; Arey, Bruce W.; Holladay, John E.

2007-03-21

89

Coupling XRD, EXAFS, and 13C NMR to study the effect of the carbon stoichiometry on the local structure of UC(1±x).  

PubMed

A series of uranium carbide samples, prepared by arc melting with a C/U ratio ranging from 0.96 to 1.04, has been studied by X-ray diffraction (XRD), (13)C nuclear magnetic resonance (NMR), and extended X-ray absorption fine structure (EXAFS). XRD determines phase uniqueness and the increase of the lattice parameter versus the carbon content. In contrast, (13)C NMR detects the different carbon environments in the lattice and in this study, clearly identifies the presence of discrete peaks for carbon in the octahedral lattice site in UC and an additional peak associated with excess carbon in hyperstoichiometric samples. Two peaks associated with different levels of carbon deficiency are detected for all hypostoichiometric compositions. More than one carbon environment is always detected by (13)C NMR. This exemplifies the difficulty in obtaining a perfect stoichiometric uranium monocarbide UC(1.00). The (13)C MAS spectra of uranium carbides exhibit the effects resulting from the carbon content on both the broadening of the peaks and on the Knight shift. An abrupt spectral change occurs between hypo- and hyperstoichiometric samples. The results obtained by EXAFS highlight subtle differences between the different stoichiometries, and in the hyperstoichiometric samples, the EXAFS results are consistent with the excess carbon atoms being in the tetrahedral interstitial position. PMID:24063301

Carvajal Nuñez, U; Martel, L; Prieur, D; Lopez Honorato, E; Eloirdi, R; Farnan, I; Vitova, T; Somers, J

2013-10-01

90

Accidental extinction in powder XRD intensity of porous crystals: Mesoporous carbon crystal CMK-5 and layered zeolite-nanosheets  

Microsoft Academic Search

CMK-5 mesoporous carbon crystals with p6mm symmetry and different carbon-wall thicknesses were prepared using furfuryl alcohol. We clearly observed that the XRD intensity of the 10 reflection diminishes at a certain thickness of carbon-wall, i.e., an “accidental extinction” happens in CMK-5. In order to make clear the condition of the “accidental extinction”, XRD intensity is analytically formulated\\/calculated for two-dimensional system

Kristina Lund; Norihiro Muroyama; Osamu Terasaki

2010-01-01

91

Pyrogenic iron(III)-doped TiO2 nanopowders synthesized in RF thermal plasma: phase formation, defect structure, band gap, and magnetic properties.  

PubMed

Iron(III)-doped TiO(2) nanopowders, with controlled iron to titanium atomic ratios (R(Fe/Ti)) ranging from nominal 0 to 20%, were synthesized using oxidative pyrolysis of liquid-feed metallorganic precursors in a radiation-frequency (RF) thermal plasma. The valence of iron doped in the TiO(2), phase formation, defect structures, band gaps, and magnetic properties of the resultant nanopowders were systematically investigated using Mössbauer spectroscopy, XRD, Raman spectroscopy, TEM/HRTEM, UV-vis spectroscopy, and measurements of magnetic properties. The iron doped in TiO(2) was trivalent (3+) in a high-spin state as determined by the isomer shift and quadrupole splitting from the Mössbauer spectra. No other phases except anatase and rutile TiO(2) were identified in the resultant nanopowders. Interestingly, thermodynamically metastable anatase predominated in the undoped TiO(2) nanopowders, which can be explained from a kinetic point of view based on classical homogeneous nucleation theory. With iron doping, the formation of rutile was strongly promoted because rutile is more tolerant than anatase to the defects such as oxygen vacancies resulting from the substitution of Fe(3+) for Ti(4+) in TiO(2). The concentration of oxygen vacancies reached a maximum at R(Fe/Ti) = 2% above which excessive oxygen vacancies tended to concentrate. As a result of this concentration, an extended defect like crystallographic shear (CS) structure was established. With iron doping, red shift of the absorption edges occurred in addition to the d-d electron transition of iron in the visible light region. The as-prepared iron-doped TiO(2) nanopowders were paramagnetic in nature at room temperature. PMID:16076205

Wang, X H; Li, J-G; Kamiyama, H; Katada, M; Ohashi, N; Moriyoshi, Y; Ishigaki, T

2005-08-10

92

XRD monitoring of ? self-irradiation in uranium-americium mixed oxides.  

PubMed

The structural evolution under (241)Am self-irradiation of U(1-x)Am(x)O(2±?) transmutation fuels (with x ? 0.5) was studied by X-ray diffraction (XRD). Samples first underwent a preliminary heat treatment performed under a reducing atmosphere (Ar/H2(4%)) aiming to recover the previously accumulated structural defects. Over all measurements (carried out over up to a full year and for integrated doses up to 1.5 × 10(18) ?-decay events·g(-1)), only fluorite U(1-x)Am(x)O(2±?) solid solutions were observed. Within a few days after the end of the heat treatment, each of the five studied samples was slowly oxidized as a consequence of their move to air atmosphere, which is evidenced by XRD by an initial sharp decrease of the unit cell parameter. For the compounds with x ? 0.15, this oxidation occurred without any phase transitions, but for U0.6Am0.4O(2±?) and U0.5Am0.5O(2±?), this process is accompanied by a transition from a first fluorite solid solution to a second oxidized one, as the latter is thermodynamically stable in ambient conditions. In the meantime and after the oxidation process, (241)Am ? self-irradiation caused a structural swelling up to ?0.8 vol %, independently of the sample composition. The kinetic constants of swelling were also determined by regression of experimental data and are, as expected, dependent on x and thus on the dose rate. The normalization of these kinetic constants by sample ?-activity, however, leads to very close swelling rates among the samples. Finally, evolutions of microstrain and crystallite size were also monitored, but for the considered dose rates and cumulated doses, ? self-irradiation was found, within the limits of the diffractometer used, to have almost no impact on these characteristics. Microstrain was found to be influenced instead by the americium content in the materials (i.e., by the impurities associated with americium starting material and the increase of cationic charge heterogeneity with increasing americium content). PMID:24266774

Horlait, Denis; Lebreton, Florent; Roussel, Pascal; Delahaye, Thibaud

2013-12-16

93

Data from the Mars Science Laboratory CheMin XRD/XRF Instrument  

NASA Technical Reports Server (NTRS)

The CheMin instrument on the Mars Science Laboratory (MSL) rover Curiosity uses a Co tube source and a CCD detector to acquire mineralogy from diffracted primary X-rays and chemical information from fluoresced X-rays. CheMin has been operating at the MSL Gale Crater field site since August 5, 2012 and has provided the first X-ray diffraction (XRD) analyses in situ on a body beyond Earth. Data from the first sample collected, the Rocknest eolian soil, identify a basaltic mineral suite, predominantly plagioclase (approx.An50), forsteritic olivine (approx.Fo58), augite and pigeonite, consistent with expectation that detrital grains on Mars would reflect widespread basaltic sources. Minor phases (each <2 wt% of the crystalline component) include sanidine, magnetite, quartz, anhydrite, hematite and ilmenite. Significantly, about a third of the sample is amorphous or poorly ordered in XRD. This amorphous component is attested to by a broad rise in background centered at approx.27deg 2(theta) (Co K(alpha)) and may include volcanic glass, impact glass, and poorly crystalline phases including iron oxyhydroxides; a rise at lower 2(theta) may indicate allophane or hisingerite. Constraints from phase chemistry of the crystalline components, compared with a Rocknest bulk composition from the APXS instrument on Curiosity, indicate that in sum the amorphous or poorly crystalline components are relatively Si, Al, Mg-poor and enriched in Ti, Cr, Fe, K, P, S, and Cl. All of the identified crystalline phases are volatile-free; H2O, SO2 and CO2 volatile releases from a split of this sample analyzed by the SAM instrument on Curiosity are associated with the amorphous or poorly ordered materials. The Rocknest eolian soil may be a mixture of local detritus, mostly crystalline, with a regional or global set of dominantly amorphous or poorly ordered components. The Rocknest sample was targeted by MSL for "first time analysis" to demonstrate that a loose deposit could be scooped, sieved to <150 microns, and delivered to instruments in the body of the rover. A drilled sample of sediment in outcrop is anticipated. At the time of writing this abstract, promising outcrops are in range and this talk will provide an update on data collected with the CheMin instrument.

Vaniman, David; Blake, David; Bristow, Tom; DesMarais, David; Achilles, Cherie; Anderson, Robert; Crips, Joy; Morookian, John Michael; Spanovich, Nicole; Vasavada, Ashwin; Yen, Albert; Bish, David; Chipera, Steve; Downs, Robert; Morrison, Shaunna; Farmer, Jack; Grotzinger, John; Stolper, Edward; Ming, Douglas; Morris, Richard; Rampe, Elizabeth; Treiman, Allan; Sarrazin, Philippe

2013-01-01

94

EPR, SEM and XRD investigation of ornamental limestone and marbles from some renowned Romanian quarries.  

NASA Astrophysics Data System (ADS)

Ornamental limestone and marble samples were collected and analysed by means of Electron Paramagnetic Resonance (EPR), Scanning Electron Microscopy (SEM) and X-Ray Diffraction (XRD), in order to evidence any systematic peculiarities able to be used in further provenance studies as well as to get more detailed information regarding geochemistry and mineralogy of three of the most important deposits from Romania. In this respect, 20 samples of limestone (Arnota quarry, Capatani Mountains and Mateias South quarry, Iezer Mountains) and 9 of calci-dolomitic marble (Porumbacu de Sus quarry, Fagaras Mountains) were collected over a significant sampling area. EPR spectroscopy, primarily used to asset the degree of homogeneity of considered samples, evidenced, for both Arnota and Mateias South limestone, the presence of a typical six hyperfine lines spectrum of Mn2+ ions in calcite but no traces of Fe ferromagnetic clusters. A more careful investigation has showed that although within the same quarry, there were no significant differences regarding EPR spectra, the resonance lines were systematic narrower in the case of Mateias South samples which suggested a lower content of divalent manganese ions. The Porumbacu calci-dolomitic marble, presented a more intricate Mn2+ spectrum, consisting of a superposition of typical dolomitic and calcitic spectra. Again, the EPR spectra were almost identical, attesting, as in the previous cases, a relative uniform distribution of paramagnetic Mn2+ ions within quarry. In the case of SEM, scattered, back scattered and absorbed electron modes were used to visualise the mineral formations on the sample surfaces while an EDAX quantitative analysis was used to determine the content of the most abundant elements. Although, at a first inspection, both groups of limestone looked almost similar, displaying a great variety of randomly orientated micro-crystalline agglomeration, only in the case of Arnota samples, we have noticed the presence of some micron size graphite inclusions, potential proxies for further provenance studies. The Porumbacu South marble showed a different pattern, characterized by a more uniform crystallite distribution, all of them presenting almost perfect cleaving surfaces. EDAX results evidenced, excepting the dominant Ca and Mg (the last one in the case of Porumbacu de Sus marble), the presence, in small quantities, of some other element such as Fe, Ni, Cu and Zn whose content represent also a good provenance proxy. XRD investigation evidenced not only of the dominant calcite and dolomite mineral phases, but also other minor mineral fraction, whose presence could be well related to the content of mentioned trace elements. Principal Component and Cluster Analysis, finally used to classify all investigated samples, allowed us to group them in three cluster in accordance with their provenance.

Covaci, D.; Costea, C.; Dumitras, D.; Duliu, O. G.

2012-04-01

95

Evaluation of Rock Powdering Methods to Obtain Fine-grained Samples for CHEMIN, a Combined XRD/XRF Instrument  

NASA Technical Reports Server (NTRS)

A miniature XRD/XRF (X-ray diffraction / X-ray fluorescence) instrument, CHEMIN, is currently being developed for definitive mineralogic analysis of soils and rocks on Mars. One of the technical issues that must be addressed to enable remote XRD analysis is how best to obtain a representative sample powder for analysis. For powder XRD analyses, it is beneficial to have a fine-grained sample to reduce preferred orientation effects and to provide a statistically significant number of crystallites to the X-ray beam. Although a two-dimensional detector as used in the CHEMIN instrument will produce good results even with poorly prepared powder, the quality of the data will improve and the time required for data collection will be reduced if the sample is fine-grained and randomly oriented. A variety of methods have been proposed for XRD sample preparation. Chipera et al. presented grain size distributions and XRD results from powders generated with an Ultrasonic/Sonic Driller/Corer (USDC) currently being developed at JPL. The USDC was shown to be an effective instrument for sampling rock to produce powder suitable for XRD. In this paper, we compare powder prepared using the USDC with powder obtained with a miniaturized rock crusher developed at JPL and with powder obtained with a rotary tungsten carbide bit to powders obtained from a laboratory bench-scale Retsch mill (provides benchmark mineralogical data). These comparisons will allow assessment of the suitability of these methods for analysis by an XRD/XRF instrument such as CHEMIN.

Chipera, S. J.; Vaniman, D. T.; Bish, D. L.; Sarrazin, P.; Feldman, S.; Blake, D. F.; Bearman, G.; Bar-Cohen, Y.

2004-01-01

96

A high pressure XRD setup at ADXRD beamline (BL-12) on Indus-2  

NASA Astrophysics Data System (ADS)

A high pressure XRD measurement setup in the angle dispersive geometry has been setup in the Angle Dispersive X-ray diffraction beamline (BL-12) in Indus-2 synchrotron facility. The X-Ray beam is collimated inside the diamond anvil cell (DAC) using a pair of cross-slit collimators and 100 micron orifice in a 400 micron thick Ta sheet. With the use of an adaptive optics to ensure a converging beam at the sample position, the need of an x-ray beam collimator is eliminated making the alignment of the DAC quite easy. The alignment of the DAC with respect to the incident x-ray beam is made by placing it on a computer controlled sample mounting and alignment stage developed specifically for this setup. Interactive software has been developed to make the alignment of the X-ray through the DAC very easy and accurate. NIST standard LaB6 powder was used for test runs, and a few fine pieces of gold served as pressure calibrator. The data was recorded on a MAR345 Image plate detector.

Ganguli, Tapas; Sinha, A. K.; Narayana, Chandrabhas; Upadhyay, Anuj; Singh, M. N.; Saxena, P.; Dubey, V. K.; Singh, I. J.; Raja, Sendhil; Vora, H. S.; Deb, S. K.

2013-03-01

97

Oxidation of amorphous Ni Zr alloys studied by XPS, UPS, ISS and XRD  

NASA Astrophysics Data System (ADS)

Amorphous Ni 36Zr 64 and Ni 24Zr 76 alloys were treated under conditions close to those used for activating Ni-Zr alloys in catalytic reactions. The composition and the structure of the surface region were investigated by X-ray photoelectron spectroscopy (XPS), ultraviolet photoelectron spectroscopy (UPS), ion scattering spectroscopy (ISS) and X-ray diffraction (XRD). The results show that exposing the amorphous alloys to 500 mbar O 2 at 523 K led to oxidized surfaces consisting of zirconia and different oxidic nickel species. On the oxidized Ni 24Zr 76 surface, only small amounts of NiO and Ni 2O 3 were found, while Ni 2O 3 was detected as the major Ni-containing species on the oxidized Ni 36Zr 64 surface. Oxidation of Ni in the alloys appeared to be inhibited by the presence of metallic Zr and started only after complete oxidation of the surrounding Zr. Annealing the oxidized alloys to 773 K led to a reduction of the surface oxides. The liberated oxygen atoms presumably diffused into the bulk, releasing metallic Ni. At the topmost layer, zirconia was reduced by carbon atoms originating from the bulk to form a ZrC-like surface compound. The exchange of Ni and Zr atoms between the surface and the bulk was enhanced by the oxidation and the annealing. The preferential oxidation of zirconium, which attracts Zr atoms from the bulk to the surface, provides the driving force for such processes.

Song, Z.; Bao, X.; Wild, U.; Muhler, M.; Ertl, G.

1998-09-01

98

XRD, TEM, IR, Raman and NMR Spectroscopy of In Situ Crystallization of Lithium Disilicate Glass  

NASA Technical Reports Server (NTRS)

The structure of a Li2O-2SiO2 (LS2) glass was investigated as a function of pressure and temperature up to 6 GPa and 750 C respectively, using XRD, TEM, IR, Raman and NMR spectroscopy. Glass densified at 6 GPa has an average Si-O-Si bond angle approx.7deg lower than that found in glass processed at 4.5 GPa. At 4.5 GPa, lithium disilicate crystallizes from the glass, while at 6 GPa a new high pressure form of lithium metasilicate crystallizes. The new phase, while having lithium metasilicate crystal symmetry, contains at least 4 different Si sites. NMR results for 6 GPa sample indicate the presence of Q4 species with (Q(sup 4))Si-O-Si(Q(sup 4)) bond angles of approx.157deg. This is the first reported occurrence of Q(sup 4) species with such large bond angles in alumina free alkali silicate glass. No five- or six- coordinated Si are found.

Fuss, T.; Mogus-Milankovic, A.; Ray, C. S.; Lesher, C. E.; Youngman, R.; Day, D. E.

2006-01-01

99

A 4-(o-chlorophenyl)-2-aminothiazole: microwave assisted synthesis, spectral, thermal, XRD and biological studies.  

PubMed

A 4-(o-chlorophenyl)-2-aminothiazole (CPAT) has been synthesized by reacting o-chloroacetophenone, iodine and thiourea under microwave irradiation as a green chemistry approach. The reactions proceed selectively and within a couple of minutes giving high yields of the products. The compound was characterized by elemental, spectral (UV-visible, IR, NMR and GC-MS), XRD and thermal analyses. The TG curve of the compound was analyzed to calculate various kinetic parameters (n, E, Z, ?S and ?G) by using Coats-Redfern (C.R.), MacCallum-Tanner (M.T.) and Horowitz-Metzger (H.M.) method. The compound was tested for the evaluation of antibacterial activity against B. subtilis and E. coli and antifungal activity against A. niger and C. albicans. The compound was evaluated for their in vitro nematicidal activity on plant parasitic nematode Meloidogyne javanica and molluscicidal activity on fresh water helminthiasis vector snail Lymnea auricularia. The compound is biologically active in very low concentration. X-ray diffraction study suggests a triclinic crystal system for the compound. PMID:23860403

Rajmane, S V; Ubale, V P; Lawand, A S; Nalawade, A M; Karale, N N; More, P G

2013-11-01

100

A 4-(o-chlorophenyl)-2-aminothiazole: Microwave assisted synthesis, spectral, thermal, XRD and biological studies  

NASA Astrophysics Data System (ADS)

A 4-(o-chlorophenyl)-2-aminothiazole (CPAT) has been synthesized by reacting o-chloroacetophenone, iodine and thiourea under microwave irradiation as a green chemistry approach. The reactions proceed selectively and within a couple of minutes giving high yields of the products. The compound was characterized by elemental, spectral (UV-visible, IR, NMR and GC-MS), XRD and thermal analyses. The TG curve of the compound was analyzed to calculate various kinetic parameters (n, E, Z, ?S and ?G) by using Coats-Redfern (C.R.), MacCallum-Tanner (M.T.) and Horowitz-Metzger (H.M.) method. The compound was tested for the evaluation of antibacterial activity against B. subtilis and E. coli and antifungal activity against A. niger and C. albicans. The compound was evaluated for their in vitro nematicidal activity on plant parasitic nematode Meloidogyne javanica and molluscicidal activity on fresh water helminthiasis vector snail Lymnea auricularia. The compound is biologically active in very low concentration. X-ray diffraction study suggests a triclinic crystal system for the compound.

Rajmane, S. V.; Ubale, V. P.; Lawand, A. S.; Nalawade, A. M.; Karale, N. N.; More, P. G.

2013-11-01

101

XRD Technique: A way to disseminate structural changes in iron-based amorphous materials  

SciTech Connect

Prevention of corrosion is a vital goal for the Department of Defense when billions of dollars are spent every year. Corrosion resistant materials have applications in all sort of military vehicles, and more importantly in naval vessels and submarines which come in contact with the seawater. It is known that corrosion resistance property can be improved by the used of structurally designed materials in the amorphous state where the atoms are arranged in a non-periodic fashion and specific atoms, tailored to the required properties can be interjected into the matrix for specific application. The XRD techniques reported here is to demonstrate the optimal conditions for characterization of these materials. The samples, which normally contain different compositions of Fe, Cr, B, Mo, Y, Mn, Si and W, are in the form of powders, ribbons and coatings. These results will be compared for the different forms of the sample which appears to correlate to the cooling rate during sample processing. In most cases, the materials are amorphous or amorphous with very small amount of crystallinity. In the ribbon samples for different compositions we observed that the materials are essentially amorphous. In most cases, starting from an amorphous powder sample, the coatings are also observed to be amorphous with a small amount of iron oxide on the surface, probably due to exposure to air.

Saw, C K; Lian, T; Day, D; Farmer, J

2007-05-24

102

High temperature in-situ XRD of plasma sprayed HA coatings.  

PubMed

The control of phase transformations in plasma sprayed hydroxyapatite (HA) coatings are critical to the clinical performance of the material. This paper reports the use of high temperature X-ray diffraction (HT-XRD) to study, in-situ, the phase transformations occurring in plasma sprayed HA coatings. The coatings were prepared using different spray power levels (net plasma power of 12 and 15 kW) and different starting powder size ranges (20-45; 45-75 microm). The temperature range employed was room temperature (approximately 26 degrees C) to 900 degrees C in normal atmosphere and pressure. High temperature differential scanning calorimetry (DSC) was also employed to investigate and determine the precise onset temperature of phase transformations during the recrystallization process. Results showed that actual onset of thermal degradation in the coating into other metastable phases like TTCP, beta-TCP and CaO occurred at 638 degrees C. The aforementioned phase transitions were independent of the selected spraying parameters. The degree of melting and thermal dissociation of HA actually determines the amount of calcium phosphate phases that are formed. A high power level of 15 kW produced a greater degree of melting, resulting in more CaO, TTCP and beta-TCP being formed as a result. PMID:11762329

Kweh, S W K; Khor, K A; Cheang, P

2002-01-01

103

XRD and XAS structural study of CuAlO2 under high pressure  

NASA Astrophysics Data System (ADS)

We present the results of x-ray diffraction and x-ray absorption spectroscopy experiments in CuAlO2 under high pressure. We discuss the polarization dependence of the x-ray absorption near-edge structure at the Cu K-edge. XRD under high pressure evidences anisotropic compression, the a-axis being more compressible than the c-axis. EXAFS yields the copper-oxygen bond length, from which the only internal parameter of the delafossite structure is deduced. The combination of anisotropic compression and the internal parameter decrease results in a regularization of the AlO6 octahedra. The anisotropic compression is related to the chemical trends observed in the lattice parameters when Al is substituted by other trivalent cations. Both experiments evidence the existence of an irreversible phase transition that clearly manifests at 35 ± 2 GPa. The structure of the high-pressure polymorph could not be determined, but it implies a change of the Cu environment, which remains anisotropic. Precursor effects are observed from the lowest pressures, which are possibly related to crystal breaking at a submicroscopic scale with partial reorientation of the crystallites.

Pellicer-Porres, J.; Segura, A.; Ferrer-Roca, Ch; Polian, A.; Munsch, P.; Kim, D.

2013-03-01

104

XRD and XAS structural study of CuAlO2 under high pressure.  

PubMed

We present the results of x-ray diffraction and x-ray absorption spectroscopy experiments in CuAlO(2) under high pressure. We discuss the polarization dependence of the x-ray absorption near-edge structure at the Cu K-edge. XRD under high pressure evidences anisotropic compression, the a-axis being more compressible than the c-axis. EXAFS yields the copper-oxygen bond length, from which the only internal parameter of the delafossite structure is deduced. The combination of anisotropic compression and the internal parameter decrease results in a regularization of the AlO(6) octahedra. The anisotropic compression is related to the chemical trends observed in the lattice parameters when Al is substituted by other trivalent cations. Both experiments evidence the existence of an irreversible phase transition that clearly manifests at 35 ± 2 GPa. The structure of the high-pressure polymorph could not be determined, but it implies a change of the Cu environment, which remains anisotropic. Precursor effects are observed from the lowest pressures, which are possibly related to crystal breaking at a submicroscopic scale with partial reorientation of the crystallites. PMID:23423689

Pellicer-Porres, J; Segura, A; Ferrer-Roca, Ch; Polian, A; Munsch, P; Kim, D

2013-03-20

105

Correlative Characterization of Li-S Batteries Using In situ TXM and XRD  

NASA Astrophysics Data System (ADS)

Sulfur is an attractive Li-ion battery cathode material candidate because of its high specific energy (2600 Wh/kg); however, it is well known that Li-S batteries suffer from capacity loss or fading. It is generally accepted that this is due to the loss of active material and the formation of nonconducting Li2S as a thin film coating the electrode. Both phenomena stem from the dissolution of active sulfur particles in the non-aqueous electrolyte as soluble long chain polysulfides form during the early stages of cell discharge. Using in situ, high resolution transmission X-ray microscopy (TXM) at SSRL beam line 6-2 and in situ X-ray diffraction (XRD) at beam line 11-3, we have explored initial discharge and charge cycle of Li-S batteries in real time. By combining these complementary methods, we can characterize the morphological changes of the active material as well as changes in crystallinity and crystal structure. We can then correlate these changes and the electrochemistry to better understand the reduction of elemental sulfur and various adaptations employed to retain battery capacity over many cycles.

Nelson, Johanna; Misra, Sumohan; Yang, Yuan; Jackson, Ariel; Cui, Yi; Andrews, Joy; Toney, Michael

2011-11-01

106

Structural studies with the use of XRD and Mössbauer spectroscopy of new high Manganese steels  

NASA Astrophysics Data System (ADS)

New high-strength austenitic and austenitic-ferritic manganese steels represent a significant potential in applications for structural components in the automotive and railway industry due to the excellent combination of high mechanical properties and good plasticity. They belong to the group of steels called AHSS (Advanced High Strength Steels) and UHSS (Ultra High Strength Steels). Application of this combination of properties allows a reduction in the weight of vehicles by the use of reduced cross-section components, and thus to reduce fuel consumption. The development and implementation of industrial production of such interesting and promising steel and its use as construction material requires an improvement of their casting properties and susceptibility to deformation in plastic working conditions. In this work, XRD, Transmission Mössbauer Spectroscopy and Conversion Electron Mössbauer Spectroscopy were employed in a study of the new high-manganese steels with a austenite and austenite-ferrite structure. The influence of the plastic deformation parameters on the changes in the structure, distribution of ferrite and disclosure of the presence of carbides was determined. The analysis of phase transformations in various times using CEMS method made possible to reveal their fine details.

Jablonska, Magdalena Barbara

2014-04-01

107

Mechanical Properties of Polycrystalline Titanium Nitride Films Measured by XRD Tensile Testing  

NASA Astrophysics Data System (ADS)

This paper describes measurement of mechanical properties of micron-thin polycrystalline titanium nitride (TiN) films. We developed a novel tensile test technique that can directly measure lateral elastic strain of a microscale single/poly-crystalline specimen by means of X-ray diffraction (XRD), which enables evaluation of not only Young's modulus but also Poisson's ratio of TiN films. TiN films having thicknesses of 0.5 ?m to 1.6 ?m are deposited onto the top and bottom surfaces of a microscale single crystal silicon (Si) specimen. The deposition is carried out by r.f. reactive magnetron sputtering under Ar partial pressure ranging from 0.7 Pa to 1.0 Pa. Average values of Young's modulus and Poisson's ratio for the Si monolayer specimen are found to be 169 GPa and 0.35, respectively, which are in close agreement with analytical values. TiN films deposited under an Ar partial pressure of 0.7 Pa have average Young's modulus of 290 GPa and Poisson's ratio of 0.36. These values gradually decrease with increasing Ar partial pressure, but are independent of TiN film thickness. Fracture strength of a TiN/Si/TiN composite specimen shows dependence on film thickness, regardless of Ar partial pressure.

Namazu, Takahiro; Inoue, Shozo; Takemoto, Hideki; Koterazawa, Keiji

108

Structures And Magnetization Of Defect-Associated Sites In Silicon  

SciTech Connect

To better understand the mechanism of the reported 'quasi-ferromagnetism' observed in Si ions self-implanted or irradiated silicon, we carry out high resolution transmission electron microscopy (HRTEM), magnetization measurements using superconducting quantum interference device (SQUID) magnetometer, and ferromagnetic resonance (FMR) measurements of the magnetic interaction of the defect-associated sites in silicon damaged by silicon self-implantation or energetic particle beams. The SQUID measurements showed that the silicon self-implanted sample has paramagnetic ordering. FMR measurements indicated the He{sup ++} irradiated sample has a ferromagnetic interaction and yields a Lande g-factor of 2.35.

Chow, L.; Gonzalez-Pons, J. C.; Barco, E. del [Department of Physics, University of Central Florida, Orlando, FL 32816-2385 (United States); Vanfleet, R. [Department of Physics, Brigham Young University, Provo, UT 84602 (United States); Misiuk, A. [Institute of Electron Technology (ITE), al. Lotnikow 32/46, Warsaw 02-668 Poland (Poland); Barcz, A. [Institute of Electron Technology (ITE), al. Lotnikow 32/46, Warsaw 02-668 Poland (Poland); Polish Academy of Science, Institute of Physics, al Lotnikow 32/46, Warsaw 02-668 Poland (Poland); Choi, E. S. [NHMFL, Florida State University, Tallahassee, FL 32310-3706 (United States); Chai, G. [Apollo Technologies, Inc. 205 Waymont Court, Suite 111, Lake Mary, FL 32746 (United States)

2008-04-24

109

Synthesis of magnetic nano-composite particles  

Microsoft Academic Search

Carbon nano-particles were synthesized using an arc-discharge apparatus. Magnetic-metal filled nano-capsules were segregated from nonmagnetic carbon particles using a magnet. TEM, XRD, EDS and Raman scattering spectroscopic examination revealed that a magnetic iron particle, 10–50 nm in diameter, was encapsulated in each carbon nano-capsule. These magnetic-metal filled carbon nano-capsules were then coated individually with amorphous silicate to provide additional oxidation

C. P Chen; T. H Chang; T. F Wang

2002-01-01

110

Quantitative shock stage assessment in olivine and pyroxene bearing meteorites via in situ micro-XRD  

NASA Astrophysics Data System (ADS)

Shock metamorphism is observed in most meteorites and impact structures [1]. Qualitative petrographic observations underpin a shock classification system [1-3] based on the deformation features in common silicates and on textural relations such as the development of maskelynite from feldspars, mobility of sulphides and metal in veins and local Fe-reduction in silicates. Shock deformation of minerals produces streaks (mosaicity) rather than discrete spots in 2D X-ray diffraction patterns, representing the progressive disruption of the crystal lattice into a mosaic of rotated domains [4,5]. Here we use in situ micro-XRD [5,6] to measure the mosaicity of olivine and pyroxene in ordinary chondrites of increasing shock stages S1 to S5 and then apply the method to achondrites with qualitatively low to high shock. X-ray diffraction data were collected in situ on polished thin sections and slab cut surfaces using a Bruker D8 Discover micro X-ray diffractometer [5], operated using CuK? radiation generated at 40 kV and 40 mA with a beam diameter of 500 ?m. Diffracted X-rays were recorded with a 2D detector, giving images with information in both the 2-theta and chi dimensions, in which each lattice plane (hkl) will have a diffraction spot or streak lying along an arc in chi of radius 2-theta (hkl). Individual reflections can be indexed and then integrated as a function of chi angle, allowing examination of the peak shape and quantitative analysis of the mosaic peak FWHM along chi. We find that both forsterite and enstatite exhibit greater mosaicity in chi with increasing shock stage: Forsterite chi ranges from <1° for S1 to >6° for S5. Enstatite chi values from the same meteorites show a more subdued growth of streak length with shock state, from ~1° to ~4°. A slab of the olivine shergottite DaG 476 exhibits forsterite mosaicity of 6.9°+/-1.1°, indicating that it has experienced shock stage S5, with shock pressures 30-45 GPa [1,4], consistent with the 40-45 GPa shock pressure estimated for DaG 476 by plagioclase refractive index [7]. These observations show that shock classification -and potentially shock pressure calibration- can be done using in situ XRD mineral data. [1] Stoffler, D. et al., (1991) GCA 55, 3845-3867. [2] Scott, E.R.D. et al., (1992) GCA 56, 4281-4293. [3] Rubin, A.E. et al., (1997) GCA 61, 847-858. [4] Horz, F. and Quiade, W.I. (1973) The Moon 6, 45-86. [5] Flemming, R.L. (2007) Can. Jour. Earth Sci. 44, 1333-1346. [6] Izawa, M.R.M. et al., (2009) LPSC XV. [7] Fritz, J. et al., (2005) MAPS 40, 1393-1411.

McCausland, P. J.; Flemming, R. L.; Izawa, M. R.

2010-12-01

111

SQUID, XRD and Raman Scattering Studies of Mn+ Implanted Gallium Arsenide  

NASA Astrophysics Data System (ADS)

In the present work, 325 keV Mn+ ions were implanted into semi-insulating GaAs substrate with various fluences varying from 1×1015 to 1×1016ions cm-2. Post annealing was carried out using 5 MeV Si+ ions irradiation at substrate temperature of 350 °C to remove the Mn+ implantation damage. The properties of as implanted and post annealed samples were measured using superconducting quantum interference device (SQUID), X-ray diffraction and Raman scattering to characterize the structural changes. Zero-field-cooled (ZFC) and field-cooled (FC) magnetization as function of temperature were recorded for sample irradiated with 5 MeV silicon ions. X-ray diffraction study revealed the presence of magnetic phase of (GaMn)As. The sharpness of LO mode peak, after irradiation with silicon ions indicated the crystilinity of the sample. The Mn-like mode and (MnAs) like mode were also observed.

Tripathi, S.; Dubey, S. K.; Yadav, A. D.; Kothari, D. C.; Panigrahi, B. K.; Nair, K. G. M.

2010-10-01

112

Corrosion of Depleted Uranium in an Arid Environment: Soil-Geomorphology, SEM\\/EDS, XRD, and Electron Microprobe Analyses  

Microsoft Academic Search

Corrosion of anthropogenic uranium in natural environments is not well understood, but is important for determining potential health risks and mobility in the environment. A site in the southwestern United States contains depleted uranium that has been weathering for approximately 22 years. Soil-geomorphic, SEM\\/EDS, XRD, and electron microprobe analyses were conducted to determine the processes controlling the uranium corrosion. Schoepite

BRENDA J. BUCK; AMY L. BROCK; WILLIAM H. JOHNSON; APRIL L. ULERY

2004-01-01

113

An exploratory method to detect tephras from quantitative XRD scans: Examples from Iceland and east Greenland marine sediments  

USGS Publications Warehouse

Tephras, mainly from Iceland, are becoming increasingly important in interpreting leads and lags in the Holocene climate system across NW Europe. Here we demonstrate that Quantitative Phase Analysis of x-ray diffractograms of the 150 um fraction and identify these same peaks in XRD scans - two of these correlate geochemically and chronologically with Hekla 1104 and 3. At a distal site to the WNW of Iceland, on the East Greenland margin (core MD99-2317), the weight% of volcanic glass reaches values of 11% at about the time of the Saksunarvatn tephra. The XRD method identifies the presence of volcanic glass but not its elemental composition; hence it will assist in focusing attention on specific sections of sediment cores for subsequent geochemical fingerprinting of tephras. ?? 2006 SAGE Publications.

Andrews, J.T.; Eberl, D.D.; Kristjansdottir, G.B.

2006-01-01

114

Synthesis and XRD/PL Studies of Pure and Sb2O3 Doped ZnO Nanophases  

SciTech Connect

Pure and Sb2O3 (0 to 5% molar fraction) doped ZnO nanophases were synthesized using a sublimation-condensation method in a solar furnace. The initial and final powders were characterized by X-ray diffraction (XRD) and photoluminescence (PL) techniques. XRD results showed no significant change in the lattice parameters and the presence of a new phase Zn7O2Sb12 in the highly doped micropowders but not in the nanopowders. The photoluminescence spectra showed a strong donor-acceptor pair (DAP) emission in the pure untreated ZnO micropowder which is drastically reduced in pure and doped nanopowders. The donor-bound excitonic band (DX) includes three well resolved peaks in the PL spectra of the doped micropowders while the spectra of doped nanopowders showed a broader band. Furthermore, the free exciton emission was absent in all doped samples.

Boulares, N.; Guergouri, K. [Mentouri University, Constantine (Algeria); Tabet, N. [King Fahd University of Petroleum and Minerals (Saudi Arabia); Monty, C. [CNRS/Promes, Odeillo 66120 Font-Romeu (France)

2007-08-22

115

NMR, XRD, IR and synchrotron NEXAFS spectroscopic studies of OPC and OPC\\/slag cement paste hydrates  

Microsoft Academic Search

This work aims to determine the fundamental similarities and\\/or differences between OPC and OPC\\/slag paste hydrates. OPC and\\u000a 35% slag pastes are investigated using five techniques: 29Si NMR, 27Al NMR, X-ray diffraction (XRD), infrared (IR) and synchrotron near edge X-ray absorption fine structure (NEXAFS) spectroscopy.\\u000a 29Si NMR provides valuable information related to the formation of the C–S–H gel, the main

Alessandra Mendes; Will P. Gates; Jay G. Sanjayan; Frank Collins

116

Evolution of crystalline aluminates from hybrid gel-derived precursors studied by XRD and multinuclear solid state MAS NMR  

Microsoft Academic Search

A hybrid gel synthesis is described which produces crystalline lanthanum hexaluminate at 1200°C without the intermediate appearance of LaAlO3. XRD in conjunction with 27Al and 139La MAS NMR indicates that until the exothermic appearance of ?-alumina at about 900°C, the gel remains amorphous and contains Al in three types of site, one of which is characterised by an NMR resonance

K. J. D MacKenzie; M Schmucker; L Mayer

1999-01-01

117

Transformation of meta-stable calcium silicate hydrates to tobermorite: reaction kinetics and molecular structure from XRD and NMR spectroscopy  

Microsoft Academic Search

Understanding the integrity of well-bore systems that are lined with Portland-based cements is critical to the successful storage of sequestered CO2 in gas and oil reservoirs. As a first step, we investigate reaction rates and mechanistic pathways for cement mineral growth in the absence of CO2 by coupling water chemistry with XRD and NMR spectroscopic data. We find that semi-crystalline

Jacqueline R Houston; Robert S Maxwell; Susan A Carroll

2009-01-01

118

Evolution of crystalline aluminates from hybrid gel-derived precursors studied by XRD and multinuclear solid-state MAS NMR  

Microsoft Academic Search

The thermal evolution of structure in a hybrid gel of YAG composition (Y3Al5O12) prepared from aluminum alkoxide and yttrium acetate was studied up to 1250°C. XRD indicates that the gels are amorphous <900°C, when they abruptly crystallize to YAG and hexagonal YAlO3. The latter exists only briefly, being fully converted to YAG by 1000°C. 27Al MAS NMR shows that after

K. J. D MacKenzie; T Kemmitt

1999-01-01

119

Controlled oxidation of FeCo magnetic nanoparticles to produce faceted FeCo/ferrite nanocomposites for rf heating applications  

E-print Network

for rf heating applications K. N. Collier,1,2 N. J. Jones,1 K. J. Miller,1 Y. L. Qin,1 D. E. Laughlin,1 for polydisperse FeCo magnetic nanoparticles MNPs synthesized using an induction plasma torch. X-ray diffraction the FeCo core and oxide shell. We show HRTEM images of MNP chaining and compare the rf heating of samples

Laughlin, David E.

120

Characterizing the Phyllosilicates and Amorphous Phases Found by MSL Using Laboratory XRD and EGA Measurements of Natural and Synthetic Materials  

NASA Technical Reports Server (NTRS)

The Curiosity Rover landed on the Peace Vallis alluvial fan in Gale crater on August 5, 2012. A primary mission science objective is to search for past habitable environments, and, in particular, to assess the role of past water. Identifying the minerals and mineraloids that result from aqueous alteration at Gale crater is essential for understanding past aqueous processes at the MSL landing site and hence for interpreting the site's potential habitability. X-ray diffraction (XRD) data from the CheMin instrument and evolved gas analyses (EGA) from the SAM instrument have helped the MSL science team identify phases that resulted from aqueous processes: phyllosilicates and amorphous phases were measure in two drill samples (John Klein and Cumberland) obtained from the Sheepbed Member, Yellowknife Bay Fm., which is believed to represent a fluvial-lacustrine environment. A third set of analyses was obtained from scoop samples from the Rocknest sand shadow. Chemical data from the APXS instrument have helped constrain the chemical compositions of these secondary phases and suggest that the phyllosilicate component is Mg-enriched and the amorphous component is Fe-enriched, relatively Si-poor, and S- and H-bearing. To refine the phyllosilicate and amorphous components in the samples measured by MSL, we measured XRD and EGA data for a variety of relevant natural terrestrial phyllosilicates and synthetic mineraloids in laboratory testbeds of the CheMin and SAM instruments. Specifically, Mg-saturated smectites and vermiculites were measured with XRD at low relative humidity to understand the behavior of the 001 reflections under Mars-like conditions. Our laboratory XRD measurements suggest that interlayer cation composition affects the hydration state of swelling clays at low RH and, thus, the 001 peak positions. XRD patterns of synthetic amorphous materials, including allophane, ferrihydrite, and hisingerite were used in full-pattern fitting (FULLPAT) models to help determine the types and abundances of amorphous phases in the martian rocks and sand shadow. These models suggest that the rocks and sand shadow are composed of approx 30% amorphous phases. Sulfate-adsorbed allophane and ferrihydrite were measured by EGA to further understand the speciation of the sulfur present in the amorphous component. These data indicate that sulfate adsorbed onto the surfaces of amorphous phases could explain a portion of the SO2 evolution in the Rocknest SAM data. The additional constraints placed on the mineralogy and chemistry of the aqueous alteration phases through our laboratory measurements can help us better understand the nature of the fluids that affected the different samples and devise a history of aqueous alteration for the Sheepbed Member of the Yellowknife Bay Fm. at Gale crater.

Rampe, Elizabeth B.; Morris, Richard V.; Chipera, Steve; Bish, David L.; Bristow, Thomas; Archer, Paul Douglas; Blake, David; Achilles, Cherie; Ming, Douglas W.; Vaniman, David; Crisp, Joy A.; DesMarais, David J.; Downs, Robert; Farmer, Jack D.; Morookian, John Michael; Morrison, Shaunna; Sarrazin, Philippe; Spanovich, Nicole; Treiman, Allan H.; Yen, Albert S.

2013-01-01

121

CONDENSED MATTER: STRUCTURE, MECHANICAL AND THERMAL PROPERTIES: Synthesis and Properties of Magnetic Composites of Carbon Nanotubes/Fe Nanoparticle  

NASA Astrophysics Data System (ADS)

Magnetic composites of carbon nanotubes (CNTs) are synthesized by the in situ catalytic decomposition of benzene at temperatures as low as 400°C over Fe nanoparticles (mean grain size = 26 nm) produced by sol-gel fabrication and hydrogen reduction. The yield of CNT composite is up to about 3025% in a run of 6 h. FESEM and HRTEM investigations reveal that one-dimensional carbon species are produced in a large quantity. A relatively high value of magnetization is observed for the composite due to the encapsulation of ferromagnetic Fe3C and/or ?-Fe. The method is suitable for the mass-production of CNT composites that contain magnetic nanoparticles.

Xu, Mei-Hua; Qi, Xiao-Si; Zhong, Wei; Ye, Xiao-Juan; Deng, Yu; Au, Chaktong; Jin, Chang-Qing; Yang, Zai-Xing; Du, You-Wei

2009-11-01

122

Solidification/stabilization of Cr(VI) with cement leachability and XRD analyses[X-Ray Diffraction  

SciTech Connect

The leachability of Cr(VI) from solidified Cr(VI)-Portland cement mixtures cured for 28 days were investigated. Cr(VI) was solidified with Type 1 Portland cement at concentrations of 0.5%, 2%, and 5% (based on K{sub 2}CrO{sub 4}) by weight of the cement. The addition of Cr(VI) increased the initial and final setting times of cement. X-ray diffraction (XRD) study indicates that Cr(VI) inhibits cement hydration process by reacting with Ca{sup 2+} during the hydration of cement, which was also supported by increased setting times. Increasing the Cr(VI) content in the cement reduced the compressive strength of the solidified cement. The leachability of Cr(VI) during the toxicity characteristics leaching procedures (TCLP) test was dependent on the initial Cr(VI) concentration and the leaching time. The treatment efficiency of cement was independent of the initial Cr(VI) concentration. The reaction products and crystalline phases were identified using the XRD. One of the reaction products identified was CaCrO{sub 4}. An empirical relationship was developed to predict the leaching of Cr(VI). Based on this relationship, the treatable amount should be limited to K{sub 2}CrO{sub 4}/cement ratio of 0.2% to meet the TCLP limit of 5 mg/l.

Wang, S.; Vipulanandan, C.

2000-03-01

123

Lead speciation in house dust from Canadian urban homes using EXAFS, micro-XRF, and micro-XRD.  

PubMed

X-ray absorption fine-structure (XAFS) spectroscopy, micro-X-ray fluorescence (?XRF), and micro-X-ray diffraction (?XRD) were used to determine the speciation of Pb in house dust samples from four Canadian urban homes having elevated Pb concentrations (>1000 mg Pb kg(-1)). Linear combination fitting of the XAFS data, supported by ?XRF and ?XRD, shows that Pb is complexed in a variety of molecular environments, associated with both the inorganic and organic fractions of the dust samples. The inorganic species of lead identified were as follows: Pb metal, Pb carbonate, Pb hydroxyl carbonate, Pb oxide, and Pb adsorbed to iron oxyhydroxides. Pb carbonate and/or Pb hydroxyl carbonate occurred in all four dust samples and accounted for 28 to 75% of total Pb. Pb citrate and Pb bound to humate were the organic species identified. The results of this study demonstrate the ability of XAFS to identify Pb speciation in house dust and show the potential to identify Pb sources from new homes versus older homes. Understanding Pb speciation and how it influences bioaccessibility is important for human health risk assessment and risk management decisions which aim to improve indoor environmental health. PMID:21591711

MacLean, Lachlan C W; Beauchemin, Suzanne; Rasmussen, Pat E

2011-07-01

124

Synthesis of metal complexes involving Schiff base ligand with methylenedioxy moiety: Spectral, thermal, XRD and antimicrobial studies  

NASA Astrophysics Data System (ADS)

Metal complexes of Zn(II), Cd(II), Ni(II), Cu(II), Fe(III), Co(II), Mn(II) Hg(II), and Ag(I) have been synthesized from Schiff base ligand, prepared by the condensation of 3,4-(methylenedioxy)aniline and 5-bromo salicylaldehyde. All the compounds have been characterized by using elemental analysis, molar conductance, FT-IR, UV-Vis, 1H NMR, 13C NMR, mass spectra, powder XRD and thermal analysis (TG/DTA) technique. The elemental analysis suggests the stoichiometry to be 1:1 (metal:ligand). The FT-IR, 1H NMR, 13C NMR and UV-Vis spectral data suggest that the ligand coordinate to the metal atom by imino nitrogen and phenolic oxygen as bidentate manner. Mass spectral data further support the molecular mass of the compounds and their structure. Powder XRD indicates the crystalline state and morphology of the ligand and its metal complexes. The thermal behaviors of the complexes prove the presence of lattice as well as coordinated water molecules in the complexes. Melting point supports the thermal stability of all the compounds. The in vitro antimicrobial effects of the synthesized compounds were tested against five bacterial and three fungal species by well diffusion method. Antioxidant activities have also been performed for all the compounds. Metal complexes show more biological activity than the Schiff base.

Sundararajan, M. L.; Jeyakumar, T.; Anandakumaran, J.; Karpanai Selvan, B.

2014-10-01

125

Coordinated spectral and XRD analyses of magnesite-nontronite-forsterite mixtures and implications for carbonates on Mars  

NASA Astrophysics Data System (ADS)

Mineral detection on Mars largely relies on laboratory data of minerals and mineral mixtures. The objective of this study is to provide reflectance spectra in the visible/near-infrared (VNIR) and mid-IR regions, X-ray diffraction (XRD) data and Mössbauer spectra of a suite of carbonate, phyllosilicate and olivine mixtures in order to facilitate identification and characterization of these minerals on Mars. Remote sensing observations indicate that combinations of these minerals are present in ancient rocks on Mars around the Isidis Basin and in Gusev crater. Magnesite, nontronite, and forsterite size fractions <125 µm were selected for this study. Results of the VNIR reflectance analyses illustrate the complexity of VNIR spectra of mixtures. Analyses of the NIR band depths near 2.3, 2.5, 3.4, and 4 µm showed clear trends with carbonate abundance, although the data are not linear. Mixtures of magnesite and nontronite exhibited a band near 2.3 µm much closer to that observed for nontronite than that for magnesite. VNIR analyses of the mixtures indicated that a small amount of forsterite in any of the mixtures contributed a large increase in the broad ~1 µm band and, hence, the red slope characteristic of Fe2+-bearing minerals. Mid-IR mixture spectra were dominated by magnesite and forsterite, and nontronite was much more difficult to detect by mid-IR spectra in the mixtures. This could be related to why phyllosilicates are detected in many locations on Mars using data collected by the Compact Reconnaissance Imaging Spectrometer for Mars, but not detected using data collected by the Thermal Emission Spectrometer. Mössbauer spectroscopy is well suited for analyses of Fe2+- and Fe3+-bearing minerals, and modeling of the peak areas gave well-correlated trends for nontronite and forsterite abundances where abundant Fe was present. XRD full-pattern fitting analyses were performed on the magnesite-forsterite series, giving results within 6 wt % of the actual values, with a mean difference between actual and calculated values of 2.4 wt %. This study provides important laboratory data for characterizing the spectral and XRD properties of mineral mixtures that will facilitate mineral identification on Mars. Carbonates, in particular, have been primarily observed at low abundances and in small outcrops, and they are frequently found mixed with other minerals. Through analyses of mineral mixtures using multiple data sets, this study seeks to provide ground truthing that will enable better coordination of carbonate detections in the dust and rocks of Mars.

Bishop, Janice L.; Perry, Kaysea A.; Darby Dyar, M.; Bristow, Thomas F.; Blake, David F.; Brown, Adrian J.; Peel, Samantha E.

2013-04-01

126

Landed XRD/XRF analysis of prime targets in the search for past or present Martian life.  

PubMed

Mars landers seeking evidence for past or present life will be guided by information from orbital mapping and from previous surface exploration. Several target options have been proposed, including sites that may harbor extant life and sites most likely to preserve evidence of past life These sites have specific mineralogic characteristics. Extant life might be gathered around the sinters and associated mineral deposits of rare active fumaroles, or held within brine pockets and inclusions in a few evaporite-mineral deposits. Possibilities for fossilization include deltaic and lake-bottom sediments of once-flooded craters, sinters formed by ancient hot-spring deposits, and the carbonate deposits associated with some evaporite systems. However, the highly varied mineralogy of fossil occurrences on Earth leads to the inference that Mars, an equally complex planet, could host a broad variety of potential fossilizing deposits. The abundance of volcanic systems on Mars and evidence for close associations between volcanism and water release suggest possibilities of organism entrapment and mineralization in volcaniclastic deposits, as found in some instances on Earth. Thus the targets being considered for exploration include a wide variety of unique deposits that would be characterized by silica or various nonsilicate minerals. Beyond these "special" deposits and in the most general case, an ability to distinguish mineralized from uncemented volcanic detritus may be the key to success in finding possible fossil-bearing authigenic mineralogies. A prototype miniaturized X ray diffraction/X ray fluorescence (XRD/XRF) instrument has been evaluated with silica, carbonate, and sulfate minerals and with a basalt, to examine the capabilities of this tool in mineralogic and petrologic exploration for exobiological goals. This instrument. CHEMIN (chemical and mineralogical analyzer), is based on an innovative low-power X ray tube, transmission geometry, and CCD collection and discrimination of diffracted and fluoresced X rays. The ability to accumulate and integrate the entire circumference of each complete Debye diffraction ring compensates for poor powder preparations, as might be produced by robotic sampling systems. With CHEMIN, a wide range of minerals can be uniquely identified. Using Rietveld analysis of the XRD results, mineral quantification is also possible. Expanded capabilities in phase analysis and constrained data solutions using quantitative XRD and XRF are within reach. PMID:11542260

Vaniman, D; Bish, D; Blake, D; Elliott, S T; Sarrazin, P; Collins, S A; Chipera, S

1998-12-25

127

Anisotropically structured magnetic aerogel monoliths  

NASA Astrophysics Data System (ADS)

Texturing of magnetic ceramics and composites by aligning and fixing of colloidal particles in a magnetic field is a powerful strategy to induce anisotropic chemical, physical and especially mechanical properties into bulk materials. If porosity could be introduced, anisotropically structured magnetic materials would be the perfect supports for magnetic separations in biotechnology or for magnetic field-assisted chemical reactions. Aerogels, combining high porosity with nanoscale structural features, offer an exceptionally large surface area, but they are difficult to magnetically texture. Here we present the preparation of anatase-magnetite aerogel monoliths via the assembly of preformed nanocrystallites. Different approaches are proposed to produce macroscopic bodies with gradient-like magnetic segmentation or with strongly anisotropic magnetic texture.Texturing of magnetic ceramics and composites by aligning and fixing of colloidal particles in a magnetic field is a powerful strategy to induce anisotropic chemical, physical and especially mechanical properties into bulk materials. If porosity could be introduced, anisotropically structured magnetic materials would be the perfect supports for magnetic separations in biotechnology or for magnetic field-assisted chemical reactions. Aerogels, combining high porosity with nanoscale structural features, offer an exceptionally large surface area, but they are difficult to magnetically texture. Here we present the preparation of anatase-magnetite aerogel monoliths via the assembly of preformed nanocrystallites. Different approaches are proposed to produce macroscopic bodies with gradient-like magnetic segmentation or with strongly anisotropic magnetic texture. Electronic supplementary information (ESI) available: Digital photographs of dispersions and gels with different water-to-ethanol ratios; magnetic measurements of an anatase aerogel containing 0.25 mol% Fe3O4 nanoparticles; XRD patterns of the iron oxide and titania nanoparticles. See DOI: 10.1039/c4nr04694c

Heiligtag, Florian J.; Airaghi Leccardi, Marta J. I.; Erdem, Derya; Süess, Martin J.; Niederberger, Markus

2014-10-01

128

Proton transfer and hydrogen bonding in the organic solid state: a combined XRD/XPS/ssNMR study of 17 organic acid-base complexes.  

PubMed

The properties of nitrogen centres acting either as hydrogen-bond or Brønsted acceptors in solid molecular acid-base complexes have been probed by N 1s X-ray photoelectron spectroscopy (XPS) as well as (15)N solid-state nuclear magnetic resonance (ssNMR) spectroscopy and are interpreted with reference to local crystallographic structure information provided by X-ray diffraction (XRD). We have previously shown that the strong chemical shift of the N 1s binding energy associated with the protonation of nitrogen centres unequivocally distinguishes protonated (salt) from hydrogen-bonded (co-crystal) nitrogen species. This result is further supported by significant ssNMR shifts to low frequency, which occur with proton transfer from the acid to the base component. Generally, only minor chemical shifts occur upon co-crystal formation, unless a strong hydrogen bond is formed. CASTEP density functional theory (DFT) calculations of (15)N ssNMR isotropic chemical shifts correlate well with the experimental data, confirming that computational predictions of H-bond strengths and associated ssNMR chemical shifts allow the identification of salt and co-crystal structures (NMR crystallography). The excellent agreement between the conclusions drawn by XPS and the combined CASTEP/ssNMR investigations opens up a reliable avenue for local structure characterization in molecular systems even in the absence of crystal structure information, for example for non-crystalline or amorphous matter. The range of 17 different systems investigated in this study demonstrates the generic nature of this approach, which will be applicable to many other molecular materials in organic, physical, and materials chemistry. PMID:24292812

Stevens, Joanna S; Byard, Stephen J; Seaton, Colin C; Sadiq, Ghazala; Davey, Roger J; Schroeder, Sven L M

2014-01-21

129

Analysis of crystalline phases in airborne particulate matter by two-dimensional X-ray diffraction (XRD2).  

PubMed

In this work, the potentiality of two-dimensional X-ray diffraction (XRD(2)) to characterise aerosol particles collected on commercial glass filters is presented. Indeed, even if routine analysis usually requires only mass determination, and rarely chemical composition, phase determination is fundamental to recognize the primary or secondary origin of the particulate matter and thus to determine the main sources of the pollution and to model contamination events. The experiments were performed at Daresbury Synchrotron (UK) Laboratory on 14.1 Beamline. The analysis of filters collected in Tuscany (Italy) is discussed with particular attention to the presence of arsenic sulfide. The first results of these experiments are very promising, showing the presence of unexpected compounds in the particulate matter of the investigated area. PMID:18175020

Bontempi, E; Benedetti, D; Zacco, A; Pantos, E; Boniotti, S; Saletti, C; Apostoli, P; Depero, L E

2008-01-01

130

Reciprocal space XRD mapping with varied incident angle as a probe of structure variation within surface depth  

SciTech Connect

In this study, we used a differential-depth X-Ray diffraction Reciprocal Spacing Mapping (XRD RSM) technique to investigate the crystal quality of a variety of SRF-relevant Nb film and bulk materials. By choosing different X-ray probing depths, the RSM study successfully revealed evolution the of materials? microstructure after different materials processes, such as energetic condensation or surface polishing. The RSM data clearly measured the materials? crystal quality at different thickness. Through a novel differential-depth RSM technique, this study found: I. for a heteroepitaxy Nb film Nb(100)/MgO(100), the film thickening process, via a cathodic arc-discharge Nb ion deposition, created a near-perfect single crystal Nb on the surface?s top-layer; II. for a mechanically polished single-crystal bulk Nb material, the microstructure on the top surface layer is more disordered than that in-grain.

Yang, Qiguang [Norfolk State University; Williams, Frances [Norfolk State University; Zhao, Xin [JLAB; Reece, Charles E. [JLAB; Krishnan, Mahadevan [AASC, San Leandro, California

2013-09-01

131

Preparation of biocompatible magnetite-carboxymethyl cellulose nanocomposite: Characterization of nanocomposite by FTIR, XRD, FESEM and TEM  

NASA Astrophysics Data System (ADS)

The preparation and characterization of magnetite-carboxymethyl cellulose nano-composite (M-CMC) material is described. Magnetite nano-particles were synthesized by a modified co-precipitation method using ferrous chloride tetrahydrate and ferric chloride hexahydrate in ammonium hydroxide solution. The M-CMC nano-composite particles were synthesized by embedding the magnetite nanoparticles inside carboxymethyl cellulose (CMC) using a freshly prepared mixture of Fe3O4 with CMC precursor. Morphology, particle size, and structural properties of magnetite-carboxymethyl cellulose nano-composite was accomplished using X-ray powder diffraction (XRD), transmission electron microscopy (TEM), Fourier transformed infrared (FTIR) and field emission scanning electron microscopy (FESEM) analysis. As a result, magnetite nano-particles with an average size of 35 nm were obtained. The biocompatible Fe3O4-carboxymethyl cellulose nano-composite particles obtained from the natural CMC polymers have a potential range of application in biomedical field.

Habibi, Neda

2014-10-01

132

Characterization of minerals in air dust particles in the state of Tamilnadu, India through FTIR, XRD and SEM analyses  

NASA Astrophysics Data System (ADS)

The abstract of this paper explains the presence of minerals in air which causes great concern regarding public health issues. The spectroscopic investigation of air dust particles of several samples in various locations in the state of Tamilnadu, India is reported. Qualitative analyses were carried out to determine the major and minor constituent minerals present in the samples based on the FTIR, XRD absorption peaks. This study also identified the minerals like quartz, asbestos, kaolinite, calcite, hematite, montmorillonite, nacrite and several other trace minerals in the air dust particles. The presents of quartz is mainly found in all the samples invariably. Hence the percentage of quartz and its crystalline nature were determined with the help of extinction co-efficient and crystallinity index respectively. The shape and size of the particulates are studied with SEM analysis.

Senthil Kumar, R.; Rajkumar, P.

2014-11-01

133

XRD Measurement of Mean Thickness, Thickness Distribution and Strain for Illite and Illite-Smectite Crystallites by the Bertaut-Warren-Averbach Technique  

Microsoft Academic Search

A modified version of the Bertaut-Warren-Averbach (BWA) technique (Bertaut 1949, 1950; Warren and Averbach 1950) has been developed to measure coherent scattering domain (CSD) sizes and strains in minerals by analysis of X-ray diffraction (XRD) data. This method is used to measure CSD thickness distributions for calculated and experimental XRD patterns of illites and illite-smectites (I-S). The method almost exactly

V. A. Drits; D. D. EBERL; J. SRODOI

1998-01-01

134

Novodneprite (AuPb3), anyuiite [Au(Pb, Sb)2] and gold micro- and nano-inclusions within plastically deformed mantle-derived olivine from the Lherz peridotite (Pyrenees, France): a HRTEM-AEM-EELS study  

NASA Astrophysics Data System (ADS)

To contribute the problem of the missing ("invisible") gold fraction in mantle rocks, olivine grains separated from orogenic lherzolite of the peridotite body of Lherz (Eastern Pyrenees, France) have been investigated by transmission electron microscopy (TEM) and electron energy loss spectroscopy (EELS). The results indicate the presence of micrometric inclusions of novodneprite, AuPb3, and anyuiite, Au(Pb,Sb)2, together with nanometric clusters of metallic gold. Both minerals have been recognised on TEM images as darker contrast inclusions and identified through selected area electron diffraction (SAED) and energy dispersive spectroscopy (EDS) analyses. Gold clusters have been indirectly identified in randomly distributed nano-sized rectangular areas that occur in TEM images obtained from the edges of olivine crystals. Within these volumes the EDS analyses reveal a constant presence of Au (0.1-0.2 wt %). High-resolution TEM (HRTEM) investigations evidence series of regularly alternating sigmoidal and ellipsoidal domains developed along [110]. The EELS investigations revealed that the Au signal (M-series lines) arises from the ellipsoidal domains. It is proposed that novodneprite and anyuiite are the result of subsolidus recrystallization of the Pyrenean lherzolites accompanied by a secondary olivine grains growth that trapped inter-granular components. Likely, a process of plastic deformation favoured the formation of edge dislocations within olivine grains and thus, the circulation through them of Au-enriched fluids. A mass balance calculation of the missing gold percentage within this lherzolite points to olivine as one of the potential hosts for about the 80 % of the "invisible" gold in form of nano-inclusions, whereas only 20 % of the whole-rock Au-budget, would be hosted within assemblages of Cu-Fe-Ni sulphides.

Ferraris, Cristiano; Lorand, Jean-Pierre

2014-08-01

135

Magnetite and magnetite/silver core/shell nanoparticles with diluted magnet-like behavior  

SciTech Connect

In the present work is reported the use of the biopolymer chitosan as template for the preparation of magnetite and magnetite/silver core/shell nanoparticles systems, following a two step procedure of magnetite nanoparticles in situ precipitation and subsequent silver ions reduction. The crystalline and morphological characteristics of both magnetite and magnetite/silver core/shell nanoparticles systems were analyzed by high resolution transmission electron microscopy (HRTEM) and nanobeam diffraction patterns (NBD). The results of these studies corroborate the core/shell morphology and the crystalline structure of the magnetite core and the silver shell. Moreover, magnetization temperature dependent, M(T), measurements show an unusual diluted magnetic behavior attributed to the dilution of the magnetic ordering in the magnetite and magnetite/silver core/shell nanoparticles systems. - Graphical abstract: Biopolymer chitosan was used as stabilization media to synthesize both magnetite and magnetite/silver core/shell nanoparticles. Results of HRTEM and NBD patterns confirm core/shell morphology of the obtained nanoparticles. It was found that the composites show diluted magnet-like behavior.

Garza-Navarro, Marco [Facultad de Ingenieria Mecanica y Electrica, Universidad Autonoma de Nuevo Leon, Av. Universidad s/n, Cd. Universitaria, San Nicolas de los Garza, Nuevo Leon 66450 (Mexico); Torres-Castro, Alejandro, E-mail: alejandro.torrescs@uanl.edu.m [Facultad de Ingenieria Mecanica y Electrica, Universidad Autonoma de Nuevo Leon, Av. Universidad s/n, Cd. Universitaria, San Nicolas de los Garza, Nuevo Leon 66450 (Mexico); Centro de Innovacion, Investigacion y Desarrollo en Ingenieria y Tecnologia, Universidad Autonoma de Nuevo Leon, Apodaca, Nuevo Leon 66600 (Mexico); Gonzalez, Virgilio; Ortiz, Ubaldo [Facultad de Ingenieria Mecanica y Electrica, Universidad Autonoma de Nuevo Leon, Av. Universidad s/n, Cd. Universitaria, San Nicolas de los Garza, Nuevo Leon 66450 (Mexico); Centro de Innovacion, Investigacion y Desarrollo en Ingenieria y Tecnologia, Universidad Autonoma de Nuevo Leon, Apodaca, Nuevo Leon 66600 (Mexico); De la Rosa, Elder [Centro de Investigaciones en Optica, A.P. 1-948, Leon Gto. 37160 (Mexico)

2010-01-15

136

Structural (XRD) and thermal (DSC, TGA) and BET analysis of materials derived from non-metal cation pentaborate salts.  

PubMed

The synthesis, structural characterization (XRD), and thermal properties of nine non-metal cation (NMC) pentaborate anion salts, [NMC][B(5)O(6)(OH)(4)] (1a-1i) is described (NMC = [NH(3)CMe(2)(CH(2)OH)](+) (a), [O(CH(2)CH(2))(2)NH(2)](+) (b), [NH(3)CMe(CH(2)OH)(2)](+) (c), [2-(2-CH(2)CH(2)OH)PyH](+) (d), [(CH(2))(4)NH(CH(2)CH(2)OH)](+) (e), [(CH(2))(5)NH(CH(2)CH(2)OH)](+) (f), [2-MeImid](+) (g), [Me(3)NCMe(2)(CH(2)OH)](+) (h), [O(CH(2)CH(2))(2)NMe(2)](+) (i). Single-crystal X-ray diffraction studies on all compounds show that they contain isolated pentaborate anions, H-bonded together in a supramolecular array, with the cations occupying the cavities within the network. Compound 1c was obtained as a partial hydrate (0.16H(2)O). TGA and DSC analysis (in air, 25-1000 degrees C) indicate that compounds 1a-1i thermally decompose via a 2 stage process to B(2)O(3). The first stage (<250 degrees C) is dehydration to condensed polymeric pentaborates {approximate composition: [NMC][B(5)O(8)] (2a-2i)}. Five condensed pentaborates (2a-c, 2e, 2g) were synthesised and characterized by powder XRD and BET analysis. These condensed pentaborates were amorphous. The isolated pentaborates intumesced at approximately 600 degrees C (occupying approximately 10 times their original volume), and then contracted back to black glassy B(2)O(3) solids at 1000 degrees C. The intumescent materials (3a), (3b), (3e), (3g), and a final B(2)O(3) sample (4b) were synthesised and isolated and their porosities determined. BET surface area analysis on the isolated pentaborates (1a-c, 1e, 1g), the condensed pentaborates (2a-c, 2e, 2g), intumesced materials (3a, 3b, 3e, 3g), and B(2)O(3) (4b) showed that they were all 'non-porous' (<1.59 m(2) g(-1)). PMID:20372719

Beckett, Michael A; Horton, Peter N; Hursthouse, Michael B; Knox, David A; Timmis, James L

2010-04-28

137

Local structural studies of directly synthesized L1 0 FePt nanoparticles by using XRD, XAS and ASAXS  

NASA Astrophysics Data System (ADS)

The FePt particles synthesized by polyol process using tetraethylene glycol (TEG) at 200 and 300 °C are superparamagnetic and ferromagnetic, respectively. The crystal structure and atomic distribution of the particles are analyzed using XRD, X-ray absorption spectroscopy and anomalous small angle X-ray scattering to understand the formation of these particles under different synthesis conditions. The results suggest that at 200 °C particles with Pt-rich FePt core and Fe-rich amorphous shell are formed. When the reaction solution is heated to 300 °C, sintering of several small particles occur. On the other hand, when H 2PtCl 6 as nucleation control agent and succinic acid as complex agent were added to the reaction solution, homogeneous FePt alloy particles with grain size of 8 nm were obtained. In the process of forming the alloy nanoparticles, small particles get sintered at the amorphous interface and crystallization progresses along with ordering, resulting in the formation of partially ordered ferromagnetic FePt.

Shinoda, K.; Sato, K.; Jeyadevan, B.; Tohji, K.; Suzuki, S.

2007-03-01

138

In Situ XAS and XRD Studies of Substituted Spinel Lithium Manganese Oxides in the 4-5 V Region  

SciTech Connect

Partial substitution of Mn in lithium manganese oxide spinel materials by Cu and Ni greatly affects the electrochemistry and the phase behavior of the cathode. Substitution with either metal or with a combination of both shortens the 4.2 V plateau and results in higher voltage plateaus. In situ x-ray absorption (XAS) studies indicate that the higher voltage plateaus are related to redox processes on the substituents. In situ x-ray diffraction (XRD) on LiCu{sub 0.5}Mn{sub 1.5}O{sub 4} shows single phase behavior during the charge and discharge process. Three phases are observed for LiNi{sub 0.5}Mn{sub 1.5}O{sub 4} and two phases are observed in the case of LiNi{sub 0.25}Cu{sub 0.25}Mn{sub 1.5}O{sub 4}. The electrolyte stability is dependent on both the operating voltage and the cathode composition. Even though Ni substituted materials have lower voltages, the electrolyte is more stable in cells with the Cu substituted materials.

McBreen, J.; Mukerjee, S.; Yang, X. Q.; Sun, X.; Ein-Eli, Y.

1998-11-01

139

Catalytic partial oxidation of methane to synthesis gas over Ni-based catalysts. 2: Transient, FTIR, and XRD measurements  

SciTech Connect

Ni/La{sub 2}O{sub 3} and Ni/Al{sub 2}O{sub 3} catalysts were studied under conditions of partial oxidation of methane to synthesis gas. Temperature-programmed oxidation and hydrogenation experiments have shown that carbon accumulation over Ni/La{sub 2}O{sub 3} during CPO remains essentially constant after 2 h time on-stream, while over Ni/Al{sub 2}O{sub 3} it increases during the initial several hours. FTIR spectroscopy of surface species formed over the Ni/La{sub 2}O{sub 3} catalyst under reaction conditions indicates that the carbonate species formed over the support do not decompose under He and O{sub 2} treatment at 600 C. XRD spectra obtained following high ({approximately}90%) or low (<10%) methane conversions show that Ni, La{sub 2}O{sub 3}, La{sub 2}O{sub 2}CO{sub 3}, NiO, and Ni{sub 3}C phases are present in the case of high methane and complete oxygen conversions, while nickel oxide, nickel carbide and, to a small extent, La{sub 2}O{sub 2}CO{sub 3} phases are present in the case of low CH{sub 4} and incomplete oxygen conversions.

Tsipouriari, V.A.; Verykios, X.E. [Univ. of Patras (Greece). Dept. of Chemical Engineering] [Univ. of Patras (Greece). Dept. of Chemical Engineering

1998-10-01

140

Magnetism and Magnetic Properties  

NSDL National Science Digital Library

Students will identify properties of magnetism and begin to develop understanding of their practical applications. Students will also begin to develop understanding of the essential nature of Earth's magnetic fields.

Schneck, Roberta

2011-10-13

141

Magnetic properties of fine SFMO particles: Superparamagnetism  

NASA Astrophysics Data System (ADS)

Magnetic properties of fine Sr2FeMoO6 (SFMO) powders were systematically studied and superparamagnetism was observed. The SFMO samples were prepared using a citrate-gel method and were characterized by X-ray diffraction (XRD), ferromagnetic resonance (FMR) and Mössbauer spectroscopy. The XRD measurements showed that the powders are nearly pure and the Rietveld refinement gave particle sizes of 31 and 197 nm and antisite disorders of 10 and 15%, respectively. The 197 nm crystallite size sample has a TC=415 K and a magnetic moment of 3.0 ?B/f.u. Several measurements made by SQUID magnetometer, FMR and Mössbauer spectroscopy showed that the 31 nm crystallite sample behaves superparamagnetically with blocking temperature TB=35 K and it has a reduced saturation magnetization of 1.0 ?B/f.u. at 5 K and effective paramagnetic moment of 3.0 ?B.

Suominen, T.; Raittila, J.; Salminen, T.; Schlesier, K.; Lindén, J.; Paturi, P.

2007-02-01

142

Magnetic hardening of high-energy ball-milled nanocrystalline LaMn 2Si 2  

NASA Astrophysics Data System (ADS)

Nanocrystalline LaMn 2Si 2 powders have been obtained by high-energy ball milling for 30 min from bulk alloys. After milling a high coercivity about 6 kOe is observed at 10 K in contrast to neglectable coercivity for the bulk LaMn 2Si 2 at 5 K. The average grain size of the optimum particles which is obtained from X-ray diffraction pattern and HRTEM picture is about 20 nm. The magnetic hardening is observed for the nanocrystalline LaMn 2Si 2, reflected in the coercivity field strength of 6 kOe at 10 K.

Elmali, Ayhan; Tekerek, Simsek; Dincer, Ilker; Elerman, Yalcin; Theissmann, Ralf; Ehrenberg, Helmut; Fuess, Hartmut

143

The unusual Lovina Ataxite: Examination of Meteoritic Microstructures and Terrestrial Weathering by ?XRD, Petrography, SEM, INAA and sXRF.  

NASA Astrophysics Data System (ADS)

The football-sized 8.2 kg Lovina ataxite is a newly classified iron meteorite that was found in Bali, Indonesia in 1981. Its unusual appearance and strong weathering have, over the years, precluded its being identified as a meteorite. Remarkable features include cm-sized pyramidal projections, or ziggurats, with mm-spaced ribs on its top surface (orientation as discovered) and deep vugs in its lower surfaces. In situ examination of Lovina's weathered ziggurats by micro X-ray diffraction (?XRD revealed that they consisted of two iron alloys: Ni-rich taenite and very Ni-rich awaruite (Ni3Fe). Although this texture is reminiscent of Widmanstätten pattern, kamacite was not observed. Magnetite was frequently observed in association with awaruite, indicating very intense weathering. Micro-XRD of several locations on a polished thin section cut near the weathered surface and a freshly polished surface of Lovina, free of weathering, revealed primarily taenite with minor troilite. Measurement of bulk grain density by He-pycnometry for the 32.5 g type specimen (cut end piece) of Lovina and other iron meteorites found that Lovina's grain density of 7.00+/- 0.02 g/cm3 was significantly less than those found for Canyon Diablo (7.37+/-0.01) and a slightly weathered Mundrabilla fragment (7.20+/-0.01), measurably reflecting the presence of the lower-density weathering products in Lovina. The presence of taenite and troilite suggested that Lovina was an ataxite, as confirmed by correlated SEM X-ray maps, petrographic and bulk INAA analysis. X-ray maps of the thin section confirmed the identities of magnetite, troilite, massive taenite, and located Ni enrichment (awaruite) in the alloy surrounding magnetite in severely weathered areas. Petrographic observations indicated the taenite to be massive, lacking exsolved kamacite spindles, daubreelite and Neumann bands, which are commonly present in ataxites. Abundant globular troilite nodules up to 0.8 mm in diameter are present. Many of the nodules are partially or totally oxidized to Fe oxides. Analysis by INAA revealed Lovina to have a composition outside the range of most grouped ataxites in group IVB. Thus, Lovina is an ungrouped ataxite. Lovina resembles other ungrouped ataxites, e.g. N'Goureyma, in its abundance of troilite nodules with a very low abundance of kamacite spindles and daubreelite, but differs in composition. Lovina's high Ni- and low Ir-content is similar to that of some ungrouped ataxites, but it differs in its relatively high Ge and Ga contents. The ziggurat structure is attributed to differential weathering within a taenite microstructure. In an effort to identify microstructures, synchrotron X-ray Fluorescence (sXRF) data have been collected using the Very sensitive Elemental and Structural Probe Employing Radiation by a Synchrotron (VESPERS) beamline at CLS. Synchrotron X-ray maps have revealed non-uniform Ni distribution across the taenite, which had appeared to be massive by petrography and SEM. This may correlate with the differential weathering behaviour of the Lovina ataxite.

Flemming, R. L.; McCausland, P. J.; Kissin, S. A.; Corcoran, P. L.; Biesinger, M. C.; McIntyre, N. S.; Fuller, M. L.; Feng, R.

2009-05-01

144

Mercury in polluted soils: speciation using micro-XRF, micro-XRD, and micro- and bulk XAFS.  

NASA Astrophysics Data System (ADS)

In this research, mercury speciation was assessed for soil samples collected inside and outside an industrial polluted area of National environmental interest located in "Val Basento" (Basilicata, Italy). Hg concentration in these soil samples ranged from 12 up to 240 mg/kg. Mercury chemical forms in these samples were identified by a combination of sequential extraction procedures, thermal desorption analyses, and different bulk- and micro-analytical techniques exploiting high intensity synchrotron generated X-rays. Bulk XANES (X-ray Absorption Near Edge Structure) and EXAFS (Extended X-ray Absorption Fine Structure) spectra were collected for direct Hg-speciation in soil samples sieved at 2mm as well as in the clay fraction (<2um), where the highest amount of mercury was concentrated. The interpretation of the complex mixture of Hg-chemical forms in the soil samples was made simpler by performing, beside bulk XAS investigations, microanalyses on soil thin sections by combined u-XRF/u-XRD (micro X-ray Fluorescence/micro X-ray Diffraction) and u-XANES, with a resolution of 20 um. The information deriving from the micro-scale was then used to understand the bulk data. m-XRF maps were collected to localize microscopic Hg-containing particles in areas of several hundreds of mm2. Simultaneous to u-XRF spectra, microdiffraction patterns were collected in each point of the map, to identify possible crystalline Hg-mineral forms or mineral associations. Once points of interest were localized, u-XANES spectra were also collected. In general, two main representative XANES spectra (S1 and S2) were observed from Hg-rich spots at the microscopic level. Interestingly, all the bulk XANES spectra from all soil samples could be fitted by a linear combination of the microscopic S1 and S2 spectra. Therefore, by fitting the S1 and S2 spectra by means of known standard spectra it was then possible to decipher Hg-speciation for all the soil samples. In conclusion, the main constituents in the soil samples were cinnabar (HgS), metacinnabar, corderoite (Hg3S2Cl2), and amorphous Hg-S-Cl phases, in different proportions. The presence of these amorphous forms was suggested by EXAFS and XRD structural analyses. The speciation obtained is also in agreement with the chemical behaviour of the soil samples as assessed by sequential extractions and thermal desorption analyses. The chemical species identified are typical of soils contaminated with wastes produced by chlor-alkali plants. Actually, a chlor-alkali plant was active in the area during the 1960-80's, and now is no more existing. In conclusion, notwithstanding the diffuse Hg-pollution in the investigated area, it seems that Hg is speciated in scarcely soluble and hardly mobilisable forms. The determination of the chemical forms of toxic elements in polluted soils is an indispensable step to identify the source of pollution, to formulate a correct risk assessment and to develop effective remediation strategies.

Terzano, R.; Santoro, A.; Spagnuolo, M.; Vekemans, B.; Medici, L.; Janssens, K.; Goettlicher, J.; Denecke, M. A.; Mangold, S.; Ruggiero, P.

2009-04-01

145

Characterization of Recrystallization and Microstructure Evolution in Lead-Free Solder Joints Using EBSD and 3D-XRD  

NASA Astrophysics Data System (ADS)

Development of vulnerable high-angle grain boundaries (and cracks) from low-angle boundaries during thermal cycling by means of continuous recrystallization was examined in fine-pitch ball grid array (BGA) packages with Sn-3.0Ag-0.5Cu (wt.%) (SAC305) lead-free solder joints. Electron backscatter diffraction (EBSD) and differential-aperture x-ray microscopy (DAXM or 3D-XRD) were used for surface and subsurface characterization. A large number of subgrain boundaries were observed in the parent orientation using both techniques. However, unlike studies of anisotropic deformation in noncubic metals at much lower homologous temperatures, no streaked diffraction peaks were observed in DAXM Laue patterns within each 1 ?m3 voxel after thermal cycling, suggesting that geometrically necessary dislocations (GNDs) are effectively absorbed by the preexisting subgrain boundaries. Storage at room temperature (0.6 T m) prior to DAXM measurement may also facilitate recovery processes to reduce local GND contents. Heterogeneous residual elastic strains were found near the interface between a precipitated Cu6Sn5 particle and the Sn grain, as well as near particular subgrain boundaries in the parent orientation. Grain boundary migration associated with recrystallization resulted in regions without internal strains, subgrain boundaries, or orientation gradients. Development of new grain orientations by continuous recrystallization and subsequent primary recrystallization and grain growth occurred in the regions where the cracks developed. Orientation gradients and subgrain structure were observed within newly formed recrystallized grains that could be correlated with slip systems having high Schmid factors.

Zhou, Bite; Bieler, Thomas R.; Lee, Tae-Kyu; Liu, Wenjun

2013-02-01

146

Characterizing the Phyllosilicate Component of the Sheepbed Mudstone in Gale Crater, Mars Using Laboratory XRD and EGA  

NASA Technical Reports Server (NTRS)

The Curiosity rover investigated the mineralogy of the Sheepbed mudstone member of the Yellowknife Bay formation in Gale crater. Data from the Chemistry and Mineralogy (CheMin) X-ray diffractometer (XRD) helped identify phyllosilicates in the two drilled samples, John Klein and Cumberland. These patterns showed peaks at low angles, consistent with (001) peaks in 2:1 swelling phyllosilicates [1]. Evolved gas analyses (EGA) by the Sample Analysis at Mars (SAM) instrument of these samples confirmed the presence of phyllosilicates through the release of H2O at high temperatures, consistent with dehydroxylation of octahedral OH in phyllosilicates [2]. CheMin data for the phyllosilicates at John Klein and Cumberland show that they are structurally similar in that their (02l) peaks are near 22.5 deg 2theta, suggesting both samples contain trioctahedral 2:1 phyllosilicates [1]. However, the positions of the (001) peaks differ: the phyllosilicate at John Klein has its (001) peak at 10 Angstroms, whereas the phyllosilicate at Cumberland has an (001) peak at 14 Angstroms. Such differences in (001) dspacings can be ascribed to the type of cation in the interlayer site [3]. For example, large monovalent cations (e.g., K(+)) have low hydration energies and readily lose their H2O of hydration, whereas small divalent cations (e.g., Mg(2+)) have high energies of hydration and retain H2O in the phyllosilicate interlayers [3,4]. The goal of this study is to determine whether differences in the interlayer cation composition can explain the CheMin data from John Klein and Cumberland and to use this knowledge to better understand phyllosilicate formation mechanisms.

Rampe, E. B.; Morris, R. V.; Ming, D. W.; Archer, P. D.; Bish, D. L.; Chipera, S. J.; Vaniman, D. T.; Blake, D. F.; Bristow, T. F.; Sutter, B.; Farmer, J. D.; Downs, R. T.; Leveille, R.; Achilles, C. A.; Crisp, J. A.; Des Marais, D. J.; Morookian, J. M.; Morrison, S. M.; Sarrazin, P. C.; Spanovich, N.; Treiman, A. H.; Yen, A. S.

2014-01-01

147

Transformation of meta-stable calcium silicate hydrates to tobermorite: reaction kinetics and molecular structure from XRD and NMR spectroscopy.  

PubMed

Understanding the integrity of well-bore systems that are lined with Portland-based cements is critical to the successful storage of sequestered CO2 in gas and oil reservoirs. As a first step, we investigate reaction rates and mechanistic pathways for cement mineral growth in the absence of CO2 by coupling water chemistry with XRD and NMR spectroscopic data. We find that semi-crystalline calcium (alumino-)silicate hydrate (Al-CSH) forms as a precursor solid to the cement mineral tobermorite. Rate constants for tobermorite growth were found to be k = 0.6 (+/- 0.1) x 10(-5) s(-1) for a solution:solid of 10:1 and 1.6 (+/- 0.8) x 10(-4) s(-1) for a solution:solid of 5:1 (batch mode; T = 150 degrees C). This data indicates that reaction rates for tobermorite growth are faster when the solution volume is reduced by half, suggesting that rates are dependent on solution saturation and that the Gibbs free energy is the reaction driver. However, calculated solution saturation indexes for Al-CSH and tobermorite differ by less than one log unit, which is within the measured uncertainty. Based on this data, we consider both heterogeneous nucleation as the thermodynamic driver and internal restructuring as possible mechanistic pathways for growth. We also use NMR spectroscopy to characterize the site symmetry and bonding environment of Al and Si in a reacted tobermorite sample. We find two [4]Al coordination structures at delta iso = 59.9 ppm and 66.3 ppm with quadrupolar product parameters (PQ) of 0.21 MHz and 0.10 MHz (+/- 0.08) from 27Al 3Q-MAS NMR and speculate on the Al occupancy of framework sites by probing the protonation environment of Al metal centers using 27Al{1H}CP-MAS NMR. PMID:19144195

Houston, Jacqueline R; Maxwell, Robert S; Carroll, Susan A

2009-01-01

148

Aragonite to Calcite Transformation Study by XRD and Esr Studies of Mn2+ in Freshwater Snail Shells:. P. Canaliculata Lamarck  

NASA Astrophysics Data System (ADS)

Electron spin resonance spectroscopy (ESR) was used to study the Mn2+ ions in snails of P. canaliculata lamarck (PCL). All these shells are abundant in Thailand. Fractions of aragonite and calcite phase in the shells have been approximately determined by ESR. The PCL shell was ground into fine powders and then four samples were separately annealed for 2 h in air at 400°C, 450°C, 500°C and 600°C, respectively. The phase transition from aragonite to calcite was monitored by X-ray diffractometer (XRD) and electron spin resonance spectrometer (ESR). Our results show that unheated PCL sample is mainly made of aragonite with only a small fraction of calcite. Annealing of the PCL powder sample at the temperature more than 450°C has resulted in the irreversible phase transformation from aragonite to calcite. The analysis of their ESR spectra has shown that Mn2+ ions partially substituted Ca2+ in the lattices. Finally, the spin Hamiltonian parameters for Mn2+ distributed in both aragonite and calcite were evaluated. Our detailed ESR spectral analyses of PCL show that Mn2+ ions enter Ca2+ sites during a biomineralization process. Typical simulated ESR parameters of PCL-500 of Mn2+ at a uniaxial site of calcite are gx=gy=2.078(1), gz=1.999(1), Ax=Ay=87.0 G, Az=89.00 G and D=115 G, respectively. It is thus possible to gain some insight of manganese incorporation into the fresh water shells during the biomineralization process.

Udomkan, N.; Limsuwan, P.; Chaimanee, Y.

149

Following the Formation of Active Co(III) Sites in Cobalt Substituted Aluminophosphates Catalysts by In-Situ Combined UV-VIS/XAFS/XRD Technique  

SciTech Connect

Cobalt substituted aluminophosphates, CoAlPO-34 (Chabazite structure) and DAF-8 (Phillipsite structure) were investigated by in situ combined XRD/EXAFS/UV-VIS technique. In-situ combined XRD, Co K-edge EXAFS and UV-Vis measurements carried out during the calcination process reveal that CoAlPO-34 containing 10 wt percent cobalt is stable and the cobalt ions are converted from Co(II) in the as synthesised form to Co(III); DAF-8 containing about 25 percent cobalt is not stable and does not show change in oxidation state.

Sankar, Gopinathan [Davy Faraday Research Laboratory, The Royal Institution of GB, 21 Albemarle Street, London W1S 4BS (United Kingdom); Daresbury Laboratory, Daresbury, Warrington, Cheshire WA4 4AD (United Kingdom); Fiddy, Steven; Harvey, Ian; Hayama, Shusaku; Bushnell-Wye, Graham [Daresbury Laboratory, Daresbury, Warrington, Cheshire WA4 4AD (United Kingdom); Beale, Andrew M. [Department of Inorganic Chemistry and Catalysis, Debye-Institute, Utrecht University, Sorbonnelaan 16, 3508 TC Utrecht (Netherlands)

2007-02-02

150

Influence of pH on the interlayer cationic composition and hydration state of Ca-montmorillonite: analytical chemistry, chemical modelling and XRD  

E-print Network

Influence of pH on the interlayer cationic composition and hydration state of Ca.ferrage@obs.ujf-grenoble.fr; Keywords : smectite, hydration state, XRD modelling, pH, chemical modelling, interlayer protons #12 after rapid equilibration (3 hours) under pH-controlled conditions (0.1-12.6 pH range). The solution

Boyer, Edmond

151

A new approach in quantitative in-situ XRD of cement pastes: Correlation of heat flow curves with early hydration reactions  

Microsoft Academic Search

XRD measurements of the hydration of synthetical cement (SyCem) were used to calculate the resulting heat flow from changes in the phase content. Calculations were performed by application of thermodynamic data. The comparison with data recorded from heat flow calorimetry was in good agreement with the calculated heat flow.The initial maximum of heat flow mainly is caused by the aluminate

Christoph Hesse; Friedlinde Goetz-Neunhoeffer; Juergen Neubauer

2011-01-01

152

XRD measurement of mean crystallite thickness of illite and illite/smectite: Reappraisal of the Kubler index and the Scherrer equation  

USGS Publications Warehouse

The standard form of the Scherrer equation, which has been used to calculate the mean thickness of the coherent scattering domain (CSD) of illite crystals from X-ray diffraction (XRD) full width data at half maximum (FWHM) intensity, employs a constant, Ksh, of 0.89. Use of this constant is unjustified, even if swelling has no effect on peak broadening, because this constant is valid only if all CSDs have a single thickness. For different thickness distributions, the Scherrer "constant" has very different values. Analysis of fundamental particle thickness data (transmission electron microscopy, TEM) for samples of authigenic illite and illite/smectite from diagenetically altered pyroclastics and filamentous illites from sandstones reveals a unique family of lognormal thickness distributions for these clays. Experimental relations between the distributions' lognormal parameters and mean thicknesses are established. These relations then are used to calculate the mean thickness of CSDs for illitic samples from XRD FWHM, or from integral XRD peak widths (integrated intensity/maximum intensity). For mixed-layer illite/smectite, the measured thickness of the CSD corresponds to the mean thickness of the mixed-layer crystal. Using this measurement, the mean thickness of the fundamental particles that compose the mixed-layer crystals can be calculated after XRD determination of precent smectitic interlayers. The effect of mixed layering (swelling) on XRD peak width for these samples is eliminated by using the 003 reflection for glycolated samples, and the 001, 002 or 003 reflection for dehydrated, K-saturated samples. If this technique is applied to the 001 reflection of air-dried samples (Kubler index measurement), mean CSD thicknesses are underestimated due to the mixed-layering effect. The technique was calibrated using NEWMOD ??-simulated XRD profiles of illite, and then tested on well-characterized illite and illite/smectite smaples. The XRD measurements are in good agreement with estimates of the mean thickness of fundamental particles obtained both TEM measurements and from fixed cations content, up to a mean value of 20 layers. Correction for instrumental broadening under the conditions employed here is unnecessary for this range of thicknesses.

Drits, V.; Srodon, J.; Eberl, D.D.

1997-01-01

153

XRD measurement of mean thickness, thickness distribution and strain for illite and illite-smectite crystallites by the Bertaut-Warren-Averbach technique  

USGS Publications Warehouse

A modified version of the Bertaut-Warren-Averbach (BWA) technique (Bertaut 1949, 1950; Warren and Averbach 1950) has been developed to measure coherent scattering domain (CSD) sizes and strains in minerals by analysis of X-ray diffraction (XRD) data. This method is used to measure CSD thickness distributions for calculated and experimental XRD patterns of illites and illite-smectites (I-S). The method almost exactly recovers CSD thickness distributions for calculated illite XRD patterns. Natural I-S samples contain swelling layers that lead to nonperiodic structures in the c* direction and to XRD peaks that are broadened and made asymmetric by mixed layering. Therefore, these peaks cannot be analyzed by the BWA method. These difficulties are overcome by K-saturation and heating prior to X-ray analysis in order to form 10-A?? periodic structures. BWA analysis yields the thickness distribution of mixed-layer crystals (coherently diffracting stacks of fundamental illite particles). For most I-S samples, CSD thickness distributions can be approximated by lognormal functions. Mixed-layer crystal mean thickness and expandability then can be used to calculate fundamental illite particle mean thickness. Analyses of the dehydrated, K-saturated samples indicate that basal XRD reflections are broadened by symmetrical strain that may be related to local variations in smectite interlayers caused by dehydration, and that the standard deviation of the strain increases regularly with expandability. The 001 and 002 reflections are affected only slightly by this strain and therefore are suited for CSD thickness analysis. Mean mixed-layer crystal thicknesses for dehydrated I-S measured by the BWA method are very close to those measured by an integral peak width method.

Drits, V.A.; Eberl, D.D.; Srodon, J.

1998-01-01

154

Synthesis and Characterization of Magnetic Metal-encapsulated Multi-walled Carbon Nanobeads  

PubMed Central

A novel, cost-effective, easy and single-step process for the synthesis of large quantities of magnetic metal-encapsulated multi-walled carbon nanobeads (MWNB) and multi-walled carbon nanotubes (MWNT) using catalytic chemical vapour deposition of methane over Mischmetal-based AB3alloy hydride catalyst is presented. The growth mechanism of metal-encapsulated MWNB and MWNT has been discussed based on the catalytically controlled root-growth mode. These carbon nanostructures have been characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM and HRTEM), energy dispersive analysis of X-ray (EDAX) and thermogravimetric analysis (TGA). Magnetic properties of metal-filled nanobeads have been studied using PAR vibrating sample magnetometer up to a magnetic field of 10 kOe, and the results have been compared with those of metal-filled MWNT.

2008-01-01

155

Comparative Study by MS and XRD of Fe50Al50 Alloys Produced by Mechanical Alloying, Using Different Ball Mills  

NASA Astrophysics Data System (ADS)

In this work we report a comparative study of the magnetic and structural properties of Fe50Al50 alloys produced by mechanical alloying using two different planetary ball mills with the same ball mass to powder mass relation. The Fe50Al50 sample milled during 48 h using the Fritsch planetary ball mill pulverisette 5 and balls of 20 mm, presents only a bcc alloy phase with a majority of paramagnetic sites, whereas that sample milled during the same time using the Fritsch planetary ball mill pulverisette 7 with balls of 15 mm, presents a bcc alloy phase with paramagnetic site (doublet) and a majority of ferromagnetic sites which include pure Fe. However for 72 h of milling this sample presents a bcc paramagnetic phase, very similar to that prepared with the first system during 48 h. These results show that the conditions used in the first ball mill equipment make more efficient the milling process.

Rojas Martínez, Y.; Pérez Alcázar, G. A.; Bustos Rodríguez, H.; Oyola Lozano, D.

2005-02-01

156

Silica-encapsulated magnetic nanoparticles: enzyme immobilization and cytotoxic study.  

PubMed

Silica-encapsulated magnetic nanoparticles (MNPs) were prepared via microemulsion method. The products were characterized by high resolution transmission electron microscopy (HRTEM) and energy-dispersive X-ray spectrum (EDS). MNPs with no observed cytotoxic activity against human lung carcinoma cell and brine shrimp lethality were used as suitable support for glucose oxidase (GOD) immobilization. Binding of GOD onto the support was confirmed by the FTIR spectra. The amount of immobilized GODs was 95 mg/g. Storage stability study showed that the immobilized GOD retained 98% of its initial activity after 45 days and 90% of the activity was also remained after 12 repeated uses. Considerable enhancements in thermal stabilities were observed for the immobilized GOD at elevated temperatures up to 80°C and the activity of immobilized enzyme was less sensitive to pH changes in solution. PMID:22269345

Ashtari, Khadijeh; Khajeh, Khosro; Fasihi, Javad; Ashtari, Parviz; Ramazani, Ali; Vali, Hojatollah

2012-05-01

157

Magnetic interaction in oxygenated alpha Fe-phthalocyanines  

NASA Astrophysics Data System (ADS)

Alpha iron phthalocyanines (?-FePc) oxygenated at low temperatures were investigated with the help of 57Fe Mössbauer spectroscopy, magnetization measurements (SQUID) and X-ray diffractometry (XRD). Mössbauer spectroscopy revealed that upon oxygenation of ?-FePc, new species were formed which could be associated with FeIIIPc oxygen adducts. Unexpectedly, magnetically split spectrum of oxygenated ?-FePc was observed below 20 K. In-field Mössbauer spectra in a 5 T external magnetic field at 5K and magnetization measurements indicate antiferromagnetic coupling in oxygenated ?-FePc.

Kuzmann, Ern?; Pechousek, Jiri; Cuda, Jan; Yin, Houping; Wei, Yen; Homonnay, Zoltán; Klencsár, Zoltán; Horváth, Attila; Machala, Libor; Kubuki, Shiro; Zoppellaro, Giorgio; Zboril, Radek; Nath, Amar

2014-10-01

158

Magnetic birefringence of iron oxyhydroxide nanoparticles stabilised by sucrose  

Microsoft Academic Search

Magnetically induced optical birefringence is used to investigate pharmaceutically important iron–sucrose aqueous suspensions. XRD and TEM measurements of the system of oxyhydroxide particles stabilised by sucrose have shown that this system contains iron oxyhydroxide in the form of 2–5nm particles. The mineral form of the iron-core is suggested to be akaganeite. Anisotropy of the optical polarizability and magnetic susceptibility of

M. Koralewski; M. Pochylski; J. Gierszewski

2011-01-01

159

Combining uXANES and uXRD mapping to analyse the heterogeneity in calcium carbonate granules excreted by the earthworm Lumbricus terrestris  

PubMed Central

The use of fluorescence full spectral micro-X-ray absorption near-edge structure (µXANES) mapping is becoming more widespread in the hard energy regime. This experimental method using the Ca K-edge combined with micro-X-ray diffraction (µXRD) mapping of the same sample has been enabled on beamline I18 at Diamond Light Source. This combined approach has been used to probe both long- and short-range order in calcium carbonate granules produced by the earthworm Lumbricus terrestris. In granules produced by earthworms cultured in a control artificial soil, calcite and vaterite are observed in the granules. However, granules produced by earthworms cultivated in the same artificial soil amended with 500?p.p.m. Mg also contain an aragonite. The two techniques, µXRD and µXANES, probe different sample volumes but there is good agreement in the phase maps produced. PMID:24365942

Brinza, Loredana; Schofield, Paul F.; Hodson, Mark E.; Weller, Sophie; Ignatyev, Konstantin; Geraki, Kalotina; Quinn, Paul D.; Mosselmans, J. Frederick W.

2014-01-01

160

Laser Raman, XRD, DSC and Ac-Impedance Analysis of Polymer Blend Electrolyte Based on Eco-Friendly Pva-Pvp Blend with NH4NO3  

NASA Astrophysics Data System (ADS)

Proton conducting polymer blend electrolytes have attractive interest because of their advantages such as processability, flexibility, electrochemical stability, easy handling and their applications to a variety of electrochemical devices such as fuel cells, chemical sensor and electrochemical displays. In the present work, the films of 50PVA-50PVP blend with different MWt% concentrations of NH4NO3 have been prepared by solution casting techniques using distilled water as a solvent. The prepared films have been investigated by different techniques such as XRD, DSC, Laser Raman and AC Impedance spectroscopy. XRD studies reveal the amorphous nature of the polymer blend-salt complexes. The glass transition temperature has been calculated from the DSC analysis. From the AC Impedance spectroscopy, the high conductivity of the 30MWt% of NH4NO3 doped 50PVA-50PVP polymer complex has been found to be the order of 1.41 × 10-3S cm-1 at room temperature.

Rajeswari, N.; Selvasekarapandian, S.; Prabaharan, S. R. S.; Kawamura, J.; Iwai, Y.; Karthikeyan, S.

2013-07-01

161

Quantitative assessment of alkali-reactive aggregate mineral content through XRD using polished sections as a supplementary tool to RILEM AAR-1 (petrographic method)  

SciTech Connect

The mineral content of 5 aggregate samples from 4 different countries, including reactive and non-reactive aggregate types, was assessed quantitatively by X-ray diffraction (XRD) using polished sections. Additionally, electron probe microanalyzer (EPMA) mapping and cathodoluminescence (CL) were used to characterize the opal-CT identified in one of the aggregate samples. Critical review of results from polished sections against traditionally powdered specimen has demonstrated that for fine-grained rocks without preferred orientation the assessment of mineral content by XRD using polished sections may represent an advantage over traditional powder specimens. Comparison of data on mineral content and silica speciation with expansion data from PARTNER project confirmed that the presence of opal-CT plays an important role in the reactivity of one of the studied aggregates. Used as a complementary tool to RILEM AAR-1, the methodology suggested in this paper has the potential to improve the strength of the petrographic method.

Castro, Nelia, E-mail: nelia.castro@ntnu.no [Norwegian University of Science and Technology (NTNU), Department of Geology and Mineral Resources Engineering, Sem Saelands vei 1, N-7491 Trondheim (Norway)] [Norwegian University of Science and Technology (NTNU), Department of Geology and Mineral Resources Engineering, Sem Saelands vei 1, N-7491 Trondheim (Norway); Sorensen, Bjorn E. [Norwegian University of Science and Technology (NTNU), Department of Geology and Mineral Resources Engineering, Sem Saelands vei 1, N-7491 Trondheim (Norway)] [Norwegian University of Science and Technology (NTNU), Department of Geology and Mineral Resources Engineering, Sem Saelands vei 1, N-7491 Trondheim (Norway); Broekmans, Maarten A.T.M. [Geological Survey of Norway, Department of Industrial Minerals and Metals, PO Box 6315 Sluppen, N-7491 Trondheim (Norway)

2012-11-15

162

Instrumental Characterization Of Coir PITH By XRD, FTIR and SEM After Radium Adsorption From Aqueous Solution Under The Presence Of Humic Acids  

NASA Astrophysics Data System (ADS)

Adsorption interactions of radium (Ra) ions onto coir pith (CP) under the presence of humic acid (HA) in the aqueous solution were investigated using X-ray diffraction (XRD), Fourier Transform Infrared Spectrophotometer (FTIR) and Scanning Electron Microscopy (SEM) techniques. XRD, IR and SEM characterization of the CP has revealed differences in the native CP and Ra ions loaded CP under the presence of HA in the aqueous solution. The X-Ray patterns showed that crystalline structure of the loaded CP exhibited a decrease in crystalline structure at around 49°-51° compared with unloaded CP. Characterization by IR revealed that participation of some surface functional groups during the Ra adsorption. SEM images for the morphological studies showed that there were slightly changes of the CP surfaces after the adsorption process.

Laili, Zalina; Omar, Muhamat; Yasir, Muhamad Samudi; Ibrahim, Mohd Zaidi; Yahaya, Mohd Yusri; Murshidi, Julie Andrianny

2010-01-01

163

Combining µXANES and µXRD mapping to analyse the heterogeneity in calcium carbonate granules excreted by the earthworm Lumbricus terrestris.  

PubMed

The use of fluorescence full spectral micro-X-ray absorption near-edge structure (µXANES) mapping is becoming more widespread in the hard energy regime. This experimental method using the Ca K-edge combined with micro-X-ray diffraction (µXRD) mapping of the same sample has been enabled on beamline I18 at Diamond Light Source. This combined approach has been used to probe both long- and short-range order in calcium carbonate granules produced by the earthworm Lumbricus terrestris. In granules produced by earthworms cultured in a control artificial soil, calcite and vaterite are observed in the granules. However, granules produced by earthworms cultivated in the same artificial soil amended with 500?p.p.m. Mg also contain an aragonite. The two techniques, µXRD and µXANES, probe different sample volumes but there is good agreement in the phase maps produced. PMID:24365942

Brinza, Loredana; Schofield, Paul F; Hodson, Mark E; Weller, Sophie; Ignatyev, Konstantin; Geraki, Kalotina; Quinn, Paul D; Mosselmans, J Frederick W

2014-01-01

164

Water–Gas Shift Reaction Over Aluminum Promoted Cu\\/CeO 2 Nanocatalysts Characterized by XRD, BET, TPR and Cyclic Voltammetry (CV)  

Microsoft Academic Search

A series of aluminum promoted Cu\\/CeO2 nanocatalysts with aluminum content in the range of 0–5wt.% were prepared by co-precipitation method and examined with respect\\u000a to their catalytic performance for the water–gas shift (WGS) reaction. The catalysts were characterized by XRD, BET, H2-TPR and cyclic voltammetry (CV) techniques. The results indicate that catalytic activity increases with the aluminum content\\u000a at first,

Lei Li; Yingying Zhan; Qi Zheng; Yuanhui Zheng; Xingyi Lin; Dalin Li; Junjiang Zhu

2007-01-01

165

Characterization of the Nickel Cobaltite, NiCo 2O 4, Prepared by Several Methods: An XRD, XANES, EXAFS, and XPS Study  

Microsoft Academic Search

The bulk structural properties of the nickel cobaltite, NiCo2O4, prepared by the thermal decomposition of carbonates, sol–gel methods, and the decomposition of hydroxides, have been examined by X-ray powder diffraction (XRD) and X-ray absorption spectroscopy (EXAFS and XANES). The results indicate, as expected, that Ni occupies the octahedral sites of the spinel structure while Co occupies both tetrahedral and octahedral

J. F. Marco; J. R. Gancedo; M. Gracia; J. L. Gautier; E. R??os; F. J. Berry

2000-01-01

166

Characterization of the Nickel Cobaltite, NiCo2O4, Prepared by Several Methods: An XRD, XANES, EXAFS, and XPS Study  

Microsoft Academic Search

The bulk structural properties of the nickel cobaltite, NiCo2O4, prepared by the thermal decomposition of carbonates, sol-gel methods, and the decomposition of hydroxides, have been examined by X-ray powder diffraction (XRD) and X-ray absorption spectroscopy (EXAFS and XANES). The results indicate, as expected, that Ni occupies the octahedral sites of the spinel structure while Co occupies both tetrahedral and octahedral

J. F. Marco; J. R. Gancedo; M. Gracia; J. L. Gautier; E. Ríos; F. J. Berry

2000-01-01

167

Crystal structure of La{sub 0.4}Sr{sub 0.6}CoO{sub 2.71} investigated by TEM and XRD  

Microsoft Academic Search

The structure of the oxygen-deficient perovskite La{sub 0.4}Sr{sub 0.6}CoO{sub 3-} (=0.29) was investigated by transmission electron microscopy (TEM) and X-ray powder diffraction (XRD). Domains between 50 and 250 nm in size were observed in the electron microscope. Weak superstructure reflections were found with both X-ray and electron diffraction. Investigations of these superstructure reflections by selected area electron diffraction (SAED) and

C. Gspan; W. Grogger; B. Bitschnau; E. Bucher; W. Sitte; F. Hofer

2008-01-01

168

Magnetic Levitation.  

ERIC Educational Resources Information Center

Discusses the principles of magnetic levitation presented in the physics classroom and applied to transportation systems. Topics discussed include three classroom demonstrations to illustrate magnetic levitation, the concept of eddy currents, lift and drag forces on a moving magnet, magnetic levitation vehicles, levitation with permanent magnets

Rossing, Thomas D.; Hull, John R.

1991-01-01

169

Synthesis and study of quantum size effect, XRD and IR spectral properties of PbS nanocrystals doped in SiO 2 xerogel matrix  

NASA Astrophysics Data System (ADS)

PbS nanocrystallites with a diameter smaller than 15 nm have been prepared in a pure silica matrix by sol-gel route. Silica xerogels containing 0.01-3 wt% of PbS were prepared by hydrolysis and polycondensation of methanolic tetramethyl orthosilicate [TMOS, Si(OCH 3) 4] in the presence of ammonium hydroxide (NH 4OH) catalyst and lead nitrate Pb(NO 3) 2 and subsequent reaction with Na 2S to form PbS nanocrystals. These PbS-nanocrystals-doped xerogels were characterised by optical absorption, X-ray diffraction (XRD) and infra-red spectroscopy (IR). Blue shift in optical absorption threshold indicate that the PbS crystallite size reduced from 16 to 5 nm with a decrease in the PbS wt% from 3 to 0.01. It was found from the XRD studies that weak and broad peaks are obtained because of nanocrystalline state of PbS. The PbS crystallite structure was found to be cubic in the SiO 2 matrix by observing the peak positions in the XRD pattern. In the IR spectra, the peaks related to PbS bonds were obtained and they are weak. It was observed that there was no change in peak position related to the SiO 2 matrix in the presence of PbS in between the SiO 2 network.

Parvathy, N. N.; Pajonk, G. M.; Rao, A. Venkateswara

1997-08-01

170

Thermal evolution of the Cl(-)-LiAl(2) layered double hydroxide: a multinuclear MAS NMR and XRD perspective.  

PubMed

Layered double hydroxides (LDHs) with a cation composition of LiAl(2) have a wide range of potential applications as catalysts, catalyst supports, and precursors for refractory oxide materials, including several industrially important lithium aluminate phases. The understanding of the calcination behavior of this group of LDH phases is essential to advancing these applications, and the research described here focuses on the thermal decomposition and structural evolution of LiAl(2)(OH)(6)Cl.nH(2)O in the temperature range of 20-1100 degrees C. (27)Al, (35)Cl, and (6,7)Li magic angle spinning nuclear magnetic resonance spectroscopy, powder X-ray diffraction, thermal analysis (including thermogravimetric and differential scanning calorimetry), and compositional analysis provide a highly consistent picture of the thermally induced phase formation and transformations of this LDH. The loss of the surface and interlayer water can begin as low as room temperature, depending on the relative humidity. Beginning at about 300 degrees C, the simultaneous volatilization of H(2)O and HCl and the exsolution of crystalline LiCl result in the formation of amorphous Li-Al-O-OH. By at least 500 degrees C, volumes with the structures of alpha-LiAlO(2) and LiAl(5)O(8) appear, and these phases become progressively more ordered with increasing temperature. LiCl begins to volatilize by 850 degrees C and is present only in trace amounts above ca. 1000 degrees C. alpha-LiAlO(2) converts to gamma-LiAlO(2) between 970 and 1100 degrees C. Because of the delithiation due to LiCl volatilization, the final products are dominated by LiAl(5)O(8), in contrast to the calcination products of previously studied LiAl(2) LDHs which are dominated by LiAlO(2). PMID:11720493

Hou, X; Kirkpatrick, R J

2001-12-01

171

Magnet Mania  

NSDL National Science Digital Library

In this activity, learners explore the relationship between electric charges and magnetic fields. Learners create a magnetic field using electricity and observe its effect on the magnetic needle of a compass.

Kansas, University O.

2006-01-01

172

XRD and NMR investigation of Ti-compound formation in solution-doping of sodium aluminum hydrides: Solubility of Ti in NaAlH4 crystals grown in THF  

SciTech Connect

Sodium aluminum hydrides have gained attention due to their high hydrogen weight percent (5.5% ideal) compared to interstitial hydrides, and as a model for hydrides with even higher hydrogen weight fraction. The purpose of this paper is to investigate the Ti-compounds that are formed under solution-doping techniques, such as wet doping in solvents such as tetrahydrofuran (THF). Compound formation in Ti-doped sodium aluminum hydrides is investigated using x-ray diffraction (XRD) and magic angle spinning (MAS) nuclear magnetic resonance (NMR). We present lattice parameter measurements of crushed single crystals, which were exposed to Ti during growth. Rietveld refinements indicate no lattice parameter change and thus no solubility for Ti in NaAlH{sub 4} by this method of exposure. In addition, x-ray diffraction data indicate that no Ti substitutes in NaH, the final decomposition product for the alanate. Reaction products of completely reacted (33.3 at. %-doped) samples that were solvent-mixed or mechanically milled are investigated. Formation of TiAl{sub 3} is observed in mechanically milled materials, but not solution mixed samples, where bonding to THF likely stabilizes Ti-based nano-clusters. The Ti in these clusters is activated by mechanical milling.

Majzoub, E H; Herberg, J L; Stumpf, R; Spangler, S; Maxwell, R S

2004-08-26

173

XRD and NMR investigation of Ti-compound formation in solution-doping of sodium aluminum hydrides : solubility of Ti in NaAlH4 crystals grown in THF.  

SciTech Connect

Sodium aluminum hydrides have gained attention due to their high hydrogen weight percent (5.5% ideal) compared to interstitial hydrides, and as a model for hydrides with even higher hydrogen weight fraction. The purpose of this paper is to investigate the Ti-compounds that are formed under solution-doping techniques, such as wet doping in solvents such as tetrahydrofuran (THF). Compound formation in Ti-doped sodium aluminum hydrides is investigated using X-ray diffraction (XRD) and magic angle spinning (MAS) nuclear magnetic resonance (NMR). We present lattice parameter measurements of crushed single crystals, which were exposed to Ti during growth. Rietveld refinements indicate no lattice parameter change and thus no solubility for Ti in NaAlH{sub 4} by this method of exposure. In addition, X-ray diffraction data indicate that no Ti substitutes in NaH, the final decomposition product for the alanate. Reaction products of completely reacted (33.3 at.%-doped) samples that were solvent-mixed or mechanically milled are investigated. Formation of TiAl{sub 3} is observed in mechanically milled materials, but not solution mixed samples, where bonding to THF likely stabilizes Ti-based nano-clusters. The Ti in these clusters is activated by mechanical milling.

Herberg, Julie L. (Lawrence Livermore National Laboratories, Livermore, CA); Maxwell, Robert S. (Lawrence Livermore National Laboratories, Livermore, CA); Stumpf, Roland Rudolph; Spangler, Scott W.; Majzoub, Eric H.

2004-08-01

174

The Formation Mechanism of the Higher Performance V3Ga Phase on the High Ga Content Cu-Ga Compound/V Diffusion Reaction Through the High-Temperature XRD Analysis  

NASA Astrophysics Data System (ADS)

V3Ga compound has a shorter radioactive decay time compared with Nb-based compounds and it will be one of the candidate superconducting magnet materials for advanced low activation fusion reactor systems.!Recently, we succeeded in developing new V3Ga wires, fabricated via the PIT process using high Ga content Cu-Ga compounds above Cu-Ga solid solution composition. Jc and Hc2 enhancements of V3Ga wire due to increasing three times of the V3Ga volume fraction were also confirmed. For the further microstructure control, in-situ observation of diffusion reaction with increase of temperature using High-Temperature X-ray diffraction (HT-XRD) was measured. Various high Ga content Cu-Ga compounds were composed with Cu3Ga (? phase: ?30at%Ga), Cu9Ga4 (? phase: ?40at%Ga) and CuGa2 (? phase: ?64at%Ga) compounds. Especially, CuGa2 compound has much lower melting point (254°C) compared with various Cu-Ga compounds. In the case of diffusion reaction including CuGa2 phase, V3Ga phase was formed by the second step diffusion reactions; the first one is solid-liquid diffusion between the dissociated Ga liquid phase and metal V, the second one is soild-solid diffusion reaction between solid phase formed by the first step reaction and metal V

Hishinuma, Y.; Kikuchi, A.; Murakami, S.; Matsuda, K.; Taniguchi, H.; Takeuchi, T.

175

Electronic and magnetic properties of Co-doped ZnO diluted magnetic semiconductor  

Microsoft Academic Search

The effect of low level Co doping (5%) on polycrystalline ZnO samples has been investigated to correlate the observed changes in their magnetic state vis à vis changes in their electronic properties. Rietveld refinement of the XRD patterns confirms single phase crystallization of the samples in the wurtzite type lattice, with no evidence of any secondary phases. The as-synthesized Co-doped

R. K. Singhal; Arvind Samariya; Y. T. Xing; Sudhish Kumar; S. N. Dolia; U. P. Deshpande; T. Shripathi; Elisa B. Saitovitch

2010-01-01

176

Structural and magnetic characterization of Co-Cu nanoparticles prepared by arc-discharge  

NASA Astrophysics Data System (ADS)

The structure and magnetic properties of the nanoparticles of immiscible system Co{20}Cu{80} prepared by means of arc-discharge, have been studied in detail. The diameters of the particles are about 20 ˜ 30 nm and a core/shell structure forms. The cores are Co-Cu solutions, which show some small Co precipitates, encapsulated with a shell of cupper oxide or cobalt oxide as observed by means of high-resolution transmission electron microscope (HRTEM) and energy dispersive X-ray (EDS). The loop shift in the hysteresis loop indicates the existence of the exchange bias between ferromagnetic and antiferromagnetic components at low temperatures. A block temperature about 180 K has been observed for as-deposited nanoparticles. For the annealed nanoparticles, the thermal magnetization at low temperatures is satisfied with Bloch's law.

You, Cai-Yin; Yang, Z. Q.; Xiao, Q. F.; Škorvánek, I.; Ková?, J.; Li, Z. J.; Liu, W.; Zhang, Z. D.

2004-10-01

177

MAGNETIC RECONNECTION, MAGNETIC HELICITY, &  

E-print Network

buoyancy, tension, and reconnection all play a role. They made the analogy that a filament is buoyant, and acts like a balloon. It is line­tied to the photosphere by the tension of magnetic field lines, which act like the tethers that hold a hot­air balloon before launch. When field lines in the filament

Canfield, Richard

178

Magnet Tower  

NSDL National Science Digital Library

In this activity, learners build magnetic towers to explore the forces and properties of magnets. This activity allows learners to experiment and play with magnets and feel first-hand the force of magnets pushing and pulling. Note: this activity requires the use of a drill and saw, which are not included in the cost of materials.

Workshop, Mission S.

2013-01-01

179

Crystal hack' to predict h, k, l from 'c' as well as 'a' values for cubic and HCP binary alloy crystals from XRD data  

NSDL National Science Digital Library

'Crystal hack' by Dr M Kanagasabapathy is used to predict h, k, l from 'c' as well as 'a' values for cubic and HCP binary alloy crystals from XRD data (2-Theta diffraction and wavelength of X-rays). d-spacing and hkl can be predicted precisely. Inbuilt data base for some elemental crystal system is included. It can be a useful tool for powder diffraction researchers / students to predict or shift in diffraction angle with hkl indices for cube-HCP binary alloy crystals.

Kanagasabapathy, M.

180

Magnetic, electronic and structural properties of Zn x Fe 3? x O 4  

Microsoft Academic Search

A series of samples ZnxFe3?xO4 have been prepared by the chemical coprecipitation technique and characterized by X-ray diffraction (XRD), vibrating sample magnetometry (VSM) and X-ray photoelectron spectroscopy (XPS). XRD demonstrates all the samples of ZnxFe3?xO4 have a spinel structure same as Fe3O4. The magnetic hysteresis loops of ZnxFe3?xO4 obtained from VSM indicate that the saturation magnetization has a maximum when

Meilan Wen; Qi Li; Yongtao Li

2006-01-01

181

Effect of deposition pressure on the structural and magnetic properties of cobalt ferrite thin films  

SciTech Connect

We present the influence of deposition pressure on the structural and magnetic properties of cobalt ferrite thin films. Thin films of Co ferrite were deposited by rf sputtering on Si (100) substrate and characterized by X - Ray Diffraction (XRD), Atomic Force Microscopy (AFM) and Vibrating Sample Magnetometer (VSM). The XRD patterns showed the formation of crystalline single phase of the films. The particle size and surface roughness of the films were strongly influence by gas pressure. Hysteresis loops measured at room temperature showed the enhancement of magnetic properties with the increase of gas pressure which is attributed to the decrease of particle size.

Nongjai, R.; Khan, S.; Ahmad, H.; Khan, I. [Department of Applied Physics, Zakir Hussain College of Engineering and Technology, A.M.U., Aligarh (India); Asokan, K. [Material Science Division, Inter University Accelerator Centre, New Delhi (India)

2013-06-03

182

Synthesis, structural and vibrational investigation on 2-phenyl-N-(pyrazin-2-yl)acetamide combining XRD diffraction, FT-IR and NMR spectroscopies with DFT calculations.  

PubMed

The optimized molecular structure, vibrational frequencies, corresponding vibrational assignments of 2-phenyl-N-(pyrazin-2-yl)acetamide have been investigated experimentally and theoretically using Gaussian09 software package. The title compound was optimized by using the HF/6-31G(6D,7F) and B3LYP/6-31G(6D,7F) calculations. The geometrical parameters are in agreement with the XRD data. The stability of the molecule arising from hyper-conjugative interaction and charge delocalization has been analyzed using NBO analysis. Gauge-including atomic orbital (1)H-NMR chemical shifts calculations were carried out and compared with experimental data. The HOMO and LUMO analysis is used to determine the charge transfer within the molecule. Molecular electrostatic potential was performed by the DFT method. First hyperpolarizability is calculated in order to find its role in non linear optics. From the XRD data, in the crystal, molecules are held together by strong C-H?O and N-H?O intermolecular interactions. PMID:25124846

Lukose, Jilu; Yohannan Panicker, C; Nayak, Prakash S; Narayana, B; Sarojini, B K; Van Alsenoy, C; Al-Saadi, Abdulaziz A

2015-01-25

183

Magnetic ordering in Cr-doped Bi2Se3 thin films  

NASA Astrophysics Data System (ADS)

We report the structural and magnetic study of Cr-doped Bi2Se3 thin films using x-ray diffraction (XRD), magnetometry and polarized neutron reflectometry (PNR). Epitaxial layers were grown on c-plane sapphire by molecular beam epitaxy in a two-step process. High-resolution XRD shows the exceptionally high crystalline quality of the doped films with no parasitic phases up to a Cr concentration of 12% (in % of the Bi sites occupied by substitutional Cr). The magnetic moment, measured by SQUID magnetometry, was found to be {\\sim}2.1\\ \\mu_\\text{B} per Cr ion. The magnetic hysteresis curve shows an open loop with a coercive field of {\\sim}10\\ \\text{mT} . The ferromagnetic transition temperature was determined to be 8.5\\ \\text{K} analyzing the magnetization-temperature gradient. PNR shows the film to be homogeneously ferromagnetic with no enhanced magnetism near the surface or interface.

Collins-McIntyre, L. J.; Harrison, S. E.; Schönherr, P.; Steinke, N.-J.; Kinane, C. J.; Charlton, T. R.; Alba-Veneroa, D.; Pushp, A.; Kellock, A. J.; Parkin, S. S. P.; Harris, J. S.; Langridge, S.; van der Laan, G.; Hesjedal, T.

2014-09-01

184

Planetary magnetism  

NASA Technical Reports Server (NTRS)

A synoptic view of early and recent data on the planetary magnetism of Mercury, Venus, the moon, Mars, Jupiter, and Saturn is presented. The data on Mercury from Mariner 10 are synthesized with various other sources, while data for Venus obtained from 120 orbits of Pioneer Venus give the upper limit of the magnetic dipole. Explorer 35 Lunar Orbiter data provided the first evidence of lunar magnetization, but it was the Apollo subsatellite data that measured accurately the magnetic dipole of the moon. A complete magnetic survey of Mars is still needed, and only some preliminary data are given on the magnetic dipole of the planet. Figures on the magnetic dipoles of Jupiter and Saturn are also suggested. It is concluded that if the magnetic field data are to be used to infer the interior properties of the planets, good measures of the multiple harmonics in the field are needed, which may be obtained only through low altitude polar orbits.

Russell, C. T.

1981-01-01

185

Magnetic Seesaw  

NSDL National Science Digital Library

In this activity, learners build a seesaw powered by magnets. Use this activity to demonstrate how a lever is a simple machine and how magnets repel and attract depending on the alignment of the poles.

Workshop, Mission S.

2013-01-01

186

Magnetism Hunt  

NSDL National Science Digital Library

In this activity about magnetism (page 4 of the PDF), learners will experiment with magnets and different objects to find out that not all metals are attracted to magnets. Even though there are only a few supplies listed, the possibilities are really endless when it comes to what learners can try to attract to the magnet. Learners make predictions and compare their predictions to actual outcomes.

Cosi

2009-01-01

187

Magnetic Pendulums  

NSDL National Science Digital Library

In this activity and demonstration about electricity and magnetism, learners observe how the current generated when one copper coil swings through a magnetic field starts a second coil swinging. Learners also explore what happens when they change the polarity of the magnet, reverse the coil, or add a clip lead to short-circuit the coils. Use this activity to illustrate how electricity and magnetism interact. The assembly of the electromagnetic swing device takes about an hour.

Exploratorium, The

2011-12-05

188

Annealing effects on the microstructure and magnetic domain structures of duplex stainless steel studied by in situ technique  

NASA Astrophysics Data System (ADS)

The effects of annealing temperature on the microstructure and the magnetic domain structures of duplex stainless steel 2507 were investigated by the magnetic force microscopy (MFM), X-ray diffraction (XRD), and electron backscattered diffraction (EBSD). The MFM and XRD results indicated that the volume fraction of ferrite phase increased with increasing annealing temperature, but the lattice constants kept constant. Moreover, with the rise of annealing temperature, the magnetic domain structure in the ferrite phase varied gradually, where the magnetic domain became thinner and the distribution turned more homogeneous. These results gave a direct evidence for the changes of microstructure and magnetic domain structure induced by the annealing treatment. EBSD analysis showed that the orientation of ferrite grains changed after annealing treatments, which coincided with the changes of the microstructure and the magnetic domain structures.

Guo, L. Q.; Zhao, X. M.; Li, M.; Zhang, W. J.; Bai, Y.; Qiao, L. J.

2012-10-01

189

Seeing Magnetism  

NSDL National Science Digital Library

This is lesson to begin learners' thinking about magnetic influence. Learners will watch a classroom demonstration about the effect of magnets on iron filings and then complete a journal assignment to record their reactions and thoughts. This is the first activity in the Mapping Magnetic Influence educators guide.

190

Superconducting magnets  

SciTech Connect

This report discusses the following topics on superconducting magnets: D19B and -C: The next steps for a record-setting magnet; D20: The push beyond 10 T: Beyond D20: Speculations on the 16-T regime; other advanced magnets for accelerators; spinoff applications; APC materials development; cable and cabling-machine development; and high-{Tc} superconductor at low temperature.

Not Available

1994-08-01

191

Magnetic Suction  

NSDL National Science Digital Library

In this activity about electricity and magnetism, learners discover how a doorbell works. A coil of wire with current flowing through it forms an electromagnet that acts similar to a bar magnet. The coil will magnetize an iron nail and attract it in a remarkably vigorous way.

Exploratorium, The

2012-11-13

192

Magnetization processes in hybrid magnets  

NASA Astrophysics Data System (ADS)

Injection-molded, oriented hybrid magnets consisting of mixtures of BaO?6Fe2O3 and MQP-Q (exchange-coupled Nd2Fe14B+?-Fe) are compared to bonded magnets made only from ferrite or MQP-Q. The magnetic fractions of the hybrid magnets consist of 80, 60, or 40 wt % ferrite blended with 20, 40, or 60 wt % MQP-Q. The microstructure was investigated by x-ray diffraction, scanning electron microscopy, atomic force microscopy, and magnetic force microscopy. Atomic and magnetic force microscopy images indicated differences between the physical and magnetic microstructures. Magnetic interactions were studied via isothermal remanence (IRM) and dc-demagnetization (DCD) remanence curves and Henkel plots. In contrast to what is observed in exchange spring magnets, the IRM and DCD susceptibilities of all magnets present peaks of nearly the same width, centered at roughly the same value of the magnetic field, consistent with weak dipolar interactions between magnetic particles. The IRM susceptibilities show structure associated with magnetic inhomogenieties in the samples.

Emura, M.; Neiva, A. C.; Missell, F. P.; Babcock, K. L.; Ormerod, J.; Constantinides, S.

1998-06-01

193

Structure and occurrences of ? green rust ? related new minerals of the ? fougérite ? group, trébeurdenite and mössbauerite, belonging to the ? hydrotalcite ? supergroup; how Mössbauer spectroscopy helps XRD.  

NASA Astrophysics Data System (ADS)

Mössbauer spectroscopy yields decisive information for interpreting x-ray diffraction (XRD) patterns in the case of `green rusts" with intercalated CO anions, i.e. the chemical analogs of the three minerals that constitute within the ? hydrotalcite ? supergroup comprising 44 minerals the " fougèrite" group where the structure stays globally unchanged. The only difference comes from the deprotonation of OH- ions at the apices of the octahedrons occupied by the Fe cations so that Fe I I ions become Fe I I I . Low angle x-ray diffraction using synchrotron radiation displays the presence of many polytypes which reflects the stacking of brucite like layers and anion interlayers so that a 2D long range order of anions stays unchanged from fougèrite to mössbauerite.

Génin, J.-M. R.; Christy, A.; Kuzmann, E.; Mills, S.; Ruby, C.

2014-04-01

194

Ceria-based Catalysts for the Production of H2 Through the Water-gas-shift Reaction: Time-Resolved XRD and XAFS Studies  

SciTech Connect

Hydrogen is a potential alternate energy source for satisfying many of our energy needs. In this work, we studied H2 production from the water-gas-shift (WGS) reaction over Ce1-x Cu x O2 catalysts, prepared with a novel microemulsion method, using two synchrotron-based techniques: time-resolved X-ray diffraction (XRD) and X-ray absorption fine structure (XAFS). The results are compared with those reported for conventional CuO x /CeO2 and AuO x /CeO2 catalysts obtained through impregnation of ceria. For the fresh Ce1-x Cu x O2 catalysts, the results of XAFS measurements at the Cu K-edge indicate that Cu is in an oxidation state higher than in CuO. Nevertheless, under WGS reaction conditions the Ce1-x Cu x O2 catalysts undergo reduction and the active phase contains very small particles of metallic Cu and CeO2-x . Time-resolved XRD and XAFS results also indicate that Cud+ and Aud+ species present in fresh CuO x /CeO2 and AuO x /CeO2 catalysts do not survive above 200 C under the WGS conditions. In all these systems, the ceria lattice displayed a significant increase after exposure to CO and a decrease in H2O, indicating that CO reduced ceria while H2O oxidized it. Our data suggest that H2O dissociation occurred on the Ovacancy sites or the Cu-Ovacancy and Au-Ovacancy interfaces. The rate of H2 generation by a Ce0.95Cu0.05O2 catalyst was comparable to that of a 5 wt% CuO x /CeO2 catalyst and much bigger than those of pure ceria or CuO.

Wang,X.; Rodriguez, J.; Hanson, J.; Gamarra, D.; Marinez-Arias, A.; Fernandez-Garcia, M.

2008-01-01

195

Magnetic investigations  

SciTech Connect

Air and ground magnetic anomalies in the Climax stock area of the NTS help define the gross configuration of the stock and detailed configuration of magnetized rocks at the Boundary and Tippinip faults that border the stock. Magnetizations of geologic units were evaluated by measurements of magnetic properties of drill core, minimum estimates of magnetizations from ground magnetic anomalies for near surface rocks, and comparisons of measured anomalies with anomalies computed by a three-dimensional forward program. Alluvial deposits and most sedimentary rocks are nonmagnetic, but drill core measurements reveal large and irregular changes in magnetization for some quartzites and marbles. The magnetizations of quartz monzonite and granodiorite near the stock surface are weak, about 0.15 A/m, and increase at a rate of 0.00196 A/m/m to 1.55 A/m, at depths greater than 700 m (2300 ft). The volcanic rocks of the area are weakly magnetized. Aeromagnetic anomalies 850 m (2800 ft) above the stock are explained by a model consisting of five vertical prisms. Prisms 1, 2, and 3 represent the near surface outline of the stock, prism 4 is one of the models developed by Whitehill (1973), and prism 5 is modified from the model developed by Allingham and Zietz (1962). Most of the anomaly comes from unsampled and strongly-magnetized deep sources that could be either granite or metamorphosed sedimentary rocks. 48 refs., 23 figs., 3 tabs.

Bath, G.D.; Jahren, C.E.; Rosenbaum, J.G. [Geological Survey, Denver, CO (USA); Baldwin, M.J. [Fenix and Scisson, Inc., Mercury, NV (USA)

1983-12-31

196

Study of hard-soft magnetic ferrite films prepared by pulsed laser deposition  

NASA Astrophysics Data System (ADS)

Soft magnetic Mg0.1Ni0.3Zn0.6Fe2O4 and hard magnetic BaFe12O19 bulk nanocrystalline ferrites were synthesized using the sol-gel auto-combustion method, and were used as targets to deposit soft-hard thin films by the pulsed laser deposition (PLD) method. Various soft-hard thin films with different preparation conditions were deposited on Si (100) substrate, which can be effectively utilized to get better magnetic properties. The prepared films were characterized by the X-ray diffraction (XRD), atomic force microscopy (AFM) and magnetic measurements. XRD confirms the presence of soft and hard phases in the thin films. Coercivity of the prepared films ranges from 1.67 to 2.66 kA/m. AFM images show clustering of grains at the film surface with a characteristic columnar growth.

Satalkar, M.; Kane, S. N.; Ghosh, A.; Raghuvanshi, S.; Tapkir, P.; Ghodke, N.; Phase, D. M.; Chaudhary, R. J.; Pasko, A.; LoBue, M.; Mazaleyrat, F.

2014-09-01

197

Structural characterization and magnetic properties of superparamagnetic zinc ferrite nanoparticles synthesized by the coprecipitation method  

NASA Astrophysics Data System (ADS)

Single phase zinc ferrite (ZnFe2O4) nanoparticles have been prepared by the coprecipitation method without any subsequent calcination. The effects of precipitation temperature in the range 20-80 °C on the structural and the magnetic properties of zinc ferrite nanoparticles were investigated. The crystallite size, microstructure and magnetic properties of the prepared nanoparticles were studied using X-ray diffraction (XRD), Fourier transmission infrared spectrum, transmission electron microscope (TEM), energy dispersive X-ray spectrometer and vibrating sample magnetometer. The XRD results showed that the coprecipitated nanoparticles were single phase zinc ferrite with mixture of normal and inverse spinel structures. Furthermore, ZnFe2O4 nanoparticles have the crystallite size in the range 5-10 nm, as confirmed by TEM. The magnetic measurements exhibited that the zinc ferrite nanoparticles synthesized at 40 °C were superparamagnetic with the maximum magnetization of 7.3 emu/g at 10 kOe.

Raeisi Shahraki, R.; Ebrahimi, M.; Seyyed Ebrahimi, S. A.; Masoudpanah, S. M.

2012-11-01

198

Electroplating hard magnetic SmCo for magnetic microactuator applications  

SciTech Connect

Patterned SmCo thin films were electroplated from an aqueous solute containing glycine by using dc and pulse dc current on the beaker level. Micromolds prepared by photolithography allow an accurate pattern transfer for patterned deposition of the material. A flux guide of a magnetic microactuator was chosen as a pattern, and Al{sub 2}O{sub 3} was used as the substrate. Au and Cr were investigated as seed layer materials. The content of Sm in the SmCo films is strongly dependent on the applied cathodic current density. A relative Sm content of up to 13.8 at. % could be determined by energy dispersive x-ray (EDX) spectroscopy. The SmCo thin films were annealed at 560 deg. C in a vacuum oven. Vibrating sample magnetometer (VSM) measurements were applied to characterize the magnetic properties. This film features hard magnetic properties with an intrinsic coercivity H{sub ci} of up to 44 kA/m. Electron probe microanalysis (EPMA) measurements showed that up to 40 at. % of O may be integrated in these films. The phases in the deposited films were determined by applying X-ray diffraction (XRD) measurements. These films consist of a mixture of SmCo alloy, Sm oxide, and Co.

Chen Jue; Rissing, Lutz [Institute for Micro Production Technology, Center for Production Technology, Leibniz Universitaet Hannover, An der Universitaet 2, 30823 Garbsen (Germany)

2011-04-01

199

Nitrogen-induced local magnetic and structural properties of sputtered FeAlN thin films  

E-print Network

the diffusion barrier of the interstitial N or C in FeN or FeC materials3 . However, x-ray diffraction (XRD structural and magnetic properties in various Fe-N materials and several iron nitride phases were identified

Ryan, Dominic

200

Magnetic switching  

SciTech Connect

Magnetic switching is a pulse compression technique that uses a saturable inductor (reactor) to pass pulses of energy between two capacitors. A high degree of pulse compression can be achieved in a network when several of these simple, magnetically switched circuits are connected in series. Individual inductors are designed to saturate in cascade as a pulse moves along the network. The technique is particularly useful when a single-pulse network must be very reliable or when a multi-pulse network must operate at a high pulse repetition frequency (PRF). Today, magnetic switches trigger spark gaps, sharpen the risetimes of high energy pulses, power large lasers, and drive high PRF linear induction accelerators. This paper will describe the technique of magnetic pulse compression using simple networks and design equations. A brief review of modern magnetic materials and of their role in magnetic switch design will be presented. 12 refs., 8 figs.

Kirbie, H.C.

1989-04-14

201

Magnet Healing?  

NASA Astrophysics Data System (ADS)

Many people are convinced that static magnets—applied to their skin—will heal ills, and many businesses sell such magnets. The biophysics of such healing was reviewed [1] together with the general biophysics of static fields. Birds and insects do use the earth’s magnetic field for navigation. While insect and frog egg development can clearly be influenced by high fields (7 T and 17 T respectively), there is no experimental evidence that small magnetic fields (of less than 0.5 T) might heal, and much evidence that they cannot heal. A puzzle to the physics community is: How to show laypersons that simple magnets (very probably) do not heal, however attractive that idea might be. [1] L. Finegold, The Physics of "Alternative Medicine": Magnet Therapy, The Scientific Review of Alternative Medicine 3:26-33 (1999).

Finegold, Leonard

2000-03-01

202

Magnetic nanoparticles  

Microsoft Academic Search

Intrinsic properties of magnetic nanoparticles are reviewed, with special emphasis on the effects of finite size on zero-temperature spin ordering, magnetic excitations, and relaxation. Effects on zero-temperature spin ordering include moment enhancement due to band narrowing in 3d transition metal particles, surface spin disorder in ferrite particles, and multi-sublattice states in antiferromagnetic oxide particles. Magnetic excitations include discretized spin wave

R. H Kodama

1999-01-01

203

Structural and Magnetic Studies of Co0.6Zn0.4Fe2O4 Nano Ferrite synthesized by Solution Combustion Method  

Microsoft Academic Search

Co0.6Zn0.4Fe2O4 nano magnetic system is prepared by solution combustion method. The powder sample is characterized by x-ray diffraction (XRD), Transmission Electron Microscope analysis (TEM), Fourier transform infrared spectroscopy (FTIR), Mössbauer Spectroscopy and super conducting quantum interference device (SQUID) (at low and room temperature). The average crystallite sizes of the prepared samples obtained from XRD is 22 nm, which is well

Ritu Rani; Pooja Dhiman; S. K. Sharma; M. Singh

2012-01-01

204

Magnetic Field Distribution of Permanent Magnet Magnetized by Static Magnetic Field Generated by HTS Bulk Magnet  

Microsoft Academic Search

Demagnetized rare earth magnets (Nd-Fe-B) can be fully magnetized by scanning them in the intense static fields over 3 T of a HTS bulk magnet which was cooled to the temperature range lower than 77K with use of cryo-coolers and activated by the field of 5 T. We precisely examined the magnetic field distributions of magnetized permanent magnets. The magnetic

Tetsuo Oka; Nobutaka Kawasaki; Satoshi Fukui; Jun Ogawa; Takao Sato; Toshihisa Terasawa; Yoshitaka Itoh; Ryohei Yabuno

2012-01-01

205

Preparation of magnetically responsive albumin nanospheres and in vitro drug release studies.  

PubMed

In this work, doxorubicin (DOX)-loaded magnetic albumin nanospheres were prepared using desolvation method in order to develop magnetically responsive nanocarrier system. Nanoparticles were characterized with zetasizer, SEM, AFM, XRD and magnetometer. In vitro DOX release was also investigated. It was found that nanoparticles had spherical shape with narrow size distributions and had magnetic responsiveness. In addition, slower drug release was observed with nanoparticulate system compared with free DOX. Moreover, the release rate should accelerate at target sites (cancer cells or tissue) where proteolytic enzymes are more abundant as known; therefore, magnetic albumin nanospheres can be effective potential DOX carrier with targeting ability. PMID:23419121

Ak, Güliz; Y?lmaz, Habibe; Sanl?er, Senay Hamarat

2014-02-01

206

Hard magnetic properties of melt-spun Co82Zr18-xTix alloys  

NASA Astrophysics Data System (ADS)

The phases and magnetic properties of Co-Zr-Ti melt-spun ribbons were studied by XRD analysis and magnetic measurements. The optimal magnetic properties of Ms=59.0 emu/g, Mr=4.0 kG, Hc=2.9 kOe, and (BH)max=3.0 MGOe were obtained in Co82Zr14Ti4 ribbons produced at a wheel speed of 30 m/s. In this work, we found that Ti was one of the few large atomic radius elements, which could improve hard magnetic properties of Co-Zr alloy.

Hou, Zhipeng; Wang, Wenquan; Xu, Shifeng; Zhang, Jinbao; Wu, Chunji; Su, Feng

2012-04-01

207

Preparation of magnetic composite microspheres by surfactant free controlled radical polymerization: Preparation and characteristics  

NASA Astrophysics Data System (ADS)

Submicron magnetic composite microspheres have been prepared by a new surfactant free controlled radical polymerization. This new approach is based on the use of diphenylethene (DPE) as radical controlling agent and no emulsifier is required. X-ray powder diffraction (XRD), thermogravimetric analysis (TGA) and transmission electron microscopy (TEM), etc. were conducted to characterize the magnetite particles and magnetic composite microspheres. The average size of the magnetic composite microspheres prepared by this new approach is 265 nm and the magnetite content of the composite microspheres is around 20%. Furthermore, the magnetic composite microspheres which surfaces have epoxy groups were also prepared.

Zhang, Hepeng; Zhang, Qiuyu; Zhang, Baoliang; Guo, Feige

2009-12-01

208

Animal Magnetism  

NSDL National Science Digital Library

This radio broadcast looks at the mysterious way in which certain animals can travel vast distances around the planet, using the magnetic field of Earth to guide them. Migrating birds, fish, sea turtles, honey bees and even bacteria have all been found to navigate using the magnetic field of Earth, sometimes over quite enormous distances and reaching targets of only a few degrees in width. There is discussion about where magnetic receptors may be within animals and that particular cells in migratory creatures contain magnetite, a substance which humans used many hundreds of years ago to create the first compass. This radio broadcast discusses animal magnetism with researchers who have been working with sea turtles, to discover just how the turtles find their way back to the same beaches every year to lay their eggs. There is explanation of how the magnetic sense in animals has two components: acting as a compass to guide them and providing them with location; and how this seems to be possible since the magnetic field gets stronger in higher latitudes and inclination angle (the angle of the magnetic field to the surface of Earth) changes over different points on Earth. The broadcast also explains why creatures such as honey bees and even bacteria need to be in tune with the magnetic field of Earth, and how magnetic sense is prevalent in many animals with seemingly no need for it. The broadcast is 29 minutes in length.

209

Planetary magnetism  

NASA Technical Reports Server (NTRS)

Planetary spacecraft have now probed the magnetic fields of all the terrestrial planets, the moon, Jupiter, and Saturn. These measurements reveal that dynamos are active in at least four of the planets, Mercury, the earth, Jupiter, and Saturn but that Venus and Mars appear to have at most only very weak planetary magnetic fields. The moon may have once possessed an internal dynamo, for the surface rocks are magnetized. The large satellites of the outer solar system are candidates for dynamo action in addition to the large planets themselves. Of these satellites the one most likely to generate its own internal magnetic field is Io.

Russell, C. T.

1980-01-01

210

Strange Magnetism  

E-print Network

We present an analytic and parameter-free expression for the momentum dependence of the strange magnetic form factor of the nucleon and its corresponding radius which has been derived in Heavy Baryon Chiral Perturbation Theory. We also discuss a model-independent relation between the isoscalar magnetic and the strange magnetic form factors of the nucleon based on chiral symmetry and SU(3) only. These limites are used to derive bounds on the strange magnetic moment of the proton from the recent measurement by the SAMPLE collaboration.

Thomas R. Hemmert; Ulf-G. Meissner; Sven Steininger

1998-11-09

211

Magnetic shielding  

DOEpatents

A magnetically-conductive filler material bridges the gap between a multi-part magnetic shield structure which substantially encloses a predetermined volume so as to minimize the ingress or egress of magnetic fields with respect to that volume. The filler material includes a heavy concentration of single-magnetic-domain-sized particles of a magnetically conductive material (e.g. soft iron, carbon steel or the like) dispersed throughout a carrier material which is generally a non-magnetic material that is at least sometimes in a plastic or liquid state. The maximum cross-sectional particle dimension is substantially less than the nominal dimension of the gap to be filled. An epoxy base material (i.e. without any hardening additive) low volatility vacuum greases or the like may be used for the carrier material. The structure is preferably exposed to the expected ambient magnetic field while the carrier is in a plastic or liquid state so as to facilitate alignment of the single-magnetic-domain-sized particles with the expected magnetic field lines.

Kerns, John A. (Livermore, CA); Stone, Roger R. (Walnut Creek, CA); Fabyan, Joseph (Livermore, CA)

1987-01-01

212

Magnetic shielding  

DOEpatents

A magnetically-conductive filler material bridges the gap between a multi-part magnetic shield structure which substantially encloses a predetermined volume so as to minimize the ingress or egress of magnetic fields with respect to that volume. The filler material includes a heavy concentration of single-magnetic-domain-sized particles of a magnetically conductive material (e.g. soft iron, carbon steel or the like) dispersed throughout a carrier material which is generally a non-magnetic material that is at least sometimes in a plastic or liquid state. The maximum cross-sectional particle dimension is substantially less than the nominal dimension of the gap to be filled. An epoxy base material (i.e. without any hardening additive) low volatility vacuum greases or the like may be used for the carrier material. The structure is preferably exposed to the expected ambient magnetic field while the carrier is in a plastic or liquid state so as to facilitate alignment of the single-magnetic-domain-sized particles with the expected magnetic field lines. 3 figs.

Kerns, J.A.; Stone, R.R.; Fabyan, J.

1987-10-06

213

Magnetic Field Safety Magnetic Field Safety  

E-print Network

Magnetic Field Safety Training #12;Magnetic Field Safety Strong Magnetic Fields exist around energized magnets. High magnetic fields alone are a recognized hazard only for personnel with certain medical conditions such as pacemakers, magnetic implants, or embedded shrapnel. In addition, high magnetic

McQuade, D. Tyler

214

Phase and Heterostructure Controlled Fabrication of Freestanding Magnetic Nanocrystals  

NASA Astrophysics Data System (ADS)

Magnetism at the nanoscale is still not fully understood. One of the major issues involved is the lack of precise experimental results. For nanoparticles, as their size shrinks the importance of surface atoms increases to such a level that they may dominate the overall magnetic performance. Clean and well defined surfaces on nanocrystals are therefore desirable to understand the surface effect with sufficient accuracy. Unfortunately, conventional fabrication techniques usually require specific surfactants or surface passivation agents, which may conceal the role of surface atoms. Here we report a unique technique that can prepare freestanding nanocrystals with controlled crystalline phase as well as desirous heterostructures. As an example, uniform L10 FePt nanoparticles with room temperature coercivity of 8.25 kOe were achieved. HRTEM analysis shows that these particles have perfect octahedron shape with only 111 surfaces exposed UHV compatible gas phase aggregation technique was used for the generation of nanoparticles. Atoms were generated from metal targets by using a magnetron sputtering gun, in which the plasma can be manipulated to provide certain circumstances for particle nucleation and growth. The materials were carried on by carrier gas from source to substrate so the nucleation and growth stages were separated in space. Monodispersity is therefore achieved together with controlled phase and structure.

Wang, Jian-Ping

2006-03-01

215

Measurement methods for surface oxides on SUS 316L in simulated light water reactor coolant environments using synchrotron XRD and XRF  

NASA Astrophysics Data System (ADS)

Synchrotron X-ray diffraction (XRD) and X-ray fluorescent (XRF) measurement techniques have been used for non-destructive characterization of surface oxide films on Type 316L austenitic stainless steels that were exposed to simulated primary water environments of pressurized water reactors (PWR) and boiling water reactors (BWR). The layer structures of the surface spinel oxides were revealed ex situ after oxidation by measurements made as a function of depth. The layer structure of spinel oxides formed in simulated PWR primary water should normally be different from that formed in simulated BWR water. After oxidation in the simulated BWR environment, the spinel oxide was observed to contain NiFe2O4 at shallow depths, and FeCr2O4 and Fe3O4 at deeper depths. By contrast, after oxidation in the simulated PWR primary water environment, a Fe3O4 type spinel was observed near the surface and FeCr2O4 type spinel near the interface with the metal substrate. Furthermore, by in situ measurements during oxidation in the simulated BWR environment, it was also demonstrated that the ratio between spinel and hematite Fe2O3 can be changed depending on the water condition such as BWR normal water chemistry or BWR hydrogen water chemistry.

Watanabe, Masashi; Yonezawa, Toshio; Shobu, Takahisa; Shoji, Tetsuo

2013-03-01

216

Analysis of ferrate(VI) compounds and super-iron Fe(VI) battery cathodes: FTIR, ICP, titrimetric, XRD, UV/VIS, and electrochemical characterization  

NASA Astrophysics Data System (ADS)

Chemical and electrochemical techniques are presented for the analysis of Fe(VI) compounds used in super-iron electrochemical storage cells. Fe(VI) analytical methodologies summarized are FTIR, ICP, titrimetric, UV/VIS, XRD Fe(VI), potentiometric, galvanostatic, cyclic voltammetry, and constant load, current or power electrochemical discharges probes. The investigated FTIR methodology becomes quantitative with introduction of an internal standard such as added barium sulfate. Electrochemical techniques which utilize a solid cathode, and spectroscopic techniques which utilize a solid sample, are preferred over solution phase techniques. The titrimetric methodology (chromite analysis) has been detailed, and adjusted to determine the extent of Fe(VI?III) oxidation power in both unmodified or coated Fe(VI) compounds. Fe(VI) compounds have also been variously referred to as ferrates or super-iron compounds, and include K 2FeO 4 and BaFeO 4. Such compounds are highly oxidizing, and in the aqueous phase the full three electron cathodic charge capacity has been realized, as summarized by reactions such as: FeO 42-+5/2H 2O+3e -?1/2Fe 2O 3+5OH -.

Licht, Stuart; Naschitz, Vera; Halperin, Leonid; Halperin, Nadezhda; Lin, Lin; Chen, Jianjun; Ghosh, Susanta; Liu, Bing

217

Composition-dependent structure of polycrystalline magnetron-sputtered V–Al–C–N hard coatings studied by XRD, XPS, XANES and EXAFS  

PubMed Central

V–Al–C–N hard coatings with high carbon content were deposited by reactive radio-frequency magnetron sputtering using an experimental combinatorial approach, deposition from a segmented sputter target. The composition-dependent coexisting phases within the coating were analysed using the complementary methods of X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), X-ray absorption near-edge spectroscopy (XANES) and extended X-ray absorption fine-structure spectroscopy (EXAFS). For the analysis of the X-ray absorption near-edge spectra, a new approach for evaluation of the pre-edge peak was developed, taking into account the self-absorption effects in thin films. Within the studied composition range, a mixed face-centred cubic (V,Al)(C,N) phase coexisting with a C–C-containing phase was observed. No indication of hexagonal (V,Al)(N,C) was found. The example of V–Al–C–N demonstrates how important a combination of complementary methods is for the detection of coexisting phases in complex multi-element coatings. PMID:24046506

Krause, Bärbel; Darma, Susan; Kaufholz, Marthe; Mangold, Stefan; Doyle, Stephen; Ulrich, Sven; Leiste, Harald; Stüber, Michael; Baumbach, Tilo

2013-01-01

218

Investigation of irradiation effects induced by self-ion in 6H-SiC combining RBS/C, Raman and XRD  

SciTech Connect

Single crystals of 6H-SiC were irradiated at room temperature and 670 K with 4 MeV C ions at two fluences: 1015 and 1016 cm2 (0.16 and 1.6 dpa at the damage peak). Damage accumulation was studied by a combination of X-ray diffraction (XRD), Raman spectroscopy and Rutherford backscattering spectrometry in channelling geometry (RBS/C) along the [0001] direction. The irradiated layer is found to be composed of a low damage region up to 1.5 lm followed by a region where the disorder level is higher, consistent with SRIM predictions. At room temperature and low fluence, typically 1015 cm2, the strain depth profile follows the dpa depth distribution (with a maximum value of 2%). The disorder is most likely due to small defect clusters. When increasing the fluence up to 1016 cm2, a buried amorphous layer forms, as indicated by e.g. Raman results where the Si C bands become broader or even disappear. At a higher irradiation temperature of 670 K, amorphization is not observed at the same fluence, revealing a dynamic annealing process. However, results tend to suggest that the irradiated layer is highly heterogeneous and composed of different types of defects.

Chaabane, Nihed [CEA, Saclay, France; Debelle, Aurelien [Universite Paris Sud, Orsay, France; Sattonnay, Gael [Universite Paris Sud, Orsay, France; Trocellier, Patrick [CEA, Saclay, France; Serruys, Yves [CEA, Saclay, France; Thome, Lionel [Universite Paris Sud, Orsay, France; Zhang, Yanwen [ORNL; Weber, William J [ORNL; Meis, Constantin [CEA, Saclay, France; Gosmain, Lionel [CEA, Saclay, France; Boulle, Alexandre [SPCTS, Limoges Cedex, France

2012-01-01

219

Synthesis, spectral, stereochemical, single crystal XRD and biological studies of 3t-pentyl-2r,6c-diarylpiperidin-4-one picrate derivatives  

NASA Astrophysics Data System (ADS)

Various substituted 3t-pentyl-2r,6c-diphenylpiperidin-4-one picrates (1-7) were synthesised and characterised by elemental analysis, FT-IR and NMR spectral studies. NMR spectral assignments were made unambiguously by their one dimensional (1H NMR and 13C NMR) and two dimensional (1H-1H COSY, HSQC, HMBC, NOESY, DEPT) NMR spectra. Single crystal XRD analysis of the compound (1) has confirmed that the complex crystallized in monoclinic system with P21/n space group. The difference in the chemical shifts between equatorial methylene proton and axial proton at C(5) [? = ?eq - ?ax] is highly negative in compounds 1-7 in contrast to the value observed for the corresponding parent piperidine-4-one and is indicative of the 1,3-diaxial interaction between the axial NH bond and axial hydrogen at C(5). The chemical shifts of the heterocyclic ring protons are influenced by the picrate anion. All the synthesised compounds exhibited good activity against S. aureus-Staphylococcus aureus bacterial strains and C. albicans fungal strains.

Savithiri, S.; Arockia doss, M.; Rajarajan, G.; Thanikachalam, V.

2014-10-01

220

Investigation of Physically and Chemically Ionic Liquid Confinement in Nanoporous Materials by a Combination of SANS, Contrast-Matching SANS, XRD and Nitrogen Adsorption  

NASA Astrophysics Data System (ADS)

In the present study, [bmim][PF6] ionic liquid (IL) was introduced into the pores of two ordered mesoporous silicas (MCM-41 and SBA-15) having different pore sizes by means of two different processes: a) with physical imbibition from a methanol solution under high vacuum and b) by chemically immobilising the IL with silanisation of the pore surface followed by reaction with butyl-methyl imidazolium chloride and anion exchange with PF6, the process termed as the "grafting to" method. Both the extent of IL entrapment and the structural properties of the IL phase under confinement were investigated by SANS, contrast-matching SANS, XRD and nitrogen adsorption measurements. The results show that the pores of chemically prepared samples are not totally filled by IL and also suggest for ordering of the silylated IL phase. On the other hand, the physically prepared samples are almost or totally filled with IL whereas no evidence for ordering of the confined IL phase was observed.

Romanos, G. E.; Stefanopoulos, K. L.; Vangeli, O. C.; Mergia, K.; Beltsios, K. G.; Kanellopoulos, N. K.; Lairez, D.

2012-02-01

221

Temperature-dependent magnetization in (Mn, N)-codoped ZnO-based diluted magnetic semiconductors  

NASA Astrophysics Data System (ADS)

The influences of Mn doping on the structural quality of the ZnxMn1-xO:N alloy films have been investigated by XRD. Chemical compositions of the samples (Zn and Mn content) and their valence states were determined by X-ray photoelectron spectrometry (XPS). Hall effect measurements versus temperature for ZnxMn1-xO:N samples have been designed and studied in detail. The ferromagnetic transitions happened at different TC should explain that the magnetic transition in field-cooled magnetization of Zn1-xMnxO:N films at low temperature is caused by the strong p-d exchange interactions besides magnetic transition at 46 K resulting from Mn oxide, and that the room temperature ferromagnetic signatures are attributed to the uncompensated spins at the surface of anti-ferromagnetic nano-crystal of Mn-related Zn(Mn)O.

Wu, Kongping; Gu, Shulin; Tang, Kun; Ye, Jiandong; Zhu, Shunming; Zhou, Mengran; Huang, Yourui; Xu, Mingxiang; Zhang, Rong; Zheng, Youdou

2012-04-01

222

Magnetic Storms  

Microsoft Academic Search

IN his article upon the recent magnetic storm (NATURE, September 30) Dr. Chree writes:- ``Another difficulty in regarding the phenomena of magnetic storms as entirely and directly due to the action of electrical currents associated with aurora is that it is a frequent occurrence-as on the present occasion-for the horizontal force to be considerably depressed below the normal value when

W. van Bemmelen

1909-01-01

223

Magnetic shielding  

DOEpatents

A magnetically-conductive filler material bridges the gap between a multi-part magnetic shield structure which substantially encloses a predetermined volume so as to minimize the ingress or egress of magnetic fields with respect to that volume. The filler material includes a heavy concentration of single-magnetic-domain-sized particles of a magnetically conductive material (e.g. soft iron, carbon steel or the like) dispersed throughout a carrier material which is generally a non-magnetic material that is at least sometimes in a plastic or liquid state. The maximum cross-sectional particle dimension is substantially less than the nominal dimension of the gap to be filled. An epoxy base material (i.e. without any hardening additive) low volatility vacuum greases or the like may be used for the carrier material. The structure is preferably exposed to the expected ambient field while the carrier is in a plastic or liquid state so as to facilitate alignment of the single-magnetic-domain-sized particles with the expected magnetic field lines.

Kerns, J.A.; Stone, R.R.; Fabyan, J.

1985-02-12

224

Magnetic Fields  

NSDL National Science Digital Library

This page and its annex describes, in trivial terms, the physics of magnetic fields and the history of its discovery. Included is the work of Halley, Oersted, Ampere and Maxwell. It also describes a way of demonstrating it in the classroom, using a vu-graph projector. Later sections #5, #5a and #6 extend this to magnetic field lines and electromagnetism.

Stern, David

2005-01-04

225

Magnetic properties of graphite oxide and reduced graphene oxide  

NASA Astrophysics Data System (ADS)

Graphite oxide (GO) and reduced graphene oxide (RGO) have been prepared using standard chemical methods. The formations of the oxides are characterized by X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) studies. Both the oxides exhibit weak superparamagnetism and hysteresis for the first time at room temperature. Magnetic moment for RGO is comparatively smaller than that of GO sample. The superparamagnetism in these oxides is attributed to the presence of single domains, each domain being cluster of defect induced magnetic moments coupled by ferromagnetic interaction. Apart from these single domain clusters there are other defect induced moments coupled by ferromagnetic interaction which show ferromagnetism and hysteresis.

Sarkar, S. K.; Raul, K. K.; Pradhan, S. S.; Basu, S.; Nayak, A.

2014-11-01

226

Magnetic mineralogy of heavy metals-contaminated soils  

NASA Astrophysics Data System (ADS)

Soils around mine and in urban areas are often contaminated by heavy metals derived from industrial and human activities [1, 2]. These contaminated soils are often characterized by a magnetic enhancement on topsoils. Many studies demonstrated that there are significant correlations between heavy metals and various magnetic parameters in contaminated soils, indicating a strong affinity of heavy metals to magnetic minerals. The magnetic particles in contaminated soils were separated by a magnetic separation technique. The rock magnetism, XRD, field emission scanning electron microscopy equiped with an energy-dispersive X-ray analyzer (FESEM/EDX) were used to characterize their magnetic mineralogy. Results of XRD analysis indicated that the magnetic particles separated from heavy metal-contaminated soils are composed of quartz, magnetite, and hematite. Based on the X-ray diffraction peak intensity, the Fe3O4 was identified as the predominant magnetic mineral phase. The high-temperature magnetization (Ms-T) curves of magnetic particles extracted from contaminated soils show a sharp Ms decrease at about 580C (the Curie temperature of magnetite), suggesting that magnetite is the dominant magnetic carrier. The hysteresis loops of contaminated soils are closed at about 100-200 mT which is consistent with the presence of a dominant ferrimagnetic mineral phase. The FESEM analysis showed a great variety of shapes of magnetic particles in contaminated soils. The most common morphology are observed in the form of spherules, with the sizes ranging from 20 to 100 um. The chemical composition of magnetic particles consist mainly of Fe, Si, Al, and Ca with minor heavy metal elements (Cu, Zn, Hg, and Cr). The semi-quantitative Fe content identified by FESEM/EDX ranged from 40 to 90%. Combined studies of rock magnetism, XRD, and FESEM/EDX indicated that magnetic mineral phases responsible for the magnetic enhancement of contaminated soils are anthropogenic origin which are coarse-grained multi-domain (MD) ferrimagnetic minerals. These spherical magnetic particles in contaminated soils are most likely related to airborne particles from coal combusition and industrial activities. Coal burning, metallurgical and industrial dusts contain a significant fraction of ferrimagnetic minerals. The magnetic particles in fly ash from coal-burning power plant have a typical spherical morphology, ranging from 10 to 100 ?m. Vehicle emissions have been suggested to be another source of magnetic particles. These anthropogenic ferrimagnetic mineral phases are directly responsible for the magnetic enhancement in the contaminated soils. Therefore, the strong magnetic signature in contaminated soils can be used as an effective tool for identifying pollution sources and quantifying pollution level of heavy metals. Acknowledgements: This research was supported by National Nature Science Foundation of China (No. 41171182 and 40971131) and the Ph.D. Programs Foundation of Ministry of Education of China (20090101110088). [1] Lu, S.G. & Bai, S.Q. (2006) J. Appl. Geophys., 60, 1-12. [2] Lu, S.G., Bai, S.Q. & Xue, Q.F. (2007) Geophys. J. Inter., 171, 568-580.

Shenggao, L.

2012-04-01

227

XRD line-broadening characteristics of M-oxides (M = Mg, Mg-Al, Y, Fe) nanoparticles produced by coprecipitation method  

SciTech Connect

Simple coprecipitation method has been used to produce nanoparticles of MgO (magnesia), MgO{center_dot}Al{sub 2}O{sub 3}(spinel), Y{sub 2}O{sub 3}(yttria) and Fe{sub 3}O{sub 4}(ferrite). The raw materials were, in respective, magnesium powder, magnesium and aluminium powders, ytrria powder, and natural sand. The coprecipitation included the use of suitable acid and base to dissolve the powders or sand and to produce precipitates, as well as the use of water to wash and purify the precipitates, and drying at relatively low temperatures, namely lower than 100 deg. C, followed by heating at 450 deg. C, 750 deg. C, 600 deg. C and 200 deg. C to produce magnesia, spinel, yttria and ferrite nanopowders, respectively. X-ray diffractometry was used to characterise the purity and nanocrystallinity of the final powders. It was found qualitatively that the powders were of high purity. Further line-broadening analysis using single-line and Rietveld-based softwares was performed to reveal the nanocrystallinity of the powders. Different line breadth values were found for the powders, indicating different crystallite sizes. It was also found that, particularly for spinel and yttria, the diffraction peaks exhibited 'longer' tails, indicating broader crystallite size distribution. The average crystallite size for the powders ranged from 3 to 70 nm. The results could then be used as 'fingerprints' for nanocrystallinity using x-ray diffractometry. The XRD crystallite sizes for yttria and ferrite nanocrystals are in fair agreement with their counterparts from electron microscopy observation.

Pratapa, S.; Susanti, L.; Insany, Y. A. S.; Alfiati, Z.; Hartono, B.; Mashuri,; Triwikantoro; Baqiya, M. A.; Purwaningsih, S.; Yahya, E.; Darminto [Department of Physics, Institute of Technology Sepuluh November (ITS), Jl. Arief Rahman Hakim, Surabaya, Indonesia 60111 (Indonesia); Taufiq, Ahmad; Fuad, Abdullah [Department of Physics, State University of Malang, Jl. Surabaya, Malang, Indonesia 60111 (Indonesia)

2010-10-24

228

Adsorption and Separation of Light Gases on an Amino-Functionalized Metal–Organic Framework: An Adsorption and In Situ XRD Study  

SciTech Connect

The NH{sub 2}-MIL-53(Al) metal-organic framework was studied for its use in the separation of CO{sub 2} from CH{sub 4}, H{sub 2}, N{sub 2} C{sub 2}H{sub 6} and C{sub 3}H{sub 8} mixtures. Isotherms of methane, ethane, propane, hydrogen, nitrogen, and CO{sub 2} were measured. The atypical shape of these isotherms is attributed to the breathing properties of the material, in which a transition from a very narrow pore form to a narrow pore form and from a narrow pore form to a large pore form occurs, depending on the total pressure and the nature of the adsorbate, as demonstrated by in-situ XRD patterns measured during adsorption. Apart from CO{sub 2}, all tested gases interacted weakly with the adsorbent. As a result, they are excluded from adsorption in the narrow pore form of the material at low pressure. CO{sub 2} interacted much more strongly and was adsorbed in significant amounts at low pressure. This gives the material excellent properties to separate CO{sub 2} from other gases. The separation of CO{sub 2} from methane, nitrogen, hydrogen, or a combination of these gases has been demonstrated by breakthrough experiments using pellets of NH{sub 2}-MIL-53(Al). The effect of total pressure (1-30 bar), gas composition, temperature (303-403 K) and contact time has been examined. In all cases, CO{sub 2} was selectively adsorbed, whereas methane, nitrogen, and hydrogen nearly did not adsorb at all. Regeneration of the adsorbent by thermal treatment, inert purge gas stripping, and pressure swing has been demonstrated. The NH{sub 2}-MIL-53(Al) pellets retained their selectivity and capacity for more than two years.

Couck S.; Stavitski E.; Gobehiya, E.; Kirschhock, C.E.A.; Serra-Crespo, P.; Juan-Alcaniz, J.; Martinez Joaristi, A.; Gascon, J.; Kapteijn, F.; Baron, G. V.; Denayer J.F.M.

2012-02-29

229

Sinus Excision, Release of Coccycutaneous Attachments and Dermal-Subcuticular Closure (XRD Procedure): A Novel Technique in Flattening the Natal Cleft in Pilonidal Sinus Treatment  

PubMed Central

INTRODUCTION The objective of this study was to analyse, prospectively, the outcome of a new technique – excision of pilonidal sinus and flattening the natal cleft by division of the coccycutaneous attachments at the lower end of the incision. PATIENTS AND METHODS Sixty-six consecutive patients with chronic pilonidal sinuses were treated between 1995 and 2001. The procedure consisted of an elliptical, wide, local excision, release of the coccycutaneous attachments and primary closure using dermal-subcuticular closure (XRD). Suction drains were used until drainage was minimal. The height of skin level at the lower angle of the wound from the coccyx was measured intra-operatively before and after division of the coccycutaneous attachments. Postoperatively, patients were assessed for hospital stay, return to normal activity, complications and recurrence. RESULTS Sixty-four patients (97%) were males, median age 27 years. The height of skin level rose from a mean of 1.8 cm (95% CI, 1.78–1.85) to a mean of 3.8 cm (95% CI, 3.77–3.88; P < 0.001). Morbidity affected 12 patients (18%), epidermal separation of the lower wound angles (6 patients), seromas (5 patients) and 1 wound dehiscence at 2 weeks. All other wounds healed primarily without dehiscence. There were no recurrences after a median follow-up of 22.5 months (range, 12–38 months). CONCLUSIONS Release of the coccycutaneous attachments is an easy technique to learn, which seems to be an effective way of flattening the natal cleft and may result in lower recurrence rate. This technique should be tried in uncomplicated pilonidal sinus disease before more complex procedures are attempted. PMID:18634729

Marzouk, Deya M; Abou-Zeid, Ahmed A; Antoniou, Anthony; Haji, Amyn; Benziger, H

2008-01-01

230

Preparation and characterization of magnetic levan particles as matrix for trypsin immobilization  

NASA Astrophysics Data System (ADS)

Magnetic levan was synthesized by co-precipitating D-fructofuranosyl homopolysaccharide with a solution containing Fe2+ and Fe3+ in alkaline conditions at 100 °C. The magnetic levan particles were characterized by scanning electron microscopy (SEM), magnetization measurements, X-ray diffractometry (XRD) and infrared spectroscopy (IR). Afterwards, magnetic levan particles were functionalized by NaIO4 oxidation and used as matrices for trypsin covalent immobilization. Magnetite and magnetic levan particles were both heterogeneous in shape and levan-magnetite presented bigger sizes compared to magnetite according to SEM images. Magnetic levan particles exhibited a magnetization 10 times lower as compared to magnetite ones, probably, due to the coating layer. XRD diffractogram showed that magnetite is the dominant phase in the magnetic levan. Infrared spectroscopy showed characteristics absorption bands of levan and magnetite (O-H, C-O-C and Fe-O bonds). The immobilized trypsin derivative was reused 10 times and lost 16% of its initial specific activity only. Therefore, these magnetic levan particles can be proposed as an alternative matrices for enzyme immobilization.

Maciel, J. C.; Andrad, P. L.; Neri, D. F. M.; Carvalho, L. B.; Cardoso, C. A.; Calazans, G. M. T.; Albino Aguiar, J.; Silva, M. P. C.

2012-04-01

231

Magnetic Bearing  

NASA Technical Reports Server (NTRS)

AVCON, Inc. produces advanced magnetic bearing systems for industrial use, offering a unique technological approach based on contract work done at Marshall Space Flight Center and Lewis Research Center. Designed for the turbopump of the Space Shuttle main engine, they are now used in applications such as electric power generation, petroleum refining, machine tool operation and natural gas pipelines. Magnetic bearings support moving machinery without physical contact; AVCON's homopolar approach is a hybrid of permanent and electromagnets which are one-third the weight, smaller and more power- efficient than previous magnetic bearings.

1996-01-01

232

Lunar magnetism  

NASA Technical Reports Server (NTRS)

Aspects of lunar paleomagnetic and electromagnetic sounding results which appear inconsistent with the hypothesis that an ancient core dynamo was the dominant source of the observed crustal magnetism are discussed. Evidence is summarized involving a correlation between observed magnetic anomalies and ejecta blankets from impact events which indicates the possible importance of local mechanisms involving meteoroid impact processes in generating strong magnetic fields at the lunar surface. A reply is given to the latter argument which also presents recent evidence of a lunar iron core.

Hood, L. L.; Sonett, C. P.; Srnka, L. J.

1984-01-01

233

Magnetic single-enzyme nanoparticles with high activity and stability  

SciTech Connect

Magnetic single-enzyme nanoparticles (SENs) encapsulated within a composite inorganic/organic polymer network were fabricated via the surface modification and in situ aqueous polymerization of separate enzyme molecule. The resultant nanoparticles were characterized by transmission electron microscope (TEM), Fourier transform infrared (FTIR) spectrometer and X-ray diffraction (XRD). These particles are almost spherical in shape and have a unique size of about 50 nm in diameter. Electrical and magnetic measurements reveal that the magnetic SENs have a conductivity of 2.7 x 10{sup -3} S cm{sup -1}, and are superparamagnetic with a saturation magnetization of 14.5 emu g{sup -1} and a coercive force of 60 Oe. Compared with free enzyme, encapsulated enzyme exhibits a strong tolerance to the variation of solution pH, high temperature, organic solvent and long-term storage, thus showing significantly enhanced enzyme performance and stability.

Yang Zhengpeng [College of Chemistry and Chemical Engineering, Central South University, Changsha 410083 (China); Institute of Materials Science and Engineering, Henan Polytechnic University, Jiaozuo 454000 (China); Si Shihui [College of Chemistry and Chemical Engineering, Central South University, Changsha 410083 (China)], E-mail: sishihui@mail.csu.edu.cn; Zhang Chunjing [College of Chemistry and Chemical Engineering, Central South University, Changsha 410083 (China); Institute of Materials Science and Engineering, Henan Polytechnic University, Jiaozuo 454000 (China)

2008-02-29

234

Magnetic Resonance  

Cancer.gov

Focus Group on Magnetic Resonance Spectroscopy (MRS) in Clinical Oncology(April 1999) To explore the technical requirements for MRS and the application of hydrogen and multinuclear spectroscopy for tumor response to therapy.

235

Magnetic Reconnection  

NASA Video Gallery

This science visualization shows a magnetospheric substorm, during which, magnetic reconnection causes energy to be rapidly released along the field lines in the magnetotail, that part of the magne...

236

Superconducting magnets  

SciTech Connect

This report provides a self-consistent description of a magnetic field in the aperture of a superconducting magnet and details how this field can be calculated in a magnet with cos theta current distribution in the coils. A description of an apparatus that can be used to measure the field uniformity in the aperture has been given. Finally, a detailed description of the magnet being developed for use in the Superconducting Super Collider is given. When this machine is built, it will be by far the largest application of superconductivity to date and promises to make possible the experimental discoveries needed to understand the basic laws of nature governing the world in which we live.

Willen, E.; Dahl, P.; Herrera, J.

1985-01-01

237

Magnetic monopoles  

SciTech Connect

In this talk on magnetic monopoles, first the author briefly reviews some historical background; then, the author describes what several different types of monopoles might look like; and finally the author discusses the experimental situation. 81 references.

Fryberger, D.

1984-12-01

238

Superconducting magnet  

NASA Technical Reports Server (NTRS)

Extensive computer based engineering design effort resulted in optimization of a superconducting magnet design with an average bulk current density of approximately 12KA/cm(2). Twisted, stranded 0.0045 inch diameter NbTi superconductor in a copper matrix was selected. Winding the coil from this bundle facilitated uniform winding of the small diameter wire. Test coils were wound using a first lot of the wire. The actual packing density was measured from these. Interwinding voltage break down tests on the test coils indicated the need for adjustment of the wire insulation on the lot of wire subsequently ordered for construction of the delivered superconducting magnet. Using the actual packing densities from the test coils, a final magnet design, with the required enhancement and field profile, was generated. All mechanical and thermal design parameters were then also fixed. The superconducting magnet was then fabricated and tested. The first test was made with the magnet immersed in liquid helium at 4.2K. The second test was conducted at 2K in vacuum. In the latter test, the magnet was conduction cooled from the mounting flange end.

1985-01-01

239

Grain Size Control of the Magnetic Nanoparticles by Solid State Route Modification  

NASA Astrophysics Data System (ADS)

The CoFe2O4 and NiFe2O4 nanoparticles were synthesized exploiting a co-precipitation method and afterward calcinated at 400 °C through two different experimental apparatus: a conventional muffle and rotatory oven. X-ray diffraction (XRD) analysis revealed that nanocrystalline ferrites grew with a face center cubic structure (fcc) and Fd3 m symmetry space group. XRD, transmission electron microscopy, and magnetic measurements confirmed the compositional homogeneity and the narrow size particle distribution (6-8 nm) of the sample thermally treated in a rotary oven, in all likelihood due to the sample's constant turning movement. The size of the magnetic particles is extremely important and influences the choice of a potential technological application. For this reason, our study emerges as a new and simple innovating procedure to control the size of magnetic nanoparticles.

Barreto, A. C. H.; Santiago, V. R.; Freire, R. M.; Mazzetto, S. E.; Sasaki, J. M.; Vasconcelos, I. F.; Denardin, J. C.; Mele, Giuseppe; Carbone, Luigi; Fechine, P. B. A.

2013-07-01

240

Magnetic behavior of nanocrystalline MnCo 2O 4 spinels  

NASA Astrophysics Data System (ADS)

A series of powders with different particle sizes of the spinel MnCo2O4 was synthesized by the Pechini method. The resulting precursor was calcined between 400 and 900C and characterized by thermogravimetric analyses (TGA), X-ray diffraction (XRD), scanning electron microscopy (SEM) and magnetization measurements. TGA analysis showed a loss of mass in the region from 200 to 650C and stability after this. XRD patterns showed an increase of the crystallite size with calcination temperature. Magnetization measurements on the sample calcined at 900C showed an unusual behavior of the hysteresis curve and irreversibility of the magnetization with field cooled (FC) and zero field cooled (ZFC) procedures. An evolution of this behavior was observed with increasing crystallite size.

Borges, F. M. M.; Melo, D. M. A.; Câmara, M. S. A.; Martinelli, A. E.; Soares, J. M.; de Araújo, J. H.; Cabral, F. A. O.

2006-07-01

241

Intercalation of amino acids into layered MnPS{sub 3}: Synthesis, characterization and magnetic properties  

SciTech Connect

Three bioorganic-inorganic hybrid nanocomposites based on amino acids into layered MnPS{sub 3} have been synthesized and characterized with powder X-ray diffraction (XRD), infrared spectroscopy (IR) and elemental analysis. The expanded MnPS{sub 3} structure as well as the characteristic IR absorption supports the successful and full intercalation of amino acids as the guests into interlayered space of MnPS{sub 3} host. The lattice spacing expansion from XRD patterns indicates that the inserted guest is arranged in the monolayer with carbon chain parallel to the layer of MnPS{sub 3}. The magnetic measurements indicate that all three nanocomposites show paramagnetism above 50 K and obey Curie-Weiss law; however, at T {sub c} of 40 K a ferrimagnetic transition is observed. The hysteresis of magnetization (M) versus magnetic field (H) at 1.85 K further confirms that these intercalation compounds are low-temperature ferrimagnets.

Zhou Huiqiong [Hubei Key Laboratory on Organic and Polymeric Opto-electronic Materials, Department of Chemistry, Wuhan University, Wuhan 430072 (China); Su Xu [Hubei Key Laboratory on Organic and Polymeric Opto-electronic Materials, Department of Chemistry, Wuhan University, Wuhan 430072 (China); Zhang Xuan [Hubei Key Laboratory on Organic and Polymeric Opto-electronic Materials, Department of Chemistry, Wuhan University, Wuhan 430072 (China); Chen Xingguo [Hubei Key Laboratory on Organic and Polymeric Opto-electronic Materials, Department of Chemistry, Wuhan University, Wuhan 430072 (China)]. E-mail: xgchen@whu.edu.cn; Yang Chuluo [Hubei Key Laboratory on Organic and Polymeric Opto-electronic Materials, Department of Chemistry, Wuhan University, Wuhan 430072 (China); Qin Jingui [Hubei Key Laboratory on Organic and Polymeric Opto-electronic Materials, Department of Chemistry, Wuhan University, Wuhan 430072 (China); Inokuchi, Makoto [Department of Materials Science and Engineering, Science University of Tokyo in Yamaguchi, Onoda, Yamaguchi 756-0884 (Japan)

2006-11-09

242

TbxBi1-xFeO3 nanoparticulate multiferroics fabricated by micro-emulsion technique: Structural elucidation and magnetic behavior evaluation  

NASA Astrophysics Data System (ADS)

Tb-doped BiFeO3 multiferroics nanoparticles fabricated via micro-emulsion route were characterized by thermogravimetric analysis (TGA), X-ray diffraction (XRD) and scanning electron microscopy (SEM). The fully characterized TbxBi1-xFeO3 nanoparticles were then subjected to magnetic behavior evaluation for various technological applications. The thermogravimetric analysis (TGA) conducted in the range 25-1000 °C predicted the temperature (~960 °C) for phase formation. XRD estimated the crystallite size 30-47 nm, while the particles size estimated by SEM was found (80-120 nm). The XRD data confirmed the rhombohedral (space group R3c) phase with average cell volume 182.66 Å3 (for BiFeO3). Various other physical parameters like bulk density, X-ray density and porosity were also determined from the XRD data and found in agreement with theoretical predictions. The magnetic studies showed that as Bi3+ was substituted by Tb3+, all magnetic parameters were altered. The maximum saturation magnetization (Ms) (0.6691 emug-1) was exhibited by Tb0.02Bi0.98FeO3 while the Tb0.00Bi1.00Fe1.00O3 showed the maximum (549 Oe) coercivity. The evaluated magnetic behavior categorized these materials as soft magnetic materials that may be useful for fabricating advanced technological applications.

Anwar, Zobia; Azhar Khan, Muhammad; Mahmood, Azhar; Asghar, M.; Shakir, Imran; Shahid, Muhammad; Bibi, Ismat; Farooq Warsi, Muhammad

2014-04-01

243

New iron-based SiC spherical composite magnetic abrasive for magnetic abrasive finishing  

NASA Astrophysics Data System (ADS)

SiC magnetic abrasive is used to polish surfaces of precise, complex parts which are hard, brittle and highly corrosion-resistant in magnetic abrasive finishing(MAF). Various techniques are employed to produce this magnetic abrasive, but few can meet production demands because they are usually time-consuming, complex with high cost, and the magnetic abrasives made by these techniques have irregular shape and low bonding strength that result in low processing efficiency and shorter service life. Therefore, an attempt is made by combining gas atomization and rapid solidification to fabricate a new iron-based SiC spherical composite magnetic abrasive. The experimental system to prepare this new magnetic abrasive is constructed according to the characteristics of gas atomization and rapid solidification process and the performance requirements of magnetic abrasive. The new iron-based SiC spherical composite magnetic abrasive is prepared successfully when the machining parameters and the composition proportion of the raw materials are controlled properly. Its morphology, microstructure, phase composition are characterized by scanning electron microscope(SEM) and X-ray diffraction(XRD) analysis. The MAF tests on plate of mold steel S136 are carried out without grinding lubricant to assess the finishing performance and service life of this new SiC magnetic abrasive. The surface roughness( R a) of the plate worked is rapidly reduced to 0.051 ?m from an initial value of 0.372 ?m within 5 min. The MAF test is carried on to find that the service life of this new SiC magnetic abrasive reaches to 155 min. The results indicate that this process presented is feasible to prepare the new SiC magnetic abrasive; and compared with previous magnetic abrasives, the new SiC spherical composite magnetic abrasive has excellent finishing performance, high processing efficiency and longer service life. The presented method to fabricate magnetic abrasive through gas atomization and rapid solidification presented can significantly improve the finishing performance and service life of magnetic abrasive, and provide a more practical approach for large-scale industrial production of magnetic abrasive.

Zhang, Guixiang; Zhao, Yugang; Zhao, Dongbiao; Zuo, Dunwen; Yin, Fengshi

2013-03-01

244

Modal mineralogy of CM chondrites by X-ray diffraction (PSD-XRD): Part 2. Degree, nature and settings of aqueous alteration  

NASA Astrophysics Data System (ADS)

Within 5 million years after formation of calcium aluminium rich inclusions (CAI), high temperature anhydrous phases were transformed to hydrous phyllosilicates, mostly serpentines, which dominate the matrices of the most primitive carbonaceous chondrites. CMs are the largest group of meteorites to provide samples of this material. To understand the nature of the availability, and role of H 2O in the early solar system - as well as the settings of aqueous alteration - defining CM petrogenesis is critical. By Position Sensitive Detector X-ray Diffraction (PSD-XRD), we determine the modal abundance of crystalline phases present in volumes >1% for a suite of CMs - extending Part 1 of this work that dealt only with CM2 falls ( Howard et al., 2009) to now include CM2 and CM1 finds. CM2 samples contain 13-31% Fe,Mg silicates (olivine + pyroxene) and from 67% to 82% total phyllosilicate (mean 75% ± 1.3 2 ?). CM1 samples contain 6-10% olivine + pyroxene and 86-88% total phyllosilicate. Magnetite (0.6-5.2%), sulphide (0.6-3.9%), calcite (0-1.9%) and gypsum (0-0.8%) are minor phases across all samples. Since phyllosilicate forms from hydration of anhydrous Fe,Mg silicates (olivine + pyroxene), the ratio of total phyllosilicate to total anhydrous Fe,Mg silicate defines the degree of hydration and the following sequence results (in order of increasing hydration): QUE 97990 < Y 791198 < Murchison < Murray < Mighei < ALHA 81002 < Nogoya ? Cold Bokkeveld ? Essebi < QUE 93005 < ALH 83100 < MET 01070 < SCO 06043. High activities of Al (mostly from reactive mesostasis) and Si help to explain the composition and structure of CM serpentines that are distinct from terrestrial standards. Our data allows inference as to CM mineralogy at the point of accretion and challenges the conceptual validity of progressive alteration sequences. Modal mineralogy also provides new insights into CM petrogenesis and hints at a component of aqueous alteration occurring in the nebula, in addition to on the CM parent body(ies).

Howard, K. T.; Benedix, G. K.; Bland, P. A.; Cressey, G.

2011-05-01

245

Modal mineralogy of CM2 chondrites by X-ray diffraction (PSD-XRD). Part 1: Total phyllosilicate abundance and the degree of aqueous alteration  

NASA Astrophysics Data System (ADS)

CM carbonaceous chondrites are samples of incompletely serpentinized primitive asteroids. Using position sensitive detector X-ray diffraction (PSD-XRD) and a pattern stripping technique, we quantify the modal mineralogy of CM2 chondrites: Mighei; Murray; Murchison; Nogoya and Cold Bokkeveld. There is a narrow range in the combined modal volume (vol%) of the most abundant phases Mg-serpentine (25-33%) and Fe-cronstedtite (43-50%). Cold Bokkeveld is anomalous in containing more Mg-serpentine (49-59%) than Fe-cronstedtite (19-27%). Even including Cold Bokkeveld, the range in modal total phyllosilicate is 73-79% (average = 75%). Total phyllosilicate abundance provides a non-ambiguous measure of the degree of aqueous alteration and indicates that these meteorites have all experienced essentially the same degree of aqueous alteration. This reflects pervasive hydration of matrix across CM2 samples. Apparent differences in the alteration of chondrules observed in petrographic studies represent various stages in the progression towards complete hydration of all components but are not manifest in significant differences in modal mineralogy. For all samples there is a limited range in olivine (6.9%) and pyroxene (5%) abundances. Modal abundances of the remaining identified phases also show a limited range: calcite (0-1.3%); gypsum (0-1.6%); magnetite (1.1-2.4%); pentlandite (0-2.1%) and pyrrhotite (1-3.8%). As expected, we observe a strong negative correlation in the modal abundance of anhydrous Fe-Mg silicates (olivine + pyroxene) and total phyllosilicate (Mg-serpentine + Fe-cronstedtite) consistent with the idea that phyllosilicate is forming by aqueous alteration of the anhydrous components. The negative correlation in the modal abundance between Mg-serpentine and Fe-cronstedtite indicates: (a) mineralogic transformation of Fe-cronstedtite to Mg-serpentine by fluid driven recrystallisation or (b) that these meteorites had different initial abundances of olivine and pyroxene. The observed positive correlation in the relative proportion of Mg-serpentine with increasing total phyllosilicate abundance reflects the evolution of increasingly Mg-rich phyllosilicate during aqueous alteration. Fe-cronstedtite is the dominant phyllosilicate, while CM chondrule olivines are forsteritic and will form Mg-serpentine during aqueous alteration. This implies that matrix olivine was more Fe-rich than chondrule olivine prior to aqueous alteration.

Howard, K. T.; Benedix, G. K.; Bland, P. A.; Cressey, G.

2009-08-01

246

Remarkable effect of the preparation technique on the state of cobalt ions in BEA zeolites evidenced by FTIR spectroscopy of adsorbed CO and NO, TPR and XRD.  

PubMed

The state of cobalt in two BEA zeolites was studied by XRD, TPR, and FTIR spectroscopy using CO and NO as probe molecules. One of the samples, CoAlBEA (0.4 wt % of Co), was prepared by conventional ion exchange and the other, CoSiBEA (0.7 wt % Co), by a two-step postsynthesis method involving dealuminated SiBEA zeolite. The introduction of Co into SiBEA leads to an increase of unit cell parameters of the BEA structure and to the consumption of silanol groups in vacant T-sites of the dealuminated zeolite. In contrast, no structural changes are observed after incorporation of cobalt into AlBEA by ion-exchange. The reduction temperature of cobalt in CoSiBEA zeolite (1130 K), is much higher than for CoAlBEA and indicates a strong interaction of cobalt ions with SiBEA. Low-temperature CO adsorption on CoAlBEA results in (i) H-bonded CO, (ii) Co(3+)-CO adducts (2,208 cm(-1)) and (iii) a small amount of Co(2+)-CO complexes (2,188 cm(-1)). In agreement with these results, NO adsorption leads to the appearance of (i) NO(+) (2,133 cm(-1), formed with the participation of the zeolite acidic hydroxyls), (ii) Co(3+)-NO (1932 cm(-1)), and (iii) a small amount of Co(2+)(NO)(2) dinitrosyls (nu(s) = 1,898 and nu(as) = 1,814 cm(-1)). Low-temperature CO adsorption on CoSiBEA leads to formation of two kinds of Co(2+)-CO adducts (2,185 and 2,178 cm(-1)). No Co(3+) cations are detected. In line with these results, adsorption of NO reveals the existence of two kinds of Co(2+)(NO)(2) dinitrosyls (nu(s) = 1,888 and nu(as) = 1,808 cm(-1) and nu(s) = 1,878 and nu(as) = 1,799 cm(-1), respectively). PMID:17004815

Mihaylova, Angelina; Hadjiivanov, Konstantin; Dzwigaj, Stanislaw; Che, Michel

2006-10-01

247

Uranium Speciation As a Function of Depth in Contaminated Hanford Sediments - A Micro-XRF, Micro-XRD, and Micro- And Bulk-XAFS Study  

SciTech Connect

Processing ponds at the Hanford, Washington Area 300 site were used for storing basic sodium aluminate and acidic U(VI)-Cu(II)-containing waste from 1943 to 1975. One result of this use is a groundwater plume containing elevated levels of U and Cu beneath the dry ponds and adjacent to the Columbia River. We have used synchrotron-based micro-X-ray fluorescence (?XRF) imaging, micro-X-ray absorption fine structure (?XANES) spectroscopy, and micro-X-ray diffraction (?XRD) techniques combined with bulk U LIII-edge X-ray absorption fine structure (XAFS) spectroscopy to determine the distribution and speciation of U and Cu through the vadose and groundwater zones beneath North Processing Pond #2 (NPP2). Sediment samples were collected from the vadose zone (8’ and 12’ depths), and a sample from the groundwater zone was collected just below the water table (12’-14’ depth). ?XRF imaging revealed two major U occurrences within the vadose and groundwater zones: (1) low to moderate concentrations of U(VI) associated with mineral surfaces (particularly chlorite), and (2) high concentration U(VI)-containing micron-sized particles associated with surface coatings on grains of muscovite and chlorite. These U(VI) hot spots are frequently spatially correlated with Cu(II) hot spots. In the groundwater zone, these particles were identified as the copper-uranyl-silicate cuprosklodowskite and the cupper-uranyl-phosphate metatorbernite. In contrast, the U-Cu-containing particles are X-ray amorphous in the vadose zone. Fits of U LIII-edge XAFS spectra by linear-combination fitting indicate that U speciation consists of ~ 75% uranyl sorbed to clays and ~25% metatorbernite-like X-ray amorphous U-Cu-phosphates (8’ depth); nearly 100% sorbed uranyl (12’ depth); and ~70% sorbed uranyl and ~30% cuprosklodowskite/metatorbernite (ground water zone). These findings suggest that the dissolution of U(VI)-Cu(II)-bearing solids as well as the desorption of U(VI), mainly from phyllosilicates, are important sources of U(VI) in the Area 300 groundwater plume.

Singer, David M.; Zachara, John M.; Brown, Gordon E.

2009-02-01

248

HRTEM Imaging of Atoms at Sub-Angstrom Resolution  

SciTech Connect

John Cowley and his group at Arizona State University pioneered the use of transmission electron microscopy (TEM) for high-resolution imaging. Images were achieved three decades ago showing the crystal unit cell content at better than 4 Angstrom resolution. This achievement enabled researchers to pinpoint the positions of heavy atom columns within the unit cell. Lighter atoms appear as resolution is improved to sub-Angstrom levels. Currently, advanced microscopes can image the columns of the light atoms (carbon, oxygen, nitrogen) that are present in many complex structures, and even the lithium atoms present in some battery materials. Sub-Angstrom imaging, initially achieved by focal-series reconstruction of the specimen exit surface wave, will become common place for next-generation electron microscopes with CS-corrected lenses and monochromated electron beams. Resolution can be quantified in terms of peak separation and inter-peak minimum, but the limits imposed on the attainable resolution by the properties of the micro-scope specimen need to be considered. At extreme resolution the ''size'' of atoms can mean that they will not be resolved even when spaced farther apart than the resolution of the microscope.

O'Keefe, Michael A.; Allard, Lawrence F.; Blom, Douglas A.

2005-04-06

249

HRTEM study comparing naturally and experimentally weathered pyroxenoids  

NASA Astrophysics Data System (ADS)

The mineralogy and chemistry of both naturally and experimentally weathered MnSiO3 chain silicate minerals (rhodonite and pyroxmangite) were compared. In natural MnSiO3, high-resolution transmission-electron microscope observations reveal that alteration begins at grain boundaries and planar defects parallel to the silicate chains that represent junctions between regions with different chain periodicities. Dissolution along these defects results in elongate etch pits that may be partly filled by smectite. Smectite (Ca0.3Mn2.2Zn0.4Al0.1Si4O10(OH)2) also develops in larger etches at grain boundaries. The Zn apparently released by weathering of coexisting sphalerite, may facilitate crystallization of manganesesmectite; rhodochrosite is also an initial product. X-ray diffraction patterns from highly altered materials reveal only rhodochrosite and quartz. Simplified reactions are H2CO3(aq)+4MnSiO3(s)=Mn3Si4O((s)+MnCO3(s) accompanied by 3H2CO3(aq)+Mn3Si4O((s)=3MnCO3(s)+4SiO2(s)+4H2O(1) Pyroxenoid dissolution is incongruent under experimental conditions. A 3-7 nm-thic layer of amorphous silica is present at the mineral surface after ˜ 2000 h of reaction in acidic and near-neutral pH solutions that were undersaturated with respect to bulk amorphous silica. This thin layer of polymeric silica, which is absent on unreacted grains, is interpreted to have formed largely by incongruent dissolution at the mineral surface as protons in solution rapidly exchange for near-surface Mn. The layer may also contain silica readsorbed back onto the surface from solution. The net result is that silica from the pyroxenoid is redistributed directly into reaction products. Upon aging in air for a year, leached layers partially recrystallize. Both natural and experimental reactions produce secondary products by direct modification of the pyroxenoid surface. Manganese does not change oxidation state in the early stages of weathering in either setting. Unlike orthosilicates, compositional variations exert only a secondary control on chain silicate dissolution rates. For all chain silicate minerals, depolymerization of the silicate anion probably limits overall dissolution rates. As the thickness of the modified layer increases, rates may be further suppressed by diffusion (through the leached surface in the case of experimental reactions, and through secondary minerals in the case of natural weathering). The rates for wollastonite are exceptional in that the mineral dissolves more rapidly than other chain silicates and because leaching reactions are more pronounced. Natural surface modification reactions appear to be distinctive in that they occur in the presence of higher concentrations of metal cations. Clay mineral formation may be promoted by periodic drying.

Banfield, Jillian F.; Ferruzzi, Giulio G.; Casey, William H.; Westrich, Henry R.

1995-01-01

250

Magnetic detection of magnetic monopoles  

SciTech Connect

The idea of magnetic monopoles has a long history, but it wasn't until Dirac's demonstration that monopoles could explain charge quantization that the modern era began. Unfortunately, experiment did not oblige by finding any monopoles so for the next fifty years monopoles were only an interesting curiosity. When 't Hooft and Polyakov demonstrated that monopoles are an inevitable consequence of gauge theories currently being used to unify the electroweak (photon-lepton) and nuclear (quark) interactions, interest was quickened. Then a solitary, uncorroborated candidate event was found last spring at Stanford which indicated that magnetic monopoles might exist. However, the monopole abundance implied by the Stanford event is in clear contradiction to bounds on their number from astronomical data. Chief among the arsenal of detection techniques have been those that are uniquely magnetic. The authors review the monopole idea with emphasis on its magnetic detection.

Trower, P.W.

1983-09-01

251

Magnetically separable nanocomposites with photocatalytic activity under visible light for the selective transformation of biomass-derived platform molecules  

EPA Science Inventory

Novel magnetically separable TiO2-guanidine-(Ni,Co)Fe2O4 nanomaterials were prepared and characterised by a series of techniques including XRD, SEM, TEM, N2 physisorption as well as XPS and subsequently tested for their photocatalytic activities in the selective transformation of...

252

Neutrino magnetic moment in a magnetized plasma  

SciTech Connect

The magnetized-plasma contribution to the neutrino anomalous magnetic moment is calculated. It is shown that, in a magnetized plasma, only part of the neutrino additional energy associated with the neutrino spin and with the magnetic-field strength contributes to the neutrino magnetic moment. It is found that, in contrast to results presented previously in the literature, the presence of a magnetized plasma does not lead to a substantial enhancement of the neutrino magnetic moment.

Mikheev, N. V., E-mail: mikheev@uniyar.ac.ru; Narynskaya, E. N., E-mail: elenan@uniyar.ac.r [Yaroslavl State University (Russian Federation)

2010-12-15

253

Neutrino magnetic moment in a magnetized plasma  

E-print Network

The contribution of a magnetized plasma to the neutrino magnetic moment is calculated. It is shown that only part of the additional neutrino energy in magnetized plasma connecting with its spin and magnetic field strength defines the neutrino magnetic moment. It is found that the presence of magnetized plasma does not lead to the considerable increase of the neutrino magnetic moment in contrast to the results presented in literature previously.

N. V. Mikheev; E. N. Narynskaya

2010-11-08

254

Synthesis and Characterization of CoFe2O4\\/Ni0.5Zn0.5Fe2O4 Core\\/shell Magnetic Nanocomposite by the Wet Chemical Route  

Microsoft Academic Search

A cobalt ferrite\\/nickel-zinc ferrite core\\/shell nanocomposite was synthesized by a polymerized complex method using iron citrate, cobalt nitrate, nickel nitrate, zinc nitrate, citric acid, ethylene glycol, benzoic acid and sodium citrate as starting materials. The XRD, TEM and VSM techniques were employed to evaluate the phase composition, morphology and magnetic properties of the samples. The XRD results indicated the coexistence

A. Honarbakhsh-Raouf; H. R. Emamian; A. Yourdkhani; A. Ataie

2010-01-01

255

Effect of composition on crystalline texture and magnetic properties of Nd 2Fe 14B thin films  

Microsoft Academic Search

NdFeB magnetic thin films have been directly fabricated onto heated quartz substrates by RF sputtering. The crystallographic texture, microstructure, phase composition, and magnetic properties of the films are investigated using XRD, SEM, EDAX, and VSM. The films consist of tetragonal Nd2Fe14B and Nd-rich phases, and present high anisotropy. For the films with relatively low Fe content, the c-axis alignment is

Wei Tang; Zhi-Qiang Jin; Jian-Ron Zhang; Gang Gu; Jian-Ming Li; You-Wei Du

1998-01-01

256

Permanent Bar Magnets  

NSDL National Science Digital Library

This is an activity about the basic properties of magnets and magnetism. Learners explore concepts such as magnetic fields and polarity, which form the basic ingredients of a study of Earth's magnetic field and the technology of magnetometers. Materials needed include bar magnets and paper clips. This is Activity 1 of Exploring Magnetism: A Teacher's Magnetism Activity Guide.

257

Nano Ag-doped ZnO particles magnetic, optical and structural studies  

NASA Astrophysics Data System (ADS)

In this work, we report the influences of annealing effects were explored on the crystallinity, morphology and magnetic properties of Ag doped ZnO nanoparticles. The XRD, SEM and vibrating sample magnetometer (VSM) were used to characterize the crystal structures, surface morphology and magnetic properties of doped and pure ZnO nanoparticles (NPs). As synthesized and annealed ZnO NPs were found hexagonal wurtzite crystal structure and the grain size increases while lattice strain decreases due to annealing. From TEM observation annealed samples were shown nanorod like structure found with Ag NPs embedded on the surface. Due to annealing effect, Ag-ZnO shows higher saturation magnetization at RT.

Shah, A. H.; Manikandan, E.; Ahmed, M. Basheer; Irdosh, M.

2013-02-01

258

Magnetic particulate matters in the ashes of few commonly used Indian cigarettes.  

PubMed

Physical aspects of tobacco samples, used in some commonly available Indian brands of cigarettes, with emphasis on their magnetic characterization before and after they get burnt into ashes, are described. The present work highlights the ultrafine nature of the cigarette ashes and provides a compositional insight of their constituent particulate matters as revealed by the XRD and SEM studies. Based on the EDX spectra, elemental distributions of different tobacco samples, before and after they get burnt, are presented. In this work, magnetic measurements of the un-burnt tobacco samples are reported. An attempt is made to shed light on the origin of magnetism observed in these samples. PMID:25049142

Bhattacharjee, Ashis; Mandal, Haradhan; Roy, Madhusudan; Kusz, Joachim; Zubko, Maciej

2014-11-01

259

Magnetism in Mo-doped Yttrium Iron Garnet  

NASA Astrophysics Data System (ADS)

Yttrium iron garnet (YIG) is a synthetic garnet and ferrimagnetic, with chemical formula Y3Fe5O12. In YIG, five iron (III) ions occupy two octahedral and three tetrahedral sites, with the yttrium (III) ions coordinated by eight oxygen ions in an irregular cube. The iron ions in the two coordination sites exhibit different spins, resulting in magnetic behavior. Bulk YIG has been synthesized systematically by solid state reaction method. The formation of pure YIG have been investigated through X-ray diffraction (XRD) beginning from weighing in molar proportions of Y2O3 and Fe2O3, mixing and grinding, pre-sintering and final sintering at 1300 ^oC. XRD study shows that YIG exhibits cubic structure with lattice constant of about 12 å. Magnetization with varying field and temperature has been measured using a SQUID magnetometer. Magnetic measurement of Mo YIG has shown that magnetic moment increase initially and then decreases with Mo doping. Detailed results will be discussed in this presentation. This work is supported by National Science Foundation (Award Number DMR-0907037).

Khanra, S.; Kolekar, Y.; Langhoff, M.; Kahol, P.; Ghosh, K.

2013-03-01

260

Magnetic comparison of abiogenic and biogenic alteration products of lepidocrocite  

NASA Astrophysics Data System (ADS)

Lepidocrocite is a potentially important Fe-bearing precursor phase for the production of nanoscale Fe-oxide particles in the environment. We present a detailed magnetic characterization of various alteration products of lepidocrocite resulting from thermal dehydroxylation reactions and bacterially induced bioreduction and remineralization, accompanied by characterization with x-ray diffraction (XRD) and transmission electron microscopy. Dehydroxylation during annealing at moderate temperatures produces a topotactic transformation from lepidocrocite to maghemite when heated in an oxidizing atmosphere, or to magnetite when heated in a reducing atmosphere. The abiotic Fe-oxide products form an oriented framework of strongly interacting superparamagnetic crystallites and are characterized by a distinctive porous nanostructure observed by electron microscopy. Lepidocrocite bioreduction by the iron-reducing bacterium Shewanella putrefaciens ATCC 8071 produces nanoscale particles of a strongly magnetic phase. This Fe(II)-bearing mineral produced by bioreduction is highly crystalline and euhedral in shape, with a broad grain size distribution and is indicated by magnetic and XRD measurements to be a cation-excess magnetite. We highlight the distinguishing microscopic characteristics of magnetite from both abiotic and bacterially induced mineralization that should allow them to be identified in natural settings. Moreover, both mechanisms of alteration represent potential pathways for the direct formation of strongly magnetic fine-grained Fe-oxide particles in sedimentary environments.

Till, J. L.; Guyodo, Y.; Lagroix, F.; Ona-Nguema, G.; Brest, J.

2014-06-01

261

High resolution switching magnetization magnetic force microscopy  

NASA Astrophysics Data System (ADS)

We introduce switching magnetization magnetic force microscopy based on two-pass scanning atomic force microscopy with reversed tip magnetization between the scans. Within this approach the sum of the scanned data with reversed tip magnetization depicts local van der Waals forces, while their differences map the local magnetic forces. Here we implement this method by fabricating low-momentum magnetic probes that exhibit magnetic single domain state, which can be easily reversed in low external field during the scanning. Measurements on high-density parallel and perpendicular magnetic recording media show enhanced spatial resolution of magnetization.

Cambel, V.; Precner, M.; Fedor, J.; Šoltýs, J.; Tóbik, J.; Š?epka, T.; Karapetrov, G.

2013-02-01

262

Magnetic light  

PubMed Central

Spherical silicon nanoparticles with sizes of a few hundreds of nanometers represent a unique optical system. According to theoretical predictions based on Mie theory they can exhibit strong magnetic resonances in the visible spectral range. The basic mechanism of excitation of such modes inside the nanoparticles is very similar to that of split-ring resonators, but with one important difference that silicon nanoparticles have much smaller losses and are able to shift the magnetic resonance wavelength down to visible frequencies. We experimentally demonstrate for the first time that these nanoparticles have strong magnetic dipole resonance, which can be continuously tuned throughout the whole visible spectrum varying particle size and visually observed by means of dark-field optical microscopy. These optical systems open up new perspectives for fabrication of low-loss optical metamaterials and nanophotonic devices. PMID:22768382

Kuznetsov, Arseniy I.; Miroshnichenko, Andrey E.; Fu, Yuan Hsing; Zhang, JingBo; Luk'yanchuk, Boris

2012-01-01

263

Synthesis and applications of quantum dots and magnetic quantum dots  

NASA Astrophysics Data System (ADS)

We have developed a new synthetic method for producing high-quality quantum dots (QDs) in aqueous solution for biological imaging applications. The glutathione-capped CdTe, ZnSe and Zn 1-xCd xSe alloyed QDs derived are tunable in fluorescence emissions between 360 nm and 700 nm. They show high quantum yields (QYs) of up to 50%, with narrow bandwidths of 19-55 nm. The synthesis of glutathione-capped QDs is simple and cost-effective compared to the conventional organometallic approaches. It can be easily scaled up for the commercial production of alloyed nanocrystals of various compositions. We have also demonstrated the fabrication of magnetic quantum dots (MQDs) through a seed-mediated approach. The formation and assembly of these bifunctional nanocomposites have been elucidated by high-resolution transmission electron microscopy (HRTEM). The MQDs exhibit superparamagnetism and tunable emissions characteristic of the components in this hybrid system. We have created biocompatible silica-coated MQDs that effectively target the cell membranes.

Ying, Jackie Y.; Zheng, Yuangang; Selvan, S. Tamil

2008-02-01

264

A silicon dioxide modified magnetic nanoparticles-labeled lateral flow strips for HBs antigen.  

PubMed

Herein we reported a new type of silicon dioxide wrapped magnetic nanoparticles-labeled lateral flow strip for detection of HBs antigen in sera. The SiO2 wrapped Fe3O4 nanocomposites were prepared and characterized by HR-TEM, FTIR and magnetometer. As-prepared nanocomposites were used to label anti-HBV surface monoclonal antibody, the lateral flow strips were constructed, and 100 specimens of sera were collected and tested. Results showed that the prepared SiO2 wrapped Fe3O4 nanocomposites were shell/core structure, well dispersed, with the size of 25 nm in diameter, the thickness of the shell was about 3 nm, their magnetic saturation intensity was 44.3 meu g(-1). Clinical sera specimens test results showed that the prepared lateral flow strips were with the detection limitation of 5 pg/mL by naked eye observation, and 0.1 pg/mL by CCD reader or MAR Analyzer, specificity was 100%. In conclusion, one kind of silicon dioxide wrapped magnetic nanoparticles-labeled lateral flow strip for ultrasensitive detection of HBs antigen was successfully developed, its ease of use, sensitiveness and low-cost make it well-suited for population-based on-the-site hepatitis B screening. PMID:22416576

Zhang, Xueqing; Jiang, Lin; Zhang, Chunlei; Li, Ding; Wang, Can; Gao, Feng; Cui, Daxiang

2011-12-01

265

Doxorubicin-loaded magnetic gold nanoshells for a combination therapy of hyperthermia and drug delivery.  

PubMed

In the present work, nanohybrid of an anticancer drug, doxorubicin (Dox) loaded gold-coated superparamagnetic iron oxide nanoparticles (SPIONs@Au) were prepared for a combination therapy of cancer by means of both hyperthermia and drug delivery. The Dox molecules were conjugated to SPIONs@Au nanoparticles with the help of cysteamine (Cyst) as a non-covalent space linker and the Dox loading efficiency was investigated to be as high as 0.32mg/mg. Thus synthesized particles were characterized by HRTEM, UV-Vis, FT-IR, SQUID magnetic studies and further tested for heat and drug release at low frequency oscillatory magnetic fields. The hyperthermia studies investigated to be strongly influenced by the applied frequency and the solvents used. The Dox delivery studies indicated that the drug release efficacy is strongly improved by maintaining the acidic pH conditions and the oscillatory magnetic fields, i.e. an enhancement in the Dox release was observed from the oscillation of particles due to the applied frequency, and is not effected by heating of the solution. Finally, the in vitro cell viability and proliferation studies were conducted using two different immortalized cell lines containing a cancerous (MCF-7 breast cancer) and non-cancerous H9c2 cardiac cell type. PMID:25170601

Mohammad, Faruq; Yusof, Nor Azah

2014-11-15

266

Magnetic Catalysis vs Magnetic Inhibition  

E-print Network

We discuss the fate of chiral symmetry in an extremely strong magnetic field B. We investigate not only quark fluctuations but also neutral meson effects. The former would enhance the chiral-symmetry breaking at finite B according to the Magnetic Catalysis, while the latter would suppress the chiral condensate once B exceeds the scale of the hadron structure. Using a chiral model we demonstrate how neutral mesons are subject to the dimensional reduction and the low dimensionality favors the chiral-symmetric phase. We point out that this effect, the Magnetic Inhibition, can be a feasible explanation for recent lattice-QCD data indicating the decreasing behavior of the chiral-restoration temperature with increasing B.

Kenji Fukushima; Yoshimasa Hidaka

2012-09-06

267

Nonequilibrium magnetic dynamics in mechanically alloyed materials  

SciTech Connect

The magnetically glassy behavior of mechanically alloyed Fe{sub 61}Re{sub 30}Cr{sub 9} is reported in detail, including a static and dynamic study of the freezing process, the observation of aging in a mechanically alloyed sample, Moessbauer analysis, and annealing experiments. Despite the clear collective character of the low-temperature change of regime, no thermodynamical spin-glass mean-field transition could be proved. On the other hand, the careful comparison of the magnetic behavior with that reported in strongly interacting fine particles systems hinted towards the presence of that kind of particles in our samples. Structural considerations based on XRD, Moessbauer, and the evolution of the ac susceptibility peaks upon annealing pointed to the existence of very fine Fe-rich clusters able to support a magnetic moment, confirming the diagnosis extracted from the magnetic dynamics analysis. The argument is strengthened by the study of the effects of milling on the freezing temperature in a second sample showing a similar behavior: Fe{sub 35}Al{sub 50}B{sub 15}. The explanation can be extended naturally to previously reported mechanically alloyed, spin-glass-like samples, which hints towards the generalization of our interpretation.

De Toro, J. A.; Lopez de la Torre, M. A.; Arranz, M. A.; Riveiro, J. M.; Martinez, J. L.; Palade, P.; Filoti, G.

2001-09-01

268

Exploring Magnetism: Investigating the forces of magnets  

NSDL National Science Digital Library

This activity is a classroom and lab investigation of magnetism. Students gather results of experiments involving the forces of magnets. They use this data to develop their own experiments to test properties of magnets.

269

Magnetic Liquids  

NASA Technical Reports Server (NTRS)

Ferrofluidics Corporation's recent innovation is a spindle for rotating computer discs that supports the disc's rotating shaft on a film of magnetic fluid instead of conventional ball bearings. According to its developers, the spindle offers greatly increased rotational stability, meaning substantially reduced vibration and mechanical noise, and non- repeatable runout. This allows disc drives to store two to 10 times more information.

1987-01-01

270

Magnetic tape  

NASA Technical Reports Server (NTRS)

The move to visualization and image processing in data systems is increasing the demand for larger and faster mass storage systems. The technology of choice is magnetic tape. This paper briefly reviews the technology past, present, and projected. A case is made for standards and the value of the standards to users.

Robinson, Harriss

1992-01-01

271

Synthesis of Mn-doped ZnO diluted magnetic semiconductors in the presence of ethyl acetoacetate under solvothermal conditions  

NASA Astrophysics Data System (ADS)

Mn-doped ZnO samples with 5%, 20% and 40% nominal Mn concentrations were prepared in the presence of ethyl acetoacetate under solvothermal conditions. UV absorption spectroscopic analysis discloses that chemical modification was achieved by reaction of Zn or Mn precursor with ethyl acetoacetate in ethanol medium. XRD and HRTEM characterizations indicate that ZnMnO 3 impurity phase was formed in the 20% and 40% Mn-doped ZnO samples while no secondary phase was present in the 5% Mn-doped sample. The 5% Mn-doped sample consists of spheroid-like particles with size of 10-50 nm and has a real Mn concentration of 3.2%. Ferromagnetism and paramagnetism coexist in the 5% Mn-doped ZnO sample at room-temperature, which may arise from ferromagnetic exchange interaction as well as small secondary phases. The 20% and 40% Mn-doped samples show large paramagnetic effects at room temperature. Small paramagnetic secondary phases and clustering of Mn are probably responsible for this.

Jing, Chengbin; Jiang, Yingjing; Bai, Wei; Chu, Junhao; Liu, Aiyun

2010-08-01

272

Magnetic liposomes for colorectal cancer cells therapy by high-frequency magnetic field treatment.  

PubMed

In this study, we developed the cancer treatment through the combination of chemotherapy and thermotherapy using doxorubicin-loaded magnetic liposomes. The citric acid-coated magnetic nanoparticles (CAMNP, ca. 10 nm) and doxorubicin were encapsulated into the liposome (HSPC/DSPE/cholesterol?=?12.5:1:8.25) by rotary evaporation and ultrasonication process. The resultant magnetic liposomes (ca. 90 to 130 nm) were subject to characterization including transmission electron microscopy (TEM), dynamic light scattering (DLS), X-ray diffraction (XRD), zeta potential, Fourier transform infrared (FTIR) spectrophotometer, and fluorescence microscope. In vitro cytotoxicity of the drug carrier platform was investigated through 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay using L-929 cells, as the mammalian cell model. In vitro cytotoxicity and hyperthermia (inductive heating) studies were evaluated against colorectal cancer (CT-26 cells) with high-frequency magnetic field (HFMF) exposure. MTT assay revealed that these drug carriers exhibited no cytotoxicity against L-929 cells, suggesting excellent biocompatibility. When the magnetic liposomes with 1 ?M doxorubicin was used to treat CT-26 cells in combination with HFMF exposure, approximately 56% cells were killed and found to be more effective than either hyperthermia or chemotherapy treatment individually. Therefore, these results show that the synergistic effects between chemotherapy (drug-controlled release) and hyperthermia increase the capability to kill cancer cells. PMID:25246875

Hardiansyah, Andri; Huang, Li-Ying; Yang, Ming-Chien; Liu, Ting-Yu; Tsai, Sung-Chen; Yang, Chih-Yung; Kuo, Chih-Yu; Chan, Tzu-Yi; Zou, Hui-Ming; Lian, Wei-Nan; Lin, Chi-Hung

2014-01-01

273

Magnetic liposomes for colorectal cancer cells therapy by high-frequency magnetic field treatment  

NASA Astrophysics Data System (ADS)

In this study, we developed the cancer treatment through the combination of chemotherapy and thermotherapy using doxorubicin-loaded magnetic liposomes. The citric acid-coated magnetic nanoparticles (CAMNP, ca. 10 nm) and doxorubicin were encapsulated into the liposome (HSPC/DSPE/cholesterol = 12.5:1:8.25) by rotary evaporation and ultrasonication process. The resultant magnetic liposomes ( ca. 90 to 130 nm) were subject to characterization including transmission electron microscopy (TEM), dynamic light scattering (DLS), X-ray diffraction (XRD), zeta potential, Fourier transform infrared (FTIR) spectrophotometer, and fluorescence microscope. In vitro cytotoxicity of the drug carrier platform was investigated through 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay using L-929 cells, as the mammalian cell model. In vitro cytotoxicity and hyperthermia (inductive heating) studies were evaluated against colorectal cancer (CT-26 cells) with high-frequency magnetic field (HFMF) exposure. MTT assay revealed that these drug carriers exhibited no cytotoxicity against L-929 cells, suggesting excellent biocompatibility. When the magnetic liposomes with 1 ?M doxorubicin was used to treat CT-26 cells in combination with HFMF exposure, approximately 56% cells were killed and found to be more effective than either hyperthermia or chemotherapy treatment individually. Therefore, these results show that the synergistic effects between chemotherapy (drug-controlled release) and hyperthermia increase the capability to kill cancer cells.

Hardiansyah, Andri; Huang, Li-Ying; Yang, Ming-Chien; Liu, Ting-Yu; Tsai, Sung-Chen; Yang, Chih-Yung; Kuo, Chih-Yu; Chan, Tzu-Yi; Zou, Hui-Ming; Lian, Wei-Nan; Lin, Chi-Hung

2014-09-01

274

Magnetic liposomes for colorectal cancer cells therapy by high-frequency magnetic field treatment  

PubMed Central

In this study, we developed the cancer treatment through the combination of chemotherapy and thermotherapy using doxorubicin-loaded magnetic liposomes. The citric acid-coated magnetic nanoparticles (CAMNP, ca. 10 nm) and doxorubicin were encapsulated into the liposome (HSPC/DSPE/cholesterol?=?12.5:1:8.25) by rotary evaporation and ultrasonication process. The resultant magnetic liposomes (ca. 90 to 130 nm) were subject to characterization including transmission electron microscopy (TEM), dynamic light scattering (DLS), X-ray diffraction (XRD), zeta potential, Fourier transform infrared (FTIR) spectrophotometer, and fluorescence microscope. In vitro cytotoxicity of the drug carrier platform was investigated through 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay using L-929 cells, as the mammalian cell model. In vitro cytotoxicity and hyperthermia (inductive heating) studies were evaluated against colorectal cancer (CT-26 cells) with high-frequency magnetic field (HFMF) exposure. MTT assay revealed that these drug carriers exhibited no cytotoxicity against L-929 cells, suggesting excellent biocompatibility. When the magnetic liposomes with 1 ?M doxorubicin was used to treat CT-26 cells in combination with HFMF exposure, approximately 56% cells were killed and found to be more effective than either hyperthermia or chemotherapy treatment individually. Therefore, these results show that the synergistic effects between chemotherapy (drug-controlled release) and hyperthermia increase the capability to kill cancer cells.

2014-01-01

275

Magnetic properties of hydrogen-included TiZrNiPd quasicrystals.  

PubMed

Quasicrystals prepared by rapid quenching of Pd-added TiZrNi ingots were hydrogenated, and effects of hydrogen for magnetic properties were compared with the unhydrogenated ones under magnetic fields from -10000 to 10000 Oe. The magnetization values obtained from vibrating sample magnetometer (VSM) were analyzed with the combination of powder X-ray diffraction (XRD) data. While its contribution is larger than that of Pd, hydrogen decreases the magnetic moments of both Pd-doped and undoped quasicrystals. As increasing the amount of absorbed hydrogen which is represented by H/M (hydrogen to host metal atom ratio) values from 0 to 1.19, the magnetization values of Ti53Zr27Ni20 quasicrystals measured at 10000 Oe significantly decreased from 0.301 to 0.212 emu/g. A careful analysis of XRD data demonstrated that the reduced interactions of magnetic dipole moments between Ni atoms, as the product of the expansion of the quasilattice constants after hydrogenation, are responsible for the decreased magnetization values in hydrogenated TiZrNiPd quasicrystal samples. PMID:22966713

Shin, Hongsik; Lee, Sang-Hwa; Jo, Youngsoo; Kim, Jae-Yong

2012-07-01

276

Magnetization Process: Hysteresis.  

National Technical Information Service (NTIS)

The magnetization process, hysteresis (the difference in the path of magnetization for an increasing and decreasing magnetic field), hysteresis loops, and hard magnetic materials are discussed. The fabrication of classroom projects for demonstrating hyste...

R. Balsamel

1990-01-01

277

Densification and magnetization of rare earth magnets  

NASA Astrophysics Data System (ADS)

Hot isostatic pressing of SmCo5 magnets has been evaluated as a means for increasing the density, remanence, and energy product of rare earth magnets. The results indicate 99% density can be achieved without loss in the magnetic properties. Magnetization studies up to 100 kOe were conducted on SmCo5 magnets and the results indicate that fields in excess of 60 kOe are required to achieve maximum values of remanence in a magnetically demagnetized magnet as is produced by running a hysteresis loop. Thermally demagnetized magnets, however, require less than 15 kOe to realize the full potential for all practical applications.

Narasimhan, K. S. V. L.; Lizzi, T.

1985-04-01

278

?-Sheet Nanocrystalline Domains Formed from Phosphorylated Serine-Rich Motifs in Caddisfly Larval Silk: A Solid State NMR and XRD Study  

PubMed Central

Adhesive silks spun by aquatic caddisfly (order Trichoptera) larvae are used to build both intricate protective shelters and food harvesting nets underwater. In this study, we use 13C and 31P solid-state Nuclear Magnetic Resonance (NMR) and Wide Angle X-ray Diffraction (WAXD) as tools to elucidate molecular protein structure of caddisfly larval silk from the species Hesperophylax consimilis. Caddisfly larval silk is a fibroin protein based biopolymer containing mostly repetitive amino acid motifs. NMR and X-ray results provide strong supporting evidence for a structural model in which phosphorylated serine repeats (pSX)4 complex with divalent cations Ca2+ and Mg2+ to form rigid nanocrystalline ?-sheet structures in caddisfly silk. 13C NMR data suggests that both phosphorylated serine and neighboring valine residues exist in a ?-sheet secondary structure conformation while glycine and leucine residues common in GGX repeats likely reside in random coil conformations. Additionally, 31P chemical shift anisotropy (CSA) analysis indicates that the phosphates on phosphoserine residues are doubly ionized, and are charge-stabilized by divalent cations. Positively charged arginine side chains also likely play a role in charge stabilization. Finally, WAXD results finds that the silk is at least 7–8% crystalline, with ?-sheet inter-plane spacings of 3.7 and 4.5 Å. PMID:23452243

Addison, J. Bennett; Ashton, Nicholas N.; Weber, Warner S.; Stewart, Russell J.; Holland, Gregory P.; Yarger, Jeffery L.

2013-01-01

279

Gas-phase synthesis of magnetic metal/polymer nanocomposites.  

PubMed

Highly magnetic metal Co nanoparticles were produced via reducing flame spray pyrolysis, and directly coated with an epoxy polymer in flight. The polymer content in the samples varied between 14 and 56 wt% of nominal content. A homogenous dispersion of Co nanoparticles in the resulting nanocomposites was visualized by electron microscopy. The size and crystallinity of the metallic fillers was not affected by the polymer, as shown by XRD and magnetic hysteresis measurements. The good control of the polymer content in the product nanocomposite was shown by elemental analysis. Further, the successful polymerization in the gas phase was demonstrated by electron microscopy and size measurements. The presented effective, dry and scalable one-step synthesis method for highly magnetic metal nanoparticle/polymer composites presented here may drastically decrease production costs and increase industrial yields. PMID:25422410

Starsich, Fabian H L; Hirt, Ann M; Stark, Wendelin J; Grass, Robert N

2014-12-19

280

Enhancement of the magnetic properties of Al/La multiferroic  

NASA Astrophysics Data System (ADS)

Nanosized multiferroic La1-xAlxFeO3 (0.00?x?0.20) samples were successfully synthesized by the citrate technique without subsequent heat treatment. All the prepared samples revealed single phase orthorhombic structure of space group Pbnm. XRD data revealed that the lattice parameters (a) decrease with increasing Al content. The magnetic susceptibility (?M) was enhanced significantly from 0.36 to 0.68 emu/g mole from LaFeO3 to La0.8Al0.2FeO3 respectively. The values of magnetization (M) and effective magnetic moment (?eff) were found to increase with increasing Al content. The enhancement of the physical and structural properties of the investigated multiferroic is possibly due to the changes in the lattice parameters, tolerance factor as well as crystallite size caused by aluminum substitution.

Ahmed, M. A.; Okasha, N.; Hussein, B.

2012-08-01

281

Controllable synthesis of nickel dendritic crystals induced by magnetic field  

SciTech Connect

We demonstrated in this paper a simple and easy method for the preparation of dendritic nickel crystals in an external magnetic field in boiling ethylene glycol (EG) solution. The structural features and morphology of the sample were investigated using powder X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The values of saturation magnetization (M{sub s}) and coercivity (H{sub c}) of the dendritic crystals characterized by using a vibrating sample magnetometer (VSM) are 170.3 emu g{sup -1} and 50.7 Oe, respectively. It was clear that the external magnetic field was the most important factor for controlling the morphology of the product.

Zhang Xia [State Key Laboratory of Solid Lubrication, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou 730000 (China); Laboratory of Special Functional Materials, Henan University, Kaifeng 475001 (China); Graduate School of Chinese Academy of Science, Beijing 100039 (China); Liu Weimin [State Key Laboratory of Solid Lubrication, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou 730000 (China)], E-mail: wmliu@lzb.ac.cn

2008-08-04

282

True North, Magnetic North  

NSDL National Science Digital Library

This activity helps students understand why compass angles need to be corrected for regional magnetic variation. The magnetic compass, perfected slowly over years of experimentation, trial, and scientific endeavor, became the sailor's most common and most reliable direction-indicating aid, but is influenced by magnetic variabilities and the location of magnetic north. Terms introduced include compass, magnetic variation, true north, and magnetic north.

283

Magnetic bearing. [for supplying magnetic fluxes  

NASA Technical Reports Server (NTRS)

A magnetic bearing is described which includes a pair of coaxial, toroidal, and permanent magnets having axially directed poles. Like poles of the permanent magnets are adjacent to each other, whereby the permanent magnets have a tendency to be urged apart along the common axis. An electromagnet is wound coaxially with the permanent magnets in such a manner that the poles are axially directed. Between the poles of each permanent magnet there is a low magnetic reluctance circuit including two series air gaps. Between the poles of the electromagnet a low reluctance path including only one air gap of each of the low magnetic reluctance circuits is provided. The low reluctance path for the electromagnet includes a ring axially translatable relative to the permanent magnets. The ring forms opposite faces of the air gaps in the magnetic circuits for each permanent magnet.

Studer, P. A. (inventor)

1975-01-01

284

Studies on the self-catalyzed Knoevenagel condensation, characterization, DPPH radical scavenging activity, cytotoxicity, and molecular properties of 5-arylidene-2,2-dimethyl-1,3-dioxane-4,6-diones using single crystal XRD and DFT techniques  

NASA Astrophysics Data System (ADS)

We have studied the self-catalyzed Knoevenagel condensation, spectral characterization, DPPH radical scavenging activity, cytotoxicity, and molecular properties of 5-arylidene-2,2-dimethyl-1,3-dioxane-4,6-diones using single crystal XRD and DFT techniques. In the absence of any catalyst, a series of novel 5-arylidene-2,2-dimethyl-1,3-dioxane-4,6-diones were synthesized using Meldrum’s acid and formylphenoxyaliphatic acid(s) in water. These molecules are arranged in the dimer form through intermolecular H-bonding in the single crystal XRD structure. Compounds have better DPPH radical scavenging activity and cytotoxicity against A431 cancer cell line. The optimized molecular structure, natural bond orbital analysis, electrostatic potential map, HOMO-LUMO energies, molecular properties, and atomic charges of these molecules have been studied by performing DFT/B3LYP/3-21G(*) level of theory in gas phase.

Suresh Kumar, G. S.; Antony Muthu Prabhu, A.; Bhuvanesh, N.

2014-10-01

285

Magnetic anomalies  

NASA Astrophysics Data System (ADS)

The implications and accuracy of anomaly maps produced using Magsat data on the scalar and vector magnetic field of the earth are discussed. Comparisons have been made between the satellite maps and aeromagnetic survey maps, showing smoother data from the satellite maps and larger anomalies in the aircraft data. The maps are being applied to characterize the structure and tectonics of the underlying regions. Investigations are still needed regarding the directions of magnetization within the crust and to generate further correlations between anomaly features and large scale geological structures. Furthermore, an increased data base is recommended for the Pacific Ocean basin in order to develop a better starting model for Pacific tectonic movements. The Pacific basin was large farther backwards in time and subduction zones surround the basin, thereby causing difficulties for describing the complex break-up scenario for Gondwanaland.

Harrison, C. G. A.

1983-04-01

286

Magnetic domains  

NASA Astrophysics Data System (ADS)

Recently a Nahm transform has been discovered for magnetic bags, which are conjectured to arise in the large n limit of magnetic monopoles of charge n. We interpret these ideas using string theory and present evidence for this conjecture. Our main result concerns the extension of the notion of bags and their Nahm transform to higher gauge theories and arbitrary domains. Bags in four dimensions conjecturally describe the large n limit of n self-dual strings. We show that the corresponding Basu-Harvey equation is the large n limit of an equation describing n M2-branes, and that it has a natural interpretation in loop space. We also formulate our Nahm equations using strong homotopy Lie algebras.

Harland, Derek; Palmer, Sam; Sämann, Christian

2012-10-01

287

Preparation of Soft Manganese Ferrite and Inventional of its Magnetic Properties and Mn55 Nuclear Magnetic Resonance  

NASA Astrophysics Data System (ADS)

In this study, Mn-ferrite has been prepared with nominal formula of MnFe2O4, using the dry conventional ceramic method. The raw materials were Mobarakeh steel company modified domestic iron oxide and Merk manganese oxide. XRD patterns of the prepared samples show that they are single phase. Magnetic measurements have been performed on the toroidal samples sintered in different temperatures, using a hystograph unit MPG100D model. The results of measurements show that optimum formation pressures to obtain maximum relative magnetic permeability and hystersis. We report here the observation of the Mn55 nuclear magnetic resonance associated with the Mn2 + ion in the ferromagnetic spinel MnFe2O4 also.

Soleimani, R.; Soleimani, M.; Gheisari Godarzi, M.; Askari, A.

2011-08-01

288

Nanoscale magnetic domain structures in epitaxial nickel thin films  

NASA Astrophysics Data System (ADS)

We have studied the magnetic domain structures in epitaxial Ni(001) and Ni(111) thin films (thickness range of 10--500 nm) grown on Cu(001)/Si(001) and Ag(111)/Si(111) substrates using Molecular Beam Epitaxy (MBE) deposition method. The magnetic domain patterns were imaged using magnetic force microscopy (MFM). The focus of this study is to understand the observed nanoscale magnetic stripe domain patterns which are characteristic of thin films with uniaxial anisotropy along the film normal. The films were structurally characterized using in-situ reflection of high energy electron diffraction (RHEED) and ex-situ x-ray diffraction (XRD) methods. Magnetic parameters such as effective magnetic anisotropy field (4piMeff), saturation magnetization and uniaxial perpendicular anisotropy energy density (Ku) were determined using both ferromagnetic resonance (FMR) and magnetometry methods. The values of 4piMeff and Ku were found to be strongly dependent on film thickness in the case of Ni(001) films. Several theoretical models of magnetic stripe domain structure have been discussed and, in particular, we have used the models developed by Kooy and Enz and Kaczer et al. to explain the observed stripe domain patterns in epitaxial magnetic thin films. We have found the above models are not adequate to explain the observed thickness dependence of domain size, unless the following two modification are made: (1) the so called mu*-correction (i.e., remove the constraint that the magnetization is rigidly fixed along the film normal) and, (2) allow the formation of closure domains. With these modifications, we have been able to successfully explain the observed thickness dependence of the stripe domain size in both Ni(001) and Ni(111) films. We have demonstrated the importance of the inclusion of mu*-correction as well as flux closure domains in the modeling of magnetic stripe domains in films with Ku < 2piMs2.

Hameed, Sithy Faleela

2000-10-01

289

Magnetic Math  

NSDL National Science Digital Library

This is a booklet containing 37 space science mathematical problems, several of which use authentic science data. The problems involve math skills such as unit conversions, geometry, trigonometry, algebra, graph analysis, vectors, scientific notation, and many others. Learners will use mathematics to explore science topics related to Earth's magnetic field, space weather, the Sun, and other related concepts. This booklet can be found on the Space Math@NASA website.

290

Magnetic Storms  

NASA Technical Reports Server (NTRS)

This talk provides a brief summary of the first conference devoted entirely to magnetic storms. Topics cover the relevant phenomena at the Sun/corona, propogation of these structures through interplanetary space, the response of the magnetosphere to interaction with these interplanetary structures, the formation of the storm time ring current (in particular the oxygen content of the ring-current), and storm ionospheric effects and ground based effects.

Tsurutani, B. T.; Gonzalez, W. D.; Kamide, Y.

1996-01-01

291

Magnetic Reconnection  

SciTech Connect

We review the fundamental physics of magnetic reconnection in laboratory and space plasmas, by discussing results from theory, numerical simulations, observations from space satellites, and the recent results from laboratory plasma experiments. After a brief review of the well-known early work, we discuss representative recent experimental and theoretical work and attempt to interpret the essence of significant modern findings. In the area of local reconnection physics, many significant findings have been made with regard to two- uid physics and are related to the cause of fast reconnection. Profiles of the neutral sheet, Hall currents, and the effects of guide field, collisions, and micro-turbulence are discussed to understand the fundamental processes in a local reconnection layer both in space and laboratory plasmas. While the understanding of the global reconnection dynamics is less developed, notable findings have been made on this issue through detailed documentation of magnetic self-organization phenomena in fusion plasmas. Application of magnetic reconnection physics to astrophysical plasmas is also brie y discussed.

Masaaki Yamada, Russell Kulsrud and Hantao Ji

2009-09-17

292

Loess magnetism  

NASA Astrophysics Data System (ADS)

Loess is a wind-blown Quaternary silt deposit that blankets vast tracts of land and in places reaches thicknesses in excess of 300 m. Over the last decade it has emerged that certain loess sections have recorded the polarity history of the geomagnetic field and now provide essentially continuous magnetostratigraphic archives covering the last 2-3 m.y. Indeed, it is the chronology provided by the magnetic polarity signature itself that was largely responsible for establishing the timing of the initiation of loess accumulation, particularly in the celebrated Chinese loess plateau, where a starting date close to the Gauss-Matuyama chron boundary (2.6 Ma) is now firmly established. This coincides with a widely documented global climatic shift and accelerated uplift of the Tibetan planteau. Many loess sections contain fossil soils (paleosols) that bear witness to warmer and wetter climatic conditions corresponding to interglacial periods in contrast to the cold, arid environments in which pristine loess accumulated and which correspond to glacial intervals. The resulting sequences of alternating loess and paleosols also manifest themselves magnetically, in this case in terms of susceptibility changes, entirely distinct from the remanence characteristics, which encode the geomagnetic polarity. The susceptibility time series obtained from localities in Alaska and China correlate remarkably well with the oceanic oxygen isotope signal and yield spectral power estimates in agreement with those predicted by the astronomical (Milankovitch) theory of ice ages. Comparisons of susceptibility patterns with corresponding profiles of 10Be concentration in loess allows major changes in rainfall to be estimated. In China, for example data spanning the last 130 kyr (corresponding to oxygen isotope stages 1-5) indicate that paleoprecipitation was almost halved (from ?540 to ?310 mm yr-1) as the warm interglacial during which paleosol S1 formed gave way to the following glacial interval in which loess layer L1 acuumulated. It has also been found that increased amounts of continent-derived dust delivered to the deep ocean correlate with loess formation and thereby permit certain broad feature of atmospheric ciruculation (paleowinds) to be worked out. Debate continues over the actual mechanism by which magnetic susceptibility becomes a climate proxy. The current consensus is that some form of in situ process must be responsible, at least in part. Detailed laboratory investigations, both on whole samples and on magnetic extracts, indicate that the enhancement observed in midlatitude weathered loess and paleosols is largely due to a magnetically ``soft'' mineral which is either magnetite (?-Fe2O3). Experimental evidence is accumulating that tiny (<100 nm) ferromagnetic particles probably generated by the activity of magnetotactic bacteria in the soil are responsible.

Heller, Friedrich; Evans, Michael E.

293

Magnetic Measurement and Magnet Tutorial, Part 3  

SciTech Connect

Magnetic measurements, like magnet design, is a broad subject. It is the intention of this lecture to cover only a small part of the field, regarding the characterization of the line integral field quality of multipole magnets (dipoles, quadrupoles and sextupoles) using compensated rotating coils. Other areas which are not covered are magnet mapping, AC measurements and sweeping wire measurements.

Tanabe, Jack

2003-07-15

294

Patterned Magnetic Nanostructures and Quantized Magnetic Disks  

E-print Network

Patterned Magnetic Nanostructures and Quantized Magnetic Disks STEPHEN Y. CHOU Invited Paper, opens up new opportunities for engineering innovative magnetic materials and devices, developing ultra-high-density magnetic storage, and understanding micromagnetics. This paper reviews the recent advances in patterned

295

Synthesis of magnetic hollow silica using polystyrene bead as a template  

NASA Astrophysics Data System (ADS)

In this paper, we report a new route to synthesize novel magnetic hollow silica nanospheres (MHSNs) using polystyrene particles as sacrificial templates, and TEOS and Fe 3O 4 as precursors. TEM, EDS, XRD, and SQUID were applied to characterize MHSNs. TEM and EDS results show that the MHSNs consist of about 200 nm of hollow cores and ˜35 nm shells with ˜10 nm of Fe 3O 4 nanoparticles embedded. The polystyrene beads were successfully removed by immersing the as-prepared silica nanocomposite in a toluene solution. XRD results demonstrate that the Fe 3O 4 magnetic nanoparticles still keep spinel structure even heated at low temperature. The surface status of the polystyrene beads and Fe 3O 4 nanoparticles has an important effect on the formation of the MHSNs. The MHSNs present a superparamagnetism at room temperature by SQUID measurement. The MHSNs have potential applications in biosystem and nanomedicine.

Wu, W.; Caruntu, D.; Martin, A.; Yu, M. H.; O'Connor, C. J.; Zhou, W. L.; Chen, J.-F.

2007-04-01

296

The photoluminescence and magnetic properties of ZnAl2O4:Mn nanocrystals  

NASA Astrophysics Data System (ADS)

The single-phase ZnAl2O4 phosphors with various components of Mn2+ dopant were fabricated by using hydrothermal method. The phosphors has been characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), photoluminescence (PL) spectra and vibrating sample magnetometer (VSM). The results of XRD and TEM measurements showed that the resultant nanoparticles were single crystal with octahedral and hexagonal shape, and after annealed, this shape had change. Green emission was observed from doped zinc aluminate with 427 nm excitation. The temperature-dependant PL spectra revealed two emission peaks which exhibited different shifting tendency with a decrease in temperature. The room-temperature hysteresis loops of zinc aluminate nanoparticles showed magnetic behavior, and the magnetism disappeared gradually with the increase of Mn2+ doping contents.

Zhang, Dong; Yin, Yuli; Liu, Yunlong; Chao, Wenbiao; Zhai, Ya

2013-08-01

297

Structural and magnetic properties of nano-NiFe2O4 prepared using green nanotechnology  

NASA Astrophysics Data System (ADS)

Nanocrystalline spinel ferrite NiFe2O4 powders were synthesized by a novel green nanotechnology derivative of sol-gel method. The effect of preparation conditions on the particle size (D) and accordingly magnetic properties was investigated using X-ray powder diffraction (XRD), Mössbauer effect spectrometer (ME) and vibrating sample magnetometer (VSM). The obtained results were compared to samples prepared using a standard ceramic method and a sol-gel technique using a citric acid route. XRD measurements reflected the spinel structure of prepared samples. The results confirmed the critical dependence of the particle size on the preparation method and heat treatment. Mössbauer effect spectroscopy measurements indicated a strong impact of the particle size on the measured spectra. A gradual decrease of the hyperfine field with decreasing D was observed. Both the saturation magnetization MS and the coercivity Hc are found to be influenced by the decrease of the particle size.

Yehia, M.; Labib, Sh.; Ismail, S. M.

2014-08-01

298

Permanent Magnets and Magnetic Fluids  

Microsoft Academic Search

Since the discovery of the extremely high magnetocrystalline anisotropy of YCo. in 1966 there has been rapidly increasing interest in the development of cobalt-rare-earth intermetallic com­ pounds as permanent magnet materials, The observed coercive forces are still only a small fraction of the anisotropy fields, and for some reason the coercive forces attainable with SmCo. are, larger than in other

J. J. BECKER

299

Effects of heat treatment on the magnetic properties of melt-spun Nd6Pr1Fe76B12Ti4C1Co3 nanocomposite ribbons  

NASA Astrophysics Data System (ADS)

In this study, the effects of different annealing temperatures on the structure and magnetic properties of Nd-Fe-B nanocomposite permanent magnetic alloys with nominal composition of Nd6Pr1Fe76B12Ti4C1Co3 have been investigated. Melt Spinning (one of the most predominant ribbon synthesize methods) with constant wheel speed of V = 25 m/s was employed to produce ribbons. As-spun ribbons were examined by using xray diffractometer (XRD) with Cu- K? radiation and differential scanning calorimetry (DSC). The ribbons were annealed at different temperatures in order to extract the best magnetic properties. The XRD and electron microscopy technique results confirm that grains are in the size of less than 50 nm. In addition, optimum magnetic properties were obtained at 720°C annealed temperature.

Sabbaghizadeh, Rahim; Hashim, Mansor

2013-01-01

300

Evaluation the Impact of Annealing on Phase Evolution, Microstructure, and Magnetic Properties of Nanocrystalline Ball-Milled LiSm Ferrite  

NASA Astrophysics Data System (ADS)

The impact of milling and subsequent annealing on the phase evolution, microstructure and magnetic properties of Li0.5Sm x Fe2.5- x O4 ( x = 0, 0.05, 0.1, 0.2) ferrite prepared by mechanical alloying was investigated. X-ray diffraction (XRD), scanning electron microscope, Fourier transform infrared spectroscopy, laser particle size analysis, and vibrating sample magnetometry were employed to characterize the prepared LiSm compound. The structure was evaluated by XRD, confirmed the formation of its single-phase spinel structure. The magnetic properties of the milled nanostructured powder were extensively affected by the annealing temperature. The substitution of samarium significantly influences the magnetic characteristics, proved by magnetization measurements at room temperature.

Mahmoudi, M.; Kavanlouei, M.; Maleki-Ghaleh, H.

2014-09-01

301

Ferroelectricity in spiral magnets.  

PubMed

It was recently observed that the ferroelectrics showing the strongest sensitivity to an applied magnetic field are spiral magnets. We present a phenomenological theory of inhomogeneous ferroelectric magnets, which describes their thermodynamics and magnetic field behavior, e.g., dielectric susceptibility anomalies at magnetic transitions and sudden flops of electric polarization in an applied magnetic field. We show that electric polarization can also be induced at domain walls and that magnetic vortices carry electric charge. PMID:16606047

Mostovoy, Maxim

2006-02-17

302

Magnetic Alloys in Nanoscale Biomaterials  

SciTech Connect

Fe-Co composition gradient and Fe-Pt multilayer alloy films were tested as catalysts for growing vertically aligned carbon nanofibers (VACNFs) by plasma-enhanced chemical vapor deposition (PECVD). The Fe-Co film yielded nanofibers with alloy tips in a wide compositional range varying from 8.15 pct Fe at the Co-rich end to 46.29 pct Fe in the middle of the wafer as determined by energy-dispersive X-ray analysis. Two Fe-Co cubic phases (SG Pm3m, Pm{bar 3}m) were identified by preliminary X-ray diffraction (XRD) measurements. Magnetic measurements showed a substantially greater hysteresis loop area and coercivity in Fe-Co catalyst nanoparticles as compared to the as deposited Fe-Co film. The Fe-Pt film did not break into FePt alloy nanoparticles under the applied processing parameters and thus the utility of FePt as a VACNF catalyst has been inconclusive.

Leventouri, T. H. [Florida Atlantic University; Melechko, Anatoli Vasilievich [ORNL; Sorge, Korey D. [Florida Atlantic University; Klein, Kate L [ORNL; Fowlkes, Jason Davidson [ORNL; Rack, P. D. [University of Tennessee, Knoxville (UTK); Anderson, Ian M [ORNL; Thompson, James R [ORNL; McKnight, Timothy E [ORNL; Simpson, Michael L [ORNL

2006-01-01

303

Phyllosilicate-poor palagonitic dust from Mauna Kea Volcano (Hawaii): A mineralogical analogue for magnetic Martian dust?  

NASA Astrophysics Data System (ADS)

The mineralogical and elemental composition of dust size fractions (<2 and <5 ?m) of eight samples of phyllosilicate-poor palagonitic tephra from the upper slopes of Mauna Kea Volcano (Hawaii) were studied by X-ray diffraction (XRD), X-ray fluorescence (XRF), visible and near-IR reflectance spectroscopy, Mössbauer spectroscopy, magnetic properties methods, and transmission electron microscopy (TEM). The palagonitic dust samples are spectral analogues of Martian bright regions at visible and near-IR wavelengths. The crystalline phases in the palagonitic dust are, in variable proportions, plagioclase feldspar, Ti-containing magnetite, minor pyroxene, and trace hematite. No basal reflections resulting from crystalline phyllosilicates were detected in XRD data. Weak, broad XRD peaks corresponding to X-ray amorphous phases (allophane, nanophase ferric oxide (possibly ferrihydrite), and, for two samples, hisingerite) were detected as oxidative alteration products of the glass; residual unaltered glass was also present. Mössbauer spectroscopy showed that the iron-bearing phases are nanophase ferric oxide, magnetite/titanomagnetite, hematite, and minor glass and ferrous silicates. Direct observation by TEM showed that the crystalline and X-ray amorphous phases observed by XRD and Mössbauer are normally present together in composite particles and not normally present as discrete single-phase particles. Ti-bearing magnetite occurs predominantly as 5-150 nm particles embedded in noncrystalline matrix material and most likely formed by crystallization from silicate liquids under conditions of rapid cooling during eruption and deposition of glassy tephra and prior to palagonitization of glass. Rare spheroidal halloysite was observed in the two samples that also had XRD evidence for hisingerite. The saturation magnetization Js and low-field magnetic susceptibility for bulk dust range from 0.19 to 0.68 Am2/kg and 3.4×10-6 to 15.5×10-6m3/kg at 293 K, respectively. Simulation of the Mars Pathfinder Magnet Array (MA) experiment was performed on Mauna Kea Volcano in areas with phyllosilicate-poor palagonitic dust and with copies of the Pathfinder MA. On the basis of the magnetic properties of dust collected by all five MA magnets and the observation that the Pathfinder MAs collected dust on the four strongest magnets, the value for the saturation magnetization of Martian dust collected in the MA experiments is revised downward from 4+/-2Am2/kg to 2.5+/-1.5Am2/kg. The revised value corresponds to 2.7+/-1.6wt% magnetite if the magnetic mineral is magnetite (using Js=92Am2/kg for pure magnetite, Fe3O4) or to 5.0+/-3.0 to 3.4+/-2.0wt% maghemite if the magnetic mineral is pure maghemite (using Js=50 to 74 Am2/kg for pure maghemite, ?-Fe2O3). Comparison of the magnetic properties of bulk Mauna Kea palagonitic dust to those for dust collected by MA magnets shows that the MA magnets extracted (culled) a subset (25-34 wt %) of composite magnetic particles from bulk dust. The extent of culling of Martian dust is not well constrained. Because the Mauna Kea palagonitic dust satisfies the essential constraints of the Pathfinder magnetic properties experiment (composite and magnetic particles capable of being collected by five MA magnets), a working hypothesis for the strongly magnetic mineral present in Martian dust and soil is magnetite (possibly Ti-bearing) formed by rapid crystallization from silicate liquids having volcanic and/or impact origins. Subsequent palagonitization of the glass produces the nanophase ferric oxide phases that dominate the spectral properties of Martian bright regions at visible and near-IR wavelengths. Magnetic and phyllosilicate-poor palagonitic dust from Mauna Kea Volcano is thus a spectral and magnetic analogue for magnetic Martian dust.

Morris, R. V.; Graff, T. G.; Mertzman, S. A.

2001-03-01

304

Magnetic Reconnection in Astrophysical and  

E-print Network

Magnetic Reconnection in Astrophysical and Laboratory Plasmas Ellen G. Zweibel1 and Masaaki Yamada2 astrophysics, magnetic fields, magnetic reconnection Abstract Magnetic reconnection is a topological rearrangement of magnetic field that converts magnetic energy to plasma energy. Astrophysical flares, from

305

Magnetic CoFe2O4/carbon nanotubes composites: fabrication, microstructure and magnetic response  

NASA Astrophysics Data System (ADS)

By combining the unique microstructure of carbon nanotubes (CNTs) with the good magnetism of CoFe2O4 ferrites, CoFe2O4/CNTs nanocomposites were prepared by the solvothermal method for the application of targeting therapy and tumor hyperthermia. X-ray diffraction (XRD), thermal gravity analysis (TGA), transmission electron microscope (TEM) and vibrating sample magnetometer (VSM) were introduced to study the influence of the solvothermal temperature, time and the CNTs content on the microstructure and magnetic properties of CoFe2O4/CNTs nanocomposites. The diameter of CoFe2O4 nanoparticles coating on the surface of CNTs and the saturation magnetization (Ms) increased with the solvothermal temperature. CoFe2O4/CNTs nanocomposites prepared at 180°C, 200°C and 220°C exhibited superparamagnetism at room temperature, while the samples prepared at 240°C and 260°C presented ferromagnetism. And the solvothermal time and CNTs content slightly affected the microstructure and magnetic properties, Ms and coercivity (Hc) increased slightly with the increasing solvothermal time and the decreasing CNTs content.

Wang, Panfeng; Xu, Jingcai; Han, Yanbing; Hong, Bo; Jin, Hongxiao; Jin, Dingfeng; Peng, Xiaoling; Li, Jing; Ge, Hongliang; Wang, Xinqing

2014-05-01

306

Effects of boron composition on tunneling magnetoresistance ratio and microstructure of CoFeB/MgO/CoFeB pseudo-spin-valve magnetic tunnel junctions  

SciTech Connect

The effect of B concentration on the tunneling magnetoresistance (TMR) of (Co{sub 25}Fe{sub 75}){sub 100-x}B{sub x}/MgO/(Co{sub 25}Fe{sub 75}){sub 100-x}B{sub x} (x = 22 and 33) pseudo-spin-valve (P-SV) magnetic tunnel junctions (MTJs) was investigated. The TMR ratios for optimally annealed MTJs with x = 22 and 33 were 340% and 170%, respectively, at room temperature. High resolution transmission electron microscopy (HRTEM) observation showed a weaker (001) texture in the MgO barrier in the MTJ with x = 33. The bottom electrode was not fully crystallized even with a considerable amount of B in the (Co{sub 25}Fe{sub 75}){sub 67}B{sub 33}, while good epitaxy was observed between (001) textured MgO and (Co{sub 25}Fe{sub 75}){sub 78}B{sub 22} electrodes.

Kodzuka, M. [Graduate School of Pure and Applied Sciences, University of Tsukuba, Tsukuba 305-0047 (Japan); Ohkubo, T. [National Institute for Materials Science, Tsukuba 305-0047 (Japan); Hono, K. [Graduate School of Pure and Applied Sciences, University of Tsukuba, Tsukuba 305-0047 (Japan); National Institute for Materials Science, Tsukuba 305-0047 (Japan); Ikeda, S.; Ohno, H. [Center for Spintronics Integrated Systems, Tohoku University, Sendai 980-8577 (Japan); Laboratory for Nanoelectronics and Spintronics, Research Institute of Electrical Communication, Tohoku University, Sendai 980-8577 (Japan); Gan, H. D. [Center for Spintronics Integrated Systems, Tohoku University, Sendai 980-8577 (Japan)

2012-02-15

307

Highly c-axis oriented ZnO:Ni thin film nanostructure by RF magnetron sputtering: Structural, morphological and magnetic studies  

NASA Astrophysics Data System (ADS)

Nickel doped zinc oxide (ZnO:Ni) thin films with different Ni concentrations were deposited on silicon substrates at 400 °C by reactive magnetron sputtering using a mixture of Ar and O2 gases. The X-ray diffraction and azimuthal patterns of the ZnO:Ni were carried out, and the quality of the strong preferred orientation of crystalline columns in the direction [0 0 1] perpendicular to the substrate surface were analysed. The grain size, distribution, and homogeneity of the thin film surfaces were studied by FE-SEM. The EDX and mapping confirmed that the Ni is incorporated into ZnO uniformly. The microstructure of the textured columns was analysed by TEM and HRTEM analyses. The average thickness and length of the columns were found to be about 50 nm and 600 nm, respectively. The rise of ferromagnetism by the influence of Ni content was studied by VSM magnetic studies at room temperature.

Siddheswaran, R.; Savková, Jarmila; Medlín, Rostislav; O?enášek, Jan; Životský, Ond?ej; Novák, Petr; Šutta, Pavol

2014-10-01

308

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

NASA Astrophysics Data System (ADS)

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 Fe0.28Co0.67Cu0.05 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.

Rodríguez-González, B.; Bran, C.; Warnatz, T.; Rivas, J.; Vazquez, M.

2014-04-01

309

Preparation, crystal structure and magnetic behavior of new double perovskites Sr 2 B? UO 6 with B?=Mn, Fe, Ni, Zn  

Microsoft Academic Search

Sr2B?UO6 double perovskites with B?=Mn, Fe, Ni, Zn have been prepared in polycrystalline form by solid-state reaction, in air or reducing conditions. These new materials have been studied by X-ray diffraction (XRD), magnetic susceptibility and magnetization measurements. The room-temperature crystal structure is monoclinic (space group P21\\/n), and contains alternating B?O6 and UO6 octahedra sharing corners, tilted along the three pseudocubic

R. M. Pinacca; M. C. Viola; J. C. Pedregosa; M. J. Martínez-Lope; R. E. Carbonio; J. A. Alonso

2007-01-01

310

Structural and magnetic properties of Co2Ti1-xFexAl (0 ? x ? 0.5) alloys  

NASA Astrophysics Data System (ADS)

In this work we studied the effect of partial Fe substitution for Ti on the structural and magnetic properties of the Co2TiAl. X-ray diffraction analysis indicates the presence of B2 type disorder for x > 0, (111) reflections are absent for x > 0 which is the characteristic of B2 type disorder. XRD analysis also shows presence of second phase. Magnetization measurements also confirm the presence of dual phase. Curie temperature of the alloys increases with increase in Fe concentration. Saturation magnetic moments agree very well with those calculated by Slater-Pauling rule.

Pal, Lakhan; Gupta, Sachin; Suresh, K. G.

2014-04-01

311

Electrodeposition of iron and iron-aluminium alloys in an ionic liquid and their magnetic properties.  

PubMed

In this work we show that nanocrystalline iron and iron-aluminium alloys can be electrodeposited from the ionic liquid 1-butyl-1-methylpyrrolidinium trifluoromethylsulfonate, [Py1,4]TfO, at 100 °C. The study comprises CV, SEM, XRD, and magnetic measurements. Two different sources of iron(ii) species, Fe(TfO)2 and FeCl2, were used for the electrodeposition of iron in [Py1,4]TfO. Cyclic voltammetry was employed to evaluate the electrochemical behavior of FeCl2, Fe(TfO)2, and (FeCl2 + AlCl3) in the employed ionic liquid. Thick iron deposits were obtained from FeCl2/[Py1,4]TfO at 100 °C. Electrodeposition of iron-aluminium alloys was successful in the same ionic liquid at 100 °C. The morphology and crystallinity of the obtained deposits were investigated using SEM and XRD, respectively. XRD measurements reveal the formation of iron-aluminium alloys. First magnetic measurements of some deposits gave relatively high coercive forces and power losses in comparison to commercial iron-silicon samples due to the small grain size in the nanometer regime. The present study shows the feasibility of preparing magnetic alloys from ionic liquids. PMID:24715034

Giridhar, P; Weidenfeller, B; El Abedin, S Zein; Endres, F

2014-05-28

312

Magnetic Nanoparticle Sensors  

PubMed Central

Many types of biosensors employ magnetic nanoparticles (diameter = 5–300 nm) or magnetic particles (diameter = 300–5,000 nm) which have been surface functionalized to recognize specific molecular targets. Here we cover three types of biosensors that employ different biosensing principles, magnetic materials, and instrumentation. The first type consists of magnetic relaxation switch assay-sensors, which are based on the effects magnetic particles exert on water proton relaxation rates. The second type consists of magnetic particle relaxation sensors, which determine the relaxation of the magnetic moment within the magnetic particle. The third type is magnetoresistive sensors, which detect the presence of magnetic particles on the surface of electronic devices that are sensitive to changes in magnetic fields on their surface. Recent improvements in the design of magnetic nanoparticles (and magnetic particles), together with improvements in instrumentation, suggest that magnetic material-based biosensors may become widely used in the future. PMID:22408498

Koh, Isaac; Josephson, Lee

2009-01-01

313

Superconducting magnet  

DOEpatents

A superconducting magnet designed to produce magnetic flux densities of the order of 4 to 5 Webers per square meter is constructed by first forming a cable of a plurality of matrixed superconductor wires with each wire of the plurality insulated from each other one. The cable is shaped into a rectangular cross-section and is wound with tape in an open spiral to create cooling channels. Coils are wound in a calculated pattern in saddle shapes to produce desired fields, such as dipoles, quadrupoles, and the like. Wedges are inserted between adjacent cables as needed to maintain substantially radial placement of the long dimensions of cross sections of the cables. After winding, individual strands in each of the cables are brought out to terminals and are interconnected to place all of the strands in series and to maximize the propagation of a quench by alternating conduction from an inner layer to an outer layer and from top half to bottom half as often as possible. Individual layers are separated from others by spiraled aluminum spacers to facilitate cooling. The wound coil is wrapped with an epoxy tape that is cured by heat and then machined to an interference fit with an outer aluminum pipe which is then affixed securely to the assembled coil by heating it to make a shrink fit. In an alternate embodiment, one wire of the cable is made of copper or the like to be heated externally to propagate a quench.

Satti, John A. (Naperville, IL)

1980-01-01

314

Magnetic Storms  

NASA Technical Reports Server (NTRS)

One of the oldest mysteries in geomagnetism is the linkage between solar and geomagnetic activity. The 11-year cycles of both the numbers of sunspots and Earth geomagnetic storms were first noted by Sabine. A few years later, speculation on a causal relationship between flares and storms arose when Carrington reported that a large magnetic storm followed the great September 1859 solar flare. However, it was not until this century that a well-accepted statistical survey on large solar flares and geomagnetic storms was performed, and a significant correlation between flares and geomagnetic storms was noted. Although the two phenomena, one on the Sun and the other on the Earth, were statistically correlated, the exact physical linkage was still an unknown at this time. Various hypotheses were proposed, but it was not until interplanetary spacecraft measurements were available that a high-speed plasma stream rich in helium was associated with an intense solar flare. The velocity of the solar wind increased just prior to and during the helium passage, identifying the solar ejecta for the first time. Space plasma measurements and Skylab's coronagraph images of coronal mass elections (CMES) from the Sun firmly established the plasma link between the Sun and the Earth. One phenomenon associated with magnetic storms is brilliant "blood" red auroras, as shown.

Tsurutani, Bruce T.; Gonzalez, Walter D.

1998-01-01

315

Development of Magnetic Refrigerator  

NASA Astrophysics Data System (ADS)

A series of R & D of magnetic refrigerators has been done in order to realize an advanced type cryocooler for superconducting magnets of maglev trains and MRI medical system. As a result of efforts on both the magnetic refrigerator and superconducting magnets, a parasitic type magnetic refrigeration system was proposed.

Ogiwara, Hiroyasu; Nakagome, Hideki; Kuriyama, Tohru

316

Magnetic fields in astrophysics  

Microsoft Academic Search

The evidence of cosmic magnetism is examined, taking into account the Zeeman effect, beats in atomic transitions, the Hanle effect, Faraday rotation, gyro-lines, and the strength and scale of magnetic fields in astrophysics. The origin of magnetic fields is considered along with dynamos, the conditions for magnetic field generation, the topology of flows, magnetic fields in stationary flows, kinematic turbulent

Ia. B. Zeldovich; A. A. Ruzmaikin; D. D. Sokolov

1983-01-01

317

Magnetic field sensor  

NASA Astrophysics Data System (ADS)

Earlier papers1-3 in this journal have described experiments on measuring the magnetic fields of current-carrying wires and permanent magnets using magnetic field probes of various kinds. This paper explains how to use an iPad and the free app MagnetMeter-3D Vector Magnetometer and Accelerometer4 (compass HD) to measure the magnetic fields.

Silva, Nicolas

2012-09-01

318

A Magnetic Personality  

NSDL National Science Digital Library

Students learn about magnets and how they are formed. They investigate the properties of magnets and how engineers use magnets in technology. Specifically, students learn about magnetic memory storage, which is the reading and writing of data information using magnets, such as in computer hard drives, zip disks and flash drives.

Integrated Teaching And Learning Program

319

Playing with Magnetism  

NSDL National Science Digital Library

This is an activity about magnetism and magnetic forces. Learners will explore objects to which a magnet is attracted or repelled, and investigate the attractive and repulsive forces of two like and two unlike magnetic poles. This is the first activity in the Exploring the Earth's Magnetic Field: An IMAGE Satellite Guide to the Magnetosphere educators guide.

320

The magnetization process: Hysteresis  

NASA Technical Reports Server (NTRS)

The magnetization process, hysteresis (the difference in the path of magnetization for an increasing and decreasing magnetic field), hysteresis loops, and hard magnetic materials are discussed. The fabrication of classroom projects for demonstrating hysteresis and the hysteresis of common magnetic materials is described in detail.

Balsamel, Richard

1990-01-01

321

Template-assisted fabrication of magnetically responsive hollow titania capsules.  

PubMed

This study reports on the fabrication of magnetically responsive hollow titania capsules by confining the superparamagnetic Fe(3)O(4) nanoparticles within a hollow and porous titania (TiO(2)) shell. The employed protocol involves precipitation of titania shell on the magnetite (Fe(3)O(4)) encapsulated polystyrene beads followed by the calcination of resulting composite particles at elevated temperature. Scanning electron microscopy and transmission electron microscopy reveal the presence of a thick, complete but irregular titania shell on the magnetic polystyrene beads after the templating process. Electron energy loss mapping image analysis has been employed to investigate the spatial distribution of titania and magnetite phases of magnetic hollow titania capsules (MHTCs). Magnetic characterization indicates that both titania-coated magnetic polystyrene beads (TMPBs) and MHTCs are superparamagnetic in nature with the saturated magnetizations of 5.6 and 8.1 emu/g, respectively. X-ray diffraction (XRD) analysis reveals that titania shell of these capsules is composed of photoactive anatase phase. Nitrogen adsorption-desorption analysis has been employed to estimate the specific surface area and the average pore diameter of the fabricated hollow structures. Photocatalytic activity of the fabricated MHTCs for the photodegradation of rhodamine 6G dye has been demonstrated and compared with that of bulk titania nanoparticles. PMID:20949923

Agrawal, Mukesh; Gupta, Smrati; Pich, Andrij; Zafeiropoulos, Nikolaos E; Rubio-Retama, Jorge; Jehnichen, Dieter; Stamm, Manfred

2010-11-16

322

Enhanced Magnetic Properties in Nanoparticle-Filled CNTs  

NASA Astrophysics Data System (ADS)

There has been much interest in magnetic polymer nanocomposites (MPNCs) recently due to potential applications for EMI shielding, tunable EM devices and flexible electronics. In past studies, using ferrite fillers, we have shown MPNCs to be magnetically tunable when passing a microwave signal through films under the influence of an external magnetic field. We extend this study to include nanoparticle-filled multi-walled carbon nanotubes (CNTs) synthesized by CVD. These high-aspect ratio magnetic nanostructures, with tunable anisotropy, are of particular interest in enhancing magnetic and microwave responses in existing MPNCs. CNTs have an average diameter and length of 300nm and 6 ?m, respectively and are partially filled with CoFe2O4 and NiFe2O4 nanoparticles (NPs) (˜ 7nm). When comparing NPs to NP-filled CNTs, TB increases by ˜ 40K and relaxation time, ?0, increases several orders of magnitude, indicating that enclosing NPs in CNTs enhances interparticle interactions. Structural and magnetic characterization were completed using XRD, TEM and Quantum Design PPMS, using VSM and ACMS options.

Stojak, K.; Chandra, S.; Khurshid, H.; Phan, M. H.; Srikanth, H.

2013-03-01

323

Poly-l-lysine-coated magnetic nanoparticles as intracellular actuators for neural guidance  

PubMed Central

Purpose It has been proposed in the literature that Fe3O4 magnetic nanoparticles (MNPs) could be exploited to enhance or accelerate nerve regeneration and to provide guidance for regenerating axons. MNPs could create mechanical tension that stimulates the growth and elongation of axons. Particles suitable for this purpose should possess (1) high saturation magnetization, (2) a negligible cytotoxic profile, and (3) a high capacity to magnetize mammalian cells. Unfortunately, the materials currently available on the market do not satisfy these criteria; therefore, this work attempts to overcome these deficiencies. Methods Magnetite particles were synthesized by an oxidative hydrolysis method and characterized based on their external morphology and size distribution (high-resolution transmission electron microscopy [HR-TEM]) as well as their colloidal (Z potential) and magnetic properties (Superconducting QUantum Interference Devices [SQUID]). Cell viability was assessed via Trypan blue dye exclusion assay, cell doubling time, and MTT cell proliferation assay and reactive oxygen species production. Particle uptake was monitored via Prussian blue staining, intracellular iron content quantification via a ferrozine-based assay, and direct visualization by dual-beam (focused ion beam/scanning electron microscopy [FIB/SEM]) analysis. Experiments were performed on human neuroblastoma SH-SY5Y cell line and primary Schwann cell cultures of the peripheral nervous system. Results This paper reports on the synthesis and characterization of polymer-coated magnetic Fe3O4 nanoparticles with an average diameter of 73 ± 6 nm that are designed as magnetic actuators for neural guidance. The cells were able to incorporate quantities of iron up to 2 pg/cell. The intracellular distribution of MNPs obtained by optical and electronic microscopy showed large structures of MNPs crossing the cell membrane into the cytoplasm, thus rendering them suitable for magnetic manipulation by external magnetic fields. Specifically, migration experiments under external magnetic fields confirmed that these MNPs can effectively actuate the cells, thus inducing measurable migration towards predefined directions more effectively than commercial nanoparticles (fluidMAG-ARA supplied by Chemicell). There were no observable toxic effects from MNPs on cell viability for working concentrations of 10 ?g/mL (EC25 of 20.8 ?g/mL, compared to 12 ?g/mL in fluidMAG-ARA). Cell proliferation assays performed with primary cell cultures of the peripheral nervous system confirmed moderate cytotoxicity (EC25 of 10.35 ?g/mL). Conclusion These results indicate that loading neural cells with the proposed MNPs is likely to be an effective strategy for promoting non-invasive neural regeneration through cell magnetic actuation. PMID:22811603

Riggio, Cristina; Calatayud, Maria Pilar; Hoskins, Clare; Pinkernelle, Josephine; Sanz, Beatriz; Torres, Teobaldo Enrique; Ibarra, Manuel Ricardo; Wang, Lijun; Keilhoff, Gerburg; Goya, Gerardo Fabian; Raffa, Vittoria; Cuschieri, Alfred

2012-01-01

324

Magnetic guns with cylindrical permanent magnets  

NASA Astrophysics Data System (ADS)

The motion of a cylindrical permanent magnet (projectile) inside a tubular permanent magnet, with both magnets magnetized axially, illustrates nicely the physical principles behind the operation of magnetic guns. The force acting upon the projectile is expressed semi-analytically as derivative of the magnetostatic interaction energy. For comparison, the forces involved are also calculated numerically using finite elements methods. Based on the conservation of the magnetostatic and kinetic energies, the exit and asymptotic velocities are determined. The derived formulas can be used to optimize the generated forces and motion of the inner cylindrical magnet.

Vokoun, David; Beleggia, Marco; Heller, Lud?k

2012-05-01

325

An X-ray diffraction (XRD) and Fourier transform infrared spectroscopic (FT-IR) investigation of the long-term effect on the solidification/stabilization (S/S) of arsenic(V) in Portland cement type-V.  

PubMed

The long-term effects on solidification/stabilization (S/S) of As5+-bearing oxyanions (AsO4(3)-) in Portland cement type-V (OPC) have been investigated by X-ray diffraction (XRD) and Fourier transform infrared spectroscopic (FT-IR) techniques. The results of this study confirm our previous results that the early hydration of cement is inhibited by the presence of AsO4(3)-, and that the inhibition is mainly caused by the formation of highly insoluble Ca3(AsO4)2 on the surface of hydrating cement particles. Arsenate analog of ettringite [Ca6(Al2O6)(SO4)3 x 32H2O] was identified in the early stages of hydration of pure Portland cement and As(V)-treated Portland cement [OPC-As(V)], but not in 10-year-old similar samples. The XRD and FT-IR results indicated interactions of oxyanions and cement particles to produce minor quantities of As5+-bearing compounds in fresh as well as in 10-year-old samples. New As5+-bearing phases, NaCaAsO4 x 7.5H2O and Ca5(AsO4)3OH were identified in the 10-year-old OPC-As(V) samples by XRD analyses. Based on these results it is concluded that Portland cement may be considered as a potential matrix to immobilize As5+-bearing wastes. PMID:15144793

Mollah, Mohammad Y A; Kesmez, Mehmet; Cocke, David L

2004-06-01

326

An X-ray diffraction (XRD) and Fourier transform infrared spectroscopic (FT-IR) investigation of the long-term effect on the solidification\\/stabilization (S\\/S) of arsenic(V) in Portland cement type-V  

Microsoft Academic Search

The long-term effects on solidification\\/stabilization (S\\/S) of As5+-bearing oxyanions (AsO3?4) in Portland cement type-V (OPC) have been investigated by X-ray diffraction (XRD) and Fourier transform infrared spectroscopic (FT-IR) techniques. The results of this study confirm our previous results that the early hydration of cement is inhibited by the presence of AsO3?4, and that the inhibition is mainly caused by the

Mohammad Y. A Mollah; Mehmet Kesmez; David L Cocke

2004-01-01

327

Intraocular magnet of Parel.  

PubMed Central

The intraocular magnet (IOM) is a new device based on permanent magnetism providing controlled energy for removal of magnetic intraocular foreign bodies. Its use is reported in 11 cases. Images PMID:3801364

Crock, G. W.; Janakiraman, P.; Reddy, P.

1986-01-01

328

Magnetism of Carbonados  

NASA Technical Reports Server (NTRS)

Origin of Carbonado is not clear. Magnetism of Carbonado comes from the surface, indicating contemporary formation of both the surface and magnetic carriers. The interior of carbonado is relatively free of magnetic phases.

Kletetschka, G.; Taylor, P. T.; Wasilewski, P. J.

2000-01-01

329

Magnetic properties of hematite (?-Fe2O3) nanoparticles prepared by hydrothermal synthesis method  

NASA Astrophysics Data System (ADS)

Hematite (?-Fe2O3) nanoparticles are successfully synthesized by using the hydrothermal synthesis method. An X-ray powder diffraction (XRPD) of the sample shows formation of the nanocrystalline ?-Fe2O3 phase. A transmission electron microscopy (TEM) measurements show spherical morphology of the hematite nanoparticles and narrow size distribution. An average hematite nanoparticle size is estimated to be about 8 nm by TEM and XRD. Magnetic properties were measured using a superconducting quantum interference device (SQUID) magnetometry. Investigation of the magnetic properties of hematite nanoparticles showed a divergence between field-cooled (FC) and zero-field-cooled (ZFC) magnetization curves below Tirr = 103 K (irreversibility temperature). The ZFC magnetization curve showed maximum at TB = 52 K (blocking temperature). The sample did not exhibit the Morin transition. The M(H) (magnetization versus magnetic field) dependence at 300 K showed properties of superparamagnetic iron oxide nanoparticles (SPION). The M(H) data were successfully fitted by the Langevin function and magnetic moment ?p = 657 ?B and diameter d = 8.1 nm were determined. Furthermore, magnetic measurements showed high magnetization at room temperature (MS = 3.98 emu/g), which is desirable for application in spintronics and biomedicine. Core-shell structure of the nanoparticles was used to describe high magnetization of the hematite nanoparticles.

Tadic, Marin; Panjan, Matjaz; Damnjanovic, Vesna; Milosevic, Irena

2014-11-01

330

Ferromagnetism in diluted magnetic Zn-Co-doped CeO2-?  

NASA Astrophysics Data System (ADS)

Several oxides doped with transition metals can be used in spintronics devices due to their conductive and magnetic properties at room temperature. In this work, samples of Ce1-2xZnxCoxO2-? were obtained by an alternative sol-gel proteic process for x=0.01, 0.05 and 0.1. The structural properties of samples were analyzed by XRD and Raman spectroscopy. Magnetization measurements revealed a ferromagnetic behavior at room temperature probably induced by oxygen vacancies.

Santos, T. S.; Folly, W. S. D.; Macêdo, M. A.

2012-08-01

331

Electronic and magnetic correlations in Mn doped ZnO nano-rods  

NASA Astrophysics Data System (ADS)

We have investigated correlation between magnetization and electronic structure in Zn0.98Mn0.02O nano-rods. Rietveld analysis of XRD patterns confirms that Mn ions incorporate at the Zn2+ sites. SQUID measurements confirm that Mn doping induces room temperature ferromagnetism (RTFM) in nano-rods and the induced magnetization is an order of magnitude higher than that in the bulk Zn0.98Mn0.02O. The XPS results show that Mn ions are in mixed valent state. Our findings show that bivalence of Mn ions and the oxygen vacancies are responsible for the observed RTFM.

Samariya, Arvind; Sharma, S. C.; Dhawan, M. S.; Sharma, P. K.; Kumar, Sudhish; Sharma, K. B.; Dolia, S. N.; Singhal, R. K.

2013-06-01

332

Study of structure and magnetic properties of rare earth doped BiFeO3  

NASA Astrophysics Data System (ADS)

RExBi1-xFeO3 (RE=La, Gd and Ho) samples were synthesized by a solid state reaction method and investigated for structure and magnetic properties. XRD shows that La and Ho dopings at A-site effectively reduce the secondary phase formation. A structural phase transition is observed to orthorhombic phase with all RE elements above certain concentration limit. La doping results in the observation of huge coercivity of 10 kOe and Ho doping results in high magnetic moment among all the RE elements. Gd and Ho doped samples show a pinching in the M-H loops with minimum HC.

Suresh, Pittala; Srinath, S.

2014-09-01

333

D.C. electrical conductivity and magnetic susceptibility of polythiophene doped with iodine  

NASA Astrophysics Data System (ADS)

Polythiophene was chemically synthesized, undoped and then re-doped with iodine. FTIR spectra confirm iodine doping. XRD analysis is used to calculate crystallinity of the samples. Electrical conductivity measurements were carried out using two probe technique in the temperature range from 300 K to 373 K. Undoped and doped samples show semi conducting nature. After doping the conductivity increases by eight orders of magnitude at 318 K. Magnetic susceptibility measurements were carried out using Guoy's method, both samples show diamagnetic nature. Conductivity and magnetic susceptibility measurements indicate that predominant charge carriers, in the iodine doped polythiophene, are bipolarons.

Chourasia, Ashish B.; Kelkar, Deepali S.

2013-06-01

334

Model a Magnet  

NSDL National Science Digital Library

This is a summative activity about magnets. Learners will observe a demonstration of the action of a magnet on a test tube of iron filings, answer questions, and, using the concepts learned in previous activities, write an essay about their understanding of the demonstration. This is the fourth activity in the Mapping Magnetic Influence educators guide. Learners should complete the other three activities in that guide (Seeing Magnetism, What Do You Know about Magnets, and Magnet Map) prior to beginning this activity.

335

Playing with Magnetism  

NSDL National Science Digital Library

In this activity students will discover that magnetism is the force produced by magnets which does all of the "holding" and that it is also a very important force in nature. This activity introduces the student to simple toy magnets to explore magnetic attraction to items which contain metal by using paper clips. Students will experience that a magnetic force is invisible and explore the magnets attracting and repelling properties.

2002-09-20

336

High Temperature, Permanent Magnet Biased Magnetic Bearings  

E-print Network

The Electron Energy Corporation (EEC) along with the National Aeronautics and Space Administration (NASA) is researching magnetic bearings. The purpose of this research was to design and develop a high-temperature (1000?F) magnetic bearing system...

Gandhi, Varun R.

2010-07-14

337

Size-dependent magnetic properties of nickel nanochains  

NASA Astrophysics Data System (ADS)

Magnetic properties with three different sizes of Ni nanochains, synthesized by a technique of wet chemical solution, have been investigated experimentally. The sample sizes (average diameter of the nano-particles) are 50, 75, and 150 nm, with a typical length of a few microns. The characterizations by XRD and TEM reveal that the samples consist of Ni nano-particles forming a one-dimensional (1D) chain-like structure. Magnetic properties have been investigated by temperature dependent magnetization M(T) and field dependent magnetization M(H) measurements. The results are explained within the context of the core-shell model. First, the freezing of disordered spins in the shell layer has resulted in a peak structure on the zero-field-cooled (ZFC) M(T) curve. The peak position is identified as the freezing temperature TF. It is well described by the de Almeida-Thouless (AT) equation for the surface spin glass state. Second, the shape anisotropy of the 1D structure has caused a wide separation between the field-cooled (FC) and ZFC M(T) curves. This is mainly attributed to the blocking of the core magnetism by an anisotropy barrier, EA. Third, by the M(H) measurement in the low field region, the open hysteresis loop measured at T = 5 KTF. This indicates that a significant part of the contribution to the magnetic irreversibility at Tmagnetization goes down substantially. These imply that, as the sample size reduces, the effect of shape anisotropy becomes larger in the magnetization reversal process and the contribution to the magnetism from the ferromagnetically ordered core becomes smaller.

He, Lin; Zheng, Wangzhi; Zhou, Wei; Du, Honglin; Chen, Chinping; Guo, Lin

2007-01-01

338

Magnetic, Electrical Transport and Impedance Spectroscopy Studies on Ti Substituted La0.67Sr0.33MnO3 Ceramics (Kajian Sifat Magnet, Angkutan Elektrik dan Spektroskopi Impedans Terhadap Seramik La0.67Sr0.33MnO3 Diganti Ti)  

Microsoft Academic Search

La0.67Sr0.33Mn1-xTixO3 samples with x = 0.0, 0.2, 0.4 and 0.6 have been prepared using the conventional solid-state reaction method. The structure, magnetic and electrical transport properties as well as the impedance spectroscopy of the samples were investigated. The powder XRD analysis showed that all samples were single phase with rhombohedral perovskite structure. The magnetization curve suggests that the Ti substituted

Z. ZALITA; S. A. HALIM; K. P. LIM; Z. A. TALIB; Z. HISHAMUDDIN; C. P. WALTER

339

Exploring Magnetic Fields  

NSDL National Science Digital Library

In this activity, students investigate the presence of magnetic fields around magnets, the sun and the earth. They will explore magnetic field lines, understand that magnetic lines of force show the strength and direction of magnetic fields, determine how field lines interact between attracting and repelling magnetic poles, and discover that the earth and sun have magnetic properties. They will also discover that magnetic force is invisible and that a "field of force" is a region or space in which one object can attract or repel another.

340

The Third Flight Magnet  

NASA Technical Reports Server (NTRS)

A self-shielded superconducting magnet was designed for the NASA Goddard Space Flight Center Adiabatic Demagnetization Refrigerator Program. This is the third magnet built from this design. The magnets utilize Cryomagnetics' patented ultra-low current technology. The magnetic system is capable of reaching a central field of two tesla at slightly under two amperes and has a total inductance of 1068 henries. This final report details the requirements of the magnet, the specifications of the resulting magnet, the test procedures and test result data for the third magnet (Serial # C-654-M), and recommended precautions for use of the magnet.

McGhee, R. Wayne

1998-01-01

341

PREFACE: Geometrically frustrated magnetism Geometrically frustrated magnetism  

Microsoft Academic Search

Frustrated magnetism is an exciting and diverse field in condensed matter physics that has grown tremendously over the past 20 years. This special issue aims to capture some of that excitement in the field of geometrically frustrated magnets and is inspired by the 2010 Highly Frustrated Magnetism (HFM 2010) meeting in Baltimore, MD, USA. Geometric frustration is a broad phenomenon

Jason S. Gardner

2011-01-01

342

Nuclear Magnetic Resonance and Magnetic Field Measurements  

NSDL National Science Digital Library

This laboratory is designed for students to become familiar with the principles and detection techniques of Nuclear Magnetic Resonance (NMR), examine the relationship between current and magnetic field in an electromagnet, and gain experience in the use of magnetic field measurement techniques.

2012-01-04

343

Structural and magnetic characterization of La0.8Sr0.2MnO3 nanoparticles prepared via a facile microwave-assisted method  

NASA Astrophysics Data System (ADS)

Nanoparticles of La0.8Sr0.2MnO3 (LSMO) with different particle sizes are synthesized by a very fast, inexpensive, reproducible, and environmentally friendly method: the microwave irradiation of the corresponding mixture of nitrates. The structural and magnetic properties of the samples are investigated by the X-Ray diffraction (XRD), Fourier transform infra-red (FT-IR) spectroscopy, field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), and magnetic (DC magnetization and AC susceptibility) measurements. The XRD study coupled with the Rietveld refinement show that all samples crystallize in a rhombohedral structure with the space group of R-3C. The FT-IR spectroscopy and FE-SEM images indicate formation of the perovskite structure of LSMO. The DC magnetization measurements confirm the decrease in the particle size effects on the magnetic properties, e.g. reduction in the ferromagnetic (FM) moment and increase in the surface spin disorder. Magnetic dynamics of the samples studied by AC magnetic susceptibility shows that the magnetic behavior of the nanometer-sized samples is well-described by the Vogel-Fulcher and critical slowing down laws. Strong interaction between magnetic nanoparticles of LSMO was detected by fitting the experimental data with the mentioned models.

Moradi, J.; Ghazi, M. E.; Ehsani, M. H.; Kameli, P.

2014-07-01

344

Structural characterization of glass-ceramics made from fly ash containing SiO2-Al2O3-Fe2O3-CaO and analysis by FT-IR-XRD-SEM methods  

NASA Astrophysics Data System (ADS)

The glass-ceramics has been proposed as a useful recycling fly ash from thermal power plants. In this study, C type fly ash containing SiO2-Al2O3-Fe2O3-CaO has been sintered to form glass-ceramic materials at different temperatures between 850 °C and 1050 °C after using powder processing based on milling and powder compaction without inorganic additives. The effect of firing temperatures between 850 °C and 1050 °C on mineralogy and microstructure of sintered samples is reported. The Fourier Transform Infrared Spectra (FT-IR), Differential Thermal Analysis (DTA), X-ray Diffraction (XRD) and Scanning Electron Microscopy (SEM) techniques were applied on the sintered powder form. From the XRD results, the amount of quartz decreases on sintering, when the sintering temperature increases. On the basis of SEM observations, new crystallites structure developed in the microstructures of the C type of fly ash samples and the glassy region decreased at the crystallization temperature.

Yilmaz, G.

2012-07-01

345

The effect of substrate temperature on the etching properties and the etched surfaces of magnetic tunnel junction materials in a CH3OH inductively coupled plasma system  

NASA Astrophysics Data System (ADS)

The etching characteristics of the magnetic films (PtMn, CoFe) and hard mask materials (W, Ta) forming a magnetic tunnel junction (MTJ) stack in a CH3OH inductively coupled plasma (ICP) system were investigated. We examined the etch rates of the metal films as a function of substrate temperature, and assessed the microstructures of the etched surfaces using high resolution transmission electron microscopy (HR-TEM). We also analyzed the surface states using X-ray photoelectron spectroscopy (XPS) and TEM electron energy loss spectroscopy (TEM-EELS). The PtMn and CoFe etch rates increased as the temperature increased, whereas the etch rates of W and Ta decreased slightly. Therefore the etch selectivity increased linearly with increasing substrate temperature. The CH3OH plasma formed nonvolatile etching byproducts with the magnetic films and hard mask metals. In the case of PtMn and CoFe, the surface composition of the etching byproducts changed with increasing temperature; the relative concentration of pure metal compared with metal oxide or carbide increased as the substrate temperature rose. The etch rate was determined by the sputtering yield of the materials formed on the etched surface; accordingly the etch rates of those magnetic films would increase due to the higher sputtering yield of pure metal.

Lee, Minsuk; Lee, Won-Jong

2012-08-01

346

Effective magnetic moment of magnetic multicore nanoparticles  

NASA Astrophysics Data System (ADS)

We carry out Monte Carlo simulations to study the effective magnetic moment ?eff in the low-field region of magnetic multicore nanoparticles. Transmission electron microscopy and scanning electron microscopy images show that these particles contain a number of magnetic nanocrystals (MNCs) randomly packed in a single cluster of total volume Vtot . We illustrate how the initial magnetic susceptibility ?0 of magnetic multicore nanoparticles can be straightforward derived from ?eff computed at zero magnetic field. We observe that dipolar interactions between MNCs and polydispersity of the MNCs contribute to increase and to decrease ?eff/Vtot , respectively, while magnetic anisotropy of the MNCs does not show any effect. In all three cases, ?eff/Vtot can be described by a linear relation to (?B/kBT)2 that we analytically derived for low applied fields.

Schaller, Vincent; Wahnström, Göran; Sanz-Velasco, Anke; Gustafsson, Stefan; Olsson, Eva; Enoksson, Peter; Johansson, Christer

2009-09-01

347

Tuning magnetic properties of CeO2 by Fe doping via an electrochemical deposition route.  

PubMed

Herein Ce(1-x)Fe(x)O(2-?) nanocomposites were investigated for dilute magnetic semiconductor (DMS) properties. Ce(1-x)Fe(x)O(2-?) nanospheres and porous nanostructures with high surface areas have been successfully prepared by electrochemical deposition at room temperature and atmospheric pressure. The structures and morphologies of Ce(1-x)Fe(x)O(2-?) deposits were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and N(2) adsorption-desorption techniques. The magnetic properties of the prepared Ce(1-x)Fe(x)O(2-?) nanospheres and porous nanostructures were studied, and they showed room-temperature ferromagnetism and giant magnetic moments. In addition, the effects of morphologies and compositions on the magnetic properties of Ce(1-x)Fe(x)O(2-?) deposits were studied. PMID:21226198

Wang, Zi-Long; Li, Gao-Ren; Liang, Jin-Hua; Tong, Ye-Xiang

2011-01-17

348

New type permanent magnet biased radial magnetic bearing in magnetic suspending reaction flywheel  

Microsoft Academic Search

To overcome the defects of the present permanent magnet biased radial magnetic bearing, a new type permanent magnet biased radial magnetic bearing in magnetic suspending reaction flywheel application is reported. The fundamental principle of the radial magnetic bearing is presented. And the radial magnetic bearing is analyzed and calculated by using equivalent magnetic circuit and finite element method (FEM). As

Jinji Sun; Jiancheng Fang; Xi Wang

2008-01-01

349

Magnetic Imaging Wolfgang Kuch  

E-print Network

Magnetic Imaging Wolfgang Kuch Freie Universit¨at Berlin, Institut f¨ur Experimentalphysik, Arnimallee 14, 14195 Berlin, Germany kuch@physik.fu-berlin.de Abstract. Imaging of magnetic domains has- ern techniques is used nowadays routinely for magnetic imaging of magnetic ma- terials

Kuch, Wolfgang

350

Miniaturized electron magnetic spectrometer  

Microsoft Academic Search

Traditionally magnetic electron spectrometers provide the most reliable electron measurements in space at energies above ?10 keV. However, the inclusion of powerful magnets presents problems for spacecraft with stringent magnetic cleanliness requirements, and the magnetic yoke required to close the instrument is bulky and heavy. To mediate the aforementioned shortcomings, we report a preliminary conceptual design on a new miniature

G. C. Ho; D. G. Mitchell; S. Livi; D. K. Haggerty; B. H. Mauk

2003-01-01

351

Miniaturized electron magnetic spectrometer  

Microsoft Academic Search

Traditionally magnetic electron spectrometers provide the most reliable electron measurements in space at energies above ~10 keV. However, the inclusion of powerful magnets presents problems for spacecraft with stringent magnetic cleanliness requirements, and the magnetic yoke required to close the instrument is bulky and heavy. To mediate the aforementioned shortcomings, we report a preliminary conceptual design on a new miniature

G. C. Ho; D. G. Mitchell; S. Livi; D. K. Haggerty; B. H. Mauk

2003-01-01

352

That Magnetic Dog  

NSDL National Science Digital Library

Learners "go fishing" with magnets and discover through exploration that not all metals are magnetic. They verify their findings by reading a nonfiction book about magnets, communicate their findings in a poster session, and write a story about what life would be like if their feet were magnets.

Morgan, Emily; Ansberry, Karen

2007-01-01

353

Hybrid superconducting magnetic suspensions  

Microsoft Academic Search

Superconductors, especially high Tc ones, are the most attractive materials to design stable and fully passive magnetic suspensions which have to control five degrees of freedom. The hybrid superconducting magnetic suspensions present high performances and a simple cooling mode. They consist of a permanent magnet bearing, stabilized by a suitable magnet-superconductor structure. Several designs are given and compared in terms

P. Tixador; P. Hiebel; Y. Brunet; X. Chaud; P. Gautier-Picard

1996-01-01

354

Magnetic propulsion systems  

Microsoft Academic Search

Magnetic propulsion systems are based on the direct interaction of the vehicle's own magnetic field with the natural magnetic field, particularly the geomagnetic one, without using jet propulsion. Three such systems are reviewed in the order of their feasibility of automatic control over the thrust force vector. One of these magnetic propulsion systems permits partial control and is competitive with

Valentine Pulatov

2001-01-01

355

Superconducting magnets 1992  

SciTech Connect

This report discusses the following topics on Superconducting Magnets; SSC Magnet Industrialization; Collider Quadrupole Development; A Record-Setting Magnet; D20: The Push Beyond 10T; Nonaccelerator Applications; APC Materials Development; High-T{sub c} at Low Temperature; Cable and Cabling-Machine Development; and Analytical Magnet Design.

Not Available

1993-06-01

356

Magnetic fields of galaxies  

Microsoft Academic Search

The current state of the understanding of the magnetic fields of galaxies is reviewed. A simple model of the turbulent dynamo is developed which explains the main observational features of the global magnetic fields of spiral galaxies. The generation of small-scale chaotic magnetic fields in the interstellar medium is also examined. Attention is also given to the role of magnetic

Aleksandr A. Ruzmaikin; Dmitrii D. Sokolov; Anvar M. Shukurov

1988-01-01

357

Electricity and Magnetism  

NSDL National Science Digital Library

In this two-part activity, students learn about electromagnetism by constructing electromagnets and observing their behavior. They will discover that there is a close relationship between electricity and magnetism in that moving magnets can induce electric currents and that electric currents can cause magnetism. They also learn that electric current flowing in a wire creates a magnetic field around it.

358

Synthesis, structural and magnetic properties of La{sub 1-x}Cd{sub x}FeO{sub 3} (0.0 {<=} x {<=} 0.3) orthoferrites  

SciTech Connect

Nanocrystalline La{sub 1-x}Cd{sub x}FeO{sub 3} (0.0 {<=} x {<=} 0.3) solid solutions have been synthesized by a single-step solution combustion method at a relatively low temperature of 400 deg. C. The combustion-synthesized solid solutions were characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), and magnetic measurements. The crystal structure examined by XRD indicates that the samples were single-phase, and crystallize in an orthorhombic (space group, Pbnm no. 62) structure. The parent and doped compounds showed canted antiferromagnetic behavior associated with an increase in magnetic moment with Cd doping. The changes in magnetic properties of the materials are correlated to the changes in structural features resulting from the Rietveld structural refinement of the materials.

Bellakki, Manjunath B. [Department of Mechanical Engineering, Colorado State University, Fort Collins, CO 80523 (United States); Manivannan, V., E-mail: mani@engr.colostate.edu [Department of Mechanical Engineering, Colorado State University, Fort Collins, CO 80523 (United States); Das, Jaydip [Department of Physics, Colorado State University, Fort Collins, CO (United States)

2009-07-01

359

Thermal and soft magnetic properties of Co40Fe22Ta8B30 glassy particles: In-situ X-ray diffraction and magnetometry studies  

NASA Astrophysics Data System (ADS)

The structural evolution of Co40Fe22Ta8B30 glassy particles has been studied by in-situ high-energy synchrotron X-ray diffraction (XRD) upon isochronal annealing. The changes in position, intensity, and full width at half maximum (FWHM) of the first and second diffuse maxima of the XRD patterns suggest the occurrence of irreversible structural relaxation upon the first heating up to a temperature close to the glass transition temperature Tg. The variations in reduced pair correlation functions upon annealing are discussed in the frame of the topological fluctuation theory for structural relaxation. Isochronal annealing of the Co40Fe22Ta8B30 glassy particles improves their soft magnetic properties through decreasing the coercivity and increasing the magnetic susceptibility, saturation magnetization, and Curie temperature.

Taghvaei, Amir Hossein; Stoica, Mihai; Kaban, Ivan; Bednar?ik, Jozef; Eckert, Jürgen

2014-08-01

360

Structure and magnetic properties of La substituted ZnFe2O4 nanoparticles synthesized by sol-gel autocombustion method  

NASA Astrophysics Data System (ADS)

ZnFe2-xLaxO4 (0magnetic properties were investigated by X-ray diffraction (XRD), infrared spectroscopy and vibrating sample magnetometer methods. The XRD results showed that the single phase La3+ substituted zinc ferrite nanoparticles exhibit partially inverse spinel structure with the crystallite size of 10-20 nm, which was also confirmed by transmission electron microscopy. The magnetic measurements show that the saturation magnetization (Ms) increases till x=0.05, due to the increase of inversity, and then decreases from x=0.05 to x=0.2, because of the decrease in the total moments with the La3+ substitution.

Masoudpanah, S. M.; Seyyed Ebrahimi, S. A.; Derakhshani, M.; Mirkazemi, S. M.

2014-12-01

361

Effect of transition Metal (Co, Ni and Cu) doping on lattice volume, band gap, morphology and saturation magnetization of ZnO nanostructures  

NASA Astrophysics Data System (ADS)

Herein, the effect of different TM (Co, Ni and Cu) doping on structural, optical and magnetic properties of ZnO nanostructures has been studied. Zn1- x TM x O (TM=Co, Ni and Cu) nanostructures were prepared by a microwave assisted chemical route and characterized by X-ray diffraction (XRD), field emission scanning electron microscopy, transmission electron microscopy (TEM), Raman spectroscopy, UV-Vis and magnetization measurements. XRD and TEM analyses showed that the TM-doped ZnO nanostructures had single phase nature with the wurtzite structure. Changes in the lattice volume, bandgap energy, morphology and the saturation magnetization of Zn1- x TM x O nanostructures were found to be dependent on the type of TM dopants. Lattice volume, bondlength and bandgap determined from XRD and UV-Vis, respectively, were found to decrease as the atomic number of the dopant increased from Co to Cu. Magnetic studies showed that all the TM-doped ZnO exhibited room temperature ferromagnetism and the decreasing trend of saturation magnetization was observed with the increase of 3d electrons number from Co to Cu.

Ahmed, Faheem; Arshi, Nishat; Anwar, M. S.; Danish, Rehan; Koo, Bon Heun

2013-05-01

362

Bio-inspired green synthesis of Fe3O4 spherical magnetic nanoparticles using Syzygium cumini seed extract  

NASA Astrophysics Data System (ADS)

A novel and bio-inspired Fe3O4 spherical magnetic nanoparticles (SMNPs) were synthesized using Syzygium cumini (S. cumini) seed extract, which is a non-toxic ecofriendly fruit waste material. S. cumini seed extract acts as a green solvent, reducing and capping agent in which sodium acetate acts as electrostatic stabilizing agent. The green synthesized nanoparticles were characterized with the help of various techniques such as X-ray diffraction (XRD), Raman spectroscopy, transmission electron microscopy (TEM), Energy-dispersive spectroscopy (EDS), Vibrating sample magnetometer (VSM), FTIR spectroscopy and nitrogen adsorption and desorption analysis techniques. The XRD study divulged that the synthesized SMNPs have inverse spinel cubic structure. The hysteresis loop of Fe3O4 nanoparticles shows an excellent ferromagnetic behavior with saturation magnetization value of 13.6 emu/g.

Venkateswarlu, Sada; Natesh Kumar, B.; Prasad, C. H.; Venkateswarlu, P.; Jyothi, N. V. V.

2014-09-01

363

Hybrid superconducting magnetic suspensions  

SciTech Connect

Superconductors, especially high T{sub c} ones, are the most attractive materials to design stable and fully passive magnetic suspensions which have to control five degrees of freedom. The hybrid superconducting magnetic suspensions present high performances and a simple cooling mode. They consist of a permanent magnet bearing, stabilized by a suitable magnet-superconductor structure. Several designs are given and compared in terms of forces and stiffnesses. The design of the magnet bearing plays an important part. The superconducting magnetic bearing participates less in levitation but must provide a high stabilizing stiffness. This is achieved by the magnet configuration, a good material in term of critical current density and field cooling. A hybrid superconducting suspension for a flywheel is presented. This system consists of a magnet thrust bearing stabilized by superconductors interacting with an alternating polarity magnet structure. First tests and results are reported. Superconducting materials are magnetically melt-textured YBaCuO.

Tixador, P.; Hiebel, P.; Brunet, Y. [CNRS-CRTBT/LEG, Grenoble (France)] [CNRS-CRTBT/LEG, Grenoble (France); Chaud, X.; Gautier-Picard, P. [CNRS-EPM-Matformag, Grenoble (France)] [CNRS-EPM-Matformag, Grenoble (France)

1996-07-01

364

Mapping Magnetic Field Lines  

NSDL National Science Digital Library

This is a lesson about the magnetic field of a bar magnet. The lesson begins with an introductory discussion with learners about magnetism to draw out any misconceptions that may be in their minds. Then, learners freely experiment with bar magnets and various materials, such as paper clips, rulers, copper or aluminum wire, and pencils, to discover that magnets attract metals containing iron, nickel, and/or cobalt but not most other materials. Next, learners experiment with using a magnetic compass to discover how it is affected by the magnet and then draw the magnetic field lines of the magnet by putting dots at the location of the compass arrow. This is the first lesson in the first session of the Exploring Magnetism teacher guide.

365

Influence of spherical assembly of copper ferrite nanoparticles on magnetic properties: orientation of magnetic easy axis.  

PubMed

The magnetic properties of copper ferrite (CuFe2O4) nanoparticles prepared via sol-gel auto combustion and facile solvothermal method are studied focusing on the effect of nanoparticle arrangement. Randomly oriented CuFe2O4 nanoparticles (NP) are obtained from the sol-gel auto combustion method, while the solvothermal method allows us to prepare iso-oriented uniform spherical ensembles of CuFe2O4 nanoparticles (NS). X-ray diffractometry (XRD), atomic absorption spectroscopy (AAS), infra-red (IR) spectroscopy, Raman spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), (57)Fe Mössbauer spectroscopy and vibrating sample magnetometer (VSM) are used to investigate the composition, microstructure and magnetic properties of as-prepared ferrite nanoparticles. The field-dependent magnetization measurement for the NS sample at low temperature exhibits a step-like rectangular hysteresis loop (M(R)/M(S) ~ 1), suggesting cubic anisotropy in the system, whereas for the NP sample, typical features of uniaxial anisotropy (M(R)/M(S) ~ 0.5) are observed. The coercive field (HC) for the NS sample shows anomalous temperature dependence, which is correlated with the variation of effective anisotropy (K(E)) of the system. A high-temperature enhancement of H(C) and K(E) for the NS sample coincides with a strong spin-orbit coupling in the sample as evidenced by significant modification of Cu/Fe-O bond distances. The spherical arrangement of nanocrystals at mesoscopic scale provokes a high degree of alignment of the magnetic easy axis along the applied field leading to a step-like rectangular hysteresis loop. A detailed study on the temperature dependence of magnetic anisotropy of the system is carried out, emphasizing the influence of the formation of spherical iso-oriented assemblies. PMID:24714977

Chatterjee, Biplab K; Bhattacharjee, Kaustav; Dey, Abhishek; Ghosh, Chandan K; Chattopadhyay, Kalyan K

2014-06-01

366

Temperature dependent XRD Investigations on Heusler Compounds  

Microsoft Academic Search

Most of the X2YZ Heusler compounds used for the produc- tion of TMR devices are based on 3d transition metals like Co for the X element and Cr, Mn, Fe, or mixtures of those for the Y element. The main group element (Z) is usually taken from the 3 rd row (Al, Si) or from the 4 th row (Ga,

B. Balke; G. H. Fecher; Johannes Gutenberg; Universitaet Mainz

2006-01-01

367

The Speciation of Arsenic in Iron Oxides in Mine Wastes from the Giant Gold Mine, N.W.T.: Application of Synchrotron Micro-XRD and Micro-XANES at the Grain Scale  

SciTech Connect

Understanding the solid-phase speciation of arsenic in soils and sediments is important in evaluations of the potential mobility of arsenic and of its bio-availability in the environment. This is especially true in mine-influenced environments, where arsenic commonly is present at concentrations two and three orders of magnitude above quality criteria for soils and sediments. Arsenic-bearing particulates dispersed through hydraulic transport or aerosol emissions can represent a persistent source of contamination in sediments and soils adjacent to past mining and metallurgical operations. The stability and mobility of arsenic associated with these phases depend on the chemical form and oxidation state of the arsenic and the interaction with post-depositional geochemical conditions. The Giant mine in Yellowknife, Northwest Territories, roasted arsenic-bearing gold ore from 1949 to 1999. The roasting process decomposed arsenic-bearing sulfides (pyrite and arsenopyrite) to produce a calcine containing fine (generally <50 {micro}m) arsenic-bearing iron oxides. We have applied synchrotron As K-edge micro X-ray Absorption Near-Edge Structure ({micro}XANES) and {micro}XRD as part of a grain-by-grain mineralogical approach for the direct determination of the host mineralogy and oxidation state of As in these roaster-derived iron oxides. The grain-scale approach has resolved potential ambiguities that would have existed had only bulk XANES and XRD methods been applied. Using combined optical microscopy, electron microprobe and {micro}XRD, we have determined that the roaster-iron oxides are nanocrystalline grains of maghemite containing <0.5 to 7 wt.% As. Some of these arsenic-bearing nanocrystalline grains are a mixture of maghemite and hematite. All roaster iron oxides, including those present in 50-year-old tailings, contain mixtures of As{sup 5+} and As{sup 3+}. The persistence of As{sup 3+} in roaster-derived maghemite in shallow subareal (oxidized) shoreline tailings for over 50 years suggests that the arsenic is relatively stable under these conditions, even though As{sup 3+} is a reduced form of arsenic, and maghemite is normally considered a metastable phase.

Walker,S.; Jamieson, H.; Lanzirotti, A.; Andrade, C.; Hall, G.

2005-01-01

368

Facility Measures Magnetic Fields  

NASA Technical Reports Server (NTRS)

Partly automated facility measures and computes steady near magnetic field produced by object. Designed to determine magnetic fields of equipment to be installed on spacecraft including sensitive magnetometers, with view toward application of compensating fields to reduce interfernece with spacecraft-magnetometer readings. Because of its convenient operating features and sensitivity of its measurements, facility serves as prototype for similar facilities devoted to magnetic characterization of medical equipment, magnets for high-energy particle accelerators, and magnetic materials.

Honess, Shawn B.; Narvaez, Pablo; Mcauley, James M.

1991-01-01

369

Magnetically operated check valve  

NASA Astrophysics Data System (ADS)

A magnetically operated check valve is disclosed having, in one aspect, a valve body and a movable poppet disposed therein. A magnet attracts the poppet to hold the valve shut until the force of fluid flow through the valve overcomes the magnetic attraction and moves the poppet to an unseated, open position. The poppet and magnet are configured and disposed to trap a magnetically attracted particulate and prevent it from flowing to a valve seating region.

Morris, Brian G.; Bozeman, Richard J., Jr.

1993-03-01

370

Mine countermeasures HTS magnet  

Microsoft Academic Search

American Superconductor has designed, manufactured, and tested a model high-temperature superconducting (HTS) magnet system for airborne mine countermeasures (MCM) for the Office of Naval Research. The magnet has a magnetic moment of 80 kA-m2, or about one-fourth that of the full-scale magnet. The magnet is a solenoid consisting of 16 layers of laminated Bi-2223 HTS wire. The coil was manufactured

Segun O. Ige; Dawood Aized; Andy Curda; Rick Medeiros; Chris Prum; Peter Hwang; Gregory Naumovich; E. Michael Golda

2003-01-01

371

High efficiency magnetic bearings  

NASA Technical Reports Server (NTRS)

Research activities concerning high efficiency permanent magnet plus electromagnet (PM/EM) pancake magnetic bearings at the University of Maryland are reported. A description of the construction and working of the magnetic bearing is provided. Next, parameters needed to describe the bearing are explained. Then, methods developed for the design and testing of magnetic bearings are summarized. Finally, a new magnetic bearing which allows active torque control in the off axes directions is discussed.

Studer, Philip A.; Jayaraman, Chaitanya P.; Anand, Davinder K.; Kirk, James A.

1993-01-01

372

High efficiency magnetic bearings  

NASA Astrophysics Data System (ADS)

Research activities concerning high efficiency permanent magnet plus electromagnet (PM/EM) pancake magnetic bearings at the University of Maryland are reported. A description of the construction and working of the magnetic bearing is provided. Next, parameters needed to describe the bearing are explained. Then, methods developed for the design and testing of magnetic bearings are summarized. Finally, a new magnetic bearing which allows active torque control in the off axes directions is discussed.

Studer, Philip A.; Jayaraman, Chaitanya P.; Anand, Davinder K.; Kirk, James A.

373

SUPERCONDUCTING MAGNET TECHNOLOGY  

Microsoft Academic Search

Superconducting magnet technology deals with the design, manufacture, and operation of superconducting magnets. A superconducting\\u000a magnet is a highly stressed device: it requires the best that engineering has to offer to ensure that it operates successfully,\\u000a is reliable, and at the same time is economically viable. A typical 10-tesla magnet is subjected to an equivalent magnetic\\u000a pressure of 40MPa (nearly

Yukikazu Iwasa

374

The Magnetic Field  

NSDL National Science Digital Library

This demonstration of the magnetic field lines of Earth uses a bar magnet, iron filings, and a compass. The site explains how to measure the magnetic field of the Earth by measuring the direction a compass points from various points on the surface. There is also an explanation of why the north magnetic pole on Earth is actually, by definition, the south pole of a magnet.

Barker, Jeffrey

375

Exploring Magnetism on Earth  

NSDL National Science Digital Library

This teacher's guide contains four lessons that provide a way for teachers to introduce students to and elaborate on Earth's changing magnetic field. It covers learning to navigate using Earth's magnetic field and compass, Earth's magnetic pole and its motion across Earth's surface, magnetic reversals on Earth, and Earth's currently declining magnetic field. These lessons have been taught primarily in math, geology, and astronomy classes.

2005-01-01

376

What is Magnetism?  

NSDL National Science Digital Library

This is an activity about magnetism and magnetic forces. Learners will explore objects to which a magnet is attracted or repelled and record information in a learning log. Additionally, learners will identify magnetic devices or phenomena they encounter at home, at school, in nature, and in other locales. This is the first activity in the Magnetic Math booklet; this booklet can be found on the Space Math@NASA website.

377

Magnetically induced ferroelectric order in frustrated magnets  

NASA Astrophysics Data System (ADS)

Magnetoelectric coupling between magnetic and ferroelectric properties has been the object of intense study over the last four decades. Our understanding of magnetoelectric materials has been greatly enhanced by a rigorous exploration of the symmetry requirements for promoting magnetic and ferroelectric orders. Multiferroic materials, having simultaneous magnetic and ferroelectric order, have recently been proposed for incorporation into a range of spintronic devices. However, many of the multiferroics identified to date have different transition temperatures for ferroelectric and magnetic orders, leading to reduced magnetoelectric coupling strengths. I will discuss some recent experiments on several new multiferroics, including TbMnO3, DyMnO3, and Ni3V2O8. These compounds are notable because the ferroelectric transition is coincident with magnetic ordering which leads to very large magnetoelectric couplings and large magnetocapacitive effects. Furthermore, using external magnetic fields to tune the magnetic structure has a pronounced effect on ferroelectricity in these systems. This allows us to destroy or promote ferroelectric order magnetically. While similar effects have been observed previously, these multiferroics remain poorly understood. I will present a model developed to explain the multiferroic order in Ni3V2O8, in which the magnetic order spontaneously breaks inversion symmetry, allowing for the development of ferroelectricity. This magnetically-induced ferroelectric order is expected to appear in a wide range of antiferromagnets, and offers a new approach for designing and understanding multiferroic materials.

Lawes, Gavin

2005-03-01

378

Pulsed-laser deposition of magnetic alloys  

NASA Astrophysics Data System (ADS)

Targets of SmCo5 and Pr2Fe17 are ablated with a quadrupled Nd:YAG pulsed laser operating at 266 nm with fluence levels of ?2 J cm-2. The plasmas are condensed on r-plane sapphire (Al2O3) maintained either at ambient room temperature of ?400 °C. Preliminary results indicate that Sm+n and Co+n recombine on room temperature substrates to form an alloy with a-axis orientation that is consistent with an hkl<200> d-spacing for hexagonal SmCo5. Rare-earth and Fe plasmas condense at ?400 °C to form alloys with c-axis orientation as indicated by a single narrow hkl<006> reflection with a HHFW of about ?(2?)=0.4°. When codeposited with N2, an interstitial alloy Re2Fe17N3-? can be formed. These newly discovered metastable alloys display high Curie temperatures (Tc), large magnetization and anisotropy fields desirable for permanent magnet applications. Preliminary XRD, (SQUID) magnetometry and Auger surveys are presented together with speculation about future work.

Lynds, L.; Cosgrove, J.; Li, Q.; Fenner, D. B.; Budnick, J. I.; Zhang, Y. D.; Neth, E. J.; Willis, W.; Suib, S. L.

1993-10-01

379

Magnetic attachment mechanism  

NASA Technical Reports Server (NTRS)

A magnetic attachment mechanism adapted for interfacing with the manipulator arm of a remote manipulator system and comprising a pair of permanent magnets of rare earth material are arranged in a stator-rotor relationship. The rotor magnet is journalled for rotation about its longitudinal axis between pole plates of the stator magnet, each of which includes an adhering surface. In a first rotary position corresponding to the ON condition, each of the poles of the rotor magnet is closely adjacent to a stator magnet pole plate of like polarity whereby the respective magnet fields are additive for producing a strong magnetic field emanating from the adhering surfaces for attracting a ferrous magnetic plate, or the like, affixed to the payload. When the rotor magnet is rotated to a second position corresponding to the OFF condition, each of the poles of the rotor magnet is disposed closely adjacent to a pole plate of unlike polarity whereby the magnetic fields of the magnets are in cancelling relationship at the adhering surfaces, which permits the release of a payload. An actuator for selectively rotating the rotor magnet between the ON and OFF positions is provided for interfacing and connecting the magnetic attachment mechanism with a manipulator arm. For affecting an optimal rigidized attachment the payload is provided with guide means cooperable with guide means on the housing of the mechanism for directing adhering surfaces of the polar plates to the ferrous plate.

Wu, Mitchell B. (inventor); Harwell, William D. (inventor)

1988-01-01

380

Synthesis and magnetic properties of cobalt ferrite (CoFe 2O 4) nanoparticles prepared by wet chemical route  

Microsoft Academic Search

Magnetic nanoparticles of cobalt ferrite have been synthesized by wet chemical method using stable ferric and cobalt salts with oleic acid as the surfactant. X-ray Diffraction (XRD) and Transmission Electron Microscope (TEM) confirmed the formation of single-phase cobalt ferrite nanoparticles in the range 15–48nm depending on the annealing temperature and time. The size of the particles increases with annealing temperature

K. Maaz; Arif Mumtaz; S. K. Hasanain; Abdullah Ceylan

2007-01-01

381

Nanocomposite Magnets: Transformational Nanostructured Permanent Magnets  

SciTech Connect

Broad Funding Opportunity Announcement Project: GE is using nanomaterials technology to develop advanced magnets that contain fewer rare earth materials than their predecessors. Nanomaterials technology involves manipulating matter at the atomic or molecular scale, which can represent a stumbling block for magnets because it is difficult to create a finely grained magnet at that scale. GE is developing bulk magnets with finely tuned structures using iron-based mixtures that contain 80% less rare earth materials than traditional magnets, which will reduce their overall cost. These magnets will enable further commercialization of HEVs, EVs, and wind turbine generators while enhancing U.S. competitiveness in industries that heavily utilize these alternatives to rare earth minerals.

None

2010-10-01

382

Studies the alterations of biochemical and mineral contents in bone tissue of mus musculus due to aluminum toxicity and the protective action of desferrioxamine and deferiprone by FTIR, ICP-OES, SEM and XRD techniques  

NASA Astrophysics Data System (ADS)

The present study has attempt to analyze the changes in the biochemical and mineral contents of aluminum intoxicated bone and determine the protective action of desferrioxamine (DFO) and deferiprone (DFP) by using Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), inductively coupled plasma optical emission spectroscopy (ICP-OES), and scanning electron microscopy (SEM) techniques for four groups of animals such as control (Group I), aluminum intoxicated (Group II), Al + DFP (Group III) and Al + DFO + DFP (Group IV) treated groups respectively. The FTIR spectra of the aluminum intoxicated bone showed significant alteration in the biochemical constituents. The bands ratio at I1400/I877 significantly decreased from control to aluminum, but enhanced it by Al + DFP to Al + DFO + DFP treated bone tissue for treatments of 16 weeks. This result suggests that DFO and DFP are the carbonate inhibitor, recovered from chronic growth of bone diseases and pathologies. The alteration of proteins profile indicated by Amide I and Amide II, where peak area values decreased from control to aluminum respectively, but enhanced by treated with DFP (p.o.) and DFO + DFP (i.p.) respectively. The XRD analysis showed a decrease in crystallinity due to aluminum toxicity. Further, the Ca, Mg, and P contents of the aluminum exposed bone were less than those of the control group, and enhanced by treatments with DFO and DFP. The concentrations of trace elements were found by ICP-OES. Therefore, present study suggests that due to aluminum toxicity severe loss of bone minerals, decrease in the biochemical constituents and changes in the surface morphology.

Sivakumar, S.; Khatiwada, Chandra Prasad; Sivasubramanian, J.

383

Studies the alterations of biochemical and mineral contents in bone tissue of mus musculus due to aluminum toxicity and the protective action of desferrioxamine and deferiprone by FTIR, ICP-OES, SEM and XRD techniques.  

PubMed

The present study has attempt to analyze the changes in the biochemical and mineral contents of aluminum intoxicated bone and determine the protective action of desferrioxamine (DFO) and deferiprone (DFP) by using Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), inductively coupled plasma optical emission spectroscopy (ICP-OES), and scanning electron microscopy (SEM) techniques for four groups of animals such as control (Group I), aluminum intoxicated (Group II), Al+DFP (Group III) and Al+DFO+DFP (Group IV) treated groups respectively. The FTIR spectra of the aluminum intoxicated bone showed significant alteration in the biochemical constituents. The bands ratio at I1400/I877 significantly decreased from control to aluminum, but enhanced it by Al+DFP to Al+DFO+DFP treated bone tissue for treatments of 16 weeks. This result suggests that DFO and DFP are the carbonate inhibitor, recovered from chronic growth of bone diseases and pathologies. The alteration of proteins profile indicated by Amide I and Amide II, where peak area values decreased from control to aluminum respectively, but enhanced by treated with DFP (p.o.) and DFO+DFP (i.p.) respectively. The XRD analysis showed a decrease in crystallinity due to aluminum toxicity. Further, the Ca, Mg, and P contents of the aluminum exposed bone were less than those of the control group, and enhanced by treatments with DFO and DFP. The concentrations of trace elements were found by ICP-OES. Therefore, present study suggests that due to aluminum toxicity severe loss of bone minerals, decrease in the biochemical constituents and changes in the surface morphology. PMID:24583473

Sivakumar, S; Khatiwada, Chandra Prasad; Sivasubramanian, J

2014-05-21

384

Magnetic shielding for magnetically levitated trains  

Microsoft Academic Search

The magnetically levitated train has on-board superconducting coils for propulsion guide and support which generate mmf of several hundred kAT. The effect of such high magnetic field on the human body, electronics devices, wrists watches, etc., is not well known. The shielding problem in Miyazaki experimental railway with the on-board shielding coils for support is investigated. When no magnetic shielding

S. Okuma; H. Sugiyama; Y. Amemiya

2009-01-01

385

Large gap magnetic suspension system  

NASA Technical Reports Server (NTRS)

The design of a large gap magnetic suspension system is discussed. Some of the topics covered include: the system configuration, permanent magnet material, levitation magnet system, superconducting magnets, resistive magnets, superconducting levitation coils, resistive levitation coils, levitation magnet system, and the nitrogen cooled magnet system.

Abdelsalam, Moustafa K.; Eyssa, Y. M.

1991-01-01

386

Magnetic properties of ?-Fe2O3 nanoparticles incorporated in a polystyrene resin matrix  

NASA Astrophysics Data System (ADS)

?-Fe2O3 magnetic nanoparticles ranging in average diameter from 3to10nm were synthesized into a polystyrene resin matrix by an ion-exchange method and characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), Mössbauer spectroscopy, and SQUID magnetometry. The average particle size as determined from XRD and TEM was found to be strongly dependent upon the initial Fe valence state of the starting chloride salt(s) and on the number of steps that the salt introduction and ion-exchange process were repeated. Regardless of the initial Fe valence state and processing conditions, Mössbauer spectroscopy confirmed that the Fe in the resulting nanoparticles existed only as Fe(III) ions and that ?-Fe2O3 was the only phase present. The values of the saturation magnetization at 5K were found to be dependent upon the processing conditions and ranged from 203to333emu/cm3 , which are significantly smaller than the bulk value (408emu/cm3) for ?-Fe2O3 . As expected, the nanoparticles exhibited superparamagnetic behavior with the magnetic moments becoming frozen with decreasing temperature as evidenced by the appearance of a six-line splitting in the Mössbauer spectra, a bifurcation in the zero-field-cooled (ZFC) and field-cooled (FC) magnetizations, and an opening in the MV -vs- H hysteresis curves. The values of magnetic anisotropy constant (1.2-2.1×106ergs/cm3) determined from the differences between the ZFC and FC magnetizations were found to be higher than the bulk value (1.1×105ergs/cm3) for ?-Fe2O3 , and are probably due to surface effects. Likewise, the nanoparticle size distributions as deduced from the blocking temperature distribution function f(TB) based on fits to the difference in the ZFC and FC magnetization curves as well as from fits of the MV -vs- H curves in the superparamagnetic regime with a Langevin function indicate fairly broad distributions of particle sizes with the particle sizes being comparable to those deduced from XRD and TEM measurements. The smaller saturated magnetization values found for these nanoparticles combined with the non-zero slope of the high-field magnetization data suggests that these nanoparticles have a non-negligible surface layer of noncollinear spins surrounding a ferrimagnetically ordered ?-Fe2O3 core.

Vaishnava, P. P.; Senaratne, U.; Buc, E. C.; Naik, R.; Naik, V. M.; Tsoi, G. M.; Wenger, L. E.

2007-07-01

387

Magnetic switch coupling to synchronize magnetic modulators  

DOEpatents

Apparatus for synchronizing the output pulses from a pair of magnetic switches is disclosed. An electrically conductive loop is provided between the pair of switches with the loop having windings about the core of each of the magnetic switches. The magnetic coupling created by the loop removes voltage and timing variations between the outputs of the two magnetic switches caused by any of a variety of factors. The only remaining variation is a very small fixed timing offset caused by the geometry and length of the loop itself. 13 figs.

Reed, K.W.; Kiekel, P.

1999-04-27

388

Magnetic switch coupling to synchronize magnetic modulators  

DOEpatents

Apparatus for synchronizing the output pulses from a pair of magnetic switches. An electrically conductive loop is provided between the pair of switches with the loop having windlings about the core of each of the magnetic switches. The magnetic coupling created by the loop removes voltage and timing variations between the outputs of the two magnetic switches caused by any of a variety of factors. The only remaining variation is a very small fixed timing offset caused by the geometry and length of the loop itself.

Reed, Kim W. (Albuquerque, NM); Kiekel, Paul (Albuquerque, NM)

1999-01-01

389

CME Magnetic Structure and Magnetic Cloud Signature  

NASA Astrophysics Data System (ADS)

An interplanetary coronal mass ejection (ICME) is the counterpart of a coronal mass ejection by definition. However, the relationship between the magnetic structures of the CMEs and that of the situ observations of ICMEs is still quite far from clear, due to observational gaps and the state of our understanding of CMEs. Some studies suggested that the magnetic cloud (MC, a group of ICMEs with fluxrope signatures) magnetic polarity follows the solar large scale magnetic field, and others suggested it follows the local magnetic field of the CME source region. Recent studies found that the relationship is more complex. While solar cycle dependence of the magnetic signature of MCs is clearly evident, the polarity of the MCs does not reverse at the same time when the solar large scale field reverses around solar maximum, but begins to have mixed polarities, and the new polarity may only prevail at the midst of the declining phase. Interestingly, in an independent study of the magnetic topology at the CME source regions, we found a similar solar cycle dependence of the bipolar and quadrupolar topologie. In this work, the link between CMEs and ICMEs is made and the results will shed light on our understanding about the relationship between CME and ICME magnetic structures and how these structures are related to solar local and large scale magnetic fields.Acknowledgement: ATM/NSF-0451438, SRT/NASA-NNG06GE51G and CISM/NSF.

Li, Yan; Luhmann, J.

2006-06-01

390

Structural and magnetic properties of Sr2FeMoO6 film prepared by electrophoresis technique  

NASA Astrophysics Data System (ADS)

Double perovskite Sr2FeMoO6 film was fabricated by electrophoresis method on single crystal Si substrate. The post-annealing treatment was carried out at 900 °C, 960 °C, 1060 °C and 1100 °C with 5% H2/Ar atmosphere. Surface micrograph, structural and magnetic properties of the film have been investigated. It is found that the annealing temperature plays an important role on the phase formation and magnetic properties. According to X-ray diffraction (XRD), single phase Sr2FeMoO6 film was obtained at annealing temperature 1100 °C, the film shows typical polycrystal property. However, the superstructure reflection assigning the ordering arrangement of Fe and Mo atoms in the perovskite structure disappears in our XRD pattern. Raman detection finds two peaks at around 440 cm-1 and 620 cm-1, which belongs to Sr2FeMoO6 phase. Consistent with XRD results, typical impurity like SrMoO4 appears at around 880 cm-1 in the film annealed at lower temperature. Microstructure investigation shows that the surface of the film is homogeneous and the grain size of particles increases with annealing temperature. Temperature dependence of magnetization reveal that the highest Curie temperature (TC=282 K) is obtained from the film annealed at 1100 °C. Owing to the large amount of anti-site defect, the highest TC is still lower than that of parent Sr2FeMoO6 powder.

Zhang, Q.; Xu, Z. F.; Liang, J.; Pei, J.; Sun, H. B.

2014-03-01

391

Electrical, dielectric and magnetic characterization of Bi-Cr substituted M-type strontium hexaferrite nanomaterials  

NASA Astrophysics Data System (ADS)

Strontium hexaferrite nanoparticles substituted with bismuth and chromium having nominal composition SrFe12-2xBixCrxO19 (x=0.2, 0.4, 0.6, 0.8) have been synthesized by the sol-gel method. The samples are characterized by X-ray diffraction (XRD), Fourier Transform Infrared (FTIR), DC electrical resistivity, magnetic and dielectric measurements. The XRD data shows that the nanoparticles are crystallized into single hexagonal magnetoplumbite phase. Room temperature DC electrical resistivity decreases on increasing the Bi-Cr contents. The dielectric constant, dielectric loss and tangent loss decrease with the frequency. The magnetic properties such as saturation magnetization (Ms), remanence (Mr) and coercivity (Hc) increase with increasing the dopant concentration up to x=0.2 and then decrease with further increase in dopant content. Coercivity decreases with increasing the dopant content up to x=0.2 then increases with further increase in dopant content. The increase in Ms and Mr while decrease in Hc indicates that the material with composition SrBi0.2Cr0.2Fe11.6O19 is suitable for magnetic recording media.

Shakoor, Sajeela; Ashiq, Muhammad Naeem; Malana, Muhammad Aslam; Mahmood, Azhar; Warsi, Muhammad Farooq; Najam-ul-Haq, Muhammad; Karamat, Nazia

2014-08-01

392

Structural, optical and magnetic properties of ZnOFe/ZnO multilayers  

NASA Astrophysics Data System (ADS)

ZnOFe/ZnO multilayers (MLs) with the constant composition and the different thickness in ZnOFe layers have been prepared by helicon plasma sputtering. The XRD patterns of ZnOFe/ZnO MLs before annealing showed only ZnO diffraction peaks while one after annealing indicated the phases of ZnO and ZnFe2O4. The magnetization curves of ZnOFe/ZnO MLs before and after annealing showed ferromagnetic behavior. The origin of ferromagnetism in ZnOFe/ZnO MLs before annealing is considered to be due to the formation of defects/vacancies resulting from the substitution of Fe3+ ions for Zn2+ ions in ZnOFe layers irrespective of the mixed Fe valence states seen in XANES spectra. The ferromagnetic behavior after annealing is due to the formation of ZnFe2O4, which was confirmed by XRD, XPS, RBS measurements.

Nakayama, H.; Kinoshita, R.; Sakamoto, I.; Yasumoto, M.; Koike, M.; Honda, S.

2013-12-01

393

Chiral magnetic conductivity  

SciTech Connect

Gluon field configurations with nonzero topological charge generate chirality, inducing P- and CP-odd effects. When a magnetic field is applied to a system with nonzero chirality, an electromagnetic current is generated along the direction of the magnetic field. The induced current is equal to the chiral magnetic conductivity times the magnetic field. In this article we will compute the chiral magnetic conductivity of a high-temperature plasma for nonzero frequencies. This allows us to discuss the effects of time-dependent magnetic fields, such as produced in heavy ion collisions, on chirally asymmetric systems.

Kharzeev, Dmitri E. [Department of Physics, Brookhaven National Laboratory, Upton New York 11973 (United States); Warringa, Harmen J. [Institut fuer Theoretische Physik, Goethe-Universitaet Frankfurt, Max-von-Laue-Strasse 1, 60438 Frankfurt am Main (Germany)

2009-08-01

394

The Magnetic Sun  

NSDL National Science Digital Library

This lesson presents an overview of phenomena related to the magnetism of the Sun, in particular to sunspots and their 11-year cycle, solar flares and magnetic disturbances on Earth caused by solar activity. It also reviews briefly the connection between electricity and magnetism. Students will learn facts about the discovery of sunspots, their intense magnetism, and their 11-year cycle. They will be introduced to solar activity associated with sunspots and their cycles, e.g. the abrupt brightenings known as solar flares. They also learn that solar activity is probably associated with the release of magnetic energy, and that such releases can propel fast plasma flows towards Earth, causing magnetic storms.

Stern, David

395

The Magnetic Field  

NSDL National Science Digital Library

This webpage is part of the University Corporation for Atmospheric Research (UCAR) "Windows to the Universe" program. It describes the nature and configuration of magnetic fields, which are the result of moving electric charges, including how they cause magnetic objects to orient themselves along the direction of the magnetic force points, which are illustrated as lines. Magnetic field lines by convention point outwards at the north magnetic pole and inward at the south magnetic pole. The site features text, scientific illustrations and an animation. Text and vocabulary are selectable for the beginning, intermediate, or advanced reader.

396

Magnetic properties of Fe doped SmCrO3 perovskite  

NASA Astrophysics Data System (ADS)

The compound SmCr1-x FexO3 perovskites were prepared by citric acid route. the samples were characterized by XRD and SEM. The temperature and field dependent magnetization measurements were carried out in the temperature range of 5K -400 K at 0.01T field and -5T to 5T field at 2K. SmCrO3 compound has shown two magnetic transition temperatures at 197 K and 38 K. The observed behavior at 197 K is the characteristic of anti-ferromagnetic ordering of Cr3+ moments with weak ferromagnetism. The drop in magnetization below 38 K is due to the spin reorientation of Sm3+ in anti ferromagnetic arrangement and Cr3+spins. the doping of Fe in SmCrO3 compound has shown a decrease in TN1 and also the two magnetization reversals at 177K and 57K. The magnetic behavior at low temperatures is (Tmagnetization reversals offers the characteristic switching of magnetization without changing the direction of the applied magnetic field.

Bakshi, Venugopal Rao; Prasad, Bandi Vittal; Gade, Narsinga Rao; Chou, C. F.; Devarasetty, Suresh Babu

2014-04-01

397

Preparation and Application of Hollow Silica/magnetic Nanocomposite Particle  

NASA Astrophysics Data System (ADS)

The hollow silica/cobalt ferrite (CoFe2O4) magnetic microsphere with amino-groups were successfully prepared via several steps, including preparing the chelating copolymer microparticles as template by soap-free emulsion polymerization, manufacturing the hollow cobalt ferrite magnetic microsphere by in-situ chemical co-precipitation following calcinations, and surface modifying of the hollow magnetic microsphere by 3-aminopropyltrime- thoxysilane via the sol-gel method. The average diameter of polymer microspheres was ca. 200 nm from transmission electron microscope (TEM) measurement. The structure of the hollow magnetic microsphere was characterized by using TEM and scanning electron microscope (SEM). The spinel-type lattice of CoFe2O4 shell layer was identified by using XRD measurement. The diameter of CoFe2O4 crystalline grains ranged from 54.1 nm to 8.5 nm which was estimated by Scherrer's equation. Additionally, the hollow silica/cobalt ferrite microsphere possesses superparamagnetic property after VSM measurement. The result of BET measurement reveals the hollow magnetic microsphere which has large surface areas (123.4m2/g). After glutaraldehyde modified, the maximum value of BSA immobilization capacity of the hollow magnetic microsphere was 33.8 mg/g at pH 5.0 buffer solution. For microwave absorption, when the hollow magnetic microsphere was compounded within epoxy resin, the maximum reflection loss of epoxy resins could reach -35dB at 5.4 GHz with 1.9 mm thickness.

Wang, Cheng-Chien; Lin, Jing-Mo; Lin, Chun-Rong; Wang, Sheng-Chang

398

Synthesis, characterization and magnetic behavior of Co/MCM-41 nano-composites  

SciTech Connect

Synthesis, structure and magnetic properties of Co/MCM-41 as magnetic nano-composites have been investigated. Mesoporous materials with different degrees of metal loading were prepared by wet impregnation and characterized by ICP, XRD, N{sub 2} adsorption, UV–vis DRS, TPR and EPMA-EDS. Cobalt oxide clusters and Co{sub 3}O{sub 4} nano-particles could be confined inside the mesopores of MCM-41, being this fact favored by the Co loading increasing. In addition, larger crystals of Co{sub 3}O{sub 4} detectable by XRD also grow on the surface when the Co loading is enhanced. The magnetic characterization was performed in a SQUID magnetometer using a maximum magnetic applied field µ{sub 0}Ha=1 T. While the samples with the higher Co loadings showed a behavior typically paramagnetic, a superparamagnetic contribution is more notorious for lower loadings, suggesting high Co species dispersion. - Graphical abstract: Room temperature hysteresis loops as a function of the Co content. Display Omitted - Highlights: • Co species as isolated Co{sup 2+}, oxide clusters and Co{sub 3}O{sub 4} nano-particles were detected. • For higher Co loads were detected, by XRD, Co{sub 3}O{sub 4} particles on the external surface. • The confining of Co species inside the mesopores was achieved by increasing Co load. • Paramagnetism from oxide clusters/nano-particles becomes dominant for higher Co loads. • Superparamagnetism can be assigned to Co species of small size and finely dispersed.

Cuello, N. [CITeQ-Universidad Tecnológica Nacional-Facultad Regional Córdoba, Maestro López esq. Cruz Roja Argentina, 5016 Córdoba (Argentina); Elías, V. [CITeQ-Universidad Tecnológica Nacional-Facultad Regional Córdoba, Maestro López esq. Cruz Roja Argentina, 5016 Córdoba (Argentina); CONICET (Argentina); Crivello, M. [CITeQ-Universidad Tecnológica Nacional-Facultad Regional Córdoba, Maestro López esq. Cruz Roja Argentina, 5016 Córdoba (Argentina); Oliva, M. [FaMAF-Universidad Nacional de Córdoba, Córdoba (Argentina); IFEG-CONICET (Argentina); Eimer, G., E-mail: geimer@scdt.frc.utn.edu.ar [CITeQ-Universidad Tecnológica Nacional-Facultad Regional Córdoba, Maestro López esq. Cruz Roja Argentina, 5016 Córdoba (Argentina); CONICET (Argentina)

2013-09-15

399

Reflectivity (visible and near IR), Moessbauer, static magnetic, and X ray diffraction properties of aluminum-substituted hematites  

NASA Technical Reports Server (NTRS)

The effect of substituting iron by aluminum in polymorphs of Fe2O3 and FeOOH on their reflectivity characteristics was investigated by comparing data on visible and NIR reflectivities and on static magnetic, XRD, and Moessbauer properties for a family of aluminum-substituted hematites alpha-(Fe,Al)2O3, with compositions where the values of the Al/(Al+Fe) ratio were up to 0.61. Samples were prepared by oxidation of magnetite, dehydroxylation of goethite, and direct precipitation. The analytical methods used for obtaining diffuse reflectivity spectra (350-2200 nm), Moessbauer spectra, and static magnetic data are those described by Morris et al. (1989).

Morris, Richard V.; Schulze, Darrell G.; Lauer, Howard V., Jr.; Agresti, David G.; Shelfer, Tad D.

1992-01-01

400

New type permanent magnet biased radial magnetic bearing in magnetic suspending reaction flywheel  

NASA Astrophysics Data System (ADS)

To overcome the defects of the present permanent magnet biased radial magnetic bearing, a new type permanent magnet biased radial magnetic bearing in magnetic suspending reaction flywheel application is reported. The fundamental principle of the radial magnetic bearing is presented. And the radial magnetic bearing is analyzed and calculated by using equivalent magnetic circuit and finite element method (FEM). As a matter of fact, the flux of permanent magnet and electromagnetic occur in any radial plane, so the axial length of the radial magnetic bearing will be lessened. Therefore, the presented radial magnetic bearing has smaller volume compared to the existing structure. It is much suitable for magnetic suspending reaction flywheel.

Sun, Jinji; Fang, Jiancheng; Wang, Xi

2008-10-01

401

Spin and orbital magnetization loops obtained using magnetic Compton scattering  

SciTech Connect

We present an application of magnetic Compton scattering (MCS) to decompose a total magnetization loop into spin and orbital magnetization contributions. A spin magnetization loop of SmAl{sub 2} was measured by recording the intensity of magnetic Compton scattering as a function of applied magnetic field. Comparing the spin magnetization loop with the total magnetization one measured by a vibrating sample magnetometer, the orbital magnetization loop was obtained. The data display an anti-coupled behavior between the spin and orbital magnetizations and confirm that the orbital part dominates the magnetization.

Itou, M.; Sakurai, Y. [Japan Synchrotron Radiation Research Institute, SPring-8, Hyogo 679-5198 (Japan)] [Japan Synchrotron Radiation Research Institute, SPring-8, Hyogo 679-5198 (Japan); Koizumi, A. [Graduate School of Materials Science, University of Hyogo, Hyogo 678-1297 (Japan)] [Graduate School of Materials Science, University of Hyogo, Hyogo 678-1297 (Japan)

2013-02-25

402

Single molecule magnets from magnetic building blocks  

NASA Astrophysics Data System (ADS)

We provide a basic set of magnetic building blocks that can be rationally assembled, similar to magnetic LEGO bricks, in order to create a huge variety of magnetic behavior. Using rare-earth centers and multipyridine ligands, fine-tuning of intra and intermolecular exchange interaction is demonstrated. We have investigated a series of molecules with monomeric, dimeric and trimeric lanthanide centers using SQUID susceptometry and Hall bar magnetometry. A home-made micro-Hall-probe magnetometer was used to measure magnetic hysteresis loops at mK temperatures and fields up to 17 T. All compounds show hysteresis below blocking temperatures of 3 to 4 K. The correlation of the assembly of the building blocks with the magnetic properties will be discussed.

Kroener, W.; Paretzki, A.; Cervetti, C.; Hohloch, S.; Rauschenbach, S.; Kern, K.; Dressel, M.; Bogani, L.; M&üLler, P.

2013-03-01

403

Magnetic Marble Run  

NSDL National Science Digital Library

Learners explore magnetism and motion as they build a simple marble run. Learners test different arrangements of plastic and cardboard tubes, bottles, and cups on a magnetic board. Learners use their marble tracks to investigate gravity, friction, motion, and momentum.

Centers, Oakland D.

2012-01-01

404

Magnetic assisted statistical assembly  

E-print Network

The objective of this thesis is to develop a process using magnetic forces to assemble micro-components into recesses on silicon based integrated circuits. Patterned SmCo magnetic thin films at the bottom of recesses are ...

Cheng, Diana I

2008-01-01

405

Experiments on Magnetic Materials  

ERIC Educational Resources Information Center

Describes the construction and use of a simple apparatus to measure the magnetization density and magnetic susceptibility of ferromagnetic, paramagnetic, and the diamagnetic solids and liquids. (Author/GA)

Schneider, C. S.; Ertel, John P.

1978-01-01

406

Metallic Magnetic Hetrostructures  

E-print Network

This work studied sputter deposited conventional spin valves (SV) and related structures. In SV layered structures, two ferromagnetic layers are separated by a non-magnetic spacer. Under an external magnetic field, the relative orientation...

Leung, Chi Wah

407

Active magnetic regenerator  

DOEpatents

The disclosure is directed to an active magnetic regenerator apparatus and method. Brayton, Stirling, Ericsson, and Carnot cycles and the like may be utilized in an active magnetic regenerator to provide efficient refrigeration over relatively large temperature ranges.

Barclay, John A. (Los Alamos, NM); Steyert, William A. (Los Alamos, NM)

1982-01-01

408

Active magnetic regenerator  

SciTech Connect

The disclosure is directed to an active magnetic regenerator apparatus and method. Brayton, stirling, ericsson, and carnot cycles and the like may be utilized in an active magnetic regenerator to provide efficient refrigeration over relatively large temperature ranges.

Barclay, J.A.; Steyert, W.A.

1982-06-01

409

Magnetic resonance angiography  

MedlinePLUS

MRA; Angiography - magnetic resonance ... Kwong RY. Cardiovascular Magnetic Resonance Imaging. In: Bonow RO, Mann DL, Zipes DP, Libby P, eds. Braunwald's Heart Disease: A Textbook of Cardiovascular Medicine . 9th ...

410

Axial Halbach Magnetic Bearings  

NASA Technical Reports Server (NTRS)

Axial Halbach magnetic bearings have been investigated as part of an effort to develop increasingly reliable noncontact bearings for future high-speed rotary machines that may be used in such applications as aircraft, industrial, and land-vehicle power systems and in some medical and scientific instrumentation systems. Axial Halbach magnetic bearings are passive in the sense that unlike most other magnetic bearings that have been developed in recent years, they effect stable magnetic levitation without need for complex active control.

Eichenberg, Dennis J.; Gallo, Christopher A.; Thompson, William K.

2008-01-01

411

Magnetic effects on thermocouples  

NASA Astrophysics Data System (ADS)

Thermometers in laboratory environment and industrial applications are often subject to extraneous, usually unwanted and uncontrolled magnetic fields. Magnetic field influence can be minimized, but cannot be fully cancelled out. Even more, in most cases, there is no awareness of the existence of magnetic fields, let alone their effect on measurement instrumentation. In the past, sensitivity to high dc magnetic fields has been investigated in cryogenics and at high temperatures. More recently, the magnetic effect on weak dc magnetic fields was presented. The goal of this paper was to analyse and empirically and experimentally prove the magnetic sensitivity of thermocouples exposed to low magnetic fields: both dc and ac. Precision and uniform alternating and direct magnetic flux densities were generated by means of permanent magnets and power amplifiers with air-cored coils. The magnetic effect on ferromagnetic and non-ferromagnetic thermocouples at liquid-nitrogen-boiling point (-196 °C), ice point (0 °C), in water (17 °C) and at melting point of gallium fixed point cell (29.7646 °C) was investigated. Magnetic-field-dependent temperature errors of up to 700 mK (at 5.3 mT: dc) and up to 1 °C (at 10 mT: ac 50 Hz magnetic fields) were detected. From the results, it can be concluded that, ideally for temperature measurements of the highest accuracy in the above-cryogenic temperature range, magnetic sensitivity should be estimated and taken into account either as the correction of an error and/or as an additional source of measurement uncertainty. Special consideration should be given to thermocouple orientation relative to the magnetic field direction, influence of metal enclosures and magnetization effects on ferromagnetic components of thermocouples.

Beguš, Samo; Bojkovski, Jovan; Drnovšek, Janko; Geršak, Gregor

2014-03-01

412

Magnetic susceptibility in QCD  

E-print Network

Magnetic susceptibility in the deconfined phase of QCD is calculated in a closed form using a recent general expression for the quark gas pressure in magnetic field. Quark selfenergies are entering the result via Polyakov line factors and ensure the total paramagnetic effect, increasing with temperature. A generalized form of magnetic susceptibility in nonzero magnetic field suitable for experimental and lattice measurements is derived, showing a good agreement with available lattice data.

V. D. Orlovsky; Yu. A. Simonov

2014-05-12

413

New aqueous magnetic fluids  

Microsoft Academic Search

New aqueous magnetic fluids constituted of nickel-zinc ferrite particles are synthesized using a soft chemical approach. Ferrofluids and solid particles are characterized using several techniques : chemical analysis, X-ray diffraction, transmission electron microscopy, infrared spectroscopy, and magnetization measurements.The stability of the aqueous magnetic fluids is studied as a function of pH and their magnetization is measured as a function of

D. Zins; V. Cabuil; R. Massart

1999-01-01

414

Exploratorium: Snacks about Magnetism  

NSDL National Science Digital Library

This web page contains a set of 12 simple experiments, or "snacks", on the topic of magnetism. Exploratorium Science Snacks are miniature versions of popular exhibits at the Exploratorium museum. This section includes activities on manipulating a grape with magnets, creating a magnetic field stronger than the Earth's, and building a motor. EDITOR'S NOTE: The materials required for most of these experiments are readily available and inexpensive, however, a few call for unusual types of magnets.

2010-01-15

415

Introduction to Magnetism  

NSDL National Science Digital Library

This is an activity about magnetism. Learners will experiment using horseshoe and bar magnets along with various materials in order to identify the effects of magnets on each other and on other materials. This is the third activity as part of the iMAGiNETICspace: Where Imagination, Magnetism, and Space Collide educator's guide. Instructions for downloading the iBook educator's guide and the associated Transmedia book student guide are available at the resource link.

416

Tunable magnetic and magnetocaloric properties of La{sub 0.6}Sr{sub 0.4}MnO{sub 3} nanoparticles  

SciTech Connect

Nanoparticles of La{sub 0.6}Sr{sub 0.4}MnO{sub 3} with different particle sizes are synthesized by the nitrate-complex auto-ignition method. The structural and magnetic properties of the samples are investigated by X-Ray diffraction (XRD), Fourier transform infra-red (FT-IR) spectroscopy, transmission electron microscopy (TEM), and DC magnetization measurements. The XRD study coupled with the Rietveld refinement shows that all samples crystallize in a rhombohedral structure with the space group of R-3?C. The FT-IR spectroscopy and TEM images indicate formation of the perovskite structure with the average sizes of 20, 40, and 100?nm for the samples sintered at 700, 800, and 1100?°C, respectively. The DC magnetization measurements confirm tuning of the magnetic properties due to the particle size effects, e.g., reduction in the ferromagnetic moment and increase in the surface spin disorder by decreasing the particle size. The magnetocaloric effect (MCE) study based on isothermal magnetization vs. filed measurements in all samples reveals a relatively large MCE around the Curie temperature of the samples. The peak around the Curie temperature gradually broadens with reduction of the particle size. The data obtained show that although variations in the magnetic entropy and adiabatic temperature decrease by lowering the particle size, variation in the relative cooling power values are the same for all samples. These results make this material a proper candidate in the magnetic refrigerator application above room temperature at moderate fields.

Ehsani, M. H., E-mail: mhe-ehsani@yahoo.com [Department of Physics, Semnan University, Semnan 35195-363 (Iran, Islamic Republic of); Kameli, P. [Department of Physics, Isfahan University of Technology, Isfahan 84156-8311 (Iran, Islamic Republic of); Ghazi, M. E. [Department of Physics, Shahrood University, Shahrood (Iran, Islamic Republic of); Razavi, F. S.; Taheri, M. [Department of Physics, Brock University, St.Catharines, Ontario L2S 3A1 (Canada)

2013-12-14

417

3D Magnetic Reluctivity Tensor of Soft Magnetic Composite Material  

Microsoft Academic Search

Soft magnetic composite (SMC) materials are particularly suitable for construction of electrical machines with complex structure and 3D magnetic flux. For design and analysis of such 3D flux machines, 3D magnetic properties of the magnetic materials should be properly determined, modeled and applied for calculating the magnetic field distribution, parameters and performance. This paper presents the 3D magnetic property measurement

Y. G. Guo; J. G. Zhu; Z. W. Lin; J. J. Zhong; H. Y. Lu; S. H. Wang

2006-01-01

418

Magnetic Fields Analogous to electric field, a magnet  

E-print Network

Magnetic Fields Analogous to electric field, a magnet produces a magnetic field, B Set up a B field two ways: Moving electrically charged particles Current in a wire Intrinsic magnetic field Basic characteristic of elementary particles such as an electron #12;Magnetic Fields Magnetic field lines Direction

Bertulani, Carlos A. - Department of Physics and Astronomy, Texas A&M University

419

Magnetism Theory Group / POSTECH Magnetism Theory Group / POSTECH  

E-print Network

Magnetism Theory Group / POSTECH #12;Magnetism Theory Group / POSTECH #12;Magnetism Theory Group / POSTECH #12;Magnetism Theory Group / POSTECH #12;Magnetism Theory Group / POSTECH J.H . Park et al. #12;'s of FeinCsm e tal The chargeandorbitalordering geom etryin YB a C o 2 O 5 S. K. Kwon etal .Magnetism Theory

Min, Byung Il

420

Rare earth permanent magnets  

Microsoft Academic Search

A survey is given of the state of the art in rare earth permanent magnet research of materials based on Nd2Fe14B. The magnetic properties of various types of interstitially modified Fe-rich rare earth intermetallics are discussed, including the possibility to apply these materials in permanent magnets.

K. H. J. Buschow; F. H. Feijen; Kees de Kort

1995-01-01