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1

Evidence from HRTEM image processing, XRD and EDS on nanocrystalline iron-doped titanium oxide powders  

Microsoft Academic Search

We investigated nanosized iron-doped TiO2 in the presence of poly(ethylene glycol) (PEG), synthesised by modified sol–gel method, by transmission electron microscopy (TEM), selected area electron diffraction (SAED), high-resolution electron microscopy (HRTEM), HRTEM image processing, energy dispersive X-ray analysis (EDS) and X-ray diffraction (XRD). XRD of as prepared sample showed very broad diffraction maxima of anatase as the dominant phase and

A. M. Tonejc; I. Djerdj

2001-01-01

2

Comparison of structural parameters of PF carbon from XRD and HRTEM techniques  

Microsoft Academic Search

A new technique to obtain structural parameters Lc, La and d, of phenol formaldehyde resin char (PFC) from TEM images has been developed. Similar structural parameters were also obtained from XRD technique and a comprehensive comparison of the results from the two techniques was made. The present study shows a good agreement between the results from the two techniques. The

Atul Sharma; Takashi Kyotani; Akira Tomita

2000-01-01

3

Hrtem Investigation of Nanocrystalline Materials  

NASA Astrophysics Data System (ADS)

The microstructural and structural investigation performed on nanocrystalline (NC) materials will be reported using TEM, SAED, EDS, HRTEM and XRD measurements. The aim of this investigation was to characterize ZrO2 and ZrO2-Y2O3 NC materials prepared by ball-milling. To elucidate the process of aloying of ZrO2-Y2O3 NC material the HRTEM image processing was applied which gave a strong support to the methods mentioned. The methods gave the evidence into a particular process on the atomic level.

Tonejc, Andjelka M.

4

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.

2013-03-01

5

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

6

Synthesis and HRTEM Electron Diffraction Characterization of Monocrystalline V2O5  

NASA Astrophysics Data System (ADS)

We have synthesized V2O5 nanorods via solvothermal synthesis. By controlling the synthesis conditions, unidirectional crystalline growth is achieved. HRTEM and XRD studies reveal that the resulting nanorods are monocrystalline and are on average 80 nm in width and readily grow to a few microns in length. Utilizing electron diffraction we investigate the growth of these nanostructures along preferential crystalline planes. XRD confirms also that the crystalline phase of the nanorods is orthorhombic.

Tafoya, Luisa; Rendon, Luis; Santiago, Patricia; Chavira, Elizabeth; Marinero, Ernesto E.; Garibay, Vicente; Gonzalez, Leonardo

2013-03-01

7

Synthesis and characterization of nickel ferrite magnetic nanoparticles  

Microsoft Academic Search

Nickel ferrite (NiFe2O4) nanoparticles are prepared by a polyvinyl alcohol (PVA) assisted sol–gel auto-combustion method. The structure, composition, morphology and magnetic properties of the gel precursor are characterized by powder XRD, FT-IR, TGA, HR-SEM, TEM, HR-TEM and VSM. XRD confirms the formation of single-phase nickel ferrite with space group of Fd3m and inverse spinel structure. The vibration properties of nanoparticles

P. Sivakumar; R. Ramesh; A. Ramanand; S. Ponnusamy; C. Muthamizhchelvan

2011-01-01

8

Temperature-dependent XRD, IR, magnetic, SEM and TEM studies of Jahn-Teller distorted NiCr2O4 powders  

NASA Astrophysics Data System (ADS)

In the present work we report detailed structural, magnetic and phonon properties of NiCr2O4 powders synthesized via a simple coprecipitation method. Temperature-dependent XRD as well as temperature-dependent IR studies reveal that cubic to tetragonal phase transition is lowered due to size effects. Observed changes in the IR spectra indicate that the paramagnetic-ferrimagnetic phase transition taking place at 74 K is related to further lowering of symmetry to orthorhombic system. Assignment of modes was proposed and factor group analyses in three possible symmetries were carried out. Our results show strong anomalies due to the Jahn-Teller tetragonal distortion and weak due to the orthorhombic distortion and onset of collinear ferrimagnetic order. Shifts of wavenumbers observed below 31 K, where the onset of antiferromagnetic ordering occurs, were attributed to spin-phonon interactions.

Ptak, M.; Maczka, M.; G?gor, A.; Pikul, A.; Macalik, L.; Hanuza, J.

2013-05-01

9

Combined XRD and XAS  

SciTech Connect

X-ray diffraction (XRD) and X-ray absorption fine structure (XAFS) are complementary techniques for investigating the structure of materials. XRD probes long range order and XAFS probes short range order. We have combined the two techniques at one synchrotron beamline, X18A at the NSLS, allowing samples to be studied in a single experiment. This beamline will allow for coordinated measurements of local and long range structural changes in chemical transformations and phase transitions using both techniques.

Ehrlich, S.N.; Hanson, J.C.; Lopez Camara, A.; Barrio, L.; Estrella, M.; Zhou, G.; Si, R.; Khalid, S. & Wang, Q.

2010-11-24

10

Magnetic properties and microstructure of carbon encapsulated Ni nanoparticles and pure Ni nanoparticles coated with NiO layer  

Microsoft Academic Search

Two kinds of nickel nanoparticles—carbon encapsulated Ni nanoparticles Ni(C) and pure Ni nanoparticles coated with NiO layers Ni(O) are successfully prepared. Structural characterizations (HR-TEM, SAED, and XRD) reveal their distinct morphological properties. Magnetization measurements for the assemblies of two kinds of Ni nanoparticles show a larger coercivity and remanence by a deviation between the zero-field-cooled and the field-cooled magnetization below

Xiang-Cheng Sun; Xing-Long Dong

2002-01-01

11

Fabrication, structure and magnetic properties of CoPt3, CoPt and Co3Pt nanoparticles  

NASA Astrophysics Data System (ADS)

A set of CoxPt100-x nanoparticles (NPs) was synthesized by the sol-gel method. The structure and magnetic properties of the produced samples were investigated by x-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SAED) and a vibrating sample magnetometer. When the Co content ranged from 25 to 75 at%, the results of XRD, HRTEM and SAED revealed the formation of L12 CoPt3, L10 CoPt and face-centred cubic Co3Pt NPs. Magnetic measurements indicated that CoPt3 and Co3Pt had soft magnetic properties. When the Co composition was 50 at%, the sample coercivity reached a giant value of ˜470 kA m-1.

Wang, Yaxin; Zhang, Xiaolong; Liu, Yang; Jiang, Yuhong; Zhang, Yongjun; Wang, Jingshu; Liu, Yanqing; Liu, Huilian; Sun, Yunfei; Beach, Geoffrey S. D.; Yang, Jinghai

2012-12-01

12

Structural, morphological, and magnetic study of nanocrystalline cobalt-copper powders synthesized by the polyol process  

Microsoft Academic Search

Nanocrystalline Co(x)Cu(100-x) (4 less than or = x less than or = 49 at. %) powders were prepared by the reduction of metal acetates in a polyol. The structure of powders was characterized by x-ray diffraction (XRD), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), extended x-ray absorption fine structure (EXAFS) spectroscopy, solid-state nuclear magnetic resonance (NMR) spectroscopy,

G. M. Chow; L. K. Kurihara; K. M. Kemner; P. E. Schoen; W. T. Elam; A. Ervin; S. Keller; Y. D. Zhang; J. Budnick; T. Ambrose

1995-01-01

13

Synthesis And Magnetic Properties Of La2NiMnO6 Nanoparticles  

NASA Astrophysics Data System (ADS)

La2NiMnO6 nanoparticles with varying particle size from 27 to 96 nm were synthesis by the sol gel method. Structural characterization was carried out using the x-ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM). Magnetization measurements showed predominantly two magnetic transitions that vary with the particle size. The variation of ferromagnetic transition temperatures, large suppression of saturation magnetic moment and the monotonically increase of the saturation magnetization (Ms) with particle size were attributed to the intrinsic antisite defects and the surface properties of the nanoparticles.

Chandrasekhar, K. Devi; Das, A. K.; Venimadhav, A.

2011-06-01

14

Structural analysis of PVC and PFA carbons prepared at 500–1000 °C based on elemental composition, XRD, and HRTEM  

Microsoft Academic Search

Temperature programmed oxidation (TPO) method to evaluate the structure of carbonaceous materials was proposed in the previous paper, and this method was applied to analyze two sets of carbons derived from PVC and PFA in the temperature range of 500–1000 °C. Amounts of H2O, CO and CO2 evolved during oxidation were accurately determined, and they were used to estimate an

Hiromi Aso; Koichi Matsuoka; Atul Sharma; Akira Tomita

2004-01-01

15

Magnetic properties of carbon-encapsulated Fe-Co alloy nanoparticles.  

PubMed

Carbon-encapsulated Fe-Co alloy nanoparticles (Fe-Co(C)) have been fabricated with different Co/Fe ratios by an efficient solid-state route using melamine as carbon source. The structure and morphology of Fe-Co(C) nanoparticles were characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM) and high-resolution transmission electron microscopy (HRTEM). The XRD characterization results reveal that all products are alloys with no carbide impurity. The TEM and HRTEM observations show that the alloy nanoparticles are encapsulated in carbon shells. Additionally, the reactions involved in the syntheses are postulated. The variation of magnetic properties of Fe-Co(C) with Co/Fe has been discussed according to the room temperature VSM measurement results. PMID:23389383

Wu, Aibing; Yang, Xuwei; Yang, Hua

2013-04-14

16

Chain-like and dinuclear coordination polymers in lanthanide (Nd, Eu) oxochloride complexes with 2,2':6',2''-terpyridine: synthesis, XRD structure and magnetic properties.  

PubMed

The solvothermal reactions (at 180 °C for 48 h) of a mixture of lanthanide chlorides (Nd, Eu) with the tridendate heterocyclic nitrogen ligand, 2,2':6',2''-terpyridine (terpy), in ethanol medium give rise to the formation of crystalline mixed chloro-hydroxo-aquo complex Ln(2)Cl(5)(OH)(H(2)O)(terpy). Its crystal structure consists of the connection of eight- and nine-fold coordinated lanthanide centers linked to each other via ?(2,3)-chloro and ?(3)-hydroxo species to form a tetranuclear unit, which are then further connected through chloro edges to generate infinite ribbons. Only one lanthanide cation in every two is chelated by terpy. Similar molar composition of the starting reactants led to the crystallization at room temperature of a second type of complex LnCl(3)(H(2)O)(terpy) (Ln = Nd, Eu). It is built up from the molecular assembly of dinuclear species containing two eight-fold coordinated lanthanide centers chelated by terpy and linked through a ?(2)-Cl edge. Luminescence spectra have been collected for the europium-based compound and indicates a strong red signal with the expected bands from the F-D transitions. The magnetic properties of the four compounds were investigated. Their behaviors correspond to that of the rare-earth ions present in the structure. The magnetic susceptibility of the neodymium-based compounds agrees with that of the Nd(III) ion with an (4)I(9/2) ground state split by crystal field. Concerning the Eu(III) derivatives, the term (7)F is split by spin-orbit coupling, the first excited states being thermally populated. Accordingly, the thermal dependence of the magnetic susceptibility was nicely reproduced by using appropriate analytical relations. The refined values of the spin-orbit coupling are consistent with the energies of the electronic levels deduced from the photoluminescence spectra. Unexpectedly, the magnetic susceptibility exhibits a hysteretic behavior in the range 45-75 K. PMID:21818485

Lhoste, Jérôme; Pérez-Campos, Ana; Henry, Natacha; Loiseau, Thierry; Rabu, Pierre; Abraham, Francis

2011-08-05

17

High-resolution Transmission Electron Microscopy (HRTEM) of Dislocations in Magnetite  

NASA Astrophysics Data System (ADS)

Magnetite is the primary mineral used for paleomagnetic and rock magnetic studies. Dislocations have been shown to significantly affect the remanent magnetization and coercivity of magnetite, and most naturally-occurring magnetite contains dislocations at a density of 108 cm-2. However our understanding of the orientation and style of dislocations in magnetite and of how these dislocations affect magnetic stability and remagnetization is limited. To better understand these effects, we must first characterize the dislocations. In a face-centered cubic mineral, dislocations are expected to form most easily in a {111} plane; however, we have observed dislocations in a variety of crystallographic orientations using high-resolution transmission electron microscopy (HRTEM). HRTEM images are sensitive to dislocations parallel to the electron beam, so it is important to image samples along multiple zone axes. The magnetite used in this study was cut from 1 cm diameter octahedra of nearly stoichiometric magnetite. Although our samples have likely experienced very little stress, we observe a variety of dislocations. The geometry of these dislocations will be incorporated in a dislocation simulator developed at Lawrence Livermore Laboratories and the resulting stress fields in a micromagnetic model.

Lindquist, A. K.; Feinberg, J. M.; Newell, A. J.

2011-12-01

18

Survey of basic XRD applications.  

SciTech Connect

This 1/2 day workshop will survey various applications of XRD analysis, including in-situ analyses and neutron diffraction. The analyses will include phase ID, crystallite size and microstrain, preferred orientation and texture, lattice parameters and solid solutions, and residual stress. Brief overviews of high-temperature in-situ analysis, neutron diffraction and synchrotron studies will be included.

Rodriguez, Mark Andrew

2010-07-01

19

A new quantitative approach for microstructural analysis of coal char using HRTEM images  

Microsoft Academic Search

HRTEM is a useful technique to observe the structure of coal char at an atomic level. To analyze the char structure quantitatively, we developed a new filtration technique for HRTEM images and a computer algorithm to obtain information such as the graphene layer size, interlayer spacing, the number of layers per stack, and its distribution from the post-filtered extracted HRTEM

A. Sharma; T. Kyotani; A. Tomita

1999-01-01

20

HRTEM as a metrology tool in ULSI processing  

SciTech Connect

Current ULSI processes involve the use of ultra-thin layers to achieve device performance. Proper control of the thickness of these layers is a manufacturing requirement. To this end accurate thickness measurement is an important metrology issue. High-resolution Transmission Electron Microscopy (HRTEM) provides a direct imaging method for materials and interfaces and can provide accurate thickness measurement. Crystal lattice images that are obtained can serve as internal calibration standards. There are a number of challenges to using this technique including careful sample preparation and choice of imaging conditions. The valid use of HRTEM as a metrology technique requires consideration of several aspects such as sample location and film properties. Optimal conditions for measuring amorphous layers are different from those for crystalline layers. We have used this technique to measure the thickness of amorphous dielectric layers (1-5 nm) and crystalline layers such as tantalum. HRTEM measurements have been used for the calibration of fab in-line metrology tools especially in those cases where the in-line tools do not already have necessary material parameters. Potential applications of this method include measurement of defect density and distribution for modeling and simulation.

Kaushik, V. S.; Prabhu, L.; Anderson, A.; Conner, J. [Physical Analysis Laboratory, Advanced Product Research and Development Laboratory, Motorola Inc., 3501 Ed Bluestein Blvd., Austin, Texas, 78723 (United States)

1998-11-24

21

Electron microscopy characterization of iron oxide nanopowders (prepared by laser pyrolysis) for magnetic fluid applications  

NASA Astrophysics Data System (ADS)

Fluids with magnetic characteristics have important values for today applications. This fluids, so called ferrofluids or magnetic fluids are in general formed by small nanoparticles with mean diameters about 10 nm and a carrier liquid. In our work we present nanopowders obtained by laser pyrolysis, which have characteristics for magnetic fluids applications. The important feature of powder was determined by means of XRD and electron microscopy techniques. The nanopowders have sizes distributed in interval from 2 nm to 10 nm. The high resolution images exhibits single particles with magnetic monodomain. Also, we investigate nanoparticles for defects. The nanoparticles forms nanoclusters, and high resolution image show adjacent particles without interface, the coupling mode is only magnetic not chemical. The powders are composed by magnetite and maghemite phase determined from XRD data, and confirmed by SAED and HRTEM work. The cell parameter calculated from the (220), (311), (511) (440) peaks of sample SF32 is 0.835 nm equal to the maghemite cell parameter.

Ciupina, V.; Prodan, G.; Morjan, I.; Dumitrache, F.; Alexandrescu, R.; Vasile, E.; Vegas, L.; Bica, D.

2007-09-01

22

Applications of HRTEM in Materials Science Problems and Dislocation Simulations  

NASA Astrophysics Data System (ADS)

Based on Pirouz's twinning model in Si [ 46] which has been successfully applied to other materials (35,24) as well, polytypic transformations in SiC can be explained (47, 51, 50). In order to get evidence for this model a study of dislocation core structures using HRTEM is performed. As a preliminary study, the glide and shuffle question in Ge is investigated. From experimental HRTEM, and image simulations including image processing, it is shown that perfect 60^circ dislocations in Ge occur predominantly in the shuffle type configuration. Simulations show that the core structure of 30 ^circ glide partials in SiC cannot be characterized using HRTEM. But 90^ circ partials can be characterized. Pirouz's cross slip mechanism has also been applied to basal twinning in sapphire (alpha - Al _2O_3) [ 49]. The HRTEM investigation of twins in Al_2O_3 reveal that basal twins are type II twins with a stacking sequence of ... ABCBAC ... for the Al sublattice which is in compliance with the proposed mechanism of formation and that rhombohedral twins are type II glide twins with a 1/6< 0111> shear. A zonal dislocation mechanism for the formation of rhombohedral twins is proposed which explains the structure of rhombohedral twins as well as the shear. The latter involves only very small shuffle motions of the anions and cations and also correctly predicts the size of rhombohedral stacking fault with local twin symmetry. Simulations of dislocation multiplication by the Frank-Read source for a 60^circ dislocation in Si reveal that the Orowan stress, i.e. the maximum line tension stress, is temperature sensitive. For an applied stress slightly higher than the Orowan stress, the back stress due to a small number of already existing loops upon a nascent dislocation (the back stress is much smaller than the line tension stress) brings the operation of the Frank-Read source to a stop. So the number of loops which stop the operation of a Frank-Read source is highly stress and temperature sensitive. The multiplication simulation may be extended to partial dislocations in polytypes which cross slip when the Frank-Read source stops due to the back stress of already existing loops. From this it may be concluded that polytypic phase transformations are also highly temperature and stress sensitive.

Geipel, Thomas

23

Magnetic and electronic structure properties of Co-doped SnO2 nanoparticles synthesized by the sol-gel-hydrothermal technique  

NASA Astrophysics Data System (ADS)

Structural, magnetic and electronic properties of Co-doped SnO2 nanoparticles sample with the concentration of 3.37% synthesized by the sol-gel-hydrothermal technique are studied in detail with experiments and ab initio calculations. Room temperature ferromagnetism is observed in this dilute magnetic semiconductor. Secondary phases and clusters of cobalt are excluded according to XRD, HRTEM, Raman, and XPS analyses. Magnetic measurements demonstrate the coexistence of ferromagnetism and paramagnetism in this sample, which is explained reasonably through our ab initio calculations in Co-doped SnO2 system.

Chen, Weibing; Li, Jingbo

2011-04-01

24

Rock magnetism investigation of highly magnetic soil developed on calcareous rock in Yun-Gui Plateau, China: Evidence for pedogenic magnetic minerals  

NASA Astrophysics Data System (ADS)

Detailed rock-magnetic and pedological analyses were conducted on the highly magnetic soils developed on calcareous rocks in the Yun-Gui Plateau of west-southern China in order to characterize its particular magnetic characteristics and pedogenesis of magnetic minerals. The magnetic concentration and mineralogy in the soils were determined by rock magnetism, powder X-ray diffraction and high resolution transmission electron microscope (HRTEM) with the energy dispersive X-ray analysis (EDX). The highly magnetic soils contained characteristics of highly weathered soils with a hue of 2.5YR, dominantly gibbsite-sesquioxide mineralogy, low organic matter content and high clay and free iron (Fed) content. Soil magnetic susceptibility (?lf) ranged from 2000 × 10- 8 to 6000 × 10- 8 m3 kg- 1; but in some layers it exceeded 6000 × 10- 8 or 6500 × 10- 8 m3 kg- 1, which was the highest magnetic soils so far found in the world. Magnetic measurements indicated that the frequency-dependent susceptibility (?lf - ?hf) ranged from 210 × 10- 8 to 720 × 10- 8 m3 kg- 1, suggesting the presence of abundant ultrafine magnetic grains. High-temperature magnetization (M-T) identified the magnetic carriers as maghemite and magnetite with a Curie point (Tc) at about 230 °C and 580 °C, respectively. XRD patterns showed that the gibbsite and hematite were main clay minerals in these highly weathered soils. HRTEM/EDX analysis showed that the pedogenic nano-scale magnetite/maghemite were responsible for the high magnetic susceptibility value of the soil. These particles varied from 20 to 100 nm in size and exhibited well crystalline nanoparticles. Magnetic enhancement in the soil profile was due to increased concentration of pedogenic superparamagnetic (SP) ferrimagnetic minerals upon pedogenesis. This study provided a strong evidence for the evolution of pedogenic magnetic minerals in the soils formed on non-magnetic parent materials. The identification in magnetic properties and mineralogy of the highly magnetic soils has significance for pedoenvironmental implications.

Lu, S. G.; Chen, D. J.; Wang, S. Y.; Liu, Y. D.

2012-02-01

25

On the acidity of saponite materials: a combined HRTEM, FTIR, and solid-state NMR study.  

PubMed

Acid clays were prepared by exchanging a synthetic saponite in HCl solutions of different concentration (0.01 and 1M, respectively). A combined experimental approach (XRD, HRTEM, N2 physisorption, solid-state MAS NMR, and TGA) was used to investigate on the structural, morphological, and textural features of the samples treated under mild and strong acid conditions. FTIR spectroscopy of adsorbed probe molecules with different basicity (e.g., CO and NH3) was used to monitor the surface acid properties and acid site distribution. XRD and SS-MAS NMR indicated that the activation under mild acid conditions does not alter the clay structure, while a deep modification of the saponite framework occurred after ion exchange in 1 M HCl solution. The presence of porous amorphous silica phase after treatment under strong acid conditions was confirmed by TEM inspection augmented by SS-MAS NMR and FTIR spectroscopy. N2 and Ar physisorption measurements suggested that cavitation phenomena occurred in saponite structure. N2 physisorption confirmed that the porosity and surface area of the samples are strongly modified upon strong acid treatment. FTIR spectroscopy of adsorbed NH3 pointed out that the H-exchange in mild conditions increased the number of surface Brønsted acid sites. Conversely, these sites are significantly depleted after treatment under strong acid conditions. The use of CO as a FTIR probe molecule, which is applied for the first time to study synthetic acid clays, allowed to monitor distribution and strength of Brønsted acid sites, whose acidity is similar to that of strong acid zeolites. The Al-OH sites with medium acidity are also found in acid-activated saponites. The distribution of strong and medium acid sites is strictly dependent on the acid conditions adopted. PMID:18251562

Bisio, C; Gatti, G; Boccaleri, E; Marchese, L; Bertinetti, L; Coluccia, S

2008-02-06

26

Advantages of aberration correction for HRTEM investigation of complex layer compounds.  

PubMed

Aberration-corrected high-resolution transmission electron microscopy (HRTEM) has been applied to resolve the atomic structure of a complex layered crystal, (PbS)(1.14)NbS(2), which comprises a high density of incommensurate interfaces. The strong suppression of image delocalization and the favourable contrast transfer under negative C(s) imaging (NCSI) conditions have been exploited for obtaining HRTEM images which directly reveal the projected crystal structure and allow to study lattice imperfections, like stacking disorder and layer undulations, with atomic scale resolution. The advantages of aberration-corrected HRTEM over conventional HRTEM are demonstrated by direct comparison of experimental images and computer simulations. PMID:20500393

Spiecker, E; Garbrecht, M; Jäger, W; Tillmann, K

2010-03-01

27

HRTEM and EELS investigation of functionalized carbon nanotubes  

NASA Astrophysics Data System (ADS)

We have successfully resolved and visualized the structure of some chemically functionalized carbon nanotubes (CNTs) using high-resolution transmission electron microscopy (HRTEM) and electron energy loss spectroscopy (EELS). To represent the chemically modified CNT, we selected three systems. The first system is oxidized and surface thiolated MWCNT, the second system is Dy3N@C80 peapods prepared by depositing trimetal nitride fullerenes into SWCNT. The formed structure is the Dy3N@C80@SWCNT. The third system is the conventional C60@SWCNT fullerene peapods, fluorinated by xenon difluoride (XeF2) up to 18% of F. We achieved detection of very low amount (0.6%) of sulfur and proved covalent bonding onto MWCNT surface. We present EELS imaging of the separated metal clusters inside endohedral metallofullerene peapod bundles and in the fluorinated C60 peapods we show homogeneous fluorination across the whole surface.

?ech, J.; Kalbá?, M.; Curran, S. A.; Zhang, D.; Dettlaff-Weglikowska, U.; Dunsch, L.; Yang, S.; Roth, S.

2007-03-01

28

Comparative investigation of NiO nano- and microstructures for structural, optical and magnetic properties  

NASA Astrophysics Data System (ADS)

Nickel oxide (NiO) nano- and microstructures were synthesized by the microwave combustion method (MCM) and the conventional combustion method (CCM) using urea as the fuel. The as-synthesized NiO powders were characterized by X-ray powder diffraction (XRD), high resolution scanning electron microscopy (HR-SEM), high resolution transmission electron microscopy (HR-TEM), energy dispersive X-ray analysis (EDX), diffuse reflectance spectroscopy (DRS), photoluminescence (PL) spectroscopy, Brunauer-Emmett-Teller (BET) analysis and vibrating sample magnetometer (VSM) analysis. The XRD results confirmed the formation of cubic phase NiO. The formation of NiO nano- and microstructures were confirmed by HR-SEM and HR-TEM and their possible formation mechanisms were also proposed. The optical absorption and photoluminescence emissions were determined by DRS and PL spectra respectively. The band gap was measured using the Kubelka-Munk model and it shows 3.36 eV for NiO (MCM) and 2.70 eV for NiO (CCM). The magnetic properties of the synthesized NiO nano- and microstructures were investigated with a vibrating sample magnetometer (VSM) and their hysteresis loops were obtained at room temperature. The relatively high saturation magnetization (21.22 emu/g) of NiO-MCM shows that it is ferromagnetic and low saturation magnetization (7.43 emu/g) of NiO-CCM confirms the superparamagnetic behavior.

Manikandan, A.; Judith Vijaya, J.; John Kennedy, L.

2013-03-01

29

Structural, optical and magnetic properties of porous alpha-Fe2O3 nanostructures prepared by rapid combustion method.  

PubMed

Porous iron oxide (alpha-Fe2O3) nanoparticles were synthesized by the microwave combustion method (MCM) using urea as the fuel. For the purpose of comparison, it was also prepared using the conventional combustion method (CCM). The as-synthesized porous alpha-Fe2O3 nanoparticles were characterized by X-ray powder diffraction (XRD), high resolution scanning electron microscopy (HR-SEM), high resolution transmission electron microscopy (HR-TEM), energy dispersive X-ray analysis (EDX), diffuse reflectance spectroscopy (DRS), Brunauer-Emmett-Teller (BET) analysis and vibrating sample magnetometer (VSM) analysis. The XRD results confirmed the formation of rhombohedral alpha-Fe2O3 phase. The formation of alpha-Fe2O3 nanoparticles was confirmed by HR-SEM and HR-TEM, and their possible formation mechanisms were also proposed. The optical absorption and the band gap were determined by DRS spectra. The surface area was derived from the nitrogen adsorption-desorption isotherms using BET analysis. The magnetic properties of the synthesized alpha-Fe2O3 were investigated with vibrating sample magnetometer (VSM) and their hysteresis loops were obtained. Both the prepared samples show ferromagnetic behavior with hysteresis curve at room temperature. The relatively high saturation magnetization (65.23 emu/g) of alpha-Fe2O3-MCM suggests that this method is suitable for preparing high-quality nanocrystalline magnetic alpha-Fe2O3 for practical applications. PMID:23763190

Manikandan, A; Vijaya, J Judith; Kennedy, L John

2013-04-01

30

Structural, morphological, and magnetic study of nanocrystalline cobalt-copper powders synthesized by the polyol process  

SciTech Connect

Nanocrystalline Co{sub {ital x}}Cu{sub 100{minus}{ital x}}(4{le}{ital x}{le}49 at.%) powders were prepared by the reduction of metal acetates in a polyol. The structure of powders was characterized by x-ray diffraction (XRD), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), extended x-ray absorption fine structure (EXAFS) spectroscopy, solid-state nuclear magnetic resonance (NMR) spectroscopy, and vibrating sample magnetometry (VSM). As-synthesized powders were composites consisting of nanoscale crystallites of face-centered-cubic (fcc) Cu and metastable face-centered cubic (fcc) Co. Complementary results of XRD, HRTEM, EXAFS, NMR, and VSM confirmed that there was no metastable alloying between Co and Cu. The NMR data also revealed that there was some hexagonal-closed-packed (hcp) Co in the samples. The powders were agglomerated, and consisted of aggregates of nanoscale crystallites of Co and Cu. Upon annealing, the powders with low Co contents showed an increase in both saturation magnetization and coercivity with increasing temperature. The results suggested that during preparation the nucleation of Cu occurred first, and the Cu crystallites served as nuclei for the formation of Co.

Chow, G.M.; Kurihara, L.K. [Laboratory for Molecular Interfacial Interactions, Center for Bio/Molecular Science and Engineering, Naval Research Laboratory, Washington, D.C. 20375 (United States); Kemner, K.M. [Condensed Matter and Radiation Division, Naval Research Laboratory, Washington, D.C. 20375 (United States); Schoen, P.E. [Laboratory for Molecular Interfacial Interactions, Center for Bio/Molecular Science and Engineering, Naval Research Laboratory, Washington, D.C. 20375 (United States); Elam, W.T. [Condensed Matter and Radiation Division, Naval Research Laboratory, Washington, D.C. 20375 (United States); Ervin, A. [Chemistry Division, Naval Research Laboratory, Washington, D.C. 20375 (United States); Keller, S.; Zhang, Y.D.; Budnick, J. [Department of Physics, University of Connecticut, Storrs, Connecticut 06269 (United States); Ambrose, T. [Department of Physics, Johns Hopkins University, Baltimore, Maryland 21218 (United States)

1995-06-01

31

Magnetic properties of nanosized Mg0.5Mn0.5(RE)0.1Fe1.9O4 ferrites synthesized by glycol-thermal method  

NASA Astrophysics Data System (ADS)

Nanosized Mg0.5Mn0.5(RE)0.1Fe1.9O4 ferrites, where RE are the rare earth elements, have been synthesized by the glycol-thermal method from pure metal chlorides. The as-prepared samples in the form of powders were characterized by X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM). The XRD and HRTEM data show formation of the single-phase cubic spinel structure. The grain sizes are found in the range 9-15 nm. Magnetic properties of the as-prepared samples were obtained at room temperature by 57Fe-Mössbauer spectroscopy and by a vibrating sample magnetometer. The distributions of Fe3+ ions were also deduced from Mössbauer measurements. The variations of grain size, lattice parameter, coercive field, magnetizations are presented as a function of the number of (RE)3+ 4f electrons. Our results show the evidence for superparamagnetic behavior of the rare earth substituted compounds. The highest grain size and magnetizations are obtained for the Gd substituted sample. We also find strong correlation of the saturation magnetizations, grain sizes and microstrains with the de Gennes factor.

Abdallah, Hafiz M. I.; Moyo, T.; Msomi, J. Z.

2013-04-01

32

Electrodeposition and magnetic properties of ternary Fe-Co-Ni alloy nanowire arrays with high squareness ratio  

NASA Astrophysics Data System (ADS)

Highly-ordered ternary Fe-Co-Ni alloy nanowire arrays with diameters of about 50 nm have been fabricated by alternating current (AC) electrodeposition into the nanochannels of porous anodic aluminum oxide templates. SEM and TEM results indicate that the alloy nanowires are highly ordered. XRD and HRTEM results show that the ternary FeCoNi alloy nanowires are polycrystalline, with HCP-FCC dual phase structure. Magnetic measurements demonstrate that the ternary alloy nanowire arrays have an obvious magnetic anisotropy with an easy magnetization direction being parallel to the nanowire arrays. Along the easy magnetization direction, the coercivity (H c ) and squareness ratio (S) increase as the annealing temperature increases, and reach a maximum level (H c = 1337 Oe, S = 0.96) at 300 °C.

Fu, P.; Chen, G.; Xu, Y.; Cai, P.; Wang, X. H.

2012-09-01

33

XRD investigation of binary alloy solidification.  

PubMed

The solidification of two binary alloys, In-10Sn and Sn-13Pb, has been investigated by X-ray diffractometry (XRD) at high temperatures. The high-temperature X-ray camera, which was mounted on a diffractometer, had a sample holder suitable for molten metals and operated in a controlled Ar atmosphere. Melts were cooled down slowly and XRD spectra were recorded step by step in order to monitor the structural evolution of the liquid prior to and during solidification. Temperature was kept constant while the XRD data were collected. The radial distribution functions (RDFs) were then determined from the spectra for each temperature. Experiments showed that atomic clusters form in the melt immediately before the appearance of the first solid. The experimental problems encountered in real-time monitoring of phase transformations involving liquid metals were looked at. To avoid convective motion in the liquid and to arrive at the best possible experimental conditions, we discussed the possibility of carrying out these studies at the reduced gravity found on the International Space Station. PMID:19426334

Montanari, Roberto; Gauzzi, Franco

2009-04-01

34

Si-SiO sub 2 Interfaces: A HRTEM (High Resolution Transmission Electron Microscopy) Study.  

National Technical Information Service (NTIS)

A High Resolution Transmission Electron Microscopy (HRTEM) study of the Si-SiO sub 2 interfaces is reported here. The study has been carried out on the thermal oxidation of (1) Si and (2) Ge implanted Si. Evolution of the Si-SiO sub 2 interface with oxide...

N. M. Ravindra D. Fathy O. W. Holland J. Narayan

1987-01-01

35

XRD, TEM, and thermal analysis of Arizona Ca-montmorillonites modified with didodecyldimethylammonium bromide.  

PubMed

An Arizona SAz-2 calcium montmorillonite was modified by a typical dialkyl cationic surfactant (didodecyldimethylammonium bromide, abbreviated to DDDMA) through direct ion exchange. The obtained organoclays were characterized by X-ray diffraction (XRD), high-resolution transmission electron microscopy (HR-TEM), high-resolution thermogravimetric analysis (HR-TG), and infrared emission spectroscopy (IES). The intercalation of surfactants greatly increased the basal spacing of the interlayers and the conformation arrangement of the loaded surfactant were assessed based on the XRD and TEM measurements. This work shows that the dialkyl surfactant can be directly intercalated into the montmorillonite without first undergoing Na(+) exchange. Moreover, the thermal stability of organoclays and the different arrangements of the surfactant molecules intercalated in the SAz-2 Ca-montmorillonite were determined by a combination of TG and IES techniques. The detailed conformational ordering of different intercalated surfactants under different conditions was also studied. The surfactant molecule DDDMA has proved to be thermally stable even at 400°C which indicates that the prepared organoclay is stable to significantly high temperatures. This study offers new insights into the structure and thermal stabilities of SAz-2 Ca-montmorillonite modified with DDDMA. The experimental results also confirm the potential applications of organic SAz-2 Ca-montmorillonites as adsorbents and polymer-clay nanocomposites. PMID:23932082

Sun, Zhiming; Park, Yuri; Zheng, Shuilin; Ayoko, Godwin A; Frost, Ray L

2013-07-25

36

Shape-controlled synthesis and magnetic properties of FePt nanocubes  

NASA Astrophysics Data System (ADS)

In this research, FePt nanocubes, octapods and polyhedra were successfully prepared with Mo(Co)6 as a reducing agent. The chemically-synthesized cubic FePt nanoparticles could easily be self-assembled into an oriented nanoarray. These ordered nanomagnet arrays were expected to achieve high-density information storage and high performance in permanent magnets. The self-assembed FePt nanocubes were chemically disordered with a face centered cubic (fcc) structure. During annealing, these particles changed to a face-centered tetragonal (fct) order. The phase structure, the micro-morphology and magnetic properties were characterized by using X-ray diffraction (XRD), High resolution transmission electron microscope (HRTEM), Scanning electron microscope (SEM) and vibrating sample magnetometer (VSM).

Zhou, Mingge; Li, Wei; Zhu, Minggang; Zhou, Dong; Hou, Yanglong

2013-08-01

37

Pore Structure and Fractal Characteristics of Activated Carbon Fibers Characterized by Using HRTEM  

Microsoft Academic Search

The pore microstructures in two viscouse rayon-based ACF samples were characterized by nitrogen adsorption and HRTEM. For TEM, a two-dimensional fast Fourier transform (FFT) of the original TEM images was performed, and pores in different size ranges were extracted by the inverse FFT (IFFT) operation. The surface fractal dimensions of the samples were evaluated by using both N2 adsorption and

Zheng-Hong Huang; Feiyu Kang; Wen Lai Huang; Jun-Bing Yang; Kai-Ming Liang; Meng-Long Cui; Zhiying Cheng

2002-01-01

38

HRTEM study of ion beam irradiation induced amorphization in ceramic materials  

SciTech Connect

Computer analysis indicates that amorphization occurs directly within the displacement cascade in Ca{sub 2}La{sub 8}(SiO{sub 4}){sub 6}O{sub 2}. The lack of discrete amorphous cascade domains in the image in irradiated {beta}-SiC indicates that amorphization occurs by point defect buildup in {beta}-SiC. The HRTEM image of UO{sub 2} contains no visible damage even after a very high ion dose at 20 K.

Wang, L.M.; Ewing, R.C. [Univ. of New Mexico, Albuquerque, NM (United States). Dept. of Earth and Planetary Sciences; Weber, W.J. [Pacific Northwest Lab., Richland, WA (United States)

1995-08-01

39

Si-SiO/sub 2/ interfaces: A HRTEM (High Resolution Transmission Electron Microscopy) study  

SciTech Connect

A High Resolution Transmission Electron Microscopy (HRTEM) study of the Si-SiO/sub 2/ interfaces is reported here. The study has been carried out on the thermal oxidation of (1) Si and (2) Ge implanted Si. Evolution of the Si-SiO/sub 2/ interface with oxide thickness and the presence of small amounts of Ge, i.e., one mono-layer at the interface and its influence on the oxidation kinetics is discussed.

Ravindra, N.M.; Fathy, D.; Holland, O.W.; Narayan, J.

1987-01-01

40

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

41

XRD and HREM studies of nanocrystalline Cu and Pd.  

National Technical Information Service (NTIS)

Consolidated powders of nanocrystalline Cu and Pd have been studied by x-ray diffraction (XRD) and high resolution electron microscopy (HREM) as part of an investigation of the mechanical behavior of nanocrystalline pure metals. XRD line broadening measur...

G. W. Nieman J. R. Weertman R. W. Siegel

1990-01-01

42

Lipase immobilized on magnetic multi-walled carbon nanotubes.  

PubMed

Magnetic iron oxide nanoparticles were loaded onto the surfaces of multiwalled carbon nanotubes (MWNTs) by the impregnation method. The obtained magnetic nanotubes were characterized with high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), and X-ray diffraction (XRD). Yarrowia lipolytica lipase was covalently immobilized on the magnetic MWNTs (M-MWNTs). M-MWNT-lipase was characterized with XPS spectra and XRD patterns. The structural change of the immobilized lipase was analyzed through circular dichroism spectroscopy. M-MWNT-lipase was utilized for the resolution of (R, S)-1-phenyl ethanol in the organic solvent of heptane. Compared to the native lipase, the lipase immobilized on M-MWNTs has significantly improved its enzymatic activity for the resolution of (R, S)-1-phenyl ethanol in heptane. M-MWNT-lipase can be easily recovered after catalysis. In addition, the effect of sonication time on the catalytic activity was also investigated. It is found that, up to 30min sonication, the catalysis by M-MWNT-lipase is almost not affected. While, the catalytic activity of the native lipase is decreased with sonication time. PMID:22115533

Tan, Huishan; Feng, Wei; Ji, Peijun

2011-10-29

43

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.

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

2008-01-01

44

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

PubMed

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 MoS(2) 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 WS(2) 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

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

2008-10-06

45

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

SciTech Connect

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 intergrowths. Species of microfibrous opal identified by HRTEM in early-formed opal-CT chert include length-slow opal-C and unidimensionally disordered length-slow opal-CT ({open_quotes}lussatite{close_quotes}). These fibers often display a microstructure characterized by an aperiodic distribution of highly strained domains that separate ordered domains located at discrete positions along the direction of the fiber axes. Microfibrous opal occurs as several types of fiber-aggregation forms. TEM revealed that the siliceous matrix in later-formed opal-CT porcelanite consists of equidimensional, nanometer-size opal-CT crystallites and lussatite fibers. Pseudo-orthorhombic tridymite (PO-2) was identified by HRTEM in one sample of opal-CT porcelanite. Burial diagenesis of chert and porcelanite results in the precipitation of opal-C and the epitaxial growth of opal-C domains on opal-CT substrates. Diagenetic maturation of lussatite was identified by TEM in banded opal-CT-quartz chert to occur as a result of solid-state ordering. The primary diagenetic silica phase transformations between noncrystalline opal, microcrystalline opal, and quartz occur predominantly by a series of dissolution-precipitation reactions. However, TEM showed that in banded opal-CT-quartz chert, the epitaxial growth of quartz on microfibrous opal enhances the rate of silica diagenesis.

Cady, S.L. [NASA Ames Research Center, Moffett Field, CA (United States); Wenk, H.R. [Univ. of California, Berkeley, CA (United States); Downing, K.H. [Lawrence Berkeley National Lab., CA (United States)

1996-11-01

46

Phase transition in Bi-based superconductive oxides examined by HRTEM  

Microsoft Academic Search

A Bi-Sr-Ca-Cu-O oxide rapidly cooled from 900°C, at which temperature the specimen is partially molten, consists of a major component of the (2201)-phase and a minor component of the impurity phases. (Ca1-zSrz)3Cu5Oy (z=0.46) and (Ca1-x, Srz)2CuO3 (z=0.09). The grains of both phases have a columnar shape. High-resolution transmission electron microscopy (HRTEM) shows that thin plates of the (2201)-phase are irregularly

Shigeo Horiuchi; Kaoru Shoda; Xiao-Jing Wu; Hiroshi Nozaki; Masayuki Tsutsumi

1990-01-01

47

First observation of In(x)Ga(1-x)As quantum dots in GaP by spherical-aberration-corrected HRTEM in comparison with ADF-STEM and conventional HRTEM.  

PubMed

In(x)Ga(1-x)As quantum dots in GaP(100) crystals prepared by the OMVPE technique are observed along the [011] direction with a newly developed 200-kV spherical aberration(Cs)-corrected HRTEM, a 200-kV annular dark-field (ADF)-STEM, and a 200-kV conventional HRTEM equipped with a thermal field-emission gun. The dots are 6-10 nm in size and strongly strained due to the misfit of about 9% with the GaP substrate and GaP cap layer. All of the cross-sectional high-resolution electron micrographs show dumbbell images of Ga and P atomic columns separated by 0.136 nm in well-oriented and perfect GaP areas, but the interpretable images are limited to those taken with the Cs-corrected HRTEM and ADF-STEM with Fourier filtering of the images. The Cs-corrected HRTEM and ADF-STEM are comparable from the viewpoint of interpretable resolution. A detailed comparison between the Cs-corrected HRTEM images and the simulated ones with electron incidence tilted by 1 degree to 5 degrees from the [011] zone axis gives information on local lattice bending in the dots from the images around 0.1 nm resolution. This becomes one of the useful techniques newly available from electron microscopy with sub-angstrom resolution. PMID:15306078

Tanaka, Nobuo; Yamasaki, Jun; Fuchi, Shingo; Takeda, Yoshikazu

2004-02-01

48

HRTEM observations of modulated structures in Ti-Pd-Cr [beta][sub 2] alloys  

SciTech Connect

Conventional and high-resolution transmission electron microscopy (HRTEM) and electron diffraction (ED) have been used to examine a series of Ti[sub 50]Pd[sub 50-x]Cr[sub x][beta][sub 2] (B2, CsCl-type crystal structure) alloys with x between 6 and 10 at.% in order to determine the nature of the modulated structures that develop on cooling. The ED and HRTEM results reveal that the modulation periodicity (inverse of the satellite spacing) varies from three (110)[sub B2] planes in the 6 at.% Cr alloy to four (110)[sub B2] planes for the 10 at.% alloy. Over the same composition range, the monoclinic angle'' (defined between (200)[sub B2]and (020)[sub B2] reflections) is found to increase linearly from 88 to 90[degrees]. It is suggested that these effects are associated with the substitution of Cr for Pd that gives rise to an electronically driven (110)[sub q]<110>[sub [var epsilon

Schwartz, A.J.; Tanner, L.E.

1992-08-01

49

Quantitative structure analysis of L10-ordered FePt nanoparticles by HRTEM  

NASA Astrophysics Data System (ADS)

We present a quantitative analysis of the structure and morphology of FePt nanoparticles from the gas phase and a statistical evaluation of the fraction of L10-ordered particles using high-resolution transmission electron microscopy (HRTEM) combined with computer simulations. The particles are generated via inert gas condensation using DC sputtering and annealed during the flight. The nucleation pressure and annealing temperature were varied in the range 0.5 mbar ?p?1.0 mbar and 873 K ?T?1273 K, respectively. We observe a decrease of the number of multiply twinned particles with increasing nucleation pressure. Furthermore, at p=1.0 mbar and T=1273 K, about 31% of the particles were found to be simply twinned, and 27% exhibit a single-crystalline structure. The formation of the ordered L10 phase in FePt nanoparticles prepared under these conditions was observed. The number of particles, which had transformed into the L10-state, was evaluated by statistical counting using HRTEM in combination with contrast simulations. We have derived criteria for the visibility of both the L10 super structure and the disordered face-centered cubic (FCC) structure depending on the orientation of the particles. Based upon these criteria, it is shown that 36% of the FePt nanoparticles are in the L10-ordered state.

Dmitrieva, O.; Rellinghaus, B.; Kästner, J.; Dumpich, G.

2007-05-01

50

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

51

Structural, magnetic, and magnetoresistive properties of electrodeposited Ni5Zn21 alloy nanowires.  

PubMed

Ni5Zn21 alloy nanowires were fabricated through template-assisted electrochemical deposition method. The morphology and microstructures of as-deposited nanowires were determined by field-emission scanning electron microscope (FE-SEM), X-ray diffraction (XRD), high-resolution transmission electron microscope (HRTEM), electron diffraction (ED), and electron probe microanalysis (EPMA). The accurate composition was measured via induced coupling plasma atomic emission spectroscopy. SEM results show that Ni5Zn21 nanowires are deposited in most of the nanopores of the template, and they are continuous and dense throughout the whole length. The XRD result demonstrates that the nanowires are mainly composed of a cubic gamma phase Ni5Zn21 alloy, but there also exists a trace of Zn-rich eta phase. HRTEM and ED reveal that the alloy nanowires are polycrystalline with the crystallite size of several tens of nanometers. EPMA of a single nanowire illustrates that there exist Ni-rich microzones in as-deposited nanowires. Subsequent magnetic measurements of the array also confirmed the existence of them. In addition, it can be further inferred that the shape of Ni-rich microzones is probably barlike or disklike, from the anisotropy of zero field cooling/field cooling (ZFC/FC) curves as well as the vortex magnetization behavior of the Ni5Zn21 nanowire array. The low-temperature magnetoresistance of the Ni5Zn21 nanowire array was also measured. Giant magnetoresistance instead of anisotropic magnetoresistance is suggested to be responsible for contributing to the magnetoresistance. PMID:17034190

Liu, Lifeng; Tian, Huanfang; Xie, Sishen; Zhou, Weiya; Mu, Shicheng; Song, Li; Liu, Dongfang; Luo, Shudong; Zhang, Zengxing; Xiang, Yanjuan; Zhao, Xiaowei; Ma, Wenjun; Shen, Jun; Li, Jianqi; Wang, Chaoying; Wang, Gang

2006-10-19

52

Quantitative atom column position analysis at the incommensurate interfaces of a (PbS)(1.14)NbS(2) misfit layered compound with aberration-corrected HRTEM.  

PubMed

Aberration-corrected HRTEM is applied to explore the potential of NCSI contrast imaging to quantitatively analyse the complex atomic structure of misfit layered compounds and their incommensurate interfaces. Using the (PbS)(1.14)NbS(2) misfit layered compound as a model system it is shown that atom column position analyses at the incommensurate interfaces can be performed with precisions reaching a statistical accuracy of ±6pm. The procedure adopted for these studies compares experimental images taken from compound regions free of defects and interface modulations with a structure model derived from XRD experiments and with multi-slice image simulations for the corresponding NCSI contrast conditions used. The high precision achievable in such experiments is confirmed by a detailed quantitative analysis of the atom column positions at the incommensurate interfaces, proving a tetragonal distortion of the monochalcogenide sublattice. PMID:21333862

Garbrecht, M; Spiecker, E; Tillmann, K; Jäger, W

2010-11-30

53

A pattern recognition method for lattice distortion measurement from HRTEM images.  

PubMed

The idea of the method is to analyse a crystal lattice by creating a grid of quadrilaterals corresponding to repeated cells that are visible in the image. This approach combines image processing elements with a continuum field theory, to create a distortion-independent similarity measure that is used to select the most appropriate among possible lattice configurations. Subsequently, displacement and distortion fields are computed from individual cell positions. The method allows one to obtain these fields even for images where a periodic cell does not necessarily appear as a single dot of intensity in a high-resolution transmission electron microscopy (HRTEM) image, which results in a lower accuracy of commonly used approaches, namely geometric phase and peak finding. The results obtained from this method are verified quantitatively by comparison with known distortion tensor distributions and Burgers vector values on both simulated and real images. PMID:22044267

Przyby?a, P

2011-11-01

54

Magnetic properties of nanometric Fe-based particles obtained by laser-driven pyrolysis  

NASA Astrophysics Data System (ADS)

Fe-based nanoparticles were prepared by laser pyrolysis method using a cross-flow reactor in which the CO2 laser radiation orthogonally crosses with the stream of Fe(CO)5, C2H2, and C2H4 gases. The as-synthesised powder was characterised by HRTEM, XRD, Mössbauer spectroscopy, and low- and high-temperature magnetic measurements. The as-synthesised powder consisted of ?-Fe and Fe3O4/?-Fe2O3 nanoparticles embedded in a pyrolytic carbon matrix. The XRD pattern of the sample exhibited broad peaks. The crystallite size dXRD was estimated using the Scherrer formula and it was 1.8 nm for ?-Fe and 1.6 nm for pyrolytic carbon. The as-synthesised nanopowder was superparamagnetic. The blocking temperature was determined from the maximum of the ZFC curve and it was 32 K. After the sample had been cooled down to 4 K, the Mössbauer Lamb factor f strongly increased.

David, B.; Pizúrová, N.; Schneeweiss, O.; Klementová, M.; Šantavá, E.; Dumitrache, F.; Alexandrescu, R.; Morjan, I.

2007-05-01

55

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

56

Dehydration of Ferrous Sulfates Monitored by XRD - Implications for CHEMIN  

Microsoft Academic Search

We have studied the stability of a number of ferrous sulfates and carried out XRD measurements to track their stability in a controlled environment. We report on the stability of and breakdown products of melanterite, rozenite, szomolonokite, halotrichite and romerite.

A. J. Brown; D. L. Bish; J. L. Bishop

2008-01-01

57

Dehydration of Ferrous Sulfates Monitored by XRD - Implications for CHEMIN  

NASA Astrophysics Data System (ADS)

We have studied the stability of a number of ferrous sulfates and carried out XRD measurements to track their stability in a controlled environment. We report on the stability of and breakdown products of melanterite, rozenite, szomolonokite, halotrichite and romerite.

Brown, A. J.; Bish, D. L.; Bishop, J. L.

2008-03-01

58

XRD studies of ?-chitin from squid pen with calcium solvent  

Microsoft Academic Search

The crystalline structure of ?-chitin from squid pen was investigated by X-ray diffraction (XRD). The purified ?-chitin was prepared from bigfin reefsquid pen. ?-Chitin was treated with saturated calcium chloride dihydrate\\/alchohol (CaCl2·2H2O\\/MeOH) solvent system at different conditions for XRD studies. The change of crystallinity of ?-chitin from squid pen was studied by using the fiber photographs on imaging plates. The

H. Nagahama; T. Higuchi; R. Jayakumar; T. Furuike; H. Tamura

2008-01-01

59

XRD and Mössbauer spectroscopy study of Ho doped BiFeO3  

NASA Astrophysics Data System (ADS)

The structural and magnetic properties of Ho substituted BiFeO3 (BHFO) have been investigated using 57Fe Mössbauer spectroscopy and X-Ray diffraction (XRD) as a function of temperature. The Mössbauer spectrum obtained at room temperature for the as-synthesized BHFO sample exhibits broadened features due to the hyperfine field distributions related to the local variation of the neighbourhood of Fe and the magnetic hyperfine splitting patterns are indicative of magnetic ordering, mostly probably screwed or slightly antiferromagnetic. The spectrum was fitted with two superimposed asymmetric sextets, with similar hyperfine magnetic fields of Bhf1 = 48.0(1) T and Bhf2 = 49.0(1) T, corresponding to rhombohedral BFO. The hyperfine fields of the magnetic components decreased systematically with increasing temperature to a `field distribution' just below the Néel temperature, TN ~ 600 K. At temperatures above 600 K, the spectral line associated with the Bi25FeO40 impurity phase dominates the spectra. This phase is confirmed by XRD measurements. From the temperature dependence of the site populations of the spectral components an average Debye temperature of ? D = 240(80) K has been estimated.

Ncube, M.; Naidoo, D.; Bharuth-Ram, K.; Billing, D.; Masenda, H.; Sahu, D. R.; Roul, B. K.; Erasmus, R. M.

2013-04-01

60

Simple XRD algorithm for direct determination of cotton crystallinity  

NASA Astrophysics Data System (ADS)

Traditionally, XRD had been used to study the crystalline structure of cotton celluloses. Despite considerable efforts in developing the curve-fitting protocol to evaluate the crystallinity index (CI), in its present state, XRD measurement can only provide a qualitative or semi-quantitative assessment of the amounts of crystalline and amorphous cellulosic components in a sample. The greatest barrier to establish quantitative XRD is the lack of appropriate cellulose standards needed to calibrate the measurements. In practical, samples with known CIs are very difficult to be prepared or determined. As an approach, we might assign the samples with reported CIs from FT-IR procedure, in which the threeband ratios were first calculated and then were converted into CIs within a large and diversified pool of cotton fibers. This study reports the development of simple XRD algorithm, over time-consuming and subjective curve-fitting process, for direct determination of cotton cellulose CI by correlating XRD with the FT-IR CI references.

Liu, Yongliang; Thibodeaux, Devron; Gamble, Gary; Bauer, Philip; VanDerveer, Don

2012-05-01

61

29Si MAS NMR, XRD and FESEM studies of rice husk silica for the synthesis of zeolites  

Microsoft Academic Search

We have used rice husk ash as a silica source for the synthesis of zeolites. Amorphous silica is a highly reactive silicon source, but not all silica which is amorphous to XRD is equally suitable. The local structure of amorphous silica was investigated by 29Si magic-angle spinning nuclear magnetic resonance (MAS NMR) and field emission scanning electron microscopy (FESEM) in

Halimaton Hamdan; Mohd Nazlan Mohd Muhid; Salasiah Endud; Endang Listiorini; Zainab Ramli

1997-01-01

62

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

63

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

64

Structural and chemical characterization of Yb2O3-ZrO2 system by HAADF-STEM and HRTEM.  

PubMed

ZrO2:Yb3+ nanocrystalline phosphors with high concentrations of ytterbium ions were prepared using the sol-gel method. X-ray diffraction, high-angle annular-dark-field scanning transmission electron microscopy (HAADF-STEM), energy dispersive X-ray spectroscopy, and high-resolution transmission electron microscopy (HRTEM) were used to characterize the nanocrystalline phosphors annealed at 1000 degrees C. Unit-cell distortion and changes in the crystalline structure of the monoclinic zirconia to tetragonal zirconia, and subsequently cubic zirconia, were observed with increased Yb concentration. Yb ions were randomly distributed into the lattice of the crystalline structure. No segregation of Yb2O3 phase was observed. The substitution of Zr atoms by Yb atoms on different crystalline phases was confirmed by the experimental results and theoretical simulations of HRTEM and HAADF-STEM. PMID:19144257

Angeles-Chavez, C; Salas, P; Díaz-Torres, L A; de la Rosa, E; Esparza, R; Perez, R

2009-02-01

65

TEM, HRTEM, electron holography and electron tomography studies of gamma' and gamma'' nanoparticles in Inconel 718 superalloy.  

PubMed

The aim of the study was the identification of gamma' and gamma'' strengthening precipitates in a commercial nickel-base superalloy Inconel 718 (Ni-19Fe-18Cr-5Nb-3Mo-1Ti-0.5Al-0.04C, wt %) using TEM dark-field, HRTEM, electron holography and electron tomography imaging. To identify gamma' and gamma'' nanoparticles unambiguously, a systematic analysis of experimental and theoretical diffraction patterns were performed. Using HRTEM method it was possible to analyse small areas of precipitates appearance. Electron holography and electron tomography techniques show new possibilities of visualization of gamma' and gamma'' nanoparticles. The analysis by means of different complementary TEM methods showed that gamma'' particles exhibit a shape of thin plates, while gamma' phase precipitates are almost spherical. PMID:19903242

Dubiel, B; Kruk, A; Stepniowska, E; Cempura, G; Geiger, D; Formanek, P; Hernandez, J; Midgley, P; Czyrska-Filemonowicz, A

2009-11-01

66

Mineralogical Transformation of Bioweathered Granitic Biotite, Studied by HRTEM: Evidence for a New Pathway in Lichen Activity  

Microsoft Academic Search

The question of whether clay minerals can be biogenically transformed as a result of lichen activity at the lichen-rock interface remains unresolved. We applied several microscopical and analytical techniques--scanning electron microscopy-back-scattered electron (SEM-BSE), energy dispersive spec- troscopy (EDS) and high-resolution transmission electron microscopy (HRTEM)--in an attempt to address this issue. Unaffected granitic biotite and bioweathered material from the granitic biotite

Jacek Wierzchos; CARMEN ASCASO

1998-01-01

67

XRD analysis and leachability of solidified phenol-cement mixtures  

Microsoft Academic Search

The microstructure and leachability of phenol from solidified phenol-Portland cement mixtures cured up to 6 months were investigated. Phenol was solidified with Type I Portland cement at concentrations of 0.5% and 2% by weight of the cement. XRD studies and pore fluid analyses indicate that phenol inhibits cement setting by reacting with the calcium hydroxide produced during the hydration of

C. Vipulanandan; S. Krishnan

1993-01-01

68

Quantitative XRD analysis of zirconia-toughened alumina ceramics  

Microsoft Academic Search

An equation is proposed to give, from XRD data, the tetragonal to monoclinic phase ratio of zirconia in a toughened alumina ceramic material. Using several X-ray wavelengths, with different depths of penetration, quantitative analyses of the tetragonal to monoclinic phase ratio of zirconia as a function of depth were performed, on an as-sintered sample as well as on treated specimens.

R. Fillit; R. P. Homerin; R. J. Schafer; R. H. Bruyas; R. F. Thevenot

1987-01-01

69

XRD Acquisition Parameters for Detection of Weak Peaks.  

National Technical Information Service (NTIS)

The use of high intensity x-ray sources provides opportunities as well as special problems in the detection of minor XRD peaks. Scattering contributions from slits along with other factors can become important and may interfere with the analysis. This fur...

P. W. Seabaugh D. B. Sullenger C. R. Hudgens M. C. Nichols D. R. Boehme

1989-01-01

70

Tailoring magnetic and photoluminescence properties in ZnS/ZnO core/shell nanostructures through Cr doping  

NASA Astrophysics Data System (ADS)

Work on doped inverted core/shell semiconductor structure and study of their magnetic and luminescence properties is very rare. We have successfully prepared core/shell (C/S) nanostructure of important semiconductors ZnS core/ZnO shell with doping of chromium in both core and shell regions for tailoring magnetic and luminescence properties. Cooperative exchange of pinned spins at the interface of core and shell magnetic regions lead to ferromagnetism in ZnS:Cr/ZnO:Cr C/S nanoparticles (NP) at room temperature. Ferromagnetic interaction enhances at low temperature. Growth of hexagonal ZnO shell on cubic ZnS NPs in coprepitous aqueous solution has been confirmed by XRD and HRTEM analysis. Substitutional transition metal Cr in ZnS core and/or ZnO shell region could induce magnetic moments, create spin ordering and pinning while on C/S interface and also domain alignment leading to different magnetic states in varied C/S architecture. Cr also induces blue photoluminescence in doped ZnS/ZnO C/S NPs thus paving a possibility of tailoring multifunctional properties in C/S semiconductors architecture.

Chawla, Santa; Sharma, Simmi; Kotnala, R. K.

2013-11-01

71

Zeolite-supported Ni and Mo catalysts for hydrotreatments. 2. HRTEM observations  

SciTech Connect

Calcined and sulfided Ni-Mo catalysts supported on ultrastable Y zeolite (USY), NaY zeolite, mordenite, and ZSM-5 were studied by high-resolution electron transmission microscopy (HRTEM) with selected-area electron diffraction (SAED) and energy-dispersive spectroscopy (EDS). Ni and Mo oxide aggregates were rarely observed in the USY-supported Ni-Mo catalyst, indicating that most of Ni and Mo may be incorporated into USY, e.g., supercavities and possibly sodalite cages. However, there were a large number of {alpha}-NiMoO{sub 4} aggregates of different particle sizes in NaY-, mordenite-, and ZSM-5-supported catalysts, and the mordenite-supported catalyst also contained MoO{sub 3} crystals. The {alpha}-NiMoO{sub 4} may be attached to the surface of substrates as individual particles or needle aggregates, it may be disseminated into mordenite particles, or it may even form an isolated sphere (in Ni-Mo/NaY) or a needle (in Ni-Mo/ZSM-5) aggregates. Thus, most of Ni and Mo in NaY-, mordenite-, and ZSM-5-supported catalysts preferentially formed aggregates, although some Mo may have been incorporated into NaY and ZSM-5. After sulfidation, small MoS{sub 2} aggregates containing some Ni were rarely but occasionally found on the surface of USY zeolite; however, there were a large number of such MoS{sub 2} aggregates on the surface of NaY. Separate and intergrown MoS{sub 2} and Ni sulfides aggregates were observed on the surface of mordenite and ZSM-5. The Ni sulfide might be identified by SAED and high-magnification images as troilite-like NiS and/or Ni{sub 9}S{sub 8}, but definitely not as NiS with millerite structure or Ni{sub 3}S{sub 2}. These results indicated that sulfidation does not extensively affect Ni and Mo that have been incorporated into the supercavity and/or sodalite cage of USY in calcined Ni-Mo/USY. The USY-supported Ni-Mo catalyst had a much higher hydrodesulfurization (HDS) activity than the other zeolite-supported catalysts.

Li, D.; Xu, H.; Guthrie, G.D. Jr.

2000-01-25

72

[Combined analyses of mixed urinary stones by XPS and XRD].  

PubMed

In order to seek the methods for the prevention and cure of urinary stones in Dongjiang valley in Guangdong province, the chemical constituents and morphology of six mixed urinary stones were analyzed by X-ray photoelectron spectroscopy (XPS) and X-ray powder diffraction (XRD). All of the six stones consisted of calcium oxalate monohydrate (COM), calcium oxalate dihydrate (COD) and hydroxyapatite. Two of them contained little ammonium magnesium phosphate. As increasing the amount of phosphate in urinary stones, the amount of COM decreased and that of COD increased, which indicated that the sediment of phosphates in the stones can inhibit the transformation from high energy COD to low energy COM. Combining XPS and XRD methods, the compositions and phases of urinary stones can be obtained accurately. PMID:12961905

Ouyang, Jian-ming

2003-04-01

73

Physical characterization of molybdenum oxycarbide catalyst; TEM, XRD and XPS  

Microsoft Academic Search

Controlled reduction of MoO3 can produce different phases of catalytic interest. One of these phases has been considered as being an oxycarbide of molybdenum. Various techniques mainly TEM but also XRD and others have been extensively used to understand the mechanism of formation and the structure of this oxycarbide. Its structure is reminiscent of the MoO3 structure as shown by

Pascale Delporte; Fre´de´ric Meunier; Cuong Pham-Huu; Philippe Vennegues; Marc J. Ledoux; Jean Guille

1995-01-01

74

Reactivity of some vanadium oxides: An EPR and XRD study  

Microsoft Academic Search

V2O5, VO2 and V2O3 fresh samples and at different times after purchase or preparation (aged samples) were investigated by chemical analysis, redox treatments, XRD and EPR. The ageing process through a reaction with water and oxygen slowly oxidize crystalline VO2 and V2O3, leading to a quasi-amorphous phase with bariandite structure (V10O24·12H2O). The role of water is the progressive demolition of

Manlio. Occhiuzzi; Dante Cordischi; Roberto Dragone

2005-01-01

75

Thermo XRD-analysis of two aged cement pastes  

Microsoft Academic Search

Summary Two hydrated and aged cement pastes from India (NCB), w\\/c=0.4, of a similar chemical composition but of a different specific surface and different strength (OPC, C-33 and C-43), hydrated at w\\/c=0.4 for 1 month, were studied by XRD after 1 year and 5-6 year ageing on contact with air. They were tested by static heating (SH) in fresh state,

E. T. Stepkowska; J. M. Blanes; A. Justo; M. A. Aviles; J. L. Perez-Rodriguez

2005-01-01

76

Quantitative XRD analysis of {110} twin density in biotic aragonites.  

PubMed

{110} Twin densities in biotic aragonite have been estimated quantitatively from the peak widths of specific reflections in powder X-ray diffraction (XRD) patterns, as well as direct confirmation of the twins using transmission electron microscopy (TEM). Influence of the twin density on the peak widths in the XRD pattern was simulated using DIFFaX program, regarding (110) twin as interstratification of two types of aragonite unit layers with mirrored relationship. The simulation suggested that the twin density can be estimated from the difference of the peak widths between 111 and 021, or between 221 and 211 reflections. Biotic aragonite in the crossed-lamellar microstructure (three species) and nacreous microstructure (four species) of molluscan shells, fish otoliths (two species), and a coral were investigated. The XRD analyses indicated that aragonite crystals in the crossed-lamellar microstructure of the three species contain high density of the twins, which is consistent with the TEM examination. On the other hand, aragonite in the nacre of the four species showed almost no difference of the peak widths between the paired reflections, indicating low twin densities. The results for the fish otoliths were varied between the species. Such variation of the twin density in biotic aragonites may reflect different schemes of crystal growth in biomineralization. PMID:22989562

Suzuki, Michio; Kim, Hyejin; Mukai, Hiroki; Nagasawa, Hiromichi; Kogure, Toshihiro

2012-09-16

77

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

78

Mössbauer, XRD and SEM studies on Kapoeta meteorite.  

NASA Astrophysics Data System (ADS)

Temperature dependent Mössbauer studies together with X-ray diffraction (XRD) and scanning electron microscopy (SEM) in conjunction with energy dispersive X-ray microanalysis have been performed on an old fall achondrite meteorite named Kapoeta. Pyroxene with a variable composition ranging from bronzite through ferrohypersthene with intermediate pigeonite has been identified as the only iron bearing mineral. The Mössbauer spectra show Fe2+ present in two different crystallographic sites M1 and M2. The population ratio Fe2+(M1)/Fe2+(M2) derived from the relative area of the subspectra reveals the degree of cation disorder.

Gismelseed, A. M.; Khangi, F.; Hag Musa, I. H.; Ibrahim, A.; Yousif, A. A.; Elzain, M. E.; Worthing, M. A.; Sutherland, H. H.

79

Two-phase nc-TiN/a-(C,CNx) nanocomposite films: A HRTEM and MC simulation study  

NASA Astrophysics Data System (ADS)

The grain growth in two-phase nanocomposite Ti-Cx-Ny thin films grown by reactive close-field unbalanced magnetron sputtering in an Ar-N2 gas mixture with microstructures comprising of nanocrystalline (nc-) Ti(N,C) phase surrounded by amorphous (a-) (C,CNx) phase was investigated by a combination of high-resolution transmission electron microscopy (HRTEM) and Monte Carlo (MC) simulations. The HRTEM results revealed that amorphous-free solid solution Ti(C,N) thin films exhibited polycrystallites with different sizes, orientations and irregular shapes. The grain size varied in the range between several nanometers and several decade nanometers. Further increase of C content (up to ~19 at.% C) made the amorphous phase wet nanocrystallites, which strongly hindered the growth of nanocrystallites. As a result, more regular Ti(C,N) nanocrystallites with an average size of ~5 nm were found to be separated by ~0.5-nm amorphous phases. When C content was further increased (up to ~48 at.% in this study), thicker amorphous matrices were produced and followed by the formation of smaller sized grains with lognormal distribution. Our MC analysis indicated that with increasing amorphous volume fraction (i.e. increasing C content), the transformation from nc/nc grain boundary (GB)-curvature-driven growth to a/nc GB-curvature-driven growth is directly responsible for the observed grain growth from great inhomogeneity to homogeneity process.

Guo, J.; Lu, Y. H.; Hu, X. J.; Shen, Y. G.

2013-06-01

80

High-temperature XRD study of thermally induced structural and chemical changes in iron oxide nanoparticles embedded in porous carbons  

Microsoft Academic Search

Magnetic carbon-based nanomaterials have promising applications in many fields owing to their biocompatibility and thermal\\/mechanical\\u000a stability. This study describes a high-temperature X-ray diffraction (XRD) study of the chemical and structural transformations\\u000a suffered by superparamagnetic iron oxide nanoparticles embedded in porous carbons. The nanoparticles were prepared from the\\u000a decomposition of iron pentacarbonyl over porous carbons, resulting in nanometer-sized iron oxides homogeneously

M. A. Schettino Jr; J. C. C. Freitas; M. K. Morigaki; E. Nunes; A. G. Cunha; E. C. Passamani; F. G. Emmerich

2010-01-01

81

An NMR, XRD and EDS study of solidification\\/stabilization of chromium with Portland cement and C 3S  

Microsoft Academic Search

Solidification \\/ stabilization (SS) of chromium with Portland cement type I and tricalcium silicate (C3S) was investigated by using the 29Si solid state magic angle spinning\\/nuclear magnetic resonance (29Si MASNMR), X-ray diffraction (XRD) and energy dispersive spectroscopy (EDS). The present study confirms that chromium nitrate can increase the extent of C3S hydration. It also confirms that the chromium ion is

Chiou-Kuo Lin; Jong-Nan Chen; Cheng-Chong Lin

1997-01-01

82

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

83

Porosity investigation of compacted bentonite using XRD profile modeling  

NASA Astrophysics Data System (ADS)

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 Ca2 + 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/cm3), the interparticle porosity was estimated to ? 3%.

Holmboe, Michael; Wold, Susanna; Jonsson, Mats

2012-02-01

84

Magnetism.  

National Technical Information Service (NTIS)

This program describes magnets and magnetic materials by pointing out the characteristics of the magnetic field, the molecular arrangement of magnetized and unmagnetized metals, the laws of attraction and repulsion, and the factors that affect the amount ...

1972-01-01

85

XRD analysis and leachability of solidified phenol-cement mixtures  

SciTech Connect

The microstructure and leachability of phenol from solidified phenol-Portland cement mixtures cured up to 6 months were investigated. Phenol was solidified with Type I Portland cement at concentrations of 0.5% and 2% by weight of the cement. XRD studies and pore fluid analyses indicate that phenol inhibits cement setting by reacting with the calcium hydroxide produced during the hydration of cement. Phenol leachability was studied using the Toxicity Characteristic Leaching Procedure (TCLP) test recommended by the U. S. EPA. The quantity of phenol leached is dependent on the initial phenol concentration and the curing time and a simple model has been proposed to predict the leachability. Phenol increases the initial and final setting times of cement. The compressive strength of the solidified cement-phenol mixtures decrease with increasing phenol content in the matrix and increase with curing time. The relationship between leaching of phenol and strength of cement-phenol mixtures has been verified.

Vipulanandan, C.; Krishnan, S. (Univ. of Houston, TX (United States). Department of Civil and Environmental Engineering)

1993-07-01

86

Synthesis and characterization of poly(divinylbenzene)-coated magnetic iron oxide nanoparticles as precursor for the formation of air-stable carbon-coated iron crystalline nanoparticles.  

PubMed

Maghemite (gamma-Fe2O3) nanoparticles of 15 +/- 3 nm diameter were prepared by nucleation of gelatin/iron oxide followed by growth of gamma-Fe2O3 films onto these nuclei. The gamma-Fe2O3 nanoparticles were coated with polydivinylbenzene (PDVB) by emulsion polymerization of divinylbenzene (DVB) in an aqueous continuous phase containing the gamma-Fe2O3 nanoparticles. The PDVB-coated gamma-Fe2O3 nanoparticles, dispersed in water, were separated from homo-PDVB nanoparticles using the high gradient magnetic field (HGMF) technique. The influence of DVB concentration on the amount of PDVB coating, on the size and size distribution of the coated gamma-Fe2O3 nanoparticles and on their magnetic properties, has been investigated. Air-stable carbon-coated iron (alpha-Fe/C) crystalline nanoparticles of 41 +/- 12 nm diameter have been prepared by annealing the PDVB-coated gamma-Fe2O3 nanoparticles at 1050 degrees C in an inert atmosphere. These nanoparticles exhibit high saturation magnetization value (83 emu g(-1)) and excellent resistance to oxidation. Characterization of the PDVB-coated gamma-Fe2O3 and of the alpha-Fe/C nanoparticles has been accomplished by TEM, HRTEM, DLS, FTIR, XRD, thermal analysis, zeta-potential, and magnetic measurements. PMID:17927999

Boguslavsky, Yonit; Margel, Shlomo

2007-09-14

87

Integration of TEM/Hrtem onservations and C-isotope geochemistry to characterize organic matter in early Archaean rocks  

NASA Astrophysics Data System (ADS)

TEM was applied to observe and characterize carbonaceous materials (CM) extracted from black cherts in the 'white smoker type' deposit of the ca.3.5Ga (model Pb/Pb ages =3.49-3.51Ga) Dresser ormation, and the overlying black argillites of the 3.46Ga Salgash Subgroup, in the Pilbara of Western Australia. These were characterized by Transmission Electron Microscopy (TEM) coupled with electron dispersive spectral analysis (EDS), High Resolution TEM (HRTEM) to determine molecular ordering, and C-isotope geochemistry. Observations using TEM and HRTEM enabled morphological and fine structure distinctions between the various populations of CM both in the Dresser and Salgash samples. These formed the basis for their interpretations. Organic petrology using reflected light microscopy was applied to whole rock samples to observe mineral-organic relationship and structure relative to host rock texture. These supported insitu, syn-depositional mode for the Dresser Formation CM. Reflectance % (Ro) of CM determined on polished whole rock samples and polished resin-embedded CM concentrates enabled the reconstruction of its thermal history. These yielded several Ro populations in the Dresser Formation samples: probable microbial cells preserved in fluid inclusions within quartz crystals, severely thermally degraded CM possibly originally belonging to microbial cells, CM coating mineral grains and reworked CM particles. On the other hand, the Salgash suite of samples from the Apex Basalt Formation yielded consistent very high Ro values corresponding to graphite stage organic metamorphism. the weak optical anisotropy of the graphite points to a defferent mode of formation than regional metamorphism. Two main graphite forms have been identified, namely a platy and tubular. The tubular form when observed in HRTEM showed nano-tubes and fullerenes. Dresser Formation samples are isotopically light in the range of -32.1 to -38.2per mil supporting a biological source. Although in TEM four distinct types of CM could be identified and characterized, C-isotope analysis was done on mixed CM concentrates where all types were present. Nevertheless, the isotopically lighter samples contained a notable input from the nonm thermally degraded microbial cells entombed within fluid inclusions, liberated during the demineralizing process. On the otther hand the "heavier" samples contained predominantly thermally degraded high Ro CM. C-isotope compositions of the Salgash CM are relatively heavy, prodiminantly between 22.5 and 28.6 per mil consistent with very high thermal stress. Furthermore, the Salgash suite of samples show a C-isotope trend where in the top part of the section the CM becomes "lighter" with depth, down to 143m depth. The latter having the "lightest" values. An inversion of this trend occurs below this depth, where CM becomes increasingly isotopically heavier. The upper part of the section is characterized by platy graphite with rare occurrence of nanotubes observed. Predominantly tubular graphite/nanotubes and fullerenes characterize sample SAL-13 at 142. depth coinciding with the isotopically lightest values. From then downwards CM becomes increasingly "heavier" signifying highest temperatures experienced. Observations in TEM and HRTEM showed an increase in the presence of void-enclosed carbon nano-spheres possibly fullerenes detached from platy graphite, often forming a condensed mess with few recognisable fused tubular structures.

Glikson, M.; Golding, S.; Duck, L.; Webb, R.

2009-04-01

88

Characteristics and genesis of maghemite in Chinese loess and paleosols: Mechanism for magnetic susceptibility enhancement in paleosols [rapid communication  

NASA Astrophysics Data System (ADS)

Morphological characteristics and microstructures of magnetic minerals extracted from Chinese loess and paleosols were investigated using powder X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM). Our results indicate that maghemite in loess-paleosol sequences was transformed from magnetite through oxidation of magnetite. Maghemite transformed from eolian magnetite during chemical weathering has low-angle grain boundaries among maghemite nano-crystals. Some nano-crystalline maghemites with nanoporous texture resulted from microbe-induced precipitation of magnetite or transformation of poorly crystalline ferric Fe (oxy)hydroxides in presence of Fe-reducing bacteria. Aggregates of euhedral maghemite nano-crystals were transformed from magnetite magnetosomes. Both microbe-induced nanoporous magnetite and microbe-produced magnetite magnetosomes are directly related to microbial activities and pedogenesis of the paleosols. It is proposed that the formation of nano-crystalline maghemite with superparamagnetic property in paleosol results in the enhancement of magnetic susceptibility, although the total amount (weight percent) of magnetic minerals in both paleosol and loess units is similar. Our results also show that nano-crystalline and nanoporous magnetite grains prefer to transform into maghemite in semi-arid soil environments instead of hematite, although hematite is a thermodynamically stable phase. This result also indicates that a decrease in crystal size will increase stability of maghemite. It is also inferred that surface energy of maghemite is lower than that of hematite.

Chen, Tianhu; Xu, Huifang; Xie, Qiaoqin; Chen, Jun; Ji, Junfeng; Lu, Huayu

2005-12-01

89

Removal of fluoride from aqueous solution by polypyrrole/Fe3O4 magnetic nanocomposite.  

PubMed

Polypyrrole (PPy)/Fe(3)O(4) magnetic nanocomposite as a novel adsorbent was prepared via in-situ polymerization of pyrrole (Py) monomer using FeCl(3) oxidant in aqueous medium in which Fe(3)O(4) nanoparticles were suspended. The adsorbent was characterized by Attenuated Total Reflectance Fourier transform infrared spectroscope (ATR-FTIR), Brunauer-Emmet-Teller (BET) method, field emission scanning electron microscope (FE-SEM), high resolution transmission electron microscope (HR-TEM), X-ray photoelectron spectroscope (XPS) and X-ray diffraction (XRD). Magnetic property of the adsorbent was measured by electron spin resonance (ESR). Subsequently, the ability of the adsorbent to remove fluoride ions from aqueous solution was demonstrated in a batch sorption mode. Results reveal that the adsorption is rapid and that the adsorbent has high affinity for fluoride, which depends on temperature, solution pH and adsorbent dose. From equilibrium modelling, the equilibrium data is well described by Freundlich and Langmuir-Freundlich isotherms while the adsorption kinetics is described by the pseudo-second-order model. Thermodynamic parameters confirm the spontaneity and endothermic nature of the fluoride adsorption. Meanwhile, the fluoride adsorption proceeds by an ion exchange mechanism. PMID:21112695

Bhaumik, Madhumita; Leswifi, Taile Yvonne; Maity, Arjun; Srinivasu, V V; Onyango, Maurice S

2010-11-02

90

Controllable synthesis, magnetism and solubility enhancement of graphene nanosheets/magnetite hybrid material by covalent bonding.  

PubMed

Hybrids of Fe(3)O(4) nanoparticles and surface-modified graphene nanosheets (GNs) were synthesized by a two-step process. First, graphene nanosheets were modified by SOCl(2) and 4-aminophenoxyphthalonitrile to introduce nitrile groups on their surface. Second, the nitrile groups of surface-modified graphene nanosheets were reacted with ferric ions on the surface of Fe(3)O(4) with the help of relatively high boiling point solvent ethylene glycol to form a GNs/Fe(3)O(4) hybrid. The covalent attachment of Fe(3)O(4) nanoparticles on the graphene nanosheet surface was confirmed by Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), energy-dispersive X-ray spectrometer (EDS) and scanning electron microscopy (SEM). TEM and HRTEM observations indicated that the sizes of the nanoparticles and their coverage density on GNs could be easily controlled by changing the concentration of the precursor and the weight ratio to GNs. Magnetic measurements showed that magnetization of the hybrid materials is strongly influenced by the reaction conditions. Chemically bonded by phthalocyanine, the solubility of as-synthesized GNs/Fe(3)O(4) hybrid materials was greatly enhanced, which was believed to have potential for applications in the fields of composites, wastewater treatment and biomaterials. PMID:21803368

Zhan, Yingqing; Yang, Xulin; Meng, Fanbin; Wei, Junji; Zhao, Rui; Liu, Xiaobo

2011-07-18

91

Synthesis, characterization and potential applications of multifunctional PEO-PPOPEO- magnetic drug delivery system.  

PubMed

Magnetic nanocomposites (MNCs) have highly been acknowledged in the diagnostics and therapeutic applications. Particularly, the multifunctional MNCs have brought a variety of possibilities in targeted drug delivery as well as non-invasive multimodality imaging. A temperature-responsive magnetic drug delivery system has been developed which is made up of superparamagnetic iron oxide nanoparticles (SIONPs) core and Pluronic shell. The magnetic cores composed of congo red conjugated to SIONPs have been proved beneficial as multimodal imaging agents, while superparamagnetic properties facile conducting the nano or micro systems to the vicinity of targeted tissue. Polymer shell formed by stimuli-responsive Pluronic F127 poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) PEO-PPO-PEO block copolymer serves as the carrier for both hydrophilic and hydrophobic drugs. X-ray diffraction (XRD) and high-resolution transmission electron microscope (HR-TEM) were used to characterize as-synthesized MNCs. Furthermore, vibrating magnetometer experiments showed MNCs having a higher magnetization value than bare magnetic nanoparticles (MNPs) and easy to conduct with an external magnetic field. The hydrodynamic size of MNCs was found to be varying in response to the stimuli temperature. Once the temperature increased, the hydrodynamic radius of MNCs decreased. In addition, the feasibility of the system as a targeted drug delivery system for Alzheimer's diseases (AD) diagnosis and therapy was studied. Searching for reliable targeting molecule, recent approaches for identification of amyloid-? (A?) and its derivatives have been evaluated. Consequently, the amyloid-derived diffusible ligands antibodies (anti-ADDLs) have been nominated as potential targeting molecules which can be attached to the MNCs system. The possibility of anti-ADDLs conjugation to DDS has been found promising for the multifunctional drug delivery system for AD diagnosis and therapy. However, further experimental studies are required to assess the performance of the proposed DDS. PMID:23237189

Dehvari, K; Lin, K-S

2012-01-01

92

An expert system for qualitative XRD analysis of sedimentary rocks  

SciTech Connect

Mineral identification using x-ray powder diffractometry (XRD) requires human judgment and heuristics. Thus, the task is admirably suited for an expert system approach. Expert systems are computer programs which emulate human expertise. The power of an expert system is derived from the knowledge the system embodies, rather than from search algorithms. An expert system helps solve problems for which well-defined algorithmic solutions are difficult to obtain. The authors have coded an expert system, XRAYS, to identify minerals via x-ray diffractograms. The system emulates the well-known manual Hanawalt method, thus avoiding the black-box approach of some computer search/match programs. The mineral subfile of the JCPDS file is stored in a database file, from which the Hanawalt groups are created. The expert system then carries out a manual search following exactly the steps prescribed for the Hanawalt method. In the program, both peak positions and intensities are represented by fuzzy numbers. Fuzzy comparisons and fuzzy arithmetic operations are employed in searching for matches. A list of candidate minerals is output in decreasing order of confidence. Other information, such as chemistry, rock type, suspected minerals, etc. can be coded as production rules, thereby further narrowing the list of candidate minerals. Examples composed of typical mineral suites in sedimentary rocks will be given.

Fang, J.H.; Chen, H.C.; Liu, C.L. (Univ. of Alabama, Tuscaloosa (United States)); Wright, D. (Shelton State College, Tuscaloosa, AL (United States))

1991-03-01

93

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

94

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

95

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

2013-02-22

96

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

97

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

98

Physical properties of magnetic macromolecule-metal and macromolecule-metal oxide nanoparticle complexes  

NASA Astrophysics Data System (ADS)

Magnetic nanoparticles are of considerable interest owing to their potential applications in biotechnology and the magnetic recording industry. Iron oxides have received much attention owing to their oxidative stability and biocompatibility; however, other transition metals and their alloys are also under investigation. Cobalt has one of the largest magnetic susceptibilities of these materials, but it readily oxidizes upon exposure to air resulting in antiferromagnetic oxide. Hence, coating cobalt nanoparticles with an oxygen-impermeable sheath would confer numerous benefits. Cobalt nanoparticles were prepared by the thermolysis of dicobalt octacarbonyl in two block copolymer micellar systems, wherein the copolymers were precursors to graphite or silica. Subsequent heat treatment of the samples at 600--700°C was conducted to condense the polymer coating around the cobalt nanoparticles and form oxygen impervious graphite or silica sheaths. Magnetic and structural characterization of these novel materials afforded pertinent information about their physical properties. Magnetic susceptometry indicated that the graphite coated cobalt nanoparticles resisted oxidation far over one year. The silica coated cobalt nanoparticles had high saturated specific magnetic moments, but the coatings were brittle and grinding the particles resulted in oxidation over time. Transmission electron microscopy (TEM), high-resolution TEM (HRTEM) and energy-filtered TEM (EFTEM) were employed to study particle size and structural differences of the cobalt nanoparticles before and after heat treatment. The mean particle size and size distribution increased for the graphite coated cobalt particles, due to particle sintering at 700°C. In the silica coated cobalt nanoparticle system, the mean particle size increased when the sample was heat-treated at 600°C leading to a bimodal distribution. This bimodal distribution was explained by a fraction of the particles sintering, while others remained discrete. When the silica system was heat treated at 700°C, the particle size and size distribution remained similar to those of the pre-heat-treated sample, indicating that no sintering had taken place. The rapid pyrolysis of the polymer at 700°C may serve to lock the cobalt nanoparticles into a silica matrix, thus preventing them from coming into contact with one another and sintering. Several diffraction techniques (selected area electron diffraction (SAD), nano-beam electron diffraction (NBD) and x-ray diffraction (XRD)) were used to probe the crystal structure of graphite and silica coated cobalt nanoparticies, which was determined to be predominantly face-centered cubic. Anisotropic magnetic nanoparticles (nanorods) have an increased magnetophoretic mobility over spherical magnetic nanoparticles with the same equatorial radius. This property makes them attractive candidates for in vivo biological applications. Anisotropic mixed ferrite nanoparticles were coated with a biocompatible hydrophilic block copolymer to render them dispersible in aqueous media. Polymer coated mixed ferrite particles exhibited magnetic properties similar to that of pure magnetite, as the total level of other transition metals in the nanoparticulate system was less than 5%. Electron energy loss spectroscopy (EELS) and (EFTEM) confirmed that the dominant elements in the mixed ferrite nanoparticles were iron and oxygen. Furthermore, HRTEM, SAD and XRD analyses indicated that the crystal structure for the mixed ferrite nanoparticles was inverse spinel. X-ray diffraction peaks at low angles for the coated mixed ferrite rods corresponded to poly(ethylene oxide) peaks, suggesting that the block copolymer employed as a dispersant was associated with the particles.

Zalich, Michael Andrew

99

In-situ HRTEM study of the reactive carbide phase of Co/MoS2 catalyst.  

PubMed

Hydrotreatment catalytic operations are commonly performed industrially by layered molybdenum sulfide promoted by cobalt or nickel in order to remove heteroelements (S, N, O) from fossil fuels and biofuels. Indeed, these heteroelements are responsible of the emission of pollutants when these fuels are used in vehicles. In this respect, previous studies made by our research group have shown that the active phase under steady state conditions is partially carbided while strong bending effects of MoS2 slabs were also observed. However, up to now, the morphology of the resulting Co/MoSxCy carbided catalyst has not been fully characterized. In the present study, for the first time, a chemical reaction between the carbon content of a TEM Cu/C grid and a freshly sulfide Co/MoS2 catalyst was in situ observed at 300 °C and 450 °C by HRTEM experimental techniques at ~10 nm of resolution. Results indicate that bending of MoS2 layers occurred due to carbon addition on MoS2 edge sites, as observed in stabilized catalysts after HDS reaction. Using a silicon grid, only cracks of MoS2 slabs were observed without bending effect confirming the role of structural-carbon in this change of morphology. PMID:22925737

Ramos, Manuel; Ferrer, Domingo; Martinez-Soto, Eduan; Lopez-Lippmann, Hugo; Torres, Brenda; Berhault, Gilles; Chianelli, Russell R

2012-07-27

100

HRTEM investigations between minerals, fluids and lithobiontic communities during natural weathering. Progress report, September 1, 1993--February 28, 1994  

SciTech Connect

HRTEM and AEM analysis of riebeckite and acmite from the interiors of moderately weathered syenite reveals that interaction of these minerals with surficial fluids resulted in the almost complete removal of Na, Ca, and Si. Fe remained relatively immobile, forming arrays of semi-oriented nanocrystalline ferrihydrite and goethite at the primary mineral-secondary mineral interface. The goethite intimately contacts an irregularly corroded amphibole surface. Smectite occurs sporadically as isolated crystallites a few layers thick which are surrounded by goethite. No obvious structural alignment between clay and amphibole or pyroxene was seen. Data suggest that almost all Si is transported in solution to more open regions between islands of nanocrystalline goethite, where it crystallizes as an Fe - rich smectite. Alteration assemblages in wider channels are comprised of euhedral goethite crystals that, within a submicron-sized area, range in size from 5--40 manometers. Sub-grain boundary structures and the porosity distribution suggests evolution of particle size by coarsening. Optical microscopy demonstrates intimate contact between lichen thalli and mineral surfaces. Lichen thalli exploit cracks and open cleavages to extend several millimeters within mineral interiors. Preliminary TEM data suggest the alteration assemblage consists of a polymer-bound mass of chemically complex aluminosilicates.

Banfield, J.F.; Barker, W.W.

1994-02-01

101

Synthesis of manganese oxide nanocrystal by ultrasonic bath: effect of external magnetic field.  

PubMed

A novel technique was used for the synthesis of manganese oxide nanocrystal by applying an external magnetic field (EMF) on the precursor solution before sonication with ultrasonic bath. The results were compared in the presence and absence of EMF. Manganese acetate solution as precursor was circulated by a pump at constant speed (7 rpm, equal to flow rate of 51.5 mL/min) in an EMF with intensity of 0.38 T in two exposure times (t(MF), 2h and 24h). Then, the magnetized solution was irradiated indirectly by ultrasonic bath in basic and neutral media. One experiment was designed for the effect of oxygen atmosphere in the case of magnetic treated solution in neutral medium. The as prepared samples were characterized with X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, transmission electron microscopy (HRTEM, TEM), energy-dispersive spectrum (EDS), and superconducting quantum interference device (SQUID) analysis. In neutral medium, the sonication of magnetized solution (t(MF), 24h) led mainly to a mixture of Mn(3)O(4) (hausmannite) and ?-MnOOH (manganite) and sonication of unmagnetized solution led to a pure Mn(3)O(4). In point of particle size, the larger and smaller size of nanoparticles was obtained with and without magnetic treatment, respectively. In addition, the EMF was retarded the nucleation process, accelerated the growth of the crystal, and increased the amount of rod-like structure especially in oxygen atmosphere. In basic medium, a difference was observed on the composition of the products between magnetic treated and untreated solution. For these samples, the magnetic measurements as a function of temperature were exhibited a reduction in ferrimagnetic temperature to T(c)=39K, and 40K with and without magnetic treatment, respectively. The ferrimagnetic temperature was reported for the bulk at T(c)=43K. A superparamagnetic behavior was observed at room temperature without any saturation magnetization and hysteresis in the measured field strength. The effect of EMF on the sample prepared in the basic medium was negligible but, in the case of neutral medium, the EMF affected the slope of the magnetization curves. The magnetization at room temperature was higher for the samples obtained in neutral medium without magnetic treatment. In addition, a horizontal shift loop was observed in neutral medium at low temperature. PMID:22221536

Bastami, Tahereh Rohani; Entezari, Mohammad H

2011-12-13

102

Combined HRTEM, X-ray microchemical and EELS fine structure analysis of planar defects in YBa2Cu3O7-?  

NASA Astrophysics Data System (ADS)

High temperature superconductors in the systems YBa2Cu3O7-? (123) and decomposed YBa2Cu4O7-? (124) often contain planar faults with (001) as the nominal fault plane. Such planar defects have been analyzed using a unique combination of high resolution TEM (HRTEM) imaging and high resolution analytical electron microscopy (HRAEM). HRTEM confirmed that these planar faults are stacking faults with double or multiple insertion of crystal planes parallel to the c-plane of the crystal, most probably Cu-O planes. X-ray microanalysis clearly showed enrichment of copper associated with these defects. EELS fine structure of Cu-L23 edge from the fault regions resembled that of pure CuO. The combined results indicate that the planar defects are in fact insertions of extra Cu-O planes in an otherwise regular 123 crystal unit cell.

Dravid, V. P.; Zhang, Hong; Marks, L. D.; Zhang, J. P.

1992-03-01

103

VESPERS: A Beamline for Combined XRF and XRD Measurements  

SciTech Connect

VESPERS (VEry Sensitive Elemental and Structural Probe Employing Radiation from a Synchrotron) is a bending magnet beamline that is just beginning construction at the Canadian Light Source. The beamline has several novel design elements that are intended to increase its operating flexibility and availability to users. First, there is a requirement to deliver a microscopic beam with a variable bandwidth, thus enabling the generation of Laue diffraction patterns and high yield X-ray fluorescence spectra from the same region preferably simultaneously. Thus, the bandpass of the VESPERS monochromator can be readily changed to focus radiation into the same 2-4 micron diameter area that is either polychromatic or having a bandwidth of 10%, 1.6% or 0.01%. This allows the user to change the diffraction pattern to suit the complexity of the crystal and the spectral signal to noise ratio to suit the detection sensitivity required. Second, the beamline is designed to have two branches capable of operating simultaneously and virtually independently using the same primary optics. These design features are accomplished using four separate beams originating at four pinholes at the entry to the Primary Optical Enclosure. The compound focus design uses spherical mirrors to focus both polychromatic and pre-monochromatic beams onto the intermediate slits. A pair of bendable K-B mirrors in the experimental hutch is used to demagnify the beam further down to micron size. The photon energy of this beamline is 6-30 keV.

Feng, Renfei [Canadian Light Source, Saskatoon, Canada; Gerson, Andrea [University of South Australia; Ice, Gene E [ORNL; Reininger, Ruben [Scientific Answers and Solutions, Madison, WI; Yates, Brian A [ORNL; McIntyre, Stewart [University of Western Ontario, The

2007-01-01

104

Phase Transition Studies of WO3 Nanoparticles by XRD and FT Raman Spectroscopy  

NASA Astrophysics Data System (ADS)

Nanoparticles of cubic tungsten trioxide are prepared by controlled chemical precipitation method. The particles are characterized by XRD and FT Raman. XRD results indicate the formation of WO3 in the cubic phase at narrow temperature range and lower temperature of annealing of the precursor sample. FT Raman spectrum indicates presence of structural water. The spectrum also indicates the distortions present in the sample.

Varghese, K. George; Vaidyan, V. K.

2008-11-01

105

Fractionation and characterization of Texas lignite class F fly ash by XRD, TGA, FTIR and SFM  

Microsoft Academic Search

Fly ash is a complicated heterogeneous material and utilization of it requires a detailed knowledge of the physical and chemical characteristics. In the present study Texas lignite class F fly ash was examined by X-ray diffractometer (XRD), thermogravimetric analyzer (TGA), Fourier transformed infrared spectrophotometer (FTIR) and scanning force microscopy (SFM). The XRD and FTIR data indicated that the bulk fly

R. K. Vempati; A. Rao; T. R. Hess; D. L. Cocke; H. V. Jr. Lauer

1994-01-01

106

TEM, XRD and Raman scattering of germanium processed by severe deformation  

Microsoft Academic Search

Nanocrystalline (NC) Ge samples processed by severe plastic deformation under high pressure (6 GPa) were investigated by transmission electron microscopy (TEM), X-ray diffraction (XRD) and Raman scattering. TEM studies of NC Ge revealed a mean grain size of about 24 nm and high angle misorientations of neighbouring grains. The XRD patterns showed decreasing peak intensities, peak broadening and a mean

R. K. Islamgaliev; R. Kuzel; E. D. Obraztsova; J. Burianek; F. Chmelik; R. Z. Valiev

1998-01-01

107

Structure, room-temperature magnetic and optical properties of Mn-doped TiO2 nano powders prepared by the sol—gel process  

NASA Astrophysics Data System (ADS)

TiO2 nano powders with Mn concentration of 0 at%-12 at% were synthesized by the sol—gel process, and were annealed at 500 °C and 800 °C in air for 2 hrs. X-ray diffraction (XRD) measurements indicate that the Mn-TiO2 nano powders with Mn concentration of 1 at% and 2 at% annealed at 500 and 800 °C are of pure anatase and rutile, respectively. The scanning electron microscope (SEM) observations reveal that the crystal grain size increases with the annealing temperature, and the high resolution transmission electron microscopy (HRTEM) investigations further indicate that the samples are well crystallized, confirming that Mn has doped into the TiO2 crystal lattice effectively. The room temperature ferromagnetism, which could be explained within the scope of the bound magnetic polaron (BMP) theory, is detected in the Mn-TiO2 samples with Mn concentration of 2 at%, and the magnetization of the powders annealed at 500 °C is stronger than that of the sample treated at 800 °C. The UV—VIS diffuse reflectance spectra results demonstrate that the absorption of the TiO2 powders could be enlarged by the enhanced trapped electron absorption caused by Mn doping.

Ding, Peng; Liu, Fa-Min; Zhou, Chuang-Cang; Zhong, Wen-Wu; Zhang, Huan; Cai, Lu-Gang; Zeng, Le-Gui

2010-11-01

108

Mössbauer and XRD Characterization of the Mineral Matter of Coal from the Guachinte Mine in Colombia  

NASA Astrophysics Data System (ADS)

The aim of this work was the characterization and differentiation, using Mössbauer spectroscopy (MS) and X-ray diffraction (XRD), of coal samples with different ash and sulfur contents obtained in three places corresponding at cuts in different seams from the Guachinte mine, Valle, Colombia. The mineral phases identified by XRD were in general kaolinite, quartz, pyrite and gypsum, and in particular dolomite and calcite. MS confirms the presence of pyrite and kaolinite, besides evidences the additional presence of jarosite which was not detected by the XRD results due their low amounts. In the high mineral matter ash sample quartz and hematite was identified by XRD, the last one confirmed by MS results. A second phase in this sample was detected by Mössbauer spectroscopy, which could be superparamagnetic hematite. Rietveld refinement for XRD pattern from a sample is reported.

Reyes, F.; Pérez Alcázar, G. A.; Barraza, J. M.; Bohórquez, A.; Tabares, J. A.; Speziali, N. L.

2003-06-01

109

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

110

A comparative study of particle size dependency of IR and XRD methods for quartz analysis.  

PubMed

Quartz (SiO2) is considered a probable carcinogen. In order to enforce health and safety standards, techniques that can accurately determine the quartz content of materials are necessary. Currently, two techniques dominate quartz analysis--the infrared (IR) spectrophotometry method and the X-ray diffraction (XRD) method. Unfortunately, there are problems associated with these techniques, such as sample preparation and particle size effect. This study focuses on particle size effect on quartz determination by both IR and XRD. Seven size groups of pure quartz samples, with mean diameters from 1.5 to 20 microns, were used. A set of samples with different quartz masses was prepared for each size group and subjected to both IR and XRD analysis. Two sets of calibration curves, one each from IR and XRD, were obtained. It was found that both IR and XRD methods are size-dependent but in an opposite way. As particle size increases, IR peak height decreases and XRD peak height increases for the same quartz content (mass). Since both methods are particle size-dependent, it is important that the standard quartz sample and samples of interest have similar particle size distributions. Specifically, when coal dust samples are ashed before analysis, the after-ashing particle size distribution should be used. Particle size distribution will change after ashing and it is the after-ashed particles that directly affect the IR and XRD analysis. PMID:8053418

Bhaskar, R; Li, J; Xu, L

1994-07-01

111

Magnetic properties of V-doped TiO2 nanocrystalline film synthesized by liquid phase deposition technique  

NASA Astrophysics Data System (ADS)

V-doped anatase TiO2 films were fabricated by a non-vacuum liquid phase deposition (LPD) technique on glass substrates. All as-prepared films are amorphous, which are highly crystallized to be anatase TiO2 after air or vacuum annealing at 600 °C. A nanocrystal structure with a grain size of about 10 nm was confirmed by XRD and high resolution transmission electron microscopy (HRTEM). It is found that in the LPD process, the in situ substitution of Ti by V ions occurred, and V atoms were distributed very uniformly in the TiO2 matrix. The air-annealed V0.025Ti0.975O2 samples are paramagnetic, while the vacuum annealed samples clearly exhibit room-temperature ferromagnetism (FM) with a magnetic moment of 1.1 ?B/V. Our results unambiguously show that oxygen vacancies play a critical role in generating FM in doped TiO2 and an F-centre mechanism for diluted FM is confirmed.

Wen, Qi-Ye; Gu, De-En; Zhang, Huai-Wu; Yang, Qing-Hui; Li, Yuan-Xun; Liu, Ying-Li; Xiao, J Q

2009-03-01

112

Mössbauer, TEM/SAED and XRD investigation on waste dumps of the Valea lui Stan gold mines  

NASA Astrophysics Data System (ADS)

The complementary investigation techniques, Mössbauer spectroscopy, transmission electron microscopy with selected area electron diffraction (TEM/SAED), X-ray diffraction (XRD) have been used to investigate the fate of the Valea lui Stan, Romania, gold-ore nanoscale-minerals during the long time of residence in the waste dumps. The preliminary investigations showed such waste dumps to contain significant amount of metals which cannot be identified by conventional methods. An intense research activity started up in order to evaluate the possibilities to recycle Valea lui Stan waste dumps and to recover metals by chemical or phytoextraction procedures. The waste dumps naturally show different mineral constituents with clay minerals as major phases, observed by XRD-technique. Although the waste dumps materials have whitish-yellowish colours, MÖSSBAUER technique evidences the presence of the finely dispersed iron bearing minerals. The authors are focusing to inspect and analyze Fe-compounds in the samples collected from Valea lui Stan's waste dumps in order to identify the magnetic phases by Mössbauer technique.

Constantinescu, Serban Grigore; Udubasa, Sorin S.; Udubasa, Gheorghe; Kuncser, Victor; Popescu-Pogrion, Nicoleta; Mercioniu, Ionel; Feder, Marcel

2012-03-01

113

A versatile and inexpensive XRD sample holder for highly radioactive or hazardous samples.  

SciTech Connect

Two XRD sample holders have been designed for use with highly radioactive samples. An injection mold that allows us to produce the holders inexpensively has been constructed for one of the holders. These holders are suitable for single-time use. The ease of use and the disposable nature have resulted in a dramatic reduction in personnel exposure and an uncontaminated XRD unit. A second holder, based on the design of the first, is used to obtain XRD patterns from powders where preferred orientation is an issue and from clays. Both holders result in negligible background, since the sample is essentially levitated in the x-ray beam. This is a benefit over other methods, such as collodion, that introduce significant background to the XRD pattern.

Strachan, Denis M. (BATTELLE (PACIFIC NW LAB)); Schaef, Herbert T. (BATTELLE (PACIFIC NW LAB)); Schweiger, Michael J. (BATTELLE (PACIFIC NW LAB)); Simmons, Kevin L. (BATTELLE (PACIFIC NW LAB)); Woodcock, Leslie J. (BATTELLE (PACIFIC NW LAB)); Krouse, Michael K. (BATTELLE (PACIFIC NW LAB))

2003-03-15

114

High Resolution Synchrotron XRF and XRD Analyses of Presolar Graphite Spheres from the Orgueil Meteorite  

NASA Astrophysics Data System (ADS)

Here we report a new attempt to apply non-destructive in-situ Synchrotron XRF and XRD techniques to three presolar graphite grains from Orgueil separates: 2 low-density grains and 1 high-density grain.

Schmitz, S.; Brenker, F. E.; Schmitt, M.; Vekemans, B.; Vincze, L.; Schoonjans, T.; Wellenreuther, G.; De Samber, B.; Falkenberg, G.; Burghammer, M.; Jadhav, M.

2012-09-01

115

In Situ Micro XRD Study of the Chelyabinsk LL5 Chondrite  

NASA Astrophysics Data System (ADS)

Non-destructive in situ micro XRD analyses were done of broken surface, shock vein and fusion crust locations for fragments from the Chelyabinsk fall. Crystal structural data shows an LL classification, moderate shock and odd phases in fusion crust.

Flemming, R. L.; McCausland, P. J. A.

2013-09-01

116

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

117

Thermo-XRD-analysis of montmorillonite treated with protonated Congo-red. Curve fitting  

Microsoft Academic Search

The adsorption of protonated Congo red (CR) by montmorillonite was investigated by thermo-XRD-analysis. Montmorillonite was loaded at pH 1 with increasing amounts of CR up to 75 mmol per 100 g clay. Diffractograms of samples treated at 420 °C showed broad peaks and were curve-fitted to determine the different basal spacings, which composed the XRD peaks. The broad peak of

Z. Yermiyahu; I. Lapides; S. Yariv

2005-01-01

118

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

Microsoft Academic Search

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

Supphadate Sujinnapram; Wandee Onreabroy; Tuangrak Nantawisarakul

2009-01-01

119

MAGNETS  

DOEpatents

This patent relates to nmgnets used in a calutron and more particularly to means fur clamping an assembly of magnet coils and coil spacers into tightly assembled relation in a fluid-tight vessel. The magnet comprises windings made up of an assembly of alternate pan-cake type coils and spacers disposed in a fluid-tight vessel. At one end of the tank a plurality of clamping strips are held firmly against the assembly by adjustable bolts extending through the adjacent wall. The foregoing arrangement permits taking up any looseness which may develop in the assembly of coils and spacers.

Hofacker, H.B.

1958-09-23

120

Clay pigment structure characterisation as a guide for provenance determination—a comparison between laboratory powder micro-XRD and synchrotron radiation XRD  

Microsoft Academic Search

Application of X-ray diffraction (XRD)-based techniques in the analysis of painted artworks is not only beneficial for indisputable\\u000a identification of crystal constituents in colour layers, but it can also bring insight in material crystal structure, which\\u000a can be affected by their geological formation, manufacturing procedure or secondary changes. This knowledge might be helpful\\u000a for art historic evaluation of an artwork

Silvie Švarcová; Petr Bezdi?ka; David Hradil; Janka Hradilová; Ivo Žižak

2011-01-01

121

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

122

The thermal behaviour of cuprite: An XRD-EXAFS combined approach  

NASA Astrophysics Data System (ADS)

Cuprite (Cu2O) is a low thermal expansion material with a negative thermal expansion coefficient below room temperature. Its peculiar thermal behaviour encompasses the increase of the shear modulus with increasing temperature, and the presence of rather intense symmetry-forbidden eeo reflections below room temperature. The thermal expansion of cuprite was studied at low temperature (between 5 and 298 K) by means of high-resolution (10-5 Å) X-ray powder diffraction at European Synchrotron Radiation Facility (Grenoble, BM16) and extended X-ray absorption fine structure (EXAFS) (BM29). Negative thermal expansion is confirmed up to 200 K, by EXAFS as well as by XRD measurements, and no sign of transition was found in XRD data. The comparison between EXAFS and XRD results provides a valuable insight into vibrational behaviour of cuprite at low temperature.

Dapiaggi, M.; Tiano, W.; Artioli, G.; Sanson, A.; Fornasini, P.

2003-01-01

123

XRD, SEM and EXAFS investigation of cobalt (II) macro cyclic complexes  

NASA Astrophysics Data System (ADS)

Cobalt (II) complexes were synthesis by chemical rout method. The samples were analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM) and Extended X-ray absorption fine structure (EXAFS). XRD analysis shows that sample is crystalline in nature and having particle size in the range of few micro meters, SEM is designed for studying of the surfaces of solid objects and EXAFS technique extract the local structure of complexes. The nearest neighboring atom distances commonly known as `bond length' were calculated using different methods and also compared with IFEFFIT method.

Mishra, Ashutosh; Ninama, Samrath; Mishra, Niyati

2012-06-01

124

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

SciTech Connect

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. [Indus Synchrotron Utilization Division, Raja Ramanna Centre for Advanced Technology, Indore-452013 (India)

2010-06-23

125

XRD study of the goethite-hematite transformation: Application to the identification of heated prehistoric pigments  

Microsoft Academic Search

When heated, yellow goethite dehydrates and transforms to red hematite. Both iron oxides were used by the Palaeolithic artists as pigments, one question being whether those people took advantage of the phase transformation. To answer this question, the dehydration of synthetic goethite was studied by XRD coupled to Rietveld refinement. It was shown that no hydroxylated hematite is formed during

C. Vignaud; G MORIN

1998-01-01

126

XRD evaluation of KOH activation process and influence of coal rank  

Microsoft Academic Search

Three Japanese coals with different rank (Ohmine, Miike and Taiheiyo coals) were activated with KOH from 300 to 850°C. Higher rank coal with lower oxygen content showed a high yield and also a large specific surface area determined by N2 adsorption isotherms. X-ray diffraction (XRD) patterns of the activated carbons were measured to characterize stacking structure of aromatic layers by

N Yoshizawa; K Maruyama; Y Yamada; E Ishikawa; M Kobayashi; Y Toda; M Shiraishi

2002-01-01

127

Micro-XRD study of beta–titanium wires and infrared soldered joints  

Microsoft Academic Search

ObjectiveThe purpose of this study was to investigate the metallurgical phases in beta–titanium soldered joints prepared by infrared soldering, using the Micro X-ray diffraction technique (Micro-XRD), and to characterize the Vickers hardness in the soldered beta–titanium wires.

Masahiro Iijima; William A. Brantley; Naoki Baba; Satish B. Alapati; Toshihiro Yuasa; Hiroki Ohno; Itaru Mizoguchi

2007-01-01

128

XRD study of calcium-phosphate crystal formation on dentine surface  

NASA Astrophysics Data System (ADS)

The characteristic sizes of elementary crystallites in the composition of dentine substrate with calciumphosphate crystal formations on its surface have been studied using x-ray diffraction (XRD) analysis for phase identification. Most probable mechanisms explaining changes in elementary crystallite sizes in the process of crystal formation were discussed.

Bessudnova, Nadezda O.; Skaptsov, Alexandr; Venig, Sergey B.; Gribov, Andrey N.; Atkin, Vsevolod S.

2013-02-01

129

The relationship between crystal morphology and XRD peak intensity on CaSO4·2H2O  

NASA Astrophysics Data System (ADS)

Each XRD peak intensity of CaSO4?2H2O crystals changes according to their morphologies. This research clarifies the relationship between XRD peak intensity and morphologies on CaSO4?2H2O crystals synthesized by reaction crystallization with various additives. As a result, as XRD relative intensity of (021) face increases, average longitude and aspect ratio decrease and needle-like or plate-like large crystals transform into granular microcrystals.

Inoue, Mikiyasu; Hirasawa, Izumi

2013-10-01

130

High temperature in-situ XRD of plasma sprayed HA coatings  

Microsoft Academic Search

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 15kW) and

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

2002-01-01

131

Determination of grain size by XRD profile analysis and TEM counting in nano-structured Cu  

Microsoft Academic Search

In this work, a serial of pure copper sample with different grain sizes from nano- to micro-scale were prepared by sparkle plasma sintering (SPS) and following anneal treatment at 873K and 1073K, respectively. The grain size distributions of these samples were determined by both X-ray diffraction (XRD) profile analysis and transmission electronic microscope (TEM) micrograph counting. Although these two methods

Yong Zhong; Dehai Ping; Xiaoyan Song; Fuxing Yin

2009-01-01

132

Formation of carbon supported PtRu alloys: an XRD analysis  

Microsoft Academic Search

Carbon supported PtRu alloys were prepared by impregnation of Pt and Ru precursors on a porous carbon support, followed by reduction of the metals with Na2S2O4. After reduction, the samples were thermal treated in argon up to 700°C. The samples were characterized by atomic absorption (AAS) and X-ray diffraction (XRD) measurements. Before thermal treatment only carbon reflexions were visible in

E. Antolini; F. Cardellini

2001-01-01

133

A new simultaneous apparatus for X-ray diffractometry and differential scanning calorimetry (XRD-DSC)  

Microsoft Academic Search

An instrument was developed for performing simultaneous X-ray diffractometric and differential scanning calorimetric (XRD-DSC) measurement using a power compensation DSC (pc-DSC). The feasibility of the technique is demonstrated by examining the thermal dehydration measurement of zinc formate dihydrate (Zn(HCO2)2·2H2O). The DSC curve shows apparent double endothermic peaks during the dehydration process, while X-ray diffraction analysis indicated that the resulting anhydrous

Tadashi Arii; Akira Kishi; Yuji Kobayashi

1999-01-01

134

A Comparative Study of Particle Size Dependency of IR and XRD Methods for Quartz Analysis  

Microsoft Academic Search

Quartz (SiO2) is considered a probable carcinogen. In order to enforce health and safety standards, techniques that can accurately determine the quartz content of materials are necessary. Currently, two techniques dominate quartz analysis—the infrared (IR) spectrophotometry method and the X-ray diffraction (XRD) method. Unfortunately, there are problems associated with these techniques, such as sample preparation and particle size effect. This

Ragula Bhaskar; Jianliang Li; Lijun Xu

1994-01-01

135

The use of thermo-XRD-analysis in the study of organo-smectite complexes  

Microsoft Academic Search

Summary Thermo-XRD-analysis is applied to identify whether or not the adsorbed organic species penetrates into the interlayer space of the smectites mineral. In this technique an oriented smectite sample is gradually heated to temperatures above the irreversible dehydration of the clay, and after each thermal treatment is diffracted by X-ray at ambient conditions. In the thermal treatment of organo-clays, under

S. Yariv; I. Lapides

2005-01-01

136

Mössbauer effect and XRD studies of iron-zinc binary alloys  

Microsoft Academic Search

Mössbauer spectroscopy and XRD were employed to characterize the microstructural properties of iron-zinc binary alloys between 0–31 at.% Fe. Samples were prepared with accuracies of ±0.5 at.% Fe, and the Mössbauer and lattice parameters were monitored as a function of iron concentration across each phase. Two iron sites were observed in the ? phase (18–31 at.% Fe), whose occupancies and

R. G. Grant; D. C. Cook

1994-01-01

137

The structural change of diphasic mullite gel studied by XRD and IR spectrum analysis  

Microsoft Academic Search

A systematic study on the structural change of diphasic mullite gel with heat treatment was carried out by combination of XRD and IR analysis. Aluminium ions are prevalently hexacoordinated in the as-received gel. After heated at high temperatures, part of them transforms to tetrahedral coordination. Phase segregation occurs at ?1000 °C, resulting in the formation of ?-Al2O3 (containing 9–11 wt.% SiO2)

Xi-Hai Jin; Lian Gao; Jing-Kun Guo

2002-01-01

138

SIMULTANEOUS XRD\\/XRF WITH LOW-POWER X-RAY TUBES  

Microsoft Academic Search

A test bench instrument constructed at MOXTEK, Inc. is capable of simultaneously capturing X-ray diffraction (XRD) and X-ray fluorescence (XRF) information using a charge-coupled device (CCD) as the X-ray detector. NASA is funding the instrument's construction because of its low-power consumption and compact size; it could be used for in-situ planetary exploration missions for mineral analysis. A powdered sample of

S. Cornaby; A. Reyes-Mena; P. W. Moody; T. Hughes; A. Stradling; T. Grow; L. V. Knight

139

Growth, XRD and dielectric properties of triglycine sulpho-phosphate (TGSP) crystals added with magnesium sulfate  

Microsoft Academic Search

Pure and magnesium sulfate-doped triglycine sulpho-phosphate (TGSP) single crystals were grown by solution method with the slow evaporation technique. Solubility of the samples in de-ionized water was found in various temperatures ranging from 30 to 60 °C. Single-crystal X-ray diffraction (XRD) studies on the grown crystals reveal the monoclinic crystal structure. Atomic absorption study (AAS) was carried out to confirm

P. Selvarajan; A. Siva Dhas; T. H. Freeda; C. K. Mahadevan

2008-01-01

140

Growth, XRD and dielectric properties of triglycine sulpho-phosphate (TGSP) crystals added with magnesium sulfate  

Microsoft Academic Search

Pure and magnesium sulfate-doped triglycine sulpho-phosphate (TGSP) single crystals were grown by solution method with the slow evaporation technique. Solubility of the samples in de-ionized water was found in various temperatures ranging from 30 to 60°C. Single-crystal X-ray diffraction (XRD) studies on the grown crystals reveal the monoclinic crystal structure. Atomic absorption study (AAS) was carried out to confirm the

P. Selvarajan; A. Siva dhas; T. H. Freeda; C. K. Mahadevan

2008-01-01

141

An integrated XRF\\/XRD instrument for Mars exobiology and geology experiments  

Microsoft Academic Search

By employing an integrated x-ray instrument on a future Mars mission, data obtained will greatly augment those returned by Viking; details characterizing the past and present environment on Mars and those relevant to the possibility of the origin and evolution of life will be acquired. A combined x-ray fluorescence\\/x-ray diffraction (XRF\\/XRD) instrument was breadboarded and demonstrated to accommodate important exobiology

L. N. Koppel; E. D. Franco; J. A. Kerner; M. L. Fonda; D. E. Schwartz; J. R. Marshall

1993-01-01

142

An in situ XRD investigation of singly and doubly promoted manganese oxide methane coupling catalysts  

Microsoft Academic Search

In situ X-ray diffraction (XRD) and concurrent measurements of catalytic performance have been used to characterize the solid phases present during various stages in the history of working methane coupling catalytic systems. Three such systems were studied: unpromoted, K-promoted, and KCl-promoted manganese oxide. In each case the effect of pulses of CHClâ on the activity, selectivity, and catalyst structure was

G. D. Moggridge; T. Rayment; R. M. Lambert

1992-01-01

143

Lattice Expansion of LSCF-6428 Cathodes Measured by In-situ XRD during SOFC Operation  

SciTech Connect

A new capability has been developed for analyzing solid oxide fuel cells (SOFCs). This paper describes the initial results of in-situ x-ray diffraction (XRD) of the cathode on an operating anode-supported solid oxide fuel cell. It has been demonstrated that XRD measurements of the cathode can be performed simultaneously with electrochemical measurements of cell performance or electrochemical impedance spectroscopy (EIS). While improvements to the technique are still to be made, the XRD pattern of a lanthanum strontium cobalt ferrite (LSCF) cathode with the composition La0.6Sr0.4Co0.2Fe0.8O3-? (LSCF-6428) was found to continually but gradually change over the course of more than 60 hours of operation in air under typical SOFC operating conditions. It was determined that the most significant change was a gradual increase in the cubic lattice parameters of the LSCF from 3.92502 Å (as determined from the integration of the first 20 hours of XRD patterns) to 3.92650 Å (from the integration of the last 20 hours). This analysis also revealed that there were several peaks from unidentified minor phases that increased in intensity over this timeframe. After a temporary loss of airflow early in the test, the cell generated between 225 and 250 mW/cm2 for the remainder of the test. A large low frequency arc in the impedance spectra suggests the cell performance was gas diffusion limited and that there is room for improvement in air delivery to the cell.

Hardy, John S.; Templeton, Jared W.; Edwards, Danny J.; Lu, Zigui; Stevenson, Jeffry W.

2012-01-03

144

XRD and FTIR crystallinity indices in sound human tooth enamel and synthetic hydroxyapatite.  

PubMed

The crystallinity index (CI) is a measure of the percentage of crystalline material in a given sample and it is also correlated to the degree of order within the crystals. In the literature two ways are reported to measure the CI: X-ray diffraction and infrared spectroscopy. Although the CI determined by these techniques has been adopted in the field of archeology as a structural order measure in the bone with the idea that it can help e.g. in the sequencing of the bones in chronological and/or stratigraphic order, some debate remains about the reliability of the CI values. To investigate similarities and differences between the two techniques, the CI of sound human tooth enamel and synthetic hydroxyapatite (HAP) was measured in this work by X-ray diffraction (XRD) and Fourier Transform Infrared spectroscopy (FTIR), at room temperature and after heat treatment. Although the (CI)XRD index is related to the crystal structure of the samples and the (CI)FTIR index is related to the vibration modes of the molecular bonds, both indices showed similar qualitative behavior for heat-treated samples. At room temperature, the (CI)XRD value indicated that enamel is more crystalline than synthetic HAP, while (CI)FTIR indicated the opposite. Scanning (SEM) and transmission (TEM) images were also used to corroborate the measured CI values. PMID:24094161

Reyes-Gasga, José; Martínez-Piñeiro, Esmeralda L; Rodríguez-Álvarez, Galois; Tiznado-Orozco, Gaby E; García-García, Ramiro; Brès, Etienne F

2013-07-19

145

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

146

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

147

Structural investigations of ?-CaAlF5 by coupling powder XRD, NMR, EPR and spectroscopic parameter calculations  

NASA Astrophysics Data System (ADS)

?-CaAlF5 was synthesized by solid-state reaction. The precise structure was refined from X-ray powder diffraction data in the monoclinic space group P21/c with lattice constants a=5.3361Å, b=9.8298Å, c=7.3271Å, and ?=109.91° (Z=4). The structure exhibits isolated chains of AlF63- octahedra sharing opposite corners.19F and 27Al solid state NMR spectra were recorded using MAS and SATRAS techniques. An EPR spectrum was recorded for ?-CaAlF5:Cr3+. The experimental spectra were simulated in order to extract the NMR and EPR parameter values. Five fluorine sites and one low symmetry aluminium site were found in agreement with the refined structure. These parameters were calculated using empirical and ab-initio methods. The agreement obtained between the calculated 19F chemical shift values, 27Al quadrupolar parameters, Cr3+ EPR fine structure parameters and the experimental results demonstrates the complementarity of XRD, magnetic resonance experiments and theoretical methodologies.

Body, M.; Silly, G.; Legein, C.; Buzaré, J.-Y.; Calvayrac, F.; Blaha, P.

2005-12-01

148

Synthesis and magnetic properties of Fe{sub 3}O{sub 4} nanoparticles  

SciTech Connect

Ferromagnetic Fe{sub 3}O{sub 4} nanoparticles with diameter of {approx}27 nm were prepared by a hydrothermal route in the presence of a surfactant, sodium bis(2-ethylhexyl)sulfosuccinate (AOT). The as-synthesized product was characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and high-resolution transmission electron microscopy (HRTEM). The hysteresis loops of the iron oxide nanoparticles were measured using a physical property measuring system (PPMS), and the results showed a superparamagnetic behavior at room temperature.

Zheng Yuanhui [State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Graduate School of Chinese Academy of Sciences, Yangqiao West Road 155, Fuzhou, Fujian 350002 (China); Cheng Yao [State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Graduate School of Chinese Academy of Sciences, Yangqiao West Road 155, Fuzhou, Fujian 350002 (China); Bao Feng [State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Graduate School of Chinese Academy of Sciences, Yangqiao West Road 155, Fuzhou, Fujian 350002 (China); Wang Yuansheng [State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Graduate School of Chinese Academy of Sciences, Yangqiao West Road 155, Fuzhou, Fujian 350002 (China)]. E-mail: yswang@fjirsm.ac.cn

2006-03-09

149

Development Of Magnetic Fe-C Nanocomposites Obtained Via The Laser Pyrolysis: Structural And Disaggregation Properties  

SciTech Connect

Fe-C) nanoparticles have been successfully synthesized using the laser pyrolysis method and variable nozzle geometries. At large nozzle diameters, XRD and SAED analysis clearly identified distinct {alpha}-Fe and Fe{sub 3}C phases. TEM and HRTEM indicated that these Fe-based nanoparticles have an average grain size of 3.5-10.2 nm. Temperature dependent Moessbauer spectra further confirm their distinct nanophases. By using a multi-step reduction procedure, Fe-C powders can be disaggregated into stable, water soluble nanoparticles.

Morjan, Ion; Alexandrescu, R.; Dumitrache, F.; Fleaca, C.; Birjega, R.; Soare, I.; Luculescu, C.-R. [National Institute for Lasers, Plasma and Radiation Physics, 111 Atomistilor, MG-36, 077125 Bucharest (Romania); Prodan, V. [Ovidius University of Constanta, 124 Mamaia, Constanta (Romania); Kuncser, V.; Filoti, G. [National Institute of Materials Physics, 105 bis Atomistilor, MG-07, 077125 Bucharest (Romania); Xu, H.; Wang, D. [Max Planck Institute of Colloids and Interfaces, Dept. of Interfaces, D-14424 Potsdam (Germany)

2010-10-06

150

IN-SITU XRD OF OPERATING LSFC CATHODES: DEVELOPMENT OF A NEW ANALYTICAL CAPABILITY  

SciTech Connect

A solid oxide fuel cell (SOFC) research capability has been developed that facilitates measuring the electrochemical performance of an operating SOFC while simultaneously performing x-ray diffraction on its cathode. The evolution of this research tool’s development is discussed together with a description of the instrumentation used for in-situ x-ray diffraction (XRD) measurements of operating SOFC cathodes. The challenges that were overcome in the process of developing this capability, which included seals and cathode current collectors, are described together with the solutions that are presently being applied to mitigate them.

Hardy, John S.; Templeton, Jared W.; Stevenson, Jeffry W.

2012-11-19

151

EXAFS and XRD studies of copper and cobalt complexes of amino acid  

NASA Astrophysics Data System (ADS)

The present paper deals with the synthesis of transition metal schiff base complexes of Para amino benzoic acid (PABA) by chemical root method. The synthesized metal complexes were characterized by XRD analysis, Extended X-ray absorption fine structure (EXAFS) is a technique that has been used for determining the metal ligand bond length using conventional X-ray source and also by EXAFS analysis using IFEFFIT programming. Bond lengths determined from these data analysis methods are compared with the bond lengths obtained from LSS, Levy's and Lytle's methods. All the complexes show the crystalline simple cubic structure. Bond lengths of the complexes are in good agreement obtained by theoretical and experimental methods.

Mishra, A.; Yadav, A.; Ninama, S.; Trivedi, A.

2012-05-01

152

Determination of equilibrium humidities using temperature and humidity controlled X-ray diffraction (RH-XRD).  

PubMed

Confined growth of crystals in porous building materials is generally considered to be a major cause of damage. We report on the use of X-ray diffraction under controlled conditions of temperature and relative humidity (RH-XRD) for the investigation of potentially deleterious phase transition reactions. An improved procedure based on rate measurements is used for the accurate and reproducible determination of equilibrium humidities of deliquescence and hydration reactions. The deliquescence humidities of NaCl (75.4+/-0.5% RH) and Ca(NO3)2 x 4 H2O (50.8+/-0.7% RH) at 25 degrees C determined with this improved RH-XRD technique are in excellent agreement with available literature data. Measurement of the hydration of anhydrous Ca(NO3)2 to form Ca(NO3)2 x 2 H2O revealed an equilibrium humidity of 10.2+/-0.3%, which is also in reasonable agreement with available data. In conclusion, dynamic X-ray diffraction measurements are an appropriate method for the accurate and precise determination of equilibrium humidities with a number of interesting future applications. PMID:17386546

Linnow, Kirsten; Steiger, Michael

2006-10-04

153

An XRD/XRF instrument for the microanalysis of rocks and minerals  

NASA Astrophysics Data System (ADS)

A breadboard setup constructed at MOXTEK, Inc., is capable of capturing both x-ray diffraction (XRD) and x-ray fluorescence (XRF) information simultaneously using a charge-coupled device (CCD) as the x-ray detector. This preliminary setup will lead to a prototype simultaneous XRD/XRF instrument. NASA is funding the instrument's construction because of its capabilities and small size; it could be used for future Mars missions for analysis of rocks. The instrument uses a CCD to capture both the energy and the spatial information of an incoming x-ray. This is possible because each pixel acts as a spatially addressable energy-dispersive detector. A powdered sample of material is placed in front of the CCD, which in turn is bombarded by a collimated x-ray beam. The instrument's critical features - namely the x-ray source, collimation optics and x-ray transparent windows - allow for the first time, to the best of our knowledge, mounting the sample outside the CCD camera. In this paper the instrument's design parameters as well as the properties of both a front-side-illuminated (FSI) CCD and back-side-illuminated (BSI) CCD as x-ray detectors are investigated.

Cornaby, S.; Reyes-Mena, A.; Pew, H. K.; Moody, P. W.; Hughes, T.; Stradling, A.; Turner, D. C.; Knight, L. V.

2001-06-01

154

Effect of relative humidity constraint on the metal exchanged montmorillonite performance: An XRD profile modeling approach  

NASA Astrophysics Data System (ADS)

This work aims at examining the effect of an applied hydrous strain on the cation exchange process of a dioctahedral smectite by quantitative XRD analysis. The hydrous constraint is created by a continuous, in situ, hydration-dehydration cycles using variation of %RH (relative humidity) rate. In order to examine the effect of the retained materials stress on the cation exchange capacity of the host materials, the starting, the intermediate and the final stressed samples are deposed in contact with saturated Cd(II), Co(II), Zn(II) and Ni(II) chloride solutions. To characterize structural changes, an XRD profile modeling approach is used. This investigation allowed us to determine parameters related to the nature, abundance, size, position, organization of exchangeable cation and water molecule in the interlamellar space, along the c* axis. Qualitatively, the hydration behavior is affected by the number of hydration-dehydration cycle, and an interstratified hydration phases due probably to a new organization of the interlamellar space content is observed. Quantitatively, the theoretical mixed layer structure (MLS) suggests the coexistence of more one "crystallite" specie which are saturated by more than one exchangeable cations indicating a partial saturation of all exchangeable sites. Using optimum structural parameter values, deduced from the theoritecals models, some equations which described the evolution of exchangeable cation amount versus the applied hydrous strain were derived.

Oueslati, Walid; Ben Rhaiem, Hafsia; Ben Haj Amara, Abdesslem

2012-11-01

155

[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

156

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

157

Using Simultaneous SHG and XRD Capabilities to Examine Phase Transitions of HMX and TATB  

SciTech Connect

Simultaneous SHG (second harmonic generation) and XRD (x-ray diffraction) capabilities have been developed at SSRL (Stanford Synchrotron Radiation laboratory) to examine the phase behavior of energetic materials, for example, HMX (octahydro- 1,3,5,7-tetranitro- 1,3,5,7-tetrmcine) and TATB (1,3,5-triamino-2,4,6 trinitrobenzene). This unique capability provides information on the evolution at the molecular level (centro and non-centrosymmetric) on material stability, phase transformation or decomposition reactions, which are important to continue refinement of computational predictions of material properties. This paper reports x-ray diffraction experiments on both HMX and TATB with increasing temperature and on simultaneous SHG and XRD experiments at fixed temperature. Our results indicate that, for HMX, the {beta} to {delta} transformation occurs over a range of temperature which do not correlate to the previously reported fast rise in SHG signal close to 17OOC as a phase transformation. No phase transition is observed for TATB, even though, previous paper shows an increase in the SHG signal.

Saw, C K; Zaug, J; Farber, D; Ruddle, C

2001-06-19

158

XRD studies of beta-chitin from squid pen with calcium solvent.  

PubMed

The crystalline structure of beta-chitin from squid pen was investigated by X-ray diffraction (XRD). The purified beta-chitin was prepared from bigfin reefsquid pen. beta-Chitin was treated with saturated calcium chloride dihydrate/alchohol (CaCl(2).2H(2)O/MeOH) solvent system at different conditions for XRD studies. The change of crystallinity of beta-chitin from squid pen was studied by using the fiber photographs on imaging plates. The results showed that the diffraction peak (010) was shifted. It means that the lattice plane (010) interplanarilly spreaded to 3.4A, when the squid pen was washed with water after treatment of Ca solvent. Furthermore, when the squid pen was dried after treatment of Ca solvent and washing with water, interplanar spacing of (010) inversely shrank to 1.1A. These results suggested that Ca solvent especially influences the plane (010) of beta-chitin structure. PMID:18036656

Nagahama, H; Higuchi, T; Jayakumar, R; Furuike, T; Tamura, H

2007-10-18

159

XRD characterisation of composite Ni-based coatings prepared by electrodeposition  

NASA Astrophysics Data System (ADS)

The present work is aimed at XRD investigation of structural parameters that influence the functional properties of Ni-W/Al2O3 electrodeposit coatings. The relationship between electrodeposition parameters and structural properties of the coatings deposited on steel substrates has been determined. XRD investigations were performed on a Bruker D8 Discover diffractometer equipped with a position-sensitive linear detector. The modified sin2? X-ray diffraction method was used to determine the macroscopic residual stresses of deposits. The crystallite size and lattice strain of the coatings were evaluated by analysis of X-ray diffraction patterns (Rietveld analysis). The crystallographic texture was analysed using the orientation distribution function (ODF) calculated from the incomplete pole figures. It was shown that the structural properties of the deposits were strongly correlated with chemical composition. X-ray diffraction patterns of all Ni-W coatings exhibit mainly the fcc phase structure of the Ni-W solid solution with a lattice parameter intermediate between those of Ni and W, which rises when the tungsten content increases. At the same time the crystallite dimension (the size of the coherent domains) was gradually reduced. It was found that Ni-W coatings containing about 40 wt.% W revealed the tensile residual stresses (2300-1200 MPa), depending on deposition conditions.

Tarkowski, L.; Indyka, P.; Be?towska-Lehman, E.

2012-08-01

160

Coupling XRD, EXAFS, and (13)C NMR to Study the Effect of the Carbon Stoichiometry on the Local Structure of UC1±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 UC1.00. 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

2013-09-24

161

Characterization of quenched high pressure phases in CaSiO3 system by XRD and 29Si NMR  

Microsoft Academic Search

We have studied quenched high pressure phases in the CaSiO3 system by x-ray diffraction (XRD) and 29Si MAS NMR, XRD study of the previously reported “?-CaSiO3 phase” synthesized at 12 GPa and 1500 °C reveals that it is actually a mixture of ?-Ca2SiO4 (larnite) and a previously unknown CaSi2O5 phase. This result is supported by the 29Si NMR spectra. Furthermore,

Masami Kanzaki; Jonathan F. Stebbins; Xianyu Xue

1991-01-01

162

SHI Induced Modifications in CdS/CuInSe{sub 2} Thin Film: XRD Analysis  

SciTech Connect

CuInSe{sub 2}(CIS nanostructured) thin films were prepared by ion exchange method at room temperature on ITO coated glass substrates in an alkaline medium. The as prepared thin films were irradiated by 120 MeV Au{sup 9+} swift heavy ion (SHI) at 5x10{sup 11} and 5x10{sup 12} ions/cm{sup 2} fluence respectively. To study the effect of irradiation, the pristine and irradiated nanostructured thin films were characterized by X ray Diffraction (XRD) and analyzed the improvement in crystalline quality and crystallite size. The observed structural modifications discussed considering the high electronic energy deposition by 120 MeV gold heavy (Au{sup 9+}) ions in CuInSe{sub 2} thin films.

Joshi, Rajesh A.; Taur, Vidya S.; Sharma, Ramphal [Thin Film and Nanotechnology Laboratory, Department of Physics, Dr. Babasaheb Ambedkar Marathwada University, Aurangabad 431004, Maharashtra (India); Ghule, Anil V. [Department of Nanotechnology, Dr. Babasaheb Ambedkar Marathwada University, Aurangabad 431004, Maharashtra (India)

2011-07-15

163

Growth, XRD and dielectric properties of triglycine sulpho-phosphate (TGSP) crystals added with magnesium sulfate  

NASA Astrophysics Data System (ADS)

Pure and magnesium sulfate-doped triglycine sulpho-phosphate (TGSP) single crystals were grown by solution method with the slow evaporation technique. Solubility of the samples in de-ionized water was found in various temperatures ranging from 30 to 60 °C. Single-crystal X-ray diffraction (XRD) studies on the grown crystals reveal the monoclinic crystal structure. Atomic absorption study (AAS) was carried out to confirm the presence of Mg2+ in the grown doped TGSP crystals. Dielectric constant and dielectric loss of undoped and magnesium sulfate-doped TGSP crystals were measured for various frequencies and temperatures. It is observed from the studies that solubility and dielectric properties like dielectric constant and dielectric loss increase when TGSP crystal is added with magnesium sulfate. Thermogravimetric and differential thermal analyses (TG/DTA) on the grown crystals have been carried out. The effect of impurity (magnesium sulfate) on structural, electrical and thermal properties of TGSP crystals has been investigated.

Selvarajan, P.; Siva Dhas, A.; Freeda, T. H.; Mahadevan, C. K.

2008-12-01

164

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

165

A high-pressure study of PbCO3 by XRD and Raman spectroscopy  

NASA Astrophysics Data System (ADS)

The pressure-induced phase transitions of PbCO3 are studied using synchrotron radiation in a diamond anvil cell at room temperature. The XRD measurement indicates that PbCO3 with an initial phase of aragonite-type structure undergoes two phase transitions at ~7.8 GPa and ~15.7 GPa, respectively. The higher-pressure phase appearing at ~15.7 GPa is stable up to 51.8 GPa. The two phase transitions are further confirmed by Raman scattering up to 23.3 GPa. During the decompression process, the high-pressure phases of PbCO3 are gradually recovered to the starting aragonite-type structure, but exhibit some hysteresis. The bulk modulus B0 of the aragonite-type structure is obtained to be 63±(3) GPa by fitting the volume-pressure data to the Birch—Murnaghan equation of states with B'0 fixed to 4.

Zhang, Yu-Feng; Liu, Jing; Qin, Zhen-Xing; Lin, Chuan-Long; Xiong, Lun; Li, Rui; Bai, Li-Gang

2013-03-01

166

Exploring hydrothermally grown potassium titanate fibers by STEM-in-SEM/EDX and XRD.  

PubMed

During lab-scale experiments on the reforming of methanol by means of water at supercritical conditions (T > 374 degrees C, p > 22.1 MPa), a tubular reactor with a titanium liner was exposed to an aqueous solvent containing methanol (5 wt%) and KHCO3 (0.3 wt%). At the end of the run, a fibrous precipitate was found at two positions in the reactor. The material was studied in a field emission scanning electron microscope equipped with an energy dispersive X-ray analysis unit (FESEM/EDX). A thin-film support technique using carbon-filmed TEM grids was applied to perform scanning transmission-type imaging (STEM-in-SEM operation) and transmission current measurements. The analysis of the hydrothermally grown fibers resulted in a potassium titanate species composed of approximately K2TiO3, which has been confirmed by X-ray diffraction (XRD). PMID:16842646

Habicht, Wilhelm; Boukis, Nikolaos; Franz, Günter; Walter, Olaf; Dinjus, Eckhard

2006-08-01

167

A Direct Observation by XRD of Reorientation in a Supramolecular Liquid Crystal Polymer Induced by Magnetic Field  

Microsoft Academic Search

Sulfonated polyaramide poly(p-phenylene-sulfo-terephthalamide), or “Sulfo Invert PPTA”, self-assembles in water to form rod-shaped supramolecular aggregates that exhibit nematic liquid crystalline behaviour at remarkably low polymer concentration. The phase diagram is found to be rather athermal, which is an indication that the nematic phase stability is dominated by entropic excluded volume interactions. We describe the transient reorientation of this supramolecular nematic

Sebastien Viale; Eduardo Mendes; Stephen J. Picken

2005-01-01

168

[SEM, XRD and FTIR investigation on crystal growth of calcium oxalate modulated by sodium tartrate].  

PubMed

Crystallization of calcium oxalate (CaOxa) was investigated in the presence of sodium tartrate (Na2 tart) of different concentration in a gel system by scanning electron microscopy (SEM), X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy. It was found that in the presence of a low concentration of Na2tart (0.01 mol x L(-1)), calcium oxalate monohydrate (COM) is the dominant crystal phase. The percentage of calcium oxalate dihydrate (COD) is less than 5%. In the XRD pattern the main diffraction peaks are (101), (020), and (202) planes of COM crystals. In the FTIR spectrum, the main asymmetric carbonyl stretching band nu(as) (COO-) and the metal-carboxylate stretch nu(s) (COO-) of COM occur at 1 618 and 1 317 cm(-1), respectively. With the concentration of Na2 tart increasing to 0. 10 and 0. 50 mol x L(-1), the percentage of COD crystals increases to 10% and 50%, respectively, and the surface area of COM crystals decreases. The diffraction peaks that assigned to the (200), (211), (411), and (213) planes of COD crystals become stronger and stronger. The temperature can influence the modulation of Na2 tart in terms of the phase composition and morphology of CaOxa crystals. As the temperature decreases, the percentage of COD increases. At a higher temperature beyond 47 degrees C, COM is the dominant phase; but COM is dominant when the temperature is lower than 27 degrees C. The nu(as) (COO-) and nu(s), (COO-) of COD crystals occur at 1 647.6 and 1 327.7 cm(-1), respectively. PMID:16883858

Zheng, Hui; Chen, Cun-Yuan; Ouyang, Jian-Ming

2006-05-01

169

Structural, static and dynamic magnetic properties of dextran coated ?-Fe(2)O(3) nanoparticles studied by (57)Fe NMR, Mössbauer, TEM and magnetization measurements.  

PubMed

The structural and magnetic properties and spin dynamics of dextran coated and uncoated ?-Fe(2)O(3) (maghemite) nanoparticles have been investigated using high resolution transmission electron microscopy (HRTEM), (57)Fe nuclear magnetic resonance (NMR), Mössbauer spectroscopy and dc magnetization measurements. The HRTEM observations indicated a well-crystallized system of ellipsoid-shaped nanoparticles, with an average size of 10 nm. The combined Mössbauer and magnetic study suggested the existence of significant interparticle interactions not only in the uncoated but also in the dextran coated nanoparticle assemblies. The zero-field NMR spectra of the nanoparticles at low temperatures are very similar to those of the bulk material, indicating the same hyperfine field values at saturation in accord with the performed Mössbauer measurements. The T(2) NMR spin-spin relaxation time of the nanoparticles has also been measured as a function of temperature and found to be two orders of magnitude shorter than that of the bulk material. It is shown that the thermal fluctuations in the longitudinal magnetization of the nanoparticles in the low temperature limit may account for the shortening and the temperature dependence of the T(2) relaxation time. Thus, the low temperature NMR results are in accord with the mechanism of collective magnetic excitations, due to the precession of the magnetization around the easy direction of the magnetization at an energy minimum, a mechanism originally proposed to interpret Mössbauer experiments in magnetic nanoparticles. The effect of the surface spins on the NMR relaxation mechanisms is also discussed. PMID:22418594

Fardis, M; Douvalis, A P; Tsitrouli, D; Rabias, I; Stamopoulos, D; Kehagias, Th; Karakosta, E; Diamantopoulos, G; Bakas, T; Papavassiliou, G

2012-03-15

170

Characterization of mullite in silicoaluminous fly ash by XRD, TEM, and 29Si MAS NMR  

Microsoft Academic Search

Mullite contained in a silicoaluminous fly ash (originating from power plant of La Maxe, near Metz in the east of France) issue from bituminous coal combustion has been studied by X-ray diffraction, nuclear magnetic resonance of 29Si spinning at magic angle, and transmission electron microscopy linked with energy-dispersive spectroscopy. By using results from X-ray diffraction [1] and nuclear magnetic resonance

S. Gomes; M. François

2000-01-01

171

Data from the Mars Science Laboratory CheMin XRD/XRF instrument  

NASA Astrophysics Data System (ADS)

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 (~An50), forsteritic olivine (~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 ~27° 2? (Co K?) and may include volcanic glass, impact glass, and poorly crystalline phases including iron oxyhydroxides; a rise at lower 2? 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 µm, 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; Bristow, , David Blake, Tom; Des Marais, David; Achilles, Cherie; Spanovich, Ashwin Vasavada, , Robert Anderson, Joy Crisp, John Michael Morookian, Nicole; Yen, Albert; Bish, David; Chipera, Steve; Downs, Robert; Morrison, Shaunna; Farmer, Jack; Grotzinger, John; Stolper, Edward; Morris, , Douglas Ming, Richard; Rampe, Elizabeth; Treiman, Allan; Sarrazin, Philippe; MSL Science Team

2013-04-01

172

Spectroscopic and XRD characterisation of zeolite catalysts active for the oxidative methylation of benzene with methane.  

PubMed

The benzene methylation with methane over zeolite catalysts was previously shown in our laboratory to require the presence of oxygen. Thus, a two-step mechanism involving the intermediate formation of methanol by partial oxidation of methane followed by the methylation of benzene with methanol in the second step, was postulated. This paper now reports the results of the characterisation of the zeolite catalysts used for the oxidative benzene methylation reaction in order to provide some information about their composition, structure, properties and their behaviour before and after the reaction. The catalysts were characterised by X-ray diffraction (XRD), inductively coupled plasma atomic emission spectroscopy (ICP-AES), X-ray fluorescence (XRF), FT-IR and solid state NMR. XRD results indicate that the crystalline structures of all the ZSM-5 and H-beta catalysts remained unchanged after batch reaction of benzene with methane over the catalysts in agreement with the observation that the catalysts recovered from the reactor could be reused without loss of activity. Elemental analyses and FT-IR data show that as the level of metal ion exchange increases, the Brönsted acid concentration decreases but this metal ion exchange does not totally remove Brönsted acidity. FT-IR results further show that only a small amount of acid sites is actually necessary for a catalyst to be active since used catalysts containing highly reduced Brönsted acidity are found to be reusable without any loss of their activity. 29Si and 27Al magic angle spinning (MAS) NMR together with FT-IR spectra also show that all the active zeolites catalysts contain some extra-framework octahedral aluminium in addition to the normal tetrahedral framework aluminium. The presence of this extra-lattice aluminium does not, however, have any adverse effect on the crystallinity of the catalysts both before and after oxidative benzene methylation reaction. There appears also to be no significant dealumination of the zeolite catalysts during reaction since their catalytic performance was retained after use. PMID:15036089

Adebajo, Moses O; Long, Mervyn A; Frost, Ray L

2004-03-01

173

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

174

Novel carbon nanotube iron oxide magnetic nanocomposites  

Microsoft Academic Search

A novel magnetic nanocomposite of ?-Fe2O3 nanoparticles decorated multiwalls carbon nanotubes (MWNTs) was synthesized for the first time by a simple chemistry precipitation method. The structure and morphology of the composite was characterized by X-ray powder diffractometer (XRD), TEM and EDS. The results of XRD and TEM show that ?-Fe2O3 nanoparticles is immobilized on the side wall of the MWNTs,

Cao Huiqun; Zhu Meifang; Li Yaogang

2006-01-01

175

Structural Characterization of Ni-Substituted Hexaaluminate Catalysts Using EXAFS, XANES, XPS, XRD, and TPR  

SciTech Connect

The structure of five Ni-substituted Ba{sub 0.75}Ni{sub y}Al{sub 12-y}O{sub 19-{delta}} hexaaluminate catalysts at various Ni loadings (y = 0.2, 0.4, 0.6, 0.8 and 1.0) was investigated using EXAFS, XANES, XPS, XRD, and TPR. As Ni-substitution into the hexaaluminate lattice is increased, the unit cell dimension decreases along the c axis. This systematic change is consistent with Ni substitution for Al{sup 3+} in the hexaaluminate crystalline structure. XANES analysis suggests that Ni-O bonding is stronger for Ni substituted into the hexaaluminate lattice, relative to that of bulk NiO. The average coordination numbers obtained from EXAFS indicate that Ni is preferentially exchanging with tetrahedrally coordinated Al{sup 3+} in the structure which predominates in regions of the hexaaluminate unit cell near the mirror plane. It is at these sites that, preferential substitution of Ni{sup 2+} likely occurs to minimize strain in the crystalline lattice.

Gardner, J.; Spivey, J; Kugler, E; Campos, A; Hissam, J; Roy, A

2010-01-01

176

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

177

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

2013-06-27

178

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

179

X-Ray Powder Diffraction (XRD) Studies on Kenaf Dust Filled Chitosan Bio-composites  

NASA Astrophysics Data System (ADS)

Kenaf dust filled chitosan bio-composites with various compositions of kenaf dust (i.e. 7%, 14%, 21% and 28%) were prepared using solution casting technique. The degree of relative crystallinity of the bio-composites was determined using XRD method. Two distinguishable crystalline peaks were observed in the 2? range of 5 to 40 ° which indexed as 020 and 110 respectively. It was noted that the maximum peak of intensity at 020 crystalline peak increased with addition of kenaf dust as well as the second maximum peak of intensity at 110. Consequently, Fourier Transform Infrared (FTIR) analysis was done to investigate the interaction between kenaf dust and chitosan matrix. From FTIR analysis, corresponding peak of chitosan was detected at wavelength of 3233.2 cm-1 indicated that there exist intermolecular interactions between kenaf dust and chitosan matrix. These results highlighted that there are greater intermolecular forces formed in chitosan with addition of kenaf dust. Intermolecular forces were attributed to the formation of inter and intra hydrogen bonding between chitosan polymer and cellulosic kenaf dust filler.

Julkapli, N. Muhd; Md Akil, H.

2008-03-01

180

[Infrared spectra and XRD characteristics of alunite in the Zijinshan gold-copper deposit].  

PubMed

The structural characteristics and composition of alunite in the Zijinshan gold-copper deposit were studied by infrared absorption spectroscopy and X-ray powder diffraction analysis. The results show that infrared spectral absorption peaks, the growth degree of crystal faces (006) and (004), and crystal cell parameters of the alunite display gradually decreasing trend from the crater to northwest along the metallogenic belt. Combined with electron probe analysis results, we go further and obtain that the alunite mainly belongs to potassium alunite, and the characteristics of infrared spectra and XRD of the alunite mainly have relation to the content of potassium of the alunite in different parts of volcanic mechanism. Near the crater, with higher temperature, it is helpful for the isomorphism replacement between sodium and potassium, the content of sodium is higher and the content of potassium is lower relatively in the alunite; and away from the crater, the temperature is relatively lower, it is against the isomorphism replacement between sodium and potassium, the content of sodium is lower, and the content of potassium is higher relatively in the alunite. PMID:24059212

Wang, Cui-Zhi; Zhang, Wen-Yuan

2013-07-01

181

FTIR spectroscopic, thermal and XRD characterization of hydroxyapatite from new natural sources  

NASA Astrophysics Data System (ADS)

The inorganic constituents of 5 different plants (leaves and stalks) were investigated by using Fourier transformer infrared spectroscopy (FTIR), X-ray diffraction (XRD) and thermal analysis including thermal gravimetric analysis (TGA), derivative thermogravimetry (DTG) and differential scanning calorimetry (DSC). These plants are Catha edulis (Khat), basil, mint, green tea and trifolium. The absorption bands of carbonate ions CO 32- was exhibited at 1446 cm -1, and the phosphate ions PO 43- was assigned at 1105 and 1035 cm -1. At high temperatures (600, 700 and 600 °C) further absorption bands of the phosphate ions PO 43- was assigned at the frequencies 572, 617, 962, 1043 and 1110 cm -1 and the vibrational absorption band of the carbonate ions CO 32- was assigned at 871, 1416 and 1461 cm -1. X-ray diffraction and thermal analysis confirm the obtained results of FITR. Results showed that the main inorganic constituents of C. edulis and basil leaves are hydroxyapatite whereas the hydroxyapatite content in the other plant samples is less than that in case of C. edulis and basil plant leaves.

Shaltout, Abdallah A.; Allam, Moussa A.; Moharram, Mohamed A.

2011-12-01

182

Crystallinity of cellulose, as determined by CP\\/MAS NMR and XRD methods  

Microsoft Academic Search

The crystallinity of six cellulose samples with different origin and treatment was determined using x-ray diffraction (XDR) and nuclear magnetic resonance with cross polarization and magic angle sample spinning (CP\\/MAS NMR) methods. The numerical results for crystallinity obtained by using curve fitting methods in both cases correlated very well. It was concluded that the values for the crystallinity can be

R. Teeäär; R. Serimaa; T. Paakkarl

1987-01-01

183

ESR and XRD investigation of effects induced by gamma radiation on PVA-TiO2 membranes  

NASA Astrophysics Data System (ADS)

The effects of gamma radiation on the local structure of PVA membranes containing TiO2 were investigated by ESR and XRD methods. An intense ESR signal is observed after irradiation at 16 KGy dose. This signal appears only for irradiated samples and it is associated with the breaking of the polymeric chain, followed by local reorganization of the polymeric segments and the apparition of the unpaired electrons and free radicals. The intensity of the signal decreases with the concentration of TiO2, indicating a shielding effect of the dopand. That the modification of local order of the polymeric chains has been modified after irradiation is confirmed by XRD method.

Todica, Mihai; Stefan, Traian; Trandafir, Diana; Simon, Simion

2013-09-01

184

Mineralogy and Magnetic Properties of Basaltic Substrate Soils: Kaho'olawe and Big Island, Hawaii  

Microsoft Academic Search

Abbreviations: DTA, differential thermal analysis; Fed, dithionite-extractable Fe; Feo, oxalate-extractable Fe; TEM, time-domain electromagnetic; TGA, thermogravimetric analysis; UXO, unexploded ordnance; VRM, viscous remanent magnetization; XRD, x-ray diffraction spectroscopy; XRF, x-ray fl uorescence spectroscopy; ?, volume-specifi c magnetic susceptibility; ?, mass-specifi c magnetic susceptibility; ?fd%, frequency-dependent magnetic susceptibility; ?lf, low-frequency mass-specifi c magnetic susceptibility; ?T, temperature-dependent magnetic susceptibility. Magnetic behavior of

Remke L. Van Dam; J. Bruce J. Harrison; Deidre A. Hirschfeld; Todd M. Meglich; Yaoguo Li; Ryan E. North

2008-01-01

185

Chromium removal by combining the magnetic properties of iron oxide with adsorption properties of carbon nanotubes  

Microsoft Academic Search

The adsorption features of multiwall carbon nanotubes (MWCNTs) with the magnetic properties of iron oxides have been combined in a composite to produce a magnetic adsorbent. Composites of MWCNT\\/nano-iron oxide were prepared, and were characterized by X-ray diffraction (XRD), field emission scanning electron microscope (FESEM) and Fourier transform infrared spectroscopy (FTIR). XRD suggests that the magnetic phase formed is maghemite

V. K. Gupta; Shilpi Agarwal; Tawfik A. Saleh

2011-01-01

186

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

187

Review of XRD-based quantitative analyses of clay minerals in soils: the suitability of mineral intensity factors  

Microsoft Academic Search

The determination of the types and relative amounts of the minerals present in soil forms an essential component of most soil characterization efforts. This paper reviews protocols for XRD-based quantitative clay mineral analysis in soils, with emphasis on methods using mineral intensity factors in combination with the so-called 100% approach. We summarize methodological differences and characteristic features and give information

Maren Kahle; Markus Kleber; Reinhold Jahn

2002-01-01

188

Charge location effect on the hydration properties of synthetic saponite and hectorite saturated by Na +, Ca 2+ cations: XRD investigation  

Microsoft Academic Search

This paper aims at comparing the effect of charge location on the hydration properties of two trioctahedral synthetic minerals: saponite and hectorite. The samples were characterised by a layer charge of 0.4 charge per half unit cell and were saturated with Na+ or Ca2+. The hydration behaviour was studied by determining the structural characteristics which were obtained by modelling XRD

M. S. Karmous; H. Ben Rhaiem; J. L. Robert; B. Lanson; A. Ben Haj Amara

2009-01-01

189

XRD and FTIR studies on a new solid electrolyte system containing Ag3PO4 and SbI3  

NASA Astrophysics Data System (ADS)

A new solid electrolyte system, 60 mole % Ag3PO4 - 40 mole % SbI3 has been prepared by melt-quenching method and characterized by XRD and FTIR techniques. The observed results tend to confirm the formation of room temperature fast ionic phases.

Suthanthiraraj, S. Austin; Sarumathi, R.

2012-06-01

190

Heat treatment and potential cycling effects on surface morphology, particle size, and catalytic activity of Pt\\/C catalysts studied by 13C NMR, TEM, XRD and CV  

Microsoft Academic Search

Pt particles of 20% Pt\\/C samples grew both by repetitive potential cycling and heat treatment. Average particle size variation is linearly proportional to the number of potential cycles while it is proportional to an exponential function of heating temperature. HR-TEM results show rough and irregular Pt surfaces in repetitively potential cycled samples and well-defined cubo-octahedrons without many defects in heat

Kee Sung Han; Yoon-Soo Moon; Oc Hee Han; Ki Ju Hwang; In Kim; Hasuck Kim

2007-01-01

191

Sol–gel route of synthesis of nanoparticles of MgFe 2O 4 and XRD, FTIR and VSM study  

Microsoft Academic Search

Nanoparticles of MgFe2O4 are synthesized using sol–gel autocombustion method. Structural studies are carried out using X-ray diffraction (XRD). The XRD pattern of MgFe2O4 provides information about single-phase formation of spinel structure with cubic symmetry. The grain size and lattice constant are obtained using XRD data. The cation distribution is also proposed theoretically. The change in site preference of cations in

A. Pradeep; P. Priyadharsini; G. Chandrasekaran

2008-01-01

192

Polycrystalline oxides formation during transient oxidation of (001) Cu-Ni binary alloys studied by in situ TEM and XRD.  

SciTech Connect

The nucleation and growth of Cu{sub 2}O and NiO islands due to oxidation of Cu{sub x}Ni{sub 1-x} (001) films were monitored, at various temperatures, by in situ ultra-high vacuum (UHV) transmission electron microscopy (TEM) and in situ synchrotron X-ray diffraction (XRD). In remarkable contrast to our previous observations of Cu and Cu-Au oxidation, irregular-shaped polycrystalline oxide islands formed with respect to the Cu-Ni alloy film, and an unusual second oxide nucleation stage was noted. In situ XRD experiments revealed that NiO formed first epitaxially, then other orientations appeared, and finally polycrystalline Cu{sub 2}O developed as the oxidation pressure was increased. The segregation of Ni and Cu towards or away, respectively, from the alloy surface during oxidation could disrupt the surface and cause polycrystalline oxide formation.

Yang, J. C.; Li, Z. Q.; Sun, L.; Zhou, G. W.; Eastman, J. A.; Fong, D. D.; Fuoss, P. H.; Baldo, P. M.; Rehn, L. E.; Thompson, L. J.; Materials Science Division; Univ.of Pittsburgh; State Univ. of New York at Binghamton

2009-01-01

193

Characterization of In/Pd and Pd/In/Pd thin films by ellipsometric, XRD and AES methods  

NASA Astrophysics Data System (ADS)

In/Pd and Pd/In/Pd thin films were prepared by thermal evaporation on the SiO 2 substrate in a vacuum. The structural and optical properties of the films were investigated by means of X-ray diffractometry (XRD), Auger electron spectroscopy (AES) and spectroscopic ellipsometry (SE). Auger depth profile studies were performed in order to determine the composition of elements in the Pd-In systems. Interdiffusion of metals was detected at room temperature. Optical properties of Pd-In composite layers formed due to the interdiffusion were derived from ellipsometric quantities ? and ? measured in the photon energy range 0.75-6.50 eV at different angles of incidence. The effective optical spectra show absorption peaks dependent on the composition of nonuniform films. The XRD patterns indicated formation of Pd 1- xIn x intermetallic phases in the samples.

Wronkowska, A. A.; Wronkowski, A.; Bukaluk, A.; Trzci?ski, M.; Okulewicz, K.

2007-01-01

194

Conventional and Micro-XRD Study of a New Ternary Zirconium, Titanium, Aluminum Alloy--Zr2TiAl  

NASA Astrophysics Data System (ADS)

Zr3Al is a cubic intermetallic compound whereas Ti3Al has a hexagonal structure. Crystallography and microstructure study of an alloy containing all three components is, therefore, interesting to study. A nominal Zr2TiAl alloy was prepared by arc melting and subsequently vacuum annealing at 1050° C for 30 days. Scanning Electron Microscopy and Energy Dispersive Spectrometry showed three phases in the material. Among the three phases the major phase was the stoichiometric alloy Zr2TiAl. Of the two minor phases present in the specimen, one was rich in Ti and the other rich in Al. In an SEM micrograph the major phase grains varied in size from 10 ?m to 50?m. Conventional XRD shows peaks due to all three phases with considerable proximity and overlap. In order to identify peaks due to individual phases micro-beam XRD was carried out and the major phase was identified.

Sornadurai, D.; Flemming, Roberta L.; Sastry, V. S.

2011-07-01

195

XRD, XPS and AFM studies of the unknown phase formed on the surface during electrodeposition of Ni W alloy  

NASA Astrophysics Data System (ADS)

XRD, XRD in situ XPS, electrochemical and AFM studies of an unknown phase formed during electrochemical deposition of Ni W alloy in a citrate electrolyte were carried out. It has been determined that a thin, highly textured film of nonstoichiometric NiWO4 was formed during codeposition of nickel and tungsten. The amount of the nickel tungstate was higher on the coating electrodeposited in electrolyte containing amine acid—asparagine. The quantity of the nickel tungstate grew in the electrodeposition period of ˜60 min and subsequently kept constant although the thickness of Ni W alloy continued to increase. The quantity of the nickel tungstate formed increased with the temperature of electrolyte, however it decreased with the pH and current density.

Jušk?nas, Remigijus; Valsi?nas, Ignas; Pakštas, Vidas; Selskis, Algirdas; Jasulaitien?, Vitalija; Karpavi?ien?, Violeta; Kapo?ius, Vidmantas

2006-11-01

196

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

197

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

198

Temperature dependence of the cation distribution in nickel aluminate (NiAl 2 O 4 ) spinel: a powder XRD study  

Microsoft Academic Search

NiAl2O4 is a largely inverse spinel, which in detail shows increasing randomisation with temperature of Ni and Al between the octahedral and tetrahedral cation sites of the spinel structure. We have used powder XRD to determine this cation distribution in various samples of NiAl2O4 quenched after annealing between 700 and 1400° C. The inversion parameter (x) can be measured with

H. St. C. O'Neill; W. A. Dollase; C. R. Ross

1991-01-01

199

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

200

Hydrated Iron Sulfate Minerals by FT-IR, ESEM and XRD: Effects of Hydration, Metal Ions, and Oxidative State  

Microsoft Academic Search

Data from the Mars Exploration Rovers (MER) and orbital remote sensing have determined that iron-bearing sulfates and iron-sulfates account for much of the mineralogical variation on Martian chemical sediments. We have begun a comprehensive study to evaluate a suite of hydrated iron sulfate minerals at different levels of oxidation or mineral phases using micro-FT-IR, ESEM and XRD. Selected minerals include

R. Mielke; D. Blaney; K. Nordstrom; C. Aplers; M. Coleman

2007-01-01

201

High resolution TEM and triple-axis XRD investigation into porous silicon formed on highly conducting substrates  

Microsoft Academic Search

The microstructure of thin porous silicon films (?1?m) formed potentiostatically on p+-type silicon in dilute HF solutions is investigated via high resolution TEM and triple-axis XRD. Average pore diameters were found to increase with increasing etching potential, changing from a mixture of micro- and mesopores to predominately square macropores once oxide growth commences. It is postulated that these square pores

T. L. Sudesh L. Wijesinghe; Shi Qiang Li; Mark B. H. Breese; Daniel J. Blackwood

2009-01-01

202

EVALUATION OF GAMMA-IRRADIATION EFFECTS ON NUCLEAR GRAPHITE BY HARDNESS MEASUREMENT, RAMAN SPECTROSCOPY, SPECIFIC ELECTRICAL RESISTIVITY AND XRD  

Microsoft Academic Search

Gamma-irradiation effects on the hardness, molecular chemical bonding structure, formation of lattice defect structures and the crystallite size of fine-grained, isotropic IG-110 nuclear graphite were evaluated by a hardness measurement, Raman spectroscopy, specific electrical resistivity, and XRD, respectively. Specimens were exposed to a Co60 gamma ray for three dose levels: i.e., 1.1 x 108 Rad (R), 1.5 x 109 R,

Se-Hwan Chi; Gen-Chan Kim; Jonghwa Chang

203

In situ NMR and XRD studies of the growth mechanism of SBA-1.  

PubMed

In situ 17O, 14N and 29Si nuclear magnetic resonance (NMR) coupled with in situ energy dispersive X-ray diffraction (EDXRD) have been used to investigate the growth of the siliceous mesoporous material, SBA-1, synthesised under acidic conditions from a micellar solution of the surfactant hexadecyltriethylammonium bromide (HTEAB) and tetraethylorthosilicate (TEOS). For the last decade, the mechanism of growth of such materials has been thought to be driven by electrostatic interactions described as a co-assembly process between the silica species (I+) and the micelles (S(+)X(-)). However, this postulated model referred to as the "charge density matching model" has never been fully supported by experimental data for the acidic syntheses. We have carried out a detailed in situ study which challenges the so-called S(+)X(-)I(+) pathway and instead suggests that a salting-out effect coupled with a drastic change in the water activity are responsible for the composite I(1)3 (SBA-1 space group Pm3n) mesophase precipitation. Substantial reorganisation of the precipitated phase then results in the final structure. PMID:19787948

Egger, C C; Anderson, M W; Tiddy, G J T; Casci, J L

2005-04-21

204

Facile Organic Solvent-Free Synthesis of Size-Controlled Hierachically Structured Magnetic Hollow Spheres and Potential Application in Adsorption for Bovine Serum Album  

Microsoft Academic Search

A series of size-controllable hierachically nanostructured magnetic hollow spheres (MHS) (250 to 2330 nm) have been fabricated by using the hard-template method involving the coprecipitation of ferrite precursor over the pre-synthesized polystyrene spheres with varied sizes under organic solvent-free conditions followed calcinations. The SEM, TEM and HRTEM results indicate that the primary nanoparticles constructing hierachically nanostructured MHS clearly show the

Cong Zhang; Hui Zhang; Bing Du; Rong Hou; Shaohuan Guo

205

Effect of annealing temperature on the structural, photoluminescence and magnetic properties of sol-gel derived Magnetoplumbite-type (M-type) hexagonal strontium ferrite  

NASA Astrophysics Data System (ADS)

Magnetoplumbite-type (M-type) hexagonal strontium ferrite particles were synthesized via sol-gel technique employing ethylene glycol as the gel precursor at two different calcination temperatures (800 and 1000 °C). Structural properties were systematically investigated via X-ray diffraction (XRD), field emission scanning electron microscopy, high resolution transmission electron microscopy (HRTEM), energy dispersive spectroscopy (EDS), thermogravimetric analysis (TGA), photoluminescence spectrophotometry and superconducting quantum interference device magnetometer. XRD results showed that the sample synthesized at 1000 °C was of single-phase with a space group of P63/mmc and lattice cell parameter values of a=5.882 Å and c=23.048 Å. EDS confirmed the composition of strontium ferrite calcined at 1000 °C being mainly of M-type SrFe12O19 with HRTEM micrographs confirming the ferrites exhibiting M-type long range ordering along the c-axis of the crystal structure. The photoluminescence (PL) property of strontium ferrite was examined at excitation wavelengths of 260 and 270 nm with significant PL emission peaks centered at 350 nm being detected. Strontium ferrite annealed at higher temperature (1000 °C) was found to have grown into larger particle size, having higher content of oxygen vacancies and exhibited 83-85% more intense PL. Both the as-prepared strontium ferrites exhibited significant oxygen vacancies defect structures, which were verified via TGA. Higher calcination temperature turned strontium ferrite into a softer ferrite.

Teh, Geok Bee; Wong, Yat Choy; Tilley, Richard D.

2011-09-01

206

Novel carbon nanotube iron oxide magnetic nanocomposites  

NASA Astrophysics Data System (ADS)

A novel magnetic nanocomposite of ?-Fe2O3 nanoparticles decorated multiwalls carbon nanotubes (MWNTs) was synthesized for the first time by a simple chemistry precipitation method. The structure and morphology of the composite was characterized by X-ray powder diffractometer (XRD), TEM and EDS. The results of XRD and TEM show that ?-Fe2O3 nanoparticles is immobilized on the side wall of the MWNTs, the size of most of the particle is <5 nm.The EDS analysis shows that the atomic ratio of Fe to O is 2:3. The magnetization curves of the MWNTs and ?-Fe2O3 decorated MWNTs were measured by VSM at room temperature, which indicate that the saturated magnetization (Ms), remanence (Mr) and coercivity (Hc) of the decorated MWNTs are much larger than those of MWNTs, and the decorated MWNTs exhibit well magnetic properties.

Huiqun, Cao; Meifang, Zhu; Yaogang, Li

2006-10-01

207

The effect of proton irradiation on magnetic properties of lithium ferrites  

Microsoft Academic Search

The effect of proton irradiation on magnetic properties of lithium ferrites has been investigated with x-ray diffraction (XRD), magnetization, and Mössbauer spectroscopy measurements. Li0.5Fe2.5O4 powders have been fabricated by the sol-gel method. Following the annealing at 700 °C, these samples have been proton irradiated with 1, 5, and 10 pC\\/mum2. The analysis of XRD patterns by Rietveld refinement method shows

Sung Wook Hyun; Taejoon Kouh; Sam Jin Kim; Chul Sung Kim

2009-01-01

208

The effect of proton irradiation on magnetic properties of lithium ferrites  

Microsoft Academic Search

The effect of proton irradiation on magnetic properties of lithium ferrites has been investigated with x-ray diffraction (XRD), magnetization, and Mo¨ssbauer spectroscopy measurements. Li0.5Fe2.5O4 powders have been fabricated by the sol-gel method. Following the annealing at 700 °C, these samples have been proton irradiated with 1, 5, and 10 pC\\/?m2. The analysis of XRD patterns by Rietveld refinement method shows

Sung Wook Hyun; Taejoon Kouh; Sam Jin Kim; Chul Sung Kim

2009-01-01

209

XRD study on the electrochemical hydriding\\/dehydriding behavior of the La–Mg–Ni–Cotype hydrogen storage alloys  

Microsoft Academic Search

Electrochemical hydriding\\/dehydriding behavior of the La–Mg–Ni-based alloy La0.7Mg0.3(Ni0.85Co0.15)3.5 consisting of a (La,Mg)Ni3 phase with the PuNi3-type rhombohedral structure and a LaNi5 phase with the CaCu5-type hexagonal structure was systematically investigated by means of X-ray diffraction (XRD) analyses. The results indicate that the PuNi3-type rhombohedral structure and the CaCu5-type hexagonal structure of the alloy are still preserved during hydriding\\/dehydriding process. For

Yongfeng Liu; Hongge Pan; Mingxia Gao; Yongquan Lei; Qidong Wang

2005-01-01

210

Preparation, thermal, XRD, chemical and FTIR spectral analysis of NiMn 2 O 4 nanoparticles and respective precursor  

Microsoft Academic Search

Metal carboxylato-hydrazinates are very good precursors for the synthesis of metal as well as mixed metal oxides as these\\u000a decompose to nanosized oxides with high surface area most of the times at comparatively lower temperatures. In the present\\u000a study one such novel precursor nickel manganese fumarato-hydrazinate (NiMn2(C4H2O4)3·6N2H4) has been prepared and characterized by XRD, FTIR and chemical analysis. The thermal

S. Y. Sawant; V. M. S. Verenkar; S. C. Mojumdar

2007-01-01

211

Microstructural Characterization of Water-Rich Boehmite (AlO(OH)): TEM Correlation of Apparently Divergent XRD and TGA Results  

SciTech Connect

An understanding of the solid-phase thermodynamics and aqueous speciation of aluminum is critical to our ability to understand and predict processes in a wide variety of geologic and industrial settings. Boehmite (AIO(OH)) is an important phase in the system Al2O3-H2O that has been the subject of a number of structural and thermodynamic studies since its initial synthesis [l] and discovery in nature [2]. Unfortunately, it has long been recognized that thermogravimetric analysis (TGA) of both synthetic and natural boehmite samples (that appear well crystallized by powder XRD methods) yields significant excess water - typically losing 16-16.5 wt. % on heating as compared with a nominal expected weight loss of 15.0 wt. % [3,4]. The boehmite used in our experiments was synthesized hydrothermally from acid-washed gibbsite (Al(OH)3) at 200°C. Powder XRD and SEM examination showed no evidence of the presence a contaminant phase. The TGA patterns do not suggest that this is due to adsorbed water, so a structural source is likely. We therefore undertook to examine this material by TEM to clarify this phenomenon.

Allard, L.F.; Anovitz, L.M.; Benezeth, P.; Coffey, D.W.; Palmer, D.A.; Porter, W.D.; Wesolowski, D.J.

1999-08-01

212

Characterization of stabilized/solidified refinery oily sludge and incinerated refinery sludge with cement using XRD, SEM and EXAFS.  

PubMed

Solidification/stabilization (S/S) of refinery oily sludge and incinerated oily sludge (ash) with cement type I42.5 and II42.5 was investigated using, X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM) combined with Energy Dispersive Spectroscopy (EDS) and Extended X-ray Absorption Fine Structure (EXAFS). The results showed that delayed ettringite formation (DEF) and major cement hydration reactions occurred. XRD analysis of S/S oily sludge samples revealed cement-bearing solid phases, such as portlandite, calcite, C(3)S, C(2)S and C(4)AF. SEM analysis, confirmed ettringite at solidified oily sludge samples. Solidified ash samples contained ettringite substituted by chromates. However, solid phases found in solidified ash samples with I42.5 cement showed minor variation in type and structure compared to those observed in solidified ash samples with II42.5 cement. Fe K edge EXAFS analysis revealed the presence of iron oxides in both S/S wastes. The comparison between spectra of the S/S resulting materials and the ones of their original components, showed that the first sphere Fe-O distances were longer than in the pure iron oxide thereby providing evidence that the resulting materials were not simple mixtures, but products of a reaction that modified the local environment of iron. PMID:18584430

Karamalidis, Athanasios K; Psycharis, Vasileios; Nicolis, Ioannis; Pavlidou, Eleni; Benazeth, Simone; Voudrias, Evangelos A

2008-08-01

213

Process monitoring and control with CHEMIN, a miniaturized CCD-based instrument for simultaneous XRD/XRF analysis  

NASA Astrophysics Data System (ADS)

There is a large variety of mining and manufacturing operations where process monitoring and control can benefit from on-site analysis of both chemical and mineralogic constituents. CHEMIN is a CCD-based instrument capable of both X-ray fluorescence (XRF; chemical) and X-ray diffraction (XRD; mineralogic) analysis. Monitoring and control with an instrument like CHEMIN can be applied to feedstocks, intermediate materials, and final products to optimize production. Examples include control of cement feedstock, of ore for smelting, and of minerals that pose inhalation hazards in the workplace. The combined XRD/XRF capability of CHEMIN can be used wherever a desired commodity is associated with unwanted constituents that may be similar in chemistry or structure but not both (e.g., Ca in both gypsum and feldspar, where only the gypsum is desired to make wallboard). In the mining industry, CHEMIN can determine mineral abundances on the spot and enable more economical mining by providing the means to assay when is being mined, quickly and frequently, at minimal cost. In manufacturing, CHEMIN could be used to spot-check the chemical composition and crystalline makeup of a product at any stage of production. Analysis by CHEMIN can be used as feedback in manufacturing processes where rates of heating, process temperature, mixture of feedstocks, and other variables must be adjusted in real time to correct structure and/or chemistry of the product (e.g., prevention of periclase and alkali sulfate coproduction in cement manufacture).

Vaniman, David T.; Bish, D.; Guthrie, G.; Chipera, S.; Blake, David E.; Collins, S. Andy; Elliott, S. T.; Sarrazin, P.

1999-10-01

214

Lead Speciation in House Dust from Canadian Urban Homes Using EXAFS Micro-XRF and Micro-XRD  

SciTech Connect

X-ray absorption fine-structure (XAFS) spectroscopy, micro-X-ray fluorescence ({mu}XRF), and micro-X-ray diffraction ({mu}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{sup -1}). Linear combination fitting of the XAFS data, supported by {mu}XRF and {mu}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.

L MacLean; S Beauchemin; P Rasmussen

2011-12-31

215

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

216

Multivariate analysis of DSC–XRD simultaneous measurement data: a study of multistage crystalline structure changes in a linear poly(ethylene imine) thin film  

Microsoft Academic Search

A multivariate analytical technique has been applied to the analysis of simultaneous measurement data from differential scanning\\u000a calorimetry (DSC) and X-ray diffraction (XRD) in order to study thermal changes in crystalline structure of a linear poly(ethylene\\u000a imine) (LPEI) film. A large number of XRD patterns generated from the simultaneous measurements were subjected to an augmented\\u000a alternative least-squares (ALS) regression analysis,

Hiroyuki Kakuda; Tetsuo Okada; Makoto Otsuka; Yukiteru Katsumoto; Takeshi Hasegawa

2009-01-01

217

Spectral Resolution for Five-Element, Filtered, X-Ray Detector (XRD) Arrays Using the Methods of Backus and Gilbert  

SciTech Connect

The generalized method of Backus and Gilbert (BG) is described and applied to the inverse problem of obtaining spectra from a 5-channel, filtered array of x-ray detectors (XRD's). This diagnostic is routinely fielded on the Z facility at Sandia National Laboratories to study soft x-ray photons ({le}2300 eV), emitted by high density Z-pinch plasmas. The BG method defines spectral resolution limits on the system of response functions that are in good agreement with the unfold method currently in use. The resolution so defined is independent of the source spectrum. For noise-free, simulated data the BG approximating function is also in reasonable agreement with the source spectrum (150 eV black-body) and the unfold. This function may be used as an initial trial function for iterative methods or a regularization model.

FEHL,DAVID LEE; BIGGS,F.; CHANDLER,GORDON A.; STYGAR,WILLIAM A.

2000-01-17

218

Phase and Structural Transformations in FexAl1-x Powder Alloys Studied by 57Fe Moessbauer Spectroscopy and XRD  

SciTech Connect

Phase composition of powder FexAlx-1 alloys prepared by self-propagated high temperature synthesis (SHS) and atomic rearrangements in B2 FeAl due to varying Al concentration and annealing have been investigated by X-ray diffraction (XRD) and 57Fe transmission Moessbauer spectroscopy (TMS). It has been established that phase composition of FeAl alloys is basically close to equilibrium phase diagram. However, some phases showed deviations from stoichiometric composition. Atomic arrangement in B2 FeAl phase demonstrated strong dependency on Al content in alloys. Some peculiarities of B2 FeAl atomic arrangement in SHS prepared FexAlx-1 alloys have been observed and discussed.

Fedotova, Julia; Zalesskii, Alexander [NC PHEP BSU, 220040 Minsk M.Bogdanovich str. 153 (Belarus); Ilyuschenko, Alexander; Talako, Tatyana; Belyaev, Alexander; Letsko, Andrei [Research Institute of Powder Metallurgy, 220071 Minsk, Platonova str. 41 (Belarus); Stanek, Jan [Institute of Physics, Jagiellonian University, 30-059 Cracow, Reymonta str 4 (Poland)

2005-04-26

219

Reversible oxidation/reduction in the CeTaO{sub 4+{delta}} system: A TEM and XRD study  

SciTech Connect

A detailed TEM and XRD study has been made of the basic crystallography (unit cells, space group symmetries, and twin relationships) of each of the three oxidized phases which occur in the CeTaO{sub 4+{delta}} system, their structural relationship to stoichiometric Ce{sup +III}TaO{sub 4}, and their temperature-dependent redox reactions. Such crystallographic knowledge is essential to understand the structural relationships between the various phases and to gain insight into the oxidation/reduction mechanisms allowing the formation of the oxidized phases. Twinning is found to be endemic in stoichiometric Ce{sup +III}TaO{sub 4} as well as in each of the oxidized Series 2, 3, and 4 phases; the twin plane relating the twin variants is derived in each case.

Drew, G.; Withers, R.L.; Larsson, A.K.; Schmid, S. [Australian National Univ., Canberra (Australia). Research School of Chemistry

1998-10-01

220

Degradation of dental ZrO2-based materials after hydrothermal fatigue. Part I: XRD, XRF, and FESEM analyses.  

PubMed

The aim was to investigate the effect of simulated low-temperature degradation (s-LTD) and hydrothermal fatigue on the degradation of three ZrO(2)-based dental materials. Lava, IPS, and NanoZr discs were randomly assigned to (1) Control-Storage in distilled water at 37°C; (2) Aging at 134°C for 5 h (s-LTD); (3) Thermocycling in saliva for 30,000 cycles (TF). XRD revealed that ZrO(2) m phase was identified in all groups but TF increased the m phase only for Lava. Under the FESEM, Lava showed no alterations under s-LTD, but displayed corrosion areas up to 60 µm wide after TF. We conclude that TF accelerated the degradation of Lava through an increase in the m phase and grain pull-out from the material surface. PMID:22447060

Perdigão, Jorge; Pinto, Ana M; Monteiro, Regina C C; Braz Fernandes, Francisco M; Laranjeira, Pedro; Veiga, João P

2012-03-23

221

Changes in the surfaces on DDOAB organoclays adsorbed with paranitrophenol-An XRD, TEM and TG study  

SciTech Connect

The adsorption of paranitrophenol on organoclays synthesised by the ion exchange of the surfactant molecule dimethyldioctadecylammonium bromide (DDOAB) of formula (CH{sub 3}(CH{sub 2}){sub 17}){sub 2}NBr(CH{sub 3}){sub 2} has been studied by X-ray diffraction (XRD), transmission electron microscopy (TEM) and thermogravimetric analysis. The expansion of the montmorillonite depends on the loading of the montmorillonite with dimethyldioctadecylammonium bromide and is related to the arrangement of the surfactant molecules within the clay interlayer. This expansion is altered by the adsorbed paranitrophenol and is observed in the transmission electron microscopic images of the organoclay with adsorbed paranitrophenol. Changes in the surfactant molecular arrangements were analysed by thermogravimetry. The paranitrophenol is sublimed simultaneously with the loss of surfactant. The dehydroxylation temperature of the montmorillonite is decreased upon adsorption of the paranitrophenol indicating a bonding between the paranitrophenol and the hydroxyl units of the montmorillonite.

Zhou Qin [Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640 (China); Inorganic Materials Research Program, School of Physical and Chemical Sciences, Queensland University of Technology, GPO Box 2434, Brisbane, QLD 4001 (Australia); Graduate University of Chinese Academy of Sciences, Beijing 100039 (China); He Hongping [Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640 (China); Inorganic Materials Research Program, School of Physical and Chemical Sciences, Queensland University of Technology, GPO Box 2434, Brisbane, QLD 4001 (Australia); Frost, Ray L. [Inorganic Materials Research Program, School of Physical and Chemical Sciences, Queensland University of Technology, GPO Box 2434, Brisbane, QLD 4001 (Australia)], E-mail: r.frost@qut.edu.au; Xi Yunfei [Inorganic Materials Research Program, School of Physical and Chemical Sciences, Queensland University of Technology, GPO Box 2434, Brisbane, QLD 4001 (Australia); Centre for Environmental Risk Assessment and Remediation, University of South Australia, Mawson Lakes, SA 5095 (Australia)

2008-12-01

222

Structural characterization of La3+ modified Bi4Ti3O12 ferroelectric ceramics by XRD and XAS techniques  

NASA Astrophysics Data System (ADS)

Bi4~xLaxTi3O12 (BLT) ceramics were prepared and studied in this work in terms of La3+~ modified the long and short range order structure. According to the results obtained from X-ray diffraction (XRD), the solubility limit (xL) of La3+ into the Bi4Ti3O12 (BIT) matrix was here found to locate slightly above x = 1.5 and all samples bellow this limit presents reflection peaks characteristic of the orthorhombic Bi4Ti3O12 sample. X-ray absorption near edge spectra (XANES) shows that the local order around Ti, Bi and La atoms is not significantly affected by the increase of La amount as well as by the fact that La atoms could be located on different Bi sites.

Santos, V. B.; Mir, M.; Mastelaro, V. R.; M'peko, J. C.; Mascarenhas, Y. P.; Hernandes, A. C.; Neves, P. P.

2009-01-01

223

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 T=415K and a magnetic moment of 3.0?/f.u. Several measurements made by SQUID magnetometer, FMR and Mössbauer spectroscopy showed that the 31 nm crystallite sample behaves superparamagnetically with blocking temperature T=35K and it has a reduced saturation magnetization of 1.0?/f.u. at 5 K and effective paramagnetic moment of 3.0?.

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

2007-02-01

224

The inconsistency in adsorption properties and powder XRD data of MOF-5 is rationalized by framework interpenetration and the presence of organic and inorganic species in the nanocavities.  

PubMed

MOF-5 is the archetype metal-organic framework and has been subjected to numerous studies the past few years. The focal point of this report is the pitfalls related to the MOF-5 phase identification based on powder XRD data. A broad set of conditions and procedures have been reported for MOF-5 synthesis. These variations have led to materials with substantially different adsorption properties (specific surface areas in the range 700 to 3400 m(2)/g). The relatively low weight loss observed for some as synthesized samples upon solvent removal is also indicative of a low pore volume. Regrettably, these materials have all been described as MOF-5 without any further comments. Furthermore, the reported powder XRD patterns hint at structural differences: The variations in surface area are accompanied by peak splitting phenomena and rather pronounced changes in the relative peak intensities in the powder XRD patterns. In this work, we use single-crystal XRD to investigate structural differences between low and high surface area MOF-5. The low surface area MOF-5 sample had two different classes of crystals. For the dominant phase, Zn(OH)2 species partly occupied the cavities. The presence of Zn species makes the hosting cavity and possibly also adjacent cavities inaccessible and thus efficiently reduces the pore volume of the material. Furthermore, the minor phase consisted of doubly interpenetrated MOF-5 networks, which lowers the adsorption capacity. The presence of Zn species and lattice interpenetration changes the symmetry from cubic to trigonal and explains the peak splitting observed in the powder XRD patterns. Pore-filling effects from the Zn species (and partly the solvent molecules) are also responsible for the pronounced variations in powder XRD peak intensities. This latter conclusion is particularly useful for predicting the adsorption properties of a MOF-5-type material from powder XRD. PMID:17341071

Hafizovic, Jasmina; Bjørgen, Morten; Olsbye, Unni; Dietzel, Pascal D C; Bordiga, Silvia; Prestipino, Carmelo; Lamberti, Carlo; Lillerud, Karl Petter

2007-03-07

225

The importance of XRD analysis in provenance and palaeoenvironmental studies of the Piedras de Afilar Formation, Neoproterozoic of Uruguay  

NASA Astrophysics Data System (ADS)

The Piedras de Afilar Formation crops out in the southeast part of Uruguay, forming part of the Tandilia Terrane (sensu Bossi et al. 2005). Pamoukaghlian et al. (2006) and Gaucher et al. (2008) have published ?13C, ?18O and U/Pb SHRIMP results, which indicate a Neoproterozoic age for this formation. The palaeoenvironment has been defined as a shallow marine platform based on the presence of interference ripples, hummocky and mega-hummocky cross-stratification. X-ray diffraction (XRD) analyses help to better constrain the palaeoenvironment: the presence of chlorite/smectite found in black shales, suggest a reducing environment, and abundant illite indicates a cold to temperate climate. Provenance studies have been undertaken that utilise a combination of detailed palaeocurrent measurements, petrographic descriptions, XRD analyses, and geochemical isotopic analyses, including U/Pb SHRIMP determinations. Mineral compositional diagrams for sandstones suggest a stable cratonic provenance. Palaeocurrents are mainly from the NNE, indicating a provenance from the cratonic areas of the Tandilia Terrane. The illite crystal index indicates diagenetic to low-metamorphic conditions for the sequence; this is important to confirm that the identified minerals are authigenic. Clay minerals identified by XRD analysis of sandstones from the siliciclastic member are illite (80 - 90%), kaolinite (5 - 10%), and chlorite (5 - 10%). This is consistent with a provenance from the cratonic areas (quartz-feldspar dominated rock types). Isotopic analyses have been undertaken to provide better constraints on the tectonic setting. U/Pb SHRIMP ages for the youngest zircons are 990 Ma (Gaucher et al. 2008), and the basal granite (Granito de la Paz) is 2056 ± 11 Ma (Hartmann et al. 2001), suggesting a provenance from the Archaean basement for the Piedras de Afilar Formation, like its counterparts in the Rio de la Plata Craton. References Bossi, J., Piñeyro, D., Cingolani, C. (2005). El límite norte del Terreno Piedra Alta (Uruguay). Importancia de la faja milonítica sinestral de Colonia. Actas XVI Congreso Argentino de Geología, de La Plata. Gaucher, C., Poiré, D.G., Finney, S.C., Valencia, V.a., Blanco, G., Pamoukaghlian, K., Gómez Peral, L. (2008). Detrital zircón ages of Neoproterozoic sedimentary successions in Uruguay and Argentina: Insights into the geological evolution of the Rio de la Plata Craton. Precambrian Research. Hartmann, L.A., Campal, N., Santos, J.O., Mc. Neughton, N.J., Schipilov, A., Lafon, J.M. (2001). Archean crust in the Rio de la Plata Craton, Uruguay - SHRIMP U-Pb zircon reconnaissance geochronology. Journal of South American Earth Science, 14, 557-570. Pamoukaghlian, K., Gaucher, C., Bossi, J., Sial, N., Poire, D.G. (2006). First C and O isotopic data for the Piedras de Afilar Formation, Tandilia Terrane, Uruguay: their bearing on correlation and age. Fifth South American Symposium on Isotope Geology, Punta del Este.

Pamoukaghlian, K.; Poiré, D. G.; Gaucher, C.; Uriz, N.; Cingolani, C.; Frigeiro, P.

2009-04-01

226

Magnetically separable composite photocatalyst with enhanced photocatalytic activity.  

PubMed

A novel magnetically separable composite photocatalyst, anatase titania-coated magnetic activated carbon (TMAC), was prepared in this article. In the synthesis, magnetic activated carbon (MAC) was firstly obtained by adsorbing magnetic Fe3O4 nanoparticles onto the activated carbon (AC), and then the obtained MAC was directly coated by anatase titania nanoparticles prepared at low temperature (i.e. 75 degrees C). The prepared samples were characterized by XRD, SEM and vibrating sample magnetometer (VSM). The composite photocatalyst can be easily separated from solution by a magnet, its photocatalytic activity in degradation of phenol in aqueous solution also has dramatic enhancement compared to that of the neat titania. PMID:18406055

Ao, Yanhui; Xu, Jingjing; Shen, Xunwei; Fu, Degang; Yuan, Chunwei

2008-03-08

227

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

2010-03-11

228

CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES: Effect of Temperature on Structural and Magnetic Properties of Laser Ablated Iron Oxide Deposited on Si(100)  

Microsoft Academic Search

We fabricate Fe3O4 thin films on Si(100) substrates at different temperatures using pulsed laser deposition, and study the effect of annealing and deposition temperature on the structural and magnetic properties of Fe3O4 thin films. Subsequently, the films are characterized by x-ray diffraction (XRD), scanning electron microscopy (SEM) and vibrating sample magnetometery (VSM). The XRD results of these films confirm the

Ramay M. Shahid; Siddiqi A. Saadat; Anwar M. Sabieh; S. Shin C

2009-01-01

229

Surface mediated Ag-Hg alloy formation under ambient and vacuum conditions—AFM and XRD investigations  

NASA Astrophysics Data System (ADS)

Thin Ag films deposited under UHV conditions on a glass support were exposed to Hg vapor at 298 K under two different conditions: vacuum, and ambient atmosphere. The influence of the amalgamation process on film topography was studied by the atomic force microscopy (AFM) method, while the composition of the amalgams was determined by means of X-ray diffraction (XRD). The obtained results indicated the different mechanism of Ag 2Hg 3 alloy formation depending on whether the amalgam is formed in a vacuum or under ambient atmosphere. This is discussed as a consequence of the influence of oxygen and different kinetics of the amalgamation process performed under both conditions. Heating of amalgam leads to gradual reconstruction of the alloy (370 K) and finally its decomposition (500 K), leaving strongly modified, discontinuous silver film. The ultimate nanostructure of the film depends on the transport mechanism of the silver nanounits during the amalgamation process. Therefore, Ag-Hg alloy formation and decomposition seems to be a practical and promising method for the preparation of discontinuous thin silver films of significant thickness and mesoscopic structure.

Nowakowski, Robert; Pielaszek, Jerzy; Du?, Ryszard

230

Composite uranium carbide targets at TRIUMF: Development and characterization with SEM, XRD, XRF and L-edge densitometry  

NASA Astrophysics Data System (ADS)

The production of radioactive ion beams (RIB) from spallation targets by irradiation with a continuous 500 MeV proton beam, has been routine at TRIUMF for several years. Based on the experience with composite refractory carbide targets a procedure for the fabrication of UC2/C targets was developed. It includes the preparation of UC2 by carbothermal reduction of UO2, the slip-casting of fine-grained UC2/C slurry on graphite foil under inert gas atmosphere and the cutting of composite target discs which are stacked up to a lamellar structure. The thermal properties of such an arrangement are adequate to withstand the high power deposition of an intense, continuous proton beam and also beneficial for the fast release of short-lived radioactive isotopes. Molecular structure, particle size and the impact of sintering of the target discs were investigated via XRD and SEM. Thickness and mass distribution were measured with position-sensitive LIII-edge densitometry. The results confirm that the properties of the UC2/C target material are well suited for RIB production at TRIUMF while there is still room for improvement with regard to uniformity of mass distribution in target disc thickness.

Kunz, Peter; Bricault, Pierre; Dombsky, Marik; Erdmann, Nicole; Hanemaayer, Vicky; Wong, John; Lützenkirchen, Klaus

2013-09-01

231

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

232

Tandem transmission/reflection mode XRD instrument including XRF for in situ measurement of Martian rocks and soils  

NASA Astrophysics Data System (ADS)

The mineralogy of the surface material of Mars is the key to disclose its present and past life and climates. Clay mineral species, carbonates, and ice (water and CO2) are and/or contain their witnesses. X-ray powder diffraction (XRPD) is the most powerful analytical method to identify and quantitatively characterize minerals in complex mixtures. This paper discusses the development of a working model of an instrument consisting of a reflection mode diffractometer and a transmission mode CCD-XRPD instrument, combined with an XRF module. The CCD-XRD/XRF instrument is analogous to the instrument for Mars missions developed by Sarrazin et al. (1998). This part of the tandem instrument enables "quick and dirty" analysis of powdered (!) matter to monitor semi-quantitatively the presence of clay minerals as a group, carbonates, and ices and yields semi-quantitative chemical information from X-ray fluorescence (XRF). The reflection mode instrument (i) enables in-situ measurements of rocks and soils and quantitative information on the compounds identified, (ii) has a high resolution and reveals large spacings for accurate identification, in particular of clay mineral species, and (iii) the shape of the line profiles observed reveals the kind and approximate amounts of lattice imperfections present. It will be shown that the information obtained with the reflection mode diffractometer is crucial for finding signs of life and changes in the climate on Mars. Obviously this instrument can also be used for other extra-terrestrial research.

Delhez, Robert; Van der Gaast, S. J.; Wielders, Arno; de Boer, J. L.; Helmholdt, R. B.; van Mechelen, J.; Reiss, C.; Woning, L.; Schenk, H.

2003-02-01

233

Investigation of the electrocatalysis for oxygen reduction reaction by Pt and binary Pt alloys: an XRD, XAS and electrochemical study  

SciTech Connect

Electrocatalysis for the oxygen reduction reaction (ORR) on five binary Pt alloy electrocatalysts (PtCr/C, PtMn/C, PtFe/C, PtCo/C and PtNi/C) supported on carbon have been investigated. The electrochemical characteristics for ORR in a proton conducting fuel cell environment has been correlated with the electronic and structural parameters determined under in situ conditions using XANES and EXAFS technique respectively. Results indicate that all the alloys possess higher Pt 5d band vacancies as compared to Pt/C. There is also evidence of lattice contraction in the alloys (supported by XRD results). Further, the Pt/C shows increase in Pt 5 d band vacancies during potential transitions from 0.54 to 0.84 V vs. RHE, which has been ration@ on the basis of OH type adsorption. In contrast to this, the alloys do not exhibit such an enhancement. Detailed EXAFS analysis supports the presence of OH species on Pt/C and its relative absence in the alloys. Correlation of the electrochemical results with bond distances and d-band vacancies show a volcano type behavior with the PtCr/C on top of the curve.

Mukerjee, S.; McBreen, J. [Brookhaven National Lab., Upton, NY (United States); Srinivasan, S. [Texas A and M Univ., College Station, TX (United States). Texas Engineering Experiment Station

1995-12-31

234

TEM, XRD and AFM study of poly( o-ethoxyaniline) films: new evidence for the formation of conducting islands  

NASA Astrophysics Data System (ADS)

The existence of conducting islands in polyaniline films has long been proposed in the literature, which would be consistent with conducting mechanisms based on hopping. Obtaining direct evidence of conducting islands, however, is not straightforward. In this paper, conducting islands were visualized in poly( o-ethoxyaniline) (POEA) films prepared at low pH, using Transmission Electron Microscopy (TEM) and atomic force spectroscopy (AFS). The size of the islands varied between 67 and 470 Å for a pH=3.0, with a larger average being obtained with AFS, probably due to the finite size effect of the atomic force microscopy tip. In AFS, the conducting islands were denoted by regions with repulsive forces due to the double-layer forces. On the basis of X-ray diffraction (XRD) patterns for POEA in the powder form, we infer that the conducting islands are crystalline, and therefore a POEA film is believed to consist of conducting islands dispersed in an insulating, amorphous matrix. From conductivity measurements we inferred the charge transport to be governed by a typical quasi-one dimensional variable range hopping (VRH) mechanism.

Leite, Fabio L.; Alves, William F.; Mir, Mirta; Mascarenhas, Yvonne P.; Herrmann, Paulo S. P.; Mattoso, Luiz H. C.; Oliveira, Osvaldo N.

2008-11-01

235

XRD, XPS, optical, and Raman investigations of structural changes of nanoCo-doped ZnO  

NASA Astrophysics Data System (ADS)

The mixed oxides Zn1-xCoxO (ZCO) (0.0 ? x ? 3.0) were prepared as nanopolycrystalline powders and thin films by a simple sol-gel process and dip coating method. Structural and microstructural analysis was carried out applying X-ray diffraction (XRD) and Rietveld method. Analysis showed that for x < 0.12, Co2+ replaces Zn2+ substitutionally yielding ZCO single phase, while for x ? 0.15 two phases are identified; ZCO and Co3O4. Replacing Zn+2 by Co+2 affects the lattice parameters in opposite ways, the parameter c decreases while a increases with an overall decrease in the ratio c/a of the wurtzite ZCO, which deviates the lattice gradually from the hexagonal structure as Co+2 increases. The IR analysis shows red shift entirely dependent on Co concentration. With increased concentration of cobalt the E2high Raman mode exhibits a redshift attributed to the phonon softening caused by the ab-plane lattice expansion, while the E2low mode shows a blueshift due to the reduced mass effect caused by cation replacement.

Heiba, Z. K.; Arda, L.

2012-08-01

236

Easy synthesis of high-purity BiFeO3 nanoparticles: new insights derived from the structural, optical, and magnetic characterization.  

PubMed

Synthesis of high-purity BiFeO3 is very important for practical applications. This task has been very challenging for the scientific community because nonstoichiometric Bi(x)Fe(y)O(z) species typically appear as byproducts in most of the synthesis routes. In the present work, we outline the synthesis of BiFeO3 nanostructures by a combustion reaction, employing tartaric acid or glycine as promoter. When glycine is used, a porous BiFeO3 network composed of tightly assembled and sintered nanocrystallites is obtained. The origin of high purity BiFeO3 nanomaterial as well as the formation of other byproducts is explained on the basis of metal-ligand interactions. Structural, morphological, and optical analysis of the intermediate that preceded the formation of porous BiFeO3 structures was accomplished. The thorough characterization of BiFeO3 nanoparticles (NPs) included powder X-ray diffraction (XRD); scanning electron microscopy (SEM) and high resolution transmission electron microscopy (HRTEM); thermogravimetric analysis (TGA); UV-vis electronic absorption (diffuse reflectance mode), Raman scattering, Mössbauer, and electron paramagnetic resonance (EPR) spectroscopies; and vibrating sample magnetometry (VSM). The byproducts like ?-Bi2O3 and 5 nm Bi2Fe4O9 NPs were obtained when tartaric acid was the promoter. However, no such byproducts were formed using glycine in the synthesis process. The average sizes of the crystallites for BiFeO3 were 26 and 23 nm, for tartaric acid and glycine promoters, respectively. Two band gap energies, 2.27 and 1.66 eV, were found for BiFeO3 synthesized with tartaric acid, obtained from Tauc's plots. A remarkable selective enhancement in the intensity of the BiFeO3 A1 mode, as a consequence of the resonance Raman effect, was observed and discussed for the first time in this work. For glycine-promoted BiFeO3 nanostructures, the measured magnetization (M) value at 20,000 Oe (0.64 emu g(-1)) was ?5 times lower than that obtained using tartaric acid. The difference between the M values has been associated with the different morphologies of the BiFeO3 nanostructures. PMID:23967797

Ortiz-Quiñonez, José Luis; Díaz, David; Zumeta-Dubé, Inti; Arriola-Santamaría, Humberto; Betancourt, Israel; Santiago-Jacinto, Patricia; Nava-Etzana, Noel

2013-08-22

237

Quantitative HRTEM analysis of FIB prepared specimens.  

PubMed

The preparation of good transmission electron microscopy specimens with minimum milling damage can be very complicated, especially from a specific area in a sample. Therefore, a novel approach for transmission electron microscopy specimen preparation using a focused ion beam system is proposed, based on the use of low energy (5 kV)Ga ions and a low incident ion angle (approximately 1 degree ) from a thickness of approximately 500 nm until the sample is electron transparent. Transmission electron microscopy specimens prepared by this method have significantly less irradiation damage, demonstrated by successful quantitative high-resolution transmission electron microscopy conducted on sapphire from data acquired using an aberration-corrected field emission gun transmission electron microscopy. Quantitative analysis was conducted by iterative digital image matching. The accuracy and sensitivity of the matching process is discussed. PMID:19094016

Baram, M; Kaplan, W D

2008-12-01

238

Interface charge transfer in polypyrrole coated perovskite manganite magnetic nanoparticles  

NASA Astrophysics Data System (ADS)

Different hybrid structures were obtained by coating magnetic nanoparticles of perovskite type manganite at optimal doping (La0.67Sr0.33MnO3,LSMO) with different quantities of polypyrrole (PPy). The amorphous layer of polypyrrole surrounding the crystalline magnetic core was observed by high resolution transmission electron microscopy (HRTEM) and analyzed by using X-ray photoelectron spectroscopy (XPS) and X-ray absorption spectroscopy (XAS) measurements in near edge structure (XANES) techniques. By analyzing the magnetic behavior of the samples one can observe that the surface modification of magnetic nanoparticles by PPy results in an increase in the saturation magnetization of the composites. The process is ascribed to paired electrons transferred from the delocalized ? states of the PPy into the outer disordered layers of the manganite. The analysis of pre-edge peak of the Mn K-edge XANES spectra in the case of PPy coated LSMO nanoparticles indicates that the charge transfer between polymer and nanoparticles is (directed) going to missing or distorted oxygen positions, hence increasing the 3d electrons' mobility and orbital hybridization between the neighboring manganese ion. As a consequence, within the surface layers of LSMO nanoparticles, both energy bands disrupted the structure, and the double exchange process between Mn ions was reestablished determining the saturation magnetizations and pre-edge features increase, respectively.

Pana, O.; Soran, M. L.; Leostean, C.; Macavei, S.; Gautron, E.; Teodorescu, C. M.; Gheorghe, N.; Chauvet, O.

2012-02-01

239

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

240

Use of an ultrasonic/sonic driller/corer to obtain sample powder for chemin, a combined XRD/XRF instrument.  

SciTech Connect

One of the technical issues that must be addressed before landing an XRD,iXRF spectrometer on an extraterrestrial body is how best to obtain a representative sample powder for analysis. For XRD powder diffraction analyses, it is beneficial to have a powder that is extremely fine grained to reduce preferred orientation effects and to provide a statistically significant number of crystallites to the Xray beam. Although a 2 dimensional detector as used in the CHEMIN instrument will produce good results with poorly prepared powders, the quality of the data will improve with the quality of the sample powder.

Chipera, S. J. (Steve J.); Bish, D. L. (David L.); Vaniman, D. T. (David T.); Sherrit, S.; Bar-Cohen, Yoseph; Blake, D.

2003-01-01

241

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

242

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

243

Memory effect of activated Mg-Al hydrotalcite: in situ XRD studies during decomposition and gas-phase reconstruction.  

PubMed

The thermal decomposition of Mg-Al hydrotalcite and the subsequent reconstruction of the decomposed products in the presence of water vapor (2 vol. % H(2)O in N(2)) have been investigated by in situ XRD. Thermographic analysis and temperature-programmed desorption MS results complemented the diffraction data. Valuable mechanistic and kinetic insights into these processes, which are of prime importance for optimal activation of this type of material for catalytic applications, were obtained. Hydrotalcite decomposition to the mixed oxide proceeds via formation at 423-473 K of an intermediate phase, consisting of a highly disordered, dehydrated, layered structure. The latter evolves by removal of interlayer water on heating, causing a shrinking of the interlayer space (it is up to 45 % smaller than in the as-synthesized hydrotalcite). Above 623 K, Mg(Al)O(x) oxide with the periclase structure is formed. Reversion of the intermediate dehydrated structure to hydrotalcite upon contact with water vapor is complete and very fast at room temperature. Recovery of hydrotalcite from the oxide calcined at 723 K is two orders of magnitude slower than rehydration of the intermediate layered structure and one order of magnitude slower than the typically practiced liquid-phase reconstruction. In contrast to the decomposition, the reconstruction mechanism does not involve an intermediate phase. The gas-phase rehydration and reconstruction was interrupted above 303 K. This is attributed to the poor wetting of the surface of the decomposed materials induced by hampered H(2)O adsorption above room temperature at the water vapor pressure applied. The Avrami-Erofe'ev model describes the reconstruction kinetics well. PMID:17029312

Pérez-Ramírez, Javier; Abelló, Sònia; van der Pers, Niek M

2007-01-01

244

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

2009-01-14

245

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

NASA Astrophysics Data System (ADS)

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 AB3 alloy 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.

Leela Mohana Reddy, A.; Ramaprabhu, S.

2008-02-01

246

Synthesis and Characterization of Nanocrystalline Magnetic Pigment via Coordinated Precursors  

Microsoft Academic Search

anocrystalline cobalt ferrite as a magnetic black pigment was synthesized via coordinated precursors with a significant decrease of the synthesis temperature using citric acid as a coordinating agent. The structure and properties of the cobalt ferrite powder were characterized by X-ray diffraction (XRD), colorimetric analysis (L * a * b * color parameters), diffuse reflectance spectroscopy and vibrating sample magnetometer

M. Gharagozlou

247

Magnetic Polymer Nanocomposites with Tunable Microwave Properties  

Microsoft Academic Search

Due to the multifunctionality, polymer nanocomposites (PNCs) have potential applications for electromagnetic interference shielding, tunable electromagnetic devices and flexible electronics. We report on synthesis, magnetic and RF characterization of polymer films loaded with varying concentrations of Fe3O4 and CoFe2O4 nanoparticles. The nanoparticles (5 ± 1 nm) were synthesized by chemical co-precipitation. Structural properties were characterized by XRD and TEM. Nanoparticles

K. Stojak; S. Pal; H. Srikanth; S. Skidmore; C. Morales; J. Dewdney; J. Wang; T. Weller

2010-01-01

248

Specialty Magnets.  

National Technical Information Service (NTIS)

A number of basic conceptual designs are explained for magnet systems that use permanent magnet materials. Included are iron free multipoles and hybrid magnets. Also appended is a discussion of the manufacturing process and magnetic properties of some per...

K. Halbach

1986-01-01

249

Silica aerogel–iron oxide nanocomposites: structural and magnetic properties  

Microsoft Academic Search

Magnetic nanocomposites formed by iron oxide particles hosted in silica aerogels pores have been synthesized by sol–gel processes and supercritical evacuation of the solvent. Two iron-containing salts have been essayed: (A) Fe(NO3)·9H2O and (B) FeNa(EDTA)·2H2O. The synthetic routes made use of the gel pores as nanoreactors. Structural and magnetic properties have been studied by combining X-ray diffraction (XRD), N2 adsorption

L. Casas; A Roig; E Rodr??guez; E Molins; J Tejada; J Sort

2001-01-01

250

Influence of magnetic field on sodium hexafluorosilicate synthesis  

Microsoft Academic Search

Sodium hexafluorosilicate (SFS) crystals were synthesized by precipitation by the reaction of hydrofluorosilicic acid and sodium carbonate at a pH of 2.5 and 3.5 and a magnetic field of 5.5T was applied immediately after precipitation for 45min at 20°C. SEM, XRD and FTIR spectroscope examined the crystals produced with and without a magnetic field.

R. Chandrasekhar

2000-01-01

251

Study on industrial wastewater treatment using superconducting magnetic separation  

Microsoft Academic Search

The mechanism of industrial wastewater treatment using superconducting magnetic separation is investigated. Fe3O4 nanoparticles were prepared by liquid precipitation and characterized by X-ray diffraction (XRD). Polyacrylic acid (PAA) film was coated on the magnetic particles using plasma coating technique. Transmission electron microscope (TEM) observation and infrared spectrum measurement indicate that the particle surface is well coated with PAA, and the

Hao Zhang; Zhengquan Zhao; Xiangdong Xu; Laifeng Li

2011-01-01

252

New T c -tuned magnetic nanoparticles for self-controlled hyperthermia  

Microsoft Academic Search

Manganese perovskite nanoparticles of the XRD size in the range of 30–49nm were synthesized via sol–gel technique employing citric acid and ethylene glycol. Their magnetic properties were investigated in the static and alternating magnetic fields. Particular attention was paid to the relation between the size of particles and resulting magnetic power losses, measured by the calorimetric heating experiments on the

E. Pollert; K. Knízek; M. Marysko; P. Kaspar; S. Vasseur; E. Duguet

2007-01-01

253

New Tc-tuned magnetic nanoparticles for self-controlled hyperthermia  

NASA Astrophysics Data System (ADS)

Manganese perovskite nanoparticles of the XRD size in the range of 30-49 nm were synthesized via sol-gel technique employing citric acid and ethylene glycol. Their magnetic properties were investigated in the static and alternating magnetic fields. Particular attention was paid to the relation between the size of particles and resulting magnetic power losses, measured by the calorimetric heating experiments on the stable water suspensions and of the hysteresis loops in the alternating fields on powdered samples.

Pollert, E.; Knížek, K.; Maryško, M.; Kašpar, P.; Vasseur, S.; Duguet, E.

2007-09-01

254

Magnetic Spinner  

NASA Astrophysics Data System (ADS)

A science toy sometimes called the ``magnetic spinner'' is an interesting class demonstration to illustrate the principles of magnetic levitation. It can also be used to demonstrate Faraday's law and a horizontally suspended physical pendulum. The levitated part contains two circular magnets encased in a plastic housing. Each magnet stays above two triangular magnets fixed to the base. The magnetic repulsive force experienced by the circular magnets is independent of their orientation; therefore, the holder of these magnets can be rotated without affecting its stability. The holder with the circular magnets can be oscillated up and down as a horizontally suspended physical pendulum.

Ouseph, P. J.

2006-12-01

255

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

256

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

257

Specialty magnets  

SciTech Connect

A number of basic conceptual designs are explained for magnet systems that use permanent magnet materials. Included are iron free multipoles and hybrid magnets. Also appended is a discussion of the manufacturing process and magnetic properties of some permanent magnet materials. (LEW)

Halbach, K.

1986-07-01

258

Determination of the Al Composition of Al{sub x}Ga{sub 1-x}N Thin Films By Means Of EDX and XRD Techniques  

SciTech Connect

In this paper, the determinations of Al composition x of Al{sub x}Ga{sub 1-x}N(0{<=}x{<=}1) thin films by means of the energy dispersive X-ray (EDX) and X-ray diffraction (XRD) analyses are reported. Through these non-destructive and contactless techniques, a large probed area of the Al{sub x}Ga{sub 1-x}N samples can be selected. Consequently, the uncertainty due to the inhomogeneity of the Al composition can be avoided. For EDX measurements, the Al composition is calculated based on the weight percent of the Al and Ga elements, while that in the XRD measurements is based on lattice constant c and Vegard's law. The results from these two independent techniques are in good agreement with each other.

Ng, S. S.; Hassan, Z.; Hassan, H. Abu

2010-07-07

259

Studies on the intercalation of naproxen into layered double hydroxide and its thermal decomposition by in situ FT-IR and in situ HT-XRD  

NASA Astrophysics Data System (ADS)

Layered double hydroxides, novel anionic clay, meet the first requirement as inorganic matrices for encapsulating functional drugs or biomolecules with negative charge in aqueous media. In this study, naproxen has been intercalated into Mg-Al layered double hydroxide by the methods of ion exchange. The structure and composition of the intercalated material have been studied by X-ray diffraction (XRD), UV-vis spectroscopy and inductively coupled plasma emission spectroscopy. A schematic model has been proposed. Furthermore, in situ Fourier transform infrared spectroscopy, in situ high-temperature XRD, and thermogravimetry (TG) have been used to characterize the thermal decomposition of the hybrid material. It has been found that the thermal stability of the intercalated naproxen is significantly enhanced compared with the pure form before intercalation, which suggests that this drug-inorganic layered material may have prospective application as the basis of a novel drug delivery system.

Wei, Min; Shi, Shuxian; Wang, Ji; Li, Yong; Duan, Xue

2004-07-01

260

Alteration of the Callovo–Oxfordian clay from Meuse-Haute Marne underground laboratory (France) by alkaline solution. I. A XRD and CEC study  

Microsoft Academic Search

The reaction of the clay fraction of the Callovo–Oxfordian hard shale formation hosting the French underground laboratory site, with high pH NaOH, KOH and Ca(OH)2 solutions has been investigated through closed system experiments at 60, 90 and 120 °C over 6, 24 and 168 h. The mineralogical composition of the run samples has been determined using X-ray diffraction (XRD) of

S. Ram??rez; P. Vieillard; A. Bouchet; A. Cassagnabère; A. Meunier; E. Jacquot

2005-01-01

261

An X-ray diffraction (XRD) and Fourier transform infrared spectroscopic (FT-IR) characterization of the speciation of arsenic (V) in Portland cement type-V  

Microsoft Academic Search

The speciation of As(V) bearing oxyanions (AsO43?) in cementitious environment has been investigated by X-ray diffraction (XRD) and Fourier Transform Infrared Spectroscopy (FT-IR). The hydration of Portland cement type-V(OPC-V) was found to be retarded in presence of AsO43?, and the retardation was caused mainly by the formation of highly insoluble calcium arsenate on the surface of hydrating cement particles. Arsenate

M. Yousuf A. Mollah; Felix Lu; David L. Cocke

1998-01-01

262

Anion and cation distributions in Fe(II–III) hydroxysalt green rusts from XRD and Mössbauer analysis (carbonate, chloride, sulphate, …); the “fougerite” mineral  

Microsoft Academic Search

Main crystallographic features of Fe(II–III) hydroxysalts usually named green rusts are known from XRD. However, Mössbauer spectroscopy often used to characterise them revealed that several Fe(II) sites exist that have not been elucidated yet. The structure is classified in green rust one, GR1, and green rust two, GR2, according to the sequence of stacking of Fe(OH)2 brucite-like layers that depends

Jean-Marie R. Génin; Christian Ruby

2004-01-01

263

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

Microsoft Academic Search

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

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

2001-01-01

264

XRD and XPS characterization of superplastic TiO2 coatings prepared on Ti6Al4V surgical alloy by an electrochemical method  

Microsoft Academic Search

X-ray diffraction (XRD) and X-Ray photoelectron spectroscopy (XPS), in conjunction with argon ion etching, were used to characterize the microstructure and the chemical composition of alkoxy-derived TiO2 coatings prepared on Ti6Al4V surgical alloy by an electrochemical method. The as-deposited oxide coatings prepared at room temperature (up to 40 µm thick) were amorphous, but transformed into nanocrystalline anatase at 550°C. Using

M. Shirkhanzadeh

1995-01-01

265

2,4-Dichlorophenoxyacetic acid (2,4-D) photodegradation using an M n+ \\/ZrO 2 photocatalyst: XPS, UV–vis, XRD characterization  

Microsoft Academic Search

Zirconium oxide materials doped with transition metals (Mn, Fe, Co, Ni and Cu) were synthesized using sol–gel methods. The powders, which were obtained, were characterized by XPS, XRD, UV–vis spectroscopy and nitrogen adsorption.The photodegradation of 2,4-dichlorophenoxyacetic acid (2,4-D), a herbicide used in agricultural applications, was used as a test reaction to study the activity of the compounds synthesized. Photodegradation studies

M. Alvarez; T. López; J. A. Odriozola; M. A. Centeno; M. I. Domínguez; M. Montes; P. Quintana; D. H. Aguilar; R. D. González

2007-01-01

266

A Chemical, XRD, and 27Al MAS NMR Investigation of Miocene Gulf Coast Shales with Application to Understanding Illite\\/Smectite Crystal-Chemistry  

Microsoft Academic Search

This study assesses the distribution of A1 and Fe in mixed-layer illite\\/smectites (I\\/S) in shales undergoing burial diagenetic changes, using evidence from 27A1 NMR, XRD, and chemical analyses. Samples studied include a sequence of mixed-layer I\\/S (ranging from 40% to 68% illite layers) in shales from a well located in the Caillou Island Oil Field, Terrebonne Parish, Louisiana, as well

Paul A. Schroeder

1993-01-01

267

Embedding magnetic nanoparticles into polysaccharide-based hydrogels for magnetically assisted bioseparation.  

PubMed

Based on the preparation of biocompatible polysaccharide-based hydrogels with stimuli-responsive properties by the copolymerization of maleilated carboxymethyl chitosan with N-isopropylacrylamide, novel magnetic hybrid hydrogels were fabricated by the in situ embedding of magnetic iron oxide nanoparticles into the porous hydrogel networks. Scanning electron microscopy (SEM) and thermogravimetric (TG) analyses showed that the size, morphology, and content of the iron oxide nanoparticles formed could be modulated by controlling the amount of maleilated carboxymethyl chitosan. As confirmed by X-ray diffractometry (XRD), equilibrium swelling ratio, and differential scanning calorimetry (DSC) measurements, the embedding process did not induce a phase change of the magnetic iron oxide nanoparticles, and the resultant hybrid hydrogels could retain the pH- and temperature-responsive characteristics of their hydrogel precursors. By investigating the partition coefficients of bovine serum albumin as a model protein, this magnetic hydrogel material was found to hold a potential application in magnetically assisted bioseparation. PMID:17926314

Liang, Yuan-Yuan; Zhang, Li-Ming; Jiang, Wei; Li, Wei

2007-11-12

268

Targeting to carcinoma cells with chitosan- and starch-coated magnetic nanoparticles for magnetic hyperthermia.  

PubMed

The delivery of hyperthermic thermoseeds to a specific target site with minimal side effects is an important challenge in targeted hyperthermia, which employs magnetic method and functional polymers. An external magnetic field is used to control the site-specific targeting of the magnetic nanoparticles. Polymer-coated magnetic nanoparticles can confer a higher affinity to the biological cell membranes. In this study, uncoated, chitosan-coated, and starch-coated magnetic nanoparticles were synthesized for use as a hyperthermic thermoseed. Each sample was examined with respect to their applications to hyperthermia using XRD, VSM, and FTIR. In addition, the temperature changes under an alternating magnetic field were observed. As in vitro tests, the magnetic responsiveness of chitosan- and starch-coated magnetite was determined by a simple blood vessel model under various intensities of magnetic field. L929 normal cells and KB carcinoma cells were used to examine the cytotoxicity and affinity of each sample using the MTT method. The chitosan-coated magnetic nanoparticles generated a higher DeltaT of 23 degrees C under an AC magnetic field than the starch-coated magnetite, and the capturing rate of the particles was 96% under an external magnetic field of 0.4 T. The highest viability of L929 cells was 93.7%. Comparing the rate of KB cells capture with the rate of L929 cells capture, the rate of KB cells capture relatively increased with 10.8% in chitosan-coated magnetic nanoparticles. Hence, chitosan-coated magnetic nanoparticles are biocompatible and have a selective affinity to KB cells. The targeting of magnetic nanoparticles in hyperthermia was improved using a controlled magnetic field and a chitosan-coating. Therefore, chitosan-coated magnetic nanoparticles are expected to be promising materials for use in magnetic targeted hyperthermia. PMID:18257079

Kim, Dong-Hyun; Kim, Kyoung-Nam; Kim, Kwang-Mahn; Lee, Yong-Keun

2009-01-01

269

X-ray diffraction microtomography (XRD-CT), a novel tool for non-invasive mapping of phase development in cement materials.  

PubMed

A recently developed synchrotron-based imaging technique, X-ray diffraction microtomography (XRD-CT), has been applied here for the first time to a complex system, the hydrating Portland cement paste, in order to monitor the evolution of microstructure and phase formation with a 3D non-invasive imaging approach. The ettringite-XRD-peak-based image reconstructions, combined with transmission microtomography (X-microCT) images, allowed to assess the ubiquitous distribution of this phase, which appears early in the hydration process and showed its preferential concentration in the relatively less compact regions of the paste. The comparison of greyscale histograms for cement pastes after 9 and 58 h from hydration showed an increase of ettringite content with age, in agreement with the quantitative Rietveld analysis of the sum patterns. By renormalizing the greyscale histograms to the relative weight fraction, as obtained from Rietveld refinements, a new technique which allows estimation of phase contents with spatial resolution has been developed. The results achievable by combining XRD-CT, X-microCT and Rietveld appear very promising to provide experimental snapshots of the cement hydration process to be compared with results obtained from computer simulations. PMID:20358183

Artioli, G; Cerulli, T; Cruciani, G; Dalconi, M C; Ferrari, G; Parisatto, M; Rack, A; Tucoulou, R

2010-04-01

270

Composition-dependent magnetic properties of BiFeO3-BaTiO3 solid solution nanostructures  

Microsoft Academic Search

We report on the Mössbauer spectra and magnetization properties of single-crystalline (BiFeO3)x-(BaTiO3)1-x solid solution nanostructures in the form of nanocubes, measuring approximately 150 to 200 nm on a side, prepared by a molten salt solid-state reaction method in the compositional range wherein 0.5<=x<=1 . Powder x-ray diffraction (XRD) and monochromatic synchrotron XRD studies indicate products of high purity, which undergo

Tae-Jin Park; Georgia C. Papaefthymiou; Arthur J. Viescas; Yongjae Lee; Hongjun Zhou; Stanislaus S. Wong; H. Zhou

2010-01-01

271

The effect of aging time and calcination temperature on the magnetic properties of ?-Fe\\/Fe 3O 4 composite  

Microsoft Academic Search

Composites of ?-Fe\\/Fe3O4 having dimensions in the range of 100–150nm have been prepared by disproportion method. The structure and morphology are investigated by XRD and TEM. XRD shows that the metal has got the BCC structure. TEM shows balls of metallic iron about 100-nm-wide stuck to magnetite grains. Magnetic measurement shows that the sample aged for 3h and calcined at

Lijun Zhao; Hua Yang; Shuiming Li; Lianxiang Yu; Yuming Cui; Xueping Zhao; Shouhua Feng

2006-01-01

272

Synthesis and characterization of ZnFe 2O 4 magnetic nanoparticles via a PEG-assisted route  

Microsoft Academic Search

ZnFe2O4 nanoparticles have been successfully prepared through a polyethylene glycol (PEG)-assisted route. XRD, FTIR, TEM and VSM were used for the structural, morphological and magnetic investigation of the product. Transmission electron microscopy analysis revealed spherical Zn-ferrite particles with a narrow size distribution. Average particle size was obtained as 12±3nm from TEM, which agrees well with the XRD-based size estimate of

Yüksel Köseo?lu; Abdülhadi Baykal; Muhammet S. Toprak; Fatma Gözüak; Ali Cemil Ba?aran; Bekir Akta?

2008-01-01

273

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

Microsoft Academic Search

We report the oxidation products and qualitative rates for polydisperse FeCo magnetic nanoparticles (MNPs) synthesized using an induction plasma torch. X-ray diffraction (XRD) and TEM showed MNPs to have a thin ferrite shell. Nanopowders were isochronally annealed to promote oxidation and XRD was used to follow the evolution of the FeCo core and the Fe3O4 and FeO oxide shells. Isothermal

K. N. Collier; N. J. Jones; K. J. Miller; Y. L. Qin; D. E. Laughlin; M. E. McHenry

2009-01-01

274

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

275

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

NASA Astrophysics Data System (ADS)

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.; Asokan, K.

2013-06-01

276

Magnetic Methods  

Microsoft Academic Search

\\u000a Everywhere on the Earth there is a natural magnetic field which moves a horizontally free-moving magnetic needle (magnetic\\u000a compass) to magnetic north. The magnetic field is a vector field, i.e., it is described by its magnitude and direction. The\\u000a magnetic field consists of three parts: the main field, a fluctuating field, and a local anomaly field.

Klaus Knödel; FRANZ KÖNIG; GERHARD LANGE; HARALD LINDNER; REINIE MEYER; KLAUS-HENRIK MITTENZWEY; ANDREAS SCHUCK; KNUT SEIDEL; PETER WEIDELT; THOMAS WONIK; DIETER EISENBURGER; RICARDO A. OLEA; HELLFRIED PETZOLD; THOMAS RICHTER

277

Neodymium Magnets.  

ERIC Educational Resources Information Center

Uses extremely strong neodymium magnets to demonstrate several principles of physics including electromagnetic induction, Lenz's Law, domain theory, demagnetization, the Curie point, and magnetic flux lines. (MDH)

Wida, Sam

1992-01-01

278

Magnetic Properties of Cd Substituted Ni-Cu Ferrites  

NASA Astrophysics Data System (ADS)

Cadmium substituted Ni-Cu Ferrites with the general formula Ni0.95-xCdxCu0.05Fe2O4 (x = 0.1, 0.2 and 0.3) were prepared by the standard double sintering ceramic method. The existences of single phase formation with crystalline size of 25-38 nm were confirmed from XRD measurements. The magnetic properties such as saturation magnetization (Ms) and Magnetic moment (?B) were studied by VSM analysis. The existence of multidomain (MD) particles in the samples was revealed from the small values of Mr/Ms.

Belavi, P. B.; Chavan, G. N.; Bammannavar, B. K.; Naik, L. R.; Kotnala, R. K.

2011-07-01

279

Investigation of magnetic properties in 57Fe/Al multilayers  

NASA Astrophysics Data System (ADS)

Fe/Al multilayer thin films prepared by ion beam sputtering, with an overall atomic concentration ratio of Fe/Al = 1:2 have been studied by x-ray diffraction spectroscopy (XRD), X-ray reflectivity (XRR) and D.C. Magnetization. These studies show the formation of Fe Al intermetallic layers. Two magnetic regions and transition temperatures of 473 and 533 K are evident from magnetization studies. Conversion Electron Mössbauer Spectroscopy (CEMS) shows formation of off-stoichiometric Fe3Al like phase and phases consisting of pure Fe and Fe-rich extended Fe Al solutions.

Jani, Snehal; Sebastian, Varkey; Lakshmi, N.; Reddy, V. R.; Venugopalan, K.; Gupta, Ajay

2008-07-01

280

OPPS: Magnets  

NSDL National Science Digital Library

This guide to a workshop for primary teachers provides an introduction to the concepts of magnets. It is designed to provide teachers with an inquiry-based learning experience to the basic concepts of magnets and magnetism. It also includes an introduction to the relations between electricity and magnetism. It is part of the Operation Primary Physical Science materials.

Kirwin, Gayle

2005-06-23

281

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

282

Galvanostatic charge-discharge tests, 57Fe and 119Sn Mössbauer and XRD measurements on novel Sn-Ni-Fe electrodeposits  

NASA Astrophysics Data System (ADS)

Novel Sn-Ni-Fe ternary alloys were successfully deposited by pulse plating technique from an electrolyte based on sodium gluconate which acts as a complexing agent. XRD results revealed the predominantly amorphous character for the majority of the deposits. 57Fe and 119Sn conversion electron Mössbauer spectroscopy indicated the formation of a paramagnetic amorphous alloy using a short on-pulse duration and where the Fe content was less than 22 wt.%. Galvanostatic charge-discharge tests of the novel Sn-Ni-Fe deposits were carried out in a model Li-ion cell and indicated that the Sn-Ni-Fe alloys have potential as an electrode material.

Lak, G. B.; Kuzmann, E.; El-Sharif, M.; Chisholm, C. U.; Stichleutner, S.; Homonnay, Z.; Sziráki, L.

2013-04-01

283

Cobalt(II) complexes of 5,7-dimethyl[1,2,4]-triazolo-[1,5-a]-pyrimidine. Spectroscopic characterization, XRD study and antimicrobial activity  

Microsoft Academic Search

Several cobalt(II) complexes of 5,7-dimethyl-[1,2,4]-tria-zolo-[1,5-a]-pyrimidine (DMTP) have been prepared and characterized by thermal and spectroscopic techniques. The crystal structure of [Co(DMTP)2(H2O)4]Br2·2H2O has been determined by XRD; the metal ion is octahedrally coordinated by two DMTP ligands through the usual N(3) site and four water molecules. Metal binding to N(3) for DMTP is consistent with the electronic properties calculated with the

María A. Romero; Juan M. Salas; Miguel Quirós; David J. Williams; José Molina

1993-01-01

284

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.

285

XRD and xanes studies of copper complexes using (diethyl 4-amino-1-phenyl-1H-pyrazole-3,5 dicarboxylate) as ligand  

NASA Astrophysics Data System (ADS)

X-ray diffraction (XRD) and X-ray absorption spectroscopic (XAS) studies have been done on three copper complexes using (diethyl 4-amino-1-phenyl-1H-pyrazole-3,5 dicarboxylate) as ligand. The X-ray diffraction studies of copper complexes have been recorded using Rigaku RINT-2000 X-ray diffractometer equipped with a rotating anode with tube voltage of 40 kV and current of 100 mA. The X-ray absorption spectra of the complexes have been recorded at Raja Ramanna Centre for Advanced Technology (RRCAT), Indore and is called beamline.

Mishra, Ashutosh; Jain, Garima

2013-06-01

286

Structural and magnetic properties of nano-crystalline Ni-Zn ferrites synthesized using egg-white precursor  

NASA Astrophysics Data System (ADS)

Nano-crystalline nickel-zinc ferrites of different compositions; Ni1-xZnxFe2O4 (x=0.0-1.0) were prepared by a precursor method involving egg-white and metal nitrates. An appropriate mechanism for the egg-white-metal complexation was suggested. Differential thermal analysis-thermogravimetry, X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR), vibrating sample magnetometer and AC-magnetic susceptibility measurements were carried out to investigate chemical, structural and magnetic aspects of Ni-Zn ferrites. XRD confirmed the formation of spinel cubic structure. The average crystallite size was calculated using line broadening in XRD patterns. Structural parameters like lattice constant, X-ray density, bond lengths and inter-cationic distance were determined from XRD data. TEM showed agglomerated particles with average size agreed well with that estimated using XRD. FT-IR spectra confirm the formation of spinel structure and further lends support to the proposed cation distribution. Zn-content was found to have a significant influence on the magnetic properties of the system. The changes in the magnetic properties can be attributed to the influence of the cationic stoichiometry and their occupancy in the specific sites.

Gabal, M. A.; El-Shishtawy, Reda M.; Al Angari, Y. M.

2012-07-01

287

Structure and magnetic properties of TbMn6Sn6-x Tix (x=0-0.9) compounds  

Microsoft Academic Search

The effects of Ti substitution for Sn on the structure and magnetic properties of TbMn6Sn6-xTix (x=0-0.9) compounds have been investigated by means of X-ray diffraction (XRD), magnetization measurements and 119Sn Mossbauer spectroscopy. The substitution of Ti for Sn results in an increase in the lattice constants and the unit-cell volumes. The magnetic ordering temperature decreases monotonically with increasing Ti content

Peng Zhao; Shao-ying Zhang; Zhao-hua Cheng; Hong-wei Zhang; Ji-Rong Sun; Bao-ben Shen; R. A. Dunlap

2001-01-01

288

Formation and optical properties of amorphous carbon film having embedded nanoparticles deposited by anodic jet carbon arc technique  

NASA Astrophysics Data System (ADS)

This paper reports the formation and optical properties of amorphous carbon film having embedded nanoparticles deposited by anodic jet carbon arc technique (AJCA). The films deposited have been characterized by x-ray diffraction (XRD), high resolution transmission electron microscope (HRTEM), and scanning electron microscope (SEM) and spectroscopy ellipsometry (SE) measurements. XRD pattern exhibits dominantly an amorphous nature of film. HRTEM investigation shows initially the amorphous structure. However, on closer examination nanoparticles were found to be embedded in the amorphous matrix. The effect of substrate bias and the magnetic field on the optical constants evaluated from SE have been studied. On comparison of deposition condition with and without magnetic field used in growing a-C films there is a change in the values of optical constants.

Tripathi, R. K.; Panwar, O. S.; Kesarwani, Ajay; Kumar, Sushil; Basu, A.

2012-10-01

289

Combined In-Situ XRD and In-Situ XANES Studies on the Reduction Behavior of a Rhenium Promoted Cobalt Catalyst  

SciTech Connect

A 10% Co 4% Re/(2% Zr/SiO2) catalyst was prepared by co-impregnation using a silica support modified by 2% Zr. The catalyst was characterized by temperature programmed reduction (TPR), in situ XRD and in situ XANES analysis where it was simultaneously exposed to H2 using a temperature programmed ramp. The results showed the two step reduction of large crystalline Co3O4 with CoO as an intermediate. TPR results showed that the reduction of highly dispersed Co3O4 was facilitated by reduced rhenium by a H2-spillover mechanism. In situ XRD results showed the presence of both, Co-hcp and Co-fcc phases in the reduced catalyst at 400 C. However, the Co-hcp phase was more abundant, which is thought to be the more active phase as compared to the Co-fcc phase for CO hydrogenation. CO hydrogenation at 270 C and 5 bar pressure produces no detectable change in the phases during the time of experiment. In situ XANES results showed a decrease in the metallic cobalt in the presence of H2/CO, which can be attributed due to oxidation of the catalyst by reaction under these conditions.

Kumar, Nitin [Louisiana State University; Payzant, E Andrew [ORNL; Jothimurugesan, K [Chevron Energy Technology Company; Spivey, James J [Louisiana State University

2011-01-01

290

Ion-pairing in aqueous CaCl2 and RbBr solutions: Simultaneous structural refinement of XAFS and XRD data  

NASA Astrophysics Data System (ADS)

We present a new methodology involving the simultaneous refinement of both x-ray absorption and x-ray diffraction spectra (x-ray absorption/diffraction structural refinement, XADSR) to study the hydration and ion pair structure of CaCl2 and RbBr salts in concentrated aqueous solutions. The XADSR method combines the x-ray absorption fine structure (XAFS) spectral analysis of both the cation and anion as a probe of their short-range structure with an x-ray diffraction (XRD) spectral analysis as a probe of the global structural. Together they deliver a comprehensive picture of the cation and anion hydration, the contact ion pair (CIP) structure, and the solvent-separated ion pair (SSIP) structure. XADSR analysis of 6.0 m aqueous CaCl2 reveals that there are ~0.26 Ca2+-Cl- CIP's separated by about 2.71 A?, while there are 3.4 SSIP's separated by about 4.98 A?. In contrast XADSR analysis of 6 m aqueous RbBr yields about 0.7 pair CIP at a bond length of 3.51 A?. The present work demonstrates a new approach for a direct co-refinement of XRD and XAFS spectra in a simple and reliable fashion, opening new opportunities for analysis in various disordered and crystalline systems.

Pham, Van-Thai; Fulton, John L.

2013-01-01

291

Using a charge-coupled device (CCD) to simultaneously gather x-ray fluorescence (XRF) and x-ray diffraction (XRD) information  

NASA Astrophysics Data System (ADS)

A breadboard setup constructed at MOXTEK, Inc., is capable of capturing both x-ray diffraction (XRD) and x-ray fluorescence (XRF) information simultaneously using a charge-coupled device (CCD) as the x-ray detector. This preliminary setup will lead to a prototype simultaneous XRD/XRF instrument. NASA is funding the project because it could be used for future Mars missions for analysis of rocks. The instrument uses a CCD to capture both the energy and the position of an incoming x-ray. This is possible because each pixel acts as a spatially addressable energy- dispersive detector. A powdered sample of material is placed in front of the CCD, which in turn is bombarded by a collimated x-ray beam. The instrument's critical features, the x-ray source, collimation optics and x-ray transparent windows need to be optimized in the size and power to allow the instrument to be portable. In this paper the instrument's design parameters as well as the properties of both the CCD as x-ray detector and the low-power consumption tube are investigated.

Cornaby, S.; Grow, T. D.; Reyes-Mena, Arturo; Moody, Paul W.; Stradling, A.; Hughes, T.; Knight, Larry V.

2002-01-01

292

Mössbauer studies on some new magnetic oxides  

NASA Astrophysics Data System (ADS)

Three new magnetic oxides have been synthesised, viz., Li2Fe3VO8, YFe3TiO8 and CaFe3VO8. XRD studies show that the first compound has a cubic symmetry of spinel type while the latter two show orthorhombic symmetry. All the three compounds are magnetic at room temperature, however, the first compound shows a large magnetic moment as compared to the other two. Their Mössbauer spectra at room temperature show distinct hyperfine split spectral lines. The present preliminary investigation indicates that the long range order is ferrimagnetic in Li2Fe3VO8 and CaFe3VO8 while in YFe3TiO8 it is more likely to be canted antiferromagnetic.

Patni, M. J.; Shringi, S. N.; Vadnere, R. V.

1987-04-01

293

Magnetically guided release of ciprofloxacin from superparamagnetic polymer nanocomposites.  

PubMed

Tailored with superparamagnetic properties the magnetic nanocomposites have been thoroughly investigated in recent past because of their potential applications in the fields of biomedicine and bioengineering such as protein detection, magnetic targeted drug carriers, bioseparation, magnetic resonance imaging contrast agents and hyperthermia. Magnetic drug targeting has come up as a safe and effective drug-delivery technology, i.e., with the least amount of magnetic particles a maximum of drug may be easily administered and transported to the site of choice. In the present work novel magnetic drug-targeting carriers consisting of magnetic nanoparticles encapsulated within a smart polymer matrix with potential of controlled drug release is described. To make such magnetic polymeric drug-delivery systems, both the magnetic nanoparticles and antibiotic drug (ciprofloxacin) were incorporated into the hydrogel. The controlled release process and release profiles were investigated as a function of experimental protocols such as percent loading of drug, chemical composition of the nanocomposite, pH of release media and strength of magnetic field on the release profiles. The structure, morphology and compositions of magnetic hydrogel nanocomposites were characterized by FT-IR, TEM, XRD and VSM techniques. It was found that magnetic nanocomposites were biocompatible and superparamagnetic in nature and could be used as a smart drug carrier for controlled and targeted drug delivery. PMID:20566063

Gupta, Rashmi; Bajpai, A K

2010-06-21

294

Variation of magnetism and structure on mechanically alloyed Fe40Co10Cu50 powder with process time and heat treatment  

Microsoft Academic Search

The effects of milling time and heat treatment on local structural changes during mechanical alloying Fe40Co10Cu50 have been investigated by means of x-ray diffraction (XRD), neutron diffraction technique, vibrating sample magnetometer, and Mo¨ssbauer spectroscopy. Mo¨ssbauer spectroscopy showed that two kinds of magnetic phases coexist in the mechanically alloyed powder, which is in agreement with XRD and neutron diffraction study. One

Seong-Cho Yu; Yong-Goo Yoo; Won-Tae Kim; C. Anderson; D. Dickson; T. Zeiske

1997-01-01

295

Magnetic and electric properties of SiO2-doped Mn ferrite by mechanical alloying  

Microsoft Academic Search

Summary form only given. A SiO2-doped Mn ferrite was prepared using high-energy ball milling and subsequent annealing. This material not only maintains the high Ms of Mn ferrite, but also possesses an increased electrical resistivity. XRD spectra are presented. The saturation magnetization and electrical resistivity annealing temperature dependences were studied.

J. Ding; Y. D. Gao

2002-01-01

296

Structural, magnetic and Mössbauer spectral studies of nanosize aluminum substituted nickel zinc ferrites  

Microsoft Academic Search

Nanosize aluminum substituted nickel zinc ferrites were prepared through aerosol route and characterized using TEM, XRD, magnetic measurements and Mössbauer spectroscopy. The particle size of as obtained samples was found to be ?10nm which increases up to ?85nm upon annealing at 1200°C. The unit cell parameter ‘a’ decreases linearly with concentration of aluminum due to the small ionic radius of

Sonal Singhal; S. K. Barthwal; Kailash Chandra

2006-01-01

297

Attempt of MgB2 Powder Alignment in Magnetic Field  

NASA Astrophysics Data System (ADS)

We have attempted magnetic alignment of MgB2 powder grains in an epoxy resin under the magnetic field of 8 T. Since we do not know of direction and magnitude of a magnetic anisotropy tensor in the normal state, we devise difference alignment schemes assuming two cases; Case I for the easy along the c-axis and Case II for the easy axis perpendicular to the c-axis. For each case, we have built different devices. For example, for Case II, we have to apply rotation perpendicular to the magnetic field. Also, the device is designed to get rid of gravitational sedimentation by rotating the powder in an epoxy resin. For assessment of the c-axis alignment, XRD measurements are utilized. However, the three XRD data for the unaligned power, the Case I and the Case II are same and show no evidence of alignment. Possible reasons for the results will be discussed in detail.

Lee, Moohee; Kang, Kihyeok; Mean, B. J.; Kim, Sung Hoon; Cho, B. K.

2010-03-01

298

ITER magnets.  

National Technical Information Service (NTIS)

As part of the summary of the Conceptual Design Activities (CDA) for the International Thermonuclear Experimental Reactor (ITER), this document describes the magnet systems for ITER, including the Toroidal Field (TF) and Poloidal Field (PF) Magnets, the S...

L. Bottura M. Hasegawa J. Heim

1991-01-01

299

Magnetic and charge derived properties of ball milled dilute magnetic semiconductor Si0.98Mn0.02  

NASA Astrophysics Data System (ADS)

The dilute magnetic semiconductor (DMS) material Si0.98Mn0.02 was prepared by a ball milling technique at two different milling periods. The samples have been analyzed for electron density distribution and local structure using powder X-ray diffraction (XRD) data sets. The results were compared with those of pure silicon. Structural changes and their implications on the bond-length distributions were analyzed and compared. Electron density distributions of the defect structure were plotted on 2D planes and along the bonding direction in the unit cell for each case using the maximum entropy method (MEM). The incorporation of transition metal ion (Mn) at substitutional sites of the host lattice (Si) is verified for Si0.98Mn0.02 from XRD and magnetic hysteresis measurements were taken using vibrating sample magnetometer (VSM). Room temperature ferromagnetism due to Mn substitution was observed in the prepared samples.

Sheeba, R. A. J. R.; Saravanan, R.; Sasikumar, S.

2013-10-01

300

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

301

Magnetizing of permanent magnets using HTS bulk magnets  

Microsoft Academic Search

A demagnetized Nd–Fe–B permanent magnet was scanned just above the magnetic pole which contains the HTS bulk magnet generating a magnetic field of 3.27T. The magnet sample was subsequently found to be fully magnetized in the open space of the static magnetic fields. We examined the magnetic field distributions when the magnetic poles were scanned twice to activate the magnet

Tetsuo Oka; Tomoki Muraya; Nobutaka Kawasaki; Satoshi Fukui; Jun Ogawa; Takao Sato; Toshihisa Terasawa

302

Conductivity and magnetic susceptibility of nanotube/polypyrrole nanocomposites  

SciTech Connect

A method has been developed to produce a carbon nanotube/conducting polymer nano-composite through in-situ polymerization of pyrrole in the carbon nanotube template. The nano-composites of carbon nanotube and polypyrrole have been characterized by SEM, TEM, XRD, Raman Scattering. The thermal stability was studied by TGA (Thermal Gravity Analysis). The measurements of conductivity and magnetic susceptibility of the composites have been studied.

Chang, B.H.; Liu, Z.Q.; Sun, L.F. [and others

2000-04-01

303

MAGNETIC POLYSACCHARIDES  

Microsoft Academic Search

Magnetic composites with superparamagnetic properties has developed a great scientific interest in the last years by their potential application in drug delivery and cell sorting systems. Alginate, starch and chitosan were used as polymeric matrixes in order to obtain magnetic nanostructured composites. Magnetic nanocrystalline particles of iron oxide were formed inside the matrix by an in situ alkaline oxidation of

F. Llanes; C. Diaz; H. Ryan; R. H. Marchessault

2002-01-01

304

Superconducting magnets  

SciTech Connect

Superconducting dipole magnets for high energy colliders are discussed. As an example, the magnets recently built for the Relativistic Heavy Ion Collider at Brookhaven are reviewed. Their technical performance and the cost for the industry-built production dipoles are given. The cost data is generalized in order to extrapolate the cost of magnets for a new machine.

Willen, E.

1996-12-31

305

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

306

Seismicity triggered by the olivine-spinel transition: new insights from combined XRD and acoustic emission monitoring during deformation experiments in Mg2GeO4  

NASA Astrophysics Data System (ADS)

Polycrystalline Mg2GeO4-olivine has been deformed (strain rates from 2.10-4/s to 10-5/s) in the deformation-DIA in 13-BM-D at GSECARS (Advanced Photon Source) at ca. 2 GPa confining pressure for temperatures between 973 and 1573 K (i.e., in the Mg2GeO4-ringwoodite field). Stress, advancement of transformation, and strain were measured in-situ using X-ray diffraction (XRD) and imaging, and acoustic emissions (AE) were recorded simultaneously. When differential stress is applied (ca. 1- to 2 GPa) and temperature is increased, the very beginning of the transformation to the ringwoodite structure (as evidenced by in situ XRD) is accompanied by AE bursts which locate within the sample. At high strain rates (>10-4/s) and low temperatures (800-900 degrees C), the number of AEs is comparable, if not larger, to that observed during the cold compression of quartz grains. The largest events always occur at a temperature slightly below that of appearance of the ringwoodite-structure phase on the XRD images patterns. This suggests that AEs are generated while the transition is still nucleation controlled (pseudo-martensitic stage). During stress-relaxation periods, the rate of AE triggering decreases, but does not completely vanish. Importantly, we still observed very large AEs at strain rates as low as approx. 10-5/ s, while at these early stages of the transformation, the samples did not show any macroscopic rheological weakening. Focal mechanism analysis of the largest AEs showed that they are all of shear type, some being even pure double couple. They radiate about the same amount of energy as typically recorded during fast crack propagation in amorphous glass material. Microstructural analysis (SEM, EBSD and TEM) highlights the presence of thin transformation bands, with plausible evidence of shear (grain distortion and grain size reduction). These bands are made of incoherent spinel and olivine nano-grains which run across germanium-olivine grain boundaries. These bands are all oriented near perpendicular to the principal compressive stress. In samples for which no AEs were recorded (hydrostatic conditions and higher temperatures and reaction progress), microstructure is different with incoherent grain growth at GB (hydrostatic conditions) and spinel-lamellae within a single germanium olivine crystal (fast reaction rate under deviatoric stress). Our observations point out that under high deviatoric stress, the olivine - spinel transition is a source of mechanical instability, which produces nano-seismicity. This may have important consequences for the understanding of deep-focus earthquakes occurring in cold and metastable olivine within the transition zone.

Schubnel, A.; Hilairet, N.; Brunet, F.; Gasc, J.; Cordier, P.; Wang, Y.; Green, H. W.

2012-04-01

307

Seismicity triggered by the olivine-spinel transition: new insights from combined XRD and acoustic emission monitoring during deformation experiments in Mg2GeO4  

NASA Astrophysics Data System (ADS)

Polycrystalline Mg2GeO4-olivine has been deformed (strain rates from 2.10-4/s to 10-5/s) in the deformation-DIA in 13-BM-D at GSECARS (Advanced Photon Source) at ca. 2 GPa confining pressure for temperatures between 973 and 1573 K (i.e., in the Mg2GeO4-ringwoodite field). Stress, advancement of transformation, and strain were measured in-situ using X-ray diffraction (XRD) and imaging, and acoustic emissions (AE) were recorded simultaneously. When differential stress is applied (ca. 1- to 2 GPa) and temperature is increased, the very beginning of the transformation to the ringwoodite structure (as evidenced by in situ XRD) is accompanied by AE bursts which locate within the sample. At high strain rates (>10-4/s) and low temperatures (800-900 degrees C), the number of AEs is comparable, if not larger, to that observed during the cold compression of quartz grains. The largest events always occur at a temperature slightly below that of appearance of the ringwoodite-structure phase on the XRD images patterns. This suggests that AEs are generated while the transition is still nucleation controlled (pseudo-martensitic stage). During stress-relaxation periods, the rate of AE triggering decreases, but does not completely vanish. Importantly, we still observed very large AEs at strain rates as low as approx. 10-5/ s, while at these early stages of the transformation, the samples did not show any macroscopic rheological weakening. Focal mechanism analysis of the largest AEs showed that they are all of shear type, some being even pure double couple. They radiate about the same amount of energy as typically recorded during fast crack propagation in amorphous glass material. Microstructural analysis (SEM, EBSD and TEM) highlights the presence of thin transformation bands, with plausible evidence of shear (grain distortion and grain size reduction). These bands are made of incoherent spinel and olivine nano-grains which run across germanium-olivine grain boundaries. These bands are all oriented near perpendicular to the principal compressive stress. In samples for which no AEs were recorded (hydrostatic conditions and higher temperatures and reaction progress), microstructure is different with incoherent grain growth at GB (hydrostatic conditions) and spinel-lamellae within a single germanium olivine crystal (fast reaction rate under deviatoric stress). Our observations point out that under high deviatoric stress, the olivine - spinel transition is a source of mechanical instability, which produces nano-seismicity. This may have important consequences for the understanding of deep-focus earthquakes occurring in cold and metastable olivine within the transition zone.

Schubnel, A. J.; Hilairet, N.; Brunet, F.; Héripré, E.; Cordier, P.; Wang, Y.

2011-12-01

308

Preparation and Properties of Various Magnetic Nanoparticles  

PubMed Central

The fabrications of iron oxides nanoparticles using co-precipitation and gadolinium nanoparticles using water in oil microemulsion method are reported in this paper. Results of detailed phase analysis by XRD and Mössbauer spectroscopy are discussed. XRD analysis revealed that the crystallite size (mean coherence length) of iron oxides (mainly ?-Fe2O3) in the Fe2O3 sample was 30 nm, while in Fe2O3/SiO2 where the ?-Fe2O3 phase dominated it was only 14 nm. Gd/SiO2 nanoparticles were found to be completely amorphous, according to XRD. The samples showed various shapes of hysteresis loops and different coercivities. Differences in the saturation magnetization (MS) correspond to the chemical and phase composition of the sample materials. However, we observed that MS was not reached in the case of Fe2O3/SiO2, while for Gd/SiO2 sample the MS value was extremely low. Therefore we conclude that only unmodified Fe2O3 nanoparticles are suitable for intended biosensing application in vitro (e.g. detection of viral nucleic acids) and the phase purification of this sample for this purpose is not necessary.

Drbohlavova, Jana; Hrdy, Radim; Adam, Vojtech; Kizek, Rene; Schneeweiss, Oldrich; Hubalek, Jaromir

2009-01-01

309

Structure and magnetic properties of Fen?Crn?N sputter-deposited films  

Microsoft Academic Search

Structure and magnetic properties of Fen?Crn?N ternary films prepared by DC magnetron facing-target sputtering have been investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), vibrating sample magnetometry (VSM) and Mössbauer effect. These films exhibit perpendicular magnetic anisotropy. We found that N2-to-Ar flow ratio, Fe-Cr target area ratio and substrate temperature during film preparation are the

D. L. Peng; T. J. Konno; K. Sumiyama; H. Onodera; K. Suzuki

1997-01-01

310

Preparation and properties of magnetic Fe 3O 4–chitosan nanoparticles  

Microsoft Academic Search

Magnetic Fe3O4–chitosan nanoparticles were prepared by the covalent binding of chitosan (CTS) onto the surface of magnetic Fe3O4 nanoparticles which were prepared by hydrothermal method using H2O2 as an oxidizer. Transmission electron microscopy (TEM) showed that Fe3O4 particles and Fe3O4–chitosan nanocomposites were regular sphere with a mean diameter of 23nm and 25nm, respectively. X-ray diffraction patterns (XRD) indicated that the

Gui-yin Li; Yu-ren Jiang; Ke-long Huang; Ping Ding; Jie Chen

2008-01-01

311

Magnetic Characterization of Electrodeposited Nanocrystalline Ni and NiFe alloys  

Microsoft Academic Search

This research study has been devoted to the study of magnetic properties and magnetic transport of nanocrystalline Ni and Ni-15% Fe alloys consisting of randomly oriented grains with an average size of 23 and 12 (nm), respectively. The structures of the deposits were confirmed by the XRD analysis using Rietveld refinement technique. The as-deposited Ni and Ni-15%Fe sample was comprised

Arabi Sahar

2011-01-01

312

Magnetic field synthesis of Fe 3O 4 nanoparticles used as a precursor of ferrofluids  

Microsoft Academic Search

Methods to synthesize magnetic Fe3O4 nanoparticles and to modify the nanoparticle surface are presented in this paper. In these methods, Fe3O4 nanoparticles were prepared by co-precipitation, and the aging of nanoparticles was improved by applied magnetic field. The obtained nanoparticles were characterized by Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), X-ray powder diffraction (XRD), and vibrating sample magnetometer

R. Y. Hong; T. T. Pan; Y. P. Han; H. Z. Li; J. Ding; Sijin Han

2007-01-01

313

Structural and magnetic properties of nanocrystalline Fe–N thin films and their thermal stability  

Microsoft Academic Search

The nanocrystalline Fe–N films with a mixture of ?-Fe3N and ?-Fe phase synthesized on NaCl (100) substrate by dc magnetron sputtering were annealed at different temperatures in order to investigate their thermal stability and magnetic properties. The structure, morphology, and magnetic properties of the samples were characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM), and superconducting quantum interference device

L. L. Wang; X. Wang; W. T. Zheng; N. Ma; H. B. Li; Q. F. Guan; D. H. Jin; Z. G. Zong

2007-01-01

314

Effects of boron-doping on the morphology and magnetic property of carbon nanotubes  

Microsoft Academic Search

Boron carbide nanotubes (nano-fibers) was prepared by B powder and carbon nanotubes (CNTs) at high temperature in a vacuumed\\u000a quartz tube. The morphology, microstructure, component and magnetic property of samples were characterized by transmission\\u000a electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and magnetic property measurement\\u000a system (MPMS) controller. The results showed that B-doping CNTs have great difference

Qi Jiang; Lan Qian; Jing Yi; Xiaotong Zhu; Yong Zhao

2007-01-01

315

Magnetic properties of bacterial magnetosomes as potential diagnostic and therapeutic tools  

Microsoft Academic Search

Suspensions of bacterial magnetosomes are investigated with respect to magnetic losses. Mean core diameter of about 30nm results from TEM, XRD and magnetic analysis. Specific loss power is determined from hysteresis loops, susceptibility spectra and calorimetry with a maximum value of 960W\\/g at 410kHz and field amplitude 10kA\\/m. Results may be understood by relaxation effects on hysteresis.

Rudolf Hergt; Robert Hiergeist; Matthias Zeisberger; Dirk Schüler; Udo Heyen; Ingrid Hilger; Werner A. Kaiser

2005-01-01

316

Magnetic properties of bacterial magnetosomes as potential diagnostic and therapeutic tools  

NASA Astrophysics Data System (ADS)

Suspensions of bacterial magnetosomes are investigated with respect to magnetic losses. Mean core diameter of about 30 nm results from TEM, XRD and magnetic analysis. Specific loss power is determined from hysteresis loops, susceptibility spectra and calorimetry with a maximum value of 960 W/g at 410 kHz and field amplitude 10 kA/m. Results may be understood by relaxation effects on hysteresis.

Hergt, Rudolf; Hiergeist, Robert; Zeisberger, Matthias; Schüler, Dirk; Heyen, Udo; Hilger, Ingrid; Kaiser, Werner A.

2005-05-01

317

Lightweight glass\\/Fe 3 O 4 -polyaniline composite hollow spheres with conductive and magnetic properties  

Microsoft Academic Search

Lightweight composite hollow spheres with conductive and magnetic properties were prepared by using Hollow Glass Spheres (HGS)\\u000a as substrate. The morphology, composition, conductive, and magnetic properties of the resultant products were characterized\\u000a by SEM, EDX, XRD, FTIR spectra, conductivity measurement, and vibrating-sample magnetometry. Polyaniline (PANI) were in situ\\u000a polymerized on HGS with increasing ratios of PANI to HGS, resulting in

Jing Wang; Huifang Xu; Jianwei Song; Haijiao Zhang; Beiling Gao; Yudong Huang

2011-01-01

318

Magnetizing of permanent magnets using HTS bulk magnets  

NASA Astrophysics Data System (ADS)

A demagnetized Nd-Fe-B permanent magnet was scanned just above the magnetic pole which contains the HTS bulk magnet generating a magnetic field of 3.27 T. The magnet sample was subsequently found to be fully magnetized in the open space of the static magnetic fields. We examined the magnetic field distributions when the magnetic poles were scanned twice to activate the magnet plate inversely with various overlap distances between the tracks of the bulk magnet. The magnetic field of the "rewritten" magnet reached the values of the magnetically saturated region of the material, showing steep gradients at the border of each magnetic pole. As a replacement for conventional pulse field magnetizing methods, this technique is proposed to expand the degree of freedom in the design of electromagnetic devices, and is proposed as a novel practical method for magnetizing rare-earth magnets, which have excellent magnetic performance and require intense fields of more than 3 T to be activated.

Oka, Tetsuo; Muraya, Tomoki; Kawasaki, Nobutaka; Fukui, Satoshi; Ogawa, Jun; Sato, Takao; Terasawa, Toshihisa

2012-01-01

319

Novelty, preparation, characterization and enhancement of magnetic properties of Mn nanoferrites using safety binder (egg white)  

Microsoft Academic Search

Nanocrystalline MnFe2O4 ferrite was prepared by using autocombustion technique (flash). The microstructure and magnetic properties are studied. The results of XRD and TEM clarified that, this ferrite is nanosized with particle size (39 nm). Magnetic measurements showed a ferromagnetic behavior with TC = 613 K, the saturation magnetization Ms = 13.71 emu\\/g, remanent magnetization Mr = 0.1694 emu\\/g and, coercivity Hc = 25.6 Oe. Natural material, egg white used as an aqueous medium

M. A. Ahmed; N. Okasha; S. I. El-Dek

2011-01-01

320

Structure and magnetic properties of multi-walled carbon nanotubes modified with iron  

NASA Astrophysics Data System (ADS)

Magnetic properties of multi-walled carbon nanotubes modified with iron (MWCNT+Fe) are studied in detail in the temperature range 4.2-300 K. Carbon encapsulated Fe nanoparticles were produced by chemical vapor deposition. Low-temperature SQUID magnetization measurements are supplemented by structural studies employing thermogravimetric (TG) analysis, transmission electron microscopy (TEM), x-ray diffraction spectroscopy (XRD), and scanning electron microscopy (SEM). The magnetic susceptibility of MWCNT+Fe was also studied above room temperature to provide a complete picture of its magnetic phase transitions.

Grechnev, G. E.; Desnenko, V. A.; Fedorchenko, A. V.; Panfilov, A. S.; Kolesnichenko, Yu. A.; Matzui, L. Yu.; Grybova, M. I.; Prylutskyy, Yu. I.; Ritter, U.; Scharff, P.

2010-12-01

321

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

322

Preparation and Characterization of Chitosan Poly(acrylic acid) Magnetic Microspheres  

PubMed Central

Spherical microparticles, capable of responding to magnetic fields, were prepared by encapsulating dextran-coated Fe3O4 nanoparticles into chitosan poly(acrylic acid) (PAA) microspheres template. The obtained magnetic microspheres were characterized by transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), X-ray powder diffraction (XRD), and thermogravimetry (TG). The results showed that the microspheres were formed and demonstrated magnetic behavior in an applied magnetic field. In addition, magnetite particles were well encapsulated and the composite particles have high magnetite content, which was more than 40%.

Guo, Liang; Liu, Guang; Hong, Ruo-Yu; Li, Hong-Zhong

2010-01-01

323

Preparation and Properties of ?-Fe3N-Based Magnetic Fluid  

PubMed Central

In this work, ?-Fe3N nanoparticles and ?-Fe3N-based magnetic fluid were synthesized by chemical reaction of iron carbonyl and ammonia gas. The size of ?-Fe3N nanoparticles was tested by TEM and XRD. Stable ?-Fe3N-based magnetic fluid was prepared by controlling the proper ratio of carrier liquid and surfactant. The saturation magnetization of stable ?-Fe3N-based magnetic fluid was calculated according to the volume fraction of the particles in the fluid. The result shows that both the calculated and measured magnetizations increase by increasing the particle concentration. With the increasing concentration of the ?-Fe3N particles, the measured value of the magnetic fluid magnetization gradually departs from the calculated magnetization, which was caused by agglomeration affects due to large volume fraction and large particle size.

2008-01-01

324

Magnetic nanostructures.  

PubMed

Characteristic results of magnetism in small particles, thin films and tunnel junctions are presented. As a consequence of the reduced atomic coordination in small clusters and thin films the electronic states and density of states are modified. Thus, magnetic moments and magnetization are affected. Generally, in clusters and thin films magnetic anisotropy plays a special role. In tunnel junctions the interplay of magnetism, spin currents and superconductivity are of particular interest. In ring-like mesoscopic systems Aharonov-Bohm-induced currents are studied. Results are given for single transition metal clusters, cluster ensembles, thin films, mesoscopic structures and tunnel systems. PMID:21393778

Bennemann, K

2010-06-02

325

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

326

Confocal ?-XRF, ?-XAFS, and ?-XRD Studies of Sediment from a Nuclear Waste Disposal Natural Analogue Site and Fractured Granite Following a Radiotracer Migration Experiment  

NASA Astrophysics Data System (ADS)

Combined ?-XRF, ?-XAFS, and ?-XRD investigations of a uranium-rich tertiary sediment, from a nuclear repository natural analogue site, and a fractured granite bore core section after a column tracer experiment using a Np(V) containing cocktail have been performed. Most ?-XRF/?-XAFS measurements are recorded in a confocal geometry to provide added depth information. The U-rich sediment results show uranium to be present as a tetravalent phosphate and that U(IV) is associated with As(V). Arsenic present is either As(V) or As(0). The As(0) forms thin coatings on the surface of pyrite nodules. A hypothesis for the mechanism of uranium immobilization is proposed, where arsenopyrite acted as reductant of ground water dissolved U(VI) leading to precipitation of less soluble U(IV) and thereby forming As(V). Results for the granite sample show the immobilized Np to be tetravalent and associated with facture material.

Denecke, Melissa A.; Janssens, Koen; Brendebach, Boris; de Nolf, Wout; Falkenberg, Gerald; Rothe, Jörg; Simon, Rolf; Somogyi, Andrea; Vekemans, Bart; Noseck, Ulrich

2007-02-01

327

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

SciTech Connect

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 reaction. During the entire main period the silicate reaction dominates hydration with a high and long first maximum of heat flow. The second but less intense heat flow maximum - only visible as a shoulder in most of the technical cements - can be attributed to an acceleration of the aluminate reaction with the enhanced dissolution of C{sub 3}A and the final formation of ettringite. Moreover, the investigation showed that the dissolution process of C{sub 3}A is directly controlled by the availability of the calcium sulfate phases.

Hesse, Christoph; Goetz-Neunhoeffer, Friedlinde; Neubauer, Juergen, E-mail: neubauer@geol.uni-erlangen.d

2011-01-15

328

Advantages of combined micro-XRF and micro-XRD for phase characterization of Ti-B-C ceramics compared with conventional X-ray diffraction.  

PubMed

Design and processing of new materials with improved high-temperature properties is one of the most challenging tasks of modern engineering. Among such materials, nonoxidic ceramics hold an important place. When optimizing the synthesis conditions of these new materials in an largely empirical manner, the use of analytical methods that can fully document the resulting phase compositions is of great importance. In this paper, we demonstrate the advantages of using combined microbeam X-ray diffraction and X-ray fluorescence over conventional X-ray diffraction as the characterization method in the specific case of Ti-B-C ceramics. Ceramic samples were synthesized by the pulse plasma method starting from high-purity powders of titanium, boron, graphite, and nickel. Different mixtures were heated in a pulsed fashion and sintered by combustion synthesis at various temperatures and time durations, as is the case during empirical optimization of a synthesis procedure. Conventional X-ray diffraction showed the presence of two phases at the end of the sintering process, TiB(2) and TiC, irrespective of the conditions employed. Scanning micro-XRF/micro-XRD on the other hand allowed one to detect and visualize the distribution of additional phases present in the sintering products, during which a dependence on sintering conditions was apparent. The micro-XRD results showed that three phases (TiB(2), TiC, and TiB) instead of two were present in samples sintered during a short time interval. The addition of metallic Ni to the initial mixture as a sintering facilitator resulted in the formation of a Ni(3)B phase. All phases proved to have strongly heterogeneous distributions above the 15-microm level with the presence of TiB(2) anticorrelated to that of TiC and TiB, emphasizing the necessity of the use of laterally resolved methods of characterization. PMID:18458886

Jaroszewicz, Jakub; De Nolf, Wout; Janssens, Koen; Michalski, Andrzej; Falkenberg, Gerald

2008-05-06

329

Superlattice induced by electron-beam irradiation in magnetic ferroelectric BiMnO3  

NASA Astrophysics Data System (ADS)

Single-phased polycrystalline BiMnO3 (hereinafter abbreviated as BMO) ceramic was fabricated via high-pressure solid-state reaction. Microstructure modification of selective grains, signalled by emergence of superlattice diffraction, was scrutinized by means of electron diffraction (ED) combined with high-resolution transmission electron microscopy (HRTEM). It was clearly evidenced that the well established C 2 monoclinic substructure (a = 9.53 Å, b = 5.61 Å, c = 9.85 Å and ? = 110.67°) of BMO (Atou et al 1999 J. Solid State Chem. 145 639) is metastable and prone to be transformed to a new pseudocubic superstructure (aapbapcap15.8 Å and ?ap?ap?ap90°) (Yang et al 2006 Phys. Rev. B 73 024114) when irradiated continuously by an electron beam. Magnetization measurement unveiled a unique ferromagnetic phase transition at 103 K, which corroborated our speculation that as-prepared BMO ceramic is free of polymorphism at ambient conditions.

Chi, Zhenhua; Yang, Hua; Li, Fengying; Yu, Richeng; Jin, Changqing; Wang, Xiaohui; Deng, Xiangyun; Li, Longtu

2006-05-01

330

Moessbauer spectroscopy studies of carbon-encapsulated magnetic nanoparticles obtained by different routes  

SciTech Connect

Carbon-encapsulated magnetic nanoparticles (CEMNPs) are nanomaterials with a core-shell structure. Their intrinsic properties result both from the unique nature of the encapsulated magnetic phases and the high chemical stability of the external carbon shells. CEMNPs may find many prospective applications, e.g., in magnetic data storage, catalysis, xerography, magnetic resonance imaging, and in biomedical applications. Herein, we present detailed structural studies of such nanostructures by Moessbauer spectroscopy, x-ray diffraction (XRD), scanning electron microscopy, and transmission electron microscopy. CEMNPs have been obtained by three different techniques: carbon arc, combustion synthesis, and radio frequency thermal plasma. The evaluation of the phase composition of the products was strongly limited due to the broadening and overlapping of the lines in XRD diffraction patterns. The presence of the semicrystalline phases, which could not been identified by XRD, was established by Moessbauer spectroscopy. Furthermore, the magnetic core phase composition was evaluated quantitatively. The products were purified before structural analyses to remove the nonencapsulated particles. The purification caused significant changes in the mass and the saturation magnetization. The Moessbauer spectra of the purified products were compared with the literature data concerning the as-produced CEMNPs.

Bystrzejewski, M.; Huczko, A.; Lange, H. [Department of Chemistry, Warsaw University, Pasteur 1 str., 02-093 Warsaw (Poland); Grabias, A.; Borysiuk, J. [Institute of Electronic Materials Technology, Wolczynska 133 str., 01-919 Warsaw (Poland)

2008-09-01

331

Mössbauer spectroscopy studies of carbon-encapsulated magnetic nanoparticles obtained by different routes  

NASA Astrophysics Data System (ADS)

Carbon-encapsulated magnetic nanoparticles (CEMNPs) are nanomaterials with a core-shell structure. Their intrinsic properties result both from the unique nature of the encapsulated magnetic phases and the high chemical stability of the external carbon shells. CEMNPs may find many prospective applications, e.g., in magnetic data storage, catalysis, xerography, magnetic resonance imaging, and in biomedical applications. Herein, we present detailed structural studies of such nanostructures by Mössbauer spectroscopy, x-ray diffraction (XRD), scanning electron microscopy, and transmission electron microscopy. CEMNPs have been obtained by three different techniques: carbon arc, combustion synthesis, and radio frequency thermal plasma. The evaluation of the phase composition of the products was strongly limited due to the broadening and overlapping of the lines in XRD diffraction patterns. The presence of the semicrystalline phases, which could not been identified by XRD, was established by Mössbauer spectroscopy. Furthermore, the magnetic core phase composition was evaluated quantitatively. The products were purified before structural analyses to remove the nonencapsulated particles. The purification caused significant changes in the mass and the saturation magnetization. The Mössbauer spectra of the purified products were compared with the literature data concerning the as-produced CEMNPs.

Bystrzejewski, M.; Grabias, A.; Borysiuk, J.; Huczko, A.; Lange, H.

2008-09-01

332

Synthesis, characterization and magnetic properties of nanocrystalline nickel  

NASA Astrophysics Data System (ADS)

Nickel nanoparticles were synthesized by thermal decomposition route with using cappant as Triphenyl phosphine (TPP). The product was characterized in details by X-ray diffraction; transmission electron microscope and Fourier transform infrared techniques. From XRD the particles size was 1.22 nm. But from TEM results it was shown that about 10nm. This was due to the particles were covered by cappant. Magnetic measurement was carried out by vibrating sample magnetometer (VSM). Magnetic measurement attributed to the result of superparamagnetic behavior at 4K and also at 300K. So nickel nanoparticles of size 1.22 nm behave as superparamagnetic particles in the temperature range 4K-300K.

Das, Sourav; Lalla, N. P.; Okram, G. S.

2013-02-01

333

Structure and magnetism in compressed iron-cobalt alloys  

Microsoft Academic Search

Combined Co K-edge XANES-XMCD and XRD measurements were used to shed light on the magnetic and structural phase diagram of the Fe1?xCox alloy under HP in the Co-rich region (x?0.5). At 0.5?x?0.75, the alloy shows a pressure-induced structural\\/magnetic phase transition from bcc-FM to hcp-non-FM phase just like pure iron but at higher pressures. The x=0.9 sample has an fcc structure

R. Torchio; S. Pascarelli; O. Mathon; C. Marini; S. Anzellini; P. Centomo; C. Meneghini; S. Mobilio; N. A. Morley; M. R. J. Gibbs

2011-01-01

334

LETTER TO THE EDITOR: Magnetic and semiconducting nanostructures by swift heavy ion irradiation of Fe20Ni80 films on Si substrates  

NASA Astrophysics Data System (ADS)

Fe20Ni80/Si interface devices have been fabricated and irradiated from swift (100 MeV) heavy (Fe7+) ions with a dose of 1014 cm-2. The current measured across the irradiated devices from room temperature (RT) to liquid nitrogen (LN2) temperature shows a positive temperature coefficient. The results were understood by considering the formation of a semiconducting and magnetic silicide nanophase as a result of ion beam mixing (which was shown from x-ray diffraction (XRD) data). The particle size was estimated to be ~25 nm from the XRD data. The induced magnetization at the interface was studied from the magnetization versus magnetic field (M-H) variation at room temperature. The magnetization shows superparamagnetic behaviour characterizing the magnetic nanoparticles.

Srivastava, P. C.; Tripathi, J. K.; Pandey, P. S.

2005-12-01

335

Magnetic Properties of LaMnO3 Nanocrystal Encapsulated in MCM-41  

SciTech Connect

LaMnO3 (LMO) nanocrystals were synthesized at various annealing temperatures using MCM-41 mesoporous silica. In this study, X-ray diffraction (XRD) measurements and magnetic property measurements were performed. XRD results showed that LMO nanocrystals of {approx}90 Aa in diameter are formed. These samples show ferromagnetic behavior below 280 K, which is nearly twice that of the critical temperature of bulk LMO crystal. The magnitude of the ferromagnetic moments is correlated with the intensity of the Bragg peaks of LMO nanocrystals. The high TC of the LMO nanocrystals might be caused by hole doping due to excess oxygen or cationic nonstoichiometry.

Kira, Hiroshi; Tamura, Hidekazu; Ando, Yuya; Onodera, Mitsugu; Murakami, Youichi [Department of Physics, Tohoku University, Sendai 980-8578 (Japan); Yamazaki, Satoshi [Shizuoka Institute of Science and Technology, Fukuroi 437-8555 (Japan); Tajiri, Takayuki; Deguchi, Hiroyuki [Faculty of Engineering, Kyushu Institute of Technology, Kitakyushu 804-8550 (Japan)

2006-09-07

336

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

337

Permanent magnets  

NASA Astrophysics Data System (ADS)

The number of materials systems used to make magnets on an industrial scale is limited. They are, in chronological order of appearance, AlNiCo (late 1930s), hard ferrites (1950s), the family of Sm-Co magnets which gave rise to two different magnet groups, SmCo 5 (late 1960s) and Sm(CoFeCuZr) 7-8 , often referred to as the "2-17" type magnets (late 1970s), and the neodymium-iron-boron or NdFeB family (mid-1980s).

Rossignol, Michel-François; Yonnet, Jean-Paul

338

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.

339

Magnetic fabrics  

NASA Astrophysics Data System (ADS)

Since Graham [1954; 1967] demonstrated in the 1950s and 1960s that magnetic anisotropy was a quick and non-destructive way of measuring rock fabric, magnetic fabric measurements have become increasingly prevalent in the study of earth and environmental processes (see Table 1 for definitions of magnetic terms). The accomplishments of U.S. workers over the past 4 years show that the U.S. community continues to contribute to the growth and development of the field. In addition to the more traditional anisotropy of magnetic susceptibility (AMS) measurements work is branching out to include anisotropy of remanence studies, particularly anisotropy of anhysteretic remanence (AAR) [McCabe et al, 1985] and anisotropy of isothermal remanence (AIR), since these parameters can be tied directly to the remanence-carrying grains in a rock and hence have relevance to the effects of magnetic fabric on natural remanent magnetization (NRM). Along with this shift is the realization, as a result of combining nonmagnetic observations (e.g.. scanning electron microscopy (SEM), finite strain measurements) with rock magnetic measurements (e.g.. hysteresis parameters), that magnetic mineral composition (paramagnetic and ferromagnetic) has an important control on magnetic anisotropy.

Kodama, Kenneth P.

1995-07-01

340

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

341

Seismicity triggered by the olivine-spinel transition: New insights from combined XRD and acoustic emission monitoring during deformation experiments in Mg2GeO4  

NASA Astrophysics Data System (ADS)

Polycrystalline Mg2GeO4-olivine has been deformed (strain rates from 2.10-4/s to 10-5/s) in the deformation-DIA in 13-BM-D at GSECARS (Advanced Photon Source) at ca. 2 GPa confining pressure for temperatures between 973 and 1573 K (i.e., in the Mg2GeO4-ringwoodite field). Stress, advancement of transformation, and strain were measured in-situ using X-ray diffraction (XRD) and imaging, and acoustic emissions (AE) full waveforms were recorded simultaneously. When differential stress is applied (ca. 1- to 2 GPa) and temperature is increased, the very beginning of the transformation to the ringwoodite structure (as evidenced by in situ XRD) is accompanied by AE bursts which locate within the sample. At high strain rates (>10-4/s) and low temperatures (800-900 degrees C), the number of AEs is comparable, if not larger, to that observed during the cold compression of quartz grains. The largest events always occur at a temperature slightly below that of appearance of the ringwoodite-structure phase on the XRD images patterns. This suggests that AEs are generated while the transition is still nucleation controlled (pseudo-martensitic stage). During stress-relaxation periods, the rate of AE triggering decreases, but does not completely vanish. The AE production rate increases again as soon as deformation is started again. Importantly, we still observed very large AEs at strain rates as low as approx. 10-5/ s. At these early stages of the transformation, the samples did not show any macroscopic rheological weakening. Focal mechanism analysis of the largest AEs showed that they are all of shear type, some being even pure double couple. They radiate about the same amount of energy as typically recorded during fast crack propagation in amorphous glass material. This suggests that they cannot only originate from the martensitic nucleation of oriented spinel-lamellae within a single germanium olivine crystal. Preliminary microstructural analysis (SEM and EBSD) highlights the presence of thin transformation bands made of incoherent spinel micro-grains which, possibly, run across germanium-olivine grain boundaries. These bands are all oriented near perpendicular to the principal compressive stress. Our observations point out that under high deviatoric stress, the olivine - spinel transition is a source of instability which produces micro-sismicity (no AEs were recorded in a similar experiment performed hydrostatically). These instabilities might eventually be precursor to brittle fracturing as observed by Green and Burnley (1989) in their deformation experiments on very similar samples. Both types of study emphasize the potential of phase transitions (with negative volume variations) in triggering brittle failure. Obviously, this has important consequences for the understanding of deep-focus earthquakes occurring in cold and metastable olivine within the transition zone.

Schubnel, A. J.; Hilairet, N.; Gasc, J.; Héripré, E.; Brunet, F.; Wang, Y.

2010-12-01

342

X-radiography, XRD and Ultrasonic Data Transfer Function Technique - Simultaneous Measurements Under Simulated Mantle Conditions in a Multi-Anvil Device  

NASA Astrophysics Data System (ADS)

The interpretation of seismic data from the Earth's deep interior requires measurements of the physical properties of Earth materials under experimental simulated mantle conditions. Elastic wave velocity measurement is an important tool for the determination of the elastic properties. Ultrasonic interferometry allows the highly precise travel time measurement at a sample enclosed in a high-pressure multi-anvil device. But the calculation of wave velocities requires the exact sample length under in situ conditions. There are two options - scanning the interfaces of the sample by XRD (Mueller et al., 2003) and X-radiography (Li et al., 2001). The multi-anvil apparatus MAX80 is equipped for both methods. Only the X-radiography is fast enough for transient measurements. Contrary to XRD measurements, imaging the sample by X-rays requires a beam diameter larger than the sample length. Therefore the fixed primary slits of Max80 were exchanged by 4-blade high precision slits of Advanced Design Consulting, Inc. A Ce-YAG-crystal converts the X-ray image to an optical one, redirected by a mirror and captured by a CCD-camera. To derive the sample length, the different brightness of sample, buffer rod and reflector at the electronic image is evaluated. Classical ultrasonic interferometry is very time consuming, because the ultrasonic waves of the frequency range under study are generated and detected one after another with a given step rate. A 60 MHz frequency sweep with 100 kHz steps lasts for more than 30 minutes. This is a serious limitation for all transient measurements, but also limits the data collection at elevated temperatures to prevent the pressure transmitting boron epoxy cubes and the anvils from overheating. The ultrasonic transfer function technique (UTF), first described by Li et al. (2002), generates all the frequencies simultaneously. Related to the results and experiences of Li the UTF-technique was developed independently at GFZ. This version allows to consider the characteristics of the specific transducer-glue-anvil combination (Mueller et al., 2003). To collect the data for the following calculation of Vp and Vs requires just few seconds. The excitation function, applied to the transducer by an arbitrary waveform generator, is the result of the summation of all sinusoidal waves inside the frequency range. The response of the system - transducer - anvil - buffer rod - sample - reflector - for each of the frequencies can be reproduced by convoluting the resulting transfer function with these monochromatic waves step by step. Some recent results on the non-quenchable high-P - low-P clinoenstatite transition and to the quartz-coesite transition will be given to discuss the different interferometric techniques, including the XRD-data and X-radiography results, necessary to detect the phase transitions under in situ conditions and to measure the sample deformation. Li, B.; Vaughan, M.T.; Kung, J.; Weidner, D.J., NSLS Activity Report 2001, 2-103-106, (2001). Li, B.; Chen, K.; Kung, J.; Liebermann, R.C.; Weidner, D.J., J. Phys.: Condens. Matter 14, 11337-11342, (2002). Mueller, H.J.; Schilling, F.R.; Lauterjung, J.; Lathe, C., Eur. J. Mineral., 15, 865-873, (2003). Mueller, H.J.; Wunder, B.; Lathe, C.; Schilling, F.R.; Eur. J. Mineral., submitted, (2004).

Mueller, H. J.; Schilling, F. R.; Lathe, C.

2004-05-01

343

Magnetic fluid micromixer with tapered magnets  

NASA Astrophysics Data System (ADS)

A magnetic fluid micromixer with high mixing efficiency using nonuniform magnetic field produced by tapered magnets is proposed. From the numerical results, the mixing efficiency increases with the saturation magnetization of the magnets. The larger the saturation magnetization is, the stronger the magnetic force acted on the magnetic fluid will be. On the other hand, asymmetric magnetic stray field that induces circulation between two fluids leads to higher mixing efficiency than a symmetric one.

Wei, Zung-Hang; Lee, Chiun-Peng

2009-04-01

344

Surface stabilized nanosized Ce(x)Zr(1-x)O(2) solid solutions over SiO(2): characterization by XRD, Raman, and HREM techniques.  

PubMed

Ce(x)Zr(1)(-)(x)O(2) solid solutions deposited over silica surface were investigated by X-ray diffraction (XRD), Raman spectroscopy (RS), and high-resolution transmission electron microscopy (HREM) techniques in order to understand the role of silica support and the temperature stability of these composite oxides. For the purpose of comparison, an unsupported Ce(x)Zr(1)(-)(x)O(2) was also synthesized and subjected to characterization by various techniques. The Ce(x)Zr(1)(-)(x)O(2)/SiO(2) (CZ/S) (1:1:2 mole ratio based on oxides) was synthesized by depositing Ce(x)Zr(1)(-)(x)O(2) solid solution over a colloidal SiO(2) support by a deposition precipitation method and unsupported Ce(x)Zr(1)(-)(x)O(2) (CZ) (1:1 mole ratio based on oxides) was prepared by a coprecipitation procedure, and the obtained catalysts were subjected to thermal treatments from 773 to 1073 K. The XRD measurements disclose the presence of cubic phases with the composition Ce(0.75)Zr(0.25)O(2) and Ce(0.6)Zr(0.4)O(2) in CZ samples, while CZ/S samples possess Ce(0.75)Zr(0.25)O(2), Ce(0.6)Zr(0.4)O(2), and Ce(0.5)Zr(0.5)O(2) in different proportions. The crystallinity of these phases increased with increasing calcination temperature. The cell a parameter estimations indicate contraction of ceria lattice due to the incorporation of zirconium cations into the CeO(2) unit cell. Raman measurements indicate the presence of oxygen vacancies, lattice defects, and displacement of oxygen ions from their normal lattice positions in both the series of samples. The HREM results reveal, in the case of CZ/S samples, a well-dispersed nanosized Ce-Zr-oxides over the surface of amorphous SiO(2). The structural features of these crystals as determined by digital diffraction analysis of experimental images reveal that the Ce-Zr-oxides are mainly in the cubic geometry and exhibit high thermal stability. Oxygen storage capacity measurements by a thermogravimetric method reveal a substantial enhancement in the oxygen vacancy concentration of CZ/S sample over the unsupported CZ sample. PMID:16852695

Reddy, Benjaram M; Lakshmanan, Pandian; Khan, Ataullah; Loridant, Stéphane; López-Cartes, Carlos; Rojas, Teresa C; Fernandez, Asunción

2005-07-21

345

Part I. Synthesis and applications of molecular sieves. Part II. The effect of temperature and support in reduction of cobalt oxide: An in situ XRD study  

NASA Astrophysics Data System (ADS)

Part I. Alkylation of aniline (PhNH2) with methanol (MeOH) over co-crystallized zeolite RHO-Zeolite X (FAU) and over zeolite Linde Type L (Sr,K-LTL) as catalysts has been studied. Co-crystallized zeolite RHO-Zeolite X (FAU) favors the formation of N,N-dimethylaniline (NNDMA), with high selectivity >90%, having an advantage over pure zeolite X(FAU) of staying active even after 10 h of reaction. Activity of co-crystallized RHO-Zeolite X (FAU) is higher than that for Sr,K-LTL in terms of production of NNDMA. Octahedral molecular sieves (OMS-2) have been reported as catalysts for oxidation reactions. Effects of using polyvinyl alcohol (PVA) and polyvinyl pyrrolidone (PVP) in the synthesis of OMS-2 have been studied. Structure of OMS-2 was kept when PVA or PVP were used as indicated by XRD and FTIR data. PVA and PVP were useful to improve the film hardness of OMS-2 applied on glass surfaces as measured by the pencil hardness test, and Knoop microhardness test. By using PVA or PVP as non-chelating agents, an increase in surface area from 59 (m2/g) to 114 (m2/g), a decrease in particle size, from 29.8 nm to 12.1 nm, and a hardness value of 4H using the pencil hardness test, and 17.73 HK by Knoops micro hardness tests for OMS-2 prepared with PVA were observed. ZK-5 (KFI) molecular sieve was synthesized in the K2O: SrO: Al2O3: SiO2: 160 H2O: THF system using conventional hydrothermal heating. Products were characterized by XRD, TGA, FESEM, EDX and TPD-MS. Molar ratios of THF/Al2O3 from 0.4 to 1.0 gives best results in terms of crystallinity and purity for the prepared ZK-5. Part II. Reduction of cobalt oxide (Co 3O4) at different temperatures and in combination with different modifiers and supported on gamma-Al2O3 was monitored by in situ X-ray diffraction. Complete reduction of cobalt oxide to the (hcp) phase is observed at 250°C. Different reduction sequence can give different results in terms of crystalline phase obtained for cobalt even if the same maximum reduction temperature is reached. Supported Co 3O4 was reduced at 350°C to CoO and Co metal (hcp). Addition of modifiers increases the ratio of cobalt metal obtained as calculated by X-ray intensity ratios.

Garces Trujillo, Luis Javier

346

Magnetic Properties of CoFe_2O4 and Fe_3O_4  

NASA Astrophysics Data System (ADS)

In order to optimize the magnetization of magnetic nanoparticles for use as Magnetic Resonance Imaging contrast agents and other in vivo biological applications, we have synthesized CoFe_2O_4(Liu, C.; Bingsuo, Z.; Rondinone, A.J.; Zhang, Z.J. J. Am. Chem. Soc.) 122, 6263 (2000). and Fe_3O_4(Shen, T.; Weissleder, R.; Papisov, M.; Bogdanov, A.; Brady, T. MRM) 29, 599 (1993). magnetic nanoparticles of sizes 5, 8, and 11nm using water-in-oil reverse micelles. Size was determined using Dynamic Light Scattering (DLS), X-Ray Diffraction (XRD), and High Pressure Liquid Chromatography (HPLC). Magnetic properties were measure from 10K-340K using SQUID magnetometry. Magnetization as a function of magnetic field has been performed at approximately body temperature ( ~310K) in order to help us determine the optimal size and composition for in vivo application.

Rodriguez, Robert; Chan, T.; Kenning, G. G.; Huang, L.; Yan, Y.

2002-03-01

347

Magnetic Colloids By Pulsed Laser Ablation  

NASA Astrophysics Data System (ADS)

Colloidal magnetic nanoparticles have been successfully synthesized by nano second pules laser ablation of a cobalt slice immersed in liquid (distilled water) medium. The focused output of 1064 nm wavelength of pulsed Nd: YAG laser operating at 40 mJ/pulse is used for ablation. The liquid enviorment allows formation of colloids with nanoparticles in uniform particle diameter. Synchrotron X-ray powder diffraction (XRD) is used for the study of structural property of synthesized nanoparticles. The magnetic properties of cobalt nanoparticles are also investigated. The coercivity of is found to be 73 Oe. The optical properties have been determined by UV-visible absorption spectroscopy and band gap found to be 2.16 and 3.60 eV.

Pandey, B. K.; Singh, M. K.; Agarwal, A.; Gopal, R.

2011-06-01

348

Functionalization-induced improvement in magnetic properties of Fe3O4 nanoparticles for biomedical applications  

NASA Astrophysics Data System (ADS)

Fe3O4 were synthesized nanoparticles by thermal decomposition method with oleic acid as the surfactant, and to make them suitable for aqueous environments, dopamine ligand exchange was carried out on the particles. The nanoparticle size and phase was quantified by transmission electron microscopy (TEM) and x-ray diffraction (XRD), respectively. Superconducting quantum interference device magnetometry confirmed superparamagnetic behavior in both nanoparticles. A surprising and significant increase in the remanence MR, saturation magnetization MS, and blocking temperature TB of the particles was found after dopamine functionalization, even though TEM and XRD studies revealed no change in the particles' size and/or structure. The results are consistent with an increase in the magnetic size of the nanoparticle core induced by the dopamine ligand exchange process. These effects are tentatively attributed to surface bonding effects that alter the canted magnetic state of the Fe3O4 nanoparticles.

Nagesha, Dattatri K.; Plouffe, Brian D.; Phan, Minh; Lewis, Laura H.; Sridhar, Srinivas; Murthy, Shashi K.

2009-04-01

349

Magnetic field annihilators: invisible magnetization at the magnetic equator  

Microsoft Academic Search

Some distributions of magnetization give rise to magnetic fields that vanish everywhere above the surface, rendering these distributions of magnetization completely invisible. They are the annihilators of the magnetic inverse problem. Known examples are the infinite sheet with constant magnetization and the spherical shell of constant susceptibility magnetized by an arbitrary internal field. Here, we show that remarkably more interesting

S. Maus; V. Haak

2003-01-01

350

Development of an x-ray diffraction camera used in magnetic fields up to 10 T  

SciTech Connect

A high-field x-ray diffraction (HF-XRD) camera was developed to observe structural changes of magnetic materials in magnetic fields up to 10 T. The instrument mainly consists of a Debye-Scherrer-type camera with a diameter of 80.1 mm, a 10-T cryocooled superconducting magnet with a 100-mm room-temperature bore, an x-ray source, a power supply, and a chiller for the x-ray source. An x-ray detector (image plate) in the HF-XRD camera can be taken out and inserted into the magnet without changing the sample position. The performance of the instrument was tested by measuring the HF-XRD for silicon and ferromagnetic MnBi powders. A change of x-ray diffraction pattern was observed due to the magnetic orientation of MnBi, showing that the instrument is useful for studying field-induced orientation processes and structural properties of field-controlled materials.

Mitsui, Yoshifuru; Takahashi, Kohki; Watanabe, Kazuo [High Field Laboratory for Superconducting Materials, Institute for Materials Research, Tohoku University, Sendai 980-8577 (Japan); Koyama, Keiichi [High Field Laboratory for Superconducting Materials, Institute for Materials Research, Tohoku University, Sendai 980-8577 (Japan); Graduate School for Science and Engineering, Kagoshima University, Kagoshima 890-0065 (Japan)

2011-12-15

351

Effects of uniformities of deposition of respirable particles on filters on determining their quartz contents by using the direct on-filter X-ray diffraction (DOF XRD) method.  

PubMed

In this study, field samplings were conducted in three workplaces of a foundry plant, including the molding, demolding, and bead blasting, respectively. Three respirable aerosol samplers (including a 25-mm aluminum cyclone, nylon cyclone, and IOSH cyclone) were used side-by-side to collect samples from each selected workplace. For each collected sample, the uniformity of the deposition of respirable dusts on the filter was measured and its free silica content was determined by both the DOF XRD method and NIOSH 7500 XRD method (i.e., the reference method). A same trend in measured uniformities can be found in all selected workplaces: 25-mm aluminum cyclone>nylon cyclone>IOSH cyclone. Even for samples collected by the sampler with the highest uniformity (i.e., 25-mm aluminum cyclone), the use of the DOF XRD method would lead to the measured free silica concentrations 1.15-2.89 times in magnitude higher than that of the reference method. A new filter holder should be developed with the minimum uniformity comparable to that of NIOSH 7500 XRD method (=0.78) in the future. The use of conversion factors for correcting quartz concentrations obtained from the DOF XRD method based on the measured uniformities could be suitable for the foundry industry at this stage. PMID:20006439

Chen, Ching-Hwa; Tsaia, Perng-Jy; Lai, Chane-Yu; Peng, Ya-Lian; Soo, Jhy-Charm; Chen, Cheng-Yao; Shih, Tung-Sheng

2009-11-13

352

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

353

Magnetic Energy  

Microsoft Academic Search

I WOULD like to comment, if rather tardily, on one paragraph of Prof. Ferraro's review1 of my book, Electromagnetism and Relativity2. He says: ``Prof. Cullwick appears to be under a misapprehension about the nature of the magnetic energy of a system of electric currents... we read that `the hypothesis is introduced that the magnetic energy of a current circuit is

E. G. Cullwick

1961-01-01

354

Magnetic Storms  

Microsoft Academic Search

DR. CHREE contends that magnetic observations have now reached a high pitch of perfection, and that their discussion is not lightly to be undertaken by outsiders. That is no doubt so, and there must be many features about magnetic storms which are known only to experts. But when we find experts in doubt on such a fundamental matter as whether

Oliver Lodge

1909-01-01

355

Magnetically Tunable Polymer Nanocomposites for RF and Microwave Device Applications  

NASA Astrophysics Data System (ADS)

There has been much interest in polymer nanocomposites (PNC) recently due to potential applications for EMI shielding, tunable electromagnetic devices and flexible electronics. We report synthesis, structural, magnetic and RF characterization on PNCs ranging from 20-80 wt-% loadings of Fe3O4 and CoFe2O4 nanoparticles (˜8nm) in a thermosetting resin from the Rogers Corporation. Nanoparticles were synthesized by thermal decomposition and characterized by XRD and TEM. Magnetic properties were studied using a Quantum Design PPMS. PNCs displayed characteristic features of superparamagnetism at room temperature and blocking at low temperature. Microwave transmission/reflection studies were done using a microstrip resonator. Strong tunability in the microwave absorption was observed. We extend our study to include nanoparticle-filled multi-walled carbon nanotubes synthesized by CVD. These high-aspect ratio magnetic nanostructures, with tunable anisotropy, are of particular interest in enhancing magnetic and microwave responses in existing PNCs.

Stojak, K.; Pal, S.; Srikanth, H.; Morales, C.; Dewdney, J.; Wang, J.; Weller, T.

2011-03-01

356

TF-XRD examination of surface-reactive TiO2 coatings produced by heat treatment and CO2 laser treatment.  

PubMed

When surface-reactive (bioactive) coatings are applied to medical implants by means of CO2 laser processing, the bioactivity of the surface of the implant can be locally modified to match the properties of the surrounding tissues to provide a firm fixation of the implant. The aim of this study was to compare the heat treated TiO2 coatings with the laser-treated TiO2 coatings in terms of amorphous-crystalline-phase development. The coatings were characterized with thin-film X-ray diffraction (TF-XRD), atomic force microscopy (AFM) and scanning electron microscopy (SEM). The TiO2 coatings heat treated at 500 degrees C known to be bioactive in SBF (simulated body fluid) consisted mainly of anatase with some rutile-phase, suggesting a predominant effect of anatase on reactivity of coatings. However, the coatings preheat-treated at 500 degrees C with further laser treatment exhibited enhanced bioactivity while consisting mainly of rutile. These findings indicated a key role of both rutile and anatase for the reactivity of the coatings. Without preheat treatment, by laser treatment alone, the amorphous titania coatings developed into mixed anatase/rutile containing coatings. This structural organization and the increase in crystal size are thus considered to be the reasons for their bioactivity. The SBF results indicate the possibility to control bioactivity by altering laser power used through the anatase/rutile crystallinity enhancement. PMID:15701375

Moritz, Niko; Areva, Sami; Wolke, Joop; Peltola, Timo

2005-07-01

357

Redox Behavior of VI B Transition Metal Ions in Rutile TiO2 Solid Solutions: An XRD and EPR Study  

NASA Astrophysics Data System (ADS)

CrO2-TiO2 (TC), MoO2-TiO2 (TMo), and WO2-TiO2 (TW), prepared by heating in vacuo at 1173-1273 K mixtures of MO2 (M=Cr, Mo, or W) and TiO2, were characterized by XRD and EPR. The transition metal ions were incorporated as isolated and clustered CrIII, MoIV, and WIV and a small fraction as isolated MoV and WV in substitutional sites. After heating in air or in O2 up to 1273 K, in TC no isolated CrV formed, whereas in TMo and TW, MIV was oxidized to MV and MVI, and MO3 was segregated. The oxidation started at 673 K and gave isolated substitutional MoV and isolated interstitial and substitutional WV. After heating in H2 up to 1073 K, TMo and TW reduction process differed: MoIV gave isolated and clustered MoIII, and MoIV-MoIV pairs gave Mo7+2 species; WIV was not reduced to WIII; and temperatures >900 K caused the segregation of metallic molybdenum and tungsten.

Cordischi, Dante; Gazzoli, Delia; Occhiuzzi, Manlio; Valigi, Mario

2000-07-01

358

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.

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

2013-01-01

359

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

360

Stability and structural evolution of Ce(IV)(1-x)Ln(III)(x)O(2-x/2) solid solutions: a coupled ?-Raman/XRD approach.  

PubMed

Several CeO(2)-based mixed oxides with general composition Ce(1-x)Ln(x)O(2-x/2) (for 0 ? x ? 1 and Ln = La, Nd, Sm, Eu, Gd, Dy, Er, or Yb) were prepared using an initial oxalic precipitation leading to a homogeneous distribution of cations in the oxides. After characterization of the Ce/Nd oxalate precursors and then thermal conversion to oxides at T = 1000 °C, investigation of the crystalline structure of these oxides was carried out by XRD and ?-Raman spectroscopy. Typical fluorite Fm ?3m structure was obtained for relatively low Ln(III) contents, while a cubic Ia ?3? superstructure was evidenced above x ? 0.4. Moreover, since Nd(2)O(3) does not crystallize with the Ia ?3?-type structure, two-phase systems composed with additional hexagonal Nd(2)O(3) were obtained for x(Nd) ? 0.73 in the Ce(1-x)Nd(x)O(2-x/2) series. The effect of heat treatment temperature on these limits was explored through ?-Raman spectroscopy, which allowed determining the presence of small amounts of the different crystal structures observed. In addition, the variation of the Ce(1-x)Ln(x)O(2-x/2) unit cell parameter was found to follow a quadratic relation as a result of the combination between increasing cationic radius, modifications of cation coordination, and decreasing O-O repulsion caused by oxygen vacancies. PMID:21714501

Horlait, D; Claparède, L; Clavier, N; Szenknect, S; Dacheux, N; Ravaux, J; Podor, R

2011-06-29

361

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...

362

Structural and magnetic properties of nanocrystalline nickel-rich Fe-Ni alloy powders prepared via hydrazine reduction  

NASA Astrophysics Data System (ADS)

Nickel-rich Fe-Ni alloy nanoparticles with different compositions were prepared by solution reduction using hydrazine as reductant. The phase composition, morphologies and magnetic properties of as-prepared and annealed samples were characterized by an X-ray diffractionmeter (XRD), a scanning electron microscope (SEM) and a vibrating sample magnetometer (VSM), respectively. XRD results show that all the samples exhibit a single phase with face-centered cubic structure before and after annealing. SEM images show that the as-prepared spherical particles are composed of smaller crystallites. VSM results indicate that the saturation magnetization decreases obviously with the increase of nickel content, while it increases with the annealing temperature. In addition, the samples transform from a half hard magnetic behavior to a typical soft magnetic behavior with the increase of annealing temperature.

Xu, Zhichao; Jin, Chuangui; Xia, Ailin; Zhang, Junyan; Zhu, Guohui

2013-06-01

363

Synthesis and study of magnetic properties of Co-doped anatase TiO2 nanoparticles  

NASA Astrophysics Data System (ADS)

Anatase phase Ti0.97Co0.03O2 nanoparticles were synthesized using two different preparation methods. The prepared samples were investigated by X-ray diffraction (XRD), X-ray fluorescence (XRF) analysis, and magnetization measurements. The particle diameters were controlled by adjusting the annealing temperature, and they ranged from 4.2-7.0 nm for Ti0.97Co0.03O2 encapsulated in amorphous SiO2, and from 14-61 nm for Ti0.97Co0.03O2 that was not encapsulated in amorphous SiO2. Magnetization measurements were performed on the 7.0-nm sample from the former sample set, and on the 14-nm sample from the latter sample set, and both these samples exhibited an identical crystal structure and an equal number of magnetic ions, as confirmed by XRF and XRD measurements. The magnetization curves for the two samples indicated their ferromagnetic behavior at room temperature. However, the magnetic parameters of saturation magnetization MS and coercive force HC were clearly different for these two samples. We attribute this difference in magnetic properties between these samples to magnetic impurities present due to the different degrees of solubility of Co ions in the TiO2 lattice.

Yano, S.; Kurokawa, A.; Takeuchi, H.; Yanoh, T.; Onuma, K.; Kondo, T.; Miike, K.; Miyasaka, T.; Ichiyanagi, Y.

2013-04-01

364

Highly accessible catalytic sites on recyclable organosilane-functionalized magnetic nanoparticles: An alternative to functionalized porous silica catalysts  

Microsoft Academic Search

Diaminosilane-functionalized cobalt spinel ferrite (CoFe2O4) magnetic nanoparticles are synthesized and used as efficient heterogeneous base catalysts for the Knoevenagel condensation of aromatic and heteroaromatic aldehydes with malononitrile. The magnetic nanoparticle catalyst is characterized by X-ray powder diffraction (XRD), transmission electron microscopy (TEM), thermogravimetric analysis (TGA), Fourier transform infrared (FTIR), and nitrogen physisorption measurements. Quantitative conversion of the reactants is achieved

Nam T. S. Phan; Christopher W. Jones

2006-01-01

365

On the Fe 3O 4\\/Mn 1? x Zn x Fe 2O 4 core\\/shell magnetic nanoparticles  

Microsoft Academic Search

Fe3O4 magnetic nanoparticles (NPs) were synthesized by the co-precipitation of Fe3+ and Fe2+ with ammonium hydroxide under hydrazine hydrate, and were characterized by X-ray powder diffraction (XRD), transmission electron microscopy (TEM) and vibrating sample magnetometer (VSM). In order to improve the particle dispersion, the bare Fe3O4 magnetic NPs were surface modified by sodium citrate under Ar protection. Mn–Zn ferrite NPs

R. Y. Hong; J. H. Li; X. Cao; S. Z. Zhang; G. Q. Di; H. Z. Li; D. G. Wei

2009-01-01

366

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

367

Influence of Au addition on magnetic properties of iron oxide in a silica-phosphate glass matrix  

NASA Astrophysics Data System (ADS)

The influence of gold particle addition on structural and magnetic ordering of iron oxide in a glass matrix was studied. The silica-phosphate glasses containing iron oxide and Au were prepared by the melt quench technique. Evolution of crystalline phases was studied by X-ray diffraction (XRD). Magnetic properties were investigated by means of a Superconducting Quantum Interference Device (SQUID) magnetometer and room temperature Mössbauer spectroscopy. The microstructure exhibited the formation of 30-40 nm size particles. The samples showed the formation of magnetite and hematite as major crystalline phases. Magnetic studies revealed the relaxation of magnetic particles. Blocking temperature of investigated sample increased with an increase of Au content implying an increase in the strength of magnetic interactions. Mössbauer spectroscopy has shown the presence of both doublets and magnetic sextets. The magnetization value increased as Au content was increased, which is attributed to the increase in magnetic and structural ordering.

Sharma, K.; Prajapat, C. L.; Meena, Sher Singh; Singh, M. R.; Yusuf, S. M.; Montagne, L.; Kothiyal, G. P.

2013-11-01

368

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

369

Analysis of "Meridiani Planum"-like evaporites using CheMin, an XRD/XRF instrument proposed for the Mars Science Laboratory (MSL)  

NASA Astrophysics Data System (ADS)

The discovery of up to 30-40 wt% sulfate salts in sediments at Meridiani Planum [1-2] indicates that evaporite sediments have played an important role in the hydrogeologic history of Mars. Data available to date support the presence of the mineral jarosite (a hydrous Fe-sulfate), Mg-sulfate, and lesser amounts of salts containing Cl and Br. One of the most exciting features of the Meridiani sediments is the possibility that the salts may be hydrated. Water storage in minerals may be a significant source of the elevated hydrogen abundances seen in some equatorial regions by the Odyssey spacecraft, with abundances up to 8-9 wt% water-equivalent present in areas where water ice should not be stable [3]. Is it possible that salt hydrates in evaporite sediments can account for some of this equatorial water? The ability to quantify mixed-salt mineralogies will be important for determining brine history on Mars. Definitive mineralogy, a key requirement of MSL, can be accomplished by the CheMin X-ray Diffraction / X-ray Fluorescence (XRD/XRF) instrument [4]. The MSL approach to investigating this kind of deposit can be based on the capabilities demonstrated by MER-B (visual petrography, Mossbauer, APXS, and Mini-TES). The enhanced drilling capability of MSL can be used to collect and transfer cores to the rock crusher for pulverizing and ultimate delivery of crushed material to CheMin. If MSL is able to traverse kilometers or tens of kilometers, CheMin characterization of changes in evaporite mineralogy, zonation in evaporite facies or the mineralogical identity of detrital grains could be used to conduct an analysis of the evaporative basin - lateral extent, water depth, salinity, facies changes, etc. The ability to quantify hydrated mineral assemblages will be important for reconstructing brine evolution and for determining the nature of interactions between brine minerals and detrital mineralogy. The important contribution of CheMin to a site like Meridiani will be to provide accurate and definitive mineralogical data of complex multi-mineral mixtures. Definitive mineralogical data will be highly useful in interpreting brine chemistry and the nature and extent of the ancient habitable zone that existed there. [1]. MER Rover web site (http://www.jpl.nasa.gov/mer2004/rover-images/mar-02-2004/images-3-2-04.html [2]. Kerr, R. A. (2004), "A wet early Mars seen in salty deposits," Science 303, 1450. [3]. Feldman, W. C., et al. (2003), "The global distribution of near-surface hydrogen on Mars," In: Sixth Int. Conf. on Mars, abstract #3218, Lunar and Planetary Institute, Houston (CD-ROM). [4]. Blake, D.F., P. Sarrazin, D.L. Bish, S. Feldman, S.J. Chipera, D.T. Vaniman, and S.A. Collins (2004), "Definitive Mineralogical Analysis of Mars Analogs Using the CheMin XRD/XRF Instrument," Lunar and Planetary Science Conf XXXV, abstr. #1373 (CD-ROM).

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

2004-12-01

370

Magnetism, Pt A.  

National Technical Information Service (NTIS)

This program defines magnets and explains the difference between natural and artificial magnets. It also discusses the characteristics of magnetic lines of force about a magnet and the laws of repulsion and attraction between magnets. It gives the factors...

1994-01-01

371

Seed-mediated synthesis, properties and application of ?-Fe2O3-CdSe magnetic quantum dots  

NASA Astrophysics Data System (ADS)

Seed-mediated growth of fluorescent CdSe quantum dots (QDs) around ?-Fe2O3 magnetic cores was performed at high temperature (300 °C) in the presence of organic surfactants. Bi-functional magnetic quantum dots (MQDs) with tunable emission properties were successfully prepared. The as-synthesized MQDs were characterized by high-resolution transmission electron microscopy (HRTEM) and dynamic light scattering (DLS), which confirmed the assembly of heterodimers. When a longer growth period was employed, a homogeneous dispersion of QDs around a magnetic nanoparticle was obtained. The magnetic properties of these nanocomposites were examined. The MQDs were superparamagnetic with a saturation magnetization of 0.40 emu/g and a coercivity of 138 Oe at 5 K. To demonstrate their potential application in bio-labeling, these MQDs were coated with a thin silica shell, and functionalized with a polyethylene glycol (PEG) derivative. The functionalized MQDs were effectively used for the labeling of live cell membranes of 4T1 mouse breast cancer cells and HepG2 human liver cancer cells.

Lin, Alex W. H.; Yen Ang, Chung; Patra, Pranab K.; Han, Yu; Gu, Hongwei; Le Breton, Jean-Marie; Juraszek, Jean; Chiron, Hubert; Papaefthymiou, Georgia C.; Tamil Selvan, Subramanian; Ying, Jackie Y.

2011-08-01

372

Rapid Serial Prototyping and Analysis of Nanomagnet-Tipped Attonewton-Sensitivity Cantilevers for Magnetic Resonance Force Microscopy  

NASA Astrophysics Data System (ADS)

Magnetic resonance force microscopy offers exciting possibilities for imaging protons and electrons in native and spin-labeled biomolecules. The central component of a magnetic resonance force microscope experiment is a custom-fabricated attonewton-sensitivity cantilever with an overhanging magnetic-nanorod tip. We have recently developed a method for making precision tips which involves 1) fabricating overhanging magnetic tips on shortened mock cantilevers, 2) using focused ion beam milling and deposition (FIB/FID) to cut the mock cantilever (and attached tip) free from the substrate, and then 3) attaching the released structure to a full-length high-sensitivity cantilever. The resulting magnets have been characterized by cantilever magnetometry, high-resolution transmission electron microscopy (HR-TEM), and nanometer-resolution electron energy loss spectroscopy (EELS). This approach to fabrication and analysis is allowing us to optimize tips for proposed single-electron-spin imaging experiments in a very short time. Rapid access to such high-quality tips will significantly advance our ability to image individual biomolecules and macromolecular complexes.

Marohn, John; Moore, Eric; Longenecker, Jonilyn

2011-03-01

373

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

374

Magnetic Monopoles.  

National Technical Information Service (NTIS)

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 referenc...

D. Fryberger

1984-01-01

375

Magnetic domains  

NASA Astrophysics Data System (ADS)

At the recently concluded International Association of Geomagnetism and Aeronomy Assembly in Exeter, U.K., magnetic domain observations on magnetite imaged for the first time by the magneto-optic Kerr effect were reported. The picture (Figure 1) shows domains on a synthetic magnetite grain where magnetic contrast is achieved by the longitudinal Kerr effect using a polarizing light microscope with an attached high-sensitivity video camera, a digital video processor and a graphics computer.Previous domain studies on magnetite were done by the Bitter technique, where magnetic colloids are attracted by magnetic gradients over domain walls. Results were at odds with theoretical predictions concerning domain sizes, and it has been questioned whether the colloid actually leaves the domains themselves unaffected or whether there are (Néel-type) domain walls that are not associated with a significant gradient.

Worm, H.-U.; Banerjee, S. K.; Ryan, P. J.; Hoffmann, V.; Appel, E.; Soffel, H.

376

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

377

Solar Magnetism  

NSDL National Science Digital Library

The Sun appears to shine at a constant rate. However, its magnetic field is actually constantly changing, and this affects energy output. These variations cause effects that extend throughout the solar system. This video segment, adapted from a NOVA television broadcast, introduces viewers to some of the effects of the sun's magnetic field, such as sunspots, auroras, and variations in the sunspot cycle which may affect Earth's climate. The segment is two minutes fifty seconds in length.

2011-05-10

378

Fabricating Co doped ZnO nanocrystallines by hydrothermal method with high pulsed magnetic field.  

PubMed

Co-doped ZnO nanocrystallines were fabricated by hydrothermal method with high pulsed magnetic field. As a new preparation method, more refined grains and diluted magnetic semiconductors (DMSs) with better performance could be obtained by the hydrothermal synthesis process under pulsed magnetic field. The samples were tested by X-Ray Diffraction (XRD), Scanning Electron Microscope (SEM), Vibrating Sample Magnetometer (VSM) and Raman scattering spectrum. The results show that the sample prepared under pulsed magnetic field has wurtzite structure with tiny crystal lattices changes. Doping Co ions into ZnO crystal lattice is also improved. Curie temperature of 2% Co doped ZnO nanocrystallines synthesized with 4T pulsed magnetic field is higher than that for without magnetic field process, and very close to the room temperature. PMID:21137920

Huang, Jin; Zhu, Mingyuan; Li, Ying; Yang, Tao; Li, Yibing; Jin, Hongming; Hu, Yemin

2010-11-01

379

Synthesis of magnetic nanofibers using femtosecond laser material processing in air  

PubMed Central

In this study, we report formation of weblike fibrous nanostructure and nanoparticles of magnetic neodymium-iron-boron (NdFeB) via femtosecond laser radiation at MHz pulse repetition frequency in air at atmospheric pressure. Scanning electron microscopy (SEM) analysis revealed that the nanostructure is formed due to aggregation of polycrystalline nanoparticles of the respective constituent materials. The nanofibers diameter varies between 30 and 70 nm and they are mixed with nanoparticles. The effect of pulse to pulse separation rate on the size of the magnetic fibrous structure and the magnetic strength was reported. X-ray diffraction (XRD) analysis revealed metallic and oxide phases in the nanostructure. The growth of magnetic nanostructure is highly recommended for the applications of magnetic devices like biosensors and the results suggest that the pulsed-laser method is a promising technique for growing nanocrystalline magnetic nanofibers and nanoparticles for biomedical applications.

2011-01-01

380

Synthesis, characterization and magnetic properties of Cr-substituted Co-Zn ferrites nanopowders  

NASA Astrophysics Data System (ADS)

Nano-crystalline ferrites; Co0.9Zn0.1Fe2-xCrxO4 (where x = 0-1) have been synthesized through thermal decomposition reaction of their respective oxalates. The effect of Cr3+ ion substitution on the structural and magnetic properties was studied. Differential thermal analysis-thermogravimetry (DTA-TG) techniques were used to characterize the oxalates decomposition reaction and following ferrite formation. X-ray diffraction (XRD), Fourier transform infrared (FT-IR), transmission electron microscopy (TEM) and vibrating scanning magnetometry (VSM) were used to characterize the structural, morphological and magnetic properties. XRD revealed single-phase cubic spinels. Both crystallite size and lattice parameter decreases with increasing Cr-content. FT-IR spectral studies confirmed the suggested cation distribution estimated through XRD measurements. TEM image showed agglomerated spherical nanoparticles with size of about 20 nm. The gradual decrease in the saturation magnetization, estimated through VSM measurements, with increasing Cr-content suggests the preferential occupation of Cr3+ ions in the octahedral sites and confirmed the suggested cation distribution while, the decrease in the coercivity values indicating the loss of magneto-crystalline anisotropy. The decrease in the Curie temperatures obtained from dc-magnetic susceptibility with the increasing chromium can be attributed to the decrease in the A-B exchange interaction.

Gabal, M. A.; Al Angari, Y. M.; Al-Agel, F. A.

2013-03-01

381

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 Zn1-xCdxSe 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

2008-03-01

382

Magnets 1: Magnetic Pick-ups  

NSDL National Science Digital Library

This lesson provides students with an understanding that certain materials are attracted to magnets while others are not. It is the first in a two-lesson series on magnets. In Magnets 1: Magnetic Pick-ups, students will look at various objects, make predictions about whether they are magnetic, and then test their predictions. This exploration is an introductory activity to magnets and magnetism.

383

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

384

Alteration history of mudrock samples from the San Andreas Fault Observatory at Depth (SAFOD) drill hole: a TEM-XRD study  

NASA Astrophysics Data System (ADS)

Studying rock alteration in active fault zones is key to understanding fault history and the interaction with mechanical, hydrological and mineralogical processes. In the SAFOD mudrocks at 3064 and 3436 m depths, abundant clay mineral phases, including mixed-layered varieties, occur in the matrix. At present, little is known about the mechanism and timing of their formation in relation to the faulting process. Based on a detailed TEM-XRD study, a preliminary assessment of the alteration history of the clay-rich rock chips is made by studying mineral character, hydration behavior, fabric and textural relationships. The mudrocks contain detrital grains of chlorite, muscovite and biotite, along with a range of authigenic illite, illite-smectite, chlorite- smectite and smectite. The predominant clay minerals are small illite packets (20-30 nm thickness) of a 1Md polytype. The illite constitutes about 75 percent of the illite-smectite mixed layer particles, showing a long- range ordering (R greater than 3). These authigenic mineral phases are probably formed during the movement of aqueous fluids along permeable fractures and veins by dissolution-precipitation reactions, and partly at the expense of larger (about 150 nm thick), deformed, detrital packets. The chlorite-smectite mixed layered phases formed via similar mechanisms, but in this case by direct alteration of detrital chlorite and biotite grains. Preliminary DTA heat flow results from a whole rock mudstone indicate a total loss of about 6 percent of total volatiles (about 2 percent interlayer water, about 4 percent crystalline water), most of which occurs during the dehydroxylation of clays (400-600 C). The timing of authigenic mineral growth in the matrix assemblages is considered to be coeval or older than localized mineralization along open fractures. The fracture precipitations are notably smectite rich and can be taken as an indication of more recent low temperature fluids of varying composition or more extensive dissolution associated with enhanced fluid flow. That these surface precipitations show some alignment along these small scale fault planes indicates a direct relationship between slip and mineral growth.

Schleicher, A. M.; van der Pluijm, B. A.; Warr, L. N.

2006-12-01

385

Synthesis and characterization of functional magnetic nanocomposites  

NASA Astrophysics Data System (ADS)

Magnetic nanoparticles and carbon nanotubes have been excellent functional materials that could be dispersed in polymer matrices for various applications. However, uniform dispersion of particles in polymers without agglomeration is quite challenging. We have fabricated PMMA/polypyrrole bilayer structures embedded with Fe3O4 magnetite nanoparticles synthesized using wet chemical synthesis. Agglomeration-free dispersion of nanoparticles was achieved by coating the particles with surfactants and by dissolving both the particles and PMMA in chlorobenzene. Structural characterization was done using XRD and TEM. Magnetic properties of the bilayer structures indicated superparamagnetic behavior that is desirable for RF applications as the magnetic losses are reduced. Our polymer nanocomposite bilayer films with conducting polymer coatings are potential candidates for tunable RF applications with integrated EMI suppression. We will also report on our studies of pumped ferrofluids flowing past carbon nanotubes that are arranged in microchannel arrays. Magnetization under various flow conditions is investigated and correlated with the hydrodynamic properties. This scheme provides a novel method of energy conversion and storage using nanocomposite materials.

Gass, J.; Sanders, J.; Srinath, S.; Srikanth, H.

2006-03-01

386

Magnets Enter the Picture  

NSDL National Science Digital Library

This book began with the basics of electricity, and now it's time to introduce the basics of magnetism. What better way to do that than to play around with magnets? In this chapter, by playing with magnets, you'll learn about the types of magnets, magnetic materials, the properties of magnets, and how the Earth creates its own magnetic field.

Robertson, William C.

2005-01-01

387

Temperature-induced phenomena in systems of magnetic nanoparticles  

NASA Astrophysics Data System (ADS)

Magnetic nanoparticle ensembles have received a lot of attention, stemming in part from their current and potential applications in biomedicine and in the development of high-density magnetic storage media. Key to the functionality of these systems are microscopic structures and mechanisms that make them exhibit unique properties and behave differently from their bulk counterparts. We studied microscopic structures and processes that dictate macroscopic properties, behavior and functionality of magnetic nanoparticle ensembles. As the temperature T strongly influences the magnetic behavior of these systems, we studied temperature dependent magnetic properties using AC-susceptibility and DC-magnetization measurements carried out over a broad range of temperatures, between 3 and 300 K. We extracted structural information from X-ray diffraction (XRD) and direct imaging techniques and correlate it with magnetic properties, in an attempt at better understanding the microscopic structures and magnetic mechanisms responsible for the macroscopic magnetic behavior. We studied ensembles of magnetic nanoparticles: nickel ferrite immobilized in a solid matrix and cobalt ferrite immersed in carrier fluid respectively, in order to explore their potential use in biomedical applications and magnetic recording. For both NiFe2O4(NFO) and Co0.2Fe2.8O4 (CFO) relaxation mechanisms were determined. Structural properties and average particle sizes were derived from XRD, including synchrotron XRD, and direct imaging techniques such as scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Temperature dependent magnetic measurements, FC-ZFC DC magnetometry, as well as AC complex susceptibility measurements at frequencies between 10 and 10,000 Hz were carried out within the temperature range 3Kmagnetization and AC susceptibility measurements were performed using a Physical Property Measurement System (PPMS), which allows measurements in magnetic fields up to 9T and within a temperature range between 2 and 350 K. For NFO, besides the expected blocking of the superspin, observed at T1 ? 45 K, we found that the system undergoes a magnetic transition at T2 ? 6 K. For the latter, frequency- and temperature-resolved dynamic susceptibility data reveal characteristics that are unambiguously related to collective spin freezing: the relative variation (per frequency decade) of the in-phase-susceptibility peak temperature is ˜0.025, critical dynamics analysis yields an exponent zv = 9.6 and a zero-field freezing temperature TF = 5.8 K, and, in a magnetic field, TF (H) is excellently described by the de Almeida-Thouless line deltaT F infinity H2/3. Moreover, out-of-phase-susceptibility vs. temperature datasets collected at different frequencies collapse on a universal dynamic scaling curve. All these observations indicate the existence of a spin-glass-like surface layer that surrounds the superparamagnetic core and undergoes a transition to a frozen state upon cooling below 5.8 K. For the CFO ferrofluid, we used temperature- and frequency-resolved AC-susceptibility measurements to investigate its magnetic relaxation above the freezing point of the liquid carrier. Our data show that both the Neel and the Brown relaxation mechanisms are operative at temperatures in the vicinity of the out-of-phase (imaginary) susceptibility peak. We separate the contributions of the two mechanisms to the overall-relaxation time, and demonstrate that Brownian relaxation plays a dominant role at all temperatures within this high-dissipation regime.

Bhuiya, Abdul Wazed

388

Magnetic fluids  

NASA Astrophysics Data System (ADS)

An overview of studies done on ferrofluids is presented, and recently discovered technological uses for such a fluid are examined. By interacting magnetization and pressure, a ferrofluid plug, held in place by a focused magnetic field imposed from the outside, serves as an airtight seal in rotating machinery. A 160 stage rotary seal has withstood a pressure differential of 66 atmospheres. The fluid has also proved useful in the design of loudspeakers, as it does not drip out of the gap in the cylindrical permanent magnet which allows the voice coil to move, thus serving as a coolant for the system. Finally, the fluid can be used to separate materials according to density, as the magnetic-levitation forces that can be established in the fluid are strong enough to float materials of any density. Other applications are being explored, such as an induced convection that can be much more vigorous than simple gravity convection when a gradient magnetic field is applied to a heated ferrofluid.

Rosensweig, R. E.

1982-10-01

389

Magnetic Bubbles  

NASA Astrophysics Data System (ADS)

Bubbles in liquids driven by a sound field are used in many disciplines: for example bubbles clean surfaces in ultrasonic water bathes, they catalyze unique chemical reactions in sonochemistry, and under special conditions even create light. However, conventional bubbles have a major limitation when placed in an acoustic field: it is extremely hard to control their position. Here we present a new type of bubble that has permanent magnetization originating from a shell of self-assembled nanoparticles, so that magnetic fields can be used to control the bubble's position independently. We will report on the recipe and the experiment to study bubble oscillations in weak magnetic fields. The magnetic susceptibility of the bubbles is proportional to their surface area,?=(9±3x10-6m)r^2, where r is the radius. Also they are compressible in moderate acoustic fields and induce a microstreaming flow with a toroidal vortex at the upper pole of the bubble. Similar microstreaming flows have been used to transport and rupture cells at small scales. Thus we envision applications in manipulation of biological materials and in microfluidic devices using acoustic and magnetic forces.

Zhao, Xue; Quinto-Su, Pedro; Ohl, Claus-Dieter

2008-11-01

390

Magnetic field confinement for magnetically levitated vehicles  

SciTech Connect

A magnetically levitated vehicle adapted for movement along a guide way, comprising: a passenger compartment; first and second primary magnet means secured on the vehicle to produce a magnetic field having a magnetic flux density extending outward from the primary magnet means, to support the vehicle above and spaced from the guide way; and a plurality of confining magnets disposed on the vehicle to confine the magnetic flux extending outward from the primary magnet means and to reduce the strength of the primary magnetic field in the passenger compartment; wherein the primary magnet means has a capacity to produce a primary magnetic field having a maximum strength of at least 200 gauss in the passenger compartment, and the confining magnets maintain the strength of the primary magnetic field in the passenger compartment below 5 gauss.

Proise, M.

1993-05-25

391

Magnetic monopole  

NASA Astrophysics Data System (ADS)

The magnetic monopole, or magnetic point source (as opposed to the conventional concept of a north-south magnetic dipole), is again in the news, as it has been off and on for the past 50 years. Perhaps it is more precise to say that another episode in the continuing search for the elusive monopole is underway.In a recent report by the National Science Foundation (Mosaic, 12, 1981, p. 19) it was stated of the monopole, ‘If there is a dogma in modern physics, it might be that in nature anything not expressly forbidden to exist by a specific law must be presumed to exist… Physicists are just going to have to get clever enough to find them.’ In the eyes of the numerous investigators who have searched, monopoles are not just objects that exist by theoretical default, they are arcane, perhaps, but real.

Bell, Peter M.

392

Planetary Magnetism  

NSDL National Science Digital Library

Until the middle of the 20th century, the Earth's magnetism seemed to be a happy accident of nature. Too many factors had to fit just right, the fluid core of the Earth, its electrical conductivity and its motions, all had to satisfy the strict requirements of dynamo theory. That was before other planets in the solar system were visited and examined. Now we know that among those planets, only Venus lacks any magnetism. The planets differ greatly in size and properties, and their fields differ, too. Yet they all seem to have dynamo fields, or (in the case of Mars and the Moon) have had them in the past. This site reviews the discovery of the magnetism of other planets and discusses their eccentricities.

Stern, David

393

Crystalline structure transformation of carbon anodes during gasification  

Microsoft Academic Search

The crystalline structure transformation of five carbon anodes during gasification in air and carbon dioxide was studied using quantitative X-ray diffraction (XRD) analysis and high-resolution transmission electron microscopy (HRTEM). XRD analysis and HRTEM observations confirmed that anodes have a highly ordered graphitic structure. The examination of partially gasified samples indicated that crystalline structure transformation occurred in two stages during gasification.

Kien N. Tran; Adam J. Berkovich; Alan Tomsett; Suresh K. Bhatia

2008-01-01

394

Immobilization of magnetic iron oxide nanoparticles on laponite discs - an easy way to biocompatible ferrofluids and ferrogels  

PubMed Central

Magnetic nanocomposites containing iron oxide (maghemite) nanoparticles, well embedded in a synthetic clay matrix (laponite) were prepared by a new one step chemical route and characterized by TEM, XRD, magnetization measurements, Mössbauer spectroscopy, DLS, and MRI measurements. The synthetic procedure leads to non-stoichiometric ?-Fe2O3 with a controllable content in the nanocomposite. Magnetic nanoparticles incorporated in the diamagnetic clay matrix exhibit a mean diameter of 13 nm, superparamagnetic behavior with a high saturation magnetization achievable at low applied magnetic fields. In-field Mössbauer spectra and ZFC/FC magnetization curves reveal a perfect ferrimagnetic ordering within nanoparticles with negligible spin frustration and interparticle interactions due to the complete coating of maghemite surfaces by the nanocrystalline laponite matrix. Magnetic iron oxide nanoparticles embedded in laponite matrix exhibit strong T2 weighted MRI contrast. The maghemite/laponite composite particles have 200 nm hydrodynamic diameter and form very stable hydrosols and/or hydrogels depending on their concentration in water.

Tzitzios, Vassilios; Basina, Georgia; Bakandritsos, Aristides; Hadjipanayis, Costas G.; Mao, Hui; Niarchos, Dimitrios; Hadjipanayis, George C.; Tucek, Jiri; Zboril, Radek

2010-01-01

395

Experimental investigation of thermal conductivity of magnetic nanofluids  

NASA Astrophysics Data System (ADS)

Two different magnetic nanofluids comprising of magnetite and Mn-Zn ferrite particles were synthesized in light hydrocarbon oil using continuous chemical process. Powder XRD and TEM image show single phase spinel structure with size of 10 nm and 6.7 nm, respectively for magnetite and Mn-Zn ferrite. Thermal conductivity of nanofluids has been studied as a function of volume fraction under transverse magnetic field. Magnetite nanofluid shows 17% enhancements in thermal conductivity for 4.7% volume fraction while Mn-Zn ferrite shows 45% enhancement at 10% volume fraction. In presence of transverse magnetic field the magnetite nanofluids shows further enhancement from 17% to 30% while no change in thermal conductivity has been observed for Mn-Zn ferrite. These results are explained considering the dipolar coupling co-efficient which for magnetite particles favors chain structures.

Parekh, Kinnari; Lee, H. S.

2012-06-01

396

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

397

Magnetic birefringence of iron oxyhydroxide nanoparticles stabilised by sucrose  

NASA Astrophysics Data System (ADS)

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 2-5 nm particles. The mineral form of the iron-core is suggested to be akaganeite. Anisotropy of the optical polarizability and magnetic susceptibility of akaganeite nanoparticles are calculated. The permanent dipole moment obtained for the nanoparticles studied was found to be negligible, in agreement with the characteristic superparamagnetic behaviour of the magnetic nanoparticles observed at room temperature. The Neel temperature of these nanoparticles is estimated as below 276 K. The results obtained are discussed against a background of the earlier studies of similar nanoscale systems.

Koralewski, M.; Pochylski, M.; Gierszewski, J.

2011-05-01

398

Magnetic Variations  

NSDL National Science Digital Library

In this activity students analyze tabulated data and convert it into a graph, search for patterns and trends, and make a prediction about future events. They discover that a graphical display of numbers may help to show patterns such as trends or varying rates of change and that such patterns sometimes can be used to make predictions about the phenomenon being graphed. This activity places the changes in Earth's magnetic field in an historical context that attemps to correct many misconceptions about Earth's magnetic field and debunk a 2003 movie that depicted dire consequences due to pole reversal.

Odenwald, Sten

399

MAGNETIC GRID  

DOEpatents

An electronic grid is designed employing magnetic forces for controlling the passage of charged particles. The grid is particularly applicable to use in gas-filled tubes such as ignitrons. thyratrons, etc., since the magnetic grid action is impartial to the polarity of the charged particles and, accordingly. the sheath effects encountered with electrostatic grids are not present. The grid comprises a conductor having sections spaced apart and extending in substantially opposite directions in the same plane, the ends of the conductor being adapted for connection to a current source.

Post, R.F.

1960-08-01

400

Effect of zinc doping on magnetic and magnetoelastic properties of cobalt ferrite synthesized by autocombustion process  

NASA Astrophysics Data System (ADS)

Zn-doped cobalt-ferrite, with nominal compositions Co1-xZnxFe2O4(0<=x<=0.3), were synthesized by a novel auto combustion technique. The structural properties of the Zn substituted ferrites have been characterized using x-ray diffraction (XRD). The as-synthesized powders were calcined at 800°C for 3 hrs and the powders were pressed into cylindrical pellets. Solid-state sintering at 1300°C for 12 hrs of the green pellets resulted in a single phase cubic-spinel structure, as observed and analyzed from the XRD spectra. Room temperature magnetic properties were studied using vibrating sample magnetometer (VSM) with field strengths up to +/- 15 kOe. Magnetoelastic properties were measured using strain gauge method in a pulsed field magnetometer. Effect of zinc doping on its magnetic and magnetoelastic properties of cobalt ferrite is discussed in this paper.

Reddy, M. Vinitha; Paul, J. Praveen; Das, Dibakar

2013-06-01

401

Effect of Pt layer thickness on perpendicular magnetic anisotropy in ultrathin Co/Pt multilayers  

NASA Astrophysics Data System (ADS)

Co/Pt multilayer structures with varying Pt layer thicknesses from 1.5 to 12 A? were deposited on Ta buffer layer by DC magnetron sputtering technique and both of their magnetic and structural properties were investigated. All the multilayers showed perpendicular magnetic anisotropy (PMA) and the enhancement in PMA is observed with increase in the Pt layer thickness. The structural investigation using XRD reveals the presence of single peak in all these multilayers, which indicate the formation of coherent Co/Pt (111) structure. The origin of PMA in these multilayer structure is due to the strain induced in the Co layer. From the full-width-half-maximum (FWHM) of the XRD patterns it is observed that the grain size is increasing with increasing the Pt layer thickness. The influence of the enhancement of the grain size is then correlated with the measured M-H hysteresis behavior and subsequently the anisotropy energy.

Kulkarni, P. D.; Krishnan, M.; Barshilia, H. C.; Chowdhury, P.

2013-02-01

402

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.

403

Self-reversal and apparent magnetic excursions in Arctic sediments  

NASA Astrophysics Data System (ADS)

The Arctic oceans have been fertile ground for the recording of apparent excursions of the geomagnetic field, implying that the high latitude field had unusual characteristics at least over the last 1-2 Myrs. Alternating field demagnetization of the natural remanent magnetization (NRM) of Core HLY0503-6JPC from the Mendeleev Ridge (Arctic Ocean) implies the presence of primary magnetizations with negative inclination apparently recording excursions in sediments deposited during the Brunhes Chron. Thermal demagnetization, on the other hand, indicates the presence of multiple (often anti-parallel) magnetization components with negative inclination components having blocking temperatures predominantly, but not entirely, below ~ 350 °C. Thermo-magnetic tests, X-ray diffraction (XRD) and scanning electron microscopy (SEM) indicate that the negative inclination components are carried by titanomaghemite, presumably formed by seafloor oxidation of titanomagnetite. The titanomaghemite apparently carries a chemical remanent magnetization (CRM) that is partially self-reversed relative to the detrital remanent magnetization (DRM) carried by the host titanomagnetite. The partial self-reversal could have been accomplished by ionic ordering during oxidation, thereby changing the balance of the magnetic moments in the ferrimagnetic sublattices.

Channell, J. E. T.; Xuan, C.

2009-06-01

404

Planetary magnetism  

Microsoft Academic Search

The field of planetary magnetism has advanced rapidly over the last four years. In fact it was not deemed necessary to review this subject in the last quadrennial report. This advance has resulted both from new data and of refined analyses of existing data files. New data have become available from Mariner 10 at Mercury, from Venera 9 and 10

C. T. Russell

1979-01-01

405

Cereal Magnets  

NSDL National Science Digital Library

In this activity, students will design a process that removes the most iron from the cereal. This activity is meant for the students to experiment with different materials using what they know about iron, magnets, and forces to design the best process for removing the iron from the cereal.

Engineering K-Ph.d. Program

406

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 magnetosphere that stretches out behind Earth. This released energy is focused down at the poles and the resulting flood of solar particles into the atmosphere, causes the auroras at the North and South Poles.

Holly Zell

2011-01-31

407

S1-state Mn4Ca complex of Photosystem II exists in equilibrium between the two most-stable isomeric substates: XRD and EXAFS evidence.  

PubMed

Photosynthetic water oxidation reaction driven by Sun and catalyzed by a unique Mn(4)Ca cluster in Photosystem II (PSII) is known to take place in an oxygen evolving complex (OEC) that cycles five serial redox states, named "Kok's S(i)-states" (i=0-4). Recently, the atomic crystal structure of PSII from Thermosynechococcus vulcanus was resolved by 1.9 Å-resolution XRD data [55]. Interestingly, it revealed an unusual oxo-bridged Mn(4)CaO(5) cluster in the dark stable S(1)-state, e.g. unusual mono-?(2)-oxo-mono-?(4)-oxo-mono-?(2)-carboxylato bridges connecting Mn(a) (terminal) and Mn(b) (central) ions with unusual atomic distance of 2.9 Å. Using the UDFT/B3LYP/lacvp** geometry optimization method and a truncated cluster model of the chemically-complete OEC put in ?=4 dielectric medium, it is shown that the OEC in S(1) must be in thermal equilibrium between the most-stable isomeric substates ("S(1a) and S(1b)") owing to the quasi-reversible structure change induced by proton migration. Coincidentally, it is found that the Mn(a)-Mn(b) distances in the Mn(4)Ca clusters in S(1a) and S(1b) are given by R(ab)=3.32 Å and 2.77 Å, respectively, so that the apparent distance between Mn(a) and Mn(b) ions in isomeric equilibrium is given by 2.94 Å, in agreement with experimental R(ab)~2.9 Å. Concomitantly, the first full-k-range EXAFS spectrum from powdered PSII [45] is used to provide the second experimental evidence for the S(1)-state OEC being in thermal equilibrium between S(1a) and S(1b)-isomers. These OEC-isomers consist of all the chemically-essential 11 amino acid residues, six cofactor ions and nine essential hydrated water molecules in their chemical ionic states around physiological pH 7, thus reasonably satisfying the biochemical charge neutrality with four Mn ions staying at the oxidation states (Mn(a)(III)/Mn(b)(IV)/Mn(c)(III)/Mn(d)(IV)) with the skeleton structures of MT-5J type and T-shaped DD-4J type. These H-bonding water molecules are found to fill a cavity connecting possible substrate/products channels so as to be arranged as an indispensable part of the catalytic Mn(4)Ca cluster in the order of "current-substrates" (W1/W2 bound to Mn(a)(III)), "next-substrates" (W4/W7) and "next-after-next-substrates" (W5/W6 bound to Ca(2+)). Results show that the Jahn-Teller effect due to Mn(a)(III) ion in these isomers can reasonably explain the very-slow-exchange and very-fast-exchange processes observed in S(1) by time-resolved (18)O-exchange mass spectroscopy. PMID:21592813

Kusunoki, Masami

2011-03-13

408

Lepidocrocite to maghemite to hematite: A pathway to have magnetic and hematitic Martian soil  

Microsoft Academic Search

We examined decomposition products of lepidocrocite, which were produced by heating the phase in air at temperatures up to 525(C for 3 and 300 hr, by XRD, TEM, magnetic methods, and reflectance spectroscopy (visible and near-IR). Single-crystal lepidocrocite particles dehydroxylated to polycrystalline particles of disordered maghemite which subsequently transformed to polycrystalline particles of hematite. Essentially pure maghemite was obtained at

Richard V. Morris; D. C. Golden; Tad D. Shelfer; H. V. Lauer Jr.

1998-01-01

409

The preparation and properties of monodisperse core-shell silica magnetic microspheres  

Microsoft Academic Search

The monodisperse core-shell silica magnetic microspheres (MMS) were synthesized by sol–gel method gelling in the emulsion.\\u000a Optical microscope (OM), field emission scanning electron microscope (FESEM), nitrogen adsorption and desorption Brunauer\\u000a Emmett Teller Procedure (BET) isotherms and Barrett-Joyner-Halenda (BJH) pore size distribution measurements, X-ray diffraction\\u000a (XRD), energy dispersive spectrometer (EDS) and vibrating sample magnetometer (VSM) were used to characterize the appearance,

Min-yi Lou; Qiu-ling Jia; De-ping Wang; Bing Liu; Wen-hai Huang

2008-01-01

410

Preparation and magnetic properties of fibrous gamma iron oxide nanoparticles via a nonaqueous medium  

Microsoft Academic Search

Fibrous shape ?-Fe2O3 nanoparticles (the length of ?850 nm; the width of ?5 nm) have been prepared using lauryl alcohol as a nonaqueous medium. The resultant products were investigated by IR, TG–DTA, XRD, TEM and magnetization measurements. For the preparation of pure ?-Fe2O3 nanoparticles, the suitable condition of the molar ratio of lauryl alcohol to iron nitrate is determined to

Zhihong Jing

2006-01-01

411

Fabrication, characterization and magnetic behaviour of alumina-doped zinc ferrite nano-particles  

Microsoft Academic Search

Zinc ferrite nano-powders with a nominal composition of ZnFe2O4 were prepared by combustion synthesis using mixture of urea and ammonium nitrate as fuel. The influence of alumina-doping on the structural, morphological and magnetic properties of ZnFe2O4 nano-particles was investigated by means of X-ray powder diffraction (XRD), infrared (IR) spectroscopy, scanning and transmission electron microscopy (SEM and TEM) and vibrating sample

N. M. Deraz

2011-01-01

412

?-ray synthesis of composite nanoparticles of noble metals and magnetic iron oxides  

Microsoft Academic Search

Composite nanoparticles composed of noble metal (Au, Pt or Pd) and iron-oxide (Fe3O4 or ?-Fe2O3) were successfully prepared by ?-ray irradiation of a suspension of iron oxide in an aqueous solution containing noble metal. Formation of the composite nanoparticles was confirmed by the techniques of magnetic separation and XRD. TEM observation revealed that the noble metal nanoparticles were immobilized on

S. Seino; T. Kinoshita; Y. Otome; T. Maki; T. Nakagawa; K. Okitsu; Y. Mizukoshi; T. Nakayama; T. Sekino; K. Niihara; T. A. Yamamoto

2004-01-01

413

Preparation and characteristics of Fe 3O 4 magnetic thin films plated on hollow glass spheres  

Microsoft Academic Search

The surface of hollow glass spheres was deposited with a layer of Fe3O4 film in the open air without using ultrasound and toxic reducing reagent NaNO2; the magnetic films of Fe3O4 were characterized by XRD, SEM and EDS. The intactness of the films was remarkably affected by temperature; it is favorable for the hollow glass spheres to be encapsulated completely

Jianhua Liu; Jing Wei; Songmei Li

2007-01-01

414

Characteristics of equilibrium, kinetics studies for adsorption of fluoride on magnetic-chitosan particle  

Microsoft Academic Search

The magnetic-chitosan particle was prepared and characterized by the SEM, XRD, FT-IR and employed as an adsorbent for removal fluoride from the water solution in the batch system. The Langmuir isotherms, Bradley's isotherm, Freundlich isotherm and Dubinin–Kaganer–Radushkevich (DKR) isotherm were used to describe adsorption equilibrium. The kinetic process was investigated using the pseudo-first-order model, pseudo-second-order model and intra-particle diffusion model,

Wei Ma; Fei-Qun Ya; Mei Han; Ren Wang

2007-01-01

415

Effects of annealing on the magnetic properties, size and strain of gold-coated Permalloy nanoparticles  

Microsoft Academic Search

Fe20Ni80@Au core-shell nanoparticles have been prepared by a multi-step microemulsion technique and the influence of annealing from 200 to 500 °C on the particles' size, morphology and magnetic properties is reported. After annealing under dilute H2 at 300 °C and above, FeNi3-structured Permalloy nanoparticles were observed in the XRD patterns with a lattice parameter of a = 3.560(2) Å. The

Brian L. Cushing; Vladimir O. Golub; Marcia Henry; Brittany L. Oliva; Ebony Cook; Corey W. Holmes; Charles J. O'Connor

2005-01-01

416

Effects of annealing on the magnetic properties, size and strain of gold-coated Permalloy nanoparticles  

Microsoft Academic Search

Fe20Ni80@Au core–shell nanoparticles have been prepared by a multi-step microemulsion technique and the influence of annealing from 200 to 500 C on the particles’ size, morphology and magnetic properties is reported. After annealing under dilute H2 at 300 C and above, FeNi3-structured Permalloy nanoparticles were observed in the XRD patterns with a lattice parameter of a = 3.560(2). The sizes

Brian L Cushing; Vladimir O Golub; Marcia Henry; Brittany L Oliva; Ebony Cook; Corey W Holmes; Charles J O’Connor

2005-01-01

417

Synthesis of magnetic hollow silica using polystyrene bead as a template  

Microsoft Academic Search

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 Fe3O4 as precursors. TEM, EDS, XRD, and SQUID were applied to characterize MHSNs. TEM and EDS results show that the MHSNs consist of about 200nm of hollow cores and ?35nm shells with ?10nm of Fe3O4

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

2007-01-01

418

HRTEM study comparing naturally and experimentally weathered pyroxenoids  

SciTech Connect

The mineralogy and chemistry of both naturally and experimentally weathered MnSiO{sub 3} chain silicate minerals (rhodonite and pyroxmangite) were compared. In natural MnSiO{sub 3}, 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 (Ca{sub 0.3}Mn{sub 2}Zn{sub 0.4}Al{sub 0.1}Si{sub 4}O{sub 10}(OH){sub 2}) also develops in larger etches at grain boundaries. The Zn apparently released by weathering of coexisting sphalerite, may facilitate crystallization of manganese-smectite; rhodochrosite is also an initial product. X-ray diffraction patterns from highly altered materials reveal only rhodochrosite and quartz. Simplified reactions are H{sub 2}CO{sub 3}(aq) + 4 MnSiO{sub 3}(s) = Mn{sub 3}Si{sub 4}O{sub 10}(OH){sub 2}(s) + MnCO{sub 3}(s) accompanied by 3H{sub 2}CO{sub 3}(aq) + Mn{sub 3}Si{sub 4}O{sub 10}(OH){sub 2}(s) = 3 MnCO{sub 3}(s) + 4SiO{sub 2}(s) + 4H{sub 2}O. Pyroxenoid dissolution is incongruent under experimental conditions. A 3-7 nm-thick layer of amorphous silica is present at the mineral surface after {approximately}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.

Banfield, J.F. [Univ. of Wisconsin, Madison, WI (United States); Ferruzzi, G.G.; Casey, W.H. [Univ. of California, Davis, CA (United States); Westrich, H.R. [Sandia National Labs., Albuquerque, NM (United States)

1995-01-01

419

Structural transformation of vapor grown carbon nanofibers studied by HRTEM  

Microsoft Academic Search

Vapor grown carbon nanofibers have been extensively manufactured and investigated in recent years. In this study commercially\\u000a available vapor grown carbon nanofibers subjected to different processing and post processing conditions were studied employing\\u000a high resolution TEM images. The analysis showed that the fibers consist primarily of conical nanofibers, but can contain a\\u000a significant amount of bamboo nanofibers. Most conical nanofibers

Joseph G. Lawrence; Lesley M. Berhan; Arunan Nadarajah

2008-01-01

420

HRTEM analysis of the nanostructure of porous silicon  

Microsoft Academic Search

The nanometric structure of porous silicon makes this material to be very suitable for its use in many different fields, including optoelectronics and biological applications. In the present work, the structure of porous silicon was investigated in detail by means of cross-sectional high-resolution transmission electron microscopy and digital image processing, together with electron energy loss spectroscopy. The structure of the

R. J. Martín-Palma; L. Pascual; A. R. Landa-Cánovas; P. Herrero; J. M. Martínez-Duart

2006-01-01

421

Electrochemical synthesis of magnetic iron oxide nanoparticles with controlled size.  

PubMed

We present a novel and facile method enabling synthesis of iron oxide nanoparticles, which are composed mainly of maghemite according to X-ray diffraction (XRD) and Mössbauer spectroscopy studies. The proposed process is realized by anodic iron polarization in deaerated LiCl solutions containing both water and ethanol. Water seems to play an important role in the synthesis. Morphology of the product was studied by means of transmission electron microscopy and XRD. In the solution containing almost 100% of water a black suspension of round shaped maghemite nanoparticles of 20-40 nm size is obtained. Regulating water concentration allows to control nanoparticle size, which is reduced to 4-6 nm for 5% of water with a possibility to reach intermediate sizes. For 3% or lower water concentration nanoparticles are of a needle-like shape and form a reddish suspension. In this case phase determination is problematic due to a small particle size with the thickness of roughly 3 nm. However, XRD studies indicate the presence of ferrihydrite. Coercivities of the materials are similar to those reported for nanoparticle magnetite powders, whereas the saturation magnetization values are considerably smaller. PMID:22207821

Starowicz, Maria; Starowicz, Pawe?; Zukrowski, Jan; Przewo?nik, Janusz; Lema?ski, Andrzej; Kapusta, Czes?aw; Bana?, Jacek

2011-11-27

422

Crystallographic and Magnetic Properties of KFeO  

Microsoft Academic Search

The crystallographic and magnetic properties of KFeO2 powder prepared by ball-mill method, have been studied by X-ray diffraction (XRD), Mossbauer spectroscopy, and vibrating sample magnetometer (VSM) measurements. The crystal structure of KFeO2 powder at room temperature is determined to be an orthorhombic structure of Pbca with its lattice constants a0=5.594,b0 =11.247, and c0=15.863 Aring by Reitveld refinement. The M-H curves

Seung Je Moon; In-Bo Shim; Chul Sung Kim

2006-01-01

423

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

424

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

425

Preparation and microwave absorption property of the core-nanoshell composite absorbers with magnetic fly-ash hollow cenosphere as nuclear  

Microsoft Academic Search

The core-nanoshell composite absorbers with magnetic fly-ash hollow cenosphere as nuclear were prepared by a solid-state reaction method. The results of X-ray diffraction analysis (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM) and vector network analyzer (VNA) analysis indicated that the hollow cenosphere is dielectric loss; the exchange-coupling interaction happens between ferrite of hollow cenosphere and nanocrystalline magnetic material

Ru-Xin Che; Ying-Juan Ni

2009-01-01

426

Preparation and microwave absorbing properties of the core-nanoshell composite absorbers with the magnetic fly-ash hollow cenosphere as core  

Microsoft Academic Search

Electromagnetic (EM) wave pollution has become the chief physical pollution for environment. The core-nanoshell composite absorbers with magnetic fly-ash hollow cenosphere as core and nanocrystalline magnetic material as shell were prepared by high-energy ball milling. The results of X-ray diffraction analysis (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM) and vector network analyzer (VNA) analysis indicated that perfect-crystalline nanomagnetic

Ruxin Che; Chunxia Wang; Yingjuan Ni; Bing Yu

2011-01-01

427

Effect of urea and glycine fuels on the combustion reaction synthesis of Mn–Zn ferrites: Evaluation of morphology and magnetic properties  

Microsoft Academic Search

The goal of this study is to evaluate the influence of the urea and glycine fuels on the synthesis of Mn–Zn ferrite by combustion reaction. The morphology and magnetic properties of the resulting powders were investigated. The powders were characterized by X-ray diffraction (XRD), nitrogen adsorption (BET), scanning and transmission electron microscopy (SEM and TEM), and magnetic measurement of M×H

A. C. F. M. Costa; V. J. Silva; C. C. Xin; D. A. Vieira; D. R. Cornejo; R. H. G. A. Kiminami

2010-01-01

428

Preparation of novel magnetic chitosan/graphene oxide composite as effective adsorbents toward methylene blue.  

PubMed

A novel magnetic composite bioadsorbent composed of magnetic chitosan and graphene oxide (MCGO) was prepared as the magnetic adsorbent toward methylene blue. The magnetic composite bioadsorbent was characterized by SEM, FTIR and XRD measurements. The effect factors including pH, contact time and temperature on the adsorption properties of methylene blue onto MCGO were investigated. The resulting shows extraordinary adsorption capacity and fast adsorption rates for removal of methylene blue. The kinetics are well-described by pseudo-second-order kinetic. The experimental data of isotherm followed the Langmuir isotherm model and the Freundlich model, respectively. This work shows that the MCGO could be utilized as an efficient, magnetically separable adsorbent for the environmental cleanup. PMID:22464421

Fan, Lulu; Luo, Chuannan; Sun, Min; Li, Xiangjun; Lu, Fuguang; Qiu, Huamin

2012-02-22

429

Magnetite-cobalt ferrite nanoparticles for kerosene-based magnetic fluids  

NASA Astrophysics Data System (ADS)

Due to the magnetic anisotropy introduced by the Co2+ ion in octahedral sites of cubic spinel ferrites, it is possible to tailor the magnetic properties by changing the cobalt content. Magnetic fluids with magnetite-cobalt ferrite nanoparticles given by the formula Co(x)Fe(3-x)O4 with x=0, 0.2 and 0.4 were prepared. Kerosene and oleic acid were used as liquid carrier and surfactant, respectively. Spherical magnetic nanoparticles were obtained by coprecipitation from metal salts and ammonium hydroxide; afterwards the magnetic fluids were obtained by a peptization process. Powder properties were characterized by X-ray diffraction (XRD), nitrogen adsorption desorption isotherma (BET), vibrating sample magnetometry (VSM) and fluids by transmission electron microscopy (TEM), thermogravimetric analyzer (TGA), VSM and the short-circuited transmission line technique.

Ayala-Valenzuela, O.; Matutes-Aquino, J.; Betancourt-Galindo, R.; García-Cerda, L. A.; Rodríguez Fernández, O.; Fannin, P. C.; Giannitsis, A. T.

2005-07-01

430

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.

431

Prussian blue based molecular magnet K0.3Mn2.85[Cr(CN)6]2.nH2O with ferrimagnetic ordering temperature of 60 K  

NASA Astrophysics Data System (ADS)

Molecular magnet based on Prussian blue analogues, K0.3Mn2.85[Cr(CN)6]2.nH2O, has been synthesized using co-precipitation method, and its structural and magnetic properties are investigated using X-ray diffraction (XRD), infra red spectroscopy (IR) and dc magnetization measurement techniques. The XRD study confirms the crystalline nature of the compound with a face centered cubic (fcc) structure (space group Fm3m). The positions of the absorption bands in the IR spectrum (~1900-2300 cm-1), confirm the formation of Prussian blue analogue. The magnetization measurement shows a soft ferrimagnetic nature of the compound with negligible coercive field. The Curie temperature (TC) and magnetization at 5 K are found to be ~60 K and ~ 8.2 ?B/f.u. respectively.

Bhatt, Pramod; Bhatt, Ranu; Mukadam, M. D.; Yusuf, S. M.

2013-02-01

432

Investigation of the composition of historical and modern Italian papers by energy dispersive X-ray fluorescence (EDXRF), X-ray diffraction (XRD), and scanning electron microscopy energy dispersive spectrometry (SEM-EDS).  

PubMed

In this work, a study concerning the composition of Italian papers from the seventeenth to the twentieth centuries was carried out using energy dispersive X-ray fluorescence spectrometry (EDXRF), X-ray diffraction (XRD), and scanning electron microscopy coupled to energy dispersive spectrometry (SEM-EDS). The analyzed samples consisted of papers employed for drawing, writing, printing, and absorbance. Observations carried out by SEM magnified the typical paper morphology. EDXRF in combination with XRD and SEM-EDS allowed the determination of calcite, gypsum, kaolin, talc, magnesite, and dolomite, used as fillers in the production of the papers studied herein. The inks present in the handwritten and printed papers, investigated by SEM-EDS and ?-EDXRF, were synthetic, Fe based, and iron gall inks. PMID:21211154

Manso, Marta; Carvalho, Maria Luisa; Queralt, Ignacio; Vicini, Silvia; Princi, Elisabetta

2011-01-01

433

Investigation of hydrogen discharging and recharging processes of Ti-doped NaAlH 4 by X-ray diffraction analysis (XRD) and solid-state NMR spectroscopy  

Microsoft Academic Search

The processes occurring in the course of two sequential hydrogen discharging and recharging cycles of Ti-doped sodium alanate were investigated in parallel using XRD analysis and solid-state NMR spectroscopy. Both methods demonstrate that in hydrogen storage cycles (Eq. (1)) the majority phases involved are NaAlH4, Na3AlH6, Al and NaH. Only traces of other, as yet unidentified phases are observed, one

B Bogdanovi?; M Felderhoff; M Germann; M Härtel; A Pommerin; F Schüth; C Weidenthaler; B Zibrowius

2003-01-01

434

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

435

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

NASA Astrophysics Data System (ADS)

The effect of B concentration on the tunneling magnetoresistance (TMR) of (Co25Fe75)100-xBx/MgO/(Co25Fe75)100-xBx (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 (Co25Fe75)67B33, while good epitaxy was observed between (001) textured MgO and (Co25Fe75)78B22 electrodes.

Kodzuka, M.; Ohkubo, T.; Hono, K.; Ikeda, S.; Gan, H. D.; Ohno, H.

2012-02-01

436

Magnetic Heads  

Microsoft Academic Search

\\u000a Figure 6.1 shows how rapidly the areal density of hard disk drives (HDD) has been increasing over the past 20 years [1]. Several\\u000a critical innovations were necessary to bring about such rapid progress in the field of magnetic recording [2]. One of the\\u000a most significant innovations from the viewpoint of material improvement was the electrodeposition of permalloy (Ni80Fe20), which was

Tokihiko Yokoshima

2010-01-01

437

Planetary Magnetism  

Microsoft Academic Search

\\u000a The fact that a small needle of lodestone suspended at its centre of mass maintains an almost constant orientation with respect\\u000a to the Earth’s body has been known for thousands of years and widely used in compasses for navigation purposes. Indeed, the\\u000a magnetic compass has been employed in China at least since the 4th century AD and used by Amalfl’s

Bruno Bertotti; Paolo Farinella; David Vokrouhlický

438

XRD Analyses of In{sub 0.10}Al{sub x}Ga{sub 0.90-x}N(0{<=}x{<=}0.20) Quaternary Alloys  

SciTech Connect

We present the structural properties of quaternary In{sub 0.10}Al{sub x}Ga{sub 0.90-x}N(0{<=}x{<=}0.20) alloys grown on sapphire substrate by molecular beam epitaxy. High resolution X-ray diffraction (HR-XRD) analyses were used to investigate the phase and crystalline quality of quaternary In{sub 0.10}Al{sub x}Ga{sub 0.90-x}N. From the XRD phase analysis, it is confirmed that the In{sub 0.10}Al{sub x}Ga{sub 0.90-x}N films had wurtzite structure and without any phase separation. In addition, it is found that the Bragg angle of the (0002)In{sub 0.10}Al{sub x}Ga{sub 0.90-x}N peak gradually increases as the Al compositions increases, indicating the decrease in the lattice constant c of the In{sub 0.10}Al{sub x}Ga{sub 0.90-x}N quaternary alloys. Apart from that, the composition of In{sub 0.10}Al{sub x}Ga{sub 0.90-x}N epilayers is determined by applying the Vegard's law. Finally, the variation of the crystalline quality as a function of Al composition is investigated through the XRD rocking curve analyses.

Yusof, Y.; Abid, M. A.; Raof, N. H. Abd; Ng, S. S.; Hassan, H. Abu; Hassan, Z. [Nano-Optoelectronics Research and Technology Laboratory, School of Physics, Universiti Sains Malaysia, 11800 Penang (Malaysia)

2010-07-07

439

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

440

Magnetic Field Measurements in Beam Guiding Magnets  

Microsoft Academic Search

Electromagnets used as beam guiding elements in particle accelerators and colliders require very tight tole-rances on their magnetic fields and on their alignment along the particle path. This article describes the methods and equipment used for magnetic measurements in beam transport magnets. Descriptions are given of magnetic resonance techniques, various induction coil methods, Hall generator measurements, the fluxgate magnetometer as

K. N. Henrichsen

1998-01-01

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