Crystal structure analysis of LaMnO_3 with x-ray diffraction technique using the Rietveld method

International Nuclear Information System (INIS)

Engkir Sukirman; Wisnu Ari Adi; Yustinus Purwamargapratala

2010-01-01

Crystal structure analysis of LaMnO_3 using the Rietveld method has been carried out. The LaMnO_3 sample was synthesized with high energy mechanical milling from the raw materials of La_2O_3 and MnO_2 with the appropriate mol ratio. Milling were performed for 10 hours, pelletized and hereinafter sintered at 1350 °C for 6 hours. The sample characterizations covered the crystal structure and electric-magnetic properties of the materials by X-ray diffraction technique using the Rietveld method and the four point probe, respectively. The Rietveld refinement results based on the X-rays diffraction data indicate that the sample of LaMnO_3 is single phase with the crystal system: orthorhombic, the space group: Pnma No. 62 and the lattice parameters: a = 55.4405(9) Å; b = 7.717(1) Å dan c = 5.537(1) Å. The material owns Magnetic Resonance (MR) respond of 7 %, the mean value of crystallite size, D = 17 nm and lattice strain, e = - 0.5 %. So, the material go through a compressive strain, and according to the Nanda's strain model, it becomes a type G antiferromagnetic insulator. Because the insulator properties of the material does not change although being hit by the external magnetic field, hence the MR respond is only caused by the order of electron spin. Therefore at room temperature, LaMnO_3_._0 just exhibits a small MR respond. (author)

Rietveld refinement with time-of-flight powder diffraction data from pulsed neutron sources

International Nuclear Information System (INIS)

David, W.I.F.; Jorgensen, J.D.

1990-10-01

The recent development of accelerator-based pulsed neutron sources has led to the widespread use of the time-of-flight technique for neutron powder diffraction. The properties of the pulsed source make possible unusually high resolution over a wide range of d spacings, high count rates, and the ability to collect complete data at fixed scattering angles. The peak shape and other instrument characteristics can be accurately modelled, which make Rietveld refinement possible for complex structures. In this paper we briefly review the development of the Rietveld method for time-of-flight diffraction data from pulsed neutron sources and discuss the latest developments in high resolution instrumentation and advanced Rietveld analysis methods. 50 refs., 12 figs., 14 tabs

Separation of the overlapping effects in spectra for WDXRF using the Rietveld method

International Nuclear Information System (INIS)

Salvador, Vera Lucia Ribeiro

2005-01-01

This work presents a new methodology for the overlapping spectra separation obtained by the technique of wavelength dispersion X-ray fluorescence (WDXRF). This methodology allows to improve the conventional analytic results and to facilitate the determination of chemical species of a same element without chemical separation, by means of the separation of coming spectra of electronic transitions of valence electrons or chemical effects in internal electrons. With the software 'GSAS-EXPGUI' and the method of Rietveld overcomes the problem of overlapping lines of the present species in the sample and it facilitates the determination of the same ones simultaneously, without the need of samples patterns and calibration curves, what means an expressive gain in relation to other techniques. The preparation of the surface of the sample for the collection of the spectrum represents a critical stage for the acting of the analysis whose effects can be minimized being used the refinement of Rietveld, that allows the determination of the relationships of the intensities of the lines put upon by means of mathematical models, what establishes the basic conditions for obtaining of more precise results in the quantitative analysis. In the case of the determination of chemical species it can separate, for example Cr (III), Cr (VI) and Fe (II), Fe(III) that present overlapping of almost 100%. (author)

Investigation on the evolution of microstructure and texture of electroplated Ni–Ti composite coating by Rietveld method

Energy Technology Data Exchange (ETDEWEB)

Zhao, Yuantao, E-mail: zhaoyuantao@sjtu.edu.cn; Cai, Fei, E-mail: caifei32@126.com; Wang, Chengxi, E-mail: sjtucxw@sjtu.edu.cn; Chai, Ze, E-mail: zechaisjtu@163.com; Zhu, Kaiyuan, E-mail: xrd125@163.com; Xu, Zhou, E-mail: xuzhou@sjtu.edu.cn; Jiang, Chuanhai, E-mail: chjiang-sjtu@hotmail.com

2015-10-30

Highlights: • Ni–Ti composite coatings were prepared by electroplating. • Morphology and Ti content of Ni–Ti coatings were studied upon SEM and EDXS. • Microstructures of Ni–Ti coatings were studied upon the Rietveld method. • The texture of Ni–Ti coatings was studied upon the pole figure. - Abstract: Rietveld refinement was utilized to investigate the evolution of microstructure and texture of the Ni–Ti composite coatings electroplated at different applied current densities. Scanning Electron Microscope and Energy Dispersive Spectroscopy were utilized to investigate the morphology and chemical composition of the coatings. Relative texture coefficients (RTC) and measured pole figures were utilized to investigate the texture evolution of the coatings. The results showed that the surface morphology of the coatings changed from a colonial structure to a polyhedral one. And the incorporated Ti content decreased with increasing applied current density. As the applied current density increased, the crystallite sizes increased and their distribution got less uniform, and the microstrain and dislocation density decreased. The results of simulated pole figures obtained from Rietveld refinement illustrated that the texture of the coatings changed from no obvious texture to a strong [2 0 0] fiber texture with increasing applied current density. The texture evolution obtained from simulated pole figures was confirmed by the result of RTC and the measured pole figures. The evolutions of the microstructure and texture were derived from the change of the applied current density and incorporated Ti content in the Ni–Ti composite coatings.

Quantitative determination of phases in ZrO{sub 2} (MgO) (Y{sub 2}O{sub 3}) using the Rietveld method; Determinacao quantitativa de fases em ZrO{sub 2} - MgO - Y{sub 2}O{sub 3} utilizando o metodo de Rietveld

Energy Technology Data Exchange (ETDEWEB)

Castro, Antonio Carlos de

2007-07-01

The key objective of this work is the crystallographic characterization of the zircon co-doped with Yttria and magnesium with the application of the Rietveld method for quantitative phase analysis of zircon polymorph (zircon monoclinic, tetragonal, and cubic). Samples of zircon polymorph were obtained from zircon doped with Yttria and magnesium at defined molar concentrations. The zircon polymorph stability during subeutetoid aging at 1350 deg C were investigated to determine ZrO{sub 2} - MgO - Y{sub 2}0{sub 3} phases degradation and to define the solid solutions stability environment. ZrO{sub 2} powders doped with 8 mol por cent of MgO and 1 mol por cent of Y{sub 2}O{sub 3}, and 9 mol por cent of MgO and 0 mol por cent of Y{sub 2}O{sub 3} have been prepared by chemical route using the co-precipitation method. These samples have been calcinate at 550 deg C, sintered at 1500 deg C and characterized by the Rietveld method using the X-ray diffraction data. The variation of the lattice parameter, changes in the phase composition and their microstructures are discussed. The application of the Rietveld method for quantitative phase analysis of zircon polymorph (zircon tetragonal and cubic) reveals no formation of tetragonal phase and indicating that the matrix is the cubic phase with low concentration of monoclinic phase.(author)

A research of the mineralogy phases of clinker in a spanish cement using the method of Rietveld

International Nuclear Information System (INIS)

Castanon, Ana M; Garcia, Granda Santiago; Guerrero, Ana M; Gomez Fernandez, Fernando

2012-01-01

In order to introduce continuously a quality control method in a Spanish cement factory to improve the final product feature new research methodology is being developed. The Rietveld method [1] has been successfully used to analyze the composition of the main phases of clinker. Using this methodologies, research has been carried out to quantize appropriately the minor phase of free lime which is extremely important in the clinker quality. This method leads to satisfactory results on samples with contents in CaO from 3%. These results are possible combining X- ray diffraction and fluorescence techniques as well as the chemical analysis data.

Rietica - a visual Rietveld program

International Nuclear Information System (INIS)

Hunter, B.A.

2000-01-01

online help explains the fundamentals of the Rietveld method, the layout of the program, the input file structure, and the visual interface

A Study on the quantification of hydration and the strength development mechanism of cementitious materials including amorphous phases by using XRD/Rietveld method

International Nuclear Information System (INIS)

Yamada, Kazuo; Hoshino, Seiichi; Hirao, Hiroshi; Yamashita, Hiroki

2008-01-01

X-ray diffraction (XRD)/Rietveld method was applied to measure the phase composition of cement. The quantative analysis concerning the progress of hydration was accomplished in an error of about the maximum 2-3% in spite of including amorphous materials such as blast furnace slag, fly ash, silica fume and C-S-H. The influence of the compressive strength on the lime stone fine powder mixture material was studied from the hydration analysis by Rietveld method. The two stages were observed in the strength development mechanism of cement; the hydration promotion of C 3 S in the early stage and the filling of cavities by carbonate hydrate for the longer term. It is useful to use various mixture materials for the formation of the resource recycling society and the durability improvement of concrete. (author)

Quantitative study of Portland cement hydration by X-ray diffraction/Rietveld analysis and independent methods

International Nuclear Information System (INIS)

Scrivener, K.L.; Fuellmann, T.; Gallucci, E.; Walenta, G.; Bermejo, E.

2004-01-01

X-ray diffraction (XRD) is a powerful technique for the study of crystalline materials. The technique of Rietveld refinement now enables the amounts of different phases in anhydrous cementitious materials to be determined to a good degree of precision. This paper describes the extension of this technique to a pilot study of the hydration of a typical Portland cement. To validate this XRD-Rietveld analysis technique, its results were compared with independent measures of the same materials by the analysis of backscattered electron images (BSE/IA) and thermogravimetric analysis (TGA). In addition, the internal consistency of the measurements was studied by comparing the XRD estimates of the amounts of hydrates formed with the amounts expected to form from the XRD estimates of the amounts of anhydrous materials reacted

Effect of data quality on quantitative phase analysis (QPA) using the Rietveld method

International Nuclear Information System (INIS)

Scarlett, N.; Madsen, I.; Lwin, T.

1999-01-01

Full text: Quantitative phase analysis using the Rietveld method has become a valuable tool in modern X-ray diffraction. XRD is a recognised research tool and has been successfully employed in the developmental stages of many industrial processes. It is now becoming increasingly important as a means of process control either (i) in site quality control laboratories or (ii) even on-line. In on-line applications, the optimisation of data collection regimes is of critical importance if rapid turn-around, and hence timely process control, is to be achieved. This paper examines the effect of data quality on the quantification of phases in well characterised suites of minerals. A range of data collection regimes has been systematically investigated with a view to determining the minimum data required for acceptable quantitative phase analyses. Data has been collected with variations in the following process factors: 1st step, width ranging from 0.01 to 0.3 deg 2θ ;2nd step, counting time ranging from 0.0125 to 4 sec/step 3rd step, upper limit in the scan range varying from 40 to 148 deg 2θ. The data has been analysed using whole-pattern (Rietveld) based methods using two distinctly different analytical approaches: (i) refinement of only pattern background and individual scale factors for each phase; (ii) refinement of unit cell dimensions, overall thermal parameters, peak width and shape in addition to the background and scale factors. The experimental design for this work included a ternary design of the three component phases (fluorite, CaF 2 ; zincite, ZnO; corundum, Al 2 O 3 ) to form seven mixtures of major and minor phases of different scattering powers and the combination of the three process factors (variables) to form a factorial plan. The final data generation plan is a combination/crossing of the three process variable factorial plan with the three component mixture plan. It allows a detailed data analysis to provide information on the effect of the process

Refinement of the crystal structure of lead titanate with different degrees of imperfection of cationic and anionic sublattices by the Rietveld method

International Nuclear Information System (INIS)

Akimov, A.I.; Savchuk, G.K.; Rubtsov, V.A.; Letko, A.K.

2003-01-01

The parameters of the crystal structure of lead titanate with different degrees of imperfection of the anionic and cationic sublattices are refined by the Rietveld method. The experiments are carried out on a DRON-4 diffractometer (CuK α radiation; 20 deg. d 5.0-6.0%

Possibilities and limitations of parametric Rietveld refinement on high pressure data. The case study of LaFeO3

International Nuclear Information System (INIS)

Etter, Martin; Mueller, Melanie; Dinnebier, Robert E.; Hanfland, Michael

2014-01-01

Parametric Rietveld refinement is a powerful technique to apply directly physical or empirical equations to the refinement of in situ powder diffraction data. In order to investigate the possibilities and limitations of parametric Rietveld refinements for high pressure data four competitive crystallographic approaches were used to carry out a full structural investigation of the orthoferrite LaFeO 3 (Pbnm at ambient conditions) under high pressure up to 47 GPa. Approach A with traditional Rietveld refinement using atomic coordinates, Approach B where the Rietveld refinement was done by using the rigid body method, Approach C where symmetry modes were used and Approach D where the newly developed method of the rotational symmetry mode description for a rigid body was used. For all approaches sequential as well as parametric refinements were carried out, confirming a second order phase transition of LaFeO 3 to a higher symmetric phase (space group Ibmm) at around 21.1?GPa and an isostructural first order phase transition at around 38 GPa. Limitations due to non-hydrostatic conditions as well as the possibilities of a direct modeling of phase transitions with parametric Rietveld refinement are discussed in detail. (orig.)

The IPNS rietveld analysis software package for TOF [time-of-flight] powder diffraction data: Recent developments

International Nuclear Information System (INIS)

Rotella, F.J.; Richardson, J.W. Jr.

1987-01-01

A system of FORTRAN programs for the analysis of time-of-flight (TOF) neutron powder diffraction data via the Rietveld method at IPNS has been modified recently, making it possible to analyze data that exhibit diffraction maxima broadened due to anisotropic strain and that can be modeled by individual atomic anharmonic thermal vibrations. The observation of noncrystalline scattering in data from some powder samples has led to the development of software to fit such scattering by a function related to a radial distribution function through Fourier-filtering techniques. The ''user friendliness'' of the IPNS Rietveld package has been enhanced by the development of ''RIETVELD,'' a menu-based VAX/VMS command language routine for interactive file manipulation and program execution

Rietveld originals : Handle with care!

NARCIS (Netherlands)

Zijlstra, H.

2009-01-01

The work of architect Gerrit Th. Rietveld (1888 – 1964) is appreciated throughout the world. Many of the well-known buildings he designed have survived to the present. Some have been restored or refurbished, depending on the condition of the building, current needs of the building users, etc.

Quantitative phase analysis of a highly textured industrial sample using a Rietveld profile analysis

International Nuclear Information System (INIS)

Shin, Eunjoo; Huh, Moo-Young; Seong, Baek-Seok; Lee, Chang-Hee

2001-01-01

For the quantitative phase analysis on highly textured two-phase materials, samples with known weight fractions of zirconium and aluminum were prepared. Strong texture components prevailed in both zirconium and aluminum sheet. The diffraction patterns of samples were measured by the neutron and refined by the Rietveld method. The preferred orientation correction of diffraction patterns was carried out by means of recalculated pole figures from the ODF. The present Rietveld analysis of various samples with different weight fractions showed that the absolute error of the calculated weight fractions was less than 7.1%. (author)

Possibilities and limitations of parametric Rietveld refinement on high pressure data. The case study of LaFeO{sub 3}

Energy Technology Data Exchange (ETDEWEB)

Etter, Martin; Mueller, Melanie; Dinnebier, Robert E. [Max-Planck-Institut fuer Festkoerperforschung, Stuttgart (Germany); Hanfland, Michael [European Synchrotron Radiation Facility (ESRF), Grenoble (France)

2014-04-01

Parametric Rietveld refinement is a powerful technique to apply directly physical or empirical equations to the refinement of in situ powder diffraction data. In order to investigate the possibilities and limitations of parametric Rietveld refinements for high pressure data four competitive crystallographic approaches were used to carry out a full structural investigation of the orthoferrite LaFeO{sub 3} (Pbnm at ambient conditions) under high pressure up to 47 GPa. Approach A with traditional Rietveld refinement using atomic coordinates, Approach B where the Rietveld refinement was done by using the rigid body method, Approach C where symmetry modes were used and Approach D where the newly developed method of the rotational symmetry mode description for a rigid body was used. For all approaches sequential as well as parametric refinements were carried out, confirming a second order phase transition of LaFeO{sub 3} to a higher symmetric phase (space group Ibmm) at around 21.1?GPa and an isostructural first order phase transition at around 38 GPa. Limitations due to non-hydrostatic conditions as well as the possibilities of a direct modeling of phase transitions with parametric Rietveld refinement are discussed in detail. (orig.)

Homogeneity characterisation of (U,Gd)O2 sintered pellets by X-ray diffraction powder analysis applying Rietveld method

International Nuclear Information System (INIS)

Leyva, Ana G.; Vega, Daniel R.; Trimarco, Veronica G.; Marchi, Daniel E.

1999-01-01

The (U,Gd)O 2 sintered pellets are fabricated by different methods. The homogeneity characterisation of Gd content seems to be necessary as a production control to qualify the process and the final product. The micrographic technique is the most common method used to analyse the homogeneity of these samples, this method requires time and expertise to obtain good results. In this paper, we propose an analysis of the X-ray diffraction powder patterns through the Rietveld method, in which the differences between the experimental data and the calculated from a crystalline structure model proposed are evaluated. This result allows to determine the cell parameters, that can be correlated with the Gd concentration, and the existence of other phases with different Gd ratio. (author)

PETROGRAPHY AND APPLICATION OF THE RIETVELD METHOD TO THE QUANTITATIVE ANALYSIS OF PHASES OF NATURAL CLINKER GENERATED BY COAL SPONTANEOUS COMBUSTION

Directory of Open Access Journals (Sweden)

Pinilla A. Jesús Andelfo

2010-06-01

Full Text Available

Fine-grained and mainly reddish color, compact and slightly breccious and vesicular pyrometamorphic rocks (natural clinker are associated to the spontaneous combustion of coal seams of the Cerrejón Formation exploited by Carbones del Cerrejón Limited in La Guajira Peninsula (Caribbean Region of Colombia. These rocks constitute remaining inorganic materials derived from claystones, mudstones and sandstones originally associated with the coal and are essentially a complex mixture of various amorphous and crystalline inorganic constituents. In this paper, a petrographic characterization of natural clinker, aswell as the application of the X-ray diffraction (Rietveld method by mean of quantitative analysis of its mineral phases were carried out. The RIQAS program was used for the refinement of X ray powder diffraction profiles, analyzing the importance of using the correct isostructural models for each of the existing phases, which were obtained from the Inorganic Crystal Structure Database (ICSD. The results obtained in this investigation show that the Rietveld method can be used as a powerful tool in the quantitative analysis of phases in polycrystalline samples, which has been a traditional problem in geology.

EL APARADOR DE RIETVELD DEL MUSEO NACIONAL DE ARTES DECORATIVAS (MADRID.

Directory of Open Access Journals (Sweden)

María Villalba Salvador

2012-01-01

Full Text Available Este artículo trata de hacer una aproximación al estudio de una de las piezas más relevantes de la historia del diseño de mobiliario de vanguardia: el aparador de Rietveld, también conocido como Buffet Elling. Su diseño data de 1919, y responde a la estética propia del autor en aquellos años posteriores a la Primera Guerra Mundial, cuyas piezas son coincidentes con los planteamientos artísticos del grupo De Stijl. Es representativo de los principios básicos de la obra de Rietveld, uno de los pioneros del funcionalismo junto con J.J.P. Oud, en cuanto a la opción por el diseño y la arquitectura, y por la producción en masa y el diseño industrial accesible al conjunto de la sociedad. Merece destacar la colaboración de Gerard A. Van de Groenekan, asistente de Rietveld a lo largo de toda su trayectoria artística. Esta pieza nos ayuda a estudiar el pensamiento de Gerrit Th. Rietvel en relación con el diseño de vanguardia.This article tries to be an approach to the study of one of the most relevant pieces of furniture in the history of the design of avant-garde furniture: Rietveld´s dresser, also known as Elling Buffet. It was designed in 1919, and it shows the author´s aesthetics in the years that followed World War I, with pieces that are much related to the artistic orientation of the group De Stijl. It clearly shows the main characteristics of Rietveld´s work, one of the pioneers of functionalism, together with J.J.P. Oud, regarding design and architecture, mass production and industrial design accessible to society as a whole. It is worth mentioning the collaboration of Gerard A. Van de Groenekan, Rietveld´s assistant throughout his artistic trajectory. This piece of furniture helps us study Rietveld´s thinking regarding avant-garde design.

Application of the Rietveld method in structural analysis of catalysts based on CuO/CeO2

International Nuclear Information System (INIS)

Neiva, L.S.; Ribeiro, M.A.; Bispo, A.; Simoes, A.N.; Gama, L.

2011-01-01

This work has as aim to synthesize catalysts composed by CuO/CeO 2 by means two distinct methods of synthesis, they are: combustion synthesis and Pechini. The catalysts composed by CuO/CeO 2 were synthesized with CuO in condition of dopant element. The value of the CuO concentration ranged between 0 and 0.5 mol. Has been done a structural analysis related to how the kind of synthesis method used influences over physical characteristic of the catalytic material. The obtained catalysts were characterized by X-ray diffraction with refinement by Rietveld method. According to results, the synthesized catalysts showed crystalline structures formed mostly by CeO 2 phase, as expected, since this is the host matrix for the dopant element. The catalysts obtained by the Pechini method presented structures with a smaller amount of segregated phases formed by CuO, according to the results of the structural analysis. (author)

Rietveld analysis using powder diffraction data with anomalous scattering effect obtained by focused beam flat sample method

International Nuclear Information System (INIS)

Tanaka, Masahiko; Katsuya, Yoshio; Sakata, Osami

2016-01-01

Focused-beam flat-sample method (FFM) is a new trial for synchrotron powder diffraction method, which is a combination of beam focusing optics, flat shape powder sample and area detectors. The method has advantages for X-ray diffraction experiments applying anomalous scattering effect (anomalous diffraction), because of 1. Absorption correction without approximation, 2. High intensity X-rays of focused incident beams and high signal noise ratio of diffracted X-rays 3. Rapid data collection with area detectors. We applied the FFM to anomalous diffraction experiments and collected synchrotron X-ray powder diffraction data of CoFe_2O_4 (inverse spinel structure) using X-rays near Fe K absorption edge, which can distinguish Co and Fe by anomalous scattering effect. We conducted Rietveld analyses with the obtained powder diffraction data and successfully determined the distribution of Co and Fe ions in CoFe_2O_4 crystal structure.

Mathematical aspects of Rietveld refinement and crystal structure ...

Indian Academy of Sciences (India)

Administrator

The core mathematics, goodness-of-fit parameters of Rietveld refinement technique is introduced for structural ... transducers in medical and solar applications (Obmann ..... Prince 1985 in Structure and statistics in crystallography (ed.).

Study of the superconducting compound Hg,Re-1223 by X-Ray diffraction with application of Rietveld method

International Nuclear Information System (INIS)

Putvinskis, Rodrigo

2008-01-01

The objective of this work was to study the crystal structure of the superconductor compound of nominal composition Hg 0,82 Re 0,18 Ba 2 Ca 2 Cu 3 O 8+δ and general formula Hg,Re- 1223 and different oxygen contents, by the X-ray diffraction technique, by using the Rietveld method. The studied samples present different oxygen stoichiometry because during the synthesis process, had been heat treated under different oxygen/argon gas mixtures in the ratios: 5:95, 10:90 and 15:85. The results of structural refinement for the samples show that different oxygen contents imply in different cell parameters, atomic positions and distances for the main phase of each sample. The segregation of two superconducting phases with the same crystal structure, but slightly different cell parameters was confirmed for the studied samples both by Rietveld analysis and anomalous X-ray diffraction experiments. It was also confirmed that one of the segregated phases does not incorporate Re cations its composition. The main phase, who incorporates the Re cations, is here called Hg,Re-1223 and the Re-free secondary phase is called Hg- 1223. It was found that the superconducting phases present different crystallite sizes and the sample treated under gas flow composed of 10% oxygen and 90% argon presents the highest fraction of superconducting phases. From these results it was possible to conclude that the sample produced from the precursor compound treated under flow of O 2 /Ar gas at the ratio 10/90 presents the better results for the synthesis of this superconducting compound. (author)

Mineralogical analysis of clays in hardsetting soil horizons, by X-ray fluorescence and X-ray diffraction using Rietveld method

International Nuclear Information System (INIS)

Prandel, L.V.; Saab, S.C.; Brinatti, A.M.; Giarola, N.F.B.; Leite, W.C.; Cassaro, F.A.M.

2014-01-01

Diffraction and spectroscopic techniques have been shown to be suitable for obtaining physical and mineralogical properties in polycrystalline soil samples, and also in their precursor compounds. For instance, the X-ray fluorescence (XRF) spectroscopy allows obtaining the elemental composition of an investigated sample, while the X-ray diffraction (XRD) technique permits obtaining qualitative and quantitative composition of the soil minerals through the Rietveld method (RM). In this study Yellow Latosol (Oxisol), Yellow Argisol (Ultisol) and Gray Argisol (Ultisol) soil samples, classified as “hardsetting soils”, extracted from areas located at Northeast and Southeast of Brazilian coast were investigated. The soils and their fractions were analyzed in an EDX-700 and an XRD-6000 (Cu K α radiation). XRF results indicate high percentages of Si and Al, and small percentage of Fe and Ti in the investigated samples. The DRX data and RM indicate that there was a predominance of kaolinite and halloysite minerals (kaolin group minerals) in the clay fractions, which are presumably responsible for the formation of kaolinitic plasma in these soils. Also, the obtained results showed that the XRF, XRD techniques and RM were very helpful for investigating the mineralogical composition of a hardsetting soil. - Highlights: ► Elemental composition of soil samples through X-Ray fluorescence. ► Mineralogical quantification through X-ray diffraction and Rietveld method. ► Oxisol and Ultisol, Brazil ‘Barreiras’ formation. ► High amounts of Si and Al oxides and low amounts of Fe and Ti oxides. ► Predominance of kaolinite in the clay fraction

Rietveld analysis using powder diffraction data with anomalous scattering effect obtained by focused beam flat sample method

Energy Technology Data Exchange (ETDEWEB)

Tanaka, Masahiko, E-mail: masahiko@spring8.or.jp; Katsuya, Yoshio, E-mail: katsuya@spring8.or.jp; Sakata, Osami, E-mail: SAKATA.Osami@nims.go.jp [Synchrotron X-ray Station at SPring-8, National Institute for Materials Science 1-1-1 Kouto, Sayo, Hyogo 679-5198 (Japan)

2016-07-27

Focused-beam flat-sample method (FFM) is a new trial for synchrotron powder diffraction method, which is a combination of beam focusing optics, flat shape powder sample and area detectors. The method has advantages for X-ray diffraction experiments applying anomalous scattering effect (anomalous diffraction), because of 1. Absorption correction without approximation, 2. High intensity X-rays of focused incident beams and high signal noise ratio of diffracted X-rays 3. Rapid data collection with area detectors. We applied the FFM to anomalous diffraction experiments and collected synchrotron X-ray powder diffraction data of CoFe{sub 2}O{sub 4} (inverse spinel structure) using X-rays near Fe K absorption edge, which can distinguish Co and Fe by anomalous scattering effect. We conducted Rietveld analyses with the obtained powder diffraction data and successfully determined the distribution of Co and Fe ions in CoFe{sub 2}O{sub 4} crystal structure.

Characterization of barium titanate powder doped with sodium and potassium ions by using Rietveld refining

International Nuclear Information System (INIS)

Andrade, M.C.; Assis, J.T.; Pereira, F.R.

2009-01-01

A solid-reaction synthesis of doped barium titanate was done by employing barium carbonates, sodium, potassium and titanium oxides with classic procedures. Rietveld refining of X ray diffraction data of perovskite samples with tetragonal symmetry was applying and show good agreement. Besides, the treatment performed from 600 deg C produces nanocrystals of barium titanate with average size of 33 nm. The presence of endothermic peaks related to BaTiO 3 formation at relatively low temperatures was determined by thermal analysis. A pseudo-Voigt Thompson-Cox-Hastings function was used to fit the standard samples of barium titanate. The Rietveld method has showed be efficient to detect the influences of temperature and doping on barium titanate microstructures. (author)

Assessment of firing conditions in old fired-clay bricks. The contribution of X-ray powder diffraction with the Rietveld method and small angle neutron scattering

Czech Academy of Sciences Publication Activity Database

Viani, Alberto; Sotiriadis, Konstantinos; Len, A.; Šašek, Petr; Ševčík, Radek

2016-01-01

Roč. 116, June (2016), s. 33-43 ISSN 1044-5803 R&D Projects: GA MŠk(CZ) LO1219 Keywords : fired- clay brick * Rietveld method * small angle neutron scattering * X-ray diffraction * firing temperature Subject RIV: AL - Art, Architecture, Cultural Heritage Impact factor: 2.714, year: 2016 http://www.sciencedirect.com/science/article/pii/S1044580316300870

Profile agreement indices in Rietveld and pattern-fitting analysis

International Nuclear Information System (INIS)

Hill, R.J.; Fischer, R.X.

1990-01-01

Two definitions of profile agreement indices are now in common use for estimating the degree of fit in Rietveld refinement and in structure-independent pattern-fitting methods of powder diffraction analysis. In the original program written by Rietveld, the background was subtracted and the 'non-peak' regions of the pattern were removed from further consideration in a preliminary data-reduction stage prior to structure refinement. However, the agreement indices used in many of the more recent programs retain the background counts in the observed step intensities and include all portions of the pattern in the sums. These latter definitions are strongly dependent on the signal-to-noise ratio and on the relative amount of 'background-only' regions and do not, therefore, provide a sound basis for comparing the degree of fit of peak profile and crystal structure model refinements in the general case. The extent of this dependence is illustrated quantitatively using conventional and synchrotron X-ray and constant-wavelength and time-of-flight neutron data sets with different inherent background levels and peak densities. The unweighted background-corrected peak-only profile agreement index R' p =Σ i vertical strokeY io -Y ic vertical stroke/Σ i vertical strokeY io -Y ib vertical stroke (and, to a lesser extent, its weighted equivalent) is recommended as the most appropriate criterion of fit for comparative work between diffraction patterns of all kinds. (orig.)

Assessment of firing conditions in old fired-clay bricks: The contribution of X-ray powder diffraction with the Rietveld method and small angle neutron scattering

Energy Technology Data Exchange (ETDEWEB)

Viani, Alberto, E-mail: viani@itam.cas.cz [Institute of Theoretical and Applied Mechanics AS CR, Centre of Excellence Telč, Batelovská 485, CZ-58856 Telč (Czech Republic); Sotiriadis, Konstantinos [Institute of Theoretical and Applied Mechanics AS CR, Centre of Excellence Telč, Batelovská 485, CZ-58856 Telč (Czech Republic); Len, Adél [Wigner Research Centre for Physics HAS, Konkoly-Thege 29-33, 1121 Budapest (Hungary); Šašek, Petr; Ševčík, Radek [Institute of Theoretical and Applied Mechanics AS CR, Centre of Excellence Telč, Batelovská 485, CZ-58856 Telč (Czech Republic)

2016-06-15

Full characterization of fired-clay bricks is crucial for the improvement of process variables in manufacturing and, in case of old bricks, for restoration/replacement purposes. To this aim, five bricks produced in a plant in Czech Republic in the past have been investigated with a combination of analytical techniques in order to derive information on the firing process. An additional old brick from another brickyard was also used to study the influence of different raw materials on sample microstructure. The potential of X-ray diffraction with the Rietveld method and small angle neutron scattering technique has been exploited to describe the phase transformations taking place during firing and characterize the brick microstructure. Unit-cell parameter of spinel and amount of hematite are proposed as indicators of the maximum firing temperature, although for the latter, limited to bricks produced from the same raw material. The fractal quality of the surface area of pores obtained from small angle neutron scattering is also suggested as a method to distinguish between bricks produced from different raw clays. - Highlights: • Rietveld method helps in describing microstructure and physical properties of bricks. • XRPD derived cell parameter of spinel is proposed as an indicator of firing temperature. • SANS effectively describes brick micro and nanostructure, including closed porosity. • Fractal quality of pore surface is proposed as ‘fingerprint’ of brick manufacturing.

Synthesis and refinement of ferroelectric ceramic BaBi4Ti4O15 (BBT) using Rietveld Methods

International Nuclear Information System (INIS)

Silva, P.M.O.; Sales, A.J.M.; Carneiro, J.C.S.; Sancho, E.O.; Sales, J.C.; Sombra, A.S.B.

2012-01-01

The lead zirconate titanate (PZT) has potential application in nonvolatile ferroelectric memory and capacitors, however this material is linked to environmental pollution. In order to remedy this problem, we propose the synthesis of the compound, BaBi 4 TI 4 O 15 (BBT) because of similarity to PZT. The phase of the BBT has been prepared by the method of solid state. Reagents (BaCO 3 , Bi 2 O 3 and TiO 2 ) were ground for 6 hours at 360 rpm in a planetary ball mill and suffered high energy heat treatment for 2 hours at temperatures of 850, 900, 950 and 1000 ° C. The calcined powder was characterized by X-ray diffraction (XRD) and refined by the program DBWSTools 2.3 Beta based on the Rietveld method. The results obtained confirmed the refinement of the single-phase with tetragonal structure BaBi 4 TI 4 O 15 for all samples. The sample calcined at 950 °C presented the best densification (7.508 g/cm³). (author)

Application of the Rietveld method in structural analysis of catalysts based on CuO/CeO{sub 2}; Aplicacao do metodo de Rietveld na analise estrutural de catalisadores a base de CuO/CeO{sub 2}

Energy Technology Data Exchange (ETDEWEB)

Neiva, L.S.; Ribeiro, M.A.; Bispo, A.; Simoes, A.N.; Gama, L., E-mail: lsoutoneiva@yahoo.com.br [Universidade Federal de Campina Grande (UFCG), PB (Brazil). Departamento de Engenharia de Materiais

2011-07-01

This work has as aim to synthesize catalysts composed by CuO/CeO{sub 2} by means two distinct methods of synthesis, they are: combustion synthesis and Pechini. The catalysts composed by CuO/CeO{sub 2} were synthesized with CuO in condition of dopant element. The value of the CuO concentration ranged between 0 and 0.5 mol. Has been done a structural analysis related to how the kind of synthesis method used influences over physical characteristic of the catalytic material. The obtained catalysts were characterized by X-ray diffraction with refinement by Rietveld method. According to results, the synthesized catalysts showed crystalline structures formed mostly by CeO{sub 2} phase, as expected, since this is the host matrix for the dopant element. The catalysts obtained by the Pechini method presented structures with a smaller amount of segregated phases formed by CuO, according to the results of the structural analysis. (author)

Synthesis of Zr-Si-O-N phases by carbonitriding reaction. Characterization of crystalline phases using the Rietveld method

Directory of Open Access Journals (Sweden)

Mazzoni A.D.

2001-01-01

Full Text Available Zirconium compounds are of great interest for ceramic application due to their excellent thermal and mechanical properties. Zirconium phases of the system Zr-O-C-N were obtained using carbonitriding reactions of zircon mineral (ZrO2.SiO2, under different reaction conditions. The reaction products were studied by X-ray diffraction (XRD using the Rietveld method. Silicon was employed as internal standard. Zirconium compounds formed were m-ZrO2 (monoclinic, beta"-zirconium oxynitride and a cubic Zr(C,N,O phase whose lattice parameter a o depends on the composition. The crystallite sizes of the three zirconium phases were determined also by XRD. The minority phases present are the ones of the Si-O-N-C system. The reaction conditions employed allows to obtain reaction products with low or without silicon content.

Determination of phases of {alpha} - Fe{sub 2}O{sub 3}: SiO{sub 2} compound by the Rietveld refinement

Energy Technology Data Exchange (ETDEWEB)

Palomares S, S.A. [Istituto Materiali Speciali per Elettronica e Magnetismo (MASPEC), Parco Area delle Scienze 37A-43010 Loc. Fontanni, Parma (Italy); Ponce C, S.; Martinez, J.R. [Facultad de Ciencias, Universidad Autonoma de San Luis Potosi, 78000 San Luis Potosi (Mexico); Ruiz, F. [Instituto Potosino de Investigacion Cientifica y Tecnologica, Av. V. Carranza 2025, San Luis Potosi (Mexico)

2002-07-01

We use a variation of the Rietveld refinement method to calculate the amorphous content of composites formed by a silica xerogel amorphous matrix and iron particles embedded into. In order to apply the Rietveld refinement to amorphous structures an initial crystalline model is assumed with the same composition as the material to be modelled. In this work we try to refine the structure of compounds using the program MAUD. It is shown how this program can be used to determine the amorphous and crystalline fractions in composites consisting of an amorphous matrix and incorporated iron oxide particles. The analysed compounds underwent different thermal treatments. (Author)

Dos artículos de Rietveld Comprensión. Nuevo Funcionalismo en la Arquitectura

Directory of Open Access Journals (Sweden)

Editor Cuaderno de Notas

1995-12-01

Full Text Available Los siguientes dos artículos de Rietveld (1888-1964 fueron publicados por primera vez en la revista i10 en 1928 y en De Vrije Bladen en 1932 respectivamente. Esta es su primera traducción al castellano, para lo que se ha partido de sus correspondientes traducciones inglesas; "Inzicht" (comprensión, en el libro de Theodore M.. Brown, The Work of G. Rietveld architect, Utrecht 1958, y "Nieuwe zakelijkheid in de Nederlandsche architectuur" (Nueva objetividad en la arquitectura holandesa, en la monografía-catálogo, Gerrit Rietveld 1888-1964. The complet works, Central Museum, Utrecht, 1992. En cuanto al último, de bastante mayor extensión, contaba originariamente con ilustraciones de obras de JA.Brinkman y L.C. van der Vlugt, A. Bodón, J. Duiker, J.J.P. Oud y Le Corbusier como único arquitecto extranjero representado, aparte de las de sus propio trabajo.

Modulation wave approach to the structural parameterization and Rietveld refinement of low carnegieite

International Nuclear Information System (INIS)

Withers, R.L.; Thompson, J.G.

1993-01-01

The crystal structure of low carnegieite, NaAlSiO 4 [M r =142.05, orthorhombic, Pb2 1 a, a=10.261(1), b=14.030(2), c=5.1566(6) A, D x =2.542 g cm -3 , Z=4, Cu Kα 1 , λ=1.5406 A, μ=77.52 cm -1 , F(000)=559.85], is determined via Rietveld refinement from powder data, R p =0.057, R wp =0.076, R Bragg =0.050. Given that there are far too many parameters to be determined via unconstrained Rietveld refinement, a group theoretical or modulation wave approach is used in order to parameterize the structural deviation of low carnegieite from its underlying C9 aristotype. Appropriate crystal chemical constraints are applied in order to provide two distinct plausible starting models for the structure of the aluminosilicate framework. The correct starting model for the aluminosilicate framework as well as the ordering and positions of the non-framework Na atoms are then determined via Rietveld refinement. At all stages, chemical plausibility is checked via the use of the bond-length-bond-valence formalism. The JCPDS file number for low carnegieite is 44-1496. (orig.)

Crystal phase analysis of SnO2-based varistor ceramic using the Rietveld method

International Nuclear Information System (INIS)

Moreira, M.L.; Pianaro, S.A.; Andrade, A.V.C.; Zara, A.J.

2006-01-01

A second addition of l mol% of CoO to a pre calcined SnO 2 -based ceramic doped with 1.0 mol% of CoO, 0.05 mol% of Nb 2 O 5 and 0.05 mol% of Cr 2 O 3 promotes the appearance of a secondary phase, Co 2 SnO 4 , besides the SnO 2 cassiterite phase, when the ceramic was sintered at 1350 deg. C/2 h. This was observed using X-ray powder diffraction, scanning electron microscopy and energy dispersive X-ray techniques. Rietveld refinement was carried out to quantify the phases present in the ceramic system. The results of the quantitative analysis were 97 wt.% SnO 2 and 3 wt.% Co 2 SnO 4 . The microstructural analysis showed that a certain amount of cobalt ion remains into cassiterite grains

Micro-structural study and Rietveld analysis of fast reactor fuels: U–Mo fuels

International Nuclear Information System (INIS)

Chakraborty, S.; Choudhuri, G.; Banerjee, J.; Agarwal, Renu; Khan, K.B.; Kumar, Arun

2015-01-01

U–Mo alloys are the candidate fuels for both research reactors and fast breeder reactors. In-reactor performance of the fuel depends on the microstructural stability and thermal properties of the fuel. To improve the fuel performance, alloying elements viz. Zr, Mo, Nb, Ti and fissium are added in the fuel. The first reactor fuels are normally prepared by injection casting. The objective of this work is to compare microstructure, phase-fields and hardness of as-cast four different U–Mo alloy (2, 5, 10 and 33 at.% Mo) fuels with the equilibrium microstructure of the alloys. Scanning electron microscope with energy dispersive spectrometer and optical microscope have been used to characterize the morphology of the as-cast and annealed alloys. The monoclinic α'' phase in as-cast U-10 at.% Mo alloy has been characterized through Rietveld analysis. A comparison of metallographic and Rietveld analysis of as-cast (dendritic microstructure) and annealed U-33 at.% Mo alloy, corresponding to intermetallic compound, has been reported here for the first time. This study will provide in depth understanding of microstructural and phase evolution of U–Mo alloys as fast reactor fuel. - Highlights: • U–Mo alloys in as-cast as well as in annealed conditions have been studied using Optical Microscope, SEM, XRD. • The monoclinic α'' phase in as-cast U-10 at.% Mo alloy has been characterized through Rietveld analysis. • The dendritic microstructure of γ-(U,Mo) and B.C.C. ‘Mo’ phase of 33 at.% U–Mo alloy have been analysed. • Rietveld analysis has been done to optimize lattice parameters and calculate phase fractions in annealed alloys. • The Vickers microhardness of U_2Mo phase shows lower hardness than two phase microstructures in annealed alloys.

Micro-structural study and Rietveld analysis of fast reactor fuels: U–Mo fuels

Energy Technology Data Exchange (ETDEWEB)

Chakraborty, S., E-mail: sibasis@barc.gov.in [Radiometallurgy Division, Bhabha Atomic Research Centre, Mumbai, 400085 (India); Choudhuri, G. [Atomic Fuels Division, Bhabha Atomic Research Centre, Mumbai, 400085 (India); Banerjee, J. [Radiometallurgy Division, Bhabha Atomic Research Centre, Mumbai, 400085 (India); Agarwal, Renu [Product Development Division, Bhabha Atomic Research Centre, Mumbai, 400085 (India); Khan, K.B.; Kumar, Arun [Radiometallurgy Division, Bhabha Atomic Research Centre, Mumbai, 400085 (India)

2015-12-15

U–Mo alloys are the candidate fuels for both research reactors and fast breeder reactors. In-reactor performance of the fuel depends on the microstructural stability and thermal properties of the fuel. To improve the fuel performance, alloying elements viz. Zr, Mo, Nb, Ti and fissium are added in the fuel. The first reactor fuels are normally prepared by injection casting. The objective of this work is to compare microstructure, phase-fields and hardness of as-cast four different U–Mo alloy (2, 5, 10 and 33 at.% Mo) fuels with the equilibrium microstructure of the alloys. Scanning electron microscope with energy dispersive spectrometer and optical microscope have been used to characterize the morphology of the as-cast and annealed alloys. The monoclinic α'' phase in as-cast U-10 at.% Mo alloy has been characterized through Rietveld analysis. A comparison of metallographic and Rietveld analysis of as-cast (dendritic microstructure) and annealed U-33 at.% Mo alloy, corresponding to intermetallic compound, has been reported here for the first time. This study will provide in depth understanding of microstructural and phase evolution of U–Mo alloys as fast reactor fuel. - Highlights: • U–Mo alloys in as-cast as well as in annealed conditions have been studied using Optical Microscope, SEM, XRD. • The monoclinic α'' phase in as-cast U-10 at.% Mo alloy has been characterized through Rietveld analysis. • The dendritic microstructure of γ-(U,Mo) and B.C.C. ‘Mo’ phase of 33 at.% U–Mo alloy have been analysed. • Rietveld analysis has been done to optimize lattice parameters and calculate phase fractions in annealed alloys. • The Vickers microhardness of U{sub 2}Mo phase shows lower hardness than two phase microstructures in annealed alloys.

Refinement by Rietveld method of a rolled sheet Al-Mg-Si 6063 alloy with preferential orientation

International Nuclear Information System (INIS)

Carrio, J.A.G.; Hattori, C.S.; Miranda, L.F.; Domingues Junior, N.I.; Lima, N.B.; Couto, A.A.; Aguiar, A.A.

2010-01-01

The Rietveld refinement of a sample with preferential orientation was accomplished using data of X ray diffraction of a rolled 6063 aluminum alloy. The refinement of the preferential orientation by spherical harmonic was accomplished using a symmetry of sample mmm (rolling) until the order of 8 and was compared with experimental pole figures. The four pole figures presented indicate a sharp texture of the planes (111), (200), (220) and (311). The calculated pole figures obtained from the refinement of the X ray diffraction spectrum can incur in mistakes of preferential orientation. This happens because the measure is restricted to the planes parallel to the surface without inference to the symmetry of the sample. (author)

Rietveld analysis and electronic bands structure on Tc superconductors systems

International Nuclear Information System (INIS)

Aldea, N.; Tiusan, C. V.; Sandu, V.

1999-01-01

A procedure for simultaneous refinement of structural and micro-structural disorder parameters for polycrystalline YBa 2 Cu 3 O 7-x system is proposed. It is based on Rietveld method combined with Fourier analysis for broadened peaks Another purpose of this paper consists in electronic structure determination studied by using the self-consistent Tight Binding Linear Muffin-Tin Orbital Atomic Spheres Approximation TB-LMTO-ASA methods. The Rietveld method uses an analytical function that describes the profiles, usually pseudo-Voigt (pV) or Pearson VII (PVII). The parameters of the analytical profiles describe its amplitude, position and peak shape. The full width at half maximum (FWHM) is supposed to vary with the diffraction angle in agreement with the Caglioti, Paoletti and Ricci's relationship. The best structural parameters are determined in the least squares sense by the minimisation a classical residual using the Marquardt method. In this case, the peak profiles were modelled by the pseudo-Voigt function corrected by the instrumental asymmetry. The physical information obtained are: scale factor, lattice parameters, atomic position and displacements, atomic occupation numbers, temperature factor (isotropy or anisotropy), preferred orientation parameter, crystalline size and micro-strain along different crystallographic directions, distributions of crystallite size and micro-strain functions. This procedure was implemented on computer code and it has a friendly graphical interface based on pull down menus technique. From the experimental point of view the X-ray diffraction data were collected using a horizontal powder diffractometer in the Bragg-Brentano (BB) geometry with a Ni filtered CuKα, λ = 1.54178 A, at room temperature using a DRON 2 set-up. The diffraction profiles were measured with a proportional gas detector, a single channel pulse-height discrimination and a standard associated counting circuit. The electronic band calculations are based on the TB

Influence of diopside: feldspar ratio in ceramic reactions assessed by quantitative phase analysis (X-ray diffraction - Rietveld method)

International Nuclear Information System (INIS)

Kuzmickas, L.; Andrade, F.R.D.; Szabo, G.A.J.; Motta, J.F.M.; Cabral Junior, M.

2013-01-01

White ceramics were produced with raw mixtures prepared with varying proportions of diopside-rich rock (0 to 20 wt.%) and potassic feldspar (40 to 20 wt.%), and fixed proportions of kaolinite (40 wt.%) and quartz (20 wt.%), fired in a temperature range from 1170 to 1210 deg C. The phases identified in the experimental ceramics were quartz, anorthite, mullite and glass, and their relative mass proportions were determined by X-ray diffraction (Rietveld method). The addition of diopside as a partial substitute for potassic feldspar causes the formation of a calcium silicate, analogous of the natural anorthite (CaSi 2 Al 2 O 8 ) in the ceramics, with proportional reduction in its glass and mullite contents. Water absorption and porosity of the ceramic bodies clearly decrease with increasing firing temperature, while the effect of the raw mixture composition on the physical and mechanical properties of the ceramics is less evident. Diopside-rich rock has low iron content (1.5 wt.% Fe 2 O 3 ) and, therefore, promotes white burning. (author)

Influence of diopside: feldspar ratio in ceramic reactions assessed by quantitative phase analysis (X-ray diffraction - Rietveld method)

Energy Technology Data Exchange (ETDEWEB)

Kuzmickas, L.; Andrade, F.R.D.; Szabo, G.A.J. [Universidade de Sao Paulo (IGc/USP), SP (Brazil). Inst. de Geociencias. Dept. de Mineralogia e Geotecnia; Motta, J.F.M.; Cabral Junior, M., E-mail: lukuzmickas@gmail.com, E-mail: dias@usp.br, E-mail: gajszabo@usp.b, E-mail: motta.jf@gmail.com, E-mail: marsis@ipt.br [Instituto de Pesquisas Tecnologicas (IPT), Sao Paulo, SP (Brazil). Secao de Recursos Minerais e Tecnologia Ceramica

2013-04-15

White ceramics were produced with raw mixtures prepared with varying proportions of diopside-rich rock (0 to 20 wt.%) and potassic feldspar (40 to 20 wt.%), and fixed proportions of kaolinite (40 wt.%) and quartz (20 wt.%), fired in a temperature range from 1170 to 1210 deg C. The phases identified in the experimental ceramics were quartz, anorthite, mullite and glass, and their relative mass proportions were determined by X-ray diffraction (Rietveld method). The addition of diopside as a partial substitute for potassic feldspar causes the formation of a calcium silicate, analogous of the natural anorthite (CaSi{sub 2}Al{sub 2}O{sub 8}) in the ceramics, with proportional reduction in its glass and mullite contents. Water absorption and porosity of the ceramic bodies clearly decrease with increasing firing temperature, while the effect of the raw mixture composition on the physical and mechanical properties of the ceramics is less evident. Diopside-rich rock has low iron content (1.5 wt.% Fe{sub 2}O{sub 3}) and, therefore, promotes white burning. (author)

Study of effect of sintering time on the 2223 phase growth Bi-Pb-Sr-Ca-Cu-O superconductor by Rietveld method

International Nuclear Information System (INIS)

Parikin; Prasuad, W; Gunawan

1996-01-01

It has been reported that the sintering time is as important for the preparation of superconductor as the sintering temperature and method. This paper reports on the finding of the optimum sintering time in the preparation of the 2223 phase bismuth (Bi) superconductor. The samples were synthesized with nominal composition 1.84 : 0.34 : 1.91 : 2.03 : 3.06 from raw materials by solid state reaction and sintered at 860 o C for five days. The resintering were done three times, i.e. 24, 48 and 96 hours. The Rietveld analysis shows that the 2223 phase grows continuously as a function of the sintering time. The highest percentage of the 2223 phase (80.64%) were obtained at 96 hours sintering time. The result suggests that the 2223 phase can be obtained effectively by sintering with sufficiently long time

Determination of Cation Distributions in Mineral Structures by use of the Rietveld Full-Profile Refinement Technique

International Nuclear Information System (INIS)

Nord, A.G.

1986-01-01

Use of the Rietveld full-profile refinement technique with X-ray or neutron powder diffraction data for the determination of divalent-metal cation distributions in three mineral structure types (farringtonite, grafonite, sarcopside) is demonstrated. The accuracy of the conventional cation distribution coefficient Ksub(D) is about 5-10 percent with 24-46 parameters to be refined, and the averaged metal-oxygen distances are reliable and well correlated to the observed cation distribution pattern. In particular the usefulness of the Rietveld technique in combination with Moessbauer spectroscopy is stressed. Some concluding remarks are also given

Influence of the milling time in the microstructural parameters of TA2O5-Al powder refined by Rietveld method

International Nuclear Information System (INIS)

Brito, R.A.; Mendes, M.W.D.; Alves Junior, C.; Costa, F.A. da; Gomes, U.U.

2009-01-01

Mechanical alloying (MA) is a solid-state powder processing technique involving repeated welding, fracturing, and re-welding of powder particles in a high energy mill. This process is used for producing of fine powders containing unique microstructures. The process starts with mixing of the powders in the desired proportion. Then, the mixture is milled using the established time in the high-energy mill. The powder particles are submitted to repeated cycles of cold working and fracture, and the final product correspond to a composite powder, containing characteristics different of the initial constituents. Ta 2 O 5 -Al powders were milled in a planetary ball mill for different times in order to evaluate the influence of the milling time in their microstructural parameters like crystallite size and micro deformation. The microstructural parameters were obtained by the Rietveld Method. The results showed that the microstructural parameters were influenced by the increase of the milling time. (author)

Structural analysis of a carbonated hydroxyapatite by the Rietveld method using different profile functions; Analise estrutural de uma hidroxiapatita carbonatada pelo metodo de Rietveld aplicando funcoes de perfil diferentes

Energy Technology Data Exchange (ETDEWEB)

Araujo, Jorge C. de [Universidade do Estado do Rio de Janeiro (UERJ), RJ (Brazil). Dept. de Matematica], e-mail: jcaraujo@iprj.uerj.br; Moreira, Elizabeth L.; Moraes, Valeria Conde Alves [Centro Brasileiro de Pesquisas Fisicas (CBPF), Rio de Janeiro, RJ (Brazil)], e-mail: beth@cbpf.br, e-mail: conde@cbpf.br; Moreira, Ana Paula D. [Universidade Federal Fluminense (UFF), Niteroi, RJ (Brazil). Inst. de Quimica. Dept. de Quimica Analitica], e-mail: duarteap@gmail.com

2008-10-15

The crystal structure of the synthetic hydroxyapatite with 12.8 ({+-} 0,64) wt. % CO{sub 3}{sup 2-} ion content was analyzed by X-ray diffraction using the Rietveld refinement method employing Pearson VII and pseudo-Voigt functions to fit the X-ray profile. The results obtained for unit cell parameters when compared to pattern hydroxyapatite showed a decrease in the a (=b) parameter and an increase in the c parameter without significant difference between the functions employed. The separation of the anisotropic broadening of reflections originated from unit cell strains indicated that this effect is dominant in reflection line broadening, principally to hkl plans with an interatomic distance lower than 2,24 angstrom. Modifications in the atomic coordinates of C atom were noted mainly in PO{sub 4}{sup 3-} (B site) and OH{sup -} (A site) sites. The average crystallite size in the crystallography axis directions (002 and 300) suggests equi axial morphology. The results obtained to CO{sub 3}{sup 2}- content were 11.72 ({+-} 0,64) wt. % to Pearson VII and 13.20 ({+-} 0,64) wt. % to pseudo-Voigt function. The refinement of the occupancy factors to C atoms in both sites PO{sub 4}{sup 3-}(B) and OH{sup -} (A) indicated higher insertion in phosphate site than hydroxide site. However, the relative occupancy of the C atom observed in the B site is lower than in the A site. (author)

Application of the Rietveld method in powders of strontium-doped lanthanum manganite calcined in different temperatures

International Nuclear Information System (INIS)

Chiba, R.; Vargas, R.A.; Martinez, L.G.; Andreoli, M.; Seo, E.S.M.

2010-01-01

The strontium-doped lanthanum manganite (LSM) is a ceramic material used as cathode in device called High Temperature Solid Oxide Fuel Cell. In this work, the LSM was synthesized by the citrate technique with the objective to get powders without the formation of secondary phases, such as lanthanum oxide and the lanthanum hydroxide, harmful for the functional performance of the device. The definitive calcination temperatures had been 700, 900 and 1100 deg C, due the decomposition of the polymeric precursors to present stabilization from 480 deg C. The analysis by X-ray diffraction of the calcined powders in different temperatures shows the formation only of phase LSM of hexagonal crystalline structure, type pseudo-perovskite. Using the refinement of Rietveld was determined the parameters and volumes of unity cells, atomic positions and occupations. These results confirm that the chemical compositions obtained are similar to the nominal. (author)

Magnesium substitution in carbonated hydroxyapatite: Structural and microstructural characterization by Rietveld's refinement

Energy Technology Data Exchange (ETDEWEB)

Lala, S. [Materials Science Division, Department of Physics, The University of Burdwan, Golapbag, Burdwan 713104, West Bengal (India); Ghosh, M.; Das, P.K. [Department of Biological Chemistry, Indian Association for the Cultivation of Science, Jadavpur, Kolkata 700 032 (India); Das, D. [UGC-DAE Consortium for Scientific Research, Kolkata 700098 (India); Kar, T. [Department of Materials Science, Indian Association for the Cultivation of Science, Jadavpur, Kolkata 700032 (India); Pradhan, S.K., E-mail: skpradhan@phys.buruniv.ac.in [Materials Science Division, Department of Physics, The University of Burdwan, Golapbag, Burdwan 713104, West Bengal (India)

2016-02-15

Four stoichiometric compositions of nanocrystalline Mg doped carbonated hydroxyapatite (cHAp) powders are synthesized by mechanical alloying (ball milling) the powder mixtures of CaCO{sub 3}, CaHPO{sub 4}.2H{sub 2}O and MgO in open air at room temperature. FTIR analysis confirms the A-type carbonation in all milled HAp powder samples (A-cHAp). Microstructure characterization in terms of lattice imperfections and phase quantification of ball milled samples are made by analyzing XRD patterns employing Rietveld's structure refinement method. Transmission electron microscopy (TEM) study of 15 mol % Mg doped A-cHAp sample reveals microstructure similar to that obtained from XRD pattern analysis. Cumulative effect of Mg substitution and mechanical alloying results in amorphization of a major part of crystalline A-cHAp, analogous to native bone mineral. Rietveld analysis reveals that the Ca2 vacancy site is energetically more favorable for occupation of Mg substitution. MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] assay test reveals sufficiently high percentage cell viability confirming the cytocompatibility of the sample. - Graphical abstract: Mg substitution for Ca2 site. - Highlights: • Single phase Mg doped A-cHAp synthesized by mechanical alloying (MA). • FTIR analysis confirms A-type carbonation in HAp. • Amorphization of a part of crystalline A-cHAp due to MA and Mg insertion. • Mg{sup 2+} ions substitute the Ca2 vacancy site. • High cell viability under MTT assay.

Profex: a graphical user interface for the Rietveld refinement program BGMN

OpenAIRE

Doebelin, Nicola; Kleeberg, Reinhard

2015-01-01

Profex is a graphical user interface for the Rietveld refinement program BGMN. Its interface focuses on preserving BGMN’s powerful and flexible scripting features by giving direct access to BGMN input files. Very efficient workflows for single or batch refinements are achieved by managing refinement control files and structure files, by providing dialogues and shortcuts for many operations, by performing operations in the background, and by providing import filters for CIF and XML crystal str...

Rietveld refinement and FTIR analysis of bulk ceramic Co3-xMnxO4 compositions

Science.gov (United States)

Meena, P. L.; Kumar, Ravi; Sreenivas, K.

2013-02-01

Co3-xMnxO4 (x = 0.0, 0.6, 1.2) prepared by solid state reaction method and characterized by powder X-ray diffraction (XRD) and Fourier transform infrared (FTIR). Lattice parameters (a), oxygen parameter (u), and ionic radii of cations have been determined through Rietveld analysis. Both a and u parameters are related to expansion of octahedral site as Mn content in Co3O4. Analysis of XRD data show that Mn (x ≤ 1.2) is accommodated at the octahedral site, while retaining the cubic spinel structure. FTIR results also confirm the same and signify strong interactions due to overlapping of Co and Mn octahedra.

Measurements of Residual Stresses In Cold-Rolled 304 Stainless Steel Plates Using X-Ray Diffraction with Rietveld Refinement Method

International Nuclear Information System (INIS)

Parikin; Killen, P; Rafterry, A.

2009-01-01

The determination of the residual stresses using X-ray powder diffraction in a series of cold-rolled 304 stainless steel plates, deforming 0, 34, 84, 152, 158, 175 and 196 % reduction in thickness has been carried out. The diffraction data were analyzed using the Rietveld structure refinement method. The analysis shows that for all specimens, the martensite particles are closely in compression and the austenite matrix is in tension. Both the martensite and austenite, for a sample reducing 34% in thickness (containing of about 1% martensite phase) the average lattice strains are anisotropic and decrease approximately exponential with an increase in the corresponding percent reduction (essentially phase content). It is shown that this feature can be qualitatively understood by taking into consideration the thermal expansion mismatch between the martensite and austenite grains. Also, for all cold-rolled stainless steel specimens, the diffraction peaks are broader than the unrolled one (instrumental resolution), indicating that the strains in these specimens are inhomogeneous. From an analysis of the refined peak shape parameters, the average root-mean square strain, which describes the distribution of the inhomogeneous strain field, was predicted. The average residual stresses in cold-rolled 304 stainless steel plates showed a combination effect of hydrostatic stresses of the martensite particles and the austenite matrix. (author)

Quantitative phase analysis of alumina/calcium-hexaluminate composites using neutron diffraction data and the Rietveld method

International Nuclear Information System (INIS)

Asmi, D.; Low, I.M.; O'Connor, B.H.; Kennedy, S.J.

2000-01-01

Full text: The Al 2 O 3 -CaO system is the basis of an important class of high-temperature refractories in the steel industry. It contains a number of stable intermediate compounds which include C 3 A, C 12 A 7 , CA, CA 2 , and CA 6 . These calcium aluminates are also important constituents of high alumina cement and have been used to produce high-strength and high-toughness ceramic-polymer composite materials. More recently, alumina composites containing 30 wt% CA 6 platelets have been developed by An et al which show characteristics of self-reinforcement and enhanced toughening through crack-bridging. In this paper, we describe the use of high-temperature neutron diffraction to monitor the in-situ phase formation and abundances of calcium aluminates (CA, CA 2 , and CA 6 ) in alumina composites containing 5-50 wt % CA 6 .at temperatures in the range 1000 - 1600 deg C. These composites were produced using reaction sintering of alumina and calcium oxide. For comparison purposes, control samples of pure α-alumina and CA 6 were also produced. Determination of relative phase abundances in these materials has been performed using the standardless Rietveld refinement method. Results show that the relative phase abundance of calcium aluminates in the composites increased with temperature and in proportion with the amount of calcium oxide present. The formation temperatures of CA, CA 2 , and CA 6 have been observed to occur at 1000 deg , 1200 deg, and ∼1350 deg C respectively, which agree well with results obtained from x-ray diffraction, synchrotron radiation diffraction and differential thermal analysis

Combined PDF and Rietveld studies of ADORable zeolites and the disordered intermediate IPC-1P

Czech Academy of Sciences Publication Activity Database

Morris, S. A.; Wheatley, P. S.; Položij, M.; Nachtigall, P.; Eliášová, Pavla; Čejka, Jiří; Lucas, T. C.; Hriljac, J. A.; Pinar, A. B.; Morris, R. E.

2016-01-01

Roč. 45, č. 36 (2016), s. 14124-14130 ISSN 1477-9226 R&D Projects: GA ČR GBP106/12/G015 Institutional support: RVO:61388955 Keywords : Distribution functions * Rietveld refinement * Zeolites Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 4.029, year: 2016

Crystal structures of new cuprates containing CO3 analyzed by the Rietveld method of neutron powder diffraction

International Nuclear Information System (INIS)

Miyazaki, Y.; Yamane, H.; Kajitani, T.; Hiraga, K.; Hirai, T.; Morii, Y.; Funahashi, S.

1993-01-01

New compounds containing CO 3 groups, Sr 2 CuO 2 (CO 3 ), (C 0.4 Cu 0.6 )Sr 2 (Y 0.86 Sr 0.14 )Cu 2 O 7 and (C 0.35 Cu 0.65 )Sr 2 (Y 0.73 Ce 0.27 ) 2 Cu 2 O 9 , were prepared as stable phases at 1273-1303 K in a flowing gas of O 2 -CO 2 . The crystal structures of these compounds were refined by means of the Rietveld analysis for neutron powder diffraction data collected using a high resolution powder diffractometer (HRPD) in the JRR-3M reactor hall of the Japan Atomic Energy Research Institute (JAERI). Positions of CO 3 groups were satisfactorily determined. The distances of C-O bonds in the CO 3 groups were around 1.3A and the O-C-O angles were almost equal to the ideal bond angle of 120deg. (author)

Micro-structural study and Rietveld analysis of fast reactor fuels: U-Mo fuels

Science.gov (United States)

Chakraborty, S.; Choudhuri, G.; Banerjee, J.; Agarwal, Renu; Khan, K. B.; Kumar, Arun

2015-12-01

U-Mo alloys are the candidate fuels for both research reactors and fast breeder reactors. In-reactor performance of the fuel depends on the microstructural stability and thermal properties of the fuel. To improve the fuel performance, alloying elements viz. Zr, Mo, Nb, Ti and fissium are added in the fuel. The first reactor fuels are normally prepared by injection casting. The objective of this work is to compare microstructure, phase-fields and hardness of as-cast four different U-Mo alloy (2, 5, 10 and 33 at.% Mo) fuels with the equilibrium microstructure of the alloys. Scanning electron microscope with energy dispersive spectrometer and optical microscope have been used to characterize the morphology of the as-cast and annealed alloys. The monoclinic α'' phase in as-cast U-10 at.% Mo alloy has been characterized through Rietveld analysis. A comparison of metallographic and Rietveld analysis of as-cast (dendritic microstructure) and annealed U-33 at.% Mo alloy, corresponding to intermetallic compound, has been reported here for the first time. This study will provide in depth understanding of microstructural and phase evolution of U-Mo alloys as fast reactor fuel.

Rietveld refinement of the structures of 1.0 C-S-H and 1.5 C-S-H

KAUST Repository

Battocchio, Francesco; Monteiro, Paulo J.M.; Wenk, Hans-Rudolf

2012-01-01

Low-Q region Rietveld analyses were performed on C-S-H synchrotron XRD patterns, using the software MAUD. Two different crystal structures of tobermorite 11 Å were used as a starting model: monoclinic ordered Merlino tobermorite, and orthorhombic

Structural Rietveld refinement and vibrational study of MgCr{sub x}Fe{sub 2−x}O{sub 4} spinel ferrites

Energy Technology Data Exchange (ETDEWEB)

Sabri, K. [Laboratoire des Sciences et technique de l’Environnement et de la Valorisation, département de Génie des Procédés, Université de Mostaganem, Mostaganem (Algeria); Rais, A., E-mail: amrais@yahoo.com [Laboratoire des Sciences et technique de l’Environnement et de la Valorisation, département de Génie des Procédés, Université de Mostaganem, Mostaganem (Algeria); Taibi, K. [Laboratoire de Science et Génie des Matériaux, USTHB, Alger, Algéria (Algeria); Moreau, M.; Ouddane, B. [Laboratory of LASIR Spectrochemistry, University of Science and Technology, 59650 Villeneuve d’Ascq (France); Addou, A. [Laboratoire des Sciences et technique de l’Environnement et de la Valorisation, département de Génie des Procédés, Université de Mostaganem, Mostaganem (Algeria)

2016-11-15

Spinel ferrites with the general formula MgCr{sub x}Fe{sub 2−x}O{sub 4} (0≤x≤1) were synthesized by the standard ceramic technique and characterized by X-ray diffraction. The XRD patterns confirmed that the mixed ferrite samples are in the cubic spinel structure which is further validated by Rietveld refinement in the space group Fd3m. The crystal structure and cell parameters were refined by Rietveld analysis. The vibrational study was achieved using Fourier Transform-InfraRed (FT-IR) and Raman spectroscopy. From FT-IR band frequencies, the force constants K{sub t} and K{sub o} , for tetrahedral (A) and octahedral (B) sites respectively, have been calculated and discussed with the trend of bond lengths obtained from Rietveld refinement. For all compositions, Raman spectra revealed the five active modes showing the vibration of O{sup 2−} ions at both the A-site and B-site ions. The frequencies trend with chromium content of both FT-IR and Raman spectra showed a shift toward higher values for all modes.

Rietveld refinement of magnetic structures from pulsed-neutron-source powder-diffraction data

International Nuclear Information System (INIS)

Robinson, R.A.; Lawson, A.C.; Larson, A.C.; Von Dreele, R.B.; Goldstone, J.A.

1994-01-01

The General Structure Analysis System, GSAS, has recently been modified to include magnetic neutron- scattering cross-sections. Low-temperature diffraction data have been taken on the hexagonal noncollinear antiferromagnet UPdSn on both the HIPD and the NPD powder diffractometers ail LANSCE. The low-resolution data reveal that the magnetic structure has orthorhombic symmetry (magnetic space group P c m'c2 1 ) between 25K and 40K, and monoclinic symmetry (magnetic space group PC 1121 ) below 25K. The high-resolution data reveal that there are structural distortions with corresponding symmetry changes in each of these phases, to give chemical space groups Cmc2 1 and P2 1 , respectively, while the paramagnetic phase above 40K has space group P6 3 mc. Using GSAS, we have refined data sets from both diffractometers simultaneously, including both magnetic and structural cross-sections. Magnetoelastic coefficients for the distortions have been extracted and we have determined the sign of the coupling between the structural monoclinicity and the magnetic monoclinicity. The magnetic results from Rietveld refinement are in good agreement with model fitting to the integrated intensities of seven independent magnetic reflections and these, in turn, agree with measurements made on the same sample using the constant-wavelength reactor technique. Our results therefore validate, to some level, both the technique of using spallation sources for complicated magnetic structures and the specifics of the GSAS Rietveld code

Rietveld quantitative phase analysis of high surface area commercial alumina doped with niobia

International Nuclear Information System (INIS)

Gomes, L.B.; Pereira, A.S.; Pokorny, A.; Bergmann, C.P.

2014-01-01

The quantification of crystalline phases present in a given material can provide important information about the phenomena related to the diffusion of new elements in a ceramic matrix, as well as the formation and precipitation of minority phases and their microstructural evaluation. In this work, a high content of niobia (16 and 32 %w.t)was added to a high specific surface commercial alumina powder. The specimens were uniaxially pressed (200 MPa) and sintered in two stages: a first step at 1100°C for 3, 6 or 9 hours followed by a second step at 1350°C for 3 hours. The crystalline phases were analyzed by X-ray Diffraction (XRD) and quantified by the Rietveld method. The morphology of the samples was evaluated by Scanning Electron Microscopy (SEM). From the results obtained, some aluminum niobates phases expected for the Al_2O_3-Nb_2O_5 system could be identified as an intergranular phase and their relative fraction was quantified. (author)

Rietveld and impedance analysis of cold and hot rolled duplex and lean duplex steels for application in paper and pulp industry

Energy Technology Data Exchange (ETDEWEB)

Esteves, Luiza; Lins, Vanessa de Freitas Cunha, E-mail: luizaeq@yahoo.com.br [Universidade Federal de Minas Gerais (UFMG), Belo Horizonte, MG (Brazil). Departamento de Engenharia Quimica; Paiva, Paulo Renato Perdigao [Centro Federal de Educacao Tecnologica de Minas Gerais (CEFET), Belo Horizonte, MG (Brazil); Viana, Adolfo Kalergis do Nascimento [APERAM South America, Timoteo, MG (Brazil)

2017-01-15

In this study, X-Ray Diffraction (XRD) and Rietveld Refinement were performed to identify and quantify the ferrite and austenite phase of cold and hot rolled duplex stainless steels (UNS S31803) and lean duplex stainless steels (UNS S32304). Electrochemical impedance spectroscopy (EIS) was applied to evaluate the chemical behavior of duplex and lean duplex stainless steels in white, green, and black liquors of paper and pulp industry. Rietveld analysis results showed a higher austenite content than the standard limit for duplex steels in the hot rolled condition. The hot rolling condition plays a major role in improving corrosion resistance in white liquor mainly for the lean duplex steel. (author)

Rietveld and impedance analysis of cold and hot rolled duplex and lean duplex steels for application in paper and pulp industry

International Nuclear Information System (INIS)

Esteves, Luiza; Lins, Vanessa de Freitas Cunha; Viana, Adolfo Kalergis do Nascimento

2017-01-01

In this study, X-Ray Diffraction (XRD) and Rietveld Refinement were performed to identify and quantify the ferrite and austenite phase of cold and hot rolled duplex stainless steels (UNS S31803) and lean duplex stainless steels (UNS S32304). Electrochemical impedance spectroscopy (EIS) was applied to evaluate the chemical behavior of duplex and lean duplex stainless steels in white, green, and black liquors of paper and pulp industry. Rietveld analysis results showed a higher austenite content than the standard limit for duplex steels in the hot rolled condition. The hot rolling condition plays a major role in improving corrosion resistance in white liquor mainly for the lean duplex steel. (author)

In-situ high-energy X-ray diffraction and batch Rietveld refinement of phase changes in titanium aluminides

International Nuclear Information System (INIS)

Whitfield, R.

2007-01-01

Full text: We have used the Rietveld refinement method for the analysis of high-energy X-ray power diffraction for quantitatve phase analysis. This method has the advantage of being able to model the multiple phases appearing in the diffraction pattern and tell us about the composition of the phases of a sample as we change the temperature. It has been applied to various TiAl compounds allowing us to follow in detail the phase transitions of the intermetallics when heated to around 1400 0 Cand subsequently cooled. Small amounts of additives like V, Cr and Gd as well as signatures from different production processes can be seen to have an effect on the phase transitions. With increasing temperature we can see the evolution of the unit cell due to thermal expansion, chemical segregation and the relative proportion of phase changes

Structural determination of new solid solutions [Y2-x Mx ][Sn2-x Mx ]O7-3x/2 (M = Mg or Zn by Rietveld method

Directory of Open Access Journals (Sweden)

Mohamed Douma

2010-12-01

Full Text Available New [Y2-x Mx][Sn2-x Mx]O7-3x/2 (0 ≤x≤ 0.30 for M = Mg and 0 ≤x≤ 0.36 for M = Zn solid solutions with the pyrochlore structure were synthesized via high-temperature solid-state reaction method. Powder X-ray diffraction (PXRD patterns and Fourier transform infrared (FT-IR spectra showed that these materials are new non-stoichiometric solid solutions with the pyrochlore type structure. The structural parameters for the solids obtained were successfully determined by Rietveld refinement based on the analysis of the PXRD diagrams. Lattice parameter (a of these solid solutions decreases when x increases in both series. All samples obtained have the pyrochlore structure Fd-3m, no. 227 (origin at center -3m with M2+ (M = Mg2+ or Zn2+ cations in Y3+ and Sn4+ sites, thus creating vacancies in the anionic sublattice.

X-ray diffraction analysis of stan nite, wurtz-stan nite and pseudo-cubic quaternary compounds by Rietveld method

Energy Technology Data Exchange (ETDEWEB)

Quintero, M.; Quintero, E.; Moreno, E.; Alvarez, S.; Rincon, C.; Grima, P.; Bocaranda, P.; Rivero, D. [Universidad de Los Andes, Centro de Estudios de Semiconductores, 5101 Merida (Venezuela, Bolivarian Republic of); Marquina, J. [Universidad de Los Andes, Centro de Estudios Avanzados en Optica, 5101 Merida (Venezuela, Bolivarian Republic of); Henao, J. A.; Macias, M. A., E-mail: mquinterg@gmail.com [Universidad Industrial de Santander, Facultad de Ciencias, Escuela de Quimica, Grupo de Investigacion en Quimica Estructural, Apdo. Aereo 678, Bucaramanga (Colombia)

2014-07-01

Room temperature X-ray powder diffraction measurements were carried out on nine polycrystalline samples of the Cu{sub 2}B{sup II}C{sup IV}X{sub 4} (B=Mn, or Fe, or Co; C=Si, or Ge, or Sn; X=S, or Se or Te) magnetic semiconductor compounds. The diffraction patterns were used to show the equilibrium conditions and to derive crystalline parameters values. The results showed that four of these compounds have a tetragonal stan nite structure with space group 142 m(N{sup o} 121), two and orthorhombic wurtz-stan nite structure with space group Pmn2{sub 1}(N{sup o} 31) and three of them and orthorhombic pseudo-cubic structure with space group F222 (N{sup o} 22). In each case, the structure was refined using the Rietveld method. When the obtained atomic parameter values for the tetragonal compounds were plotted as a function of molecular weight W, it was found that the values of the atomic positions, the cation-anion bond distances, tetragonal distortion and internal distortion of the compounds containing S and /or Se lay on different lines. Also, it was found that when the experimental points of the cation-anion bond distances d{sub Cu-VI}, d{sub II-VI} and d{sub IV-VI} were plotted against the effective lattice parameter a{sub c} = (V/N){sup 1/3}, a linear variation of these distances with a{sub c} was obtained. Values of the ionic energy gap C{sub i} and homopolar energy gap E{sub h} using the Phillips-Van Vechten scheme, with the present experimental crystallographic results as well as using the atomic data, were determined. It was found that the observed and predicted values of C{sub i} and E{sub h} lie on the same straight line. (Author)

Gerrit Rietveld. Casas después de la Schroeder

Directory of Open Access Journals (Sweden)

Rafael García

1997-07-01

Full Text Available Las historias de la arquitectura moderna han incidido una y otra vez en un reducido número de obras que por su insistente atención, han llegado a convertirse en hitos imprescindibles. Entre estos edificios canónicos y prácticamente obligados, está la célebre casa Schröder-Schräder (1924' del arquitecto holandés Gerrit Rietveld. Ampliamente conocida por el público interesado, su gran popularidad ha tenido sin embargo, el efecto de dejar en segundo plano el resto de su obra arquitectónica. A ello se debe añadir además, el hecho de que su trayectoria está fundamentalmente asociada al movimiento neoplasticista, lo que ha tenido por resultado desviar la atención de una obra posterior, más difícilmente clasificable. Sin embargo, ello no significa que dicha obra sea en absoluto carente de atractivo.

The role of iron in tetrahedrite and tennantite determined by Rietveld refinement of neutron powder diffraction data

DEFF Research Database (Denmark)

Andreasen, Jens Wenzel; Makovicky, Emil; Lebech, Bente

2008-01-01

Rietveld refinement of neutron powder diffraction data on four samples of synthetic, iron-bearing tetrahedrite (Cu12-xFexSb4S13) with x = 0.28, 0.69, 0.91, 2.19 and four samples of synthetic tennantite (Cu12-xFexAs4S13) with x = 0.33, 0.38, 0.86, 1.5 indicate unambiguously that iron is incorporated...

Structural studies of TiC1−xOx solid solution by Rietveld refinement and first-principles calculations

International Nuclear Information System (INIS)

Jiang, Bo; Hou, Na; Huang, Shanyan; Zhou, Gege; Hou, Jungang; Cao, Zhanmin; Zhu, Hongmin

2013-01-01

The lattice parameters, structural stability and electronic structure of titanium oxycarbides (TiC 1−x O x , 0≤x≤1) solid solution were investigated by Rietveld refinement and first-principles calculations. Series of TiC 1−x O x were precisely synthesized by sintering process under the vacuum. Rietveld refinement results of XRD patterns show the properties of continuous solid solution in TiC 1−x O x over the whole composition range. The lattice parameters vary from 0.4324 nm to 0.4194 nm decreasing with increasing oxygen concentration. Results of first-principles calculations reveal that the disorder C/O structure is stable than the order C/O structure. Further investigations of the vacancy in Ti 1−Va (C 1−x O x ) 1−Va solid solution present that the structure of vacancy segregated in TiO-part is more stable than the disorder C/O structure, which can be ascribed to the Ti–Ti bond across O-vacancy and the charge redistributed around Ti-vacancy via the analysis of the electron density difference plots and PDOS. - Graphical abstract: XRD of series of titanium oxycarbides (TiC 1−x O x , 0≤x≤1) solid solution prepared by adjusting the proportion of TiO in the starting material. Highlights: • Titanium oxycarbides were obtained by sintering TiO and TiC under carefully controlled conditions. • Rietveld refinement results show continuous solid solution with FCC structure in TiC 1−x O x . • The disorder C/O structure is stable than the order C/O structure. • Introduction of vacancy segregated in TiO-part is more stable than disorder C/O structure. • Ti–Ti bond across O-vacancy and the charge redistributed around Ti-vacancy enhance structural stability

Analysis of Polymorphic Nanocrystals of TiO2 by X-Ray Rietveld Refinement and High-Resolution Transmission Electron Microscopy: Acetaldehyde Decomposition

Directory of Open Access Journals (Sweden)

R. Carrera

2008-01-01

Full Text Available In this work, TiO2 nanocrystals were synthesized by the sol-gel method. These materials were annealed at 200 and 500∘C; and characterized by the XRD-Rietveld refinement; and by BET and TEM. As for the low-temperature-treated sample (200∘C, nanocrystals with small crystallite sizes (7 nm and high abundance of anatase, coexisting with the brookite phase, were obtained. Meanwhile, the sample annealed at 500∘C showed an increased crystallite size (22 nm and an important polymorphic increment. The sample annealed at 200∘C showed a high activity in the photocatalytic decomposition of acetaldehyde.

Effect of powder sample granularity on fluorescent intensity and on thermal parameters in x-ray diffraction Rietveld analysis

International Nuclear Information System (INIS)

Sparks, C.J.; Specht, E.D.; Ice, G.E.; Kumar, R.; Zschack, P.; Shiraishi, T.; Hisatsune, K.

1991-01-01

The effect of sample granularity on diffracted x-ray intensity was evaluated by measuring the 2θ dependence of x-ray fluorescence from various samples. Measurements were made in the symmetric geometry on samples ranging from single crystals to highly absorbing coarse powders. A characteristic shape for the absorption correction was observed. A demonstration of the sensitivity of Rietveld refined site occupation parameters is made on CuAu and Cu 50 Au 44 Ni 6 alloys refined with and without granularity corrections. These alloys provide a good example of the effect of granularity due to their large linear x-ray absorption coefficients. Sample granularity and refined thermal parameters obtained from the Rietveld analysis were found to be correlated. Without a granularity correction, the refined thermal parameters are too low and can actually become negative in an attempt to compensate for granularity. A general shape for granularity correction can be included in refinement procedures. If no granularity correction is included, data should be restricted to above 30 degrees 2θ, and thermal parameters should be ignored unless extreme precautions are taken to produce >5 μm particles and high packing densities

Synthesis and structural characterisation using Rietveld and pair distribution function analysis of layered mixed titanium-zirconium phosphates

International Nuclear Information System (INIS)

Burnell, Victoria A.; Readman, Jennifer E.; Tang, Chiu C.; Parker, Julia E.; Thompson, Stephen P.; Hriljac, Joseph A.

2010-01-01

Crystalline metal (IV) phosphates with variable zirconium-to-titanium molar ratios of general formula (Ti 1-x Zr x )(HPO 4 ) 2 .H 2 O have been prepared by precipitation of soluble salts of the metals with phosphoric acid and heating the amorphous solids in 12 M H 3 PO 4 in an autoclave. The new materials are structurally characterised by Rietveld analysis of synchrotron X-ray powder diffraction data and pair distribution function (PDF) analysis of high energy synchrotron X-ray total scattering data. A broad range of zirconium-titanium phosphate solid solutions were formed showing isomorphous substitution of titanium by zirconium in the α-titanium phosphate lattice and vice versa for titanium substitution into the α-zirconium phosphate lattice. In both cases the solubility is partial with the coexistence of two substituted phases observed in samples with nominal compositions between the solubility limits. - Graphical abstract: Layered phosphates of general formula (Ti 1-x Zr x )(HPO 4 ).H 2 O have been prepared by the hydrothermal treatment of amorphous gels in phosphoric acid and characterised by Rietveld analysis of high resolution synchrotron X-ray powder diffraction data and pair distribution function analysis of high energy synchrotron X-ray total scattering data.

Rietveld structure refinement and elastic properties of MgAlxCrxFe2-2xO4 spinel ferrites

Science.gov (United States)

Thummer, K. P.; Tanna, Ashish R.; Joshi, Hiren H.

2017-05-01

MgAlxCrxFe2-2xO4 (x = 0.1, 03 & 0.6) ferrites are synthesized by solid state reaction method. The Rietveld refinement of X-ray diffraction (XRD) data confirms the cubic spinel structure with Fd3m space group. The Fourier Transform Infrared Transmission Spectroscopy (FTIR) is employed to study elastic properties of present systems at 300K. The force constants for tetrahedral (A) and octahedral (B) sites of the spinel lattice are determined by infrared spectral and X-ray diffraction analysis. The elastic constants like bulk modulus, rigidity modulus, Young's modulus, Poisson's ratio and Debye temperature are determined. The vibrational frequency of both the interstitial sites increases as Al-Cr content increases hence the force constant and elastic moduli for all the samples are found to increase for the present ferrite system.

Profex: a graphical user interface for the Rietveld refinement program BGMN.

Science.gov (United States)

Doebelin, Nicola; Kleeberg, Reinhard

2015-10-01

Profex is a graphical user interface for the Rietveld refinement program BGMN . Its interface focuses on preserving BGMN 's powerful and flexible scripting features by giving direct access to BGMN input files. Very efficient workflows for single or batch refinements are achieved by managing refinement control files and structure files, by providing dialogues and shortcuts for many operations, by performing operations in the background, and by providing import filters for CIF and XML crystal structure files. Refinement results can be easily exported for further processing. State-of-the-art graphical export of diffraction patterns to pixel and vector graphics formats allows the creation of publication-quality graphs with minimum effort. Profex reads and converts a variety of proprietary raw data formats and is thus largely instrument independent. Profex and BGMN are available under an open-source license for Windows, Linux and OS X operating systems.

Rietveld refinement and electronic structure studies for the Sm2FeMnO6 new complex perovskite

International Nuclear Information System (INIS)

Landinez Tellez, D.A.; Munevar, J.A.; Arbey Rodriguez, J.M.; Fajardo, F.; Roa-Rojas, J.

2008-01-01

We report synthesis and crystalline structure study of the Sm 2 FeMnO 6 new complex perovskite, by X-ray diffraction experiments and through the application of Rietveld refinement. Results revealed the crystallization of system in a structure given by Pmn21 (no. 31) space group and lattice parameters a=7.621(1) A, b=5.675(3) A and c=5.378(3) A. Ab initio calculations of density of states (DOS) and electronic structure were carried out for this perovskite-like system by the density functional theory (DFT) and using the full-potential linearized augmented plane waves (FP-LAPW) method. All calculations were carried out using spin polarization. Material evidences a conductor-like character, predominantly due to d-xy Fe orbital of the spin down channel. Magnetic response of system has contributions of Fe and Mn spin up orientation. The calculated magnetic moment in cell was 34.48 μ B and the magnetic moment in interstitial was 1.54 μ B

Study of selection and purification of Brazilian bentonite clay by elutriation: a XRF, SEM and Rietveld analysis

Energy Technology Data Exchange (ETDEWEB)

Alves, J.L.; Zanini, A.E.; Souza, M.E. de; Nascimento, M.L.F., E-mail: jeff_eq@yahoo.com.br, E-mail: mlfn@ufba.br [Universidade Federal da Bahia (UFBA/PROTEC/PEI), Salvador, BA (Brazil). Departamento de Engenharia Quimica

2016-01-15

Clays obtained from nature have a lot of impurities. Therefore, for best using of these materials, it is necessary its selection and purification. Thus, the aim of this work is to separate and to purify the smectite fractions using water as a solvent at a low flux mixed with a bentonite clay extracted from a mine in Vitoria da Conquista - Bahia / Brazil. For this a separation method of fractions of expandable clays based on the Stokes' Law was applied - this process is called elutriation, in order to ensure and to expand possible industrial applications of this material. The samples were characterized by analysis of X-ray diffraction, X-ray fluorescence and scanning electron microscopy. The Rietveld method enabled the quantification of main phase minerals: montmorillonite, kaolinite, nontronite and quartz, reaching 85% in mass of montmorillonite phase at the end of the process. Results showed that the method used was efficient to remove almost all quartz, carbonates and organic matter from the sample. It was also observed a monomodal grain size distribution of elutriated materials with thinner grains, around (18.1 ± 1.8) μm at the end of the process. It has been concluded that the method developed and applied showed promising characters to be applied to elutriate kilograms of clays and could be used in industrial scale. (author)

Study of selection and purification of Brazilian bentonite clay by elutriation: a XRF, SEM and Rietveld analysis

Directory of Open Access Journals (Sweden)

J. L. Alves

2016-03-01

Full Text Available Abstract Clays obtained from nature have a lot of impurities. Therefore, for best using of these materials, it is necessary its selection and purification. Thus, the aim of this work is to separate and to purify the smectite fractions using water as a solvent at a low flux mixed with a bentonite clay extracted from a mine in Vitória da Conquista - Bahia / Brazil. For this a separation method of fractions of expandable clays based on the Stokes' Law was applied - this process is called elutriation, in order to ensure and to expand possible industrial applications of this material. The samples were characterized by analysis of X-ray diffraction, X-ray fluorescence and scanning electron microscopy. The Rietveld method enabled the quantification of main phase minerals: montmorillonite, kaolinite, nontronite and quartz, reaching 85% in mass of montmorillonite phase at the end of the process. Results showed that the method used was efficient to remove almost all quartz, carbonates and organic matter from the sample. It was also observed a monomodal grain size distribution of elutriated materials with thinner grains, around (18.1 ± 1.8 μm at the end of the process. It has been concluded that the method developed and applied showed promising characters to be applied to elutriate kilograms of clays and could be used in industrial scale.

Study of selection and purification of Brazilian bentonite clay by elutriation: a XRF, SEM and Rietveld analysis

International Nuclear Information System (INIS)

Alves, J.L.; Zanini, A.E.; Souza, M.E. de; Nascimento, M.L.F.

2016-01-01

Clays obtained from nature have a lot of impurities. Therefore, for best using of these materials, it is necessary its selection and purification. Thus, the aim of this work is to separate and to purify the smectite fractions using water as a solvent at a low flux mixed with a bentonite clay extracted from a mine in Vitoria da Conquista - Bahia / Brazil. For this a separation method of fractions of expandable clays based on the Stokes' Law was applied - this process is called elutriation, in order to ensure and to expand possible industrial applications of this material. The samples were characterized by analysis of X-ray diffraction, X-ray fluorescence and scanning electron microscopy. The Rietveld method enabled the quantification of main phase minerals: montmorillonite, kaolinite, nontronite and quartz, reaching 85% in mass of montmorillonite phase at the end of the process. Results showed that the method used was efficient to remove almost all quartz, carbonates and organic matter from the sample. It was also observed a monomodal grain size distribution of elutriated materials with thinner grains, around (18.1 ± 1.8) μm at the end of the process. It has been concluded that the method developed and applied showed promising characters to be applied to elutriate kilograms of clays and could be used in industrial scale. (author)

Rietveld refinement, dielectric and magnetic properties of Nb modified Bi0.80Ba0.20FeO3 ceramic

Science.gov (United States)

Jangra, Sandhaya; Sanghi, Sujata; Agarwal, Ashish; Rangi, Manisha

2018-05-01

Bi0.80Ba0.20Fe0.95Nb0.05O3 ceramic has been prepared via conventional solid state reaction method. Structure analysis was carried out by X-ray diffraction (XRD) technique at room temperature. XRD pattern confirmed the crystalline nature of prepared sample. Rietveld analysis used for further structural investigations and confirmed the existence of rhombohedral symmetry (R3c space group). The dielectric response shows dispersion at lower frequency range and becomes frequency independent at high frequency. The approximation of conduction mechanism is determined by the temperature dependent behavior of frequency exponent `s'. Fitting results suggests the applicability of small polaron conduction mechanism at lower temperatures and CBH model at higher temperature. Room temperature magnetic measurements give the evidence of significant enhancement in magnetic properties with remanent magnetization (Mr = 0.1218 emu/g) and coercive field (Hc = 3.5342 kOe).

Application of low current intensity electrolytic treatment for the chlorides extraction in underwater archaeological objects of iron. Observation of the mineralogical phases evolution through XRD-Rietveld

International Nuclear Information System (INIS)

Bethencourt, M.; Gil, M. L. A.; Fernandez-Lorenzo, C.; Santos, A.

2004-01-01

With the purpose of optimising a suitable methodology for the conservation of an archaeological object of iron, a low current intensities electrolytic treatment has been applied, to a piece of cast iron, proving to be effective in the extraction of chloride ions from the structure of akaganeite, principal corrosion product of iron in the marine medium. The monitoring of the electrolytic treatment has been proven by applying the Rietveld method to the patterns XRD of samples extracted from the corroded surface before and after the treatment. This method has permitted the unequivocal determination of the akaganeite and its chemical composition. This identification has been corroborated by means of SEM and EDS. After the electrolytic treatment, akaganeite was not present in the sample. (Author) 9 refs

Crystal structures of iron bearing tetrahedrite and tennantite at 25 and 250 degrees C by means of Rietveld refinement of synchrotron data

DEFF Research Database (Denmark)

Friese, K.; Grzechnik, A.; Makovicky, E.

2008-01-01

Rietveld refinement of X-ray synchrotron data was performed for two synthetic tetrahedrite samples, with 0.61 and 1.83 Fe atoms, and two synthetic tennantite samples with 0.10 and 1.23 Fe atoms p.f.u. M-12(Sb,As)(4)S-13. Measurements were performed at 25 and 250 degrees C. For both the phases...

Crystal structure refinement of Ba5Nb4O15 and Ba5Nb4O15-x by Rietveld analysis of neutron and X-ray diffraction data

International Nuclear Information System (INIS)

Pagola, S.; Leyva, G.; Casais, M.T.; Alonso, J.A.; Rasines, I.; Carbonio, R.E.

1996-01-01

Both X-ray and neutron diffraction data were analyzed by the Rietveld method, taking as starting structural model that of the Ba 5 Ta 4 O 15 structure. The results of such an analysis show that the progressive elimination of oxygen ions produce only small changes in the structure. A decrease in the unit-cell parameters as the number of oxygen vacancies increases has been observed, which can be correlated with a gradual loss of oxygen ions in the close-packed layers. No ordering of the oxygen vacancies was found even in the sample with the highest x value, x=0.56. (orig.)

Neutron irradiated uranium silicides studied by neutron diffraction and Rietveld analysis

International Nuclear Information System (INIS)

Birtcher, R.C.; Mueller, M.H.; Richardson, J.W. Jr.; Faber, J. Jr.

1989-11-01

Uranium silicides have been considered for use as reactor fuels in both high power and low enrichment applications. However, U 3 Si was found to become amorphous under irradiation and to become mechanically unstable to rapid growth by plastic flow. U 2 Si 2 appears to be stable against amorphization at low displacement rates, but the extent of this stability is uncertain. Although the mechanisms responsible for plastic flow in U 3 Si and other amorphous systems are unknown, as is the importance of crystal structure for amorphization, it may not be surprising that these materials amorphize, in light of the fact that many radioactive nuclide - containing minerals are known to metaminctize (lose crystallinity) under irradiation. The present experiment follows the detailed changes in the crystal structures of U 3 Si and U 3 Si 2 introduced by neutron bombardment and subsequent uranium fission at room temperature. U-Si seems the ideal system for a neutron diffraction investigation since the crystallographic and amorphous forms can be studied simultaneously by combining conventional Rietveld refinement of the crystallographic phases with Fourier-filtering of the non-crystalline scattering component

Rietveld refinement of Y2O3 using the pearson VII profile shape function

International Nuclear Information System (INIS)

Smrcok, L.

1989-01-01

Very good agreement between the observed and the calculated intensities was obtained using the Pearson VII profile shape function. The variable exponent m could be refined only in the damped iterations involving exclusively the profile parameters. Simultaneous refinement of the m with the positional and/or thermal parameters has led to large oscillations of the shifts of almost all parameters. Precision of the refined atomic coordinates is better than those from previously published Rietveld refinement and is comparable with single crystal results. The degree of serial correlation in residuals has been determined by the use of the Durbin-Watson d statistic. Normal probability plot based on δR i has been almost linear with the slope greater than one. The weighting scheme with w i = 1/y oi has proved to be good first approximation. (author)

Rietveld profile analysis of calcined AlPO/sub 4/-11 using pulsed neutron powder diffraction

Energy Technology Data Exchange (ETDEWEB)

Richardson, J.W. Jr.; Pluth, J.J.; Smith, J.V.

1988-08-01

Aluminium phosphate, AlPO/sub 4/, M/sub r/=121.95, orthorhombic, Icmm (disordered Al, P), Icm2 (ordered Al, P), a=13.5333(8), b=18.4845(10), c=8.3703(4) A, V=2094 A/sup 3/, Z=20, D/sub x/=1.93 g cm/sup -3/, T approx. = 295 K, R/sub wp/=0.031, R/sub F//sup 2/=0.109 (Icmm) and R/sub wp/=0.027, R/sub F//sup 2/=0.058 (Icm2) for 1017 independent reflections. Sample calcined at 873 K and dehydrated at 573 K. Time-of-flight neutron powder diffraction data were taken on the GPPD diffractometer at the Argonne National Laboratory Intense Pulsed Neutron Source. The structure was refined by Rietveld profile analysis in the range d=0.86-3.91 A in two space groups: Icmm assuming no ordering of Al and P, and Icm2 assuming strict alternation of Al and P on tetrahedral nodes. (orig./BHo).

Synthesis and characterization photocatalyst of titanium oxide obtained by the Pechini; Sintese e caracterizacao fotocatalitica do oxido de titanio obtido pelo Metodo Pechini

Energy Technology Data Exchange (ETDEWEB)

Ribeiro, P.C.; Costa, A.C.F.M.; Lira, H.L. [Universidade Federal de Campina Grande (UFCG), PB (Brazil). Departamento de Engenharia de Materiais; Sasaki, J.M. [Universidade Federal do Ceara (UFC), Fortaleza, CE (Brazil). Departamento de Fisica; Santos, S.K., E-mail: pollyanacae@yahoo.com.br [Universidade Federal do Rio de Janeiro (UFRJ), RJ (Brazil). Departamento de Engenharia Quimica

2011-07-01

The photocatalysis using TiO{sub 2} semiconductor has shown great efficiency in the treatment of toxic pollutants and non-biodegradable materials, commonly present in air and domestic and industrial effluents. Thus, the aim of this work is to study the evaluation of photocatalytic activity of TiO{sub 2} samples synthesized by the Pechini method at a ratio of citric acid / metal cation of 2:1 and 4:1. The synthesized samples were characterized by X-ray diffraction, quantification of phases using the Rietveld method of refinement of the structure and after analyzed in photocatalytic bench tests using methyl red dye. The results showed that in a 2:1 ratio, the sample resulted in the formation of 100% of anatase phase, while in the 4:1 ratio sample showed 73.51% of anatase phase and 10.5% of rutile phase. The 4:1 sample showed the best performance discoloring over 70% of the dye for a period close to 24h. (author)

Presence of a monoclinic (Pm) phase in the morphotropic phase boundary region of multiferroic (1 − x)Bi(Ni{sub 1/2}Ti{sub 1/2})O{sub 3}-xPbTiO{sub 3} solid solution: A Rietveld study

Energy Technology Data Exchange (ETDEWEB)

Pandey, Rishikesh, E-mail: akhilesh-bhu@yahoo.com, E-mail: aksingh.mst@itbhu.ac.in; Singh, Akhilesh Kumar, E-mail: akhilesh-bhu@yahoo.com, E-mail: aksingh.mst@itbhu.ac.in [School of Materials Science and Technology, Indian Institute of Technology (Banaras Hindu University), Varanasi 221005 (India)

2014-07-28

We present here the results of structural studies on multiferroic (1 − x)Bi(Ni{sub 1/2}Ti{sub 1/2})O{sub 3}-xPbTiO{sub 3} solid solution using Rietveld analysis on powder x-ray diffraction data in the composition range 0.35 ≤ x ≤ 0.55. The stability region of various crystallographic phases at room temperature for (1 − x)Bi(Ni{sub 1/2}Ti{sub 1/2})O{sub 3}-xPbTiO{sub 3} is determined precisely. Structural transformation from pseudo-cubic (x ≤ 0.40) to tetragonal (x ≥ 0.50) phase is observed via phase coexistence region demarcating the morphotropic phase boundary. The morphotropic phase boundary region consists of coexisting tetragonal and monoclinic structures with space group P4mm and Pm, respectively, stable in composition range 0.41 ≤ x ≤ 0.49 as confirmed by Rietveld analysis. The results of Rietveld analysis completely rule out the coexistence of rhombohedral and tetragonal phases in the morphotropic phase boundary region reported by earlier workers. A comparison between the bond lengths for “B-site cations-oxygen anions” obtained after Rietveld refinement, with the bond length calculated using Shannon-Prewitt ionic radii, reveals the ionic nature of B-O (Ni/Ti-O) bonds for the cubic phase and partial covalent character for the other crystallographic phases.

Rietveld refinement and dielectric relaxation of a new rare earth based double perovskite oxide: BaPrCoNbO{sub 6}

Energy Technology Data Exchange (ETDEWEB)

Bharti, Chandrahas, E-mail: bharti.chandrahas@gmail.com [Sensor and Actuator Division, CSIR-Central Glass and Ceramic Research Institute, 196, Raja SC Mullick Road, Kolkata 700032 (India); Das, Mrinmoy K.; Sen, A. [Sensor and Actuator Division, CSIR-Central Glass and Ceramic Research Institute, 196, Raja SC Mullick Road, Kolkata 700032 (India); Chanda, Sadhan; Sinha, T.P. [Department of Physics, Bose Institute, 93/1, Acharya Prafulla Chandra Road, Kolkata-700009 (India)

2014-02-15

A new rare earth based double perovskite oxide barium praseodymium cobalt niobate, BaPrCoNbO{sub 6} (BPCN) is synthesized by solid-state reaction technique. Rietveld analysis of X-ray diffraction (XRD) data shows that the compound crystallizes in a perovskite like tetragonal structure which belongs to the I4/mmm space group with lattice parameters a=b=5.6828(9) Å, c=8.063(2) Å. Structural analysis reveals 1:1 ordered arrangement for the Co{sup 2+} and Nb{sup 5+} cations over the six-coordinate B-sites of BPCN. The superlattice line (1 0 1) at 2θ=19.10° arising from the alternate ordering of Co{sup 2+} and Nb{sup 5+} sites is observed in the XRD pattern which confirms the presence of cation ordering in BPCN. Fourier transform infrared spectrum shows two phonon modes of the sample due to the antisymmetric NbO{sub 6} stretching vibration. The relaxation dynamics of the conductive process in BPCN is investigated in the temperature range 303 to 503 K and in the frequency range 100 Hz to 1 MHz using impedance spectroscopy. The relaxation mechanism of the sample in the framework of electric modulus formalism is modeled by Davidson–Cole model (DCM). The values of α (distribution of relaxation time) for the DCM varies from 0.1 to 0.3 which suggests the asymmetric distribution of relaxation time for BPCN. The activation energy of the sample, calculated from both conductivity and modulus spectra, are found to be almost the same ∼0.4 eV, which indicates that the conduction mechanism for BPCN is polaron hopping. The scaling behaviour of the imaginary part of electric modulus suggests that the relaxation follows the same mechanism at various temperatures. - Graphical abstract: Rietveld refinement plot for BPCN. Inset shows the schematic presentation of the BPCN tetragonal unit cell. The Co{sup 2+} atoms are located at the centers of the CoO{sub 6} (blue) octahedra. The Nb{sup 5+} atoms are located at the centers of the NbO{sub 6} (green) octahedra. Display Omitted

Structural and electrochemical characterization of calcium cobaltites (Ca{sub 3}Co{sub 4}O{sub 9}) obtained by the modified Pechini Method; Caracterizacao estrutural e eletroquimica de cobaltita de calcio (Ca{sub 3}Co{sub 4}O{sub 9}) obtida pelo Metodo Pechini modificado

Energy Technology Data Exchange (ETDEWEB)

Silva, R.M.; Aquino, F. de M.; Macedo, D. A. de, E-mail: rinaldo_mendesa@hotmail.com [Universidade Federal da Paraiba (UFPB), Joao Pessoa, PB (Brazil)

2016-07-01

This work deals with the synthesis and characterization of calcium cobaltite (Ca{sub 3}Co{sub 4}O{sub 9}, C349), a p-type semiconductor with high Seebeck coefficient (S), high electrical conductivity and low thermal conductivity that has emerged as thermoelectric material. The synthesis method used to obtain the compound C349 uses commercial gelatin as complexing and polymerizing agent. The obtained material was characterized by X-ray diffraction with Rietveld refinement of the diffraction data. The results indicated that the modified Pechini method using gelatin allows to obtain powders of calcium cobaltite (with monoclinic structure) associated with a small content (2% by volume) of Co{sub 3}O{sub 4} with cubic structure. Impedance spectroscopy measurements in air indicated that the composite C349/Co{sub 3}O{sub 4} is a promising material for use as solid oxide fuel cell cathode.(author)

Rietveld refinement of the crystal structures of Rb2XSi5O12 (X = Ni, Mn

Directory of Open Access Journals (Sweden)

Anthony M. T. Bell

2016-02-01

Full Text Available The synthetic leucite silicate framework mineral analogues Rb2XSi5O12 {X = Ni [dirubidium nickel(II pentasilicate] and Mn [dirubidium manganese(II pentasilicate]} have been prepared by high-temperature solid-state synthesis. The results of Rietveld refinements, using X-ray powder diffraction data collected using Cu Kα X-rays, show that the title compounds crystallize in the space group Pbca and adopt the cation-ordered structure of Cs2CdSi5O12 and other leucites. The structures consist of tetrahedral SiO4 and XO4 units sharing corners to form a partially substituted silicate framework. Extraframework Rb+ cations sit in channels in the framework. All atoms occupy the 8c general position for this space group. In these refined structures, silicon and X atoms are ordered onto separate tetrahedrally coordinated sites (T-sites. However, the Ni displacement parameter and the Ni—O bond lengths suggest that for the X = Ni sample, there may actually be some T-site cation disorder.

Rietveld refinement and dielectric studies of Bi{sub 0.8}Ba{sub 0.2}FeO{sub 3} ceramic

Energy Technology Data Exchange (ETDEWEB)

Kaswan, Kavita, E-mail: kaswan.kavita@gmail.com; Agarwal, Ashish; Sanghi, Sujata; Rangi, Manisha; Jangra, Sandhaya; Singh, Ompal [Department of Applied Physics, Guru Jambheshwar University of Science and Technology, Hisar 125001, Haryana (India)

2016-05-23

Polycrystalline Bi{sub 0.8}Ba{sub 0.2}FeO{sub 3} ceramic has been synthesized via conventional solid state reaction technique. The Rietveld refinement of x-ray powder diffraction revealed that the sample has a rhombohedral crystal structure (space group R3c). With increase in temperature, the values of dielectric constant (ϵ′) and dielectric loss (tan δ) are found to be increase at different frequencies which may be the result of increase in the number of charge carriers and their mobilities due to the thermal activation. Further the ac conductivity data is analyzed by using Jonscher’s universal power law. The values of frequency exponent ‘s’ lies in the range 0.2 ≤ s ≤ 0.7 and decreases with increase in temperature which can be explained on the basis of CBH (Correlated Barrier Height) model.

Rietveld refinement of the structures of 1.0 C-S-H and 1.5 C-S-H

KAUST Repository

Battocchio, Francesco

2012-11-01

Low-Q region Rietveld analyses were performed on C-S-H synchrotron XRD patterns, using the software MAUD. Two different crystal structures of tobermorite 11 Å were used as a starting model: monoclinic ordered Merlino tobermorite, and orthorhombic disordered Hamid tobermorite. Structural modifications were required to adapt the structures to the chemical composition and the different interlayer spacing of the C-S-H samples. Refinement of atomic positions was done by using special constraints called fragments that maintain interatomic distances and orientations within atomic polyhedra. Anisotropic crystallite size refinement showed that C-S-H has a nanocrystalline disordered structure with a preferred direction of elongation of the nanocrystallites in the plane of the Ca interlayer. The quality of the fit showed that the monoclinic structure gives a more adequate representation of C-S-H, whereas the disordered orthorhombic structure can be considered a more realistic model if the lack of long-range order of the silica chain along the c-direction is assumed. © 2012 Elsevier Ltd. All rights reserved.

In situ X-ray Rietveld analysis of Ni-YSZ solid oxide fuel cell anodes during NiO reduction in H2

International Nuclear Information System (INIS)

Reyes Rojas, A; Esparza-Ponce, H E; Fuentes, L; Lopez-Ortiz, A; Keer, A; Reyes-Gasga, J

2005-01-01

A synthesis and characterization of solid oxide fuel cell (SOFC) anodes of nickel with 8%mol yttrium stabilized zirconia (Ni-YSZ) is presented. Attention was focused on the kinetics and phase composition associated with the transformation of NiO-YSZ to Ni-YSZ. The anodes were prepared with an alternative synthesis method that includes the use of nickel acetylacetonate as an inorganic precursor to obtain a highly porous material after sintering at 1400 deg. C and oxide reduction (NiO-YSZ → Ni-YSZ) at 800 deg. C for 8 h in a tubular reactor furnace using 10% H 2 /N 2 . The obtained material was compressed by unidirectional axial pressing into 1 cm-diameter discs with 15-66 wt% Ni and calcinated from room temperature to 800 deg. C. A heating rate of 1 deg. C min -1 showed the best results to avoid any anode cracking. Their structural and chemical characterization during the isothermal reduction were carried out by in situ time-resolved X-ray diffraction, refined with the Rietveld method (which allowed knowing the kinetic process of the reduction), scanning electron microscopy and X-ray energy dispersive spectroscopy. The results showed the formation of tetragonal YSZ 8%mol in the presence of nickel, a decrement in the unit cell volume of Ni and an increment of Ni in the Ni-YSZ anodes during the temperature reduction. The analysis indicated that the Johnson-Mehl-Avrami equation is unable to provide a good fit to the kinetics of the phase transformation. Instead, an alternative equation is presented

Rietveld refinement and dielectric properties of (Na{sub 0.5}Bi{sub 0.5}TiO{sub 3})-(Bi{sub 0.8}Ba{sub 0.2}FeO{sub 3}) ceramics

Energy Technology Data Exchange (ETDEWEB)

Kaswan, Kavita, E-mail: kaswan.kavita@gmail.com; Agarwal, Ashish; Sanghi, Sujata; Singh, Ompal [Department of Applied Physics, Guru Jambheshwar University of Science and Technology, Hisar-125001 (India)

2015-06-24

(1-x)(Na{sub 0.5}Bi{sub 0.5}TiO{sub 3})-x(Bi{sub 0.8}Ba{sub 0.2}FeO{sub 3}) lead free ceramics (NBT, NBT-BBFO; x = 0.0, 0.1 respectively) have been synthesized by conventional solid state reaction method. Crystalline phase of sintered ceramics was investigated at room temperature using X-ray diffraction. Rietveld refinement of XRD data performed by FullProf revealed that both the samples exhibited rhombohedral structure with R3c space group. Dielectric properties of these ceramics were studied at different temperatures in a wide frequency range using impedance analyzer. Dielectric constant and dielectric loss were found to be increase with increase of BBFO content. The prepared ceramics exhibit a broad maximum in dielectric permittivity at 593K and dispersive permittivity at high temperatures. The NBT-BBFO sample shows a relaxor ferroelectric behavior at different frequencies.

Preparation and Crystal Structures of Some AIVB2IIO4 Compounds: Powder X-Ray Diffraction and Rietveld Analysis

Directory of Open Access Journals (Sweden)

K. Jeyadheepan

2014-01-01

Full Text Available The AIVB2IIO4 compounds such as cadmium tin oxide (Cd2SnO4 or CTO and zinc tin oxide (Zn2SnO4 or ZTO are synthesized by solid state reaction of the subsequent binary oxides. The synthesized powders were analyzed through the powder X-ray diffraction (PXRD. Cell search done on the PXRD patterns shows that the Cd2SnO4 crystallizes in orthorhombic structure with space group Pbam and the cell parameters as a=5.568(2 Å, b=9.894(3 Å, and c=3.193(1 Å and the Zn2SnO4 crystallizes as cubic with the space group Fd3 -m and with the cell parameter a=8.660(2 Å. Rietveld refinement was done on the PXRD patterns to get the crystal structure of the Cd2SnO4 and Zn2SnO4 and to define the site deficiency of atoms which causes the electrical properties of the materials.

Characterization of an ecological binder for mortars obtained from recycling of ladle furnace slag; Caracterizacao de aglomerante ecologico para argamassas obtido a partir da reciclagem de escoria de forno panela

Energy Technology Data Exchange (ETDEWEB)

Marinho, A.B.; Santos, C.M.; Fontes, W.C.; Matias, A.C.P.; Brigolini, G.J.; Peixoto, R.A.F. [Universidade Federal de Ouro Preto (UFOP), MG (Brazil). Departamento de Engenhaira Civil; Carvalho, J.F., E-mail: josemaria.carvalho@ufv.br [Universidade Federal de Vicosa (UFV), MG (Brazil). Departamento de Engenharia Civil

2016-07-01

A sustainable binder obtained from recycling of a ladle furnace slag from Piracicaba, Sao Paulo, was produced in Laboratory of Construction Materials of Federal University of Ouro Preto (UFOP). A characterization work was performed and the results are presented. The physical, chemical and mineralogical properties was obtained using, among others, the following techniques: X-ray fluorescence (XRF), X-ray diffraction (XRD) with Rietveld refining method, optical microscopy and Scanning electronic microscopy (SEM) with energy dispersive spectroscopy (EDS). The chemical analysis showed predominance of CaO and SiO{sub 3}; the mineralogical analysis pointed the predominant presence of calcium-olivine, merwinite and pyroxene and; the images showed predominance of angulous and elongated grains. According to results, the material was classified as a hydraulic binder, with characteristics comparable to hydraulic limes. (author)

Electronic structure and magnetic properties of FeWO{sub 4} nanocrystals synthesized by the microwave-hydrothermal method

Energy Technology Data Exchange (ETDEWEB)

Almeida, M.A.P. [INCTMN-DQ-Universidade Federal de Sao Carlos, Sao Carlos, P.O. Box 676, 13565-905, SP (Brazil); Cavalcante, L.S., E-mail: laeciosc@bol.com.br [INCTMN-Universidade Estadual, Paulista, P.O. Box 355, 14801-907, Araraquara, SP (Brazil); Morilla-Santos, C.; Filho, P.N. Lisboa [MAv-Universidade Estadual, Paulista, P.O. Box 473, 17033-360, Bauru, SP (Brazil); Beltran, A.; Andres, J.; Gracia, L. [Department de Quimica Fisica i Analitica, Universitat Jaume I, E-12071 Castello (Spain); Longo, E. [INCTMN-DQ-Universidade Federal de Sao Carlos, Sao Carlos, P.O. Box 676, 13565-905, SP (Brazil); INCTMN-Universidade Estadual, Paulista, P.O. Box 355, 14801-907, Araraquara, SP (Brazil)

2012-11-15

This communication reports that FeWO{sub 4} nanocrystals were successfully synthesized by the microwave-hydrothermal method at 443 K for 1 h. The structure and shape of these nanocrystals were characterized by X-ray diffraction, Rietveld refinement, and transmission electron microscopy. The experimental results and first principles calculations were combined to explain the electronic structure and magnetic properties. Experimental data were obtained by magnetization measurements for different applied magnetic fields. Theoretical calculations revealed that magnetic properties of FeWO{sub 4} nanocrystals can be assigned to two magnetic orderings with parallel or antiparallel spins in adjacent chains. These factors are crucial to understanding of competition between ferro- and antiferromagnetic behavior. Highlights: Black-Right-Pointing-Pointer Monophasic FeWO{sub 4} nanocrystals were synthesized by the microwave-hydrothermal method. Black-Right-Pointing-Pointer Rietveld refinement and clusters model for monoclinic structure Black-Right-Pointing-Pointer Magnetic properties of FeWO{sub 4} nanocrystals at different temperatures.

ESTUDIO DE LAS FASES MINERALÓGICAS DEL CLÍNKER EN UNA CEMENTERA ESPAÑOLA, UTILIZANDO EL MÉTODO DE RIETVELD

Directory of Open Access Journals (Sweden)

ANA M. CASTAÑÓN

2012-01-01

Full Text Available Con el objetivo de implantar un método de control de calidad de forma continua en una fábrica de cementos española, para mejorar las características del producto final, se están desarrollando nuevas metodologías de caracterización. El método de Rietveld [1] se ha utilizado con éxito para analizar la composición de las fases principales del clínker. Utilizando esta metodología, se ha llevado a cabo un estudio para cuantificar adecuadamente la fase minoritaria de Cal Libre, de gran importancia en la calidad del clínker. El método ha permitido obtener unos resultados satisfactorios en muestras cuyos contenidos superan el 3% de CaO. Estos resultados son posibles combinando adecuadamente las técnicas de difracción y fluorescencia de rayos-X, así como los resultados del análisis por vía química.

The analysis of powder diffraction data

International Nuclear Information System (INIS)

David, W.I.F.; Harrison, W.T.A.

1986-01-01

The paper reviews neutron powder diffraction data analysis, with emphasis on the structural aspects of powder diffraction and the future possibilities afforded by the latest generation of very high resolution neutron and x-ray powder diffractometers. Traditional x-ray powder diffraction techniques are outlined. Structural studies by powder diffraction are discussed with respect to the Rietveld method, and a case study in the Rietveld refinement method and developments of the Rietveld method are described. Finally studies using high resolution powder diffraction at the Spallation Neutron Source, ISIS at the Rutherford Appleton Laboratory are summarized. (U.K.)

Aplicación de tratamiento electroquímico a baja intensidad de corriente para la extracción de cloruros en objetos arqueológicos de hierro de procedencia subacuática. Observación de la evolución de fases mineralógicas mediante XRD-Rietveld

Directory of Open Access Journals (Sweden)

Bethencourt, M.

2004-12-01

Full Text Available With the purpose of optimising a suitable methodology for the conservation of an archaeological object of iron, a low current intensities electrolytic treatment has been applied, to a piece of cast iron, proving to be effective in the extraction of chloride ions from the structure of akaganeite, principal corrosion product of iron in the marine medium. The monitoring of the electrolytic treatment has been proven by applying the "Rietveld" method to the patterns XRD of samples extracted from the corroded surface before and after the treatment. This method has permitted the unequivocal determination of the akaganeite and its chemical composition. This identification has been corroborated by means of SEM and EDS. After the electrolytic treatment, akaganeite was not present in the sample.

Con objeto de optimizar una metodología adecuada para la conservación de una pieza de hierro arqueológico de fundición, se ha aplicado un tratamiento electrolítico a bajas intensidades de corriente, demostrando su efectividad en la extracción de iones cloruro de la estructura de akaganeita, principal producto de corrosión del hierro en medio marino. La monitorización del proceso se ha comprobado aplicando el método Rietveld a los patrones XRD de muestras extraídas de la superficie corroída antes y después del tratamiento. Este método ha permitido la determinación inequívoca de la akaganeita y la composición química de este oxihidróxido de hierro no estequiométrico. Dicha identificación se corrobora mediante SEM y EDS. Después del tratamiento electrolítico la akaganeita no está presente en la muestra.

Preparation and characterization of novel nanocomposites of inorganic/polysaccharide type =

Science.gov (United States)

Oliveira, Fabiane Costa

O uso de polimeros naturais no ambito da preparacao de nanocompositos nao tem sido tao amplamente estudado quando comparado com os polimeros sinteticos. Assim, esta tese tem como objectivo estudar metodologias para a preparacao de novos materiais nanocompositos sob a forma de dispersoes e filmes utilizando polissacarideos como matriz. A tese esta dividida em cinco capitulos sendo o ultimo capitulo dedicado as conclusoes gerais e a sugestoes para trabalhos futuros. Inicialmente e apresentada uma breve revisao bibliografica sobre os principais temas colocando esta tese em contexto. Consideracoes sobre o uso de polimeros naturais e a sua combinacao com a utilizacao de nanoparticulas inorganicas para a fabricacao de novos bionanocomposites sao descritas e os objectivos e outline da tese sao tambem apresentados. No segundo capitulo, a preparacao de particulas de silica puras ou modificadas bem como a sua caracterizacao por FTIR, SEM, TEM, TGA, DLS (tamanho e potencial zeta) e medicoes de angulo de contacto sao discutidas. De modo a melhorar a compatibilidade da silica com os polissacarideos, as particulas SiO2 foram modificados com dois compostos do tipo organosilano: 3- metacril-oxipropil-trimetoxissilano (MPS) e 3-aminopropil-trimetoxissilano (APS). As particulas SiO2 MPS foram posteriormente encapsuladas com de poli(metacrilato de glicidilo) utilizando a tecnica de polimerizacao em emulsao. A utilizacao dos nanocompositos resultantes na preparacao de dispersoes de bionanocompositos nao foi bem sucedida e por esse motivo nao os estudos nao foram prosseguidos. O uso de SiO2 APS na preparacao de dispersoes bionanocomposite foi eficiente. No terceiro capitulo e apresentada uma revisao sobre dispersoes bionanocompositas e respectiva caracterizacao destacando aspectos fundamentais sobre reologia e microestrutura. Em seguida, e discutido o estudo sistematico realizado sobre o comportamento reologico de dispersoes de SiO2 utilizando tres polissacarideos distintos no que

Solution combustion method for synthesis of nanostructured hydroxyapatite, fluorapatite and chlorapatite

Science.gov (United States)

Zhao, Junjie; Dong, Xiaochen; Bian, Mengmeng; Zhao, Junfeng; Zhang, Yao; Sun, Yue; Chen, JianHua; Wang, XuHong

2014-09-01

Hydroxyapatite (HAP), fluorapatite (Fap) and chlorapatite (Clap) were prepared by solution combustion method with further annealing at 800 °C. The characterization and structural features of the synthesized powders were evaluated by the powder X-ray diffraction (XRD, Fourier transform infrared spectroscopy (FT-IR), scanning electron microscope (SEM) and transmission electron microscopy (TEM) techniques. Characterization results from XRD and Rietveld analysis revealed that OH- in the HAP lattice were gradually substituted with the increase of F- and Cl- content and totally substituted at the molar concentration of 0.28 and 0.6, respectively. The results from FI-IR have also confirmed the incorporation of substituted anions in the apatite structure.

Rietveld refinement of the crystal structure of perovskite solar cells using CH3NH3PbI3 and other compounds

Science.gov (United States)

Ando, Yuji; Ohishi, Yuya; Suzuki, Kohei; Suzuki, Atsushi; Oku, Takeo

2018-01-01

The crystal structures of perovskite thin films including CH3NH3PbI3, CH3NH3Pb1-xSbxI3, and CH3NH3PbI3-yCly in the solar cell configuration were studied by using Rietveld refinement. For the CH3NH3PbI3 and CH3NH3Pb1-xSbxI3 samples, satisfactory agreement with the measured profiles was obtained with a weighted profile R-factor (Rwp) of as low as 3%. It was shown that the site occupancy of methylammonium (MA) was decreased in the antimonized cell due to the compensation effect of an increased positive charge brought about by replacing Pb2+ with Sb3+. Photovoltaic measurements showed that the power conversion efficiency was enhanced by adding a small amount of Sb to the CH3NH3PbI3 cell, but it was monotonically decreased as the mole fraction of Sb exceeded 0.03. This variation of the conversion efficiency was considered as a result of suppressed crystallization of PbI2 and carrier recombination via MA vacancies in the antimonized cells. In the case of CH3NH3PbI2.88Cl0.12 sample, the agreement with the measured profile with an Rwp of as high as 7% suggested the co-existence of cubic and tetragonal phases in the chlorinated cell.

Validation of the method of quantitative phase analysis by X-ray diffraction in API: case of Tibolone

International Nuclear Information System (INIS)

Silva, R P; Ambrósio, M F S; Epprecht, E K; Avillez, R R; Achete, C A; Kuznetsov, A; Visentin, L C

2016-01-01

In this study, different structural and microstructural models applied to X-ray analysis of powder diffraction data of polymorphic mixtures of known concentrations of Tibolone were investigated. The X-ray data obtained in different diffraction instruments were analysed via Rietveld method using the same analytical models. The results of quantitative phase analysis show that regardless of the instrument used, the values of the calculated concentrations follow the same systematics with respect to the final errors. The strategy to select a specific analytical model that leads to lower measurement errors is here presented. (paper)

Analysis of the zirconia structure by 'ab initio' and Rietveld methods

International Nuclear Information System (INIS)

Bechepeche, A.P.; Nasar, R.S.; Longo, E.; Treu Junior, O.; Varela, J.A.

1995-01-01

The zirconia was doped with 0,113 mol of Mg O e 0,005 mol of Ti O 2 , and it was calcined in 1550 d eg C and it was analyzed by XRD. The results shows that pure zirconia contains 96,19% of monoclinic phase and 3,18% of cubic. However, the doping magnesia stabilizes the zirconia in 17,24 of monoclinic; 29,63 of tetragonal and 53,13% of cubic phase. The addition of titanium in zirconia gives 25,85% of tetragonal phase and 37,66% of cubic, and this shows the no stabilizing action of this transition metal. By the other side, the results with ab-initio calculating shows the same tendency resulting in the next values of total energy: pure zirconia - monoclinic -11.316,86ua; tetragonal -8742,09 ua and cubic -8742,80 ua and Zr O 2 Ti O 2 system - monoclinic -9463,02 ua, tetragonal -9459,39 ua and cubic -9459,97 ua (author)

Phase quantification of mullite-zirconia and zircon commercial powders using PAC and XRD techniques

Energy Technology Data Exchange (ETDEWEB)

Rendtorff, Nicolas M.; Conconi, Maria S.; Aglietti, Esteban F. [Centro de Tecnologia de Recursos Minerales y Ceramica (CETMIC: CONICET-CIC) (Argentina); Chain, Cecilia Y.; Pasquevich, Alberto F. [Universidad Nacional de La Plata, Departamento de Fisica, IFLP, Facultad de Ciencias Exactas (Argentina); Rivas, Patricia C. [CONICET (Argentina); Martinez, Jorge A., E-mail: toto@fisica.unlp.edu.ar; Caracoche, Maria C. [Universidad Nacional de La Plata, Departamento de Fisica, IFLP, Facultad de Ciencias Exactas (Argentina)

2010-06-15

The short range technique of the Perturbed Angular Correlation (PAC) and x-ray diffraction (Rietveld) methods have been employed to determine the phase content in commercial mullite-zirconia and zircon raw materials that are ordinarily used to produce ceramic materials. The PAC technique, which probes zirconium-containing compounds at nanoscopic level, showed that zircon contains crystalline ZrSiO{sub 4} and an important amount of a structurally distorted zircon, which is also observed accompanying monoclinic zirconia in mullite-zirconia. This particular zircon phase was not detected by the long range x-ray diffraction-Rietveld technique. After an annealing treatment, important changes in crystalline contents of the powders allow confirming, by the x-ray diffraction-Rietveld method, the preexistence of this particular zircon phase. This fact must be taken into account when preparing multicomposites based on the present raw materials.

Rietveld refinement of the orthorhombic Pbca structures of Rb2CdSi5O12, Cs2MnSiO5O12, Cs2CoSi5O12 and Cs2NiSi5O12 leucites by synchrotron X-ray powder diffraction

International Nuclear Information System (INIS)

Bell, A.M.T.; Henderson, C.M.B.

1996-01-01

Analysis of high-resolution synchrotron X-ray powder diffraction patterns for hydrothermally synthesized Rb 2 CdSi 5 O 12 and Cs 2 MnSi 5 O 12 leucite analogues, and dry-synthesized Cs 2 CoSi 5 O 12 and Cs 2 NiSi 5 O 12 leucite analogues showed that they have an orthorhombic Pbca structure. The structures have been refined by the Rietveld method, showing that the tetrahedrally coordinated atoms (Si, Cd, Mn, Co and Ni) are ordered on separate sites. The Cs 2 MnSi 5 O 12 , Cs 2 CoSi 5 O 12 and Cs 2 NiSi 5 O 12 leucite samples are unusual in containing SiO 4 tetrahedra which are more distorted, on average, than the larger MnO 4 , CoO 4 and NiO 4 tetrahedra. The JCPDS file numbers for Rb 2 CdSi 5 O 12 , Cs 2 MnSi 5 O 12 and Cs 2 CoSi 5 O 12 are 46-1491, 46-1492 and 46-1493, respectively. (orig.)

Nano sized La2Co2O6 double perovskite synthesized by sol gel method

Science.gov (United States)

Solanki, Neha; Lodhi, Pavitra Devi; Choudhary, K. K.; Kaurav, Netram

2018-05-01

We report here the synthesis of double perovskite La2Co2O6 (LCO) compound by a sol gel route method. The double perovskite structure of LCO system was confirmed via X-ray diffraction (XRD) analysis. Further, the lattice parameter, unit cell volume and bond length were refined by means of rietveld analysis using the full proof software. Debye Scherer formula was used to determine the particle size. The compound crystallized in triclinic structure with space group P-1 in ambient condition. We also obtained Raman modes from XRD spectra of poly-crystalline LCO sample. These results were interpreted for the observation of phonon excitations in this compound.

Study and characterization of the hexa ferrite Ba{sub 2}Co{sub 2}Fe{sub 12}O{sub 22} (Co{sub 2}-Y); Sintese e caracterizacao da hexaferrita Ba{sub 2}Co{sub 2}Fe{sub 12}O{sub 22} (Co{sub 2}-Y)

Energy Technology Data Exchange (ETDEWEB)

Pires Junior, G.F.M.; Rodrigues, H.O. [Universidade Federal do Ceara (DETI/UFC), Fortaleza, CE (Brazil). Dept. de Teleinformatica; Sales, J.C [Universidade Estadual Vale do Acarau (UVA), Fortaleza, CE (Brazil). Dept. de Engenharia; Sancho, E.O. [Universidade Federal do Ceara (UFC), Fortaleza, CE (Brazil). Dept. de Engenharia de Materiais; Sombra, A.S.B. [Universidade Federal do Ceara (LOCEM/UFC), Fortaleza, CE (Brazil). Dept. de Fisica. Lab. de Telecomunicacoes e Ciencias e Engenharia de Materiais

2009-07-01

The objective of this work is to synthesize and to characterize the Hexaferrita Ba2Co{sub 2}Fe{sub 12}O{sub 22} (Co{sub 2}Y). The Y-type Hexaferrita (Co{sub 2}Y) was prepared by the ceramic conventional method. The mixed powder by 1 h was calcined at 1050 deg C for 3 h. After of the calcination the powders were characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD) using a diffractometer DMAXB of the Rigaku (Japan), CuK{sub {alpha}} radiation ({lambda}=1.5405 angstrom) in a tax of 0.5 deg /min and linear band (20 deg at 80 deg) in 2{theta}. The characterization more detailed by XRD was made using the DBWS9807a program that uses the method of Rietveld for refinement of crystalline structures and confirmed the isolated attainment of the phase (Co{sub 2}Y) with hexagonal crystalline structure (a = b = 5,8560 angstrom and c = 43,4977 angstrom; {alpha} = {beta} = 90 deg and {gamma} = 120 deg) with density and volume of the unit cell calculated of 5.45 g/cm{sup 3} and 1292,3 angstrom respectively. (author)

Analysis of the zirconia structure by `ab initio` and Rietveld methods; Analise da estrutura da zirconia por metodos `Ab initio` e de Rietveld

Energy Technology Data Exchange (ETDEWEB)

Bechepeche, A.P.; Nasar, R.S.; Longo, E. [Sao Carlos Univ., SP (Brazil). Dept. de Quimica; Treu Junior, O.; Varela, J.A. [UNESP, Araraquara, SP (Brazil). Inst. de Quimica

1995-12-31

The zirconia was doped with 0,113 mol of Mg O e 0,005 mol of Ti O{sub 2}, and it was calcined in 1550{sup d}eg C and it was analyzed by XRD. The results shows that pure zirconia contains 96,19% of monoclinic phase and 3,18% of cubic. However, the doping magnesia stabilizes the zirconia in 17,24 of monoclinic; 29,63 of tetragonal and 53,13% of cubic phase. The addition of titanium in zirconia gives 25,85% of tetragonal phase and 37,66% of cubic, and this shows the no stabilizing action of this transition metal. By the other side, the results with ab-initio calculating shows the same tendency resulting in the next values of total energy: pure zirconia - monoclinic -11.316,86ua; tetragonal -8742,09 ua and cubic -8742,80 ua and Zr O{sub 2} Ti O{sub 2} system - monoclinic -9463,02 ua, tetragonal -9459,39 ua and cubic -9459,97 ua (author) 3 figs., 2 tabs.

Method for fitting crystal field parameters and the energy level fitting for Yb3+ in crystal SC2O3

International Nuclear Information System (INIS)

Qing-Li, Zhang; Kai-Jie, Ning; Jin, Xiao; Li-Hua, Ding; Wen-Long, Zhou; Wen-Peng, Liu; Shao-Tang, Yin; Hai-He, Jiang

2010-01-01

A method to compute the numerical derivative of eigenvalues of parameterized crystal field Hamiltonian matrix is given, based on the numerical derivatives the general iteration methods such as Levenberg–Marquardt, Newton method, and so on, can be used to solve crystal field parameters by fitting to experimental energy levels. With the numerical eigenvalue derivative, a detailed iteration algorithm to compute crystal field parameters by fitting experimental energy levels has also been described. This method is used to compute the crystal parameters of Yb 3+ in Sc 2 O 3 crystal, which is prepared by a co-precipitation method and whose structure was refined by Rietveld method. By fitting on the parameters of a simple overlap model of crystal field, the results show that the new method can fit the crystal field energy splitting with fast convergence and good stability. (condensed matter: electronic structure, electrical, magnetic, and optical properties)

A simple dissolved metals mixing method to produce high-purity MgTiO3 nanocrystals

International Nuclear Information System (INIS)

Pratapa, Suminar; Baqiya, Malik A.; Istianah,; Lestari, Rina; Angela, Riyan

2014-01-01

A simple dissolved metals mixing method has been effectively used to produce high-purity MgTiO 3 (MT) nanocrystals. The method involves the mixing of independently dissolved magnesium and titanium metal powders in hydrochloric acid followed by calcination. The phase purity and nanocrystallinity were determined by making use of laboratory x-ray diffraction data, to which Rietveld-based analyses were performed. Results showed that the method yielded only one type magnesium titanate powders, i.e. MgTiO 3 , with no Mg 2 TiO 4 or MgTi 2 O 5 phases. The presence of residual rutile or periclase was controlled by adding excessive Mg up to 5% (mol) in the stoichiometric mixing. The method also resulted in MT nanocrystals with estimated average crystallite size of 76±2 nm after calcination at 600°C and 150±4 nm (at 800°C). A transmission electron micrograph confirmed the formation of the nanocrystallites

Microstructural study of Ce1-xGdxO2-δ (x = 0.1 and 0.2) nano crystallized powders synthesized by the polymeric precursor method

International Nuclear Information System (INIS)

Cela, B.; Macedo, D.A.; Souza, G.L.; Paskocimas, C.A.; Martinelli, A.E.; Nascimento, R.M.

2009-01-01

Gadolinia-doped ceria powders (Ce 1-x Gd x O 2-δ ) were prepared with substitution of 10 and 20% of the dopant element by the polymeric precursor method. This method makes possible the attainment of homogeny powder in molecular level, ideal to application in Solid Oxide Fuel Cell (SOFC) component. In this work, the particulated materials were calcinated in a range from 500 °C to 900 °C and structurally characterized by X-Ray Diffraction (XRD). The sintering behaviors of the compact samples were determined by dilatometric analyses. The results showed the method efficiency to attain monophasic nanopowder with cubic crystalline structure starting at 700 °C. The crystallite average size and crystalline parameter were determined by the Rietveld refinement method. (author)

A new method of Debye-Scherrer pattern integration on two-dimensional detectors, demonstrated for the new structure powder diffractometer (SPODI) at the FRM-II in Garching

CERN Document Server

Elf, F; Artus, G R J; Roth, S

2002-01-01

The expected diffraction patterns of the new powder diffractometer SPODI, currently under construction at the FRM-II in Garching, will be smeared Debye-Scherrer rings as depicted by Monte Carlo (MC) simulations. To overcome this disadvantage, a concept based on the combination of MC simulations and empirical approximation methods is developed to reverse the smearing by deconvolution and then summing up along the rings, including corrections for different arc lengths, resulting in conventional one-dimensional diffraction patterns suitable for Rietveld-refinement programs without further processing. (orig.)

Characterization of working iron Fischer-Tropsch catalysts using quantitative diffraction methods

Science.gov (United States)

Mansker, Linda Denise

This study presents the results of the ex-situ characterization of working iron Fischer-Tropsch synthesis (F-TS) catalysts, reacted hundreds of hours at elevated pressures, using a new quantitative x-ray diffraction analytical methodology. Compositions, iron phase structures, and phase particle morphologies were determined and correlated with the observed reaction kinetics. Conclusions were drawn about the character of each catalyst in its most and least active state. The identity of the active phase(s) in the Fe F-TS catalyst has been vigorously debated for more than 45 years. The highly-reduced catalyst, used to convert coal-derived syngas to hydrocarbon products, is thought to form a mixture of oxides, metal, and carbides upon pretreatment and reaction. Commonly, Soxhlet extraction is used to effect catalyst-product slurry separation; however, the extraction process could be producing irreversible changes in the catalyst, contributing to the conflicting results in the literature. X-ray diffraction doesn't require analyte-matrix separation before analysis, and can detect trace phases down to 300 ppm/2 nm; thus, working catalyst slurries could be characterized as-sampled. Data were quantitatively interpreted employing first principles methods, including the Rietveld polycrystalline structure method. Pretreated catalysts and pure phases were examined experimentally and modeled to explore specific behavior under x-rays. Then, the working catalyst slurries were quantitatively characterized. Empirical quantitation factors were calculated from experimental data or single crystal parameters, then validated using the Rietveld method results. In the most active form, after pretreatment in H 2 or in CO at Pambient, well-preserved working catalysts contained significant amounts of Fe7C3 with trace alpha-Fe, once reaction had commenced at elevated pressure. Amounts of Fe3O 4 were constant and small, with carbide dpavg 65 wt%, regardless of pretreatment gas and pressure, with

Iron insertion and hematite segregation on Fe-doped TiO2 nanoparticles obtained from sol-gel and hydrothermal methods.

Science.gov (United States)

Santos, Reginaldo da S; Faria, Guilherme A; Giles, Carlos; Leite, Carlos A P; Barbosa, Herbert de S; Arruda, Marco A Z; Longo, Claudia

2012-10-24

Iron-doped TiO(2) (Fe:TiO(2)) nanoparticles were synthesized by the sol-gel method (with Fe/Ti molar ratio corresponding to 1, 3, and 5%), followed by hydrothermal treatment, drying, and annealing. A similar methodology was used to synthesize TiO(2) and α-Fe(2)O(3) nanoparticles. For comparison, a mixture hematite/titania, with Fe/Ti = 4% was also investigated. Characterization of the samples using Rietveld refinement of X-ray diffraction data revealed that TiO(2) consisted of 82% anatase and 18% brookite; for Fe:TiO(2), brookite increased to 30% and hematite was also identified (0.5, 1.0, and 1.2 wt % for samples prepared with 1, 3, and 5% of Fe/Ti). For hematite/titania mixture, Fe/Ti was estimated as 4.4%, indicating the Rietveld method reliability for estimation of phase composition. Because the band gap energy, estimated as 3.2 eV for TiO(2), gradually ranged from 3.0 to 2.7 eV with increasing Fe content at Fe:TiO(2), it can be assumed that a Fe fraction was also inserted as dopant in the TiO(2) lattice. Extended X-ray absorption fine structure spectra obtained for the Ti K-edge and Fe K-edge indicated that absorbing Fe occupied a Ti site in the TiO(2) lattice, but hematite features were not observed. Hematite particles also could not be identified in the images obtained by transmission electron microscopy, in spite of iron identification by elemental mapping, suggesting that hematite can be segregated at the grain boundaries of Fe:TiO(2).

Structure of the new Tl(Ba sub 1.0 Sr sub 1.0) PrCu sub 2 O sub 7-x by Rietveld analysis

International Nuclear Information System (INIS)

Yang, P.; Fun, H. K.; Lee, T.J.; Ku, H.C.; Lai, C.C.

1994-01-01

The crystalline structure of Tl(Ba sub 1.0 Sr sub 1.0)PrCu sub 2 O sub 7-x was obtained at room temperature from x-ray powder diffraction with CuK sub α radiation using Rietveld analysis. Tl(Ba sub 1.0 Sr sub 1.0)PrCu sub 2 O sub 7-x isomorphous at both room temperature (300 K) and low temperature (100 K) with TlBa sub 2 ca Cu sub 2 O sub 7-x type (1212) structure, crystallized with space group P4/mmm and one formula in the unit cell. At 300 K, cell parameters a=3.8892(2) A, c=12.3099(6) A, the structure was refined with 25 parameters to R sub WP = 6.30%, R sub P = 4.38% for 3551 step intensities and R sub b = 5.01%, R sub f = 4.20% for 156 reflections. The goodness of fitting S=3.18. At 100K, cell parameters a=3.8866(4) A, c= 12.289(1) A, the structure was refined with 26 parameters to R sub WP = 8.42%, R sub P = 6.21% for 2676 step intensities and R sub b = 6.72%, R sub f = 5.28% for 120 reflections. The goodness of fitting S=2.32. Reasonable anisotropic thermal parameters were obtained. The compositions of Ba and Sr atoms were refined to about Ba sub 1.1 Sr sub 0.9 compared with the stoichiometric Ba sub 1.0 Sr sub 1.0

Microstructural studies on variation of defect parameters in Zr–Sn

Indian Academy of Sciences (India)

... modified Rietveld method and Warren–Averbach method taking silicon as standard. ... This analysis confirms that the growth fault, , is totally absent or negligibly ... faulting tendency abruptly drops to a level of negligible presence or zero.

Structural, magnetic and optical characterization of Ni{sub 0.8}Zn{sub 0.2}Fe{sub 2}O{sub 4} nano particles prepared by co-precipitation method

Energy Technology Data Exchange (ETDEWEB)

Kannan, Y.B., E-mail: ybkans@gmail.com [Department of Physics, Arumugam Pillai Seethai Ammal College, Tiruppattur 630211 (India); Saravanan, R. [Research Centre & PG Department of Physics, The Madura College, Madurai 625011 (India); Srinivasan, N. [Research Centre & PG Department of Physics, Thiagarajar College, Madurai 625009 (India); Praveena, K. [School of Physics, Univeristy of Hyderabad, Hyderabad 500046 (India); Sadhana, K. [Material Research Center, Indian Institute of Science, Bangalore 560012 (India)

2016-12-01

Bond strength values, between tetrahedral sites and octahedral sites atoms in the unit cell, are evaluated using maximum entropy method (MEM) for the Ni{sub 0.8}Zn{sub 0.2}Fe{sub 2}O{sub 4} nano ferrite particles, prepared by co-precipitation method and sintered at 900 °C. The spinel structure is confirmed from the XRD analysis done using the Rietveld method. Substitution of zinc ion causes increase in lattice parameter value. Thermal behavior, morphology, magnetic properties and optical band gap energy values of the sample are determined by using thermogravimetric analysis and differential thermal analysis, scanning electron microscope, vibrating sample magnetometer and UV–VIS–NIR techniques respectively. Low value of saturation magnetization is attributed to the disorder in cation distribution.

Crystallite Size and Microstrain Measurement of Cathode Material after Mechanical Milling using Neutron Diffraction Technique

Directory of Open Access Journals (Sweden)

A. Fajar

2010-12-01

Full Text Available The measurements of neutron diffraction patterns of commercially product and 10 hour mechanically milled cathode material lithium cobaltites (LiCoO2 have been performed. Rietveld analysis using FullProf does not show the change of crystal structure due to milling process, but the diffraction pattern has a lower intensity and the diffraction-line was broadening. The results of line-broadening study on milled sample using Rietveld methods detected that the microstrain was occurred in the sample with value 0.127080(35 % and the average crystallite size was 424.78(20 Å.

Quantitative firing transformations of a triaxial ceramic by X-ray diffraction methods

Directory of Open Access Journals (Sweden)

M. S. Conconi

2014-12-01

Full Text Available The firing transformations of traditional (clay based ceramics are of technological and archeological interest, and are usually reported qualitatively or semiquantitatively. These kinds of systems present an important complexity, especially for X-ray diffraction techniques, due to the presence of fully crystalline, low crystalline and amorphous phases. In this article we present the results of a qualitative and quantitative X-ray diffraction Rietveld analysis of the fully crystalline (kaolinite, quartz, cristobalite, feldspars and/or mullite, the low crystalline (metakaolinite and/or spinel type pre-mullite and glassy phases evolution of a triaxial (clay-quartz-feldspar ceramic fired in a wide temperature range between 900 and 1300 ºC. The employed methodology to determine low crystalline and glassy phase abundances is based in a combination of the internal standard method and the use of a nanocrystalline model where the long-range order is lost, respectively. A preliminary sintering characterization was carried out by contraction, density and porosity evolution with the firing temperature. Simultaneous thermo-gravimetric and differential thermal analysis was carried out to elucidate the actual temperature at which the chemical changes occur. Finally, the quantitative analysis based on the Rietveld refinement of the X-ray diffraction patterns was performed. The kaolinite decomposition into metakaolinite was determined quantitatively; the intermediate (980 ºC spinel type alumino-silicate formation was also quantified; the incongruent fusion of the potash feldspar was observed and quantified together with the final mullitization and the amorphous (glassy phase formation.The methodology used to analyze the X-ray diffraction patterns proved to be suitable to evaluate quantitatively the thermal transformations that occur in a complex system like the triaxial ceramics. The evaluated phases can be easily correlated with the processing variables and

Quantitative firing transformations of a triaxial ceramic by X-ray diffraction methods

International Nuclear Information System (INIS)

Conconi, M.S.; Gauna, M.R.; Serra, M.F.; Suarez, G.; Aglietti, E.F.; Rendtorff, N.M.

2014-01-01

The firing transformations of traditional (clay based) ceramics are of technological and archaeological interest, and are usually reported qualitatively or semi quantitatively. These kinds of systems present an important complexity, especially for X-ray diffraction techniques, due to the presence of fully crystalline, low crystalline and amorphous phases. In this article we present the results of a qualitative and quantitative X-ray diffraction Rietveld analysis of the fully crystalline (kaolinite, quartz, cristobalite, feldspars and/or mullite), the low crystalline (metakaolinite and/or spinel type pre-mullite) and glassy phases evolution of a triaxial (clay-quartz-feldspar) ceramic fired in a wide temperature range between 900 and 1300 deg C. The employed methodology to determine low crystalline and glassy phase abundances is based in a combination of the internal standard method and the use of a nanocrystalline model where the long-range order is lost, respectively. A preliminary sintering characterization was carried out by contraction, density and porosity evolution with the firing temperature. Simultaneous thermo-gravimetric and differential thermal analysis was carried out to elucidate the actual temperature at which the chemical changes occur. Finally, the quantitative analysis based on the Rietveld refinement of the X-ray diffraction patterns was performed. The kaolinite decomposition into metakaolinite was determined quantitatively; the intermediate (980 deg C) spinel type alumino-silicate formation was also quantified; the incongruent fusion of the potash feldspar was observed and quantified together with the final mullitization and the amorphous (glassy) phase formation.The methodology used to analyze the X-ray diffraction patterns proved to be suitable to evaluate quantitatively the thermal transformations that occur in a complex system like the triaxial ceramics. The evaluated phases can be easily correlated with the processing variables and materials

Quantitative firing transformations of a triaxial ceramic by X-ray diffraction methods

Energy Technology Data Exchange (ETDEWEB)

Conconi, M.S.; Gauna, M.R.; Serra, M.F. [Centro de Tecnologia de Recursos Minerales y Ceramica (CETMIC), Buenos Aires (Argentina); Suarez, G.; Aglietti, E.F.; Rendtorff, N.M., E-mail: rendtorff@cetmic.unlp.edu.ar [Universidad Nacional de La Plata (UNLP), Buenos Aires (Argentina). Fac. de Ciencias Exactas. Dept. de Quimica

2014-10-15

The firing transformations of traditional (clay based) ceramics are of technological and archaeological interest, and are usually reported qualitatively or semi quantitatively. These kinds of systems present an important complexity, especially for X-ray diffraction techniques, due to the presence of fully crystalline, low crystalline and amorphous phases. In this article we present the results of a qualitative and quantitative X-ray diffraction Rietveld analysis of the fully crystalline (kaolinite, quartz, cristobalite, feldspars and/or mullite), the low crystalline (metakaolinite and/or spinel type pre-mullite) and glassy phases evolution of a triaxial (clay-quartz-feldspar) ceramic fired in a wide temperature range between 900 and 1300 deg C. The employed methodology to determine low crystalline and glassy phase abundances is based in a combination of the internal standard method and the use of a nanocrystalline model where the long-range order is lost, respectively. A preliminary sintering characterization was carried out by contraction, density and porosity evolution with the firing temperature. Simultaneous thermo-gravimetric and differential thermal analysis was carried out to elucidate the actual temperature at which the chemical changes occur. Finally, the quantitative analysis based on the Rietveld refinement of the X-ray diffraction patterns was performed. The kaolinite decomposition into metakaolinite was determined quantitatively; the intermediate (980 deg C) spinel type alumino-silicate formation was also quantified; the incongruent fusion of the potash feldspar was observed and quantified together with the final mullitization and the amorphous (glassy) phase formation.The methodology used to analyze the X-ray diffraction patterns proved to be suitable to evaluate quantitatively the thermal transformations that occur in a complex system like the triaxial ceramics. The evaluated phases can be easily correlated with the processing variables and materials

Solution combustion method for synthesis of nanostructured hydroxyapatite, fluorapatite and chlorapatite

Energy Technology Data Exchange (ETDEWEB)

Zhao, Junjie; Dong, Xiaochen; Bian, Mengmeng [School of Chemistry and Materials Engineering, Changshu Institute of Technology, Changshu (China); Zhao, Junfeng, E-mail: daidai02304@163.com [School of Chemistry and Materials Engineering, Changshu Institute of Technology, Changshu (China); Jiangsu Laboratory of Advanced Functional Materials, Changshu Institute of Technology, Changshu (China); Zhang, Yao; Sun, Yue [School of Chemistry and Materials Engineering, Changshu Institute of Technology, Changshu (China); Chen, JianHua; Wang, XuHong [School of Chemistry and Materials Engineering, Changshu Institute of Technology, Changshu (China); Jiangsu Laboratory of Advanced Functional Materials, Changshu Institute of Technology, Changshu (China)

2014-09-30

Highlights: • We report a synthesis of HA, Fap and Clap vio a modified solution combustion method. The nucleation of β-TCP was inhibited in the abundant-calcium system (Ca/P = 2.3>>1.67) in this study. F{sup −} brushed into the structure of HA and replace the position of OH{sup −} is easier than that of Cl{sup −}. - Abstract: Hydroxyapatite (HAP), fluorapatite (Fap) and chlorapatite (Clap) were prepared by solution combustion method with further annealing at 800 °C. The characterization and structural features of the synthesized powders were evaluated by the powder X-ray diffraction (XRD, Fourier transform infrared spectroscopy (FT-IR), scanning electron microscope (SEM) and transmission electron microscopy (TEM) techniques. Characterization results from XRD and Rietveld analysis revealed that OH{sup −} in the HAP lattice were gradually substituted with the increase of F{sup −} and Cl{sup −} content and totally substituted at the molar concentration of 0.28 and 0.6, respectively. The results from FI-IR have also confirmed the incorporation of substituted anions in the apatite structure.

Synthesis and characterization of Fe{sub 3}O{sub 4} nanoparticles stabilized by polyvinylpyrrolidone / polyethylene glycol with variable mass ratios; Sintese e caracterizacao de nanoparticulas de Fe{sub 3}O{sub 4} estabilizadas pelo sistema polivinilpirrolidona/polietilenoglicol em proporcoes massicas variaveis

Energy Technology Data Exchange (ETDEWEB)

Silva, F.A.S. da; Campos, M.F. de; Rojas, E. E.G., E-mail: fernandasampaio@id.uff.br [Universidade Federal Fluminense (EEIMVR/UFF), Volta Redonda, RJ (Brazil)

2014-07-01

Magnetic nanoparticles are devices able to optimize cancer treatments. In particular, magnetite nanoparticles are very effective in producing heat to cause lysis of tumor cells. However, in order that nanoparticles are internalized without causing damage to body they must be coated by biocompatible material. In this work, Fe{sub 3}O{sub 4} nanoparticles were coated by a polymer blend: polyethylene glycol / polyvinylpyrrolidone. Some variations in mass ratio of polymer mixture were made. The effect of varying mass ratio in polymers was investigated. Samples were characterized by X-ray diffraction and Rietveld analysis. Moreover, hysteresis curves were analyzed. The results indicate good agreement between mass proportions used and physical and magnetic properties of nanocomposite. (author)

Analysis and interpretation of diffraction data from complex, anisotropic materials

Science.gov (United States)

Tutuncu, Goknur

Most materials are elastically anisotropic and exhibit additional anisotropy beyond elastic deformation. For instance, in ferroelectric materials the main inelastic deformation mode is via domains, which are highly anisotropic crystallographic features. To quantify this anisotropy of ferroelectrics, advanced X-ray and neutron diffraction methods were employed. Extensive sets of data were collected from tetragonal BaTiO3, PZT and other ferroelectric ceramics. Data analysis was challenging due to the complex constitutive behavior of these materials. To quantify the elastic strain and texture evolution in ferroelectrics under loading, a number of data analysis techniques such as the single peak and Rietveld methods were used and their advantages and disadvantages compared. It was observed that the single peak analysis fails at low peak intensities especially after domain switching while the Rietveld method does not account for lattice strain anisotropy although it overcomes the low intensity problem via whole pattern analysis. To better account for strain anisotropy the constant stress (Reuss) approximation was employed within the Rietveld method and new formulations to estimate lattice strain were proposed. Along the way, new approaches for handling highly anisotropic lattice strain data were also developed and applied. All of the ceramics studied exhibited significant changes in their crystallographic texture after loading indicating non-180° domain switching. For a full interpretation of domain switching the spherical harmonics method was employed in Rietveld. A procedure for simultaneous refinement of multiple data sets was established for a complete texture analysis. To further interpret diffraction data, a solid mechanics model based on the self-consistent approach was used in calculating lattice strain and texture evolution during the loading of a polycrystalline ferroelectric. The model estimates both the macroscopic average response of a specimen and its hkl

Synthesis of LiNi0.8Co0.1Mn0.1O2 cathode material by chloride co-precipitation method

Institute of Scientific and Technical Information of China (English)

李灵均; 李新海; 王志兴; 伍凌; 郑俊超; 李金辉

2010-01-01

LiNi0.8Co0.1Mn0.1O2 was prepared by a chloride co-precipitation method and characterized by thermogravimetric analysis, X-ray diffractometry with Rietveld refinement,electron scanning microscopy and electrochemical measurements.Effects of lithium ion content and sintering temperature on physical and electrochemical performance of LiNi0.8Co0.1Mn0.1O2 were also investigated. The results show that the sample synthesized at 750℃with 105%lithium content has fine particle sizes around 200 nm and homogenous sizes distribution.The initial discharge capacity for the powder is 184 mA·h/g between 2.7 and 4.3 V at 0.1C and room temperature.

On the use of a composite moderator at the IBR-2 reactor: Advantages for the neutron-diffraction texture analysis of rocks

Czech Academy of Sciences Publication Activity Database

Bulavin, M. V.; Vasin, R.N.; Kulikov, S.A.; Lokajíček, Tomáš; Levin, D.M.

2016-01-01

Roč. 10, č. 4 (2016), s. 677-686 ISSN 1027-4510 Institutional support: RVO:67985831 Keywords : cold moderator * neutron-diffraction texture analysis * phase analysis * Rietveld method Subject RIV: DB - Geology ; Mineralogy

The study of disorder and nanocrystallinity in C–S–H, supplementary cementitious materials and geopolymers using pair distribution function analysis

KAUST Repository

Meral, Cagla; Benmore, C.J.; Monteiro, Paulo J.M.

2011-01-01

Significant progress was achieved with the application of Rietveld method to characterize the crystalline phases in portland cement paste. However, to obtain detailed information on the amorphous or poorly crystalline phases, it is necessary

Study and characterization of the BBT (BaBi{sub 4}Ti{sub 4}O{sub 15}) ceramic added with 1 wt. % Nb{sub 2}O{sub 5}; Estudo e caracterizacao da ceramica BBT (BaBi{sub 4}Ti{sub 4}O{sub 15}) dopada com 1% de Nb{sub 2}O{sub 5}

Energy Technology Data Exchange (ETDEWEB)

Silva, P.M.O.; Sales, A.J.M.; Freitas, D.B.; Oliveira, R.G.M.; Sombra, A.S.B., E-mail: paulo2003@gmail.com [Universidade Federal do Ceara (UFC), Fortaleza, CE (Brazil); Sales, J.C. [Universidade Estadual Vale do Acarau (UVA), Fortaleza, CE (Brazil)

2012-07-01

This study aims to synthesize and characterize the ceramic BBT (BaBi{sub 4}TI{sub 4}O{sub 15}) doped with 1% by mass of the densification Nb2O5 to improve the products. The phase of the BBT has been found by solid state reaction. The mixed oxides starting processed by high-energy milling in planetary mill reactor polymer and spheres of zirconia and calcined at 850°C/3h. Later, 'bulks' prepared with the calcined powder were sintered at 950°C/3h. The calcined powder was characterized by X-ray diffraction data and refined by the beta 3.2 DBWSTools program using the Rietveld method. The grain morphology and distribution of pores on the surface of the 'bulks' were analyzed by Scanning Electron Microscopy. The result confirmed the refined to obtain the single phase with tetragonal structure BaBi{sub 4}TI{sub 4}O{sub 15} density of 5.088 g/cm3 calculated in the unit cell. SEM analysis by SEM showed improved densification of the doped. (author)

The new insight into the structure-activity relation of Pd/CeO2-ZrO2-Nd2O3 catalysts by Raman, in situ DRIFTS and XRD Rietveld analysis.

Science.gov (United States)

Yang, X; Yang, L; Lin, J; Zhou, R

2016-01-28

Pd/CeO2-ZrO2-Nd2O3 (CZN) catalysts with different CeO2/ZrO2 molar ratios were synthesized and have been characterized by multiple techniques, e.g. XRD in combination with Rietveld refinement, UV-Raman, XPS and in situ DRIFTS. The XRD pattern of CZN with CeO2/ZrO2 molar ratios ≥1/2 can be indexed satisfactorily to the fluorite structure with a space group Fm3̄m, while the XRD patterns of CZ12 only display diffraction peaks of the tetragonal phase (S.G. P42/nmc). Nd addition can effectively stabilize the cubic structure of the CZN support and increase the enrichment of defect sites on the surface, which may be related to the better catalytic activity of Pd/CZN12 catalysts compared with Pd/CZ12. The presence of moderate ZrO2 can increase the concentration of O* active species, leading to accelerate the formation of nitrate species and thus enhance the catalytic activity of NOx and HC elimination. The Pd-dispersion decreases with the increasing Zr content, leading to the decreased CO catalytic activity, especially for the aged catalysts. The change regularity of the OSC value is almost the same with the in situ dynamic operational window, demonstrating that the in situ dynamic operational window is basically affected by the OSC value.

Synthesis and characterization of nanosized ceria powders by microwave-hydrothermal method

International Nuclear Information System (INIS)

Bonamartini Corradi, A.; Bondioli, F.; Ferrari, A.M.; Manfredini, T.

2006-01-01

Nanocrystalline ceria powders (CeO 2 ) have been prepared by adding NaOH to a cerium ammonium nitrate aqueous solution under microwave-hydrothermal conditions. In particular the effect of the synthesis conditions (time, pressure and concentration of both the precursor and the precipitant agent solutions) on the physical properties of the crystals have been evaluated. Microwave-hydrothermal treatment of 5 min at 13.4 atm allows to obtain almost crystallized powders (amorphous phase 4%) as underlined by Rietveld-reference intensity ratio (RIR) results

Crystal structure and ionic conduction path of solid electrolytic materials by high temperature neutron diffraction method

International Nuclear Information System (INIS)

Yashima, Masatomo; Nomura, Katsuhiro

2005-01-01

Research of the distribution of oxide ions and the ionic conduction path of bismuth oxide (Bi 2 O 3 ), cerium oxide (CeO 2 ) and lanthanum gallate ((La 0.8 Sr 0.2 )(Ga 0.8 Mg 0.15 Co 0.05 )O 3-δ ) is stated. The high temperature neutron diffraction method, analytical method such as Rietveld method, crystal structure analysis of ionic conductor and MEM (Maximum- Entropy Method) are explained. The nuclear density distribution of oxide ions in bismuth oxide showed so larger distribution in the direction of and than Bi ions that the oxide ions conducted these direction in the crystal. The nuclear density distribution of oxide ions of cerium oxide indicated larger distribution in the direction of than Ce ions and its tendency was remarkable at high temperature. Accordingly, the oxide ions conducted in the direction of and . The oxide ions distribution in lanthanum gallate compound was larger and complicated than positive ions. The oxide ions conducted to by describing an arc between the two stable positions. The nuclear density on the conduction path increased with increasing temperature. This above result corresponded to increase of oxide ion conductivity in the area. (S.Y.)

Preferred orientation of ettringite in concrete fractures

KAUST Repository

Wenk, Hans-Rudolf; Monteiro, Paulo J. M.; Kunz, Martin; Chen, Kai; Tamura, Nobumichi; Lutterotti, Luca; Del Arroz, John

2009-01-01

distribution of ettringite crystals. Diffraction images are analyzed using the Rietveld method to obtain information on textures. The analysis reveals that the c axes of the trigonal crystallites are preferentially oriented perpendicular to the fracture

Effect of synthesis methods with different annealing temperatures on micro structure, cations distribution and magnetic properties of nano-nickel ferrite

Energy Technology Data Exchange (ETDEWEB)

El-Sayed, Karimat [XRD Lab, Physics Department, Faculty of Science, Ain-Shams University, Cairo (Egypt); Mohamed, Mohamed Bakr, E-mail: mbm1977@yahoo.com [XRD Lab, Physics Department, Faculty of Science, Ain-Shams University, Cairo (Egypt); Hamdy, Sh.; Ata-Allah, S.S. [Reactor Physics Department, NRC, Atomic Energy Authority, P.O. Box 13759, Cairo (Egypt)

2017-02-01

Nano-crystalline NiFe{sub 2}O{sub 4} was synthesized by citrate and sol–gel methods at different annealing temperatures and the results were compared with a bulk sample prepared by ceramic method. The effect of methods of preparation and different annealing temperatures on the crystallize size, strain, bond lengths, bond angles, cations distribution and degree of inversions were investigated by X-ray powder diffraction, high resolution transmission electron microscope, Mössbauer effect spectrometer and vibrating sample magnetometer. The cations distributions were determined at both octahedral and tetrahedral sites using both Mössbauer effect spectroscopy and a modified Bertaut method using Rietveld method. The Mössbauer effect spectra showed a regular decrease in the hyperfine field with decreasing particle size. Saturation magnetization and coercivity are found to be affected by the particle size and the cations distribution. - Highlights: • Annealed nano NiFe{sub 2}O{sub 4} was prepared by different methods. • The crystallite sizes are critical. • Mössbauer spectra show superparamagnetic doublet. • Cations distributions by MÓ§ssbauer and Bertaut method are constituents. • Cations distribution are significantly affects the magnetic properties.

Application of a dynamic-nanoindentation method to analyze the local structure of an Fe-18 at.% Gd cast alloy

Energy Technology Data Exchange (ETDEWEB)

Choi, Yong; Baik, Youl [Dept. of Materials Science and Technology, Dankook University, Cheonan(Korea, Republic of); Moon, Byung M. [Liquid Processing and Casting Technology R and D Group, KITECH, Incheon (Korea, Republic of); Sohn, Dong Seong [Nuclear Engineering Department, UNIST, Ulsan (Korea, Republic of)

2017-04-15

A dynamic nanoindentation method was applied to study an Fe-18 at.% Gd alloy as a neutron-absorbing material prepared by vacuum arc-melting and cast in a mold. The Fe-18 at.% Gd cast alloy had a microstructure with matrix phases and an Fe-rich primary dendrite of Fe9Gd. Rietveld refinement of the X-ray spectra showed that the Fe-18 at.% Gd cast alloy consisted of 35.84 at.% Fe3Gd, 6.58 at.% Fe5Gd, 16.22 at.% Fe9Gd, 1.87 at.% Fe2Gd, and 39.49 at.% β-Fe17Gd2. The average nanohardness of the primary dendrite phase and the matrix phases were 8.7 GPa and 9.3 GPa, respectively. The fatigue limit of the matrix phase was approximately 37% higher than that of the primary dendrite phase. The dynamic nanoindentation method is useful for identifying local phases and for analyzing local mechanical properties.

The formation and structure of mechano-synthesized nanocrystalline Sr{sub 3}Fe{sub 2}O{sub 6.4}: XRD Rietveld, Mössabuer and XPS analyses

Energy Technology Data Exchange (ETDEWEB)

Al-Rawas, A.D., E-mail: arawas@squ.edu.om [Department of Physics, Sultan Qaboos University, P.O. Box 36, 123 Al-Khoud, Muscat (Oman); Widatallah, H.M.; Al-Harthi, S.H. [Department of Physics, Sultan Qaboos University, P.O. Box 36, 123 Al-Khoud, Muscat (Oman); Johnson, C. [Chemistry Department, Open University, Walton Hall, Milton Keynes MK7 6AA (United Kingdom); Gismelseed, A.M.; Elzain, M.E.; Yousif, A.A. [Department of Physics, Sultan Qaboos University, P.O. Box 36, 123 Al-Khoud, Muscat (Oman)

2015-05-15

Highlights: • The formation of mechano-synthesized nanocrystalline Sr{sub 3}Fe{sub 2}O{sub 7−δ} is investigated. • Pre-milling the reactants substantially lowers the formation temperature. • The core and surface structures were studied. • XRD and {sup 57}Fe Mössbauer spectroscopic analyses indicate the δ-value to be 0.60. • XPS shows a complex surface structure for the mechanosynthesized Sr{sub 3}Fe{sub 2}O{sub 7−δ} nanoparticles. - Abstract: The influence of ball milling and subsequent sintering of a 3:1 molar mixture of SrCO{sub 3} and α-Fe{sub 2}O{sub 3} on the formation of Sr{sub 3}Fe{sub 2}O{sub 7−δ} double perovskite is investigated with different analytical techniques. Milling the mixture for 110 h leads to the formation of SrCO{sub 3}-α-Fe{sub 2}O{sub 3} nanocomposites and the structural deformation of α-Fe{sub 2}O{sub 3} via the incorporation of Sr{sup 2+} ions. Subsequent sintering of the pre-milled reactants’ mixture has led to the partial formation of an SrFeO{sub 3} perovskite-related phase in the temperature range 400–600 °C. This was followed by the progressive development of an Sr{sub 3}Fe{sub 2}O{sub 7−δ} phase that continued to increase with increasing sintering temperature until a single-phased nanocrystalline Sr{sub 3}Fe{sub 2}O{sub 7−δ} phase was attained at 950 °C (12 h). This temperature is ∼350 °C lower than the temperature at which the material is prepared conventionally using the ceramic method. The evolution of different structural phases during the reaction process is discussed. Rietveld refinement of the X-ray diffraction data shows a value of 0.60 for the oxygen deficiency δ, in consistency with the Fe{sup 3+}/Fe{sup 4+} ratio derived from the {sup 57}Fe Mössbauer data recorded at both 300 K and 78 K. The Mössbauer data suggests that the Sr{sub 3}Fe{sub 2}O{sub 6.4} nanoparticles are superparamagnetic with blocking temperatures below 78 K. The surfaces of the Sr{sub 3}Fe{sub 2}O{sub 6

Applying the X-ray diffraction analysis for estimating the height and width of nanorods in low symmetry crystal multiphase materials

Science.gov (United States)

Mokhtari, Ali; Soleimanian, Vishtasb; Dehkordi, Hamed Aleebrahim; Dastafkan, Kamran

2017-11-01

In this work the potential of Rietveld refinement procedure is used to study the shape and size of non-spherical nanocrystallites. The main advantages of this approach are that not only it can successfully extend to all nanomaterials with different crystal symmetries but also it can evaluate the various phases of multiple materials comparing to electron microscopy methods. Therefore, between seven crystal systems, the formulation of monoclinic and hexagonal crystals is developed. This procedure is applied for the mixture of sodium carbonate and zinc oxide nanocrystallites at different fractions of doped gadolinium oxide. It is found that the crystallites of sodium carbonate and zinc oxide have the rod and ellipsoidal shapes, respectively. The microstructure results are compared with the results of scanning electron microscopy imaging. Good agreement is achieved between the results of scanning electron microscopy and Rietveld methods.

Accurate quantitative XRD phase analysis of cement clinkers

International Nuclear Information System (INIS)

Kern, A.

2002-01-01

Full text: Knowledge about the absolute phase abundance in cement clinkers is a requirement for both, research and quality control. Traditionally, quantitative analysis of cement clinkers has been carried out by theoretical normative calculation from chemical analysis using the so-called Bogue method or by optical microscopy. Therefore chemical analysis, mostly performed by X-ray fluorescence (XRF), forms the basis of cement plan control by providing information for proportioning raw materials, adjusting kiln and burning conditions, as well as cement mill feed proportioning. In addition, XRF is of highest importance with respect to the environmentally relevant control of waste recovery raw materials and alternative fuels, as well as filters, plants and sewage. However, the performance of clinkers and cements is governed by the mineralogy and not the elemental composition, and the deficiencies and inherent errors of Bogue as well as microscopic point counting are well known. With XRD and Rietveld analysis a full quantitative analysis of cement clinkers can be performed providing detailed mineralogical information about the product. Until recently several disadvantages prevented the frequent application of the Rietveld method in the cement industry. As the measurement of a full pattern is required, extended measurement times made an integration of this method into existing automation environments difficult. In addition, several drawbacks of existing Rietveld software such as complexity, low performance and severe numerical instability were prohibitive for automated use. The latest developments of on-line instrumentation, as well as dedicated Rietveld software for quantitative phase analysis (TOPAS), now make a decisive breakthrough possible. TOPAS not only allows the analysis of extremely complex phase mixtures in the shortest time possible, but also a fully automated online phase analysis for production control and quality management, free of any human interaction

Multiscale Biological Materials

DEFF Research Database (Denmark)

Frølich, Simon

of multiscale biological systems have been investigated and new research methods for automated Rietveld refinement and diffraction scattering computed tomography developed. The composite nature of biological materials was investigated at the atomic scale by looking at the consequences of interactions between...

Synthesis, structural and ferromagnetic properties of La1–x Kx ...

Indian Academy of Sciences (India)

2016-08-26

Aug 26, 2016 ... Synthesis, structural and ferromagnetic properties of La1–KMnO3 (0.0≤ 0.25) phases by solution combustion method ... Structural parameters were determined by the Rietveld refinement method using powder XRD data. Parent ... The ratio of the Mn3+/Mn4+ was determined by the iodometric titration.

Characterization of aerosols containing radiopharmaceuticals

International Nuclear Information System (INIS)

Cunha, Kenya Dias da; Santos, Maristela Souza

2008-01-01

The objective of this study is to present the main lines of action of the Laboratorio de Caracterizacao de Aerossois (LCA /IRD) in the study of aerosols, the techniques available and the capability of these techniques as a tool in the biokinetics behavior study of radiopharmaceuticals and evaluating the particle exposed individuals containing these molecules. The LCA provides the following analytical techniques: spectrometry alpha, gamma and alpha counting and gross beta; PIXE (Particle Induced X rays Emission) and mass spectrometry-based flight time measurement of molecular ions ( 252 Cf-PDMS - 252 Cf-Plasma Desorption Mass Spectrometry). This technique is used to identify compounds mass to 10 000 a.m.u. The combination of these techniques has been applied to the study in vitro of the toxicology of the metals and radionuclides both in the respiratory tract as in the gastrointestinal

Synthesis and characterization of La(Cr,Fe,Mn)O{sub 3} nanoparticles obtained by co-precipitation method

Energy Technology Data Exchange (ETDEWEB)

Fabian, F.A., E-mail: fernandafabianro@gmail.com [Universidade Federal de Sergipe, Campus Prof. Aluísio Campos, Departamento de Física, 49100-000 São Cristóvão, SE (Brazil); Pedra, P.P.; Filho, J.L.S. [Universidade Federal de Sergipe, Campus Prof. Aluísio Campos, Departamento de Física, 49100-000 São Cristóvão, SE (Brazil); Duque, J.G.S.; Meneses, C.T. [Universidade Federal de Sergipe, Campus Prof. Alberto Carvalho, Departamento de Física, 49500-000 Itabaiana, SE (Brazil)

2015-04-01

Magnetic and structural properties have been investigated in La(Cr,Fe,Mn)O{sub 3} nanoparticles obtained by co-precipitation method. The X-ray diffraction measurements allied to Rietveld method confirm the formation of LaCrO{sub 3}, LaFeO{sub 3} and LaMnO{sub 3} nanoparticles with crystal structure orthorhombic (Pbnm), orthorhombic (Pnma) and rhombohedral (R-3c), respectively. We also verified an decreasing in the average crystallite size from 73 to 26 nm, depending of the transition metal. The magnetic measurements reveal an antiferromagnetic behavior for the LaCrO{sub 3} sample with T{sub N}~289 K, and a weak ferromagnetic ordering for the LaMnO{sub 3} sample with T{sub c}~200 K. - Highlights: • La(Cr,Fe,Mn)O{sub 3} nanoparticles were synthesized by coprecipitation method. • XRD results confirm the formation single phase in the compounds studied. • Magnetic property in the La(Fe,Cr,Mn)O{sub 3} nanoparticles dependent on the TM. • La(Cr,Fe)O{sub 3} nanoparticles presented behavior antiferromagnetic and LaMnO{sub 3} ferromagnetic.

Investigation on the formation of Cu-Fe nano crystalline super-saturated solid solution developed by mechanical alloying

Energy Technology Data Exchange (ETDEWEB)

Mojtahedi, M., E-mail: m.mojtahedi@gmail.com [School of Materials Science and Engineering, Iran University of Science and Technology, Narmak, Tehran 16846-13114 (Iran, Islamic Republic of); Goodarzi, M.; Aboutalebi, M.R. [School of Materials Science and Engineering, Iran University of Science and Technology, Narmak, Tehran 16846-13114 (Iran, Islamic Republic of); Ghaffari, M. [Department of Electrical and Electronics Engineering, UNAM-Institute of Materials Science and Nanotechnology, Bilkent University, Ankara 06800 (Turkey); Soleimanian, V. [Department of Physics, Faculty of Science, Shahrekord University, P.O. Box 115, Shahrekord (Iran, Islamic Republic of)

2013-02-15

Highlights: Black-Right-Pointing-Pointer The deformation of the mechanically alloyed Cu-Fe powder is anisotropic. Black-Right-Pointing-Pointer The Rietveld method is more proper and results in smaller crystallite size than the Scherer and Williamson-Hall methods. Black-Right-Pointing-Pointer A dual phase super saturated solid solution achieved after 96 h of milling of the mixtures with 30, 50 and 70 wt.% of Iron. Black-Right-Pointing-Pointer A final proportion of approximately 85% FCC and 15% BCC structure obtained in all of the applied compositions. - Abstract: In this study, the formation of super saturated solid solution in the binary Cu-Fe system was investigated. Three powder blends with 30, 50 and 70 wt.% of Fe were milled for different times to 96 h. The variations of lattice parameter and inter-planar spacing were calculated and analyzed using X-ray diffraction analysis (XDA). The anisotropy of lattice deformation in the FCC phase was studied and the obtained results were compared to milled pure Cu powder. Furthermore, crystallite size was calculated using Scherer formula in comparison with Rietveld full profile refinement method. Considering the previous studies about the formation of non-equilibrium FCC and BCC phases, the phase evolution has been discussed and the proportion of each phase was calculated using Rietveld refinement method. Supplementary studies on the evolution of microstructure and formation of solid solution were carried out using high resolution transmission electron microscopy (HRTEM). Finally, high angle annular dark field (HAADF) imaging was utilized to find out the level of homogeneity in the resulting phases. While true alloying takes place in each phase, the final structure consists of both FCC and BCC nano-crystallites.

Synthesis, magnetic properties and Moessbauer spectroscopy for the pyrochlore family Bi{sub 2}BB Prime O{sub 7} with B=Cr and Fe and B Prime =Nb, Ta and Sb

Energy Technology Data Exchange (ETDEWEB)

Blanco, Maria C. [INFIQC (CONICET), Dpto. de Fisicoquimica, Fac. de Ciencias Quimicas, U.N.C., Cordoba (X5000HUA) (Argentina); Franco, Diego G. [INFIQC (CONICET), Dpto. de Fisicoquimica, Fac. de Ciencias Quimicas, U.N.C., Cordoba (X5000HUA) (Argentina); Centro Atomico Bariloche - CNEA, Av. E. Bustillo 9500, S.C. de Bariloche (8500), R.N. (Argentina); Jalit, Yamile; Pannunzio Miner, Elisa V. [INFIQC (CONICET), Dpto. de Fisicoquimica, Fac. de Ciencias Quimicas, U.N.C., Cordoba (X5000HUA) (Argentina); Berndt, Graciele; Paesano, Andrea [Departamento de Fisica, Universidade Estadual de Maringa, Parana (Brazil); Nieva, Gladys [Centro Atomico Bariloche - CNEA, Av. E. Bustillo 9500, S.C. de Bariloche (8500), R.N. (Argentina); Carbonio, Raul E., E-mail: carbonio@mail.fcq.unc.edu.ar [INFIQC (CONICET), Dpto. de Fisicoquimica, Fac. de Ciencias Quimicas, U.N.C., Cordoba (X5000HUA) (Argentina)

2012-08-15

The samples Bi{sub 2}BB Prime O{sub 7}, with B=Cr and Fe and B Prime =Nb, Ta and Sb were prepared by solid state method. The crystallographic structure was investigated on the basis of X-ray powder diffraction data. Rietveld refinements show that the crystal structure is cubic, space group Fd-3m. The Bi{sup 3+} cation on the eight-coordinate pyrochlore A-site shows displacive disorder, as a consequence of its lone pair electron configuration. There is also a considerable A-site disorder shown by Rietveld Analysis and confirmed in the case of the iron containing samples with Moessbauer spectroscopy. The magnetic measurements show paramagnetic behavior at all temperatures for the Cr oxides. The Fe pyrochlores show antiferromagnetic order around 10 K.

Computation of X-ray powder diffractograms of cement components ...

Indian Academy of Sciences (India)

Computation of X-ray powder diffractograms of cement components and its application to phase analysis and hydration performance of OPC cement. Rohan Jadhav N C Debnath. Volume 34 Issue 5 August 2011 pp 1137- ... Keywords. Portland cement; X-ray diffraction; crystal structure; characterization; Rietveld method.

On the Stress-Induced Formation of R-Phase in Ultra-Fine-Grained Ni-Rich NiTi Shape Memory Alloys

Czech Academy of Sciences Publication Activity Database

Olbricht, J.; Yawny, A.; Pelegrina, J.L.; Dlouhý, Antonín

42A, č. 9 (2011), s. 2556-2574 ISSN 1073-5623 R&D Projects: GA ČR GA106/09/1913 Institutional research plan: CEZ:AV0Z20410507 Keywords : martensitic transformations * rietveld method * single-crystals Subject RIV: JG - Metallurgy Impact factor: 1.545, year: 2011

Estudo de propriedades estruturais e opticas de multicamadas epitaxiais emissoras de luz baseadas em InGaN/GaN

Science.gov (United States)

Pereira, Sergio Manuel de Sousa

Esta tese apresenta os resultados de uma investigacao experimental em filmes epitaxiais emissores de luz baseados em InxGa1-xN. O InxGa1-xN e uma liga semicondutora ternaria do grupo III-N muito utilizada como camada activa numa gama de dispositivos optoelectronicos em desenvolvimento, incluindo diodos emissores de luz (LEDs) e diodos laser (LDs), para operacao na regiao do visivel e ultravioleta do espectro electromagnetico. Neste estudo, caracterizam-se as propriedade opticas e estruturais de camadas simples e pocos quânticos multiplos (Multiple Quantum Wells, MQWs) de InxGa1-xN/GaN, com enfase nas suas propriedades fisicas fundamentais. O objectivo central do trabalho prende-se com a compreensao mais profunda dos processos fisicos que estao por tras das suas propriedades opticas, preenchendo o fosso existente entre aplicacoes tecnologicas e o conhecimento cientifico. Nomeadamente, a tese aborda os problemas da medicao da fraccao de InN (x) em multicamadas ultrafinas sujeitas a tensoes, a influencia da composicao e das tensoes microscopicas nas propriedades opticas e estruturais. A questao relativa a segregacao de fases em multicamadas de InxGa1-xN/GaN e tambem discutida a luz dos resultados obtidos. A metodologia seguida assenta na integracao de resultados obtidos por tecnicas complementares atraves de uma analise sistematica e multidisciplinar. Esta abordagem passa pela combinacao de: 1) Crescimento de amostras por deposicao epitaxial em fase de vapor organometalico (MOVPE) com caracteristicas especificas de forma a tentar isolar parâmetros estruturais, tais como espessura e composicao; 2) Caracterizacao nanoestrutural por microscopia de forca atomica (AFM), microscopica electronica de varrimento (SEM), difraccao de raios-X e retro-dispersao de Rutherford (RBS); 3) Caracterizacao optica a escalas complementares por: espectroscopia de absorcao optica (OA), fotoluminescencia (PL), catodoluminescencia (CL) e microscopia confocal (CM) com analise espectral. Com

Crystal structure and magnetic properties of La2−x(Sr0.5Ca0.5)1+xMn2O7 (x=0.6, 0.8 and 1.0) Ruddlesden–Popper manganites

International Nuclear Information System (INIS)

Raju, K.; Song, M.S.; Lee, J.Y.

2014-01-01

Double layer perovskite (Ruddlesden–Popper) manganites with the nominal composition of La 2−x (Sr 0.5 Ca 0.5 ) 1+x Mn 2 O 7 (x=0.6, 0.8 and 1.0) were synthesized via a solid state reaction route. X-ray and neutron diffraction were performed at room temperature and the crystal structure was refined using the Rietveld method based on the space group, I4/mmm. The temperature variation of the susceptibility revealed a spin glass transition at 28 K for x=0.6, a charge ordering transition at 245 K and a Neel transition at 170 K for x=1.0. - Highlights: • Lanthanum based double layered manganites were prepared by doping with the same amounts of Sr and Ca. • X-ray and neutron diffraction were performed and the crystal structure was refined using the Rietveld method. • Different magnetic transitions were observed depending upon the doping concentration. • Qualitative explanation for the various observed phenomena was given

Structure and physical properties of the LaBiFe2O6 Perovskite produced by the modified Pechini method

International Nuclear Information System (INIS)

Palacio, Johny Andrés Jaramillo; Bello, Elixir William Barrera; Landínez-Téllez, David A.; Roa-Rojas, Jairo; Cagigas, Julián Andrés Munévar; Arnache, Oscar

2017-01-01

In this paper the synthesis of the LaBiFe 2 O 6 material by the modified Pechini method is reported. Structural, morphologic, magnetic and optic experimental studies were performed. Rietveld refinement of x-ray diffraction patterns revealed that LaBiFe 2 O 6 crystallizes in an orthorhombic perovskite structure (space group Pnma, ⧣ 62). Scanning electron microscopy images showed the nanometric feature of grains. X-ray dispersive spectroscopy permitted to infer the obtaining of the LaBiFe 2 O 6 expected stoichiometry. Results of magnetic susceptibility as a function of temperature and field magnetization evidenced mixed ferromagnetism and superparamagnetism behavior at T=300 K. Mössbauer spectroscopy supported the superparamagnetic and ferromagnetic responses as a result of the nanogranular morphology and anisotropy effects. Spectrum of diffuse reflectance suggest that this material behaves as a semiconductor with energy gap E g =2.13 eV. (author)

Development and applications of the reverse neutron time-of-flight method with Fourier-type beam chopper

International Nuclear Information System (INIS)

Antson, O.

1991-09-01

The neutron powder diffraction method has been applied to the crystal structure analysis of high-temperature superconductors such as La 0 .8Sr 0 .2CuO 4 - y , YBa 2 Cu 3 O 7 - y and Bi 2 Sr 2 CaCu 2 O 8 + y optically active yttriumformate Y(HCOO) 3 , and β phase of deuterated acetonitrile, CD 3 CN. The structural information, containing symmetry, positional and thermal parameters, occupation factors and the order parameter, was obtained by measuring the coherent elastic scattering cross-section. The Rietveld profile refinement method was used for the extraction of structural parameters from experimental data. The diffraction spectra were obtained by measuring the time-of-flight distribution of neutrons with a Fourier-type beam chopper. The neutron diffraction spectrum is created by the on-line synthesis of the cross-correlation function between the beam modulation function and the detector intensity. Such an operational mode, called the reverse time-of-flight method, has many unique properties. The possibility of filtering out a low-frequency part of a diffraction spectrum, eg. incoherent background, by a properly selected band-pass filter has been studied. One of the practical applications of the reverse time-of-flight method, the Mini-Sfinks facility, is described with technical details, and its operational characteristics are compared with other high-resolution instruments

In Situ High Resolution Synchrotron X-Ray Powder Diffraction Studies of Lithium Batteries

DEFF Research Database (Denmark)

Amri, Mahrez; Fitch, Andy; Norby, Poul

2015-01-01

allowing diffraction information to be obtained from only the active material during battery operation [2]. High resolution synchrotron x-ray powder diffraction technique has been undertaken to obtain detailed structural and compositional information during lithiation/delithiation of commercial LiFePO4...... materials [3]. We report results from the first in situ time resolved high resolution powder diffraction experiments at beamline ID22/31 at the European Synchrotron Radiation Facility, ESRF. We follow the structural changes during charge of commercial LiFePO4 based battery materials using the Rietveld...... method. Conscientious Rietveld analysis shows slight but continuous deviation of lattice parameters from those of the fully stoichiometric end members LiFePO4 and FePO4 indicating a subsequent variation of stoichiometry during cathode delithiation. The application of an intermittent current pulses during...

Magnetic ordering in the rare earth iron germanates HoFeGe2O7 and ErFeGe2O7

DEFF Research Database (Denmark)

Cascales, C.; Puebla, E.G.; Klimin, S.

1999-01-01

RFeGe2O7 (R = Ho, Er) have been prepared in polycrystalline form, and their crystal structures have been refined from room-temperature high-resolution neutron diffraction data by the Rietveld method. Both materials are isostructural, space group P2(1)/m (no. 11), Z = 4. The most interesting feature...

Synthesis, structure and thermoelectric properties of La1 ...

Indian Academy of Sciences (India)

Structural parameters for all the compounds were confirmed by the Rietveld refinement method usingpowder X-ray diffraction (XRD) data and exhibit the rhombhohedral crystal structure with space group R-3c (No. 167). Thescanning electron microscopy study reveals that the particles are spherical in shape and sizes, in the ...

Intrinsic dependence of the magnetic properties of CoFe{sub 2}O{sub 4} nanoparticles prepared via chemical methods with addition of chelating agents

Energy Technology Data Exchange (ETDEWEB)

Mendonça, E.C. [Núcleo de Pós-Graduação em Física, Campus Prof. José Aluísio de Campos, UFS, 49100-000 São Cristóvão, SE (Brazil); Tenório, Mayara A. [Departamento de Física, Campus Prof. Alberto Carvalho, UFS, 49500-000 Itabaiana, SE (Brazil); Mecena, S.G.; Zucolotto, B.; Silva, L.S. [Núcleo de Pós-Graduação em Física, Campus Prof. José Aluísio de Campos, UFS, 49100-000 São Cristóvão, SE (Brazil); Jesus, C.B.R. [Instituto de Física Gleb Wataghin, UNICAMP, C. P. 6165, 13083-970 Campinas, SP (Brazil); Meneses, C.T. [Núcleo de Pós-Graduação em Física, Campus Prof. José Aluísio de Campos, UFS, 49100-000 São Cristóvão, SE (Brazil); and others

2015-12-01

In this work, the effect of addition of different chelating agents on the magnetic properties of cobalt ferrite nanoparticles produced by the combining of both co-precipitation and hydrothermal methods is reported. The Rietveld analyses of X-ray diffraction patterns reveal that our samples are single phase (space group: Fd-3m) with small average sizes. The weight losses observed in the thermogravimetric measurements together with the M×H curves show that the organic contamination coming from chelating agent decomposition can give rise to misinterpretation of the magnetization measurements. Besides, analyses of the zero-field-cooled (ZFC) and field-cooled (FC) magnetization measurements and the M×H curves measured at room temperature allows us to state that both the average blocking temperature and particles size distribution are sensitive to the kind of chelating agent. - Highlights: Superparamagnetism. Chelating agents. Organic contamination.

Rietveld refinement, impedance spectroscopy and magnetic properties of Bi{sub 0.8}Sr{sub 0.2}FeO{sub 3} substituted Na{sub 0.5}Bi{sub 0.5}TiO{sub 3} ceramics

Energy Technology Data Exchange (ETDEWEB)

Kumari, Rekha [Department of Applied Physics, Guru Jambheshwar University of Science & Technology, Hisar 125001, Haryana (India); Ahlawat, Neetu, E-mail: neetugju@yahoo.co.in [Department of Applied Physics, Guru Jambheshwar University of Science & Technology, Hisar 125001, Haryana (India); Agarwal, Ashish; Sanghi, Sujata [Department of Applied Physics, Guru Jambheshwar University of Science & Technology, Hisar 125001, Haryana (India); Sindhu, Monica [Department of Physics, MKJK College, Rohtak 124001, Haryana (India); Ahlawat, Navneet [Matu Ram Institute of Engineering and Management, Rohtak 124001, Haryana (India)

2016-09-15

We herein presented the investigation on the structural, electrical and magnetic properties of (1−x)(Na{sub 0.5}Bi{sub 0.5}TiO{sub 3})–x(Bi{sub 0.8}Sr{sub 0.2}FeO{sub 3}) polycrystalline ceramic samples, with x=0.1, 0.3, 0.5 and 0.7. These samples were prepared by conventional solid state reaction method and the crystalline phase of prepared ceramics was identified with the help of X-ray diffraction pattern. Rietveld analysis of the obtained XRD data confirmed that all the synthesized samples adopt the rhombohedral crystal structure with R3c space group. Impedance spectroscopic measurements were performed on all the compositions in the frequency range 10 Hz–5 MHz to probe the electrical microstructure of polycrystalline (1−x)(Na{sub 0.5}Bi{sub 0.5}TiO{sub 3})–x(Bi{sub 0.8}Sr{sub 0.2}FeO{sub 3}) ceramics, which changes significantly as a function of x (content of BSFO). A significant increase in dielectric constant has been observed with increase in BSFO concentration, which was attributed to enhancement of oxygen vacancies. Detailed study of impedance complex plane plots revealed the presence of non-Debye type relaxation for all the prepared systems and enabled us to separate the contribution from grains and grain boundaries. Equivalent circuit model (R{sub g}CPE{sub g})(R{sub gb}CPE{sub gb})(R{sub e}CPE{sub e}) was employed to explain the impedance data for all the prepared samples. The activation energies obtained from electric modulus as well as dc conductivity increase with increase in BSFO content, which approaches the value 1 eV and indicates an Arrehenius type thermally activated process. Remnant magnetization (M{sub r}) and coercive field (H{sub c}) are found to be increase with BSFO concentration. - Highlights: • (1−x)NBT–xBSFO (x=0.1, 0.3, 0.5, 0.7) ceramics were prepared. • There is no change in crystal structure. • These can be used as data storage materials.

Determination of the stoichiometric rate in UO2 samples

International Nuclear Information System (INIS)

Moura, Sergio C.; Lima, Nelson B. de; Sassine, Andre; Bustillos, Jose Oscar Vega

2000-01-01

The gravimetric and voltammetric methods for determination of non-stoichiometric O/U ratio in uranium dioxide used as nuclear fuel are discussed in this work. The oxidation of uranium oxide is very complex due to many phase changes. Gravimetric and voltammetric methods do not detect phase changes. The results of this work shown that, to evaluate both methods is requiring to be done Rietveld methods by X-ray diffraction data to identify the uranium oxide phase changes. (author)

Study of non stoichiometric uranium dioxide samples (UO2)

International Nuclear Information System (INIS)

Moura, Sergio C.; Lima, Nelson B. de; Bustillos, Jose O.V.

1999-01-01

The gravimetric and voltammetric methods for determination of non-stoichiometric O/U ratio in uranium dioxide used as nuclear fuel are discussed in this work. The oxidation of uranium oxide is very complex due to many phase changes. gravimetric and voltammetric methods do not detect phase changes. The results of this work shown that, to evaluate both methods is requiring to be done Rietveld methods by x-ray diffraction data to identify the uranium oxide phase changes. (author)

Investigation of microstructural and optical properties of La0.8Ca0.2FeO3 nanostructure synthesized via gel combustion method

Science.gov (United States)

Naseem, Swaleha; Ali, S. Asad; Khan, Wasi; Khan, Shakeel

2018-05-01

Ca substituted LaFeO3 orthoferrite nanostructure perovskite has been synthesized by gel combustion method using citric acid as a fuel. The structural and optical properties were investigated by various tools. The structural analysis through Rietveld refinement of the XRD data revealed single phase of orthorhombic structure in R-3c space group of the sample without presence of any other impurity phase. Scanning electron microscopy (SEM) image exhibits non-uniform distribution of the nanoparticles in agglomerated form. The purity of the sample and stoichiometric ratio of the elements were established through energy dispersive x-ray spectroscopy (EDS). FTIR spectroscopy measurement predicts the presence of various band relation of the chemical species of Ca with LaFeO3. Optical properties were explored through UV-visible absorption spectroscopy that showed absorption edge at 347 nm and energy band gap was estimated as 3.47eV using Tauc's relation.

Bulletin of Materials Science | Indian Academy of Sciences

Indian Academy of Sciences (India)

Finally microstructural defect parameters such as domain size (), r.m.s. microstrain 〈 2 〉1/2, twin fault ('), spacing fault () and deformation stacking fault () were evaluated in these alloys by Fourier line shape analysis using Rietveld method in which the X-ray diffraction profiles of these alloys were described by the ...

Enhancement of magnetic properties of Co2MnSi Heusler alloy prepared by mechanical alloying method

International Nuclear Information System (INIS)

Rabie, Naeemeh; Gordani, Gholam Reza; Ghasemi, Ali

2017-01-01

Highlights: • Ferromagnetic Heusler alloys of Co 2 MnSi were synthesized at low temperature. • There is an at least 30% reduction in the phase formation temperature. • Saturation magnetization of alloy was increased significantly after annealing. - Abstract: Ferromagnetic Heusler alloys of Co 2 MnSi were synthesized by mechanical alloying method at low temperature. The effect of milling time and annealing process on structural and magnetic properties of ferromagnetic alloy samples were studied by X-ray diffraction, scanning electron microscopy and vibration sample magnetometer methods, respectively. Structural characteristics such as crystallite size, phase percentage, and lattice parameter determined using the Rietveld method. The values of these parameters were obtained 362.9 nm, 5.699 Å and 98.7%, respectively for annealed sample. Magnetization studies show that the Co2MnSi phase is formed at 15 h of milling and is optimized after 20 h of milling. VSM results showed that saturation magnetization (M s ) of milled samples reduces from 112 to 75 (emu/g) with increasing milling time and then increased gradually to 95 emu/g. The effect of post-annealing on the structural and magnetic properties of milled samples was also investigated. The saturation magnetization of annealed sample (120 emu/g) is higher than the optimum milled sample (95 emu/g) due to increasing preferential ordered L2 1 structure.

Crystal structure and magnetic properties of La{sub 2−x}(Sr{sub 0.5}Ca{sub 0.5}){sub 1+x}Mn{sub 2}O{sub 7} (x=0.6, 0.8 and 1.0) Ruddlesden–Popper manganites

Energy Technology Data Exchange (ETDEWEB)

Raju, K.; Song, M.S.; Lee, J.Y., E-mail: jylee@yu.ac.kr

2014-05-01

Double layer perovskite (Ruddlesden–Popper) manganites with the nominal composition of La{sub 2−x}(Sr{sub 0.5}Ca{sub 0.5}){sub 1+x}Mn{sub 2}O{sub 7} (x=0.6, 0.8 and 1.0) were synthesized via a solid state reaction route. X-ray and neutron diffraction were performed at room temperature and the crystal structure was refined using the Rietveld method based on the space group, I4/mmm. The temperature variation of the susceptibility revealed a spin glass transition at 28 K for x=0.6, a charge ordering transition at 245 K and a Neel transition at 170 K for x=1.0. - Highlights: • Lanthanum based double layered manganites were prepared by doping with the same amounts of Sr and Ca. • X-ray and neutron diffraction were performed and the crystal structure was refined using the Rietveld method. • Different magnetic transitions were observed depending upon the doping concentration. • Qualitative explanation for the various observed phenomena was given.

Structure and physical properties of the LaBiFe{sub 2}O{sub 6} Perovskite produced by the modified Pechini method

Energy Technology Data Exchange (ETDEWEB)

Palacio, Johny Andrés Jaramillo; Bello, Elixir William Barrera; Landínez-Téllez, David A.; Roa-Rojas, Jairo, E-mail: jroar@unal.edu.com [Grupo de Física de Nuevos Materiales, Universidad Nacional de Colombia, Bogotá DC (Colombia); Cagigas, Julián Andrés Munévar [Laboratory for Muon Spin Spectroscopy, Paul Scherrer Institut (Switzerland); Arnache, Oscar [Grupo de Estado Sólido, Universidad de Antioquia, Medellín (Colombia)

2017-10-15

In this paper the synthesis of the LaBiFe{sub 2}O{sub 6} material by the modified Pechini method is reported. Structural, morphologic, magnetic and optic experimental studies were performed. Rietveld refinement of x-ray diffraction patterns revealed that LaBiFe{sub 2}O{sub 6} crystallizes in an orthorhombic perovskite structure (space group Pnma, ⧣ 62). Scanning electron microscopy images showed the nanometric feature of grains. X-ray dispersive spectroscopy permitted to infer the obtaining of the LaBiFe{sub 2}O{sub 6} expected stoichiometry. Results of magnetic susceptibility as a function of temperature and field magnetization evidenced mixed ferromagnetism and superparamagnetism behavior at T=300 K. Mössbauer spectroscopy supported the superparamagnetic and ferromagnetic responses as a result of the nanogranular morphology and anisotropy effects. Spectrum of diffuse reflectance suggest that this material behaves as a semiconductor with energy gap E{sub g} =2.13 eV. (author)

Enhancement of magnetic properties of Co{sub 2}MnSi Heusler alloy prepared by mechanical alloying method

Energy Technology Data Exchange (ETDEWEB)

Rabie, Naeemeh; Gordani, Gholam Reza; Ghasemi, Ali, E-mail: ali13912001@yahoo.com

2017-07-15

Highlights: • Ferromagnetic Heusler alloys of Co{sub 2}MnSi were synthesized at low temperature. • There is an at least 30% reduction in the phase formation temperature. • Saturation magnetization of alloy was increased significantly after annealing. - Abstract: Ferromagnetic Heusler alloys of Co{sub 2}MnSi were synthesized by mechanical alloying method at low temperature. The effect of milling time and annealing process on structural and magnetic properties of ferromagnetic alloy samples were studied by X-ray diffraction, scanning electron microscopy and vibration sample magnetometer methods, respectively. Structural characteristics such as crystallite size, phase percentage, and lattice parameter determined using the Rietveld method. The values of these parameters were obtained 362.9 nm, 5.699 Å and 98.7%, respectively for annealed sample. Magnetization studies show that the Co2MnSi phase is formed at 15 h of milling and is optimized after 20 h of milling. VSM results showed that saturation magnetization (M{sub s}) of milled samples reduces from 112 to 75 (emu/g) with increasing milling time and then increased gradually to 95 emu/g. The effect of post-annealing on the structural and magnetic properties of milled samples was also investigated. The saturation magnetization of annealed sample (120 emu/g) is higher than the optimum milled sample (95 emu/g) due to increasing preferential ordered L2{sub 1} structure.

Magnetic phase transitions in strongly chained semiconductor compounds TIFeS2 and TIFeSe2

International Nuclear Information System (INIS)

Asgerov, E.B.; Madadzada, A.I.; Beskropvniy, A.I.; Asgerov, E.B.; Mehdiyeva, R.N.; Madadzada, A.I.; Ismayilov, D.I.; Kerimova, E.M.

2014-01-01

Full text: The analysis of diffraction data was carried out by the Rietveld method using the programs VMRIA and FullProf, using as a starting model for the calculations of neutron diffraction profile of X-ray data. The neutron data showed that over the entire temperature range of these compounds have a monoclinic crystal structure symmetry

Characterization of vaterite synthesized at various temperatures and stirring velocities without use of additives

Czech Academy of Sciences Publication Activity Database

Ševčík, Radek; Pérez-Estébanez, Marta; Viani, Alberto; Šašek, Petr; Mácová, Petra

2015-01-01

Roč. 284, November (2015), s. 265-271 ISSN 0032-5910 R&D Projects: GA ČR(CZ) GP14-20374P; GA MŠk(CZ) LO1219 Keywords : synthesis * vaterite * Rietveld method * morphology * nanoindentation Subject RIV: AL - Art, Architecture, Cultural Heritage Impact factor: 2.759, year: 2015 http://www.sciencedirect.com/science/article/pii/S0032591015005239

Characterisation and development of fine porosity in magnesium potassium phosphate ceramics

Czech Academy of Sciences Publication Activity Database

Viani, Alberto; Radulescu, A.; Pérez-Estébanez, Marta

2015-01-01

Roč. 161, December (2015), s. 628-630 ISSN 0167-577X R&D Projects: GA MŠk(CZ) LO1219 Keywords : amorphous materials * chemically-bonded ceramics * microstructure * Rietveld-RIR method * small-angle neutron scattering * specific surface area Subject RIV: AL - Art, Architecture, Cultural Heritage Impact factor: 2.437, year: 2015 https://juser.fz-juelich.de/record/255737

Deriving Quantitative Crystallographic Information from the Wavelength-Resolved Neutron Transmission Analysis Performed in Imaging Mode

Directory of Open Access Journals (Sweden)

Hirotaka Sato

2017-12-01

Full Text Available Current status of Bragg-edge/dip neutron transmission analysis/imaging methods is presented. The method can visualize real-space distributions of bulk crystallographic information in a crystalline material over a large area (~10 cm with high spatial resolution (~100 μm. Furthermore, by using suitable spectrum analysis methods for wavelength-dependent neutron transmission data, quantitative visualization of the crystallographic information can be achieved. For example, crystallographic texture imaging, crystallite size imaging and crystalline phase imaging with texture/extinction corrections are carried out by the Rietveld-type (wide wavelength bandwidth profile fitting analysis code, RITS (Rietveld Imaging of Transmission Spectra. By using the single Bragg-edge analysis mode of RITS, evaluations of crystal lattice plane spacing (d-spacing relating to macro-strain and d-spacing distribution’s FWHM (full width at half maximum relating to micro-strain can be achieved. Macro-strain tomography is performed by a new conceptual CT (computed tomography image reconstruction algorithm, the tensor CT method. Crystalline grains and their orientations are visualized by a fast determination method of grain orientation for Bragg-dip neutron transmission spectrum. In this paper, these imaging examples with the spectrum analysis methods and the reliabilities evaluated by optical/electron microscope and X-ray/neutron diffraction, are presented. In addition, the status at compact accelerator driven pulsed neutron sources is also presented.

The peak in neutron powder diffraction

International Nuclear Information System (INIS)

Laar, B. van; Yelon, W.B.

1984-01-01

For the application of Rietveld profile analysis to neutron powder diffraction data a precise knowledge of the peak profile, in both shape and position, is required. The method now in use employs a Gaussian shaped profile with a semi-empirical asymmetry correction for low-angle peaks. The integrated intensity is taken to be proportional to the classical Lorentz factor calculated for the X-ray case. In this paper an exact expression is given for the peak profile based upon the geometrical dimensions of the diffractometer. It is shown that the asymmetry of observed peaks is well reproduced by this expression. The angular displacement of the experimental profile with respect to the nominal Bragg angle value is larger than expected. Values for the correction to the classical Lorentz factor for the integrated intensity are given. The exact peak profile expression has been incorporated into a Rietveld profile analysis refinement program. (Auth.)

Synthesis and characterization of Cr2O3 nanoparticles through sol-gel proteic method

International Nuclear Information System (INIS)

Medeiros, Angela Maria de Lemos

2007-01-01

In the last years, nanoparticles have becoming important to several researchers. This research reside in the fact that new and uncommon physical and chemical properties, absent in the same material in macro and microscopic size, are observed in this new scale. The subject of this study is obtaining chromium oxide nanoparticles (Cr 2 O 3 ) by sol–gel proteic process using gelatin as an organic precursor. This process appears as a new alternative for the synthesis of oxides for great applications with high efficiency and low cost. The interest in that material is due to the several applications such as green pigments, coverings of materials for thermal protection and mainly as catalyst of countless products originating from of the industry of the petroleum, among others. This new route, using chromium salt as chromium source, produces nanoparticles with average particle size between 20 and 60nm. These values were obtained for different crystallographic direction by means of X-Ray Diffraction (XRD) technique and the structure refinement by Rietveld method were applied in several samples prepared at different temperatures. Other techniques have been used in order to complement the XRD results. (author)

Zeta potential study of Sb2S3 nanoparticles synthesized by a facile polyol method in various surfactants

Science.gov (United States)

Saxena, Monika; Okram, Gunadhor Singh

2018-05-01

In the present work, we report the successful synthesis of stibnite Sb2S3 nanoparticles (NPs) by a facile polyol method using various surfactant. The structural and optical properties were investigated by X-ray diffraction (XRD), Raman spectroscopy and Zeta potential. Rietveld refinement of XRD data confirms the single phase orthorhombic crystal structure of stibnite Sb2S3. Presence of six obvious Raman modes further confirmed their stoichiometric formation. Effect of different surfactants on the surface charge of Sb2S3 NPs was studied using Zeta potential measurement in deionized water at different pH values. They reveal that these NPs are more stable when it was synthesized in presence of EDTA than that of CTAB or without surfactant samples with high zeta potential. The isoelectronic point was found at pH = 6.4 for pure sample, 3.5 and 7.2 for CTAB and not found for EDTA Sb2S3 samples. This information can be useful for many industrial applications like pharmaceuticals, ceramics, waste water treatment and medicines.

Low-temperature synthesis and characterization of anatase TiO2 nanoparticles by an acid assisted sol–gel method

International Nuclear Information System (INIS)

Leyva-Porras, C.; Toxqui-Teran, A.; Vega-Becerra, O.; Miki-Yoshida, M.; Rojas-Villalobos, M.; García-Guaderrama, M.

2015-01-01

The synthesis of anatase TiO 2 nanoparticles by an acid-assisted sol–gel method at 25 and 80 °C is described. Specifically, acetic acid (AA) was used and the evolution of the anatase phase with the amount of AA was observed. The results of X-ray diffraction (XRD) and transmission electron microscopy (TEM) both showed that a pure anatase phase was obtained with particle size smaller than 5 nm. Structural refinements and quantitative determination of phase composition was achieved by using the Rietveld method. The particle size distribution became slightly narrower as the amount of AA was increased. Raman spectroscopy showed that when the amount of AA was increased a small amount of brookite was present at the contamination level. The anatase phase was studied by differential thermal analysis (DTA), providing phase stability up to 600 °C. These and other results were discussed in terms of particle size and structure. Likewise, the formation of the anatase phase under these synthesis conditions was explained. - Highlights: • Synthesis of anatase TiO 2 nanoparticles by an acid assisted sol–gel method at mild conditions. • Microstructure characterization by XRD, TEM and Raman spectroscopy. • Observation of the formation and evolution of the anatase phase as acetic acid was increased. • Anatase thermal stability up to 600 °C and band gap range between 3.2 and 3.5 eV. • A simplified method which can be considered as a green chemistry process

Direct observations of the MOF (UiO-66) structure by transmission electron microscopy

KAUST Repository

Zhu, Liangkui

2013-01-01

As a demonstration of ab initio structure characterizations of nano metal organic framework (MOF) crystals by high resolution transmission electron microscopy (HRTEM) and electron diffraction tomography methods, a Zr-MOF (UiO-66) structure was determined and further confirmed by Rietveld refinements of powder X-ray diffraction. HRTEM gave direct imaging of the channels. © 2013 The Royal Society of Chemistry.

Incident spectrum determination for time-of-flight neutron powder diffraction data analysis

International Nuclear Information System (INIS)

Hodges, J. P.

1998-01-01

Accurate characterization of the incident neutron spectrum is an important requirement for precise Rietveld analysis of time-of-flight powder neutron diffraction data. Without an accurate incident spectrum the calculated model for the measured relative intensities of individual Bragg reflections will possess systematic errors. We describe a method for obtaining an accurate numerical incident spectrum using data from a transmitted beam monitor

Neutron scattering study of combustion-synthesized Ce1− xCuxO2− x

Indian Academy of Sciences (India)

Powder neutron diffraction and Hi- neutron diffraction data have been recorded and analysed in order to obtain the local and long range order of Cu in Cu-doped CeO2 with three doping levels of Cu. Rietveld method and MCGR techniques of data analysis for the two types of data reveal that the Cu ion is in the 2+ ...

Nanocystalline ZnO films prepared via polymeric precursor method (Pechini)

Energy Technology Data Exchange (ETDEWEB)

Sanchez, C.; Doria, J.; Paucar, C.; Hernandez, M. [Laboratorio de Materiales Ceramicos y Vitreos, Universidad Nacional de Colombia, Sede Medellin, A.A. 568, Medellin (Colombia); Mosquera, A.; Rodriguez, J.E. [Grupo CYTEMAC, Universidad del Cauca, Calle 5 No 4-70, Popayan (Colombia); Gomez, A. [Departamento de Ingenieria de Materiales, Universidad Nacional de Colombia, sede Medellin, A.A. 568, Medellin (Colombia); Baca, E. [Grupo de Ingenieria de Nuevos Materiales, Universidad del Valle, A.A. 25360 Cali (Colombia); Moran, O., E-mail: omoranc@unal.edu.c [Laboratorio de Materiales Ceramicos y Vitreos, Universidad Nacional de Colombia, Sede Medellin, A.A. 568, Medellin (Colombia)

2010-09-01

The polymeric precursor method (Pechini) was employed to prepare high-quality nanocrystalline zinc oxide (ZnO) films. Briefly, the process started off with the preparation of a coating solution by the Pechini process followed by a coating of the glass substrates by a dip-coating technique and subsequent heat-treatment of the as-deposited films up to 550 {sup o}C for 30 min. The Rietveld profile analysis of the X-ray diffraction (XRD) spectra revealed the wuerzite structure as expected for ZnO with a P6{sub 3}mc symmetry. No additional peaks were observed that would correspond to any secondary crystalline phase. The average crystallites size was 20 nm as calculated by Sherrer's equation. UV-vis spectroscopy showed sharp ultraviolet absorption edges at {approx}380 nm. The absorption edge analysis yielded optical band gap energy of 3.24 eV with electronic transition of the direct transition type. The Fourier transform infrared (FTIR) analysis showed asymmetric and symmetric stretching modes of the carboxyl group (C=O). Scanning electron microscope (SEM) analysis revealed a crack-free surface morphology indicating that coating of the amorphous glass substrates was homogeneous on large surface areas. The temperature dependent conductivity featured a typical semiconducting-like behavior with resistivity approaching 3x10{sup -1} {Omega} cm at 220 K.

Low-temperature synthesis and characterization of anatase TiO{sub 2} nanoparticles by an acid assisted sol–gel method

Energy Technology Data Exchange (ETDEWEB)

Leyva-Porras, C. [Centro de Investigación en Materiales DIP-CUCEI, Universidad de Guadalajara, Av. Revolución # 1500, Col. Olímpica, C.P. 44430, Guadalajara (Mexico); Centro de Investigación en Materiales Avanzados, S.C. (CIMAV), Alianza Norte No. 202, Parque de Investigación e Innovación Tecnológica (PIIT), Carretera Aeropuerto km. 10, C.P. 66600, Apodaca, N.L. (Mexico); Toxqui-Teran, A.; Vega-Becerra, O. [Centro de Investigación en Materiales Avanzados, S.C. (CIMAV), Alianza Norte No. 202, Parque de Investigación e Innovación Tecnológica (PIIT), Carretera Aeropuerto km. 10, C.P. 66600, Apodaca, N.L. (Mexico); Miki-Yoshida, M. [Centro de Investigación en Materiales Avanzados, S.C. (CIMAV), Miguel de Cervantes No. 120, Parque Industrial Chihuahua, C.P. 31109, Chihuahua (Mexico); Rojas-Villalobos, M.; García-Guaderrama, M. [Centro de Investigación en Materiales DIP-CUCEI, Universidad de Guadalajara, Av. Revolución # 1500, Col. Olímpica, C.P. 44430, Guadalajara (Mexico); and others

2015-10-25

The synthesis of anatase TiO{sub 2} nanoparticles by an acid-assisted sol–gel method at 25 and 80 °C is described. Specifically, acetic acid (AA) was used and the evolution of the anatase phase with the amount of AA was observed. The results of X-ray diffraction (XRD) and transmission electron microscopy (TEM) both showed that a pure anatase phase was obtained with particle size smaller than 5 nm. Structural refinements and quantitative determination of phase composition was achieved by using the Rietveld method. The particle size distribution became slightly narrower as the amount of AA was increased. Raman spectroscopy showed that when the amount of AA was increased a small amount of brookite was present at the contamination level. The anatase phase was studied by differential thermal analysis (DTA), providing phase stability up to 600 °C. These and other results were discussed in terms of particle size and structure. Likewise, the formation of the anatase phase under these synthesis conditions was explained. - Highlights: • Synthesis of anatase TiO{sub 2} nanoparticles by an acid assisted sol–gel method at mild conditions. • Microstructure characterization by XRD, TEM and Raman spectroscopy. • Observation of the formation and evolution of the anatase phase as acetic acid was increased. • Anatase thermal stability up to 600 °C and band gap range between 3.2 and 3.5 eV. • A simplified method which can be considered as a green chemistry process.

First-principles calculation on electronic properties of zinc oxide by zinc–air system

Directory of Open Access Journals (Sweden)

Ahmad Azmin Mohamad

2017-07-01

Full Text Available First-principles calculations are performed to study the electronic properties of zinc oxide (ZnO formed on an anode after discharging a Zn–air system. Prior to calculation, the ZnO is characterised by X-ray diffraction using Rietveld refinement. Diffracted patterns proved the formation of single phase ZnO, while Rietveld analysis shows that the ZnO has a hexagonal wurtzite structure with lattice parameters, a = 3.244 and c = 5.199 Å. Geometry optimisation of the hexagonal wurtzite structure of the ZnO is performed using various exchange–correlation energy functionals. The local density approximation functional method is used to explain the structure, electronic band structure and density of state properties of hexagonal ZnO. The calculated energy band gap was 0.75 eV while the density of states reveals that the O 2p (the top valence band and Zn 4s (the bottom conduction band states domination.

Evaluation of the phase composition of (NH4)2SO4 + (NH4)H2PO4 mixtures by X-ray diffractometry

International Nuclear Information System (INIS)

Ortiz, Angel L.; Cumbrera, Francisco L.; Perez, Jose; Vas, Beatriz del; Perez, Eduardo

2009-01-01

The phase composition of standard (NH 4 ) 2 SO 4 + (NH 4 )H 2 PO 4 mixtures was investigated by X-ray diffractometry (XRD) using the internal-standard, reference-intensity-ratio, and Rietveld methods. It was found that the Rietveld method yields the most accurate phase-composition measurements, with an average error of ∼2 wt.%. It was also found that the internal-standard method is only effective in determining the phase composition if the calibration curve for (NH 4 )H 2 PO 4 is used, giving an average error of ∼6.5 wt.%. On the contrary, the internal-standard method with the calibration curve of the (NH 4 ) 2 SO 4 phase and the reference-intensity-ratio method are not valid. The inappropriateness of these two methods was attributed to graininess in the (NH 4 ) 2 SO 4 phase, with the attendant deviation of its diffracted intensities from the theoretical values. Direct scanning electron microscopy observations of the morphology of the powder particles in the mixtures showed clear evidence of the large agglomerates formed because the individual powder particles are partially sintered together during milling, thus corroborating the graininess determined by the XRD analyses. Finally, the implications of the present study for the quantitative phase-composition analysis of (NH 4 ) 2 SO 4 + (NH 4 )H 2 PO 4 mixtures, which are of great technological importance for the fire prevention industry, are discussed.

Zeta potential and Raman studies of PVP capped Bi2S3 nanoparticles synthesized by polyol method

Science.gov (United States)

Tarachand, Sathe, Vasant G.; Okram, Gunadhor S.

2018-05-01

Here we report the synthesis and characterisation of polyvinylpyrrolidone (PVP) capped Bi2S3 nanoparticles via one step catalyst-free polyol method. Raman spectroscopy, dynamic light scattering and zeta potential analysis were performed on it. Rietveld refinement of powder XRD of PVP capped samples confirmed the formation of single phase orthorhombic Bi2S3 for all PVP capped samples. The presence of eight obvious Raman modes further confirmed the formation of stoichiometric Bi2S3. Dynamic light scattering (DLS) studies show a clear increase in hydrodynamic diameter for samples made with increasing PVP concentration. Particle size obtained from DLS and XRD (using Scherrer's formula) combine with change in full width half maxima of Raman modes collectively suggest overall improvement in crystallinity and quality of product on introducing PVP. In zeta potential (ζ) measurement, steric hindrance of carbon chains plays very crucial role and a systematic reduction of ζ value is observed for samples made with decreasing PVP concentration. An isoelectric point is obtained for sample made with low PVP (1g). Present results are likely to open a window for its medical and catalytic applications.

Synthesis and characterization of NiO nanoparticles by Pechini method; Sintese e caracterizacao de nanoparticulas de NiO pelo metodo Pechini

Energy Technology Data Exchange (ETDEWEB)

Nascimento, A; Ribeiro, M A; Costa, A C.F.M.; Gama, L [Universidade Federal de Campina Grande (UFCG), PB (Brazil). Dept. de Engenharia de Materiais; Bernardi, M I.B. [Universidade de Sao Paulo (IFSC/USP), Sao Carlos, SP (Brazil). Inst. de Fisica

2009-07-01

In recent years, ultrafine magnetic particles of NiO have attracting the attention because of its unknown behavior, enormous scientific potential and technological application. Some of its more important properties are accented magnetic moments, double dynamic exchange, quantization of wave of spin and etc. In this context, this work has for objective to synthesize and to characterize nanoparticles of NiO for the Pechini method. The powder was analyzed by X-rays diffraction. The results of scanning electron microscopy, adsorption of nitrogen. The analysis of X-rays diffraction of the sample showed single-phase peaks of NiO, with crystallite size close to 38 nm. The surface area was 6.44 m{sup 2}/g. The image from scanning electron microscopy shows soft homogeneous agglomerates. The Pechini synthesis was efficient in the production of powders of NiO nano metrics and single-phase. (author)

A novel LaFeO3−XNX oxynitride. Synthesis and characterization

International Nuclear Information System (INIS)

Sierra Gallego, G.; Marín Alzate, N.; Arnache, O.

2013-01-01

Highlights: ► LaFeO 3 perovskite synthesized by auto combustion method. ► LaFeO 3−X N X oxynitride produced by ammonolysis reaction. ► Oxynitride characterized by XRD, Rietveld, SEM, EDX, BET, Raman, TGA and FTIR. ► Partial replacement of oxygen by nitrogen increases slightly the cell parameters. ► TGA shows that oxynitride start to decompose in air above 550 °C. Evolution of N 2 and NO was detected. - Abstract: A perovskite LaFeO 3 was synthesized by auto combustion method and then LaFeO 3−X N X oxynitride was produced by ammonolysis reaction. The synthesized LaFeO 3−X N X oxynitride was characterized by X-ray diffraction (XRD), Rietveld refinement, scanning electron microscopy (SEM), energy dispersive X-ray (EDX), Brunauer–Emmett–Teller (BET) nitrogen adsorption, particle size distribution, Raman spectroscopy, thermogravimetric analysis (TGA) and Fourier transform infrared spectroscopy (FTIR). Nitrogen effect into the perovskite structure was confirmed by DRX. The structure refinement using the Rietveld method indicates that partial replacement of oxygen by nitrogen increases slightly the cell parameters of the LaFeO 3 perovskite. FTIR analysis show that bands at 995 and 1070 cm −1 in the oxynitrides spectra could be assigned to the stretching vibration modes of Fe–N bonds in the FeO 6−X N X octahedral. Thermogravimetric analysis (TGA) showed that LaFeO 3−X N X oxynitride series start to decompose in air above 550 °C. During the decomposition it was found that some amount of nitrogen stays retained in the structure forming intermediate compounds. MS analysis of the gaseous products reveals the evolution of N 2 and NO, suggesting a complex reaction mechanism. To our knowledge, there are no reports on the synthesis and characterization of the LaFeO 3−X N X oxynitrides.

Synthesis of Bi{sub 25}FeO{sub 39} by molten salts method and its Mössbauer spectrum

Energy Technology Data Exchange (ETDEWEB)

Flores Morales, Shirley Saraí; León Flores, Jesús A.; Pérez Mazariego, José Luis, E-mail: mazariego@ciencias.unam.mx; Marquina Fábrega, Vivianne; Gómez González, Raúl W.

2017-01-01

A sample of Bi{sub 25}FeO{sub 39} was synthesized by the molten salts method in 2 h at 750 °C with KCl-KBr as reaction media. The sample was characterized with X-ray powder diffraction and Mössbauer spectroscopy. The Rietveld refinement of the X-ray diffraction confirms that a sillenite type structure with a cell parameter a=10.190(4) Å was achieved, with only small traces of Bi{sub 2}O{sub 3}. In order to get a Mössbauer spectrum with a good signal to noise ratio, the synthesis was made using 95% enriched α–{sup 57}Fe{sub 2}O{sub 3}. To our knowledge, this is the first time that a Mössbauer spectrum for the Bi{sub 25}FeO{sub 39} has been recorded. The nonappearance of a magnetic sextet confirms its paramagnetic behavior. The measured Mössbauer parameters (IS=0.20±0.004 mm/s and QS=0.2±0.07 mm/s) correspond to Fe{sup +3} in very symmetric surroundings, and rule out some interpretations given to the doublet observed in some Mössbauer spectra of BiFeO{sub 3}.

Facile synthesis of B-type carbonated nanoapatite with tailored microstructure

Energy Technology Data Exchange (ETDEWEB)

Gualtieri, Magdalena Lassinantti, E-mail: magdalena.gualtieri@unimore.it [Dipartimento Ingegneria “Enzo Ferrari”, Università degli studi di Modena e Reggio Emilia, I-41125 Modena (Italy); Romagnoli, Marcello, E-mail: marcello.romagnoli@unimore.it [Dipartimento Ingegneria “Enzo Ferrari”, Università degli studi di Modena e Reggio Emilia, I-41125 Modena (Italy); Hanuskova, Miriam, E-mail: Miriam.hanuskova@unimore.it [Dipartimento Ingegneria “Enzo Ferrari”, Università degli studi di Modena e Reggio Emilia, I-41125 Modena (Italy); Fabbri, Elena, E-mail: Elena.fabbri@unimore.it [Dipartimento Ingegneria “Enzo Ferrari”, Università degli studi di Modena e Reggio Emilia, I-41125 Modena (Italy); Gualtieri, Alessandro F., E-mail: Alessandro.gualtieri@unimore.it [Dipartimento di Scienze Chimiche e Geologiche, Università degli studi di Modena e Reggio Emilia, I-41121 Modena (Italy)

2014-12-15

Nanolime and a phosphate-based chelating agent were used to synthesize B-type carbonated apatite. Developed Rietveld refinement strategies allowed one to determine process yield, product crystallinity as well as structural (unit cell) and microstructural (size, strain) parameters. The effect of synthesis temperature (20–60 °C) as well as Ca/P ratio (1.5–2.5) and solid content (10–30 wt%) of the starting batch on these properties were investigated. FTIR, TEM and gas adsorption data provided supporting evidence. The process yield was 42–60 wt% and found to be governed by the Ca/P ratio. The purified products had high specific surface area (107–186 m{sup 2}/g) and crystallinity (76–97%). The unit cell parameters, correlated to the degree of structural carbonate, were sensitive to the Ca/P ratio. Instead, temperature governed the microstructural parameters. Less strained and larger crystals were obtained at higher temperatures. Long-term aging up to 6 months at 20 °C compensated for higher crystal growth kinetics at higher temperature. - Graphical abstract: Controlled synthesis of carbonated apatite at moderate temperatures using nanolime and sodiumhexametaphosphate as starting reagent. - Highlights: • Chemical synthesis of nano-sized apatite with tailored microstructure was performed. • Colloidal Ca(OH){sub 2} and a phosphorus-based chelating agents were used as reagents. • The method is simple and reproducible which facilitate industrial process scale-up. • Rietveld refinement strategies for product characterization were developed. • Rietveld analyses provided yield, microstructural and structure information.

Facile synthesis of B-type carbonated nanoapatite with tailored microstructure

International Nuclear Information System (INIS)

Gualtieri, Magdalena Lassinantti; Romagnoli, Marcello; Hanuskova, Miriam; Fabbri, Elena; Gualtieri, Alessandro F.

2014-01-01

Nanolime and a phosphate-based chelating agent were used to synthesize B-type carbonated apatite. Developed Rietveld refinement strategies allowed one to determine process yield, product crystallinity as well as structural (unit cell) and microstructural (size, strain) parameters. The effect of synthesis temperature (20–60 °C) as well as Ca/P ratio (1.5–2.5) and solid content (10–30 wt%) of the starting batch on these properties were investigated. FTIR, TEM and gas adsorption data provided supporting evidence. The process yield was 42–60 wt% and found to be governed by the Ca/P ratio. The purified products had high specific surface area (107–186 m 2 /g) and crystallinity (76–97%). The unit cell parameters, correlated to the degree of structural carbonate, were sensitive to the Ca/P ratio. Instead, temperature governed the microstructural parameters. Less strained and larger crystals were obtained at higher temperatures. Long-term aging up to 6 months at 20 °C compensated for higher crystal growth kinetics at higher temperature. - Graphical abstract: Controlled synthesis of carbonated apatite at moderate temperatures using nanolime and sodiumhexametaphosphate as starting reagent. - Highlights: • Chemical synthesis of nano-sized apatite with tailored microstructure was performed. • Colloidal Ca(OH) 2 and a phosphorus-based chelating agents were used as reagents. • The method is simple and reproducible which facilitate industrial process scale-up. • Rietveld refinement strategies for product characterization were developed. • Rietveld analyses provided yield, microstructural and structure information

Synthesis and characterization of Ni{sub 0.7}Zn{sub 0.3}Fe{sub 2}O{sub 4} ferrospinel: performance evaluation for methyl and ethyl esterification; Sintese e caracterizacao do ferroespinelio Ni{sub 0,7}Zn{sub 0,3}Fe{sub 2}O{sub 4}: avaliacao de desempenho na esterificacao metilica e etilica

Energy Technology Data Exchange (ETDEWEB)

Mapossa, A.B., E-mail: mapossabenjox@gmail.com [Curso de Quimica, Dept. de Ciencias Naturais, Universidade Pedagogica de Mocambique, Delegacao de Manica, Chimoio (Mozambique); Dantas, J.; Diniz, V.C.S.; Costa, A.C.F.M. [Universidade Federal de Campina Grande (UFCG), PB (Brazil). Programa de Pos-Graduacao em Ciencia e Engenharia de Materiais; Silva, M.R. [Universidade Federal de Itajuba (UNIFEI), MG (Brazil). Dept. de Fisica; Kiminami, R.H.G.A. [Universidade Federal de Sao Carlos (UFSCar), SP (Brazil). Departamento de Engenharia de Materiais

2017-04-15

Ni{sub 0.7}Zn{sub 0.3}Fe{sub 2}O{sub 4} ferrospinel was synthesized by combustion and its catalytic performance in methyl and ethyl esterification of the soybean oil was investigated. The samples were characterized by X-ray diffraction, Rietveld refinement analysis, energy dispersive X-ray fluorescence spectroscopy, Fourier transform infrared spectroscopy, textural analysis, scanning electron microscopy, density by picnometry, particle size analysis, thermogravimetric analysis, magnetic measurements, and catalytic tests. The synthesis was efficient resulting in a ferrospinel with single phase Ni{sub 0.7}Zn{sub 0.3}Fe{sub 2}O{sub 4} with crystallite size of 20 nm, high surface area (86 m{sup 2}/g) and saturation magnetization of 18 emu/g. The ferrospinel had promising catalytic activity in both reaction conditions studied, being more active in the conversion of soybean oil to biodiesel in methyl esterification with an average conversion of 93.9±2.8%. (author)

Electromagnetic attenuation analysis of Ni{sub 0.4}Zn{sub 0.6}Fe{sub 2O4} obtained by citrate precursor method; Analise da atenuacao de radiacao eletromagnetica de Ni{sub 0.4}Zn{sub 0.6}Fe{sub 2O4} obtido pelo metodo de citrato precursor

Energy Technology Data Exchange (ETDEWEB)

Hwang, K. [Centro Tecnico Aeroespacial (CTA-IAE), Sao Jose dos Campos, SP (Brazil). Inst. de Atividades Espaciais. Div. Materiais; Moura, A.E.G.; Nasar, R.S.; Nasar, M.C. [Universidade Federal do Rio Grande do Norte (UFRN), Natal (Brazil). Dept. de Quimica; Pereira, J.J. [Universidade de Taubate, SP (Brazil)

2010-07-01

In this work, two types of synthesized Ni{sub 0,4}Zn{sub 0,6}Fe{sub 2}O{sub 4} by citrate precursor method. The first type was calcined at 350 deg C for 3.5 h, and the second, after calcination, it was subjected to heat treatment at 600 deg C for 2h in argon atmosphere. Both types were analyzed by X-ray diffraction (XRD) and equipment waveguide. The data were investigated by Rietveld refinement method and showed the NiZn ferrite phase with crystallite size of 12.2 +- 0.1 nm (350 deg C) and 166.7 +- 3.6 nm (600 deg C). The heat treatment also influenced the values of electric permittivity and magnetic permeability, and attenuation of electromagnetic radiation in the frequency range in microwave (8-12 GHz). The sample treated attenuates more and allows its application with thinner, making it attractive its use as absorber material in this frequency range. (author)

Dielectric and magnetic characterization of the electroceramic Ba2Co2Fe12O22 doped with Bi2O3 for applications in electronics components

International Nuclear Information System (INIS)

Pires Junior, G.F.M.; Sales, A.J.M.; Rodrigues, H.O.; Sombra, A.S.B.

2012-01-01

The objective of this work is to study the dielectric and magnetic properties of electroceramics (Ba 2 Co 2 Fe 12 O 22 - Co 2 Y) doped with (3; 5 and 10 wt%) of Bi 2 O 3 in order to promote better dielectric and magnetic properties for applications in electronics. Phase Co 2 Y was obtained through the method of solid-state reaction. The structural characterization was performed by X-ray Diffraction using the Rietveld refinement. Magnetic hysteresis curves of the samples were obtained at room temperature. The Impedance Spectroscopy was used in the study of the dielectric function of frequency in the range 100-100 MHz, at room temperature. It follows that the Rietveld refinement confirmed the structure to the hexagonal crystalline phase obtained. The curve analysis confirmed the magnetic hysteresis behavior of the ferrimagnetic samples. Furthermore, the samples showed large values of dielectric permittivity (30.8) and small dielectric loss (3,66 x10 -1 ) at 100 MHz for the sample B1, making them passive miniaturization. (author)

The structure of denisovite, a fibrous nanocrystalline polytypic disordered `very complex' silicate, studied by a synergistic multi-disciplinary approach employing methods of electron crystallography and X-ray powder diffraction

Directory of Open Access Journals (Sweden)

Ira V. Rozhdestvenskaya

2017-05-01

Full Text Available Denisovite is a rare mineral occurring as aggregates of fibres typically 200–500 nm diameter. It was confirmed as a new mineral in 1984, but important facts about its chemical formula, lattice parameters, symmetry and structure have remained incompletely known since then. Recently obtained results from studies using microprobe analysis, X-ray powder diffraction (XRPD, electron crystallography, modelling and Rietveld refinement will be reported. The electron crystallography methods include transmission electron microscopy (TEM, selected-area electron diffraction (SAED, high-angle annular dark-field imaging (HAADF, high-resolution transmission electron microscopy (HRTEM, precession electron diffraction (PED and electron diffraction tomography (EDT. A structural model of denisovite was developed from HAADF images and later completed on the basis of quasi-kinematic EDT data by ab initio structure solution using direct methods and least-squares refinement. The model was confirmed by Rietveld refinement. The lattice parameters are a = 31.024 (1, b = 19.554 (1 and c = 7.1441 (5 Å, β = 95.99 (3°, V = 4310.1 (5 Å3 and space group P12/a1. The structure consists of three topologically distinct dreier silicate chains, viz. two xonotlite-like dreier double chains, [Si6O17]10−, and a tubular loop-branched dreier triple chain, [Si12O30]12−. The silicate chains occur between three walls of edge-sharing (Ca,Na octahedra. The chains of silicate tetrahedra and the octahedra walls extend parallel to the z axis and form a layer parallel to (100. Water molecules and K+ cations are located at the centre of the tubular silicate chain. The latter also occupy positions close to the centres of eight-membered rings in the silicate chains. The silicate chains are geometrically constrained by neighbouring octahedra walls and present an ambiguity with respect to their z position along these walls, with displacements between neighbouring layers being

Synthesis and structural investigation of new Co1-xNixTeO4 (x = 0, 0.2, 0.5, 0.8 and 1) compounds

Science.gov (United States)

Patel, Akhilesh K.; Singh, Harishchandra; Suresh, K. G.

2018-05-01

The new polycrystalline compounds Co1-xNixTeO4 (x = 0, 0.2, 0.5, 0.8 and 1) were prepared by sol-gel method and their structural properties have been studied. Structural investigation through Rietveld method shows monoclinic structure with space group P21/c for all compounds. All compounds polyhedral structure found to be in octahedral form with cations (M) at the center and six oxygen atoms at corner of octahedral structure. The lattice parameters variation with Ni substitution are found to be decreasing with Ni substitution.

Comment on 'Pressure-induced changes in transport properties of layered La1.2Ca1.8Mn2O7'

International Nuclear Information System (INIS)

Ganguly, R.; Siruguri, V.; Gopalakrishnan, I.K.; Yakhmi, J.V.

2000-01-01

We show that the compound La 1.2 Ca 1.8 Mn 2 O 7 does not form with layered Sr 3 Ti 2 O 7 -type structure as reported by Kamenev et al. [Phys. Rev. B 56, R12 688 (1997)]. Detailed analysis of the powder x-ray diffraction pattern of this compound (synthesized by using the solid-state method) by Rietveld method shows that it forms a multiphase mixture comprising hole-doped perovskite manganates (La 1-x Ca x MnO 3 ) as the majority phases and CaO as the minority phase

Structural and magnetic study of CoCr{sub 2}O{sub 4} thin films obtained by employing the sol-gel method

Energy Technology Data Exchange (ETDEWEB)

Del Toro, A.D.; Garcia, R.P.; Davila, Y.G.; Gomes, J.L.; Goncalves, L.P.; Hernandez, E.P. [Universidade Federal de Pernambuco (UFPE), PE (Brazil)

2016-07-01

Full text: In this work we made a study about the structural and magnetic properties of cobalt chromite. We obtained samples in a film format and also in chromite nanopowder. Both, the powder and films were fabricated by the sol-gel chemical method, the film were deposited by the spin coating technique followed by an appropriate heat treatment at 500 °C. The used substrate was glass based on silica and we studied the rotating speed parameter during deposition. The initial aim of the work was the study of the influence of rotating speed on the quality of cromite films. The crystallinity of samples was confirmed by diffraction X-ray (XRD). The lattice parameters were determined using the Rietveld method from which we calculate grain size of 8.6 nm. The scanning electron microscopy (SEM) showed granular films with good homogeneity and we observed the dependence of the rotating speed on the quality of the deposited films. The magnetic properties were measured using a vibrating sample magnetometer (VSM). For powder samples we obtained Curie temperature of 94 K, which is a phase transition from ferrimagnetic to paramagnetic. The applied magnetic field during in the characterization of the film was oriented parallel to the plane of the substrate and we observed a high coercivity. The Curie temperature value for the films was 93 K, similar to the powder samples. (author)

Structural and optical study of CaF{sub 2} nanoparticles produced by a microwave-assisted hydrothermal method

Energy Technology Data Exchange (ETDEWEB)

Bezerra, Claudiane dos S., E-mail: cdsantos20@gmail.com; Valerio, Mário E.G.

2016-11-15

CaF{sub 2} nanoparticles were synthesized by the microwave-assisted hydrothermal method. With the addition of the ethylenediamine (EDA) as chelating agent, the size of the particles was reduced. The CaF{sub 2} exhibit single phase identified for X-ray diffraction (XRD) and confirmed by Rietveld refinement. Scanning electron microscopy (SEM) images showed nanoparticles with non-uniform morphology and statistical analysis of collections of particles reviewed that the EDA decreases both the average particle size and average aspect ratio of the particles. The chemical composition of the surface of the particles was investigated by X-ray Photoelectron Spectroscopy (XPS) and the results indicated the presence of reasonable amounts of hydroxyl groups and oxygen ions in the samples produced with EDA. Radioluminescence (RL) measurements showed that both types of nanoparticles presented intrinsic scintillation emission formed by two main bands and that the CaF{sub 2} samples produced without EDA presented higher emission intensity. The broad RL band centered at approximately 293 nm is related to self-trapped exciton (STE) emission of calcium fluoride, while the band at 428 nm can be due to the presence of F centers. The STE excitation and optical band gap were measured through photoluminescent excitation spectra in the VUV range.

Ferrimagnetism and spin excitation in a Ni–Mn partially inverted spinel prepared using a modified polymeric precursor method

Energy Technology Data Exchange (ETDEWEB)

Ferreira, Rafael A. [Programa de Pos-Graduação em Ciência e Tecnologia de Materiais (POSMAT), Universidade Estadual Paulista, Faculdade de Ciências, Caixa Postal 473, 17033-360 Bauru, São Paulo (Brazil); Institut des Sciences Chimiques de Rennes – UMR 6226, Université de Rennes 1, F-35042 Rennes (France); Tedesco, Julio C.G.; Birk, Jonas O. [The Niels Bohr Institute, University of Copenhagen, DK-2100 Copenhagen (Denmark); Kalceff, Walter, E-mail: wkalceff@uts.edu.au [School of Physics and Advanced Materials, University of Technology Sydney (UTS), P.O. Box 123, Broadway, NSW 2007 (Australia); Yokaichiya, Fabiano [Laboratório Nacional de Luz Síncrotron (LNLS), Caixa Postal 6192, CEP 13083-970 Campinas, São Paulo (Brazil); Comissao Nacional de Energia Nuclear (CNEN), Instituto de Pesquisas Energeticas e Nucleares (IPEN), Reactor Multiproposito Brasileiro - RMB, Avenida Lineo Prestes 2242, Bloco A, Cidade Universitaria Armando Salles de Oliveira, Sao Paulo (Brazil); Rasmussen, Nina [The Niels Bohr Institute, University of Copenhagen, DK-2100 Copenhagen (Denmark); Peña, Octavio [Institut des Sciences Chimiques de Rennes – UMR 6226, Université de Rennes 1, F-35042 Rennes (France); Henry, Paul F. [European Spallation Source ESS AB, Box 176, 22100 Lund (Sweden); Simeoni, Giovanna G. [Heinz Maier-Leibnitz Zentrum (MLZ) and Physics Department, Technische Universität München, Lichtenbergstr. 1, 85748 Garching (Germany); Bordallo, Heloisa N. [The Niels Bohr Institute, University of Copenhagen, DK-2100 Copenhagen (Denmark); European Spallation Source ESS AB, Box 176, 22100 Lund (Sweden); and others

2014-07-01

We demonstrate that a Ni–Mn oxide partially inverted spinel (Ni{sub 1−ν}Mn{sub ν})[Ni{sub ν}Mn{sub 2−ν}]O{sub 4} having inversion degree ν ≈ 0.8 and produced by a modified polymeric precursor method exhibits behaviour previously reported only in monophased samples. The structure of the specimen was determined using Rietveld analysis of X-ray and neutron powder diffraction data, showing that at room temperature the material crystallizes in the Fd3{sup ¯}m space group with a lattice constant a = 8.392 Å. Combining magnetization measurements with neutron powder diffraction, we show that the magnetic structure of this spinel is associated with the interplay between the ferromagnetic and antiferromagnetic lattices which coexist due to the cations' presence on both tetrahedral and octahedral sites. Our analysis of the neutron diffraction data confirms the postulated magnetic structure involving a star-like moment arrangement, arising from competition for the B (octahedral) spinel sites by the Ni and Mn cations. Finally, we show that strong magnetic fluctuations are observed in the inelastic neutron scattering data. - Highlights: • Ni–Mn oxide partially-inverted spinel made by modified polymeric precursor method. • Magnetic measurements showed a ferrimagnetic and a parasitic magnetic transition. • NPD revealed a magnetic structure consistent with a star-like moment arrangement. • INS measurements indicated four distinct temperature-dependent magnetic regimes.

Quantitative analysis of crystalline and remaining glass phases in CaO-B2O3-SiO2 ternary system glass ceramics

International Nuclear Information System (INIS)

He Ming; Wu Mengqiang; Zhang Shuren; Zhou Xiaohua; Zhang Ting; Chen Song

2010-01-01

Research highlights: → As for CBS ternary system glass ceramics, due to the complex phase compositions, many methods could be difficult to determine quantitatively the absolute amounts of crystalline and remaining oxides. In this study, an available method based on the Rietveld method was used to quantitatively analyze the relative weight fraction and densities of crystalline phases. These above data are used to obtain a table of both relative weight fraction of crystalline phases and densities of all phases including CBS LTCC. Using volume additivity rule, it is possible to analysis quantitatively the absolute weight fraction of crystalline phases and also the oxides molar content in the remaining glass. - Abstract: Based on Rietveld method of X-ray techniques and volume additivity rule, a new method was developed to quantitatively analyze the phase composition of CaO-B 2 O 3 -SiO 2 ternary system glass ceramics. Lattice parameters, densities and relative weight fractions of crystalline phases in CaO-B 2 O 3 -SiO 2 ternary system were obtained by X-ray diffraction (XRD) refinement. According to the relative weight fraction of crystalline phases and densities of various components, the volume additivity rule was revealed by calculating the absolute weight fraction of crystalline phases of CaO-B 2 O 3 -SiO 2 glass ceramics. In addition, molar contents of the oxides in the remaining glass can also be determined by this method. Comparing this method with internal standard method, it is found that the maximum deviations of the crystallinity and the absolute weight fraction of crystalline phases are less than 2.6% and 2.9%, respectively. As a result, quantitative evaluation of CaO-B 2 O 3 -SiO 2 ternary system glass ceramics can be achieved using this method.

Compressive strain-dependent bending strength property of Al2O3-ZrO2 (1.5 mol% Y2O3) composites performance by HIP

International Nuclear Information System (INIS)

Reyes-Rojas, A.; Esparza-Ponce, H.; De la Torre, S.D.; Torres-Moye, E.

2009-01-01

Nanometric powders and sintered ceramics of Al 2 O 3 -ZrO 2 (1.5 mol% Y 2 O 3 ) prepared by hot isostatic pressing HIP have been studied. A detailed crystallographic study has been performed through X-ray diffraction, Williamson-Hall method, Rietveld method and high-resolution electron microscopy HREM analysis. The crystallographic structure data, such as domain size, lattice parameters, wt% phase, and micro-strain direction have been obtained using Rietveld refinement and Williamson-Hall methods. The results revealed that the compressive strain (ε) increased from 0.56 to 1.18 (10 -3 ) as the t-ZrO 2 content increased too. The HREM interface study conducted along the [0 0 0 1]Al 2 O 3 ||[0 0 1]ZrO 2 zone axis revealed a micro-strain lattice distortion accumulated at the grain boundary due to the ZrO 2 martensitic phase transformation on cooling, t-ZrO 2 grains coalescence and to the grain growth of α-Al 2 O 3 which cause elongated tetragonal crystals. Micro-strain lattice distortion is adjusted by the shear displacements of the planes (1 1 0) and (11-bar0) along [1-bar10] and [1-bar1-bar0] crystallographic directions, respectively; these planes are arrested by the (101-bar0) alumina plane. In this case, semi-coherent interfaces were observed along the grain boundary. It is verified that the bending strength increased in connection with the strain accumulation and amount of tetragonal structure

Method of semi-automatic high precision potentiometric titration for characterization of uranium compounds; Metodo de titulacao potenciometrica de alta precisao semi-automatizado para a caracterizacao de compostos de uranio

Energy Technology Data Exchange (ETDEWEB)

Cristiano, Barbara Fernandes G.; Dias, Fabio C.; Barros, Pedro D. de; Araujo, Radier Mario S. de; Delgado, Jose Ubiratan; Silva, Jose Wanderley S. da, E-mail: barbara@ird.gov.b, E-mail: fabio@ird.gov.b, E-mail: pedrodio@ird.gov.b, E-mail: radier@ird.gov.b, E-mail: delgado@ird.gov.b, E-mail: wanderley@ird.gov.b [Instituto de Radioprotecao e Dosimetria (IRD/CNEN-RJ), Rio de Janeiro, RJ (Brazil); Lopes, Ricardo T., E-mail: ricardo@lin.ufrj.b [Universidade Federal do Rio de Janeiro (LIN/COPPE/UFRJ), RJ (Brazil). Coordenacao dos Programas de Pos-Graduacao de Engenharia. Lab. de Instrumentacao Nuclear

2011-10-26

The method of high precision potentiometric titration is widely used in the certification and characterization of uranium compounds. In order to reduce the analysis and diminish the influence if the annalist, a semi-automatic version of the method was developed at the safeguards laboratory of the CNEN-RJ, Brazil. The method was applied with traceability guaranteed by use of primary standard of potassium dichromate. The standard uncertainty combined in the determination of concentration of total uranium was of the order of 0.01%, which is better related to traditionally methods used by the nuclear installations which is of the order of 0.1%

A new approach to texture measurements: Orientation distribution function (ODF) determination by Rietveld refinement

International Nuclear Information System (INIS)

Vondreele, R.; Larson, A.; Lawson, A.; Sheldon, R.; Wright, S.

1996-01-01

The preferred orientation of crystal grains within a manufactured part is described most fully by its orientation distribution function (ODF), which is a mapping of the probability of each of the possible grain orientations with respect to the exterior dimensions. Traditionally, an ODF is determined from pole figures for a relatively small number of reflections. These pole figures are measured with x-rays or neutrons using short detector scans over the center of an individual diffraction peak for a large number of different sample orientations. This is efficient if the selected diffraction peaks are reasonably strong (relative to background) and well separated, such as in pure fcc and bcc metals. It is also appropriate for constant wavelength sources where collection of individual diffraction peak intensities is a reasonably efficient use of the source. However, the traditional method is not very efficient for neutron diffraction at a spallation source such as LANSCE where the entire diffraction pattern is accessible for each sample setting. Moreover, a different approach is necessary for complicated diffraction patterns, such as from composite materials, intermetallic compounds, high T c ceramics, polyphasic minerals and polymers where there is expected to be heavy overlap of adjacent diffraction peaks. In addition, the large number of settings normally collected for an individual pole figure may not be necessary, since the entire pattern is obtained at each setting. Thus, a new method of ODF analysis needs to be developed to handle the more complex diffraction patterns obtained from modern technological materials as well as take advantage of the particular characteristics of spallation neutron sources. This project sought to develop the experimental procedures and the mathematical treatment needed to produce an orientation distribution function (ODF) directly from full diffraction patterns from a sample in a limited number of orientations

Sintering effect on structural, magnetic and optical properties of Ni{sub 0.5}Zn{sub 0.5}Fe{sub 2}O{sub 4} ferrite nano particles

Energy Technology Data Exchange (ETDEWEB)

Kannan, Y.B., E-mail: ybkans@gmail.com [Department of Physics, Arumugam Pillai Seethai Ammal College, Tiruppattur 630211 (India); Saravanan, R. [PG & Research Department of Physics, The Madura College, Madurai 625011 (India); Srinivasan, N. [PG & Research Department of Physics, Thiagarajar College, Madurai 625009 (India); Ismail, I. [Advanced Materials and Nanotechnology Laboratory, Institute of Advanced Technology, University Putra Malaysia, 43400 Serdang, Selangor (Malaysia)

2017-02-01

Ni{sub 0.5}Zn{sub 0.5}Fe{sub 2}O{sub 4} nano ferrite particles have been prepared by mechanical alloying via high energy ball milling and sintered at different temperatures from 700 °C to 1000 °C. Spinel structure is confirmed from the analysis of XRD data. Rietveld refinement method is employed to refine the XRD powder data and the structural parameters are calculated from the refinement. Small amount of hematite phase is found in all samples. The SEM, EDAX and XRF analysis reveals respectively the morphology, stoichiometric composition and purity of the powder samples. Using Maximum Entropy Method (MEM) the values of the bond strength between various sites interactions in ferrites are evaluated and compared with theoretical predictions of strengthening/weakening of various sites interactions from the values of interionic distances and interionic bond angles. Ferromagnetic nature of the samples is confirmed from the vibrating sample magnetometer study. The obtained low saturation magnetization values are attributed to presence of second phase. The optical band gap energy of the samples was determined by using UV–VIS techniques. - Highlights: • Raw XRD data were refined using Rietveld refinement method using JANA 2006 software. • Fraction of zinc ions occupies at B site. • Bond strength between the atoms at A-site and B-site is studied by employing maximum entropy method (MEM). • From the MEM result, numerical values of the bond strength between various interactions (A–B, A–A, B–B) have been evaluated. • Various sites interactions results are compared with that of hitherto existing theoretical predictions.

Synthesis and electrochemical properties of KPb_4_−_xCa_x(PO_4)_3 (0 ≤ x ≤ 1.5) for oxidation of cadmium at graphite electrode

International Nuclear Information System (INIS)

Lahrich, Sara; Manoun, Bouchaib; El Mhammedi, Moulay Abderrahim

2017-01-01

Chemically modified carbon paste electrode (CPE) for cadmium (II) analysis has been constructed by mixing KPb_4_−_xCa_x(PO_4)_3 (0 ≤ x ≤ 1.5) (CaLA) and graphite powder. The lacunar apatite was synthesized using solid reaction and characterized by X-ray diffraction (XRD), infrared spectroscopy (IR) and Raman spectroscopy. The refinement study was carried out using Rietveld method where the obtained results show a good agreement between the observed and calculated patterns. The detection of cadmium (II) was investigated in acetate buffer (pH 4.5) using differential pulse anodic stripping voltammetry (DPASV). The limit of detection obtained under the optimized experimental conditions was 5.35 × 10"−"7 mol L"−"1 with a relative standard deviation of 2.37%. Possible interferences were tested and evaluated in 5.0 × 10"−"5 mol L"−"1 cadmium (II) in the presence of other inorganic ions. Finally, the proposed method was successfully applied to determine cadmium (II) in seawater and mussel samples. Hence, the satisfactory results confirm the applicability of this sensor in practical analysis. - Highlights: • Synthesis and characterization of new lacunar apatites KPb_4_−_xCa_x(PO_4)_3 (0 ≤ x ≤ 1.5). • Structural refinement of these compounds using Rietveld method. • A study of Ca doping effect in lacunar apatites for detecting Cd (II). • The electrochemical oxidation of Cd (II) was performed at CaLA-CPE using DPASV. • The proposed method was evaluated to detect cadmium in seawater and mussel samples.

Mg doped Li2FeSiO4/C nanocomposites synthesized by the solvothermal method for lithium ion batteries.

Science.gov (United States)

Kumar, Ajay; Jayakumar, O D; Jagannath; Bashiri, Parisa; Nazri, G A; Naik, Vaman M; Naik, Ratna

2017-10-14

A series of porous Li 2 Fe 1-x Mg x SiO 4 /C (x = 0, 0.01, 0.02, 0.04) nanocomposites (LFS/C, 1Mg-LFS/C, 2Mg-LFS and 4Mg-LFS/C) have been synthesized via a solvo-thermal method using the Pluronic P123 polymer as an in situ carbon source. Rietveld refinement of the X-ray diffraction data of Li 2 Fe 1-x Mg x SiO 4 /C composites confirms the formation of the monoclinic P2 1 structure of Li 2 FeSiO 4 . The addition of Mg facilitates the growth of impurity-free Li 2 FeSiO 4 with increased crystallinity and particle size. Despite having the same percentage of carbon content (∼15 wt%) in all the samples, the 1Mg-LFS/C nanocomposite delivered the highest initial discharge capacity of 278 mA h g -1 (∼84% of the theoretical capacity) at the C/30 rate and also exhibited the best rate capability and cycle stability (94% retention after 100 charge-discharge cycles at 1C). This is attributed to its large surface area with a narrow pore size distribution and a lower charge transfer resistance with enhanced Li-ion diffusion coefficient compared to other nanocomposites.

Study of structural and optical properties of CaMoO{sub 4} nanoparticles synthesized by the microwave-assisted solvothermal method

Energy Technology Data Exchange (ETDEWEB)

Botelho, G., E-mail: gleice.lorena@gmail.com [INCTMN-UFSCar, Universidade Federal de São Carlos, P.O. Box 676, 13565-905, São Carlos, SP (Brazil); Nogueira, I.C. [Instituto Federal do Maranhão, PPG em Engenharia de Materiais, 65030-005, São Luís, MA (Brazil); Moraes, E. [INCTMN-UFSCar, Universidade Federal de São Carlos, P.O. Box 676, 13565-905, São Carlos, SP (Brazil); Longo, E. [INCTMN-UNESP, Universidade Estadual Paulista, P.O. Box 355, CEP, 14801-907, Araraquara, SP (Brazil)

2016-11-01

Calcium molybdate (CaMoO{sub 4}) nanoparticles were synthesized by using a rapid assisted-microwave solvothermal method. X-ray diffraction measurements, Fourier transform Raman and Fourier transform infrared spectroscopies, revealed that the samples all have a scheelite-type tetragonal structure. In addition, the data obtained from the Rietveld refinements revealed distortions of the [Ca−O] and [Mo−O] bonds that led, in turn, to distortions of the [CaO{sub 8}] and [MoO{sub 4}] clusters. The presence of irregular spherical-like CaMoO{sub 4} nanoparticles and the corresponding crystallographic arrangement were confirmed and determined via transmission electron microscopy and high resolution transmission electron microscopy, respectively. First-principles quantum mechanical calculations based on the density functional theory at the B3LYP level were employed in order to understand the band structure and density of states of CaMoO{sub 4} in the excited singlet and triplet states. Furthermore, the optical properties were investigated by performing ultraviolet–visible spectroscopy and photoluminescence (PL) measurements. Maximum PL emission of CaMoO{sub 4} powders was detected in the green-region wavelength of the electromagnetic spectrum; this emission was attributed to the distorted [MoO{sub 4}] clusters. - Highlights: • Effect of propane-1,3-diol in the synthesis of nanoparticles by a rapid method. • Utilization of first-principles quantum mechanical calculations. • Investigation of photoluminescent properties of CaMoO{sub 4} nanoparticles.

Influence of milling time on microstructure and magnetic properties of Fe{sub 80}P{sub 11}C{sub 9} alloy produced by mechanical alloying

Energy Technology Data Exchange (ETDEWEB)

Taghvaei, A.H. [Department of Materials Science and Engineering, Shiraz University of Technology, Shiraz (Iran, Islamic Republic of); Ghajari, F., E-mail: fati.ghajari@gmail.com [Department of Materials Science and Engineering, Shiraz University, Shiraz (Iran, Islamic Republic of); Markó, D. [IFW Dresden, Institute for Complex Materials, Helmholtzstr. 20, 01069 Dresden (Germany); Prashanth, K.G. [IFW Dresden, Institute for Complex Materials, Helmholtzstr. 20, 01069 Dresden (Germany); Additive manufacturing Center, Sandvik AB, 81181 Sandviken (Sweden)

2015-12-01

Fe{sub 80}P{sub 11}C{sub 9} alloy with amorphous/nanocrytalline microstructure has been synthesized by mechanical alloying of the elemental powders. The microstructure, thermal behavior and morphology of the produced powders have been studied by X-ray diffraction (XRD), differential scanning calorimetry (DSC) and scanning electron microscopy (SEM), respectively. The crystallite size, lattice strain and fraction of the amorphous phase have been calculated by Rietveld refinement method. The results indicate that the powders microstructure consists of α-Fe(P,C) nanocrystals with an average diameter of 9 nm±1 nm dispersed in the amorphous matrix after 90 h of milling. Moreover, the fraction of amorphous phase initially increases up to 90 h of milling and then decreases after 120 h of milling, as a result of mechanical crystallization and formation of Fe{sub 2}P phase. The magnetic measurements show that while the saturation magnetization decreases continuously with the milling time, the coercivity exhibits a complicated trend. The correlation between microstructural changes and magnetic properties has been discussed in detail. - Highlights: • Glass formation was investigated in Fe{sub 80}P{sub 11}C{sub 9} by mechanical alloying. • Structural parameters were calculated by Rietveld refinement method. • Milling first increased and then decreased the fraction of amorphous phase. • Magnetic properties were significantly changed upon milling.

The nature of the photoluminescence in amorphized PZT

International Nuclear Information System (INIS)

Silva, M.S.; Cilense, M.; Orhan, E.; Goes, M.S.; Machado, M.A.C.; Santos, L.P.S.; Paiva-Santos, C.O.; Longo, E.; Varela, J.A.; Zaghete, M.A.; Pizani, P.S.

2005-01-01

The polymeric precursor method was used to synthesize lead zirconate titanate powder (PZT). The crystalline powder was then amorphized by a high-energy ball milling process during 120 h. A strong photoluminescence emission was observed at room temperature for the amorphized PZT powder. The powders were characterized by XRD and the percentage of amorphous phase was calculated through Rietveld refinement. The microstructure for both phases was investigated by TEM. The optical gap was calculated through the Wood and Tauc method using the UV-Vis. data. Quantum mechanical calculations were carried out to give an interpretation of the photoluminescence in terms of electronic structure

Effect of vanadium doping on structural and magnetic properties of defective nano-nickel ferrite

Science.gov (United States)

Heiba, Zein K.; Mohamed, Mohamed Bakr; Wahba, Adel Maher; Almalowi, M. I.

2018-04-01

Nano-nickel ferrites defected by vanadium doping (NiV x Fe2-1.67 x O4, 0 ≤ x ≤ 0.25) were prepared using a simple sol gel method. Rietveld analysis revealed a nonmonotonic change in lattice parameter, oxygen parameter and magnetization upon doping with vanadium. Cation distributions suggested from either Rietveld analysis or from experimental magnetic moments were in a good agreement. For low doping values ( x = 0.05), vanadium was residing mainly in octahedral sites, while for samples with vanadium content ( x ≥ 0.1) a significant part of vanadium ions resided at tetrahedral sites; a result which has been confirmed by the analysis of Fourier-transform infrared (FTIR) spectrums obtained for the samples. The transmission electron microscope (TEM) image showed fine spherical particles with size of ˜ 11 nm. All samples showed a superparamagnetic nature with a nonmonotonic change of either magnetization ( M S) or coercivity (H C) with the content of nonmagnetic V5+. The cation occupancies indicated presence of an enormous number of vacancies through doping with high valence cation V5+, making present samples potential electrodes for Li- or Na-ion batteries.

Quantitative phase analysis and microstructure characterization of magnetite nanocrystals obtained by microwave assisted non-hydrolytic sol–gel synthesis

Energy Technology Data Exchange (ETDEWEB)

Sciancalepore, Corrado, E-mail: corrado.sciancalepore@unimore.it [Department of Engineering “Enzo Ferrari”, University of Modena and Reggio Emilia, Via Pietro Vivarelli 10, 41100 Modena (Italy); Bondioli, Federica [Department of Industrial Engineering, University of Parma, Parco Area delle Scienze, 181/A, 43124 Parma (Italy); INSTM Consortium, Via G. Giusti 9, 51121 Firenze (Italy); Manfredini, Tiziano [Department of Engineering “Enzo Ferrari”, University of Modena and Reggio Emilia, Via Pietro Vivarelli 10, 41100 Modena (Italy); INSTM Consortium, Via G. Giusti 9, 51121 Firenze (Italy); Gualtieri, Alessandro [Department of Chemical and Geological Science, University of Modena and Reggio Emilia, Via S. Eufemia 19, 41121 Modena Italy (Italy)

2015-02-15

An innovative preparation procedure, based on microwave assisted non-hydrolytic sol–gel synthesis, to obtain spherical magnetite nanoparticles was reported together with a detailed quantitative phase analysis and microstructure characterization of the synthetic products. The nanoparticle growth was analyzed as a function of the synthesis time and was described in terms of crystallization degree employing the Rietveld method on the magnetic nanostructured system for the determination of the amorphous content using hematite as internal standard. Product crystallinity increases as the microwave thermal treatment is increased and reaches very high percentages for synthesis times longer than 1 h. Microstructural evolution of nanocrystals was followed by the integral breadth methods to obtain information on the crystallite size-strain distribution. The results of diffraction line profile analysis were compared with nanoparticle grain distribution estimated by dimensional analysis of the transmission electron microscopy (TEM) images. A variation both in the average grain size and in the distribution of the coherently diffraction domains is evidenced, allowing to suppose a relationship between the two quantities. The traditional integral breadth methods have proven to be valid for a rapid assessment of the diffraction line broadening effects in the above-mentioned nanostructured systems and the basic assumption for the correct use of these methods are discussed as well. - Highlights: • Fe{sub 3}O{sub 4} nanocrystals were obtained by MW-assisted non-hydrolytic sol–gel synthesis. • Quantitative phase analysis revealed that crystallinity up to 95% was reached. • The strategy of Rietveld refinements was discussed in details. • Dimensional analysis showed nanoparticles ranging from 4 to 8 nm. • Results of integral breadth methods were compared with microscopic analysis.

Quantitative phase analysis and microstructure characterization of magnetite nanocrystals obtained by microwave assisted non-hydrolytic sol–gel synthesis

International Nuclear Information System (INIS)

Sciancalepore, Corrado; Bondioli, Federica; Manfredini, Tiziano; Gualtieri, Alessandro

2015-01-01

An innovative preparation procedure, based on microwave assisted non-hydrolytic sol–gel synthesis, to obtain spherical magnetite nanoparticles was reported together with a detailed quantitative phase analysis and microstructure characterization of the synthetic products. The nanoparticle growth was analyzed as a function of the synthesis time and was described in terms of crystallization degree employing the Rietveld method on the magnetic nanostructured system for the determination of the amorphous content using hematite as internal standard. Product crystallinity increases as the microwave thermal treatment is increased and reaches very high percentages for synthesis times longer than 1 h. Microstructural evolution of nanocrystals was followed by the integral breadth methods to obtain information on the crystallite size-strain distribution. The results of diffraction line profile analysis were compared with nanoparticle grain distribution estimated by dimensional analysis of the transmission electron microscopy (TEM) images. A variation both in the average grain size and in the distribution of the coherently diffraction domains is evidenced, allowing to suppose a relationship between the two quantities. The traditional integral breadth methods have proven to be valid for a rapid assessment of the diffraction line broadening effects in the above-mentioned nanostructured systems and the basic assumption for the correct use of these methods are discussed as well. - Highlights: • Fe 3 O 4 nanocrystals were obtained by MW-assisted non-hydrolytic sol–gel synthesis. • Quantitative phase analysis revealed that crystallinity up to 95% was reached. • The strategy of Rietveld refinements was discussed in details. • Dimensional analysis showed nanoparticles ranging from 4 to 8 nm. • Results of integral breadth methods were compared with microscopic analysis

An inexpensive and efficient method for the synthesis of BTO and STO at temperatures lower than 200 deg. C

Energy Technology Data Exchange (ETDEWEB)

Bacha, Elsy, E-mail: m.gooley@elsevier.com [Institut de Recherche en Electrotechnique et Electronique de Nantes Atlantique, E.A. 1770, Universite de Nantes, 2 rue de la Houssiniere, 44322, Nantes (France); Deniard, Philippe; Richard-Plouet, Mireille; Brohan, Luc [Institut des Materiaux Jean Rouxel, Universite de Nantes, CNRS, UMR 6502, Universite de Nantes, 2 rue de la Houssiniere, 44322, Nantes (France); Gundel, Hartmut W. [Institut de Recherche en Electrotechnique et Electronique de Nantes Atlantique, E.A. 1770, Universite de Nantes, 2 rue de la Houssiniere, 44322, Nantes (France)

2011-06-30

During the past decade the reduction in size of functional architectures has been a dominating trend in many fields of science and technology. The search for electronic materials that can be cheaply solution-processed into nanopowders, while simultaneously providing quality device characteristics, represents a major challenge for material scientists. Solvothermal process is used in order to obtain fine nanoparticles of BaTiO{sub 3} and SrTiO{sub 3} at low temperatures by using an inorganic, ionic precursor. Rietveld refinement proves the presence of a mixture of 65% tetragonal and 35% cubic nanoparticles in the barium titanate powder with an average size of 73 nm and 67 nm, respectively. FTIR shows that an acid treatment allows the elimination of carbonate impurities.

An inexpensive and efficient method for the synthesis of BTO and STO at temperatures lower than 200 deg. C

International Nuclear Information System (INIS)

Bacha, Elsy; Deniard, Philippe; Richard-Plouet, Mireille; Brohan, Luc; Gundel, Hartmut W.

2011-01-01

During the past decade the reduction in size of functional architectures has been a dominating trend in many fields of science and technology. The search for electronic materials that can be cheaply solution-processed into nanopowders, while simultaneously providing quality device characteristics, represents a major challenge for material scientists. Solvothermal process is used in order to obtain fine nanoparticles of BaTiO 3 and SrTiO 3 at low temperatures by using an inorganic, ionic precursor. Rietveld refinement proves the presence of a mixture of 65% tetragonal and 35% cubic nanoparticles in the barium titanate powder with an average size of 73 nm and 67 nm, respectively. FTIR shows that an acid treatment allows the elimination of carbonate impurities.

Modifications in the rhombohedral degree of distortion and magnetic properties of Ba-doped BiFeO3 as a function of synthesis methodology

International Nuclear Information System (INIS)

Rojas-George, G.; Silva, J.; Castañeda, R.; Lardizábal, D.; Graeve, O.A.; Fuentes, L.; Reyes-Rojas, A.

2014-01-01

We present an analysis of crystallographic symmetry and the origin of the pseudo-cubic character of doped BiFeO 3 . Specifically, barium-doped bismuth ferrite, Bi 1−x Ba x FeO 3 (x = 0.05, 0.075, 0.1, 0.125), perovskite-type nanoparticles have been synthesized by implementing five modifications to the sol–gel technique (citric acid-assisted sol–gel method, ethylene glycol method, tartaric acid-assisted sol–gel method, polyvinyl alcohol–ethylene glycol method, and EDTA complexing sol–gel method) and their final pseudo-cubic character is discussed. The effect of the carboxylic groups and hydroxyl groups during synthesis is critical to obtain single phase BBFO. Fourier transform infrared spectroscopy and thermogravimetric analysis is used to study the decomposition and thermal behavior of the precursors and their relation to the final nanoparticle characteristics. X-ray diffraction analysis shows a single phase with symmetry changes for four of the five synthesis methodologies employed. Only the EDTA complexing sol–gel method, where EDTA is used as dissolver and chelating agent, is not satisfactory in all concentration ranges. Rietveld results suggest that the degree of distortion of the rhombohedral symmetry in the crystallized BiFeO 3 powders decreases 12% as a result of progressive substitution of Bi 3+ by Ba 2+ and that there is no shift from rhombohedral to tetragonal symmetry. Magnetization properties of samples with a low-distortion rhombohedral structure show higher magnetic saturation and remanent magnetization than samples with high-distortion rhombohedral structure. - Highlights: • Ba–BiFeO 3 : rhombohedral distortion degree is highly affected by the chemical method. • Rietveld results show no shift in BBFO from rhombohedral to tetragonal symmetry. • The low-distortion rhombohedral structure show higher magnetic saturation. • To stabilize a metal complex is necessary a balance between COOH − and OH − groups

Characteristics of Nanosize Spinel NixFe3-xO4 Prepared by Sol-Gel Method Using Egg White as Emulsifying Agent

Directory of Open Access Journals (Sweden)

Rudy Situmeang

2015-07-01

Full Text Available In this study, sol-gel method using egg white as emulsifying agent was applied to prepare nano size spinel NixFe3-xO4 (with x = 0.2–1. Sample preparation was carried out by mixing the solution of Fe(NO33.9 H2O and Ni(NO33.6 H2O with egg white, and then the sample was stirred thoroughly using magnetic stirrer. After freeze–drying process, the sample was subjected to calcination treatment and subsequently characterized. The phase composition was evaluated using the X-ray diffraction (XRD technique, followed by quantitative analysis using Rietveld and Debye-Scherrer Methods. The functionality of the sample was identified using Fourier Transform Infrared (FTIR spectroscopy, and surface morphology and elemental composition were analyzed using scanning electron microscopycoupled with electron dispersive spectroscopy (SEM/EDS. The results of XRD characterization indicated that materials consist of various crystalline phases, with NiFe2O4 as a major phase. FTIR Analysis revealed the existence of both Lewis and Brønsted–Lowry acid sites, with Lewis acid as the prominent site. The sample was found to display relatively homogeneous surface morphology, having the crystallite size in the range of 33 to 61 nm according to the Debye-Scherrer equation. The EDS data indicated that the ratio of Fe/Ni is in agreement with the composition of the raw materials used.

Effect of lanthanide on the microstructure and structure of LnMn0.5Fe0.5O3 nanoparticles with Ln=La, Pr, Nd, Sm and Gd prepared by the polymer precursor method

International Nuclear Information System (INIS)

Romero, Mariano; Faccio, Ricardo; Martínez, Javier; Pardo, Helena; Montenegro, Benjamín; Plá Cid, Cristiani Campos; Pasa, André A.

2015-01-01

The synthesis of LnMn 0.5 Fe 0.5 O 3 perovskite nanoparticles by the polymer precursor method showed a strong intrinsic dependence with different lanthanides (Ln=La, Pr, Nd, Sm and Gd). The polymerization level reached in the polymer precursor was proportional to the atomic number of lanthanide with exception of samarium, which showed the formation of a different precursor based in a citrate chelate with ethyleneglycol bonded as adduct. The increasing level of polymerization of the polymer precursors showed the formation of large-size perovskite nanoparticles after its calcination. SAXS and TEM analyses suggested that nanoparticles obtained, using this method, have a squared-like microstructure in connection with the polymer precursor microstructure. Structural analysis showed an orthorhombic structure with a slight decline in the Jahn–Teller distortion when the atomic number of lanthanide increases. Mössbauer spectroscopy showed the presence of a majority site in agreement with the Pbnm orthorhombic structure best fitted with Rietveld refinements and in some cases, a more distorted site attributed to local inhomogeneities and oxygen vacancies. - Highlights: • Precursor polymerization level is lower in the presence of lighter lanthanides. • Lighter lanthanide perovskite nanoparticles after calcination are lower-sized. • Nanoparticles obtained by this method have lamellae microstructure. • Jahn–Teller distortion declines for heavier lanthanide perovskites. • Oxygen vacancy phase was observed in lighter lanthanide perovskites

Catalytic oxidation of n-hexane promoted by Ce1−xCuxO2 catalysts prepared by one-step polymeric precursor method

International Nuclear Information System (INIS)

Araújo, Vinícius D.; Lima, Maurício M. de; Cantarero, Andrés; Bernardi, Maria I.B.; Bellido, Jorge D.A.; Assaf, Elisabete M.; Balzer, Rosana; Probst, Luiz F.D.; Fajardo, Humberto V.

2013-01-01

Ceria-supported copper catalysts (Ce 1−x Cu x O 2 , with x (mol) = 0, 0.01, 0.03, 0.05 and 0.10) were prepared in one step through the polymeric precursor method. The textural properties of the catalysts were investigated by X-ray diffraction (XRD), Rietveld refinement, N 2 -physisorption (BET surface area), electron paramagnetic resonance (EPR), UV–visible diffuse reflectance and photoluminescence spectroscopies and temperature-programmed reduction (TPR). In a previous study ceria-supported copper catalysts were found to be efficient in the preferential oxidation of CO. In this study, we extended the catalytic application of Ce 1−x Cu x O 2 systems to n-hexane oxidation and it was verified that the catalysts were highly efficient in the proposed reaction. The best performance (up to 95% conversion) was observed for the catalysts with low copper loads (Ce 0.97 Cu 0.03 O 2 and Ce 0.99 Cu 0.01 O 2 , respectively). The physicochemical characterizations revealed that these behaviors could be attributed to the copper species present in the catalysts and the interaction between CuO and CeO 2 , which vary according to the copper content. - Highlights: • Synthesis of CuO/CeO2 catalysts by the one-step polymeric precursor method. • 95% n-hexane conversion on Ce0.97Cu0.03O2 catalyst. • Redox properties play a key role in the catalytic performance

Application of SR Methods for the Study of Nanocomposite Materials for Hydrogen Energy

Science.gov (United States)

Sadykov, V. A.; Pavlova, S. N.; Vinokurov, Z. S.; Shmakov, A. N.; Eremeev, N. F.; Fedorova, Yu. E.; Yakimchuk, E. P.; Kriventsov, V. V.; Bolotov, V. A.; Tanashev, Yu. Yu.; Sadovskaya, E. M.; Cherepanova, S. V.; Zolotarev, K. V.

This work summarizes results of synchrotron radiation (SR) studies of the real/defect structure of nanocrystalline/nanocomposite oxide materials, which determines their functional properties in hydrogen energy field as catalysts and mixed ionic electronic conductors (cathodes and anodes of solid oxide fuel cells, oxygen separation membranes). For nanocrystalline ceria-zirconia mixed oxide prepared via modified Pechini route using ethanol solution of reagents, a high spatial uniformity of cations distribution between domains along with the oxygen sublattice deficiency revealed by full-profile Rietveld refinement of SR diffraction data provide structure disordering enhancing oxygen mobility. For PrNi0.5Co0.5O3-δ - Ce0.9Y0.1O2-δ nanocomposite extensive transfer of Pr cations into fluorite domains generates a new path of fast oxygen diffusion along chains of Pr3+ - Pr4+ cations as directly proved by analysis of the unit cell relaxation after changing pO2 in perfect agreement with data obtained by oxygen isotope heteroexchange.

Terra-cotta figurines from the Roman theatre of Malaga (Spain: An archaeometric study

Directory of Open Access Journals (Sweden)

Compaña, J. M.

2014-06-01

Full Text Available A series of 22 figured Phoeno-Punic and Roman terra-cottas, of high relevant archaeological and patrimonial values, have been studied. The samples were recovered in the Roman Theatre of Malaga (Spain. A thorough analysis including stereomicroscopy, elemental analysis by WDXRF, mineralogical analysis by XRPD coupled with the Rietveld method, and SEM, has been carried out. Highly diluted fused glass beads probed to be enough for the X-ray fluorescence analyses, minimizing the damage to the samples. For selected samples, in addition to the classical use of the Rietveld method, the G-factor external-standard approach has been employed to get full quantitative crystalline and amorphous phase analysis. The analytical results allow proposing a local regional provenance for the main part of the samples, being a relevant data for several artifacts, not contextualized due to stratigraphic alterations in the site. In addition, some relevant samples, for instance a theatrical mask fragment (TRC005, are likely foreign. The overall amorphous is not negligible in phase quantification, accounting for up to 50 wt %. Technologically, all terra-cotta samples are similar, made of calcareous clays, fired at ~700-950 ºC.Se han estudiado 22 terracotas figuradas feno-púnicas y romanas, de alto valor arqueológico y patrimonial. Las muestras proceden de las excavaciones del Teatro romano de Málaga (España. El análisis realizado incluye estereomicroscopía, análisis elemental mediante WDXRF, análisis mineralógico cuantitativo mediante el método de Rietveld de los datos de XRPD y SEM. Para minimizar el daño realizado a las muestras, se prepararon perlas muy diluidas, que han demostrado ser suficientes para los análisis de fluorescencia de rayos-X. Para muestras selectas, además del análisis usual mediante el método de Rietveld, se ha utilizado el método del estándar externo mediante el factor-G para obtener análisis cuantitativos de fases cristalinas y

Structural and physicochemical properties of nickel manganite NiMn{sub 2}O{sub 4-δ}synthesized by sol-gel and ultra sound assisted methods

Energy Technology Data Exchange (ETDEWEB)

Alburquenque, D. [Materials Chemistry Department, USACH, Ave L.B.O' Higgins 3363, Santiago 9170022 (Chile); Metallurgy Department, USACH, Ave Ecuador 3469, Santiago 9170124 (Chile); Troncoso, L.; Denardin, J.C. [Physics Department, USACH, Ave. Ecuador 3493, Santiago 9170124 (Chile); Butera, A. [Atomic Center, CNEA, Ito. Balseiro, Bariloche Rio Negro 84000 (Argentina); Padmasree, K.D. [Cinvestav, U.Saltillo, Monterrey Km 13.5, Saltillo CP 25900 (Mexico); Ortiz, J.; Herrera, F. [Materials Chemistry Department, USACH, Ave L.B.O' Higgins 3363, Santiago 9170022 (Chile); Marco, J.F. [Institute of Physical Chemistry “Rocasolano”, CSIC, Serrano 119, Madrid 28006 (Spain); Gautier, J.L., E-mail: juan.gautier@usach.cl [Materials Chemistry Department, USACH, Ave L.B.O' Higgins 3363, Santiago 9170022 (Chile)

2016-07-05

In this work we present the structural, magnetic and surface characterization of the ceramic nickel manganite oxide NiMn{sub 2}O{sub 4-δ} synthesized by two methods: sol-gel and ultrasound-assisted sol-gel using nitrate salts as precursors. We have characterized the non-stoichiometric samples NiMn{sub 2}O{sub 4-δ} using different physicochemical analyses. X-ray diffraction and Rietveld refinement of the X-ray data indicated that the samples crystallize in the Fd3m space group characteristic of cubic spinel-related oxides. The specific surface area of the oxides was 1.3 m{sup 2}/g (SG) and 16.3 m{sup 2}/g (UASG). SEM results showed particle agglomerates of 1.05 μm (SG) and 0.85 μm (UASG). Temperature dependence magnetization measurements were performed and a ferrimagnetic transition was identified at 103 K and 105 K depending on the preparation method (SG and UASG, respectively). The observed Curie constant was found to vary from 7.4 to 7.7 cm{sup 3} K mol{sup −1} and hysteretic magnetization vs. applied field curves at different temperatures were obtained. XPS studies of these oxides reveal the presence of Ni{sup 2+}, Mn{sup 2+}, Mn{sup 3+} and Mn{sup 4+} ions at the surface. A probable ionic distribution as a function of the synthesis method is proposed. - Highlights: • Nickel manganite was synthesized by sol gel synthesis and a novel ultrasound-assisted sol gel method. . • Bulk and surface cation distributions are proposed. • Physicochemical properties, including magnetic and surface area measurements, were studied for both types of samples.

Compressive strain-dependent bending strength property of Al{sub 2}O{sub 3}-ZrO{sub 2} (1.5 mol% Y{sub 2}O{sub 3}) composites performance by HIP

Energy Technology Data Exchange (ETDEWEB)

Reyes-Rojas, A. [Centro de Investigacion en Materiales Avanzados S.C. (CIMAV), Miguel de Cervantes 120, Complejo Industrial Chihuahua, Cd. de Chihuahua, Chihuahua (Mexico)], E-mail: armando_reyesmx@yahoo.com.mx; Esparza-Ponce, H. [Centro de Investigacion en Materiales Avanzados S.C. (CIMAV), Miguel de Cervantes 120, Complejo Industrial Chihuahua, Cd. de Chihuahua, Chihuahua (Mexico); De la Torre, S.D. [Centro de Investigacion e Innovacion Tecnologica (CIITEC)-IPN, D.F. Mexico (Mexico); Torres-Moye, E. [Centro de Investigacion en Materiales Avanzados S.C. (CIMAV), Miguel de Cervantes 120, Complejo Industrial Chihuahua, Cd. de Chihuahua, Chihuahua (Mexico)

2009-04-15

Nanometric powders and sintered ceramics of Al{sub 2}O{sub 3}-ZrO{sub 2} (1.5 mol% Y{sub 2}O{sub 3}) prepared by hot isostatic pressing HIP have been studied. A detailed crystallographic study has been performed through X-ray diffraction, Williamson-Hall method, Rietveld method and high-resolution electron microscopy HREM analysis. The crystallographic structure data, such as domain size, lattice parameters, wt% phase, and micro-strain direction have been obtained using Rietveld refinement and Williamson-Hall methods. The results revealed that the compressive strain ({epsilon}) increased from 0.56 to 1.18 (10{sup -3}) as the t-ZrO{sub 2} content increased too. The HREM interface study conducted along the [0 0 0 1]Al{sub 2}O{sub 3}||[0 0 1]ZrO{sub 2} zone axis revealed a micro-strain lattice distortion accumulated at the grain boundary due to the ZrO{sub 2} martensitic phase transformation on cooling, t-ZrO{sub 2} grains coalescence and to the grain growth of {alpha}-Al{sub 2}O{sub 3} which cause elongated tetragonal crystals. Micro-strain lattice distortion is adjusted by the shear displacements of the planes (1 1 0) and (11-bar0) along [1-bar10] and [1-bar1-bar0] crystallographic directions, respectively; these planes are arrested by the (101-bar0) alumina plane. In this case, semi-coherent interfaces were observed along the grain boundary. It is verified that the bending strength increased in connection with the strain accumulation and amount of tetragonal structure.

Optical and structural characterization of SrZr0,1Ti0,9O3

International Nuclear Information System (INIS)

Delgado–Niño, Pilar; López–Rivera, S.A.; Mestres–Vila, Lourdes; Martínez–Sarrión, María Luisa; Valencia–Ríos, Jesús S.

2012-01-01

In this work, the ceramic compound SrTi 0.90 Zr 0,1 O 3 (SZT) was synthesized by the citrate method. This solid showed a 12 nm crystallite size, reflecting the high degree of crystallinity obtained by this synthesis route. Differential and gravimetric thermal analysis showed that the solid was formed from 520 °C; the chemical composition was determined by ICP–AES4, giving a stoichiometry corresponding to the SrTi 0.90 Zr 0.10 O 3 formula, and proved to be compatible with the X-ray diffraction data, refined by the Rietveld method. The morphology was explored by means of SEM and TEM, finding a homogenous particles distribution, arranged in lumps, susceptible to density changes by sintering between 1000 °C and 1200 °C. The photoluminescence (PL) spectrum shows a band between 470 nm and 520 nm, corresponding to the Ti and Zr ions 3d electronic transition. The SZT crystal structure is tetragonal with space group I4/mcm, number (140). - Highlights: ► The ceramic nano structured compound SrTi 0.90 Zr 0,1 O 3 was synthesized by the citrate method. ► Differential and gravimetric thermal analysis showed the right thermodynamical parameters ► Good agreement between the crystal structure, group theory and the optical properties was obtained. ► The sized and high crystallinity of the nanoparticules was confirmed by SEM and TEM. ► Crystal structure is tetragonal with space group I4/mcm was found by X-ray and Rietveld refinement.

Texture, residual stress and structural analysis of thin films using a combined X-ray analysis

International Nuclear Information System (INIS)

Lutterotti, L.; Chateigner, D.; Ferrari, S.; Ricote, J.

2004-01-01

Advanced thin films for today's industrial and research needs require highly specialized methodologies for a successful quantitative characterization. In particular, in the case of multilayer and/or unknown phases a global approach is necessary to obtain some or all the required information. A full approach has been developed integrating novel texture and residual stress methodologies with the Rietveld method (Acta Cryst. 22 (1967) 151) (for crystal structure analysis) and it has been coupled with the reflectivity analysis. The complete analysis can be done at once and offers several benefits: the thicknesses obtained from reflectivity can be used to correct the diffraction spectra, the phase analysis help to identify the layers and to determine the electron density profile for reflectivity; quantitative texture is needed for quantitative phase and residual stress analyses; crystal structure determination benefits of the previous. To achieve this result, it was necessary to develop some new methods, especially for texture and residual stresses. So it was possible to integrate them in the Rietveld, full profile fitting of the patterns. The measurement of these spectra required a special reflectometer/diffractometer that combines a thin parallel beam (for reflectivity) and a texture/stress goniometer with a curved large position sensitive detector. This new diffraction/reflectivity X-ray machine has been used to test the combined approach. Several spectra and the reflectivity patterns have been collected at different tilting angles and processed at once by the special software incorporating the aforementioned methodologies. Some analysis examples will be given to show the possibilities offered by the method

Structural refinement, photoluminescence and Raman spectroscopy of wurtzite Mn-doped Zn O pellets

Energy Technology Data Exchange (ETDEWEB)

Marquina, J.; Martin, J.; Luengo, J.; Vera, F.; Roa, L. [Centro de Estudios Avanzados en Optica, Universidad de los Andes, Merida 5101 (Venezuela, Bolivarian Republic of); Gonzalez, J. [Centro de Estudios de Semiconductores, Universidad de los Andes, Merida 5101 (Venezuela, Bolivarian Republic of); Rodriguez, F.; Renero L, C.; Valiente, R. [Malta-Consolider Team, CITIMAC, Facultad de Ciencias, Universidad de Cantabria, Santander 69005 (Spain); Delgado, G. E., E-mail: marquinajesus@gmail.com [Laboratorio de Cristalografia, Facultad de Ciencias, Universidad de los Andes, Merida 5101 (Venezuela, Bolivarian Republic of)

2017-11-01

We report the results of the Rietveld refinement, photoluminescence and Raman spectroscopy of Mn-doped Zn O ceramic pellets. Rietveld refinement shows that samples crystallize in the wurtzite structure and for the Mn-doped sample indicated that the Mn atoms substitute the Zn tetrahedral crystallographic sites in the Zn O host lattice. The emission and absorption spectra of Mn-doped Zn O have been investigated in the visible-UV region and the data have been interpreted in terms of the wurtzite Zn O electronic structure. Two broad bands, one due to superposition between donor bound excitons (DX) and free excitons (FX) and other due free-to bond excitonic recombination (FB) dominates the low-temperature photoluminescence spectra of Mn-doped Zn O bulk. In the Raman spectrum, an extra mode at ∼520 cm{sup -1} has been observed in agreement with earlier works, and it is an indicator for the incorporation of Mn{sup +2} ions into the Zn O host matrix since it is not is observed in Zn O pristine. Rietveld refinement of the X-ray diffraction patterns, energy-dispersive X-ray spectroscopy (EDS) technique, and Raman spectroscopies were performed to study these effects. (Author)

Grain size dependent phase stabilities and presence of a monoclinic (Pm) phase in the MPB region of (1-x)Bi(Mg_1_/_2Ti_1_/_2)O_3_-_xPbTiO_3

International Nuclear Information System (INIS)

Upadhyay, A.; Singh, A.K.

2016-01-01

The results of the room temperature structural studies on (1-x)Bi(Mg_1_/_2Ti_1_/_2)O_3_-_xPbTiO_3 ceramics using Rietveld analysis of the powder X-ray diffraction data in the composition range 0.28≤x≤0.45 are presented. The morphotropic phase boundary region exhibits coexistence of monoclinic (space group Pm) and tetragonal (space group P4mm) phases in the composition range 0.33≤x≤0.40. The structure is nearly single phase monoclinic (space group Pm) in the composition range 0.28≤x≤0.32. The structure for the compositions with x≥0.45 is found to be predominantly tetragonal with space group P4mm. Rietveld refinement of the structure rules out the coexistence of rhombohedral and tetragonal phases in the morphotropic phase boundary region reported by earlier authors. The Rietveld structure analysis for the sample x=0.35 calcined at various temperatures reveals that phase fraction of the coexisting phases in the morphotropic phase boundary region varies with grain size. The structural parameters of the two coexisting phases also change slightly with changing grain size. (author)

Experimental and first principle study of the structure, electronic, optical and luminescence properties of M-type GdNbO4 phosphor

Science.gov (United States)

Ding, Shoujun; Zhang, Haotian; Zhang, Qingli; Chen, Yuanzhi; Dou, Renqin; Peng, Fang; Liu, Wenpeng; Sun, Dunlu

2018-06-01

In this work, GdNbO4 polycrystalline with monoclinic phase was prepared by traditional high-temperature solid-state reaction. Its structure was determined by X-ray diffraction and its unit cell parameters were obtained with Rietveld refinement method. Its luminescence properties (including absorbance, emission and luminescence lifetime) were investigated with experiment method and the CIE chromaticity coordinate was presented. Furthermore, a systematic theoretical calculation (including band gap, density of states and optical properties) based on the density function theory methods was performed on GdNbO4. Lastly, a comparison between experiment and calculated results was conducted. The calculated and experiment results obtained in this work can provide an essential understanding of GdNbO4 material.

Synthesis and electrochemical properties of KPb{sub 4−x}Ca{sub x}(PO{sub 4}){sub 3} (0 ≤ x ≤ 1.5) for oxidation of cadmium at graphite electrode

Energy Technology Data Exchange (ETDEWEB)

Lahrich, Sara [Univ Hassan 1, Laboratoire de Chimie et Modélisation Mathématique, Faculté Polydisciplinaire, 25000 Khouribga (Morocco); Univ Hassan 1, Laboratoire Sciences des Matériaux, des Milieux et de la Modélisation, Faculté Polydisciplinaire, 25000 Khouribga (Morocco); Manoun, Bouchaib [Univ Hassan 1, Laboratoire Sciences des Matériaux, des Milieux et de la Modélisation, Faculté Polydisciplinaire, 25000 Khouribga (Morocco); El Mhammedi, Moulay Abderrahim, E-mail: elmhammedi@yahoo.fr [Univ Hassan 1, Laboratoire de Chimie et Modélisation Mathématique, Faculté Polydisciplinaire, 25000 Khouribga (Morocco)

2017-02-15

Chemically modified carbon paste electrode (CPE) for cadmium (II) analysis has been constructed by mixing KPb{sub 4−x}Ca{sub x}(PO{sub 4}){sub 3} (0 ≤ x ≤ 1.5) (CaLA) and graphite powder. The lacunar apatite was synthesized using solid reaction and characterized by X-ray diffraction (XRD), infrared spectroscopy (IR) and Raman spectroscopy. The refinement study was carried out using Rietveld method where the obtained results show a good agreement between the observed and calculated patterns. The detection of cadmium (II) was investigated in acetate buffer (pH 4.5) using differential pulse anodic stripping voltammetry (DPASV). The limit of detection obtained under the optimized experimental conditions was 5.35 × 10{sup −7} mol L{sup −1} with a relative standard deviation of 2.37%. Possible interferences were tested and evaluated in 5.0 × 10{sup −5} mol L{sup −1} cadmium (II) in the presence of other inorganic ions. Finally, the proposed method was successfully applied to determine cadmium (II) in seawater and mussel samples. Hence, the satisfactory results confirm the applicability of this sensor in practical analysis. - Highlights: • Synthesis and characterization of new lacunar apatites KPb{sub 4−x}Ca{sub x}(PO{sub 4}){sub 3} (0 ≤ x ≤ 1.5). • Structural refinement of these compounds using Rietveld method. • A study of Ca doping effect in lacunar apatites for detecting Cd (II). • The electrochemical oxidation of Cd (II) was performed at CaLA-CPE using DPASV. • The proposed method was evaluated to detect cadmium in seawater and mussel samples.

Tin-Platinum catalysts interactions on titania and silica

International Nuclear Information System (INIS)

Nava, N.; Del Angel, P.; Salmones, J.; Baggio-Saitovitch, E.; Santiago, P.

2007-01-01

Pt-Sn was supported on titania and silica, and the resulting interactions between the components in prepared samples and the resulting interactions between the components before and after treatment with hydrogen were characterized by Moessbauer spectroscopy, X-ray diffraction, Rietveld refinement, high-resolution transmission electron microscopy (HRTEM) and catalytic tests data. Results show the presence of Pt and SnO 2 after calcinations, and Pt 3 Sn, PtSn and PtSn 3 after reduction. Rietveld analysis shows that some Ti 4+ are replaced by Sn 4+ atoms in the titania structure. Finally, HRTEM and the practically absence of activity observed confirms that metallic platinum is encapsulated

Crystal growth, structure, defects, mechanical and spectral properties of Nd{sub 0.01}:Gd{sub 0.89}La{sub 0.1}NbO{sub 4} mixed crystal

Energy Technology Data Exchange (ETDEWEB)

Ding, Shoujun; Lu, Wancheng; Xu, Jinrui [Anhui Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Hefei, Anhui Province (China); University of Science and Technology of China, Hefei (China); Zhang, Qingli; Luo, Jianqiao; Liu, Wenpeng; Sun, Guihua; Sun, Dunlu [Anhui Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Hefei, Anhui Province (China)

2017-10-15

A novel mixed laser crystal of Nd:GdLaNbO{sub 4} (Nd:GLNO) was grown successfully by conventional Czochralski method. The unit cell parameters were obtained by Rietveld refinement method. The density of the as-grown crystal was measured by Archimedean buoyancy method and calculated in theory. Absorption spectrum of Nd:GLNO crystal was recorded at room temperature, and 11 absorption peaks were assigned. The defects of Nd:GLNO crystal were revealed by using chemical etching method with phosphoric acid as etchant. The mechanical properties (including hardness, yield strength, elastic stiffness constant, fracture toughness and brittleness index) were systemically estimated based on Vickers hardness test. All these obtained results play a quite important role in further investigation of Nd:GLNO crystal. (orig.)

Symmetry breaking and electrical conductivity of La0.7Sr0.3Cr0.4Mn0.6O3-δ perovskite as SOFC anode material

International Nuclear Information System (INIS)

Reyes-Rojas, A.; Alvarado-Flores, J.; Esparza-Ponce, H.; Esneider-Alcala, M.; Espitia-Cabrera, I.; Torres-Moye, E.

2011-01-01

Research highlights: → Perovskite-type La 0.7 Sr 0.3 Cr 0.4 Mn 0.6 O 3-δ -NiO nucleation kinetics. Symmetry-breaking by introducing Ni 2+ cations at 1050 deg. C. Phase transition from high temperature aristotype R3-bar c to hettotype I4/mmm. At low Ni concentration ρ resistivity decreases when increasing the temperature. For Ni concentration higher than 25% ρ resistivity increases. - Abstract: This work is focused on nanocrystalline solid oxide fuel cell synthesis and characterization (SOFC) anodes of La 0.7 Sr 0.3 Cr 0.4 Mn 0.6 O 3-δ (perovskite-type) with Nickel. Perovskite-type oxide chemical reactivity, nucleation kinetics and phase composition related with La 0.7 Sr 0.3 Cr 0.4 Mn 0.6 O 3-δ -NiO to La 0.7 Sr 0.3 Cr 0.4 Mn 0.6 O 3-δ -Ni transformation have been analyzed. SOFC anode powders were obtained by sol-gel synthesis, using polyvinyl alcohol as an organic precursor to get a porous cermet electrode after sintering at 1365 deg. C and oxide reduction by hydrogen at 800 deg. C/1050 deg. C for 8 h in a horizontal tubular reactor furnace under 10% H 2 /N 2 atmosphere. Composite powders were compressed into 10-mm diameter discs with 25-75 wt% Ni. Electrical and structural characterization by four-point probe method for conductivity, scanning electron microscopy (SEM), X-ray energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), and Rietveld method were carried out. Symmetry-breaking by phase transition from high temperature aristotype R3-bar c to hettotype I4/mmm has been identified and confirmed by XRD and Rietveld method which can be produced by introducing Ni 2+ cations in the perovskite solid solution. Rietveld analysis suggests that Ni contents are directly proportional to La 0.7 Sr 0.3 Cr 0.4 Mn 0.6 NiO 3.95 tetragonal structure cell volume and inversely proportional to Ni cubic structure cell volume after reduction at 1050 deg. C. Kinetic analysis indicated that the Johnson-Mehl-Avrami equation is able to provide a good fit to phase

Effect of Preparation Method on Phase Formation Process and Structural and Magnetic Properties of Mn2.5Ge Samples

Directory of Open Access Journals (Sweden)

R. Sobhani

2016-12-01

Full Text Available In this paper, the phase formation process of Mn2.5Ge samples, prepared by mechanical alloying of Mn and Ge metal powders and annealing, has been studied. Results showed that in the milled samples the stable phase is Mn11Ge8 compound with orthorhombic structure and Pnam space group. The value of saturation magnetization increases by increasing milling time from 0.2 up to 1.95 (Am2Kg-1. The remanece of the samples increases by increasing the milling time while the coercivity decreases. Annealing of 15-hour milled sample results in disappearance of Mn and Ge and the formation of new phases of Mn3Ge, Mn5Ge2, Mn5Ge3 and Mn2.3Ge. Mn3Ge is the main phase with Do22 tetragonal structure and I4/mmm space group which is stable and dominant. The enhancement of saturation magnetization in the annealed sample is related to the formation of three new magnetic phases and the increase of coercivity is due to the presence of Mn3Ge compound with tetragonal structure. Studies were replicated on samples made by arc melting method to compare the results and to investigate the effect of the preparation method on phase formation and structural and magnetic properties of the materials. In these samples the saturation value was in range of 0.2 up to 1.95 (Am2Kg-1 depending on preparation methods. Rietveld refinement shows that Mn2.3Ge sample prepared from arc melted under 620oC anealing is single phase. Magnetic analysis of this sample show a saturation magnetization of 5.252(Am2Kg-1 and 0.005 T coercive field.

Characterization of hydroxyapatite substituted with silicon; Caracterizacao de hiroxiapatita substituida com silicio

Energy Technology Data Exchange (ETDEWEB)

Silva, H.M. da; Soares, G.A., E-mail: helena@metalmat.ufrj.b [Universidade Federal do Rio de Janeiro (COPPE/UFRJ), RJ (Brazil). Coordenacao dos Programas de Pos-graduacao em Engenharia. Lab. de Biomateriais para Engenharia Ossea; Mateescu, M.; Anselme, K. [Universite de Haute-Alsace (UHA/IS2M), Mulhouse (France). Inst. de Science des Materiaux; Palard, M.; Champion, E. [Universite de Limoges (France). Fac. des Sciences et Techniques

2009-07-01

Incorporation of silicon (Si) ions into hydroxyapatite structure (HA) influences on physical, chemical and physiological properties. Some studies reported the improved bioactivity Si substitution, and it also accelerates the biomineralization process. The main objective of this work is to characterize stoichiometric hydroxyapatite and hydroxyapatite substituted with 1.13% in weight of Si (SiHA) using a wet precipitation method followed by a heat treatment. SEM/EDS, AFM, DRX and FTIR analyses were used to characterize the samples. EDS and FTIR results confirmed the presence of Si. Silicon induces small changes on crystal structure of HA, not detected on X-ray diffraction patterns of sintered tablets of SiHA and HA. No secondary phases were observed, that indicates the Si had entered the HA lattice. (author)

Characterization of superconducting coil for fault current limitation

International Nuclear Information System (INIS)

Polasek, Alexander; Dias, Rodrigo; Niedu, Daniel Brito; Ogasawara, Tsuneharu; Oliveira Filho, Orsino Borges de; Serra, Eduardo Torres; Gomes Junior, George; Amorim, Helio Salim

2010-01-01

The increasing power demand has been raising fault currents up to dangerous levels. Superconducting fault current limiters are a promising solution for this problem. In the present work, we studied a superconducting Bi-2212 coil that is used for fault current limitation. Samples were analyzed by XRD, SEM/EDS and measurement of critical temperature (Tc). The Rietveld method was employed for phase quantification. Relatively high Bi-2212 fractions were found. However, Tc varies from a sample to another one. Variations of local Tc are attributed to variations of oxygen content in Bi- 2212 phase. (author)

Synthesis and characterization of K{sub 2}Ln{sub 2/3}Ta{sub 2}O{sub 7}·nH{sub 2}O (Ln= La, Pr, Nd), layered tantalates photo catalysts for water splitting

Energy Technology Data Exchange (ETDEWEB)

Valencia S, H.; Tavizon, G. [UNAM, Instituto de Quimica, Ciudad Universitaria, 04510 Ciudad de Mexico (Mexico); Pfeiffer, H. [UNAM, Instituto de Investigaciones en Materiales, Ciudad Universitaria, 04510 Ciudad de Mexico (Mexico); Acosta, D. [UNAM, Instituto de Fisica, Ciudad Universitaria, 04510 Ciudad de Mexico (Mexico); Negron M, A., E-mail: hvalencia@utp.edu.co [UNAM, Instituto de Ciencias Nucleares, Ciudad Universitaria, 04510 Ciudad de Mexico (Mexico)

2015-07-01

Three compounds of the K{sub 2}Ln{sub 2/3}Ta{sub 2}O{sub 7} (Ln = La, Nd, Pr) cation-deficient Ruddlesden-Popper series were prepared by the Pechini (polymeric complex) method. The crystal structures of the hydrated form of these compounds were determined by Rietveld analysis of the X-ray power diffraction data and High Resolution Transmission Electron Microscopy (HRTEM). The samples were also analyzed to determine specific area (Bet), degree of hydration (Thermogravimetric analysis), and photo catalytic activity for hydrogen evolution from water and aqueous methanol solution. (Author)

Barium strontium titanate powders prepared by spray pyrolysis

International Nuclear Information System (INIS)

Brankovic, G.; Brankovic, Z.; Goes, M.S.; Paiva-Santos, C.O.; Cilense, M.; Varela, J.A.; Longo, E.

2005-01-01

Ultasonic spray pyrolysis (SP) has been investigated for the production of the barium strontium titanate (BST) powders from the polymeric precursors. The processing parameters, such as flux of aerosol and temperature profile inside the furnace, were optimized to obtain single phase BST. The powders were characterized by the methods of X-ray diffraction analysis, SEM, EDS and TEM. The obtained powders were submicronic, consisting of spherical, polycrystalline particles, with internal nanocrystalline structure. Crystallite size of 10 nm, calculated using Rietveld refinement, is in a good agreement with results of HRTEM

Structural, dielectric and magnetic studies of Ba and Nb codoped BiFeO{sub 3} multiferroics

Energy Technology Data Exchange (ETDEWEB)

Jangra, Sandhaya, E-mail: sndh17@gmail.com; Sanghi, Sujata; Agarwal, Ashish; Kaswan, Kavita; Rangi, Manisha; Singh, Ompal [Department of Applied Physics, Guru Jambheshwar University of Science and Technology, Hisar, Haryana-125001 (India)

2016-05-23

Polycrystalline materials with composition Bi{sub 0.8}Ba{sub 0.2}Fe{sub 1-x}Nb{sub x}O{sub 3} (x= 0.07, 0.10) were prepared via solid state reaction method. Preliminary analysis of structure was performed by XRD technique and confirmed formation of single phase crystalline materials. Rietveld refinement reveled that these materials have rhombohedral phase with R3c space group. Dielectric constant increased with temperature and Nb concentration. Ba and Nb co-doping suppress the spiral spin structure and produce net magnetization.

Structural study of the semimagnetic semiconductor Zn{sub 0.5}Mn{sub 0.5}In{sub 2}Te{sub 4}

Energy Technology Data Exchange (ETDEWEB)

Delgado, G.E. [Laboratorio de Cristalografia, Departamento de Quimica, Facultad de Ciencias, Universidad de Los Andes, Merida (Venezuela); Sagredo, V. [Laboratorio de Magnetismo en Solidos, Departamento de Quimica, Facultad de Ciencias, Universidad de Los Andes, Merida (Venezuela)

2009-02-15

The semimagnetic semiconductor alloy Zn{sub 0.5}Mn{sub 0.5}In{sub 2}Te{sub 4} was refined from an X-ray powder diffraction pattern using the Rietveld method. This compound crystallizes in the space group I anti 42m (N {sup circle} 121), Z=2, with unit cell parameters a=6.1738(1)A, c=12.3572(4)A, V=471.00(2)A3, c/a=2.00. This material crystallizes in a stannite-type structure. (copyright 2009 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

Synthesis and characterization of K2Ln2/3Ta2O7·nH2O (Ln= La, Pr, Nd), layered tantalates photo catalysts for water splitting

International Nuclear Information System (INIS)

Valencia S, H.; Tavizon, G.; Pfeiffer, H.; Acosta, D.; Negron M, A.

2015-01-01

Three compounds of the K 2 Ln 2/3 Ta 2 O 7 (Ln = La, Nd, Pr) cation-deficient Ruddlesden-Popper series were prepared by the Pechini (polymeric complex) method. The crystal structures of the hydrated form of these compounds were determined by Rietveld analysis of the X-ray power diffraction data and High Resolution Transmission Electron Microscopy (HRTEM). The samples were also analyzed to determine specific area (Bet), degree of hydration (Thermogravimetric analysis), and photo catalytic activity for hydrogen evolution from water and aqueous methanol solution. (Author)

Correlação entre dados estruturais e bandas de vibração no infravermelho para a fase espinélio Zn7-xNi xSb2O12 Correlation between structural data and infraved vibrational bands of the Zn7-xNi xSb2O12 spinel phase

Directory of Open Access Journals (Sweden)

L. Gama

2000-12-01

Full Text Available A fase espinélio Zn7-xNi xSb2O12 tem apresentado propriedades magnéticas importantes, comportando-se como spin-glass. Desde que estas propriedades são fortemente dependentes da configuração precisa dos átomos nesta estrutura, foram utilizados neste trabalho, com o intuito de clarificar essa configuração, a espectroscopia de infravermelho, aliada ao refinamento de estruturas pelo método de Rietveld. O espectro de infravermelho mostra nas condições de contorno estudadas a presença de três das quatro bandas ativas comuns aos espinélios. Conforme resultados do refinamento pelo método de Rietveld, o níquel substitui o zinco primeiramente no sítio octaédrico e, em altas concentrações (x > ou = 3, migra para o sítio tetraédrico. Essa migração é indicada pelo "splitting", em torno de 520 cm-1, para (x > ou = 3, apresentado no espectro de infravermelho quando a banda n2 é afetada pela mudança do cátion bivalente.The Zn7-xNi xSb2O12 spinel phase shows important magnetic properties with a spin-glass behavior. As these properties are strongly dependent on the atomic configuration in the spinel structure, infrared spectroscopy and the structure refining by the Rietveld analysis have been studied. The infrared spectrum presents three to four of the common spinel active modes. The Rietveld analysis shows that Ni firstly substitutes for Zn in the octahedral site and, for large (x > or = 3 concentrations, migrates to the tetrahedral site. The indication of that migration is the splitting at approximately 520 cm-1, shown in the infrared spectrum when the nu 2 band is modified by the substitution of the divalent cation.

Transformation of Goethite to Hematite Nanocrystallines by High Energy Ball Milling

Directory of Open Access Journals (Sweden)

O. M. Lemine

2014-01-01

Full Text Available α-Fe2O3 nanocrystallines were prepared by direct transformation via high energy ball milling treatment for α-FeOOH powder. X-ray diffraction, Rietveld analysis, TEM, and vibrating sample magnetometer (VSM are used to characterize the samples obtained after several milling times. Phase identification using Rietveld analysis showed that the goethite is transformed to hematite nanocrystalline after 40 hours of milling. HRTEM confirm that the obtained phase is mostly a single-crystal structure. This result suggested that the mechanochemical reaction is an efficient way to prepare some iron oxides nanocrystallines from raw materials which are abundant in the nature. The mechanism of the formation of hematite is discussed in text.

Tin-Platinum catalysts interactions on titania and silica

Energy Technology Data Exchange (ETDEWEB)

Nava, N. [Instituto Mexicano del Petroleo Lazaro Cardenas 152, 07730 Mexico, D.F. (Mexico)], E-mail: tnava@imp.mx; Del Angel, P. [Instituto Mexicano del Petroleo Lazaro Cardenas 152, 07730 Mexico, D.F. (Mexico); Salmones, J. [Instituto Politecnico Nacional-ESIQIE UPALM, 07738 Mexico, D.F. (Mexico); Baggio-Saitovitch, E. [Centro Brasileiro de Pesquisas Fisicas, Rua Dr. Xavier Sigaud 150, 22290-180 Rio de Janeiro, Brasil (Brazil); Santiago, P. [Instituto de Fisica, UNAM, Mexico, D. F., 04510 Mexico (Mexico)

2007-09-30

Pt-Sn was supported on titania and silica, and the resulting interactions between the components in prepared samples and the resulting interactions between the components before and after treatment with hydrogen were characterized by Moessbauer spectroscopy, X-ray diffraction, Rietveld refinement, high-resolution transmission electron microscopy (HRTEM) and catalytic tests data. Results show the presence of Pt and SnO{sub 2} after calcinations, and Pt{sub 3}Sn, PtSn and PtSn{sub 3} after reduction. Rietveld analysis shows that some Ti{sup 4+} are replaced by Sn{sup 4+} atoms in the titania structure. Finally, HRTEM and the practically absence of activity observed confirms that metallic platinum is encapsulated.

Local and average structures of 0.7Pb(Mg1/3Nb2/3)O3 - 0.3PbZrO3

International Nuclear Information System (INIS)

Krishna, P.S.R.; Shinde, A.B.; Narasimhan, S.L.; Tiwari, V.S.; Singh, G.

2005-01-01

The local and average structure of 0.7Pb(Mg 1/3 Nb 2/3 )O 3 - 0.3PbZrO 3 (PMN-PZ) was studied by neutron diffraction. The Rietveld refinement was carried out to determine the average, long-range crystallographic structure, while the pair density function (PDF) analysis was used in studying the local atomic structure. The local atomic structure determined by the PDF analysis, was found to be significantly different from the average crystallographic structure determined by the Rietveld analysis. These results show that the conflict between the local structural preference and the average structure is not limited to relax or ferroelectric oxides, but may be widely prevalent in mixed-ion ferroelectrics. (author)

Hydrothermal synthesis, characterization, and thermal properties of alumino silicate azide sodalite, Na8[AlSiO4]6(N3)2

Science.gov (United States)

Borhade, A. V.; Wakchaure, S. G.; Dholi, A. G.; Kshirsagar, T. A.

2017-07-01

First time we report the synthesis, structural characterization and thermal behavior of an unusual N3 - containing alumino-silicate sodalite mineral. Azide sodalite, Na8[AlSiO4]6(N3)2 has been synthesized under hydrothermal conditions at 433 K in steel lined Teflon autoclave. The structural and microstructural properties of azide sodalite mineral was characterized by various methods including FT-IR, XRD, SEM, TGA, and MAS NMR. Crystal structure have been refined by Rietveld method in P\\bar 43n space group, indicating that the N3 - sodalite has cubic in lattice. High temperature study was carried out to see the effect of thermal expansion on cell dimension ( a o) of azide sodalite. Thermal behavior of sodalite was also assessed by thermogravimetric method.

Processing of ZnO nanocrystals by solochemical technique

International Nuclear Information System (INIS)

Gusatti, M.; Speckhahn, R.; Silva, L.A.; Rosario, J.A.; Lima, R.B.; Kuhnen, N.C.; Riella, H.G.; Campos, C.E.M.

2009-01-01

In the present work, we report the synthesis of high quality ZnO nanocrystals by solochemical technique. This synthetic strategy has been shown to have advantages over other methods of producing nanostructures in terms of low cost, efficiency, simplicity and uniformity of crystal structure. Zinc chloride solution at room temperature was mixed with sodium hydroxide solution at 50°C to produce ZnO nanocrystals. Transmission electronic microscopy (TEM) and X-ray powder diffraction (XRD) were used to characterize the ZnO nanocrystals obtained. The structure of ZnO was refined by the Rietveld Method from X-ray diffraction data. These methods showed that the product consisted of pure ZnO nanocrystals and has, predominantly, a rod-like morphology. (author)

Grain size dependent phase stabilities and presence of a monoclinic (Pm) phase in the morphotropic phase boundary region of (1−x)Bi(Mg{sub 1/2}Ti{sub 1/2})O{sub 3}-xPbTiO{sub 3} piezoceramics

Energy Technology Data Exchange (ETDEWEB)

Upadhyay, Ashutosh; Singh, Akhilesh Kumar, E-mail: akhilesh-bhu@yahoo.com, E-mail: aksingh.mst@itbhu.ac.in [School of Materials Science and Technology, Indian Institute of Technology (Banaras Hindu University), Varanasi 221005 (India)

2015-04-14

Results of the room temperature structural studies on (1−x)Bi(Mg{sub 1/2}Ti{sub 1/2})O{sub 3}-xPbTiO{sub 3} ceramics using Rietveld analysis of the powder x-ray diffraction data in the composition range 0.28 ≤ x ≤ 0.45 are presented. The morphotropic phase boundary region exhibits coexistence of monoclinic (space group Pm) and tetragonal (space group P4 mm) phases in the composition range 0.33 ≤ x ≤ 0.40. The structure is nearly single phase monoclinic (space group Pm) in the composition range 0.28 ≤ x ≤ 0.32. The structure for the compositions with x ≥ 0.45 is found to be predominantly tetragonal with space group P4 mm. Rietveld refinement of the structure rules out the coexistence of rhombohedral and tetragonal phases in the morphotropic phase boundary region reported by earlier authors. The Rietveld structure analysis for the sample x = .35 calcined at various temperatures reveals that phase fraction of the coexisting phases in the morphotropic phase boundary region varies with grain size. The structural parameters of the two coexisting phases also change slightly with changing grain size.

Synthesis of LiFePO4/C composites based on natural iron stone using a sol gel method

Science.gov (United States)

Angela, Riyan; Islam, Humaatul; Sari, Vamellia; Latif, Chaironi; Zainuri, Mochamad; Pratapa, Suminar

2017-01-01

Synthesis of LiFePO4/C composites has been carried out using a sol gel method. The Fe precursor was made from a natural iron stone of Tanah Laut, South Kalimantan, while the other raw materials were commercial Li2CO3 powder and NH4H2PO4 powder with HCl and water as solvents. Citric acid was used as the carbon source in the synthesis. This study used a molar ratio of 1:1:2 for Li:Fe:P with variation of added citric acid of 1.5 and 2.5 g. The solutions were dried in air at 100°C. The dried powders were characterized using DSC-TGA and then calcined at 600 and 700°C under argon environment for 10 hours. The calcined powders were characterized by X-ray diffractometry (XRD), scanning electron microscopy-energy dispersive x-ray (SEM-EDX), and LCR meter. It was found that the samples contained LiFePO4 as the dominant phase and LiFeP2O7 and Fe2O3 as secondary phases. The analysis showed that the addition of citric acid influenced the electronic conductivity of the composites. A Rietveld relative weight fraction of up to 94.7% was achieved in the synthesis at temperature 600°C. The LFP/C sample exhibited electronic conductivity of 4.56×10-3 Scm-1 which was six times of that of the pure LFP.

Modifications in the rhombohedral degree of distortion and magnetic properties of Ba-doped BiFeO{sub 3} as a function of synthesis methodology

Energy Technology Data Exchange (ETDEWEB)

Rojas-George, G. [Centro de Investigación en Materiales Avanzados S.C., Miguel de Cervantes 120, Complejo Industrial Chihuahua, Chihuahua, Chih. 31109 (Mexico); Silva, J. [Universidad Autónoma de Ciudad Juárez, Ave. del Charro 450 Norte, Cd. Juárez, Chih. 32310 (Mexico); Castañeda, R.; Lardizábal, D. [Centro de Investigación en Materiales Avanzados S.C., Miguel de Cervantes 120, Complejo Industrial Chihuahua, Chihuahua, Chih. 31109 (Mexico); Graeve, O.A. [Department of Mechanical and Aerospace Engineering, University of California, San Diego, 9500 Gilman Dr. – MC 0411, La Jolla, CA 92093-0411 (United States); Fuentes, L. [Centro de Investigación en Materiales Avanzados S.C., Miguel de Cervantes 120, Complejo Industrial Chihuahua, Chihuahua, Chih. 31109 (Mexico); Reyes-Rojas, A., E-mail: armando.reyes@cimav.edu.mx [Centro de Investigación en Materiales Avanzados S.C., Miguel de Cervantes 120, Complejo Industrial Chihuahua, Chihuahua, Chih. 31109 (Mexico)

2014-07-01

We present an analysis of crystallographic symmetry and the origin of the pseudo-cubic character of doped BiFeO{sub 3}. Specifically, barium-doped bismuth ferrite, Bi{sub 1−x}Ba{sub x}FeO{sub 3} (x = 0.05, 0.075, 0.1, 0.125), perovskite-type nanoparticles have been synthesized by implementing five modifications to the sol–gel technique (citric acid-assisted sol–gel method, ethylene glycol method, tartaric acid-assisted sol–gel method, polyvinyl alcohol–ethylene glycol method, and EDTA complexing sol–gel method) and their final pseudo-cubic character is discussed. The effect of the carboxylic groups and hydroxyl groups during synthesis is critical to obtain single phase BBFO. Fourier transform infrared spectroscopy and thermogravimetric analysis is used to study the decomposition and thermal behavior of the precursors and their relation to the final nanoparticle characteristics. X-ray diffraction analysis shows a single phase with symmetry changes for four of the five synthesis methodologies employed. Only the EDTA complexing sol–gel method, where EDTA is used as dissolver and chelating agent, is not satisfactory in all concentration ranges. Rietveld results suggest that the degree of distortion of the rhombohedral symmetry in the crystallized BiFeO{sub 3} powders decreases 12% as a result of progressive substitution of Bi{sup 3+} by Ba{sup 2+} and that there is no shift from rhombohedral to tetragonal symmetry. Magnetization properties of samples with a low-distortion rhombohedral structure show higher magnetic saturation and remanent magnetization than samples with high-distortion rhombohedral structure. - Highlights: • Ba–BiFeO{sub 3}: rhombohedral distortion degree is highly affected by the chemical method. • Rietveld results show no shift in BBFO from rhombohedral to tetragonal symmetry. • The low-distortion rhombohedral structure show higher magnetic saturation. • To stabilize a metal complex is necessary a balance between COOH{sup �

Synthesis and characterization of nanostructured CaZrO{sub 3} and BaZrO{sub 3}

Energy Technology Data Exchange (ETDEWEB)

Ibiapino, Amanda Laura; Figueiredo, Laysa Pires de [Departamento de Quimica, Instituto de Ciencias Exatas e da Terra, Universidade Federal do Mato Grosso, MT (Brazil); Lascalea, Gustavo E. [LISAMEN/CONICET, Ciudad de Mendoza (Argentina); Prado, Rogerio Junqueira, E-mail: rjprado@ufmt.br [Instituto de Fisica, Universidade Federal do Mato Grosso, Cuiaba - MT (Brazil)

2013-09-01

In this work, nanostructured samples of barium zirconate (BaZrO{sub 3}) and calcium zirconate (CaZrO{sub 3}) were synthesized by the gel-combustion method, using glycine as fuel. The ceramic powders were calcined at 550 Degree-Sign C for 2 h and subsequently heat treated at 1350 Degree-Sign C for 10 min (fast-firing). The X-ray diffraction technique was employed to identify and characterize the crystalline phases present in the synthesized powders, using the Rietveld method. Monophasic nanostructured samples of BaZrO{sub 3} and CaZrO{sub 3} presenting average crystallite sizes of around 8.5 and 10.3 nm, respectively, were found after fast-firing. (author)

Žena jako tvůrkyně

Czech Academy of Sciences Publication Activity Database

Hnídková, Vendula

2012-01-01

Roč. 91, č. 9 (2012), s. 542-544 ISSN 0042-4544 Institutional support: RVO:68378033 Keywords : Dutch architecture * modern architecture * Gerrit Rietveld Subject RIV: AL - Art, Architecture, Cultural Heritage

Synthesis and characterization of Sn doped TiO{sub 2} photocatalysts: Effect of Sn concentration on the textural properties and on the photocatalytic degradation of 2,4-dichlorophenoxyacetic acid

Energy Technology Data Exchange (ETDEWEB)

Rangel-Vázquez, I.; Del Angel, G.; Bertin, V. [Departamento de Química, Universidad Autónoma Metropolitana-Iztapalapa, Av. San Rafael, Atlixco No 1865, México 09340 D.F. (Mexico); González, F. [Departamento de Ingeniería de Procesos e Hidráulica, Universidad Autónoma Metropolitana-Iztapalapa, Av. San Rafael, Atlixco No 1865, México 09340 D.F. (Mexico); Vázquez-Zavala, A.; Arrieta, A. [Departamento de Química, Universidad Autónoma Metropolitana-Iztapalapa, Av. San Rafael, Atlixco No 1865, México 09340 D.F. (Mexico); Padilla, J.M. [Universidad Tecnológica del Centro de Veracruz, Área de Tecnología, Av. Universidad Carretera Federal Cuitláhuac-La Tinaja No. 350, Cuitláhuac, Veracruz 94910 (Mexico); Barrera, A. [Universidad de Guadalajara, Centro Universitario de la Ciénega, Av. Universidad, Número 1115, Col. Linda Vista, Apdo. Postal 106, Ocotlán Jal. (Mexico); Ramos-Ramirez, E. [Departamento de Química, División de Ciencias Naturales y Exactas, Campus Guanajuato de la Universidad de Guanajuato Noria Alta S/N, Col. Noria Alta, Guanajuato, Gto. C.P. 36050 (Mexico)

2015-09-15

Abstract: TiO{sub 2} and Sn-doped TiO{sub 2} materials were prepared by sol–gel method using titanium and tin alkoxides at different Sn concentration (0.1 mol%, 0.5 mol%, 1 mol%, 3 mol% and 5 mol%). Samples were characterized by thermo gravimetric analyzer with differential scanning calorimeter (TGA–DSC), X-ray Rietveld refinement, N{sub 2} adsorption (BET), transmission electron microscopy (TEM), UV–vis spectroscopies technology and Raman spectroscopy. Only anatase phase was observed in pure TiO{sub 2}, whereas anatase and brookite were obtained in Sn-doped TiO{sub 2} samples. Sn dopant acts as a promoter in phase transformation of TiO{sub 2}. The Rietveld refinements method was used to determine the relative weight of anatase and brookite, and crystallite size as a function of Sn concentration after calcination of samples at 673 K. It was also demonstrated the incorporation of Sn{sup 4+} into the anatase TiO{sub 2} structure. Sn{sup 4+} inhibits the growth of TiO{sub 2} crystallite size, which leads to an increase of the specific surface area of TiO{sub 2}. From XRD analysis, the solid solution limit of Sn{sup 4+} into TiO{sub 2} is 5 mol% Sn. The photocatalytic activity on Sn{sup 4+} doped TiO{sub 2} was determined for the 2,4-dichlorophenoxyacetic acid reaction. The maximum in activity was attributed to the coexistence of anatase and brookite phases in the appropriate ratio and crystallite size.

Synthesis and Characterization of Nano Scale YBCO

International Nuclear Information System (INIS)

Sukirman, E.; Wisnu AA; Yustinus P; Sahidin W, D.; Rina M, Th.

2009-01-01

Synthesis and characterization of the nano scale YBCO superconductor have been performed. The nano scale superconductor was synthesized from YBCO system (YBa 2 Cu 3 O 7-X ). Raw materials, namely Y 2 O 3 , BaCO 3 , and Cu°, were balanced and mixed with ethanol using magnetic steering as a churn in a beaker glass. Then, the precursor was calcined at T k = 900°C for 5 hours and repeated it until three times. The resulting precursor was ground by using High Energy Milling (HEM) for t = 0, 30, 50, 70, and 90 hour and hereinafter precursors are successively referred as YKM-00, YKM-30, YKM-50, YKM-70, and YKM-90. The resulting powders phase were characterized by means of x-ray diffraction technique using the Rietveld analysis method. Precursor of YKM-90 was pressed into pellets, and then sintered at various temperatures and periods. The sample phase was then characterized by using the Rietveld analysis method based on the x-ray diffraction data. The crystallites size were calculated using Scherrer formula. Results of analysis indicate that by minimizing crystallites size, period of sinter can be shortened from 10 to 1 hour, resulting crystallite size of D = 925 Å, critical current density of J c = 4 A / cm 2 , and can be grown of about 15 weight % of 211-phase in a matrix of 123-phase. The decrease of crystallite size will generate a change in physical properties dramatically, if the crystallite size of the material, D is smaller or equal to the coherence length of 10 Å. (author)

The cation inversion and magnetization in nanopowder zinc ferrite obtained by soft mechanochemical processing

International Nuclear Information System (INIS)

Milutinović, A.; Lazarević, Z.; Jovalekić, Č.; Kuryliszyn-Kudelska, I.; Romčević, M.; Kostić, S.; Romčević, N.

2013-01-01

Graphical abstract: - Highlights: • Nano powder of ZnFe 2 O 4 prepared by a soft mechanochemical route after 18 h milling. • Phase formation controlled by XRD, Raman spectroscopy and magnetic measurements. • Size, strain and cation inversion degree determined by Rietveld refinement. • We were able to estimate the degree of inversion at most 0.348 and 0.4. • Obtained extremely high values of saturation magnetizations at T = 4.5 K. - Abstract: Two zinc ferrite nanoparticle materials were prepared by the same method – soft mechanochemical synthesis, but starting from different powder mixtures: (1) Zn(OH) 2 /α-Fe 2 O 3 and (2) Zn(OH) 2 /Fe(OH) 3 . In both cases a single phase system was obtained after 18 h of milling. The progress of the synthesis was controlled by X-ray diffractometry (XRD), Raman spectroscopy, TEM and magnetic measurements. Analysis of the XRD patterns by Rietveld refinement allowed determination of the cation inversion degree for both obtained single phase ZnFe 2 O 4 samples. The sample obtained from mixture (1) has the cation inversion degree 0.3482 and the sample obtained from mixture (2) 0.400. Magnetization measurements were confirmed that the degrees of the inversion were well estimated. Comparison with published data shows that used method of synthesis gives nano powder samples with extremely high values of saturation magnetizations: sample (1) 78.3 emu g −1 and sample (2) 91.5 emu g −1 at T = 4.5 K

Structural and magnetic properties of nanocrystalline stannic substituted cobalt ferrite

Energy Technology Data Exchange (ETDEWEB)

Abbas, Y.M., E-mail: ymabbas@live.com [Physics Department, Faculty of Science, Suez Canal University, Ismailia (Egypt); Mansour, S.A. [Physics Department, Faculty of Science, Suez Canal University, Ismailia (Egypt); Physics Department, Faculty of Science, King AbdulAziz University, Rabegh (Saudi Arabia); Ibrahim, M.H. [Physics Department, Faculty of Science, Suez Canal University, Ismailia (Egypt); Physics Department, Faculty of Science, King AbdulAziz University (Saudi Arabia); Ali, Shehab. E., E-mail: shehab_ali@science.suez.edu.eg [Physics Department, Faculty of Science, Suez Canal University, Ismailia (Egypt)

2012-09-15

The structural and magnetic properties of the spinel ferrite system Co{sub 1+x}Fe{sub 2-2x}Sn{sub x}O{sub 4} (x=0.0-1.0) have been studied. Samples in the series were prepared by the ceramic technique. The structural and microstructural evolutions of the nanophase have been studied using X-ray powder diffraction and the Rietveld method. The refinement result showed that the type of the cationic distribution over the tetrahedral and octahedral sites in the nanocrystalline lattice is partially an inverse spinel. Far infrared absorption spectra show two significant absorption bands, around 600 cm{sup -1} and 425 cm{sup -1}, which are respectively attributed to tetrahedral (A) and octahedral [B] vibrations of the spinel. Scanning Electron Microscopy (SEM) was used to study surface morphology. SEM images reveal particles in the nanosize range. The transmission electronic microscope (TEM) reveals that the grains are spherical in shape. TEM analysis confirmed the X-ray results. The magnetic properties of the prepared samples were characterized by using a vibrating sample magnetometer. - Highlights: Black-Right-Pointing-Pointer The spinel ferrite system has been formed at 1000 Degree-Sign C by using ceramic techniques. Black-Right-Pointing-Pointer Structural and microstructural evolutions have been studied using XRD and the Rietveld method. Black-Right-Pointing-Pointer The refinement result showed cationic distribution in the lattice is partially an inverse spinel. Black-Right-Pointing-Pointer The transmission electronic microscope analysis confirmed the X-ray results. Black-Right-Pointing-Pointer Magnetic properties of the samples were characterized by using a vibrating sample magnetometer.

Structural and magnetic properties of nanocrystalline stannic substituted cobalt ferrite

International Nuclear Information System (INIS)

Abbas, Y.M.; Mansour, S.A.; Ibrahim, M.H.; Ali, Shehab. E.

2012-01-01

The structural and magnetic properties of the spinel ferrite system Co 1+x Fe 2−2x Sn x O 4 (x=0.0–1.0) have been studied. Samples in the series were prepared by the ceramic technique. The structural and microstructural evolutions of the nanophase have been studied using X-ray powder diffraction and the Rietveld method. The refinement result showed that the type of the cationic distribution over the tetrahedral and octahedral sites in the nanocrystalline lattice is partially an inverse spinel. Far infrared absorption spectra show two significant absorption bands, around 600 cm −1 and 425 cm −1 , which are respectively attributed to tetrahedral (A) and octahedral [B] vibrations of the spinel. Scanning Electron Microscopy (SEM) was used to study surface morphology. SEM images reveal particles in the nanosize range. The transmission electronic microscope (TEM) reveals that the grains are spherical in shape. TEM analysis confirmed the X-ray results. The magnetic properties of the prepared samples were characterized by using a vibrating sample magnetometer. - Highlights: ► The spinel ferrite system has been formed at 1000 °C by using ceramic techniques. ► Structural and microstructural evolutions have been studied using XRD and the Rietveld method. ► The refinement result showed cationic distribution in the lattice is partially an inverse spinel. ► The transmission electronic microscope analysis confirmed the X-ray results. ► Magnetic properties of the samples were characterized by using a vibrating sample magnetometer.

High-pressure studies of a ThMn sub 1 sub 2 -type actinide compound: UFe sub 5 Al sub 7

CERN Document Server

Halevy, I; Kimmel, G; Atzmony, U; Pereira, L C J; Goncalves, A P; Schäfer, W

2002-01-01

The ternary inter-metallic compound, UFe sub 5 Al sub 7 , crystallize in a tetragonal ThMn sub 1 sub 2 type structure. In the as-cast samples a residual phase of FeAl (approx 2% wt) was identified in the grain boundaries. The amount of the residual cubic phase of FeAl was determined by Rietveld analysis and reduced by the annealing process. UFe sub 5 Al sub 7 maintains the tetragonal symmetry as a function of pressure, while FeAl keeps the cubic structure as was determined by the Rietveld analysis. The volume-pressure curve calculated from the x-ray analysis is V/V sub 0 = 0.87 for UFe sub 5 Al sub 7 at 26.0 GPa.

Temperature-Induced Desorption of Methyl tert-Butyl Ether Confined on ZSM-5: An In Situ Synchrotron XRD Powder Diffraction Study

Directory of Open Access Journals (Sweden)

Elisa Rodeghero

2017-02-01

Full Text Available The temperature-induced desorption of methyl tert-butyl ether (MTBE from aqueous solutions onto hydrophobic ZSM-5 was studied by in situ synchrotron powder diffraction and chromatographic techniques. This kind of information is crucial for designing and optimizing the regeneration treatment of such zeolite. The evolution of the structural features monitored by full profile Rietveld refinements revealed that a monoclinic (P21/n to orthorhombic (Pnma phase transition occurred at about 100 °C. The MTBE desorption process caused a remarkable change in the unit-cell parameters. Complete MTBE desorption was achieved upon heating at about 250 °C. Rietveld analysis demonstrated that the desorption process occurred without any significant zeolite crystallinity loss, but with slight deformations in the channel apertures.

X-ray and electron diffraction studies of the structures of pseudo-perovskite compounds Pb2(Sc,Ta)O6 and Pb2(Mg,W)O6

International Nuclear Information System (INIS)

Baba-Kishi, K.Z.; Cernik, R.J.

1992-01-01

Electron diffraction patterns, X-ray precession patterns and synchrotron Rietveld powder diffraction profiles were used to study the crystal structure of the pseudo-perovskite compound Pb 2 (Sc, Ta)O 6 (PST). The results of a Rietveld refinement and single-crystal X-ray precession studies showed that PST has a lower symmetry than the cubic Fm3m in the paraelectric state. The remarkable similarities between the crystal structures of the antiferroelectric Pb 2 (Mg, W)O 6 (PMW) and ferroelectric PST are studied in detail by electron diffraction and it is suggested that PST is a weak or frustrated antiferroelectric oxide. The influence of the degree of structural long-range order on the existence of an antiferroelectric phase transition in PST and PMW is discussed. (orig.)

New methods for removal of pollutants from exhaust gases

Energy Technology Data Exchange (ETDEWEB)

Braestrup, F.

2009-06-15

with the electrode materials during sintering and formed different oxides. In-situ high temperature neutron diffraction was performed on ZnFe{sub 2}O{sub 4} in order to determine the cation distribution and to understand the electronic resistivity as well as the dilatometry measurement of the material. Data were analyzed with the Rietveld refinement method and results showed that cations start to rearrange at around 600 deg. C which, to some extend, confirm the behaviour of the resistivity data and the dilatometry measurement. X-ray adsorption spectroscopy was performed on MgFe{sub 2}O{sub 4}, NiFe{sub 2}O{sub 4}, NiCr{sub 2}O{sub 4}, ZnFe{sub 2}O{sub 4} and NiCrFeO{sub 4}. This was done in order to investigate possible changes in oxidation states of the transition elements. In the case of ZnFe{sub 2}O{sub 4} the cation distribution was tried analyzed in order to compare the results with Rietveld refinements on high temperature neutron diffraction. Results show that it was difficult to obtain a good quality refinement without violating the bond distances with respect to reported values found by neutron diffraction and literature. MgFe{sub 2}O{sub 4} and NiFe{sub 2}O{sub 4} were also analyzed in different gases at 400 deg. C and results show that NO and NO{sub 2} adsorb very strongly on MgFe{sub 2}O{sub 4} and decreases the X-ray signal significantly. A change in oxidation state of Ni was observed in atmospheres containing NO{sub 2}. (author)

Crystal structure and tautomerism of Pigment Yellow 138 determined by X-ray powder diffraction and solid-state NMR

DEFF Research Database (Denmark)

Gumbert, Silke D.; Körbitzer, Meike; Alig, Edith

2016-01-01

The crystal structure of C.I. Pigment Yellow 138 was determined from X-ray powder diffraction data using real-space methods with subsequent Rietveld refinements. The tautomeric state was investigated by solid-state 1D and 2D multinuclear NMR experiments. In the crystals, the compound exhibits...... the NH-tautomer with a hydrogen atom situated at the nitrogen of the quinoline moiety. Direct evidence of the presence of the NH-tautomer is provided by 1H–14N HMQC solid-state NMR at very fast MAS. Solid-state dispersion-corrected density functional theory calculations with BLYP-D3 confirm...

Synthesis of ceramic catalytic system based on CuO/CeO{sub 2} for preferential oxidation reaction of CO; Sintese de sistemas cataliticos ceramicos de CuO/CeO{sub 2} destinados a reacao de oxidacao preferencial do CO

Energy Technology Data Exchange (ETDEWEB)

Neiva, L.S.; Ribeiro, M.A.; Bispo, A.; Gama, L., E-mail: lsoutoneiva@yahoo.com.b [Universidade Federal de Campina Grande (UFCG), PB (Brazil). Unidade Academica de Engenharia de Materiais

2010-07-01

The aim this is work is to develop catalysts based on CuO/CeO{sub 2} by means two different types of synthesis methods: combustion synthesis and Pechini. CuO/CeO{sub 2} catalysts were synthesized with 0.5 mol of CuO for both synthesis methods used. The catalysts were characterized by XRD with the Rietveld refinement, EDX and textural analysis by the BET method. The results show that both methods of synthesis led to the formation of catalysts with segregated phases formed on the structures of the obtained materials, such segregated phases were formed by the presence of catalytic active species CuO and these phases had different characteristics depending on the type of method synthesis used. Small differences were observed in the evaluation of textural characteristics of the catalysts developed in this work according to the synthesis method employed. (author)

Rietveld analysis, dielectric and impedance behaviour of Mn /Fe ion ...

Indian Academy of Sciences (India)

Figure 1 compares X-ray diffraction patterns of pow- ders calcined at temperature .... ground, absorption coefficient, atomic positions, two theta zero error, thermal ... attributed to segregation of Mn and Fe at grain boundaries. (Dai et al 1995).

Structure of Pigment Yellow 181 dimethylsulfoxide N-methyl-2-pyrrolidone (1:1:1) solvate from XRPD + DFT-D

International Nuclear Information System (INIS)

Streek, Jacco van de

2015-01-01

The relatively complex structure of a triclinic disolvate was solved from low-resolution laboratory powder diffraction data through the intermediate use of dummy atoms and the combination with quantum-mechanical calculations. With only a 2.6 Å resolution laboratory powder diffraction pattern of the θ phase of Pigment Yellow 181 (P.Y. 181) available, crystal-structure solution and Rietveld refinement proved challenging; especially when the crystal structure was shown to be a triclinic dimethylsulfoxide N-methyl-2-pyrrolidone (1:1:1) solvate. The crystal structure, which in principle has 28 possible degrees of freedom, was determined in three stages by a combination of simulated annealing, partial Rietveld refinement with dummy atoms replacing the solvent molecules and further simulated annealing. The θ phase not being of commercial interest, additional experiments were not economically feasible and additional dispersion-corrected density functional theory (DFT-D) calculations were employed to confirm the correctness of the crystal structure. After the correctness of the structure had been ascertained, the bond lengths and valence angles from the DFT-D minimized crystal structure were fed back into the Rietveld refinement as geometrical restraints (‘polymorph-dependent restraints’) to further improve the details of the crystal structure; the positions of the H atoms were also taken from the DFT-D calculations. The final crystal structure is a layered structure with an elaborate network of hydrogen bonds

Layered B-site cation ordering: A key factor in ferrimagnetism of Y{sub 2}MnCrO{sub 6}

Energy Technology Data Exchange (ETDEWEB)

Hao, Lin [Department of Physics, University of Science and Technology of China, Hefei, Anhui (China); Yang, Lei [Collaborative Innovation Center for Magnetoelectric Industry, China Three Gorges University, Yichang, Hubei (China); Lee, Ming-Hsien; Lin, Tseh-Hsing [Department of Physics, Tamkang University, Taipei, Taiwan (China); Zhang, ZhongFeng; Xie, XiangNan [Department of Physics, University of Science and Technology of China, Hefei, Anhui (China); Zhu, Hong, E-mail: zhuh@ustc.edu.cn [Department of Physics, University of Science and Technology of China, Hefei, Anhui (China)

2014-07-15

Highlights: • Rietveld refinement and first-principles calculations are performed for Y{sub 2}MnCrO{sub 6}. • The layered B-site cation ordering is a more reliable structure for Y{sub 2}MnCrO{sub 6}. • Y{sub 2}MnCrO{sub 6} has an insulating ferrimagnetism (0 0 1)-ordered ground state. • The layered ordered pattern plays a key role for the ferrimagnetism in Y{sub 2}MnCrO{sub 6}. - Abstract: We report the Rietveld refinement of powder X-ray diffraction (XRD) pattern and first-principles calculations for the half-Cr{sup 3+} doped YMnO{sub 3} compound. The Rietveld refinement results suggest that the compound has a monoclinic structure with the Mn{sup 3+}/Cr{sup 3+} layers alternately stacking along the [0 0 1] direction. The first-principles calculations show that the structure with layered B-site cation ordering has the lowest total energy; meanwhile, the insulating ferrimagnetic state is more favored compared to the ferromagnetic state, which is in agreement with the reported experimental results. Based upon Goodenough’s model of semi-covalent exchange, we argue that the anisotropic magnetic couplings between the Mn{sup 3+}/Cr{sup 3+} cations ordered in layered pattern play an important role for the ferrimagnetism in the compound.

Understanding the formation and growth of Ag nanoparticles on silver chromate induced by electron irradiation in electron microscope: A combined experimental and theoretical study

International Nuclear Information System (INIS)

Fabbro, Maria T.; Gracia, Lourdes; Silva, Gabriela S.; Santos, Luís P.S.; Andrés, Juan; Cordoncillo, Eloisa; Longo, E.

2016-01-01

Ag 2 CrO 4 microcrystals were synthesized using the co-precipitation method. These microcrystals were characterized through X-ray diffraction (XRD) with Rietveld analysis, field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM) with energy-dispersive spectroscopy (EDS), micro-Raman (MR). XRD patterns and Rietveld refinement data showed that the material exhibits an orthorhombic structure without any deleterious phases. FE-SEM and TEM micrographs revealed the morphology and the growth of Ag nanoparticles on Ag 2 CrO 4 microcrystals during electron beam irradiation. These events were directly monitored in real-time. Their optical properties were investigated using ultraviolet-visible (UV–vis) diffuse reflectance spectroscopy that allowed the calculation of the optical band gap energy. Theoretical analyses based on the density functional theory level indicate that the incorporation of electrons is responsible for structural modifications and formation of defects on the [AgO 6 ] and [AgO 4 ] clusters, generating ideal conditions for the growth of Ag nanoparticles. - Graphical abstract: Theoretical representation of the Ag 2 CrO 4 orthorhombic structure. Display Omitted - Highlights: • The Ag 2 CrO 4 microcrystals indicate an orthorhombic structure. • The formation of Ag 0 promotes Ag-nanoparticle growth on the surface of the Ag 2 CrO 4 . • Electron irradiation of the material induces the formation of Ag vacancies.

Effect of laser irradiation on Ag4In12Sb56Te28

Science.gov (United States)

Chinnusamy, Rangasami

2018-04-01

Ag4In12Sb56Te28 has been synthesized by melt-quench method. Phase homogeneity, crystal structure and effect of laser irradiation have been investigated using X-ray diffraction (XRD) and Raman spectroscopy. Rietveld refinement of crystal structure revealed that Ag4In12Sb56Te28 is a multiphase system with AgIn3Te5, Sb8Te3 and Sb phases. Combined optical microscopy and Raman spectroscopy have been used to understand the distribution of different phases on the surface of the samples, which substantiated the results of Rietveld analysis. Interaction of 20 mW laser beam with samples has been investigated using Raman measurements. The results have shown that regions with large phase fraction of AgIn3Te5 become amorphous during laser-sample interaction, but the starting phase remains nearly same after the interaction. Regions with AgIn3Te5 and nearly equal or larger amount of Sb8Te3 have shown significant growth of α-Sb2O3 during and after laser-sample interaction. Regions rich in Sb have shown formation of AgIn3Te5 and growth of α-Sb2O3 during and after interaction. These observations have been explained based on the maximum temperature rise at different regions during laser-sample interaction.

Room temperature neutron diffraction and magnetic studies of multiferroic Pb{sub 0.9}Bi{sub 0.1}Fe{sub 0.55}Nb{sub 0.45}O{sub 3} solid solution

Energy Technology Data Exchange (ETDEWEB)

Dadami, S. T.; Matteppanavar, S.; Shivaraja, I.; Angadi, B., E-mail: brangadi@gmail.com [Department of Physics, Bangalore University, Bangalore-560056 (India); Rayaprol, S.; Deshpande, S. K. [UGC-DAE-CSR, Mumbai Centre, BARC, Mumbai-400085 (India)

2016-05-23

The Pb{sub 0.9}Bi{sub 0.1}Fe{sub 0.55}Nb{sub 0.45}O{sub 3} (PBFNO) solid solution was synthesized by single step solid state reaction method and the optimized parameters are 700°C for 2hr (calcination) and 800°C for 3hr (sintering). The formation of desired material was confirmed using X-Ray Diffraction (XRD) and Neutron Diffraction (ND) studies. The structural and magnetic properties of the sintered pellets were investigated at room temperature (RT) through XRD, ND and Magnetic (M-H) studies. The structural analysis was carried out by Rietveld refinement through the Full Prof program. Rietveld refined XRD and ND patterns confirms the monoclinic structure with Cm space group and obtained cell parameters from the ND data are a = 5.651(2) Å, b = 5.658(2) Å, c = 4.005(1) Å and α = 90°, β = 89.98(1)°, γ = 90°. RT M-H curve studies have been carried out. It shows the clear opening of hysteresis (M–H) loop, is evidenced as the existence of weak ferromagnetism at RT. The M-H data shows existence weak ferromagnetism embedded in an antiferromagnetic matrix structure. The dielectric constant with frequency shows the formation of barrier layers at the grain and grain boundary interfaces gives rise to interfacial space charge polarization.

Influence of mineralizer agents on the growth of crystalline CeO2 nanospheres by the microwave-hydrothermal method

International Nuclear Information System (INIS)

Deus, R.C.; Cilense, M.; Foschini, C.R.; Ramirez, M.A.; Longo, E.; Simões, A.Z.

2013-01-01

Cystalline ceria (CeO 2 ) nanoparticles have been synthesized by a simple and fast microwave-assisted hydrothermal (MAH) under NaOH, KOH, and NH 4 OH mineralizers added to a cerium ammonium nitrate aqueous solution. The products were characterized by X-ray powder diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), Fourier transformed-IR and Raman spectroscopies. Rietveld refinement reveals a cubic structure with a space group Fm3m while infrared data showed few traces of nitrates. Field emission scanning microcopy (FEG-SEM) revealed a homogeneous size distribution of nanometric CeO 2 nanoparticles. The MAH process in KOH and NaOH showed most effective to dehydrate the adsorbed water and decrease the hydrogen bonding effect leaving a weakly agglomerated powder of hydrated ceria. TEM micrographs of CeO 2 synthesized under MAH conditions reveal particles well-dispersed and homogeneously distributed. The MAH enabled cerium oxide to be synthesized at 100 °C for 8 min.

Catalytic oxidation of n-hexane promoted by Ce{sub 1−x}Cu{sub x}O{sub 2} catalysts prepared by one-step polymeric precursor method

Energy Technology Data Exchange (ETDEWEB)

Araújo, Vinícius D., E-mail: dantas@ursa.ifsc.usp.br [Instituto de Física, Universidade de São Paulo – USP, 13560-970 São Carlos, SP (Brazil); Lima, Maurício M. de [Instituto de Ciencia de los Materiales, Universidad de Valencia, E-46071 Valencia (Spain); Fundación General, Universitat de Valencia, Valencia (Spain); Cantarero, Andrés [Instituto de Ciencia de los Materiales, Universidad de Valencia, E-46071 Valencia (Spain); Bernardi, Maria I.B. [Instituto de Física, Universidade de São Paulo – USP, 13560-970 São Carlos, SP (Brazil); Bellido, Jorge D.A. [CAP-Engenharia Química, Universidade Federal de São João Del-Rei – UFSJ, São João Del-Rei, MG (Brazil); Assaf, Elisabete M. [Instituto de Química, Universidade de São Paulo – USP, 13560-970 São Carlos, SP (Brazil); Balzer, Rosana; Probst, Luiz F.D. [Departamento de Química, Universidade Federal de Santa Catarina – UFSC, 88040-900 Florianópolis, SC (Brazil); Fajardo, Humberto V. [Departamento de Química, Universidade Federal de Ouro Preto – UFOP, 35400-000 Ouro Preto, MG (Brazil)

2013-11-01

Ceria-supported copper catalysts (Ce{sub 1−x}Cu{sub x}O{sub 2}, with x (mol) = 0, 0.01, 0.03, 0.05 and 0.10) were prepared in one step through the polymeric precursor method. The textural properties of the catalysts were investigated by X-ray diffraction (XRD), Rietveld refinement, N{sub 2}-physisorption (BET surface area), electron paramagnetic resonance (EPR), UV–visible diffuse reflectance and photoluminescence spectroscopies and temperature-programmed reduction (TPR). In a previous study ceria-supported copper catalysts were found to be efficient in the preferential oxidation of CO. In this study, we extended the catalytic application of Ce{sub 1−x}Cu{sub x}O{sub 2} systems to n-hexane oxidation and it was verified that the catalysts were highly efficient in the proposed reaction. The best performance (up to 95% conversion) was observed for the catalysts with low copper loads (Ce{sub 0.97}Cu{sub 0.03}O{sub 2} and Ce{sub 0.99}Cu{sub 0.01}O{sub 2}, respectively). The physicochemical characterizations revealed that these behaviors could be attributed to the copper species present in the catalysts and the interaction between CuO and CeO{sub 2}, which vary according to the copper content. - Highlights: • Synthesis of CuO/CeO2 catalysts by the one-step polymeric precursor method. • 95% n-hexane conversion on Ce0.97Cu0.03O2 catalyst. • Redox properties play a key role in the catalytic performance.

Characterization and concentration of manganese ore waste; Caracterizacao e concentracao de rejeito de minerio de manganes

Energy Technology Data Exchange (ETDEWEB)

Lima, Rosa Malena Fernandes; Pereira, Eder Esper; Reis, Erica Linhares; Silva, Glaucia Regina da [Universidade Federal de Ouro Preto (UFOP), MG (Brazil)

2010-07-01

In this work is presented the tests results of characterization and concentration by gravity and flotation methods carried out with a manganese sample waste. By optical microscopy, SEM/EDS and X-ray diffractometry were identified the Mn minerals spessartite (20%), tephroite (15%), rhodonite (5%), rhodochrosite and carbonates minerals (29%), opaque minerals and others (16%), micaceus minerals (6%) and quartz (4%). It was obtained Mn metallurgical recovery of 58% with Mn concentrate contents varying from 30 to 32.5%. The concentrates SiO{sub 2} contents of flotation were until 1.5% smaller than those contents of gravity method concentrates. (author)

Determination of mineral abundances in samples from the exploratory studies facility using x-ray diffraction

International Nuclear Information System (INIS)

Roberts, S.; Viani, R.

1998-01-01

Tuff samples collected from the Exploratory Studies Facility (ESF) were X-rayed to estimate relative mineral abundances. X-ray analysis was performed on sub-samples of specimens collected from both the Single Heater Test (SHT) and Drift Scale Heater Test (DST) that were used for thermomechanical measurements, as well as samples collected from cores retrieved from boreholes in the Drift Scale Test Area. The abundance of minerals that could affect the behavior of the host rock at repository relevant temperatures is of particular interest. These minerals include crystobalite, which undergoes a phase transition and volume change at elevated temperature (-250 'C), and smectite and clinoptilolite that can dehydrate at elevated temperature with accompanying volume reduction. In addition, the spatial distribution of SiO, polymorphs and secondary minerals may provide evidence for deducing past fluid pathways. The mineral abundances tabulated here include data reported previously in three milestone reports (Roberts and Viani, 1997a,b; Viani and Roberts, 1996) but re-analyzed (see below), as well as previously unreported data. Previous X-ray diffraction analyses of samples from the ESF (Roberts and Viani, 1997a; Viani and Roberts, 1996) utilized the matrix flushing method of Chung (1974) and an internal intensity standard (corundum) to quantify the abundances of the phases present. Although the method is adequate for obtaining relative abundances, its accuracy and precision is limited by the inherent differences between the external standards used to compute the reference intensity ratio and the mineral phases in the sample. In a subsequent report (Roberts and Viani, 1997b) mineral abundances were obtained using the Rietveld method of whole X-ray pattern fitting (Snyder and Bish, 1989; Young, 1993). The Rietveld technique has the potential to be both more accurate and more precise for estimating mineral abundances (Snyder and Bish, 1989)

Expanding the structural landscape of niclosamide: a high Z ' polymorph, two new solvates and monohydrate H_A

DEFF Research Database (Denmark)

Sovago, Ioana; Bond, Andrew D.

2015-01-01

to be twinned by twofold rotation around that axis. The acetonitrile molecules occupy channels in the structure. A complete structure is provided for niclosamide monohydrate, C13H8Cl2N2O4·H2O, polymorph HA, obtained by Rietveld refinement against laboratory powder X-ray diffraction data. It has been suggested...... that this compound is related to the methanol solvate of niclosamide [Harriss, Wilson & Radosevljevic Evans (2014). Acta Cryst. C70, 758-763], but it is found that the two are not fully isostructural: they contain isostructural two-dimensional layers, but the layers are arranged differently in the two structures....... This suggests that HA may have the potential for polytypism, and features in the Rietveld difference curve indicate that a polytype fully isostructural with the methanol solvate might be present....

Effect of titania on the characteristics of a Tin-Platinum catalyst

Energy Technology Data Exchange (ETDEWEB)

Morales-Gil, P., E-mail: moralesp@imp.mx; Nava, N. [Instituto Mexicano del Petróleo (Mexico); Baggio-Saitovitch, E. [Centro Brasileiro de Pesquisas Físicas (Brazil)

2015-06-15

Pt-Sn bimetallic catalysts dispersed on alumina are commonly used for reforming and dehydrogenation reactions. In this research work, Pt and Sn were supported on titania. The resulting interactions between the components in the prepared samples, before and after treatment with hydrogen, were studied by Mössbauer spectroscopy, X-ray diffraction and Rietveld refinement. The results show the presence of Pt and SnO{sub 2} after calcinations. After the reduction process, metallic Pt, PtSn, and Pt{sub 3}Sn alloys were identified. The Rietveld refinement analysis shows that some Ti{sup 4+} atoms were replaced by Sn{sup 4+} atoms in the titania structure. Finally, the Mössbauer spectroscopy and X-ray diffraction results indicate that metallic platinum and SnO{sub 2} are encapsulated by a TiOx layer.

Optical and Piezoelectric Study of KNN Solid Solutions Co-Doped with La-Mn and Eu-Fe

Directory of Open Access Journals (Sweden)

Jesús-Alejandro Peña-Jiménez

2016-09-01

Full Text Available The solid-state method was used to synthesize single phase potassium-sodium niobate (KNN co-doped with the La3+–Mn4+ and Eu3+–Fe3+ ion pairs. Structural determination of all studied solid solutions was accomplished by XRD and Rietveld refinement method. Electron paramagnetic resonance (EPR studies were performed to determine the oxidation state of paramagnetic centers. Optical spectroscopy measurements, excitation, emission and decay lifetime were carried out for each solid solution. The present study reveals that doping KNN with La3+–Mn4+ and Eu3+–Fe3+ at concentrations of 0.5 mol % and 1 mol %, respectively, improves the ferroelectric and piezoelectric behavior and induce the generation of optical properties in the material for potential applications.

Crystallographic changes in lead zirconate titanate due to neutron irradiation

Directory of Open Access Journals (Sweden)

Alexandra Henriques

2014-11-01

Full Text Available Piezoelectric and ferroelectric materials are useful as the active element in non-destructive monitoring devices for high-radiation areas. Here, crystallographic structural refinement (i.e., the Rietveld method is used to quantify the type and extent of structural changes in PbZr0.5Ti0.5O3 after exposure to a 1 MeV equivalent neutron fluence of 1.7 × 1015 neutrons/cm2. The results show a measurable decrease in the occupancy of Pb and O due to irradiation, with O vacancies in the tetragonal phase being created preferentially on one of the two O sites. The results demonstrate a method by which the effects of radiation on crystallographic structure may be investigated.

Self-propagating high-temperature synthesis of TiC-WC composite materials

International Nuclear Information System (INIS)

Mas-Guindal, M.J.; Contreras, L.; Turrillas, X.; Vaughan, G.B.M.; Kvick, A.; Rodriguez, M.A.

2006-01-01

TiC-WC composites have been obtained in situ by self-propagating high-temperature synthesis (SHS) from a mixture of compacted powders of elemental titanium, tungsten and graphite. The Rietveld method has proved to be a useful tool to quantify the different phases in the reaction and calculate the cell parameters of the solid solution found in the products. The reaction has also been followed in real time by X-ray diffraction at the European Synchrotron Radiation Facility (ESRF ID-11 Materials Science Beamline). The mechanism of the reaction is discussed in terms of the diffusion of liquid titanium to yield titanium carbide with a solid solution of tungsten. The microstructures of the materials obtained by this method are presented

Influence of mineralizer agents on the growth of crystalline CeO{sub 2} nanospheres by the microwave-hydrothermal method

Energy Technology Data Exchange (ETDEWEB)

Deus, R.C. [Universidade Estadual Paulista-Unesp - Faculdade de Engenharia de Guaratingueta, Av. Dr. Ariberto Pereira da Cunha, 333 Bairro Portal das Colinas, CEP 12516-410 Guaratingueta-SP (Brazil); Cilense, M.; Foschini, C.R. [Universidade Estadual Paulista-Unesp - Instituto de Quimica - Laboratorio Interdisciplinar em Ceramica (LIEC), Rua Professor Francisco Degni s/n, CEP 14800-90 Araraquara, SP (Brazil); Ramirez, M.A. [Universidade Estadual Paulista-Unesp - Faculdade de Engenharia de Guaratingueta, Av. Dr. Ariberto Pereira da Cunha, 333 Bairro Portal das Colinas, CEP 12516-410 Guaratingueta-SP (Brazil); Longo, E. [Universidade Estadual Paulista-Unesp - Instituto de Quimica - Laboratorio Interdisciplinar em Ceramica (LIEC), Rua Professor Francisco Degni s/n, CEP 14800-90 Araraquara, SP (Brazil); Simoes, A.Z., E-mail: alezipo@yahoo.com [Universidade Estadual Paulista-Unesp - Faculdade de Engenharia de Guaratingueta, Av. Dr. Ariberto Pereira da Cunha, 333 Bairro Portal das Colinas, CEP 12516-410 Guaratingueta-SP (Brazil); Universidade Federal de Itajuba-Unifei - Campus Itabira, Rua Sao Paulo, 377 Bairro Amazonas, CEP 35900-37 Itabira, MG (Brazil)

2013-02-15

Cystalline ceria (CeO{sub 2}) nanoparticles have been synthesized by a simple and fast microwave-assisted hydrothermal (MAH) under NaOH, KOH, and NH{sub 4}OH mineralizers added to a cerium ammonium nitrate aqueous solution. The products were characterized by X-ray powder diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), Fourier transformed-IR and Raman spectroscopies. Rietveld refinement reveals a cubic structure with a space group Fm3m while infrared data showed few traces of nitrates. Field emission scanning microcopy (FEG-SEM) revealed a homogeneous size distribution of nanometric CeO{sub 2} nanoparticles. The MAH process in KOH and NaOH showed most effective to dehydrate the adsorbed water and decrease the hydrogen bonding effect leaving a weakly agglomerated powder of hydrated ceria. TEM micrographs of CeO{sub 2} synthesized under MAH conditions reveal particles well-dispersed and homogeneously distributed. The MAH enabled cerium oxide to be synthesized at 100 Degree-Sign C for 8 min.

Co-existence of tetragonal and monoclinic phases and multiferroic properties for x ⩽ 0.30 in the (1 − x)Pb(Zr{sub 0.52}Ti{sub 0.48})O{sub 3}–(x)BiFeO{sub 3} system

Energy Technology Data Exchange (ETDEWEB)

Sharma, Subhash; Singh, Vikash [Department of Physics and Materials Science and Engineering, Jaypee Institute of Information Technology, A-10, Sector-62, Noida 201307, Uttar Pradesh (India); Kotnala, R.K. [National Physical Laboratory (CSIR), Dr. K.S. Krishnan Marg, New Delhi 110012 (India); Ranjan, Rajeev [Department of Materials Engineering, Indian Institute of Science, Bangalore 560012 (India); Dwivedi, R.K., E-mail: rk.dwivedi@jiit.ac.in [Department of Physics and Materials Science and Engineering, Jaypee Institute of Information Technology, A-10, Sector-62, Noida 201307, Uttar Pradesh (India)

2014-11-25

Highlights: • Synthesis of (1 − x)PbZr{sub 0.52}Ti{sub 0.48}O{sub 3}–(x)BiFeO{sub 3} with x ⩽ 0.30 by sol–gel method. • Structural phase transformation with x has been revealed by Rietveld analysis. • Raman analysis supports structural phase transition. • Occurrence of MC is a strong evidence of magneto-electric coupling. • Enhance magnetization is obtained in the dominant monoclinic phase for x ⩾0.15. - Abstract: Compositions with x ⩽ 0.30 in the system (1 − x)Pb(Zr{sub 0.52}Ti{sub 0.48})O{sub 3}–(x)BiFeO{sub 3} were synthesized by sol–gel method. Rietveld analysis of X-ray diffraction data reveals tetragonal structure (P4mm) for x ⩽ 0.05 and monoclinic (Cm) phase along with the existence of tetragonal phase for 0.10 ⩽ x ⩽ 0.25 and monoclinic phase for x = 0.30. Transformation of E(2TO) and E + B1 vibrational modes in the range 210–250 cm{sup −1} (present for x ⩽ 0.25) into A′ + A″ modes at ∼236 cm{sup −1} for x = 0.30, and occurrence of new vibrational modes A′ and A″ in Raman spectra for x ⩾ 0.10 unambiguously support the presence of monoclinic phase. Occurrence of remnant polarisation and enhanced magnetization with concentration of BiFeO{sub 3} indicates superior multiferroic properties. Variation of magneto-capacitance with applied magnetic field is a strong evidence of magneto-electric multiferroic coupling in these materials.

Structural and magnetic properties of Co50Ni50 powder mixtures

International Nuclear Information System (INIS)

Loudjani, N.; Bensebaa, N.; Dekhil, L.; Alleg, S.; Sunol, J.J.

2011-01-01

In the present work, morphological, structural, thermal and magnetic properties of nanocrystalline Co 50 Ni 50 alloy prepared by high energy planetary ball milling have been studied by means of scanning electron microscopy, X-ray diffraction, and differential scanning calorimetry. The coercivity and the saturation magnetization of alloyed powders were measured at room temperature by a vibration sample magnetization. Morphological observations indicated a narrow distribution in the particle and homogeneous shape form with mean average particle size around 130 μm 2 . The results show that an allotropic Co transformation hcp→fcc occurs within the three first hours of milling and contrary to what expected, the Rietveld refinement method reveals the formation of two fcc solid solutions (SS): fcc Co(Ni) and Ni(Co) beside a small amount of the undissolved Co hcp. Thermal measurement, as a function of milling time was carried out to confirm the existence of the hcp phase and to estimate its amount. Magnetic measurement indicated that the 48 h milled powders with a steady state particles size have the highest saturation (105.3 emu/g) and the lowest coercivity (34.5 Oe). - Highlights: → By using the Rietveld refinement method we found that Co 50 Ni 50 alloy, milled for 48 h, contains two fcc solid solutions: fcc Co(Ni) and Ni(Co), beside a small amount of the undissolved Co hcp. DSC measurement as a function of milling time was carried out to confirm the existence of the hcp phase and to estimate its amount. → By means of imageJ we found the area distribution and not just the diameter distribution. → The coercivity is strongly related to the particles size distribution.

Characterization of poly pyrrole/montmorillonite electro polymerised onto Pt; Caracterizacao de filmes PPy/montmorilonita eletropolimerizados sobre Pt

Energy Technology Data Exchange (ETDEWEB)

Castagno, K.R.L., E-mail: katiarlc@pelotas.ifsul.edu.b [Instituto Federal Sul-rio-grandense (IFSul), RS (Brazil). Dept. de Quimica; Azambuja, D.S.; Dalmoro, V.; Mauller, R.S. [Universidade Federal do Rio Grande do Sul (UFRGS), Pelotas, RS (Brazil). Inst. de Quimica

2010-07-01

In this study films of polypyrrole/montmorillonite (PPy/MT) were electropolymerized on platinum in order to evaluate the performance of this technique in the preparation of nanocomposite materials and to determine the thermal properties and conductivity of the composites. The films were synthesized from a solution containing pyrrole, dodecylbenzene sulfonate, acid and two types of clays: montmorillonite-Na + (MT-Na) and montmorillonite-30B (MT-M). The characterization of the films we have used FT-IR, TEM, XRD, TGA, DSC and resistivity measurement by the four-point van der Pauw method. The study showed that the adopted method of exfoliation and the electropolymerization method used, allows obtaining nanocomposite materials. Analyses of FT-IR, TEM and XRD show that the clays are exfoliated in the polymer matrix. Thermal analysis of the films indicates that the addition of clay reflects an enhancement in the thermal properties of the matrix of PPy, but decreases the conductivity of the same. (author)

Application of powder X-ray diffraction and the Rietveld method to the analysis of oxidation processes and products in sulphidic mine tailings

DEFF Research Database (Denmark)

Balic Zunic, Tonci; Katerinopoulou, Anna; Edsberg, Anders

2011-01-01

silica were applied as proper models. The procedures developed on test mixtures result in estimated errors of determination typically lower than 2 wt%. The approach was applied to the analysis of the complex problem of estimating mass balance in oxidized mine tailings from the Nanisivik Mine, Nunavut......, Canada revealing an oxidized proportion of 9 % of total pyrite content in the well drained tailings during a period of 8 years and a negligible oxidation in the water-covered tailings....

In-situ PXRD studies of ZnO nanoparticle growth: How do various salts influence the hydrothermal growth of ZnO?

DEFF Research Database (Denmark)

Bøjesen, Espen Drath

ZnO is a material of great scientific and everyday relevance; it is used widely in all sorts of application. Synthesis of ZnO nanoparticles can be performed by a wide assortment of methods and a tremendous variety of sizes and shapes, it has been suggested that ZnO is the one known compound showing...... the broadest range of nanostructures. Previously many different in-situ characterization methods have been used to investigate the ZnO formation under various synthesis conditions; these include UV-VIS and SAXS. These methods were primarily used to give information on particle size of ZnO formed using soft...... chemical methods and non-aqueous solvents. In our work we have studied the formation of ZnO during hydrothermal syntheses using in-situ powder X-ray diffraction, thus enabling us to extract crystallographic as well as microstructural information. The data was analyzed using Rietveld refinement and whole...

Kunst voorbij identiteit en differentiatie

NARCIS (Netherlands)

F.D.R. Maet (Frank)

2005-01-01

textabstractFrank Maet heeft opleidingen gevolgd in theater (Kleine Academie Brussel) en beeldende kunst (Rietveld Academie Amsterdam) en vervolgens filosofie gestudeerd (V.U.Brussel). Zijn eindverhandeling zocht naar invloeden van de esthetica op de wetenschapsfilosofie (met voornamelijk aandacht

Synthesis, crystal structure and spectroscopy properties of Na 3AZr(PO 4) 3 ( A=Mg, Ni) and Li 2.6Na 0.4NiZr(PO 4) 3 phosphates

Science.gov (United States)

Chakir, M.; El Jazouli, A.; de Waal, D.

2006-06-01

Na 3AZr(PO 4) 3 ( A=Mg, Ni) phosphates were prepared at 750 °C by coprecipitation route. Their crystal structures have been refined at room temperature from X-ray powder diffraction data using Rietveld method. Li 2.6Na 0.4NiZr(PO 4) 3 was synthesized through ion exchange from the sodium analog. These materials belong to the Nasicon-type structure. Raman spectra of Na 3AZr(PO 4) 3 ( A=Mg, Ni) phosphates present broad peaks in favor of the statistical distribution in the sites around PO 4 tetrahedra. Diffuse reflectance spectra indicate the presence of octahedrally coordinated Ni 2+ ions.

Preferred orientation of ettringite in concrete fractures

KAUST Repository

Wenk, Hans-Rudolf

2009-05-15

Sulfate attack and the accompanying crystallization of fibrous ettringite [Ca6Al2(OH)12(SO4) 3·26H2O] cause cracking and loss of strength in concrete structures. Hard synchrotron X-ray microdiffraction is used to quantify the orientation distribution of ettringite crystals. Diffraction images are analyzed using the Rietveld method to obtain information on textures. The analysis reveals that the c axes of the trigonal crystallites are preferentially oriented perpendicular to the fracture surfaces. By averaging single-crystal elastic properties over the orientation distribution, it is possible to estimate the elastic anisotropy of ettringite aggregates. © 2009 International Union of Crystallography.

Crystal-Chemical Analysis of Soil at Rocknest, Gale Crater

Science.gov (United States)

Morrison, S. M.; Downs, R. T.; Blake, D. F.; Bish, D. L.; Ming, D. W.; Morris, R. V.; Yen, A. S.; Chipera, S. J.; Treiman, A. H.; Vaniman, D. T.;

D2B, a new high resolution neutron powder diffractometer at ILL Grenoble

International Nuclear Information System (INIS)

Hewat, A.W.

1987-01-01

Applications of high resolution neutron powder diffraction to materials science have grown rapidly in the past 10 years, with the development of Rietveld methods of profile refinement, and new high resolution diffractometers and multidetectors. Materials studied range from catalysts to zeolites, and from battery electrodes to prestressed superconducting wires. Although the techniques have now been adapted for X-ray and synchrotron radiation, neutron powder diffraction retains unique advantages. In this paper we describe the design and first test measurements on the latest high resolution powder diffractometer D2B at ILL Grenoble. A review of the applications is published in Chemica Scripta (1986). (author) 9 refs., 6 figs., 2 tabs

On the determination of crystallinity and cellulose content in plant fibres

DEFF Research Database (Denmark)

Thygesen, Anders; Oddershede, Jette; Lilholt, Hans

2005-01-01

A comparative study of cellulose crystallinity based on the sample crystallinity and the cellulose content in plant fibres was performed for samples of different origin. Strong acid hydrolysis was found superior to agricultural fibre analysis and comprehensive plant fibre analysis for a consistent...... determination of the cellulose content. Crystallinity determinations were based on X-ray powder diffraction methods using side-loaded samples in reflection (Bragg-Brentano) mode. Rietveld refinements based on the recently published crystal structure of cellulose I beta followed by integration of the crystalline...... and 60 - 70 g/ 100 g cellulose in wood based fibres. These findings are significant in relation to strong fibre composites and bio-ethanol production....

A non-invasive analysis of 'proto-majolica' pottery from southern Italy by TOF neutron diffraction

Energy Technology Data Exchange (ETDEWEB)

Barilaro, D; Crupi, V; Majolino, D; Venuti, V [Dipartimento di Fisica, Universita di Messina, Contrada da Papardo, Salita Sperone 31, PO Box 55, 98166, Sant Agata, Messina (Italy); Barone, G [Dipartmento di Scienze Geologiche, Universita di Catania, Corso Italia 55, 95129 Catania (Italy); Tigano, G [Soprintendenza Beni Culturali ed Ambientali di Messina, Sezione Archeologica, Viale Boccetta 38, 98100 Messina (Italy); Imberti, S [Consiglio Nazionale delle Ricerche, Istituto Sistemi Complessi: Sezione di Firenze, Via Madonna del Piano 10, 50019 Sesto Fiorentino (Italy); Kockelmann, W [ISIS Facility, Rutherford Appleton Laboratory, Didcot OX11 0QX (United Kingdom)], E-mail: vvenuti@unime.it

2008-03-12

The employment of time-of-flight (TOF) neutron diffraction allowed for the quantitative determination of mineral phase contents of the ceramic bulk of several pottery fragments coming from Milazzo and Messina (Sicily, southern Italy). From an historical-artistic point of view, all the samples were dated back to the 12th to 13th centuries AD and classified as belonging to the 'proto-majolica' ceramic class. The adopted procedure is absolutely non-destructive, so that measurements were performed on the entire fragments without any sampling. The information derived, by applying the Rietveld analysis method, allowed us to formulate hypotheses concerning the fabrication processes of the artefacts.

X-ray powder diffraction analysis of liquid-phase-sintered silicon carbide ceramics

Energy Technology Data Exchange (ETDEWEB)

Ortiz, A.L.; Sanchez-Bajo, F. [Universidad de Extremadura, Badajoz (Spain). Dept. de Electronica e Ingenieria Electromecanica; Cumbrera, F.L. [Universidad de Extremadura, Badajoz (Spain). Dept. de Fisica

2002-07-01

In an attempt to gain a comprehensive understanding of the microstructural evolution in liquid-phase-sintered silicon carbide ceramics, the effect of the starting {beta}-SiC powder has been studied. Pellets of two different {beta}-SiC starting powders were sintered with simultaneous additions of Al{sub 2}O{sub 3} and Y{sub 2}O{sub 3} at 1950 C for 1 hour in flowing argon atmosphere. Here we have used X-ray diffraction to obtain the relative abundance of the resulting SiC polytypes after sintering. The significant influence of the defects concentration on the {beta} to {alpha} transformation rate has been determined using the Rietveld method. (orig.)

Applicability of empirical correlations for estimating global solar radiation

International Nuclear Information System (INIS)

Gopinathan, K.K.; Baholo, M.

1987-01-01

Three empirical models suggested by different investigators, for estimating monthly mean daily global radiation on a horizontal surface, are compared statistically to test their universal applicability. The models thus compared are those suggested by Rietveld, Glover and McCulloch and Gopinathan. The models are compared by calculating the root mean square error, mean bias error and mean relative percentage error values. The model suggested by Gopinathan yields the best results in terms of root mean square, mean bias and mean percentage errors. The model by Rietveld is the second best and the model by Glover and McCulloch comes at third place. However, the differences in the magnitude of errors among the three models are very small and all the three models can be considered to be accurate for global radiation estimation for any location in the world

Synthesis and crystal structure of the quaternary compound AgFe{sub 2}GaTe{sub 4}

Energy Technology Data Exchange (ETDEWEB)

Delgado, Gerzon E., E-mail: gerzon@ula.ve [Laboratorio de Cristalografía, Departamento de Química, Facultad de Ciencias, Universidad de Los Andes, Mérida 5101 (Venezuela, Bolivarian Republic of); Quintero, Eugenio; Tovar, Rafael; Grima-Gallardo, Pedro; Quintero, Miguel [Centro de Estudio de Semiconductores, Departamento de Física, Facultad de Ciencias, Universidad de Los Andes, Mérida 5101 (Venezuela, Bolivarian Republic of)

2014-11-15

Highlights: • New quaternary compound. • Synthesis from solid state reaction. • Crystal structure. • Rietveld refinement. - Abstract: The crystal structure of the quaternary compound AgFe{sub 2}GaTe{sub 4}, belonging to the system I–II{sub 2}–III–VI{sub 4}, was characterized by Rietveld refinement using X-ray powder diffraction data. The powder pattern was composed by 84.5% of the principal phase AgFe{sub 2}GaTe{sub 4} and 15.5% of the secondary phase FeTe. This material crystallizes with stannite structure in the tetragonal space group I-42m (N° 121), Z = 2, unit cell parameters a = 6.3409(2) Å, c = 12.0233(4) Å, V = 483.42(3) Å{sup 3}, and is isostructural with CuFe{sub 2}InSe{sub 4}.

Neutron diffraction studies on Ca1− xBaxZr4P6O24 solid solutions

Indian Academy of Sciences (India)

P6O24 compositions from combined Rietveld refinements of powder X-ray and neutron diffraction data. All the studied compositions crystallize in rhombohedral lattice (space group R-3 No. 148). A continuous solid solution is concluded from ...

Minimization of absorption contrast for accurate amorphous phase quantification: application to ZrO.sub.2./sub. nanoparticles

Czech Academy of Sciences Publication Activity Database

Suzuki-Muresan, T.; Deniard, P.; Gautron, E.; Petříček, Václav; Jobic, S.; Grambow, B.

2010-01-01

Roč. 43, Part 5 (2010), 1092-1099 ISSN 0021-8898 Institutional research plan: CEZ:AV0Z10100521 Keywords : x-ray diffraction * Rietveld refinement * nanoparticles Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 3.794, year: 2010

Mineralogical and chemical characterization of iron-, manganese-, and copper-containing synthetic hydroxyapatites

Science.gov (United States)

Sutter, B.; Ming, D. W.; Clearfield, A.; Hossner, L. R.

2003-01-01

The National Aeronautics and Space Administration's (NASA) Advanced Life Support (ALS) Program is evaluating the use of Fe-, Mn-, and Cu-containing synthetic hydroxyapatite (SHA) as a slow release fertilizer for crops that might be grown on the International Space Station or at Lunar and Martian outposts. Separate Fe-, Mn-, and Cu-containing SHA materials along with a transition-metal free SHA (pure-SHA) were synthesized using a precipitation method. Chemical and mineralogical analyses determined if and how Fe, Mn, and Cu were incorporated into the SHA structure. X-ray diffraction (XRD), Rietveld refinement, and transmission electron microscopy (TEM) confirmed that SHA materials with the apatite structure were produced. Chemical analyses indicated that the metal containing SHA materials were deficient in Ca relative to pure-SHA. The shift in the infrared PO4-mu 3 vibrations, smaller unit cell parameters, smaller particle size, and greater structural strain for Fe-, Mn-, and Cu-containing SHA compared with pure-SHA suggested that Fe, Mn, and Cu were incorporated into SHA structure. Rietveld analyses revealed that Fe, Mn, and Cu substituted into the Ca2 site of SHA. An Fe-rich phase was detected by TEM analyses and backscattered electron microscopy in the Fe-containing SHA material with the greatest Fe content. The substitution of metals into SHA suggests that metal-SHA materials are potential slow-release sources of micronutrients for plant uptake in addition to Ca and P.

Effect of molybdenum on structure, microstructure and mechanical properties of biomedical Ti-20Zr-Mo alloys.

Science.gov (United States)

Kuroda, Pedro Akira Bazaglia; Buzalaf, Marília Afonso Rabelo; Grandini, Carlos Roberto

2016-10-01

Titanium has an allotropic transformation around 883°C. Below this temperature, the crystalline structure is hexagonal close-packed (α phase), changing to body-centered cubic (β phase). Zirconium has the same allotropic transformation around 862°C. Molybdenum has body-centered cubic structure, being a strong β-stabilizer for the formation of titanium alloys. In this paper, the effect of substitutional molybdenum was analyzed on the structure, microstructure and selected mechanical properties of Ti-20Zr-Mo (wt%) alloys to be used in biomedical applications. The samples were prepared by arc-melting and characterized by x-ray diffraction with subsequent refinement by the Rietveld method, optical and scanning electron microscopy. The mechanical properties were analyzed by Vickers microhardness and dynamic elasticity modulus. X-ray measurements and Rietveld analysis revealed the presence of α' phase without molybdenum, α'+α″ phases with 2.5wt% of molybdenum, α″+β phases with 5 and 7.5wt% of molybdenum, and only β phase with 10wt% of molybdenum. These results were corroborated by microscopy results, with a microstructure composed of grains of β phase and lamellae and needles of α' and α″ phase in intra-grain the region. The hardness of the alloy was higher than the commercially pure titanium, due to the action of zirconium and molybdenum as hardening agents. The samples have a smaller elasticity modulus than the commercially pure titanium. Copyright © 2016 Elsevier B.V. All rights reserved.

Room temperature mechanosynthesis and microstructure characterization of nanocrystalline Si{sub 0.9}Al{sub 0.1}C

Energy Technology Data Exchange (ETDEWEB)

Bandyopadhyay, S. [Department of Physics, The University of Burdwan, Golapbag, Burdwan, 713104, West Bengal (India); Dutta, H. [Department of Physics, Vivekananda College, Burdwan, 713103, West Bengal (India); Kar, T. [Department of Materials Science, Indian Association for the Cultivation of Science, Jadavpur, Kolkata, 700032, West Bengal (India); Pradhan, S.K., E-mail: skp_bu@yahoo.com [Department of Physics, The University of Burdwan, Golapbag, Burdwan, 713104, West Bengal (India)

2016-02-01

This article reports the synthesis and microstructure characterization of nanocrystalline Si{sub 0.9}Al{sub 0.1}C powder obtained by mechanical milling the mixture of Si, Al and graphite powders at room temperature under inert atmosphere. XRD patterns of ball-milled powders clearly reveal the nucleation of Si{sub 0.9}Al{sub 0.1}C phase after 5 h of milling and the stoichiometric cubic Si{sub 0.9}Al{sub 0.1}C is formed after 10 h of milling with crystallite size of ∼3 nm. Microstructure of ball-milled powders in terms of different lattice imperfections is characterized by employing both Rietveld's method of structure refinement using XRD data and high resolution transmission electron microscope (HRTEM). HRTEM micrographs of 10 h milled powder substantiate the formation of nanocrystalline Si{sub 0.9}Al{sub 0.1}C compound without any contamination and confirm the findings of Rietveld analysis using XRD data. - Highlights: • Cubic Si{sub 0.9}Al{sub 0.1}C is formed after 5 h of milling of Si, Al and graphite powders. • Nanocrystalline Si{sub 0.9}Al{sub 0.1}C with particle size ∼3 nm is obtained after 10 h milling. • Average particle size of Si{sub 0.9}Al{sub 0.1}C from XRD analysis and HRTEM is very close.

Tunable-color luminescence via energy transfer in NaCa13/18Mg5/18PO4:A (A = Eu2+/Tb3+/Mn2+, Dy3+) phosphors for solid state lighting.

Science.gov (United States)

Li, Kai; Fan, Jian; Mi, Xiaoyun; Zhang, Yang; Lian, Hongzhou; Shang, Mengmeng; Lin, Jun

2014-11-17

A series of NaCa13/18Mg5/18PO4(NCMPO):A (A = Eu(2+)/Tb(3+)/Mn(2+), Dy(3+)) phosphors have been prepared by the high-temperature solid-state reaction method. The X-ray diffraction (XRD) and Rietveld refinement, X-ray photoelectron spectroscopy (XPS), photoluminescence (PL), cathodoluminescence (CL), decay lifetimes, and PL quantum yields (QYs) were utilized to characterize the phosphors. The pure crystalline phase of as-prepared samples has been demonstrated via XRD measurement and Rietveld refinements. XPS reveals that the Eu(2+)/Tb(3+)/Mn(2+) can be efficiently doped into the crystal lattice. NCMPO:Eu(2+)/Tb(3+)/Mn(2+) phosphors can be effectively excited under UV radiation, which show tunable color from purple-blue to red including white emission based on energy transfer from Eu(2+) to Tb(3+)/Mn(2+) ions. Under low-voltage electron beam bombardment, the NCMPO:A (A = Eu(2+)/Tb(3+)/Mn(2+), Dy(3+)) display their, respectively, characteristic emissions with different colors, and the CL spectrum of NCMPO:0.04Tb(3+) has the comparable intensity to the ZnO:Zn commercial product. In addition, the calculated CIE coordinate of NCMPO:0.04Tb(3+) (0.252, 0.432) is more saturated than it (0.195, 0.417). These results reveal that NCMPO:A (A = Eu(2+)/Tb(3+)/Mn(2+), Dy(3+)) may be potential candidate phosphors for WLEDs and FEDs.

Evaluation of structural vacancies for 1/1-Al-Re-Si approximant crystals by positron annihilation spectroscopy

Science.gov (United States)

Yamada, K.; Suzuki, H.; Kitahata, H.; Matsushita, Y.; Nozawa, K.; Komori, F.; Yu, R. S.; Kobayashi, Y.; Ohdaira, T.; Oshima, N.; Suzuki, R.; Takagiwa, Y.; Kimura, K.; Kanazawa, I.

2018-01-01

The size of structural vacancies and structural vacancy density of 1/1-Al-Re-Si approximant crystals with different Re compositions were evaluated by positron annihilation lifetime and Doppler broadening measurements. Incident positrons were found to be trapped at the monovacancy-size open space surrounded by Al atoms. From a previous analysis using the maximum entropy method and Rietveld method, such an open space is shown to correspond to the centre of Al icosahedral clusters, which locates at the vertex and body centre. The structural vacancy density of non-metallic Al73Re17Si10 was larger than that of metallic Al73Re15Si12. The observed difference in the structural vacancy density reflects that in bonding nature and may explain that in the physical properties of the two samples.

Poly(vinylpyrrolidone)/silver nanoparticles: preparation and characterization; Nanoparticulas de prata/poli(vinilpirrolidona): obtencao e caracterizacao

Energy Technology Data Exchange (ETDEWEB)

Andrade, P.F.; Goncalves, M.C. [Instituto de Quimica - UNICAMP, Campinas, SP (Brazil)], e-mail: patandrade@iqm.unicamp.br

2010-07-01

In this work silver nanoparticles were prepared by chemical reduction method using PVP as dispersant agent. The formation of silver nanoparticles was investigated by UV-vis optical spectroscopy and X-ray diffraction. FT-IR spectroscopy confirmed the formation of Ag/PVP complex. The transmission electron microscopy images indicated that the concentration of Ag{sup +} precursor influenced the nanoparticles dispersion and size distribution significantly. The results indicated that dispersed nanoparticles with uniform size distribution can be prepared by this methodology to obtain polymeric nano composites. (author)

Influence of Y and La substitution on particle size, structural and magnetic properties of nanosized nickel ferrite prepared by using citrate precursor method

Energy Technology Data Exchange (ETDEWEB)

Anh, Luong Ngoc [International Training Institute for Materials Science (ITIMS), Hanoi University of Science and Technology, 1 Dai Co Viet Road, Hanoi (Viet Nam); Loan, To Thanh, E-mail: totloan@itims.edu.vn [International Training Institute for Materials Science (ITIMS), Hanoi University of Science and Technology, 1 Dai Co Viet Road, Hanoi (Viet Nam); Duong, Nguyen Phuc [International Training Institute for Materials Science (ITIMS), Hanoi University of Science and Technology, 1 Dai Co Viet Road, Hanoi (Viet Nam); Vietnam-Japan International Institute for Science of Technology (VJIIST), Hanoi University of Science and Technology, 1 Dai Co Viet Road, Hanoi (Viet Nam); Soontaranon, Siriwat [Synchrotron Light Research Institute, 111 University Avenue, Suranaree, Muang, Nakhon Ratchasima 30000 (Thailand); Viet Nga, Tran Thi; Hien, Than Duc [International Training Institute for Materials Science (ITIMS), Hanoi University of Science and Technology, 1 Dai Co Viet Road, Hanoi (Viet Nam)

2015-10-25

The compounds with the formulas NiFe{sub 2}O{sub 4}, NiFe{sub 1.9}Y{sub 0.1}O{sub 4} and NiFe{sub 1.9}La{sub 0.1}O{sub 4} were prepared by citrate precursor method and followed by heat treatment in air at 600 °C for 5 h. Crystal structure, valence state, chemical bonding and composition of the samples were studied rigorously by XRD, SXRD, XANES, FTIR and ICP–AES. Rietveld refinement of XRD and SXRD patterns reveals that the samples crystallize in single spinel phase with almost inverted structure in which the substituted ions Y{sup 3+} and La{sup 3+} locate in the octahedral sites and about ten percents of nickel atoms were found at the tetrahedral sites. Morphology and particle size were studied by SEM and TEM. The results show that the samples are composed of clustered nanoparticles with mean particle size decreases approximately from 20 nm in NiFe{sub 2}O{sub 4} sample to 10 nm in the substituted ones. The magnetic measurements were carried out by means of a VSM. Spontaneous magnetization, magnetic coercivity, Curie temperature, superparamagnetic transition temperature, interparticle interaction energy and effective anisotropy were determined and explained on the basis of the surface and finite–size effects and cation distribution. - Highlights: • Y{sup 3+} and La{sup 3+} substituted NiFe{sub 2}O{sub 4} nanoparticles are synthesized by citrate precursor method involving less energy. • XRD, SXRD and FTIR spectra reveal the crystallographic site occupancy of Y{sup 3+} and La{sup 3+}. • Compositions and valence states of cations are verified by ICP-AES and XANES. • Y{sup 3+} and La{sup 3+} substitution decreases the mean particle size to about 10 nm. • Influence of rare earth substitution and finite size in magnetic properties are investigated.

Synthesis of nano intermetallic Nb{sub 3}Sn by mechanical alloying and annealing at low temperature

Energy Technology Data Exchange (ETDEWEB)

López, M., E-mail: marlope@udec.cl [Department of Materials Engineering, Universidad de Concepción, Edmundo Larenas 270, Concepción (Chile); Jiménez, J.A. [Department of Physical Metallurgy, Centro Nacional de Investigaciones Metalúrgicas, C.S.I.C., Av. Gregorio del Amo 8, 28040 Madrid (Spain); Ramam, K.; Mangalaraja, R.V. [Department of Materials Engineering, Universidad de Concepción, Edmundo Larenas 270, Concepción (Chile)

2014-11-05

Highlights: • Intermetallic Nb{sub 3}Sn nano grains were synthesized by powder metallurgy route. • Structure analysis was studied using a multiphase Rietveld refinement fit. • The presence of Nb{sub 3}Sn 86% and NbO 8% was identified. • More tin content in the equilibrium Nb–Sn diagram was obtained. • Magnetic properties show Nb{sub 3}Sn powders are soft super paramagnetic materials. - Abstract: In this study, intermetallic Nb{sub 3}Sn of nanometer-sized grains was synthesized by powder metallurgy route. Elemental powders of Nb and Sn in the stoichiometric proportions were mechanically alloyed for 3 h in a high-energy mill under a protective atmosphere of argon. X-ray diffraction patterns of milled powders confirmed the formation of a Nb(Sn) solid solution evidenced by the presence of Nb peaks only, which are shifted to higher angles. Rietveld refinements used to analyze this XRD pattern indicated a better fit when a tetragonal structure with the space group I4/mmm is used instead the Nb cubic lattice with space group Im−3m. Size-strain analysis from line-broadening of peak profiles by using “double-Voigt” approaches showed that the broadening is due to both a small crystallite size (around 6 nm) and microstrains. Subsequent heat treatment of the Nb(Sn) powder mixture was required for the formation of the Nb{sub 3}Sn ordered phase. X-ray diffraction patterns obtained after a thermal treatment at 700 °C for 1 h were fitted using a multiphase Rietveld refinement. Although the resulting powders are composed mainly by Nb{sub 3}Sn (up to 87 weight%), certain amount of other intermetallic phases like Nb{sub 6}Sn{sub 5}, NbSn{sub 2} and Nb and Sn oxides were also determined. In agreement with the Rietveld refinement analysis, microprobe analysis also revealed that changes in chemical composition at different sites of powder particles are preserved even after annealing at 700 °C. Magnetic properties measured at 300 K on resulted Nb{sub 3}Sn powders

Magnetic and ferroelectric characteristics of Gd 3 + and Ti 4 + co ...

Indian Academy of Sciences (India)

The crystallographicsite occupancies of Gd and Ti were confirmed by Rietveld refinement of XRD data,Mössbauer spectroscopy and magnetization measurements. An enhancement in ferromagnetic properties along with moderate ferroelectricproperties have been observed after co-doping. There was an increasing trend in ...

The iron member of the CPO-27 coordination polymer series: Synthesis, characterization, and intriguing redox properties

DEFF Research Database (Denmark)

Märcz, Matthias; Johnsen, Rune; Dietzel, Pascal D.C.

2012-01-01

The microporous coordination polymer CPO-27-Fe was synthesized from iron salts and 2,5-dihydroxyterephthalic acid by microwave assisted solvothermal synthesis. The crystal structures of the as-synthesized compounds were determined by Rietveld refinement from powder X-ray diffraction data using...

'The End of Sitting' : An Empirical Study on Working in an Office of the Future

NARCIS (Netherlands)

Withagen, Rob; Caljouw, Simone R.

Background Inspired by recent findings that prolonged sitting has detrimental health effects, Rietveld Architecture Art Affordances (RAAAF) and visual artist Barbara Visser designed a working environment without chairs and desks. This environment, which they called The End of Sitting, is a sculpture

RAAAF's office landscape The End of Sitting : Energy expenditure and temporary comfort when working in non-sitting postures

NARCIS (Netherlands)

Caljouw, Simone R.; de Vries, Rutger; Withagen, Rob

2017-01-01

An earlier study suggested that the activity-inviting office landscape called "The End of Sitting", designed by Rietveld Architecture Art Affordances (RAAAF), should be considered as an alternative working environment to prevent sedentary behavior. The End of Sitting lacks chairs and tables but

Quantitative analysis of retained austenite in laser melted martensitic stainless steel

CSIR Research Space (South Africa)

Seleka, T

2007-11-01

Full Text Available of this study was to determine if X-ray diffraction (XRD) was sufficient for quantifying the volume percentage of retained austenite. After a preliminary qualitative analysis, a Rietveld full pattern refinement program was used to quantify the volume percentage...

Interstitial positions of tin ions in alpha-(FerichSn)(2)O-3 solid solutions prepared by mechanical alloying

DEFF Research Database (Denmark)

Jiang, Jianzhong; Lin, Rong; Nielsen, Kurt

1997-01-01

The microstructure of samples of 91, 85, and 71 mol % alpha-Fe-2-O-3-SnO2. prepared by mechanical alloying, has been studied by x-ray diffraction with Rietveld structure refinements, On the basis of the structure refinements to the whole x-ray diffraction patterns for the four as-milled samples, ......, it is found that tin ions do not substitute iron ions in the solid solution, although this model is generally assumed in the literature. The Sn4+ ions occupy the empty octahedral holes in the lattice of the alpha-Fe2O3 phase.......The microstructure of samples of 91, 85, and 71 mol % alpha-Fe-2-O-3-SnO2. prepared by mechanical alloying, has been studied by x-ray diffraction with Rietveld structure refinements, On the basis of the structure refinements to the whole x-ray diffraction patterns for the four as-milled samples...

Thermal-annealing effects on the structural and magnetic properties of 10% Fe-doped SnO{sub 2} nanoparticles synthetized by a polymer precursor method

Energy Technology Data Exchange (ETDEWEB)

Aragón, F.H., E-mail: fermin964@hotmail.com [Núcleo de Física Aplicada, Instituto de Física, Universidade de Brasília, Brasília DF 70910-900 (Brazil); Instituto de Ciências Biológicas, Pós-graduação em Nanociência e Nanobiotecnologia, Universidade de Brasília, Brasilia DF 70919-970 (Brazil); Coaquira, J.A.H. [Núcleo de Física Aplicada, Instituto de Física, Universidade de Brasília, Brasília DF 70910-900 (Brazil); Nagamine, L.C.C.M.; Cohen, R. [Instituto de Física, Universidade de São Paulo, São Paulo SP 05508-090 (Brazil); Silva, S.W. da [Núcleo de Física Aplicada, Instituto de Física, Universidade de Brasília, Brasília DF 70910-900 (Brazil); Instituto de Ciências Biológicas, Pós-graduação em Nanociência e Nanobiotecnologia, Universidade de Brasília, Brasilia DF 70919-970 (Brazil); and others

2015-02-01

In this work, we present the experimental results of Sn{sub 0.9}Fe{sub 0.1}O{sub 2} nanoparticles synthesized by a polymer precursor method. Studies were performed in the as-prepared (AP) and thermally-annealed (TA) samples. The X-ray diffraction (XRD) data analysis carried out using the Rietveld refinement method shows the formation of only the rutile-type structure in the AP sample and this phase remains stable for the TA sample. Additionally, the mean crystallite size shows an increase from ∼4 nm to ∼17 nm after the annealing and a clear reduction of the residual strain has also been determined. Micro-Raman spectroscopy measurements show the formation of an iron oxide phase (likely α-Fe{sub 2}O{sub 3}) after the thermal treatment. Magnetic measurements show a paramagnetic behavior for the AP sample and the coexistence of a weak ferromagnetism and paramagnetism for the TA sample. The magnetically-ordered contribution of the TA sample has been assigned to the formation of the hematite phase. DC and AC magnetic features of the TA sample are consistent with a cluster-glass behavior which seems to be related to the magnetic disorder of spins located at the particle surface. Those spins clusters seem to be formed due to the diffusion of iron ions from the core of the particle to the surface caused by the annealing process. - Highlights: • Thermal annealing effects in the 10% Fe-doped SnO{sub 2} nanoparticles have been studied. • XRD data analysis shows the formation of the rutile-type structure. • Raman measurements show the formation of small amount of α-Fe{sub 2}O{sub 3} after the annealing. • Paramagnetic and magnetically ordered phases were determined after the annealing. • Spin clusters likely at the particle surface have been formed after the annealing.

Investigation of structural and electrical properties of La0.7(Ba1-xCax)0.3MnO3 compounds by sol-gel method

International Nuclear Information System (INIS)

Winarsih, Suci; Kurniawan, Budhy; Manaf, Azwar; Nanto, Dwi; Imaduddin, Agung; Hendrik; Saptari, Sitti Ahmiatri

2016-01-01

In this paper, we explored structural and electrical properties of La 0.7 (Ba 1-x Ca x ) 0.3 MnO 3 (x = 0; 0.03; and 0.05) compounds. The general structure of perovskite manganites is AMnO 3 (A= trivalent rare earth with divalent ion-doped). Average A-site cation size, external pressure, and the variance of the cation size σ 2 are one of many factors that affected to magneto-transport properties of manganites as reported by others. In this work we focus only on the electrical properties in La 0.7 Ba 0.3 MnO 3 Ca-doped compound which may influence crystal structure resulting resistivity phenomena under magnetic field influence. All samples were synthesized by sol-gel method from which fine powders were obtained. The X-ray powder diffraction pattern of powder materials shows that all samples are fully crystalline with a rhombohedral structure. Rietveld refinement shows that the presence of calcium has changed some crystal structural parameters such lattice parameter, Mn–O bond length, and Mn–O–Mn angles. The electrical resistivity of all synthesized materials investigated by four point probe method using Cryogenic Magnet in the temperature range of 50-300 K under influence a magnetic field shows resistivity temperature dependent. In fact presence of calcium has reduced the resistivity. It might occure because it has made an enhancement in the mobility of hopping electrons. The magnetic external field causes the resistivity decreased for all samples because host spin align by delocalizing the charge carries so electron itinerant through the lattice suggested by other authors. Both calcium dopant concentration and the applied external magnetic field shows strong correlation in reduction of resistivity.

The study of disorder and nanocrystallinity in C-S-H, supplementary cementitious materials and geopolymers using pair distribution function analysis

International Nuclear Information System (INIS)

Meral, Cagla; Benmore, C.J.; Monteiro, Paulo J.M.

2011-01-01

Significant progress was achieved with the application of Rietveld method to characterize the crystalline phases in portland cement paste. However, to obtain detailed information on the amorphous or poorly crystalline phases, it is necessary to analyze the total scattering data. The pair distribution function (PDF) method has been successfully used in the study of liquids and amorphous solids. The method takes the Sine Fourier transform of the measured structure factor over a wide momentum transfer range, providing a direct measure of the probability of finding an atom surrounding a central atom at a radial distance away. The obtained experimental characteristic distances can be also used to validate the predictions by the theoretical models, such as, molecular dynamics, ab initio simulations and density functional theory. The paper summarizes recent results of PDF analysis on silica fume, rice husk ash, fly ash, ASR gel, C-S-H and geopolymers.

Crystal growth, defects, and mechanical and spectral properties of a novel mixed laser crystal Nd:GdYNbO{sub 4}

Energy Technology Data Exchange (ETDEWEB)

Ding, Shoujun; Dou, Renqin [Chinese Academy of Sciences, Anhui Institute of Optics and Fine Mechanics, Hefei, Anhui Province (China); University of Science and Technology of China, Hefei (China); Liu, Wenpeng; Zhang, Qingli; Peng, Fang; Luo, Jianqiao; Sun, Guihua; Sun, Dunlu [Chinese Academy of Sciences, Anhui Institute of Optics and Fine Mechanics, Hefei, Anhui Province (China)

2017-01-15

A mixed laser crystal of Nd-doped GYNO crystal was grown successfully by Czochralski method. The crystal belongs to monoclinic system with space group I2/a, the structural parameters are obtained by the X-ray Rietveld refinement method. The defects and dislocations along three crystallographic orientations were studied by using the chemical etching method with the phosphoric acid etchant. The mechanical properties (including hardness, yield strength, fracture toughness, and brittle index) of the crystal were estimated by Vickers hardness test. The transmission spectrum was measured at room temperature, and the absorption peaks were assigned. Spectral properties of the as-grown crystal were investigated by Judd-Ofelt theory, and the Judd-Ofelt intense parameters Ω{sub 2,4,6} were obtained to be 9.674 x 10{sup -20}, 2.092 x 10{sup -20}, and 4.061 x 10{sup -20} cm{sup 2}, respectively. (orig.)

The Embodied Brain: Towards a Radical Embodied Cognitive Neuroscience

Directory of Open Access Journals (Sweden)

Julian eKiverstein

2015-05-01

Full Text Available In this programmatic paper we explain why a radical embodied cognitive neuroscience is needed. We argue for such a claim based on problems that have arisen in cognitive neuroscience for the project of localizing function to specific brain structures. The problems come from research concerned with functional and structural connectivity that strongly suggests that the function a brain region serves is dynamic, and changes over time. We argue that in order to determine the function of a specific brain area, neuroscientists need to zoom out and look at the larger organism-environment system. We therefore argue that instead of looking to cognitive psychology for an analysis of psychological functions, cognitive neuroscience should look to an ecological dynamical psychology. A second aim of our paper is to develop an account of embodied cognition based on the inseparability of cognitive and emotional processing in the brain. We argue that emotions are best understood in terms of action readiness (Frijda 1986, 2007 in the context of the organism’s ongoing skillful engagement with the environment (Rietveld 2008; Bruineberg & Rietveld 2014; Kiverstein & Rietveld 2015. States of action readiness involve the whole living body of the organism, and are elicited by possibilities for action in the environment that matter to the organism. Since emotion and cognition are inseparable processes in the brain it follows that what is true of emotion is also true of cognition. Cognitive processes are likewise processes taking place in the whole living body of an organism as it engages with relevant possibilities for action.

Effect of Cu{sup 2+} and Ni{sup 2+} substitution at the Mn site in (La{sub 0.63}Ca{sub 0.37})MnO{sub 3}: A neutron powder diffraction investigation

Energy Technology Data Exchange (ETDEWEB)

Martinelli, A., E-mail: alberto.martinelli@spin.cnr.it [CNR-SPIN, C.so Perrone 24, 16152 Genova (Italy); Ferretti, M. [CNR-SPIN, C.so Perrone 24, 16152 Genova (Italy); Dipartimento di Chimica e Chimica Industriale, Università di Genova, Via Dodecaneso 31, 16146 Genova (Italy); Castellano, C. [Università degli Studi di Milano, Dipartimento di Chimica Strutturale e Stereochimica Inorganica, Via G. Venezian 21, 20133 Milano (Italy); Cimberle, M.R. [IMEM-CNR, Via Dodecaneso 33, 16146 Genova (Italy); Ritter, C. [Institute Laue—Langevin, 6 rue Jules Horowitz, 38042 Grenoble Cedex 9 (France)

2013-04-15

The crystal and magnetic structures of the (La{sub 0.63}Ca{sub 0.37})(Mn{sub 1−x}TM{sub x})O{sub 3} compounds (x=0.00, 0.03, 0.08; TM=Cu{sup 2+}, Ni{sup 2+}) were investigated between 5 K and 300 K by means of dc magnetic measurements and neutron powder diffraction analysis followed by Rietveld refinement. Both substituting cations lead to a reduction of the long range ferromagnetic ordering temperature; ferromagnetism is strongly suppressed in the 8% Cu-substituted sample, where long- and short-range FM magnetic orders coexist together with short-range A-type AFM order. This particular feature can be related to the Jahn–Teller character of Cu{sup 2+}, absent in Ni{sup 2+}, and suggests the occurrence of a quantum critical point in the (La{sub 0.63}Ca{sub 0.37})(Mn{sub 1−x}Cu{sub x})O{sub 3} system. - Graphical abstract: Rietveld refinement plot of (La{sub 0.63}Ca{sub 0.37})(Mn{sub 0.92}Cu{sub 0.08})O{sub 3} showing in the inset the coexistence of broad A-type AFM peaks with FM ones. Highlights: ► (La{sub 0.63}Ca{sub 0.37})MnO{sub 3} was substituted with Ni and Cu. ► Neutron powder diffraction and Rietveld refinement were carried out. ► A quantum critical point possibly occurs in the (La{sub 0.63}Ca{sub 0.37})(Mn{sub 1−x}Cu{sub x})O{sub 3} system.

L-tyrosine hydrochloride crystals under high pressures via Raman Spectroscopy

Energy Technology Data Exchange (ETDEWEB)

Santos, C.A.A.S.; Facanha Filho, P.F.; Santos, A.O. dos; Ribeiro, L.H.L.; Victor, F.M.S.; Abreu, D.C.; Carvalho, J.O.; Soares, R.A.; Sousa, J.C.F.; Lima, R.C.; Cavaignac, A.O. [Universidade Federal do Maranhao (UFMA), MA (Brazil)

2016-07-01

Full text: Amino acid single crystals have been attracted researchers in recent years due to their potential applications as second harmonic generator. The goal of this work is to produce semi organic single crystals of L-tyrosine hydrochloride (LTHCl) and verify the behavior of their vibrational normal modes under high pressures and the stability of material in these conditions extremes. The LTHCl single crystals were produced for solubilization of amino acid L-tyrosine in hydrochloric acid by slow evaporation technique of the solvent in room temperature. The technique of X-ray diffraction (XRD) and the refinement of structure by the Rietveld method were used to confirm the crystal structure. The LTHCl crystal belongs to the monoclinic crystal system having two molecules per unit cell. The refinement by the Rietveld method showed good results with Rwp = 8.49% and Rp = 6.29% with S = 1.13. Raman scattering measurements as a function of pressure was performed in a piece of crystal from the ambient pressure to 7.2 GPa and Nujol was used as pressure medium. It was observed the appearance of a weak band around 163 cm-1 between pressures of 0.5 and 1.0 GPa, which characterize an phase transition undergone by the crystal. Moreover, this band gains intensity as pressure increases while gradual decreasing relative intensity of the very strong band at 123 cm-1 for all range of pressure also was observed. In fact, almost all bands of the spectra have undergone strong decreasing up to 7.2 GPa. However, on release of pressure the crystal has reached the original phase again. Therefore, the results showed this material cannot be suitable for the application (NLO) in this range of pressure. (author)

Synthesis and characterization of L-tyrosine hydrochloride crystals submitted to high and low temperatures

Energy Technology Data Exchange (ETDEWEB)

Santos, C.A.A.S.; Facanha Filho, P.F.; Ribeiro, L.H.L.; Victor, F.M.S.; Abreu, D.C.; Santos, A.O. dos; Carvalho, J.O.; Soares, R.A.; Sousa, J.C.F.; Lima, R.C.; Cavaignac, A.O. [Universidade Federal do Maranhao (UFMA), MA (Brazil)

2016-07-01

Full text: New materials are emerging and generate advances in nonlinear optics that studies the phenomena related to changes in optical properties when occurs interaction of light with the matter. Semi organic crystals present such properties. The goal is this work is to produce semi organic single crystal of L-tyrosine hydrochloride (LTHCl) and verify their thermal stability when subjected to high and low temperatures. The single crystals of LTHCl were produced for solubilization of amino acid L-tyrosine in hydrochloric acid using slow solvent evaporation technique at a constant temperature of 25 deg C. The X-ray diffraction (XRD) and refining by the Rietveld method were used to confirm the structure of the material. The thermal stability was investigated using DSC, TGA-DTA. The LTHCl crystal belongs to the monoclinic system, with two molecules per unit cell. The refinement by the Rietveld method showed good results with Rwp= 8.49% and Rp= 6.29% with S=1.13. Thermal analysis shown an endothermic event at about 160°C, which can be associated with phase transition occurred in LTHCl crystal. It was also observed that the crystal melting point occurs at a temperature of 230°C. No water of crystallization was found in the crystal structure, which was confirmed by Raman spectroscopy and thermal analysis. From the Raman spectroscopy experiments in function of temperature, no significant changes was observe in the behavior of vibrational normal modes between temperatures of -253 and 170 deg C. Finally, a monoclinic crystal system LTHCl is stable up to 160°C at high temperatures and -253°C at low temperatures. Therefore, our investigation has proved that LTHCl crystals can be used in this range of temperature without the lost of their nonlinear optical properties. (author)

Synthesis and optical properties of Pr and Ti doped BiFeO{sub 3} ceramics

Energy Technology Data Exchange (ETDEWEB)

Singh, Vikash, E-mail: vikash.singh@abes.ac.in [Department of Physics and Materials Science and Engineering, Jaypee Institute of Information Technology, Noida (U.P.), India-201307 (India); Applied Science and Humanities, ABES EC, Ghaziabad (U.P), India-201009 (India); Sharma, Subhash; Dwivedi, R. K. [Department of Physics and Materials Science and Engineering, Jaypee Institute of Information Technology, Noida (U.P.), India-201307 (India)

2016-05-23

Bi{sub 1-x}Pr{sub x}Fe{sub 1-x}Ti{sub x}O{sub 3} ceramics with x = 0.00, 0.10 and 0.20 were synthesized by solid state reaction method. Rietveld fitting of diffraction data reveals structural transition from rhombohedral phase (R{sub 3C}) for x ≤ 0.10 to orthorhombic phase (P{sub nma}) for x = 0.20. FTIR spectra exhibit broad absorption bands, which may be due to the overlapping of Fe-O and Bi-O vibrations in these ceramics. UV-visible spectroscopy results show strong absorption of light in the spectral range of 400-600 nm, indicating optical band gap in the visible region for these samples.

CHARACTERIZATION AND PROCESSING OF SCALES FROM THE MECHANICAL DESCALING OF CARBON STEELS FOR RECYCLING AS COATING PIGMENTS

Directory of Open Access Journals (Sweden)

Anderson de Oliveira Fraga

2014-10-01

Full Text Available The large volume of solid wastes generated as scales in Steel Mills accounts to circa 1% to 2% of the total steel production and has led to studies aiming the recycling of scales, usually resulting in products of low added value. In this study, scales from the mechanical descaling of SAE 1045 steel were characterized by SEM and by quantitative X-Ray diffraction (Rietveld method, as well as by differential thermal analysis, aiming to develop its pretreatment for the further use as lamellar pigments in anticorrosive coatings of high added value. Aspect ratios between 1:50 and 1:100 were obtained by the processing of scales, which allows the replacement of other micaceous iron oxides.

X-ray diffraction analysis of KY3F10 nanoparticles doped with Nd and preliminary studies for its use in high-dose radiation dosimetry

International Nuclear Information System (INIS)

Ichikawa, Rodrigo U.; Linhares, Horacio M.S.M.D.; Silva, Andre S.B. da; Teixeira, Maria I.; Ranieri, Izilda M.; Turrillas, Xavier; Martinez, G.

2017-01-01

In this work, the structure and microstructure of Nd:KY 3 F 10 nanoparticles was probed using X-ray synchrotron diffraction analysis. Rietveld refinement was applied to obtain cell parameters, atomic positions and atomic displacement factors to be compared with the ones found in literature. X-ray line profile methods were applied to determine mean crystallite size and crystallite size distribution. Thermoluminescent (TL) emission curves were measured for different radiation doses, from 0.10kGy up to 10.0kGy. Dose-response curves were obtained by area integration beneath the peaks from TL. The reproducibility of the results in this work has shown that this material can be considered a good dosimetric material. (author)

Synchrotron diffraction characterization of nanostructured KY3F10:Tb

International Nuclear Information System (INIS)

Ichikawa, Rodrigo U.; Teixeira, Maria I.; Ranieri, Izilda M.; Martinez, Luis G.; Linhares, Horacio M.S.M.D.; Turrillas, Xavier

2015-01-01

Nanostructured rare-earth fluorides materials are being intensively studied recently due to their potential applications in high-dose dosimetry. Particularly, nanostructured Tb-doped KY 3 F 10 has shown satisfactory results to be used in this area. In the present work, the structure and microstructure of KY 3 F 10 :Tb was investigated by means of X-ray synchrotron diffraction. One of the samples was analyzed as synthesized and another after a heat treatment. Rietveld refinement of synchrotron diffraction data was applied to obtain cell parameters, atomic positions and atomic displacement factors and the results were compared to values found in literature. X-ray line profile analysis methods were applied to determine mean crystallite sizes and their distribution. (author)

Cubic to tetragonal phase transition of Tm3+ doped nanocrystals in oxyfluoride glass ceramics

International Nuclear Information System (INIS)

Li, Yiming; Fu, Yuting; Shi, Yahui; Zhang, Xiaoyu; Yu, Hua; Zhao, Lijuan

2016-01-01

Tm 3+ ions doped β-PbF 2 nanocrystals in oxyfluoride glass ceramics with different doping concentrations and thermal temperatures are prepared by a traditional melt-quenching and thermal treatment method to investigate the structure and the phase transition of Tm 3+ doped nanocrystals. The structures are characterized by X-ray diffraction Rietveld analysis and confirmed with numerical simulation. The phase transitions are proved further by the emission spectra. Both of the doping concentration and thermal temperature can induce an O h to D 4h site symmetry distortion and a cubic to tetragonal phase transition. The luminescence of Tm 3+ doped nanocrystals at 800 nm was modulated by the phase transition of the surrounding crystal field

Synthesis and characterization of LnAg(WO{sub 4})(MoO{sub 4})

Energy Technology Data Exchange (ETDEWEB)

Fernandez-Martinez, F. [Universidad Politecnica de Madrid, E.U.I.T. Industrial, Ronda de Valencia 3, 28012 Madrid (Spain)], E-mail: francisco.fernandezm@upm.es; Colon, C.; Montero, J.L.; Atanes, E. [Universidad Politecnica de Madrid, E.U.I.T. Industrial, Ronda de Valencia 3, 28012 Madrid (Spain); Rivero, C. [Universidad Politecnica de Madrid, E.T.S.I. Telecomunicaciones, Avda. Complutense s/n, Ciudad Universitaria, 28040 Madrid (Spain)

2008-02-28

Polycrystalline LnAg(WO{sub 4})(MoO{sub 4}) powders, with Ln = La to Lu and Y, have been obtained by ceramic method. Rietveld refinement for all compounds reveals that they present tetragonal symmetry, space group I4{sub 1}/a (No. 88), where the Ln{sup 3+}/Ag{sup +} ions are located in the 4a atomic positions, since the W/Mo are randomly distributed into 4b crystal sites. In these compounds, a and b lattice parameters take values between those corresponding to tungstate and molybdate compounds. A progressive decrease in the lattice parameters is observed in going from La to Lu derivatives as a consequence of the well-known lanthanide contraction.

X-ray diffraction analysis of KY3F10 nanoparticles doped with Nd and preliminary studies for its use in high-dose radiation dosimetry

Energy Technology Data Exchange (ETDEWEB)

Ichikawa, Rodrigo U.; Linhares, Horacio M.S.M.D.; Silva, Andre S.B. da; Teixeira, Maria I.; Ranieri, Izilda M.; Turrillas, Xavier; Martinez, G., E-mail: ichikawa@usp.br, E-mail: andre.santos.silva@usp.br, E-mail: miteixeira@ipen.br, E-mail: iranieri@ipen.br, E-mail: lgallego@ipen.br, E-mail: horaciolinhares@id.uff.br, E-mail: xturrillas@icmab.es [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil); Universidade Federal Fluminense (INFES/ UFF), Niteroi, RJ (Brazil); Institut de Ciència de Materials de Barcelona (ICMAB / CSIC) (Spain)

2017-07-01

In this work, the structure and microstructure of Nd:KY{sub 3}F{sub 10} nanoparticles was probed using X-ray synchrotron diffraction analysis. Rietveld refinement was applied to obtain cell parameters, atomic positions and atomic displacement factors to be compared with the ones found in literature. X-ray line profile methods were applied to determine mean crystallite size and crystallite size distribution. Thermoluminescent (TL) emission curves were measured for different radiation doses, from 0.10kGy up to 10.0kGy. Dose-response curves were obtained by area integration beneath the peaks from TL. The reproducibility of the results in this work has shown that this material can be considered a good dosimetric material. (author)

Synthesis of silver doped hydroxyapatite nanospheres using Ouzo effect

Directory of Open Access Journals (Sweden)

Marija Prekajski

2016-09-01

Full Text Available Nanoemulsion technique, based on Ouzo effect, was applied for synthesis of the pure and silver doped (2.5 and 5 mol% calcium hydroxyapatite (HAp. After calcination at 500 °C fully crystallized powders were obtained. X-ray powder diffraction analysis accompanied with Rietveld refinement revealed that the synthesized powders were single-phase hydroxyapatite. Raman spectroscopy also confirmed that the synthesized powders were single-phase. The obtained HAp particles were spherical in shape and their sizes were in the nanometer range which was revealed by field emission scanning electron microscopy analysis (FESEM. The successful synthesis of the single-phase Ag doped HAp showed that nanoemulsion method is a simple technique for obtaining pure and doped hydroxyapatite nanospheres.

X-Ray diffraction study of strain hardening and annealing in an UNS S31803 duplex stainless steel

International Nuclear Information System (INIS)

Aguiar, Denilson Jose Marcolino de; Padilha, Angelo Fernando

2010-01-01

In the present work the phenomena of strain hardening, formation and reversion of the strain induced alpha-prime martensite (α', CCC, Ferromagnetic) in an UNS S31803 duplex stainless steel have been studied. Initially, the microstructure of the material in the solution annealed condition was characterized with aid of several complementary techniques of microstructural analysis. The volumetric fraction, crystalline structure, chemical composition, size and morphology of the two phases (ferrite and austenite) have been determined. The phenomena of strain hardening, formation and reversion of strain induced martensite in the austenite phase and recovery of austenite and ferrite phases have been studied, predominantly by using X-ray diffraction and the Rietveld method. (author)

Preparation and structural study of LaMnO3 magnetic material

International Nuclear Information System (INIS)

Moreno, L.C.; Valencia, J.S.; Landinez Tellez, D.A.; Arbey Rodriguez M, J.; Martinez, M.L.; Roa-Rojas, J.; Fajardo, F.

2008-01-01

We report the crystallographic parameters of LaMnO 3 obtained from X-ray diffraction data and electronic properties predictions using the density functional theory (DFT). LaMnO 3 was prepared by the citrate precursor method (CPM). The initial solution was 0.1 M of each cation and the citrate nitrate relation was one. The solution was dried at 373 K; the yielded foam was annealed at 873 K and then was characterized by X-ray diffraction. Diffraction peaks show that the space group is R-3c (no. 167) with a=b =5.523 A and c=13.324 A (rhombohedrally distorted perovskite). Structural results of the Rietveld method have a matching of 97% with that obtained from the Structure Prediction Diagnostic Software. DFT calculation reveals a half-metallic character and its magnetic moment is about 2.0 μ B

Microstructure characterization and cation distribution of nanocrystalline cobalt ferrite

Energy Technology Data Exchange (ETDEWEB)

Abbas, Y.M., E-mail: ymabbas@live.com [Suez Canal University, Faculty of Science, Physics Department, Ismailia (Egypt); Mansour, S.A.; Ibrahim, M.H. [Suez Canal University, Faculty of Science, Physics Department, Ismailia (Egypt); Ali, Shehab E., E-mail: shehab_physics@yahoo.com [Suez Canal University, Faculty of Science, Physics Department, Ismailia (Egypt)

2011-11-15

Nanocrystalline cobalt ferrite has been synthesized using two different methods: ceramic and co-precipitation techniques. The nanocrystalline ferrite phase has been formed after 3 h of sintering at 1000 deg. C. The structural and microstructural evolutions of the nanophase have been studied using X-ray powder diffraction and the Rietveld method. The refinement result showed that the type of the cationic distribution over the tetrahedral and octahedral sites in the nanocrystalline lattice is partially an inverse spinel. The transmission electronic microscope analysis confirmed the X-ray results. The magnetic properties of the samples were characterized using a vibrating sample magnetometer. - Highlights: > The refinement result showed that the cationic distribution over the sites in the lattice is partially an inverse spinel. > The transmission electronic microscope analysis confirmed the X-ray results. > The magnetic properties of the samples were characterized using a vibrating sample magnetometer.

Structures and solid solution mechanisms of pyrochlore phases in the systems Bi2O3-ZnO-(Nb, Ta)2O5

International Nuclear Information System (INIS)

Tan, K.B.; Khaw, C.C.; Lee, C.K.; Zainal, Z.; Miles, G.C.

2010-01-01

Research highlights: → Combined XRD and ND Rietveld structural refinement of pyrochlores. → Structures and solid solution mechanisms of Bi-pyrochlores. → Bi and Zn displaced off-centre to different 96g A-site positions. → Summary of composition-structure-property of Bi-pyrochlores. - Abstract: The crystal structures of two pyrochlore phases have been determined by Rietveld refinement of combined X-ray and neutron powder diffraction data. These are stoichiometric, Bi 1.5 ZnTa 1.5 O 7 and non-stoichiometric Bi 1.56 Zn 0.92 Nb 1.44 O 6.86 . In both structures, Zn is distributed over A- and B-sites; Bi and Zn are displaced off-centre, to different 96g A-site positions; of the three sets of oxygen positions, O(1) are full, O(2) contain vacancies and O(3) contain a small number of oxygen, again in both cases. Comparisons between these structures, those of related Sb analogues and literature reports are made.

Physical-mechanical characterization of hydroxyapatite-titanium oxide composites made by the polymeric sponge method; Caracterizacao fisico-mecanica de compositos porosos de hidroxiapatita-titania confeccionados pelo metodo da esponja polimerica

Energy Technology Data Exchange (ETDEWEB)

Galdino, A.G.S.; Zavaglia, C.A.C. [Universidade Estadual de Campinas (FEM/UNICAMP), SP (Brazil)

2011-07-01

Bioceramics have been used as bone reconstruction materials since last decades, where hydroxyapatite is one of the most used for this purpose. However, hydroxyapatite's mechanical strength is not so high when compared to other bioceramics. This work aimed on characterizing physically and mechanically composites of HA-TiO{sub 2}. Samples were made by the polymeric sponge method with 70% - 30% wt., 60% - 40% wt. and 50% - 50% wt. of HA - TiO{sub 2}, calcined at 550 deg C for sponge burning and sintered at 1250 deg C, 1300 deg C and 1350 deg C. Samples were submitted to mechanical essays of compression and Hardness Vickers and to physical essays of water absorption, apparent density, burning linear retraction and apparent density. Results showed relatively better than those of pure hydroxyapatite and they are in accordance with the literature. (author)

Sr2CeO4: Electronic and structural properties

International Nuclear Information System (INIS)

Rocha, Leonardo A.; Schiavon, Marco A.; Nascimento, Clebio S.; Guimarães, Luciana; Góes, Márcio S.; Pires, Ana M.; Paiva-Santos, Carlos O.

2014-01-01

Highlights: • Sr 2 CeO 4 it was obtained from the heat treatment of Ce 3+ -doped strontium oxalate. • Rietveld analysis made it possible to obtain information about crystalline structure. • Experimental band gap value was compared with theoretical obtained by Sparkle/PM7. • The materials obtained shows intense photoluminescence and scintillator properties. - Abstract: This work presents on the preparation and photoluminescent properties of Sr 2 CeO 4 obtained from the heat treatment of Ce(III)-doped strontium oxalate (10, 25 and 33 mol%). The oxalate precursors were heat treated at 1100 °C for 12 h. The structure of this photoluminescent material was evaluated by the Rietveld method. The route used in this work to prepare the materials showed to be viable when compared to other synthesis reported in the literature. The Sr 2 CeO 4 material showed a broad and intense band emission with a maximum around 485 nm. The quantitative phase analysis showed that the Sr 2 CeO 4 photoluminescent phase is the majority one compared to the impurity phases of SrCeO 3 and SrCO 3 . From all results it was possible to verify a complete elimination of the CeO 2 phase for the sample obtained from the heat treatment of oxalate precursor containing 33 mol% of cerium(III). The material showed excellent properties for possible candidate as scintillator materials, and in the improvement of efficiency of solar cells when excited in the UV–vis region. The CIE chromaticity diagram it is also reported in this work

Synthesis and characterization of Ge–Cr-based intermetallic compounds: GeCr3, GeCCr3, and GeNCr3

International Nuclear Information System (INIS)

Lin, S.; Tong, P.; Wang, B.S.; Huang, Y.N.; Song, W.H.; Sun, Y.P.

2014-01-01

Highlights: • Polycrystalline samples of GeCr 3 , GeCCr 3 , and GeNCr 3 are synthesized by using solid state reaction method. • A good quality of our samples is verified by the Rietveld refinement and electrical transport measurement. • We present a comprehensive understanding of physical properties of GeCr 3 , GeCCr 3 , and GeNCr 3 . -- Abstract: We report the synthesis of GeCr 3 , GeCCr 3 , and GeNCr 3 polycrystalline compounds, and present a systematic study of this series by the measurements of X-ray diffraction (XRD), magnetism, electrical/thermal transport, specific heat, and Hall coefficient. Good quality of our samples is verified by quite small value of residual resistivity and considerably large residual resistivity ratio. Based on the Rietveld refinement of XRD data, the crystallographic parameters are obtained, and, correspondingly, the sketches of crystal structure are plotted for all the samples. The ground states of GeCr 3 , GeCCr 3 , and GeNCr 3 are paramagnetic/antiferromagnetic metal, and even a Fermi-liquid behavior is observed in electrical transport at low temperatures. Furthermore, the analysis of the thermal conductivity data suggests the electron thermal conductivity plays a major role in total thermal conductivity for GeCr 3 at low temperatures, while the phonon thermal conductivity is dominant for GeCCr 3 and GeNCr 3 at high temperatures. The negative value of Seebeck coefficient and Hall coefficient indicate that the charge carriers are electron-type for GeCr 3 , GeCCr 3 , and GeNCr 3

Synthesis and characterization of Gd{sub 2}O{sub 3} doped UO{sub 2} nanoparticles

Energy Technology Data Exchange (ETDEWEB)

Soldati, A.L., E-mail: asoldati@cab.cnea.gov.ar [Centro Atómico Bariloche (CAB) – Comisión Nacional de Energía Atómica (CNEA), Av. Bustillo 9500, CP: 8400 Bariloche (Argentina); Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Av. De los Pioneros 2300, CP: 8400 Bariloche (Argentina); Gana Watkins, I. [Centro Atómico Bariloche (CAB) – Comisión Nacional de Energía Atómica (CNEA), Av. Bustillo 9500, CP: 8400 Bariloche (Argentina); Fernández Zuvich, A. [Centro Atómico Bariloche (CAB) – Comisión Nacional de Energía Atómica (CNEA), Av. Bustillo 9500, CP: 8400 Bariloche (Argentina); Instituto Balseiro, Universidad Nacional de Cuyo, Av. Bustillo 9500, CP: 8400 Bariloche (Argentina); Napolitano, F.; Troiani, H. [Centro Atómico Bariloche (CAB) – Comisión Nacional de Energía Atómica (CNEA), Av. Bustillo 9500, CP: 8400 Bariloche (Argentina); Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Av. De los Pioneros 2300, CP: 8400 Bariloche (Argentina); and others

2016-10-15

UO{sub 2} nanoparticles doped with 4, 8, 10 and 15 wt% Gd{sub 2}O{sub 3}were synthesized by a reverse strike method. Crystal structure and chemical homogeneity were evaluated using a combination of X-ray diffraction and microscopy tools. An exhaustive study of the composition and its homogeneity at the micro and at the nanometer level was carried out in this nuclear fuel material. Field Emission Gun Scanning and Transmission Electron Microscopy images revealed the presence of micrometer scale agglomerates of nanoparticles, with rounded morphology and an average crystallite size of 100 nm. Rietveld refinements of high-statistic X-ray Diffraction data determined the crystal structure and composition. Furthermore, Energy Dispersive Spectroscopy using a 2 nm{sup 2} spot on the sample surface determined a Gd concentration variation around the average of ±5% in different spots of a single crystallite and of ±10% between different crystallites. However, when measuring large amounts of nanoparticles the concentration averages, producing a homogeneous composition distribution at the micrometer scale. - Highlights: • Synthesis of 4, 8, 10 and 15wt% Gd{sub 2}O{sub 3} doped UO{sub 2} nanoparticles. • Crystallite sizes around 100 nm and rounded morphology. • 90% Gd distribution homogeneity between particles for the less concentrated sample. • High Statistic X-ray Rietveld analysis determined an U{sub 1−x}Gd{sub x}O{sub 2−δ} fcc structure. • Phases with similar crystal structure and symmetry, but different lattice parameter.

Synthesis, structural and electrical characterizations of DySr.sub.5./sub.Ni.sub.2.4./sub.Cu.sub.0.6./sub.O.sub.12-δ./sub..

Czech Academy of Sciences Publication Activity Database

Hamdi, S.; Ouni, S.; Chaker, H.; Rohlíček, Jan; Ben Hassen, R.

2011-01-01

Roč. 184, č. 11 (2011), s. 2897-2901 ISSN 0022-4596 Institutional research plan: CEZ:AV0Z10100521 Keywords : Rietveld refinement * K 2 NiF 4 -type structure * electrical resistivity * oxygen vacancies * iodometric titration Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 2.159, year: 2011

Structural and electrical properties of Nd.sub.1.7./sub.Ba.sub.0.3./sub.Ni.sub.0.9./sub.Cr.sub.0.1./sub.O.sub.4+δ./sub. compound

Czech Academy of Sciences Publication Activity Database

Jammali, M.; Hassen, R.B.; Rohlíček, Jan

2012-01-01

Roč. 27, č. 3 (2012), s. 184-188 ISSN 0885-7156 Institutional research plan: CEZ:AV0Z10100521 Keywords : X-ray diffraction * sol-gel * Rietveld refinement * adiabatic small polaron hopping model * semi-conductive behaviour Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 0.544, year: 2012

Assessment of the potential hazard represented by natural raw materials containing mineral fibres -The case of the feldspar from Orani, Sardinia (Italy)

Czech Academy of Sciences Publication Activity Database

Gualtieri, A. F.; Gandolfi, N. B.; Pollastri, S.; Rinaldi, R.; Sala, O.; Martinelli, G.; Bacci, T.; Paoli, F.; Viani, Alberto; Vigliaturo, R.

2018-01-01

Roč. 350, May (2018), s. 76-87 ISSN 0304-3894 R&D Projects: GA MŠk(CZ) LO1219 Keywords : feldspar * tremolite * Rietveld * SEM * EMPA Subject RIV: DB - Geology ; Mineralogy OBOR OECD: Mineralogy Impact factor: 6.065, year: 2016 https://www.sciencedirect.com/science/article/pii/S0304389418300888

Methane storage mechanism in the metal-organic framework Cu3(btc)2: An in situ neutron diffraction study

NARCIS (Netherlands)

Getzschmann, J.; Senkovska, I.; Wallacher, D.; Tovar, M.; Fairen-Jimenez, D.; Düren, T.; van Baten, J.M.; Krishna, R.; Kaskel, S.

2010-01-01

The adsorption of deutero-methane (CD4) in Cu3(btc)2 (HKUST-1) was investigated at 77 K using high-resolution neutron powder diffraction. Rietveld refinement of the neutron data revealed a sequential filling of the rigid framework at distinct preferred adsorption sites, and showed the importance of

Thermoelastic and structural properties of ionically conducting cerate perovskites: (II) SrCeO3 between 1273 K and 1723 K

DEFF Research Database (Denmark)

Knight, Kevin S.; Haynes, Richard; Bonanos, Nikolaos

2015-01-01

The temperature dependence of the crystal structure and the thermoelastic properties of SrCeO3 have been determined from Rietveld refinement of high resolution, neutron time-of-flight powder diffraction data collected in 5 K intervals between 1273 K and 1723 K. No evidence was found for critical ...

The study of disorder and nanocrystallinity in C–S–H, supplementary cementitious materials and geopolymers using pair distribution function analysis

KAUST Repository

Meral, Cagla

2011-07-01

Significant progress was achieved with the application of Rietveld method to characterize the crystalline phases in portland cement paste. However, to obtain detailed information on the amorphous or poorly crystalline phases, it is necessary to analyze the total scattering data. The pair distribution function (PDF) method has been successfully used in the study of liquids and amorphous solids. The method takes the Sine Fourier transform of the measured structure factor over a wide momentum transfer range, providing a direct measure of the probability of finding an atom surrounding a central atom at a radial distance away. The obtained experimental characteristic distances can be also used to validate the predictions by the theoretical models, such as, molecular dynamics, ab initio simulations and density functional theory. The paper summarizes recent results of PDF analysis on silica fume, rice husk ash, fly ash, ASR gel, C-S-H and geopolymers. © 2011 Elsevier Ltd. All rights reserved.

Effect of the Addition of Potassium or Lithium on the Columbite Precursor Microstructure

Directory of Open Access Journals (Sweden)

Alberto A. Cavalheiro

2002-10-01

Full Text Available Pechini method has been used to synthesize MN powders with stoichiometric control. By this method, K and Li-doped MN in the range from 0.1 to 5.0 mol% of dopants have been obtained at relatively lower temperatures than it is possible with the conventional mixture of oxides. The results from BET analysis indicated that the doped powders have lower surface area and the attrition milling promotes an increase in surface area values for all powders. Rietveld method was used to calculate the mean crystallite size and the microstrain in the crystal. With additions of up to 5.0 mol% of K or 2.0 mol% of Li, it is possible to obtain MN as a solid solution. Both dopants change the cell parameters of the columbite phase crystal, reduce the microstrain, and increase the main crystallite size. The analysis of results from SEM indicates that powders prepared with addition of dopants are more agglomerate than pure PMN powder.

Magnetic and Structural Investigations of Nanocrystalline Cobalt-Ferrite

Directory of Open Access Journals (Sweden)

I. Sharifi

2012-10-01

Full Text Available Cobalt ferrite is an important magnetic material due to their large magneto-crystalline anisotropy, high cohercivity, moderate saturation magnetization and chemical stability.In this study, cobalt ferrites Nanoparticles have been synthesized by the co-precipitation method and a new microemulsion route. We examined the cation occupancy in the spinel structure based on the “Rietveld with energies” method. The Xray measurements revealed the production of a broad single ferrite cubic phase with the average particle sizes of about 12 nm and 7nm, for co-precipitation and micro-emulsion methods, respectively. The FTIR measurements between 400 and 4000 cm-1 confirmed the intrinsic cation vibrations of the spinelstructure for the two methods. Furthermore, the Vibrating Sample Magnetometer (VSM was carried out at room temperature to study the structural and magnetic properties. The results revealed that by changing the method from co-precipitation to the reverse micelle the material exhibits a softer magnetic behavior in such a way that both saturation magnetization and coercivity decrease from 58 to 29 emu/g and from 286 to 25 Oe, respectively.

Mineralogical characteristics of Ettringites synthesized from solutions and suspensions

International Nuclear Information System (INIS)

Goetz-Neunhoeffer, F.; Neubauer, J.; Schwesig, P.

2006-01-01

Due to the wide technical importance of Ettringite (3CaO.Al 2 O 3 .3CaSO 4 .32H 2 O) in hydrated cement based systems, four different synthesis methods were applied to get a better overview on how and under what favoring conditions Ettringite can be formed. In the first step different precipitation methods resulting in Ettringite were established. For all methods Al 3+ was supplied by aqueous CO 2 -free solution of Al 2 (SO 4 ) 3 .18H 2 O. As a source of CaO-supply a clear solution and otherwise a Ca(OH) 2 -suspension was utilized. Four synthesis routes with and without sucrose were employed. Variation of reaction parameter like temperature, time of reaction, pH-value of synthesis solution and influence of additional Gypsum were investigated. The qualitative phase analysis was performed by X-ray diffraction method (XRD). Morphological aspects of some synthesis products were studied by scanning electron microscopy (SEM). Finally lattice and structural parameter of the Ettringites were determined by refinement of XRD-pattern using the Rietveld-Method

National Nanotechnology Laboratory (LNNano) open facilities for scientific community: new methods for polymeric materials characterization; Instalacoes abertas a comunidade cientifica no Laboratorio Nacional de Nanotecnologia (LNNano): novos metodos de caracterizacao de materiais polimericos

Energy Technology Data Exchange (ETDEWEB)

Silva, Cristiane A.; Santos, Ramon H.Z. dos; Bernardes, Juliana S.; Gouveia, Rubia F., E-mail: rubia.gouveia@lnnano.cnpem.br [Centro Nacional de Pesquisa em Energia e Materiais (LNNano/CNPEM), Campinas, SP (Brazil). Laboratorio Nacional de Nanotecnologia

2015-07-01

National Nanotechnology Laboratory (LNNano) at the National Center for Energy and Materials (CNPEM) presents open facilities for scientific public in some areas. In this work will be discussed the facilities for mainly the polymeric community, as well as new methods for the characterization. Low density polyethylene (LDPE) surfaces were characterized by X-ray microtomography and X-ray photoelectron spectroscopy (XPS). The results obtained by microtomography have shown that these surfaces present different contrasts when compared with the bulk. These differences are correlated with the formation of an oxidized layer at the polymer surface, which consequently have a greater X-ray attenuation. This hypothesis is confirmed by XPS, which shows LDPE surface layers are richer in carbonyl, carboxyl and vinyl groups than the bulk. This work presents that microtomography can be used as a new method for detection and characterization of polymer surface oxidation. (author)

Structural and compositional stability of the mechanically alloyed (Fe,Mo)-Al at elevated temperatures

Czech Academy of Sciences Publication Activity Database

Jirásková, Yvonna; Buršík, Jiří; Roupcová, Pavla; Jančík, D.; Čížek, J.

2015-01-01

Roč. 168, NOV (2015), s. 108-116 ISSN 0254-0584 R&D Projects: GA MŠk(CZ) ED1.1.00/02.0068 Institutional support: RVO:68081723 Keywords : Magnetic properties * Electron microscopy * Rietveld analysis * Phase transitions Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 2.101, year: 2015

HgO-added YBa2Cu3O7− δ superconductors

Indian Academy of Sciences (India)

The structural studies were carried out by neutron scattering and Rietveld analysis. The neutron scattering revealed that Hg is not incorporated in the Y-123 system and has shown optimum oxygen concentration. The significant role played by the HgO is to provide oxygen ambient through its decomposition, thus changing ...

Quantitative X-ray diffraction analysis of development of Z phase in 12%Cr–Nb–V–N steel

DEFF Research Database (Denmark)

Di Nunzio, P. E.; Cipolla, L.; Vipraio, S. Tiberi

2010-01-01

. A quantitative determination of the volume fractions of the extracted nitrides that had formed after aging treatments at 650uC for up to 10 000 h was carried out by an X-ray diffraction procedure, based on the Rietveld approach. The investigation of the Z phase evolution by the Johnson...

Characterization of cellulose nanowhiskers; Caracterizacao do nanowhiskers de celulose

Energy Technology Data Exchange (ETDEWEB)

Nascimento, Nayra R.; Pinheiro, Ivanei F.; Morales, Ana R.; Ravagnani, Sergio P.; Mei, Lucia, E-mail: 25nareis@gmail.com [Universidade Estadual de Campinas (UNICAMP), SP (Brazil)

2015-07-01

Cellulose is the most abundant polymer earth. The cellulose nanowhiskers can be extracted from the cellulose. These have attracted attention for its use in nanostructured materials for various applications, such as nanocomposites, because they have peculiar characteristics, among them, high aspect ratio, biodegradability and excellent mechanical properties. This work aims to characterize cellulose nanowhiskers from microcrystalline cellulose. Therefore, these materials were characterized by X-ray diffraction (XRD) to assess the degree of crystallinity, infrared spectroscopy (FT-IR), transmission electron microscopy (TEM) to the morphology of nanowhiskers and thermal stability was evaluated by Thermogravimetric Analysis (TGA). (author)

Synthesis and characterization of Ruddlesden-Popper (RP) type phase LaSr2MnCrO7

International Nuclear Information System (INIS)

Singh, Devinder; Singh, Rajinder

2010-01-01

New Ruddlesden-Popper (RP) type phase LaSr 2 MnCrO 7 has been synthesized by ceramic method. Rietveld profile analysis shows that the phase crystallizes with tetragonal unit cell in the space group 14/mmm. The electrical resistivity of the phase has been measured in the temperature range of 10-300 K using Leybold closed cycle helium cryostat. The phase shows insulator-metal (I-M) transition at low temperature, the phenomenon often associated with giant magnetoresistance. 3D variable range hopping governs the electrical conduction in the insulator region above the I-M transition temperature. Magnetic susceptibility of the phase has been measured in the temperature range of 100-300 K. Magnetic studies suggest that the phase is ferromagnetic. (author)

Magnetic and transport properties of Nd{sub 1.67}Sr{sub 0.33}NiO{sub 4}

Energy Technology Data Exchange (ETDEWEB)

Zaghrioui, M. [Laboratoire d' Electrodynamique des Materiaux Avances, UMR 6157 CNRS-CEA, Universite Francois Rabelais, IUT de Blois, C.S. 2903, 3 place Jean Jaures 41029 Blois cedex (France)]. E-mail: zaghrioui@univ-tours.fr; Giovannelli, F. [Laboratoire d' Electrodynamique des Materiaux Avances, UMR 6157 CNRS-CEA, Universite Francois Rabelais, IUT de Blois, C.S. 2903, 3 place Jean Jaures 41029 Blois cedex (France); Pruvost, S. [Laboratoire d' Electrodynamique des Materiaux Avances, UMR 6157 CNRS-CEA, Universite Francois Rabelais, IUT de Blois, C.S. 2903, 3 place Jean Jaures 41029 Blois cedex (France); Poirot, N. [Laboratoire d' Electrodynamique des Materiaux Avances, UMR 6157 CNRS-CEA, Universite Francois Rabelais, IUT de Blois, C.S. 2903, 3 place Jean Jaures 41029 Blois cedex (France); Monot-Laffez, I. [Laboratoire d' Electrodynamique des Materiaux Avances, UMR 6157 CNRS-CEA, Universite Francois Rabelais, IUT de Blois, C.S. 2903, 3 place Jean Jaures 41029 Blois cedex (France)

2006-10-15

Nd{sub 1.67}Sr{sub 0.33}NiO{sub 4} polycrystals have been prepared by modified sol-gel method and subsequent annealing. X-ray diffraction analysis, electrical resistivity, magnetic susceptibility and thermal magnetisation have been measured. Rietveld analyses show a tetragonal or pseudo-tetragonal K{sub 2}NiF{sub 4}-type structure. The resistivity measurements present a change in conduction mode close to 230 K, which corresponds to the charge ordering temperature. Below this temperature, the material adopts a variable range hopping conduction mode; and above, the conduction follows adiabatic thermal activated mode. The magnetic measurements show paramagnetic behaviour in the range of 80-300 K. Moreover, the magnetic susceptibility data show a sign of the charge ordering transition about 230 K.

Magnetic and transport properties of Nd1.67Sr0.33NiO4

International Nuclear Information System (INIS)

Zaghrioui, M.; Giovannelli, F.; Pruvost, S.; Poirot, N.; Monot-Laffez, I.

2006-01-01

Nd 1.67 Sr 0.33 NiO 4 polycrystals have been prepared by modified sol-gel method and subsequent annealing. X-ray diffraction analysis, electrical resistivity, magnetic susceptibility and thermal magnetisation have been measured. Rietveld analyses show a tetragonal or pseudo-tetragonal K 2 NiF 4 -type structure. The resistivity measurements present a change in conduction mode close to 230 K, which corresponds to the charge ordering temperature. Below this temperature, the material adopts a variable range hopping conduction mode; and above, the conduction follows adiabatic thermal activated mode. The magnetic measurements show paramagnetic behaviour in the range of 80-300 K. Moreover, the magnetic susceptibility data show a sign of the charge ordering transition about 230 K

Synchrotron diffraction characterization of nanostructured KY{sub 3}F{sub 10}:Tb

Energy Technology Data Exchange (ETDEWEB)

Ichikawa, Rodrigo U.; Teixeira, Maria I.; Ranieri, Izilda M.; Martinez, Luis G., E-mail: ichikawa@usp.br, E-mail: miteixeira@ipen.br, E-mail: iranieri@ipen.br, E-mail: lgallego@ipen.br [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil); Linhares, Horacio M.S.M.D., E-mail: horacio_marconi@yahoo.com.br [Universidade Federal Fluminense (INFES/UFF), Santo Antonio de Padua, RJ (Brazil); Turrillas, Xavier, E-mail: turrillas@gmail.com [Institut de Ciència de Materials de Barcelona (ICMAB/CSIC), Dept. of Crystallography, Bellaterra (Spain)

2015-07-01

Nanostructured rare-earth fluorides materials are being intensively studied recently due to their potential applications in high-dose dosimetry. Particularly, nanostructured Tb-doped KY{sub 3}F{sub 10} has shown satisfactory results to be used in this area. In the present work, the structure and microstructure of KY{sub 3}F{sub 10}:Tb was investigated by means of X-ray synchrotron diffraction. One of the samples was analyzed as synthesized and another after a heat treatment. Rietveld refinement of synchrotron diffraction data was applied to obtain cell parameters, atomic positions and atomic displacement factors and the results were compared to values found in literature. X-ray line profile analysis methods were applied to determine mean crystallite sizes and their distribution. (author)

Crystal structure of the low-temperature forms of cesium and rubidium orthophosphates

International Nuclear Information System (INIS)

Voronin, V.I.; Proskurina, N.V.; Goshchitskij, B.N.; Berger, I.F.; Sheptyakov, D.V.; Burmakin, E.I.; Stroev, S.S.; Shekhtman, G.Sh.

2008-01-01

Making use of the neutron diffraction data base Rietveld method one for the first time determined and made more clear the crystal structure of the low-temperature modifications of Cs 3 PO 4 cesium and Rb 3 PO 4 rubidium orthophosphates. Cs 3 PO 4 and Rb 3 PO 4 were found to be isostructural one as to K 3 PO 4 . The structure is a rhombic one (Pnma, Z=4 sp.gr.) with the following elementary cell parameters: a = 1.23177(6) nm, b=0.88948(4) nm, c=0.64197(3) nm and a = 1.17362(2) nm, b=0.81046(1) nm, c=0.615167(9) nm for Cs 3 PO 4 and Rb 3 PO 4 respectively [ru

Structural and luminescence properties of europium(III)-doped zirconium carbonates and silica-supported Eu3+-doped zirconium carbonate nanoparticles

International Nuclear Information System (INIS)

Sivestrini, S.; Riello, P.; Freris, I.; Cristofori, D.; Enrichi, F.; Benedetti, A.

2010-01-01

The synthesis, morphology and luminescence properties of europium(III)-doped zirconium carbonates prepared as bulk materials and as silica-supported nanoparticles with differing calcination treatments are reported. Transmission electron microscopy and X-ray diffraction analyses have, respectively, been used to study the morphology and to quantify the atomic amount of europium present in the optically active phases of the variously prepared nanomaterials. Rietveld analysis was used to quantify the constituting phases and to determinate the europium content. Silica particles with an approximate size of 30 nm were coated with 2 nm carbonate nanoparticles, prepared in situ on the surface of the silica core. Luminescence measurements revealed the role of different preparation methods and of europium-doping quantities on the optical properties observed.

Magnetic properties of multiferroic TbMnO{sub 3} doped with Al

Energy Technology Data Exchange (ETDEWEB)

Perez, F. [Centro de Ciencias de la Materia Condensada, Universidad Nacional Autonoma de Mexico, Km. 107.5 Carretera Tijuana-Ensenada, Ensenada, B.C. (Mexico); Escudero, R. [Instituto de Investigaciones en Materiales, Universidad Nacional Autonoma de Mexico, A. Postal 70-360, Mexico, D.F. 04510 (Mexico); Heiras, J.

2007-07-01

The synthesis, characterization, and magnetic properties of polycrystalline Tb{sub 1-x}Al{sub x}MnO{sub 3} with x=0.05 and 0.1 is reported. Samples were synthesized by the conventional solid state reaction method producing single phase compounds. Rietveld refinements indicate that Al substitutes Tb in the structure. Samples were highly porous with grain sizes up to {proportional_to}10 {mu}m. The magnetic measurements show a magnetic ordering, starting from antiferromagnetism, for the undoped sample, to a weak ferromagnetic phase coexisting with the antiferromagnetic phase for the two x values. The magnetic ordering is attributed to two different contributions of Mn and Tb sublattices. (copyright 2007 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

Synthesis and characterization of the Fe-18%Ni-12%Co-4,9%Mo-1,5%Ti alloy

International Nuclear Information System (INIS)

Nunes, G.C.S.; Biondo, V.; Nunes, M.V.S.; Paesano Junior, A.; Sarvezuk, P.W.C.; Blanco, M.C.

2014-01-01

The Fe-18%Ni-12%Co-4,9%Mo-1,5%Ti was made by arc-melting and submitted to different heat treatments, for solubilization in the γ - phase (austenite), followed by cooling to the room temperature, and also for further aging. The prepared alloys were characterized by X-ray diffraction (Rietveld method) and Mössbauer spectroscopy. The results showed that the cooling induced the system to a martensitic transformation, crystallizing it into a cubic structure (martensite). The crystallographic parameters and the hyperfine parameters obtained by Mössbauer Spectroscopy are consistent with those found in literature for Maraging-350 steels. The aging treatments generates the formation of reversed austenite in relative amounts that vary with the temperature and time of treatment. (author)

Atomistic Properties of Solids

CERN Document Server

Sirdeshmukh, Dinker B; Subhadra, K G

2011-01-01

The book deals with atomistic properties of solids which are determined by the crystal structure, interatomic forces and atomic displacements influenced by the effects of temperature, stress and electric fields. The book gives equal importance to experimental details and theory. There are full chapters dedicated to the tensor nature of physical properties, mechanical properties, lattice vibrations, crystal structure determination and ferroelectricity. The other crystalline states like nano-, poly-, liquid- and quasi crystals are discussed. Several new topics like nonlinear optics and the Rietveld method are presented in the book. The book lays emphasis on the role of symmetry in crystal properties. Comprehensiveness is the strength of the book; this allows users at different levels a choice of chapters according to their requirements.

Quantitative Mineralogical Analysis of Mars Analogues Using CHEMIN Data and Rietveld Refinement

Science.gov (United States)

Bish, D. L.; Sarrazin, P.; Chipera, S. J.; Vaniman, D. T.; Blake, D.

2004-01-01

Mineralogical analysis is a critical component of planetary surface exploration. Chemical data alone leave serious gaps in our understanding of the surfaces of planets where complex minerals may form in combination with H, S, and halogens. On such planets (e.g., Mars) a single chemical composition may represent a range of mineral assemblages. For example, Viking chemical analyses of excavated duricrust indicate that Mg and S are correlated and 10% MgSO4 (anhydrous weight) is a likely cementing agent. Pathfinder chemical data support a similar abundance of MgSO4 in the most altered materials. However, there are many possible Mg-sulfates with widely varying hydration states (including dehydrated and 1-, 2-, 3-, 4-, 5-, 6-, and 7-hydrates). In addition, other sulfate minerals such as gypsum (CaSO4 .2H2O) and other salts containing Cl may also exist. X-ray diffraction (XRD) has the ability to decipher mixtures of these phases that would be difficult, if not impossible to unravel using only chemical or spectral data.

Rietveld refinement of KLaTiO4 from X-ray powder data

Directory of Open Access Journals (Sweden)

Bai-Chuan Zhu

2011-04-01

Full Text Available Potassium lanthanum titanate(IV, KLaTiO4, has been synthesized by conventional solid-state reaction. It crystallizes isotypically with the NaLnTiO4 (Ln = La, Pr, Nd, Sm, Eu, Gd, Y and Lu family. Five of the six atoms in the asymmetric unit (one K, one La, one Ti and two O atoms are situated on sites with 4mm symmetry, whereas one O atom has 2mm. site symmetry. The crystal structure can be described as being composed of single layers of distorted corner-sharing TiO6 octahedra extending parallel to (001. The layers are alternately separated by K+ and La3+ cations along [001]. The coordination number of both K+ and La3+ cations is nine, resulting in distorted KO9 and LaO9 polyhedra.

Preparation of high-performance ultrafine-grained AISI 304L stainless steel under high temperature and pressure

Directory of Open Access Journals (Sweden)

Peng Wang

2016-08-01

Full Text Available Bulk ultra-fine grained (UFG AISI 304L stainless steel with excellent mechanical properties was prepared by a high-temperature and high-pressure (HTHP method using nanocrystalline AISI 304L stainless steel powders obtained from ball milling. Samples were sintered in high-pressure conditions using the highest martensite content of AISI 304L stainless steel powders milled for 25 h. Analyses of phase composition and grain size were accomplished by X-ray diffraction and Rietveld refinement. By comparing the reverse martensite transformation under vacuum and HTHP treat, we consider that pressure can effectively promote the change in the process of transformation. Compared with the solid-solution-treated 304L, the hardness and yield strength of the samples sintered under HTHP are considerably higher. This method of preparation of UFG bulk stainless steel may be widely popularised and used to obtain UFG metallic materials with good comprehensive performance.

Study and characterization of the BNO (BiNbO_4) ceramic added with 3 wt. % CuO

International Nuclear Information System (INIS)

Sales, A.J.M.; Pires Junior, G.F.M.; Rodrigues, H.O.; Sombra, A.S.B.; Sales, J.C.

2011-01-01

The objective of this work is to synthesize and characterize the BNO (BiNbO_4) ceramic added with 3 wt. % CuO to improvements in densification. The BNO was prepared by conventional ceramic method. The powders milled for 2 h were calcined at 850 °C for 3 h. After calcination the powders we re characterized by X-ray diffraction (XRD). The detailed characterization of XRD was performed using the program DBWS9807a which uses the Rietveld method for refinement of crystal structures. The refinement confirmed the acquisition of isolated α-BNO phase with orthorhombic crystal structure (a = 5.6792Å, and b = 11.7081Å c = 4.9823Å; α = β = γ = 90) and density of the unit cell calculated 6.61g/cm3. Micrographs, to analyze densification behavior and grain size were obtained using a Scanning Electron Microscope model TESCAN manufactured by Bruker AXS detector. (author)

Microstructure characterization and cation distribution of nanocrystalline cobalt ferrite

International Nuclear Information System (INIS)

Abbas, Y.M.; Mansour, S.A.; Ibrahim, M.H.; Ali, Shehab E.

2011-01-01

Nanocrystalline cobalt ferrite has been synthesized using two different methods: ceramic and co-precipitation techniques. The nanocrystalline ferrite phase has been formed after 3 h of sintering at 1000 deg. C. The structural and microstructural evolutions of the nanophase have been studied using X-ray powder diffraction and the Rietveld method. The refinement result showed that the type of the cationic distribution over the tetrahedral and octahedral sites in the nanocrystalline lattice is partially an inverse spinel. The transmission electronic microscope analysis confirmed the X-ray results. The magnetic properties of the samples were characterized using a vibrating sample magnetometer. - Highlights: → The refinement result showed that the cationic distribution over the sites in the lattice is partially an inverse spinel. → The transmission electronic microscope analysis confirmed the X-ray results. → The magnetic properties of the samples were characterized using a vibrating sample magnetometer.

Chemical and structural characterization of natural phosphate of ...

African Journals Online (AJOL)

Powder X-ray diffraction fitting results confirm that compound belongs to the apatite family crystallising in the hexagonal system, space group P63/m. The cell parameters are: a = 9.3547(5) Å; c = 6.8929(4) Å. KEY WORDS: Natural phosphate, Fluoroapatite, Infrared, X-Ray diffraction, Rietveld structure refinement. Bull. Chem ...

Investigation of structural and electrical properties of La{sub 0.7}(Ba{sub 1-x}Ca{sub x}){sub 0.3}MnO{sub 3} compounds by sol-gel method

Energy Technology Data Exchange (ETDEWEB)

Winarsih, Suci; Kurniawan, Budhy, E-mail: bkuru07@gmail.com; Manaf, Azwar [Physics Department, Universitas Indonesia, Depok 16424 (Indonesia); Nanto, Dwi [Department of Physics Education, Universitas Islam Negeri Syarif Hidayatullah, Jakarta 15412 (Indonesia); Imaduddin, Agung; Hendrik [Metallurgical Research Center, Lembaga Ilmu Pengetahuan Indonesia, Puspiptek-Serpong 15314 (Indonesia); Saptari, Sitti Ahmiatri [Faculty of Science and Technology, Universitas Islam Negeri Syarif Hidayatullah, Jakarta 15412 (Indonesia)

2016-06-17

In this paper, we explored structural and electrical properties of La{sub 0.7}(Ba{sub 1-x}Ca{sub x}){sub 0.3}MnO{sub 3} (x = 0; 0.03; and 0.05) compounds. The general structure of perovskite manganites is AMnO{sub 3} (A= trivalent rare earth with divalent ion-doped). Average A-site cation size, external pressure, and the variance of the cation size σ{sup 2} are one of many factors that affected to magneto-transport properties of manganites as reported by others. In this work we focus only on the electrical properties in La{sub 0.7}Ba{sub 0.3}MnO{sub 3} Ca-doped compound which may influence crystal structure resulting resistivity phenomena under magnetic field influence. All samples were synthesized by sol-gel method from which fine powders were obtained. The X-ray powder diffraction pattern of powder materials shows that all samples are fully crystalline with a rhombohedral structure. Rietveld refinement shows that the presence of calcium has changed some crystal structural parameters such lattice parameter, Mn–O bond length, and Mn–O–Mn angles. The electrical resistivity of all synthesized materials investigated by four point probe method using Cryogenic Magnet in the temperature range of 50-300 K under influence a magnetic field shows resistivity temperature dependent. In fact presence of calcium has reduced the resistivity. It might occure because it has made an enhancement in the mobility of hopping electrons. The magnetic external field causes the resistivity decreased for all samples because host spin align by delocalizing the charge carries so electron itinerant through the lattice suggested by other authors. Both calcium dopant concentration and the applied external magnetic field shows strong correlation in reduction of resistivity.

Resveratrol-loaded poly({epsilon}-caprolactone) microparticles: preparation and characterization; Microparticulas de poli({epsilon}-caprolactona) contendo resveratrol: preparacao e caracterizacao

Energy Technology Data Exchange (ETDEWEB)

NONE

2011-07-01

Resveratrol-loaded poly({epsilon}-caprolactone) (PCL) microparticles were obtained by simple emulsion/solvent evaporation method. Three drug-loaded formulations were prepared with the aim of investigating the influence of composition on the encapsulation efficiency. Morphological and spectroscopic methods were performed for these materials. The microparticles revealed residual moisture close to 1.5% and encapsulation efficiency above 80%. Spherical shape and smooth surface were observed by SEM. No pores were either verified. Resveratrol-loaded microparticles showed an average particle size of around 50 {mu}m. X-ray diffraction analysis demonstrated that the microencapsulation reduced the drug crystallinity. The FTIR results suggest that no chemical bond was formed between polymer and drug. (author)

Nanostructured synthetic hydroxyapatite and dental enamel heated and irradiated by ER,CR:YSGG: characterized by FTIR and XRD; Hidroxiapatita sintetica nanoestruturada e esmalte dental aquecidos e irradiados por laser de Er,Cr:YSGG: caracterizacao por FTIR e por DRX

Energy Technology Data Exchange (ETDEWEB)

Rabelo Neto, Jose da Silva

2009-07-01

The study evaluate the physical changes and/or chemical that occurs in synthetic hydroxyapatite (HAP) and in enamel under action of thermal heating in oven or laser irradiation of Er,Cr:YSGG that may cause changes in its structure to make them more resistant to demineralization aiming the formation of dental caries. The synthetic HAP was produced by reaction of solutions of Ca(NO{sub 3}) and (NH{sub 4}){sub 2}HPO{sub 4} with controlled temperature and pH. The enamel powder was collected from the bovine teeth. Samples of powder enamel and synthetic HAP were subjected to thermal heating in oven at temperatures of 200 deg C, 400 deg C, 600 deg C, 800 deg C and 1000 deg C. For the laser irradiation of materials, were made with 5,79 J/cm{sup 2} of irradiation, 7,65 J/cm{sup 2}, 10,55 J/cm{sup 2} and 13,84 J/cm{sup 2} for synthetic HAP and 7,53 J/cm{sup 2}, 10,95 J/cm{sup 2}, and 13,74 J/cm{sup 2} for the enamel. The samples were evaluated by X-ray diffraction (XRD) for analysis of crystallographic phases and analysis by the Rietveld method, to determine their respective proportions in the material, as well as results of changes of the lattice unit cell parameters (axis-a, axis-c and volume), crystallites sizes and the occupation rate of sites of Ca and P atoms. The samples were analyzed by Fourier transform infrared spectroscopy (FTIR), which should compositional changes due to treatment related to carbonate, phosphate, adsorbed water and hydroxyl radicals content. The infrared was used to measure the surface temperature generated by the laser beam in the solid samples of enamel. Besides the major hydroxyapatite crystallographic phases, there was formations of octa calcium phosphate (OCP) and phase {beta} of tricalcium phosphate ({beta}-TCP ) in enamel heated at 800 deg C. There was reduction of the axis-a, volume and size of crystallites to the temperatures between 400 degree C and 600 deg C and also on laser irradiated samples. Above the temperature of 600 degree C it

Investigation of structural and magnetic properties of Ni0.5Zn0.5Fe2O4 nano powders prepared by self combustion method

International Nuclear Information System (INIS)

Sudheesh, V.D.; Nehra, J.; Vinesh, A.; Sebastian, V.; Lakshmi, N.; Dutta, Dimple P.; Reddy, V.R.; Venugopalan, K.; Gupta, Ajay

2013-01-01

Graphical abstract: Display Omitted Highlights: ► Ni 0.5 Zn 0.5 Fe 2 O 4 prepared by self combustion with uniform/nonuniform heating. ► Characterized using TEM, XRD, in-field Mössbauer and DC magnetometry. ► Leads to bimodal (S1) and very narrow size distribution (S2) type nano samples. ► S1 has magnetic properties of bulk Ni 0.5 Zn 0.5 Fe 2 O 4 . ► Although very even sized, S2 large magnetic anisotropy distribution. -- Abstract: Nano powders of Ni 0.5 Zn 0.5 Fe 2 O 4 have been synthesized by the self-combustion method at a relatively low temperature of 473 K under conditions of non-uniform and uniform heating. Rietveld fitting of X-ray diffractograms confirm the formation of the pure spinel phase in both samples. Transmission electron microscopy indicates that the sample prepared under non-uniform heating has a bimodal particle size distribution (average values 16 nm and 6 nm) while the one prepared under uniform heating has a very narrow particle size distribution (average size 4 nm). Low temperature, in-field Mössbauer spectroscopic studies clearly show surface spin contributions. The hyperfine fields and Curie temperature of the non-uniformly heated sample are in good agreement with those reported for the corresponding bulk samples. Despite having a very narrow particle size distribution, the uniformly heated sample has a large anisotropy distribution which is evident in the broad transition visible in the temperature dependent magnetization curve. It is also corroborated by the fact that the experimental magnetization curve at room temperature requires two Langevin functions for satisfactory reproduction.

Local structure and disorder in crystalline Pb9Al8O21

International Nuclear Information System (INIS)

Hannon, Alex C.; Barney, Emma R.; Holland, Diane; Knight, Kevin S.

2008-01-01

Crystalline Pb 9 Al 8 O 21 is a model compound for the structure of non-linear optical glasses containing lone-pair ions, and its structure has been investigated by neutron powder diffraction and total scattering, and 27 Al magic angle spinning NMR. Rietveld analysis (space group Pa3-bar (No. 205), a=13.25221(4) A) shows that some of the Pb and O sites have partial occupancies, due to lead volatilisation during sample preparation, and the non-stoichiometric sample composition is Pb 9-δ Al 8 O 21-δ with δ=0.54. The NMR measurements show evidence for a correlation between the chemical shift and the variance of the bond angles at the aluminium sites. The neutron total correlation function shows that the true average Al-O bond length is 0.8% longer than the apparent bond length determined by Rietveld refinement. The thermal variation in bond length is much smaller than the thermal variation in longer interatomic distances determined by Rietveld refinement. The total correlation function is consistent with an interpretation in which AlO 3 groups with an Al-O bond length of 1.651 A occur as a result of the oxygen vacancies in the structure. The width of the tetrahedral Al-O peak in the correlation function for the crystal is very similar to that for lead aluminate glass, indicating that the extent of static disorder is very similar in the two phases. - Graphical abstract: Combined neutron powder diffraction and total scattering, and 27 Al NMR on crystalline Pb 9 Al 8 O 21 shows it to be a non-stoichiometric compound with vacancies due to PbO volatilisation. A detailed consideration of the thermal and static disorder is given, showing that glass and crystal phases have very similar disorder at short range

Study of the lattice parameter evolution of PWR irradiated MOX fuel by X-Ray diffraction; Etude de l'evolution du parametre cristallin des combustibles MOX irradies en rep par la methode de diffraction des rayons X

Energy Technology Data Exchange (ETDEWEB)

Clavier, B

1995-07-01

Fuel irradiation leads to a swelling resulting from the formation of gaseous (Kr, Xe) or solid fission products which are found either in solution or as solid inclusions in the matrix. This phenomena has to be evaluated to be taken into account in fuel cladding Interaction. Fuel swelling was studied as a function of burn up by measuring the corresponding cell constant evolution by X-Ray diffraction. This study was realized on Mixed Oxide Fuels (MOX) irradiated in a Pressurized Water Reactor (PWR) at different burn-up for 3 initial Pu contents. Lattice parameter evolutions were followed as a function of burn-up for the irradiated fuel with and without an annealing thermal treatment. These experimental evolutions are compared to the theoretical evolutions calculated from the hard sphere model, using the fission product concentrations determined by the APPOLO computer code. Contribution of varying parameters influencing the unit cell value is discussed. Thermal treatment effects were checked by metallography, X-Ray diffraction and microprobe analysis. After thermal treatment, no structural change was observed but a decrease of the lattice parameter was measured. This modification results essentially from self-irradiation defect annealing and not from stoichiometry variations. Microprobe analysis showed that about 15% of the formed Molybdenum is in solid solution In the oxide matrix. Micrographs showed the existence of Pu packs in the oxide matrix which induces a broadening of diffraction lines. The RIETVELD method used to analyze the X-Ray patterns did not allow to characterize independently the Pu packs and the oxide matrix lattice parameters. Nevertheless, with this method, the presence of micro-strains in the irradiated nuclear fuel could be confirmed. (author)

Structures and solid solution mechanisms of pyrochlore phases in the systems Bi{sub 2}O{sub 3}-ZnO-(Nb, Ta){sub 2}O{sub 5}

Energy Technology Data Exchange (ETDEWEB)

Tan, K.B., E-mail: tankb@science.upm.edu.m [Department of Chemistry, Faculty of Science, Universiti Putra Malaysia, 43400 Serdang, Selangor (Malaysia); Khaw, C.C. [Department of Engineering, Universiti Tunku Abdul Rahman, 53300 Setapak, Kuala Lumpur (Malaysia); Lee, C.K. [Academic Science Malaysia, 902-4 Jalan Tun Ismail, 50480 Kuala Lumpur (Malaysia); Zainal, Z. [Department of Chemistry, Faculty of Science, Universiti Putra Malaysia, 43400 Serdang, Selangor (Malaysia); Miles, G.C. [Department of Engineering Materials, The University of Sheffield, Mappin Street, Sheffield, S1 3JD (United Kingdom)

2010-10-22

Research highlights: {yields} Combined XRD and ND Rietveld structural refinement of pyrochlores. {yields} Structures and solid solution mechanisms of Bi-pyrochlores. {yields} Bi and Zn displaced off-centre to different 96g A-site positions. {yields} Summary of composition-structure-property of Bi-pyrochlores. - Abstract: The crystal structures of two pyrochlore phases have been determined by Rietveld refinement of combined X-ray and neutron powder diffraction data. These are stoichiometric, Bi{sub 1.5} ZnTa{sub 1.5}O{sub 7} and non-stoichiometric Bi{sub 1.56}Zn{sub 0.92}Nb{sub 1.44}O{sub 6.86}. In both structures, Zn is distributed over A- and B-sites; Bi and Zn are displaced off-centre, to different 96g A-site positions; of the three sets of oxygen positions, O(1) are full, O(2) contain vacancies and O(3) contain a small number of oxygen, again in both cases. Comparisons between these structures, those of related Sb analogues and literature reports are made.

Analysis of neutron diffraction spectra acquired in situ during stress-induced transformations in superelastic NiTi

International Nuclear Information System (INIS)

Vaidyanathan, R.; Bourke, M.A.; Dunand, D.C.

1999-01-01

Neutron diffraction spectra were obtained during various stages of a reversible stress-induced austenite to martensite phase transformation in superelastic NiTi. This was accomplished by neutron diffraction measurements on bulk polycrystalline NiTi samples simultaneously subjected to mechanical loading. Analysis of the data was carried out using individual lattice plane (hkl) reflections as well as by Rietveld refinement. In the Rietveld procedure, strains in austenite were described in terms of an isotropic (hkl independent) and an anisotropic (hkl dependent) component. At higher stresses, austenite lattice plane reflections exhibited nonlinear and dissimilar elastic responses which may be attributed to the transformation. The texture evolution is significant in both austenite and martensite phases during the transformation and two approaches were used to describe this evolving texture, i.e., an ellipsoidal model due to March - Dollase and a generalized spherical-harmonic approach. The respective predictions of the phase fraction evolution as a function of applied stress were compared. A methodology is thus established to quantify the discrete phase strains, phase volume fractions, and texture during such transformations. copyright 1999 American Institute of Physics

Effect of molybdenum on structure, microstructure and mechanical properties of biomedical Ti-20Zr-Mo alloys

Energy Technology Data Exchange (ETDEWEB)

Kuroda, Pedro Akira Bazaglia [UNESP - Univ Estadual Paulista, Laboratório de Anelasticidade e Biomateriais, 17.033-360, Bauru, SP (Brazil); IBTN/Br – Institute of Biomaterials, Tribocorrosion and Nanomedicine, Brazilian Branch, 17.033-360 Bauru, SP (Brazil); Buzalaf, Marília Afonso Rabelo [USP – Universidade de São Paulo, Departamento de Ciências Biológicas, 17.012-901, Bauru, SP (Brazil); Grandini, Carlos Roberto, E-mail: betog@fc.unesp.br [UNESP - Univ Estadual Paulista, Laboratório de Anelasticidade e Biomateriais, 17.033-360, Bauru, SP (Brazil); IBTN/Br – Institute of Biomaterials, Tribocorrosion and Nanomedicine, Brazilian Branch, 17.033-360 Bauru, SP (Brazil)

2016-10-01

Titanium has an allotropic transformation around 883 °C. Below this temperature, the crystalline structure is hexagonal close-packed (α phase), changing to body-centered cubic (β phase). Zirconium has the same allotropic transformation around 862 °C. Molybdenum has body-centered cubic structure, being a strong β-stabilizer for the formation of titanium alloys. In this paper, the effect of substitutional molybdenum was analyzed on the structure, microstructure and selected mechanical properties of Ti-20 Zr-Mo (wt%) alloys to be used in biomedical applications. The samples were prepared by arc-melting and characterized by x-ray diffraction with subsequent refinement by the Rietveld method, optical and scanning electron microscopy. The mechanical properties were analyzed by Vickers microhardness and dynamic elasticity modulus. X-ray measurements and Rietveld analysis revealed the presence of α′ phase without molybdenum, α′ + α″ phases with 2.5 wt% of molybdenum, α″ + β phases with 5 and 7.5 wt% of molybdenum, and only β phase with 10 wt% of molybdenum. These results were corroborated by microscopy results, with a microstructure composed of grains of β phase and lamellae and needles of α′ and α″ phase in intra-grain the region. The hardness of the alloy was higher than the commercially pure titanium, due to the action of zirconium and molybdenum as hardening agents. The samples have a smaller elasticity modulus than the commercially pure titanium. - Highlights: • Ti-20Zr-Mo system alloys were developed. • β-Stabilizer effect of Zr in the presence of another β-stabilizer element • Alloys with low elastic modulus.

Bulletin of Materials Science | Indian Academy of Sciences

Indian Academy of Sciences (India)

We have studied for the first time the effect of Ag addition (0–15 wt%) to the superconducting system, Nd 1.85 Ce 0.15 CuO 4 , on its crystal structure and local structural features, using synchrotron X-ray diffraction(SXRD) and Raman spectroscopy, respectively. SXRD and subsequent Rietveld refinement studies on powders ...

Structural behaviour of AgNO3 at low temperatures by neutron ...

Indian Academy of Sciences (India)

[4] F El-Kabbany, Y Badr, G Said and S Taha, Appl. Phys. A43, 65 (1987). [5] Z Shen, W F Sherman and G R Wilkinson, J. Mol. Struct. 175, 395 (1988). [6] R Rodriguez-Carvajal, FULLPROF: A Program for Rietveld Refinement, profile matching and integrated intensity, version 3.1 (LLB, France) (1995). [7] R Feyerherm, M F ...

Structural, vibrational and luminescence properties of the (1−x)CaWO{sub 4}−xCdWO{sub 4} system

Energy Technology Data Exchange (ETDEWEB)

Taoufyq, A. [Institut Matériaux Microélectronique et Nanosciences de Provence, Aix Marseille Université, CNRS, Université de Toulon, IM2NP UMR 7334, 83957, La Garde (France); Laboratoire Matériaux et Environnement LME, Faculté des Sciences, Université Ibn Zohr, BP 8106, Cité Dakhla, Agadir, Maroc (Morocco); CEA/DEN, Département d’Études des Réacteurs, Laboratoire Dosimétrie Capteurs Instrumentation, CEA Cadarache, 13108, Saint-Paul-lez-Durance (France); Société CESIGMA, Signals and Systems, 1576 Chemin de La Planquette, 83130 La Garde (France); Guinneton, F.; Valmalette, J-C.; Arab, M. [Institut Matériaux Microélectronique et Nanosciences de Provence, Aix Marseille Université, CNRS, Université de Toulon, IM2NP UMR 7334, 83957, La Garde (France); Benlhachemi, A.; Bakiz, B. [Laboratoire Matériaux et Environnement LME, Faculté des Sciences, Université Ibn Zohr, BP 8106, Cité Dakhla, Agadir, Maroc (Morocco); Villain, S. [Institut Matériaux Microélectronique et Nanosciences de Provence, Aix Marseille Université, CNRS, Université de Toulon, IM2NP UMR 7334, 83957, La Garde (France); and others

2014-11-15

In the present work, we investigate the structural, microstructural, vibrational and luminescence properties of the system (1−x)CaWO{sub 4}−xCdWO{sub 4} with x ranging between 0 and 1. Polycrystalline samples were elaborated using a coprecipitation technique followed by thermal treatment at 1000 °C. The samples were then characterized using X-ray diffraction, scanning electron microscopy, Raman spectroscopy and luminescence analyses. X-ray diffraction profile analyses using Rietveld method showed that two kinds of solid solutions Ca{sub 1−x}Cd{sub x}WO{sub 4} having scheelite and wolframite structures, with respectively tetragonal and monoclinic crystal cells, were observed, with a biphasic system for compositions x=0.6 and 0.7. The scanning electron microscopy experiments showed a complex evolution of morphologies and crystallite sizes as x increased. The vibration modes of Raman spectra were characteristic of composition-dependent disordered solid solutions with decreasing wavenumbers as x increased. Luminescence experiments were performed under UV-laser light irradiation. The energies of emission bands increased linearly with cadmium composition x. The integrated intensity of luminescence reached a maximum value for the substituted wolframite phase with composition x=0.8. - Graphical abstract: Luminescence on UV excitation (364.5 nm) of (1−x)CaWO{sub 4−x}CdWO{sub 4} system, elaborated from coprecipitation technique at 1000 °C, with 0Rietveld method. • A maximum of luminescence is obtained for an intermediate composition x=0.8.

Photoluminescence properties of cerium oxide nanoparticles as a function of lanthanum content

International Nuclear Information System (INIS)

Deus, R.C.; Cortés, J.A.; Ramirez, M.A.; Ponce, M.A.; Andres, J.; Rocha, L.S.R.

2015-01-01

Highlights: • CeO 2 nanoparticles were obtained by microwave-hydrothermal method. • Rietveld refinement reveals a cubic structure. • KOH mineralizer agent exhibit weak agglomeration at low temperature and shorter time. - Abstract: The structural and photoluminescent properties at room temperature of CeO 2 and La-doped CeO 2 particles were undertaken. The obtained particles were synthesized by a microwave-assisted hydrothermal method (MAH) under different lanthanum contents. X-ray diffraction (XRD), Fourier transform infrared (FT-IR), Fourier transform Raman (FT-Raman), Ultra-violet spectroscopy (UV–vis) and photoluminescence (PL) measurements were carried out. XRD revealed that the powders are free of secondary phases and crystallize in the cubic structure. Raman data show that increasing La doping content increase oxygen vacancies due to lattice expansion. The UV/vis absorption spectroscopy suggested the presence of intermediate energy levels in the band gap of structurally ordered powders. Lanthanum addition creates oxygen vacancies and shifts the photoluminescence in the low energy range leading to intense PL emission

Fine control of the amount of preferential <001> orientation in DC magnetron sputtered nanocrystalline TiO2 films

International Nuclear Information System (INIS)

Stefanov, B; Granqvist, C G; Österlund, L

2014-01-01

Different crystal facets of anatase TiO 2 are known to have different chemical reactivity; in particular the {001} facets which truncates the bi-tetrahedral anatase morphology are reported to be more reactive than the usually dominant {101} facets. Anatase TiO 2 thin films were deposited by reactive DC magnetron sputtering in Ar/O 2 atmosphere and were characterized using Rietveld refined grazing incidence X-ray diffraction, atomic force microscopy and UV/Vis spectroscopy. By varying the partial O2 pressure in the deposition chamber, the degree of orientation of the grains in the film could be systematically varied with preferred <001> orientation changing from random upto 39% as determined by March-Dollase method. The orientation of the films is shown to correlate with their reactivity, as measured by photo-degradation of methylene blue in water solutions. The results have implications for fabrication of purposefully chemically reactive thin TiO 2 films prepared by sputtering methods

Synthesis and characterization photocatalyst of titanium oxide obtained by the Pechini

International Nuclear Information System (INIS)

Ribeiro, P.C.; Costa, A.C.F.M.; Lira, H.L.; Sasaki, J.M.; Santos, S.K.

2011-01-01

The photocatalysis using TiO 2 semiconductor has shown great efficiency in the treatment of toxic pollutants and non-biodegradable materials, commonly present in air and domestic and industrial effluents. Thus, the aim of this work is to study the evaluation of photocatalytic activity of TiO 2 samples synthesized by the Pechini method at a ratio of citric acid / metal cation of 2:1 and 4:1. The synthesized samples were characterized by X-ray diffraction, quantification of phases using the Rietveld method of refinement of the structure and after analyzed in photocatalytic bench tests using methyl red dye. The results showed that in a 2:1 ratio, the sample resulted in the formation of 100% of anatase phase, while in the 4:1 ratio sample showed 73.51% of anatase phase and 10.5% of rutile phase. The 4:1 sample showed the best performance discoloring over 70% of the dye for a period close to 24h. (author)

A novel broadband emission phosphor Ca2KMg2V3O12 for white light emitting diodes

International Nuclear Information System (INIS)

Li, Junfu; Qiu, Kehui; Li, Junfeng; Li, Wei; Yang, Qian; Li, Junhan

2010-01-01

A novel broadband emission phosphor Ca 2 KMg 2 V 3 O 12 was first synthesized by solution combustion method. The X-ray diffraction showed that Ca 2 KMg 2 V 3 O 12 phase can be obtained at 600-900 o C through combustion route. The crystal structure of this material was refined by Rietveld method using powder X-ray diffraction. It crystallizes in cubic system and belongs to space group Ia3d with z = 8, a = 0.12500 nm. The excitation band of Ca 2 KMg 2 V 3 O 12 peaks at 320 nm in a region between 260 nm and 425 nm, and the emission spectrum exhibits an intense band centered at about 528 nm covering from 400 nm to 800 nm. The colour coordinates of samples prepared at different ignition temperatures are in a range of x = 0.323-0.339, y = 0.430-0.447.

Doping effect on the structural properties of Cu1-x(Ni, Zn, Al and Fe)xO samples (0

Science.gov (United States)

Amaral, J. B.; Araujo, R. M.; Pedra, P. P.; Meneses, C. T.; Duque, J. G. S.; dos S. Rezende, M. V.

2016-09-01

In this work, the effect of insertion of transition metal, TM (=Ni, Zn, Al and Fe), ions in Cu1-xTMxO samples (0method is studied through experimental and computational methods. The analyses of X-ray diffraction (XRD) patterns using Rietveld refinement show that i) at x=0, all samples present a monoclinic crystal system with space group C2/c and ii) for increasing the TM-doping, Ni and Zn-doped samples show a small amount of spurious phases for concentrations above x=0.05. Based on these results, a defect disorder study for using atomistic computational simulations which is based on the lattice energy minimization technique is employed to predict the location of the dopant ions in the structure. In agreement with XRD data, our computational results indicate that the trivalent (Al and Fe ions) are more favorable to be incorporated into CuO matrix than the divalent (Ni and Zn ions).

Layered ordering of vacancies of lead iron phosphate Pb{sub 3}Fe{sub 2}(PO{sub 4}){sub 4}

Energy Technology Data Exchange (ETDEWEB)

Malakho, A.P. [Moscow State Univ., Dept. of Material Science (Russian Federation); Morozov, V.A.; Pokholok, V.; Lazoryak, B.I. [Moscow State Univ., Dept. of Chemisty (Russian Federation); Morozov, V.A.; Van Tendeloo, G. [Antwerp Univ., EMAT (Belgium)

2005-07-01

Lead iron phosphate Pb{sub 3}Fe{sub 2}(PO{sub 4}){sub 4} has been synthesized by solid state method and characterized by X-ray powder and electron diffraction, differential scanning calorimetry, Moessbauer and infrared spectroscopy. A structural model for Pb{sub 3}Fe{sub 2}(PO{sub 4}){sub 4} is proposed and is refined by the Rietveld method. The compound crystallizes in the monoclinic space group P2{sub 1}/c with a=9.0065(6) Angstroms, b=9.0574(6) Angstroms, c=9.3057(6) Angstroms, {beta}=116.880(4) degrees, V=677.10(8) (Angstroms){sup 3}, Z=2, R{sub wp}=3.52%, R{sub p}=2.66%. It exhibits a structure with a three-dimensional open framework. The 3D framework is formed by PO{sub 4} tetrahedra and FeO{sub 6} octahedra connected via common vertices. 3/4 of cavities in the framework are occupied by lead and 1/4 are vacant. (authors)

Room temperature ferromagnetism in Th{sub 1-x}Fe{sub x}O{sub 2-{delta}} (x = 0.0, 0.05, 0.10, 0.15, 0.20 and 0.25) nanoparticles

Energy Technology Data Exchange (ETDEWEB)

Jayakumar, O.D. [Chemistry Division, Bhabha Atomic Research Centre, Mumbai 400085 (India); Gopalakrishnan, I.K. [Chemistry Division, Bhabha Atomic Research Centre, Mumbai 400085 (India)], E-mail: ikgopal@barc.gov.in; Vinu, A. [Nano-Ionics Materials Group, Fuel Cell Materials Center, National Institute for Materials Science, 1-1 Namiki, Tsukuba, Ibaraki 305-0044 (Japan); Asthana, A. [Advanced Electron Microscopy Group, National Institute for Materials Science, 1-1 Namiki, Tsukuba, Ibaraki 305-0044 (Japan); Tyagi, A.K. [Chemistry Division, Bhabha Atomic Research Centre, Mumbai 400085 (India)

2008-08-11

Nanocrystalline (Th{sub 1-x}Fe{sub x})O{sub 2-{delta}} particles with different Fe concentrations (x = 0.0, 0.05, 0.10, 0.15, 0.20 and 0.25) have been prepared by a gel combustion method. Rietveld refinement analyses of X-ray diffraction data revealed the formation of an impurity free cubic type Th{sub 1-x}Fe{sub x}O{sub 2-{delta}} structure up to x = 0.20. This observation is further confirmed from the detailed studies conducted on 10 at.% Fe doped ThO{sub 2} using high-resolution transmission electron microscopy (HRTEM) imaging and indexing of the selected-area electron diffraction (SAED) patterns. DC magnetization studies as a function field indicate that they are ferromagnetic with Curie temperature (T{sub c}) well above room temperature.

Synthesis and structural studies on cerium substituted La0.4Ca0.6MnO3 as solid oxide fuel cell electrode material

Science.gov (United States)

Singh, Monika; Kumar, Dinesh; Singh, Akhilesh Kumar

2018-04-01

For solid oxide fuel cell electrode material, calcium doped lanthanum manganite La0.4Ca0.6MnO3 (LCMO) and cerium-incorporated on Ca-site with composition La0.40Ca0.55Ce0.05MnO3 (LCCMO) were synthesized using most feasible and efficient glycine-nitrate method. The formation of crystalline single phase was confirmed by x-ray diffraction (XRD). The Rietveld analysis reveals that both systems crystallize into orthorhombic crystal structure with Pnma space group. Additionally, 8 mole % Y2O3 stabilized ZrO2 (8YSZ) solid electrolyte was also synthesized using high energy ball mill to check the reaction with electrode materials. It was found that the substitution of Ce+4 cations in LCMO perovskite suppressed formation of undesired insulating CaZrO3 phase.

Gd0.6Sr0.4Fe0.8Co0.2O3-δ: A novel type of SOFC cathode

DEFF Research Database (Denmark)

Kammer Hansen, Kent; Søgaard, Martin; Mogensen, Mogens Bjerg

2007-01-01

The fabrication and electrochemical activity of a type of solid oxide fuel cell (SOFC) cathode is described in this paper. In search of new cathodes a Gd0.6Sr0.4Fe0.8Co0.2O3-delta compound was synthesized using the glycine-nitrate method. It turned out that this was a two-phase compound consisting...... of two perovskite phases, a cubic and an orthorhombic phase, as shown by Rietveld refinements. These two phases were synthesized and a cone-shaped electrode study was undertaken. It was shown that the composite cathode had an electrochemical activity superior to that of the two single-phase perovskites......, indicating that the unique microstructure of this type of cathode is essential for achieving high electrochemical activity toward the reduction of oxygen in a SOFC....

Tailoring of K0.8Al0.7Fe0.15Si2.25O6 Leucite Based Dental Ceramic Material

Directory of Open Access Journals (Sweden)

Aleksandar Kremenović

2016-06-01

Full Text Available Potassium based ceramic materials composed from leucite in which 5 % of Al is exchanged with Fe and 4 % of hematite was synthesized by mechanochemical homogenization and annealing of K2O-SiO2-Al2O3-Fe2O3 mixtures. Synthesized material was characterized by X-ray Powder Diffraction (XRPD and Scanning Electron Microscopy coupled with Energy Dispersive X-ray spectroscopy (SEM/EDX. The two methods are in good agreement in regard to the specimen chemical composition suggesting that a leucite chemical formula is K0.8Al0.7Fe0.15Si2.25O6. Rietveld structure refinement results reveal that about 20 % of vacancies exist in the position of K atoms. This work is licensed under a Creative Commons Attribution 4.0 International License.

Characterization of an ecological binder for mortars obtained from recycling of ladle furnace slag

International Nuclear Information System (INIS)

Marinho, A.B.; Santos, C.M.; Fontes, W.C.; Matias, A.C.P.; Brigolini, G.J.; Peixoto, R.A.F.; Carvalho, J.F.

2016-01-01

A sustainable binder obtained from recycling of a ladle furnace slag from Piracicaba, Sao Paulo, was produced in Laboratory of Construction Materials of Federal University of Ouro Preto (UFOP). A characterization work was performed and the results are presented. The physical, chemical and mineralogical properties was obtained using, among others, the following techniques: X-ray fluorescence (XRF), X-ray diffraction (XRD) with Rietveld refining method, optical microscopy and Scanning electronic microscopy (SEM) with energy dispersive spectroscopy (EDS). The chemical analysis showed predominance of CaO and SiO_3; the mineralogical analysis pointed the predominant presence of calcium-olivine, merwinite and pyroxene and; the images showed predominance of angulous and elongated grains. According to results, the material was classified as a hydraulic binder, with characteristics comparable to hydraulic limes. (author)

On the possibility of using polycrystalline material in the development of structure-based generic assays

Energy Technology Data Exchange (ETDEWEB)

Allaire, Marc, E-mail: allaire@bnl.gov; Moiseeva, Natalia [National Synchrotron Light Source, Brookhaven National Laboratory, Upton, NY 11973-5000 (United States); Botez, Cristian E. [Department of Physics and Astronomy, Stony Brook University, Stony Brook, NY 11794-3800 (United States); Engel, Matthew A. [National Synchrotron Light Source, Brookhaven National Laboratory, Upton, NY 11973-5000 (United States); Department of Biomedical Engineering, Stony Brook University, Stony Brook, NY 11794-2580 (United States); Stephens, Peter W. [National Synchrotron Light Source, Brookhaven National Laboratory, Upton, NY 11973-5000 (United States); Department of Physics and Astronomy, Stony Brook University, Stony Brook, NY 11794-3800 (United States)

2009-04-01

The correlation coefficients calculated between raw powder diffraction profiles can be used to identify ligand-bound/unbound states of lysozyme. The discovery of ligands that bind specifically to a targeted protein benefits from the development of generic assays for high-throughput screening of a library of chemicals. Protein powder diffraction (PPD) has been proposed as a potential method for use as a structure-based assay for high-throughput screening applications. Building on this effort, powder samples of bound/unbound states of soluble hen-egg white lysozyme precipitated with sodium chloride were compared. The correlation coefficients calculated between the raw diffraction profiles were consistent with the known binding properties of the ligands and suggested that the PPD approach can be used even prior to a full description using stereochemically restrained Rietveld refinement.

Low-temperature synthesis and structural properties of ferroelectric K 3WO 3F 3 elpasolite

Science.gov (United States)

Atuchin, V. V.; Gavrilova, T. A.; Kesler, V. G.; Molokeev, M. S.; Aleksandrov, K. S.

2010-06-01

Low-temperature ferroelectric G2 polymorph of K 3WO 3F 3 has been prepared by chemical synthesis. Structural and chemical properties of the final product have been evaluated with X-ray powder diffraction (XRD), scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). Structure parameters of G2-K 3WO 3F 3 are refined by the Rietveld method from XRD data measured at room temperature (space group Cm, Z = 2, a = 8.7350(3) Å, b = 8.6808(5) Å, c = 6.1581(3) Å, β = 135.124(3) Å, V = 329.46(3) Å 3; RB = 2.47%). Partial ordering of oxygen and fluorine atoms has been found over anion positions. Mechanism of ferroelectric phase transition in A 2BMO 3F 3 oxyfluorides is discussed.

On the possibility of using polycrystalline material in the development of structure-based generic assays

International Nuclear Information System (INIS)

Allaire, Marc; Moiseeva, Natalia; Botez, Cristian E.; Engel, Matthew A.; Stephens, Peter W.

2009-01-01

The correlation coefficients calculated between raw powder diffraction profiles can be used to identify ligand-bound/unbound states of lysozyme. The discovery of ligands that bind specifically to a targeted protein benefits from the development of generic assays for high-throughput screening of a library of chemicals. Protein powder diffraction (PPD) has been proposed as a potential method for use as a structure-based assay for high-throughput screening applications. Building on this effort, powder samples of bound/unbound states of soluble hen-egg white lysozyme precipitated with sodium chloride were compared. The correlation coefficients calculated between the raw diffraction profiles were consistent with the known binding properties of the ligands and suggested that the PPD approach can be used even prior to a full description using stereochemically restrained Rietveld refinement

Dynamic processes of domain switching in lead zirconate titanate under cyclic mechanical loading by in situ neutron diffraction

International Nuclear Information System (INIS)

Pojprapai, Soodkhet; Luo, Zhenhua; Clausen, Bjorn; Vogel, Sven C.; Brown, Donald W.; Russel, Jennifer; Hoffman, Mark

2010-01-01

The performance of ferroelectric ceramics is governed by the ability of domains to switch. A decrease in the switching ability can lead to degradation of the materials and failure of ferroelectric devices. In this work the dynamic properties of domain reorientation are studied. In situ time-of-flight neutron diffraction is used to probe the evolution of ferroelastic domain texture under mechanical cyclic loading in bulk lead zirconate titanate ceramics. The high sensitivity of neutron diffraction to lattice strain is exploited to precisely analyze the change of domain texture and strain through a full-pattern Rietveld method. These results are then used to construct a viscoelastic model, which explains the correlation between macroscopic phenomena (i.e. creep and recovered deformation) and microscopic dynamic behavior (i.e. ferroelastic switching, lattice strain).

Enhanced local piezoelectric response in the erbium-doped ZnO nanostructures prepared by wet chemical synthesis

Directory of Open Access Journals (Sweden)

Reza Zamiri

2017-03-01

Full Text Available Pure and erbium (Er doped ZnO nanostructures were prepared by simple and cost effective wet chemical precipitation method. The successful doping with phase purity of prepared ZnO nanostructure was confirmed by X-ray diffraction (XRD and their Rietveld analysis. The change in structural morphology of nanoscale features of prepared ZnO nanopowders on Er doping was observed from their scanning electron microscopy (SEM images. The presence of Er in prepared ZnO nanopowder was further confirmed from corresponding energy dispersive X-ray spectroscopy (EDX spectra of scanned SEM images. Piezoelectric properties of before (green samples and after sintering of consolidated compact of synthesized nanopowders were successfully measured. The out-of-plane (effective longitudinal and in-plane (effective shear coefficients of the samples were estimated from the local piezoresponse.

Effect of divalent (Sr, Ba) doping on the structural and magnetic properties of BiFeO{sub 3}

Energy Technology Data Exchange (ETDEWEB)

Rangi, Manisha, E-mail: mrangi100@gmail.com; Sanghi, Sujata; Agarwal, Ashish; Jangra, Sandhaya; Singh, Ompal [Department of Applied Physics, Guru Jambheshwar University of Science and Technology, Hisar, Haryana- 125001 (India)

2015-06-24

The effect of divalent substitution on the crystal structure and magnetic properties of BiFeO{sub 3} has been investigated using X-ray diffraction and magnetic measurements technique. Single phase Bi{sub 0.8}A{sub 0.2}FeO{sub 3} (A= Sr, Ba) multiferroics have been synthesized by solid state reaction method. Rietveld analysis of the XRD patterns revealed that the prepared ceramics exhibit rhombohedral structure with space group R3c. M–H hysteresis loops were recorded at 5K revealed that Sr and Ba substitution transformed antiferromagnetic BiFeO3 into weak ferromagnetic. The enhanced magnetization with Sr and Ba addition is confirmed by the MT curve recorded at 1T. It is closely related to intrinsic structural distortion and modification of the antiparallel spin structure.

Magnetocaloric effect and transport properties of Gd5Ge2(Si1-x Sn x )2 (x=0.23 and 0.40) compounds

International Nuclear Information System (INIS)

Campoy, J.C.P.; Plaza, E.J.R.; Nascimento, F.C.; Coelho, A.A.; Pereira, M.C.; Fabris, J.D.; Raposo, M.T.; Cardoso, L.P.; Persiano, A.I.C.; Gama, S.

2007-01-01

We report a study about the structural properties of polycrystalline samples of nominal composition Gd 5 Ge 2 (Si 1- x Sn x ) 2 (x=0.23, 0.40) that closely influence their physical behavior particularly related to electric resistivity and magnetocaloric (MCE) effect. The samples were characterized by X-ray diffraction (XRD) using the Rietveld refinement method, metallographic analyses, 119 Sn Moessbauer spectroscopy, DC magnetization and electrical transport measurements. It was identified a Gd 5 Si 2 Ge 2 -monoclinic phase for x=0.23 and a Sm 5 Sn 4 -orthorhombic phase (type II) for x=0.40, both with two non-equivalent crystallographic sites for the Sn ions. We were able to infer on the role of tin on the magnetic and transport properties in these compounds

New approach for extraction of cellulose from tucumã's endocarp and its structural characterization

Science.gov (United States)

Manzato, L.; Rabelo, L. C. A.; de Souza, S. M.; da Silva, C. G.; Sanches, E. A.; Rabelo, D.; Mariuba, L. A. M.; Simonsen, J.

2017-09-01

The recycling of plant wasted materials into useful products represents a green alternative to prevent environmental problems. Tucumã palm fruit (Astrocaryum aculeatum Meyer) is widely used in Amazon region for food and crafts. Due to the large amount of wasted Tucumã's endocarp, this work proposes a new approach for extraction of cellulose and its structural characterization. X-ray Diffraction (XRD), Rietveld Refinement, Scanning Electron Microscopy (SEM), Infrared-transform Fourier Spectroscopy (FTIR) and Thermal Analysis (TG/DSC) have been used for characterization of the extracted cellulose. XRD patterns of the in natura tucumã's endocarp has showed a natural crystalline content embedded in a non-crystalline matrix. Nanocrystals of cellulose have been observed in the XRD pattern of the extracted cellulose, showing a good agreement with type II. Rietveld refinement allowed the cell parameters obtainment (a = 8.43(1) Å, b = 9.50(1) Å, c = 9.39(3) Å and γ = 118.43(4)°). Apparent average crystallite size and microstrain were, respectively, 20.0 Å and 0.1%. Two different methods were applied for estimative of crystallinity percentage. In the first method the height ratio between the intensity of the crystalline peak and the total intensity after the subtraction of the non-crystalline content was applied, leading to 48.5%. The second approach was performed using the amorphous area and the total area of the (1 1 0) peak from the experimental diffractogram, leading to 31.5%. The difference in crystallinity percentage concerning these two used approaches may be explained due to the first method does not consider the broad peaks resulted from nanocrystals diffraction. FTIR spectroscopy has evidenced a cellulose type II structure. SEM images showed micrometric sized fibers with ranged thicknesses. However, a new morphology of spherical nanostructures was observed on the type II matrix fibers. Thermal analysis suggests that the extracted cellulose have low thermal

In situ high-pressure measurement of crystal solubility by using neutron diffraction

Science.gov (United States)

Chen, Ji; Hu, Qiwei; Fang, Leiming; He, Duanwei; Chen, Xiping; Xie, Lei; Chen, Bo; Li, Xin; Ni, Xiaolin; Fan, Cong; Liang, Akun

2018-05-01

Crystal solubility is one of the most important thermo-physical properties and plays a key role in industrial applications, fundamental science, and geoscientific research. However, high-pressure in situ measurements of crystal solubility remain very challenging. Here, we present a method involving high-pressure neutron diffraction for making high-precision in situ measurements of crystal solubility as a function of pressure over a wide range of pressures. For these experiments, we designed a piston-cylinder cell with a large chamber volume for high-pressure neutron diffraction. The solution pressures are continuously monitored in situ based on the equation of state of the sample crystal. The solubility at a high pressure can be obtained by applying a Rietveld quantitative multiphase analysis. To evaluate the proposed method, we measured the high-pressure solubility of NaCl in water up to 610 MPa. At a low pressure, the results are consistent with the previous results measured ex situ. At a higher pressure, more reliable data could be provided by using an in situ high-pressure neutron diffraction method.

Diffraction study of the retained austenite content in TRIP steels

Energy Technology Data Exchange (ETDEWEB)

Gnaeupel-Herold, T., E-mail: tg-h@nist.gov [NIST Center for Neuron Research, 100 Bureau Dr., Gaithersburg MD 20899-6102 (United States); University of Maryland, Department of Material Science and Engineering., College Park MD 20742-2142 (United States); Creuziger, A., E-mail: adam.creuziger@nist.gov [NIST Metallurgy Division, 100 Bureau Dr., Gaithersburg MD 20899-8553 (United States); Kent State University, Kent, OH 44242 (United States)

2011-04-25

Research highlights: {yields} Novel orientation averaging scheme for retained austenite content measurement. {yields} assumption of random grain orientation generally not justified. {yields} Averaging scheme allows to disregard texture. {yields} unlike Rietveld method, averaging method does not orientation density function. {yields} Two independent (hkl) are necessary for retained austenite content. - Abstract: The results of a study of using neutron diffraction for determining the retained austenite content of TRIP steels are presented. The study covers a wide area of materials, deformation modes (uniaxial, biaxial and plane strain), strains, and the retained austenite content as a result of these variables. It was determined using basic principles of statistics that a minimum of two reflections (hkl) for each phase is necessary to calculate a phase mass fraction and the associated standard deviation. Texture from processing the steel is the largest source of uncertainty. Through the method of complete orientation averaging described in this paper, the texture effect and with it the standard deviation of the austenite mass fraction can be substantially reduced, regardless of the type or severity of the texture.

Structural and spectroscopic investigation of lanthanum-substituted ...

Indian Academy of Sciences (India)

Administrator

and one Y atom form two alternated equilateral triangles at level 1/4 and 3/4 centred on ..... Carpena et al observed that the localization of Nd. 3+ ions in the cationic sites depended ... Atomic coordinates, occupancy factors and thermal parameters after Rietveld refinement of Sr10–xLax(PO4)6–x. (SiO4)xO samples. Wyckoff.

Obtention and characterization of biodiesel; Obtencao e caracterizacao do biodiesel

Energy Technology Data Exchange (ETDEWEB)

Santos, Leonidas B.O. dos; Caitano, Moises; Aranda, Donato A.G.; Mothe, Cheila G. [Universidade Federal do Rio de Janeiro (UFRJ), RJ (Brazil)

2004-07-01

Biodiesel is an ester resulting from the transesterification reaction of an alcohol and an oil obtained from biomass. The products of the transesterification are an ester and the glycerol. The biodiesel and the petroleum commercial diesel have similar properties, and they can be mixed and used in diesel motors. The use of biodiesel will allow a better exploration of the energetic potential of our cultures. The biodiesel has some advantages compared to others combustibles, such as adaptability to usual diesel motors and non-generation of NO{sub x} and SO{sub x} compounds. Many experiments with biodiesel have been made in Brazil since the 70's. This work made samples of biodiesel by transesterification batch reactions to many blends of soybean oil and residual fry oil, at room temperature, using mechanical mixture or magnetic agitation by a magnetic stirrer, using as catalysts sodium methoxide and potassium hydroxide. For each obtained sample tests to determine the Acidity Index (ABNT-MB-74), Saponification Index (ABNT-MB-75), Iodine Wijz Index (ABNT-MB- 77), thermal analysis by DTA and TG (TA Instruments SDT 2960, 30 to 800 deg C, 10 deg C/min at nitrogen atmosphere) and rheological test (Haake RS 150 Rheo Stress rheometer) were done. (author)

Biopolymer chitin: extraction and characterization; Biopolimero quitina: extracao e caracterizacao

Energy Technology Data Exchange (ETDEWEB)

NONE

2011-07-01

The biopolymers are materials made from renewable sources such as soybean, corn, cane sugar, cellulose and chitin. Chitin is the most abundant biopolymer found in nature, after cellulose. The chemical structure of chitin is distinguished by the hydroxyl group, of structure from cellulose, located at position C-2, which in the chitin is replaced by acetamine group. The objective of this study was to develop the chitin from exoskeletons of Litopenaeus vannamei shrimp, which are discarded as waste, causing pollutions, environmental problems and thus obtain better utilization of these raw materials. It also, show the extraction process and deacetylation of chitosan. The extraction of chitin followed steps of demineralization, desproteinization and deodorization. Chitin and chitosan were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and the thermals properties were analyzed by thermogravimetry (TG/DTG). (author)

Energetic characterization of Amazonian biomass; Caracterizacao energetica de biomassas amazonicas

Energy Technology Data Exchange (ETDEWEB)

Feitosa Netto, Genesio Batista; Oliveira, Antonio Geraldo de Paula; Coutinho, Hebert Willian Martins; Nogueira, Manoel Fernandes Martins; Rendeiro, Goncalo [Universidade Federal do Para (UFPA), Belem, PA (Brazil). Dept. de Engenharia Mecanica

2006-07-01

In order to asses the potentiality of Amazon biomasses to generate power, either to supply electric energy to the grid or as fuel to plants supplying power for off-grid location, data for their proximate analysis must be available. A literature review on the subject indicated a lack of information and data concerning typical Amazon rain forest species. This work aimed to characterize (proximate analysis) 43 Amazon species in order to evaluate the energy resource from woody biomass wastes in Amazon region. Higher heating value, carbon, volatile and ash contents were measured in a dry basis. The measurements were performed obeying the following Brazilian standards, NBR 6923, NBR 8112, NBR 8633, NBR 6922. (author)

Rietveld analysis of phase separation in annealed and leach tested Cm-doped perovskite

International Nuclear Information System (INIS)

White, T.J.

1995-01-01

A quantitative powder X-ray diffraction study was made of actinide doped perovskite of bulk composition Ca 0.98919 An 0.98919 Al 0.01081 O 3 where An corresponded to approximately equimolar proportions of Cm-244 and Pu-240. Sections of this sample accumulated irradiation doses up to 7.51 x 10 17 alpha decay events per gram (α/g). The damaged samples were treated in two ways. First, to establish the critical temperature for structural recovery under the reducing conditions of geological repositories, isochronal annealing was carried out at 600, 800, 1,000 and 1,100 C for 12 hours in graphite crucibles. Two groups of perovskites that had previously sustained doses of 4.5 x 10 17 and 7.4 x 10 17 α/g were tested in this way. For the former group, these conditions resulted in up to 9 weight percent (wt%) of available actinide separating as a fluorite-type dioxide near the perovskite surface. In the latter group, calcium was reduced to the metal which vaporized, leaving an excess of refractory titanium that crystallized as rutile. Second, material which has sustained doses of 1.6--4.0 x 10 17 alpha decays per gram was subjected to an MCC-1 leach test for two months at 90 C using a pH ∼ 2 solution. Under these conditions surficial perovskite dissolved congruently to release calcium into solution while the titanium reprecipitated as anatase. The implications of these results for the ultimate disposal of perovskite-bearing polyphase nuclear waste ceramics are considered

Naphthenic acid characterization and distribution in crude oils; Caracterizacao e distribuicao de acidos naftenicos em petroleos

Energy Technology Data Exchange (ETDEWEB)

Guimaraes, Regina C.L.; Gomes, Alexandre de O. [PETROBRAS S.A., Rio de Janeiro, RJ (Brazil)

2008-07-01

Naphthenic acid corrosion was observed for the first time during the distillation process of some kind of crude oils in 1920. Recent reports about naphthenic acid corrosion have been found in China, India, Venezuela, Eastern Europe, Russia and the USA. In Brazil, heavy and acid crude oil processing is rising. Some brazilian crude oils have TAN around 3,0 mg KOH/g. The presence of relatively high levels of naphthenic acids in crude oils is a bane of petroleum refiners; and more recently, of producers as well, who have reported problems during production with calcium and sodium naphthenate . Essentially, these acids which are found to greater or lesser extent in virtually all crude oils are corrosive and tend to cause equipment failures, lead to high maintenance costs and may pose environmental disposal problems. In order to give these information to PETROBRAS, The Research and Development Center of PETROBRAS (CENPES) has been working in house and with brazilian universities developing analytical technicians to know better molecular structures and distribution of these acids compounds in crude oils. This work presents the actual methods and some results from these developments. (author)

Structural properties and hyperfine characterization of Sn-substituted goethites

Energy Technology Data Exchange (ETDEWEB)

Larralde, A.L. [INQUIMAE, Departamento de Quimica Inorganica, Analitica y Quimica Fisica, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires (Argentina); Ramos, C.P. [Departamento de Fisica de la Materia Condensada, GIyA - CAC - CNEA, Av. Gral. Paz 1499 (1650), San Martin, Bs. As. (Argentina); Arcondo, B. [Departamento de Fisica, Facultad de Ingenieria, Universidad de Buenos Aires, Av. Paseo Colon 850 (C1063ACV), Bs. As. (Argentina); Tufo, A.E. [INQUIMAE, Departamento de Quimica Inorganica, Analitica y Quimica Fisica, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires (Argentina); Saragovi, C. [Departamento de Fisica de la Materia Condensada, GIyA - CAC - CNEA, Av. Gral. Paz 1499 (1650), San Martin, Bs. As. (Argentina); Sileo, E.E., E-mail: sileo@qi.fcen.uba.ar [INQUIMAE, Departamento de Quimica Inorganica, Analitica y Quimica Fisica, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires (Argentina)

2012-04-16

Highlights: Black-Right-Pointing-Pointer Pure and tin-doped goethites were synthesized from Sn(II) solutions at ambient pressure and 70 Degree-Sign C. Black-Right-Pointing-Pointer The Rietveld refinement of PXRD data indicated that Sn partially substituted the Fe(III) ions. Black-Right-Pointing-Pointer The substitution provoked unit cell expansion, and a distortion of the coordination polyhedron. Black-Right-Pointing-Pointer {sup 119}Sn Moessbauer spectroscopy revealed that Sn(II) is incorporated as Sn(IV). Black-Right-Pointing-Pointer {sup 57}Fe Moessbauer spectroscopy showed a lower magnetic coupling as tin concentration increased. - Abstract: Tin-doped goethites obtained by a simple method at ambient pressure and 70 Degree-Sign C were characterized by inductively coupled plasma atomic emission spectrometry, scanning electron microscopy, Rietveld refinement of powder X-ray diffraction data, and {sup 57}Fe and {sup 119}Sn Moessbauer spectroscopy. The particles size and the length to width ratios decreased with tin-doping. Sn partially substituted the Fe(III) ions provoking unit cell expansion and increasing the crystallinity of the particles with enlarged domains that grow in the perpendicular and parallel directions to the anisotropic broadening (1 1 1) axis. Intermetallic E, E Prime and DC distances also change although the variations are not monotonous, indicating different variations in the coordination polyhedron. In general, the Sn-substituted samples present larger intermetallic distances than pure goethite, and the greatest change is shown in the E Prime distance which coincides with the c-parameter. {sup 119}Sn Moessbauer spectroscopy revealed that Sn(II) is incorporated as Sn(IV) in the samples. On the other hand, Fe(II) presence was not detected by {sup 57}Fe Moessbauer spectroscopy, suggesting the existence of vacancies in the Sn-doped samples. A lower magnetic coupling is also evidenced from the average magnetic hyperfine field values obtained as tin

On the role of Fe3+ ions in FexOy/C catalysts for hydrogen production from the photodehydrogenation of ethanol

International Nuclear Information System (INIS)

Galindo-Hernández, Félix; Wang, Jin-An; Chen, Lifang; Bokhimi, Xim; Gómez, Ricardo; Pérez-Larios, Alejandro; Nava Entzana, Noel

2013-01-01

Graphical abstract: In Fe x O y /C photocatalyts important effect of Fe 3+ ions in the photodehydrogenation of the ethano was noticed. -- Highlights: • Iron oxides supported on carbon are photoactive catalysts. • Photoactivity in dehydrogenation of ethanol depends of the amount of Fe 3+ ions present in the catalysts. • The capacity of UV–vis absorbance by the Fe x O y /C catalysts is significantly dependent of the amount of Fe 3+ ions. • A maximum of rate constant, K = 2125 μmol h −1 , was obtained from the sample with 30 wt% Fe. -- Abstract: Fe x O y /C photocatalysts at different iron content were prepared by the incipient wet impregnation method and calcined at 773 K. The photocatalysts were characterized by means of nitrogen adsorption–desorption isotherms, surface fractal dimension, non-local density functional theory, X-ray diffraction, Rietveld refinement and UV–vis spectroscopy. The photocatalytic activity was evaluated using the photodehydrogenation of ethanol as a model reaction for the production of hydrogen. The specific surface areas of Fe x O y /C substrates, with 15, 20 and 30 wt% iron content, diminished from 638 to 490 m 2 /g, as the iron content increased. X-ray diffraction analysis showed that iron oxides coexist as wustite and magnetite in samples with Fe contents of 15 and 20 wt%; for sample with 30 wt% Fe, wustite, magnetite and hematite phases were observed. The photophysical, textural and structural properties were modified by the hematite phase formed by thermal treatment. The Rietveld refinements denoted changes in occupancy of Fe 3+ and Fe 2+ in Fe x O y crystallites. A relationship between the Fe 3+ ions content and the reactivity for the hydrogen production from the photodehydrogenation of ethanol (from 1360 to 2125 μmol h −1 ), was evidenced

Temperature-dependent evolution of RbBSi2O6 glass into crystalline Rb-boroleucite according to X-ray diffraction data

International Nuclear Information System (INIS)

Levin, Aleksandr A.; Filatov, Stanislav K.; Krzhizhanovskaya, Maria G.; Paufler, Peter; Bubnova, Rimma S.; Russian Academy of Sciences, St. Petersburg; Meyer, Dirk C.; Technische Univ. Bergakademie Freiberg

2013-01-01

The temperature-dependent evolution of the glass into a crystalline phase is studied for a rubidium borosilicate glass of composition 16.7 Rb 2 O . 16.7 B 2 O 3 . 66.6 SiO 2 employing X-ray diffraction (XRD) data. A glass sample was prepared by melt quenching from 1500 within 0.5 hour. The glass sample was step-wise annealed at 13 distinct temperatures from 300 C up to 900 C for 1 h at every annealing step. To investigate changes in the glass structure, angle-dispersive XRD was applied by using an energy-resolving semiconductor detector. The radial distribution functions (RDFs) were calculated at every stage. For polycrystalline states the crystal structure of the samples with different thermal history was refined using the Rietveld method. Comparing correlation distances estimated from RDFs of glass and polycrystalline samples and mean interatomic distances calculated for polycrystalline samples by using atomic coordinates after Rietveld refinement, it is concluded that the borosilicate glass under study is converted into the crystalline state in the temperature range of 625-750 C (i.e. in the temperature range close to the glass transition range 620-695 C as determined by differential scanning calorimetry by using of heating rate of 20 K/min) at an average heating rate of about 0.35 K/min. When the heating rate is increased up to 10 or 20 K/min, the crystallisation temperature shifts sharply up to 831-900 C and 878-951 C, respectively. XRD data give evidence that distinctive traces of cubic RbBSi 2 O 6 appear from glass at about 625 C and a two-phase range exists up to 750 C. After annealing at higher temperatures (800-900 C) the crystal structure practically does not change any more. (orig.)

Site preference of rare earth doping in palladium-iron-arsenide superconductors

Energy Technology Data Exchange (ETDEWEB)

Stuerzer, Christine; Schulz, Anne; Johrendt, Dirk [Department Chemie, Ludwig-Maximilians-Universitaet Muenchen (Germany)

2014-12-15

The solid solutions (Ca{sub 1-y}RE{sub y}Fe{sub 1-x}Pd{sub x}As){sub 10}Pd{sub z}As{sub 8} with RE = La, Ce, and Pr were synthesized by solid state methods and characterized by X-ray powder diffraction with subsequent Rietveld refinements [(CaFeAs){sub 10}Pt{sub 3}As{sub 8}-type structure (''1038 type''), P anti 1, Z = 1]. Substitution levels (Ca/RE, Fe/Pd, and Pd/□) obtained from Rietveld refinements coincide well with the nominal values according to EDS and the linear courses of the lattice parameters as expected from the ionic radii. The RE atoms favor the one out of five calcium sites, which is eightfold coordinated by arsenic. This leads to significant stabilization of the structure, and especially prevents palladium over-doping in the iron-arsenide layers as observed in the pristine compound (CaFe{sub 1-x}Pd{sub x}As){sub 10}Pd{sub z}As{sub 8}. While the stabilization energy is estimated to about 40 kJ.mol{sup -1} by electronic structure calculations, the reason for the diminished Fe/Pd substitution through RE doping is still not yet understood. We suggest that the electrons transferred from RE{sup 3+} to the (Fe{sub 1-x}Pd{sub x})As layer makes higher palladium concentrations unfavorable. Anyway the reduced palladium doping enables superconductivity with critical temperatures up to 20 K (onset) in the RE doped Pd1038 samples, which could not be obtained earlier due to palladium over-doping in the active iron-arsenide layers. (Copyright copyright 2014 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

Green mediated synthesis and characterization of ZnO nanoparticles using Euphorbia Jatropa latex as reducing agent

Directory of Open Access Journals (Sweden)

M.S. Geetha

2016-09-01

Full Text Available Presently the progress of green chemistry in the synthesis of nanoparticles with the use of plants has engrossed a great attention. This study reports the synthesis of ZnO using latex of Euphorbia Jatropa as reducing agent. As prepared product was characterized by powder X-ray diffractometer (PXRD, Fourier transform infra-red spectroscopy (FTIR, scanning electron microscopy–energy dispersive spectroscopy (SEM–EDS, transmission electron microscopy (TEM, X-ray photo electron spectroscopy (XPS, Rietveld refinement, UV–Visible spectroscopy and photoluminescence (PL. The concentration of plant latex plays an important role in controlling the size of the particle and its morphology. PXRD graphs showed the well crystallisation of the particles. The average particle size was calculated using Scherrer equation and advanced Williamson Hall (WH plots. The average particle size was around 15 nm. This result was also supported by SEM and TEM analyses. FTIR shows the characteristic peak of ZnO at 435 cm−1. SEM and TEM micrographs show that the particles were almost hexagonal in nature. EDS of SEM analysis confirmed that the elements are only Zn and O. EDS confirmed purity of ZnO. Atomic states were confirmed by XPS results. Crystal parameters were determined using Rietveld refinement. From UV–Visible spectra average energy gap was calculated which is ∼3.63 eV. PL studies showed UV emission peak at 392 nm and broad band visible emission centred in the range 500–600 nm. The Commission International de I'Eclairage and colour correlated temperature coordinates were estimated for ZnO prepared using 2 ml, 4 ml and 6 ml Jatropa latex. The results indicate that the phosphor may be suitable for white light emitting diode (WLED. The study fruitfully reveals simple, fast, economical and eco friendly method of synthesis of multifunctional ZnO nanoparticles (Nps.

Effect of laser welding parameters on the austenite and martensite phase fractions of NiTi

Energy Technology Data Exchange (ETDEWEB)

Oliveira, J.P., E-mail: jp.oliveira@campus.fct.unl.pt [CENIMAT/i3N, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa (Portugal); Braz Fernandes, F.M. [CENIMAT/i3N, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa (Portugal); Miranda, R.M. [UNIDEMI, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa (Portugal); Schell, N. [Institute of Materials Research, Helmholtz-Zentrum Geesthacht, Max-Planck-Str. 1, D-21502 Geesthacht (Germany); Ocaña, J.L. [Centro Láser UPM, Universidad Politécnica de Madrid, Edificio “La Arboleda”, Ctra. Valencia, km 7,300, Campus Sur UPM, 28031 Madrid (Spain)

2016-09-15

Although laser welding is probably the most used joining technique for NiTi shape memory alloys there is still a lack of understanding about the effects of laser welding parameters on the microstructural induced changes: in both the heat affected and fusion zones martensite may be present, while the base material is fully austenitic. Synchrotron X-ray diffraction was used for fine probing laser welded NiTi joints. Through Rietveld refinement the martensite and austenite phase fractions were determined and it was observed that the martensite content increases towards the weld centreline. This is related to a change of the local transformation temperatures on these regions, which occurs due to compositional variation in those regions. The martensite phase fraction in the thermally affected regions may have significant implications on functional properties on these joints. - Highlights: •Synchrotron X-ray diffraction was used for fine probing of the microstructure in laser welded NiTi joints. •Rietveld refinement allowed to determine the content of martensite along the heat affected and fusion zones. •The martensite content increases from the base material towards the weld centreline.

Crystallographic parameters of magnetic Pr{sub 2}Fe{sub 14−x}Co{sub x}B-type alloys determined using anomalous x-ray diffraction with synchrotron radiation

Energy Technology Data Exchange (ETDEWEB)

Galego, E., E-mail: egalego@ipen.br; Serna, M.M.; Ramanathan, L.V.; Faria, R.N.

2017-02-15

Anomalous x-ray synchrotron diffraction was used to determine the crystallographic parameters of PrFeCoB-based magnetic alloys. The effect of cobalt concentration on the crystallographic parameters of the magnetically hard Pr{sub 2}Fe{sub 14−x}Co{sub x}B phase was studied. The results indicate that addition of cobalt has a marked effect on crystal structure. Variation of the c parameter decreased twice as much as the a parameter with increase in Co content. The positions of inequivalent atoms of the magnetically hard matrix phase ϕ in the Pr-based alloys were determined using Rietveld refinement. This permitted determination of the relative distance of each inequivalent atom from its nearest neighbors. Cobalt occupied the 16k{sub 2} site and Fe had a tendency to occupy the 8j{sub 2} sites located between the Kagomé layers. - Highlights: • Good magnetics properties can be achieved with addition of 4% and 8% Co. • Rietveld refinement is proposed for crystallographic parameters studies. • Co has preference to substitute Fe in 16k{sub 2} site and avoid the 8j{sub 2} site.

Mn"4"+-activated BaSiF_6 red phosphor: Hydrothermal synthesis and dependence of its luminescent properties on reaction conditions

International Nuclear Information System (INIS)

Zhou, Qiang; Zhou, Yayun; Lu, Fengqi; Liu, Yong; Wang, Qin; Luo, Lijun; Wang, Zhengliang

2016-01-01

In this work, a series of BaSiF_6:Mn"4"+ red phosphors were synthesized through a hydrothermal route. The crystal structure and morphology were characterized by powder X-ray diffraction (XRD) with Rietveld refinement, scanning electron microscopy (SEM), and energy dispersive spectrometer (EDS) in detail. The influence of reaction conditions, including the concentration of KMnO_4 and HF, reaction temperature and time, on the photoluminescence properties were investigated systematically. It can emit intense red light (∼636 nm) under blue light (∼458 nm) illumination. The white LED device based on YAG:Ce–BaSiF_6:Mn"4"+ mixture shows warm white light with low color temperature and high correlated color index, which reveals its potential application in WLED. - Highlights: • The crystal structure of BaSiF_6:Mn"4"+ has been verified using Rietveld refinement. • The optimum hydrothermal reaction condition for BaSiF_6:Mn"4"+ has been confirmed. • The white LED based on YAG:Ce–BaSiF_6:Mn"4"+ mixture presents warmer white light than that only with YAG:Ce.

Mn{sup 4+}-activated BaSiF{sub 6} red phosphor: Hydrothermal synthesis and dependence of its luminescent properties on reaction conditions

Energy Technology Data Exchange (ETDEWEB)

Zhou, Qiang; Zhou, Yayun [Key Laboratory of Comprehensive Utilization of Mineral Resources in Ethnic Regions, Joint Research Centre for International Cross-border Ethnic Regions Biomass Clean Utilization in Yunnan, School of Chemistry & Environment, Yunnan Minzu University, Kunming, 650500 (China); Lu, Fengqi [MOE Key Laboratory of New Processing Technology for Nonferrous Metals and Materials, College of Materials Science and Engineering, Guilin University of Technology, Guilin, 541004 (China); Liu, Yong [Key Laboratory of Comprehensive Utilization of Mineral Resources in Ethnic Regions, Joint Research Centre for International Cross-border Ethnic Regions Biomass Clean Utilization in Yunnan, School of Chemistry & Environment, Yunnan Minzu University, Kunming, 650500 (China); Wang, Qin [College of Chemistry and Chemical Engineering, Yunnan Normal University, Kunming, Yunnan, 650500 (China); Luo, Lijun [Key Laboratory of Comprehensive Utilization of Mineral Resources in Ethnic Regions, Joint Research Centre for International Cross-border Ethnic Regions Biomass Clean Utilization in Yunnan, School of Chemistry & Environment, Yunnan Minzu University, Kunming, 650500 (China); Wang, Zhengliang, E-mail: wangzhengliang@foxmail.com [Key Laboratory of Comprehensive Utilization of Mineral Resources in Ethnic Regions, Joint Research Centre for International Cross-border Ethnic Regions Biomass Clean Utilization in Yunnan, School of Chemistry & Environment, Yunnan Minzu University, Kunming, 650500 (China)

2016-02-15

In this work, a series of BaSiF{sub 6}:Mn{sup 4+} red phosphors were synthesized through a hydrothermal route. The crystal structure and morphology were characterized by powder X-ray diffraction (XRD) with Rietveld refinement, scanning electron microscopy (SEM), and energy dispersive spectrometer (EDS) in detail. The influence of reaction conditions, including the concentration of KMnO{sub 4} and HF, reaction temperature and time, on the photoluminescence properties were investigated systematically. It can emit intense red light (∼636 nm) under blue light (∼458 nm) illumination. The white LED device based on YAG:Ce–BaSiF{sub 6}:Mn{sup 4+} mixture shows warm white light with low color temperature and high correlated color index, which reveals its potential application in WLED. - Highlights: • The crystal structure of BaSiF{sub 6}:Mn{sup 4+} has been verified using Rietveld refinement. • The optimum hydrothermal reaction condition for BaSiF{sub 6}:Mn{sup 4+} has been confirmed. • The white LED based on YAG:Ce–BaSiF{sub 6}:Mn{sup 4+} mixture presents warmer white light than that only with YAG:Ce.

Electrical characterization of zirconia-niobium and zirconia-titanium composites; Caracterizacao eletrica dos compositos zirconia-niobio e zirconia-titanio

Energy Technology Data Exchange (ETDEWEB)

Reis, S.T. dos

1994-12-31

Zirconia-niobium and zirconia-titanium composites were made by powder mixing, cold pressing, and vacuum sintering at 1600{sup 0} C. The metallic particles were added in the proportion of 0-50% by volume. Electrical resistivity measurements were performed by the two probes and the four probes d.c. method as a function of metallic particle concentration. Electrical resistivity of these composites decreased sharply in the region of 30-40 vol% Nb or Ti, in agreement with the percolation theory. Tests in an induction furnace were performed to check the self-heating response of these composites. (author). 33 refs, 40 figs, 11 tabs.

Preparation, characterization and certification of uranium isotope reference materials; Preparacao, Caracterizacao e certificacao de materiais de referencia isotopicos de uranio

Energy Technology Data Exchange (ETDEWEB)

Oliveira Junior, Olivio Pereira de

2006-07-01

This work describes the preparation, characterization and certification of a set of uranium isotope reference materials ranging from 0.5 to 20.0 % of {sup 235}U in mass. The most important concepts of metrology in chemical measurements were applied so that the certified quantities in these materials could be directly traceable to the International System of Units (SI). As a consequence of this approach, these materials can be used in the instruments calibration, estimation of measurement uncertainty, method validation, assessment of performance of analysts, quality control routines and interlaboratory comparison programmes. The most advanced methods and techniques in mass spectrometry, that is, gas source mass spectrometry (GSMS), thermal ionisation mass spectrometry (TIMS) and inductively coupled plasma mass spectrometry (ICPMS) were investigated to identify which are the dominant components in the uncertainty and to quantify its contribution to the final value of the measurement uncertainty of the isotopic ratio. The results obtained were then compared to verify which are the methods and techniques associated to the lowest measurement uncertainty values. The isotope amount ratio n({sup 235}U)/n({sup 238}U) was certified in the materials produced to expanded uncertainties ranging from 0.02 to 0.10 % and the ratios n({sup 234}U)/n({sup 238}U) and n({sup 236}U)/n({sup 238}U), to uncertainties ranging from 0.03 to 2.20 %. These values fully comply to the requirements of the isotopic characterization of nuclear fuel as well as the analysis of environmental samples for nuclear safeguards. (author)

Solvothermal growth of a ruthenium metal-organic framework featuring HKUST-1 structure type as thin films on oxide surfaces.

Science.gov (United States)

Kozachuk, Olesia; Yusenko, Kirill; Noei, Heshmat; Wang, Yuemin; Walleck, Stephan; Glaser, Thorsten; Fischer, Roland A

2011-08-14

Phase-pure crystalline thin films of a mixed-valence Ru(2)(II,III) metal-organic framework with 1,3,5-benzenetricarboxylate (btc) as a linker were solvothermally grown on amorphous alumina and silica surfaces. Based on the Rietveld refinement, the structure of Ru-MOF was assigned to be analogous to [Cu(3)(btc)(2)] (HKUST-1). This journal is © The Royal Society of Chemistry 2011

Qualitative study the effect of conditions milling of 95.5Sn/4.0Ag/0.5Cu, (wt%) nanopowder; Estudo qualitativo do efeito das condicoes de moagem de alta energia da liga Sn-4,0Ag-0,5Cu (% peso)

Energy Technology Data Exchange (ETDEWEB)

Manzato, L., E-mail: lizandro@ifam.edu.b [Instituto Federal de Educacao, Ciencia e Tecnologia do Amazonas (IFAM/CMDI), Manaus, AM (Brazil). Campus Manaus Distrito Industrial; Anglada-Rivera, J. [Instituto Federal de Educacao, Ciencia e Tecnologia do Amazonas (IFAM/CMC), Manaus, AM (Brazil). Campus Manaus Centro; Oliveira, M.F. de [Universidade de Sao Paulo (EESC/USP), Sao Carlos, SP (Brazil). Escola de Engenharia

2010-07-01

The SAC-405, Sn-4.0Ag-0.5Cu (wt%) nanopowders, which has potential applications in microelectronics, such as lead-free solder, were obtained by high energy milling. The purpose of this study was to investigate the structural changes of the SAC-405 produced by high energy milling with times of 12, 24 and 48, under an atmosphere of hydrogen and power grinding 40:1. The crystallite size and micro-deformations of the nanopowders was measured by X-ray diffraction (XRD) using Rietveld method. Preliminary results show that it is possible to obtain nanopowders by mechanical alloying for the SAC-405 alloy with average particle size of 10 {approx} 18 nm. There are also strong indications of a reduction of {approx} 7 deg C melting temperature of the dust that is characteristic of nano-sized particles. (author)

Structure of La2Cu2O5 by high-resolution synchrotron X-ray powder diffraction

International Nuclear Information System (INIS)

La Placa, S.J.; Bringley, J.F.; Scott, B.A.; Cox, D.E.

1993-01-01

Dicopper(II) dilanthanum pentaoxide, La 2 Cu 2 O 5 , M r =484.90, orthorhombic, Pbam. At T=300 K: a=5.5490(1), b=10.4774(2), c=3.8796(1) A, V=225.557(8) A 3 , Z=2, D x =7.139 g cm -3 , λ=1.2000 A. Final R I =6.20, R p =14.6 and R wp =20.61%, 124 independent reflections observed. The structure has been refined from high-resolution synchrotron X-ray powder diffraction data using the Rietveld method. It is of the oxygen-defect perovskite type and is composed entirely of corner-shared CuO 5 square pyramids, which share oxygen vacancies forming vacancy tunnels along the c axis. The La atoms reside at a perovskite-like A-site and are tenfold coordinated by oxygen. (orig.)

Synthesis and characterization of Sm0.5Ba0.5MnO3-δ as anode materials for solid oxide fuel cells

International Nuclear Information System (INIS)

Abdalla, A. M.; Radenahmad, N.; Bakar, M. S. Abu; Petra, Pg M .I.; Azad, A. K.

2016-01-01

The material performance is a crucial issue in the current fuel cell technology, and for this reason we present this new series of Samarium family which can be used as electrode giving a high performance in a particular application. Sm 0 . 5 Ba 0 . 5 MnO 3-δ was prepared by solid state reaction method and characterized by using X-ray diffraction (XRD), and thermogravimetric analysis (TGA). Rietveld analysis of XRD data shows that the material has an Orthorhombic crystal structure with cell parameter a = 3.883(1) Å b = 3.8742(5) Å c = 7. 762(4) Å, in the Pmmm space group. TGA analyses shows that the materials is going to decrease by 0.32%. The density of the materials was calculated from structural refinement and found to be 8.372 gm/cm 3 . (paper)

Qualitative study the effect of conditions milling of 95.5Sn/4.0Ag/0.5Cu, (wt%) nanopowder

International Nuclear Information System (INIS)

Manzato, L.; Anglada-Rivera, J.; Oliveira, M.F. de

2010-01-01

The SAC-405, Sn-4.0Ag-0.5Cu (wt%) nanopowders, which has potential applications in microelectronics, such as lead-free solder, were obtained by high energy milling. The purpose of this study was to investigate the structural changes of the SAC-405 produced by high energy milling with times of 12, 24 and 48, under an atmosphere of hydrogen and power grinding 40:1. The crystallite size and micro-deformations of the nanopowders was measured by X-ray diffraction (XRD) using Rietveld method. Preliminary results show that it is possible to obtain nanopowders by mechanical alloying for the SAC-405 alloy with average particle size of 10 ∼ 18 nm. There are also strong indications of a reduction of ∼ 7 deg C melting temperature of the dust that is characteristic of nano-sized particles. (author)

The Effect of Multiple Shot Peening on the Corrosion Behavior of Duplex Stainless Steel

Science.gov (United States)

Feng, Qiang; She, Jia; Wu, Xueyan; Wang, Chengxi; Jiang, Chuanhai

2018-03-01

Various types of shot peening treatments were applied to duplex stainless steel. The effects of shot peening intensity and working procedures on the microstructure were investigated. The domain size and microstrain evolution in the surface layer were characterized utilizing the Rietveld method. As the shot peening intensity increased, the surface roughness increased in the surface layer; however, it decreased after multiple (dual and triple) shot peening. The mole fraction of strain-induced martensite as a function of the intensity of shot peening was evaluated by XRD measurements. Both potentiodynamic polarization curves and salt spray tests of shot-peened samples in NaCl solution were investigated. The results indicate that traditional shot peening has negative effects on corrosion resistance with increasing shot peening intensity; however, the corrosion rate can be reduced by means of multiple shot peening.

Formation and quantification of calcium titanate with the perovskite structure from alternative sources of titanium

International Nuclear Information System (INIS)

Gralik, G.; Raupp-Pereira, F.; Hotza, D.; Labrincha, J.A.; Zanelli, C.; Dondi, M.

2014-01-01

This study aimed to evaluate and quantify the formation of calcium titanate (CaTiO3) with perovskite structure from alternative sources of titanium (rutile, ilmenite). Commercial raw materials of the high purity were also characterized as reference. With base in the characterization by X-ray fluorescence of the mineral springs different compositions were formulated and subsequently sintered for 2 h in resistive furnace at temperatures in the range 1000 to 1400°C. After thermal processing the samples were analyzed by X-ray diffraction and the quantification of phases formed by the Rietveld method obtained. The results show that the formation and the amount of calcium titanate minerals from alternative sources depend on factors related to stages of sintering and impurities. The microstructures of the compositions were analyzed by SEM/EDS and bulk density also measured. (author)

Neutron scattering studies of nuclear and magnetic structures of YBa2(Cu1-yZny)3O6+x

International Nuclear Information System (INIS)

Villeneuve, R.; Mirebeau, I.; Collin, G.; Bouree, F.

1994-01-01

Structural effects of zinc substitution in YBCO have been studied by neutron diffraction in order to determine the substitution site of zinc atoms. Electron neutron diffraction experiments are performed on YBa 2 (Cu 1-y Zn y ) 3 O 6+x powders. Nuclear structures have been refined using the Rietveld method on powders of compositions x=1 and y ranging from 0.01 to 0.06. The results suggest a solubility limit of zinc in the copper planes at y ≅ 0.04 and zinc may start to substitute for chain copper sites for higher y values. Magnetic structure of a y=0.02 and x=0.05 powder has been studied by neutron elastic diffraction. The antiferromagnetic structure is not affected by non-magnetic zinc atoms but the ordering temperature is strongly reduced. 2 figs., 11 refs

Size Tunable Synthesis of Highly Crystalline BaTiO3 Nanoparticles using Salt-Assisted Spray Pyrolysis

International Nuclear Information System (INIS)

Itoh, Yoshifumi; Lenggoro, I. Wuled; Okuyama, Kikuo; Maedler, Lutz; Pratsinis, Sotiris E.

2003-01-01

Highly crystalline, dense BaTiO 3 nanoparticles in a size range from 30 to 360nm with a narrow size distribution (σ g = 1.2-1.4) were prepared at various synthesis temperatures using a salt-assisted spray pyrolysis (SASP) method without the need for post-annealing. The effect of synthesis temperature on particle size, crystallinity and surface morphology of the nanoparticles were characterized by X-ray diffraction and scanning/transmission electron microscopy. The nature of the crystalline structure was analyzed by Rietveld refinement and Raman spectroscopy. The particle size decreased with decreasing operation temperature. The crystal phase was transformed from tetragonal to cubic at a particles size of about 50nm at room temperature. SASP can be used to produce high weight fraction of tetragonal BaTiO 3 nanoparticles down to 64nm in a single step

Study on the piezoelectric behavior and structural changes of strontium doped PZT

International Nuclear Information System (INIS)

Silva, M.S. da; Lemos, L.; Souza, E.F.; Cavalheiro, A.A.; Longo, E.; Zaghete, M.A.

2014-01-01

Lead zirconate titanate, with Zr/Ti ratio of 53/47 was prepared by the polymeric precursor method. The powders were doped with 0.0, 0.2, 0.4 and 0.6 mol% of Sr 2+ and the effects of Sr 2+ additions on piezoelectric properties and on the phase constitution were investigated by XRD. The percentages of tetragonal and rhombohedral phases were calculated through Rietveld refinement. The results indicated that addition of Sr 2+ ions in the amount of 0.4 mol% in the ceramic structure maximally increase the values of piezoelectric parameter to d 33 = 289 μC/N and K p = 0.43. The values found for the piezoelectric properties were among the highest at the concentration of 0.4 mol% of strontium and this composition showed the highest structural change from the rhombohedral to the tetragonal phase perovskita. (author)

Preparation and characterization of the fish reference material; Preparacao e caracterizacao de um material de referencia de peixe

Energy Technology Data Exchange (ETDEWEB)

Ulrich, Joao Cristiano

2011-07-01

The certified reference materials (CRMs) play an important role in obtaining measurement results traceable to the International System of Units, through an unbroken chain of comparisons. Thus, the demand for new certified reference materials (CRMs) increases every day in all areas of knowledge. The availability of reference materials, mainly in Brazil is still incipient, given that the demand far exceeds the available variety of these materials. The amount of certified reference materials available in the country is insufficient to meet the need of the scientific community and demands for development of new methodologies. Among the many areas in need of reference materials, we highlight the importance for the food trade balance for these products within the country. The certification of food products, intended both for export and for domestic consumption, requires analysis methods that provide precise and accurate results to ensure product quality. This paper describes the preparation and certification of a reference material in the fish matrix in mercury and methylmercury. The study brings together since the stage of material selection, preparation, development of homogeneity and stability studies and characterization. The certification was performed by means of measurements using two analytical techniques, flow injection analysis - cold vapor atomic absorption spectrometry (FIA-CV-AAS) and isotope dilution applied to mass spectrometry (IDMS), which is a primary method. In this work the standards of the ISO 30 (ABNT 30-34) and ISO Guide 35 was used as the basis for the preparation and characterization of the material. For the calculation of uncertainties was used the GUM and Eurachem guide. As a result, was produced and certified a lot of material in relation to the concentration of mercury (Hg = 0.271 {+-} 0.057 mg g{sup -1}) and methylmercury (MeHg = 0.245 {+-} 0.038 mg g{sup -1}), and informational values of lead and arsenic. (author)

Chemistry characterization and samples beryllium process impurity determination; Caracterizacao quimica e determinacao de impurezas de amostras de processo de berilio

Energy Technology Data Exchange (ETDEWEB)

Carvalho, Leonel Mathry de

1992-12-01

Brazil is the greatest world producer of beryl (3 Be O.Al{sub 2}O{sub 3}.6SiO{sub 2}) and has recently begun to produce beryllium compounds by means of a pilot plant constructed at Governador Valadares city (Minas Gerais - Brazil). The aim of this work was the determination of trace level impurities and macro constituents in the tenth % range to support analytical control process of plant production and characterization of beryllium compounds. The impurities separations and purification process was developed by two steps procedure. The first one using EDTA complexation has separated and reduced some impurities to less than 1 {mu}g/ml level. In the second one it was used a chelating resin (Chelex 100) and the separation efficiency was about 75 to 97 % related with the element tested. High pure berylium oxide standard was obtained from purification of Be(OH)2. The R X fluorescence presented only traces of Cu and Si < 1 % Fe and Mn, Zn, Ca, Al, Na and S were completely removed. The beryllium content was determined by direct atomic emission spectroscopy in argon plasma (Dcp) and compared with classic gravimetric method as Be O. The results were in agreement (49,2+/-0,2 % and 48,3+/-0,1 % respectively) between 95 % of confidence. A low temperature gravimetric method for beryllium determination was also studied using Oxine with microwave furnace. A total of 24 elements including macro and trace level were determined by Dcp and/or spectrophotometric methods. The Be/B separation was studied using anionic resin in poly alcohols medium. A more detailed study of equilibrium conditions is necessary. This work was realized at Laboratorio de Analise Mineral (LAM) of Comissao Nacional de Energia Nuclear - Rio de Janeiro (CNEN). (author)

Development and characterization of the lead iodide semiconductor detector; Desenvolvimento e caracterizacao do detector semicondutor de iodeto de chumbo

Energy Technology Data Exchange (ETDEWEB)

Oliveira, Icimone Braga de

2001-07-01

A methodology for purification and growth of PbI{sub 2} crystal as well as for its characterization as a room temperature radiation detector was developed in this work. Commercial salts were purified using the zone refining method and, for the purified material growth, the Bridgman method was used. To calculate the purification efficiency, studies of the decrease impurities concentrations were made in the salts and in three sections of the materials purified, using the neutron activation analysis technique. The results showed that the impurities segregate preferentially in the ingot final section. A significant decrease of the impurities concentration in function of the purification pass number was observed. The grown crystals presented good crystalline quality according to the results of the X-ray diffraction analysis. To evaluate the crystal as a semiconductor detector, measurements of dark leakage current, resistivity and the response of ({sup 241}Am) alpha particle and ({sup 241}Am, {sup 57}Co, {sup 133}Ba and {sup 137}Cs) gamma rays were carried out. The radiation response is strongly dependent on the crystals purity. The crystals purified with 500 passes exhibited energy resolution of 10% for {sup 241} Am alpha particle and the gamma rays resolution was compatible with the literature. The photosensibility of the PbI{sub 2} crystal found in the wavelength from 400 to 600 nm range suggests an another application at this crystal as a photodetector to be coupled to scintillators. (author)

Optimization of synthesis technique and luminescent properties in Eu{sup 3+}-activated NaCaPO{sub 4} phosphor for solid state lighting applications

Energy Technology Data Exchange (ETDEWEB)

Ratnam, B.V. [Department of Physics, Changwon National University, Changwon 51140 (Korea, Republic of); Sahu, Mukesh K.; Vishwakarma, Amit K.; Jha, Kaushal [Luminescent Materials Research Lab (LMRL), Department of Applied Physics, Delhi Technological University, Delhi 110042 (India); Woo, Hyun-Joo [Department of Physics, Changwon National University, Changwon 51140 (Korea, Republic of); Jang, Kiwan, E-mail: kwjang@changwon.ac.kr [Department of Physics, Changwon National University, Changwon 51140 (Korea, Republic of); Jayasimhadri, M., E-mail: jayaphysics@yahoo.com [Luminescent Materials Research Lab (LMRL), Department of Applied Physics, Delhi Technological University, Delhi 110042 (India)

2017-05-15

Europium activated NaCaPO{sub 4} phosphor has been synthesized by various synthesis techniques such as solid-state reaction (SSR), molten salt synthesis (MSS) and sol-gel combustion (SGC) method to optimize the synthesis procedure. The comparative investigations of structural and luminescent properties have been studied to know the best synthesis method. The XRD patterns and Rietveld refinement analysis of the synthesized phosphors confirmed the single phase orthorhombic structure of NaCaPO{sub 4}. Excitation spectra indicate the strong absorption in near ultraviolet (n-UV) region and the emission spectra exhibit strong emission band at 595 nm corresponds to {sup 5}D{sub 0}→{sup 7}F{sub 1} transition under n-UV (λ{sub ex}=392 nm) excitation. The SGC route synthesized phosphor exhibit intense emission than that of the SSR and MSS method. Therefore, the effect of dopant (Eu{sup 3+}) concentration on the emission intensity and concentration quenching mechanism has been discussed in detail for the Eu{sup 3+} doped NaCaPO{sub 4} phosphor synthesized by SGC method. The CIE chromaticity coordinates have been calculated for the phosphors synthesized by SSR, MSS and SGC methods to reveal the emitting color and also to know the utility of this phosphor for white LEDs.

Investigation of structural and magnetic properties of Ni{sub 0.5}Zn{sub 0.5}Fe{sub 2}O{sub 4} nano powders prepared by self combustion method

Energy Technology Data Exchange (ETDEWEB)

Sudheesh, V.D.; Nehra, J.; Vinesh, A. [Department of Physics, Mohanlal Sukhadia University, Udaipur 313001, Rajasthan (India); Sebastian, V. [Department of Physics, Nirmalagiri College, Kuthuparamba 670701, Kerala (India); Lakshmi, N., E-mail: nambakkat@yahoo.com [Department of Physics, Mohanlal Sukhadia University, Udaipur 313001, Rajasthan (India); Dutta, Dimple P. [Chemistry Division, Bhabha Atomic Research Centre, Mumbai 400085 (India); Reddy, V.R. [UGC-DAE CSR, University Campus, Khandwa Road, Indore 452001, M.P. (India); Venugopalan, K. [Department of Physics, Mohanlal Sukhadia University, Udaipur 313001, Rajasthan (India); Gupta, Ajay [UGC-DAE CSR, University Campus, Khandwa Road, Indore 452001, M.P. (India)

2013-02-15

Graphical abstract: Display Omitted Highlights: ► Ni{sub 0.5}Zn{sub 0.5}Fe{sub 2}O{sub 4} prepared by self combustion with uniform/nonuniform heating. ► Characterized using TEM, XRD, in-field Mössbauer and DC magnetometry. ► Leads to bimodal (S1) and very narrow size distribution (S2) type nano samples. ► S1 has magnetic properties of bulk Ni{sub 0.5}Zn{sub 0.5}Fe{sub 2}O{sub 4}. ► Although very even sized, S2 large magnetic anisotropy distribution. -- Abstract: Nano powders of Ni{sub 0.5}Zn{sub 0.5}Fe{sub 2}O{sub 4} have been synthesized by the self-combustion method at a relatively low temperature of 473 K under conditions of non-uniform and uniform heating. Rietveld fitting of X-ray diffractograms confirm the formation of the pure spinel phase in both samples. Transmission electron microscopy indicates that the sample prepared under non-uniform heating has a bimodal particle size distribution (average values 16 nm and 6 nm) while the one prepared under uniform heating has a very narrow particle size distribution (average size 4 nm). Low temperature, in-field Mössbauer spectroscopic studies clearly show surface spin contributions. The hyperfine fields and Curie temperature of the non-uniformly heated sample are in good agreement with those reported for the corresponding bulk samples. Despite having a very narrow particle size distribution, the uniformly heated sample has a large anisotropy distribution which is evident in the broad transition visible in the temperature dependent magnetization curve. It is also corroborated by the fact that the experimental magnetization curve at room temperature requires two Langevin functions for satisfactory reproduction.

Photoluminescence properties of cerium oxide nanoparticles as a function of lanthanum content

Energy Technology Data Exchange (ETDEWEB)

Deus, R.C. [Universidade Estadual Paulista, Unesp —Faculdade de Engenharia de Guaratinguetá, Av. Dr Ariberto Pereira da Cunha 333, Bairro Pedregulho, P.O. Box 355, 12.516-410 Guaratinguetá, São Paulo, Brazil, (Brazil); Cortés, J.A., E-mail: leandrosrr89@gmail.com [Universidade Estadual Paulista, Unesp —Faculdade de Engenharia de Guaratinguetá, Av. Dr Ariberto Pereira da Cunha 333, Bairro Pedregulho, P.O. Box 355, 12.516-410 Guaratinguetá, São Paulo, Brazil, (Brazil); Ramirez, M.A. [Universidade Estadual Paulista, Unesp —Faculdade de Engenharia de Guaratinguetá, Av. Dr Ariberto Pereira da Cunha 333, Bairro Pedregulho, P.O. Box 355, 12.516-410 Guaratinguetá, São Paulo, Brazil, (Brazil); Ponce, M.A. [Instituto de Investigaciones en Ciencia y Tecnología de Materiales (INTEMA) (CONICET-Universidad Nacional de Mar del Plata), Juan B. Justo 4302, 7600 Mar del Plata (Argentina); Andres, J. [Laboratório Interdisciplinar em Cerâmica, Instituto de Química, Universidade Estadual Paulista, P.O. Box 355, 14801-907 Araraquara, São Paulo (Brazil); Rocha, L.S.R. [Universidade Estadual Paulista, Unesp —Faculdade de Engenharia de Guaratinguetá, Av. Dr Ariberto Pereira da Cunha 333, Bairro Pedregulho, P.O. Box 355, 12.516-410 Guaratinguetá, São Paulo, Brazil, (Brazil); and others

2015-10-15

Highlights: • CeO{sub 2} nanoparticles were obtained by microwave-hydrothermal method. • Rietveld refinement reveals a cubic structure. • KOH mineralizer agent exhibit weak agglomeration at low temperature and shorter time. - Abstract: The structural and photoluminescent properties at room temperature of CeO{sub 2} and La-doped CeO{sub 2} particles were undertaken. The obtained particles were synthesized by a microwave-assisted hydrothermal method (MAH) under different lanthanum contents. X-ray diffraction (XRD), Fourier transform infrared (FT-IR), Fourier transform Raman (FT-Raman), Ultra-violet spectroscopy (UV–vis) and photoluminescence (PL) measurements were carried out. XRD revealed that the powders are free of secondary phases and crystallize in the cubic structure. Raman data show that increasing La doping content increase oxygen vacancies due to lattice expansion. The UV/vis absorption spectroscopy suggested the presence of intermediate energy levels in the band gap of structurally ordered powders. Lanthanum addition creates oxygen vacancies and shifts the photoluminescence in the low energy range leading to intense PL emission.

Effect of pb on the magnetic interactions of the M-type hexaferrites

Energy Technology Data Exchange (ETDEWEB)

Guerrero, A.L., E-mail: azdlobo@gmail.com [Instituto de Física de la Universidad Autónoma de San Luis Potosí, Álvaro Obregón No. 64, Col. Centro, San Luis Potosí, S.L.P. 78000, México (Mexico); Mirabal-García, M. [Instituto de Física de la Universidad Autónoma de San Luis Potosí, Álvaro Obregón No. 64, Col. Centro, San Luis Potosí, S.L.P. 78000, México (Mexico); Palomares-Sánchez, S.A.; Martínez, J.R. [Facultad de Ciencias de la Universidad Autónoma de San Luis Potosí, Álvaro Obregón No. 64, Col. Centro, San Luis Potosí, S.L.P. 78000, México (Mexico)

2016-02-01

This work reports the magnetic interactions of M-type lead hexaferrites. The samples were prepared using the solid state reaction method varying the lead concentration and compensating its lost by thermal treatment in order to obtain pure phases. The structural characterization was made through X-ray diffraction and the Rietveld refinement method. The morphology and grain-growth analysis were carried out using scanning electron microscopy. The magnetic interactions were studied through isothermal remanence (IRM) and DC demagnetization (DCD) remanence curves and through the construction of Henkel plots. By analyzing deviations from the Stoner–Wohlfarth model for non-interacting particles, it was determined the way in which lead modifies the interaction state in the hexaferrites. The experimental results show that the demagnetizing interactions prevail in systems with high lead content, and as lead concentration diminishes the intensity of magnetic interactions also decreases giving rise to magnetizing interactions - Highlights: • Construction of Henkel Plots of substituted hexaferrites. • Evaluation of magnetostatic and exchange interactions. • Effect of lead substitution on magnetic properties of the hexaferrites.

Development of standard reference samples for diffractometry

International Nuclear Information System (INIS)

Galvao, Antonio de Sant'Ana

2011-01-01

In this work, samples of standard reference materials for diffractometry of polycrystals were developed. High-purity materials were submitted to mechanical and thermal treatments in order to present the adequate properties to be used as high-quality standard reference materials for powder diffraction, comparable to the internationally recognized produced by the USA National Institute of Standards and Technology NIST, but at lower costs. The characterization of the standard materials was performed by measurements in conventional X-ray diffraction diffractometers, high resolution neutron diffraction and high-resolution synchrotron diffraction. The lattice parameters were calculated by extrapolation of the values obtained from each X-ray reflection against cos 2 θ by the Least-Squares Method. The adjustments were compared to the values obtained by the Rietveld Method, using program GSAS. The materials thus obtained were the α-alumina, yttrium oxide, silicon, cerium oxide, lanthanum hexaboride and lithium fluoride. The standard reference materials produced present quality similar or, in some cases, superior to the standard reference materials produced and commercialized by the NIST. (author)

Structural characterisation of 1- and 2-dimensional transition metal polymers using powder neutron diffraction

International Nuclear Information System (INIS)

James, M.

1999-01-01

Powder neutron diffraction provides an alternate technique for the structural study of transition metal polymers and finds utility over standard X-ray methods in two significant ways. Firstly, due to a different instrument geometry, preferred orientation effects are removed from the system. The second advantage gained by utilising neutrons is that H atoms in the sample contribute much more to the nuclear scattering of the diffraction profile - allowing their atomic position to be accurately determined. In X-ray diffraction studies, where H atoms typically account for only ∼3-5% of the scattering from the sample, it is essentially impossible to refine their position in the molecular structure. The structures of several transition metal polymers have been determined using neutrons from the HIFAR reactor at ANSTO and the Powder Diffractometers HRPD and MRPD, along with Rietveld refinement methods. The 1-dimensional polymer dibromobis(thiazole)nickel(II) illustrated in the paper is characteristic of these types of systems which are comprised of transition metal centres bridged by halogen atoms with pendant amine side groups

Crystal structure and charge density analysis of Li2NH by synchrotron X-ray diffraction

International Nuclear Information System (INIS)

Noritake, T.; Nozaki, H.; Aoki, M.; Towata, S.; Kitahara, G.; Nakamori, Y.; Orimo, S.

2005-01-01

Complex hydrides, such as lithium amide (LiNH 2 ) and lithium imide (Li 2 NH), have recently been noticed as one of the most promising materials for reversible hydrogen storage. In this paper, we reveal the bonding nature of hydrogen in Li 2 NH crystal by synchrotron powder X-ray diffraction measurement at room temperature. The crystal structure was refined by Rietveld method and the charge density distribution was analyzed by maximum entropy method (MEM). The Li 2 NH crystal is anti-fluorite type structure (space group Fm3-bar m) consisting of Li and NH. Hydrogen atom occupies randomly the 48h (Wyckoff notation) sites around N atom. The refined lattice constant is a=5.0742(2)A. The charge density distribution around NH anion in Li 2 NH is almost spherical. The number of electrons within the sphere around the Li and NH is estimated from the obtained charge density distribution. As the result, the ionic charge is expressed as [Li 0.99+ ] 2 [NH] 1.21- . Therefore, it is confirmed experimentally that Li 2 NH is ionically bonded

Characterization of a wollastonite glass-ceramic material prepared using sugar cane bagasse ash (SCBA) as one of the raw materials

Energy Technology Data Exchange (ETDEWEB)

Teixeira, Silvio R., E-mail: rainho@fct.unesp.br [Universidade Estadual Paulista — UNESP, Faculdade de Ciências e Tecnologia — FCT, 19060-900 Presidente Prudente — SP (Brazil); Souza, Agda E. [Universidade Estadual Paulista — UNESP, Faculdade de Ciências e Tecnologia — FCT, 19060-900 Presidente Prudente — SP (Brazil); Carvalho, Claudio L.; Reynoso, Victor C.S. [Universidade Estadual Paulista — UNESP, Faculdade de Engenharia de Ilha Solteira — FEIS, 15385-000 Ilha Solteira – SP (Brazil); Romero, Maximina; Rincón, Jesús Ma. [Instituto de Ciencias de la Construccion Eduardo Torroja — IETCC, CSIC, 28033 Madrid (Spain)

2014-12-15

Glass-ceramic material prepared with sugar cane bagasse ash as one of the raw materials was characterized to determine some important properties for its application as a coating material. X-ray diffraction patterns showed that wollastonite-2M (CaSiO{sub 3}) was the major glass-ceramic phase. The Rietveld method was used to quantify the crystalline (60 wt.%) and vitreous (40 wt.%) phases in the glass-ceramic. The microstructure (determined by scanning electron microscopy) of this material had a marble appearance, showing a microporous network of elongated crystals with some areas with dendritic, feather-like ordering. Microhardness data gave a mean hardness value of 564.4 HV (Vickers-hardness), and light microscopy disclosed a greenish brown colored material with a vitreous luster. - Highlights: • We studied the properties of a glass-ceramic material obtained from sugarcane ash. • This material has the appearance and hardness of natural stones. • A refining method gave information about its amorphous and crystalline phases. • This material has potential to be used as coating plates for buildings.

Characterization of a wollastonite glass-ceramic material prepared using sugar cane bagasse ash (SCBA) as one of the raw materials

International Nuclear Information System (INIS)

Teixeira, Silvio R.; Souza, Agda E.; Carvalho, Claudio L.; Reynoso, Victor C.S.; Romero, Maximina; Rincón, Jesús Ma.

2014-01-01

Glass-ceramic material prepared with sugar cane bagasse ash as one of the raw materials was characterized to determine some important properties for its application as a coating material. X-ray diffraction patterns showed that wollastonite-2M (CaSiO 3 ) was the major glass-ceramic phase. The Rietveld method was used to quantify the crystalline (60 wt.%) and vitreous (40 wt.%) phases in the glass-ceramic. The microstructure (determined by scanning electron microscopy) of this material had a marble appearance, showing a microporous network of elongated crystals with some areas with dendritic, feather-like ordering. Microhardness data gave a mean hardness value of 564.4 HV (Vickers-hardness), and light microscopy disclosed a greenish brown colored material with a vitreous luster. - Highlights: • We studied the properties of a glass-ceramic material obtained from sugarcane ash. • This material has the appearance and hardness of natural stones. • A refining method gave information about its amorphous and crystalline phases. • This material has potential to be used as coating plates for buildings

Drastic effect of the Mn-substitution in the strongly correlated semiconductor FeSb2.

Science.gov (United States)

Kassem, Mohamed A.; Tabata, Yoshikazu; Waki, Takeshi; Nakamura, Hiroyuki

2017-06-01

We report the effects of Mn substitution, corresponding to hole doping, on the electronic properties of the narrow gap semiconductor, FeSb2, using single crystals of Fe1- x Mn x Sb2 grown by the Sb flux method. The orthorhombic Pnnm structure was confirmed by powder X-ray diffraction (XRD) for the pure and Mn-substituted samples. Their crystal structure parameters were refined using the Rietveld method. The chemical composition was investigated by wavelength-dispersive X-ray spectroscopy (WDX). The solubility limit of Mn in FeSb2 is x max ˜ 0.05 and the lattice constants change monotonically with increasing the actual Mn concentration. A drastic change from semiconducting to metallic electronic transports was found at very low Mn concentration at x ˜ 0.01. Our experimental results and analysis indicate that the substitution of a small amount of Mn changes drastically the electronic state in FeSb2 as well as the Co-substitution does: closing of the narrow gap and emergence of the density of states (DOS) at the Fermi level.

Crystal structure and transport properties of gamma-Na sub x CoO sub 2 (x=0.67 approx 0.75)

CERN Document Server

Ono, Y; Miyazaki, Y; Kajitani, T; Ishii, Y

2003-01-01

Crystal structure and transport properties of gamma-Na sub x CoO sub 2 have been studied in the range of x=0.67-0.75. Single-phase samples were prepared by sintering mixture of raw materials, Na sub 2 CO sub 3 (99.5%) and Co sub 3 O sub 4 (99.9%). Na/Co composition ratio (x) was determined by inductively coupled plasma (ICP) analysis. The crystal structure parameters were refined by Rietveld analysis of powder neutron diffraction intensities, assuming P6 sub 3 /mmc type space symmetry. Little changes in the crystal structure are noticed, except for Na contents. Electric resistivity rho and Seebeck coefficient S were measured at temperatures between 380 K and 1000 K by the standard four-probe method and temperature gradient method, respectively. The rho-T curves exhibit the thermal hysteresis in the initial measurement. But, in the following measurement, the thermal hysteresis is significantly suppressed. The S was slightly higher in the sample with x = 0.75 than in the others at any temperatures. Power factor...

Structure and magnetic properties of flux grown single crystals of Co3-xFexSn2S2 shandites

Science.gov (United States)

Kassem, Mohamed A.; Tabata, Yoshikazu; Waki, Takeshi; Nakamura, Hiroyuki

2016-01-01

We report a successful single crystal growth of the shandite-type half-metallic ferromagnet Co3Sn2S2, and its Fe-substituted compounds, Co3-xFexSn2S2, by employing the flux method. Although Fe3Sn2S2 is unstable phase, we found that using the self Sn flux enables us to obtain single phase crystals up to x=0.53. The chemical composition of the grown plate-shaped single crystals was examined using wavelength-dispersive X-ray spectroscopy. The shandite structure with R 3 ̅m symmetry was confirmed by powder X-ray diffraction and the crystal structure parameters were refined using the Rietveld method. Magnetization measurements show suppression of the ferromagnetic order upon Fe-substitution , as well as in other substituted systems such as In- and Ni-substituted Co3Sn2S2. The almost identical magnetic phase diagrams of the Fe- and In-substituted compounds indicate that the electron number is dominantly significant to the magnetism in the Co-based shandite.

Revisiting elastic anisotropy of biotite gneiss from the Outokumpu scientific drill hole based on new texture measurements and texture-based velocity calculations

Science.gov (United States)

Wenk, H.-R.; Vasin, R. N.; Kern, H.; Matthies, S.; Vogel, S. C.; Ivankina, T. I.

2012-10-01

A sample of biotite gneiss from the Outokumpu deep drilling project in Finland was investigated by Kern et al. (2008) for crystal preferred orientation and elastic anisotropy. Considerable differences between measured acoustic velocities and velocities calculated on the basis of texture patterns were observed. Measured P-wave anisotropy was 15.1% versus a Voigt average yielding 7.9%. Here we investigate the same sample with different methods and using different averaging techniques. Analyzing time-of-flight neutron diffraction data from Dubna-SKAT and LANSCE-HIPPO diffractometers with the Rietveld technique, much stronger preferred orientation for biotite is determined, compared to conventional pole-figure analysis reported previously. The comparison reveals important differences: HIPPO has much better counting statistics but pole figure coverage is poor. SKAT has better angular resolution. Using the new preferred orientation data and applying a self-consistent averaging method that takes grain shapes into account, close agreement of calculated and measured P-wave velocities is observed (12.6%). This is further improved by adding 0.1 vol.% flat micropores parallel to the biotite platelets in the simulation (14.9%).

Mineralogical characterization of beach sand minerals: traditional and modern approaches

International Nuclear Information System (INIS)

Krishnamurthy, P.

2016-01-01

Precise identification of beach sand minerals is an essential prerequisite for the reserve estimation of a given deposit and also in the subsequent evaluation of the process flow sheet for its optimal recovery. Traditional methods that are used for the identification of the beach sand minerals such as magnetite, hematite, ilmenite, rutile, anatase, zircon, garnet, sillimanite, monazite, quartz and others include heavy liquid separation (bromoform and methylene iodide) and studying the optical properties of the grains from different fractions so as to identify the specific phases in a sample. Grain counting of specific minerals from a given sievefraction under a petrological microscope to estimate the mode and their subsequent conversion in to weight percent fractions forms the critical second stage that is followed by the reserve estimates. These methodologies are tedious and time consuming often involving a few days for a single sample. The paper introduces the numerous instrumental methods (XRF, XRD - Rietveld and CCSEM) of mineral speciation and their qualification in with case studies from the west coast deposits in India

Ab-initio structure determination of novel strontium-containing layered silicate AES-18 synthesized using mechanochemical reaction

Energy Technology Data Exchange (ETDEWEB)

Ikeda, Takuji [AIST Tohoku, Sendai (Japan). Research Center for Compact Chemical System; Ideta, Chiaki; Yamamoto, Katsutoshi [Kitakyushu Univ. (Japan). Faculty of Environmental Engineering

2013-07-01

A new strontium-containing layered silicate, alkaline earth-containing silicate (AES)-18 [chemical composition: Si{sub 16}O{sub 24}(OH){sub 16} . {Sr(OH)_2}{sub 8} . (KOH){sub 2}], was synthesized utilizing a mechanochemical reaction in which an admixture of strontium hydroxide, which unfavorably precipitates in conventional syntheses, and a fumed silica (Aerosil) was allowed to react in the solid phase. The crystal structure of AES-18 was elucidated by the charge-flipping method using powder X-ray diffraction data, and the obtained structure was refined by a combination with the Rietveld method and the maximum entropy method (MEM). The structure analyses showed a tetragonal symmetry with a = 0.912738(3) nm, c = 1.628120(8) nm, and the space group P4{sub 2}/mnc. Two silicate layers composed of Q{sup 3} local structure [(-SiO){sub 3}Si-OH], 7-coordinated Sr{sup 2+} cations, and K{sup +} cations were included in a unit cell, and a Sr{sub 4}(OH){sub 17} cluster was formed between adjacent silicate layers. The framework topology of AES-18 containing 4- and 8-Si-membered rings was similar to that of paracelsian.

Synthesis and characterization of TiC nanopowders via sol-gel and subsequent carbothermal reduction process

Science.gov (United States)

Chen, Xu; Fan, Jinglian; Lu, Qiong

2018-06-01

TiC nanocrystalline powders were synthesized by in-situ carbothermic reduction of Ti-O-C precursor under vacuum atmosphere. And the Ti-O-C precursor was formed by sol-gel method from titanium butyrate (TBOT) and sucrose. To obtain stable sol, TBOT was directly added into mixed solution which contains water, sucrose, acetic acid (AcOH) and acetylacetone (ACAC). This procedure is more convenient and economical because it avoids the use of alcohol which is used as solvent in most reports of alkoxide hydrolysis sol-gel method. TG-DSC, XRD, FTIR and SEM/TEM were employed to analyze and characterize the product during the entire process. The phase composition and crystalline structure parameters of powders with different C/Ti molar ratio were investigated by Rietveld refinement method, and elemental quantitative analysis of the samples were performed. Furthermore, the optimal parameters of carbothermal reduction were obtained and the grain growth mechanism was demonstrated. The results show that TiC nanocrystalline powders (C/Ti molar ratio is 3.5 in the precursor) were synthesized at 1300 °C for 2 h, which have near standard lattice parameter, well crystallinity and fine average grain size ( 37.4 nm).

Biosynthesised ZnO : Dy3+ nanoparticles: Biodiesel properties and reusable catalyst for N-formylation of aromatic amines with formic acid

Science.gov (United States)

Reddy Yadav, L. S.; Raghavendra, M.; Sudheer Kumar, K. H.; Dhananjaya, N.; Nagaraju, G.

2018-04-01

ZnO nanoparticles doped with trivalent dysprosium ions (Dy3+) were prepared through the green combustion technique using E. tirucalli plant latex as a fuel. The fundamental and optical properties of the samples are examined via the X-ray diffraction, FTIR, UV-visible analytical methods and morphology by scanning electron microscope and transmission electron microscope. Rietveld refinement results show that the ZnO : Dy3+ were crystallized in the wurtzite hexagonal structure with space group P63mc (No. 186). The average particle size of ZnO : Dy3+ prepared with the different concentration of latex was found to be in the range 30-38nm, which is also confirmed by TEM analysis. A rapid and convenient method for the one-pot preparation of N-formamide derivatives aromatic amines and amino acid esters has been developed using Dy3+ doped ZnO as a catalytic agent. This method provides an efficient and much improved modification over reported protocols regarding yield, clean and work-up procedure milder reaction conditions. In this work, Pongamiapinnata oil was recycled for the preparation of biodiesel via Dy3+ doped ZnO as a catalytic agent.

Synthesis and characterization of hydroxyapatite-doped silver nanoparticles; Sintese e caracterizacao de hidroxiapatita dopada com nanoparticulas de prata

Energy Technology Data Exchange (ETDEWEB)

Andrade, Flavio Augusto Cavadas da Silva; Rollo, Joao Manuel Domingos de Almeida, E-mail: flavio.andrade@usp.br [Universidade de Sao Paulo (EESC/FMRP/IQSC/USP), Sao Carlos, SP (Brazil). Programa de Pos-Graduacao Interunidades Bioengenharia; Rigo, Eliana Cristina da Silva; Vercik, Andres; Vercik, Luci Cristina de Oliveira; Valencia, German Ayala; Ferreira, Leticcia Gaviao [Universidade de Sao Paulo (USP), Pirassununga, SP (Brazil). Faculdade de Zootecnia e Engenharia de Alimentos. Departamento de Ciencias Basicas

2012-07-01

Hydroxyapatite-doped silver nanoparticles was obtained by immersing the powder in increasing dilutions of a solution containing AGNPS which were synthesized in different times and were characterized by UV-vis spectroscopy. The X-ray diffraction (XRD)studies demonstrate no change in the major phase of HA. Scanning Electron Microscopy (SEM) revealed morphological characteristics of powders after doping and the presence of silver was confirmed by energy dispersive X-ray (EDAX) analysis.The antibacterial effect of the doped powders was evaluated using strain of Staphylococcus aureus by disc-diffusion test. The zone of inhibition was found to vary with the amount of silver nanoparticle in the doped powder even for low concentrations of AgNPs. These results indicate that the method of immersion hydroxyapatite in solutions containing AgNPs is promising to obtain bioactive materials with low cytotoxicity and antibacterial effects. (author)

Exploring the Room-Temperature Ferromagnetism and Temperature-Dependent Dielectric Properties of Sr/Ni-Doped LaFeO3 Nanoparticles Synthesized by Reverse Micelle Method

Science.gov (United States)

Naseem, Swaleha; Khan, Shakeel; Husain, Shahid; Khan, Wasi

2018-03-01

This paper reports the thermal, microstructural, dielectric and magnetic properties of La0.75Sr0.25Fe0.65Ni0.35O3 nanoparticles (NPs) synthesized via reverse micelle technique. The thermogravimetric analysis of as-prepared NPs confirmed a good thermal stability of the sample. Powder x-ray diffraction data analyzed with a Rietveld refinement technique revealed single-phase and orthorhombic distorted perovskite crystal structure of the NPs having Pbnm space group. The transmission electron microscopy images show the crystalline nature and formation of nanostructures with a fairly uniform distribution of particles throughout the sample. Temperature-dependent dielectric properties of the NPs in accordance with the Kramers-Kronig transformation (KKT) model, universal dielectric response model and jump relaxation model have been discussed. Electrode or interface polarization is likely the cause of the observed dielectric behavior. Due to grain boundaries and Schottky barriers of the metallic electrodes of semiconductors, the depletion region is observed, which gives rise to Maxwell-Wagner relaxation and hence high dielectric constants. Magnetic studies revealed the ferromagnetic nature of the prepared NPs upon Sr and Ni doping in LaFeO3 perovskite at room temperature. Therefore, these NPs could be a potential candidate as electrode material in solid oxide fuel cells.

Structure and decomposition of the silver formate Ag(HCO{sub 2})

Energy Technology Data Exchange (ETDEWEB)

Puzan, Anna N., E-mail: anna_puzan@mail.ru; Baumer, Vyacheslav N.; Mateychenko, Pavel V.

2017-02-15

Crystal structure of the silver formate Ag(HCO{sub 2}) has been determined (orthorhombic, sp.gr. Pccn, a=7.1199(5), b=10.3737(4), c=6.4701(3)Å, V=477.88(4) Å{sup 3}, Z=8). The structure contains isolated formate ions and the pairs Ag{sub 2}{sup 2+} which form the layers in (001) planes (the shortest Ag–Ag distances is 2.919 in the pair and 3.421 and 3.716 Å between the nearest Ag atoms of adjacent pairs). Silver formate is unstable compound which decompose spontaneously vs time. Decomposition was studied using Rietveld analysis of the powder diffraction patterns. It was concluded that the diffusion of Ag atoms leads to the formation of plate-like metal particles as nuclei in the (100) planes which settle parallel to (001) planes of the silver formate matrix. - Highlights: • Silver formate Ag(HCO{sub 2}) was synthesized and characterized. • Layered packing of Ag-Ag pairs in the structure was found. • Decomposition of Ag(HCO{sub 2}) and formation of metal phase were studied. • Rietveld-refined micro-structural characteristics during decomposition reveal the space relationship between the matrix structure and forming Ag phase REPLACE with: Space relationship between the matrix structure and forming Ag phase.

Phase relations and crystal structures in the systems (Bi,Ln)2WO6 and (Bi,Ln)2MoO6 (Ln=lanthanide)

International Nuclear Information System (INIS)

Berdonosov, Peter S.; Charkin, Dmitri O.; Knight, Kevin S.; Johnston, Karen E.; Goff, Richard J.; Dolgikh, Valeriy A.; Lightfoot, Philip

2006-01-01

Several outstanding aspects of phase behaviour in the systems (Bi,Ln) 2 WO 6 and (Bi,Ln) 2 MoO 6 (Ln=lanthanide) have been clarified. Detailed crystal structures, from Rietveld refinement of powder neutron diffraction data, are provided for Bi 1.8 La 0.2 WO 6 (L-Bi 2 WO 6 type) and BiLaWO 6 , BiNdWO 6 , Bi 0.7 Yb 1.3 WO 6 and Bi 0.7 Yb 1.3 WO 6 (all H-Bi 2 WO 6 type). Phase evolution within the solid solution Bi 2- x La x MoO 6 has been re-examined, and a crossover from γ(H)-Bi 2 MoO 6 type to γ-R 2 MoO 6 type is observed at x∼1.2. A preliminary X-ray Rietveld refinement of the line phase BiNdMoO 6 has confirmed the α-R 2 MoO 6 type structure, with a possible partial ordering of Bi/Nd over the three crystallographically distinct R sites. - Graphical abstract: A summary of phase relations in the lanthanide-doped bismuth tungstate and bismuth molybdate systems is presented, together with some additional structural data on several of these phases

Structure and decomposition of the silver formate Ag(HCO2)

International Nuclear Information System (INIS)

Puzan, Anna N.; Baumer, Vyacheslav N.; Mateychenko, Pavel V.

2017-01-01

Crystal structure of the silver formate Ag(HCO 2 ) has been determined (orthorhombic, sp.gr. Pccn, a=7.1199(5), b=10.3737(4), c=6.4701(3)Å, V=477.88(4) Å 3 , Z=8). The structure contains isolated formate ions and the pairs Ag 2 2+ which form the layers in (001) planes (the shortest Ag–Ag distances is 2.919 in the pair and 3.421 and 3.716 Å between the nearest Ag atoms of adjacent pairs). Silver formate is unstable compound which decompose spontaneously vs time. Decomposition was studied using Rietveld analysis of the powder diffraction patterns. It was concluded that the diffusion of Ag atoms leads to the formation of plate-like metal particles as nuclei in the (100) planes which settle parallel to (001) planes of the silver formate matrix. - Highlights: • Silver formate Ag(HCO 2 ) was synthesized and characterized. • Layered packing of Ag-Ag pairs in the structure was found. • Decomposition of Ag(HCO 2 ) and formation of metal phase were studied. • Rietveld-refined micro-structural characteristics during decomposition reveal the space relationship between the matrix structure and forming Ag phase REPLACE with: Space relationship between the matrix structure and forming Ag phase.

The use of HPLC identification and quantification of isoflavones content in samples obtained in pharmacies = O uso do HPLC na identificação e quantificação dos teores de isoflavonas em amostras obtidas de farmácias de manipulação = O uso do HPLC na identificação e quantificação dos teores de isoflavonas em amostras obtidas de farmácias de manipulação

Directory of Open Access Journals (Sweden)

Daniel Mantovani

2011-01-01

Full Text Available Nowadays, there is a great interest in the research and the production of functional foods, such as isoflavones. Which present proven action on the prevention of health problems, such as cancer and cardiovascular diseases. Considering the importance of soybeansupplements standardization, this study aimed identifying and quantifying the isoflavones in products sold at different pharmacies. Isoflavones samples were acquired in six different pharmacies specialized in the production of phytotherapic medications. The isoflavones were extracted, quantified and identified in HPLC. None of the samples, from different pharmacies, presented the isoflavones content presented on the label, i.e., 20 mg. In relation to the isoflavones profile, the highest levels found were of daidzein, with up to 66.8 } 0.09 ƒÊg, being the lowest levels the ones of genistein. It is necessary, therefore, the adoption of methods for thestandardization and characterization of the raw materials used by different pharmacies. It would assure the isoflavones content, once they are essential for the effects prescribed by the professionals in the medical area.O uso do HPLC na identificacao e quantificacao dos teores de isoflavonas em amostras obtidas de farmacias de manipulacao. Atualmente ha um grande interesse na pesquisa e producao de alimentos funcionais, como as isoflavonas, que apresentam comprovada acao na prevencao de males, como o cancer e as doencas cardiovasculares. Considerando a importancia da padronizacao dos suplementos de soja,o objetivo do presente estudo foi de identificar e quantificar as isoflavonas em produtos comercializados em diferentes farmacias de manipulacao. Amostras de isoflavonas foram adquiridas em seis diferentes farmacias especializadas em manipulacao de fitoterapicos. As isoflavonas foram extraidas, identificadas e quantificadas em CLAE. Nenhuma das amostras, das diferentes farmacias de manipulacao, apresentou os teores de isoflavonas indicado no

Effects of In{sub 3+} substitution on structural properties, cation distribution and Mössbauer spectra of CoFe{sub 2}O{sub 4} ferrite

Energy Technology Data Exchange (ETDEWEB)

Kumar, Ravi, E-mail: ranade65@gmail.com [Centre for Material Science and Engineering, National Institute of Technology Hamirpur (H.P.)-177005 (India); Pandit, Rabia; Sharma, K. K.; Kaur, Pawanpreet [Department of Physics, National Institute of Technology Hamirpur (H.P.)-177005 (India)

2014-04-24

The use of non-destructive, high resolution technique namely Mössbauer spectroscopy is discussed in detail for the investigation of structural and magnetic properties of Fe based indium substituted cobalt ferrites. The polycrystalline samples of CoFe{sub 2−x}In{sub x}O{sub 4} (x = 0.2, 0.6) were prepared by double sintering solid state reaction method. To ensure a single phase formation of the as prepared samples the X-ray diffraction (XRD) data of the powdered samples was Rietveld refined using Fd3m space group. An excellent agreement is obtained between the integrated intensity ratios of 57 Fe spectra at A- and B-sites and those calculated on the basis of cation distribution the cation distribution obtained data analysis. The results of Mössbauer spectra and cation distribution are also correlated well with magnetization versus applied field (M-H) study.

The role of Sr doping on structure and microstructural properties of LaFeO{sub 3}

Energy Technology Data Exchange (ETDEWEB)

Jain, Pranat, E-mail: pranatjain@gmail.com; Srivastava, Sanjay, E-mail: s.srivastava.msme@gmail.com [Department of Materials Science & Metallurgical Engineering, Maulana Azad National Institute of Technology, Bhopal-4620003 (India); Gupta, Nitish, E-mail: nitish.nidhi75@gmail.com [Department of App. Chemistry, Shri G.S. Institute of Technology and Science, 23 Park Road Indore 452003 (India)

2016-05-06

The doping of Strontium in LaFeO{sub 3} and its influence on the structural and microstructure properties were studied thoroughly. A few sets of Sr doping in La{sub (1-x)}Fe{sub x}O{sub 3}, where x=0.00, 0.02, and 0.06 were made through the solution combustion synthesis method using urea as fuel. X-ray diffraction was applied to get information about the structure and purity. The Rietveld refinement on X-ray diffraction peaks have been done, in order to calculate various structural parameters. The morphology of La{sub (1-x)}Sr{sub x}FeO{sub 3} nanoscale particles has been confirmed by field emission scanning electron microscopy (FESEM) technique. Differential scanning calorimetry (DSC) signals demonstrated the antiferromagnetic to paramagnetic transition (T{sub N}). The FTIR spectra was provided the information about various vibration modes in samples.

Hydrolysis of dilute acid-pretreated cellulose under mild hydrothermal conditions.

Science.gov (United States)

Chimentão, R J; Lorente, E; Gispert-Guirado, F; Medina, F; López, F

2014-10-13

The hydrolysis of dilute acid-pretreated cellulose was investigated in a conventional oven and under microwave heating. Two acids--sulfuric and oxalic--were studied. For both hydrothermal conditions (oven and microwave) the resultant total organic carbon (TOC) values obtained by the hydrolysis of the cellulose pretreated with sulfuric acid were higher than those obtained by the hydrolysis of the cellulose pretreated with oxalic acid. However, the dicarboxylic acid exhibited higher hydrolytic efficiency towards glucose. The hydrolysis of cellulose was greatly promoted by microwave heating. The Rietveld method was applied to fit the X-ray patterns of the resultant cellulose after hydrolysis. Oxalic acid preferentially removed the amorphous region of the cellulose and left the crystalline region untouched. On the other hand, sulfuric acid treatment decreased the ordering of the cellulose by partially disrupting its crystalline structure. Copyright © 2014 Elsevier Ltd. All rights reserved.

XANES study on Ruddlesdan-Popper phase, Lan+1NinO3n+1 (n = 1, 2 and ∞)

International Nuclear Information System (INIS)

Park, Jung-Chul; Kim, Dong-Kuk; Byeon, Song-Hu; Kim, Don

2001-01-01

Ruddlesden-Popper phase, La n+1 Ni n O 3n+ 1 (n = 1, 2, and ∞) compounds were prepared by citrate sol-gel method. We revealed the origin of the variation of the electrical conductivities in La n+1 Ni n O 3n+1 (n= 1, 2, and ∞) using resistivity measurements, Rietveld analysis, and X-ray absorption spectroscopy. According to the XANES spectra, it is found that the degree of 4pπ - 4pσ energy splitting between 8345 eV and 8350 eV is qualitatively proportional to the elongation of the out-of-plane Ni-O bond length. With the decrease of 4pπ-4pσ splitting, the strong hybridization of the σ-bonding between Ni-3d and O-2p orbitals creates narrow antibonding σ bands, which finally results in the lower electrical resistivity. (au)

Effect of dissolution kinetics on flotation response of calcite with oleate

Directory of Open Access Journals (Sweden)

D. G. Horta

Full Text Available Abstract Phosphate flotation performance can be influenced by the dissolution kinetics of the minerals that compose the ore. The purpose of this work was to investigate the effect of dissolution kinetics on flotation response with oleate (collector of calcites from different origins and genesis. The calcite samples were first purified and characterized by x-ray Fluorescence (XRF and the Rietveld method applied to x-ray Diffractometry data (RXD. Experiments of calcite dissolution and microflotationwere performed at pH 8 and pH 10.The pH effect on the calcite dissolution and flotation indicates the possible influence of the carbonate/bicarbonate ions provided by the CO2 present in the air. In addition, the flotation response is greater as the dissolution increases, making more Ca2+ ions available to interact with collector molecules. This result corroborates the surface precipitation mechanism proposed foroleate adsorption on the calcite surface.

Correlation between thermal vibration and conductivity in La0.9Sr0.1B0.9Mg0.1O3-δ, B=Al, Ga and Sc

DEFF Research Database (Denmark)

Lybye, Dorthe; Nielsen, K.

2004-01-01

In order to obtain abetter understanding of the oxide ion conductivity in perovskites, the structure of La(0.9)Sr(0.1)Bo(9)Mg(0.1)O(3 - delta), B=Al, Ga and Sc, have been investigated by time-of-flight powder neutron diffraction at room temperature, 270, 470, 750, 850 and 950 degreesC. For all...... compounds, at all temperatures, structural and anisotropic thermal parameters were refined by full profile Rietveld methods to weighted profile R values less than 0.063. The changes in difference nuclear densities, Deltarho, due to changes in temperature are illustrated by difference density maps around...... the atoms. The observed difference densities are described mainly by zeroth- and second-order spherical harmonics (quadrupolar functions), the nature of which vary with atomic site. The difference density maps provide a direct picture of the average in space and time of changes in atomic thermal vibrations...

Microstructure characterization of nanocrystalline TiC synthesized by mechanical alloying

International Nuclear Information System (INIS)

Ghosh, B.; Pradhan, S.K.

2010-01-01

Nanocrystalline TiC is produced by mechanical milling the stoichiometric mixture of α-Ti and graphite powders at room temperature under argon atmosphere within 35 min of milling through a self-propagating combustion reaction. Microstructure characterization of the unmilled and ball-milled samples was done by both X-ray diffraction and electron microscopy. It reveals the fact that initially graphite layers were oriented along and in the course of milling, thin graphite layers were distributed evenly among the grain boundaries of α-Ti particles. Both α-Ti and TiC lattices contain stacking faults of different kinds. The grain size distribution obtained from the Rietveld's method and electron microscopy studies ensure that nanocrystalline TiC particles with almost uniform size (∼13 nm) can be prepared by mechanical alloying technique. The result obtained from X-ray analysis corroborates well with the microstructure characterization of nanocrystalline TiC by electron microscopy.

Structural, dielectric and magnetic properties of Bi{sub 0.8}Ba{sub 0.2}Fe{sub 0.6}Mn{sub 0.4}O{sub 3} ceramic

Energy Technology Data Exchange (ETDEWEB)

Rangi, Manisha, E-mail: mrangi100@gmail.com; Sanghi, S.; Agarwal, A.; Kaswan, K.; Jangra, S.; Singh, O. [Department of Applied Physics, Guru Jambheshwar University of Science and Technology, Hisar 125001, Haryana (India)

2016-05-23

Polycrystalline Bi{sub 0.8}Ba{sub 0.2}Fe{sub 0.6}Mn{sub 0.4}O{sub 3} ceramic was synthesized via conventional two stage solid state reaction method. The crystal structure is examined via powder x-ray diffraction and Rietveld refinement revealed that the sample has a rhombohedral crystal structure (space group R3c). The dielectric response of the sample was analyzed in the frequency range 10 Hz to 5 MHz at different temperature. The values of dielectric constant (ε′) and dielectric loss factor (tan δ) increases with increasing temperature at different frequencies which may be the result of increase in the number of charge carriers and their mobilities due to the thermal activation. M-H hysteresis loop was recorded at room temperature up to a field of 15 kOe which shows that there is slightly enhancement in magnetization with co-doping.

Structural study of caesium-based britholites Sr7La2Cs(PO4)5(SiO4)F2

International Nuclear Information System (INIS)

Boughzala, K.; Gmati, N.; Bouzouita, K.; Ben Cherifa, A.; Gravereau, P.

2010-01-01

Several studies demonstrated the ability of britholites to retain radionuclides such as the caesium and actinides. Therefore, three compounds with formulas Sr 8 LaCs(PO 4 ) 6 F 2 , Sr 7 La 2 Cs(PO 4 ) 5 (SiO 4 )F 2 and Sr 2 La 7 Cs(SiO 4 ) 6 F 2 , were prepared by solid state reaction. However, it seems that only the mono-silicated composition was obtained in a pure state. In this present work, the X-ray diffraction and magnetic nuclear resonance have been used to investigate the structure for this composition. The results showed that in fact this phase was not pure, but it was mixed with a secondary phase, SrLaCs(PO 4 ) 2 . The refinement by the Rietveld method allowed also to precise the distribution of La 3+ and Cs + ions between the two cationic sites of the apatite. (authors)

Local-site cation ordering of Eu{sup 3+} ion in doped PbTiO{sub 3}

Energy Technology Data Exchange (ETDEWEB)

Mendez-González, Y. [Departamento de Física Aplicada, Instituto de Cibernética, Matemática y Física, ICIMAF, 15 No. 551, Vedado, La Habana 10400 (Cuba); Pentón-Madrigal, A., E-mail: arbelio@fisica.uh.cu [Facultad de Física-Instituto de Ciencia y Tecnología de Materiales, Universidad de La Habana, San Lázaro y L, Vedado, La Habana 10400 (Cuba); Peláiz-Barranco, A. [Facultad de Física-Instituto de Ciencia y Tecnología de Materiales, Universidad de La Habana, San Lázaro y L, Vedado, La Habana 10400 (Cuba); Figueroa, Santiago J.A. [Brazilian Synchrotron Light Laboratory (LNLS)/Brazilian Center of Energy and Materials (CNPEM), CP 6192, 13083-970, Campinas, SP (Brazil); Oliveira, L.A.S. de [Polo Xerém, Universidade Federal do Rio de Janeiro, Estrada de Xerém, 27 Xerém, Duque de Caxias, RJ (Brazil); Concepción-Rosabal, B. [Facultad de Física-Instituto de Ciencia y Tecnología de Materiales, Universidad de La Habana, San Lázaro y L, Vedado, La Habana 10400 (Cuba)

2014-02-01

X-ray diffraction (XRD), extended X-ray absorption fine structure (EXAFS), and scanning electron microscopy experiments were carried out in the (Pb{sub 0.88}Eu{sub 0.08})TiO{sub 3} ferroelectric compound with a perovskite type structure. Qualitative EXAFS analysis has shown that Eu{sup 3+} ions substitute to Pb{sup 2+} and Ti{sup 4+} ions at A and B sites of the ABO{sub 3} structure, respectively. The XRD pattern refinement was consistent with the Eu{sup 3+} substitution at both A and B sites, which provides the formation of donor and acceptor-type defects. The shape of the observed X-ray lines profiles has shown features, which are known for this kind of ferroelectric material to be typical of the ferroelectric domains microstructure. A phenomenological model has been used for fitting the diffraction profiles by the Rietveld method.

Structural, optical and dielectric properties of Sn0.97Ce0.03O2 nanostructures

Science.gov (United States)

Ahmed, Ateeq; Siddique, M. Naseem; Ali, Tinku; Tripathi, P.

2018-05-01

In present work, 3% cerium doped SnO2 (Sn0.97Ce0.03O2) nanoparticles (NPs) have been synthesized by sol-gel method. The prepared sample has been characterized by using various techniques such as XRD, UV-visible absorption spectroscopy and LCR meter measurements. Structural Rietveld refinement of XRD data reveals that (Sn0.97Ce0.03O2) sample has a pure single phase tetragonal structure with space group (P42/mnm) without creating any impurity phase such as cerium oxide. UV-visible spectroscopy determines band gap value 3.47 eV for (Sn0.97Ce0.03O2) NPs using Tauc's relation. Dielectric constant and loss decreased with increase in frequency while ac conductivity was found to increase with increase in frequency. The observed dielectric results has been explained in the light of Maxwell-Wagner model.

High-resolution inelastic neutron scattering and neutron powder diffraction study of the adsorption of dihydrogen by the Cu(II) metal-organic framework material HKUST-1

Science.gov (United States)

Callear, Samantha K.; Ramirez-Cuesta, Anibal J.; David, William I. F.; Millange, Franck; Walton, Richard I.

2013-12-01

We present new high-resolution inelastic neutron scattering (INS) spectra (measured using the TOSCA and MARI instruments at ISIS) and powder neutron diffraction data (measured on the diffractometer WISH at ISIS) from the interaction of the prototypical metal-organic framework HKUST-1 with various dosages of dihydrogen gas. The INS spectra show direct evidence for the sequential occupation of various distinct sites for dihydrogen in the metal-organic framework, whose population is adjusted during increasing loading of the guest. The superior resolution of TOSCA reveals subtle features in the spectra, not previously reported, including evidence for split signals, while complementary spectra recorded on MARI present full information in energy and momentum transfer. The analysis of the powder neutron patterns using the Rietveld method shows a consistent picture, allowing the crystallographic indenisation of binding sites for dihydrogen, thus building a comprehensive picture of the interaction of the guest with the nanoporous host.

Thermal expansion analysis and structural characteristics of the (Pb, Ca)TiO{sub 3} solid solutions from 150 to 570 K; Analise da expansao termica volumetrica e das caracteristicas estruturais de solucoes solidas de (Pb, Ca)TiO{sub 3} entre 150 e 570 K

Energy Technology Data Exchange (ETDEWEB)

Estrada, F.R.; Eiras, J.A.; Garcia, D., E-mail: frestrada@df.ufscar.br, E-mail: eiras@df.ufscar.br, E-mail: ducinei@df.ufscar.br [Universidade Federal de Sao Carlos (UFSCar), SP (Brazil). Departamento de Fisica. Grupo de Materiais Ferroicos

2017-01-15

Ceramic samples of lead modified calcium titanate (Pb{sub 1-x}Ca{sub x} TiO{sub 3}) with calcium concentration between 0.24≤x≤0.55 were prepared and analyzed in order to determine the structural origin of the negative thermal expansion observed in this ferroelectric system. The Rietveld structural refinement method was used to assess the thermal evolution of the structural parameters using powder X-ray diffraction data collected between 150 and 570 K. Since the Pb{sub 1-x}Ca{sub x} TiO{sub 3} phase diagram and space groups are still unknown for the temperature range investigated, the structural analyses were based on adjustments of the refinement protocol. The results revealed the existence of a correlation between symmetry transitions and anomalies in the thermal expansion of the unit cell, being such transitions not necessarily of the ferroelectric-paraelectric nature. (author)

Application of Powder Diffraction Methods to the Analysis of the Atomic Structure of Nanocrystals: The Concept of the Apparent Lattice Parameter (ALP)

Science.gov (United States)

Palosz, B.; Grzanka, E.; Gierlotka, S.; Stelmakh, S.; Pielaszek, R.; Bismayer, U.; Weber, H.-P.; Palosz, W.; Curreri, Peter A. (Technical Monitor)

2002-01-01

The applicability of standard methods of elaboration of powder diffraction data for determination of the structure of nano-size crystallites is analysed. Based on our theoretical calculations of powder diffraction data we show, that the assumption of the infinite crystal lattice for nanocrystals smaller than 20 nm in size is not justified. Application of conventional tools developed for elaboration of powder diffraction data, like the Rietveld method, may lead to erroneous interpretation of the experimental results. An alternate evaluation of diffraction data of nanoparticles, based on the so-called 'apparent lattice parameter' (alp) is introduced. We assume a model of nanocrystal having a grain core with well-defined crystal structure, surrounded by a surface shell with the atomic structure similar to that of the core but being under a strain (compressive or tensile). The two structural components, the core and the shell, form essentially a composite crystal with interfering, inseparable diffraction properties. Because the structure of such a nanocrystal is not uniform, it defies the basic definitions of an unambiguous crystallographic phase. Consequently, a set of lattice parameters used for characterization of simple crystal phases is insufficient for a proper description of the complex structure of nanocrystals. We developed a method of evaluation of powder diffraction data of nanocrystals, which refers to a core-shell model and is based on the 'apparent lattice parameter' methodology. For a given diffraction pattem, the alp values are calculated for every individual Bragg reflection. For nanocrystals the alp values depend on the diffraction vector Q. By modeling different a0tomic structures of nanocrystals and calculating theoretically corresponding diffraction patterns using the Debye functions we showed, that alp-Q plots show characteristic shapes which can be used for evaluation of the atomic structure of the core-shell system. We show, that using a simple

Characterization of application of acu sandstone in ceramic mass; Caracterizacao da aplicacao do arenito acu na massa ceramica

Energy Technology Data Exchange (ETDEWEB)

Nobrega, L.F.P.M.; Souza, M.M.; Gomes, Y.S.; Fernandes, D.L., E-mail: junior.luiz09@hotmail.com [Universidade Federal do Rio Grande do Norte (DIAREN/UFRN), Natal, RN (Brazil). Laboratorio de Processamento Mineral e Residuo

2016-07-01

The sandstone is a sedimentary rock formed mainly by quartz grains. In Rio Grande do Norte, there is the Potiguar Basin with the Jandaira and Acu Formations. The latter consists of thick layers of whitish-colored sandstones. It stands out as a water storage facility in the state, but it is also used for building aggregates. This article aimed at the use of the sandstone of this formation in the ceramic mass for coating. Initially, the material was sampled. It went through the comminution process to achieve the required granulometry. After this, three formulations were made to incorporate this new material into the traditional ones. The methods were performed according to ISO 13816. After sintering at 1200 °C, the specimens were subjected to the physical tests. A positive result was obtained for the use of the Acu sandstone in low concentrations. It is clear, therefore, its use in ceramics for coating.

Doping effect on the structural properties of Cu{sub 1−x}(Ni, Zn, Al and Fe){sub x}O samples (0

Energy Technology Data Exchange (ETDEWEB)

Amaral, J.B. [Faculdade Estácio de Sergipe, 49020-530 Aracaju, SE (Brazil); Araujo, R.M. [Coordenação de Química, IPISE/PIC, Faculdade Pio Décimo, 49095-000 Aracaju, SE (Brazil); Pedra, P.P. [CETEC, Universidade Federal do Recôncavo da Bahia, 44380-000 Cruz das Almas, BA (Brazil); Meneses, C.T.; Duque, J.G.S. [Departamento de Física, Universidade Federal de Sergipe, Campus Prof. Alberto Carvalho, 49500-000 Itabaiana, SE (Brazil); Rezende, M.V. dos S, E-mail: mvsrezende@gmail.com [Departamento de Física, Universidade Federal de Sergipe, Campus Prof. Alberto Carvalho, 49500-000 Itabaiana, SE (Brazil)

2016-09-15

In this work, the effect of insertion of transition metal, TM (=Ni, Zn, Al and Fe), ions in Cu{sub 1−x}TM{sub x}O samples (0method is studied through experimental and computational methods. The analyses of X-ray diffraction (XRD) patterns using Rietveld refinement show that i) at x=0, all samples present a monoclinic crystal system with space group C2/c and ii) for increasing the TM-doping, Ni and Zn-doped samples show a small amount of spurious phases for concentrations above x=0.05. Based on these results, a defect disorder study for using atomistic computational simulations which is based on the lattice energy minimization technique is employed to predict the location of the dopant ions in the structure. In agreement with XRD data, our computational results indicate that the trivalent (Al and Fe ions) are more favorable to be incorporated into CuO matrix than the divalent (Ni and Zn ions). - Graphical Abstract: The effect of insertion of transition metal, TM (=Ni, Zn, Al and Fe), ions in Cu{sub 1−x}TM{sub x}O samples (0method is studied through experimental and computational methods. Display Omitted.

Characterization of beta radiation fields using radiochromic films; Caracterizacao de campos de radiacao beta utilizando filmes radiocromicos

Energy Technology Data Exchange (ETDEWEB)

Benavente, Jhonny A.; Silva, Teogenes A. da, E-mail: jabc@cdtn.b [Centro de Desenvolvimento da Tecnologia Nuclear (CDTN/CNEN-MG), Belo Horizonte, MG (Brazil). Programa de Pos-Graduacao em Ciencia e Tecnologia das Radiacoes, Minerais e Materiais; Meira-Belo, Luiz C.; Reynaldo, Sibele R. [Centro de Desenvolvimento da Tecnologia Nuclear (CDTN/CNEN-MG), Belo Horizonte, MG (Brazil)

2011-07-01

The objective of this work was to study the response of radiochromic films for beta radiation fields in terms of absorbed dose. The reliability of the EBT model Gafchromic radiochromic film was studied. A 9800 XL model Microtek, transmission scanner, a 369 model X-Rite optical densitometer and a Mini 1240 Shimadzu UV spectrophotometer were used for measurement comparisons. Calibration of the three systems was done with irradiated samples of radiochromic films with 0.1; 0.3; 0.5; 0.8; 1.0; 1.5; 2.0; 2.5; 3.0; 3.5; 4.5 e 5.0 Gy in beta radiation field from a Sr-90/Y-90 source. Calibration was performed by establishing a correlation between the absorbed dose values and the corresponding radiochromic responses. Results showed significant differences in the absorbed dose values obtained with the three methods. Absorbed dose values showed errors from 0.6 to 4.4%, 0.3 to 31.8% and 0.2 to 47.3% for the Microtek scanner, the X-Rite Densitometer and the Shimadzu spectrophotometer, respectively. Due to the easy acquisition and use for absorbed dose measurements, the densitometer and the spectrophotometer showed to be suitable techniques to evaluate radiation dose in relatively homogeneous fields. In the case of inhomogeneous fields or for a two dimension mapping of radiation fields to identify anisotropies, the scanner technique is the most recommended. (author)

Marble waste characterization as a desulfurizing slag component for steel; Caracterizacao do residuo de marmore como componente de escorias dessulfurantes para aco

Energy Technology Data Exchange (ETDEWEB)

Coleti, J.L.; Grillo, F.F.; Tenorio, J.A.S. [Universidade de Sao Paulo (USP), SP (Brazil); De Oliveira, J.R. [Instituto Federal do Espirito Santo (IFES), ES (Brazil)

2014-07-01

The current steel market requires from steel plants better quality of its products. As a result, steel plants need to search for improvements and costs reduction in its process. Hence, the residue of marble containing significant quantities of calcium and magnesium carbonates, raw materials of steel refining slag, was characterized in order to replace the conventional lime used. Therefore, it will be possible to reduce the cost and volume of waste produced by the ornamental rock industry. The following methods were applied to test the waste potential: SEM with EDS, x-ray diffraction, x-ray fluorescence (EDX), Thermogravimetry (TG) and analysis of surface area and particle size by the BET method using dispersion leisure. The results indicated the feasibility of waste as raw material in the composition of desulfurizing slags. (author)

Synthesis and characterization of tungsten or calcium doped PZT ceramics; Sintese e caracterizacao do PZT dopado com W ou Ca

Energy Technology Data Exchange (ETDEWEB)

Santos, D.M.; Caracas, L.B.; Noronha, R.G.; Santos, M.M.T. dos [Universidade Federal do Maranhao (UFMA), Sao Luis, MA (Brazil). Dept. de Desenho e Tecnologia. Curso de Desenho Industrial; Paiva-Santos, C.O., E-mail: denilson@ufma.b [Universidade Estadual Paulista (IQ/UNESP), Araraquara, SP (Brazil). Inst. de Quimica

2009-07-01

Pure and doped (tungsten or calcium) PZT ceramics were prepared by association of the polymeric precursor and partial oxalate method. The phase formation was investigated by thermal analysis (TG/DSC) and X-ray diffraction (XRD). The affect of W or Ca doping PZT and their electrical properties was evaluated. Substitution of W by Ti and Ca by Pb leads to an increase of Curie temperature and broadening of dielectric constant. A typical hysteresis loop was observed at room temperature and the remnant polarization was increased with the content of W and Ca. (author)

Compaction of lithium-silicate ceramics using spark plasma sintering

Czech Academy of Sciences Publication Activity Database

Kubatík, Tomáš František; Lukáč, František; Mušálek, Radek; Brožek, Vlastimil; Stehlíková, K.; Chráska, Tomáš

2017-01-01

Roč. 61, č. 1 (2017), s. 40-44 ISSN 0862-5468 R&D Projects: GA ČR GB14-36566G Institutional support: RVO:61389021 Keywords : Li2Si2O5 * Li2SiO3 * Spark plasma sintering (SPS) * Quantitative Rietveld refinement * X-ray diffraction (XRD) Subject RIV: JG - Metallurgy OBOR OECD: Materials engineering Impact factor: 0.439, year: 2016 http://www.ceramics-silikaty.cz/index.php?page=cs_detail_doi&id=789

Neutron powder diffraction studies of Hydrogen and Denterium in Palladium Phosphides

International Nuclear Information System (INIS)

Andersson, Y.

1986-01-01

The use of the Rietveld-type profile refinements on neutron powder diffraction intensity data for determining crystallographic positions of hydrogen and deuterium in metal hydrides is illustrated by results obtained on some hydrogenated and deuterated palladium phosphides. The structural features of the solid solutions of hydrogen and deuterium in Pd/sb15/P/sb2/ Pd/sb6/P and Pd/sb3/P/sb1-u/ (0< u<0.28) are briefly presented and discussed

On the role of Fe{sup 3+} ions in Fe{sub x}O{sub y}/C catalysts for hydrogen production from the photodehydrogenation of ethanol

Energy Technology Data Exchange (ETDEWEB)

Galindo-Hernández, Félix, E-mail: felixgalindo@gmail.com [Universidad Nacional Autónoma de México (U.N.A.M.), A.P. 20-364, México City, D.F. 01000 (Mexico); Instituto Mexicano del Petróleo (I.M.P.), Eje Central Lázaro Cárdenas Norte 152 Col. San Bartolo Atepehuacan, México City, D.F. 07730 (Mexico); ESIQIE, Instituto Politécnico Nacional, Col. Zacatenco, Av. Politécnico s/n, México City, D.F. 07738 (Mexico); Wang, Jin-An; Chen, Lifang [ESIQIE, Instituto Politécnico Nacional, Col. Zacatenco, Av. Politécnico s/n, México City, D.F. 07738 (Mexico); Bokhimi, Xim [Universidad Nacional Autónoma de México (U.N.A.M.), A.P. 20-364, México City, D.F. 01000 (Mexico); Gómez, Ricardo; Pérez-Larios, Alejandro [Department of Chemistry, Universidad Autónoma Metropolitana-Iztapalapa, San Rafael Atlixco 186, A.P. 55-534, México City, D.F. 09340 (Mexico); Nava Entzana, Noel [Instituto Mexicano del Petróleo (I.M.P.), Eje Central Lázaro Cárdenas Norte 152 Col. San Bartolo Atepehuacan, México City, D.F. 07730 (Mexico)

2013-12-15

Graphical abstract: In Fe{sub x}O{sub y}/C photocatalyts important effect of Fe{sup 3+} ions in the photodehydrogenation of the ethano was noticed. -- Highlights: • Iron oxides supported on carbon are photoactive catalysts. • Photoactivity in dehydrogenation of ethanol depends of the amount of Fe{sup 3+} ions present in the catalysts. • The capacity of UV–vis absorbance by the Fe{sub x}O{sub y}/C catalysts is significantly dependent of the amount of Fe{sup 3+} ions. • A maximum of rate constant, K = 2125 μmol h{sup −1}, was obtained from the sample with 30 wt% Fe. -- Abstract: Fe{sub x}O{sub y}/C photocatalysts at different iron content were prepared by the incipient wet impregnation method and calcined at 773 K. The photocatalysts were characterized by means of nitrogen adsorption–desorption isotherms, surface fractal dimension, non-local density functional theory, X-ray diffraction, Rietveld refinement and UV–vis spectroscopy. The photocatalytic activity was evaluated using the photodehydrogenation of ethanol as a model reaction for the production of hydrogen. The specific surface areas of Fe{sub x}O{sub y}/C substrates, with 15, 20 and 30 wt% iron content, diminished from 638 to 490 m{sup 2}/g, as the iron content increased. X-ray diffraction analysis showed that iron oxides coexist as wustite and magnetite in samples with Fe contents of 15 and 20 wt%; for sample with 30 wt% Fe, wustite, magnetite and hematite phases were observed. The photophysical, textural and structural properties were modified by the hematite phase formed by thermal treatment. The Rietveld refinements denoted changes in occupancy of Fe{sup 3+} and Fe{sup 2+} in Fe{sub x}O{sub y} crystallites. A relationship between the Fe{sup 3+} ions content and the reactivity for the hydrogen production from the photodehydrogenation of ethanol (from 1360 to 2125 μmol h{sup −1}), was evidenced.

On the “possible” synergism of the different phases of TiO 2 in photo-catalysis for hydrogen production

KAUST Repository

Wahab, A.K.

2017-05-19

The effect of TiO2 phase composition on the photocatalytic hydrogen production of water/ethanol (95/5 volume ratio) has been studied in order to understand the structural effect (and associated electronic properties) on the reaction within the so called “synergistic effect” concept. Within the investigated series of 1wt.% Pt/TiO2 with initial particle dimension of ca. 15nm the highest hydrogen production rate per unit area was observed for catalysts composed of 80% anatase, 18% rutile and 2% brookite. The associated particle sizes for this catalyst were 44, 82 and 33nm for the three phases, respectively. XRD patterns analyzed by the Rietveld method as well as X-ray absorption near-edge spectra (XANES) of the Ti K-edge mapped the phase transformation from anatase/brookite to rutile where it appears that the brookite phase is initially transformed to anatase phase. XRD patterns and Raman shift were found to be more sensitive to subtle changes in phase composition when compared to UV-vis absorbance or XANES of the Ti K-edge. The photocatalytic reaction for the complete series was conducted in identical condition and with excess photon flux in order to extract accurate reaction rates. In addition to the observed multi-phase effects on the reaction rate, other parameters extracted from the Rietveld refinement of the X-ray diffraction patterns were found to be useful. In particular, at the narrow window where the reaction rate was found to be maximum, the c-dimension of the anatase phase had values in the range 9.510–9.515Å. These c-dimension values are between those observed for nanoparticles with less than 20nm in size and those for larger particles with a size above 50nm. Results from this work indicate that the synergism between anatase and rutile on the photocatalytic reaction for hydrogen production, often attributed to increase the charge carrier life time, may be linked to the lattice expansion of the anatase phase which in turn would affect its electronic

Correlation between the nanocrystalline Sm(Fe,Mo){sub 12} and its out of equilibrium phase Sm(Fe,Mo){sub 10}

Energy Technology Data Exchange (ETDEWEB)

Khazzan, S. [CMTR, ICMPE, UMR7182, CNRS - Université Paris Est, 2-8 rue Henri Dunant, F-94320 Thiais (France); Laboratoire Matériaux Organisation et Propriétés, Faculté des Sciences de Tunis, Université de Tunis El Manar, 2092 Tunis (Tunisia); Bessais, L., E-mail: bessais@glvt.cnrs.fr [CMTR, ICMPE, UMR7182, CNRS - Université Paris Est, 2-8 rue Henri Dunant, F-94320 Thiais (France); Van Tendeloo, G. [EMAT, University of Antwerp, B-2020 Antwerp (Belgium); Mliki, N. [Laboratoire Matériaux Organisation et Propriétés, Faculté des Sciences de Tunis, Université de Tunis El Manar, 2092 Tunis (Tunisia)

2014-08-01

Nanostructured Sm–Fe–Mo semi-hard magnetic material exhibiting enhanced magnetic properties can be produced by ball milling followed by recrystallization. Milled samples were annealed for 30 min in a vacuum at different temperatures (T{sub A}) between 700 and 1190 °C. The effects of heat treatment and Mo content on structural and magnetic property changes have been investigated by means of X-ray diffraction using the Rietveld method, transmission electron microscopy and magnetic measurements. For samples annealed at T{sub A}>900°C the tetragonal ThMn{sub 12}-type structure is identified, while for 700Rietveld analysis gives a stoichiometry ratio equal to 1:10, for the out of equilibrium hexagonal phase, which is described with three crystallographic transition metal sites: 3g is fully occupied, 6l occupation is limited to hexagons surrounding the Fe dumbbell pairs 2e. We have performed a magnetic and structural study of nanocrystalline metastable P6/mmm Sm(Fe{sub 1−x}Mo{sub x}){sub 10}, correlated with structural transformation towards its equilibrium derivative I4/mmm Sm(Fe{sub 1−x}Mo{sub x}){sub 12}. A maximum of the coercive field H{sub C} (H{sub C}>5kOe) has been observed for the new hexagonal P6/mmm phase suggesting that nanocrystalline Sm(Fe,Mo){sub 10}, is a semi-hard material, and is potential candidate for magnetic recording. - Highlights: • A study of the structure and magnetic properties of SmFeMo compound. • A new out of equilibrium P6/mmm-type structure was found. • Correlation between the 1/12 phase and its out of equilibrium 1/10 phase.

Synthesis of Group IVB Metals Oxicarbides by Carboreduction Reactions

Directory of Open Access Journals (Sweden)

A.D. Mazzoni

2002-10-01

Full Text Available The metals of the group IV B (Ti, Zr, Hf present a series of carbides and oxicarbides with scientific and technological interest. Many of these compounds belong to the subsystem "MO - MC" of the pseudoternary "MO - MN - MC" system (where M = Ti, Zr or Hf. In this work carboreduction reactions of TiO2 and ZrO2 were performed in argon atmosphere, using temperatures from 1250° to 1650° and reaction times of 120 min. The oxicarbides obtained were in the range TiC0.16O0.84 to TiC0.73O0.27 and ZrC0.46O0.54 to ZrC0.90O0.10. respectively. The reaction products were characterized by X-ray diffraction (XRD, with the calculation of their cell constants by means of the Rietveld method. Scanning Electron Microscopy (SEM was used in the characterization of powdered materials. Additionally, the carborreduction reaction was followed by weight loss.

Structural, magnetic and electric behavior of the new Ba2TiMoO6 material

International Nuclear Information System (INIS)

Alarcon-Suesca, C.E.; Opel, M.; TellezLandínez Téllez, D.A.; Roa-Rojas, J.

2012-01-01

We report synthesis and characterization of the structural, morphologic and ferroelectric behavior of the complex perovskite Ba 2 TiMoO 6 . Samples of Ba 2 TiMoO 6 were synthesized through standard solid state reaction methods. Crystalline structure was studied by means of X-ray diffraction experiments and Rietveld-like analysis. Results reveal that material crystallizes in a tetragonal structure, space group P4/mnm (no. 123), with cell parameters a=3.8557 Å and c=11.8678 Å. The tolerance factor of perovskite was determined to be 1.04. Surface morphology was examined using Scanning Electron Microscopy, which shows the micrometric granular character of samples with 1.0-5.0 μm mean grain size. Ferroelectric response of material was established from curves of polarization as a function of applied electric field. Our results reveal that Ba 2 TiMoO 6 double perovskite evidences a ferroelectric hysteretic behavior at ambient temperature and paramagnetic ordering. © 2011 Elsevier Science. All rights reserved.

Structure-process-yield interrelations in nanocrystalline cellulose extraction

Energy Technology Data Exchange (ETDEWEB)

Hamad, W.Y.; Hu, T.Q. [FPInnovations, Vancouver, BC (Canada). Paprican Div.

2010-06-15

An understanding of the effect of hydrolysis conditions on yields of extracted water-insoluble cellulose materials is needed in order to understand the full potential of the extracted materials and the extent of their applications. This study provided a detailed analysis of the extraction of highly crystalline water-insoluble cellulose nanomaterials from commercial bleached kraft pulps using a sulfuric acid hydrolysis process. The process-yield-structure interrelations of the extracted materials were evaluated. The reproducibility of the hydrolysis process was evaluated, and methods of optimizing the yield of the extracted nanomaterials were explored. A Ruland-Rietveld analysis was used to resolve X-ray diffraction patterns and characterize crystallite size, crystalline and amorphous areas, and to determine the crystallinity of the extracted materials. The study showed that sulfation determines the yield of the materials and imparts the unique solid-state characteristics of the nanomaterials. The nanomaterials possessed iridescent patterns typical of chiral nematic materials. 27 refs., 3 tabs., 7 figs.

Powder neutron diffraction study on Pb2Sr2YCu3O8+δ(δ = 0.0 and 1.67)

International Nuclear Information System (INIS)

Fujishita, Hideshi; Sato, Masatoshi; Morii, Yukio; Funahashi, Satoru.

1993-01-01

Powder neutron diffraction patterns of Pb 2 Sr 2 YCu 3 O 8+δ (δ = 0.0 and 1.67) were analyzed by Rietveld method. For δ = 0, it had been indicated, by powder X-ray diffraction, that the structure was a monoclinic one. The R factors of the present analysis for the monoclinic structure were about 3/4 of those for the previous orthorhombic ones. The structure was almost the same as the previous X-ray result except z (02). For the annealed phase, the tetragonal and the orthorhombic structures had been presented by X-ray diffraction and by neutron diffraction, respectively. The R factors of the present analysis for the orthorhombic structure were about 5/6 of those for the tetragonal structure. The distance between the Pb plane and the oxygen deficient Cu plane was found to become larger in proportion to δ, though there occurs a phase separation in low δ region. (author)

Crystal structure of calcioburbankite and the characteristic features of the burbankite structure type

International Nuclear Information System (INIS)

Belovitskaya, Yu.V.; Pekov, I.V.; Gobechiya, E.R.; Kabalov, Yu.K.; Subbotin, V.V.

2001-01-01

The crystal structure of calcioburbankite (Na,Ca) 3 (Ca,RE,Sr,Ba) 3 (CO 3 ) 5 found in carbonatites from Vuoriyarvi (North Kareliya) was solved by the Rietveld method. The experimental data were collected on an ADP-2 diffractometer (λCuK α radiation; Ni filter; 16.00 deg. 1 + α 2 ) reflections was 455). All the calculations were performed within the sp. gr. P6 3 mc; a = 10.4974(1) A, c = 6.4309(1) A, V = 613.72(1) A 3 ; R wp = 2.49%. The structure was refined with the use of the anisotropic thermal parameters for the (Na,Ca) and (Sr,Ba,Ce) cations. The comparison of the crystal structures of all of the known hexagonal representatives of the burbankite family demonstrates that the burbankite structure type (sp. gr. P6 3 mc) is stable, irrespectively of the occupancy of the ten-vertex polyhedra predominantly with Ca, Sr, or Ba cations and the occupancies of the positions in the eight-vertex polyhedra

Synthesis of Ca{sub 3}CO{sub 4}O{sub 9} via solid state reaction; Sintese de Ca{sub 3}CO{sub 4}O{sub 9} via reacao no estado solido

Energy Technology Data Exchange (ETDEWEB)

Melo, K.P.; Dutra, R.P.S.; Marques, K.A.; Junior, S.M.S.; Brasileiro, C.T.; Coutinho, S.V.C.R.; Souza, T.; Chagas, T.F.; Silva, R.M.; Macedo, D.A., E-mail: kliviamelo@outlook.com [Universidade Federal da Paraiba (UFPB), Joao Pessoa, PB (Brazil)

2016-07-01

Solid oxide fuel cells (SOFCs) stand out as the most promising today's energy conversion technologies. In the development of cathode materials for SOFC, calcium cobaltate (Ca3Co4O9, C349) appears as a potential alternative to traditional lanthanum manganites. In this work, C349 was prepared via solid state reaction of stoichiometric mixtures containing CaCO3 from mollusk shells, in natura (M1) and heat treated at 550 ° C (M2), and Co3O4 obtained by citrate method. The M1 and M2 mixtures were calcined at 800 (powder) and 900 ° C (tablets) for 12 h. The crystal structure and phase composition of the powder and the reaction products were studied by X-ray diffraction Rietveld refinement of the diffraction data. The results showed the formation of free C349 secondary stages, showing a good alternative to use waste from seafood shells as raw material for obtaining high-value ceramics.(author)

Synthesis of Ca_3CO_4O_9 via solid state reaction

International Nuclear Information System (INIS)

Melo, K.P.; Dutra, R.P.S.; Marques, K.A.; Junior, S.M.S.; Brasileiro, C.T.; Coutinho, S.V.C.R.; Souza, T.; Chagas, T.F.; Silva, R.M.; Macedo, D.A.

2016-01-01

Solid oxide fuel cells (SOFCs) stand out as the most promising today's energy conversion technologies. In the development of cathode materials for SOFC, calcium cobaltate (Ca3Co4O9, C349) appears as a potential alternative to traditional lanthanum manganites. In this work, C349 was prepared via solid state reaction of stoichiometric mixtures containing CaCO3 from mollusk shells, in natura (M1) and heat treated at 550 ° C (M2), and Co3O4 obtained by citrate method. The M1 and M2 mixtures were calcined at 800 (powder) and 900 ° C (tablets) for 12 h. The crystal structure and phase composition of the powder and the reaction products were studied by X-ray diffraction Rietveld refinement of the diffraction data. The results showed the formation of free C349 secondary stages, showing a good alternative to use waste from seafood shells as raw material for obtaining high-value ceramics.(author)

Synthesis and characterization of bismuth alkaline titanate powders

Energy Technology Data Exchange (ETDEWEB)

Torres-Huerta, A.M., E-mail: atorresh@ipn.mx [CICATA-Altamira, Instituto Politecnico Nacional, Km. 14.5 Carretera Tampico Puerto Industrial Altamira, Altamira, Tamps. 89600 (Mexico); Dominguez-Crespo, M.A. [CICATA-Altamira, Instituto Politecnico Nacional, Km. 14.5 Carretera Tampico Puerto Industrial Altamira, Altamira, Tamps. 89600 (Mexico); Hernandez-Perez, M.A. [ESIQIE, Metalurgia, Instituto Politecnico Nacional, Mexico, D. F (Mexico); Garcia-Zaleta, D.S. [CICATA-Altamira, Instituto Politecnico Nacional, Km. 14.5 Carretera Tampico Puerto Industrial Altamira, Altamira, Tamps. 89600 (Mexico); Brachetti-Sibaja, S.B. [CICATA-Altamira, Instituto Politecnico Nacional, Km. 14.5 Carretera Tampico Puerto Industrial Altamira, Altamira, Tamps. 89600 (Mexico); Instituto Tecnologico de Ciudad Madero, Av. 1o. de Mayo esq. Sor Juana Ines de la Cruz s/n Col. Los Mangos C.P.89440 Cd. Madero Tamaulipas (Mexico)

2011-06-15

In this work, samples of bismuth alkaline titanate, (K{sub 0.5}Na{sub 0.5}){sub (2-x/2)}Bi{sub (x/6)}TiO{sub 3}, (x = 0.05-0.75) have been prepared by conventional ceramic technique and molten salts. Metal oxides or carbonates powders were used as starting raw materials. The crystalline phase of the synthesized powders was identified by the X-ray diffraction (XRD) and particle morphology was characterized by scanning electron microscopy (SEM). Solid state reaction method was unsuccessful to obtain pellets. From XRD results, a rhombohedral structure was detected and the parameter lattice were estimated to be a = 5.5478 A and {alpha} = 59.48{sup o}. These parameters were used to refine the structure by Rietveld analysis. SEM results showed several morphologies. Apparently, bismuth is promoting the grain growth whose sizes vary from 30 nm to 180 nm It is expected that these materials can be utilized in practical applications as substitutes for lead zirconatetitanate (PZT)-based ceramics.

Synthesis of hydroxyapatite and structural refinement by X-ray diffraction

International Nuclear Information System (INIS)

Araujo, Jorge Correa de

2007-01-01

A sample of hydroxyapatite was synthesized and its crystalline structure was analyzed by X-ray diffraction by means of the Rietveld method. Two functions were used to fit the peak profiles, modified Voigt (TCHZ) and Pearson VII. The occupational factors and lattice parameters obtained by both models show that the sample does not contain relevant cationic substitutions. The interatomic distances from Ca1 to oxygens O1, O2 and O3 were adequate for a pure hydroxyapatite without defect at site Ca1. Besides, the use of multiple lines in planes (300) and (002) associated with the model Pearson VII resulted in good agreement with the TCHZ model with respect to the size-strain effects with an ellipsoidal shape of crystallites. In conclusion, the procedures adopted in the synthesis of hydroxyapatite produced a pure and crystalline material. The experimental results of transmission electron microscopy confirmed the predicted shape of crystals. (author)

Synthesis of hydroxyapatite and structural refinement by X-ray diffraction; Sintese da hidroxiapatita e refinamento estrutural por difracao de raios-X

Energy Technology Data Exchange (ETDEWEB)

Araujo, Jorge Correa de [Universidade do Estado do Rio de Janeiro (UERJ), Sao Goncalo, RJ (Brazil). Faculdade de Formacao de Professores; Sena, Lidia [Instituto Nacional de Metrologia, Normalizacao e Qualidade Industrial (INMETRO), Duque de Caxias, RJ (Brazil). Div. de Metrologia de Materiais; Bastos, Ivan Napoleao [Universidade do Estado do Rio de Janeiro (UERJ), Nova Friburgo, RJ (Brazil). Inst. Politecnico]. E-mail: jcaraujo@iprj.uerj.br; Soares, Gloria Dulce de Almeida [Universidade Federal do Rio de Janeiro (UFRJ), RJ (Brazil)

2007-07-01

A sample of hydroxyapatite was synthesized and its crystalline structure was analyzed by X-ray diffraction by means of the Rietveld method. Two functions were used to fit the peak profiles, modified Voigt (TCHZ) and Pearson VII. The occupational factors and lattice parameters obtained by both models show that the sample does not contain relevant cationic substitutions. The interatomic distances from Ca1 to oxygens O1, O2 and O3 were adequate for a pure hydroxyapatite without defect at site Ca1. Besides, the use of multiple lines in planes (300) and (002) associated with the model Pearson VII resulted in good agreement with the TCHZ model with respect to the size-strain effects with an ellipsoidal shape of crystallites. In conclusion, the procedures adopted in the synthesis of hydroxyapatite produced a pure and crystalline material. The experimental results of transmission electron microscopy confirmed the predicted shape of crystals. (author)

Synthesis and characterization of ceramics BNO (BiNbO4) added to 10% of CuO

International Nuclear Information System (INIS)

Sales, A.J.M.; Silva, P.M.O.; Rodrigues Junior, C.A.; Sombra, A.S.B.

2012-01-01

The study of the synthesis and structural characterization of ceramic BiNbO4 and behavior of density when added 10% by weight of CuO, with a view to applications in ceramic capacitors, are presented in this work. The BiNbO4 was prepared by conventional ceramic method. The milled powders were calcined for 2 hours at 850 °C for 3 hours and characterized by using a diffractometer Rigaku DMAXB of Co-α radiation. A more detailed characterization by XRD was performed using the program DBWS9807a using the Rietveld refinement of crystal structures, which confirmed the achievement of the α-BNO phase with orthorhombic structure. Were produced buks with the calcined powder, they were sintered at 925 °C. In order to study the grain morphology and distribution of pores in the ceramic body, the surface of the sample by adding 10% of CuO was analyzed by Scanning Electron Microscopy which confirmed a better densification. (author)

Production of ferroelectric ceramic SrBi_2Nb_2O_9 (SBN) by high energy milling and their characterization

International Nuclear Information System (INIS)

Sancho, E.O.; Pires Junior, G.F.M.; Rodrigues, H.O.; Sombra, A.S.B.; Sales, J.C.

2011-01-01

Bismuth compounds, such as SrBi_2Nb_2O_9 (SBN), lead-free, is an alternative to the use of PZT because of its excellent ferroelectric properties, especially regarding the change of polarization. SBN is synthesized by the method of the solid state by high energy ball milling in reactive polymer with zirconia beads, which were subsequently doped with Bi_2O_3 and La_2O_3 aiming to promote intentional changes in the chemical structure of the ceramic, resulting in changes in properties electrical, magnetic and optical materials. The quantitative analysis obtained by Rietveld refinement confirmed the orthorhombic crystal structure with lattice parameters (a = 5.5158 Å, b = 5.5133 Å and c = 25.0765 Å, α = β = γ = 90 °) for indices convergence S = 1.72 (goodness of fit), where S is given by the ratio RWP / Rexp. And, the Raman shifts at 174, 204, 570 and 834 cm-1 indicated the formation of SBN perovskita type. (author)

Synthesis and characterization of BNO (BiNbO4) ceramics added to 3% of ZnO

International Nuclear Information System (INIS)

Sales, A.J.M.; Pires Junior, G.F.M.; Rodrigues, H.O.; Sousa, D.G.; Sales, J.C.; Sombra, A.S.B.

2012-01-01

This work describes the synthesis and study of the structural characterization of ceramic BiNbO4 and density behavior when added 3% by weight of ZnO with a view to use in capacitors. The manufacture of BiNbO4 was made by conventional ceramic method. The powders were milled for two hours, calcined at 850 ° C for 3 h and characterized by XRD with Diffractometer Rigaku DMAXB of Co-α radiation. A more detailed XRD characterization was performed with the program DBWS9807a using the Rietveld refinement of crystal structures, which confirmed the achievement of phase -α-BiNbO4. Were made 'buks' with the calcined powder and these were sintered at 1025 ° C. In order to study the grain morphology and distribution of pores in the ceramic body, the surface of the sample with addition of 3% by weight of ZnO was analyzed by Scanning Electron Microscopy which confirmed a better densification. (author)

Study of SrBi4Ti4O15 (SBTi) dielectric properties of doped PbO

International Nuclear Information System (INIS)

Rodrigues Junior, C.A.; Silva Filho, J.M.; Freitas, D.B.; Oliveira, R.G.M.; Sombra, B.; Sales, J.C.

2012-01-01

The ceramic SrBi 4 Ti 4 O 15 (SBTI), cation-deficient perovskite A 5 B 4 O 15 , was prepared by the method of solid state reaction and then doped with PbO (in the range 2-10% by weight). The samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and impedance spectroscopy at room temperature. The X-ray analysis was performed by the Rietveld refinement. The micrographs of the samples show globular-shaped grains (doped PbO). The dielectric properties: dielectric constant (Κ' or έ) and dielectric loss tangent (tan δ), were measured at room temperature in the frequency range 100 Hz - 1 MHz dielectric properties of these 1 MHz sample doped with 10 % PbO showed the dielectric constant Κ'= 168.34 and dielectric loss tangent tanδ, = 7,1.10 -2 . These results show a good possibility of miniaturization of electronic devices such as capacitors. (author)

Structural and microstructural comparative analysis on metallic alloys of composition Cu{sub y%}-Ni{sub x%}-Me (Me = Sn, Cr, Al, Pt)

Energy Technology Data Exchange (ETDEWEB)

Marques, I.M.; Okazaki, A.K.; Silveira, C.R. da; Carvalhal, M.A.; Monteiro, W.A.; Carrio, J.A.G. [Physics Department, CCH, Presbyterian Mackenzie University, Materials Science and Technology Centre, Sao Paulo, SP (Brazil); Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil)], e-mail: jgcarrio@mackenzie.br

2010-07-01

This work presents a comparative study of microstructural and electrical properties of polycrystalline material Cu-Ni alloys synthesized by conventional and powder metallurgy. A sample of Cu{sub 99,33%} Ni{sub 0,23%} Pt{sub 0,43%} was produced in electric furnace with voltaic arc and various samples containing Al, Sn and Cr as third element were produced by powder metallurgy. The microstructure of the samples was studied by optical microscopy, Vickers micro hardness and x rays powder diffraction. Their electrical conductivity was measured with a milliohmeter Agilent (HP) 4338B. Refinements of the crystalline structure of the samples were performed by the Rietveld method, using the refinement program GSAS. The refinement results and Fourier differences calculations indicate that the copper matrix structure presents not significant distortions by the used amounts of the other metal atoms. The refinement of non structural parameters allowed the micro-structural characterization. The dependence of the micro-structure with thermal and mechanical treatments is studied. (author)

Phase transition and enhanced magneto-dielectric response in BiFeO{sub 3}-DyMnO{sub 3} multiferroics

Energy Technology Data Exchange (ETDEWEB)

Tripathy, Satya N., E-mail: satyanarayantripathy@gmail.com; Pradhan, Dillip K., E-mail: dillip.pradhan79@gmail.com [Department of Physics and Astronomy, National Institute of Technology, Rourkela 769008 (India); Pradhan, Dhiren K.; Palai, Ratnakar; Katiyar, Ram S. [Department of Physics and Institute for Functional Nanomaterials, University of Puerto Rico, San Juan, Puerto Rico 00936 (United States); Mishra, Karuna K. [Condensed Matter Physics Division, Indira Gandhi Centre for Atomic Research, Kalpakkam 603102 (India); Sen, Shrabanee [Sensor and Actuator Division, Central Glass and Ceramics Research Institute, Kolkata 700032 (India); Paulch, Marian [Institute of Physics, University of Silesia, Uniwersytecka 4, 40-007 Katowice (Poland); Scott, James F. [Department of Physics, Cavendish Laboratory, University of Cambridge, Cambridge CB3 OHE (United Kingdom)

2015-04-14

We report systematic studies on crystal structure and magneto-dielectric properties of (1 − x) BiFeO{sub 3}-x DyMnO{sub 3} (0.0 ≤ x ≤ 0.2) nanoceramics synthesized by auto-combustion method. Rietveld refinement of X-ray diffraction data indicates a structural transition from R3c to R3c + Pn2{sub 1}a at x = 0.1. Field emission scanning electron micrographs display a decrease in grain size with increase in x. The presence of dielectric anomalies around antiferromagnetic transition temperature implies the magnetoelectric coupling. Dielectric measurements showed decrease in magnetic ordering temperature with increasing x in agreement with differential scanning calorimetry results. A significant increase in magnetization has been found with increasing DyMnO{sub 3} substitution. Magneto-impedance spectroscopy reveals a significant change (∼18%) in dielectric permittivity at H = 2 T for x = 0.2.