Search

Your search keyword '"Turrillas, Xavier"' showing total 39 results
Start Over Author "Turrillas, Xavier"
39 results on '"Turrillas, Xavier"'

2. Mineralogical analysis of Brazilian Portland cements by the Rietveld method with emphasis on polymorphs M1 and M3 of alite

Author

Ministerio de Economía y Competitividad (España), Ministerio de Ciencia, Innovación y Universidades (España), Agencia Estatal de Investigación (España), Turrillas, Xavier [0000-0002-3419-2229], Rossetto, Cleusa M., Carezzatto, Geraldo L., Martinez, Luis G., Pecchio, Marcelo, Turrillas, Xavier, Ministerio de Economía y Competitividad (España), Ministerio de Ciencia, Innovación y Universidades (España), Agencia Estatal de Investigación (España), Turrillas, Xavier [0000-0002-3419-2229], Rossetto, Cleusa M., Carezzatto, Geraldo L., Martinez, Luis G., Pecchio, Marcelo, and Turrillas, Xavier

Abstract

Eight samples of Portland cement and a clinker provided by the Brazilian Association of Portland Cement were analysed with different laboratory diffractometers and a synchrotron instrument to determine the statistical variability in the determination of the mass percentage of the main crystalline phases. Five laboratories participated in the experiment. Data collection was performed by each laboratory following its own internal procedures for a standard Rietveld analysis of mineral phases. Both Cu and Mo radiations were used. Reflection geometries—with and without sample rotation—and transmission geometries were also used. The synchrotron diffraction pattern was acquired from a rotating capillary and a wavelength of 0.41290 Å. Analysis of all diffraction patterns was performed with the help of TOPAS Academic v. 6 with the specific purpose of determining the proportions of polymorphs M1 and M3 of alite, since their ratio must be taken into account for the subsequent development of the mechanical properties of concrete.

Published
2023

3. Arsenite sorption and co-precipitation with calcite

Author

Roman-Ross, Gabriela, Cuello, Gabriel, Turrillas, Xavier, Fernandez-Martinez, Alejandro, and Charlet, Laurent

Subjects
Physics - Chemical Physics, Physics - Geophysics
Abstract

Sorption of As(III) by calcite was investigated as a function of As(III) concentration, time and pH. The sorption isotherm, i.e. the log As(III) vs. log [As(OH)3 degrees / Assat] plot is S-shaped and has been modelled on an extended version of the surface precipitation model. At low concentrations, As(OH)3 degrees is adsorbed by complexation to surface Ca surface sites, as previously described by the X-ray standing wave technique. The inflexion point of the isotherm, where As(OH)3 degrees is limited by the amount of surface sites (ST), yields 6 sites nm-2 in good agreement with crystallographic data. Beyond this value, the amount of sorbed arsenic increases linearly with solution concentration, up to the saturation of arsenic with respect to the precipitation of CaHAsO3(s). The solid solutions formed in this concentration range were examined by X-ray and neutron diffraction. The doped calcite lattice parameters increase with arsenic content while c/a ratio remains constant. Our results made on bulk calcite on the atomic displacement of As atoms along [0001] direction extend those published by Cheng et al., (1999) on calcite surface. This study provides a molecular-level explanation for why As(III) is trapped by calcite in industrial treatments., Comment: 9 pages

Published
2008
Full Text
View/download PDF

4. Arsenic uptake by gypsum and calcite: Modeling and probing by neutron and x-ray scattering

Author

Fernandez-Martinez, Alejandro, Cuello, Gabriel J., Roman-Ross, Gabriela, Johnson, Mark R., Bardelli, Fabrizio, Turrillas, Xavier, and Charlet, Laurent

Subjects
Physics - Chemical Physics
Abstract

Here we report on two structural studies performed on As-doped gypsum (CaSO4 2H2O) and calcite (CaCO3), using neutron (D20-ILL) and x-ray (ID11-ESRF) diffraction data and EXAFS (BM8-ESRF). The aim of this study is to determine whether As gets into the bulk of gypsum and calcite structures or is simply adsorbed on the surface. Different mechanisms of substitution are used as hypotheses. The combined Rietveld analysis of neutron and x-ray diffraction data shows an expansion of the unit cell volume proportional to the As concentration within the samples. DFT-based simulations confirm the increase of the unit cell volume proportional to the amount of carbonate or sulphate groups substituted. Interpolation of the experimental Rietveld data allows us to distinguish As substituted within the structure from that adsorbed on the surface of both minerals., Comment: Proceedings of the Eighth International Conference on Neutron Scattering

Published
2007
Full Text
View/download PDF

6. Assessing the pozzolanic activity of cements with added sugar cane straw ash by synchrotron X-ray diffraction and Rietveld analysis

Author

Calligaris, Guilherme A., Franco, Margareth K.K.D., Aldrige, Laurence P., Rodrigues, Michelle S., Beraldo, Antonio Ludovico, Yokaichiya, Fabiano, Turrillas, Xavier, and Cardoso, Lisandro P.

Subjects
X-rays -- Diffraction, Radiation -- Analysis, Cement -- Analysis -- Mechanical properties, Business, Construction and materials industries
Abstract

ABSTRACT Sugar and alcohol industries generate large amount of wastes that could produce ashes of great reactivity with pozzolan properties. The objective of this paper is to evaluate the pozzolanicity [...]

Published
2015
Full Text
View/download PDF

12. Cation distribution of Mn-Zn ferrite nanoparticles using pair distribution function analysis and resonant X-ray scattering

Author

Ichikawa, Rodrigo U, Parra, João PRLL, Vallcorba, Oriol, Peral Alonso, Inmaculada, Yoshito, Walter K, Saeki, Margarida J, Turrillas, Xavier, Martinez, Luis G, Ichikawa, Rodrigo U, Parra, João PRLL, Vallcorba, Oriol, Peral Alonso, Inmaculada, Yoshito, Walter K, Saeki, Margarida J, Turrillas, Xavier, and Martinez, Luis G

Published
2018
Full Text
View/download PDF

16. Arsenate incroporation in gypsum probed by neutron, X-ray scattring and density functional theory modeling

Author

Fernandez-Martinez, Alejandro, Cuello, Gabriel J., Johnson, Mark R., Bardelli, Fabrizio, Roman-Ross, Gabriela, Charlet, Laurent, and Turrillas, Xavier

Subjects
Arsenic -- Chemical properties, Arsenic -- Structure, Gypsum -- Structure, Gypsum -- Analysis, Neutrons -- Diffraction, Neutrons -- Analysis, Chemicals, plastics and rubber industries
Abstract

Crystallography is used for studying the synthetic gypsum coprecipitated with arsenic at different concentrations and pH values and neutron and X-ray diffraction are used for analyzing the solid phases. The charge redistribution within the structure ion substitutions of either the protonated or the unprotonated arsenate species has shown an increase in the covalency in the interaction between [Ca.sup.2+] and As[O.sub.4.sup.3-], whereas the interaction between [Ca.sup.2+] and HAs[O.sub.4.sup.2-] has remained predominantly ionic.

Published
2008

34. Neutron Thermodiffractometry Study of Calcium Zirconate/Magnesium Oxide Formation in the ZrO2-CaO-MgO System.

Author

Serena, Sara, Caballero, Angel, Sainz, M. Antonia, Convert, Pierre, Campo, Javier, and Turrillas, Xavier

Subjects
MAGNESIUM compounds, RAW materials, NEUTRON diffraction, THERMAL analysis, THERMOGRAVIMETRY, CERAMICS
Abstract

The reaction process to obtain CaZrO3/MgO specimens In the ZrO2-CaO-MgO system from two mixtures of natural and synthetic raw materials were analyzed by neutron thermodiffractometry; differential thermal analysis-thermogravimetry (DTA-TG) also was used. The results from the different techniques provided a complete description of the decomposition and reaction process In the samples and proved that high-temperature neutron diffraction is a powerful tool for analyzing in situ reactions up to 1250°C in both mixtures. In the present work, the evolution of the crystalline phases, the mechanism and temperature of formation of CaZrO3, and the activation energy were properly established in terms of the neutron thermodiffraction study. [ABSTRACT FROM AUTHOR]

Published
2004
Full Text
View/download PDF

35. Decomposition of Dolomite Monitored by Neutron Thermodiffractometry.

Author

De Aza, Antonio H., Rodríguez, Miguel Angel, Rodríquez, José Luis, De Aza, Salvador, Pena, Pilar, and Turrillas, Xavier

Subjects
DOLOMITE, CHEMICAL decomposition
Abstract

Examines the decomposition of dolomite monitored by neutron thermodiffractomery. Application of Rietveld refinement and raw intensity data; Stages of dolomite composition; Chemical analysis of dolomite.

Published
2002
Full Text
View/download PDF

37. Location of Hsites in the fast proton-conductor H3OSbTeO6pyrochlore

Author

Alonso, José Antonio and Turrillas, Xavier

Abstract

The defect pyrochlore H3OSbTeO6oxide is an excellent proton conductor, showing a conductivity value of 10−1S cm−1at 30 °C under saturated water vapor partial pressure. It can be prepared by ion exchange from KTeSbO6pyrochlore in sulfuric acid at 453 K for 12 h. The full characterization of the structure of the H3OSbTeO6pyrochlore, including the location of the H3Ounits within the three-dimensional framework, has been carried out by neutron powder diffraction. A first Rietveld refinement of the SbTeO6−framework was performed in the Fd3mspace group a 10.15101 ; a difference Fourier map enabled the unambiguous location of the O2 atoms from the H3Oions at 32e x,x,x positions, and subsequently the H atoms at 96g x,x,z. The H3OSbTeO6crystal structure is constituted by a network of randomly distributed SbVO6and TeVIO6octahedra linked by their corners with Sb,Te–O1–Sb,Te angles of 136.2°. Hydronium ions are located off-center around the large 8a cages of the pyrochlore. The geometry of the O2–H3units is that of an almost regular tetrahedron, with O2 atoms at the center and the three H atoms in three of the vertices; the fourth vertex is supposed to be occupied by the O2 lone pair. The three O2–H bonds have equal distances of 1.0208 . The H3Ounits are linked to the O1 framework oxygens by weaker hydrogen bonds, with O1–H bond lengths of 1.6497 . The relatively large thermal factors of O2 and H, of 2.5 and 3.7 2, respectively, suggest that both kinds of atoms are not static at fixed positions but could be dynamically fluctuating between crystallographically equivalent sites.

Published
2005
Full Text
View/download PDF

39. Insights into the Local Structure of Tb-Doped KY 3 F 10 Nanoparticles from Synchrotron X-ray Diffraction.

Author

Ichikawa RU, Linhares HMSMD, Peral I, Baldochi SL, Ranieri IM, Turrillas X, and Martinez LG

Abstract

Pure and Tb-doped nanocrystalline KY 3 F 10 specimens were synthesized by coprecipitation, and portions of the samples underwent further heat treatment at 600 °C in a fluorinated atmosphere. Synchrotron X-ray diffraction patterns acquired at 30 keV allowed to determine both long- and short-range ordered structures by Rietveld and pair distribution function (PDF) analyses, respectively. PDF examination of the as-synthesized sample allowed to discern a slight deviation from the basic cubic building unit because the Y-F bond lengths could be explained in S.G. I 4/ mmm with cell parameters a = 8.1520(9) Å and c = 11.5876(29) Å, whereas Rietveld analysis could equally well fit both the cubic and tetragonal descriptions for the heat-treated specimens. Also, PDF revealed that the as-synthesized sample exhibited less structural coherence than the heat-treated one., Competing Interests: The authors declare no competing financial interest.

Published
2017
Full Text
View/download PDF

Catalog

Books, media, physical & digital resources
See catalog results