Aportaciones a la teoría y a la práctica de la absorciometría de rayos X en la discontinuidad de absorción

Tesis - Universidad Complutense de Madrid, 1980.Depto. de Química InorgánicaFac. de Ciencias QuímicasTRUEProQuestpu

Aportaciones a la teoría y a la práctica de la absorciometría de rayos X en la discontinuidad de absorción

Tesis - Universidad Complutense de Madrid, 1980.Depto. de Química InorgánicaFac. de Ciencias QuímicasTRUEProQuestpu

High-sensitivity piezoelectric perovskites for magnetoelectric composites

© 2015 National Institute for Materials Science. A highly topical set of perovskite oxides are high-sensitivity piezoelectric ones, among which Pb(Zr,Ti)O3 at the morphotropic phase boundary (MPB) between ferroelectric rhombohedral and tetragonal polymorphic phases is reckoned a case study. Piezoelectric ceramics are used in a wide range of mature, electromechanical transduction technologies like piezoelectric sensors, actuators and ultrasound generation, to name only a few examples, and more recently for demonstrating novel applications like magnetoelectric composites. In this case, piezoelectric perovskites are combined with magnetostrictive materials to provide magnetoelectricity as a product property of the piezoelectricity and piezomagnetism of the component phases. Interfaces play a key issue, for they control the mechanical coupling between the piezoresponsive phases. We present here main results of our investigation on the suitability of the high sensitivity MPB piezoelectric perovskite BiScO3-PbTiO3 in combination with ferrimagnetic spinel oxides for magnetoelectric composites. Emphasis has been put on the processing at low temperature to control reactions and interdiffusion between the two oxides. The role of the grain size effects is extensively addressed.This work has been funded by the Spanish MINECO through projects MAT2011-23709 and AIB2010PT-00332. Collaboration between ICMM and CEMES is framed within the COST Action MP0904. Serviciencia S L (Spain) participation in the design and built-up of a novel magnetoelectric measurement system is acknowledged. HA thanks the Ramón y Cajal Programme for financial support.Peer Reviewe

Dispositivo para la aplicación de la absorciometría de rayos X en la discontinuidad de absorción al análisis de muestras líquidas

Referencia OEPM: U0258935.-- Fecha de solicitud: 11/06/1981.-- Titular: Consejo Superior de Investigaciones Científicas (CSIC).Dispositivo para la aplicación de la absorciometría de rayos X en la discontinuidad de absorción al análisis de muestras líquidas, caracterizado porque consta de un cuerpo mecanizado en PVC, de forma rectangular y espesor variable, en cuyo centro se ha practicado un orificio circular de diámetro variable, y de dos tapas que encajan herméticamente en el reborde circular de dicho orificio y que consisten en un arco circular de aluminio que sostiene una fina lámina de una sustancia de absorción muy pequeña en la zona de longitudes de onda en la que se trabaja; en la parte superior de la cubeta se practican dos pequeños orificios que permiten la introducción de las muestras líquidas mediante una jeringuilla. Un dispositivo, caracterizado porque opcionalmente puede adaptársele una tapa que permite variar el espesor efectivo del dispositivo; esta tapa consta de una parte cilíndrica de distintas medidas que encajan herméticamente en el orificio central de la cubeta aprisionando las finas láminas que actúan como ventana.Peer reviewe

Electrical properties of ferroelectric BiMnO3-PbTiO3 under tailored synthesis and ceramic processing

Conductivity is a main issue in research on multiferroic perovskite oxides, which makes the characterization of their ferroelectric properties difficult, and for several compounds even to unambiguously state their ferroelectric nature. In this report, we use ferroelectric BiMnO3-PbTiO3 as a model system to study the relationships among synthesis, processing, and conductivity in ABO3 perovskite oxides with magnetically active cations in the B-site. Three single phase, dense ceramic materials processed by conventional sintering, hot pressing, or spark plasma sintering (SPS) of powders synthesized by either wet chemistry or mechanochemical activation were studied. Impedance spectroscopy analysis was carried out to obtain grain and grain boundary conductivities for the three materials, along with activation energies. Mechanosynthesis is shown not to modify the mechanism of bulk or boundary conductivity, but only the carrier concentration, while SPS processing results in a low temperature, additional conduction mechanism. © 2013 Copyright Taylor and Francis Group, LLC.This research was funded by MICINN (Spain) through project MAT2011-23709. HA thanks MICINN for funding through the RyC Programme. Collaboration of ICMM with CEMES is framed within the COST Action MP0904 (European Science Foundation, COST Programme).Peer Reviewe

Bi4Ti3O12 Ceramics from Powders Prepared by Alternative Routes: Wet No-Coprecipitation Chemistry and Mechanochemical Activation

The processing of ferroelectric Bi4Ti3O12 ceramics from powders prepared by wet no-coprecipitation chemistry (WNCC) and mechanochemical activation (MCA) has been investigated. Dense ceramics were obtained at sintering temperatures as low as 900°C. Exaggerated grain growth was observed for samples from WNCC, but not for those from MCA. Dielectric properties are discussed in relation to the type and concentration of defects, which is smaller for ceramic samples from WNCC. The activation energy of the dielectric relaxation for ceramics from MCA suggests that additional VO•• are present at the pseudoperovskite [Bi2Ti3O10]2− block in this case.Peer reviewe

Synthesis of nanocrystalline zinc ferrite powders from sulphuric pickling waste water

A low temperature method was used to synthesise nanocrystalline zinc ferrite powders from sulphuric pickling water (SPW), a waste 31 21 product of the steelmaking industry. The synthesis method consisted of coprecipitation of a bi-ionic Fe /Zn solution with 1M 31 21 n-butylamine. Fe from the SPW and Zn provided by ZnO were mixed at a molar ratio of 2.0. The precursor obtained in this manner showed a 2-line X-ray diffraction pattern similar to that of ferrihydrite. Thermal treatment of the precursor at |375 8C led to the formation of pure, fine-particle and stoichiometric ZnFe O powders. This process allows the total recovery of the iron in the SPW, as a product of 2 4 added value. The fine powders were characterised by XRD, FTIR, TG/DSC and SEM. The BET specific surface and the magnetic properties of the powders were also determined.The authors would like to thank the European Commission (Convention 7261/02/512) and the CICYT (project MAT94-0799 for funding of the study. They are also indebted to Dr. Patricia Crespo of the Facultad de Ciencias F´ısicas (UCM) for performing the magnetic determinations.Peer reviewe

Synthesis of mixed ferrite with spinel-type structure from a stainless steelmaking solid waste

Acid recovery plant powder, a solid by-product of the stainless steel industry with high iron, chromium and nickel content, was used to synthesise a nanocrystalline zinc–chromium–nickel ferrite in order to recover the total metal content of this waste as a valuable ferric product. Zn2+ was provided by dissolving ZnO in HNO3 and precipitation with 1M n-butylamine solution. The cubic spinel-type ferrite obtained, at temperature as low as 350°C, was characterised by X-ray powder diffraction, scanning and transmission electron microscopy.The authors would like to thank Mr. J. Berjano from [12] P. Poix, Cr. Acad. Sci. (Paris) 268 (1969) 1139. ICMM-Madrid (CSIC), Mr. F. Pinto from CCMA (CSIC) and Mr. P. Aparicio from CENIM(CSIC) for the technical assistance with the X-ray powder diffraction, SEM and TEM respectively.Peer reviewe

The effect of the starting solution on the physico-chemical properties of zinc ferrite synthesized at low temperature

Fine particle zinc ferrite powders (ZnFe2O4) were synthesized by co-precipitation of a bi-ionic Fe3+/Zn2+ solution with 1 M n-butylamine at low temperature. Ferric nitrate and ferrous sulphate solutions were used as the starting material to investigate the effect of the source of iron on particle size, morphology, thermal behaviour and surface area of the final products. ZnFe2O4. In both cases, Zn2+ ions were provided by ZnO. The ferrous ions of the sulphate solution were previously oxidized with H2O2 in sulphuric medium. The cubic spinel-type structure of the ferrite product was obtained at a lower temperature when nitrate solution was used. Zinc ferrite of smaller particle size and higher surface area was obtained when ferrous sulphate was used as the starting solution. The ferrite precursors produced at room temperature and final products were characterized by X-ray powder diffraction, Fourier transformed infrared spectroscopy, thermal analyses, scanning and transmission electron microscopy and nitrogen adsorption volumetry.Peer reviewe

Synthesis of nickel-chromium-zinc ferrite powders from stainless steel pickling liquors

A low-temperature method was used to synthesize a nickel–chromium–zinc ferrite from stainless steel pickling liquor, a waste product of the steel industry, which is listed in most industrialized countries as a toxic and hazardous waste. This article reports the recovery (as a valuable ferric product) of the total metal content of this waste (namely, iron, chromium, nickel, and minor manganese), by coprecipitation of the multi-ionic solution and Zn2+ (provided by ZnO) with 1 M n-butylamine at room temperature. The spinel-type ferrite produced was characterized by x-ray diffraction, thermogravimetric analysis and differential scanning calorimetry, and scanning electron microscopy. Its recorded magnetization of 2600 emu cm−3 allows its use in different magnetic applications. Furthermore, the synthesis method is a low-cost technology that yields a more environmentally friendly final effluent.Peer reviewe