TEM-HRTEM study on the dehydration process of nanostructured Mg–Ca hydroxide into Mg–Ca oxide

The dehydration process from Mg0.97Ca0.03 (OH)2 nanoparticles (brucite type hexagonal structure) to Mg0.97Ca0.03O (periclase type cubic structure) was studied by Transmission Electron Microscopy (TEM-HRTEM), Electron Diffraction (SAED), Electron Energy Loss Spectroscopy (EELS) and image analysis. The transformation process was monitored in function of the reaction time applying 200 and 300 KV. Changes in porosity were possible to observe only during the irradiation with 200 KV. Depending on the irradiation time, the changes were gradual, producing an increase from the particle's edge towards the inner region. Different stages were observed, corresponding to the amount of water extracted from the particle, until finally a decrease in porosity and particle shrinkage occurs, coinciding with the formation of the Mg–Ca oxide. However, when samples were exposed to 300 KV, the dehydration process was much faster, and the pores structure was destroyed in a shorter time in comparison with lower doses of radiation. High resolution electron microscopy (HRTEM) applying 300 kV allowed identifying the progressive changes from brucite to periclase, including the formation of an intermediate dehydrated phase. The transformation along [0001]brucite and View the MathML sourcebrucite orientations was monitored determining differences in the kinetic of reaction related to the presence of point defects affecting the atomic lattice.This present research was funded by the Community of Madrid under the GEOMATERIALES 2 project (S2013/MIT-2914), by the Complutense University of Madrid’s Research Group: “The Alteration and Conservation of Stone Heritage” (921349), the Autonomous Region Program of Madrid, MULTIMAT-CHALLENGE (ref. S2013/MIT‐2862), the Innovation and Education Ministry ref. (MAT2013-47460-C5-5-P) and the Mat201019837/C06-05 projects.Peer reviewe

Production of Sponge Iron Powder by Reduction of a By-product of the Steelmaking Industry

Ref. Revista/libro: Proceedings of the International Powder Metallurgy Congress & Exhibition (PM2010). Volumen I. Editors: European Powder Metallurgy Association (EPMA). Florencia (Italia), October 2010.Rolling mill scale is a solid steelmaking by-product that contains metallic iron (Fe), wustite (FeO), hematite (α-Fe2O3) and magnetite (Fe3O4). It also contains traces of non-ferrous metals, alkaline compounds and oils from the rolling process. A study is made of the reduction of mill scale to sponge iron, in covered crucibles, using coke at different temperatures (1050º-1150ºC) and times (3-12 h). The final treatment of the samples was carried out in a hydrogen atmosphere furnace at 900ºC for 0.5 h. The reduced samples are studied by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Oxygen analysis is carried out by combustion in a LECO oven. The reduction of mill scale allows the new use and development of this material to obtain sponge iron that can be re-used to the electric furnace as metallic load in steel manufacturing or as a raw material in the production of iron-base powder metallurgy parts.European Powder Metallurgy Association (EPMA).Peer reviewe

Synthesis of Ce/Ru Doped ZnO photocatalysts to the degradation of emerging pollutants in wastewater

Semiconductor nanoparticles (NPs) and nanowires (NWs) of doped ZnO system with different dopant content have been synthesized by Polyol-Mediated Thermolysis (PMT) process and Vapour-Solid (VS) reaction. The average crystallite size, morphology, specific surface area, and direct band gap have been evaluated. The structural and functional characteristics have been studied by X-Ray Diffraction techniques (XRD), Field Emission Scanning Electron Microscope (FESEM), High Resolution Transmission Electron Microscopy (HRTEM), Brunauer, Emmett and Teller (BET) method, UV-Vis Diffuse Reflectance Spectra (DRS), UV-Vis Spectroscopy, and Photoluminescence measurements (PL). Also, the photocatalytic activities of pure and doped ZnONPs were evaluated by removal rate of Methylene Blue (MB) under UV irradiation (365 nm) at room temperature. XRD patterns revealed the common hexagonal ZnO Wurtzite-type structures with a preferred orientation of (101) plane. Secondary phases as CeO2, Ce2O3, Ce, RuO2, Ru3O4, Ruhave been identified. For both dopant, Ceand Ru, and for all the concentrations in the precursor solution, FESEM and HRTEM showed NPswith morphologies ranging from spherical/ellipsoidal to hexagonal. The size of NPs was observed to decrease (from ~30 to ~16 nm) with increasing doping concentration due to the interaction between the Ce-O-Zn or Ru-O-Zn ions. EDS results confirmed the incorporation of Ce or Ru ions into ZnO lattice.Using the Kubelka-Munk treatment on the diffuse reflectance spectra, the direct band gap energy has been estimated to be slightly lower than 3.0 eV in both, the Ce and Ru-doped samples. Compared with pure ZnO NPs, the PL spectra of the doped NPs showed red-shifted UV emission and an enhanced blue emission with the typical broad green-yellow emission. The results showed that photocatalytic efficiency of doped ZnO NPs was always enhanced

Procedimiento de obtención de esponjas metálicas

Titulares: Universidad Carlos III de Madrid. - Consejo Superior de Investigaciones CientíficasProcedimiento de obtención de esponjas metálicas. La presente invención proporciona un procedimiento para obtener una esponja metálica a partir de un material metálico que comprende: i) reducción de un material metálico mediante tratamiento con un material carbonoso en horno con atmósfera de aire; y ii) reducción del producto obtenido en la etapa anterior mediante tratamiento en horno de atmósfera de hidrógeno. En particular, la invención describe la obtención de esponja de hierro a partir de cascarilla por el procedimiento anterior.Peer reviewe

Effect of temperature and reaction time of the synthesis of nanocrystalline brucite

Mg(OH)2 nanoparticles has been successfully synthesized by means of the hydrothermal method. The effect of the reaction time and the synthesis temperature on the nanoparticles obtained has also been studied. The physic-chemical properties of the synthesized brucite samples have been characterized by X-Ray-diffraction (XRD), scanning electron microscopy/energy dispersive X-rays analysis (SEM/EDX), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), thermogravimetry/ differential scanning Calorimetry (TG-DSC) and in situ high-temperature X-ray diffraction (XRD). The influence of the synthesis parameters in the brucite samples has been discussed in detail. Furthermore, it has been shown that the increase of temperature from 180 to 200ºC improves the crystallinity degree of Mg(OH)2 nanostructured particles and also, promotes the formation of plates with bigger uniform size. As well, the increase in the time reaction induces the formation of bigger size brucite plates. So, this hydrothermal method has been shown to be a really promising method for the large scale production.Peer Reviewe

Structural, morphological and luminescence properties of nanocrystalline up-converting Y1.89Yb0.1Er0.01O3 phosphor particles synthesized through aerosol route

Nanocrystalline up-converting Y₂ O₃Yb³⁺ Er³⁺ phosphor particles were processed in a dispersed system-aerosol, generated ultrasonically at 1.3 MHz from common nitrate precursor solution having fixed ytterbium-to-erbium concentration ratio. The appropriate process parameters: residence time 21 s, carrier gas (air) flow rate 1.6 dm3/min, synthesis temperature 900 °C, led to the formation of un-agglomerated spherical nanostructured secondary particles, having mean particle size of approx 450 nm, composed of primary nanoscaled (20 nm) subunits. In order to reach targeting phase crystallinity, the as-prepared particles were additionally annealed at 1100 °C in air for 12, 24 and 48 h, respectively. Particle structure, morphology and purity were analyzed by X-ray powder diffraction (XRPD), scanning electron microscopy (FESEM/SEM), analytical and high resolution transmission electron microscopy (TEM/HRTEM) in combination with energy dispersive X-ray analysis and Fourier Transform Infrared Spectroscopy (FTIR). All samples crystallized in a cubic bixbyte-structure, space group Ia-3. The crystallite size changed with annealing time from 30 nm in as-prepared sample to 135 nm in sample annealed for 48 h, respectively. Emission spectra were assigned to the following trivalent erbium f–f electronic transitions: ²H₉/₂ → ⁴I₁₅/₂ (blue: 407–420 nm), (²H₁₁/₂̦ ⁴S₃/₂) → ⁴I₁₅/₂ (green: 510–590 nm), and ⁴F₉/₂ → ⁴I₁₅/₂ (red: 640–720 nm). The significant improvement of the emission decay times were observed after thermal treatment and this effect is correlated further with the structural and morphological particles characteristics. For the anneal-ing time of 12 h a quite high emission decay times were achieved (blue: 0.14 ms, green: 0.32 ms and red: 0.39 ms).This research is financially supported through the Project #172035 of the Ministry of Science and Education of the Republic of Serbia. OM especially acknowledge the University Carlos III, Madrid, Spain-Santander Bank Chairs of Excellence program and JSPS 2011/2012 fellowship, Japan.Publicad

Milling Process of Petroleum Coke for Sintered Steel Applications

The effect of milling on different properties of a petroleum coke has been evaluated. The material was subjected to planetary milling at two different rates (400 and 600 rev min-1) for different times up to 48 h. The milled material was characterised by scanning electron microscopy, X-ray diffraction, sieve analysis, thermal analysis, chemical analysis, specific surface area and compressibility has been undertaken. The results show that the milling produces a very quick loss of the crystal structure of the coke and a rapid comminution, which lead to large increases in specific surface area and compressibility losses. The coke has shown a high activity through the milling process, absorbing a great quantity of oxygen. The increase in milling time shifts its thermal decomposition to lower temperatures.Authors want to acknowledge the financial support of Spanish Education Ministry, through Project PTR1995-0724-OP.Publicad

Aerosol route as a feasible bottom-up chemical approach for up-converting phosphor particles processing

Proocedings of: Fourth Conference on the Characterization and Control of Interfaces for High Quality Advanced Materials. Kurashiki, Japan, 02-05 September 2012.The opportunities of the hot wall aerosol synthesis, i.e. conventional spray pyrolysis (CSP) method are demonstrated for the generation of highly spherical three-dimensional (3D) nanostructured phosphor particles with uniformly distributed components, phases and nano-clustered inner structure. With the presumption that certain particle morphology is formed during the evaporation/drying stage, the aerosol transport properties and powder generation are correlated with the particles structural and morphological features. With the help of various analyzing techniques like Field Emission Scanning Electron Microscopy (FE-SEM), Transmission Electron Microscopy (TEM) coupled with energy dispersive X-ray Analysis and STEM mode (TEM/EDS), X-ray Powder Diffraction (XRPD) and fluorescence measurements the feasible processing of up-conversion rare-earth Y2O3:Er, Yb phosphors powders are discussed.The financial support for this work is provided by the Ministry of Education, Science and Technological Development of the Republic of Serbia Project No. 172035 and JSPS fellowship, 2011/2012 (O.M.).Publicad

Synthesis and characterization of rare earth oxide nanostructured particles doped with Eu for luminescent applications obtained by aerosol method

Gadolinium and Ytrium oxides doped with europium (Gd2O3:Eu, Y2O3:Eu) have luminiscent properties. Such properties are improved with the use of nanostructured materials with spherical geometry and narrow particle size distribution. Besides, luminescent properties enhance with a homogeneous distribution of dopant centers in the host matrix material. In this paper the synthesis and characterization of gadolinium and yttrium doped with different proportions of Europium are shown. Nanostructured particles were synthesized through Spray Pyrolysis route in a tubular furnace at different temperatures, and subjected to different post-thermal treatments. Scanning electron microscopy (SEM-EDS), transmission electron microscopy (TEM) and X-ray diffractometry (XRD) were used for the morphological, chemical and structural characterization of the nanoparticles

Nanostructured alumina particles synthesized by the Spray Pyrolysis method: microstructural and morphological analysis

Ultrafine particles or nanoparticles (ranging between a few nanometers to 100 nm) are of considerable interest for a wide variety of applications, ranking from catalyst to luminescence ceramics, due to their unique and improved properties primarily determined by size, composition and structure. This study presents the preparation and characterization of nanostructured spherical alumina particles by the Spray Pyrolysis method for the application in reinforcements of metal-matrix composites (MMCs). Synthesis procedure includes aerosol formation ultrasonically from alumina nitrate water solution and its decomposition into a tubular flow reactor at 700 ºC. The obtained particles are spherical, smooth, amorphous and in non-agglomerated state. Microstructural and morphological analyses were carried out using X-ray powder diffraction (XRD), scanning electron microscopy (SEM/EDS) and analytical and high resolution transmission electron microscopy (TEM/HRTEM). Keywords: Spray Pyrolysis; Alumina; Nanostructured Particles; Isothermal TreatmentThe authors gratefully appreciate the financial support of the Ministry for Education and Science of Spain, Juan de la Cierva Program JCI-2005-1892-13 (M.I. Martín), MAT2006-02458 project, Sabatic Grant SAB 2004-0035 and Project142010, Ministry of Science, Serbia (O. Milosevic).Peer reviewe