BOLETIN 5180 PDF

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The Journal of the Spanish Ceramic and Glass Society publishes scientific articles and communications describing original research and reviews relating to ceramic materials and glasses. The main interests are on novel generic science and technology establishing the relationships between synthesis, processing microstructure and properties of materials.

Papers may deal with ceramics and glasses included in any of the conventional categories: The Impact Factor measures the average number of citations received in a particular year by papers published in the boletih during the two boleti years. CiteScore measures average citations received per document published.

SRJ is a boleyin metric based on the idea that not all citations are the same. SJR uses a similar algorithm as the Google page rank; it provides a quantitative and qualitative measure of the journal’s impact.

SNIP measures contextual citation impact by 510 citations based on the total number of citations in a subject field. This research focuses on the synthesis and characterization of six ceramic perovskite oxides based on La 0. The oxides were obtained in two reaction stages, starting from corresponding nitrate salts boletih citric acid until boltin of a solid metal complex consistent with citrate species.

The characterization by X-ray diffraction XRDscanning electron microscopy SEM and X-ray energy dispersive spectroscopy EDX confirms the obtention of a homogeneous perovskite structure in all analyzed phases. The evaluation 1580 crystallite size by means of the Debye—Scherrer equation establishes a nanometric prevalence around 3.

The electrical characterization of materials by solid-state impedance spectroscopy allowed identifying a particular behavior depending on the microstructure of solids for potential applications in SOFC devices. These systems are a suitable option for the reduction of oil consumption, allowing the chemical transformation of hydrogen and oxygen into electrical energy, without limitations related with typical thermodynamic cycles Carnot cycleachieving high efficiency levels [1].

Within the main SOFC components, the anode is one of the most relevant electrodes, since it allows the main reaction in which the hydrogen oxidation occurs; additionally, it must conduct electrons and ions in a definite asset. The most common material used is metallic ceramic of yttrium-stabilized zirconia, which employs powdered nickel as a contact agent Ni—YSZ [2—4].

This material presents a high catalytic activity and conductivity; however, it has low redox stability, low H 2 S tolerance of the fuel feed [5] and allows the formation of carbon deposits that block the access to the three-phase boundary, reducing the efficiency of the fuel cells [6—9].

Although typical solid-state reaction processes have been bkletin as a mechanism to obtain this type of materials for anodic applications, the implementation of new or improved synthesis routes has allowed the development of fast methods 5810 by optimal reaction rates and low cost as in the case of combustion technique, in which, a self-sustaining exothermic redox reaction from a gel is thermally treated until formation of a solid foam citric complexes that bolftin with the oxidant source represented by the nitrates, to form the corresponding metal oxides with nanometric sizes.

The success of this process focuses on homogeneity and purity of obtained solids due to appropriate mixture of the components in an aqueous medium, followed by holetin exothermic redox reaction between boletun fuel and an oxidizer, enabling a rapid reaction that dissipates the heat of combustion and limit the crystal growth process, reducing the possibility of premature local partial sintering among the primary particles [15].

Under the boetin considerations, this work analyzes the effect of the optimization of a method of chemical synthesis that involves the combustion of citrate species to obtain homogeneous and pure oxide phases based on La 0.

The molar relation between the metal nitrates and citrate in each composition was 1. The results were analyzed and compared with spectral databases to verify the effectiveness of the proposed synthesis method.

The morphological and textural properties of solids were evaluated by scanning electron microscopy SEM on a FEI Quanta r equipment, using uncoated specimens at different magnifications, allowing to establish some surface characteristics derived from synthesis method. The composition of the material was corroborated through analysis by microprobe of energy dispersive X-ray EDX in a spectrometer S4 Bopetin Bruker sequential X-ray equipment by scattering of wavelengths.

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Finally, the electrochemical characterization was performed at room temperature to get an approximation of electrical behavior of solids in an AUTOLAB potentiostat—galvanostat 5108 a modified cell.

The tests were performed in pellets of 8 mm radius and 2 mm thickness, between The geometry of the pellets was 51180 with the use of a reference cell and adapted for this purpose to prevent interference in the electrical responses. The samples were characterized and identified as shown in Table Samples with corresponding compositions in La 0.

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Analysis by UV spectroscopy confirmed the obtention of metal oxide species, associated with electronic transitions located at and nm, where the small variation in absorbance bloetin associated with the level of cation modification. The binding energy associated with each wavelength, using the Planck equation, display transition energies around 1.

Such transitions are characteristic for elements of transition series with d configuration [29—31]. The band-gap boletln obtained for each system are shown in Table 1where it is clear that a semiconductor behavior marked for the sample with the highest concentration of nickel cation, with a value of 1. These values obtained are in agreement with the studies of Strehlow et al. The infrared spectroscopy boletln FTIR allowed to evaluate and identify obletin effectiveness of synthesis process.

Transmittance signals obtained from boletij organic precursors, with corresponding bonds and type of vibrations. The results confirm that progressive insertion of chromium cation in the structure causes a change in the structural parameters of ceramic, allowing evolution from a rhombohedral arrangement related with the LSNO sample until an orthorhombic structure associated with the LSCO sample.

This could explain the change in conformation of X-ray diffraction patterns, as shown in Fig. According to Oliveira et al. However, in the case of pure compositions of La 0. X-ray diffraction patterns for La 0. According to Sakai and Waernhus et al. Reason why, the formation of this compund is related directly with the interaction and mobility between nickel and chromium cations in the stabilization process of crystalline phases, where strontium cation shows an important role in the stabilization of the perovskite structure.

Therefore, vacancies and mobility of ions during thermal treatments cause deficiencies in the A site of the structure, which provoke that B site elements to form binary oxides; this is the reason why the crystal phases of pure LSNO and LSCO solids remain stable along the synthesized boletni.

Table 3 shows the cell parameters and the crystal characteristics obtained for each sample, which displays the concentration of chromium cation and the systematic distortion of rhombohedral crystalline structure related with LSNO sample until stabilization of an orthorhombic arrangement of LSCO oxide, in coherence with the perovskite structure and the type and size of atomic bonding of atoms [43].

Cell parameters and crystal systems obtained for perovskite samples. The crystal sizes of all samples were calculated using bolefin Debye—Scherrer equation, using the intensity of highest signals in experimental X-ray patterns, whose data are shown in Fig. Comparison of bpletin size and chromium cation content on La 0. According to X-ray diffraction results of Fig.

A more detailed analysis is shown in Fig. The red line in Fig. The crosses represent the experimental pattern, and the blue line, the difference between theoretical and experimental patterns, boetin the effectiveness of the proposed synthesis method for the obtention of a chromite crystalline phase, the oxide displayed a perovskite structure with a Pnma 62 space group. Rietveld refinement profile for the LSCO system. Tables 4 boltein 5 summarize bolehin statistical parameters, atomic positions, and cell volume obtained from Rietveld refinement.

Structural and statistical parameters obtained by Rietveld refinement. Atomic positions used in the Rietveld refinement. Results derived from scanning electron microscopy are shown in Fig.

From the point of view of microstructure, obtained oxides are sufficiently heterogeneous to facilitate the migration and the transport of gas to active phase sites.

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This is the reason why the proposed methodology may achieve the maximum efficiency of materials. Thus, the materials with a high degree of densification and crystallization may limit the mass transport, whereas materials with a high concentration of surface defects can generate low mechanical strength for electrocatalytic applications related with the migration of gas species [45]. The obtained values do not exceed a difference of 0. Two curves are shown for each sample: Bode impedance plots compiled for the La 0.

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According with Alvarado bkletin al. On the other hand, for LSNCO4 and LSCO oxides, the obtained impedance signals are related with an opposite behavior associated with an ionic conductivity effect, in which the value of electrical conductivity decreases notably and the charge transferring are fully identified with high electrical resistivity values boletjn. These results are explained according to several authors, by the nature of modification cation that favors major structural changes, influencing significantly the conductive properties of oxides [46—50].

According to previous studies and the present work [51,52]the bolstin chromites, modified with nickel, are characterized by a mixed ionic and electronic behavior that improves the oxidation of hydrogen fuel in the surface of the catalyst as an important alternative in design of materials for solid oxide fuel cells.

Resistance values related to the content of the chromium cation in the La 0. Such compounds, contribute to consolidation of homogeneous and nanometric scale phases with a range of textural, morphological and surface properties of relevance in design of anodic electrocatalysts for solid oxide fuel cells.

The structural analyses performed through X-ray diffraction XRD showed the bopetin of crystalline phases according to proposed methodology with nanometric sizes between 3. The analysis by energy dispersive of X-ray spectroscopy shows that the cation contents correspond with the proposed values without evidence of species volatilization. The scanning electron microscopy SEM analysis confirmed a series of textural and surface properties for the obtention of heterogeneous solids with high surface defects concentration for eventual electrocatalytic activity.

The results derived from impedance spectroscopy at room temperature permit to identify the best ceramic composition in bolefin of resistance and conductivity with a strong correlation between nickel concentration and conductivity, in accordance with previous works. On the contrary, the LSNCO4 and LSCO samples with a low nickel content showed a pronounced decrease in electrical conductivity and it is related to the increase of the resistance of materials in accordance with an exponential behavior.

Current results indicate that there is no presence of constant phase elements capacitance or inductive effects in the mainline of each sample. Previous article Next article. November – December Pages Synthesis and characterization of La 0. Central del NorteTunja, Colombia. This item has received. Under a Creative Commons license. Show more Show less.

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Samples with corresponding compositions in La0. Transmittance signals obtained from metalorganic precursors, bboletin corresponding bonds and type of vibrations. The electrical characterization of materials by solid-state impedance spectroscopy allowed identifying a particular behavior depending on the microstructure of solids for potential applications in SOFC devices.

These systems are a suitable option for the reduction of oil consumption, boleyin the chemical transformation of hydrogen and oxygen into electrical energy, without limitations related with boketin thermodynamic cycles Carnot cycleachieving high efficiency levels [1].

The success of this process focuses 1580 homogeneity and purity of obtained solids due to appropriate mixture of the components in an aqueous medium, followed by an exothermic redox reaction between the fuel and an oxidizer, enabling a bolstin reaction that dissipates the heat of combustion and limit the crystal growth process, reducing the possibility of premature local partial sintering among the primary particles [15].

The results were analyzed and compared with spectral databases to verify the effectiveness of the proposed synthesis method.

The geometry of the pellets was corrected with the use of a reference cell and adapted for this purpose to prevent interference in the electrical responses.

Results and discussion Ultraviolet spectroscopy UV The samples were characterized and identified as shown in Table 1. Transmittance signals obtained from metal organic precursors, with corresponding bonds and type of vibrations. Cell parameters and crystal systems obtained for perovskite samples. Rietveld refinement profile for the LSCO system. Structural boletun statistical parameters obtained by Rietveld refinement.

Atomic positions used in the Rietveld refinement. Solid oxide fuel cells: Acta, 45pp. Hydrogen Energy, 36pp. The effect of current density on H 2 S-poisoning of nickel-based solid oxide fuel cell anodes.