Search

This article presents the production and structural and magnetic characterization of the Bi1-xYxFeO3 System x = 0 and 0.07. The samples were obtained by solid state reaction method and characterized by x-ray diffraction (XRD), electron microscopy scanning (SEM) and Mössbauer spectroscopy. The analysis by Rietveld refinement, allowed to determine that system Bi1-xYxFeO3 crystallizes in the Group R3c (161) rhombohedral. The obtained results allowed to conclude that the replacement of Bi by ions of and influence the appearance of Bi2Fe4O9 impurities, without affecting the structural response of the samples with the increase of doping yttrium. [ABSTRACT FROM AUTHOR]

In this article we study and analize the surface physical propierties in samples of Colombian flat glass, specifically soda-lime glass, by scanning electronic microscopy (SEM), atomic force microscopy (AFM) and differential thermal analisys (DTA). The SEM results detected surface deposits of Ti and Co and infused whose chemical analisys indicated that over 92% is SiO2. The microscopic roughness, analized by AFM, was associated with the aging time of the sample. It was observed the influence of diluid cement on surface properties. DTA allowed detect changes related to absorption of molecular water and, at high temperatures, the removal of bound water. [ABSTRACT FROM AUTHOR]

Copper oxide (CuO) has been broadly used in different technological and biological applications. However, based on the literature review, there are few reports describing the synthesis of tungsten doped copper oxide and its biological applications, although CuO and W (tungsten) based nanomaterials have been reportedly already synthesized. In this study we synthesized novel CuO and CuO/W (at.1%, 2% and 4%) nanoparticles and explored their tungsten content-dependent bactericide activity. In order to obtain the materials, was used a co-precipitation method which is of low cost. The synthesized materials were characterized by x-ray diffraction (XRD); XRD results indicated that only the sample with at.1% of W presented pure Tenorite phase. Diffuse reflectance spectroscopy (DRS) allowed to obtain the band gap energy values; CuO/W (at.2%) sample exhibited the minimum value of 2.62 eV. Grains sizes ranging from 39.78 to 53.47 nm were established through field emission—scanning electronic microscopy (FE-SEM), and these sizes were confirmed by transmission electron microscopy (TEM). Doping with W also influenced the morphology obtained in all cases. BET (Brunauer, Emmett, Teller) analysis allowed to establish an increase in specific surface area and pore size with W doping. The particle size was determined by dynamic light scattering (DLS). The bactericidal properties were tested using well diffusion method for Escherichia coli and Staphylococcus aureus bacteria. Bactericide response of CuO nanoparticles was improved by the inclusion of W dopant into the CuO structure, leading to an expansion in the inhibition zone for the CuO/W (at.1%) sample; inhibition halo diameters were 1.5 and 12 mm for CuO and CuO/W (at.1%), respectively. Hence, it was possible to infer the remarkable importance of the crystalline phase, morphology, particle size and specific superficial area of the CuO/W (at.1%) nanoparticles in its bactericide performance. WO3 secondary phase affected the bactericide response of the materials obtained at at.2% and at.4% of tungsten content. [ABSTRACT FROM AUTHOR]

Nanoparticles of Ce1−xPrxO2 (X: 0.6 and 0.8), were synthesized by the combustion method using citric acid as chelating and fuel agent. The X‐ray diffraction patterns and Rietveld refinements confirm that samples shown as a single phase in a cubic fluorite structure, with an increase in the lattice parameter as a function of Pr concentration. The crystallite size domains obtained by the Scherrer formula, confirm values around 10 and 37 nm. The scanning electron microscopy images, show that the solids are composed of dense heterogeneous aggregates. The X‐ray photoelectron spectroscopy, reveals that oxides are composed of cerium and praseodymium cations in oxidation states 4+ and 3+ respectively. The TPR‐H2 profiles indicate that cerium and praseodymium cations present in the obtained systems are completely reduced to Ce3+ and Pr3+ at temperatures above 790°C. The impedance spectroscopy data at room temperature showed that the conduction processes for the two systems take place at the grain boundaries. The Ce0.2Pr0.8O2 system offer lower resistance, due to the high amount of Pr3+ ions inserted in the structure and the high amount of oxygen vacancies formed in the synthesis process. [ABSTRACT FROM AUTHOR]

Plasma technology is a science that is in a constant evolution from its beginnings, from applications from materials treatment until environmental applications. Particularly the glow discharge plasma offers a wide variety of uses, including plasma-chemical applications and thermo-chemical materials treatment. In the present work seeks to exploit the heat generation by the low pressure glow discharge, which is due to kinetic energy transfer from the plasma toward the electrodes. For this purpose a cylindrical reactor that generates a low-pressure glow discharge in gas argon was designed. The discharge cathode constitutes the internal electrode, while the anode, which also constitutes the chamber wall, is a metallic cylinder concentric to the cathode. To sustain the glow discharge a source of pulsed direct current is used and the discharge was generated at several currents in different gas atmospheres (N2, H2 y Ar). Through electrical measurements of the discharge parameters, power and energy consumption of the reactor is determined. These are compared with the values obtained for a commercial heating device based on electrical resistance. [ABSTRACT FROM AUTHOR]

In this paper we analyzed the La1.5+xBa1.5+x-yCayCu3Oz system, based on the production of samples that are in the range of single phase, pure phase, proposed by West [1]. We report the production and characterization La1.1Ba1.4Ca0.5Cu3Oz, La1.1Ba1.5Ca0.4Cu3Oz, La1.1Ba1.6Ca0.3Cu3Oz, La1.2Ba1.3Ca0.5Cu3Oz, La1.2Ba1.4Ca0.4Cu3Oz, La1.3Ba1.2Ca0.5Cu3Oz, systems, in contrast to those reported in previous articles [2]. The material was produced by the solid state reaction method (SSR) with a sintered temperature between 820 and 850 °C. The morphological characterization with respect to the granular behavior using the Scanning Electron Microscopy (SEM) technique is showed; the structural characterization is obtained submitting the specimen to X Rays Diffraction (DRX) and the structural parameters are got implementing the Rietveld refinement method in software FullProf; the material results to possess tetragonal unitary cells type P4/mmm perovskite with a ≈ 3.89 Å, b ≈ 3.89 Å and c ≈ 11.60 Å. Systems have a pure phase, single phase as proposed by West. The critical temperature is compared with the parameters x and y. En este artículo analizamos el sistema La1.5+xBa1.5+x-yCayCu3Oz, basados en la producción de muestras que se encuentran en el rango de fase única, fase pura, propuesta por West [1]. Reportamos la producción y caracterización de los sistemas La1.1Ba1.4Ca0.5Cu3Oz, La1.1Ba1.5Ca0.4Cu3Oz, La1.1Ba1.6Ca0.3Cu3Oz, La1.2Ba1.3Ca0.5Cu3Oz, La1.2Ba1.4Ca0.4Cu3Oz, La1.3Ba1.2Ca0.5Cu3Oz, en contraste con los reportados en artículos previos [2]. Las muestras fueron producidas por el método de reacción de estados solido (SSR) con una temperatura de sinterizado de 850 °C. Se presenta la caracterización morfológica referente al comportamiento granular utilizando la técnica de Microscopía electrónica de barrido (SEM); La caracterización estructural, se determinó sometiendo las muestras a la técnica de Difracción de Rayos X (DRX) y los parametros estructurales a partir del metodo de refinamiento Rietveld en el sofware FullProf. Los materiales resultantes tipo perovskita poseen celdas unitarias tetragonal tipo P4/mmm con a ≈ 3.89 Å, b ≈ 3.89 Å y c ≈ 11.60 Å. Los sistemas tienen fase única, fase pura como lo propone West. La temperatura crítica es comparada con los parametros x e y. [ABSTRACT FROM AUTHOR]

In this paper it is analyzed the system La1,5+xBa1,5+x-yCayCu3Oz, based on the production of samples that are in the range of single phase, pure phase, proposed by West [1]. The structural analysis was carried out starting from X Rays Diffraction (XRD), being able to establish a first indication of the presence of pure phase in the system La1,5+xBa1,5+x-yCayCu3Oz , which was corroborated through the refinement Rietveld. Structural parameters of the samples were obtained by the standard method of reaction of solid state. This first indication was also corroborated with measures of Scanning Electronic Microscopy (SEM), and the elementary composition was verifyed through Energy for Dispersion of X Rays (EDX). Finally, and having into account the carried out analysis, it is shown that most of the samples present superconductor characteristics of high planar anisotropy and that although the total range proposed by West corresponds to superconductor systems, not all the samples present pure phase. [ABSTRACT FROM AUTHOR]

In this work is carried out by means of statistical methods an analysis of the parameters of confiability, of the roughness measure that provides the software SPIP, comparing it with experimental data obtained with AFM, for different samples of commercial glass. They also intend the good conditions of sampling to obtain a reliable analysis of the quality of the glass as for superficial parameters of roughness and topography. Finally we intends the roughness like a pursuit method in the control of quality at industrial level, using the technique of AFM and correlating it with the software SPIP. [ABSTRACT FROM AUTHOR]

Cobaltite-like materials having metal-insulator transitions are relevant in the consumer electronics market. In this work, we present the structural, magnetic, and electrical properties of Ba1-xNaxCoO3 (with x = 0.25, 0.5, 0.75) cobaltite. All samples were synthesized using a solid-state reaction process. Their crystal structure was determined using X-ray diffraction (XRD) data by the Rietveld method, which showed that all the samples were crystallized in the orthorhombic space group C2221 (N.° 20). The microstructure of the sintered samples was characterized by scanning electron microscopy (SEM). The magnetic susceptibility measurements confirmed a paramagnetic behavior for x ≥ 0.5 in the temperature range that was used. Likewise, a broad peak around 33 K in the sample x = 0.25, and characteristic of antiferromagnetic behaviors were observed. On the other hand, resistivity contributed to determining the insulating behavior of samples where x = 0.5 and x = 0.75. In contrast, at low sodium content (x = 0.25), a metal-insulator transition was observed with transition temperature near 105 K. [ABSTRACT FROM AUTHOR]

This paper reports the synthesis and characterization of Bi1-x Lux FeO3 (x = 0.00, 0.02, and 0.04) produced by solid-state reaction, in order to evaluate the influence of lutetium on the structural and magnetic properties of bismuth ferrite (BiFeO3). The samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), and magnetic analysis by vibrating sample magnetometer (VSM) in the temperature range from 50 to 320 K. The obtained results allowed confirming the formation of crystalline materials of rhombohedral structure, space-group R 3 c (161), defined morphology and particle sizes between 2.25 and 4.50 µm. The Lu3+ insertion in the structure caused an increase in magnetization, purity of BiFeO3, and a decrease in the synthesis temperature as compared with the reported in the literature. [ABSTRACT FROM AUTHOR]

This research describes the synthesis and characterization of the Pr3-XEuXBa5Cu8O18-δ system with modification levels (x = 0, 0.5, 1, 1.5, 2 and 2.5). The synthesis process was achieved by solid state reaction (SSR). Precursor oxides of Pr6O11, Eu2O3, BaO and CuO were used with purities up to 99.999%. Calcination temperatures were handled at 850 ° C, sintering at 900 ° C and oxygenation at 910 ° C. The structural characterization was determined by X-ray diffraction (XRD). A structural analysis was carried out with Rietveld refinement, where the coexistence of two phases TR358 and TR123 was evidenced. The net parameters were obtained and a perovskite-orthorhombic crystal structure with spatial group Pmmm (47) was achieved. It was concluded that the increase of the X modification level with Eu in the Pr3- XEuXBa5Cu8O18-d system has a large impact on the percentage composition of the phases and structural parameters. The increase or decrease of the value of the net parameters in structure 358 and 123 is affected by the mixture of oxidation states of Pr with those of Eu, causing the cell size to change. [ABSTRACT FROM AUTHOR]

Force Sensing Resistors (FSRs) exhibit considerable amounts of hysteresis and repeatability error inhibiting their usage in applications that require high-accurate force readings. This paper presents the hysteresis characterization and modeling of the Tekscan A201-1 FSR employing the Preisach Operator (PO) function. In order to compensate for hysteresis during sensor operation, the inverse PO was numerically found on the basis of the Closest Match Algorithm (CMA). A test bench, capable of handling sixteen sensors simultaneously, was built, which allowed the characterization and later testing of the CMA. Grip force profiles were applied to the sensors during testing and the experimental results showed a considerable reduction in the force estimation error compared with the linear regression method proposed by the manufacturer. These results enable a wider use of FSRs in applications with tight accuracy requirements. Finally, a generalized sensor model for hysteresis compensation that simplifies the obtaining of PO parameters is presented. [ABSTRACT FROM AUTHOR]

Conductive polymer composites are manufactured by randomly dispersing conductive particles along an insulating polymer matrix. Several authors have attempted to model the piezoresistive response of conductive polymer composites. However, all the proposed models rely upon experimental measurements of the electrical resistance at rest state. Similarly, the models available in literature assume a voltage-independent resistance and a stress-independent area for tunneling conduction. With the aim of developing and validating a more comprehensive model, a test bench capable of exerting controlled forces has been developed. Commercially available sensors—which are manufactured from conductive polymer composites—have been tested at different voltages and stresses, and a model has been derived on the basis of equations for the quantum tunneling conduction through thin insulating film layers. The resistance contribution from the contact resistance has been included in the model together with the resistance contribution from the conductive particles. The proposed model embraces a voltage-dependent behavior for the composite resistance, and a stress-dependent behavior for the tunneling conduction area. The proposed model is capable of predicting sensor current based upon information from the sourcing voltage and the applied stress. This study uses a physical (non-phenomenological) approach for all the phenomena discussed here. [ABSTRACT FROM AUTHOR]

[Display omitted] • Coprecipitation method was used to adjust the properties of magnetite nanoparticles. • The stirring speeds during the production step change the average particle size. • All produced nanoparticles showed superparamagnetic behaviors. • Magnetic parameters such as the M S , M R , H C and χ(T) depended on the particle size. • Nanoparticles shown strong effects of spin-glass type behavior. This work presents a rapid and facile method to produce and adjust the magnetic and physical properties of magnetic nanoparticles. SEM and DRX characterizations, as well as magnetic hysteresis curves and magnetic susceptibility curves, were performed to study changes in the nanoparticles as a function of two stirring speeds: 1000 and 3000 rpm. The formation of spherical nanoparticles was observed at both speeds, but the small ones (72 nm) were obtained at the highest stirring speed. However, at this speed, the magnetite nanoparticles showed to be partially oxidized to hematite. Magnetic curves reveal the superparamagnetic and spin-glass behavior of both kinds of nanoparticles. The blocking and irreversibility temperature of the nanoparticles was not perceived even at room temperature. [ABSTRACT FROM AUTHOR]