J. C. Sales

Models Manufacturing of Crystal Systems: An Introduction to Ceramic Materials

It is presented a teaching methodology that uses models to better understanding and visualization of crystal systems, considering the large number of students with limited vision spatial perception. The understanding of the relationship between the structure of materials with their properties is essential for engineering students in which it’s possible to relate mechanical properties through knowledge of the crystalline structure of the material, such as machining, heat treatment, mechanical forming processes, etc. The parameter identification of: number of atoms, coordination number, atomic packing factor and density is emphasized in the crystalline systems. Students first study the structure of the crystalline solid and the main crystal systems, key issues for further understanding of the remaining content. Knowing the structure of crystalline solids and understanding its applicability in engineering, makes all the difference to motivate students during the course. With the inclusion of this methodology there has been a better understanding of the concepts related to crystalline systems, as the students build their own structures with the most suitable material chosen by them.

High quality of logic gates from the return arm of a Sagnac fiber interferometer

Abstract In this paper, we analyze the characteristics of obtaining logic functions and logic gates in the reflected output of the Sagnac interferometer by unbalancing the interferometer through the effects of group velocity dispersion and self-phase modulation, mapped by the influence of the extinction ratio (XR) and also analyze the logic gates of better quality by proposing accuracy precision ratio (PR) defined. We studied the phase variation in the phase inserted to the input and we analyzed the related parameters of modulation. We investigated intrinsic features of reflection of the Sagnac interferometer and obtained the logic gates AND, OR, and XOR, and the logical functions ZERO, ONE, and . A specific situation happens when ρ = 0.3 and , where we find the logic gates AND, OR, and XOR. Of all results, the XOR logic gate was obtained in a greater phase variation interval. The XR had the highest contrast when ρ = 0.2 and |ɛ| = 0.028 W1/2. The proposed reconfigurable theoretical set-up gives a contribution to the design of optical networks by the analysis of the obtained logic gates and logic functions in an all-optical environment. The best quality logic gate is the AND gate presenting the |PRTOTAL| = 34.99 when .

Influence of Addition of CaO and SiO2 in Microstructure of Hexaferrite BaXSr1-XFe12O19

This study is aimed to verify the influence of adding SiO2 and CaO in the sintering temperature of hexaferrite, obtained by standard ceramic methods. The powders were weighed in stoichiometric amounts, milled for 1 hour under a high energy mill and calcined at 1000 °C/24h. To study the effect of concentration of additives on the microstructure of the hexaferrite samples were prepared without additives, and with simultaneous addition of SiO2 and CaO, wherein the total concentration of the additive was 1%. The morphology and particle size of the samples were determined by SEM and the crystal structure was determined by XRD and the phases were quantified by the Rietveld method. The XRD data showed the predominance of magnetoplumblico structure with hexagonal symmetry and space group P63/mmc. All samples have distributed grain heterogeneously, clustered in different masses, with acute forms and some of them featuring hexagonal shapes with different sizes.

Structural Characterization for Ceramic Pyrochlores of Bi-Zn-Nb-O

Ceramic pyrochlores, the basis of Bi2O3-ZnO-Nb2O5 (BZN), have dielectric properties of great interest, such a high dielectric constant (ε), a low dielectric loss tangent (tan δ) and a low coefficient of capacitance with temperature (TCC). The system has two main phases, Bi1,5ZnNb1,5O7 (α) and Bi2Zn0,67Nb1,33O7 (β) with cubic and orthorhombic crystal structures, and very different dielectric properties. The purpose of this article was to synthesize chemically homogeneous ceramic pyrochlores BZN-α and BZN-β, using the ceramic method in obtaining nanopowders and their characterizations by scanning electron microscopy (SEM), X-Ray Diffraction (XRD), and the Rietveld refinement method of the structures. The powders were weighed in stoichiometric proportions and calcined at 700 °C/2h, they were sintered at 900, 950 and 1000 °C/2h. A pure BZN-α phase was obtained, while the BZN-β has remained in phases as Bi5Nb3O15 and BiNbO4.

Signal coupling in nonlinear hybrid optical structures: A numerical approach

The numerical study of intensity-dependent picosecond solitonic pulse coupling in nonlinear fiber grating couplers, configured with in-phase or out-of-phase uniform Bragg gratings, is reported in the present work. The time domain non-linear coupled-mode equations that model the coupling dynamics in the devices under investigation are solved numerically by the choice of a fourth-order modified predictor-corrector method. The switching performance of the devices have been investigated as a function of the input power. Characteristically, the coupling effect is dependent on the operational power level, geometry, and, in particular, the mismatching between the adjacent gratings. In the linear regime, the numerical results indicate that the relative shift of the gratings can strongly modify the reflectivity of the optical modes, impacting on the extraction efficiency. As the intensity of the input pulses increases, the hybrid character of the devices vanishes, being the coupling results very similar, independently of the proposed arrangement.