Héctor Camacho-Montes

EFFECTIVE COEFFICIENTS FOR TWO PHASE MAGNETO-ELECTROELASTIC FIBROUS COMPOSITE WITH SQUARE SYMMETRY CELL IN-PLANE MECHANICAL DISPLACEMENT AND OUT-OF-PLANE ELECTRIC AND MAGNETIC FIELD CASE

ABSTRACT The purpose of the present work is to determine the magneto-electroelastic effective properties of reinforced piezoelectric composite materials with unidirectional cylindrical fibers periodically distributed in a square array through the Asymptotic Homogenization Method (AHM). The case when mechanical displacement is in-plane and electric and magnetic fields are out-of-plane is studied. Each periodic cell of the medium is a binary composite wherein both constituents are homogeneous magneto-electroelastic materials with transversely isotropic properties. Closed-form expressions for the overall properties are obtained. Numerical calculations are carried out for the BaTiO3/CoFe2O4 composite. A good match is obtained between AHM and other calculations reported in the literature. These results may be considered as congruent with the experimental experience.

From Nano to Bulk: Computer- and Synchrotron-Aided Investigation of the Structure-Properties Relationship

A brief review of structure-properties relationships, at different scales, is given. Structure analysis puts emphasis on the use of synchrotron radiation. X-ray absorption fine structure (XAFS) and scattering-diffraction complement each other to provide local and average crystal structure, as well as nano- to mesoscopic aggregate structures. Software development is presented and case studies are divulged. Properties characterization at atomic scale is performed by first principles methods. Space-time crystal symmetry analysis leads to pertinent selection rules for electromagnetic properties. Electric polarization is calculated via the Berry-phase model. Crystallographic texture plays a significant role on materials properties. Programs ANAELU and SAMZ for texture-properties analysis are presented.

Development of FeOOH nanoarrays using magnetic cations

In this work, FeOOH arrays were obtained using two different magnetic cations. The nanoparticles were grouped into a package having different orientations through the van der Waals interaction with the magnetic cations. With Fe2+, the FeOOH nanoparticles have a rod shape with a 30-nm diameter and approximately 1-micron length, and are aligned in a star structure. With Co2+, a somatoidal shape was observed, with 20-nm diameter and 150-nm length and a pathway structure to the array. The chemical synthesis method was used to obtain the nanoarrays. The morphology and the average size of the nanorods and nanowires were determined using Field Emission Scanning Electron Microscopy (FESEM). Fourier Transform Infrared Spectroscopy (FTIR) was used to study the interaction between the nanorods and the cobalt ions. The phases of the material were identified using X-ray Diffraction.Graphical abstract