Published in 2024

Al-doped BaFe12O19 hexaferrites: Dopant distribution in the crystal lattice and its effect on the magnetic order

BaFe12O19 hexaferrite Aluminum- doping Magnetic order Mössbauer spectroscopy

Authors: V. Bilovol, R. Martínez García, M. Pagnola, S. Ferrari, F. Morales, J. Żukrowski, M. Sikora

Journal: JMMM

Description:

We hereby conducted studies on the distribution of aluminum ions in the crystal lattice of doped BaFe12-xAlxO19 hexaferrite nanoparticles (x = 0.5, 1.0, 1.5 at. %) and their effect on the magnetic order of the ferrite. 57Fe Mössbauer spectroscopy, X-ray absorption spectroscopy, X-ray diffraction and magnetic measurements were used to elucidate the incorporation of Al3+ into the barium hexaferrite (BaM) lattice. As a result, the positions of the dopant in the complex lattice with five non-equivalent positions of Fe3+ ions were discussed. The relationship between the percentage of aluminum as dopant ion, its location in the BaM lattice, and the changes in the magnetic order of the hexaferrite nanoparticles was quantified. For the different amount of Al3+, the iron ions are replaced in the octahedral crystallographic sites by aluminum ions. No such replacement occurs in the case of the tetrahedral and bi-pyramidal crystallographic sites. This preferential ionic substitution gives rise to changes in the magnetic order of the BaM that is expressed by changes in the values of the hyperfine fields and the Curie temperature (Tc), which decreased approximately 30 °C for every 0.5 at.% of aluminum per f.u. The mean value of the modulus of the exchange coupling constant was estimated as a function of the percentage of Al3+ from the measured Tc value.

Published in 2023

The role of cluster microstructure on the exchange coupling interaction between magnetically hard and soft phases

Authors: S. Ferrari, R. Martínez García, F. Morales, M. Pagnola

Journal: Solid State Sciences

Published in 2023

Manufacturing and Measuring Techniques for Graphene-Silicone-Based Strain Sensors

Authors: Jorge Peña-Consuegra, Marcelo R. Pagnola, Jairo Useche, Pagidi Madhukar, Fabio D. Saccone, Andrés G. Marrugo

Journal: JOM

Published in 2022

Union by Co-Lamination of Aluminum and Magnetic alloy obtained by Rapid Solidification

Authors: -

Journal: Transactions on Energy Systems and Engineering Applications

Published in 2022

Structural and magnetic properties of a BaFe12O19/NiFe2O4 nanostructured composite depending on different particle size ratios

NIFEO BAFEO Magnetic Properties Chinese and American standards

Authors: R. Martínez García; V. Bilovol; S. Ferrari; P. de la Presa; P. Marín; M. Pagnola

Journal: Journal of Magnetism and Magnetic Materials

Description:

A nanostructured magnetic composite based on hexagonal ferrite BaFe12O19 (magnetically hard) and cubic ferrite NiFe2O4 (magnetically soft) is synthesized. The hexagonal ferrite precursor is obtained by the Sol-Gel method using citric acid as a coordinating agent. The precursor obtained is heated at different temperatures to get nanoparticles with different sizes. Cubic ferrite is obtained by chemical co-precipitation, method and the nanoparticle growth process is controlled with different heat treatments. The hexagonal and cubic ferrite nanoparticles are mixed providing low energy. Three samples of this kind of composite are obtained with a different ratio of particle size. The composites are a mixture where there are clusters of the minority phase NiFe2O4 distributed in a matrix of the main phase BaFe12O19. Both ferrite phases are composed of nanoparticles with an average size less than 50 nm without tensions in the crystal lattice. These structural parameters were compared between the composites and their precursor ferrites. The relationship between the composite microstructures and their magnetic properties is analyzed. A weak exchange coupling was detected between the component magnetic phases of the composites. Depending on the synthesis conditions, some samples exhibit monodomain or a multidomain regime. The higher BH product appears for composites from ferrites with a nanoparticle size ratio approximately equal to one. The structural characterization is carried out by X-ray diffraction. The homogeneity of the composition in the volume of the nanostructured composites is analyzed with a field emission scanning electron microscope equipped with energy dispersive spectroscopy for the analysis of the element mapping. The magnetic study is carried out through measurements of magnetization as a function of the applied field (M vs. H) at 300 K.

Published in 2022

Crack Formation in Chill Block Melt Spinning Solidification Process: A Comparative Analysis Using OpenFOAM®

Authors: M. R. Pagnola, F. Barceló, J. Useche

Journal: JOM

Published in 2021

Radial Distribution Function Analysis and Molecular Simulation of Graphene Nanoplatelets Obtained by Mechanical Ball Milling

Authors: M. R. Pagnola, F. Morales, P. Tancredi, L. M. Socolovsky

Journal: JOM

Published in 2020

Key Aspects in the design of silicone/graphene-based strain sensors for structural monitoring

Authors: -

Journal: 2020 IX International Congress of Mechatronics Engineering and Automation (CIIMA)

Published in 2020

A model for the simulation of the chill block melt spinning (CBMS) process using OpenFOAM®

OPEN FOAM VOLUME OF FLUIDS CBMS Vogel-Fulcher-Tammann

Authors: Marcelo Barone; Francisco Barceló; Marcelo Pagnola; Axel Larreteguy; Andrés G. Marrugo; Jairo Useche

Journal: International Journal of Thermal Sciences

Description:

This work shows the results of a numerical model developed to simulate the CBMS technique for the production of the Fe78Si9B13 metallic magnetic ribbons for application in electronics. The model proposes a numerical approximation to a Vogel-Fulcher-Tammann (VFT) expression as a method in the solidification process. This approximation is introduced into the “compressibleInterFoam” routine, included in the OpenFOAM® suite, originally developed for the simulation of two immiscible, non-isothermal and compressible fluids. This routine solves, the phase fraction transport using the Volume of Fluids (VOF) approach. The boundary conditions imposed in the model were experimentally validated by digital image analysis with a high-speed camera at 5602 fps for the determination of the temperature profiles. The phase change is represented as a growth of several orders of magnitude of the alloy viscosity (μ) as the temperature (T) decreases, reaching solidification around the crystallization temperature (Tg). Also, we establish the condition of initial stability of CBMS process (R > 1.5) for Peclet numbers close to 400, and the validity up to limits of rotation in the wheel close to 40 m s−1. The proposed methodology is validated with previous work. Encouraging results show that the solution of the CBMS process can be adequately simulated with the proposed approach.

Published in 2018

Análisis y simulación del modelo térmico y viscoso del proceso de melt spinning

Authors: -

Journal: -