Examinando por Autor "Pérez Alcázar, Germán"
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- PublicaciónSólo datosStructural and Magnetic Properties Study of Fe50Si50 Powders with Different Microparticle Sizes(Journal of Superconductivity and Novel Magnetism, 2018-08-22) Trujillo Hernández, Juan Sebastián; González Perdomo, Jhon Fredy; Oyola Lozano, Dagoberto; Rojas Martínez, Yebrayl; Pérez Alcázar, Germán; Bustos Rodríguez, HumbertoThe structural properties and magnetic behavior of the Fe50Si50 system were determined using X-ray diffraction (XRD), Mössbauer spectrometry (MS), vibration sample magnetometry (VSM), and scanning electron microscopy (SEM). Samples of Fe50Si50 were melted using an arc furnace, then powder was obtained through a diamond file, and this was passed through different sieves. Finally, nanoparticles of this system were produced by means of surfactant-assisted mechanical alloying. XRD confirmed the presence of the FeSi (CS) and Fe5Si3 structural phases. By transmission MS, it was observed that at room temperature the spectrum is formed by three general components, a doublet associated with the FeSi (CS) phase and two sextets associated with the Fe5Si3 phase; this gives the idea of the distribution of the sizes of particles present in the sample. By VSM, the soft magnetic behavior of the system was ratified and it was determined that the biggest saturation magnetization corresponds to the smallest particles.
- PublicaciónSólo datosStructural, Magnetic and mechanical hardness characterization of the alloy Nd16(Fe 76-xNix)B8 with x = 0, 10, 20 and 25(Applied Physics A: Materials Science and Processing, 2018-09-18) Trujillo Hernández, Juan Sebastián; Pérez Alcázar, Germán; Tabares Giraldo, Jesús AnselmoIn this work, samples of the alloy Nd16 (Fe76−x Nix) B8 with x = 0, 10, 20, and 25 were produced by arc melting under an Ar atmosphere and heat treated at 1073 K during 30 min, and then quenched in ice–water mixture. X-ray diffraction (XRD), Mössbauer spectroscopy (MS), and vibrating sample magnetometry (VSM) were used to characterize the properties of the obtained samples. Microhardness tests were performed too. XRD results found Nd2Fe14B and Nd1.1Fe4B4 as main phases. It is found for x = 0, 10, 20, and 25, lattice parameters a and c, and the volume of Nd2Fe14B and Nd1.1Fe4B4 phases, which decrease with the increase of nickel content. The parameter a of the Nd1.1Fe4B4 phase has a tendency to increase in value compared to the parameter c which has a tendency to decrease with the concentration of nickel; this behavior causes the lattice to dilate in a and it is compressed in c, indicating that Ni atoms are preferably entering along c. The two phases parallel to crystallite sizes are greater than the perpendicular ones, indicating that the crystallite shape is not spherical but elongated in that direction. XRD results for all samples doped with Ni indicate that the crystallite sizes are of the nanometer order and range between 5 and 90 nm. It is evident the addition of this element does not damage the structural formation of Nd2Fe14B phase. MS shows seven magnetic sites (16k1, 16k2, 8j1, 8j2, 4c, 4e, and sb d) and a paramagnetic phase (doublet) corresponding to the phases found by XRD. The mean hyperfine magnetic field of the samples decreases with the increase in the concentration of Ni. According to the decrease of the percentage of the area and the hyperfine magnetic field of 16k2, 8j2, and 4c sites’ phase Nd2Fe14B in Ni-doped samples, preference of nickel atoms to replace iron atoms at these sites was established. It can see also the relative area of the site d (Nd1.1Fe4B4) which decreases with Ni concentration. VSM results showed that the major phase Nd2Fe14B is the hard magnetic phase, while the paramagnetic phase Nd1.1Fe4B4 is the minority phase. There is a general trend of microhardness increase with nickel content, attributable to nickel doping which reduces the lattice parameters and porosities in the sample improving its hardness.