B
J
Last name: BLÁZQUEZ GÁMEZ
First name: Javier Sebastián
Premio Extraordinario de Doctorado US
An overall rise in the citation parameters used in the metrics of scientifc publications (i.e. journal impact factor, JIF) has taken place since the last decade of the previous century, coinciding with the electronic distribution of (and access to) scientifc literature. This infation like tendency is herein analyzed in the area of Materials...
The effect of partial substitution of Ge for B in Fe78Co5Zr6B10Cu1 alloy on the microstructure, crystallization process and magnetic properties of the amorphous and nanocrystalline alloys was studied. Special attention was focused on the saturation magnetization response at high temperature and its dependence on the microstructure. Although the...
The influence of the partial substitution of B by Ge on the magnetocaloric response of Fe78Co5Zr6B10Cu1 is studied. Ge addition produces a reduction in the temperature at which the peak entropy change takes place, as well as a slight decrease in the magnitude of the peak, SM pk . The refrigerant capacity, RC, and its field dependence is also...
Amorphous and nanocrystalline Fe–Zr–B–Cu alloys with partial substitution of Co for Fe and Ge for B have been studied by Mössbauer spectrometry (MS). The compositional and microstructural dependence of the different hyperfine parameters were related to the results obtained by X-ray diffraction (XRD) and saturation magnetization measurements....
Bulk nanocrystalline Al88Mm5Ni5Fe2 alloys have been produced by consolidation of pulverised melt-spun ribbons at high pressure. Different production procedures were explored to improve the quality of compaction of the resulting bulk samples. Quality of compaction of samples pressed at room temperature is clearly improved by increasing applied...
The effect of Co addition on the magnetocaloric effect of amorphous alloys with Nanoperm-type composition has been studied for temperatures above room temperature. Co addition produces an increase in the maximum magnetic entropy change and a shift of its associated temperature to higher temperatures. The maximum refrigerant capacity (RC) value...
The field dependence of the magnetic entropy change can be expressed as SM Hn. For soft magnetic amorphous alloys n=1 well below the Curie temperature TC , n=2 in the paramagnetic range, and n 0.75 for T=TC. The first value can be explained with simple arguments, n=2 is a consequence of the Curie-Weiss law, but n TC deviates from mean field...
FeCoNbBCu alloys have been studied by Mössbauer spectrometry. A high contribution of the interfacial region in the nanocrystalline samples to the hyperfine field distribution is detected. The possible presence of B in the nanocrystalline grains is also discussed. Low values of the hyperfine field with respect to the disordered α-FeCo phase...
After mechanical alloying Fe 70Zr 30 composition from pure starting powders, an amorphous phase with Curie temperature T C = 244 K and an intermetallic compound (that should be non-stoichiometric Zr-rich fcc Fe 2Zr phase) with T C = 355 K are formed. Residual α-Fe crystallites are also found. The multiphase character of this system yields a...
The recrystallization process in FeCoNbBCu nanocrystallinealloys is evidenced from thermomagnetic results as a significant decrease in magnetization at the second crystallization stage. The lowering in the volume fraction of α-FeCo crystals indicates that some of these crystals contribute to the boride phases formed. Electron microscopy images...
The classical theory of Johnson-Mehl-Avrami-Kolmogorov (JMAK) is widely used to describe the kinetics of crystallization even when the premises required for its application are not strictly fulfilled. In this paper we propose a procedure to obtain the JMAK parameters of the independent transformations that simultaneously occur during a...
Thermal evolution of Fe neighbourhood in a supersaturated bcc Fe(Ge,Nb) solid solution, obtained as the final product of mechanical alloying of Fe75Ge20Nb5, was studied. No changes in Fe neighbourhood were detected after heating up to 473 K, although differential scanning calorimetry shows a clear deviation of the baseline at 400 K. After...