Examinando por Autor "Prado, Javier de"

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Development of flexible filler ribbons by melt spinning for joining W to CuCrZr material for heat sink application
(Elsevier, 2022) Izaguirre, Ignacio; Prado, Javier de; Sánchez, Maria; Salazar, D.; Ureña, Alejandro
This paper studies the use of the melt-spinning technique as an alternative filler fabrication route to obtain flexible 80Cu-20Ti ribbons, which presents flexible and adaptability properties to cover the divertor or first wall pipe in future fusion reactors. The results showed that best conditions are achieved using a 0.8 mm diameter of the nozzle and 30 m/s of the linear wheel-speed. This condition allows to change the microstructure of the fabricated ribbons giving rise to a lower Cu4Ti intermetallic phase formation enhancing the adaptability properties. Ribbon dimensions are high enough to cover the perimeter of the pipe. Best conditions were selected to use as filler material in W-CuCrZr brazed joints at 960 ◦C. The results showed the consecution of high metallic continuity interfaces. Besides, the selected brazing conditions did not cause any thermal effect in the W base material but caused a softening effect in the CuCrZr base material as a consequence of the coarsening process of the hardening precipitates.
MOF-derived α-Fe2O3@Fe3O4 on carbon fiber fabric for lithium-ion anode applications
(Elsevier, 2024-06-15) González-Banciella, Andrés; Martínez-Díaz, David; Prado, Javier de; Utrilla, María Victoria; Sánchez, María; Ureña, Alejandro
Owing to the current development in emerging fields as electric motoring, biomedical sensors or new generation of mobile phones, new functionalities are required for the new generation of Li-ion batteries as flexibility or structurality. Thus, Metal-Organic Framework (MOF)-derived α-Fe2O3@Fe3O4 coating on carbon fiber fabric has been developed in this study for Lithium-ion battery anode purposes. MOF-derived synthesis is a well-known strategy to obtain Transition Metal Oxides (TMOs) which better electrochemical performance than bare TMOs. On the other hand, synthesis on carbon fiber fabric allows to develop new electrodes for multifunctional energy storage devices in which the coating provides high specific capacity, while the carbon fiber substrate provides stiffness but high flexibility, mechanical strength, and electrical conductivity. This TMO coating was achieved by a novel MOF MIL-100 direct synthesis on carbon fiber and subsequent calcination, the effects of calcination on the composition, texture and morphology of the coating, as well as its electrochemical performance, were studied. As the best result, calcinated samples during 2 h showed the optimal synergic effects between the coating and carbon fiber, exhibiting a specific capacity of 328.6 mAh/g at 25 mA/g, an excellent rate capability and a capacity retention of 89.7 % after 100 galvanostatic charge-discharge cycles. Nevertheless, it is important to note that the novelty of this work is not only based on the electrochemical performance but also on the novel synthesis of MIL-100 directly over the carbon fibers. This novel synthesis opens the way to new variety of TMO coatings for electrodes of all-solid-state energy storage devices
Unveiling the electrochemical threshold properties of novel aluminum‑copper bimetallic foils anodes for high reversibility li-ion batteries
(Elsevier, 2025-09-30) Prado, Javier de; Børresen, Børre T.; Utrilla, Victoria; Ureña, Alejandro
High-reversibility aluminum‑copper bimetallic anodes have been characterized to determine the threshold specific capacity necessary to ensure a highly reversible process when used as anodes in Li-ion batteries. By controlling the intercalation step, the formation of a β-AlLi surface layer on the aluminum side is promoted. This layer effectively mitigates the stress generated during the expansion and contraction associated to the charging/discharging process. The threshold specific capacity was assessed by applying four different charging steps, corresponding to 5 %, 10 %, 20 %, and 50 % of the experimental specific capacity of aluminum, over 100 galvanostatic charge/discharge cycles. Additionally, the effects of different current densities (0.5 and 1 mA/cm2) and two aluminum qualities (1XXX and 3XXX) on the reversibility of the reactions and capacity loss were analyzed. The results indicated that charging steps corresponding to a specific capacity of 200 mA.h.g−1 were identified as the threshold capacity for achieving reversible anode behavior. Although this property is the most critical factor, the threshold point also depends on various factors such as the aluminum alloy used for the bimetallic anodes and the current density applied. The use of the 3XXX alloy, which is underexplored in the literature for this application, has shown to improve electrochemical (EC) behavior, in some cases doubling the number of cycles in which the anode exhibits reversible EC behavior. Conversely, higher current densities lead to rapid volume changes, and the resulting stress cannot be relieved, thereby affecting the anode's service life.
Wettability and microstructural evolution of copper filler in W and EUROFER brazed joints
(Springer, 2024) Izaguirre, Ignacio; Prado, Javier de; Sánchez, María; Ureña, Alejandro
In terms of wettability, active systems are characterized by a reduction in interfacial energy as the time at specific conditions is increased. This article aims to investigate the evolution of wettability and microstructure, which undergoes a critical transformation at temperatures and dwell times near brazing conditions due to their significant impact on resultant mechanical properties. The objective is to enhance wettability and prevent the formation of different phases that can occur rapidly within the brazing window conditions. Up to 1105 °C, complete fusion of the filler does not occur. However, once it happens, the expansion of the copper filler in EUROFER increases up to 400%, and the contact angle reduces from 100° to 10°, indicating an active wetting behavior. On the other hand, when copper is used with tungsten, an inert behavior is observed, maintaining the contact angle around 70°. Brazed joints carried out under the most promising wetting conditions demonstrated that at 1110 °C-1 min, various phenomena began to occur. This includes solid-state diffusion of copper in the EUROFER, following the austenitic grain boundaries, and partial dissolution of Fe in the copper braze. Increasing the brazing time from 2 to 5 min achieved high interfacial adhesion properties and controlled the diffusion layer and Fe-rich band formed at the W-braze interface, resulting in the best mechanical results (295 MPa).