Larumbe Abuin, Silvia
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Larumbe Abuin
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Silvia
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Física
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Publication Open Access Heatable magnetic nanocomposites with Fe3O4 nanocubes(Elsevier, 2022-09-27) Larumbe Abuin, Silvia; Lecumberri, Cristina; Monteserín, María; Fernández, Lorea; Medrano Fernández, Ángel María; Garayo Urabayen, Eneko; Gómez Polo, Cristina; Ciencias; Zientziak; Institute for Advanced Materials and Mathematics - INAMAT2The development of magnetic self-heating polymers is an area of great interest for many applications. The intrinsic magnetic properties of the magnetic fillers play a key role in the final heating capability of these nanocomposites. Thus, it has been already reported the improvement of the heating efficiency on Fe3O4 magnetic nanocubes with respect to spherical nanoparticles with the similar mean size1. This result is due to the contribution of the magnetic anisotropy giving rise to higher magnetic coercivity and as consequence, higher SAR (Specific Absorption Rate) values. In this work, well- defined Fe3O4 nanocubes were synthesized through thermal decomposition processes with a mean particle diameter around 70 nm (TEM) (Fig. 1). The SAR values were estimated through the measurement of the AC hysteresis loops, obtaining values of around 900 W/g for the dispersion of the nanocubes in water and values of 350 W/g for the nanocubes dispersed in agar (0.5% wt), with a frequency of 403 kHz and a field amplitude of 30kA/m . In this case, the decrease of the SAR values is due to the inmovilization of the particles in the medium and hence, the Brownian movement of the particles. The temperature increase was also characterized, where a clear enhancement of the heating properties was obtained for nanocubes comparing with spherical nanoparticles of similar mean diameter (Fig. 2). Finally, the heating capacity of the nanocomposites (30% weight of magnetic nanoparticles) was studied through the application of an external AC magnetic field with a Helmholtz coil (319 kHz, 400A, 200G approximately, induction equipment model EasyHeat Ambrell). The effect of the thickness of the polymeric discs on the final temperature achieved was studied (2 and 4 mm thickness and 30 mm diameter). Thus, temperatures of 100 °C or 250 °C were reached after 2 min for the nanocomposites with thicknesses of 2 and 4 mm respectively.Publication Open Access Evaluation of functionalized coatings for the prevention of ice accretion by using icing wind tunnel tests(MDPI, 2020) Rivero Fuente, Pedro J.; Rodríguez Trías, Rafael; Larumbe Abuin, Silvia; Monteserín, María; Ingeniaritza; Institute for Advanced Materials and Mathematics - INAMAT2; Ingeniería; Universidad Pública de Navarra / Nafarroako Unibertsitate Publikoa, PJUPNA1929Ice accretion presents serious safety issues, as airplanes are exposed to supercooled water droplets both on the ground and while flying through clouds in the troposphere. Prevention of icing is a main concern for both developers and users of aircraft. The successful solution of this problem implies the combination of active and passive methods and the use of advanced sensors for early detection of icing and monitoring of ice accretion and de-icing processes. This paper focuses on the development of passive solutions. These include advanced anti-icing coatings deposited by a variety of chemical methods including sol-gel, advanced paints based on polyester combined with fluorinated derivatives and applied by electrostatic spray deposition and conventional silicone-based paints modified by adding alumina nanoparticles. Water contact angle has been measured in all cases, demonstrating the hydrophobic character of the coatings. An ice accretion test has been carried out in a laboratory scale icing wind tunnel (IWT) located in a cold climate chamber. Three different studies have been undertaken: ice accretion measurement, durability of the anti-icing behavior after several icing/de-icing cycles and ice adhesion testing by means of the double lap shear test (DLST) methodology. All the studied coatings have shown significant anti-icing behavior which has been maintained, in some cases, beyond 25 cycles. Although these results are still far from any possible application for aeronautic components, they provide interesting insights for new developments and validate the laboratory scale tests.Publication Open Access Fe-C nanoparticles obtained from thermal decomposition employing sugars as reducing agents(Elsevier, 2020) Cervera Gabalda, Laura María; Pérez de Landazábal Berganzo, José Ignacio; Garayo Urabayen, Eneko; Monteserín, María; Larumbe Abuin, Silvia; Martín, F.; Gómez Polo, Cristina; Zientziak; Institute for Advanced Materials and Mathematics - INAMAT2; Ciencias; Gobierno de Navarra / Nafarroako Gobernua; Universidad Pública de Navarra / Nafarroako Unibertsitate PublikoaThe aim of the work is to present a comparative analysis (structural and magnetic) of Fe-C nanocomposites obtained by the thermal decomposition of sugars (fructose, glucose and sucrose) employing FeCl3 as Fe3+ precursor. The thermal decomposition was followed through Thermogravimetry (TGA) and Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction, High Resolution Transmission Electron Microscopy (HRTEM) and Raman spectroscopy. The results indicate the reduction of Fe3+ under the performed thermal treatments and the achievement at high annealing temperatures of Fe-C nanostructures (coexistence of α-Fe and Fe3C nanoparticles surrounded by a carbon matrix). The magnetic characterization performed by dc SQUID magnetometry, shows an antiferromagnetic response in the initial stages of the decomposition process, and a ferromagnetic behavior linked to the Fe-based nanoparticles. The magnetic induction heating was analyzed through the ac hysteresis loops. Moderate Specific Absorption Rate (SAR) is obtained in Fe-C nanoparticles (~ 70 W/gFe), ascribed to the large nanoparticle size. The combination of porous carbon structure and ferromagnetic response of the Fe-C nanoparticles (i.e. local temperature increase under ac magnetic field) enlarge the emerging applications of these carbonaceous nanocomposites.