Speaker
Description
There is a great need to control the thermal expansion (TE) in the technology industry, where devices can be degraded due to differences in TE. Negative thermal expansion (NTE) arises as a key to customize the TE. [1] Recent advances at the nanoscale, more precisely nanomaterials with 1D architecture have revealed that TE is a size-dependent feature. [2] FeCo alloys thin films have been proved to possess both a giant and negative magnetostriction [3] being also are considered invar alloy’s [4] owning almost zero TE in the transition from ferromagnetic to paramagnetic [5]. Besides, FeCo alloys have diversified applications such as magnetic recording and catalysts [6], motivating the customization of TE in FeCo alloys at nanoscale.
In this work, we synthesized nanowires (NWs) of FexCox-1 (x=10,50,90) [7] through DC electrodeposition using anodic nanoporous alumina as templates [8]. The latter was produced by aluminium anodization which is a highly efficient method to grow self-organized nanoporous in hexagonal distribution with various dimensions [8]. Three solutions with different ionic concentrations of Fe and Co were prepared to obtain the different stoichiometries [7]. An accurate study of electrodeposition potential was performed for each solution to obtain the most efficient and highest deposition rate. This was possible by adapting the Faraday law of electrolysis to a self-ordered hexagonal nanoporous substrate. The morphological and structural characterization of the obtained FexCox-1 NWs with different diameters was carried out by scanning electron microscopy (SEM) and X-ray diffractometry (XRD), respectively.
Ongoing work includes XRD measurements as a function of temperature to determinate the TE coefficient of the FexCox-1 NWs with different diameters. We intend to model the customization of TE of these NWs by varying the key parameters of stoichiometry, diameter and length.
References
[1] Belo, Joao et al., Physical Review B., 100, 134303 (2019).
[2] Li, Qiang et al., Accounts of Chemical Research, 52 (2019).
[3] Hunter, Dwight et al., Nature Communications, 2, 518 (2011).
[4] K.H.J. Buschow and E.P. Wohlfarth, ISBN: 978-0-444-87477-1 (1990).
[5] M. Takahashi, F. Ono, and K. Takakura, AIP Conference Proceedings, 29, 562-563 (1976).
[6] Popova, Anna, Journal of Physics Conference Series, 345, 012030 (2012).
[7] Bran, Cristina et al., Journal of Physics D Applied Physics, 48. 145304 (2015).
[8] Sousa, Célia et al., Applied Physics Review, 1 031102 (2014).
