Seminars and Events

Seminars and Events

Materials for Information Technologies

Coordinator: Harvey Amorín 


28 November 2018, 15:00 h. Salón de Actos

Structural Magnetostrictive Alloys: From Flexible Sensors to Energy Harvesters and Magnetically Controlled Auxetics

Alison B. Flatau
University of Maryland, USA

Novel sensors and energy harvesting transducers take advantage of the significantly expanded design space made possible by recent advances in structural magnetostrictive alloys. These alloys can be machined and welded, have high fracture toughness, and can actuate, sense, and carry load while subjected to tension, compression, and bending. The talk includes an introduction to magnetostrictive materials and transduction, and a discussion on the use of low-cost rolling and annealing methods in lieu of more costly crystal growth methods for making bulk iron-gallium (Galfenol) and iron-aluminum (Alfenol) alloys. The process of using magnetostrictive materials to convert mechanical energy into magnetic energy and then into electrical energy is explained and demonstrated using sensors and energy harvesting devices as examples. Examples of magnetostrictive devices include prototypes ranging in size from nanowire-based pressure sensors to huge structures floating in the ocean that convert wave energy into electrical power for “community-scale” energy needs. The recent discovery of a particularly unique attribute of these alloys, their auxetic behavior, will also be discussed. In both Galfenol and Alfenol, both strain and magnetic fields can produce simultaneous increases in lateral and longitudinal dimensions, with measured values of the resulting Poisson ratio being not only negative, but as low as -2.0 in some cases. Mechanical, aerospace and civil engineers should find the discussion on the use of magnetic fields to control auxetic behavior quite interesting.



05 July 2018, 12:00 h. Sala de Juntas

Spectroscopic studies of dispersion and orientation of carbon nanotubes and graphene in aqueous inks and related nanomaterials

Eric ANGLARET
Laboratoire Charles Coulomb, CNRS, Université de Montpellier, France

Processing single-walled carbon nanotubes (SWNT) and single-layer graphene (SLG) into thin films or composite nanomaterials are key issues to take advantage of their mechanical, electrical and optical properties. In this talk, we will review our recent results, and primarily optical spectroscopy studies (absorption, Raman and photoluminescence), of the dispersion and orientation of SWNT and SLG in aqueous inks [1-9] as well as the properties of liquid crystals [1-3], thin films [3-5] or composites [6-7] prepared from these inks.

[1] Dispersion and orientation of single walled carbon nanotubes in a chromonic liquid crystal, N. Ould-Moussa, et al, Liq. Cryst. 40, 1 (2013).
[2] Liquid crystals of carbon nanotubes and graphene, C. Zakri et al, Phil. Trans. Royal Soc. (2013).
[3] Anisotropic thin films of single wall carbon nanotubes from aligned lyotropic nematic suspensions, C. Zamora-Ledezma et al, Nanoletters 8, 4103 (2008).
[4] Conductivity anisotropy of assembled and oriented carbon nanotubes, C. Zamora-Ledezma et al, Phys. Rev. E 85, 062701(5) (2012).
[5] Morphology and anisotropy of thin conductive inkjet printed lines of single-walled carbon nanotubes, F. Torres-Canas et al, Mat. Res. Exp. 4 (2017)
[6] Orientational order of carbon nanotubes in stretch-aligned photoluminescent composites, C. Zamora-Ledezma, et al, Phys. Rev. B 80, 113407 (2009)
[7] Dispersion and individualization of SWNT in surfactant-free suspensions and composites of hydrosoluble polymers, F. Torres-Canas et al, J. Phys. Chem. C 119, 703 (2015).
[8] Surfactant-free single-layer graphene in water, G. Bepete et al, Nat. Chem. (2016).
[9] Raman Signatures of Single Layer Graphene Dispersed in Degassed Water, “Eau de Graphene”, G. Bepete et al, J. Phys. Chem. C 120, 28204 (2016)



       

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