Investigating the electrochemical windows of ionic liquids

Radar-absorbing materials are used in stealth technologies for concealment of an object from radar detection. Resistive and/or magnetic composite materials are used to reduce the backscattered microwave signals. Inability to control electrical properties of these materials, however, hinders the realization of active camouflage systems. Here, using large-area graphene electrodes, we demonstrate active surfaces that enable electrical control of reflection, transmission and absorption of microwaves. Instead of tuning bulk material property, our strategy relies on electrostatic tuning of the charge density on an atomically thin electrode, which operates as a tunable metal in microwave frequencies. Notably, we report large-area adaptive radar-absorbing surfaces with tunable reflection suppression ratio up to 50 dB with operation voltages o5 V. Using the developed surfaces, we demonstrate various device architectures including pixelated and curved surfaces. Our results provide a significant step in realization of active camouflage systems in microwave frequencies.

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“…The ionic liquid electrolyte [deme][Tf2N] provides the optimum performance (see Supplementary Table 1) 57 .…”

Section: Resultsmentioning

confidence: 99%

Graphene-enabled electrically switchable radar-absorbing surfaces

et al. 2015

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“…Both effects are ignored in the theory but would modify Eq. (12). Anticipating the discussion below, the qualitative agreement between the theory and simulations is excellent, nevertheless.…”

Section: Monte-carlo Simulationsmentioning

confidence: 69%

Charging Ultrananoporous Electrodes with Size-Asymmetric Ions Assisted by Apolar Solvent

Rochester¹,

Kondrat

Pruessner³

et al. 2016

J. Phys. Chem. C

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We develop a statistical theory of charging quasi single-file pores with cations and anions of different sizes as well as solvent molecules or voids. This is done by mapping the charging onto a one-dimensional Blume-Emery-Griffith model with variable coupling constants. The results are supported by three-dimensional MonteCarlo simulations in which many limitations of the theory are lifted. We explore the different ways of enhancing the energy storage which depend on the competitive adsorption of ions and solvent molecules into pores, the degree of ionophilicity and the voltage regimes accessed. We identify new solvent-related charging mechanisms and show that the solvent can play the rôle of an "ionophobic agent" effectively controlling the pore ionophobicity. In addition, we demonstrate that the ion-size asymmetry can significantly enhance the energy stored in a nanopore.

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“…Ionic liquids based on the FAP anion reveal an excellent electrochemical (Fig.3) [5,[7][8][9][10] and thermal stability [5,11,12]. They are less viscous than corresponding ionic liquids with the [PF 6 ] -anion [5,13,14].…”

Section: Tris(perfluoroalkyl)phosphate (Fap) Ionic Liquidsmentioning

confidence: 99%