Adriana Ispas

Pulse plating of tantalum from 1-butyl-1-methyl-pyrrolidinium bis(trifluoromethylsulfonyl)amide ionic liquids

Abstract This paper briefly reviews the preparation of layers of reactive metals and compounds from ionic liquids (ILs) using pulsed electrodeposition. Special focus is given to tantalum electrodeposition from the IL 1-butyl-1-methyl-pyrrolidinium bis(trifluoromethylsulfonyl)amide [BMP][TFSA] onto Ti substrates at room temperature by potentiostatic square pulses. It has been shown that by varying the pulse plating parameters (such as the potential of the on pulse, as well as the frequency and the duty cycle) the morphology of the deposits can be optimised. Thus, experimental conditions have been identified with which uniform and crack free deposits can be obtained.

An electrochemical quartz crystal microbalance study on adsorption of single walled carbon nanotubes onto poly[3,4-ethylenedioxythiophene] layers

Deposition by adsorption of single walled carbon nanotubes (SWCNTs) onto electrodeposited poly[3,4-ethylenedioxythiophene] (PEDOT) films is reported. Electrochemical quartz crystal microbalance (EQCM) measurements in dispersive mode reveal resonance frequency decrease as well as growth of acoustic resistance during the SWCNT deposition. These data were interpreted in terms of increasing of the roughness of the surface and the corresponding change of surface impedance. The thus in situ obtained estimates of size and irregularities agree with ex situ scanning electron microscopy data. Transmission electron microscopy was used to analyze the size and the morphology of the SWCNTs, which were mostly occurring as bundles of nanotubes rather than individual ones. Electroactivity of PEDOT and PEDOT-SWCNT films was studied with regard to the detection of dopamine.

Effect of nano-Al2O3 particles and of the Co concentration on the corrosion behavior of electrodeposited Ni–Co alloys

Incorporation of nano-Al2O3 particles into a Ni–Co alloy by electrodeposition influences the corrosion properties, morphology, and structure of the layers. The resistance against corrosion of Ni–Co/Al2O3 composite films deposited on stainless steel was investigated in a 0.1-M NaCl solution by potentiodynamic polarization. The presence of nanoparticles improves the corrosion resistance of Ni–Co/nano-Al2O3 deposits when compared to pure Ni–Co alloy. Moreover, by increasing the pH of the electrodeposition bath and the content of Co in the alloy, the resistance against corrosion is furthermore improved. The morphology of the deposits before and after their corrosion was analyzed by scanning electron microscopy. The presence of the embedded alumina particles in the Ni–Co alloys was one of the key factors that limited further propagation of corrosion on the metallic surface. Preferential corrosion attack, in the form of a pitting corrosion, was located mainly at the grain boundaries.

Nucleation and Growth of Metal Layers under the Influence of a Magnetic Field

The effects induced by an external magnetic field with flux densities up to 0.7 T on the nucleation and growth of Ni layers will be discussed here. We will show that both the direction of the superimposed magnetic field and the direction of the natural convection with regard to the electrode surface affect the nucleation and growth processes. The nucleation rates increased considerably when the natural convection and the additional convection generated by the magnetic field acted in the same direction.

Electrodeposition of NiFe Alloys in a Magnetic Field

The effects induced by a static magnetic field that was superimposed during the electrodeposition of NiFe alloy were investigated. It was found that the iron content of the alloy, the partial current due to hydrogen evolution reaction, the morphology and the texture of the alloys change when the magnetic field is applied perpendicular to the electric field lines. Beside changes in the morphology on a microscopic scale, no other significant effects were obtained when the magnetic field lines and the electric field lines were parallel to each other. The effects observed were considered to be induced by the additional convection generated by the interaction between the MHD convection and the natural convection.

Understanding the charge storage mechanism of conductive polymers as hybrid battery-capacitor materials in ionic liquids by in situ atomic force microscopy and electrochemical quartz crystal microbalance studies

Safe and sustainable energy storage systems with the ability to perform efficiently during large numbers of charge/discharge cycles with minimum degradation define the main objective of near future energy storage technologies. Closing the gap between high power and energy per unit weight requires new materials that can act as a battery and capacitor at the same time. Conductive polymers have attracted attention as hybrid battery-capacitor materials. However, their potential impact has not been fully investigated because their behaviour, especially in non-aqueous electrolytes such as ionic liquids, is not completely understood. Here, we aim to clarify the fundamental functionality of these hybrid characteristics while studying the interaction between a conductive polymer and an ionic liquid by in situ atomic force microscopy and electrochemical quartz crystal microbalance. The main achievement is the visualisation of the morphological modifications of the conductive polymer depending on the state of charge. These modifications significantly influence the viscoelastic material properties of the polymer. Our combined findings provide a model which explains why conductive polymers behave like (pseudo)-capacitors at a high state of charge and as batteries at a low state of charge. This understanding enables application-orientated synthesis of conductive polymers and their use as high-performance energy storage materials.