Rui F. M. Lobo

Kinetic measurements during transient film growth on zinc

The electrochemical behaviour of zinc has been extensively studied in alkaline and acid media, but only a few studies have been reported in neutral solutions, particularly in deaerated media. Zinc passivation in neutral medium and the effect of the ClO4- ion on the nucleation and growth of the passive layer is studied in this paper by a transient technique at different electrolyte concentrations and applied potentials. ZnO growth rate was shown to decrease with increasing electrolyte concentration. Moreover, passive layer growth occurred followed by pitting nucleation and growth. Film growth and pit nucleation are explained by means of the Macdonald and Engell-Stolica models.

The possibility to predict crack patterns on dynamic fracture

The maximum energy dissipation principle (MEDP), for dynamics fracture systems far from equilibrium, proposed by Slepyan was modified. This modification includes a decoupling between the injected and dissipated energies by adding a time delay and a description of the ruggedness produced by dissipation patterns. A time delayed energy conservation equation is deduced and dynamical equations that describe the dynamical system evolution were obtained in analogous way to the Slepyan’s calculations. The conditions for the rising of the instability process were presented by a bifurcation map. These results show that the theoretical framework proposed can describe the instability process along with dissipation patterns formation. This proposal was applied to dynamics fracture where it was possible to explain the results obtained by Fineberg–Gross for the fast crack propagation in PMMA. For unstable or dynamical crack propagation it is shown the possibility to predict crack patterns using this MEDP for other experimental configurations.

Synthesis of carbon nanotube—nanodiamond hierarchical nanostructures and their polyurea nanocomposites

Hierarchical carbon nanostructures (HCNs) comprising functionalized nanodiamond particles (ND) covalently bonded to carbon nanotubes (CNTs) through urea or ethylene diamine linkers were synthesized using wet chemistry technique. Atomic force microscopy, transmission electron spectroscopy, and scanning electron spectroscopy reveal the pearl-necklace-like morphology of new HCNs with up to 50% of the CNT surface decorated by ND particles. Nanocomposites fabricated using polyuria/polyurethane hybrid polymer matrix and 0.2 wt.% of HCNs as a reinforcing filler show a 64% increase in tensile and elongation strength at break relatively to neat polymer.

Local Probes in Energy Storage

The paradigm of real clean and sustainable energy technologies without having a climate impact will demand new solutions for energy storage. Nanotechnology provides a clue for such endeavor since the advances in scanning probe microscopy (SPM) enable to study properties at the nanoscale which are crucial in energy storage modern technologies. The SPM methods emerged as a tool to address several nanoscale multi-functionalities of energy storage materials as they play a role in rechargeable batteries towards optimization of energy density and lifetime.

Emergent Local Probe Techniques

New local probe techniques continue to be developed for studying several particular interactions at the nanoscale and also as ideal tools for nano-patterning at this scale. Their applications in electrochemistry and friction phenomena have a special relevance for improving energy efficiency and energy storage devices. Friction represents a drawback in increasing energy efficiency performances of micro-electromechanical devices. The SPM techniques are also the ideal tools to study friction at the nanoscale and understanding the force that arises from the zero-point field may enable its control and so improving the non-contact motion of molecular motors and nanomachines. For sub-micron distance between two bodies, the Casimir force far exceeds the gravitational force. Thus, precision measurements of the Casimir force can be used for checking unification theories of the existence of extra dimensions along with a host of new particles that lead to deviations from Newtonian gravity in the 100 nm distance range.

Molecular Beam-Thermal Desorption Spectrometry (MB-TDS) Monitoring of Hydrogen Desorbed from Storage Fuel Cell Anodes

Different types of experimental studies are performed using the hydrogen storage alloy (HSA) MlNi3.6Co0.85Al0.3Mn0.3 (Ml: La-rich mischmetal), chemically surface treated, as the anode active material for application in a proton exchange membrane fuel cell (PEMFC). The recently developed molecular beam—thermal desorption spectrometry (MB-TDS) technique is here reported for detecting the electrochemical hydrogen uptake and release by the treated HSA. The MB-TDS allows an accurate determination of the hydrogen mass absorbed into the hydrogen storage alloy (HSA), and has significant advantages in comparison with the conventional TDS method. Experimental data has revealed that the membrane electrode assembly (MEA) using such chemically treated alloy presents an enhanced surface capability for hydrogen adsorption.

On the Features of Ultramicroelectrodes

Ultramicroelectrodes offer several unique characteristics which enable new types of electrochemical measurements. These include: 1) small size; 2) minimisation of iR effects; 3) rapid response; and 4) steady-state response at moderate times. These features enable experiments as diverse as in vivo electrochemistry, electrochemistry in pharmacology, nanoelectrochemistry, electrochemistry in solvents such as benzene, microsecond electrochemistry, and flow-rate independent electrochemistry. Thus, it is apparent that the use of ultramicroelectrodes has become a rapidly growing area of interest. In this paper, the attributes of ultramicroelectrodes, its construction, the equations of diffusion, and key applications of electrochemistry at ultramicroelectrodes, are analysed.

Electrochemical reduction of AQ27DS in aqueous solution

It is known that anthraquinone derivatives act as aqueous sulphide oxidation catalysts, so the redox chemistry of the compound anthraquinone 2,7-disulphonate (AQ27DS) stimulated our interest, as reported here. AQ27DS was reduced in aqueous solution at pH 9.0 to give a deep red coloured air-sensitive solution. Cyclic voltammetry and exhaustive electrolysis indicated that the anthraquinone was reversibly reduced in a two electron, one proton process at a variety of electrode surfaces. From limiting current results at a rotating disc electrode, the diffusion coefficient of AQ27DS was calculated to be 3.37 x 10-10 m2 s-1. Spectroscopic results confirmed that AQ27DSH- was the major reduced species, but also indicated that the di-anion (AQ27DS2-) and radical species AQ27DS• were also present. ESR spectroscopy showed that the radical was formed via a comproportionation reaction between the di-anion and the AQ27DS starting material. The peak separation from voltammetry enabled the comproportionation constant (Kc) to be estimated, and it was found to be in the range of 0.4 to 4.