The effect of potential bias on the formation of ionic liquid generated surface films on Mg alloys

An electrochemical approach to the formation of a protective surface film on Mg alloys immersed in the ionic liquid (IL), trihexyl(tetradecyl)phosphonium–bis 2,4,4-trimethylpentylphosphinate, was investigated in this work. Initially, cyclic voltammetry was used with the Mg alloy being cycled from OCP to more anodic potentials. EIS data indicate that, under these circumstances, an optimum level of protection was achieved at intermediate potentials (e.g., 0 or 0.25 V versus Ag/AgCl). In the second part of this paper, a small constant bias was applied to the Mg alloy immersed in the IL for extended periods using a novel cell design. This electrochemical cell allowed us to monitor in situ surface film formation on the metal surface as well as the subsequent corrosion behaviour of the metal in a corrosive medium. This apparatus was used to investigate the evolution of the surface film on an AZ31 magnesium alloy under a potential bias (between ±100 mV versus open circuit) applied for over 24 h, and the film evolution was monitored using electrochemical impedance spectroscopy (EIS). A film resistance was determined from the EIS data and it was shown that this increased substantially during the first few hours (independent of the bias potential used) with a subsequent decrease upon longer exposure of the surface to the IL. Preliminary characterization of the film formed on the Mg alloy surface using ToF-SIMS indicates that a multilayer surface exists with a phosphorous rich outer layer and a native oxide/hydroxide film underlying this. The corrosion performance of a treated AZ31 specimen when exposed to 0.1 M NaCl aqueous solution showed considerable improvement, consistent with electrochemical data.

The electrochemical surface forces apparatus : the effect of surface roughness, electrostatic surface potentials, and anodic oxide growth on interaction forces, and friction between dissimilar surfaces in aqueous solutions

We present a newly designed electrochemical surface forces apparatus (EC-SFA) that allows control and measurement of surface potentials and interfacial electrochemical reactions with simultaneous measurement of normal interaction forces (with nN resolution), friction forces (with μN resolution), and distances (with Å resolution) between apposing surfaces. We describe three applications of the developed EC-SFA and discuss the wide-range of potential other applications. In particular, we describe measurements of (1) force–distance profiles between smooth and rough gold surfaces and apposing self-assembled monolayer-covered smooth mica surfaces; (2) the effective changing thickness of anodically growing oxide layers with Å-accuracy on rough and smooth surfaces; and (3) friction forces evolving at a metal–ceramic contact, all as a function of the applied electrochemical potential. Interaction forces between atomically smooth surfaces are well-described using DLVO theory and the Hogg–Healy–Fuerstenau approximation for electric double layer interactions between dissimilar surfaces, which unintuitively predicts the possibility of attractive double layer forces between dissimilar surfaces whose surface potentials have similar sign, and repulsive forces between surfaces whose surface potentials have opposite sign. Surface roughness of the gold electrodes leads to an additional exponentially repulsive force in the force–distance profiles that is qualitatively well described by an extended DLVO model that includes repulsive hydration and steric forces. Comparing the measured thickness of the anodic gold oxide layer and the charge consumed for generating this layer allowed the identification of its chemical structure as a hydrated Au(OH)3 phase formed at the gold surface at high positive potentials. The EC-SFA allows, for the first time, one to look at complex long-term transient effects of dynamic processes (e.g., relaxation times), which are also reflected in friction forces while tuning electrochemical surface potentials.

Occurrence of anodic current and corrosion of steel in aqueous media under fluctuating cathodic protection potentials

Excursion of cathodic protection (CP) potential from the designed "safe" CP level resulting from various forms of electrical interference signals are observed rather frequently in industrial applications, in particular in the pipeline industry; however, the influence of such potential fluctuations on the corrosion behavior of steel under CP conditions does not yet appear to be fully understood. In this work, the effects of anodic transients that periodically shift the potential of a CP protected steel electrode from-1,200 mVAg/AgCl to-750 mVAg/AgCl on the corrosion of a steel electrode in aqueous media was investigated using square wave polarization. Anodic currents were measured that lasted for significant periods of time upon stepping the CP potential up to a less cathodic potential at various frequencies (1 h, 30 s, 10 s, 5 s, and 1 s). Part of such anodic currents is found to cause steel corrosion, and this is explained on the basis of understanding the Fe/H2O equilibrium.

Fiji’s sugar, tourism and garment industries : a survey of performance, problems and potentials

Sugar, tourism and garment industries are three of Fiji’s major industries. These industries have been undergoing some serious problems during the past decade. This paper analyses the performance of these industries, examines the problems besieging them, and looks at the potentials these industries have for the country. The paper also offers some suggestions which policy makers in Fiji could consider in order to ensure that these industries continue to benefit Fiji.

Towards a cyberspatial pedagogy : exploring synchronous online learning potentials

It has been a quarter of a century since William Gibson (1984) coined the term cyberspace in his seminal science fiction novel Neuromancer. Subsequently, a proliferation of online teaching technologies have emerged supporting Virilio’s (1991) contention that, “time and space have ceased to function as meaningful dimensions to human thought and action.” The aim of this presentation is to discuss and demonstrate the innovative modification of an online, synchronous learning environment, Elluminate Live! (eLive), which allows participants to transcend the spatial dimension. Specifically, we present an example of good practice which aimed to enhance student engagement by implementing a structured online tutorial series which replicated the entire first year psychology on-campus tutorial series in the eLive environment. We discuss Student Evaluation of Teaching and Units (SETU) results which support the utility of this pedagogic strategy. Finally, we outline various challenges for the virtual teacher who wishes to implement a structured learning program in the eLive environment.
Gibson, W 1984, Neuromancer, Ace Books, New York, USA.
Virilio, P 1991, The aesthetics of disappearance, Semiotext(e), New York, USA.

Electrochemistry at negative potentials in Bis(trifluoromethanesulfonyl)amide ionic liquids

The bis(trifluoromethanesulfonyl)amide (TFSA) anion is widely studied as an ionic liquid (IL) forming anion which imparts many useful properties, notably electrochemical stability. Here we present electrochemical and spectroscopic evidence indicating that reductive decomposition of the bis(trifluoromethanesulfonyl)amide (TFSA) anion begins at ~ −2.0 V vs. Fc+/Fc, well before the reported cathodic limit for many of these ILs. These processes are shown to be dependent upon the electrode substrate and are influenced by the water content of the IL. Supporting ab initio calculations are presented which suggest a possible mechanism for the anion decomposition. The products appear to passivate the electrode surface and the implications of this behaviour are discussed.

The potentials and pitfalls of social networking sites such as Facebook in higher education contexts

Popular social networking sites such as Facebook demonstrate an emerging opportunity for students and educators within formal higher education contexts to share ideas, celebrate creativity and participate in an environment which offers immediate feedback from others who belong within a specific network. As this is an emerging use of the technology, an autoethnographic approach has helped capture the potentials and pitfalls of incorporating social networking within higher education. The findings highlight implications for the key stakeholders in higher education.

Effect of surface roughness and electrostatic surface potentials on forces between dissimilar surfaces in aqueous solution

The first surface force measurements under electrochemical potential control between a metal and a ceramic surface across a liquid medium (water) are reported. Our experiments also investigate and reveal how increasing levels of surface roughness and dissimilarity between the potentials of the interacting surfaces influence the strength and range of electric double layer, van der Waals, hydration, and steric forces and how this contributes to deviations from DLVO theory at small distances within aqueous solution.

Potentials of social media for tacit knowledge sharing amongst physicians : preliminary findings

Tacit knowledge sharing amongst physicians, such as the sharing of clinical experiences, skills, or know-how, or know-whom, is known to have a significant impact on the quality of medical diagnosis and decisions. This paper posits that social media can provide new opportunities for tacit knowledge sharing amongst physicians, and demonstrates this by presenting findings from a review of relevant literature and a survey conducted with physicians. Semi-structured interviews were conducted with ten physicians from around the world who were active users of social media. Initial thematic analysis revealed eight themes as potential contributions of social web tools to facilitate tacit knowledge flow amongst physicians. The emergent themes are defined, linked to the literature, and supported by instances of interview transcripts. Findings presented here are preliminary, and final results will be reported after accomplishing all phases of data collection and analysis.

Using immersive and interactive approaches to interpreting traumatic experiences for tourists: potentials and limitations

This chapter uses three cases studies - the Melbourne Watch House Experience, the Titanic international travelling exhibition and the interpretation centre underneath the Memorial for the Murdered Jews of Europe in Berlin to discuss the ethics and politics involved in using strategies of interpretation that foster identification with victims.

Electrochemical etching of aluminium alloy in ionic liquids

AA5083 aluminium alloy has been shown to be partially passivated by a 2-step anodic pre-treatment in Trihexyl(tetradecyl)phosphonium bis(trifluoromethylsulfonyl)amide ([P6,6,6,14][NTf2]) ionic liquid. Surface characterisation revealed that an electrochemical etching process had occurred, comparable to acid etching of aluminium. Scanning electron microscopy/energy dispersive x-ray spectroscopy results have established that magnesium dealloyed from the Mg2Si intermetallic particles and metal fluorides were deposited onto the remaining Mg2Si sites, which subsequently led to decreased anodic corrosion kinetics (to one third of the control) as well as an increase in the corrosion and pitting potentials. This unique electrochemical etching process offers a simple and quick method to improve the corrosion resistance of an aluminium alloy as it leads to a more uniform surface, in terms of defect size and distribution, compared to conventional acid etching. This process has the potential to be used as a pre-treatment to inhibit corrosion of AA5083 alloy.