Andrea G. Bishop

Implementing Web 2.0 technologies in higher education: A collective case study

Web 2.0 technologies are becoming more popular in the everyday lives of students. As a result, teachers and designers have begun to explore their use in formal education. This paper presents evaluation findings from a collective case study of six Web 2.0 implementations in Australian higher education. The research was undertaken as part of a larger study that sought to understand how todays students use information and communication technologies to support their learning. Conducted across three universities, the research included a range of disciplines, class sizes and year levels. A common evaluation strategy was used in order to collect comparable data from which commonalities and differences could be identified. This paper provides an overview of the study, describes the methodology used, summarises the implementation experiences of staff and students involved and presents the key findings. The results suggest that most students had little prior experience with relevant technologies and that many struggled to see the value of using Web 2.0 technologies for learning and teaching, both of which have important implications for the design of appropriate learning tasks. While the argument can be made for improving the design through better task-technology alignment, this study also highlights inherent tensions between Web 2.0 and educational practices.

The influence of lithium salt on the interfacial reactions controlling the thermal stability of graphite anodes

The influence of lithium salt on the interfacial reactions controlling the thermal stability of graphite anodes

Surface analysis of LiMn2O4 electrodes in carbonate based electrolytes

LiMn2O4 is ideal as a high-capacity Li-ion battery cathode material by virtue of its low toxicity, low cost, and the high natural abundance of Mn. Surface related reactions and bulk kinetics have been the major focus of this work. The main techniques exploited have been: electrochemical cycling, X-ray diffraction, X-ray photoelectron spectroscopy, infrared spectroscopy and thermal analysis.Interface formation between the LiMn2O4 cathode and carbonate-based electrolytes has been followed under different pre-treatment conditions. The variables have been: number of charge/discharge cycles, storage time, potential, electrolyte salt and temperature. The formation of the surface layer was found not to be governed by electrochemical cycling. The species precipitating on the surface of the cathodes at ambient temperature have been determined to comprise a mixture of organic and inorganic compounds: LiF, LixPFy (or LixBFy, depending on the electrolyte salt used), LixPOyFz (or LixBOyFz) and poly(oxyethylene). Additional compounds were found at elevated temperatures: phosphorous oxides (or boron oxides) and polycarbonates. A model has been presented for the formation of these surface species at elevated temperatures. The cathode surface structure was found to change towards a lithium-rich and Mn3+-rich compound under self-discharge. The reduction of LiMn2O4, in addition to the high operating potential, induces oxidation of the electrolyte at the cathode surface.A novel in situ electrochemical/structural set-up has facilitated a study of the kinetics in the LiMn2O4 electrode. The results eliminate solid-phase diffusion as the rate-limiting factor in electrochemical cycling. The electrode preparation method used results in good utilisation of the electrode, even at high discharge rates.

Ion diffusion in molten salt mixtures

The molten salts, 1-methyl,3-ethylimidazolium trifluoromethanesulfonate (triflate salt, MeEtImTf) and 1-methyl,3-ethylimidazolium bis(trifluoromethanesulfonimide) (imide salt, MeEtImNTf2) are colourless ionic liquids with conductivities of the order of 10−2 S cm−1 at room temperature. DSC measurements revealed subambient melting and glass transition temperatures. Analysis of the anion and cation diffusion coefficients suggested that the cation was the dominant charge carrier and that the motion was largely independent of the anion. Haven ratios (HRs) of 1 and 1.6 were determined for the imide and triflate salts, respectively, at 30°C (303 K). Values greater than one imply some degree of ionic association, suggesting that aggregation is present in the triflate salt. Mixing of the salts to form binary systems resulted in enhanced conductivities which deviated from a simple law of mixtures. Thermal analysis showed no evidence of a melting point with only a glass transition observed. Corresponding diffusion measurements for the binaries appeared to show a weighted average of the diffusion coefficients of the pure components. The increased conductivity can be attributed to an increase in the number of charge carriers as a result of decreased ion association in the binary.

Transport properties in a family of dialkylimidazolium ionic liquids

The transport properties of 1,3-methylalkylimidazolium based ionic liquids are sensitive to their chemical structure. In this work, two key features of the chemical structure were investigated: the role of the anion and the length of the alkyl chain. Four different anions were examined for the 1,3-methylethylimidazolium salt (MeEtImX): bromide (Br−), iodide (I−), trifluoromethanesulfonate (Tf−) and bis(trifluoromethanesulfonyl)amide (NTf2−) anions. Increasing the size of the anion resulted in a decrease of the melting point and a slight increase in the cation diffusion coefficient. The differences in cation diffusion behaviour reflect the differences in viscosity, with much higher viscosities expected for the halide salts. In contrast to this diffusion behaviour, the melt conductivities are all very similar. The inconsistency between the calculated conductivity (based on diffusion measurements) and the conductivity measured, however, is attributed to correlated ion motions and/or the diffusion of neutral species that do not contribute to the conductivity. The effect of the length of the alkyl substituent was also studied for 1,3-methylalkylimidazolium iodide (MeRImI). Increasing the length of the alkyl chain, from methyl to a linear heptyl chain, suppresses the melting point and decreases both the conductivity and cation diffusion coefficients. In this case, the viscosity, as well as the size of the cation, influence ion transport in these materials.

Carbon electrode morphology and thermal stability of the passivation layer

Thermal stability of the solid electrolyte interface (SEI)-layers formed on graphite, mesocarbon microbeads and carbon-black anodes is shown to be dependent on the type lithium salt used in the electrolyte. Exothermic breakdown of the passivation layers formed on cycled electrodes using LiCF3SO3 or LiN(CF3SO2)2 in EC/DMC electrolyte solutions is compared on the basis of DSC, XPS and confocal Raman spectroscopy measurements. Lithium ions in intercalated carbon electrodes are shown not to be involved in the exothermic reactions below 250°C. However, changes are observed in the chemical composition of the SEI-layers using XPS on electrodes stored at 150°C.

Ftir study of ion-pairing effects in plasticized polymer electrolytes

The effect of plasticizer on the ubiquitous ion-pairing observed in polymer electrolytes has been investigated using FTIR as a probe of the local environment of the triflate ion in sodium and lithium triflate based electrolytes. Plasticizers having a range of properties, such as, propylene carbonate, and dimethyl formamide (DMF), have been investigated in the pure state for comparison with the polymer (a random copolymer of ethylene oxide at propylene oxide (mol ratio 3: 1)). The different plasticizers exhibited strikingly different effects on the triflate ion bands normally observed in polyether salt systems. In particular, the cation associated triflate ion bands at 1288 and 1248 cm−1 and the band at 1272 cm−1 which has variously been assigned to the free ion and also to the strongly aggregated anion, are different. PC produces a rapid disappearance of the “free” ion band in favour of the monodentate ion pair. On the other hand, DMF strongly enhances the band near 1270 cm−1 at salt concentrations higher than 0.7 mol kg−1. These observations are discussed in terms of recent ab initio calculations of the triflate vibrational bands.

Bioavailability of dissolved organic carbon and fulvic acid from an Australian floodplain river and billabong

Dissolved organic carbon (DOC) is a vital resource for heterotrophic bacteria in aquatic ecosystems. The bioavailability of fulvic acid, which comprises the majority of aquatic DOC, is not well understood. The present study examined the bioavailability of bulk DOC and fulvic acid from two contrasting but inter-related water bodies: the Murrumbidgee River and adjacent Berry Jerry Lagoon. Bacteria utilised fulvic acids; however, bulk DOC was more bioavailable. Bacteria were able to utilise Murrumbidgee River DOC and fulvic acid more readily than Berry Jerry Lagoon DOC and fulvic acid, suggesting that the quality of carbon may be an important factor to consider when evaluating lateral exchange of nutrients between the main channel and floodplain. Chemical characteristics of fulvic acids appeared to explain some of the variation in fulvic acid bioavailability. The higher the molecular weight and complexity of the fulvic acid, the longer it took for bacteria to utilise the substrate (lag phase), but the larger the number of bacteria that grew on the substrate. The present study calls attention to the need for further multidisciplinary studies to address the quality of carbon in riverine-floodplain ecosystems.

Allochthonous DOC in floodplain rivers: identifying sources using solid phase microextraction with gas chromatography

Abstract.Models of carbon transport are an important mechanism for conceptualizing and assessing the significance of matter and energy sources in streams. The development of a fingerprinting technique that identifies the origins of dissolved organic carbon (DOC) would be invaluable for the development of more sophisticated carbon budget models and improving our understanding of energy flow in river systems. This study explores the potential for solid phase microextraction – gas chromatography (SPMEGC) as a technique for fingerprinting DOC leached from allochthonous source materials (e.g., red gum leaves, willow leaves, couch grass, alluvial soil) collected from a floodplain river in NSW, Australia. The SPME-GC technique is a portable, solventless extraction technique that can detect semi-volatile and volatile organic compounds (SV and VOC) including terpenes, fatty acids, fatty acid esters, ketones, alcohols, and aldehydes, and, importantly, has detection limits approaching parts-per-trillion. The semi-volatile and volatile organic compounds found in DOC leachate solutions produced complex chromatograms, consisting of over 100 individual DOC compounds from each allochthonous source. Hierarchical cluster analysis based on peak presence-absence revealed that each of the source materials produce different chemical profiles. The results indicate that the SPMEGC technique in conjunction with multivariate analyses has considerable potential for identifying source specific chemotaxonomic markers in DOC from riverine habitats. These markers may then be used to test and validate existing models of river function by identifying the origins of DOC contributing to instream metabolism.

Ion association and molar conductivity in polyether electrolytes

The ion association behaviour observed in our earlier studies of a polyether electrolyte system at elevated temperatures, was reminiscent of the molar conductivity behaviour typical of low dielectric constant systems. Further investigation of this relationship has led to some suggestions about the types of ionic species present in the polymer electrolyte systems. FT-IR spectroscopy has been used in this work to contrast ion association in an amorphous polyether electrolyte with two liquid electrolytes, N,N-dimethylformamide and tetraethylenegylcol dimethylether, containing lithium trifluoromethan sulfonate.