Novel LiMnPO4 nanocomposite material for high-power lithium battery cathodes

Lithium ion batteries are emerging as one of the most promising technology for high powered energy storage applications. LiMnPO4, is currently one of the most promising cathode materials for lithium batteries considering its low cost, environmental safety, high theoretical capacity and operating voltage (4.1 V vs Li/Li+), achievable within the stability window of conventional carbonate ester-based electrolytes. The practical use of LiMnPO4 is however limited by several intrinsic obstacles: (1) low electrical and ionic conductivity; (2) kinetic limits of Li+ diffusion and; (3) large volume change between LiMnPO4 and MnPO4 phases during charge/discharge cycles. In this dissertation, a novel sol-gel procedure has been developed to produce LiMnPO4 and carbon coating derived from the in-situ addition of sucrose. This work has shown how the purity of the prepared materials can be modulated by the temperature and atmosphere used. Focusing on how the inclusion of a two-step heating regime can help produce phase pure LiMnPO4 at a lower temperature. Results have shown that variations in the thermal treatment of the dried gel precursor can produce pure LiMnPO4 or produce an impure phase such as Mn2P2O7. It also shows that the temperature at which pure, stable and highly crystalline LiMnPO4 is produced can be reduced significantly (400°C instead of 900ºC). The electrochemical performance was best at when tested under higher temperatures of 40°C and for products synthesised with the final heating step at 700°C. Further, when analysing LiMnPO4/carbon composite, the G band peak shifted to a lower wavenumber with increased temperature due to the increase in delocalised π electrons caused by the transformation of alkenic C=C chains to aromatic hexagonal rings. It was found that the ID/IG ratios of the carbon increased with temperature, confirming an increase in D band peak intensity, attributed to the material being in a pyrolysis state. This is critical information as it indicates that the material is not yet in a graphitised stage and that the ID/IG ratio does not imply the extent of graphitisation but confirms that the carbon is approaching the state of graphitisation. Because of the close link between the electric conductivity and delocalisation of the π electrons, this study shows that the optimisation of the heat-treatment of the LiMnPO4/carbon composite is critical to the rate capability of the cathode material

Foreign banks, profits, market power and efficiency in PICs: some evidence from Fiji

Studies on bank profitability vis-à-vis market power and efficiency span a number of years, many countries, regions and methods. Yet, the experiences of the Pacific’s small states – where foreign banks are widespread and bank profits relatively high – remain unknown, leaving policy-makers ill-informed regarding relevant policy development. This study fills a huge gap in literature by providing some evidence on the issue in a Pacific Island context. Two market power hypotheses – the structure-conduct-performance (SCP) and the relative market power (RMP) hypotheses together with two measures of the efficient structure (ES) hypothesis – X and scale efficiencies are estimated. The nonparametric data envelopment analysis (DEA) technique is used to estimate efficiency scores for banks in Fiji over the period 2000 to 2010 and the dynamic GMM to estimate the relationships between market power and efficiency vis-à-vis profitability. Results show that the RMP and ES hypotheses might hold, but not the SCP. Profits appear to persist over time. Policy implications are considerable including that any suggestions to limit further mergers and acquisitions of banks in the region may have to be properly debated

Determining Glucose Isomerization Mechanisms on Lewis Acidic Beta Zeolites Using Isotropic Tracer Studies and 1H NMR

Biofuels synthesized from biomass sources are becoming necessary for sustainable production due to their significantly lower net CO2 production than fuels synthesized from fossil-based carbon sources such as petroleum. Catalytic pathways for the primary biomass-to-biofuels reaction pathway include the isomerization of glucose to fructose, which can be catalyzed by either Lewis acids or bases. Isolated metal atoms and metal oxide particles on Beta zeolites serve as active sites that catalyze this reaction through a Lewis acid 1,2-intramolecular hydride shift or by a Lewis base proton transfer mechanism, respectively. The Lewis acid mechanism has proven to have higher fructose selectivity than the Lewis base mechanism. Determining the glucose-fructose isomerization mechanism provides critical information about the active site placement in catalysts prepared by different methods, making it an ideal test of quality control for new material syntheses. Using glucose reactants deuterated at the second carbon, catalytic reaction mechanisms could be determined by tracing the location of the deuterium atom in the sugar products using 1H NMR spectroscopy. Comparison of fructose product spectra with an unlabeled fructose standard was used to show that glucose isomerization to fructose followed the Lewis acidic pathway on the samples in this study. The outcomes of these isotopic labeling studies provide insight into the placement of Lewis acid metals in zeolite frameworks and help to further understand this important step in biomass conversion to biofuels

Modeling the Aqueous-Phase Copper Ion-Exchange Behavior onto SSZ-13 Zeolites

Copper-exchanged zeolites are utilized as catalysts for the selective catalytic reduction of nitrogen oxides, which are atmospheric pollutants found in diesel engine exhaust. The total amount of copper ions and the types of copper species (Cu(II) or Cu(II)OH) exchanged onto a zeolite can be varied. Copper is exchanged onto SSZ-13 (an aluminosilicate zeolite with the chabazite topology) during a process known as aqueous ion exchange, where the zeolite is mixed in a copper-containing solution. The distribution of copper on SSZ-13 is influenced by exchange conditions, including the molarity, temperature, and pH of the copper solution. The effect of exchange conditions on the amount and type of copper exchanged onto SSZ-13 has not been thoroughly investigated. In order to study these effects, ion exchange experiments were performed with solutions containing different copper concentrations and pHs. The copper loading (wt%) of each SSZ-13 sample was determined by atomic absorption spectroscopy (AAS). Data from AAS shows that SSZ-13 samples exchanged in solutions with higher copper molarities have higher copper loadings. Further exchanges are being done to test the effects of pH on the amount and type of copper species exchanged onto SSZ-13 through characterization by AAS and temperature programmed desorption (TPD). Using the collected data, a model will be developed to predict the amount and distribution of copper on SSZ-13 based on the exchange conditions

COVID-19, domestic agricultural supply chains and food security: the case of Fiji

In this paper the impact of COVID-19 on domestic agricultural supply chains in Fiji is studied using the Sigatoka Valley (the main vegetable production centre of Fiji) and the municipal market in Sigatoka town as a case study. A survey of farmers and markets vendors was carried out to collect data to map out key impacts (and challenges) faced by farmers and vendors in either producing or sourcing produce for sale to customers. Analysis of survey data reveals that the COVID-19 pandemic has delivered shocks to both the supply and the demand side of the agricultural supply chain. Policy implications are also discussed

Obstacles to bank financing of micro and small enterprises: empirical evidence from the Pacific with some policy implications

In recognizing on one hand the importance of the micro and small enterprise (MSE) sector for the growth and development of economies in the Pacific subregion and on the other, the financing constraints of the sector, the authors surveyed a group of MSEs in a Pacific island country and found that the sector may be particularly constrained by bank interest rates, fees and charges, and collateral requirements. This situation holds implications for policy, and the authors propose an initiative led by the banking sector to improve the situation. Keeping in mind an economy's specific financial, regulatory, economic and other structures and circumstances, voluntary or mandatory, it seems as if direct or indirect bank involvement appears vital. The implications for economic growth and development are considerable.Griffith Business School, Department of Accounting, Finance and EconomicsNo Full Tex

Partial compartmentalisation of HIV-1 subtype C between lymph nodes, peripheral blood mononuclear cells and plasma

HIV-1 compartmentalisation is likely to have important implications for a preventative vaccine as well as eradication strategies. We genetically characterised HIV-1 subtype C variants in lymph nodes, peripheral blood mononuclear cells and plasma of six antiretroviral (ART) naïve individuals and four individuals on ART. Full-length env (n = 171) and gag (n = 250) sequences were generated from participants using single genome amplification. Phylogenetic relatedness of sequences was assessed, and compartmentalisation was determined using both distance and tree-based methods implemented in HyPhy. Additionally, potential associations between compartmentalisation and immune escape mutations were assessed. Partial viral compartmentalisation was present in nine of the ten participants. Broadly neutralising antibody (bnAb) escape was found to be associated with partial env compartmentalisation in some individuals, while cytotoxic T lymphocyte escape mutations in Gag were limited and did not differ between compartments. Viral compartmentalisation may be an important consideration for bnAb use in viral eradication