https://ogma.newcastle.edu.au/vital/access/ /manager/Index en-au 5 https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:55190 Wed 24 Apr 2024 12:59:00 AEST ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:46009 Wed 10 Apr 2024 15:33:13 AEST ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:50922 Wed 06 Mar 2024 15:07:13 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:42008 Tue 16 Aug 2022 16:51:29 AEST ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:55296 Tue 14 May 2024 15:37:32 AEST ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:651 5 M), where alpha-MnO2 is formed, and high temperatures (>80degreesC) where beta-MnO2 is formed. The structural variety of gamma-MnO2 in this domain of stability is interpreted in terms of: (i) the fraction of De Wolff defects (P,), which is found to increase as the H2SO4 concentration is decreased and the temperature is increased; (ii) microtwinning (T-w), which despite being less statistically significant, is found to follow a similar trend; (iii) the cation vacancy fraction; (iv) the Mn(III) fraction. Both the latter structural properties decrease as the temperature is increased; but decreasing the H2SO4 concentration leads to a decrease in cation vacancy fraction and an increase in Mn(III) fraction. These structural characteristics, in particular the De Wolff defects, are interpreted on a molecular level in terms of soluble Mn(III) intermediate condensation, in which the electrolyte conditions determine the relative proportions of equatorial-axial edge sharing (ramsdellite domains only), and equatorial-axial corner sharing (both ramsdellite and pyrolusite domains) that occurs. Morphological differentiation is easily established due to the different characteristics of each phase. gamma-MnO2 exists as fine needles (250 nm x 50 nm), beta-MnO2 is formed as much larger columns (1 mum x 100 nm), while alpha-MnO2 is present as small spheres of up to 400 nm in diameter. Electrochemical characterization by voltammetry in an aqueous 9 M KOH electrolyte demonstrates that the performance of gamma-MnO2 Samples is comparable with that of commercial EMD, whereas alpha- and beta-MnO2 suffer from diffusional limitations which lower their operating voltage. For gamma-MnO2, superior performance results when lower temperatures and H2SO4 concentrations are used. This corresponds to intermediate levels of De Wolff defects and microtwinning, and to a cation vacancy fraction minimum.]]> Thu 25 Jul 2013 09:10:27 AEST ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:21126 Sat 24 Mar 2018 07:53:54 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:43454 3). Sorption closely followed pseudo second order kinetics and was best described by the Langmuir model. FTIR analysis suggested that chemisorption was the predominant mechanism of Be sorption. Desorption was very low and best described by the Freundlich model. The low desorption reflected the high K_d (up to 6624 L/kg), and the presence of hysteresis suggested partially irreversible binding of Be with active surfaces of the soil matrix (minerals, SOM, oxyhydroxides of Fe/Al/Mn etc.). Intra-particle diffusion of Be and entrapment in the pores contribute to the irreversible binding. The sorption behaviour of Be helped to explain the relative immobility of Be at the site despite the significant quantities of Be disposed. Soil physicochemical properties were significant for Be sorption, through influencing both the uptake and desorption, and this demonstrates the implications of these measurements for evaluating potential future risks to the environment.]]> Mon 19 Sep 2022 15:12:20 AEST ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:31930 Mon 09 Apr 2018 09:26:09 AEST ]]>