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Available from: sciencedirect.com
[Show abstract] [Hide abstract] ABSTRACT: A composite membrane based on a non-stoichiometric composition of BPO4 with excess of PO4 (BPOx) was synthesised and characterised for medium temperature fuel cell use (120–180 °C). The electrolyte was characterised by FTIR, SS-NMR, TGA and XRD and showed that the B–O is tetrahedral, in agreement with reports in the literature that boron phosphorus oxide compounds at B:P < 1 are exclusively built of borate and phosphate tetrahedra. Platinum micro electrodes were used to study the electrolyte compatibility and stability towards oxygen reduction at 150 °C and to obtain kinetic and mass transport parameters. The conductivities of the pure BPOx membrane electrolyte and a Polybenzimidazole (PBI)-4BPOx composite membrane were 7.9 × 10−2 S cm−1 and 4.5 × 10−2 S cm−1 respectively at 150 °C, 5%RH.
Available from: Evangelos Ioannis Papaioannou
[Show abstract] [Hide abstract] ABSTRACT: Here, we show how a membrane can be designed and operated to achieve ‘uphill’ permeation of carbon dioxide against its own chemical potential difference by employing the transport of carbonate ions with coupled ‘downhill’ permeation of oxygen. Absolute values of the carbon dioxide permeability of the order of 106 Barrers are achieved experimentally over more than 200 h of operation. These permeabilities are some four orders of magnitude greater than polymeric gas separation membranes. We believe that these high permeabilities are due to the effective use of the oxygen chemical potential difference across the membrane as a driving force for carbonate transport.
Available from: Adam P. Harvey
[Show abstract] [Hide abstract] ABSTRACT: Reactive precipitation of TiO2 in a spinning disc reactor (SDR) has been performed. Physical parameters such as rotational speed, disc surface texture, and operating parameters such as flowrate, ratio of water to precursor and location of feed introduction points have been studied in terms of their effects on TiO2 particle size, particle size distribution (PSD) and particle yield. Smaller particles of less than 1 nm mean diameter with narrower PSDs are generally formed at higher yields at higher disc speeds, higher flowrates and on grooved disc surfaces, all of which provide the best hydrodynamic conditions for intense micromixing and near ideal plug flow regime in the fluid film travelling across the disc surface. Similar observations are made for particle characteristics at higher water/TTIP ratios which are attributed to the increased rate of the hydrolysis reaction favouring nucleation over growth. The introduction of the TTIP feed stream into the water stream away from the centre of the disc is also conducive to the generation of smaller and more uniformly sized particles due to the greater energy dissipation for improved micromixing at these locations. Comparisons with reactive-precipitation of TiO2 in a conventional stirred tank reactor (STR) also demonstrate that the SDR performs better in terms of much improved particle characteristics and higher TiO2 yields per unit processing time. This is attributed to more uniform and intense mixing conditions in the smaller volume, continuous SDR than in the STR.
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