Studies on New Zealand cenozoic mollusca, including the eocene mollusca of McCullough's Bridge, Waihao River, South Canterbury

The molluscs discussed in this account are from two exposures in the Waihao River: a) the "classical" McCullough's Bridge locality (including the stratotype of the Tahuian ) which has yielded 189 species, 167 of them from the 2 m. thick Tahu Member of early Kaiatan age, the others from beds of late Bortonian to Kaiatan age; b) a recently discovered outcrop of tuffaceous sediments [Kapua Tuffs, also Kaiatan but younger than the beds at a)] from which 46 species are recorded. 26 species are common to the Tahu Member and Kapua Tuffs. Molluscs indicate that the Tahu Member (and probably Kapua Tuffs) was deposited in subtropical waters of normal salinity at depths of at least 150-200 m. Neither fauna shows much similarity to other Arnold Series faunas, largely because of ecological factors. In the systematic section, 206 species-group taxa are recorded and discussed. One new subfamily (of Nuculidae), 20 new genus-group taxa and 78 new species-group taxa are proposed and a further 25 new species are recorded but not named. A new supraspecific classification of the Nuculidae, based primarily on shell structure, is presented and the described New Zealand Cenozoic and Recent species are assigned to the relevant genus-group taxa. Reviews are also given of New Zealand internally costate pectens, the genus Falsicolus Finlay, 1930 (Fasciolariidae) and the New Zealand turrids formerly referred to Marshallena Finlay, 1927 and Marshallaria Finaly & Marwick, 1937. The following synonymies are proposed: Magnatica powelli Laws, 1932 with M. Planispira (Suter, 1917), Tubena Marwick, 1943 with Gegania Jeffreys, 1884, Zexilia tenuilirata and Z. sub-marginata Laws, 1935 with Exilia (Zexilia) waihaoensis Suter, 1917, Eoturris neglecta with E. complicate (Suter, 1917) and Cordieria haasti and C. verrucosa Finlay, 1930 with C. rudis (Hutton, 1885)

Enhanced performance of polybenzimidazole-based high temperature proton exchange membrane fuel cell with gas diffusion electrodes prepared by automatic catalyst spraying under irradiation technique

Gas diffusion electrodes (GDEs) prepared by a novel automatic catalyst spraying under irradiation (ACSUI) technique are investigated for improving the performance of phosphoric acid (PA)-doped polybenzimidazole (PBI) high temperature proton exchange membrane fuel cell (PEMFC). The physical properties of the GDEs are characterized by pore size distribution and scanning electron microscopy (SEM). The electrochemical properties of the membrane electrode assembly (MEA) with the GDEs are evaluated and analyzed by polarization curve, cyclic voltammetry (CV) and electrochemistry impedance spectroscopy (EIS). Effects of PTFE binder content, PA impregnation and heat treatment on the GDEs are investigated to determine the optimum performance of the single cell. At ambient pressure and 160 o C, the maximum power density can reach 0.61 W cm-2, and the current density at 0.6 V is up to 0.38 A cm-2, with H /air and a platinum loading of 0.5 mg cm-2 on both electrodes. The MEA with the GDEs shows good stability for fuel cell operating in a short term durability test.Web of Scienc

Optimisation of electrophoretic deposition parameters for gas diffusion electrodes in high temperature polymer electrolyte membrane fuel cells

Electrophoretic deposition (EPD) method was used to fabricate gas diffusion electrodes (GDEs) for high temperature polymer electrolyte membrane fuel cells (HT PEMFC). Parameters related to the catalyst suspension and the EPD process were studied. Optimum suspension conditions are obtained when the catalyst particles are coated with Nafion® ionomer and the pH is adjusted to an alkaline range of about 8 e10. These suspensions yield good stability with sufficient conductivity to form highly porous catalyst layers on top of the gas diffusion layers (GDLs). GDEs were fabricated by applying various electric field strengths of which 100 V cm-1 yields the best membrane electrode assembly (MEA) performance. Compared to an MEA fabricated by the traditional hand sprayed (HS) method, the EPD MEA shows superior performance with a peak power increase of about 73% at similar platinum (Pt) loadings. Electrochemical Impedance Spectroscopy (EIS) analysis shows lower charge transfer resistance for the MEA fabricated via the EPD method compared to the HS MEA. The EPD GDE exhibits a greater total pore area (22.46 m2 g-1) compared to the HS GDE (13.43 m2 g-1) as well as better dispersion of the Pt particles within the catalyst layer (CL).Web of Scienc

High temperature (HT) polymer electrolyte membrande fuel cells (PEMFC) - A review

One possible solution of combating issues posed by climate change is the use of the High Temperature (HT) Polymer Electrolyte Membrane (PEM) Fuel Cell (FC) in some applications. The typical HT-PEMFC operating temperatures are in the range of 100e200 o C which allows for co-generation of heat and power, high tolerance to fuel impurities and simpler system design. This paper reviews the current literature concerning the HT-PEMFC, ranging from cell materials to stack and stack testing. Only acid doped PBI membranes meet the US DOE (Department of Energy) targets for high temperature membranes operating under no humidification on both anode and cathode sides (barring the durability). This eliminates the stringent requirement for humidity however, they have many potential drawbacks including increased degradation, leaching of acid and incompatibility with current state-of-the-art fuel cell materials. In this type of fuel cell, the choice of membrane material determines the other fuel cell component material composition, for example when using an acid doped system, the flow field plate material must be carefully selected to take into account the advanced degradation. Novel research is required in all aspects of the fuel cell components in order to ensure that they meet stringent durability requirements for mobile applications.Web of Scienc

Influence of Valence Electron Concentration on Laves Phases: Structures and Phase Stability of Pseudo‐Binary MgZn2–xPdx

A series of pseudo‐binary compounds MgZn2–xPdx (0.15 ≤ x ≤ 1.0) were synthesized and structurally characterized to understand the role of valence electron concentration (vec) on the prototype Laves phase MgZn2 with Pd‐substitution. Three distinctive phase regions were observed with respect to Pd content, all exhibiting fundamental Laves phase structures: 0.1 ≤ x ≤ 0.3 (MgNi2‐type, hP24; MgZn1.80Pd0.20(2)), 0.4 ≤ x ≤ 0.6 (MgCu2‐type, cF24; MgZn1.59Pd0.41(2)), and 0.62 ≤ x ≤ 0.8 (MgZn2‐type, hP12: MgZn1.37Pd0.63(2)). Refinements from single‐crystal X‐ray diffraction indicated nearly statistical distributions of Pd and Zn atoms among the majority atom sites in these structures. Interestingly, the MgZn2‐type structure re‐emerges in MgZn2–xPdx at x ≈ 0.7 with the refined composition MgZn1.37(2)Pd0.63 and a c/a ratio of 1.59 compared to 1.64 for binary MgZn2. Electronic structure calculations on a model “MgZn1.25Pd0.75” yielded a density of states (DOS) curve showing enhancement of a pseudogap at the Fermi level as a result of electronic stabilization due to the Pd addition. Moreover, integrated crystal orbital Hamilton population (ICOHP) values show significant increases of orbital interactions for (Zn,Pd)–(Zn,Pd) atom pairs within the majority atom substructure, i.e., within the Kagomé nets as well as between a Kagomé net and an apical site, from binary MgZn2 to the ternary “MgZn1.25Pd0.75”. Multi‐centered bonding is evident from electron localization function (ELF) plots for “MgZn1.25Pd0.75”, an outcome which is in accordance with analysis of other Laves phases

The impact pseudotachylitic breccia controversy:Insights from first isotope analysis of Vredefort impact-generated melt rocks

Besides impact melt rock, several large terrestrial impact structures, notably the Sudbury (Canada) and Vredefort (South Africa) structures, exhibit considerable occurrences of a second type of impact-generated melt rock, so-called pseudotachylitic breccia (previously often termed “pseudotachylite” – the term today reserved in structural geology for friction melt in shear or fault zones). At the Vredefort Dome, the eroded central uplift of the largest and oldest known terrestrial impact structure, pseudotachylitic breccia is well-exposed, with many massive occurrences of tens of meters width and many hundreds of meters extent. Genesis of these breccias has been discussed variably in terms of melt formation due to friction melting, melting due to decompression after initial shock compression, decompression melting upon formation/collapse of a central uplift, or a combination of these processes. In addition, it was recently suggested that they could have formed by the infiltration of impact melt into the crater floor, coming off a coherent melt sheet and under assimilation of wall rock; even seismic shaking has been invoked. Field evidence for generation of such massive melt bodies by friction on large shear / fault zones is missing. Also, no evidence for the generation of massive pseudotachylitic breccias in rocks of low to moderate shock degree by melting upon pressure release after shock compression has been demonstrated. The efficacy of seismic shaking to achieve sufficient melting as a foundation for massive pseudotachylitic melt generation as typified by the breccias of the Sudbury and Vredefort structures has so far remained entirely speculative. The available petrographic and chemical evidence has, thus, been interpreted to favor either decompression melting (i.e., in situ generation of melt) upon central uplift collapse, or the impact melt infiltration hypothesis. Importantly, all the past clast population and chemical analyses have invariably supported an origin of these breccias from local lithologies only