Influence of hydrogen contamination by mercury on the lifetime of the PEM-type fuel cell

The subject of this study is the influence of traces of mercury present in the hydrogen originating e.g. from the amalgam technology of brine electrolysis on the lifetime of PEM-type fuel cell. Accelerated tests were used in order to record deterioration of laboratory fuel cells’ performance. The power output decrease observed was only partly reversible. As was proven by XPS spectroscopy, the cell performance deterioration originates from the interaction between mercury and the platinum catalyst. The lifetime of the fuel cell was assessed on the basis of the experiments performed as 7000 h for an average mercury concentration in the hydrogen of 10 μg N m⁻³. This is a sufficient value to permit utilization of the hydrogen from this source as a fuel for the fuel cell. It should be kept in the mind, however, that this value was obtained on the basis of the accelerated durability tests.     

Synthesis and characterization of olivine LiNiPO4 for aqueous rechargeable battery

LiNiPO₄ belongs to a family of olivine type compounds, with members LiMPO₄ where M = Fe, Mn, Co or Ni are transition metals. The lithium nickel phosphate was prepared and characterized in order to evaluate a new potential cathode material for our ongoing research in aqueous rechargeable batteries. Annealing the final product is critical in obtaining the stoichiometric LiNiPO₄ pure phase; conventional cooling to a room temperature leads to an indication of Li₃PO₄ and NiO secondary phases as impurities. The synchrotron infrared radiation (SR-IR) as a source for IR spectroscopy pins down the differences in the chemical bonding for annealed and conventional cooled LiNiPO₄ samples. The cyclic voltammetric and galvanostatic studies showed annealed LiNiPO₄ is electrochemically active from which lithium ions can be de-intercalated during oxidation process leading to an amorphous NiPO₄ and a minor product of nickel(II) hydroxide (β-NiOOH). During subsequent reduction, lithium ions are not fully intercalated, however, the structure is reversible and adequate for multiple cycles. The high potential in LiNiPO₄ looks to be very attractive in terms of high energy density, given the efficiency is improved.     

An inequality for the empirical D.F. in the non–I.I.D. case

A generalization to the non-i.i.d. case of an inequality for the empirical df. due to Mason (1981) is proved     

Strain Dependence of the Uniaxial Compression Response of Vegetable Shortening

Many soft food materials, including vegetable shortening, exhibit complex rheological behavior. For shortening, a precise determination of rheological behavior is necessary to understand its functionality as a food ingredient. Commercial vegetable shortening was subjected to monotonic and cyclic uniaxial compression tests at a wide range of loading rates. The elastic modulus determined from unloading was a function of strain, varying between 740 kPa in the shortening’s strain hardening region to 220 kPa at large strain where perfect plasticity had developed. Visual analysis of shortening specimens during the compression process showed that a rate-dependent stress overshoot was attributable to the development of a shear band following strain hardening. An elastoviscoplastic constitutive model was developed to define the complex rate-dependent compression response of vegetable shortening. Using the fundamental parameters obtained from the different types of compression tests, the proposed model accurately predicted the uniaxial compression response of vegetable shortening over a wide range (three decades) of compression rates. A model with predictive capabilities of large strain properties is desirable because shortening is subject to large strain in essentially all applications.