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Mo2C has previously been demonstrated as an effective catalyst layer to enable stable H2 permeation through vanadium foils at high temperatures. In this study, this approach was extended to several group V metal foils (V, Nb, and Ta) as well as mixed gas testing. The best permeability was achieved with V, and an activation process was developed to recover the performance of V foils displaying evidence of oxidation. Nb foils yielded ~ 20% the permeability of V, while Ta was too brittle to operate effectively. Mo2C/V membranes were operated at feed conditions well above the ductile-to-brittle transition pressure without embrittlement; however, the H2 permeability of Mo2C/V membranes was significantly attenuated at lower temperatures (

In this work, we discuss an observed reduction of magnesium from a MgO/MgAl 2 O 4 ceramic substrate by permeating hydrogen in thin-film Pd membranes. Membranes were fabricated via electroless plating of Pd on a porous MgO/MgAl 2 O 4 substrate and tested under pure hydrogen permeation conditions between 500 °C and 700 °C. It was observed that a rapid and severe hydrogen flux decline occurred at 700 °C, whereat up to 96% of the hydrogen flux was lost within 40 h of operation. Using energy dispersive x-ray spectroscopy and x-ray photoelectron spectroscopy, it was concluded that the flux loss occurred due to alloying and a subsequent surface segregation of Mg in the Pd film. In contrast, a control test in which the membrane was soaked in hydrogen at 700 °C without permeation resulted in only very slight or potentially no MgO reduction or alloying with the Pd. The significantly enhanced reduction of MgO/MgAl 2 O 4 during membrane operation is attributed to the chemical potential provided by atomic hydrogen permeating through the membrane.

The effects of high pressure gas exposure on the hydrogen flux though Pd films were explored. It was observed that exposure of a Pd membrane to N 2 , Ar, or CO 2 at 3.0 MPa and 500 °C caused a substantial decline in hydrogen flux within 24 h that only recovered to ca. 60% of its initial value after 24 h of subsequent hydrogen exposure. Atomic force microscopy images revealed that the Pd surface became smoother with a reduction in density of nanoscale features after high pressure exposure, consistent with an observed transition in rate limiting step from bulk diffusion to surface kinetics. The rate of flux loss was found to have an apparent activation energy of 39 kJ mol −1 , which is consistent with values reported for Pd surface self-diffusion. This effect was not observed when the exposure gas was helium or at pressures 2 impurities (ca. 1%) in the feed.

Dense vanadium-based membranes offer high permeability and perfect selectivity to hydrogen isotopes, maintain favorable neutronic properties, and are compatible with liquid metals such as PbLi. These properties make vanadium membranes a promising fusion fuel cycle technology for processes such as tritium extraction from PbLi and exhaust processing. Surface contamination has a deleterious effect on the gas-phase hydrogen permeation through vanadium, and the reported permeabilities range from 10-14 to 10-7 mol m-1 s-1 Pa-0.5. Thin dense films of palladium applied to clean vanadium surfaces enable a consistently high hydrogen permeability. In this study, uncoated vanadium resulted in deuterium permeabilities ranging from 2.8 × 10-11 to 6.4 × 10-9 mol m-1 s-1 Pa-0.5 at 300 °C–700 °C, respectively. Post-test analysis revealed a VOx surface layer and VCx subsurface layer formed on the feed side, while the as-received surface oxide dissolved leaving a submonolayer oxide on the permeate surface. The Pd-coated V resulted in a maximum deuterium permeability of 2.1 × 10-7 mol m-1 s-1 Pa-0.5 at 375 °C upon activation of the Pd surface by oxidation and reduction. The deuterium permeation declined upon heating to 500 °C due to intermetallic diffusion between the Pd and V. The Mo2C-coated V resulted in deuterium permeabilities ranging from 2.7 × 10-10 to 1.8 × 10-9 at 500 °C–700 °C, respectively, and a post-test analysis found the carbon in the Mo2C layer had dissolved into the V near the interface.

The effects of gold concentration on the carbon tolerance of palladium-based composite membranes was studied under the presence of high CO concentrations. Membranes with PdAu compositions up to 41% Au by mass were exposed to 50/50H2/CO gas atmospheres and both hydrogen flux and permeate purity were monitored over time. The highest gold concentration (41 wt%) had no measurable degradation in membrane performance in terms of either hydrogen permeate purity or hydrogen permeation flux during the 48 h exposure; in contrast, the pure palladium membrane suffered total degradation during the same exposure time. Furthermore, for lower gold concentrations, X-ray diffraction patterns suggested that carbon entered the membrane film and could be removed by exposure to hydrogen and a non-CO containing gas mixture over time; however, removal of the carbon adversely affected hydrogen permeate purity. Interestingly, some of the observed hydrogen permeate purity decline could be reversed upon re-exposure to the CO gas mixture. It is hypothesized that carbon loading in the palladium films causes lattice expansion and may even fill pore defects, thus lowering non-hydrogen leaks through the Pd membrane films. This study suggests that a membrane exposed to a CO mixture should not be cycled between CO and non-CO environments, but rather run continuously for best performance. Additionally, the choice of Pd-alloy metal and composition should be considered in regard to its carbon solubility to best predict lifetime performance.

We utilized density functional theory to examine HF generation in lithium-ion battery electrolytes from reactions between H2O and the decomposition products of three electrolyte additives: LiPF6, LiPOF4, and LiAsF6. Decomposition of these additives produces PF5, AsF5, and POF3 along with LiF precipitates. We found PF5 and AsF5 react with H2O in two sequential steps to form two HF molecules and POF3 and AsOF3, respectively. PF5 (or AsF5) complexes with H2O and undergoes ligand exchange to form HF and PF4OH (AsF4OH) with an activation barrier of 114.2 (30.5) kJ mol−1 and reaction enthalpy of 14.6 (−11.3) kJ mol−1. The ethylene carbonate (EC) electrolyte forms a Lewis acid–base complex with the PF4OH (AsF4OH) product, reducing the barrier to HF formation. Reactions of POF3 were examined and are not characterized by complexation of POF3 with H2O or EC, while PF5 and AsF5 complex favorably with H2O and EC. HF formation from POF3 occurs with a reaction enthalpy of −3.8 kJ mol−1 and a 157.7 kJ mol−1 barrier, 43.5 kJ mol−1 higher than forming HF from PF5. HF generation in electrolytes employing LiPOF4 should be significantly lower than those using LiPF6 or LiAsF6 and LiPOF4 should be further investigated as an alternative electrolyte additive.

THE broad generalization has been established that the fowl has a sense of taste. An extensive discussion of the subject is offered by Engelmann (1957). The effect of taste on feed and fluid intake has been reported by Kare and Pick (1960). Further elucidation of this subject appears warranted. A series of experiments was designed to determine if chicks will discriminate between acid and alkaline solutions and to define, precisely, the influence of pH on acceptance, rejection, or preference. MATERIALS AND METHODS These experiments were conducted using the methods described by Kare et al. (1957). They were carried out in a special building where the environment was kept relatively constant. Light was provided from 6:00 a.m. to 8:00 p.m. Barred Plymouth Rock-Rhode Island Red cross-bred day-old cockerels from a single hatchery were used. Sixteen chicks per pen for the first eight experiments and thereafter ten chicks per pen were placed …