Search results for "CONDUCTIVITY"
showing 10 items of 1988 documents
Comparison of different acquisition patterns for 2D tomographic resistivity surveys
2015
A systematic comparison is presented between some 2D resistivity models and their images by the inversion of synthetic datasets relating to three different arrays, suitable for multichannel data acquisitions (dipole-dipole (DD), Wenner-Schlumberger (WS) and multiple gradient (MG)). The goal is to study how the measurement errors affects the resolution of the tomographic models and the ability to retrieve correct information on buried targets. We considered different data acquisition patterns, gradually increasing the complexity of the combinations of potential spacing and dipolar distance. To this end we increased the number of current dipoles to obtain approximately the same amount of meas…
Double cross-linked polyetheretherketone proton exchange membrane for fuel cell
2012
Abstract The proton exchange membrane based on polyetheretherketone was prepared via two steps of cross-linking. The properties of the double cross-linked membrane (water uptake, proton conductivity, methanol permeability and thermal stability) have been investigated for fuel cell applications. The prepared membrane exhibited relatively high proton conductivity, 3.2 × 10 −2 S cm −1 at room temperature and 5.8 × 10 −2 S cm −1 at 80 °C. The second cross-linking significantly decreased the water uptake of the membrane. The performance of direct methanol fuel cell was slightly improved as compared to Nafion ® 117 due to its low methanol permeability. The results indicated that the double cros…
Methanol and proton transport through chitosan-phosphotungstic acid membranes for direct methanol fuel cell
2020
Composite chitosan-phosphotungstic acid membranes were synthesized by ionotropic gelation. Their liquid uptake is higher for thin membranes (23 ± 2 μm), while it is lower (~70%) for thicker membranes (50-70 μm). Polarization curves recorded using single module fuel cell at 70°C allowed to estimate a peak power density of 60 mW cm−2 by using 1 M as methanol and low Pt and Pt/Ru loadings (0.5 and 3 mg cm−2) at the cathode and at the anode, respectively. Electrochemical impedance spectroscopy was used to estimate the membrane conductivity and to model the electrochemical behavior of methanol electrooxidation inside the fuel cell revealing a two-step mechanism mainly responsible of overall kine…
Cross-linked PEEK-WC proton exchange membrane for fuel cell
2009
Abstract The low cost proton exchange membrane was prepared by cross-linking water soluble sulfonated-sulfinated poly(oxa- p -phenylene-3,3-phthalido- p -phenylene-oxa- p -phenylene-oxy-phenylene) (SsPEEK-WC). The prepared cross-linked membrane became insoluble in water, and exhibited high proton conductivity, 2.9 × 10 −2 S/cm at room temperature. The proton conductivity was comparable with that of Nafion ® 117 membrane (6.2 × 10 −2 S/cm). The methanol permeability of the cross-linked membrane was 1.6 × 10 −7 cm 2 /s, much lower than that of Nafion ® 117 membrane.
Covalent-ionically cross-linked polyetheretherketone proton exchange membrane for direct methanol fuel cell
2010
Abstract In this paper, the proton exchange membrane prepared by covalent-ionically cross-linking water soluble sulfonated–sulfinated poly(oxa- p -phenylene-3,3-phthalido- p -phenylene-oxa- p -phenylene-oxy-phenylene) (SsPEEK-WC) is reported. Compared with covalent cross-linked PEEK-WC membrane, this covalent-ionically cross-linked PEEK-WC membrane exhibits extremely reduced water uptake and methanol permeability, but just slightly sacrificed proton conductivity. The proton conductivity of the covalent-ionically cross-linked PEEK-WC membrane reaches to 2.1 × 10 −2 S cm −1 at room temperature and 4.1 × 10 −2 S cm −1 at 80 °C. The methanol permeability is 1.3 × 10 −7 cm 2 s −1 , 10 times …
Reducing electric and thermal energy needs in buildings by using innovative envelope materials - Laboratory results of bio-composites embodying tomat…
2018
The life style of building occupants is continuously arising towards conditions that are more comfortable involving, on turn, the growing of the electric energy consumptions for climatization purposes. This calls for the improvement of the efficiencies of equipment along with environmental performance of building materials. Laboratory analyses of samples of mixed materials, utilizing tomato stems harvested in Sicily and Cataluña, have been conducted Thermal conductance and mechanical properties have been detected for different rates of bio-component and inert materials. First results of the thermal properties seem to situate such bio-composites among the insulating building materials, for a…
Effect of disorder produced by cationic vacancies at theBsites on the electronic properties of mixed valence manganites
1999
An alloy series of single-phased polycrystalline ${\mathrm{La}}_{1\ensuremath{-}x}{\mathrm{Na}}_{x}{\mathrm{MnO}}_{3+\mathrm{\ensuremath{\delta}}} (0l~xl~0.15)$ has been synthesized in order to study the effect of disorder on the electronic properties of mixed valence manganites. The synthetic variables allow one to maintain a constant proportion of ${\mathrm{Mn}}^{4+}$ in the samples $({\mathrm{Mn}}^{3+}{/\mathrm{M}\mathrm{n}}^{4+}=2.1\ifmmode\pm\else\textpm\fi{}0.2),$ while the similar size of ${\mathrm{La}}^{3+}$ and ${\mathrm{Na}}^{+}$ ions results in no appreciable change in the tolerance factor of the perovskite structure throughout the series. In this way, the sodium content x contro…
Comparing Beerkan infiltration tests with rainfall simulation experiments for hydraulic characterization of a sandy-loam soil
2017
[EN] Saturated soil hydraulic conductivity, K-s, data collected by ponding infiltrometer methods and usual experimental procedures could be unusable for interpreting field hydrological processes and particularly rainfall infiltration. The K-s values determined by an infiltrometer experiment carried out by applying water at a relatively large distance from the soil surface could however be more appropriate to explain surface runoff generation phenomena during intense rainfall events. In this study, a link between rainfall simulation and ponding infiltrometer experiments was established for a sandy-loam soil. The height of water pouring for the infiltrometer run was chosen, establishing a sim…
New synthetic strategies for the enhancement of the ionic conductivity in Ce0.8Sm0.2O2-x
2013
Introduction Samarium-doped ceria has been widely investigat-ed for electrochemistry applications as full density elec-trolyte for intermediate temperature solid oxide fuel cells (IT-SOFC), between 500°C and 800°C [1]. One of the main challenges for the ceria-based electrolytes is to decrease the resistivity at the grain boundary zone, especially in this low temperature range. Microstructure and morphology of the powder play a fundamental role on the densification behaviour and grain boundary properties, thus affecting the overall conductivity of electrolytes [2]. In this light, solution combustion syn-thesis (SCS) represents a flexible method to produce ultra fine powders with suitable mic…
"Table 26" of "Measurement of the differential cross-sections of inclusive, prompt and non-prompt J/psi production in proton-proton collisions at sqr…
2013
Breakdown of sources of systematic uncertainty on the non-prompt J/psi fraction measurements, for the bin 1.75<|y|<2.0, as a function of the J/psi pT.