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ProGasMix FC (FC as in Fuel Cell) is a unique tool for students and researchers in materials science, suitable for use with the ProboStat or other systems using variable controlled atmospheres. It offers the economy, simplicity, and insight to those that value versatility and wide ranges of mixing. Partial pressures are calculated from flowmeter readings via accompanying software. The ProGasMix FC is a versatile rotameter-based manual gas mixer especially developed for laboratory investigations of the properties of oxides at high temperatures vs T, pO2, pH2O etc. (see methods page) or fuel cell tests with humidification of fuel and/or oxidant. The mixer includes safety features for overpressure (gas blockage). The mixer is based on the unique "Oslo mixer" at University of Oslo. It has been used in countless studies of conductivity and other properties as a function of pO2, pH2O, etc., and is especially known for its ability to deliver two mixtures suitable for concentration cell measurements (of for instance transport numbers of oxide ions and protons independently), permeation studies and fuel cell component tests. ProGasMix FC mixes any connected three gases into one or two mixtures. First mixture is input gas #1 diluted with input gas #2, even down to ppm ratios. A second mixture can be modified from the first for concentration cell measurements by diluting more with gas #2, or made from input gases #2 and #3 for example for fuel cell tests. Humidity of both mixtures individually can be controlled from 100% relative/~3% atm (at 25ºC) down to 0.3% relative, or the wetting can be skipped to obtain dry gas mixtures. For higher water contents the made mixture can be humidified externally after the mixer with optional humidifier unit. The mixer also has provision to connect custom wetting stages for example for D2O. Compared to mass-flow meter based system of equal features, the ProGasMix is order of magnitude less expensive and will last virtually forever. ProGasMix FC requires no frequent maintenance, repairs or calibration. The mixer is simple, serviceable, and "transparent" to the user, making it easy for users to understand what goes on inside the mixer. The rotameters are slightly less accurate than mass flow controllers, but as the mixtures typically span pO2 or pH2O over several orders of magnitude (logarithmically) the few percent linear error of rota-meters become negligible. Allows
Specifications
Physical description
For further details see methods page and read the ProGasMix manual |
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Stability of NASICON materials against water and CO2 uptake
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Solid State Ionics
Time of Publication: 2016
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| Abstract | The stability in ambient conditions of a scandium-based NASICON material, Na3.4Sc2Si0.4P2.6O12, was investigated using impedance spectroscopy, thermogravimetry/differential scanning calorimetry (TG/DSC) and multinuclear magic angle spinning nuclear magnetic resonance spectroscopy (MAS NMR). The presence of H2O and CO2 in samples stored in ambient air could be evidenced as well as its impact on the ionic conductivity of the samples. The detected amounts of water and CO2 in the samples had no influence on the measured conductivities at room temperature, which confirmed the absence of protonic conduction in hydrated samples. A loss of conductivity during heating of hydrated samples was due to a loss of contact between the ceramic and the electrode used for the conductivity measurement. The recommendation for handling of NASICON-type materials is therefore: samples require storage in an Ar-filled glove box or in a dry environment to avoid artefacts during high temperature measurements. Nevertheless, the stability of the NASICON-type materials is confirmed since their conductivity is not affected by the moisture. |
| Keywords | Ionic conductivity; NASICON; Sodium; Scandium; ProGasMix |
| Remark |
http://dx.doi.org/10.1016/j.ssi.2016.11.006 Link |
Functional properties of La0.99X0.01Nb0.99Al0.01O4−δ and La0.99X0.01Nb0.99Ti0.01O4−δ proton conductors where X is an alkaline earth cation
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Journal of the European Ceramic Society
Time of Publication: 2014-12
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| Abstract | Lanthanum niobates with general formulas of La0.99X0.01Nb0.99Al0.01O4−δ and La0.99X0.01Nb0.99Ti0.01O4−δ (X = Mg, Ca, Sr or Ba) were synthesized via the conventional solid state reaction. Specimens with relative density above 96% were produced after sintering. Structural and phase composition studies revealed predominant monoclinic Fergusonite structure for the majority of samples. SEM and TEM studies elucidated the effect of the used dopant combinations on grain growth, micro-crack formation and secondary phase formation. Results from microstructural study were correlated to the grain interior and grain boundary conductivities for selected samples (La0.99Sr0.01Nb0.99Al0.01O4−δ and La0.99Sr0.01Nb0.99Ti0.01O4−δ). The majority of co-doped niobates exhibited appreciable protonic conductivity under humid atmospheres at intermediate temperatures. Sr- or Ca-doped compounds displayed the highest total conductivities with values for LSNA equal to 6 × 10−4 S/cm and 3 × 10−4 S/cm in wet air and in wet 4% H2–Ar (900 °C), respectively. Additionally, thermal expansion was studied to complete functional characterization of co-doped LaNbO4. |
| Keywords | Proton-conducting ceramic materials, Hydrogen transport ceramic membranes, Rare earth ortho-niobates, Acceptor-doped lanthanum niobates, ProGasMix |
| Remark | Link |
Synthesis and Characterization of Nonsubstituted and Substituted Proton-Conducting La6–xWO12–y
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Inorganic Chemistry
Publisher: ACS Publications,
Time of Publication: 2013
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| Abstract | Mixed proton–electron conductors (MPEC) can be used as gas separation membranes to extract hydrogen from a gas stream, for example, in a power plant. From the different MPEC, the ceramic material lanthanum tungstate presents an important mixed protonic–electronic conductivity. Lanthanum tungstate La6–xWO12–y (with y = 1.5x + δ and x = 0.5–0.8) compounds were prepared with La/W ratios between 4.8 and 6.0 and sintered at temperatures between 1300 and 1500 °C in order to study the dependence of the single-phase formation region on the La/W ratio and temperature. Furthermore, compounds substituted in the La or W position were prepared. Ce, Nd, Tb, and Y were used for partial substitution at the La site, while Ir, Re, and Mo were applied for W substitution. All substituents were applied in different concentrations. The electrical conductivity of nonsubstituted La6–xWO12–y and for all substituted La6–xWO12–y compounds was measured in the temperature range of 400–900 °C in wet (2.5% H2O) and dry mixtures of 4% H2 in Ar. The greatest improvement in the electrical characteristics was found in the case of 20 mol % substitution with both Re and Mo. After treatment in 100% H2 at 800 °C, the compounds remained unchanged as confirmed with XRD, Raman, and SEM. |
| Keywords | ProGasMix |
| Remark |
lanthanum tungstate La6–xWO12–y Link |
