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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.
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Editors’ Choice—Necessity to Avoid Titanium Oxide as Electrocatalyst Support in PEM Fuel Cells: A Membrane Durability Study
Pt/TiO 2 as electrocatalyst was found to significantly increase the rate of the membrane chemical degradation in a polymer electrolyte membrane (PEM) fuel cell. The increased degradation was proved to be due to TiO x (TiO 2 or Ti 4 O 7 ), which is widely recognized as a promising corrosion-resistant electrocatalyst support. The membrane degradation (thinning) appears to be preferentially in the side facing anode electrode. Migrated Ti species as a result of TiO x dissolution during fuel cell operation in an acidic environment was quantified by electron probe microanalysis (EPMA). Total fluorine inventory loss of the membrane strongly depends on the quantity of migrated Ti species (likely Ti 3+ and/or Ti 4+ ). The membrane chemical degradation induced by TiO x is proposed to be due to dissolved ionic Ti species reacting with H 2 O 2 through a Fenton reaction. TiO x is determined to be inviable as electrocatalyst support for PEM fuel cells, and future research is suggested to be directed toward alternative oxides with similar corrosion-resistance.
Siloxane Deposition on the Ni-YSZ Solid Oxide Fuel Cell Anode Exposed to Bio-Syngas
Siloxane, a common contaminant present in biogas, is known for adverse effects on cogeneration prime movers. In this study, the siloxane deposition products and mechanism in the solid oxide fuel cell nickel-yttria stabilized zirconia (Ni-YSZ) anode are investigated analytically and experimentally. An SOFC with Ni-YSZ anode and pure Ni/YSZ pellets were exposed to a simulated biogas-reformate fuel with octamethylcyclotetrasiloxane (D4) contamination at 750 °C. The electrochemical characterization results show that the SOFCs performance degradation caused by D4 contamination is irreversible. Morphology and XRD results illustrate that silicon and carbon deposition can both be detected in the anode and pellets. Graphite, SiC and SiO2 are all possible products based on the results of XRD test. Here, according to the formation of graphite and SiC, the new mechanism suggests that carbon is also an essential factor in siloxane contamination of Ni-YSZ anodes besides silicon, which can be explained by the catalytic and electrochemical analysis.
The new K, Pb-bearing uranyl-oxide mineral kroupaite: Crystal-chemical implications for the structures of uranyl-oxide hydroxy-hydrates
Abstract Kroupaite (IMA 2017-031), ideally KPb0.5[(UO2)8O4(OH)10]·10H2O, is a new uranyl-oxide hydroxylhydrate mineral found underground in the Svornost mine, Jáchymov, Czechia. Electron-probe micro-analysis (WDS) provided the empirical formula (K1.28Na0.07)Σ1.35(Pb0.23Cu0.14Ca0.05Bi0.03Co0.02Al0.01)Σ0.48 [(UO2)7.90(SO4)0.04O4.04(OH)10.00]·10H2O, on the basis of 40 O atoms apfu. Sheets in the crystal structure of kroupaite adopt the fourmarierite anion topology, and therefore kroupaite belongs to the schoepite-family of minerals with related structures differing in the interlayer composition and arrangement, and charge of the sheets. Uptake of dangerous radionuclides (90Sr or 135Cs) into the structure of kroupaite and other uranyl-oxide hydroxy-hydrate is evaluated based on crystal-chemical considerations and Voronoi-Dirichlet polyhedra measures. These calculations show the importance of these phases for the safe disposal of nuclear waste.
The Effect of Operational Temperature on the Performance and Durability of Solid Oxide Fuel Cells and Solid Oxide Electrolysis Cells
Solid oxide fuel cells (SOFC) and solid oxide electrolysis cells (SOEC) have received great interest due to their highly effective reversibility as power generation and H2 production system without releasing any greenhouse gases into environment. The LSCF electrode exhibits a higher structural and performance stability under both SOFC and SOEC operation due to its mixed ionic and electronic conductivity, and there is no immediate delamination taking place during the initial several hundred hours operation. However, the LSCF based air electrode still presents significant performance degradation (with the increased resistance) over the prolonged operation, such as over 1000 hours of operation under SOFC and SOEC. The influence factors for the cell’s performance and stability need to be optimized to improve the power generation for SOFC and H2 production for SOEC. The effects of operational temperature on the performance and durability for both SOFC and SOEC are electrochemical operation dependent. The performance and performance durability for the first 1500h were currently studied under optimized operational temperature for reversible SOFC/SOEC.
Improved separators for silver oxide-zinc and silver oxide-cadmium cells for spacecraft application Second quarterly progress report, 10 Feb. - 9 May 1965
Separators for silver oxide-zinc and silver oxide- cadmium cells for spacecraft application
Improved separators for silver oxide-zinc and silver oxide-cadmium cells for spacecraft application Third quarterly progress report, 10 May - 9 Aug. 1965
Improved separators for silver oxide-zinc and silver oxide-cadmium cells - flexibility and electrolytic conductivity in modified methyl cellulose polyacid films
Improved separators for silver oxide-zinc and silver oxide-cadmium cells for spacecraft application Final report, Nov. 10, 1964 - Nov. 10, 1965
Improved separators for silver oxide-zinc and silver oxide-cadmium cells for spacecraft application
Improved separators for silver oxide-zinc and silver oxide-cadmium cells for spacecraft application
Barrier properties of membrane separators for silver oxide-zinc and silver oxide-cadmium spacecraft batteries
Nitrous oxide production in far-ultraviolet photolysis of nitric oxide.
Nitrous oxide production in far UV photolysis of static nitric oxide system, using gas chromatographic technique
Injection and migration of charges in the oxide of a metal-oxide-semiconductor structure
Injection of charges in oxide of metal oxide semiconductor structure
High temperature oxidation of Co-10 W/0 Cr alloys. II - Oxidation kinetics.
Cobalt chromium alloys high temperature oxidation kinetics, discussing thermographic study of oxidation rate and oxygen pressure role
Thermal expansion anisotropy of oxides and oxide solid solutions.
Thermal expansion properties of oxides and oxide solid solutions measured for improved expansion coefficient search
Vaporization of chromium oxides from the surface of TD-NiCr under oxidizing conditions
Vaporization of chromium oxides from surface of TD-NiCr under oxidizing conditions
Oxide dispersed copper alloys by surface oxidation
Oxide dispersed Cu alloys preparation by surface oxidation of powders, considering structural stability and stress rupture properties
Thermal emissivity and solar absorptivity of aluminum coated with double layers of aluminum oxide and silicon oxide
Thermal emissivity and solar absorptivity of Al coated with surface layers of aluminum oxide and silicon oxide, describing fabrication techniques and performance measurements
Oxidative vaporization kinetics of chromium (III) oxide in oxygen from 1270 to 1570 K
Rates of oxidative vaporization of Cr2O3 on preoxidized resistively heated chromium were determined in flowing oxygen at 0.115 torr for temperatures from 1270 to 1570 K. Reaction controlled rates were obtained from experimental rates by a gold calibration technique. These rates were shown to agree with those predicted by thermochemical analysis. The activation energy obtained for the oxidative vaporation reaction corresponded numerically with the thermochemical enthalpy of the reaction. A theoretical equation is given for calculating the rate from thermodynamic data by using boundary layer theory.
Enhancement of oxidative vaporization of chromium (III) oxide and chromium by oxygen atoms
Rates of oxidative vaporization of Cr2O3 were found to be markedly enhanced in the presence of O atoms. Investigations were conducted over the temperature range 470 to 1520 K. For Cr2O3 the enhancement was about 10 to the 9th power at 820 K in oxygen containing 2.5 percent atoms. Rapid oxidative vaporization of bare chromium was observed below 1070 K, the rate being about one-half that of Cr2O3. Results are interpreted in terms of thermochemical analysis.