scholarly journals Insulative Phase Formation and Polarization Resistance of PrBaCo2−xCuxO5+δ under Thermal Stress

2021 ◽  
Vol 12 (1) ◽  
pp. 151
Author(s):  
Kanghee Jo ◽  
Jooyeon Ha ◽  
Taeheun Lim ◽  
Heesoo Lee
Keyword(s):  
Thermal Stress ◽  
Phase Formation ◽  
Polarization Resistance ◽  
Oxygen Vacancies ◽  
Secondary Phase ◽  
Crystal Structure Analysis ◽  
Secondary Phases ◽  
Oxidation Number ◽  
Cu Doping ◽  
Thermal Deterioration

The degradation behavior of PrBaCo2−xCuxO5+δ (x = 0, 0.2, 0.5) under thermal stress was investigated in terms of phase formation and polarization resistance. The tetragonal phase was indexed in all compositions of PBCCux, and the secondary phase, BaO, was identified after thermal degradation in the crystal structure analysis. BaO formation is induced by the nature of perovskite to terminate the surface with AO layer. For pristine specimens, the oxygen vacancy peak ratio was increased from 57% to 60% according to the decrease in the average oxidation number of the B-site ion with Cu doping. After thermal deterioration, the oxidation number of B-site ions was increased, and the M = O bonding peak increased due to the decrease in oxygen vacancies and BaO formation according to the thermal stress. In all compositions, the electrical conductivity decreased from 1000 S/cm to 17 S/cm, and the polarization resistance increased approximately 200 times. These results are considered to be related to the increase in the oxidation number of B-site ions along with the formation of secondary phases.

Identification of Secondary Phases Formed During Unsaturated Reaction of UO2 with EJ-13 Water

1989 ◽  
Vol 176 ◽  
Author(s):  
J. K. Bates ◽  
B. S. Tani ◽  
E. Veleckis ◽  
O. J. Wronklewicz
Keyword(s):  
Phase Formation ◽  
Secondary Phase ◽  
Yucca Mountain ◽  
Solution Chemistry ◽  
Spent Fuel ◽  
Secondary Phases ◽  
Secondary Phase Formation

ABSTRACTA set of experiments, wherein UO2 has been contacted by dripping water, has been conducted over a period of 182.5 weeks. The experiments are being conducted to develop procedures to study spent fuel reaction under unsaturated conditions that are expected to exist over the lifetime of the proposed Yucca Mountain repository site. One half of the experiments have been terminated, while one half are ongoing. Analyses of solutions that have dripped from the reacted UO2 have been performed for all experiments, while reacted UO2 surfaces have been examined for the terminated experiments. A pulse of uranium release from the UO2 solid, combined with the formation of schoepite on the surface of the UO2, was observed between 39 and 96 weeks of reaction. Thereafter, the uranium release decreased and a second set of secondary phases was observed. The latter phases incorporated cations from the EJ-13 water and include boltwoodite, uranophane, sklodowskite, compreignacite, and schoepite. The experiments are continuing to monitor whether additional changes in solution chemistry or secondary phase formation occurs.

Effect of Sintering Conditions on the Phase Formation and Microstructure of Bi-2223/Ag/Ni Composite-Sheathed Tapes

2013 ◽  
Vol 745-746 ◽  
pp. 239-242
Author(s):  
Xing Pin Chen ◽  
Meng Liu ◽  
Xiao Wei Yu ◽  
Ming Ya Li
Keyword(s):  
Heat Treatment ◽  
Phase Formation ◽  
Microstructure Evolution ◽  
Significant Influence ◽  
Sintering Temperature ◽  
Secondary Phase ◽  
Secondary Phases ◽  
Different Temperatures ◽  
Sintering Conditions ◽  
Powder In Tube

Effect of sintering conditions in the first heat treatment on the phase and microstructure evolution of Bi-2223/Ag/Ni composite-sheathed tapes fabricated by powder-in-tube method was studied. Samples were sintered at different temperatures for different time in an atmosphere of 14.5% O2. The results showed that this higher O2 atmosphere improved the content of Bi-2223 phase. XRD and SEM results showed that Bi-2223 content increased with the extension of the dwelling time. Meanwhile, the sintering temperature had significant influence on the Bi-2223 content and secondary phase dimensions as well. With the increase of the sintering temperature, the Bi-2223 content reached to a maximum at 834. With further increase of sintering temperature, the Bi-2223 phase was decomposed to Bi-2212 and others secondary phases.

scholarly journals Prediction of Radioactive Waste Glass Durability by the Hydration Thermodynamic Model: Application to Saturated Repository Environments

1989 ◽  
Vol 176 ◽  
Author(s):  
Carol M. Jantzen ◽  
W. Gene Ramsey
Keyword(s):  
Free Energy ◽  
Dissolution Rate ◽  
Phase Formation ◽  
Thermodynamic Model ◽  
Functional Dependence ◽  
Secondary Phase ◽  
Deionized Water ◽  
Secondary Phases ◽  
Durability Test ◽  
Secondary Phase Formation

ABSTRACTThe effects of groundwater chemistry on glass durability were examined using the hydration thermodynamic model. The relative durabilities of SiO2, obsidian, basalt, nuclear waste glasses, medieval window glasses, and a frit glass were determined in tuffaceous (J–13) groundwater, basaltic (GR–4) groundwater, WIPP–A brine, and Permian Basin brine (PBB–3) using the monolithic MCC–I durability test. In the groundwater–dominated MCC–l experiments, the interaction of the glasses and the initial groundwater (leachant) caused the formation of unique assemblages of secondary phases. The secondary phase formation, in turn, controlled the final groundwater (leachate) pH and ionic strength, I[t].Correlations of the final leachate pH and I[t] with the Si release from the glass indicated that it is the influence of the secondary phase formation on the leachate pH and I[t] that controls the final dissolution rate of the glass. Since I[t] and the pH of the leachates are functions of the precipitation reactions, inclusion of the experimentally determined solution pH in the free energy of hydration model provides for the functional dependence of the dissolution rate on the secondary precipitation. Therefore, superposition of the linear equation for the groundwater and deionized water experiments occurs and the hydration free energy model can be used to compare glass durability in deionized water and in repository groundwaters.

Dopant-Site Determination in Y- and Sc-Doped (Ba0.5Sr0.5)(Co0.8Fe0.2)O3−δby Atom Location by Channeling Enhanced Microanalysis and the Role of Dopant Site on Secondary Phase Formation

2015 ◽  
Vol 22 (1) ◽  
pp. 113-121 ◽  
Author(s):  
Matthias Meffert ◽  
Heike Störmer ◽  
Dagmar Gerthsen
Keyword(s):  
Phase Formation ◽  
Electronic Conductivity ◽  
Site Occupancy ◽  
Secondary Phase ◽  
Secondary Phases ◽  
Oxide Formation ◽  
Separation Membranes ◽  
Secondary Phase Formation ◽  
Homogenization Temperatures ◽  
Cation Sites

Abstract(Ba0.5Sr0.5)(Co0.8Fe0.2)O3−δ(BSCF) is a promising material with mixed ionic and electronic conductivity which is considered for oxygen separation membranes. Selective improvement of material properties, e.g. oxygen diffusivity or suppression of secondary phase formation, can be achieved by B-site doping. This study is concerned with the formation of Co-oxide precipitates in undoped BSCF at typical homogenization temperatures of 1,000°C, which act as undesirable nucleation sites for other secondary phases in the application-relevant temperature range. Y-doping successfully suppresses Co-oxide formation, whereas only minor improvements are achieved by Sc-doping. To understand the reason for the different behavior of Y and Sc, the lattice sites of dopant cations in BSCF were experimentally determined in this work. Energy-dispersive X-ray spectroscopy in a transmission electron microscope was applied to locate dopant sites exploiting the atom location by channeling enhanced microanalysis technique. It is shown that Sc exclusively occupies B-cation sites, whereas Y is detected on A- and B-cation sites in Y-doped BSCF, although solely B-site doping was intended. A model is presented for the suppression of Co-oxide formation in Y-doped BSCF based on Y double-site occupancy.

Secondary phase formation by liquid immiscibility in Ca3Ta(Ga1−xAlx)3Si2O14 melt

2019 ◽  
Vol 522 ◽  
pp. 117-124
Author(s):  
Yuki Honda ◽  
Hiromasa Niinomi ◽  
Jun Nozawa ◽  
Junpei Okada ◽  
Satoshi Uda
Keyword(s):  
Phase Formation ◽  
Secondary Phase ◽  
Liquid Immiscibility ◽  
Secondary Phase Formation

scholarly journals In situ nuclear-glass corrosion under geological repository conditions

2019 ◽  
Vol 3 (1) ◽  
Author(s):  
Mathieu Debure ◽  
Yannick Linard ◽  
Christelle Martin ◽  
Francis Claret
Keyword(s):  
Pure Water ◽  
Secondary Phase ◽  
Predictive Modelling ◽  
Diffusion Experiment ◽  
Secondary Phases ◽  
Glass Corrosion ◽  
Geological Repository ◽  
High Level ◽  
Rock Supports

Abstract Silicate glasses are durable materials but laboratory experiments reveal that elements that derive from their environment may induce high corrosion rates and reduce their capacity to confine high-level radioactive waste. This study investigates nuclear-glass corrosion in geological media using an in situ diffusion experiment and multi-component diffusion modelling. The model highlights that the pH imposed by the Callovo–Oxfordian (COx) claystone host rock supports secondary-phase precipitation and increases glass corrosion compared with pure water. Elements from the COx rock (mainly Mg and Fe) form secondary phases with Si provided by the glass, which delay the establishment of a passivating interface. The presence of elements (Mg and Fe) that sustain glass alteration does not prevent a significant decrease in the glass-alteration rate, mainly due to the limited species transport that drives system reactivity. These improvements in the understanding of glass corrosion in its environment provide further insights for predictive modelling over larger timescales and space.

Simulation of Poly-Disperse Multiphase Systems via Computational Fluid Dynamics

2006 ◽  
Author(s):  
Daniele L. Marchisio ◽  
Marco Vanni ◽  
Antonello A. Barresi ◽  
Giancarlo Baldi
Keyword(s):  
Method Of Moments ◽  
Fluid Model ◽  
Secondary Phase ◽  
Primary Phase ◽  
Momentum Balance ◽  
Multiphase Model ◽  
Secondary Phases ◽  
Discrete Events ◽  
Multiphase Systems ◽  
Two Phases

Multiphase systems, such as sprays and aerosols, are characterized by the existence of a continuous primary phase and a disperse secondary phase. The interaction between the two phases and/or the chemical reactions can affect both composition and characteristic velocity of the primary and secondary phases, as well as the size distribution of the secondary phase. In order to describe these systems, the continuity, mass balance and momentum balance equations as well as additional equations for turbulence, must be solved. Nevertheless if there is the need to account for the evolution of the secondary phase because of continuous and discrete events the population balance equation must be solved. In this work two very efficient ways to cope with these issues will be presented. In particular the use of the quadrature method of moments coupled with the mixture multiphase model, and the multi-fluid model will be presented and discussed.

PH3 Effects on the Electrochemical Degradation of SOFC Anode

2011 ◽  
Author(s):  
Huang Guo ◽  
Gulfam Iqbal ◽  
Bruce S. Kang
Keyword(s):  
Electrochemical Performance ◽  
Secondary Phase ◽  
Anode Surface ◽  
Electrochemical Degradation ◽  
Secondary Phases ◽  
Nickel Phosphate ◽  
Secondary Phase Formation ◽  
Cell Anode ◽  
Fuel Cell Anode ◽  
Ppm Level

Solid Oxide Fuel Cell anode is readily degraded by trace amount of Phosphine (PH3) contaminant that is found in coal-derived syngas. PH3 interacts with the anode material and affects its electrochemical performance by forming secondary phases. In this paper, the influence of the ppm level of PH3 with moisture is investigated on the formation of secondary phases and hence on anode electrochemical performance degradation. Nickel yttria-stabilized zirconia (Ni-YSZ) anode shows immediate and severe electrochemical degradation due to PH3 in moist hydrogen condition attributed to the nickel-phosphate secondary phase formation. Whereas in dry hydrogen condition, nickel-phosphide is preferred to form on the anode surface that shows less deleterious effects on SOFC performance as compared to nickel-phosphate.

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