An overview of thermotransport in fluorite-related ionic oxides

Abstract In this overview, we summarize the phenomenon of thermotransport (the close coupling of mass transport and heat transport) in two fast ion conductors: yttria-doped zirconia and gadolinia-doped ceria. We focus on two recent molecular dynamics calculations using the Green-Kubo formalism. We show that the Onsager thermotransport cross coefficient (mass-heat coupling) is negative, meaning that oxygen ions would drift, in principle, to the hot side in a temperature gradient. Simulation results presented in this overview show reasonable agreement with available experimental data for thermal conductivity. Results of this study suggest that the coupling between mass and heat transport in oxygen ion electrolytes could have significant effect for practical applications.

Download Full-text

Entropic stabilization plays a key role in the non-uniform distribution of oxygen ions and vacancy defects in gadolinium-doped ceria

Physical Chemistry Chemical Physics ◽

10.1039/d0cp03743e ◽

2021 ◽

Author(s):

Methary Jaipal ◽

Bharathi Bandi ◽

Abhijit Chatterjee

Keyword(s):

Uniform Distribution ◽

Doped Ceria ◽

Vacancy Defects ◽

Oxygen Ions ◽

Oxygen Ion ◽

Ion Movement ◽

Entropic Stabilization ◽

Entropic Effects ◽

Gadolinium Doped Ceria

A new theory describing oxygen ion movement and distribution in YSZ and GDC shows that entropic effects are significant.

Download Full-text

Doped Ceria Based Solid Oxide Fuel Cell Electrolytes and their Sintering Aspects: An Overview

Materials Science Forum ◽

10.4028/www.scientific.net/msf.835.199 ◽

2016 ◽

Vol 835 ◽

pp. 199-236 ◽

Cited By ~ 1

Author(s):

Pradyot Datta

Keyword(s):

Power Generation ◽

Fuel Cell ◽

Solid Oxide Fuel Cell ◽

Operating Temperature ◽

Solid Oxide ◽

Ion Conductivity ◽

Doped Ceria ◽

Oxide Fuel ◽

Oxygen Ion Conductivity ◽

Oxygen Ion

Depletion of fossil fuel at an alarming rate is a major concern of humankind. Consequently, researchers all over the world are putting a concerted effort for finding alternative and renewable energy. Solid oxide fuel cell (SOFC) is one such system. SOFCs are electrochemical devices that have several advantages over conventional power generation systems like high efficiency of power generation, low emission of green house gases and the fuel flexibility. The major research focus of recent times is to reduce the operating temperature of SOFC in the range of 500 to 700 °C so as to render it commercially viable. This reduction in temperature is largely dependent on finding an electrolyte material with adequate oxygen ion conductivity at the intended operating temperature. One much material is Gadolinia doped Ceria (CGO) that shows very good oxygen ion conductivity at the intended operation temperature. The aim of this overview is to highlight the contribution that materials chemistry has made to the development of CGO as an electrolyte.

Download Full-text

An insight into the structure, conductivity and ion dynamics of Sr-Sm co-doped ceria oxygen ion conductors: Effect of defect interaction

Solid State Sciences ◽

10.1016/j.solidstatesciences.2018.10.007 ◽

2018 ◽

Vol 86 ◽

pp. 69-76 ◽

Cited By ~ 2

Author(s):

Sk. Anirban ◽

Abhigyan Dutta

Keyword(s):

Doped Ceria ◽

Ion Dynamics ◽

Defect Interaction ◽

Oxygen Ion ◽

Oxygen Ion Conductors ◽

Insight Into ◽

Co Doped ◽

Ion Conductors

Download Full-text

X-ray diffraction study of oxygen-conducting compoundsLn2Mo2O9(Ln= La, Pr)

Acta Crystallographica Section B Structural Science Crystal Engineering and Materials ◽

10.1107/s2052520614006623 ◽

2014 ◽

Vol 70 (4) ◽

pp. 669-675 ◽

Cited By ~ 3

Author(s):

Alexander M. Antipin ◽

Olga A. Alekseeva ◽

Natalia I. Sorokina ◽

Alexandra N. Kuskova ◽

Michail Yu. Presniakov ◽

...

Keyword(s):

Room Temperature ◽

Cubic Phase ◽

X Ray Diffraction ◽

Ion Migration ◽

Transmission Microscopy ◽

Coordination Environment ◽

X Ray ◽

Oxygen Ions ◽

Oxygen Ion ◽

Oxygen Ion Migration

The La2Mo2O9(LM) and Pr2Mo2O9(PM) single crystals are studied using precision X-ray diffraction and high-resolution transmission microscopy at room temperature. The crystal structures are determined in the space groupP213. La and Pr atoms, as well as Mo1 and O1 atoms, are located in the vicinity of the threefold axes rather than on the axes as in the high-temperature cubic phase. In both structures studied, the O2 and O3 positions are partially occupied. The coexistence of different configurations of the Mo coordination environment facilitates the oxygen-ion migration in the structure. Based on the X-ray data, the activation energies of O atoms are calculated and the migration paths of oxygen ions in the structures are analysed. The conductivity of PM crystals is close to that of LM crystals. The O2 and O3 atoms are the main contributors to the ion conductivity of LM and PM.

Download Full-text

Microstructural and Compositional Characterization of SiC-On-Insulator Structures

Microscopy and Microanalysis ◽

10.1017/s1431927600017177 ◽

1999 ◽

Vol 5 (S2) ◽

pp. 770-771

Author(s):

Manabu Ishimaru ◽

Robert M. Dickerson ◽

Kurt E. Sickafus

Keyword(s):

Ion Implantation ◽

Integrated Circuit ◽

High Speed ◽

Scanning Transmission Electron Microscope ◽

Oxygen Ions ◽

Oxygen Ion ◽

Transmission Electron ◽

Scanning Transmission ◽

Oxygen Ion Implantation

As the size of Si integrated circuit structures is continually reduced, interest in semiconductor-oninsulator (SOI) structures has heightened. SOI structures have already been developed for Si using oxygen ion implantation. However, the application of Si devices is limited due to the physical properties of Si. As an alternative to Si, SiC is a potentially important semiconductor for high-power, high-speed, and high-temperature electronic devices. Therefore, this material is a candidate for expanding the capabilities of Si-based technology. In this study, we performed oxygen ion implantation into bulk SiC to produce SiC-on-insulator structures. We examined the microstructures and compositional distributions in implanted specimens using transmission electron microscopy and a scanning transmission electron microscope equipped with an energy-dispersive X-ray spectrometer (STEM-EDX).Figures 1(a) and 2(a) show bright-field images of 6H-SiC implanted with 180 keV oxygen ions at 650 °C to fluences of 7xl017 and 1.4xl018 cm−2, respectively. Three regions with distinct image contrast are apparent in Figs. 1(a) and 2(a), as indicated by A, B, and C.

Download Full-text

Enhancing the Thermal Performance of Slender Packed Beds through Internal Heat Fins

Processes ◽

10.3390/pr8121528 ◽

2020 ◽

Vol 8 (12) ◽

pp. 1528

Author(s):

Nico Jurtz ◽

Steffen Flaischlen ◽

Sören C. Scherf ◽

Matthias Kraume ◽

Gregor D. Wehinger

Keyword(s):

Heat Transfer ◽

Heat Transport ◽

Thermal Performance ◽

Internal Heat ◽

Spherical Particles ◽

Reactor Wall ◽

Packed Beds ◽

Radial Heat ◽

Simulation Results ◽

The Impact

Slender packed beds are widely used in the chemical and process industry for heterogeneous catalytic reactions in tube-bundle reactors. Under safety and reaction engineering aspects, good radial heat transfer is of outstanding importance. However, because of local wall effects, the radial heat transport in the vicinity of the reactor wall is hindered. Particle-resolved computational fluid dynamics (CFD) is used to investigate the impact of internal heat fins on the near wall radial heat transport in slender packed beds filled with spherical particles. The simulation results are validated against experimental measurements in terms of particle count and pressure drop. The simulation results show that internal heat fins increase the conductive portion of the radial heat transport close to the reactor wall, leading to an overall increased thermal performance of the system. In a wide flow range (100<Rep<1000), an increase of up to 35% in wall heat transfer coefficient and almost 90% in effective radial thermal conductivity is observed, respectively.

Download Full-text

On parameterization of heat conduction in coupled soil water and heat flow modelling

Soil and Water Research ◽

10.17221/21/2012-swr ◽

2012 ◽

Vol 7 (No. 4) ◽

pp. 125-137 ◽

Cited By ~ 7

Author(s):

J. Votrubová ◽

M. Dohnal ◽

T. Vogel ◽

M. Tesař

Keyword(s):

Thermal Conductivity ◽

Soil Water ◽

Heat Transport ◽

Preferential Flow ◽

Thermal Conditions ◽

Industrial Applications ◽

Soil Thermal Conductivity ◽

Vegetation Season ◽

Simulation Results ◽

The Impact

Soil water and heat transport plays an important role in various hydrologic, agricultural, and industrial applications. Accordingly, an increasing attention is paid to relevant simulation models. In the present study, soil thermal conditions at a mountain meadow during the vegetation season were simulated. A dual-continuum model of coupled water and heat transport was employed to account for preferential flow effects. Data collected at an experimental site in the &Scaron;umava Mountains, southern Bohemia, during the vegetation season 2009 were employed. Soil hydraulic properties (retention curve and hydraulic conductivity) determined by independent soil tests were used. Unavailable hydraulic parameters were adjusted to obtain satisfactory hydraulic model performance. Soil thermal properties were estimated based on values found in literature without further optimization. Three different approaches were used to approximate the soil thermal conductivity function, λ(θ): (i) relationships provided by Chung and Horton (ii) linear estimates as described by Loukili, Woodbury and Snelgrove, (iii) methodology proposed by Côté and Konrad. The simulated thermal conditions were compared to those observed. The impact of different soil thermal conductivity approximations on the heat transport simulation results was analysed. The differences between the simulation results in terms of the soil temperature were small. Regarding the surface soil heat flux, these differences became substantial. More realistic simulations were obtained using λ(θ) estimates based on the soil texture and composition. The differences between these two, related to neglecting vs. considering λ(θ) non-linearity, were found negligible.

Download Full-text

CFD Simulation of Heating a Cu Pipe with a Safe H2/O2 Flame

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.611-612.1553 ◽

2014 ◽

Vol 611-612 ◽

pp. 1553-1559

Author(s):

Lars Kjäldman ◽

Jouni Syrjänen

Keyword(s):

Reasonable Agreement ◽

Cfd Simulation ◽

Temperature History ◽

Measured Temperature ◽

Dynamics Modeling ◽

Computational Fluid Dynamics Modeling ◽

History Of ◽

Modeling And Experiments ◽

Simulation Results ◽

The Eu

As part of the EU/SME project SafeFlame (www.safeflameproject.eu ) the heating of a Cu pipe by a H2/O2 flame has been modeled and the results are compared to experiments. CFD (Computational Fluid Dynamics) modeling has been utilized to study the flow and combustion in the flame and the heat transfer from the flame to the pipe. The simulation results are compared with the measured temperature history of the pipe at different locations and with the visual flame. The influence of distance between the burner and the pipe and of using two opposite H2/O2 flames on the heating rate of the pipe has been investigated. Reasonable agreement between modeling and experiments has been obtained. The reasons for differences between modeling and experimental results are discussed.

Download Full-text

Stresses in Ion Assisted Deposited Oxide Thih Films

MRS Proceedings ◽

10.1557/proc-316-929 ◽

1993 ◽

Vol 316 ◽

Cited By ~ 1

Author(s):

M. Ghanashyam Krishna ◽

Mansour Al Robaee ◽

S. Kanakaraju ◽

K. Narasimha Rao ◽

S. Mohan

Keyword(s):

Substrate Temperature ◽

Compressive Stress ◽

Tensile Stresses ◽

Oxygen Ions ◽

Oxygen Ion ◽

Argon Ion Bombardment ◽

Current Densities ◽

Stress Behaviour ◽

Ion Species ◽

Argon Ion

ABSTRACTThin films of Ceria, Titania and Ziroonia have been prepared using Ion Assisted Deposition(IAD). The energy of ions was varied between 0 and 1 keV and current densities up to 220 μA/cm were used. It was found that the stress behaviour is dependent on ion species, i.e. Argon or Oxygen, ion energy and current density and substrate temperature apart from the material. While oeria files showed tensile stresses under the influence of argon ion bombardment at ambient temperature, they showed a sharp transition from tensile to compressive stress with increase in substrate temperature. When bombarded with oxygen ions they showed a transition from tensile to compressive stress with increase in energy. The titania films deposited with oxygen ions, on the other hand showed purely tensile stresses. Zirconia films deposited with oxygen ions, however, showed a transition from tensile to compressive stress.

Download Full-text