Flexible multiphysics simulation of porous electrodes: Conformal to 3D reconstructed microstructures

Lynch, Matthew L.; Ding, Dong; Harris, William M.; Lombardo, Jeffrey J.; Nelson, George J.; Chiu, Wilson K. S.; Liu, Meilin

doi:10.1016/j.nanoen.2012.08.002

Cited by 56 publications

(44 citation statements)

References 57 publications

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“…52 Computational studies showed that oxygen vacancies tend to be created on the LSM surface under the SOFC operational conditions due to the significantly reduced formation energy, 53,54 while the high cathodic polarization enhances the formation of oxygen vacancies at the electrode/electrolyte interface. 31,[55][56][57] The presence of positively charged oxygen vacancies would make the surrounding atoms polarized toward the vacancies. 54 In the case of mixed ionic and electronic conductor (Ba,Sr)(Co,Fe)O 3-δ (BSCF), the presence of highly concentrated oxygen vacancies can result in a local lattice perturbation and a local charge redistribution, as well as expansion of the lattice volume.…”

Section: Nanosims Icp-oes and Xps-mentioning

confidence: 99%

A Fundamental Study of Boron Deposition and Poisoning of La_0.8Sr_0.2MnO₃Cathode of Solid Oxide Fuel Cells under Accelerated Conditions

Chen

Liu

Guagliardo

et al. 2015

J. Electrochem. Soc.

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Borosilicate glass and glass-ceramics are the most common sealant materials for planar solid oxide fuel cells (SOFCs). This study focuses on the fundamentals of deposition and poisoning of volatile boron species from the borosilicate glass on the electrocatalytic activity and microstructure of La 0.8 Sr 0.2 MnO 3 (LSM) cathodes under accelerated SOFC operation conditions, using EIS, SEM, FIB-SEM, HRTEM, NanoSIMS, XPS and ICP-OES. The presence of boron species poisons and deteriorates the electrochemical activity and stability for the O 2 reduction reaction on the LSM cathodes. Boron deposition occurs randomly on the LSM electrode surface under open circuit but is driven to the electrode/electrolyte interface region under cathodic polarization conditions, resulting in the formation of LaBO 3 and Mn 2 O 3 and the disintegration of the LSM perovskite structure. The preferential boron deposition at the interface is most likely due to the increased activity of the highly energetic lanthanum at LSM lattice sites at the three phase boundary region under cathodic polarization conditions, accelerating the reaction rate between the gaseous boron species and energetic La. This study provides a fundamental insight into the boron deposition and its interaction with SOFC cathodes. Solid oxide fuel cells (SOFCs) are an energy conversion device to directly transfer the chemical energy of fuels to electrical energy, and are the most efficient and least polluting energy conversion technology among various kinds of fuel cells. One critical issue of the development of reliable and durable SOFCs is the gradual degradation of activity at the cathode side during long-term operation, due to the attack by volatile impurities such as chromium from the Fe-Cr interconnect, sulfur from the air stream and boron from borosilicate-based glass sealants. 1-3Borosilicate glass and glass-ceramic materials are the most common sealants to seal the edge of planar SOFCs to hermetically separate fuels supplied to the anode and air to the cathode. [4][5][6][7][8][9] The sealing and thermomechanical properties and the compatibility and interface between glass-ceramic sealant materials, metallic interconnect and electrolyte have been extensively studied. 8,[10][11][12][13][14] However, under the SOFC operation condition boron species from the borosilicate glass are highly volatile to form BO 2 under dry conditions and B 3 H 3 O 6 under wet, reducing conditions. 2,15 Earlier studies show that volatile species from glass sealants can significantly affect the microstructure of LSM electrodes.16 Komatsu et al. 17 used glass to seal an anode-supported planar cell and found that the concentration of boron in the cathode exhaust gas trapped by a water condenser increased with the operation time during the long-term test at 800• C for 6500 h. We recently carried out a series of detailed studies on the effect of boron poisoning on electrode performance of the most common (La,Sr)MnO 3 (LSM), (La,Sr)(Co,Fe)O 3 (LSCF) and (Ba,Sr)(Co,Fe)O 3 (BSCF) cathodes, by heat-...

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Section: Nanosims Icp-oes and Xps-mentioning

confidence: 99%

A Fundamental Study of Boron Deposition and Poisoning of La_0.8Sr_0.2MnO₃Cathode of Solid Oxide Fuel Cells under Accelerated Conditions

Chen

Liu

Guagliardo

et al. 2015

J. Electrochem. Soc.

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“…Such materials know a huge variety of applications, such as heat conduction enhancement in polyesters [8] or energy storage systems [9], to mention a few. As far as goes nanostructured materials for thermoelectric systems [10][11][12][13], a decrease in the thermal conductivity is often sought for in order to increase the figure of merit ZT [5,6,14]. The figure of merit is not only inversely dependent on the thermal conductivity, but also depends on the electric conductivity, which are both size-dependent [7].…”

Section: Introductionmentioning

confidence: 99%

An extended thermodynamic model for size-dependent thermoelectric properties at nanometric scales: Application to nanofilms, nanocomposites and thin nanocomposite films

Machrafi

2016

Applied Mathematical Modelling

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A new mathematical model is developed, describing size-dependent subcontinuum thermoelectric properties from an extended thermodynamic point of view. This model takes into account the non-local effects of heat transfer through phonons and electrons that are important at nanometric scales. These phenomena are extended to apply also for electric transfer as well as the Seebeck coefficient. This model includes at nanoscale size-dependent electron and phonon thermal conductivities, electric conductivity, Seebeck coefficient and carrier concentrations. We compared nanofilms to nanocomposites and assessed their thermoelectric performances in the form of a figure of merit using as an example Bismuth and BismuthTelluride materials. It appeared that the figure of merit increases considerably for nanofilms and nanocomposites with respect to bulk materials. This is caused by the scattering of phonons and electrons. Our model shows that this scattering effect is not only present at the boundary or particle-matrix interface of the nanosized material, but also within it. The effect of particle size and surface specularity has been investigated, showing that a decreasing value of the particle size and specularity increases the scattering effect and improves the thermoelectric properties. An extension towards thin films of nanocomposite has been presented.

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“…The resistor network is often drawn from randomly packed electronic and ionic spherical particles in which one particle is essentially represented by one vertex in the resistor network, and each vertex is assigned a resistance to represent a particular phase in an SOFC electrode. Recently, the 3D imaging of experimental SOFC electrode microstructures has been made possible through focused ion beam-scanning electron microscope (FIB-SEM) or X-ray computed tomography (XCT) techniques [8][9][10][11][12][13][14]36]. This has in turn further promoted the development of modeling methods to derive effective conductivities based on complex real 3D microstructures.…”

Section: Introductionmentioning

confidence: 99%

“…This has in turn further promoted the development of modeling methods to derive effective conductivities based on complex real 3D microstructures. Examples of these include the lattice Boltzmann method (LBM) [9], finite-volume-based methods such as computational fluid dynamics (CFD) [13], and finite-element-based approaches such as COMSOL multiphysics [14]. These approaches have been used to investigate the effects of microstructural properties such as particle size and porosity on effective conductivities.…”

Section: Introductionmentioning

confidence: 99%

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Towards the 3D Modelling of the Effective Conductivity of Solid Oxide Fuel Cell Electrodes – Validation against experimental measurements and prediction of electrochemical performance

Rhazaoui

Cai

Kishimoto

et al. 2015

Electrochimica Acta

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Flexible multiphysics simulation of porous electrodes: Conformal to 3D reconstructed microstructures

Cited by 56 publications

References 57 publications

A Fundamental Study of Boron Deposition and Poisoning of La_0.8Sr_0.2MnO₃Cathode of Solid Oxide Fuel Cells under Accelerated Conditions

A Fundamental Study of Boron Deposition and Poisoning of La_0.8Sr_0.2MnO₃Cathode of Solid Oxide Fuel Cells under Accelerated Conditions

An extended thermodynamic model for size-dependent thermoelectric properties at nanometric scales: Application to nanofilms, nanocomposites and thin nanocomposite films

Towards the 3D Modelling of the Effective Conductivity of Solid Oxide Fuel Cell Electrodes – Validation against experimental measurements and prediction of electrochemical performance

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Flexible multiphysics simulation of porous electrodes: Conformal to 3D reconstructed microstructures

Cited by 56 publications

References 57 publications

A Fundamental Study of Boron Deposition and Poisoning of La0.8Sr0.2MnO3Cathode of Solid Oxide Fuel Cells under Accelerated Conditions

A Fundamental Study of Boron Deposition and Poisoning of La0.8Sr0.2MnO3Cathode of Solid Oxide Fuel Cells under Accelerated Conditions

An extended thermodynamic model for size-dependent thermoelectric properties at nanometric scales: Application to nanofilms, nanocomposites and thin nanocomposite films

Towards the 3D Modelling of the Effective Conductivity of Solid Oxide Fuel Cell Electrodes – Validation against experimental measurements and prediction of electrochemical performance

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A Fundamental Study of Boron Deposition and Poisoning of La_0.8Sr_0.2MnO₃Cathode of Solid Oxide Fuel Cells under Accelerated Conditions

A Fundamental Study of Boron Deposition and Poisoning of La_0.8Sr_0.2MnO₃Cathode of Solid Oxide Fuel Cells under Accelerated Conditions