scholarly journals Kinetic Monte Carlo Simulations of Oxygen Diffusion in Environmental Barrier Coating Materials

MRS Advances ◽  
2018 ◽  
Vol 3 (10) ◽  
pp. 511-518 ◽  
Author(s):  
Brian S. Good
Keyword(s):  
Monte Carlo ◽  
Water Vapor ◽  
Bond Coat ◽  
Oxygen Diffusion ◽  
Kinetic Monte Carlo ◽  
Ceramic Matrix Composite ◽  
Low Oxygen ◽  
Coating Materials ◽  
Environmental Barrier ◽  
Oxygen Diffusivity

ABSTRACTCeramic Matrix Composite (CMC) materials are of interest for use in next-generation turbine engine components, offering a number of significant advantages, including reduced weight and high operating temperatures. However, in the hot environment in which such components operate, the presence of water vapor can lead to corrosion and recession, limiting the useful life of the components. Such degradation can be reduced through the use of Environmental Barrier Coatings (EBCs) that limit the amount of oxygen and water vapor reaching the component. Candidate EBC materials include Yttrium and Ytterbium silicates. In this work we present results of kinetic Monte Carlo (kMC) simulations of oxygen diffusion, via the vacancy mechanism, in Yttrium and Ytterbium disilicates, along with a brief discussion of interstitial diffusion.An EBC system typically includes a bond coat located between the EBC and the component surface. Bond coat materials are generally chosen for properties other than low oxygen diffusivity, but low oxygen diffusivity is nevertheless a desirable characteristic, as the bond coat could provide some additional component protection, particularly in the case where cracks in the coating system provide a direct path from the environment to the bond coat interface. We have therefore performed similar kMC simulations of oxygen diffusion in this material.

scholarly journals Kinetic Monte Carlo Simulation of Oxygen Diffusion in Ytterbium Disilicate

MRS Advances ◽  
2016 ◽  
Vol 1 (17) ◽  
pp. 1203-1208 ◽  
Author(s):  
Brian S. Good
Keyword(s):  
Monte Carlo ◽  
High Temperature ◽  
Oxygen Diffusion ◽  
Density Functional ◽  
Defect Formation ◽  
Kinetic Monte Carlo ◽  
Interstitial Oxygen ◽  
Temperature Oxidation ◽  
Electron Volt ◽  
Formation Energies

ABSTRACTYtterbium disilicate is of interest as a potential environmental barrier coating for aerospace applications, notably for use in next generation jet turbine engines. In such applications, the transport of oxygen and water vapor through these coatings to the ceramic substrate is undesirable if high temperature oxidation is to be avoided. In an effort to understand the diffusion process in these materials, we have performed kinetic Monte Carlo simulations of vacancy-mediated and interstitial oxygen diffusion in Ytterbium disilicate. Oxygen vacancy and interstitial site energies, vacancy and interstitial formation energies, and migration barrier energies were computed using Density Functional Theory. We have found that, in the case of vacancy-mediated diffusion, many potential diffusion paths involve large barrier energies, but some paths have barrier energies smaller than one electron volt. However, computed vacancy formation energies suggest that the intrinsic vacancy concentration is small. In the case of interstitial diffusion, migration barrier energies are typically around one electron volt, but the interstitial defect formation energies are positive, with the result that the disilicate is unlikely to exhibit experience significant oxygen permeability except at very high temperature.

scholarly journals Water Vapor Corrosion Behavior of Yb2SiO5 Environmental Barrier Coatings Prepared by Plasma Spray-Physical Vapor Deposition

Coatings ◽  
2020 ◽  
Vol 10 (4) ◽  
pp. 392 ◽  
Author(s):  
Chao Wang ◽  
Min Liu ◽  
Junli Feng ◽  
Xiaofeng Zhang ◽  
Chunming Deng ◽  
...  
Keyword(s):  
Water Vapor ◽  
Porous Structure ◽  
Plasma Spray ◽  
Vapor Deposition ◽  
Physical Vapor Deposition ◽  
Ceramic Matrix Composite ◽  
Environmental Barrier Coatings ◽  
Environmental Barrier ◽  
Barrier Coating ◽  
Water Vapor Corrosion

Tri-layer Si/mullite/Yb2SiO5 environmental barrier coating (EBC) was prepared on the SiCf/SiC ceramic matrix composite (CMC) by plasma spray-physical vapor deposition (PS-PVD). The EBC samples were carried out with water vapor corrosion at 1300 °C for 200 h. After steam corrosion, Yb2SiO5 layer forms a gradient porous structure. This is mainly due to the inclusion of SiO2-rich layer which is precipitated from the gasification inside the coating and existing a small amount of Yb2O3 separately. During the corrosion process, water vapor infiltrates into the coating and reacts with the SiO2 and Yb2O3 to generate volatile substances. This forms a porous structure to make the coating brittle, resulting in mud cracks finally. In addition, the results show that the Yb2SiO5 can react with the water vapor at the coating surface, forming an Yb2Si2O7 top layer.

Oxygen diffusion through environmental barrier coating materials

2020 ◽  
Vol 46 (11) ◽  
pp. 19545-19549 ◽  
Author(s):  
Guangxu Zhao ◽  
Baosheng Xu ◽  
Ke Ren ◽  
Gang Shao ◽  
Yiguang Wang
Keyword(s):  
Oxygen Diffusion ◽  
Coating Materials ◽  
Environmental Barrier ◽  
Environmental Barrier Coating ◽  
Barrier Coating

scholarly journals Kinetic Monte Carlo Investigation of the Effects of Vacancy Pairing on Oxygen Diffusivity in Yttria-Stabilized Zirconia

2011 ◽  
Vol 1331 ◽  
Author(s):  
Brian S. Good
Keyword(s):  
Monte Carlo ◽  
Solid Electrolytes ◽  
Oxygen Vacancies ◽  
Nearest Neighbor ◽  
Kinetic Monte Carlo ◽  
High Energy ◽  
Oxygen Diffusivity ◽  
Low Concentrations ◽  
Migration Barriers ◽  
Monte Carlo Investigation

ABSTRACTYttria-stabilized zirconia’s high oxygen diffusivity and corresponding high ionic conductivity, and its structural stability over a broad range of temperatures, have made the material of interest for use in a number of applications, for example, as solid electrolytes in fuel cells. At low concentrations, the stabilizing yttria also serves to increase the oxygen diffusivity through the presence of corresponding oxygen vacancies, needed to maintain charge neutrality. At higher yttria concentration, however, diffusivity is impeded by the larger number of relatively high energy migration barriers associated with yttrium cations. In addition, there is evidence that oxygen vacancies preferentially occupy nearest-neighbor sites around either dopant or Zr cations, further affecting vacancy diffusion. We present the results of ab initio calculations that indicate that it is energetically favorable for oxygen vacancies to occupy nearest-neighbor sites adjacent to Y ions, and that the presence of vacancies near either species of cation lowers the migration barriers. Kinetic Monte Carlo results from simulations incorporating this effect are presented and compared with results from simulations in which the effect is not present.

Combined DFT and kinetic Monte Carlo study of a bridging-spillover mechanism on fluorine-decorating graphene

2020 ◽  
Author(s):  
Jing-hua Guo ◽  
Jin-Xiang Liu ◽  
Hongbo Wang ◽  
Haiying Liu ◽  
Gang Chen
Keyword(s):  
Monte Carlo ◽  
First Principles ◽  
Kinetic Monte Carlo ◽  
Monte Carlo Study ◽  
First Principles Calculations ◽  
Graphene Surface

In this work, combining the first-principles calculations with kinetic Monte Carlo (KMC) simulations, we constructed an irregular carbon bridge on the graphene surface and explored the process of H migration...

scholarly journals A semi-grand canonical kinetic Monte Carlo study of single-walled carbon nanotube growth

AIP Advances ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 045306
Author(s):  
Georg Daniel Förster ◽  
Thomas D. Swinburne ◽  
Hua Jiang ◽  
Esko Kauppinen ◽  
Christophe Bichara
Keyword(s):  
Monte Carlo ◽  
Carbon Nanotube ◽  
Kinetic Monte Carlo ◽  
Monte Carlo Study ◽  
Single Walled Carbon Nanotube ◽  
Single Walled Carbon ◽  
Carbon Nanotube Growth ◽  
Nanotube Growth ◽  
Grand Canonical

scholarly journals A Novel Kinetic Modeling Framework for the Polycondensation of Sugars Using Monte Carlo and the Method of Moments

Processes ◽  
2021 ◽  
Vol 9 (5) ◽  
pp. 745
Author(s):  
Dimitrios Meimaroglou ◽  
Sandrine Hoppe ◽  
Baptiste Boit
Keyword(s):  
Monte Carlo ◽  
Kinetic Modeling ◽  
Method Of Moments ◽  
Kinetic Monte Carlo ◽  
Kinetic Scheme ◽  
Modeling Framework ◽  
Industrial Sectors ◽  
The Monte Carlo Method ◽  
Reacting Systems ◽  
High Degree

The kinetics of the hydrolysis and polycondensation reactions of saccharides have made the subject of numerous studies, due to their importance in several industrial sectors. The present work, presents a novel kinetic modeling framework that is specifically well-suited to reacting systems under strict moisture control that favor the polycondensation reactions towards the formation of high-degree polysaccharides. The proposed model is based on an extended and generalized kinetic scheme, including also the presence of polyols, and is formulated using two different numerical approaches, namely a deterministic one in terms of the method of moments and a stochastic kinetic Monte Carlo approach. Accordingly, the most significant advantages and drawbacks of each technique are clearly demonstrated and the most fitted one (i.e., the Monte Carlo method) is implemented for the modeling of the system under different conditions, for which experimental data were available. Through these comparisons it is shown that the model can successfully follow the evolution of the reactions up to the formation of polysaccharides of very high degrees of polymerization.

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