Molecular scale insight of pore morphology relation with mechanical properties of amorphous silica using ReaxFF

Vo, Truong Quoc; He, Bang Gui; Blum, Michael; Damone, Angelo; Newell, Pania

doi:10.1016/j.commatsci.2020.109881

Cited by 22 publications

(9 citation statements)

References 72 publications

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“…The strain rates of interest were selected to be comparable with the diffusive crack filling rates and ranged between 3.4 × 10 6 and 3.4 × 10 7 s −1 . These strain rates are at least three orders of magnitude lower than those investigated in other MD studies that simulated the mechanical behavior of silica by applying strain (Chowdhury et al, 2016;Vo, Reeder, et al, 2020;Vo, He, et al, 2020).…”

Section: Methodsmentioning

confidence: 79%

Corrosive Influence of Carbon Dioxide on Crack Initiation in Quartz: Comparison With Liquid Water and Vacuum Environments

Simeski

Ihme

2023

JGR Solid Earth

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The stimulation of crack growth in quartz and siliceous materials by injecting carbon dioxide (CO2) represents a key technology in long‐term carbon storage and in the development of natural gas wells. While this technology is widely used, the molecular impact of CO2 interactions on the solid matrix is only incompletely understood. In this work, we employ reactive molecular dynamics simulations to study how the CO2 fluid environment affects the mechanical properties of pre‐cracked single‐crystal quartz. The thermodynamic conditions of interest are those relevant to subsurface reservoirs. We report how structural properties of quartz—bond length distribution and crack tip shape—evolve upon introduction of a fluid. These properties are directly related to macroscopic quantities of the global stress–strain curves, thus reaffirming the inherent coupling across multiple scales for fluid–solid interactions in the subsurface. We find that CO2 reduces the fracture toughness of quartz by 12.1% compared to that of quartz in vacuum, thereby promoting crack growth and enhancing fluid transport in the subsurface.

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Section: Methodsmentioning

confidence: 79%

Corrosive Influence of Carbon Dioxide on Crack Initiation in Quartz: Comparison With Liquid Water and Vacuum Environments

Simeski

Ihme

2023

JGR Solid Earth

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“…Motivated by findings from several recent attempts to homogenize the fracture toughness, in this work we decouple the plastic disspation from fracture degradation and propose a novel coalescence dissipation to model the coupling between plasticity and fracture. Rodriguez et al [32], Chowdhury et al [33], and Vo et al [34] found that ligament length, shape, and orientation of defects at the micro-scale influence the Mode-I fracture toughness. We postulate that the presence of plastic flow (or dislocations at the micro-scale) alters those properties related to defects, and at the continuum level, some configurational energy has been dissipated prior to crack initiation, effectively reducing the fracture toughness.…”

Section: Introductionmentioning

confidence: 99%

A variational phase-field model For ductile fracture with coalescence dissipation

Talamini

Stershic

et al. 2021

Comput Mech

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A novel phase-field for ductile fracture model is presented. The model is developed within a consistent variational framework in the context of finite-deformation kinematics. A novel coalescence dissipation introduces a new coupling mechanism between plasticity and fracture by degrading the fracture toughness as the equivalent plastic strain increases. The proposed model is compared with a recent alternative where plasticity and fracture are strongly coupled. Several representative numerical examples motivate specific modeling choices. In particular, a linear crack geometric function provides an "unperturbed" ductile response prior to crack initiation, and Lorentz-type degradation functions ensure that the critical fracture strength remains independent of the phase-field regularization length. In addition, the response of the model is demonstrated to converge with a vanishing phase-field regularization length. The model is then applied to calibrate and simulate a three-point bending experiment of an aluminum specimen with a complex geometry. The effect of the proposed coalescence dissipation coupling on simulations of the experiment is first investigated in a two-dimensional plane strain setting. The calibrated model is then applied to a three-dimensional calculation, where the calculated load-deflection curves and the crack trajectory show excellent agreement with experimental observations. Finally, the model is applied to simulate crack nucleation and growth in a specimen from a recent Sandia Fracture Challenge.

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“…Considering that the main chemical composition of nano-silica is amorphous silica, the orthorhombic amorphous SiO 2 cell with an edge dimension of a few nanometers is often selected to build a representative molecular model for nano-silica. The amorphous structure is obtained from the melt-annealing-equilibrium process from the crystalline structures, which is a common method for generating amorphous materials in experiments or simulations. − The initial crystalline silica model is obtained from the unit cell of the α-cristobalite structure, as shown in Figure . A simulation cell with a size of 19.9 Å × 19.9 Å × 20.8 Å is first built and then subjected to the melt-annealing-equilibrium procedure to acquire the amorphous silica model.…”

Section: Computational Methodsmentioning

confidence: 99%

Interactions between Amorphous Silica and Sodium Alumino-Silicate Hydrate Gels: Insight from Reactive Molecular Dynamics Simulation

Guan

et al. 2023

J. Phys. Chem. C

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Nano-modification has been an effective approach to improving the mechanical properties and durability of geopolymer materials. This study investigates the interaction between amorphous nano-silica and sodium alumino-silicate hydrate (NASH) gel at the atomic level. A realistic composite model is constructed to characterize the geopolymerization reaction on the amorphous nano-silica substrate. The atomic structure, dynamic properties, and mechanical performances of NASH gels with Si/Al ratios from 1.5 to 3.0 are compared to investigate the role of amorphous silica in geopolymers. The reaction between the two phases is observed in the interfacial transition zone (ITZ), with a thickness of around 10 Å. With the incorporation of amorphous silica, the reaction degree and complexity of the generated alumino-silicate skeleton structure in NASH gel have been improved by approximately 10 and 6%, respectively. Consequently, the NASH gel modified by silica exhibits a denser structure and a lower ion diffusion rate than the neat NASH gel, particularly at a low Si/Al ratio. Moreover, the simulation results indicate that the tensile strength of the ITZ is higher than that of NASH with or without amorphous silica, while the tensile strength of the silica-modified NASH gel is 10–40% higher than that of the neat NASH gel. The NASH gel modified by silica can achieve the optimum uniaxial tensile strength of around 4.1 GPa at Si/Al ratios of 2.5 and 3.0. Thus, this study has proved the reactivity of nano-silica in geopolymers and profiled its positive effects on NASH gel at the atomic level.

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Molecular scale insight of pore morphology relation with mechanical properties of amorphous silica using ReaxFF

Cited by 22 publications

References 72 publications

Corrosive Influence of Carbon Dioxide on Crack Initiation in Quartz: Comparison With Liquid Water and Vacuum Environments

Corrosive Influence of Carbon Dioxide on Crack Initiation in Quartz: Comparison With Liquid Water and Vacuum Environments

A variational phase-field model For ductile fracture with coalescence dissipation

Interactions between Amorphous Silica and Sodium Alumino-Silicate Hydrate Gels: Insight from Reactive Molecular Dynamics Simulation

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