Yingtian Yu
University of California, Los Angeles
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Featured researches published by Yingtian Yu.
Frontiers in Materials | 2015
Bu Wang; Yingtian Yu; Young Jea Lee; Mathieu Bauchy
Understanding, predicting and eventually improving the resistance to fracture for silicate materials is of primary importance to design tougher new glasses suitable for advanced applications. However, the fracture mechanism at the atomic level in amorphous silicate materials is still a topic of debate. In particular, there are some controversies about the existence of ductility at the nanoscale during crack propagation. Here, we present simulations of fracture of three archetypical silicate glasses, using molecular dynamics. The simulations clearly show that, depending on their composition, silicate glasses can exhibit different degrees of ductility at the nanoscale. Additionally, we show that the methodology used in the present work can provide realistic predictions of fracture energy and toughness.
Physical Review B | 2016
Bu Wang; Yingtian Yu; Mengyi Wang; John C. Mauro; Mathieu Bauchy
Author(s): Wang, Bu; Yu, Yingtian; Wang, Mengyi; Mauro, John C; Bauchy, Mathieu | Abstract: The existence of nanoscale ductility during the fracture of silicate glasses remains controversial. Here, based on molecular dynamics simulations coupled with topological constraint theory, we show that nano-ductility arises from the spatial heterogeneity of the atomic networks rigidity. Specifically, we report that localized floppy modes of deformation in under-constrained regions of the glass enable plastic deformations of the network, resulting in permanent change in bond configurations. Ultimately, these heterogeneous plastic events percolate, thereby resulting in a non-brittle mode of fracture. This suggests that nano-ductility is intrinsic to multi-component silicate glasses having nanoscale heterogeneities.
Physical Review Letters | 2015
Yingtian Yu; Mengyi Wang; Dawei Zhang; Bu Wang; Gaurav Sant; Mathieu Bauchy
The question of whether glass continues to relax at low temperature is of fundamental and practical interest. Here, we report a novel atomistic simulation method allowing us to directly access the long-term dynamics of glass relaxation at room temperature. We find that the potential energy relaxation follows a stretched exponential decay, with a stretching exponent β=3/5, as predicted by Phillipss diffusion-trap model. Interestingly, volume relaxation is also found. However, it is not correlated to the energy relaxation, but it is rather a manifestation of the mixed alkali effect.
Scientific Reports | 2016
Isabella Pignatelli; Aditya Kumar; Kevin G. Field; Bu Wang; Yingtian Yu; Yann Le Pape; Mathieu Bauchy; Gaurav Sant
Concrete, used in the construction of nuclear power plants (NPPs), may be exposed to radiation emanating from the reactor core. Until recently, concrete has been assumed immune to radiation exposure. Direct evidence acquired on Ar+-ion irradiated calcite and quartz indicates, on the contrary, that, such minerals, which constitute aggregates in concrete, may be significantly altered by irradiation. More specifically, while quartz undergoes disordering of its atomic structure resulting in a near complete lack of periodicity, calcite only experiences random rotations, and distortions of its carbonate groups. As a result, irradiated quartz shows a reduction in density of around 15%, and an increase in chemical reactivity, described by its dissolution rate, similar to a glassy silica. Calcite however, shows little change in dissolution rate - although its density noted to reduce by ≈9%. These differences are correlated with the nature of bonds in these minerals, i.e., being dominantly ionic or covalent, and the rigidity of the mineral’s atomic network that is characterized by the number of topological constraints (nc) that are imposed on the atoms in the network. The outcomes have major implications on the durability of concrete structural elements formed with calcite or quartz bearing aggregates in nuclear power plants.
Physical Review Letters | 2016
Mathieu Bauchy; Mengyi Wang; Yingtian Yu; Bu Wang; N. M. Anoop Krishnan; Franz-Joseph Ulm; Roland J.-M. Pellenq
Upon loading, atomic networks can feature delayed irreversible relaxation. However, the effect of composition and structure on relaxation remains poorly understood. Herein, relying on accelerated molecular dynamics simulations and topological constraint theory, we investigate the relationship between atomic topology and stress-induced structural relaxation, by taking the example of creep deformations in calcium silicate hydrates (C─S─H), the binding phase of concrete. Under constant shear stress, C─S─H is found to feature delayed logarithmic shear deformations. We demonstrate that the propensity for relaxation is minimum for isostatic atomic networks, which are characterized by the simultaneous absence of floppy internal modes of relaxation and eigenstress. This suggests that topological nanoengineering could lead to the discovery of nonaging materials.Upon loading, atomic networks can feature delayed viscoplastic relaxation. However, the effect of composition and structure on such a relaxation remains poorly understood. Herein, relying on accelerated molecular dynamics simulations and topological constraint theory, we investigate the relationship between atomic topology and stress-induced relaxation, by taking the example of creep deformations in calcium--silicate--hydrates, the binding phase of concrete. Under constant shear stress, C--S--H is found to feature delayed logarithmic shear deformations. We demonstrate that the propensity for relaxation is minimum for isostatic atomic networks, which are characterized by the simultaneous absence of floppy internal modes of relaxation and eigen stress. This suggests that topological nano-engineering could lead to the discovery of non-aging materials.
Journal of Chemical Physics | 2018
Yingtian Yu; N. M. Anoop Krishnan; Morten Mattrup Smedskjær; Gaurav Sant; Mathieu Bauchy
The surface reactivity and hydrophilicity of silicate materials are key properties for various industrial applications. However, the structural origin of their affinity for water remains unclear. Here, based on reactive molecular dynamics simulations of a series of artificial glassy silica surfaces annealed at various temperatures and subsequently exposed to water, we show that silica exhibits a hydrophilic-to-hydrophobic transition driven by its silanol surface density. By applying topological constraint theory, we show that the surface reactivity and hydrophilic/hydrophobic character of silica are controlled by the atomic topology of its surface. This suggests that novel silicate materials with tailored reactivity and hydrophilicity could be developed through the topological nanoengineering of their surface.
MRS Proceedings | 2015
Yingtian Yu; Bu Wang; Young Jea Lee; Mathieu Bauchy
© 2015 Materials Research Society. Understanding, predicting and eventually improving the resistance to fracture of silicate materials is of primary importance to design new glasses that would be tougher, while retaining their transparency. However, the atomic mechanism of the fracture in amorphous silicate materials is still a topic of debate. In particular, there is some controversy about the existence of ductility at the nano-scale during the crack propagation. Here, we present simulations of the fracture of three archetypical silicate glasses using molecular dynamics. We show that the methodology that is used provide realistic values of fracture energy and toughness. In addition, the simulations clearly suggest that silicate glasses can show different degrees of ductility, depending on their composition.
Journal of Non-crystalline Solids | 2016
Yingtian Yu; Bu Wang; Mengyi Wang; Gaurav Sant; Mathieu Bauchy
Acta Materialia | 2016
Mathieu Bauchy; Bu Wang; Mengyi Wang; Yingtian Yu; Mohammad Javad Abdolhosseini Qomi; Morten Mattrup Smedskjær; Christophe Bichara; Franz-Josef Ulm; Roland J.-M. Pellenq
Journal of Chemical Physics | 2015
Bu Wang; Yingtian Yu; Isabella Pignatelli; Gaurav Sant; Mathieu Bauchy