Topological origin of phase separation in hydrated gels

JOURNAL OF COLLOID AND INTERFACE SCIENCE

卷:590

Article

Zhao, Cheng^1,2  Zhou, Wei¹  Zhou, Qi²  Wang, Zhe²  Sant, Gaurav^3,4,5  Guo, Lijie⁶  Bauchy, Mathieu^2,5 

[1] Wuhan Univ, State Key Lab Water Resources & Hydropower Engn S, Wuhan 430072, Peoples R China

[2] Univ Calif Los Angeles, Dept Civil & Environm Engn, Phys AmoRphous & Inorgan Solids Lab PARISlab, Los Angeles, CA 90095 USA

[3] Univ Calif Los Angeles, Dept Civil & Environm Engn, Lab Chem Construct Mat LC2, Los Angeles, CA 90095 USA

[4] Univ Calif Los Angeles, Calif Nanosyst Inst CNSI, Los Angeles, CA 90095 USA

[5] Univ Calif Los Angeles, Inst Carbon Management ICM, Los Angeles, CA 90095 USA

[6] BGRIMM Technol Grp, Natl Ctr Int Res Green Met Min, Beijing 100160, Peoples R China

关键词: Hydrated colloidal gels;    Phase separation;    Molecular dynamics;    Topological constraint theory;    Atomic stress;   

DOI  :  10.1016/j.jcis.2021.01.068

来源: Elsevier

【 摘 要 】

Hypothesis: Depending on their composition, hydrated gels can be homogeneous or phase-separated, which, in turn, affects their dynamical and mechanical properties. However, the nature of the structural features, if any, that govern the propensity for a given gel to phase-separate remains largely unknown. Here, we argue that the propensity for hydrated gels to phase-separate is topological in nature. Simulations: We employ reactive molecular dynamics simulations to model the early-age precipitation of calcium-alumino-silicate-hydrate (C-A-S-H) gels with varying compositions, i.e., (CaO)(1.7)(Al2O3)(x)(SiO2)(1-x)(H2O)(3.7 + x), By adopting topological constraint theory, we investigate the struc- tural origin of phase separation in hydrated gels. Findings: We report the existence of a homogeneous-to-phase-separated transition, wherein Si-rich (x <= 0.10) C-A-S-H gels are homogeneous, whereas Al-rich (x > 0.10) C-A-S-H gels tend to phase-separate. Furthermore, we demonstrate that this transition is correlated to a topological flexible-to-rigid transition within the atomic network. We reveal that the propensity for topologically-overconstrained gels to phase-separate arises from the existence of some internal stress within their atomic network, which acts as an energy penalty that drives phase separation. (C) 2021 Elsevier Inc. All rights reserved.

【 授权许可】

Free