Simulation of the tensile properties of silica aerogels: the effects of cluster structure and primary particle size

Abstract

A new two-level model is proposed to investigate the relationship between the mechanical properties and microstructure of silica aerogels. This two-level model consists of the particle-particle interaction model and the cluster structure model. The particle-particle interaction model is proposed to describe interactions between primary particles, in which the polymerization reaction between primary particles is considered. The cluster structure model represents the geometrical structure of silica aerogels, and it is established using a modified diffusion-limited colloid aggregation (DLCA) algorithm. This two-level model is used to investigate the tensile behavior of silica aerogels based on the discrete element method (DEM). The numerical results show that the primary particle size has significant effects on the elastic modulus and tensile strength of silica aerogels. Moreover, the power-law relationships between tensile properties and aerogel density are dependent on the variation of the primary particle radius with density. The present results can explain the difference among different experimental exponents to a certain extent. In comparison with experimental data within a wide density range, this two-level model provides good quantitative estimations of the elastic modulus and tensile strength of silica aerogels after the size effects of the primary particle are considered. This paper provides a fundamental understanding of the relationship between the mechanical properties and microstructure of silica aerogels. The two-level model can be extended to study the mechanical properties of other aerogels and aerogel composites.

Simulation and Analysis of Mechanical Properties of Silica Aerogels: From Rationalization to Prediction

“…It is known that the tensile properties of porous silica aerogels are largely dependent on the particular orientations among ligaments and the length scale of ligaments, which determine the interconnectivity orders, and thus affect the overall modulus and strength of silica aerogels. For example, Liu et al [ 37 ] once reported that the neck radius in the silica network as well as the strength and stiffness of the particle chains inversely decreases with the increase of the ligament size. Therefore, one possible reason for different fitting curves in our study compared with literature results [ 31 , 32 ] could be due to that the ligament diameter in our case is fixed.…”

Synthesis and biomedical applications of aerogels: Possibilities and challenges

“…Several physicochemical characterization methods, mainly 29 SiNMR, Small Angel X-Ray or Neutron Scattering (SAXS or SANS) and light scattering techniques provide information about the denseness and structural evolution at the nanoscale in the gel network [85]. Due to this fact, several numerical models and computer simulation techniques based on particle aggregation algorithms are proposed to explain the aerogel nanostructuration upon the variance of preparation parameters [86,87]. Martin [88] and Schaefer [89] proposed a number of equilibrium A C C E P T E D M A N U S C R I P T The 29 Si NMR and Raman spectroscopy [93] studies can largely confirm the Iler assumption by monitoring the network evolution in the solution and identifying A C C E P T E D M A N U S C R I P T…”

Interfacial properties of carboxylic acid functionalized CNT/polyethylene composites: A molecular dynamics simulation study

“…However, this load could keep the SWNT sliding A c c e p t e d M a n u s c r i p t 22 once the motion of the SWNT is activated by, say, an impact. The existence of the translation state between the strong and weak interface may bring a more notable influence on the dynamical properties of the composite rather than the quasi-static nanotube pulling-out behavior.…”

“…By molecular mechanics simulation, they also found that a capped CNT presents a higher pull-out force than that of the corresponding open-ended CNT [21]. As the MD simulation is mostly limited to systems with several nanometers and tens of particles [22,23], a large proportion of atoms, whether CNT atoms or polymer ones, have to be located in the region where the "end effect" is intense. Thus the results of the pull-out simulation are sensitive to the CNT "end effect" because in the pull-out process the periodic boundary condition is difficult to be applied in the axial direction of the CNT.…”