272787 Simulating the Mechanical Properties of Silica Aerogels by Means of a Coarse-Grained Flexible Model

Tuesday, October 30, 2012
Hall B (Convention Center )
Carlos Ferreiro, Materials Science and Engineering, University of Texas at Dallas, Richardson, TX and Lev Gelb, University of Texas at Dallas, Richardson, TX

Aerogels are materials with very low densities and high surface areas prepared through sol-gel processing. The unique properties of aerogels make them very attractive for many applications,[1] but their highly compliant nature hinders their applicability. The bulk moduli of aerogels are related to their density by a power-law relation [2] with exponent between 3 and 4 [3].  Some previous attempts at modeling the mechanical properties of these systems have been made, using finite-element method (FEM) modeling of structures generated using a diffusion-limited cluster-cluster aggregation (DCLA) algorithm [4,5].  More recently, Gelb [6] introduced a coarse-grained flexible model where Langevin dynamics are used to mimic the gelation process of the aerogel primary particles.  This model also naturally includes the effects of relaxation and fluctuation on the gel structure.  Using this model, we study the mechanical properties of aerogels as a function of both the primary particle size and the material density. These simulations provide a better understanding of the nature of the dependence of moduli on structural properties, as well as of the roles of gel network relaxation and plastic deformation.

(1)    J. L. Gurav, et al., J. Nanomat. 2010 (2010).
(2)    G. W. Scherer, Adv. Coll. Int. Sci.  76-77 (1998) 321.
(3)    G. W. Scherer, et al., J. Non-Cryst. Solids 186 (1995) 316.
(4)    H.-S. Ma, et al., J. Non-Cryst. Solids 277 (2000) 127.
(5)    H.-S. Ma, et al., J. Non-Cryst. Solids 285 (2001) 216.
(6)    L. D. Gelb, J. Phys. Chem. C 111 (2007) 15792.

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