Abstract
In this paper, the Diffusion Limited Cluster Aggregation (DLCA) method is employed to reconstruct the three-dimensional network of silica aerogel. Then, simulation of nitrogen adsorption at 77 K in silica aerogel is conducted by the Grand Canonical Monte Carlo (GCMC) method. To reduce the computational cost and guarantee accuracy, a continuous-discrete hybrid potential model, as well as an adsorbed layer thickness estimation method, is employed. Four different structures are generated to investigate impacts of specific surface area and porosity on adsorptive capacity. Good agreement with experimental results is found over a wide range of relative pressures, which proves the validity of the model. Specific surface area and porosity mainly affect nitrogen uptake under low pressure and high pressure, respectively.
Highlights
Silica aerogels are materials with high porosity, high specific surface area (SSA) and low density.They are promising in many applications, such as in heat insulators [1], drug delivery [2], effluent disposal [3,4] and fuel storage
There is a little gap between the adsorption isotherms of the two nitrogen models
Electrostatic potential is not taken into consideration due to limited computational resources, which is responsible for the overall lower adsorption amount
Summary
Silica aerogels are materials with high porosity, high specific surface area (SSA) and low density. They are promising in many applications, such as in heat insulators [1], drug delivery [2], effluent disposal [3,4] and fuel storage. These applications are based on their extraordinary properties of low thermal conductivity and good absorbability, which is caused by high porosity and nano-scale pores. Three factors contribute to the thermal conductivity of silica aerogels: solid conductivity, gas transport and radiation. Just as in simulations that explored the design principles of metal-organic framework (MOF) [8,9] for certain purposes, molecular simulation may guide us in surface modification of silica aerogels to achieve better performance in the fields mentioned above
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