# High-Temperature Induced Sintering Strengthening of Mechanical Properties of Porous Silica: A Molecular Dynamics Study

## TL;DR

This study uses simulations to explore how high temperatures affect the mechanical properties of silica aerogels, revealing a balance between weakening and strengthening effects.

## Contribution

The study identifies the competition between thermal softening and sintering-induced strengthening in silica aerogels under high temperatures.

## Key findings

- Thermal softening reduces fracture strength by up to 49.6% at 1800 K under tensile loading.
- Sintering increases elastic modulus by ~20% in high-density samples under compressive loading at 1300 K.
- Ductility increases significantly with fracture strain extending to 80% at high temperatures.

## Abstract

Silica aerogels are critical for thermal protection in extreme environments; however, their mechanical response mechanisms under high temperatures remain elusive. This study employs large-scale molecular dynamics simulations to systematically investigate the mechanical behavior of silica aerogels (0.43–0.71 g/cm3) across a temperature range of 298–1800 K. The results reveal a fundamental competition between thermal softening and sintering-induced strengthening. Under tensile loading, the thermal softening effect dominates, leading to a significant fracture strength reduction of up to 49.6% at 1800 K, while simultaneously enhancing ductility, extending fracture strain to 80%. Conversely, under compressive loading, the sintering effect induced by temperatures above 900 K outweighs softening, resulting in a ~20% increase in the elastic modulus for high-density samples at 1300 K. Microstructural analysis attributes this enhancement to the preferential collapse of large pores and densification into an atomic-scale micropore range (0.5–1.0 nm). This work elucidates how the interplay between softening and sintering dictates material failure or strengthening, providing a microscopic theoretical basis for designing thermal shock-resistant materials for new energy batteries.