Three-Dimensional Graphene Hybrid SiO2 Hierarchical Dual-Network Aerogel with Low Thermal Conductivity and High Elasticity

Liwei Zhang,Qiangqiang Zhang,Baoqiang Zhang,Kunkun Song,Peng He,Jingxiang Zhang,Ruixian Huang

doi:10.3390/coatings10050455

Abstract

We describe lightweight three-dimensional (3D) graphene hybrid SiO2 aerogels (GSAs) with hierarchically robust interconnected networks fabricated via an in situ deposition procedure after a hydrothermal assembling strategy with graphene oxide sheets. The nano-/micron-thick SiO2 coating conformably grew over porous graphene templates with two constituents (e.g., graphene and SiO2) and formed chemically bonded interfaces. In addition, it significantly refined the primary graphene pores by hundreds of microns into smaller porous patterns. Studies of its mechanical properties verified that the graphene interframework made the ceramic composites elastic, while SiO2 deposition enhanced the strength required it to resist deformation. The higher SiO2 contents resulted in lower elasticity but larger strength because of the apparent nanosize effect of SiO2 ceramic thickness; GSAs with a density of 82.3–250.3 mg/cm3 (corresponding to SiO2 sol with concentration ranging from 5 to 20 wt %) could reach a good balance of strength and elasticity. Benefiting from hierarchical micronetworks consisting of semiclosed or closed pores, GSAs offer excellent thermal-insulation performance, with thermal conductivity as low as 0.026 W/(m·K). GSAs offer improved fire-resistant capacity rather than that of pure carbon-based aerogels via the synergic protection of SiO2 ceramic accretion. This highlights the promising applications of GSAs as lightweight thermal-shielding candidates for industrial equipment, civil architectures, and defense transportation vehicles.

Highlights

Thermal-insulation materials are increasingly needed, and have been derived from natural resources or synthetic products [1]
After processing the two constituents, graphene hybrid SiO2 aerogels (GSAs) microstructures maintained the honeycomb patterns of GA template, and had changes in pore shape and size; GSA pore changed interconnected microstructures with pore dimensions that ranged from hundreds of nanometers to tens of microns
After processing the two constituents, GSA microstructures maintained the Coatings 2020, 10, x FORof template, and had changes in pore shape and size; GSA pore changed to quadrangle from the primary circle shape of the graphene template, with the initial larger size to quadrangle from the primary circle shape of the graphene template, with the initial larger size divided into dual networks on a smaller scale

Summary

Introduction

Thermal-insulation materials are increasingly needed, and have been derived from natural resources or synthetic products [1]. Most conventional ceramic insulators have poor elasticity that compromise possible deformation under complex mechanical–thermal fields, while organic or carbon components usually have low flaming retardancy and thermal stability under high temperature in aerobic conditions [6,7,8]. These issues have led to major tragedies, including that of the space shuttle Columbia, due to local cracks—the final failure was due to the intrinsic brittleness of ceramic-based insulation materials [9].

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Discussion

Conclusion