Three-Dimensional-Printed Silica Aerogels for Thermal Insulation by Directly Writing Temperature-Induced Solidifiable Inks

Abstract

Silica aerogels are attractive materials for various applications due to their exceptional performances and open porous structure. Especially in thermal management, silica aerogels with low thermal conductivity need to be processed into customized structures and shapes for accurate installation on protected parts, which plays an important role in high-efficiency insulation. However, traditional subtractive manufacturing of silica aerogels with complex geometric architectures and high-precision shapes has remained challenging since the intrinsic ceramic brittleness of silica aerogels. Comparatively, additive manufacturing (3D printing) provides an alternative route to obtain custom-designed silica aerogels. Herein, we demonstrate a thermal-solidifying 3D printing strategy to fabricate silica aerogels with complex architectures via directly writing a temperature-induced solidifiable silica ink in an ambient environment. The solidification of silica inks is facilely realized, coupling with the continuous ammonia catalysis by the thermolysis of urea. Based on our proposed thermal-solidifying 3D printing strategy, printed objects show excellent shape retention and have a capacity to subsequently undergo the processes of in situ hydrophobic modification, solvent replacement, and supercritical drying. 3D-printed silica aerogels with hydrophobic modification show a super-high water contact angle of 157°. Benefiting from the low density (0.25 g·cm–3) and mesoporous silica network, optimized 3D-printed specimens with a high specific surface area of 272 m2·g–1 possess a low thermal conductivity of 32.43 mW·m–1·K–1. These outstanding performances of 3D-printed silica aerogels are comparable to those of traditional aerogels. More importantly, the thermal-solidifying 3D printing strategy brings hope to the custom design and industrial production of silica aerogel insulation materials.

Proton Donor-Regulated Mechanically Robust Aramid Nanofiber Aerogel Membranes for High-Temperature Thermal Insulation

“…Decreasing heat transfer through advanced thermal insulators is an effective way to improve energy efficiency and reduce the world’s total energy consumption. − Thermal insulation is also urgently needed for many personal thermal protection systems in harsh environments. So far, a variety of advanced thermal insulators have been developed, including mineral wool, fiberglass, polymer-based foams, and aerogels. ,− Among them, aerogel-based nanoporous materials are considered to be one of the ideal candidates due to their high porosity, large surface area, low apparent density, and low thermal conductivity. − Although the development of inorganic aerogels ( e . g ., silica-based aerogels) is predominant in aerogel products, the application of traditional inorganic aerogels for thermal insulation is severely limited due to the drawbacks of their inherent brittleness and highly collapsible structure …”

Additive Manufacturing of Resilient SiC Nanowire Aerogels

“…Additive manufacturing, also referred to as three-dimensional (3D) printing, shines light on the fabrication of aerogels with fairly complex macroscopic and microscopic structures. − 3D printing can build materials with designed structures with high precision and high speed, which thus provides convenience in customizing the macroscopic geometries and microstructure of aerogels. − Direct ink writing (DIW) is an extrusion-based 3D printing method that can be used to fabricate both closed and open porous structures with pore size precision ranging from millimeter to micrometer scales. − Through modification of the inks with different materials, polyurethane, graphene, − and silica aerogels , with modified mechanical properties and functions have been printed. For example, through the organization of hierarchical load-bearing networks constructed by emulsified/foamed ceramic inks, the mechanical efficiency of the porous structures can also be enhanced even at high porosities of 94% .…”

Research progress and applications of silica-based aerogels – a bibliometric analysis

“…Other solidification methods are proposed because solidification implemented by ammonia vapor is difficult to achieve scale production. For example, Wang et al 58 proposed thermal-solidifying SAs by DIW ( Fig. 4d ).…”

“…It avoids weak processability and enlarges the application elds of prepared products. 3D printing, especially direct ink writing (DIW), [25][26][27]58,131 are used to produce SAs through three steps: ink synthesis, 3D printing, and drying. DIW needs inks that are non-Newtonian uids, whose viscosity decreases with the shear rate increases.…”