Anisotropic 3D Nanofibrous Porous Material Fabrication by a Liquid Film-Assisted Gas Templating Strategy for Thermal Insulation

In
the last decade, three-dimensional nanofibrous porous materials
(3D NPMs) have been attracting widespread interest ranging from thermal
insulation to biological engineering. However, their practical application
is always limited by the complex and high-cost fabrication process.
Here, inspired by the mechanism of fermentation to produce cooked
wheaten food, a general scalable strategy, namely, liquid film-assisted
gas templating, is designed to fabricate anisotropic 3D NPMs from
two-dimensional nanofibrous membranes (2D NFMs) without the tedious
and time-consuming fabrication process. The successive production
of gas promotes the bending of nanofiber layers and the increase of
the gap between the adjacent layers, thereby forming numerous new
interconnections, leading to cellular pore structures. Attributing
to the maintenance of the continuous nature of the fibers and their
layers, as well as the formation of new joints, the as-prepared 3D
NPM exhibits anisotropic and superior mechanical properties. The high
porosity and low density of the 3D NPM endow it with an outstanding
thermal insulation performance, and the thermal conductivity can reach
up to 0.045 W m–1 K–1. Additionally,
the 3D NPM also shows potential applications in terms of oil adsorption,
waterproofing, and gas permeability. Finally, the criteria for this
process are given based on theoretical simulation and analysis, and
the universality of this strategy has been confirmed through fabricating
various 3D NPMs of inorganic, organic, and composite materials.