Bio-Inspired Aramid Fibers@silica Binary Synergistic Aerogels with High Thermal Insulation and Fire-Retardant Performance

Abstract

Flame-retardant, thermal insulation, mechanically robust, and comprehensive protection against extreme environmental threats aerogels are highly desirable for protective equipment. Herein, inspired by the core (organic)-shell (inorganic) structure of lobster antenna, fire-retardant and mechanically robust aramid fibers@silica nanocomposite aerogels with core-shell structures are fabricated via the sol-gel-film transformation and chemical vapor deposition process. The thickness of silica coating can be well-defined and controlled by the CVD time. Aramid fibers@silica nanocomposite aerogels show high heat resistance (530 °C), low thermal conductivity of 0.030 W·m−1·K−1, high tensile strength of 7.5 MPa and good flexibility. More importantly, aramid fibers@silica aerogels have high flame retardancy with limiting oxygen index 36.5. In addition, this material fabricated by the simple preparation process is believed to have potential application value in the field of aerospace or high-temperature thermal protection.

Improvement of the Mechanical Properties of Silica Aerogels for Thermal Insulation Applications through a Combination of Aramid Nanofibres and Microfibres

“…It was not possible to estimate the size of the NTeij from the SEM images. The size of the NKP obtained here is similar to those reported in [24,28] also from Kevlar.…”

“…The aerogels in this work achieved attracting thermal conductivities when they were prepared by less complex methods. The lowest value obtained here is not as low (23.7-26.3 mW m −1 K −1 ) as that in [24] with an ANF aerogel prepared by directional freezing but is comparable with that of the ANF aerogel prepared by wet-spinning combined with freeze-drying (34 mW m −1 K −1 ) [23], as well as with that of the ANF aerogels coated with Si dried by supercritical CO 2 (30-40 mW m −1 K −1 ) [28]. Similar values, 33.9 mW m −1 K −1 [35],…”

“…This was expected since bulk density is related to the linear shrinkage; therefore, similar behaviours were observed. The values of the aerogel composites were comprised between 161-317 kg m −3 , comparable with those of the ANF aerogels coated with Si dried by supercritical CO 2 (96-298 kg m −3 ) [28]. The lowest value of bulk density (161 kg m −3 ) was obtained with the NKP and Technora ® combination, which presents the lowest shrinkage (16.4%).…”

“…In this sense, to improve the mechanical strength of aerogels, we report here, for the first time, the use of ANF to reinforce silica aerogels. As far as we know, there are no studies reporting on ANF-reinforced silica aerogels, except one work in which aerogels prepared from ANF were coated with a silica shell by chemical vapour deposition and the composites were dried by CO 2 supercritical drying [28]. Herein, we used a mixture of aramid fibres (AF) and ANF to boost the strength of the silica aerogels which were dried by ambient pressure, a safer and less expensive process than supercritical drying.…”

Polyimide aerogel/aramid fiber composite with high mechanical strength and thermal insulation for thermal protective clothing

“…Due to the stability of their molecular structure, polyimide materials have excellent mechanical properties and thermal stability (Fan et al, 2018;Jang et al, 2021). PI is a new kind of thermal insulation material, and polyimide aerogel also has the excellent thermal properties of polyimide and the characteristic of high thermal insulation of aerogel (Feng and Yu, 2021;Zhao et al, 2021;Quan et al, 2022;Zhou et al, 2023). At the same time, PI aerogel has the two characteristics of flame retardancy and heat insulation, which can not only effectively improve the brittleness of inorganic aerogel materials and poor mechanical properties but also expand the application of organic aerogel in heat insulation and flame retardant materials (Almeida et al, 2021;Wang et al, 2022).…”