Strong, Tough, Shell-Cross-Linked Aramid Nanofibrous Aerogel Fibers for Thermally-Protective Textiles

Aerogel textiles show remarkable promise for thermal protection under extreme conditions. However, challenges in the mass production of aerogel fibers and their low strength still impede practical applications. Here, we report shell-cross-linked aramid nanofibrous aerogel fibers (ScANFAFs) fabricated via a stepwise sol–gel coupled wet-spinning strategy. This strategy enables rapid gelation of the shell flow of the aramid nanofiber (ANF) sol through the fast reprotonation and cross-linking reactions of the H-lacking ANFs to form a strong and tough shell layer, while the core sol undergoes slow gelation to obtain a porous nanofibrous core layer. Given this composite structure, ScANFAFs achieve a strength of 83.2 MPa, a toughness of 15.05 MJ·m–3, high porosity (>96%), and high specific surface area (286.8 m2·g–1). The mechanical robustness of ScANFAFs meets the requirements for weaving by using an automated loom. The resulting aerogel textiles exhibit low thermal conductivity (0.032 W·m–1·K–1), excellent thermal protection over a wide temperature range, and outstanding thermal stealth capabilities in extreme cold and ambient conditions. This work points to a promising direction for the multifunctional thermal protection of aerogel fibers and textiles

Strong, Tough, Shell-Cross-Linked Aramid Nanofibrous Aerogel Fibers for Thermally-Protective Textiles

Aerogel textiles show remarkable promise for thermal protection under extreme conditions. However, challenges in the mass production of aerogel fibers and their low strength still impede practical applications. Here, we report shell-cross-linked aramid nanofibrous aerogel fibers (ScANFAFs) fabricated via a stepwise sol–gel coupled wet-spinning strategy. This strategy enables rapid gelation of the shell flow of the aramid nanofiber (ANF) sol through the fast reprotonation and cross-linking reactions of the H-lacking ANFs to form a strong and tough shell layer, while the core sol undergoes slow gelation to obtain a porous nanofibrous core layer. Given this composite structure, ScANFAFs achieve a strength of 83.2 MPa, a toughness of 15.05 MJ·m–3, high porosity (>96%), and high specific surface area (286.8 m2·g–1). The mechanical robustness of ScANFAFs meets the requirements for weaving by using an automated loom. The resulting aerogel textiles exhibit low thermal conductivity (0.032 W·m–1·K–1), excellent thermal protection over a wide temperature range, and outstanding thermal stealth capabilities in extreme cold and ambient conditions. This work points to a promising direction for the multifunctional thermal protection of aerogel fibers and textiles

Strong, Tough, Shell-Cross-Linked Aramid Nanofibrous Aerogel Fibers for Thermally-Protective Textiles

Aerogel textiles show remarkable promise for thermal protection under extreme conditions. However, challenges in the mass production of aerogel fibers and their low strength still impede practical applications. Here, we report shell-cross-linked aramid nanofibrous aerogel fibers (ScANFAFs) fabricated via a stepwise sol–gel coupled wet-spinning strategy. This strategy enables rapid gelation of the shell flow of the aramid nanofiber (ANF) sol through the fast reprotonation and cross-linking reactions of the H-lacking ANFs to form a strong and tough shell layer, while the core sol undergoes slow gelation to obtain a porous nanofibrous core layer. Given this composite structure, ScANFAFs achieve a strength of 83.2 MPa, a toughness of 15.05 MJ·m–3, high porosity (>96%), and high specific surface area (286.8 m2·g–1). The mechanical robustness of ScANFAFs meets the requirements for weaving by using an automated loom. The resulting aerogel textiles exhibit low thermal conductivity (0.032 W·m–1·K–1), excellent thermal protection over a wide temperature range, and outstanding thermal stealth capabilities in extreme cold and ambient conditions. This work points to a promising direction for the multifunctional thermal protection of aerogel fibers and textiles

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

High-performance thermal insulators are urgently desired for energy-saving and thermal protection applications. However, the creation of such materials with synchronously ultralow thermal conductivity, lightweight, and mechanically robust properties still faces enormous challenges. Herein, a proton donor-regulated assembly strategy is presented to construct asymmetric aramid nanofiber (ANF) aerogel membranes with a dense skin layer and a high-porous nanofibrous body part. The asymmetric structure originates from the otherness of the structural restoration of deprotonated ANFs and the resulting ANF assembly due to the diversity of available proton concentrations. Befitting from the synergistic effect of the distinct architectures, the resulting aerogel membranes exhibit excellent overall performance in terms of a low thermal conductivity of 0.031 W·m–1·K–1, a low density of 19.2 mg·cm–3, a high porosity of 99.53%, a high tensile strength of 11.8 MPa (16.5 times enhanced), high heat resistance (>500 °C), and high flame retardancy. Furthermore, a blade-scraping process is further proposed to fabricate the aerogel membrane in a continuous and scalable manner, as it is believed to have potential applications in civil and military fields

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

High-performance thermal insulators are urgently desired for energy-saving and thermal protection applications. However, the creation of such materials with synchronously ultralow thermal conductivity, lightweight, and mechanically robust properties still faces enormous challenges. Herein, a proton donor-regulated assembly strategy is presented to construct asymmetric aramid nanofiber (ANF) aerogel membranes with a dense skin layer and a high-porous nanofibrous body part. The asymmetric structure originates from the otherness of the structural restoration of deprotonated ANFs and the resulting ANF assembly due to the diversity of available proton concentrations. Befitting from the synergistic effect of the distinct architectures, the resulting aerogel membranes exhibit excellent overall performance in terms of a low thermal conductivity of 0.031 W·m–1·K–1, a low density of 19.2 mg·cm–3, a high porosity of 99.53%, a high tensile strength of 11.8 MPa (16.5 times enhanced), high heat resistance (>500 °C), and high flame retardancy. Furthermore, a blade-scraping process is further proposed to fabricate the aerogel membrane in a continuous and scalable manner, as it is believed to have potential applications in civil and military fields

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

High-performance thermal insulators are urgently desired for energy-saving and thermal protection applications. However, the creation of such materials with synchronously ultralow thermal conductivity, lightweight, and mechanically robust properties still faces enormous challenges. Herein, a proton donor-regulated assembly strategy is presented to construct asymmetric aramid nanofiber (ANF) aerogel membranes with a dense skin layer and a high-porous nanofibrous body part. The asymmetric structure originates from the otherness of the structural restoration of deprotonated ANFs and the resulting ANF assembly due to the diversity of available proton concentrations. Befitting from the synergistic effect of the distinct architectures, the resulting aerogel membranes exhibit excellent overall performance in terms of a low thermal conductivity of 0.031 W·m–1·K–1, a low density of 19.2 mg·cm–3, a high porosity of 99.53%, a high tensile strength of 11.8 MPa (16.5 times enhanced), high heat resistance (>500 °C), and high flame retardancy. Furthermore, a blade-scraping process is further proposed to fabricate the aerogel membrane in a continuous and scalable manner, as it is believed to have potential applications in civil and military fields

12-week but not 6-week curcumin treatment induced a significant increase of BrdU-positive cells in dentate gyrus.

<p>A and B: BrdU immunhistology results from the representative slices of 6-week curcumin-treated rats and controls, respectively. C: the statistical results of 6-week curcumin treatment on hippocampal neurogenesis. D and E: BrdU immunhistology results from the representative slices of 12-week curcumin-treated rats and controls, respectively. F: the statistical results of 12-week curcumin treatment on hippocampal neurogenesis. The yellow arrows: the BrdU-positive cells. In C and F, data were expressed as mean ± SEM. *: P<0.05.</p

Functional categories of genes affected by curcumin.

<p>Percentages of genes whose expression levels are changed by curcumin were indicated.</p

Experimental design of this study.

<p>Curcumin was given to the aged rats in food for 6 (short-term) or 12 weeks (long-term). Behavioural tests were performed on the last two weeks of curcumin administration and BrdU were injected daily for ten days on the last ten days. Rats were killed for immunihistological and biochemical analysis at the end of curcumin treatment.</p

Relative expression levels of relevant genes in the hippocampus of the aged rats.

<p>A, B: after 6-week curcumin treatment; C, D: after 12-week curcumin treatment;. A, C: the results of real time PCR; B, D: the comparisons of the relative gene expressions compared to control rats between the results of quantitative PCR and microarray experiments. Student <i>t</i>-test, *P<0.05, **P<0.01 compared to control rats.</p