Aerogel Fibers Research Articles

Sheath-core structured Ca-alginate/PVA aerogel fibers via directed freezing wet-spinning

Biomass-based aerogel fibers have attracted increasing attention due to their renewable nature. However, their disadvantages, such as low mechanical strength, poor long-range order, and easy combustion, are still significant challenges. Herein, a directed freezing-assisted forced stretching strategy is developed to fabricate sheath-core structured Ca-alginate/polyvinyl alcohol (Ca-A/PVA) aerogel fibers with Long-range-ordered pores. The Ca-A/PVA aerogel fibers (3:2 m/m) exhibit the best comprehensive mechanical properties in terms of low thermal conductivity of 0.0524 W·m−1·K−1, a density of 0.1614 g·cm−3, a porosity of 89.9 %, a tensile strength of 8.72 MPa, a tensile modulus of 249.7 MPa, a toughness of 1.98 MJ∙m−3, and a self-extinguishing time from the fire of <1.2 s. The Ca-A/PVA fabrics showed a maximum absolute temperature difference of 11.4 °C at −20 °C and 14.0 °C at 60 °C compared to the plate temperature. The presented strategy is generalizable to other alginate-based aerogel fibers (e.g., alginate/guar gum).

Polymer-Encapsulated Aerogel Fibers Prepared via Coaxial Wet Spinning with Stepwise Coagulation for Thermal Insulation

Polymer-Encapsulated Aerogel Fibers Prepared via Coaxial Wet Spinning with Stepwise Coagulation for Thermal Insulation

Interfused core-shell heterogeneous graphene/MXene fiber aerogel for high-performance and durable electromagnetic interference shielding.

Flexible, lightweight, and durable electromagnetic interference (EMI) shielding materials are urgently required to solve the increasingly serious electromagnetic radiation pollution. Transition metal carbides/nitrides (MXenes) are promising candidates for EMI shielding materials because of their excellent metallic electrical conductivity. However, MXenes are highly susceptible to oxidization when exposed to wet environments, leading to the loss of their functional properties and degradation of reliability and stability. Herein, an interfused core-shell heterogeneous reduced graphene oxide (rGO)/MXene aerogel (GMA) is designed for the first time via coaxial wet spinning and freeze-drying. The fabricated GMAs exhibit excellent EMI shielding performance, and the EMI shielding effectiveness (SE) and specific EMI SE can be up to 83.3dB and 3119dB·cm3/g, respectively, which is higher than most carbon-based and MXene-based aerogels and foams. More importantly, GMAs have only a 17.4% degradation in EMI shielding performance after 120days due to the protection of hydrophobic graphene sheath, exhibiting superior EMI shielding durability to its MXene film counterpart. Moreover, the hydrophobic GMAs exhibit good oil/water separation and thermal insulation performance. The interfused core-shell GMAs are highly promising for applications in durable EMI shielding, thermal insulation, oil/water separation and sensors, etc.

Elytra-mimetic ceramic fiber aerogel with excellent mechanical, anti-oxidation, and thermal insulation properties

High-performance thermally insulating aerogel with low density, high porosity, and low thermal conductivity characteristics was widely used in heat insulation. However, the large-scale application of aerogel was still limited by its brittleness and infrared radiation transparency at high-temperature. Fiber composite aerogel had achieved significant progress, but its anti-oxidation ability was poor, and its thermal insulation required further improvement at ultra-high temperatures. Herein, inspired by the structure of elytra, nanoparticle fiber (NF) was prepared by electrospinning of coaxial fiber loaded with opacifier and antioxidant nanoparticles. The NF was incorporated into the SiBCN aerogel to prepare NF/SiBCN ceramic fiber aerogel. The mechanical properties were improved by fiber networks. The shell structure increased the antioxidant properties. Heat conduction and heat convection were suppressed by the aerogel, while heat radiation was reduced by the coaxial fiber. The results showed that the ceramic fiber aerogel exhibited superior mechanical, antioxidant, and ultra-low thermal conductivity properties.

Hierarchically porous polyimide aerogel fibers based on the confinement of Ti3C2Tx flakes for thermal insulation and fire retardancy

Thermally insulating and flame-resistant fibers/textiles have drawn enormous attention attributing to their great application prospects in personal thermal management and protective clothing. Nevertheless, conventional natural fibers and synthetic fibers are insufficient for advanced thermal regulation. Herein, an in-situ polymerization method and wet-spinning technique are employed for the continuous and scalable fabrication of polyimide (PI) aerogel fibers utilizing monolayered Ti3C2Tx flakes as the pore-generating agents. Benefiting from the intimate interfacial interaction between MXene and the macromolecular chains, hierarchical porosity is constructed in the composite aerogel fibers due to the confinement of the interconnected PAA/Ti3C2Tx networks during liquid-solid phase separation. As a result, the PI/Ti3C2Tx aerogel fibers manifest significantly enhanced mechanical properties (tensile strength of 26 MPa), large specific surface area (145 m2 g−1), excellent flame resistance, and remarkable thermal insulation performance (with a low thermal conductivity of 36 mW m−1 K−1), which can be readily weaved into flexible textiles for practical thermal regulating applications. This approach is expected to pave a new way for the fabrication and application of high-performance thermal insulating fibers and textiles.

Bamboo pulp-based electret fiber aerogel with enhanced electret performance by P-phenylenediamine modification for simulated radioactive aerosol purification in confined spaces

Radioactive aerosols in confined spaces of workplaces are the main source of internal radiation hazards for staff. Therefore, biomass-based electret fiber materials as alternatives of petroleum-based polymers will be of great potential in capturing radioactive aerosols due to its biodegradability, renewability and electrostatic effects. Herein, a fabrication strategy of bamboo pulp-based electret fiber aerogels by corona polarization is reported grounded on p-phenylenediamine (PPD)-modified bamboo pulp fibers (BCFs) and ethyl cellulose (EC). The morphology, chemical structure, and physical properties of BCFs before and after modification, as well as the electret properties and purification performance of fiber aerogel were analyzed. The results showed that PPD can be grafted uniformly on the surface of BCFs, making the fibers transform from irregular cylindrical shape with hierarchical surface to regular cylindrical shape with smooth surface, and can improve the surface potential of the fibers, one of the considerably great electret properties, from 0.00 kV to 1.33 kV when the graft amount of PPD was 0.500 g/g. The improvement in surface potential, leading by the grafted PPD structure which is a charge-trapping site confirmed by stoichiometric calculations, enhance the electrostatic trapping effect of the fibers on radioactive aerosol particles and shorten the purification time from 26 min to 15 min. Moreover, the electret fiber aerogel with modified BCFs (named as PPD-DABCFs) has a low air resistance of 56 Pa at the flow speed of 5.3 cm·s−1, a light base weight of 62.7 g·m−2 and a long service life. Therefore, the bamboo pulp-based electret fiber aerogel has a promising application in the field of radioactive aerogel purification.

Ultralight aerogel textiles based on aramid nanofibers composites with excellent thermal insulation and electromagnetic shielding properties

Ultralight, flexible and robust aerogel fibers based on aramid nanofiber/modified carbon nanotubes are prepared via a facile wet spinning method following with a freeze-drying technique. The aerogel textiles based on the strong aerogel fibers exhibit excellent thermal insulation properties within a wide range of temperature (−30–200 °C), which can be attributed to their ultralow density (5–12 mg/cm3) and high specific areas (123–219 m2/g). Moreover, the optimized aerogel textiles (with a thickness of 0.92 mm) show high-efficient electromagnetic shielding performance with a value exceeding 30 dB in the X-band. Overall, those aerogel textiles exhibit great potential for applications as thermal insulation and electromagnetic shielding equipment under harsh environments.

Cotton-derived 3D carbon fiber aerogel to in situ support Bi2O3 nanoparticles as a separation-free photocatalyst for antibiotic removal

Because of abundant oxygen-based groups, natural cotton is adopted as the precursor to in situ fabricate a three-dimensional (3D) Bi2O3-supported carbon fiber aerogel (Bi2O3/CF). The calcination temperature plays an important role in the crystal composition of Bi species and the specific surface area of the aerogel. When the calcination temperature is 800 °C, the Bi2O3/CF product exhibits the highest tetracycline (TC) removal efficiency, including large adsorbability and superior photocatalytic activity. Furthermore, its 3D porous network architecture provides a multidimensional open framework for the free mobility of solution and rapid diffusion of reactants and products. In the flowing system, the 3D Bi2O3/CF aerogel can implement the continuous and stable elimination of pollutants for a long time, and it does not require any separation operation. Consequently, the 3D Bi2O3/CF aerogel is expected as a promising functional material to massively remove organic pollutants from industrial wastewater.

Nanoscale Kevlar Liquid Crystal Aerogel Fibers.

Aerogel fibers, the simultaneous embodiment of aerogel porous network and fiber slender geometry, have shown critical advantages over natural and synthetic fibers in thermal insulation. However, how to control the building block orientation degree of the resulting aerogel fibers during the dynamic sol–gel transition process to expand their functions for emerging applications is a great challenge. Herein, nanoscale Kevlar liquid crystal (NKLC) aerogel fibers with different building block orientation degrees have been fabricated from Kevlar nanofibers via liquid crystal spinning, dynamic sol–gel transition, freeze-drying, and cold plasma hydrophobilization in sequence. The resulting NKLC aerogel fibers demonstrate extremely high mechanical strength (41.0 MPa), excellent thermal insulation (0.037 W·m–1·K–1), and self-cleaning performance (with a water contact angle of 154°). The superhydrophobic NKLC aerogel fibers can cyclically transform between aerogel and gel states, while gel fibers involving different building block orientation degrees display distinguishable brightness under polarized light. Based on these performances, digital textiles woven or embroidered with high- and low-orientated NKLC aerogel fibers enable up to 6.0 Gb information encryption in one square meter and on-demand decryption. Therefore, it can be envisioned that the tuning of the building blocks’ orientation degree will be an appropriate strategy to endow performance to the liquid crystal aerogel fibers for potential applications beyond thermal insulation.

Preparation and high-temperature service performance of hierarchically pore-structured BN fiber aerogels

Multifunctional aerogels with high porosity and good thermal insulation have attracted much attention in the field of energy and aerospace engineering. In this work, a three-dimensional BN fiber aerogel with hierarchically porous structure was prepared through a freeze-drying combined with in-situ carbothermal reduction nitridation route. The synthesized BN fiber aerogel exhibits a specific surface area of 154.3 m2/g, a high porosity of 96.8% and hydrophobicity. Moreover, the BN fiber aerogel shows a low thermal conductivity of 0.051 W/(m·K) and excellent thermal insulation properties owing to its hierarchical porous structure. Particularly, the BN fiber aerogel still maintains its low thermal conductivity and a rather high mechanical strength after re-heated at 1473 K for 3 h in Ar atmosphere, suggesting excellent high-temperature service performance. The successfully developed multifunctional BN fiber aerogel holds promising potential in high-temperature thermal insulation fields.

Multifunctional graphene/carbon fiber aerogels toward compatible electromagnetic wave absorption and shielding in gigahertz and terahertz bands with optimized radar cross section

Lightweight absorption-dominated electromagnetic interference (EMI) shielding materials with multifunctional integration of multiband absorption, mechanical durability and thermal insulation are urgently required in the practical application of next-generation communication technology combined with flexible electronics. In this work, ultralight and mechanically durable graphene/carbon fiber composite aerogels (CGAs) are synthesized via solvothermal reaction and freeze-drying. The as-prepared CGAs demonstrate excellent compatible electromagnetic wave absorption and shielding performance in both gigahertz (GHz) and terahertz (THz) bands without addition of magnetic component. Specifically, a broad efficient absorption bandwidth of 8.72 GHz at 2–18 GHz and a high mean absorptivity of 97.4% at 0.3–1.5 THz are achieved, respectively. Furthermore, absorbing coatings with CGAs have been proved to contribute to remarkable radar cross section reduction of 39.06 dBm2 by computer-assisted simulation. Additionally, the compressible CGA demonstrates superior and stable EMI shielding performance under in-situ compression. The EMI shielding effectiveness exceeds 35 dB in X-band when a compression ratio of 78.9% is applied. Moreover, CGAs are thermally insulating and self-extinct, making them reliable in practical application. This work provides a series of promising multifunctional lightweight EMI shielding materials for future high-frequency wireless communication.

Multi-scale thermal, energetic and economic analysis of composite insulating materials made of silica aerogel in a fibrous inorganic mat

Composite materials made of silica aerogel in a fibrous inorganic mat, hereafter called “aerogel blankets”, represent promising insulating materials that can overcome the low mechanical resistance of monolithic aerogels, while preserving their very low thermal conductivity. Firstly, this paper details an experimentally validated mathematical model to predict the aerogel blankets’ effective thermal conductivity, as a function of the blankets' density, fiber volume fraction, and temperature. Secondly, an experimental test building retrofitted internally with a layer of needle glass fiber (NGF) aerogel blanket is monitored, and its thermal behavior is compared to the baseline case before the retrofit. The retrofitted wall U-value is derived from experimental data series using stationary and transient parametric methods. Then, a validated whole building Energy Plus numerical model is used to predict the annual energy consumption of a detached single-family house retrofitted with an NGF aerogel blanket, in the climates of Brussels (Belgium), Nice (France), and Stockholm (Sweden). Lastly, a 1-D COMSOL multiphysics model evaluates the economic profitability of installing the blanket as an interior thermal insulation system. Results show that the aerogel blankets have an effective thermal conductivity of about 0.0165 W.m−1.K−1. The designed mathematical model can reliably predict the gaseous conduction in the blanket, but deviations from the experimental measurements appear when considering the radiative and solid conduction components. The blanket's effective thermal conductivity increases with fiber volume fraction and temperature while its dependency curve to density is concave, with a minimum for densities of around 140 kg.m−3. Retrofitting a wall with 2.5 cm of NGF aerogel blanket as an internal insulation system almost doubles the thermal resistance of the experimental wall and decreases the heating load by more than 40 % in all tested climates. Internal thermal insulation with aerogel blankets is more profitable than conventional insulation materials, in places of high floor area price, because it can preserve the indoor living space.

Hierarchical SiC fiber aerogel toward microwave attenuation and thermal insulation application

Materials with structural hierarchy have drawn great attenuation due to their fascinating physical and mechanical properties given by the unique microstructures. In this study, hierarchical SiC fiber aerogel was successfully developed via a simple method by using carbonized silk fiber mat as a template and subsequent in-situ growth of SiC nanowires array through carbothermal reduction at high temperature. The formation mechanisms of hierarchical SiC fiber aerogel based on a vapor-solid-liquid process were discussed. Owing to the highly porous structure supported by SiC nanowires, the aerogel could show an ultralight density of 0.04 g/cm 3 and a compression fatigue resistance of 10 cycles at 40% strain with small and stable energy loss coefficients. The electromagnetic (EM) investigation suggests that the aerogel could serve as a wideband microwave attenuator with a minimal reflection loss (RL) of − 68 dB and a maximum effective attenuation bandwidth (EAB, RL<−10 dB) of 7.2 GHz when embedded in silicone matrix at 10 wt% loading ratio. Additionally, the hierarchical SiC fiber aerogel reveals remarkably low thermal conductivity of 0.027 W/m·K, suggesting enormous potential for thermal insulation. • Hierarchical SiC fiber aerogel have been fabricated by in-situ grown synthesis method. • Lightweight, wideband microwave absorber with low thermal conductivity is obtained. • The effects of hierarchical structure on the enhanced performance are elaborated.

Efficient cellulose aerogel biosorbents functionalized by nanosized zero-valent iron: Isotherms, kinetics, thermodynamics and mechanism of tellurium adsorption

Fabrication of eco-friendly and efficient biosorbents played a crucial role in adsorbing tellurium from wastewater, yet which was confronted with large obstacles to achieve a high adsorption capacity and biocompatibility simultaneously. Herein, a simple and economical strategy for adsorbing tellurium by nanosized zero-valent iron/ cellulose fiber hybrid aerogel (nZVI/CFA) is proposed. Cellulose fiber aerogel (CFA) was firstly fabricated by freeze-drying the cellulose fibers that were extracted from agricultural waste maize bracts. Then, the nZVI was uniformly anchored on the porous network skeleton structure of CFA by liquid-phase reduction. The nZVI/CFA exhibited mesoporous structure with a large specific surface area (399.85 m2/g), uniform pore size (3.92 nm) and pore volume (0.47 cm3/g). According to the kinetics and isothermal model, the tellurium adsorption by nZVI/CFA was uniform and endothermic-chemical on the monolayer surface. Due to the highly exposed specific surface area, more active sites and the synergistic effect of electrostatic attraction, reduction and substitution, nZVI/CFA has a high adsorption capacity (119.32 mg/g). As a low-cost and efficient biosorbent, nZVI/CFA provided a new idea for the treatment with other abandoned photovoltaic materials and agricultural waste.

Controllable Strong and Ultralight Aramid Nanofiber-Based Aerogel Fibers for Thermal Insulation Applications

Controllable Strong and Ultralight Aramid Nanofiber-Based Aerogel Fibers for Thermal Insulation Applications

Smart multi-responsive aramid aerogel fiber enabled self-powered fabrics

Wearable electronics and systems with self-powered real-time responses to various stimuli, such as mechanical, electrical, thermal and optical signals，are eagerly desired, however still remain great challenges. Herein, smart fibers with multi-response to external stimuli are developed via wet spinning porous aramid aerogel nanofibers while utilized as a three-dimensional hierarchical percolating skeleton for silver nanowires (AgNWs) interwoven MXene conductive network. The coaxial AgNWs/MXene@ aramid aerogel nanofibers with entangled heterostructures effectively avoid “trade-off” effect between high electrical conductivity and mechanical flexibility of smart fibers. Meanwhile, the hierarchical porous structure of aerogel conductive fibers induced strong capillary force and confinement to polyethylene glycol, which has a wide range of phase transition temperature and huge enthalpy to store tremendous thermal energy. After further encapsulated with transparent fluorosilicone resin, the stabilized smart fiber exhibits excellent self-cleaning properties with water and oil repellent. Furthermore, the woven aerogel fabrics coupled with thermoelectric generator realized efficient reversible energy conversion and storage as well as solar-thermal-electrical power generation for all-weather electricity power supply, which could drive the operation of wearable electronics and car models without batteries, providing an efficient strategy for outdoor travel and lunar rover continuous operating. The smart aramid aerogel fibers and fabrics hold great promise for next generation of self-powered wearable systems.

Multifunctional biomass carbon fiber aerogel based on resource utilization of agricultural waste-peanut shells for fast and efficient oil–water/emulsion separation

In this work, the flexible, ultralight, hydrophobic and multi-functional biomass carbon (BC) aerogel was prepared, and the porous network structure provides efficient oil transmission and storage channels (the porosity of 98.39%). With the extraordinary wettability, the BC aerogel maintains stable hydrophobicity (>135°) and the maximum water contact angle is 141°. BC aerogel exhibits the great reusability of elastic material after multiple intensive compressions. Simultaneously, B-C aerogel holds a wonderful absorption capacity for various oils and organic solvents (27–50 g/g), possessing an extraordinary recyclability (94%). Furthermore, BC aerogel can also be taken as the separation filter of oil/water mixture (1561.19 L m−2 h−1, 99.13%) and used to separate emulsion with relatively stable surface activity (1039.49 L m−2 h−1, 91.93%). The research provides a green strategy for preparing hydrophobic oil-absorbing materials from low-cost materials and has the great application potential in oil–water/emulsion treatment and environmental protection.

Polyimide/boron nitride composite aerogel fiber-based phase-changeable textile for intelligent personal thermoregulation

Aerogel fibers, which are beneficial for enhancing the thermal response and preventing the leakage of phase-changeable materials (PCMs) during phase change process, are excellent candidates for phase-changeable textiles with excellent thermoregulating performance. Herein, polyimide/boron nitride (PI-BN) composite aerogel fibers with highly porous structure and good mechanical strength have been prepared by freeze-spinning technique, which could be served as the heat conduction path and skeleton for PCMs. Into the pores of the PI-BN aerogel textile was incorporated polyethylene glycol (PEG) by vacuum impregnation to obtain phase-changeable PI-BN/PEG textile. The high thermal conductivity of PI-BN skeleton could endow the quick thermal response rate of PI-BN/PEG textile upon the phase change process, while the high porosity of aerogel fiber could allow high loading of PEG and inhibit liquid leakage during phase change process. The resultant PI-BN/PEG composite textile has high thermal conductivity (5.34 W m−1 K−1), high enthalpy (125.2 J g−1) and excellent work stability after 100 heating-cooling cycles, accounting for the desired thermoregulating performance. Moreover, polydimethylsiloxane (PDMS) has been coated on the surface of PI-BN/PEG textile, endowing the textile hydrophobicity, waterproofness and washability, indicating its great potential as candidate for personal thermal management.

“Finger coral-like” ceramic fiber aerogels with enhanced high-temperature thermal insulation, anti-oxidation, and mechanical performance

Ceramic fiber aerogels are widely used in high temperature insulation. Thermal insulation under extreme conditions requires materials that can withstand sharp thermal shocks and extended high-temperature exposure. However, the oxidation resistance of traditional ceramic aerogels under a high temperature environment(above 1000 °C) is significantly reduced. Moreover, the strength degradation and structural collapse easily occurred, restricting their application. In this study, “Finger Coral” ceramic fibers aerogels were obtained using precursor infiltration pyrolysis (PIP) and electrospinning technology. The chemical composition, morphology, thermal insulation, mechanical properties and isothermal oxidation properties of SiCBN/SiC/disilicates nanoparticles (IP) ceramic aerogels were tested. The experimental results showed that the aerogel exhibited excellent mechanical and antioxidant properties over a wide range of temperatures. SiCBN/SiC/IP aerogel with a thickness of 2cm can achieve the heat insulation effect of the hot surface temperature from 1600 to 75 °C, and the thermal conductivity at 1600 °C was only 0.036 W·m−1·K−1. After 12 h of cyclic isothermal oxidation, the weight gain was only 5.17%. The material is expected to be used as a thermal insulation material in the hypersonic vehicles.

In Situ Loading of Polypyrrole onto Aramid Nanofiber and Carbon Nanotube Aerogel Fibers as Physiology and Motion Sensors.

Nanocomposite conductive fiber has been newly developed as a lightweight material with high flexibility and strong weavability, which can meet the requirements of flexible wearable devices. Herein, lightweight porous aramid nanofibers (ANF) and carbon nanotube (CNT) aerogel fibers coated with polypyrrole (PPy) layers are prepared by a wet spinning method for motion detection and information transmission. The ANF/CNT/PPy aerogel fiber with low density (56.3 mg/cm3), conductivity (6.43 S/m), and tensile strength (2.88 MPa) were used as motion sensors with high sensitivity (0.12) and long life (1000 cycles). At the same time, the differential conductivity of aerogel fibers is utilized to reduce the information transmission time (up to 46%). High- and low-temperature-resistant (-196 to 100 °C) aerogel fibers are also available as a quick heater and ionic solution detector. In summary, the prepared ANF/CNT/PPy aerogel fiber can be used as a multifunctional sensor for human-health detection and motion monitoring.