Aerogel Fibers Research Articles

Rutile titanium dioxide and graphene-like OCN tailoring free-standing carbon fiber aerogel as polysulfide anchoring materials for lithium–sulfur batteries

The rational design of a host material with strong adsorption and excellent electrical conductivity function for sulfur cathode to suppress the shuttle effects of soluble lithium polysulfide (LiPS) is crucial to advance the lithium–sulfur (Li–S) battery for future commercial applications. In this work, we designed a three-dimensional (3D) carbon fiber aerogel with graphene-like oxygenated carbon nitrogen (OCN) and TiO2 (OCNF–TiO2) as a sulfur anchoring material for Li–S battery and explored the regulating effects of TiO2 on the electrochemical performances. The OCNF–TiO2/S cathode presents an initial discharge-specific capacity of 1039 mAh/g (0.1C), a rate capacity of 690 mAh/g at 1C, a cycling performance with a capacitance retention of 72.1%, and the decay of 0.13% per cycle after 200 cycles at 0.5C.

Preparation of high‐hydrophobic polyvinyl alcohol‐based composite aerogel fibers containing organosilicon for effective thermal insulation

AbstractPolyvinyl alcohol (PVA) aerogel fibers exhibit encouraging potential as thermal insulation materials, but their hydrophilicity easily results in severe collapse of the aerogel pore structure. Therefore, hydrophobic modification of PVA aerogel fibers is of significance to their structural stability and durability. Here, a novel process was proposed to continuously generate high‐hydrophobic PVA‐based composite aerogel fibers containing polymethylsilsesquioxane (PMSQ) by introducing methyltrimethoxysilane (MTMS) through freeze‐thawing, freeze‐spinning, and freeze‐drying processes. With optimized freezing time and MTMS content, the PVA‐based composite solution showed good spinnability, and the resulting PVA/PMSQ (PVASi) aerogel fibers were endowed with markedly enhanced hydrophobicity and excellent weavability due to sufficient mechanical properties. Most importantly, the aerogel fibers possessed excellent hydrophobic structural stability after 12 h or 50‐cycle soaking and 50‐cycle washing. Benefiting from these superior characteristics, the aerogel fibers were demonstrated to be effective thermal insulators in high humidity (>90% relative humidity) and after washing for 50 cycles.

Bioinspired Thermochromic Textile Based on Robust Cellulose Aerogel Fiber for Self-Adaptive Thermal Management and Dynamic Labels.

Aerogel fiber has emerged recently for incorporation in personal thermal management textiles due to its flexibility, scalability, and ultrahigh porosity, which allows the body to keep warm via thermal isolation without energy consumption. However, the functionalization and intellectualization of cellulose-based aerogel fibers have not yet been fully developed. Herein, we propose a biomimicking design inspired by polar bear and Siamese cat hair that combines porous cellulose aerogel fiber (CAF) with reversible thermochromic microcapsules to mimic biological sensory and adaptive thermoregulation functions. The produced CAF has a controllable pore structure, a large specific surface area (230 m2/g), and excellent mechanical strength (∼15 MPa). Low-temperature darkening microcapsules have been incorporated into the robust CAF to spontaneously adjust color by perceiving the ambient temperature. The functional aerogel fiber fabric achieves high thermal insulation and photothermal modulation simultaneously at temperatures below 18 °C. The temperature of the thermochromic fabric was higher by 6 °C than that of the sample without the microcapsules at a light intensity of 0.2 W/cm2. In addition, the aerogel fibers mixed with two types of thermochromic microcapsules exhibit three color switches with fast response, a color-control precision of 0.2 °C, and good cycling performance. This smart aerogel fibers hold great promise for self-adaptive thermal management, temperature indication, information transfer, and anticounterfeiting in textiles.

Fiber Sedimentation and Layer-By-Layer Assembly Strategy for Designing Biomimetic Quasi-Ordered Mullite Fiber Aerogels as Extreme Conditions Thermal Insulators.

Ceramic fiber aerogels are attractive thermal insulating materials. In a thermomechanical coupling environment, however, they often show limited mechanical strength and considerably increased heat transfer which can lead to thermal runaway. In this paper, inspired by bird's nest and nacre, we demonstrate a sample strategy combining fiber sedimentation and layer-by-layer assembly to fabricate ultrastrong mullite fiber aerogels (MFAs) with quasi-ordered structures. The fibrous layers and fiber bridges are constructed in a fiber sedimentation self-assembly process. The fiber sedimentation technique optimizes the structure of the MFAs by regulating the fiber orientation. Owing to the quasi-ordered structure, the fabricated MFAs exhibit the integrated properties of high compression fatigue resistance, temperature-invariant compression resilience from -196 to 1300 °C, and low thermal conductivity (0.034 W·m-1·K-1). By deliberately pressing multilayer MFAs into a thin paper, we substantially enhance the load-bearing capacity of the MFAs and achieve large temperature differences (563 °C) between the cold and hot surfaces by using a thin layer of MFAs (3-5 mm) under the simulated high-temperature (685 °C) and high-pressure (0.9 MPa) environment test. The combination of compression resistance, mechanical flexibility, and excellent thermal insulation provides an appealing material for efficient thermal insulation in extreme environments.

Function Graded Carbon Micro‐Structures for Powerless Photon Sensing with Intriguing µm‐Scale Position Sensitivity

AbstractPartial laser treatment is introduced to carbon‐based microfibers to generate excellent photon sensing capability without bias. This treatment brings about a Seebeck coefficient distribution along the sample's length, out of which a photovoltage with no external bias is generated and sensed. Using a line‐shaped laser spot, carbon microfiber (CMF), graphene microfiber (GMF), and graphene aerogel fiber (GAF) are investigated for their response to µm‐scale photon irradiation. A higher sensitivity for the incident photon is found for the GAF with no position sensitivity. More Seebeck coefficient variation is also observed for the GAF considering the amount of laser power used for the laser treatment. A weaker Seebeck coefficient spatial variation is observed for the GMF compared with the GAF. However, its photovoltage shows an abrupt magnitude change from the laser‐treated region to the non‐treated one. Despite the low spatial variation of the Seebeck coefficient for the CMF, it features an excellent and accurate position‐sensitive photoresponse with polarization change over a distance of ≈100 µm. Such unique capability prompts novel applications in using partially annealed CMF for sensing the position of optical beams at the microscale.

Anti-cracking coating with wrinkled morphology for enhancing oxidation resistance of carbon-based fiber aerogel

In our previous work, ceramic precursor coating with wrinkled morphology was obtained by cross-linking gradient generated from ultraviolet and cross-linking agent to improve the anti-cracking of the coating in the pyrolysis. However, the cross-linking gradient was difficult to control with ultraviolet and cross-linking agent. Herein, a simple method was proposed to form the wrinkled morphology of the coating by the steady-state temperature gradient field generated from constant temperature pre-treatment. Composite aerogels were prepared by pyrolysis at high temperature. The thermal insulation and oxidation resistance of the composite aerogels were explored. The heat transfer behavior within the composite aerogels was analyzed by simulation. The results showed that the stored strain of wrinkled morphology counteracted the shrinkage of ceramic precursor polymer during the pyrolysis, which prevented the cracking of the coating. Compared with the aerogels of our previous work, the composite aerogels of this work demonstrated improved thermal insulation and oxidation resistance.

Ionic Liquid Directed Spinning of Cellulose Aerogel Fibers with Superb Toughness for Weaved Thermal Insulation and Transient Impact Protection.

Aerogel fibers, combining the nanoporous characteristics of aerogels with the slenderness of fibers, have emerged as a rising star in nanoscale materials science. However, endowing nanoporous aerogel fibers with good strength and high toughness remains elusive due to their high porosity and fragile mechanics. To address this challenge, this paper reports supertough aerogel fibers (SAFs) initially started from ionic-liquid-dissociated cellulose via wet-spinning and supercritical drying in sequence. The supertough nanoporous aerogel fibers assembled with cellulose nanofibers exhibit a high specific surface area (372 m2/g), good mechanical strength (30 MPa), and large elongation (107%). Benefiting from their high strength and elongation, the resultant cellulose nanoporous aerogel fibers show ultrahigh toughness up to 21.85 MJ/m3, much outperforming the known aerogel materials in the literature. Moreover, the toughness of this nanoporous aerogel fiber is 7.4 times higher than that of human knee ligaments, and its specific toughness is comparable to that of commonly used solid polyester fibers. In addition, we also verified the weavability, desirable thermal insulation performance, and supertoughness to resist the transient impact of SAFs. The long-sought strategy to simultaneously resolve the strength and toughness of nanoporous aerogel fibers, in combination with the biodegradable nature of the cellulose, provides multifaceted opportunities for broad potential applications, including lightweight wearable textiles and beyond.

Redox Responsive Sol–Gel Transition: A New Concept for Continuous Spinning of High-Performance and Recyclable Aerogel Fibers

Redox Responsive Sol–Gel Transition: A New Concept for Continuous Spinning of High-Performance and Recyclable Aerogel Fibers

Tuning the Degree of Protonation to Prepare Ultra-light and High Thermal Insulation Mullite Nanofiber Aerogels

Ceramic fiber aerogels play an important role in thermal insulation due to their high specific surface area and porosity. They have great potential in aircraft, the military industry, and metal smelting. Although traditional ceramic fiber has the advantages of high-temperature resistance, its brittleness, tensile resistance, and high production cost, greatly limit the application of ceramic aerogels. Using the sol-gel method and electrostatic spinning technique, we controlled the fibers’ random winding and mechanical properties by controlling the protonation of the spinning fluid. We prepared ultralightweight, flexible, and highly insulated mullite nanofiber aerogels with a volume density as low as 7 mg / cm3, thermal conductivity as low as 27 mW m−1 K−1, excellent thermal stability at 1,300 °C, high thermal insulation and retention of up to 50% of the ceramic fiber after initial compression. This material’s fabrication process and excellent insulation properties propose new opinions on the lightweight and durable insulation materials needed for aerospace and military insulation.

Three-Dimensional-Network-Structured Bismuth-Based Silica Aerogel Fiber Felt for Highly Efficient Immobilization of Iodine.

The effective capture and deposition of radioactive iodine in the spent fuel reprocessing process is of great importance for nuclear safety and environmental protection. Three-dimensional (3D) fiber felt with structural diversity and tunability is applied as an efficient adsorbent with easy separation for iodine capture. Here, a bismuth-based silica aerogel fiber felt (Bi@SNF) was synthesized using a facile hydrothermal method. Abundant and homogeneous Bi nanoparticles greatly enhanced the adsorption and immobilization of iodine. Notably, Bi@SNF demonstrated a high capture capacity of 982.9 mg/g by forming stable BiI3 and Bi5O7I phases, which was about 14 times higher than that of the unloaded material. Fast uptake kinetics and excellent resistance to nitric acid and radiation were exhibited as a result of the 3D porous interconnected network and silica aerogel fiber substrate. Adjustable size and easy separation and recovery give the material potential as a radioactive iodine gas capture material.

Three-Dimensional Porous ZnO-Supported Carbon Fiber Aerogel with Synergistic Effects of Adsorption and Photocatalysis for Organics Removal

A three-dimensional (3D) ZnO-supported carbon fiber aerogel (ZnO/CFA) was successfully prepared by using natural cotton with hydrophilicity as the precursor. The facile synthetic strategy includes two steps: Zn2+ exchange on the surface of cotton and thermal treatment at high temperatures. Particularly, the calcination temperature was found to greatly affect the content, dispersity, and size of supported ZnO nanoparticles, and the product obtained at 600 °C (ZnO/CFA-600) exhibited both high ZnO loading and well-dispersed ZnO nanoparticles. Therefore, ZnO/CFA-600 has superior photocatalytic activity for tetracycline (TC) degradation under UV light irradiation compared with others. Additionally, the unique 3D crosslinking network inside the ZnO/CFA generates an open channel for the rapid migration and diffusion of reactants and products. In a dynamical water-treated system, the 3D porous ZnO/CFA-600 continuously works for TC removal without any separation operation and maintains high synergistic performance of adsorption and photocatalysis for at least 8 h. Consequently, the 3D porous ZnO/CFA product, with its large adsorbability and high photoactivity, shows a lot of industrial potential in wastewater treatments.

Plastic-Swelling Preparation of Functional Graphene Aerogel Fiber Textiles

Plastic-Swelling Preparation of Functional Graphene Aerogel Fiber Textiles

Bio-inspired gradient multilayer ceramic fiber aerogel loaded with TaSi2 and WSi2: Fabrication, anti-oxidation and thermal insulation

Aerogel is widely used in the field of thermal insulation. However, aerogel exhibits brittleness and infrared radiation transparency at high temperatures. Fiber composite aerogel achieved great progress, but the homogeneous structure hardly allowed heat convection, heat conduction, and heat radiation to be controlled simultaneously. In this paper, inspired by bamboo’s multilayer and gradient structure, SiC fiber loaded with TaSi2 and WSi2 antioxidant particles was prepared by electrostatic spinning. The fiber was incorporated into the silicoboron carbonitride (SiBCN) aerogel to prepare gradient multilayer SiC/SiBCN ceramic fiber aerogel. The fiber network enhanced the mechanical properties. Antioxidant particles improved antioxidant performance. Heat radiation was reduced through the fiber, while heat conduction and heat convection were decreased by the aerogel. The results showed that the ceramic fiber aerogel exhibited ultra-low thermal conductivity, excellent infrared radiation shielding, and antioxidation performance. This study is expected to provide new ideas for constructing high-temperature thermal insulation ceramic fiber aerogel.

Thermal oxidation etched carbon fiber aerogels with hierarchical pore structure as high-performance oil adsorbent

Thermal oxidation etched carbon fiber aerogels with hierarchical pore structure as high-performance oil adsorbent

Elimination of organic contaminants from water by microporous carbon fiber aerogel obtained from cotton

Elimination of organic contaminants from water by microporous carbon fiber aerogel obtained from cotton

Double-network polyimide/silica aerogel fiber for thermal insulation under extremely hot and humid environment

Aerogel fibers display good flexibility, low density and high porosity, making them highly promising as wearable thermal-insulating textiles. However, the inferior thermal insulating property in hot and humid environment resulting from the poor thermal stability and water penetration hampers their use in harsh environments. Herein, we report a double-network organic/inorganic aerogel fiber for thermal insulation under extremely hot and humid environment prepared by co-gelation and freezing-spinning technique. Through the co-gelation strategy, a homogeneous organic/inorganic poly(amic acid)/SiO2 (PAA/SiO2) gels can be obtained, benefiting for the stable spinning process. The resultant polyimide/silica (PI/SiO2) aerogel fibers with unique organic/inorganic double-network structure display good mechanical strength, exceptional thermal stability (up to 500 °C) and low thermal conductivity (75.6 mW m−1 K−1 at 350 °C). Furthermore, the PI/SiO2 aerogel fabrics reveal hydrophobicity and can effectively prevent thermal transfer in hot and humid environment with thermal conductivity of 58.8 mW m−1 K−1 at 80 °C and relative humidity of 100%, about 60% lower than that of silica aerogels. It is expected that such PI/SiO2 aerogel fibers/fabrics will be applied as a novel textile for thermal insulation in hot and humid environments.

Muscular Kevlar aerogel fibers appealing to thermal insulation with a symbiotic core-sheath structure

High-performance aerogels offer a broad application prospect owing to their various features such as high specific surface area and attractive thermal insulation. However, their porous structure confers weak mechanical properties to aerogels. The strategy of coaxial wet-spinning was implemented to strengthen Kevlar aerogel fibers and improve their usability. Prepared Kevlar aerogel fibers have a symbiotic core–sheath structure, with a blurred division between core and sheath. In addition, the breaking stress of Kevlar aerogel fibers can reach 2.6 MPa, which is four times that of the core, presenting a significant improvement in tensile strength compared to those in previous studies. Moreover, Kevlar aerogel fibers exhibit superior thermal stability, which is inherited from Kevlar fibers, and decomposed after 480 °C. Moreover, their high porosity and high specific area (∼400.5 m2·g−1) endow them with outstanding thermal insulation properties. When fabrics woven from these fibers are exposed to a 300 °C hot plate, the temperature on the surface can be 110 °C lower, resulting in a significant temperature gradient of 83 °C·mm−1. In total, the resultant Kevlar aerogel fibers with a symbiotic core–sheath structure are used as fillers for protective clothing or fire insulation blankets and similar items.

Thermal resistance prediction of aerogel fabrics after repeated washing based on small-sample data

Aerogel fibers utilized in thermal protective apparel exhibit exceptional heat insulation capabilities; however, concerns arise regarding potential degradation due to the detachment of aerogel particles during repeated washing. Accurate prediction of aerogel fiber thermal resistance is critical for assessing hydrothermal aging in aerogel textiles, yet the precision of such predictions is significantly hindered by limited sample data and numerous uncertainties constrained by testing time and expenses. The present study endeavors to ascertain the optimal parameters dictating aerogel fabric thermal resistance post-washing and establish a prediction model based on these variables using small-sample data. Four aerogel fabric candidates were selected and subjected to multiple washing cycles (0, 1, 5, 10, 15, and 20 cycles). Gray relational analysis (GRA) was initially employed to prioritize the primary thermal resistance parameters, thereby identifying the interrelations among various factors and circumventing the unreasonable equal treatment of samples in conventional gray predictions. Subsequently, a discrete gray linear regression (DGLR) algorithm was proposed and validated to estimate thermal resistance using input from four principal fabric parameters: the fabric weight, thickness, air permeability, and surface temperature distribution coefficient. The findings revealed that the GRA-DGLR model achieved relatively high accuracy, closely aligning with the experimental results. Following repeated washing, aerogel fabric thermal resistance diminished, with the air permeability, weight, thickness, and surface temperature distribution coefficient ranked in descending order of significance. This investigation highlights the considerable impact of repeated washing on aerogel fabric thermal resistance and the efficacy of the GRA-DGLR model in estimating this parameter.

Preparation of para-aramid aerogel fiber structurally colored by light scattering through wet spinning and supercritical drying

This research is an investigation of the preparation conditions for para-aramid aerogel fibers that are structurally colored by Rayleigh scattering, an angle-independent structural color. It is well known that structural color has the angle dependence of colors. However, there is currently a desire for materials with angle-independent structural color. During the fibers’ spinning process, the microstructures of the fibers are generated. The effect of spinning conditions is investigated by measuring the optical properties of the wet gel fibers. The neutralization speed of negatively charged PPTA fibrils has a significant impact on the formation of the dense microstructure. Spinning under the fast neutralization speed condition makes it possible to achieve the blue-colored fiber derived from Rayleigh scattering. The influence of neutralization speed on the microstructure of the fibers is confirmed by FE-SEM characterization. Furthermore, spinning using a narrow inner diameter needle decreases the whiteness component derived from Mie scattering of the fibers, resulting in a more vivid blue color. The angle-independent structurally colored fibers hold great promise for application in clothing, interiors, and industrial materials.

PVA/sodium alginate multi-network aerogel fibers, incorporated with PEG and ZnO, exhibit enhanced temperature regulation, antibacterial, thermal conductivity, and thermal stability

This paper presents a novel approach for the fabrication of polyvinyl alcohol (PVA)/sodium alginate (SA) aerogel fibers with a multilayered network structure using wet spinning and freeze-thaw cycling techniques. The multiple cross-linking networks regulate the pore structure, leading to the formation of stable and tunable multilevel pore architectures. PEG and nano-ZnO were successfully loaded onto the PVA/SA modified aerogel fibers (MAFs) using vacuum impregnation. MAFs exhibited excellent thermal stability at 70 °C without leakage after 24 h of heating. Furthermore, MAFs demonstrated excellent temperature regulation performance, with a latent heat of 121.4 J/g, which accounts for approximately 83 % of PEG. After modification, the thermal conductivity of MAFs was significantly improved, and they exhibited excellent antibacterial properties. Therefore, MAFs are expected to be widely used in intelligent temperature-regulating textiles.