Nanofibrous Aerogels Research Articles

Nacre‐Mimetic Multi‐Mechanical Synergistic Ceramic Aerogels with Interfacial Bridging and Stress Delocalization

AbstractElastic ceramic aerogels are exceptionally suitable for thermal insulating applications, but lacking multi‐mechanical synergistic high strength remains a deficiency. Inspired by the robust protective shells of mollusks in nature, which feature distinct hierarchical ordered structures, exhibiting strong and tough mechanical properties, a system construction and structural governing strategy is proposed to allow the nanostructure to assemble strong and flexible ceramic aerogels. Through the design of a hierarchical multi‐arched structure configurated binary‐soldering‐assemble interfacial topology interlocking, concentrated stress is effectively discrete. This biomimetic strategy enables the effective dissipation of mechanical energy, resulting in ceramic aerogels with exemplary compressive resilience, bendability, tensile resistance, and their strength exceeding that of other nanofibrous aerogels by up to tenfold. Additionally, the flexible aerogels also show remarkable thermal resistance from −196 to 1100 °C and superior thermal insulation capabilities (39.72 mW m−1 K−1), making them more suitable for the applications.

Fabrication of highly carboxylated nanofibrous aerogels under mild conditions and their protein adsorption performance

The development of high-performance media for protein adsorption in bio-purification is highly desired, particularly in biological pharmaceuticals. In this study, we demonstrate a simple, versatile and mild strategy to construct a nanofibrous aerogel (NFA)-based adsorption media for protein purification. Pyromellitic dianhydride (PMDA) was selected to in-situ graft onto poly(ethylene-co-vinyl alcohol) (PE-co-PVA) nanofibers in aerogels through liquid phase grafting. The obtained PE-co-PVA/PMDA NFAs (PPNAs) possessed superb underwater elasticity, compression fatigue resistance and shape-memory performance. With an open porous network, abundant adsorption ligands, and surface hydrophilicity, the PPNAs exhibited a significant adsorption capacity of 1019.71 mg/g and a short equilibrium time of 3.0 h, surpassing that of commercial and reported nanofiber-based adsorbents. Additionally, the PPNAs demonstrated good dynamic adsorption performance for protein driven solely by gravity. Furthermore, the PPNAs showed reusability, selectivity, acid and alkaline resistance, and practical potential of extracting lysozyme form egg white solution. The successful scale-up of such aerogel-based adsorbents can open up new way for the development and design of next-generation protein adsorption media for bio-purification applications.

Elastic and layered carbon/silica composite nanofibrous aerogels through solution blow spinning

Carbon fibrous aerogels, distinguished by low density, outstanding mechanical properties and thermal stability, hold great promise for applications in aerospace, military, and environmental protection. However, large-scale production and precise structure control of carbon fibrous aerogels present significant challenges. Herein, solution blow spinning combined with rotating receiving apparatus was employed to fabricate elastic lamellar carbon/silica nanofibrous aerogels (CSNFAs). The utilization of receiving apparatus for traction enabled efficient assembly of PAN nanofiber networks into layered and stacked structure. Interlayer spacing of CSNFAs could be finely tuned within range of 30–250 μm by adjusting speed with range of 500–1000 RPM. The mesoporous architecture of CSNFAs, along with their intrinsic properties, significantly enhanced adsorption capabilities. Integration of lamellar structure enabled precise control over thermal stability. Capitalizing on laminated structure, CSNFAs exhibited excellent compressive elasticity while maintaining exceptional super elasticity across extreme temperatures ranging from 600 °C to −196 °C. CSNFAs guaranteed reliable performance across a wide temperature range and supported repeated use.

Multiphase Symbiotic Engineered Elastic Ceramic-Carbon Aerogels with Advanced Thermal Protection in Extreme Oxidative Environments.

Elastic aerogels can dissipate aerodynamic forces and thermal stresses by reversible slipping or deforming to avoid sudden failure caused by stress concentration, making them the most promising candidates for thermal protection in aerospace applications. However, existing elastic aerogels face difficulties achieving reliable protection above 1500°C in aerobic environments due to their poor thermomechanical stability and significantly increased thermal conductivity at elevated temperatures. Here, a multiphase sequence and multiscale structural engineering strategy is proposed to synthesize mullite-carbon hybrid nanofibrous aerogels. The heterogeneous symbiotic effect between components simultaneously inhibits ceramic crystalline coarsening and carbon thermal etching, thus ensuring the thermal stability of the nanofiber building blocks. Efficient load transfer and high interfacial thermal resistance at crystalline-amorphous phase boundaries on the microscopic scale, coupled with mesoscale lamellar cellular and locally closed-pore structures, achieve rapid stress dissipation and thermal energy attenuation in aerogels. This robust thermal protection material system is compatible with ultralight density (30mg cm-3), reversible compression strain of 60%, extraordinary thermomechanical stability (up to 1600°C in oxidative environments), and ultralow thermal conductivity (50.58mW m-1 K-1 at 300 °C), offering new options and possibilities to cope with the harsh operating environments faced by space exploration.

Butane Tetracarboxylic Acid Grafted on Polymeric Nanofibrous Aerogels for Highly Efficient Protein Absorption and Separation.

Developing high-performance and low-cost protein purification materials is of great importance to meet the demands for highly purified proteins in biotechnological industries. Herein, a facile strategy was developed to design and construct high-efficiency protein absorption and separation media by combining aerogels' molding techniques and impregnation processes. Poly (ethylene-co-vinyl alcohol) (EVOH) nanofibrous aerogels (NFAs) were modified by grafting butane tetracarboxylic acid (BTCA) over them in situ. This modification was carried out using polyphosphoric acid as a catalyst. The resulting EVOH/BTCA NFAs exhibited favorable comprehensive properties. Benefiting from the highly interconnected porous structure, good underwater compressive properties, and abundant absorption ligands, the obtained EVOH/BTCA NFAs possessed a high static absorption capacity of 1082.13 mg/g to lysozyme and a short absorption equilibrium time of about 6 h. A high saturated dynamic absorption capacity for lysozyme (716.85 mg/g) was also realized solely by gravity. Furthermore, EVOH/BTCA NFAs displayed excellent reusability, good acid and alkaline resistance, and unique absorption selectivity performance. The successful synthesis of such aerogels can provide a potential candidate for next-generation protein absorbents for bio-separation and purification engineering.

Highly Flexible and Superelastic Graphene Nanofibrous Aerogels for Intelligent Sign Language.

Highly flexible and superelastic aerogels at large deformation have become urgent mechanical demands in practical uses, but both properties are usually exclusive. Here a trans-scale porosity design is proposed in graphene nanofibrous aerogels (GNFAs) to break the trade-off between high flexibility and superelasticity. The resulting GNFAs can completely recover after 1000 fatigue cycles at 60% folding strain, and notably maintain excellent structural integrity after 10000 cycles at 90% compressive strain, outperforming most of the reported aerogels. The mechanical robustness is demonstrated to be derived from the trans-scale porous structure, which is composed of hyperbolic micropores and porous nanofibers to enable the large elastic deformation capability. It is further revealed that flexible and superelastic GNFAs exhibit high sensitivity and ultrastability as an electrical sensors to detect tension and flexion deformation. As proof, The GNFA sensor is implemented onto a human finger and achieves the intelligent recognition of sign language with high accuracy by multi-layer artificial neural network. This study proposes a highly flexible and elastic graphene aerogel for wearable human-machine interfaces in sensor technology.

Carbon Nanofibrous Aerogels Derived from Electrospun Polyimide for Multifunctional Piezoresistive Sensors.

The fabrication of carbon aerogels with ultralow density, high electrical conductivity, and ultraelasticity still remains substantial challenges. This study utilizes electrospun polyimide aerogel as the source to fabricate flexible carbon nanofibrous aerogel (PI-CNA) capable of multifunctional applications. The lightweight PI-CNA based piezoresistive sensor shows a wide linear range (0-217 kPa), rapid response/recovery time, and fatigue resistance (12,000 cycles). More importantly, the superior pressure sensing enables the PI-CNA for all-range healthcare sensing, including pulse monitoring, physiological activity detection, speech recognition, and gait recognition. Moreover, the EMI SE and the A coefficient of the PI-CNA reach 45 dB and 0.62, respectively, indicating the outstanding absorption dominated EMI shielding effects due to the multiple reflections and absorption. Furthermore, PI-CNA exhibits satisfying Joule heating performance up to 120 °C with rapid response time (10-30 s) under low supply voltages (1.5-5 V) and possesses sufficient heating reliability and repeatability in long-term repeated heating/cooling cycles. The fabricated PI-CNA shows significant potential applications in wearable technologies, energy conversion, electronic skin, and artificial intelligence.

Covalently Interconnected Thermoplastic Polymeric Nanofiber/Carbon Nanotube Composite Nanofibrous Aerogels for Piezoresistive Sensors

Covalently Interconnected Thermoplastic Polymeric Nanofiber/Carbon Nanotube Composite Nanofibrous Aerogels for Piezoresistive Sensors

Graphene‑Assisted Assembly of Electrically and Magnetically Conductive Ceramic Nanofibrous Aerogels Enable Multifunctionality

AbstractCeramic aerogels are gaining increasing attention due to their low density, high‐temperature resistance, and excellent chemical stability. However, conventional ceramic aerogels are hindered by their intrinsic brittleness and limited dielectric properties, which restrict their scalable manufacturing and multifunctional applications. Here, ultralight, biomimetic porous, electrically and magnetically conductive ceramic nanofibrous aerogels composed of silicon dioxide (SiO2) nanofibers, graphene, and metal–organic framework (MOF) derivatives are prepared through an ice‐templating freeze‐casting followed by annealing approach. The renewable SiO2 nanofibers form robust bonding points with graphene, constructing interconnected high‐porosity aerogels with good mechanical resilience. This allows for efficient integration of MOF‐derived magnetic nanoparticles associated with a synergistic mechanical enhancement. The synergies of the dielectric and magnetic components, combined with the uniformly arranged sheet‐like cell walls which facilitate the outstanding electromagnetic wave absorption performance. Moreover, the hydrophobic ceramic aerogels showcase excellent magnetothermal conversion, contributing to the application in wireless therapy, antibacterial, and magnetothermal deicing. Furthermore, the nanofibrous aerogels exhibit good thermal stability and insulation properties, rendering them highly suitable for thermal management devices in extreme conditions. With the renewable, convenient, and scalable manufacturing method, these multifunctional ceramic nanofibrous aerogels thus hold great promise in electromagnetic protection, wireless heating, and next‐generation thermal management devices.

Lightweight, Compressible, and Multifunctional Organic–Inorganic Nanofibrous Aerogels for Enhanced Microwave Absorption

Lightweight, Compressible, and Multifunctional Organic–Inorganic Nanofibrous Aerogels for Enhanced Microwave Absorption

An efficient fabrication method of lightweight aramid nanofibrous aerogels for high-efficient sound absorption and thermal properties

The aramid nanofibrous aerogels (ANFs) have various application prospects due to their ultra-light, high porosity and excellent properties of aramid fibers. However, the preparation of ANFs requires long preparation time and their ultra-dense pore structure leads to poor sound penetration and high sound energy reflectivity, which ultimately makes the overall sound absorption performance of ANFs poor. Therefore, a strategy for synthesis of ANFs is designed to achieve light weight, excellent thermal insulation performance and significantly improve sound absorption properties. This strategy combines cell pulverizing, pump-filtration molding, and directional freezing to ensure structural strength of the aerogel without the addition of cross-linking agents, and this process enables the ANFs to introduce in macro-pores while keeping nano-pores. The structure of multi-layered pores effectively reduces the reflectivity of incident acoustic energy and improves the sound absorption coefficient. The interconnected macro-pores and interlaced small pores of ANFs provide good sound absorption performance (sound absorption average (SAA) = 0.338), excellent flame retardant and thermal insulation properties (thermal conductivity = 0.0635 W (m*K)−1) with ultralight (density = 40.5 mg cm−3) in a thinner thickness (15 mm), which extend the potential of ANFs in areas of noise control and thermal insulation. In addition, the structure of multi-scaled pores can also be formed inside other aerogels by using the method of cell pulverization and filtration preparation, which can be helpful for improving their properties of thermal insulation and sound absorption.

Biomimetic Bouligand chiral fibers array enables strong and superelastic ceramic aerogels

Ceramic aerogels are often used when thermal insulation materials are desired; however, they are still plagued by poor mechanical stability under thermal shock. Here, inspired by the dactyl clubs of mantis shrimp found in nature, which form by directed assembly into hierarchical, chiral and Bouligand (twisted plywood) structure exhibiting superior mechanical properties, we present a compositional and structural engineering strategy to develop strong, superelastic and fatigue resistance ceramic aerogels with chiral fibers array resembling Bouligand architecture. Benefiting from the stress dissipation, crack torsion and mechanical reinforcement of micro-/nano-scale Bouligand array, the tensile strength of these aerogels (170.38 MPa) is between one and two orders of magnitude greater than that of state-of-the-art nanofibrous aerogels. In addition, the developed aerogels feature low density and thermal conductivity, good compressive properties with rapid recovery from 80 % strain, and thermal stability up to 1200 °C, making them ideal for thermal insulation applications.

Vapor phase synthesis of metal–organic frameworks on a nanofibrous aerogel creates enhanced functionality

Vapor-phase synthesis of metal–organic frameworks (MOFs) on nanofibrous aerogels provides a hierarchically porous and mechanically robust material platform for use in a multitude of applications, from carbon dioxide capture to heavy metal removal.

Lightweight, flexible, and conductive PEDOT:PSS coated polyimide nanofibrous aerogels for piezoresistive pressure sensor application

Conductive PEDOT:PSS-coated polyimide nanofibrous aerogels as piezoresistive pressure sensors.

Fatigue-resistant and thermal insulating polyimide nanofibrous aerogels with temperature-invariant flexibility and nanofiber–lamella crosslinking architecture

The PINAs with a novel nanofiber–lamella crosslinking architecture exhibited excellent thermal insulation, flexibility and elasticity over a wide temperature range (−196 to 300 °C).

Direct Synthesis of Polyimide Curly Nanofibrous Aerogels for High-Performance Thermal Insulation Under Extreme Temperature.

Maintaining human body temperature is one of the basic needs for living, which requires high-performance thermal insulation materials to prevent heat exchange with external environment. However, the most widely used fibrous thermal insulation materials always suffer from the heavy weight, weak mechanical property, and moderate capacity to suppress heat transfer, resulting in limited personal cold and thermal protection performance. Here, an ultralight, mechanically robust, and thermally insulating polyimide (PI) aerogel is directly synthesized via constructing 3D interlocked curly nanofibrous networks during electrospinning. Controlling the solution/water molecule interaction enables the rapid phase inversion of charged jets, while the multiple jets are ejected by regulating charge density of the fluids, thus synergistically allowing numerous curly nanofibers to interlock and cross-link with each other to form porous aerogel structure. The resulted PI aerogel integrates the ultralight property with density of 2.4mg cm-3, extreme temperature tolerance (mechanical robustness over -196 to 300 °C), and thermal insulation performance with ultralow thermal conductivity of 22.4mW m-1 K-1, providing an ideal candidate to keep human thermal comfort under extreme temperature. This work can provide a source of inspiration for the design and development of nanofibrous aerogels for various applications.

Multiscale Synergetic Bandgap/Structure Engineering in Semiconductor Nanofibrous Aerogels for Enhanced Solar Evaporation.

Solar-driven interface evaporation has been identified as a sustainable seawater desalination and water purification technology. Nonetheless, the evaporation performance is still restricted by salt deposition and heat loss owing to weak solar spectrum absorption, tortuous channels, and limited plane area of conventional photothermal material. Herein, the semiconductor nanofibrous aerogels with a narrow bandgap, vertically aligned channels, and a conical architecture are constructed by the multiscale synergetic engineering strategy, encompassing bandgap engineering at the atomic scale and structure engineering at the nano-micro scale. As a proof-of-concept demonstration, a Co-doped MoS2 nanofibrous aerogel is synthesized, which exhibits the entire solar absorption, superhydrophilic, and excellent thermal insulation, achieving a net evaporation rate of 1.62 kg m-2 h-1 under 1 sun irradiation, as well as a synergistically efficient dye ion adsorption function. This work opens up new possibilities for the development of solar evaporators for practical applications in clean water production.

A strategy to fabricate hierarchical microporous architecture of polyimide nanofibrous aerogels with efficient electromagnetic wave absorption and thermal insulation

The aviation industry requires advanced aerogels that combine both electromagnetic wave (EM) attenuation and thermal insulation capabilities. This work involved the fabrication of Ti3C2Tx MXene/polyimide nanofibrous (PINF) aerogels through freeze-drying and thermal imidization. The hierarchical microporous architecture was formed by the interconnected primary pores induced by the removal of ice crystals and secondary pores from the PINF web. The unique highly porous 3D network of the nanofibrous aerogel provided well-matched impedance and enhanced multiple reflections and scattering of EM waves. The polar functional groups and defects on MXene induced dipole polarization, and the heterointerfaces between the PINFs and MXene enhanced the interfacial polarization. Consequently, the MXene/PINF aerogels exhibited efficient microwave absorption, showing a minimum reflection loss (RLmin) of −37.9 dB and an effective absorption bandwidth (EAB) of 3.3 GHz. Moreover, nanofibrous aerogels also exhibited low thermal conductivity and remarkable compression properties, making them suitable for utilization in complex environments.

Bacterial cellulose nanofibrous aerogels grafted with citric acid for absorption and separation of protein

Bacterial cellulose nanofibrous aerogels grafted with citric acid for absorption and separation of protein

Prediction of thermal conductivity for polyimide nanofiber aerogel based on three 3D FEM models

Polyimide (PI) nanofibrous aerogels (NFAs) have garnered significant attention for their exceptional mechanical and thermal properties, making them promising materials for heat insulation applications. However, there is a lack of comprehensive research on heat transfer of PI NFAs on the modeling and prediction. Therefore, three modified unit cells with the features of PI NFA backbone were constructed for the finite element simulation. Subsequently, the comparisons of our results with experimental data from available literature were conducted. It indicated that the cubic unit cell fitted well with the experimental values when the density was lower than [Formula: see text], while the Weaire–Phelan unit cell demonstrated good agreement when the density was higher than [Formula: see text]. A series of parametric studies were performed and indicated that the thermal conductivity is proportional to the nanofiber diameter, whereas inversely proportional to the pore size and porosity. Our research will provide novel insights to the selection of parameters for industrial manufacturing of thermal insulation materials in aerospace, energy, protection, etc.