Superhydrophobic Aerogel Research Articles

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.

Facile synthesis of mechanically flexible and super-hydrophobic silicone aerogels with tunable pore structure for efficient oil-water separation

Silicone aerogels are promising in efficient thermal insulating and oil absorbent materials due to the low density, low thermal conductivity, and unique micro-/nano- porous structure. However, poor mechanical reliability and water repellency along with the complicated processing greatly hinder their potential applications in emerging fields. Herein, we report a lightweight, wide-temperature mechanically flexible and surface super-hydrophobic silicone aerogels with tuned cross-linked network via a facile ambient drying process. Poly (methylhydridosiloxane) (PMHS) with different hydrogen contents was utilized to react with vinylmethyldimethoxysilane under Pt catalyst via hydrosilylation reaction and thus tune the cross-linking network in silicone aerogel effectively. The optimized PMHS-based silicone aerogels as-prepared exhibit a low density of 70–150 mg cm−3, good mechanical reliability in both liquid nitrogen and high-temperature condition of 200 °C, excellent compressive resilience after 100 cyclic compressions, and outstanding surface water repellency with water contact angle of ∼165° and water sliding angle of <3°. As expected, such multi-functional PMHS aerogels show a better thermal insulating performance than the commercial polymer foam materials. Furthermore, the as-prepared silicone aerogels not only display outstanding absorption capacity for both floating and sunken oil/solvent but also demonstrate excellent continuous oil/water separation efficiency. Clearly, the versatile PMHS-based aerogel prepared in this work may provide a new route for the design and development of high-performance silicone aerogel materials.

Facile fabrication of corn stover-based aerogel for oil/water separation

Owing to the excellent adsorption capacity and high selectivity, aerogel have attracted considerable attention recently as promising sorbent materials for oil–water separation. Although many preparation methods for aerogel have been reported, green, facile, and low-cost fabrication is still a challenge. Herein, we reported the preparation of superhydrophobic and superoleophilic aerogel for oil and organic solvents collection from water. The crushed corn stover was treated with sodium hydroxide and hypochlorous acid to obtain the biomass cellulose fibers. The aerogels were produced using polyvinyl alcohol binder, followed by a freeze-drying method. It showed high porosity (98.26–99.01%) and low density (15.15–24.95 mg/cm3). After modified with hexadecyltrimethoxysilane by chemical vapor deposition, the aerogel exhibited superior superhydrophobicity and showed excellent adsorption capacity (75 g/g). The adsorbed oil and organic solvents can be recovered by extrusion or centrifugation, and the aerogel showed stable performance and excellent reusability. Besides, the aerogel can separate various water-in-oil emulsions with separation efficiencies up to 99.94% and flux as high as 5529 L•m−2•h−1. Taken together, the results illustrate that the aerogel hold promise for the fields of oil recovery and environmental protection.

Superhydrophobic hybrid silica-cellulose aerogel for enhanced thermal, acoustic, and oil absorption characteristics

Superhydrophobic hybrid silica-cellulose aerogel for enhanced thermal, acoustic, and oil absorption characteristics

Ultralight, compressive and superhydrophobic methyltriethoxysilane-modified graphene aerogels for recyclable and selective organic pollutants adsorption from water

Physical adsorption is considered to be a more effective, green and economical way to remove organic pollutants. However, it still remains a challenge to simultaneously obtain the adsorbent materials with low density, high adsorption capacity and selectivity, and superior elasticity to satisfy multiple reusing. Herein, we developed a one-step solvothermal co-assembly method to produce methyltriethoxysilane (MTES)-modified graphene aerogels (MGAs). The MGA possesses low density, high porosity, fantastic elasticity and high specific surface area. It can be completely recovered under 1,000 cyclic compression tests of 90 % high strain. The compressive and ultralight MGA could be used as adsorbent for various organic liquids with high capacity (290–620 g/g), exceeding most of previously reported absorption materials. The sorbed organic pollutants could be recovered through mechanical absorption-squeezing procedure. The MGA retains about 97% original absorption capacity after 20th cycles. Hydrophobic methyl groups of MTES were successfully grafted onto graphene oxide (GO), which solidified the frameworks of graphene aerogel and made the MGA a good candidate for selective oil/water separation. Consequently, this novel manufacturing method and excellent performance make the MGA exhibits remarkable application potential for water treatment.

Superhydrophobic, elastic and anisotropic cellulose nanofiber aerogels for highly effective oil/water separation

Nanocellulose-based aerogels have gradually attracted attention in the field of oil/water separation owing to their light weight, excellent absorption properties, and environmental-friendliness. Herein, we report a facile and easily scalable method for fabricating superhydrophobic, elastic and anisotropic cellulose nanofiber (CNF) aerogels. Directional freeze-drying, soaking in polydimethylsiloxane (PDMS) solution and heat treatment were applied to obtain anisotropic and aligned CNF-PDMS aerogel sheets and blocks with superhydrophobicity and high elasticity. The CNF-PDMS aerogel sheets could realize continuous oil/water separation by filtration with a flux up to 2800 L·m−2·h−1 and a separation efficiency of 99.9%. The CNF-PDMS aerogel blocks could separate the oil/water mixture by the absorption–extrusion, and could also be applied in real-time continuous oil/water separation by vacuum suction with a flux as high as 145 L·h−1·g−1 and a separation efficiency of 99.9%. Overall, our anisotropic CNF-PDMS aerogels are the promising materials for low-cost rapid oil/water separation in multiple separation pathways.

Synthesis of super-hydrophobic and self-cleaning magnetic graphene aerogel with excellent microwave absorption properties

The well-established structure and ultra-fine nanoparticles are vital for high-performance microwave absorption materials. Herein, three-dimensional hydrophobic graphene aerogels decorated with ultra-fine Fe3O4 nanocrystals composites (HGAFX, X stands for pyrolysis temperature) were successfully constructed via chemically self-assembly and in situ pyrolysis. Remarkably, the hybrids with only 5% filling contents exhibited excellent microwave absorption performance (MAP) in terms of both minimum reflection loss (RLmin) and effective absorption bandwidth (EAB), outperforming the most reported microwave absorbers. Moreover, the magnetic graphene aerogels composites possess strong hydrophobicity, endowing them attractive functions of self-cleaning, waterproof, anti-icing, and corrosion resistance. Importantly, experimental results and theoretical calculations indicate that superior MAP can be carried out by reasonably regulating the electromagnetic parameters. Considering the excellent absorption capacities, our strategy opened a novel way for anchoring ultra-small nanoparticles on graphene sheets as highly effective synergistic microwave absorbers at low filling contents.

Superior stable, hydrophobic and multifunctional nanocellulose hybrid aerogel via rapid UV induced in-situ polymerization

Nanocellulose-based aerogels are potential candidates for the various advanced fields, but the poor structural stability and hydrophily restrains the practical applications. Herein, we report a facile strategy to in-situ polymerizes the polydimethylsiloxane on the anisotropic nanocellulose/chitosan aerogel matrix via UV-induced thiol-ene click reaction in 30 s. A superhydrophobic and elastic nanocellulose-based aerogel with a “stiff-soft” double network structure was fabricated. The inherited porous anisotropic structure and chemical-bonded interlocking interface render the hybrid aerogels with ultralight (9.42 mg/cm3), high porosity (99.29%), and hydrophobicity (contact angle of ~168.0°). Moreover, the hybrid aerogel demonstrated robustness (321 kPa), brilliant elasticity (full recovery from 80% compression), outstanding structure stability (>1000 cycles of compression). The reported strategy paves a new way for fabricating high-performance nanocellulose-based aerogel used for thermal insulation and oil absorption in harsh conditions.

Superhydrophobic aerogel membrane with integrated functions of biopolymers for efficient oil/water separation

A novel type of superhydrophobic biopolymer aerogel membrane (T-SA/lignin x /rGO-MTMS) is prepared for purifying oily wastewater. • A novel type of superhydrophobic biopolymer aerogel membrane between lignin and sodium alginate (T-SA/lignin x /rGO-MTMS) was prepared. • Confirmation of cooperative interaction between lignin and sodium alginate. • Demonstration of high-efficiency cyclicity for oil/water separation. • Degradable oil/water separation membranes. Superhydrophobic membranes have been playing crucial role in efficient remediation of organic pollutants contaminated water, especially for oily discharged wastewater. Taking advantages of the inherent features of graphene oxide (GO), sodium alginate (SA) and lignin, a novel type of superhydrophobic biopolymer aerogel membrane (T-SA/lignin x /rGO-MTMS) was prepared by freeze-casting technique and subsequent chemical vapor deposition, during which trimethoxymethylsilane (MTMS) silylation growth was achieved for the supreme protuberance, leading to the formation of rough and hydrophobic surface that favorably looks like a hedgehog carrying apples. Due to the air cushion induced by cooperative interaction between rough lignin particles and SA of 3D porous network with gas as a dispersion medium, and crumpled GO nanosheets, as-fabricated membrane with integrated functions of biopolymers possessed superhydrophobic surface characteristics (WCA = 161°). More favorably, utilizing the inherent molecular features, lignin has been successfully employed to de-oxidize GO during this preparative concept. By virtue of the low-surface-energy reduced GO (rGO) and abundant protuberance, T-SA/lignin x /rGO-MTMS exhibited potential cycling performance even with 10 cycles of oil/water separation and oil sorption. This study might shed light on the value-added utilization of integrated functions of biopolymers for designing task-specific functional materials for various applications.

Superhydrophobic waste paper-based aerogel as a thermal insulating cooler for building

Daytime subambient radiative cooling is a most promising alternative to electricity-free building cooling. However, optical performance degradation arising from surface contamination and inevitable parasitic heat gain still pose unprecedented challenges to cool building at subambient temperatures. This paper proposed a superhydrophobic cellulose aerogel cooler (SHB-CAC) as building envelope by integrating self-cleaning capacity, passive daytime radiative cooling and thermal insulation to reduce environmental heat gain. The SHB-CAC demonstrates high solar reflectance (93%) and long-wave infrared emittance (91%), accomplishing a temperature drop of 8.5 °C lower than the ambient under sunlight of 800 W/m2 in the outdoor experiment. Notably, the SHB-CAC possesses low thermal conductivity (28 mW/(m∙K)) that suppresses parasitic heat gain from warmer surrounding and reduces cooling energy consumption. The self-cleaning property resulting from superhydrophobicity protects SHB-CAC from water wetting and dust contamination but also maintains its good surface radiation capacities under different humidity environment. A building energy simulation was conducted and results showed that 43.4% of cooling energy on average could be saved compared to the building baseline consumption, if SHB-CAC was widely used in China, indicating that the strategy of optical and thermal conductivity management of cooler has the potential to reduce the energy consumption of buildings.

Biomass poplar catkin fiber-based superhydrophobic aerogel with tubular-lamellar interweaved neurons-like structure

Superhydrophobic aerogels are attractive candidates in controlling oil spills. The major challenges for existing aerogels are the construction of mechanical endurance as well as accessible of building materials. Herein, a newfangled biomass superhydrophobic aerogel (M-PCF/CS) with both superior compressibility and oil caption speed is fabricated by assembling poplar catkin fiber (PCF) hollowed-out shell of 330 nm and chitosan (CS) into tubular-lamellar interweaved neurons-like structure. The resultant aerogels (porosity ~ 96.12%), with flexuous PCF as the elastic buffer and second-pore capillaries, exhibit large longitudinal and transverse compressibility, endurable fatigue tolerance, fast oil sorption rate with a capacity of 28.8–78.1 g/g at 5–25 s. In parallel, the aerogels are tolerant of NaCl, UV radiation, and organic solvents without superhydrophobic variation and a case of oil spill remediation via pump-supported experiment shows that the aerogels facilely achieve continuous oil recycling from seawater by 23052–43956 L·m–2·h–1. Furthermore, the resultant M-PCF/CS, with assistance of an oscillator, can be applied to separate oil/water emulsions with efficiency of 98.07–99.11%. The successful fabrication of this material provides a new design strategy for the construction of mechanically robust aerogels for speedy and economical cleanup of oil pollutants from water.

Superhydrophobic, Elastic and Anisotropic Cellulose Nanofiber Aerogels for Highly Effective Oil/Water Separation

Superhydrophobic, Elastic and Anisotropic Cellulose Nanofiber Aerogels for Highly Effective Oil/Water Separation

Superhydrophobic Aerogel Blanket with Magnetic and Solar Heating Effect Enables Efficient Continuous Cleanup of Highly Viscous Crude Oil

Superhydrophobic Aerogel Blanket with Magnetic and Solar Heating Effect Enables Efficient Continuous Cleanup of Highly Viscous Crude Oil

Superhydrophobic and Multifunctional Aerogel Enabled by Bioinspired Salvinia Leaf‐Like Structure

AbstractThe biomimetic exploration of functionalized materials is still of great importance to chemists and materials scientists, although the majority of the ingenious structures and functions of organisms are not simulated precisely. Here, taking inspiration from the strongly hydrophobic properties of the Salvinia leaf, a novel superhydrophobic and multifunctional aramid‐polyimide nanocomposite aerogel with Salvinia leaf‐like structures is fabricated (abbreviated to Bio‐ANFPI aerogel). The Bio‐ANFPI‐1 aerogel surface is covered with many of the generated spherical and hemispherical silica nanoparticles by a in situ siloxane polycondensation method, analogous to the Salvinia leaf surface, which facilitates the construction of the superhydrophobic aerogels (Bio‐ANFPI‐2) based on the Cassie‐Baxter model. It is found that the maximum stress and compressive modulus of the Bio‐ANFPI‐2 aerogel are improved by 174% and 245%, respectively. Further, the Bio‐ANFPI‐2 aerogel exhibits superhydrophobicity, with a water contact angle of 152° and a rolling angle of 8.3°. In addition, the aerogels possess a low thermal conductivity, excellent metal ion absorption capacity, and impressive absorption capacity of oil that maintained its initial value at ≈80% after 50 cycles at 88% compression. Overall, this work can enable a more general and practical manner of fabricating biomimetic high‐performance lightweight materials.

Preparation and characterization of super hydrophobic aerogels derived from tunicate cellulose nanocrystals

First time aerogels composite with super hydrophobic properties were developed by using tunicate cellulose nanocrystals (TCNC), which expanded the application scope of animal cellulose resources. In this study, the TCNC was firstly cross-linked with silica and methyltrimethylsilane (MTMS), further coated with fluorodopa to form an aerogel with super hydrophobic properties. The aerogel was characterized by scanning electron microscope (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectra (FT-IR), and X-ray photoelectron spectroscopy (XPS). Results indicated that the contact angle of aerogel was 158.7°, which showed good hydrophobicity. The composite aerogel has superior stability in wide pH range, after 72 h immersion in pH = 0 and 12 solutions, the contact angle was still greater than 150°. The aerogel shows excellent oil-water separation ability and it can be repeatedly used more than 10 times. The separation efficiency can all reach more than 90% for different water-oil mixtures. This synthesized super hydrophobic aerogels derived from tunicate cellulose has greatly extended the application of marine animal celluloses.

A facile method to prepare superhydrophobic nanocellulose-based aerogel with high thermal insulation performance via a two-step impregnation process

A facile method to prepare superhydrophobic nanocellulose-based aerogel with high thermal insulation performance via a two-step impregnation process

Lightweight, elastic and superhydrophobic multifunctional nanofibrous aerogel for self-cleaning, oil/water separation and pressure sensing

Developing a durable, lightweight, and robust aerogel with multifunctional characteristics is greatly desirable but remains challenging these days. Herein, an environment-friendly and original nanofibrous aerogel with integrative performance was constructed through the combination of nanofibrous aerogels’ forming technique and post-treatment modification approach. The obtained aerogel has a hierarchical porous structure consisting of flexible polyacrylonitrile nanofibers (PANF), a functional polyvinyl alcohol (PVA) polymer, conductive carbon nanotubes (CNTs), and hydrophobic octadecylamine functionalized reduced graphene oxide (ODA-rGO), endowing it with ultralow density (20.54 mg cm−3), superior compressibility and recoverability, outstanding fatigue resistance over 1000 cycles. The hydrophobic ODA-rGO coating imparts the hydrophilic PANF/CNT aerogel superhydrophobicity (154°), contributing to a splendid self-cleaning ability. Additionally, the aerogel was capable of realizing excellent oil/water separation performances. Both organic solvents and soybean oil could be adsorbed by the aerogel with high adsorption capacity (36.07 to 65.09 g g−1) and good stable in recycling as a result of its hierarchical porous structure and good hydrophobicity. It was noteworthy that the aerogel composite can be used as a piezoresistive sensor, exhibiting high sensitivity (33 kPa−1 in the range of 0–2 kPa), low detection limit (1% strain), fast response (160 ms), and good durability (over 1000 cycles). Further, it was demonstrated that the composite can be used to monitor various human activities in real time. These advantages make it an excellent candidate for smart garments, high-efficient oil/water separation and human motion detection.

Biomass-derived oriented neurovascular network-like superhydrophobic aerogel as robust and recyclable oil droplets captor for versatile oil/water separation

Using tubular kapok fibers (KF) and sodium alginate (SA) as the natural building block, we put forward a novel oriented neurovascular network-like superhydrophobic aerogel with robust dry and wet compression resilience by directional freeze-drying and chemical vapor deposition. In the block, SA forms aligned channel structures providing space for rapid oil transmission, while KF serves as vascular-like capillaries acting as instant “tentacle” to capture the tiny oil droplets in water, facilitating fascinating oil capture efficiency for versatile oil/water separation, The aerogel after dry and wet compression (under a strain of 60%) can recover 96.0% and 97.3% its original, respectively, facilitating stable oil recovery (81.1–89.8%) by squeezing, high separation efficiency (99.04–99.64%) and permeation flux separating oil contaminants from water. A pump-supported experiment shows the aerogel efficiently collecting oil contaminants from the water’s surface and bottom by 11503–25611 L·m−2·h−1. Particularly, the aerogel as robust oil droplets captor facilely achieves isolation of 99.39–99.68% emulsified oils from oil/water emulsions by novel oil trapping mechanism which simply involves exerting kinetic energy on emulsified oils through repeated oscillation, potentially indicating a simple and efficient alternative to membrane-based oily wastewater remediation via filtration.

Superhydrophobic graphene aerogel beads for adsorption of oil and organic solvents via a convenient in situ sol-gel method

Herein, superhydrophobic graphene aerogel beads (SGA beads) were fabricated by one-step in situ sol-gel method in coagulation bath containing octadecylamine (ODA). Through modification with ODA, long alkyl chain with low surface energy was grafted onto graphene oxide (GO) sheets and many nanoscale wrinkles were observed on the surface of graphene sheets, which afford a remarkable water contact angle of 153°. The SGA beads possessed low density (14.4 mg/cm3), high porosity (96.9%), and specific surface area of 18.49 m2/g. As expected, this macro-porous network structure presented excellent absorption capacity for oil and organic solvents, with a value of 52-178 g/g. Furthermore, the SGA beads displayed good elasticity (rebound under 70% strain) and oil/water selectivity. The adsorbed organic solvents could be recovered by continuous absorption-combustion process. Therefore, such a simple fabrication process and superior properties make the resulting SGA beads present great application potential towards spill oil and organic pollution cleanup.

Sustainable and superhydrophobic cellulose nanocrystal-based aerogel derived from waste tissue paper as a sorbent for efficient oil/water separation

Extraction of cellulose nanocrystals (CNCs) from wastes is a valuable strategy from the environmental and economical points of view. Herein, a novel and cost-effective method for the preparation of superhydrophobic, environmentally friendly, and recyclable bio-aerogel by freeze-drying the aqueous suspension of CNCs extracted from waste tissue paper and polyvinyl alcohol (PVA) in the presence of hydrolyzed tetraethyl orthosilicate (TEOS) sol has been developed for the first time. The highly porous (98.42 %), ultralow density (0.017 g/cm3), and superhydrophobic (WCA of 154.93°±4.14) CNCs/PVA/TEOS aerogel can selectively remove oily contaminants from water (BET surface area of 76 m2/g). The aerogel showed a high sorption capacity in the range of 69−168 g/g for 6 oils and 8 organic solvents. The reusability experiments showed the aerogel could maintain more than 92 % of its sorption capacity even after 20 cycles of sorption-squeezing. The cyclic compressive stress-strain tests confirmed the good mechanical properties of the aerogel with 89 % of shape recovery after 50 cycles. The CNCs/PVA/TEOS aerogel can be used as a recyclable sorbent for removing oils/organic solvents from water.