Composite Aerogels Research Articles

Graphene-wrapped (Ni,Co)Se2 carbon nanowires toward high performance hybrid supercapacitors

To probe the next generation of flexible supercapacitors for practical application, small size, excellent electrical conductivity, low cost, Eco-friendly and excellent capacitance are prerequisites. However, due to dissatisfied electrical conductivity, limited surface area and low porosity, which results in few active sites and long ion transport channels, electrochemical improvements are needed for bimetallic selenide-based flexible supercapacitors. Hence, novel three dimensional graphene (3DG) encapsulated cobalt-nickel selenide carbon nanowires [3DG/(Co,Ni)Se2 CNWs] composite aerogels was successfully fabricated through a modified self-templating approach. The assembled 3DG/(Co,Ni)Se2 CNWs electrode showcases outstanding electrochemical performance, achieving a high specific capacitance of 1286 F g−1 at 1 A g−1 attributed to its combination structure of carbon based materials and nanowires. It demonstrates excellent cycling stability, with a capacity retention of 88 % after 3000 cycles at 2 A g−1. The prepared 3DG/(Co,Ni)Se2 CNWs//active carbon (AC) asymmetric flexible all-solid-state supercapacitors demonstrates outstanding electrochemical properties, achieving an energy density of up to 28 Wh kg−1 at a power density of 800 W kg−1. Even after 6000 cycles at 5 A g−1, it retains 84.15 % of its specific capacitance, thus presenting a new direction for energy storage applications.

Enhancing the properties and morphology of starch aerogels with nanocellulose

The following study deals with the preparation of starch and starch-cellulose aerogels. The addition of cellulose nanocrystals and bacterial nanocellulose to starch led to composite aerogels with remarkable properties, e.g., high surface areas, high adsorption capacities, and outstanding morphological characteristics. Specific surface areas up to 220 m2/g have been reached. As the content of the nanocellulose in the aerogels increased, the textural, thermal, and morphological properties improved significantly. The behavior of the starch and starch-cellulose aerogels was studied, to investigate their swelling behavior and stability in aqueous media. Lastly, the aerogels were impregnated with xanthohumol and usnic acid. The presence of cellulose improved the aerogel sorption capacity and the xanthohumol intake. The impregnated aerogels preserved highly porous and sophisticated structures.

In situ growth of HKUST-1 on electrospun polyacrylonitrile nanofibers/regenerated cellulose aerogel for efficient methylene blue adsorption

Dyes, as organic pollutants, are causing increasingly severe environmental problems. Metal-organic frameworks (MOFs) are considered promising dye adsorbents; however, their application is limited due to their powder or solid particle forms and limited reusability. Therefore, this study proposes an innovative approach to develop a novel MOF-based composite aerogel, specifically a HKUST-1/polyacrylonitrile nanofibers/regenerated cellulose (HKUST-1/PANNs/RC) composite aerogel adsorbent, for the adsorption of pollutants in water. This adsorbent was successfully prepared using a simple method combining covalent crosslinking, quick freezing, freeze-drying, in-situ growth synthesis, and solvothermal techniques. The HKUST-1/PANNs/RC composite aerogel exhibits a significantly large specific surface area, which is approximately 64 times greater than that of PANNs/RC (10.45 m2·g−1), with a specific surface area of 669.9 m2·g−1. The PANNs serve as a support framework, imparting excellent mechanical properties to the composite aerogel, enhancing its overall stability and recoverability. Additionally, the composite aerogel contains numerous -COOH and -OH groups on its surface, providing strong acid resistance and facilitating interactions with pollutant molecules through electrostatic interactions, π-π conjugation, n-π* interactions, and hydrogen bonding, thereby promoting the adsorption process. Using methylene blue (MB) as a probe molecule, the study results demonstrate that the HKUST-1/PANNs/RC composite aerogel has an adsorption capacity of 522.01 mg·g−1 for MB (25 h), exhibiting excellent adsorption performance. This composite aerogel shows great potential for application in water pollution control.

Preparation and electromagnetic wave absorption properties of CAU-Al MOF and graphene oxide aerogel composites

The application of microwave technology has penetrated all aspects of life, but also lead to the electromagnetic pollution, therefore the research of high efficiency microwave absorption materials has been widely concerned. In this work, a new type of Al based CAU-10-H MOF was prepared by hydrothermal method. The particles were polyhedral in size of 2 [Formula: see text]m. After high temperature annealing, the interplanar spacing increased with the annealing temperature, and the lattice structure was destroyed at 400°C. CAU-Al/rGO aerogels were prepared by freeze-drying of hydrogels. With the increase of CAU-Al content and the annealing temperature, the carbon crystallinity decreases, and the pores of the aerogels became larger and fluffier. The real parts of permittivity of CAU-Al/rGO aerogels were between 5 and 30, which can be tuned by the annealing temperature and CAU-Al content. For the microwave absorption performance, the CAU-Al/rGO aerogel with a ratio of 3:1 achieved the minimum reflection loss of −37.8 dB at 3 mm. Moreover, the CAU-Al/rGO aerogels showed a wide effective bandwidth, which reached 5.1 GHz under the thickness of 2.5 mm. Therefore, the CAU-Al/rGO aerogels could be used as a kind of broadband microwave absorber with excellent microwave absorption performance.

Coupled physicochemical dual-crosslinking Ti3C2Tx composite aerogels for the selective adsorption of gallium ions in acid fly ash leaching

Herein, in order to extract Ga3+ from acid fly ash leaching, we propose a functionalized Ti3C2Tx-based MXene composite aerogel adsorbent for Ga3+ adsorption. The prepared physicochemical dual-crosslinking network aerogel MPHG-40 possesses good Ga3+ adsorption performance (132.52 mg g−1) at the pH of 3 and Ga3+ initial concentration of 50 mg L−1 within 6 h. After five adsorption-desorption cycles, the material shows good mass retention and a 95.65 % retention of its initial adsorption capacity, compared to most reported adsorbents. The optimized adsorbent realized good selective adsorption of Ga3+ against Cu2+, Zn2+, Fe3+, and Al3+ in a simulated acid fly ash leaching with the selective coefficient of 8.63, 96.10, 4.49, and 28.30, respectively. The adsorption may comply with a combined mechanism of physical adsorption, electrostatic interactions, ion-exchange mechanism, and ligand chelation, dominated by chemical adsorption, as identified by theoretical calculations based on density functional theory and experimental data. The three-dimensional solid adsorbent constructed in this study provides a new strategy for selective adsorption of Ga3+, making it possible to be applied to solid waste utilization of fly ash.

Super-flexible and low-shrinkage polyimide aerogel composites with excellent thermal insulation: Boosted by SiO2 micron aerogel powder

Polyimide (PI) aerogel composites were synthesized using 4,4′-diaminodiphenyl ether (ODA) and 1,3-bis(4-aminophenoxy)neopentane (BAPN) as diamine monomers, and biphenyl-3,3′,4,4′-tetracarboxylic dianhydride (BPDA) as dianhydride monomers. This study examined the impact of varying proportions of SiO2 micron aerogel powder and the addition of BTC on the properties of the composites. The prepared composites showed ultra-high flexibility (180° folded) with the thickness of 3–4 mm, high thermal stability (95 % weight retention at 501 °C) and thermal insulation performance with ultralow thermal conductivity of 0.033 W/(K·m).

Binary surfactant-optimized silica aerogel slurries for building materials: Effects of formulation and content

Developing silica aerogel slurries is a strategic approach for incorporating silica aerogels into matrix materials to enhance the efficiency of aerogel composites. This study introduces a novel binary surfactant mixture, using a 1:4 ratio of polyether L62 and CTAC, optimized for the performance of aerogel slurries. Our extensive testing reveals that this formulation significantly reduces the surface tension to 24.25 mN/m and achieves a remarkable thermal conductivity of 26.7 mW/m/K, while maintaining high hydrophobicity with a contact angle exceeding 125°. The slurries exhibit a wet density of 0.48 g/cm³ and a dry density of 0.098 g/cm³, emphasizing the lightweight nature of the aerogel composites. Additionally, the study illustrates that while increasing the surfactant concentration optimally raises the aerogel content, excess surfactant adversely affects the thermal insulation properties. Microstructural analysis confirms that the binary surfactant mixture effectively modifies the aerogel surface, overcoming the dispersal limitations associated with aerogel's hydrophobic groups. This breakthrough in slurry formulation greatly enhances both the insulating and water-repellent capabilities of silica aerogels, offering a viable engineering solution for developing high-performance aerogel composites for thermal insulation applications.

Novel atmospheric pressure drying method for silica-based aerogel insulation: Inspired with the adult process of damselflies

The high production cost and extremely weak mechanical properties of SiO2 aerogels have been two major challenges hindering its widespread application. Atmospheric pressure drying (APD) has always been regarded as the optimal process to reduce costs. However, traditional APD is cumbersome, still uses a large amount of expensive raw materials, and is extremely immature. In this study, a novel APD was developed, inspired by the wing changes during adult damselfly process. Inorganic silica source/water was used as the raw material, and CO2 was used instead of low surface tension solvent to stabilize the aerogel skeleton structure in situ, and ultimately aerogel material was obtained. The thermal conductivity of pure aerogels was as low as 0.0264 W/(m·K), the porosity reached 94.7 %, and the preparation cycle was only 28.5 h. The thermal stability of the skeleton structure and the chemical stability of surface were investigated and showed the hydrophobicity to withstand temperatures up to 400 °C. Aerogel composites feature low thermal conductivity of 0.0283 W/(m·K), and prominent thermal insulation properties over a wide temperature range of 50–300 °C. For traditional APD, this method shortens preparation cycle by 1–6 times. Compared with the commercial aerogel, the cost is reduced by 38.2 %, and the process is simple and environmentally friendly under the premise of ensuring excellent performance.

Underoil superhydrophilic nanofiber-based composite aerogels for efficient separation of water/oil mixtures and water-in-oil emulsions

Oily wastewater has caused serious environmental problems. To achieve efficient separation of oil/water mixtures and surfactant-stabilized water-in-oil emulsions, electrospinning, directional freeze-casting and thermal treatment techniques were combined to fabricate anisotropic and aligned nanofiber-based composite aerogels with underwater superoleophobicity and underoil superhydrophilicity. No toxic crosslinking agents or organic solvents were used during the whole fabrication process. The composite aerogels without any surface modification possessed the ability to selectively absorb water from oil/water mixtures to realize effective separation oil and water. Furthermore, the composite aerogels could separate surfactant-stabilized water-in-oil emulsions by gravity-driven filtration. When used for gravity-driven separation of Span80 stabilized water-in-petroleum ether emulsion, the flux and corresponding separation efficiency reached 2423 L·m−2·h−1 and 99.8 %, respectively. The used composite aerogel could be readily recycled by rinsing and freeze-drying without using any organic solvent, because it displayed underoil superhydrophilicity and excellent anti-oil property. Differing from the separation materials that have been previously documented, the nanofiber-based composite aerogels could act as both absorption materials and gravity-driven filtration materials. In summary, the composite aerogels developed in this study show great potential for efficient separation of oil and water.

Thermal insulating performance of thermal protection system with sandwich structure based on Al2O3/SiC composites aerogels

The thermal protection system (TPS) are an indispensable component of aerospace vehicles that can withstand harsh aerothermal conditions during the reentry process. Recently, the sandwich structures of TPS have been widely used to meet the development trend of structure-performance integrated design. In this study, a TPS with a sandwich structure based on Al2O3 aerogels reinforced by SiC nanowire are proposed. The Al2O3/SiC composites aerogels are synthesized via the low-cost method, including sol-gel, freeze-casting and high-temperature treatments processes. The microstructure, phase composition, thermal insulation and compressive resistance of composite aerogels at different SiC nanowires content are investigated in detail. The resulting Al2O3/SiC composites aerogels, exhibiting better compressive strength and thermal stability with the increase of SiC nanowires content, achieve the purpose of being an excellent thermal insulation material of TPS at high temperature. The characterization of thermal insulating performances of the TPS are also evaluated by the oxyacetylene torch testing. The TPS shows extraordinary high-temperature resistance, and the average linear ablation rate and mass ablation rate are 0.0032 mm/s and 0.005 g/s, respectively, which can satisfy the requirement of TPS for aerospace vehicles under ultra-high temperature conditions.

Investigation of synergistic effects incorporating esterified lignin and guar gum composite aerogel for sustained oil spill cleanup

The recently developed aerogel demonstrates a high capacity for pollutant absorption, making it an environmentally friendly option for oily water treatment. In an effort to reduce the adverse effects of the black liquor accumulation in the pulp industry, this study focused on utilizing the mentioned abundant bio-resource lignin, which can be applied to various high-value applications such as 3D porous materials for oil spill cleanup. Lignin, precipitated from the black liquor, was esterified using maleic anhydride as the esterifying reagent to enhance the hydrophobicity. Then, the composite aerogel fabricated from esterified lignin and guar gum (GG) was successfully prepared through the facile freeze-drying, using glutaraldehyde (GA) as the cross-linker. The resulting aerogel exhibited high porosity values exceeding 95%, low density (27.4 mg/cm3), and an impressive absorption capacity of 32.5 g/g for sunflower oil. These results demonstrate the potential of black liquor utilization as a bio-waste source of lignin and highlight the cost-effective guar gum-esterified lignin composite aerogel, which exhibits remarkable oil absorption capabilities and environmental sustainability promotion.

Multiscale characterization of effective mechanical properties of graphene-chitosan composite aerogels

This work reports on numerical characterizations of effective mechanical properties associated with graphene-polymer composite aerogels produced using an environmentally friendly freeze-drying process. To this purpose, a multiscale approach was implemented, in which geometrical configurations were constructed based on the results of experimental characterizations. A homogenization procedure based on molecular mechanics, the Milton method, and the asymptotic homogenization method was applied. In the asymptotic homogenization method, cell problems were formulated and solved within a representative volume element using the finite element method. After validating the numerical model through experimental results from compression tests, a parametric study on the influence of microstructural parameters of the materials, such as dispersion state, aspect ratio, volume fraction of nanoinclusions, and material porosity, on the macroscopic mechanical behavior of the composite aerogels was conducted. The simulation results provided a deeper understanding of the mechanisms that enhanced the mechanical properties of such aerogels by adding various graphene derivatives, allowing for adjustments in the elaboration process to obtain materials with improved mechanical properties.

Facile synthesis of ternary potato-like Bi2O2CO3/β-Co(OH)2 wires/carbon aerogel heterostructures for supercapacitor applications

Advanced carbon-based materials supported by metal oxides are considered as potential candidates to achieve sustainable, green, and low-cost electrode materials for energy storage devices. Herein this work Bi2O2CO3/β-Co(OH)2/carbon aerogel composite has been successfully prepared via a simple solvothermal approach. The structural characterizations indicate a uniform and numerous potato-structured Bi2O2CO3 and β-Co(OH)2 nanowires anchored on carbon aerogel. In addition, the presence of carbon aerogel between Bi2O2CO3 and β-Co(OH)2 can effectively improve the ion transportation mechanism and also provide the regular framework for material stabilization. By combining these advantages, the synthesized materials modified with nickel foam as a working electrode delivers a higher specific capacitance value of 621.52 Fg−1 at 2 Ag−1 with a good capacitance retention of 97 % after the incessant 5000 cycles test. Such remarkable electrochemical results suggest the promising applications of Bi2O2CO3 and β-Co(OH)2 on stabilized carbon aerogel as alternate electrode material for supercapacitor applications.

Low-density, large-sized SiCnw/SiOC composite aerogels with excellent thermal insulation, microwave absorption, and thermostability

Polymer-derived ceramic aerogels are promising materials for thermal insulation and microwave absorption in harsh environments because their microstructures can be controlled at the molecular level. Silicon oxycarbide (SiOC) aerogels are considered as potential high-temperature electromagnetic wave (EMW) absorbers, but their application range is limited by complex preparation process and unsatisfactory microwave-absorption performance. This paper reports a new SiC nanowire/SiOC composite aerogel (SCA) synthesized through the sol–gel process, environmental pressure drying, and high-temperature treatment. The SCA performance is adjusted by controlling the ratio of SiC nanowires, obtaining low thermal conductivities (0.04–0.042 W m−1 K−1) and excellent mechanical properties (4.37–5.45 MPa). Increasing the SiC nanowire content gradually increases the EMW absorption capacity of SCA. The optimal reflection loss is −53.64 dB and the effective absorption bandwidth is 3.88 GHz, substantially higher than that of SiOC aerogels. This high performance is mainly attributable to the appropriate impedance matching characteristics and strong polarization loss ability. Moreover, the performance of the composite aerogels was retained after long-term treatment in an air environment at 800 °C. SCA also exhibits excellent high-temperature insulation and flame retardancy. Owing to its light weight, strong microwave-absorption ability, good thermal insulation performance, and oxidation resistance, SCA is a highly promising alternative material for use in extreme environments.

Intelligent Tunable Wave-Absorbing CNTs/VO2/ANF Composite Aerogels Based on Temperature-Driving.

The development of new electromagnetic absorbing materials is the main strategy to address electromagnetic radiation. Once traditional electromagnetic wave-absorbing materials are prepared, it is difficult to dynamically change their electromagnetic wave-absorbing performance. Facing the complexity of the information age and the rapid development of modern radar, it is significant to develop intelligent modulation of electromagnetic wave-absorbing materials. Here, CNTs/VO2/ANF composite aerogels with dynamic frequency tunability and switchable absorption on/off were synthesized. Based on the phase change behavior of VO2, the degree of polarization and interfacial effects of multiple heterogeneous interfaces between VO2 and CNTs and aramid nanofibers (ANFs) were modulated at different temperatures. With the increase in temperature (from 25 to 200 °C), the maximum absorption frequency of the frequency tunable aerogel is modulated from 12.24 to 8.56 GHz in the X-band, and the absorption intensity remains stable. The maximum effective switching bandwidth (ΔEAB) of the wave-absorbing switchable aerogel is 3.70 GHz. This study provides insights into intelligent electromagnetic wave absorption performance and paves the way for temperature-driven application of intelligent modulation of electromagnetic absorbers.

Chitosan aerogel loaded with biogenic palladium nanoparticles CH/Pd NPs exert antibacterial activity and wound addressing application in vitro and in vivo against bacterial skin infections

Bacterial skin infections that infect wounds and burns are considered one of the most serious medical problems that lead to delay wound healing, toxicity and even death. Therefore, there is an urgent need to develop an effective pharmaceutical material that promotes the treating of skin bacterial infections. Within this, we aimed in this study to synthesis and assess the effectiveness of novel chitosan/palladium nanoparticles (CH/Pd NPs) aerogel composites in treating bacterial skin infections and wound healing. Green method was employed for synthesis of Pd NPs using Allium sativum (A. sativum) extract, while crosslinking process and freeze-drying cycle were utilized for preparation of CH/Pd NPs aerogel composites. The prepared Pd NPs and CH/Pd NPs aerogel composite were thoroughly characterized using UV–vis, FTIR, XRD and SEM. The GC–MS analysis revealed that the main components in the A. sativum were diallyl disulfide (55.88 %) and diallyl trisulfide (24.34 %) which were among the four identified components. Additionally, the total phenols and flavonoids contents were 61.3 mg GAE/100 g and 18.8 mg QE/100 g, respectively. The swelling capacity of CH/Pd NPs aerogel microspheres reach 400 % with blood compatibility and slightly hemolysis ratio about 0.4 %. In vitro, the antibacterial studies demonstrated that loading Pd NPs with CH aerogel microspheres enhanced their effectiveness against MDR bacteria with complete inhibition for all bacterial strains growth. The CH/Pd NPs aerogel microspheres exhibited a significant inhibitory effect on biofilm formation. The biofilm inhibition percentage was found to be 87 % against the biofilm of S. aureus and 80 % against the biofilm of P. aeruginosa. In vivo infection model in rats, CH and CH/Pd NPs aerogel films stimulated skin tissue formation and healing wounds completely in 6 days with highly reduced in MDR and biofilm producing bacterial count. Finally, CH/Pd NPs aerogel composites represent a promising therapeutic strategy for the effective and enhanced healing of infected wounds.

Ultra-light, ultra-resilient and ultra-flexible, multifunctional composite carbon nanofiber aerogel for physiological signal monitoring and hazard warning in extreme environments

The emergence of multimodal wearable flexible self-powered electronic devices undoubtedly plays a positive role in areas such as healthcare and energy. However, the preparation of three-dimensional elastic bodies suitable for humidity, temperature, and pressure sensing often involves complex fabrication processes, internal network discontinuities, and difficulties in achieving applications in extreme environments. In this paper, a one-step preparation of three-dimensional fluffy and interlayer porous nanofiber precursors is achieved using direct electrostatic spinning technology. Subsequently, high-temperature calcination and in situ polymerization processes were used to obtain multifunctional composite carbon nanofiber aerogels (MCCNA), which are characterized by ultra-lightness, super elasticity, three-dimensional fluffiness, and interlayer porousness, and are suitable for extreme environments. The ultra-light (53.67 mg cm−3) MCCNA can accurately detect humidity signals over an extremely wide range (10 %RH to 95 %RH), with a minimum temperature response time of 0.5 K. Its pressure response time is only 20 ms, and even after 5000 cycles of pressure loading, it still maintains a stable electrical signal response. Most notably, through demonstration, MCCNA can monitor the actions of firefighters in high-temperature and complex situations such as fires. Furthermore, it can monitor and provide high-temperature warnings for the temperature thresholds in the microenvironment of firefighting suits. The developed self-powered flexible wearable electronic device holds outstanding prospects for applications in healthcare, energy, and extreme conditions.

Preparation and adsorption properties of cotton linters and coal-gangue-based cellulose/SiO2 composite aerogels

Preparation and adsorption properties of cotton linters and coal-gangue-based cellulose/SiO2 composite aerogels

In situ crosslinking of silica aerogel with reactive carbon fiber for high mechanical property, thermal insulation and superhydrophobicity

In this study, a novel silicon hydroxyl groups decorated long carbon chain grafted carbon fiber was synthesized, and a facile fabrication method was developed to produce reactive carbon fiber-silica aerogel composite with chemical crosslinking structure. Scanning electron microscopy images showed that silica aerogel matrix is wrapped on the surface of reactive carbon fibers. The reactive carbon fibers facilitated obstacle in shrinkage, and aerogel composites exhibited microporous behavior with average diameter of about 1.8 nm. Fourier-transform infrared and X-ray photoelectron spectroscopy confirmed the strong interfacial interaction between reactive carbon fibers and silica matrix. The modification mechanism of silicon hydroxyl groups decorated long carbon chain grafted carbon fiber, and the chemical crosslinking in aerogel composite were proposed. The reactive carbon fiber-silica aerogel composites synthesized in this work had been proved to have low density, excellent mechanical property, good tailoring performance, improved thermal stability, low thermal conductivity, high flame retardancy, high thermal insulation property, and superhydrophilicity. Hence, this work provided a theoretical basis for improving the performance and expanding the application of silica aerogel.

Experimental and molecular dynamics studies on thermal insulation at high-temperature of SiO2/Al2O3 composite aerogel

SiO2 aerogels have attracted significant attention due to numerous merits and unique physiochemical properties. However, it is challenging to work at high temperatures due to the weak thermal stability. Here, SiO2 aerogels enhanced by Al2O3 particles were prepared by sol-gel method in order to improve its thermal insulation property. The resulting SiO2/Al2O3 composite aerogels possessed porous three-dimensional pores and nano network skeleton structure. Due to the effective amalgamation of silicon and aluminum systems, the weight loss of SiO2/Al2O3 composite aerogels is less than 20% with the increase of temperatures, indicating that thermal stability is improved compared with the original SiO2 aerogels. By investigating temperature changes of specimens during heating processes, SiO2 aerogels with higher Al2O3 contents presents lower average temperature and slowly increase in temperature. This phenomenon illustrates that the Al2O3 particle in SiO2 aerogels can act as a barrier to insulate heat transfer. The effects of temperature, Al2O3 content, and strain on thermal insulation properties of SiO2/Al2O3 composite aerogels are calculated by molecular dynamics simulation method. Based on a series of computional experiments, the increases of temperature and strain have a negative influence on thermal insulation, however, Al2O3 content have a positive impact on this property which is well agreed with the experimental results. The deep understanding of the effects of the introduction of Al2O3 in SiO2 aerogels provides a method for creating excellent thermal insulation materials in heat protection field.