Network Of Aerogel Research Articles

Effects of crosslinker concentration on curing process and performances of needled fiber preform reinforced phenolic aerogel composite using process simulation and comprehensive experiments

A kind of needled quartz/carbon fiber preform reinforced phenolic aerogel composite (NQCF/PR) was fabricated through impregnating needled fiber preform with phenolic resin precursor solution, followed by sol–gel polymerization and solvent drying. The needled fiber preform serves as lightweight quasi-three-dimensional reinforcement, while phenolic aerogel matrix provides high porosity and low thermal conductivity. During fabrication of aerogel composite part using vacuum-assisted resin infusion process, distribution of crosslinker hexamethylenetetramine (HMTA) in precursor solution can be problematic, as precipitated crosslinker particles may be filtered by fibrous preform. In this study, the impact of HMTA filtration induced heterogeneous structure on subsequent curing process was investigated using process simulation. Temperature effects of sol–gel polymerization and solvent evaporation were considered through establishment of corresponding kinetic models. Impacts of heterogenous structure on distribution of temperature, resin curing degree and solvent conversion degree in large hemispherical aerogel composite structure were investigated. This leads to variations in gel network and pore structure of aerogel, thereby affecting final material performance. Based on experimental results, as HMTA concentration increases, compressive performance of NQCF/PR obviously increases. Among these, NQCF/PR with 4.7 wt% HMTA provides a balance of lightweight nature (0.25 g/cm3), excellent thermal insulation property (0.052 W·m−1·K−1) and compressive performance (strength of 0.35 MPa).

Bridging biomimetic and bioenergetics scaffold: Cellulose-graphene oxide-arginine functionalized aerogel for stem cell-mediated cartilage repair

The avascular nature of cartilage tissue limits inherent regenerative capacity to counter any damage and this has become a substantial burden to the health of individuals. As a result, there is a high demand to repair and regenerate cartilage. Existing tissue engineering approaches for cartilage regeneration typically produce either microporous or nano-fibrous scaffolds lacking the desired biological outcome due to lack of biomimetic dual architecture of microporous construct with nano-fibrous interconnected structures like the native cartilage. Most of these scaffolds also fail to suppress ROS generation and provide sustained bioenergetics to cells, resulting in the loss of metabolic activity under avascular microenvironment of cartilage. A dual architecture microporous construct with nano-fibrous interconnected network of cellulose aerogel reinforced with arginine-coated graphene oxide (CNF-GO-Arg aerogel) was developed for cartilage regeneration. The designed dual-architectured CNF-GO-Arg aerogel using dual ice templating assembly demonstrates 80 % strain recovery ability under compression. The release of Arginine from CNF-GO-Arg aerogel supported 41 % reduction in intracellular ROS activity and promoted chondrogenic differentiation of hMSCs by shifting mitochondrial bioenergetics towards oxidative phosphorylation indicated by JC-1 dye staining. Overall developed CNF-GO-Arg aerogel provided multifunctionality via biomimetic morphology, cellular bioenergetics, and suppressed ROS generation to address the need for regeneration of cartilage.

Immunometabolic checkpoint-mediated macrophage metabolic reprogramming accelerates infected wound healing

Immunometabolic disorders, triggered by excessive oxidative stress, lead to macrophage dysfunction, consequently impeding the healing of infected wounds. The uncontrolled accumulation of reactive oxygen species (ROS) in infected wounds is primarily attributed to persistent bacterial infections, excess exudate, and hypoxia. Herein, an immunometabolic checkpoint-mediated macrophage metabolic reprogramming strategy based on a nanofiber aerogel loaded with catalase (CAT) and tannic acid (TA) is proposed. The three-dimensional porous network of the nanofiber aerogel effectively absorbs exudates, maintains wound dryness, and prevents tissue saturation. CAT catalyzes oxygen generation, alleviates hypoxia, and reduces ROS, while TA acts as a natural antioxidant and antibacterial agent, collaboratively mitigating oxidative stress and bacterial infections. More importantly, the CAT-TA nanofiber aerogel, as an immunometabolic checkpoint regulator, can reshape the glutathione (GSH) metabolic pathway, enhancing intrinsic antioxidative capacity, allowing the reversion of macrophage functions, and ultimately promoting wound healing. This macrophage metabolism therapy (MMT), centered on the modulation of immunometabolic checkpoint, effectively enhances the regenerative capacity of infected wounds and provides a pioneering perspective for the treatment of regeneration disorders in infected tissues.

Constructing lightweight ternary interpenetrating network of carbon fabric/siloxane/phenolic aerogels for long-time high-temperature thermal protection

Lightweight ablative material has served the critical role of protecting space vehicles upon hypersonic entry. However, low oxidation resistance hinders its long-time high-efficiency service in a high-temperature oxidizing atmosphere. Herein, we prepared a lightweight ternary interpenetrating network of three-dimensional carbon fabric, siloxane aerogel, and phenolic aerogel, which are structurally interpenetrating in macro-, micron-to nanoscale and chemically crosslinking at the molecular scale, resulting in a unique combination of low-density (∼0.3 g/cm3), good thermal stability and oxidation resistance, outstanding mechanical properties, and ultralow thermal conductivity. More intriguingly, long-time thermal protection performance (zero surface recession and temperature below 60 °C at 38 mm in-depth after being exposed to 1300 °C for 20 min). The findings of this work provide not only a great potential candidate material for long-time thermal protection in aviation and aerospace applications but also a simple but efficient approach to fabricating multifunctional binary, ternary, and even multiple interpenetrating networks.

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.

Hollow glass microspheres embedded in porous network of chitosan aerogel used for thermal insulation and flame retardant materials

In recent years, biopolymer aerogels as thermal insulation materials have received widespread attention due to natural abundance, cost-efficiency, and environment-friendly. However, the flammability and low strength hinder its practical application. Hollow glass microspheres (HGMs) as an inorganic thermal insulation filler have been filled in biopolymer aerogels to improve flame retardancy. However, the structure formed by HGMs embedded porous network of biopolymer aerogel has rarely been investigated, which not only reduce thermal conductivity through high porosity, but also adjust the filling volume of HGMs and achieve uniform distribution through chemical cross-linking. Herein, a biopolymer aerogel composite was assembled by chitosan aerogel (CSA) and different volume of HGMs by chemical cross-linking, freeze-drying, and silylation modification processes. When the filling volume fraction of HGMs reached 40 %, a skeleton structure was initially formed. The composites with HGMs volume of 40 %–60 % exhibited low density, high porosity, low thermal conductivity, good mechanical property, and excellent flame retardancy. According to GB 8624-2012 standard for classification, the composite with 60 % HGMs achieved class A1 non-combustible.

Developing a carbon composite hydrogel with a highly conductive network to improve strain sensing performance

Both carbon aerogels and conductive hydrogels have provoked immense research interest as flexible sensing materials. However, conventional carbon aerogels show limited stretchability, while conductive hydrogels generally show limited conductivity. Herein, we develop a carbon composite hydrogel with a highly conductive network by encapsulating a cellulose fiber-derived carbon aerogel with a liquid metal-based conductive hydrogel formed by the in situ free radical polymerization of acrylic acid. The as-prepared carbon composite hydrogel inherits its high conductivity from the cellulose fiber-derived carbon aerogel and its good stretchability, adhesion and self-healing properties from the liquid metal-based hydrogel. Moreover, the carbon composite hydrogel possesses a high tensile strength and toughness due to the rigid network of the carbon aerogel. When serving as the tensile strain sensing material, the carbon composite hydrogel shows a very high sensitivity (gauge factor = 13.1 in the strain range of 400–500%), ultralow detection limit (0.1%), quick response and recovery time (166 ms at the strain of 1%) and excellent durability (1000 cycles under at 10% and 100% strains). In addition, the carbon composite hydrogel can obtain good temperature tolerance, adapt to high humidity and sustain its good sensing performance at low and high temperatures simply by coating a layer of glycerin on its surface. This work broadens the prospects for the design and preparation of conductive hydrogel-based strain sensors, and it facilitates their application in monitoring the biomedical signals of humans.

Constructing a continuous reduced graphene oxide network in porous plant fiber sponge for highly compressible and sensitive piezoresistive sensors

Flexible pressure sensors as wearable electronic devices to monitor human health have attracted significant attention. Herein, a simple and effective carbonization-free method is proposed to prepare a compressible and conductive reduced graphene oxide (rGO)–modified plant fiber sponge (defined as rGO-PFS). The introduced GO can not only coat on the surface of plant fibers, but also form a large amount of aerogel with microcellular structure in the macroporous PFS. After reduction treatment, the rGO-PFS can form a double-continuous conductive network of rGO aerogel. With the improvement of polydimethylsiloxane (PDMS), the rGO-PFS@PDMS composite exhibits outstanding compressibility (up to 60% compression strain), excellent durability (10,000 stable compression cycles at 50% strain), high sensitivity (234.07 kPa−1 in a pressure range of 20 ~ 387.2 Pa), low detection limit (20 Pa), and rapid response time (28 ms) for practical wearable applications.Graphical A compressible and conductive reduced graphene oxide–modified plant fiber sponge is prepared by a simple and effective carbonization-free method. With the improvement of polydimethylsiloxane, the sponge exhibits outstanding compressibility, durability, high sensitivity, low detection limit, and rapid response time for practical wearable applications.

Full biomass-derived multifunctional aerogel for solar-driven interfacial evaporation

Developing high-efficient utilization of thermal energy, excellent water transport path and mechanical stablility of biochar based solar-driven interfacial evaporator (SDIE) is critical for but still challenge. Herein, a three-dimensional network of porous scaffolds aerogel is prepared by cross-linking hydrophilic plantain cellulose (PC) and biomass hollow carbon tubes (HCTs) with excellent photothermal properties. The HCTs and PC winding with each other, the water adsorption by PC and desorption by HCTs which improve water evaporation. Under 1.0 sun illumination, the optimized PC@HCTs aerogel temperature on gas-liquid interface rapidly reach to 46.7 °C and the evaporation rate is 1.86 kg m−2h−1. In addition, PC@HCTs aerogel possess excellent water evaporation under high concentration of salt solutions and salt tolerance ability. Moreover, the PC@HCTs aerogel has obvious purification effect for seawater, heavy metal ion solution, oil-water emulsion and organic dye wastewater. Importantly, the dry PC@HCTs possesses excellent hardness while hyperelasticity in water. More importantly, the PC@HCTs aerogel with green recyclability which change the growth environment of sand and plants healthier, thus take materials from nature and final regress to nature. This work has the great scientific significance to promote the actual use of biochar based solar steam evaporators.

Emerging Trends in Nanotechnology: Aerogel-Based Materials for Biomedical Applications.

At present, aerogel is one of the most interesting materials globally. The network of aerogel consists of pores with nanometer widths, which leads to a variety of functional properties and broad applications. Aerogel is categorized as inorganic, organic, carbon, and biopolymers, and can be modified by the addition of advanced materials and nanofillers. Herein, this review critically discusses the basic preparation of aerogel from the sol-gel reaction with derivation and modification of a standard method to produce various aerogels for diverse functionalities. In addition, the biocompatibility of various types of aerogels were elaborated. Then, biomedical applications of aerogel were focused on this review as a drug delivery carrier, wound healing agent, antioxidant, anti-toxicity, bone regenerative, cartilage tissue activities and in dental fields. The clinical status of aerogel in the biomedical sector is shown to be similarly far from adequate. Moreover, due to their remarkable properties, aerogels are found to be preferably used as tissue scaffolds and drug delivery systems. The advanced studies in areas including self-healing, additive manufacturing (AM) technology, toxicity, and fluorescent-based aerogel are crucially important and are further addressed.

Graphene aerogel stabilized phase change material for thermal energy storage

Phase change material (PCM) with thermal energy storage capacity has been a hot topic due to the advantages of satisfying the demand for energy storage, saving and conversion. In this work, graphene oxide (GO) was introduced to prepare a three-dimensional (3D) continuous network of graphene aerogel (GA) via a simple hydrothermal process, and the GA was further employed to pack polyethylene glycols (PEG). Benefited from the abundant porous structure and high specific surface area, the mass fraction of PEG in the composite PCM was up to 96.0 wt%. Besides, the heat latent of the composite was 223.2 J/g, illustrating a high energy storage density. Moreover, due to the crosslinking graphene skeleton and its inherent high thermal conductivity, the heat transfer rate was enhanced to 116% of the pure PEG. This work could simultaneously solve the drawbacks of leakage and low thermal conductivity of PCM. And the composite PCM could be considered as a clean, energy-saving and recycled material in the application of building heat preservation.

Ultrasound-assisted preparation of Fe(OH)3@bacterial cellulose aerogel for efficient removal of organic contamination in water

As an abundant and renewable polymer, bacterial cellulose-based aerogel (BCA) loading with Fe(OH)3 nanoparticles was successfully prepared by ultrasound-assisted treatment and exhibited excellent adsorption efficiency for dye removal from polluted water. Wastewater containing toxic synthetic dyes is causing serious damage to the ecological environment and human health, and more attention has been paid to the nanoscale materials for water purification because of their unique structure and large specific surface area. With the help of ultrasonic waves, iron and hydroxide ions could fully penetrate the complex network of cellulose aerogel and generate the uniformed Fe(OH)3 particles, homogeneously being located all over the adsorbent. The physical adsorption from the multi-scaled pore structure in cellulosic aerogel and the chemical formation of electrostatic interaction and the hydrogen bonds between Fe(OH)3 and Congo red (CR) synergistically acted and significantly improved the absorbability. Finally, the maximum adsorption capacity of CR was achieved to 335 mg/g at natural conditions, which was higher than many reported values. The kinetics of the adsorption under different temperatures, pH, and time were comparatively measured, and the physical and structural characteristics were also investigated in detail using XPS, SEM, EDS, XRD, etc., technologies. Importantly, this approach is expected to provide a simple and operable process for fabricating cellulose-based aerogel and broadening the fields of applications.

Silica-Based Aerogel Composites Reinforced with Reticulated Polyurethane Foams: Thermal and Mechanical Properties.

In this work, silica aerogel composites reinforced with reticulated polyurethane (PU) foams have been manufactured having densities in the range from 117 to 266 kg/m3 and porosities between 85.7 and 92.3%. Two different drying processes were employed (ambient pressure drying and supercritical drying) and a surface modification step was applied to some of the silica formulations. These composites, together with the reference PU foam and the monolithic silica aerogels, were fully characterized in terms of their textural properties, mechanical properties and thermal conductivities. The surface modification with hexamethyldisilazane (HMDZ) proved to improve the cohesion between the reticulated foam and the silica aerogels, giving rise to a continuous network of aerogel reinforced by a polyurethane porous structure. The samples dried under supercritical conditions showed the best interaction between matrixes as well as mechanical and insulating properties. These samples present better mechanical properties than the monolithic aerogels having a higher elastic modulus (from 130 to 450 kPa), a really exceptional flexibility and resilience, and the capacity of being deformed without breaking. Moreover, these silica aerogel-polyurethane foam (Sil-PU) composites showed an excellent insulating capacity, reaching thermal conductivities as low as 14 mW/(m·K).

Carbon hybrid aerogel-based phase change material with reinforced energy storage and electro-thermal conversion performance for battery thermal management

Driven by the growing of electric vehicle, there is an unmet need to develop wide-range temperate management of Li-ion battery. Promising phase change materials (PCMs) with reinforced energy storage and conversion performance can cool battery by heat storage and heat battery by electro-thermal conversion. Herein, carbon hybrid aerogel by integrating MOF-derived carbon (MOFC) and graphene oxide (GO) aerogel was fabricated to encapsulate lauric acid as LA@MOF-C/GO PCM composite. Densely network of the hybrid aerogel works to enhance electrical/thermal conductivities while synergistic effect between MOF-C and GO helps to improve PCM loading capacity. Consequently, the PCM composite exhibited enhanced heat storage and electro-thermal conversion performances including low input voltage (2.2 V), high electro-thermal efficiency (90%), and enhanced enthalpy (140 J/g), thermal conductivity (1.35 W/mK) and shape-stability (10 °C above m.p.). The LA@MOF-C/GO composite worked efficiently to improve battery performance under environment temperature ranging from 45 °C to −20 °C, which shows great potential in thermal management of electric vehicle battery.

Studies on the silver incorporated titania aerogel nanostructure as a photoanode in quasi solid dye- sensitized solar cells

Dye-sensitized solar cells (DSSC) have a significant impact on photovoltaic technology because of their quick, low-cost manufacture, light weight, and high power conversion efficiency (PCE). Numerous research works were undergone on different titania nanostructure used as photoanode in DSSC. High surface area titania nanoarchitecture has effective for more dye absorption to improve the cell performance. Titania aerogels have a high specific surface area and high porosity compared to other titania nanostructures. Incorporation of noble metals into titania aerogel enhanced PCE. In noble metals, silver has promising material because of its cost-effective, less ohmic resistance etc. compared to Au. In this work, we prepared silver doped titania aerogel and studied its photovoltaic performance in the quasi solid DSSC performance. Silver-incorporated titania aerogel was synthesized by the facile sol–gel route. Structural, optical, photovoltaic properties and cell stability of a prepared photoanode material were measured. PXRD revealed that the anatase phase is retained after the incorporation of silver. HRSEM images and EDS spectra confirmed the interconnecting network of titania aerogel and the presence of silver respectively. Due to the Localized Surface Plasmonic Resonance (LSPR) effect, the absorption spectra of the composite exhibited a red-shift around 650 nm. PL spectra showed the decreasing intensity in composites which is the evidence of suppressing electron-hole recombination and improving electron injection. The incorporation of silver has improved the photon absorption capability of the photoanode tends to enhance photocurrent density as well as PCE of QS-DSSC.

Graphene Aerogel Supported Fe−Co Selenide Nanocubes as Binder‐Free Anodes for Lithium‐Ion Batteries

AbstractMetal selenides as anode materials of lithium‐ion batteries (LIBs) has received considerable attention recently. In order to boost the electronic conductivity and alleviate the volume change of electrode materials upon the cycles, a facile strategy is employed in this work, where Prussian blue analogue (PBA) nanocubes are encapsulated into three‐dimensional (3D) network of graphene aerogel (GA), followed by a high‐temperature selenization treatment to isolate the composite of FeCoSe2@GA. The composite can be directly employed as free‐standing anode materials of LIBs. Studies reveal that the FeCoSe2@GA electrode demonstrates an intriguing cycle stability and rate capability with a specific capacity of ∼500 mAh g−1 at 100 mA g−1 after 100 cycles. The outstanding lithium‐storage properties can be attributed to the 3D porous feature as well as the strong confinement effect of GA for FeCoSe2 particles, which provides a large number of ion‐exchange channels, and prevents the severe agglomeration and large volume expansion of active particles during the charge/discharge process.

Graphene aerogel modified carbon fiber reinforced composite structural supercapacitors

This paper reports the design of a structural supercapacitor using a continuous network of graphene aerogel (GA) impregnated on carbon fiber (CF) fabrics to prepare CF reinforced composite. The GA is synthesized by hydrothermal process of Graphene oxide precursor that enabled the thermal reduction and self-assembly of GA onto the CF fabrics. Composite supercapacitor is prepared by resin infusion technique using GA-modified CF, dielectric electrospun veil separator and an ionic liquid modified epoxy electrolyte. The modification of CFs with highly interconnected and porous GA has provided a significant improvement in the surface area of CFs, resulting in excellent electron transport properties. CF fabrics with 28% GA loading exhibited a capacitance of 92.5 F g−1 at 1 mVs−1, which is 550 times higher than the capacitance of neat CFs and provides an excellent capacitance retention of 98% after 10000 charge-discharge cycles. GA-modified CF reinforced composites yield the highest capacitance of 56 mF g−1. This study provides a practical method for multifunctional, light weight, CF reinforced composites for energy storage applications.

Highly thermally conductive phase change composites with excellent solar-thermal conversion efficiency and satisfactory shape stability on the basis of high-quality graphene-based aerogels

Although nontoxic organic phase change materials (PCMs) with high energy densities are promising for storing and releasing latent heat reversibly during their melting and solidifying processes, their major shortcomings of melt leakage and poor thermal conduction limit their wide applications. To accommodate a typical PCM of 1-octadecanol and enhance its thermal conduction and structural stability, high-quality graphene-based aerogels are fabricated by hydrothermally reducing graphene oxide/graphene nanoplatelets (GNPs) suspensions followed by air-drying and thermal annealing at 2800 °C. The hydrothermally reduced graphene oxide (RGO) sheets construct an interconnecting network during the hydrothermal reduction process. By varying the content of GNPs, shrinkage of the RGO/GNP hydrogel during air-drying could be regulated effectively. Crucially, graphitization of the air-dried RGO/GNP hybrid aerogel removes residual oxygen-containing groups of RGO and heals its lattice defects. The high-quality graphene aerogel is well suitable for accommodating 1-octadecanol, and the resultant phase change composite exhibits an ultrahigh thermal conductivity of 9.50 W m−1 K−1 at a graphene content of 13.3 wt%. Furthermore, thanks to the efficient light absorption feature and highly conductive network of the graphene-based aerogel, its 1-octadecanol phase change composite possesses an excellent solar-thermal energy conversion ability with a high efficiency of 84%. The phase change composites on the basis of the high-quality graphene-based aerogels would be highly promising for solar-thermal energy conversion and storage.

Modification of surface structure and mechanical properties in polyimide aerogel by low-energy proton implantation

In this work, the structure and mechanical properties of polyimide aerogel under low energy proton implantation were investigated. The results indicated that the three-dimensional network of aerogel would become densification and even transform into the layer-by-layer structure with increasing the proton fluence. Furthermore, the layer-by-layer structure was observed firstly near the end of the proton range and then expanded gradually out to the sample surface, moreover the layered region tends to be thicker with the proton fluence. The results of fluorescence spectroscopy and Raman spectra indicated that the molecular chains of polyimide would be degraded firstly and then rearrange to form amorphous carbonized structure. The nano-indentation results shown that the average contact pressure and elastic modulus of the implanted surface were detected about twice that of the as-received aerogel. This work paths a new way of proton implantation to control the surface structure and mechanical properties of organic aerogel.

Cobalt Oxide Nanocubes Encapsulated in Graphene Aerogel as Integrated Anodes for Lithium‐Ion Batteries

AbstractThe development of metal oxides as anodes of lithium‐ion batteries is severely limited because of their poor conductivity and serious volume expansion during the cycles. This work focuses on the improvement of electronic conductivity and cycle stability of metal oxides. The nanocubes of Prussian blue analogues are firstly encapsulated in the network of graphene aerogel (GA), and then the Co3O4@GA composites are synthesized after the subsequent calcination treatment. The resulting products are used as free‐standing and high‐performance anodes of LIBs, and the optimal electrode delivers a specific capacity of 624 mAh g−1 at 100 mA g−1 after 100 cycles together with a good cycle stability. The extraordinary lithium‐storage performances can be ascribed to the synergistic interaction between metal oxides and GA substrate. The incorporation of GA improves the electrode conductivity and alleviates the aggregation and volume expansion of metal oxide particles upon cycling, whereas cobalt oxides contribute a high specific capacity.