Applications Of Aerogels Research Articles

Controllable preparation of aerogel/expanded perlite composite and its application in thermal insulation mortar

The extremely low strength and high cost of aerogel limit its applicability in energy-efficient buildings. In this paper, the controllable preparation method of aerogel/expanded perlite (AEP) was developed, and the particle gradation effect on AEP thermal insulation mortar (AEPM) was assessed, which provided an effective way for the application of aerogel and AEP in buildings. The results showed that the acid/base catalysis two-step method was imperative for preparing AEP. It was also found that the pH of SiO2 hydrosol should be controlled within 3.2–3.5, and the corresponding gel time of SiO2 hydrosol was 30–90 min. The impregnation-adsorption process of EP adsorbing SiO2 hydrosol should be completed before the initial viscosity of 3 mPa·s changes. The amount of SiO2 hydrosol adsorbed by EP had a logarithmic relationship with the adsorption time under the adsorption of ambient pressure (AP), whereas its linear relationship with the adsorption pressure under the adsorption of vacuum pressure (VP) was found. The pores of expanded perlite (EP) were filled with well-structured aerogel due to the controlled preparation of AEP. Thus, the AEP bulk density increased by 24%-50% compared with EP. However, the thermal conductivity decreased by 14.6%-31.8%, and the particle strength of AEP was not significantly improved compared with that of EP. AEPM prepared by AEP showed typical characteristics of high strength and low thermal conductivity. The compressive strength of AEPM was 6.5% lower than that of EPM but more than twice that of AERM, while the corresponding water absorption and thermal conductivity were 27.6% and 26.6% lower than EPM. As a new nano-micron porous composite, AEP has great applicability in developing thermal insulation materials, phase change materials, and adsorption materials.

Visualization Analysis and Knowledge Mapping the Research of Aerogels Applied in Buildings

With the deepening of aerogel research and the popularization of its application, the demands for energy saving in the construction field has brought aerogels into the limelight. To explore state-of-the-art research and development trends related to aerogels applied in construction, CiteSpace was used to conduct a quantitative analysis based on the Web of Science core database. Results show that: (1) in the past 10 years, the number of papers on aerogels in the field of constructions has increased significantly; (2) the top producing countries in the aerogel field are mainly China and the United States, and the top two research institutions are all Chinese institutions (Univ Sci & Technol China and Chinese Acad Sci); (3) the main publishing journals are ENERGY AND BUILDINGS, CONSTRUCTION AND BUILDING MATERIALS, and CHEMICAL ENGINEERING JOURNAL; (4) the hot keywords are thermal insulation, silica aerogel, thermal conductivity, phase change material, mechanical property, graphene aerogel, self-assembly, energy saving, etc.; (5) aerogel is mostly used in building insulation, mainly in the form of aerogel glass, aerogel mortar, aerogel felt, and aerogel coating. In summary, in addition to systematically strengthening theoretical research, it is necessary to optimize the technical process and reduce costs in order to effectively promote aerogels in construction energy conservation and carbon reduction. Through this study, the current situation, hot spots, and development trend of aerogel application in construction can be revealed systematically. Overall, this study helps advance research on aerogels applied in buildings and help in tackling energy efficiency challenges.

Flexible and Transparent Bagasse Aerogels for Thermal Regulation Glazing

The preparation of functional composite aerogels for building envelopes, especially for building glazing as the key climate moderator, has been widely investigated to improve the sustainability of buildings. Unfortunately, the prohibitive costs, mechanical brittleness, and optical opacity limit the current development and application of composite aerogels. Herein, using the controllable extraction of cellulose from bagasse, a low-cost (less than $3 per square foot), flexible (>15% elastic deformation under 0.02 MPa) bagasse aerogel film with high visible-light transparency (>80% transmittance of visible light) and superinsulation (0.0158 W m–1 K–1) was developed. These properties were achieved by constructing a uniform three-dimensional network structure using elastic polysiloxane and a mixture of cellulose nanofibers and cellulose nanocrystals in an equal proportion. This cellulosic aerogel film would have the latent potential of application in highly glazed modern buildings to reduce the energy loss from windows.

Ultralow thermal conductivity of single-atom doped carbon aerogel synthesized with a facile ambient-pressure-drying strategy

Carbon aerogel is an attractive material for thermal insulation due to the porous character and high stability at high temperature. However, the wide application of carbon aerogel for thermal insulation is hindered by complicated supercritical-drying technology and high thermal conductivity of the pure carbon skeleton. Herein, a facile ambient-pressure-drying technology is developed for synthesizing Fe–N4 doped carbon aerogel through catalyzing the polymerization reaction of monomers under a Fe sol, with copolymer F127 as enhancement phase for wet-hydrogel. The whole process does not have any solvent exchange or aging procedure. The prepared carbon aerogel has an ultralow thermal conductivity of 0.048 W/(m ∙ K) at room temperature, with negligible 2% shrinkage during ambient-pressure-drying process and excellent mechanical behavior with stress of 0.58 MPa at 10% strain. The thermal conductivity of carbon-fiber reinforcement carbon aerogel is 0.158 W/(m ∙ K) at 1100 °C, and has an elasticity modulus of 108.3 MPa. Based on an ideal model, density functional theory calculations reveal that doping Fe–N4 can significantly enhance the anharmonicity of carbon-based materials and thus reduce the lattice thermal conductivity by more than 10 times. This work presents a facile and low-cost method for synthesizing carbon aerogel with single-atom doping for promising applications in thermal insulation.

Application of Nanocellulose-Based Aerogels in Bone Tissue Engineering: Current Trends and Outlooks.

The complex or compromised bone defects caused by osteomyelitis, malignant tumors, metastatic tumors, skeletal abnormalities, and systemic diseases are difficult to be self-repaired, leading to a non-union fracture. With the increasing demands of bone transplantation, more and more attention has been paid to artificial bone substitutes. As biopolymer-based aerogel materials, nanocellulose aerogels have been widely utilized in bone tissue engineering. More importantly, nanocellulose aerogels not only mimic the structure of the extracellular matrix but could also deliver drugs and bioactive molecules to promote tissue healing and growth. Here, we reviewed the most recent literature about nanocellulose-based aerogels, summarized the preparation, modification, composite fabrication, and applications of nanocellulose-based aerogels in bone tissue engineering, as well as giving special focus to the current limitations and future opportunities of nanocellulose aerogels for bone tissue engineering.

Graphene Oxide/Styrene-Butadiene Latex Hybrid Aerogel with Improved Mechanical Properties by PEI Grafted GO and CNT.

Graphene oxide aerogel (GOA) has wide application prospects due to its low density and high porosity. However, the poor mechanical properties and unstable structure of GOA have limited its practical applications. In this study, polyethyleneimide (PEI) was used to graft onto the surface of GO and carbon nanotubes (CNTs) to improve compatibility with polymers. Composite GOA was prepared by adding styrene-butadiene latex (SBL) to the modified GO and CNTs. The synergistic effect of PEI and SBL, resulted in an aerogel with excellent mechanical properties, compressive resistance, and structural stability. When the ratio of SBL to GO and GO to CNTs was 2:1 and 7:3, respectively, the obtained aerogel performance was the best, and the maximum compressive stress was 784.35% higher than that of GOA. The graft of PEI on the surface of GO and CNT could improve the mechanical properties of the aerogel, with greater improvements observed with grafting onto the surface of GO. Compared with GO/CNT/SBL aerogel without PEI grafting, the maximum stress of GO/CNT-PEI/SBL aerogel increased by 5.57%, that of GO-PEI/CNT/SBL aerogel increased by 20.25%, and that of GO-PEI/CNT-PEI/SBL aerogel increased by 28.99%. This work not only provided a possibility for the practical application of aerogel, but also steered the research of GOA in a new direction.

Optical Design of Silica Aerogels for On‐Demand Thermal Management

AbstractSilica aerogels, a type of porous material featuring extra low density and thermal conductivity, have drawn increasing interest from both academia and industry owing to their excellent thermal insulation performance. However, thermal insulation is always the single consideration when silica aerogels are used for thermal management. In this study, the on‐demand thermal management (ODTM) of silica aerogel with either passive thermal insulation, passive heating, or passive cooling in different environments is revealed. The ODTM behavior of silica aerogels can be simply fulfilled through their optical property variations such as solar light transparency and infrared emissivity, which are controllable via the microstructures of the building blocks and surface composition design. Robust solar heating of 25 °C higher than the ambient in the daytime and sub‐ambient cooling of 7 °C at night is achieved with the traditional transparent silica aerogel. Interestingly, sub‐ambient cooling of 5 °C in the daytime and a warmer state on cold nights is achieved by modifying its solar transmittance and infrared emissivity. This study guides a comprehensive understanding of the thermal management behavior of silica aerogels and leads to ODTM applications of silica aerogels by tailoring their optical and thermal conductivity properties.

Application Progress of Cellulose Aerogel Modified by GMA

Cellulosic aerogels have attracted much attention because of their low density, high porosity and low thermal conductivity in many modified composite materials. Glycidyl methacrylate (GMA) is a new type of polymeric monomer with low cost, low toxicity, good biocompatibility, and easy chemical modification that has emerged in recent years, and it was widely used in the modification of rubber, fiber and other polymer materials. Cellulose composite aerogel, which is constructed by using GMA as a bridge to connect other materials, has rich functionality and shows great application potential in biomedicine, catalysis, adsorption and other fields. In this paper, the classification and properties of aerogels and cellulose are briefly described at first, then the synthesis methods of cellulose aerogels are introduced, and the applications of composite aerogels synthesized from cellulose modified by GMA in various fields in recent years are reviewed. This paper reviews the application of GMA-modified cellulose composite aerogels about the heavy metal and dye adsorption, biological tissues, wound dressings, drug carriers, biosensor and catalytic carriers. Finally, the future development prospect and current limitations of GMA modified cellulose aerogel are briefly introduced.

Ultraprecise 3D Printed Graphene Aerogel Microlattices on Tape for Micro Sensors and E‐Skin

Abstract3D printed graphene aerogels hold promise for flexible sensing fields due to their flexibility, low density, conductivity, and piezo‐resistivity. However, low printing accuracy/fidelity and stochastic porous networks have hindered both sensing performance and device miniaturization. Here, printable graphene oxide (GO) inks are formulated through modulating oxygen functional groups, which allows printing of self‐standing 3D graphene oxide aerogel microlattice (GOAL) with an ultra‐high printing resolution of 70 µm. The reduced GOAL (RGOAL) is then stuck onto the adhesive tape as a facile and large‐scale strategy to adapt their functionalities into target applications. Benefiting from the printing resolution of 70 µm, RGOAL tape shows better performance and data readability when used as micro sensors and robot e‐skin. By adjusting the molecular structure of GO, the research realizes regulation of rheological properties of GO hydrogel and the 3D printing of lightweight and ultra‐precision RGOAL, improves the sensing accuracy of graphene aerogel electronic devices and realizes the device miniaturization, expanding the application of graphene aerogel devices to a broader field such as micro robots, which is beyond the reach of previous reports.

Preparation of Nanocellulose-Based Aerogel and Its Research Progress in Wastewater Treatment.

Nowadays, the fast expansion of the economy and industry results in a considerable volume of wastewater being released, severely affecting water quality and the environment. It has a significant influence on the biological environment, both terrestrial and aquatic plant and animal life, and human health. Therefore, wastewater treatment is a global issue of great concern. Nanocellulose's hydrophilicity, easy surface modification, rich functional groups, and biocompatibility make it a candidate material for the preparation of aerogels. The third generation of aerogel is a nanocellulose-based aerogel. It has unique advantages such as a high specific surface area, a three-dimensional structure, is biodegradable, has a low density, has high porosity, and is renewable. It has the opportunity to replace traditional adsorbents (activated carbon, activated zeolite, etc.). This paper reviews the fabrication of nanocellulose-based aerogels. The preparation process is divided into four main steps: the preparation of nanocellulose, gelation of nanocellulose, solvent replacement of nanocellulose wet gel, and drying of nanocellulose wet aerogel. Furthermore, the research progress of the application of nanocellulose-based aerogels in the adsorption of dyes, heavy metal ions, antibiotics, organic solvents, and oil-water separation is reviewed. Finally, the development prospects and future challenges of nanocellulose-based aerogels are discussed.

Monolithic chitosan-silica composite aerogel with comprehensive performances prepared by SBG-FD method

Silica aerogels are viewed as potential thermal insulation materials because they are highly porous, adiabatic and lightweight. The lack of mechanical strength and hygroscopicity are the main barriers to their application. In order to tackle these issues, a direct sol-blending-gel combing freezing drying (SBG-FD) technique is used to create trimethylchlorosilane (TMCS)-modified natural polysaccharide-reinforced chitosan-silica aerogel (CS-T-SA) in this work. This brand-new CS-T-SA possesses three-dimensional network structure, and its thermal conductivity reaches 0.0360 W m−1 k−1 at 30 °C with bulk density as low as 0.0485 g cm−3 and volume shrinkage to a minimum of 5%. Hydrophobic modification with TMCS gives the composite aerogel a promisingly high hydrophobicity with the water contact angle of 135.1°. In comparison to conventional silica aerogels, the chitosan-silica aerogels exhibit improved mechanical characteristics, with no brittle rupture up to at least 80% strain and stress at 80% strain values of 0.285–0.486 MPa. Remarkably, aerogel monoliths can be machined and sculpted using tools. This demonstration to produce monolithic and machinable, mesoporous aerogels with low-density from bio-sourced, renewable and nontoxic precursors, combined with good thermal stability and hydrophobicity opens up new possibilities for biopolymer-silica aerogel applications and represents a significant approach toward the commercialization of biopolymer-silica aerogels.

Self-interlocked down Biomass-based carbon fiber aerogel for highly efficient and stable solar steam generation

Carbon aerogels have demonstrated superior properties for generating clean water through sustainable solar steam generation. However, the complex, time-consuming preparation process and the various harmful chemicals involved seriously inhibit the development and applications of carbon aerogels. Herein, down biomass-based carbon fiber aerogel (DCFA) consisting of physically self-interlocked carbon fibers was developed through the simple low-temperature carbonization of natural down cluster (DC) for highly effective solar evaporation. The resulting DCFA has a large amount of carbon (>80 %) and small amounts of sulfur and nitrogen due to its natural disulfide bonds and amino groups, suggesting a unique self-doped carbon property. The low density and high porosity of the DCFA increased the total solar absorbance and suppressed the energy loss during evaporation. As a result, the DCFA possessed solar absorbance of 97.03 %, as well as high evaporation rates of 2.05 and 2.11 kg·m−2·h−1 for the treatment of saline water and dye water, respectively, which are higher than most reported results. Moreover, the resulting DCFA could self-float without external assistance, demonstrating that it could be a facile evaporator in practical applications. Additionally, the DCFA retained its evaporation performance after 10 times tests for the evaporation of 3.5 wt% saline water and actual dye wastewater, indicating a long-term capacity for practical employment. These findings suggest that the DCFA could be a feasible alternative for solar-driven evaporation. Simultaneously, the simple, efficient, and chemical-free strategy will inspire subsequent research on the construction of fiber-based functional aerogels and their further development/application in water treatment, thermal insulation, energy generation, energy storage, and other related areas.

Characterization of cellulose nanocrystals prepared by different delignification methods and application of ultra-light, hydrophobic aerogels as oil absorbent in food systems

In this study, cellulose nanocrystals (CNCs) were isolated and characterized from sugarcane pith (SP), a renewable, low-cost agro-industrial residue. The effects of bleaching methods on CNCs morphology and physicochemical properties were investigated. Then, an ultralight and hydrophobic nanocellulose-based aerogel was fabricated as an oil absorbent for food systems. The results showed that hydrogen peroxide bleached CNC retained its good characteristics (a whisker-like shape, L/D 38, CrI 72.1%, zeta potential −29.97 ± 0.05 mV) and the typical shear-thinning rheological behavior, an eco-friendly delignification. In addition, the obtained MTMS-modified aerogels exhibited ultralight density (0.031–0.053 g/cm3), high porosity (96.45–97.44%), lipophilicity (water contact angle as high as 130.2 ± 5.8°), and reusability. Furthermore, their absorption capacity was up to 49.8 g/g, with a wide range of catering oils and organic solvents. This study provides insight into the high value-added utilization of agro-industrial residues and the application of nanocellulose-based aerogels for oil-water separation in food systems.

SiO2 aerogel multiscale reinforced by glass fibers and SiC nanowhiskers for thermal insulation

SiO2 aerogel attracts much interest as thermal insulation material due to ultra-low density and excellent thermal performance at room temperature. However, the poor mechanical property and a mass of heat transfer by radiation in high temperature limit application of aerogels. Herein, a novel aerogel composite multiscale reinforced by glass fibers felt with SiC nanowhiskers (SiCnw) (AFS) was prepared. SiCnw were evenly distributed in glass fibers felts by freeze-drying method to form a uniform multiscale felt. The SiCnw inside felts provided more contact point with aerogel to increase the interfacial adhesion force so that compressive stress of aerogel composites with 4% volume fraction SiCnw was increased to 0.29 MPa. SiCnw blocked infrared radiation to decrease the heat transfer. Therefore, thermal conductivity at 500℃ of aerogel composite with 4% volume fraction SiCnw was only 0.040 W/(m·K). In a word, SiCnw reduced the sensitivity of thermal conductivity to temperature. AFS showed potential in the field of medium and high temperature insulation.

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.

Multifunctional nano-cellulose aerogel for efficient oil–water separation: Vital roles of magnetic exfoliated bentonite and polyethyleneimine

Discharge of oily wastewater have caused serious environmental pollution and resources waste. Due to the characteristics of hydrophobic and porous, aerogel has been proved to be a kind of promising oil-adsorbing materials for oil adsorption and recovery. However, dissatisfactory adsorption properties and recovery ability of aerogel for oil pollution treatment were still critical issues hindering aerogel applications. Magnetic exfoliated bentonite (MBTex) possesses good magnetic separation property, anti-mold ability and anti-extruding strength. Meanwhile, Polyethyleneimine (PEI) can cross-link with nano-cellulose to form sponge-like structure and prevent the corrosion of magnetic media. Basing on the above-mentioned characteristics of MB and PEI, a new carboxy cellulose nanofibers/polyethyleneimine/magnetic exfoliated bentonite (CNF-C/PEI/MBTex) aerogel was synthesized using simple hydrothermal and chemical vapor deposition (CVD) methods, and the adsorption and recovery ability of different oil on samples were investigated. The results showed that CNF-C/PEI/MBTex aerogel exhibited superhydrophobic properties (contact angle 151°), excellent mechanical properties (full recovery at 80% pressure), anti-mold properties (the anti-mold efficiency was more than 90%) and magnetic responsivity. Furthermore, CNF-C/PEI/MBTex aerogel exhibited high oil adsorption capacity (24.6 ∼ 77.8 times higher than its original weight) and can recover the adsorbed oil by simple hand squeezing (the adsorption capacity still exceeds 90% after 20 cycles). In summary, the present work provides a valuable reference for the synthesis of high-performance adsorbent materials for oil–water separation using cost-effective clays combined with polymers.

Silica Aerogel: Synthesis, Characterization, Applications, and Recent Advancements

AbstractSilica aerogels have drawn considerable attention due to their low density (almost 95% of the total volume is composed of air), hydrophobicity, optical transparency, low conductivity of heat, and large surface to volume ratio. Sol–gel processing is used to prepare aerogels from molecular precursors. To replace the pore fluid with air while retaining the solid network, a supercritical drying process (the most frequent approach) is used. However, recent technologies use atmospheric pressure to allow for liquid removal followed by chemical alteration of the gel's internal layer, which leaves only a silica network with a porous structure filled with air. This study discusses the sol–gel method for preparing silica aerogels and their various drying processes. Furthermore, various areas of applications of silica aerogels, including electronics, construction, aerospace, purification of water and air, sensing, catalyst, biomedical, absorbent, food packing, textile, etc., are also discussed. Lastly, this review provides a perception of the recent scientific progress along with the futuristic development of silica aerogel.

Biomedical applications of silica-based aerogels: a comprehensive review

Biomedical applications of silica-based aerogels: a comprehensive review

Combining granular aerogels with additively manufactured porous structures for broadband sound absorption

Our recent investigation [1] showed that the absorption behavior of granular aerogel agglomerates with average particle diameters less than 50μm is dominated by periodically spaced, high absorption peaks and troughs. While the absorption peaks, especially at lower frequencies, are desirable from an engineering application perspective, overcoming the loss in high frequency performance remains a challenge. Furthermore, the practical application of granular aerogels is limited by the difficulty in handling them. In this work, we propose a new design for a broadband noise absorber achieved by layering the aerogel granules within a 3D printed porous network. The design provides a robust method of incorporating aerogels within noise reduction packages and can be tailored by altering the rigid porous network and the layering arrangement. In this presentation, we present our preliminary findings regarding the fabrication and testing of such hybrid sound absorbers. [1] Dasyam A, Xue Y, Bolton JS, Sharma B. Effect of particle size on sound absorption behavior of granular aerogel agglomerates. Journal of Non-Crystalline Solids. 2022 Dec 15;598:121942.

A Review of the Mechanical Properties of Graphene Aerogel Materials: Experimental Measurements and Computer Simulations

Graphene aerogels (GAs) combine the unique properties of two-dimensional graphene with the structural characteristics of microscale porous materials, exhibiting ultralight, ultra-strength, and ultra-tough properties. GAs are a type of promising carbon-based metamaterials suitable for harsh environments in aerospace, military, and energy-related fields. However, there are still some challenges in the application of graphene aerogel (GA) materials, which requires an in-depth understanding of the mechanical properties of GAs and the associated enhancement mechanisms. This review first presents experimental research works related to the mechanical properties of GAs in recent years and identifies the key parameters that dominate the mechanical properties of GAs in different situations. Then, simulation works on the mechanical properties of GAs are reviewed, the deformation mechanisms are discussed, and the advantages and limitations are summarized. Finally, an outlook on the potential directions and main challenges is provided for future studies in the mechanical properties of GA materials.