Aerogel Production Research Articles

Aerogel Production and Determination of Its Thermophysical and Characteristic Properties

Porous materials are at the forefront of research in terms of providing superior insulation properties and energy efficiency. The most important point that makes porous materials different and unique is the space inside the pore. Aerogel has become the insulation material that stands out as the most interesting alternative in this context. In this study, the production of aerogel insulation materials with high insulation properties, suitable mechanical properties and different contents was aimed. Silica aerogels are synthesized using the sol-gel technique with Hydrolysis, Condensation, Aging, Solvent change and Surface modification, Drying main steps in general. According to the results obtained, it was determined that the densities of the aerogels produced were in the range of 0.66 to 1.053 g/ml and the thermal conductivity values were in the range of 0.067 to 0.097 W/mK. The results show that many opportunities are available to improve the insulation property of aerogel, which is considered an important insulation material of the future.

Flame-resistant and thermally-insulating aerogels with a double-network structure via benzoxazine/melamine composite precusors

Polybenzoxazine/Melamine (PBa/MS) double network aerogels were prepared using melamine foam (MS) as the backbone and bisphenol A-type benzoxazine (Ba) as the maxtrix. The effect of Ba concentration in the sol-gel on the performance of the double network aerogel was investigated. During the combustion, the PBa/MS composite aerogel exhibited self-extinguishing performance. Compared with PBa-18%, the contact angle of PBa-18%/MS composite aerogel was 18° higher, and the heat release peak (PHRR) and total smoke production (TSP) of the composite aerogel decreased by 7% and 39%, respectively. These values indicate that MS can significantly reduce the release of heat and smoke from the PBa aerogel, thus improving its flame retardancy. In addition, the composite aerogel formed a denser and more complete carbon layer during combustion, which blocks both heat and mass transfer. Thus, the resulting PBa/MS dual-network composite aerogels obtained in the current work are expected to meet the demands for flame-retardant, hydrophobic thermal insulation materials in many fields.

Water-Based Route for Dopamine and Reduced Graphene Oxide Aerogel Production

Water-Based Route for Dopamine and Reduced Graphene Oxide Aerogel Production

Investigation of the Uniformity of Gel Shrinkage by Imaging Tracer Particles Using X‐Ray Microtomography

Mass transfer and structural changes in the polymer matrix need to be understood for a rational optimization of the biopolymer‐based aerogels production. Herein, the uniformity of changes that occur in the gel structure during the aerogel production by a newly developed method which is based on the imaging of metal tracer particles using X‐ray microtomography (X‐ray micro‐CT) alongside the application of point pattern techniques such as the K‐nearest‐neighbor (KNN) distances is studied. Agar is initially used as a system of validation for the developed method, after which other polysaccharide and protein‐based gels such as alginate, whey protein isolate (WPI), and gelatine are studied. The KNN distance is seen to reduce from hydrogel to aerogel. Furthermore, by means of the KNN distances, the biopolymers are observed to experience a nonuniform distribution of tracer particles correlating to nonuniform shrinkage. Densification at specific sites of the gel represented by lower KNN distance values could be distinguished for each biopolymer. Finally, the spatially resolved polymer network density profile is estimated from the KNN distance by correlating it to experimentally determined polymer network density.

Electronic Modulation Strategy for Mass-Producible Ultrastrong Multifunctional Biomass-Based Fiber Aerogel Devices: Interfacial Bridging.

The emergence of green flexible aerogel electronics based on natural materials is expected to solve part of the global environmental and energy crisis. However, it is still challenging to achieve large-scale production and multifunctional stable applications of natural biomass fiber aerogel (BFA) materials. Herein, we exploit the interfacial bridging between the flower-type titanium dioxide nanoarray (FTNA) and natural fiber substrates to modulate the electronic structure and loss mechanism to achieve multifunctional properties. Specifically, the fibrous substrate with wrinkled features induces lattice strain in titania through precise interfacial bridging, effectively improving the intrinsic properties of the BFA materials. This interfacial bridging regulation strategy is also confirmed by X-ray absorption fine structure spectroscopy (XAS). More importantly, the construction of BFA products for different macroscopic and multifunctional applications through simple processing methods will facilitate the transition from natural materials to multifunctional flexible electronics. Therefore, the as-prepared blanket-type BFA (TCBFA) has good mechanical properties, electromagnetic protection properties, thermal stealth properties, high-temperature flame retardancy, and UV resistance. Meanwhile, the membrane-type (TCBFAM) multifunctional wearable fiber aerogel device exhibits superior flexibility, efficient Joule heating performance, and a smart response. This regulation strategy provides another concept for the design and innovation of green multifunctional fiber-integrated aerogels.

Acid‐Assisted Toughening Aramid Aerogel Monoliths with Ultralow Thermal Conductivity and Superior Tensile Toughness

AbstractResisting extreme loading and thermal ablation encountered by aerospace devices demands for high performance engineering materials. Aerogels have achieved satisfactory thermal insulation but the intrinsic brittleness of porous skeletons fail to ensure their normal operation under severe stress fields. Herein, aramid nanofibers (ANFs) are processed into tough 3D aerogel monoliths via a multi‐scale toughening strategy, involving unidirectional freeze‐casting‐enabled microstructure orientation and acid‐assisted nanofiber cross‐linking. Scalable production of ANFs aerogels is realized through fast air‐drying without excessive energy consumption. The aligned sheets in ANFs aerogels enable extreme thermal conductivity of 15.8 mW m−1 K−1, superinsulation from −130 to 300 °C, and durable combustion protection for 20 min. Particularly, highly aggregated nanofibers assemble into dense ANFs skeletons, endowing the tough aerogels with superior specific tensile strength (89 MPa cm3 g−1), ultra‐high toughness (1.3 MJ m−3), and impressive fracture energy (7.36 kJ m−2). Such mechanical properties are highly resistant to harsh environments, including water erosion (7 days) and high temperature baking (30 days). Moreover, ANFs aerogels exhibit two to three times more energy dissipation than commercial foams against ballistic impact at 140 m s−1. This integrated mechanical and thermal robustness may pioneer the potential application in impact‐thermal coupled safeguard for aerogel materials.

Carboxymethyl cellulose-derived porous carbon aerogel decorated with Fe3O4-Fe nanoparticles for tunable microwave absorption

The production of magnetic biomass-derived carbon-based aerogels has made outstanding contributions to green chemistry and sustainable development so as to alleviate the growing electromagnetic pollution problems. In particular, carboxymethyl cellulose (CMC) possessing three-dimensional (3D) porous structure, low density and biodegradability is an effective precursor for the preparation of magnetic carbon aerogels. In this work, lightweight porous Fe3O4-Fe/carbon aerogels (FFCA) were synthesized by depositing magnetic metals on chitosan (CS)-reinforced CMC via a facile and eco-friendly strategy. The 3D porous structure and non-homogeneous conductive network endow the FFCA aerogels with comprehensive properties. Specifically, the introduction of magnetic material and the carbonization process under the temperature gradient result in tunable electromagnetic parameters and good impedance matching, allowing electromagnetic waves to enter the absorber and dissipate as much as possible. For instance, the FFCA prepared at 900 °C exhibits the impressive microwave absorption performance due to the synergistic transition between magnetic permeability and dielectric constant, with the minimum reflection loss of −45.5 dB at 2.6 mm and the effective absorption bandwidth of 3.7 GHz. This work provides an important reference for the design of eco-friendly CMC-based magneto-dielectric synergistic microwave absorption materials.

Ultralight covalent organic frame graphene aerogels modified platinum-magnetite nanostructure for direct methanol fuel cell

In order to fully utilise porous structures, the production of structures from covalent organic frameworks is of great importance. At this point, graphene aerogel (GA) production with ascorbic acid, a green reducing agent, is presented. It was observed that the GAs obtained in this context were stacked in 3D and exhibited an ultralight and highly porous structure. In addition, GAs were modified with PtFe3O4 for methanol oxidation studies and compared with PtFe3O4 to observe the effect of GA. The obtained nanostructure was characterised by TEM, SEM, FTIR, Raman and XRD. Also, the particle size was found to be 12.53 nm according to Debye Scherer formula. Electrochemical analyses were performed for the obtained structures. According to the results; electrocatalytic activity increased 8.72 times with the inclusion of GAs in the structure. In addition, according to long-term stability tests, it was observed that it showed 3 times more current at the end of 4000 s and provided high stability in the 500 cycle test. It was determined by EIS and CO stripping tests that GAs increased the electrical conductivity in the structure and offered higher surface area. With this study, it was shown that aerogel offers a very high potential in methanol oxidation studies using its porous structure.

Repurposing the single-used-plastic for development of hydrophobic aerogels for remediation of oil spill and organic solvents

Currently, around 400 million tonnes of synthetic polymers are being dumped as waste annually and by this rate by 2050 the ocean would contain more such waste compared to the total weight of fish. As recycling could solve part of this problem, recently such waste is being reused for various purposes like composite preparation, oil production and various other use such as production of foams, sponges, and aerogels. However, there is a relatively limited literature available on the utilization of polyethylene polymer (like LDPE). The study presented in this article indicated that LDPE-based polymers could be reused (after modification) for preparation of hydrophobic, lightweight, and porous aerogels that have oil-spills and organic solvent adsorption capacity. The aerogels showed contact angle of 121.9o, bulk density below 0.25 g/cm3, and were found to be semi-crystalline. The aerogels showed oil and solvent adsorption more than that for their untreated counterparts. Also, the aerogels were found to be recycled for more than five cycles with very minimum loss of efficacy. This area of producing oil sorbents from single used plastic wastes is still very open for further research and seems to be a promising route for both waste reduction, and the synthesis of value-added products. This could be one of the most sustainable approaches for efficient single-used plastic wase management and environment clean-up.

Fabrication, Performance, and Potential Applications of MXene Composite Aerogels.

Aerogel, known as one of the remarkable materials in the 21st century, possesses exceptional characteristics such as high specific surface area, porosity, and elasticity, making it suitable for a diverse range of applications. In recent years, MXene-based aerogels and MXene composite aerogels as functional materials have solved some limitations of traditional aerogels, such as improving the electrical conductivity of biomass and silicon aerogels, further improving the energy storage capacity of carbon aerogels, enhancing polymer-based aerogels, etc. Consequently, extensive research efforts have been dedicated to investigating MXene-based aerogels, positioning them at the forefront of material science studies. This paper provides a comprehensive review of recent advancements in the preparation, properties, and applications of MXene-based composite aerogels. The primary construction strategies employed (including direct synthesis from MXene dispersions and incorporation of MXene within existing substrates) for fabricating MXene-based aerogels are summarized. Furthermore, the desirable properties (including their applications in electrochemistry, electromagnetic shielding, sensing, and adsorption) of MXene composite aerogels are highlighted. This paper delves into a detailed discussion on the fundamental properties of composite aerogel systems, elucidating the intricate structure-property relationships. Finally, an outlook is provided on the opportunities and challenges for the mass production and functional applications of MXene composite aerogels in the field of material engineering.

Carbon Nanofiber-Sodium Alginate Composite Aerogels Loaded with Vitamin D: The Cytotoxic and Apoptotic Effects on Colon Cancer Cells.

Colorectal cancer (CRC) is the fourth most commonly diagnosed cancer and the third leading cause of cancer-related deaths worldwide. A substantial body of literature supports the crucial role of vitamin D (VD) in the etiology, progression, prognosis, and treatment of cancer. Recent clinical studies have found an inverse correlation between CRC incidence and serum VD levels. However, the low water solubility of VD and its anticarcinogenic activity at supraphysiological plasma levels, which causes hypercalcemia, required carrier systems. Carbon-based nanomaterials are excellent eco-friendly candidates, with exceptional chemical resistance, efficient mechanical properties, and negligible weight. Furthermore, composite aerogels manufactured from these nanomaterials have gained interest due to their extensive surface areas and porous structures, which make them suitable for delivering drugs. Our research aimed to study the development of composite aerogels loaded with VD by utilizing carbon nanofibers (CNFs) in an aerogel matrix provided to colon cancer cells. For this purpose, Aero1 as a drug delivery system was first prepared and characterized using XRD, FTIR, and SEM methods. Biochemical methods were employed to evaluate the antiproliferative, apoptotic, and anti-migratory effects on colon cancer cells. FTIR and XRD measurements confirmed the production of aerogels. SEM analysis revealed that aerogels have a non-uniform surface. The findings showed that aerogels can effectively deliver VD to the colon cancer cells, while also inhibiting cancer cell proliferation and migration. This research suggests that the Aero1 drug delivery system could be a valuable tool in the fight against colon cancer and other health issues.

Hollow Particles Obtained by Prilling and Supercritical Drying as a Potential Conformable Dressing for Chronic Wounds.

The production of aerogels for different applications has been widely known, but the use of polysaccharide-based aerogels for pharmaceutical applications, specifically as drug carriers for wound healing, is being recently explored. The main focus of this work is the production and characterization of drug-loaded aerogel capsules through prilling in tandem with supercritical extraction. In particular, drug-loaded particles were produced by a recently developed inverse gelation method through prilling in a coaxial configuration. Particles were loaded with ketoprofen lysinate, which was used as a model drug. The core-shell particles manufactured by prilling were subjected to a supercritical drying process with CO2 that led to capsules formed by a wide hollow cavity and a tunable thin aerogel layer (40 μm) made of alginate, which presented good textural properties in terms of porosity (89.9% and 95.3%) and a surface area up to 417.0 m2/g. Such properties allowed the hollow aerogel particles to absorb a high amount of wound fluid moving very quickly (less than 30 s) into a conformable hydrogel in the wound cavity, prolonging drug release (till 72 h) due to the in situ formed hydrogel that acted as a barrier to drug diffusion.

Non-supercritical drying synthesis of hydrophobic, low-density, and high surface area silica aerogel using a sonication technique

Replacing the solvent in silica aerogel production with air is critical in getting the desired physical properties. Even though drying by evaporation under ambient pressure is thought to be the simplest way, it shrinks and collapses the gel network. In this research, uniform sol was prepared by sonication at room temperature. The surface of the developed wet gel was modified with trimethylchlorosilane (TMCS) after solvent exchange. The prepared aerogels underwent various characterization techniques to evaluate their functional, structural, morphological, surface, and thermal properties. The textural and physical characteristics of prepared silica aerogel were examined in relation to the precursor concentration, catalysts that affect the density of silica aerogel, volumetric shrinkage, and gelation time. The silica aerogel was found thermally stable up to 800 °C while hydrophobicity retained up to 350 °C. The contact angle of prepared aerogels confirms their hydrophobic nature. Field emission scanning electron microscopy (FE-SEM) and X-Ray Diffraction (XRD) results demonstrate the porous nature of silica aerogel. The Brunauer-Emmett-Teller (BET) surface area analysis revealed that the surface area and the pore radius were 784 m2/g and 36 Å, respectively.

Superior broadband sound absorption in hierarchical ultralight graphene oxide aerogels achieved through emulsion freeze-casting

Ultra-lightweight aerogels have profound applications as advanced multi-functional sound-absorbing materials. At present, conventional aerogels are associated with pores with sizes too small for effective sound absorption in the audible range. In this work, we fabricated a hierarchically porous ultralight graphene oxide (GO) aerogel through a novel emulsion freeze-casting process of an air-in-water emulsion. Microstructural analysis of the aerogels reveals a hierarchical pore morphology consisting of highly inter-connected pores produced from the emulsion bubbles and the micro-pores produced by freeze-casting. Sound absorption measurements revealed that an aerogel with a surfactant-to-GO weight ratio of 1:1 displays an average absorption coefficient of up to 0.86 at a broadband frequency range between 250 Hz and 6300 Hz, a vast improvement by up to 58% as compared to conventional GO aerogels. Numerical microstructural models were developed to model the acoustic absorption phenomenon and understand the mechanisms behind enhanced sound absorption. These models identified the enhanced acoustic absorption as attributed to the increased air-wetting area as derived from the high reticulation rate in this hierarchical microstructure. Overall, we demonstrate the potential of leveraging the highly inter-dependent material-process-structure relationships of GO aerogel production to achieve hierarchical GO aerogels as advanced ultralight sound-absorbing materials.

Recent Advances in Nanocellulose Aerogels for Efficient Heavy Metal and Dye Removal.

Water pollution is a significant environmental issue that has emerged because of industrial and economic growth. Human activities such as industrial, agricultural, and technological practices have increased the levels of pollutants in the environment, causing harm to both the environment and public health. Dyes and heavy metals are major contributors to water pollution. Organic dyes are a major concern because of their stability in water and their potential to absorb sunlight, increasing the temperature and disrupting the ecological balance. The presence of heavy metals in the production of textile dyes adds to the toxicity of the wastewater. Heavy metals are a global issue that can harm both human health and the environment and are mainly caused by urbanization and industrialization. To address this issue, researchers have focused on developing effective water treatment procedures, including adsorption, precipitation, and filtration. Among these methods, adsorption is a simple, efficient, and cheap method for removing organic dyes from water. Aerogels have shown potential as a promising adsorbent material because of their low density, high porosity, high surface area, low thermal and electrical conductivity, and ability to respond to external stimuli. Biomaterials such as cellulose, starch, chitosan, chitin, carrageenan, and graphene have been extensively studied for the production of sustainable aerogels for water treatment. Cellulose, which is abundant in nature, has received significant attention in recent years. This review highlights the potential of cellulose-based aerogels as a sustainable and efficient material for removing dyes and heavy metals from water during the treatment process.

Fast production of silica aerogel using methyltrimethoxysilane by ambient drying process for superior chemical adsorption properties

Fast production of silica aerogel using methyltrimethoxysilane by ambient drying process for superior chemical adsorption properties

Advanced Fabrication and Multi-Properties of Aluminum-Based Aerogels from Aluminum Waste for Thermal Insulation and Oil Absorption Applications

Metal-based aerogels have attracted numerous studies due to their unique physical, structural, thermal, and chemical properties. Utilizing aluminum waste, a novel, facile, environmentally friendly approach to aluminum-based aerogels is proposed. In this work, the aluminum-based aerogels produced do not use toxic chemicals unlike conventional aerogel production. Aluminum powder, with poly(acrylic acid) and carboxymethyl cellulose as binders, is converted into aluminum-based aerogels using the freeze-drying method. The aluminum-based aerogels have low density (0.08-0.12 g/cm3) and high porosity (93.83-95.68%). The thermal conductivity of the aerogels obtained is very low (0.038-0.045 W/m·K), comparable to other types of aerogels and commercial heat insulation materials. Additionally, the aerogels can withstand temperatures up to 1000 °C with less than 40% decomposition. The aerogels exhibited promising oil absorption properties with their absorption capacity of 9.8 g/g and 0.784 g/cm3. The Young's modulus of the aerogels ranged from 70.6 kPa to 330.2 kPa. This study suggests that aluminum-based aerogels have potential in thermal insulation and oil absorption applications.

Characterization and assessment of aerogel-modified asphalt binders

ABSTRACT Conventional asphalt has been used along the time with relatively satisfactory performance. However better performance in terms of development, environment, and economic benefits needs to be addressed. Asphalt binder modification has been one of the most common methods to improve the performance of bitumen over time. The objective of this study is to provide insight into the modification of asphalt binders to reduce thermal cycling by introducing Aerogel. Several tests were conducted including Softening Point (SP), Rotational Viscosity (RV), Dynamic Shear Modulus (G*), Multiple Stress Creep Recovery (MSCR), Flexural Creep Stiffness (BBR), Binder Bond Strength (BBS), and Thermal Conductivity (TC) tests. The response of five aerogel products was assessed based on performance. The outcomes of this study were encouraging and promising. Thermal resistance properties and cost per kilogram of each product were used to determine the more suitable aerogel product for further utilisation. The addition of aerogel reduced the susceptibility to damaging thermal effects of bitumen, reducing the permanent deformation and thermal cracking potential. However, the implementation of aerogel in binder must be enhanced to overcome the workability and safety concerns, which restrict the feasibility of its usage.

Pectin-based aerogel particles for drug delivery: Effect of pectin composition on aerogel structure and release properties

In this work, nanostructured pectin aerogels were prepared via a sol-gel process and subsequent drying under supercritical conditions. To this end, three commercially available citrus pectins and an in-house produced and enzymatically modified watermelon rind pectin (WRP) were compared. Then, the effect of pectin's structure and composition on the aerogel properties were analysed and its potential application as a delivery system was explored by impregnating them with vanillin. Results showed that the molecular weight, degree of esterification and branching degree of the pectin samples played a main role in the production of hydrogels and subsequent aerogels. The developed aerogel particles showed high specific surface areas (468–584 m2/g) and low bulk density (0.025–0.10 g/cm3). The shrinkage effect during aerogel formation was significantly affected by the pectin concentration and structure, while vanillin loading in aerogels and its release profile was also seen to be influenced by the affinity between pectin and vanillin. Furthermore, the results highlight the interest of WRP as a carrier of active compounds which might have potential application in food and biomedical areas, among others.

Silica aerogels: from materials research to industrial applications

ABSTRACT Silica aerogels are advanced materials with outstanding properties, including high specific surface area and porosity, low thermal conductivity, density, dielectric constant, and refractive index. However, the excellent properties of silica aerogels have shown limited utility in industrial applications, primarily as thermal insulation materials, where they hold only a small (1.1–2.6%) market share. The emergence of clean energy technologies stimulated renewed interest in silica and other aerogels. Here the recent advances in the production and applications of silica aerogels are summarized, and the current challenges and future development opportunities are discussed. The conventional and emerging syntheses and characterization methods of silica aerogels are introduced, followed by a discussion on thermophysical properties and potential applications. The fabrication processes of silica aerogels are analysed at different industry development stages. Recent advances in aerogels research are considered, highlighting the obstacles and possible solutions for the successful translation and industry uptake and focusing on the emerging applications in electric vehicles and building insulation.