Aerogel Research Articles

Optimization of magnesium silica aerogel production and evaluation as a food additive: a comparative study of water glass and bio-based sodium silicate source as a precursor

Optimization of magnesium silica aerogel production and evaluation as a food additive: a comparative study of water glass and bio-based sodium silicate source as a precursor

Jute-reinforced hybrid biocomposite incorporated with low thermal conductive silica aerogel for improved resistance to conductive and radiative heat

This study aims to develop jute-reinforced polypropylene composites by incorporating low-heat conductive silica aerogel for enhanced thermal performance, envisioning their utilization as heat-insulating panels in buildings. The fabrication of hybrid composites using a heat press molding technique showed a significant improvement in thermal properties due to incorporating aerogel into the material. The lowest obtained thermal conductivity of hybrid composite was 0.0986 W/m·K, which was almost halved (0.1704 W/m·K) to the material without aerogel. The radiative heat resistance of hybrid composites was also improved with the aerogel in the material. Additionally, composites with higher amounts of aerogel showed superior flame resistance and thermal stability at high temperatures. The hybrid composites, however, demonstrated a decrease in tensile strength due to the presence of aerogel particles at the interface of composites. The composite without aerogel displayed the highest tensile strength of 64.67 MPa, which was the lowest (47.87 MPa) for the material with the maximum amount of aerogel. The fractographic investigation also revealed the existence of aerogel particles and their random distribution at the interface of the material. The low water absorption owing to reduced interfacial vacuities and the existence of super-hydrophobic aerogel in the interior of composites indicated their durability in humid conditions without deteriorating the dimensional stability. The outcomes of the study revealed a considerable effect of aerogel on the thermal performance of composites and ascertained their excellence as a prospective heat-insulating material for conserving thermal energy by minimizing heat transfer from inside to outside of the building and vice versa.

Life cycle assessment of silica aerogel produced from waste glass via ambient pressure drying method

Silica aerogels are excellent insulation materials, but they possess high embedded costs and their production includes many energy-intensive steps. A novel protocol developed to produce silica aerogel from waste soda lime glass via ambient pressure drying was assessed regarding sustainability. Upcycling waste materials and implementing a low-energy drying technique are aimed at increasing the sustainability of aerogels. This study presents a cradle-to-gate life cycle assessment (LCA) of this process on a laboratory scale (reactor volume of 0.5 l) as well as on a modeled industrial scale (reactor volumes of 100 l and 1000 l). The environmental impacts associated with each scale, as well as with each step of the production, were calculated and summarized with an environmental cost indicator in euros for each process. Potential end-of-life scenarios were considered to explore waste treatment approaches. Results show that electricity consumption is a major contributor to environmental impact, especially at the laboratory scale. However, at the industrial scale, efficiency is significantly improved, thereby drastically decreasing the impact of electricity. Additionally, the contributions of raw materials have a larger environmental impact than those of waste disposal, indicating that it is crucial to focus on the reduction and re-usage of reactants and solvents.

Water-Enhancing Gels Exhibiting Heat-Activated Formation of Silica Aerogels for Protection of Critical Infrastructure During Catastrophic Wildfire.

A promising strategy to address the pressing challenges with wildfire, particularly in the wildland-urban interface (WUI), involves developing new approaches for preventing and controlling wildfire within wildlands. Among sprayable fire-retardant materials, water-enhancing gels have emerged as exceptionally effective for protecting civil infrastructure. They possess favorable wetting and viscoelastic properties that reduce the likelihood of ignition, maintaining strong adherence to a wide array of surfaces after application. Although current water-enhancing hydrogels effectively maintain surface wetness by creating a barricade, they rapidly desiccate and lose efficacy under high heat and wind typical of wildfire conditions. To address this limitation, unique biomimetic hydrogel materials from sustainable cellulosic polymers crosslinked by colloidal silica particles are developed that exhibit ideal viscoelastic properties and facile manufacturing. Under heat activation, the hydrogel transitions into a highly porous and thermally insulative silica aerogel coating in situ, providing a robust protective layer against ignition of substrates, even when the hydrogel fire suppressant becomes completely desiccated. By confirming the mechanical properties, substrate adherence, and enhanced substrate protection against fire, these heat-activatable biomimetic hydrogels emerge as promising candidates for next-generation water-enhancing fire suppressants. These advancements have the potential to dramatically improve the ability to protect homes and critical infrastructure during wildfire.

Lightweight and hydrophobic silica aerogel/glass fiber composites with hierarchical networks for outstanding thermal and acoustic insulation

Silica aerogels are regarded as potential thermal and acoustic insulation materials with low density and porous structure. However, the hydrophilicity due to surface hydroxyl groups and the low mechanical intensity have limited its further application. Generally, it can be achieved by adjusting the process parameters of the sol-gel to refine the structure of silica aerogels and optimize performance. In this study, we adopted an appropriate modification strategy of incorporating glass fiber felts as the reinforcing phase and trimethylchlorosilane (TMCS) as the hydrophobic modifier. By adjusting the solvent exchange time, the micro-nano structure, i.e. hierarchical networks, was optimized. The TMCS-modified silica aerogel/glass fiber/hot-melt fiber composites (TSGMs) exhibited great sound insulation, and the maximum sound transmission loss (STL) was up to 34 dB at 6300 Hz. Compared to unmodified, STL improved by 8 dB in simulated practical applications. In addition, TSGMs also exhibited high hydrophobicity with a water contact angle of 147° and excellent thermal insulation with a thermal conductivity of 0.0345 W (m k)-1. The results could contribute to the refinement in the preparation process of silica aerogel composites and use in the fields of thermal and acoustic insulation.

Understanding cone crack formation in cosmic dust aerogel collectors by low-velocity similitude impact test

Low-density silica aerogel is an ideal medium for capturing cosmic dust in space, as the perforated tracks provide valuable insights into the characteristics of interplanetary particles. However, the mechanism behind track formation remains unclear. This paper examines the skirt-shaped or cone-in-cone cracks commonly observed in both ground experiments and returned aerogel samples. Similitude impact tests using various techniques compare cone cracks formed at different velocities. Results show that cone cracks typically form at lower impact velocities. Additionally, impact tests with hard spherical projectiles at speeds below 50 m/s, conducted using an electromagnetic coilgun, produced multiple tracks with single cone cracks. The impact process is captured in real-time using a high-speed camera, and the formation mechanism is investigated. A theoretical model, based on contact mechanics and energy methods, is developed to quantify the relationship between cone crack morphology and projectile impact parameters. The model's accuracy is validated through experimental results. This study reveals the formation of cone cracks in penetration tracks within silica aerogel. The proposed model identifies the energy absorption mechanism during single cone crack formation, potentially improving the understanding of key parameters (initial size, composition, velocity distribution, astrophysical source) from the perforated tunnels in cosmic dust aerogel collectors.

Overview of Multifunctional (Ultra-)Lightweight Materials for a Sustainable Future

Abstract In line with the ongoing advancement of high-performance materials that are multifunctional and environmentally friendly, this paper provides an overview of recent developments in lightweight and ultra-lightweight multifunctional materials. We primarily examine the various types of low-density multifunctional materials, their production techniques, and their applications within the context of a sustainable future. From a structural point of view, ultra-light materials are classified into three main groups: aerogels, foam, and micro/ nanolattice. In terms of composition, they can be derived from ceramic, metallic, or polymeric materials. This overview pays particular attention to silica, carbon and composite aerogels, as well as metal, ceramic (carbon), and polymer foams.

Aerogel‐Driven Interface Rapid Self‐Gelation Enables Highly Stable Zn Anode

AbstractThe practical application of Zn metal anodes is currently hindered by uncontrolled dendritic growth and water‐induced parasitic reactions that are closely related to the solvation structure and interfacial transport kinetics of Zn2+. Herein, a facile interface self‐gelation strategy is proposed to stabilize Zn anode by introducing ‐OH‐rich silica aerogel (HSA) on Zn anode surface. The unique interconnected network structure and strong hydrophilia of HSA made the aqueous electrolyte near Zn anode gel rapidly and spontaneously, resulting in the formation of a water‐poor gel interface layer. The interface layer can effectively accelerate the desolvation process and reduce water molecule activity near anode surface through hydrogen bonding interaction, thus achieving rapid Zn migration kinetics and alleviating side reactions. In addition, the well‐defined aerogel nanochannels can provide a fast Zn2+ migration path and homogenize Zn2+ flux, enabling rapid and uniform Zn deposition. As a result, the HSA‐modified Zn (HSA@Zn) anode exhibits excellent long‐term cycling stability (over 6000 h at 4 mA cm−2), and the feasibility for practical application of this HSA@Zn anode is further demonstrate in full cells. The aerogel‐driven interface self‐gelation strategy propose in this work provides new insights into the design of advanced Zn anode for aqueous zinc‐ion batteries.

Better than linear strength scaling of multifunctional ceramic truss lattice materials

Driven by the goal of creating exceptionally strong and lightweight thermal insulators to enable the operation of a vacuum airship on Venus, conditions where ceramic truss lattice materials provide better than linear scaling of strength with respect to variations in relative density have been found. This enhanced scaling relationship is a consequence of the pressure sensitive shear strength of ceramic materials. A new Gibson-Ashby type scaling relationship is developed between strength and relative density. Elementary analysis is used to formulate theoretical limits for the compressive strength, minimum density, and minimum thermal conductivity for truss lattice materials subjected to hydrostatic pressure loads. Shape optimization using the covariance matrix adopted evolutionary strategy (CMA-ES) and highly resolved finite element models is conducted on silicon carbide Kelvin cells with variable cross-section axisymmetric struts considering three failure modes: buckling, tensile rupture, and shear failure. The optimized designs closely adhere to and validate the newly developed analytical scaling relationship with better than linear strength scaling. These optimized designs are found to withstand the extreme loading conditions on Venus while providing up to 43 kgm3 of buoyancy. The thermal conductivity of the optimized designs are computed and found to be less than 0.5 WmK, with one design outperforming silica aerogels at elevated temperature.

Silica Aerogel in Microfluidic Channels: Synthesis, Chip Integration, Mechanical Reinforcement, and Characterization.

Silica aerogels are highly porous materials with unique properties such as high specific surface area, high thermal insulation, and high open porosity. These characteristics make them attractive for several applications in closed microfluidic channels such as BioMEMS, catalysis, and thermal insulation. However, aerogel-filled microchannels have not been reported in the literature yet because of the complexity of creating a process that controls the integration, shrinkage, and mechanical stability of these materials inside a closed channel. In this work, a process is presented to integrate aerogels in microchannels with reproducibility, mechanical stability, and no shrinkage. This protocol is based on the filling of channels during the gelation, which is crucial to avoid shrinkage, CO2 supercritical drying, and mechanical additives (polyethylene glycol and carbon nanotubes). Furthermore, the influence of polyethylene glycol and carbon nanotubes on the compressive strength, porosity, and specific surface area is investigated. Following the suggested process protocol, the integration of different aerogel compositions (with and without reinforcement) is successfully achieved in the microchannels without shrinkage and cracks. This research opens up new possibilities for the use of different aerogels in microfluidics with structural integrity and enhanced functionality.

The impact of aluminum oxide deposition on the high-temperature resistance of silica aerogels

The impact of aluminum oxide deposition on the high-temperature resistance of silica aerogels

Innovative silica aerogel fiberglass walls and roofs: A path to lower carbon emissions and higher energy savings

ABSTRACT Buildings account for a significant portion of global energy use and consumption. Buildings have substantial energy consumption due to the use of heating, ventilation, and cooling systems. It is evident that the insulation materials used in the design of building envelopes can efficiently reduce the cost of air conditioning by reducing external heat gains and losses. Additionally, the use of environmentally friendly and cost-effective can be beneficial from an environmental standpoint. This paper aims to evaluate the potential for cost savings in the air conditioning of buildings incorporated with silica aerogel fiberglass insulation in hollow concrete bricks (wall) and hollow roof tile (roof). Silica aerogel fiberglass insulation is extensively used for heat insulation purposes, including building insulations, due to its superior thermal insulation and flame retardant properties. The thermo-physical properties of silica fiberglass insulation and building materials were determined experimentally as per ASTM D 5334 standards. Twenty distinct building design concepts are investigated in this study, each featuring insulation-integrated concrete blocks composed of silica aerogel fiberglass: (WEM1) insulation layer in the outer side, (WEM2) insulation layer in the center, (WEM3) insulation layer in the inner side, (WEM4) insulation layers in the outer-middle, (WEM5) insulation layers in the middle-inner, and (WEM6) insulation layers in the outer-inner sides. Additionally, two arrangements of insulation-stuffed roof tiles, REM1 above the RCC and REM2 below the RCC. In addition, novel building designs integrated with insulation were analyzed numerically, related to environmental conditions that refer to two different scenarios in India (hot dry and composite climates). Thermo-economic analysis of novel wall and roof designs with silica fiberglass insulation materials on air-conditioning costs, carbon dioxide emissions, and payback time are compared with conventional roof and wall patterns. The thermo-economic analysis was carried out based on the number of degree-hours of heating and cooling to determine the building’s annual energy usage. The building model arrangement (WEM6-REM1), which consists of an insulation composite wall (WEM6) and insulation roof tile (REM1), demonstrated the greatest annual air conditioning cost savings of 3.4 $/m2/year and 1.74 $/m2/year when compared to conventional building design for climatic conditions of Kurnool and Gauhati. The building model arrangement (WEM6-REM1) composed of silica fiberglass aerogel insulation exhibits the highest reduction in carbon emissions of 65 kg/kWh and 33 kg/kWh, when compared to conventional building design analyzed in both hot-arid; (Kurnool) and composite (Gauhati) climatic conditions. The placement of insulation in the roof alone (REM1) has the shortest payback duration of 2.15 years. The results of this study point to a viable approach to enhancing building design decision-making and narrowing the performance gap in sustainable and energy-efficient strategies.

Development of a multifunctional bio-based insulation material with corncob and silica aerogel

Bio-based insulation materials with superior comprehensive properties are crucial to building energy conservation. This study aims to develop a multifunctional bio-based insulation material that integrates good insulation, mechanical strength, and waterproofing. In this work, using corncob as the raw material, foamed geopolymer as the binder, silica aerogel and silicone oil as additives, a novel bio-based insulation material was prepared. Moreover, the effect of corncob size, silica aerogel content and silicone oil content on the microstructure, density, thermal conductivity, compressive strength, water absorption, moisture absorption and water contact angle properties were discussed. The results showed that, a desirable bio-based insulation material with a corncob size of 20 mesh, silica aerogel/geopolymer mass ratio (A/G) being 1.71 %, silica aerogel/ silicone oil mass ratio (A/O) being 0.2, is recommended, of which the thermal conductivity is 0.111 W/(m.K) with the compressive strength being 2.2 MPa, the density being 350 kg/m3, the water absorption being 7.1 %, the moisture absorption being 9.4 % and the water contact angle being 133°. With a simple preparation process, low cost and low energy consumption, this bio-based insulation material has good application prospects in buildings. Meanwhile, the preparation method of bio-based insulation materials proposed in this study provides new ideas for the development of multifunctional insulation materials in the future.

Temperature-irrelevant superhydrophobic polyimide–SiO2 aerogels with a confined shrinkage strategy for high-temperature thermal protection (>400 °C)

Polyimide (PI) aerogels often experience substantial volume shrinkage when exposed to temperatures above 200 °C. Furthermore, research regarding the hydrophobic characteristics of PI aerogels under high-temperature conditions is limited. Herein, a confined shrinkage strategy was proposed, and the PI–SiO2 aerogels were prepared with ultralow thermal shrinkage and high-temperature superhydrophobic properties. Micrometer-sized silica aerogel powders were used in this strategy as shrinkage inhibitors during the production of PI aerogels. The silica aerogel powders were then pulled together using the PI chain and braced to each other, limiting the shrinkage of the PI aerogel matrix attached to the powders. Results indicated that the prepared aerogel experienced a shrinkage of only 6.2 % after heat treatment at 400 °C for 1 h in a muffle furnace. The surface area of the sample decreased from 669 m2/g to 649 m2/g after heat treatment, revealing a reduction of only 2.7 %. Previous studies have never reported this remarkable thermal stability. Furthermore, the aerogel exhibited superhydrophobic properties with a water contact angle of 157.4° and a water rolling angle of approximately 0° at 300 °C due to its high surface roughness.

Mesoscopic structure modeling of silica aerogels using cluster‐cluster aggregation

AbstractSilica aerogels are nanostructured materials known for their low density, high porosity, and excellent thermal insulation properties. Among silica aerogels, organosilane‐derived aerogels have received considerable interest for their additional chemical functionalities such as hydrophobicity and flexibility. This work investigates the mesoscopic modeling of such aerogels, extending an aggregation based model developed for conventional silica aerogels. The pH of sol–gel polymerizations is one of the most critical reaction and processing parameters in determining the porosity, density, strength, and transparency of the resulting gels. Achieving optical transparency in aerogels depends on the presence of homogeneous mesoporous network structures. To account for the effect of pH, a relationship between pH and adhesion probability was incorporated into a three‐dimensional cluster‐cluster aggregation (CCA) model, providing insight into the gelation process. In addition, size‐dependent diffusivities are considered in this study. By incorporating different factors into the CCA model, the gelation kinetics are evaluated. The obtained mesoscopic structure is compared with experimental characterizations, together with preliminary mechanical simulations.

Advancing sustainable molded packaging: Integrating silica aerogel into recycled paper pulp for the fabrication of thermally and mechanically stable superhydrophobic composites

In recent years, the growing demand for sustainable packaging has significantly fueled the quest to explore novel approaches that enhance the applicability of renewable alternatives. This study leverages the unique properties of silica aerogel (SA) to address the limitations of traditional molded pulp products. By integrating SA into recycled paper pulp (RP), we aimed to improve water resistance, thermal stability, and mechanical properties. Composites were prepared with varying SA concentrations (1–10 %). Contact angle measurements showed enhanced hydrophobicity, with RP/SA3 % achieving a contact angle of 152.09°, compared to 122.39° for neat RP. The tensile index (TI) of RP/SA composites with 3 % SA increased by 21.09 % compared to neat RP, indicating better mechanical strength. Thermal conductivity significantly decreased, with RP/SA10 % reducing from 0.155 W m−1·K−1 in neat RP to 0.088 W m−1·K−1, a 43.2 % improvement in thermal insulation. Additionally, composites with 1 % and 3 % SA maintained high biodegradability, showing over 50 % degradation after six weeks in soil. These results suggest that incorporating SA into RP composites enhances their functionality without compromising biodegradability, offering a promising solution for sustainable packaging. As regulatory bodies emphasize resource management and waste reduction, the potential of these innovative and environmentally friendly packaging solutions becomes increasingly significant.

Effects of Moisture Content on the Radiative Properties and Energy-Saving Performance of Silica Aerogel Windows.

The thermal insulation performance of windows is crucial for energy-efficient buildings. Windows are typically the weakest part of the building envelope, regarding thermal insulation. Due to its excellent thermal insulation and high transparency, silica aerogel shows great promise as a window material. However, moisture can impact the effectiveness of the aerogel, leading to poor visibility and reduced thermal insulation. This study simulated a silica aerogel with varying moisture levels using the combination of diffusion-limited cluster aggregation, discrete dipole approximation, and Monte Carlo methods. The effects of the moisture content, thickness, porosity, and particle size on thermal conductivity, solar transmittance, and haze were analyzed. Visual properties of the aerogels were also considered. The energy consumption of a 30 m2 room under different climates was simulated using TRNSYS to assess the energy-saving potential of silica aerogel glass. The findings indicate that a higher moisture content leads to decreased solar transmittance and increased thermal conductivity of aerogels. Silica aerogel glass is more energy efficient than single-layer float glass, with the dry aerogel performing better in cold climates but worse in hot climates. This study provides insights for designing aerogel glass that optimizes solar transmittance and thermal insulation to enhance building comfort and energy efficiency.

Foldable sandwich fabric-based composites with thermal insulation and low emissivity for highly efficient infrared stealth

Fabric-based infrared (IR) stealth composites with thermal insulation and low emissivity are desirable for improving IR camouflage of military targets and thermal management of special environments. Therefore, a flexible and foldable composite fabric with a sandwich structure is delicate designed in this work aiming to realize dual-modes IR effects. Polyester fabric chemically plated with copper-nickel (Cu/Ni@PF) and aluminum foil (AF) are on the top and bottom, respectively, acting as low emissivity layers. The medium layer is constructed by silica aerogel microspheres (SAM) with thickeners and waterborne polyurethanes (WPU) functioned as thermal insulation. The thermal conductivity of as-prepared composite fabric is only 0.05904 W/(m·K). When the AF is heated to 70 °C, the introduction of the SAM in the medium layer with the thickness of 300 μm makes Cu/Ni@PF as top surface exhibit a obvious temperature difference of 11.7 °C, demonstrating excellent thermal insulation. The AF maintains a low emissivity of less than 0.2, and the emissivity of Cu/Ni@PF was also as low as 0.296 at 8–14 μm, which can effectively shield the IR signal. Thanks to the Cu/Ni@PF as the top surface, the radiation temperature displays only 36.3 °C when heated at 70 °C, which meaning the dramatic IR signal strength reduce. Therefore, this dual-modes flexible and foldable composite can be a potential candidate in the IR stealth fields.

Effect of Strain Rate on the Structure Properties of Silica Aerogel

Silica aerogel is a versatile material used in adsorption, filtration, and thermal insulation. However, its mechanical strength is a notable weakness, making it prone to damage. This study utilized molecular dynamics simulations to investigate the mechanical properties of aerogels. We compared the simulation results with the data from the experiments. The dimensionless specific surface areas of both are nearly identical at densities below 0.7 g/cm³. We explored the impact of strain rate on aerogel properties. The compression rate had minimal effects on stress and density during uniaxial compression. The specific surface area exhibited an initial increase followed by a decrease with a rising compression rate, peaking at 2 1/ns. Furthermore, we determined the solid thermal conductivity of the aerogel, which was 0.0764 W/(m·K) without strain. The solid thermal conductivity showed little variation with compression rate but was highly sensitive to density. The stretching rate during uniaxial stretching influenced the heat transfer coefficient, density, specific surface area, and stress. However, in the low-strain region (strain < 0.3), the tensile rate had a negligible impact on these performance metrics. This investigation offers a theoretical analysis of the mechanical properties of aerogels, establishing a foundational understanding of their efficient application.

Hierarchical Ceramic Nanofibrous Aerogels for Universal Passive Radiative Cooling

AbstractSolar‐induced thermal challenges in buildings, cold chain logistics, and spacecrafts may be overcome by integrating passive radiative cooling (PRC) with aerogels having thermal insulation (TI). Herein, a universal radiative cooling silica aerogel (UCSA) is prepared through the simple regeneration and freeze‐drying of commercial quartz fiber membranes. The optically engineered UCSA with a hybrid structure (silica nanofibers/microbeads) achieves remarkable solar reflectance (RS.E. = 98.1%) and atmospheric transparency window emittance (εATW = 92.1%) under Earth conditions, with a theoretical daytime cooling power of 103.3 W m−2. In the harsh space environment, it exhibits ultrahigh average solar reflectance (RS.E. = 99.1%) and broadband mid‐infrared emittance (εMIR = 90%), achieving a cooling power of 354.1 W m−2. Compared to single‐functional approaches, UCSA synergistically integrates the PRC and TI performance for excellent thermal management capability. Moreover, this ceramic aerogel can resist temperatures up to 830 °C, safeguarding building occupants and spacecraft electronics. Furthermore, UCSA passes environmental aging and thermal vacuum outgassing tests for long‐term viability both on Earth and in space. Finally, a USCA‐covered box achieves an average sub‐ambient cooling of 18.6 °C when exposed to sunlight. In summary, UCSA opens a path for energy‐efficient and sustainable cooling strategy with universal applications.