Aerogel Research Articles

Impact of High Power Laser Fluence on the Chemical Signatures of Silica Aerogel Films

Impact of High Power Laser Fluence on the Chemical Signatures of Silica Aerogel Films

Experimental and numerical investigations on phase change thermal storage foam concrete based on CaCl2∙6H2O/silica aerogel composite phase change material

A new type of phase change thermal storage foam concrete was developed by effectively incorporating a composite phase change material (CPCM) into foam concrete. The CPCM was obtained by using 75 wt% CaCl2∙6H2O as PCM and 25 wt% silica aerogel as carrier, with a phase change temperature of 27.0 °C and an enthalpy value of 110.9 J/g. The mechanical and thermal properties of the obtained phase change thermal storage foam concrete blocks were investigated experimentally, along with a numerical analysis of their heat transfer characteristics. The experimental results demonstrated that after adding CPCM, the thermal performances of foam concrete blocks significantly increased, under the condition of their dry densities and compressive strengths met the specification requirements. Adding 20 wt% CPCM, the enthalpy value, specific heat capacity, thermal conductivity and thermal inertia of foam concrete block respectively reached 37.0 J/g, 1782.0 J/(kg∙K), 0.131 W/(m·K) and 770.9, with appropriate phase change temperature (27.2 °C). Numerical analysis for the heat transfer characteristics of the phase change thermal storage foam concrete wall revealed that optimal thermal insulation and thermal storage performances were achieved when the wall contained 20 wt% CPCM and thickness of 80 mm. In this case, the model exhibited a temperature wave attenuation factor of 6.66, the temperature amplitude of 5.84 K and a decline of 9.87 K for the highest temperature of the wall as well as delay time of 198,000 s, effectively regulating indoor temperature and saving energy. Therefore, the as-prepared phase change thermal storage foam concrete had great potential for application in building energy conservation.

Enhancing thermal stability and electrical conductivity performance of silica aerogel via graphene oxide integration

Enhancing thermal stability and electrical conductivity performance of silica aerogel via graphene oxide integration

One-pot synthesis of rationally-designed flexible, robust, and hydrophobic ambient-dried molecularly-bridged silica aerogels with efficient and versatile oil/water separation applications

One-pot synthesis of rationally-designed flexible, robust, and hydrophobic ambient-dried molecularly-bridged silica aerogels with efficient and versatile oil/water separation applications

Correction to: Plastic deformation and heat-enabled structural recovery of monolithic silica aerogels

Correction to: Plastic deformation and heat-enabled structural recovery of monolithic silica aerogels

Bio-Templated Aerogel Fibers: Heterogeneous Spinodal Architecting and In Situ Fibrillation of Thermoplastic Polyurethane-Silica on Nanostructured Cellulose Nanofiber Scaffold for Enhanced Thermomechanical Performance.

This study addresses the inherent fragility and fractal limitations of traditional silica aerogels by developing a bio-templated aerogel fiber. Integrating cellulose nanofibers (CNFs), thermoplastic polyurethane (TPU), and silica aerogel (SA) in a dimethyl sulfoxide (DMSO) dispersion, a gel-spinning technique was employed to create aerogel fibers with superior thermomechanical performance. CNF also provided excellent rheological modification for successful spinnability, fast gelation, and fiber formation. The unique hierarchical structure of these fibers, formed through hot-stretching and surface modification, combined the superior mechanical strength and flexibility of TPU with the exceptional insulation properties of CNF and SA. The CNF network, encapsulated within the SA particles, formed a core-shell structure, axially aligned, that significantly enhances the thermal stability and mechanical performance of the fibers while maintaining a lightweight and porous architecture. Comprehensive morphological, thermal, and mechanical analyses were conducted to evaluate the properties of the developed aerogel fibers. Fourier transform infrared (FTIR) spectroscopy and nuclear magnetic resonance (NMR) spectroscopy verified the successful surface modification and grafting reactions on CNF, contributing to improved hydrophobicity and thermal insulation. Adjusting the CNF content allowed for tailoring of the thermomechanical characteristics, with a notable 294% increase in tensile strength from 5.3 to 15.6 MPa and an enhanced crystallization temperature from 106 to 119.97 °C. Furthermore, cyclic tensile and compression tests validated the durability and shape recovery capabilities of the aerogel fibers, making them promising candidates for high-performance applications in extreme environments. The thermal conductivity validated by experimental data further highlights the potential of CNF-based aerogel fibers as sustainable and multifunctional materials for advanced thermal insulation, mechanical reinforcement, and flexible structural applications.

Application of hydrophobic catalyst in formaldehyde-ethylene condensation reaction.

Using hydrophobic aerogel (AGL) as the carrier, the catalyst supported p-toluene sulfonic acid (p-TSA) is synthesized, and the impact of the hydrophobicity of the catalyst on the formaldehyde-ethylene condensation reaction is investigated. Water contact angle, XRD, N2 adsorption/desorption, IR, and thermogravimetric analysis are used to characterize the catalyst. The outcomes demonstrate the ability of p-TSA to be loaded onto the carrier and the strong hydrophobicity of the catalyst when using AGL as the carrier. The elemental analysis results indicate that when AGL is employed as the carrier, the catalyst not only has more active sites than the SiO2-supported catalyst, but can also effectively limit the loss of active sites, reducing the loss rate from 25.82% to 15.03%. The findings demonstrate that 1,3-dioxane (1,3-DX) had a higher selectivity, rising from 16.2% to 33.3% when using AGL as the carrier. It is discovered that 1,3-propanediol (1,3-PDO) can be directly synthesized with a selectivity of up to 80.5% by employing acetic acid as a solvent in place of water.

Refined prediction of thermal transport performance in amorphous silica

Thermal transport in amorphous silica (a-SiO2) and silica aerogel is critically important for thermal protection and microelectronics applications. However, notable disparities exist between the predicted and measured thermal conductivity of a-SiO2. Inspired by the dual-phonon theory proposed by Luo et al. [Nat. Commun. 2020, 11, 2554] for crystalline materials, this work introduces a dual-diffuson transport method for amorphous materials. The criterion based on the thermal diffusivity is employed to differentiate between normal diffusons and phonon-like diffusons. Herein, the thermal conductivity of a-SiO2 is investigated by combining a modified Allen-Feldman (AF) theory with the dual-diffuson transport method. The present method is validated well by the measurement using the transient plane source (TPS) method. In addition, the results indicate that normal diffusons primarily govern the thermal transport in a-SiO2, with only a minor contribution from phonon-like diffusons. The temperature dependence of specific heat capacity and mode linewidth contributes to the positive temperature-dependent thermal conductivity. The quantum effect of specific heat capacity is the primary influencing factor in the temperature range of 100–1000 K, while the mode linewidth becomes dominant at higher temperatures. Finally, a theoretical framework for predicting the solid thermal conductivity of silica aerogel is introduced by including the temperature effect on the inherent thermophysical properties of the backbone. This work uncovers the physical mechanisms underlying temperature-dependent thermal transport in a-SiO2 and silica aerogels.

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.

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.