Layered Inorganic Silicate Aerogel Pillared by Nanoclusters for High Temperature Thermal Insulation

Ultralight and Flexible Subnanowire Aerogels for Intrinsically Hydrophobic Thermal Insulation

Aerogels are regarded as the next generation of thermal insulators; however, conventional aerogels suffer from issues such as brittleness, low moisture resistance, and a complex production process. Subnanowires (SNWs) are emerging materials known for their exceptional flexibility, toughness, intrinsic hydrophobicity, and gelling capabilities, making them ideal building blocks for flexible, tough, hydrophobic, and thermally insulating aerogels. Herein, we present a simple and scalable strategy to construct SNW aerogels by freeze-drying hydroxyapatite (HAP) SNW dispersions in cyclohexane. The resulting aerogels consist of three-dimensional porous flakes composed of thin layers of SNW bundles. They exhibit numerous outstanding properties, including ultralow density (12.33 mg·cm-3), high porosity (99.15%), remarkable flexibility and toughness, and excellent thermal insulation properties (27.53 mW·m-1·K-1). Because the HAP SNWs consist of hydroxyapatite cores capped with hydrocarbon chains, the aerogels demonstrate intrinsic hydrophobicity (138° water contact angle) and superior thermal stability compared to polymer foams. Furthermore, the HAP SNW aerogels can effectively shield against infrared radiation due to their low thermal conductivity. This work suggests that SNWs can serve as superior building blocks for flexible, tough, and intrinsically hydrophobic aerogels, paving the way for future applications in thermal insulation.

Superstrong Lightweight Aerogel with Supercontinuous Layer by Surface Reaction

Breaking the thermal, mechanical and lightweight performance limit of aerogels has pivotal significance on thermal protection, new energy utilization, high-temperature catalysis, structural engineering, and physics, but is severely limited by the serious discrete characteristics between grain boundary and nano-units interfaces. Herein, a thermodynamically driven surface reaction and confined crystallization process is reported to synthesize a centimeter-scale supercontinuous ZrO2 nanolayer on ZrO2-SiO2 fiber aerogel surface, which significantly improved its thermal and mechanical properties with density almost unchanged (≈26 mg cm-3). Systematic structure analysis confirms that the supercontinuous layer achieves a close connection between grains and fibers through Zr─O─Si bonds. The as-prepared aerogel exhibits record-breaking specific strength (≈84615 N m kg-1, can support up to ≈227 272 times aerogel mass) and dynamic impact resistance (withstanding impacts up to 500 times aerogel mass and up to 200 cycling stability at 80% strain). Besides, its temperature resistance has also been greatly optimized (400 °C enhancement, stability at 1500 °C). This work will provide a new perspective for exploring the limits of lightweight, high strength, and thermal properties of solid materials.

Programmable Shape-Morphing Enables Ceramic Meta-Aerogel Highly Stretchable for Thermal Protection

Ceramic aerogels hold significant potential for thermal insulation, yet their mechanical stretchability and thermal stability fall short in extreme environments. Here, the study presents a programmable shape-morphing strategy aimed at engineering a binary network topology structure within ceramic aerogels to effectively dissipate stress and block heat transfer. The special topology design, which includes kirigami lamellated aerogels for bearing loading stress and randomly assembled aerogels for mechanical energy pre-storage to transfer tensile stress, effectively achieves unexpected mechanical tensile properties and thermal stability. The resulting robust meta-aerogels demonstrate remarkable structural stability with topology-derived mechanical tensile of up to 85% strain, excellent resilience to 500 cycles of 50% tensile strain, 1000 cycles of 60% buckling strain, and 500 cycles of 50% compressive strain, temperature-invariant tensile recovery capability; simultaneously, low thermal conductivity of 33.01 mW m-1 K-1 and tensile-invariant thermal insulation makes the ceramic meta-aerogels an ideal substitute material for various applications.

Fireproof Cavity Structure with Enhanced Impact Resistance and Thermal Insulation toward Safeguarding

Developing devices emphasizing safety protection is becoming increasingly important due to the widespread occurrence of impact damage and thermal hazards. Herein, the F-SSG/TPU-based circular cavity structure (FC) is developed through a convenient and efficient template method, which can effectively achieve anti-impact and thermal insulation for protection. The flame-retardant shear stiffening gel/thermoplastic urethane (F-SSG/TPU) is synthesized through the dynamic interaction between the SSG, TPU, and modified ammonium polyphosphate (APP@UiO-66-NH2) by thermo-solvent reactions. The developed FC can dissipate the impact force from 4.19 to 0.99 kN at 45 cm impacting heights, indicating good anti-impact performance. Moreover, the thermal insulation test demonstrates that the FC achieves a temperature drop of 76 °C at 160 °C attributed to the unique cavity structure design. Under the continuous shock of high-temperature flame, FC remains intact, and its performance is almost undamaged. These results elaborate that the designed FC can effectively resist various damage, such as high-temperature shock and collision. Then, a wearable wristband integrated with FC is developed which exhibits superior impact resistance and heat insulation properties compared with commercial wristbands. In short, this cavity structure based on high-performance F-SSG/TPU material shows promising potential applications in the protection field.

Elastic SiC Aerogel for Thermal Insulation: A Systematic Review

SiC aerogels with their lightweight nature and exceptional thermal insulation properties have emerged as the most ideal materials for thermal protection in hypersonic vehicles; However, conventional SiC aerogels are prone to brittleness and mechanical degradation when exposed to complex loads such as shock and mechanical vibration. Hence, preserving the structural integrity of aerogels under the combined influence of thermal and mechanical external forces is crucial not only for stabling their thermal insulation performance but also for determining their practicality in harsh environments. This review focuses on the optimization of design based on the structure-performance of SiC aerogels, providing a comprehensive review of the inherent correlations among structural stability, mechanical properties, and insulation performance. First, the thermal transfer mechanism of aerogels from a microstructural perspective is studied, followed by the relationship between the building blocks of SiC aerogels (0D particles, 1D nanowires/nanofibers) and their compression performance (including compressive resilience, compressive strength, and fatigue resistance). Moreover, the strategy to improve the high-temperature oxidation resistance and insulation performance of SiC aerogels is explored. Lastly, the challenges and future breakthrough directions for SiC aerogels are presented.

Interpenetrated Multinetwork Hybrid Aerogels by Layered Montmorillonite and One-Dimensional Hydroxyapatite Fibers for Heat and Fire Insulation

It is of practical significance to develop aerogels with effective thermal insulation characteristics together with fireproof properties as well as high mechanical strength. Here, an interpenetrated multinetwork hybrid aerogel realizing thermal insulation, flame retardancy, and high compression modulus is demonstrated. Specifically, one-dimensional hydroxyapatite nanowires (HAP) played dual roles as the aerogel support skeleton to entangle with layered montmorillonite (MMT) each other to form a three-dimensional interpenetrated multinetwork structure and to optimize the thermal conductivity by adjusting the pore space in current HAP/MMT/PVA hybrid aerogels. Therefore, the interpenetrated multinetwork hybrid aerogels exhibit superior thermal insulation performance in room temperature (0.033 W m-1 K-1, 298 K, air conditions) and largely enhanced ultrahigh compression modulus (80 MPa). Moreover, the obtained hybrid aerogels also exhibit excellent flame retardancy and self-extinguishing smoke suppression properties (peak heat release rate and total smoke production as low as 92.44 kW m-2 and 0.1 m2, respectively), which is the outstanding interpenetrated multinetwork hybrid aerogel that has achieved synergistic improvement in heat and fire insulation and mechanical performance. Therefore, the interpenetrated multinetwork hybrid aerogels are promising candidates for efficient heat insulation, fire prevention, and mechanically robust applications.

Carbon/ZrO2 aerogel composite microtube superfoam

High-performance thermal insulation materials with broad application prospects have attracted great attention. The introduction of new microstructures into thermal protection materials can significantly improve the thermal insulation performance. The tubular microstructure has obvious advantages such as thermal insulation, lightweight, mechanical, and other properties. Therefore, the microtubular structure has become an important reference microstructure for the development of high-performance thermal insulation materials. In this paper, the carbon/ZrO2 aerogel composite microtube superfoams with excellent thermal protection properties were prepared by a vacuum filtration and high-temperature carbonization method. The ZrO2 aerogel precursor solution can be quickly and uniformly adsorbed on the inner and outer walls of cellulose microtubules. These adsorbed ZrO2 aerogel precursor solution films can be converted into ZrO2 alcohol gel shells under the acceleration and promotion effect of citric acid at 65 °C. The micromorphology of the ZrO2 aerogel shell on the inner and outer walls of the composite microtubes can be efficiently controlled by the concentration of the ZrO2 aerogel precursor solution and the carbonization temperature. The carbon/ZrO2 aerogel composite microtube superfoam exhibits a lower thermal conductivity, lower density, good mechanical properties, and high ablation resistance. The thermal conductivity of the carbon/ZrO2 aerogel composite microtube superfoam is as low as 0.040 ± 0.001 W m-1 K-1. The residual rate of the carbon/ZrO2 aerogel composite microtube superfoam is still as high as 84.33% after butane flame ablation for up to 3600 seconds.