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The multiscale structural engineering strategy presents a powerful method for tailoring the structural attributes of materials at various levels, enabling the flexible control and manipulation of their electromagnetic properties. Nonetheless, orchestrating the multiscale architecture of polymer‐derived carbon aerogels specifically for microwave absorption poses significant challenges. Herein, aramid‐derived hard carbon nanofiber aerogel microspheres (CNFAMs) featuring a hierarchical skin‐core structure are fabricated through a wet‐spinning technique, combined with reprotonation‐mediated self‐assembly and carbonization processes. The presence of large‐scale voids between neighboring microspheres and the microscale porosity within the microspheres themselves improves impedance matching and promotes microwave reflection and scattering. The distinct graphitic domains and defects serve as pivotal elements for conduction and polarization losses, significantly impacting microwave attenuation. By meticulously tailoring the macroscale dimensions, microscale porous architecture, and nanoscale domains, the optimized CNFAMs demonstrate a remarkable absorption bandwidth of 9.62 GHz at an ultralow filling of 0.97 wt%. Additionally, the implementation of application‐oriented microwave absorption through the innovative integration of polysilsesquioxane‐CNFAMs in a host–guest aerogel is explored. This composite system brings together broadband absorption, superhydrophobicity, thermal insulation, resistance to freezing, and robust tolerance to harsh environments. Such a multifaceted approach is designed to tackle the growing challenges associated with complex electromagnetic environments effectively. [ABSTRACT FROM AUTHOR]

The objective of this research was to develop a high-performance flexible silica aerogel composite for thermal insulation under high-temperature and thermal–force coupling conditions. Based on synthesis of flexible silica aerogels with methyltrimethoxysilane as the precursor, flexible silica aerogel composites were developed by wet-impregnating ceramic fiber felt. Morphology, microstructure, chemical structure, hydrophobicity, and compression performance evolutions of the flexible silica aerogels and their composite counterparts with temperature revealed that the resulting flexible silica aerogel samples have excellent stability at 900 °C. Flexible silica aerogel composites show 100 and 70% recovery with 50% strain after treatment at 500 and 900 °C, respectively. Thermal insulation performance of the flexible silica aerogel composites was comprehensively studied from different aspects, including thermal conductivity, thermal shield behavior under high-temperature and thermal–force coupling conditions, and thermal shock resistance. Thermal conductivities of the flexible silica aerogel composite at 25–1100 °C are lower than those of most reported aerogel composites. Coupling of force under high temperature leads to degradation of thermal insulation performance, owing to deformation with compression. The synthesis method of the flexible silica aerogel is facile and inspiring, and the flexible silica aerogel composites have promising prospects in thermal insulation under high-temperature and thermal-stress coupling conditions, such as suppressing thermal runaway propagation of lithium-ion batteries. [ABSTRACT FROM AUTHOR]

Nanoporous composites have been extensively applied in aerospace applications for their outstanding thermal insulation and ablation resistance. A ceramizable polysilazane (PSZ)‐modified phenolic resin (PSZ‐PR)/carbon fiber fabric (PSZ‐PR/CF) aerogel composite was synthesized through ambient pressure drying (APD). The homogeneous nanopore structure and improved thermal stability of the PSZ‐PR aerogel matrix provided the composites with good performance (thermal conductivity as low as 0.126 W/(m·K)). The PSZ‐PR/CF composites achieved high compressive strength (up to 43.75 MPa), tensile strength (59.22–124.75 MPa), and bending strength (23.35–97.94 MPa). Furthermore, the generation of ceramization products during the oxyacetylene flame ablation process, specifically SiC and Si3N4, enhanced the ablation resistance of PSZ‐PR/CF composites: the linear ablation rates are as low as 0.112 and 0.018 mm/s at 4.18 MW/m2 (20 s) and 1.20 MW/m2 (120 s) of oxyacetylene heat flow, respectively. The corresponding maximum back temperatures are only 51.0°C and 60.3°C. Notably, the carbon/ceramic network is still present in the ablation layer to protect the carbon fibers from oxidation. This ceramizable PSZ‐PR/CF composite has good potential for application in the field of thermal protection. Highlights: PSZ improves thermal stability and ablation properties of PSZ‐PR/CF.The PSZ‐PR/CF composites exhibit excellent mechanical and ablation properties.The ceramic products improve the scouring resistance of aerogel matrixes.The ceramizable PSZ‐PR/CF was prepared by low‐cost ambient pressure drying. [ABSTRACT FROM AUTHOR]

Ceramic aerogels are promising candidates for high-temperature thermal resistance and thermal insulation materials. However, their application can be restricted by their brittleness when exposed to harsh conditions. Herein, this study has developed a novel synthesis process based on a sol-gel method and carbothermal reduction-nitridation to produce a porous TiN composite aerogel from an organic/inorganic hybrid. The resulting TiN displays a polyhedral particle size of around 30–60 nm with nanoscale pores. In addition, the TiN aerogel demonstrates a high BET-specific surface area of 653.42 m2/g and a very low thermal conductivity of 0.046 W/(m·K). Furthermore, the TiN aerogel composite displays a good thermal difference with no shrinkage and cracks of the morphology during the butane blazing torch at 1300 °C for 10 min under air environment, demonstrating its excellent thermal insulation property and anti-oxidation characteristics. The gas-solid reaction mechanism of TiN aerogel based on the Gibbs free energy calculations is also proposed. [ABSTRACT FROM AUTHOR]

Aerogels, with ultra-low density and thermal conductivity, are key materials for the development of high-efficient thermal insulations. Yet, their low compressive strength, oxidation behavior, and poor thermal stability limit their further development. Herein, we have prepared a novel monolithic mullite aerogel using the RF/Al 2 O 3 -SiO 2 aerogel organic/inorganic hybrid as the precursor, followed by the CO 2 supercritical drying, and high-temperature mullitization. The resulting mullite aerogel displays typical "pearl-necklace" three-dimensional network, with the average pore size at around 10–20 nm, showing a large BET specific surface of 481 m2/g. The compressive strength of the mullite aerogel is as high as 15.5 MPa, much larger than those of the reported ceramic aerogels. The mullite aerogel exhibits excellent thermal insulation property, and the mass loss is only 2.5% after the butane torch evaluation with 1300 °C for 10 min under air, showing its rather excellent anti-oxidation performance, and the anti-oxidation mechanism is also proposed. • A novel monolithic mullite aerogel for high temperature thermal insulation is developed. • The aerogel shows large BET specific surface area with excellent thermal insulation property. • The aerogel displays much higher mechanical strength as compared with the reported aerogels. • The mechanism of superior anti-oxidation property for mullite aerogel is proposed in this work. [ABSTRACT FROM AUTHOR]

The objective of this research was to develop a reinforced silica aerogel composites with enhanced thermal insulation performance under thermal-force coupling conditions. Phenolic -reinforced silica aerogel composites (RAs) were synthesized via a sol-immersion-gel process based on the in-situ polymerization of resorcinol (R), formaldehyde (F), and triaminopropyltriethoxysilane (APTES). Ambient pressure drying (APD) was used to dry the gels. Samples with different carbon/silica ratios, RA12, RA13, and RA14, were synthesized by controlling the R/APTES molar ratio at 1/2, 1/3, and 1/4. The densities of the RA12, RA13 and RA14 samples were 0.32 ± 0.005, 0.34 ± 0.006, and 0.37 ± 0.003 g/cm3. The thermal conductivity of the RA12, RA13, and RA14 samples were 0.024, 0.026, and 0.027 W/(m·K). The existence of the phenolic network favored the mechanical strength of the RAs, RA14 showed compressive strength, tensile strength, and three-point bending strength of 4.3 MPa at 20% strain, 2.4 MPa, and 8.4 MPa at 1.45% strain. The RAs showed excellent thermal insulation performance on a customized apparatus, the back temperature was as low as 219.82 °C and 330.67 °C within 60 min in the environments of 600 °C −0.01 MPa and 600 °C −0.9 MPa. The excellent thermal-shock performance of RAs was also demonstrated under flame exposure from a butane torch, with a temperature difference of 878 °C within 30 min being reported. The excellent thermal insulation performance of RAs under thermal-force coupling conditions reveals a widespread application perspective in the field of new energy vehicles power battery thermal protection. [ABSTRACT FROM AUTHOR]

Inorganic thermal insulation materials can greatly reduce heat loss from high-temperature equipment, thereby supporting energy-saving technologies. Among these nano-SiO 2 composites have promising application potential, which is limited by their existing preparation methods. This study aims to develop a low-cost high-performance thermal insulator. Nano-SiO 2 composites were prepared by the wet impregnation of glass fibre felt with nano-SiO 2 aqueous slurry and ambient pressure drying. The density of the composite linearly increased from 0.17 to 0.24 g/cm3 when the solid content of the slurry was increased from 5% to 15%. As the density of the composite increased, the thermal conductivity at 300–700 °C decreased. The introduction of SiC to the composites significantly improved their thermal insulation performance. The composite with SiC exhibited a thermal conductivity of 0.1334 W/(m·K) at 700 °C, which is better than its commercial counterpart of SiO 2 aerogel felt. The rear surface temperatures of the composites at 700 °C with different pressures of 0.01–0.1 MPa were investigated to comprehensively understand the thermal insulation performances. Overall, a facile, efficient, safe, and eco-friendly preparation for nano-SiO 2 composites have good prospect in the field of industrial energy saving. [ABSTRACT FROM AUTHOR]

Since the lotus effect was reported by Barthlott and Neinhuis in 1997, superhydrophobic and superoleophobic materials have received much attention due to special rough morphology and great potential applications in self-cleaning, anti-fouling, corrosion-resistance, and other fields. However, the conventional preparation process of superamphiphobic materials is complicated, including pre- and post-treatments which are used to achieve micro-nano hierarchical structures and low surface energy. In this study, we used methyltrimethoxysilane (MTMS) and 1,1,2,2- tetrahydroperfluorodecyltrimethoxysilane (FAS-17) as precursors and successfully prepared superamphiphobic FAS-17/MTMS composite aerogel via facile sol-gel method. Three-dimensional networks and long fluorocarbon chains formed micro-nano hierarchical structures. As-prepared aerogels had water contact angle (WCA) of 153.68°, oil contact angle (OCA) of 156.28°, water sliding angle (WSA) of 3.32° and oil sliding angle (OSA) of 4.57°, suggesting excellent superamphiphobic performance. Besides external superamphiphobicity, the cross section of sample also exhibited great liquid-repellency with WCA of 160.43° and OCA of 153.43°. Moreover, although cracked into powders with particle size of 0.1 mm, aerogel sample still retained its liquid-repellency with WCA of 122.85° and OCA of 128.01°, respectively. After thermal treatment under 200 ℃ for 2 h, the aerogel sample had WCA of 152.45° and OCA of 135.67°, showing excellent thermal stability. Taking advantage of low thermal conductivity and superamphiphobic properties, superamphiphobic aerogel has potential for fabricating self-cleaning and thermal insulating materials. [Display omitted] • In-situ fabrication of superamphiphobic aerogel by MTMS and fluoroalkysliane. • The unique three-dimensional networks yield superamphiphobic property. • Aerogel powders maintain liquid-repellency. • As-prepared aerogel has good thermal stability. [ABSTRACT FROM AUTHOR]

• Silica aerogel with a specific surface area of 916 m2/g was synthesized from water glass via a facile one-pot sol-gel process. • Silica aerogel has a specific surface area of 510 m2/g after treatment at 700 °C. • Thermal shock with 1100 °C flame demonstrated excellent thermal stability and insulation performance of glass fiber reinforced silica aerogel composite. • Thermal conductivity of the silica aerogel composite at 500 and 700 °C is 0.07215 and 0.12136 W/(m·K), respectively. This research aimed to develop a low-cost, high-performance silica aerogel thermal insulation material. Silica aerogel (SA) with a specific surface area of 917 m2/g was synthesized from water glass via a facile one-pot sol-gel process. Silica aerogel composite (SAC) was prepared by wet impregnation of glass fiber felt. Comprehensive study on the structure evolution of the SA and SAC with temperature reveals the excellent stability of the SA and SAC at 700 °C. Thermal insulation performance of the SAC was comprehensively studied from different aspects, including thermal conductivity, thermal shield behavior under high temperatures, and thermal shock resistance. Thermal conductivities of the SAC containing silicon carbide (SiC) named SAC-SiC at 100–700 °C are lower than those of most reported aerogel composites as well as commercial tetraethyl orthosilicate-derived silica aerogel composites. Thermal shock with 1100 °C flame demonstrated excellent thermal stability and insulation performance of the SAC-SiC. [Display omitted] [ABSTRACT FROM AUTHOR]

Schematic diagram of the preparation procedures of PEG/rGO-HT and PEG/rGO-MI samples. • Different techniques are carried out for preparing the PCM/aerogel composites. • The structures evolution and chemical interactions within PCM composites are revealed. • The PCM composite possesses excellent thermal stability and extremely large latent heat. Form-stable phase change material (PCM) composites is fabricated by vacuum-assisted melting infiltration (PEG/rGO-MI) technique, while the sample prepared by hydrothermal reduction method (PEG/rGO-HT) is also provided as control. PEG-6000 and reduced graphene oxide (rGO) are used as PCM and the porous supporting material, respectively. PEG molecules are fully filled in the connecting pore matrix of rGO aerogel with disordered arrangements for the PEG/rGO-HT sample, while distributed in the lamellar gaps of rGO nanoflakes with a regular orientation due to hydrogen bonding interactions for the PEG/rGO-MI sample. The C/O atomic ratios increase from 2.03% to 3.12% and 2.3%, respectively, for the PEG/rGO-HT and PEG/rGO-MI samples, indicating an increased sp2-hydridized C and simultaneously a decreased fraction of oxygen-containing functional groups. The Liquid leakages indicate that they both possess shape-stabilized property. The PCM mass percentage is 85.6% for the PEG/rGO-HT sample, while up to 96.6% for the PEG/rGO-MI sample. The melting latent heat of the PEG/rGO-HT sample is 139.4 J/g, whereas it is 205.2 J/g for the PEG/rGO-MI sample, much larger than that of most published works. The PEG/rGO-MI sample also exhibits excellent short-term thermal insulation property, which has promising application in complex environment for thermal energy management. [ABSTRACT FROM AUTHOR]

In this work, palmitic acid (PA) is used as the PCM, while a novel kind of 3D porous carbon/silica composite aerogel (CSA) is involved as porous supporting material to prepare the form-stable PCM composites (PA/CSA). The carbon aerogel supported PCM composite (CA/PA) is provided as control. PCM infiltration mainly occurs for the large pores rather than micropores or mesopores. PA molecules are physically well combined with CA and CSA due to capillary force and surface tension. The addition of amorphous CA and CSA limits the crystalline growth of PA molecules. The CA/PA shows a separated and layered structure while the CSA/PA presents a CSA@PA core-shell structure with a rough surface due to large pores within the CSA pore matrix. The PCM loading mass fraction of CSA/PA (82.2%) is much larger than that of CA/PA (64.1%), and liquid leakage test indicates its excellent form-stabilization property. The melting point and melting latent heat of CA/PA sample is 39.73 °C and 96.27 J/g, respectively, while the melting latent heat of the CSA/PA sample is as high as 187.7 J/g. The CSA/PA possesses excellent thermal stability during cycling test and its short-term thermal insulation property has also been verified in this study. (a) Schematic diagram of the vacuum-assisted melting infiltration process and (b) the photographs of the resulting (left) CA/PA and (right) CSA/PA samples. Image 1 • A novel 3D porous C/SiO 2 aerogel supported PCM composite (CSA/PA) is firstly synthesized. • The structures evolution and interior interactions within CSA/PA PCM composite is revealed. • The PA/CSA possesses extremely large latent heat and excellent short-term thermal insulation property. [ABSTRACT FROM AUTHOR]

• Mesoporous Si 3 N 4 aerogel is firstly synthesized via the urea assisted sol-gel technique. • Si 3 N 4 aerogel possesses a tremendously large BET specific surface area. • Si 3 N 4 aerogel has an excellent thermal insulation property. • Formation mechanism of Si 3 N 4 aerogel is revealed. Si 3 N 4 aerogel, which is one of the most promising materials for application as high-temperature thermal insulation, is synthesized by the urea-assisted sol-gel technique, followed by the supercritical drying, carbonization, carbothermal reduction and carbon combustion processes. The effects of heat treatment temperatures on the physicochemical and textural evolution of mesoporous Si 3 N 4 aerogel are investigated. Si 3 N 4 aerogel is formed when the heat treatment temperature increases to 1500 °C, whereas it transforms into SiC phase with a further higher temperature of 1600 °C. The SEM analysis confirms the existence of Si 3 N 4 nanoparticles, and the particle size of Si 3 N 4 nanoparticles is around 20–40 nm, with pore size around 20–40 nm. The XPS measurement reveals that Si 3 N 4 aerogel is composed of 74.4% Si 3 N 4 phase, with lower content of 25.6% SiO 2. Si 3 N 4 aerogel possesses a large BET specific surface area of 519.6 m2/g, which results from the mesoporous pores left after carbon combustion. This value is much larger than that of the conventional Si 3 N 4 porous ceramics and Si 3 N 4 nano materials ever reported. The BJH adsorption average pore diameter of Si 3 N 4 aerogel is around 11.8 nm, with a large pore volume of 3.5 cm3/g. Si 3 N 4 oxidation with forming amorphous SiO 2 layer on the surface is observed by the TG measurement. Moreover, the resulting Si 3 N 4 aerogel shows low bulk density of 0.075 g/cm3, as well as low thermal conductivity of 0.045 W/(m·K) at room temperature. The mechanism of Si 3 N 4 formation is based on the VS growth between C, SiO 2 and N 2. The structures evolution and formation mechanism of Si 3 N 4 aerogel are also investigated in this study. [ABSTRACT FROM AUTHOR]

• PVDF aerogel was fabricated by phase inversion induced sol-gel process followed by supercritical drying. • PVDF aerogel possessed a water contact angle of 126° and a thermal conductivity of 0.03602 W/(m·K). • PVDF aerogel had good thermal stability up to 400 °C in aerial environment. A polyvinylidene fluoride (PVDF) aerogel was fabricated by a phase inversion induced sol-gel process along with supercritical drying. The PVDF aerogel exhibited a hierarchical structure consisting of agglomerates and micron-size voids. The agglomerates consisted of nanoparticles and nanopores. The PVDF aerogel showed a water contact angle of 126° and was thermally stable up to 400 °C in aerial environment. The thermal conductivity of the PVDF aerogel was as low as 0.03602 W/(m·K). The PVDF aerogel is promisingly applied in thermal insulation under humid conditions and water treatment. [ABSTRACT FROM AUTHOR]

C/silica (RF/SiO 2) aerogel (RFSA) was synthesized via a one-step sol-gel process and supercritical fluid drying. Then, monolithic silicon nitride (Si 3 N 4) aerogel (SNA) was prepared via carbothermal nitridation of the RFSA in flowing N 2. The effects of the RFSA density and carbothermal temperature on the formation of the SNA were investigated. The evolution of the physical properties, chemical structure, morphology, pore structure, and thermal performance of the SNA was examined. Si 3 N 4 nanocrystals were formed from the RFSA at a carbothermal temperature of 1500 °C. The as-prepared SNA had a low density (0.127 g/cm3), large specific surface area (445 m2/g) and low thermal conductivity (0.04909 W/(m·K)), which were far better than those of its state-of-art counterparts. Because of its good thermal stability, the SNA can be used as a thermal insulator and support at high temperatures. [ABSTRACT FROM AUTHOR]

In order to overcome the brittleness of traditional aerogels, we report the copolymer of polysiloxane as a precursor for the fabrication of high-performance aerogels. The copolymer of poly (methyl methacrylate-co-vinylmethyldimethoxysilane) was synthesized by radical copolymerization, using methyl methacrylate (MMA) and vinylmethyldimethoxysilane (VMDMS), and multifunctional silane compounds including the VMDMS, vinyltrimethoxysilane (VTMS) and tetraethyl orthosilicate (TEOS) were used to promote the formation of the cross-linked network. Our reported aerogels have excellent mechanical properties and stability. Moreover, the recovery of these aerogels can be improved by more than 14% after heat treatment, which can recover over 80% of the original height. The morphologies and microstructures of these co-polymer aerogels were characterized by field emission scanning electron microscopy (FE-SEM), high-resolution transmission electron microscopy (HRTEM), Brunauer-Emmett-Teller (BET) and pore size distribution. The structural and chemical compositions were analyzed by 1H NMR spectra and Fourier transform infrared spectra (FTIR). The thermal analysis was evaluated by differential scanning calorimetric (DSC) and thermogravimetric analysis (TG), and the thermal insulation properties and the mechanical properties were determined by a thermal conductivity analyzer and uniaxial compression testing, respectively. The specific compressive strength of our reported aerogels is in the range of 6.99–27.70 MPa, the multi-point specific surface area is in the range of 752–1271 m2g-1, and thermal insulation performance is 0.030–0.061 W m−1 K−1. Finally, we suggest that radical copolymerization can also be employed for other co-polymer aerogels, including the monomers of C C double bonds. Image 1 • Co-polymer aerogels show good resilience and mechanical strength. • Annealed co-polymer aerogels have improved recoverability. • Radical copolymerization can also be applied for other vinyl monomers to prepare co-polymer aerogels. [ABSTRACT FROM AUTHOR]

The fragility, hydrophilicity and high cost fabrication of aerogels have limited their applications in industrial and civilian fields. Herein, we have described a method for preparing a novel flexible and hydrophobic silica aerogel by using the co-precursors method via ambient pressure drying technique. The optimal MTMS volume percentage is determined at 60%. The resulting aerogel obtains agglomerated particles with diameters at ~20–30 nm and mesopores at several tens of nanometers. The Si-C-H bond ratio maintains at 13. 36% after heat treatment at 300 °C, which results in the high water contact angle of 153.9°. Moreover, the 300 °C heat treated aerogel has a much more homogeneous microstructure with its BET specific surface area as large as 895.5 m2/g. The oxidation peak of -CH 3 groups is observed at 492 °C. The aerogel exhibits an excellent flexibility under 50 compression cycles, as well as a superior thermal insulation property. [ABSTRACT FROM AUTHOR]