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Suppressing thermal runaway (TR) propagation within Lithium-ion battery (LIB) modules/packs/systems is one of the key factors to ensure the safety utilization of electric vehicles and energy storage systems. This contribution aims at introducing Silica Aerogel Sheets (SAS) into high energy density modules to suppress the TR propagation. The SAS, synthesized via a sol-gel process followed by supercritical fluid drying, possess almost an ideal thermal insulator characteristic due to the low thermal conductivity of 0.020 W/(m·K) at room temperature. The SAS are inserted between two adjacent pouch cells (LiNi 0.86 Co 0.07 Mn 0.07 O 2 /graphite, 320 Wh.kg−1) to assemble high energy density modules. A single pouch cell, subjected to the TR test with an Accelerating Rate Calorimetry, releases a huge amount of heat energy (1083 kJ/kg) with the maximum temperature beyond 800 °C. In the open area test site for TR propagation experiments, it can be observed that violent jet and flame burst from the cell, which is designed to undergo TR first and trigger the TR propagation of the modules. The results show that only one single layer of SAS cannot stop the TR propagation or fire spreading. However, more layers of SAS (three in the experiments) can successfully suppress the TR propagation and block fire progression. The temperature of the adjacent cell only reaches 105.4 °C. Therefore, the SAS with acceptable thickness can suppress the TR propagation successfully to improve the safety of the LIB modules. [ABSTRACT FROM AUTHOR]

A novel C/SiO 2 /SiC ternary aerogel is derived from catechol-formaldehyde/silica hybrid aerogel (CF/SiO 2 ) via a one-step sol-gel method followed by carbonization and carbothermal reduction processes under flowing argon. The effects of the carbon/silica molar ratios on the physicochemical properties of the C/SiO 2 binary and C/SiO 2 /SiC ternary aerogel are investigated. The mechanism of the textural and structural evolution for the novel C/SiO 2 /SiC ternary aerogel is further discussed based on the experimental results and the calculated Gibbs free energy changes at different SiO partial pressure. The SiC layer is first formed on the surface of the composite aerogel via the solid-vapor reaction at 1400 °C while SiC nanoparticles form at 1500 °C. The C/SiO 2 /SiC ternary aerogel possesses a rather high specific surface area (746.87 m 2 /g), a high micropore volume (0.2279 cm 3 /g) and a high porosity (89.10%). The oxidation resistance is improved for 100 °C when compared with the carbon based aerogel. The ternary aerogel obtains a high compressive strength (1.86 MPa) and a low thermal conductivity (0.053 W/m*K), which is suitable for high efficient thermal insulation uses both in inert and oxidative atmosphere. [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]

The applications of silica aerogels are restricted due to their intrinsic fragile property. Polymerization of di-isocyanates can be templated onto the mesoporous surface of the –NH 2 group modified silica clusters, resulting in the conformal crosslinked coating on surface of silica clusters. Aminopropyltriethoxysilane (APTES), as the silica co-precursor and amine group modification agent, is involved containing tetramethyl orthosilicate (TMOS) silica precursor, while hexamethylene diisocyanate (HDI) is incorporated as the polymer crosslinking agent. The effects of different amounts of APTES on the physicochemical properties of the resulting crosslinked aerogels are investigated. The results show that the optimized APTES/TMOS volume ratio can be determined at 0.5:1. The resulting optimal crosslinked silica aerogel possesses large BET specific surface area of 150.9 m2/g, low thermal conductivity of 0.037 W/(m·K), and the Young's modulus is as large as 18 MPa under strain of 4.2%, much higher than that in the previously published works. The polymerization reaction mechanism forming the polyurethane chains has also been proposed. In addition, the interactions between silica clusters and polymer chains are studied by molecular mechanics and molecular dynamics. The interactions are mainly dependent on non-bonding energy, and the electrostatic energy has decisive impact on the combination of silica clusters and polymer chains. The density field of C, H, N, O, and Si elements overlaps with each other, indicating that the polymer crosslinked silica aerogel maintains typical three-dimensional porous structure. The N element enriches in the region between silica clusters, further verifying the formation –CONH–(CH 2) 6 –CONH- polyurethane chains, which is actually responsible for the much enhanced mechanical property. [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]

• 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]

Highlights • Foam concrete reinforced silica aerogel (FC-SA) has been prepared using a combined sol-gel route, vacuum impregnation method and fast ethanol supercritical drying technique. • The foam concrete reinforced silica aerogel has a surface area of 405.3 m2/g. • The thermal conductivities of FC-SA is as low as 0.049 W•m−1 K−1 (30°C). • In cold and hot areas, the use of FC-SA to replace traditional concrete materials can greatly reduce both of space heating/cooling energy consumption and cooling water consumption. Abstract With the increasing number of commercial buildings in the United States, the energy consumption for space air conditioning is continuously rising. Considering the external building envelope an important role to generate cooling and heating loads, we developed a new high performance building material for building envelope application. Hence, a novel foam concrete reinforced SiO 2 aerogel (FC-SA) material was synthesized via sol-gel technique, vacuum impregnation method and rapid supercritical drying process. The samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), thermogravimetric / differential scanning calorimetry (TG-DSC), N 2 adsorption-desorption test (BET) and transient plane source method (TPS). The prepared composite had a high degree of aerogel filling (74% volume of matrix) and the aerogel component still maintained a porous nanostructure. Besides, FC-SA showed a large specific surface area of 405.3 m2/g and high pore volume of 1.28 cm3/g. Meanwhile, the introduction of aerogel has little effect on the mechanical strength of the matrix material. According to the test results, the thermal insulation performance of foam concrete has been found greatly improved with silica aerogel composition. The thermal conductivity of FC-SA composite was measured as low as 0.049 W m−1 K−1 at room temperature (30°C), which was a 48.4% decrease from foam concrete. Finally, the energy saving simulation results showed that in cold and hot areas, the use of FC-SA to replace traditional concrete materials can greatly reduce both of energy consumption and cooling water consumption. Graphical abstract Image, graphical abstract [ABSTRACT FROM AUTHOR]

Microencapsulated composite material using Na 2 SO 4 as core and SiO 2 as shell for high temperature thermal energy storage is prepared. The effects of silica mass percentages within the Na 2 SO 4 @SiO 2 PCM composites on thermal conductivity, thermal stability, melting temperature, and latent heat are investigated. No new phases are formed during the encapsulation process. The spherical silica nanoparticles with diameters at around 300 nm are well decorated on the surface of Na 2 SO 4 . The PCM composite with 5.4% silica addition is determined as the optimal sample due to its excellent comprehensive properties. The inhibition of liquid leakage during melting can be effectively realized. The thermal conductivity of Na 2 SO 4 @SiO 2 PCM under high temperatures (600–800 °C) can be increased to 0.59 W/(m K), 0.62 W/(m K), and 0.87 W/(m K), respectively. The initial and peak melting temperatures of the Na 2 SO 4 @SiO 2 are tested at 885.20 °C and 887.91 °C, respectively. The latent heat is determined as high as 170.6 J/(g K), and the total heat storage density including latent and sensible heat with a temperature span of 100 °C is 390.6 J/g, and the mass loss is observed < 1% under 1000 °C. In addition, the latent heat loss percentage after 50 thermal cycle tests is ≤ 4.3%. [ABSTRACT FROM AUTHOR]

Monolithic silica aerogels (SiO 2 ) are prepared using the tetraethylorthosilicate (TEOS) as precursor via a rapid supercritical extraction method (RSCE). The effect of heat treatment on the textural and physical characteristics of RSCE-samples are compared with those of the other two conventional supercritical extraction method, i.e. the alcohol supercritical extraction (ASCE) and CO 2 supercritical extraction (CSCE). This new RSCE method offers many distinct advantages. The precursor recipe employs TEOS, ethanol, water, diluted hydrochloric acid to catalyst hydrolysis, and ammonia to accelerate the condensation rate. One advantage is the relative simplicity of this method: liquid precursors are poured into the supercritical ethanol drying apparatus following the hydrolysis of the TEOS and the solutions are directly sent to the supercritical extraction point of ethanol without previous aging and solvent exchanges procedures as would be the case for conventional aerogel. Thus, it is much more cost-saving and it produces little waste during the overall fabrication. The total fabrication time from mixing the precursors to taking out can be shortened to as low as 6 h, which is much less time consuming than the conventional ones (usually ca. 4–7 days). All the as-dried SiO 2 samples derived from different methods are essentially amorphous, and SiO 2 crystallization first occurs for the ASCE sample at 1100 °C. The average pore diameters of the as-dried ASCE, CSCE and RSCE samples are 12.70 nm, 14.97 nm and 13.80 nm, respectively, which is consistent with the results of transmission electron microscopy (TEM) analysis. The specific surface area of the as-dried RSCE silica aerogel may reach 915.9 m 2 /g after 700 °C, which is larger than the other two samples. The thermal conductivities of the different fiber reinforced RSCE SiO 2 aerogel composites are ca. 0.027 W m − 1 K − 1 , comparable to the ASCE and CSCE aerogel composites. The RSCE method can also be well applied to the fabrication of aerogels based on other precursor recipes. [ABSTRACT FROM AUTHOR]

To develop a high emissivity coating on the low thermal conductivity ZrO 2 ceramic insulation for reusable thermal protective system, the MoSi 2 –ZrO 2 –borosilicate glass multiphase coatings with SiB 6 addition were designed and prepared with slurry dipping and subsequent sintering method. The influence of SiB 6 content on the microstructure, radiative property and thermal shock behavior of the coatings has been investigated. The coating prepared with SiB 6 included the top dense glass layer, the surface porous coating layer and the interfacial transition layer, forming a gradient structure and exhibiting superior compatibility and adherence with the substrate. The emissivity of the coating with 3 wt% SiB 6 addition was up to 0.8 in the range of 0.3–2.5 μm and 0.85 in the range of 0.8–2.5 μm at room temperature, and the “V-shaped grooves” surface roughness morphology had a positive effect on the emissivity. The MZB-3S coating showed excellent thermal shock resistance with only 1.81% weight loss after 10 thermal cycles between 1773 K and room temperature, which was attributed to the synergistic effect of porous gradient structure, self-sealing property of oxidized SiB 6 and the match of thermal expansion coefficient between the coating and substrate. Thus, the high emissivity MoSi 2 –ZrO 2 –borosilicate glass coating with high temperature resistance presented a promising potential for application in thermal insulation materials. [ABSTRACT FROM AUTHOR]