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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]

Lightweight phenolic matrix composites are highly potential in ablative thermal protective materials for future aerospace vehicles, and hybrid modification is considered as one of effective ways to improve the oxidation and ablation resistance of phenolic matrix. Herein, the co-continuous silica zirconium hybrid phenolic resin (SZRx) was synthesized, which can be used to prepare lightweight ablation resistant aerogel composites by the sol-gel method. The SZRx aerogel showed stable porous structure and excellent hydrophobicity, and the silicon zirconium hybrid greatly improved the high temperature carbon residue and oxidation resistance of phenolic resin. The SZRx aerogel composites also possessed excellent integrated characteristics of heat protection and insulation, with a linear ablation rate as low as 0.032 mm/s and a back temperature below 200 °C. The synergistic effect of silicon and zirconium formed the multiphase ceramic layer (C, SiO 2 , SiC and ZrO 2) with the sea-island-like structure on the surface of the composite material, which can effectively resist high-temperature ablation and aerodynamic exfoliation. This can indicate that silicon zirconium dual element hybrid phenolic resin is the highly competitive matrix for lightweight and ablation resistant composite materials. [Display omitted] [ABSTRACT FROM AUTHOR]

Ambient pressure drying (APD) of silica aerogels has emerged as an attractive method adapting to large-scale production. Spring-back is a unique phenomenon during APD of silica aerogels with volume expansion after its shrinkage under capillary force. We attribute the intense spring-back at elevated drying temperatures to a dense structure formed on the surface and the formation of positive internal pressure. Furthermore, an APD-assisted foaming method with an in situ introduction of NH4HCO3 was proposed. NH4HCO3 decomposing at drying temperatures hastened the emergence of positive pressure, thereby increasing the expansion volume. Compared to the previous method, the porosity of silica aerogel increased from 82.2% to 92.6%, and mesopore volume from 1.79 cm3 g−1 to 4.54 cm3 g−1. By adjusting the amount of the silicon source, silica aerogels prepared by the APD-assisted foaming method generated higher volume expansion and lower thermal conductivity. After calcination to remove undecomposed ammonium salts, the hydrophobic silica aerogel with a density of 0.112 g cm−3 reached a mesopore volume of 5.07 cm3 g−1 and a thermal conductivity of 18.9 mW m−1·K−1. This strategy not only improves the thermal insulation properties, but also offers a significant advancement in tailoring silica aerogels with specific porosity and mesopore volume for various applications. [ABSTRACT FROM AUTHOR]

Thermally stable high-performance phenolic resin aerogels (PRAs) are of great interest for thermal insulation because of their light weight, fire retardancy and low thermal conductivity. However, the drawbacks of PRA synthesis, such as long processing time, inherent brittleness and significant shrinkage during drying, greatly restrict their wide applications. In this work, PRAs were synthesized at ambient pressure through a near-net shape manufacturing technique, where boron-containing thermosetting phenolic resin (BPR) was introduced into the conventional linear phenolic resin (LPR) to improve the pore characteristics, mechanical properties and thermal performances. Compared with the traditional LPR-synthesized aerogel, the processing time and the linear shrinkage rate during the drying of the PRAs could be significantly reduced, which was attributed to the enhanced rigidity and the unique bimodal pore size distribution. Furthermore, no catastrophic failure and almost no mechanical degradation were observed on the PRAs, even with a compressive strain of up to 60% at temperatures ranging from 25 to 200 °C, indicating low brittleness and excellent thermo-mechanical stability. The PRAs also showed outstanding fire retardancy. On the other hand, the PRAs with a density of 0.194 g/cm3 possessed a high Young's modulus of 12.85 MPa and a low thermal conductivity of 0.038 W/(m·K). [ABSTRACT FROM AUTHOR]

Flexible SiC nanowire aerogel felt has excellent foldability, high-temperature resistance, and thermal insulation properties. However, the large-scale and high-efficiency production of SiC nanofiber aerogel felt remains a challenge. In this work, a three-dimensional network-structured short-chopped carbon fiber felt was used as a template for preparing SiC nanowire aerogel felt. The short-chopped carbon fibers were combed and dispersed using an airflow in a carding machine to obtain the desired felt. This method enables rapid and uniform preparation of carbon fiber felt, enhancing the efficiency of SiC nanowire aerogel felt production. The experimental results showed that the aerogel felt was mainly composed of β-SiC nanowires with a density of 5.29 g/cm3. Additionally, the SiC nanofiber aerogel felt exhibited remarkable superelasticity and low thermal conductivity (0.013 W/m·K). This research contributes to the practical application of flexible SiC nanowire aerogel felt in the field of thermal insulation. • Carding machine dispersed carbon fiber. • Fabrication of large size SiC nanofiber aerogel felt. • SiC nanofiber aerogel felt has flexibility and low thermal conductivity. [ABSTRACT FROM AUTHOR]

The thermal performance of the building envelope is significant in energy-efficient construction. Because concrete is widely used in civil engineering, options to reduce its R-value should be considered. This study explores the thermal and structural properties of aerogel-enhanced concrete. Silica aerogel powder was mixed with fine-grained concrete at 15 vol.%. Two series of samples were prepared to identify the preferred technology. The first series of samples were mixed without isopropyl alcohol; for the second series, the alcohol was mixed with silica aerogel before mixing into the dry mix. The thermal conductivity, compressive strength, and bending resistance of the specimens were measured. The presence of silica aerogel admix resulted in a decrease in the compressive strength of the specimens by 30% compared with that of the reference samples and a reduction in the bending strength of the samples by 9% compared with that of the reference samples. For the first and second series of samples, the K-values of the aerogel-enhanced specimens varied in the range from 0.83 W/(m·K) to 1.13 W/(m·K), respectively. To further decrease the thermal conductivity, gypsum putty was then added to the specimens, resulting in the K-values further decreasing to 0.64 W/(m·K) and 0.84 W/(m·K), respectively. The calculation of heat losses through 1 m2 of the aerogel-enhanced concrete wall was performed. It has been shown that energy expenses for heating can be lowered by 30%. The calculation of the greenhouse gas emissions from the combustion of fuel required for heating was also considered. The emissions decreased by 30.2% compared with the reference sample. Microscopic examination of the face and section surfaces of the sample revealed a significant number of pores compared with conventional fine-grain concrete. [ABSTRACT FROM AUTHOR]

The effects of octaphenylsilsesquioxane (OPS), fumed silica, and silica aerogel on the thermal insulation properties of ethylene propylene diene monomer (EPDM) rubber were studied. On this basis, two kinds of fillers with good performances were selected to study the thermal insulation of an EPDM full-formula system. The results show that the addition of fumed silica or silica aerogel had a positive effect on the thermal insulation performance of EPDM rubber and its composite. A 30 wt% silica aerogel can be well dispersed in the EPDM rubber system and with a lower thermal conductivity compared with fumed silica. EPDM composite with 23.4 wt% fumed silica can produce more char residues at 1000 °C than at 500 °C in a burn-through test and formed the compact and porous char at 1000 °C, which had a lowest thermal conductivity. EPDM composite with fumed silica cannot be burned through 1000 °C burning, and comparison with silica aerogel revealed that it achieved the lowest back temperature and had a temperature of 388 °C after 800 s. [ABSTRACT FROM AUTHOR]

Lightweight ablative materials owing to their low density, high efficiency heat insulation and excellent designability, which are considered as the most promising candidate materials in the field of aerospace ablative thermal protection. In this work, a polycarbosilane (PCS) in-situ reinforced carbon felt/phenolic (PR/C f) aerogel composite is reported. The surface of aerogel and carbon fiber was coated with PCS protective layer by sol gel method and secondary vacuum impregnation process. The aerogel composite material possesses low density (0.264–0.307 g/cm3), hydrophobic, low thermal conductivity (0.121–0.178 W/(m·K)) and significant high compressive strength (12.89 MPa). When the oxygen acetylene flame with high heat flow density ablates for 20 s, it shows high efficiency in heat protection and insulation, and the linear ablation rate is as low as 0.089 mm/s. The PL/PR/C f aerogel composite shows competitive and broad application prospects in the field of ablation heat protection in the future. [ABSTRACT FROM AUTHOR]

Traditional graphene-based films normally possess high thermal conductivity (TC) only along a single direction, which is not suitable for thermal interface materials (TIMs). Here, a graphene film with excellent bidirectional TC and mechanical properties was prepared by hot-pressing super-elastic graphene aerogel (SEGA). Thermal annealing at 1800 °C improves the further restacking of graphene sheets, bringing high structure stability to SEGA for enduring the hot-pressing process. The junctions and nodes between the graphene layers in the hot-pressed SEGA (HPSEGA) film provide bidirectional heat transport paths. The in-plane TC and through-plane TC of HPSEGA film with a thickness of 101 μm reach 740 Wm−1K−1 and 42.5 Wm−1K−1, respectively. In addition, HPSEGA film with higher thickness still maintains excellent thermal transport properties due to the interconnected structure reducing the effect of the defects. The infrared thermal images visually manifest the excellent thermal-transfer capability and thermal-dissipation efficiency of the HPSEGA films, indicating the great potential as advanced bidirectional TIMs. [ABSTRACT FROM AUTHOR]

To understand the transient heat transfer characteristics of nanoporous aerogel insulating composites, solving the inverse heat transfer problem would be crucial for identifying the temperature-dependent thermal properties of composites. In this study, with constructed a forward model to numerically investigate the heat transfer in composites, a deep neural network (DNN) model and a particle swarm optimized deep neural network (PSO-DNN) model are conducted to rapidly estimate the effective temperature-dependent thermal conductivity of the desiccated and moist composites from the temperature response measurements. With the DNN model, the retrieved thermal conductivities for desiccated composites possess low deviation to experimental measurements (<3.2%) and constantly low errors (<5.2%) from 280 K to 1080 K. The precision of the DNN solver could be enhanced by adjusting the hyperparameters of the neural networks using PSO. The retrieved thermal conductivities possess low deviation from experiments (<2.5%) and low relative errors within 1.5%. Furthermore, the robustness of the PSO-DNN solver is discussed when commercial thermocouple measurement errors are considered, within retrieving the thermal properties of desiccated and moist aerogel composites. [ABSTRACT FROM AUTHOR]

Biomass aerogels have attracted wide attention due to their excellent thermal insulation properties, but their low mechanical strength and high susceptibility to combustion limit their application. To address these limitations, a novel composite aerogel was prepared by combining chitosan aerogel (CS) and hydroxyapatite nanowires (HAP) via phytic acid (PA) cross‐linking and freeze‐drying. It was found that the maximum compressive strength and modulus of CS/HAP aerogel were 1.13 and 0.67 MPa, respectively. The minimum thermal conductivity of CS/HAP(0.5) composite aerogel was 0.03921 W m−1 K−1, indicating its good thermal insulating property. Moreover, the CS/HAP composite aerogel also showed excellent flame‐retardant properties. The heat release rate (HRR) and total heat release from combustion (THR) were significantly lower than those of the CS aerogel, with values of 35.2 kW m−2 and 3.7 MJ m−2, respectively, compared to 169.6 kW m−2 and 5.4 MJ m−2. The total smoke release (TSR) was also at a low level, reaches 0.4 m2 m−2. Highlights: Propose a novel chitosan aerogel composited with inorganic nano‐reinforced HAP.High mechanical strength of CS/HAP composite aerogel are illustrated.Exhibit excellent thermal insulation performance of CS/HAP aerogel.HAP and PA largely improves the flame retardancy of the chitosan aerogel. [ABSTRACT FROM AUTHOR]

Three-dimensional (3D) spacer fabric has the characteristics of a light weight and high strength, and its unique three-dimensional structure gives it great potential for development in terms of insulation. For the purpose of further improving the thermal insulation performance of 3D spacer fabric, the fabric was treated with silica aerogel while solving the problem of powdering during use. Firstly, the electronic Jacquard machine was modified for weaving spacer fabrics. The ground warp yarns were controlled by two groups of heald frames with various positions of heald eye, forming a double-shuttle. The longitudinal warp yarns were controlled by the Jacquard healdwine to prepare a spacer Jacquard fabric with a spacing of 5 mm. Secondly, polyurethane foam was applied as a carrier to compound with silica aerogel. The experimental results demonstrate that the strength of the composite fabrics is significantly increased, while the toughness is decreased. With the increase in silica aerogel content, the pore size of foam becomes smaller, and the degree of foam fragmentation increases, showing a trend of increasing thermal insulation performance followed by a decreasing insulation performance. When the aerogel content is 3.3%, the composite fabric has the optimal thermal insulation performance. [ABSTRACT FROM AUTHOR]

Novel phenolic resin/silicone aerogels (PR-Si) were prepared through a facile sol-gel polymerization and ambient pressure drying process without solvent exchange. Without the addition of an additional catalyst, the hydroxyl condensation reaction between the siloxane oligomer and the phenolic resin resulted in the silicon being incorporated into the PR. The obtained aerogels exhibited high compressive strength (0.84–21.11 MPa) and low thermal conductivities [0.046–0.077 W/(m·K)]. The introduction of a Si–O network structure in the PR effectively improved the mechanical properties and thermal stability of aerogels. It is clear from the TGA plot that the mass loss temperature of the PR-Si aerogel was increased by 73 and 79 °C for the weight loss temperatures of 5 and 10% compared to cured pure PR. [ABSTRACT FROM AUTHOR]

Epoxy resin (EP) composites with satisfactory thermal and tribological performance are highly required for engineering moving components. However, the simple addition of fillers leaded to the serious filler agglomeration and limited promotion in tribological properties. In this work, we constructed a new kind of three-dimensional (3D) reduced graphene oxide (RGO)/Si3N4 hybrid aerogel for EP composites, which was prepared by a facile hydrothermal self-assembly method followed by freeze-drying technique. As a result, the dispersibility of Si3N4 whiskers was greatly improved through wrapping of polydopamine—polyethyleneimine copolymer (PDA—PEI) copolymer and physical spacing of 3D skeleton. Furthermore, benefiting from the synergistic effect of RGO and Si3N4@PDA—PEI in the thermal network, the thermal conductivity of RGO/Si3N4 hybrid aerogel (GSiA)—EP increased by 45.4% compared to that of the neat EP. In addition, the friction coefficient and wear rate of GSiA—EP decreased by 83.7% and 35.8%, respectively. This work is significant for opening a tribological performance enhancement strategy though constructing 3D hybrid architecture. [ABSTRACT FROM AUTHOR]

Non-oxide ceramic aerogel draws increasing attention in area of thermal insulation because of its low density, high temperature resistance and good chemical/thermal stability. Here, a BCN-TiN composite aerogel was prepared by an in-situ carbothermal reduction/nitridation method, using melamine (C3N6H6), boric acid (H3BO3), chitosan ((C6H11NO4)n) and titanium dioxide (TiO2) as raw materials. The aerogel prepared at 1473 K showed a porosity high up to 97.6 pct with a density of 0.05 g/cm3. When testing at a temperature of 673 K, the thermal conductivity value of as-obtained composite aerogel was as low as 0.135 W/(m K). Moreover, the lightweight BCN-TiN aerogel had the high-temperature stability (at least 1473 K) and good compression strength, which ensures it a potential high-temperature insulation material in inert atmosphere. [ABSTRACT FROM AUTHOR]

Herein, a direct comparison of the thermal conductivity and stability of different silica‐fiber‐reinforced silica aerogels is presented. The thermal performance under high‐temperature exposure within an arc‐heated facility is evaluated by means of thermal propagation and stability. All aerogel materials, tested within this study, outperform the high‐temperature fiber‐based insulation mat in terms of thermal protection. Modification of the aerogels in the composition and opacification leads to an improvement of thermal insulation properties as well as of thermal stability against the high temperature. All materials are prepared in the form of cylindrical disks of 100 mm diameter having a thickness of 20 mm. Based on classic silica aerogel, an opacified silica aerogel and an aerogel in mullite composition, inorganic fiber‐reinforce composites have been prepared and tested, and their performance is discussed comparatively. The specimens with mullite composition are intended to form mullite in situ during application to avoid energy‐costly pretreatment. [ABSTRACT FROM AUTHOR]

Summary: Avocado seed (Persea americana Miller) is a by‐product of fruit processing and is considered a potential alternative source of starch. The use of starches from unconventional sources can be an alternative to replace modified starches as a functional ingredient in food systems. This study aimed to extract and characterise starch from avocado seed varieties Fortuna and Hass and produce aerogels. Starches were characterised by physical, chemical, thermal and morphological properties. The aerogels were produced by physical crosslinking and evaluated for water absorption capacity and physical properties. The starch extraction yield was 12%, and the granules had oval and spherical morphology. Amylose content ranged from 41.95% to 49.46%, and relative crystallinity from 22% to 25% for Hass and Fortuna, respectively. The Fortuna starch showed higher pasting temperature, peak viscosity, peak time and final viscosity values. Aerogels had excellent structural characteristics and had not deformed after 24 h of hydration; the Fortuna starch aerogels showed higher water absorption and mechanical resistance. The properties of avocado seed starch indicate a vast potential for application in food industries and for developing biodegradable packaging with excellent physical properties and excellent water retention capacity. [ABSTRACT FROM AUTHOR]

Inorganic aerogels have exhibited many superior characteristics with extensive applications, but are still plagued by a nearly century-old tradeoff between their mechanical and thermal properties. When reducing thermal conductivity by ultralow density, inorganic aerogels generally suffer from large fragility due to their brittle nature or weak joint crosslinking, while enhancing the mechanical robustness by material design and structural engineering, they easily sacrifice thermal insulation and stability. Here, we report a chemically bonded multi-nanolayer design and synthesis of a graphene/amorphous boron nitride aerogel to address this typical tradeoff to further enhance mechanical and thermal properties. Attributed to the chemically bonded interface and coupled toughening effect, our aerogels display a low density of 0.8 mg cm−3 with ultrahigh flexibility (elastic compressive strain up to 99% and bending strain up to 90%), and exceptional thermostability (strength degradation <3% after sharp thermal shocks), as well as the lowest thermal conductivities in a vacuum (only 1.57 mW m−1 K−1 at room temperature and 10.39 mW m−1 K−1 at 500°C) among solid materials to date. This unique combination of mechanical and thermal properties offers an attractive material system for thermal superinsulation at extreme conditions. [ABSTRACT FROM AUTHOR]

Over the past decade, cellulose microtube-based foam materials have gained immense traction for their potential applications in construction, transportation, electronics, and so on with the gradual deterioration of the environment and the rapid depletion of fossil resources. However, the cellulose microtube-based foam materials have some disadvantages-the poor thermal insulation properties derived from the large and uneven pore structure, the low mechanical strength derived from the fewer microtube bonding points, and so on. These disadvantages limit their wide usage. In this paper, we are committed to enhance the performance of the cellulose microtube-based (CMT) foam materials, using aramid nanofiber (ANF) aerogel to fill the large and uneven pore structure of the CMT foam materials. The ANF suspension can be quickly and evenly adsorbed by the large and uneven porous structure of the CMT foam materials. The ANF aerogels can fill in the pores of the CMT foam materials uniformly. The morphology, microstructure, BET surface area, pore structure, and mechanical strength of the cellulose microtube/aramid nanofiber (CMT/ANF) composite foam can be effectively tuned by the concentration of the ANF suspension. The CMT/ANF-0.6 composite foam has the best thermal insulation properties. The temperature difference of the CMT/ANF-0.6 composite foam was 47, 72 and 109 °C when the temperature of the hot stage was 107, 155 and 208 °C. [ABSTRACT FROM AUTHOR]

Aerogels, due to their unique features like lightweight, ultra-low thermal conductivity, and design variations, have gotten a lot of interest in thermal insulation, photocatalysis, and protective areas. Besides their superior thermal properties, aerogel thermal insulation and photocatalyst materials also possess many inherent flaws, such as handling issues, high manufacturing costs, and low strength as well as toughness. The most persuasive and successful ways to improve photocatalytic and thermal insulating qualities while lowering costs are composition optimization and microstructure reconstruction. Their high surface area and porosity make them ideal for enhancing the efficiency and capacity of these devices. Research may lead to more efficient and longer-lasting energy storage solutions. This review describes the characteristics, microstructural reconstruction, design variation, and properties of all aerogel fabrication techniques and provides a comprehensive overview of scientific achievements linked to them. The effectiveness of raw material compositions, properties, and mechanical parameters are also discussed. The major goal of this review is to highlight the aerogel-based materials and design variations and to explore the most potential development trends for photocatalysis and thermal applications. The industrial as well as technical applications of silica aerogels are also highlighted. This review highlights futuristic applications of aerogel-based textile materials to alleviate the CO2 burden on our atmosphere, either by providing next-level thermal insulation or by employing them in CO2 mitigating technologies such as CO2 capture. [ABSTRACT FROM AUTHOR]

This paper presents the effect of drying control agents on the physicochemical and thermal properties of hydrophobic silica aerogels derived via the ambient pressure drying (APD) method by a surface silylation using a TMCS/n-hexane mixture. The structural and physicochemical properties of synthesized DMF-modified and unmodified hydrophobic silica aerogels were characterized using Brunauer–Emmett–Teller (BET) analysis, thermo-gravimetric analysis, FT-IR, and Raman spectroscopic techniques. Based on the obtained results, the differences in structure between samples before and after a surface silylation and the effect of drying control agents were documented. The structural measurements confirmed the efficient silylation process (TMCS/n-hexane), as well as the presence of DMF residues of hydrogen bonded with unreacted Si-OH silanol groups within the silica backbone after surface modification. Based on TG analysis, it was found that DMF addition improves thermal resistance (up to 320 °C) and hydrophobic character of prepared aerogel. Modification of the silica aerogel synthesis process by DMF also resulted in a significant increase in BET—the specific surface area, for the unmodified aerogel was ~828 m2/g, and for the DMF-modified aerogel more than 1200 m2/g—much higher than the value of silica aerogels available on the market. [ABSTRACT FROM AUTHOR]

In this work, the results of investigations of polyurethane materials were presented. Innovative materials based on polyurethane-polyisocyanurate (PUR/PIR) foam were obtained. Different types of additives (flame retardants, aerogels – additives that decrease thermal conductivity) are used in the composition of PUR/PIR foam. Foams are a type of composite composed of two phases: continuous (polyurethane polymers) and dispersed (composed of gases). All samples have been tested for thermal parameters: thermal conductivity, specific heat, and thermal diffusivity. Then they have been compared with each other and with a reference sample (RS) without additives. Based on the research, it was shown that innovative insulation materials were characterized by thermal conductivity λ in the range of 0.0254–0.0294 W/(m · K). The thermal properties of foams depending on the type and chemical composition of the material. Depending on the used substrates, their molar ratio, type, synthesis conditions, modifying agents and catalysts, a different polyurethane material is obtained.

This study investigated the thermal, mechanical, and oil absorption-retention properties at various temperatures (20°C, 30°C, 40°C, 50°C, and 60°C) of three-dimensional (3D) weft-knitted spacer fabrics with optimal performance of silica aerogel coating that demands exceptional attention. Silica aerogels and (silica aerogels + poly(vinyl-alcohol)) sols were prepared and coated on 3D weft-knitted spacer fabrics to study and compare the basic properties, i.e. thermal resistance, thermal conductivity, tensile strength, initial modulus, compression, bending rigidity, wettability, oil absorption, and retention capacity. The scanning electron microscopy and Fourier transform infrared spectroscopy studies were completed to understand the influence of both coatings on 3D weft-knitted spacer fabrics such as surface morphology and molecular interaction. The tensile, bending, and compression tests of 3D weft-knitted spacer fabrics were accomplished to check their durability, bendability, and compressibility. All the coated samples (both silica aerogels and (silica aerogels + poly(vinyl-alcohol))) showed greater thermal resistance (0.0971 ± 0.0003 m2 KW−1 and 0.0912 ± 0.0005 m2 KW−1) and lower thermal conductivity (0.0309 ± 0.0001 Wm−1 K−1 and 0.0329 ± 0.0002 Wm−1 K−1) with better thermal stability than the uncoated samples, most specifically coated sample 5. Besides, coated sample 5 exposed higher oil absorption ((7.91 ± 0.06 g/g and 7.88 ± 0.06 g/g) and (7.56 ± 0.04 g/g and 7.53 ± 0.04 g/g)) and retention ((90.10 ± 0.53% and 89.07 ± 0.55%) and (92.47 ± 0.49% and 91.43 ± 0.47%)) capacity for vegetable and engine oil in all conditions, especially at 40°C. The outcomes demonstrated that both coatings played a vital role in the thermal, mechanical, and wettability properties of 3D weft-knitted spacer fabrics with statistically significant performance (p < 0.05). Moreover, these new types of sorbents (3D weft-knitted spacer fabrics) have better consequences in most cases than conventional knitted, woven, and nonwoven sorbents. Hence, these 3D weft-knitted spacer fabrics could be used for industrial applications as eco-friendly and multifunctional oil sorbent materials. [ABSTRACT FROM AUTHOR]

Silica aerogels and their derivatives have outstanding thermal properties with exceptional values in the thermal insulation industry. However, their brittle nature restricts their large-scale commercialization. Thus, enhancing their mechanical strength without affecting their thermal insulating properties is essential. Therefore, for the first time, highly thermally stable poly(acrylamide-co-acrylic acid) partial sodium salt is used as a reinforcing polymer to synthesize hybrid P(AAm-CO-AAc)-silica aerogels via epoxy ring-opening polymerization in the present study. Functional groups in P(AAm-CO-AAc) partial sodium salts, such as CONH2 and COOH, acted as nucleophiles for the epoxy ring-opening reaction with (3-glycidyloxypropyl)trimethoxysilane, which resulted in a seven-fold enhancement in mechanical strength compared to that of pristine silica aerogel while maintaining thermal conductivity at less than 30.6 mW/mK and porosity of more than 93.68%. Moreover, the hybrid P(AAm-CO-AAc)-silica aerogel demonstrated improved thermal stability up to 343 °C, owing to the synergetic effect between the P(AAm-CO-AAc) and the silica aerogel, corresponding to the thermal stability and strong covalent bonding among them. These excellent results illustrate that this new synthetic approach for producing hybrid P(AAm-CO-AAc)-silica aerogels is useful for enhancing the mechanical strength of pristine silica aerogel without impairing its thermal insulating property and shows potential as an industrial heat insulation material. [ABSTRACT FROM AUTHOR]

Construction of biomass-based wearable aerogel heater with enhanced thermal insulation property plays a significant role in preventing heat loss for personal thermal management. Inspired by natural creatures' utilization own hollow microstructures to resist the extremely cold surroundings, we report an eco-friendly strategy to construct calcium alginate (CA) /kapok fiber (KF)/carbon nanotubes (CNTs) active-cum-passive aerogel heater with desired economic feasibility, sustainability and efficient thermal insulation performance. The renewable cellulose hollow KF disrupts the heat transfer pathway and enabled CA/KF/CNT lower thermal conductivity (0.024 W/m·K) and ultralight density (0.027 g/cm3). The CNTs in the aerogel heater not only provided excellent conductivity for realizing Joule-heating but also enhanced the photothermal conversion capability from solar irradiation, ensuring extra self-heating ability without power supply. According to energy-saving analysis, the total energy saved in China per year was 6.03 × 109 kWh when using the developed aerogel heater instead of the traditional heating method. This developed biomass aerogel heater in this work exhibits great potential to be applicable in the fields of wearable personal thermal management to enhance the adaptability of human body in cold environment. Our work may inspire the study of biomass-derived wearable heaters for solving global energy issues. [ABSTRACT FROM AUTHOR]

The cellulose (Cel)-polyvinyl alcohol (PVA)-sodium alginate (SA) composite aerogels are prepared by adding PVA and SA to the Cel suspension, followed by freeze-drying. The structure and properties of Cel-PVA-SA composite aerogels are determined by FT-IR, scanning electron microscopy, thermogravimetric analysis, limiting oxygen index method and cone calorimetry. The results reveal that sodium alginate is uniformly distributed within the aerogels. The as-synthesized composite aerogels possess excellent compressive resilience properties. In addition, the addition of sodium alginate significantly reduces the flammability of cellulose. Therefore, this study provides a simple method to prepare green flame-retardant Cel-PVA composite aerogels materials, and the aerogels demonstrate excellent potential for application in construction materials. [ABSTRACT FROM AUTHOR]

Aerogels, the lowest-density solids in the world, have very effective thermal insulation properties with their extremely high surface area and porous structure. Recently, there has been an increasing interest in using aerogels in the textile industry, especially to obtain functional and technical textiles. In this study, thermal and solar properties of polyester fabrics coated at different concentrations (1 %, 2 %, and 4 %) of aerogels with different particle sizes (~ 8 µm, 0 - 80 µm, 0 - 0.5 mm) were investigated. It was observed that the aerogel particle size and concentration had a significant effect on the thermal and solar properties, and the lowest thermal conductivity coefficient and thermal resistance values (0.036 W/mK and 14.33 m2 K/W, respectively) appeared at the largest particle size and maximum concentration. In contrast, the solar reflectance values of the coated samples decrease up to 62 % with increasing aerogel particle size. In a conclusion, the coating method with aerogel powders could be applied to improve the thermal insulation and solar protection properties of mainly curtains, tents, tarpaulins, and sportswear fabrics. [ABSTRACT FROM AUTHOR]

In this work, 1-aminoethyl-3-methylimidazolium bromide ionic liquid was used to modify the surface of graphene nanosheets (GNs) through "π–π" interaction to achieve good dispersion and conductivity. By introducing ionic liquid-modified graphene nanosheets (IGNs) into the PI matrix, the ultra-lightweight and multifunctional IGNs/PI aerogels were prepared via freeze-drying and thermal imidization. Benefiting from the porous structure and the introduction of conductive IGNs, the IGNs/PI aerogels exhibit excellent electromagnetic wave (EMW) absorption properties, compression properties, thermal insulation properties and thermal stability. Notably, when the volume content of IGNs is 10%, the IGNs/PI-10 aerogels show the best EMW absorption performance with a minimum reflection loss (RLmin) of −24.8 dB at 2.44 mm and an effective absorption bandwidth (EAB) of 3.6 GHz at 3.00 mm. These promising characteristics including excellent EMW absorption, compression properties and thermal insulation endow IGNs/PI aerogels great application prospects as multifunctional EMW absorbers. [ABSTRACT FROM AUTHOR]

In this study, we investigated the tunable porous structure of SiCN(O)-derived ceramic aerogels by changing the molecular structure of the polysilazanes from linear to branched. We also studied the effect of molecular structure on the thermal insulation properties of ceramic aerogels. As the percentage of branched molecular structure in the polysilazane precursor increased, the internal microscopic pore structure of the aerogels changed from macroporous to mesoporous. The specific surface areas and pore volumes of the ceramic aerogels prepared with different precursors increased after pyrolysis at 1000 °C, ranging from 3.7 to 255.9 m2/g and 0.01–0.36 cm3/g, respectively. The corresponding thermal conductivities increased slightly as the aerogels contracted after pyrolysis. The low thermal conductivity (0.046 W/(m·K) at minimum) can be attributed to the decrease in pore size caused by adjusting the precursor structure, which limits the thermal conduction of gas in the porous aerogel materials. [ABSTRACT FROM AUTHOR]

High-performance thermally insulating aerogel with low density, high porosity, and low thermal conductivity characteristics was widely used in heat insulation. However, the large-scale application of aerogel was still limited by its brittleness and infrared radiation transparency at high-temperature. Fiber composite aerogel had achieved significant progress, but its anti-oxidation ability was poor, and its thermal insulation required further improvement at ultra-high temperatures. Herein, inspired by the structure of elytra, nanoparticle fiber (NF) was prepared by electrospinning of coaxial fiber loaded with opacifier and antioxidant nanoparticles. The NF was incorporated into the SiBCN aerogel to prepare NF/SiBCN ceramic fiber aerogel. The mechanical properties were improved by fiber networks. The shell structure increased the antioxidant properties. Heat conduction and heat convection were suppressed by the aerogel, while heat radiation was reduced by the coaxial fiber. The results showed that the ceramic fiber aerogel exhibited superior mechanical, antioxidant, and ultra-low thermal conductivity properties. • A novel 'particle/fiber/aerogel' composites were constructed for thermal insulation. • The composites exhibited fire resistance and ultralow thermal conductivity at 1300 °C. • The composites had low density and excellent mechanical properties. • Coaxial fiber had self-healing and anti-oxidation properties at ultra-high temperatures. [ABSTRACT FROM AUTHOR]

A nonconventional material with remarkable thermal and acoustic insulation properties from aerogels category was experimentally made. Produced from a recycled commercial waste (polyethylene terephthalate-PET) and an industrial by-product (fly ash) as well as a biomaterial (psyllium husk) used for the first time as a binder by mixing with water, the aerogel was subjected to a freeze-drying process. The determination of the product characteristics highlighted extremely low densities (0.022-0.041 g· cm-3), very low thermal conductivities (0.035-0.037 W·m-1·K-1), very high porosities (97.8-98.5 %), mechanical properties superior to those of an unreinforced gel (compression strength of 9.5-16.4 kPa and Young's modulus of 4.15-18.93 kPa), and excellent noise absorption properties (noise reduction coefficient of 0.30-0.33). The manufacturing process of this inexpensive product allows for a clean environment. [ABSTRACT FROM AUTHOR]

The main aim of this research is to improve the protective thermal performance of fabrics. Flame-resistant fabrics characterizing comparable thermal properties were chosen, cotton fabric with a flame-retardant finish and Nomex® fabric. To improve thermal parameters the coating mixture, based on silica aerogel, was applied on one side of the sample surface. Parameters such as the thermal conductivity, resistance to contact, and radiant heat were determined based on the standards, which set high expectations for the protective clothing. Analysis of the coated fabrics surfaces was conducted based on confocal microscopy. It was found that the coating mixture caused a decrease in thermal conductivity. All the modified fabrics reached 1st efficiency level of protection against contact and radiant heat. The best sample from the point of view of protection against contact and radiant heat was modified cotton fabric with a flame-retardant finish. The coating mixture contained 45 wt% of silica aerogel. Moreover, better adhesion of the coating mixture to the cotton fabric compared with Nomex® fabric was observed. [ABSTRACT FROM AUTHOR]

Thermal camouflage is one of the most effective ways to guarantee the security and survival of military objects against infrared (IR) detectors. However, with the rapid development of IR detection technology, the IR thermal camouflage of objects and weapons has become more and more difficult, and advanced thermal camouflage materials are urgently needed to meet the demands of warfare. So far, two dimensional (2D) nanomaterials have demonstrated excellent performances with low IR emissivity, optoelectronic tunability, and compatible stealth capabilities. Among them, graphene and MXenes are the most attractive 2D materials used for thermal camouflage applications. Here we present a review of recent progress on the thermal camouflage properties of graphene and Ti 3 C 2 T x MXene in the form of composite film, microcapsule and aerogel structures, a summary of current understanding of the working principle of thermal camouflage materials, and current limitations and future opportunities in graphene and Ti 3 C 2 T x MXene research and development. [ABSTRACT FROM AUTHOR]

The oriented pore structure of wood endows it with a variety of outstanding properties, among which the low thermal conductivity has attracted researchers to develop wood‐like aerogels as excellent thermal insulation materials. However, the increasing demands of environmental protection have put forward new and strict requirements for the sustainability of aerogels. Here, we report an all‐natural wood‐inspired aerogel consisting of all‐natural ingredients and develop a method to activate the surface‐inert wood particles to construct the aerogel. The obtained wood‐inspired aerogel has channel structure similar to that of natural wood, endowing it with superior thermal insulation properties to most existing commercial sponges. In addition, remarkable fire retardancy and complete biodegradability are integrated. With the above outstanding performances, this sustainable wood‐inspired aerogel will be an ideal substitute for the existing commercial thermal insulation materials. [ABSTRACT FROM AUTHOR]

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[Display omitted] Advanced thermal-insulation materials for human use in high-temperature and ultra-low-temperature environments have received extensive attention. However, facile synthesis of aerogels with excellent mechanical and thermal properties via freeze-drying or electrospinning alone is still challenging. We hypothesized that a polyimide aerogel with high mechanical strength and good thermal-insulation performance and suitability for various applications at high and low temperatures could be prepared facilely using a simple and novel preparation strategy that combines electrospinning, freeze-drying, and in situ thermal crosslinking. Polyamideimide (PAI) nanofibers loaded with bismaleimide (BMI) were electrospun and dispersed into a polyamic acid aqueous solution. PAI/BMI-nanofiber-reinforced polyimide (IBNR-PI) aerogels with an interpenetrating network structure were prepared by freeze-drying and heat treatment. The IBNR-PI aerogels possessed extremely low volume density (26 mg cm−3) and high porosity (94.92%). Most importantly, they showed high tensile strength and good compressive fatigue resistance with plastic deformation of only 7% after 1000 compression cycles. The aerogels also showed a significantly low thermal conductivity (30.06 mW m−1 K−1) and excellent thermal insulation over a wide temperature range. Thus, the IBNR-PI aerogels are excellent candidates for thermal-insulation materials at high and low temperatures. [ABSTRACT FROM AUTHOR]

In this work, we reported that aramid pulps (AP) reinforced clay aerogel composites with improved mechanical strength, good thermal insulation and fire resistance based on the combination of AP, Poly(vinyl alcohol) (PVA) and sodium montmorillonite (MMT), which present a promising prospect in the thermal insulation application. The PVA-MMT-APx (x: denotes the mass content of AP) aerogel composites present an isotropic "lamella-honeycomb" porous structure, which endows them with excellent comprehensive performance. With the AP content increasing, the extremely low density is kept, ranging between 67–73 mg/cm3, and the low thermal conductivity is maintained within 40.9–47.9 mW·m−1·K−1. The mechanical strength is significantly improved with the maximum compressive modulus increasing from 2.95 to 5.96 MPa and the specific modulus rising from 44.03 to 81.64 MPa∙cm3/g. Their detailed heat transfer process has been analyzed, which provides a deep understanding to the low thermal conductivity of the PVA-MMT-APx aerogel composites. Based on the combination of thermogravimetric analysis and combustion behavior, the PVA-MMT-APx aerogel composites are demonstrated to possess improved thermal stability and fire resistance. This study puts forward a facile approach to utilizing AP to reinforce clay aerogel composites, which provides new insight into the development of thermal-insulating, fire-safe and high-strength thermal insulation materials. [ABSTRACT FROM AUTHOR]

The serious problem of energy consumption and the requirement for sustainable development has attracted people's extensive attention. The application of high‐efficiency thermal insulation materials can reduce consumption and waste in the process of energy transfer, and is the most effective way to save energy and protect the environment. Among many thermal insulation materials, silica aerogel, especially biomass fiber‐reinforced silica aerogel with good mechanical strength, shows great practical application potential. In this article, the collagen fiber‐silica aerogel composite (MCFF@SiO2) was successfully prepared by in situ sol–gel method and freeze‐drying method, innovatively using skin collagen fiber matrix with natural porous skeleton as reinforcing template. MCFF@SiO2 has good thermal stability, and has a hierarchical porous structure formed by filling nanoscale mesopores of silica aerogel in the macropores of collagen fiber matrix, thus delaying the spread of heat. Particularly, MCFF@SiO2 exhibits good thermal insulation performance, and its thermal conductivity is 0.068 W/(m K), which is lower than that of MCFF. In addition, MCFF@SiO2 shows superhydrophobicity, good mechanical properties, excellent flame retardancy, and self‐extinguishing performance. The prepared composite aerogels have potential application value in the field of thermal management, and this work is expected to provide inspiration for the preparation of biomass‐based porous functional materials. [ABSTRACT FROM AUTHOR]

To adjust the thermal safety of hydrophobic silica aerogel, layered double hydroxide (LDH)/silica aerogel (SA) composites were prepared by an in-situ sol-gel process at ambient pressure. This study found the physical combination of SA and MgAl-LDH based on the FTIR spectra and phase composition of LDH/SA. The N2 sorption analysis confirms that the introduction of MgAl-LDH does not change the mesoporous attribution of LDH/SA significantly. With the increase in MgAl-LDH addictive content, the low density (0.12–0.13 g/cm3), low thermal conductivity (24.28–26.38 mW/m/K), and large specific surface area (730.7–903.7 m2g) of LDH/SA are still maintained, which can satisfy the requirements of thermal insulation. The TG-DSC analysis demonstrates that the endothermic effects and metal oxides formed during the MgAl-LDH decomposition are beneficial to the improvement of the thermal stability of LDH/SA composites. In addition, it was found that the gross calorific values of LDH/SA composites decrease with an increase in MgAl-LDH addictive content, all of which are lower than that of the pure SA. The research outcomes indicate that the thermal safety of LDH/SA composites is enhanced significantly by doping MgAl-LDH without impairing too many of the excellent properties, which benefits their expansion in the thermal insulation field. [ABSTRACT FROM AUTHOR]

Flexible pressure sensors embody outstanding mechanical and sensing performance, particularly in the fields of personal health monitoring and artificial intelligence, while catering to multifunctional applications resilient against harsh weather conditions. Among these, Ti 3 C 2 T x MXene-based aerogel materials with high surface area and excellent conductivity have attracted a lot of attention. However, there are big challenges in improving the mechanical properties at low densities and designing multi-level pore structures. Herein, the prepared silane monomers (MP) are firstly synthesized by 3-(Trimethoxysilyl) propyl methacrylate (MPTES) and polyethylene glycol diacrylate (PEGDA), then polydopamine-modified silicon dioxide (PDA-SiO 2) nanofibers employed with MXene nanosheets form covalent cross-linking nanofiber aerogels. The multi-level stable structure improves both mechanical strength and elasticity. The assembled MXene/MP/PDA-SiO 2 pressure sensors exhibit a high sensitivity of −0.83 kPa−1, a rapid response time of 48 ms, a minimum 1 % strain detection limit, and reliable stability over 10,000 cycles. Furthermore, these sensors can be used for human motion detection and health diagnostics, and show good personal thermal management performance. This work holds a promising candidate for the next generation of multifunctional flexible electronic devices. [ABSTRACT FROM AUTHOR]

The development of lightweight shape memory materials with exceptional thermal insulation properties is highly important in aerospace applications. Herein, shape memory polyimide (PI) aerogels was fabricated by molecularly designed PI molecular chains through freeze gelation and subsequent thermal imidization. The freezing conditions were controlled to regulate the porous microstructures of the aerogels. The interactions between PI chains formed physically crosslinked netpoints, which could overcome the expansive force and capillary force, thereby creating a stable porous structure. Because shape memory was thermally activated, the shape memory mechanisms associated with the thermal conductivity of the aerogels were comprehensively explored. Upon decreasing the pore size, dense frameworks were formed, contributing to the improved thermo-mechanical and compressive properties. Moreover, the heat transfer efficiency in the aerogel skeleton was enhanced, resulting in a rapid shape recovery response. Benefiting from the physically crosslinked structures, including entangled chains and π-π interactions, the fabricated PI aerogels demonstrated exceptional shape fixation and recovery capabilities. These findings may provide guidelines for designing smart aerogels for aerospace applications. [Display omitted] • Shape memory polyimide aerogels with tunable porous microstructures were fabricated. • The size of the micropores was regulated by controlling the freezing conditions. • The reduction of pore size accelerated the shape recovery process. • The comprehensive exploration of the shape memory mechanisms was conducted. [ABSTRACT FROM AUTHOR]

In the field of building energy conservation, the development of biodegradable biomass aerogels with excellent mechanical performance, flame retardancy and thermal insulation properties is of particular importance. Here, a directional freeze-drying method was used for fabricating composite sodium alginate (SA) aerogels containing functionalized ammonium polyphosphate (APP) flame retardant. In particular, APP was coated with melamine (MEL) and phytic acid (PA) by a supramolecular assembly process. Through optimizing the flame retardant addition, the SA-20 AMP sample exhibited excellent flame retardant and thermal insulation properties, with the limiting oxygen index of 38.2 % and the UL-94 rating of V-0. Such aerogels with anisotropic morphology demonstrated a low thermal conductivity of 0.0288 (W/m·K) in the radial direction (perpendicular to the lamellar structure). In addition, as-obtained aerogels displayed remarkable water stability and mechanical properties, indicating significant potential for practical applications. [Display omitted] • A high-efficiency flame retardant was synthesized. • AMP has a good interface compatibility with sodium alginate. • SA-20 AMP reached V-0 rating and the LOI value was 38.2 %. • Directional freezing endows SA-20 AMP with outstanding thermal insulation properties. [ABSTRACT FROM AUTHOR]

[Display omitted] • A method is developed for the regulation of secondary unstable dendrites during ice crystal growth. • The flexible polyimide (PI) aerogels possesses a micro/nano multi-scale porous skeleton. • The PI aerogels are characterized by ultra-low density and exceptional thermal insulation. The freeze-casting is widely utilized as a tool for regulating micro-scale pore structures in the fabrication of flexible polyimide (PI) aerogels for applications in adsorption, filtration, and fire-retardant. Herein, a confinement-controlled freeze-casting method is developed to fabricate PI aerogels with excellent thermal insulation properties by designing multi-scale structural adaptability. In a confinement-controlled system, the enhanced solid/solid and solid/liquid interface interactions in the solution dispersion system induce dendritic evolution of ice crystals. Under the directional freezing, grown dendritic ice crystals squeeze the loaded particles to form polyamic acid salt (PAAs) cryogels. Followed by template removal and thermal imidization, PI aerogels with a micro/nano-scale slit-like porous structure were obtained. The PI aerogels are characterized by ultra-low density (as low as 9.82 mg/cm3) and exceptional thermal insulation performance (25.0 mW/(m·K) at 25 °C). [ABSTRACT FROM AUTHOR]

Heat consumption is a serious energy waste, especially in an extremely cold environment. In view of their excellent advantages, several kinds of aerogels with different functions were emerged successively and served as critical materials in various areas. In this contribution, a simple strategy was developed to fabricate a high-fidelity and high-performance organic/inorganic composite aerogel by integrating dianhydrid-end capped polyamide acid (PAA) precursor and multi-amino functionalized hydroxyapatite (m-AmHA; used as the inorganic cross-linkers) in different feed ratios. Followed by the freeze-drying and thermal imidization treatments, the chemical cross-linked polyimide (PI) and HA based aerogels (HA x @PI, in which x represents the percentage of HA content) were obtained. The synergistic effect of inorganic filler and microporous structure of aerogel led to a great improvement of mechanical and thermal properties. Most importantly, the resultant HA x @PI aerogels could maintain their excellent physicochemical properties in several extreme environments such as ultra hot (300 °C), extreme cold (-196 °C; liquid nitrogen), water soaking (2 h, 40 °C), acid (pH 2.0; 1 h, 40 °C) and alkali (pH 12.0; 1 h, 40 °C) conditions. Based on these outstanding properties, we believe that such HA x @PI composite aerogels with low cost and high performances endowed them to be an ideal candidate to be employed in several harsh environments in addition to the conventional insulation and flame-retardant materials. • Uniformity dispersed HA contained polyimide-based aerogels were fabricated. • The mechanical properties, flame resistance, and thermal insulation properties were enhanced with the doping of HA. • Such aerogels could withstand several harsh environments, including ultra hot, extreme cold, water soaking, acid and alkali conditions, without influence on their physicochemical properties. [ABSTRACT FROM AUTHOR]

Blown films based on low-density polyethylene (LDPE)/linear low-density polyethylene (LLDPE) and silica aerogel (SA; 0, 0.5, 1, and 1.5 wt.%) were obtained at the pilot scale. Good particle dispersion and distribution were achieved without thermo oxidative degradation. The effects of different SA contents (0.5–1.5 wt.%) were studied to prepare transparent-heat-retention LDPE/LLDPE films with improved material properties, while maintaining the optical performance. The optical characteristics of the composite films were analyzed using methods such as ultraviolet–visible spectroscopy and electron microscopy. Their mechanical characteristics were examined along the machine and transverse directions (MD and TD, respectively). The MD film performance was better, and the 0.5% composition exhibited the highest stress at break. The crystallization kinetics of the LDPE/LLDPE blends and their composites containing different SA loadings were investigated using differential scanning calorimetry, which revealed that the crystallinity of LDPE/LLDPE was increased by 0.5 wt.% of well-dispersed SA acting as a nucleating agent and decreased by agglomerated SA (1–1.5 wt.%). The LDPE/LLDPE/SA (0.5–1.5 wt.%) films exhibited improved infrared retention without compromising the visible light transmission, proving the potential of this method for producing next-generation heat retention films. Moreover, these films were biaxially drawn at 13.72 MPa, and the introduction of SA resulted in lower draw ratios in both the MD and TD. Most of the results were explained in terms of changes in the biaxial crystallization caused by the process or the influence of particles on the process after a systematic experimental investigation. The issues were strongly related to the development of blown nanocomposites films as materials for the packaging industry. [ABSTRACT FROM AUTHOR]

In this study, a low-cost thermoset such as unsaturated polyester resin (UPR) was used for the preparation of lightweight and thermal insulation polymer composite using rice husk-derived silica aerogel (SA) as filler. For the first time, hydrophilic and hydrophobic silica aerogel (SA) of similar physical properties were added to the UPR to study the effects of SA surface polarity on the mechanical tensile and thermal properties of the composites. The composites with 40% and 60% of SA filler by volume were prepared via direct mixing and cured at room temperature using methyl ethyl ketone peroxide. The UPR composites were characterized and compared using density measurement, hot-disc thermal conductivity analyzer, universal testing machine, Fourier transform infrared spectroscopy, scanning electron microscopy and thermogravimetric analysis. The results of this study indicate that the filler–matrix interaction appears to be dependent on the type of SA (hydrophobic or hydrophilic), due to noticeable differences in the data values. UPR composites containing hydrophilic SA exhibit lower density and thermal conductivity due to a higher volume of preserved SA pores. Both hydrophobic and hydrophilic SA could increase the tensile stiffness, but composite with hydrophilic SA exhibit higher fracture strain, indicating higher toughness. On the other hand, composites with hydrophobic SA produced stronger hydrogen bonding interaction which increases resin viscosity and led to rougher surface morphology. However, the addition of SA, regardless of surface polarity and volume concentration had little or no effect on thermal stability except that the composite with hydrophobic SA gives a slightly higher char yield. [ABSTRACT FROM AUTHOR]

Aerogels are excellent thermal insulation materials with extremely low thermal conductivity. However, the practical applications of traditional oxide aerogels, such as SiO 2 and Al 2 O 3 aerogels, are limited by the disadvantages of easy sintering and intrinsic brittleness. SiC is a good candidate for new aerogel due to its superior stability and good properties from room to high temperatures. However, it is generally supposed that SiC cannot be employed as thermal insulation material because of its high intrinsic thermal conductivity. We herein developed SiC nanowire aerogel with quite low thermal conductivity using freeze-drying method. The fabricated SiC nanowire aerogel exhibits ultra-high porosity (∼99.5%), excellent high-temperature stability (∼1700 °C), extremely low thermal conductivity (0.035 W/(m⋅K)) and good compressive flexibility. The low thermal conductivity is resulted from ultra-high porosity and multi-level nanostructures. Flexible compression behavior is attributed to the capability of moving and buckling of SiC nanowires, originating from both ultra-high porosity and strong connection between nanowires. This exploration highlights the flexible SiC nanowire aerogel as a promising high temperature thermal insulation material. [ABSTRACT FROM AUTHOR]

High‐performance thermal protective composites with lightweight, micro‐ ablation and high‐efficient thermal insulation are urgently required for thermal protection systems in advanced hypersonic speed vehicles. However, the practical applications of thermal protective composites have long been hampered by the main issues such as low mass residual rate and poor long‐term antioxidation of the matrix in high‐temperature aerobic environments. Here, we report a novel silica‐polybenz oxazine (SiO2‐PBO) aerogels with interpenetrated networks, possessing the ability to antioxidation, thermal insulation, and flame‐retardant properties. The resulting SiO2‐PBO aerogels exhibit low density (0.25 g/cm3), low thermal conductivity (0.035 W/(m·K)), and superior peak heat release rate value (15.3 W/g). Moreover, the mass residual rate is up to 70.46 wt% in the N2 atmosphere and remains 57.83 wt% despite existing in the air atmosphere and experiencing the highest temperature of 800°C. Briefly, SiO2‐PBO aerogels as‐prepared could be a potential matrix for a new gene ration of high‐performance thermal protective composites in the future. [ABSTRACT FROM AUTHOR]

A cost-effective solution for the synthesis of high-porosity TiO2 aerogels, which can be used as a mesoporous perovskite network charge-carrier material during the manufacture of solar cells, is described. The effects of the synthesis parameters (precursor (titanium (IV) isopropoxide (TIP) and tetrabutyl orthotitanate (TBOT)), additional solvent exchange (n-hexane (nH), cyclohexane (CH), and diethyl ether (DE)), subcritical drying (800 mbar vacuum, 70 °C, 8 h), aging, and calcination on the aerogel's structure have been investigated. Methods of XRD, FT-IR, BET, Raman, STA, SEM, UV–vis, and thermal conductivity measurements were applied to find out the relation between the synthesis conditions and the properties of the synthesized aerogels. Amorphous aerogels are polydispersed systems with the highest probability of pore diameter from 0.5 to 15 nm. An nH-exchanged, aged aerogel synthesized from the precursor TIP shows the highest diameter of pores. After calcination, the aerogels tend to crystallize into an anatase phase and the size of the crystallites depends on the precursor's nature. Calcination leads to a significant increase in both the apparent and true density of the aerogels, and it also results in an increase in porosity and thermal conductivity. [ABSTRACT FROM AUTHOR]