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Herein, a novel flexible SiO 2 aerogel composite nanofiber membrane with strawberry-like structure and excellent thermal insulation properties, in which SiO 2 aerogel particles act as thermal insulation filler, was prepared by electrospinning technology. With the addition of nano-pore structure SiO 2 aerogel particles, the heat transfer path of the fibers inside the membrane became discontinuous, endowing the as-prepared membrane an ultra-low thermal conductivity of 30.3 mW/(m⋅K) and large surface area of 240 m2/g. Moreover, the nanofibers membrane also possesses the combined merits of excellent fire resistance, high-temperature stability, and temperature-invariant flexibility, rendering it a promising in the application of insulation and gas adsorption. The successful preparation of this flexible nanofiber membrane paves a new way to design materials with excellent thermal insulation and adsorption properties. [ABSTRACT FROM AUTHOR]

Environmental noise has been regarded as major noise pollution with severe hazards to human physical and mental health. The common commercial fiber sound-absorption materials have insufficient low frequencies wave absorbing and fire-resistant ability, limiting their wide application. To solve these problems, a novel strategy combining flexible nanofibers and rGO/MXene nanosheets was proposed to fabricate rGO/MXene/SiO 2 nanofibers composite aerogel with hierarchically porous structure, which possessed an extremely low density of 9.8 mg/cm3 and superior low-frequency sound absorption ability (NRC value of 0.51). The obtained composite aerogel possessed a large deformation up to 80% (corresponding compressive stress of 17 kPa) and quickly recovered. In addition, the as-prepared aerogel could be easily produced on a large scale, providing a reference for the development of new generation of sound-absorbing products. [ABSTRACT FROM AUTHOR]

Forming fibers for fabric insulation is difficult using aerogels, which have excellent thermal insulation performance but poor mechanical properties. A previous study proposed a novel method that could effectively improve the mechanical properties of aerogels and make them into fibers for use in fabric insulation. In this study, composite aerogel fibers (CAFs) with excellent mechanical properties and thermal insulation performance were prepared using a streamlined method. The wet bacterial cellulose (BC) matrix without freeze-drying directly was immersed in an inorganic precursor (silicate) solution, followed by initiating in situ sol-gel reaction under the action of acidic catalyst after secondary shaping. Finally, after surface modification and ambient drying of the wet composite gel, CAFs were obtained. The CAFs prepared by the simplified method still had favorable mechanical properties (tensile strength of 4.5 MPa) and excellent thermal insulation properties under extreme conditions (220 °C and −60 °C). In particular, compared with previous work, the presented CAFs preparation process is simpler and more environmentally friendly. In addition, the experimental costs were reduced. Furthermore, the obtained CAFs had high specific surface area (671.3 m²/g), excellent hydrophobicity, and low density (≤0.154 g/cm3). This streamlined method was proposed to prepare aerogel fibers with excellent performance to meet the requirements of wearable applications.

Aerogels are nanoporous materials with excellent properties, especially super thermal insulation. However, owing to their serious high brittleness, the macroscopic forms of aerogels are not sufficiently rich for the application in some fields, such as thermal insulation clothing fabric. Recently, freeze spinning and wet spinning have been attempted for the synthesis of aerogel fibers. In this study, robust fibrous silica-bacterial cellulose (BC) composite aerogels with high performance were synthesized in a novel way. Silica sol was diffused into a fiber-like matrix, which was obtained by cutting the BC hydrogel and followed by secondary shaping to form a composite wet gel fiber with a nanoscale interpenetrating network structure. The tensile strength of the resulting aerogel fibers reached up to 5.4 MPa because the quantity of BC nanofibers in the unit volume of the matrix was improved significantly by the secondary shaping process. In addition, the composite aerogel fibers had a high specific area (up to 606.9 m2/g), low density (less than 0.164 g/cm3), and outstanding hydrophobicity. Most notably, they exhibited excellent thermal insulation performance in high-temperature (210 °C) or low-temperature (−72 °C) environments. Moreover, the thermal stability of CAFs (decomposition temperature was about 330 °C) was higher than that of natural polymer fiber. A novel method was proposed herein to prepare aerogel fibers with excellent performance to meet the requirements of wearable applications.

Nowadays, besides the use of conventional insulations (plastic foams and wool materials), aerogels are one of the most promising thermal insulation materials. As one of the lightest solid materials available today, aerogels are manufactured through the combination of a polymer with a solvent, forming a gel. For buildings, the fiber-reinforced types are mainly used. In this paper, the changes both in the thermal performance and the material structure of the aerogel blanket are followed after thermal annealing. The samples are put under isothermal heat treatments at 70 °C for weeks, as well as at higher temperatures (up to 210 °C) for one day. The changes in the sorption properties that result from the annealing are presented. Furthermore, the changes in the thermal conductivity are followed by a Holometrix Lambda heat flow meter. The changes in the structure and surface of the material due to the heat treatment are investigated by X-ray diffraction and with scanning electron microscopy. Besides, the above-mentioned measurement results of differential scanning calorimetry experiments are also presented. As a result of using equipment from different laboratories that support each other, we found that the samples go through structural changes after undergoing thermal annealing. We manifested that the aerogel granules separate down from the glass fibers and grow up. This phenomenon might be responsible for the change in the thermal conductivity of the samples.

Chemical warfare agents (CWAs) pose huge threats to ecological environments, agriculture, and human health due to the turbulent international situation in contemporary society. Zirconium hydroxide (Zr(OH) 4 ) has captured the prime focus as an effective candidate for CWA decomposition but is often hindered by the isolated powder form. Here, we demonstrate a scalable three-dimensional space-confined synthetic strategy to fabricate nanoflake-engineered zirconic fibrous aerogels (NZFAs). Our strategy enables the stereoscopic Zr(OH) 4 nanoflakes vertically and evenly in situ grown on the interconnected fibrous framework, remarkably enlarging the surface area and providing rich active sites for CWA catalysis. The as-synthesized NZFAs exhibit intriguing properties of ultralow density (>0.37 mg cm -3 ), shape-memory behavior under 90% strain, and robust fatigue resistance over 10 6 compression cycles at 40% strain. Meanwhile, the high air permeability, prominent adsorptivity, and reusability make them state-of-the-art chemical protective materials. This work may provide an avenue for developing next-generation aerogel-based catalysts and beyond.

• Pesentation of a new coefficient for vapour up-taking through material testing. • Presentation of new moisture conversion coefficients of Aerogel. • Effect of the vapour in the thermal conductivity of aerogel. • Substantial effect of the moisture and ice in the thermal conductivity was deduced. • New theory for the thermal conductivity. Insulation materials are mainly porous or fibrous materials. Therefore, the presence of moisture can easily cause problems inside the materials, and in the whole building structure. For correct calculations of heat and moisture transfer problems in building applications, practitioners need design values. Design thermal values are deduced and calculated from declared values which are reached from laboratory measurements. This is the case for both insulation and building materials. If the design environments are different from those where the declared values should be used, the data have to be changed to the relevant conditions. There are standards giving suggestions on how to calculate the design values of thermal insulation materials, however, their database and tables are insufficient regarding the values of the super insulation materials. In this paper, a calculation method will be presented so as to specify the design thermal conductivities of a glass fiber-reinforced aerogel. The calculation method is based on measurement results, where the lambda values were measured treating the samples in a humid environment. As a result, the moisture conversion coefficient for the thermal conductivities is obtained after measuring the humid thermal conductivities of materials. Moreover, a new calculation method will also be presented to estimate the vapor absorption coefficient from humidity measurements. Furthermore, the effects of ice and freeze on the thermal conductivities of the aerogel samples are characterized, too. The thermal conductivities were measured in a Holometrix type heat flow meter, while for the wetting a Venticell 111 type drying apparatus and a Climacell 11 climatic chamber were applied. Moreover, the cooling treatment was executed in a freezing room. In addition, new theory for the thermal conductivity was given, for moist/frost insulation materials. Image, graphical abstract [ABSTRACT FROM AUTHOR]