Search

A low-density, high-specific surface area, high-strength and large-sized carbon aerogel preparation process is a key technology in the industrial application of aerogel science. In recent years, ingenious nanostructure design, along with salt templates, drying optimization and other strategies have been applied by numerous scientists. As a result, the specific surface area of carbon aerogel has significantly increased and the density reduced. However, the preparation of high-strength and large-sized intact carbon aerogel at low cost is still a challenge due to the limitations of thermal treatment equipment and drying process. In this study, we propose an improved preparation method of ambient pressure solvothermal polymerization and auxiliary ambient pressure drying by the principle of acid–base two-step catalysis using resorcinol and furfural as raw materials. Resultantly, the condensation and cross-linking reaction process is stabilized by the ambient pressure solvothermal polymerization, which effectively reinforces the interfacial bonding between primary particles and forms a high-strength skeleton. The breaking strength of the aerogels reach up to 9.74 MPa. The auxiliary ambient pressure drying can greatly reduce the drying shrinkage and density of the aerogel and solve the problems of drying deformation and cracking of large-sized carbon aerogel. The drying shrinkage and density of the obtained carbon aerogels are reduced to 3.22% and 0.203 g/cm3, respectively, and the specific surface area reaches 675.057 m2/g. Moreover, the large-sized sample (70 mm (d) × 25 mm (h)) can also be prepared by this method since the strength of skeleton can resist the capillary force of pore structure, and the nanoporous architecture can be perfectly retained. Therefore, this study provides a new preparation scheme for the industrial large-scale production and application of carbon aerogel. [ABSTRACT FROM AUTHOR]

[Display omitted] • A carbon-graphene composite aerogel (CFGOA) with a new Janus hierarchical porous structure was designed. • A facile synthesis strategy was designed for the Janus structured CFGOA which exhibited high-efficiency SIE desalination and salt resistance. • The aerogel exhibits superior seawater evaporation rate of 3.42 kg·m−2·h−1 in actual seawater with no salt crystallization. • The aerogel achieves non-saline crystallization evaporation even under hypersaline water. Solar-Driven Interfacial Evaporation (SIE) holds great promise in the field of seawater desalination. However, salt accumulation caused by long-term operation in marine environment significantly affects the evaporation rate and efficiency of SIE materials. Despite various structured SIE materials have been developed previously, critical challenges remain in high-efficient evaporation while preventing salt crystallization. Herein, a unique Janus hierarchical porous structure carbon-graphene composite aerogel (CFGOA) was designed and fabricated by a facile synthesis strategy for efficient and salt-resistance SIE seawater desalination. The CFGOA features double-region structure with separate surface wettability within its all-carbon framework, integrating a hydrophobic top light-absorbing rGO layer and a hydrophilic bottom porous carbon layer. Density, salt resistance performance and equivalent evaporation enthalpy are optimized by regulation the hierarchical porous structure of the CFGOA. Under 1 sun illumination, the CFGOA exhibits an outstanding evaporation rate of 3.42 kg·m−2·h−1 in actual seawater (∼3.64 wt%) without salt crystallization. Furthermore, the CFGOA achieve non-saline crystallization evaporation even under hypersaline water (up to 20.2 wt%). The CFGOA combine efficient photothermal conversion, smooth water supply channels, effective thermal insulation, and salt resistance effect. This work is expected to offer a fascinating strategy to the development of SIE materials for seawater desalination. [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]

[Display omitted] • A novel lightweight and high-strength SiC/MWCNTs nanofibrous aerogel is in-situ derived from a RGO/MWCNTs aerogel. • The aerogel exhibits superior wave-absorbing properties even under thin thickness and low filling ratio. • The aerogel exhibits excellent RCS attenuation performance in C-band, X-band, and Ku-band. Developing Silicon carbide (SiC) -based materials with the characteristics of "lower filling ratio, thinner matching thickness, lighter material mass, and better microwave absorption performance" is an important focus of current research. In this work, SiC/Multi-walled carbon nanotubes (MWCNTs) nanofibrous aerogel was prepared using a selective in situ derivatization strategy with Reduced Graphene Oxide (RGO)/MWCNTs aerogels as templates. It is found that when the filling ratio is only 15 %, the minimum reflection loss of the aerogel can reach −57.36 dB. When the matching thickness is only 1.5 mm, the effective microwave absorption bandwidth can reach 3.34 GHz. Moreover, the aerogel exhibits good multi-band microwave absorption performance, significantly reducing the radar cross section (RCS) in C-band, X-band, and Ku-band. In addition, the aerogel features low density and high mechanical strength, with a density as low as 0.046 g/cm3, and specific strength and specific modulus of 4.35 kN·m/kg and 12.39 kN·m/kg, respectively. This work not only provides a new synthesis strategy for the preparation of novel silicon carbide/carbon-based materials, but also contributes to the development of light-weight, high-strength and high-performance microwave absorbing materials. [ABSTRACT FROM AUTHOR]