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]

In this paper, continuous SiC fiber-reinforced Ti60 (SiC f /Ti60) composites were fabricated by preparing SiC f /Ti60 precursor wires from matrix-coated fibers and hot isostatic pressing (HIP) consolidation. The microstructures of the precursor wires and composites were investigated using XRD, SEM, EPMA, EBSD, and TEM, which led to the microstructure evolution of the composites. The conclusions of this study are as follows. 1. A reaction layer (RL) with a thickness of approximately 0.1 μm already exists at the interface of the precursor wires during the preparation. The HIP process accelerates the diffusion of the carbon coating with the Ti60 matrix, resulting in an increase in the thickness of the RL to approximately 0.5 μm. This layer is primarily composed of fine-grained TiC layer || discontinuous silicides || coarse-grained TiC layer. 2. The matrix of SiC f /Ti60 precursor wires contains α-Ti (∼ 1.9 μm), S2 (∼ 50 nm), and β-Ti (∼ 50 nm), in the matrix, β-Ti is precipitated from α-Ti, and HIP makes α-Ti, S2, and β-Ti grow to ∼ 2.4 μm, ∼ 200 nm, and ∼ 300 nm, respectively. 3. There are 〈0001〉//axial direction (AD) and 〈10−10〉//AD fiber textures in the matrix of the precursor wires, and HIP makes the matrix undergo a plastic deformation dominated by dislocation slip, and the pole density of the two kinds of textures are both increased. • Detailed study of precursor wires to SiC f /Ti60 composites interface and matrix microstructure evolution during hot isostatic pressing. • Sample preparation and characterization using advanced techniques such as FIB, EBSD, TKD, and TEM, etc. • During hot isostatic pressing, the reaction layer is transformed from fine-grained TiC to fine-grained TiC layer || discontinuous silicides||coarse-grained TiC layer. • During hot isostatic pressing, β-Ti and S2 silicides are precipitated from the Ti60 matrix, and the pole density of α-Ti changes. [ABSTRACT FROM AUTHOR]

[Display omitted] • Four DFs were yielded from quinoa and highland barley by enzymatic methods. • Quinoa and highland barley-derived DFs rich in pectin and β-glucan, respectively. • Pectin-rich SDF obtained from quinoa significantly inhibited the pasting of rice starch. • Quinoa IDF exhibited the highest efficacy in reducing rice starch digestibility. This study investigated the potential of highland barley and quinoa dietary fibers, rich in β-glucan and pectin respectively, as cost-effective and nutritionally valuable physical modifiers for rice starch (RS). HPAEC revealed differences between the monosaccharide composition of soluble and insoluble dietary fibers sourced from highland barley and quinoa (HSDF, HIDF, QSDF and QIDF). Results from both RVA and DSC analysis revealed that the addition of low amounts of dietary fiber significantly modified the pasting properties of RS. Notably, the addition of quinoa soluble dietary fiber (QSDF) significantly inhibits the formation of a stable gel network in rice starch, even at low concentrations (0.1 %), as confirmed by rheological measurements. Furthermore, the incorporation of QSDF effectively reduces the content of rapidly digestible starch in rice starch by 15.6 % and increases the content of slowly digestible starch, from 23.36 % ± 3.02 % to 31.07 % ± 3.98 %. By leveraging the compositional richness of these fibers, this research opens up novel opportunities for developing functional food products with improved nutritional profiles, as well as for improving texture and reducing glycemic index (GI) in starch-based foods. [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]

The ice-template freeze-casting strategy combining the static sol–gel and subsequent freeze-drying process is developed for the synthesis of aerogel fibers. In this process, the three-dimentional (3D) monolithic hydrogel assembled by 0D primary particles is disintegrate into 1D fibrous geometries with a precise nanostructure regulation (0D) by ice templates. [Display omitted] • A ice-template freeze-casting method is developed for the facile fabrication of aerogel fibers. • The synthesis enable a precise regulation of fibrous geometries with mesoporous structure. • The aerogel fibers have a good thermal insulation and noise reduction performance. Aerogel fibers inherit the merits of aerogel and fibrous materials, such as ultralow density, large specific surface area and high flexibility, demonstrating great potential as the next generation functional fibers. Herein, an ice-template freeze-casting strategy is developed to prepare polysilsesquioxane aerogel long fibers (PALFs) similar to natural fibers in structure. During the freeze-casting, the strong mutual interaction between solid and liquid phases in the hydrogel induces uniform nucleation and continuous growth of ice crystals in confined spaces. The three-dimensional monolithic hydrogel is gradually deconstructed into one-dimensional fibrous geometries by the growing columnar ice crystals. The obtained PALFs exhibit the polygonal cross-section with a uniform mesoporous structure. After simple physical assembly, the monolithic PALFs exhibit good thermal insulation performance (as low as 25.0 mW/(m·K) at 25 °C) and high-efficiency absorption of broadband sound waves (with a noise reduction coefficient up to 0.58). [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]