Nanoengineering Super Heat-Resistant, Strong Alumina Aerogels

Because of ultralow thermal conductivity, excellent catalytic activity, and better heat resistance than silica aerogel, alumina-based aerogel has drawn great interest as thermal insulators and catalysts. However, it is too fragile and sinters above 1000 °C (it shrinks drastically, >50%, and leaves the surface area as low as 10–70 m²/g at 1300 °C), which badly limits its high-temperature applications. Herein, super heat-resistant, strong alumina aerogels are prepared via a novel acetone-aniline in situ water formation (ISWF) method combined with novel modification techniques: supercritical fluid modification (SCFM) and hexamethyldisilazane gas phase modification. The heat resistance of alumina aerogel is enhanced up to 1300 °C via this method. The shrinkage of the optimized alumina aerogel is reduced to as low as 1 and 5% and the corresponding surface area reaches up to 152–261 and 125–136 m²/g after being heated to 1200 and 1300 °C for 2 h, respectively. The strength is significantly increased by more than 120% through SCFM. It also exhibits excellent thermal insulation properties at temperatures up to 1300 °C. This may significantly contribute to their practical ultrahigh-temperature applications in thermal insulations, catalysts, catalyst supports, etc

Super Black Material from Low-Density Carbon Aerogels with Subwavelength Structures

Many scientists have devoted themselves to the study of the interaction between subwavelength structures and electromagnetic waves. These structures are commonly composed of regular arrays of subwavelength protuberances, which can be artificially designed. However, extending from 2D periodic patterns to 3D disordered subwavelength structures has not been studied yet. In this study, we studied the total diffuse reflectivity of carbon aerogels with various 3D networks of randomly oriented particle-like nanostructures by using normally incident visible light (430–675 nm). We observed that the different 3D network nanostructures of carbon aerogels, especially for the structures with the minimum size, reduced the reflectivity effectively. It was found that the key mechanism for the subwavelength-structure-induced ultralow reflectivity property is due to the decrease of the amplitude of electron vibration forced by the electromagnetic wave, which provides a simple method for designing perfect black materials

Reaction-Induced Microsyneresis in Oxide-Based Gels: The Assembly of Hierarchical Microsphere Networks

Rigid and stable networks composed of litchi-shaped microspheres were formed via hierarchical self-assembly (SA) of oxide-based nanoparticles (NPs). The phenomenon of the apparent changes from NPs networks to microspheres networks after the gelation was similar to normal microsyneresis. However, in-situ composition evolution results indicate that the SA is driven by interparticle dehydration, but not affinity difference between the network for itself and for the solvent. In-situ small-angle X-ray scattering (SAXS), UV–vis–NIR, and electric conductivity were used to study the microsyneresis process. To further demonstrate the mechanism, extra complexant was added and successfully restrained the NPs–microsphere transition by inactivating the surface hydroxyl of the NPs. Considering the structural similarity, this work may provide a new approach to control the assemblies of diverse oxide-based NPs

A Facile and Versatile Post-Treatment Method to Efficiently Functionalize 3D-Printed Carbon Aerogels via Introducing Tailored Metal Elements

The rigorous viscoelastic rheology limits the ink formulation for 3D-printed carbon aerogels (CAs), making their functional customization challenging. Herein, we functionalize 3D-printed CAs via a unique combination of liquid phase deposition and thermal treatment. The electrodes’ improved areal capacitance after functionalization is 3949 mF cm–2, exceeding that of the pure 3D-printed CA electrode by 33.4%, which is superior by comparison with the carbonaceous electrodes reported previously. These impressive results highlight the effectiveness of this strategy for further functionalization of 3D-printed CAs. Moreover, numerous other potential applications, including catalysis, electromagnetic shielding, and solar steam generation, may be inspired by these findings