Zirconia aerogels for thermal management: Review of synthesis, processing, and properties information architecture

Zirconia aerogels are porous nanomaterials with high specific surface areas and low thermal conductivities that are suitable for a wide range of functions. The applications of zirconia aerogels include numerous uses in thermal management systems that are specifically beneficial in aeronautics and aerospace systems. This review seeks to detail the synthesis, processing, and characterization of these unique materials. However, the many distinctive synthesis pathways and processing conditions of zirconia aerogels can make the optimization of these materials difficult, potentially inhibiting further development. Independent variables in the synthesis process alone include zirconium precursor, rare earth stabilizer, solvent system, gelation agent, and surfactant templating agent. If only two distinct options were available for each synthetic variable, there would be up to 32 different synthetic pathways; if there were three options for each variable, 243 different synthetic pathways would be possible. Apart from the gel synthesis, processing conditions, including drying method, drying temperature, drying solvent, and sintering temperature, as well as various techniques used to characterize aerogels, need to be considered. To mitigate the sheer volume of synthetic parameters, this review uses an architected information structure to contemplate approximately 600 aerogel materials, along with the synthesis and processing conditions that make each material unique. By utilizing this information structure, containing over 10,000 relationships amongst 3,800 nodes, the connection between specific properties of zirconia aerogels and the pathways used to produce them can be more easily visualized, leading to a more effective understanding of the many variables that are used in the synthesis and processing of these materials. This review seeks to utilize data science in a way that can elucidate structure-property relationships in colloidal chemistry, providing a more efficient way to evaluate the synthesis and processing of materials with high experimental dimensionality.

Superelastic and superhydrophobic bacterial cellulose/silica aerogels with hierarchical cellular structure for oil absorption and recovery

Bacterial cellulose aerogels/silica aerogels (BCAs/SAs) are prepared using three-dimensional self-assembled BC skeleton as reinforcement and methyltriethoxysilane derived silica aerogels as filler through vacuum infiltration and freeze drying. The BCAs/SAs possess a hierarchical cellular structure giving them superelasticity and recyclable compressibility. The BCAs/SAs can bear a compressive strain up to 80% and recover their original shapes after the release of the stress. The BCAs/SAs exhibit super-hydrophobicity with a contact angle of 152° and super-oleophilicity resulting from the methyl groups on the surface of silica aerogel filler. This endows the BCAs/SAs outstanding oil absorbing capability with the quality factor Q from 8 to 14 for organic solvents and oils. Moreover, the absorbed oil can be retrieved by mechanically squeezed with a recovery of 88% related to the superelastic ability of the composites. In addition, the oil absorbing of BS/SAs could be well maintained with the quality factor Q about 11 for gasoline after harsh conditional treatment down to -200 °C and up to 300 °C. Such outstanding elastic and oleophilic properties make the BC/SAs tremendous potential for applications of oil absorbing, recovery and oil-water separation.

Robust urethane-bridged silica aerogels available for water-carved aerosculptures

Novel in situ bridged silica precursors were used to synthesize robust aerogels for aerosculptures carved with aqueous solvents.

Synthesis of aerogels: from molecular routes to 3-dimensional nanoparticle assembly

Colloidal nanocrystals are extensively used as building blocks in nanoscience, and amazing results have been achieved in assembling them into ordered, close-packed structures. But in spite of great efforts, the size of these structures is typically restricted to a few micrometers, and it is very hard to extend them into the macroscopic world. In comparison, aerogels are macroscopic materials, highly porous, disordered, ultralight and with immense surface areas. With these distinctive characteristics, they are entirely contrary to common nanoparticle assemblies such as superlattices or nanocrystal solids, and therefore cover a different range of applications. While aerogels are traditionally synthesized by molecular routes based on aqueous sol-gel chemistry, in the last few years the gelation of nanoparticle dispersions became a viable alternative to improve the crystallinity and to widen the structural, morphological and compositional complexity of aerogels. In this Review, the different approaches to inorganic non-siliceous and non-carbon aerogels are addressed. We start our discussion with wet chemical routes involving molecular precursors, followed by processing methods using nanoparticles as building blocks. A unique feature of many of these routes is the fact that a macroscopic, often monolithic body is produced by pure self-assembly of nanosized colloids without the need for any templates.

A robust salt-tolerant superoleophobic aerogel inspired by seaweed for efficient oil–water separation in marine environments

A robust salt-tolerant superoleophobic aerogel was fabricated by a simple combined freeze-drying and ionic cross-linking method for oil–seawater separation.

Highly flexible silica aerogels derived from methyltriethoxysilane and polydimethylsiloxane

The rapid synthesis of low-density, highly hydrophobic silica aerogels was performedviaambient pressure drying.