Evolution of textural characteristics of surfactant-mediated mesoporous zirconia aerogel powders prepared via ambient pressure drying route

Thermally stable mesoporous tetragonal zirconia through surfactant-controlled synthesis and Si-stabilization

Thermally stable, highly mesoporous Si-stabilized ZrO₂ was prepared by sol–gel-synthesis. By utilizing the surfactant dodecylamine (DDA), large mesopores with a pore width of ∼9.4 nm are formed. Combined with an NH₃-treatment on the hydrogel, a high specific surface area of up to 225 m² g⁻¹ and pore volume up to 0.46 cm³ g⁻¹ are obtained after calcination at 973 K. The individual contributions of Si-addition, DDA surfactant and the NH₃-treatment on the resulting pore system were studied by inductively coupled plasma with optical emission spectrometry (ICP-OES), X-ray diffraction (XRD), N₂ sorption, and transmission electron microscopy (TEM). Electron tomography was applied to visualize and investigate the mesopore network in 3D space. While Si prevents the growth of ZrO₂ crystallites and stabilizes the t-ZrO₂ phase, DDA generates a homogeneous mesopore network within the zirconia. The NH₃-treatment unblocks inaccessible pores, thereby increasing specific surface area and pore volume while retaining the pore width distribution.

Schematic representation of ZrO₂ crystallites; (a) monoclinic ZrO₂, (b) tetragonal ZrO₂ following Si-stabilization, (c) mesoporous t-ZrO₂ following Si-stabilization and use of surfactant dodecylamine.

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.