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.