Nanostructured Alumina from Freeze-Dried Precursors

Abstract

Nanocrystalline alumina has been obtained on the 100-g scale by thermal decomposition of precursors resulting from the freeze-drying of aqueous solutions of different aluminium-containing products, namely aluminium acetate and aluminium L-lactate. Samples prepared at different temperatures (from 873 to 1573 K in steps of 100 K) were characterized by X-ray powder diffraction, scanning and transmission electron microscopy, and surface area measurements. In the acetate case, the transformation sequence to allow it to be thermal sprayed and deposited on a stainless steel substrate. X-ray powder diffraction data show that γ-Al 2 O 3 is the major phase in the coating, which includes also α-Al 2 O 3 particles. SEM results offer evidences on the nanostructured character of the coating.

Large scale synthesis of nanostructured zirconia-based compounds from freeze-dried precursors

“…In this context, ''powder processing methods for the preparation of submicrometer and nanostructured powders in a controlled form, with a wide range of compositions, sizes, and morphologies, need to be improved'' [12]. In practice, our group has widely reported on the competitive advantages of the freeze-drying method [13][14][15] for obtaining a diversity of nanostructured materials (oxides, nitrides, carbides, intermetallics) as polycrystalline powders with controlled characteristics (composition and particle morphology) [12,[16][17][18].…”

Nanostructured Solids from Freeze‐Dried Precursors: Multigram Scale Synthesis of TiO2‐Based Powders

“…However, a drawback frequently associated with multicomponent systems lies in the stoichiometric control and the cationic distribution (homogeneity) . In general, processing methods for the preparation of submicrometer and nanostructured powders in a controlled form, with a wide range of compositions, sizes, and morphologies, need to be improved …”

“…Our group has widely reported on the possible competitive advantages that the freeze‐drying method could offer in this context . The freeze‐dried precursors obtained from a sprayed solution can lead to a diversity of nanostructured materials (oxides, nitrides, carbides, intermetallics) after an adequate thermal treatment in a controlled atmosphere .…”

“…Our group has widely reported on the possible competitive advantages that the freeze‐drying method could offer in this context . The freeze‐dried precursors obtained from a sprayed solution can lead to a diversity of nanostructured materials (oxides, nitrides, carbides, intermetallics) after an adequate thermal treatment in a controlled atmosphere . It allows the exploration of wide ranges of metal compositions (stoichiometries) in the case of complex systems, and the intimate mixing of the components in the precursor powders decreases the diffusion distances and generally results in very small sized particles after relatively soft treatments.…”

“…It allows the exploration of wide ranges of metal compositions (stoichiometries) in the case of complex systems, and the intimate mixing of the components in the precursor powders decreases the diffusion distances and generally results in very small sized particles after relatively soft treatments. On the other hand, the essential equipment required is commercially available and permits operating with high volumes (appropriate for multigram scale preparations), which can also can result in satisfactory production rates …”