Synthesis of pseudoboehmite – effect of acetate ion

Abstract

Pseudoboehmite (AlOOH.xH 2 O) is one of the precursors of alumina. Its calcination produces different phases of alumina and at 1200º C the most stable phase, α-alumina, is formed. The synthesis of pseudoboehmite by the sol-gel process results in a product with high purity, high specific surface area, and high reproducibility. The aging of the pseudoboehmite at temperatures above room temperature results in pseudoboehmites with distinct properties. In this work we report the synthesis of pseudoboehmite by the sol-gel process, using aluminum nitrate and aluminum chloride as precursors, and investigate the effect of acetate ion on crystallinity, adsorption capacity, particle morphology, thermal properties and specific surface area. The X-ray diffraction data of the synthesized pseudoboehmites in the presence of the acetate ion revealed high quality nanoparticles.

Production of Al2O3-SiC composites from micrometer α-Al2O3 powder obtained via sol-gel

“…Because pseudoboehmite without heating is an aluminum hydroxide AlO(OH) phase, water alters interplanar distances in a crystalline structure showing widening peaks [10][11]. The transitional metastable phases of Al 2 O 3 , α, θ, δ and γ were identified after heat treatment at 1000 • C. When heating was at 1200 • C, the α-Al 2 O 3 phase is exclusively present, corresponding to the most stable phase of aluminum oxide [5][6][7][10][11]. Therefore, 1200 • C is the appropriate temperature to produce α-Al 2 O 3 .…”

“…Under moderate reaction conditions produced through a colloidal suspension, a pseudo-crystallized aluminum hydroxide gel is obtained [4,6]. Hence pseubohemite (AlOOH.xH 2 O) is a synthetic aluminum hydroxide gel that acts he as a precursor to transition of alumina: AlOOH, γ, δ and α-Al 2 O 3 , depending on the heat-treatment conditions [2,7].…”