Síntese e caracterização de hidróxidos de alumínio com duas dimensões nanométricas (morfologia fibrilar) ou com uma dimensão nanométrica (morfologia de placas/lâminas).

Abstract

Dedico essa Tese a ele, meu querido mestre, Prof. Dr. Pérsio de Souza Santos, uma pessoa notável e atenciosa, um profissional incomparável e brilhante, para sempre guardarei a lembrança de seus ensinamentos, sua paixão pelos estudos e seu carinho. A ele, minha eterna admiração e respeito, um muito obrigado por todo o auxilio na composição dessa Tese e pelas ricas experiências compartilhadas; foi uma honra tê-lo conhecido. Saudades.

Synthesis and Characterization of Boehmites Obtained from Gibbsite in Presence of Different Environments

“…Boehmite crystals have the form of thin plates with nanometric thickness, not the form of diamond-like tricky "near 3D" crystals as observed in the previous work of Rocha 63 . To date we have no adequate explanation to this discrepancy.…”

“…The hypothesis that presence of acetate ion in the reaction medium was sufficient to produce boehmite crystals with morphologies with one or two dimensions in nanometer range (thin "2D" or "1D" particles) suggested by Rocha 63 was not confirmed since the hydrothermal process 3 (aqueous solution of potassium acetate at its natural alkaline pH) resulted in thick lamellar boehmite particles ( Figure 4C). However, apparently the presence of acetate ion has led to a decrease in thickness of the boehmite crystals formed comparing to the thickness of the crystals prepared in deionized water medium, which has a "3D" morphology ( Figure 4A).…”

“…• process 2: in an aqueous medium in the presence of acetic acid (HAc) (molar ratios: 1 Processes 3 and 4 were carried out to deepen the observation made in previous work done in our laboratory by Rocha 63 , according to which the acetate ion present in the reaction medium would be essential to obtain particle morphology with at least one nanometric dimension (morphologies "2D" or "1D").…”

“…It has been suggested in Rocha's mentioned work 63 that the presence of acetate ion in the aqueous reaction medium would be essential for obtaining "2D" morphology.…”

“…To the authors' knowledge, there are no reports published in the scientific literature dealing with hydrothermal transformation of a Bayer commercial gibbsite in boehmite in aqueous acidic medium. In a previous study conducted in our laboratory by Rocha 63 , boehmite was prepared from In this study, results related to boehmite synthesis by hydrothermal processes starting from a Bayer commercial gibbsite are reported. The processes have been conducted from aqueous suspensions with initial acidic or alkaline pH, without or with acetate ion, at 160 o C for 72h to 168h.…”