Hydrothermal Synthesis of Well-Crystallised Boehmite Crystals of Various Shapes
Materials Research, Vol. 12, No. 4, 437-445, 2009 © 2009 Hydrothermal Synthesis of Well-Crystallised Boehmite Crystals of Various Shapes Pérsio de Souza Santosa, Antonio Carlos Vieira Coelhoa*, Helena de Souza Santosb, Pedro Kunihiko Kiyoharab aLaboratório de Matérias-Primas Particuladas e Sólidos Não Metálicos, Departamento de Engenharia Metalúrgica e de Materiais, Escola Politécnica, Universidade de São Paulo – USP, Av. Prof. Luciano Gualberto, Travessa 3, 380, 05508-970 São Paulo - SP, Brazil bLaboratório de Microscopia Eletrônica – LME, Departamento de Física Geral, Instituto de Física – IF, Universidade de São Paulo – USP, CP 66318, 05315-970 São Paulo - SP, Brazil Received: May 26, 2009; Revised: September 10, 2009 Aluminium monohydroxide, also known as aluminium oxyhydroxide (boehmite – AlO[OH]), is water insoluble but crystallises into microcrystals of various shapes. When, by X-ray diffraction, the microcrystals present a basal reflexion (d[020]) of 0.611 nm, the crystalline structure is referred to as “well-crystallised” boehmite. Natural and synthetic crystals of well-crystallised boehmite can have a plate-like shape with either a rhombic or hexagonal profile. Synthetic crystals can also be lath-like or ellipsoid in shape. The purpose of this paper is to present a method of hydrothermal synthesis using a single temperature (200 °C) for preparing plate-like crystals of well- crystallised boehmite with ellipsoid, rhombic, hexagonal, and lath-like profiles by using different precursors. Our observations suggest that all of these shapes are stages of growth of the microcrystals of well-crystallised boehmite along the c-axis direction of the rhombic crystals. Keywords: aluminium hydroxide, boehmite, pseudoboehmite, fibrillar pseudoboehmite 1.
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