Synthesis of nano-particles of ZnO/Al 2O 3 in a premixed flame

Abstract

Materials with very high specific surface areas can be synthesized by combustion of volatilized precursors together with an additional fuel like methane, hydrogen etc. The structure and properties of the product powder can be varied depending on the temperature and particle residence time in the high temperature zone and on the precursor concentration. The vapour phase synthesis of zinc and copper oxide composites by combustion in a premixed flame of aluminum acetylacetonate and zinc acetylacetonate is investigated. The laboratory setup consists of a burner where premixed methane, air and precursor vapours are combusted above a flame arrestor and saturation units where the precursors are evaporated into a nitrogen stream. This burner setup provides a very homogenous flame environment and ensures a low precursor concentration in the flame zone. The synthesized particles are collected on polycarbonate filters and are characterized by their specific surface area, aggregate size distribution, their morphology as observed by TEM and by their atomic structure and crystalline dimensions by x-ray diffraction. This talk will focus on the relationships between the particle synthesis and processing and the morphology of the product particles. The composite particles consist of zinc oxide deposited on top of an γ-aluminum structure probably due to the different vapour pressures of the oxides. Thereby the alumima serve as a structural support for a high surface area zinc oxide powder. The specific surface areas are 25 m 2/g and 200 m 2/g for pure zinc oxide and pure alumina respectively and the surface area of the composite powders varies within these limits.