High-Rate Formation of Nano-Scale Alumina Particles
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HIGH-RATE FORMATION OF NANO-SCALE ALUMINA PARTICLES L. Reinhart A. Davis T.F. Morse D.C. Paine Division of Engineering, Brown University Providence, R.I. 02912, (401)863-3930
A. Kilian
IL Abstract In this paper we report a new approach to the problem of high rate formation of nanophase powders. In our experiments we were able to make aluminum oxide particles in the size range from 5 to 140 nm (peaking sharply at 35 nm) at a rate of 3 g/min. The starting material was a mixture of aluminum-tri-sec-butoxide and sec-butanol. An aerosol was made from this solution and subsequently burned in a special torch, described below. The resulting particles were spherical and no necked regions were observable between them. In a practical application, our technique allows a large production rate while still approaching the ideal of nano-scale monodispersed particles. The work was extended to the formation of zirconium oxide particles with quite similar results in the size distribution.
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Introduction
During the past several years a large number of methods for the production of nanoscale particles has been reported (see e.g. [5],[6]). Although many of the techniques appear to be promising most of the methods suffered the drawback of low production rates. A large rate of production is an important requirement for such a process in an industrial application. The method proposed here can be easily scaled up to higher production rates through optimization of the aerosol generator and modification of the geometry of the torch. Since liquid or highly soluble solid alkoxide precursors exist for a variety of elements [11, we expect that this method will be applicable to a large number of different nano scale oxides. Even more interesting might be the the formation of multicomponent oxides (e.g. bariumtitanate) from sources such as the double alkoxide of titanium and barium. The materials produced in these experiments should be useful for precursors in the production of structural ceramics. Since no chlorine was used in the formation of the particles the product should be also interesting also for catalyst applications (particles produced from volatile inorganic chlorides can retain up to 2% chlorine and are considered useless for many catalyst applications).
Mat. Res. Soc. Symp. Proc. Vol. 249. 01992 Materials Research Society
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Experimental setup
The torch used in these experiments was originally developed for the production of oxide glass particles in the fabrication of optical fiber preforms, [2]. Microscopic examination of the resulting particles led to the concept of applying this technique to the formation of ceramic powders. The experimental arrangement is shown in Figures 1 and 2.
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Figure 1: Sideview of the torch and rest of setup
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Figure 2: Topview of the torch The aerosol generator is an ultrasonic 60 kHz atomizing nozzle made by Sonotec. The tip is excited with the acoustic waves from an piezo electric crystal inside the nozzle housing. The liquid is pumped into the
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