ISSUE 1/2009

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Michael Reuß und Lorenz Ratke, Cologne, Germany 
Characterization of Carbon-AeroSands

Organic aerogels used as a binding material for sand cores and moulds lead to the so-called AeroSands. The bonding bridges consist of a nanostructured open porous aerogel instead of a conventional polymer. Instead of using polymeric aerogels as a binder one can also use carbon aerogels. Carbon aerogels are obtained from pyrolysis of polymeric aerogels, i. e. after heat treatment under vacuum at temperatures of 1000 °C. We optimized the manufacturing process and the quality of the polymeric and Carbon- AeroSands. We varied the kind of sand, using Quartz, AlodurTM, MinelcoOlivineTM, Zirconia sand and CerabeadsTM from Hüttenes-Albertus, the amount of liquid binder from 2.5 to 20 wt % and the drying and annealing heat treatment of the polymeric AeroSand (temperatures 250 °C to 1000 °C). We measured the bending strength and tracked the pyrolysis process by X-ray diffraction, thermogravimetry and scanning electron microscopy. The bending strength of AeroSands exhibits a maximum after a heat treatment of 250 °C. The strength depends on the inverse square root of the average sand grain size.

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