Characterisation of Carbon-AeroSands

Abstract

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, Alodur, MinelcoOlivine, Zirconia sand and Cerabeads 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.