Aerogel-filled metals: a syntactic cellular material

A new filler material is presented and tested to produce light-weight aluminium alloy composites: the pore space between nano-structured silica-aerogel granulates is infiltrated with Al-alloy melts. Since these filler materials have vanishing density (100 kg m−3), they need not to be removed from the final cast product. Their shape, size and volume fraction determine the materials' properties. Different methods were used to prepare metal-aerogel syntactic foam composites: centrifugal casting, squeeze and suction casting. The last method gave the best results, using an Al–11Si melt. We produced circular and rectangular bars up to 500-mm length. The composite material has a density of around 900 kg m−3, a yield stress of 8 MPa and absorbs 8 kJ kg−1 mechanical energy.