Development of aerogel additives for the foundry industry

Abstract

The quality of cast products can be improved by using high-temperature stable aerogels or xerogels within sand cores that are able to adsorb gases deriving from thermal decomposition of resins used as sand grain binders. We developed pure TEOS (tetraethoxysilane) and pure MTMS (methyltrimethoxysilane) aerogels as well as mixed MTMS/TEOS aerogels to yield high-temperature stable aerogels by pyrolysis that are considered capable to improve the casting process of copper-based alloys. Aerogel samples were synthesized from pure TEOS or MTMS precursors or from different MTMS/TEOS ratios by using NH4Faq as catalyst. Wet gels were dried under ambient pressure and were pyrolyzed to yield SiOC aerogels. After pyrolysis the samples were characterized by density, nitrogen adsorption (BET, BJH), scanning electron microscopy and thermogravimetric analysis. Examinations on sand core behavior and cast surface quality were performed by adding the most promising material in granular form as an additive (inner surface area: 890 m2/g) in different volume percentage to the sand grain mixture. For this application we synthesised liters of aerogels.