Use of geopolymeric cements as a refractory adhesive for metal and ceramic joins

Geopolymer cements (GPs) possess the ability to form high-strength, thermally-stable, and near-net shape structures at room temperature. It has been found that GPs can also be used to bond both metals and ceramics. Unlike organics, geopolymers can be heated to elevated temperatures and are easier to apply as compared to refractory adhesives. Many refractory adhesives require at least one, if not multiple curing steps, at elevated temperatures before they can be used in service. Geopolymers, however, need only be cured once at relatively low temperatures (40 - 80°C) to complete their curing process. Geopolymers contain no organic carriers often found in refractory adhesives, and can be processed from inexpensive and relatively non-toxic materials, i.e. waterglass and calcined aluminosilicate clays. This study details how geopolymer cements can be used to bond 6061-T6 aluminum alloy, 1008/1010 steel, alumina, and borosilicate glass at both ambient and elevated temperatures (25 - 450°C). Shear strength values of various samples were determined according to ASTM D1002-01 (single) and ASTM D3528-96 (double) shear lap tests. The microstructure and chemical composition of the geopolymer bond as well as interface were studied with scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) in the SEM.