USE OF GEOPOLYMERIC CEMENTS AS A REFRACTORY ADHESIVE FOR METAL AND CERAMIC JOINS Jonathan Bell, Matthew Gordon and Waltraud Kriven University of Illinois at Urbana-Champaign Department of Materials Science and Engineering Urbana, IL 61801, USA ABSTRACT 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 o 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 o 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. INTRODUCTION Joseph Davidovits coined the term “geopolymer” in 1979 for mineral binders formed by adding an aluminosilicate source to a high pH, concentrated alkali solution. 1 Since this time geopolymers have been used in a variety of applications such as structural blended cements, advanced composites (i.e. fiber mesh reinforced) 2 , toxic waste encapsulation 3 , acid and fire resistant cements, bricks, industrial sealants, and adhesives. A typical processing scheme would involve the addition of an aluminosilicate powder such as metakaolin to potassium or sodium- based waterglass solution, subsequent mixing, and placement in a furnace to cure. Curing times for geopolymers range from as little as 5 minutes to several days depending on the starting materials and curing conditions. For example, using a higher surface area aluminosilicate powder or increasing the curing temperature generally leads to a faster setting time. The viscosity of the geopolymer paste can be varied by controlling the amount of water used, while intrinsic porosity and strength can be tailored via alkaline chemistry variation and use of secondary additives respectively. 4 The goal of this study is to explore the use of geopolymer adhesives on aluminum, steel and borosilicate glass in order to determine which materials would be useful for future consideration. The microstructure and diffusion across the geopolymer / substrate interface will also be studied using a scanning electron microscope (SEM) equipped with an energy dispersive analysis (EDS) capability.