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Formation of Leucite Crystals from Metakaolin-Based Geopolymer using Kaolin and Bentonite

A. El-Maghraby, K. F. Khaled and Khaled M. Elsabawy

Inorganic polymerization of Al2O3- and SiO2- containing materials in strong alkali environments often results in products generally referred to as geopolymers. A novel technique called the geopolymer technique will be studied. The geopolymer technique was initially applied for preparation of monolithic materials, starting from metakaolin and reactive silica under the presence of strong alkaline solutions. Leucite crystals having nanosize were prepared by heating a powder mixture of metakaolin, K2SiO4 and KOH. The geopolymer thus obtained were fired at elevated temperature up to 11000C and were examined by XRF, XRD and SEM techniques. The results show that meta kaolin, K2SiO3 solution and KOH to regulate the pH to form geopolymer, which may crystallize into cristoballite and lecuite, respectively, under thermal treatment. Kbased geopolymer (K2O.Al2O3. 4SiO2. 11H2O) was investigated due to its attractive refractory properties and ability to convert to leucite (KAlSi2O6) on heating and the comparisons between clay and bentonite to obtain leucite at low potassium silicate solution. A further increase in temperature to 1100oC led to the formation of leucite crystals. K-geopolymer was found to offer many of the benefits such as lower sintering temperatures and compositional control without the high costs.