In recent years,freeze gelation process has been used as a novel shaping method for manufacture of advanced and complex shaped ceramic products.In this process,gelation of a particulate silica sol binder is induced by freezing,allowing production of low shrinkage (＜1％)ceramics with near net shape.Nevertheless,there is not any report about the use of this process in refractory industry.In this research,alumina castables containing colloidal silica binder were prepared and freezed to induce gelation.After defrost,the samples were dried and fired at different temperature followed by measuring their physical and mechanical properties (BD,AP and CCS).The results of green mechanical strength were compared with samples containing MgO powder as gelling additive.Also microstructure of the samples was studied by scanning electron microscopy.The results showed that by using freeze gelation process alumina mullite refractory bodies with improved properties can be made which is a result of nanostructured nature of colloidal silica imposed to the microstructure,leading to mullite formation at low temperatures.Finally,the potentials of the process for application in refractory industry were suggested.
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