Most packed beds contain heterogeneous microstructures with relatively big defects and pores, causing a large reduction in compressive strength and reliability. Recently, the need for fabricating reliable ceramic Raschig rings with high strength has increased due to their applications in processes where a high diametrical stress is applied. In manufacturing these materials, the strength and reliability are basically affected by the mixing ratio of reinforcing materials such as alumina and zirconium silicate. However, the firing process should be controlled to achieve the desired properties. Therefore, the objective of this investigation was to evaluate the firing behavior, technological properties and microstructure of a typical extruded ceramic Raschig ring. The technological properties of rings prepared with different amounts of alumina and zirconium silicate sintered at 1150, 1200 and 1250 oC were evaluated by measuring the shrinkage, water absorption, porosity and strength. The reliability of rings was studied by Weibull's statistical theory. The results showed that the addition of 10% alumina or 5% zirconium silicate into the ring composition improves the Weibull modulus considerably. Finally, the optimum particle size of alumina was determined to improve the mechanical characteristics. It was found to be less than 38 μm. The results obtained can be useful in industrial applications.

Keywords: Ceramics, Sintering, Mechanical properties, Defects.