Transformation Potential of Kalemaden Clay – 220 to Technological Ceramics

Abstract

In this study, the Clay – 220 mineral of Turkish origin from Kalemaden A.S., having a composition of the quarts, kaolinite, feldspar and the others with the weight percent of 36.20, 12.66, 48.03 and 3.11, respectively, was used as a raw material to investigate its transferability potential to a technological ceramic. The mineral was in the form of conglomerate rocks, which were prepared in the consecutive mineral processing procedures before taken it to the stage where carbothermal reduction - nitridation (CRN) was performed in an atmosphere controlled environment. Various process parameters, i.e., temperature, time and N2 – flow rate were tested in order to optimise the CRN process. SiAlON was formed at temperatures as low as 1300oC and its content increased with reaction temperature up to 1475oC. Above 1425oC, SiC becomes more predominant phase in the powdered product after CRN. Fine powders formed at temperature of 1350oC, which is the lowest value reported among the current literature, contain single crystalline phase of β-SiAlON. The results indicated that the best transformations and yield to the SiAlON ceramic were occurred on the previously prepared Clay – 220 samples in powder form that were processed at 1350oC for 6 hours with nitrogen flow rate of 1 lt/min.