Morphological and structural analysis of ceramic materials composite by Kaolinite and Alumina

Abstract

In this work, we report the preparation, structural and electrical characterization, morphological analysis and hardness measurements of ceramic materials composed of kaolinite Al₂(Si₂O₅(OH)₄ and alumina AL₂O₃. Samples were prepared from mixtures of precursor oxides starting with 100% alumina and increased the kaolinite concentration on steps of 10% up to complete 100% of kaolinite. The samples were sintered by the method of solid state reaction at temperatures of 1150, 1250 and 1350 °C. We found that the alumina samples are stable at the different temperatures of synthesis. The samples of kaolinite at 100% suffer a change phase depending on the sinterization temperature, noting that at 1350 °C yields 87% mullite and 13% cristobalite. The presence of quartz was only detected in samples with 100% kaolinite for sinterization temperatures of 1150 and 1250 °C. All samples with a mixture of alumina and kaolinite showed the presence of mullite, which is increased when the content of kaolínite is high or when the sinterization temperature is increased. This allows us to infer that the introduction of alumina optimizes the process of mullite formation hy their reaction with the SiO₂ that remainder from the kaolinite. The sample with 100% alumina has a Mohs hardness of about 5, and this is increased with the content of kaolinite, until a Mohs hardness of about 6 to the sample with 100% kaolinite. The dielectric constant of these materials is around 27.82.