Characterization and mechanical properties of phosphate-kaolin clay

The effects of phosphate additions on the mechanical and morphological properties of kaolin were investigated. Phosphate additions were orthophosphoric acid H3PO4, potassium dihydrogen phosphate KH2PO4, potassium monohydrogen phosphate K2HPO4 and potassium phosphate K3PO4. The phosphate additions were fixed at 10% w/w. The green and sintered phosphate-bonded products were characterized by means of X-ray diffraction (XRD), infrared spectroscopy (IR), thermal analysis (ATD-ATG), dilatometry, scanning electron microscopy (SEM) and the Brazilian test. The properties of the phosphate-bonded clay bodies were affected by new mineral phases resulting from the reaction between phosphates and kaolin, which subsequently enhanced the mechanical strength and the densification of sintered ceramic products. The phosphate compounds react at 1100°C with aluminium and silica from kaolin to provide new compounds which are AlPO4 and KAlSi2O6. We retain that including phosphate compounds, it is possible to gain more than 200°C of sintering temperature while having the same strength or even a greater one than that of kaolin. [Display omitted]