Mechanochemical synthesis of alumina–zirconia nanocomposite powder

Abstract

The alumina–zirconia nanocomposite powder has been synthesised by mechanical activation of a dry powder mixture of AlCl₃, ZrCl₄ and CaO. Mechanical milling of the above raw materials with the conditions adopted in this study resulted in the formation of a mixture consisting of crystalline CaO and amorphous aluminium and zirconium chlorides phases. There was no sign of chemical reaction occurring during milling stage as evidenced by X-ray diffraction (XRD) studies. Subsequent heat treatment of the milled powder at 350°C resulted in the occurrence of displacement reaction and the formation of ZrO₂ and Al₂O₃ particles within a water soluble CaCl₂ matrix. The effect of higher temperature calcination on the phase development in this powder mixture was followed by XRD analysis. Scanning electron microscopy and differential thermal analysis were also used in the characterisation of the powders. Perhaps the most important observation in this study was the formation of α-Al₂O₃ phase at a very low temperature of 400°C.