Enhancement of thermal shock resistance of reaction sintered mullite–zirconia composites in the presence of lanthanum oxide

Synthesis and characterization of mullite–zirconia nanostructured composite by combined mechanical activation and reaction sintering

“…Therefore, they cannot be done during the mechanical alloying process. According to the Gibbs free energy change for reaction (2), the onset temperature for mullite-zirconia formation is $1100°C. However, this is a theoretical temperature and in practice, mullite formation during reaction sintering starts at temperatures higher than $1450°C [10].…”

“…Mullite (3Al 2 O 3 Á2SiO 2 ), which is the only stable compound in the alumina-silica system at ambient conditions, is a suitable compound for high temperature applications owing to its excellent properties like high melting point, low coefficient of thermal expansion, high chemical stability, high creep resistance and sufficient hardness [1][2][3]. However, mullite by itself suffers from low fracture toughness ($2 MPa m 1/2 ) at room temperature and difficulties in sintering to full density [4,5].…”

“…Furthermore, reaction sintering is the only method in which natural minerals like zircon can be used as starting material. Nevertheless, this process needs very high temperatures (>1600°C) to reach complete mullitization [2,10].…”

Effect of temperature on the reaction sintering of mechanically activated ZrSiO4–Al2O3 mixture

“…ZrSiO 4 can be dissociated to SiO 2 and ZrO 2 according to the following reaction [19]: 6 The resulting SiO 2 has a high reaction activity and can react with the Al 2 O 3 to form mullite [19]:…”

“…Moreover, it is the only synthesis process in which natural minerals like zircon can be used directly [6]. Nevertheless, the main drawback of reaction sintering is that it needs high processing temperatures (>1600 °C) to reach complete formation of mullite [7].…”