Effect of fuel type on morphology and reactivity of combustion synthesised MgAl2O4 powders

Two types of stoichiometric MgAl2O4 spinel powders were prepared by combustion synthesis routes, using sucrose (SCS) or urea (UCS) as fuel. For comparative purposes a stoichiometric MgAl2O4 powder was also prepared by solid state reaction synthesis (SS powder). Pressed compacts of the three powder types were sintered at various temperatures ranging-from 1575 to 1625degreesC for 2 h. After grinding, SCS and SS powders had very narrow particle size distributions, with average particle sizes of 3.17 and 4.13 mum respectively, whereas UCS powder showed a wide particle size distribution with an average particle size of 37.76 mum. Their corresponding surface areas were found to be 65.8, 8.67, and 8.06 m(2) g(-1). The SCS MgAl2O4 powder sintered at 1625degreesC for 2 h had a bulk density of 3.44 g cm(-1) (96% of theoretical), an apparent porosity of 1.76%, and water absorption of 0.519%. The superior properties of SCS powders compared with other spinel powders are attributed to the higher surface area induced by the larger size of the sucrose molecule and the greater amount of gas evolved during sucrose combustion.