Synthesis and Sintering of Magnesium Aluminate Spinel Nanopowders Prepared by Precipitation Method using Ammonium Hydrogen Carbonate as a Precipitant

Abstract

Magnesium aluminate spinel (MgAl2O4) is widely used in many engineering applications due to its high melting point (2135°C), high mechanical strength, chemical inertness, and good optical properties. Precipitation method is recognized as a convenient and cost-effective method for the synthesis of nanopowders. In this present work, MgAl2O4 nanopowders were prepared by precipitation method using ammonium hydrogen carbonate as a precipitant. The precipitated precursors were a mixture of ammonium dawsonite (NH4Al (OH)2CO3·H2O) and hydrotalcite (Mg6Al2(CO3)(OH)16·4H2O). After calcining at 1100°C for 2 hours, The MgAl2O4 nanopowders with particle size of 20-170 nm were obtained. The sinterability of the MgAl2O4 nanopowders was evaluated by sintering compacts of the MgAl2O4 nanopowders at temperature of 1300-1650°C for 2 hours. The relative density of the sintered MgAl2O4 ceramics reached about >97% of theoretical density after sintering at 1500°C for 2 hours. The Vicker’s hardness of the sintered ceramics reached a value of 1414 HV (13.9 GPa) after sintering at 1650°C for 2 hours.