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

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.

Study on the Prepartion of Slag Haycite for Phosphorus Removal Using Ammonium Hydrogen Carbonate as Pore Former

Porous slag haycite for phosphorus removal was made from slag, as the main raw material, clay, as binder, and ammonium hydrogen carbonate, as a pore forming agent. And the influence of material ratio and sintering condition were investigated. The best ratio of steel slag: Clay: ammonium hydrogen carbonate was 53.5%:42.5%:4% as ascertained, and the best sintering temperature 800°C, sintering time 60min. The porosity of slag haycite was 2 times more than original slag, and the specific surface area was increased evidently, thus very conducive to microbial growth.