Synthesis of resins as alpha-alumina precursors by the Pechini method using microwave and infrared heating

A polymeric method based on the Pechini process was successfully used to synthesize alpha-alumina. Different resins have been prepared in order to compare the effect of the heating source (microwave or conventional IR radiation) during the polyesterification reaction, the importance of the starting aluminium salt and the ratios between reactants. The resin precursor and the product powders were fully characterized in order to investigate the polymer decomposition and the characteristic of the resulting alumina. It is concluded that the control of the ethylene glycol to citric acid ratio is important to obtain weak agglomerated particles, which are required to achieve soft porous precursors. Comparing with a conventional infrared source, the 2.45 GHz-microwave heating reduces the polyesterification reaction time to a great extent followed by a solid polymeric resin formation; however, the reaction mechanisms do not change. The best final alumina powder was synthesised by applying the microwave radiation to a precursor resin obtained from the thermal reaction of the aluminium lactate with small amounts of ethylene glycol as the polymerizant agent.