Premixed Flame-Assisted Spray Pyrolysis Synthesis of Lithium Manganese Oxide Particles

Production of LiMn2O4 from aqueous solutions containing LiNO3 and Mn(NO3)2•4H2O in a premixed flame-assisted spray pyrolysis reactor was investigated. The effect of air to fuel flow ratio and residence time on flame length, flame temperature, product crystallinity, mean particle diameter, and yield were investigated. The effect of fuel flow and the concentration of the reactant solution on the average particle size and yield were studied. According to the thermal gravimetry test, LiNO3 decomposed to Li2O at 700°C and Mn(NO3)2 decomposed to manganese oxides between 180°C to 500°C. Also, the mixture of reactants converted to LiMn2O4 at about 480°C. The XRD patterns revealed Mn2O3 as the main impurity. The average size of the crystals was in the range of 20 to 50 nm. The dynamic light scattering test showed that the maximum and the minimum mean particle sizes were 436 and 210 nm, respectively. The highest product separation efficiency was 30%. Further investigation is needed to identify and quantify loss mechanisms such as wall deposition and gas-phase nucleation leading to filter bypass. Future improvements could include optimizing reactor geometry, using cyclone separators more effectively, and modifying the flame configuration to reduce particle loss.