Influence of atomization conditions on spray drying lithium iron phosphate nanoparticle suspensions

Removing solvents from nanoparticle solid suspensions requires the same diligence as drying pharmaceutical ingredients. LiFePO4 nanoparticles suspension in water oxidize, sinter, and Li3PO4 segregates on the surface when they dry in a furnace. Spray drying preserves the material properties because contact times are on the orders of seconds; furthermore, the atomized droplets ensure particles are small (5 mu m to 20 mu m) and dispersed. A Yamato GA-32 (120 mm inner diameter) spray dried in co-current flow a nanoparticle suspension of LiFePO4 in water, with a solid content up to 60 %. Atomization gas velocities of 140 m s-1 to 350 m s-1 agglomerated the nanomaterial into spherical particles that ranged from 3 mu m to 10 mu m. The particle diameters ranged from 10 mu m to 20 mu m at atomization velocities of 50 m s-1 to 140 m s-1. At this condition, yield was lower because the semi-dried particles adhere on the wall. At 150 circle C to 200 circle C the surface area reached 26 m2g-1 while from 50 circle C to 100 circle C it varied from 14 m2 g-1 to 20 m2 g-1. The trend for mesoporosity versus spray drying temperature is the same as for surface area: pore volumes are higher (0.18 cm3g-1) above 200 circle C and 20 % lower below 200 circle C. Drying temperature modifies drying speed; low temperatures compact the powders more than high temperature which results in lower surface area and porosity.