Microfluidic spray drying is a versatile route to synthesize functional particles, as the technique is scalable with sufficient yields for practical use and easy product recovery, whilst allowing for subsequent processing as necessary. Here a microfluidic jet spray drier producing single trajectory droplets with identical thermal history was used to obtain monodisperse particles with precise morphology. The method employed a moderate temperature range (< 300 degrees C), and was able to handle multi-component precursors to form solid particles in a single step. Spray drying of a stable colloidal suspension containing iron chloride, lactose, and silica nanoparticles produced microcomposites with platelet-like morphology due to the nanoparticles in the precursor. Subsequent calcination caused the formation of iron oxide crystals of 10 nm-1 mu m on the surface of the particles. Both calcination period and post-drying conditions affected the magnetic properties of the composites, with the increase in magnetization correlating well with the proportion of magnetite phase in the iron oxide crystals. The reaction pathways pertaining to the formation of different iron oxide phases are discussed. (C) 2011 Elsevier Ltd. All rights reserved.