On the Properties of Uniform Magnetic Microcomposites Assembled Via Microfluidic Spray Drying

A microfluidic jet spray, which produces single trajectory droplets having identical thermal history, was used to obtain monodisperse particles with precise morphology. The method employed a moderate temperature range (£ 300^oC), and was able to handle multi-component precursors to form solid particles in a single step. A stable colloidal suspension containing iron chloride, lactose, and silica nanoparticles was processed to produce microcomposites with a platelet-like morphology due to the nanoparticles. Calcination caused the formation of iron oxide crystals of 10 nm to 1 μm on the surface of the particles (Figure 1). The calcination period and the post-drying conditions both affected the magnetic properties of the product and it was found that the increase in magnetization correlated well with the proportion of magnetite. This work demonstrates that microfluidic spray drying is a versatile route for synthesising functional particles, being scalable with sufficient yield for practical use and easy product recovery, while allowing for subsequent processing if necessary. The reaction pathways occurring in the particle formation are discussed.

Figure 1 - Schematic diagram of the possible scenario for crystal formation on the particle surface.