Microfluidic spray drying as a versatile assembly route of functional particles

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 °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 μm 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.

Schematic demonstrating the formation of iron oxide crystals on the spray-dried particle surface with post-drying treatment by calcinations .Figure optionsDownload high-quality image (152 K)Download as PowerPoint slideHighlights
► Spray drying is a scalable route to form functional particles with zero waste.
► Uniform magnetic particles assembled via microfluidic spray drying.
► Post-treatment affects the magnetic properties of particles.
► Formation of iron oxide phases depends on reaction pathways at a specific condition.