Morphologies developed by the drying of droplets containing dispersed and aggregated layered double hydroxide platelets

Despite much interest in the structures formed from droplets of suspension as they dry, there are few studies involving plate-like particles. Layered double hydroxide suspensions were prepared with pH adjusted to give well-dispersed and flocculated variants that were characterised by sedimentation and rheology measurements. In the well-dispersed suspension, the three-phase boundary was pinned and radial flow created a peripheral wall. The platelet structure involved local flat packing but was replete with scrolls that result from the recirculation flows in the droplets as they dry. In contrast, the flocculating suspension produced flatter droplet relics and the microstructure consisted of ordered domains which were disoriented with respect to each other. Although of scientific interest, the control of these structures will make it possible to use direct ink-jet printing to build 3D shapes for the preparation of aligned, ordered nanocomposites based on plate-like particles in which platelet preferred orientation mimics the structures found in nacre.

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► Dispersed and flocculating suspensions of 3 μm LDH platelets were characterised.
► The flocculating suspension produced flatter droplet relics with ordered domains.
► Well-dispersed platelet relics produced the ‘coffee ring effect’ with more chaotic assembly.
► This work guides the assembly of platelets as reinforcements for nacre-like nanocomposites.