Continuous morphology-controllable precipitation strategy for europium oxalate hydrates via microchannel reactor

Abstract

A flow chemistry based continuous morphology-controllable precipitation strategy was successfully developed for synthesis of europium oxalate hydrate microparticles. The effects of flow ratio between raw materials within microchannels on the crystal structure, morphology and particle size distribution of the precipitated products were firstly studied. The results shown that both high yield and controllable morphology were achieved for Eu³⁺ precipitation reactions under its low concentration condition. The effects of supersaturation, mixing intensity, and reaction temperatures were also investigated in detail, which proved the continuous preparation of layered microparticles with concentrated size distribution can be achieved by this strategy. Multiple characterizations and comparison experiment synergistically reveal that the feed flow ratios of nitric acid and oxalic acid determines the morphology and particle size distribution due to affecting the mixing degree and phase composition of the precipitation reaction. In addition, the phase and morphology conversion of precipitates after calcination treatment were also studied, the as-calcined metal oxide powder exhibited a decent photoluminescence characteristic. In summary, this work demonstrates a promising precipitation strategy within micro-channels for mass controllable production of high-quality metal oxide materials.

Graphical abstract