Controllable synthesis of hierarchical micro/nano structured FePO₄ particles under synergistic effects of ultrasound irradiation and impinging stream

Hierarchical micro/nano-structured FePO₄ (FP) particles were environmental-friendly and controllable synthesized through synergistic intensification of ultrasound and impinging streams. Nano-scale FP seeds were firstly synthesized via ultrasound irradiation intensified impinging stream reaction (UISR), where the enhanced turbulent micromixing in the impinging streams benefits the nucleation process while the application of ultrasound to the impinging streams further intensifies such micromixing. The ultrasound frequency and power applied were 20 kHz and 600 W. The hierarchical micro/nano-structured FP particles are obtained when taking sufficient reaction time and stirring FP nano-seeds in a continuous stirring tank reactor (CSTR). Effects of the sonochemical pre-treatment, mean residence time and rotation speed on the physical-chemical properties of FP were investigated systematically. The characterization revealed that under the optimum operating condition, the FP particles presented near-spherical hierarchical micro/nano-structure, consisting of nanoscale primary grains. The mechano-chemical effects on the synthesized FP particles during different synthesis process were also studied.