Study On The Regulation Of Synthesis Of Nano-materials Based On Droplet Flow In Microchannels

All of the unique physical and chemical properties are highly dependent on the size and shape of nanoparticles,which depends on the crystal nucleation and growth process of the synthetic reaction.In industrial synthesis,the mixing degree of reactor directly affects the nucleation and growth of crystal.However,the uneven distribution of reaction conditions in time and space in a traditional reactor brings challenges to the controllable synthesis of nanomaterials.Microfluidic technique provides a new opportunity for the precise control of the synthetic reaction process.Based on the microfluidic technique,the precise control of liquid-liquid two-phase flow was realized and a variety of nanomaterials with small particle size and narrow particle size distribution were prepared.The specific research content is as follows:?1?Structure design and improvement of micro-channel reactor:the T-shaped single-stage micro-channel feeding mode was adopted,and the spiral channel was designed for more effective on the two-droplets mixing enhancement.By optimizing the outlet structure of the microreactor,the aggregation of solid particles at the outlet was alleviated,and the problem of channel blockage in the synthesis process of nanomaterials was avoided.The device was then used to prepare zirconia and zinc oxide nanoparticles within droplets.It can run continuously for more than 24 hours,and there is no nanoparticles attached to the wall and outlet of the microchannel.More than 94%of the products were obtained after the micro-reactor was run once.?2?Investigation on the flow behavior of liquid-liquid two phase flow in the microreactor:based on the the precipitation reaction of CaCO₃,the whole flow behavior of droplet in immiscible liquid-liquid two-phase flow system has been studied numerically and analytically.With the microscopic imaging technique,the real time monitor for the whole droplet flow behavior in the liquid-liquid two-phase flow was operated.The whole droplet flow was divided into three stages:droplet formation,droplet pairing and droplet fusion.The formation mechanism of each flow stage of droplet was studied by precise regulation of operating conditions,which ensured the feasibility and stability of liquid-liquid two-phase flow in the synthesis reaction of nanomaterials.?3?Preparation and characterization of Fe₃O₄ nanoparticles:Based on the optimization of the flow process of liquid-liquid two-phase flow in the new anti-clogging microreactor,Fe₃O₄nanoparticles with the average grain size of 6-8 nm and narrow particle size distribution were obtained.The effects of components concentration,reaction temperature and feed flow rate on the average particle size and size distribution were investigated,and the results showed that precise control of droplet size and synthesis process was beneficial to the preparation of high quality nanoparticles in particle size control and particle size distribution.?4?Preparation and characterization of other nanoparticles:the synthesis of ZrO₂ and Fe₄[Fe?CN?₆]₃ nanopaticles were operated through the combination of microfluidics and traditional curing.The results show that the nanomaterials have the advantages of small particle size,high purity and uniform particle size distribution.The whole synthesis process is simple to operate and has excellent universality.