Synthesis Of Nano-CeO₂ Based On The Microfluidic Technology

Microfluidics refers to a technology that can realize precise control of microfluids within the microscale of 10^-18to 10^-9L.Compared with traditional methods for synthesizing nano materials,microfluidics has great advantages such as excellent reaction control,high efficiency of mass and heat transfer,minimal reagent waste,and high safety,which enables it to be used in the synthesis of various nano materials.And the nano rare earth oxides（REOs）have been a significant type among those nano materials.As a typical representative of nano-REOs,the nano-Ce O₂has attracted extensive attention due to its high oxygen migration rate and reversible conversion between Ce⁴⁺and Ce³⁺,and it has been applied widely in the fields of catalysis,polishing,war industry,etc.and played a very significant role in those important fields due to its unique optical and electrical properties.However,it is difficult to realize the customization of nano-Ce O₂by the traditional methods,such as precipitation,hydrothermal,sol-gel,etc.In view of the great advantages of the microfluidics and the research status of nano-Ce O₂,then this work tries to introduce the microfluidic technology into the synthesis of nano-Ce O₂.Given the specific issues of the flow channel blockage and low flux existed in the preparation of nano-Ce O₂by the microfluidic method,the reaction system and microfluidic chip were designed accordingly and precisely.Besides,the continuous synthesis of nano-Ce O₂by microfluidics was also investigated systematically to explore the application potential of microfluidic technology for efficient preparation of high-performance nano-Ce O₂,including the technical route and process conditions.The specific research contents are as follows:（1）The problem of flow channel blockage occurred in the synthesis process of nano-Ce O₂by microfluidics had been solved by investigating and designing the reaction system composed of glycol-dimethyl silicone oil,which exhibits high viscosity.And such reaction system could work continuously for 3000 min without any flow channel blockage.Then the primary goal of continuous preparation of nano-Ce O₂by microfluidics has been achieved initially.（2）To issue another problem existed in the preparation of nano-Ce O₂by microfluidics,the low flux,a 3D stacked microfluidic chip with a“H”section as the interlayer connection,which can not only balance the flow velocity fluctuations of microfluidics,but also improve the alignment accuracy of multi-layer geometric structures simultaneously,had been innovatively proposed and designed.The research on the droplet production performance of this novel 3D chip confirmed that it can produce uniform and monodisperse microdroplets with higher flux,successfully addressing the issue of low flux.（3）Based on the study of high-viscosity reaction system of glycol-dimethyl silicone oil and the 3D stacked microfluidic chip above.The effects of synthesis conditions such as reaction temperature,holding time at reaction temperature and heating method on the particle size,shape and distribution,and the crystallization degree of synthesized nano-Ce O₂were further investigated.The results show that the optimal reaction temperature range for the glycol-dimethyl silicone oil system was140～160℃.It is difficult to obtain the nano-Ce O₂below 140℃,while the reaction product showed a gel-like state over 160℃.The effect of holding time on the product yield was greater than that on the morphology and size,and the yield increased first and then remained unchanged with the extension of holding time.For the heating method,it could affect both the particle size and shape of the product,and the transformation of spherical and cubic shape and the adjustment of particle size could be realized by introducing and controlling the heating method of oil bath and microwave.