Study On Fluidization Of Nanoparticle Agglomerate And Atomic Layer Deposition Model

In recent years,nanoparticles?1-100nm?have been widely applied in various fields due to their unique physical and chemical properties and nanometer effects.The fluidization of nanoparticles,which combines nanoparticle materials and fluidized bed technology,is one of the most promising technologies.Nanoparticles fluidization can not only promote the good mixing and reaction of nanoparticles,but also realize the batch preparation of nanoparticles.Coated with other functional materials on the surface of nanoparticles,the formation of unique core-shell structural materials can enhance and improve the application performance of nanoparticles.In this paper,nanoparticles fluidization and nanoparticle atomic layer deposition surface coating technology are studied,including the influence of temperature on the nanoparticle fluidization characteristics and gas diffusion within the nanoparticle agglomerates and the calculation of atomic layer deposition model calculations.The nanoparticle fluidization experiments under different temperature conditions show that:under different temperature conditions,the nanoparticle fluidization phenomenon is obviously different.As the temperature gradually increases from room temperature?25??to400?,the maximum bed expansion ratio decreased first and then increased,and the maximum bed expansion ratio at 200?is the smallest.The bed collapse experiment showed a similar pattern,and the bed collapse rate was the lowest at 200?.Through the first temperature-raising and then cooling experiment,it was found that the maximum bed expansion ratio was similar at the same temperature,indicating that the nanoparticles did not sinter;in addition,this conclusion can also be drawn based on the fluidized bed particle sampling analysis results.Based on the experimental results of the bed expansion ratio,the average size of the agglomerates under different temperature conditions was estimated using the Richardson-Zaki equation.With the temperature increased from room temperature?25??to 400?,the average size of the agglomerates increased from 226?m to 410?m.Further investigated the influence of temperature on the bed material quality loss.Under long time?3hours?fluidization experimental conditions,the bed material quality loss was found to be in the range of 10%to 17%.With the temperature decreasing first and then increasing,and the quality loss of the bed material was minimum at 200?.Gas diffusion and atomic layer deposition in nanoparticle agglomerates are analyzed.Under the pressure of 1atm and 1Torr,the diffusion patterns of gas precursors in different sizes of nanoparticle agglomerates are different.Through the time scale analysis of the gas precursor in different sizes of nanoparticles,it is found that under the pressure of 1 atm and 1Torr,the agglomerates of nanoparticles can be treated as monodispersed porous media and bidispersed porous media.In the atomic layer deposition process of alumina,the precursor reaction process is divided into two parts:adsorption and reaction.The adsorption efficiency of H₂O is higher than that TMA,but the reaction rate is relatively low.With the increase of temperature,the growth per cycle?GPC?reaches saturation becomes slower and the saturation value decreases.