Molecular Dynamics Study On The Growth Of Cerium Carbonate Crystal Regulated By NPEO

The physical and chemical properties of cerium carbonate,such as its morphology and size,determine its application in production and life.The preliminary experiment of the research group found that using nonylphenol polyoxyethylene?NPEO?as a template can synthesize fusiform cerium carbonate?Ce₂?CO₃?₃?,but the mechanism of action of nonylphenol polyoxyethylene ether in the growth process of cerium carbonate is not yet clear.In this paper,through a combination of simulation and experiment,the mechanism of NPEO in the growth of cerium carbonate crystals was studied.Complementing each other and verifying each other through computer simulations and experiments enable us to understand the experimental phenomena from macro to micro.The main research contents and results are as follows:The preliminary experiment did not consider the effect of NPEO molecular weight on the morphology of cerium carbonate,so in this paper,different concentrations of NP-40,NP-20 and NP-15 were used as template agents,and ammonium bicarbonate?NH₄HCO₃?was used as the precipitant to prepare carbonic acid.Cerium particles,to study the effect of NPEO on the morphology of cerium carbonate crystals.The morphology of the cerium carbonate crystals synthesized at the optimal concentration of the three template agents was analyzed by SEM.It was found that with the increase of the NPEO concentration,the cerium carbonate crystals went through hexagonal flakes-fusiform flakes-fusiform with a certain thickness The order of appearance changes.The cerium carbonate particles synthesized by three different molecular weight NPEO particles were characterized.The cerium carbonate prepared with NP-15 as a template has the advantages of uniform particle size and small size.Using XRD and infrared spectroscopy to analyze the powder phase and the function of the functional group,it is concluded that the phase of the prepared powder is cerium carbonate octahydrate,and the EO group of nonylphenol polyoxyethylene ether does not form a complex with the cerium ion.The simulation part uses the method of molecular dynamics simulation to analyze the effect of NPEO on the three crystal planes and the cause of the morphology and size of cerium carbonate.A coarse-grained model was used to discuss the evolution of the aggregation behavior of nonylphenol polyoxyethylene ether in aqueous solution,the effect of NPEO concentration on its aggregation configuration was studied,and the molecular weight of the diffusion coefficient of NPEO molecular chain in solution was discussed.The influence of NPEO on the crystal growth was analyzed.The temperature,potential energy,non-bonding energy,interaction energy,and deformation energy in different crystal plane systems are compared,and the regulation effect of NPEO in the crystal growth process is analyzed from the perspective of energy.The results show that as the concentration increases,the NPEO aggregate phase undergoes the changing order of premicelle-spherical micelle-worm-like micelle.Due to the different aggregation of configurations,NPEO has different regulation effects on crystal growth,thus adjusting different morphologies of cerium carbonate crystals.The order of diffusion coefficient of NPEO with different molecular weights in aqueous solution is NP-15>NP-20>NP-40.The larger the diffusion coefficient,the more vigorous the movement of NPEO in the reaction system and the greater the regulation and inhibition of crystal growth.The higher the nucleation energy barrier of the crystal plane,the smaller the size of cerium carbonate particles synthesized with NP-15 as a template.The dominant?202?plane and the inferior?242?plane are obtained,which explains the selective growth of cerium carbonate thickness along the?242?plane.Combined with the model changes before and after the dynamics,the radial distribution function and the NPEO bond lengthprobability density curve,the interaction mode between NPEO and cerium carbonate crystal plane is analyzed,and it is concluded that the electrostatic force plays a leading role in the regulation of NPEO on the crystal plane.