Molecular Simulation And Microscopic Mechanical Properties Analysis Of Sepiolite Under Different Temperatures And Moisture Contents

Pure sepiolite crystal has a special layer chain structure,and its specific surface area is large,showing strong rheological,adsorption and catalytic properties.It has been widely used in chemical,building materials,aerospace and other fields.It is found that iron,calcium and potassium ions in ore have great influence on the adsorption capacity of sepiolite for water molecules.At the same time,the change of water content and working temperature will lead to the change of ore microstructure and the difference of macroscopic mechanical properties.In this paper,molecular dynamics simulation method is used to construct three kinds of ion microscopic models in sepiolite interlayer domain.and the adsorption mechanism of water molecules was studied.The interaction mechanism and physical properties of sepiolite on water molecules at different temperatures were simulated.This paper mainly discusses the following aspects :(1)The Sorption module in Materials Studio software was used to simulate the crystal structure of sepiolite to adsorb water molecules.Three kinds of ion sepiolite were constructed,and the microstructure of sepiolite was tried to change.Then,the adsorption mechanism of sepiolite on water molecules was discussed from the aspects of cation placement,adsorption heat and adsorption energy,radial distribution function and adsorption isothermal curve.It was found that the presence of cations enhanced the adsorption performance of sepiolite,indicating that the anion binding points in the model increased with the increase of cations,and the calcium ion model in the interlayer domain of sepiolite had the largest adsorption capacity for water molecules.(2)The Forcite module was used to simulate the temperature range from room temperature to 125 °C for the calcium ion crystal model in the from room temperature to 125 °C.The dynamic analysis of the interlayer ions of sepiolite crystal structure after the adsorption of water molecules was carried out.The adsorption law of water molecules on sepiolite crystal microstructure at different temperatures was studied from the three aspects of self-diffusion coefficient,mean square displacement and radial distribution function.The results show that with the increase of temperature,the diffusion coefficient of water molecules in sepiolite increases,and the diffusion coefficient of calcium ions increases first and then decreases.Because the increase of temperature intensifies the interaction between water molecules and sepiolite,and the crystal structure of sepiolite is destroyed,which hinders the diffusion of calcium ions.(3)By using the mechanical properties taskbar in Forcite module to adsorb water molecules on sepiolite crystal,the change of crystal mechanical properties is analyzed,and the change rules of Young ’ s modulus,bulk modulus,shear modulus and stress-strain at different temperatures are analyzed.The influence of mechanical properties on the microstructure and mechanical properties of sepiolite crystal structure is studied.The results show that with the increase of temperature,the mechanical quantities of sepiolite have a decreasing trend,which is due to the increase of water content,the hydration effect of sepiolite is intensified,and the mechanical properties are reduced.(4)The experimental data of water molecules adsorbed by sepiolite under different ions,time,temperature and concentration were analyzed by different experiments.Compared with the results of molecular dynamics simulation,the experimental results show that the temperature and ion concentration play an important role in the process of calcium ion enhancing the adsorption performance of sepiolite.The mechanical tensile test shows that the temperature has a significant effect on the structural change of sepiolite,and the experimental results are consistent with the simulation results.Theoretical analysis,simulation and experimental data show that the microstructure of sepiolite changes under different water content and temperature.Thermodynamic and kinetic analysis can provide a theoretical basis for the adsorption mechanism and mechanical properties of sepiolite under different working conditions.It is of great significance to further study the surface activity and adsorption of sepiolite,and can effectively expand the application field of sepiolite.