Molecular Dynamics Simulation Study On The Surface And Interfacial Interaction Of Rare Earth Oxide Patticles

Rare earth oxide-cerium oxide is a multifunctional material with extensive applications in chemical mechanical polishing (CMP), catalyst, ultraviolet absorption materials and fuel cell. It usually uses modifier to improve the compatibility between the CeO2particles and organic matrix for a better performance in industry. Therefore, it is significant to investigate the interaction between CeO2surface and surfactant as well as the interfacial properties between ceria and organic matrix for a great development and practical application value. The molecular dynamics (MD) method has been proven to be a valuable tool to study the surface and interfacial interaction between inorganic materials, polymer matrix. It could not only provide detailed, atomistic level insight into the interaction between CeO2with surfactants and polymer but also saving a lot of time for the screening of surfactants and solvents. This research can promote the widespread application of rare earth metal oxides.The adsorption of silane coupling agent at different CeO2surfaces in different solutions are studied by molecular dynamics simulation. Both single adsorbed silane molecule and multiple adsorbed silanes are modeled and the adsorption energy, radial distribution functions, orientation and alignment of these adsorbates are analyzed. Silane molecules exhibit stronger interaction with CeO2(111) surface than that with surface (110) and (100). The polarity of solvent affects the orientation and alignment of silanes at solid surface. In addition, the interaction between silane and the solid surface increased with the decrease of the polarity of the solvents. Meanwhile, the number of adsorbed silane molecules within a silane layer depends on the polarity of the solvents, which is1.28silanes/nm2and2.14silanes/nm2in water and in organic solvents, respectively.We study the roles of three different kinds of silane coupling agents in the interfacial interaction of cerium oxide/polyurethane composites by molecular dynamics simulation. The silane coupling agents are y-methacryloxypropyltrimethoxy silane (KH570), aminopropyltrimethoxy silane (APS) and triethoxy silylpropyl isocyanate (ICPTES). The results show that the adsorption energy of PU chains with CeO2(111) surface is lower than with surface (110) and (100). Although the addition of silane coupling agents could enhance the combination of CeO2/PU system, the method of addition has a significant influence on the interfacial interaction of the composites. Especially, the silane coupling agents APS could enhance the compatibility of CeO2(111) surface and PU chains. Both silanes and PU chains adsorb on CeO2(111) surface when the surfactants modifying PU chains, which resulting in a lower adsorption energy between CeO2(111) surface and PU chains. However, a compact silanes layer structure is formed on CeO2(111) surface at the condition of silanes coupling agent modifying CeO2(111) surface. The PU chains can’t interact with CeO2(111) surface directly due to the formation of silanes layer, which lead a higher adsorption energy between CeO2(111) surface and PU chains.