Molecular Dynamics Simulation Of CuO Sintering Process In Cu-based Oxygen Carrier Particle

Cu-based oxygen carrier?OC?,which is able to release and absorb O₂ repeatedly,is a promising material for chemical looping with oxygen uncoupling?CLOU?.However,the OC suffers from tendency towards sintering at temperature suitable for CLOU,which leads to defluidization and low reactivity of the OC particles.A detailed understanding of the sintering mechanism in OC particles is necessary for improving the OC performance.In this work,molecular dynamics?MD?simulation has been conducted to gain insight into the sintering mechanism of CuO and the effects of different supports?TiO₂,ZrO₂ and SiO₂?on the sintering resistance of Cu-based OC.The sintering simulation of pure CuO nanoparticles is first conducted.At the high temperatures?from 973 K to 1273 K?,as the distance of Cu-O bond in CuO NPs remains constant,the arrangement of the internal atoms shows clearly lattice arrangement.During the sintering process,the CuO NPs first rotate with respect to one another and have an initial contact,then the surface atoms migrate to the contact area and form a neck region between the particles.The mean square displacement of the initial interior and surface atoms indicates that the surface diffusion is the dominant mechanism in the sintering of CuO NPs.The particle in higher temperature tends to cost more time to contact with each other,but the higher temperature would cause a deeper sintering degree finally.The sintering degree will be enlarged with the rising of particle number.Then,the sintering simulation of supported CuO nanoparticles is conducted.The CuO particle supported by ZrO₂ slab tends to be more stable and shows better sintering resistance than TiO₂,and SiO₂ slab,and the particle supported by SiO₂ slab tends to have no difference from the unsupported CuO in sintering resistance.This indicates that the adsorption of SiO₂ slab is very weak and the SiO₂ may only plays the role of dispersant in the Cu based OCs.As temperatures rise,there is an increasing discrepancy between the sintering resistance of CuO particles supported by different materials.