Molecular Dynamics Simulation Of Thermal Conductivity Of GO-cement Composites

With the rapid development of modern construction,road and bridge and water conservancy projects,the performance of cement composite materials has been more and more demanding.As far as the thermal conductivity of cement composite is concerned,reducing the thermal conductivity is beneficial to structural thermal insulation,and improving the thermal conductivity can reduce the harm caused by the structure easy to produce thermal cracks.Therefore,it is of great significance to study the change rule of the thermal conductivity of new cement composite.Many nanomaterials such as graphene have been applied to the modification of cement composites,and their influence on the thermal conductivity of cement composites needs to be paid attention to.Molecular dynamics simulation of thermal conductivity can provide an efficient numerical calculation method for the study of the influence of nanomaterials on the thermal conductivity of cement composites,and provide an important theoretical reference for relevant experimental design.In this paper,the application of molecular dynamics method in the study of thermal conductivity of nano-cement composites was systematically studied by taking graphene oxide-cement composites as the research object.The molecular dynamics calculation models of C-S-H gel,GO and GO-C-S-H gel composites were established respectively,and the effects of oxygen concentration on the thermal conductivity of GO and the effects of GO on the thermal conductivity of cement composites were studied.The main work of this paper is as follows.(1)The Jennite gel model was selected as the initial configuration of C-S-H gel,and the molecular dynamics calculation model was established with Materials Studio software.Compass force field and NPT constant temperature ensemble were selected to optimize the geometry and dynamics of the structure.The thermal conductivity of C-S-H gel was calculated by anti-non-equilibrium dynamics method.The application of molecular dynamics method in the thermal conductivity of cement composite was studied systematically.(2)Materials Studio software was used to construct graphene structural models and amorphous structural models of GO with different oxygen concentrations.Compass force field and NPT constant temperature ensemble were selected for geometric optimization and dynamic relaxation.Anti-non-equilibrium dynamic method was used to calculate the thermal conductivity of GO.The effect of oxygen concentration on the thermal conductivity of graphene oxide was studied.With the increase of the number of oxygen-containing functional groups of GO,the heat conduction of GO first increased and then decreased.When the oxygen concentration was 18.1%,the heat conduction coefficient of GO reached the maximum,75.311W/m·K.(3)Take the Jennite model as the base of the GO-C-S-H gel composite material,and use the intercalation function of Materials Studio software to combine it with GO with different oxygen concentrations,and establish the molecular dynamics calculation model of GO-C-S-H gel composite material.The effect of graphene oxide on the thermal conductivity of cement composite was studied.With the increase of oxygen-containing functional groups on the graphene,namely the continuous increase of the oxygen concentration of GO,the heat conductivity of GO-cement composite increased rapidly,reached the maximum value and then decreased.When the oxygen concentration was 18.2%,the heat conductivity of GO-cement composite reached the maximum value of 31.943W/m·K.This change is consistent with the effect of oxygen concentration on the thermal conductivity of GO.