Simulation Of Thermal Transport In Superlattice And Yttria-stabilized Zirconia

Low thermal conductivity materials have important applications in many fields such as thermal insulation and thermoelectric conversion devices.It is a common method to study low-thermal-conductivity materials by controlling the phonon transport by changing the nanostructure of the material,and then changing the thermal conductivity of the material to obtain a lower thermal conductivity value.Low thermal conductivity stacked superlattice materials and low thermal conductivity nanocomposites materials have important applications in thermoelectric materials and thermal barrier coating materials,respectively.In this thesis,molecular dynamics method and atomic Green’s function method are used to simulate the thermal transport properties of low thermal conductivity stacked Al As/Ga As superlattice and low thermal conductivity yttria-stabilized zirconia to construct nanostructures with low thermal conductivity.Firstly,the non-equilibrium molecular dynamics method and atomic Green’s function method were used to study the thermal transport properties of low-thermalconductivity stacked superlattice materials.Atomic Green’s function method was used to calculate the interfacial phonon transmission coefficient for the one-dimensional superlattice atomic chain model.It was proved that the stacked superlattice structure can suppress phonon transport.The results show that a single superlattice interface layer effectively blocks phonon transport because it forms a phonon band gap.When multiple superlattices of different periods are stacked in series,phonons can be blocked over a wider spectral range.This proves that the use of stacked superlattice structures can effectively control phonon transport in materials.Then,the thermal conductivity of the Al As/Ga As superlattice at low temperature is simulated and calculated by nonequilibrium molecular dynamics method.It is clearly obtained that the thermal conductivity of the material can be effectively reduced by stacking the superlattice structure.The results match.In summary,the thermal transport control of the material is realized by stacking superlattice materials.This research has certain reference value for the design of future superlattice materials.Next,the equilibrium molecular dynamics method was used to study and calculate the thermal transport properties of yttria-stabilized zirconia with low thermal conductivity nanostructures.According to the simulation results,the amorphous yttria stabilized zirconia has a low thermal conductivity value.A nanocomposite structure composed of amorphous yttria-stabilized zirconia and yttria-stabilized zirconia crystal particles is constructed,and the thermal conductivity value of the composite structure is between the two materials,which is related to the volume fraction of the crystal particles.Through the above research,we fully understand the heat transport properties in some solid materials.The construction of stacked superlattice structures and nanoparticle composite structure can effectively control the phonon transport in the material,thereby effectively reducing the thermal conductivity.