Properties Of Molecular Topological Index As Well As The Applications In Phase Change Materials Of Electronic Devices

With the increasing miniaturization and high integration of electronic devices,the power of electronic components becomes larger and larger,while their physical sizes are becoming smaller,and their heat flux density is increased gradually,which leads to higher temperature affecting their performance,more effective temperature control is repuired.The so-called phase change temperature control is a promising method employing the phase change process of phase change materials to achieve the temperature control of electronic devices by store or release energy.Phase change thermal control has been widely used in thermal control of spacecraft and portable electronic devices recently because it has the advantages of small size,compact structure,energy saving and reliable performance.In the technology of phase change temperature control,the thermophysical properties of phase change materials are the focus of attention,which affect the seletion and application scope of phase change materials.Molecular topological index is a topological invariant defined on molecule structure graph of the compound.It is closely related to the physical and chermical properties of the corresponding compound materials.In this thesis,two kinds of molecular topological indices(augmented Zagreb index,harmonic index)and paraffin phase change materials are studied in terms of using molecular topological indices to predict the thermophysical properties of phase change materials.The main works are summarized as follows:(1)From the research on the molecular structure models of trees,unicyclic graphs and two-trees,we obtained the minimal values and the corresponding extremal graphs of the augmented Zagreb index on trees and unicyclic graphs with perfect matchings,and the two-trees with the minimum and the second minimum harmonic index were also obtained.The relation between the harmonic index and the chromatic number of graphs was obtained.A conjecture on the harmonic index was also proved in this thesis.It provides theoretical basis and calculation method for establishing a mathematical model which can predict the phase transtition temperature and latent heat of paraffins.(2)The augmented Zagreb index of line,total and subdivision graphs was studied.The extreme values on augmented Zagreb index of line,total and subdivision graphs were presented,and the corresponding extremal graphs were characterized.It will provide theoretical guidance for the design of phase change materials in the temperature control technology of electronic devices.(3)The augmented Zagreb index,harmonic index and Balaban center index of paraffin phase change materials were calculated.Some QSPR models were established by the methods of simple linear regression,multiple linear regression and polynomial regression.The phase transition temperature and latent heat of paraffins were predicted respectively.The models were tested by model analysis(the value of correlation coefficient and significance probability etal)and residual analysis.The results show that the QSPR models established in this paper were reasonable,meaningful and reliable,which can provide a new research idea for the selection of high temperature phase change materials in electronic deivces.