Preparation And Theoretical Simulation Of Graphene/copper Composite For The IGBT Of High Speed Train

With the rapid development of rail transit technology and equipment,the power density of power electronic devices such as train IGBT continues to increase,and the influence of thermal fatigue on devices becomes more and more significant,which puts forward higher performance requirements for electronic packaging and electronic cooling materials.In this thesis,RGO/CuTi composites were prepared by means of matrix alloying and spark plasma sintering.The composite material has high thermal conductivity,low thermal expansion coefficient and high yield tensile strength.The interface structure and products of the composite were studied by means of test characterization.The first-principles calculation software based on density functional theory is used to simulate the composite interface.The main research results are as follows:?1?The ball-milling treatment of CuTi mixed powder makes the CuTi mixed powder have a high specific surface area,which is conducive to the uniform dispersion of RGO in the mixed powder.During sintering,relatively low SPS temperature?700??and short holding time?5 min?were used to form Ti₈C₅interfacial phase in situ at the composite interface.Ti₈C₅ phase is formed by the reaction between the active carbon source in the amorphous carbon nanometer layer/nanoparticle in G and Ti in the Cu Ti matrix and nucleation growth.Ti₈C₅ phase plays a role of a rivet at the interface,making the G and the CuTi matrix tightly combined,improving the load transfer capacity of the interface and reducing the thermal resistance of the interface.The yield strength and tensile strength of 1.5 vol%RGO/CuTi composites increased by 106.2%and 57.7%respectively,yield-tensile ratio and uniform elongation increased by 68.2%and 13.7%separately compared with unreinftorced Cu Ti alloys.1.5 vol%RGO/CuTi composite has a thermal conductivity of 358 W/m·K,which is 6.9%higher than that of pure Cu,and a CTE value of 15.4 ppm/k,which is 10.9%lower than that of unreinforced CuTi alloy.?2?According to the first-principles calculation,when the composite interface is simulated,the adsorption energy of G/Ti adsorption model is high,and the interaction between G and Ti atoms is strong.When G adsorbs Cu atoms and Ti atoms at the same time,G preferentially interacts with Ti atoms,and Ti-C covalent bond and Ti-Cu metal bond exist at the same time at Ti atoms.In G/CuTi interface model,the electron interaction between atoms at the interface is greater than that between outer atoms.The electron transfer at G/CuTi interface is greater than that at G/Cu interface.The covalent effect at G/CuTi interface is stronger and the interface bonding strength is higher.