Preparation And Thermal Management Application Of Carbon-Based Metal Composites

With the rapid development of microelectronics technology,heat dissipation of electronic components has gradually become a hot topic in the industry.The life and efficiency of devices are related to their heat dissipation.If the heat can not dissipated in time,the local temperature of components is too high,which causes devices to melt or even fail.Therefore,high thermal conductivity materials are urgently needed in the packaging of electronic devices.The third generation of thermal management materials,represented by graphene and diamond,which are carbon-based materials and metal composites,have attracted much attention due to their high thermal conductivity,low thermal expansion coefficient and low density.However,due to the non-wettability between graphene/diamond and copper metal,significant interface problems exist in carbon-based/copper composites.Therefore,this paper sets the diamond/copper composite and nitrogen-doped graphene/metal（silver and bronze）as the research object based on the requirements of high thermal conductive composites,regulation of the metallization of diamond surface by using molten salt technology,densification of the composite with hot-pressing technology,and obtaining the high heat conductivity of metallization（Ti,Cr,Mo,etc.）of diamond/copper composite materials.Additionally,the silk fibroin solution made of natural and non-pollution silk is used as carbon source,and mixed with metal nitrate solution.The graphene nitride/metal particle composite material is synthesized by microwave plasma technology in one step,and the densification of the composite material is achieved based on hot-pressing technology.The specific research contents are as follows:（1）Optimizing diamond surface metalization processIn this paper,the surface of diamond is metalized by molten salt treatment technology.The effects of sintering temperature and raw material ratio on the morphology and crystallization degree of the coating were discussed.At the same time,the thickness of the metal layer is controlled by controlling different mass ratios of metal and diamond powder.This paper focuses on the metalize diamond surface with three different metals or metal oxides（Ti,Cr,Mo O₃）.The results show that:（1）the best sintering temperature of Ti-metalized diamond is 750 ℃,the best mass ratio of diamond to Ti is 5:0.3,and the thickness of the carbide layer obtained is 320 nm.The metalized layer has good crystallization and high film continuity.（2）The optimum sintering temperature of Cr metalized diamond and the mass ratio of diamond to Cr powder are 950 ℃ and 5:0.3,respectively.And the thickness of carbide layer is only 650 nm.（3）The best sintering temperature of Mo metalized diamond is 1100 ℃,the best mass ratio of diamond to Mo trioxide is 1:1,and the thickness of Mo₂C film on the diamond surface is only 175 nm.Based on the above optimal conditions,the obtained diamond surface metalized coatings show good surface morphology and crystallinity,which is conducive to the interface bonding between diamond and copper.（2）Preparation and characterization of metalized diamond/copper composite thermal conductive materialsDiamond/copper composite thermal management materials were prepared by metalized diamond.Firstly,the influence of the volume fraction of diamond on the thermal properties of composites in the process of hot-pressing sintering was studied.Meanwhile,the internal interface structure of diamond/copper composites under different volume fractions was analyzed.Secondly,the influence of metalized diamond surface structure and thickness on the thermal properties of copper-based materials was studied.The final result of experiment confirms that copper-based/diamond composite has the best thermal performance when the volume fraction of diamond is 50%.For different diamond surface metalized composite materials,the maximum thermal conductivity of metalized（Ti）diamond/copper composite is 483.62 W/（m·K）metalized（Cr）composite is 400.69 W/（m·K）,and metalized（Mo）composite is 691.93 W/（m·K）.（3）Preparation and thermal characterization of nitrogen graphene/metal（Ag,Cu）composite materialsFirstly,a method to prepare metal-graphene composites by in-situ growth was proposed.Metal-nitrogen doped graphene（Me-NGs）powdered composites were prepared by homogeneous mixing of silk fibroin solution with metal nitrates（Ag NO₃,Cu（NO₃）₂）,drying to form a film,and using microwave plasma technology.The composition and molecular structure of the composites were analyzed by various chemical characterization techniques.The composition and molecular structure of the composite was analyzed by a variety of chemical characterization techniques.Secondly,metal/nitrogen-doped graphene powder composite was sintered into sheets by hot pressing to increase the compactness of the composite.At the same time,the thermal properties of NGs,Cu-NGs and Ag-NGs flake composites were studied,and the thermal properties of Ag-NGs sheet composites with different Ag⁺doping concentrations were studied by regulating the content of silver nitrate.The results show that the thermal properties of the composites doped with metal ions are improved,and the Ag-NGs composite has the best thermal properties.Moreover,the thermal properties of composites are directly proportional to Ag⁺concentration.Finally,experiments prove that the metal/graphene composites not only have good thermal properties,but also have good catalytic properties.In the electrocatalytic test,the 0.1M Ag-NGs composite material achieved a 4e^-transfer process,with an onset voltage of 0.95 V and a peak voltage of 0.65 V.