| Diamond/copper composites was considered to be a new generation of heat dissipation materials in the field of microelectronic devices,weapons and equipment,power batteries,aerospace and others as its high thermal conductivity and adjustable coefficient of thermal expansion(CTE).High thermal conductivity of composites depends on the thermal property of the diamond particle and copper,as well as the volume fraction,particle size,inter-phase,pore and other factors.Theoretical study is confronted with numerous difficulties,because of the complexity of the composites interior.In order to further study the relationship between the thermal properties and the microstructure,the effect of the volume fraction,particle size,inter-phase and pore on the thermal conductivity of the composites was studied by finite element method.Not only to further fill the theoretical framework of thermal conductivity of composites,but also for specific experimental preparation to provide specific guidance and theoretical explanation.Thermal conductivity of composites was simulated by finite element method.The four particle and multi-particle random distribution models of composites in plane were established.The effect of diamond volume fraction,particle size,inter-phase and pore on thermal conductivity of composites was investigated.The simulation value of composites with different diamond volume fraction and size was compared with those of reference literature.The simulation results reveal that the thermal conductivity of the composites increases with an increase of the volume fraction and particle size.Thermal conductivity of Diamond/Cu composites is better than Diamond/Al composites and Diamond/Ag composites.The presence of inter-phase reduces the thermal conductivity of the composites.The simulation value shows a well agreement with the experiment value as the diamond volume fraction is less than 40%.With higher volume fraction,the simulation value is obviously higher than the experimental value.When the diamond particle size ranges from 82.5 μm to 110 μm,the simulation value is in consistence with to the experimental value.When the diamond particle size is less than66 μm or surpasses 165 μm,a significant difference exists between the simulation value and the experimental value.However,the overall trend is in consistence with the experimental result.As the thermal conductivity of the inter-phase is very low and the thermalresistance is high,which makes the temperature gradient at the interface position is relatively large.The thermal conductivity of composites increases with increasing of thermal conductivity of inter-phase,increasing speed gradually slow down.The thermal conductivity of composites have a significant decline when the thermal conductivity of inter-phase was in the range 0 W/(m·K)to 60 W/(m·K).When the thermal conductivity of the inter-phase is more than 60 W/(m·K),the thermal conductivity of the composites increases slowly.The thermal conductivity of the composites decreases with an increase of inter-phase thickness.As the inter-phase is WC,with the increase of the thickness of WC from 0.2 μm to 1.6 μm,the thermal conductivity of composites decrease from 833W/(m·K)to 703 W/(m·K)with the descending ratio of 16.61%;However,as the inter-phase is TiC or Cr3C2,with the increasing of the thickness of TiC or Cr3C2,the downward trend of the thermal conductivity relatively high.The descending ratio is32.20% and 43.88%,respectively.The thermal conductivity of the composites decreases with the increase of porosity.When the porosity increases from 1% to 10%,the thermal conductivity decreases from625.2 W/(m·K)to 293.4 W/(m·K).With the increase of aperture,thermal conductivity is increasing.When the aperture increases from 2 μm to 9 μm,the thermal conductivity increases from 200.9 W/(m·K)to 582 W/(m·K).When the pore area is equal,the pore shape changes from circular to triangular,that is,with the increase of the perimeter of the pores,the thermal conductivity decreases. |
PDF Full Text Request