Research On Interface Structure Design And Perforance Control Of Diamond(W_xC)/Aluminum Composites

As a popular candidate for a new generation of thermal management materials with high thermal conductivity,the interface structure of Diamond/Al composite material determines the material's performance to a large extent which is the focus of material design and control.In this paper,the interface structure of tungsten-plated Diamond/Al composite material is designed by combining first-principles calculations and interface theoretical thermal conductivity calculations.Combined with the experiment,the interface structure of the composite material was controlled by the high temperature diffusion reaction treatment of tungsten-plated diamond,and the interface properties and comprehensive performance of different coating types of diamond/aluminum composite materials were studied.Based on the first principles calculation,the bulk and surface properties of diamond,aluminum,tungsten and its carbides in the tungsten-plated Diamond/Al composite material are calculated.The surface energies of diamond(100)and(111)crystal faces are 5.82 J·m^-2 and 8.59 J·m^-2,respectively.The difference in surface energy explains the difference between the two crystal faces in the interface reaction.The most stable surfaces in aluminum and tungsten crystals are Al(111)and W(110)crystal faces,respectively.By calculating the binding energy and enthalpy of formation of the compound,it is determined that the two most stable crystal structures of the W-C binary phase are h-WC and?-W₂C.An interface model of the Diamond/Al phase relationship is built,and the selectivity of the Diamond/Al interface bonding is theoretically explained through the analysis of the interface properties.Further research on the properties of diamond/tungsten and diamond/tungsten carbide interfaces found that,compared with aluminum,the bonding tendency between the interface between tungsten and its carbides and diamond is stronger,and the range of the interface area involved in charge transfer is larger,and the formed bonding strength is higher,so it can effectively improve the interface bonding strength of the composite.Among them,the Diamond₍₁₀₀₎/W₂C₍₀₀₁₎interface has the highest bonding strength,and its interface adhesion work is 10.18 J·m^-2.In addition,tungsten and its carbides can also greatly increase the density of states of the C-2p orbitals at the Fermi level in the diamond interface zone,which improves the interface bonding and effectively promotes the heat conduction of electrons at the interface.The interface theoretical thermal conductivity calculation results based on different models show that W,WC and W₂C phases within a certain thickness can effectively improve the interface thermal conductivity,while the formation of intermetallic compounds Al₄W,Al₅W and Al₁₂W phases is not good for the heat transfer at the interface.Subsequently,the tungsten-plated diamond is treated by high temperature diffusion reaction,and the interface structure of the composite material is adjusted by changing the type and content of the surface coating phase of the diamond.Studies have shown that the tungsten coating on the diamond surface undergoes several stages of surface graphitization,selective reaction,dispersion growth,complete transformation,and selective cracking during high-temperature treatment.Three interface structures were observed at the interface of diamond/aluminum composites with different coating types,namely Al/Diamond direct contact interface,Al/Al₅W/Al/Diamond reactive interface and Al/W_xC/Diamond transition interface.Among the tungsten-plated diamond/aluminum composite materials treated at 900°C for 4 hours,the Al/W_xC/Diamond transition type dominates.Due to the good bonding strength of this type of interface and the lower interface thermal resistance,the composite material has reached the highest performance.The highest thermal conductivity is 660W·m^-1·K^-1,and the flexural strength is 353.86MPa.After 200thermal shocks,the thermal conductivity of the composite material has the lowest drop of 3.89%.