Study On The Interface And Thermal Conductivity Of Diamond/Al Composites

The preparation of Diamond/Al composite and its thermal stability in variable temperature environment have always been the research focus of researchers.The Diamond particles were coated with Al,Cr,Ti,Ti-Cu coatings by salt bath and electroless Ni plating.Diamond/Al composite was prepared by pressureless infiltration.X-ray diffraction(XRD)was used to analyze the phase of Fe based amorphous alloy.The characteristic temperature point of Fe based amorphous powder was measured by DSC.Scanning electron microscope(SEM)was used to observe the interface bonding and the micro morphology of the interface products.The material elements were analyzed by EDS.The thermal diffusivity of the composite was measured by laser thermal conductivity analyzer(LFA 447).The experimental results show that:The in-situ self-exothermic heat during the crystal transformation of Fe based amorphous alloy is fully utilized to improve the fluidity of Al liquid and enhance the interface bonding of Diamond/Al composite.After crystallization,the nucleation and growth of multi-component crystals of Fe-based amorphous alloy increased the interfacial thermal resistance of the composite and reduced the thermal conductivity of Diamond/Al composite.The introduction of Fe based amorphous improves the thermal stability of Diamond/Al composite.The thermal stability of Diamond/Al composite increases by 10.3%in the test temperature range.Too much Fe based amorphous alloy or too long preparation time will lead to carbonization of Diamond particles.It is proved that the diamond interface first generated nano-Si O₂.It is found that there are two formation mechanisms of Si O₂on diamond surface,one is formed by oxidation of Si powder,the other is formed by chemical reaction of Si powders and Al₂O₃ powders.Through the study of microstructure,the densification process of nano-Si O₂-Al₂O₃ composite layer is discussed,and the possible nucleation and growth mechanism of four kinds of nanostructures are analyzed.The experimental results show that the interface bonding of Ti coated composite is more excellent,and the fracture mode is transgranular fracture.Diamond particles have strong binding force to the matrix,and the matrix is compact without obvious defects such as pores and cracks.The highest thermal conductivity of the uncoated diamond/aluminum composite is 392Wm^-1k^-1.The highest thermal conductivity of Ti coated diamond aluminum composite is 386 Wm^-1k^-1.Compared with the composite material without coating on the diamond surface,Ti coating improves the wettability of the matrix Al and diamond when the holding time reaches 90 minutes at the melt infiltration temperature.When the holding time reaches 210 min at the melt infiltration temperature,the burning process of diamond can be delayed.