Study On The Etching Of Diamond Surface And The Preparation And Properties Of Copper-based Composites

With its high hardness and strength,diamond shows excellent grinding performance in the field of abrasives and also has excellent thermal conductivity.In general,it is often used as a reinforcing phase to make a metal base with high thermal conductivity and low expansion coefficient.Diamond could be used as electronic packaging material;however,the surface is smooth and chemically inert.The wettability of the metal matrix is very poor,resulting in poor interface bonding and reduced thermal conductivity.Therefore,it is necessary to optimize the interface structure of the diamond and the matrix to improve the thermal conductivity of the material.In this article,the iron-nickel alloy powder was used to corrode the diamond for increasing its surface roughness and the bonding area between the two phases.Then,copper-based alloying method was employed to improve the wettability between the two phases and optimize the interface of the composite material in both directions,further improving the overall performance of the composite material in a way of combined effect.The main research is as follows:(1)Iron-nickel alloy powder is used for surface treatment of diamond,focusing on the effect of temperature on the morphology,structure and performance of each crystal face of diamond.When the initial temperature is 800?,obvious corrosion marks appear on the(100)surface of diamond.As the temperature rises,the original crystal faces of the diamond gradually disappear.The corrosion parts on the(111)plane are distributed more uniformly,and most of them are triangular corrosion pits with smooth bottom,and the corrosion shape of the(100)crystal plane is generally square or inverted pyramid.The bottom surface of the corrosion pit is relatively rough,but the corrosion degree of the(111)plane is less than the(100)crystal plane.(2)The effect of holding time and the content of iron-nickel powder on the corrosion of diamond was systematically studied.Within a certain range,the corrosion depth and surface corrosion rate of diamond firstly showed a slow increase,and then the impact was gradually reduced.As the holding time increases,the impact on the diamond(100)surface is greater.When the holding time lifted from 60 min to90 min,the corrosion depth of the(100)surface increases from 3.2?m to 6.8?m,an improvement of 2.13 times,and the surface corrosion rate was increased by 1.89times,which boosted from 45%to 85%.The mass ratio of iron-nickel powder and diamond has little difference in the rate of influence on each crystal face of diamond;nevertheless,the degree of corrosion to diamond will be greatly reduced when the ratio of iron-nickel powder is in a small range.(3)The corrosion mechanism of diamond is briefly discussed.When the temperature rises,molten metal atoms begin to adsorb and wet the diamond,resulting in point defects.Under the further catalysis of the metal,the diamond sp~3 structure carbon occurs layer by layer.and the phase transition collapses into sp~2 structure graphitic carbon.After graphitization,the carbon atoms diffuse into the corrosive with the concentration gradient as the driving force.After rapid annealing from high temperature,the supersaturated carbon atoms will adhere to the diamond corrosion surface in the form of crystals.A small amount of graphite layer is formed.(4)The overall performance of diamond/Cu-based composites with different surface roughness was compared.In pure Cu-based composites,the diamond did not undergo graphitization.With the increase of diamond surface roughness,the interface bonding has been improved,which not only reduces the interface gap,but also enlarges the contact area,so that the relative density of the composite material increases from 87.1%to 89.6%;the thermal conductivity increases from 165(W/m K)to 187(W/m K),with an increasing extent of 13.3%,which effectively strengthened the interface bonding and improved the performance of the material.However,the overall performance of the composite material is still poor,and the thermal conductivity and relative density are low.(5)The overall performance of diamond/Cu-B and Cu-Cr-based composites with different roughness were analyzed and compared.During the sintering process,a small amount of B or Cr was added to the copper matrix,which facilitated two-phase interface reacting to form the corresponding carbide,forming a chemical bond and greatly improving the thermal conductivity and density of the composite material.With the increase of the diamond surface roughness,the diamond/Cu-B matrix composites gradually form a zigzag polygonal interface coupling from the plane interface,which increases the interface area between the two phases and the heat conduction channel,and the high-roughness diamond/copper interface treated at 900?for 90 min generates B4C,which increases the chemical bonding force between the two phases,and the thermal conductivity and relative density gradually increase.The thermal conductivity increases from 361(W/m K)to 422(W/m K),the increase reached 16.9%,and the relative density of the composite material improved from 92.3%to 95.8%.The thermal conductivity of the diamond/Cu-Cr-based composite material increases firstly and then decreases.The thermal conductivity of the composite material prepared with low-roughness diamond treated at 900°C for 60 min is the largest,reaching 396(W/m K),high-roughness diamond.Not only did Cr3C2 be formed at the copper/copper interface,but the diamond was also graphitized,resulting in a decrease in the performance of the diamond and another decrease in the thermal conductivity of the composite material.