| Diamond is widely used in the precision machining of brittle materials and stone cutting because of its high hardness,strength,and good chemical stability.At the same time,due to its high thermal conductivity,it is considered as a next generation of electronic packaging materials which meet requirement of the high power dens ity,miniaturization and reliability of modern microelectronic devices.The key which improve the properties of the composite is to improve the interface bonding between the diamond and the matrix due to the weak bonding between diamond and matrix.In this paper,the etching methods which increase the surface roughness are used to improve the interface bonding of the composite and increase the properties of the composite.The main contents are as follows:The diamond particles were etched through the molten salt method and the oxygen atmosphere method respectively.The square etching pit and the triangle etching pit were produced on the{100}and{111}surfaces of the diamond,respectively.With the increased of the temperature,the etching rate and the size of the etching pit increased obviously.When the temperature upped to 800?,the angle of the diamond particles was eroded seriously.At the same temperature,the stability of the{100}surface is higher than that of the{111}surface.The formation mechanism of etching pits under the condition of oxidation etching was investigated.The shape of the etching pit is determined by the surface atomic structure,temperature and oxygen concentration.After increased the temperature and the oxygen concentration,the crystal direction of the square etching pit of the diamond{100}surface was changed.The surface morphology of the diamond was greatly influenced by the etching temperature and oxygen partial pressure under the oxygen atmosphere etching.The{111}surface showed a higher instability under the oxygen atmosphere,the etching reaction was more intensed and the roughness increased obviously.The shape of the etching pits on the{100}surface was irregular,and the square etching pits were formed only in a few positions,showed a higher stability that than etched with the molten salt.At the low etching temperature,the side crystal direction of the square pits on the{100}face etched by oxygen atmosphere was 45 degrees in deflection compared to the side of square pit which was generated by the molten salt.The samples were coated with Ti through the salt bath method.With increased of coating temperature,the coating tended to be complete and the coaing thickness increased.The appropriate etching degree helps to form a complete coating on the diamond.Compared with untreated diamond,the etched diamond had more complete coating.The effect of the two etching methods on the coating morphology were compared.The{111}surface which etched by oxygen atmosphere had higher activity.At the same coating temperature,the coating thickness on the{111}surface of the diamond increased obviously under oxygen atmosphere condition.The diamond particles which treated with different etching parameter and coating condition was used to prepared the composite materials,the suitable coating thickness,etching degree and prolonging the hot pressing time can help to improve the bending property of composite materials.The composite samples including diamond etched 15min at 700?and coated at 850?which were prepared under 700?30min have max bending properties,up to 400MPa.The increased of oxygen concentration had not reduced the performance of matrix materials.The copper matrix which contain Ti powders was mixed with the etching diamond particles to prepare the composites.With the increased of the etching degree of diamond,the thermal conductivity of the composites decreased firstly and then increased.Diamond surfaces with propriate etching degree can be coated with uniform cladding layer which had moderate thickness.The thermal conductivity of the composites prepared by etching diamond particles which was etched 30min at 700? is 512W·m-1·K-1. |
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