Study On Technology And Mechanism Of Chemical Copper Coating On Silicon Carbide Surface

Silicon carbide（SiC）has outstanding advantages such as high hardness,good wear resistance,high temperature resistance,and low price.It is one of the ideal reinforcements for the preparation of aluminum matrix composites.The interfacial bonding between reinforcement and aluminum matrix plays an important role in the properties of metal matrix composites.However,the problems of poor interface wettability between SiC_p reinforcement and aluminum matrix and easy interfacial reaction resulting in equal brittleness of Al₃C₄ have not been solved.It is found that copper plating on the surface of SiC_p can effectively solve these problems.Therefore,this paper usesα/β-SiC_p as raw material,and uses electroless plating process to coat a uniform and dense copper film on its surface.Thermodynamics,process conditions,microscopic mechanism and other aspects are systematically studied.The main research contents and conclusions are as follows:（1）Using the existing thermodynamic data such as standard generation Gibbs free energy and complex stability constant,thermodynamic calculations were performed,and theφ-p H diagram of Cu-H₂O system and the concentration of copper hydroxyl coordination components of Cu-H₂O system at different temperatures were drawn.The relationship diagram with p H,the relationship map of molar fraction of EDTA-H₂O system with p H value and the relationship diagram of Cu²⁺concentration logarithm of Cu-EDTA-H₂O system with p H value.Analysis of these thermodynamic diagrams shows that the stable existence range of Cu²⁺is small,it is difficult to obtain Cu directly from Cu²⁺reduction,and the stable range of Cu²⁺cannot be expanded by increasing the temperature.To avoid the formation of Cu（OH）₂precipitation,it is necessary not only to increase the temperature,but also to control the p H>10.The complex ion Y^4-,which has a complex effect on Cu²⁺,begins to appear at p H>8.Y^4-can control the concentration of free Cu²⁺in the plating solution through its complexation with Cu²⁺.Combined with the condition that formaldehyde,the reducing agent for electroless copper plating,must have a reducing effect when the p H value is greater than 11,it can be determined that the temperature of the electroless copper plating should be controlled at about 70°C in theory,and the p H value should be controlled within the range of 11～13.（2）Based on the results of copper-clad thermodynamic analysis,copper-clad SiC_p（Cu@SiC）composite powders were prepared under different process conditions using micron-scaleαandβSiC_p as raw materials,respectively.By analyzing the morphology and composition of SiC_p before and after chemical copper cladding,as well as the change in weight gain rate and grain size after copper cladding,it can be seen that the crystal type has no obvious effect on the effect of chemical copper cladding,and the optimal process ofα-SiC_p andβ-SiC_p chemical copper cladding The conditions are:bath temperature 50℃,bath p H 12.0,Cu SO₄·5H₂O 8 g/L,reducing agent formaldehyde 10 m L/L,stabilizer content 40 mg/L,and loading SiC 1～2 g/L.Under this process condition,bothα-SiC_p andβ-SiC_p are uniformly coated with a dense copper film layer.In addition,the influence of the loading amount on the thickness of the copper-clad film is very obvious,indicating that the copper-clad amount of the Cu@SiC composite powder can be controlled by the loading amount.（3）Nano-scale Cu@SiC composite powders were prepared using nano-scaleα/β-SiC_p as raw material under the optimal process conditions of micron-scaleα/β-SiC_p chemical copper cladding.The characterization analysis by SEM,TEM,XRD and FT-IR shows that the Cu@SiC composite powder has no Cu₂O diffraction peak,the copper-clad film is well combined with the substrate,and has a clear phase interface.Bothα-SiC_p andβ-SiC_p surface copper cladding layers exhibit（111）crystal plane preferential orientation growth.The mechanism of each pretreatment process of electroless plating and the process of electroless copper coating was analyzed,and it was determined that the electroless copper coating on the surface of SiC_p was the law of first plane and then island growth,and the growth model of copper coating was established.