| Metallic coating composite powders is a new type of powder metallurgy materials with multiphase and composite property. Due to its great varieties and special performance, it has been extensively applied in the industries including national defense industry, mechanical manufacture, and chemical industry etc.In the microscopic view, the coating powder features in multiphase, coated integrality and the characteristics of its various components can be shown according to different needs; In the macroscopic view, coating powders has character of its homogeneous property, which realizes uniform metallic phase fabric of products, and meanwhile greatly reduces or eliminates the defects of unstable performance and non-homogeneous components of products caused by non-uniform blending. In addition, the coating composite powders is able to change surface properties of powders and accordingly improve the technical property of powder, and prepare powder metallurgy materials and products of better performances.Copper(Ⅱ) sulfate pentahydrate, formaldehyde solution (37%), ethylenediamine tetraacetic acid disodium salt, potassium sodium tartate, 2-2'-dipyridyl and sodium hydroxide were used as raw materials,by the corresponding oxidation and deoxidization reaction of electroless Plating, the products of oxidation and deoxidization reaction were aggraded on the surface of micron squama graphite powders. The graphite composite powders were obtained after passivating , washing and dryness. The preparation conditions and performances in practice of graphite composite powders were studied chiefly.The effects of temperature, the main salt, the reductant and loading capacity on the deposition rate and the coating ratio has been researched through single factor experiments. And the composite powders' microscopic structure, surface topography, and elements in coating were also analyzed by adopting advanced testing methods including XRD,SEM, EDAX and tridimensional microscopy etc. The results indicate that the copper deposition and the coating ratio increase with the increase of the concentration of temperature, the main salt and the reductant while decrease with the increase of the loading capacity. A complete and consistent cladding that is well-combined with the matrix can be formed with appropriate deposition rate and coating ratio. What is more, processing parameters were optimized through contrast tests. The optimal conditions of the electroless copper plating system are as follows: copper(Ⅱ) sulfate pentahydrate 20.0g/L, formaldehyde solution (37%) 25.0ml/L, ethylenediamine tetraacetic acid disodium salt 25.0g/L, potassium sodium tartate 14.0g/L, 2-2'-dipyridyl 20mg/L, temperature 50℃, pH value 12, loading capacity 5.0g/L and electromagnetic blender.Composite powders with better copper deposition could be obtained in the optimal condition. The deposition rate was about 0.06mol/L and the coating ratio was about 50%. SEM results indicated that copper deposited as dot first and expanded to be patches then. XRD and EDAX examinations found the coating crystalline state and no impurity presented.The reactive behavior with oxygen of composite powders and graphite powders was studied via analyzing the TG-DTA curves in air atmosphere. The first peak value temperatures reacting with oxygen were between 270℃and 310℃. The contact angles were measured after punched and the results showed that the wettability of composite powders were better than graphite powders.
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