Research On Preparation Of Cu-coated Graphite Powders With Ultrasonic Flow Electroplating Copper

Cu-coated graphite powders is a new type of powder metallurgy materials with multiphase and composite property.Due to its special performance,it has been extensively applied in the industries including national defense industry,mechanical manufacture,and chemical industry etc. There are two main techniques to fabricate Cu-coated graphite powders. Electroless plating is extensively used. However, electroless plating has many complicated pretreatment of the graphite, unstable plating bath, complicated composition and high production cost. Electroplating possess many advantages, such as high deposition rate and stable bath, low cost of production, etc. So,electrodeposition is a technique of cleaning production as compared with electroless plating, which accords with continuable stratagem need.In order to overcome the problems of the traditional graphite plating, such as low current efficiency, reunion of the powders, agglomeration on the surface of cathode, we have designed the ultraonsonic flow electrodeposition device in this paper.A kind of micron-ranged squama-shaped graphite was used as the raw material, which was coated with copper by ultrasonic flow electrodeposition. The main results were gained as following:1. The compositions and operation conditions of fabricating Cu-coated graphite powders are:CuSO425 g·dm-3, NaH2PO2·H2O 10 g·dm-3, H2SO4 10 cm3·dm-3, graphite powders concentration 15 g·dm-3, CH3COOH 10 cm3·dm-3, C18H229SO3Na 100 mg·dm-3, current density 30 A·dm-2, ultrasonic frequency 20 kHz, flow velocity 12 dm3·min-1, bath temperature 60℃.2. When NaH2PO2·H2O is added to the plating bath, it can minish polarization resistance of electrodeposition and improve the morphology of the coating.3. Composite powders are well distributed in the bath through imposing ultrasonic. Agglomeration of powders caused by the co-deposition of the podwers and copper can be prevented on the surface of cathode. At the same time, polarization of concentration will be reduced though the strong agitation of solution owing to formation of shoot flow by ultrasonic cavitation.4. A continuous three dimensional web structure can be clearly observed on SEM images of Cu-C composite materials made of Cu-coated graphite. This Cu web structure can improve the conductance of electrical brush, wear resistance, the transverse rupture strength and interface cohesion between copper and graphite, decrease the porosity of composites.5. As compared with the traditional electrodeposited equipment and process, the ultrasonic flow electrodeposition can greatly shorten the process flow, improve the current efficiency, economize the 30% cost of production. It is possible to realize the industrialization of large scale production of Cu-coated graphite powders through electrodeposition.