Copper/Multi-Walled Carbon Nanotube Composite Film

Multi-wall carbon nanotubes (MWCNT) have extensive potential applications in fields of composite materials in the future, due to its peculiar mechanical, electronic, chemical properties and unique one-dimensional structure. Nowadays, metal/MWCNT composite have been actively pursued because of enhanced mechanical and electrical characteristics more than those of pure metal. In this paper, electrodeposition technology (direct current electrodeposition and pulse-electrodeposition) was introduced to prepare copper/multi-walled carbon nanotubes (Cu/MWCNT) composite film from the acidic copper sulfate solution containing purified MWCNT. The influences of technological parameters on the electrodeposition of Cu/MWCNT composite film had been studied, such as MWCNT concentration in the solution, pH value and current density. Meanwhile, the formation mechanism of Cu/MWCNT composite film by electrocodeposition, especially the significant effect of MWCNT on Cu reduction, had been investigated by electrochemical measurements including cathodic polarization, cyclic voltammetry (CV) and electrochemical impedance spectrums (EIS). The formation procedures of Cu/MWCNT composite electrodeposition consisted of four important stages. The results are showed as follows:Pulse electrodeposition was better than direct current electrodeposition to fabricate Cu/MWCNT composite film, which was formed as a closely packaged film with a considerable high MWCNT content. The optimum parameters for electrocodeposition had been found out:1.0g·L-1 MWCNT in the solution, Jp=20 A·dm-2, ton=40 ms, toff= 960 ms. Moreover, one end of MWCNT was embedded deeply in the copper matrix with the other end protruding from the surface of the composite coating. This ideal bonding state may enhance electric conductivity of Cu/MWCNT composite film.Results from cathodic polarization, CV and EIS indicated that MWCNT can promote the reduction of cupric ions thereby accelerate the whole electrocodeposition process. The electrochemical formation procedures of Cu/MWCNT composite film included four stages as follows:The first stage, MWCNT adsorbed cupric ions in the composite platting bath and became Cu2+/MWCNT complexes. The second stage the electrophoresis of Cu2+/MWCNT complexes toward the cathode happened under the influence of electric field force. The third stage when Cu2+/MWCNT complexes arrived at cathode, reduction of Cu took place through two consecutive charge transfer steps. The reduction of Cu was accelerating because of existing of MWCNT. At last, the three dimension network of MWCNT on the Cu coating was built up with more and more MWCNT inserted into the growing copper. The electrochemical formation mechanism of Cu/MWCNT composite film is helpful for us to further understand electrocodeposition of metal/MWCNT composites.