## 3 Results and Discussions
### Effects of Electrodeposition Parameters on Morphology and Composition of the Ni/SiCw Composite
Moreover, the mass transfer process of metal ions and whiskers to the cathode surface could be enhanced at an appropriate electrodeposition temperature [24]. Therefore, it is indispensable to evaluate the effect of electrolyte temperature on the composite for the purpose of obtaining the high content of SiCw in the coating with smooth and uniform morphology. In this experiment, the temperature of electrolyte ranging from 20 \({}^{\circ}\)C to 60 \({}^{\circ}\)C were investigated at a stirring speed of 200 rpm and a current density 18 mA/cm\({}^{2}\). As illustrated in Figure 2, the dendrites and nodules could be observed clearly at a lower temperature (Figure 2a), while the smooth and luminous surface accompanied by the increasing whisker content was obtained at a temperature rising to 50 \({}^{\circ}\)C (Figure 2d).In addition, the nickel grains became finer, and the composite coatings were also strengthened after adding the whiskers. However, the whiskers tended to aggregate and decreased its content in composite coatings when the temperature was exceeding 50 \({}^{\circ}\)C, which resulted in the deposited grains was coarse and oversized. In general, both the average kinetic energy of ions and the viscosity of electrolytic could be consolidated by increasing the electrolyte temperature, which all consequently facilities the transportation of whiskers. Besides, the diffusion mobility of metal ions adsorbed on the cathode surface would be increased on the electrode surface, which resulted in an increase of the whiskers contents in composites coating. Whereas, the anions diffusion rate, the overpotential and the electric field force of the cathode reduced when the temperature reached to a specific value, which was detrimental to the whiskers embedded into the nickel matrix. In addition, the electrolyte would evaporate seriously at a higher temperature, thus, affecting the deposition of active ingredients onto the cathode and covsing the surface of composites. As a result, the excessively high temperature led  
Figure 2: SEM images of Ni/SiC\(w\) composite coating fabricated from the electrolyte at stirring speed of 200 rpm, and current density of 18 mA/cm\({}^{2}\), and temperatures of (**a**) 20 \({}^{\circ}\)C, (**b**) 30 \({}^{\circ}\)C, (**c**) 40 \({}^{\circ}\)C, (**d**) 50 \({}^{\circ}\)C, (**e**) 60 \({}^{\circ}\)C.  
to a reduction of the SiC_w_ adsorption ability and the cathode electric field force, which ultimately reduced the SiC_w_ content in the composite coatings. In order to prevent the precipitation and agglomeration of SiC_w_ in the electrolyte, mechanical stirring was adopted as a key technology in electroplating process, due to the high surface energy of the SiC_w. Particularly, the content of particles in composite coatings is depended largely on the strength of stirring, which is advantageous to the uniform distribution of particles in electrolyte and the successful transportation to cathode surface [23]. Figure 3 shows the SEM images relating to the morphology of Ni/SiC_w_ coatings fabricated at a different stirring speed. The conditions of current density and temperature were 18 mA/cm\({}^{2}\) and 50 \({}^{\circ}\)C, and the stirring speed was controlled at 0, 100, 300, and 500 rpm, respectively. Due to the gravity, a large number of whiskers accumulated and covered the major cathode surface without stirring, which resulted in an increase of the cathode overpotential and a decrease of the discharged metal ions near the cathode. Therefore, metal ions discharged at the corner and appeared dendrites or nodules in the composite coatings under the condition without stirring. With the increasing strength of stirring, the mass transfer rate of electrolyte and the effective concentration of whisker were also increased accordingly, which could promote the transportation of SiC_w_ and increase the whisker content in the composite coatings.