## 3 Results and Discussions
### Effects of Electrodeposition Parameters on Morphology and Composition of the Ni/SiCw Composite
This might be due to the high content of Ni and its high scattering factor leading to higher peak intensities compared to those of SiC_w_[25]. Figure 6 shows the XRD pattern for the applied SiC whiskers. Comparing to the standard card, SiC particles was fit to No. 29-1129 exactly. Figure 7 shows the XRD patterns and its crystallographic orientation indexes of the Ni/SiC_w_ composite coatings fabricated at a different current density. As shown in Figure 7a, at low current density (2 mA\(\cdot\)cm\({}^{-2}\)), the composite coating exhibits a strong (111) plane preferred orientation and a relatively low intensity of peaks (200) and (220). However, the intensity of (111) and (220) peak gradually reduce with the increase of current density, while the (200) peak increased obviously. Particularly, when the current density increased to 40 mA\(\cdot\)cm\({}^{-2}\), the value of (200) peak intensity reaches the strongest, and the other peaks are almost disappeared. These results mean that the current density alters the texture of the composites and enhances the (200) reflections, which is in good agreement with the literature reported observation (the current efficiency of Ni deposition reached high values of over 97%) [26]. XRD analyses show that the texture coefficient of the deposits varies with current density. From Figure 7b and Table 3, the calculated results exhibit that the texture coefficient of (111) and (220) orientation decreases from 0.91 to 0.05 and 0.43 to 0.18, respectively; while the (200) orientation index increases from 0.66 to 2.9. The variation of preferred orientation implied two possible reasons. One is the growth axis of the nickel grain mainly depends on the applied current density. There is a trend for dominating surface textures with increasing current density, as follows--(110) \(<\) (211) \(<\) (100). This means that \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Samples**} & \multicolumn{4}{c}{**Weight Fraction (wt. \%)**} \\ \cline{2-5}  & **Ni** & **Si** & **C** & **O** \\ \hline a & 98.66 & — & 0.32 & 1.02 \\ b & 95.18 & 1.47 & 0.55 & 2.80 \\ c & 90.88 & 3.48 & 1.00 & 4.64 \\ d & 85.57 & 5.39 & 1.48 & 5.56 \\ e & 76.32 & 8.83 & 4.67 & 10.18 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Weight fraction of the composite coatings as deposited at different conditions. Figure 6: XRD pattern of the SiC whiskers. (110), (211) and (100) texture are preferred orientation at very low current, medium and high current, respectively [27]. This also can be explained by the theory of nucleation energy (W\({}_{hkl}\)) [28; 29] as Equation (2). \[W_{hkl}=\frac{B_{hkl}}{\frac{z^{F}_{hkl}}{N_{a}^{2}\eta-A_{hkl}}}, \tag{2}\]  
where A\({}_{hkl}\) and B\({}_{hkl}\) are material parameters of the crystallographic direction (_hkl_); Na and F are the constant of Avogadro and Faraday, respectively; z is the number of electrons, and \(\eta\) is the over-voltage of cathodic polarization. For face-centered cubic metals, at low over-voltage, W111 \(<\) W100 \(<\) W110, while W100 \(<\) W111 at high over-voltage [26]. This phenomenon indicates that when particular nucleation energy is lower than other types of nucleation energy, the crystals of the deposited metal will exhibit particular preferred orientation. The other is the incorporated whiskers provides the occurrence of new nuclei and limits the growth of the original crystal grains [30; 31], which facilitates more nucleation sites and the grain size refined. As mentioned above, the crystalline structure of Ni-W/SiC deposits is also affected by the factor of the SiC\(w\) content in the composites. Figure 8 shows the XRD patterns and its crystallographic orientation indexes of the Ni/SiC\(w\) composite coatings electroplated at 20, 30, 40, 50, 60 \({}^{\circ}\)C, respectively. With the temperature elevated,