XRD profiles for the Ni / ZrO2 – TiO2 and Ni / CeO2 – ZrO2 – TiO2 nanocomposite coatings presented in Fig. 5.33, and Fig. 5.34. The diffraction peaks are matched with the JCPDS record using PAN analytical Xpert high score plus software. The direction of crystalline plane growth, Phase quantification are Recorded, measured crystalline size at the prominent sharp peak of (111) shown in Fig. 5.33 for Ni / ZrO2 – TiO2 and in Fig. 5.34 for Ni / CeO2 – ZrO2 – TiO2 nanocomposite coatings. The calculated crystalographic values recorded in Table 5.6 and Table 5.7, respectively.
In Fig. 5.33, For the Ni / ZrO2 – TiO2 nanocomposite coatings made by the direct current, the ZrO2-TiO2 peak exhibited lower intensity. Ni anions more activated by the applied continuous potential, there may be no sufficient energy to activate ceramic particles in the bath. The higher electrical energy may be wastage by continuous current deposition for nanocomposite coating.
The deposits by rectangular waveform at a 50% duty cycle not shown in the Ni – ZrO2-TiO2 phase.The adsorbed ZrO2 – TiO2 secondary phase particle composition is less for the deposits at a 50% duty cycle. It may occur due to the bigger ZrO2-TiO2 particles that might not have enough time to embed into the Ni metal matrix during pulse on time. As the duty cycle increases from 10% to 100%, i.e., pulse on-time increases, and Off time decreases. Shorter TOFF provided less chance for ZrO2-TiO2 particles to reach the double layer. Therefore, less ZrO2-TiO2 particles achieved the cathode surface, and the amount of the incorporated ZrO2-TiO2 decreases. However, because the longer pulse off- time at a low duty cycle, the bigger particles on the coating surface would drop to the bath under stirring during TOFF. Therefore, the amount of ZrO2-TiO2 could increase with the increase of the duty cycle for the big particle size. The explanation for this discrepancy ascribed to the different particle sizes. The particle contents should decrease by increasing the duty cycle. Therefore, in the present work, the gravity effect, stirring force, and added CTAB surfactant significantly affected ZrO2-TiO2 particle incorporation. Deposits made by the triangular waveform by decreasing the duty cycle represent the increasing of the prominent peak intensity of Ni -ZrO2-TiO2 and binary nanocomposite ZrO2-TiO2 phase. According to the present results, the double layer’s replenishment could be the dominant effects for the ZrO2-TiO2 contents decrease, with the duty cycle increasing from 10% to 50%. During the higher duty cycle from 50% to 100%, the gravity effect and stirring force may be attributed to the fact that the ZrO2-TiO2 contents increase with the duty cycle increasing. A decrease in the concentration of the electroactive species in the cathode diffusion layer during pulse on time is assumed and incorporated into the model at lower duty cycles. Furthermore, the metal ion concentration will decrease with an increasing number of pulse cycles, i.e., at a lower frequency. It is particularly prevalent in systems with astronomical duty cycles (50% and higher) where full recovery is highly unlikely during pulse off-time.
In the pulsed deposition, when a square wave used, the current density immediately increases to the maximum value and remains constant during the pulse on-time. The continuous high cathodic current encouraged Ni / ZrO2-TiO2 crystal growth. The reduction of ZrO2-TiO2 atomic nuclei will lead to a decrease in the number of nickel crystallites and an increase in size and, consequently, to a decrease in the active surface area of the deposited nickel. On the other hand, if the nucleation rate can be increased at the beginning of the process since the electrodeposition continues to increase the pulse of time, the growth of the entire crystal will be steep. This method can produce well-dispersed catalyst particles. Rectangular and triangular waveforms have periods of the lower edge.
X-ray diffracted patterns of all developed coatings crystalline sizes at (111) prominent peak, which is the most reliable preferred orientation in FCC materials. The crystalline size of the deposited Ni / ZrO2-TiO2 nanocomposites reduced by reducing the duty cycle observed in table 5.6. the phase quantification of NiO, Ni /ZrO2-TiO2, and Zirconium, titanium oxide systems, were significantly dependent upon the duty cycle and waveform used.