**4. Dopant technology derived from sol-enhanced plating and future industrial application of sol-enhanced coatings**

In order to utilize this novel sol-enhanced technology and promote this technology into real production, the dopant technology has been developed based on the sol-enhanced method. Different types of sol were added into various commercial electrolytes to study their effects on the plating bath and property of coatings. Comprehensive investigations on the technical datasheet for different types of sol are being conducted. Table 2 briefly summarized the different types of sol which can take significant effect on commercial baths according to our studies. It can be seen that this sol dopant technology can be used in almost all types of commonly used commercial baths, which gives a broad application prospect.


**Table 2.** The sols have significant effect on the commercial baths

The sol-enhanced coatings have a highly dispersed nano-structure with superior performance. This sol-enhanced technology based on a simple and feasible process which is also compatible with the commercial solution. Therefore, it has great economic potential and market value in the future industrialization. For example, the micro-hardness of sol-enhanced Ni-P and Ni-B coating can reach up to above ~1000 HV, the same level of the widely used hard chrome coatings which require an environmentally harmful fabrication process. Hence, this solenhanced coating technology provides a potential replacement to the hard chrome coatings process [4]. On the other hand, the mechanical property of sol-enhanced Au and Ag coating can be increased up to more than 20% while keep the same level of conductivity and surface gloss. These research outcomes will find wide applications such as jewelry, craftwork and electronics.

A combination of different coatings can maximize the performance and functionality of coating by utilizing the different properties of each layer. Recently, we apply multi-layer technology to new sol-enhanced coatings systems in order to optimize the surface properties of coatings [20, 30-31]. Electroless double-layered Ni-P/Ni-P-XZrO2 coatings with different phosphorus (P) contents have been prepared. The high P inner layer provides high corrosion resistance while the sol-enhanced composite outer layer provides excellent mechanical properties. This controllable duplex electroless coating system possesses excellent anticorrosion and mechan‐ ical properties. Pilot scale production and tests are being conducted in order to realize the future industry applications.
