Electrochemical Processing and Thermal Properties of Functional Core/Multi-Shell ZnAl/Ni/NiP Microparticles

Area of Science:

• Materials Science
• Surface Engineering
• Electrochemistry

Background:

• Electroless deposition on zinc (Zn) and its alloys is difficult due to zinc's negative potential and tendency for poor surface layer formation.
• Existing methods are limited, with no prior reports on micro/nano powder coatings.

Purpose of the Study:

• To develop a robust method for creating compact, uniform Ni/NiP shells on Zn-based alloy microparticles.
• To investigate the mechanism and optimize conditions for this two-step coating process.
• To evaluate the thermal stability and functional properties of the resulting core-shell powders.

Main Methods:

• A two-step process involving controlled galvanic displacement of nickel (Ni) in an ethanol-based bath.
• Subsequent Ni-Phosphorus (NiP) autocatalytic deposition in an alkaline aqueous solution.
• Characterization of shell formation, thermal stability via differential scanning calorimetry (DSC), and encapsulation efficiency.

Main Results:

• Successfully formed compact, uniform, and conformal Ni/NiP shells on Zn-based alloy microparticles without agglomeration.
• Achieved high thermal storage capability (98.5%) and encapsulation ratio (66.5%).
• Demonstrated excellent thermal stability with no significant morphological changes or ZnAl alloy leakage post-DSC testing.

Conclusions:

• The proposed two-step electroless deposition method effectively overcomes challenges associated with coating zinc alloys.
• This technique enables the creation of functional Ni/NiP coatings on Zn-based materials, including powders.
• The process opens avenues for utilizing electroless deposition on bulk and powdered zinc-based materials for advanced applications.