Laboratory Preparation and Characterization of Electroless Nickel Coated Powders of Industrially Produced Aluminium and Iron(III) Oxides

Abstract

Small batches of two oxide powders falling in the particle size range of about 30-230 μm were received from industrial sources and were electroless nickel (EN) coated in order to prepare properly modified reinforcing particles for further laboratory experiments with the Laser Melt Injection (LMI) technique to produce particle reinforced steel composite surface layers. The partially calcined alumina (Al2O3) as well as the hydrothermally recycled crystalline iron(III) oxide precipitate were characterized first to check their exact size ranges, specific surface areas and major chemical contaminants so that the best possible EN plating technique would be selected and applied. It was revealed soon that the sensitization and activation pre-treatment steps could not be omitted and after their proper adjustment, also the composition and pH of a relatively commonly used hypophosphite reducing type bath had to be modified to the given purpose. Eventually a slightly alkaline EN bath was successfully prepared with which both industrial oxide powders surface could be nickel coated soundly, which final result was demonstrated also by several metallographic testing techniques showing the microstructure of the quite evenly and fully coated oxide particles.

Effect of pH on the characteristics of electroless Ni-P coatings

“…By controlling bath parameters (bath composition, pH, temperature), the physical and mechanical properties of the coatings can be modified within a certain range [6]. Ni-P coatings can be deposited effectively on steel [7][8][9], aluminium and aluminium alloys [10,11], other metals and alloys [12][13], plastics [14][15] and ceramics as well [16][17].…”

Synthesis of nickel coatings with high surface area on the ceramic powders

“…A creation of new architectures of functional materials is important for combination of their unique properties, including heat conductivity and electroconductivity, strength and plasticity, stability and reactivity. This makes it necessary to synthesize new composite materials, as well as research of the conditions for the manufacture of new products based on them [1][2]. Nickel combined with alumina extremely interesting for use in many applications, such as catalysis, soldering, corrosion-resistant coating, functionally graded metal-ceramic composites, fuel cells and others [3][4][5][6][7].…”