Reusing oxide-based pulverised fly ash and medical waste particles to develop electroless nickel composite coatings (Ni-P/fly ash and Ni-P/SiO2-Al2O3)

Abstract

Recycling and reusing materials from waste have become a nexus in the development of sustainable materials, leading to more balanced technologies. In this study, we developed a composite coating by co-depositing recycled ceramic particles, pulverised fly ash (PFA) and medical ceramics (MC), into a nickel-phosphorus matrix using a typical electroless plating process. Scanning electron microscopy (SEM) images indicated well-dispersed particles in the Ni-P matrix. However, compared with the MC particles, the PFA particles were distributed scantily with a lower content in the matrix, which could be due to the less impingement effect during the co-deposition. A modified microstructure with refined grains was obtained for the PFA-incorporated composite coating, as seen in the SEM micrograph. The X-ray diffraction result of the MC-incorporated composite coating showed the formation of NixSiy phases in addition to the typical Ni3P phases for the heat-treated electroless Ni-P coatings. Upon heat treatment, the PFA-reinforced composite coating, due to a modified microstructure, exhibited a higher microhardness up to HK0.05 818, which is comparable to that of the traditional SiC particle-embedded composite coating (HK0.05 825). The findings can potentially open up a new strategy to further advance the green approach for industrial surface engineering.