A hBN/B-Si-Al-O-glass composite coating growth on SiCp/Al composite using one-step PEO with nanoparticle addition for outstanding electrical insulation performance

Abstract

A comprehensive study of the formation of electrical insulation coatings on SiCp/Al composite using plasma electrolytic oxidation (PEO) in an electrolytic system with hBN nanoparticles has been carried out. A complete coating can be formed under a high positive voltage (550–600 V) in a short period of time (3 min), and the coating is mainly composed of the hBN crystal phase as well as some amorphous phases. The high temperature of the local plasma in the PEO process impels these amorphous phases to form an amorphous B-Si-Al-O glass phase. As the treatment time goes on, the cross-sectional porosity of the coating first decreases rapidly and then increases slowly. This is attributed to the fact that the nanoparticles continuously deposit and sinter to repair the larger pores during the coating growth process, hence reducing porosity. Within 6 min, the coating thickness rapidly increases to 133.3 μm, showing excellent electrical insulation performance (with a breakdown voltage of 1460 ± 28 V, volume resistance of 5.52 ± 0.26 G·Ω, electrical resistivity of 4.18 × 1010 Ω∙cm) and high optical band gap value (above 5 eV), which is suitable for electronic packaging or dielectric materials.