Stability and electrophoretic deposition of nano-SiC assisted by PEI

Abstract

Silicon carbide (SiC) coating is one of the best candidates for protection of carbon materials from oxidation at high temperatures. This paper describes the stability of 5 gl⁻¹ SiC nano-particles suspension in alcoholic solvents and applying it on graphite by electrophoretic deposition (EPD) method. Different suspensions in ethanol, methanol, and isopropanol were prepared with polyethylene imine (PEI) as a surfactant. The effects of suspension medium on the stability of suspensions in the presence of 3 wt% of PEI were investigated by visual inspection (sedimentation height). As a result, suspension of nano-sized SiC in ethanol at pH =10, the most stable suspension, were selected to study the effect of PEI amount on suspension stability. Visual inspection, particle size distribution, and zeta potential were measured as a function of PEI dosage. Suspension with 6 wt% PEI obtaining the minimum sedimentation height, the maximum zeta potential (+37.6 mV), and the least particle size possessed better stability. Nano-sized SiC coating was applied on the graphite from optimum suspension with different values of voltage and deposition time. The film obtained at voltage of 40 V and duration of 50 s had lower micro-cracks and uniform surface. The thicknesses of green coating were measured about 30 μm.

Graphical Abstract

Keywords:

• Electrophoretic deposition
• particle size distribution
• Zeta potential
• PEI
• SiC