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
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