Preparation Of Al₂O₃ Coating On Stainless Steel Substrate

Compared with the traditional particle catalysts, metal monoliths have high integral geometry spicific surface, low bed pressure drop and specific heat, good heat transfer, and high mechanical strength. The use of metal catalyst in some fast reactions which can be easily influenced by transfer rate, strong exothermic reactions or multiphase flow disperse three-phase reactions which are sensitive to the mixture degree, is helpful to realize zero discharge, low energy consumption and the safe operation of cleaning process and has broad application prospects. However, the metallic monoliths can not be applied in practice because of the low specific surface area. It is necessary to deposit the ceramic oxide washcoat with high surface area over metallic monoliths. Since thermal expansion coefficient of the metallic support is different from the ceramic oxide washcoat, the adhesion of washcoat is poor which results the washcoat chap and flake away.To solve this problem, Al2O3 coating and Ni-Al2O3 buffer coating were prepared by electrophoretic deposition (EPD), after that Al2O3 washcoating was prepared by dipping method on the stainless steel surface. The washcoat of coating quality was measured by XRD, EDX and SEM, ultrasonic vibration test. The main works are as following:The effects of the content of Al2O3, solution pH value, bath temperature, deposition voltage and time on the nano-Al2O3 contents in the composite coatings were investigated.Stabla alumina sol was prepared using SB powder as raw material, HNO3 as peptizaor. The influence of preparation condition, including H+/Al, SB concentration, peptization temperature and additive on the stability of alumina sol was studied.Alumina sol mixed with ethanol as EPD solution, the solution of EPD was made up of alumina sol and ethanol. The influence of The concentration of Al2O3 powde, the volume content of sol the voltage and time of deposition was studied.Finally, the Al2O3 washcoat was prepared by dip coating using alumina sol as binder. The influence of the sol concentration, solid content, coating additives and the transfer coating on the coating properties were investigated. The results show that, the dipping solutions composed by 1.35 mol/1 aluminum sol,35-40% solid Al2O3 content, mPEG/msol 0.1 additives, it can obtain uniform,2.16wt% Al2O3 loading after coating two times, with the coating fall off only 11.2% after 30 min ultrasonic vibration. The transfer coating can improve the loading of Al2O3 coating and the strength of coating combined with metal substrate.