Microstructure and application of alumina-supported Cu-based coating prepared by cold spray

Abstract

Cold spray technology is a recently developed surface modification method, which is widely used in various fields including the catalyst industry. Owing to their low reaction temperature, high activity, and high hydrogen selectivity, Cu-based catalysts are widely used in methanol steam reforming for hydrogen production. Cold spray is an efficient method for fabricating supported Cu-based catalysts for hydrogen production. However, in the cold spray process, the feedstock powder shape significantly affects the coating formation. In this study, we used two types of feedstock powders (consisting of dendritic Cu and clustered Al2O3) with different morphologies for fabricating Cu and Al2O3 coatings by cold spray on an Al substrate. A Cu + Al2O3 composite coating was also prepared by the cold spray method. The microstructures of the Cu, Al2O3, and Cu + Al2O3 coatings were investigated before and after methanol steam reforming. All the three feedstock powders were successfully deposited on the Al substrate. The coatings formed using the Cu and Cu + Al2O3 feedstock powders were multilayered and highly porous. Only slight deformation was observed in the micro-spherical structure of the Cu particle branches. In the case of the composite coating, Al2O3 particles were broken into pieces and were non-uniformly distributed. The bonding strength between the coating and the substrate was strong enough. After the methanol steam reforming process, the quality of the composite coating improved; however, the Cu coating showed carbon deposition. In order to obtain high-quality coatings, special attention should be paid to the feedstock particle shape and deposition of easily broken feedstock materials. The microstructural investigation of such coatings can be useful for understanding their fabrication mechanism. The fabrication method used in this study can be used as a novel method for fabricating supported catalysts.