An efficient method for enhancing adhesion and uniformity of Al2O3 coatings on nickel micro-foam used in micropacked beds

Abstract

• An efficient coating method to overcome the capillary force was proposed. • The pore size on substrate surface can be controlled by the pretreatment conditions. • Correlation was proposed with excellent practicality for predicting the pore size. • Squeezing of Al 2 O 3 particles in the pores can improve the adhesion of coatings. Methods of coating Al 2 O 3 on nickel micro-foam were compared and screened, aiming to overcome the capillary force and prepare the micro-foam monolithic catalyst coatings. The surface of micro-foam substrate was pretreated by a chemical etching method to improve the adhesion of the coatings on the substrate. The results showed that the slurry circulation at 162 ml·min −1 was evaluated as the optimal method. The pore size on the substrate surface can be controlled by changing the pretreatment conditions. An empirical correlation was also proposed, showing an excellent practicality for predicting the pore size. The adhesion of the coatings with substrate pretreatment was significantly better than that without substrate pretreatment. The minimum value of mass loss after ultrasonic vibration was 3.9%. This mainly attributes to the squeezing of Al 2 O 3 particles in the pores of substrate surface. The coatings on nickel micro-foam are hopefully used in micropacked beds for catalytic reactions.