Unravelling the Effects of Surface Modification Pre-Treatments on Porous Hastelloy X Supports for H2 Selective Pd-based Membranes Preparation with a Statistical Approach

Metal-based supports require specific pre-treatments to reach the surface quality needed for achieving thin Pd layers deposition without defects. Hastelloy X supports with high surface roughness and large pore diameter are acquired and pre-treated via polishing and chemical etching. They are then asymmetrically filled with alpha-Al2O3 of decreasing particle size (18 mu m, 5 mu m and 1.5 mu m) and equipped with a gamma-Al2O3 interdiffusion barrier. Each pre-treatment step is thoroughly characterized and elucidated with ANalysis Of VAriance (ANOVA) as statistical tool, introducing a hybrid observational-statistical approach to infer on a population of membrane supports. The analysis allowed to set average surface roughness (Ra) < 0.8 mu m, average profile height (Rz) < 7 mu m, in-pore leveling (Delta) < 6 mu m, as targets for support pre-treatments reproducibility. The target average pore diameter after asymmetric filling was identified as 100-500 nm, while the target average pore diameter after interdiffusion barrier deposition was below 100 nm. The most effective particle size for in-pore leveling was identified as <= 5 mu m, and the most effective particle size for average pore diameter reduction as 18 mu m.