Surface modification of coked alumina refractories by the deposition of sol-gel derived silica coatings

In this work Cu, Sn, and Ti nanoparticles were incorporated into solutions for the sol-gel deposition of silica coatings on coked alumina substrates. Cu-Sn-Ti ternary alloys were used aiming to improve the chemical affinity between silica and water. After heat treatment in an argon atmosphere, the coating adherence on samples was examined by scanning electron microscopy (SEM), scratch, and tape tests. The wettability behavior of the prepared materials was also investigated. It was observed that the presence of silica coatings on coked substrates increased their affinity for water. It is an important result since the hydrophobic behavior of coked linings inhibits the deposition of repair materials on their surface, which decreases their life sDpan and leads to financial losses in petrochemical applications. Evaluation of the samples by SEM indicated the presence of a nearly uniform silica film on the coated substrates. Moreover, tape and scratch tests indicated that there was good adhesion between the silica coatings and alumina substrate because no delamination or peeling was observed in these tests. The use of a Cu-Sn-Ti alloy composed of 60 wt%Cu - 35 wt%Sn - 5 wt%Ti led to smoother materials when compared to a 40 wt%Cu - 50 wt%Sn -10 wt%Ti alloy. Nonetheless, no difference in terms of roughness was noticed for specimens heat treated at 110, 750 or 1050 degrees C.