The influence of the Cr–Al foil texture on morphology of adhesive Al2O3 layers in monolithic environmental catalysts

FeCrAl as a Catalyst Support

“…α-Fe, body-centered cubic, in the FeCrAl bulk determines the morphology of the Al 2 O 3 formed during oxidation. Folding, stretching, and bending (mechanical deformations) of the support change the shape and the orientation of Fe and therefore the thickness of the final Al 2 O 3 . The oxidation rate, and thus the nature and thickness of the coating, varies with the oxidative environment composition (air, H 2 O, O 2 , and O 2 plus SO 2 ), temperature, time, substrate origins, and geometry.…”

“…Folding, stretching, and bending (mechanical deformations) of the support change the shape and the orientation of Fe and therefore the thickness of the final Al 2 O 3 . 104 The oxidation rate, and thus the nature and thickness of the coating, varies with the oxidative environment composition (air, H 2 O, O 2 , and O 2 plus SO 2 ), temperature, time, substrate origins, and geometry. The chemical composition of the superficial coating changes with temperature: below 900 °C mixtures of Fe, Cr, and Al oxides form.…”

Effect of Acid Treatment on the High-Temperature Surface Oxidation Behavior of FeCrAlloy Foil Used for Methane Combustion Catalyst Support

“…Although FeCrAlloy is comparatively thermally resistant and oxidation-resistant, its exposure to a high-temperature and high-oxidation environment leads to a preferential migration of the Al atoms toward the surface and formation of an oxide layer. This intermediate layer is crucial to the stability of the final catalyst and a structure of the layer with good affinity to the high temperature catalyst (i.e., hexaaluminate) is preferred. , The Al 2 O 3 layer formed is preferably as dense as possible, which further enhances the oxidation resistance . Nevertheless, if the Al atoms in the alloy are overconsumed, the Cr atoms will migrate outward to the surface of the alloy, which results in the collapse of the alloy.…”

“…Several methods have been adopted to improve the oxidation resistance of the alloy, such as doping with one or two rare-earth elements (Ti, Zr, Hf, La), − and preannealing treatment in a hydrogen atmosphere. , It was proposed that the preannealing treatment reduced the growth rate of Al 2 O 3 layer by limiting the oxygen diffusion along the Al 2 O 3 grain boundaries …”

“…10,11 The Al 2 O 3 layer formed is preferably as dense as possible, which further enhances the oxidation resistance. 12 Nevertheless, if the Al atoms in the alloy are overconsumed, the Cr atoms will migrate outward to the surface of the alloy, which results in the collapse of the alloy. Therefore, the growth rate of the Al 2 O 3 layer becomes a measure of the oxidation resistance of the FeCrAlloy.…”