It has the advantages of fast burning, small volume, high mechanical strength, prominent
heat-resistance, etc. It is widely used in exhaust gas purification.
Firstly metallic substrate should be pretreated in order to generate a transition layer which is
required to solve the mismatched heat expansion between metallic substrate itself and the active layer.
On the transition layer, it is coated with rare earth catalyst, while in active layer is coated with noble
metal like Pt, Pd, and Rh.