Modification mechanism of the aluminum–zirconium coupling agent in anti-erosion coating for cement kilns

In order to improve the properties of refractories for cement kilns, reduce the energy loss in the calcination process of cement kiln. In this work, the anti-erosion coatings were prepared by the slurry method using alumina as the filler of coating and aluminum–zirconium coupling agent (DH-550) as additive. The steric effects mechanism of DH-550 was investigated through Fourier transform infrared spectrometer (FTIR), high-temperature abrasion resistance tests, and microstructure analysis after erosion. The results show that the substrate without coatings exhibits poor erosion and abrasion resistance. Upon the addition of DH-550, the hydrolysis of Al₂O₃ generates an increased density of surface hydroxyl groups, which facilitate the chemisorption of DH-550 onto the Al₂O₃ surface, forming a protective organic–inorganic hybrid layer. The grafted DH-550 molecules introduce steric hindrance effects, thereby effectively increasing interparticle distances and mitigating agglomeration. Consequently, Al₂O₃ is uniformly distributed on the substrate surface after drying, enabling the formation of 3Al₂O₃·2SiO₂ and Al₂TiO₅ phases at the interface during the high-temperature heat treatment. The pores are filled by Al₂TiO₅ formation, and a dense protective layer is subsequently formed, leading to significantly improved erosion resistance. The overall performance of the sample is optimal when the DH-550 addition amount is 2 wt%.