Study On Preparation And Deuterium Permeation Resistance Of Al₂O₃-TiO₂ Composite Coatings

Tritium permeation is one of the key problems in fusion reactor and integrating ceramic tritium permeation barrier(TPB)coatings with a certain thickness on the surface of structural material can effectively reduce tritium permeability.Al2O3 coating stands out among many ceramic coatings due to their high permeation reduction factor.However,crystalline alumina,especially ?-phase Al2O3 with the most stable chemical state,usually requires extremely high deposition temperature or annealing temperature.In this paper,Al2O3 coatings and Al2O3-TiO2 composite coatings were fabricated on 316L stainless steel substrate by radio frequency magnetron sputtering.It was found that compared with pure Al2O3 coatings,the deuterium permeation resistance of Al2O3-TiO2 composite coatings was enhanced due to the reduced oxygen-vacancy defects,improved crystallinity and compactness.The main experimental results are as follows:(1)Al2O3 coatings and A12O3-TiO2 composite coatings with a thickness of about 300 nm were prepared on 3 16 L stainless steel by adjusting appropriate process parameters.The Al2O3 coating prepared at room temperature is amorphous and oxygen-deficient.Annealing treatment(600?900?)can theoretically improve the anaerobic condition and crystallinity,but the Al2O3 coating annealed at 800? is still amorphous.Compared with pure Al2O3 coating,the three groups of Al2O3-TiO2 composite coatings with different Ti content show coexistence of TiO2 and Al2O3 phases after annealing at 800?,the content of oxygen vacancy defects on the surface is reduced,and the crystallinity and compactness are improved.Among them,Al2O3-TiO2 composite coating with 15.56%Ti content exhibits the highest crystallinity,lowest oxygen vacancies and best compactness(2)Deuterium permeation tests were carried out on 316L stainless steel coated with pure Al2O3 coating and Al2O3-TiO2 composite coating with 15.56%Ti content using the 316L stainless steel as a reference.The results show that the deuterium permeation pressure index of 316L stainless steel with Al2O3-TiO2 composite coating is 0.71,indicating the deuterium permeation process is controlled by both bulk diffusion and surface effect.Compared with bare 316L stainless steel,the coated 3 16L stainless steel effectively prevents deuterium permeation.Among them,Al2O3-TiO2 composite coating has better deuterium permeation resistance than the pure Al2O3 coating due to the lower porosity and oxygen-vacancy defects and better crystallinity.