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 α-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.