Study On The Growth Mechanism And Corrosion Resistance Of Tantalum Surface Oxide Fil

Tantalum has been successfully applied in the chemical industry,electronic industry,biological materials and other fields due to the excellent corrosion resistance.The corrosion resistance of Ta is attributed to the formation of a stable oxide layer Ta₂O₅ on its surface.However,the natural Ta₂O₅ is very thin,and tantalum quickly experience severe localized corrosion since the oxide layer is destroyed and exposed to corrosive media.Studies have shown that modulating the grain orientation or preparing oxide films on the surface can improve the corrosion resistance of Ta.Therefore,in this thesis,the grain corrosion orientation of Ta coatings prepared by chemical vapor deposition with obvious grain orientation was studied,and the corrosion activity of different crystal faces of Ta was investigated by first-principles calculations.Meanwhile,the effects of anodic oxidation and ion beam etching on the growth of oxide films and corrosion resistance of Ta were investigated separately for rolled Ta,and the O adsorption behaviour of different crystalline surfaces of Ta was studied.The following conclusions were obtained:（1）The grain orientation corrosion of chemical vapour deposited Ta coatings showed that the island particles of Ta coatings deposited at 1100℃grew uniformly and had small size.The texture proportion of（110）plane is higher than that of other samples.It also had a higher corrosion potential(E_corr)value of 0.128 V and a lower corrosion current density(I_corr)value of 0.788μA.cm^-2,which provided the best corrosion resistance.The simulated polarization curves showed that（110）had the weakest chemical activity and the best corrosion resistance,which was in accordance with the experimental trend.（2）The anodic oxidation of rolled Ta showed that the thickness and density of the oxide film were increased by increasing the anodic oxidation potential and time.Ta_20-60had the highest E_corr value of 0.009 V and the lowest I_corr value of 0.501μA.cm^-2,which showed the highest quality and corrosion resistance.The growth of the oxide film was controlled by the diffusion and migration of vacancy defects,growing towards the Ta matrix at the Ta-oxide film interface and into the solution at the oxidation-solution interface.（3）The ion beam etching of rolled Ta showed that the surface activity of Ta was improved by increasing the etching energy.By increasing the etching energy,the formation of Ta₂O₅ was promoted on the surface,the thickness of the oxide film was increased and the corrosion resistance was improved.By increasing the etching time,the surface roughness of Ta was increased,the thickness of oxidation film and corrosion resistance was decreased.The oxidation film of Ta_1000-30 was the densest,which reduced ion diffusion in corrosive solution effectively and had the best corrosion resistance.（4）First-principles calculations showed that the activity of Ta（110）,（200）and（211）surfaces was increased,the adsorption sites of O atom were increased significantly,and the absolute values of the adsorption energy were increased after the introduction of vacancy defects.