Modification Of Magnesium Alloy Micro Arc Oxidation Film By Atomic Layer Deposition

In-situ growth of the micro arc oxidation films on magnesium alloy surfaces is one of the most efficient methods to solve the corrosion problem of magnesium alloys, but the porous structure and insulation limit the applications of magnesium alloys. In this thesis, atomic layer deposition(ALD) technique is ultilized to deposite the Al-doped Zn O(AZO) films, which are anti-corrosive, transparent, and conductive, on the sufaces of magnesium alloy micro arc oxidation films to improve their conductivity and anti-corrosive capacity, with the aim of providing a theoretical basis for the broad applications of magnesium alloys.During the prepation of AZO films by ALD, the impacts of the ALD technique parameters, including deposition temperature and pressure, the thickness of the films, Al doping concentration, etc. on the conductivity of AZO films have be en investigated. SEM, XRD, XPS, and Hall effect testing instrument are used to examine the surface appearance, composition, and conductivity of AZO films. The results show that a uniform, dense, and(100) face-preferred AZO film with over 80% transmittance could be produced under the conditions of 150?C~175?C, 0.15~0.20 torr, and the film’s thickness over 100 nm. Al doping concentration plays an important role in the conductivity of the AZO films. With the increase of Al doping concentration, the conductivity of the AZO films rises. The resistivity of the AZO films reaches the minimum, 7.2×10-4 Ω?cm, when Al doping concentration is 3.4%. The further increase of Al doping concentration causes the increase of the resistivity and the decrease of the conductivity.AZO films are deposited on the sufaces of magnesium alloy micro arc oxidation films, and the surface appearance, composition, conductivity, and anti-corrosion capacity of the modified films are studied. The results show that with the increase of AZO thickness, the conductivity and anti-corrosion capacity of the modified films rise gradually; when the thickness is over 150 nm, the resistivity decearses to 4.5 Ω?cm from 1×107 Ω?cm, and the corrosion potential increases to-0.550 V from-1.322 V; the resistivity and the corrosion potential almost stay put as the thickness continues to grow. The improvement of the anti-corrosion capacity of the modified films by AZO via ALD is mainly because the cracks and pores of the original films are filled by AZO, increasing the water contact angle to 130.78° from 45.02°, and slowing down the entrance of the corrosive materials.