The Study On Preparation And Properties Of N-Doped TiO₂ Films On Stainless Steel

The investigation and applications of antibacterial materials have been widely conducted in recent years due to the damaging effect of harmful bacteria. Stainless steel is widely used in food processing equipment, kitchenware, medical apparatus and daily appliances. Thus the development of stainless steel with excellent antibacterial properties is of great significance. With the aim of improving the antibacterial property of stainless steel, N-doped TiO2 films were prepared on stainless steel by plasma surface alloying and thermal oxidation duplex technique. For comparison, TiO2 films were prepared on stainless steel. Meanwhile, surface properties, mechanical performances, photocatalytic activities, antibacterial properties, tribological properties, corrosion-wear behaviors and corrosion properties of films have been studied. The main results have been obtained as follows:(1) The modification layers are composed of a pure diffusion layer or a duplex layer of diffusion layer and surface coating. A gradient distribution of elements existed in modification layer results in improving strength-toughness and enhances bonding strength for modification layers on stainless steel.(2) N-doped TiO2 may result in the real band gap narrowing and consequently a redshif of the optical absorption edge. The visible light photoactivities of N-doped TiO2 were greatly improved as compared with the undoped TiO2. Methylene blue aqueous solution degradation rate of N-doped TiO2 is 1.7 times compared with the undoped TiO2 under visible light for 6 hour.(3) The result of antibacterial test showed that un-modified stainless steel had no antibacterial activity. TiO2 and N-doped TiO2 modification layers increased the rate of cell reduction against Escherichia coli and Staphylococcus aureus. The antibacterial property against Staphylococcus aureus excelled to Escherichia coli obviously in the same condition. N-doped TiO2 modification layer performed excellent antibacterial property against Escherichia coli and Staphylococcus aureus, the rate of cell reduction was 100% and 86% respectively.(4) The tribological properties and mechanism of the modification layers have been studied by ball-on-disc test. TiO2 and N-doped TiO2 modification layer all increase the wear resistance of stainless steel substrate remarkably. Under unlubricated condition, N-doped TiO2 modification layer all have low coefficients of friction and high wear resistance when the coutpart is GCrl5 ball. When the courpart is Si3N4 ball, TiO2 and N-doped TiO2 modification layer have no antifriction effect on stainless steel, but TiO2 and N-doped TiO2 modification layers improve the wear resistance of stainless steel. The excellent wear resistance of TiO2 and N-doped TiO2 modification layer comes from their strong enough load-bearing capacity and bonding strength.(5) Eelectrochemistry tests show that TiO2 and N-doped TiO2 modification layers don't reduce stainless steel's corrosion resistance in Hanks'solution. Corrosion resistace of N-doped TiO2 modification layer is better than of TiO2 modification layer. According to the surface topography of corrosion, stainless steel has the phenomenon of pitting corrosion and suface modified stainless steel show uniform corrosion.(6) The corrosion-wear behaviors of stainless steel, TiO2 and N-doped TiO2 modification layers have been studied. In Hanks'solution, TiO2 and N-doped TiO2 modification layers all have smaller coefficients of friction and higher wear resistance than that of stainless steel substrate. Among them, N-doped TiO2 modification layer has better corrosion-wear resistance. The good corrosion-wear performances of TiO2 and N-doped TiO2 modification layers are due to their strong corrosion resistance and wear resistance.