| 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. TiN is often utilized to strengthen the surface of stainless steel due to its good wear resistance, corrosion resistance and beautiful color. In order to endow TiN with antibacterial ability, Cu and Zn antibacterial elements are introduced into TiN films. In this dissertation, TiN/Cu-Zn nanomultilayers and nanocomposite films have been fabricated on stainless steel by dual magnetron sputtering technique. Deposition parameters have been optimized to improve the surface properties, such as hardness, wear resistance and corrosion resistance, as well as antibacterial properties. Scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray diffraction (XRD), high resolution transmission electron microscopy (HRTEM) and X-ray photoelectron spectroscopy (XPS) are employed to study the structure of films. According to empirical electron theory of solids and molecules (EET), the electronic structure of TiN/Cu interface has been determinated, and the relationship between the electron density of TiN/Cu interface and the interface stress, film structure has been analyzed. Antibacterial mechanism of the films is also investigated.The experimental results show that when the Cu-Zn layers are thin, Cu-Zn layers are discontinuous due to strong inclining to conglomeration of Cu and Zn. Thus TiN-framework multilayer has been formed. Because the plastic deformation in thin Cu-Zn layers is difficult, the framework multilayers possess high hardness and good wear resistance. However, the hardness and wear resistance of multilayers decrease with increasing thickness of TiN layers and Cu-Zn layers due to a huge plastic flow occurring in thick Cu-Zn layers. The corrosion resistance of multilayers is affected significantly by the thickness of Cu-Zn layers. When Cu-Zn layers are thick, it is easy to form corrosion channel in Cu-Zn layers and the films are destroyed by peeling off. Consequently, the corrosion resistance of multilayers deteriorates evidently. However, good corrosion resistance has been obtained in framework multilayers owing to the inhibition of corrosion channel in discontinuous Cu-Zn layers. There exist proper deposition parameters, such as deposition pressure of 0.4-0.56Pa and bias voltage of DC 80V complex impulse 200V, which contribute to good performance of multilayers.SEM and HRTEM results show that the growth of TiN columnar structure is influenced slightly in composite films with low Cu and Zn doped. The Cu and Zn exist as very tiny crystallites or disorder structure surrounding the TiN crystallites. The grain size of TiN decreases with increasing Cu and Zn concentration. In contrast, high Cu and Zn content induces coarse structure due to the growth of copper grains. The composite film with concentration of 10.38 at.% Cu and 2.19 at.% Zn exhibits high microhardness and wear resistance. The passivation potential has been substantially improved with small amount of Cu-Zn. However, the surface properties such as hardness, wear resistance and corrosion resistance decrease because of the coarsening of Cu and Zn crystal.The calculation results based on empirical electron theory of solids and molecules (EET) show that the interface electron density difference of TiN(111)//Cu(111) and TiN(100)//Cu(100) is large, leading to high interface stress. Therefore, it is difficult to form steady coherent growth structure, and misfit dislocation occurs in Cu layers to relax coherent stress, giving rise to the decrease of hardness of multilayers.The antibacterial properties of the multilayers are influenced by the modulation period. The antibacterial effect of multilayers with thin Cu-Zn layers is sensitive to the thickness of TiN layrs, while it is insensitive to the thickness of TiN layers when Cu-Zn layers are thicker. The multilayers with increasing thickness of TiN layers and Cu-Zn layers are destroyed easily by quick dissolution of Cu-Zn layers, though they possess good antibacterial effect. The antibacterial effect of composite films is dependent on Cu and Zn concentration. The antibacterial effect against E. coli reaches 99.9 % when Cu and Zn content reach 12.51 at.% and 2.07 at.% respectively. Because of the existence of Cu-Zn enriched layers the framework multilayers can offer large quantity of antibacterial ions. Moreover, the multilayers with discontinuous Cu-Zn layers can modulate the releasing rate of Cu and Zn ions. Consequently, the framework multiayers are featured by steady ion releasing rate and long term antibacterial effect. The composite films show higher releasing rate at initial immersion time, and then the releasing rate reduces due to the barren of Cu and Zn ions in near surface after long term releasing. Comparing with that of composite films, framework multilayers demonstrate long-term antibacterial effect. The films possess strong antibacterial effect owing to the synergistic effect of Cu and Zn ions and the antibacterial effect against E. coli reaches above 96% within 1-2 hours. The woolen cloth wear test shows that the antibacterial properties do not change after wear test. The framework multilayers and composite films can inhibit or kill the bacteria on surface, but show slightly influence on bacteria surrounding.
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