Inorganic Compounds

Titanium and titanium alloys have many attractive properties including relatively high specific strength and modulus, good corrosion resistance and biocompatibility. Therefore, they are widely used in many branches of industries. However, titanium and titanium alloys have found modest use in general engineering applications, mainly because of their meager tribological properties. In order to improve such properties, one promising way of titanium surface engineering is through the formation of titanium oxynitrides (TiNxOy) in the top surface.

Titanium oxynitrides have a great importance in many sectors of applications because of their enormous physical and chemical properties that exceed the properties of titanium nitrides or titanium oxides. In particular, titanium oxynitrides are widely used in medicine and in chemical industries because of excellent combination of chemical and mechanical properties

Nowadays, there is a growing interest in the methods of thermo-chemical treatment connected with diffusion saturation of material surface by different elements. The processes such as oxidizing, carburizing and nitriding can increase the wear and corrosion resistance, decrease the coefficient of friction and easily harden the surface of the material. One such way to enhance the physical and electrochemical properties of titanium is by modifying the surface microstructure through oxynitriding, to produce of titanium oxynitrides (TiNxOy).

A number of intermediate phases of general composition TiOxNy called titanium oxynitrides are found midway between TiN and TiO2. Preparation of titanium oxynitrides through either oxidation of TiN or nitridation of TiO2 is not straightforward. On the one hand, the oxidation of the TiN quickly leads to formation of TiO2, and on the other, nitrogen implantation in TiO2 leads to substantial reconstruction of the surface due to strong reduction and only a small amount (2− 3%) of implanted nitrogen can be reached.

Titanium oxynitride (TiOxNy) films are widely used, where the oxygen to nitrogen (O/N) ratio determines the field of application, e.g. nitrogen-rich films are used as anti-reflective coatings or biomaterials while oxygen-rich films are applied for thin film resistors or solar selective collectors. In particular, nitrogen doping of titanium oxide (TiO2) is essential for the absorption within the visible light wavelength for photo-catalytic and photovoltaic applications.