Investigation of the high temperature corrosion behavior of ceramic materials containing boron

In this Thesis work, high temperature oxidation behavior of three boron-containing compounds; titanium diboride, zirconium diboride and boron carbide were studied. Oxidation studies were conducted mostly in air at temperatures between 300 and 1200 Celcius degrees. Additionally, two applications of boron-containing materials were also investigated.It was observed that solid and protective oxides titanium dioxide and zirconium dioxide formed over titanium diboride and zirconium diboride, respectively, at high temperatures. Weight gains of these two borides changed with changes in both the temperature and the oxidation time. Because boron carbide could not form solid oxidation products, its high temperature oxidation behavior was controlled by the formation and evaporation of boron-containing liquid phase such as boron oxide which was molten at the test temperatures of this study. The presence of a liquid phase was indicated by the agglomeration of the oxidized boride powders and by the weight losses of the boron carbide samples after their long-term oxidaton in both air and water vapor. Formation of the solid, liquid or gasesous oxidation products also affected the kinetic aspects of the boride oxidation.As an application of boron-containing materials, titanium diboride-based composite production by using the vacuum arc melting method was investigated. Experimental results conducted showed that processing of bulk products by this method will be difficult. However, the process can be applied to modify material surfaces. In the other application, thermochemically formed iron boride layer was observed to decrease the oxidation attack of the steel substrate at 800 Celcius degrees, in air, by forming protective oxidation products containing glassy phases.