Abstract
The surface of titanium foil can be modified by heating in the air, in a N2 flow, and in an NH3 flow. Upon heating in the air, the elemental Ti gradually transforms to Ti3O at 550 °C and to rutile TiO2 at above 700 °C. Treatment in a N2 flow leads similarly to Ti3O at 600 °C and TiO2 at 700 °C, although the overall reaction is slower. Meanwhile, nitridation in the N2 flow is minimal, even at 900 °C. Heat treatment in an NH3 flow produces nitride phases through the ammonolysis of the hexagonal Ti. With an ammonolysis at 900 °C, trigonal Ti2N and cubic TiN form together while, at higher temperatures, TiN is dominant. The TiN layer can also be obtained via the ammonolysis of the TiO2 coating, that is, by the sequential treatments of Ti in the air and then in an NH3 flow. The titanium nitride layers have particulate microstructures and varying degrees of porosity, depending on the ammonolysis temperature and time. The TiO2-derived TiN has a significantly higher capacitance than TiN derived directly from Ti. The optimally prepared TiN specimen exhibits an areal specific capacitance of 66.2 F/cm2 at 0.034 mA/cm2.
Published Version
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