In the presence of microwave radiation, nitridation of metallic titanium in air becomes possible instead of the thermodynamically favorable oxidation. In this study, β-Ti-Cr alloy powders were synthesized to these nitrides by microwaves, using the fact that a solid solution of β-Ti-Cr is similar to pure β-Ti in terms of the electronic structure. The alloy powders were heated to a temperature of 1000 °C or higher by microwaves at a high oxygen partial pressure (PO2=2 × 10-1atm), and were analyzed by both wavelength-dispersive X-ray spectroscopy and X-ray diffraction. Nitridation was achieved for the β-Ti-Cr alloy, but not for a Ti-Fe alloy. The results can be explained using the average energy of electrons in 3d orbitals. Furthermore, multilayer structures made of nitrides and oxides were observed. The powders had a temperature-space distribution in the microwave field and the multi-layer structures corresponded to this distribution.
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