Features of hafnium nitridization in production of high-temperature thermoelectric converters based on bimetallic pairs Hf-Ti, Hf-Zr, Hf-Nb

The kinetic dependences of hafnium nitridation at temperatures of 1900, 2200 and 2500 °C were established. The choice of temperature is justified by the conditions of nitridation of metal pairs Hf-Ti, Hf-Zr and Hf-Nb. By nitriding Hf-Ti, Hf-Zr and Hf-Nb pairs while preserving the shape of the original metal blanks, binary compact nitrides were synthesized, and the features of the hafnium nitriding process in these bimetallic systems were determined. The sequence of phase and structural transformations occurring in individual hafnium in the composition of each nitriding pair has been established. The formation of hafnium nitride ceramics occurs with the formation of three- and two-layer gradient structures. Ceramics close to the stoichiometric composition of HfN are formed at temperatures of 2200 °C and above. The magnitude of the thermo-EMF of the Hf-Ti, Hf-Zr and Hf-Nb systems was assessed, the nature of the dependence of the Seebeck coefficient on the nitriding time was established and its value was estimated.