L.C. Feng

Study of a Ceramic Thermocouple for Al Production

A ceramic thermocouple (CTC) was assembled using SiC as the cathode and MoSi2 as the anode for the temperature test of the aluminum electrolysis. The NiFe2O4 was sprayed on the surface of SiC cathode for increasing the corrosion resistance ability in the cryolite. The corrosion behavior of NiFe2O4 in the cryolite was investigated. The results of the corrosion tests show that the NiFe2O4 has a very low corrosion rate in the cryolite, and a corrosion layer was formed during the corrosion test. The mechanisms of the NiFe2O4 corrosion are reactive corrosion and particles flaking. The thermo emf of SiC-MoSi2 CTC was tested from 25 °C to 1300 °C in air. The results show that thermo emf has a linear relationship with the temperature dependence, and reached 350 mV at 1300 °C. The CTC which consists of SiC-MoSi2 prepared in the same batch has a preferable interchangeability. By holding temperature at 1300 °C, the deviation of thermo emf is 0.5 %, which is better than the criterion of industry thermocouple, 0.75 %. The CTC response time was also analyzed.