TITANIUM DIBORIDE AND MOLYBDENU SILICIDE COMPOSITE COATING ON CATHODE CARBON BLOCKS IN ALUMINUM ELECTROLYSIS CELLS BY ATMOSPHERIC PLASMA SPRAYING

摘要

Self-propagating high-temperature synthesis (SHS) with reduction process was used to fabricate the TiB_2 powder from TiO_2-B_2O_3-Mg system. The TiB_2-MoSi_2 composite was prepared by adding MoSi_2 to TiB_2 powder and coated on the cathode carbon blocks by atmospheric plasma spraying (APS). Various properties of the coated carbon block such as the chemical and electrochemical stability, the corrosive resistance, thermal shock resistance, wettability and service life in molten cryolite-alumina and aluminum liquids were tested. The microstructure of the coating, the interfacial bonding between the coating and the carbon substrate, thermal expansion performance and electrical resistivity of the coating, the effect of different process parameters e.g. spray distance, additive MoSi_2 content on the coating were also studied. These research results indicate that the TiB_2-MoSi_2 composite coating cathodes by APS have the potential to give significant benefits to the aluminum electrolysis process in terms of energy coast saving and extended cell life.