Electrochemical Preparation Of TaC And Ni-TaC Composite Powder In Molten Salt

Due to the excellent properties of high melting point,high hardness and good wear resistance,TaC is widely used in many industrial fields.The addition of TaC into hard alloys can improve the performance of cemented carbide effectively.TaC is usually used as protective coatings to enchance the properties of the substrates.In addition,TaC also has an important application in electron tubes.At present,the methods of preparing tantalum carbide include carbothermal reduction and mechanical alloying.Although raw materials for the reduction are easy to obtain and reduction mechanism is clear,these methods are not completely satisfactory because of the harsh conditions,high energy consumption,low quality product.Therefore,it is necessary to develop a simple,low energy consumption and high productivity process to prepare TaC.In this study,cathodic pellets were prepared by a sintering process of Ta2O5 and C mixture,and TaC was produced by electrochemical reduction of the pellet in CaCl2-NaCl molten salt.Additionly,NiO was added to the raw material,which was reduced to Ni elemental after the sintering of the pellets.Then preparation of Ni-TaC compound powder was performed.The influence of the respective amount of Ni and carbon,as well as the size of carbon particles on the reduction was considered.The mechanism for the preparation of TaC and Ni-TaC was discussed by analyzing the partially reduced samples for various durations.During the preparation,Ta2O5 was electrochemically reduced to Ta,which would react with carbon to generate TaC.Meanwhile,a series of calcium tantalates were formed from the reactions of Ta2O5 and carbon,and the subsequently reduction of the tantalates occurred,following by the carbonization of the reduced Ta.Once the the amount of carbon in the precursor was inadequate for the,Ta2C as well as Ta was detected in the product.Moreover,it was found that the carbon powder with amorphous structure and relatively smaller particle size was favorable for the carbonization.During the reduction of NiO/Ta2O5/C mixture,severals Ni-Ta alloys were generated by the participation of Ni into the reduction.Then the alloys would react with carbon to form Ni-TaC.The introduction of Ni was available for the complete reduction of the cathodic pellet.The enhancement of the amount of Ni could affect the morpholoy and elements distribution of the final product.