Preparation And Characterization Of Niobium Carbide By DC Arc Method

Carbides have been widely used in mechanical cutting,manufacturing anti-wear,mineral mining,high-temperature parts due to their excellent characteristics such as high melting point and hardness,extremely high thermal and mechanical stability,and high chemical resistance.And related fields such as nuclear reactors.Among them,niobium carbide and its parent metal niobium have very similar electrical and magnetic properties,making it a good research topic in recent years because of its good properties in hardness,wear resistance,thermal conductivity,and corrosion resistance.In this paper,the characteristics of the high temperature gradient of the DC arc plasma method are used to control the main process parameters to synthesize multi-morphology niobium carbide microcrystals.The XRD,Cryogenic magnetism characterization tests are carried out.The experimental results are as follows:(1)By controlling the main process parameters(working current,atmosphere,air pressure,etc.)of the DC arc plasma method,mushroom spheres,cacti,saddles,zigzag arrays,square flakes,etc.are prepared.The niobium carbide crystallites summarize the effects of process parameters on the growing samples.(2)Under a nitrogen atmosphere,if the nitrogen pressure is kept constant and the working current is increased,the product gradually changes from a mixture of niobium nitride and niobium carbide to pure niobium carbide;if the working current is kept constant,the nitrogen pressure is increased,The product also gradually changed from a mixture of niobium nitride and niobium carbide to pure niobium carbide.(3)The band structure of niobium carbide is theoretically calculated through the CASTEP module of MS.The band structure shows that niobium carbide is a compound with conductivity at room temperature and has a higher band density on the Fermi surface.According to BCS theory,niobium carbide can form more Cooper pairs and have a higher superconducting transition temperature.(4)The low-temperature Meissner effect test of niobium carbide crystallites shows that the superconducting transition temperature of niobium carbide crystallites is around 11.7K.From the M-H(hysteresis loop)image at low temperature,it can be seen that the superconducting state of niobium carbide belongs to the second type of superconductor,and there are mixed states of superconducting state and normal state.