Fabrication And Mechanical/Electrical Properties Of Porous TiN Ceramics

Titanium nitride（TiN）porous ceramics have good electrical conductivity compared to conventional nitride porous ceramics and are expected to be used as electrode materials in energy storage applications.The preparation methods of traditional porous TiN ceramics are mainly direct nitriding method and carbothermal reduction method.The porous TiN ceramics prepared have problems such as difficult pore structure control,incomplete nitriding,high production cost,and difficulty in industrialization.Based on the current research status,this paper proposes a gel-casting and pressureless sintering preparation process.The influence of sintering temperature,solid loading and sintering aids on the pore structure of porous TiN ceramics was studied,and the relationship between the porosity structure and its mechanical and electrical properties was established.Firstly,in this paper,the non-ionic surfactant polyethylene glycol was used as a dispersant,and the pH value of the slurry was adjusted with an aqueous ammonia solution.The effect of solid loading on the rheological properties of the TiN ceramic slurry was investigated.The results show that as the solid loading of the slurry increases,the distance between the particles decreases,which promotes the interaction between the particles and hinders the movement of the particles,thereby increasing the viscosity of the slurry.And the effects of monomer,initiator and catalyst content on the gelation time of the slurry were also studied.During the molding process,if the gelation time is too short,the local gelation will be too fast;If the gelation time is too long,the particles will precipitate and the uniformity of the green body will be affected.The optimal molding process is:AM 3 wt.%,APS 0.3 wt.%,TEMED 0.1 wt.%,and solid loading variation of 40-55 wt.%.Secondly,the effects of sintering temperature,solid loading and sintering aids on the porosity,pore microscopic morphology,pore size and pore size distribution of porous TiN ceramics were studied.The results show that with the increase of sintering temperature and solid loading,the pore distribution of TiN porous ceramics is uniform,and the porosity and pore size decrease slowly.The variation ranges are 41.8⁵9.8%and 2.2³.8μm,respectively.The use of Y₂O₃-TiO₂ combined sintering aids makes the porosity of porous TiN ceramics decrease to 27.8⁵2.0%,but the pore distribution remains uniform.Finally,the mechanical and electrical properties of TiN porous ceramics under different conditions were studied,and the relationship between pore structure and mechanical and electrical properties was established.The results show that the flexural strength and electrical conductivity of porous TiN ceramics gradually increase with the increase of solid loading and sintering temperature and the decrease of porosity.The change range is 14.2³4.6 MPa and 7.9²3.1×10³ S?m^-1,respectively.With the introduction of Y₂O₃-TiO₂ combined sintering aids,Y₂TiO₅ and Y₂Ti₂O₇ phases are produced during the sintering process,which further promotes grain growth and pore wall connections,and their flexural strength and electrical conductivity increase to45.2¹01.6 MPa and 1.6⁵.3×10⁴ S?m^-1,respectively.