Research On The Synthesis Of Textured Ti₂SnC Ceramic And Its Electrical Conductivity

A new ceramic material Ti2SnC,has attracted much worldwide attention due to its unique properties such as high electrical conductivity,machinability, self-lubricity and resistance to corrosion.The hexagonal crystal structure endows Ti₂SnC with an anisotropic property.However,the synthesized Ti₂SnC exhibits an isotropic property owing to the random distribution of polycrystals,resulting in the disappearance of some excellent properties along specified crystallographic orientation.In this work,a textured Ti₂SnC ceramic was synthesized using the templated grain growth method and its electrical conductivity was investigated.The main contents of this work include:preparation of Ti₂SnC template grain, oriental distribution of the templated grain in matrix powder,sintering processing and study the electrical conductivity of the textured Ti₂SnC ceramic.Powders of Ti,Sn and C with a mole ratio of 2:1.1:1 were mixed(denoted as 2Ti/1.1Sn/C mixture).The C powder is active carbon,being subjected to ball milling for 4 h in a planetary ball mill with agate balls at the rotate speed of 250 r/min.After pressureless sintering at 1200℃for 2 h,a Ti₂SnC powder was synthesized.The assynthesized Ti₂SnC powder was treated with a hot HCI solution in ultrasonic instrument for 6 h,Ti₂SnC templates with size of less than 10μm and thickness less than 1μm were obtained.15%,25%,35%and 45%(weight ratio) Ti₂SnC templates were added to 2Ti/1.1Sn/C mixture with distilled water,whose weight is 70%of all the powders, and 1 wt.%hydroxypropyl methyl cellulose(HPMC) as binder,forming a slurry.Tape casting experiment was performed in self-made equipment.The green tapes with thickness of 0.5 mm was cut and stacked,and then degreased.After that,the green bodies were hot pressed at 1200℃under 30MPa for 2 h.The synthesized samples were characterized using X-ray diffractometry(XRD) and scanning electron microscopy (SEM).The XRD result shows that the textured Ti₂SnC ceramic with 35%templated grains has a high Lotgering,f=47.6%.SEM observation shows that the templated grains distributed and grew along tape-casting direction,forming a textured microstructure. The textured Ti2SnC ceramic with 35%templated grains has a high density of 98.4%. Its electrical conductivity is 3.69×10⁶Ω^-1·m^-1,which is about two times as high as that of untextured Ti₂SnC ceramic with 1.74×10⁶Ω^-1·m^-1.