Synthesis And Property Research Of Zr Doped Nano Layered Ti₃SiC₂ MAX Phase

Ti₃SiC₂ MAX phase ceramic material is the one of the most notable numerous MAX phase,and has a good combination property,such as low density?4.52 g/cm³?,high thermal conductivity coefficient?43 W/?m·K??,high melting point?3200??and high elasticity modulus?326 GPa?.The layered structure with silicon atomic layer connected by TiC octahedron makes it have a good machinability as well.Despite the Ti₃SiC₂ has such excellent comprehensive performance,however,compared with the traditional ceramic material such as Si₃N₄,Al₂O₃,the hardness of Ti₃SiC₂ is relatively low,and material loss will be rapid in long-term erosion friction environment.The formation of solid solution in Ti₃SiC₂ is a very good method to improve the mechanical properties.Spark plasma sintering method was used to synthesize Ti₃SiC₂ MAX phase and Ti_3-xZr_xSiC₂ MAX phase solid solutions.The synthesized Ti₃SiC₂ MAX phase and Ti_3-xZr_xSiC₂ MAX phase solid solutions were investigated by XRD,SEM,EDS,EPMA,respectively.The best material preparation technology was optimized finally.The hardness,modulus of elasticity,erosion resistance,friction resistance,oxidation resistance at high temperature and self-healing properties of the prepared materials were tested and studied.Applying Ti powder,Zr powder,Si powder and TiC powder as starting materials,the best technology of Ti₃SiC₂ MAX phase preparation by using SPS technology was 1Ti-1Si-1.9TiC-1450?-1 h-50 MPa,the grains of synthesized Ti₃SiC₂ MAX was pure,uniform fine,and the impurity content phase was limited to 2 vol.%.Zr atoms were found to successfully substitute the vacancy of Ti atoms in Ti₃SiC₂ MAX phase and formed stable Ti_3-xZr_xSiC₂ MAX phase solid solutions.The sintering temperature raised with the Zr solid solution content adding,and also brought more impurity in sample,Zr atoms were found to be dissolved in TiC phase,forming Ti_1-yZr_yC solid solution.Rietveld refinement found that crystal constant a,constant c and c/a increased linearly with the Zr solid solution content adding in Ti_3-xZr_xSiC₂ MAX phase solid solutions,When x in Ti_3-xZr_xSiC₂ MAX solid solution increased from 0 to 0.51,the lattice constant a of Ti_3-xZr_xSiC₂ MAX solid solution increased from 3.0666 A to 3.1172 A,and the lattice constant c increased from 17.6683 A to 17.8643 A,which was in accordance with Vegard's law,and implied an ideal solid solution was formed.The hardness and modulus of elasticity of Ti_3-xZr_xSiC₂ MAX solid solution increased with the adding of Zr atom solid solution content in Ti_3-xZr_xSiC₂ MAX solid solution.When x increased from 0 to 0.51,the nanoindentation hardness of Ti_3-xZr_xSiC₂ MAX phase solid solution increased from 12.8±1 GPa to 16.3±1.1 GPa,and the modulus of elasticity increased from 255±22 GPa to 290±24 GPa.The hardness,elastic modulus,resistance to erosion behavior,resistance to friction behavior of synthesized Ti_2.73Zr_0.27SiC₂ MAX phase solid solution was found to be better than that of Ti₃SiC₂ MAX phase,which should be attributed to the composite strengthening effect of residual TiC in Ti_2.73Zr_0.27SiC₂ MAX phase solid solution and the solid solution strengthening effect caused by Zr atom solid solution.The"quasi-plastic" behavior of Ti₃SiC₂ MAX phase in the damage zone under different mechanical testing conditions,like metal material,was observed,including grain bending,dislocation slip line,twist band formation,grain pull-out and a small number of grain boundary cracks.The oxidation resistance of Ti₃SiC₂ MAX phase and Ti_2.91Zr_0.09SiC₂ MAX solid solution in air showed that the oxidation kinetics curves of Ti₃SiC₂ MAX phase and Ti_2.91Zr_0.09SiC₂ MAX solid solution followed the parabola law in the range of 1000 to 1200?.The oxidation layer of Ti₃SiC₂ MAX phase was a multi-layer structure composed of Ti02 and SiO₂.With the increase of oxidation temperature,the oxidation rate increased rapidly.The formation of continuous dense SiO₂ layer was the reason for protecting Ti₃SiC₂ MAX phase ceramic from being oxidized.The oxidation layer of Ti_2.91Zr_0.09SiC₂ was similar to that of Ti₃SiC₂ MAX phase and the oxidation activation energy of Ti_2.91Zr_0.09SiC₂ was higher than that of Ti₃SiC₂,which indicated that the oxidation resistance of Ti₃SiC₂ can be increased by substituting part of Ti atoms by Zr atoms in Ti₃SiC₂ to form solid solution.Ti₃SiC₂ MAX phase ceramic had good self-healing property at high temperature.The slits filled with TiO₂ and SiO₂ produced by oxidation of Ti₃SiC₂ MAX phase was the reason for self-healing.