Study On Preparations And Properties Of 312 MAX Phases（Ti₃AC₂, A=Al,Si,Sn）

Mn+1AXn(MAX) phase materials a family of advanced materials, which possess the advantageous property of ceramic and metal, are thermally and electrically conductive materials. Both Titanium Silicon Carbide(Ti3Si C2) and Titanium Aluminium Carbide(Ti3Al C2) are MAX phase materials. Ti3 Al C2 was the priority and prepared by pressureless sintering and Spark Plasma Sintering in this study.Ti3Al C2 was sintered by using a tube furnace with flowing high-purity Ar. The sample with starting molar ratio Ti C: Ti: Al=2: 1: 1 was pressed at 800 MPa before sintering. The reasonable temperature range is 1400-1500 ℃ to get Ti3 Al C2 with Ti C as impurity. However, Ti3 Al C2 with Ti C as impurity was otained by Spark Plasma Sintering at 1200 ℃ for 10 min under a pressure of 30 MPa, which is different to pressureless sintering. The results with Ti C/Ti/Al as starting materials are obviously better than the one with Ti/Al/C as starting materials.In this thesis, quarternary Ti3Si(1-x)AlxC2(x=0-1) MAX phase materials were prepared by SPS and characterized by Rietveld Refinement. Effect of Al addition on the lattice parameters was investigated, thus proving a better result than the data from the literature. Quarternary Ti3Sn(1-x)AlxC2(x=0-1) MAX phase materials were prepared by tube furnace with concern of the low melting point Sn. The main product was Ti3 Sn C2 when x=0; When x=0.1, the product was like the one with x=0; The crystal orientation is distinct in the XRD diagrams when x=0.3-0.7, which is not seen in the Ti3Si(1-x)AlxC2(x=0-1) MAX phases; The main product was like the one with x=0.9. The phase becomes Ti3(Sn Al)C2 because of the solid solution effect of Al.Ti3Sn C2 was obtained by pressureless sintering with starting molar ratio Ti C: Ti: Sn=2: 1: 1 at 1600 ℃ for 60 min under a pressure of 800 MPa. The impurities in the product were Sn and Ti C. Ti2 Sn C are stable during the high temperature(1200-1450 ℃) due to the synthesis of Ti3 Sn C2 in high temperature.Synthesis mechanisms of Ti3 Al C2 with starting molar ratio Ti C: Ti: Al=2: 1: 1 were investigated with the aid of NETZSCH STA 449 C, the equipment of Differential Scanning Calorimetry. Chemical reactions start with elementary substances, Al and Ti, to get complicated Al-Ti intermetallic compounds, and the reaction products were obtained at different temperatures. Ti2 Al C was obtained from the reaction between Ti C and Al-Ti intermetallic compounds, then to get Ti3 Al C2 at a higher temperature. The same to the synthesis mechanisms of Ti3 Sn C2 with starting molar ratio Ti C: Ti: Sn=2: 1: 1.