Titanium Aluminum Carbide And Copper/Titanium Aluminum Carbide Composites

This thesis details our efforts to investigate the preparation methods of Ti₃AlC₂ powders and reaction type Cu/Ti₃AlC₂ composites and the relevant scientific basis for the first time.Nearly pure Ti₃AlC₂ have been synthesized by calcining a mixtures of titanium, aluminum and graphite powders with the mol ratio of Ti∶ Al ∶C = 3∶ 1.1∶ 1.8 under an Ar atmosphere. However, a thermal explosion phenomenon always generates when volume of the starting materials is larger, which not only induces a large quantity of TiC and other impurities to form, but also is a latent menace for security of the calcining furnace used.Using Sn powders as additives effectively inhibited the generating of the thermal explosion, and thus the technical difficulty was successfully resolved. In fact, the addition of Sn not only inhibited the generating of the thermal explosion, but also made the lower limit temperature drop and the range of temperature extend. Typically, the Ti₃AlC₂ as a puff bulk can be synthesized at the calcining temperatures of 1350℃ to 1500℃, and the purity can reach about 98% in volume. Furthermore, using the Sn additives, the polycrystalline Ti₃AlC₂ bulk can be reliably synthesized in-situ by hot-pressing the mixtures of titanium, aluminum and graphite powders.The results of x-ray diffraction (XRD) and transmission electron microscopy (TEM) showed that the Sn added probably entered into the Al layer of Ti₃AlC₂ crystal lattice and formed a Ti₃Al_1-xSn_xC₂ (x ≤ 0.2) solid solution or a Ti₃AlC₂/Ti₂SnC eutectic. Because the differences in crystal structure and physicochemical natures are small between Ti₃AlC₂ and Ti₃Al_1-xSn_xC₂ or Ti₃AlC₂/Ti₂SnC, the existing of Ti₃Al_1-xSn_xC₂ or Ti₃AlC₂/Ti₂SnC has almost no effect on material's properties, and they are identified factually with difficulty.In order to prepare Cu/Ti₃AlC₂ composites, the reaction mechanisms between Ti₃AlC₂ and Cu were investigated in detail. The effects of reactive temperature and ratio of Cu and Ti₃AlC₂ on reactive behavior and produce were explored via DSC analysis, phase diagram analysis, XRD and SEM analysis. The results showed that Al of Ti₃AlC₂ and Cu will generate a two-way diffusion at above the temperatures of about 800℃. Consequently, Cu enters into Al layers of Ti₃AlC₂, and Al from Ti₃AlC₂ enters into Cu to form Cu-Al alloy or intermetallic compounds. When the content of Ti₃AlC₂ is less than 63.47 vol.% in the Cu/Ti₃AlC, a sub-micro-layered structure making up of TiCo.67 layers and Cu-Al alloy layers with 125nm within a Ti₃AlC₂ grain are formed, where Ti₃C₂ layer...