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Abstract.: Polycrystalline Ti2SnC was prepared by a novel solid–liquid reaction synthesis and simultaneous densification method using elemental Ti, Sn and graphite as starting materials. The method is a one-step process and it provides the advantages of simultaneous synthesis and densification. The microstructure evolution during the high temperature processing was described and the reaction route was described. The reaction path for the formation of Ti2SnC can be described in the following steps. Sn melted at 230 °C, which provided a favorable liquid circumstance for the reactions between Ti and Sn to form Ti–Sn intermetallic compounds. At high temperatures, TiCx formed and reacted with Ti–Sn intermetallics at ∼1100 °C to yield ternary carbide Ti2SnC. The material prepared by this method was dense and showed a layered anisotropic microstructure. The electrical conductivity of polycrystalline Ti2SnC was metallic and anisotropic due to the anisotropic microstructure. The Vickers hardness was 3.7 GPa and the flexural strength was 313 MPa. Under compression, Ti2SnC was damage tolerant at room temperature and deformed plastically at above 1000 °C.

AbstractTi3SiC2is a so-called not-so-brittle ceramic that combines the merits of both metals and ceramics. However, many previous works demonstrated that its bonding nature and properties were strongly related to TiC. In this paper the crystallographic relations between Ti3SiC2and TiC were established and described based on the transmission electron microscopy investigation on the Ti3SiC2/TiC interface in Ti3SiC2based material. At Ti3SiC2/TiC interface, the following crystallographic relationships were identified,: (111)TiC//(001)Ti3SiC2, (002) TiC//(104)Ti3SiC2, and [110]TiC//[110]Ti3SiC2. Based on the above interfacial relations an interfacial structure model was established. The structure of Ti3SiC2could be considered as two-dimensional closed packed layers of Si periodically intercalated into the (111) twin boundary of TiC0.67(Ti3C2). The intercalation resulted in the transformation from cubic TiC0.67to hexagonal Ti3SiC2. In the opposite case, de-intercalation of Si from Ti3SiC2caused the transformation from hexagonal Ti3SiC2to cubic TiC0.67Understanding the crystallographic relations between Ti3SiC2and TiC is of vital importance in both understanding the properties and optimizing the processing route for preparing pure Ti3SiC2.

AbstractCu/Ti3SiC2composite, a new electrofriction material, was prepared, for the first time, by PM method. The microstructure, mechanical and electrical properties of the Cu/Ti3SiC2composites were investigated and were compared with those of Cu/graphite composites. The results demonstrated that Cu/Ti3SiC2composites had superior mechanical properties over Cu/graphite composites. At filer content of less than 20 vol%, the electrical conductivity for Cu/Ti3SiC2composites was higher than that for Cu/graphite composites; at high filer content, the electrical conductivity for Cu/Ti3SiC2composites was lower than that for Cu/graphite composites because of the presence of residual pores. It was found that like Cu/graphite composite, Cu/Ti3SiC2was a self-lubricated material. The compressive yield strength, Brinell hardness, relative ratio of compressive for Cu-30 vol% Ti3SiC2composites are 307 MPa, 140, 15.7% respectively.

Abstract:  Titanium silicon carbide (Ti3SiC2) is a damage tolerance material that is expected to be used in a number of high temperature applications. In this work, the microstructure and damage tolerance mechanism of Ti3SiC2 was investigated. The result demonstrated that the Ti3SiC2 ceramics prepared by the in-situ hot pressing/solid-liquid reaction process had a dual microstructure, i.e., large laminated grains were distributed within small equiaxial grains. This microstructure is analogous to that of platelets reinforced ceramic matrix composites. The bending test using single-edge-notched-beam specimens revealed that Ti3SiC2 was a damage tolerance material. The damage tolerance mechanisms for Ti3SiC2 are basal plane slip, grain buckling, crack deflection, crack branching, pull-out and delamination of the laminated grains.