| 其他摘要 | The antiperovskite compounds have attracted extensive attention due to their possession of many interesting physical properties such as superconductivity, nearly zero temperature coefficient of resistivity, giant magnetoresistance, etc. Ti3AlC is the only one antiperovskite compound in the Ti-Al-C system and it may combine interesting physical properties and good mechanical properties which endow it the potential applications as functional/structural materials. However, there are very limited reports on the properties of Ti3AlC because of the difficulty in preparing pure and dense samples. Thus, the preparation of pure and dense bulk Ti3AlC and systematic investigation of its mechanical and physical properties become significantly important, which will improve our understanding of the antiperovskite compounds, as well as facilitate the design of structural/functional materials.
In this paper, dense bulk Ti3AlC was prepared by an in-situ reaction/hot pressing method; the mechanical and physical properties were measured. The main work and conclusions are as follows:
(1) Dense bulk Ti3AlC containing about 2.68 wt% of TiC was prepared by an in-situ reaction/hot pressing method using Ti, Al, and graphite as starting materials. The influences of sintering temperature and starting material compositions on the phase compositions of the products were investigated. The possible reaction route was proposed.
(2) The microstructure was characterized by SEM and TEM. SEM observation revealed the equiaxed morphology of the Ti3AlC grains and the average diameter of the grains was about 24 μm. The TEM investigation showed that there were no amorphous phases at the grain boundary.
(3) The mechanical properties of Ti3AlC were measured using the as-prepared samples. At room temperature, its Vickers hardness, bending strength, compressive strength, and fracture toughness were 7.8 GPa, 182 MPa, 708 MPa, and 2.6 MPa•m1/2, respectively. The fracture mode of Ti3AlC was transgranular. Both the Vickers indentation and fracture surface confirmed the brittleness of Ti3AlC. The Young’s modulus, bulk modulus, shear modulus and Possion’s ratio were 209 GPa, 140 GPa, 83 GPa and 0.25, respectively. The Young’s modulus decreased with the increase of temperature and at 1210oC, the remaining value was about 170 GPa.
(4) Physical properties such as coefficient of thermal expansion, molar heat capacity, thermal conductivity and electrical resistivity at room temperature were investigated. The coefficient of thermal expansion of Ti3AlC between 150 and 1200oC was 10.1×10-6 k-1. Both the molar heat capacity and thermal conductivity increased with temperature. At 300 and 1373 K, the molar heat capacity of Ti3AlC were 87 and 143 J•(mol•K)-1, and the thermal conductivity were 8.19 and 15.6 W•(m•K)-1, respectively. The electrical resistivity of Ti3AlC at room temperature was about 1.55 μΩ•m. |
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