Study On The Mechanical Lubricating Materials Of Nitride Max Phase’s Preparation And Properties

The mechanical lubricating materials of nitride MAX phases, especially Ti2 Al N and Ti4 Al N3, posses a remarkable combination of good self-lubricating properties, irradiation damage resistance and ceramic and metallic properties, due to their layered structure and unique bonding characteristics, which comprised of alternate slabs of Tin+1Nn and pure Al atomic planes. These distinctive features make Ti2 Al N and Ti4 Al N3 a promising candidate for mechanical lubricating materials and nuclear fuel cladding structural materials.In this thesis, ternary Ti2 Al N and Ti4 Al N3 were synthesized via microwave sintering(MWS) process. High-purity Ti2 Al N with orientation growth behavior was synthesized by a MWS method. The synthesis process, the phase and microstructure evolution were discussed. Its mechanism for the orientation growth was proposed. High-purity Ti4 Al N3 was also successfully synthesized and the effects of process conditions and starting material on the synthesis of Ti4 Al N3 under the MWS conditions were studied. At last, the dense Ti2 Al N and Ti4 Al N3 samples were obtained by re-sintering the prepared samples using a spark plasma sintering(SPS) method, respectively. In addition, the microstructures, physical properties and tribological properties of the as-prepared dense Ti2 Al N and Ti4 Al N3 ceramics were characterized. The corrosion behaviors of Ti2 Al N and Ti4 Al N3 in HF acid were studied. Moreover, Ti2 Al N and Ti4 Al N3 were irradiated with 70 ke V He ions, and the damage evolutions were characterized mainly by microstructure observations and the structure simulations, respectively.As a result, the basic properties at room temperature of dense Ti2 Al N and Ti4 Al N3 were in agreement with the reports. The friction coefficients of Ti2 Al N and Ti4 Al N3 in a stable stage were close and the friction and wear mechanisms were similar. A further study shows that, for Ti2 Al N, the side surface with no orientation had a better tribological property than the top face. The tribological property of Ti4 Al N3 was better than Ti2 Al N. Compared the stability of Ti4 Al N3 with Ti2 Al N in HF, Ti4 Al N3 phase was more stable and the result indicated that Ti4 Al N3 phase was expected to be used to prepare a two-dimensional sheet of nitride materials.The as-fabricated Ti2 Al N and Ti4 Al N3 were irradiated with 70 ke V He ions at different doses, respectively. The reported structural transformation mechanism of MAX phase by irradiation at present cannot explain the structural changes of Ti2 Al N and Ti4 Al N3 after irradiation. At low doses, Ti2 Al N and Ti4 Al N3 were similar and the simulation and experimental results were not consistent with electron diffraction. At higher doses, unlike Ti2 Al N, the microstructure of Ti4 Al N3 had not changed significantly and the microstructure still maintained as the low radiation dose, which was not form twins FCC structure.