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The densification behaviors of MgO‐doped‐Al2O3 ceramics in the flashing stage and the steady stage were investigated using the classic kinetic model. The results show that the most densification of MgO‐doped Al2O3 was completed during the flashing stage. The densification mechanism transferred from particle rearrangement resulted from Columbic force among particles under the effect of electrical field in the flashing stage to the lattice diffusion in the steady stage. Therefore, the densification rate in the steady stage dramatically decreased. Additionally, the estimated densification activation energy in the steady stage of flash sintering is 396 kJ/mol, much lower than the activation densification of lattice diffusion measured from conventional sintering, likely due to the effect of electric field/current‐induced point defects on the diffusion. [ABSTRACT FROM AUTHOR]

The nearly fully dense ultra‐high pure (>99.99%) α‐Al2O3 ceramics were prepared by flash sintering at the furnace temperature of 1300°C. Compared with the samples sintered at 1300 and 1650°C without electrical field, the flash‐sintered samples exhibited remarkably improved density and finer grains. The flash‐sintered samples also exhibited high hardness, which is even higher than that of the hot‐pressed sample. Therefore, it is believed that flash sintering could be an effective technique for the preparation of ultra‐high pure alumina ceramics. [ABSTRACT FROM AUTHOR]

Herein, the effects of electrical field on the microstructure and mechanical properties of flash sintered (FS-ed) MgO-doped-Al 2 O 3 ceramics were investigated. The results showed that compared with pressureless sintered sample without electrical field, the relative density of FS-ed alumina ceramics were remarkably enhanced, and increased from 91.92% to 99.36%, then decreased to 94.73% since the applied electric field increased from 2500 V/cm to 5000 V/cm. In addition, the FS-ed MgO-doped-Al 2 O 3 ceramics exhibited ultra-fine grain (mean grain size ≤0.32 μm) and homogeneous microstructures. The mechanical properties including hardness and fracture toughness of the FS-ed specimens mainly depended on their relative densities and microstructures. Consequently, they possessed excellent hardness and fracture toughness, reaching 20.89 GPa and 4.44 MPa m1/2, respectively. [ABSTRACT FROM AUTHOR]

MgO-doped-Al 2 O 3 ceramic discs were fabricated by flash sintering (FS) and pressureless sintering (PS). The results showed that MgO-doped Al 2 O 3 exhibited typical characteristics of flash sintering under an electric field in excess 2500 V/cm. Compared with the PS- fabricated specimen, the flash sintered specimens exhibited sub-micron grains (≤760 nm) and homogeneous microstructures. The relative density of the flash sintered MgO-doped Al 2 O 3 ceramics increased with current density, reaching 99.91 % when the current density increased to 7 mA/mm2. The FS-fabricated sample exhibited higher hardness (21.02 GPa) and fracture toughness (3.46 MPa m1/2) than PS-fabricated sample. [ABSTRACT FROM AUTHOR]

A novel Al plating layer was deposited on the CoCrNiAlY–YSZ–RSZ dual - ceramic thermal barrier coating. The hot corrosion behaviors of these coatings in molten sulfate mixture were studied by the detail characterizations. This coating without Al plating possessed a fast mass gain trend, severe elemental diffusion and rapid TGO growth during the hot sulfate exposure, resulting in a significant increase in mass gain from 6.12 mg/cm2 at 20 h to 13.67 mg/cm2 at 100 h and aggravated coating fracture. In comparison, a continuously dense Al 2 O 3 barrier layer formed on the coating's surface, preventing or delaying the infiltration of the molten sulfate and oxygen, and eventually led to an enhanced corrosion resistance. This coating with Al plating showed a slight mass gain from 8.20 mg/cm2 at 20 h to 9.31 mg/cm2 at 100 h, but also exhibited very slow TGO growth and stable structure. The potential molten sulfate corrosion mechanisms of these coatings with and without Al plating were systematically discussed. [ABSTRACT FROM AUTHOR]