Jie Mao

Platinum plays a crucial role in the superior high-temperature oxidation resistance of Pt-modified nickel aluminide (PtAl) coatings. However, PtAl coatings usually serve in thermo-mechanical coupling environments. To investigate whether Pt contributes to the high-temperature mechanical properties of PtAl coating, stress rupture tests under 1100 °C/100 MPa were performed on PtAl coatings with varying Pt contents. The different coatings were obtained by changing the thickness of the electroplated Pt layer, followed by a diffusion heat treatment and the aluminizing process in the present work. The results of the stress rupture tests indicated that an increasing Pt content resulted in a significant decrease in the stress rupture life of PtAl-coated superalloys under 1100 °C/100 MPa. Theoretical calculations and microstructural analysis suggested that an increased coating thickness due to the Pt content is not the main reason for this decline. It was found that the cracks generated close to the substrate in high-Pt-coated superalloys accelerated the fracture failure.

Photocatalytic coatings can degrade volatile organic compounds into non-toxic products, which has drawn the attention of scholars around the world. However, the pollution of dust on the coating adversely affects the photocatalytic efficiency and service life of the coating. Here, a series of TiO₂-polyfluoroalkoxy (PFA) coatings with different contents of PFA were fabricated by suspension plasma spraying technology. The results demonstrate that the hybrid coatings contain a large number of circular and ellipsoidal nanoparticles and a porous micron-nano structure due to the inclusion of PFA. According to the optimized thermal spraying process parameters, TiO₂ nanoparticles were partially melted to retain most of the anatase phases, whereas PFA did not undergo significant carbonization. As compared to the TiO₂ coating, the static contact angle of the composite coating doped with 25 wt.% PFA increased from 28.2° to 134.1°. In addition, PFA strongly adsorbs methylene blue, resulting in a greater involvement of methylene blue molecules in the catalyst, where the catalytic rate of hybrid coatings is up to 95%. The presented nanocomposite coatings possess excellent photocatalytic and self-cleaning properties and are expected to find wider practical applications in the field of photocatalysis.

Spherical Gd ₂ Zr ₂ O ₇ hollow powders with a mean size of 8.8 μm were fabricated as feedstock for thermal barrier coatings (TBCs) by spray‐drying. The single‐ceramic‐layer (SCL) Gd ₂ Zr ₂ O ₇ TBCs and double‐ceramic‐layer (DCL) Gd ₂ Zr ₂ O ₇ /YSZ TBCs with quasi‐columnar structure were successfully fabricated by plasma spray‐physical vapor deposition (PS‐PVD). Tensile and water‐quenching tests were applied to evaluate TBCs performances. The results show that adhesion strength of SCL Gd ₂ Zr ₂ O ₇ TBCs and DCL Gd ₂ Zr ₂ O ₇ /YSZ TBCs is 36.5 MPa and 15.4 MPa, respectively. The delamination of SCL Gd ₂ Zr ₂ O ₇ TBCs and DCL Gd ₂ Zr ₂ O ₇ /YSZ TBCs in the tensile test takes place at the middle and bottom of Gd ₂ Zr ₂ O ₇ layer, respectively, due to relatively lower fracture toughness of Gd ₂ Zr ₂ O ₇ layer. After 40 cycles of water‐quenching test, DCL Gd ₂ Zr ₂ O ₇ /YSZ TBC surface keeps relatively intact, while SCL Gd ₂ Zr ₂ O ₇ TBC surface shows 20% visible destroyed regions, which demonstrates that DCL Gd ₂ Zr ₂ O ₇ /YSZ TBCs have a better thermal shock resistance than SCL Gd ₂ Zr ₂ O ₇ TBCs. The cracks in the SCL system propagate near thermally grown oxide (TGO) due to thermal mismatch and TGO growing stress, while cracks in the DCL system propagate in the Gd ₂ Zr ₂ O ₇ layer due to its relatively lower fracture toughness.

Highly dispersed gadolinium zirconate (GZ) nanoparticles with fluorite microstructure were successfully synthesized using a co-precipitation method, and their phase composition and microstructure, formation mechanism, and grain growth kinetics were investigated. The results suggest that the nanoparticles were obtained through hydroxide dehydration followed by solid phase reaction. High dispersion was accomplished using ethanol solvent to reduce the hydrogen bond and sodium dodecyl benzene sulfonate (SDBS) surfactant to increase the electrostatic repulsion between the nanoparticles. The grain growth activation energy of GZ powders calcined at lower temperature (< 1200 °C) is 86.5 kJ/mol (Ql), and the grain growth activation energy of GZ powders calcined at higher temperature (> 1200 °C) is 148.4 kJ/mol (Qh). The current study shows that the optimal process to synthesize dispersed GZ nanoparticles includes ethanol solvent, 3 wt.% SDBS surfactant, and 1100 °C as calcining temperature.