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Thermal barrier coating (TBC) is a kind of thermal insulation and protective ceramic material, which can effectively improve the working temperature and service life of aero-engine. It has important economic value and strategic position in this field. With the further improvement of thrust-to-weight ratio, the traditional YSZ coating no longer can meet the technical requirements of the new generation engine. In recent years, scholars both at home and abroad have shown that rare earth doping can improve the performance of TBCs to a certain extent. Therefore, rare earth doping modification has become the focus of the development of new high-performance TBCs. In this paper, the applications of rare earth doping in high-performance TBCs are summarized, with emphasis on the effects of rare earth doping on the mechanical, thermal-physical and corrosion resistance of TBCs to molten CMAS. The problem of performance deterioration of TBCs when rare earth is over doped and the deficiency in rare earth selection standard is discussed. Moreover, it is considered that the selection basis of rare earth doping amount and type will be the research focus of TBC materials in the next generation. How to further improves the performance of TBCs is the future development direction of rare earth doped TBCs.

Using first-principle calculations, the surface energy, cohesive energy, and electronic properties of α-MnO2 and rutile TiO2 nanorods and microfacets were investigated and clarified to, in the first instance, determine the evolution mechanism. The results show that the surface energies of α-MnO2 nanorods and microfacets conform to function 1.0401 Jm−2 + N × 0.608 Jm−2, while the surface energies of the rutile TiO2 nanorods and microfacets are governed by a 1.0102 × 1.1997 rule. Their electronic properties, such as the Mulliken population and Mulliken charge, can only be normalized by their surface areas to attain a linear function. Meanwhile, the surface energy of α-MnO2 with the nanostructure closely conforms to the function for normalized Mulliken population and Mulliken charge as f(x)=102.9×x+0.101 with an R2 value of 0.995. Thus, our research into the evolution mechanism affecting the surface effect of nanometer materials will be useful for investigating the intrinsic mechanism of the nanometer effect and doping process of metallic dioxide catalysts. [ABSTRACT FROM AUTHOR]

Although previous papers have reported the desorption process of antimony (Sb) ions adsorbed on α-MnO 2 nanomaterials, some trace Sb(OH) 4 - molecular observed in experiments have not been understood clearly. Using two models as popular bulk surface and new microfacet, several parameters, such as adsorption energy, bond length, total density of state (TDOS) and activation energy, were calculated to research and analyze the catalytic reaction of Sb oxides on α-MnO 2 . The results show that the bulk surface model has the "mirror effect" in revealing the catalytic property of α-MnO 2 nanorods. Using MnO 2 [(100 × 110)] microfacet model, a new molecular Sb(OH) 4 - molecular appears in the reaction process of Sb(OH) 3  + H 2 O → Sb(OH) 4 -  + H + . Further comparing the geometric morphology and TDOS of Sb(OH) 4 - with Sb(OH) 6 - molecular, it is found that their bonding length, dihedral and energy orbital of bonding peaks are too close to set the Sb(OH) 4 - as the precursor product of Sb(OH) 6 - molecular. Then the desorption process of Sb ions on α-MnO 2 nanorods is virtually transformed into Sb(OH) 3  → Sb(OH) 4 -  → Sb(OH) 6 - way in aqueous solution. Thus, our findings open an avenue for detailed and comprehensive theoretical studies of catalytic reaction by nanomaterials., (Copyright © 2018 Elsevier B.V. All rights reserved.)