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In order to achieve flexible applications of superconducting thin film materials in devices, the surface quality of the film is critical. The thickness of the film is one of the important factors affecting its surface quality. In this paper, Bi2212 superconducting thin films of different thicknesses were prepared on LaAlO 3 (100) and SrTiO 3 (100) single crystal substrates by sol-gel method and the effects of film thickness and different heterogeneous structures on their crystallographic, morphological and superconducting properties were investigated. The results showed that the roughness gradually increased with increasing Bi2212 thickness at the initial stage of film growth and stabilized after reaching a certain thickness, while the superconducting properties were destroyed at very small sample thickness, which was consistent in both single-crystal substrate films. In the Bi2212/LaAlO 3 structure, the surface quality of the sample was excellent with a roughness of 5.4 nm at a thickness of about 18 nm for Bi2212, and the growth of the precipitated phase was inhibited to a greater extent. The film also had good superconductivity. This work provided a further research basis for the preparation of high quality Bi2212 films and offers further possibilities for their practical application. [Display omitted] • Preparation of epitaxially grown multi-component functional thin films-Bi2212 superconducting films. • Effective regulation of film thickness. • Effective improvement of the surface quality of the film by regulating the thickness of the film. • Modelling the variation process of the effect of film thickness on its surface quality. [ABSTRACT FROM AUTHOR]

Graphical abstract Abstract The objective of this study is to investigate the differences of emulsion stability evaluated by phase separation proportion and Turbiscan Stability Index (TSI). The relationship between emulsion stability and oil displacement efficiency was also investigated. An alkaline-surfactant-polymer (ASP) solution and a surfactant-polymer (SP) solution were both selected to prepare emulsions, respectively. The instability process of emulsions was studied by the multiple light scattering as well as the bottle test. The opposite stability results, evaluated by the TSI and the phase separation proportion separately, of same emulsion are observed. The discrepancies resulted from diverse influence of emulsion instability types in test methods. The main instability type in ASP emulsions is creaming, whereas in SP emulsions is flocculation and coalescence. The influence of creaming is more notable in bottle test. However, in TSI calculation, not only creaming but also flocculation and coalescence are recorded and counted particularly. The stability results obtained by the bottle test and the multiple light scattering method were similar for emulsions prepared with different concentrations of ASP or SP solution. Injection pressure change in core flooding experiments can be better explained by TSI of the emulsion. [ABSTRACT FROM AUTHOR]