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Chemical solution deposition is a promising technology to fabricate YBCO superconducting thin films due to its low-cost advantage. However, the decreasing of critical current density ( J c ) usually occurred in the fabrication of multi-layered YBCO films. In this study, Ag and Au heterogeneous interlayers were fabricated by using sputtering deposition in order to improve the bi-layered YBCO films, and the influence of crystallization temperature from 740 ∘C to 800 ∘C was investigated. It was found that J c could be enhanced by both interlayers relative to the counterparts without interlayers, and the effect of Ag interlayer was superior to that of Au interlayer. When the crystallization temperature was 800 ∘C, the optimal sample with Ag interlayer had a J c 3.65 MA/cm2, which was about twice of the J c of its counterpart. The surface morphologies and cross-sections were observed by using scanning electron microscope, and the content variations of c-axis oriented grains were measured by using Raman spectroscopy, which could help to investigate the influences of interlayers on the microstructure of YBCO films. The possible reasons for the improvement effects of Ag and Au interlayers were discussed based on the experimental results.

An optimization method of chromogenic agent was mainly studied to detect the concentration of metal ions in zinc metallurgy wastewater based on ultraviolet-visible spectrometry. Firstly, a chromogenic agent was selected to reduce the sensitivity of Zn(II) that solved the problem of spectral masking caused by high concentration of Zn(II). However, the range of noiseless wavelength, linearity of Zn(II) and additivity of absorbance were serious influenced by the dosage of chromogenic agent. So, a multi-objective optimization method with the target of maximum range of noiseless wavelength, maximum linearly dependent coefficient of Zn(II) and the optimum additivity of absorbance was proposed to optimize the dosage of chromogenic agent. Finally, the optimization result are verified by feature interval association-partial least squares regression. The average relative errors of Zn(II), Cu(II), Co(II) and Ni(II) were 5.43%, 6.65%, 6.24% and 6.87%, respectively. It indicates that the detection method using optimal chromogenic agent exhibit high-precision and low-error for analyzing the concentration of Zn(II), Cu(II), Co(II) and Ni(II).

Over the past few years, supercapacitors based on graphene/polyaniline (rGO/PANI) composites have gained immense attention. The electrochemical performance of rGO/PANI composites can be improved by controlling their morphology and structure. However, very few studies have been carried out on amine-functionalized graphene/polyaniline (F-rGO/PANI) composites. In this study, amine-functionalized graphene (F-rGO) and mesoporous graphene (PF-rGO) were composited with PANI. The results showed that the specific capacitance of the F-rGO/PANI composites could be improved by controlling their morphology. The mesoporous structure of F-rGO contributed to the improvement in the cycling stability and energy density of the composites. At a current density of 0.5 A g−1, the specific capacitances of F-rGO/PANI20–0.5h and PF-rGO/PANI are 597 F g−1 and 489 F g−1, respectively; these values are remarkably higher than that of pure PANI (400 F g−1). F-rGO/PANI20-0.5th and PF-rGO/PANI maintained specific capacitances of 75% and 89%, respectively, which were significantly higher than that of pure PANI; this was observed even after 2000 cycles of charge and discharge had been completed at a current density of 1 A g−1. The energy density of PF-rGO/PANI reaches 34.9 W h kg−1 at the power density of 1.27 kW kg−1. This study is expected to provide an effective basis for the future research of graphene-based composite electrode materials for supercapacitors.